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HANDBOOK ON ENGINEERING
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HANDBOOK ON
ENGINEERING
THE PRACTICAL CARE AND MANAGEMENT
OF
DYNAMOS, MOTORS, BOILERS, ENGINES, PUMPS,
INSPIRATORS AND INJECTORS, REFRIGERATING
MACHINERY, HYDRAULIC ELEVATORS, ELEC-
TRIC ELEVATORS, AIR COMPRESSORS, ROPE
TRANSMISSION AND ALL BRANCHES1
OF STEAM ENGINEERING.
BY
HENRY C. TULLEY,
Engineer and Member Board of Engineers, St. Louis.
SIXTH EDITION— SIXTH IMPRESSION
Revised and Enlarged
McGRAW-HILL BOOK COMPANY, INC;.
239 WEST 39TH STREET. NEW YORK
LONDON: HILL PUBLISHING CO., LTD.
6 & 8 BOUVERIE ST., B. C.
Entered according to Act of Congress, in the year 1900, by
HENEY C. TULLEY,
In the Office of the Librarian of Congress, at Washington.
Copyrighted, 1907.
INTRODUCTION.
The object of the Author in preparing this work has been to
present to the practical engineer a book to which he can, with
confidence, refer to for information regarding every branch of
his profession.
Up to the date of the publication of this book, it was impossi-
ble to find a plain and practical treatise on the steam boiler, steam
pump, steam engine, and dynamo, and how to care for them;
electric and hydraulic elevators, and how to care for them ; and
all other work that an engineer is apt to come in contact with in
his profession.
An experience of over twenty-five years with all kinds of en-
gines and uoilers, pumps, and all other kinds of machinery, ena-
bles the Author to fully understand the kind of information most
needed by men having charge of steam engines of every descrip-
tion, and what they should comprehend and employ.
With this object in view, the Author has carefully made note of
his past experience, and has also made note of things that came
to his notice while visiting different engine rooms, and accord-
ingly, has taken up each subject singly, excluding therefrom,
everything not strictly connected with steam engineering.
Particular attention has been given to the latest improvements
in all classes of steam engines, with rules and formulas ac-
cording to the best modern practice, which, it is hoped, will be
of great value to engineers, as nothing of the kind has heretofore
been published.
This book also contains ample instructions for setting up, lining,
reversing and setting the valves of all classes of engines.
THE AUTHOR.
IV?
on)
CONTENTS.
For Alphabetical Index to Subjects, see page 963.
CHAPTER I.
PAGE
THE ELEMENTARY PRINCIPLES OF ELECTRICAL MA-
CHINERY j
A permanent magnet 1 to 2
Two-bar magnet 3 to 6
A magnet needle 3
Magnetic lines of force 6
Lines of force 6 to 14
Magnetic force 13
To find the lifting capacity of a magnet 13
CHAPTER II.
THE PRINCIPLES OF ELECTROMAGNETIC INDUCTION 14 to 22
The armature cores 23 to 27
CHAPTER III.
TWO-POLE GENERATORS AND MOTORS ........ 27
The simplest type of armature winding 27 to 29
Two-pole generators and motors 27 to 30
The general arrangement of the field and armature in a two-pole
machine 33 to 36
The reason why brushes are set differently on motors than on
dynamos 36 to 37
v
VI CONTENTS.
CHAPTER IV.
PAGE,
MULTIPOLAR MACHINES 38
Multipolar machines 38 to 39
Setting the brushes on a four-pole machine 40
Setting the brushes on an eight-pole machine 41
The lap and wave winding for four-pole machine* . . . . . 42 to 46
CHAPTER V.
SWITCH BOARD, DISTRIBUTING CIRCUITS, AND SWITCH
BOARD INSTRUMENTS 47
Generators of the constant potential type 47 to 48
The switch-board arranged for two generators of the shunt
type 49 to 54
Switch-board for three-wire system 56 to 57
To wire a large building with a lighting and power system . 58 to 60
The ammeter 60
Circuit breakers 62 to 63
The electromotive force in volts, etc 63
CHAPTER VI.
ELECTRIC MOTORS 64
Motors and their connections 64 to 73
The strength of an electric current, etc 73
The watt 73
The ampere 73
Candle power 73
CHAPTER VII.
INSTRUCTIONS FOR INSTALLING AND OPERATING SLOW
AND MODERATE SPEED GENERATORS AND MOTORS . . 74
To remove the armature 74
Assembling the parts 74
Filling the bearings 74
To complete the assembly 74
Starting 74
Care of commutator 75
CONTENTS. yj|
If commutator gives trouble *
General directions for starting dynamos . 7fi
Bringing dynamos to full speed . . . ' 77
Connecting one dynamo with another 78
Switching dynamos into circuit 7g
How dynamos may be connected together
Dynamos in parallel 7g
Directions for running dynamos and motors 80
Precautions in running dynamos . . - 81
Personal safety '. . . , ,81
CHAPTER VIII.
WHY COMMUTATOR BRUSHES SPARK AND WHY THEY DO
NOT SPARK 82 to 84
The way in which the current is shifted, etc 84, 85
Diagram illustrating the same 85
If the commutated coil, etc 86
Even when the machine is properly proportioned, etc 87
Sparking 87 to 91
Noise - 91 to 92
Heating in dynamo or motor 93 to 94
The effect of the displacement of the armature 94 to 98
Table of carrying capacity of wires 99, 101
Insulation resistance 100
Soldering fluid 101
Table showing the size of wire of different metals that will be melted
by currents of various strengths . 102
CHAPTER IX.
INSTRUCTIONS FOR INSTALLING AND OPERATING APPA-
RATUS FOR ARC LIGHTING.
Brush arc light generator . . . . . 0 . . 10*
Multiple circuit Brush arc generator . . . 0 105
Armature circuits of Brush machine .., 0 .... o ... 106
Diagram of multiple circuits . «. .... 107
Current regulator for Brush arc generator . , . . . . . » .
Position of brushes on arc lighting generator ,109
Vlll CONTENTS.
PAGE.
Setting brushes of arc light generator 110
Care of the commutator and brushes Ill
Series system of arc lighting 112
Transformers for series system , 113
General Electric Co.'s transformer 114
Operation of transformer, series system 115
Sizes of General Electric transformers 116
Switchboards for arc lighting apparatus 117
General Electric Co.'s switchboards , ... 118
Switchboard for Westinghouse system 119
Westinghouse transformers, series system 120
Western Electric Co.'s regulator 121
Regulator for constant current series system . . * 122
Adams-Bagnall regulator 123
Fort Wayne Electric Co.'s regulator 124
General arrangement of Fort Wayne circuits 125
Fort Wayne system of arc lighting , 126
Alternating current, constant current circuits 127
General Electric Co.'s enclosed arc lamp 128
Westinghouse lamp 129
Lamp for series alternating current circuits 130
Fort Wayne lamp 131
CHAPTER X.
Western Electric Co.'s lamp 132
Actuating clutches for enclosed lamps 133
Westinghouse, Western Electric and Fort Wayne clutches . . . 134
Carbon holders . 1 35
Enclosed direct current lamps 136
General Electric Go's, lamp 137
Voltage of General Electric Co.'s lamp 138
Westinghouse and Fort Wayne enclosed lamps 139
Fort Wayne lamp for direct current circuits 140
Enclosed lamps for power circuits 141
Construction and operation of enclosed lamps 142
Series arc lamps for power circuits 143
CONTENTS.
Westinghouse direct current enclosed lamp
Cut-out for General Electric lamp ,
Constant potential enclosed lamps
Fort Wayne constant potential lamp ...'.'.'
Westinghouse lamp . . .....
General Electric Co.'s lamp . .
Fort Wayne street lighting system ......
Lamp used with Fort Wayne system , 151
Luminous or flaming arc lamp , . . ..... 152
The Excello lamp • '••...,.,..'."-
Excello lamp for direct current . . . . 154
Life of carbons in the Excello lamp .......
Directions for care of lamps ........... 156
How to trim lamps . ..... ....... 157
Care of dashpot and globes „ ...... . 153
How to install arc lamps , ....... . e 150
CHAPTER Xa.
INCANDESCENT WIRING TABLES ....... 161 to 162
Amperes per motor, table .............. 169,170
Volts lost at different per cent drop .......... 171, 172
Amperes per lamp,table ................ 173
Approximate weight of " O. K." triple braided weatherproof copper
wire ...................... 174
Table showing difference between wire gauges in decimal parts of an
inch ...................... 175
Electric light conductors, table ...... ...... . . 176
CHAPTER XI.
THE STEAM ENGINE ............ .... 177
The selection of an engine ............... 177
The gaia by expansion ......... •• ...... 183
Table of cut-off in parts of the stroke . . ......... 183
The steam engine governor ............ 183 a»d 1J
The fly-wheel .................... 184
Horse power .................... *'
Care and management of a steam engine . „ ........ 185
X CONTENTS.
PAGE.
Lubrication of an engine 186
Selecting an oil for an engine 187
The piston packing 187
Crank-pins , . 188
Connecting rod brasses 189
Knocking in engines 189 to 190
The main bearings '. . . . 190 to 192
Repairs of engines 191
Fitting a slide valve 191
Eccentric straps 192
Heating of journals 193
Automatic engines 194
To find the dead centers . . . . • 195
View of tandem compound engine and its foundation 198
How to line an engine 199 to 203
View of twin tandem compound engine, showing arrangement of
piping 200
CHAPTER XIa.
Directions for setting up, adjusting and running the improved Cor-
liss steam engine 205
Adjustment of Corliss valve gear with single and double eccentrics. 206
Adjustment with two eccentrics .• 215
The compound engine 222
Horse power of compound engine 232
Condensing engines 232
Condensers 235 to 253
Setting the piston type of valve 261
Setting the cut-off valve . . 266
Flat valve riding cut- off .' ... 268
Starting and running a compound engine 253
. CHAPTER XII.
THE STEAM ENGINE — CONTINUED 274
What is work 274
What is power 274
Horse power, stroke and weights of engine 273,275
General proportions of engine 275
CONTENTS. xj
Rules for weights of fly-wheels ...... AGE*
View of the Russell engine ......
Setting the valves of Russell engines ..... 277
View of the Porter-Allen engine ......
Description of the Porter-Allen engine ...... ' 282-287
Directions for setting the valves, and running the Porter-Allen
................... 271,288
The Porter governor ............ 289
The Armington and Sims engine ...... * 290*
Setting the valve in an Armington and Sims engine . . 290
The Harrisburg engine ......... 291
The care and management of the Harrisburg engine . . 291-296
The Mclntosh and Seymour high speed engine . . 296
How to set the valves of an M. and S. engine ..... 296
The Ideal engine ........... . 298
Instructions for starting and operating Ideal engines .... 298-306
Instructions for indicating Ideal engines .......... 306
The Westinghouse compound engine ........ . 308
Westinghouse compound., diagram of cylinders ........ 309
How to set the valve on a Westinghouse engine ....... 307
Some points on cylinder lubrication ............ 309
Automatic lubricators ........ ...... 310,312
Setting a plain slide valve with link motion ....... 313, 318
Valve setting for engineers ...... ;*> ...... 318,322
View of a slide valve engine showing the point of taking steam . .321
View of a slide valve engine showing the point of cut-off . . . .321
View showing the position of the valve when compression
begins ................ . . . 321, 322
CHAPTER XIII.
TAKING CHARGE OF A STEAM POWER PLANT ..... 323
Economy in steam power plants ... ........ 327, 32
Priming in boilers . . . . .............. 3!
Table of properties of saturated steam ........... 31
High pressure steam ............... ; 132, 33
Using steam full stroke .............. 335,337
Xll CONTENTS.
PAGE.
Slide valve engines . 337
Regular expansion engines 338
Automatic cut-off engines 339,340
The Gardner spring governor 341, 344
The Gardner standard governor 342, 344
CHAPTER XIV.
A FEW REMARKS ON THE INDICATOR 345
The use of the indicator in setting valves, etc 346
A card from a throttling engine 347, 349
A card from an automatic cut-off engine 350
Calculating mean effective pressure 351
The theoretical curve 353, 357
A card from a Corliss engine 357
A stroke card 358
A steam chest card 359
Eccentric out of place, cards 360,361
Eccentric cards 361,365
How to take an indicator diagram 365
Cards from " Eclipse " ice machine .. . . . . . . . . . 371,373
A collection of diagrams, which illustrate very nicely the peculiari-
ties and difference in the action of throttling and automatic en-
gines . 375, 379
CHAPTER XV.
ECONOMY AND OPERATION OF STEAM ENGINES .... 380
The question whether or not more steam is used when an engine is
made to run faster without changing either the cut-off or the pres-
sure 380
How to increase the power of a Corliss engine . . . . . . 381, 382
How to increase the power of an engine having a throttling governor 383
How to increase the horse power of an engine having a shaft gov-
ernor 385
How to line an engine with a shaft placed at a higher or a lower
level . . 385, 387
How to line the engine with a shaft to which it is to be coupled
clireel}, .,,....,...<,,,...•... 387
CONTENTS.
PAGE.
How to set a slide valve in a hurry ......... 3g8
A few things for an engineer to remember ....
The travel of a slide valve ............ u 39Q
Loss of heat from uncovered steam pipes ...... .391
Rules and problems appertaining to the steam engine . . . 392, 395
To find the water consumption of a steam engine ..... 395 397
Table of sizes of boiler feed pump ............ 397
CHAPTER XVI.
THE STEAM BOILER 398
The force of steam and where it comes from ...... 398, 400
The energy stored in steam boilers 400, 401
Special high pressure boilers 401
Types of boilers 402
Horse power of boilers • . . . 402, 404
The rating of boilers 404
Working capacity of boilers 405, 406
Code of rules for making boiler tests 407,414
Definitions as applied to boilers and boiler material 415
Heat and steam • . . 416,421
Selection of a boiler ....... 422, 425
Boiler trimmings 426, 432
The care and management of a boiler 433, 437
Water for use in boilers 438,448
CHAPTER XVII.
USE AND ABUSE OF THE STEAM BOILER . . . . . 449, 453
Design of steam boilers . *54> 455
Forms of steam boilers . ' . . . • 456
Setting steam boilers 456> 457
Defects in the construction of steam boilers . 457,453
Improvements in steam boilers • *59> 4<
Strength of riveted seams 4(ilJ *(
Maximum pitches for riveted lap joints . . . . • *'
Iron plates and iron rivets, double riveted lap joints 467
XIV CONTENTS.
PAGE.
Zigzag riveting and chain riveting 468, 472
Single riveted lap joints, iron plates 469
Steel plates and steel rivets, S. R. L. J 470
Steel plates and steel rivets, D. R. L. J 471
Strength of stayed flat boiler surfaces » 473
Boiler stays 474, 477
Chart to find steam pipe for heating water 478
Chart to find boiler power to heat water 479-483
Data relating to ventilation 484
Sizes of mains and branches, — table of pipe 485
Pulsation in steam boilers 487, 488
Weight of square and round iron per lineal foot 488
Water columns for boilers 489
Steam gauges 489, 490
Safety valves 491,499
Table of the rise of safety valves 494
Safety valve rules 497
Table of heating surfaces in square feet 501
Centrifugal force . 501
CHAPTER XVIII.
THE WATER TUBE SECTIONAL BOILER 502
The down draft furnace 503, 522
View of boiler setting and furnace common in the East 513
Vertical tubular boilers 514, 521
Proper water column connections 515
Table of pressures allowable in boilers 516
Fire line in boiler settings 520
Proper location of gauge cocks 521
Number of bricks required for boiler setting . . . • 522
Specifications for a sixty-inch 6-inch flue boiler 524
Banking flres 531
Instructions for boiler attendants 532
Rules and problems anent steam boilers . 536
Steam jets for smoke prevention 542
CONTENTS. xv
CHAPTER XIX.
PAGE.
THE STEAM PUMP ^
The Worthmgton compound pump 544
View of steam valves properly set t 545
The Deane steam pump ( ^ 5^6
View of steam valves properly set ( . 547
The Cameron steam pump , ( 543
Explanation of steam end 543
View of steam valves properly set . 543
The Knowles steam pump ...... 550
Explanation of steam valves 550
View of steam valves properly set 552
The Hooker steam pump 553
Operation of the Hooker pump 553
View of steam valves properly set 555
The Blake steam pump 555
Operation of the Blake pump 556
View of steam valves properly set 558
Miscellaneous pump questions and answers 559 and 571
How to set the steam valves of a duplex pump 567
View of steam valves properly set 568
Proper pipe connections 569
View of pipe connections 570
Pumps refusing to lift water 577
Corrosion in water pipes 579
Pumping acids 579
Selecting boiler for a steam pump 580
The Worthington water meter - .581
Table of water pressure due to height 582
Table of decimal equivalents of IGths, 32nds and 64ths of an inch . 583
Capacity of tanks in U. S. gallons 584
Capacity of square cisterns in U. S. gallons . . 585
Weight of water 685
Cost of water 587
Loss by friction of water in pipes a
How water may be wasted **
Ignition points of various substances 68S
XVI CONTENTS.
CHAPTER XX.
PAGE.
THE INJECTOR AND INSPIRATOR 591
First appearance of the injector 592
Range of the inspirator and injector 592
General directions for piping injectors 594
Care and management of injectors 599,602
Directions for connecting and operating the Hancock inspirator . . 597
Water between 32° and 212° Fah 602
Steam pump problems 603
Water pipe problems 608
CHAPTER XXI.
MECHANICAL REFRIGERATION 619
How it is produced 619
Principles of operation 620
Operation of apparatus 620
Function of the pump and condenser 62 1
What does the work 621
Mechanical cold easily regulated 622
Utilizing the cold 622
Brine system 622
Direct expansion system 623
Rating of the machine in tons capacity 623
Difference in the ratings 623
Instructions for operating refrigerating machinery 624
Steam condensers 627
Air in the system « 628
Gases in the plant 628
A few tests for ammonia 631
Testing for water by evaporation 631
Lubrication of refrigerating machinery . 632
Effects of ammonia on pipes . 633
To charge the system with ammonia 634
Process of mechanical refrigeration 635
View of the " Eclipse " compressor 637
How heat is removed 636
Section of De La Vergne compressors 638, 639
Diagram of De La Vergne system 640
CONTENTS. xv jj
PAGE.
General arrangement of refrigerating plant . . „ • 641
De La Vergne ice-making plant . . . .642
Ice-making plant, showing distilling apparatus ...... 643
Electrically-driven ammonia compressor 645
Horizontal-vertical refrigerating machine „ 646
Location of high and low pressure gauges . , 647
CHAPTER XXII.
SOME PRACTICAL QUESTIONS USUALLY ASKED ENGI-
NEERS WHEN APPLYING FOR LICENSE . '.
Reasons why pumps do not work
Priming in boilers 648
Foaming in boilers 648
In case of low water in a boiler 649
Best economy in running an engine . 650
What is valve lead 653,666,668
What is meant by expansion of steam 654
Describe the Corliss valve gear 654
What is lap on a valve . . . . 654,666,670*
Taking up lost motion in an engine . 654
Direct and indirect valve motion 668-
To test a piston for leakage of steam . 669
CHAPTER XXIII.
INSTRUCTIONS FOR LINING UP EXTENSION TO LINE SHAFT 672
Simplicity in steam piping 674
Cutting pipe to order 675
Feed water required for small engines 676
Heating feed water 676
Bating boilers by feed water . * .... 676
Weights of feed wa^er and of steam 677
Feed water heaters 678
Table showing the units of heat required to convert one pound of
water at the temperature of 32° Fah., into steam at different pres-
sures 679
Table showing gain in use of feed water heaters, and percentage of
heat required to heat water for different feed and boiling tempera-
tures, as compared with a feed and boiling temperature of 212° . 680
XV1H CONTENTS.
-
PAGE.
Pure water 681
The temperature and pressure of saturated steam 684
Something for nothing • . 686
Melting point of metals 687
Chimneys 688 to 694
Weight of steel smoke stacks per linear foot 694
CHAPTER XXIV.
HORSE POWER OF GEARS 695
Table of H. P. of shafts 697
Prime movers 697
Wheel gearing 698
The pitch line of a gear wheel 698
To find the pitch of a wheel . 698
To find the chordal pitch 699 to 703
To find the diameter of a wheel 699 to 703
To find the number of teeth for a wheel 699 to 703
To find the proportional radius of a wheel or pinion 700
To find the diameter of a pinion 700
To find the circumference of a wheel 700
To find the number of revolutions of a wheel or pinion ^ . 700 to 701
Stress on gear teeth 705
A train of wheels and pinions 701
Table of diameters and pitches of wheels 704
Curves of teeth . 705
Construction of gearing 706
Bevel wheels 707
Worm-screw 708
Proportions of teeth of wheels 709
To find the depth of a cast-iron tooth 709
To find the horse-power of a tooth 710
Calculating the speed of gears 710
When time must be regarded 711
Table of weight of a square foot of sheet iron 712
Screw cutting 713
Transmission of power by manila rope 714, 812, 813
Decimal equivalents of one foot by inches 714
Table of transmission of power by wire ropes 715 and 8 14
CONTENTS. x-lx
CHAPTER XXV.
ELECTRIC ELEVATORS
The Otis elevator ...
........
Belt driven elevators . ' 'TIC
• • • • « « 1 lo« 7*5
Direct connected elevators .......... 717 730
The motor-starting switch ......... ' 71g
The elevator machine brake ....... ' 72n
The main hand rope ......... . . , ' 721
View of connections of gravity motor controller to elevator .' 722
View of connections of gravity motor controller with separate rope
attachment ............... ^ 72g
Direct connected electric elevators ........ t 730
Automatic stops ............. 9 733
View of circuit connections .......... , < 734
The starting resistance ...... ......... 735
The switch lever .................. 736
Cutting out the series field coils ..." .......... 737
The safety brake magnet ................ 739
The proper care of machines ............ 739; 779
How to start the car . ................ 743
The car switch ................... 748
The slack cable switch ................ 749
Electric control for private house elevators ......... 749
View of wiring for private houses ............. 750
The Sprague Electric Co.'s elevators ........... 756
View of operative circuits for Sprague screw elevator ..... 762
The pilot motor ....... ' ............ 763
Care of electric elevators ............... 765
Directions for the care and operation of electric elevators .... 765
CHAPTER XXVI.
ELECTRIC ELEVATORS 769
Drum type, limits for tall buildings 769
Motor and drum speeds 769
Diagram of Frazer duplex type 770
General arrangement and operation of duplex type 771
Duplex elevator motor , • 772
XX CONTENTS.
PAGE.
Running qualities of the duplex type elevator . 773
Objections to the duplex elevat >r 773
Wiring diagram of the Frazer duplex elevator 774
Controller for the duplex motor 775
Frazer limit switch 776
Detail view of Frazer controller 777
The traction type of elevator . . . . , , 778
Diagram of the traction type 779
Considerations concerning traction-type motors 780
Cable-drive elevator machine 781
Counter-balance used with cable-drive type , . 782
Compl te installation of cable-drive elevator , 783
Wiring diagram for traction elevator 784
Controlling device for electric elevator 785
Line wires for traction type 787
Operation of car and limit switches 787
CHAPTER XXVII.
THE DRIVING POWER OF BELTS 788
The average strain or tension at which belting should be run . . . 788
Rules and problems anent belting 788, 797
Notes on belts 790
Transmitting power of belts 795
Table of horse-power of belts 796,799
Directions for adjusting belting 798
Horse power of belting 799
CHAPTER XXVIII.
AIR COMPRESSORS, THERMOMETERS, THE METRIC SYS-
TEM, AND ROPE TRANSMISSION 800
Losses in air compressors 800
Capacity of air compressors 800
Contents of a cylinder in cubic feet for each foot in length .... 801
The McKierman air compressor 801
The Bennett automatic air compressor 803
The Ingersoll-Sergeant air compressor 803
The Pohle air lift system 807
CONTENTS. xx j
PAGE.
The metric system 80)
Thermometers t gu
Rope transmission 812
Horse-power transmitted by hemp ropes 813
To test the purity of hemp ropes 814
Wire rope data . 0 • 814
CHAPTER XXIX.
ALTERNATING CURRENT MACHINERY 815
The principles of alternating currents 815
Diagrams representing a generator of either continuous or alter-
nating currents 817
Diagrams showing the relations between alternating currents and
e.m.fs 821,824
One reason why alternating currents vary, etc 825
Diagrams showing the way in which sine curves are used, etc. . . 826
Polyphase currents 832
Unbalanced three-phase currents, etc 834
Inductive action in alternating current circuits, etc 834
The angle of lag between the current, etc 837
By the use of condensers, etc 8*°
The general principle of construction of a condenser, etc 841
Mutual induction 84:2
Transformers 8'
The action in a transformer 8
The object in using transformers 8
Alternating current generators 8
Diagram illustrating a simple alternating current generator ... 853
Alternator of the multipolar type 8
How alternating current generators are run ....••••• 8
If an alternator is of the multipolar type 854
A revolving field alternator 857
An inductor alternator
Alternating current generators
Alternators run in parallel
Starting alternators connected in parallel
The way in which synchronizing lamps are connected . .
Compensating and compounding alternators
XX11 CONTENTS.
PAGE.
Field magnetizing currents a .. 867
Alternating current motors . . 867
Two-phase revolving field synchronous motor « . 869
Power factor • 870
Induction and other types of motors 871
Principle of the induction motor • 872
Induction motors if very small 877
Three-phase induction motors 877
While induction motors are very satisfactory machines 878
Rotary transformers and rotary converters . . ....... 878
Principle of the rotary transformer 879
Alternating current distributions 882
Starting 886
Parallel running of alternators . 887
Types suitable for parallel operation . . . . • 887
Division of load 887
Compound alternators 887
Belted machines 888
Direct coupled machines 888
Starting 889
Shutting down 890
Care of machines 890
CHAPTER XXXo
TABLES —
Actual ratios of expansion 935
Ammonia gas per ton refrigeration „ . 898
Boiling points of various substances „ . . . . . 907
Capacity of duplex pumps 893
Capacity of low pressure pumps . 984
Capacity of reservoir in gallons 910
Coal burned per square foot of grate 908
Cost of coal per annum 909
Diameters, circumferences and areas of circles , . . 895
Horsepower for one pound m.e.p 924
Horsepower of slide-valve engines 922
CONTENTS. xxjj;
PAGE.
Horsepower per ton of refrigeration 904
Horsepower to compress one cu. ft. ammonia . .
Hyberbolic logarithms ' gg2
Iron and steel hoisting ropes ' 91g
Iron and steel transmission ropes 918
Mean absolute pressures 925
Mean pressure of diagram, ammonia compressor . . 902
Measurements of riveted seams 929-934
Melting points of fusible plugs . t 907
Melting points of various substances t 997
Piston speed in feet per minute . 912
Power gained by adding condenser 923
Properties of ammonia 597
Properties of brine solution 900
Properties of carbonic acid 900
Properties of saturated steam 330, 913
Properties of sulphur dioxide 898
Reaumur, Fah. and Celsius thermometers 903
Ropes for inclined planes 920
Speed and capacity of centrifugal pumps 927
Sizes and dimensions of Corliss engines 926
Sizes of cylinders for compound pumps 923, 927
Specifications for riveted seams 928
Transmission of power by ropes 921
Weight and strength of iron bolts 906
Weight of rivets and bolts 905
Horizontal return tubular boilers 937, 938-939
Table of wages e . 924
Air for Rock drills 934
Areas of segments of circles . . . o . 935
Staying boiler heads 938
Table of Steam Pressure per square inch allowable on lap
welded flues made in sections ' • • 952, 953
Steam Pressure allowable on lap-welded flues 952, 953
CHAPTER XXXI,
HYDRAULIC ELEVATORS 964
Types of elevator machines 954
Horizontal pushing type 955, 957
Actuating lever in the car a a - • - • •• .956
XXIV CONTENTS.
PAGE.
Elevation of horizontal machine 958
Plan of elevator cylinder and sheaves 960
Pilot and main valves 961
Morse and Williams horizontal pushing type 962
Horizontal elevators, pulling type 963
Whittier pulling type 964
Valve of Whittier machine 965
Automatic stop for Whittier machine 967
Otis vertical elevator 968
Otis vertical elevator system 969
The Otis valve 970
Valve construction 971
Otis machine with pilot valve control 972
Method of operating Otis pilot valve 973
Main valve with pilot valve control 974
Details of Otis pilot valves 975
Otis differential and pilot valve 977
Main valve with magnet-operated pilot . » 978
Pipe connections for magnet-operated pilot 979
Otis main valve with magnet control 981
Pipe connections for Otis main valve 982
Private house elevator, push-button control 984
Floor controller for push-button system 985
Wiring diagram for push-button system 987
Double power hydraulic elevators 987
High pressure hydraulic elevators 988
Otis double pressure type 989
High pressure horizontal machine , 991
Hydraulic elevator system with inverted plunger 993
Valves used with inverted plunger type . • . . . 995
Automatic stop valve for plunger type 996
Speed controller for plunger type . . s , ,...*>.. 998
Plunger elevators ».-... 998
Accumulators used with plunger type .....»•••*. 999
Valve for accumulator 1000
Plunger elevator, complete installation s . 1002
Plunger Elevator Co'.s machine 1004
Details of plunger elevators 1006
CONTENTS. xxy
PAGB.
Pilot and automatic stopping valves 1007
Valve for elevator control
Elevator for pilot valve control .............
How to pack vertical cylinder machine . t 10i2
Plunger elevator with hand rope control 1013
Valve for hand rope control .1014
Packing vertical cylinder piston from top 1015
Packing vertical cylinder valves .1016
Packing piston rods 1016
Water for use in hydraulic elevators 1017, 1022
Causes for car settling . . 1019
Elevator enclosures and their care 1019
Standard hoisting rope , 1021
Cables and how to care for them 1021
Leather cup packings for valves 1022
Closing down elevators , 1022
Lubrication for hydraulic elevators • 1023
Useful information 1023
Decimal equivalents of an inch 1021
Water , 1024
Elevator safeties 1025
Otis wedge safety 1026
Safety governor, single acting 1028
Otis roller safety 1029
Governor rope for roller safety 1030
Lifting rope for roller safety 1031
Brake safety for iron guides « 1032
Governor rope for brake safety
Morse and Williams, brake safety 1°35
Pratt brake safety 1036
Otis double acting safety governor . . li
Pipes and Tanks. Contents in cubic feet; in U. S. gallons . . .1039
Friction and lubrication 1(
Uses of friction 1(
Coefficient of friction 1(
Illustrating laws of friction 1(
1044
Laws of friction
Theory of lubrication *'
Petroleum oils -
XXVI CONTENTS.
PAGE
The conditions which produce the greatest difference in
ordinary lubrication 104
The best lubricant 104
Cylinder and valve lubrication 104!
Wet steam 105'
Lubrication of refrigerating machinery 105
Different makes of refrigerating machines 1054
HANDBOOK ON ENGINEERING.
CHAPTER I.
THE ELEMENTARY PRINCIPLES OF ELECTRICAL
MACHINERY.
The operation of electric generators, or dynamos, as they are
ordinarily called, and also that of electric motors, depends upon
a simple relation between electricity and magnetism, which will
be explained in a simple manner in the following paragraphs.
s
[JT
Fig. 4.
Fig. 1. Fig. 2. Fig. 3.
Forms of magnets.
A permanent magnet, as is well known, is a bar of steel which
possesses the power of attracting pieces of iron. These bars may
be made straight, as in Fig. 1, or in the form of a U, as in Fig.
2, or in any other shape desired. The strength of a permanent
magnet depends upon the kind of steel of which it is made, and
1
2 HANDBOOK ON ENGINEERING.
also upon the temper it is given. Generally speaking, the harder
the steel the stronger the magnet. A bar of soft steel, or wrought
iron, cannot be made into a permanent magnet of any noticeable
strength, but if such a bar is covered with a coil of wire, as shown
in Figs. 3 and 4, and a current of electricity is passed through
the wire, the bar will be converted into a very strong magnet so
long as the current flows. As soon as the electric current stops
flowing through the wire, the magnetism of the bar will die out.
Magnets of the last-named type are called electro-magnets, as
they do not possess magnet properties except when the electric
current flows around them. Electro-magnets, when energized by
sufficiently strong electric currents, can be far more powerful than
the permanent magnets, and on that account they are used in
electric generators and motors. In addition to being a stronger
magnet, the electro-magnet has the advantage that it can be
magnetized and demagnetized almost instantly, by simply cutting
off the exciting electric current, and on this account they can be
used for parts of electrical machines and apparatus, for which the
permanent magnet would be entirely unsuited.
If we test the attractive power of a magnet, we will find that
it is greatest at the ends, the force at the middle point being
scarcely noticeable. A bar such as Fig. 1 or Fig. 3 might hold a
piece of iron weighing several pounds , if presented to either end ,
while at the middle point, it might not be able to sustain more
than an ounce or two. Owing to this fact, the ends are called
the poles of the magnet.
When a magnet is suspended from its center, like a scale beam,
and allowed to swing freely, it will be found that it will come to
rest in a north and south position, and no matter how violently it
may be moved around, it will always come to a state of rest
with the same end pointing towards the north. On this ac-
count, the ends are called north and south poles, the north pole
being the end that points toward the north.
HANDBOOK ON ENGINEERING. 3
If two bar magnets are suspended side by side with the
north end of one at the top and the north end of the other
at the bottom, as illustrated in Fig. 5, they will attract each
other; but if both magnets have the north end at the top, they
will push away, as shown in Fig. 6. It is evident that there is
a good reason for this difference in action, and this reason we
can obtain by experiment.
a
a
Figs. 5 and 6. Showing effect of changing the poles.
A magnet needle, such as is used in the mariner's compass, is
simply a small magnet. If we place a magnet bar, as shown in
Fig. 7, and then set near to it, in different positions, a compass
containing a very small needle, we will find that in these several
positions the direction of the needle will be about as is indicated
by the small arrows marked b on the curved lines a a; the arrow
pointing towards the north end, or pole of the needle. The
reason why the needle will take up these positions is that the north
end of the bar attracts the south end of the needle, and pushes
away the north end, just as in Figs. 5 and 6, and the south end
of the bar acts in the same way ; so that there is a tug of war
going on, so to speak, between the attractions and repulsions of
4 HANDBOOK ON ENGINEERING.
the two ends of the bar upon the two ends of the needle, the
result being that the position assumed by the needle is the re-
sultant of these several forces. When the needle is near the
\
V
Of
y
^pp^''
. Figs. 7 and 8. Illustrating lines of force.
north pole of the bar, its south end is attracted with the greatest
force, and when near the south end of the bar, the north end ex-
periences the greatest attraction.
If we were to place the exploring needle in all possible posi-
tions near the magnet and trace lines parallel with it, in these
positions, we would obtain a large number of curves about the
shape of those shown in Fig'. 8. As these curves represent the
direction into which the magnet needle is turned at the various
points in the vicinity of the magnet, they represent the direction
in which the combined forces of the two poles act at these two
points, hence, these lines are called magnetic lines of force.
HANDBOOK ON ENGINEERING.
When two magnets are suspended as in Fig. 5, the lines of
force of both will be in the same direction as is indicated in Fig.
9 by the arrow heads on the curves a a. That this is true can be
seen from Fig. 7, in which it will be seen that the arrow heads
point toward the south pole and away from the north pole.
As the north pole of a magnet has an attraction for the south
pole, we can readily see that there is an endwise pull in the
lines of force, which tends to make them contract, like rubber
bands, hence, we can imagine the lines a a in Fig. 9 to contract
and thus draw the two magnet bars together.
The repulsion of the two magnets, when the north poles are at
the same end, is illustrated in Fig. 10. Here we see that the lines
of force passing on the outside of the bars, as indicated by
lines a a, are unobstructed, and can assume their natural posi-
a
s
JV
Figs. 9 and 10. Lines of force in two bar magnets.
tion, but those that pass between the bars, along line c, are
pressed out of position. If we assume that the lines of
make an effort to retain their position, like so many wir<
6 HANDBOOK ON ENGINEERING.
springs, then we can see that the repulsion is due to the effort that
the lines make to assume their natural form in the space between
the bars.
Magnetic lines of force have no real existence, they simply in-
dicate the direction in which the force acts, but if we keep this
fact in mind, it helps us to understand magnetic actions, if we
treat the lines of force as if they were something real. This fact
will become more evident as we proceed.
Lines of force always pass from the north to the south pole
through the space between these poles, and through the magnet
itself, they are assumed to pass from the south to the north pole.
The form of the lines of force depends upon the relative position
of the north and south poles. In Fig. 9 they are curved, as
a
<s
JV
55==
S JV
Fig. 11. Lilies of force between ends of magnets.
the magnets are placed side by side, but if the bars were arranged
end to end, as in Fig. 11, the lines of force would be straight, as
is shown at a. From the north end of the right side magnet, the
lines of force would pass in curved line, as in Fig. 10, to the south
pole of the magnet on the left side, thus completing the magnetic
chain, or circuit, as it is called.
If we take the two magnet bars of Fig. 1 1 and stand them on
end, as in Fig. 12, and suspend a bent wire C in the manner
shown, effects can be produced that are interesting and instruct-
ive, as they illustrate the principle upon which generators and
motors act. The wire C should be journaled at D D, so as to
swing with as little friction as possible, and its ends are to be con-
nected with a battery J5, by means of fine wires a and b ; a switch
being provided at c so as to stop the flow of current when desired.
HANDBOOK ON ENGINEERING. 7
If the switch c is opened, so that no current flows through C, the
latter will not be disturbed, and if we give it a swing, it will oscil-
late back and forth, like a clock pendulum, and in a few seconds
come to rest in the position in which it is shown. If the switch
is closed, C will at once swing out of the stream of magnetic lines
of force and will remain in that position as long as the current
from the battery passes through it. The direction in which C
Fig. 12. Showing the principle of the electric generator
will swing will depend upon the direction of the current through
it. If with the wires a and b connected with the battery, in the
manner shown, the wire C swings to the right side, then if a is
connected with e, and b with d, the direction of swing will
reversed ; that is, C will swing toward the left.
From this experiment we see that the magnetic lines of
can develop a repulsive force against an electric current, ai
the direction of the repulsion depends upon the direct*
8
HANDBOOK ON ENGINEERING.
electric current with respect to the direction of the lines of force.
We shall now explain why this repulsion is developed, and this
we can illustrate by the following experiments: —
If we arrange three wires as shown in Figs. 13, 14 and 15, so
as to run north and south, the upper end being north, and place
over these magnet needles D D D, pivoted at e e e, we will find
that if there is no current flowing through the wire, the needle
will point toward the north, or be parallel with the wire, as is
Fig. 13. Fig. 14. Fig. 15.
Showing effect of current on the needle.
shown in Fig. 14. If the current flows through the wire from
south to north, the north end of the needle will swing to the right,
as in Fig. 15, and if the current flows through the wire from north
to south, the north end of the needle will swing toward the left,
as in Fig. 13. From this we see that an electric current can
repel a magnet, and that the direction in which it repels it depends
upon the direction of the current.
If we stand the three wires on end, as shown in Figs. 16, 17
and 18, in which A B C represent the wires as seen from above,
we will find out more about the relation between electric currents
HANDBOOK ON ENGINEERING. 9
and magnets. If we place four small magnet needles around each
one of the wires, as shown at a a a a, we will find that those
around the center wire, through which no current flows, will all
a
Fig. 16. Fig. 17. Fig. 18.
Wires surrounded by magnetic lines of force.
point toward the north, as shown, while those around the wire
Fig. 16, through which a current flows upward, that is, away from
the center of the earth, will point in a direction opposite to that
in which the hands of a clock move; and in wire Fig. 18, in
which the electric current flows down toward the center of the
earth, the north ends of all the needles will point in the direction
in which the hands of a clock move, that is, just opposite to those
in Fig. 16.
Figs. 19 and 20. Directions of lines of force.
From these actions, we infer at once that when an electrio
current flows through a wire, the latter becomes surrounded
with magnetic lines of force, as is illustrated in Figs. 19 and 20,
10 HANDBOOK ON ENGINEERING.
and that there is a fixed relation between the direction of the
current and that of the lines of force. At A, Fig. 19, the direc-
tion of the lines of force is shown for a current moving up-
ward, and at J5, Fig. 20, the direction of the lines of force is
that due to a current moving downward through the wire.
Inasmuch as an electric current flowing through a wire is
surrounded by magnetic lines of force, we can say that a com-
plete electric current consists of two parts, one the current proper,
which traverses the wire, and the other the magnetic casing which
envelops the wire. It is the action between the latter part of the
current and the lines of force of magnets that develops the
current in a generator, or the power in a motor.
With the aid of Figs. 21 and 22, we can now show how the
force is developed that thrusts the wire to one side in Fig. 12.
The lines of force of the magnet, which constitute what is called
the magnetic field, will flow from the north pole at the top to the
south pole at the bottom, as is shown in Figs. 21 and 22. If the
electric current flows through the wire C from the back toward
the front, the lines of force developed around it will have the
direction shown in Fig. 21. As lines of force cannot flow in op-
posite directions in the same space, the lines of the field will swing
over to the left side of the wire, but in doing so they will be
stretched out of the straight form, and they will also push the
lines surrounding the wire out of their central position. Under
these conditions, which are illustrated in Fig. 21, the effort made
by the field lines to straighten out, together with the effort made
by the wire lines to return to the central position, will develop a
thrust between the wire and the field, and thus force the former
out toward the right side.
If the direction of the current through the wire is reversed so
as to flow from front to back, the direction of the lines of force
around the wire will be reversed, and will be as in Fig. 22. Under
these conditions, the lines of force of the magnetic field will
HANDBOOK ON ENGINEERING. jj
swing over to the right side of the wire, and thus the thrurt will
be in the opposite direction.
Fig. \2 represents the principle of an electric motor in ite sim
plest form, and from it we see that the force that causes the
armature to rotate is developed by the repulsion between the mag-
netism of the field magnet and the magnetism that surrounds the
wires wound upon the armature.
V
Figs. 21 and 22. Showing effect of magnetic Aeld.
It is self-evident that if we undertake to force the wire C
through the magnetic field in the opposite direction to that in
which it swings, we will have to make an effort to do so ; that is,
if we try to move the wire from right to left in Fig. 21, or from
left to right in Fig. 22, we will have to apply power. Now nature
is a strict accountant and does not allow any power to be lost ;
therefore, all the energy we expend in moving the wire through
the magnetic field must appear in some other form, and the form
in which it appears is as an electric current that is generated in
12 HANDBOOK ON ENGINEERING.
the wire. If we were to remove the battery in Fig. 12 and put
in its place an instrument to indicate the presence of a current in
the wire, we would find that ,>hen we move the latter in the
opposite direction to that in which it moves under the influence of
the current, we generate a current; that is, we convert the device
into a simple electric generator. If in Fig. 21, we move the wire
from right to left, the direction of the current generated in the
wire will be the same as that of the current which causes the wire
to swing in the opposite direction, that is, from back toward the
front. As it is a poor rule that does not work both ways, we
would naturally infer that if moving the wire from right to left
develops a current from back to front, movement in the opposite
direction would develop a current from front to back ; and such
is actually the case. This fact can be demonstrated by Fig. 12.
Suppose that in this figure we hold C stationary in the central
position, and then pass a current through from back toward the
front ; this current would exert a force to swing C to the right
side. If we release the wire, it will swing to the right and as
soon as it begins to move, the current will become weaker, show-
ing that the movement of the wire developed therein a current in
the opposite direction. If we force the wire over to the left side,
the current flowing through it will begin to increase as soon as
the wire moves.
All the foregoing shows us that when a wire is moved through
a magnetic field, a current will be generated in it if it forms part
of a closed circuit, and it makes no difference whether there is a
current already flowing in the wire or not. When the wire is
caused to move through the magnetic field by a current flowing
through it from an external source, the current developed in it will
be in opposition to that which comes from the external source,
and, as a consequence, the movement produces an actual reduc-
tion of the strength of current flowing through the wire. The
stronger the magnetic field and the greater the velocity of the
HANDBOOK ON ENGINEERING. 13
wire, the stronger the current generated in opposition to the driv-
ing current, and, therefore, the weaker the latter. It is on this
account that if a motor is allowed to run free, the faster it runs
the weaker the current through it becomes, as the actual current
in every case can only be the difference between the main driving
current and the one developed in the wire, which latter runs in
the opposite direction.
Magnetic force is measured in units that are based upon the
centimeter gram second system which is too technical to be ex-
plained in a few words. Briefly stated a unit of magnetic force
will exert a pull of unit mechanical force at a unit distance.
The force of magnets is measured either by the total force of
the magnet, or by the force exerted by each unit of cross-section.
When the measurement is based upon the total force of the mag-
net, the unit is called a Maxwell ; thus we speak of the total flux
of a magnet as so many maxwells. When the , measurement is
referred to the force per unit of cross-section, it is spoken of as
the magnetic density, or density of magnetization, and the unit
used is called a Gauss ; thus we speak of a magnet as having a
density of so many gausses per square centimeter, or square
inch of cross-section. The density of magnetization is deter-
mined by a rule given on page 46.
The lifting capacity of a magnet can be determined by the
following rule : —
TO FIND THE LIFTING CAPACITY OF A MAGNET IN POUNDS.
Multiply the area of cross-section of the magnet pole in square
inches, by the square of the density of magnetization per square
inch, and divide this product by 72 millions.
This rule gives the pull for one pole. For horse shoe magnets
double the figures. If the object lifted is not in contact with
the poles the pull will be less than rule gives.
14 HANDBOOK ON ENGINEERING
CHAPTER II.
THE PRINCIPLES OF ELECTROMAGNETIC INDUCTION.
By electromagnetic induction, is meant the induction of electric
currents by magnetic action. In the preceding chapter it has been
shown that if we move a wire through a magnetic field, an electric
current will be generated in it, providing its ends are joined, so
as to form a closed circuit. If the ends are not joined, then there
will be no current developed, because, an electric current cannot
flow except in a closed circuit. When the ends of the wire are
not joined, the movement through the field develops simply an
electromotive force. Electromotive force is that force which
causes an electric current to flow when there is a circuit in which
it can flow. Electromotive force is a long-winded name and on
that account it is always abbreviated into e.m.f., so that here-
after when these letters are used, it will be understood that they
stand for electromotive force.
Metals and all other substances that allow electric currents
to flow through them are called conductors, while glass, mica,
wood, paper and many other similar forms of matter that do not
allow currents to flow through them are called insulators. The
difference between conductors and insulators is only one of
degree, for there is no known substance that is an absolute non^
conductor of electricity ; that is, a perfect insulator ; and there is
no substance that does not resist to some extent the passage of a
current — that is, there is no such thing as a perfect conductor.
Some substances, like damp paper or wood, which stand midway
between good conductors and good insulators, can be regarded as
Cither one or the other, depending upon the service for which they
are used. For currents of very low e.m.f., they would be in-
HANDBOOK ON ENGINEERING. 15
sulators, but for currents of very high e.m.f., they would be
conductors.
The current that will flow through any circuit when impelled
by an e.m.f., will have a strength that will depend upon the
amount of resistance that opposes its flow. As all conducting
materials are not of the same degree of conductivity, their relative
values are determined by the amount of resistance they interpose
to the flow of the current. The resistance of a conductor is
measured in units called ohms; the strength of current is
measured in units called amperes, and the e.m.f. is measured in
units called volts. The relation between these units is such that
an e.m.f . of one volt will cause a current of one ampere to flow
in a circuit having a resistance of one ohm.
When a wire is moved through a magnetic field, the e.m.f.
induced in it will be determined by the strength of the field and
the velocity with which the wire moves, and will not be affected
in any way by the resistance of the circuit of which the wire
forms a part. If the resistance is very great, the strength of
current generated will be very low, and if the resistance is very
low the current will be strong, but in either case the e.m.f. will
be the same.
If movement of the wire in one direction develops an e.m.f.
in a given direction through the circuit, then movement of the
wire in opposite direction will reverse the direction of the e.m.f.
Thus, in Fig. 23, which represents a magnetic field between
the poles N $, if wire a is moved 'from right to left, it will have
induced in it an e.m.f. that will be from back to front, and if
the direction of motion of the wire is reversed, the e.m.f. will
also be reversed. This will be true whether the wire is near the
N pole or S pole. This being the case, it can be seen that if
a represents the end of a wire moving in the direction of arrow
d, and b the end of a wire moving in the opposite direction, the
e.m.f. 'sin these two wires will be in opposite directions. The
16
HANDBOOK ON ENGINEERING.
direction of the e.m.f . in a will be up from the paper toward
the observer, and the direction of the e.m.f. in b will be down
through the paper. If these two wires are secured to a shaft
placed in the center of the field, then by the continuous rotation
Figs. 23 and 24. Illustrating the principle of the armature.
of the shaft, the two wires can be made to revolve around the
circular path shown.
If these two wires are joined at the ends, as shown in Fig. 24,
they will form a closed loop, and although the direction of the
induced e.m.f. in the two sides will be opposite, when compared
to a fixed point in space, they will be in the same direction so
far as the loop is concerned ; that is, both e.m.f.'s will develop
currents that will flow through the wire in the same direction.
Returning to Fig- 23 it will be noticed that if the wires re-
volve around the circular path at a uniform velocity, their move-
ment in the direction of line c c will not be uniform, but will be
the greatest when the wires are in the position shown, and least,
when they cross the line c c. In fact, when the wires cross line
c c their motion in the direction of this line will be zero, for this
HANDBOOK ON ENGINEERING. 17
is the point where the direction of movement reverses No*
the magnitude of the e.m.f. induced in the wire is proportional'
to the veloorty in the direction of the line c c, hence, when the
wires are crossing this line, the e.m.f. will be zero, and when
they are one-quarter of a turn ahead of the line, the e.ra.f will
be the highest.
In Fig. 24 we see that in side «, the direction of the current
is toward the front, and in 6 it is the reverse; now, when «
moves through half a turn, it will take the place of b, and the
direction of the e.m.f. induced in it will be the same as in b in
the figure ; that is, it will be the reverse of what it is when pass-
ing in front of the pole N. This being the case, it is evident
that each time the loop makes a half-revolution, the direction of
the current generated in it reverses.
Fig. 25. Arrangement of the collector rings.
As the loop in Fig. 24 is closed, the current generated in it
would be of no practical value, but if we cut the wire at one
side and connect the ends with rings as shown at a and b in Fig.
25, then by means of collecting brushes c c we can take the cur-
18
HANDBOOK ON ENGINEERING.
rent off through the wires d d. This current, however, would
consist of a series of impulses that would flow in opposite direc-
tions, each one starting from nothing and increasing to its greatest
Fig. 26. Construction of simple commutator.
strength when the loop reaches the position shown in the figure,
and then declining and reaching the zero value when the loop
reaches the vertical position. Such a current is called an alter-
nating current, because it flows first in one direction and then in
the opposite direction. All forms of machines that generate cur-
rents by electromagnetic induction, develop alternating currents,
but in the class of machines known as direct or continuous current,
a rectifying device is used which rectifies the current before it
reaches the external circuit. This rectifying device is called a
commutator, and is illustrated in its simplest form in Fig 26. In
this illustration it will be noticed that the ends of the wire, instead
of being attached to two independent rings, placed side by side,
are secured to two half-rings, placed opposite each other. The
brushes c d, through which the current is taken off, are held
stationary ; therefore, as can be readily seen, c will make contact
HANDBOOK ON ENGINEERING. 19
with a during one-half of the revolution, and with b during the
other half ; and this will also be the case with brush d. Now, as
the half-rings with which the brushes are in contact change at
each half revolution, it follows that by properly setting the
brushes, they can be made to pass from one-half ring to the other
at the very instant when the direction of the current in the loop
reverses, so that through each brush there will be a succession of
current impulses, but all in the same direction.
The device shown in Fig. 25 is a perfect alternating current
generator, and that shown in Fig. 26 is a perfect direct current
generator. In both cases, however, the e.m.f. induced is so
low as to be of no practical value. To obtain serviceable
machines, capable of developing the e.m.f. and current strength
required in practice, it is necessary to provide very strong mag-
netic fields and to rotate in these a large number of loops of wire.
In order that the operation of such machines may be understood,
we will first show how the powerful magnetic fields are obtained.
In Fig. 27 two wires are shown as seen from the end, these
being marked A and B. The lines of force surrounding them are
m '
*^^4t fa J \ v \^ — 'o-**^~~^' /<
i_ '^'^4-J ' ^ \ \ ^ — "^ ^*~-**"^s /
:^—'*1' i \\ v I X^ /
Figs. 27 and 28. Effects of direction of current in wires.
in directions that correspond to opposite directions of current in
the wires. In wire A, the current flows away from the observer.
As can be seen, the lines of force of both wires have to crowd into
20 HANDBOOK ON ENGINEERING.
the space between the wires, for on the outside of A the two sets
of lines would meet each other head on, and this would also be
the case on the right side of wire JB. This crowding of the lines,
of force into the space between the wires causes them to distort
from their natural position and instead of being central with the
wires, are eccentric to them. If we take a long wire through
which a current is flowing and bend it into a loop, we will see
that if the current flows out through one side, it will return
through the other side, so that in the two sides of the loop the
current will flow in opposite directions. This being the case,
Fig. 27 can be regarded as showing the two sides of such a loop,
and from it we find that the effect of such a loop is to concentrate
within its interior nearly all the lines of force that surround the
wire.
In Fig* 28 the two wires A and B are surrounded with lines
of force that correspond to the same direction of current. In
this case it will be noticed that in the space between the wires the
lines of force flow in opposite directions ; hence, only a few of the
lines will follow this path, simply that number surrounding each
wire that can traverse the space without encroaching upon the
path of the lines belonging to the other wire. If the two wires
are very near to each other i practically all the lines of force of
both wires will join forces, so to speak, and pass around the two
wires. Now, if we wind a wire into a coil of many turns, the
direction of the current in the several turns will be the same, so
that the lines of force of all the turns will combine into one large
stream and circulate around the entire coil side, no matter how
many turns of wire it may contain. From this it can be seen
that if we have a current of , say, ten amperes, we can make it
produce just as powerful magnetic effect as a current of one
thousand amperes, by simply increasing the number of turns of
wire in the coil. A current of ten amperes passing through a coil
of wire containing one hundred turns, will have the same magnet-
HANDBOOK ON ENGINEERING. 21
ism in effect, as a current of one hundred amperes passing through
a coil of ten turns, or as a current of one thousand amperes pass-
ing through a coil of a single turn.
If we place at the side of a wire through which an electric
current is flowing a piece of iron, as is shown in Fig. 29, the
effect will be that the lines of force will no longer flow in circular
paths, as indicated by the circle a, but will be deflected in the
manner illustrated, by the presence of the iron. If, instead of
Figs. 29 and 30. Lines of force through wires and magnets.
the straight iron bar, we substitute a ring of iron, as in Fig. 30,
nearly all the lines of force will be concentrated in the metal, and
the magnetic field in the space (7, between the ends of the ring,
will be vastly greater than at any other point. The explanation
of these actions is that all forms of matter oppose .the develop-
ment of magnetic force, but some offer greater resistance than
others. Iron, steel, nickel, and one or two other metals, offer
less resistance to the magnetic lines of force than air, and are
said to have a higher magnetic permeability. Nickel is only a
slight improvement on air, but steel and iron are far superior,
iron being of about two to three times the permeability of hard-
22
HANDBOOK ON ENGINEERING.
ened steel, and about one thousand times the permeability of air,
when magnetized to the density ordinarily used in practice. The
iron in Figs. 29 and 30, therefore, becomes the path of the lines
of force, because it interposes a much lower resistance. Owing
to this difference in the resistance of iron and air, it is possible
to make an iron magnet core of any desired form, and to con-
centrate within it nearly all the lines of force developed by the
current flowing through the wire wound upon it. The presence
of the iron not only serves to concentrate the magnetism in it,
but as it reduces the resistance opposing the development of
the magnetism, it enables the field to be made vastly stronger
than it could be with air alone, say a thousand times as great.
If we make & magnet in the form of Fig. 31, with a coil of
wire around the part jB, practically all the lines of force will flow to
Fig. 31. Principle of construction of bipolar machine.
the poles N $, and will pass through the air space between them.
If this air space is nearly filled with a cylindrical mass of iron, A,
the strength of the magnet will be increased, for, by doing this,
HANDBOOK ON KNU1NKKR1NU. 23
we replace air which is a poor magnetic conductor, by iron wliieh
is a far superior conductor. Electric motors and generators are
made with a cylindrical mass of iron at A, which is the armature
Fig. 32. Solid core.
Ring core.
core, and the air space between it and the faces of the poles of the
field magnet is made just sufficient to accommodate the wire
coils, and by this means the field strength is increased as much as
possible.
The armature cores are sometimes made solid, as in Fig. 32,
and sometimes as a ring, as in Fig. 33. When they are solid,
the lines of force cross through them in straight lines, see Fig.
32 ; and when they are ring form, the lines follow the ring and do
not penetrate the interior space.
If the single loop of Fig. 24 is replaced by a coil containing
many turns of wire, the e.m.f. induced in it will be increased in
proportion with the number of turns of wire in the coil, so that by
using such a coil in a field such as shown in Fig. 31, a high
e.m.f. can be obtained. This e.m.f., however, would be alter-
nating, and if the current were rectified by means of a commu-
24 HANDBOOK ON ENGINEERING.
tator, it would not be of uniform strength, but would fluctuate
from a maximum value to zero. Just how the current would
fluctuate and how the construction can be changed so as to get rid
of the fluctuation, we can explain by presenting a diagram that
illustrates the alternating current as it flows in the armature coil,
and the rectified current as it leaves the commutator.
In Fig* 34> let the distance / /*,, h i, i w, along the line//
represent half -revolutions of the coil, and let distances measured
on the vertical line c d represent the strength of current, distances
above/ being current flowing in one direction, and distances below
/being for current flowing in the opposite direction. Let us con-
sider the instant when the coil is passing the point where the
e.m.f. induced is zero ; then this instant will be represented
by the point /, at the left of the diagram, and the curve a
will start from this point ; as at that instant, the current which it
represents has no value. As the coil rotates, the current begins
to grow, and this fact we indicate by causing curve a to gradually
Figs. 34 and 35. Illustrating flow of alternating current.
rise above the horizontal line. At the quarter turn, the current
reaches its greatest strength, thus this forms the highest point of
curve a, and is midway between / and h. From this point
HANDBOOK ON ENGINEERING. 25
onward, the current declines and becomes zero, when the rotation
of the coil has reached one-half of a revolution, which is repre-
sented by the point h. In the next half -revolution, the current
Fig. 86. Two coils on armature. Fig. 37. Four coils on armature.
flows in the reverse direction, but has the same maximum strength
and increases and decreases at the same rate; therefore, the curve
6, drawn below the horizontal line, represents the reverse current ;
and point i corresponds to one complete revolution, so that
beyond i the curves a and b are repeated in systematic order.
Now, if we provide a commutator to rectify this current, all
we can accomplish is to turn curve b upside down and transfer it
to the upper side of the horizontal line, as in Fig. 35 ; but, as
will be seen, all we accomplish by this act is to obtain a current
that flows always in the same direction, but at each half-revo-
lution it drops down to a zero value.
If we wind two coils upon the armature, placing them at right
angles with each other, as is indicated by A and B in Fig. 36,
then if the currents of these two coils are rectified, they will bear
the relation toward each other shown at the upper line in Fig. 38,
the a a curves in solid lines representing the current from the A
coil, and the b b curves in broken lines, representing the current
from the B coil. As will be seen, when one of these currents is
zero, the other is at its greatest value, so that if we run both into
26
HANDBOOK ON ENGINEERING.
the same circuit, the lowest value of the combined current would
be equal to the maximum of either one of the single currents,
and the maximum value would be equal to the sum of the two
currents when the coils are on the eighths of the revolution.
Fig. 38. Showing effect of larger number of coils.
This resulting current is shown on the lower line in Fig. 38 by
the curve d d. From this curve we see that the number of
fluctuations in the current has been doubled, but the variation in
the strength is greatly reduced. If we wound four coils upon
the armature, as indicated by A B C Z>, in Fig. 37, the number
of undulations in the combined current would be again doubled,
but the fluctuation would be very much less. If the number of
coils is increased to twenty-five or thirty, the fluctuations in the
current become so small as to be hardly worth noticing.
With coils such as shown in Fig. 26, a separate commutator
would have to be provided for each coil, and this would render
the machine very complicated, if the number of coils were even
six or eight ; hence, in actual machines, the winding of the coils
is modified so as to be able to use a single commutator for any
number of coils. This construction will be explained in the
next chapter.
HANDBOOK ON KNOINKKRING.
27
CHAPTER III.
TWO POLE GENERATORS AND MOTORS.
The simplest type of armature winding is that used with ring
cores, and is illustrated in Fig. 39. As will be seen, it is simply
a continuous winding all the way around the circle, the end of
the last turn of wire being connected with the beginning of the
first turn, so as to form an endless coil. If wires are attached at
a and &, and a current is passed through, it will divide into two
halves, one part flowing through the wire above a 6, and the other
part through the wire below a b. In the upper half of the wire,
the direction of the current in the front sides of the turns will be
toward the center of the ring, as is indicated by the arrow heads,
and in the lower half it will be away from the center. If, in-
Figs. 39 and 40. Windings on ring armatures.
stead of attaching wires at a and b we place stationary springs, so
as to press against the wire, then we could revolve the ring, and
still the current would enter and leave the wire at the same points.
Small armatures are often made in this way, but for regular
28 HANDBOOK ON ENGINEERING.
.
machines it is more desirable to provide a commutator as shown
in Fig. 40 at (7, and then the several segments can be connected
with the wire at regular intervals. In the figure, the commutator
is provided with twelve segments, and these connect with the
armature wire at every fourth turn, so that the wire is divided
into twelve coils of four turns each.
The only difference between this diagram and a regular gen-
erator armature of the ring type, is that it shows the wire coils
spread out with a considerable space between them, and only in
one layer, while in the actual machine, the wire is wound close
together and generally, in several layers; but no matter how many
layers there may be, or how many turns in a coil, the principle of
winding is the same.
We have shown the ring winding first, because it is so simple
that it can be understood with the most superficial explanation.
The drum winding, which is used to a much greater extent, is the
same in principle as the ring, but owing to the fact that the coils
cross each other at the ends, it appears to be decidedly different.
By the aid of Figs. 41 to 44, the drum winding can be made per-
fectly clear.
Fig, 4J shows a ring armature core with a single coil wound
upon it ; and Fig. 42 shows a drum core, with a single coil wound
upon it. In the ring, only one side of the coil appears upon the
outer surface of the armature, but in the drum, as there is no
open space for the coil to thread through, both sides of the coil
must be placed upon the outer surface. The side B of the coil
may be called the live side, as it is the one from which the ends
project, and the lower side c, may be called the dead side. Since
only the live side of the coil has ends to be connected, it can be
readily seen that if in the drum winding we leave spaces between
the live sides for the dead sides, and then connect the ends of the
live sides by jumping over the dead side between them, that we
will have the same order of connection as in the ring winding.
HANDBOOK ON ENGINEERING.
b
29
Fig. 41. Ring armature core. Fig. 42. Drum armature core.
The dead side of each coil adjoins the live side of a coil that is, in
reality, half a circumference away from it; thus, in Fig. 43, the
live side of coil a is at the top and the dead side is at the bottom ;
while the live side of coil n is at the bottom and the dead side is
at the top. The live sides of these two coils are on opposite sides
of the armature, so that the coil side to the right of a is simply
Figs. 43 and 44. Windings of drum armature.
30 HANDBOOK ON ENGINEERING.
the dead side of a coil whose live side is on the other side of the
armature. In Fig. 44 the two coils a and b are adjoining coils,
for the coil side between them is the dead side of coil n,. To con-
nect the armature, therefore, we join end 2 of coil a with end 1
of coil Z>, and the end 2 of coil b would jump over a dead sjdeand
connect with end 1 of coil c. Coil c, however, would appear to
be two coils ahead of £>, just as b appears to be two coils ahead
of a.
In winding drum armatures, the coils are generally placed in
pairs, as shown in Fig. 43 and also in Fig. 44. The object of
this is simply to make the ends of the armature look more even.
A drum armature can be wound out of a continuous wire, by
simply making a loop to take the place of the ends 1 and 2, and
then skipping a space, as shown by coils a and b in Fig. 44. After
the armature is half covered, there will be spaces left between the
coils, these spaces being of the width of a coil ; we then proceed
to fill up the vacant spaces, and when they are all filled, the last
coil put in will be the proper position to connect with the first
one wound. A little practice with a piece of twine and a wooden
cylinder, will enable any one to find out in short order how to
wind drum armatures.
The two types of winding just explained, are those used
with two pole machines,- motors as well as generators. It may
be added that there is no difference, electrically, between a motor
and a generator, and any machine can be used for either service.
Motors, however, are somewhat modified in design so as to make
them more suited to the work they have to perform. The modi-
fication consists mainly in protecting the parts liable to be injured
by objects falling upon them.
The general arrangement of the field and armature in a two
pole machine is shown in Fig. 31. The design can be changed in
a vast number of ways, but it will always be two- pole, or bipolar,
as it is called, if only two poles are presented to the armature.
HANDBOOK ON ENGINEERING.
31
Generators and motors are arranged so that the current that
magnetizes the field may be the whole current that flows in the
circuit, or only a part of it. When the whole current passes
through the field magnetizing coils, the machine is said to be of
the series type ; this name being given because the armature wire
and the field coils are connected in series, so that the current first
passes through one and then through the other. If the field
coils are traversed by only a portion of the current, the machine
Fig. 45. Showing series connection. Fig. 46. Showing shunt connection.
is said to be of the shunt type, owing to the fact that the field is
supplied with a current that is shunted from the main circuit.
Generators and motors are also arranged so that there are two
sets of field coils and one is traversed by the whole current, and
the other by a portion thereof. The best way to understand
these different types of connection is by means of simple diagrams
that show the wire coils of the field and the outline of the arma-
ture. Such diagrams are presented in Figs. 45 to 50. Fig. 45
32
HANDBOOK ON ENGINEERING.
represents the series connection, A being the armature, C the
commutator, and M the field coil. The direction of the current
is indicated by the arrow heads. Fig. 46 is the shunt connection,
and the arrow heads show the direction of the currents in the case
of a generator. As will be seen, at d the field current branches
off from the main line and returns to it at a, after having passed
through the field coil. Fig. 47 shows the type in which the field is
magnetized by two sets of coils, one being in series with the main
circuit and the other in shunt. As will be noticed, all the
armature current passing out through wire d, goes through coil
F, except the portion that is shunted at c, into the shunt coil M.
This type of winding is called compound, being a combination
of the series and shunt. When the shunt coil is connected as in
Fig. 47. Field magnetized by two sets of coils.
Fig. 48. Illustrating long shunt.
Fig. 47, it is called a short shunt, and when as in Fig. 48, it is a
long shunt. In the first case, the coil M shunts the armature
only, and in the second, it shunts the coil F also.
HANDBOOK ON ENGINEERING. 33
Figs* 49 and 50 show the shunt and compound types for
motors, and as will be noticed, the only difference between them
and the generator diagrams, is that the direction of the current
Fig:. 49. Shunt type of motor.
Compound type of motor.
in the shunt coils is not the same. This difference in direction is
due to the fact that in the generator the armature generates the
current that passes through coil M; hence, at point d, the cur-
rent flows up to the main line and down to the field coil. In the
motor, the current comes from an external source through main
7i, and thus passes from a to the armature, and also to the field
coil, thus traversing the latter in the opposite direction. In the
series coil F, the direction of the current is the same in both
machines.
Generators are made so as to keep the strength of the current
constant, and allow the voltage to vary as the demands of the
service may require ; or they may be wound so as to keep the
voltage constant and allow the current strength to vary. Machines
34 HANDBOOK ON ENGINEERING.
of the first class are called constant current, and are
used principally for arc lighting. Machines of the second
class are called constant potential and are the kind used
for incandescent lighting, for electric railways and for the
operation of motors of every description. For constant current
generators the series winding is used in connection with some
kind of regulating device that prevents the current strength from
varying more than the small fraction of an ampere. The shunt
and compound windings are used for constant potential genera-
tors. If the armature wire had no resistance, the shunt winding
would enable a generator to maintain a constant voltage at its
terminals, no matter how much the strength of the current might
vary ; but armatures without resistance cannot be made ; there-
fore, a shunt-wound machine will develop a slightly lower voltage
with full current than with a weak one, but the difference will
not be more than three to five per cent. By the aid of the com-
pound winding, the generator can be made so as to develop the
same voltage with light or full load, and if desired, the voltage
can be made to increase as the current increases. If a com-
pound generator is so proportioned that the voltage is the same
for weak and strong currents, it is said to be evenly-compounded,
and if the voltage increases as the current increases, it is said to
be over-compounded. If the voltage is five per cent higher, with
full load than with no load, the generator is said to be over-com-
pounded five per cent, and if the increase is ten per cent, it is
said to be over-compounded ten per cent.
The way in which a compound generator increases the volt-
age can be readily understood from an examination of Fig. 47.
The current that passes through the shunt coil M, is practically
one of the same strength at all times ; therefore, the magnet-
izing effect of this coil does not change. Through coil F the
whole current passes, hence, the magnetizing effect of this coil
increases as the current strength increases. Now the total field
HANDBOOK ON ENGINEERING. 35
magnetism is that due to the combined action of the two coils, so
that as the action of F increases, the strength of the field in-
creases. If F has only a few turns of wire, it will only help
slightly to magnetize the field ; therefore, its increased effect, due
to increase in current, will not be very noticeable ; but if F has
many turns, it will develop a large proportion of the field magnet-
ism, and, under this condition, the change in current strength
will make a decided change in the strength of the field, and thus
in the voltage, for the voltage is directly proportional to the
strength of the field.
In motors, the coil F can be connected so as to act with
coil Jf, or against it. If both coils act together, the motor is
compound-wound ; and if F acts against M, the motor is differ-
entially-wound. A compound- wound motor will slow down more
with a heavy load than a simple shunt machine, but it will carry
the load with a smaller current, and, on this account, this wind-
ing is commonly used for elevator motors. A differential motor
will hold up the speed better with a heavy load than a simple
shunt machine, but it will take a correspondingly larger current
to do the work. The differential winding is not used to any great
extent, except in cases where it is desired to obtain as uniform a
velocity as possible.
In explaining the principles of armature winding, it was shown
that the commutator brushes must make contact with the com-
mutator on the sides, that is, that in Fig. 51, they would be
placed on the diameter n n. In actual machines, they are either
ahead of this line, as in Fig. 52, or back of it, as in Fig. 53.
The first position is that of the generator and the second that of
the motor. The reason why the brushes have to be set ahead of
line n n in a generator, and back of the line in a motor, is that
the armature current develops a magnetization of its own, and this
reacts upon the magnetism of the field so as to twist the lines of
force out of their true path. If we look at Fig. 39, we can see
36 HANDBOOK ON ENGINEERING.
that the direction of the current through the wires is such that
the magnetizing effect produced upon the armature core is the
same as it would be if the wire were wound in the way indicated
by the vertical lines in Fig. 51. Now this current will develop a
magnetization in the direction of line nn; that is, at right angles
to the field magnetism. These two magnetic forces of the arma-
ture and the field, engage in a tug of war, and the result is that
the actual magnetization that acts upon the armature wire is the
combined effect of the two. ' If the strength of the field magnetism
Fig. 51. Fig. 52. Fig. 53.
Showing proper position of brushes.
is proportional to line c a, and the strength of the armature mag-
netization is proportional to line c &, then the actual magnetiza-
tion will be equal to line c d, and in the direction d d. In Fig.
52, which represents a generator, if the current in the field coils
passes over the front side in the direction of arrow *', and the
armature revolves in the direction of arrow cZ, then the armature
current will be in the direction of arrow / and the armature mag-
netization will be in the direction of arrow h. The field magneti-
zation will be from N to $, therefore, the resulting magnetization
will be in the direction of line a a. Now the proper position for
HAMDBOOK ON ENGINEERING.
37
the brushes is on a line at right angles to the direction of the
field, hence, they mast rest upon line c c. If the machine is a
motor, the only change effected will be that the direction of the
armature current will be reversed, so that arrow / will point
downward instead of upward, and the magnetism of the armature
will be directed to the right as shown by arrow c. Under these
conditions, the actual direction of the field magnetism will be that
of line b &, and upon line e e, at right angles to this the brushes
must be set.
WIRING TABLE FOR 110- VOLT, 16 CANDLE POWER LAMPS.
(Size of Wire in B. & S. Gauge.)
«w cc
o p,
2*
^^
DISTANCE IN FEET TO CENTER OF DISTRIBUTION.
20
25
30
35
40
45
50
60
70
80
90
100
120
140
160
180
200
2
20
19
19
19
19
19
19
19
18
18
17
16
16
15
15
14
13
3
19
19
19
19
19
18
18
17
16
16
15
15
14
13
13
12
12
4
19
19
19
18
18
17
16
16
15
14
14
13
13
12
11
11
10
5
19
19
18
17
16
16
16
15
14
14
13
13
].' 11
11
10
10
6
19
18
17
16
16
15
15
14 14
13
13
12
11
11
10
10
9
7
18
17
16
16
15
15
14
14
13
12
12
11
11
10
9
9
8
8
18
17
16
15
15
14
14
13
12
12
11
11
10
9
9
8
8
9
17
16
15
15
14
14
13
12
12
11
11
10
9
9
8
8
7
10
17
16
15
14
14
13
13
12
11
11
10
10
9
8
8
7
7
12
16
15
14
14
13
13
12
11
11
10
10
9
8
8
7
7
6
14
15
14
13
13
12
12
11
10
10
9
9
8
7
7
6
6
5
16
15
14
13
12
12
11
11
10
9
9
8
8
7
6
6
5
5
18
14
13
12
11
11
10
10
9
9
8
8
7
6
6
5
5
4
20
14
13
12
11
11
10
10
9
8
8
7
7
6
5 5
4
4
25
13
12
11
10
10
9
9
8
7
7
6
6
5
4
4
3
3
30
12
11
10
10
c
8
8
7
6
6
5
5
4
a
3
3
2
35
11 10
10
9 8
8
7
7
6
K
5
4
4
3
2
2
1
40
11
10
c
8 8
7
7
6
5
B
4
4
3
2
1
1
1
45
10
9
8
8 7
7
6
5
^
4
4
3
2
2
1
1
0
50
9
c
8
7
7
6
6
5
4
4
3
3
2
1
1
0
0
60 8
70 7
8
7
7
7
7
6
6
5
6
5
5
4
4
4
CO CO
c
o
2
2
2
2
1
1
1
1
0
0
0
80
6l 6
6
5
5
4
4
3
2
2
1
1
u
0
90
6
6
f
5
4
4
J
2
2
1
1
0
0
100
5
5
5
4
4
3
3
2
1
1
0
0
38
HANDBOOK ON ENGINEERING.
CHAPTKJLt IV.
MULTIPOLAR MACHINES.
The only difference between a bipolar and multi polar machine
is, that the latter has two poles, and the former has two or more
pairs of poles. In consequence of this difference in the number
Fig. 54. Showing four-pole machine.
of poles, the armature winding has to be slightly modified, as will
be presently explained. Fig. 54 illustrates a four-pole machine
HANDBOOK ON ENGIN BERING.
39
and, as will be noticed, the N and S poles alternate around the
circle. This arrangement is followed, no matter what the number
of poles may be.
The advantage of the multipolar construction is that it in-
creases the capacity of the machine for a given size and weight.
Figs. 55 to 57 illustrate the gain effected in weight. The first
figure shows a two-pole machine, the second a four-pole and the
third an eight-pole, the three being of the same capacity. The
poles of the second machine are half as wide as those of the first,
as there are twice as many. The other parts are reduced in like
proportion. In Fig. 57, the poles are one-quarter as wide as in
Fig. 55. Fig. 56. Fig. 57.
Effect of increasing the Dumber of poles.
Fig. 55, as there are four times as many. On account of the
reduction in the width of the poles, the armatures can be increased
in diameter as the number of poles is increased, without increas-
ing the outside dimensions of the machine, so that in reality,
Fig. 56 is somewhat more powerful than Fig. 55, and Fig. 57 is
still more powerful.
The fields of multipolar machines are wound the same as
those of the bipolar ; that is, as series, shunt or compound.
Figs. 58 to 60 show the three types of winding for a four-pole
machine and Fig. 61 is a diagram of compound winding for an
eight-pole generator. The number of commutator brushes used is
equal to the number of poles, although with one type of armature
40
HANDBOOK ON ENGINEERING.
winding, two brushes are sufficient, no matter how many poles
the machines may have. In practice, however, even with this
winding, the number of brushes is generally made equal to the
number of poles.
With a four-pole machine the brushes can be connected in a
simple manner, as shown in Figs. 58 to 60, but with a greater
number of poles, two rings are generally provided, to which the
brushes are connected in the manner shown in Fig. 62.
Figs. 58 and 59. Connection of brushes on four-pole machine.
Looking at Fig. 54, it can be seen that if the current flows up
from the paper, under the N poles, it will flow down through the
paper, under the S poles ; hence, the armature coils in a four-
pole machine must span only one-quarter of the circumference,
and not one-half, as in the two-pole armature. For a six-pole
armature, the coils must span one-sixth of the circumference,
and for an eight-pole, one-eighth, and so on, for any higher
number of poles.
There are two types of winding for multipolar armatures, one
being called the lap, or parallel winding, and the other the wave
HANDBOOK ON ENGINEERING.
41
42
HANDBOOK ON ENGINEERING.
or series winding. Fig. 62 is a diagrammatic illustration of the
lap winding, and Fig. 63 of the wave winding, both for four poles.
Fig. 62. Diagram of lap winding.
The small circles around the outside of the armature represent
bars or wires, which are connected with the commutator segments
by means of the solid lines, and with each other at the opposite
side of the armature, by means of the broken lines.
If we start from coil side, or bar 1 on the left, and follow the
connections as guided by the numbers, we will finally reach 32,
and thus come back to left side brush a, which is the starting
point. As will be seen, bar 1 connects at the back of armature,
HANDBOOK ON ENGINEERING.
43
with bar 2, and then over the front, the connection runs in the
backward direction, to bar 3 ; thence, forward again, at the back
end, to bar 4, and again backward over the front, to bar 5. The
connections, therefore, lap over each other and it is on this
account, that it is called a lap winding.
Fig* 63 shows the wave winding, and it will be noticed that if
we start from bar 1 at the top, we advance around the right to bar
2, and then we go further ahead to bar 3, and in like manner
advance to bar 4, the connections in every case advancing in the
Fig. 63. Diagram of wave win
same direction around the circle. It will be further noticed that
the connections run zig-zag from side to side of the armature core
44 HANDBOOK ON ENGINEERING.
as they advance, thus forming a wave-like path for the current,
and it is on this account that this style of connection is called
wave winding.
With the lap winding, the brushes a a are connected with each
other, and so are the b b brushes. In the wave winding, two
brushes set one-quarter of the circle from each other, will take
the current off properly as indicated by a and b in Fig. 63, but
four brushes can also be used.
In Fig* 54, the brushes are shown midway between the poles,
while in Figs. 62 and 63, they are opposite the poles. This dif-
ference in position is due to the fact that in the last two named
figures, the connections between the armature coils and the com-
mutator segments do not run in radial lines from either side, but
one connection bends backward and the other forward. In
actual machines, the connections are run as in these diagrams, and
in some cases, one of the sides runs in a radial direction; there-
fore, in some generators, the brushes are opposite the poles, and
in others they are between them.
Diagrams 62 and 63 show coils of a single turn, but by regard-
ing the broken lines as representing the position of the end of the
coil at front as well as the back of the armature, and the solid
lines as simply the ends of the wire that connect with the com-
mutator segments, they become accurate representations of coils
of any number of turns.
The coils of multipolar armatures are made on forms, and in
the finished state are placed upon the armature core. Some coils
are so formed as to bend down over the ends of the armature, and
are then given the form at the ends, shown in Fig. 64, so they
may fit into each other. In some machines, the coils do not bend
down over the ends of the armature, but run out parallel with
the shaft. Armatures so wound are sometimes said to have a
barrel winding, and the coils, if laid out upon a flat surface,
would present the appearance of Fig. 65 ; that is, if they con-
HANDBOOK ON ENGINEERING.
abed
45
Figs. 64 and 65. Armature windings.
tained more than one turn. If of the single-turn type, they
would look like Fig. 66, if for a lap winding; and like Fig. 67,
if for a wave winding, the ends d d being joined and then con-
nected with the commutator segments.
In connecting the field coils of multi polar machines, it is
necessary to be careful not to make mistakes, so that some of the
abc
ab c
d ' 'd d
Figs. 66 and 67. Drum and barrel windings
46 HANDBOOK ON ENGINEERING.
coils will act to magnetize the field in the wrong direction. By
studying Fig. 27 and the explanation of it, the direction of the
magnetic lines of force with respect to the direction of the current
through the magnetizing coils, can be clearly understood, and
then there will be no difficulty in determining the proper way in
which to connect the coil ends, for all we have to do is to make
the connections such that if one pole is N the one next to it is S.
With two-pole machines, it is also necessary to be careful not to
connect the field coils improperly; that is, if there is more than
one coil, and in most machines this is the case.
The current that energizes a magnet is called the magnetizing
force and is measured in ampere turns. The ampere turns are
obtained by multiplying the number of turns of wire in coil, by
the amperes of current flowing through it.
All forms of matter resist the development of magnetic force.
This resistance is called magnetic reluctance. The reluctance of
air is much greater than that of iron or steel, but is constant;
that of iron and steel is not. If one thousand ampere turns
develop a certain magnetic density in a circuit composed wholly
of air, two thousand ampere turns will double this density. In
iron and steel it will require much more than double the ampere
turns to double the magnetic density.
If in a magnetic circuit ten inches long, 100 ampere turns
develop a certain density, it will require 200 ampere turns to
develop the same density if the magnetic circuit is double the
length.
HANDBOOK ON ENGINEERING. 47
CHAPTER V.
SWITCH-BOARDS, DISTRIBUTING CIRCUITS AND SWITCH-
BOARD INSTRUHENTS.
Generators of the constant potential type are made so as to
develop a certain voltage at a given velocity, but in some cases it
is not practicable to run them at the exact speed for which they
are designed ; and in others, it is desired to vary the voltage
slightly, hence, all machines are provided with means for chang-
ing the e.m.f. slightly. This regulating device is also necessary
in cases where the load is for a time light, and for the balance of
the time heavy ; for, as we have shown, the voltage will vary to
some extent with changes in the strength of the current. If
the generator is at some distance from the points where the cur-
rent is used, the drop of voltage in the lines will be greater with
strong currents ; hence, when the load is heavy, it is necessary to
increase the voltage developed by the generator. As it is not
advisable to change the speed of the engine, the variation of volt-
age is obtained by changing the strength of the current that
flows through the shunt field coils, and this is accomplished by
providing a resistance that can be cut in or out of the shunt coil
circuit, as is illustrated in Fig. 68, in which R represents the
resistance, or field regulator, as it is called. When the lever is
moved to the extreme left position, all the regulator resistance is
cut out of the circuit, and then the voltage of the generator is
the highest that can be obtained with the speed at which it is run-
ning. When the lever is moved to the extreme right, all the
resistance of the regulator is introduced into the shunt coil cir-
cuit, and then the voltage is the lowest. By placing the lever in
48
HANDBOOK ON ENGINEERING.
intermediate positions between the extremes right an-d left, differ-
ent voltages may be obtained.
To be able to operate a generator furnishing current to a sys-
tem of distributing wires, it is necessary to have a number of
a,
d
R
Fig. 08. Resistance regulator for shunt coil.
instruments and other devices, included in the circuit, some of
which are absolutely indispensable, and others of which are simply
conveniences, and may be looked upon as luxuries. The various
devices required are shown in Fig. 69. The generator is shown
at M, and at e the field regulator is placed, and it is connected
with one of the generator armature terminals and with one end
of the shunt coil wires by means of wires cif d. The wires c c
run from the generator terminals to the voltmeter F, and thus
enable us to see what the voltage is at all times. Wires a and b
convey the current to the external circuit, with which they can be
connected or disconnected by means of switches ss ss. At A an
ammeter is placed which indicates the strength of current in
HANDBOOK ON ENGINEERING.
49
amperes. The ammeter can be placed in either a or 6, as the
same strength current flows in both. At// safety fuses are pro-
vided, so as to open the circuit in case the current becomes so
strong as to be capable of overheating the generator wire. If one
of the line wires runs out into the open air, and is carried along on
poles, we will have to provide a lightning arrester, as shown at ft,
this being connected with the ground as at g. If both lines run
into the open air, an arrester must be placed in both ; and if
both are confined to the interior of a building, no arresters will
be required. From the points m m branch circuits may be run
off in as many directions as necessary, and by providing switches
s s, these can be connected or disconnected from the main line
when desired.
This crude arrangement would enable us to operate the system
successfully, but it would not be so convenient as a more methodi-
Fig. 69. Instruments required in the circuit.
cal grouping of the several devices and instruments. It repre-
sents the way things were done in the early days of electric light-
ing, but at the present time, instead of having the several parts
scattered about in a helter-skelter fashion, they are all assembled
4
50
HANDBOOK ON ENGINEERING.
upon a large panel, which is called a switch-board. Fig. 70 give
the general arrangement of wiring and location of devices for i
simple board arranged for one generator feeding into five externa
\n \P
Fig. 70. General arrangement of switchboard.
HANDBOOK ON ENGINEERING. 51
cated by the lines n _p, //, being safety fuses. The wires i i con-
vey the main current from the generator to a circuit breaker Z>,
which is simply a switch that is constructed so that it will open
automatically when the current becomes too strong. From the
circuit breaker, the current passes through wires a and b to the
main switch F, and by wire c, it runs from here to the ammeter
A and from the latter by wire c? to a rod 1 which is called a bus
bar. The upper side of the main switch is connected directly
with bus 2. The voltmeter is connected with two busses by the
wires e e. The field regulator is located back of the board at J£,
and is connected in the shunt coil circuit by means of wires h h.
The switch of the regulator E is connected with a hand-wheel on
the front of the switch-board, so that the attendant can watch
the voltmeter as he turns the wheel and thus see just what affect
the movement is producing on the voltage.
In addition to the devices shown in Fig. 70, we can, if desired,
provide a recording ammeter, a recording voltmeter and a watt-
meter ; the first two would give us a record of the amperes and
volts for a certain length of time, generally 24 hours, and the
last one would register the amount of electrical energy. We
could also provide ammeters for each one of the distributing cir-
cuits, so as to know the strength of current in each one.
If we desire to arrange the switch-board for two generators,
and these are of the shunt type, we will require no changes in
Fig. 70, except to provide another regulator and a main switch
and circuit breaker for the additional machine. This arrange-
ment of board is suitable for a single compound wound generator",
or any number of shunt wound machines, but if we have two or
more compound generators, the connections between these and
the bus bars will have to be somewhat modified.
The modifications required in a switch-board for two or more
compound generators can be made clear by the aid of Figs. 71
and 72, In the first figure, we can see that if the current return-
52
HANDBOOK ON ENGINEERING.
ing from the main line through n divides into wires a and 6, it
will remain divided until it passes through the armatures and the
F coils of the two machines, and thence through wires e e, it will
Fig. 71. Connections from machines to switchboard.
reunite again in wire p. In Fig. 72, the two parts of the current
will flow through wires d d to the single wire e, and then divide
into wires//, and thus reach the coils F F, and, finally, through
wires h 7i, reach p. In Fig. 71, if the right side armature gen-
erates more current than the other one, the F coil of that gener-
ator will be traversed by the strongest current, for in each machine
the strength of current in the armature and the F coil will be
nearly the same. Now, if the right side machine generates the
strongest current, it is because its voltage is the highest, but the
fact that its F coil will be traversed by the strongest current will
make its voltage still higher, thus increasing the difficulty. In
Fig. 72, the current flowing through the two F coils will be the
same, no matter how much the two armature currents may differ,
HANDBOOK ON ENGINEERING.
53
for these come together in wire e, and passing from this to the two
F coils, the current will divide in equal amounts. As can be
seen, the effect of adding the wires d d, e and //in Fig. 72 is to
equalize the currents that flow through the F coils, and thus pre-
vent, as far as possible, the unequal action of the generators.
When two or more compound generators are connected so
as to feed into the same general circuit, the connections are
made in accordance with Fig. 72. Fig. 73 illustrates a switch-
board for two compound generators, and, as will be noticed, the
most striking difference between it and Fig. 70, is that there
are three bus bars instead of two. One of these busses is
called the equalizer, and it takes the place of wires d d e and
Fig. 72. Arrangement of equalizing connections.
//in Fig. 72. The equalizing connections run from generator
wires/ to the main switches S, and thence to bus 1. The h wires
of the generators run to one side of the circuit breakers D E,
54
HANDBOOK ON ENGINEERING.
and thence to the middle blades of the S switches, and from these
to the bus 2. The generator wires run to the outside blades o:
•
ff
Fig. 73. Switchboard for two compound generators.
the circuit breakers, and from these to the ammeters A A, anc
thence to bus 3. The voltmeters are connected with wires k am
/, and thus indicate the e.m.f.'s of the generators.
HANDBOOK ON ENGINEERING. 55
If another generator were added, it would be connected with
the bus bars in the same way.
In starting two or more compound- wound generators, one
machine is started first, and then the second is run up to full
speed, and its voltage is adjusted by means of the regulator R, so
as to be the same as that of the machine that is running. When
the voltages of the two machines are equal, the main switch of
the second machine is closed so as to connect it with the bus bars.
This action will generally make a slight change in the voltage of
the second machine, causing it to run up or down a trifle ; and as
a result by looking at the ammeters, we will find that it is taking
more or less than its share of the load. If such is the case, we
manipulate the regulator R, until the loads are properly divided.
Whether the voltage of the second machine will rise or fall after
it is connected with the bus bars, will depend upon the extent to
which it is compounded ; if slightly compounded, the voltage will
drop, and if heavily compounded, it will rise.
The switch-boards illustrated are adapted to what is called the
two- wire system of distribution, but in cases where it is desired
to transmit the current to a considerable distance, without using
extra large wire, the three-wire system of distribution is
employed. This system is illustrated in Figs. 74 to 76.
Suppose we have two generators as indicated at G O in these
diagrams, and let the direction of the current through both be
from bottom toward the top ; then it is evident, that if we remove
the middle wire 0, the lower machine will deliver current into the
upper one, and if each generator develops an e.m.f. of 115 volts,
the combined e.m.f. will be 230 volts, and this will be the
pressure between the bottom and top wires ; but the voltage
between either wire and the center one will only be 115. Suppose
we have a number of lamps connected between wire P and the
center wire 0, and an equal number of lamps between 0 and N,
as \s shown in Fig. 74 ; then it is evident that the same amount
HANDBOOK ON ENGINEERING.
of current will flow through both sets, arid as a consequence, a
the current that passes from the upper generator into wire P wi
go directly through both sets of lamps to the lower wire N, an
thus return to the lower side of the bottom generator. Und<
Arrangements of three- wire system.
these conditions, the lamps will be acted upon by 115 volts eact
but the current will be driven through the circuit by a voltage c
230. Now, if the voltage is doubled, four times the number c
lamps can be supplied with the same size wires ; hence, the cos
of line wire per lamp will be reduced to one-fourth. Suppose
that instead of having the lamps equally divided as in Fig. 14
HANDBOOK ON ENGINEERING. 57
they are arranged as in Fig. 75 ; then since the current fed into
the system from the upper wire P is only sufficient for five lamps,
while there are seven lamps in the lower section, it follows that
through wire 0 a current sufficient for two lamps must be sup-
plied. The way in which the currents would flow in this case is
clearly indicated by the arrows.
In Fig* 74, it will be seen that if we removed the middle wire,
the lamps would not be affected, for none of the current comes
through it; but in Fig. 75, if we cut the middle wire, two of the
lower lamps would be unprovided for. From this it will be seen
that the object of the middle wire is simply to provide the extra
current required for the side that carries the largest number of
lamps. If the lights are so arranged that on both sides of the
central wire 0 the number is practically the same at all times,
the center wire can be made very small, but such perfect balance
cannot be obtained always, and on that accouut, the center, or
neutral wire, as it is called, is made of the same size as the
others, except in large systems, in which it is sometimes not more
than one-third the size.
As motors require large amounts of current, they are nearly
always made to operate with a voltage of 230, and are connected
with the outside wires of the system, as is shown in Fig. 76, in
which a a a a and c c c c indicate lamps connected between the
sides and the neutral wire, and ABC are motors connected
across the outside lines.
When a switch-board is arranged for two generators connected
with a three-wire system, we use three bus bars, just as in Fig.
70, but discard the equalizing connection, and connect the
generators with the busses in the same way as they are connected
with wires N 0 and P in Figs. 74 to 76. If we have a number of
generators feeding into the three- wire system, then we connect
each set with an equalizer bus; that is, provide two sets of
busses, and the P and N busses of these two sets we connect
58
HANDBOOK ON ENGINEERING.
with a third set in the proper order for the three-wire system,
and from the latter busses the external circuits are fed.
If we desire to supply a larger building with a lighting and
power system, we can run the wires in almost any way, providing
we make connections with the lamps and motors, but if we adopt
Fig. 77. Light and power system for building.
a systematic arrangement it will require less labor to operate the
plant, and when anything goes wrong we will be able to locate
the difficulty with much less trouble and in less time. The best
way to accomplish this is by the use of small switch-boards
located at different points in the building, these becoming centers
HANDBOOK ON ENGINEERING. f)9
of distribution, from which all the lamps are supplied. The
general arrangement of such a system dan be understood from
Fig. 77, in which B represents the main switch-board, located in
the engine room, and e e e the several floors upon which the lights
are located. From the main switch-board we run up four lines,
one to each floor, and locate secondary boards at C C and D DD.
We can also run out lines directly from the board to the lamp
circuits as at c c c c. From the boards C (7, we run circuits to
smaller boards, as shown at J5J, F, A, A, A, and b b b. From
each one of these small boards we can run out circuits to the
lamps.
These small switch-boards are called panel boards or boxes,
and also distribution boards. They are made of all sizes from
eight or ten inches square, up to four or five feet, and are
arranged to feed into one or two, or fifty or sixty circuits,
supplying anywhere from five or six lights up to a thousand or
more.
The construction of distribution boards can be understood
from Figs. 78 and 79, the first being arranged for the three-
wire system, and the second for the two- wire. Fig. 78 is ar-
ranged to feed ten circuits, and is provided with one main switch
by means of which the entire box can be disconnected from the
main line. The distributing circuits are provided with proper
safety fuses on the outside wires, so that if anything goes wrong
and the current increases to a dangerous point, the circuit will be
open. No fuse is placed on the middle wire, as it is not neces-
sary, and might result in cutting out both sides of the circuit
when only one was disabled.
Fig* 79 is a mor'e complete panel, because each one of the six
distribution circuits is provided with a switch, so that it is pos-
sible to disconnect any of the circuits without interfering with the
others. In some cases a distribution board of this kind is the
only thing that will answer the purpose, but in others, the more
60
HANDBOOK ON ENGINEERING.
simple construction of Fig. 78 answers just as well. The fuses
in Fig 78 are shown at E F. These fuses are sometimes made so
that they can be used as switches ; that is. they can be pulled out
Fig. 78. Board for three-wire system.
Fig. 79. Board for two-wire system.
of place and thus open the circuit, and if one blows out it can be
removed and a new fuse be put in, and then it can be replaced,
thus placing the disabled circuit in service without interfering
with the others.
The ammeters and voltmeters used on switch-boards depend
for their operation upon the repulsion between magnetic lines of
force. A great many different constructions are used, but most
of them operate upon the principles illustrated in Fig. 80 or 81.
If a small bar of iron c is placed between the poles of a permanent
magnet, as in Fig. 80, it will be held in the horizontal position by
the attraction of the magnet. If it is surrounded by a stationary
coil of wire &? through which a current of electricity passes, then
HANDBOOK ON ENGINEERING. 61
it will be under the influence of two forces, one the attraction of
the poles N S of the magnet, and the other the attraction of the
lines of foice developed by the current flowing through coil b.
The action of the latter will tend to swing the rod c into the ver-
tical position . The force of the magnet will remain constant, but
the force of the coil will vary with the strength of the current
passing through it ; hence, the stronger the current the more the
bar c will be swung around into the vertical position. If we pro-
vide a small counter- weight, as shown in the illustration, to resist
the action of the coil, we will have a means that will enable us to
adjust the movement of the bar, so that it will swing around
through a given angle for a given increase in current. If a
pointer a is secured to c it will swing over the scale as shown,
when c is rotated by the action of the coil.
If coil b is mounted so that it may swing around the center
pivot, we can discard bar c, for then as soon as a current traverses
&, the lines of force developed around it will be attracted by
Figs. 80 and 81. Principles of ammeter and voltmeter.
those of the permanent magnet, and will exert a twisting force so
as to place the axis of the coil parallel with the lines of force
passing from N to S. In this case as in the previous case, the
6B HANDBOOK ON ENGINEERING.
effort to twist b around will be proportional to the strength of
the current, hence, the stronger the current the greater the
swing. Ammeters and voltmeters are made on these principles,
and the only difference in the two instruments is in the size of
the wire used for the coils.
Figs* 82 and 83 illustrate the principle upon which circuit
breakers are made. In Fig. 82, suppose a current flows through
magnet 2£, then it will attract the lever A, the latter being made
Figs. 82 and 83. Principles of circuit breakers.
of iron. If the current is weak it may not develop a sufficient
attractive force in E to lift the weight D, and in that case A will
remain where it is. If, however, the current is increased until E
becomes strong enough to lift Z>, then A will move over toward
the magnet, and the catch " a " falling behind it, will not allow
it to return to its former position until placed there by hand.
When A swings over, it carries J5, and thus breaks the connec-
tion with C and opens the circuit. Thus it will be seen that by
properly adjusting the weight D and the magnet E, we can set the
device so as to open the circuit whenever the current reaches a
certain strength. This is the principle upon which circuit break-
HANDBOOK ON ENGINEERING. 63
•*rs act, but such a device as Fig. 82 would be of no service for
lighting circuits, because the distance by which 0 and B are
separated is too small to break the current. By modifying the
construction as in Fig. 83, we can obtain a device that will give a
wide separation at the breaking point. In this construction , the
lever A when drawn towards the magnet, strikes the catch a, so
as to release lever .B, and then the weight D throws the latter
down to the position shown in broken lines, thus giving a wide
separation between F and (7. By moving the weight on the lower
arm at A, the device can be adjusted so as to act with different
strengths of current.
Circuit breakers as actually constructed, do not have the
appearance of this diagram, but they operate on the principle
illustrated by it.
The electromotive force in volts developed in the armature of
a motor, or generator, can be determined if we know the number
of wires upon the outer surface, the number of maxwells of mag-
netic flux that pass through the armature, and the revolutions per
second. The rule for the calculation is as follows : —
Multiply the number of wires on the outer surface of the arma-
ture by the maxwells of magnetic flux and by the revolutions per
second, and divide this product by 100,000,000.
This is the rule for two pole armatures. For multipolar arma-
tures with series, or wave winding, use same rule making the
flux equal to the sum of the fluxes issuing from all the positive poles.
For multipolar armatures with a lap, or parallel winding, use
same rule but take the flux issuing from one pole only.
To obtain the pull in pounds of a motor armature at one foot
radius use the following rule : —
Multiply the number of wires on the outer surface of armature
by the amperes of armature current, and by total number of max-
wells of magnetic flux passing through armature, and divide this
product by 852,000,000. See pages 13 and 46.
64 HANDBOOK ON ENGINEERING.
'
CHAPTER VI.
ELECTRIC MOTORS.
'
Motors are made so as to run at a constant velocity, or for
variable speed. For the latter type of machine, the field coils are
wound in series, and for constant speed the shunt winding is used.
A motor of either kind cannot be started successfully without
placing an external resistance in the armature circuit, because,
when the armature is at a standstill, there is nothing but the
resistance of the wire to hold the current back, and as a result, if
no extra resistance is provided, the first rush of current would be
very great. As soon as the armature begins to revolve, an e.m.f .
is induced in its wires, and this acts in opposition to the e.m.f.
of the line current ; that is, it acts like a back pressure, and holds
the current back. On this account, the e.m.f. of a motor is
called a counter e.m.f., and it is abbreviated into c. e.m.f.
The way in which the external resistance is connected with
a motor is illustrated in Fig. 84, in which M is the motor and
R the external resistance. D is a main switch, by means of
which the motor is connected with the main line. This switch is
closed first, and then switch F is moved to the right until it cov-
ers the first contact of the resistance R. The current can then
pass directly to the field shunt coils through wire e, and thence by
wire a, return to the main line. The armature current, however,
has to first pass through the resistance R, before it can reach wire
i, and thus the armature. As soon as the armature begins to
speed up, the switch F is advanced, step by step, and in a few
seconds it is moved to the extreme right position, in which all the
resistance R is cut out of the armature circuit. When F reaches
this position, the motor should be running at full speed.
HANDBOOK ON ENGINEERING.
65
If the current should stop while the motor is running, the
machine would stop, also, and then, if the current were turned
on again, the motor would be caught with the armature connected
across the line without an external resistance, and as it would be
at a standstill, the current would rise to an enormous strength.
To prevent this, the switch F is always opened whenever the motor
stops. The attendant may forget to do this, however; therefore
automatic switches have been devised that will open themselves
whenever the current dies out.
Fig. 84. External resistance connected with motor.
A simple switch provided with a resistance so as to be suited
to start a motor, is called a motor-starter, and one that in addi-
tion is provided with means for automatically flying to the open
position whenever the current fails, is called an automatic under-
load starter.
If the motor is very much overloaded, its speed will slow down
and the current will increase in strength. If the overload is suf-
ficient, the current will become so strong as to be able to burn out
66
HANDBOOK ON ENGINEERING.
the armature ; hence, it is desirable to provide a circuit breaker
that will open the circuit when the current becomes so strong as
to be liable to burn out the machine. Motor-starters are made
with a circuit-breaking attachment, and are then called automatic
overload motor-starters. A device that combines the under and
overload starter, features is called an automatic under and over-
load starter, and by some people it is called -a u no voltage " and
" overload starter."
When motors were first introduced, a great deal of trouble
was experienced with the starters, owing to the fact that they
were arranged so that when the motor was stopped, the connection
with the field coils was broken. Now, the current flowing through
the field coils objects to stop flowing when the connection is
broken, and, consequently, it continues to flow between the end of
switch F in Fig. 84, and the last of the contacts of R, until the
distance is more than the e.m.f. of the current can overcome.
Principle of motor starter.
This action produces serious sparking at the last terminal, and in
addition, produces a severe strain upon the insulation of the
HANDBOOK ON ENGINEERING. 07
field coils, because, as the current is headed off in one direction,
it tries to find an outlet in another. This action is what is
Fig. 86. Another style of motor starter.
commonly called the "kick of the motor field." All this
trouble can be obviated by connecting the starter with the motor
in such a way that the field circuit is never opened, as is shown
in Fig. 84. As this is quite an important device it is presented
in a more simple form in Fig. 85, in which it will be seen that
the field coils and armature are permanently connected, so that
when switch S opens the circuit, the field current can flow through
the armature, until it dies out. All first-class concerns make
motor starters with this connection, at the present time. Some
of them add the curved contact e. Without this contact, it can
be seen that when the switch S is moved to the top position, the
68 HANDBOOK ON ENGINEERING.
resistance R is simply transferred from the armature to the field
circuit, and that the current going to the field coils has to pass
through this resistance. As this resistance is insignificant in
comparison with that of the shunt coils, it makes little difference
whether it is left in the field circuit or not, but by the addition of
e it can be cut out.
Variable speed motors are always arranged so that the speed
may be changed by hand as conditions may require. Trolley-car
motors are of this type, and so are the motors used for printing
presses, and many other kinds of work. Figs. 86 to 88 show
arrangements by means of which the speed may be varied with
series wound motors. In Fig. 86, E is the starting box and F is
the speed regulator. In the act of starting, the switches are in
the position shown. To start, the switch S and E is turned so
as to close the circuit with the resistance R all included. S is
moved toward the left as the armature speeds up, and reaches
the last position when full speed is attained. If the switch of F
is now closed, a portion of the current will be diverted from the
armature, and thus its rotating force will be reduced, and thereby
its speed. This method of speed control is also arranged so
that the two switches act together, so as to introduce resistance
into the motor circuit, and at the same time divert more or less
of the current around the armature. It is not used extensively,
as all the current that passes through F is just so much thrown
away.
In Fig. 87 the speed is controlled by means of the switch F,
which cuts out portions of the field coils and this changes the
strength of the field. With this arrangement, if a portion of
the field is cut out, the motor will run faster, because the c.e.m.f
will be reduced, therefore, the armature current will be increased.
To obtain a wide range of regulation, it is necessary to wind a
large number of turns of wire on the field, so that with all the
wire in service, the speed may be the lowest required.
HANDBOOK ON ENGINEERING.
69
Fig. 88 shows another arrangement that varies the strength of
the field by diverting a portion of the current through switch F.
It gives as wide a range of regulation as Fig. 87, but is not so
economical.
Figs- 86 and 88 cannot be used to regulate the speed of shunt
motors, but Fig. 87 can. The first two named figures, if used
Fig. 87. Regulator for shunt motor.
with a shunt motor, would simply afford a third path through
which current could pass from one side of line to the other, that
is, from the p to the n wires, but this would not materially affect
the strength of current that would flow through the armature and
field coils. They work with series wound motors, because the
current is not shunted from wire p to wire n but simply from
one side of the armature, or the field, to the other.
70
HANDBOOK ON ENGINEERING.
Fig* 89 shows an arrangement by means of which a shunt
motor can be made for variable speed. In this case, the switch
Fig* 88. Device for varying strength of field.
and resistance E is simply an ordinary starter, and F is a resist-
ance that is introduced in the field circuit, so as to vary the
strength of the field. With this arrangement the slowest speed is
obtained when all the resistance of F is out of the circuit.
The direction in which a motor runs can be reversed by sim-
ply reversing" the direction of the current through the armature.
Any of the arrangements for varying the speed can be used in
connection with reversible motors by arranging the switch so as
HANDBOOK ON ENGINEERING.
71
to reverse the armature connections. Fig. 90 will give a fair
idea of the way in which a reversing switch is made. This repre-
sents the type of switch used most generally for this purpose, and
it is known as the cylinder switch. It is the kind used on trol-
ley-cars. The vertical row of circles numbered from one to
eleven represents stationary contact pieces, to which the terminals
of the motor, the line and the resistance are attached. The
shaded parts B B are metal plates that are secured to the
surface of a cylinder, that is so located that as it is turned in one
direction or the other, these plates slide over the stationary con-
tacts. If the cylinder is turned so that the plates on the right
side slide over the contacts, the motor will run in one direction,
and if the cylinder is turned in the other direction, the motor will
be reversed. Suppose the right side plates slide over the con-
Fig. 89. Device for varying speed of shunt motor.
tacts, then the current from^> will pass to contact 2, and thence
to wire a, and to the left-side of the field. Through wire d it
will return from the field to contact 5, and by means of
T2,
HANDBOOK ON ENGINEERING.
plates N and T, which are connected as shown at JX1, it will reach
contact 3 and wire fr, which runs to the lower side of the arma-
ture. From the top of the armature, through wire c, the current
will return to contact 4 and through plates S and M and the con-
nection X will reach contact 6 , which by one of the wires e con-
Fig. 90. Principle of reversing device.
nects with the left-side of the resistance U. From the right-side
of this resistance, the current will pass to contact 10, and thus
to contact 11, through the cylinder plate, and in that way reach
line wire n.
If the cylinder is turned further around, contact 7 will be cov-
ered by plate M , and this will cut one section of D. By a further
HANDBOOK ON ENGINEERING. 73
movement, contact 8 will be covered, thus cutting out another
section, and by continuing the movement, all of D can be cut out.
If the cylinder is turned so as to slide the left-side plates over
the contacts, the change effected will be that contact 5 will be
connected with 4 instead of with 3, and contact 6 will be con-
nected with 3 instead of 4, thus reversing the direction of the
current through the armature.
The strength of an electric current is measured in amperes.
The electromotive force that drives an electric current through a
circuit is measured in volts. The resistance that a wire or other
circuit offers to the passage of an electric current through it is
measured in ohms.
The unit of resistance, the ohm, is the resistance of a column
of mercury about 40 inches long and about five hundredths of an
inch in diameter, or, to be more exact, 106 centimeters long, and
one millimeter in diameter.
THE WATT.
The watt is the unit of electric power — the volt-ampere, the
power developed, and is equal to TJ^ of one horse power. A con-
venient multiple of this is called the Kilowatt, written K. W., and
is equal to 1,000 watts.
THE AHPERE.
The ampere is the practical unit of electric current, such a cur-
rent [or rate of flow, or transmission of electricity] as would
pass, with an electromotive force of one volt, through a circuit
whose resistance is equal to one ohm ; a current of such a strength
as would deposit from solution .006084 grains of copper per
second.
CANDLE POWER.
The candle power is the unit of light ; and a standard candle
is a candle of definite composition which with a given consump-
tion in a given time, will produce a light of a fixed and definite
brightness. A candle which burns 120 grains of spermaceti wax
per hour, or two grains per minute, will give an illumination
equal to one standard candle.
74 HANDBOOK ON ENGINEERING.
CHAPTER VII.
INSTRUCTIONS FOR INSTALLING AND OPERATING SLOW AND
MODERATE SPEED GENERATORS AND HOTORs!
To remove the armature, take off the brush-holders, brush
yoke, pulley and bearing caps and put a sling on the armature, as
shown in accompanying illustration. A spreader of suitable
length should be used and its location adjusted to prevent the
rope from drawing against the flange or end connections.
In assembling, marked parts of the machine should be assem-
bled strictly according to the marking. Clean all connection
joints carefully before clamping them together. Wipe the shaft-
bearing sleeves and oil cellars perfectly clean and free from grit.
Place the bearing sleeves and oil rings in position on the shaft
and then lower the armature into place, taking care that the oil
rings are not jammed or sprung. As soon as the armature is in
position, pour a little oil in the bearing sleeves, put the caps on
the boxes and screw them down snugly. The top field should
next be put on and bolted firmly into position, and a level placed
on the shaft to check the leveling of the foundation.
Fill the bearings with the best grade of thin lubricating oil and
do not allow it to overflow. Oil throwing is usually due to an
excess of oil and can be avoided by care in filling the oil cellars.
To complete the assembly, place the pulley on the shaft, draw
up the set screws and put on the brush rigging and connection
blocks.
STARTING.
Before putting on the belt, see that all screws and nuts are
tight and turn the armature by hand to see that it is free and
HANDBOOK ON ENGINEERING.
75
does not rub or bind at any point. Put on the belt with the
machine so placed on the rails as to have the minimum distance
between pulley centers. Start the machine up slowly and see
that the oil rings in bearings are in motion. As the machine
Fig. 91. Method of raising an armature.
comes up to speed, tighten the belt till it runs smoothly, and run
the machine long enough without load to make sure that the bear-
ings are in perfect condition. The bearings, when running,
should be examined at least once a week.
iCARE OF COMMUTATOR.
The commutator brushes and brush-holders should at all
times be kept perfectly clean and free from carbon or other dust.
Wipe the commutator from time to time with a piece of canvas
lightly coated with vaseline. Lubricant of any kind should be
applied very sparingly.
76 HANDBOOK ON ENGINEERING.
If a commutator when set up begins to give trouble by rough-
ness, with attendant sparking and excessive heating, it is neces-
sary to immediately take measures to smooth the surface. Any
delay will aggravate the trouble, and eventually cause high tem-
peratures, throwing off solder, and possibly displacement of the
segments. No. 0 sandpaper, fitted to a segment of wood, with a
radius equal to that of the commutator, if applied in time to the
surface when running at full speed (and if possible with brushes
raised), and kept moving laterally back and forth on the commu-
tator, will usually remedy the fault.
DIRECTIONS FOR STARTING DYNAMOS.
General* — Make sure that the machine is clean throughout,
especially the commutator, brushes, electrical connections, etc.
Remove any metal dust, as it is very likely to make a ground or
short circuit.
Examine the entire machine carefully, and see that there are
no screws or other parts that are loose or out of place. See that
the oil-cups have a sufficient supply of oil, and that the passages
for the oil are clean and the feed is at the proper rate. In the
case of self -oiling bearings, see that the rings or other means for
carrying the oil work freely. See that the belt is in place and
has the proper tension. If it is the first time the machine is
started, it should be turned a few times by hand, or very slowly,
in order to see if the shaft revolves easily and the belt runs in
center of pulleys.
The brushes should now be carefully examined and adjusted
to make good contact with the commutator and at the proper
point, the switches connecting the machine to the circuit being
left open. The machine should then be started with care and
brought up to full speed, gradually if possible; and in any case
HANDBOOK ON ENGINEERING. 77
the person who starts either a dynamo or a motor should closely
watch the machine and everything connected with it, and be ready
to throw it out of circuit if it is connected, and shut down and
stop it instantly if the least thing seems to be wrong, and should
then be sure to find out and correct the trouble before starting
again.
STARTING A DYNAMO.
In the case of a dynamo it is usually brought up to speed
either by starting up a steam-engine or by connecting the
dynamo to a source of power already in motion. The former
should, of course, only be attempted by a person competent to
manage steam-engines and familiar with the particular type in
question. This requires special knowledge acquired by experi-
ence, as there are many points to consider and attend to, the
neglect of any of which might cause serious trouble. For ex-
ample, the presence of water in the cylinder might knock out the
cylinder-head ; the failure to set the feed of the oil-cups properly
might cause the piston-rod, shaft, or other part, to cut. And
other great or small damage might be done by ignorance or care-
lessness. The mere mechanical connecting of a dynamo to a
source of power is usually not very difficult; nevertheless, it
should be done carefully and intelligently, even if it only requires
throwing in a friction-clutch or shifting a belt from a loose pul-
ley. To put a belt on a pulley in motion is difficult and danger-
ous, particularly if the belt is large or the speed is high, and
should not be tried except by a person who knows just how to do
it. Even if a stick is used for this purpose, it is apt to be caught
and thrown around by the machinery, unless it is used in exactly
the right way.
It has been customary to bring dynamos to full speed before
the brushes are lowered into contact with the commutator ; but
78 HANDBOOK ON ENGINEERING.
this is not necessary, provided the dynamo is not allowed to turn
backwards, which sometimes occurs from carelessness in starting,
and might injure copper brushes by causing them to catch in the
commutator. If the brushes are put in contact before starting,
they can be more easily and perfectly adjusted and the e.m.f .
will come up slowly, so that any fault or difficulty will develop
gradually and can be corrected ; or the machine can be stopped,
before any injury is done to it or to the system. In fact, if the
machine is working alone on a system, and is absolutely free from
any danger of short-circuiting any other machine or storage bat-
tery on the same circuit, it may be started while connected to the
circuit, but not otherwise. If there are a large number of lamps
connected in the circuit, the field magnetism and voltage might
not be able to " build up " until the line is disconnected an
instant.
If one dynamo is to be connected with another, or to a circuit
having other dynamos or a storage battery working upon it, the
greatest care should be taken. This coupling together of
dynamos can be done perfectly, however, if the correct method is
followed, but is likely to cause serious trouble if any mistake is
made.
SWITCHING DYNAHOS INTO CIRCUIT.
Two or more machines are often connected to a common cir-
cuit. This is especially the case in large buildings where the
number of lamps required to be fed varies so much that one
dynamo may be sufficient for certain hours, but two, three or
more machines may be required at other times. The various
ways in which this is done depending upon the character of the
machines and of the circuit and the precautions necessary in
each case make this a most important and interesting subject,
which requires careful consideration.
Dynamos may be connected together either in parallel (mul-
tiple arc) or in series.
HANDBOOK ON ENGINEERING. 79
DYNAMOS IN PARALLEL.
In this case the + terminals are connected together or to the
same line, and the — terminals are connected together or to the
other line. The currents (i. e. amperes) of the machines are
thereby added, but the e.m.f . (volts) are not increased. The
chief condition for the running of dynamos in parallel is that
their voltages shall be equal, but their current capacities may be
different. For example : A dynamo producing 10 amperes may
be connected to another generating 100 amperes, provided the
voltages agree. Parallel working is, therefore, suited to constant
potential circuits. A dynamo to be connected in parallel with
others or with a storage battery, must first be brought up to its
proper speed, e.m.f., and other working conditions, otherwise,
it will short-circuit the system, and probably burn out its
armature. Its field magnetism must, therefore, be at full
strength, owing to the fact that it generates no e.m.f. with
no field magnetism. Hence, it is "well to find whether the pole
pieces are strongly magnetized by testing them with a piece of
iron, and to make sure of the proper working of the machine in
all other respects before connecting the armature to the circuit.
It is a common accident for the field-circuit to be open at some
point, and thus cause very serious results. In fact, a dynamo
should not be connected to a circuit in parallel with others until
its voltage has been tested and found to be equal to, or slightly
(not over 1 or 2 per cent) greater than that of the circuit. If the
voltage of the dynamo is less than that of the circuit, the current
will flow back into the dynamo and cause it to be run as a motor.
The direction of rotation is the same, however, if it is shunt-
wound, and no great harm results from a slight difference of
potential. But a compound-wound machine requires more careful
handling.
80 HANDBOOK ON ENGINEERING.
DIRECTIONS FOR RUNNING DYNAMOS AND MOTORS.
In the case of a machine which has not been run before, or
has been changed in any way, it is of course wise to watch it
closely at first. It is also well to give the bearings of a new
machine plenty of oil at first, but not enough to run on the arma-
ture, commutator or any part that would be injured by it, and
to run the belt rather slack until the bearings and belt have got-
ten into easy working condition. If possible a new machine
should be run without load or with a light one for an hour or
two, or several hours in the case of a large machine ; and it is
always wrong to start a new machine with its full load, or even a
large fraction of it.
This is true even if the machine has been fully tested by its
manufacturer and is in perfect condition, because there may be
some fault in setting it up, or some other circumstance which
would cause trouble. All machinery requires some adjust-
ment and care for a certain time to get it into smooth working
order.
When this condition is reached, the only attention required
is to supply oil when needed, keep the machine clean and see
that it is not overloaded. A dynamo requires that its voltage or
current should be observed and regulated if it varies. The per-
son in charge should always be ready and sure to detect the
beginning of any trouble, such as sparking, the heating of any
part of the machine, noise, abnormally high or low speed, etc. ;
before any injury is caused, and to overcome it by following
directions given elsewhere. Those directions should be pretty
thoroughly committed to mind, in order to facilitate the prompt
detection and remedy of any trouble when it suddenly occurs, as
is apt to be the case. If possible, the machine should be shut
HANDBOOK ON ENGINEERING.
81
down instantly when any trouble or indication of one appears, in
order to avoid injury and give time for examination.
Keep all tools or pieces of iron or steel away from the machine
while running, as they might be drawn in by the magnetism, and
perhaps get between the armature and pole-pieces and ruin the
machine. For this reason, use a zinc, brass or copper oil-can
instead of iron or " tin " (tinned iron).
Particular attention and care should be given to the commu-
tator and brushes to see that the former keeps perfectly smooth
and that the latter are in proper adjustment. (See Sparking).
Never lift a brush while the machine is delivering current,
unless there are one or more other brushes on the same side to
carry the current, as the spark might make a bad burnt spot on
the commutator.
Touch the bearing's and field-coils occasionally to see that
they are not hot. To determine whether the armature is running
hot, place the hand in the current of air thrown out from it by
centrifugal force.
Special care should be observed by any one who runs a dynamo
or motor to avoid overloading it, because this is the cause of most
of the troubles which occur.
BATTERIES.
Name of Cell.
E.M.F.
Material in Plates.
Electrolyte.
Bunsen . .
1.95
Zinc.
Carbon.
Nitric and Sulphuric Acid.
Grove .
1.93
«
ft
a it tt {t
Gravity . .
LOG
a
Copper.
( Copper Sulphate.
\ Zinc "
Leclanche
1.45
<(
Carbon.
Sal Ammoniac.
Dry Cell . .
1.49
tt
f<
Sal Ammoniac Paste.
EdisonLelande
0.9
u
CopperOxide
Caustic Potash.
Lead Storage .
1.98
Lead.
Lead.
Sulphuric Acid.
-32 HANDBOOK ON ENGINEERING.
CHAPTER VIII.
WHY COMMUTATOR BRUSHES SPARK AND WHY THEY DO
NOT SPARK.
A long list of reasons might be given why commutator brushes
spark, and why they do not spark, but by such a procedure no
light would ,be thrown on the subject, because the reasons would
not be understood unless fully explained. It is preferable to
explain the subject and let the reader tabulate the reasons after
digesting the explanation of the principles involved.
Whenever an electric current is interrupted, a spark is pro-
duced and it makes no difference how the current is generated,
or what kind of a conductor it is flowing through. To break
a current without a spark is not a possibility; hence, if we
desire to open a circuit without producing a spark, the only way
to accomplish the result is by killing the current before the
circuit is opened. The brushes resting on the commutator of a
motor or a generator have to transmit to the armature and take
away from it the current that is generated, in the case of a
generator, or the current that drives the machine in the case of a
motor. If the brushes were made so narrow that they could only
make contact with one commutator segment at a time, it would
be impossible to run the machine without producing very destruc-
tive sparks. Commutators, however, are not made in this way.
The insulation between the segments is narrow, and the brushes
are wide enough to be always in contact with two segments, and
part of the time with three. Suppose that the proportions are
such that during most of the time the brush only touches two
HANDBOOK ON ENGINEERING. 83
segments, as shown in Fig. 92. With these proportions it will be
seen, that so long as there are two segments in contact with each
brush, it is a possibility \>r the current to be diverted through
one of them only. Suppose that at the instant when the forward
segment is passing from under the brush, all the current flows
through the rear segment ; then it is quite evident that the first-
named segment will break away from contact with the brush with-
out making a spark, for there will be no current flowing from it
to the brush.
All the foregoing: is self-evident, but it will be suggested that
although the brush can break away from the front segment with-
out producing a spark, it cannot do the same thing with the rear
segment, for all the current is flowing through this one. While
it is true that when the forward segment passed from under the
brush all the current was flowing through the rear segment, it is
not true that the current continues to follow this path. As soon
as the front segment passes from under the brush, the rear one
becomes the forward segment, and while it is advancing to the
point where it must pass from under the brush, the current can
be transferred to the next segment back of it which now plays
the part of rear segment. Thus we see that to be able to run a
machine without producing sparks at the commutator, all we have
to do is to provide means whereby the current is transferred from
one segment to the one back of it as the commutator revolves, so
that when the segments pass from under the brush there is no
current flowing through them. This result is accomplished more
or less perfectly in all machines, made by responsible firms.
There are machines on the market that have been designed by
men who are not well enough posted in the principles of electrical
science to obtain proper proportions, and these are not propor-
tioned so as to shift the current from the forward to the rear
segment as fast as the machine revolves ; such machines always
produce more or less serious sparking.
84 HANDBOOK ON ENGINEERING.
If a machine is accurately made and the armature coils and
commutator segments are properly spaced and sufficient in num-
ber, it is possible to get the brushes so there will be little or no
spark at a given load ; but if the current strength be increased or
reduced, the sparks will appear, and the more the current is
changed the larger the sparks will be, the increasing current
producing the greatest sparking.
The way in which the current is shifted from the front to the
rear segment will be explained in connection with Fig. 92. In this
figure, A represents a portion of the core of a ring armature.
The shaft upon which it is mounted is shown at D, and P N are
the corners of the poles between which it rotates. The small
blocks C represent a portion of the commutator segments, which
we have placed outside of the armature, so as to make the diagram
as simple as possible. For the same reason we have shown the
armature coils as made of two turns of wire each. The line F
divides the space between the ends of the poles into two equal
parts, and the line E divides the armature into two halves
on which the directions of the induced currents is opposite. In
all the coils to the right of line E the currents are induced in
a direction away from the shaft, and in all the coils to the left
of line E the currents flow toward the shaft, all of which is
clearly indicated by the arrow heads placed upon the lines repre-
senting the coils. The outline B represents the end of one of the
brushes, and from the direction in which it is inclined it will be
understood that the armature revolves in a direction counter to
that of the hands of a clock.
When the armature is in the position shown, the current flow-
ing in the coils to the right of line E passes to segment &, and
thus reaches the brush, while the current flowing in the coils
to the left of line E reaches segment a, and through this passes
to the brush. As the brush rests upon segments a and b the
coil with which they connect is short-circuited, and therefore a
HANDBOOK ON ENGINEERING.
85
current can flow in it in any direction, or there may be no cur-
rent. To be able to run without spark, or to obtain perfect
commutation, as it is called, the current in this short-circuited
coil, when in the position shown, should be zero, or nearly so.
This coil, which is short-circuited by the brush, is called the corn-
mutated coil, or the coil undergoing commutation. It will be
noticed that this commutated coil is in a position just forward of
Fig. 02. Portion of core of ring armature.
the line E ; hence, the action of pole P will be to develop a
current in it that will flow in the same direction as the current
in the coils ahead of it, that is, in the coils to the left. Now if
this current flowed through the brush, it would be in a direction
contrary to that of the arrow at a; hence it would act to check
the current flowing from the front segment a to the brush, and
would divert it through the commutated coil to the rear segment
86 HANDBOOK ON ENGINEERING.
b. If the action of pole P upon the commutated coil is sufficiently
vigorous, the current developed in it will be as strong as the cur-
rent in the coils ahead of it, by the time the end of the segment
is about to break away from the brush ; and this being the case
there will be no current from segment a to the brush, and conse-
quently, no spark. If the action of pole P is not strong enough,
then there will be a small current from segment a to the brush
when they separate, and as a result, a small spark. If the action
of pole P on the commutated coil is too vigorous, then the current
developed in it will be too great, and it will not only divert all
the current coming from the forward coils, through the commuta-
ted coil to segment &, but in addition will develop a local current
that will circulate through the end of the brush, and, therefore,
when the separation occurs, there will be a current flowing from
the brush to the front segment, and consequently a spark.
If the commutated coil were placed astride of line E, the
action of pole P upon it would be no greater than that of pole N, so
that no current would be developed in it while undergoing com-
mutation. The farther the coil is in advance of line J£, when short-
circuited by the brush, the stronger the action of pole P upon it ;
therefore, the strength of the current developed in the commutated
coil can be increased by moving the brush farther away from pole P.
Hence, by trial, a point can be found where the current developed
will be just sufficient for the purpose and no more. This is true,
supposing the current developed by the armature to remain con-
stant, but, if it varies, the current in the commutated coil will be
either too great or too small. If, when the brushes are set, the
armature is delivering a current of, say, twenty amperes, then the
current flowing through the coils to the left of the brush will be
ten amperes, and the current in the commutated coil will also be
ten amperes. If the armature current increases to forty amperes,
the current in the forward coils will be twenty amperes, and as that
in: the commutated coils will still be ten amperes, it will have only
HANDBOOK ON ENGINEERING. 87
one-half the strength required for perfect commutation. In prac-
tice, however, it is found that if the commutator have a sufficient
number of segments, and the proportions of the machine are such
that the line E remains practically in the same position for all
strengths of armature current, then, if the brushes are set so as to
run sparkless with an average load, they will run so nearly spark-
less with a heavy or light load as to make it difficult to detect the
difference.
Even when a machine is properly proportioned, the brushes
may spark badly if they are not set in the proper position and
with the proper tension. If the tension is not right, they will
spark no matter where they are set. If the tension is too light,
they will spark, because they will chatter and thus jump off the
surface of the commutator. If the tension is too great, they will
spark because they will cut the commutator, and then the latter
will act as a file or grindstone and cut away particles from the
brushes, and these will conduct the current from segment to seg-
ment, as well as from the segment to the brush. Whenever a com-
mutator is seen to be covered with fine sparks, some of which run
all the way around the circle, it may be depended upon that the
surface is rough, due in most cases to too much pressure on the
brushes, and the remedy is to smoothitup and reduce the tension
and set the brushes where they will run with the smallest spark.
When the brushes begin to spark they rarely cure themselves and
the longer they are allowed to run with a heavy spark the worse
they will get.
Of all the troubles which may occur, sparking is the only one
which is very different in the different types of machines. In
some its occurrence is practically impossible. In others, it may
result from a number of causes. The following cases of sparking
apply to nearly all machines, and they cover closed-coil dynamos
and motors completely.
Cause J* — Brushes not set at the neutral point.
88 HANDBOOK ON ENGINEERING.
Symptom* — Sparking, varied by shifting the brushes with
rocker-arm.
Remedy* — Carefully shift brushes backwards or forwards
until sparking is reduced to a minimum.
The usual position for brushes in two-pole machines is
opposite the spaces between the pole-pieces.
Cause 2* — Commutator rough, eccentric, or has one or more
" high bars " projecting beyond the others, or one or more flat
bars, commonly called " flats," or projecting mica, any one of
which causes brush to vibrate, or to be actually thrown out of
contact with commutator.
Symptom* — Note whether there is a glaze or polish on the
commutator, which shows smooth working ; touch revolving com-
mutator with tip of finger-nail, and the least roughness is
perceptible, or feel of brushes, to see if there is any jar. If the
machine runs at high-voltage (over 250), the commutator or
brushes should be touched with a small stick or quill to avoid
danger of shock. In the case of an eccentric commutator, careful
examination shows a rise and fall of the brush when commutator
turns slowly, or a chattering of brush when running fast.
Remedy* — Smooth the commutator with a fine file or fine sand-
paper, which should be applied by a block of wood which exactly
fits the commutator (in latter case, be careful to remove any sand
remaining afterward ; and never use emery) . If bearing is loose
put in new one. If commutator is very rough or eccentric, it
should be taken out and turned off.
Cause 3* — Brushes make poor contact with commutator.
Symptom* — Close examination shows that brushes touch only
at one corner, or only in front or behind, or there is dirt on sur-
face of contact. Sometimes, owing to the presence of too much
oil or from other cause, the brushes and commutator become very
dirty and covered with smut. They should then be carefully
cleaned by wiping with oily rag or benzine, or by similar means.
HANDBOOK ON ENGINEERING. 89
Occasionally a " glass-hard " carbon brush is met with. It
is incapable of wearing to a good seat or contact and will only
touch in one or two points, and should be discarded.
Remedy* — File, bend, adjust or clean brushes until they rest
evenly on commutator, with considerable surface of contact and
with sure but light pressure.
It sometimes happens that the brushes make poor contact,
because the brush-holders do not turn or work freely.
Cause 4* — Short-circuited coil in armature or reversed coil.
Symptom* — A motor will draw excessive current, even when
running free without load. A dynamo will require considerable
power even without any load.
The short-circuited coil is heated much more than the others,
and is very apt to be burnt out entirely ; therefore, stop machine
immediately. If necessary to run machine to locate the short-
circuit, one or two minutes is long enough, but it may be re-
peated until the short-circuited coil is found by feeling the arma-
ture all over.
An iron screw-driver or other tool held between the field-
magnets near the revolving armature vibrates very perceptibly
as the short-circuited coil passes. Almost any armature, par-
ticularly one with teeth, will cause a slight but rapid vibration of
a piece of iron held near it, but a short-circuit produces a
much stronger effect only once per revolution.
The current pulsates and torque is unequal at different parts
of a revolution, these being particularly noticeable when arma-
ture turns rather slowly. If a large portion of the armature is
short-circuited, the heating is distributed and harder to locate.
In this case a motor runs very slowly, giving little power, but
having full-field magnetism.
Remedy* — A short circuit is often caused by a piece of solder
or other metal getting between the commutator bars or their con-
nections with the armature, and sometimes the insulation between
90 HANDBOOK ON ENGINEERING.
or at the ends of these bars is bridged over by a particle of metal.
In any such case the trouble is easily found and corrected. If,
however, the short-circuit is in the coil itself, the only real cure is
to rewind the coil.
One or more ' ' grounds ' ' in the armature may produce effects
similar to those arising from a short circuit.
Cause 5* — Broken circuit in armature.
Symptom* — Commutator flashes violently while running, and
commutator-bar nearest the break is badly cut and burnt ; but in
this case no particular armature coil will be heated, as in the last
case and the flashing will be very much worse, even when turn-
ing slowly. This trouble, which might also be confounded
with a bad case of " high- bar " or eccentricity in commutator
(sparking), is distinguished from it by slowly turning the arma-
ture, when violent flashing will continue if circuit is broken,
but not with eccentric commutator or even with " high bar."
Remedy* — The trouble is often found where the armature
wires connect with the commutator and not in the coil itself, and
the break may be repaired or the loose wire may be resoldered or
screwed back in place. If the trouble is due to a broken com-
mutator connection and it cannot be fixed, then connect the dis-
connected bar to the next by solder, or " stagger " the brushes ;
that is, put one a little forward and the other back so as to bridge
over the break. If the break is in the coil itself, rewinding is
generally the only cure.
Cause 6* — Weak field-magnetism.
Symptom* — Any considerable vibration is almost sure to pro-
duce sparking, of which it is a common cause. This sparking
may be reduced by increasing the pressure of the brushes on the
commutator, but the vibration itself should be overcome by the
remedies referred to above.
Cause 7* — Chatter of Brushes. The commutator sometimes
HANDBOOK ON ENGINEERING. 91
becomes sticky when carbon brushes are used, causing friction,
which throws the brushes into rapid vibration as the commutator
revolves, similarly to the action of a violin-bow.
Symptom* — Slight tingling or jarring is felt in brushes.
Remedy* — Clean commutator and oil slightly. This stops it
at once.
NOISE.
Cause 8* — Vibration due to armature or pulley being out of
balance.
Symptom* — Strong vibration felt when the hand is placed
upon the machine while it is running. Vibration changes greatly
if speed is changed.
Remedy* — The easiest method of finding in which direction
the armature is out of balance is to take it out and rest the shaft
on two parallel and horizontal A-shaped metallic tracks suffici-
ently far apart to allow the armature to go between them. If the
armature is then slowly rolled back and forth, the heavy side will
tend to turn downward. The armature and pulley should always
be balanced separately. An excess of weight on one side of the
pulley and an equal excess of weight on the opposite side of the
armature will not produce a balance while running, though it^
does when standing still ; on the contrary, it will give the shaft
a strong tendency to "wobble." A perfect balance is only
obtained when the weights are directly opposite, i. e., in the
same line perpendicular to the shaft.
Cause 9* — Armature strikes or rubs against pole pieces.
Symptom* — Easily detected by placing the ear near the pole-
pieces, or by examining armature to see if its surface is abraded
at any point, or by examining each part of the space between
armature and field, as armature is slowly revolved, to see if any
92 HANDBOOK ON ENGINEERING.
portion of it touches or is so close as to be likely to touch when
the machine is running. Or turn armature by hand when no
current is on, and note if it sticks at any point.
Remedy. — Bind down any wire, or other part of the armature
that may project abnormally, or file out the pole-pieces where the
armature strikes, or center the armature so that there is a uni-
form clearance between it and the pole-pieces at all points.
Cause JO* — Singing or hissing of brushes. This is usually
occasioned by rough or sticky commutator, or by tips of brushes
not being smooth, or the layers of a copper brush not being held
together and in place. With carbon brushes, hissing will be caused
by the use of carbon which is gritty or too hard. Vertical carbon
brushes, or brushes inclined against the direction of rotation, are
apt to squeak or sing. A new machine will sometimes make
noise from rough commutator, no matter how carefully it is
turned off, because the difference in hardness between mica and
copper causes the cut of the tool to vary, thus forming inequali-
ties which are very minute, but enough to make noise. This
can be best smoothed by running.
Remedy* — Apply a very little oil or vaseline to the com-
mutator with the finger or a rag. Adjust the brushes or smooth
the commutator. Carbon brushes are apt to squeak in starting
up, or at slow speed. This decreases at full speed, and can
usually be reduced by moistening the brush with oil, care being
taken not to have a ay drops, or excess of oil. Shortening or
lengthening the brushes sometimes stops the noise. Run the
machine on open circuit until commutator and brushes are
worn smooth.
For alternating current machinery and principles of alternating
current see page 815.
HANDBOOK ON ENGINEERING. 93
HEATING IN DYNAHO OR MOTOR.
General Instructions* — The degree of heat that is injurious or
objectionable in any part of a dynamo or motor is easily deter-
mined by feeling the various parts. If the heat is bearable for a
few moments, it is entirely harmless. But if the heat is unbear-
able for more than a few seconds, the safe limit of temperature
has been passed, except in the case of commutators in which
solder is not used ; and it should be reduced in some of the ways
that are given above. In testing with the hand, allowance should
always be made for the fact that bare metal feels much hotter
than cotton, etc. If the heat has become so great as to produce
an odor or smoke, the safe limit has been far exceeded and the
current should be shut off and the machine stopped immediately,
as this indicates a serious trouble, such as a short-circuited coil or
a tight bearing. The machine should not again be started until
the cause of the trouble has been found and positively overcome.
Of course neither water nor ice should ever be used to cool elec-
trical machinery, except possibly the bearings of large machines,
where it can be applied without danger of wetting the other
parts.
Feeling for heat will answer in ordinary cases, but of course,
the sensitiveness of the hand differs, and it makes a very great
difference whether the surface is a good or bad conductor of heat.
The back of the hand is more sensitive and less variable than the
palm for this test. But for accurate results a thermometer
should be applied and covered with waste or cloth to keep in
the heat. In proper working the temperature of no parts of
the machine should rise more than 45° C., or 81° F. above the tem-
perature of the surrounding air. If the actual temperature of
94 HANDBOOK ON ENGINEERING.
the machine is near the boiling point, 100° C., or 212° F., it is
seriously high.
It is very important in all cases of heating to locate correctly
the source of heat in the exact part in which it is produced. It
./s a common mistake to suppose that any part of a machine which
is found to be hot is the seat of the trouble. A hot bearing may
cause the avmature or commutator to heat or vice versa. In
every case, all parts of the machine should be felt to find which
is the hottest, since heat generated in one part is rapidly diffused
throughout the entire machine. It is generally much surer and
easier in the end to make observations for heating by starting
with the whole machine perfectly cool, which is done by letting it
stand for one or more hours or over night, before making the
examination. When ready to try it, run it fast for three to five
minutes, with the field magnets charged ; then stop, and feel all
parts immediately. The heat will be found in the right place, as
it will not have had time to diffuse from the heated to the cool
parts of the machine. Whereas, after the machine has run some
time, any heating effect will spread until all parts are equal in
temperature, and it will then be almost impossible to locate the
trouble.
Excessive heating of commutator, armature, field magnets, or
bearings may occur in any type of dynamo or motor, but it can
almost always be avoided by proper care and working conditions.
THE EFFECT OF THE DISPLACEHENT OF THE ARMATURE.
If a machine is old, it is more than likely the shaft will be
found out of center, and if this fact is discovered at a time when
things are not working as they should, it is taken for granted this
is the cause of the trouble. What is true of shafts out of the
HANDBOOK ON ENGINEERING.
95
center is true of several other things that are liable to get out of
place. For the present it will be sufficient to investigate just
what effect the displacement of the shaft can have.
Fig1* 93 illustrates an armature of a two-pole machine which is
out of center in one direction, and Fig. 94 shows another two-pole
armature out of center in a direction at right angles to that
shown in the first figure. The condition shown in Fig. 93 could
be produced by a heavy armature running in rather light bear-
ings for several years, and the side displacement of Fig.94could
be produced by the tension of an extra tight belt. The mechan-
Figs. 93 and 94. Showing armature out of center.
ical effect of both these conditions would be to increase the pres-
sure on the bearings, as the part a of the armature would be
drawn toward the poles of the field with greater force than the
opposite side. The downward pull, due to the attraction of the
magnetism, would be greater in Fig. 9 3 than the side pull in Fig.
9 4 supposing both armatures and fields to be the same in both
cases, and the displacement of the shafts equal. This difference
is due to the fact that in Fig. 93 the magnetism of both poles is
concentrated at the lower corners on account of the shorter air
gap ; hence both sides pull much harder on the lower side. In
^(5 HANDBOOK ON ENGINEERING.
Fig. 94 the pull of the N pole is greater than that of the other,
simply because in the latter the magnetism is more dispersed, but
the difference in the density on the two sides will not be very
great. If the bearings of a machine, with the armature dis-
placed, as indicated, have shown any signs of cutting, or if they
run unusually warm, their condition will be improved by putting
in new bearings that will bring the shaft central.
If the armature is of the drum type, the displacement of the
shaft will have no effect upon it electrically. This is owing to the
fact that all the armature coils are wound from one side of
the core to the other, and, therefore, at all times, every
coil has one side under the influence of one pole and the other
side under the influence of the opposite pole, and if one
side is acted upon strongly by one pole, it will be acted
upon feebly by the other. If the armature is of the ring type,
then the displacement of the shaft will affect it electrically, for
in a ring armature, the coils on one side are acted upon by
the pole on that side, only, and as the magnetic field from one
pole will be stronger than that from the other (that is, considering
the action upon equal halves of the armature) , the voltage devel-
oped in the coils on one side of the armature will be greater than
that developed on the other side.
The effect of the disturbance of the electrical balance will be
that the brushes will spark badly, because the voltage of the cur-
rent generated on one side of the armature will be greater than
that of the current on the other side. Hence, when these two
currents meet at the brushes, the strong one will tend to drive
the weak one backward. If, while the armature is out of center,
we wish to adjust the brushes so as to get rid of the excessive
sparking, all we have to do is to set them to the right of the cen-
ter line, as in Fig. 94 so that the wire on the left side will cover a
greater portion of the circumference than the right.
.
HANDBOOK ON ENGINEERING. 97
In a multipolar machine, the displacement of the armature
will have the same effect mechanically as in the two-pole type ;
nmltipolar armatures are connected in two different ways, one of
which is called the wave or series winding, and the other the lap
or parallel winding. In the first named type of winding, the
ends of all the coils on the armature are connected with each
other and with the commutator segments in such, a manner that
there are only two paths through the wire for the current ; there-
fore, these two armature currents pass under all the poles and
the voltage of each current is the combined effect of all the poles.
From this very fact, it can be clearly seen that it makes no
difference what the distance between the several poles and arma-
ture may be, for if some are nearer than the others, the only
effect will be that these poles will not develop their share of the
total voltage, but whatever their action may be, it will be the
same on the coils in both circuits.
When a multipolar armature is connected so as to form a
parallel or lap winding, then the connections between the coil
ends, and between these ends and the commutator segments, are
such that as many paths are provided for the current as there are
poles, and each one of these paths is located under one pole, and
as a consequence, the voltage developed in it is proportional to
the action of this pole. The diagram Fig. 95 illustrates a six-pole
armature with the ends of the field poles, and the arrows a a, b 6,
c c, indicate the six separate divisions of the coils in which the
branch currents are developed. Now, it can be clearly seen that
as the armature is nearer to the lower poles than to any of the
others, the action of these will be the strongest. Hence, the cur-
rents a a will be stronger than the others and will have a higher
voltage.
The two upper currents are weaker than the side ones and
7
98
HANDBOOK ON ENGINEERING.
their voltage is also lower, so that, the current returning to the
commutator through the brushes at the upper corners, will not
divide equally, but the larger portion will be drawn into the coils
on the side ; and as the upper coils will have to fight to hold their
own, so to speak, there will be a disturbance of the balance that
Fig. 95* Diagram of six-pole armature.
is re-quired for smooth running. The result will be heavy spark-
ing at these brushes. In the great majority of cases, if the brushes
of a multipolar machine spark on account of the armature being
out of center, the only cure is to reset the bearings, if they are
adjustable, and if they are not, to put in new ones.
HANDBOOK ON ENGINEERING.
99
Table of Carrying Capacity of Wires* — Below is a table which
must be followed in placing interior conductors, showing the
allowable carrying capacity of wires and cables of ninety-eight
per cent conductivity, according to the standard adopted by the
American Institute of Electrical Engineers.
TABLE A.
TABLE B.
Rubber-Covered
Weatherproof
Wires.
Wires.
B. A S. G.
Amperes.
Amperes.
Circular Mile.
18
3
5
1,624
16
6
8
2,583
14
12
16
4,107
12
17
23
6,530
10
24
32
10,380
8
33
46
16,510
6
46
65
26,250
5
54
77
33,100
4
65
92
41,740
3
76
110
52,630
2
90
131
66,370
1
107
156
83,690
0
127
185
105,500
00
150
220
133,100
000
177
262
167,800
0000
210
312
211,600
Circular MJls
200,000
200
300
300,000
270
400
400,000
330
500
500,000
390
590
600,000
450
680
700,000
500
760
800.000
550
840
90u,000
600
920
100 HANDBOOK ON ENGINEERING.
TABLE A.
TABLE B.
Rubber-Covered
Weatherproof
Wires.
Wires.
Circular Mile.
Amperes.
Amperes.
1,000,000
650
1,000
1,100,000
690
1,080
1,200,000
730
1,150
1,300,000
770
1,220
1,400,000
810
1,290
1,500,000
850
1,360
1,600,000
890
1,430
1,700,000
940
1,490
1,800,000
970
1,550
1,900,000
1,010
17610
2,000,000
1,050
1,670
The lower limit is specified for rubber-covered wires to pre=
vent gradual deterioration of the high insulations by the heat
of the wires, but not from fear of igniting the insulation, The
question of drop is not taken into consideration in the above
tables.
Insulation Resistance* — The wiring in any public building
must test free from grounds ; i. e., the complete installation must
have an insulation between conductors and between all conduc-
tors and the ground (not including attachments, sockets, recep-
tacles, etc.) of not less than the following: -
Up to 5 amperes, 4,000,000 Up to 200 amperes, 100,000
" 10 " 2,000,000 " 400 25,000
" 25 " 800,000 " 800 " 25,000
" 50 " 400,000 " 1,600 " 12,500
" 100 " 200,000
All cutouts and safety devices in place in the above.
Where lamp sockets, receptacles and electroliers, etc., are con-
nected, one-half of the above will be required.
HANDBOOK ON ENGINEERING. 101
Soldering Fluid* — a. The following formula for soldering
fluid is suggested : —
Saturated solution of zinc chloride, 5 parts.
Alcohol, 4 parts.
Glycerine, 1 part.
Bell or Other Wires* — a. Shall never be run in same duct
with lighting or power wires.
Table of Capacity of Wires. —
a~
CO 02
*<*
PQ
19
1,288
0
fc
Vr— i
M
QQ
18
1,624
...
...
3
17
2,048
...
...
0..
16
2,583
...
...
6
15
3,257
...
...
...
14
4,107
...
...
12
12
6,530 .
...
...
17
...
9,016
7
19
21
.0.
11,368
7
18
25
...
14,336
7
17
30
0..
18,081
7
16
35
...
22,799
7
15
40
...
30,856
19
18
50
..0
38,912
19
17
60
..«
49,077
19
16
70
..0
60,088
37
18
85
...
75,776
37
17
100
..0
99,064
61
18
120
.0.
124,928
61
17
145
...
157,563
61
16
170
102
HANDBOOK ON ENGINEERING.
8
8,
198,677 61 15 200
250,527 61 14 235
296,387 91 15 270
373,737 91 14 320
413,639 127 15 340
When greater conducting area than that of B. & S. G. is re-
quired, the conductor shall be stranded in a series of 7, 19, 37,
61, 91 or 127 wires, as may be required; the strand consisting
of one central wire, the remainder laid around it concentrically,
each layer to be twisted in the opposite direction from the pre-
ceding.
TABLE SHOWING THE SIZE OF WIRE OF DIFFERENT METALS THAT
WILL BE MELTED BY CURRENTS OF VARIOUS STRENGTHS.
Strength
of
Current
in
Amperes.
DIAMETER OF WIRE IN THOUSANDTHS OF AN INCH.
Copper.
Aluminum.
Platinum.
• German
Silver.
Iron.
Tin.
1
.002
.003
.003
.003
.005
.007
2
.003
.004
.005
.005
.008
.011
3
.004
.005
.007
.007
.010
.015
4
.005
.006
.008
.008
.012
.018
5
.006
.008
.010
.010
.014
.021
10
.009
.012
.016
.016
.022
.033
15
.013
.016
.020
.020
.028
.044
20
.015
.019
.025
.025
.034
.053
25
.018
.022
.029
.029
.040
.062
30
.020
.025
.032
.032
.045
.069
35
.022
.028
.036
.036
.050
.077
40
.025
.030
.039
.039
.055
.084
50
.027
.033
.042
.042
.059
.091
60
.029
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HANDBOOK ON ENGINEERING. 1Q3
CHAPTER IX.
ARC LIGHTING APPARATUS.
INSTRUCTIONS FOR INSTALLING AND OPERATING APPARA-
TUS FOR ARC LIGHTING.
Within the past few years the arc lighting industry has under-
gone a decided transformation, new systems of lighting, together
with new forms of lamps, generators and accessory apparatus,
having practically superceded the older types. In so far as the
manufacture of arc lighting apparatus is concerned, the new has
entirely replaced the old. The latter, however, is still to be
found in operation in many parts of the country, but is rapidly
being replaced.
In the early days of the electrical industry, arc lamps were of
the type now known as " Open arc, " and were connected in
series in circuits that were supplied with current from constant
current generators, commonly called u Arc dynamos. " In about
the year 1894, what is now known as the " Enclosed arc " lamps
came into use. These lamps found favor with incandescent
lighting stations, because they could be operated successfully on
their circuits, and were economical owing to the fact that the car-
bons would last from 100 to 150 hours, which is about twenty
times as long as they last in the open arc lamp.
The enclosed lamps did not meet with favor with the regular
arc lighting stations because to burn with a strong and steady
light, they must be adjusted for a much longer arc, and this
means a much higher voltage, consequently a smaller number of
lamps on the circuit. It can readily be seen that no matter what
the advantages offered by the enclosed lamp might be, they
104 HANDBOOK ON ENGINEERING.
would not impress an arc light station manager favorably when he
found that to make them operate well he would have to reduce
the number of lamps on a 65 light circuit to 45 or 50. Owing to
this fact, the enclosed lamps were confined exclusively to the Ed-
ison incandescent light circuits in the beginning of their career.
Soon thereafter, however, they began to be used on alternating
current incandescent lighting circuits. Next they found their
way onto power circuits, and at about the same time " Arc
lighting " transformers were devised, by means of which lamps
could be run in series, with alternating currents, in precisely the
same way as the old open arc lamps were run from arc dynamos.
This latter system, using " Arc lighting *' transformers, or regu-
lating transformers as they are commonly called, in connection
with the enclosed lamps, may truly be said to be the successor
of the original arc lighting system.
Many of the old time arc light dynamos that were wound for a
current of 6.6 amperes, to operate 1200 candle power lamps are
now used to operate enclosed arc lamps of the nominal 2000
candle power, but the number of lamps in the circuit is reduced
to about two-thirds. Some of the 10 ampere dynamos have been
rewound so as to give a current of 6 amperes, with a correspond-
ingly increased voltage, and these also are used to operate en-
closed lamps. The manufacture of arc light generators has been
abandoned by nearly all the former makers, with the exception of
the Brush Company, in so far as we know. As the latter type of
arc generator is still made, and as many of these machines are in
use, and probably will be for years to come, it is thought advis-
able to describe it briefly herein.
The latest type of brush arc generator is shown in Fig. 96. This
illustration also shows the way in which the lamp circuits are
arranged. As will be noticed there are four independent cir-
cuits, that are connected with the upper set of binding posts of
the connection board in the upper right hand corner of the figure.
HANDBOOK ON ENGINEERING.
105
The wires coming from the generator are connected with the lower
set of binding posts of the connection board. By means of this
Fig. 96. Multiple Circuit Brush Arc Lighting Generator.
arrangement, it is possible, as can be easily seen, to connect any
one of the generator circuits, with any one of the lamp circuits.
The generator is connected so as to feed current into four circuits,
that are connected with each other, but at the same time are in-
dependent. The object of dividing the current into four separate
circuits is to reduce the voltage on each one, not only to make it
safer, but also to reduce the strain on the insulation. The old 65
light brush machines fed current to open arc lamps that required
106 HANDBOOK ON ENGINEERING.
45 volts each, so that the total voltage of the machine was about
3000. The enclosed arc lamps now used require about 80 volts
each, so that to operate 65 on one circuit would require an e. m. f.
of about 5000 volts, which would bring so great a strain on the
insulation as to cause frequent disturbances, not to say anything
about the greater danger the men operating the apparatus would
be exposed to.
Fig. 97. Diagram Showing Arrangement of Circuits in Brash
Multiple Circuit Arc Lighting Generator.
The modern Brush generators of 100 light capacity, develop an
e. m. f. of about 8000 volts, but as this is divided among four
circuits, the e. m. f. acting on each one is only 2000 volts.
The way in which the Brush generator is wound so as to
supply four circuits, is easily explained. Looking at Fig. 96, it
will be seen that there are four separate pairs of commutator
HANDBOOK ON ENGINEERING. 107
rings, each one of which is made the same as the single pair used
on a single circuit machine. It will also be seen that the arma-
ture is wound with a large number of narrow coils, their actual
number being 32. If these coils were numbered 1234, 12
34, — 1 2 3 4, all the way around the circle, then if the connec-
tions were traced out, it would be found that all the No. 1 coils
are connected with one pair of commutator rings, ail the No. 2
coils with another pair of commutator rings, all the No. 3 coils
with the third set of rings, and all the No. 4 coils with the fourth
pair of commutator rings. This way of connecting the armature
coils with the commutator rings can be more fully understood
from the diagram Fig. 97, in which 1, 2, 3, 4, represent the four
sets of armature coils, and, A, JB, 0, Z>, represent the four lamp
circuits. In looking at this diagram it will be seen that although
the lamps are connected in four independent circuits, these cir-
cuits are not actually disconnected from each other, but are con-
nected through the several sets of armature coils. Thus the A
circuit, starts from the end of the No. 1 set of coils, and ends at
the entering end of No. 2 set of coils. Passing through this set
of coils the current enters the B lamp circuit, and thence passes
through the No. 3 armature coils, to the C lamp circuit, and
through the No. 4 armature coils to the D lamp circuit and thus
to the entering end of the No. 1 coils. The switches a b c d,
shown in Fig. 97, are the same as those seen on the switch board
mounted on the generator in Fig. 96, and are for the purpose of
cutting out any one of the lamp circuits if it is desired.
An arc light generator must be so arranged that it will keep
the strength of the current uniform, and vary the voltage in ac-
cordance with the number of lamps in operation . The enclosed
lamps require a current of about 6 amperes so that the generator
must be regulated so as to give this amount of current regard-
less of the number of lamps in operation. To accomplish this
result a regulator is used, which is secured to the base of the
108
HANDBOOK ON ENGINEERING.
generator directly under the commutator, as clearly shown in
Fig. 96. This regulator acts by varying the strength of the cur-
rent that passes through the field coils of the generator, and it
regulates the voltage in each one of the four lamp circuits owing
to the fact that these circuits are connected with each other
HANDBOOK ON ENGINEERING.
109
through the armature coils. Thus if there were five lamps burn-
ing in circuit A and five in circuit (7 while in circuit B the full
number of 25 were in operation, then the greater part of the volt-
age of coils 2 and 3 would act on the fully loaded circuit U,
while the small remaining portions would act on the lightly loaded
circuits A and C.
Fig. 99. Diagram Showing Position of Brushes on
Brash Generator.
An enlarged view of the regulator is shown in Fig. 98 at A,
and the way in which it operates is fully illustrated in the line
drawing B. In order that the operation of the regulator may be
fully understood it is necessary to say that the field coils of the
generator are connected in parallel with a resistance, and that the
action of the regulator is to reduce the resistance in the parallel
circuit, when the voltage of the generator is to be reduced, and
to increase this resistance when the voltage is to be increased. If
110 HANDBOOK ON ENGINEERING.
the resistance in the circuit, that is parallel with the field, is re-
duced, more current will pass through it, and, therefore, less cur-
rent will pass through the generator field coils hence the voltage
will be reduced. Increasing the resistance in the parallel circuit
will have the opposite effect. From diagram B, Fig. 98, it will
be seen that the regulator is driven from the generator shaft by
a belt, which rotates a small oil pump which draws oil from a
tank and forces it through a valve T, the ports of which are
never completely closed ; so that even when it is in the central
position oil can flow through. The valve is controlled by an
electro magnet F whose armature U moves lever II. The
strength of magnet F varies with the strength of the current gen-
erated. A spring G acts to pull lever H in the opposite direc-
tion from that in which the magnet acts, hence, the stronger the
latter the more the valve is raised, and the weaker it is the more
jPis pulled down by G. The tension of G is adjusted by a nut
R. This nut is adjusted so that the valve T is held in the cen-
tral position when the current is of the proper strength. If the
current becomes too strong magnet F pulls down U and raises T
thus forcing oil on the upper side of piston S and allowing it to
flow out from the under side. This action forces piston X around
clockwise. The shaft upon which X is mounted carries at its in-
ner end gearing that moves the rheostat lever A so as to reduce
the resistance and thus lower the field current, when the genera-
tor current drops below the normal, the reverse action takes
place, and resistance is cut in by the movement of A in the op-
posite direction. When A is rotated the gear Z swings the arm
N and thus the position of the commutator brushes is varied with
the strength of the field current, so as to automatically keep the
spark of the proper length, which should be about J" for light
load, to |" for full load.
In order that a Brush generator may run well it is necessary
that the brushes be properly set. The brushes should project
HANDBOOK ON ENGINEERING. Ill
from the holder about 5^", and all the sets should be in line.
They can be brought into line by setting those at one end first,
then rotate the rocker until the end of the brush is on a line with
the end of a copper segment, as shown in Fig. 99. Then set
the brush at the other end of the commutator so as to come in
line with the end of the copper segment, the same as the first
one. The other brushes can be brought into line by using
a hard wood straight edge. The two sets of brushes must be
placed 90 degrees apart, which can be accomplished by setting
them to the edges of the copper segments following each other,
as is clearly shown in Fig. 99.
The brushes should be set so that they bear on the commuta-
tor at the end and for a distance of about J" back. If they are
too long they will not bear t-t the end and will thus increase the
sparking, and if too short they will drop unto the commutator
slots and injure the copper tips.
The commutator should be cleaned off with fine sand paper
every day as soon after stopping as possible. To keep the seg-
ments all even and true, the sand paper can be placed around a
stick planed true and held against the commutator while it is
running. It is better to remove the brushes, when polishing the
commutator, and make sure that the current is open.
As the current of these machines is of very high voltage, they
must be handled with great care, to avoid injury. A rubber mat
should be provided for the attendant to stand upon, and no one
should ever touch any part of the machine if not standing on
rubber, or thoroughly dry wood, known by trial to be a safe in-
sulator. Only one hand should be used in handling any part of
the machine, unless it is not running. It is a good idea to use
rubber gloves when working around these machines.
HANDBOOK ON ENGINEERING.
CHAPTER X.
THE ALTERNATING CURRENT SERIES ARC LIGHTING
SYSTEM.
In alternating current arc lighting systems of the series type,
a special type of transformer is used, which is commonly called a
regulating transformer, or a constant current transformer. The
general principles^ and the operation of transformers is fully ex-
plained in the section on alternating currents. In this connection
it will be sufficient to say that in alternating current systems, the
currents sent out from the central station are of a much higher
voltage than is required to operate the lamps or other apparatus
in which the current is used. This high primary current voltage
is used so as to be able to transmit a large amount of energy with
wires of small size. At the receiving end of the line the current
is passed through transformers that generate secondary currents
of whatever voltage may be required. For the operation of in-
candescent lamps, motors and other devices, constant potential
currents are necessary ; that is, currents that keep the voltage
constant but change the strength, or amperes. For series arc
lighting it is necessary to have currents that are just the opposite
of this ; that is, the amperes remain constant, but the volts in-
crease and decrease as the number of lamps increase and de-
crease. A transformer acting in its natural way will develop a
constant potential secondary current ; therefore, to make it de-
velop a constant current with variable potential, it is necessary
to resort to mechanical means.
HANDBOOK ON ENGINEERING.
113
The way in which transformers are arranged so as to develop
constant currents is very simple as well as effective, it consists
Fig. 100. Constant Current Transformer for General Electric
Series Alternating Arc Lighting System.
merely in constructing the transformer so that one of the coils
may be moved close up or far away from the other. If the two
coils, primary and secondary, are close together, the effect of the
primary upon the secondary will be much greater than if they are
far apart ; hence, when close together the voltage generated in
the secondary will be high, and when far apart the voltage of the
secondary will be low. From this it will be seen that to make a
transformer so that it will regulate the voltage in proper propor-
tion for any number of lamps in the circuit, all that is necessary
is that the distance between the coils be varied in a manner to
agree with the variation in the number of lamps,
8
114
HANDBOOK ON ENGINEERING.
THE GENERAL ELECTRIC CONSTANT CURRENT
TRANSFORMER.
How the proper movement of the transformer coil is accomp-
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lished can be made clear by means of Fig. 100, which shows a
General Electric Regulating transformer with the outer casing re-
moved. Looking at this illustration it will be seen that there is a
rocking lever, which carries at one end a weight, while to the
other end the upper coil of the transformer is attached. The ob-
ject of the weight is to balance the coil so that a very small up-
ward force will move the latter upward. Generally, the lower,
stationary coil is the primary, and the upper, movable coil, is the
secondary, The currents flowing in these two coils repel each
other, in the same way that magnet poles of the same polarity re-
pel each other. If the current in the secondary becomes too
strong, the repelling force is increased, and the upper coil is
raised. The raising of this coil causes the current to reduce,
because the further apart the coils are the weaker the inductive
action of the primary upon the secondary. If the current in the
secondary becomes too weak the upward push will be reduced
and the coils will come closer together, and as a result the
secondary current will be increased. In either case the change in
the position of the secondary coil will have the effect of returning
the current in the secondary to the proper strength ; that is, if it
is too strong it will be reduced, and if it is too weak it will be in-
creased. The counterbalance weight is so proportioned that the
excess of weight in the movable coil is just enough to balance the
upward push of the current when the latter is of the proper
strength. This being the case, it can be seen that if the rocking
beam is mounted so as to swing freely, and the transformer is set
so that the coil will not rub against the iron core, the apparatus
will respond to very small changes in the strength of the current.
This apparatus, like a steam engine governor, can be made so as
to be sensitive, and if too sensitive, it will have a pumping ac-
tion, that is, the rocking beam will acquire a see-saw movement,
and the current will increase and decrease in time with the move-
ment, thus causing the lamps to bum unsteady The manufac-
116
HANDBOOK ON ENGINEERING.
turers, by actual trial adjust the weight to the point that will give
the closest regulation without causing a pumping action.
These regulating transformers are made in many sizes, the
General Electric Company make them from 6 to 100 lamp capac-
ity. The smaller sizes are constructed so as to be cooled by the
currents of air that naturally circulate through them. The larger
A B
Fig. 102. Front and Back Yiews of Switchboard Shown
in Diagram Fig. 101,
sizes are provided with a tight casing which is filled with oil,
this construction being used so as to cool off the coils more
thoroughly than they would be with air. If the transformer is of
the air cooled type, a dash pot is generally provided to prevent
the movable coil from moving too rapidly when a large number of
HANDBOOK ON ENGINEERING.
117
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HANDBOOK ON ENGINEERING.
lamps are cut in or out of the circuit at a time. The oil cooled
transformers do not require a dash pot because the oil retards
the movement of the coil.
From Fig. 101, the way in which a regulating transformer,
such as shown in Fig. 100, is connected with the primary circuit.
Fig. 104. Front, Back and Side Yiews of Switchboard
Shown in Diagram Fig. 108.
and with the lamp circuit, can be easily understood. At G is a
wiring diagram showing all the connections, and A and B show
in outline, the front and side view of the switchboard. As the
explanatory notes on these diagrams are complete, no further ex-
planation will be necessary.
HANDBOOK ON ENGINEERING.
119
Fig. 102 gives photographic views of the front and back of the
switchboard, respectively.
Fig. 105. Westinghouse Constant Current Transformer for
Series Alternating Arc Lighting.
Fig. 106. Front, Back and Side Views of Switchboard used with
Westinghouse Series Alternating Arc Lighting System.
120 HANDBOOK ON ENGINEERING.
The diagram (7, Fig. 101, shows the circuit connections for a
small size transformer feeding into a single lamp circuit, but
large transformers are commonly arranged so as to feed into two
lamp circuits. Fig. 103 shows the outline A, of the front, and
JB, of the side of a switchboard, for a large transformer feeding
into two lamp circuits, and the wiring diagram C. The front, side
and back of this switchboard are shown in Fig. 104.
THE WESTINQHOUSE CONSTANT CURRENT TRANSFORMER.
Fig. JOS is a photographic view of the regulating transformer
made by the Westinghouse Company. There is some difference
in the details of construction between this transformer, and the
one shown in Fig. 100, but the principle of action is the same.
In this design, there are two movable coils instead of one, and
the stationary coil is secured between them. The counterbalanc-
ing weights are connected with the movable coils through chains
that run over large sheaves, each coil being independently coun-
terbalanced, as it must be, for in this arrangement, when the
upper coil rises, the top one will move down. The two coils,
however, can be connected with separate lamp circuits, and then
each one will move according to the demands of its circuit, and
without reference to the movement of the other.
Fig. 106 is a photographic view of the front and back of the
Westinghouse switchboard, used in connection with the regulat-
ing transformers. The transformer Fig. 105, is of the oil cooled
type, and of 100 lamp capacity. With the air cooled transform-
ers this company provide a dash pot that is constructed with a
valve that retards the movement of the coils when they come to-
gether, more than when they separate, so that the current may
not increase in strength too rapidly.
REACTANCE COIL CONSTANT ALTERNATING CURRENT
REGULATORS.
The General Electric and the Westinghouse, regulating trans-
formers, are transformers arranged so as to generate a secondary
HANDBOOK ON ENGINEERING. 121
current of constant strength and variable voltage, by being so
constructed that the distance between the primary and sec-
ondary coils may be varied, being increased to lower the voltage
and reduced to increase it. There is another way in which a
constant secondary current can be obtained, and this consists in
using what is commonly called a choke coil or reactance coil, and
arranging this so that its choking effect may be varied automati-
cally as the voltage required varies. To make clear the action of
choking coils it will be necessary to say that when an alternating
current passes through a coil of wire, it reacts upon itself, that is,
it tends to generate a current flowing in the opposite direction.
It cannot generate such a current, but it can develop a back
pressure or e. m. f. and this will reduce the flow of current. If
the coil of wire is wound upon paper tube, the choking action
will be very much less than it will be if a core made of finely lam-
inated iron is inserted within the tube. With a little reflection it
can be seen that with this difference existing between the effect
of a core of iron and no core, the choking action can be varied
by providing an iron core that can be drawn in or out of the coil.
THE WESTERN ELECTRIC REGULATOR FOR CONSTANT
ALTERNATING CURRENTS.
The Western Electric Company make a regulator for series al-
ternating arc lighting that operates on the principle explained in
the foregoing. A side view of this regulator is shown in Fig.
107. The wire coil is suspended from one end of a rocking beam
which carries at its other end a counter-balancing weight. This
coil with the iron core and the side pieces constitutes what is
commonly called a solenoid magnet. Such magnets exert a pull
upon the iron core when a current passes through the coil, and
the magnitude of the pull increases with the strength of the cur-
rent. From this it will be seen that when current passes through
the coil of Fig. 107, the pull exerted draws it upward, the
122 HANDBOOK ON ENGINEERING.
stronger the current the higher the position to which the coil is
drawn. Now the choking action of the coil will increase as the
uoil is raised, because more of the iron core will be within it.
The choking action reduces the strength of the current ; there-
fore, as the coil is raised by the increased pull due to the in-
creased current, the choking action is increased, and the increase
in current strength is checked. By properly adjusting the
•
Fig. 107. Western Electric Regulator for Constant Current
Series Alternating Arc Lighting System.
counterbalancing weight, the apparatus can be made so that a
very small increase in current strength will move the coil up to
its highest position, and as it only requires a small movement of
the coil to effect a considerable change in the strength of the cur-
rent, it can be seen that the regulating action can be made very
accurate. It is said that these regulators will respond to a vari-
ation of one-tenth of an ampere in the current strength, when
Carefully adjusted.
HANDBOOK ON ENGINEERING. 123
THE ADAMS-BEGNALL REGULATOR FOR CONSTANT
ALTERNATING CURRENTS.
Fig> 108 shows another choke coil regulator made by the
Adams-Begnall Electric Company. Comparing this illustration
with Fig. 107 it will be seen that while the principle of operation
is the same, there is a considerable difference in the design. An
important feature about this regulator is the arrangement of the
dash pot. It is found in practice that the retarding action of the
Fig. 108. Adams-Begnall Regulator for Constant Current
Series Alternating Arc Lighting Systems.
dash pot is not required to correct small changes in the strength
of current, because such changes are corrected by a very small
movement of the coil, so that in such cases the dash pot is really
objectionable. When, however, a large number of lamps are
cut in or out of the circuit at one time, there is a tendency to
greatly increase or decrease the current, and then the coil must
124 HANDBOOK ON ENGINEERING.
move over a considerable distance to keep the current constant.
If the coil moves over a long distance it will acquire a velocity
that will carry it beyond the mark, and thus over regulate, unless
its motion is retarded; hence, the dash pot is desirable to con-
trol the movement of the coil when it has to move over long dis-
tances, but not for short distances. In the regulator Fig. 108
this result is accomplished by providing a certain amount of lost
motion in the connections between the coil and the dash pot rod,
so that the coil has to move through some distance to take up
the slack in these connections before the dash pot plunger is
moved. This last motion is sufficient to cover the range of reg-
ulation over which the best results are obtained when the coil
moves freely.
THE FORT WAYNE REGULATOR FOR CONSTANT
ALTERNATING CURRENTS.
Fig. J09 is a side view of the regulator made by the Fort
Wayne Electric Works. This regulator, like the two last de-
Fig. 109. Fort Wayne Regulator for Constant Current Series
Alternating Arc Lighting System.
scribed, is of the choke coil, or reactance coil type. The dis-
tinctive feature of this regulator is that the iron core, as well as
the wire coil are made movable, and when the latter moves up,
HANDBOOK ON ENGINEERING.
125
the core moves down. The two parts are suspended from the
opposite ends of rocking levers, the distances from the point of
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126 HANDBOOK ON ENGINEERING.
balances the coil, thus making the former take the place of the
counterbalancing weight in Fig. 107 and 108.
With the choke coil, or reactance type of regulator, the arc
light circuit can be connected directly with the primary alterna-
ting current mains, if the voltage of the latter is high enough.
In cases where the primary voltage is too low, an ordinary step
up transformer is used to generate a secondary current of the
proper voltage.
The following wiring diagrams, which show the way in which
the Fort Wayne apparatus is connected in the circuit, will
serve to illustrate the general arrangement of all types of react-
ance coil regulators, as the difference between them is in the
details, and not in the general principle of operation.
Diagram A of Fig. 110 shows the connections between the bus
bars of the primary circuit, and the arc lamp circuit for the
Fort Wayne system when no step-up transformer is used. This
arrangement is possible if the primary voltage is 1100 or 2200.
With the former voltage an arc lamp circuit with 12 lamps can
be operated, and with the 2200 volts 25 lamps can be used. For
a greater number of lamps, a step-up transformer is required.
As a rule, it is considered preferable to use a transformer in all
cases, whether the primary voltage is high enough or not, as by
this arrangement the lamp circuit is completely isolated from the
main line.
In this diagram the regulator is shown with the coil and core
in the position they assume when the lamp circuit is short cir-
cuited, when the circuit is first connected with the main line bus
bars, this is not the position of the regulator, in fact the coil is in
the bottom or full load position. On this account a special re-
actance coil is provided, as shown in the diagram, the office of
which is to hold back the current, momentarily, until the regu-
lator assumes its proper position. When the starting switch is
closed this coil is cut out.
HANDBOOK ON ENGINEERING. 127
Diagram B, Fig. 110, is a more elaborate arrangement which
shows the connections when a step-up transformer is used, and
in addition includes a watt meter, a potential transformer for the
latter, and a current transformer for the ammeter. These two
last named transformers are provided simply to obtain currents
of the proper voltage and strength for the instruments they
actuate.
The operation of starting a Fort Wayne arc lamp circuit is as
follows : — Looking at diagram J., Fig 110, the first operation is
to close the plug switches that connect with the primary bus bars.
This being done the current will flow from the upper bus bar
through the regulator, the reactance coil and the lower part of
the starting switch, back to the lower bus bar. The current pas-
sing through the regulator will at once move it to the no load
position, so that if now the starting cwitch is moved to the posi-
tion that short circuits the reactance coil, no damage will be
done, as the regulator will be in position to check the
flow of current. During this time the lamp circuit has been
short circuited through the lower connection of the starting
switch, but the final movement of this switch opens the lamp
circuit. The explanation of diagram jB, Fig0 110, is the same as
the foregoing, for as will be seen the introduction of the step-up
transformer does not alter the switching arrangements.
ALTERNATING CURRENT ENCLOSED ARC LAMPS FOR CON-
STANT CURRENT SERIES CIRCUITS.
Alternating current arc lamps for series circuits are of the
differential type. They are manufactured by the large companies
and by many small concerns. All of them are practically the
same in principle of operation, being provided with a clutch act-
ing directly upon the carbon, and mechanism to actuate the
clutch.
The lamp of this type made by the General Electric Company
128
HANDBOOK ON ENGINEERING.
is illustrated in Fig. Ill A showing the external appearance,
and B the actual mechanism. The way in which the lamp oper-
ates can be understood from the diagram (7, which shows the
parts in the position they assume when the current is turned off.
The switch at the upper right hand corner short circuits the lamp,
making a direct connection from one binding post to the other.
When this switch is opened, the current first passes through the
Fig. 111. General Electric Enclosed Arc Lamp for
Series Alternating Current Circuits.
HANDBOOK ON ENGINEERING. 129
but as the carbons burn away, the increased length of the arc will
cause the current through the shunt magnet to increase, thus in-
creasing the pull of the latter. As the shunt magnet gradually
strengthens, it gradually pulls up its end of A thereby bringing
the carbons closer together, and when A has been lowered enough
at its left hand end, the clutch strikes the stop and permits the
carbon to slip through. If the carbon should fail to feed, or the
circuit through the lamp should open through any cause, the
shunt magnet will become strong enough to pull up its end of A
until the cut out switch is closed.
In this lamp as shown in this diagram, the upper carbon holder
slides within a tube and connection between it and the wire lead-
ing from the series magnet is made through a flexible cable. The
General Electric Company also makes lamps in which the upper
carbon holder is attached to a cross-head that slides between two
parallel rods, but the method of conveying the current to the
upper carbon remains the same, that is, by a flexible cable.
The adjusting weight on A is for the purpose of adjusting
the lamp so as to operate with more or less current. If the
weight is moved toward the clutch rod end, the arc is short-
ened and the voltage lowered. Movement in the opposite di-
rection produces the opposite effect. A dash pot, shown
at D, is provided to prevent too violent movement of the
clutch lever A.
THE WESTINGHOUSE ALTERNATING CURRENT LAMP FOR
CONSTANT CURRENT SERIES CIRCUITS.
The external appearance of the Westinghouse enclosed lamp
is shown at A in Fig. 112, the mechanism of the constant cur-
rent series type is shown at B, and a diagramatic representation
of the latter is given in (7. It will be seen from this diagram
that this lamp has all the parts shown in Fig. Ill, although they
9
130
HANDBOOK ON ENGINEERING.
differ considerably in form and are not in the same position. The
series and shunt magnets act upon the opposite ends of lever A,
and an adjusting weight is provided to regulate the length of the
arc. The cut-out switch, although differently located, is actuated
in the same mariner. The upper carbon holder slides within a
tube and connection is made with it through a flexible cable.
In the General Electric lamp the tube is slotted, and an ex-
Fig. 112. Westinghouse Enclosed Arc Lamp for Series
Alternating Current Circuits.
•
tension from the upper carbon holder passes through this slot and
connects with the cable. In the Westinghouse lamp the cable is
attached to the top of the carbon holder and runs up within the
tube to the upper end where it is secured.
HANDBOOK ON ENGINEERING.
131
THE FORT WAYNE ALTERNATING CURRENT ENCLOSED
LAMPS.
The external appearance of a Fort Wayne "Wood" enclosed
arc lamp is shown at A in Fig. 113, and the mechanism of the
lamp for series alternating current circuits is shown at B. Al-
though there is a considerable difference in the design of the
Type Sa Lamp
Form C
B
Figr. 113. Fort Wayne "Wood" Enclosed Arc Lamp for
Series Alternating Current Circuits.
mechanism, the principle of operation is the same as in the lamps
already described, so that in so far as the electrical connections
are concerned it could be represented diagram atically by either
of the two diagrams shown in connection with Figs. Ill and 112.
ID the design of the mechanism the most important differences are in
132
HANDBOOK ON ENGINEERING.
the arrangement of the magnets, and in the means for conveying
current to the upper carbon holder. The magnets instead of be-
ing placed side by side at the top of the lamp are set one above
the other, and they act upon an armature made in the form of a
letter H. There are two series *coils and two shunt coils, the for-
mer being at the top and surrounding the upper legs of the arma-
ture, while the latter are at the bottom and surround the lower
A B C
Fig. 114. Western Electric Enclosed Arc Lamp for Series
Alternating Current Circuits.
legs of the armature. The long coil seen at the left of the lamp
is the starting resistance. The connection with the upper carbon
holder is made by providing the fatter with contacts made in the
form of springs, that rub against the inner surface of the tube
within which the holder slides.
The appearance of the Western Electric Company's enclosed
arc lamp is shown at A in Fig. 114. The mechanism for the se-
HANDBOOK ON ENGINEERING.
133
ries alternating current type is shown at .Band (7, the first illus-
tration being a side view of the mechanism, and the second a
front view. This lamp is provided with double coil magnets, and,
as will be seen, they pull down on the lever that actuates the
clutch rod. The coil located at the top of the lamp, is the start-
ing resistance. The tube within which the upper carbon holder
slides is of rectangular form and so is the upper end of the car-
B
Fig. 115. Types of Clutches Used in Enclosed Arc Lamps.
bon holder. Connection with the circuit is made through a cop-
per ribbon which is bent in zig-zag fashion so as to compress
when the carbon holder is pushed up and extend when it drops
down as the carbon is consumed.
The construction of enclosed lamps is so simple that there are
but few details that require special explanation, since all the
working parts are well shown in the illustrations already pre-
sented. The clutch is made in every case, so as to grip directly
134 HLNDBOOK ON ENGINEERING.
upon the carbon, instead of upon a carbon rod. as is the case
.with open arc lamps. For the latter type of lamp a clutch acting
on the carbon directly would not give satisfactory results owing
to the fact that the arc is very short, but in the enclosed arc
lamps the arc is about three times as long, hence, such accuracy
of movement in feeding the carbons down is not required.
Fig* \15 shows three types of clutches, A being the design
used by the Western Electric Company, B the design of the Fort
Wayne Electric Works, and C the design of the Westinghouse
Company.
The Western Electric Clutch is of the type called double
clutch, and as can be easily seen consists of two clamping rings,
the lower one being held up by the top one. When the carbon
feeds down the lower ring strikes the stop and as soon as it set-
tles sufficiently to release its hold, the carbon slips through.
This shortens the arc and strengthens the shunt magnets so that
they draw up their end of the clutch lever and prevent further
feeding of the carbon .
The Fort Wayne clutch, shown at B, consists of a sleeve to
which a clamping lever is connected. The whole device is held
by this lever so that it clamps the carbon until the sleeve has
moved so far down as to rest on the stop and permit the lifting
end of the lever to drop far enough to release the rod.
The Western Electric and the Fort Wayne clutches are made
wholly of metal, and in fact most clutches are so made. The
Westinghouse Company, however, use a clutch which is made of
a porcelain centre and a metallic supporting band, as is well shown
at (7. The porcelain ring is the clutch proper, and the metallic
band is provided simply to hold it. This band is made with
clinching points on both sides so as to hold the ring firmly. The
object of using a porcelain ring is to prevent current from pass-
ing through the clutch to the carbon. If the clutch is made of
metal there is a remote possibility of current passing through it,
HANBBOOK ON ENGINEERING.
135
and if it should, in sufficient quantity, the carbon might be
burned away so as to form a depression into which the clutch
could drop and thus prevent the lamp from feeding.
In Fig. \\6, are shown the Fort Wayne upper carbon holder
at A, the Western Electric upper carbon holder at B, and at C
the square tube within which this holder slides, together with the
B
Fig. 116. Upper Carbon Holders Used with Enclosed Arc Lamps.
copper ribbon that conveys the current from the upper end of the
tube to the top of the carbon holder.
As shown in the foregoing, the General Electric and the West-
jnghouse lamps are made so as to convey the current to the upper
carbon holder through a cable, and this construction is the one
most generally used ; the two arrangements of Fig. 116, are, how-
ever, worthy of being described as their constructions differ from
136 HANDBOOK ON ENGINEERING.
each other and from general usage. The Fort Wayne carbon
holder is provided with collector springs at its upper end, and
these rub against the under surface of the tube into which the
holder and carbon telescope when the latter is of full length. As
these springs slide over the inner surface of the tube they keep it
bright j and also maintain their own contact points bright, so that
a good electric connection is always insured.
In the Western Electric upper carbon holder, I?, Fig. 116, the
upper end is made square, so as to prevent it from turning, while
sliding up and down in the tube C. This arrangement is neces-
sary because a copper ribbon bent in zig-zag fashion is placed in-
side the tube, and one end is secured to the top of the carbon
holder, while the other end is fastened to the top of the tube. If
the holder could twist around, it would soon get the ribbon in
such a shape that it would bind against the sides of the tube and
prevent the carbon from moving freely.
DIRECT CURRENT ENCLOSED ARC LAHPS OF THE
CONSTANT POTENTIAL TYPE.
Enclosed arc lamps are used extensively at the present time on
incandescent lighting, constant potential circuits, direct current
and alternating current. These lamps are in great favor for
indoor lighting, owing to the fact that they operate with low
voltage currents that are not dangerous. All the arc lamp man-
ufacturers make lamps of this type.
A general Electric constant potential lamp is shown in Fig.
117 at A. The mechanism is seen at B and a diagram illustrat-
ing the principle of operation is given at C. As will be seen
from the latter figure, the construction is very simple. There is
but one set of magnet coils, and these pull directly upon the clutch
rod. The construction is simple because the principle of action
makes it possible to use simple construction. In the series lamps
described in the foregoing, it is necessary to have magnet coils
HANDBOOK ON ENGINEERING.
137
connected in shunt to the arc as well as coils in series with the
arc. This arrangement is required because the current remains
practically constant, hence, the pull of the series magnets varies
next to nothing ; therefore, these magnet coils alone cannot cause
the upper carbon to feed down as the arc lengthens out. The
shunt magnet coils, however, become stronger as the arc becomes
longer, because the resistance of the latter is increased, hence,
as the carbons burn away, the strength of the shunt magnet in-
General Electric Enclosed Arc Lamp for Constant
Potential Direct Current Circuits.
creases and lifting its end of the actuating lever, depresses the
clutch rod, causing the clutch to strike the stop when the carbons
have burned away enough to require feeding. In a constant
potential lamp the current weakens as the arc lengthens and thus
the pull of the magnet is reduced. As the length of the arc
138
HANDBOOK ON ENGINEERING.
gradually increases, the magnet pull gradually reduces, so that
the clutch rod slowly descends until the clutch strikes the stop
and permits the carbon to slip through. The long coil seen on
the left side of the diagram is simply a resistance used to balance
the portion of the voltage not required for the lamp. These
lamps operate with a voltage of about 75 to 80 and as the cur-
rent voltage is from 110 to 115, a resistance has to be used to
HANDBOOK ON ENGINEERING. 139
balance <the extra 35 volts0 The illustration B and the diagram
C show clearly the upper carbon holder and the way in which it
is guided between parallel rods ; the former shows the way in
which the magnet armature is connected directly with the clutch.
In the diagram G it will be seen that the wire from the P binding
post is connected with a ring midway between the ends of the
resistance coil. This is a contact ring that is provided so that
by sliding it up or down more or less of the resistance can be cut
into the circuit. When the ring is in the position that intro-
duces the proper amount of resistance, it is made fast so that it
may not become displaced thereafter.
THE WESTINGHOUSE CONSTANT POTENTIAL LAHP.
Fig* \ f 8 shows the mechanism of the Westinghouse constant
potential lamp at B. In this design the balancing resistance is
wound upon a large porcelain spool and occupies the upper part
of the lamp casing. The actuating magnet coils are directly
below it. The external appearance of the lamp is shown at A in
Fig. 118, and a diagrammatic representation of the mechanism and
circuit connections is given at C. From this diagram it will be
seen that the connections with the circuit are the same as in the
General Electric lamp. The portion of the resistance coil that
is cut into the circuit is adjusted by means of a sliding contact
B which presses against the surface of the resistance wire, the
latter being bare. When B has been moved to the proper posi-
tion the screw at A is tightened and this holds B in position.
THE FORT WAYNE CONSTANT POTENTIAL LAMP.
Fig. U9 shows the mechanism of the Fort Wayne constant
potential lamp at A. The first impression gained from looking
at this illustration is that the construction is entirely different in
principle from the two lamps of this type already described;
such, however, is not the case. The apparent difference is due
140
HANDBOOK ON ENGINEERING.
to the fact that the balancing, or steadying, resistance" as it is
also called, is placed in the separate cylindrical part directly
above the lamp. In the wiring connections of the lamp there
is a difference that is quite noticeable. In the diagram B it will
be seen that in addition to the ordinary balancing resistance,
shown at the top of the diagram, there are two resistances, one
for regulating the strength of the current and the other for ad-
justing the voltage. The latter resistance is in reality a part of
steadying resistance
Fig. 119. Fort Wayne Enclosed Arc Lamp for Constant
Potential Direct Current Circuits.
the steadying resistance, that portion that has to be cut in or out
of the circuit to obtain the proper voltage at the arc. The cur-
rent adjusting resistance, however, is an addition, and is for the
purpose of adjusting the lamp for different strengths of current.
The normal current is 5 amperes, but by means of the current
HANDBOOK ON ENGINEERING.
141
adjusting resistance it may be reduced or increased considerably,
one ampere about. The reduced current will give less light and
the increased current more light with the same voltage.
DIRECT CURRENT ENCLOSED LAMPS FOR OPERATION ON
POWER CIRCUITS, MULTIPLE SERIES SYSTEM.
The lamps described in the preceding section are used on in-
candescent Mghting circuits of 110 to 125 volts, and each lamp
A B C
Fig. 120. Fort Wayne Multiple Series System Lamp for Op-
eration on Power Circuits Direct Current.
is connected directly across the line, just the same as incan-
descent lamps are. Enclosed arc lamps are also used on 220 and
500 volt circuits. With the first named voltage they are con-
nected two in "series, and with the second, five in series. Lamps
Of this type, which we will describe in this section are called
142 HANDBOOK ON ENGINEERING.
" Multiple series lamps. " The mechanism of these lamps is
somewhat different from that of the simple constant potential
lamps used on 110 volt incandescent lighting circuits, and in the
case of most manufacturers the external appearance is slightly
modified. The external appearance of the Fort Wayne lamp of
this type is shown at A in Fig. 120. By comparing it with Fig.
119 it will be seen that the resistance drum on top of the lamp
proper is considerably longer. A comparison between the me-
chanism of the two lamps will at once reveal the fact that in internal
construction there is quite a difference. The arrangement and
operation of this mechanism can be clearly understood from the
diagrammatic representation of it at C in Fig. 120. Looking at
this diagram it will be seen that there are two magnets, a series
and a shunt. There is also a cut-out and a cut-out resistance,
the latter being made equal to the normal resistance of the arc.
The cut-out and its resistance are required so that if the lamp is
turned out intentionally, or cuts itself out through the failure of
the carbons to feed, the other lamps connected in series with it
will not be affected. If the resistance were not used, the cur-
rent would increase decidedly when one lamp is cut out, even if
there are five in series. Cutting out the second light would make
a still further increase in the current, and this increase would
probably be sufficient to burn out the magnet coils of the three
lamps left in the circuit. The steadying resistance shown to the
left of the cut-out resistance is for the purpose of balancing
the voltage not required for the lamp proper. If five lamps are
connected in series on a 500 volt circuit, the voltage correspond-
ing to each lamp will be 100, and as the voltage of the arc is
about 75, there must be an additional resistance able to balance
about 25 volts. Some of this resistance is placed in the voltage
adjusting resistance, but the bulk of it is in the top resistance.
When the lamp is switched into circuit by turning the switch to
the " On " position, as in the diagram, the current from binding
HANDBOOK ON ENGINEERING.
143
post P passes to the switch, thence to the upper carbon, through
the arc to the lower carbon, and then through the series magnet
coil and the steadying resistance to the N binding post. The
current for the shunt magnet coil starts from the left side
switch contact, and passing through the shunt coil connects
with the wire running from the upper end of the series coil
to the righ. side of the resistance. The circle that repre-
144 HANDBOOK ON ENGINEERING.
sents the cut-out contact is connected with the right side of the
cut-out resistance, so that when the cut-out acts, post P is con-
nected directly with post JV through the cut-out and steadying
resistances.
The mechanism of the Westingnouse multiple series lamp is
shown at A, in Fig. 121, a diagrammatic representation of the
same is given at B, and the lamp complete is shown at C. As
will be seen there are two magnets, a series and a shunt, just as in
the Fort Wayne lamp. The voltage and current adjusting re-
sistances are not used, but in their stead a weight is placed upon
the clutch actuating lever, and the necessary adjustment is ob-
tained by setting this weight in the proper position. In each
lamp there is placed a cut-out resistance, that is equal to the re-
sistance of the arc when burning normally. This resistance is
shown at the lower portion of the diagram. The way in which
the cut-out acts is so clearly shown as to require no explanation.
The resistance to balance the excess of voltage is located in the
drum above the lamp, but in many cases the drum is not used,
and the resistance is placed in a separate casing adapted to be
fastened to the wall.
The General Electric Company make a lamp for multiple series
operation that is practically the same as their 110 volt constant
potential lamp. The only difference between it and the latter is
that it is provided with an adjusting weight by means of which
the several lamps in a series are made to move the clutch lever
alike for the same strength of current. This adjusting weight is
carried on a bell crank pivoted on the under side of the cap of the
lamp, as is clearly shown at J3, in Fig. 122. The other end of
the bell crank is connected with the magnet armature through a
link. By properly setting the weight on the lever in the several
lamps, all will work the same, the magnet of each one holding its
armature in the same position for the same current strength. By
HANDBOOK ON ENGINEERING.
145
means of this simple mechanical device the shunt magnet is dis*
pensed with, and the mechanism is correspondingly simplified.
In most cases this lamp is not provided with a cut-out, so that
if a lamp fails to operate it will go out and so will the other lamps
in the series with it. The operation of the lamp is considered to
be so reliable that unless it is an unusual case no cut-out is provided.
When a cut-out is installed it is placed in a separate casing and
A B C
Fig. 122. General Electric Multiple Series Arc Lamp
for Power Circuits Direct Current.
is suspended above the lamp as shown in A, Fig. 122. This cut-
out is so arranged that if a lamp goes out it can be removed to be
readjusted without interfering with the operation of the other
lamps in the series. The wiring diagram for this cut-out is shown
at 0, and as will be seen it consists of the cut-out resistance and
a magnet directly under it. The coil of this magnet is connected
in series with the lamp so that it will hold the switch under it
10
146 HAr^rfOOK ON ENGINEERING.
open as long as current flows through the lamp, but it current
fails to pass through the lamp the switch will close and the cur-
rent will pass through the cut-out resistance, and, as can be seen,
the lamp can then be disconnected without opening the circuit.
ENCLOSED ARC LAMPS FOR CONSTANT POTENTIAL
ALTERNATING CURRENT CIRCUITS.
The only difference between constant potential arc lamps for
alternating and for direct currents is that in the latter a balan-
cing or steading resistance is used to balance the voltage not util-
ized in the lamp, while in the former a choke coil is employed to
perform the same office. A choke coil cannot be used in the di-
rect current lamps, because it will not have any choking effect
when traversed by a direct current. For information on this
point see the section on alternating currents.
A resistance coil placed in the circuit absorbs energy in pro-
portion to the voltage it balances, so that in a direct current lamp
on a 110 volt circuit, if the resistance balances 35 volts, and the
arc 75, then the energ}7 made useful in the lamp will be to the en-
ergy lost in the resistance as 75 is to 35. A choke coil does not
absorb energy in proportion to the voltage it balances, or any-
thing like this amount. A choke coil sets up a back pressure,
but the actual amount of energy it absorbs is only that neces-
sary to pass the current through the wire, and this is generally
only a small percentage of the portion of the voltage balanced.
Owing to this fact alternating current lamps on constant potential
circuits are far more efficient in so far as the use of the electrical
energy is concerned, than direct current lamps ; for while the lat-
ter lose 25 to 30 per cent of the energy, the former only lose two
or three per cent. Direct current lamps, however, give more
light for the same amount of electrical energy, so that the practi-
cal result is about the same for both types.
HANDBOOK ON ENGINEERING.
147
The mechanism of a Fort Wayne alternating current constant
potential lamp is shown at A in Fig. 123, and a diagrammatic rep-
resentation of the same is given at B. Comparing this latter il-
lustration with the diagram of Fig. 119, it will be seen that they
look very much alike, in fact the only difference is that the
steadying resistance of the latter is replaced by a reactance,
choke coil. In other respects the two lamps are the same. In
A
B
Fig. 123. Fort Wayne Arc Lamp for Constant Potential
Alternating Current Circuits.
the direct current lamp, means .are provided for cutting in more
or less of a voltage regulating resistance, which as already stated
is really a part of the steadying resistance ; in the alternating
current lamp, the reactance coil is made with a number of con-
148
HANDBOOK ON ENGINEERING.
nections to different parts of its convolutions, so that more or less
of it may be cut into the circuit.
In the construction of the magnet cores of the alternating and
the direct current lamps there is a decided difference. The direct
current lamps are made with solid iron cores, but the magnets of
the alternating current lamps have laminated cores, made of very
thin sheet iron or soft steel. This difference is necessary owing
A B
Fig. 124. Westinghonse Lamp for Constant Potential
Alternating Current Circuits.
to the fact that in a solid core the alternating current would in-
duce an electric current that would soon make the metal very hot
and the strength of the magnet w»ould be practically nothing.
The mechanism of the Westinghouse constant potential lamp
for alternating currents is shown at A in Fig. 124. A diagram
of the same is ahown at B. Comparing Figs. 118 and 124 it
HANDBOOK ON ENGINEERING.
149
will be seen that the resistance coil of the former is replaced by a
reactance coil. The direct current lamp, Fig. 118, has two mag-
net coils to pull down the clutch actuating lever, while the alter-
nating current lamp, Fig. 124, has only one coil, but both lamps
operate in the same way. By comparing the diagrams of the two
lamps their similarity is seen at once.
The mechanism, the external appearance, and the diagram of
Fig. 125. General Electric Lamp for Constant Potential
Alternating Current Circuits.
connections of the General Electric constant potential lamp are
given in Fig. 125. The principle of operation of this lamp is the
same as that of the other two explained in the foregoing. The
diagram shows very clearly how the magnet pulls directly upon
the clutch connecting link.
150
HANDBOOK ON ENGINEERING.
THE FORT WAYNE HULTIPLE ALTERNATING CURRENT
STREET ARC LIGHTING SYSTEM.
The Fort Wayne Company make an alternating current street
lighting system of the constant potential type that is intended for
small towns or for places where there are several centres in which
Fort Wayne System.
General Plan of Multiple Alternating Current
Street Arc Lighting System.
Fig. 126.
numerous lights are used, these centres being some distance from
each other and from the central station. The general principle
of the system is to generate an alternating current of high voltage
HANDBOOK ON ENGINEERING.
151
at a central station, and to convey this to the centres of distribu-
tion where it is utilized in arc lamps through individual trans-
formers which develop secondary currents of the voltage and
amperage required for the lamps. The system is designed so as
to be used for incandescent lighting as well as arc.
Fig. 127. Fort Wayne Enclosed Are Lamp Used with
System Illustrated in Diagram Fig. 126.
The diagram Fig. 126, shows the general arrangement of the
system. The alternator and switchboard shown are supposed to
be located at the central station, probably several miles distant.
The wires coming from the alternator are connected with lower
terminals of the two pole switch and also the arc circuit switch.
From the upper terminals of the two pole switch the connections
152 HANDBOOK ON ENGINEERING.
run out to the transmission lines, the ammeter being connected in
one of these connections. At the centres of distribution these
line wires are connected with the primary coils of step-down
transformers that furnish current for incandescent lighting.
From the upper terminal of the arc circuit switch a connection
runs out to a third transmission line which also goes to the cen-
tres of distribution. At these centres, the primary coils of small
transformers, each one of sufficient capacity to operate one arc
lamp, are connected with the arc transmission main, and one of
the incandescent mains, as clearly shown in the diagram. These
small transformers are proportioned so that they give a secondary
current of about 6 amperes and 77 volts, or just sufficient to op-
erate a lamp. The transformers which are shown directly above
the lamp in the diagram, are placed in any convenient position,
generally at the top of the arc light pole.
As the transformer furnishes a current of the proper voltage
for the lamp no reactance coil is required in the latter, and as a
consequence the construction is considerably simplified, as can be
seen from Fig. 127 which shows the lamp mechanism at A and
the diagram of connections at B.
LUMINOUS OR FLAMING ARC LAHPS.
Open arc lamps frequently give a poor light owing to the fact
that the carbons are of inferior quality, and as a result are va-
porized by the heat of the arc. This vapor burns and produces
a reddish or purple flame that not only changes the color of the
light, but reduces its brilliancy. By experimenting with carbons
of different composition it has been found that the flame pro-
duced can be varied in color, and at the same time can be intens-
ified so that it will give a strong light. Thus that which was
originally an objectionable feature of arc lamps has been made
use of in developing a new type of lamp in which the flaming ac-
HANDBOOK ON ENGINEERING.
153
tion is increased, and the brilliancy of the flame is depended
upon to give the color of light desired, and also the intensity.
Lamps that operate on this principle are called Flaming arc
lamps and also Luminous arc lamps. At the present time they
are used quite extensively in Europe, and are rapidly gaining
headway in this country, owing to the fact that they give more
ABC
Fig. 128. Excello Luminous Arc Lamp.
A. —Diagram of Mechanism and Circuit Connections for Direct Current Lamp.
C.— Diagram of Mechanism and Circuit Connections for Alternating Current
Lamp.
light for the same amount of current energy and the light is of a
very fine color, being nearly white.
THE EXCELLO LUMINOUS ARC LAMP.
In Fig* 128, the Excello Luminous Arc Lamp is shown, the
154 HANDBOOK ON ENGINEERING.
diagram A being that of the direct current lamp, and C that of
the alternating current lamp. As will be seen, in both diagrams,
the carbon rods are set at an incline toward each other, and are
held up by chains that pass around a drum. The weight of the
carbon rods furnishes the force required to rotate the drum, and
clock work controls the velocity of rotation when the catch /is
drawn out of the way.
In the direct current lamp, diagram A, there is a series mag-
net at the side of the drum, which depresses rod b when the cur-
rent is turned on, and through the links at the bottom separates
the carbons. The shunt magnet n then becomes strong enough
to draw e around and lift b and cause the slider d to bring the
carbons together to strike the arc. As the carbons burn away e
rotates further owing to the fact that the shunt magnet n becomes
stronger. When e moves far enough /is pulled out of the way and
then the clock work begins to rotate and the chains on the drum
unwind thus permitting the carbons to feed down. When the
carbons are fully consumed, a small detent on the chain stops the
further feeding and then when the arc becomes sufficiently long
the current breaks and the lamp goes out.
The diagram C shows the alternating current lamp. In this
lamp there is a small disc that is rotated in one direction by the
action of the series magnet H and in the opposite direction by
the shunt magnet N. When the current is turned on the series
magnet H rotates the disc in a direction that lifts and separates
the carbons. As the carbons separate, the force of the shunt
magnet increases and gradually counteracts the force of H so
that when the arc is of the proper length, the disc stops turning.
As the carbons burn away the shunt magnet becomes stronger and
then by overpowering H causes the disc to rotate in the opposite
direction thus causing the carbons to feed down.
These lamps are made so as to run with currents of 6.8, 10
HANDBOOK ON ENGINEERING.
155
and 12 amperes, and are burned two in series on 115 volt circuits,
or four in series on 230 volts. For the same amount of electri-
cal energy they give more light than regular enclosed arc lamps.
The carbons last about 18 hours. The light is clear white, but
for advertising purposes it can be made of different colors by
changing the composition of the carbons. Just above the arc is
A B
Fig. 129. General Electric Luminous Arc Lamp.
placed a small porcelain reflector i which acts as a protector of the
parts above the flame and also as a reflector.
Fig* J29 shows a flaming arc lamp made by the General Electric
Company. At A is seen the external appearance of the lamp
while B shows the mechanism. In this lamp the lower carbon is
156 HANDBOOK ON ENGINEERING.
a composition contained in an iron tube and is fed upward by the
magnets above the arc through the side connection as. shown in
B. The main frame of the lamp consists of a central tube of
good size that serves as a chimney to carry off the fumes from
the arc. The lower carbon burns for about 150 hours. In place
of an upper carbon, a copper disc is used and this is of such size
that it remains comparatively cool so that its life is about 2000
hours. The arc remains in the same position all the time so that
a reflector made of enameled iron can be secured stationary just
above the arc.
This lamp is made for direct currents to operate in series and
consumes a current of four amperes at an e. m. f . of about 75
volts. Its light giving efficiency is said to be very high.
GENERAL DIRECTIONS FOR THE CARE AND OPERATION OF
ENCLOSED ARC LAMPS OF ALL TYPES.
It is not practicable to give in this book detailed directions for
the operation and care of each and every make of enclosed arc
lamp on the market, as there are so many of them that such di-
rections would fill a volume by themselves. In what follows di-
rections are given that apply to all types of lamps, but any one
desiring minute directions relative to any particular lamp can
easily obtain them by applying to the manufacturers who publish
instruction books that contain all this information.
Carbons: For alternating, as well as direct current lamps,
only the highest grade of carbons should be used, as they not
only give a better and more steady light, but they last much
longer.
For direct current lamps only solid carbons should be used.
For alternating current lamps one of the carbons should be
solid and the other cored.
No carbons should be used that are not perfectly straight,
round and smooth, if they are not smooth rub them with a piece
of sand paper to take off the blisters and lumps.
HANDBOOK ON ENGINEERING. 157
It is necessary that the carbons be very nearly the proper di-
ameter to enable the lamp to feed properly. The manufacturers
furnish a gauge provided with two holes, and all carbons that
pass through the smaller hole as well as those that will not pass
through the larger hole are to be rejected as too large and too
small to be used. The maximum variation from the standard di-
ameter is not quite one hundredth of an inch either under or over
size.
In direct current lamps, if the upper carbon is 12" long, the
lower one should be 5J" and in almost every case the stump
left in the upper holder when the carbons have burned out is used
for the lower carbon in the next trimming, as it is of ample length
for the purpose.
For alternating current lamps the upper carbon 12" and the
lower one 7". Most of the carbons used are ^" diameter, but
T7^" and |" are also used in direct current lamps. Some lamps
are also made so as to use 9" carbons in the upper holder.
If the lamps are in good order, with tight fitting globes, and
the carbons are first class, they should burn for about 150 hours
before requiring retrimming, that is for 12" upper carbon, J" di-
ameter. This is the life for direct current ; for alternating cur-
rent lamps the life is about 100 hours.
How to trim lamps : In trimming or renewing the carbons in
a lamp care should be taken that the upper carbon is pushed up
as far as it will go, so as to make a good contact with the holder.
So as to facilitate this operation it is best to use carbons with a
tapering end.
Be sure that the carbon slides freely through the clutch and the
metal cap of the enclosing globe.
Remove the dust from around the gas check and see that the
mechanism all works freely, if this is not done, the lamp will not
burn well, and will probably lengthen the arc and thus shorten
the life of the carbons.
158 HANDBOOK ON ENGINEERING.
Never put oil in the dash pot, it is made to work dry.
To secure a good light the inner enclosing globe should be
cleaned every time new carbons are put in, so as to remove the
coating deposited by the gas from the arc. In large stations it
is the custom, generally, to provide duplicate lower carbon
holders, and these are trimmed and secured to the globe and are
then placed in baskets provided with partitions to receive them.
They are carried by the trimmers in a wagon and then in trim-
ming the lamps the old globe with the lower carbon holder is re-
placed by the new one. This saves the trouble of cleaning the
globe and inserting the lower carbon at the lamp.
In order that the life of the carbons may be long it is necessary
that the enclosing globe be fitted perfectly tight, if air can get in
the carbons will soon burn out. Owing to this fact the edge of
the globes should be well examined every time the lamp is
trimmed to make sure that there are no pieces nicked out, and
care should be taken to see that the globes come down properly
to their seats, and make a tight joint. Never try to burn an en-
closed arc lamp with the enclosing globe removed. Keep all the
electrical contacts tight.
Be sure that the dash pots always work freely.
Make sure that the upper carbon does not bind.
Lamps should be suspended from a strong support.
The clutch should work smoothly and reliably.
Use no crooked, rough, dirty or inferior carbons.
Always have top carbon positive. If you do not know whether
it is positive or not, light the lamp for a few minutes, then put it
out and the top carbon will remain hot longer than the lower one,
if it is positive.
Do not use any inner globes that are cracked, nicked or do not
fit tightly against their seats.
Use no oil on any part of the lamp where it can possibly get on
the carbons, as this will cause flickering and flaming.
HANDBOOK ON ENGINEERING. 159
Keep under side of gas cap clean and bright by wiping at each
trimming. The bright metal attracts the gases and prevents
them from depositing on the globe.
Remove the casing that encloses the mechanism occasionally
and inspect the parts carefully for possible faults.
Keep the space between carbon bushings in the gas cap clean
and free from dust.
Renew the bushings whenever they show much wear, as increase
in the diameter of the hole permits more air to enter the globe
around the carbon and this shortens the life of the carbons.
Be sure to wipe inner globes clean at each trimming so as to
prevent deposits from forming. Should deposits form that can-
not be wiped off, they can be removed with a weak solution of
muriatic acid.
Never run alternating current lamps on the wrong frequency.
Many alternating lamps are made to run on different frequencies
by slightly changing the connections. For information as to how
to make these changes see instruction books of the makers of the
lamp.
Installing lamps : Lamps should not only be installed in places
where they will destribute light over the greatest possible area,
but also where they are easily accessible when it is desired to
trim or inspect them.
Outdoor lamps should be suspended from 25 to . 30 feet from
the ground, to give the best service, and in positions where their
light will be obstructed as little as possible. The distance be-
tween lamps should not be more that about 300 feet to obtain
satisfactory illumination. The globes used for outdoor lighting
should be clear, for the inner as well as the outer globe.
For indoor lighting the inner globe should be ground glass or
opal, the outer one clear glass. For outdoor lighting metal re-
flectors are commonly used, but no reflector is used with indoor
lamps.
HANDBOOK ON ENGINEERING,
CHAPTER Xa.
Incandescent Wiring Table.
Table on two following pages is arranged to enable wiremen to
select the right sizes of wire for service connections and inside
work. The figures at the top indicate distance in feet to center
of distribution, in reality half the length of the circuit ; the four
columns at the left showing the number of 16-candle power lamps
at various voltages; the other, figures showing the sizes of wire,
Brown & Sharpe gauge, to be used for distributing the number of
lamps stated at the distances indicated and with the loss of 1
volt.
For example: To distribute 30 lamps of 110 volts at a dis-
tance of 80 feet with a loss of 1 volt. In colamn of 110-volt
lamps find the number 30, then follow the same line of figures to
the right until the column headed 80 is reached, and it appears
that No. 6 wire must be used.
The same table may be used for other losses than 1 volt by
dividing the given number of lamps by the number of volts to be
lost, then with this product proceed as before in the table.
For example : To distribute 30 lamps of 110 volts at a distance
of 80 feet with a loss of 2 volts, divide 30 by 2 which gives 15,
then find 15 in the column headed 110 volts and follow the same
line of figures to the right until column headed 80 is reached, and
it is found that No. 8 wire must be used.
No wire smaller than No. 14 is shown in the table as the Na-
tional Board of Fire Underwriters prohibits the use of a smaller
size. Odd sizes smaller than No. 5 are not commercial and are
therefore omitted.
HANDBOOK ON ENGINEERING.
Incandescent Wiring: Table.
Sixteen Candle Power Lamps. Lo«s One Volt
TABLE No. 1. Sizes of Wire are by B. & S. Gauge.
161
52 Volt
3i
110 Volt
34
220 Volt
4
550 Volt
4
Distance in feet to center
of Distribution.
Watt
Watt
Watt
Watt
Lamps
Lamps
Lamps
Lamps
1
20'
25'
30'
35*
40'
45'
1
2
3
9
14
14
14
14
14
14
2
4
7
18
14
14
14
14
14
14
3
6
11
28
14
14
14
14
14
14
4
8
15
37
14
14
14
14
14
14
5
Iff
18
46
14
14
14
14
12
12
6
12
23
56
14
14
14
12
12
12
7
15
26
65
14
14
12
12
12
10
8
17
30
74
14
12
12
12
10
10
9
19
33
83
14
12
12
10
10
10
10
21
37
93
12
12
12
10
10
10
12
25
44
111
12
10
10
10
8
8
14
30
52
130
12
10
10
8
8
8
16
34
59
148
10
10
8
8
8
8
18
38
66
107
10
8
8
8
8
6
20
42
74
185
10
8
8
8
6
6
25
63
92
232
8
8
6
6
6
6
80
63
111
278
8
6
6
6
5
5
$5
74
130
324
6
6
6
5
5 I
4
40
85
148
371
6
6
6
5
4
4
45
95
166
428
5
5
5
4
4
3
60
106
185
464
5
5
4
4
3
3
55
116
203
510
4
4
4
3
3
2
€0
127
222
557
4
4
4
3
2
2
65
138
240
603
3
3
3
3
2
2
70
148
260
650
3
3
3
2
2
1
75
159
277
696
2
2
2
2
1
1
80
170
296
742
2
2
2
2
1
1
90
191
333
835
1
1
1
1
1
0
100 212
il
370
92$
1
1
1
1
0
0
Iff2 HANDBOOK ON ENGINEERING
Incandescent Wiring, Table.
Sixteen Candle Power Lamps, Loss, One Volt.
TABLE No. la. Sizes of Wire are by B. & S. Gauge.
DISTANCE IN FKET TO CENTER OP DISTRIBUTION.
60'
60'
70'
80'
HO'
100'
120'
140'
IbO'
180'
200'
14
14
14
14
14
14
14
14
14
14
12
14
14
14
14
14
12
12
12
10
10
10
14
14
12
12
12
10
10
10
8
8
8
12
12
12
10
10
10
8
8
8
8
6
12
10
10
10
10
8
8
8
6
6
6
10
10
10
8
8
8
8
6
6
6
6
10
10
8
8
8
8
G
G
G
5
5>
10
8
8
8
8
G
G
6
5
5
4
10
8
8
8
6
G
6
5
5
4
4
8
8
8
G
G
G
5
5
4
4
a
8
8
6
G
6
5
5
4
3
3
2
8
C
6
G
5
5
4
3
3
2
2
6
C
6
5
5
4
3
3
2
2
1
0
G
5
5
4
4
a
2
2
1
1
6
5
5
4
4
3
2
2
1
1
0
5
5
4
3
3
2
1
1
0
0
OOi
5
4
3
2
2
1
1
0
0
00
00
4
3
o
2
1
1
0
00
00
000
000
3
2
2
1
1
0
00
00
000
000
0000
3
2
1
1
0
0
00
000
000
0000
0000
2
1
1
0
0
00
000
000
0000
0000
1
*
1
0
0
00
00
000
0000
0000
\
1
0
00
00
000
000
0000
0000
I
0
0
00
00
000
0000
0000
1
0
00
00
000
000
0000
0
0
00
OOQ
000
0000
(0000
! .
0
00
00
000
000
0000
0
00
000
000
0000
0000
00
000
000
0000
0000
163
Feet x 2 x 10,70.
TABLE No. 2.
Feet
to end of
Circuit.
Ft. x2x!0.70.
Feet
to end of
Circuit.
Ft.x2xlO.70.
Feet
to end of
Circuit.
Ft. x2x 10.70.
5
107
185
3,969
365
7,8.11
10
214
190
4,066
370
7,918
15
321
195
4,173
375
8,025
20
428
200
4,280
380
8,132
25
535
205
4,387
385
8,239
30
642
210
4,494
390
8,346
35
749
215
4,601 :
395
8,453
40
856
220
4,708
400
8,560
45
963
225
4,815
405
8,667
50
,070
230
4,922
410
8,774
55
,177
235*
5,029
415
8,381
60
,284
240
5,136
420
8,988
65
,391
245
6,243
425
9,095
70.
.498
250
6,350
430
9,202
75
,605
255
5,457
435
9,309
80
J12
260
5,564
440
9,416
85
,819
265
6,671
44$
9,523
90
,926
270
5,778
450
9,630
95
2,033
215
6,885 .
455
9,737
100
2,140
280
5,992
460
9,844
105
2,247
285
6,099
465
9,951'
110
2,354
290
6,206
470
10,058
115 '
2,461
295
6,313
475
10,165
120
2,568
300
6,420
480
10,272
125
2,675
305
6,527
485
10,379
130
§,782
310
6,634
490
10,486
135
2,889
315
6,741 i
495
10,693
140
2,996
320
6,848
600
10,700
145
3,103
325
6,955
510
10,914.
150
3,210
330
7,06fc
520
11,128.
155
3,317
335.
7,169
530
11,342
160
3,424
340
7,276
640
11,555
165
3,531
345
7,383
550
11.770
170
'3,638
350
7,490
560
11,984
175
8,745
355
7,«97
570
12,198
180
3,852
360
7,704
580
12,412
HANDBOOK ON ENGINEERING.
Feet x 2 x 10.70.
TABLE No. 2.
Feet
to end of
Circuit.
Ft. x2x!0.70.
Feet
to end of
Circuit.
Ft.x2xlO.70
Feet
to end of
Circuit.
Ft. X2X10.7Q
690
12,626
970
20,753
1,350
28,890
600
12,840
980
20,972
1,360
29,104
610
13,054
900
21,186
1,370
29,318
620
13,268
1,000
21,400
1,380
29,535?
630
13,482
1,010
21,614
1,390
29,746
640
13,^696
1,020
21 j #28
1,400
29,960
650
13,910
1,030
22,042
1,410
30,174
660
14,124
1,040
22,256
1,420
30,388
670
14,338
1,050
22,470
1,430
30,602
680
14,552
1,060
1; 22,684
1,440
30,810
6'JO
14,766
1,070
22,898
1,450
31,030
700
14,980
1,080
23,112
1,460
31,244'
710
15,194
1,090
23,326
1,470
31,458'
1720
15,408
1,100
23,540
1,480
31,672
730 i
J5,622
1,110
i! 23,764
1,490
31,886
1740
'15,836
1,120
23,968
1,500
32,100
750
16,050
1,130
24,182
1,510
32,314
760 i
56,264
1,140
24,396
1,520
32,528
770 ..;
16,47®
1,150
24,610
1,530
82,742
780
16,692
1,160
24,824
1,540
82,956
790
16,906
1,170
25,038
1,550
33,170
800
f7,120
1,180
25,252
1,560
33,384
810
17,334
1,190
25,466
1,570
33,598
820
17,548
1,200
25,680
1,580
33,812
830-
17,762
1,210
25,894
1,590
84,026
840
17,976
1,220
26,108
1,600
34,240
850
18,190
1,230
26,322
1,610
34,454
860
18,404
1,240
26,536
1,620
34,668
870
18,618
1,250
26,750
1,630
34,882
880
18,832
1,260
26,964
1,640
35,096
890
19,046
1,270
27,178
1,650
35,310
900
19,260
1,280
27,392
1,660
35,524
910
19,474
1,290
27,606
1,670
35,738
920
19,688
1,300
27,820
1,680
35,952
930
19,902
1,310
28,034
1,690
36,166
940
20,116
1,320
28,248
1,700
36,380
950
20,330
1,330
28,462
1,710
86,594
960
20,544
1,340
28,676
1,720
36,808
HANDBOOK ON ENGINEERING,
163
Feetx 2x10.70.
No. 2.
Feet
Feet
Feet
to end of
Ft.x2xlO.70.
to end of
Ft.x2xlO.70.
to end of
Ft.x2xlO,70.
Circuit.
Circuit.
Circuit.
1,730
37,022
2,450
52,430
4,250
90,950
,740
37,236
2,500
53,500
4,300
92,020
,750
37,450
2,550
54,570
4350
93090
,760
37,664
2,600
55,640
4,400
94,160
,770
37,878
2,650
56,710
4,450
95,230
,780
38,092
2,700
67,780
4,500
96300
J90
38,306
2,750
58,850
4,550
97,370
,800
38,520
2,800
59,920
4,600
98,440
,810
38,734
2,850
60,990
4,650
99,510
,820
38,948
2,900
62,060
4,700
100,580
,830
39,162
2,950
63,130
4,750
101,650
,840
39,376
3,000
64,200
4,800
102,720
,850
39,590
3,050
65,270
4,850
103,790
,860
39,804
3,100
66,340
4,900
104,860
,870
40,018
3,150
67,410
4,950
105,930
,880
40,232
3,200
68,480
6,000
107,000
,890
40,446
3,250
69,550
6,050
108,070
,900
40,660
3,300
70,620
6,100
109,140
,910
40,874
3,350
71,690
5,150
110,210
,920
41,088
3,400
72,760
5,200
111,280
,930
41,302
3,450
73,830
5,250
112,350
,940
41,516
3,500
74,900
6,300
113,420
,950
41,730
3,550
75,970
5,350
114,400
1,960
41,944
3,600
77,040
5,400
115,560
1,970
42,158
3,650
78,110
5,450
116,63Q
1,980
42,372
3,700
79,180
6,500
117,700
1,-990
42,586
3,750
80,250
5,550
118,770
2,000
42,800
3,800
81,320
5,600
119,840
2,050
43,870
3,850
82,390
6,650
120,910
2,100
44,940
3,900
83,460
5,700
121,980
2,150
46,010
3,950
84,530
6 750
123,050
2,200
47,080
4',000
85,600
5,800
124,120
2,250
48,150
4,050
86,670
5,8*0
125,190
2,300
49,220
4,100
87,740
5,900
126,260
2,350
50,290
4,150
88,810
6,950
127,330
2,400
51,360
4,200
89,880
6,000
128,400
166
TAB»-B No. 2.
HANDBOOK OK ENGINEERING*
Feet x2x 10.70.
Miles.
Ft.x2xlO.70
Miles.
Ft.x2xlO.70
Miles.
Ft.x2xlO.70
ft
564,960
4
451,968
74
847,440
1
112,992
4*
508,464
8
903,936
14
169,488
5 i
664.960
64
960.432
2 j
225,984
54
621,456
9
1,016,928
24
282,480
6
677,952
94
1,073,424
8
838,976
6J
734.448
10
1,129,920
•i
895,472
7
790,944
(A)
(B)
(C)
Feet x 2 x 10.7 x Amperes
^Volts lost
Feetx 2x 10.7 x Amperes
Circular mils.
Circular mils x volts lost
= Circular mi}s.
= Volts lost.
= Amperes.
Feetx 2x10. 7
In calculating the sizes of wire as shown in the Incandescent
Wiring Table a formula (A) has been used in wliich there is a
Constant 10.7, the number of circular mils in a copper wire which
would have a resistance of one ohm for one foot of length. One
ampere through one ohm resistance loses one volt* To determine
the size of wire necessary for carrying a given current a given
distance in feet, multiply the number of feet by 2 to obtain the
actual length of circuit, multiply this product by the constant
10.7 and it will give the circular mils necessary for one ohm re-
sistance, multiply this by the amperes and it gives the circular
mils necessary for the loss of one volt. Divide this- last result;
by the volts lost and it gives the circular mils necessary. Hence
the formula "A."
By simply transposing the terms we obtain formula " B," which
can be used to determine the volts lost in a given length of wire
Of certain size carrying a certain, number of amperes.
HANDBOOK ON ENGINEERING. 167
Again, by another change in the terms, we obtain formula
" C," which shows the number of amperes which a wire of given
size and length will carry at a given number of volts lost.
Table No. 2 has been arranged for the purpose of saving time
in the use of these formulas. It shows the result of Feet x 2 x
10.7 for various distances over which it may be desired to trans-
mit current.
A few examples will assist in showing the use of the formulas
and tables.
Suppose we wish to distribute 300 16 c. p. 3.5 watt lamps of
110 volts at a distance of 490 feet with a loss of 10 per cent.
Using formula A,
490 feet x 2 x 10.7 (find it in table No. 2) = 10486.
300 lamps of 110 volts = 152.7 amperes.
(See table No. 3 for amperes per lamp, and multiply by 300)
10 per cent loss on 110 volt system = 12.22 volts. (See
table No. 4.)
10486 x 152.7 amperes = 1601212 circ. mils, -v-12.22 volts
lost= 131032 circ. mils.
In our table it shows the size of wire for this number of circ.
mils, to be 00.
To check this and determine exactly the volts lost in this cir-
cuit by using No. 00 wire use formula B, as follows :
10,486 x 152.7amperes= 1601212 —- 133079 circ. mils. =
12.03 volts lost.
Suppose it is desired to distribute 1,000 lamps at a distance of
1950 feet by 3-wire system, viz., 220 volts, with a loss of 10 per
cent.
Using formula A,
1950 feet x 2 x 10.7 (see table) == 41730.
1000 lamps on 220 volt system =291 amperes.
(See table No. 5 for amperes per lamp, and multiply by
1000.)
168 HANDBOOK ON ENGINEERING.
10 per cent on 220 volt system = 24.44 volts lost. (See
table No. 4.)
41730 x 291 amperes = 12143430 -;- 24.44 volts lost
= 496867 circ. mils.
500000 circ. mils., the nearest commercial size, should be
used.
Check this as before by formula B.
41730 x 291 amperes == 12 143430 -=- 500000 circ. mils.
= 24.29 volts lost.
Suppose we wish to deliver 100 h. p. to a 500 volt motor, at
a distance of 4850 feet with 10 per cent loss :
Again using formula A,
4850 feet x 2 x 10.7 = 103790.
100 h. p. at 500 volts = 160 amperes. (See table No. 3.)
10 per cent loss on 500 volts system =55. 5 volts. (See
table No. 4.)
103790 x 160 amperes = 16606400 -f- 55.5 volts = 299215
circ. mils.
30000 circ. mils, cable should be used.
Check this as before by formula B.
103790 x 160 amperes = 16606400 -f- 300000 circ. mils.
= 55.35 volts lost.
To ascertain how many amperes could be carried to a distance
of 4850 feet with 500 volts with ten per cent loss, use formula C :
4850 feet x 2 x 10.7 = 103790.
10 per cent loss on 500 volts system = 55.5 volts.
300000 circ. mils, x 55.5 volts lost-;- 103790 = 160.42 am-
peres, which as will appear by reference to table No. 3,
will permit the use of 100 h. p. motor.
HANDBOOK ON ENGINEERING.
169
TABLE No. 3.
Amperes per Motor.
H. P.
Per Cent
Efficiency
Watts.
VOLTS.
110
115
120
i
65
860
7.82
7.48
7.17
i
65
1148
10.4
9.98
9.57
2
66
2295
20.8
20.0
19.1
2h
75
2487
22.6
21.6
20.7
H
75
3480
31.6
30.3
29.0
5
80
4662
42.4
40.5
38.8
74
80
6994
63.6
60.8
68.3
10
85
8776
79.8
76.3
73.1
15
85
13166
120.
114.
110.
20
90
16578
151.
144.
138.
25
90
20722
188.
180.
173.
80
90
24867
226.
216.
207.
40
90
33155
301.
288.
276.
50
90
41444
377.
360.
345.
70
90
68022
628.
605.
484.
90
90
74600
678.
649.
622.
100
93
80215
729.
697.
668.
125
93
100269
912.
872.
836.
150
93
120323
1094.
1046. -
1003.
The above table Js arranged to show the amperes per motor at dif *
ierent voltages lor several sizes of motors at efficiencies obtained in
ordinary practice.
170
HANDBOOK ON ENOINEERING.
TABLE Ko.8.
Amperes per Motor.
VOLTS,
125
220
250
500
525
550
6.88
8.91
3.44
1.72
1.64
1.56
9.18
5.22
4.59
2.30
2.19
2.09
18.4
10.4
9.18
4.59
4.37
4.17
19.9
11.8
9.95
^197
4.74
4.52
27.8
15.8
13.9
v6.96
6.63
6.33
87.3
21.2
18.6
9.32
8.88
8.48
66.0
31.8
28.0
14.0
13.3
12.7
70.2
39.9
85.1
17.6
16.7
16,0
105.
59.8
52.6
26.3
25.1
23.9
188.
75-4
66.3
33.2
31.6
SO.l
166.
94.2
82.9
41.4
39.5
37. 7
199.
113*
99.4
49.7
47.4
45.2
265.
151.
1,33.
66.3
63.2
60. a
382.
188.
166.
82.9
79.0
75.4
464.
264.
232.
116.
111.
106.
597.
339.
298.
149.
142.
136.
642.
365.
321.
160.
153.
146.
802,
456.
401.
200.
191.
182.
963,
547,
481.
241.
229.
219.
The above table is arranged to show the amperes per motor at
different voltages for Several 01338 of motors at efficiencies QbtainecMn
HANDBOOK ON ENGINEERING.
171
Volts- Lost at Different Per Cent Drop*
Voltage at Lamp or Distribution Point, Top Row.
TABLE No. 4.
VOLTS
52
75
ICO
110
220
400
\%
.261
.376
.502
.552
1.10
2.01
\%
.525
.757
1.01
1.11
2.22
4.04
\Vh
.787
1.14
1,52
1.67
3.35
6.09
2%
1.06
1.53
2.04
2.24
4.48
8.10
2*%
1.33
1.92
2.56
2.82
5.64
10.25
3%
1.61
2.31
3.09
3.40
6.80
12.37
4%
2.16
3.12
4.16
4.58
9.16
16.06
b%
2.73
3.94
5.26
5.78
11.57
21.05
f>%'
3.31
4.78
6.38
7.02
14.04
25.53
1%
3.91
5.C4
7.52
8.27
16.55
30.10
•*%
4.52
6o52
8.69
9.56
19.13
34.78
9%
5.14
7.41
9.89
10.87
21.75
39.56
10%
5.77
8.33
11.11
12.22
24.44
44.44
12%
7.09
10.22
13.63
14.99
29.99
54.54
13%
7.76
11.10
14.04
16.43
32.87
59.76
14%
8.46
12.20
16.27
17.90
35.81
65.1
15%
9.17
13.23
17.64
19.41
38.82
70.5
20%
13.
18.75
25.
27.50
55.
100,
25%
17.33
25.
33.33
36.66
73.33
133.
The above table shows the loss In voltage between dynamos and
distribution point at different per cents and for various voltages.
172
HANDBOOK ON ENGINEERING.
Yolts Lost at Different Per Cent Drop.
Voltage at Lamp or Distribution Point. Top Row.
TABLE No. 4.
500
600
800
1000
1200
2000
2.51
3 01
402
5 02
C.03
10.05
6 06
6.66
8.08
10.10
12.12
20.2
7.61
9.13
12.1
152
18.2
30.4
10 2
12.2
, 16 3
204
24.4
40.8
12 8
15 3
20.5
25.6
30.7
51.2
15.4
18.5
24.7
30.9
37.1
61.8
20.8
24.9
33.3
41.6
49 9
83.3
26.3
31.5
42.1
52.6
63.1
105.
81.9
38.2
51.
63.8
76. 5
127.
37.6
45.1
60.2
752
90.3
150.
43.4
62.1
69.5
86.9
104.
173.
49.4
59.3
79.1
98.9
118.
197.
555
66.6
88 8
111.
133.
222.
61.7
71.1
98 8
123.
148.
247.
68.1
81.8
109.
136.
163.
272.
74 7
89.6
119.
149.
179.
298.
81.3
97.6
130.
162.
195.
325.
88.2
105.
141.
176.
211.
352,
125.
150.
200.
250.
300.
400.
166.
200.
266.
333.
400.
666.
,By adding the volts given in the table to the voltage at motor or lamp
the result shows the voltage necessary at dynamo for voltage required
at point of distribution,
HANDBOOK ON ENGINEERING.
173
S
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174
HANDBOOK ON ENGINEERING.
APPROXIMATE WEIGHT AND MEASUREMENT Of "0. K." TRIPLE 5RAIDED
TABLE No. 6 WEATHERPROOF COPPER WIRE.
B. & S. Gauge No.
Feet Per Pound
Pounds Per 1000 Ft.
Pounds Per Mile
0000
1.30
767
4050
000
1.59
629
3320
00
2.02
495
2610
0
2.45
407
2150
1
3.22
310
1640
2
4.00
250
1320
3
5.03
199
1050
4
6.10
164
865
5
7.43
135
710
6
9.00
in
587
8
13.54
74
390
10
18.85
53
280
12
28.54
35
185
14
40.61
25
130
16
60.00
17
88
18
75.43
13
70
TABLE OF MAGNETIZING FORCE IN AMPERE TURNS REQUIRED PER
INCH OF LENGTH OP MAGNETIC CIRCUIT.
Magnetic Den-
sity per Square
inch in
Gausses.
MAGNETIZING FORCE IN AMPERE TURNS
Air.
Cast Iron.
Steel.
Wrought Iron.
5,000
1,567
3.80
2.85
1.50
10,000
3,134
5.35
4.25
2.40
15,000
4,701
6.80
5.35
3.20
20,000
6,268
8.00
6.30
3.90
25,000
7,835
10.30
7.50
4.60
30,000
9,402
16.20
8.80
5.30
35,000
10,969
28.70
10.20
5.90
40,000
12,536
49.00
11.70
6.50
45,000
14,103
80.00
13.40
7.10
50,000
15,670
160.00
15.40
8.20
55,000
17,237
240.00
17.80
9.50
60,000
18,804
350.00
20.70
11.00
65,000
20,371
490.00
24.10
13.50
70,000
21,938
650.00
28.00
17.00
75,000
23,505
34.00
21.80
80,000
25,072
42.00
27.50
HANDBOOK ON ENGINEERING.
Table Showing Difference Between Wire Ganges in Decimal Parts
TABLE No. 1 of an Inch.
2
*l
*3
6«
K
American or
Brown &
8harpe.
Birmingham or
Stubs'.
WnshburnA Moen
Manufacturing
Co., Worcester,
Mass.
Trenton Iron Co.,
Trenton. N. J.
Mew British.
1
la
52
3*
fia
22
o«
No. of Wire.
41
000000
.46
000000
00000
.43
.46
00000
0000
.46
.454
.393
.4
.4
0000
000
.40964
.425
.362
.36
.372
000
00
.3648
.38
.331
.33
.348
00
o
.32495
.34
.307
.305
.324
0
1
.2893
.3
.283
.285
.3
I
2
.25763
.284
.263
.265
.276
2
8
22942
.259
.244
.245
.252
3
.20431
.238
.225
.225
.232
4
5
.18194
.22
.207
.205
.212
5
6
.16202
.203
.192
.19
.192
6
7
.14428
.18
.177
.175
.176
1
8
.12849
.165
.162
.16
.16
8
9
.11443
.148
.148
.145
.144
9
10
.10189
.134
.135
.13
.128
10
11
.090742
.12
.12
.1175
.116
11
12
.080808
.109
.105
.105
.104
12
13
'.071961
.095
092
.0925
.092
13
14
15
16
17
18
19
20
21
22
.23
24
25
26
27
28
29
30
31
•32
83
84
36
•86
37
.064084
.057068
.05082
.045257
.040303
.03589
.031961
.028462
.025347
.022571
.0201
.0179
.01594
,014195
.012641
.011267
,010025
.008928
.00795
.00708
.006304
.005614
.005
.004453
.083
.072
.065
.058
.049
.042
.035
.032
.028
.025
.022
.02
.018
.016
.014
.013
.012
.01
.009
.008
•007
.005
.004
.08
.072
.063
.054
.047
.041
,035
.032
.028
.025
.023
.02
.018
.017
.016
.015
.014
,0135
.013
.011
.01
.0095
009
.0085
.08
.07
.061
.0525
.045
.039
.034
.03
.27
.024
.0215
.019
.018
.017
.016
.015
.014
.013
.012
.011
.01-
.009
.008
.00125
.08
.072
.064
.056
,048
.04
.036
.032
.028
.024
.022
.02
.018
.0164
.0148
.0136
.0124
.0116
.0108
.01
.0092
.0084
.0076
.0068
083
,072
.065
.058
.049
.04
.035
0315
.0295
.027
.025
.023
.0205
.01875
.0165
.0155
.01375
.01225
.01125
.01025
.0095
,009
.0075 t
.0965
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
.003965
,XX)8
.0065
.006
.00575
38
89
40
.003531
.003144
• ;
.0075
.007
.00575
.005 j
.0052
.0048
.005
.0045
39
46
170
HANDBOOK ON ENGINEERING.
Weather-
proof in-
sulation.
•pnnoj
J9d 5^0 J
•pnnoj
s s
Is
tp to ci
* O V-< -«• -H C* C7»
O^T. O^UJ CCS
Weather-
proof In-
sulation.
Jddepunoj
8§§
r«r-O5 c-ir-M o to co
•^90 J 000* I
JOd
00 t
10
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igh
5
a
o
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5«ort> oo
laotf 000^
^od.epunoj
CO-*O5 ^OD T
CO O O O 00 «
00 00
Safe Cing
Capacity
in Amperes.
arryi
acit
II
CO -oa
ss
?S §ScS Sg^
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1
I g- Q-5
HANDBOOK ON ENGINEERING. 177
THE STEAM ENGINE.
CHAPTER XI.
THE SELECTION OF AN ENGINE.
There are so many conflicting statements in regard to the
merits and demerits of the several engines placed in the market
that one is often confused in judgment, and scarcely knows how
to proceed in the matter of selection.
It is easy to advise that " When you are ready to buy, select
the best engine, for in the long run the best is the cheapest."
No one would pretend to deny this as a general rule, yet there are
circumstances which so materially modify this rule that it would
seem to a casual observer to be entirely set aside. There are
localities in which the price of fuel is so low that it scarcely war-
rants the doubling of the price on an engine to save it ; and in
such localities the owners usually want an engine of the very
simplest construction ; hence, they almost invariably select an
ordinary slide valve engine with a throttling governor. This
selection is made for several reasons, among which are low first
cost, simple in detail, remoteness from the manufacturer or from
repair shops.
For small powers in which it is desirable that the investment
be as low as consistent with commercial success, the engine
selected should be fitted with a common slide valve ; this will in
general apply to all engines having cylinders eight inches or less
in diameter.
If upon a thorough canvass of the situation, it then be thought
advisable to employ an automatic cut-off engine, the next ques-
tion would probably be whether it shall be fitted with a positive
or some one of the various "drop" movements now in the
market.
12
178 HANDBOOK ON ENGINEERING.
For the smaller sizes, say 8 to 24 inches diameter of cylinder
it will perhaps be found more desirable to use an automatic slide
cut-off, of which there are now several varieties offered through
the trade. This style of engine has the advantage of being low-
priced, efficient and economical.
Small engines are usually required to run at pretty high
speed ; there is a very decided advantage in this on the score of
economy, as a small engine running at a high speed will be quite
as efficient as a large engine running at a slow speed, with the
further advantage that the former will not cost in original outlay
more than about two-thirds of the latter, while the cost of operat-
ing will be no greater per indicated horse-power.
The slide valve is still used to the almost total exclusion of all
other kinds in locomotives. It is doubtful whether a better valve
for that particular use can be devised. It is simple, efficient', and
readily obeys the action of the link when controlled or adjusted
by the engineer. For portable engines and the smaller stationary
engines it leaves little to be desired in point of simplicity.
One objection to a slide valve is that it cannot readily be made
to cut off steam at, say, half -stroke or less, without interfering
with the exhaust. In ordinary practice f to f seems to be where
most slide valves cut off as a minimum, perhaps | would repre-
sent nearer the actual average conditions.
It can easily be shown that this is very wasteful of steam, and
consequently not economical in fuel ; but as there are cases in
which the loss in fuel is fully gained by other advantages, the
ordinary slide valve will, in all probability, continue to be
used.
High speed engines* — The general tendency seems now to be
in the direction of a horizontal engine with a stroke of medium
length having a rapid piston speed and a rapid rotation of crank
shaft, rather than a longer stroke with a less rate of revolution.
This rapid movement of piston and crank shaft permits the use of
HANDBOOK ON ENGINEERING. 179
small fly-wheels and driving pulleys, and thus very materially
reduces the cost of an engine for a given power.
To illustrate this, it may be said that a 16 x 48 inch engine
using steam at 80 Ibs. pressure and cutting off J stroke, running
at the rate of 60 revolutions per minute, may be replaced by
an engine having a 13 x 24 inch cylinder, running at the rate of
200 revs, per minute, the pressure of steam and point of cut-
ting off remaining the same, both engines being non-condensing
and representing the best examples of their kind. The differ-
ence between 60 and 200 revolutions per minute in millwright
work is very great, but there is a constantly growing demand for
an engine which shall meet such a requirement whenever it
shall present itself ; by this it is not to be understood an engine
which shall be used at either speed indiscriminately, but rather a
type of engine which shall be economical in fuel, and shall be of
a kind by which the rate of revolution may be such as to suit the
millwright's work without loss of economy in working, and with-
out excessive outlay for the engine itself in proportion to power
developed.
Slow speed engines are designed and built from a standpoint
entirely different from that of high speed engines ; in the former
case the reciprocating parts are made as light as possible, con-
sistent with safety. The fly-wheel is large in diameter and made
with a very heavy rim, especially is this the case with auto-
matic cut-off engines of long stroke and slow revolution of crank
shaft.
In High speed engines the reciprocating parts are often of
great weight, in order to insure the utmost smoothness of running.
The piston and cross-head are made of unusual weight that at the
bginning of the stroke they may require a large part of the steam
pressure to set them in motion ; this absorbing of power at the
beginning of the stroke is for the purpose of temporarily storing
it up in the reciprocating parts that it may be given off at the
180 HANDBOOK ON ENGINEERING.
later portions of the stroke, by imparting their momentum to the
crank ; thus at the beginning of the stroke, these reciprocating
parts act as a temporary resistance, but once in motion they tend
by their inertia to equalize the pressure on the crank pin, and so
produce not only smooth running, but a very uniform motion.
Results to be obtained in practice* — The best automatic non-
condensing engines furnish an indicated horse-power for about
three pounds of good coal, depending somewhat upon the fitness
of the engine for the work and the quality of the coal. With a
condenser attached, a consumption as low as two pounds has been
reported, but this is an exceptional result, 2J pounds may be
quoted as good practice. The larger the engine the better the
showing, as compared with smaller engines.
For ordinary slide valve engines, the coal burned per indicated
horse-power will vary from 9 to 12 Ibs., for the sake of illustra-
tion, we will say 10 Ibs., and that the engine is of such size as
would require for a year's run $3,000 worth of coal; now an
ordinary adjustable cut-off engine with throttling governor, ought
to save at least half that amount of coal, or say $1,500 per year ;
if the best automatic engine were employed using 2 J Ibs. of coal
per horse-power, a further saving of $750 per year could be
effected, or between the two extremes $2,250 per year in saving
of coal, without interfering in anyway with the power, with the
exception perhaps, that the automatic engine will furnish a better
power than the former engine. It is easy to see that it is true
economy to buy the best engine and pay the extra cost of con-
struction, if the saving of fuel is an element entering into the
question of selection.
The cost of an engine for any particular service is always to
be taken into consideration, for it is possible to contract for a
certain saving of coal at too high a price, not simply when paid
out as the original purchase money, but with this economy of
fuel, the purchaser may have many vexatious and damaging
HANDBOOK ON ENGINEERING. 181
delays caused by the breaking of the automatic mechanism of the
engine. All such delays, which would not have occurred to an
ordinary or simpler engine, are to be charged against any saving
credited to the engine, which failed in producing a regular and
constant power. Take a flouring mill for example, producing 400
barrels per day ; it is easy to see how a single day's stoppage
would interfere with the trade and shipment by the proprietors,
yet it would require a very small break in an engine that would
require less than a day for repairs.
This does not argue against high grade engines, but the pur-
chaser should be certain that the engine when once on its founda-
tions shall be as free from dangers of this kind as any other
engine of similar economy.
There are engines, which, from their peculiar construction
appear to be very complex, and this objection is often urged
against them, while the fact is the complexity is apparent rather
than real. Take the Corliss engine, for example ; it is doubtful
whether there is another automatic cut-off engine in successful
use in this or any other country which has cost less for repairs
during the last ten or twenty years. It is true it contains a great
many separate pieces in the valve mechanism, but the pieces
themselves are simple, durable, easily accessible and always in
sight. These several parts are not liable to excessive wear, but
such as there is can be readily adjusted.
The engines to be preferred are those in which the valve
adjusting mechanism is outside of the steam chest and which is in
plain sight at all times when the engine is in motion.
Location of engine* — This will depend upon circumstances,
but it is far from true economy to place an engine in a dark cellar,
or in some inconvenient place above ground. The engine as the
prime mover, should have all the care and attention which may be
needed to insure regular and efficient working.
Machinery in the dark is almost sure to be neglected. If the
182 HANDBOOK ON ENGINEERING.
design of the building, or the nature of the business, is such that
the engine must be located underground, there should be some
provision for letting in the daylight ; the extra expense incurred
will soon be saved by the order, cleanliness and fewer repairs
required.
The engine should always be close to, but not in the boiler
room. Many a high-priced engine has had its days of usefulness
shortened by the abrasive action of fine ashes and coal dust
coming in contact with the wearing surface. There should always
be a wall or tight partition between the engine and fire room.
The foundations for an engine should be large and deep.
Too many manufacturers in marking dimensions of foundation
drawings for engines, make them altogether too shallow. The
stability of an engine depends more on the depth than on the
breadth of the foundations. Stone should be used for founda-
tions rather than brick, but if the latter must be used they should
be hard burned and laid in a good cement rather than a lime
mortar. If the bottom of the pit dug for the engine foundation
be wet, or the soil uncertain in its stability, it is a good plan to
make a solid concrete block about a foot and a half thick, on
which the foundation may be continued to the top. If such a
concrete block be made with the right kind of cement it will be
almost as hard and solid as a whole stone.
The most economical engine is the one in which high pressure
steam can be used during such portion of the stroke as may be
necessary, then qickly cut off by a valve, which shall not inter-
fere with the exhaust at the opposite end of the cylinder, and
allow the steam to expand in the cylinder to a pressure, which
shall not fall below that necessary to overcome the back pressure
on the piston. In general, the most successful cut-off engines
use the boiler pressure for a distance of one-fifth to three-eighths
of the stroke from the beginning; at this point the steam is cut
off and allowed to expand throughout the balance of the stroke.
HANDBOOK ON ENGINEERING
183
The gain by expansion consists in the admission of steam at a
pressure much above the average required to do the work, and
allowing it to follow but a small portion of the stroke, then ex-
panding to a lower than the average pressure at the end of the
stroke. The mean effective pressure on the piston is that by
which the power of the engine is measured, hence, it follows that
the higher economy is to be reached, other things[being equal, where
the mean effective pressure on the piston is highest when com-
pared with the terminal pressure, or the pressure at the end of the
stroke. In order to get this, a high initial pressure is used ; the
steam follows as short a distance as possible to keep the motion
regular under a load, and then expanding down to as near tho
atmospheric pressure as possible.
The following table exhibits at a glance the performance of a
non-condensing engine cutting off at different portions of the
stroke. The initial pressure of steam being in each case eighty
pounds per square inch.
CUT-OFF IN PARTS OF THE STROKE.
1
10
2
10
3
10
4
To
5
To
Mean effective pressure .
18
35
48
.57
65
Terminal pressure . . .
11
20
30
39
48
Pounds water per h'r per
H. P
27
24
25
27
28
Fractions are omitted in the above table and the nearest whole
number given.
Governor- — Any automatic device by which the speed of an
engine is controlled may properly be called a governor. There
184 HANDBOOK ON ENGINEERING.
are now two distinct methods by which the steam supplied to an
engine is thus brought under control. The first is usually applied
to side valve engines having a fixed cut-off, and consists in the
adjustment of a valve by which the pressure of steam in the
cylinder is increased or diminished in order to maintain a con-
stant rate of revolution with a variable load. The second device
consists in a mechanism by which the whole boiler pressure is
admitted to the cylinder, which is allowed to follow the piston to
such portion of the stroke as will maintain a regular rate of revo-
lution ; the steam is then suddenly cut off at each half revolution
of the engine, thus furnishing a greater or less volume of steam at
a constant pressure. Neither of these two varieties of governors
will act until a change in the rate of revolution of the engine
occurs, and this change will either admit more or less steam as it
is slower or faster than that for which the governor is adjusted.
The commonest form of a governor consists of a vertical shaft to
which are hinged two arms containing at their lower ends a ball
of cast iron ; as the shaft revolves the balls are carried outward
by the action of what is commonly called centrifugal force ; the
greater the rate of revolution the farther will the balls be carried
outward ; advantage is taken of this property to regulate the ad-
mission of steam to the engine. The action of the balls and that
of the valve include two distinct principles and should be consid-
ered separately ; an excellent valve may be manipulated by an
indifferent governor and so produce unsatisfactory results ; on the
other hand, the governor mechanism may be satisfactory in its
operation, but being connected with a valve not properly balanced ,
is likely to cause a variable rate of revolution in the engine.
Fly- wheel* — The object in attaching a fly-wheel to an engine
is to act as a moderator of speed. The action of the steam in the
cylinder is variable throughout the stroke, against which the rev-
olution of a heavy wheel acts as a constant resistance and limits
the variations in speed by absorbing the surplus power of the first
HANDBOOK ON ENGINEERING. 185
portion of the stroke, and giving it out during the latter portion.
The fly-wheel is simply a reservoir of power, it neither creates nor
destroys it, and the only reason why it is attached to an engine is
to simply regulate the speed between certain permitted variations,
which are necessary to cause the governor to act, and to equalize
the rate of revolution for all portions of the stroke, thus con vert-
ing a variable reciprocating motion into a constant rotary one. It
is considered good practice to make the diameter of the fly-wheel
four times the length of the stroke for ordinary engines, in which
the stroke is equal to twice the diameter of the cylinder. This
may be taken as a fair proportion in engine building, and furnishes
a wheel sufficiently large to equalize the strain and reduce any
variation in speed to within very narrow limits, if the engine is
supplied with a proper governor. The greater the number of
revolutions at which the engine runs, the smaller in diameter may
be the fly-wheel, and it may also be largely reduced in weight for
engines developing the same power.
Horse-power- — By this term is meant 33,000 pounds raised
one foot high in one minute. The horse-power of an engine may
be found by multiplying the area of the p.iston in square inches
by the mean effective pressure: this will give the total
pressure on the piston ; multiply this total pressure by the
length of the stroke of the piston in feet ; this will give the
work done in one stroke of the piston ; multiply this product by
the number of strokes the piston makes per minute, which will
give the total work done by the steam in one minute ; to get the
horse-power, divide this last product by 33,000. From this
deduct, say, 20 per cent, for various losses, such as friction, con-
densation, leakage, etc.
CARE AND MANAGEMENT OF A STEAfl ENGINE
It is to be supposed to begin with that the engine is correctly
designed and well made, and that, after a suitable selection of an
186 HANDBOOK ON ENGINEERING.
engine for the work to be done, nothing now remains except
proper care and management.
Lubrication* — The first and all-important thing in regard to
keeping an engine in good working order is to see that it is
properly lubricated. This does not imply, neither is it intended
to encourage, the use of oil to excess ; all that is needed is simply
a film of oil between the wearing surfaces. It is marvelous hew
small a quantity of oil is required when of good quality and con-
tinuously applied. There are several self-feeding lubricators in
the market which have been tested for years and area pronounced
success; these include crank-pin oilers, in which the oscillatory
motion of the oil makes a very efficient self -feeding device, the
flow being regulated by means of an adjustable opening to the
crank-pin, or in the adjustment of a valve by which its lift is reg-
ulated by each throw of the crank ; and in others by a continual
flow through a suitable tube containing a wick or other porous
substance. For stationary engines, it is desirable that the main
body of the oiler be made of glass that the flow of oil may be
closely watched and adjusted accordingly. For the reciprocating
and rotary parts of the engine, a modification of the above men-
tioned oilers may be used. They are of various patterns and
devices and many of them very good. It is also a good plan to
have some device by which the cross-head at each end of each
stroke will take up and carry with it a certain amount of oil ; for
the lower half of the slide this is not difficult to arrange ; for the
upper side an automatic feeder placed in the middle of the slides
will provide ample lubrication.
For oiling the main bearing there should be two separate
devices, one an automatic glass oiler; and in addition, a large
tallow cup attached to the cap of the bearing. This cup should
be filled with tallow mixed with powdered plumbago ; the open-
ings from the bottom of the cup to the shaft should be not less
than quarter inch for small engines, and three-eighths to half -inch
HANDBOOK ON ENGINEERING. 187
for larger ones ; so long as the main bearing runs cool the tallow
will remain in the cup unmelted ; but if heating begins, the tallow
will melt and run down on the surface of the revolving shaft, and
thus provide an efficient remedy when needed. For oiling the
valves and piston, a self -feeding lubricator should be attached to
the steam pipe ; this by a continuous flow of oil will be found not
only satisfactory in its practical working, but economical in the
use of oil.
In selecting an oil for an engine, it is in general better to use a
mineral rather than animal oil, especially for use in the valve
chest and cylinder. The objection to an animal oil, and espe-
cially to tallow or suet, is that it decomposes by the action of heat,
often coating the surface of the steam chest, the piston ends and
the cylinder heads with a deposit of hard fatty matter ; or forms
into small balls not unlike shoemakers' wax. There is no such
decomposition and formation in connection with mineral oils,
which may now be had of uniform quality and consistency, and
at much lower prices than animal oils.
The slide valve should be kept properly set and should be
examined occasionally to see that the face and seat are in good
condition. So long as this is the case, the valve mechanism and
the valve itself must be let alone nnd not tampered with,
The piston packing1 will need looking after occasionally to
see that it does not gum up and stick fast, which it is very likely
to do when the cylinder is lubricated with tallow or animal oil.
The rings should fit the cylinder snugly and should be under
as little tension as possible and insure perfect contact. If the
rings are set out too tight they are liable to scratch or cut the
cylinder ; if too loose, the steam will blow through from one end
of the cylinder, past the piston and into the other. In adjusting
the springs in the piston, care must be exercised that the adjust-
ments are such as will keep the piston rod exactly central, to
prevent springing the rod, or causing excessive wear on the stuf-
188 HANDBOOK ON ENGINEERING.
fing-box. There are several packings, which do not require this
adjustment, the rings being narrow, and either expanding by
their own tension or by means of springs underneath. The only
thing to be done with such a packing is to keep it clean, and
when lubricated with a mineral oil this is not a difficult matter.
If it groans, take rings out and file sharp edges off.
The stuffing-boxes whether for the piston or valve-stem need
to be looked after carefully, and to prevent leaking, will require
tightening from time to time. There are several kinds of ready-
made packings in the market, containing rubber, canvas, hemp,
soapstone, asbestos and other substances which form the basis of
a good durable packing. These can be had in sizes suitable for
all ordinary purposes, and their use is recommended. In the
absence of any of these, a packing made of clean manilla or hemp
fiber will serve a useful purpose. Formerly it was the only sub-
stance used, but is being gradually superseded by the other kinds
mentioned above. In packing the small and delicate parts, such
as a governor stem, a good packing is made by pleating together
three or more strands of cotton candle-wick. This is soft, pliable,
free from anything like grit, and will not get hard until soaked
with grease and baked into a brittle fiberless substance not easily
described.
Crank-pins* — There are few things more troublesome to an
engineer than a hot crank-pin, and it is sometimes very difficult
to get at the real reason why it heats. Among the principal rea-
sons for heating are: the main shaft is not " square " with the
engine, or, that the pin is not properly fitted to the crank ; or,
perhaps, it is too small in diameter — defects which are to be
remedied as soon as practicable. Heating is often caused by the
boxes being keyed too tightly, or by insufficient lubrication.
There are now several good self -feeding lubricators in the market
which will supply the oil to a crank-pin continuously ; these are
recommended rather than the old style of oil cup, which was
HANDBOOK ON ENGINEERING. 189
not only uncertain, but doubtful in its action. Many trouble-
some crank-pins have been cured of heating by this simple matter
of constant lubrication. When the crank-pin is rather small for
the engine and the load variable, there is a possibility of having
a hot pin at any time ; it is advisable to have ready some simple
and effective expedient to be applied when it does occur ; for this
there is perhaps nothing better and safer than a mixture of good
lard oil and sulphur.
Connecting tod brasses* — In quick running engines the
brasses should be fitted metal to metal ; or if this is not desir-
able, several strips of tin or sheet brass should be inserted be-
tween them and keyed up tight. This gives a rigidity to a
joint which is difficult to secure when the brasses have a certain
amount of play in the strap. It is a common practice to bore the
brasses slightly larger than the pin, so that when fitted to it the
hole shall be slightly oval, and thus permit a freer lubrica-
tion than is secured by a close fit around the whole circum-
ference.
Knocking* — There are several causes which, combined or
singly, tend to produce knocking in steam engines. In most
cases the difficulty will be found to be in the connecting rod
brasses ; but whether in the crank-pin end or at the cross-head is
not easily determined in all cases. A very slight motion will
often produce a very disagreeable noise ; the remedy is, in most
cases, very simple, and consists in simply tightening the brasses
by means of the key or other device that may have been pro-
vided for their adjustment. In adjusting a key it is the common
practice to drive it down as far as it will go, marking with a
knife blade the upper edge of the strap, then drive the key back
until it is loose ; after which drive it down again, until the
line scratched on the key is within J or J inch of the top of the
strap. The size of the strap joint and the judgment of the per-
son in charge must decide the best distance. This may be done
190 HANDBOOK ON ENGINEERING.
at both ends of the connecting rod. On starting the engine, the
cross-head and crank-pin mast be carefully watched, and upon
the slightest indication of heating, the engine should be stopped
and the key driven back a little farther. A slight warmth is not
particularly objectionable, and will, as a general thing, correct
itself after a short run. Knocking is sometimes occasioned by
a misfit, either in the piston, or crosss-head and the piston-rod.
These connections should be carefully examined, and under no
circumstances should lost motion be permitted at either end
of the piston rod.
If the means of securing are such that the person in charge can
properly fasten the piston to the rod, he should see that it is kept
tight ; if not, then it should be sent to the repair shop at once, as
there is no telling when an accident is likely to overtake an engine
with a loose piston.
The connection between the piston-rod and cross-head is usu-
ally fitted with a key and furnishes a ready means of tightening
the joint, if proper allowance has been made for the draft of the
key. In case there has not, the piston-rod and cross-head should
be filed out so that the draft of the key will insure a good tight
joint when driven down.
The main bearing should be examined and if there should be
too much lateral movement of the shaft, the side boxes might
then be adjusted until the shaft turns freely, but has no motion
other than a rotary one. The cap to the main bearing should also
be carefully examined, as it may need screwing down and thus
prevent an upward movement of the shaft at each stroke ; this
applies more particularly to quick running engines.
Engines which have been in use for some time are likely to have
a knock caused by the piston striking the head. This is brought
about by having a very small clearance in the cylinder and in not
providing, by suitable liners, for the wear of the connecting rod
brasses. In case of this kind, liners should be inserted behind
HANDBOOK ON ENGINEERING. 191
the brasses in the connecting rod, or new brasses put in, which
will restore the piston to its original position.
Knocking may be caused by defects in the construction of the
engine ; such, for example, as not being in line, the crank-pin not
at right angles to the crank, the shaft may be out of line, etc.
Whenever the cause is one in which it can be shown that it is
a constructive defect, there is but one remedy, and that is the re-
placing of that part, or the assembling of the whole until
perfect truth is had in alignment of all the parts. This will
require the services of an experienced engineer but all improperly
fitting pieces should be replaced by new ones as a safeguard
against accident, which is likely sooner or later to overtake badly
fitting pieces.
If the boiler is furnishing wet steam, or priming, so as to force
water into the steam pipe, it will collect in the cylinder and will
not only cause knocking, but on account of its being practically
incompressible there is danger of knocking out a cylinder head,
bending the piston-rod, or doing other damage to the engine.
The cylinder cocks should be opened to drain any collected water
away from the cylinder.
Repairs* — Whenever it is necessary to make repairs the work
should be done at once ; oftentimes a single day's delay will in-
crease the extent and cost fourfold. If an engine is properly
designed and built, the repairs required ought to b.e very trivial
for the first few years it is run, if it has had proper care. It may
be said in reply to this "true, but accidents will happen in spite
of every care and precaution." That accidents do occur is true
enough ; that they occur in spite of every care and precaution is
not true. In almost every case, accidents may be traced directly
back to either a want of care, negligence, or to a mistake.
Fitting slide-valves* — The practice of fitting a slide-valve to
its seat by grinding both together with oil and emery, is wrong
and should never be resorted to. The proper way to fit the sur-
192 HANDBOOK ON ENGINEERING.
faces is by scraping ; this insures a more accurate bearing to
begin with, and will also be entirely free from the fine grains
of emery which find their way and become imbedded in the
pores of the casting, and are thus liable to cut the valve face and
destroy its accuracy. The scraping of the valve and seat has a
beneficial effect by causing the removal of the fine particles of
iron, which are loosened by the action of the cutting tool in the
planing machine, and which ought to be fully removed before the
engine leaves the manufacturers' hands. Aside from this, it is
doubtful whether the scraping amounts to anything practically,
for the reason that the cylinder and valve are fitted cold, and their
relative positions are distorted by the action of the heat of the
steam, once the engine is in use. The scraping, which simply
renders the valve face and seat smooth and hard, is all that is
sufficient to begin with, and may be re-scraped after the valve
has been in use a few days, should it be found necessary,
which will not often be the case in small and ordinary sized
engines.
Eccentric straps are likely to need repairs as soon as any-
thing about an engine. They should be carefully watched at
all times. If they are likely to run hot, it is also probable
there is more or less abrasion or cutting going on, and if
prompt measures are not taken to arrest it, they are likely to
cut fast to the eccentric, and a breakage is sure to occur.
When the straps begin to heat, the bolts should be slackened
a little, and at night, or perhaps at noon, the straps should be
taken off and all cuttings carefully removed with a scraper
(not with a file) ; the rough surfaces on the eccentric should
be removed in the same manner.
The straps should be run loose for a few days, gradually
tightening as a good wearing surface is obtained.
The main bearing, if neglected, is a very troublesome journal
to keep in order. The repairs generally needed are those which
HANDBOOK ON ENGINEERING. 193
attend overheating and cutting. The shaft, whenever possible,
should be lifted out of the bearing, and both the shaft, bottom of
main bearing and side boxes, carefully scraped and made perfectly
smooth. It sometimes occurs that small beads of metal project
above the surface of the shaft which are often so hard that neither
a scraper nor file will remove them ; chipping is then resorted to
and the fitting completed with a file and fine emery cloth.
Heating* of journals. — A very common cause for the heating
of journals having brasses and boxes composed of two halves, is
that both halves alter their shape from causes attending their
wear. Thus, most engineers will have noticed that, although
there is no wear between the sides of a brass and the jaws of a
box, yet in time the brass becomes a loose fit in the box. Now,
since the sides of the brass have, when fitted, no movement in the
box, it is evident that this cannot have proceeded from wear be-
tween those surfaces, and it remains t) find what causes this
looseness. Most engineers will also have observed that though
the bottom or bedding surfaces of a brass and of the. box may
have been carefully filed to fit each other when new, yet if in the
course of time the brasses be taken out and examined, and more
especially the bottom brass that receives the weight, the file marks
will become effaced on all parts where the surfaces have bedded
together well, the surface having a dull bronze and condensed
appearance. This is caused by the vibrations under pressure hav-
ing condensed the metal. Now, this condensation of the metal
moves or stretches it, and causes the sides of the brass to move
away from the sides of the box, and, consequently, to close upon
the journal, creating excessive friction that may often, and very
often does, cause heating. It is for this reason that on such
brasses the sides of the brass boxes are by a majority of engi-
neers, eased away at and near the joint, and it follows from this
cause the same easing away is a remedy.
Governor* — It not infrequently occurs that after an ordinary
194 HANDBOOK ON ENGINEERING.
throttling engine has been used a few years, the speed becomes
variable to such a degree that it interferes with the proper run-
ning of the machinery. This occurrence can generally be traced
directly to the governor. When it does occur, the governor
should be taken apart and thoroughly examined ; if the needed
repairs are such as can be easily made in an ordinary repair shop,
they should be made at once ; if not, a new governor should be
purchased. The price of governors is now so low that it is better
and more economical to buy a new one than loose the time and
pay the bills for repairing an old one.
AUTOMATIC ENGINES.
In the care and management of this class of engines, it is diffi-
cult to say jnst what particular attention they need, owing to the
variety of styles and the peculiarities of each. As a rule, how-
ever, they require first, to be kept well oiled ; second, to be kept
clean ; third, to be kept well packed ; and fourth, to be left alone
nights and Sundays. There is little doubt that there has been
more direct loss rasulting from a ceaseless tinkering with an
engine than results from legitimate wear and tear to which the
engine is subjected. It is not to be inferred from the preceding
remark that builders of this class of engines are infallible ; it
might be difficult to prove any such assertion in case it was made ;
but it may be said with truth, that the engines of this class now
.in the market are carefully designed, well proportioned, of good
materials and workmanship, and as examples of mechanism are
entitled to take very high rank. Engineers know of several
engines of this class which have not cost their owners for repairs
so much as five dollars in five years' constant use. It is essential
to the economical working of these engines that the cut-off
mechanism be in good order and properly adjusted. Whenever
the valves need resetting, the final adjustment should be made
HANDBOOK ON ENGINEERING. 195
with a load on the engine and with the indicator attached to the
cylinder, the valves being set by the card rather than by the eye.
No general rule can be given for setting the valves, as the prac-
tice varies with the size and speed of the engine ; nor is any rule
needed, for the indicator will furnish all the data required. The
adjustments may then be made so as to secure prompt admission,
sharp cut-off, prompt release, and the proper compression.
TO FIND THE DEAD CENTERS.
When setting the valve of an engine by measuring the lead, as
is the usual method, it is necessary that the crank be accurately
placed on the dead centers at each end of the stroke. Sometimes
an engineer, when adjusting the valves of his engine, will attempt
to place the crank on the dead center by watching for the point
at which the travel of the cross-head stops, or by the appearance
of the connecting-rod as related to the crank. These methods are
totally unreliable for obtaining accurate results, especially the
first one mentioned. The travel of the cross-head and the piston
near the point of reversal of motion is very slow when compared
with the valve. The velocity of travel of the valve is at nearly
its maximum amount when the crank is on the dead center, and a
slight error in finding the dead center point makes a very appre-
ciable error in the position of the valve, with a subsequent error
in its proper setting.
There are several methods for finding the dead center. The
method that can be recommended and the one that should always
be used when the dead center of an engine is to be fonnd is that
familiarly known as " tramming." The dead centers when found
by this method, are geometrically accurate, no matter if the engine
is out of level or if the shaft is above or below the axis of the
cylinder. Some simple tools are required which are generally
available, with the exception of the trams, which may be readily
196
HANDBOOK ON ENGINEERING.
made for the purpose. Two trams are required, one of which
should be 6" or 7" long and the other about 24" or 30", as the
condition may require. The smaller tram may be made of i
steel wire with the points turned over at right angles to the body,
so as to project about 1". The points should be sharpened so
that a hair line may be drawn by them. The larger tram should
be made from rod of at least f " diameter and the points made in
the same way as for the smaller tram. Oftentimes, the long tram
Fig. 130. Finding the dead center.
is made with one leg longer than the other, on account of being
handier to reach some stationary part, but this is a minor point,
which has nothing to do with the principle to be described. The
other tools required are a light hammer, a prick-punch a pair of
10" or 12" wing dividers and a hermaphrodite caliper, or a scrib-
ing block. A piece of chalk will also be found convenient to
facilitate scribing lines on the metal parts with the trams or
dividers. Fig. 130 shows the use of the trams.
Having the necessary tools, we are ready to begin operations, —
and may start at either end of the stroke, as circumstances may
favor. The fly-wheel is turned so that the crank stands at
about the angle shown in the accompanying illustration, which
HANDBOOK ON ENGINEERING. 197
may, however, be approximated as the operator may desire. The
effort made, being to give sweep enough to the cross-head to
allow accurate measurements and still not have such an excessive
arc on the fly-wheel as to make its bisection difficult.
A prick mark is made on the guides, or some convenient sta-
tionary point, as at .B, and an arc struck on the cross-head with
the small tram. At the same time, an arc is scribed on the rim
of the fly-wheel at 6r, using some convenient point for the lower
point of the tram as at 7T, The fly-wheel is now turned until
the crank passes the center and the cross-head travels back until
the scribed line will coincide exactly with the point of the tram
when held in the same position as in the first case. When this
point has been reached, the wheel is stopped and a second arc is
scribed on the fly-wheel rim at F with the tram J. The herma-
phrodite caliper, or the scribing block, is now used to scribe a
concentric line D E on the fly-wheel rim and the arc C F is
bisected with the dividers. When the center H has been accu-
ately located, it should be carefully prick-marked. The scribing
of the concentric line D E is a refinement that is not strictly
necessary if care be taken to locate the points of the dividers at
the same distance from the outer periphery of the wheel in each
instance when finding the center H. The marks left by the lathe
tool will sometimes be plain enough for a guide. When the center
H has been found, the fly-wheel is turned so that the point of the
tram will fall into the prick-mark H when its lower end is in the
stationary point K. When this condition is effected, the crank
is exactly on the dead center and the position of the valve may
be taken with confidence that its location at the dead center point
is accurately found. The same procedure is followed to place the
crank on the dead center at the opposite end of the stroke.
The cut on page 198 is an elevation of Tandem Compound
Engine, showing engine erected on brick foundation. It also
shows a line through cylinders ; also a line over the shaft.
198
HANDBOOK ON ENGINEERING.
HANDBOOK ON ENGINEERING. 199
These lines are used in the erection of a new engine, or to line
up an old one, or with an engine that is out of line. The cut also
shows how the foundation is made ; also how the anchor bolt
is fastened.
The cut on page 200 shows how to pipe a Twin Tandem
Compound Condensing Engine. The plan shows two receivers,
iieaters, relief valves, gate valves, etc., and is so arranged
that either side can be run independently of the other. It
also shows how to line a pair of these engines by following
the lines and noting the distance between each line. An engineer
would have no trouble in lining up a pair of these engines.
HOW TO LINE AN ENGINE.
The method followed when lining different types of engines,
such as vertical, horizontal, portable etc. is as follows: —
The method followed in lining any piston engine is essentially
the same in all cases, as far as determining when adjustments are
needed. The method of making the adjustments after the char-
acter and amount of them is determined, depends entirely on the
construction of the engine, and will necessarily have to be deter-
mined in each individual case, Lining an engine consists of ad-
justing the guides so they shall be parallel to the bore of the
cylinder, and in such a position that the center of the piston
socket of the cross-head shall coincide with the axis of the cylin-
der. Under these conditions only, can the piston and cross-head
travel through the stroke freely, and without distorting any of the
parts. After this adjustment has been made, the truth of the
right-angle position of the shaft must be determined as being
"out of square;" this will make an engine run badly, and is
often the unsuspected cause of much trouble to engineers. We
will assume that we have an engine with four-bar or locomotive
guides, and that the connecting rod, cross-head, back cylinder
200
HANDBOOK ON ENGINEERING.
HANDBOOK ON ENGINEERING.
201
head and piston have been removed. If the engine is of the
horizontal type the first step will properly be to ascertain if the
engine is level on the foundation, and if not, proceed to make it
so. After having leveled the engine, stretch a smooth linen
line, as shown in Fig. 133, through the bore of the cylinder and
the stuffing-box, to a point beyond the shaft, where it should be
attached to an iron rod driven into the floor. The other end is
fastened to a cross-bar bolted across the face of the cylinder to
Fig. 183. Lining up an engine.
two of the studs, as shown in Fig. 133, or the bar may preferably
be somewhat longer than one-half of the diameter of the cylinder,
and with a saw cut for a short distance lengthwise at the inner
end. In this case, it is held by only one of the cylinder studs
and can be somewhat more easily adjusted. The line or cord is
adjusted to approximately the proper position, and is drawn taut
and fastened through the cross-bar by being tied to a short stick
that is too long to pass through the hole. In this position it is
held by the friction, and can be readily adjusted to the required
position. An assistant is required to move the line in the direc-
tions indicated, as the work proceeds, and then we are ready to
center it in the cylinder. The only tool required for this purpose
is a light pine stick of slightly less length than the radius of the
202 HANDBOOK ON ENGINEERING.
bore, and it should have an ordinary pin pushed into the head for
a ' 'feeler." Now adjust the line in the cylinder so that the head
of the pin will just tick the line from four points of the counter-
bore, which is always the part of the cylinder to work from, as it
is not affected by the wear. The line should then be adjusted
to the center of the other end of the cylinder, but not from the
stuffing-box, as this is likely to be out of center somewhat.
Make the adjustment at this end from the counterbore, if pos-
sible, the same as in the first instance, and then it will be neces-
sary to try the position of the line in the back end of the cylinder
as the changes made at the other end will affect it slightly. After
the line is truly centered, we are ready to adjust the guides.
With some types of cross-heads, it is possible to use the cross-
head for determining the proper location of the guides, but with
the ordinary form, such as shown in Fig. 133, this cannot be done
but we will need a tool similar to that shown in sketch, which
consists simply of a piece of flat iron long enough to reach across
the guides, and having a hole drilled and tapped in the center for
the thumb-screw. This thumb-screw is adjusted so that its point
is the same distance from the lower side of the bar, as the lower
face of the wings of the cross-head are from the center of the
piston socket. To find this distance, lay a straight edge across
the end of the cross-head and draw the line A B, and then, hav-
ing found the center of the hole, the measurement may be accur-
ately taken. The lower guides are now adjusted by the tool, so
that the point of the screw will tick the line throughout the
length, and then the top guides are put in position with the cross-
head in place and adjusted for a proper working fit.
Before removing the line from the cylinder, however, the shaft
should be tested for the truth of its right-angle position, which
may be done by calipering between the crank disc and the line at
the points H and J. If the distances are equal, the shaft is
square with the bore of the cylinder, providing, of course, that
HANDBOOK ON ENGINEERING. 203
the disc is faced true with the shaft. If there is any doubt as to
its accuracy, turn the shaft as nearly half way around as the
crank-pin will admit without disturbing the line. Then caliper
the distance of a point on the disc that will not be far removed
from the first position, thus reducing the chance for error. If
the shaft shows 4 ' out ' ' move the outward bearing until the meas-
urements show equal in both positions. The horizontal truth of
the shaft can be found by laying a level on it and if " out,"
raise or lower the out-board bearing until the level shows fair.
Work of this kind requires skill and patience and belongs prop-
erly to the sphere of the chief engineer. It requires a delicacy of
touch and an appreciation of what is meant by close measurement
that can come only through experience. In centering the line,
one should be able to detect when it is as little as T^TF of an inch
out of center. A piece of ordinary tissue paper is about .00125
inch thick. A man should be able, therefore, to adjust a line so
accurately that if the " feeler," with one or more pieces of the
paper under it, just clips the line, it will miss the line when one
thickness is removed. While it may not always be necessary to
work as closely as this, a person cannot expect to line up engines
successfully until he has a full knowledge of what this degree of
accuracy means.
Engine Formulas.
Diam. cyl. for given H.P. = -,/ __ 33000 XH.P. ^
v Piston speed XM.E.P. '
Stroke in feet = P^ton speed in feet per min.
Revs. X 2
Piston speed in feet per min.
Keys, per min. = Length of stroke in feet X 2
83000 XH.P. _
Piston speed = Areft Qf p.gton in gq inches x M E p>
33000 XH.P.
Area of piston in sq. ins. = M.E.P.X piston speed
33000 X H. P.
M.E.P. required = Area of ristOnX Piston speed
204
HANDBOOK ON ENGINEERING.
HANDBOOK ON ENGINEERING. 205
CHAPTER XIa.
DIRECTIONS FOR SETTING UP ADJUSTING AND RUNNING
THE CORLISS STEAM ENGINE.
Location of foundation* — The foundation must be at right
angles with main line shaft. If main line shaft is not already in
position, then foundation must be set by two points, located and
connected with a line parallel with the buildings, and at right
angles to an imaginary line through center of cylinder.
Foundation plans should show all center lines. If a templet
is furnished to locate the foundation accurately for the mason, the
center line of engine cylinder and guides and right angle for
crank center are drawn thereon.
Cap Stones* — Examine carefully the lap faces of cap stpnes
and, if necessary, have them trimmed off by cutter or mason, so
that each is true and level, and in exactly the plane shown in
foundation plan.
Cylinders and frame* — Put engine cylinder and frame in
position and bolt them together.
Lining; off crank shaft and out-end bearing. — Stretch a
line at right angles to main center line, through main bearing to
represent center line of crank shaft. See that this line is exactly
in the center and level. By this line place out-end bearing square
and true. Put crank shaft in its bearings after bottom box has
been placed in main bearings. Insert quarter boxes and adjust-
ing wedges into main bearing and put cap on.
To ascertain that shaft is at exact right angles to main center
line, turn engine shaft until the crank pin comes nearly to the
206 HANDBOOK ON ENGINEERING.
main center line, then with a pair of calipers, or rule, measure from
shoulder of crank-pin to line, and after noting this distance, turn
the crank back towards opposite center until pin is in same
relative position to line, and measure again. If both measurements
do not correspond, out-end bearing must be moved either way as
required, until measurements show equal. Then take up slack
around shaft in main bearing, being careful not to force the
adjusting wedge too tight.
Fly-wheels* — The fly-wheel is next placed on shaft and firmly
keyed in position.
Placing1 valve gear* — Steam and exhaust valve covers or bon-
nets on valve gear side are next bolted to place, taking care that
no dirt or foreign substance gets between the surface underneath
the covers.
Valve stems are inserted from opposite or front of cylinder and
the valves put in after them, the T head of valve stem entering
slot in valve. Couple up all valve gear parts, i. e., disc plate
valve-steam cranks, valve-connecting rods, dash-pots and dash-pot
rods, vajye-rod rocker, eccentric and straps on crank-shaft, first
and second eccentric rods. The dash-pots should be thoroughly
cleaned and oiled before putting in place.
ADJUSTMENT OF CORLISS VALVE GEAR WITH SINGLE AND
DOUBLE ECCENTRICS.
A brief description of the essential parts of the Corliss engine
valve gear will assist in obtaining a clear conception of the
subject.
When a single eccentric drives both steam and exhaust valves
the range of cut-off is limited to about half the piston stroke.
This Tvill become obvious by considering the following necessary
conditions ; —
HANDBOOK OF ENGINEERING
207
After the eccentric has reached the extreme of its throw as
shown in Fig. 135 in either direction all valve gear motions are
reversed.
Fig. 135. Showing eccentric in extreme position.
The steam valve must be released before the eccentric motion
is reversed, for if the hook does not strike the knock-off cam
during its forward motion, it cannot strike it during its return
motion.
The maximum exhaust opening, or the middle of the exhaust
period, must occur when the eccentric is at the extreme of its
throw as in Fig. 135.
Now, in order to release the expanded steam in the cylinder
before the commencement of the return stroke and to secure the
exhaust closure a little before the end of the return stroke, the
middle of the exhaust period or the extreme of the eccentric
throw must evidently occur before the middle of the return
stroke, and, therefore, the extreme throw of the eccentric in the
opposite direction must occur before the middle of the forward
stroke, and the valve must be released before this point is reached
if released at all.
It will be understood from the foregoing that late release and
late exhaust closures are conditions imposed by the single
eccentric valve gear, and these conditions agree very well with
moderate rotative speed ; but at higher speed earlier release and
208 HANDBOOK ON ENGINEERING.
more compression may be required. This may be effected by
moving the eccentric forward on the shaft, but the reversing of
the steam valve motion would then occur at an earlier stage of
the forward stroke and the range of cut-off would be correspond-
ingly shortened. Earlier exhaust closure could be had by giving
the exhaust valve more lap, but this would involve a later release
of the expanded steam at the end of the stroke. On the other
hand, shortening the exhaust lap would give earlier release but
insufficient or no compression.
In Figs* 136 and 137 similar capital letters of reference indicate
the same parts of the mechanism.
Fig. 136 shows all the essential parts of the valve gear. The
steam valves work in the chambers S 8 and the exhaust valves
work in the chambers E E. The double-armed levers D D
work loosely on the hubs of the steam bonnets ; they are con-
nected to the wrist-plate B by thr rods K K, the levers M M are
keyed to the valve stems J J, and are also connected by the rods
0 0 to the dash-pots P P. The double-armed levers D carry at
their outer ends what are called steam hooks FF, these being pro-
vided with hardened steel catch plates, which engage with arms
M M, making the arm M and the hook F work in unison until
steam is to be cut off. At this point another set of levers or cams
G 6r, which are connected by the cam rods II H, to the governor?
come into play, causing the catch plates on the hooks F to release
the arms M M, the outer ends of which are then pulled downwards
by the dash-pot plunger, causing the steam valves to rotate on
their axis and thus cut off steam. These are the essential fea-
tures of the Corliss gear.
The exhaust valve arms N are connected to the wrist-plate by
the rods L Z/, and it is seen that all the valves receive their
motion from the wrist- plate B; the latter receives its motion
from the hook-rod A; this rod is generally attached to
a rocker arm not shown; to this arm the eccentric rod is
HANDBOOK ON ENGINEERING.
210
HANDBOOK ON ENGINEERING,
also attached. The rocker arm is usually placed about mid-
way between the wrist-plate and eccentric, and in the center
of its travel stands in a vertical position.
The setting of the valves is not a difficult matter, when, on
the wrist-plate, its support, valves and cylinder, the customary
marks have been placed for finding the relative positions of
wrist-plate and valves.
0 c
•- H
>t
'
Q-
f*l- t Af
j^ ft. ^
Fig. 187. Diagram of Corliss gear and valves.
Now, referring to Fig. 137, when the back bonnets of the valve
chambers have been taken off, there will generally be found a mark
or line, r, on the end of each steam valve s s, coinciding with the
working or opening edge of each valve ; another line, £, will be
found on each face of the steam valve chamber coinciding with
the working edge of the steam port. The exhaust valves and
their chambers are marked in a similar way, i. e., the line u on
the end of each exhaust valve coincides with the working edge of
the valve, and the line #, on the face of ^ach exhaust valve
HANDBOOK ON ENGINEERING. 211
chamber, coincides with the working edge of the exhaust port.
On the hub of the wrist-plate will be found three lines n, c, w,
placed in such a way that when the line c coincides with the
line b on wrist -plate, the wrist plate will stand exactly in the
center of its motion, and when the line b coincides with either
of the lines TI, ft, the wrist -plate will be at one of the extreme
ends v or w of its travel.
In setting the valves, the first step will be to set the wrist-
plate in its central position, so that the lines b and c will coin-
cide, and fasten the wrist-plate in this position by placing a
piece of paper between it and the washer R on its supporting
pin. Now set the steam valves so that they will have a slight
amount of lap, that is to say, the lines r, r, must have moved a
little beyond the lines £, t. The amount of this lap depends
much on individual preference and experience ; it ranges from
^ to J for small engines, and from J to | inch for compara-
tively large engines. This lap is obtained by lengthening or
shortening the rods K K\>y means of the adjusting nuts.
Now place the exhaust valves e, e, by lengthening or shorten-
ing the rods L L by means of the adjusting nuts, in a position
so that the working edges will just open the exhaust ports, or,
in other words, place the lines u and x in line with each other
as indicated in illustration.
The next step will be to adjust the rocker arm. . Set this arm
in a vertical position by means of a plumb line, and connect the
eccentric rod to it ; then turn the eccentric around on the shaft,
and see that the extreme points of travel are at equal distances
from the plumb line. To secure this a little adjustment in the
stub end of the eccentric rod may be necessary. Now connect the
hook rod A to the wrist-plate. The paper between the wrist-
plate and the washer on the supporting pin should now be taken
out, so that the wrist-plate,which is connected to the valves, can
be swung on its pin. Now turn the eccentric around on the shaft
212 HANDBOOK ON ENGINEERING.
in order to determine the extreme points of travel of the wrist-
plate. If all parts have been correctly adjusted, the line b will
coincide with the lines w-, n, at the extreme points of travel ; if
this is not the case, the hook rod will have to be adjusted at its
stub end so as to obtain the desired equalized motion of the
wrist-plate.
The next step will be to set the valves correctly with reference
to the position of the crank ; to do this the length of the rods K,
K, L, and L must not be changed, but the following mode of
procedure should be followed : Place the crank on one of its dead
centers (see page 195) and turn the eccentric loosely on the shaft
in the direction in which the engine is to run, until the steam
valve nearest to the piston shows an opening or lead of -J^- to -fa
inch. After the proper lead has been given to this valve, secure
the eccentric, and turn the shaft with eccentric in the same direc-
tion in which the engine is to run until the crank is on the oppo-
site dead center, and notice if the opening or lead at this end of
the cylinder is the same as on the other steam valve ; if not,
shorten or lengthen slightly, as may appear necessary, the con-
nection between the wrist-plate and eccentric. Of course much
adjustment in the length of these connections is not admissible
without resetting the valves with reference to the wrist-plate. The
compression on an engine is a very important factor, upon which
cool and quiet running depends. With exhaust valves line and
line about 5 per cent compression is secured, which is equal to If
for 36" stroke and 2" for 42" stroke. In case more compression
is desired, the exhaust valves must be given a little lap.
To set the exhaust valves for a given compression, say, 2
inches, first measure off 2 inches from the ends of the cross- head
travel as shown in Fig. 138 (not from the ends of the guide).
Then turn the crank in the direction it is to run until the end of
the crosshead reaches the line on the guide. Adjust the exhaust
valve corresponding to this end of the stroke so that it just closes
HANDBOOK ON ENGINEERING.
213
the port. Turn the crank over the center and back on the return
stroke until the opposite end of the cross-head reaches the line on
the opposite end (to the first mark) of the guide. Then adjust
the exhaust valve corresponding to this end of the stroke so that
it just closes the port. Both exhaust valves will then close the
ports when the piston reaches a point 2 inches from the working
end of the guide and the engine will then have exactly 2 inches
Fig. 138. Laying out compression marks on guide.
compression. If this is found to be too much or too little, as
determined by the running qualities of the engine, it may be
varied either way by adjusting the length of the rods L and L,
being careful to turn each nut exactly the same amount.
The only thing which remains now to be done is to adjust the
cam rods H, H, to produce an equal cut-off at each end of the
cylinder. On the column of most Corliss engine governors will
be found a stop device, sometimes in the form of a loose pin,
some form of cam motion or movable collar. This device is for
the purpose of preventing the governor from reaching its lowest
position, for when it reaches the latter position the valves should
not hook on. Should the governor belt break or become ineffect-
214 HANDBOOK ON ENGINEERING.
ive, the governor will stop and reach its lowest position on the
column, thereby bringing the safety cam Y in underneath the
inner member of the hook F which prevents the latter from
engaging arm Jf, and as the valves cannot hook on when it is in
this position the admission of steam to the cylinder is entirely
shut off and the engine will come to a standstill.
It will be apparent that the stop on the governor column should
be removed or otherwise rendered inoperative as soon as the
engine has attained full speed, and should again be placed in
active position when stopping the engine in the usual way. As
the stop just mentioned determines the lowest position of the
governor at which the valves should hook up, it should be kept
in place while the foregoing adjustments are being made.
Next, unhook the reach rod from the wrist-plate and by means
of the starting bar move the wrist-plate over until the lines b and
n are nearly opposite each other. The head end valve should
now have opened the port to nearly the limit, which may be
ascertained by the marks on the ends of the valve. Now, adjust
the governor rod H so that the projection or cam on the disk G
operated by the governor will come in contact with the inner
member of the steam hook F, so that the valve will be tripped or
released when the marks b and n are exactly in line. As all
governors do not move an equal amount to produce a given
change in the point of cut-off, it will be safer to hook the reach
rod on the wrist-plate and have the engine turned in the direction
in which it is to run, until the head end valve is released, than to
adjust the cut-off with the use of the starting bar only. To
prove the correctness of the cut-off adjustment, raise the gover-
nor balls to a position where they probably would be when at
work and block them there ; then, with the connections made
between the eccentric and the wrist-plate, turn the engine shaft
slowly in the direction in which it is to run, and when the
valve is released, measure upon the slide the distance which
HANDBOOK ON ENGINEERING.
215
the crosshead has moved from its extreme position. Continue to
turn the shaft in the same direction, and, when the other valve is
released, measure the distance through which the crosshead has
moved from its extreme position, and if the cut-off is equalized,
these two distances will be equal to each other. If they are not,
adjust the length of the cam rods until the points of cut-off are
equal distances from the beginning of the stroke. Replace the
back bonnets and see that all connections have been properly
made, which will complete the setting of the valves.
Fig. 139. Diagram of doable eccentric gear.
ADJUSTMENT WITH TWO ECCENTRICS.
In order to obtain a greater range of cut-off in Corliss engines
a separate steam and exhaust eccentric is used. With two eccen-
trics the admission and exhaust valves can be adjusted independ-
ently, and steam may be cut off anywhere, nearly to the end of
the stroke.
The work of setting the valves of a Corliss engine having two
216
HANDBOOK ON ENGINEERING.
HANDBOOK ON ENGINEERING. 217
eccentrics is not particularly complicated as many engineers seem
to think. After inspecting the type of releasing gear employed
and knowing in which direction the engine is to run, finding the
direction in which to turn the eccentric becomes a very simple
matter. When setting the steam valves we have one eccentric to
turn as in the case of the single eccentric engine, and when set-
ting the exhaust valves another eccentric must be turned, but this
does not add complication to the work, although it requires a
little more time. The work of centralizing the positions of the
various parts, equalizing the movements and setting and adjust-
ing the valve gear is practically the same as with the single eccen-
tric engine. Set the wrist-plate central as shown in Fig. 139, and
adjust the valve rods ; but in this case the steam valves are set
with negative lap, which is usually a little less than half the
port opening. The first step is to set the exhaust eccentric
(as it is generally placed next to the bearing). To do this
turn the engine until the piston is in the position shown
in Fig. 140, so as to obtain a compression of about 5
per cent of the stroke. Then turn the exhaust eccentric
loosely on the shaft in the direction the engine is to run, until the
exhaust valves are line and line. Then secure the eccentric and
turn the engine on the other end in the same position to prove
the correctness of the other exhaust valve.
The next step is to set the steam eccentric ; place the crank
on either one of its dead centers, then turn the steam eccentric
loosely on the shaft until the steam valve on the same end the
piston is, has the required opening or lead, which varies from -fa"
to Ty.
These directions apply to engines in which the reach rod from
the eccentric is connected to the wrist-plate above the center
pin R, Fig. No. 136. When the reach rod is connected to wrist-
plate below the pin jR, the eccentric should be turned the opposite
direction to that in which the engine is to run.
218
HANDBOOK ON ENGINEERING.
HANDBOOK ON ENGINEERING.
219
The arrangement of the steam rods in Fig. 136 is in every re-
spect satisfactory in connection with a single eccentric valve gear,
for in that case a slow initial valve motion is imperative, and it is
obtained by the lateral movement of the radius rod. But with
two eccentrics quicker initial motion is feasible and desirable, and
it is obtained by reversing the valve motion as in Fig. 139. Sepa-
rate eccentrics require separate wrist-plates, which are usually
placed on the same pin.
Fig. 142. Diagram showing steam distribution.
Figs* 141 and 142 show how the eccentrics may be placed on the
shaft. The steam eccentric is at point 4, Fig. 141, the exhaust
eccentric is at point 1, Fig. 142, and the crank is at its dead center
at C. Individual eccentric circles are shown for the sake of clear-
ness. An imaginary motion of the eccentric will point out the
various events. Referring to Fig. 141, near point 2, at the end of
220
HANDBOOK ON ENGINEERING.
the throw, the hook connects with the steam valve ; at point 3
the steam edges are at the point of separating and the eccen-
tric motion 2-3 determines the initial valve motion. When the
eccentric is at point 4 the crank is at its dead center as
shown. At point 5 the steam wrist-plate is in its central position
and in that position the valve does not cover the port, as with
the single eccentric gear, but the port is open to a certain extent,
determined by the eccentric motion 3-5. Point 7 marks the end
Fig. 148. Diagram showing steam distribution.
of the throw, and the corresponding position of the crank is at C1
at about three-quarters of the piston stroke, and the limit of cut-
off is a little later. If the hook does not strike the knock-
off cam the valve will remain open until closed by the return
stroke of the eccentric at point 9, near the middle of the
return piston stroke. The exhaust action is discernible, Fig. 141.
HANDBOOK ON ENGINEERING.
221
It is similar to the single eccentric action, but with this differ-
ence, that the release at point 5 occurs at about 95 per cent of
the stroke, and the exhaust is also cut off at about 95 per cent
of the return stroke at point 8.
The motion of the exhaust valve after it has closed the port is
determined by the eccentric motion 8-2-5, and full period of
exhaust opening is obtained by the eccentric motion 5-7-8. In
case the exhaust valve motion is designed and set with lap, Fig.
143 shows the effect lap has on the exhaust valves. The lap when
wrist-plate is central is determined by motion A-B. It will be
Fig. 144. Relative position of valves and crank pin.
noticed that the compression begins at A at about 90 per cent of
the stroke, and the release at E occurs at 98 per cent of the
return stroke and the exhaust opening E, (7, A, is shortened.
Where lap is used on the exhaust valve it has the effect of making
earlier compression and later release. A valve gear designed to
be operated by a single eccentric cannot very well be made to cut
off much later than at half stroke, even when a separate exhaust
eccentric is added. For the slow initial valve motion requires at
least half the throw of the eccentric, and the other half is not
sufficient for a late cut-off, and it will readily be seen from an in-
spection of Figs. 137 and 139, that a quicker initial valve motion in
222 HANDBOOK ON ENGINEERING.
.
Fig. 137 would involve radical changes in the valve gear. However,
the range of cut-off may be extended by moving the eccentric
back, sacrificing the lead, and to this there is no objections when
it does not involve later release. The advantage gained by a
second eccentric would consist in more compression and earlier
release. After setting the valves and making the final adjustment,
if it is convenient an indicator should be applied to the engine
when at work to verify the adjustment of the valves for the best
possible conditions for economical operation.
Fig. 143 indicates position of eccentric at f cut-off, which can
be extended some by giving the steam valves a little more nega-
tive lap, but as this shortens the amount of lap when closed, it
may cause leakage in the steam valves.
'
COMPOUND ENGINE.
The compound engine is practically two single engines con-
nected together and so arranged that the exhaust steam from
one engine passes into and becomes the c ' live " steam for the
other, in other words the first, or high pressure cylinder receives
its supply of steam from the boiler and the second or low
pressure cylinder receives its supply from the high pressure
cylinder. The object of the compound engine is to enable the
steam to expand to the lowest possible pressure with the least
loss by condensation. When steam expands its temperature
decreases, so that by the time the piston reaches the end of the
stroke the temperature of the steam and consequently the tem-
perature of the cylinder walls is considerably below the temper-
ature of the incoming steam. The fresh steam of high tempera-
ture coming from the boiler comes in contact with the walls of
the cylinder which have been cooled to the temperature of the
exhaust steam, and the result is a considerable portion of the
fresh steam is condensed, the latent heat serving to reheat the
HANDBOOK ON ENGINEERING.
223
224 HANDBOOK ON ENGINEERING.
cylinder walls. It will be understood that were it possible to
keep the cylinder at a higher temperature, less steam would be
condensed in warming it at each stroke and consequently more
steam would be available for useful work. In the compound
engine the steam is expanded partly in one cylinder and partly
in the other so that the difference between the temperatures of the
incoming and exhaust steam in each cylinder is greatly reduced.
By this means steam may be expanded from a given initial pres-
sure to a given final pressure with a loss of nearly twenty-five
per cent less than would be incurred were the same expansion to
take place in a single cylinder. It is due principally to avoiding
the loss by cylinder condensation that the compound engine,
considered as a type of engine, can perform nearly twenty-five
per cent more work with the same weight of steam than can be
obtained when the steam is expanded in one cylinder only.
In order to utilize the low pressure steam escaping from the
high pressure cylinder it is necessary to provide a larger area
of piston so that the low pressure steam acting on a large sur-
face will do as much work as the high pressure steam acting on a
smaller area. It is for this reason that the low pressure cylinder
of compound engines is always made larger than the high pressure
cylinder. The required size of low pressure cylinder for a given
size of high pressure, depends upon the number of times the
steam is to be expanded, the initial steam pressure and the nature
of the work the engine is intended for. For steady loads the
difference in the size of the two cylinders may be greater than
where the load is constantly changing between wide limits as
nearly always occurs in street railway service.
Compound engines, as this term is generally employed, are
built of two types, the tandem compound, Fig. 145, and the cross
compound, Fig. 146. In the tandem compound the work of both
pistons is transmitted to the crank through one piston rod, cross-
head and connecting rod, while in the cross compound there are
HANDBOOK ON ENGINEERING.
225
226 HANDBOOK ON ENGINEERING.
two complete engines placed side by side, the cranks of which
are generally set 90 degrees apart. It will be seen that in the
tandem compound engine it makes but little difference from the
mechanical standpoint whether the work is divided evenly between
the two c}7linders or not because both pistons move in unison
and drive the same crank. In the cross compound engine it is
necessary, in order to secure a uniform turning effort at the
shaft, to have the work divided as nearly equally between the
two cylinders as the conditions will permit. In the tandem com-
pound engine the principal consideration is the proper working
of the steam, and the sizes of the cylinders are determined by
the number of expansions to be effected in both cylinders, or
the total number of expansions, as it is called, and the initial
pressure. As the equal division of the work between the two
cylinders in compound engines is essential, the ratio of the cylin-
ders is generally for noncondensing 2i to 1 for 100 Ibs., 2J to 1
for 125 Ibs., and 3 to 1 for 150 Ibs. initial pressure, and for con-
densing 3 to 1 for 100 Ibs., 3J to 1 for 125 Ibs., and 4 to 1 for
150 Ibs., initial pressure.
The number of expansions required in a compound engine is
represented by the quotient of the absolute initial pressure divided
by the absolute terminal pressure. If steam is to be used at 105
pounds gauge pressure and is to be expanded down to 10 pounds
105 + 15
absolute in the low pressure cylinder, there will be r^ = 12
HANDBOOK ON ENGINEERING. 227
3.2, equals ratio of cylinders. Care should be taken in non-
condensing engines so that the ratio of the low pressure cylinder
is not too large, as in such cases the steam in low pressure cylin-
der would expand to less than the atmospheric pressure, and
thus make loops on indicator card which would incur a serious
loss.
The calculation of the diameters of cylinders for a compound
condensing engine when the data are given, follows. Take an
engine that is to develop 500 horse power with an initial pressure
of 105 pounds gauge, or 120 pounds absolute, the steam to be
expanded to a terminal pressure of 6 pounds absolute. The total
expansion of steam in both cylinders is 120 -r- 6 =20.
Expansion in each cylinder = ^/ 20 =4.47.
Point of cut-off in each cylinder, per cent of stroke = =
22.3 per cent, 1 + hyp. log. of expansion in each cylinder = 1 +
hyp. log. 4.47 = 2.497.
Terminal and back pressure in high pressure cylinder, and the
120
initial pressure in the low = j^: = 26.8 pounds.
Mean effective pressure in h. p. cyl. =26.8 X2.497 — 26.8
= 40.11 pounds.
Mean effective pressure in 1. p. cyl. (assuming 3 Ibs. back
press.) = 6 X 2.497 — 3 = 11.98 pounds.
If half the work is to be done in each cylinder, which is de-
sirable in cross compound engines, each cylinder must do 250
horse power of work. Assuming the piston speed to be 600 feet
per minute, the area of the low pressure cylinder is
33000 XH.P. 33,000 X 250
Piston speed X effective press. == 600 X H-98 = L47* 7 SqU8
inches =38 ins. diameter.
33,000 X 250
Area of high pressure cylinder by same rule is : — I
OUU /\ 4U.XJ.
= 342.3 square inches = 21 inches diameter.
228
HANDBOOK ON ENGINEERING.
Ratio of cyl. =
40.11
11.98
= 3.3 to one.
The clearance and the areas of the piston rods have not been
taken account of by separate processes in the foregoing calcu-
lations. These should always be included when making calcu-
lations involving the pressure and expansion of steam in engine
cylinders. The method of finding the number of expansions
taking place in a compound engine may be readily understood
by referring to the diagram, Fig. 147. The shaded area in the
Fig. 147. Relative volume of high and low pressure cylinders.
smaller cylinder represents the initial volume of steam in the
high pressure cylinder, that is to say, this represents the volume
of steam taken from the boiler for one stroke, or during one-half
revolution. The point of cut-off is at one-third stroke and the
area of the low pressure cylinder is three times that of the high
pressure cylinder. It will be seen that when the low pressure
piston moves to one-third stroke the volume of the cylinder F
behind the piston is equal to the volume of the entire high pres-
sure cylinder. This shows that the capacity or contents of the low
pressure cylinder is three times that of the high so that for every
HANDBOOK ON ENGINEERING.
229
volume of steam and therefore for every expansion taking place in
the high pressure cylinder there will be three volumes, and three
expansions taking place in the low pressure cylinder. This
shows why the total number of expansions in a compound engine
is the number in the high pressure cylinder multiplied by the
number in the low pressure cylinder. In the diagram, Fig. 147,
when the small piston reaches the end of the stroke the steam
will have expanded three times, that is, it will occupy three times
the space it did at the point of cut-off. Now when the large
piston reaches the end of the stroke each of the three volumes a,
a and a, Fig. 148, will have been expanded three more times and
the total will be 3 X 3 = 9 expansions, that is, the original volume
a, Fig. 147, will then occupy nine times the space it did when
0
Fig. 148. Showing number of expansions in both cylinders.
first let into the high pressure cylinder. To find the number of
expansions in a compound engine multiply the number of expan-
sions in the high pressure cylinder by the number in the low, or
multiply the number of expansions in the high pressure cylinder
by the ratio of cylinder areas ; the product will be the number
required.
Again referring to Fig. 148, it will be seen that the low pressure
cylinder must receive a high-pressure cylinderf ul of steam at each
230 HANDBOOK ON ENGINEERING.
stroke otherwise the pressure in the receiver and the back pressure
on the high pressure piston will rise too high and a loss of power
will result, or if the pressure be too low in the larger cylinder the
small piston will drive the larger one which will again result in
loss of power. It has been shown that the volume of both
cylinders vary in proportion to the areas, that is, if the areas are
as 1 to 3 then when both pistons have reached, say, one-third
stroke the volume of one will be 3 times the volume of the other,
and when the larger piston in this case travels one-third of the
stroke- the capacity of the low pressure cylinder behind the piston
will then be equal to the whole of the smaller cylinder and will be
capable of containing all the steam used during a full stroke of
the smaller piston, or a high-pressure cylinderful of steam. This
steam then expands during the remaining two-thirds of the stroke.
Now it will be readily understood that if a cut-off valve were pro-
~ Vacuum
Figs* 149 and 150. Diagram from h. p. and 1. p. cylinders.
vided on the low pressure cylinder and is set to cut off at less than
one-third stroke (with a ratio of cylinder areas 1 to 3) the low
pressure cylinder will not take a high pressure cylinderful of
steam when steam is cut off, and the pressure in the receiver must
necessarily rise. Reducing the volume of steam entering the low
pressure cylinder apparently tends to lessen the work done by the
larger piston and consequently more work must apparently be
HANDBOOK ON ENGINEERING. 231
done by the high pressure piston. This in turn causes a later
cut-off in the small cylinder as shown in Fig. 149, dotted lines,
which serves to neutralize the effect of the higher back pressure
so that while the cut-off has been made later, the mean effective
pressure remains practically the same. The higher back pressure
on the small piston means a higher initial pressure in the low
pressure cylinder, see Fig. 150 dotted lines, which causes more
power to be developed in the latter cylinder. Thus it is seen
that, within certain limits, shortening the cut-off in the low pres-
sure cylinder puts more of the load upon the low pressure piston.
On the other hand when the low pressure piston is doing more
work than the high pressure, the cut-off in the low pressure
cylinder maybe lengthened. This permits the low pressure
cylinder taking more steam and consequently the receiver pressure
and the back pressure on the high pressure piston are reduced
and the work done by the high pressure piston is thus increased.
By manipulating the cut-off on the low pressure cylinder the load
on the two pistons may be equalized or very nearly so except
when the engine is considerably underloaded or overloaded. The
range of maximum economy is not as great with the compound as
with the simple engine, that is to say, the loads :$aay be varied
more widely from the point where the best economy is obtained,
in the simple engine than in the compound which is due to the
large difference in cylinder areas in the latter engine. At very
early cut-off both the high pressure and the low pressure cylinders
work the steam very similarly to the simple engine and as the loss
by cylinder condensation increases with an increase in the range
of temperatures it follows that an underloaded compound engine
is but little if any more economical than a simple engine working
with a similar initial point of cut-off.
In compound automatic cut-off engines the point of cut-off will
be nominally the same in both cylinders, we say nominally (in
name only) because the initial pressure and the extent of the
232 HANDBOOK ON ENGINEERING.
vacuum have some influence upon the receiver pressure and the
mean effective pressure in the low pressure cylinder. In most
compound engines in which the cut-off mechanism of both cylin-
ders are operated by a single governor, provision is made for
adjusting the cut-off of the low pressure cylinder relative to that
in the high, so that while the nominal cut-off may be, say, one-
fourth stroke, the actual points of cut-off maybe one-fourth in the
high pressure and T5^ in the low pressure cylinder, the governor,
however, varying both points of cut-off as the load changes.
HORSE POWER OF COMPOUND ENGINE.
Little can be done in finding the horse power of compound en-
gines without the indicator because of the uncertainty of the points
of cut-off and consequently of the back pressure and mean effec-
tive pressures. The mean effective pressure in each cylinder may
be computed by using assumed data, by the same rules given
for simple engines, but it will readily be understood that assumed
data furnishes assumed results only. Knowing the mean effective
pressure areas and speed of the pistons the horse power of a
compound engine is found as follows: Multiply the area of
the high pressure piston by its mean effective pressure and
divide by the area of the low pressure piston, then add this quotient
to the mean effective pressure in the low pressure cylinder.*
Call this answer 1. Multiply the area of the low pressure
piston by the piston speed in feet per minute and by answer 1,
and divide the last product by .33, 000; the quotient will be
the indicated horse power.
CONDENSING ENGINES.
It has been explained that the atmosphere exerts a pressure
of about 15 Ibs. per square inch on all surfaces with which it
* This quantity is to be taken as the M. E. P. when finding steam con-
sumption of compound engine.
HANDBOOK ON ENGINEERING. 233
is in contact. The atmosphere is in contact with one side of
an engine piston when the exhaust is open, and, consequently,
the steam in pushing the piston forward, has to overcome this
atmospheric pressure of 15 Ibs. per square inch. The useful
pressure of steam is, therefore, whatever pressure there is
above the pressure of the atmosphere, and this is the pressure
that the steam gauge shows. When the gauge says 60 Ibs. we
really have 75 Ibs., but 15 Ibs. of it does not count, because it
is balanced by the atmospheric pressure on the other side of
the piston. If we had sixty-pound steam pressing on the pis-
ton and could get rid of the atmospheric pressure on the side
of the piston, the steam would exert a force of 75 Ibs. per square
inch, a very respectable gain, indeed. We might remove the air
pressure by pumping it out, but the amount of power required in
doing the pumping would be equal precisely to all gain hoped for,
plus the friction of the pump; therefore, there would be an
actual loss in the operation. But there is another way of remov-
ing the air pressure. It has been explained that a cubic inch of
water vaporizes and expands into a cubic foot of steam at -atmos-
pheric pressure. If, after getting this cubic foot of steam, we
take the heat out of it, we again turn it into the cubic inch of
water. Assume the engine cylinder to hold just a cubic foot of
steam, and assume that the stroke is complete and ready for the
exhaust valve to open and permit this foot of steam to escape,
and assume that this cubic foot of steam has expanded
down to atmospheric pressure, that is, 15 Ibs., absolute pressure.
Now, instead of opening the cylinder to the atmosphere, we dose
the cylinder with cold water. The heat leaves the steam and
goes into the water and the steam turns to water, leaving in the
cylinder the condensed steam in the form of a cubic inch of
water. The steam formerly filled the cylinder, and now it fills
but a cubic inch of it, consequently, we have produced in the
cylinder a vacuum, which has the effect of adding about 15 Ibs.
234 HANDBOOK ON ENGINEERING.
per square inch, to the force of the steam on the other side of the
piston, by virtue of removing that much resistance to its forward
motion. The heat,which was in the steam, has gone into the con-
densing water, except the trifle that remains in the cubic inch of
condensed steam. We must get this condensed steam out of the
cylinder, and it will be an advantage to pump it back into the
boiler, for it is pure and it is hot.
This is the general principle of the condensing engine. It
gives us the grand advantage of a heavy increase in the useful
pressure acting to push the piston forward ; it gives us pure
water for use in the boiler, and it saves in the feed- water the
heat that would otherwise go out of the exhaust pipe. But it is
not practicable to condense the steam in the cylinder by dosing
the cylinder with cold water. In practice, the steam is allowed
to go into a separate condensing vessel, called the condenser.
The condenser is precisely the opposite of the boiler. The boiler
is the machine for putting heat into the steam to vaporize it, and
the condenser is the machine for taking heat out of the steam and
turning it into water again. In the condensing engine, one of
these machines is pushing on the piston and the other machine is
pulling on the piston. The gain by condensing is so great that
it is a profitable piece of business to apply a condenser to any
large non-condensing engine. The condenser requires a pump to
withdraw the water of condensation, and this pump must be in
reality an air-pump. In practice, they employ an air-pump and
condenser combined in one structure, separate from the engine,
and driven either by rod connection from the engine, or by a belt
from the engine, or by an independent steam device. The arrange-
ment will depend much upon the situation. The belt-driven pump
permits of the condenser being set in any convenient position
independent of the engine.
HANDBOOK ON ENGINEERING. 235
CONDENSERS.
When steam expands in the cylinder of a steam engine, its
pressure gradually reduces and ultimately becomes so small that
it cannot profitably be used for driving the piston. At this stage,
a time has arrived when the attenuated vapor should be disposed
of by some method, so as not to exert any back pressure or
resistance to the return of the piston. If there were no atmos-
pheric pressure, exhausting into the open air would effect the
desired object. But, as there is in reality a pressure of about
14.7 pounds per square inch, due to the weight of the super-
incumbent atmosphere, it follows that steam in a non-condensing
engine cannot economically be expanded below this pressure, and
must eventually be exhausted against the atmosphere, which
exerts a back pressure to that extent.
It is evident that if this back pressure be removed, the engine
will not only be aided by the exhausting side of the. piston being
relieved of a resistance of 14.7 pounds per square inch, but
moreover, as the exhaust or release of the steam from the engine
cylinder will be against no pressure, the steam can be expanded
in the cylinder quite, or nearly, to absolute 0 of pressure, and
thus its full expansive power can be obtained.
Contact, in a closed vessel, with a spray of cold water, or with
one side of a series of tubes, on the other side of which cold
water is circulating, deprives the steam of nearly all its latent
heat, and condenses it. In either case the act of condensation is
236 HANDBOOK ON ENGINEERING.
almost instantaneous. A change of state occurs and the vapor
steam is reduced to water. As this water of condensation only
occupies about one sixteen-hundredths of the space filled by
the steam from which it is formed, it follows that the remainder
of the space is void or vacant, and no pressure exists. Now, the
expanded steam from the engine is conducted into this empty or
vacuous space, and, as it meets with no resistance, the very limit
of its usefulness is reached.
The vessel in which this condensation of steam takes place is
the condensing chamber. The cold water that produces the con-
densation is the injection water ; and the heated water, on leaving
the condenser, is the discharge water. To make the action of the
condensing apparatus continuous, the flow of the injection water
and the removal of the discharge water, including the water from
the liquefaction of the steam, must likewise be continuous.
The vacuum in the condenser is not quite perfect, because the
cold injection water is heated by the steam and emits a vapor of
a tension due to the temperature. When the temperature is 110
degrees Fahr. , the tension or pressure of the vapor will be
represented by about 4" of mercury ; that is, when the mercury in
the ordinary barometer stands at 30", a barometer with the space
above the mercury communicating with the condenser, will stand
at about 26". The imperfection of vacuum is not wholly traceable
to the vapor in the condenser, but also to the presence of air, a
small quantity of which enters with the injection water and with
the steam ; the larger part, however, comes through air leaks and
faultly connections and badly packed stuffing boxes. The air
would gradualty accumulate until it destroyed the vacuum, if
provision were not made to constantly withdraw it, together with
the heated water by means of a pump.
The amount of water required to thoroughly condense the
steam from an engine is dependent upon two conditions : the total
beat and volume of the steam, and the temperature of the injection
HANDBOOK ON ENGINEERING.
237
water. The former represents the work to be done, and the latter
the value of the water by whose cooling agency the work of con-
densation of the steam is to be accomplished. Generally stated,
with 26" vacuum, the injection water at ordinary temperature, not
exceeding 70° Fahr., from 20 to 30 times the quantity of water
evaporated in the boilers will be required for the complete
liquefaction of the exhaust steam. The efficiency of the injection
water decreases very rapidly as its temperature increases, and at
80° and 90° Fahr. , very much larger quantities are to be employed.
Under the conditions of common temperature of water and a
vacuum of 26" of mercury, the injection water necessary per
H. P. developed by the engine, will be from 1J gallons per minute
when the steam admission is for one-fourth of the stroke, up to
two gallons per minute, when the steam is carried three-fourths of
the stroke of the engine.
WEIGHT OF WATER REQUIRED TO CONDENSE 1 POUND OF
STEAM.
Temp, of
Hot Well.
Back Press,
in Cylinder.
Lbs.
Temperature of Injection Water, Degs. F.
40
50
60
70
80
90
100
.94
17.8
21.4
26.8
35.7
53.5
107.
110
1.27
15.1
17.7
21.2
26.5
35.3
53.
120
1.68
13.1
15.
17.5
21.
26.3
35.
130
2.21
11.6
13.
14.9
17.3
20.8
26.
140
2.88
10.3
11.4
12.9
14.7
17,2
20.6
For other temperatures use the following formulas: —
JET CONDENSER. SURFACE CONDENSER.
Weight of water per Weight of water per
Ib. steam condensed =
1170
Ib. steam condensed =
H + 32 — Ti
_ , . ti _ ^
In which T = temperature of hot well, t = temperature of the injec-
tion water, TI = temp. of condensed steam, ti = temp of circulating
water leaving, and t2, the temp, of the circulating water entering the
condenser, H = total heat in steam above 32° F.
238
HANDBOOK ON ENGINEERING.
CHANGING FROM NONCONDENSING TO CONDENSING.
When it becomes necessary or desirable to change a simple
noncondensing engine to a simple condensing engine, or to change
a compound noncondensing to a compound condensing engine,
a slight change in the adjustment of the exhaust valves of the
simple engine and of the exhaust valves on the low pressure cyl-
inder of the compound will in nearly all cases be found necessary
in order to preserve the running qualities of the engine. The
cause for this change may be explained as follows : In the first
place it should be borne in mind that the pressure of steam varies
inversely (oppositely) as the volume, and that when considering
the volume and pressure of steam, all pressures are taken or
measured above a perfect vacuum or above zero, in other words,
only absolute pressures are to be considered. If 10 cubic feet of
steam at zero gauge pressure, or at atmospheric pressure, which
is 15 pounds absolute, be compressed into a space containing 5
2/a,cutttn Line..
Fig. 151. Showing point of exhaust closure non-condensing.
cubic feet, the pressure of the steam will be raised to 30 pounds
absolute, or 30 — 15 = 15 pounds by the gauge. Thus reducing
toe volume one-half serves to double the pressure. It will be
HANDBOOK ON ENGINEERING. 239
understood that this rule works both ways, namely, if the volume
be doubled the pressure will be reduced one-half. Applying this
principle to an engine, suppose the pressure during the return
stroke in Figure 151 is 18 pounds absolute, and that the exhaust
valve closes when the piston reaches the point A. The volume of
steam entrapped in the cylinder at this point in the stroke is taken
as the original volume. When the piston moves to the point B,
the volume will have been reduced one-half, and consequently the
pressure will have been doubled and will have risen to 36 pounds.
When the piston reaches the point (7, the volume will be but one-
fourth of the original volume, and consequently the pressure will
be four times the pressure of the original volume, or 18x4 = 72
pounds absolute, or 72 — 15—57 pounds by the gauge. As the
space x represents the clearance, the steam cannot be further
compressed so that the pressure of compression in this case is 72
pounds absolute, or 57 pounds gauge pressure. Suppose that
the engine runs perfectly smooth and noiselessly with that amount
of compression. If the compression be increased or decreased
the engine will be apt to pound and possibly to run warm. Now
suppose the engine be changed to condensing and that the back
pressure be reduced to 4 pounds absolute. If the adjustment of
the exhaust valves be not changed compression will begin at the
same point in the return stroke. Referring to Figure 152, it will
be seen by the full lines that the pressure of the original volume
is now 4 pounds absolute. When the piston reaches the point
the volume will be one-half of the original volume and conse-
quently the pressure will be doubled, and will now be 8 pounds
absolute. When the piston reaches the point (7, the volume of
steam will be reduced to one-fourth the original volume, and the
pressure will be four times the pressure of the original volume, or
16 pounds absolute, which is 1 pound by the gauge. It will thus
be seen that if the engine requires 57 pounds compression in
order to run smoothly it cannot be expected to run smoothly with
240
HANDBOOK ON "ENGINEERING.
only 1 pound compression by the gauge. In order to obtain the
same pressure at the end of compression with steam of lower pres-
sure the exhaust valve must close the port earlier in the return
stroke. With the Corliss engine this may be accomplished by
adjusting the radial rods connecting the exhaust valves with the
wrist plate and in slide valve engines by adding exhaust or inside
lap to the valve. To find the number of times the volume of the
clearance x must be increased in order to lower the pressure from
72 pounds to 4 pounds absolute, divide the pressure of compres-
C 3 A l/a*,u,K,tn Line
Fig. 152. Showing point of exhaust closure condensing.
sion by the back pressure thus 72 -~ 4 = 18 times. Now, by
simply reversing this rule it will be seen that, in order that steam of
4 pounds may be compressed to a pressure of 72 pounds the volume
must be reduced to fa of the original volume, therefore the origi-
nal volume a must be equal to 18 times the volume of the clearance
space x as shown by the dotted lines in Figure 152. Now, when
the exhaust valve closes at a, Figure 152, the pressure is 4
pounds ; at b the volume is but one-half, and the pressure 8
pounds ; at c the volume is one-fourth and the pressure 16 pounds ;
at d the volume is -j^ °f the original volume a, and the pressure
is 18x4 =^72 pounds, which is the pressure required for smooth
HANDBOOK ON ENGINEERING. 241
running. It will thus be seen that the same pressures are required
whether running noncondensing or condensing, and that in order
to get the same pressure of compression when running condens-
ing as when running noncondensing, the exhaust valve must close
earlier in the return stroke.
It will also be understood that when changing from condens-
ing to noncondensing the order of things must be reversed, viz.,
the exhaust valve must close the port later in the return stroke
because the higher the back pressure, the greater will be the
pressure of compression. This explains why a condensing engine
pounds and heats when the vacuum becomes impaired or is lost
altogether. In this case the back pressure rises from that
obtained when running condensing to the pressure obtained non-
condensing and consequently the compression is much too high
for smooth running. On the other hand when changing from
noncondensing to condensing the back pressure is so low that
scarcely any compression can be obtained, and if the engine
requires considerable compression it is apt to pound and heat
when the change is made provided the exhaust valves are not
readjusted.
It frequently happens that the change from noncondensing to
condensing is made at the end of the week, and in this case it is
desirable to adjust the valves on Sunday to their approximate
position by means of the marks on the valves, so as to avoid, as
far as possible, any trouble when starting up on Monday morn-
ing. Under these circumstances it is desirable to estimate the
extent of the change necessary in the adjustment of the valves.
Multiply the length of the stroke in inches by the percentage of
clearance and by one-fourth the absolute pressure of compression
when running noncondensing ; this product is the approximate
point of exhaust closure when running condensing. Then
lay off this distance, beginning at the ends of the guides.
When the crosshead is within this distance of the end of
16
242 HANDBOOK ON ENGINEERING.
the return stroke, the exhaust valve should have just
closed the port. For illustration, suppose an 18x42 Corliss
engine is to be changed from noncondensing to condensing. The
clearance is 3 per cent and the pressure of compression is 44
pounds absolute. The clearance is equal to 42x.03 = 1.26 inches
of the stroke, and one-fourth of the pressure of compression
when running noncondensing is 44 -v- 4 = 11 pounds, so that the
distance to be laid off on the guides is 1.26x11 = 13.86 or 13|
inches, that is, when the back pressure is reduced to 4 pounds
absolute by the condenser, the exhaust valve should close when
the piston reaches a point 13 £ inches from the ends of the return
stroke in order to obtain approximately the same compression as
when running noncondensing.
It will be understood that this is merely a method of approxi-
mating the pressure and should not be relied upon except for
making temporary adjustments.
The only reliable method of setting the exhaust valves when
making changes of this kind is by means of the indicator be-
cause the pressures vary from several causes the effect of which
cannot be calculated with a sufficient degree of accuracy for this
purpose. This is true of both the simple and compound engines,
the same method being used with the low pressure cylinder of the
compound as with the simple or single cylinder engine.
TYPES OF CONDENSER.
Condensers may be divided into three general types or classes
known as the surface, the jet and the siphon condensers. The
latter type is sometimes referred to as the barometric condenser.
The surface and jet condensers require an air pump and these two
types are either direct driven or independent. The direct driven
condenser is now little used for stationary work, being confined
almost entirely to marine engines, and even there the independent
HANDBOOK ON ENGINEERING. 243
condenser is being very extensively used. The direct connected
condenser is driven either by a belt or a direct connection to the
crosshead of the main engine. The working vacuum is not obtain-
able in the direct connected condenser until after the engine is started
and has made several revolutions. The disadvantage of the direct
connected condenser is that the speed is always proportional to
the speed of the engine so that the vacuum can only be regulated
by changing the supply of injection or circulating water as the
case may be. The independent condensers are driven by a steam
cylinder forming a part of the condenser apparatus so that the
vacuum can be maintained by regulating the supply of condensing
water, and also by changing the speed of the air pump irrespec-
tive of the speed of the engine. The greater flexibility of the
independent condenser enables it to maintain the working vacuum
under widely changing loads and speeds. The cost of operating
the latter type of condenser is greater than of the direct driven
types because the power required for direct driving is obtained at
the same cost per horsepower as that delivered by the engine,
while the cost of operating the independent condenser is practi-
cally the same as that of an ordinary steam pump. This apparent
loss can be largely avoided by utilizing the exhaust steam from
the condenser for heating the feed water.
The following illustrations represent the three principal con-
structions of condenser to be found in the average stationary
practice.
A sectional view of the surface condenser with air and circu-
lating pumps attached is shown in Fig. 153. It consists of a
shell, usually of cast iron, containing a large number of small
brass or copper tubes through which the condensing, or circulat-
ing water as it is called, is pumped by the circulating pump.
The water enters the chamber at one end of the condensing
chamber and flows through one bank of tubes into a chamber at
the opposite end and thence back again and out at the top into
244
HANDBOOK ON ENGINEERING.
the discharge pipe. The steam enters the condensing chamber
at the top where the current is divided by a baffle plate, which
sends the steam in both directions and distributes it more evenly
over the cool tubes, the steam being condensed by coming in
contact with the tubes, the temperature of which is the same as
that of the circulating water flowing through them. The con-
densed steam collects in the bottom of the condensing chamber
and flows into the suction pipe of the air pump, which also removes
the air and aids in maintaining the vacuum. The steam cylinder
Fig. 158. Diagram of Surface Condenser.
is placed between the air and circulating pumps, the pistons
being connected to the same piston rod.
Surface condensers embody two constructions or arrangements
of tubes. In one the tubes are connected to tube plates, the
arrangement being similar in every way to the return tubular
boiler. The other construction is known as the double tube con-
denser in which two sets of tubes are employed, one within the
other as shown in Fig. 153. The circulating water flows through
HANDBOOK ON ENGINEERING. 245
the inner tubes and returns through the outer or larger ones.
This construction has the advantage in that the outer tubes are
kept at practically the same temperature throughout their length,
thus increasing the efficiency of the tube surface. Water will
absorb heat more rapidly when flowing at a high velocity than at
a low velocity, consequently the double tube condenser can be
made smaller for a given capacity than the single tube type. The
air pump discharges into the hot well, and as the circulating
water does not come in contact with the steam, either before or
after it is condensed, the water in the hot well is always pure, or
nearly so, and suitable for use in the boilers. When the surface
condenser is employed the steam passes from the low pressure
cylinder into the hot well and consequently some provision should
be made for removing the oil from the exhaust steam. Greasy
condenser tubes are not as efficient as clean ones and for this
reason it is advisable to place the oil extractor between the low
pressure cylinder and the condenser. Any oil that may pass
through the extractor and into the hot well may be avoided by
taking the supply to the boiler feed pump at a point below the
surface of the water in the hot well.
The surface condenser is particularly valuable where the water
is unfit for use in the boilers and for this reason it is used more
largely for marine than for stationary work.
The surface condenser furnishes the more reliable means of
measuring the steam consumption of engines and pumps because
the discharge of the air pump in a given time represents exactly
the quantity of water required by the engine in the same length
of time.
Fig. 154 is a sectional view of the independent jet condenser.
The external appearance, and sometimes the minor details of con-
struction, will vary slightly in this style of condenser but it is
fortunate for engineers that the principles involved and the
practical operation of jet condensers are precisely the same in all.
246
HANDBOOK ON ENGINEERING.
The steam and water cylinders and valves of the jet condenser
are identical to similar parts of the ordinary direct acting pump,
in fact, the jet condenser is a direct acting pump with a simple
condensing chamber connected to the pump suction. The con-
densing chamber resembles an air chamber in form, except that it
Fig. 154. Independent Jet Condenser.
is larger, and it is provided with an inlet for the exhaust steam
and an outlet for the injection or condensing water. The inlet
for the water is carried down to the spherical part of the condens-
ing chamber and terminates in a cone-shaped spraying device,
which throws the water out in an umbrella-shaped film against
the sides of the chamber. The exhaust steam enters above the
HANDBOOK ON ENGINEERING. 247
,
spray and cannot reach the pump below without passing into the
spray of cold water, which condenses it. The mixture of con-
densed steam and injection water is then drawn into the pump
and is finally discharged into the hot well. The admixture of
the condensed- steam with the injection water improves the quality
of the water in the hot well, provided means are employed for
removing the oil from the exhaust steam, thus rendering the water
better fitted for use in the boilers. The injection water is
regulated by means of a hand wheel at the top of the condensing
chamber which regulates the position of the cone at the end of the
water inlet.
When engines are lightly loaded, or liable to be for any length
of time, it is especially desirable to provide a safety device which
Tig. 155. Device for Breaking the Vacuum.
will break the vacuum when the water rises to a certain height in
the condensing chamber. If this is not done injury to the engine
is liable to occur at any time because should the speed of the
pump slacken, thus permitting water to accumulate in the con-
densing chamber, the vacuum will be impaired and the low
•
248
HANDBOOK ON ENGINEERING.
pressure cylinder will then act as an air pump, owing to the small
amount of steam admitted and the low pressure due to expansion,
and will thus draw the water into the cylinder probably wrecking
the cylinder completely. A simple safety device adapted to pre-
vent injury to the engine as the result of flooding the condenser
is illustrated in Fig. 155. It consists of a simple float con-
Fig. 156. Method of connecting up a Jet Condenser.
nected to an air valve at the side of the condensing chamber so
that when the water level rises high enough to raise the float, air
is admitted and the vacuum immediately destroyed. The ex-
haust steam from the engine then flows out through the atmos-
pheric relief valve into the atmosphere, and the engine is con-
HANDBOOK ON ENGINEERING. 249
verted into a noncondensing engine automatically and without
stopping.
Jet condensers will raise water for condensing purposes from 16
to 20 feet although it is desirable to keep the lift as low as pos-
sible because the higher the lift, the more it costs to operate the
condenser and consequently the net saving by running condensing
is correspondingly less.
The jet condenser requires precisely the same care as the direct
acting pump except that greater pains must be taken to prevent
the leakage of air and water. An engineer who can keep a direct
acting pump in first-class running order need have little trouble
in caring for a condenser whether it be large or small.
Fig. 156 illustrates the method of connecting the jet condenser
with the engine. When the exhaust steam from the condenser
cannot be profitably used for heating the feed water it can be
turned into the engine exhaust pipe, or into the condensing
chamber direct, and the condenser thus be made to run condens-
ing also.
The siphon condenser is illustrated in Fig. 157, and is the
simplest form of condenser in use at the present time. The
exhaust steam enters the somewhat contracted condensing cham-
ber through the cone-shaped nozzle, while the condensing water
enters at the side and surrounds the cone, the water issuing into
the chamber below through the annular orifice formed between
the cone and the walls of the condensing chamber. The water
issues at rather high velocity and expels the air from the exhaust
pipe. The steam upon leaving the cone-shaped nozzle flows into
an inverted cone, formed by the film of water issuing from the
annular orifice which condenses the steam. The condensed steam
and injection water flow at rather high velocity down through the
contracted neck, where the stream is solidified, into the tail pipe,
thence into the hot well. The neck of the condensing chamber is
contracted, thus forming a combining tube, for the purpose, of
250
HANDBOOK ON ENGINEERING.
giving the water sufficient velocity to maintain a siphon-like
action that draws the steam from the exhaust pipe and causes a
vacuum to exist in it. This style of condenser should be placed
34 feet above the level of the water in the hot well. An atmos-
pheric discharge or relief valve is placed at the top which
opens automatically when the vacuum is destroyed thus permit-
ting the exhaust steam to flow into the atmosphere. The siphon
Fig. 157. Siphon Condenser.
condenser will raise the condensing water to a height of from 15
to 18 feet so that when the water supply is located within that
distance of the top of the condenser no pump is required, the
condenser continuing to siphon over the water as long as steam
is condensed. When the condenser is operated without a pump
a starting pipe will be necessary ; this pipe connecting the water
supply with the tail pipe as shown in Fig. 158. When starting
the condenser, the valve in the starting pipe is opened, and the
HANDBOOK ON ENGINEERING.
251
water flowing through this and down the tail pipe will gradually
exhaust the air from the upper part of the tail pipe until sufficient
vacuum is formed to draw the water up to the condenser and
start the water flowing through it. When this is done the valve
in the starting pipe is closed, and the engine started.
Fig. 158. Siphon Condenser and Starting Talve.
Fig. 159 shows the method of connecting a siphon condenser
with the engine. In this illustration the condensing water is
supplied by a pump.
It frequently becomes necessary to destroy the vacuum and to
stop the engine on short notice, and for this reason it is desirable
to have some means of opening the atmospheric relief valve at the
top of the condenser. This is especially desirable when the con-
denser is arranged to siphon the water because any failure of the
condenser with a light load on the engine would result in water
being drawn into the low pressure cylinder and probably wrecking
it. An arrangement for thus breaking the vacuum is shown in
Fig. 159.
The water in the hot well consists of a mixture of condensing
252
HANDBOOK ON ENGINEERING.
water and condensed steam so that if the water is to be used in
the boilers means should be provided for removing the oil from
the exhaust steam, and the supply to the boiler feed pump
Fig. 159. Siphon Condenser connected to Engine and Pump.
should be taken at a point considerably below the water level in
the hot well.
The siphon condenser, when properly proportioned and con-
nected up maintains a good vacuum and possesses the advantage
HANDBOOK ON ENGINEERING. 253
that it contains no moving parts and nothing to get out of order,
while it is adapted to engines of all sizes, and under all condi-
tions which will permit it to be elevated to a height of 34 feet
above the level of the water in the hot well.
The quantity of condensing water required by the siphon con-
denser is the same as for the jet condenser and may be found by
means of the formulas on page 237.
STARTING AND RUNNING A COMPOUND CONDENSING
ENGINE.
The principal aim of the engineer in charge of a plant is to
keep his engine running, and to run safely, and when running
condensing the object also is to maintain the vacuum. The
vacuum is formed by removing the air from the exhaust pipe and
its immediate connections, including the condenser. Therefore
when air leaks in or is admitted through a valve either intentionally
or otherwise the vacuum will at once be destroyed. It will be
understood from this that all air leaks should be carefully stopped.
The principal points to receive attention when testing for air leaks
are, the stuffing boxes on both the engine and the condenser, and
also on the valves in pipes leading to and from the condenser.
A condensing engine and its condenser should be provided with
a solid foundation and be securely bolted to it. Vibration in the
piping is a common cause of leaky joints, and air leaks will affect
the vacuum very seriously. It is a good plan to test the exhaust
and condenser piping occasionally while the engine is running.
A lighted candle held close to the joints will serve to locate aleak,
which should be marked with a piece of chalk so as to be readily
found when an opportunity occurs to make repairs.
The vacuum may be reduced and even destroyed by too much
water as well as by too little. When too little water is admitted
all the steam is not condensed, and the accumulation of uncon-
254 HANDBOOK ON ENGINEERING.
densed steam raises the pressure in the condenser until finally the
back pressure valve opens and the engine exhausts into the atmos-
phere and, of course, becomes a noncondensing engine. When
too much water is admitted the air pump becomes flooded, the
volume of the condenser is decreased, .the injection interfered with,
and air gradually accumulates, causing the vacuum to become
less, sometimes rapidly and at others quite gradually depending
on the excess of water.
The condenser should be run at as low a speed as possible and be
able to discharge the necessary quantity of water, and to main-
tain the required vacuum. When air leaks occur the speed of the
condenser must be increased with the same load on the engine
and with other conditions the same, so that when it becomes nec-
essary to gradually increase the speed it indicates that leakage is
occurring either at some point in the exhaust piping, in the in-
jection pipe leading to the condenser or in the valves or piston in
the condenser itself. It is not profitable to allow the packing in
the stuffing boxes on the engine and condenser, and on the valves
in the piping, to remain as long as it will apparently work air tight
because when old packing begins to give out it generally becomes
useless in a very short time, and, furthermore, it seldom admits
of any adjustment with beneficial results. It is better to renew
the packing at shorter intervals and know that when a gland is
tightened the leakage will be stopped.
Generally speaking the higher the vacuum the better, but this
is not always true. When engines are very lightly loaded and have
but little resistance above that due to friction, it is sometimes
better economy to reduce the vacuum, thus slightly increasing the
period of admission, because the engine uses steam expansively
and the condenser does not, so that a part of the steam required
by the condenser can be used to better advantage in the engine
cylinder. It sometimes occurs that the boilers are too small,
and where an exhaust steam feed water heater is placed in the
•
HANDBOOK ON ENGINEERING. 255
low pressure exhaust pipe it will frequently be found more eco-
nomical to reduce the vacuum and thus send the feed water to
the boilers at a higher temperature. The regulation of the vacuum
under ordinary conditions should be governed by the position of
the governor as well as by the vacuum gauge, the object being to
maintain a vacuum that will keep the governor at the highest
position. Under certain conditions of load the cut-off will be
found to be shorter with 26 inches than with 27 or 28 inches
vacuum. The receiver pressure also has something to do with
the position of the governor. The receiver is usually a plain
metal cylinder placed beneath the engine room floor, and to which
the exhaust pipe from the high pressure cylinder and the steam pipe
to the low pressure cylinder are connected. The high pressure
cylinder exhausts into the receiver and the low pressure cylinder
takes its steam from the receiver. It will be understood from
this that the receiver virtually serves as the boiler for the low
pressure cylinder. The pressure in the receiver is generally a
little lower than the terminal pressure in the high pressure cylin-
der, while the receiver pressure and the initial pressure in the low
pressure cylinder are practically the same.
What is known as a reheater, which is sometimes used in con-
nection with compound engines, is merely a coil of steam pipe
placed in the receiver, steam of higher temperature than that of
the exhaust from the high pressure cylinder being admitted to the
coil which heats the steam in the receiver to a temperature higher
than that due to the pressure, thus serving to reduce the loss due
to condensation in the low pressure cylinder, and incidentally
improving the economy of the engine as a whole. Changing the
receiver pressure will oftentimes alter the position of the governor
by improving the distribution of the load between the high and
low pressure cylinders. It should be remembered in this con-
nection that lengthening the point of cut-off in the low pressure
cylinder reduces the receiver pressure and consequently tends to
256 HANDBOOK ON ENGINEERING.
throw more of the load on the high pressure cylinder, while short-
ening the cut-off in the low pressure cylinder tends to throw more
of the load on to the low pressure cylinder. The receiver pressure
is governed by two things, viz., the amount of steam put into it,
and the amount of steam drawn out of it. If the low pressure
cylinder draws more out of it than the higher pressure cylinder
puts into it, the pressure must fall because the volume is thus in-
creased. Engine cylinders are generally so proportioned that the
receiver pressure will be from 4 to 6 pounds lower than the ter-
minal pressure in the high pressure cylinder when the engine has
a fair load. When an engineer knows what the terminal pressure
in the high pressure cylinder is it is not difficult to set the cut-offs
to produce the desired results. When the high pressure exhaust
valves pound and lift from the seats it may be safely assumed that
the receiver pressure is higher than need be, and it will generally
be found practicable to lessen the pressure, which may be done
by lengthening the period of admission in the low pressure cylin-
der, being careful to note exactly the extent of the adjustment
because there is the possibility of other things causing the valves
to pound, and in that case the cut-off should be shortened again
exactly the same amount to which it had been lengthened.
For usual ratios of cylinder volumes, viz., from 3 to 1 or 4 to
1, and under average conditions of load on condensing engines,
a boiler pressure of 80 or 90 pounds will produce a receiver pres-
sure of about 5 pounds ; 100 pounds will produce from 7 to 10
pounds; 125 pounds from 12 to 15, and 150 pounds from 18 to
20 pounds. The receiver pressure frequently rises from 1 to 3
pounds with changes of load.
The best results are generally obtained when the load is equally
divided between the high and low pressure cylinders. The gov-
ernor should thus remain at the highest obtainable point with any
given load and with a moderately high vacuum, say 26 or 26 £
inches. The extent of changes to produce these results cannot
HANDBOOK ON ENGINEERING. 257
be foretold, but must be ascertained by experiment in each
case.
When about to start a compound condensing engine the first
thing to be done is to see that all the water is drained out of the
piping. If the engine is a Corliss or other four-valve engine the
high* pressure cylinder will readily get rid of the water, but this
water drains into the receiver, and if not removed will enter the
low pressure cylinder when the engine is started, and probably
wreck it. If there is a separator it should be carefully drained.
Then the pipe above the engine throttle, then the cylinder and
lastly the receiver. If these parts are thoroughly drained before
starting, what little water may enter the low pressure cylinder,
due to condensation in the high pressure cylinder and receiver,
will cause no trouble or damage provided the engine is started
slowly so as to give the water time to pass out through the exhaust
ports. The steam line to the condenser should also be drained
down to the condenser throttle so that when it is time to start the
condenser it can be done without delay.
About 20 minutes before time for starting the plant begin to
warm the cylinders. Place the wrist plates at their central posi-
tion. Open the throttle a little and also the live steam valve to
the receiver. Allow the receiver drain to remain open a little
until after starting. Then open the oil cups and the cylinder
lubricators and see that they are feeding the proper quantity of
oil.
If it is not desirable for any reason to start the engine in
advance of the other machinery, the wrist plates can be worked
back and forth a few times by hand, after which the throttle and
receiver valve should be closed, leaving the wrist plates in the
central position. A little practice will indicate how wide the
throttle can be opened and how high the receiver pressure may be
allowed to rise without moving the engine when working the
wrist plates. After warming the cylinders, the condenser may be
17
258 HANDBOOK ON ENGINEERING.
started. If the air pump is in proper running order the vacuum
gauge will soon indicate the vacuum, which ought to be increased to
about 25 inches. If the exhaust from the steam cylinder of the
condenser is run into the condensing chamber, the injection water
should be turned on after the air pump has made three or four
strokes, otherwise the injection water may be turned on immediately
upon starting the engine, or before if desired. When the run-
ning position of the injection valve is not known it may be tried at
from one-half to two-thirds open. When the air pump is running
properly inspect the overflow to see that the water is discharged
properly and freely. Considerable water will be discharged from
the condenser if the injection valve is open and the condenser is
working properly.
Returning to the engine, hook in the low pressure reach rod
and then the high pressure. Then open the throttle a little and
start the engine slowly so that any slight condensation which
may have accumulated can be worked out more slowly. After
the engine has made one or two revolutions attention should be
paid to the vacuum gauge to see that the condenser is getting the
proper amount of water. It is probable the injection valve will
have to be opened wider. The engine should be worked up to
speed gradually so that proper attention can be given to the
regulation of the injection water as the steam flowing into the
condenser gradually increases.
When the engine is up to speed and before the load is thrown
on it is a good plan to go to the end of the condenser discharge
pipe and find out how hot the water is. This may be done with
the hand. The water should be decidedly cooler than the hand,
but if not, more injection water must enter the condenser.
When the load is thrown on, it is a safe plan to again test the dis-
charge water and if the condenser is working properly it will now
be perceptibly warmer than the hand. It may be about as warm
as a person would ordinarily heat water for washing the hands.
HANDBOOK ON ENGINEERING. 259
When the discharge becomes' so hot as to be unbearable to the
bandit is a sign of impending danger, viz., that of losing the
vacuum.
It is a good plan to have a small auxiliary injection pipe con-
nected to the city mains or to the delivery pipe of any cold
water pump, which can be used to supplement the main injection
in emergencies of this kind. When a jet condenser lifts its own
water, it must lose the suction, as it is called, whenever it loses
the vacuum, so that without the aid of the auxiliary injection
pipe it can seldom regain the vacuum without allowing the
engine to exhaust into the atmosphere until the condenser can be
cooled. When xhe load suddenly increases and the discharge
becomes too hot, the normal temperature can generally be quickly
restored by opening the auxiliary injection valve. The auxiliary
injection is generally provided on condensers. It may enter
anywhere in the exhaust pipe. An auxiliary injection can be
made of a piece of 1£ or 2-inch pipe about 3 feet long, per-
forated with small holes so as to make a sprayer head, the sprayer
head being connected with the same sized pipe from the city main
or pump. The auxiliary injection is in every sense an emergency
apparatus and should be carefully watched while in operation,
and shut off as soon as the need of it ceases because it is not
automatic and if allowed to run unnoticed there is danger of
flooding the condenser and exhaust pipe and of working water
back to the engine. When the load on the engine is fairly steady,
or when the load fluctuates uniformly between certain limits the
condensing apparatus will require very little attention. The same
precautions should be taken with a condenser that raises its own
water as with a boiler feed pump, viz., to see that nothing inter-
feres with its continued operation, that the suction pipe is properly
protected so that no obstruction may enter and that the discharge
is always free.
It is sometimes necessary to change from noncondensing to
condensing without stopping the engine. In this case the gate
260 HANDBOOK ON ENGINEERING.
valve in the exhaust pipe leading to the condenser will be found
closed because this valve should always be closed when the con-
denser is not in use, otherwise the steam would be apt to injure
the valves in the condenser. The air pump is first started and
the injection valve opened in the same manner as when about to
start the engine, and is opened to the running position with a
load. When the condenser is working properly an assistant
should be stationed at the back pressure valve ready to close it
when signaled by the engineer. The gate valve in the exhaust
pipe is then partly opened, the engineer watching the vacuum
gauge to note the point at which the vacuum begins to drop. At
that moment he signals the assistant, who then closes the back
pressure valve. The gate valve is then opened wide. When
opening the gate valve, and before the back pressure valve is
closed, care must be taken not to continue to open the valve after
the vacuum begins to fall, otherwise the vacuum will be quickly
lost entirely.
When changing from condensing to noncondensing all that is
necessary is to close the gate valve in the exhaust pipe and stop
the condenser. As soon as the pressure in the exhaust pipe
equals that of the atmosphere, the back pressure valve opens
automatically.
The surface condenser is worked in the same manner as the jet
condenser, which has just been described. There is an extra
pump, which must keep the circulating water flowing through the
condenser tubes ; that much work being taken off the air pump.
The air pump has air and some water to handle in the same
manner as though it pumped the cooling water. Both these
pumps, together with the pump of the jet condenser, require the
same care and attention that the boiler feed pump does or any
pump that lifts water by suction.
When stopping a condensing engine, stop the engine first, then
the condenser, then shut off the oil cups and lubricators and
lastly open the drips.
HANDBOOK ON ENGINEERING.
261
SETTING THE PISTON TYPE OF VALVE.
The simple piston valve admitting steam between the pistons
is, in operation, the reverse of the plain D slide valve, which ad-
mits steam at the outer edges, or ends of the valve. To make
this still clearer it may be said that were the live steam to enter
through the exhaust cavity of the D slide valve its operation and
the position of the eccentric relative to the crank would be iden-
WMMWr/////J^<.
Fig. 160. Similarity between the slide and piston valves.
tical to the piston valve. Fig. 160 illustrates the similarity of
action and eccentric positions were these conditions to obtain.
In these types of valve, as ordinarily employed, the steam is
admitted at the ends of the slide valve, and between the pistons
or at the middle of the piston valve. The change from the end
to the middle of the valve necessitates a change in the position
of the eccentric relative to the crank in order to have the direc-
tion of rotation remain the same. The positions of the eccentric
when driving the simple D valve, and the piston valve, are indi-
262
HANDBOOK ON ENGINEERING.
cated in Fig. 161. It will be noticed that the crank revolves in the
same direction in both cases, and that when the crank leaves the
dead center, moving in the direction of the arrow, the same port,
viz., the one at the head end of the cylinder, will be opened at the
same time and to the same extent. This proves the positions as(
shown to be correct and illustrates why the eccentric must be
moved in the same direction the engine is to run with the D valve,
and in the opposite direction with the piston valve, in order to
secure the same direction of rotation in the engine.
f
Fig* 161* • Valves opening: the ports for admission.
When setting valves it is a good plan to obtain as much uni-
formity of methods as possible, because of the liability to con-
fusion when methods involving different movements of the
eccentric are employed. In all the directions that follow it is
assumed that the crank is placed on the dead center (sae page
195) nearest the cylinder so that when setting the different styles
of valves, the same steam port will always be opened first, namely,
the one at the head end of the cylinder. The engine, it will be
HANDBOOK ON ENGINEERING.
263
seen, 'is thus treated as though it contained but one steam port,
which greatly simplifies matters.
In order to show that each particular form of valve of the same
type does not require different methods for its proper adjustment,
both the simple piston valve and the main valve of the round riding
cut-off are illustrated together, the same directions applying to
both.
Where marks appear upon the valve stem, or seat, it becomes
an easy matter to set a valve quickly and correctly but when these
do not appear a different method must be pursued for obtaining
them. First remove the chest covers at both ends of the chest
Fig. 162. Templates used in setting piston valves.
and also the valve (both styles) from the chest and lay it upon a
clean place on the floor, or bench. Procure a piece of sheet steel
about T\ inch thick and file it to the form shown in Fig. 162.
Make the length of the gauge thus formed equal to the thickness
of the piston on the valve plus the lead, which may betaken as ^
inch. Replace the valve in the chest and connect it to the valve
stem. Turn the eccentric from one extreme position to the other
and see that the valve opens the ports an equal amount. It is not
necessary that the ports be opened exactly wide, the object being
to secure exactly the same opening at each end of the valve. If
the head end port is opened farther than the other, the eccentric
264 HANDBOOK ON ENGINEERING.
rod should be lengthened an amount equal to one-half the differ-
ence, and should the port at the crank end be opened farthest,
the eccentric rod should be shortened a like amount.
Turn the eccentric to the extreme position farthest from the
cylinder. Then place the small end of the gauge against the inner
edge of the port, and with a scriber make a fine line (a) on the
seat as shown in Fig. 163. Remove the gauge, and turn the eccen-
tric in the same direction the engine is to run until the end of the
valve reaches the fine line on the seat. Secure the eccentric to
the shaft, being careful not to move the eccentric in either direc-
tion. Now turn the crank in the direction it is to run until the
eccentric reaches the extreme position nearest the cylinder. The
gauge is now placed against the edge of the opposite port and a
Fig. 163. Showing the use of the template.
fine line drawn on the seat, at the end of the gauge, in the same
manner as shown in Fig. 163. Turn the crank to the dead center
farthest from the cylinder when the end of the valve should have
just reached the line on the seat. If it does not, the crank
should be turned sufficiently to enable the distance between the
valve and the mark, being measured. The eccentric rod is then
to be adjusted so as to move the valve a distance equal to one-
half of what the valve lacks of exactly reaching the line on the
seat. The valve will then open both ports to the extent of the
16
HANDBOOK ON ENGINEERING. 265
lead when the crank occupies the exact dead centers. It is very
desirable to have a method of setting the valve without removing
the chest covers. By the aid of simple gauges this can be readily
accomplished. Take a piece of steel wire and sharpen the
ends and bend into the form shown in Fig. 164. With a prick
punch make a mark (&) on the guide block, place one end of
gauge in this mark and make another mark (c) where the opposite
end of the gauge touches the valve stem. This gauge enables
the valve stem being disconnected from the valve stem guide
block, and the chest cover put on, and the stem afterward con-
nected up again in exactly the same position (see page 243).
Having made this second gauge, place the crank on the exact
dead center nearest the cylinder. Then make a prick punch mark
(d) on the stuffing-box, place one end of the gauge in this mark
and then make a second mark (e) where the other end of the
gauge touches the valve stem. It will readily be seen that when
testing the setting of the valve all that is necessary is to place
the crank on the dead center nearest the cylinder, then place the
gauge in the mark (d) on the stuffing-box, and have the eccentric
moved until the punch mark (e) on the valve stem falls under
the point of the gauge. The valve will then have opened
the port to the extent of the lead, because it was in
this position when the gauge and the marks were first
made. If the punch marks are nicely made and not too large
the extent of the lead opening may be measured at both ports,
by turning the crank to the opposite dead center and making a
second punch mark (/) on the valve stem by means of the gauge.
These two guages should be carefully preserved from injury and
from being mislaid so that in case of emergency, such as the
slipping of an eccentric, the latter can be returned to its correct
position without unnecessary loss of time.
266
HANDBOOK ON ENGINEERING.
SETTING THE CUT=OFF VALVE.
The following directions are applicable to both the flat slide
and the round types of slide valves.
The point of latest cut-off is seldom known exactly by the
average engineer because of its unimportance while the engine is
in running order, and as this point varies with different engines
it is advisable to discard it as an element in valve setting. First
place the main valve in its position of mid -travel, that is, place
it centrally over the ports. This may be accomplished by finding
the center between the punch marks (/) and (e) on the valve
stem, bringing the center mark g under the point of the gauge in
the manner shownin Fig. 164. The travel of thecut-off valve must
first be equalized which is accomplished by turning the cut-off
Fig. 164. Trams for setting the cut-off valve.
eccentric to its extreme positions and noting the travel of the
cut-off valve over the ports of the main valve. The cut-off eccen-
tric rod should be lengthened or shortened so that the cut-off
valve will travel evenly over the ports in the main valve. This,
of course, is obtained by measuring the distance from the edge
of the ports in the main valve to the ends of the cut-off valve when
the latter occupies its extreme positions.
First, assume the engine to have a fixed, or a hand-adjusted
cut-off, and that the cut-off valve is to be set to cut off steam at
HANDBOOK ON ENGINEERING.
267
one-half stroke. Place the crank on the dead center (see page
195) and the full part of the cut-off eccentric the same. Then
measure off one-half the length of the stroke from the end of the
cross-head as in Fig. 165 and make a light line/ on the guide. Turn
the engine in the direction it is to run until the end of cross-head
Fig. 165. Method of equalizing the cut-off.
reaches the line / on the guide. The piston will now have com-
pleted one-half its stroke. Turn the cut-off eccentric in the
direction the engine is to run until the cut-off valve opens the
port in the main valve wide and just closes the port again in the
main valve.
Secure the cut-off eccentric to the shaft at this point.
Turn the crank over to the opposite dead center and far enough
beyond the center so that the same end of the crosshead will have
again reached the line (/) on the guide as in Fig. 165. The piston
will now have completed one-half of the return stroke and the
cut-off valve should have just closed the port in the main valve.
If the cut-off valve has moved too far, or notfar enough, measure
the amount it lacks of just closing the port and then adjust the
cut-off eccentric rod an amount equal to one-half the amount of
268 HANDBOOK ON ENGINEERING.
the discrepancy. The cut-off valve will then close the port in the
main valve at exactly the same point in both forward and return
strokes.
When an automatic cut-off engine, in which the cut-off
eccentric is operated by a shaft governor, first block out the
weights to their extreme position or against the stops, the travel
of the cut-off valve having been previously equalized in the
manner explained above. Then turn the crank to the dead center,
preferably the one nearest the cylinder, and turn the full part of
the cut-off eccentric to the same position as a starting point.
Then turn the eccentric in the direction the engine is to run until
the cut-off valve opens the port in the main valve to the extent of
the lead or from ^ to -^ inch. Secure the governor wheel to
the shaft at this point. Turn the crank to the opposite dead
center and see that the cut-off valve has opened the port in the
main valve to the same extent , If it hac not done so, adjust the
length of the eccentric rod an amount equal to one-half the differ-
ence between the two lead openings. Take out the blocks and
the work will be completed. It will readily be understood that,
were the speed of the engine to reach a point, where the
governor weights strike the stops, the cut-off valve will admit
only steam enough to fill the clearance, which should always be
done, because while it does not tend to accelerate the speed it
does prevent forming a vacuum in the cylinder, and from drawing
in whatever may happen to be in the vicinity of the end of the
exhaust pipe. The point of latest cut-off will then take care of
itself and will occur at that point for which the valve and gear
were designed.
FLAT VALVE RIDING CUT-OFF.
In medium and slow speed engines it is very desirable to have
a uniform point of release and constant compression. If the
engine is of the automatic cut-off variety the point of cut-off will
HANDBOOK ON ENGINEERING. 269
necessarily change with each change of load, and if the steam is
released, and the point of compression determined by the valve
effecting the cut-off, it is plain that as the cut-off varies, the point
of exhaust and of compression must also vary proportionately.
In order to secure a uniform amount of lead, a constant point of
release and of compression, it is necessary that the valve deter-
mining these points be given a constant travel. Then in order to
produce a variable cut-off a separate cut-off valve must be pro-
vided. This is the object of the riding cut-off. The main valve
determines the lead, point of release and point of exhaust closure
and as the travel of the main valve relative to the crank is un-
changeable these functions always remain the same. The duty of
the cut-off valve is simply to close the ports in the main valve,
and it determines the point of cut-off only. It will be seen, there-
fore, that with this arrangement of valves, constant lead, exhaust
Fig. 166. Riding cut-off — Showing yalyes and eccentrics.
opening and constant compression are secured while the point of
cut-off is constantly changing with the load. Keeping these fun-
damental facts in mind, it is readily seen that the main valve of
the riding cut-off is, in operation, exactly the same as the ordi-
nary D slide valve having a fixed travel. In the riding cut-off
the travel of the cut-off valve is fixed, so far as length of stroke
is concerned, but the times of closing the ports in the main valve
are variable and are determined either by hand adjustment or by
the governor, depending upon whether the engine is a throttling
or an automatic cut-off engine. The points of cut-off are
changed by rolling the cut-off eccentric around on the shaft.
270
HANDBOOK ON ENGINEERING.
The farther the cut-off eccentric is set in advance of
the crank the earlier in the stroke will steam be cut off,
and, the nearer together the two eccentrics are set, the later
will the cut-off occur. The main valve is generally designed
to cut off steam at f or J stroke, so that if the cut-
off valve and main valve move together the point of cut-off
will be determined by the main valve and will occur at f or
| stroke. Now if the cut-off eccentric (c) be set ahead of
the main eccentric (m) as in Fig. 166, it will reach the end of its
stroke and start back again before the main eccentric has com-
pleted the stroke, thus the cut-off valve moves in one direction
and the main valve in the opposite direction and that point in the
piston stroke at which the centers of the two valves meet will be
the point of cut-off. If the cut-off eccentric be set nearly oppo-
site the main eccentric it is evident that when the main valve
reaches one-half of the outward stroke the cut-off valve will have
reached nearly one-half of the return stroke and the cut-off will
occur at about this point in the piston stroke, which will be
approximately one-fourth stroke.
Fig. 167. Setting yalyes of the riding cut-off.
When setting the valves, first equalize the port opening of the
main valve. This is accomplished by turning the main eccentric
from one extreme position to the other seeing that both ports in
the valve seat leading into the cylinder are opened exactly the
same amount. It is not necessary that these ports be opened
exactly wide ; the object is to see that both ports are opened to
the same extent when the eccentric is in its extreme positions.
HANDBOOK ON ENGINEERING. 271
Having equalized the travel of the main valve place the crank on
the dead-center, see page 195, and turn the full side of the main
eccentric to a corresponding position. Then turn the eccentric
in the direction the engine is to run until the port in the main
valve, corresponding to the position of the crank or piston, opens
the port leading into the cylinder to the amount of the lead, which
may be taken as ^ inch. Now, before moving the engine make
a gauge of the form shown in Fig. 167. Put a punch mark on the
stuffing-box, and, placing one end of the gauge in this mark, draw a
fine line on the valve stem at the opposite point of the gauge.
Turn the crank to the opposite dead-center and note the amount
of lead opening. If it is not the same as first obtained adjust the
eccentric rod to the extent of one-half the difference. Then place
the gauge in the punch mark on the stuffing-box and draw a fine
line at the opposite point of the gauge.
Turn the crank back again to its first position and note the
lead. If it is found to be equal at both ends, apply the
gauge again and this time make a light punch mark at the outer
point of the gauge. Then put a similar punch mark on the fine
line representing the lead at the opposite end of the valve travel.
By means of these marks it will be possible to set the main valve
correctly without removing the steam chest cover. Now divide
the distance between the two punch marks and put a third punch
mark at the middle. Turn the crank around in the direction
the engine is to run until the middle punch mark falls under the
outer point of the gauge. The main valve will now be at the
middle of its travel. The travel of the cut-off valve must now be
equalized so that the latter valve will travel equal distances be-
yond the ports in the main valve. This is accomplished in pre-
cisely the same manner as with the main valve. Having
equalized the travel of the cut-off valve, turn the crank in the
direction the engine is to run until the cross-head reaches the point
in the stroke at which the cut-off is to occur, which is to be de-
272 HANDBOOK ON ENGINEERING.
signated by a line drawn on the guide. Now turn the cut-off
eccentric in the same direction until it reaches its extreme position.
Continue to move the eccentric until the cut-off valve just closes
the port in the main valve. Secure the cut-off eccentric to the
shaft at this point. Then turn the crank around until the cut-
off takes place on the return stroke and see if it corresponds to
the point on the previous stroke. If not, adjust the length of
the cut-off eccentric rod an amount equal to one-half the differ-
ence.
It is important to be able to set the cut-off valve also without
taking off the steam chest cover. One punch mark only is re-
quired for this. Place the main valve in its position of mid-
travel by means of the gauge. Then put a punch mark on the
stuffing-box of the cut-off valve stem and, placing the gauge in
this mark, put another at the opposite end of the gauge on the
cut-off valve stem. See Fig. 167.
This method furnishes a simple and quick means of setting
both the main and cut-off valves when an eccentric slips. All
that is necessary is to place the crank on the dead-center and
bring the proper punch mark under the point of the gauge. Then
bring the main valve to its position of mid-travel and with the
gauge bring the cut-off valve to its proper position.
The foregoing directions for setting the cut-off eccentric apply
to the hand-adjusted gear only. When the cut-off eccentric is
operated by the governor, the travel is equalized in precisely
the same manner as when hand-adjusted. After equalizing the
travel of the cut-off valve, place the crank on the dead-center.
The main valve, which is invariably set first, will now open the
port, corresponding to the position of the piston to the extent of
the lead. Next block out the governor weights against the stops.
Turn the full side of the cut-off eccentric to correspond to that of
the crank as a starting-point. Then turn the cut-off eccentric
(governor wheel), around on the shaft in the direction the engine
HANDBOOK ON ENGINEERING. 273
is to run until the port in the main valve is opened to the extent
of the lead. Secure the governor wheel to the shaft. Turn the
crank to the opposite dead-center and see that the cut-off valve
opens the port in the main valve to the same extent. If the
difference is slight it may be equalized by adjusting the length
of the cut-off eccentric rod an amount equal to one-half the differ-
ence of the lead openings. Should the difference be great, say,
one-half inch, that is, should the cut-off valve lack one-half inch
of opening the port in the main valve, it indicates that the cut-off
valve is too long, which is apt to be the case where two cut-off
valves are employed on the same stem. The valve may be
shortened by moving the two parts closer together, moving each
part one-fourth of the amount the cut-off valve lacked of opening
the port in the main valve. Then begin over again to set the
cut-off eccentric and if the adjustments have been carefully made
it will open the ports correctly at both ends of the main valve.
After fastening the main eccentric and the governor wheel securely
to the shaft remove the blocks from the governor weights and the
job will be finished.
When the valve gear contains a rocker-shaft of the construc-
tion shown on page 322, the eccentric must be turned in the
opposite direction to that in which the engine is to run, until the
main valve opens the port leading into the cylinder, to the extent
of the lead.
To Find Arerage Length of Stroke of Piston.
Revs, per Mln.
25 to 90 Dlam. of cyl. X 2.5 = Length of stroke In inches.
90 " 176 " " x 2 = "
175 " 300 " "X 1.33= " " "
Single Acting, " " x 1 = "
Weight of Engines per Cubic Foot Cyl. Volume.
Girder Frame. Box Frame.
Lowspeed 4800Lbs. 4400 Lbs.
Highspeed 6000 " 4800 *«
Cross compound non -condensing 8600 "
Cross compound condensing 9300 |
Tandem compound condensing 8650
Tandem compound non-condensing °°7d
274 HANDBOOK ON ENGINEERING.
CHAPTER XII.
THE STEAM ENGINE. — CONTINUED.
Work consists of the sustained exertion of force through space.
The unit of work, the foot-pound, is a force' of one pound exerted
through one foot space. The work done in lifting one pound ten
feet, or ten pounds one foot, is ten foot-pounds.
Power is the rate of work, or the number of foot-pounds ex-
erted in a unit of time. The unit of power is the horse-power,
and equals 33,000 foot-pounds exerted in a minute, or 550 foot-
pounds exerted in a second, or 1,980,000 foot-pounds exerted in
an hour. An engine developing fifty horse-power, exerts 27,500
foot-pounds per second, 1,650,000 foot-pounds in a minute. It
could raise (friction neglected) 41,250 pounds forty feet in one
minute.
A belt running over a .pulley at 4,000 feet per minute, pulling
with a force of 240 pounds (fair load for a 4-inch belt) will
transmit
240x4.000
— OQ QQQ — equal thirty horse-power (nearly).
If moving at 1,100 feet pe'r minute, the result would be
240x1,100
• — QQ QQQ — *equa~l eight horse-power.
A gear-wheel, the cogs of which transmit a pressure of 1,800
pounds (fair load for 1J" pitch 6" face) to the cogs of its mate,
the periphery velocity of the wheels being ten feet per second,
transmits
1,800x10
equal thirty-three horse-power nearly.
HANDBOOK ON ENGINEERING. 275
If speed was 360 feet per minute, it would transmit
1,800x360
— QQ QQQ — equal twenty horse-power nearly.
The horse-power developed by a steam engine consists of two
primary factors, Piston Speed and Total Average Pressure of
steam upon the piston.
Piston speed depends upon the stroke of engine and the num-
ber of revolutions per minute. An engine with stroke of twelve
inches, making 300 revolutions per minute, has a piston speed of
2 x 12 x 300
— r-^-; equal 600 feet per minute.
La
Piston speed of an engine with 24" stroke at 150 revolutions
per minute :
2x24x150
T^- equal 600 feet per minute.
L4
Total average pressure depends on area of piston and mean
effective pressure per square inch exerted on piston throughout
stroke. The mean effective pressure (M. E. P.) in any case can
only be accurately obtained by means of the steam engine indi-
cator, and depends upon the load engine is carrying.
GENERAL PROPORTIONS.
Diameter of steam pipes :
Slide-valve engine, J diameter of piston.
Automatic high-speed engines, | diameter of piston.
Corliss engine, T3^ diameter of piston.
Diameter of exhaust pipes :
Slide-valve engine, | diameter of piston.
Automatic high-speed engine, f diameter of piston.
Corliss engine, f to f diameter of piston.
276 HANDBOOK ON ENGINEERING.
Displacement of piston
Clearance spaces : in °ne stroke.
Slide-valve engine 0.06 to 0.08
Automatic high-speed engine, single valve . 0.08 to 0.15
Automatic high-speed engine, double valve . 0.03 to 0.05
Automatic cut-off engine, Corliss type, long
stroke 0.02 to 0.04
Weights of engines per rated horse-power :
Slide-valve engine 125 to 135 Ibs.
Automatic high-speed engine 90 to 120 Ibs.
Corliss engine 220 to 250 Ibs.
Fly-wheels, weight per rated horse-power :
Slide-valve engine 33 Ibs.
Automatic high-speed engine 25 to 33 Ibs.
(According to size and speed.)
Corliss engine 80 to 120 Ibs.
(According to size and speed.)
RULES FOR FLY-WHEEL WEIGHTS, SINGLE CYLINDER
ENGINES.
Let d = diameter of cylinder in inches.
S = stroke of piston.
D = diameter of fly-wheel in feet.
R = revolutions per minute.
W = weight of fly-wheel in pounds.
d2 S
For slide-valve engines, ordinary duty . W= 350,000 jyTlp
d* S
For slide-valve engines, electric lighting. W= 700,000 ^ ^
d? S
For automatic high-speed engines . . W= 1,000,000 ™ j*
HANDBOOK ON ENGINEERING.
For Corliss engines, ordinary duty . . W= 700,000
277
d* S
U* IP
d* 8
For Corliss engines, electric lighting . W = 1,000,000 -™ —
Fig. 168. The Russell engine.
-
SETTING THE VALVE ON A RUSSELL ENGINE, SINGLE VALVE
TYPE. THE SAHE PRINCIPLE LAID DOWN IN THE SET-
TING OF THE COHMON SLIDE VALVE MUST BE ADHERED
TO.
The style of valve is shown in cut, Fig. 169. It is, to some
extent, a moving steam chest with the steam all within itself ,
admitting only enough steam into the chest to keep the valve to
its seat, against the maximum tendency to leave it. This pres-
sure in the chest is found with the valve as at present propor-
tioned, to be about 45 per cent of that contained within the
valve. The cut shows the valve and section of cylinder so
plainly as to render any detailed explanation of same almost
unnecessary.
278
HANDBOOK ON ENGINEERING.
The eccentric operating the valve is under control of the gover-
nor, as shown in cut Fig. 170, which regulates the speed of the
engine by sliding the eccentric across the shaft, either forward or
backward, as the weights change their position, thereby cutting
the steam off earlier or later in the stroke, as the governor, or
more properly, the weights adjust themselves to the load.
When the eccentric is moved across the shaft in a direction
that reduces its 'eccentricity, the steam is cut off earlier in the
Fig. 169. Sectional view of Russell steam valve.
stroke; when the eccentric is moved in the opposite direction,
the steam is cut off later in the stroke. The extreme range of
this cut-off is from 0 to | of the engine's stroke, and this
whole range of adjustment is under complete control of the
governor.
To preserve & certain determined speed with the smallest pos-
sible variation, as changes occur in the load or pressure, is the
function of the governor. The cut-off must always be propor-
tioned to the load. When the engine is running empty, the steam
is cut off at the beginning of the stroke and the governor weights
are at their extreme outer position. With a heavy load, steam
follows farther and the weights are nearer their inner position . Be-
16
HANDBOOK ON ENGINEERING.
279
tween these two limits, any number of positions of the weights, and
corresponding angular positions of the eccentric, may be had ; and
Fig. 170. The Russell shaft governor.
as the steam is thus adapted to the load in each position, it follows
that a slight increase or decrease in speed must make a change in
the cut-off and bring the engine again to standard speed.
280 HANDBOOK ON ENGINEERING.
In setting the valves it is necessary to mark the ports in the
valve face at the outer edge of the steam chest, and also to mark
on the back of the valve the ports in its face, so that it may be
adjusted after being placed in the chest, in which position it pre-
sents a blank surface that, without these marks, would afford no
means for knowing its position.
In placing the valve in the chest, see that it fits perfectly
against the seat and that the bottom bearing, on which the valve
rides, is at right angles to the valve seat, and in such a condition
that the valve will not be tipped away from its seat, but rather
against it. This latter condition will be insured by easing off
the bottom strip at the inner corner, so that the valve would
bear hardest at the outer edge. The hinge nut, into which the
valve stem is screwed, as well as its trunnion bearings, should
fit so that the valve lays closely to its seat, rather than be held
away from it.
Having extended the marks of the ports as well in the valve
seats as in the valve itself, to the outside, it now becomes neces-
sary to get the center of the travel of the eccentric and connect
the valve and rody so that the valve will travel equally on either
side of this center. The throw of the eccentric leads the crank in
the direction the engine runs, and with the eccentric properly
located, as it cannot help being, because .it is attached to the
governor and the governor is keyed to the shaft, the lead will
remain the same with the governor weights in their outer as well
as in their inner positions.
These valves are usually marked with the engine on the center
at either end, marks corresponding with the admission edges of
valve and seat. The hinge nut connection makes it convenient to
examine these valves without disconnecting or disturbing any
adjustments made. The valve rod has right and left-hand threads
for adjustment, and final adjustment can be made without taking
off the steam chest cover.
17
HANDBOOK ON ENGINEERING.
281
1
a
282
HANDBOOK ON ENGINEERING.
Fig. 172. Governor connections — Porter- Allen engine.
THE ADJUSTABLE PRESSURE PLATES.
Description of these plates* — The construction of these pres-
Mire plates and the method of ad justing them are fully represented
jathe sections of the cylinder, Figs. 173 and 174.
On the lowei4 side of the horizontal section Fig. 173, both
admission valves are shown, working between their opposite
parallel seats, one of which is formed on the cylinder, and the
other on the pressure plates, the latter having cavities opposite
the ports.
The valve at the farther end of the cylinder is at the
extremity of its lap, while the one at the crank end has com-
menced to open the four passages for admission of the steam.
HANDBOOK ON ENGINEERING.
283
The vertical cross-section, Fig. 174, passes through the middle
of one pressure plate and shows its form and the means
employed for its adjustment. It is made hollow and most of
Fig. 173. Cylinder and yalves — Porter- Allen engine.
the steam supplied to two of the openings passes through it.
It is arched to resist the pressure of the steam without deflec-
tion. It rests on two inclined supports, one above and the
other below the valve. These inclines are steep, so that the
plate will be sure to move freely down them under the steam
pressure, and also that it may be closed up to the valve with
only a small vertical movement. It is prevented from moving
down these inclines by a screw, passing through the bottom
of the chest, the point of which, as also the plug against which
it bears, is of hardened steel.
The pressure plate is held in its correct position by projections
in the che^t, on one side, and tongues projecting from the cover
on the other, which bear against it near each end, as shown.
284
HANDBOOK ON ENGINEERING.
Between these guides, it is capable of motion up and down its
inclined supports, and also directly back and forth between the
valve and the cover.
The pressure of steam is always on this plate, and tends to
force it down the incline to rest on the valve. By means of
the screw it is forced against the steam pressure, up the in-
clines and away from the valve. This adjustment is capable of
great precision, so that the valve works with entire freedom
between its opposite seats, and still is steam-tight.
How these plates act as relief valves* — Whenever the pres-
sure in the cylinder exceeds that in the chest, the admission
Fig. 1&4. Cross-section of cylinder and valves.
pressure plate is instantly moved back to contact with the cover,
thus affording an ample passage for the discharge of water
before it can exert a dangerous strain. This plate is superior
HANDBOOK ON ENGINEERING.
285
in this action to any of the ordinary forms of relief valve, both
in the area opened, and also in being self -adjusted to the pressure,
and opening fully the instant that is exceeded.
How to keep the admission valves tight* — These valves,
though moving in complete equilibrium, are liable to slight wear.
Fig. 175. Section of Porter-Allen steam valve.
This should be taken up as it appears, by letting down the
pressure plates. The construction of these plates and the method
of adjusting them, are shown in the accompanying sections, made
through the steam chest at one end of the cylinder. Of these,
the drawings are horizontal sections, showing the four-openings of
286
HANDBOOK ON ENGINEERING.
the valve — first, when commencing to open, with arrows indicating
the course of the steam ; and, second, at the extreme point of its
lap; while Figs. 176 and 177 are vertical sections, showing the
Fig. 176. Cross-section of pressure plate.
pressure plate — first, when by turning the bolt d forward it is
forced up the inclines and away from the valve, producing a leak ;
and second, when it is let down to its proper working position.
A is the port, B the valve, and C the pressure plate. The latter
Fig. 177. Porter- Allen valve and pressure plate,
is made with a trussed-back and so cannot be deflected by the
steam pressure. Through the passage thus formed, the steam
reaches two of the openings.
HANDBOOK ON ENGINEERING. 287
The pressure plate rests on two inclined supports, c, c, and
the pressure of the steam forces it down these inclines as far
as the bolt d underneath will allow. This bolt holds the plate
just off from the valve, so that the latter moves freely,
and is still steam tight. Whenever leakage appears, a minute
turning of this bolt backwards lets the pressure plate down and
closes it.
Provision is made for readily detecting the least leakage, as
follows : When the engine is warmed up in its normal working
condition, open the indicator cocks, or in the absence of these,
remove the plugs from the top of the cylinder, unhook the link
rod, and set the valves by the starting bar so that both ports are
covered, and turn on the steam. If the valve leaks at the end of
the cylinder, which is not then open to the atmosphere or the
condenser, the steam will blow out at the opening provided, having
no other outlet. Then let down its pressure plate by backing the
bolt very carefully till the leak disappears. The valve should
still move freely when the leak has disappeared, and the pressure
plate must not be let down any closer than is necessary for this
purpose.
Leakage at the opposite end of the cylinder will not generally
be seen, the steam escaping freely by the open exhaust. To test
its valve in the same manner, the engine must be turned on to the
opposite stroke. These examinations should be made from time
to time.
In the small engines, which have no starting bar, the valve rod
can be disconnected and moved by hand to test this point.
An engine should never be started till it is warmed up. The
valves warm quicker than the supports on which the pressure
plates rest, and are tight between their seats by expansion, until
the temperatures have become nearly equalized. Provision for
detecting and stopping any leak of steam is the crowning
excellence of this valve.
288 HANDBOOK ON ENGINEERING.
DIRECTIONS FOR SETTING THE VALVES OF THE PORTER-
ALLEN ENGINE.
To set the admission valves* — Place the engine on one of its
dead centers as explained on page 195. Then raise the governor,
bringing the center of the block between the centers of the
trunnions of the link.
"With the governor remaining up, set the valve that is about
to open, giving to it a lead of from Ty to T3¥" , according to
the size of the engine. High speed requires considerable lead.
Repeat this for the other valve on the opposite center.
On letting the governor down, the crank remaining on the
dead center, it will be seen that the valve is moved a short dis-
tance. This motion of the valve, produced by moving the block
from the trunnions to the extremity of the link while the crank
stands on the center, is the same in amount on either center and
takes place in the same direction ; namely, towards the crank.
Its effect is, therefore, to cover the port nearest the crank and to
enlarge the opening of the port farthest from it ; so that the lead,
which is equal at the earliest point of cut off, is at the crank end
of the cylinder gradually diminished, and at the back end increased
in the same degree as the steam follows farther.
The effect of this is to equalize the opening and cut-off move-
ments, so that, on setting the governor at any elevation whatever
and turning the engine over, the openings made and the points of
cut-off will be found to be identical on the opposite strokes, from
the commencement up to the maximum admission. This differ-
ence in the lead is also singularly adapted to the difference in the
piston velocity at the two ends of the cylinder.
In case the indicator shows that the lead of either admission
valve requires to be changed, this is done without opening the
chest, by lengthening or shortening the stem at the socket of
HANDBOOK ON ENGINEERING.
its guide, bearing in mind that each valve moves towards the
middle of the cylinder to open its port.
To set the exhaust valves* — These have an invariable motion,
and are admirably adapted to their purpose. They are set so as
to open before the end of the stroke enough to give ample lead,
and close again when the piston is on the return stroke, early
enough to effect the required compression.
All the valves are held between pairs of brass nuts, of which
the inner one is flanged. These nuts must be securely locked,
and should be so set upon the valve that it is free to adjust itself
between the nuts while yet sufficiently tight that no ' ' lost motion ' '
exists. To avoid the consequences of a mistake, care should be
taken, before closing the valve chests, to turn the engine slowly
through an entire revolution, while the movements of the valves
are carefully watched, so as to insure that they have not been so
set as to bring the valves or their nuts into contact with the ends
of the chest at the extremes of their movements.
The governor* — The Porter governor, original in its type,
stands unexcelled as adapted to stationary engines, requiring close
regulation. The active parts are very light, the power being
derived from a high rotative speed, causing a sensitiveness in its
movements that will arrest fluctuations and produce uniformity in
the running of the engine. It has been so perfected that at the
present day it is easily adapted to the requirements of any class
of work necessitating a governor, and is especially desirable for
an engine where a steady speed is necessary.
The speed of this governor being constant, makes it equally
efficient upon an engine running either at a high or low number
of revolutions. That is to say, the speed of engine can be
altered from time to time by changing the governor pulley, the
governor itself continuing to run at the same speed and under the
same strains, and being stationary, it is always open to observa-
tiop-
290
HANDBOOK ON ENGINEERING.
The Ar mmgton and Sims engine, as is well known, is of the
high speed type, and in its earlier form was designed with double
eccentrics, one inside of the other. These eccentrics are operated
by the shaft governor, and the compound motion produced by the
movements of the two eccentrics is such that the valve has equal
lead for all points of cut-off.
Fig. 178. Yalye gear of the Armington & Sims automatic engine.
The method of setting the valve is very simple, for all engines
of this make are sent out with the valve stem and slide marked at
points C and B in the sketch, and these points should be set just
three inches apart. The following are the directions which the
builders supply : —
" If the distance between B and C is just three inches you will
know that the valve is all right. If, however, you wish to put in
a new valve and adjust, then remove the steam-chest cover and
place the engine on the center as follows: Place line marked A,
which is on the crank pin side, with line on opposite side of rim
marked F (not shown in drawing), level with engine; now take
out, or loosen up the springs and block the weights out so that
the distance betweendweights and pin at D E will be | of an inch ;
adjust the valve-stem at the guide so that by turning the engine over
HANDBOOK ON ENGINEERING.
291
from one center to the other the lead will be the same at both
ports ; then make a new mark distinctly on the valve-rod, so that
the distance B C will be the standard three inches. See Fig. 178.
u It is not possible to reverse the direction of running without
sending to the factory for new parts. The governor is not con-
structed so that one set of parts can be used for running both
ways."
THE CARE AND MANAGEMENT OF HARRISBURQ ENGINES.
It is essential to the successful operation of any high-class and
expensive machinery, that the person in charge be gifted with a
fair degree of intelligence and alertness, and while it is not
attempted to formulate new rules as a guide to the person in
Fig, 179. Sectional elevation of Harrisburg standard four-valve
tandem compound engine.
charge of an engine, the fact must not be overlooked that a great
deal depends upon the skill and judgment of the operator himself,
and that it is manifestly impossible to give rules other than of a
general character and which may frequently have to be modified
to suit the different conditions that may arise. However, the
292 HANDBOOK ON ENGINEERING.
following are some suggestions for the convenience of operating
engineers : —
When engines of these styles have been properly erected, the
steam, exhaust and drain connections completed, and the piston
and valve rods packed, the operator should be careful to see that
all parts are in proper position and firmly secured.
The bed should be thoroughly cleansed inside and a good
quality of machine oil poured into the reservoir beneath the crank,
until it is just in contact with the crank disc.
A mineral oil only should be used, and of medium viscosity.
Fill the eccentric lubricating cup and flush the main bearings
with the oil.
The cylinder lubricator should be filled with a first-class qual-
ity of cylinder oil, of heavy body.
The best oils obtainable are the most economical, without
question.
Careful preparations before starting engine* — The cylinder
and steam chest drain valve should now be opened, and the
throttle valve carefully started just enough to allow a small quan-
tity of steam to flow through the cylinder and out through the
drain pipes, but not enough to actually start the engine in
motion.
After the cylinder and valves have been thoroughly heated
and any water standing in the steam pipes thus blown off, start
the oil flowing in the cylinder lubricator cup. A general survey
of the engine should now be taken and if everything is found to
be in proper condition, carefully open the throttle valve and bring
the engine gradually up to speed, when it should be noted that
the governor is controlling the machine. Examine the bearings
and eccentric to see if the oil is flowing properly, and make sure
that every part is operating smoothly, after which the drain valves
may be closed.
Adjustments for wear* — When the engine has been in opera-
HANDBOOK ON ENGINEERING. 293
tion long enough to necessitate the adjustment of the working
parts, care should be used to avoid adjusting them so close as to
cause heating, and the following general rules should be
observed : —
The caps on the main bearings should always have sufficient
liners underneath to enable the nuts on the bearing studs to draw
the cap down solidly upon them and not pinch the shaft, which
should be free to revolve in its bearings without unnecessary play.
Adjustment of crank-end connecting rod* — In adjusting the
connecting rod box at the crank pin end the same general rules
should be observed regarding the liners under the cap, the large
nuts drawn solidly upon it, the small nuts firmly jammed, and
the cotter pins placed in position.
The adjustment of the box should then be tested with a lever
about 12 inches in length, the adjustment being so made that
with a lever of this length the operator can easily move the end of
the connecting rod sufficiently to take up the side play between
the flanges on the crank pin and the ends of the box. The
adjustment should never be made so close that this side movement
cannot be observed.
Adjustment of cross-head pin box* — The adjustment of the
connecting rod box at the cross-head pin end should be made by
removing the name plate from the engine frame and placing the
crank on the center nearest the cylinder, then with the wrench
provided for that purpose, slack off both wedge screws at the
upper and lower sides of the connecting rod, and draw the wedge
up until it is solid against the box, then slack off that screw
about a sixth of a turn and draw up the other so as to firmly lock
the wedge; this method prevents the box from pinching the
cross-head pin.
The " flats " on the cross-head pin should always be at the
top and bottom to avoid wearing a shoulder, and the nut on the
end should be drawn up firmly, but not so much as to spring the
294 HANDBOOK ON ENGINEERING.
bosses of the cross-head together, nor yet enough to make the
box tight on the ends.
Proper adjustment of cross-head in the guides is made by
liners of paper or tin, placed between the bronze shoes and the
body of the cross-head.
Adjustment of cross-head shoes* — In order to do this it is
necessary to remove the pin and the end of the connecting rod
from the cross-head, and with a wooden lever placed in the pin
hole turn the cross-head until the shoes are out of the guides,
then remove the shoes and place the liners beneath them. Care
should be used that the cross-head does not fit the guides too
closely, and that it can be moved freely with a short lever from
one end of the guides to the other, while disconnected from the
connecting rod.
The cross-head should never be run very close and should
always be free enough to allow long and continuous runs without
causing the top of the bed over the guides to feel uncomfortably
warm to the touch.
Attachment of cross-head to piston rod* — When making any
adjustments of the cross-head, it is well for the operator to assure
himself that the lock nut, which prevents the piston rod from
turning in the boss at the end of the cross-head, is securely in place.
All but the largest Harrisburg engines are tested under steam
before leaving the works, and the valves set with the indicator.
The distance from the cylinder head end of the valve, when
the crank is on the center nearest the cylinder, is marked on the
end of the cylinder directly underneath the steam chest cover.
If from any cause the valve should become deranged, place the
crank on the center described and with a scale or rule, see that
the valve position corresponds to the dimension marked on the
end of the cylinder ; and if out of position, it can easily be re-
adjusted by means of t^he device provided for that purpose, at the
outer end of the valve stem.
HANDBOOK ON ENGINEERING. 295
On the Harrisburg Ideal engines, where the ball joint con-
nection is used between the valve stem and the eccentric rod, the
wear is followed up by filing the end of the bronze connection
that the cap is screwed against, which holds the ball in place.
And on the Harrisburg Standard engines, where the ram box
connection is used, the adjustment is made by filing the half of
the bronze box, which is attached to the end of the eccentric rod
that connects with the ram.
Adjustment of eccentric strap* — The eccentric strap adjust
ment is made by liners placed between the halves of the strap and
double nutted bolts. When adjustment is necessary, the other
end of the eccentric rod should be disconnected and after drawing
up the strap bolts it should be tested by giving the strap a half
revolution about the eccentric. If it is found that the friction
between the strap and eccentric is sufficient to support the weight
of the rod, the bolts should be loosened until the strap moves
freely without lost motion. The double nuts should then be
locked and the cotter-pins replaced in the ends of the bolts.
How to alter engine speed* — The governor used on all Har-
risburg engines is the centrally balanced centrifugal inertia type.
A few words of explanation may be of service to operating
engineers.
The weight arms are constructed with differential weight
pockets, to allow of a considerable range of speed adjustment
without altering the tension of the springs. If an increase in
speed is desired, remove weights of an equal thickness from the
weight pockets of the levers, and add weights of an equal thick-
ness to obtain a decrease in speed. If an increased speed
causes the governor to " race " or " weave," move the clamp in
the -slot, to which the outer end of the spring is attached, farther
from the small end of the weight lever. If this does not entirely
correct this sensitive condition, screw the plug into the spring
until the racing ceases. If the decrease of speed so obtained
renders the governor too sluggish in action, move the clamp in the
296 HANDBOOK ON ENGINEERING.
slot in the opposite direction. If this does not improve the regu-
lation, and the speed is lower than desired, add weights of an
even thickness, increasing the spring tension until the proper
speed is obtained. The main lever bearings, which are equipped
with anti-friction steel rollers, should be oiled about once a week,
and taken out and cleaned about once a month ; the other joints
fitted with compression grease cups, should be treated in the same
manner. About once a month, also, the springs should be dis-
connected and the governor and valve gear tested by hand, to make
sure all joints are working freely.
The foregoing will apply also to the Harrisburg Standard and
Ideal compound engines, and, in general, to the Harrisburg self-
oiling four- valve engines. Adjustment for wear in the valve
gear connection of the latter type of engines is obtained by filing
the halves of the bronze boxes on the ends of the rods connecting
the valves with the wrist- plates and rocker arms, and on the
wrist-plate and rocker arm pins, by means of bronze shoes let
into the sides of the bearings, the wear being followed up by the
screws provided with lock-nuts, and all bearings lubricated by
means of compression grease cups. The Harrisburg Corliss en-
gines,of the larger sizes, are provided with quarter-boxes in the
main bearings with wedge and screw adjustment, and are built self-
oiling or otherwise, according to size. The lubrication of the prin-
cipal bearings is accomplished by means of oil cups, and the valve-
gear connections by means of conveniently arranged grease cups*
McINTOSH AND SEYHOUR HIGH SPEED ENGINE.
How to set the valve* — When the engine is sent out from
the shop, the valves are set and trammed with three -inch tram
from the valve rod to the valve rod slide at 0 D, and from the
eccentric rod to the eccentric rod head at E F, on the valve slide
end, and a tram is furnished with the engine, or a new tram can
be made with exactly three inches distance between the points ,
which will suffice.
HANDBOOK ON ENGINEERING.
297
In case the tram marks become lost, or, owing to wear of
the valve gear, the length of connection is altered, the proper
procedure is to put the engine on one center, and then on the
Fig. ISO. A sectional cut of Mclntosh and Seymour high-speed
engine, showing valve and governor.
other, and observe the leads which occur when the governor is in
the normal position of rest. See Fig. 180. The lead on the crank
end should be three times as much as the lead on the head end, if
the connection between the valve and eccentric is of proper length.
When the valve is set this way, the cut-off on the two ends
of the cylinder will be approximately equal at one-quarter cut-off
on the smaller size engines having inside governors. ;
Preliminary to adjusting connections between the valve and
eccentric, care should be taken that the mark on eccentric G H,
corresponds to the mark on the pendulum.
In examining the steam leads, as described above, it should
be noted that the surface B on the valve has nothing to do with
the steam distribution, but it is merely to give ample wearing sur-
face, and that the steam is admitted to the cylinder through the
port which is between B and the steam edge,which is at A* and
the lead should be measured between this steam edge and the
298 HANDBOOK ON ENGINEERING.
edge of the port leading to the cylinder. On engines of larger
size having outside governors, a similar method should be em-
ployed in setting the valves, except that the trams are four inches
from point to point, and should be used between the valve rod
slide and valve rod, and the eccentric rod and the eccentric
rod head at governor end, instead of slide end, as above.
.
INSTRUCTIONS FOR STARTING AND OPERATING IDEAL
ENGINES.
Before starting engine* — Open cylinder cocks and throttle
valves sufficiently to warm the cylinder and valve. Place sufficient
oil in the basin under the crank so it will stand one inch above the
bottom of crank discs. When receiving a new "engine from the
shops with visible stuffing-box and water drain, before tilling
the crank case with oil, previous to starting, pour water in opening
Fig. 181. The Ideal high speed engine.
in frame into pocket under piston rod stuffing-box, until water
overflows through trap connected therewith attached to outside of
frame. Fill cylinder lubricator and start it to feeding. Fill oil
HANDBOOK ON ENGINEERING.
299
pump, and pour engine oil into pocket on main bearings. Fill
eccentric oiler and start it feeding. After the steam chest and
cylinder are warm, turn the engine over by hand to see that all is
free and right to start.
Open the throttle valve gradually, start engine slowly. After
the engine is up to speed, pump five or six strokes of oil into
cylinder with oil pump. The oil should flow in streams through
both pipes on the crank cover into the pockets of the main shaft
bearings.
This oil passes from the main bearings through the crank pin
and is distributed over cross-head pin and slides. Occasionally
clean out the oil passages in crank pin.
Supply , as needed, a little fresh oil to the basin, and if the
oil in the engine bed becomes thick, gritty or dirty, so as not to
flow freely through oil passages, draw it off and replace with fresh
oil. Filter the old oil and use it over continuously. Use a pure
mineral oil that will not thicken by the churning it receives.
Serious damage and cutting of the cylinder and valve will
result from allowing the lubricator to cease feeding, even for a
few minutes. If the engine is a new one from the shops, feed
plenty of oil through the lubricator and oil pump for the first
few weeks after starting. Use one drop of oil per minute for each
ten horse-power, or ten drops per minute for 100 horse-power
engine, for the first thirty days ; after which, one-half this amount
will be sufficient, if the oil is of good quality. If the boiler is
priming or foaming, use double the quantity of oil to protect the
cylinder and piston from cutting. A little graphite fed into
cylinder is very beneficial.
The governor* — Fill the cups on governor bearing with grease
and give the cap J turn every day. Screw the cap to the stuffing-
box on dash-pot loosely, only using the hand to turn the cap.
The governor should be taken apart every two or three months
and bearings cleaned with coal oil to remove gum. If governor
300 HANDBOOK ON ENGINEERING.
has a dash-pot, it should be refilled with glycerine once or twice
a year. Oil may be used in the dash-pot in place of glycerine,
unless the engine is in a cold room where the oil is liable to
congeal. To refill dash-pot, unscrew cover on end.
In taking the governor apart, allow the sliding block, which
holds the end of the governor spring,to remain with its outer edge
on a line with a mark across the face of the slide, and in re-
adjusting the spring, place the same tension on it as .before,
which can be ascertained by measuring the length of the thread
through the nuts before slacking up the spring. If trouble is
had with springs breaking it is because of their being worked
under too much tension. The speed of the governor is changed
by moving the weight on the lever.
To increase the speed of the engine, move the weight on the
governor lever near to the fulcrum pin. To reduce the speed,
move the weight out toward the end of the lever. Tightening the
spring will also increase the speed, but will cause the engine to
" race," unless at the same time the block,which holds the end of
the spring, is moved toward the center of the wheel. The proper
way to change the speed is by moving the weight, allowing the
spring to remain in its marked position.
Moving the block, which holds the spring, towards the rim of
the wheel, will make the governor more sensitive and regulate
more closely ; but if moved too far, this will cause the governor
to " race." Moving the block towards the hub of the wheel has
a tendency to stop the u racing," but if moved too far the speed
of the engine will be reduced with the increased load. If any of
the bearings of the governor bind, or require oiling or cleaning,
the governor will " race." These bearings should be kept clean
and in good condition and the stuffing-box to the dash pot must
not be screwed up tight, as that will cause the governor to " race ' '
when set for close regulation.
The face of the slide is marked with a line where the outer
HANDBOOK ON ENGINEERING.
edge of block which holds the spring should be. Figures stamped
on the face of the slide, give length of end of eye-bolt extending
through nuts. This gives the right tension to the spring.
Tightening the spring will give closer regulation, but will cause
the governor to " race " if the spring is too tight. " Racing "
caused by over-tension of spring, can be stopped by moving block
nearer to center of wheel.
To set valve* — When necessary to ascertain if the steam
valve is properly set, proceed as follows : Take off the cover or
elbow on outer end of steam chest, so access can be had to end
of valve. Turn the engine over until the valve has traveled as
far as it will go towards end of steam chest. Then measure from
the end of steam chest to the end of the valve, and this distance
should be represented by the figures in inches and fractions
on end of steam chest. If measurements do not agree, set valve
by screwing the valve stem at the ball joint.
Square* braided flax packing is the best kind for piston rod and
valve stem. Don't screw the glands up tight ; allow them to leak
a little. The valve stem has only exhaust steam — don't pack it
tight. Screw it up by hand only. Screwing the piston rod gland
up tight may cause the piston to thump or pound the cylinder,
and heat and cut the piston rod.
Safety caps* — The safety caps attached to drip valve under
the cylinder are intended to break, in order to save damage to the
engine if water enters cylinder. They will protect the engine
from breaking if the amount of water is not too large to pass
through the valves and pipes. If they break, they have accom-
plished their purpose and new ones should be attached.
Eccentric* — Take up lost motion by reducing the brass liners
between the lugs on eccentric strap, and unscrew and dis-
connect the ball joint on the eccentric rod to see that the eccen-
tric strap will turn freely on the eccentric. If a close fit it will
heat, cut, seize and break the eccentric rod or valve stem. Allow
302 HANDBOOK ON ENGINEERING.
the eccentric strap to run loose ; no harm if it knocks a little.
It will not wear out of round on account of running loose ; it is
dangerous to run with the strap snug.
Ball joint* — Take up lost motion in the ball joint, on the valve
stem, by unscrewing the joint at eccentric rod and turning or
filing off the face of the brass part attached to the valve stem,
so as to allow the male part to screw in a greater distance.
Connecting rod* — Take up the lost motion on the crank pin
bearing b}^ removing the cap and taking out two of the steel
liners ; take one from each side, put the cap back and set the
nuts up snug. Disconnect the cross-head end of the rod by re-
moving cross-head pin, and try lifting the rod up and down to
see that it does not pinch the crank pin. If it pinches the pin
when the bolts are drawn up snug, place the liners back or substitute
thinner ones. Always screw the cap back solid on the liners, and
keep in sufficient liners so the cap will not pinch the pin when the
bolts are screwed down snug. NEVER RUN THE ENGINE WITHOUT
HAVING THE CAP SCREWED UP SOLID AGAINST THE ROD, with
liners between if needed, to make the proper fit. When liners
are removed be sure to take out an equal amount from each side,
because taking out more on one side only is liable to throw
the cap at an angle in tightening up the bolts, which, in time,
will cause the bolt to break and is liable to wreck the engine.
The brass in the cross-head end of the connecting rod is set up
3y a wedge. This wedge is drawn down by the steel bolt until
the brass is forced solid against the shoulders in the end of the
connecting rod, which prevents any movement of the brass.
The upper bolt is used to lock the wedge in position ; also in
withdrawing the wedge when the brass is to be removed.
To take up lost motion in the cross-head end of the connecting
rod, remove the brass and file an equal amount, even and square,
from each edge of the brass, so as to allow the brass part to come
up to the pin. When filing the brass, try the pin in the rod
HANDBOOK ON ENGINEERING.
and do not file enough to allow the brass to pinch the pin when
the wedge is screwed down solid. If, by mistake, too much is
filed off, put in a sheet of copper or sheet brass liner, so the
wedge may be drawn snug without pinching the pin.
Cross-head* — For adjusting the lower cross-head slide, take
out the cross-pin, turn cross-head J round with the lower
brass slipper opposite opening in engine frame ; loosen nuts and
insert paper or thin metal strips between cross-head and slipper.
The top slide will never require adjustment. The lower slide
should run five years before requiring lining or adjustment.
Turn the cross-head pin J way around every three months. This
will prevent it wearing out of round.
Main bearings* — To take up lost motion in the main shaft
bearings, remove the cap and file, scrape or plane an equal
amount from each of the babbitt metal liners or strips, which are in
the main bearings under the inside edge of the cap. Remove the
metal evenly, so the liners will remain of equal thickness at each
end. Do not remove enough from the liners to allow the cap to
pinch the shaft when the nuts are screwed down snug. If, by
mistake, too much metal is removed, put in paper strips on top of
the liners so the cap can be screwed down solid without pinching
the shaft. Ascertain when the cap pinches the shaft by turn-
ing the engine over by hand ; it will not turn freely when the cap
is too tight. With proper care the main bearings will run two
years before requiring adjustment. NONE OF THE BEARINGS OF
THE ENGINE SHOULD BE SO TIGHT AS TO PREVENT TURNING THE
ENGINE FREELY OVER BY HAND. Always test the engine in this
manner after adjusting bearings.
If a bearing heats* stop the engine immediately, take out shaft
or box, clean out the cuttings, scrape smooth, clean out oil pass-
ages and run bearings loose.
Heating or cutting will never occur if liners are put in so caps
cannot be set up to pinch the bearings and they receive proper
304 HANDBOOK ON ENGINEERING.
lubrication with oil free from grit or dirt. After adjusting any
of the bearings, run the engine for a few minutes ; then stop the
engine and feel the bearings which have been adjusted to see if
they are running cool. This precaution may obviate having to
shut down the engine while performing regular duty.
Do not allow the engine to run with bearings so loose as to
thump or pound, as this will cause the bearings to wear out of
round. If the shaft or wheels run out of true or wabble, it is
because the main bearings are loose and should be taken up.
The engine will run smooth and noiseless if bearings are properly
adjusted.
THE STEAfl CHEST.
Fig. J82 shows a section through cylinder and valve. The steam
chest is bored out and fitted with a pair of cylinders or bushings,
182. Cylinder and valve — Ideal engine.
which have supporting bars across the ports, to prevent any pos-
sibility of the valve catching upon the ports.
The valve is of the hollow piston type — a hollow tube with a
piston at each end. The live steam is entirely upon the outside
19
HANDBOOK ON ENGINEERING.
305
of this piston, pressing equally on each end ; the exhaust steam is
entirely on the inside of the piston, so the valve is perfectly bal-
Fig. 188. Tandem compound Ideal engine.
anced and can easily be moved by hand when under full boiler
pressure.
Fig. \ 84 is a cross-section of cylinder and valve of the Tandem
Compound engine. The cylinders of the Ideal Compound engine
inFig. 184, the stuffing-box between the two cylinders, is dispensed
with entirely. It is replaced by a long sleeve of anti-friction
metal. This sleeve is light and free to adjust itself central with
the rod. Grooves are turned on the inner surface, so as to form
a water packing.
Both valves of engine are controlled by the same governor on
the same stem, moving together and varying in stroke as the load
and steam pressure vary. This gives the advantage of automatic
cut-off in both cylinders and dispenses with the complication of
double eccentrics, rock arms, slides and stuffing-boxes.
306
HANDBOOK ON ENGINEERING.
and keep clearance spaces at minimum, which thus gives a quick
and wide opening at the beginning of the stroke, in order to
reduce the pressure on exhaust end of high-pressure piston.
Fig. 184. Section of cylinders of Ideal compound engine.
The cover of this valve is held in place by springs and will
lift and prevent excessive pressure in the cylinder from water or
other causes.
FOR INDICATING IDEAL ENGINES.
The illustration, Fig. 185, shows the reducing motion attached
to engine ready for taking indicator cards.
To apply the Ideal indicator rig: Screw slotted stud in
cross-head pin, first removing the cap screw. Set the slot per-
pendicular to line of motion of cross-head. Set cross-head
exactly in center of its travel. Fasten on top of bed where oil
funnel is placed, first removing the oil funnel.
Lever should be adjusted so it will travel in slot without strik-
HANDBOOK ON ENGINEERING.
307
ing bottom, or passing out at top. Make sure that lever wiE
travel freely in slot without binding. Select a hole on string
carrier that will give the necessary motion to indicator drum.
Fig. 185. Method of attaching indicator to Ideal engine.
With string attached from indicator through hole, so adjust this
carrier that lines drawn on polished surface shall come exactly
parallel with string. Make all adjustments while cross-head is
in center of its travel.
HOW TO SET THE VALVE ON A WESTINGHOUSE COMPOUND
ENGINE.
The only exact and final setting of the valve is by means of
the indicator. As the valves are permanently set and all adjust-
ments made before the engine is shipped, it is not supposed that
308
HANDBOOK ON ENGINEERING.
1;he engineer will have occasion to reset them. 'Should the neces-
sity for setting the valves arise, however, the following method
will be sufficiently accurate : Break joints and take off the throttle-
valve. The steam ports in the bushing will then be seen through
the steam connection S. (This opening is on the side in fact, but
is here shown on the top for convenience.) Bring the high-
pressure piston exactly to the top of its stroke by turning the
shaft in the direction the engine runs. This may be ascertained
Fig. 186. Westinghonse compoun _
by either taking off the water relief valve and measuring through
its port, or more conveniently, by bringing the middle of the key-
way in the shaft exactly over the center of the shaft. The key-
ways are planed exactly with the cranks, so that the position of
the key way is the position of the high-pressure piston. With
this piston at the top of its stroke, the valve edge a a, should
show about T^ of an inch port or lead, and be moving towards
the right when standing behind the engine. If out, it may be
brought to position by screwing the valve-stem into or out of the
:
HANDBOOK ON ENGINEERING.
309
valve, which is tapped to receive it. Be sure and set the jam nut
solid when through.
Fig. 187. Cylinders of Westingliouse compound.
SOME POINTS ON CYLINDER LUBRICATION.
In the first place, use the best automatic feed cup that can
be secured. Don't be satisfied with the old-fashioned direct
feed, or a cheap automatic. A good cup will save many a hun-
dred per cent on its cost in a year. Don't get the kind which, on
account of its peculiarity of feed, is adapted for a light oil only ;
it will then be shut out from using a dark oil, which may
be far more serviceable and economical in every respect. Get
a cup where the drop of oil cuts off square and passes either
down or up through a glass tube into the steam pipe. This
kind will feed oil perfectly ; it is well to use this kind.
Take good care of the cup. Don't let it leak around
the glass tubes or other joints, for if it does the water will escape
as it condenses, and the oil will clog up the escape pipe and
stop feeding. Use in it only the best grades of cylinder oil,
made by large manufacturers of established reputation. Don't
run in the cylinders any kind of poor stuff that may be offered,
because it is cheap ; it is a dangerous experiment. Feed a good
310 HANDBOOK ON ENGINEERING.
oil sparingly — don't drench the cylinder. Too much oil is a»
bad as water in the cylinder. Engineers have been known to run
a couple of quarts per day of cheap oil into an ordinary sized
cylinder, and thought they were doing just right ; this is positive
abuse of an engine. In almost all cases where too much oil is fed, —
cut it down. Two to four drops per minute on engines from 50
to 150 H. P. are all that is necessary, if the oil is good. Just
enough to do the work and no more, will afford best results. As
long as the valve stem does not cause trouble, rest assured the
valves are working smoothly.
AUTOMATIC LUBRICATORS.
An automatic sight feed lubricator should be furnished
with every engine which enables the engineer to see the oil as it
is fed drop by drop to the engine. The construction of these
lubricators is such that the steam entering a chamber is condensed
and this water of condensation finds its way into another com-
partment of the lubricator, wherein is contained the oil to be fed
to the engine. The drop of water, by reason of its greater spe-
cific gravity, seeks the bottom of this oil compartment and forces
out an equivalent bulk of oil into the steam pipe, whence it is
carried by the current of steam into the cylinders and is distrib-
uted upon the wearing surfaces intended to be lubricated. This
method insures regularity and economy.
There are numerous automatic lubricators made by various
manufacturers throughout the country, many of which will per-
form their functions successfully. The illustrations on the
opposite page represent what may be called the standard type of
hydrostatic lubricator employed for lubricating the valves and
pistons of steam engines.
This is the up-feed cup, showing an external view and sec-
tional view of the same. Attachment is made to the steam-pipes
HANDBOOK ON ENGINEERING.
311
at the points F and K. In operation, the condensing chamber F
provides for the condensation of steam, which enters at the pipe F.
This water of condensation passes down through the valve D and
through the tube P shown in the section and discharges into the
bottom of the oil vessel A. This vessel is filled with oil when the
cup is started, the height of oil being shown in the index glass J.
Figs. 188 and 189. Sight feed cylinder lubricator.
The operation is as follows : The valve N being opened, the valve
D is opened and the drop of water is allowed to pass from the
condensing chamber F downward through the water tube and into
the bottom of the oil chamber -4, where it displaces a drop of oil
of equal bulk on account of its greater gravity, and this drop of
oil is forced out past the valve E, making its appearance in the
feed glass H, as it starts on its way to the steam-pipe. It is
carried by the current of steam to the engine and lubricates the
valve and the pistons. When the oil cup is empty, the valve D
312
HANDBOOK ON ENGINEERING.
is closed and the drain valve G is opened, which will allow the
water in the oil chamber to be blown out preparatory to the re-
filling at the plug C. By opening the valves G and Z>, steam will
be blown through the sight glass J, thereby clearing the same
from any clogging up of the oil, which would disfigure it. The
amount of oil to be fed by the lubricator will be regulated by the
valve 7), controlling the amount of water admitted, and the valve
E controlling the discharge of the oil into the sight glass. The
valve N is to be left wide open in operation and its object is to
provide jfor the accidental breaking of the glass H.
Fig. 190. Proper method of attaching cup to prevent the oil from
dropping into the well, and not going into the cylinder.
These cups should be attached to the steam pipe, in strict ac-
cordance with the instructions contained in the box in which the
lubricator is packed. The greatest enemy to proper performance
is leakiness ; all joints must be absolutely tight, otherwise the
HANDBOOK ON ENGINEERING. 313
water of condensation, instead of performing its duty of displac-
ing the oil, will ooze out at the leaks and the cup will refuse to
work. In most cases, provision is made for a column of water
which may stand 12" or more in height and enable the cup to
work more positively, by giving it a greater pressure in the dis-
placement chamber, due to the height of the column. A suitable
oil is essential to the proper working of such a lubricator, as well
as to the proper lubricating of a steam engine. An improper oil
will not feed through the cup as it should, on account of its dis-
position to disintegrate and go off in bubbles, when exposed to
the heat of the steam.
SETTING A PLAIN SLIDE VALVE WITH LINK NOTION.
The setting of a slide valve operated by a link motion does
not differ materially in principle from the method pursued when
setting the ordinary slide valve driven by one eccentric. A link
motion may be considered as a means of driving a valve by two
independent .eccentrics, either of which controls the functions of
the valve wholly or in part, according to the position of the link.
Thus when the link is in either extreme position, the eccentric
driving that end of the link in line with the link-block pin may be
considered as being entirely in control of the valve action, and,
vice versa, when the link occupies the other extreme position of
its throw, as actuated by the reverse lever, the other eccentric
becomes possessed of the controlling function. Practically,
however, the operation of the link motion is very complicated and
the movement of one eccentric materially modifies the action of
the other. Since the interfering action is least at the extreme
positions of the link and greatest in mid-gear, the plan is followed
of setting the valve with the link in full gear both forward and
backward motion, and, as before stated, the procedure is on the
theory of independent action of the eccentrics.
314
HANDBOOK ON ENGINEERING.
In the accompanying diagram, a link motion is shown driving
a plain slide valve without the intervention of a rocker. Each
eccentric is set with reference to the crank pin, the same as it
would be with a simple slide-valve engine. The eccentric A is
set on the shaft with the same angular advance, QMO, as would
be required for an ordinary engine to run in the direction indi-
cated by the arrow. Now, since the crank pin is at (7, if it were
necessary to reverse the simple engine with one eccentric, it would
be necessary to change the position of the eccentric so that instead
of being ahead of the bottom quarter line QJf, it would be ahead
Fig. 191. Diagram of link reversing gear.
of the top quarter line PM by an amount of angular advance made
necessary by the lap and lead of the valve. Therefore, the eccen-
tric would come in the position of the eccentric A1, or with its
center line coinciding with MN^ giving it the angular advance
PMN. Now it should be clear that if an engine is to be equipped
with two eccentrics, so that it may run with equal facility in
either direction, they will occupy the positions A and A1. We
will suppose that an engine having a link motion is to be over-
hauled and the valve motion to be properly set. This will mean
that the eccentrics will be properly located for the correct angular
advance, and that the eccentric rods will be adjusted to the right
length. When these conditions are obtained, the valve should
HANDBOOK ON ENGINEERING. 315
perform its functions properly in both forward and backward
motions, and also when the link is " hooked up."
Before starting to set the valve, it is best to take a general
survey of the valve motion parts and see if the eccentrics are
somewhere near the proper location on the shaft relative to the
crank-pin. If they are obviously much out of position, they
should be shifted and adjusted as near the correct position as
possible by the eye ; doing this at the beginning will often save
confusion and much time. The dead centers will be found by the
method given on page 195. The operation should be carefully
performed, as upon it depends the success of the work. After
having found the dead centers and having them marked so that no
mistake will occur when " catching " them with the tram, the
valve positions may be taken for the four positions , that is, front
and back centers -in forward motion, and the front and back
centers in backward motion. Put the reverse lever in full gear in
one motion or the other, whichever is most convenient, and turn
the fly-wheel in the direction the engine would run for the given
reverse lever position. Suppose the link stands in the position
shown in the diagram, the fly-wheel should be turned in the direc-
tion indicated by the arrow until the dead center is reached,
which is known when the tram drops into the prick mark. The
position of the valve is then noted and a measurement taken. If
the valve shows the steam port open, measure the distance with a
steel scale, or it may be done by sharpening a stick wedge-shaped
and shoving it into the opening. By noting the depth to which
it goes at the valve face the opening can be readily measured on
the removal of the wedge. We will suppose the distance is found
to be 4". The measurement should be set on a sheet of paper
o
laid out as follows : —
FORWARD MOTION. BACKWARD MOTION.
Front center, Front center,
Back centero Back center, f" lead.
316 HANDBOOK ON ENGINEERING.
It will be seen that the valve opening is set down as being
|" lead, and as being on the back center in the backward motion.
After having verified the measurement taken, the engine can be
" turned over " in the same direction as before until the opposite
dead center is caught by the tram. It may be found that the
valve does not show open in this position but covers the steam
port. To find the position of the valve edge relative to the steam
port, scribe a line in the valve seat face along the edge of the
valve and then turn the fly-wheel until the valve uncovers the
steam port. The distance the valve laps over when the crank is
on this dead center can then be readily measured. Suppose the
distance is found to be ^". It is set down on the log as
follows : —
FORWARD MOTION. BACKWARD MOTION.
Front center. Front center, J" blind.
Back center. Back center, f " lead,
The valve position is put down as being £" blind, which is the
same as saying that it has i" negative lead, and is fully as com-
prehensive as the latter term. The reverse lever should now be
thrown into the opposite gear and the measurements taken for
both front and back centers the same as has been described for
the backward motion. It may now be supposed that when all the
measurements have been taken the log reads as follows : —
FORWARD MOTION. BACKWARD MOTION.
Front center, J" blind. Front center, |" blind.
Back center, T5F" lead. Back center, f " lead.
When in forward motion, the valve is open Ty on the back
center and lacks J" of being open when the crank is on the front
center. The total lead due to the angular position of the
eccentric is ^" minus J" = Ty. One-half the total lead should
be given to each edge of the valve so that it will be necessary to
lengthen the eccentric rod Bl, ^" + i" = -£s" to get the valve
HANDBOOK ON ENGINEERING. 317
fnto its proper position. A little reflection will show the reason
for lengthening the eccentric rod J51. In speaking of the front
and back centers, they are taken to coincide with the crank and
head ends of the cylinder. When the piston is at the crank end
of the cylinder, the crank is on the front center. By referring to
the log it will be seen that to adjust the backward eccentric rod
B, it will also be necessary to lengthen it. The valve is |" blind
on the front center and has |<* lead on the back center. The
total lead is, therefore, f" minus £"= J". One-half J"=J",
which being added to the amount the valve is lapped on the front
center, makes J", or the amount the eccentric rod B will have to
be lengthened to make the valve open equally at each end of the
piston stroke. The opening the valve has when the crank is on
the centers is called the lead and in the case of the backward
motion, it is found that after the eccentric rod is lengthened, the
lead is |", which -is too much for most cases and in this one we
can assume that -fa" would be about right.
Before explaining the adjustment of the eccentric for the cor-
rect angular advance, it will be in order to call attention to the
necessity of making the adjustment for the eccentric rod lengths
first. The eccentric rods are lengthened or shortened, as the
case may require, by inserting or removing liners between the
eccentric rods and straps at E. Other forms of construction
provide different means for adjustment, but the principle is the
same in each. It will be noted that the correct length for the
two motions is obtained by adjusting the eccentric rod corre-
sponding to that motion. Any attempt to correct an irregularity
by changing the length of the valve rod F will result erroneously,
unless both eccentric rods require the same amount of movement
and in the same direction. After having adjusted the eccentric
rods to the correct lengths, the angular advance of the eccentric
A can be changed. Place the crank on a dead center and have
the reverse lever thrown in the backward motion and then
318 HANDBOOK ON ENGINEERING.
loosen the set screws that hold the eccentric to the shaft and tarn
it towards the crank until the valve shows open J^" , and then
tighten the set screws on the shaft. After all the adjustments
have been effected, it is always advisable to turn the engine over
again and catch all the dead centers, so that the correctness of
the adjustments can be verified. After taking the new log, it
will usually be found that some slight irregularities have been
introduced, especially if any of the adjustments have been consid-
erable, as the changes made for one motion will affect the other
slightly.
The link motion shown in the cut is so connected that the lead
increases as the link is shifted towards the center. If the eccen-
tric rods be oppositely connected to the link, the engine will run
in an opposite direction for a given reverse lever position and the
lead will decrease as the lever is shifted towards the center. The
link motion for hoisting engines is quite commonly connected in
this manner, for the reason that the engine will stop when the
lever is put on the center, which is not the case when connected
as shown. Of course, in such a case, the admission and cut-off
take place at the same position in the stroke and the compression
is high, but with a light load the engine will run on the center,
which is considered objectionable in the case of the hoisting
engine.
VALVE-SETTING FOR ENGINEERS.
Plain slide- valve* — The plain slide-valve, while the simplest
valve made, is perplexing to one who has not made a study
of it. Unless one understands the principles of the valve
and its connections, he will probably meet with trouble when he
attempts to set it. We will first place the engine (see p. 195)
on the dead center, and will simply explain the other steps
that have to be taken. In the first place, it should be understood
what result is obtained by adjusting the position of the eccentric
HANDBOOK ON ENGINEERING. 319
and the length of the valve stem. The position of the eccentric,
when the valve is set, depends upon which way the engine is to
run and whether the valve is connected directly to the eccentric
or whether it receives its motion through a rocker which reverses
the motion of the eccentric. When the valve is direct connected,
the eccentric will be ahead of the crank by an amount equal to 90°,
plus a small angle called the angular advance. When a reversing
rocker is used, the eccentric will be diametrically opposite this
position, or it will have to be moved around 180° and will follow
instead of lead the crank. Shifting the eccentric ahead has the
effect of making all the events of the stroke come earlier, and
moving it backwards has the effect of retarding all the events.
Lengthening or shortening the valve stem cannot hasten or retard
the action of the valve, and its only effect is to make the lead or
cut-off, as the case. may be, greater on one end than on the other.
The general practice is to set a slide-valve so that it will
have equal lead. The lead is the amount that the valve
is open when the engine is on tfre center. To set the valve,
therefore, put the engine on the center, remove the steam-chest
cover so as to bring the valve into view, and adjust the eccentric
to about the right position to make the engine turn in the direction
desired. Now make the length of the valve-spindle such that the
valve will have the requisite amount of lead, say T^ of an inch,
the amount, however, depending upon the size and speed of
the engine. Turn the engine over to the other center and measure
the lead at the end. If the lead does not measure the same as
before, correct half the difference by changing the length of the
valve-stem, and half by shifting the eccentric. Suppose, for
example, that the lead proved to be too great on the head end by
half an inch. Lengthening the valve-stem by half of this, or £
inch, would still leave the lead i inch too much on the crank
end. That is to say, the valve would then open too soon at both
head and crank ends, and to correct this, the eccentric would
320 HANDBOOK ON ENGINEERING.
.
have to be moved back far enough to take up the other quarter-
inch. Sometimes it is not convenient to turn the engine over by
hand, in which case the valve may be set for equal lead as fol-
lows: To obtain the correct length of the valve-stem, loosen the
eccentric and turn it into each extreme position, measuring the
total amount that the valve is open to the steam ports in each
case. Make the port opening equal for each end by changing the
length of the valve-stem. This process will make the valve-
stem length as it should be. Now put the engine on a center and
move the eccentric around until the valve has the correct lead and
fasten the eccentric in that position. This will determine the
angular advance of the eccentric.
The plain slide valve* — The function of the slide-valve is
to admit steam to the piston at such times when its force can be
usefully expended in propelling it, and to release it when its pres-
sure in the cylinder is no longer required. Notwithstanding its
extreme simplicity as a piece of mechanism, no part of the engine
is more puzzling to the average engineer when the problem to be
solved is to determine beforehand the results which will be pro-
duced by a given construction and adjustment, or the proportions
and adjustment required to produce given results. All who have
had any experience in constructing and setting slide-valves are
aware, in a general way, that the events of the stroke cannot
be independently adjusted; for instance, a cut-off earlier than
about -| of the stroke.
To set a slide valve* — The valve should be set in such a man-
ner that when the engine is on the dead center, the part admitting
the steam to the cylinder is open a small amountas shown in Fig. 1 85 ,
which is called lead. The object of lead is to enable the steam
to act as a cushion against the piston before it arrives at the end
of the stroke, to cause it to reverse its motion easily, and also to
supply steam of full pressure to the piston the instant it has passed
dead center. The lead required varies in different engines from
HANDBOOK ON ENGINEERING
321
to ^ without regard to size or kind. Fig. 192 also shows the
position of eccentric, which should always be set ahead of the
Fig. 192. At point of taking steam
crank at an angle of 90°, plus another angle, called the " angular
advance." When the valve is to have lead the angular advance
must be a little greater than when no lead is desired.
193. At point of cut-off.
Fig. J93 shows the position of eccentric at point of cut-off ; also
position of piston.
Fig. 194. Position when compression begins.
Fig. J94 shows position of valve when compression begins. It
also shows position of eccentric, The compression at the left
21
322
HANDBOOK ON ENGINEERING.
end, towards which the piston is moving, has just commenced,
and the exhaust is about to take place from the other end.
Fig. 195. At point of taking steam.
Fig* J95 shows the position of eccentric and valve in an engine
with a rocker-arm.
fig. 106. At point of cut-off.
Fig- J96 shows the position of valve and eccentric nt point of
cut-off.
Fig. 197. Showing point of compression.
HANDBOOK ON ENGINEERING, 323
CHAPTER XIII.
TAKING CHARGE OF A STEAH POWER PLANT.
It is frequently the case that an engineer, on assuming charge
of a steam power plant, proceeds as though he were thoroughly
familiar with the condition of the engine, boiler and entire sur-
roundings. He plunges headlong into his duties, without first
taking his bearings. A skillful physician on taking a case, would
not proceed in this manner ; neither would a lawyer. The physi-
cian would feel the patient's pulse, look at his tongue, take his
temperature, observe his color and ask a number of questions, all
for the purpose of enabling him to make a correct diagnosis of
the patient's ailment. The first duty of an engineer, when he
takes charge of a plant, is to ascertain the arrangement and con-
dition of the plant. Since the boiler is the most important mem-
ber of the plant, it should be the first to engross his attention, and
it, together with its connections, should be examined as closely as
time and surrounding conditions will permit. He should look the
boiler all over, internally and externally, if possible, in search of
324 HANDBOOK ON ENGINEERING
mud, scale, grooving, pitting and defective braces. The furnace
should be examined next, in view of burnt-out brickwork, grate
bars and door linings. It may be that the furnace has distorted
or cramped proportions, or it may be too large. The bridge-wall
may be so constructed as to huddle the flames in one spot on the
fire sheets of the boiler ; or it may be of such shape and in such
condition as to cause the ignited gases to become dissipated in
the combustion chamber. Even the combustion chamber itself
may require the service of a bricklayer. He should next examine
the safety valve and see that it is of ample capacity to relieve the
boiler of surplus steam, and that it is in thorough working order.
The first duty of an engineer when entering his plant at any
time, is to ascertain how the water in the boiler stands, or,
in other words, just how much water the boiler contains. He
should open the gauge cocks first and note what comes from each
in turn ; then open the cocks or valves connecting the glass gauge
and note the water line there shown. He should also blow the
water column out, in case any sediment may have choked any of
the passages, which would be liable to give a false impression as
to the actual quantity of water contained in the boiler. Should
the water be found at tho correct height, he may now proceed to
get up steam ; open the damper, pull down the banked fire and
spread it evenly over the grate, adding a quantity of green fuel.
Allow the steam to rise slowly ; do not force it. This applies
especially to raising steam in a boiler which has been cold, as the
expansion of the parts of the boiler due to the heat should take
place slowly and evenly; otherwise, the life of the boiler will be
shortened. While waiting for the steam to come up to the desired
point, the engineer should now get his engine ready for the day's
run. Fill all the oil cups and cylinder lubricator, so as to be
ready to operate as the engine starts. With a hand oil squirt
can, go around all the small brasses, connections, etc., and, in a
word, well lubricate all the parts where friction takes place. If
HANDBOOK ON ENGINEERING.
he uses an oil pump for the cylinder and valves, it would be
well to inject a small quantity of cylinder oil before the engine is
started, while the stop-valve is open, during the time the engine is
being " warmed up." After the engine cylinder is warmed
through, the fire should again be looked at, and dealt with
according to the indications. Of course, the water gauge glass
must be looked at frequently, not only while raising steam in the
morning, but at all times while the boiler is in operation.
Everything being in readiness, the engine is started slowly at
first, the speed being gradually increased until the limit is reached.
The day's run is now fairly commenced. A boiler should be
blown down one gauge every morning before starting the day's
run to get rid of 'the mud, scale or anything that is held in
mechanical suspension in the water. Before starting in the
morning and at noon is the best time to do this, as the sediment
has settled to the bottom during the night, after the circulation
of the water has stopped. When blowing a boiler down, always
remember to open the blow- valve slowly — be careful not to blow
too long, and then to close the valve slowly.
An engineer or attendant cannot be too careful in handling
the many appliances with which a steam plant is equipped. The
principal things to which an engineer should give his attention
during the operation of his boiler day by day are, as follows:
The maintenance of the water at the proper level, as near as pos-
sible, and avoiding fluctuations in the pressure of steam. See
that the firing is done correctly and economically so as to obtain
from every pound of coal all that is possible under the con-
ditions existing. The raising of the safety valve from its seat,
at least once daily ; the blowing out of the water column twice
daily, or oftener, if the water used is very dirty ; the frequent
opening of the water gauge cocks, or try cocks, as they are
sometimes called, and not depending entirely on the gauge glass
for the correct height of water ; the blowing down of the boiler
326 HANDBOOK ON ENGINEERING.
one gauge every day ; the keeping of all valves, cocks, fittings,
steam and water-tight, clean and in good working order.
When shutting down the plant for the night, the fires should
be cleaned out and the live coals shoved back on the grates and
banked ; that is, green coal should be thrown upon them, suffi-
ciently thick to cover all the glowing fuel. Pump in the water
until it reaches the top of the glass gauge. This should be done
to insure a sufficient quantity from which to blow down in the morn-
ing, and also to allow for any small leaks. Then close the cocks or
valves connecting the glass gauge. Should this glass break dur-
ing the night and the valves be left open, there would not be much
water to start with in the morning. Leave the damper open a
little, just sufficient to allow the gases which will rise from the
banked fires to escape up the chimney. Finally, make sure that
all the valves about the plant which should be closed, are closed ;
and all those which should be left open, are open. Of course,
the foregoing is applicable to a plant where there is no night
engineer. But in any case, no matter how many assistants an
engineer may have under his control, he should be familiar with
all details of the plant under his charge.
One of the most important points in connection with the opera-
tion of a steam boiler, is the preventing of corrosion, both
internally and externally. One of the best aids to secure the
well working and longevity of the steam boiler, or, in fact, the
whole plant, is by being regular and punctual in a certain course
of treatment, which has been proven to be effectual and beneficial
in its results. All conditions do not require the same methods of
treatment; therefore, it is absolutely necessary that the engineer
in charge familiarize himself with all the conditions under which
his plant is running, for then, and then only, can he intelligently
prescribe and act accordingly. Above all, let him remember
the adage, " Eternal vigilance is the price of safety," especially
where a steam boiler is concerned.
HANDBOOK ON ENGINEERING. 327
ECONOMY IN STEAM PLANTS.
In these days of close figuring upon expense in office buildings
and manufacturing plants, what may at first appear insignificant
items may actually make all the difference between a good margin
of profit and an actual loss.
The fuel expense is one of the largest in the operation of the
majority of plants, and any reduction which can be made in the
amount of fuel used, while maintaining the same amount of power,
is considered a direct gain. The evaporation of more than nine
pounds of water per pound of coal, is looked upon with suspicion
by many, as it is not thought possible to obtain more than this
amount in even the best designed and well regulated furnaces and
boilers, especially when the firing is done by hand. The actual
value of the fuel depends upon the way in which it is used, fully
as much as on any other factor. The heat unit in the coal should
be as much as possible utilized, as in one pound of good steam
coal there is about 14,000 B. T. U., and about 10,000 of this
amount can be utilized, so that 4,000 heat units are lost. The
mixture of gases in a furnace depends upon the amount of air
used. One pound of coal requires, theoretically, about twelve
pounds of air to bum completely. But, in practice, about twice
this amount is required in the present boiler furnace. To have
good combustion coal requires a good draft. The gases are con-
sumed near the fire, and the waste gases carry the heat to the
boiler on their way to the stack. The boiler ought to have suffi-
cient heating surface, or the hot wasted gases ought to travel a
sufficient distance to be cooled down to about 350 degrees Fah-
renheit ; which temperature is found high enough to produce a
good draft in a stack of, at least, 100 feet high.
How a bad draft will unnecessarily increase the coal bill, is
this: That of all the fuel burnt to perform certain work, a cer-
tain proportion is consumed to keep the heat of the furnace up
328 HANDBOOK ON ENGINEERING.
to say, 212 degrees Fahr., without making any steam whatever
which is available for work. This quantity varies from 20 to 30
percent, according to conditions, which are affected by various
causes, such as leakages of steam, air, or water. Now, the only
available power for work which we get from our fuel is the margin
between this, say thirty per cent required for the said purpose,
and what we generate above that. An engineer should notice the
general condition of his boiler or boilers, and the equipments of
same ; he should examine the boiJer both inside and outside,
ascertain the dimension of grates, heating surfaces, and all im-
portant parts. The area of heating surfaces is to be computed
from the outside diameter of water-tubes, and the inside diameter
of fire-tubes. All the surfaces below the main water level which
have water on one side and products of combustion on the other,
are to be considered as water-heating surfaces. If he finds that
the boiler does not come up to what he thinks it should, he should
put the boiler and all its appurtenances in first-class condition.
Clean the heating surfaces inside and outside of boiler, remove
all scale from flues and inside of boiler ; remove all soot
from inside of flues, all ashes from the flame-bed or com-
bustion chamber, and all ashes from smoke connections. Close
all air leaks in the masonry and poorly fitted cleaning door.
See that the damper in britching or smoking-flue will open wide
and close tight. Test for air leaks through the crevices, by
passing the flame of a candle over cracks in the brick work. A
good, attentive fireman, who understands his business and will
keep his bars properly covered without choking his fires, is really
worth double the wages of an ignorant or inattentive one, as his
coal bills would certainly prove. All an engineer can do is to
keep the steam piston and valve or valves tight. Also the drains
from his engine, and all drains on steam traps in the plant tight ;
also, his engine cleaned and well-oiled, and not keyed up too tight.
If in a heating plant, he should see that the back pressure valve is
HANDBOOK ON ENGINEERING.
329
at all times tight, as it does not take much of a le.ak to show a
difference in his coal bill at the end of a month. He should keep
all valves in the pumps in his plant tight, and see that the pump
piston is packed, but not too tight. After a pump is packed, he
should be able to move it back and forth by hand ; if the pump
valves leak he can take them out and smooth them up with sand-
paper. He should see that the feed-water to the boiler is at least
208 degrees Fahrenheit ; if it is under 204 degrees, his heater is not
right, as the poorest heater will heat the feed- water to 204 ; it
would be well to overhaul the heater — it may be full of scale ; or,
if an open heater, the spray may be off. In most first-class
plants, the feed-water is 212 Fahrenheit.
PRIMING.
The term priming is understood by engineers to mean the
passage of water from the boiler to the steam cylinder, in the
shape of spray, instead of vapor. It may go on unseen, but it is
generally made manifest by the white appearance of the steam as
it issues from the exhaust-pipe as moist steam, which has a white
appearance and descends in the shape of mist, while dry steam
has a bluish color and floats away in the atmosphere. Priming
also makes itself known by a clicking in the cylinder, which is
caused by the piston striking the water against the cylinder head
at each end of the stroke. Priming is generally induced by a
want of sufficient steam-room in the boiler, the water being car-
ried too high, or the steam-pipe being too small for the cylinder,
which would cause the steam in the boiler to rush out so rapidly
that, every time the valve opened, it would induce a disturbance
and cause the water to rush over into the cylinder with the steam.
HANDBOOK ON ENGINEERING.
TABLE OF PROPERTIES OF SATURATED STEAM.
8
2 .
,3
2
8 5
d
«J
rt
§
Pressure in
pounds per
square inct
above vacu
Temperatu
in degrees
Fahrenheit
Total heat
in heat uni
from water
at 32°.
Heat in liqi
from 32°
in units.
Heat of vap
Ization or
latent heat
heat units.
s?5
tm
££§§,
Volume of
one pound
.in cubic fee
Factor of
equivalent
evaporatioi
at 212°.
Total press
above
vacuum.
1
101.99
1113.1
70.0
1043.0
0 00299
334 5
.9661
1
2
126.27
1120 5
94 4
10-26.1
0.00576
17* 6
.97*8
2
3
141.62
1125.1
109.8
1015 3
0 0<>844
118 5
.9786
3
4
153 09
1128.6
121 4
1007 2
0 01107
90 33
.98-22
4
5
162.34
1131 5
130 7
1000 8
0 01366
73 21
.9852
5
6
170.14
1133.8
138 6
995.2
0 01622
61 65
.9876
6
7
176 90
11*5 9
145.4
990.5
0 01874
53 39
.9897
7
8
182 92
1137 7
151.5
986 2
0.02125
47.06
.9916
8
9
188.33
1139 4
256 9
982 5
0.02374
42 12
.9934
9
10
193.25
1140 9
161 9
979 0
0 02621
38 15
.9949
10
15
213 03
1146.9
181 8
965 1
0.03826
26 14
1.000*
15
20
227 95
1151.5
196.9
954 6
0.05023
19 91
1.0051
20
25
240.04
1155.1
209 1
946.0
0 06199
16.13
1 0099
25
30
250 27
1158.3
219 4
938 9
0 07360
13 59
1.0129
30
35
259.19
1161.0
228.4
932.6
0 08608
11 75
1.0157
35
40
267.13
1168 4
236 4
927.0
0.09644
10.37
1.0182
40
45
274.29
1165.6
243.6
92-2.0
0 1077
9.285
1.0205
45
50
280.85
1167 6
250.2
917 4
0 1188
8.418
1.0225
60
55
286 89
1169 4
256.3
913 1
0.1299
7 698
1 0245
55
60
292.51
1171.2
261 9
909 3
0 1409
7-097
1.0263
60
65
297 77
1172.7
267.2
905.5
0 1519
6 58*
1.0-280
65
70
302 71
1174.3
272.2
902 1
0 1628
6 143
1.0295
70
75
307 38
1175.7
276.9
898 8
0.17*6
5 760
1 0309
75
80
311 80
1177.0
281.4
895 6
0.1843
5 4;i6
1.0323
80
85
316.02
1178 3
285.8
892 5
0.1951
5 126
1 0337
85
90
3-20.04
1179 6
290 0
889 6
0.2068
4 859
1.0350
90
95
323.89
1180 7
294.0
886 7
0 2165
4.619
1.0362
95
100
327 58
1181 9
297.9
884 0
0.2271
4.403
1.0374
100
105
331 13
1182.9
301 6
881 3
0 2378
4.205
1.0385
105
110
334 56
1184 0
305 2
878 8
0 2484
4 026
1 0396
110
115
337.86
1185 0
308.7
876 3
0.2589
3 862
1.0406
115
!20
341.05
1186.0
312.0
874.0
0.2695
3.711
1 0416
120
125
344 13
1186 9
315.2
b71 7
0.2800
3 571
1.0426
125
130
347.12
1187 8
318.4
869 4
0.2904
3 444
1.0435
130
140
352.85
1189.6
324.4
866 1
0 3113
3 212
1 045*
140
150
358.26
1191 2
830.0
861 2
0 3321
3 Oil
1.0470
lf.0
}£Q
363 40
1192.8
335.4
857-4
0 3530
2 833
1.0486
160
170
368 29
1194.3
340.5
853 8
0.3737
2.676
1 0502
170
180
372.97
1195 7
345.4
850.3
0.3945
2.635
1.0517
180
190
377.44
1197 1
350.1
847 0
0.4153
2.408
1 0631
190
200
381.73
1198 4
354.6
84* 8
0.4359
2.294
1 0545
200
225
891 79
1201 4
365.1
8*6.3
0 4876
2.051
1 0576
2-25
250
400.99
1204.2
374.7
829.5
0.5393
1.854
1.0605
250
275
409 50
1206.8
383.6
823 2
0.5913
1 691
1 06*2
275
300
417.42
1209.3
391 9
817 4
0.644
1 553
1 0657
3<0
325
424.82
1211.5
399.6
811 9
0.696
1 437
1.0680
3-25
360
4*1 90
1213.7
406.9
806.8
0.748
1.337
1 0703
350
375
438 40
1215.7
414 2
801 5
0 800
1 250
1.0724
375
400
445.15
1217.7
421.4
796 3
0.853
1.172
1 0745
400
500
466.57
1224.2
444.3
779.9
1.065
.939
1.0812
600
HANDBOOK ON ENGINEERING. 331
The gauge pressure is about 15 pounds (14.7) less than the
total pressure, so that in using this table, 15 must be added to
the pressure as given by the steam gauge. To ascertain the
equivalent evaporation at any pressure, multiply the given evap-
oration by the factor of its pressure, and divide the product by
the factor of the desired pressure. Each degree of difference in
temperature of. feed-water makes a difference of .00104 in the
amount of evaporation. Hence, to ascertain the equivalent
evaporation from any other temperature of feed than 212°, add to
the factor given as many -times .00104 as the temperature of
feed-water is degrees below 212°. For other pressures than those
given in the table, it will be practically correct to take the pro-
portion of the difference between the nearest pressures given in
the table. Example : If a boiler evaporates 3000 Ibs. of water
per hour from feed- water at 200 degs. Fah. into steam at 100
Ibs. per sqr. in. by the gauge, what is the equivalent evaporation
" from and at"212°? Ans. 3159.24 Ibs.
Operation : Temperature of feed-water = 200 degs.
Then, 212 — 200 = 12 —difference in temperature.
Then, 15 added to the gauge pressure = 115.
Looking in the above table we find the factor 1.0406.
Then, .00104 X 12 =.01248.
And, 1.0406
.01248
1.05308
Then, 3000 X 1.05308 = 3159.24 Ibs. the equivalent evapo-
ration.
The H. P. of this boiler would be 91.57.
332 HANDBOOK ON ENGINEERING.
HIGH PRESSURE STEAM.
It is generally believed that high-pressure steam is cheaper to
use and costs but little more to generate than low pressure steam.
A study of a table of the properties of saturated steam, to be
found on another page in this book, will show why high-pressure
steam is economical to generate, and a few calculations will
prove instructive by showing what may be excepted from its use.
To generate one pound of steam at 25 Ibs. pressure, absolute,
requires an expenditure of 1,155 thermal units, and to generate
steam at 200 Ibs. pressure, absolute, requires 1,198 thermal units,
or an increase of only 43 thermal units for an increase of 175 Ibs.
pressure. Further investigation shows that the temperature of
steam at 25 Ibs. pressure is 240° and at 200 Ibs. pressure, 382°,
the difference, 142, being the number of degrees that the tem-
perature of steam is raised with an expenditure of 43 thermal
units. To put it in another way, the temperature of the steam
has been raised nearly 60 per cent, with an increase of less
than 4 per cent in the number of thermal units. It is con-
venient to consider that the generation of steam takes place
by two different steps, one of which is raising the water from
32° to the temperature corresponding to the pressure of the
steam, and the other is giving off the steam at this pressure,
which process absorbs a quantity of heat that becomes latent
or non-sensible. At 25 Ibs. pressure, the sensible heat
required to raise one Ib. of water from 32° to 240° is
209 units, and to raise it from 32° to 382 degrees, the
temperature of steam at 200 Ibs. pressure requires 355 thermal
units. The increase in the sensible heat of the water, there-
fore, is 355 minus 209 = 146 units, or about the same as the tem-
perature increase for these two pressures, which is 142°. It is thus
clear that the total increase in the number of heat units in steam
raised from 25 Ibs. to 200 Ibs. pressure is small (43° as found
HANDBOOK ON ENGINEERING.
above) because the laten heat absorbed in the formation of the
steam decreases as the pressure increases. It requires less heat
to generaU steam froir water raised to 382° at 200 Ibs. pressure,
than from water previously raised to 240° at 25 Ibs. pressure.
To generate higher pressure steam, therefore, we must first
apply enough heat to bring the water to a temperature
corresponding to the higher pressure. This heat will be
nearly proportionate to the increase in temperature. Then
enough heat must be applied to the water to generate the steam,
the amount of heat required for this purpose decreasing as the
pressure increases. The combined result of these two processes
is that it takes only a very small increase in the total heat to pro-
duce the higher pressure steam. The idea may be suggested that
if this higher pressure is obtained at the cost of so small an expen-
diture of heat, it would not be reasonable to expect a large gain
in economy from it, since it is not possible for the steam to do a
greater amount of work than the equivalent of the heat which it
contains. This would be true were it not for the fact that the
larger part of the heat in the steam is rejected during the ex-
haust. To illustrate, suppose an engine to exhaust at atmos-
pheric pressure, or, at about 15 Ibs., absolute, and that the steam
is saturated. As may be determined from the steam tables, there
would be ejected 1,147 heat units per pound of steam^ or 51
heat units less than were found to be in a pound of steam at
200 Ibs. pressure. That is to say, under the above assumption,
there are available only 51 heat units per pound of steam to do
the work in the engine cylinder when the steam pressure is 200
Ibs. But we also found that the increase in the heat units in
raising the steam pressure from 25 to 200 Ibs. was 43, and hence
the increase in proportion to the number available is large,
although the increase in proportion to the total number required
334 HANDBOOK ON ENGINEERING.
to generate the steam is small. This shows why high-pressure
steam is economical to generate and profitable to use. It should
be stated that the only way in which the full benefit can be de-
rived from high pressure-steam is by using the steam expansively,
keeping the terminal pressure at release as low as possible. We
will not take the space to give the calculations to prove this,
but will compare a few results of calculations. Suppose steam
to be used in a theoretically perfect engine at the pressure
of 25 Ibs., 50 Ibs., 100 Ibs. and 200 Ibs. We will assume that
in each case the cut-off is at one-third stroke, giving three
expansions and a terminal pressure of one-third the initial pres-
sure. The steam consumptions will then be, respectively, about
16J, 16, 15 J, and 14 Ibs. per horse-power, showing that gain
from the increase in pressure is very slight. On the other hand,
suppose the expansions to be carried to the atmospheric pressure
in each case. The consumptions will then be about 27, 15, 11
and 8 Ibs. respectively, showing a marked decrease.
Still another point should be mentioned in relation to the
relative gain that is to be expected with the increase in pressure.
Comparing the last figure, it will be observed that the decrease
in consumption when the pressure increased from 25 to 50 Ibs-
was 27 minus 15 = 12 Ibs., or 44 per cent. Again, when
the pressure doubled from 50 to 100 Ibs., the consumption
decreased only 4 Ibs., or 27 per cent; and when the pressure was
again doubled to 200 Ibs., the consumption only decreased 3 Ibs.,
or about 27 per cent. It is evident from this that the saving
from an increase in steam pressure grows less as the pressure
increases, and this is found to be the case in actual practice.
There is another reason for this, also, coming from the losses
incident to cylinder condensation and re-evaporation, which is
more marked where there is a wide range in pressures than where
the pressures are more uniform throughout the stroke. It is found
that where the steam pressure is much above 100 Ibs. gauge pres-
HANDBOOK ON ENGINEERING. 335
sure, no gain will result from a further increase in pressure with-
out compounding, the advantage of the compound engine being
that the extremes of temperature in the cylinders are not so great
as with a simple engine.
USING STEAfl FULL STROKE.
The steam engine is nothing in the world but an enlargement
upon the end of the steam pipe, containing a piston against
which the steam in the boiler may press. The piston moves a
certain distance, and then the steam is allowed to press upon its
other side, while the steam on the first side is allowed to flow into
the atmosphere and go to waste. The slide-valve is the device or-
dinarily employed to admit the steam, alternately, to opposite sides
of the piston, and to permit the free outflow of steam from the
reverse side of the piston. As the steam presses upon the pis ton,
the piston moves forward with a force equal to the pressure of
steam per square inch, multiplied by the number of square inches
of piston surface. Steam occupies the entire space from the sur-
face of the water in the boiler, to the piston of the engine. The
steam space, therefore, includes the steam space of the boiler, the
steam pipe, the steam chest, and the cylinder space upon one side
of the piston. As the piston moves, the entire steam space be-
comes a little larger, by reason of the cylinder space becoming
longer. Thus it will be seen that all of the steam in the boiler
and pipe and engine, would expand a trifle and the pressure
become somewhat reduced, were it not for the fact that new
steam is made by the fire as fast as the piston moves forward.
By this means the steam is maintained at about uniform pressure.
It will be seen that the pressure is produced upon the piston
by the generation of new steam from the water, that is, the fire
causes the water to generate a quantity of steam, and this quantity
of steam forces its way into the other steam, exerting a force
upon the whole body of steam and pushing the piston ahead.
336 HANDBOOK ON ENGINEERING.
If an engine piston has a surface of 100 square inches and
a stroke of ten inches, it follows that the piston will yield a
thousand cubic inches additional steam space by its movement
during one stroke, and consequently, the fire will be called upon
to produce 1,000 cubic inches of new steam for each single stroke
of the engine. If the pressure of the steam be eighty pounds to
the square inch, the engine piston will move with the force of
8,000 pounds. When the engine has completed one stroke, we
find an amount of power exerted equal to 8,000 pounds moved
ten inches, and we then open the exhaust valve and empty into
the atmosphere 1,000 cubic inches of eighty-pound steam. We
keep on doing this for each stroke. Now our attention is par-
ticularly called to the fact that when we empty the steam out of
the cylinder, it is just as good as when it went into the cylinder ;
that is, it was 1,000 cubic inches of steam at a pressure of eighty
pounds to the square inch, and when it goes into the atmosphere
it will expand into over 6,000 cubic inches, at fifteen pounds
pressure to the square inch, or the same pressure as the atmos-
phere. This 1,000 cubic inches of steam which we dumped out
of the cylinder, is precisely the same quality of steam as the
steam which we have penned up in the boiler ; and which we have
to be making new all the time in order to keep the engine run-
ning. Such is the operation of the steam engine which receives
its steam the full length of the stroke ; and such an engine may
be described briefly, as a very wasteful machine, which throws
away steam as good as it receives it, and which requires the gen-
eration of a cylinder full of full pressure steam for each stroke.
It should be readily understood that when the piston has com-
pleted its stroke, and just before the exhaust valve is opened to
allow the steam to escape, the cylinder contains 1,000 cnbic
inches of steam at eighty pounds pressure, which it is capable of
expanding into many thousand cubic inches at constantly de-
creasing pressure. The first step in the improvement of such an
HANDBOOK ON ENGINEERING. 337
engine would be to so arrange things as to get some benefit from
this enormous power of expansion. The full stroke engine does
not get one-half of the power before it throws the steam away.
The engine which we would have referred to would yield a power
of 8,000 pounds moved ten inches at each single stroke ; 33,000
pounds moved one foot in one minute is a horse-power ; 66,000
pounds moved half a foot would be the same. An engine using
steam full stroke is such an extravagant contrivance that we, now-
adays, seldom find them in use. There are certain classes of
engines built, fitted with link motions for driving the valve, and
they are arranged so as to carry their steam full stroke, but pro-
vision is also, made for quickly hooking up the link and suppress-
ing the full-stroke feature.
SLIDE VALVE ENGINES.
If we have an engine arranged to receive its steam full stroke
and to dump the steam out into the air in as good condition as it
was received, and we wish to get some of the benefits of the
expansive power of the steam, there is a simple way of doing it
and without any great change in the engine, and that is, to
lengthen out the slide valve so that after the cylinder is half full
of steam, the valve will shut and let no more steam enter. Dur-
ing the balance of the stroke, the entire power comes from the
gradual expansion of the steam shut up in the cylinder, and it
will be readily seen that whatever power we succeed in getting out
of the expansion of the steam, is pure gain. The lower the pres-
sure of the steam is when it is exhausted into the air, the more it
has expanded, the more power we have gotten out of it, and the
more we have gained. It may be said in a few words, that all
slide-valve engines are now arranged to work their steam expans-
ively. But it is, unfortunately, found that the slide-valve pos-
sesses a peculiar defect, which prevents the system being carried
very far. We can lengthen out a slide-valve so as to cut the
338 HANDBOOK ON ENGINEERING.
steam off at nay desired point of the stroke, and we must then
increase the throw of the eccentric in order to properly operate
the long valve. But the minute we do this we find that we have
interfered, to a certain extent, with the proper operation of the
exhaust. No matter what we do about the admission of steam or
about cutting off before the end of the stroke, we must arrange
our exhaust to take place at a certain point at the end of the
stroke. It is found in practical operations that this necessary
quality of the slide-valve prevents our arranging it to cut off the
steam properly at an earlier point than about five-eighths or three-
quarter stroke. The consequence is, that an engine with two feet
stroke will receive steam 18 inches, then have 6 in. of expansion.
It may be fairly said, in a general way, that about all the slide-
valve engines now manufactured, cut off the steam at about five-
eighths or three-quarters stroke ;and it may be further said that this
is about all we can get out of a slide-valve engine. Even the trifling
expansion got from such engines as this, represents an immense
amount of money in the course of a year in large establishments,
but it is not good enough for anyone who seeks even a decent
investiment of money, in power-getting appliances.
REGULAR EXPANSION ENGINES.
A liberal expansion of steam being desirable and the slide-
valve proving totally incapable of providing for such expansion,
the first step in the desired direction is to totally discard the
slide valve. The Corliss valve is a cylindrical piece, oscillating
in a cylindrical hole. The valve does not fill this hole, but seats
against one side only. Hence the fitting qualities are about the
same as with the slide-valve and, in fact, the principle is about
the same, the Corliss representing a portion of the slide-valve,
rolled into the form of a cylinder and operating in a concave seat.
We must not only discard the slide-valve arrangement, but in
the valve arrangement which we select, we must secure an abso-
HANDBOOK ON ENGINEERING. 339
lute independence between the steam admission part of the sys-
tem and the exhaust part. The slide-valve is one chunk of cast
iron, letting in and cutting off steam at its outside edges, and
opening and closing the exhaust by its inside edges. When one
of these valve edges moves, everything else has to move. There
is, consequently, no independence of action. In the Corliss
engine there are parts to let steam into the cylinder and to quit
letting it in at the proper time, and there are valves to let it out
at the proper time, and they are perfectly independent of each
other in all of their movements. The consequence of this
arrangement is, that the steam valve may open, steam flow into
the cylinder, the valve suddenly shut and chop the steam off
short, the piston move forward in its stroke by the expansion of
the confined steam, and finally, be let out by the opening of the
exhaust valve, which has all the time stood ready for the dis-
charge. Here we have a regular expansion engine. We can cut
the steam off as early in the stroke as we desire, and hence, have
any degree of expansion we desire. And we can do this without
interfering with the exhaust valves. It is found, in practice,
that an engine cutting off at about one-fifth of its stroke and
expanding the other four fifths, will yield the fairest practical
economy.
AUTOMATIC CUT=OFF ENGINES.
In order that those not posted may understand what is meant by
the term " Automatic Cut-off Engines," we will have to go back a
step. Take, for instance, a full-stroke engine. It ought to be
well understood how the ordinary governor does its work. Sup-
pose, for instance, that there is no governor, and that we regulate
the speed of the engine by having a man stand at the throttle-valve
all the time. If the engine runs too fast, he shuts the throttle-
valve a little. This makes the steam pipe so small that the steam
cannot flow fast enough to keep the pressure up, and consequently
340 HANDBOOK ON ENGINEERING.
the speed goes down. If the engine runs too slow, he opens the
throttle- valve and lets the steam flow free, so as to maintain
higher pressure. Thus it will be seen that the man at the throttle
regulates the engine by altering the pressure with which the steam
acts upon the engine. An ordinary engine governor is simply a
man at the throttle. When the engine runs too fast the balls fly
out, the governor valve shuts a little and the pressure of steam
entering the engine is reduced, and so on through all the
changes continually taking place. All steam engines, in which
the regulation of steam is effected by means of a governor operat-
ing upon a throttle, are called throttling engines. They operate
by reducing the pressure of the steam admitted to the engine, and
thereby taking so much of the vitality out of the steam. It is
entirely the wrong way to do it. After once spending our
money to get up pressure in the boiler, we should make the
greatest possible use of that pressure, so long as we are taking
the steam from the boiler. It is, therefore, desirable that
the full boiler pressure should be admitted to our cylinder;
and the question arises as to how we shall be able to regulate
the speed if we do not tinker with this pressure. The automatic
engine regulates the speed by the simple act of altering the point
of cut-off. If the engine is cutting off at one-fifth stroke, we get
a power equal to the incoming force of steam for one-fifth of the
stroke, and the expansion of the steam for the other four-fifths of
the stroke. If the engine runs too slow we cut the steam off a
little later and thereby increase the average pressure during the
expansion. The automatic engine, then, is an engine, which cuts
off the steam at an earlier point in the stroke, if the engine runs
too fast, and cuts it off at a later point if it runs too slow. It is
the duty of the governor to say just when the steam valve should
close and not let any more steam into the cylinder. In the Cor-
liss engine the steam valves open wide at the beginning of the
stroke and let full boiler pressure smack in against the piston.
HANDBOOK ON ENGINEERING. Ml
After the piston has advanced to, say one-fifth of its stroke, the
valve shuts up as quick as a flash and the expansion begins. If
the engine starts too slow, the governor will hold the steam valve
open a trifle longer, but will not interfere with its full opening at
the beginning of the stroke, or with its flash-like closing when
the cut-off is to take place. During all these operations of the
governor and the admission valves, the exhaust valves are let
entirely alone, and they continue their work unchanged. It will
thus be seen that the expansion engine makes provision for the
utmost economy in the use of steam, and with the automatic fea-
ture added to it, provides that this economy shall not be sacrificed
for the purpose of regulating the speed.
THE GARDNER SPRING GOVERNORS.
Construction* — Two balls are rigidly connected to the upper
ends of two flat, tapering, steel springs — the lower ends of the
springs being secured to a revolving sleeve ,which receives rotation
through mitre gears ; links connect the balls to an upper revolv-
ing sleeve, which is free to move perpendicularly.
The valve stem passes up through a hollow standard upon which
the sleeves revolve, and is furnished with a suitable bearing in the
upper sleeve ; the closing movement of the valve is upward, and
is obtained in the following manner : The balls at the free ends of
the springs furnish the centrifugal force and the springs are the
main centripetal agency (gravity is not employed). As the balls
fly outward, under the centrifugal influence, they move in a curved
horizontal path which may be described as an arc, modified by a
radius of changing length — the radius being represented by the
length and position of the springs ; the links represent a radius
of lesser length, while the sleeve to which the lower ends of the
links are pivoted, being free to rise and fall, nullifies the effect of
the links in determining the arc in which the balls travel. As the
342
HANDBOOK ON ENGINEERING.
balls move outward in their peculiar path, the sleeve is drawn up-
ward by the links, and, as the balls move inward, the sleeve is
pushed downward. The change of speed is obtained by increas-
Fig. 108. The Gardner standard governor — class
automatic safety stop and speeder.
"A" with
ing or decreasing the centripetal resistance > and accomplished by
the action of a spiral spring pivoted against the lever, and by
means of a shaft and arm against the valve-stem in the direction
to open the valve ; a thumb-screw is used to adjust the compres-
HANDBOOK ON ENGINEERING.
sion. A convenient sawyer's lever is attached to the shaft and
a reliable automatic safety stop is furnished when desired.
Fig> f 98 on the preceding page represents the Gardner Standard
Governor, Class "A."
This is a gravity governor, having an automatic safety stop
and speeder. It is made in sizes from 1 £ inches to 16 in., and
is especially adapted to the larger type of stationary engines. In
action, the centrifugal force of the pendulous balls is opposed
by the resistance of a weighted lever, the speed being varied by
the position of the weight. The automatic safety stop is very
simple in construction and reliable in action. It is accomplished
by allowing a slight oscillation of the shaft bearing, which is sup-
ported between centers and held in position by the pull of the
belt ; a projection at the lower part of the shaft bearing supports
the fulcrum of the speed lever. If the belt breaks or sups off
the pulley, the support of the fulcrum is forced back, so as to
allow the fulcrum to drop and instantly close the valve. The
valve is not affected by steam current and both valve and seats
are made of special composition, that effectually resists wear
and the cutting action of the steam. The governor is made for
all pressures, all parts being made by the duplicate system, with
special machinery.
Fig, 199 on the following page represents Class "B" gov-
ernor— a combination of the gravity and spring designs.
They are made in sizes from f to 10 inches inclusive, and are
adapted to all styles of engines. They are provided with speeder
and sawyer's lever, but are not automatic. In the Class " B "
governor the centrifugal force of the pendulous balls operates
against the resistance of a coiled steel spring, inclosed within a
case and pivoted on the speed lever by means of a screw ; the
amount of compression of the spring can be changed so as to give
a wide range of speed. A continuation of the speed lever makes
a convenient sawyer's hand lever, which controls the valve by
344 HANDBOOK ON ENGINEERING.
means of a cord. Sizes £ to 1J in., inclusive, have an adjustable
frame, which can be set at any desired angle in relation to the
Fig. 199. The Gardner standard governor— Class "B."
valve chamber. The valve and chamber are the same as used on
Class " A " governor, and they are made with the same care and
style of workmanship.
HANDBOOK ON ENGINEERING.
345
CHAPTER XIV.
A FEW REHARKS ON THE INDICATOR.
The steam-engine indicator is an instrument designed to show
the steam pressure in the cylinder at all points in the stroke. It
consists primarily, of a piston of known area capable of moving
in a cylinder and resisted by a coil spring of known strength.
To this piston is attached, by means of suitable piston rod and
levers, a pencil capable of tracing a line corresponding to the
motion of the indicator piston. This line is traced on a paper
slip attached to the drum of the indicator, which drum is con-
nected to some moving part of the engine in such a way as to have
a back and forward movement, coincident with the steam piston
of the engine.
Fig. 200. Exterior and interior of indicator.
By referring to the above sectional view of an indicator, which
is generally recognized as the best type, the construction will be
readily understood.
346 HANDBOOK ON ENGINEERING.
THE USE OF THE STEAH EiNQINE INDICATOR IN SETTING
VALVES AND THE INVESTIGATION OF SOME OF THE DE-
FECTS BROUGHT OUT BY THE INDICATOR CARDS.
The steam-engine indicator has come into such general use
that to-day there are but few men running engines who are not
familiar with its construction and manner of attachment to en-
gines, and the method of calculating horse power from cards.
The indicator is attached to pipes tapped into the cylinder heads,
or into the barrel of the cylinder opposite the counterbore, beyond
the travel of the piston rings. The indicator consists of a cylin-
der with piston and compression spring and a drum attached to a
coiled spring, used for returning the same. The pressure of steam
on the piston of the indicator compresses the spring above it.
The motion of the piston is carried by a piston-rod to a pencil
motion, which multiplies the motion of the spring some five or six
times. The springs are marked 20, 40, 80, etc. This meaning
that 80 Ibs. pressure per square inch on the indicator piston
(or whatever the spring may be marked) will cause the pencil
at the end of the pencil-arm to move an inch. The pencil marks
on paper, which is fastened on a drum. This drum is moved by
the cross-head of the engine, through some form of reducing
motion, such as pantograph, lazy-tongs, brumbo pulley, etc. To
obtain the horse power, we first need the mean pressure equiva-
lent to the variable pressure on the card. This is most easily
found by dividing the area of the card by the length, giving the
height of a rectangular card of equivalent area, and then multi-
plying this height by the scale of the spring. The mean effective
pressure per square inch on the piston, times the area of the pis-
ton in square inches, times the speed of the piston in feet per
minute, divided by 33,000, gives the horse power. If there is a
loop at either end of the card, the area of this loop is to be sub-
tracted from the larger area before finding the mean height of
HANDBOOK ON ENGINEERING.
347
the card, since such a loop represents work opposed to the work-
ing side of the piston. In getting areas by means of a planimeter,
no attention need be given to the loops. By following the lines
in order, as drawn by the indicator pencil, the loops will be sub-
tracted from the main card, for if the main body of the card is
traced in a right-handed rotation, the loops will be traced in a
left-handed rotation.
DIAGRAM ANALYSIS.
Figs* 20 J and 202 are from throttling engines ; the former repre-
senting good performances for that class of engine, and the latter,
Fig. 201. Diagram from a throttling engine.
in some respects, which the engineer will readily recognize, bad
performances*
348 HANDBOOK ON ENGINEERING.
.
Figs. 203, 204, and 205, are from automatic8 ; Fig. 203 repre-
senting what is now considered rather too light a load for best
practical economy ; Fig. 204 about the best load, and Fig. 205
is from a condensing engine.
Line A B is the induction line, and B C the steam line ; both
together representing the whole time of admission.
(7 is about the point of cut-off, as nearly as can de determined
by inspection. It is mostly anticipated by a partial fall of pres-
sure due to the progressive closure of the valve.
The usual method is, to locate it about where the line changes
its direction of curvature.
C D is the expansion curve. D is the point of exhaust.
D E is the exhaust line, which begins near the end of the stroke
and terminates at the end of the stroke, or, at latest, before the
piston has moved any considerable distance on its return stroke.
The principal defect of Fig.202 is, that this line occupies nearly
all the return stroke. E Fis the back pressure line, which, in
non-condensing engines, should be coincident with, or but little
above, atmospheric pressure. In Fig. 205 it is below the atmos-
pheric line to the extent of the vacuum obtained in the cylinder.
Some authorities would call it the vacuum line in Fig. 205 but that
name properly belongs to a line representing a perfect vacuum.
jFMsthe point of exhaust closure (slightly anticipated by rise
of pressure) and F A the compression curve, which, joining the
admission line at A, completes the diagram proper, forming a
closed figure.
G G is the atmospheric line traced when the piston of the indi-
cator is subject to atmospheric pressure, above and below alike.
Some pull the cord by hand when tracing it, to make it longer
than the diagram. H H is the vacuum line, which, when re-
quired, is located by measurement such a distance below the
atmospheric line as to represent the atmospheric pressure at the
time and place as nearly as can be ascertained. The mean
HANDBOOK ON ENGINEERING. 349
atmospheric pressure at the sea level is 14.7 pounds. For higher
altitudes, the corresponding mean pressure may be found by
multiplying the altitude by .00053, and subtracting the product
from 14.7. When a barometer can be consulted, its reading in
inches multiplied by .49 will give the pressure in pounds.
FIfr. 202. Diagram from a throttling engine.
1 is the clearance line* representing by its distance from the
nearest point of the end of the diagram at the admission end, as
compared with the whole length, the whole volume of clearance
known to be present. Its use is mainly to assist in constructing
ft theoretical expansion curve by which to test the accuracy of the
Actual one.
Calculating mean effective pressure* — Since the simplification'
«ad popularization of the planimeter, no engineer who has occa*
350
HANDBOOK ON ENGINEERING.
sion to compute the " indicated horse-power " (IHP) of engines
should be without one; for, if properly handled, the results
Fig. 203. Diagram from an automatic cut-off engine*
obtained by them are more accurate and more quickly obtained
than by any other process. The diagram is pinned to a smooth
board covered with a sheet of smooth paper, the pivot of the leg
pressed into the board at a point which will allow the tracing point
to be moved around the outline of the diagram without forming
unnecessarily extreme angles between the two legs, and a slight
indentation made in the line at some point convenient for begin-
ning and ending ; for it is vitally important that the beginning and
ending shall be at exactly the same point. The reading of the
wheel is taken, or it is placed at zero, and the tracing point is
HANDBOOK OF ENGINEERING.
351
passed carefully around the diagram, following the lines as closely
as possible, moving right-handed, like the hands of a watch. The
reading obtained (by finding the difference between the two, if
the wheel has not been placed at zero) is the area of the diagram
in square inches, which, multiplied by the scale of the diagram,
and divided by its length in inches, gives the mean effective
pressure.
The process of finding the mean effective pressure by
ordinates* — Divide the diagram into 10 equal parts as shown by
the full lines in Fig. 204 : when performing this work a frequent
mistake is made, viz.,
Fig* 204. Erecting the or di nates.
making all the spaces equal. The end ones should be half the
width of the others, since the ordinates stand for the centers of
352
HANDBOOK ON ENGINEERING.
equal spaces. Ten is the most convenient and usual number of
ordinates, though more would give more accurate results. The
aggregate length of all the ordinates (most conveniently measured
consecutively on a strip of paper) divided by their number, and
multiplied by the scale of diagram, will give the mean effective
Fig. 205. Diagram from a condensing engine.
pressure. A quick way of making a close approximation to the
mean effective pressure of a diagram is, to draw line a 6, Fig. 206,
touching at a, and so that space d will equal in area spaces c and
e, taken together, as nearly as can be estimated by the eye.
Then a measure,/, taken at the middle, will be the mean effective
pressure. With a little practice, verifying the results with the
planimeter, the ability can soon be acquired to make estimates in
HANDBOOK ON ENGINEERING.
353
this way with only a fraction of a pound of error with diagrams
representing some degree of load. With very high initial pres-
sure and early cut-off, it is not so available.
a
Fig. 206. Mer nod of estimating the mean pressure.
The indicated horse-power. — IHP is found by multiplying
together the area of the piston (minus half the area of the piston-
rod section, when great accuracy is desired), the mean effective
pressure and the travel of the piston in feet per minute, and
dividing the product by 33,000. It is sometimes convenient to
know the HP constant of an engine, which is the HP for one
revolution at one pound mean effective pressure. This multiplied
by the mean effective pressure, and by the number of revolutions
per minute, gives the IHP.
THEORETICAL CURVE.
Testing expansion curves. — It is customary to assume that
steam, in expanding, is governed by what is known as Mariotte's
law, according to which its volume and pressure are inversely pro-
23
354
HANDBOOK ON ENGINEERING.
portional to each other. Thus, if a cubic foot of steam at, say,
100 pounds pressure be expanded to 2 cubic feet, its pressure
will fall to 50 pounds, and proportionately for all other degrees
of expansion. The pressures named are lt total pressures ; " that
is, they are reckoned from a perfect vacuum. A theoretic ex-
pansion curve which will conform to the above theory may be
\
\,
\
s.
10
Fig. 207. Locating the trne expansion curve.
traced by the following method : Referring to Fig. 207, having
drawn the clearance and vacuum lines as before explained, draw
any convenient number of vertical lines, 1, 2, 3, 4, 5, etc., at
equal distances apart, beginning with the clearance line and num-
ber them as shown. Decide at what point in the expansion curve
HANDBOOK ON ENGINEERING.
of the diagram we desire the theoretic curve to coincide with it.
Suppose we choose line 10, on which we find the indicated pres-
sure to be 25 pounds. Multiply this pressure by the number of
the line (10) and divide the product (250) by the numbers of
each of the other lines in succession. The quotients will be the
pressures to be set off in the lines. Thus, 250 divided by 9 gives
27.7, the pressure on line 9 ; and so for all the others. The
same curve may also be traced by several geometric methods, one
of which is as follows, referring to Fig. 208 : —
E
H
Fig. 208. Drawing the hyperbolic curve.
Having drawn the clearance and vacuum lines as before,
select the desired point of coincidence, as a, from which draw the
perpendicular a A. Draw A B at any convenient height above or
near the top of the diagram, and parallel to the vacuum line D C.
From A draw A C and from a draw a b parallel to D (7, and from
356 HANDBOOK ON ENGINEERING.
its intersection with A B, erect the perpendicular b c, locating the
theoretical point of cut-off on A B. From any convenient num-
ber of points in A B (which may be located without measurement)
as E, F, 6r, H, draw lines to (7, and also drop perpendiculars E e,
Ff, Gg, Hli, etc. From the intersection of E 0 with b c, draw a
horizontal to e, and the same for each of the other lines F <7,
G (7, H C; establishing points e,/, #, ft, in the desired curve.
Any desired number of points may be found in the same way.
But this curve does not correctly represent the expansion of
steam. It would do so if the steam during expansion remained
or was maintained at a uniform temperature ; hence, it is called
the isothermal curve, or curve of same temperature. But, in fact,
steam and all other elastic fluids fall in temperature during expan-
sion, and rise during compression ; and this change of temperature
augments the change of pressure slightly ; so that if, as before
assumed, a cubic foot of steam at 100 pounds total pressure be
expanded to two cubic feet, the temperature will fall from nearly
328° to about 278°, and the pressure instead of falling to fifty
pounds, will fall a trifle below 48 pounds. A curve in which the
pressure due to the combined effects of volume and resulting
temperature is represented, is called the adiabatic curve, or curve
of no transmission ; since, if no heat is transmitted to or from the
fluid during change of volume, its sensible temperature will
change according to a fixed ratio, which will be the same for the
same fluid in all cases. It is not necessary to give any of the
usual methods of tracing the adiabatic curve, since the isothermal
curve is the one generally used for that purpose. And while it is
incorrect in that it does not show enough change of pressure for a
given change of volume, the great majority of actual diagrams are
still more incorrect in the same direction ; so that when a diagram
conforms to it as closely as the one used in these illustrations, it
is considered a remarkably good one. A sufficiently close
approximation to the adiabatic curve to enable the non-profes-
HANDBOOK ON ENGINEERING. 357
sional engineer to form an idea of the difference between the two,
may be produced by the following process: Taking a similar
diagram to those used for the foregoing illustrations, we fix on a
point A near the terminal, where the total pressure is 25 pounds.
As before, this point is chosen in order that the two curves may
coincide at that point. Any other point might have been chosen
for the point of coincidence ; but a point in that vicinity is generally
chosen so that the result will show the amount of power that
should be obtained from the existing terminal. This point is 3.3
inches from the clearance line, and the volume of 25 pounds is
996 ; that is, steam at that pressure has 996 times the bulk of
water. Now, if we divide the distance of A from the clearance
line by 996, and multiply the quotient by each of the volumes of
the other pressures indicated by similar lines, the products will be
the respective lengths of the lines measured from the clearance
line, the desired curve passing through their other ends. Thus,
the quotient of the first, or 25-pound pressure line divided by
996 is .003313; this multiplied by 726, the volume of 25-pound
pressure, gives 2.4, the length of the 25-pound pressure line ; and
so on for all the rest.
Fig* 209 shows a card taken from a Corliss engine, running at a
speed of about ninety revolutions per minute. On account of the
slow speed and the quick
admission obtained by this
form of valve gear, but lit-
tle compression is needed.
For high speed engines,
there is much more com-
pression. At high speeds,
the expansion line of the _, .... ._ . . 7: — r.
Fig. 209. Diagram from Corliss
indicator card, instead of engine.
being a smooth curve like that shown in Fig. 209 , is of ten a wavy
line, due to oscillations of the spring in the indicator.
358 HANDBOOK ON ENGINEERING.
Fig. 2 JO represents what is called a stroke card. The indicator
shows us the pressure on
one side of the piston for
a revolution. When we
calculate the horse-power
from a card, we are as-
suming that the back pres-
sure and compression
line on the other side of
" "- the piston are the same as
Fig. 210. Showing a stroke card. shown on the card. This
may or may not be the case. In calculating the total horse-power
for the two ends of the cylinder, any error from this cause affect-
ing the calculation for one end of the cylinder, will be nearly
balanced by an opposite error in the calculations for the other end,
so that the final result is practically correct. If it were not for
the piston-rod making the area of one side of the piston smaller
than on the other, there would be absolutely no error arising
from this. The stroke card shows the pressure on opposite
sides of the piston at all points of the stroke. The difference
between the lines at any point is the effective push per square
inch. This card is constructed by using the steam and expan-
sion lines of the card from one end, and the back pressure
and compression lines for the same stroke, from the card taken
on the other end. In constructing diagrams for very accurate
work, the ratio of the areas of the two sides of the piston have
to be considered ; the pressure above the atmosphere for one
side being multiplied by this ratio. It will be seen that up to
the point of cut-off, the difference of pressure, or effective pres-
sure, is nearly constant ; this difference grows less, due to the
drop along the expansion curve, till at the point where the
two lines cross, the pressure on the two sides balances. Be-
yond this point, the pressure exerted to hold the piston back
HANDBOOK ON ENGINEERING.
359
Is greater than that exerted to push it ahead. The energy stored in
the fly-wheel during the first part of the stroke is given out here
near the end of the stroke to help the engine over the dead point.
STEAfl CHEST CARDS.
By attaching one indicator to the steam chest of an engine,
and another to one end of the cylinder, it can be seen
whether the pipes and ports are of sufficient size. A
sloping steam line on an indicator card may be due to too
small a steam pipe, or too
small steam ports', or to
both of these combined.
This does not apply, of
course, to engines using
throttling governors.
Fig»2n shows the effect
of too small steam pipe.
When steam is admitted
Fig. 211. Steam chest card on
forward stroke.
to the cylinder, there is a
drop in pressure in the
chest. This drop becomes greater in amount as the speed of the
piston increases. At cut-
off, the flow of steam into
the cylinder stops, then
the pressure in the chest
reaches boiler pressure.
If there is no great drop
in the line on the steam
chest card, and a consid-
erable drop in the steam
Fig. 212. Steam chest card on
forward stroke.
too small.
line of the card, it would
mean that the ports are
Such a case is shown by Fig. 212.
360
HANDBOOK ON ENGINEERING.
Fig. 213. Steam chest card on
forward stroke.
If there is a drop in
the chest line up to cut-
off, and a still greater
drop in the steam line
of the card, it would
indicate that both the
steam ports and the
steam pipe were too
small. Fig. 213 shows
such a case.
ECCENTRIC OUT OF PLACE.
Fi g*s* 214 to 2 \1 inclusive, show cards taken from a Corliss en-
gine having the eccentric out of adjustment. Similar cards would
be obtained from any en-
gine having all the valves
moved by one eccentric.
The plain slide valve and
the locomotive, especially
in full gear, would give
similar cards for the same
derangements of eccen-
tric.
Fig. 2*4 was taken with Figg. 214 and 21g. Effects o(
the eccentric a trifle less Of eccentric.
than 90° ahead of the crank, or about 20° behind where it belongs
on this particular engine.
Fig*2J5 shows the eccentric moved too far ahead of the crank.
By comparison with Fig. 209, it will be seen that moving the
eccentric back makes all the events of the stroke, such as admis-
sion, release and compression and cut-off, in the case of engines
without automatic cut-off governor, come later ; while moving
the eccentric ahead brings these events earlier.
HANDBOOK ON ENGINEERING.
361
Figs. 2J6 and 217 are similar to Figs. 214 and 215, the only dif-
ference being that eccentric is moved a greater distance out of plane.
In Fig. 2 \6 the admission
is very late. Release does
not occur until after the
piston has started on the
return stroke, the steam,
until released, being com-
pressed back along the ex-
pansion curve. This com-
pression is always a trifle ^ 216 „„ M7>._ Eccentric
below the expansion line, diagrams.
due to the fact that some of the steam has condensed in the
interval between the end of the stroke and the release.
Figf. 2J7 shows too much compression and too early a release.
Steam is compressed above boiler pressure in the cylinder, when
the valve lifts and the steam escapes into the chest.
Cards like Figs. 214 and 215 are very common.
ECCENTRIC DIAGRAMS.
As small distances near the ends of the indicator cards repre-
sent a large angular motion of the crank, the events occurring at
the ends of the card are so squeezed together that it is hard to
tell from the card just what any peculiarity in the lines may be
due to. The eccentric rod working the valves of the engine will
be moving at its greatest speed when the crank is near the centers
and the piston near the ends of the stroke ; since the eccentric is
about 90° ahead of the crank. If the motion of the indicator
drum is taken from the eccentric rod instead of the cross-head, the
card will be changed in shape, compression and release coming
near the middle of the card ; these are spread out over consider-
able length, the cut-off, expansion and backpressure lines coming
near the ends of the card.
362
HANDBOOK ON ENGINEERING.
Figf*2J8 gives a steam card drawn, assuming that the expansion
and compression lines are hyperbolic. The eccentric card for this
has been plotted, and cor-
responding points marked
with the same letters. The
F F
Fig. 218. Combined diagram. Fig. 219. Ordinary diagram.
compression curve, extending from F to A, is a double curve.
Admission occurs at A, cut-off at B, release at (7, and compres-
sion at F.
Figs* 2 19 and 220 show cards taken from an engine having tight
valves and a tight piston. Corresponding points on the two cards
are lettered the same. For a
cut-off later than half stroke,
the steam line on the eccen-
tric card doubles on itself, as
shown in Figs. 220 and 222.
The peculiar bend shown
by the dotted lines on com-
Fig. 220. Eccentric diagram.
pression curve of the steam card,
Fig. 218, is developed on the
eccentric card into a well marked
flat place. Evidently this rep-
resents a loss of pressure at this
point, which may be attributed
to one or more of three causes : pig. 221. Eccentric diagram.
first, leakage by the piston ;
second, leakage by the exhaust valves ; third, a rapid condensa-
HANDBOOK ON ENGINEERING. 363
tion of steam. If by leakage, it is probable that there is steam
blowing by all through the stroke.
Near the end of the stroke the pis-
ton is moving at so slow a rate that
the leakage overbalances the com-
pression. It frequently happens
that the pressure drops off at the
end of compression, making the Fig. 222, Eccentric diagram.
upper end of the compression line
resemble an inverted letter U. If the leakage is by the piston,
it will appear or may be made to appear near release, as will be
explained later. The effect of compressing steam is to dry it,
or, if dry already, to superheat it. While it may be possible in
some cases for some of the drop here to be due to condensation,
in the majority of cases leakage is the trouble.
Fig. 223 shows the effect of a bad leakage by the piston. This
leakage is made evident by the appearance of the upper end of
the compression curve
and by the increase in
pressure along the expan-
sion line just before re-
lease. By referring to
the stroke card, it will be
seen that near this point
Fig. 223. Effects of leakage. *he pressures on the oppo-
site side of the piston are
the greater, so that the leakage is now into the side on which the
card is being taken. Unless compression on one side conies
earlier than release on the other side, this method would fail.
In most engines the valves are set so that compression does
come earlier, and all four valve engines can be easily set so
as to delay release on one end, and to hasten compression on the
other end. In the case of a Corliss engine, this means simply
364
HANDBOOK ON ENGINEERING*
the changing the length of the rods leading from the wrist-plate
to the valve arm. This change can be made with the engine run-
ning. It is possible that a card like Fig. 223 might be obtained
from a four-valve engine having a leaky steam valve on one end
and a leaky exhaust valve on the other end.
Fig* 224 represents the head end and the crank end cards
taken from a plain slide valve engine. The valve has equal
steam lap and equal exhaust lap. The only trouble in this case
Fig. 224. Effects of changing length of ralye stem.
is that the valve spindle is too short. Shortening the valve spin-
dle decreases the outside lap of the valve and increases the inside
lap for the head end side, and increases the outside lap and de-
creases the inside lap for the crank end side. As will be seen by
the cards, the head end has the cut-off lengthened, the release
delayed, and the compression hastened; the crank-end has the
cut-off shortened, the release hastened, and the compression de-
layed. If the valve spindle were too long the cards shown would
be interchanged, the crank end card being the one marked head
end.
THE STEAM ENGINE INDICATOR.
Benefits derived and information ascertained from its use* —
The benefits derived, and the information ascertained from the
use of the steam-engine indicator are varied and important.
HANDBOOK ON ENGINEERING. 365
The office of the indicator is to furnish a diagram of the
action of the steam in the cylinder of an engine during one or
more revolutions of the crank, from which is deduced the follow-
ing data : Initial pressure in cylinder ; piston stroke to cut-off ;
reduction of pressure from commencement of piston stroke to cut-
off ; piston stroke to release ; terminal pressure ; gain in econ-
omy due expansion ; counter pressure, if engine is worked
non-condensing ; vacuum as realized in the cylinder, if engine is
worked condensing ; piston stroke to exhaust closure, usually
reckoned from zero point of stroke ; value of cushion ; effect of
lead and mean effective pressure on the piston during complete
stroke. The indicator diagram, when taken in connection with
the mean area and stroke of piston and revolution of crank
for a given length of time, enables us to ascertain the power de-
veloped by engine ; and when taken in connection with the mean
area of piston, piston speed and ratio of cylinder clearance,
enables us to ascertain the steam accounted for by the indicator.
The mean power developed by engine compared with the
steam delivered by boilers, furnishes cost of power in steam,
and when compared with the coal, furnishes cost of the power in
fuel.
The diagram also enables us to determine with precision the
size of steam and exhaust ports necessary, under given conditions,
to equalize the valve functions ; to measure the loss of pressure
between boiler and engine ; to measure the loss of vacuum be-
tween condenser and cylinder ; to determine leaks into and out
of the cylinder ; to determine relative effects of jacketed and
un jacketed cylinders ; and to determine effects of expansion in
one cylinder, and in two or more cylinders.
TO TAKE A DIAGRAM.
Connecting cord* — The indicator should be connected to the
engine cross-head by as short a length of cord as possible. Cord
366 HANDBOOK ON ENGINEERING.
having very little stretch, such as accompanies the instrument,
should be used ; and in cases of very long lengths, wire should
be used. The short piece of cord connected with the indicator is
furnished with a hook ; and at the end of the cord, connected
with the engine, a running loop can be made by means of the
small plate sent with each instrument ; by which the cord can be
adjusted to the proper length, and lengthened or shortened as
required.
Selecting a spring* — It is not advisable to use too light a
spring for the pressure. Two inches are sufficient for the height
of diagram, and the instrument will be less liable to damage if
the proper spring is used. The gauge pressure divided by 2
will give the scale of spring to give a diagram two inches high at
that pressure.
To attach a card* — This may be done in a variety of ways,
either by passing the ends of it under the spring clips, or by
folding one end under the left clip, and bringing the other end
around under the right; but, whatever method is applied, care
should be taken to have the card rest smoothly and evenly on the
paper drum. Now attach the cord from the reducing motion to
the engine ; but be certain the cord is of the proper length, so as
to prevent paper drum from striking the inner stop in drum
movement on either end of the stroke.
Tension of drum spring* — The tension of the drum spring
should be adjusted according to the speed of the engine ; in-
creasing for quick running, and loosening for slower speeds.
The steam should not be allowed into the indicator until it has
first been allowed to escape through the relief on side of cock, to
see if is clean and dry. If clean and dry, allow it into the indi-
cator, and allow piston to play up and down freely.
After taking diagram, turn the handle of cock to a horizontal
position, so as to shut off steam from piston, and apply pencil to
the paper to take the atmospheric line.
HANDBOOK ON ENGINEERING. 367
In applying pencil to the card, always use the horn-handle
screw, to regulate pressure of pencil upon paper to produce as
fine a line as possible. After the atmospheric line is taken, turn
on steam, and press the pencil against card during one revolution.
When the load is varying, and the average horse-power re-
quired, it is better to allow the pencil to remain during a number
of revolutions, and to take the mean effective pressure from the
average of the several diagrams.
Fig. 225* Diagram from a Russell engine.
Fig. 225 was taken from a Russell engine 13" x 20", running
205 revolutions per minute, boiler pressure 98 Ibs., scale of
spring 60 Ibs. Duty, electric lighting.
After sufficient number of diagrams have been taken, remove
the piston, spring, etc., from the indicator, while it is still upon
the cylinder ; allow the steam to blow for a moment through the
indicator cylinder ; and then turn attention to the piston, spring,
and all movable parts, which may be thoroughly wiped, oiled and
cleaned. Particular attention should be paid to the springs, as
their accuracy will be impaired if they are allowed to rust ; and
great care should be exercised that no grit or substance be intro-
duced to cut the cylinder, or scratch the piston. Be careful
368
HANDBOOK ON ENGINEERING.
always not to bend the steel bars or rods. The heat of the steam
blown through the cylinder of the indicator will be found to have
dried it perfectly, and the instrument may be put together with
the assurance that it is all ready for use when required. It is a
saving of time to keep indicator in order. Any engineer can
easily perform the operation without further instruction.
Fig. 226. Another diagram from Russell engine.
Fig. 226 was taken from a Russell engine 16" x 24", running
157 revolutions per minute, boiler pressure 70 Ibs., scale of
spring 40 Ibs. Duty, flouring mill.
Fig. 227. Friction load. Fig. 228. Fail load.
HARRISBURG IDEAL SIMPLE SINGLE VALVE ENGINE.
HANDBOOK ON ENGINEERING.
369
Fig. 229. Graduated load. Fig. 230. Extreme load variation.
HARRISBURG IDEAL SIMPLE SINGLE VALVE ENGINES
Fig. 231. High pressure Fig. 232. Low pressure
diagrams. diagrams.
HARRISBURG IDEAL COMPOUND SINGLE VALVE ENGINE.
Fig. 233. Friction diagrams. Fig. 234. Full load diagrams.
HARRISBURG STANDARD SIMPLE SINGLE VALVE ENGINE.
370
HANDBOOK ON ENGINEERING.
Fig. 236. Friction load. Fig. 236. Full load.
HARRJSBURG STANDARD SIMPLE FOUR-VALVE ENGINE.
Fig. 237. High pressure
diagrams.
Fig. 238. Low pressure
diagrams.
HARRISBUKG STANDARD COMPOUND FOUR-VALVE ENGINE.
The indicator diagrams from Fig. 227 to 238 were taken from
the Harrisburg Ideal and Standard engines. An engineer will
see from these cards the kind of card he should get from a high
speed engine of this class.
Fig* 239 is from a Frick Corliss engine, driving a Frick com-
pressor : —
Steam Cylinder 19"x28".
Steam . .. 95 Ibs.
Revs. . ... . . . • . . • 58
Cond. Press. . . . . . . . . 164 Ibs.
Back Press. 27 Ibs.
HANDBOOK ON ENGINEERING.
371
Engine, 19" x 28".
Steam, 95 Ibs.
Revs. 58 Ibs.
Cond. Press.. 164 Ibs.
Back Press.. 27 Ibs:
Fig. 239. Diagram from 19" x 28" Eclipse Corliss.
INDICATOR DIAGRAMS FRONT 50-TON "ECLIPSE"
MACHINE.
JR. Hand Ptimp*
12*" x 28".
Scale. 120 //*.
Fig. 240. Diagram from right hand Eclipse pump.
Fig, 240 is R. Hand Pump, 12£" x 26", Scale, 120 Ibs,
372
HANDBOOK ON ENGINEERING.
\
L.- Hand Picmp.
12J" x 28".
Scale, J20M*.
Fig. 241. Diagram from left hand Eclipse pump.
Fig* 241 is L. Hand Pump. 27|" x 28". Scale, 120 Ibs
Engine, 80" x 36"
Steam, 75 /fo.
Revs. 44
Conrf. /VMS., 162
Back Press.,
Fig. 242. Diagram from 30" x 36" Eclipse machine.
Figs* 242 to 244, are diagrams from a 100-ton " Eclipse "
machine.
HANDBOOK ON ENGINEERING. 373
INDICATOR DIAGRAMS FROM 100-TON "ECLIPSE"
MACHINE.
Fig. 243. Diagram from right hand pump.
Fig. 244. Diagram from left hand pump.
374
HANDBOOK ON ENGINEERING.
Fig. 245. Diagrams from a Ball engine.
HANDBOOK ON ENGINEERING.
It will be interesting to note that when the eccentric is simply
moved forward or backward around the shaft by the action of the
governor, all the events of the stroke — admission, release, cut-off
and compression : — will be hastened or retarded together ; but if
the eccentric be so designed that the governor will shift it across
the shaft instead of around it, the admission and release will be
effected differently, and in the opposite direction from the cut-off
and compression. If, for example, the cut-off is made to occur
earlier in the stroke, the compression will occur earlier /also, but
the admission and release will occur later instead of earlier. By
combining the two movements of the eccentric and having the
governor move it partly around and partly across the shaft, it is
possible to keep the admission and release nearly constant, while
the cut-off and compression vary. This result is attained to a
certain extent in the best single-valve engines. Besides ttiese two
types, there are numerous other styles of engines in wliich the
point of cut-off is varied automatically. Instead of a shaft gov-
ernor with a shifting eccentric, a weighted pendulum governor is
sometimes employed to operate the link, or radius rod of some
one of the various link motions. Sometimes there are separate
admission and exhaust valves, the former being under the con-
trol of a shaft governor, and the latter operated by a fixed eccen-
tric, so that the points of admission and cut-off only are varied,
while the points of release and compression, which depend upon
the exfiaust valve, remain fixed. There are a great many modifi-
cations of the Corliss engine, as originally constructed by
Geo. H. Corliss, and there are many engines which, while not re-
sembling the Corliss engine, have some arrangement whereby the
cut-off valves are tripped.
On pages 374 and 376 is a collection of diagrams, which
illustrate very nicely the peculiarities and difference in the action
of throttling and automatic engines. The four diagrams on
page 374 were taken from a Ball automatic, in an electric light
376
HANDBOOK ON ENGINEERING.
Fig. 246. Diagrams from a Dickson throttling engine.
HANDBOOK ON ENGINEERING. 377
station. The first diagram was taken late in the afternoon when
the engine was started and before any load was thrown on to the
machine, and the three succeeding cards were taken at intervals
later in the evening as the number of lights increased and the
load became heavier. Two or three important points are to be
noticed in connection with these diagrams. First, the initial
pressure of the steam at the point of admission is very nearly the
same in all four cards, the slight variations being due chiefly to a
variation in the boiler pressure. Second, the length of the cut-off
increases with the load. The compression also becomes later as
the cut-off lengthens, and while there is also a change in the points
of admission and release, it is not as marked as the changes in cut-
off and compression, for reasons that have already been explained.
Taking the cards on page 376, we have four excellent examples
of the action of a throttling engine. These cards are from a
Dickson engine, taken at the same station and under the same
conditions as the Ball engine cards, with the exception that in
this case both head and crank-end diagrams were taken on the
same cards, while only the head end diagrams from the Ball
engine are shown. The two sets of diagrams are well adapted
for comparison, because both engines are of the single-valve typej
with the valve moved by one eccentric.
The points to be noted are, first, that the points of cut-off are
the same, namely at about J stroke, in all the throttling cards,
and second, that the power of the engine is increased by the action
of the governor in opening a throttle valve wider, allowing steam
to enter the cylinder at higher pressure.
It was stated at the outset that automatic regulation is the
most approved method for regulating the speed of steam engines
at the present time. It is generally believed and it is probably
true, that automatic engines give better economy than throttling
engines and that they regulate a little more closely. It will
readily be seen that when the governor of the automatic engine
378 HANDBOOK ON ENGINEERING.
changes position, it measures out just the quantity of steam that
will be required to keep the engine within the speed limits during
the following stroke. The effect of this regulation, moreover, is
felt at one point in the stroke only — the point of cut-off — so that
any change in the governor up to the time when the piston nears
the point of cut-off will produce an immediate change in the
quantity of steam admitted. In the throttling engine, on the
other hand, the regulation is effected during the whole stroke up to
the point of cut-off, and the full effect of any change of the gov-
ernor cannot be felt until the next stroke. With regard to the
relative economy of the two types, it should be kept in mind that
the throttling engine is generally of cheap construction, has large
clearance, a single, unbalanced slide-valve that does duty for both
entering and exhaust steam and aside from the throttling feature,
is inferior to the average automatic engine. It is reasonable to
suppose, therefore, that at least a part of the large steam con-
sumption generally attributed to the throttling engine is due to
its inferior design and construction and not to its method of
governing.
For example, take the case of the Ball and the Dickson engines,
from which cards are shown. They both have a single slide-
valve, but the former runs at higher speed than the latter and its
valve is balanced, so that for these reasons it would be expected
to be a little more economical. We should not expect, however,
that a test would show any decided superiority that could be
attributed to the method of governing. If we were to compare
the average throttling engine with the most approved type of
automatic engine, like the Corliss, we should find that the effi-
ciency of the latter was much higher. The gain, however, would
be due to a large extent to the small clearance spaces, separate
steam and exhaust valves, and other important features of the
Corliss engine, rather than to its automatic cut-off. It is not
the purpose to discuss here why these features give improved
HANDBOOK ON ENGINEERING. 379
economy over the single valve, but simply call attention to the
fact that they exert an important influence. The exact influence,
which the throttling or automatic features exert apart from the
general constructive features of the engine is hard to determine.
It is known that high-pressure steam is more economical to use
than low pressure steam and the automatic engine, which pre-
serves nearly the boiler pressure up to the point of cut-off, gains
on this account. On the other hand, it is known that the most
economical point of cut-off for a non-condensing engine is about
one-third stroke, and when it becomes very much less than this
there is a serious drop in the economy. A very short cut-off
with high-pressure steam produces so great a variation in the
temperature during one stroke of the piston that the cylinder
condensation becomes excessive. For very light loads, therefore,
it would be better to throttle the steam than to shorten the cut-off.
It is necessary for all engines to have a reserve of power and
hence the cut-off of throttling engines must come late in the
stroke. If it were early in the stroke, there would not be enough
reserve power with the reduction in the pressure of the steam that
is necessary with this type. The late cut-off produces poor
economy when the load is heavy, because there will then be a
high terminal pressure, and a large amount of heat, corresponding
to this pressure, will be thrown away. A throttling engine there-
fore, may be expected to do better at light loads than at heavy
ones, and in fact, may do a little better at light loads than the
automatic engine. If a throttling engine could be run so as not
to vary much from its most economical load, and could be de-
signed to have the good features of the best automatic engines,
with the cut-off at an earlier period in the stroke, it would prob-
ably be nearly or quite as well as the automatic engine. Under
the conditions that they have to run, however, the automatic engine
will keep the lead, although, as explained above, its superiority
is not due entirely to the automatic feature.
380 HANDBOOK OF ENGINEERING.
CHAPTER XV.
ECONOMY AND OPERATION OF ENGINES.
Engineers over the country have been discussing whether or
not more steam is used when an engine is made to run faster without
changing either the cut-off or the back pressure. Some, strange as
it may seem, have actually held to the opinion that, since the cut-
off is not changed, no more steam is used, and hence, if it were
possible to make an engine run faster without changing the cut-off,
it would be doing more work than before without any increase in
the consumption of steam. Of course, this is wrong. The speed
of an engine, almost any engine, may easily be increased without
changing the cut-off, and when this is done, the engine will do
more work and will use more steam. It is utterly impossible to
get something for nothing out of a steam-engine, or out of any
engine or appliance. The only way in which a steam-engine can
be made to do more work without using more steam is to increase
its efficiency. And when everything else is kept the same and the
speed only of an engine increased, the efficiency is very slightly
increased. The condensation is decreased with an increase of
speed, but the decrease would be so slight for most cases that it
would hardly be worth considering. When an engine is cutting
off at a certain part of the stroke, it uses at every stroke a cer-
tain weight of steam which depends upon the initial pressure of
the steam, clearance volume of the engine and the point of cut-
off. If the engine makes 400 strokes per minute (200 revolu-
tions, if a double acting engine) the weight of steam used will be
HANDBOOK ON ENGINEERING.
400 times the weight used in one stroke ; but if the engine be
made to make 500 strokes per minute, the weight of steam used
per minute will be, neglecting the small difference in condensa-
tion, 500 times the weight used in one stroke.
HOW TO INCREASE THE SPEED, OR INCREASE THE POWER
OF A CORLISS ENGINE.
There are three ways in which this can be done. Take, for
example, a 24" x 48" simple Corliss engine making 70 revolu-
tions per minute, the boiler gauge pressure 80 Ibs. per square
inch, one-quarter cut-off, or cut-off 12 inches from the beginning
of the stroke ; the mean effective pressure, say about 42 Ibs. per
sq. in., the governor pulley on the main shaft 10 inches in diam-
eter, the pulley on the governor shaft 7 in. in diameter, and the
friction of engine, cylinder clearance, condensation, etc., left
entirely out of the question. It is desired to increase the speed
of this engine to 80 revolutions per minute, and in this manner
increase its horse-power.
First method* — Regardless of piston rod, the area of the pis-
ton is 452.4 square inches, nearly. The piston speed of this
engine is 560 feet per minute, and its horse-power 322, nearly.
452.4x42x560
Thus: Qo/wm ~ =322. So that the horse-power of this
ooUUU
engine at 70 revolutions per minute is 322, nearly, and this is
what the manufacturer's catalogue gives. Now, in order to get
80 revolutions per minute, take the 7-inch pulley off the governor
shaft, and put in its place an 8-inch pulley. Thus : 70 : 80 : :
7:8. Then, the governor balls will revolve in the same relative •
plane that they did before, and the cut-off will remain the same ;
that is, at one-quarter, or 12 in. of the stroke. Thus, 7: 10::
70 : 100. And 8 : 10 : : 80 : 100. So the governor balls make 100
revolutions per minute, both before and after making the change.
382 HANDBOOK ON ENGINEERING.
Now, with the engine speeded up to 80 revolutions per minute,
we get 46 more horse-power. Thus: Piston speed equals 640
452.4x42x640
feet per minute. Then, — SSOCK) - = ^^ horse-power,
nearly. And 368 minus 322 =46. Now, it would appear that
we are getting 46 horse-power more for nothing, but such is not
452.4x12x2x70
the case. For, - VIZR -- =439.8 + , or nearly 440
cubic ft. of steam per minute, at 80 Ibs. boiler pressure, are
452.4x12x2x80
required to develop 322 horse-power. And,
= 502.6+ or nearly 503 cubic ft. of steam per minute, at 80
Ibs. boiler pressure, are required to develop 368 horse-power.
Then, 503 minus 440 = 63 cubic feet more of steam at 80 Ibs.
boiler pressure, which means more water evaporated per minute
and more coal burned per hour.
Second method* — Retain the same engine speed and the same
cut-off, but increase the boiler pressure from 80 to 90 Ibs. Then
80: 90: : 42 : 47 + , call it 48 Ibs. mean effective pressure.
452.4x48x560
Then, - SSOOQ - == ^^ horse-power, nearly, the same as
before, and as given in the manufacturer's catalogue. We are
now using 440 cubic feet of steam per minute at 90 Ibs. pressure,
with an increase of 6 Ibs. M. E. P. ; consequently, more coal per
hour must be burned.
Third method* — Retain the same boiler pressure, that is 80
Ibs., and weight the governor so as to make the balls revolve in a
lower plane in order to give a later cut-off. Thus, 322 : 368 ::
J:f. That is, the cut-off must take place at about % of the
stroke instead of at J. Then, J:f::42:48. That is the
M. E. P. will be 48 Ibs. per square inch with a cut-off at % of the
452.4x48x560
stroke. Then, - 33000 - == ^68 horse-power, the same as
HANDBOOK ON ENGINEERING. 383
before. But, % of 48 = 13f , or 13.71 inches nearly, so that,
instead of cutting off at 12 inches with 80 Ibs. boiler pressure,
we are cutting off at 13.71 inches and using 63 cubic feet more
452.4 x 13. 71x 2x70
steam per minute. Thus, = 503, nearly.
1728
And, 503 minus 440=63, that is, we must use 63 cubic feet
more of steam per minute at 80 Ibs. boiler pressure, in order to
get 46 more horse-power, which means the evaporation of more
water per minute, and the burning of more coal per hour.
HOW TO INCREASE THE HORSE-POWER OF AN ENGINE
HAVING A THROTTLING GOVERNOR.
There are three ways in which this can be done, also. We
will take, for example, a plain slide-valve engine 10 x 16 inches,
making 150 re volutions per minute, with T9^ cut-off, and M. E. P.
say 31£ Ibs. per square inch, with a boiler pressure of 60 Ibs.
by gauge. The governor pulley on the main shaft 6 inches
in diameter, and the pulley on the governor shaft 4 inches
in diameter. The horse-power of this engine is about 30.
Thus, 16x2 = 2f ft., and 150 x 2| = 400 ft., the piston speed.
\a
10 x 10 x. 7854x31.5x400 = horse_power, nearly.
33000
It is now desired to run the engine at 180 revolutions per
minute in order to develop 6 horse-power more. In order to
obtain these results, the governor pulley must be enlarged, so as
to make the governor balls revolve in the same plane at 180 revo-
lutions per minute, that they now do at 150 revolutions. Thus,
4:6:: 150: 225, that is, the governor balls are now making
225 revolutions per minute. And 150 : 180 : : 4 : 4.8. Con-
sequently, the governor pulley must be increased to 4.8 inches in
384 HANDBOOK ON ENGINEERING.
diameter. Then, 4.8 : 6 : : 180 : 225, that is, the governor balls,
after the change, making the same number of revolutions as
before. At 18J3 revolutions per minute, the piston speed is 480
feet per minute. Thus, = 21. And, 180 x 2| = 480.
12
Then, 78>54^3Q1^x480^ 36 horse-power, nearly. It might
seem from the above that we are getting 6 horse-power more for
nothing ; but such is not the case. For, cutting off at T9F is
equivalent to cutting off at 9 inches of the stroke.
™ 78.54x9x2x150
Then, _ _ _ = 123 cubic ft., nearly.
1728
78.54x9x2x180
— — 147 cubic feet, nearly. And,
1728
147 minus 123 — 24. So that for 6 horse-power more, we are
using 24 cubic feet more of steam per minute, at 31.5 Ibs. M. E. P. ,
which means more water evaporated per minute and more coal
burned per hour.
If the boiler pressure may be safely increased, we can get 6
horse-power more out of the engine without increasing its speed,
by running the boiler pressure up to 75 Ibs. by gauge. Thus 75
Ibs. boiler pressure would give about 37.8 Ibs. M. E. P. with T9^
cut-off. Then, ^8. 54 x 37.8 x 400 = 36 horse_power nearly.
33000
In this case no change should be made in the governor, nor in
the speed of the engine. We can also get 6 horse-power more
out of this engine by cutting off later, say at |, in order to get
37.8 Ibs. M. E. P. But a later cut-off is not desirable, because
it is not economical of steam, and besides, it would require a new
valve, new eccentric, or a change in the length of a rocker arm, if
not a change of the valve-seat, because the travel of the valve
would have to be increased.
HANDBOOK ON ENGINEERING. 385
HOW TO INCREASE THE HORSE-POWER OF AN ENGINE
HAVING A SHAFT GOVERNOR.
Suppose it is desired to increase the speed of the engine from 250
to 275 revolutions per minute, cutting off at i stroke. In this
case the governor springs should be so adjusted that the throw of
the eccentric will be the same at 275 revolutions that it was at 250
revolutions. This will require an increased consumption of steam
per minute at the same initial cylinder pressure as before making
the change, consequently more fuel will be required. If the speed
of the engine is not to be changed, an increase of the horse-power
may be obtained by increasing the initial cylinder pressure, if the
condition of the boiler will so permit. Or, the initial cylinder
pressure may remain unchanged and the governor springs and
levers so adjusted as to give a later cut-off, say at |^ or T7^ of the
stroke, or whatever may be required to offset the increased per-
manent load, the speed of the engine remaining unchanged. Any
one of the changes above described would necessitate an increased
consumption of fuel.
HOW TO LINE THE ENGINE WITH A SHAFT PLACED AT A
HIGHER OR A LOWER LEVEL.
We will suppose the latter shaft not yet in place, but to be
represented by a line tightly drawn. From two points as far
apart as practicable, drop plumb lines nearly, but not quite,
touching this line. Then by these strain another line parallel
with the first, and at the same level as the center line of
the engine, and at right angles with this stretch another represent-
ing this center line, and extend both each way to permanent walls
on which their terminations, when finally located, should be care-
fully marked, so they can at any time be reset. The problem is
to get the latter line exactly at right angles with the former.
Everything depends upon the accuracy with which this right
25
386
HANDBOOK ON ENGINEERING.
angle is determined. It is done by the method of right-angle
triangles. There are two ways of applying this method. In the
first, one end of a measuring line is attached to some point of
line No. 1, and its other end is taken successively to points on
line No. 2 on opposite sides of the intersection, as illustrated in
the following figure, in which A B is a portion of line No. 1, and
C D of line No. 2, the direction of which is to be determined,,
B F and B G are the same measuring line fixed at B, and applied
to the line C D successively at the points F and G. The dis-
Fig. 247. Lining engine with line shafting.
tances B F and B G being, therefore, the same, when E F is
equal to E G, the lines A B and C D are at right angles with each
other. In the second, application is made of the law that the square
of the hypothenuse of a right-angle triangle is equal to the sum
of the squares of the other two sides. Thus 32 -j- 42 = 52. So if
the above figure E B = 4, E F=3, and B F=6, the angle at
E is a right-angle. Any unit of measure may be used, a foot is
generally the convenient one ; so any multiple of these numbers
may be taken; as, for example, 6, 8 and 10. Respecting the
comparative advantages of these two ways, the situation will of ten
determine which is to be preferred. In the former, the diagonal
HANDBOOK ON ENGINEERING. 387
being the same line, fixed at B and brought successively to the
points F and 6?, its length is immaterial, though generally the
longer the better ; and the only point to be determined is the
equality of E F and E G, which may be compared with each
other by marks on a rod. In the latter, the proportionate
lengths, 3, 4 and 5, or their multiples, must be exactly measured.
It is better adapted to places where a floor is laid and the meas-
urements can be transferred by trammels. The result should be
verified by repeating the operation on the opposite side of the
intersection at E, and when so verified we have, in fact, the first
process, without the additional and unnecessary trouble of deter-
mining the relative lengths of the lines. Care should be taken
when a measuring line is used, to avoid errors from its elasticity „
On this account, a rod is often employed. Points on the lines
are best marked by tying on a white thread.
HOW TO LINE THE ENGINE WITH A SHAFT TO WHICH IT IS
TO BE COUPLED DIRECT.
In this case, it is supposed that the engine bed and the bear-
ings for the shaft are already approximately in position. They
are leveled by a parallel straight edge and a spirit level. To line
them horizontally, a line must be run through the whole series of
bearings and continued to a permanent wall at each end, and its
terminating points, when determined, carefully marked, as already
directed. A piece of wood is tightly set in each end of each
bearing and the surfaces of these are painted white or chalked.
Then the middle of each piece being found by the compasses, two
fine lines are drawn across it, equally distant from the middle, and
having between them a space a little wider than the thickness of
the line. The line being tightened, nearly touching the blocks,
or, if long, having its sag supported by them, the two marks on
each block must be seen, one on each side of the line, with the
line of white between.
388 HANDBOOK ON ENGINEERING.
HOW TO SET A SLIDE VALVE IN A HURRY.
Open the cylinder cocks; then open the throttle slightly, so
as to admit a small amount of steam to the steam-chest. Roll
the eccentric forward in the direction the engine runs, until steam
escapes from the cylinder cock at the end where the valve should
begin to open. Now screw the eccentric fast to the shaft. Roll
the crank to the next center and ascertain if steam escapes at the
same point, at the opposite end of the cylinder. If so, ring the
bell and go ahead. The valve gear can be run until an oppor-
tunity occurs to remove cover from steam-chest and examine the
valve.
DO YOU DO THESE THINGS?
A writer in a magazine asks and answers the following
pertinent questions : —
Do you take a squirt-can in one hand and project a stream of
oil as far as you can throw it, in order to save going to the oil
hole itself ?
If you do, don't do it any more ; willful waste is downright
robbery.
Do you use an oil can at all for oiling, except on emergency, or
for the moment ?
If you do, don't do it any more, for much better lubrication
can be had by automatic apparatus.
Do you keep an old tin coffee-pot full of suet on the steam-
chest, and every time you have nothing else to do, pour a dipper-
f ul into the steam-chest ?
If you do, stop it and get a sight-feed cup, which will save
you the labor of slushing the cylinder and save the cylinder and
valve-seats, the piston and follower, and all other places touched
by the grease.
HANDBOOK ON ENGINEERING. 389
Do you feed the boiler until the water is out of sight in the
glass, then shut off the feed, put in a big fire and sit down in
a dark corner with a four-horse brier pipe and smoke, until you
happen to think that maybe- the water is low?
If you do these things you should notify the coroner that some
day his services will be needed, but it is better to cease the prac-
tice mentioned before the coroner comes.
Do you stop leaks about the boiler as fast as they occur, or do
you wait until the places sound like a snake's den before you stir?
If you do, you waste heat, which is the same word as money,
only differently spelled. Every jet of hot water leaking from a
steam boiler is just so much money thrown away, and if it was
your money you would be bankrupt in a short time, in some
boiler rooms.
Do you take a screw wrench and yank away at a bolt or nut
under steam pressure?
If you do, there will come a time, sooner or later, when you
will do so once too often, and either kill yourself or some one else.
Bolts and nuts are liable to strip or break if tampered with under
pressure, and they never tell any one beforehand when they are
going to do it.
Do you attempt to stop pounding in the engine by laying for
the crank-pin as it comes round, and trying to hit the key once in
a while ?
If you do, ask the strap and neck of the connecting-rod how
he likes it, when you don't hit the key and do hit the oil cup?
Do you pack the piston by taking it out of the cylinder, lay-
ing it on the floor, setting out the rings, and then when the piston
will not go into the cylinder, try to batter it in with a four-foot
stick of cord wood?
If you do, you should reform, and pack the piston in the
cylinder where it belongs, being sure to get it central by meas-
uring from the lathe center in the end of the piston rod.
390
HANDBOOK ON ENGINEERING.
Do you put a new turn of packing on top of the old, hard-
burned stuff when the piston rod leaks steam ?
If you do, you will have a scored piston rod and broken gland
bolts some day. Packing under heat and pressure gets so hard
that it cuts like a file when left in the stuffing-box, and as one
begins to leak all the old stuff should be pulled out and new put
in its place.
THE TRAVEL OF A SLIDE VALVE.
Figs. 248 and 249. The throw of the eccentric.
The travel of a slide valve is found as follows : The maximum
port opening at the head end, plus the maximum port opening at
the crank end, plus the lap at the head end, plus the lap at the
crank end. Therefore, If" + If" + f" + f"=4J", the re-
quired travel of valve. Incidentally, it may be well to mention
that the travel of a valve may also be obtained from the eccentric,
by subtracting the thin part of the eccentric from the thick
part as per Fig. 248, or again, by taking twice the distance between
the center of rotation and center of the eccentric. This distance
on the eccentric is the end valve travel, and is termed the c G throw ' '
of the eccentric. In the above question, the travel may also be
HANDBOOK ON ENGINEERING.
391
found by the aid of the diagram, Fig. 249, which is explained as
follows: From the center^., with a radius of £ inch (lap),
describe a circle BCD. From any point in the circumference,
say B, lay off the distance B E equal to the maximum port open-
ing, If" ; from the center A, with a radius A E, describe the
circle E F G; the diameter of the circle E F G is equal to the
travel of the valve, which is 4J". Let the reader try this with
another set of figures, to prove the correctness of the diagram.
LOSS OF HEAT FROM UNCOVERED STEAM PIPES.
The following table shows the loss of heat through naked sfceam
pipes, wrought iron, of standard sizes. The best covering for a
steam pipe is hair felt from one to two inches thick, depending on
the diameter of the pipe, say one inch thick for pipe from 1 to 4
inches in diameter, and two inches or more for larger pipes.
Such covering will save at least 96 per cent. Cheaper coverings
will save from 75 to 90 per cent. The chief value of the table is
as an aid in estimating the saving that can be made by covering
the pipe. The money loss by naked pipe being known, the sav-
ing can be estimated and the cost of the covering will decide its
value as an investment.
TABLE OF MONEY LOSS FROM 100 FEET OF NAKED STEAM PIPE, FOB
ONE YEAR OF 3000 WORKING HOURS. .
•335.
STEAM PRESSURES.
||t|
50
60
70
80
90
100
fc-oo.2
Ibs.
Ibs.
Ibs.
Ibs.
Ibs.
Ibs.
1
$13.15
$13.70
$14.20
$14.66
$15.08
$15.47
H
16.58
17.29
, 17.92
18.49
19.02
19.51
\L
18.98
19.78
20.51
21.17
21.77
22.33
2
23.72
24.73
25.63
26.45
27.21
27.91
2£
28.72
29.94
31.03
32.03
32.94
33.79
3
34.97
36.45
37.78
38.99
40.10
41.14
4
44.93
46.86
48.57
50.13
51.56
52.89
5
55.57
57.92
60.04
61.96
63.73
65.38
6
66.27
69.08
71.60
73.89
76.01
77.96
392 HANDBOOK ON ENGINEERING.
RULES AND PROBLEMS APPERTAINING TO THE STEAM
ENGINE.
To find the H. P. of a simple non-condensing engine : —
Rule* — Multiply the net area of the piston in square inches,
by the mean effective pressure in pounds per square inch, and by
the velocity of the piston in feet per minute, and divide the last
product by 33,000. The quotient will be the gross H. P. Sub-
tract from this from ten to twenty per cent for friction in the
engine itself, and the remainder will be the delivered H. P.
Example* — The area of the piston is 500 sqr. ins. Half the
area of the piston-rod is 5 sqr. ins. The M. E. P. is 50 Ibs.
per sqr. in. The stroke is 3 feet, and the revolutions per minute
125. The friction is 10 per cent. What is the delivered H. P.
of the engine? Ans. 506.25 H. P.
Operation* — 3 ft. X 2 = 6 ft. twice the stroke.
Then, 500 — 5 = 495 sqr0 ins. net area of piston.
And, 125 X 6 = 750 ft. the piston speed per minute.
And, =^562.5.
33,000
Then, 562.5 X -90 = 506.25. The delivered H. P.
For a condensing engine : — Add the vacuum to the M. E. P.
and proceed as above.
The M. E. P. is the average pressure in the cylinder, less the
back pressure.
To find the H. P. of a compound noncondensing engine : —
The usual method of calculating the H. P. of a multiple cyl-
inder engine is to assume that all the work is done in the low
pressure cylinder alone, and that such a M. E. P. is obtained in
that cylinder as will give the same H. P. as is given by the whole
engine.
Rule* — Find the ratio of areas of the high and low pressure
cylinders, — when of the same stroke, as they usually are, — and
HANDBOOK ON ENGINEERING. 393
multiply it by the number of expansions in the high pressure
cylinder, for the total number of expansions in both cylinders.
Find the hyperbolic logarithm corresponding to this result and
add 1 to it, and divide the sum by the total number of expan-
sions. Multiply this result by the absolute steam pressure, and
subtract the back pressure. Subtract again the loss in pressure
between cylinders, and the remainder will be the M. E. P. Then
multiply the net area of the low pressure cylinder by this M. E. P.
and by the piston speed in feet per minute and divide by 33,000.
Deduct the friction in the engine itself and the remainder will be
the delivered H. P.
Example* — Given a tandem compound engine with cylinders
20" and 32" diameter, and 4 feet stroke, making 75 revolutions
per minute, boiler gauge pressure 125 Ibs. per sqr. in., J cut-off
in high pressure cylinder, back pressure 15J Ibs. per sqr. in.,
drop in pressure between cylinders 15 per cent, and friction in
engine 10 per cent. What is the H. P. delivered of this engine?
Ans. 338.4 H. P.
Operation* — Neglecting the areas of the piston rods, we
have : —
20 X 20 X .7854 — 314.16 sqr. ins. area of high pressure
cylinder.
And, 32 X 32 x .7854 = 804,2 sqr. ins. area of low pressure
cylinder.
Then, 804.2 -f- 314.16 =2.56 = the ratio between cylinders.
And, 2.56 X 4 = 10.24 = the total number of expansions.
The hyperbolic logarithm of 10.24 = 2.328. (Seetableonp. 892.)
And, 1 + 2.328 = 3.328.
Then, 3.328 ~ 10.24 = .325.
Also, 125 + 15 = 140 Ibs., the absolute pressure.
And, .325 X 140 =45.5 Ibs., forward pressure.
And, 45.5 — 15.25 = 30.25 Ibs., the M. E. P.
.
394 HANDBOOK ON ENGINEERING.
And, 30.25 X .85^25.7 Ibs. =the M. E. P. less the
44 drop."
Then, 804.2 X25.7X8X75_ p>
33,000
And, 376 X .90 = 338.4 H. P. delivered.
For a compound condensing engine, proceed as above, except
that the condenser pressure, due to impaired vacuum, only should
be subtracted from the forward pressure.
To find the linear expansion of a wrought-iron pipe or bar : —
Rule, — Multiply the length of the pipe or bar in indies by
the increase in temperature, and by the constant number .0007,
and divide the last product by 100.
Example* — Given a 6-inch wrought-iron pipe 75 feet long.
Steam pressure 150 Ibs. by gauge. Temperature of pipe when
put up 60 degs. Fah. What is its linear expansion? Ans.
2 ins. nearly.
Operation* — The diameter of the pipe is immaterial.
Then, 150 Ibs. pressure = 366 degs.
And, 366 — 60 •= 306 degs.
Also, 75 X 12 = 900 inches length of pipe.
Then, ' ^1.9278 inch.
For copper, use the constant number .0009 ; for brass, use
.00107 ; for fire-brick, use .0003, and proceed as above.
To find the proper diameter of steam pipe for an engine : —
The velocity of steam flowing to an engine should not exceed
6,000 feet per minute.
Rule. — Multiply the area of the~piston in square inches by the
piston speed in feet per minute, and divide by 6,000 ; and divide
again by .7854, and extract the square root for the diameter of the
pipe and take the nearest commercial size.
Example* — Given a 20" X 48" Corliss engine making 72 revo-
lutions per minute. What should be the diameter of its steam
pipe? Ans. 6 inches.
HANDBOOK ON ENGINEERING. 395
Operation.— 20 X 20 X .7854 =314.16 sqr. ins.
And, 48" X 2 X 72 =576 ft. the piston speed.
And> 314.16 X 576 =30>15>
6,000
Then, . 1^. = 6.1". Take 6" pipe.
To find the water consumption of a steam engine: —
The most reliable method for determining this, is to make an
evaporation test, that is, to measure the water fed to the boiler in
a given time and delivered to the engine in the form of steam.
But as this method entails considerable trouble and expense, it is
frequently figured from indicator diagrams. This plan, however,
does not insure correct results, because the amount of water ac-
counted for by the indicator is considerably less than it should be
owing to cylinder condensation and leakage, so that it might be
possible that only 80 per cent of the water passing through the
cylinder would be accounted for by the indicator. But the cal-
culation, used in connection with an evaporation test, will reveal
the extent of the losses caused by cylinder condensation and
leakage, by deducting the amount of water found by computation
from the amount of water fed to the boiler while making an
evaporation test.
Rule* 4- Divide the constant number 859,375 by the M. E. P.
of any indicator card, and divide this quotient by the volume of
its total terminal pressure, the result will be the theoretical con-
sumption in pounds of water per horse power per hour.
The constant number 859,375 is found as follows: —
Compute the size of an engine that will give just one horse-
power at one pound M. E. P. per square inch, thus:
Area of piston equals 412.5 sqr. inches.
Stroke equals 4 feet, and revolutions per minute equal 10.
396
HANDBOOK ON ENGINEERING.
Then, the piston speed is (4 x 2 X 10) 80 feet per minute.
A * 412.5X1X80
33,000
To find how much water it would take to run this engine one
hour, allowing 62 1 Ibs. to the cubic foot of water, proceed as
follows : —
Twice the stroke equals 96 inches.
412.5 X 96
Then _nzir_l_l_LI- equals 22.91666 cubic feet for one revo-
1728
lution.
And, 22.91666 X 10 equals 229.1666 cubic feet for 10 revolu-
tions, or for one minute.
Then, 229,1666 X 60 X 62 £ equals 859,375 Ibs. of water used
per hour.
SCALE 40
M. E. P.
37. 6 LBS.
Fig. 250. Finding steam consumption from the diagram.
Fig. 250 is not an actual indicator card, but answers to
illustrate the rule.
A A is the atmospheric line, and from A to A is the whole
stroke.
VV is the vacuum line.
Points (a) and (b ) are equally distant from the vacuum line.
The point (a) is taken at or very near the point of release.
HANDBOOK ON ENGINEERING.
397
Example. — From the indicator card Fig. 250 compute the water
consumption, the M. E. P. being 37.6 Ibs. per square inch, the
scale of spring used in the indicator being 40, the distance from
point (a) to point (6) being 3.03 inches, the stroke AA being
3.45 inches, and the pressure at point (a) being 25 Ibs. per sqr.
inch absolute. Ans. 20.14 Ibs.
Operation*— 859,375 ~ 37.6 = 22,855.7.
Now, the absolute pressure at point (a) is 25 Ibs., and steam
tables give 996 as the volume of steam at this pressure, that is,
steam at this pressure has 996 times the bulk of the water from
which it was generated.
Then, 22,855.7 -f- 996 = 22.94 Ibs. of water. But as the
period of consumption is represented by (&) (a), AA being the
whole stroke, the following correction is required: The distance
from point (a) to point (6) is 3.03 ins. Then, 22.94 X 3.03 =
69.5080. And the whole stroke or length of line AA is 3.45
ins.
Then, 69.5080-^-3.45 =20.14 Ibs. of water per indicated
horse power per hour.
Boiler Feed or Pressure Pumps.
SIZES AND CAPACITIES.
tl
1
I.
CJ
IJ
O
Capacity per minute at
ordinary speed.
!»
¥
5
r
I*
10
12
14
16
18
20
14
i*
I
ft
J*
5
6
7
8
10
12
14
.031
.05
.07
.11
.25
.35
1.02
1.47
2.00
2.61
5.44
11.75
16.00
150 Strokes. 34 gals.
150 " 4iJ£ •'
74 "
104 "
]?* "
42
49
69
85
102
147
200
261
408
588
800
150
150.
150
125
125
125
100
100
100
100
100
100
75
50
50
10
17x.5
18x 5
26x 6
28x7
31 x 8
44x13
45x14
45x14
55x16
55x16
67x19
67x19
67x20
67x20
80x22
110x27
111x29
25
40
60
.90
130
160
200
250
300
400
600
398 HANDBOOK ON ENGINEERING.
CHAPTER XVI.
THE STEAM BOILER.
THE FORCE OF STEAM AND WHERE IT GOMES FROfl.
If water be heated it will expand somewhat, and will finally
burst forth into vapor. The vapor will expand enormously, and
naturally occupy more space than the water from which it is
formed. A cubic inch of water will make a cubic foot of steam ;
that is, the water has been expanded by heat to seventeen hundred
times its original bulk. The steam is very elastic ; the water was
not. When we say that a cubic inch of water will form a cubic
foot of steam, we mean that it will do so when the steam is allowed
to rise naturally from the water without any confinement. If the
steam is confined, as it would be in a boiler, it could not expand,
and consequently would not. If the steam is allowed to rise into the
atmosphere from an open vessel, the pressure of the steam would be
precisely the same as the pressure of the atmosphere, that pressure
being about fifteen pounds to the square inch. An ordinary steam
gauge only takes notice of the pressure above the atmospheric
pressure. When the hand of the steam gauge stands at zero, it
indicates that there is no pressure above the ordinary pressure of
the atmosphere. An ordinary steam gauge not connected with
anything has the atmosphere acting upon it in both directions, the
same as the atmosphere acts upon everything when it can reach
both sides. If the air be pumped out of the steam gauge, the
atmosphere will then act upon one side, and the hand will move
backward until it stands at fifteen points less than zero. In
this condition the steam gauge indicates the absolute zero of
pressure. If now the air be allowed to re-enter where it was
pumped out, it will begin to exert its pressure upon the jsteara
: . ! -
HANDBOOK ON ENGINEERING. 399
gauge, and the hand will move forward ; when the full air
pressure is on, the gauge hand will stand at its usual zero.
To gx> into this matter in order that it may be understood
that the real pressure of steam is always fifteen pounds greater
than ordinary steam gauges indicate. In all of the finer cal-
culations relating to the action of steam, its total pressure must
be known, and this total pressure is to be counted from the
absolute zero. The real pressure of steam is always the steam
gauge pressure, plus fifteen pounds. When a steam gauge shows
fifty pounds, the steam really has a pressure of sixty-five pounds.
The fifteen pounds of this pressure is nullified by the atmospheric
pressure, and the steam gauge shows us our useful pressure. As
before stated, a cubic inch of water will make a cubic foot of
steam at atmospheric pressure ; that is, fifteen pounds to the
square inch, abolute pressure, or zero by the steam gauge. If
this cubic inch of water was made into steam in a boiler holding
just a cubic foot, the steam gauge would show zero. If the boiler
was only large enough to hold half a cubic foot, the steam would
all be in the boiler, and being con lined in half its natural space,
it would have double pressure. It would have an absolute pres-
sure of thirty pounds to the square inch, and the steam gauge
would indicate fifteen pounds. If this steam was then allowed to
pass into a chamber holding a cubic foot, the steam would expand
until it filled the chamber, and its pressure would go down again
to fifteen pounds absolute. In short, the pressure is in reverse
proportion to the amount of space it occupies. The pressure of
steam may be doubled by compressing the steam into
one-half its former volume, and so on. After water is
turned into steam, the steam may be made hotter, but
it is not very much expanded. The pressure of steam
is increased by forcing more steam into the space occupied.
If a boiler contains steam at 50 Ibs. pressure, we may increase
the pressure by adding more steam, and thus compressing all the
400 HANDBOOK ON ENGINEERING.
steam that the boiler contains. In the ordinary operation of a
steam boiler, the fire turns the water into steam and the more
steam there is made and confined, the greater the pressure will
be. If the steam is constantly flowing out of the boiler into an
engine, the pressure in the boiler must be kept up by continually
making new steam to take the place of that drawn off. If we
make steam as fast as it is drawn off, and no faster, the pressure
will remain the same. If we make steam faster than the engine
draws it off, the pressure will rise, and if it is drawn off faster
than we make it, the pressure will go down.
The pressure of the steam is due to its desire to expand into a
larger body, and it acts outwardly in every direction against
everything upon which it presses. If we crowd 600 cu. ft. of
steam in a boiler, which will only hold 100 cu. ft., the steam will
be held compressed into one-sixth its natural bulk, and will thus
have a pressure of 90 Ibs., and the steam gauge will show 75 Ibs.
If a hole 1 in. square be cut in the boiler, and a weight of 75 Ibs.
be laid over the hole, the steam will just lift the weight. If the
atmospheric pressure could be removed from one sq. in. of the
top of the weight, the steam would then be capable of lifting a
90 Ib. weight. The force which this steam will exert to lift a
weight, or any similar thing against which it acts, will equal the
pressure per square inch multiplied by the number of square
inches which the steam acts upon. It will thus be readily under-
stood that if we lead a pipe from the boiler and fit a piston in the
pipe, the steam will tend to force this piston out of the pipe.
THE ENERGY STORED IN STEAM BOILERS.
A steam boiler is not only an apparatus by means of which the
potential energy of chemical affinity is rendered actual and avail-
able, but it is also a storage reservoir, or a magazine, in which a
quantity of such energy is temporarily held ; and this quantity,
HANDBOOK ON ENGINEERING. 401
always enormous, is directly proportional to the weight of water
and of steam which the boiler at the time contains. The energy
of gunpowder is somewhat variable, but a cubic foot of heated
water under a pressure of 60 or 70 Ibs. per square inch, has about
the same energy as one pound of gunpowder ; at a low red heat,
it has about forty times this amount of energy.
The letters B. T. U. are the initial letters of the words British
Thermal Unit, and are used as abbreviations of those words.
The British Thermal Unit is the unit of heat used in this country
and England, and may be said to be the amount of heat required
to raise the temperature of one pound of pure water from 39 to 40
degrees Fahr. It is often necessary to distinguish between
B. T. U. used in this country and the French thermal unit used in
France and most of the countries of Europe. The French ther-
mal unit is called the calorie, and is the heat required to raise the
temperature of one kilogram of water one degree centigrade.
Safety at high pressure depends entirely upon the design,
material, and workmanship, and it is a question that may be re-
garded as settled long since, that a steam boiler properly con-
structed and designed for a working pressure of 150 pounds is as
safe as a properly constructed boiler designed for eighty pounds,
with the chances in favor of the high pressure, for the reason that
less care is taken in selecting boilers for the ordinary pressure, as
anything in the shape of a boiler is regarded, fry careless people,
as good enough for the lower pressures, with which they have
become so familiar as to become almost too careless.
SPECIAL HIGH PRESSURE BOILERS.
The extending use of compound steam engines, which make
necessary the employment of high steam pressures, calls for steam
boilers specially designed to successfully operate under working
pressures ranging from 100 to 160 pounds. These boilers must
be safe and economical and of such construction as to afford
26
402 HANDBOOK ON ENGINEERING.
access for examination and repair, moderate in first cost and
maintenance and of simplest possible form. Fortunately, the
controlling conditions are not difficult to meet, and there are sev-
eral well-tried and approved types Of steam boilers from which to
make a selection, choice being governed by the space at dis-
posal, arrangement of plant, kind of fuel and other circum-
stances.
TYPES OF BOILERS.
Four types that are very succesfully used, and they represent
good practice for high pressure w^>rk, being respectively the Hori-
zontal Tubular, and Vertical Fixe Box Tubular Boilers. The Fire
Box Locomotive Tubular Boiler may safely be added to this list
and gives most excellent results.
THE WATER TUBE BOILER.
Steam boilers must be designed with reference to the pres-
sure of steam to be carried, and when so designed and constructed
are quite as safe at one pressure as another, preference being
given to the type that is simplest in form and the least liable to
destruction, not so much jj reason of the pressure carried as by
failure to provide for the strains of expansion and contraction
within itself.
HORSE POWER OF BOILERS.
In determining the proper size or evaporating capacity of a
boiler to supply steam for a given purpose, it is necessary to con-
sider the number of pounds of dry steam actually required per
hour at the stated pressure. The standard horse power rating
for any steam boiler is 34^ pounds of water evaporated (made into
steam) from feed water at 212°, per hour. The total pounds
steam required for any purpose per hour on this basis divided by
34J will give the standard boiler horse power required. Manu-
HANDBOOK ON ENGINEERING. 403
facturers of steam boilers sometimes rate the horse power of their
boilers by so many square feet of heating surface per horse power ;
8 to 15 sq. ft. of heating surface, they figure, equals one horse
power. This rating does not represent the actual capacity of the
steam boiler, the only safe guide being the evaporative perform-
ance in pounds of steam from water at 212° to steam at 212°.
Some boilers will evaporate this with 8 sq. ft., some requiring
from 15 to 18 sq. ft., hence, the absurdity of rating horse power
of boilers of unlike construction by the square feet of heating
surface. But as the practice is an old one in the case of the
well-known tubular boiler, so deservedly popular and used more
than any other kind, good practice is to allow approximately as
follows: —
Allow for each Horse Power-
Steam for Heating, etc. .... 15 sq. ft. heating surface.
For Plain Throttle Engine, ... 15 " " "
For Simple Corliss Engine ... 12 " " "
For Compound Corliss Condensing . 10 " " "
Hence, a boiler for heating purposes or furnishing steam for —
Plain Slide engine with 1,500 sq. ft. surface, equals . 100 H. P.
For Simple Corliss Engine, same boiler " . 125 H. f.
For Compound Condensing Engine " . . 150 H. P.
The best method is to compare boilers by their evaporative
efficiency and not by heating surface.
The following is an approximate consumption of steam per
indicated horse power per hour for engine : —
Plain Slide Engine . 60 to 70 pounds.
High Speed Automatic Engine . . . . . 30 to 50 . "
Simple Corliss Engine' 25 to 35 "
Compound Corliss Engine . . . . . . 15 to 20 "
Triple Expansion Engine . . . ... . 13 to 17 <;
404 HANDBOOK ON ENGINEERING.
depending upon the horse power, steam pressure, condition of
engine, load, etc.
Each pound of first-class steam coal consumed under a well-
proportioned steam boiler, well managed, should evaporate 10
pounds of water at 212° into dry steam at 212°. The average
boiler throughout the country, with ordinary fuel and manage-
ment, ranges from 5 to 8 pounds steam per pound of coal, and it
would scarcely be safe to make fuel guarantees per horse power
of engine without a counter guarantee on the part of the pur-
chaser, when his old boiler is used, that the fuel economy is based
on an evaporative efficiency of a given weight of water evaporated
per pound of coal per hour in his boiler. The usual practice is
to ignore the boiler altogether and guarantee pounds of steam
per indicated horse power per hour used by the engine. This
affords an exact method and is not hampered by unknown con-
ditions, and places all tests on an equal or comparative basis.
THE RATING OF BOILERS.
It is considered usually advisable to assume a set of practically
attainable conditions in average good practice, and to take the
power so obtainable as the measure of the power of the boiler in
commercial and engineering transactions. The unit generally
assumed has been usually the weight of steam demanded per horse
power per hour by a fairly good steam engine. In the time of
Watt, one cubic foot of water per hour was thought fair ; at the
middle of the last century, ten pounds of coal was a usual
figure, and five pounds, commonly equivalent to about 40 Ibs. of
feed water evaporated, was allowed the best engines. After the
introduction of the modern forms of engine, this last figure was
reduced 25 per cent, and the most recent improvements have still
further lessened the consumption of fuel and of steam. By general
consent the unit has now become thirty pounds of dry steam per
HANDBOOK ON ENGINEERING. 405
horse power per hour, which represents the performance of non-
condensing engines. Large engines, with condensers and com-
pound cylinders, will do still better. A committee of the
American Society of Mechanical Engineers recommended thirty
pounds as the unit of boiler power, and this is now generally
accepted. They advised that the commercial horse-power be
taken as an evaporation of 30 Ibs. of water per hour from a feed
water temperature of 100° Fahr. into steam at 70 Ibs. gauge pres-
sure, which may be considered equal to 34 £ Ibs. of water evapo-
ration, that is, 34 J Ibs. of water evaporated from a feed water
temperature of 212° Fahr. into steam at the same temperature.
This standard is equal to 33,305 British thermal units per hour.
A boiler rated at any stated power should be capable of
developing that power with easy firing, moderate draught and
ordinary fuel, while exhibiting good economy, and at least
one-third more than its rated power to meet emergencies.
WORKING CAPACITY OF BOILERS.
The capacity or horse-power of a boiler, as rated for purposes
of the trade, is commonly based upon the extent of heating
surface which it contains. The ordinary rating was for a long
time 15 sq. ft. of surface per horse-power. At the present time
most of the stationary boilers are sold on the basis of from 10 to
12 sq. ft. per horse-power, the power referred to being the unit
of 30 Ibs. evaporation per .hour. This method of rating is arbi-
trary, inasmuch as it is independent of any condition pertaining
to the practical work of the boiler. The fact that 10 or 12 sq.
ft. of surface is sold for one horse-power is no guarantee that this
extent of surface will have a capacity of one horse-power when
the boiler is installed and set to work. The boiler in service
and the boiler in the shop are two entirely different things, and
where one passes to the other, the trade rating disappears. New
406 HANDBOOK ON ENGINEERING.
conditions, such as draft, grate surface, kind of fuel and man-
agement, then take effect, and these have a controlling influence
upon the working capacity. The working power may be found
to be much less than the arbitrary rate, or it may be a much
larger quantity ; all depending upon the surrounding conditions,
attention is had to this subject, because it is important in some
cases to have a clearer understanding as to what is the working
capacity of a boiler. Suppose a boiler manufacturer enters into
an agreement to install a boiler, which will have a capacity of 100
horse-power. Suppose that on account of poor draft, low grade
of fuel, or unfavorable surroundings, all of which are known
beforehand, the boiler develops the power named only with the
most careful handling. Is the working capacity, under the cir-
i cumstances, 100 horse-power? Assuredly not, for the purchaser
could not depend upon it in ordinary running for that amount of
power. Yet the builder may claim that he has fulfilled his
contract.
The former boiler test committee of the American Society of
Mechanical Engineers established a working rate for boiler capac-
ity which meets such cases in a definite and satisfactory manner.
They realized that for the purpose of good work, a boiler should
be capable of developing its capacity with a moderate draft and
easy firing; and that it should be capable of doing one-third more
in cases of emergency. In other words, a boiler which is sold
for 100 horse-power should develop 133^ horse-power under con-
ditions giving a maximum capacity. .In the instance cited above,
the boiler should have been capable of giving 100 horse-power
with such ease that there would be a reserve of 33| horse-power
available when urged to this extra power. According to this
rule, the capacity of a boiler in a working plant would be found
by determining how much water it can evaporate under conditions
which will give its maximum capacity ; that is, with w^de open
damper, with the maximum draft available arid with the best con-
HANDBOOK ON ENGINEERING. 407
ditions as to the handling of the fire, and in this way ascertain
the maximum power available under these circumstances. Hav-
ing found this maximum quantity, the working capacity or the
rated power would be determined by deducting from the maxi-
mum 25 per cent. This rule, it will be seen, does not take into
account the extent of the heating surface or the trade rating, but
it deals solely with the capabilities of the boiler under the con-
ditions which pertain to its work.
CODE OF RULES FOR BOILER TESTS.
Starting and stopping a test* — A test should last at least
ten hours of continuous running, and twenty-four hours whenever
practicable. The conditions of the boiler and furnace in all
respects should be, as nearly as possible, the same at the end
as at the beginning of the test. The steam pressure should be
the same ; the water level the same ; the fire upon the grates
should be the same in quantity and condition ; and the walls, flues,
etc., should be of the same temperature. To secure as near an
approximation to exact conformity as possible in conditions of
the fire and in the temperature of the walls and flues, the follow-
ing method of starting and stopping a test should be adopted : —
Standard method* — Steam being raised to the working pres-
sure, remove rapidly all the fire from the grate, close the damper,
clean the ash-pit, and, as quickly as possible, start a new fire with
weighed wood and coal, noting the time of starting the test and
the height of the water level while the water is in a quiescent
state, just before lighting the fire. At the end of the test, re-
move the whole fire, clean the grates and ash-pit, and note the
water-level when the water is in a quiescent state ; record the time
of hauling the fire as the end of the test. The water-level should
be as nearly as possible the same as at the beginning of the test.
If it is not the same, a correction should be made by computa-
408 HANDBOOK ON ENGINEERING.
tion, and not by operating pump after test is completed. It will
generally be necessary to regulate the discharge of steam from the
boiler tested by means of the stop-valve for a time while fires are
being hauled at the beginning and at the end of the test, in order
to keep the steam pressure in the boiler at those times up to the
average during the test.
Alternate method* — Instead of the standard method above
described, the following may be employed where local conditions
render it necessary : At the regular time for slicing and cleaning
fires have them burned rather low, as is usual before cleaning,
and then thoroughly cleaned ; note the amount of coal left on the
grate as nearly as it can be estimated ; note the pressure of steam
and the height of the water-level — which should be at the medium
height to be carried throughout the test — at the same time ; and
note this time as the time for starting the test. Fresh coal which
has been weighed, should now be fired. The ash-pits should be
thoroughly cleaned at once before starting. Before the end of the
test the fires should be burned low, just as before the start, and
the fires cleaned in such a manner as to leave the same amount
of fire, and in the same condition, on the grates as on the start.
The water-level and steam pressure should be brought to the same
point as at the start, and the time of the ending of the test should
be noted just before fresh coal is fired.
DURING THE TEST.
Keep the conditions uniform, — The boiler should be run con-
tinuously without stopping for meal times, or for rise or fall of
pressure of steam due to change of demand for steam. The
draught being adjusted to the rate of evaporation or combustion
desired before the test is begun, it should be retained constant
during the test by means of the damper. If the boiler is not con-
nected to the same steam pipe with other boilers, an extra outlet
HANDBOOK ON ENGINEERING. 409
for steam with valve in same should be provided, so that in case
the pressure should rise to that at which the safety valve is set, it
may be reduced to the desired point by opening the extra outlet,
without checking the fire. If the boiler is connected to a main
steam pipe with other boilers, the safety valve on the boiler being
tested should be set a few pounds higher than those of the other
boilers, so that in case of a rise in the pressure the other boilers
may blow off, and the pressure be reduced by closing their dam-
pers, allowing the damper of the boiler being tested to remain
open, and firing as usual. All the conditions should be kept ai
nearly uniform as possible, such as force of draught, pressure of
steam and height of water. The time of cleaning the fires will
depend upon the character of the fuel, the rapidity of combustion
and the kind of grates. When very good coal is used and the
combustion not too rapid, a ten-hour test may be run without any
cleaning of the grates, other than just before the beginning and
just before the end of the test. But in case the grates have to be
cleaned during the test, the intervals between one cleaning and
another should be uniform.
Keeping the records* — The coal should be weighed and
delivered to the firemen in equal portions, each sufficient for about
one hour's run, and a fresh portion should not be delivered until
the previous one has all been fired. The time required to con-
sume each portion should be noted , the time being recorded at the
instant of firing the first of each new portion. It is desirable that
at the same time the amount of water fed into the boiler should
be accurately noted and recorded, including the height of the
water in the boiler, and the average pressure of steam and tem-
perature of feed during the time. By thus recording the
amount of water evaporated by successive portions of coal, the
record of the test may be divided into several divisions, if desired
at the end of the test, to discover the degree of uniformity of com-
bustion, evaporation and economy at different stages of the test.
410 HANDBOOK ON ENGINEERING.
.
PRIMING TESTS.
In alt tests in which accuracy of results is important, calori-
meter tests should be made of the percentage of moisture in the
steam, or of the degree of superheating. At least ten such
tests should be made during the trial of the boiler, or so many as
to reduce the probable average error to less than one per cent,
and the final records of the boiler tests corrected according to the
average results of the calorimeter tests. On account of the
difficulty of securing accuracy in these tests, the greatest care
should be taken in the measurements of weights and temperatures.
The thermometers should be accurate to within a tenth of one
degree, and the scales on which the water is weighed to within
one-hundredth of a pound.
ANALYSES OF GASES.
•
Measurement of air supply, etc* — In tests for purposes of
scientific research, in which the determination of all the variables
entering into the test is desired, certain observations should be
made which are in general not necessary in tests for commercial
purposes. These are the measurements of the air supply, the
determination of its contained moisture, the measurement and
analysis of the flue gases, the determination of the amount of heat
lost by radiation, of the amount of infiltration of air through the
setting, the direct determination by calorimeter experiments of
the absolute heating value of the fuel, and (by condensation of
all the steam made by the boiler) of the total heat imparted to
the water.
The analysis of the flue gases is an especially valuable
method of determining the relative value of different methods of
firing, or of different kinds of furnaces. In making these
analyses, great care should be taken to procure average samples
HANDBOOK ON ENGINEERING.
411-
since the composition is apt to vary at different points of the flue,
and the analyses should be intrusted only to a thoroughly com-
petent chemist, who is provided with complete and accurate
apparatus. As the determination of the other variables men-
tioned above are not likely to be undertaken except by engineers
of high scientific attainments, and as apparatus for making them
is likely to be improved in the course of scientific research, it is
not deemed advisable to include in this code any specific direc-
tions for making them.
RECORD OF THE TEST.
A " log " of the test should be kept on properly prepared
blanks, containing headings as follows : —
PRESSURES.
TEMPERATURES.
FUEL.
FEED WATER.
8c
«
.
£
bJD
oj
id
ed
2
<u
p
bJD
cS
P
o
TIME.
Barome
1
1
W)
<M
Externa
Boiler r
.
V
P
E
Feed w£
Steam.
i
S
Pounds
1
H
b
' 0
s
REPORTING THE TRIAL.
The final results should be recorded upon a properly prepared
blank, and should include as many of the following items as are
adapted for the specific -object for which the trial is made. The
items marked with a * may be omitted for ordinary trials, but are
desirable for comparison with similar data from other sources.
412 HANDBOOK ON ENGINEERING.
Resources of the trials of a
Boiler at
To determine
1. Date of trial . . .
2. Duration of trial .
DIMENSIONS AND PROPORTIONS.
3. Grate-surface wide long area
4. Water-heating surface
5. Superheating surface
6. Ratio of water-heating surface to gr^te-
surface
AVERAGE PRESSURES.
7. Steam pressure in boiler, by gauge . . Ibs.
*8. Absolute steam pressure Ibs.
*9. Atmospheric pressure, per barometer . in.
10. Force of draught in inches of water . in.
AVERAGE TEMPERATURES.
*11. Of external air deg.
*15. Of fire-room deg.
*13. Of steam deg.
14. Of escaping gases deg.
15. Of feed-water deg.
FUEL.
16. Total amount of coal consumed . . . Ibs.
17. Moisture in coal per cent.
18. Dry coal consumed Ibs.
19. Total refuse, dry pounds equals . . . per cent.
20. Total combustible (dry weight of coal,
item 18, less refuse, item 19) . . . Ibs.
*21. Dry coal consumed per hour . . . Ibs.
*22. Combustible consumed per hour . . . Ibs.
HANDBOOK ON ENGINEERING. 413
RESULTS OF CALORIMETRIC TESTS.
23. Quality of steam, dry steam being taken
as unity
24. Percentage of moisture in steam . . 0 per cent.
25. Number of degrees superheated ... deg.
WATER.
26. Total weight of water pumped into boiler
and apparently evaporated .... Ibs.
27. Water actually evaporated, corrected for
quality of steam Ibs.
28. P^quivalent water evaporated into dry
steam from and at 212° F Ibs.
*29. Equivalent total heat derived from fuel
in B. T. U B. T. U.
*30. Equivalent water evaporated in dry
steam from 212° F. per hour . . . Ibs.
ECONOMIC EVAPORATION.
31. Water actually evaporated per pound of
dry coal, from actual pressure and
temperature . • Ibs.
32. Equivalent water evaporated per pound
of dry coal, from 212° F Ibs.
33. Equivalent water evaporated per pound
of combustible from and at 212° F. . Ibs.
COMMERCIAL EVAPORATION.
34. Equivalent water evaporated per pound
of dry coal with one-sixth refuse, at 70
Ibs. gauge pressure, from temperature of
100° F., equals item tests 33 X. 0.7249
pounds Ibs.
f Corrected for inequality of water level and of steam pressure at
beginning and end of test.
414
HANDBOOK ON ENGINEERING.
* KATE OF COMBUSTION.
35. Dry coal actually burned per sq. foot of
grate-surface per hour . . . .
Per sq. ft. of grate
Consumption of dry surface
coal per hour. Coal
assumed with one-
sixth refuse.
*36.
*37.
*38.
Per sq. ft. of water
heating surface .
Per sq. foot of least
area for draught.
RATE OF EVAPORATION.
39. Water evaporated from and at 212° F. per
square foot of heading surface per hour.
Per sq. ft. of grate
Water evaporated per
hour from temperature
of 100° F. into steam
of 70 Ibs. gauge pres-
sure.
*40.
*41.
*42.
surface .
Per sq. ft. of heat-
ing surface .
Per sq. ft. of least
area for draught.
COMMERCIAL HORSE POWER.
43. On basis of 30 Ibs. of water per hour
evaporated from temperature of 100° F.
into steam of 70 Ibs. gauge pressure
(34£ Ibs. from and at 212°) ...
44. Horse-power, builders' rating at
sq. ft. per horse-power . . . , .
45. Per cent developed above or below rating
IDS.
ibs.
Ibs.
Ibs.
Ibs.
Ibs.
H. P.
per cent.
* NOTE. Items 20, 22, 33, 34, 36, 37, 38 are of little practical value.
For if the result proves to be less satisfactory than expected on the
actual coal, it is easy for an expert fireman to decrease No. 20 by simply
taking out some partly consumed coal in cleaning fires, and thus make a
fine showing on that simply ideal or theoretical unit, the u pound com-
bustible." The question at issue is always what can be done with an
actual coal, not the " assumed coal " of items 34, 36, 37 and 38.
HANDBOOK ON ENGINEERING. 415
DEFINITIONS AS APPLIED TO BOILERS AND BOILER
flATERIALS.
Cohesion is that quality of the particles of a, body which causes
them to adhere to each other, and to resist being torn apart.
Curvilinear seams* — The curvilinear seams of a boiler are
those around the circumference.
Elasticity is that quality which enables a body to return to its
original form after having been distorted, or stretched by jsome
external force.
Internal radius* — The internal radius is one-half of the diam-
eter, less the thickness of the iron. To find the internal radius
of a boiler, take one-half of the external diameter and substract
the thickness of the iron.
Limit of elasticity* — The extent to which any material may be
stretched without receiving a permanent " set."
Longitudinal seams* — The seams which are parallel to the
length of a boiler are called the longitudinal seams.
Strength is the resistance which a body opposes to a disinte-
gration or separation of its parts.
Tensile strength is the absolute resistance which a body makes
to being torn apart by two forces acting in opposite direc-
tions.
Crushing strength is the resistance which a body opposes to
being battered or flattened down by any weight placed upon it.
Transverse strength is the resistance to bending or flexure, as
it is called.
Torsional strength is the resistance which a body offers to
any external force which attempts to twist it round.
Detrusive strength is the resistance which a body offers to
being clipped or shorn into two parts by such instruments as
shears or scissors.
Resilience or toughness is another form of the quality of
416 HANDBOOK ON ENGINEERING.
strength ; it indicates that a body will manifest a certain degree
of flexibility before it can be broken ; hence, that body which
bends or yields most at the time of fracture is the toughest.
"Working strength* — The term " working strength " implies
a certain reduction made in the estimate of the strength of ma-
terials, so that when the instrument or machine is put to use, it
may be capable of resisting a greater strain than it is expected on
the average to sustain.
Safe working pressure, or safe load* — The safe working pres-
sure of steam-boilers is generally taken as £ of the bursting pres-
sure, whatever that may be.
Strain in the direction of the grain, means strain in the direc-
tion in which the iron has been rolled ; and in the process of man-
ufacturing boiler-plates, the direction in which the fibres of the
iron are stretched as it passes between the rolls.
Stress* — By the term " stress " is meant the force which acts
directly upon the particles of any material to separate them.
HEAT AND STEAM.
The steam engine is a machine for the conversion of heat into
power in motion. The heat is generated by the combustion of
fuel ; the transmission is accomplished through the agency of
steam ; the power is made available and brought under control by
means of the engine.
The effect of heat upon water is to vaporize it, if there be inten-
sity enough, the heat will, under proper conditions, cause water to
boil ; the vapor produced by boiling is called steam, and steam
under pressure is a product which is the end and aim of that por-
tion of that steam engine known as the boiler and furnace. The
steam engine then is to be considered as a form of the heat
engine ; of which the furnace, boiler, and the engine itself are to
be regarded as separate portions of the same mechanism.
HANDBOOK ON ENGINEERING. 417
The conditions demanded .upon economic grounds to secure
the highest efficiency in the steam engine are : —
1. A proper construction of the furnace so as to secure the
perfect combustion of fuel.
2. The heat generated in the furnace must be transferred to the
water in the boiler without loss.
3. The circulation in the boiler must be so complete that the
heat from the furnace may be quickly and thoroughly diffused
throughout the whole body of water.
4. The construction of an engine that will use the steam with-
out loss of heat, except so much as may be necessary to perform
work required of the engine.
5. The recovery of heat from exhaust steam.
6. The absence of friction and back pressure in the working of
the engine.
It is superfluous to say that these conditions are not fulfilled
in any engine of the present day. At best the combustion of
fuel is only approximately perfect, the losses being due to several
causes, among which are, - unburned fuel falling through the
spaces in the grates and mingling with the ashes. This, with
.some kinds of coal, and improper firing, amounts to a large
> Tcentage of the furnace waste. It is not possible with any
present method of setting boilers to transfer all the heat of the
furnace to the water in the boiler ; nor can there be, for the
reason that the temperature of the escaping gases must not be
lower than that of the steam in the boilers, or direct loss will result
in the radiation of heat from the tubes or flues in the boiler, by
MIS reheating the gases to the steam temperature. If the steam
pressure is 80 Ibs. per square inch above the atmosphere, the cor-
responding temperature due to this pressure is 324° Fahr. The
temperature of the escaping gases ought not, therefore, to be less
than 350° Fahr., where they leave the boiler flues or tubes to pass
off into the chimney. If the temperature of the furnace be taken
27
HANDBOOK ON ENGINEERING.
.
at 2,000° Fahr., and the escaping gases at 400° Fahr., it will be
seen that one-fifth of the heat generated in the furnace is passing
off without performing work. This is a very great loss, and
these figures understate, rather than correctly give, the loss from
this one source. Efforts have been made to utilize the tempera-
ture of these waste gases by making them heat feed -water by
means of coils, or by that particular disposition of pipes and
connection known as an economizer. Others have turned it into
account by making it heat the air supplied the fuel on the grates.
Any heat so reclaimed is money saved, provided it does not cost
more to get it than it is worth in coal to generate a similar quan-
tity of heat. It is doubtful whether the loss in this particular
direction can be brought below 20 per cent of the fuel burned, at
least, by any method of saving now known.
The loss by bad firing and by a bad construction of furnace
is often a large one. It has been demonstrated experimentally
that 20 to 30 per cent of fuel can be saved by a proper construc-
tion and operation of the furnace. The direct causes of loss are,
too low temperature of furnace for properly burning fuels, espe-
cially such as are rich in hydro-carbon gases ; or, by the admis-
sion of too much cold air over or back of the fire ; or, by the
admission of too little air under the fire so that carbonic oxide gas
is generated instead of carbonic acid gas, the former being a
product of incomplete, the latter the product of complete
combustion. The relative heating powers of fuel burned, resulting
in the production of either of these two gases being as follows : -
Heat Units.
1 pound of carbon burned to carbonic acid gas . . 14,500
1 pound of carbon burned to carbonic oxide . . . 4,500
Units of heat lost by burning to carbonic oxide . ^10,000
It will be seen that here is an enormous source of loss, and all
that is required to prevent it is a proper construction of furnace.
HANDBOOK ON ENGINEERING. 419
Smoke is a nuisance which ought to be prohibited by stringent
legislation. There is no good reason for its polluting presence in
the atmosphere, defiling everything with which it comes in con-
tact. Smoke regarded as a source of direct loss is greatly over-
estimated ; the fact is, the actual amount of coal lost to produce
smoke is very trifling. The presence of smoke indicates a low
temperature of furnace or combustion chamber ; if the temper-
ature were sufficiently high and the furnace properly constructed,
smoke could not be generated. The prevention of smoke is
easily accomplished, and with it a more economical combustion
of hydro-carbon fuels.
Radiation* — A considerable loss of heat occurs by radiation
from the furnace walls ; this may be prevented in part by making
the walls hollow, with an air space between. If a force blast is
used the air may be admitted at the back end of the boiler setting
and by passing through between the walls will become heated,
and if conveyed into the ash pit at a high temperature will greatly
assist combustion and thus tend to a higher economy.
Air required* — In regard to the quantity of air required, it
will vary somewhat with the fuel used, but in general, 12 pounds
of air are sufficient to completely burn one pound of coal ; prac-
tically, however, 15 to 25 pounds are furnished, being largely in
excess of that which the fire can use, and must pass off with the
gases as a waste product. This surplus air enters cold and
leaves the furnace heated to the same temperature as that of the
legitimate and proper products of combustion, and thus directly
operates to the lowering of the furnace temperature.
Measurement of heat* — A heat unit is that quantity of heat
necessary to raise the temperature of one pound of water one
degree, from 39° to 40° Fahr., this being the temperature of the
greatest density of water. A thermal unit, a heat unit, or unit
of heat, all mean the same thing. Experiments have been made
to determine the mechanical equivalent of a heat unit, and it is
420 HANDBOOK ON ENGINEERING.
found to be equal to 778 pounds raised one foot high. This is
sometimes called "Joule's equivalent," after Dr. Joule, of
England ; it is also known as the dynamic value of a heat unit.
Knowing" the number of heat units in a pound of coal enables
us to calculate the amount of work it should perform. Let us
suppose a pound of coal to be burned to carbonic acid gas,
and to develop during its combustion 14,000 heat units, then:
14,000x778 equals 10,892,000 foot pounds.
That is to say, if one pound of coal were burned under the
above conditions it would have a capacity for doing work repre-
sented by the lifting of ten millions of pounds one foot high
against the action of gravity. Suppose this to be done in one
hour, then we should expect to get from one pound of coal an
equivalent of 5.45 H. P. It is well known that only a very
small fraction of such equivalent is secured in the very best
modern practice. The question is, where does this heat go,
and why is it so small a portion of it is actually utilized ? The
losses may be accounted for in several ways, and, perhaps, as
follows : —
The heat wasted in the chimney .... 25 per cent.
Through bad firing 10 "
Heat accounted for by the engine (not indicated) 10 "
Heat by exhaust steam 55 "
100 per cent.
This is about 2 pounds of coal per hour per indicated horse
power, which is regarded as a very high attainment, and is
seldom reached in ordinary cut-off engines. It requires good
coal, good firing, and an economical engine to get an indicated
horse power from two pounds of coal burned per hour. As
coal varies in quality it is a better plan to deduct the ashes
and other incombustible matter, and take the net combustible
as a basis of comparison. The best coal when properly burned
HANDBOOK ON ENGINEERING. 421
is capable of evaporating 12 pounds of water from and at a
temperature of 212° Fahr. The common evaporation is about
half that amount, and with the best improved furnaces and care-
ful management, it is seldom that 10 pounds of water is exceeded,
and is to be regarded as a high rate of evaporation. In experi-
mental tests, 12 pounds have been reported, but it is doubtful
whether there is any steam boiler and furnace which is con-
stantly yielding any such results.
Circulation of water in a boiler is a very important feature to
secure the highest evaporative results. Other things being equal,
the boiler which affords the best circulation of water will be found
to be the most economical in service. Circulation is greatly hin-
dered in some boilers by having too many tubes ; in others, by
introducing in the water space of the boiler too many stays and
making the water spaces too narrow. To secure the highest
economy there must be thorough circulation from below upwards,
in the boiler. There is no doubt that a great deal of heat is lost
because the construction is such as to hinder a free flow of water
around the tubes and sides of the boiler.
The construction of an engine that will use steam without loss
of heat, except so much as may be necessary to perform work
required of it, is a physical impossibility. Among the sources of
loss in an engine are : radiation, condensation of steam in un-
jacketed cylinders, and the enormous loss of heat occasioned by
exhausting the steam into the atmosphere.
Radiation is usually classed among the minor losses in a steam
engine. There is a considerable loss of heat caused by radiation
from steam boilers and pipes exposed to the atmosphere, and not
protected by a suitable covering. Much of this heat may be
saved by employing a non-conducting material as a covering,
which, though not preventing all radiation, will save enough heat
to make its application economical. It is well known that some
bodies conduct and radiate heat less rapidly than others, but it
422 HANDBOOK ON ENGINEERING.
must not be understood that the absolute value of such a cover-
ing is inversely proportioned to the conducting power of the
material employed, because, in its application, the outer surface
is enlarged and the radiation will be going on less actively at any
given point, but the enlarged surface exposed reduces somewhat
the apparent gain.
SELECTION OF A BOILER.
The selection of a boiler for a particular service will naturally
suggest the following questions : —
1 . What kind of a boiler shall it be ?
2. Of what material shall it be made?
3. What size shall it be in order to furnish a certain power?
In reply to the first question, it is to be expected there will be
wide differences of opinion, varying with the locality, usage, and
service for which it is intended. One of the first things to be
taken into account in the selection of a boiler is the quality of
water to be used in it for generating steam. If the water is pure,
then it makes little difference what kind of boiler be selected, so
far as incrustation affects selection. If the water is hard and
will deposit scale upon evaporation, then a boiler should be
selected which will admit of thorough inspection and removal of
any deposit formed within it.
For hard water, the ordinary flue boiler will be found a good
one, as it is favorable to a thorough circulation of water, and
permits easy access to all parts of it for examination and clean-
ing. It does not, however, present the extent of heating surface
for a given space that tubular boilers offer ; but with hard water
the boiler is quite as economical if kept in good condition.
The difficulty with tubular boilers when used in connection
with hard water is that the tubes will in a short time become
coated with scale ; this prevents the transmission of heat, not
only, but impairs the circulation of the water around them.
HANDBOOK ON ENGINEERING. 423
Both of these are opposed to economy in the fact that it requires
more coal to generate a given weight of steam in the first case ;
and second, by reason of deficient circulation the plates over the
fire are likely to become overheated and burnt and so become
dangerous ; thus directly contributing to accident or disaster.
The matter of circulation in boilers is one which should have
careful attention in making a selection. There is little trouble in
this regard with any of the ordinary types of boilers so long as
they are clean and new, and properly proportioned. Nor is there
likely to be any difficulty thereafter if the water is soft and clean.
Circulation is often seriously impaired by putting in too many
tubes in a boiler, the effect of which is to so fill up the space that
the heated particles of water forcing their way upwards from
below meet with so much resistance that they can hardly over-
come it, and the result is that a boiler does not furnish from one-
fourth to one-half as much steam for a given weight of fuel as it
should, from this very cause.
Boilers intended for use in distant localities where the facilities
for repairs are meager or entirely wanting, and fuel low priced,
should be of the simplest description. Cylinder boilers or two-
flue boilers will perhaps be found most suitable. These are
largely used by coal miners, blast furnaces, saw mills, and other
branches of industry, which must, of necessity, be removed from
the larger towns and engineering work shops.
In selecting a boiler for a mill of any kind where they burn
shavings or offal, or any other place in which the fuel is of
a similar description and the firing irregular, there should be
large water capacity in the boiler that it may act as a reser-
voir of power in much the same way that a fly wheel acts as
a regulator for a steam engine. It is a common notion among
wood workers that firing with shavings or light fuel is " easy
on the boiler." There is abundant reason to doubt this.
The suddenness and rapidity with which an intense fire is kin-
424 HANDBOOK ON ENGINEERING.
died in the furnace, filling all the furnace space and the tubes with
flame, and with an intense heat which envelops all within the limits
of draft opening, continuing thus for a few minutes only, and as
suddenly going out, can hardly be regarded as the ideal furnace.
Yet there are thousands of just such furnaces at work, and it is
altogether probable that little or no change will be made in them
by this class of manufacturers, at least in the near future. In
regard to the selection of a boiler for this service, we are brought
back again to the question of hard or soft water. The decision
should be largely influenced by this, but whatever type of a boiler
is selected there should be a surplus of boiler power of at least 20
per cent, that is, if a 50 horse-power boiler is needed to do the
Work, put in one of 60 horse-power ; this will prevent the fluctua-
tions of speed in the engine which are sure to follow a reduction of
boiler pressure.
This increase in boiler power ought not to be simply that of
tube surface, but should also include extra water space. The
reserve power of a boiler is in the water heated up to a temperature
corresponding to the steam pressure ; when this pressure is
lowered, the water then gives off steam corresponding to the lower
pressure ; the more water the more steam ; and in this way the
water in the boiler stores up heat when overtired , to give it off
again when the fire is low, and so acts a regulator of pressure, a
thing that extra tube surface cannot do. This kind of firing is
apt to induce priming, and for this reason a boiler should be
selected having a large water surface. Horizontal boilers are, in
general, to be preferred over vertical ones for mills, because of the
larger water surface exposed in proportion to the heating surface.
If a tubular boiler is selected, the water line above the tubes
should be not higher than two-thirds the diameter of the boiler
measured from the bottom, and the boiler should be made having
the upper edge of the top row of tubes at least three inches below
this ; there should also be a clear space up through the center of
HANDBOOK ON ENGINEERING.
the boiler of sufficient width to insure a perfect circulation of
water.
Horizontal tubular boilers are to be recommended when pure
soft water is used. They combine at once the qualities of great
strength without excessive bracing, large heating surface, high
evaporative capacity without liability to priming, and are conve-
nient of access for external and internal examination when set in
the furnace.
Firebox boilers, or locomotive boilers, as they are commonly
called, are best adapted for small powers and with a fuel which
deposits but little soot in the tubes. This kind of boiler is sup-
plied with portable or agricultural engines and is very well adapted
for that particular service. In canvassing the desirability of
this kind of a boiler for stationary use, we must again refer to the
kind of water to be used in it. If the water is soft and clean
there is then no particular objection to a boiler of this construc-
tion being used for small powers ; if the water is hard and will
form scale, it ought not to be chosen, but a flue boiler selected
instead.
Vertical boilers are used in great numbers for small engines,
heating, etc. They have the merit of being compact and low
priced. A common defect in the construction of this kind of
boiler is that too many tubes are put in the head in the fire box,
thereby preventing a proper circulation of water between them.
This defect in construction induces priming, with all its attendant
annoyances and dangers. This style of boiler is not suited to
hard water, but pure soft water only. These boilers should be
provided with hand holes above the crown sheet and around the
bottom of the water legs ; at least three at each place mentioned.
In regard to the material of which a boiler shall be made there is
but the simple choice between iron and steel.
Steel for boilers should not be of too high tensile strength ;
55,000 to 60,000 pounds tensile strength per square inch makes
426 HANDBOOK ON ENGINEERING.
the best boilers. If the steel is of too high a grade it will take a
temper, and, therefore, is utterly unfit for use in steam boilers ;
if the steel is of too low tensile strength it is apt to be loose or
spongy. Among the advantages steel possesses over iron may be
mentioned the circumstance that it is a practically homogeneous
material when properly made and rolled, consequently, it is nearly
as strong in one direction as it is in another. In this respect,
steel is superior to iron plate of equal thickness, because the latter
is made up of several pieces of iron welded together and in rolling
into the plate it becomes fibrous, and thus of unequal strength,
being greatest in the direction of the fiber, and least, when tested
across it.
BOILER TRIMMINGS.
HANDBOOK ON ENGINEERING. 427
lever and weight, or whether it be fitted with a spring. The
former is the usual manner of loading a safety valve and has but
few objections. For portable engines and locomotives safety
valves are loaded with springs, which by suitable adjustment may
be made to blow off at any desired pressure.
The following rule is that enforced by the U. S. Government
in fixing the area of safety valves for ocean and river service, when
the ordinary lever and weight safety valve is employed : —
Rule* — When the common safety valve is employed it shall
have an area of not less than one square inch for each two square
feet of grate surface.
Another rule is to multiply the pounds of coal burned per
hour by 4 ; this product is to be divided by the steam pressure,
to which a constant number 10 is added.
EXAMPLE : What would be the proper area for a safety valve
for a boiler having a grate surface 5 feet square and burning 12
pounds of coal per hour per square foot of grate ; the steam
pressure being 75 pounds per square inch ?
5x5 equal 25 square feet of grate.
25 x 12 equal 300 Ibs. of coal per hour.
300x4 equal 1200.
75 plus 10 equal 85 equal steam pressure with 10 added, then
1200 ~- 85 equal 14.11 inches area, or 4J inches diameter.
A feed pipe should be at least twice the area over that which is
regarded as simply necessary to supply the boiler with water, as
sediment or scale is likely to form in it, which will materially re-
duce its area. In localities where the water is hard the feed
pipes should be disconnected near the boiler and examined occa-
sionally to ascertain whether or not scale is forming in them.
In general, the sizes of feed pipes leading from the pump
to the boiler are fixed by the size of tap used by the maker of
the pump. It is not well to reduce the diameter of the pipe and
the size should be the same throughout. Care should be
428 HANDBOOK ON ENGINEERING.
cised in putting pipes in place that no strain be brought upon them
by imperfect fitting, as it is certain to lead to leaky joints at some
time or other. It is also desirable that the pipes be as short and
straight as possible. Feed pipes should never be placed under
ground if it is possible to make any different disposition of them.
In locating pipes it is desirable to arrange for the expansion of
the boiler, as well as for that of the pipes themselves. In select-
ing a pump it should have a much larger capacity than that needed
to supply the boiler, as there are many things which affect the
working of a pump, such as a defective suction pipe, leaky valves,
etc. It is the practice of most manufacturers to give the capacity
of their pumps in gallons of water delivered per minute, from
which it is easy to select a suitable size ; but the speed given in
the tables at which the pump is to run is generally faster than
that which it is desirable to run them. As a general thing, and
without referring to any particular maker or design, it is a good
plan to select a pump having four times the capacity actually
needed for the boiler ; then the speed may be reduced to half that
given in the table, and will require less repairs, and will be a more
satisfactory purchase in the long run.
In selecting an injector or inspirator, the size should not
greatly exceed that actually required to supply the boiler. In
making the steam connections the pipes should start from the
steam space of the boiler and should not be branches merely from
the other steam pipes ; neither should the diameters of the pipes
be less than that which the instrument calls for. The pipes
should be as short and straight as practicable ; abrupt bends
should always be avoided in the suction pipes. If the water is
taken from a place in which there are floating particles of wood,
leaves, etc., a strainer should be used; a large sheet metal box
with perforated sides, makes a good strainer ; the openings ought
not too greatly exceed an eighth of an inch in diameter, and should
be several times the area of the suction pipe.
HANDBOOK ON ENGINEERING. 429
A check valve should be fitted with a valve between it and the
boiler, so that in the event of its not working satisfactorily it may
be taken apart, cleaned and replaced without stopping for exami-
nation or repairs.
The blow-off pipe should be so arranged that it will entirely
drain the boiler of water ; it is also a good plan to set a boiler
with a slight inclination toward the blow-off pipe that it may be
thoroughly drained ; an inclination of two inches in twenty feet
works well in practice. The blow-off pipe is usually fitted at the
back end of the boiler.
The steam pipe may be connected at any convenient point on
the top of the boiler. If the boiler is to furnish steam for an
engine only, the common practice is to make the diameter of the
pipe one-fourth that of the cylinder. The steam pipe should be
as short and straight as possible. If bends are to be introduced
in steam pipes it is better to have a long curved bend than the
abrupt right-angle fitting usually employed for the purpose. It
is also a good plan to provide a stop-valve next to the boiler to
shut off the steam and prevent it condensing in the steam pipe at
night, or other long stoppages.
The gauge cocks should not be less than three in number, and
may be of any of the various kinds now in the market. For
stationary boilers, the Mississippi gauge cock is, perhaps, as
good as any. For portable engines a compression gauge-cock is,
perhaps, the best. The lower gauge-cock should be at least
2" above the tubes or crown sheet, the middle 2" above the first
ordinary water line, the upper 2" to 3" above the second, de-
pending on the size of the boiler.
A glass water gauge should be provided for each boiler and
should be so located that the water level in the boiler when at the
lower end of glass shall be one inch above the top of flue. When
glass gauges are so fitted the fireman can always tell at a glance
just how much water he has above the flues or crown sheet ; it
430 HANDBOOK ON ENGINEERING.
also permits the easy test of accuracy by trying the gauge-cocks
with the water at a certain known level. Too much dependence
must not be placed on the glass water-gauge alone, but should be
used in connection with the gauge-cocks.
A steam gauge is a very important appendage to a steam
boiler, and should be chosen with special reference to accuracy
and durability. The ordinary gauges now in the market are the
bent tube and the diaphragm gauges. It matters little which of
the two kinds is selected, provided it is a good and first-class
gauge. A steam gauge should be compared with a standard test
gauge at least once a year, to see that it is correct. The
importance of this will be fully apparent when it is known that it
furnishes the only means by which the fireman is to judge of the
steam pressure in the boiler. A siphon should be attached to
every gauge, and provision should also be made for draining the
gauge or siphon, to prevent freezing when steam is off the boiler.
Neglect of this may endanger the accurate reading of the steam
gauge and render it useless.
Steam dome* — This is a reservoir for steam riveted to the
upper portion of the shell and communicated by a central opening
with the steam space in the boiler. When this reservoir forms a
separate fixture and is attached to the boiler by cast or wrought
iron nozzles, it is then called a steam drum. The latter answers
all the purposes for stationary boilers that the former does, and
is to be preferred because of the smaller openings in the shell of
the boiler. A considerable number of boiler explosions have
been traced directly to the weakness of the shell, caused by the
large opening in and imperfect staying of the shell underneath
the dome. When a dome is employed and has a large hole under-
neath, the strength of the shell is impaired in two ways: 1. By
reducing the longitudinal sectional area of shell through the cen-
ter of opening cut for it, which weakness cannot wholly be made
good by a strengthening ring around the opening. 2. By causing
HANDBOOK ON ENGINEERING. 431
a tension equal to that on the crown area of steam dome, upon
the annular part of the shell covered by the flange of the dome.
The weakest part of the boiler shell will be where the distance
from rivet hole at the base of the dome to edge of plate is least.
It is difficult, owing to the complex nature of the strains, to form
a rule whereby to determine how much the strength of the shell
is impaired by using a dome ; but it is quite apparent from gen-
eral experience that they are in many cases a source of weakness,
and the larger the dome connection with the shell, the greater the
liability to rupture. This tendency to rupture is due to the fact
that the dome, with its connecting flange, is practically inelastic ;
that portion of the shell of the boiler covered by the dome is, as
soon as the pressure is introduced on both sides of the plate,
simply a curved brace. The pressure of the steam in the boiler
has a tendency to straighten the shell under the dome and thus
brings about a series of complex strains, which are not easily rem-
edied by any system of bracing, so that on the whole it is prefer-
able to use a small connecting nozzle with a drum above it, rather
than to rivet a large dome directly to the shell.
Dry pipe* — This is a pipe having numerous small perforations
on its upper side, and inserted in the upper part of the steam space
of the boiler. This pipe does not dry the steam, but acts
mechanically by separating the steam from the water when the
latter is in a violent state of agitation, and is liable to be carried
in bulk toward or into the steam pipe. The object of these numer-
ous small holes in the pipe is that a small quantity of steam may
be taken from a large number of openings at one time, and thus
carried over a larger extent of surface than that afforded by a
single opening, and by this single device checking the tendency to
priming.
Steam boiler furnaces are receiving more attention now than
perhaps ever before. The question of economy of fuel is being
closely studied, and there is now an effort to save much of the
432 HANDBOOK ON ENGINEERING.
heat, which had formerly been allowed to go to waste. The main
thing in furnace construction is to get perfect combustion. With-
out this there must be of necessity a great loss constantly going
on. There are some losses which it is difficult to prevent, for
example — the loss by the admission of too much air in the ash
pit ; the loss by incomplete combustion ; the loss occasioned by
the heated gases escaping up the chimney ; the loss by radia-
tion ; but, chief among these, is that of incomplete combustion.
To burn a pound of coal requires about twenty-four pounds of air,
or, say 300 cubic feet. Most boiler settings permit from 200 to 300
feet to pass through the fire. It is needless to point out the
great source of loss arising from this one cause alone. This may
be prevented in a measure by having a suitable damper in the
chimney, and regulating the flow of escaping gases by it, instead
of the ash pit doors. If the furnace is so constructed that the
fuel is imperfectly burned, so that carbonic oxide instead of car-
bonic acid gas is formed, the loss is very great. This results
often from too little air supply and too low temperature in the
furnace. The furnace doors should be provided with an opening
leading into the space between the door proper and the liner ;
this opening ought to have a sliding or revolving register by which
the admission of air may be controlled. By this means, the
quantity of air admitted above the fire may be adjusted to its
needs by a little attention on the part of the fireman. The liner
to the furnace door should have a number of small holes in it,
rather than a solid plate, with a space around the edges. Great
care should be exercised in the construction of furnace walls,
that the materials and workmanship be good throughout. The
entire structure should be brick. The outer walls may be of
good hard red brick, but the interior walls, around the furnace
and bridge wall, should be of fire brick. The best quality of fire
brick for withstanding an intense heat are very, very strong and
tenacious ; the structure is open and they are free from black
HANDBOOK ON ENGINEERING. 433
spots, due to sulphuret of iron in the clay ; if well burned they
will not be very light colored on the outside, and will have a
clear ring when struck.
Fire brick should be dipped in a thin mortar made of fire clay,
rather than in a lime and sand mortar, such as is used in ordinary
red brickwork. In laying up these portions of a boiler furnace
requiring fire brick, provision should be made in the original wall
for replacing the fire brick and without disturbing the outer
brickwork.
CARE AND MANAGEMENT OF A BOILER.
It is not enough that a boiler be of approved design, made of
the best materials, and put together in the best manner ; that it
have the best furnace and the most approved feed and safety
apparatus. These are all desirable, and are to be commended,
but cleanliness and careful management are quite essential to get-
ting high results, and are also conducive to long use in service.
Pumps* — Special attention should be given at all times to the
feed and safety apparatus ; the pumps should be in good working
order ; it is preferable that they be independent steam pumps
rather than pumps driven by the engine, or by a belt ; they should
be kept well packed and the valves in good condition.
Firing* — Kindle a fire and raise steam slowly ; never force a
fire so long as the water in the boiler is below the boiling point.
The fire should be of an even height, and of such a thickness as
will be found best for the particular fuel to be burned, but should
be no thicker than actually necessary. In regard to the size of
coal used, that will depend upon circumstances. If anthracite
coal is used, it should not, for stationary boilers, be larger than
ordinary stove coal. For bituminous coal, which is always shipped
in lumps as large as can be conveniently handled, the size will
vary somewhat in breaking, but it may in general be used in
larger lumps than anthracite. If the coal is likely to cake in burn-
28
434 HANDBOOK ON ENGINEERING.
ing, the fire should be broken up quite frequently with a slice bar,
or it will fuse into a large mass in the center of the furnace and
lower the rate of combustion. If the coal is likely to form a con-
siderable quantity of clinker, or enough to become troublesome, it
may be advantageous to increase the grate area and thus lower
the rate of combustion per square foot of grate, and have a fire of
less intensity. The fire should be kept free from ashes, and the
ash pit should be kept clean. Whenever the fire door of a steam
boiler furnace is opened, the damper should be closed to prevent
the sudden reduction of temperature underneath, which is likely
to injure the boiler by contraction, and thus render it likely to
spring a leak around the riveted joints. Some firemen are very
careless in this respect, and there is little doubt that many a dis-
agreeable job of repairing a leaky seam might be prevented by
this simple precaution.
Gauge cocks should be used constantly to keep them free from
any accumulation of sediment. It is a very common practice to
rely wholly on the indications of the glass water gauge for the
water level in the boiler. This is all wrong and should be dis-
continued, if once begun. The glass water gauge serves a very
useful purpose, but it should not be wholly relied on in practice.
In using the ordinary gauge cocks, the ear more than the eye,
detects the water level, and thus acts as a check on the indications
given by the glass gauge.
Water gauges should be tested several times during the day to
see that they are clear, and to keep them free from any sediment
likely to form around the lower opening to the water in the
boiler. If this is not attended to, the water gauge is likely to
indicate a wrong water level and a serious accident may be the
result.
Steam or pressure gauges are likely to become set after long
use and should be tested at least once, or better still, twice a year
by a standard gauge known to be correct. They should also be
HANDBOOK ON ENGINEERING. 435
tested every few days if the boilers are constantly under steam
by turning off the steam and allowing the pointer to run back to
zero. If there are two or more boilers set together in one battery,
and each boiler has its own steam gauge, and which will, starting
from the zero point, indicate the same pressure on all the gauges,
they may be assumed to be correct.
Blow-off cocks or valves should be examined frequently and
should never be allowed to leak. In general a cock is to be pre-
ferred to a valve, but both is safer than one ; if the latter is
selected it should be some one of the various u straight- way
valves," of which there are now several in the market. If the
cock is a large one, and especially if it has either a cast iron shell
or plug, it should be taken apart after each cleaning out of the
boilers, examined, greased with tallow and returned.
Blowing out* — This should be done at least once a day,
except in the very rare instances in which water is used that will
not form a scale. The water should not be let out of a boiler or
boilers until the furnace is quite cold , as the heat retained in the
walls is likely to injure an empty boiler directly by overheating
the plates, and indirectly by hardening the scale within the
boiler. Bad effects are likely to follow when a boiler is emptied
of its water before the side walls have become cool ; but greater
injury is likely to result when cold water is pumped into an empty
boiler heated in this manner. The unequal contraction of the
boiler is likely to produce leaky seams in the shell and to loosen
the tubes and stays. It is a better plan to allow the boiler to
remain empty until it is quite cold, or sufficiently reduced in tem-
perature to permit its being filled without injury. Many boilers
of good material and workmanship have been ruined by the
neglect of this simple precaution.
Fusible plugs should be carefully examined every six months,
as scale is likely to form over the portion projecting into the
water space. It is only a question of time when this scale
436 HANDBOOK ON ENGINEERING.
would form over the end of the plug, and thick enough to with-
stand the pressure of steam and thus fail in the accomplishment of
the very object for which it was introduced. This applies espe-
cially to the fusible plugs inserted in the crown sheets of portable
engine boilers.
Cleaning tubes* — This should be done every day if bitumin-
ous coal is used. A portable steam jet will be found an extremely
useful contrivance which will keep them reasonably clean by blow-
ing out the loose soot and ashes deposited in the tubes. Every
two or three days, or at least once a week, a tube scraper or stiff
brush should be used to take out all the ashes or soot adhering
to the tubes and which cannot be blown out with the jet. Flues
may be cleaned the same way but will not require to be done so
frequently.
Low water* — If from any cause the water gets low in the
boiler, bank the fire with ashes or with fresh coal as quickly as
possible, shut the damper and ash pit doors and leave the fire
doors wide open ; do not disturb the running of the engine but
allow it to use all the steam the boiler is making; do not
under any circumstances attempt to force water in the boiler.
After the steam is all used and the boiler cooled sufficiently to be
safe, then the water may be admitted and brought up to the reg-
ular working height ; the damper opened and the fires allowed to
burn and steam raised as usual; provided, no injury has been
done the boiler by overheating.
Foaming and priming are always troublesome and often danger-
ous. Some boilers prime almost constantly, because of their bad
proportion, and will require the constant care of the person in
charge, especially at such times as the engine may be using the
steam up to the full capacity of the boiler. In a case of this kind,
an increase in pressure will often check, but will not entirely
prevent it ; nothing short of an increase of water surface, or a
better circulation of water, or a larger steam room will afford a
HANDBOOK ON ENGINEERING. 437
complete remedy. If the foaming or priming is due to a sudden
liberation of steam, or on account of impure feed water it may be
checked by closing the throttle valve to the engine and opening
the fire door for a few minutes. The surface blow may be used
with advantage at this time, by blowing off the impurities collected
on the surface of the water. The feed pump may be used if
necessary, but care should be exercised that too much cold water
be not forced into the boiler, and thus lose time by having to
wait for the accumulation of the regular steam pressure required
for the engine. The dangers attending foaming or priming are :
the laying bare of heating surfaces in the boiler, and of breaking
down the engine by working water into the cylinder. The com~
monest damage to the engine being either the breaking of a cylin-
der head, or the cross-head, or the breaking of the piston. Wbeu
boilers are new and set to work for the first time priming is a very
frequent occurrence ; in fact, it may be said that for the first few
days there is always more or less of it. All that is needed during
this time is a little care on the part of the attendant to see that
the water is kept up to the required level in the boiler ; it is also
recommended that the throttle valve to the engine be partially
closed to prevent any very great variation of pressure in the
boiler, and thus prevent water passing over with the steam
in such quantities as to become dangerous. If a boiler
continues to prime* after it has had a weeR's work and
then thoroughly cleaned, the causes are to be attributed to
other than the grease and dirt in it, which are inseparable from
the manufacture. As already said, priming may be caused by a
sudden reduction of pressure ; that is, a boiler may be working
smoothly and well with, say, 80 pounds pressure ; if an increase
of load be suddenly applied to an engine so as to reduce the
pressure to 70 or 60 pounds, this sudden reduction of pressure
will almost always cause priming ; the less the steam space in the
boiler, the greater the tendency to prime, and the greater the
438 HANDBOOK ON ENGINEERING.
difficulty in checking it. The only permanent cure for this is
more boiler power ; as a temporary expedient, the engine should
be throttled sufficiently to make the drain upon the boiler con-
stant instead of intermittent. If the duty required of an engine
is irregular, the steam pressure should be carried higher ; in any
case similar to the above, it is recommended that the pressure be
increased to 90 or 100 pounds and the throttling to begin with
the increased drain upon the boiler. But this is at best a mere
makeshift, and a larger boiler power becomes imperative both
on the score of economy and safety.
WATER FOR USE IN BOILERS.
Water is never pure, except when made so in a laboratory or
by distillation ; the impurities may be divided into four classes :
1. Mechanical impurities. 2. Gaseous impurities. 3. Dissolved
mineral impurities. 4. Organic impurities.
(a) Mechanical impurities may be both mineral and organic.
The commonest suspended impurity in water is mud or sand ;
these may be removed by filtration or by allowing the water to
stand long enough to let them settle to the bottom of the tank or
cistern and then carefully drawing the water from the top, and
without disturbing the bottom.
(b) Gaseous impurities in water vary somewhat according to the
localities from which they are obtained. The commonest gases
found in the water are an excess of oxygen, nitrogen and carbonic
acid. These have no effect on water intended for steam boilers.
(c) Dissolved mineral impurities in water are of the most
varied description, and are almost always found in it. Among
these are found salts of iron, sulphate and carbonates of lime ;
sulphate and carbonates of magnesia ; salt and alkalies, such as
soda, potash, etc. ; acids, such as sulphuric, phosphoric, and
others. All of these are more or less injurious to steam boilers.
The most objectionable are the salts of lime and magnesia, which
impart to water that property known as hardness. When such
HANDBOOK ON ENGINEERING. 439
water is used in a steam boiler a scale will gradually form, which
will, in a short time, become very troublesome.
(d) Organic impurities are present, to a certain extent, in
most waters. They are sometimes present in the water in suffi-
cient quantities to give it a very decided color and taste.
The presence of organic matter in water is often dangerous to
health, and may be a means of spreading contagious diseases,
but has little or no bad effect in any water used for steam boilers.
In general, water is regarded by engineers as being either soft,
hard or salt.
Ebullition is the motion produced in a liquid by its rapid
conversion into vapor. When heat is applied to the bottom of a
boiler, the particles of water in contact with the plates become
heated and immediately expand, and becoming specifically lighter,
pass upwards through the colder body of water above ; the heat of
the furnace is in this way diffused throughout the whole body of
water in the boiler by a translation of the particles of water from
below upwards, and from top to bottom in regular succession.
After a time this liquid mass becomes heated to a degree in which
there is a violent agitation of the whole body of water, steam is
given off and it is said to boil. The temperature at the boiling
point of water, at ordinary atmospheric pressure, is 212° Fahr.,
and increases as the pressure of steam above it increases.
Distilled water for boilers is not to be recommended without
some reservation. Chemically pure water, and especially water
which has been redistilled several times, has a corrosive action on
iron which is often very troublesome. The effect on steel plates
by the use of water several times redistilled, such, for example, as
that supplied for heating buildings, is well known ; information is
yet wanting which shall point with certainty to the exact change
which the water undergoes and explain why its action on or
affinity for steel is so greatly intensified. It has been suggested
as a means of neutralizing this corrosive action of the water, to
440 HANDBOOK ON ENGINEERING.
introduce with the feed other water, which shall have the prop-
erty of forming a scale and continuing it long enough and at such
intervals as will permit the formation of a thin scale in the interior
of the boiler. However objectionable this may seem at first
sight, it is at present the best practical solution of the difficulty.
Scale is a bad conductor of heat and is opposed to economical
evaporation. It is estimated that a thickness of half an inch of
hard scale firmly attached to a boiler plate will require a temper-
ature of about 700° Fahr. in the boiler plate in order to raise and
maintain an ordinary steam pressure of 75 pounds. The mis-
chievous effects of accumulated scale in the boiler, especially in
the plates immediately over the fire, are : (1) preventing the water
from coming in contact with the plates, and thus directly con-
tributing to the overheating of the latter; and (2) by causing a
change of structure in the plates and the consequent weakening
brought about by this continual overheating, which would, in a
short time, render an iron or a steel plate wholly unfit for use in
a steam boiler. The two principal ingredients in boiler scale are
lime and magnesia. The lime, when in combination with
carbonic acid, forms carbonate of lime ; when in combination with
sulphuric acid, it then becomes sulphate of lime. This is also
true of magnesia.
Carbonate of lime will form in the boiler as a loose powder,
which is held mechanically in suspenion ; while in this stage it
may be blown out of the boiler without injury to it ; but it is
seldom that a pure carbonate is formed in the boiler as there are
other impurities in the water with which it combines to form a
hard scale. This is especially true in such waters as also contain
sulphate of lime in solution. This fine powder (carbonate of
lime), will form a hard scale should any adhere to the sides or
bottom of a boiler ; in any case where the boiler is blown out dry
while the furnace walls are still hot; and this, in itself, forms an
excellent reason why boilers should stand until the furnace walls
HANDBOOK ON ENGINEERING. 441
are cold before blowing out. When emptied, nearly or all of this
slushy deposit may be washed out of the boiler by means of a
hose.
Sulphate of lime is not so easily got rid of, as it is heavier than
carbonate of lime and adheres to the plates while the boiler is at
work. It is the most troublesome scale steam engineers have to
deal with ; it is very difficult to remove and by successive layers
becomes dangerous, on account of the thickness to which it
eventually accumulates.
The carbonates of lime and magnesia may be largely arrested
by passing the feed water through a suitable heater and lime
extractor. It must be apparent to every one that any device
which will accomplish this is a very desirable attachment to a
steam boiler. As it is not possible to eliminate all the foreign
matter in the water from it, recourse is often had to the use of
solvents and chemical agencies for the prevention of scale. Some
of these are very simple and within easy reach ; others are sur-
rounded by an atmosphere of uncertainty and the real nature of
the compound is hidden under a meaningless trade-mark. For
carbonate of lime, potato has been found to be very service-
able in preventing the formation of scale ; its action appears to
be that of surrounding the particles of lime with a coating of
starch and gelatine, and thus preventing the cohesion of these
particles to form a mass. Various astringents have been used for
this purpose, such as extracts of oak and hemlock bark, nutgalls,
catechu, etc., with varying success.
Carbonate of soda has been used and with very great success in
some localities, not only in preventing, but in actually removing
scale already formed. It acts on carbonate of lime, not only, but
on the sulphate also. It is clean, free from grit, and is quite
unobjectionable in the boiler ; one or more pounds per day, de-
pending on the size of the boiler, may be admitted through the
pump with the feed water ; or admitted in the morning before
442 HANDBOOK ON ENGINEERING.
firing up, by simply mixing with water and pouring into the boiler
through the safety valve or other opening.
Tannate of soda has been similarly employed and is an excel-
lent scale preventive. It will also act as a solvent for scale
already formed in the boiler, acting on sulphate as well as carbon-
ate of lime.
Crude petroleum has been found very beneficial in removing
the hard scale composed principally of sulphate of lime.
Zinc in steam boilers* — The employment of zinc in steam
boilers, like that of soda, has been adopted for two distinct
objects: (1) to prevent corrosion, and (2) to prevent and
remove incrustation. To attain the first object, it has been used
chiefly in marine boilers, and for the second, chiefly in boilers fed
with fresh water. In order that the application of zinc in marine
boilers may be effective, it is necessary that the metallic contact
should be insured. If galvanic action alone is relied upon for the
protection of the plates and tabes, it will doubtless be diminished
materially by the coating of oxide that exists between all joints of
plates, whether lapped or butted, and also between the rivets and
the plates. Assuming the preservative action of zinc to be proved
when properly applied, we have now two systems for preventing
the internal decay of marine boilers, viz. : allowing the plates and
tubes to become coated with scale, and employing zinc. It
remains to decide which of these two systems is the best with
respect to economy and practicability.
We come now to consider the use of zinc for preventing arid
removing incrustation.
At one time it was considered that the action of zinc in pre-
venting incrustation was physical or mechanical. The particles
of zinc, as it wasted away, were supposed to become mixed
amongst the solid matter precipitated from the water, in such a
manner as to prevent it adhering together, so as to form a hard
scale ; or the particles of zinc were supposed to become deposited
HANDBOOK ON ENGINEERING. 443
upon the plates, and so prevent the scale from adhering to them.
Then it was suggested that the zinc acted chemically, and now, it
is the generally received opinion that its action is galvanic in
preventing incrustation as well as in preventing corrosion. When
the water contains an excess of sulphates or chlorides over the
carbonates, the acid of the former will form soluble salts with the
oxide of zinc, the surface of the zinc will be kept clean, and the
galvanic current, to which the efficiency of the zinc is due, will be
maintained. On the other hand, should there be a preponderat-
ing amount of carbonates, the zinc will be covered first with oxide,
then with carbonates and its useful action arrested and stopped.
It is quite as important that the zinc should be in metallic con-
tact with the plates when used to prevent incrustation, as when
employed to prevent corrosion. The application of zinc for the
former purpose should never be attempted without first having the
water analyzed in order to ascertain whether it is likely to be
effective. The use of zinc in externally fired boilers should be
attempted with great caution, as when efficacious in preventing
the formation of a hard scale, it is liable to produce a heavy
sludge that may settle over the furnace plates and lead to over-
heating. On the whole we cannot but regard the evidence as to
the effect of zinc upon incrustation as being very conflicting.
Leaks should be stopped as soon as possible after their dis-
covery ; the kind of leak will indicate the treatment necessary.
If it occurs around the ends of the tubes, it may be stopped by
expanding the tubes anew ; if in a riveted joint, it should be care-
fully examined, especially along the line of the rivets and care
should be exercised in determining whether there is a crack
extending from rivet to rivet along the line of the holes ; should
this prove to be the case, the boiler is then in an extremely
dangerous condition and under no circumstances should it be
again fired up until suitable repairs have been made which will
insure its 'safety.
444 HANDBOOK ON ENGINEERING.
Blisters occur in plates which are made up of several thick-
nesses of iron and which from some cause were not thoroughly
welded before the final rolling into plates. When such a plate
comes in contact with the heat of the furnace the thinnest portion
of the defective plate 4t buckles " and forms what is called a
blister. As soon as discovered, there should be thorough exami-
nation of the plate and if repairs are needed there should be as
little delay as possible in making them. If the blister be very
thin and altogether on the surface it may be chipped and dressed
around the edges ; if the thickness is equal or exceeds Ty the
blister should be cut off and patched, or a new plate put in.
Patching boilers* — When a boiler requires patching it is bet-
ter to cut out the defective sheets and rivet in a new one ; or if
this cannot be done, a new piece large enough to cover the defect
in the old sheet may be riveted over the hole from which the
defective portion has been cut. If this occurs in any portion of
the boilei subject to the action of fire, the lap should be the same
as the edges of the boiler seams, and should be carefully calked
around the edges after the riveting. Whenever the blisters occur
in a plate, patching is a comparatively simple thing as against the
repairs of a plate worn by corrosion. In the latter case, the
defective portions of the plate should be entirely removed and the
openings should show sound metal all around and of full thick-
ness. If this cannot be obtained within a reasonable sized open-
ing then the whole plate should be removed.
It often occurs that a minor defect is found in a plate and at a
time when it is not convenient to stop for repairs ; in such an
event a " soft" patch is often applied. This consists of a piece
of wrought iron carefully fitted to that portion of the boiler plate
needing repairs ; holes are fitted in both plates and patch, and
" patch bolts " provided for them. A thick putty consisting of
white and red lead with iron borings or filings in them placed
evenly over the inner surface of the patch, which is then tightly
HANDBOOK ON ENGINEERING. 445
bolted to the boiler plate. This is best but a temporary make-
shift and ought never to be regarded as a permanent repair. A
mistake is often made of making a patch of thicker metal than
that of the shell of the boiler needing it. A moment's reflection
ought to show the absurdity of putting on a T5F or f patch on an
old J inch boiler shell ; yet it is not so rare as one would imagine.
A piece of new iron T3^" thick will, in most cases, be found to be
stronger than that portion of a J" old plate needing repairs.
Inspection* — A careful external and internal examination of a
boiler is to be commended for many reasons. This should be as
frequent as possible and thoroughly done ; it should include the
boiler not only, but all the attachments which affect its working
or pressure. Particular attention should be paid to the examina-
tion of all braces and stays, safety valve, pressure gauges, water
gauges, feed and blow-off apparatus, etc. ; these latter refer more
particularly to constructive details necessary to proper manage-
ment and safety. The inspection would obviously be incomplete,
did it not include an examination into the causes of " wear and
tear," and determine the extent to which it had progressed.
Among the several causes which directly tend to rendering a
boiler unsafe, may be mentioned the dangerous results occasioned
by the overheating of plates, thus changing the structure of the
iron from fine granular, or fibrous, to coarse crystalline. This
may easily be detected by examination, and will in general be
found to occur in such cases where the boilers are too small for
the work, are fired too hard, or have a considerable accumulation
of scale or sediment in contact with the plates. Blistered plates
are almost instantly detected at sight, so also is corrosion, from
whatever cause it may have proceeded.
Corrosion of boiler plates* — Iron will corrode rapidly when
subjected to the intermittent action of moisture and dryness.
Land boilers are less subject to corrosion than marine boilers.
The corrosion of a boiler may be either external or internal. Ex-
446 HANDBOOK ON ENGINEERING.
ternal corrosion may, in general, be easily prevented by carefully
caulking all leaks in the boiler ; by preventing the dropping of
water on the plates, such, for example, as from a leaky joint in
the steam pipe or from the safety valve. A leaky roof, by allow-
ing a continual or occasional dropping of water on the top of a
boiler, especially if the boiler is not in constant use, would pro-
mote external corrosion. Sometimes external corrosion is caused
by the use of coal having sulphur in it, and acts in this way : The
sulphur passes off from the fire as sulphurous oxide, which often
attaches to the sides of a boiler ; so long as this is dry no especial
mischief is done ; but if it comes in contact with a wet plate the
sulphurous oxide is converted into sulphuric acid over so much
of the surface as the moisture extends ; this acid attacks, and
will, in time, entirely destroy the boiler plate. Internal corrosion
is not so easily accounted for and is very difficult to correct,
especially when it occurs above the water line. It is generally
believed to be due to the action of acids in the feed water.
Marine boilers are especially subject to internal corrosion when
used in connection with surface condensers. A few years ago it
was generally supposed to be due to galvanic action but that idea
is now almost entirely given up. From the fact that boilers using
distilled water fed into them from surface condensers are more
liable to internal corrosion than other boilers, has led to the theory
that it is the pure water that does the mischief, and that a water
containing in slight degree a scale-forming salt, is to be preferred
to water which is absolutely pure. Whatever maybe the truth or
falsity of this theory, it is a well established fact that distilled
water has a most pernicious action on various metals, especially
on steel, lead and iron. This action is attributed to its peculiar
property, as compared with ordinary water, of dissolving free
carbonic acid. One of the worst features in connection with
internal corrosion is that its progress cannot be easily traced on
account of the boiler being closed while at work. As it does not
HANDBOOK ON ENGINEERING. 447
usually extend over any very great extent of surface, the ordinary
hydraulic test fails to reveal the locality of corroded spots ; the
hammer test, on the contrary, rarely fails to locate them, if the
plates are much thinned by its action.
Testing boilers* — It is the general practice to apply the
hydraulic test to all new steam boilers at the place of manufacture,
and before shipment. The pressure employed in the test is from
one and a half to twice the intended working steam pressure.
This test is only valuable in bringing to notice defects which
would escape ordinary inspection. It is not to be assumed that
it in any way assures good workmanship, or material, or good
design, or proper proportions ; it simply shows that the boiler
being tested is able to withstand this pressure without leak-
ing at the joints, or distorting the shell to an injurious degree.
Bad workmanship may often be detected at a glance by an expe-
rienced person. The material must be judged by the tensile
strength and ductility of the sample tested. The design and pro-
portions are to be judged on constructive grounds, and have little
or nothing in common with the hydraulic test. The great majority
of buyers of steam boilers have but little knowledge on the sub-
ject of tests, and too often conclude that if they have a certified
copy of a record showing that a particular boiler withstood a test
of say, 150 Ibs., it is a good and safe boiler at 75 to 100 Ibs.
steam pressure. If the boiler is a new one and by a reputable
maker, that may be true ; if it has been used and put upon the
market as a second-hand boiler, it may be anything but safe at
half the pressure named. By the hydraulic test, the braces in a
boiler may be broken, joints strained so as to make them leak,
bolts or pins may be sheared off, or so distorted as to be of little
or no service in resisting steam when pressure is on.
Hammer test* — The practice of inspecting boilers by sounding
with a hammer is, in many respects, to be commended. It
requires some practical experience in order to detect blisters and
448
HANDBOOK ON ENGINEERING.
tlie wasting of plates, by sound alone. The hammer test is
especially applicable to the thorough inspection of old boilers. It
frequently happens in making a test that a blow of the hand
hammer will either distort it, or be driven entirely through the
plate ; and it is just here that the superiority of this method of
testing over, or in connection with the hydraulic test, becomes
fully apparent. The location of stays, joints and boiler fittings all
modify and are apt to mislead the inspector if he depends upon
sound alone. There is a certain spring of the hammer and a clear
ring indicative of sound plates, which are wanting in plates much
corroded or blistered. The presence of scale on the inside of the
boiler has a modifying action on the sound of the plate. When a
supposed defect is discovered, a hole should be drilled through
the sheet by which its thickness may be determined, as well as
its condition.
In order to thoroughly inspect a boiler, the inspector should
crawl into the boiler (when it is possible to do so) and he should
look for pitting and grooving of plates, test all braces, and
examine all inlets and outlets.
TOTAL STORED ENERGY OP STEAM BOILERS.
Grate
Surface.
Heating
Surface.
Steam
Pressure.
Rated
Energy in Foot Pounds Stored in the
feq. Ft.
Sq. Ft.
Lbd.
H. P.
Water.
Steam.
Total.
15
120
100
10
46605200
676698
47281898
15
875
125
425
64253160
1302431
65556691
20
400
150
35
80572050
2377357
8294 9407
20
1200
125
600
64452270
1766447
66218718
22
1070
125
525
52561075
1483896
54044971
30
852
75
60
60008790 1022731
51031521
30
1350
125
650
69148790 21358U2
71284692
32
768
75
300
71272370 1462430
72734800
36
730
30
60
57570750
709310
58260060
50
1119
75
350
107408340 2316392
109724732
70
2806
100
250
172455270
2108110
1745633feO
72
1755
30
180
102628410
1643854
104272264
72
2324
bO
200
90531490
1570517
92101987
100
3000
100
250
227366000
3513830
230879830
HANDBOOK ON ENGINEERING. 449
CHAPTER XVII.
USE AND ABUSE OF THE STEAM-BOILER.
Steam-boilers* — A steam-boiler may be defined as a close
vessel, in which steam is generated. It may assume an endless
variety of forms, and can be constructed of various materials.
Since the introduction of steam as a motive power a great variety
of boilers have been designed, tried and abandoned; while many
others, having little or no merit as steam generators, also have
their advocates and are still continued in use. Under such cir-
cumstances, it is not surprising that quite a variety of opinions
are held on the subject. This difference of opinion relates not
only to the form of boiler best adapted to supply the greatest
quantity of steam with the least expenditure of fuel, but also to
the dimensions or capacity suitable for an engine of a given num-
ber of horse-power ; and while great improvements have been
made in the manufacture of boiler materials within the past
fifteen years, yet the number of inferior steam-boilers seem to
increase rather than diminish. It would be difficult to assign any
reasonable cause for this, except that, of late years, nearly the
whole attention of instructors and mechanical engineers has been
directed to the improvement and perfection of the steam-engine,
and practical engineers, following the example set by the leaders,
devote their energies to the same object. This is to be regretted,
as the construction and application of the steam-boiler, like the
steam-engine, is deserving of the most thorough and scien-
tific study, as on the basis of its employment rest some
of the most important interests of civilization. Until quite
recently, the idea was very generally entertained that the
purely mechanical skill required to enable a person to join
450 HANDBOOK ON ENGINEERING.
-
together pieces of metal, and thereby form a steam-tight and
water-tight vessel of given dimensions, to be used for the gen-
eration of steam to work an engine, was all that was needed ;
experience has shown, however, that this is but a small portion of
the knowledge that should be possessed by persons who turn their
attention to the design and construction of steam-boilers, as the
knowledge wanted for this end is of a scientific as well as of a
mechanical nature. As the boiler is the source of power and the
place where the power to be applied is first generated, and alsc
the source from which the most dangerous consequences may arise
from neglect or ignorance, it should attract the special attention
of the designing and mechanical engineer, as it is well known
that from the hour it is set to work, it is acted upon by destroy-
ing forces, more or less uncontrollable in their work of destruc-
tion. These forces may be distinguished as chemical and
mechanical. In most cases they operate independently, though
they are frequently found acting conjointly in bringing about the
destruction of the boiler, which will be more or less rapid accord-
ing to circumstances of design, construction, quality of material,
management, etc. The causes which most affect the integrity of
boilers and limit their usefulness are either inherent in the mate-
rial, or due to a want of skill in their construction and manage-
ment ; they may be enumerated as follows : —
First, inferior material ; second, slag, sand or cinders being
rolled into the iron ; third, want of lamination in the sheets ;
fourth, the overstretching of the fiber of the plate on one side and
puckering on the other in the process of rolling, to form the circle
for the shell of a boiler ; fifth, injuries done the plate in the pro-
cess of punching ; sixth, damage induced by the use of the drift-
pin ; seventh, carelessness in rolling the sheets to form the shell,
as a result of which the seams, instead of fitting each other
exactly, have in many instances to be drawn together by bolts,
which aggravates the evils of expansion and contraction when the
HANDBOOK ON ENGINEERING. 451
boiler is in use ; eighth, injury done the plates by a want of skill
in the use of the hammer in the process of hand-riveting ; ninth,
damage done in the process of calking.
Other causes of deterioration are unequal expansion and con-
traction, resulting from a want of skill in setting ; grooving in the
vicinity of the seams ; internal and external corrosion ; blowing
out the boiler when under a high pressure and filling it again with
cold water when hot ; allowing the fire to burn too rapidly after
starting, when the boiler is cold ; ignorance of the use of the pick
in the process of scaling and cleaning ; incapacity of the safety-
valve ; excessive firing ; urging or taxing the boiler beyond its
safe and easy working capacity; allowing the water to become
low, and thus causing undue expansion ; deposits of scale accum-
ulating on the parts exposed to the direct action of the fire,
thereby burning or crystallizing the sheets or shell ; wasting of the
material by leakage and corrosion ; bad design and construction
of the different parts ; inferior workmanship and ignorance in the
care and management. All these tend with unerring certainty to
limit the age and safety of steam boilers. On account of want of
skill on the part of the designer and avarice on the part of the
manufacturer, or perhaps both reasons, boilers are sometimes so
constructed as to bring a riveted seam directly over the fire, the
result of which is that in consequence of one lap covering the
other, the water is prevented from getting to the one nearest the
fire, for which reason the lap nearest the fire becomes hotter and
expands to a much greater extent than any other part of the
plate ; and its constant unequal expansion and contraction, as
the boiler becomes alternately hot and cold, inevitably results in a
crack. Such blunders are aggravated by the scale and sediment
being retained on the inside, between the heads of the rivets,
which should be properly removed in cleaning.
The tendency of manufacturers to work boilers beyond their
capacity, especially when business is driving, is too great in this
452 HANDBOOK ON ENGINEERING.
country ; and no doubt many boiler explosions may be attributed
to this cause. Boilers are bought, adapted to the wants of the
manufactory at the time, but, as business increases, machinery
is added to supply the demand for goods, until the engine is
overtasked, the boiler strained and rendered positively danger-
ous. Then again, it not unfrequently occurs that engines in
manufactories are taken out and replaced by those of increased
power, while the boilers used with the old engine are retained in
place, with more or less cleaning and patching, as the case may
require. Now, it is evident to any practical mind that boilers
constructed for a twenty horse power engine are ill adapted to
an engine of forty horse power, more especially if those boilers
have been used for a number of years. In order to supply
sufficient steam for the new engine, with a cylinder of increased
capacity, the boiler must be worked beyond its safe working
pressure, consequently excessive heating and pressure greatly
weaken it and endanger the lives of those employed in the vicinity.
The danger and impracticability of using boilers with too
limited steam room may be explained thus : Suppose the entire
steam room in a boiler to be six cubic feet, and the contents of
the cylinder which it supplies to be two cubic feet ; then at each
stroke of the piston one-third of all the steam in the boilers is
discharged, and consequently, one-third of the pressure on the
surface of the water before that stroke is relieved ; hence, it will
be seen that excessive fires must be kept up in order to generate
steam of sufficiently high temperature and pressure to supply the
demand. The result is that the boilers are strained and burned.
Such economy in boiler power is exceedingly expensive in fuel,
to say nothing of the danger. Excessive firing distorts the fire-
sheets, causing leakage, undue and unequal expansion and con-
traction, fractures, and the consequent evils arising from external
corrosion. Excessive pressure arises generally from a desire on
the part of the steam-user to make a boiler do double the work for
HANDBOOK ON ENGINEERING. 453
which it was originally intended. A boiler that is constructed to
work safely at from fifty to sixty pounds was never intended to
run at eighty and ninety pounds ; more especially if it had been
in use for several years. Boilers deteriorated by age should have
their pressure decreased, rather than increased.
One of the first things that should be done in manufacturing
establishments would be to provide sufficient boiler power and, in
order to do this, the work to be done ought to be accurately cal-
culated and the engine and boilers adapted to the results of this
calculation. Steam users themselves are frequently to blame for
the annoyances and dangers arising from unsafe boilers and those
of insufficient capacity. From motives of false economy they are
too easily swayed in favor of the cheaper article, simply because
it is cheap, when they should consider they are purchasing an
article which, of almost all others, should be made in the most
thorough manner and of the best material. In view of the fearful
explosions that occur from time to time, every steam user should
secure for his use the best and safest. The object of a few
dollars as between the work of a good, responsible maker and
that of an irresponsible one, should not for one moment be
entertained.
It is very bad policy for steam-users to advertise for estimates
for steam-boilers, or to inform all the boilermakers in the town
or city that a boiler or boilers to supply steam for an engine of a
certain size is needed, because in this way steam-users frequently
find themselves in the hands of needy persons, who, in their
anxiety to get an order, will sometimes ask less for a boiler than
they can actually make it for ; consequently, they have to cheat
in the material, in the workmanship, in the heating surface and in
the fittings. As a result, the boiler is not only a continual source
of annoyance, but, in many instances, an actual source of danger.
The most prudent course, and in fact the only one that may be
expected to give satisfaction, is to contract with some responsible
434 HANDBOOK ON ENGINEERING.
manufacturer that has an established reputation for honesty,
capability and fair dealing, and who will not allow himself to be
brought in competition with irresponsible parties for the purpose
of selling a boiler. There are thousands of boilers designed, con-
structed and set up in such a manner as to render it utterly
impossible to examine, clean or repair them. Generally, in such
cases, in consequence of imperfect circulation, the water is
expelled from the surface of the iron at the points where the
extreme heat from the furnace impinges, and, as a result, the
plates become overheated and bulge outward, which aggravates
the evil, as the hollow formed by the bulge becomes a receptacle
for scale and sediment. By continued overheating, the parts
become crystallized and either crack or blister ; this, if not
attended to and remedied, will eventually end in the destruction
of the boiler. Many boilers, to all appearance well made and of
good material, give considerable trouble by leakage and fracture,
owing to the severe strains of unequal expansion and contraction
induced by the rigid construction, the result of a want of skill in
the original design.
•
DESIGN OF STEAM-BOILERS.
It has become a general assertion on the part of writers on the
steam-boiler that the most important object to be attained in its
design and arrangement is thorough combustion of the fuel.
This is only partially true as there are other conditions equally
important, among which are strength, durability, safety, economy
and adaptability to the particular circumstances under which it is
to be used. However complete the combustion may be, unless
its products can be easily and rapidly transferred to the water,
and unless the means of escape of the steam from the surfaces on
which it is generated is easy and direct, the boiler will fail to
produce satisfactory results, either in point of durability or
economy of fuel.
HANDBOOK ON ENGINEERING. 455
Strength means the power to sustain the internal pressure to
which the boiler may be subjected in ordinary use, and under
careful and intelligent management. To secure durability, the
material must be capable of resisting the chemical action of the
minerals contained in the water, and the boiler ought to be
designed so as to procure the least strain under the highest state
of expansion to which it may be subjected — be so constructed
that all the parts will be subjected to an equal expansion, con-
traction, push, pull and strain, and be intelligently and thoroughly
cared for after being put in use. These objects, however, can
only be obtained by the aid of a knowledge of the principles of
mechanics, the strength and resistance of materials, the laws of
expansion and contraction, the action of heat on bodies, etc.
The economy of a steam boiler is influenced by the following con-
ditions: cost and quantity of the material, design, character of the
workmanship employed in its construction, space occupied, capa-
bility of the material to resist the chemical action of the ingredi-
ents contained in the water, the facilities it affords for the
transmission of the heat from the furnace to the water, etc. The
safety of any structure depends on the designer's knowledge of
the principles of mechanics, the resistance of materials and the
action of bodies as influenced by the elements to which they are
exposed ; and -in the case of steam boilers, the safety depends on
the judgment of the designer, the quality of the material, the
character of the workmanship and the skill employed in the man-
agement. Safety is said to be incompatible with economy, but
this is undoubtedly a mistake, as an intelligent economy includes
permanence and seeks durability. Adaptability to the peculiar
purposes for which they are to be used is one of the first objects
to be sought for in the design and construction of any class of
machines, vessels or instruments, and it is undoubtedly this that
gave rise to the great variety of designs, forms and modifications
of steam boilers in use at the present day, which are, with very
456 HANDBOOK ON ENGINEERING.
few exceptions, the result of thought, study, investigation and
experiment.
FORMS OF STEAfl-BOILERS.
According to the well-known law of hydrostatics, the pressure
of steam in a close cylindrical vessel is exerted equally in all
directions. In acting against the circumference of a cylinder,
the pressure must, therefore, be regarded as radiating from the
axis, and exerting a uniform tensional strain throughout the
inclosing material.
Familiarity with steam machinery, more especially with boil-
ers, is apt to beget a confidence in the ignorant which is not
founded on a knowledge of the dangers by which they are contin-
ually surrounded ; while contact with steam, and a thoroughly
elementary knowledge of its constituents, theory and action, only
incline the intelligent engineer and fireman to be more cautious
and energetic in the discharge of their duties. Many regard
steam as an incomprehensible mystery ; and although they may
employ it as a power to accomplish work, know little of its
character or capabilities. Steam may be managed by common
sense rules as well as any other power ; but if the laws which
regulate its use are violated, it reports itself, and often in louder
tones than is pleasant. If steam-boilers in general were better
cared for than they are, their working age might be greatly in-
creased. Deposits of incrustation, small leaks and slight cor-
rosion, are too often neglected as matters of little consequence,
but they are the forerunners of expensive repairs, delay and
disaster.
SETTING STEAM-BOILERS.
While engineers differ very much in opinion respecting the best
manner of setting boilers, they all readily allow that the results
obtained, as regards economy of fuel and the generation of steam,
HANDBOOK QN ENGINEERING. 457
depend in a great measure on the arrangement of the setting.
Particularly is this the case with horizontal tubular boilers, and
there have been numerous plans introduced to obtain a maximum
of steam with a minimum of fuel. Some of the most practical
designs and best laid plans are frequently rendered useless for
want of knowledge on the part of those whose duty it is to exe-
cute or carry them out. This has perhaps been more frequently
the case as regards the setting of steam boilers than any other
class of machines, as it is customary for owners of steam boilers
to depend too much on the knowledge of masons and bricklayers ;
consequently, a great many blunders have been made which
necessitated changes in the size of gratebars, alteration of brick-
work, alteration of flues, chimney, etc., with a list of other annoy-
ances, such as insufficiency of steam, poor draught, or something
else. In setting or putting in boilers, all the surface possible should
be exposed to the action of the heat of the fire, not only that the
heat may be thus completely absorbed, but that a more equal ex-
pansion and contraction of the structure may be obtained. Long
boilers are often hung by means of loops riveted to the top of
them and connected to crossbeams and arches resting on masonry
above them, by means of hangers. This is a very .mischievous
arrangement, unless turn-buckles, or some other contrivance, are
used to maintain a regular strain on all the hangers, as long boil-
ers exposed to excessive heat are apt to lengthen on the lower
side and relieve the end hangers of any weight; consequently,
the whole strain is transmitted to the central hanger, which has a
tendency to draw the boiler out of shape — in many instances
inducing excessive leakage, rupture, and, eventually, explosion.
DEFECTS IN THE CONSTRUCTION OF STEAM-BOILERS.
The following cuts illustrate some of the mechanical defects
that impair the strength and limit the safety and durability of
458
HANDBOOK ON ENGINEERING.
steam boilers. All punched holes are conical, and unless the
sheets are reversed after being punched, so as to bring the
small sides of the holes together, it will be impossible to fill them
with the rivets. Fig. 251 shows the position of the rivet in the
hole without the sheets being reversed ; and it will be observed
that, as very little of the rivet bears against the material, the ex-
pansion and contraction of the boiler have a tendency to work it
loose. It is apparent that such a seam would not possess over
one-third the strength that it would if the holes in the sheets
Fig. 251.
Fig. 252.
258.
Fig. 254.
Fig. 255.
Fig. 256.
Showing positions of rivet in rivet hole.
were reversed and thoroughly filled with the rivet, as shown in
Fig. 252. Fig. 253 represents what is known in boilermaking
as a blind hole, which means that the holes do not come opposite
each other when the seams are placed together for the purpose of
riveting. Fig. 254 shows the position of the rivet in the blind hole
after being driven. It will be observed that the heads of the
rivet, in consequence of its oblique position in the hole, bear only
on one side, and that even the bearing is very limited, and
through the expansion and contraction of the boiler, is liable to
HANDBOOK ON ENGINEERING. 459
work loose and become leaky. Such a seam would be actually
weaker than that presented in Fig. 251. Fig. 255 shows the
metal distressed and puckered on each side of the blind hole in the
sheets, which is the result of efforts on the part of the boiler-
maker, by the use of the drift-pin, to make the holes correspond
for the purpose of inserting the rivet. Fig. 256 shows the metal
broken through by the same means. Now, it will be observed
that nearly all the above defects are the result of ignorance and
carelessness, showing a want of skill in laying out the work, as
well as a want of proper appliances for that purpose. The evils
arising from such defects are greatly aggravated by the fact that
they are all concealed, frequently defying the closest scrutiny, and
are only revealed by those forces which unceasingly act on boilers
when in use. Such pernicious mechanical blunders ought to be
condemned, as they are always the forerunners of destruction
and death. There can be no reason why boilers should not be
constructed with the same degree of 'accuracy, judgment and skill
as is considered so essential for all other classes of machinery.
IMPROVEMENTS IN STEAM BOILERS.
Until quite recently the steam boiler has undergone very little
improvement. This arose, perhaps, from the fact that men of
intelligence and mechanical genius directed their thoughts and
labors to something more inviting and less laborious than the
construction of steam boilers. Consequently, that branch of
mechanics was left almost entirely to a class of men that had not
the genius to rise in their profession or improve much in anything
they attempted. As a result ignorance, stupidity and a kind of
brute force were the predominant requirements in the construc-
tion of the steam boiler ; but within the past few years this state
of things has been changed, as some very important improvements
have been made, not only in the manufacture of the material of
which boilers are made, but also in the mode of constructing
460 HANDBOOK ON ENGINEERING.
them. The imposing, powerful and accurate- boiler machinery in
use at the present time is an evidence that the attention of emi-
nent mechanics and manufacturers is directed to the steam boiler,
and that in the future its improvement will keep pace with that of
the steam engine.
Boiler plate is now rolled of sufficient dimensions to form the
rings for boilers of any diameter with only one seam, obviating
the necessity of bringing riveted seams in contact with the fire;
as was usually the case in former times. In the manner of laying
off the holes for the rivets, accurate steel gauges have taken the
place of the old-fashioned wooden templet, thereby removing the
evils induced by blind holes, and obviating the necessity of using
the drift-pin. So, also, in the method of bending the sheets to
form the requisite circle — with a better class of machinery, the
work is now mo re accurately performed. The old process of chip-
ping is, in nearly all the large boilershops, superseded by planing
the bevels on the edge of the sheet, preparatory to calking. Recent
improvements in u calking " have resulted in perfect immunity from
the injuries formerly inflicted on boilers in that process.
In most establishments of any repute in this country, riveting is
done by machinery, which is (as is well known to all intelligent
mechanics) very much superior to hand riveting. It is only
small shops that enter into rivalry to secure orders and build
cheap boilers, using poor material and an inferior quality of
mechanical skill, that use the same old crude appliances — in
many cases the merest makeshifts — that were in use a quarter of
a century ago, and constructed without regard to any of the rules
of design that are considered so essential in appliances for the
construction of all other classes of machinery. Every engineer
should inform himself on the subject of the safe working pressure
of boilers, and when he finds the limit of safety has been reached,
he should promptly inform his employer and use his influence to
have the boiler worked within the bounds of safety.
HANDBOOK ON ENGINEERING. 461
To find the heating surface of a water tube boiler : —
Rule* — Add the combined outside area of the tubes in square
feet to one-half the area of the shell of the steam drum in square
feet and the sum will give the total heating surf ace 0
Example f* — What is the heating surface of a water tube
boiler having fifty tubes, each three inches outside diameter and
fifteen feet long, and the steam drum thirty-two inches in
diameter and fifteen feet long ?
Operation* — 3 X 3.1416 equals 9.4248 inches, the circumfer-
ence of one tube. 15 X 12 equals 180 inches the length of one
9.4248 X 180
tube. • JIT" " e(luals 11-781 square feet in one tube, and
11.781 X 50 equals 589.05 square feet of heating surface in fifty
32 X 3.1416
tubes. Then, ^ equals 8.3776 linear feet the circum-
ference of the steam drum and 8.3776 X 15 equals 125.664 square
125.664
feet of heating surface in steam drum, and 5 equals 62.832
square feet, half the heating surface of steam drum.
Then, 589.05 plus 62.832 equals 651.882 square feet, the total
heating surface. Answer.
STRENGTH OF RIVETED SEAflS.
The strength of a riveted seam depends very much upon the
arrangement and proportion of the rivets ; but with the best
design and construction, the seams are always weaker than the
solid plate, as it is always necessary to cut away a part of
the plate for the rivet holes, which weakens the plate in three
ways: 1st, by lessening the amount of material to resist the
strains ; 2d, by weakening that left between the holes ; 3d, by
disturbing the uniformity of the distribution of the strains.
462 HANDBOOK ON ENGINEERING.
COMPARATIVE STRENGTH OF SINGLE AND DOUBLE
RIVETED SEAMS.
On comparing the strength of plates with riveted joints, it will
be necessary to examine the sectional areas taken in a line through
the rivet holes, with the section of the plates themselves. It is
obvious that in perforating a line of .holes along the edge of a
plate, we must reduce its strength. It is also clear that the plate
so perforated will be to the plate itself nearly as the areas of their
respective sections, with a small deduction for the irregularities
of the pressure of the rivets upon the plate ; or, in other words,
the joint will be reduced in strength somewhat more than in the
ratio of its section through that line to the solid section of the
plate. It is also evident that the rivets cannot add to the strength
of the plates, their object being to keep the two surfaces of the
lap in contact. When this great deterioration of strength at the
joint is taken into account, it cannot but be of the greatest
importance that in structures subject to such violent strains as
boilers, the strongest method of riveting should be adopted. To
ascertain this, a long series of experiments was undertaken by
Mr0 Fairbairn. There are two kinds of lap joints, single and
double riveted. In the early days of steam-boiler construction,
the former were almost universally employed ; but the greater
strength of the latter has since led to their general adoption for
all boilers intended to sustain a high steam pressure. A riveted
joint generally gives way either by shearing off the rivets in the
middle of their length, or by tearing through one of the plates in
the line of the rivets.
In a perfect joint, the rivets should be on the point of shearing
just as the plates were about to tear ; but, in practice, the rivets
are usually made slightly too strong. Hence, it is an established
rule to employ a certain number of rivets per linear foot, which
for ordinary diameters and average thickness of plate, are about
HANDBOOK ON ENGINEERING. 463
six per foot or two inches from center to center ; for larger
diameters and heavier iron, the distance between the centers
is generally increased to, say 2 j- or 2i inches : but in such
cases it is also necessary to increase the diameter of the rivet,
for while |, or even J inch rivets will answer for small diameters
and light plate, with large diameters and heavy plate, experi-
ence has shown it to be necessary to use f to J rivets. If
these are placed in a single row, the rivet holes so nearly
approach each other that the strength of the plates is much
reduced ; but if they are arranged in two lines, a greater number
may be used, more space left between the holes and greater
strength aud stiffness imparted to the plates at the joint.
Taking the value of the plate before being punched, at 100, by
punching the plate it loses 44 per cent of its strength ; and, as a
result, single-riveted seams are equal to 56 per cent, and double-
riveted seams to 70 per cent of the original strength of the plate.
It has been shown by very extensive experiments at the Brooklyn
Navy Yard, and also at the Stevens Institute of Technology,
Hoboken, N. J., that double-riveted seams are from 16 to 20 per
cent stronger than single-riveted seams — the material and work-
manship being the same in both cases :
Taking the strength of the plate at " . 100
The strength of the double-riveted joint would then be . . 70
The strength of the single-riveted would be 56
To find the thickness of plates for the shell of a cylindrical
boiler for a required safe working pressure in pounds per square
inch : —
Rule* — Multiply the required pressure per square inch by the
radius of the shell in inches, and by the constant number 6 for
single riveted side seams, and divide the last product by the
tensile strength of the plates. For double riveted side seams use
the constant number 5 instead of 6.
Example J* — What should be the thickness of plates for a boiler
60 inches in diameter, with single riveted side seams, for a work-
464
HANDBOOK ON ENGINEERING.
ing pressure of 125 pounds per square inch, the tensile strength
of the plates being 60,000 pounds per square inch?
125 X 30 X 6
Operation* — -- 6Q QQQ -- equals .375 or 3/8 in. Answer.
Example 2* — What should be the thickness of plates for a
boiler 60 inches diameter, with double riveted side seams, for a
working pressure of 150 pounds per square inch, the tensile
strength of plates being 60,000 pounds per square inch.
150 X 30 X 5
Operation* — -- 60~000 - e(luals -375 or 3/8 in. Answer.
The following formulas* equivalent to those of the British
Board of Trade, are given for the determination of the pitch,
distance between rows of rivets, diagonal pitch, maximum pitch,
and distance from centers of rivets to edge of lap of single and
double riveted lap joints, for both iron and steel boilers: —
Let p = greatest pitch of rivets, in inches ;
n = number of rivets, in one pitch ;
jpd = diagonal pitch, in inches ;
d = diameter of rivets, in inches ;
T = thickness of plate, in inches;
V= distance between rows of rivets, in inches ;
E = distance from edge of plate to center of rivet, in inches.
TO DETERMINE THE PITCH.
•
Iron plates and iron rivets —
^X.7854Xtt f
P=- —%,— - + ef .
Example : First, for single-riveted joint —
Given, thickness of plate (T)=£ inch, diameter of rivet
(d) = £ inch. In this case, n = I. Required, the pitch.
Substituting in formula, and performing operation indicated.
Piteh = + f = 2.077 inches.
HANDBOOK ON ENGINEERING. 465
For double-riveted joint —
Given, t = £ inch, and d = $% inch. In this case, n = 2.
Then —
Pitch = (il)'X.7854X2 , _ 2>886 ^
^
For steel plates and steel rivets : —
28 X «P X » , .
P~- 28 XT + d"
Example, for single-riveted joint : Given, thickness of plate = \
inch, diameter of rivet — -^f inch. In this case, n = l.
Then —
Example, for double-riveted joint : Given, thickness of plate —
inch, diameter of rivet — J inch, n = 2. Then —
2 + = 2.85 inches.
FOR DISTANCE FROM CENTER OF RIVET TO EDGE OF LAP.
v 3X<*
E= ~^
Example : Given, diameter of rivet (d) =| inch ; required, the
distance from center of rivet to edge of plate.
E = ^^= 1.312 inches,
2
for single or double riveted lap joint.
FOR DISTANCE BETWEEN ROWS OF RIVETS.
The distance between lines of centers of rows of rivets for
double, chain-riveted joints (F) should not be less than twice the
diameter of rivet, but it is more desirable that V should not be
i 4* M •+ *
less than — - — •
466 HANDBOOK ON ENGINEERING .
Example under latter formula: Given, diameter of rivet — |
inch, then —
F^(4X|) + 1 = 2.25 inches.
For ordinary, double, zigzag -riveted joints,
V=^
10
Example : Given, pitch = 2.85 inches, and diameter of rivet = J
inch, then —
V (11 X 2.85 +4 X|) (2.85 +4 X |) ''
— — - = 1.
.„. . ,
487 inches.
DIAGONAL PITCH.
For double, zigzag-riveted lap joint. Iron and steel.
Example: Given, pitch = 2. 85 inches, and eZ — J inch, then —
j
MAXIMUM PITCHES FOR RIVETED LAP JOINTS.
For single-riveted lap joints, maximum pitch =(1.31 X
For double-riveted lap joints, maximum pitch =(2.62 X T) -f If.
Example: Given a thickness of plate = % inch, required, the
maximum pitch allowable.
For single-riveted lap joint, maximum pitch = (1.31 X i) +
If = 2.28 inches.
For double-riveted lap joint, maximum pitch = (2.62 X i) +
If = 2. 935 inches.
The following tables, taken from the handbook of Thomas W.
Traill, entitled "Boilers, Marine and Land, their Construction
HANDBOOK ON ENGINEERING.
467
and Strength," may be taken for use in single and double riveted
joints, as approximating the formulas of the British Board of
Trade for such joints : —
IRON PLATES AND IRON RIVETS.
DOUBLK-RIVKTED LAP JOINTS.
Thickness
of plates.
Diameter
of rivets.
Pitch of
rivets.
Center of
rivets to
edge of
plates.
Distance between rows
of rivets.
Zigzag
riveting.
Chain
riveting.
T
d
P
E
V
V
A
1
2.272
.937
1.145
1.750
32
tt
2.386
.984
1.202
1.812
f
n
2.500
1.031
. .260
1.875
it
.23
i2
2.613
1.078
.317
1.937
Jv
2.727
1.125
.374
2.000
1
i|
2.826
.171
.426
2.062
jj-
2.886
.218
.465
2.125
H
J
2.948
.265
.504
2.187
ft
3.013
.312
.544
2.250
if
Sf
3.079
.359
.585
2.312
1
3.146
.406
.626
2.375
ft
3.216
.453
.667'
2.437
1 3.284
.500
.709
2.500
fl
1A 3.355
.546
.751
2.562
1
1A 3.426
.593
.794
2.625
if
1A 3.498
.640
.836
2.687
1$
H 3.571
.687
1.879
2.750
fj
1A 3.645
.734
1.923
2.812
{
1A 3.718
.781
1.966
2.875
H
iA 3.793
.828
2.009
2.937
II
U 3.867
.875
2.053
3.000
ft
1A 3.942
.921
2.096
3.062
i
1A
4.018
1.968
2.140
3*125
On the following page, Fig. 257 shows a zigzag, and Fig. 258
a chain riveted joint.
468
HANDBOOK ON ENGINEERING.
[
I
- -f — t-4. -.- — I — - ...
I I
6 -<±>--
) O 4
Fig. 257. Zigzag rireted joint.
o -e-
Fig. 258. Chain riveted joint.
HANDBOOK ON ENGINEERING.
IRON PLATES AND IRON RIVETS.
SINGLE-KIVETED LAP JOINTS,
469
CD
__*—
Thickness of
plates.
Diameter of
rivets.
Pitch of
rivets.
Center of rivets to
edge of plates.
T
d
.P
E
«'
r
.524
.937
T
\
.600
.676
.753
.984
.031
.078
|
.829
.125
•
I
!4
.905
•171
•
v
1
1.981
.218
-
i
"L
2.036
.265
.
2.077
.312
**
\\
2.120
.359
*g
ft
2.164
.406
I
If
2.210
.453
2.256
.500
I
1
iA-
2
A
2.304
2.352
2.400
.546
.593
.640
]
I
2.450
.687
;
1
A
2.500
.734
',
1
2.550
.781
.
|
2.601
.828
'
2.652
1.875
1
s
2.703
2.755
1.921
1.968
470 HANDBOOK ON ENGINEERING.
STEEL PLATE AND STEEL RjVETS.
SINGLE-RIVETED LAP JOINTS.
. — t ------ , ---
\
O
ET
•
•?(""•
\E
Thickness of
plates.
Diameter of
rivets.
Pitch of
rivets.
Center of rivets
to edge of
plates.
r
<*
P
E
1
Ll
1.562
.031
A
i
i
1.633
.078
A
!
1.704
.125
H
i 1.775
.171
I
^
|
1.846
.218
¥
^
J-
1.917
.265
j
1.988
.312
if
-.
|
2.036
.359
|
-|
2.071
.406
iJ
i
i
2.108
.453
iff
f
2.146
.500
II
1-3
L2
2.186
.546
I*
2.227
.593
21
J
S
2.269
.640
Ll
1
2.312
.687
32
A
2.356
.734
|
j
s
2.400
.781
32
!
5
2.445
.828
1$
S
2.500
.875
32
12
a2
2.562
.921
|
1,
4
2.623
.968
II
ij
2.687
2.015
a
Q
2.750
2.062
HANDBOOK .ON ENGINEERING.
471
STEEL PLATE AND STEEL RIVETS.
DOUBLE -RIVETED LAP JOINTS.
Distance between rows
Center of
of rivets.
Thickness
Diameter
Pitch of
rivets to
of plates.
of rivets.
rivets.
edge of
plates.
Zigzag
Chain
riveting.
riveting.
T
d
P
E
'V
V
A
H
2.291
1.031
1.187
1.875
H
1 1
2.395
.078
1.240
1.937
I
i
2.500
.125
1.295
2.000
ii
II
2.604
.171
1.349
2.062
A
fl
2.708
.218
1.403
2.125
15.
3 2
• 32"
2.803
265
1.453
2.187
£
2 850
.312
1.487
2.250
32f
2.900
.359
1.522
2.312
¥
if
2.953
.406
1.558
2.375
t|
32
3.008
.453
1.595
2.437
1
1
3.064
.500
1.631
2.500
i
fA
3.122
3.181
.546
.593
1.669
1.707
2.562
2.625
23
32
h4
3.241
1.640
1.745
2.687
if
3.302
1.684
1.784
2.750
If
3.364
1.734
1.823
2.812
If
i-ig.
3.427
1.781
1.863
2.375
|1
i _ i .
3490
1.828
1.902T
2.937
£-
3.554
1.875
1.942
3.000
fl
r
3.618
1.921
1.981
3.062
le
i-^
3.683
1.968
2.021
3.125
tl
lit
3.748
2.015
2.061
3.187
1
11
3.814
2.062
2.102
3.250
I
On the following page Fig. 259 shows a zigzag riveted joint
and Fig. 260 a chain riveted joint with steel plate and steel
rivets.
472
HANDBOOK ON ENGINEERING.
;i*~- ?.
6
.•-i —
I
O
E
Fig. 259. Zigzag riveted joint.
-+-
I
I
O -0-
E
*
r
Fig. 260. Chain riveted joint.
HANDBOOK ON ENGINEERING. 473
STRENGTH OF STAYED AND FLAT BOILER SURFACES.
The sheets that form the sides of fire-boxes are necessarily
exposed to a vast pressure, therefore, some expedient has to be
devised to prevent the metal at these parts from bulging out.
Stay-bolts are generally placed at a distance of 4£ inches from
center to center, all over the surface of fire-boxes, and thus the
expansion or bulging of one side is prevented by the stiffness or
rigidity of the other. Now, in an arrangement of this kind, it
becomes necessary to pay considerable attention to the tensile
strength of the stay-bolts employed for the above purpose, since
the ultimate strength of this part of the boiler is now transferred
to them, it being impossible that the boiler plates should give way
unless the stay-bolts break in the first instance. Accordingly,
the experiments that have been made by way of test of the
strength of stay-bolts, possess the greatest interest for the practi-
cal engineer. Mr. Fairburn's experiments are particularly val-
uable. He constructed two flat boxes, 22 inches square. The
top and bottom plates of one were formed of £ inch copper, and
of the other, f inch iron. There was a 2£ inch water-space to each,
with ^| inch iron-stays screwed into the plates and riveted on the
ends. In the first box the stays were placed five inches from
center to center, and the two boxes tested by hydraulic pressure.
In the copper box, the sides commenced to bulge at 450 Ibs.
pressure to the sq. in. ; and at 815 Ibs. pressure to the sq. in.
the box burst, by drawing the head of one of the stays through
the copper plate. In the second box, the stays were placed at
4-inch centers; the bulging commenced at 515 Ibs. pressure to
the sq. in. The pressure was continually augmented up to 1,600
Ibs. The bulging between the rivets at that pressure was one-
third of an inch ; but still no part of the iron gave way. At
1,625 Ibs. pressure the box burst, and in precisely the same way
as in the first experiment — one of the stays drawing through the
474 HANDBOOK ON ENGINEERING.
iron plate and stripping the thread in plate. These experiments
prove a number of facts of great value and importance to the
engineer. In the first place, they show that with regard to iron
stay-bolts, their tensile strength is at least equal to the grip of
the plate.
The grip of the copper bolt is evidently less. As each stay,
in the first case, bore the pressure on an area of 5 x 5 — 25 square
inches, and in the second on an area 4x4 i= 16 sq. inches, the
total strains borne by each stay were, for the first, 815 x25 =
20,375 pounds on each stay; and for the second, 1,625 x 16 =
26,000 Ibs. on each stay. These strains were less, however, than
the tensile strength of the stays, which would be about 28,000
Ibs. The properly stayed surfaces are the strongest part of boil-
ers, when kept in good repair.
BOILER STAYS.
Advantage is usually taken of the self-supporting property of
the cylinder and sphere, which enables them, in most cases, to be
made sufficiently strong without the aid of stays or other support.
But the absence of this self-sustaining property in flat surfaces
necessitates their being strengthened by stays or other means.
Even where a flat or slightly dished surface possesses sufficient
strength to resist the actual pressure to which it is subjected, it is
yet necessary to apply stays to provide against undue deflection
or distortion, which is liable to take place to an inconvenient de-
gree, or to result in grooving, long before the strength of plates
or their attachments is seriously taxed. Boiler stays, in any
case, are but substitutes for real strength of construction. They
would be of no service applied to a sphere subject to internal
pressure ; and the power of resistance would be exactly that of
the metal to sustain the strain exerted upon all its parts alike.
The manner in which stays are frequently employed renders them
a source of weakness rather than an element of strength. When
HANDBOOK ON ENGINEERING.
475
the strain is direct the power of resistance of the stay is equal to
the weight it would sustain without tearing it asunder ; but when
the position of the stay is oblique to the point of resistance, any
calculation of their theoretic strength or value is attended with
certain difficulties. All boilers should be sufficiently stayed to
insure safety, and the material of which they are made, their
shape, strength, number, location and mode of attachment to the
boiler, should all be duly and intelligently considered. Boiler
stays should never be subjected to a strain of more than one-
eighth of their breaking strength. The strength of boiler stays
may be calculated by multiplying the area in inches between the
stays by the pressure in pounds per square inch.
Rule for finding the strain allowed on a diagonal boiler head
brace or stay ; also rule for finding the number of stays required
for a certain size crown sheet.
Iron stays should not be subjected to a greater stress than
from 7,000 to 9,000 pounds per square inch of section, and if
they are located obliquely, the diameter will need to be increased
an amount that depends on the angle of the stay to the shell.
Find the area in square inches to be supported by the stay, and
multiply it by the pressure per square inch, multiply. the product
by the length of the diagonal stay, and divide the result by the
perpendicular length from the flat surface to the end of the stay.
The quotient will be the stress on the stay, and to obtain the
diameter, divide the stress by the allowable stress per square inch
of section, and the quotient
mmmm * by .7854. The square root of
the last quotient will be the
diameter of the stay.
Thus, in the accompanying
diagram, we wish to find the
Fis. 261. Diagonal boiler stay, diameter of the diagonal stay
A, which supports an area 6" x 8" or 48 square inches. The
476 HANDBOOK ON ENGINEERING.
length of the stay is 25", and the perpendicular distance be-
tween the stayed surface and the end of the stay is 24.148".
The boiler pressure is 100 pounds gauge, so that the
pressure on the surface supported will be 48 x 100 or 4,800
pounds. We multiply 4,800 by 25 and divide the product by
24.148", which gives 4,970, nearly. The quotient of 4,970,
divided by 7,000 equals .71; .71, divided by .7854 equals
.9039, and the square root of this is .95 or .95", the diameter of
a stay that will support 48 square inches in the position shown.
A convenient formula for finding the diameter of oblique stays
D equals
cosB
D equals diameter of the stay.
A " area in square inches to be supported.
P " pressure per square inch.
L " safe load per square inch of stay section.
B " angle between the shell and the stay.
Using the preceding problem as an example and referring to
the same diagram, we have angle B equal to 15°, and all the other
dimensions as previously given. Therefore,
T. , Q J48 X 100
D equals 1.13A — °
\ 7C
7000 X .96593
The diameter of the stay, when the above is simplified, is
.9526", or practically 1". A rule for finding the pitch of stays
for any flat surface is given below.
J. A safe formula for the strength of stayed flat surfaces is
that given by Unwin's Machine Design. When the spacing of
the stays is desired, assuming that it is the same in each direc-
tion, we have,
a equals 3 t
N/Z
\2 p
HANDBOOK. ON ENGINEERING. 477
where a equals spacing of stays or rivets in inches,/ equals safe
working strength of the plate, t equals thickness of plate, and p
equals boiler pressure. Expressed as a rule, this reads : Divide
the safe strength of the plate by twice the pressure ; extract the
square root of the quotient and multiply the final result by three
times the thickness of the plate. The result will be the spacing
of the stays in inches. For example, boiler pressure 100 pounds,
plate 1/2 inch thick, safe strength of plate, 10,000 pounds per
square inch ; 2j9 equals 2 x 100 equals 200 ; f/2p equals 10000/200
equals 50; V^O equals 7.07; 3£ equals 3/2 equals 1-1/2 equals
1.5; 7.07x1.5 equals 10.6 for the spacing. In making such a
calculation care must be exercised not to assume too high values
for the strength of the plate. It is not safe to count on more
than 60,000 pounds for the strength of steel plates and 40,000
for iron. The working strength must be taken not higher than 1/6
of this, or 10,000 for steel and 6,666 for iron, and lower values
still would be better, say 9,000 for steel and 6,000 for iron.
2* The safe pressure for a boiler to carry, so far as the
flat, stayed surfaces are concerned, may be found from the
above formula by transposing it a little, as follows: —
9 Z2/
p equals ~^T
Now, applying this to the above example, we have p equals
9 x.52 x 10000 9 x .25 x 10000
2x110.25 2x110.25
22500
duction equals ^^-^ equals 102, or substantially the pressure
£i ZO»oO
assumed in the first example.
RIVETED AND LAP-WELDED FLUES.
The following table shall include all riveted and lap-welded
flues exceeding 6 inches in diameter and not exceeding 40 inches
in diameter not otherwise provided by law, as required by U. S. Gov.
478
HANDBOOK ON ENGINEERING.
CHART TO FIND STEAM PIPE NEEDED FOR HEATING
WATER IN TANKS
From careful experiments it is found that one square foot of
pipe, filled with steam and immersed in water, will condense
0.155 Ibs. of steam per hour for each Faht. degree of difference
between the temperature of the steam and the mean temperature
of the water. The Ideal Fitter.
Steam condensed per square root 01 pipe per hour in Lbs.
^ « N co co •* o to' to' t^ oo » o o -' e; n m •* o to £* £ oo » c o -j
g
II
I
Chart <fc A M
Example. — It is required to condense 500 Ibs. of steam per
hour in a pipe coil immersed in the water of a storage tank.
Temperature of steam in the pipe 220
Initial temperature of the water 40
Terminal temperature of the water 160
Mean temperature of the water * 100
Temp, difference between steam and water . . . 120
HANDBOOK ON ENGINEERING. 479
CHART TO FIND STEAM PIPE NEEDED FOR HEATING
WATER IN TANKS. — Continued
How many square feet of pipe must the coil contain?
Referring to Chart A, find the horizontal line marked 120
degrees temperature difference, which intersects the diagonal
line at the vertical line reading 18.60 Ibs. (the quantity of steam
one sq. ft. will condense in one hour), and as 500 Ibs. is to be
condensed divide 500 by 18.60, which gives 27 sq. ft. of pipe.
To condense 500 Ibs. in two hours will require half of 27, or 13.5
sq. ft.
These experiments were made with 1| inch black iron pipe.
Galvanized iron pipe would doubtless be better, as it would not
corrode so quickly. Brass pipe would be the best to use, not so
much for its higher conductivity as for its resistance to the action
of impure water.
I CHART TO FIND BOILER POWER REQUIRED TO HEAT
SWIMMING POOLS
In heating large bodies of water, large boilers are employed,
and when anthracite coal is burned in them, there will be avail-
able, from each pound of coal burned, 8333 B. T. U. or 8.6
Ibs. water will be evaporated, and on this basis the chart is con-
structed.
One square foot of grate will burn 8 Ibs. anthracite coal per
hour, whieh is the index for finding the size boiler required for a
given quantity of work.
The horizontal lines on Chart " B " represent water in U. S.
gallons, which may be increased by any suitable multiplier, pro-
viding the coal and steam required are increased in like propor-
tion.
The figures at the bottom of vertical lines show the eoal re-
quired, each line representing 10 Ibs., and those at the top the
480
HANDBOOK ON ENGINEERING.
steam generated by the combustion of the quantity of coal on the
same vertical line — each line representing 86 Ibs. of steam.
The diagonal lines represent the rise, or increase, in tempera-
ture of the water per hour in Faht. degrees.
Water in U. S. gallons
iiiiiiiili.
!(__ I ip
(X -----
\2&) ' *
:j; = f|||l:: N$
2 * "
5" 160 — j>:: — zifl;::
7c:-_ <: _,i_^^^7 7^/2
l:::i^j^z:i^^! 1290
t* \\\\\\\ ;Ei::;;!f:;z5
/f;::/::/^"^;:::;;:::: 1720
,^ ^: ^i_ ^
ji_^2.IJ_l2l^i *rJ
W ::-l::::-2f:-zf:2f
O OKn " ' ~
7_::z :_z!:zzL_ _: 2150 »
?. 250 •?; / I / 7
"•z.iz-;-?::: a.
HI - , '- _x S - f7 . 77 -
;:::z:: :::::::::::::::: s.
w > 300 -?--.p-^---^-_7 7
i:^:^?::::::::::::::::2580^
o^ S- — ?<: ' — -^--r ^-
/--/~^i±. 3010 |
o S350::::-:::^::;:::::-:::z
3 o 400^-"-"---?- /----/--^
i^:::::::::::::::::::::3440*
0 E. --^ — 7--- ---Z.___z_. z!^
78L"" §
J S «of--7--:
|! --3870g«
L . _ D
CO
g" S 5002:::_: :2.::::z:::::::^:
:_::":: :__::__:::_::>::: 4300 S.
S 5' 7 ;z---z~/z^~~~
:::::::::::::::::::::::::473o3
^ • :i::::::i::::S--Oi::::::
^ flo° _/ — z::2ij!
5160g
650 ^ 2_ tfi*" ~ I
__. ._ _:_:_--__:: 5580 ss
g ./ ?::!j^
QB --7--1-7
-.
:::::::::::::::::::::::. I6020S
.
860-:^:-::=:::::=:::::::::::
6880
Chart
HANDBOOK ON ENGINEERING. 481
CHART TO FIND BOILER POWER REQUIRED TO HEAT
SWinniNd POOLS — Continued
Example 1 . — What size boiler is required to warm the water
n a swimming pool, containing 130,000 gallons, from 40° to 80Q
n 24 hours.
By reference to Chart B it is found that the horizontal line
narked 1000 gallons intersects the 40 degree diagonal line at
;he 40 Ib. vertical line, showing that 40 Ibs. of coal are required
;o add 40 degrees to 1000 gallons of water. Then 100,000 gal-
ons will require 100 times as much coal, or 4000 Ibs. In the
jame manner 3000 gallons require 120 Ibs., and 30,000
gallons will require ten times 120, or 1200 Ibs., making a total
)f 5,200 Ibs. of coal which must be burned to add 40 degrees to
L30,000 gallons of water.
Having 24 hours in which to heat the pool, divide 5200 Ibs,
>y 24, and it is found that 216 pounds of coal must be burned
)er hour for 24 hours. Now as 8 Ibs. of coal is burned per
iour on one sq. ft. of grate, divide 216 by 8, which shows that
)oilers containing 27 sq. ft. of grate must be provided. Each
'rate section of the usual 36 inch Sectional Boiler contains 2
jq. ft. of grate and cast iron Sectional Boilers have one less
'rate section than the total number of sections in the boiler.
Co obtain the 27 sq. ft. of grate, select two which will have
14 sq. ft. in each.
HEATING POOLS BY STEAM COILS.
Example 2 — If the pool is to be heated by steam coils and
;he temperature of the steam is 215°, find the mean temperature
)f the water is 40 + 80 ^- 2 = 60° and 215 — 60 = 155
legrees temperature difference between steam and water.
Turn to Chart A, which shows that with this temperature
482 HANDBOOK ON ENGINEERING.
difference 1 sq. ft. of pipe will condense 24 Ibs. of steam per
hour, and as 216 Ibs. of coal must be burned per hour, find by
interpolation in Chart B tha'o 216 Ibs. of coal will evaporate
1857 Ibs. steam, which divide by 24 and find shall require in
round figures 78 sq. ft. of condensing pipe in the pool. The
boilers will be the same size as for water.
78 sq. ft. is equal to 180 linear feet of 1£ in. pipe, 156 ft. 1£
in., or 125 ft. of 2 in. If but 12 hours can be allowed to do the
work, double the hourly consumption of coal and steam and
furnish boilers of double the capacity required for 24 hours' time.
CHART TO FIND BOILER POWER REQUIRED TO HEAT
SWIMMING POOLS — Continued.
As there will now be twice as much steam to condense in an
hour, double the quantity of condensing coil.
There is, however, another factor which must not be overlooked.
In large bodies of water, warmed in the manner just described,
there will be a zone, of which the condensing pipe is the center,
where the mean temperature of the water will be much higher
than figured in the foregoing, unless artificial means are em-
ployed to agitate the water and keep it all at an even tempera-
ture. It will, therefore, be good practice to add at least 50 per
cent to the condensing coil when used in large bodies of still water.
CHART TO FIND TANK HEATER CAPACITY FOR RAISING
WATER IN TANKS TO A SPECIFIC TEMPERATURE.
Power in small tank heaters, 7000 B. T. U. per pound coal:
Size round grate in tank heaters 10" 12" 15" 18" 21" 24" 27" 30"
Average hard coal capacity, Ibs. 25 40 75 120180225 300 370
Average h'd coal available, Ibs. 20 32 60 96 145 180 240 300
Max coal consump'n per hr., Ibs. 4.4 6.310 14 16.325 32 40
(8 Ibs. persq. ft. grate per hr.)
Duration of fire, hrs. in decimals, 4.5 5.1 6. 6.8 6.9 7.2 7.5 7.5.
Example: What size tank heater running at maximum ca-
pacity will add 140 degrees to 120 gallons of water in one hour?
By referring to Chart " C" we find the 120 gallon horizontal
"
HANDBOOK ON ENGINEERING.
483
line intersects the 140 degrees temperature line at the 20 pound
vertical coal line, and a reference to data at bottom of Chart
" C " shows that a heater with 24-inch grate will burn 25 pounds
coal per hour running at maximum capacity, which would be the
correct size to select.
The figures on Chart " C " are based on the work being ac-
complished in one hour, and in the above example 20 pounds of
coal must be burned in one hour to produce the required energy,
but it is obvious that 20 pounds of fuel must be used whether
the work is done in one or ten hours. If the time is two hours,
select a heater that will burn 10 pounds per hour, or a 15-inch
grate. The 10-inch grate will do the work in 4* hours; the 12
inch grate in 4 hours.
POUNDS or ANTHBACrrt COAL RtQumco pen noun
POUNDS Of AyHMOTC tjOM, REQUIUCO Ptff MOU« .
Chart "C."
CHART TO FIND TANK HEATER CAPACITY FOR RAISING
WATER IN TANKS TO A SPECIFIC TEflPERATURE.
484 HANDBOOK ON ENGINEERING.
The vertical lines represent coal in pounds. The horizontal
lines represent water in gallons. The diagonal lines represent
temperatures.
DATA RELATING TO VENTILATION.
Loss of heat caused by —
First. B. T. U. necessary to warm air.
Second. B. T. U. absorbed by walls.
Third. B. T. U. absorbed by ceiling.
Fourth. B. T. U. absorbed by floor.
Fifth. B. T. U. absorbed by windows.
Sources of heat in rooms (Schuman, authority) : —
First. B. T. U. generated by occupants.
Second. B. T. U. generated by gas, lamps or candles.
Third. B. T. U. generated by heating apparatus.
An adult requires each hour for respiration and transpiration
215 cubic feet or 215x.077 = 165 pounds, and generates 290
B. T. U. of which 99 units are in form of vapor and 191 units
radiate to surrounding objects.
APPROXIflATE.
An adult vitiates per hour 2.15 cu. ft. air.
Each cubic ft. gas burned requires 8.5 cu. ft. air.
Each Ib. oil burned requires 150 cu. ft. air.
Each Ib. candles burned requires 160 cu. ft. air.
B. T. U. generated by an adult per hour, 191.
B. T. U. generated by burning l.cu. ft. gas, 600.
B. T. U. generated by burning 1 Ib. oil or candles, 15,000 to
18,000.
Average gas burner consumes approximately 4 cu. ft. gas per
hour, which equals 2400 B. T. U. per hour.
Each flame from oil lamp 430 to 515 B. T. U. per hour.
Each candle 454 to 545 B. T. U. per hour.
NOTE. — Above information is quoted from standard authorities.
Not guaranteed.
HANDBOOK -ON ENGINEERING.
485
Table of Mains and Branches
Main
1 in. will supply 2
IJin.
14 in.
2 in.
24 in.
3 in.
3£ in.
'4 in.
44 in.
5 in.
6 in.
7 in.
8 in.
Branch
fl
a
2
2
1
2
1
1
1
2
1
2
24
24
34
34
4
4
6
6
in.
in.
in.
in.
in.
in.
in.
in.
in.
and
and
or
and
and
and
and
and
and
1
1
1
1
1
1
1
1
1
1;
2
3
2
3
3
3
4
5
H
i
in
£i
in
in
in
in
in
Q.
n.
y
•)
'j
•3
')
•1
, or 1
, or 2
and 1
, or 2
or 1
cr 1
or 4
or 3
or 5
2
2
2
3
4
3
4
4
in.
in.
in.
in.
in.
in.
in.
in.
and 1
and 1
or 3
and 4
and 1
and 1
or 10
and 1
and 2
|in.
1 in.
llin.
14 in.
IJin.
14 in.
2 in.
2 in.
2£ in.
2£ in.
2 in.
2 in.
2 in.
Capacities of Wrought Iron Pipe
Inside diameter Inches
1
U
14
2
24
3
34
4
5
6
Length of Pipe ^
per square foot of >
2.9
2.3
2.0
1.6
1.32
1.09
0.95
0.84
0.68
0.57
external surface J
Square feet; surface \
per 1 lineal foot J
0.34
0.43
0.50
0.62
0.75
0.92
1.05
1.18
Ml
1.74
Expansion of Wrought Iron Pipe
Temperature
of the Air
when
Pipe is fitted
Length of
Pipe when
fitted
Length of Pipe when heated to
215°
265°
297°
338°
Zero
100 feet
Ft. In.
100 1.72
Ft. In.
100 2.12
Ft. In.
100 2.31
Ft. In.
100 2.70
32°
100 "
100 1.47
100 1.78
100 2.12
100 2.45
64°
100 "
100 1.21
100 1.61
100 1.87
100 2.19
486
HANDBOOK ON ENGINEERING.
firmly riveted , with good and substantial rivets, through the hubs
of such flanges ; and no such hubs shall project from such flanges
less than 2 inches in any case.
Steam pipes of iron or steel, when lap- welded by hand or
machine, with their flanges welded on, shall be tested to a hydro-
static pressure of at least double the working pressure of the
steam to be carried and properly annealed after all the work
requiring fire is finished. When an affidavit of the manufacturer
is furnished that such test has been made and annealed, they may
be used for power purposes.
WROUGHT IRON WELDED PIPE.
DIMENSIONS, WEIGHTS, ETC., OF STANDARD SIZES FOR STEAM, GAS,
WATER, OIL, ETC.
1 inch and below are butt- welded, and tested to 300 pounds
per square inch hydraulic pressure.
1J inch and above are lap-welded, and tested to 500 pounds
per square inch hydraulic pressure.
i
5
utside Di-
ameter.
xternal Cir-
jumference.
o c3 *""£
li
I*
xternal
Area.
Bngth of
Pipe con-
taining one
cubic foot. 1
reight per
:t. of length.
o.of threads! 1
per inch of
screw.
intents in
*Gallons
per foot.
"eight of
Water per
foot of
Length.
O
0
H
h-3
H
3
j£-
K
O
&
Inch.
Inches.
Inches.
Feet.
Inches.
Inches.
Feet.
Lbs.
Lbs.
§
40
1.272
9 44
.012
.129
2500.
.24
27
.0006
.005
I
.54
1.696
7.075
049
229
1385.
.42
18
.0026
.021
.67
2 . 121
5.657
.110
.358
751.5
.56
18
.0057
.047
I
.84
2.652
4 502
.196
.554
472.4
.84
14
.0102
.085
1.05
3 299
3.637
.441
.866
270.
1.12
14
.0230
.190
I1
1 31
4.134
2.903
.785
1.357
166.9
1.67
iii
.0408
.349
}j
1 66
5.215
2.301
1 227
2.164
96.25
2.25
.0638
.527
1.9
5.969
2.01
1.767
2.835
70.65
2.69
jj i
.0918
.760
2
2.37
7.461
1.611
3.141
4.430
42.36
3.66
iis
.1632
1.356
2»
2.87
9.032
1.328
4 908
6.491
30.11
5.77
8
.2550
2.116
3
3 5
10.996
1 091
7.068
9.621
19.49
7.54
8
.3673
3.049
34
4.
12.566
.955
9.621
12.566
14.56
9.05
8
.4998
4.155
4
4.5
14.137
.849
12.566
15.904
11.31
10.72
8
.6528
5.405
5.
15.708
.765
15.904
19.635
9.03
12.49
8
.8263
6.851
5
5 56
17.475
.629
19.635
24.299
7.20
14.56
8
1.020
8.500
6
6.62
20.813
.577
28.274
34.471
4.98
18.76
8
1.469
12.312
7
7.62
23 954
.505
38.484
45.663
3.72
23.41
8
1.999
16.662
8
8.62
27.096
.444
50.265
58.426
2.88
28.34
8
2.611
21.750
9
9 68
30.433
.394
63.617
73.715
2,26
34.67
8
3.300
27.500
10
10.75
33.772
.355
78.540
90.792
1.80
40.64
8
4.081
34.000
HANDBOOK ON ENGINEERING.
487
PULSATION IN STEAfl-BOILERS.
Pulsation in steam-boilers, though not discernible to the eye,
as in animated nature, goes on intermittently in some boilers
whenever they are in use. It is induced by weakness and want
of capacity in the boiler to supply the necessary quantity of
steam, and sometimes is caused by the boiler being badly de-
signed, thereby admitting of a great disproportion between the
heating-surface and steam-room. Boilers are frequently found in
factories that were originally not more than of sufficient capacity
to furnish the necessary quantity of steam, but, as business
increased, it became necessary to increase the pressure and also
the speed of the engine ; or, perhaps to replace it with a larger
one, which has to be supplied with steam from the same boiler.
The result is, each time the valve opens to admit steam to the
cylinder, about one-third of the whole quantity in the boiler is
admitted, thus lowering the pressure ; the next instant, under the
influence of hard firing, or, perhaps, a forced draught, the steam
is brought to the former pressure, and so on ; this lessening and
increasing the pressure continues while the engine is in motion,
which has an effect on the boiler similar to the breathing of an
animal.
The strains induced By this pulsation are transmitted to the
weakest places, viz., the line of the rivet holes, and that marked
by the tool in the process of
calking ; the result is, the plate
is broken in two, as shown in
the above cut. The manner in
which the break takes place
may be illustrated by filing a
small nick, or drilling a small
hole, in a piece of hoop or band-
iron, and then bending back
Fig. 262. Cracked plate.
488
HANDBOOK ON ENGINEERING.
and forth, when it will be discovered that the material will break
just at that point, however slight the nick or small the hole may
be. Pulsation is frequently very severe in the boilers of tug-
boats when commencing to start a heavy tow, and also in loco-
motives when starting long trains. Some frightful explosions of
the boilers of tug-boats and locomotives have occurred under
such circumstances. Pulsation, if permitted to continue, is sure
to effect the destruction of the boiler. It is always made mani-
fest by the vibrations of the pointers on steam gauges, or an
unsteadiness in the mercury column. It may be remedied, to a
certain extent, by adding a larger steam dome, but this has a
tendency to weaken the boiler and render it more unsafe. The
only sure preventive of such a silent and destructive agent is to
have the boiler of sufficient capacity in the first place.
WEIGHT OF SQUARE AND ROUND IRON PER LINEAR FOOT.
SIDE
OR
DIAM.
Weight,
Square.
Weight,
Round.
SIDE
OR
DIAM.
Weight,
Square.
Weight.
Round.
SIDE
OR
DIAM.
Weight,
Square.
Weight,
Round.
iV
.013
.01
2
13.52
10.616
5
84.48
66.35
?
.053
.041
i
15.263
11.988
*
93.168
73.172
iV
.118
.093
17.112
13.44
I
102.24
80.304
1
.211
,165
i
19.066
14.975
1
111.756
87.776
.475
.373
I
21.12
16.588
I
.845
.663
i
23.292
18.293
6
121.664
95.552
1.32
1.043
i
25.56
20.076
\
132.04
103.704
1
1.901
1.493
i
27.939
21.944
i
142.816
112.16
I
2.588
2.032
154.012
120.96
3
30.416
23.888
i
3.38
2.654
i
35.704
28.04
7
165.632
130.048
I
4.278
3.359
*
41.408
32.515
\
177.672
139.544
5.28
4.147
47.534
37.332
i
190.136
149.328
1
6.39
5.019
203.024
159.456
£
7.604
5.972
4
54.084
42.464
$
8.926
7.01
i?
61.055
47.952
8
216.336
169.856
1
10.352
8.128
h
68.448
53.76
1
11.883
9333
\
76.264
59.9
9
273.792
215.04
HANDBOOK ON ENGINEERING. 489
WATER COLUHNS.
Every boiler should be equipped with a safety water column.
Next to keeping the steam pressure within the limits of safety,
the most important point to be observed in operating steam boilers
is the maintenance of the proper water level. If the water level
is too low, there is danger of burning the tubes and plates and?
perhaps, of wrecking the boiler ; if it is too high, water is liable to
be carried along with the steam and cause damage in the engine,
while a constant variation in the water level produces a waste of fuel
and unsteady pressure, and impairs the life of the boiler. Safety
water columns have been devised for the purpose of insuring owners
of steam boilers against accidents of this kind. They are so ar-
ranged that any variation in the water level beyond reasonable lim-
its will be loudly proclaimed by means of a suitable steam whistle.
STEAM-GAUGES.
The object of the steam-gauge is to indicate the steam pressure
in the boiler, in order that it may not be increased far above that
at which the boiler was originally considered safe ; and it is as a
provision against this contingency that a really good gauge is a
necessity where steam is employed, for no guide at all is vastly
better than a false one. The most essential requisites of a good
steam-gauge are, that it be accurately graduated, and that the
material and workmanship be such that no sensible deterioration
may take place in the course of its ordinary use. The pecuniary
loss arising from any considerable fluctuation of the pressure of
steam has never been properly considered by the proprietors of
engines. If steam be carried too high, the surplus will escape
through the safety-valve, and all the fuel consumed to produce
such excess is so much dead loss. On the other hand, if there be
at any time too little steam, the engine will run too slow, and
every lathe, loom, or other machine driven by it, will lose its
speed and, of course, its effective power in the same pro-
490 HANDBOOK ON ENGINEERING.
portion. A loss of one revolution in ten at once reduces the pro-
ductive power of every machine driven by the engine ten per cent,
and loses to the proprietor ten per cent of the time of every
workman employed to manage such machine. In short, the loss
of one revolution in ten diminishes the productive capacity of the
whole concern ten per cent, so long as such reduced rate con-
tinues ; while the expenses of conducting the shop (rent, wages,
insurance, etc.) all run on as if everything was in full motion.
A variation to this amount is a matter of frequent occurrence,
and is, indeed, unavoidable, unless the engineer is afforded
facilities to prevent it. A very little reflection will satisfy any
one that it must be a very small concern, indeed, in which a half-
hour's continuance of it would not produce a result more than
enough to defray the cost of a very expensive instrument to pre-
vent it. If the engineer, to avoid this loss, keeps a surplus of
steam constantly on hand, he is constantly wasting the steam,
and consequently, fuel, thus incurring another loss, which
though less alarming than the first will yet be serious and render
any instrument most desirable which can prevent it. It is, there-
fore, of great importance to the proprietors of engines to have an
instrument which can constantly indicate the pressure in the
steam boilers with accuracy. This would enable the engineer to
keep his steam at a constant pressure, thus avoiding waste of fuel
on the one hand, and the still more serious loss of the productive
power of the shop on the other. An instrument, therefore, con-
stantly indicating the pressure of steam, reliable in its character,
and, with ordinary care, not subject to derangement, is evidently
a desideratum both to the engineer and proprietor. The impor-
tance of such an instrument, as a preventive of explosion, and of
the frightful consequences to life and limb and ruinous pecuniary
results of such disaster, is obvious on the slightest consideration ;
but the value of the instrument, in the economical results of its
daily use is by no means properly appreciated.
HANDBOOK ON ENGINEERING. 491
SAFETY-VALVES.
The form and construction of this indispensable adjunct to the
steam boiler are of the highest importance, not only for the pres-
ervation of life and property, which would, in the absence of that
means of " safety" be constantly jeopardized, but also to secure
the durability of the steam boiler itself. And yet, judging from
the manner in which many things called safety-valves have been
constructed of late years, it would appear that the true principle
by which safety is sought to be secured by this most valuable ad-
junct is either not well understood, or is disregarded by many
engineers and boiler makers.
Boiler explosions have in many cases occurred when, to all
appearances, the safety-valves attached have been in good work-
ing order ; and coroners' juries have not unfrequently been
puzzled, and sometimes guided to erroneous verdicts by scientific
evidence adduced before them, tending to show that nothing was
wrong with the safety-valves, and that the devastating catastro-
phies could not have resulted from overpressure, because in such
case the safety-valve would have prevented them. It is supposed
that a gradually increasing pressure can never take place if the
safety-valve is rightly proportioned and in good working order.
Upon this assumption, universally acquiesced in, when there is no
accountable cause, explosions are attributed to the u sticking "
of the valves, or to "bent" valve-stems, or inoperative valve-
springs. As the safety-valve is the sole reliance, in case of neg-
lect or inattention on the part of the engineer or fireman, it is
important to examine its mode of working closely. Safety-valves
are usually provided with a spindle or guide-pin, attached to the
under side, and passing through a cross-bar within the boiler,
directly under the seating of the valve, which may be seen in
Figr, 263. Lever and weight safety-valve,
corresponding to the pressure required in the boiler. Another
difficulty is that the safety-valve levers sometimes get bent, and
the weight, consequently hangs on one side of the true center ;
this, it will be seen, causes the valve to rest more heavily on one
side than on the other, and the greater the added weight the
greater the difficulty. The seats of safety-valves should be
examined frequently to see that no corrosion has commenced ; as
valves, especially if leaky, become corroded and often stick fast,
so that no little force is required to raise them. If, when a
safety-valve is properly weighted, it should be found leaking, do
not put on extra weights, but immediately make an examination,
and in all probability the seat or guide-pin will be found cor-
roded, or there will be foreign matter between the valve and its
HANDBOOK ON ENGINEERING. 493
seat. By taking the lever in the hand and raising it from its seat
a few times, any substance that may have kept it from its seat
will be dislodged ; or it may turn out on examination that the
lever had deviated from some cause from a true center. Such
difficulties can be easily righted, but extra weight should never be
added, as it only aggrevates the trouble instead of remedying it.
When the weight of the safety-valve is set on the lever at safe
working pressure, or at the distance from the fulcrum necessary
to maintain the pressure required to work the engine, any
extra length of lever should then be cut off as a precaution,
to prevenf the moving out of the weight on the lever, for the
purpose of increasing the pressure, as, while the lever remains
sufficiently long, the weight can be increased to a dangerous
extent without attracting any attention ; while if the lever is cut
off at the point at which the safe working pressure is designated,
any extra increase of pressure can only be accomplished by add-
ing more weight to the lever, which is tolerably sure to attract the
attention of some one interested in the preservation of the lives
and property of persons in the immediate vicinity.
The bolts that form the connection between the lever, fulcrum
and valve-stem should be made of brass, in order to prevent the
possibility of corrosion, "sticking " or becoming magnetized, as
it is termed ; and for the same reason, the valve and seat should
be made of two different metals. When safety-valves become
leaky they should be taken out and reground on their seats, for
which purpose pulverized glass, flour of emery, or the fine grit or
mud from grinding stone troughs are the most suitable material ;
but whether they leak or not, they should be taken apart at least
once a year and all the working parts cleaned, oiled and read-
justed. The safety-valve is designed on the assumption that it
will rise from its seat under the statical pressure in the boiler
when this pressure exceeds the exterior pressure on the valve, and
that it Will remain off its seat sufficiently far to permit all the
494 HANDBOOK ON ENGINEERING.
steam which the boiler can produce to escape around the edges of
the valve. The problem then to be solved is : What amount of
opening is necessary for the free escape of the steam from the
boiler under a given pressure? The area of a safety-valve
is generally determined from formulae based on the velocity
of the flow of steam under differet pressures, or upon the
results of experiments made to ascertain the area necessary for
the escape of all the steam a boiler could produce under a given
pressure. But as the fact is now generally recognized by
engineers that valves do not rise appreciably from their seats
under varying pressures, it is of importance that in practice
the outlets round their edges should be greater than those based
on theoretical considerations. The next point to be considered is
how high any safety valve will rise under the influeuce of a given
pressure! This question cannot be determined theoretically, but
has been settled conclusively by Burg, of Vienna, who made
careful experiments to determine the actual rise of safety-valves
above their seats. His experiments show that the rise of the
valve diminishes rapidly as the pressure increases.
'
TABLE SHOWING THE RISE OF SAFETY-VALVES, IN PARTS OF AN
INCH, AT DIFFERENT PRESSURES.
Lbs, Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs.
12 20 35 45 50 60 70 80 90
-ffV sV iV li? ifa yis
4*8 A -
Taking ordinary safety-valves, the average rise for pressures
from 10 to 40 pounds is about ^ of an inch from 40 to 70
pounds about ¥L, and from 70 to 90 pounds about ^^ of an
inch. The following table gives the re'sult of a series of experi-
ments made at the Novelty Iron Works, New York, for the pur-
pose of determining the exact area of opening necessary for
HANDBOOK ON ENGINEERING.
495
safety-valves for each square foot of heating surface, at different
boiler pressures.
TABLE.
Vi «
fl*bC
^ <D
342 be
^ 0?
p3 43 be
HH O S?
cS vg
S O aj
"" ^.g
rs o <£
§P
§«|
OX> t,
o * «
o&%
MCS ^
•g
^ •
^a
« . ®
d * £"
•g tiH
rt OD P.
'C oW
a«>1<
?gw
5-g S
O «M <M
•S^S w
O ** «M
5-og
fl S
o> 3 £
"-• d ^®
o p |
^ .OgJ
.gi
*- "° ®
S PH^
°MS«2
pft*
0|H£*«2
sa^
®^faj
W) ®
g££g
t« V
ea -t-Li
tn C
eg • • ^
£.5 "5
2-S5
^000200
2-S5
£(/3{fiOT
s
^
fi;
^
PH
^
0.25
.022795
10
.005698
70
.001015
0.5
.021164
20
.003221
80
.000892
1
.018515
30
.002244
90
.000796
2
.014814
40
.001 ; 23
100
.000719
3
.012345
50
.001398
150
.000481
4
.010582
60
.001176
200
.000364
5
.009259
TABLE OF COMPARISON BETWEEN EXPERIMENTAL RESULTS AND
THEORETICAL FORMULAE.
Boiler Pressure, 45 pounds.
Boiler Pressure, 75 pounds.
Heating
Surface.
Area of open-
ing found by
experiment.
Area of open-
ing according
to formulae.
Heating
Surface.
Area of open-
ing fonnd by
experiment..
Area of open-
ing according
to formulae.
Sq. Ft.
Sq. Ins.
Sq. Ins.
Sq. Ft.
Sq. Ins.
Sq. Ins.
100
. .089
.09
100
.12
.12
200
.180
.19
200
.24
.24
500
.45
.48
500
.59
.59
1000
.89
.94
1000
1.20
1.18
2000
1.78
1.90
2000
2.40
2.37
5000
4.46
4.75
5000
6.00
6.95
496 HANDBOOK ON ENGINEERING.
Now, if we compare the area of openings, according to these
experiments, with Zeuner's formula which is entirely theoretical,
it will be observed that the results from the two sources are
almost identical, or so nearly so as not to make any material
difference. In the absence of any generally recognized rule, it
is customary for engineers and boiler-makers to proportion safety-
valves according to the heating surface, grate surface, or horse-
power of the boiler. While one allows one inch of area of
safety-valve to 66 square} feet of heating surface, another gives
one-inch area of safety-valve to every four-horse power ; while a
third proportion's his by the grate surface — it being the custom
in such cases to allow one inch of safety-valves to 2 square
feet of grate surface. This latter proportion has been proved by
long experience and a great number of accurate experiments to,
be capable of admitting of a free escape of steam without allowing
any material increase of the pressure beyond that for which the
valve is loaded, even when the fuel is of the best quality, and the
consumption as high as 24 pounds of coal per hour per square
foot of grate surface, providing of course that all the parts are
in good working order. It is obvious, however, that no valve
can act without a slight increase of pressure, as, in order to lift
at all, the internal pressure must exceed the pressure due to the
load.
The lift of safety-valves, like all other puppet valves, de-
creases as the pressure increases, but this seeming irregularity is
but what might be required of an orifice to satisfy conditions in
the flow of fluids, and may be explained as follows : A cubic foot
of water generated into steam at one-pound pressure per square
inch above the atmosphere, will have a volume of about 1,600
cubic feet. Steam at this pressure will flow into the atmosphere
with a velocity of 482 feet per second. Now suppose the steam
was generated in five minutes, or in 300 seconds, and the area of
an orifice to permit its escape as fast it is generated be re-
HANDBOOK ON ENGINEERING. 497
quired, 1600 x 144 -*- (482 x 300) will give the area of the orifice,
1| square inches. If the same quantity of water be generated into
steam at a pressure of 50 pounds above the atmosphere, it will
possess a volume of 440 cubic feet and will flow into the atmos-
phere with a velocity of 1791 feet per second. The area of an
orifice, to allow this steam to escape in the same time as in the
first case, may be found as follows: 440 x 144 -r- (1791 x 300),
the result will be ^ square inches, or nearly £ of a square inch, the
area required. It is evident from this that a much less lift of the
same valve will suffice to discharge the same weight of steam
under a high pressure than under a low one, because the steam
under a high pressure not only possesses a reduced volume, but a
greatly increased velocity ; it is also obvious from these consider-
ations, that a safety-valve, to discharge steam as fast as the boiler
can generate it, should be pioportioned for the lowest pressure.
RULES.
Rule, — For finding the weight necessary to put on a safety-
valve lever when the area of valve, pressure, etc., are known:
Multiply the area of valve by the pressure in pounds per square
inch ; multiply this product by the distance of the valve from the
fulcrum ; multiply the weight of the lever by one-half its length
(or its center of gravity) ; then multiply the weight of valve and
stem by their distance from the fulcrum ; add these last two prod-
ucts together, subtract their sum from the first product, and
divide the remainder by the length of the lever ; the quotient will
be the weight required.
EXAMPLE.
Area of valve, 12 in 65 13 8
Pressure, 65 Ibs. 12 16 4
Fulcrum, 4 in. . 780 208 62
82
498 HANDBOOK ON ENGINEERING.
Length of lever, 32 in 4 13
Weight of lever, 13 Ibs
Weight of valve and stem, 8 Ibs. . . . . 3120 208
240 32
32)2880 240
90 Ibs.
Rule for finding the pressure per square inch when the area of
ralve, weight of ball, etc., are known: Multiply the weight of ball
by length of lever, and multiply the weight of lever by one-half its
length (or its center of gravity) ; then multiply the weight of
valve and stem by their distance from the fulcrum. Add these
three products together. This sum, divided by the product of
the area of valve, and its distance from the fulcrum, will give the
pressure in pounds per square inch.
EXAMPLE.
Area of valve, 7 in 50 12 6
Fulcrum, 3 in 30 15 3
Length of lever, 30 in 1500 180 18
Weight of lever, 12 Ibs 180
Weight of ball, 50 Ibs 18 7
Weight of valve and stem, 6 Ibs
21)1698 3
80.85 Ibs. 21
Rule for finding the pressure at which a safety-valve is
weighted when the length of the lever, weight of ball, etc., are
known : Multiply the length of lever in inches by the weight of
ball in pounds ; then multiply the area of valve by its distance
HANDBOOK ON ENGINEERING. 499
from the fulcrum ; divide the former product by the latter ; the
quotient will be the pressure in pounds per square inch.
EXAMPLE.
Length of lever, 24 in 52 7
Weight of ball, 52 Ibs 24 3
Fulcrum, 3 in. . . 208 21
Area of valve, 7 in 104
21)1248
59. 42 Ibs.
The above rule, though very simple, cannot be said to be
exactly correct, as it does not take into account the weight of the
lever, valve and stem.
Rule for finding center of gravity of taper levers for safety-
valves : Divide the length of lever by two (2) ; then divide
the length of lever by six (6), and multiply the latter quotient
by width of large end of lever less the width of small end,
divided by width of large end of lever plus the width of small end.
Subtract this product from the first quotient, and the remainder
will be the distance in inches of the center of gravity from large
end jf lever.
EXAMPLE.
Length of lever 36 in.
Width of lever at large end 3 c
Width of lever at small end 2 '
36 divided by 2 = 18 minus 1,2 = 36.8 in. 36 divided by 6 =
6X1=6 divided by 5 = 1.2.
Center of gravity from large end, 16.8 in.
The safety-valve has not received that attention from engi-
neers and inventors which its importance as a means of safety
500 HANDBOOK ON ENGINEERING.
so imperatively deserves. In the construction of most other
kinds of machinery, continual efforts have been made to secure
and insure accuracy ; while in the case of the safety-valve, very
little improvement has been made either in design or fitting. It
is difficult to see why this should be so, when it is known that
deviations from exactness, though trifling in themselves, when
multiplied, not only affect the free action and reliability of
machines, but frequently result in serious injury, more partic-
ularly in the case of safety-valves.
Safety-valves should never be made with rigid stems, as, in
consequence of the frequent inaccuracy of the other parts, the
valve is prevented from seating, thereby causing leakage ; as a
remedy for which, through ignorance or want of skill, more
weight is added on the lever, which has a tendency to bend
the stem, thus rendering the valve a source of danger instead
of a means of safety. The stem should, in all cases, be fitted
to the valve with a ball and socket joint, or a tapering stem
in a straight hole, which will admit of sufficient vibration to
accommodate the valve to its seat. It is also advisable that
the seats of safety-valves, or the parts that bear, should be as
narrow as circumstances will permit, as the narrower the seat
the less liable the valve is to leak, and the easier it is to repair
when it becomes leaky.
All compound or complicated safety-valves should be avoided,
as a safety-valve is, in a certain sense, like a clock — any
complication of its parts has a tendency to affect its reliability
and impair its accuracy.
It has been too much the custom heretofore for owners of steam
boilers to disregard the advice and suggestions of their own en-
gineers and firemen, even though men of intelligence and experi-
ence, and to be governed entirely by the advice of self-styled
experts and visionary theorists.
HANDBOOK ON ENGINEERING.
501
TABLE OF HEATING SURFACE IX SQUARE FEET IN HORI-
ZONTAL TUBULAR BOILERS.
Diam. of Boiler in inches
24
30
32
34
36
38
40
*2
44
48
f Heating surface of shell
per foot of length.
4.19
5.24
5.57
5.93
6.28
6.63
6.98
7.73
7.68
8.38
Diameter of Tube or Flue
in inches.
2
24
3
34
4
44
5
6
7
8
Whole External Heating
surface per foot length.
.524
.655
.785
.916
1.05
1.18
1.31
1.57
1.83
2.09
60
52
54
56
58
60
62
64
66
68
70
72
8.73
9.08
9.42
9.77
10.12
10.47
10.82
11.17
11.52
11.87
12.22
12.57
9
10
11
12
13
14
15
16
17
18
19
20
2.36
2.62
2.88
3.14
3.40
3.66
3.93
4.19
4.45
4.71
4.96
5.24
CENTRIFUGAL FORCE.
The centrifugal force of a body depends upon its weight Win
pounds ; distance R in feet it is from the center of rotation, and
the number of revolutions N it makes about that center each
WEN*
minute and equals — 9933 — *
Multiply the weight in pounds by radius in feet, by square
of number of revolutions, and divide by 2933 = centrifugal force
in pounds.
502 HANDBOOK ON ENGINEERING.
CHAPTER XVIII.
THE WATER TUBE BOILER.
The water tube boiler has been a growth of many years
and of many different minds. There are some two and a
half million horse-power in daily service in the United States
alone, and the number is rapidly increasing. Large orders for
this type of boiler have often been repeated, adding proof that its
principles are correct and appreciated by those having them in
use and in charge. This being the case, purchasers should note
well the points of difference in the various water tube boilers
claiming their attention, and particularly see that the claims
made for them are embodied in their actual construction. The
general principles of construction and operation of this class of
steam boilers are now well known to engineers and steam users.
In selecting a water tube boiler there are several vital points to
be considered : —
1st. Straight and smooth passages through the headers of ample
area, insuring rapid and uninterrupted circulation of the water.
2d. The baffling of the gases (without throttling or impeding
the circulation of the water) in such a way that they are com-
pelled to pass over every portion of the heating surface.
3d. Sufficient liberating surface in the steam drums to
insure dry steam, with large body of water in reserve to draw
from.
4th. A steam reservoir or steam drum.
5th. Simplicity in construction ; accessibility for cleaning and
inspection.
6th. A header, which in its design provides for the unequal
expansion and contraction.
HANDBOOK ON ENGINEERING.
503
Fig. 264. O'Brien horizontal safety water tube boiler.
Manufactured by the John O'Brien Boiler Works Company,
of St. Louis, U. 8. A.
This type of water tube boiler when provided with a cross-drum
to reduce the head room required is adapted to, and is oftentimes
used in heating plants.
Down draft furnace* — A great many of these boilers are fit-
ted with the down draft furnaces, and the above illustration shows
the style of same, together with the manner in which they are
connected.
A full and complete description of these furnaces is given on
page 522.
Description* — In construction, this type of boiler consists
504 HANDBOOK ON ENGINEERING.
simply of a front and rear water leg or header, made approx-
imately rectangular in shape, overhead combination steam and
water drum or drums and with circulating water tubes, as
shown in cut, which extend between and connect both front and
rear headers, being thoroughly expanded into the tube sheets.
The tubes are inclined on a pitch of one inch to the foot and the
rear header being longer than the front one, the overhead drum
connecting both headers lies perfectly level when the boiler is set
in position. The connection of the headers with the combined
steam and water drum is made in such a manner as to give prac-
tically the same area as the total area of the tubes, so there is no'
contraction of area in the course of circulation ; and extending
between and connecting the inside faces of the water legs,
which form end connections between these tubes and the com-
bined steam and water drums or shells, placed above and parallel
with them, also a steam drum above these, assures absolutely dry
steam and a large steam space, also a large water space. The water
legs are made larger at the top, about 11 inches wide, and at the
bottom about 7 inches wide, which is a great advantage, allowing
the globules of steam to pass quickly up the water legs to the
steam and water drums. The water, as it sweeps along the
drums, frees itself of steam ; then it goes down the back connec-
tion until it meets the inclined tubes, meeting on its passage a
gradually increasing temperature, till the furnace is again reached,
where the steam formed on the way is directly carried up in the
drum as before. The tubes extend between and connect both the
front and rear headers and are thoroughly expanded into the
tube sheets. Opposite the end of each tube there is an oval
hand-hole slightly larger than the tube proper through which it
can be withdrawn. It will be noted that the throat of each
water leg is 1^ times the total tube area. The rapid and
unimpeded circulation tends to keep the inside surface clean and
floats the scale-making sediment along until it reaches the back
HANDBOOK ON ENGINEERING.
505
water leg, where it is carried down and settles in the bottom of leg,
where it is blown off at regular intervals.
Fte. 265. Formation of front water leg in O'Brien boiler.
Steadiness of wate* level — The large area of surface at watei
line and the ample passages for circulation, secure a steadiness
506 HANDBOOK ON ENGINEERING.
of water level peculiar to this type. This is a most im-
portant point in boiler construction and should always be consid-
ered when comparing boilers. The water legs are stayed by hol-
low stay-bolts of hydraulic tubing of large diameter, so placed that
two stays support each tube and hand-hole and are subjected to only
very slight strain. Being made of heavy material, they form the
strongest parts of the boiler and its natural supports. The water
legs are joined to the shell by flanged and riveted joints and the
drum is cut away at these two points to make connection with in-
side of water leg, the opening thus made being strengthened by
special stays, so as to preserve the original strength. The shells
are cylinders with heads dished to form part of a true sphere.
The sphere is everywhere as strong as the circular seam of the
cylinder, which is well known to be twice as strong as the side
seam ; therefore, the heads require no stays. Both the cylinder
and the spherical heads are, therefore, free to follow their natural
lines of expansion when put under pressure.
The illustration on page 505 plainly shows the formation of
the front water leg or header in this type of water tube boiler.
It will be seen that the hand plates are all oval in shape, a] low-
ing each one to be removed from its respective hole ; also, the
manner of bracing with hollow stay-bolts is shown.
Note that the feed pipes for supplying boiler run back to rear
water leg and discharge therein.
Walling' in* — In setting the boiler, its front water leg is placed
firmly on a set of strong, cast-iron columns bolted and braced to-
gether by the door frames and dead-plates and forming the fire
front. This is the fixed end. The rear water legs rest on rollers
which are free to move on cast-iron plates firmly set in the ma-
sonry of the low and solid rear wall. Thus the boiler and its walls
are each free to move separately during expansion or contraction,
without loosening any joints in the masonry.
On the lower, and between the upper tubes, are placed light
HANDBOOK ON ENGINEERING. 507
fire-brick tiles. The lower tier extends from the front water leg
to within a few feet of the rear one, leaving there an upward pass-
age across the rear ends of the tubes for the flame. The upper
tier closes into the rear water leg and extends forward to within
a few feet of the front one, thus leaving an opening for the gases
in front. The side tiles extend from side walls to tile bars and
close up to the front water leg and front wall, and leave open the
final uptake for the waste gases.
The gases being thoroughly mingled in their passage between
the staggered tubes, the combustion is more complete, and the
gases impinging against the heating surface perpendicularly, in-
stead of gliding along the same longitudinally, the absorption of
the gas is more thorough. The draft area, being much
larger than in fire tube boilers, gives ample time for the
absorption of the heat of the gases before their exit to the
chimney.
DESCRIPTION OF THE HEINE SAFETY BOILER.
The boiler is composed of lap- welded wrought-iron tubes ex-
tending between and connecting the inside faces of two " water
legs," which form the end connections between these tubes and
a combined .steam and water drum or " shell " placed above and
parallel with them. Boilers over 200 horse-power have two such
shells. These end chambers are of approximately rectangular
shape, drawn in at top to fit the curvature of the shells. Each is
composed of a head plate and a tube sheet flanged all around
and joined at bottom and sides by a butt strap of same material,
strongly riveted to both. The water legs are further stayed by
hollow stay-bolts of hydraulic tubing of large diameter, so placed
that two stays support each tube and hand-hole and are subjected
to only very slight strain. Being made of heavy metal, they form
the strongest parts of the boiler and its natural supports. The
508 HANDBOOK ON ENGINEERING.
water le-s are joined to the shell by flanged and riveted joints,
the drum i cut away at these two points to make connects
with inside of water leg, the opening thus made being strength-
ened by bridges and special stays so as to preserve 1
strength.
48
HANDBOOK ON ENGINEERING. 509
The shells are cylinders with heads dished to form parts of a
true sphere. The sphere is everywhere as strong as the circle
seam of the cylinder, which is well known to be twice as strong as
its side seam. Therefore, these heads require no stays. Both
the cylinder and its spherical heads are, therefore, free to follow
their natural lines of expansion when put under pressure. Where
flat heads have to be braced to the sides of the shell, both suffer
local distortions where the feet of the braces are riveted to them,
making the calculations of their strength fallacious. This they
avoid entirely by their dished heads. To the bottom of the front
head a flange is riveted, into which the feed-pipe is screwed.
This pipe is shown in the cut with angle valve and check valve
attached. On top of shell, near the front end, is riveted a steam
nozzle or saddle, to which is bolted a tee. This tee carries the steam
valve on its branch, which is made to look either to front, rear,
right or left ; on its top the safety valve is placed. The saddle
has an area equal to that of stop valve and safety valve combined.
The rear head carries a blow-off flange of about same size as the
feed flange, and a manhead curved to fit the head, the manhole
supported by a strengthening ring outside. On each side of the
shell a square bar, the tile-bar, rests loosely in flat hooks riveted
to the shell.. This bar supports the side tiles, whose other ends
rest on the side walls, thus closing the furnace or flue on top.
The top of the tile-bar is two inches below low water line. The
bars rise from front to rear at the rate of one inch in twelve.
When the boiler is set, they must be exactly level, the whole
boiler being then on an incline, i. e., with a fall of one inch in
twelve from front to rear. It will be noted that this makes the
height of the steam space in front about two-thirds the diam-
eter of the shell, while at the rear the water occupies two-thirds
of the shell, the whole contents of the drum being equally divided
between steam and water. The importance of this will be ex-
plained hereafter.
510
HANDBOOK ON ENGINEERING.
The tubes extend through the tube sheets, into which they are
expanded with roller expanders ; opposite the end of each and in
the head plates, is placed a hand-hole of slightly larger diam-
.
Fig. 267. Details of construction — Heine boiler.
eter than the tube, and through which it can be withdrawn.
These hand-holes are closed by small cast-iron hand-hole plates,
, by an ingenious device for locking, can be removed in a
HANDBOOK .ON ENGINEERING. 511
few seconds to inspect or clean a tube. The accompanying cut
shows these hand-hole plates marked H. In the upper corner
one is shown in detail, H2 being the top view, H* the side view
of the plate itself, the shoulder showing the place for the gasket.
Hl is the yoke or crab placed outside to support the bolt and nut.
Inside of the shell is located the mud drum D, placed well
below the water line, usually parallel to and 3 inches above the
bottom of the shell. It is thus completely immersed in the hot-
test water in the boiler. It is of oval section, slightly smaller
than the manhole, made of strong sheet-iron with cast-iron heads.
It is entirely inclosed except about 18 inches of its upper
portion at the forward end, which is cut away nearly parallel to
the water line. Its action will be explained below. The feed-
pipe F enters it through a loose joint in front ; the blow-off pipe
N is screwed tightly into its rear-head, and passes by a steam-
tight joint through the rear-head of the shell. Just under the
steam nozzle is placed a dry pan or dry pipe A. A deflection
plate L extends from the front head of the shell, inclined up-
wards, to some distance beyond the mouth or throat of the front
water leg. It will be noted that the throat of each water leg is
large enough to be the practical equivalent of the total tube area,
and that just where it joins the shell it increases gradually in
width by double the radius of the flange.
Erection and walling in* — In setting the boiler, its front
water leg is placed firmly on a set of strong cast-iron columns,
bolted and braced together by the door frames, deadplate, etc.,
and forming the fire front. This is the fixed end. The rear
water leg rests on rollers, which are free to move on cast-iron
plates firmly set in the masonry of the low and solid rear wall.
Wherever the brickwork closes in to the boiler, broad joints are
left which are filled in with tow or waste saturated with fireclay,
or other refractory but pliable material. Thus the boiler and its
walls are each free to move separately during expansion or con-
512 HANDBOOK ON ENGINEERING.
traction without loosening any joints in the masonry. On the
lower, and between the upper tubes, are placed light firebrick
tiles. The lower tier extends from the front water leg to within
a few feet of the rear one, leaving there an upward passage across
the rear ends of the tubes for the flame, etc. The upper tier
closes in to the rear water leg and extends forward to within a
few feet of the front one, thus leaving the opening for the gases in
front. The side tiles extend from side walls to tile bars and close
up to the front water leg and front wall, and leave open the final
uptake for the waste gases over the back part of the shell, which
is here covered above water line with a rowlock of firebrick rest-
ing on the tile bars. The rear wall of the setting and one paral-
lel to it arched over the shell a few feet forward, form the uptakes.
On these and the rear portion of the side walls is placed a light
sheet-iron hood, from which the breeching leads to the chimney.
When an iron stack is used, this hood is stiffened by L and T
irons so that it becomes a truss carrying the weight of such stack
and distributing it to the side walls.
Heine boiler and its operation* — The boiler being filled
to middle water line, the fire is started on the grate. The
flame and gases pass over the bridge wall and under the
lower tier of tiling, finding in the ample combustion chamber
space, temperature and air supply for complete combustion,
before bringing the heat in contact with the main body of the
tubes. Then, when at its best, it rises through the spaces be-
tween the rear ends of the tubes, between rear water leg and back
end of the tiling, and is allowed to expand itself on the entire
tube heading surface without meeting any obstruction. Ample
space makes leisurely progress for the flames, which meet in turn
all the tubes, lap round them, and finally reach the second uptake
at the forward end of the top tier of tiling, with their temperature
reduced to less than 900° Fahrenheit. This has been measured
here, while wrought iron would melt just above the lower.tubes at
HANDBOOK ON ENGINEERING.
513
rear end. showing a reduction of temperature of over 1,800° Fahr.
between the two points. As the space is studded with water
tubes, swept clean by a positive and rapid circulation, the absorp-
tion of this great amount of heat is explained. The gases next
travel under the bottom and sides of shell and reach the uptake
at just the proper temperature to produce the draft required.
This varies, of course, according to chimney, fuel required, etc.
With boilers running at their rated capacity, 450° Fahrenheit are
Fig. 2<»8. A furnace that is used in the Eust.
seldom exceeded. Meanwhile, as soon as the heat strikes the
tubes, the circulation of the water begins. The water nearest the
surface of the tubes becoming warmer, rises, and as the tubes are
higher in front, this water flows towards the front water leg
where it rises into the shell, while colder water from the shell
falls down the rear water leg to replace that flowing forward and
upward through the tubes. This circulation, at first slow, in-
33
514
HANDBOOK ON ENGINEERING.
creases in speed as soon as steam begins to form. Then the
speed with which the mingled current of steam and water rises in
the forward water leg will depend on the difference in weight of
this mixture, and the solid and slightly colder water falling down
the rear water leg. The cause of its motion is exactly the same
as that which produces draft in a chimney.
Fig. 269. Plain vertical tubular boiler.
This cut shows the place for gauge cocks and water glass in an
upright boiler.
HANDBOOK ON ENGINEERING.
515
cf)d)6ocMooooo
ooooo boooo
ooooo ooooo
ooooo ooooo
oooo oooo
O wr^fk O
Fig. 270. Showing the water-column in its proper place.
516
HANDBOOK ON ENGINEERING.
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HANDBOOK ON ENGINEERING.
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Fig. 271. Showing the proper place for closing in the boiler on
the side — also the space between side of boiler and
side walls.
HANDBOOK ON ENGINEERING.
521
Fig. 272. Showing the proper place for grange-cocks in a sub-
merged tube boiler.
522
HANDBOOK ON ENGINEERING.
THE AMOUNT OF MATERIAL REQUIRED TO BRICK
UP BOILERS OF DIFFERENT SIZE.
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72"x22'
18'
10^500
2,500
18 bu.
88
8
9 bbl.
72"x20'
18'
10,000
2,300
18 bu.
80
8
8 bbl.
72"xl8'
18'
9,500
2,200
17 bu.
72
7
8 bbl.
60"x20'
18'
9;500
2,200
17 bu.
80
7
8 bbl.
60"xl8'
18'
9,000
2,000
16 bu.
72
7
8 bbl.
54"x20'
18'
8,700
1,900
15 bu.
80
6
8 bbl.
54"xl8'
18'
. 8,000
1,800
15 bu.
72
6
8 bbl.
54"xl6'
18'
7,500
,700
14 bu.
64
6
7 bbl.
48"xl8'
18'
7,500
,600
14 bu.
72
6
7 bbl.
48"xl6'
18'
7,200
,500
14 bu.
64
5
• 7 bbl.
42"xl8'
18'
7,000
,400
12 bu.
72
5
7 bbl.
42"xl6'
18'
6,500
,300
12 bu.
64
4
7 bbl.
If 13" wall i less on Red Brick.
THE DOWN DRAUGHT FURNACE.
The down draught furnace is known as being one of the best
smoke preventing furnaces in the market, while at the same time
the cheapest kind of coal can be used.
The down draught furnace makes a -good smoke record, even
with overworked boilers, doing variable work, and with a marked
economy in fuel. All experience with the down draught furnace,
seems to indicate that smoke from boiler furnaces can now be
abated by practical means, without hardship, no matter what the
type of boiler.
Directions for firing the down draught furnace* — When
firing the furnace, throw the coal evenly over the entire grate
surface, from 6 to 8 inches in depth, a little heaviest at the
rear end of the furnace. Do not put in too much coal —
burn more air and economize fuel if possible, and
HANDBOOK ON ENGINEERING.
523
do not pile up the coal in front near the door. Never fire any
fresh coal on the lower grates ; let in air below the lower grates.
When poking the fire, run the slice-bar down between the water
grates and back the full length of the grates ; then rafse the slice-
bar and gently shake the coal, and then pull it out without stir-
ring up the fire. Never turn the fire over so that black coal gets
down upon the water grates, unless there is a large clinker to re-
move. Never give the top grates a general cleaning, so as to
leave a portion of the grates uncovered and the remainder with a
hot lire on them, as this causes an uneven expansion in the differ-
ent tubes forming the water grates, and is liable either to bend
the tubes or strip off the threads where they enter the drums.
When the top fire becomes clogged with clinkers so that it is hard
r
Fig. 273. Down draught furnace.
to keep up steam, run in the slice-bar and raise the clinkers to
the top of the fire ; remove the large clinkers, leave the small ones
alone, and put on afresh fire. The lower grates must have proper
524
HANDBOOK ON ENGINEERING.
attention. The coals must be raked over evenly and all holes
filled up, particular care being taken that the grates are perfectly
covered all over. If considerable coals have accumulated on the
••jjfJL 7-i~- -litr-i
. . yO-l" J
Fig. 274. Yiew of the down draught furnace.
lower grates and the air spaces are closed with ashes or clinkers,
the slice-bar must be used and the clinkers raised up and turned
over and the larger ones removed. It is best to remove the clink-
ers every two or three hours, leaving the coals to burn up.
SPECIFICATIONS FOR ONE SIXTY-INCH HORIZONTAL SIX-
INCH FLUE BOILER.
General directions* — There will be one boiler 20 feet long from
out to out of heads and 60 inches inside diameter.
Material, quality, thickness, etc* — Material in shell of the
above named boiler to be made of homogeneous flange steel T5F"
thick, having a tensile strength of not less than 60,000 Ibs. to
HANDBOOK ON ENGINEERING.
525
526 HANDBOOK ON ENGINEERING.
the square inch of section, with not less than 56 per cent ductil-
ity, as indicated by contraction of area at point of fracture under
test, or by an elongation of 25 per cent in length of 8 inches.
Heads must be ^" thick and of the same quality of steel as that
in the shell. All plates and heads must be plainly stamped with
the maker's name, and tensile strength.
Tubes, size, number and arrangement* — The boiler must
contain 18-6" lap- welded flues, riveted to the heads with ten £"
rivets in each head ; said flues must be made of charcoal iron of the
best American make, standard thickness, equal to the National
Tube Works Company's make. All flues must have at least 3
inch clear space between them, and not less than 3 inches
between flues and shell. All flanging of heads must be free from
flaws or cracks of any description, and properly annealed in an
annealing oven before riveting to the boiler. If 4-inch flues are
wanted in place of 6 -inch, the boiler must have 44 best lap-
welded tubes, 4" in diameter and 20 feet long, set in vertical and
horizontal rows, with a clear space between them, vertically and
horizontally of !£", except the central vertical space, which is to
be 4 inches. Holes for tubes to be neatly chamfered off on the
outside. Tubes to be set with a Dudgeon expander, and beaded
down at each end.
Riveting* — The longitudinal • seams of the boiler must be
above the fire line, and have a TRIPLE row of rivets ; all rivets to
be |" in diameter ; and all rivets to be of sufficient length to
form upheads equal in size to the pressed heads of same. The
rivets in the longitudinal seams must be spaced 3J" apart
from center to center, and the rows of same to be pitched 2T3^"
apart from center to center, so as to give an efficiency of the
joint of TYo- per cent of the solid plate. Transverse seams to
be single riveted with same size rivets as those in the longitudinal
seams pitched 2" apart from center to center. Care must be
taken in punching and drilling holes that they may come fair in
HANDBOOK ON ENGINEERING. 527
construction; the use of adrift-pin to bring blind, or partially
blind holes in line will be sufficient cause for the rejection of
the boiler.
Calking* — The edges of the plates to be planed and beveled
before making up the boilers, and the calking to be done with
round nose tools, pneumatically driven ; no split or wedge calk-
ing will be allowed.
Bracing* — There must be 22 braces in the boiler, one inch area
at least, be nine above the flues on the front head and nine similar
ones on the back head, none of which shall be less than 3' 6" long,
made of good refined iron and securely riveted to the heads ; the
other end to be extended to the shell of boiler and riveted thereto
with two £'' rivets. Care must be exercised in the setting of
them, so they may bear uniform tension. There must be two
braces below flues, one on each side of manhead, and riveted to
the heads with two X" rivets. The back end of brace to be ex-
o
tended backward to side of shell and riveted thereto by means
of two J" rivets ; and two braces in back end above flues, one
on each side and riveted the same as the other two below
flues.
Manholes* — The boiler to have two manholes of the Hercules
or Eclipse pattern, same to be of size 10" x 15", one located in
front head, beneath the flues, and the other in rear head above
the flues, and each to be provided with a lead gasket, grooved lid,
two yokes and two bolts. The proportion of the whole to be
such as will leave it as strong as any other portion of the head of
like area.
Steam drum* — The boiler must be provided with one steam
drum 30" in diameter by 5' in length, shell plates of which are to
be Ty thick and heads |" thick, of the same quality of material
as that in the boiler. The heads must be bumped to a radius so
as to give as near as practicable equal strength as to that in the
shell without bracing. The longitudinal seams of the drum are
528 HANDBOOK ON ENGINEERING.
to be double riveted with -J--J-" diameter rivets, pitched 2J" apart
from center to center, so as to give an efficiency of the joint of
74 per cent of the solid plate.
Manhole in drum* — The drum must be provided with Her-
cules or Eclipse patented manhole, same to be of size 10"xl5",
located in the center of one head, and to be provided with a
grooved lid, lead gasket, two jokes and two bolts. The propor-
tion of the whole to be such as will leave it as strong as any other
portion of the head of like area.
To attach to boilers. — The steam drum must be attached to
the boiler by means of two flange steel connecting legs, 8" in
diameter by 12" in length, and securely riveted to boiler and
steam drum shell.
Mud drum* — Boiler must be provided with one mud drum
24" in diameter and of sufficient length so that each end may
come flush with the outside of the boiler walls on each side ; the
quality and thickness of steel to be the same as that specified for
the steam drum, and all seams to be single riveted ; said mud
drum to be provided with one Hercules or Eclipse patent manhole
in one end, and to be of size 9" x 14", supplied with a grooved
lid, lead gasket, two yokes and two bolts.
To attach to boiler* — The mud drum is to be attached to
boiler by means of 8" diameter steel connecting leg, about 16" in
length, properly riveted to boiler and mud drum shells.
Flanges* — The boiler to have one 8" wrought steel flange riv-
eted on top of steam drum ; one wrought steel flange 4" in diam-
eter, about 5 feet from front end of boiler for safety valve one
2" wrought steel flange on after end of boiler over the center of
mud leg for supply pipe — all flanges to be threaded ; 2" hole in
mud drum for blow-off ; also 2 1J" holes, one on top of boiler
and one on end near bottom of boiler for water column.
Fusible plugs* — To have two fusible plugs ; one inserted in
shell from inside on second sheet, or about 5' from forward end, 1
HANDBOOK ON ENGINEERING. 529
inch above flues ; one plug inserted in top of flue, not more than
three feet from after end.
Trimmings* — Furnish one 4" spring or dead weight safety
valve, 4" diameter ; one water combination column ; provide same
with two 1 J" valves for the steam and water connections between
the boiler and column, and one %" valve for blow-pipe ; said blow-
pipe to be connected with ashpit ; said combination barrel to be
4'' diameter, IS'1 long, and made of cast-iron. Also, furnish one
water gauge having a f'x 15" Scotch glass tube, bodies polished
with wood wheels and guards, rods, bodies threaded f " ; three
gauge cocks |" register pattern, polished brass bodies ; one steam
gauge with 10" dial; one 2" brass feed valve with 2" check
valve ; one 2" gate valve for blow-off from mud drum ; also one
asbestos packed stop-cock for same, so as to insure against the
possibilities of a leak through the blow-pipe. Water column to
have crosses in place of ells. Crosses to have brass plugs.
Castings, gr ates, doors, etc* — The boiler must be provided
with a heavy three-quarter fire front of neat design, having double
firing and ashpit doors, anchor bolts for anchoring fire cronts in
place, heavy deadplates, a full set of fire liners 9" deep for sup-
porting firebrick on end, front and rear bearing bars ; a full set
of ordinary grate bars 4 ft. long, soot door and frame for cleaning
out rear ashpit ; a full set of skeleton arch plates ; 12 heavy buck
staves 9i' long, provided with tie rods, nuts and washers, heavy
back stand with plate and expansion rollers ; also furnish wrought
plates to cover mud drum.
Fire tools* — Furnish in addition to above two sets of fire tools
consisting of two pokers, two hoes, two slice-bars, two claws, and
one six-inch flue brush with |" pipe for handle.
Breeching* — Boiler must have a breeching fitted to front head
and fastened thereto by means of bolts, stays and suitable pieces
of angle iron, bent to conform to circle of boiler. The underside
of breeching is to run across the head between the lower flues and
34
530 HANDBOOK ON ENGINEERING.
the manhole, leaving the manhole freely exposed ; the sides of
breeching are to be made of T3¥" steel, the front and doors of |"
steel ; said doors to be hung by means of strap hinges, provided
with suitable fastenings so as to give free access to all flues when
open.
Uptake and damper* — An uptake having an area of 1221
square inches must be fitted to top of breeching. Said uptake
must be of convenient form for attaching to a stack 40" in diam-
eter and provided with a close-fitting damper having a steel hand
attachment, so that same may be operated conveniently from the
boiler room floor.
Smoke stack* — There is to be provided for the above boiler
one smoke stack 40" in diameter by 90 feet in height, half of
which is to be made of No. 8, and the other half of No. 10 best
black sheet steel throughout, and supplied with two sets of four
guy rods, each consisting of f " galvanized wire cable guy strand
with turn-buckles for same.
In general* — The above-mentioned boiler must be made of
strictly first-class material and workmanship throughout, and sub-
jected to a hydrostatic pressure of 150 pounds to the square inch
before leaving the works of the manufacture.
Painting boiler breeching* — Smoke stack and boiler front,
steam and mud drum, and all trimmings, to have two good coats
of coal tar.
Masonry* — Boiler to be set in good substantial masonry, of
hard burned brick and good mortar, made of clean, sharp sand
and fresh burned lime. Walls to be 18" thick0 The outside walls
to be laid up of selected hard burned brick, with close joints
struck smooth and rubbed down. The sides, end and bridge
walls, and boiler front, to have a foundation of 24" wide and 12'
deep, laid in Portland cement. The ash pit to be paved with
hard burned brick set on edge firmly, imbedded in Portland
cement. For a distance of seven feet in front of the boiler and
HANDBOOK ON ENGINEERING. 531
continuing across entire width of front of boiler setting to be
paved with hard burned brick set on edge, firmly imbedded in
sand. The walls to be carried up to the full height and a row-
lock course of brick 4" thipk to be carried over top of boiler from
side wall to side wall, extending the whole length of boiler, and
the entire arch to be plastered over on the outside with mortar.
The bridge walls to be 24", carried up to within 6"* of under
side of boiler. The top of bridge wall to be of fire brick and
made in the form of an inverted arch, conforming to the shell of
the boiler. The space under boiler and back of bridge wall to
the back end of boiler, to be filled in with earth or sand and the
top paved with brick, and tapering from bridge wall back to back
end to 12"* at back end, and in a similar form and shape, that is,
inverted arch. The uptake for returning the smoke and heat at
back end of boiler, to be arched over from rear wall against the
back head of boiler 2" above the tubes, the arch being made of arch
fire brick, and backed up with red brick. Furnace to be lined
throughout with first quality fire brick, dipped in fire clay with
close joints and fire brick rubbed to place, from a point 2" below
grates, to where it safes in against boiler, and to be continued fire
brick as far back as the rear end of setting and across rear end of
same ; it being the intent that all interior surfaces of the setting
with which the heat comes in contact, shall be faced with fire
brick. Every sixth course to be a header course.
Smoke connections* — The connection from boiler to chimney
to be made of No. 12 black iron, with cleaning door and damper
in same.
BANKING FIRES.
Different engineers pursue different methods in banking fires.
One method is to push the fire back one-third towards the bridge
wall, and clean off the grate in front. Then shovel in from 150
to 300 Ibs. of fine coal on top of the fire, closing ash-pit doors
* These distances should be doubled for bituminous coal.
532 HANDBOOK ON ENGINEERING.
and leaving furnace doors open, with damper open enough to let
the gases escape. Others bank after this fashion but close all
doors and air holes, leaving the damper partially open. Another
method is to level the fire all over the, grate, and shovel in from
150 to 500 Ibs. of fine coal, — depending on the size of the
grate, — and then cover the whole surface with wet ashes to a
good depth, so that no fire nor flame can be seen, then close the
ash-pit doors, leaving the furnace doors ajar, and leave the
damper partially open so that the gases may escape. In the
morning, rake out the ashes, clean the fire, and throw in fresh
coal.
INSTRUCTIONS FOR BOILER ATTENDANTS.
The following instructions apply more particularly to horizontal
return tubular boilers, although in a general way they are appli-
cable to all types of boilers.
Never start a fire under a boiler until you are positively certain
that there is sufficient water in the boiler, — at least two gauges
of water. Do not trust to the water gauge alone, but try the
gauge cocks also, and try them at intervals during the day, be-
cause the water gauge pipe connections may be choked and cause
a false water level.
Before starting a fire be sure that the blow-off cock is closed
and not leaking.
Before it is time to start the engine, pump up three gauges of
water, and blow off one gauge, in order to get rid of mud and
other sediment. If the boiler b.as a surface blow-off, — commonly
called a ct skimmer," — blow off the scum before stopping the
engine for the day.
When the day's work is done, leave three gauges of water in
the boiler, to allow for leakage and evaporation during the night.
Never raise steam hurriedly. Sudden changes of temperature
may produce fractures, or start leaks.
HANDBOOK ON ENGINEERING. 533
la starting a fire in a furnace, a good plan is to cover the grate
with a thin layer of coal and to place the shavings and wood on
the coal and then light the shavings.
The advantage of placing a covering of coal on the grate before
the wood and shavings, is that it is a saving of fuel, as the heat
that would be transmitted to the bars is absorbed by the coal, and
the bars are also protected from the extreme heat of the fresh
fire.
Lift the safety-valve, — if of the lever pattern, — every morn-
ing while raising steam, and satisfy yourself that it is in good
working order, and that the ball is set at the proper point on the
lever. The most disastrous explosions have occurred with boilers
whose safety-valves had been stuck down or overloaded.
Keep the boiler shell free of soot. Soot is a very good non-
conductor of heat, and considered worse than scale inside of a
boiler.
Keep your boiler tubes free from soot and dust. Choked tubes
impair the draft. The tubes should be cleaned twice a week, or
oftener.
Soot collects also in a stack or chimney and in the connection
between the breeching and stack, and interferes with the draft,
Open your boiler every two weeks, or, as often as necessary,—
depending on the kind of feed-water used, — and clean out the
mud and scale. At the same time examine all of the stays, and
see that they are taut and in good order. Also, look for pitting
around the mud-drum connection, and for grooving in the side
seams. Examine all outlets and pipe connections, and look for
indications of " bagging " in the furnace sheets.
Clean off the fusible plugs both inside and outside of the boiler.
A fusible plug covered with soot on the fire side, and with scale
on the water side, is no longer a u safety plug." Renew the
filling in safety plugs, at least once a year. They are filled with
pure Banca tin.
534 HANDBOOK ON ENGINEERING.
Be perfectly satisfied that your boiler is in good condition
internally before you close it up.
Just as soon as you have fastened the man-head in its place >
turn on the feed-water until you get at least three gauges of water.
Fires have been built under empty boilers, and will be again, if
you forget to turn on the feed water after cleaning out.
Do not empty a boiler while it is under steam pressure, but
allow it to get cold before letting the water run out.
If you are in a great hurry and can't wait for the boiler to cool
down, nor for the brickwork or anything else to cool down, draw
the fire and open the furnace and ash-pit doors, then turn on the
feed water, and from time to time blow out, until the steam gauge
shows no pressure ; then shut .off the feed-water, raise the safety
valve, open the blow-off cock, then open up the boiler.
Before opening a man -hole, lift the safety-valve, so as to be
sure that there is neither pressure nor vacuum in the boiler.
Look well after the brick -work surrounding your boiler, and
stop all cracks in the walls with mortar or cement, as soon as
discovered. They impede the draft, and cool the plates of the
boiler, causing a waste of fuel.
See that the bridge wall is in perfect condition, because a gap
in the bridge wall might cause a " bag " in the boiler by concen-
trating the flames on one spot.
Never allow any bare places on the grate, nor any accumulation
of ashes, or dead coal in the corners of the furnace, as such
places admit great quantities of cold air into the furnace, and
render the combustion very imperfect.
In firing with anthracite coal, do not poke and stir up the fire,
as with soft coal, but let it alone.
In firing soft slack coal, fire very lightly but frequently, carry-
ing a thin fire.
In firing with soft lump coal, carry a thick fire, say from six
to eight inches deep, according to the size of the furnace.
HANDBOOK ON ENGINEERING. 535
In firing up, you may spread the fresh coal evenly all over the
grate, or, you may push the live coals back towards the bridge-
wall, leaving a thin bed of live coals near the furnace doors, and
spreading the fresh coal on top of it. This is called carrying a
coking fire. Some prefer the one and some the other method of
firing.
In case you should find the water in the boiler out of sight,
and a heavy fire in the furnace, don't get rattled, and don't lose
your head. Open the furnace doors, and close the ash-pit doors,
and cover the fire with wet ashes, or damp clay, completely
smothering it. Let everything else alone, including the safety
valve and the engine. Now wait until the boiler cools down and
the gauge shows no pressure, then turn on the feed-water.
On the other hand, if there is but very little fire in the furnace,
you may draw the fire, instead of covering it with ashes or clay.
If your boiler foams badly and you are uncertain as to the
water level, stop the engine, and the true water level will show
itself at once.
If your boiler primes and water is carried over to the engine,
it shows that there is want of sufficient steam room in the boiler.
Either put a dry-pipe in the boiler, or, increase the steam pressure
if the boiler will safely stand it.
Never attempt to calk a leaky seam in a boiler under steam
pressure, because the jar caused by the hammer blows might
cause a rupture of the seam. Better to be on the safe side
always when repairs are required in a steam boiler, and wait until
the boiler is cold. The above applies to steam pipes and valve
casings, also.
Never open any steam valves suddenly, nor close them sud-
denly either, because it is highly dangerous to do so, particularly
if there is considerable water in the pipes. The effect is the same
as water hammer in water pipes.
Smoke is caused by too little air supply, or by the flames being
536 HANDBOOK ON ENGINEERING.
prematurely cooled. Therefore, after firing up with fresh coal,
it might be necessary to leave the furnace doors ajar in order to
supply sufficient air above the fuel.
Remember that it takes nearly 24 cubic feet of air for the
proper combustion of one pound of soft coal. Hard coal does
not require so much.
Each and every boiler in a battery should have its own inde-
pendent safety-valve and steam gauge.
If you are obliged to force your fire, watch your furnace sheets
for indications of " bagging," if the water space below the lowest
row of tubes is cramped. Water-tube boilers are less liable to
suffer from the effects of forced fires than shell boilers.
With an intensely hot fire under a shell boiler, the furnace
sheets are liable to bag, unless there is ample water space be*
tween the shell of the boiler and the bottom row of tubes.
The use of mineral oil to remove or prevent boiler scale, is not
to be recommended.
Have your feed water analyzed, and use a scale preventer
adapted to its requirements.
By all means endeavor to secure a steady furnace temperature,
and a steady steam pressure, for herein lies much economy of
fuel. Fluctuations are wasteful.
Put a damper in your chimney and adjust it to the needs of
your furnace. Try to prevail on your employer to put in a shak-
ing grate. It will enable you to carry a steady furnace temper-
ature, and also enable you to keep the air spaces in your grate
free and open without breaking up your fire.
RULES AND PROBLEMS RELATING TO STEAM BOILERS.
To find the safe working pressure : —
U* S* Rule. — Multiply one-sixth (|) of the lowest tensile
strength found, stamped on any plate in the cylindrical shell,
HANDBOOK ON ENGINEERING. 537
by the thickness — expressed in inches or parts of an inch — of
the thinnest plate in the same cylindrical shell, and divide by the
radius or half diameter — also expressed in inches — and the
result will be the pressure allowable per square inch of surface
for single riveting ; to which add 20 per cent for double riveting,
when all the holes have been " fairly drilled " and no part of
such hole has been punched.
A* S. of M* E* Rule* — First, find the tensile strength of the
solid plate between the centers of two adjacent rivet holes. Call
this factor A. •
Next, find the tensile strength of the solid plate between the
centers of two adjacent rivet holes, less the diameter of one rivet
hole. Call this factor B.
Next, find the shearing strength of the rivets. Call this
factor C.
Now divide whichever is the smaller factor B or C by J., and
the quotient will give the strength of the joint as compared with
the solid plate — expressed as a percentage. Then multiply the
tensile strength of the plates by the thickness of plates — in frac-
tional parts of an inch — and multiply this product by the per-
centage as found above, and divide this last product by the
radius of the shell in inches, and the quotient will be the bursting
pressure.
Divide this quotient by the factor of safety and the result will
give the safe working pressure.
Example* — What is the safe working pressure for a steel
boiler 60 inches in diameter, with side seams double riveted,
tensile strength of plates 60,000 Ibs. per sqr. in., thickness of
plate | inch. Diameter of rivet holes £f inch, pitch of rivets 3J
inches, shearing strength of rivets 38,000 Ibs. per sqr. in., and
factor of safety 5 ?
Ans. By U. S. rule, 150 Ibs. per sqr. in.
By A. S. of M. E. rule, 106J Ibs. per. sqr. in.
538 HANDBOOK ON ENGINEERING.
Operation by U. S. rule : —
60,000
— ^ — = 10,000. And, 10,000 X f = 37,500.
3750
And, -3Q-= 125. And, 125 X. 20 =25.
Then, 125+25 = 150,
Operation by A. S._of M. E. rule: —
f" = .3 75".
I*" = . 9375".
Then, 60,000 X 3J X .375 = 73,125 Ibs., the strength of the
solid plate between the centers of two adjacent rivet holes. Call
this factor A. Also, 3J- = 3.25.
Then, 3.25 — .9375 = 2.3125.
And, 60,000 X 2.3125 X .375 = 52,031.25 Ibs. the strength
of the plate between two adjacent rivet holes. Call this factor B.
Then, .9375 X -9375 X .7854 = .69029 of a square inch, the
area of one rivet hole. There are two rows of rivets.
Then, .69029 X 2 = 1.38058 sqr. ins. the area of two rivet
holes combined.
Then, 38,000 X 1.38058 =52,462.04 Ibs., the resistance of
rivets to shearing. Call this C. Now since B is less than (7,
divide 52,031.25 by 73,125 and get as a quotient .71 +, thus
showing the strength of the joint to be more than 71 per cent of
the strength of the solid plates.
Then, 60,000 X^875 X .71 = ^5 ^ per sqr< .^ ^
bursting pressure.
And, L- = 106.5 Ibs. per sqr. in., the safe working
5
pressure.
HANDBOOK ON ENGINEERING. 539
To find the horse power of a horizontal return tubular boiler,
from its heating surface : —
Rule* — Find the heating surface in square feet, of the shell
of the boiler, measuring from one fire line to the other. Next
find the internal heating surface of all the tubes in square feet.
Add the two results together and divide their sum by 12, and the
quotient will be the H. P. approximately. The heads are
omitted.
Example* — What is the H. P. of a horizontal return tubular
boiler 60 inches in diameter and 20 feet long, with 44 four-inch
tubes each 20 feet long, the distance from fire line to fire line
being 9 feet? Ans. 86.65 H. P.
Operation* — The internal diameter of a 4-inch tube is 3.732
inches.
Then, 20 X 9 — 180 square feet of heating surface in the
shell.
3.732 X3-!41^ .9770376 ft., the circumference of
12
one tube in feet.
And, .9770376 X 20 X 44 = 859.793 + sqr. ft., the total
heating surface of the tubes.
Then, 180+859-793 = 86.65 nearly.
12
To find the factor of evaporation : —
Rule. — From the total number of heat units in one pound of
steam at the given pressure, subtract the number of heat units in
one pound of the feed water at its given temperature, and divide
the remainder by 965.7, which is a constant.
Example*— A boiler evaporates 6,000 Ibs. of water per hour
from feed water at 210 degrees into steam at 125 Ibs. gauge pres-
540 HANDBOOK ON ENGINEERING
sure, what is the equivalent evaporation " from and at," 212°?
What is the H. P. of the boiler?
Ans. Equiv. evap. 6276 Ibs.
H. P. 182, nearly.
Operation* — The total number of heat units in steam at 125
Ibs. per sqr. in. gauge pressue is 1221.5351.
The number of heat units in feed-water at 210 degrees
equals 210.874. The latent heat of steam at atmospheric pres-
sure, equals 965.7.
Then, 1221.5351 — 210.874 = 1010.6611.
And, - — '- — — = 1.046, the factor of evaporation.
965.7
And, 6000 X 1-046 = 6276 the equivalent evaporation.
Then, = 181.9 H. P.
34.5
To find how many pounds of steam at a given absolute pressure
will flow through an orifice of one square inch area in one sec-
one? : —
Rule* — Divide the absolute pressure by the constant number 70.
Example* — How many pounds of steam at 85 Ibs. per sqr. in.
gauge pressure, will flow through an orifice one inch in diameter,
in one second? Ans. 1.122 Ibs.
Operation* — A hole 1 inch in diameter has an area of .7854
of a sqr. inch.
And 85 + 15 = 100 Ibs. absolute.
Then, 122
The weight of a cubic foot of steam at 100 Ibs. per sqr. in.
1 122
absolute pressure is .2307 of a pound. Then, ' Q?i = 4.86 -{-
cubic feet.
HANDBOOK ON ENGINEERING. 541
To find the width of a reinforcing ring for a round hole in a flat
surface, when the ring must contain as many square inches as
were cut out of the plate, and when the ring and the plate are of
the same thickness : —
Rule* — Find the area of the hole in square inches and multi-
ply it by 2. Divide this product by .7854 and extract the square
root of the quotient for the diameter of the ring over all. Sub-
tract the diameter of the hole from the diameter over all, and
divide the remainder by 2 for the width of the ring.
Example* — What should be the width of a reinforcing ring for
a hole 10 inches in diameter, the metal cut out, and the metal in
the ring being | in. thick? Ans. 2T^ inches.
Operation* — 10 X 10 X .7854 = 78.54 sqr. ins. area of hole.
And, 78.54 X 2 •= 157.08 sqr. ins. in both hole and ring.
157.08
And' T7854":
And,
And, 14.142 — 10 z= 4.142.
• 4.142
Then, — ~ — — 2.071" or practically 2^".
To find the width of a reinforcing ring for an elliptical manhole
in a flat surface, when the ring must contain as many square
inches as are contained in the hole, and the metal cut out and
metal in the ring are of the same thickness : —
Rule* — Square the short diameter of the hole and add to it six
times the short diameter multipled by the long diameter, and to
this product add the square of the long diameter, and extract the
square root of the sum. From this root subtract the sum of the
short diameter added to the long diameter, and divide the re-
mainder by 4 for the width of the ring.
Example* — What should be the width of a reinforcing ring
for a manhole 11" X 15"? Ans. 2J£ inches.
542 HANDBOOK ON ENGINEERING.
Operation.— 11" X 11" = 121.
And, 11 X 15 X6=990.
And, 15 X 15 = 225.
Then, 121 + 990 + 225 = 1336.
And, V 1336 = 36.551.'
And, 11 + 15 = 26.
Then, 36.551 — 26 = 10.551.
10.551
And, — j — = 2.637 + ins. the width of the ring, or, prac-
tically 2J£ ins.
Then, 2.637X2 = 5.274".
And, 11 + 5.274 = 16.274" short diameter of ring over all.
And, 15 + 5.274 = 20.274" long diameter over all.
Proof: 20.274 X 16.274 X .7854= 259.13 + square inches
area of hole and ring.
And, 15 X 11 X -7854 = 129.59 + sqr. ins. area of hole alone.
Then, 259.13—129.59 = 129.54.
THE AHOUNT OF STEAM USED WITH VALVE OPEN WIDE,
WITH STEAfl JETS AS A SMOKE PREVENTIVE.
STEAM JETS.
Given two boilers with separate furnaces, having 4 steam jets
in each furnace, and each jet T^- inch in diameter, the steam pres-
sure being 100 Ibs. per sqr. inch by the gauge. How many
pounds of steam at this pressure will flow through the 8 nozzles
in 12 hours? Answer. 1739 Ibs. nearly.
Operation : TV" = .0625 ".
Then, .0625 X -0625 X .7854 = .003067968750 sqr. inch,
area of 1 jet.
HANDBOOK ON ENGINEERING. 543
And, .003067968750 X 8 = .02454375 sqr. inch, the com-
bined area of 8 jets.
Also, 100 + 15 = 115 Ibs. per sqr. inch, the absolute steam
pressure,
115
And, _ — = 1.64 Ibs. of steam per second that will flow
through an orifice of 1 square inch area.
Then, 1.64 X .02454375 = .04025175 Ibs. of steam per second
flowing through the 8 jets.
Again: There are 43,200 seconds in 12 hours.
Thus: 12X60X60 = 43,200.
Then, .04025175 X 43,200 = 1738.8756 Ibs. of steam will
flow through 8 jets in 12 hours' time.
Taking a high speed automatic cut-off engine using 20 Ibs. of
steam per H. P. per hour, the 8 steam jets would waste enough
steam in 12 hours to run —
A 10 H. P. engine for 8£ hours.
A 20 " " " 4£ "
A 40 " " " 2J •
An 80 " " " 1^ «
Thus 10 X 20 = 200.
And, — _ = 8i nearly.
9OO
20 X 20 = 400.
And, = 4i nearly.
80 X 20 = 1600.
And, — f — = lA nearly.
1 1600 J
544
HANDBOOK ON
CHAPTER XIX
THE STEAM PUMP,
Fig. 276. The Worthington compound pump.
THE WORTHINQTON COMPOUND PUMP.
In the arrangement of steam cylinders here employed, the steam
is used expansively, which cannot be done in the ordinary form.
Having exerted its force through one stroke upon the smaller
steam piston, it expands upon the larger during the return stroke,
and operates to drive the piston in the other direction. This is,
in effect, the same thing as using a cut-off on a crank engine,
only with the great advantage of uniform and steady action upon
the water.
HANDBOOK ON ENGINEERING.
645
Compound cylinders are recommended in any service where
the saving of fuel is an important consideration. In such cases,
their greater first cost is fully justified, as they require 30 to 33
per cent less coal than any high-pressure form on the same work,
Fig. 277. Showing a sectional view of the Wortliington
compound pump.
This cut shows the steam valves properly set.
On the larger sizes, a condensing apparatus is often added, thus
securing the highest economical results.
Any of the ordinary forms of steam pumps can be fitted with
compound cylinders.
It should be remembered that, as the compounds use less steam
their boilers may be reduced materially in size and cost, compared
with those required by the high-pressure form. This principle of
expansion without condensation cannot be used with advantage
where the steam pressure is below 75 Ibs.
35
546
HANDBOOK ON ENGINEERING.
Fig. 278. The Deane direct acting pump.
Fig. 279. Sectional view of the Deane pamp.
DEANE DIRECT ACTING STEAM PUMP.
The operation of the steam valves* — In the Deane steam
pump a rotary motion is not developed by means of which an
HANDBOOK ON ENGINEERING.
547
eccentric can be made to operate the valve. It is, therefore,
necessary to reverse the piston by an impulse derived from itself
at the end of each stroke. This cannot be effected in an ordinary
single-valve engine, as the valve would be moved only to the cen-
ter of its motion, and then the whole machine would stop. To
overcome this difficulty, a small steam piston is provided to move
the main valve of the engine. In the Deane steam pump, the
lever 90, which is carried by the piston rod, comes in contact
Fig. 280. Showing the valves properly set.
with the tappet when near the end of its motion, and by means
of the valve-rod 24, moves the small slide-valve which operates
the supplemental piston 9. The supplemental piston, carrying
with it the main valve, is thus driven over by steam and the
engine reversed. If, however, the supplemental piston fails
accidentally to be moved, or to be moved with sufficient prompt-
ness by steam, the lug on the valve-rod engages with it and
compels its motion by power derived from the main engine.
548
HANDBOOK ON ENGINEERINGS
Fig. 281. Sectional view of the Cameron pump.
The above is a sectional view of the steam end of a Cameron
pump.
Explanation : A is the steam cylinder ; (7, the piston ; Z>, the
piston rod ; L, the steam chest; F^ the chest piston or plunger,
the right-hand end of which is shown in section ; 6r, the slide
valve ; H, a starting bar connected with a handle on the outside ;
II are reversing valves ; KK&YQ the bonnets over reversing valve
chambers ; and E E are exhaust ports leading from the ends of
steam chest direct to the main exhaust, and closed by the revers-
ing valve //; Nis the body piece connecting the steam and water
cylinder.
HANDBOOK ON ENGINEERING. 549
Operation of the Cameron pump : Steam is admitted to the
steam chest, and through small holes in the ends of the plunger ;
F fills the spaces at the ends and the ports E E as far as the
reversing valves II; with the plunger F and slide valve G in
position to the right (as shown in cut), steam would be admitted
to the right-hand end of the steam cylinder A, and the piston C
would be moved to the left. When it reaches the reversing valve
/ it opens it and exhausts the space at the left-hand end of the
plunger .F, through the passage E; the expansion of steam at the
right-hand end changes the position of the plunger F, and with it
the slide valve 6r, and the motion of the piston C is instantly
reversed. The operation repeated makes the motion continuous.
In its movements, the plunger F acts as a slide valve to shut off
the ports E E, and is cushioned on the confined steam between
the ports and steam chest cover. The reversing valves I I are
closed immediately the piston C leaves them , by pressure of steam
on their outer ends, conveyed direct from the steam chest.
Operation* — Supposing the steam piston C moving from right
to left: When it reaches the reversing valve / it opens it and
exhausts the space on the left-hand end of the plunger F, through
the passage E, which leads to the exhaust pipe ; the greater pres-
sure inside of the steam chest changes the position of the plunger
F and slide valve 6r, and the motion of the piston C is instantly
reversed. The same operation repeated at each stroke makes the
motion continuous. The reversing valves //are closed by a pres-
sure of steam on their large ends, conveyed by an unseen passage
direct from the steam chest. When a pump is first connected,
remove the bonnets K K and valves 1 1 and blow steam through
to remove any dirt, oil or gum that may be lodged in the steam
ports. Take valve F, valve G and //out and wipe off with
clean waste, and then oil and put back. Then see that the pack-
ing is not too tight. When a Cameron pump has been run a long
time, the plunger F becomes worn and leaks enough steam to
550
HANDBOOK ON ENGINEERING.
cause the valve F to become balanced. The effect of this is, the
pump will remain on the end ; to- overcome this, take out plunger
F, or piston, as it is called by some, and drill the little hole that
you will find in the ends of same a little larger, say about one-
fourth larger ; that will increase the pressure on both ends of
plunger F; as soon as the piston comes in contact with valve 7
the steam is exhausted to exhaust pipe.
Fig. 282. Sectional view of the Knowles pump.
THE KNOWLES DIRECT ACTING STEAH PUMP.
Explanation of steam valves, etc* — The Knowles, in fact, all
first-class direct acting steam pumps, are absolutely free from what
is termed a " dead center," when in first-class order.
This feature in the Knowles pump is secured by a very simple
and ingenious mechanical arrangement, i. e., by the use of an
auxiliary piston, which works in the steam chest and drives the
main valve. This auxiliary or tc chest piston," as it is called, is
driven backward and forward by the pressure of steam, carrying
HANDBOOK ON ENGINEERING.
551
with it the main valve, which valve, in turn, gives steam to the
main steam piston that operates the pump. This main valve is a
plain slide valve of the B form, working on a flat seat. The chest
piston is slightly rotated by the valve motion ; this rotative move-
ment places the small steam ports, I), E, F (which are located in
Fig. 283. The Kuowles direct acting steam pump.
the under side of the said chest pision) , in proper contact with
corresponding ports A B cut in the steam chest No. 31. The
steam entering through the port at one end and filling the space
between the chest piston and the head, drives the said piston to
the end of its stroke and, as before mentioned, carries the main
slide valve with it. When the chest piston has traveled a certain
distance, a port on the opposite end is uncovered and steam there
enters, stopping its further travel by giving it the necessary
552
HANDBOOK ON ENGINEERING.
cushion. In other words, when the rotative motion is given to
the auxiliary or valve -driving piston by the mechanism outside,
it opens the port to steam admission on one end, and at the same
time opens the port on the other end to the exhaust.
Fig. 284. Showing the valves properly set.
Operation of the Knowles pump is as follows : The piston rod,
\vith the tappet arm, moves backward and forward from the
impulse given by the steam piston. At the lower part of this
tappet arm is attached a stud or bolt, on which there is a friction
roller. This roller coming in contact with the " rocker bar" at
the end of each stroke, operates the latter. The motion given the
44 rocker bar " is transmitted to the valve rod by means of the
connection between, causing the valve rod to partially rotate.
This action, as mentioned above, operates the chest piston, which
carries with it the main slide valve, the said valve giving steam to
the main piston. The operation of the pump is complete and
HANDBOOK ON ENGINEERING. 553
continuous. The upper end of the tappet arm does not come in
contact with the tappets on the valve rod, unless the steam pres-
sure from any cause, should fail to move the chest piston, in which
case the tappet arm moves it mechanically.
ADJUSTMENT OF THE KNOWLES PUMP.
1. Should the pump run longer stroke one way than the other,
simply lengthen or shorten the rocker connection (part 25) so
that rocker bar (part 23) will touch rocker roller (20) equally
distant from center (22).
2. Should a pump hesitate in making its return stroke, it is be-
cause rocker roller (20) is too low and does not come in contact
with the rocker bar (23) soon enough. To raise it, take out
rocker roller stud (20 A), give the set screw in this stud a suffi-
cient downward turn, and the stud with its roller may at once be
raised to proper height.
3. Should valve rod (17) ever have a tendency to tremble,
slightly tighten up the valve rod stuffing box nut (28) . When
the valve motion is properly adjusted, tappet tip (1 6) should
not quite touch collar (15) and clamp (27). Rocker roller
(20), coming in contact with rocker bar (23) will reverse the
stroke.
Operation and construction of the
HOOKER DIRECT ACTING STEAM=PUMP.
The parts being in position, as shown, the steam on being ad-
mitted to the center of the valve chamber, brings its pressure to
bear on the main and supplemental flat slide valve 4 and 7, and
also within the recess in the center of the supplemental piston 6.
The recess incloses the main valve 4, so that this valve will move
with the supplemental piston whenever the steam is supplied to
554
HANDBOOK ON ENGINEERING.
and exhausted from each end of this piston. The live steam
passes through the left-hand ports A l Bl, driving the main piston
2 to the right, and the exhaust passes out through the right-hand
ports A and C under the cavity in the main valve 4 to the atmos-
phere. As the main piston nears the right hand port, the valve
lever 15, which is attached to the piston rod 3, brings the dog 17,
in plate 16, in contact with the valve arm 15, and moves the sup-
plemental valve 7 to the right, thus supplying live steam to the
Fig. 285. Plan and sectional views of Hooker pnmp.
right of the supplemental piston 6', and exhausting from the left
through the ports e e. As the supplemental piston incloses the
main valve, this valve is carried with it to the left. Steam now
enters the right-hand ports A B and is exhausted from the left-
hand main port A. The engine commences its return stroke and
the operation just described becomes continuous. As the main
piston (2) closes the main port (A) to the right, it is arrested on
compressed exhaust steam. The main valve 4 having closed the
auxiliary ports (_B) leading to that end of the main cylinder, the
HANDBOOK ON ENGINEERING.
555
Fig. 286. Showing the steam valves properly set.
etearn being supplied through both the main and auxiliary ports,
but released through the main ports only.
BLAKE STEAM PUHP.
Description of the Blake steam pump. — The Blake steam
pump is absolutely positive in its action ; that is to say, the
operation at the slowest speed under any pressure, is perfectly
continuous, and the pump is never liable to stop as the main valve
passes its center, if the pump is in good order. An ingenious and
simple arrangement is used in the Blake pump to overcome the
'•' dead center," as will be seen from the engraving, Fig. 288.
Operation of the Blake steam pump. —The main or pump
driving piston A could not be made to work slowly were the
valve to derive its movement soJely from this piston ; for
556
HANDBOOK ON ENGINEERING.
when this valve had reached the center of its stroke, in which
position the ports leading to the main cylinder would be closed,
Fig. 287. The Blake steam pump.
no steam could enter the cylinder to act on said piston, con-
sequently, the latter would come to rest, since its momentum
would be insufficient to keep it in motion, and the main
valve would remain in its central position or tc dead cen-
ter." To shift this valve from its central position and
admit steam in front of the main piston (whereby the motion
of the piston is reversed and its action continued), some agent
independent of the main piston must be used. In the Blake
pump, this independent agent is the supplemental or valve-driving
piston B. The main valve, which controls the admission of steam
to. and the escape of steam from, the main cylinder, is divided
into two parts, one of which, (7, slides upon a seat on the main
cylinder, and, at the same time, affords a seat for the other part,
HANDBOOK ON ENGINEERING .
557
Z>, which slides upon the upper face of C. As shown in the en-
graving, D is at the left-hand end of its stroke, and C at the
opposite, or right-hand end of its stroke. Steam from the steam-
chest J is, therefore, entering the right-hand end of the main
cylinder through the ports E and H, and the exhaust is escap-
ing through the ports Hl and H71, K and M, which causes the
Fig. 288. Sectional views of steam cylinder, valves, etc., of the
Blake steam pump.
main piston A to move from right to left. When this piston has
nearly reached the left-hand end of its cylinder the valve motion
558
HANDBOOK ON ENGINEERING.
(not shown) moves the valve-rod P, and this causes (7, together
with its supplemental valve R and S Sl (which form, with (7, one
casting) to be moved from right to left. This movement causes
steam to be admitted to the left-hand end of the supplemental
cylinder, whereby its piston B will be forced toward the right,
carrying D with it to the opposite or right-hand end of its stroke ;
for the movement of S closes N (the steam port leading to the
Fig. 289. Showing the valves properly set,
right-hand end), and the movement of S1 opens N1 (the port
leading to the opposite, or left-hand end). At the same time the
movement of 0 opens the right-hand end of the cylinder to
the exhaust through the exhaust ports X and Z. The ports C
and D now have positions opposite to those shown in the engrav-
ings, and steam is, therefore, entering the main cylinder through
the ports El and Hl, and escaping through the ports H, E, K
and Jf, which will cause the main piston A to move in the op-
HANDBOOK ON ENGINEERING. 559
posite direction, or from left to right, and operations similar to
those already described will follow, when the piston approachee
the right-hand end of its cylinder. By this simple arrangement
the pump is rendered positive in its action ; that is, it will in-
stantly start and continue working the moment steam is admitted
to the steam chest. The main piston A cannot strike the head of
the cylinder, for the main valve has a lead ; or, in other words,
steam is always admitted in front of said piston just before it
reaches either end of its cylinder, even should the supplemental
piston B be tardy in its action and remain with D at that end,
toward which the piston A is moving ; for C would be moved far
enough to open the steam port leading to the main cylinder, since
the possible travel of C is greater than that of D. The supple-
mental piston B cannot strike the heads of its cylinders, for in its
alternate passage beyond the exhaust ports X and X, it cushions
on the vapor intrapped in the ends of this cylinder.
MISCELLANEOUS PUHP QUESTIONS.
Q. What is a pump? A. It is hard to get a definition that
will cover the whole ground. A pump may be said to be a
mechanical contrivance for raising or transferring fluids ; and as a
general thing consists of a moving piece working in a cylinder or
other cavity ; the device having valves for admitting or retaining
the fluids.
Q. What two classes of operations are included in the term
"raising" fluids? A. They may be raised by drafting or suc-
tion, from their level to that of the pump ; they may be raised
from the level of the pump to a higher level.
Q. Do pumps always "raise" by either method, from one
level to a higher one, the liquid which they transfer? A. No ; in
many cases the liquid flows by gravity to the pump ; and in some
it is delivered at a lower level than that at which it is received.
560 HANDBOOK ON ENGINEERING 0
Q. Where a pump is not used for raising a liquid to a higher
level, for what is it generally used ? A. To increase or decrease
its pressure.
Q. What classes of Liquids are handled by pumps ? A. Air,
ammonia, lighting gas, oxygen, etc.
Q. Name some liquids which are handled by pumps? A.
Water, brine, beer, tan liquor, molasses, acids and oils.
Q. Where it is not specified whether a pump is for gas or for
liquid, which is generally understood? A. Liquid.
Q. What gas is most frequently pumped? A. Air.
Q. What liquid is generally understood if none other is speci-
fied for a pump? A. Water.
Q. Can pumps handle hot and cold liquids? A. Yes; though
cold are easier handled than hot.
Q. What is the difference between a fluid and a liquid? A.
Every liquid is a fluid ; every fluid is not a liquid. Air is a fluid ;
water is both a fluid and a liquid. Every liquid can be poured
from one vessel to another.
SUCTION.
Q. What causes the water to rise in a pump by so-called
suction? A. The unbalanced pressure of the air upon the surface
of the liquid below the pump, forces the water up into the suction
pipe when the piston is withdrawn from the liquid.
Q. How much is the pressure of the atmosphere? A. At the
sea level about 14.71bs. per square inch, or 2116.8 Ibs. per square
foot.
Q. In what direction is this pressure exerted? A. In every
direction equally.
Q. What tends to prevent the water from being lifted? A.
The force of gravity, which is the result of the attraction of the
earth.
HANDBOOK ON ENGINEERING. 56'1
Q. In what direction does the force of gravity act? A. In
radial lines towards the center of the earth.
Q. With what force does this gravity act? A. That- depends
upon the substance upon which it is acting.
Q. Why do you refer to the level of the sea in speaking of the
pressure of the air and the weight of water? A. Because the air
pressure becomes less as, in rising above the sea level, we recede
from the center of the earth, and the weight of a given quantity
of water or any other substance becomes less than it is at the level
of the sea, as we approach to or recede from the center of the
earth.
Q. How is it that the weight of any substance becomes less if
you go either above or below the sea level? A. The farther you
go from the earth, the less its attraction and the less a given
body will weigh upon a spring balance. The farther down into
the earth you go, the nearer you get to the center of the earth, at
which, there being attraction upon all sides, any body would
weigh nothing. Going from the surface of the earth towards its
center, then, a body weighs less and less upon a spring balance.
Q. Why do you specify a spring balance? A. Because in
weighing by counterpoise, both the body to be weighed and the
counterpoise by which it is weighed, would change their weights
in the same proportion, as the position with regard to the center
of the earth was changed.
Q. What are the causes which principally prevent pumps from
lifting up to the normal maximum? A. Friction ; leakage of air
into the suction, chokes in the suction pipe.
Q. Can a liquid be " drafted" without the expenditure of
work ? A. No ; in drafting a liquid to the full height to which it
can be drafted, at least as much power must be expended as
would lift the same weight of liquid that height by any mechan-
ical means ; only the amounts of friction being different.
Q. Then what advantage is there in having a pump draft its
36
562 HANDBOOK ON ENGINEERING.
water to the full possible height, over having it force the watei
the full height? A. Convenience in having the pump higher up.
Q. Can a pump throw water higher or farther, with a given
expenditure of power, where it flows in, than where it must draft
its water? A. Yes; on the same principle that it can throw
farther or force harder when the water is forced to its suction
side than where it merely flows in.
Q. What is the use of the suction chamber? A. To enable
the pump barrel to fill where the speed is high ; to prevent
pounding, when the pump reverses.
Q. Upon what does the lifting capacity of a pump depend?
A. When the pump is in good order its lifting capacity depends
mainly upon the proportion of clearance in the cylinder and valve
chamber to the displacement of the piston and plunger.
Q. Which will lift farther, an ordinary piston pattern pump or
a plunger pump? And why? A. Other things being as nearly
equal as they can be made between these two pumps, the piston
pump will lift the farther of the two, because the plunger pump
has the most clearance.
Q. What is the advantage of the suction chamber? A. To
assist the pump in drafting, especially at high speed.
Q. What is the advantage of the air chamber? A. To make
the stream steady.
Q. What difficulty is sometimes met with in using an air
chamber? A. Where the pressure is very great sometimes the
air is absorbed by the water, and thus the cushion is detroyed.
FORCING.
Q. What will be the volume of the air in the air chamber of a
force pump, when the pump is forcing against a head of 67.6
feet? A. It will be reduced to half its ordinary volume, because
it will be at the pressure of two atmospheres.
HANDBOOK ON ENGINEERING.
563
Fig. 290. Pump cylinder fitted with liner.
The above cut shows a pump with a removable cylinder
or liner, and is packed with fibrous packing set out by adjustable
set screws and nuts. This style of a pump is the best for small
water-works or elevators, or where a pump is used where the
water is muddy or sandy.
To find the horse power necessary to elevate water to a
given height: Multiply the total weight of the water in pounds
by the height in feet and divide the product by 33,000 (an allow-
ance of 25 per cent should be added for water friction, and a further
allowance of 25 per cent for loss in steam cylinder.)
The heights to which pumps will force water when running at
564 HANDBOOK ON ENGINEERING.
100 feet piston speed per minute, and the suction and discharge
pipes being of moderate length, will be found by dividing the area
of the steam piston by the area of the water piston, and multi-
plying the quotient by the steam pressure. Deduct 40 per cent
for friction and divide the remainder by .434.
Example* — To what height will an 8-inch steam piston, with
a 5-inch water piston, force water, the steam pressure being 80
Ibs. by gauge? Ans. 283 ft. nearly.
Operation* — Area of steam piston = 50. 26 sq0 ins.
" " water " =19.63 " "
Then, ^^ = 2.56. And 2.56 X 80 = 204.80 Ibs.
19.63
Then, 204.80 less 40% = 122.88 Ibs.
And, 122f8 = 283 + feet.
An allowance must be made where long pipes are used.
The normal speed of pumps is taken at 100 piston feet per
Jninute, which speed can be considerably increased if desired.
For feeding* boilers, a speed of 25 to 50 lineal feet per minute
is most desirable.
A gallon of water, U. S. Standard, weighs 8^ Ibs. and contains
231 cubic inches.
A cubic foot of water weighs 62.425 Ibs. and contains 1,728
cubic inches, or 7J gallons.
Doubling the diameter of a pipe increases its capacity four
times.
Friction of liquids in pipes increases as the square of the
velocity.
To find the area of a piston, square the diameter and multiply
by ,7854.
HANDBOOK ON ENGINEERING. 565
Boilers require, for each nominal horse-power, about one cubic
foot of feed water per hour.
In calculating* horse power of tubular or flue boilers, consider
15 square feet of heating surface equivalent to one nominal horse-
power.
To find the pressure in pounds per square inch of a column
of water, multiply the height of a column in feet by .434.
Approximately, we say that every foot of elevation is equal to
one-half Ib. pressure per square inch ; this allows for ordinary
friction.
The area of the steam piston, multiplied by the steam pressure,
gives the total amount of pressure that can be exerted. The
area of the water piston, multiplied by the pressure of water per
square inch, gives the resistance. A margin must be made
between the power and the resistance to move the pistons at the
required speed — say from 20 to 40 per cent, according to speed
and other conditions.
To find the capacity of a cylinder in gallons : Multiplying the
area in inches by the length of stroke in inches will give the total
number of cubic inches ; divide this amount by 231 (which is the
cubical contents of a gallon of water) and quotient is the capacity
in gallons.
To find quantity of water elevated in one minute running at 100
feet of piston speed per minute : Square the diameter of water
cylinder in inches and multiply by 4.
Example: Capacity of a five-inch cylinder is desired. The
square of the diameter (5 inches) is 25, which, multiplied by 4,
gives 100, which is gallons per minute, approximately.
Q. What is the reason that a steam pump of the horizontal
double acting type should throw an intermitting stream under
pressure, like the stream from milking .a cow, only not quite so
bad as that? Have tried valves of different sizes, with different
amount of rise, springs or valves of different tension, different
066 HANDBOOK ON ENGINEERING.
.
kinds of packing in water piston, and different sized water ports
or passages, without any apparent difference. A. Steam pumps
of the horizontal double-acting type are not alone in throwing an
Intermitting stream. The same thing shows up in vertical single-
acting pumps ; but all horizontal double-acting pumps do not so
behave. The steam fire engine shows that no type of pump is
exempt from ;t squirting."
Q. How may this squirting be lessened? A. By increasing
the suction valve area ; by giving more suction chamber and
more air chamber.
*********
Q. What is a sinking pump ? A. One which can be raised and
lowered conveniently, for pumping out drowned mines, etc.
Q , Into what main general classes may reciprocating cylinder
pnmps be divided? A. Into single acting and double acting.
Q. What is a single acting reciprocating pump ? A. One in
which each reciprocation or single stroke in one direction causes
one influx of fluid, and each reciprocation or single stroke in the
opposite direction causes one discharge of fluid. In other words,
the pump, as regards its action, is single ended.
Q. What is a double acting reciprocating pump ? A. One in
which each end acts alternately for suction and discharge. Re-
ciprocation of the piston in one direction causes an influx of
fluid into one end of the pump from the source, and a discharge
of fluid at the opposite end ; on the return stroke the former
suction end becomes the discharge end. In other words, the
pump is double ended in its action ; or is " double-acting."
Q. What is the special advantage of having double-acting
pump cylinders? A. The column of water is kept in motion
more constantly, and hence there is less jar ; smaller pipes may
be u«ed.
***********
Q. How may those pumps which are driven by steam against a
HANDBOOK ON ENGINEERING. 567
steam piston be divided? A. Into those which have a fly wheel
and those which have no fly wheel.
Q. Into what classes may those pumps which are driven by
steam, without a flywheel, be divided? A. Into direct acting
and duplex.
Q. What is the advantage of a fly wheel steam pump? A.
Steadiness of action ; the capability of using the steam expan-
sively.
Q. What are the disadvantages of fly wheel pumps? A. Great
weight ; inability to run them very slowly without gearing down
from the fly wheel shaft, as the wheel must run comparatively
rapidly.
Q. What is a direct-acting steam pump? A. One in which
there is no rotary motion, the piston being reversed by an impulse
derived from itself at or near the end of each stroke. There is
but one steam cylinder for one water cylinder ; the valve motion
of the steam cylinder being controlled by the action of the steam
in that cylinder.
HOW TO SET THE STEAfl VALVES ON A DUPLEX PUMP.
The steam valves on duplex pumps generally have no outside
lap, consequently, in their central position, they just cover the
steam ports leading to the opposite ends of cylinder.
By lost motion is meant, the distance a valve-rod travels
before moving the valve; if the steam-chest cover is off the
amount of lost motion is shown by the distance the valve can be
moved back and forth before coming in contact with the valve-
rod nut. The object of lost motion is to allow one pump to
almost complete its stroke before moving the valve of its fellow
engine. As the steam piston is nearing the end of its stroke, it
moves the valve of its fellow engine, admitting steam and start-
ing its fellow engine as it lays down its own work ; in other words,
568
HANDBOOK ON ENGINEERING.
the other picks it up. The amount of lost motion required is
enough to allow each piston to complete its stroke ; in other words,
if there was no lost motion, as the pistons would pass the
center of their travel, they would move the valve of theii
fellow engine, and the result would be a very short stroke.
Fig. 291. Showing the steam valves properly set.
To set the steam valves, move the steam piston towards the
steam cylinder head until it comes in contact with the head ; mark
with a scribe on the piston-rod at the face of the stuffing-box
follower on steam end ; then move the piston to its contact stroke
on the opposite end and make another mark on the piston-rod,
exactly half way between the face of the stuffing-box follower on
the steam end, and the first mark. Then move the piston back
until the middle mark is at the face of piston-rod stuffing-box
follower on the pump end. This operation brings the piston
exactly in the middle of the stroke. Then take off the steam
HANDBOOK ON ENGINEERING. 569
chest cover, place the slide-valve in the center, exactly over the
steam ports. Place the slide-valve nut in exact center between
the jaws of the slide-valve, screw the valve-rod through the nut
until the eye on the valve-rod head comes in line with the eye of
the valve-rod link ; slip the valve-rod head pin through head and
the valve is set. Repeat the same operation on the other side of
the pump. Where a pump is fitted with four hexagon valve-rod
nuts, two either end of the slide-valve, instead of one nut in the
center of the valve, set and lock these hexagon nuts at equal dis-
tances from the outer end of the slide-valve jaws, allowing a little
lost motion, varying from J" on high-pressure pumps, to, say,
i" on low service pumps, on each side of valve ; if the steam
piston hits the head, take up some of the lost motion ; if the
steam piston should not make a full stroke, give more lost motion.
PROPER MANNER OF ARRANGING PIPE CONNECTIONS.
For trie purpose of showing good arrangement, the following
cut is presented, Fig. 292.
On long lifts it is necessary to provide the suction pipe S
with a foot-valve F. By the use of a foot-valve, the pipe and
cylinders are constantly kept charged with water, allowing the
pump to start without having to free itself and the suction pipe
of air. In case of a long lift, the vacuum chamber V is also
essential. This may be readily constructed by using a tee in place
of the elbow E, extending the suction pipe and placing a cap
upon the top. In order to keep the water back when the pump is
being examined or repaired, a gate valve should be placed in the
delivery pipe. It sometimes happens that, either purposely or
through a leak in the foot-valve, the suction chamber becomes
empty. For the purpose of charging the suction pipe and cylin-
der a " charging pipe " P is placed outside the check valve,
connecting the delivery pipe D with the suction. In order that
570
HANDBOOK ON ENGINEERING.
the pump, in starting, may free itself of air, a check valve Cand
a " starting pipe" A should be provided. This pipe may be
Fig. 292. Proper arrangement of pipe connections.
led to any convenient place of discharge. After the pump has
started, the valve in the starting pipe should be closed gradually.
Faulty connections are generally the cause of the improper action
HANDBOOK ON ENGINEERING. 571
of a pump. Great care should, therefore, be taken to have
everything right before starting. A very small leak in the suc-
tion will cause a pump to work badly.
Q. What is the peculiarity of the duplex type? A. There are
two steam cylinders and two water cylinders ; the piston of one of
these cylinders works the valve of the other cylinder, and vice versa.
Neither half can work alone. This name is entirely arbitrary.
Q. What would you call a pumping machine in which there are
two steam cylinders, each operating a water cylinder in line with
it ; each half being a perfect pumping machine independent of the
other side? A. A " double " pump.
Q. Can a direct acting steam pump use steam expansively?
A. Not to any extent ; in fact, there would be danger of sticking
upon the centers in most cases, if there was lap and expansion.
Q. What is the reason that a single cylinder engine cannot well
reverse itself without a fly wheel, by means of the ordinary single
D valve? A. Because when the valve was at mid-travel, both
ports of the valve seat would be closed by the valva faces, and
neither exhaust nor admission take place.
Q. What means are employed in a direct acting steam pump to
move the valve ? A. A small supplementary piston is used ; this
supplementary piston being actuated by the main piston in any
one of several different ways.
Q. What are the principal ways of working the supplementary
piston from the main piston? A. (1) The main piston strikes
the tappet of a small valve, which opens an exhaust passage in
one end of the cylinder, containing a supplementary piston, and
having live steam pressing upon both ends of the supplementary
piston ; (2) by the main piston striking a rod passing through
the cylinder head, and moving a lever, which controls the motion
of the part of the main valve to which is attached the valves which
moves the supplementary piston ; (3) the main piston rod carries
a tappet arm, which twists the stem of the supplementary piston,
572 HANDBOOK ON ENGINEERING.
thus uncovering ports which cause its motion ; (4) a projection
upon the main piston rod engages the stem and operates the valve
which moves the supplementary piston, but if that valve should
not, by means of its steam passages, cause quick enough or sure
enough motion of the supplementary piston, a lug upon this stem
moves the supplementary piston.
Q. In the first of these four classes, what is the principal
element in the valve motion? A. A difference in area between
the eduction port of the supplemental piston and its induction port
Q. What is the principal feature in the second class? A. A
regular slide valve letting steam upon alternate ends of the sup-
plemental piston.
Q. In the third class, what is the main feature? A. A twist-
ing motion in the supplemental piston.
Q. In the fourth class, what is the principal feature? A.
Movement of the supplemental piston by steam controlled by a
slide valve, and by the mechanical action of the slide valve itself
if its steam distribution is defective.
Q. What are the objections to most pumps of the direct actiig
type? A. The unbalanced condition of the auxiliary pistons in
the exhaust side, causing a loss of steam when the parts are worn,
the choking up of the small ports for the auxiliary pistons, by the
gumming and caking of the oil therein.
Q. Can the ordinary direct acting steam pump use steam
expansively? A. No.
Q. How may this be done? A. Ity compounding.
Q. What is to be taken into consideration in the use of com-
pound steam pumps? A. That they are designed for a certain
range of pressure — say from 80 to 120 pounds boiler pressure,
and will do their best work between these pressures.
Q. Have all direct acting steam pumps intermittent valve
motion ? A. No ; there are some which have continuous valve
motion.
HANDBOOK ON ENGINEERING. 573
Q. In most direct-acting steam pumps, are the auxiliary piston
heads made together or in separate pieces ? A. Together.
Q. They are in contact with the steam in the chest? A. Yes.
Q. What should be said about the location of a pump? A. It
should be as near the source of supply as is convenient.
Q. What may be said about convenience in repairs? A. The
pump should have room left upon all sides ; and upon both ends
equal to its length, for the removal of the piston rods in case of
repairs.
Q. If the floor is not strong enough, how may a good founda-
tion be made ? A. By digging two or three feet into the ground
and building up the proper height with stone or brick laid in
strong cement, with a cap stone.
Q. What may be said about suction pipes? A. They must be
as large as possible ; the longer they are the greater in diameter
they should be ; they should be as straight as possible, and as
free from bends and valves ; they must be air-tight ; they must
not bo allowed to get obstructed by foreign substances.
Q. W hat may be said about the area of strainer holes? A.
They should have an aggregate area about five times that of the
suction pipe.
Q. Where are foot valves necessary ? A. Upon long suctions
or high lifts.
Q. Should two pumps take their suction from one pipe ? A. It
should be avoided, unless the pipe is very large ; and in case both
suctions should be arranged so that one of the pumps should not
have to draft at right-angles to the flow of water going to the other
pump.
Q. What arrangement should be made where it is necessary to
have two pumps draft from one suction? A. There should be a
Y connection.
Q. What is a good way to reduce the friction in suction pipes
where there are many bends ? A. To use bends of wrought-
574 HANDBOOK ON ENGINEERING.
iron pipe of as long a radius as possible, instead of oast-iron
elbows.
Q. What may be said about the lower end of the suction pipe?
A. It should generally have a strainer ; and if the lift is over 12
to 15 feet, should have a foot valve.
Q. What is a good thing to do with the discharge pipe near
the pump? A. To put a valve in it near the pump, to keep
the water in the pipe when the water end is to be opened for
inspection or repairs.
Q. What provision should be made for priming the pump? A.
There should be a pipe with a stop valve in it connected from the
discharge pipe beyond this check valve, or from some other source
of supply, to the suction pipe, for the purpose of priming the
pump.
Q. When the pump is in position for piping, what care should
be taken? A. That the pipes are of proper length, so as not to
bring any undue strain upon them in connecting them to the pump
as in that case they will be liable to give trouble by breaking or
working the joints loose and leaking.
Q. Does any pipe have an effective diameter as great as its
nominal diameter? A. No; because the sides retard the flow of
the liquid ; there is a neutral film of liquid which practically does
not move.
Q. Upon what does the thickness of this film of liquid depend?
A. Upon the viscosity (commonly miscalled the " thickness ")
of the liquid ; upon the roughness, material and diameter of the
pipe ; the pressure, etc.
Q. When long lines of pipe are used, should the diameter of the
pipe be the same all the way along, or should there by sections
be decreasing diameter, as the distance from the pump increases ?
A. Most emphatically, the pipe diameter should remain constant
clear out to the end.
HANDBOOK .ON ENGINEERING. 575
TAKING CARE OF A PUMP.
Q. What can be said about taking care of a pump? A. In
places where an inferior grade of labor is employed, oil and dirt
are sometimes found covering the steam chest and pump to the
depth of an inch in thickness ; stuffing boxes are allowed to go
leaky and get loose ; the valve motion is never looked after ; lost
motion is never taken up, and the pump will be let run in a slip-
shod way for months, until some accident occurs. This will
sometimes exist in places where the engine is well taken care of.
Q. Should not as good care be taken of a steam pump as of
an engine? A. Yes. It is a steam engine, and the fact that it
has generally but little adjustability, should not render it liable to
lack of care.
Q. What is a very common thing for pump runners to do when
anything happens ? A. To condemn the pump at once without
finding out the cause of the trouble.
Q. What is one reason of this? A. The man who understands
an ordinary engine, will often become quite perplexed when he
examines the steam end of a direct acting steam pump, because
he does not comprehend the principal feature of its construc-
tion— that all direct acting steam pumps which have no fly
wheels and cranks, must generally have an auxiliary piston in
order to carry them over the " dead center." A direct acting
steam pump is really a double engine ; a plain, flat slide valve
admitting steam to a small piston, which in turn operates the
main valve, which gives steam by the usual arrangement to the
main piston.
Q. What would save firemen and engineers much trouble with
steam pumps? A. If they would take the trouble to examine
their pumps carefully, and find out the way their valves were
arranged and actuated.
Q. Upon what does the successful performance of a pump
576 HANDBOOK ON ENGINEERING.
depend, in great measure? A. Upon its proper selection from
among the many patterns differing from each other in size, pro-
portion and general arrangement.
Q. What may be said about the selection of pumps? A.
Pumps are often selected improperly for their work. As an illus-
tration, a man who wishes to use a circulating pump for a surface
condenser, where the water pressure upon the pump cylinder will
never exceed 5 to 10 pounds, will buy a pump intended for boiler
feed work, and having its steam cylinder about three times the
area of its pump cylinder.
Q. What will be the result in such a case? A. There will be
little or no pressure in the steam cylinder when working on the
condenser ; and while there is pressure sufficient to move the
main piston, there is not enough to operate the auxiliary piston
with positiveness.
Q. In ordering a pump, or in asking estimates, what informa-
tion should be given? A. In ordering a pump, it is to the inter-
est of the purchaser to fully inform the maker or seller on the
following questions : 1st. For what purpose is the pump to be
used? What is the average steam pressure? 2d. What is the
liquid to be pumped ; and is it hot or cold, clear or gritty, fresh,
salt, alkaline or acidulous? 3d. What is the maximum quantity
to be pumped per minute or hour? 4th. To what height is the
liquid to be lifted by suction, and what is the length of the suction
pipe, and the number of elbows or bends? 5th. To what height
is the liquid to be pumped, and what is the length of discharge
pipe?
Q. How can an engineer familiarize himself with the direction
of the auxiliary steam and exhaust passages: A. By means of
a piece of wire.
Q. What is the special thing to look after in duplex pumps?
A. That all packings are adjusted uniformly on both sides.
Q. What would be the result of having the packings different
HANDBOOK ON ENGINEERING. 577
upon the two sides of a duplex pump? A. The machinery would
run unsteadily.
Q. If a pump works badly, what should be about the first thing
to look at? A. The connections.
Q. When a pump is first connected, what should be done?
A. It should be blown through to remove dirt ; if it be of the
class which will permit of removing the bonnets and blowing
through, that should be done.
Q. What pump piston speed is recommended for continuous
boiler feeding service? A. About 50 feet per minute.
Q. What may be said about the care and use of steam pumps
of all kinds? A. It is important that the pump be properly and
thoroughly lubricated ; that all stuffing-box, piston and plunger
packings be nicely adjusted ; not so tight as to cause undue fric-
tion ; nor so slack as to leak badly.
Q. In which end of a steam pumping machine is there most
likely to be trouble? A. In the water end.
Q. If a pump slams and hammers in its water end, is it neces-
sarily defective in its water cylinder? A. No; it may be that
there is no suction chamber, or not enough ; or sometimes it slams
because the suction pipe is not large enough.
Q. What are very common defects in cheap grades of pumps?
A. Too little valve area in the pump end ; too great lift for the
valves.
Q. What are the principal causes of pumps refusing to lift
water from the source of supply? A. Among these may be
mentioned leaky suction pipes, worn out pistons, plungers, pack-
ings or water valves ; rotten gaskets on joints in piping or pump ;
and sometimes a failure to properly prime the pump as well as
the suction pipe.
Q. What is one great cause of a pump refusing to lift water
when first started? A. It often happens that a pump refuses to
lift water while the full pressure against which it is expected to
37
578 HANDBOOK ON ENGINEERING.
work is resting upon the discharge valves, for the reason that the
air within the pump chamber is not dislodged, but only compressed,
by the motion of the plunger. It is well, therefore, to arrange
for running without pressure until the air is expelled and water
follows ; this is done by placing a valve* in the delivery pipe
and providing a waste delivery, to be closed after the pump has
caught water.
Q. Sometimes when starting, the water may not come for a
long time ; what is the best thing to do in this case? A. First,
open the little air cock, which is generally located in the top of
the pump, between the discharge valves and the air chamber, to
let off any accumulation of air, which may there be confined
under pressure. Very often, by relieving the pump of this air
pressure, it will pick up its water by suction and operate
promptly.
Q. What precaution must be taken in priming the pump? A.
The air cock, which should be provided at the top of the pump,
should be opened to allow the escape of the air from the suction
pipe and from the pump, and then the valve in the priming pipe
should be opened. The pump should then be started slowly, as
it aids in more completely filling the pump cylinders, which
otherwise, might not occur and the pump might fail to lift water.
Q. Is there any advantage in having air in the suction? A.
Sometimes a small amount of air let into the suction will cause less
jarring when the duty is very heavy.
Q. What may be said about pumping hot water? A. Where
the hot water is very hot, it should gravitate to the pump, instead
of an attempt being made to draft it.
Q. In the plunger pumps, 'what is about the only wearing part
of the water end? A. The packing of the plunger stuffing-boxes.
Q. How can a pump be prevented from freezing? A. By
having draining cocks and opening them when the pump is
idle.
HANDBOOK ON ENGINEERING. 579
Q. What may be said about leather piston packing for water
cylinders? A. For cold water, or sandy, gritty water, the
leather packing has many points to commend it ; it makes a
tight piston, and one that is the least destructive to pump
cylinders.
Q. What is the best way to handle the square packing mostly
employed, which is composed of alternate layers of cotton and
rubber? A. Cut the lengths a trifle short, then there will be
room for the packing to swell and not cause too much friction. We
have known pistons where this precaution has not been taken to
be fastened so securely in the cylinder by the swelling of the dry
packing, that full steam pressure could not move tliem.
Q. What is the remedy in such a case? A. Remove the
follower, take out the different layers of packing and shorten their
lengths.
Q. What is the reason that some soft waters corrode pipes so
often? A. Because they contain a large proportion of oxygen.
Q. Will a pump with a 6" water cylinder and a 6" steam cylin-
der force water into a boiler, the discharge from water cylinder
being 4" diameter; boiler pressure, 80 Ibs.? A. A pump with a
6" water cylinder and 6" steam cylinder will not force water into
the boiler which supplies it, no matter what the steam pressure,
nor what the size of discharge pipe. It will not move. The
pressures would be equalized and there would be nothing to over-
come friction of steam and water in pipes, and cylinder. The
foregoing case supposes that the water is to be lifted to the pump ;
or at least that there shall be no head ; also, that there shall be
no fall from pump to boiler. If there were sufficient head or fall
to overcome all the various frictions, and no lift, the pump
would apparently work ; but really, the water piston would be
dragging the steam piston along.
Q. How may acids be pumped? A. By what is known as
blowing up ; that is, by employing a pump to put pressure upon
580 HANDBOOK ON ENGINEERING.
the acid in a closed vessel, thereby forcing it through a pipe
placed in the bottom of the vessel.
Q. In case any wearing part of a pump gets to cutting, what
should be done? A. If it is not practicable to stop the pump nor
to reduce its speed, the part which is getting damaged should be
given very liberal oiling.
Q. What is the best oil for this purpose? A. That depends on
the nature of the cutting surfaces, and on the pressure therein ;
the mineral oils are generally more cooling than others, although
they have less body to resist squeezing.
%
CALCULATING THE BOILER FOR A STEAM PUMP.
The amount of work which a bgiler has to do is very easy of
determination. Given the largest number of gallons which a
pump will be required to pump per minute, and the height in feet
from the surface of the well from which the water is drawn, to
the point'of discharge, you can easily tell by multiplying by 8| —
the weight in pounds of one gallon — the number of foot pounds
of power consumed per minute in lifting the water, adding a cer-
tain percentage for friction of the machine and of water in the
pipe, we have the total number of foot pounds consumed per
minute, and this divided by 33,000 will be the horse power
consumed.
The allowance for friction will vary with the style, size and
condition of the pump, the size of the pipe, and, above all, the
manner in which the pipe is connected up, the number of right
angle turns, etc.
This may be arrived at in another way. A column of water
2.3 feet in height exerts a pressure of one pound. Allowing the
.3 for friction, we can, by dividing the total left in feet by two,
get at the pressure per square inch, which is being exerted against
the water piston or plunger, and multiplying by the number of
HANDBOOK ON ENGINEERING. 581
square inches in that piston gives the total pressure against which
the pump is working. This multiplied by the piston speed in feet
minutes, and divided by 33,000, will give the lift in horse power.
In this case, as in the other, the lift must be calculated from the
surface of the supply, and not from the pump, when the pump is
lifting its supply. If the water flows to the pump it must be
calculated from the height of the water cylinder. An allowance
of, say, 25 per cent, -should be made above the horse power thus
shown, in order to provide for contingencies, and to be on the
safe side.
In selecting a boiler to do this work, it must be borne in mind
that a boiler which is sold for a certain horse power, is supposed
to be able to furnish that power in connection with a good steam
engine , and they are not apt to be overrated . Now , the steam pump
as usually built, does not approach in economy the ordinary steam
engine, and, therefore, a boiler which will develop, twenty-five
horse power in connection with a good engine would be too small
for a pump which was required to do the same amount of work.
The evaporation of 30 pounds of water per hour from feed at 100
degrees Fahr. into steam of 70 Ibs. pressure, has been adopted by
several authorities as a horse power. Any good automatic cut-off
will run on this amount of water, and if an estimate can be made
of the comparative performance of the pump under consideration,
a close approximation to the desired size of boiler can be made.
THE WORTHINGTON WATER METER.
The counter registers cubic feet ; one foot being 7T%8^ gallons,
United States standard. It is read in the same way as registers
of gas meters. The following example and directions may be of
use to those unacquainted with the method: If a pointer is
between two figures, the smaller one must invariably be taken.
Suppose the pointers of the dials to stand as in the engraving.
582
HANDBOOK ON ENGINEERING.
The reading is 6,874 cubic feet. From the dial marked ten wa
get the figure 4 ; from the next, marked hundred, the figure 7 ;
from the next, marked thousand, the figure 8 ; from the next,
Fig. 293. Worthington water meter,
marked ten thousand, the figure 6. The next pointer being
between ten and 1, indicates nothing. By subtracting the read*
ing taken at one time, from that taken at the next, the consump-
tion of water for the intermediate time is obtained.
TABLE OF PRESSURE DUE TO HEIGHT.
s
H
li
ft .
a*
W> W
-3 x
5j
Si
P .
«> ,d
s .
II
ft .
0.43
2.16
4.33
6.49
8.66
10.82
12.99
15.16
17.32
19.49
21.65
23.82
25.99
28 15
30.32
32.48
34 65
36.82
38.98
41.15
43 31
HANDBOOK ON ENGINEERING.
583
TABLE OF DECIMAL EQUIVALENTS OF Sths, 16ths,
32ds AND 64ths OF AN INCH.
Sths.
32ds.
64ths.
64ths.
i = .125
SV = .03125
/4- = .015625
f| = .546875
I = .25
-3% = .09375
^ = .046875
i = .578125
| = .375
-359- == .15625
•ft = .078125
-J = .609375
i = .50
3£ _ .21875
•h = .109375
jfi = .640625
| = .625
^ = .28125
•fy = .140625
|| = .671875
I = .75
Ji = .34375
iri = .171875
|| = .703125
1 = .875
$ = .40025
ir| = .203125
jj = .734375
Jf = .46875
ir| = .234375
|| = .765625
LJ = .53125
irj = .265625
i = .796875
leths.
if = 059375
irf •== .296875
f = .828125
|^ = .65625
Ji = .328125
| = .859375
A- = .0625
f| = .71875
I = .359375
f} = .890625
A = 1875
|4 = .78125
Jf = .390625
^ = .921875
-,V = .3125
f| = .84375
|f == .421875
i = .953125
f6- = .4375
|f = .90625
§} == .453125
|| = .984375
A = .5025
|i = .96875
J = .484375
H = .6875
|3 _- .515625
|| = .8125
[f = .9375
LATENT HEAT OF LIQUIDS, UNDER A PRESSURE
OF 30 INCHES OF MERCURY.
(TREATISE ON HEAT, BY THOMAS BOX.)
Latent Heat
in Units.
Increase of Tempe-
rature of Liquid,
if Heat had not
become Latent.
Water
966
966°
Hegnault.
Alcohol
457
735°
Ure.
Ether
313
473°
a
Oil of Turpentine
184
390°
tt
184
443°
1C
The boiling point of different liquids varies; and the boiling point
of a liquid varies with the pressure
584
HANDBOOK ON ENGINEERING.
O 00 00 b-
r-^ CO
O
00 iQ Oi
00
• . 02
* 00 P
S ajD
2§*
•w^ O -~
5 jj|
a 5 S rv
HANDBOOK ON ENGINEERING. 585
CAPACITY OF SQUARE CISTERNS IN U. S. GALS.
5X5
5X6
5X7
5X8
5X9
5X10
6X6
6X7
6X8
6X9
6X10
5 ft..
935
1122
1309
1496
1683
1870
1346
1571
1795 2020
2244
54 ft..
1028
1234
1440
1645
1851
2057
1481
1728
1975
2221
2469
6 ft..
1122
1346
1571
1795
2019
2244
1615
1885
2154
2423
2693
64ft.-
1215
1459
1702
1945
2188
2431
1750
2042
2334
2625
2917
7 ft..
1309
1571
1833
2094
2356
2618
1884
2199
2513
2827
3142
74ft..
1403
1683
1963
2244
2524
2800
2019
2356
2693
3029
3366
8 ft..
1496
1795
2094
2393
2693
2992
2154
2513
2872
3231
3592
84ft..
1589
1907
2225
2543
2861
3179
2288
2670
3052
3433
3816
9 ft..
1683
2020
2356
2693
3029
3366
2423
2827
3231
3635
4041
94ft..
1776
2132
2487
2842
3197
3553
2558
2984
3412
3837
4265
10 ft..
1870
2244
2618
2992
3366
3470
2692
3142
3591
4039
4489
6X11
6X12
7X7
,7X8
7X9
7X10
7XH
7X12
8X8
8X9
5 ft..
2468
2693
1832 2094
2356
2618
2880
3142
2394
2693
54 ft. .
2715
2962
2016
2304
2592
2880
3168
3456
2633
2962
6 ft..
2962
3231
2199
2513
2827
3142
3456
3770
2872
3231
64ft..
3209
3500
2382
2722
3063
3403
3744
4084
3112
3500
7 ft..
3455
3770
2565
2932
3298
3665
4032
4398
3351
3770
74ft..
3702
4039
2748
3141
3534
3927
4320
4712
3590
4039
8 ft..
3949
4308
2932
3351
3770
4189
4608
5026
3830
4308
84ft..
4196
4577
3115
3560
4005
4451
4896
5340
4069
4578
9 ft..
4443
4847
3298
3769
4341
4712
5184
5655
4308
4847
94ft..
4689
5116
3481
3979
4576
4974
5472
5969
4548
5116
10 ft..
4936
5386
3664
4188
4712
5236
5760
6283
4788
5386
WEIGHT OF WATER.
1 cubic inch 03617 pound.
12 cubic inches 434 pound.
1 cubic foot (salt) 64.3 pounds.
1 cubic foot (fresh) 62.425 pounds.
1 cubic foot 7.48 U. S. Gallons.
NOTE. — The center of pressure of a body of water is at two-thirds
the depth from the surface.
To find the pressure in pounds per square inch of a column of water,
multiply the height of the column in feet by .434. Every foot elevation
is called (approximately) equal to one-half pound pressure per square
inch.
586
HANDBOOK ON ENGINEERING.
SHOWING U. S. GALLONS IN GIVEN
CUBIC FEET.
NUMBER OF
Cubic
Feet.
Gallons.
Cubic
Feet.
Gallons.
Cubic Feet.
Gallons.
0.1
0.75
50
374.0
9,000
67,324.6
0.2
1.50
60
448.8
10,000
74,805.2
0.3
2.24
70
523.6
20,000
149,610.4
0.4
2.99
80
598.4
30,000
224,415.6
0.5
3.74
90
673.2
40,000
299,220.7
0.6
4.49
100
748.0
50,000
374,025.9
0.7
5.24
200
1,496.1
60,000
448,831.1
0.8
5.98
300
2,244.1
70,000
523,636.3
0.9
6.73
400
2,992.2
80,000
598,441,5
1
7.48
500
3,740.2
90,000
673,246.7
2
14.9
600
4,488.3
100,000
748,051.9
3
22.4
700
5,236.3
200,000
1,496,103.8
4
29.9
800
5,984.4
300,000
2,244,155.7
5
37.4
900
6,732.4
400,000
2,992,207.6
6
44.9
1,000
7,480.0
500,000
3,740,259.5
7:
52.4
2,000
14,961.0
600,000
4,488,311.4
8
59.8
3,000
22,441.5
700,000
5,236,363.3
9
67.3
4,000
29,922.0
800,000
5,984,415.2
10
74.8
5,000
37,402.6
900,000
6,732,467.1
20
149.6
6,000
44,883.1
1,000,000
7,480,519.0
30
224.4
7,000
52,363.6
40
299.2
8,000
59,844.1
From the above any cubic feet reading can readily be converted into
U. S. gallons, as follows:
How many gallons are represented by 53,928 cubic feet?
50,000 cubic feet = 374,025.9 gallons.
3,000 « " = 22,441.5 "
900 " " = 6,732.4 "
20 <f " =. 149.6 "
8 " " = 59.8 "
53,928 cubic feet =* 403,409.2 gallons
HANDBOOK ON ENGINEERING.
587
SHOWING COST OF WATER AT STATED RATES
PER 1000 GALLONS.
Number
of
Cubic
Feet.
COST PER 1000 GALLONS.
5
Cents.
6
Cents.
8
Cents.
10
Cents.
15
Cents.
20
Cents.
25
Cents.
30
Cents.
20
$0 007
$0.009
$0.012
$0-015
$0.021
$0.030
$0.037
$0.045
40
0.015
0.018
0.024
0.030
0.045
0 060 0.075
0.090
60
0.022
0.027
0.036
0.045
0.066
0.090
0.112
0.135
80
0.030
0.036
0.048
0.060
0.090
0 120
0.150
0.180
100
0.037
0.049
0.060
0.075
0.111
0.150
0.187
0.224
200
0.075
0.090
O.f20
0.150
0.225
0.299
0.374
0.449
300
0.112
0.135
0.180
0.224
0.336
0.449
0.561
0.673
400
0.150
0.180
0.239
0.299
0.450
0.598
0-748
0.898
500
0.188
0.224
0.299
0.374
0.564
0.748
0.935
1.122
600
0.224
0.269
0.359
0.449
0.448
0.898
1.122
1.346
700
0.262
0.314
0.419
0.524
0-786
1.047
1.309 1-571
800
0.299
0.350
0.479
0.598
0-897
1.197
1.496 1-795
900
0.337
0.404
0.539
0.673
1.011
1 346
1.683 2.020
1,000
0-374
0.449
0.598
0.748
1.122
1 496
1.870
2.244
2,000
0.748
0.898
1.197
1.498
2.244
2.992
3.740
4-488
3,000
1.122
1.346
1-795
2-244
3.366
4.488
5.610
6*732
4,000
1.496
1.795
2-393
2.992
4.488
5.984
7.480
8.976
5,000
1.870
2.244
2-992
3-740
5.610
7.480
9.350
11.220
6,000
2.244
2.692
3.590
4.488
6.732
8.976
11.220
13.464
7,000
2.618
3-141
4.189
5.236
7.854
10.472
13.090
15.708
8,000
2.992
3.590
4-787
5-984
8.976
11.968
14.961
17.953
9,000
3.366
4.039
5.385
6.732
10.098
13.464
16-831
20.197
10,000
3.74
4.488
5-984
7-480
11.122
14.961
• 18.701
22.441
20,000
7.48
8.976
11.96&
14.961
22.443
29.992
37-402
44.882
30,000
11.22
13.46
17.95
22-44
33.664
44.88
56.10
67.32
40,000
14.96
17.95
23-94
29.92
44.885
59.84
74-10
89.77
50,000
18.70
22.44
29.92
37.40
56.103
74.80
93-50
112.20
60,000
22.44
26.92
35.90
44.88
67.323
89.76
112.20
134.64
70,000
26.18
31-41
41.89
52.36
78.543
104.72
130.90
157-08
80,000
29.92
35.90
47-87
59.84
89.766
119.68
149.61
179.53
90,000
33-. 66
40.39
53.85
67.32
100. 98b
134 64
168-31
201.97
100,000
37.40
44.88
59.84
74.80
111.22
149.61
187-01
224.41
200,000
74.81
89.76
119.68
149.61
224.43
299 22
374.02
448-82
300,^00
112.20
134.64
179.53
224.41
336.64
448.83
561.03
673.24
400,000
149-61
179.53
239.37
299.22
448-85
598 44
748.05
897-66
500,000
187.01
224.41
299.22
374.02
561.03
748.05
935.06
1122.07
600,000
224.41
269.29
359.06
448 83
673-23
897.66
1122.07
1346.49
700,000
261.81
314.18
418.90
523.63
785-43
1047.27
1309.08
1570.88
800,000
299 22
359.06
478.75
598.44
897-66
1196 88
1496.10
1795.32
900,000
336.62
403.94
538.59
673.24
1009- 86
1346.49
1683.11
2019.73
1,000,000
374.02
448.83
598.44
748.05
1122,06
1498.10
1870.12
2244.15
HANDBOOK ON ENGINEERING.
OOOOOO
i-t
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CO tO CO Oi
oood
o •o'ooo'ooo'o'oor-i
•OOOOOOOOOOOt-i
•O i—1 -r-ieieOUtCOaOOicNOO
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.
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HANDBOOK ON ENGINEERING.
589
SHOWING HOW WATER MAY BE WASTED.
GALLONS DISCHARGED PER HOUR THROUGH VARIOUS SIZED ORIFICES
UNDER STATED PRESSURES.
=
-M
Diameters of Orifices in Inches and Fractions of an Inch.
"S S
3 S <D
HH
£| |
i
1
i
1
1
1
l£
11
H
2
m
inch
inch
inch
inch
inch
inch
inch
inch
inch
inch
Cu GO
20
8.66
300
720
1260
1920
2760
4920
7380
11100
15120
19740
40
17.32
450
960
1800
2760
3960
6720
10920
15720
21360
27960
60
25.99
540
1200
2160
3480
4800
8580
13380
19200
26220
34260
80
34.65
620
1380
2460
3840
5580
9840
15480
22260
30300
39540
100
43.31
690
1560
2760
4320
6240
11040
17280
24900
33900
44280
120
51.98
780
1780
3000
4740
6840
12120
18960
27240
37440
48480
140
60.64
816
1860
3300
5100
7320
13020
20160
29460
39080
52320
150
64.97
840
1920
3420
5280
7620
13560
21180
30480
41460
54120
175
75.80
900
2040
3660
5700
8220
14640
22800
32880
44940
58560
2CO
86.63
960
2220
3900
6120
8760
15600
25020
35880
47880
62580
235
101.79
1080
2460
4320
8280
11160
17100
26760
38520
52260
68460
The pressure or head of water is taken at the orifice, no allowance
being made for friction in the pipe. In practical calculations to deter-
mine the height which water can be thrown, the head consumed by the
friction of the water in flowing from the source to the orifice must be
considered.
IGNITION POINTS OF VARIOUS SUBSTANCES.
Phosphorus ignites at . , .... 150° Fahr.
Sulphur " " . . . . 500° «
Wood " " . . . . . . . . = c . . . 800° "
Coal . " " . . . .......... 1000° "
Lignite, in the form of dust, ignites at . . , . . c . . 150° "
CaimelCoal, " "" " . . ...... 200° "
Coking Coal, " " " . . . . . . . . 250° "
Anthracite, " « " " 300° "
590 HANDBOOK ON ENGINEERING.
CHAPTER XX,
THE INJECTOR AND INSPIRATOR.
The energy of motion of a body is well known to be the prod-
act of its mass by the half square of its velocity ; hence, it is
possible to communicate to a body of little weight a large amount
of energy by moving it fast enough, and in fact, the energy of
motion would only be limited by the speed which can be given
the body. In this way a small weight of steam flowing from an
orifice into a properly shaped jet of water is condensed, while the
velocity of the steam is greater than if flowing into air ; the
energy thus communicated is made sufficiently great by increasing
the weight of steam, which can be done by increasing the area of
the steam way, until we find such jet pumps adapted to many
purposes. There are, however, two which are of interest to us
in this connection, the well-known injector and inspirator, with
the large number of lifting and non-lifting varieties, all differing
in details as to form of nozzles, area of passages, distances
between nozzles, and that class of instruments in which, after a
certain energy and velocity have been reached, the operation is
rep'eated. These might be called " consecutive " instruments.
The illustrations in this book show some of the simplest and
adjustable kinds. Within a few years the principle of increase of
energy by increase of mass or velocity has been applied by in-
creasing the mass of steam used until we find that not only can a
few pounds weight of steam put into a boiler, a good many more
pounds of water at a much higher temperature than it had, but
that in a non-condensing engine it is possible, by using the ex-
haust in part, to put into the boiler at a much higher pressure
HANDBOOK ON ENGINEERING. 591
and temperature, a weight of water, which is still greater than
that of the steam moving it.
When the injector first made its appearance it was, by many,
considered as almost a paradox, especially by those who looked
at the question as one of hydrostatics only. That steam from a
boiler could put water back into it at the same pressure, and over-
come the friction of the passages without the aid that a steam
pump had of a difference of piston areas, was to them a puzzle ,
The use of exhaust steam at atmospheric pressure for the purpose
of putting water into a boiler at a pressure of 150 Ibs. per square
inch, would be to such minds utterly incomprehensible. The use
of an injector and inspirator, has this to recommend them, that
the feed-water cannot be introduced into the boiler cold or nearly
so> but must be warmed by contact with the steam, and the value
of this has been already shown. In small boilers where no heater
is used, an exhaust injector is better than a pump, and so is an
ordinary injector ; but the former includes in itself an exhaust
heater, saving a portion of heat from the exhaust, besides taking
the power as heat also ; while, with the common injector, the
heat for power and raising temperature are both derived from the
live steam in the boiler. The latter portion of heat is, of course,
directly returned to the boiler without loss, but that for power is
necessarily expended. As to the amount of power used by pump
and injector compared with each other, it would seem that the
pump is most efficient. There have been many comparative trials
of pump and injector, but the results have usually been unsatis-
factory from contained discrepancies.
Injectors are of the automatic type, so named on account of their
ability to restart when for any reason the supply of either water
or steam is momentarily interrupted. This is one of the simplest
of its type, all parts being accessible by the simple use of a mon-
key wrench. Taking off the bottom plug, the lower interior jet
592 HANDBOOK ON ENGINEERING.
follows it out, as does also the upper or steam jet, by removing
the coupling nut. On this account and for other reasons auto-
matic Injectors have become very popular, as the engineer is
enabled to make his own repairs where parts are interchangeable
as in this Injector. In installing an Injector, great care must be
exercised in getting tight pipe connections, especially in the
suction or water supply pipe, as the least particle of air admitted
to this pipe will ruin the vacuum, hence the starting or working
of the machine. Before connecting an Injector, from the fact
that there is a chance of iron scale or other refuse being in the
steam pipe, it should be blown out thoroughly before the Injector
is connected, otherwise whatever is in this pipe will be blown
into the Injector at the first opening of the steam valve and the
jets entirely clogged. It takes but the smallest particle of refuse
of any kind lodged in the delivery tube to destroy the working
of an Injector. Many engineers wonder why after an Injector
has been in use for only a short time it will not work as when
first put on. They do not seem to realize that in most all water
there is a great deal of solid matter, all of which is deposited by
the action of the steam on the interior and the jets of the Injector.
This sediment increases very rapidly, and very soon all tapers
and horizontal drill holes have become contracted and the range
of the Injector destroyed. A solution of ten parts of muriatic
acid to one part of water will cut away almost all the sediment so
lodged on the jets, and by disconnecting the Injector and
immersing the same in the above solution over night this sedi-
ment is almost sure to be dissolved.
RANGE OF THE INSPIRATOR AND INJECTOR.
The Steam pressure at which an injector will start and the
highest steam pressure at which it will work constitute what is
termed the "range" of an injector, and the inspirator varies with
the vertical lift and the temperature of the feed water.
HANDBOOK ON ENGINEERING.
593
It must also be borne in mind that the same style of construc-
tion in an injector and inspirator, while it confines them to about a
specific range between its lowest starting and highest working points,
permits of variation as to what the lowest starting point shall be.
A style of construction, which gives a range (on say a 2-foot lift)
of 25 Ibs. to 155 Ibs. would permit of a range of 35 Ibs. to 165
Ibs. (in fact, to a little higher than 165 Ibs.). Different manu-
facturers, therefore, vary as to the starting point in their stand-
ard machines — aiming to cover the range which they deem most
desirable. Nearly all have adopted about 25 Ibs. on a 2-foot lift,
as lowest starting point.
Fig. 294. The World injector.
POSITIVE OR DOUBLE TUBE INJECTORS.
As before stated, this class of injector is provided with two sets
f tubes or jets, one set adapted to lift the water and deliver it to
88
594 HANDBOOK ON ENGINEERING.
the second set, which forces the water into the boiler. By this
arrangement, it is apparent that inasmuch as the lifting jets
supply a proportionate amount of water with varying steam pres-
sures, a wider range is obtainable than with an automatic in-
jector. In the following cases, it is better to use the double tube
injectors : —
1. Where the feed water is of too high a temperature to be
handled by the automatic injectors.
2. When a great range of steam variation is accompanied by
the condition of a long lift.
The World injector is one of the simplest boiler feeders of the
double tube type of injectors. It is entirely self contained. It
is supplied even with its own check valve and operated entirely
by a single lever, a quarter of a turn of which starts the lifting,
after which the completion of the single revolution sets the injector
working to boiler.
•
.
GENERAL SUGGESTIONS FOR PIPING-UP INJECTORS AND
INSPIRATORS AND SUGGESTIONS THAT SHOULD BE
CAREFULLY FOLLOWED WHEN MAKING PIPE CONNEC-
TIONS.
Steam* — Connect steam pipe with highest parts of boiler and
never connect with a steam pipe used for any other purpose. We
would recommend a globe valve being placed in the steam pipe
next to boiler which can be closed in case it is desired to take off
.
the injector. At all other times it can be left open. When the
steam connection is made, be sure and take off the injector before
the steam is turned on the machine. Then blow out the steam
pipe with at least forty pounds steam, which will remove all dirt
and scale.
Suction* — This pipe must be tight, and if there is a valve in it
the stem must be well packed.
To test the suction pipes for leaks, plug up the end of the pipe
HANDBOOK ON ENGINEERING.
595
and then screw on a common iron cap on the overflow ; or if that
is not at hand, unscrew cap X, and place a piece of wood on
top of valve ; replace the cap and the wood will hold the valve
from rising ; then turn on the steam, which will locate all leaks.
Fig. 295. Complete piping for injector.
All pipes, whether steam, suction or delivery, must be of the
same or greater size than the corresponding branch of each injec-
tor. Have all piping as short and as straight as possible, and
especially avoid short turns.
596 HANDBOOK ON ENGINEERING.
If any old pipe is used, see that it is not partially filled or
stopped up with rust.
If the injector or inspirator has to lift the water very high ot
draw it very far, have the suction pipe a size or two larger than
called for by the suction branch of the injector or inspirator.
Have the water supply (suction) pipe independent of any other
connection. The suction pipe must be absolutely air tight ; the
slightest leak, in most cases, will prevent the injector or inspirator
from forcing water into the boiler.
Always place a globe valve in the suction pipe as close to the
injector as possible, and place it so that it will shut down against
the water side and see that the stem is packed tight.
When using the injector or inspirator as NON-LIFTING, put two
globe valves in the suction, one close to the injector, the other as
far from it as you can conveniently, keeping the one farthest from
the injector or inspirator tolerably close throttled. This will
repay anyone for their trouble. The check valve may be next
to boiler with a valve between it and boiler, the farther from
injector the better. If the injector forces through a heater, place
check valve between injector and heater. Also place a valve
between heater and check valve so the latter can be taken out
if necessary.
Size of pipes* — If injector or inspirator has over 10 feet lift,
or a long draw, use suction pipe from strainer to valve a size
larger than the connection on injector, reducing when it reaches
the valve.
In all other cases, use for all pipes same size as injector
connection.
Blow-off* — Always blow out steam thoroughly BEFORE CON-
NECTING INJECTOR, so as to remove any dirt, rust or scale that
may be in the pipes.
Caution* — The suction pipe must be ABSOLUTELY TIGHT
throughout. To make sure that it is so, test the suction as directed.
HANDBOOK ON ENGINEERING. 597
DIRECTIONS FOR CONNECTING AND OPERATING THE
HANCOCK INSPIRATOR.
44 Stationary " pattern* — Connect as shown by cut Fig. 296,
showing exterior and section. For full instructions, see page 598.
For a lift of 5 ft., 15 Ibs. steam pressure is required.
*» " 10 " 20 " <4 " u
*' « 15 u 25 4k " u 4t
u ** 20 u 35 " u u "
u " 25 u 45 " u u u
Operation* — Open overflow valves Nos. 1 and 3 ; close forcer
steam valve No. 2 and open the starting valve in the steam pipe.
When the water appears at the overflow, close No. 1 valve ; open
No. 2 valve one-quarter turn and close No. 3 valve. The inspir-
ator will then be in operation.
NOTE. — No. 2 valve should be closed with care to avoid damag-
ing the valve seat. When the inspirator is not in operation, both
overflow valves Nos. 1 and 3 should be open to allow the water to
drain from it. No adjustment of either steam or water supply is
necessary for varying steam pressures, but both the temperature
and quantity of the delivery water can be varied by increasing or
reducing the water supply. The best results will be obtained
from a little experience in regulating the steam and water supply.
If the suction pipe is filled with hot water, either cool off both it
and the inspirator with cold water, or pump out the hot water by
opening and closing the starting valve suddenly. To locate a leak
in the suction pipe, plug the end, fill it with water, close No. 3
valve and turn on full steam pressure. Examine the suction pipe
and the water will indicate the leak. If the inspirator does not
lift the water properly, see if there is a leak in the suction pipe.
Note if the steam pressure corresponds to the lift as above speci-
fied, and if the sizes of pipe used are equal in size to inspirator
connections. If the inspirator will lift the water, but will not de-
liver it to the boiler, see if the check valve in the delivery pipe is
598
HANDBOOK ON ENGINEERING.
in working order and does not u stick." Air from a leak in the
suction connections, will prevent the inspirator from delivering
the water to the boiler, even more than it will in lifting it only. If
No. 1 valve is damaged, or leaks, the inspirator will not work
properly. No. 1 valve can be easily removed and ground.
STtAM
Feed to
Boiler.
Suction.
Overflow.
ISP
3
Fig. 296. Hancock inspirator.
To remove scale and deposits from inspirator jets or parts,
disconnect the inspirator and plug both the suction and delivery
outlets with corks. Open No. 2 valve and fill the inspirator with
a solution of one part muriatic acid and ten parts water0 Allow
this solution to remain in the inspirator over night, then wash it
thoroughly in clear water.
NOTE. — It is not generally necessary to return an inspirator
for repairs. The repair parts required can be ordered and the
inspirator readily put in order.
.HANDBOOK ON ENGINEERING. 599
TO DISCOVER CAUSE OF DIFFICULTIES.
WHEN INJECTOR FAILS TO GET THE WATER.
1. The supply may be cut off by : (a) Absence of water at the
source, (b) Strainer clogged up. (c) The suction pipe, hose
or valve stopped up ; or if a hose is used, its lining may be loose
(a frequent cause of trouble).
2. A large leak in the suction (note that a small leak will pre-
vent injector from working, but not from getting the water).
3. Suction pipe or water very hot. Open drip-cock, turn
steam on slowly, then shut it off quickly. This will cause the
cool air to rush into the suction pipe and cool it off. Repeat if
necessary.
4. Lack of steam pressure for the lift ; or, in some instances,
too much steam pressure. If the steam pressure is very high, the
injector will get the water more readily if the steam is turned on
slowly and the drip-cock left open until the water is got.
IF THE INJECTOR GETS THE WATER BUT DOES NOT FORCE IT TO
THE BOILER.
1. No globe valve on the suction with which to regulate the
water, or else the supply water not properly regulated.
2. Dirt in delivery tube.
3. Faulty check valve.
4. Obstruction between inj.ector and check valve, or between
check valve and boiler.
5. Small leak in suction pipe admitting air to the injector
along with the supply water. It is ten to one this is the cause of
the difficulty every time.
6. Be sure and understand the directions for starting before
condemning the injector.
600 HANDBOOK ON ENGINEERING.
U. S. INJECTOR.
IF THE INJECTOR STARTS BUT "BREAKS."
1. Supply water not properly regulated. If too much water,
the waste or overflow will be cool ; if too little, the water will be
very hot.
2. Leaky supply pipe admitting air to the injector. It is ten
to one this is the cause of difficulty. The suction must be air
tight ; test as directed.
Fig. 297. Showing the U. S. injector and pipe connections.
8. Dirt or other obstruction, such as lime, etc., in delivery tubet
4. Connecting steam pipe to pipe conducting steam to other
points besides the injector, er not having suction pipe independent.
HANDBOOK ON ENGINEERING.
601
5. Sometimes a globe valve is used on the suction connection
that has a loose disc, and after starting the disc is drawn down^
thus partially closing the valve; it is, of course, equivalent to
giving the injector too little water. To remedy this, take the
globe valve off and reverse it end for end.
To clean* — To clean injector, unscrew plug 0, and the re-
movable jet inside resting in it will follow the plug out.
. Turn on steam (not less than forty pounds) and all dirt will be
blown out. Examine all passages and drill hole's and see that no
dirt or scale has lodged in them. Replace jet by setting it in the
plug (which acts as a guide) and screw into place tightly. Be
careful not to bruise any jets, and use no wrenches on body of
injector.
SIZES AND CAPACITIES OF U. S. INJECTOR.
SIZE.
ALL PIPE
CONNECTIONS.
CAPACITY
GALLONS PER HOUR.
HORSE POWER.
MAX.
MIN.
oo ...
lj
1
1
1J
If
l|
H
2
2
2
2}
2j
n.
36
65
90
125
170
250
340
475
575
750
9'20
1350
1750
2275
2820
3400
3650
4000
15
28
40
60
75
125
' 140
250
300 '
350
450
675
850
1000
1300
1700
1800
1950
1 t
3
6
8
15
20
30
40
60
70
85
120
165
230
295
375
460
500
0 4
8
10
15
20
30
40
60
70
95
120
165
230
295
375
460
500
600
o
i
2
3
4 ..
5
6 ..
7
8 ..
9
10...
11
12
13 .
14
15 ..
16
To test for leaks. — Plug up end of water supply pipe, then
fit a piece of wood into cap Z, so that when screwed down it will
hold check valve in place, then turn on steam and it will locate
leak. Do not fail to do this in case of any trouble.
TO START AND STOP INJECTOR.
To start* — Open full the globe valve in water supply first,
and then globe valve in steam pipe wide open. If water issues
from overflow, throttle the valve // until discharge stops. Reg-
602
HANDBOOK ON ENGINEERING.
ulate injector with water supply valve, not by steam valve.
When water supply is above the injector, in starting open steam
valve first.
To stop* — Close the steam valve. The water valve H need
not be closed unless the injector is used as a non-lifter, or lift is
considerable.
PRICE LIST, CAPACITY, HORSE POWER, ETC. OF PENBERTHY
INJECTOR.
Size.
Price.
Pipe Connections.
Capacity per Hour.
1 to 4 ft lift, 50 to 75
Ibs. Pressure.
Horse
Power.
GO.
A
$16 00
18 00
Steam. Suet
2* 2
2 2
ion. De
1
1<
1
2
2
iv
| i(
;
.
cry,
D.
Maximt
80 g
120
165
250
340
475
575
750
920
1300
1740
2270
2820
m.
al.
Minlmu
55 g
70
90
135
165
300
350
4 0
500
700
900
1100
1400
m.
al.
4 to 8
8 to 10
10 to 15
15 to 25
25 to 35
35 to 50
50 to 60
60 to 95
95 to 162
120 to 150
165 to 230
230 to 2:>()
290 to 365
A A
B
20 00
25 00
BB
C ..
CC.
D...
E .
EK
F .
FF.
30 00
40 00
45 00
55 00
60 00
75 00
90 00
110 00
125 00
HANDBOOK ON ENGINEERING. 603
To find the number of gallons of water delivered by a steam
pump in one minute, when the diameter and stroke of water
piston, and the number of strokes per minute are given : —
Rule* — Square the diameter of water piston and multiply the
result by .7854. Multiply this product by the stroke of the
water piston in inches ; and multiply this product by the number
of strokes per minute, and divide the result by 231.
Example* — How many gallons of water per minute will a
steam pump deliver, whose water cylinder is 6 inches in diameter
and 12 inches stroke, making 60 strokes per minute?
Ans. 88.128 galls.
Operation : 6 X 6 X .7854 28.2744.
28.2744 X 12 X 60
And, ~iar~ - = 88-128-
To find the relative proportion between the steam and water
pistons.
Rule* — Multiply the area of the pump piston by the resistance
of the water in pounds per square inch ; and divide the product
by the pressure of steam in pounds per square inch. The quotient
will give the area of steam piston in square inches to balance the
resistance. To this quotient add from 30 to 100 per cent of it-
self,— depending on the speed of the pump, — and divide the
sum by .7854, and extract the square root of the quotient for the
diameter of the steam piston.
Example* — What should be the diameter of the steam piston
to force water against a pressure of 125 pounds per square inch,
the diameter of water piston being 6 ins. and the steam pressure
60 Ibs. per square inch? Ans. 10 J inches.
Operation: 6 X6 X .7854 = 28.2744 sqr. ins.
And, 28.2744 X 125 ^= 3534.3 pounds the total resistance.
3534.3
Then, ~~ — = 58.9 square inches the area of steam piston.
004 HANDBOOK ON ENGINEERING.
We will add 50 per cent for friction in pump and in delivery
pipe, and for a moderate speed of pump.
Then, 58.9 X .50 = 29.45.
And, 58.9 + 29.45=88.35.
88.35
And, -TT = 112.49 sqr iris.
Then, y 112.49 = 10.6 ins. the diameter of the steam piston.
To find the pressure against which a pump can deliver water,
when the diameter of steam piston, pressure of steam in pounds
per square inch, and diameter of water piston are given : —
Rule* — Multiply the area of steam piston by the pressure of
steam in pounds per square inch, and divide the product by the
area of the pump piston, and deduct from 30 to 50 per cent for
friction in the delivery pipe and in the pump itself.
Example* — The area of the steam piston is 112 square inches,
and the area of water piston is 28 square inches, and the steam
pressure is 60 Ibs. per square inch, against what pressure can the
pump deliver water, the resistance from friction being 48 per cent?
Ans. 125 Ibs. per sqr. in., nearly.
112X60
Operation: — 28 — ~ 24:0*
And, 240 X -48 = 115.20.
Then, 240 — 115.20 = 124.8.
To find the steam pressure required when the diameter of the
steam piston, the diameter of the water piston, and the resistance
against the pump in pounds per square inch are given : —
Rule, — Multiply the area of water piston by the resistance on
the pump in pounds per square inch, and divide the product by
the area of the steam piston.
HANDBOOK ON ENGINEERING. 605
Example* — The resistance against the pump, including fric-
tion, is 240 pounds per square inch. The area of steam piston
is 112 square inches, and the area of water piston is 28 square
inches. What pressure of steam is required to operate the pump ?
Ans. 60 Ibs. per sqr. in.
- 240 X 28
Operation: — — — =60.
Now anything over 60 Ibs. will operate the pump, and the faster
it is run the higher must be the pressure above 60 pounds.
To find the diameter of water piston when the diameter of
steam piston, the steam pressure in pounds per square inch, and
the resistance against the pump piston in pounds per square inch
are given : —
Rule* — Multiply the area of steam piston in square inches by
the steam pressure in pounds per square inch, and divide the
product by the resistance in pounds per square inch on the water
piston.
Example* — The resistance against the pump, including fric-
tion, is 240 pounds per square inch ; the area of steam piston is
112 square inches, the steam pressure is 60 pounds per square
inch, what should be the diameter of water piston?
Ans. 6 inches.
Operation j 112X6-° = 35.65 sqr. ins. Call it 36 sqr. ins.
Then, ^W = 6.
To find the horse power required in a steam pump to feed a
boiler with a given number of pounds of water per hour against a
given pressure of steam : —
Rule* — Multiply the velocity of flow of water in feet per min-
ute by the total pressure against which the water is pumped in
pounds per square incL, and divide the product by 33,000, and
the quotient will be the horse power.
606 HANDBOOK ON ENGINEERING.
Example* — What horse power is required to feed a boiler
with 600 gallons of water per hour against a total resistance of
112 IbSo per square inch, including the friction in the delivery
pipe, lift of water in suction pipe, weight of check valve, and
friction in the pump itself? Ans. 1 H. P» nearly.
Operation: 600 X 231 = 138,600 cubic inches of water per
hour.
138,600
And, — TiTj — = 2310 cubic inches of water per minute.
2310
And, —rg— =192.5 feet per minute > the velocity of the
water o
The total resistance is 112 Ibs. per sqr. in0
Then, 192.5 X 112 = 21560 foot pounds.
21560
And' 3^000 = -6"H.P.
Now add say 50 per cent and we have .653 X .50 =.3265.
And, .653 + .3265 = .9795.
This pump will feed a boiler as shown above, or it will deliver
600 gallons of water per hour under a head of 258 feet.
& ^
112
Thus,
To find the horse power of boiler required to furnish steam for
a pump running at its fullest capacity.
Rule* — Multiply the number of gallons of water delivered by
the pump in one minute by 8£. Multiply this product by the
total height in feet to which the water is to be lifted, measuring
vertically from the source of supply to the point of delivery, and
divide the result by 33,000. Add from 50 to 75 per cent to the
quotient for loss from friction of water in the pipe, friction in
the pump, waste of steam in the cylinder, and other contingencies,
and the result will give the horse power of boiler required.
HANDBOOK ON ENGINEERING. 607
Example* — What horse power of boiler is required to run a
steam pump lifting 800 gallons of water per minute to a height of
163 ft. from the source of supply? Ans. 50 H. P., nearly.
Operation : 800 X 8£ = 6667 Ibs. of water.
And, 6667 X 163 = 1,086,721 footpounds.
1,086,721
And' -337000- =33H'P-' near1^'
Then, 33 X .50 = 16.50.
And, 33 + 16.5 = 49.5.
To find the diameter of discharge nozzle for a steam pump,
when the diameter and stroke of the water piston and the number
of strokes per minute are given, and the maximum flow of water
in feet per minute is given : —
Rule. — Find the cubic contents of the water cylinder for one
stroke in cubic feet, and multiply it by the number of strokes per
minute. Multiply this product by 144 and divide the result by
the velocity of the water in feet per minute, and the quotient will
be the area of pump nozzle in square inches.
Example* — The diameter of water cylinder is 10 inches, and
the stroke of piston is 12 inches, and the speed is 50 strokes per
minute. The velocity of water required is 500 feet per minute,
what should be the diameter of pump discharge nozzle?
Ans. 3J ins., nearly.
Operation: 10 X 10 X .7854 = 78.54 sqr. ins. area of piston.
And, 78.54 X 12 = 942.48 cubic inches in the cylinder for one
stroke.
And, ' = .5454 of a cubic foot for one stroke.
And, .5454 X 50 = 27.27 cubic feet for 50 strokes per minnte.
27 27 X 144
Then, - ""XnrT ~~ == 7-853? s(lr' ins' tlie area of tlie
\1^1 = 3.
\.7854
And, = 3.1 ins. the diameter.
608 HANDBOOK ON ENGINEERING.
Xo find the approximate size of suction pipe when its length
does not exceed 25 ft. and when there are not more than two
elbows in the same : —
Rule* — Square the diameter of water cylinder in inches and
multiply it by the speed of the piston feet in per minute ; divide
this product by 200, and divide this quotient by .7854 and
extract the square root, and the result will be the diameter of
suction pipe, except for very small pipes when it should be made
larger than the size given by the rule, in order to lessen the friction
of the moving water.
Example* — The diameter of water cylinder is 6 ins., the stroke
of piston is 12 ins., and the number of strokes per miuuteis 60,
what should be the diameter of suction pipe? Ans. 4 ina»
And, i|i= ,3.75.
Then, «J13.75 = 3.7 ins. There is no pipe of this size made,
BO take 4-inch pipe.
To find the velocity in feet per minute necessary to discharge
a given number of gallons of water per minute through a straight
smooth iron pipe of a given diameter, regardless of friction : —
Rule* — Reduce the gallons to cubic feet and multiply by 144,
and divide the product by the area of the pipe in square inches.
Example* — What should be the velocity of the water to dis-
charge 100 gallons of water per minute through a 4-inch pipe?
Ans. 149 ft. per minute.
Operation j — -£- — =13 cubic feet.
And, 13 X 144 — 1872 cubic inches placed in a continuous
line.
Then, 4 X 4 X -7854 = 12.5664 square inches, the area of
pipe.
And, _==
12.5664
HANDBOOK ON ENGINEERING. 609
To find the velocity in feet per minute of water flowing through
a pipe of given diameter, when the diameter of water cylinder and
speed of piston in feet per minute are given : —
Rule* — Multiply the area of water cylinder in square inches
by the piston speed in feet per minute, and divide the product by
the area of the pipe in square inches.
Example* — The diameter of water cylinder is 8 ins., and the
piston speed is 100 ft. per minute, and the diameter of discharge
pipe is 4 ins., what is the velocity of the water in the discharge
pipe? Ans. 400 ft. per minute.
Operations 8 X 8 X .7854 = 50.26 sqr. ins. area of the
water piston.
And, 50.26 X 100 = 5026.
The area of the pipe is 12.56 sqr. ins.
Then, =-. 400.
' 12.56
To find the number of gallons of water discharged per minute
through a circular orifice under a given head : —
Rule*— Find the velocity of discharge in feet per second and
multiply it by 60, then multiply this product by the area of the
orifice in square feet, and multiply this last product .by 7.48, and
the result will be the gallons discharged per minute.
Example. — How many gallons of water will be discharged per
minute through an orifice 4 inches in diameter under a head of 81
feet? Ans. 2829.7 galls.
Operation: «J81 = 9. And, 9 X 8.025 = 72.225 feet per
second, the velocity of discharge. The factor 8.025 is a con-
stant for any head, and is found thusly: —
v'2 X32.2 =8.025.
Or, the velocity of discharge may be found in this manner ; —
y2 X 82.2 X 81 = 72.22 feet per second, that is, the veloc-
ity in feet per second equals the square root of the acceleration
39
610 HANDBOOK ON ENGINEERING.
due to gravity multiplied into the head in feet. Continuing the
operation, we have : —
72.225 X 60 = 4333.5 feet per minute.
And, 4 X 4 X -7854 = 12.5664 sqr. ins. area of orifice.
And, — = .0873 of a square foot, the area of orifice.
144
also.
Then, 4333.5 X -0873 = 378.3 cubic feet.
And, 378.3 X 7.48 = 2829.7 galls.
NOTE. — With a ring orifice only 64 per cent of the above
amount of water would be discharged, and with a funnel-shaped
orifice only 82 per cent.
To find the number of gallons of water discharged per minute
under a given pressure in pounds per square inch : —
Rule* — Divide the given pressure in pounds per square inch
by .433 in order to get the head in feet, and then proceed accord-
ing to the foregoing rule.
Example* — • How many gallons of water will be discharged per
minute through an orifice one square inch in area, under a pres-
sure of 35.073 Ibs. per square inch? Ans. 81 galls, per minute.
35.073
Operation: 4oo —81 ft., head equivalent to the given
pressure.
And, >/2 X 32.2 X81 = 72.225 ft. per second the velocity.
And, 72.225 X 60 = 4333.5.
Also, rrr = .00694 of a square foot, equals the area of the
orifice.
And, 4332.5 X .00694 =.30.07449.
And, 30.07449 X 7.48 = 224.9 galls.
Then, deducting 64 per cent, we have: —
224.9 X .64= 143.9.
And, 224.9 — 143.9 =81.
HANDBOOK ON ENGINEERING. 611
To find the area of orifice in square ins. necessary to discharge
a given number of gallons of water per minute under a given
head in feet : —
Rule* — Divide the number of gallons by the constant number
15.729 multiplied into the square root of the head, and the result;
will be the area of orifice in square inches.
Example* — What must be the area of orifice to discharge
1778.5 gallons of water per minute under a head of 81 feet?
Ans. 12.56 sqr. ins.
Operation: >/8T = 9.
And, 9 X 15. 729 = 141.6.
1778.5
Then, — — =12,56.
To find how many gallons of water will flow through a straight
smooth iron pipe in one minute under a given pressure in pounds
per square inch, or head in feet : —
Rule* — Multiply the inside diameter of the pipe in feet by the
head in feet, and divide the product by the length of pipe in feet.
Extract the square root of the quotient and multiply it by 48,
and the product will be the velocity of flow in feet per second.
Multiply this result by 12 to reduce it to inches, and by 60 for
the flow per minute, and multiply again by the area of the pipe in
square inches, and divide by 231 for the gallons discharged per
minute.
Example* — How many gallons of water will be discharged per
minute through a 4-inch pipe 2000 feet long, under a head of 92
feet? Ans. 230 galls, per minute,
Operation : 4 ins. = .33 of a foot.
And, 92 X .33 = 30.36.
30.36
And' 2000"
12 HANDBOOK ON ENGINEERING .
And, V^l5 =.1225.
Then. .1225 X 48 X 12 = 70.56 ins. per second.
And, 70.56 X 60 =4233.60 ins. per minute.
Then, 4 X 4 X .7854 = 12.56 sqr. ins. the area of the pipe.
And, 4233.60 X 12.56 =53174.016 cubic ins.
53174.016
Then, — -- = 230.2.
Example. — Assume two wells A and B with their mouths on
a level. Well A is 26 ft. deep, and well B is 40 ft. deep. Well
A is fed by natural springs and has a depth of water of 5 feet.
The distance between the wells is 600 feet. How many gallons
of water will a 1 inch pipe, laid perfectly straight and level,
syphon over in one minute providing well B is always pumped
dry, and that the pipe extends into well A 26 feet, and into well
B 38 feet, using bends instead of elbows?
Ans. 4 galls, per minute.
Operation. — The head equals 38 feet.
The diameter of the pipe equals .0833 foot.
Then, 600 + 38 + 26 = 664 ft. total length of pipe.
And, 38 X -0833 = 3.1654.
3.1654
And,
And, V .0047 = .068.
Then, .068 X 48 = 3.264 ft. velocity per second.
And, 3.264 X 60 = 195.840 ft. velocity per miD.
The area of pipe equals .7854 sqr. inch.
Then, 195.840 X .7854 = 153.8127.
And, 153.8127X7.48 = 1150.52.
1150.52
And, — ^-JT — = 8 nearly, gallons.
HANDBOOK .ON ENGINEERING. 613
Deducting 50 per cent on account of 2 bends and friction, we
have 4 gallons per minute syphoned over.
To find the head in feet due to friction in a pipe running
full : -
Rule* — Multiply the length of the pipe in feet by the square
of the number of gallons per minute, and divide the product by
1,000 times the 5th power of the diameter of the pipe in inches.
The quotient less 10 per cent is the head in feet necessary to over-
come the friction.
NOTE. — The head is the vertical distance from the surface of
the water in the tank or reservoir, to the center of gravity of the
lower end of the pipe, when the discharge is into the air, or, to
the level surface of the lower reservoir when the discharge is under
the water.
Example* — A 2-inch pipe 100 feet long and running full,
discharges 50 gallons of water per minute, what is the head in
feet due to friction? Ans. 7.029 feet.
Operation : 2 X 2 X 2 X 2 X 2 = 32 = the 5th power of the
diameter of the pipe.
And, 50 X 50 = 2500.
And, 2500 X 100 = 250,000.
Also, 32 X 1,000 = 32,000.
Then> iw = 7'81-
And, 7.81 less 10 percent of itself equals 7.029.
The resistance to the flow of water in pounds per square inch>
due to friction, is found by dividing the friction head by 2.3.
7.029
Thus, ^-^g- = 3.051bs.
To find the size of pump required to feed a boiler of a given
capacity : —
614 HANDBOOK ON ENGINEERING.
Rule* — Multiply the number of pounds of water evaporated
per pound of coal by the number of pounds of coal burned per
sqr. foot of grate surface per hour, and multiply this product by
the number of square feet of grate surface in the boiler furnace.
This will give the number of pounds of water evaporated by the
boiler in one hour. Divide this by 60 to find the evaporation per
minute, and divide again by 8| in order to get the evaporation in
gallons per minute ; add from 10 to 15 per cent to the last result
for leakage and other contingencies, and select a pump that will
deliver the gross number of gallons of water per minute at any
speed that may be desired, usually taken, however, at fifty feet
per minute.
Example* — What should be the dimensions of the water end
of a steam pump, and what should be the speed of piston to sup-
ply a boiler having a grate surface of 20 square feet, and burning
15 pounds of coal per square foot of grate, and evaporating 9
pounds of water per pound of coal per hour?
Operation: 20 X 15 X 9 =2700 pounds of water evapo-
rated per hour.
2700
And, = 45 Ibs. of water evaporated per minute.
60
And, -— = 5.4 galls, per minute.
Then, 5.4 plus 10 per cent of itself, equals 6 galls, nearly per
per minute.
Referring to a pump maker's catalogue we find that a single
pump 3£" X 2J" X 5", making 90 strokes per minute, will do
the work, or, a duplex pump 3" X 2" X 3", making 100 strokes
per minute will do the work equally as well. Again, adding 10
per cent to the pounds of water evaporated per minute we have,
45 + 4.5 =49.5 pounds. And, 49.5 X 27.71 = 1371.64 cubic
inches displacement in the water cylinder per minute, and at 90
strokes per minute we have 15.24 cubic inches displacement per
stroke.
HANDBOOK .Off ENGINEERING. 615
Thus, 1371*64 = 15.24, which is all that is required for our
yo
boiler.
Now, taking the above single pump we have: 2.25 X 2.25 X
.7854 X 5 = 19.8 cubic inches displacement per stroke. And,
taking the duplex pump we have: 2 X 2 X .7854 X 3 X 2 =
18.8 cubic ins. displacement for each double stroke of the piston,
or, plunger, showing that either pump is of ample capacity to
feed the boiler at a fair piston speed.
To find the duty of a pumping engine when the number of
pounds of coal burned, the number of gallons of water pumped,
the pressure in pounds per square inch against which the pump
piston works, and the height of suction are given : —
Rule* — Find the head in feet against which the pump works,
by multiplying the pressure by 2.3, add the suction in feet
to this head in order to get the total head. Multiply the
gallons of water by 8J to get the pounds of water deliv-
ered. Then multiply the total number of pounds of water
by the head in feet, and divide the product by the number of
pounds of coal divided by 100, and the result will give the duty
in foot pounds. The duty of a pumping engine is the number of
pounds of water raised one foot high for each 100 pounds of coal
burned.
Example* — What is the duty of an engine pumping 2,890,000
gallons of water in 12 hours against a pressure of 30 pounds per
sqr. inch, the suction being 12 feet, and coal burned 24,470
pounds? Ans. 8,070,426 foot pounds.
Operation: 30 X 2.3 = 70 nearly the head in feet.
And, 2,890,000 X 8£ == 24,083,333 pounds of water.
Also, 70 + 12 = 82 ft. total lift of water.
And, 24,083,333 X 82 = 1,974,833,306 Ibs. of water lifted
one foot high in 12 hours.
Then, ^=,244.7.
616 HANDBOOK ON ENGINEERING.
And) 1,974888806 = 8>070>426.
To find the horse power of a pumping engine : —
Rule* — Divide the number of pounds of water raised one foot
high in one minute by 33,000.
Example* — What is the H. P. of the pumping engine given
in the above example? Ans. 83.11 H. P.
Operation: 12 X 60 = 720 minutes.
And, 1'974'833'8Q6 == 2,742,824 Ibs. of water raised one foot
7 &0
high in one minute 0
Then, ''^ 83.11.
33,000
To find the capacity of a pump to feed a boiler it is necessary
to know how much water the boiler is capable of evaporating per
minute or per hour. Each horse power of boiler capacity corre-
sponds to an evaporation of thirty pounds of water per hour. It
is good practice to operate a pump slowly and continuously, and
for this reason the pump running at its normal speed should be
capable of supplying about twice as much water as the boiler
evaporates under usual conditions.
To find the diameter of water cylinder to deliver a certain num-
ber of gallons of water per minute, when the stroke of the piston
and the number of strokes per minute are given : —
Rule* — Multiply the number of gallons by 231, and divide the
product by the stroke of the piston, and divide this quotient by
the number of strokes per minute, and divide this last quotient
by .7854, then extract the square root of the result for the
diameter of the water piston.
Example* — A battery of boilers evaporate 100,000 pounds of
water in one hour, what should be the diameter of water cylinder
to supply this battery, the stroke of piston being 12 inches and
making 100 strokes per minute? Ans. 7 inches.
HANDBOOK ON ENGINEERING. 617
100,000
Operation: ^Q — -=1666| pounds of water evaporated in
one minute.
L666|
And, ' Qt ' = 200 galls, evaporated in one minute. Then
following the above rule we have : —
200X231 = 46200.
46200
And, -jg— ^3850.
3850
And, -J0JJ- ^38.5.
38.5
And' 77854 ==49-
Then, j/49 = 7" the required diameter.
To determine the H. P. of boiler a steam pump of given
dimensions will supply when the number of strokes per minute
are given : —
Rule* — Multiply the area of the piston is square inches by the
stroke of piston in inches, and this product divided by 231 will
give the gallons per stroke. Multiply this quotient by the num-
ber of strokes per minute for the number of gallons per minute,
and by 60 for the number of gallons per hour. Multiply this
product by 8^ to find the number of pounds of water per hour
deliA'ered by the pump, and divide this product by 30 for the
H. P. of boiler the pump will supply. This rule is based upon the
assumption that the full capacity of the water cylinder is deliv-
ered at each stroke, no allowance being made for slippage, leak-
age, or short strokes.
Example* — • The water piston of a steam pump is 6 inches in
diameter and has a stroke of 12 inches, making 100 strokes per
Vfeinute, what H. P. of boiler will the pump supply?
Ans. 2448 H. P.
618 HANDBOOK ON ENGINEERING .
Operation: 6 X 6 X .7854 =28.2744 sqr. ins. area of
piston .
And, 28.2744 X 12 = 339.2928 cubic inches for one stroke.
339 2928
And, — i - — 1.4688 galls, per stroke.
Z6 1
And, 1.4688 X 100 = 146.88 galls, per minute.
And, 146.88 X 60 = 8812.8 galls, per hour.
And, 8812.8 X 8£ = 73,440 pounds of water per hour.
73440
Then, Qn = 2448 H. P. of boilers.
oU
Watt allowed one cubic foot (62£ Ibs.) of water per H. P. per
hour. Then taking this allowance instead of 30 as above, we
73440
would have, go - =1175 H. P. of boilers which the above pump
b J.O
would be suitable for, and which could be run very slowly, thus
prolonging the life of the pump.
Even though a suction pipe should be perfectly air tight, a
perfect vacuum cannot be formed in it, because water contains
air, and even the coldest water gives off some vapor tending to
impair the vacuum. Twenty-eight feet is a very good lift for a
pump taking its water by suction.
Pnmp Formulas.
Gals, per Min. = .0034 X Diameter2 X Stroke in ins. X No. of
Strokes.
Sq. of Diam. = Gals, per Min. -fr (.0034 X Stroke in ins. X
No. of Strokes).
Square of Diameter X 34
Length of Stroke = Gals, per Min. - No. of Stroke8
Square of Diameter X 34
No. of Strokes = Gals, per Min. - - Length of Stroke
HANDBOOK ON ENGINEERING.
619
CHAPTER XXI.
MECHANICAL REFRIGERATION.
About the first thing asked by persons who are becoming
interested in the subject of refrigerating and ice-making is, " Tell
me how the thing is done ? "
Mechanical refrigeration, primarily, is produced by the evapo-
ration of a volatile liquid which will boil at low temperature, and
by means of a special apparatus the temperature and desired
amount of refrigeration is placed under control of the operator.
Simplest Apparatus
Brine Tank or Concealer A.
Fig. 298. Elememtal refrigerating apparatus.
The simplest form of refrigerating mechanical apparatus
consists of three principal parts: A, an u evaporator," or, as
sometimes called, a " congealer," in which the volatile liquid is
vaporized; -B, a combined suction and compressor pump, which
620
HANDBOOK ON ENGINEERING.
sucks, or properly speaking, " aspirates " the gas discharged by
the compressor pumps, and under the combined action of the
pump pressure and cold condenser, the vapor is here reconverted
into a liquid, to be again used with congealer. We now see the
function of the compressor pumps and condensers.
PRINCIPLES OF OPERATION.
The action of all refrigerating machines depends upon well-
defined natural laws that govern in all cases, no matter what type
of apparatus or machine is used, the principle being the same in
all ; while processes may slightly vary, the properties of the par-
ticular agent and manner of its use affecting, of course, the
efficiency or economic results obtained.
Watef Suppl/
j^CondenserO
B B U H B y U B
— ^^^JSy EXPANSIONS
i Brine Tank or Congealer A.
Compression
Refrigerating
Apparatus
Three Parts
Fig. 299. Outline drawing of mechanical compression system.
OPERATION OF APPARATUS.
I
See Fig* 299* The apparatus being charged with a sufficient
quantity of pure ammonia liquid, which we will, for simplicity,
assume to be stored in the lower part of the condenser 0, a small
cock or expansion valve controlling a pipe leading to the congealer
HANDBOOK ON ENGINEERING. 621
or brine tank A, is slightly opened, thus allowing the liquid to
pass in the same office as a tube or flue in steam boiler and having
precisely the same function, it may be called heating or
steam making service. The amount of water capable of being
boiled into steam in a boiler depends upon the square feet of
heating surface, temperature of fire and pressure of steam ; and
the same is true of the capacity of heating surface pre-
. sented by the coils in the evaporator. The heat is transmitted
through the coils from surrounding substance to the ammonia
liquid, which is boiled into a vapor the same as water is boiled
into steam in a steam boiler ; as previously explained, the heat
thus becomes cooler ; the amount taken up and made negative
being in proportion to the pounds of liquid ammonia evaporated.
FUNCTION OF THE PUMP AND CONDENSER.
The office of the compressor, pump and condenser is to re-
convert the gas after evaporation into a liquid, and make the
original charge of ammonia available for use in the same appa-
ratus, over and over again. It will appear to the reader, after
having carefully followed the text, that the pump and condenser
might be dispensed with, but these conditions may only be eco-
nomically realized when the at present expensive ammonia
liquid can be obtained in great quantities and at less cost than
the process of reconverting the vapor into a liquid by compression
machinery and condenser on the spot.
WHAT DOES THE WORK?
The real index of the amount of cooling work possible is the
number of pounds of ammonia evaporated between the observed
range of temperature. To make the above clear, we will add
that each pound of ammonia during evaporation is capable of
Storing up a certain quantity of heat, and that the simplest forms
622 HANDBOOK ON ENGINEERING.
of refrigerating apparatus might consist, as shown by engraving,
of two parts, to wit : A congealer and a tank of ammonia. In this
apparatus the ammonia is allowed to escape from the tank into
the congealer as fast as the coils therein are capable of evapo-
rating the liquid into a gas. When completely evaporated the
resulting vapor is allowed to escape into the atmosphere, which
means it is wasted, the supply being maintained by furnishing
fresh tanks of ammonia as fast as contents are exhausted. This
process, while simple, would be tremendously expensive, costing
at the rate of about $200 per ton, refrigerating or ice-melting
capacity. To recover this gas and reconvert to a liquid on the
spot in a comparatively inexpensive manner, is the object to be
obtained.
MECHANICAL COLD EASILY REGULATED.
This being under the control of the cock or valve leading from
the condenser called an expansion valve. As the gas begins to
form in the evaporator, the compressor pump B is set in motion
at such a speed as to carry away the gas as fast as formed, which
is discharged into the condenser under such pressure as will bring
about a condensation and restore the gas to the liquid state ; the
operation being continuous so long as the machinery is kept in
motion.
UTILIZING THE COLD.
To utilize the cold thus produced for refrigerating, two meth-
ods are in use, the first of which is called the brine system ; the
second is known to the trade as the direct expansion system, both
of which systems will be explained at some length.
BRINE SYSTEM.
In this method, the ammonia evaporating coils are placed in a
tank, which is filled with strong brine made of salt, which is well
known not to freeze at temperature as low as zero. This is the brine
HANDBOOK. ON ENGINEERING. 623
tank or congealer A. The evaporating or expansion of the ammo-
nia in these coils robs the brine of heat, as heretofore explained,
the process of storing cold in the brine going on continuously and
being regulated, as required, at the gas expansion valve. To
practically apply the cold thus manufactured, the chilled brine or
non-freezing liquid is circulated by means of a pump through
coils of pipe which are placed on the ceilings or sides of the apart-
ments to be refrigerated, the process being analogous to heating
rooms by steam.
THE BRINE COOLS THE ROOMS.
The cold brine in its circuit along the pipes becomes warmer
by reason of taking up the heat of the rooms, and is finally
returned to the brine tank, where it is again cooled by the ammo-
nia coils, the operation, of course, being a continuous one.
DIRECT EXPANSION SYSTEM.
By this method, the expansion or evaporating coils are not put
in brine tanks, but are placed in the room to be refrigerated, and
the ammonia is evaporated in the coils by coming in direct con-
tact with the air in the room to be refrigerated, no evaporating
tank being used.
RATING OF THE MACHINE IN TONS CAPACITY.
For the information of the unskilled reader, we will state that
machines are susceptible of two ratings; that is, either their
capacity is given in tons of ice they will produce in one day (24
hours), called ice-making capacity ; or they are rated equal to the
cooling work done by one ton of ice-making per day (24 hours),
called refrigerating capacity.
DIFFERENCE IN THESE RATINGS
Ordinarily the ice-making capacity is taken at about one-half
of the refrigerating capacity, but this is only approximate,
624 HANDBOOK ON ENOINKKR1NG.
INSTRUCTIONS FOR OPERATING REFRIGERATING AND ICE-
MAKING HACHINERY.
First, a competent engineer should be placed in charge of the
plant, and he should be held responsible for the performance of
the plant.
He should have charge of all help in the engine room, tank-
room, and all men who work around the plant.
He should acquaint himself with all pipe and valves about
the plant, so that in case of trouble, he will know what
to do.
Valves should be provided in suitable places, so that if it be-
comes necessary, he can transfer the ammonia from one part of
the plant to another ; before attempting to transfer the ammonia,
the engineer in charge should carefully see that he fully under-
stands where the ammonia is to be put, and that there is suffi-
cient space to contain same. In making transfers, always run
the machine very carefully.
When starting the engine, start slowly, and before the pumps
show a vacuum in the coils, open the regulating valve slightly,
and then speed up the engine gradually.
The back pressure should be kept at about 15 pounds above
zero, depending on the frost shown on suction pipe. When the
machine is run to its full capacity, it should show frost on
the suction pipe just above the brine tank ; in some machines, it
is necessary to freeze back to machine, as the frost takes up the
heat of compression and takes the place of the water jacket.
In general, the engineer in starting the machine, will first see
that the discharge valves are open, then start the machine slowly,
and open the suction valves slowly. When the machine is fully
up to speed, watch the gauges and note the pressure. The con-
denser pressure should be somewhere between 150 and 180 Ibs.
HANDBOOK -ON ENGINEERING. 625
depending upon the temperature of the water and atmosphere.
The suction or back pressure should be about 20 pounds, unless the
temperature of the brine in the tanks is below 18 degrees ; if it is,
the low pressure should be reduced in proportion ; the frost on
the suction pipe will determine the back pressure to be carried.
It is advisable to use as high a back pressure as possible without
frosting back.
Regulate the low pressure by means of the feed valves. The
pressure should rise slowly ; watch carefully to see that the feed
valves work regularly so that each valve may supply the proper
amount of ammonia to the coils .
The frosting of the valves will indicate how they are working,
and a little practice will enable the engineer to judge of this.
When the ammonia disappears from the liquid receiver, it is
possible that too much feed has been given the coils, and that they
are flooded ; it is well to shut off the main liquid valve to the
tanks and pump them out until the back pressure falls to about
five pounds ; the valve can then be opened and the regular
operation resumed.
This pumping down is for the purpose of getting the ammonia
all out of the tank coils, where it will sometimes lie; when this is
the case, the suction line to the machine will be frosted, even
when the tanks are not below temperature of 18 degrees ; when
the tanks are below 18 degrees, frost will generally appear in the
suction line to the machine.
In case of a leak in the pipe, the connections are made to the
pumps so that the large valves on the suction and discharge pipes
may be closed, and the small by-pass valves opened and by
running the machine slowly, the discharge pipe system can be
pumped into the suction and brine tanks. In case of a leak
in the suction side, it is only necessary to shut off the liquid
valve and pump all of the ammonia up into the condenser and keep
it there by shutting the valve.
When shutting down a machine, close the liquid valve on the
626 HANDBOOK ON ENGINEERING.
brine tank, and run the machine until the pressure is brought
down to zero on the gauge. Do not create a vacuum, because
air is liable to leak into the pumps through the stuffing
boxes.
It is well to watch the compressor carefully for leaks ; a
leak into the cylinder either through leaky discharge valves,
the gaskets or the cylinder head gasket between the cylinder
and the discharge port, will materially reduce the compressor
capacity. It will not take long for a compressor to waste a ton
of coal.
If the engineer in charge of a compressor has a chance, he
should take off the cylinder head and examine the cylinder
gasket. If it looks bad, replace it with a new one; rub the
valves to their seats with flour of emery and oil, and see that they
have a good bearing ; also examine the valve cage gaskets.
A good test for a compressor, to see whether all connections
are tight about the compressor, is to connect a pressure gauge to
the indicator connection ; compress the gas in the cylinder
so as to have a high pressure. Note the pressure on the gauge.
If it does not decrease, the compressor and connections are
tight. . If it decreases rapidly, either the valves need regrinding,
or the piston needs new rings, or the cylinder should be rebored,
or all these troubles may exist at the same time.
All pipe and fittings between the machine and condenser,
should be looked after as all flanges are provided with lead
gaskets, and these flanges should be examined occasionally, and
when the plant is shut down and allowed to cool, the flanges
should be tightened up.
The pipes of the condensers should be kept as clean as
possible, so that the water will flow evenly over all pipes alike,
in order to extract as much heat as possible from the ammonia.
The colder the ammonia can be kept in the condenser, the
HANDBOOK ON ENGINEERING. 627
more work it will do in the tanks ; on this account, well water 18
to be preferred.
The oil trap on the line from the machine to the condenser,
should be examined once every ten days and the oil drawn off.
If the system gets clogged with oil, and where there is more than
one tank, pump the brine into the other tanks and when the brine
is all out of the tank, disconnect the coil at top and bottom, con-
nect steam, attach a gauge, and then drive a pine plug in bottom
of coil and put about 30 pounds of steam on coil for ten or
twenty minutes ; on the bottom of the return header is a purge
cock that must be opened frequently, while the steam is on
coil. Then knock plug out of coil at bottom, and let the steam
come through coil for a short time, and then disconnect the steam
and connect the air pump to the coil and put on thirty pounds
air pressure for ten minutes ; all coils must be treated in the
same way.
If there is only one tank, the coils must be taken out of tank
and blown out, or the brine pumped into the cans. At the
same time, the expansion valves must be overhauled. After all
coils and headers are connected the whole should be tested for
leaks, first, under air pressure, and second, with ammonia and a
sulphur stick while the tank is empty.
The sulphur sticks are prepared by dipping a stick of wood
into melted sulphur. The sticks are then burned close to where
leaks are suspected. Any leak is at once indicated by a white
smoke.
•
STEAH CONDENSERS.
Steam and ammonia condensers should be kept clean and free
from all scale, and should be supplied with sufficient water to
condense the steam and ammonia.
628 HANDBOOK ON ENGINEERING.
THE REBOILERS.
The reboilers are for the purpose of removing any air or
gases which may be in the steam. The water in the reboilers
should at all times be kept boiling, for if it is not, the ice will be
white. The regulating valves on the reboilers should be exam-
ined often, to see that they are not sticking. A steam connection
should be provided in the flat coolers, so that after shutting off
the water, which flows over the cooler, and the water from the
reboilers, steam may be blown through it from the top downward
and out at the bottom of the coil ; this should be done frequently,
land it will be found to save the filters.
The oil separator should be examined at least once a year and
cleaned. The object of this separator is to remove the oil from
the steam, and, if working properly, there should be a small
stream of water and oil flowing from the drain.
AIR IN THE SYSTEM.
When air or permanent gases are in the system, it will be
manifested by unusually high condenser pressure, and the effi-
ciency of the machine will be reduced. To remove the air, attach
a bent piece of one-fourth inch pipe to the small valve placed on the
top of the condenser ; place the other end of the pipe in a bucket
of water ; open the valve slightly, and if air is present, it will
bubble up through the water, while the ammonia will produce a
crackling noise, the same as when steam is turned into water,
GASES IN THE PLANT.
Accumulation of gases in a plant sometimes consists of atmos-
pheric air, but sometimes also of hydrogen and nitrogen, due to
the decomposition of ammonia.
HANDBOOK -ON ENGINEERING. 629
The best way to remove these gases from the system, is by
drawing them off at the top of the ammonia condenser coils,
where a small valve will be found on top of each coil where a
small pipe may be attached to the small valves ; put the other end in
a bucket of water. If, on opening the valve, bubbles are seen to
escape through the water, the valve should be kept open as long
as such bubbles appear ; when a crackling noise is heard in the
water, close the valve.
Every engineer should keep himself posted as to the exact
clearance existing between the piston and the head or heads of
the compressor. A convenient way to ascertain this, is to
remove one of the valves from the compressor head and insert a
piece of soft lead rolled in the shape of a wire through the valve
chamber into the cylinder and pinch the machine over until the
piston of the compressor squeezes the lead against the head.
When the lead is withdrawn, the exact clearance will be shown.
If the valves pound, it may be that the valves have too much
lift. Try a stiffer spring. A spring that is too stiff will also
cause valves to pound.
Never create a vacuum in an ammonia system, unless it is
absolutely necessary to repair a leak or for similar purposes ; it
will have a tendency to admit air into the system ; the air must be
kept out ; pump to zero on the gauge, but no lower.
Never put any ammonia in a plant until it has been tested ;
this can be done by drawing a sample out of the drum and seeing
that it will all evaporate and leave no residue.
Keep a record of the temperatures of brine and condensing
water, and evaporating and condensing pressures.
It is a good plan to have a duplicate set of valves on hand, all
ready to replace any leaky valve.
A leaky suction valve is sometimes the cause of considerable
loss in capacity. It can be located by heat on the suction con-
nection or by the hiss that is ever present when a valve leaks,
or by the appearance of the valve.
630 HANDBOOK ON ENGINEERING.
Test the oil that is being used in the compressors by subject-
ing a sample to low temperature — get a bottle of the oil and
cover with fine ice and salt ; the result will demonstrate whether
it will stand a low temperature or not. If the oil gets thick and
gummy, and a separation occurs, leaving a thin transparent,
watery liquid, in which the heavy part of the oil settles, and
which gives off an odor like benzine. Reject the oil, as it will
produce gases in the system, and give trouble.
Oil may be tested with ammonia gas ; animal fat will saponify
when subjected to alkali tests.
In ice plants, the engineer should see that the ice is always
pulled regularly. The distilled water is supplied regularly and
it should be used in the same way ; pull but one can and refill
before pulling the next.
Keep the brine in the tanks over the top pipe ; at the end of
the season, when the plant is shut down, leave the cans in the
brine for if the cans are taken out, the brine will be lowered and
where the pipes are exposed, they will rust very fast ; keep the
tank covers clean. The strength of the brine should be about 80
on a saltometer.
If ice forms on the coils, the brine is weak, and the brine must
be strong enough so it will not freeze.
In making repairs to coils, while immersed in brine the work-
men should besmear their arms and hands with cylinder oil, or
lard or tallow, as that will enable them to keep them in the brine
longer.
In case the temperature of the brine rises above 30 de-
grees, do not attempt to reduce the temperature without first
examining the cans to see whether the ice has thawed loose from
them; in case it has thawed, pull all ice and refill the cans
before reducing temperature ; if this is not done, the freezing of
the water around the ice in the cans will burst them.
HANDBOOK ON ENGINEERING. 631
TESTING FOR WATER BY EVAPORATION.
As shown by the engraving, screw into the ammonia flask a
piece of bent one-quarter inch pipe, which will allow a small bot-
tle to be placed so as to receive the discharge irom it. This test
bottle should be of thin glass with wide neck, so that quarter-inch
pipe can pass readily into it, and of about 12 cubic inches capac-
ity. Put the wrench on the valve and tap it gently with a ham-
mer. Fill the bottle about one-third full and throw sample out
in order to purge valve, pipe and bottle. Quickly wipe off mois-
ture that has accumulated on the pipe, replace the bottle and open
Fig. 300. Showing connections to flask.
valve gently, filling the bottle about half full. This last operation
should not occupy more than one minute. Remove the bottle at
once and insert in its neck a stopper with a vent hole for the
escape of the gas. A rubber stopper with a glass tube in it is
the best, but a rough wooden stopper, loosely put in, will answer
the purpose. Procure a piece of solid iron that should weigh not
less than eight or ten pounds, pour a little water on this and place
the bottle on the wet place. The ammonia will at once begin to
boil, and in warm weather will soon evaporate. If any residuum,
pour it out gently, counting the drops carefully. Eighteen drops
are about equal to one-tenth of an ounce, and if the sample taken
632
HANDBOOK OX ENGINEERING.
amounts to, say, 6 cubic inches, we can readily approximate the
percentage of the liquid remaining.
Fig. 301. Sectional view of 10-ton refrigerating machine.
LUBRICATION OF REFRIGERATING MACHINERY.
It is well to speak of this, for the reason that it is an important
subject ; and some users of machinery think that a cheap, low
HANDBOOK ON ENGINEERING. 633
grade of oil is really the cheapest. To disabuse their minds of
this idea and suggest the necessity of high grade oils, both on the
score of economy and to keep the machinery at all times in
efficient running order, we suggest the following: First-class
refrigerating machinery calls for the use of at least three different
kinds of oil, Nos. 1, 2 and 3, each of high grade : —
No* J* For use in the steam cylinder, and is known in the trade
as cylinder oil. This ranges in price from 50c, to $1 per gallon.
Good cylinder oil should be free from grit, not gum up the valves
and cylinder, should not evaporate quickly on being subjected to
heat of the steam, and when cylinder head is removed, a good
test is to notice the appearance of the wearing surfaces ; they
should be well coated with lubricant which, upon application of
clean waste, will not show a gummy deposit or blacken. Use this
oil in a sight feed lubricator with regular feed, drop by drop.
No* 2* For use of all bearing and wearing surfaces of machine
proper — an oil that will not gum, not too limpid, with good
body, free from grit or acid and of good wearing quality, flowing
freely from the oil cups at a fine adjustment without clogging,
and a heavier grade should be used for lubricating the larger
bearings.
No* 3* For use in compressor pumps. This oil should be what
is called a cold test, or zero oil, of best quality.
Best paraffine oil is sometimes used ; as also a clear West Vir-
ginia crude oil. This oil, when subjected to a low temperature,
should not freeze.
EFFECTS OF AMMONIA ON PIPES.
Ammonia has no chemical effect upon iron ; a tank, pipe or
stop-cock may be in constant contact with ammonia for an in-
definite time and no action will be apparent. The only protec-
tion, therefore, that ammonia-expanding pipes require is from
corrosion on the outer surface. As long as the pipes are covered
634 HANDBOOK ON ENGINEERING.
with snow or ice, corrosion does not occur ; the coating of ice
thoroughly protects them from the oxidizing effect of the atmos-
phere ; but alternate freezing and thawing requires protected sur-
faces, which are best obtained by applying a coat of paint every
season.
Expansion coils having to withstand but a maximum working
pressure of thirty pounds per square inch, are constructed with
such absolute security, in whole and in detail, as to make them
one of the most perfect pipe constructions on a large scale ever
applied in practice.
Fig. 302. Position of tank to be emptied.
TO CHARGE THE SYSTEM WITH AMMONIA.
Position of the tank should be as shown, the outlet valve
pointing upwards and the other end of the tank raised 12" to 15".
The connection between the outlet valve of the tank and the
inlet cock of the system should be a |" pipe. In charging, open
valve of the tank cautiously to test connection ; if this is tight,
open valve fully ; start machine and run slowly till tank is empty.
The tank is nearly empty when frost begins to appear on it ; run
the machine till suction gauge reaches atmospheric pressure. If
it holds at this pressure when machine is stopped, the tank is
empty ; if not, start up again. In disconnecting, close the valve
on the tank first, the inlet cock of the system. Weigh tank
HANDBOOK (ON ENGINEERING. 635
before and after emptying ; each standard tank contains from 100
to 110 pounds of ammonia.
PROCESS OF MECHANICAL REFRIGERATION.
The process of mechanical refrigeration is simply that of
removing heat, and mechanism is necessary, because the rooms
and articles from which the heat is to be removed are already as
cold, or colder than their surroundings, and consequently, the
natural tendency is for the heat to flow into them instead of out of
them. The fact that a body is already cold does not prevent the
removal of more heat from it and making it still colder. The term
cold describes a sensation and not a physical property of matter ;
the coldest bodies we commonly meet with are still possessed of a
large quantity of heat, part of which, at least, can be abstracted
by suitable means. The only means by which heat can be
removed from a body is to bring in contact with it a body colder
than itself. This is the function that ammonia performs in
mechanical refrigeration. It is so manipulated as to become
colder than the body we wish to cool. The heat thus abstracted
by it is got rid of by such further manipulation that (while still
retaining the heat it has absorbed) it will be hotter than ordi-
nary cold water, and therefore, part with its heat to it. Ammonia
thus acts like a sponge. It sops up the heat in one place and
parts with it in another, the same ammonia constantly going
backward and forward to fetch and discharge more heat. The
complete cycle of operation comprises three parts : —
1st. A compression side, in which the gas is compressed.
2d. A condensing side, generally consisting of coils of pipe,
in which the compressed gas circulates, parts with its heat and
liquefies.
3d. An expansion side, consisting also of coils of pipe,
in which the liquefied gas re-expands into a gas, absorbs heat,
and performs the refrigerating work.
()36 HANDBOOK ON ENGINEERING.
In order to render the operating continuous, these three sides
or parts are connected together, the gas passing through them in
the order named. The liquefied gas is allowed to flow into the
expansion or evaporating coils, where it vaporizes and expands
under a pressure varying from 10 to 30 pounds above that of the
atmosphere, when ammonia is the agent in use. The gas then
passes into the compressor, is compressed and forced into the
condensers, where a pressure from 125 to 175 pounds per square
inch usually exists ; here liquefaction takes place and the re-
sulting liquefied gas is allowed to flow to a stop-cock having a
minute opening, which separates the compression from the expan-
sion side of the plant. The expansion side consists of coils of
pipe similar to those of the condensing side, but used for the
reverse operation, which is the absorption of heat by the vapor-
ization of liquefied gas instead of the expulsion of heat from it,
as in the former operation. Heat is conducted through the ex-
pansion or cooling coils to, and is absorbed by, the vaporizing
and expanding liquefied gas within such coils, for the reason that
they are connected to the suction or low pressure side of the
apparatus from which the compressors are continually drawing
the gas and thereby reducing the pressure in said coils, as already
stated, to a pressure of 10 to 30 pounds above the atmosphere;
it being kept in mind that liquefied ammonia in again assuming
a gaseous condition, has the power or capacity of reabsorbing,
upon its expansion, a large quantity of heat. The liquefied gas
entering these coils through the minute openings of the stop-cock,
above referred to, is relieved of a pressure of 125 to 175 pounds,
the amount requisite to maintain it in a liquid condition, when it
begins to boil, and in so doing passes into the gaseous state. To
do this it must have heat, which can be supplied only from the
substance surrounding the pipes, such as air, brine, wort, etc.
As a natural result the surrounding substances are reduced in
temperature, or cooled.
HANDBOOK ON ENGINEERING.
637
PURGING VALVE
IDICATOR VALVE
Sectional yiew of « Eclipse" Compressor.
638
HANDBOOK ON ENGINEERING.
304. Section of De La Vergne Donble-Acting Vertical Ammonia
Compressor.
HANDBOOK ON ENGINEERING.
639
640
HANDBOOK ON ENGINEERING.
THE DE LA VERQNE SYSTEM.
The diagram on page 640 is seen to be extremely simple in
conception. Ammonia gas is received by the compressor ^
from which it is discharged into the pressure tank B. The gas
continues into the condenser, where it is liquified and collects in
the liquid storage tank D. The liquid ammonia is taken off from
the bottom of the second tank and passes through the expansion
cock E into the expansion or refrigerating coil, where it boils
into vapor. This is drawn off into the compressor to pass around
again in the order above described. Before entering the com-
pressor the gas passes through the scale separator or trap shown
near the gauge plate where any scale or foreign matter is re-
moved from the ammonia.
Fig. 306. A Diagram of the De La Vergne System.
HANDBOOK ON ENGINEERING.
64!
642 HANDBOOK ON ENGINEERING.
On page 641 is shown in diagram the general arrangement of
a standard De La Vergne Refrigerating System with horizontal
machine. The hot gas discharged by the compressor passes
first to the pressure tank from whence it passes up the riser
marked hot gas line, through a check valve and down a header
through two inch pipes and soft seated globe valves of the same
size to the individual stands of atmospheric condensers at the bot-
tom, and as the liquid forms, it is drawn off at different levels
through the several small pipes shown in the illustration, and
passes into the liquid header from where it goes to the liquid
tank. The outlet from the liquid header rises a few inches to form
a gooseneck, which maintains a liquid seal on the condenser and
prevent gas from the pressure tank from getting into the liquid
line leading to the expansion coils. The liquid line from the con-
denser is provided, just before it reaches the liquid tank, with a
pocket into which any scale or foreign matter is precipitated.
DE LA VERGNE CAN ICE MAKING PLANT.
In the distilling apparatus for can ice plants, illustrated on
page 643 , the exhaust steam from the engine which drives the
compressor is passed first through a grease separator A, in which
the exhaust steam impinging on the water in the bottom of the
shell and the baffle plate between the inlet and the outlet, pre-
cipitates and entrained oil. From the grease separator the steam
passes the usual boiler feed water heater J5, and is finally con-
densed in the surface steam condenser (7, the condensation from
which together with that from the feed water heater passes to the
combined skimmer and reboiler D.
In the reboiler the ebullition is effected in a central tank, con
centric to which is a second or outer tank, the space between the
two being utilized as a skimming tank. The overflowing wate
in the jacket of the skimming tank prevents radiation of hea
from the reboiling tank proper, and there being no ebullition in
HANDBOOK ON ENGINEERING.
643
644 HANDBOOK ON ENGINEERING.
this outer tank to disturb the surface of the water, skimming is
effected with a minimum loss of sweet water.
From the reboiler the water passes to the hot water storage
tank, E.
In order to keep the remaining parts of the distilled water sys-
tem filled at all times and thereby prevent any re-absorption of
air which might otherwise take place, a regulating mechanism is
employed which in case of low water in the hot water storage
tank, closes the valve through which the water passes into the
hose of the can filler.
Ordinarily the hot, reboiled, distilled water from tank E, passes
through the condensed water cooling coil F, over which is
showered cold water from the main supply line. The hot dis-
tilled water enters this cooler from below, and leaving the top of
the water-cooling coil, it then again passes downward and through
the deodorizer H. This device consists of a cylindrical shell of am-
ple dimensions filled with charcoal. The water is introduced
through a strainer under a false bottom so perforated as to give
the upward flow of water an even distribution over the entire
cross section of the filter bed. At the top the water passes a
second strainer from which it flows to the can filler.
The liquid ammonia leaves the liquid tank at the bottom
through the main liquid line, a branch from which after passing
through a strainer is connected with the main suction line just
above the compressor cylinder, and supplies liquid for regulating
compressor temperatures while starting up, pumping out, etc.
Just outside the main liquid valve a small connection is made
into the main liquid line to which ammonia drums may be con-
nected for charging the system. Beyond this connection the
main line passes to the cold storage rooms and branches out to
the individual expansion valves on the various cooling coils.
The ammonia gas returning from each coil passes through a
two inch soft metal seated globe valve, which together with the
HANDBOOK ON ENGINEERING.
645
0,
o
be
£
646
HANDBOOK ON ENGINEERING.
expansion valve allows the individual coils to be pumped out,
shut off and disconnected.
The main suction line is provided with a scale separator or
trap which prevents any scale or other foreign substances from
entering and damaging the compressor and valves.
The compressor is lubricated by means of a small oil pump
shown attached to the right hand side of the machine. The oil
from this pump is forced through a three-way cock, through the
Fig. 310* Twin cylinder compressor, witn
steam cylinders
piston rod stuffing box lantern and into the oil pot situated
just above the stuffing box. The second line leading from the
three-way cock connects with the pressure tank and through this
line the oil carried over with the ammonia gas may be blown back
through a strainer into the lubricating system.
The system is arranged with by-passes so that the ammonia
from any part of the whole of the high pressure side can be
pumped out and discharged into the low pressure side.
HANDBOOK ON ENGINEERING. 647
Through the connection between the suction and equalizing lines
(shown just above the gauge board in the cut), any one stand of
the condensers can be pumped out singly.
Both the liquid and pressure tanks are provided with gauge
glasses so that the height of tlie oil or liquid ammonia can be
readily observed at any time.
The condensers are provided with a purging and equalizing
header running the entire width of the battery of condensers con-
nected with each stand through a half-inch soft metal seated
valve. The impure gases collecting at the top of the condensers
may be purged from the header through the blow-off valve.
Any ammonia gas entering the oil pot from the stuffing box
lanterns or from the oil blown back from the back pressure tank
passes up through the equalizer from the oil pot and enters the
main suction from the top. A continuation of this furnishes the
low pressure gauge connection, while the high pressure gauge is
connected to the pressure tank.
648 HANDBOOK ON ENGINEERING.
CHAPTER XXII.
SOflE PRACTICAL QUESTIONS USUALLY ASKED OF EN-
GINEERS WHEN APPLYING FOR LICENSE.
Q. If you were called on to take charge of a plant, what would
be your first duty? A. To ascertain the exact condition of the
boiler and all its attachments (safety-valve, steam-gauge, pump,
injector) and engine.
Q. How often would you blow off and clean your boilers if
you had ordinary water to use? A. Twice a month.
Q. What steam pressure will be allowed on a boiler 50" diam-
eter, f" thick, 60,000 T. S. £ of tensile strength factor of safety?
A. One-sixth of tensile strength of plate, multiplied by thick-
ness of plate, divided by one-half of the diameter of boiler, gives
safe working pressure.
Q. How much heating surface is allowed per horse-power by
builders of boilers ? A. 12 to 15 feet for tubular and flue boilers.
Q. How do you estimate the strength of a boiler? A. By its
diameter and thickness of metal.
Q. Which is the best, single or double riveting? A. Double
riveting is from 16 to 20 per cent stronger than single.
Q. How much grate surface do boiler-makers allow per horse-
power? A. About f of a square foot.
Q. Of what use is a mud drum on a boiler, if any? A. For
collecting all the sediment of a boiler.
Q. How often should it be blown out? A. Three or four times
a day, in the morning before starting, and at noon.
Q. Of what use is a steam dome on a boiler? A. For storage
of dry steam.
HANDBOOK ON ENGINEERING. 649
Q. What would you do if you should find your water gone
from sight very suddenly? A. If a light fire draw and cool off
as quickly as possible ; if a heavy fire cover with wet ashes or
slack coal. Never open or close any outlets of steam when your
water is out of sight.
Q. What precautions should you take to blow down a part of
the water in your boiler while running with a good fire? A.
Never leave the blow-off valve, and watch the water level.
Q, How much water would you blow off at once while running ?
A. Never blow off more than one gauge of water at a time while
running.
Q. What precautions should the engineer take when necessary
to stop with heavy fires? A. Close dampers, put on injector
or pump, and if a bleeder is attached, use it.
Q. What is an engineer's first duty on entering a boiler-room?
A. To ascertain the true water level, and look at steam gauge.
Q. When should a boiler be blown out? A. After it is cooled
off — never while it is hot.
Q. When laying up a boiler what should be done? A. Clean
thoroughly inside and out ; remove all ' 4 Rust ' ' and paint rust
places with red lead ; examine all stays and braces to see if any
are loose or badly worn.
Q. Of what use is the indicator? A. The indicator is used to
determine the power developed by an engine, to serve as a guide
in setting valves and showing the action of steam in the cylinder.
Q. How would you increase the power of an engine? A. To
increase the power of an engine, increase the speed, or get higher
pressure of steam ; or use less expansion.
Q. How do you find the horse-power of an engine?
area of piston X M.E.P. X piston speed.
33,000.
Q. Which has the most friction, a perfectly fitted, or an im-
perfectly fitted valve or bearing? A. An imperfect one.
650 HANDBOOK ON ENGINEERING .
Q. How hot can you get water under atmospheric pressure with
exhaust steam? A. 212°.
Q. Does pressure have any influence on the boiling point? A.
Yes.
Q. Which do you think is the best economy, to run with your
throttle wide open or partly shut? A. Always have the throttle
wide open on a governor engine.
Q. At what temperature has iron the greatest tensile strength?
A. About 600°.
Q. About how many pounds of water are required to yield one
horse-power with our best engines? A. From 15 to 30.
Q. What is meant by atmospheric pressure? A. The weight
of the atmosphere.
Q. What is the weight of atmosphere at sea level? A. 14.7
pounds per square inch.
Q. What is the coal consumption per hour per indicated horse-
power? A. Varies from 1| to 7 Ibs.
Q. What is the consumption of coal per hour on a square foot
of grate surface? A. From 10 to 12 Ibs.
Q. What is the water consumption in pounds per hour per
indicated horse-power? A. From 15 to 45 Ibs.
Q. How many pounds of water can be evaporated with one
pound of best soft coal? A. From 7 to 10 Ibs.
Q. How much steam will one cubic inch of water evaporate
under atmospheric pressure? A. One cubic foot of stearo
( approximately) .
Q. What is the weight of a cubic foot of fresh water? A.
62.425 Ibs.
Q. What is the weight of a cubic foot of wrought iron? A.
480 Ibs.
Q. What is the last thing to do at night before leaving the
plant? A. Look around for greasy waste, hot coals, matches, 01
anything which could fire the building.
HANDBOOK ON ENGINEERING. 651
Q. What is the weight of a square foot of one-half inch boiler
plate? A. 20 Ibs.
Q. How much wood equals one ton of soft coal for steam pur-
poses? A. About 4,000 Ibs. of wood.
Q. What is the source of all power in the steam engine? A.
The heat stored up in the coal.
Q. How is the heat liberated from the coal ? A. By burning
it — that is, by combustion.
Q. Of what does coal consist? A. Carbon, hydrogen, nitro-
gen, sulphur, oxygen and ash.
Q. What are the relative proportions of these that enter into
coal? A. There are different proportions in different specimens
of coal, but the following shows the average per cent : Carbon,
80 ; hydrogen, 5 ; nitrogen, 1 ; sulphur, 2 ; oxygen, 7 ; ash, 5.
Q. What must be mixed with coal before it will burn? A.
Air.
Q. Of what is air composed? A. It is composed of nitrogen
and oxygen in the proportion of 77 per cent nitrogen to 23 of
oxygen.
Q. What parts of the air mix with what parts of coal? A.
The oxygen of the air mixes with the carbon and hydrogen of the
coal.
Q. How much air must mix with coal? A. 300 cubic feet of
air for every pound of coal.
Q. How many pounds of air are required to burn one pound of
carbon? A. From 20 to 24, generally taken at 24.
Q. How many pounds of air to burn one pound of hydrogen?
A. Thirty-six.
Q. Is hydrogen hotter than carbon? A. Yes, 41 times hotter.
Q. What part of the coal gives out the most heat? A. The
hydrogen does part for part, but as there is so much more of
carbon than hydrogen in the coal, we get the greatest amount of
heat from the carbon.
652 HANDBOOK ON ENGINEERING.
Q. In how many different ways is heat transmitted? A,
Three, by radiation, by conduction and convection.
Q. If the fire consisted of glowing fuel, show how the heat
enters the water and forms steam ? A. The heat from the glow-
ing fuel passes by radiation through the air space above the fuel
to the furnace crown ; there it passes through the iron of the
crown by conduction ; there, it warms the water resting on the
crown, which then rises and parts with its heat to the colder water
by conduction till the whole mass of water is heated ; then the
heated water rises to the surface and parts with its steam, so a
constant circulation is maintained by convection,
Q. Of what does water consist? A. Oxygen and hydrogen.
Q. In what proportion? A. Eight of oxygen to one of
hydrogen, by weight.
Q. What are the different kinds of heat? A. Latent heat,
sensible heat and sometimes, total heat.
Q. What is meant by latent heat? A. Heat that does not
affect the thermometer and which expends itself in changing the
nature of a body, such as turning ice into water or water into steam.
Q. Under what circumstances do bodies get latent heat? A.
When they are passing from a solid state to a liquid state, or from
a liquid to a gaseous state.
Q. How can latent heat be recovered? A. By bringing the
body back from a state of gas to a liquid, or from that of a liquid
to that of a solid.
Q. What is meant by a thermal unit? A. The heat necessary
to raise one pound of water, at any temperature — one degree
Fan.
Q. If the power is in coal, why should we use steam? A. Be-
cause, steam has some properties which make it an invaluable
agent for applying the energy of the heat to the engine.
Q. What is steam ? A. It is an invisible vapor generated
from water by the application of heat.
Q. What are the properties which make it so valuable to us ?
HANDBOOK ON ENGINEERING. 653
A. 1. The ease with which we can condense it. 2. Its great
expansive power. 3. The small space it occupies when con-
densed.
Q. Why do you condense the steam? A. To form a vacuum
and so destroy the back pressure that would otherwise be on the
piston, and thus get more useful work out of the steam.
Q. What is vacuum? A. A space void of air.
Q. How do you maintain a vacuum? A. By the steam used
being constantly condensed by the cold water or cold tubes, and
the air pump constantly clearing the condenser of air.
Q. Why does condensing the used steam form a vacuum? A.
Because a cubic foot of steam at atmospheric pressure shrinks
into about a cubic inch of water.
Q. What do you understand by the term horse-power? A. A
horse-power is equivalent to raising 33,000 Ibs. one foot per min-
ute, or 550 Ibs. raised one foot per second.
Q. What do you understand by lead on an engine's valve? A.
Lead on a valve is the admission of steam into the cylinder be-
fore the piston starts its stroke.
Q. What is the clearance of a cylinder as the term is applied
at the present timer A. Clearance is the space between the
cylinder head and the piston head, with ports included.
Q. What are considered the greatest improvements on the
stationary engine in the last forty years? Ac The governor, the
Corliss valve gear, and the triple expansion engine.
Q. What is meant by triple expansion engine ? A. A triple
expansion engine has three cylinders, using the steam expansively
in each one.
Q. Is there any danger of a well-fitted and tightly-keyed fly-
wheel coming loose? A. Yes ; water in the cylinder by produc-
ing a heavy jar would tend to loosen a fly-wheel and frequently
reversing an engine under a load arid high speed, would tend to
produce the same effect.
654 HANDBOOK ON ENGINEERING.
Q. What is a condenser as applied to an engine ? A. The con-
denser is a receptacle into which the exhaust steam enters and is
there condensed.
Q. What are the principles which distinguish a high-pressure
from a low-pressure engine? A. Where no condenser is used and
the exhaust steam is open to the atmosphere it is high pressure.
Q. About how much gain is there by using the condenser? A.
17 to 25 per cent, where cost of water is not figured.
Q. What do you understand by the use of steam expansively?
A. Where steam admitted at a certain pressure is cut off and
allowed to expand to a lower pressure.
Q. How many inches of vacuum give the best results in a con-
densing engine? A. Usually considered 25".
Q. What is meant by a horizontal tandem engine? A. One
cylinder being behind the other, with two pistons on same rod.
Q. What is a Corliss valve gear ? A. (Describe the half moon,
or crab-claw gear, or oval-arm gear with dash pots.)
Q. From what cause do belts have the power to drive shafting?
A. By friction or adhesion.
Q. What do you understand by lap? A. Outside lap is that
portion of valve which extends beyond the ports when valve is
placed on the center of travel ; and inside lap is that portion of
valves which projects -over the ports on the inside or towards the
middle of valve.
Q. What is the use of inside lap? A. To give the engine
compression.
Q. Where is the dead center of an engine? A. The point
where the crank and the piston rod are in the same right line.
Q. In what position would you place an engine to take up any
lost motion of the reciprocating parts ? A. Place the engine in
the position where the least wear takes place on the journals.
That is, in taking up the wear of crank-pin brasses, place the
engine on either dead center, as when running, there is little wear
HANDBOOK ON ENGINEERING. 655
upon the crank-pin at these points. If taking up the cross-head
pin brasses — without disconnecting and swinging the rod —
place the engine at half stroke, which is the extreme point of
swing of the rod, there being the least wear on the brasses and
cross-head pin in this position.
Q. What benefits are derived from using fly-wheels on steam
engines ? A. The energy developed in the cylinder while the steam
is doing its work, is stored up in the fly-wheel, and given out by
it while there is no work being done in the cylinder — that is,
when the engine is passing the dead centers. This tends to keep
the speed of the engine shaft steady.
Q. Name several kinds of reducing motions, as used in indi-
cator practice? A. The pantograph, the pendulum, the brumbo
pulley, the reducing wheel.
Q. How can an engineer tell from an indicator diagram whether
the piston or valves are leaking? A. Leaky steam valves will
cause the expansion curve to become convex ; that is, it will not
follow hyperbolic expansion, and will also show increased back
pressure. But if the exhaust valves leak also, one may offset the
other, and the indicator diagram would show no leak. A leaky
piston can be detected by a rapid falling in the pressure on the
expansion curve immediately after the point of cut-off. It will
also show increased back pressure. A falling in pressure in the
upper portion of the compression curve shows a leak in the exhaust
valve.
Q. What would be the best method of treating a badly scaled
boiler, that was to be cleaned by a liberal use of compound? A.
First, open the boiler up and note where the loose scale, if any,
has lodged. Wash out thoroughly and put in the required
amount of compound. While the boiler is in service, open the
blow-off valve for a few seconds, two or three times a day, to be
assured that it does not become stopped up with scale. After
running the boiler for a week, shut it down, and when the
HANDBOOK ON ENGINEERING .
pressure is down and the boiler cooled off, run the water out and
take off the hand-hole plates. Note what affect the compound
has had on the scale, and where the disengaged scale has lodged.
Wash out thoroughly and use judgment as to whether it is advis-
able to use a less or greater quantity of compound, or to add
a small quantity daily. Continue the washing out at short
intervals, as many boilers have been buined by large quan-
tities of scale dropping on the fire sheets and not being
removed.
Q. What is an engineer's first duty upon taking charge of a
steam plant? A. The first duty of an engineer assuming charge
of a steam plant is to familiarize himself with his surroundings,
ascertain the duty required of each and every piece of machinery
contained therein, and in just what condition each one is.
Let us discuss it at length, assuming that when just engaged he
is informed as to the nature of the work required of the plant
in question, namely: Whether it is a heating plant, electric
lighting, hydraulic or electric elevator, power station, or any
other kind of the various steam plants in existence. Of course,
a great deal depends upon the size and kind of plant under con-
sideration and the number of men employed, hours in operation,
and some other things in general which most engineers know of.
He should first see just what his plant contains "from cellar
to garret," so to speak ; whether all that is contained has to run
continually, or almost so, and what can be depended on in case
anything should suddenly become deranged or give out entirely.
Next, he should ascertain the general condition of everything,
going over each portion in turn, as time and opportunity permit,
and conclude from what he has seen how much longer it may
be run safely and economically. It will be remembered that a
piece of machinery may be run safely and yet not with economy.
So, if he should wait for the safety limit to be reached,
without taking other things into consideration, he might wait
HANDBOOK ON ENGINEERING. 657
a long time and in so doing waste many dollars of his
employer's money before it was thought necessary to reno-
vate, repair or renew. In going over everything, examining
each part critically, it would be well to make copious notes, and,
sketches might be added, to which the engineer can again refer.
It sometimes happens that engineers, in making an examination
of machinery, do not take dimensions or make sketches of certain
parts, which have to be repaired, or perhaps renewed, thinking
that the next time the apparatus is looked at will do for that.
Now, it sometimes happens that the " next time " is the time
when some accident occurs, finding him unprepared, causing con-
fusion, in the midst of which the making of sketches and taking
of dimensions cannot be thought of. All such should be done at
the first opportunity, and spare parts of the different machinery
should be kept on hand, especially in the case of a plant which
has only the machinery which is constantly in use. Another point
of importance to which an engineer should give attention, is to
ascertain the quantity and kind of supplies which are on hand,
that he may know when to make requisition for more, and so not
run short, as he otherwise might do. It is also important to see
what tools the plant contains and upon what he can depend in
case of the break -down of any part of the machinery. Of course
all the above cannot be done in one day, but no time should be
lost in doing all these things as early as possible, for the sooner
he gets all the particulars and details of his plant at his
"fingers' ends," the lighter will be his own labors, and the
more free will his mind be to think and act intelligently for the
emergencies of the future. Therefore, by performing this first
duty as early and thoroughly as possible, the succeeding ones will
be comparatively easy to handle and perform, for the reason that
he will be prepared for them.
Q. Define and explain the difference between sensible and
latent heat? A. The difference between sensible and latent heat
42
658 HANDBOOK ON ENGINEERING.
is explained thus : Sensible heat may be measured with a ther-
mometer, that is, it affects the mercury in a thermometer, caus-
ing it to rise in the stem so that the degree of heat may be
measured on the graduated scale affixed. Latent heat does not
affect the thermometer. Bodies get latent heat when they are
passing from a solid state to a liquid state, and also when passing
from a liquid to a gaseous state ; and moreover, this latent heat
can be recovered bj bringing a body back from a gaseous to a
liquid state, and from liquid to solid. Water is most com-
monly seen under the three forms of matter just mentioned,
namely, solid, ice ; liquid, water ; gaseous, steam. The following
method has -been used to explain how latent heat exists :
A quantity of powdered ice is placed in a vessel and brought
into a very warm room. As long as it remains as ice, it may be
any degree of heat below 32° Fahr., but the instant it begins to
melt, owing to the heat of the room, a thermometer placed in it
will record 32° Fahr. The thermometer will continue at 32° as long
as there is any ice in the vessel, but just as soon as the last piece of
ice has melted it will begin to rise, and continue to do so until the
water boils, when it will stand at 212° ; but although the water
goes on receiving heat after this, the instrument will stand at 212°
until all the water has boiled away. Now, a great amount of heat
must have entered the water since the ice began to melt, but it has
no effect on the thermometer, which continues at 32°, as noted
above ; the heat that has so entered is called ' ' the latent heat of
water." The heat that has entered the water from boiling
till it all becomes steam is called the " latent heat of steam."
The latent heat of water has been found to be 143° Fahr.
and the latent heat of steam, at the pressure of the atmosphere,
is 966°. This is the way the above was determined: A
quantity of water at a temperature of 32° Fahr. is made to
boil, and the time taken to do so noted ; in this case, it took one
hour. The water must be kept boiling until it has all evaporated.
HANDBOOK ON ENGINEERING. 659
and the time noted from boiling till evaporation, which in this
case will be 5^ hours. Therefore,
Temperature of boiling point, ' . . 212°
Temperature of water at first, 32°
Heat that has entered the water in one hour, . . „ . 180°
Number of hours boiling, e . . 51
900
60
Heat that has entered during the 5i hours, . 9 . . 960°
From this we see that the heat necessary to form steam, instead
of being only 212°, must be 966° + 212° = 1178°, or 5£ times as
great. Therefore, if it were not for latent heat, we would require
to burn 5J times the amount of coal that we now do to generate
steam. The sensible and latent heats alter with the pressure, but
as the sensible increases the latent decreases, and, roughly
speaking, the total heat, or the sum of the two, is the same. In
connection with the foregoing questions, we would recommend the
reader to spend a little time in looking over the " steam tables,"
and make comparisons between the different quantities noted
therein. By so doing he will get an exact knowledge of the prop-
erties of saturated steam.
Q. Explain the term tc clearance/' as used in connection with
an engine cylinder ? A. There are two kinds of clearance, cylinder
clearance and piston clearance . Cylinder clearance means the space
or volume, which exists between the piston and the valve, when
the piston is exactly at the beginning of the stroke and the crank
is on the dead center. This volume can be found by taking care-
ful and exact measurements and making calculations from them,
but a more correct way is to fill the space with water, noting the
quantity used, and so make calculations to find the cubic con-
660 HANDBOOK ON ENGINEERING.
tents. The cubic contents of the clearance space is a certain per-
centage of the total volume of the cylinder itself and such clear-
ance is expressed as so much per cent. This clearance causes a
small loss of steam each stroke, owing to the difference between
the initial and compressive pressure. Piston clearance is the
space between the piston and cylinder head when the crank is on
the dead center. This clearance is necessary to prevent the
cylinder head being knocked out, in case of an unusual quantity
of water gaining entrance to the cylinder while the engine is
running at its usual speed ; and also to admit of the crank-pin
and wrist-pin brasses being keyed up at certain intervals. The
way to find the piston clearance of an engine is as follows :
First, disconnect the wrist-pin end of the connecting rod from
the cross-head, and with a bar push back the cross-head until
the piston strikes the cylinder head ; then make a mark with
a scriber or sharp chisel, on both the sides of the cross-head and
on the guide in which the cross-head runs ; these marks must be
exactly in line with each other while the piston is in the above
stated position. Next, move the piston to the other end of the
cylinder till it strikes the head, and make a mark on the guide
similar to that on the other end, using the same mark which was
made on the cross-head. The new mark must also be in line with
this, as at the first mentioned end. We now have a mark at
each end of the guide, which represents the place at which the
piston strikes the cylinder head, when they alternately coincide
with the mark on the cross-head itself. Now, connect the rod
to the cross-head again and place the engine or crank on the center.
Next, produce or extend the mark on the cross-head to the guide,
this time using a pencil instead of a chisel and scriber. The
distance between the new pencil mark and the first mark made
on the guide is the amount of piston clearance which exists at
that end of the cylinder. Repeat the operation on the other end
and we will obtain the clearance existing there. If these clear-
HANDBOOK ON ENGINEERING. 661
ances are not equal, as indicated by the marks, make them so
by the means provided for in the design of the piston rod and
crosshead. After the clearance has been equalized, the pencil
marks may be obliterated and marks similar to the first ones may
be cut in, thus leaving a permanent mark, which can be seen while
the engine is running, and from which can be determined whether
the clearance is lessening, and at which end.
Q. What is the pressure of the atmosphere at the sea level, and
how determined? A. The pressure of the atmosphere is generally
spoken of as 15 Ibs. per square inch, but as the pressure of the
atmosphere is constantly varying at any one spot, corrections
have to be made according to the reading of a barometer.
Generally speaking, 15 is as nearly correct as engineers require
it. The pressure of the atmosphere can be ascertained by the
following experiment: Take a glass tube about 33 inches long,
having a bore equal to a square inch in section. Let one end of
the tube be closed in or capped, so that it can contain a fluid.
Then fill it with pure mercury, carefully expelling any air bub-
bles. When it is full, cover the open end of the tube with a piece
of glass and invert the whole tube. Place the open end into a
cup of mercury, the surface of which is subject to the pressure of
the air, and then withdraw the piece of glass. The mercury in
the tube will drop about three inches and then stop. When it
has ceased to fall, again cover the end of the tube with the glass.
Lift the tube out of the cup and remove the glass so that the
mercury may run out into a scale-pan provided for that purpose.
Upon actually weighing the mercury lately contained in the tube,
it will be found to weigh 14.7 Ibs. The mercury will stop falling
in the tube at 30 inches, or at the sea level. Hence, we know
that the atmosphere balances, or exerts a pressure of 14. Tibs,
per square inch at the sea level.
Q. Upon what does the efficiency of a surface condenser de*
pend? A. The efficiency of a surface condenser depends upon:
662 HANDBOOK ON ENGINEERING.
1st, the proper amount of cooling surface ; 2d, the rapidity with
which the water is made to circulate through the tubes ; 3d, the
water being made to flow in an opposite direction to the steam.
The temperature of the circulating water also has a bearing on
the question, as it is obvious that the colder the water the more
effective it will be in condensing the steam.
Q. A feed pump has a steam cylinder of 6 inches in diameter,
and water cylinder of 4 inches diameter ; assuming the steam
pressure carried to be 80 Ibs. per square inch throughout the
stroke, what will be the balancing pressure per square inch
against the water piston, friction being entirely neglected, and
gauge pressure being used? A. In this question, we first find
the area, the number of square inches contained in the steam
piston. Thus : The diameter = 6 in. and 62 x .7854 = the area.
Worked out it appears thus: 62 means that 6 is to be
squared, or multiplied by itself, or 6 x 6 = 36 square inches,
and 36 square inches multiplied by the constant .7854 =
28.27 square inches area contained in the steam piston.
Since the pressure is stated to be 80 Ibs. per square inch, then
28.2 7 x 80 = total pressure on the piston in pounds, or 2261.60
Ibs. Now, we will find the area of the water piston, which is 4
inches in diameter, 42 x .7854 = 12.5664 square inches contained
in the water piston. Therefore, the water piston, with an area
of 12.56 sq. in., has to have a resistance against which it will act
of 2261.60 Ibs., in order to balance the pressure against the
steam piston. Hence, the pressure per square inch can be found
by dividing 2261.60, or 2261.60 divided by 12.56 == 180 Ibs. per
square inch, the balancing pressure on the 4-inch water piston.
Q. State what you consider a good standard of strength for
steel boiler plate? A. The American Boiler Makers' standard,
as used, is as follows : Tensile strength, from 55,000 to 60,000
Ibs. per square inch section ; elongation in 8 inches, 20 per cent
for plates | inch thick and under; 22 per cent for plates f to |
HANDBOOK ON ENGINEERING. 663
inches ; 25 per cent for plates J inch and under ; the specimen
test piece must bend back on itself when cold, without showing
signs of fracture ; for plates over | inch thick, specimens must
withstand bending 180° (or half way) round a mandrel 1J times
the thickness of the plate. The chemical requirements are as
follows: Phosphorus, not over .04 per cent; sulphur, not over
.03 per cent.
Q. What is meant by the heating surface of a boiler? A. The
heating surface of a boiler is that surface of plates or tubes on
one side of which is water, and on the other, hot gases. It has
been decided that the surface next the water shall be reckoned,
the value to be given in square feet. In a fire tube, or tubular
boiler, it will include the under side of the shell from fire-line to
fire-line (usually about one-half of it), the tubes and such part of
the back-tube sheet as is below the back arch and not taken up
by the tube ends. For a water-tube boiler, the heating sur-
face will include the tubes, such part of the headers as are
in contact with the hot gases, and the lower part (about one-*
half) of the steam drum. In calculating the heating surface,
none should be taken which has steam on one side and hot gases
on the other, as such parts tend to superheat the steam, and are
known as superheating surfaces.
Q. What is a boiler horse-power? A. A boiler horse-power
has been recently defined as the evaporation of 34J pounds of
water per hour from a feed water temperature of 212° Fahr.
into steam at a temperature of 212° Fahr., and at a pressure of
one atmosphere. Under these conditions each pound of water
evaporated will take up 966 heat units, and the 34| Ibs. will take
34J x 966 — 33,327 heat units per hour. Hence, to find the
horse-power of a boiler, it is necessary to find the heat units
delivered per hour to the water and divide that number by 33,327.
Q. What will be the heating surface of a fire-tube boiler 6
feet in diameter, having 150 tubes 3 inches in diameter and 15
664 HANDBOOK ON ENGINEERING.
feet long? A. Each tube will have a heating surface equal to its
outside area, since the water is on the outside of the tubes. The
area of a cylinder 3 in. in diameter and 15 ft. long will be the
circumference times the length ; 3 in. = 1 ft. and the circumfer-
ence = 3.1416 x£ = .7854 ft.; this, times the length 15 ft.
— 11.78 sq. ft. for one tube ; for 150 tubes, it will be 150 times
that = 1767 sq. ft. The lower half of the shell is usually con-
sidered as heating surface. The circumference of a circle 6 ft. in
diameter is 6x3.1416 = 18.85 ft. and the area of the shell =
18.85x15 = 282. 75 sq. ft. Half this will be 141.37 sq. ft.
For the back end or tube plate, the total area will be the diameter
squared times .7854 = 62 x .7854 sa 28.27 sq. ft. ; -f of this will
be below the arch, and f of 28.27 = 18.85 sq. ft. From this
must be subtracted the area of the ends of the tubes. The end
area of one tube is Q)2 x .7854 = .049 sq. ft., and for 150
tubes it is 150 times that, or 7.35 sq. ft. The heating surface of
the tube plate will then be 18.85 minus 7.35 = 11.5 sq. ft. The
'front tube plate is not considered, because the gases are cooled
too much to be effective by the time they have passed through
the tubes. The total heating surface is 1767 + 141.37 + 11.5
= 1919.87 sq. ft.
Q. On what does the efficiency of a boiler depend? A. The
efficiency of any piece of machinery is the ratio of the energy made
useful to that furnished. The object of the boiler is to make steam ;
hence, the enegy used is that which has gone into the steam. The
proportion of the heat generated in the furnace which is transferred
to the steam, will depend on the thickness of the plates of the
boiler, on their condition as to cleanliness, on the amount of time
during which the gases are in contact with the plates in their
passage from furnace to chimney, on the completeness with which
all parts of the gases are brought in contact with the plates, and on
the temperature of the hot gases. Evidently, heat will pass through
a thin plate more readily than through a thick one, and more
HANDBOOK ON ENGINEERING. 665
readily through a clean plate than through one on which a non-
conducting coating of soot or scale has formed ; the more time
available for the transfer of heat, the greater will be the amount
transferred ; the more complete the contact between plates and
gases, the more opportunity will there be for the transfer of heat,
and the higher the temperature of the gases, the more rapidly
will the heat be transferred. To have a boiler efficient, it is
necessary to have plenty of heating surface, so that the hot gases
will have time for contact, to keep the plates clean, to have good
circulation of the gases, and to keep their temperature high by
preventing radiation and allowing as little air to enter the furnace
as is needed for good combustion. The efficiency of the furnace,
that is, the ratio of the heat generated in the furnace to that con-
tained in the coal, is a separate matter, though often the two are
lumped together. It depends on the adaptation of the furnace to
the kind and size of coal used, on the size of the combustion
chamber and on the proper firing of the coal.
Q. On what its satisfactory working? A. In order to
work satisfactorily, a boiler must not only be efficient, but must
make steam rapidly, must make dry steam, must be easily fired
and cleaned, and must be capable of standing a considerable
amount of forcing without serious priming. To get rapid steam
making, it is necessary to have good circulation of the water in the
boiler ; to get dry steam, plenty of steam space is needed, so that
the steam may circulate slowly and allow the water to drop out of
it ; easy firing means a low fire door of good size, and a rather
short grate ; easy cleaning means accessible parts, good sized
man-holes, good sized and well placed hand-holes, a large blow-
off and a short boiler ; the prevention of priming when carrying
an overload is a difficult matter ; the tendency to such an occur-
rence depends largely on the feed-water used ; plenty of steam
space and good circulation are helpful, but some waters will foam
in spite of all precautions.
666 HANDBOOK ON ENGINEERING.
Q. Suppose a slide valve cutting off at £ stroke, and a | cut-
off is desired, how would you proceed? A. Put on a new valve
with more outside lap. This would require a greater travel of the
valve, and therefore would increase the throw of the eccentric,
also.
Q. Which requires the greater outside lap, cutting off at T9^ oi
the stroke, or cutting off at |? A. Cutting off at T9¥. The
earlier the cut-off, the greater should be the outside lap.
Q. Are all plain slide valves made alike, as regards the exhaust
cavity of the valve? A. No ; sometimes they are made '•' line and
line " inside, that is, the width of the exhaust cavity is equal to
the distance between the inner edges of the two steam ports ; and
again, the width of the exhaust cavity is made greater or less than
this distance, according as an earlier or later release is desired.
Q. What is the effect of giving inside lap to a slide valve? A.
It delays the release and increases the compression.
Q. What is the effect of giving inside lead to a slide valve?
A. It gives an early release and decreases the compression.
Q. Suppose a simple slide valve engine with a fly-ball governor,
and the governor belt should break or slip off, what would
happen? A. If it were a plain governor the engine would race ;
but if a governor with an automatic stop, the engine would slow
down and stop.
Q. What two forces are opposed to each other in a case of fly-
ball governor? A. Centrifugal force, tending to throw the balls
away from the governor staff, and the force of gravity, tending to
draw the balls to the staff.
Q. What other name is given to a fly-ball governor? A. It is
also called a throttling governor, because the steam in passing
through the governor valve is throttled, choked, or wire-
drawn.
Q. Are all fly-ball governors throttling governors? A. No;
the governor of a Porter-Allen engine and those of all Corliss
HANDBOOK ON ENGINEERING. 667
engines, while of the fly-ball type, are not throttling governors,
because the steam does not pass through them.
Q. If the governor shaft of a fly-ball governor on a plain slide-
valve engine should break, could the engine be run? A. Yes;
by regulating the speed of the engine by hand at the throttle-
valve.
Q. Describe an automatic cut-off engine? A. In this class of
engines, as the load on the engine becomes greater or less, the
steam entering the cylinder is cut off later or earlier, and it is
done through a fly-ball governor in the case of a Corliss engine,
or through a shaft-governor or regulator in the case of a high-
speed engine.
Q. In an automatic cut-off high-speed engine with shaft-gov-
ernor, is the eccentric fastened to the shaft? A. It is not. It
is so arranged as to move freely across the shaft, in order to per-
mit the center of the eccentric to approach or to recede from the
center of the shaft, according as the load on the engine decreases
or is increased. And herein lies the chief difference between a
plain slide-valve and an automatic cut-off slide-valve engine.
Q. If the connecting rod of an engine had box liners at both
ends and in taking it down the liners were all mixed up, how
could the length of the rod from center to center of boxes be
found? A. Put the cross-head in the middle of its stroke —
after finding the piston striking points — and then measure from
the center of the cross-head wrist to the center of the main shaft.
If the piston clearance at both ends of the cylinder is known, the
piston may be pushed to the crank end of the cylinder until it
touches the head, and the distance from the center of the cross-
head wrist to the center of the main shaft found, to which should
be added the length or throw of the crank, and also the piston
clearance at the crank end of the cylinder.
Q. But suppose it were more convenient to push the piston to
the head end of the cylinder, what then? A. Find the distance
668 HANDBOOK ON ENGINEERING.
from the center of cross-head wrist to center of main shaft and
deduct the throw of the crank, and also the clearance.
Q. How is the length of the valve stem and of the eccentric
rod found for a plain slide valve engine having a rock shaft? A.
If the motion of the slide valve is parallel with the motion of the
piston, the length of the valve stem may be found by measuring
in a horizontal line from the center of the valve seat to the center
of the rock shaft ; and for the eccentric rod by measuring from
the center of the rock shaft, horizontally, to the center of the
main shaft, which would include one-half the yoke.
Q. What is a direct, and also an indirect valve motion? A.
When there is no rock shaft between the eccentric and the valve
to compound the motion, it is called " direct/' and when a rock
shaft intervenes, it is called an tc indirect " valve motion.
Q. Is the valve motion of a Corliss engine direct or indirect?
A. It is direct.
Q. How so ; it has a rock shaft between the eccentric and
the wrist plate? A. Even so, it is a direct valve motion; because
all connections to the rock-shaft arm are above the center of the
shaft, consequently, the motion is simple and not compound.
Q. When is an engine said to " run under," and when to " run
over? " A. When the crank pin is above the center of the main
shaft and the pin moves towards the cylinder, the engine is said
to " run under ; " and when it moves away from the cylinder, the
engine is said to " run over."
Q. What is meant by lead of valve, and what is it for? A.
Lead is the amount that the port is open to steam when the crank
is on its center. It is given in order to allow the full pressure of
steam to come on the piston at the beginning of the stroke, and
to provide a cushion for the piston.
Q. Could not cushion for the piston be obtained in some other
manner? A. Yes, by producing compression by an early closing
of the exhaust.
HANDBOOK ON ENGINEERING. 669
Q. Suppose a slide valve had f " lap and no lead, and it was
desired to give it -+-' lead, how should it be done? A. By mov-
ing the eccentric.
Q. Why could it not be done by altering the length of the
eccentric rod ? A. Because the eccentric rod does not establish
the amount of lead ; it simply equalizes the lead given by
moving eccentric.
Q. How would you test the piston of a steam engine to see
whether it was steam-tight or not? A. Put the crank on the
outboard center ; remove the cylinder head on the head end ;
block the cross-head and admit steam to the crank-end of
cylinder and note the effect. The fly-wheel, or the cross-head
may be securely blocked and the piston tested in this manner at
different points in the stroke.
Q . W hy are two eccentrics and two wrist plates put on some Corliss
engines ? A. One eccentric is for the induction valves to lengthen
the range of the cut-off ; the other for the exhaust valves to admit
of early release, without excessive compression. With a Corliss
engine having but one eccentric, the limit of cut-off is at less than
one-half stroke, but with two eccentrics the cut-off may be still
later in the stroke," and still release the steam at the proper time.
Q. What is meant by a ic blocked up " governor en a Corliss
engine? A. When the safety stop is "in, "the governor is said
to be blocked up.
Q. With a blocked up governor, suppose the main driving belt
should break, what would be the result? A. The engine would
race and would, perhaps, be wrecked.
Q. What is meant by the fire line of a horizontal cylindrical
boiler ? A. It is the height to which the shell is exposed to the
action of the flames.
Q. How high should the fire line be run? A. It maybe run as
high as the lower gauge cock water level, although it is frequently
run no higher than the top row of flues.
670 HANDBOOK ON ENGINEERING.
Q. What causes a chimney or smoke-stack to draw? A. The
difference in the temperature of the air inside the chimney and
that outside. The air inside expands and exerts less pressure
than the outside air, which rushes in to equalize the pressure.
Q. What does the amount of grate surface determine? A. It
determines the amount of coal that can be burned per hour, and
consequently, the amount of steam that can be generated.
Q. What is the object in giving a slide valve outside lap? A.
To save steam by cutting off the flow of steam into the cylinder
before the piston reaches the end of its stroke. For example:
With 24 in. stroke of piston and | cut-off, the flow of steam to
the piston is cut off when the piston has moved 15 inches and it
is driven the remaining 9 inches by the expansive force of the
steam.
Q. What amount of refrigerating water is required for a con-
denser? A. For a surface condenser about 50 times, and for a
jet condenser 30 times the amount of water evaporated in the
boiler ; more or less than these quantities being required accord-
ing to the temperature of the exhaust steam.
Q. Suppose your condenser was out of order and undergoing
repairs, could you run the engine? A. Yes; by attaching an
exhaust pipe to the engine and exhausting into the atmosphere.
Q. With a lever safety valve, should the end of the valve stem
upon which the lever rests, be square or concave? A. Neither
one; it should be pointed, so that the lever will always bear
directly on a line with the center of the valve stem.
Q. What is the proper proportion of a safety valve lever? A.
About 7 to 1 ; that is, if the distance from the center of the
valve to the fulcrum is 1 inch, the distance from the center of the
valve to the end of the long arm of the lever should be about 7
inches.
Q. How should the grates be set in a boiler furnace? A.
They should be set level, because this plan will enable the fire-
HANDBOOK ON ENGINEERING.
man to more easily carry a bed of fuel of uniform depth ; besides,
it is less laborious to clean the fire than when the grates are lower
at the bridge wall.
Q. What is momentum? A. It is the product of the mass or
bulk of a moving body, taken in pounds or tons, multiplied by the
velocity of the moving mass, generally taken in feet per second.
Q. Will an injector work at the same steam pressure wnen it
lifts the water as when the water flows to it under pressure ? A.
No ; when the water flows to an injector under pressure it will
work down to the lowest steam pressures, but when lifting the
water it requires a steam pressure of ten pounds or over to work
the injector.
Q. What is the greatest height to which an injector will lift
water? A. That depends upon the starting steam pressure.
There are injectors that will lift water two feet with 10 Ibs.
steam pressure, five feet with 30 Ibs., and from 12 to 25 feet with
60 Ibs. and over.
Q. If the pulley on the main shaft of an engine driving a fly-
ball governor be reduced in diameter, what affect will it have on
the speed of the engine? A. The speed of the engine will be
increased.
Q. Which is the greater, the bursting or the collapsing pressure
of a boiler tube? A. A boiler tube will collapse under less pres-
sure than would be required to burst it.
Q. Should a horizontal externally fired boiler be set level or
with a pitch? A. It is customary to set such a boiler one inch
lower at the end to which the blow-off pipe is attached, in order
to drain the boiler readily.
Q. In a slide valve engine with a connecting rod, will the valve
cut off the same at both ends of the stroke if it has equal lap and
lead? A. No ; owing to the angularity of the connecting rod.
Q. Is it proper to close the damper with a banked fire? A.
The damper should never be closed tightly while there is fire.
672
HANDBOOK ON ENGINEERING.
CHAPTER XXIII.
INSTRUCTIONS FOR LINING UP EXTENSION TO LINE SHAFT.
The erection of a line shaft, or an extension to one, is a
job that should have the services of a competent millwright or
machinist, as it is one calling for experience and considerable
skill.
The following drawing will serve to illustrate the operation. A
linen line or fine wire should be stretched beneath the shaft and
parallel to it, and extending beyond the termination of the
extension.
4JL,
L1NE
VA
Fig. 311. Method of lining up shafting.
To set the line parallel to the main line shaft, hang the plumb-
bobs A A over the shaft, as shown in the sketch, and then adjust
the line until it just touches the lines supporting the bobs, with-
out disturbing their position. If the plumb-bobs give trouble by
swaying, set pails of water so that the bobs will be immersed ;
this will stop the swaying without destroying their truth. The
plumb-bobs may just as well be old nuts or similar pieces of iron,
HANDBOOK ON ENGINEERING. 673
A
as the regulation type, since the result will be exactly the same.
After getting the line adjusted to the desired position, suspend
the plumb-bobs A A along the direction of the extension, so that
their supporting cords will just touch the line without disturbing it.
The new section of the shaft is now brought in position sideways
until it also touches the cords of the plumb-bobs ^4 A , which, of
course, locates it parallel with the main shaft in a horizontal plane.
To get it to the right height, enter the shaft coupling of the new
part into coupling of the main shaft, and then adjust until the
shaft shows level when tested with an accurate spirit level. A
level suitable for this work should be of iron and planed on the
under side with a V-groove, which will always locate it parallel
with the shaft when testing it. Before leveling the new part of
the shaft, it will be necessary to try the shaft already in position,
as it may not be level. If found " out " it should be leveled,
but sometimes this will not be possible or feasible, in which case
it will be necessary to set the new part at the same inclination.
To do this, test the main shaft and find how much it is out, and
adjust the level by strips of paper until it shows " fair." The
paper should be secured to the level by glue or other means and
used on the new shaft in that condition, always keeping the level
with the " packed" end pointing in the same direction. After
getting the new part in position, it is well to test it before con-
necting it to the main part ; that is, it should be turned by hand
to determine if the frictional resistance is excessive or not. After
connecting with the main part, it is not a bad idea to test it again
by hand, if possible. With a long shaft it may be necessary to
disconnect the farther sections and remove the belts from the
connected machines. In this way a fair idea of the frictional
resistance may be obtained. As before stated, this work requires
experience and skill, and should properly be done by one thor-
oughly competent for the work ; for, while his services may seem
a trifle expensive, it will usually be found to pay better in the
43
674 HANDBOOK ON ENGINEERING.
long run, as the frictional resistance of an improperly lined shaft
will quickly consume coal enough to pay the difference.
SIMPLICITY IN STEAM PIPING.
In building steam power plants, and especially in arranging
the piping connections for them, simplicity is a characteristic the
value of which is often too little appreciated. It should be borne
in mind that extra valves and duplicate piping mean a very
considerable amount of capital lying at waste to meet a contin-
gency, which may, in all probability, never arise, not to speak of
the care and attention required to keep piping and valves which
are rarely used in shape for service. Another point which ought
to be realized in the design of piping, is that every square foot of
uncovered surface, as in flanges and the like, causes the loss of
about one dollar per year in condensation of steam , and each square
foot of uncovered surface represents the loss of nearly one-quarter
of this amount. The principle of construction is to design the
piping with the utmost simplicity possible ; without any double
connections, put it up so that no accidents can happen to it. It
is argued that this is impossible, but it is equally impossible to
insure absolute immunity against " shut downs," of greater or
less duration, by any amount of duplex connections, for even
the blowing out of a single gasket can blow down a whole battery
of boilers before a 12 -inch valve can be closed and another
opened. With the more extensive introduction of high-pressure
valves and fittings, it is possible, by proper design, to reduce
the liability to accident very nearly to the point of absolute
safety, and by the introduction of one or two extra valves, it is
generally possible to divide the plant into sections, any one of
which can, if occasion demands, be operated independently. No
fixed rules can be laid down and the line between absolute sim-
plicity and necessary complexity must be drawn separately for
each plant with due regard to the work it has to perform , but it
HANDBOOK ON ENGINEERING.
675
should be remembered that the more simple a plant can be made
to accomplish the work with absolute reliability, the greater the
achievement in economy of first cost, and in availability and
economy of operation.
Fig. 312. Diagram showing screwed yalve and fittings.
St^^rW—itt) I &
T
Fig. 313. Diagram showing flanged valye and fittings.
CUTTING PIPE TO ORDER.
In placing orders for pipe, a diagram should be made, accord-
ing to above cuts. Great care should be taken in making a
diagram for large pipe ; all measurements should be from centers.
When flanged fittings are used, state if desired drilled, and if
with bolts and gaskets complete. If it is desired that the
67G
HANDBOOK ON ENGINEERING.
fittings be made tight, then mark such pieces at point joint is
desired, on diagram.
FEED=WATER REQUIRED BY SHALL ENGINES.
Pressure of Steam
in Boiler, by
Gauge.
Pounds of Water
per Effective
Horse -power per
Hour.
Pressure of Steam
in Boiler, by
Gauge.
Pounds ot Water
per Effective
Horse- power per
Hour.
10
118
60
75
15
111
70
71
20
105
80
68
25
100
90
65
30
93
100
63
40
84
120
61
50
79
160
58
HEATING FEED-WATER.
Feed-water, as ^ comes from the wells or hydrants j has ordi-
narily a temperature of from 35° in winter to from 60 to 70° in
summer. Much fuel can be saved by heating this water by the
exhaust steam, whose heat would otherwise be wasted. Until
quite recently, only non-condensing engines utilized feed -water
heaters but lately they have been introduced with success between
the cylinder and the air-pump in condensing engines. The
saving in fuel due to heating feed-water is given on page 680.
RATING BOILERS BY FEED-WATER.
The rating of boilers has, since the Centennial Exposition in
1876, been generally based on 30 pounds feed-water per hour per
horse-power. This is a fair average for good non-condensing engines
working under about 70 to 100 ponnds pressure. But different
HANDBOOK ON ENGINEERING.
677
pressures and different rates of expansion change the require-
ments for feed-water. The following table gives Prof. R. H.
Thurston's estimate of the steam consumption for the best classes
of engines in common use when of moderate size and in good
order : —
WEIGHTS OF FEED WATER AND OF STEAM.
NON-CONDENSING ENGINES. — R. H T.
Steam Pressure.
Lbs. per H. P. per Hour. — Ratio of Expansion.
Atmos-
phere.
Lbs. per
sq. ID.
2
3
4
£
7
10
3
45
40
39
40
40
42
45
4
60
35
34
36
36
38
40
5
75
30
28
27
26
30
32
6
90
28
27
26
25
27
29
7
105
26
25
24
23
25
27
8
120
25
24
23
22
22
21
10
150
24
23
22
21
20
20
CONDENSING ENGINES.
2
30
30
28
28
30
35
40
3
45
28
27
27
26
28
32
4
60
27
26
25
24
25
27
5
75
26
25
25
23
22
24
6
90
26
24
24
22
21
20
8
120
25
23
23
22
21
20
10
150
25
23
22
21
20
19
Small engines having greater proportional losses in friction, in
leaks, in radiation, etc., and besides receiving generally less care
678 HANDBOOK ON ENGINEERING.
in construction and running than larger ones, require more feed
water (or steam) per hour.
FEED WATER HEATERS.
Inattention to the temperature of feed water for boilers is en-
tirely too common, as the saving in fuel that may be effected by
thoroughly heating the feed water — by means of the exhaust
steam in a properly constructed heater — would be immense, as
may be seen from the following facts : A pound of feed water en-
tering a steam boiler at a temperature of 50° Fahr., and evapo-
rating into steam of 60 Ibs. pressure, requires as much heat as
would raise 1157 Ibs. of water 1 degree. A pound of feed water
raised from 50° Fahr. to 220° Fahr. requires 987 thermal units
of heat, which if absorbed from exhaust steam passing through a
heater, would be a saving of 15 per cent in fuel. Feed water at a
temperature of 200° Fahr., entering a boiler, as compared in point
of economy, with feed water at 50°, would effect a saving of over
13 per cent in fuel ; and with a well-constructed heater there ought
to be no trouble in raising the feed water to a temperature of 212°
Fahr. If we take the normal temperature of the feed water at 60°,
the temperature of the heated water at 212° and the boiler pressure
at 20 Ibs., the total heat imparted to the steam in one case is
1192.5° minus 60° = 1132. 5°; and in the other case, 1192.5°
minus 212° = 980.5°, the difference being 152°, or a saving of
152/1132.5 = 13.4 per cent. Supposing the feed water to enter
the boiler at a temperature of 32° Fahr., each pound of water will
require about 1200 units of heat to convert it into steam, so that
the boiler will evaporate between 6| and 7^ Ibs. of water per
pound of coal. The amount of heat required to convert a pound
of water into steam varies with the pressure, as will be seen by
the following table : —
HANDBOOK ON ENGINEERING.
679
TABLE SHOWING THE UNITS OF HEAT REQUIRED TO CONVERT ONE POUND
OF WATER, AT THE TEMPERATURE OF 32° FAHR., INTO STEAM AT
DIFFERENT PRESSURES.
Pressure of
Pressure of
Steam in Ibs. per
Units of Heat.
Steam in Ibs. per
Units of Heat.
Sq. In. by Gauge.
Sq. In. by Gauge.
1
1,148
110
,187 '
10
1,155
120
,189
20
1,161
130
,190
30
,165
140
,192
40
,169
150
,193
50
,173
160
,195
60
,176
170
,196
70
,178
180
,198
80
,181
190
,199
90
1,183
200
,200
100
1,185
If the feed water has any other temperature the heat necessary
to convert it into steam can easily be computed. Suppose, for
instance, that its temperature is 65°, and that it is to be converted
into steam having a pressure of 80 Ibs. per square inch. The
difference between 65 and 32 is 33; and subtracting this from
1181 (the number of units of heat required for feed water hav-
ing a temperature of 32°), the remainder, 1148, is the number of
units for feed water with the given temperature. Yet it must be
understood that any design of heater that offers such resistance
to the free escape of the exhaust steam as to neutralize the gain
that would otherwise be obtained from its use, ought to be
avoided, as the loss occasioned by back pressure on the exhaust,
in many instances, counteracts the advantages derived from the
heating of the feed water.
Feed water heaters are a most important feature of a good
steam plant. First, by utilizing the heat of the exhaust steam
680
HANDBOOK ON ENGINEERING.
from the engine or waste gases in chimney, the feed water may be
heated to about 210° Fahr., with ease, before entering boilers,
by this means saving fuel and increasing capacity of boiler.
Second. By heating the water, the boilers are protected from
serious and unequal strain, as the difference of temperature be-
tween incoming water and outgoing steam may be kept about 1 10°
(210° to 320°). Third. Every heater must necessarily be a
water purifier, as the mud and lime are eliminated, to some degree
at least, before the water reaches the boiler, by heat.
TABLE.
SHOWING GAIN BY USE OF FEED WATER HEATER. PERCENTAGE OF
HEAT REQUIRED TO HEAT WATER FOR DIFFERENT FEED AND BOILING
TEMPERATURES, AS COMPARED WITH A FEED AND BOILING TEM-
PERATURE OF 212°.
Boiling
•T) • A.
Initial Temperature of feed water.
IrOint.
Fahr.
32°
50°
68°
86°
104°
122°
140°
158°
176°
194°
212°
212
1.19
1.17
1.15
1.13
1.11
1.10
1.08
.06
1.04
1.02
1.00
230
1.20
1.18
1.16
1.14
1.12
1.10
1.08
.06
.04
1.02
1.01
248
1.20
1.18
1.16
1.14
1.13
1.11
1.09
.07
.05
1.03
1.01
266
1.21
1.19
1.17
1.15
1.13
1.11
1.09
.07
.06
1.04
1.02
284
1.21
1.20
1.18
1.16
1.14
1.12
1.10
.08
.06
.04
1.02
302
1.22
1.20
1.18
1.16
1.14
1.12
l.ll
1.09
.07
.05
.03
320
1.22
1.21
1.19
1.17
1.15
1.13
1.11
1.09
.07
.05
.03
338
1.23
1.21
1.19
1.17
1.15
1.14
1.12
1.10
.08
.06
.04
356
1.23
1.22
1.20
1.18
1.16
1.14
1.12
1.10
1.08
.06
.04
374
1.24
1.22
1.20
1.18
1.17
1.15
1.13
1.11
1.09
.07
.05
392
1.24
1.23
1.21
1.19
1.17
1.15
1.13
1.11
1.09
1.07
.06
410
1.25
1.23
1.22
1.20
1.18
1.16
1.14
1.12
1.10
1.08
.06
428
1.25
1.24
1.22
1.20
1.18
1.16
1.14
1.12
1.11
1.09
.07
There are two distinct types of heaters in which heat is derived
from exhaust steam. These are known as closed and open
heaters. Each has its advantages and disadvantages. The
closed heater is constructed so that the water is forced under pres-
HANDBOOK ON ENGINEERING. 081
sure through tubes or chambers surrounded by the exhaust steam,
the heat being transmitted through the walls of the tubes and cham-
bers. The open heater is a vessel in which the feed water comes
into direct contact with the exhaust steam, by spraying or inter-
mingling. The heated water is pumped hot into the boiler.
The closed heater has tbe advantage of permitting the water to
pass through the pump cold and in that state is easily handled.
To pump hot water from an open heater requires special care in
piping and packing the feed pump. The closed heater, being a
purifier (if any lime is present in water, a portion is bound to be
precipitated by heat), should be cleaned, a job about as difficult
as cleaning a boiler ; or blown out, which is never a satisfactory
method. In the precipitation of lime by heat, carbonic acid gas
is set free and chemists say that this gas in a nascent state (just
being born) attacks iron and brass. Whatever the cause, experi-
ence has demonstrated that ordinary wrought iron, steel and
brass, corrode under this action. The open heater, being usually
a large chamber, is accessible for cleaning out, and if made with
ordinary care will last a long time. A leak in it is not a serious
matter, while a leak in the closed heater means a waste of hot
water into the exhaust pipe. The open heater has, at times,
been the cause of serious mishaps. In it the steam and water
mix ; with any stoppage in exit of feed water, there is danger
of flooding the cylinder of the steam engine through exhaust
pipe, causing a wreck. The more modern forms of these heaters
and the experience obtained in their use have reduced this
difficulty to a minimum.
WATER.
Pure water at 62° F. weighs 62.355 pounds per cubic foot, or
8i Ibs. per U. S. gallon; 7.48 gallons equal 1 cu. ft. It takes
30 Ibs., or 3.6 gal. for each horse-power per hour. It would be
difficult to get at the total daily horse-power of steam used in the
682 HANDBOOK ON ENGINEERING.
U. S., but it reaches into the billions of gallons of feed water per
day. The importance of knowing what impurities exist in most
feed waters, how these act on a boiler and how they may be re-
moved is, therefore, patent to every intelligent engineer. We give
therefore, the thoughts of some prominent investigators on the
subject.
Prof* Thurston says : —
" Incrustation and sediment are deposited in boilers, the one
by the precipitation of mineral or other salts previously held in
solution in the feed water, the other by the deposition of mineral
insoluble matters, usually earths, carried into it in suspension or
mechanical admixture. Occasionably also, vegetable matter of a
glutinous nature is held in solution in the feed water, and, pre-
cipitated by heat or concentration, covers the heating surfaces
with a coating almost impermeable to heat, and hence, liable to
cause an overheating that may be very dangerous to the struc-
ture. A powdery mineral deposit sometimes met with is equally
dangerous, and for the same reason. THE ANIMAL AND VEGE-
TABLE OILS AND GREASES CARRIED OVER FROM THE CONDENSER OR
FEED WATER HEATER ARE ALSO VERY LIKELY TO CAUSE TROUBLE.
Only mineral oils should be permitted to be thus introduced, and
that in minimum quantity. Both the efficiency and safety of the
boiler are endangered by any of these deposits.
" The amount of the foreign matter brought into the steam
boiler is often enormously great. A boiler of 100 horse-power
uses, as an average, probably a ton and a half of water per
hour, or not far from 400 tons per month, steaming ten hours
per day ; and even with the water as pure as the Croton at
New York, receives 90 pounds of mineral matter, and from
many spring waters a ton, which must be either blown out or
deposited. These impurities are usually either calcium carbon-
ate or calcium sulphate, or a mixture ; the first is most com-
mon on land, the second at sea. Organic matters often
HANDBOOK ON ENGINEERING. 683
harden these mineral scales and make them more difficult of
removal.
"The only positive and certain remedy for incrustation and
sediment, once deposited, is periodical removal by mechanical
means at sufficiently frequent intervals to insure against injury by
too great accumulation. Between times, some good may be done
by special expedients suited to the individual case. No one
process and no one antidote will suffice for all cases.
" Where carbonate of lime exists, sal-ammoniac may be used
as a preventive of incrustation, a double decomposition occur-
ring resulting in the production of ammonia carbonate and
calcium chloride — both of which are soluble, and the first of
which is volatile. The bicarbonate may be in part precipitated
before use by heating to the boiling point, and thus breaking
up the salt and precipitating the insoluble carbonate. Solutions
of caustic lime and metallic zinc act in the same manner.
Waters containing tannic acid and the acid juices of oak,
sumach, logwood, hemlock, and other woods, are sometimes
employed, but are apt to injure the iron of the boiler, as may
acetic or other acid contained in the various saccharine matters
often introduced into the boiler to prevent scale, and which
also make the lime-sulphate scale more troublesome than when
clean. Organic matter should never be used.
c c The sulphate scale is sometimes attacked by. the carbonate of
soda, the products being a soluble sodium sulphate and a pulver-
ulent insoluble calcium carbonate, which settles to the bottom like
other sediments and is easily washed off the heating surfaces.
Barium chloride acts similarly, producing barium sulphate and
calcium chloride. All the alkalies are used at times to reduce
incrustations of calcium sulphate, as is pure crude petroleum, the
tannate of soda and other chemicals.
" The effect of incrustation and of deposits of various kinds, is
to enormously reduce the conducting power of heating surfaces ;
684 HANDBOOK ON ENGINEERING.
so much so, that the power, as well as the economic efficiency of
a boiler, may become very greatly reduced below that for which it
is rated, and the supply of steam furnished by it may become
wholly inadequate to the requirements of the case.
"It is estimated thaty1^ of an inch (0.16 cm.) thickness of
hard scale on the heating surface of a boiler will cause a waste
of nearly one-eighth of its efficiency, and the waste increases as the
square of its thickness. The boilers of steam vessels are
peculiarly liable to injury from this cause where using salt water,
and the introduction of the surface condenser has been thus
brought about as a remedy. Land boilers are subject to incrus-
tation by the carbonate and other salts of lime and by the deposit
of sand or mud mechanically suspended in the feed water.
THE TEMPERATURE AND PRESSURE OF SATURATED
STEAM.
The accompanying diagram and explanation, taken from the
technical publication, The Locomotive, will be found much more
convenient for reference than steam tables. The description says
that one of the most fundamental and best known facts in steam
engineering is that saturated steam has a certain definite tem-
perature for each and every definite pressure ; and in all books
on steam we find tables of corresponding temperatures and pres-
sures, by the use of which we are enabled to find out what
the temperature of the steam is when we know what the pres-
sure is, and vice versa. For accurate work these tables are all
right ; but when (as is usually the case) we do not need to
know either the temperature or the pressure with any very
great precision, a diagram which presents the facts directly to
the eye is much more convenient. Such a diagram is presented
herewith. On the left-hand side of each vertical line are
marked the pressures, and on the right-hand side of the same
lines are marked the corresponding temperatures. The pres-
50—-
u* -
— 235'
45
40—1
- — 235* - — -
35——2SO' 55— _
30
—275*
—270'
25 — 1
10
Us
HANDBOOK ON ENGINEERING.
100— |
'1*9 H
685
-230*
SO-
^-r260', 70-r
15— — 250 65—
60
^-210'
-220'
740—
— — ^ /25^
-J/5'
-— J/0*
115
110 —
705 —
700 —
/SO —
175—
7^5 —
— J45*
— J40*
155—
Us ~
— 380'
—37S*
-370*
3H, Comparative diagram showing the temperature and
pressure «f saturated steam.
686 HANDBOOK ON ENGINEERING.
sures are all gauge pressures, that is, they represent the direct
gauge reading or pressure above that of the atmosphere. The
temperatures are on the Fahrenheit scale. The diagram is based
upon Prof. Cecil H. Peabody's steam tables, it is therefore
assumed that the average atmospheric pressure is 14.70 pounds
per square inch.
A few examples will make the use of the diagram clear: (1)
What is the temperature of saturated steam when it's pressure,
above the atmosphere, is 75 pounds per square inch? Ans. We
find 75 pounds on the left-hand side of the second vertical line,
and looking on the other side of the line we see that the corre-
sponding temperature is just a fraction of a degree less than 320
degrees Fahr. (2) What is the temperature of saturated steam
when its pressure, above the atmosphere, is 197 Ibs. per square
inch? Ans. We find 197 Ibs. on the left-hand side of the last
vertical line. It is not marked in figures, but 195 is so marked,
and 197 is two divisions higher than 195. Looking opposite to
197 we see that the corresponding temperature is about half way
between 386 degrees and 387 degrees. Hence, we conclude that
the temperature of saturated steam at the given pressure is about
386^°. (3) When the temperature of saturated steam is 227°,
what is its pressure? Ans. We find 227° on the right-hand
side of the first line, two divisions above 225° ; and looking
opposite to it, we see that the gauge pressure corresponding to
this temperature is almost exactly five pounds. (4) When the
temperature of saturated steam is 363°, what is its pressure?
Ans. We find 363° on the right-hand side of the third vertical
line, three divisions above 360°, and looking on the other side of
the vertical line, we see that the corresponding gauge pressure is
about 144J Ibs. to the square inch.
SOMETHING FOR NOTHING.
In the first place, it should be remembered that in mechanics
the measure of work done is the foot pound, a term which defines
'
HANDBOOK ON ENGINEERING.
68?
itself. A foot pound of work is the amount of energy required to
lift one pound one foot high. A foot pound, therefore, is the
product of force and distance, force being simply a push or a
pull. A machine can be made to increase the acting force, as
is seen in the case of a crane, where the weight lifted is much
greater than the force applied at the handle by the operator. It
is also possible to increase the distance moved by some part of a
machine, but it must be done by applying a greater force as in
the case of a steam engine, where the distance moved by the belt
is greater than the space passed over by the piston, but the total
pressure of the steam against the piston is greater than the
effective pull exerted by the belt.
Melting Points of Metals and Solids.
Deg. Fahr.
Deg. Fahr.
Antimony
melts at
.... 951
Platinum melts at
.... 4680
Bismuth
cc
.... 476
Potassium
tt
.... 136
Brass
tt
.... 1900
Saltpeter
te
.... 600
Cadmium
"
.... 602
Steel
tt
. 2340 to 2520
Cast Iron
ft
. 1890 to 2160
Sulphur
(t
.... 225
Copper
ft
.... 1890
Silver
ft
.... 1250
Glass
tt
.... 2377
Tin
ft
.... 420
Gold
ft
.... 2250
Wrought Iron
. 2700 to 2880
Lead
ft
.... 594
Zinc
ft
.... 740
Ice
tt
.... 32
Aluminum
ft
.... 1260
In both the crane and the steam engine, however, the applied
force multiplied by the distance through which it moves in a given
time, must be enough greater than the product of the force at the
crane hook or the rim of the fly-wheel, and the distance through
688 HANDBOOK ON ENGINEERING.
which it moves to make up for the loss through friction in the
machine itself. The foot pounds of work done by any machine
whatever must always be less than the foot pounds put into the
machine in the same length of time. A study of this principle
and of the methods of applying it, is all that is necessary to
enable one to decide upon the soundness of the claims made for
any power multiplying device. A British Thermal Unit (B. T.
U.) is the amount of heat required to raise the temperature of a
pound of water 1° Fahr., and its dynamic value is 778 Ibs. raised
to a height of one foot.
CHIMNEYS.
Chimneys are required for two purposes: 1st, to carry off
obnoxious gases ; 2d, to produce a draft, and so facilitate com-
bustion. The first requires size, the second, height. Each pound
of coal burned yields from 13 to 30 pounds of gas, the volume of
which varies with the temperature. The weight of gas to be car-
ried off by a chimney, in a given time, depends on three things —
size of chimney, velocity of flow and density of gas. But as the
density decreases directly as the absolute temperature, while the
velocity increases with a given height, nearly as the square root
of the temperature, it follows that there is a temperature at which
the weight of gas delivered is a maximum. This is about 550°
above the surrounding air. Temperature, however, makes so
little difference that at 550° above the quantity is only 4 per cent
greater than at 300°. Therefore, height and area are the only
elements necessary to consider in an ordinary chimney. The in-
tensity of draft is, however, independent of the size, and depends
upon the difference in weight of the outside and inside columns of
air, which varies nearly as the product of the height into the
difference of temperature. This is usually stated in an equiva-
lent column of water, and may vary from 0 to possibly 2 inches.
After a height has been reached to produce draft of sufficient
HANDBOOK ON ENGINEERING.
689
Fig. 315. Section and deration cf steel stack.
HANDBOOK ON ENGINEERING.
intensity to burn fine, hard coal, provided the area of the chimney
is large enough, there seems no good mechanical reason for add-
ing further to the height, whatever the size of the chimney
required. Where cost is no consideration, there is no objection
to building as high as one pleases ; but for the purely utilitarian
purpose of steam making, equally good results might be attained
with a shorter chimney at much less cost. The intensity of draft
required varies with the kind and condition of the fuel and the
thickness of the fires. Wood requires the least, and fine coal or
slack the most. To burn anthracite slack to advantage, a draft
of 1J inch of water is necessary, which can be attained by a well-
proportioned chimney 175 feet high. Generally, a much less
height than 100 feet cannot be recommended for a boil!er, as the
lower grades of fuel cannot be burned as they should be with a
shorter chimney.
The proportioning of chimneys is very largely a matter of expe-
rience and judgment. Various rules have been formulated for
this purpose, but they all vary more or less. A chimney must
have sufficient cross- section to easily carry off the products of
combustion, and be high enough to produce sufficient draft for
complete and rapid combustion. Where there is a choice between
a high narrow stack and a lower wide one, the nature of the fuel
should decide the matter ; as a rule, the taller stack is preferable.
The amount of fuel to be burnt per square foot of grate per hour
has been increasing in modern practice; therefore, the old rules do
not fit the case any more. Then again, it makes a difference how
many boilers are to run into the same chimney. The heaviest
work of the chimney is immediately after firing, since the friction
through the fresh coal is greater and the temperature less then
than some minutes later. But it would be bad practice to fire all
boilers or all doors simultaneously. Hence, the second boiler
does not require as much area as the first ; say, 75 per cent will
do. After that there comes the additional consideration that as
HANDBOOK ON ENGINEERING,
rlM
691
Fig. 316. Section ami elevation of brick slack.
692
HANDBOOK ON ENGINEERING.
the diameter of the stack increases, the friction in stack and
breeching decreases rapidly. Therefore, for the third and each
succeeding boiler, 50 per cent of the first area will suffice. But
as more are added, the height should be increased, more espe-
cially if the horizontal flue from boiler to stack increases in length,
as it usually will. A good rule is to make the height 25 times
the diameter, with possibly a gradual decrease in the ratio to 20
times the diameter for the larger chimneys. Thus a 4-foot diame-
ter would call for 100 feet height, and a 5-foot, for 120 feet, a
6-foot for 140 feet, and a 10-foot for 200 feet height.
TABLE OF SIZES OF CHIMNEYS.
«l
ja
3
0>
i
Diameter and Nominal Horse Power.
20"
26"
30"
34"
36"
40"
44"
50"
54"
58"
60"
64"
72"
78"
70 ft.
80ft.
90ft.
100 ft.
110ft.
120 ft.
40
50
60
75
100
120
130
150
150
175
175
200
200
225
250
300
340
360
375
400
425
430
455
500
500
550
600
600
650
700
750
825
900
930
990
1050
.
I
IRON CHIMNEY STACKS.
In many places iron stacks are preferred to brick chimneys.
Iron chimneys are bolted down to the base so as to require no
stays. A good method of securing such bolts to the stack is
shown in detail in the figure on page 693. Iron stacks require to be
kept well painted to prevent rust, and generally, where not bolted
down, as here shown, they need to be braced by rods or wires to
surrounding objects. With four such braces attached to an
angle iron ring at f the height of stack, and spreading laterally at
HANDBOOK ON ENGINEERING.
693
least an equal distance, each brace should have an area in square
inches equal to y^1^ the exposed area of stack (dia. x height) in
feet. Stability or power to withstand the overturning force of
Fig. 817. Holding down bolts and lugs.
the highest winds, requires a proportionate relation between the
weight, height, breadth of base, and exposed area of the chimney.
This relation is expressed in the equation
dh*
ri __ TIT"
0 b T'
in which d equals the average breadth of the shaft ; k =. its
height ; b = the breadth of base — all in feet ; W = weight of
chimney in Ibs., and C = a coefficient of wind pressure per
694
HANDBOOK ON ENGINEERING.
square foot of area. This varies with the cross-section of tbe
chimney, and = 56 for a square, 35 for an octagon and 28 for a
round chimney. Thus a square chimney of average breadth of
8 feet, 10 feet wide at base and 100 feet high, would require to
weigh 56x8x100x10=448,000 Ibs., to withstand any gale
likely to be experienced. Brickwork weighs from 100 to 130
Ibs. per cubic foot; hence, such a chimney must average 13
inches thick to be safe. A round stack could weigh half as
much, or have less base.
WEIGHT OF SHEET LAP RIVETED STEEL SMOKE STACKS,
PER FOOTo
THICKNESS.
DIJL.
No.
18
No.
16
No.
14
NO.
12
No.
10
No.
8
A"
aV
i"
A"
A"
ii"
i"
H"
A"
W
V9
12"
8
10
13
17
21
254
314
37
42
47
524
58
63
68i
734
78}
84
14"
<-»i
114
15J
20
24*
29}
36}
42
484
544
62i
67
734
79i
85
91
97
16"
10*
13
174
23
28
34
42
49
56
63
70
77
84
91
98
105
112
18"
Hi
14i
26
31|
47
55
63
71
79
86
94
102
110
118
126
20"
13
16
22
2^}
35*
42*
52
60
69
78
86
95
104
113
121
131
138
22"
24"
14*
154
HI
19*
24J
264
3lf
34i
38|
42
51
54
59
63|
73
784
82
88
91
98
99
108
108
118
118
128
127
137
137
147
146
157
26"
16|
21
28}
37
454
63
734
84
94
105
115
126
137
147
158
168
28"
18
31
40
49
694
67
78
89*
100
111
122
134
145
156
167
179
80"
244
33
42}
52|
71
83
95"
1064
118
130
142
154
166
178
190
32"
35
45i
56
68
75
874
1004
113
125
138
150
163
175
188
201
34"
28
37
48;
594
72J
80
93
106
119
132
146
160
173
186
199
212
36"
39
51
63
76J
85
100
114
128
143
158
173
188
202
216
230
38"
3lf
41*
53|
664
90
105
120
135
151
166
182
198
213
227
242
40"
33|
43*
68
70
85
94
110
126
142
158
174
191
208
224
239
254
42"
35
45}
59J
734
89*
98
115
132
149
166
183
200
217
234
260
266
44"
36}
48
62
77
934
103
121
138
155
173
191
209
227
245
262
279
4«"
65
804
97}
107
126
144
162
181
199
218
237
255
273
291
48"
40
524
68
84
102
112
131
150
169
188
208
227
247
266
284
303
60"
52"
64"
54}
57
71
74
77
874
91
944
106J
1104
114}
116
121
124
136
142
147
156
162
168
176
182
189
195
203
211
216
224
233
236
245
254
258
266
276
277
287
298
296
307
319
315
328
349
68"
80
98*
119*
133
158
180
202
225
248
270
294
317
340
363
58"
83
102
123*
137
164
186
209
232
256
280
304
327
351
375
60"
86
106
127*
142
169
192
215
240
264
289
314
338
362
387
62"
89
110
131}
146
174
198
222
247
273
298
324
349
374
400
6i"
....
92
114
136
151
179
204
229
255
281
307
333
359
885
412
HANDBOOK ON ENGINEERING. 695
CHAPTER XXIV.
HORSE=POWER OF GEARS.
To determine the horse-power, which any gear-wheel will trans-
mit, four facts are required to be known : —
1st. The kind of wheel, whether spur, bevel, spur mortise, or
bevel mortise. 2d. The pitch. 3d. The face. 4th. The velocity
of pitch circle in feet per second.
Generally, the fourth fact is not known. It can be found if
the pitch diameter of the wheel in inches and the number of revo-
lutions per minute are given, for it can be obtained from them by
the following rule : —
Rule, — Given the pitch diameter in inches and the number of
revolutions per minute ; to find the velocity of pitch line in feet
per second.
First, multiply the pitch diameter (in inches) by the number
of revolutions per minute. Second, divide the product thus found
by 230. The quotient is the velocity required.
Example. — What is the velocity of the pitch circle of a
gear-wheel in feet per second, the pitch diameter = 43 inches,
the revolutions per minute =125?
43 x 125 divided by 230 = 23.4 feet per second.
Table A shows the greatest horse-power, which different kinds
of gears of 1-inch pitch and 1-inch face will safely transmit at
various pitch-line velocities. To find the greatest horse-power
which any other pitch and face will safely transmit, the following
rule can be used : —
Rule* — Given, the pitch (in inches), face (in inches), velocity
of pitch circle (in feet per second), and kind of gear ; to find the
greatest horse-power that can be safely transmitted.
First. Find the horse-power in Table A, which the given kind
696
HANDBOOK ON ENGINEERING.
of wheel with 1-inch pitch and 1-inch face will transmit at the
given velocity. Second. Multiply the pitch by the face. Third.
Multiply the horse-power found by the product of pitch by face.
The final product is the horse-power required.
Example. — What is the greatest horse-power that a bevel-
wheel, 43" pitch diameter, 2" pitch, 6" face, and 125 revolutions
per minute will safely transmit?
From previous example, we have found the pitch-line velocity
to be 23.4 feet per second, which is nearest to a velocity of 24
feet per second in Table A.
First, the horse-power which a bevel wheel of 1" pitch and 1'
face will transmit is (from table) at this velocity 4.931.
Second, the product of pitch by face is 2x6 = 12.
Third, 12x4.931 —59.17 horse-power. Answer.
Whenever it is desirable to know about the average horse-
power that any wheel will transmit, f or | of the results obtained
by the rule above should be taken.
TABLE A. — TABLE SHOWING THE HORSE-POWER WHICH DIFFERENT
KINDS OF GEAR WHEELS OF ONE INCH PITCH AND ONE INCH FACE
WILL TRANSMIT AT VARIOUS VELOCITIES OF PITCH CIRCLE.
1
2
3
4
5
Velocity of
pitch circle in
ft. per sec.
Spur Wheels.
Spur Mortise
Wheels.
Bevel Wheels.
Bevel
Mortise
Wheels.
2
1.338
.647
.938
.647
3
1.756
.971
1.227
.856
6
2.782
1.76
1.76
1 363
12
4.43
3.1
3.1
2.16
18
5.793
4.058
4.058
2.847
24
7.052
4.931
4.931
3.447
30
8.182
5.727
5.727
4.036
36
9.163
6.314
6.414
4.516
42
10.156
7.102
7.102
4963
48
10.683
7.680
7.680
5.411
HANDBOOK ON ENGINEERING.
697
NOTE. — When velocities are given, which are between those
in table, the horse-power can be found by interpolation.
Thus, the horse-power for spur wheels at 14 feet velocity is
found as follows : —
14 minus 12 = !
18 " 12 = (
5.793 minus 4.43= 1.363.
Then £ of 1.363 == .454 and .454 + 4.43 = 4. 884 horse-power.
TABLE B. — SHAFTING. — HORSE- POWER TRANSMITTED BY VARIOUS
SHAFTS, AT 100 REVOLUTIONS PER MINUTE UNDER VARIOUS CON-
DITIONS.
1
2
3
4
1
2
3
4
Shafts
Shafts
Diameter
of Shaft.
Line
Shafts.
Shaft as
. a Prime
Mover.
Under
Slight
Bending
Diameter
of Shaft.
Line
Shafts.
Shaft as
a Prime
Mover.
Under
Slight
Bending
Strain.
Strain.
1H'
.7
.4
1.3
*w
40.
20.
80
1.3
.7
2.6
3if"
49.
25.
97-
1-Jg.'
2.4
1.2
4.7
^tV
70.
35.
139.
jll'
3.8
1.9
7.6
4i|'
96.
48.
192.
itf
5.8
2.9
11.5
5-V
126.
64.
256.
2iV
8.3
4.2
16.6
45*
167.
84.
334.
2ft;
11.5
15.5
5.8
7.8
23.
31.
1
266.
399.
133.
200.
532.
797.
2^'
20.
10.
40.
8||;
570.
285.
1139.
8iV
26.
13.
51.
783.
.392.
•I 566.
3&"
33.
17.
65.
This table gives the horse-power that various sizes of shafts
will safely transmit at 100 revolutions per minute under various
conditions.
Prime movers are those shafts in which the variation above
and below the average horse-power transmitted is great, also
where the transverse strain due to belts or heavy pulleys is large,
such as jack-shafts, crank-shafts, etc.
698 HANDBOOK ON ENGINEERING.
WHEEL GEARING.
The pitch line of a wheel is the circle upon which the pitch
is measured, and it is the circumference by which the diameter,
or the velocity of the wheel, is measured. The pitch is the arc
of the circle of the pitch line, and is determined by the num-
ber of teeth in the wheel. The true pitch (chordal), or that
by which the dimensions of the tooth of a wheel are alone
determined, is a straight line drawn from the centers of two
contiguous teeth upon the pitch line. The line of centers is
the line between the centers of two wheels. The radius of a
wheel is the semi-diameter running to the periphery of a tooth.
The pitch radius is the semi-diameter running to the pitch line.
The length of a tooth is the distance from its base to its ex-
tremity. The breadth of a tooth is the length of the face of
wheel. The teeth of wheels should be as small and numerous
as is consistent with strength. When a pinion is driven by
a wheel, the number of teeth in the pinion should not be
less than eight. When a wheel is driven by a pinion, the
number of teeth in the pinion should not be less than ten.
The number of teeth in a wheel should always be prime to the
number of the pinion ; that is, the number of teeth in the
wheel should not be divisible by the number of teeth in the
pinion, without a remainder. This is in order to prevent the
same teeth coming together so often as to cause an irregular
wear of their faces. An odd tooth introduced into a wheel is
termed a hunting-tooth or cog.
TO COMPUTE THE PITCH OF A WHEEL.
Rule* — Divide the circumference at the pitch-line by the num-
ber of teeth.
Example. — Awheel 40 in. in diameter, requires 75 teeth;
what is its pitch ?
3.1416 x40=
HANDBOOK ON ENGINEERING. 699
TO COMPUTE THE CHORDAL PITCH.
— Divide 180° by tHe number of teeth, ascertain the sin.
of the quotient, and multiply it by the diameter of the wheel.
Example. — The number of teeth is 75 and the diameter 40
in. ; what is the true pitch ?
i^_ = 2° 24' and sin. of 2° 24' = .04188, which x 40 = 1.6752 in.
TO COMPUTE THE DIAMETER OF A WHEEL.
Rule* — Multiply the number of teeth by the pitch, and divide
the product by 3. 1416.
Example. — The number of teeth in awheel is 75, and the
pitch 1.675 in. ; what is the diameter of it?
75x1.675
3.1416
= 40 in.
TO COMPUTE THE NUMBER OF TEETH IN A WHEEL.
Rule* — Divide the circumference by the pitch.
TO COMPUTE THE DIAMETER WHEN THE TRUE PITCH IS GIVEN.
Rule* — Multiply the number of teeth in the wheel by the true
pitch, and again by .3184.
Example. — Take the elements of the preceding case.
75 x 1.6752 x .3184 == 40 in.
TO COMPUTE THE NUMBER OF TEETH IN A PINION OR FOLLOWER TO
HAVE A GIVEN VELOCITY.
Rule* — Multiply the velocity of the driver by its number of
teeth, and divide the product by the velocity of the driven.
Example. — The velocity of a driver is 16 revolutions, the
number of its teeth 54, and the velocity of the pinion is 48 ; what
is the number of its teeth ?
= 18 teeth.
48
700 HANDBOOK ON ENGINEERING.
2. A wheel having 75 teeth is making 16 revolutions per min-
ute. What is the number of teeth required in the pinion to make
24 revolutions in the same time?
16 x 75
24
= 50 teeth.
TO COMPUTE THE PROPORTIONAL RADIUS OF A WHEEL OR PINION.
Rule* — Multiply the length of the line of centers by the num-
ber of teeth in the wheel for the wheel, and in the pinion for the
pinion, and divide by the number of teeth in both the wheel and
the pinion.
TO COMPUTE THE DIAMETER OF A PINION, WHEN THE DIAMETER OF
THE WHEEL AND NUMBER OF TEETH IN THE WHEEL AND PINION
ARE GIVEN.
Rule* — Multiply the diameter of the wheel by the number of
teeth in the pinion, and divide the product by the number of teeth
in the wheel.
Example. — The diameter of a wheel is 25 in., the number of
its teeth 210, and the number of teeth in the pinion 30 ; what is
the diameter of the pinion ?
25x30
210
= 3.57 in.
TO COMPUTE THE CIRCUMFERENCE OF A WHEEL.
Rule* — Multiply the number of teeth by their pitch.
TO COMPUTE THE REVOLUTIONS OF A WHEEL OR PINION.
Rule* — Multiply the diameter or circumference of the wheel or
the number of its teeth, as the case may be, by the number of its
revolutions, and divide the product by the diameter, circumfer-
ence, or number of teeth in the pinion.
Example. — A pinion 10 in. in diameter is driven by a wheel
HANDBOOK ON ENGINEERING. . 701
2 ft. in diameter, making 46 revolutions per minute ; what is the
number of revolutions of the pinion ?
2 x 12 x 46
10
= 110.4 revolutions.
TO COMPUTE THE RELATIVE VELOCITY OF A PINION.
Rule* — Divide the diameter, circumference or number of teeth
in the driver, as the case may be. by the diameter, etc., of the
pinion.
WHEN THERE IS A SERIES OR TRAIN OF WHEELS AND PINIONS.
Rule* — Divide the continued product of the diameter, circum-
ference, or number of teeth in the wheels by the continued
product of the diameter, etc., of the pinions.
Example. — If a wheel of 32 teeth drive a pinion of 10, upon
the axis of which there is one of 30 teeth, driving a pinion of 8?
what are the revolutions of the last?
32 30 960
77, x — = -57- =12 revolutions.
1U o oU
Ex. 2. — The diameters of a train of wheels are 6, 9, 9, 10 and
12 in. ; of the pinions, 6, 6, 6, 6, and 6 in. ; and the number of
revolutions of the driving shaft or prime mover is 10 ; what are
the revolutions of the last pinion ?
6 x 9 x 9 x 10 x 12 x 10 583200
= ==_ 75 revolutions.
6x6x6x6x6 7776
TO COMPUTE THE PROPORTION THAT THE VELOCITIES OF THE WHEELS
IN A TRAIN WOULD BEAR TO ONE ANOTHER.
Rule* — Subtract the less velocity from the greater, and divide
the remainder by one less than the number of wheels in the train ;
the quotient is the number, rising in arithmetical progression from
the less to the greater velocity.
702 HANDBOOK ON ENGINEERING.
Example. — What should be the velocities of three wheels to
produce 18 revolutions, the driver making 3 ?
18 minus 3 = 15 _ K
— = 7.5 = number to be added to velocity of the
3 minus 1=2
iriver = 7.5 + 3 = 10.5 and 10.5 + 7.5 = 18 revolutions.
Hence, 3, 10.5 and 18 are the velocities of the three wheels.
GENERAL ILLUSTRATIONS.
1. A wheel 96 inches in diameter, making 42 revolutions per
minute, is to drive a shaft 75 revolutions per minute, what should
be the diameter of the pinion ?
96x42
=53.76 m.
75
2. If a pinion is to make 20 revolutions per minute, required
the diameter of another to make 58 revolutions in the same time.
58 divided by 20 = 2.9 = the ratio of their diameters. Hence
if one to make 20 revolutions is given a diameter of 30 in., the
other will be 30 divided by 2.9 = 10.345 in.
3. Required the diameter of a pinion to make 12 J revolutions
in the same time as one of 32 in. diameter making 26.
32x26 „ -„ .
66.56 in.
12.5
4. A shaft making 22 revolutions per minute, is to drive another
shaft at the rate of 15, the distance between the two shafts upon
the line of centers is 45 in. ; what should be the diameter of the
wheels ?
Then, 1st, 22 + 15 : 22 : : 45 : 26.75 = inches in the radius of
the pinion.
2d. 22 + 15 : 15 : : 45 : 18.24 = inches in the radius of the spur.
5. A driving shaft, making 16 revolutions per minute, is to
drive a shaft 81 revolutions per minute, the motion to be com-
municated by two geared wheels and two pulleys, with an inter-
mediate shaft ; the driving wheel is to contain 54 teeth, and the
HANDBOOK ON ENGINEERING. 703
driving pulley upon the driven shaft is to be 25 in. in diameter ;
required the number of teeth in the driven wheel, and the diameter
of the driven pulley. Let the driven wheel have a velocity of
V 16x81=36 a mean proportional between the extreme veloci-
ties 16 and 81.
Then, 1st, 36 : 16 : : 54 : 24 = teeth in the driven wheel.
2d. 81: 36:: 25: 11. 11= inches diameter of the driven pulley.
6. If , as in the preceding case, the whole number of revolutions
of the driving shaft, the number of teeth in its wheel and the
diameter of the pulley are given, what are the revolutions of the
shafts ?
Then, 1st, 18 : 16 : : 54 : 48 = revolutions of the intermediate
shaft.
2d. 15 : 48 : : 25 : 80 = revolutions of the driven shaft.
TO COMPUTE THE DIAMETER OF A WHEEL FOR A GIVEN PITCH AND
NUMBER OF TEETH.
Rale* — Multiply the diameter in the following table for the
number of teeth by the pitch, and the product will give the diam-
eter at the pitch circle.
Example. — What is the diameter of a wheel to contain 48
teeth of 2.5 in. pitch?
15.29x2.5 = 38.225 in.
TO COMPUTE THE PITCH OF A WHEEL FOR A GIVEN DIAMETER AND
NUMBER OF TEETH.
Rule* — Divide the diameter of the wheel by the diameter in
the table for the number of teeth, and the quotient will give the
pitch.
Example. — What is the pitch of a wheel when the diameter of
it is 50.94 in., and the number of its teeth 80?
50.94
. 9 ,„
25.47 -^ln-
704
HANDBOOK ON ENGINEERING.
PITCH OF WHEELS.
A TABLE WHEREBY TO COMPUTE THE DIAMETER OF A WHEEL FOR A
GIVEN PITCH, OR THE PITCH FOR A GIVEN DIAMETER.
From 8 to 192 teeth.
S
03
,c
|
j
03
^
£
a
g
«M 03
03
•nt;
03
<M 03
"03
** 03
03
s- 03
"S
•H
g
cs
0 0)
I
0 03
I
0 03
g
003
B
z;
5
5z
5
&
5
fc
S
&
5
8
2.61
45
14.33
82
26.11
119
37.88
156
49.66
9
2.93
46
14.65
83
26.43
120
38.2
167
49.98
10
3.24
47
14.97
84
26.74
121
38.52
158
50.3
11
3.55
48
15.29
85
27.06
122
38.84
159
50-61
12
3.86
49
16.61
86
27.38
123
39.16
160
50.93
13
4.18
50
15.93
87
27.7
124
39.47
161
51.25
14
4.49
51
16.24
88
28.02
125
39.79
162
51.57
15
4.81
52
16.66
89
28.33
126
40.11
163
51.89
16
5.12
53
16.88
90
28.65
127
40.43
164
52.21
17
5.44
54
17.2
91
28.97
128
40.75
165
52.52
18
5.76
55
17.52
92
29.29
129
41.07
166
52.84
19
6.07
56
17.8
93
29.61
130
41.38
167
53.16
20
6.39
57
18.15
94
29.93
131
41.7
168
53.48
21
6.71
58
18.47
95
30.24
132
42.02
169
53.8
22
7.03
59
18.79
9«
30.56
133
42.34
170
54.12
23
7.34
60
19.11
97
30.88
134
42.66
171
54.43
24
7.66
61
19.42
98
31.2
135
42.98
172
54.75
25
7.98
62
19.74
99
31.52
136
43.29
173
55.07
26
8.3
63
20.06
100
31.84
137
43.61
174
55.39
27
8.61
64
20.38
101
32.15
138
43.93
175
55.71
28
8.93
65
20.7
102
32.47
139
44.25
176
56.02
29
9.25
66
21.02
103
32.79
140
44.57
177
56.34
30
9.57
67
21.33
104
33.11
141
44.88
178
56.66
31
9.88
68
21.65
105
33.43
142
45.2
179
56.98
32
10.2
69
21.97
106
33.74
143
45.52
180
57.23
33
10.52
70
22.29
107
34.06
144
45.84
181
57.62
34
10.84
71
22.61
108
34.38
145
46.16
182
57.93
35
11.16
72
22.92
109
34.7
146
46.48
183
58.25
36
11.47
73
23.24
110
35.02
147
46.79
184
58.57
37
11.79
74
23.56
111
35.34
148
47.11
185
58.89
38
12.11
75
23.88
112
35.65
149
47.43
186
59.21
39
12.43
76
24.2
113
35.97
150
47.75
187
59.53
40
12.74
77
24.52
114
36.29
151
48.07
188
59.84
41
13.06
78
24.83
115
36.61
152
48.39
189
60.16
42
13.38
79
25.15
116
36.93
163
48.7
190
60.48
43
13.7
80
25.47
117
37.25
154
49.02
191
60.81
44
14.02
81
25.79
118
37.66
155
49.34
192
61.13
HANDBOOK ON ENGINEERING.
TO COMPUTE THE STRESS THAT MAY BE BORNE BY A TOOTH.
Rule* — Multiply the value' of the material of the tooth to re-
sist transverse strain, as estimated for this character of stress, by
the breadth and square of its depth, and divide the product by
the extreme length of it in the decimal of a foot.
TO COMPUTE THE NUMBER OF TEETH OF A WHEEL FOR A GIVEN
DIAMETER AND PITCH.
Rule* — Divide the diameter by the pitch, and opposite to the
quotient in the preceding table is given the number of teeth.
TEETH OF WHEELS.
Epicycloidal* — In order that the teeth of the wheels and pin-
ions should work evenly and without unnecessary rubbing fric-
tion, the face (from pitch line to top) of the outline should be
determined by an epicycloidal curve, and the flank (from pitch
line to base) by an hypocycloidal. When the generating circle is
equal to half the diameter of the pitch circle, the hypocycloid de-
scribed by it is a straight diametrical line, and consequently the
outline of a flank is a right line and radial to the center of the
wheel. If a like generating circle is used to describe face of a
tooth of other wheel or pinion respectively, the wheel and pinion
will operate evenly.
Involute* — Teeth of two wheels will work truly together when
surfaces of their face is an involute ; and that two such wheels
should work truly, the circles from which the involute lines for
each wheel are generated must be concentric with the wheels,
with diameters in the same ratio as those of the wheels.
Curves of teeth* — In the pattern shop, the curves of epicy-
cloidal or involute teeth are defined by rolling a template of the
generating circle on a template corresponding to the pitch line,
a scriber on the periphery of the template being used to define
45
70b
HANDBOOK ON ENGINEERING.
the curve. Least number of teeth that can be employed in pin-
ions having teeth of following classes, are: involute, 25;
epicycloidal, 12 ; staves or pins, 6.
CONSTRUCTION OF GEARING.
If the dimensions of two wheels are determined, as well as
the size of the teeth and spaces, the wheel is drawn as shown
in figure. The star ting-
point for the division of
the wheels is where the
two pitch circles meet
in A. It is advisable
to determine the exact
diameters of the wheels
by calculation, if the
difference between
them is remarkable ; for
any division upon two
circles of unequal size
by means of a divider, jolg. 313. involute gear teeth.
is incorrect, because the latter measures the chord instead of the
arc. From the point A we construct the epicycloid (7, by rolling
the circle A upon 5, as its base line. That short piece of the epi-
cycloid, from the pitch line to the face of the tooth, is the curva-
ture for that part of the tooth and the wheel B. This curvature
obtained for one side of the tooth, serves for both sides of it, and
also for all the teeth in the wheel. The lower part of the tooth,
or that inside the pitch -line, is immaterial to the working of the
wheel ; this may be a straight line, as shown by the dotted lines
which are in the direction of the diameters, or may be a curved
line, as is seen in the wheel A. This line must be so formed as
not to touch the upper or curved part of the tooth. The root of
\
HANDBOOK ON ENGINEERING.
707
the tooth, or that part of it which is connected with the rim of the
wheel, is the weakest part of the tooth, and may be strengthened
by filling the angles at the corners. The curvature for the teeth
in the wheel A is found in a similar manner to that of B. The
pitch circle A serves now as a base line, and the circle B is rolled
upon it, to obtain the circle D. This line forms the curvature for
the teeth of A, and serves for all the teeth in A — also for both
sides of the teeth. In most practical cases the curvature of the
teeth is described as a. part of a circle, drawn from the center of
the next tooth, or from a point more or less above or below that
center, or the radius greater or less in strength than the pitch of
the wheel. Such circles are never correct curves, and no rule can
be established by which their size and center meets the form of
the epicycloid.
BEVEL WHEELS.
If the lines C A and B C represent the prolonged axes, which
are to revolve with different or similar velocities, the position and
sizes of the wheels for
driving these axes are
determined by the dis-
tance of the wheels from
the point C. The diame-
ters of the. wheels are as
the angles a and b and
inversely as the number
of revolutions. These
angles are, therefore, to
be determined before the
319. Bevel gears. wheels can be drawn.
By measuring the distances from C to the line E, or from C to
F, the sizes of the wheels are determined. These lines E, F and
D F, are the diameters for the pitch lines ; from them the form
708
HANDBOOK ON ENGINEERING
of the tooth is described on the beveled face of the wheel. If
the form of the tooth is described on the largest circle of the
wheel, all the lines from this face run to the point (7, so that when
the wheel revolves around its axis, all the lines from the teeth
concentrate in the point (7, and form a perfect cone. Curvature,
thickness, length and spaces are here calculated as on face
wheels ; the thickness is measured in the middle of the width of
the wheel.
WORM-SCREW.
If a single screw A works in a toothed wheel, each revolution
of the screw will turn the wheel one cog ; if the screw is formed
of more than one thread, a corresponding number of teeth will be
moved by each revolution.
With the increase of the
number of threads, the side
motion of the wheel and
screw is accelerated ; and
when the threads and num-
ber of teeth are equal, an
angle of 45° is required for
teeth and thread, provided
their diameters also are
equal. This motion causes
a great deal of friction and ™.
Fig. 320. Worm and worm wheel.
it is only resorted to where no other means can be employed to
produce the required motion. In small machinery, the worm is
frequently made use of to produce a uniform, uninterrupted
motion ; the screw, in such cases, is made of hardened steel and
the teeth of the wheel are cut by the screw which is to work in
the wheel. If the form of the teeth in the wheel is not curved
and its face is concave so as to fit the thread in all points, the
screw will touch the teeth but in one point and cause them to be
liable to breakage.
HANDBOOK ON ENGINEERING. 709
PROPORTIONS OF TEETH OF WHEELS.
Tooth*— -In computing the dimensions of a tooth, it is to be
considered as a beam fixed at one end, the weight suspended
from the other, or face of the beam ; and it is essential to con-
sider the element of velocity, as its stress in operation, at high
velocity with irregular action, is increased thereby. The dimen-
sions of a tooth should be much greater than is necessary to resist
the direct stress upon it, as but one tooth is proportioned to bear
the whole stress upon the wheel, although two or more are
actually in contact at all times ; but this requirement is in
consequence of the great wear to which a tooth is subjected?
the shocks it is liable to from lost motion when so worn as to
reduce its depth and uniformity of bearing, and the risk of the
breaking of a tooth from a defect. A tooth running at a low
velocity may be materially reduced in its dimensions compared
with one running at high velocity and with a like stress. The
result of operations with toothed wheels, for a long period of
time, has determined that a tooth with a pitch of 3 inches and a
breadth 7.5 inches will transmit, at a velocity of 6.66 feet per
second, the power of 59.16 horses.
TO COMPUTE THE DEPTH OF A CAST-IRON TOOTH.
1. When the stress is given.
Rule* — Extract the square root of the stress, and multiply it
by .02.
Example. — The stress to be borne by a tooth is 4886 Ibs. ;
what should be its depth?
1/4886 x .02 = Io4 in.
2. When the horse-power is given.
Rule* — Extract the square-root of the quotient of the horse-
power divided by the velocity in feet per second, and multiply it
by .466.
710 HANDBOOK ON ENGINEERING.
Example. — The horse-power to be transmitted by a tooth is
60, and the velocity of it at its pitch-line is 6.66 feet per second ;
what should be the depth of the tooth ?
60 x .466 = 1.398 in.
6.66
TO COMPUTE THE HORSE -POWER OF A TOOTH.
Rule* — Multiply the pressure at the pitch-line by its velocity
in feet per minute, and divide the product by 33,000.
CALCULATING SPEED WHEN TIME IS NOT TAKEN INTO ACCOUNT.
Rule* — Divide the greater diameter, or number of teeth,
by the lesser diameter or number of teeth, and the quotient is
the number of revolutions the lesser will make, for one of the
greater.
Example. — How many revolutions will a pinion of 20 teeth
make, for 1 of a wheel with 125 ?
125 divided by 20 =±= 6.25 or 6J revolutions.
To find the number of revolutions of the last to one of the first,
in a train of wheels and pinions : —
Rule* — Divide the product of all the teeth in the driving by
the product of all the teeth in the driven ; and the quotient equals
the ratio of velocity required.
Example 1. — Required the ratio of velocity of the last, to 1
of the first, in the following train of wheels and pinions, viz. :
pinions driving — the first of which contains 10 teeth, the second
15, and third 18. Wheels driven, first teeth 15, second 25,
10x15x18
and third 32. ^ — ^ — ^-0 — .225 of a revolution the wheel
10 X ^0 X O&
will make to one of the pinion.
Example 2. — A wheel of 42 teeth giving motion to 1 of 12,
on which shaft is a pulley of 21 inches diameter, driving 1 of 6 ;
HANDBOOK ON ENGINEERING. 711
required the number of revolutions of the last pulley to 1 of the
42x21
first wheel, j^ g— 12.25 or 12J revolutions.
NOTE. — Where increase or decrease of velocity is required to
be communicated by wheel- work, it has been demonstrated that
the number of teeth on each pinion should not be less than 1 to
6 of its wheel, unless there be some other important reason for a
higher ratio.
WHEN TIME MUST BE REGARDED.
Rule* — Multiply the diameter or number of teeth in the driver
by its velocity in any given time, and divide the product by the
required velocity of the driven ; the quotient equals the number
of teeth or diameter of the driven, to produce the velocity
required.
Example 1. — If a wheel containing 84 teeth makes 20 revolu-
tions per minute, how many must another contain, to work in
contact, and make 60 revolutions in the same timer
80 x 20 divided by 60 =27 teeth.
Example 2. — From a shaft making 45 revolutions per minute
and with a pinion 9 inches diameter at the pitch-line, we wish
to transmit motion at 15 revolutions per minute ; what, at the
pitch-line, must be the diameter of the wheel?
45 x 9 divided by 15 = 27 inches.
Example 3. — Required the diameter of a pulley to make 16
revolutions in the same time as one of 24 inches making 36.
24x36 divided by 16 == 54 inches.
The distance between the centers, and the velocities of two wheels
being given, to find their proper diameters : —
Rule* — Divide the greatest velocity by the least ; the quo-
tient is the ratio of diameter the wheels must bear to each other.
Hence, divide the distance between the centers by the ratio -|- 1 ;
the quotient equals the radius of Lhe smellier wheel ; and subtract
712 HANDBOOK ON ENGINEERING.
the radius thus obtained from the distance between the centers ;
the remainder equals the radius of the other.
Example. — The distance of two shafts from center to center
is 50 in. and the velocity of the one 25 revolutions per minute,
the other is to make 80 at the same time ; the proper diameters
of the wheels at the pitch line are required.
80 divided by 25=3.2, ratio of velocity, and 50 divided by
3.2+ 1 = 11.9, the radius of the smaller wheel ; then 50 minus
11.9 =38.1, radius of larger ; their diameters are 11.9x2 = 23.8
and 38.1x2 = 76.2 in.
To obtain or diminish an accumulated velocity by means of
wheels and pinions, or wheels, pinions and pulleys, it is necessary
that a proportional ratio of velocity should exist, and which is
thus attained ; multiply the given and required velocities together ;
and the square root of the product is the mean or proportionate
velocity.
Example. — Let the given velocity of a wheel containing 54
teeth equal 16 revolutions per minute, and the given diameter of
an intermediate pulley equal 25 in., to obtain a velocity of 81
revolutions in a machine ; required the number of teeth in the
intermediate wheel and diameter of the last pulley.
->/ 81x16 = 36 mean velocity ; 54 x 16 divided by 36 = 24
teeth, and 25x36 divided by 81 = 11.1 in., diameter of pulley.
TABLE OF THE WEIGHT OF A SQUARE FOOT OF SHEET IRON IN
POUNDS AVOIRDUPOIS.
No. 1 is T5^ of an inch ; No. 4, J ; No. 11, -|, etc.
No. on wire gauge, 1 2 3 4 5 6 7 8 9 10 11 12
Poundsavoir., 12.512 11 10 9 8 7.5 7 6 5.68 5 4.62
No. on wire gauge, 13 14 15 16 17 18 19 20 21 22
Poundsavoir., 4.31 4 3.95 3 2.5 2.18 1.93 1.62 1.5 1.37
HANDBOOK ON ENGINEERING. 713
SCREW-CUTTING .
In a lathe properly adapted, 'screws to any degree of pitch, or
number of threads in a given length, may be cut by means of a
leading screw of any given pitch, accompanied with change wheels
and pinions ; coarse pitches being effected generally by means of
one wheel and one pinion with a carrier, or intermediate wheel,
which cause no variation or change of motion to take place ; hence,
the following : —
Rule* — Divide the number of threads in a given length of the
screw which is to be cut, by the number of threads in the same
length of the leading screw attached to the lathe, and the quotient
is the ratio that the wheel on the end of the screw must bear to
that on the end of the lathe spindle.
Example. — Let it be required to cut a screw with 5 threads
in an inch, the leading screw being of J inch pitch, or containing
2 threads in an inch ; what must be the ratio of wheels applied ?
5 divided by 2 = 2.5, the ratio they must bear to each other.
Then suppose a pinion of 40 teeth be fixed upon for the spindle ;
40 x 2.5 = 100 teeth for the wheel on the end of the screw.
But screws of a greater degree of fineness than about 8 threads
in an inch are more conveniently cut by an additional wheel and
pinion, because of the proper degree of velocity being more
effectively attained, and these, on account of revolving upon a
stud, are commonly designated the stud- wheels, or stud-wheel
and pinion ; but the mode of calculation and ratio of screw are the
same as in the preceding rule. Hence, all that is further neces-
sary is to fix upon any three wheels at pleasure, as those for the
spindle and stud-wheels ; then multiply the number of teeth in
the spindle-wheel by the ratio of the screw and by the number of
teeth in that wheel or pinion, which is in contact with the wheel
on the end of the screw ; divide the product by the stud-wheel in
contact with the spindle-wheel, and the quotient is the number of
teeth required in the wheel on the end of the leading screw.
714
HANDBOOK ON ENGINEERING.
Example. — Suppose a screw is required to be cut containing
25 threads in an inch, and the leading screw, as before, having
two threads in an inch, and that a wheel of 60 teeth is fixed upon
for the end of the spindle, 20 for the pinion in contact with the
screw-wheel, and 100 for that in contact with the wheel on the
end of the spindle ; required the number of teeth in the wheel for
the end of the leading screw.
25 divided by 2 = 12.5, and 6°X^Q5^20 = 150 teeth.
Or suppose the spindle and screw wheels to be those fixed upon,
also any one of the stud-wheels, to find the number of teeth in the
other.
150x100 60x12.5x20
= 20 teeth, or - ^^ - — 100 teeth.
60x12.5
150
Transmission of Power by Manilla Rope,
power Transmitted.
Horse-
Feet per minute ....
1000
1500
2000
2500
3000
3500
4000
4500
5000
Diameter of Rope . |
(( U I
" • " ! a
" " . 14
" " . u
<c « . .2
11
31
6*
74
10
13
21
*i
74
11
15
194
34
64
10*
15
20
26
44
8
13
18
25
33
54
10
15
22
30
39
64
11
18
26
35
46
7
13
20
30
40
52
8
15
23
34
45
59
9
16
26
37
50
65
Inches Expressed in Decimals of a Foot.
1
k
1
1
2
3
4
5
.0208
.0417
.0626
.0833
.1667
.2500
.3333
.4167
6
7
8
9
10
11
12
.5000
.5833
.6667
.7610
.8333
.9167
1.000
HANDBOOK ON ENGINEERING.
TABLE OF TRANSMISSION OF POWER BY
WIRE ROPES.
This table is based upon scientific calculations, careful observations
and experience, and can be relied upon when the distance exceeds 100
feet. It is also found by experience that it is best to run the wire rope
transmission at the medium number of revolutions indicated in the table,
as it makes the best and smoothest running transmission. If more
power is needed than is indicated at 80 to 100 revolutions, choose a
larger diameter of sheave.
1
Diameter of
Sheave in ft.
Number of
Revolutions.
Diameter of
Rope.
Horse -
Power.
Diameter of
Sheave in ft.
Number of
Revolutions.
Diameter of
Rope.
Horse -
Power.
3
80
|
3
7
140
A
35
3
100
|
4
8
80
1
26
3
120
1
4
8
100
1
32
3
140
4£
8
120
1
39
4
80
1
4
8
140
1
45
4
100
1
5
9
80
{At
\ 47
i 48
4
120
I
6
9
100
{At
1 58
/ 60
4
140
I
7
9
120
{At
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716 HANDBOOK ON ENGINEERING.
CHAPTER XXV.
ELECTRIC ELEVATORS.
In factories, warehouses and business buildings, freight, and in
some instances passenger elevators, are operated by machines
that are arranged to be driven by a belt. Such machines are
variously called belted elevators, factory elevators and sometimes
warehouse elevators.
In factories where there is a line of shafting kept running
continuously, they are driven from it. As a rule the elevator
machine is driven from a countershaft which latter is belted to
the line shaft. Very often the elevator machine is driven
directly from the line shaft. As the line shaft runs always in the
same direction, the only way in which the elevator machine can
be made to run in both directions is by the use of two belts, one
open and the other crossed, or some form of gearing that will
accomplish the same result. The common practice is to use
double belts. Either one of these belts can be made to drive by
using friction clutches, or by having tight and loose pulleys, and
a belt shifter. The latter arrangement is the most common.
In buildings where there is no line of shafting, power for oper-
ating the elevator machine must be derived from some kind of
motor installed expressly for the purpose. Nowadays electric
motors are very extensively used for this purpose, and the com-
bination of an elevator machine and an electric motor to drive it is
very generally called an electric elevator, although in reality it is not
such, but simply a belted elevator machine driven by an electric
motor. It has become so common, however, to call such com-
binations electric elevators, that true electric elevators are generally
designated as " direct connected electric elevators."
HANDBOOK ON ENGINEERING. 711
The first impression would be that in the combination of a
belted elevator machine, and an electric motor to drive it, as the
motor simply furnishes the power to set the machine in motion,
there can be nothing about the combination that requires any
special elucidation. Such a conclusion, however, would not be
correct, for there are several ways in which the combination can
be arranged, and in what follows we propose to explain these
several combinations, pointing out the important features of
each.
The simplest way in which a motor can be installed to drive
an elevator, is to arrange it so as to drive the counter shaft con-
tinuously, in which case the elevator is stopped and started by
throwing the belts on the tight or the loose pulley. Although
this is a very simple arrangement, it is not desirable unless the
elevator is kept in service all the time. In buildings where the
elevator is used only at intervals, a great amount of power is
wasted if the shafting is kept running all the time ; hence it is
desirable to arrange the motor so that it can be stopped when the
elevator is stopped, and started whenever the elevator is to be
used.
If the motor is arranged so as to run all the time, it is provided
with a simple motor-starting switch, the same as is used for any
motor installed to operate machinery of any kind. If the motor
is started and stopped whenever the elevator is started and stopped,
it is necessary to provide a motor-starter that can be operated
from the elevator car. A very common way of arranging a motor
to start and stop with the elevator is illustrated in the diagram
Fig. 321.
In this diagram the elevator car is shown at (7, with the lifting
ropes running over the sheave F at the top of the elevator
shaft, and then down and around the drum A of the elevator
machine. This drum is driven by means of screw gearing, as a
rule, with driving pulleys on the screw shaft as shown at B. The
718
HANDBOOK ON ENGINEERING.
driving motor is shown at Jf, and the counter-shaft to which it is
belted is at D. In this arrangement the elevator machine is pro-
vided with a tight center pulley and loose pulleys on the two sides.
The belts are shown on the loose pulley s? one being open and the
Fig* 321. Belt driven electric elevator.
other being crossed „ The countershaft carries a drum wide
enough to allow for the side movement of the belts when one or
the other is shifted upon the tight center pulley by the belt shifter
$. To operate the elevator car, a hand rope is provided which
HANDBOOK ON ENGINEERING. 719
runs up the elevator shaft at one side of the car from bottom to
top of building. This rope is shown in the diagram at J, and
runs around two small sheaves a a. The lower one of these sheaves
is provided with a crank pin, which moves the connecting rod 6,
and thus rocks the lever r, and thereby moves the belt shifter s.
To cause the car to ascend the hand rope I is pulled down, and
to make the car descend, the hand rope is pulled up. As will be
seen from this explanation, the lower sheave a will rotate in one
direction when the hand rope is pulled to make the car go up, and
in the opposite direction when the rope is pulled to make the car
run down. In the diagram, sheave a is shown in the stop posi-
tion, therefore when the hand rope is pulled down so as to make
the car run up, the sheave will turn in a direction opposite to the
movement of the hands of a clock, and thus the belt shifter will
be moved to the right, and the open belt will be run onto the tight
center pulley. If the hand rope is pulled up sheave a will rotate
in the direction of the hands of a clock, and the belt shifter will
move toward the left and thus shift the crossed belt onto the tight
pulley. The rope p is a stop rope and is connected with the two
sides of the hand rope in the manner shown, so that when the car
is running in either direction, if p is pulled hard it will bring I to
the position shown in the diagram, and thus stop the car. This
rope can be dispensed with, but the objection is that in pulling
the hand rope I to stop the car it may be pulled too far and then
the car will not only be stopped but it will be caused to run in
the opposite direction.
The motor starting switch'is shown at E, the line wires being
connected with the two top binding posts. The lever c c is in one
piece and is independent of lever e, but both swing around the
same pivot. At m, a dash pot is provided which acts to prevent
the too rapid movement of lever e. As will be noticed, lever c
has a projection which holds lever e up. The operation of this
motor starter is as follows : When the hand rope I is pulled in
720 HANDBOOK ON ENGINEERING.
either direction, the rope h draws lever c towards the left and
causes it to make contact with the switch jaw./. In this way the
current from the upper binding post which is connected with j
through wire g, passes to lever e, and thus to the starting resist-
ance, which is indicated by the dotted lines t, to binding post ft,
from where it goes to the motor armature through wire d, and re-
turns through the other wire d to the upper binding post at the
right side, which is connected with the opposite side of the main
line, thus completing the circuit. The field current branches off
from the upper end of the starting resistance i and reaches the
field coils through wire /, and through the lower wire / reaches
the return armature wire d and thus the opposite side of the cir-
cuit. When the rope h pulls lever c over toward the left, the lever
e does not follow it, as it is held up by the dash pot m. The
weight on the end of e gradually overcomes the resistance of the
dash pot, and thus causes lever e to move downward slowly. The
velocity at which e moves downward is graduated by adjusting
the opening in the dash pot through which the oil flows.
From the foregoing it will be seen that the starter E is made so
as to accomplish automatically just what a man accomplishes
when he moves the lever of an ordinary motor-starter ; that is, it
first closes the circuit through the motor, by bringing lever c into
contact withj; and then allows lever e to move slowly so as
to cut the resistance i out of the armature circuit gradually.
When the elevator is stopped, by pulling the hand rope I to the
stop position, the rope h slacks up and then the weight on the end
of lever c causes it to descend, and thus return lever e to the posi-
tion shown in the diagram, and also to break the circuit between
c and j.
The elevator machine A is provided with a brake, which is
actuated by the belt shifter s, so that when the belts are shifted
upon the side pulleys, as shown in the diagram, the brake is put
on, and thus the machine is stopped. As soon as the belt shifter
HANDBOOK ON ENGINEERING. 721
is moved to set the car in motion the brake is raised, so as to
allow the machine to run free.
This arrangement is used very extensively, although the motor-
starting switch is not always made in strict accordance with the
one shown at E. In fact, there are a great many different designs
on the market, but they all accomplish the same result, although
the means employed may be very different.
Although it is very advantageous to have the motor arranged
as in Fig. 321, so that it may be stopped and started together with
the elevator, there is one objection to it which is sometimes re-
garded as serious, and that is, that as it requires a great amount
of power to start an elevator from a state of rest, the motor will
take a very strong current in the act of starting. To get around
this objection, it is a common practice to provide a separate rope
for starting the motor, and then when it is desired to use the ele-
vator, the motor rope is pulled first, and in half a minute or so,
the main hand rope is pulled. In this way the motor gets a start
ahead of the elevator., and the headway of the motor armature
helps to set the elevator car in motion, so that the current taken
by the motor to start the elevator is very much reduced.
When a separate rope is used to start the motor in advance of
the elevator, the starter E, or the levers connecting with it, are
made so that while the motor can be started independently of the
elevator car, when the main hand rope is pulled, to stop the car,
it also stops the motor. If this arrangement were not provided,
the operator might stop the elevator and forget to stop the motor,
in which case the latter would keep on running and waste power.
The main hand rope I is provided with stops at top and
bottom of the elevator shaft, so that the car may be stopped auto-
matically should the operator forget to pull the hand rope at the
proper time.
It is the universal practice with elevator machines of the type
shown in Fig. 321 to counterbalance the elevator car, but we have
not shown a counterbalance in this diagram as it would only serve
722
HANDBOOK ON ENGINEERING.
to complicate its appearance, and it is not necessary to show it as
the electrical features will be the same whether there is a counter-
balance or not. This diagram also shows a separate rope h for
actuating the starter E, but in actual machines E is generally
CONTROLLER
ELEVATOR
MOTOR
Fig. 322. Connections of gravity motor controller.
rig. ozz. ^oniieciioiis 01 gruviij iiioior coin uiivr.
operated from the lower sheave a, which also actuates the belt
shifter.
Fig. 322 is a diagram tnat shows the way in which one of the
various motor starters in actual use is connected with the motor
HANDBOOK ON ENGINEERING,
723
and the operating hand rope. In this illustration A is the lower
sheave a of Fig. 321, and ^represents the hoisting drum and E the
driving pulleys of the elevator machine, G being the lifting ropes
from which the car is suspended. The sheave A is rotated
MOTOR.
Fig. 328. Gravity controller with rope attachment,
through one quarter of a turn in either direction by the pull on
the hand rope J5, and when so rotated shifts the belt shifter and
also lifts the brake from the brake-wheel. At the same time the
crank pin C pulls up the connecting rod, and thus the upper end
724 HANDBOOK ON ENGINEERING.
of rod c, which takes the place of lever c in Fig. 321. In this
way the switch blades in the lower end of c are raised into con-
tact with the clips jf/, which take the place of contact Jin Fig. 321,
and thus the circuit is closed. A projection s on c holds the
switch e in the upper position, but when c is raised, s goes up with
it, and then e is free to descend by the force of gravity acting
upon the weight w. The dash pot m is set so as to retard the
movement of e as much as may be desired. The outer end of e
glides over the contacts i in its downward movement, and thus
cuts out of the armature circuit the starting resistance. This
resistance is contained in the controller box.
Fig, 323 shows the same type of controller as in Fig. 322, but it
is arranged so that the motor may be started ahead of the elevator.
The separate motor-starting rope is shown at H. When this rope
is pulled, it elongates the spiral spring K which is connected with
the stud 6r fixed in the upper end of rod c. The rope H is pulled
up enough to stretch K until the lever Z>is lifted, H being attached
to its outer end I. When D is lifted sufficiently, its inner end dis-
engages the stud G, and allows it to slide upward in the slot
shown in dotted lines, in the lower end of the connecting rod.
In this way the motor is started ahead of the elevator machine.
If now the elevator machine is started, by pulling on the main
hand rope FF, the crank pin C' on the hand rope sheave will lift
the connecting rod (7, and when it reaches its upper position, the
catch-lever D will drop into the position shown in the illustration,
and thus lock the stud Gr, so that when the elevator is stopped,
the rotation of the hand rope sheave will push rod G downward
and thus stop the motor, as well as shift the belts and stop the
elevator machine.
In the three illustrations shown the motor is run always in the
same direction and the reversing of the direction of rotation of
the hoisting drum is effected by the use of double belts and a
belt shifter, or friction clutches, which cause one or the other of
HANDBOOK ON ENGINEERING. 725
the belts to do the driving. The way in which machines of this
726 HANDBOOK ON ENGINEERING.
This figure shows the position of the motor, the countershaft
and the elevator machine with reference to the elevator shaft.
This illustration is so clear that an explanation of it would be
superfluous.
In relation to the installation of elevator plants of this type
all that need be said is that the motor must be of the shunt
type, the same as those used for driving machines of any kind.
A series wound motor, such as are used for electric railway
cars, must not be used. Shunt wound motors cannot run above a
certain speed, unless forced to do so by power applied from an
external source, and in such an event they become generators of
electricity and thus resist rotation. On this account, when they
are used for elevator service, they not only move the elevator car,
but when the latter is descending under the influence of a heavy load
and tends to run away, the motor, at once begins to act as a gen-
erator, and is thus converted into a brake, which holds the car and
prevents it from attaining a speed much above the normal ; in
fact, the difference between the car velocity when lifting a heavy
load, and when running down under the influence of a similar load
is hardly enough to be noticed by any one not familiar with the
elevator.
The motor in these combinations is to be given the same care
as those used for other purposes ; that is, it must be kept clean
and the brushes properly set so as to run with as little spark as
is possible. The controller switch requires more attention than the
motor starters used with stationary motors, for the simple reason
that it is used to a much greater extent. Every time the elevator
is started or stopped the controller switch is actuated, hence, the
switch levers are subjected to a considerable amount of wear, and
the contacts are liable to become rough, either by cutting or by
being burned on account of making imperfect contact. On this
account the contact must be well examined at least once every
day, and if burned or rough must be smoothed up. It is also
HANDBOOK ON ENGINEERING.
727
necessary to see that all parts of the controller are properly se-
cured, that none of the screws or pins are working out, and that
the contacts and switch levers are not out of their normal posi-
tion.
Fig. 325. Wiring used with reversible motor.
As electric motors can be run as well in one direction as the
other, and as all that is required to make any motor reversible is
to provide a reversing switch, it can be seen at once that by mak-
ing use of such a switch, the direction of movement of the ele«
728 HANDBOOK ON ENGINEERING.
vator car can be reversed by simply reversing the motor, and thus
do away with the complication of a countershaft and tight and
loose pulleys. Owing to this fact elevator machines are now
made so as to be used with reversing motors. These are usually
called single-belt machines. The way in which such machines
are connected with the motor and the type of controller required
can be understoood from the diagram Fig. 325.
As will be seen, the principal difference in the machine itself
is that the tight and loose pulleys are replaced by a single tight
pulley, which is only wide enough to carry the driving belt.
Usually an extra pulley is provided for the brake, and this brake
is mechanically operated in the same manner as upon machines
provided with shifting belts. Another modification, which is
sometimes used, but is not shown in the diagram, is the arrange-
ment of a brake so that same is operated by a magnet
instead of by mechanical means. With this arrangement the
magnet is arranged so that when the machine is in motion, the
current passing through the magnet coil acts to lift the brake,
and when the machine stops, the magnet lets go, and the brake
goes on. By arranging the brake in this way it becomes perfectly
safe ; for if the brake magnet fails to act, the brake will not be
raised, and the machine will not move ; that is, failure of the
device to work properly will not permit the elevator car to move,
thus calling attention to the fact that something is out of order.
The operation of the reversing controller is as follows : the
current from the line wires passes along the dotted connections
h h to the contacts 1,1, i,i. The upper left hand i contact is con-
nected with the lower right hand one, and the upper right hand
with the lower left hand. The switch lever c is connected with
lever e by means of the two springs r r, so that c may be moved
either up or down without carrying e with it. The curved con-
tact o is connected with,/, while g is connected with the ends of the start-
ing resistance n n by means of the wire / and the two wires s s. The
HANDBOOK ON ENGINEERING. 729
contacts y y are connected to k and the lower left-hand contact i is con-
nected to x. If the hand rope I is pulled so as to carry lever c upward,
the current from the left side line wire will pass through the upper left
side contact i, to o, thence to j and through wire b to the motor arma-
ture, returning through the other b wire to gr, then via / and lower s to
the lower end of n, over the lever e, to the inner end of lever c which will
be in contact with the upper right-hand i contact and finally to the right
side line wire. The current for the field magnet coils will be drawn from
the upper left side i contact to the adjacent y contact, thence to con-
tact k, through the fields and back to x, finally to the left side line wire.
As lever c has been moved upward, the upper spring r will be
compressed, and the lower one will be stretched, hence a force
will be exerted to move e downward over the lower contacts n and
thus cut out the starting resistance. As in the case of the con-
troller in Fig. 321 the dash pot m by its resistance retards the move-
ments of e, so as to cut out the resistance as gradually as may be
desired.
In the chapter on stationary motors it is shown that to prevent
destructive sparking, when the starting switch is opened, the
armature and field coils are connected so as to form a permanently
closed loop. This style of connection is used in the non-revers-
ing controller of Fig. 321, but it cannot be employed with a re vers-
ing controller, because both ends of the armature circuit must be
free, so that they may be reversed when the direction of rotation
is reversed. As this connection cannot be made, a very common
expedient resorted to to prevent serious sparking when the switch
is opened is to connect a string of incandescent lamps across the
terminals of the field circuit, as is indicated at v v v. These
lamps, together with the field coils, form a closed, circuit, so that
when the switch is opened, the field can discharge through the
lamps, and thus avoid sparking at the controller contacts. The
only objection to this arangement is that all the current that
passes through the lamps is wasted, but by placing two or three
730 HANDBOOK ON ENGINEERING.
in series the loss is reduced to an insignificant amount. Another
way in which the sparking is subdued, but only to a slight ex-
tent, is by connecting the brake magnet coil with the binding
posts x and fc, which is the simplest and most generally used con-
nection. The brake magnet coil together with the field coils form
a closed loop when connected with x and ft, but when the main cir-
cuit is opened, the currents flowing in the two coils meet each other
at x and ~k flowing in opposite directions, hence they both follow
along the main circuit and try to jump across the gaps at the
switch, and thus produce about as much sparking as if they were
connected independently of each other. In tracing out the path
of the current when lever c is moved upward, it was shown that the
left side line went directly to the upper commutator brush. Now
when c is moved downward, this same line wire runs to the lower
commutator brush since the connections between the two upper
i contacts and the two lower ones are crossed. To reverse the
direction of rotation of a motor all that is required is to reverse
the direction of the current through the armature, that through
the field remaining unchanged, hence it will be seen that by cross-
ing the connections between the upper and lower i contacts, the
direction of rotation of the motor is reversed when the c lever is
moved in opposite directions.
DIRECT CONNECTED ELECTRIC ELEVATORS.
The machines explained in the foregoing pages are simply
combinations of an electric motor and a belt driven electric ma-
chine, but, as already stated, they are commonly spoken of as
44 electric elevators." In what follows it is proposed to explain
the construction and operation of true electric elevators, which
are called 44 direct connected machines " to distinguish them from
the combinations so far described.
There are many designs of direct connected electric elevators
HANDBOOK ON ENGINEERING.
731
now upon the market, and it would be out of the question to un-
dertake to describe all of them in the space that can be devoted
to the subject in this book. On that account the discussion will
be confined to the designs that are most extensively used. The
explanations here given, however, will be sufficient to enable any
Fig. 326. The Otis direct connected elevator.
one to understand the operation of any of the machines not de-
scribed because the difference in the principle of operation is
only slight.
732 HANDBOOK ON ENGINEERING.
Perhaps the type of direct connected electric elevator that
is most extensively used is the Otis drum elevator with hand
rope control which is illustrated in Fig. 326. This machine has
been upon the market for twelve years or more, and is still one of
the standard Otis machines. It is called a hand rope control
machine because the starting and stopping is controlled by the
movement of a hand rope that passes through the elevator car.
In the illustration, the sheave around which the hand rope passes
can be seen located on the front end of the drum shaft. In a
modification of the design, this sheave is mounted upon a sep-
erate shaft but the way in which it acts is the same as in the pres-
ent design. When the hand rope is pulled the sheave is
rotated and the horizontal bar, running from it to the
controller box, which is mounted on top of the motor?
shifts the starting switch so as to run the machine in
the direction desired. At the same time, the vertical lever ex-
tending upward from the side of the brake wheel, lifts the brake
and thus frees the motor shaft so that it may revolve unobstructed.
The motor carries a worm on the end of the armature shaft which
gears into the under side of a worm wheel mounted upon the
drum shaft. This worm wheel runs in a casing seen just back of
the hand rope sheave wheel. The sheave mounted upon the shaft
directly above the drum is for the purpose of guiding the coun-
terbalance ropes, which run up from the back of the drum. In
some buildings these ropes can be run up straight from the back
of the drum, but in most cases they must run up in the elevator
shaft in the space between the car and the side of the shaft. As
these ropes wind upon the drum from one side to the other, the
guiding sheave must move endwise on the shaft, hence it is called
a traveling, or vibrating sheave. The levers seen projecting to
the right of the machine from a small shaft just above the drum
are what is called a slack cable stop, and their office is to stop
the machine if the lifting cable becomes slack through the wedg-
HANDBOOK ON ENGINEERING. 733
ing of the car in the elevator, shaft or any other cause. These
levers are held in the position shown when the lifting ropes are
tight, but drop out of position if the rope slackens up, and in
dropping they release a lever, which holds the weight seen under
the hand rope sheave. The movement of this lever operates a
catch that engages with the hand rope sheave and thus the hori-
zontal bar that operates the brake and the controller switch is
brought to the stop position and the rotation of the hoisting drum
is stopped.
The hand rope has fastened to it at the top and bottom of the
elevator shaft stops that are moved by the car when it reaches
either end of its travel, and thus the elevator machine is stopped
automatically. This arrangement is the same as that used with
the belt driven machines already described, but as an additional
safety, a stop motion is provided on the machine itself, so that if
the stops on the hand rope become displaced, the car will still be
stopped automatically at the top and bottom landings. This stop
motion is seen on the end of the shaft, just in front of the hand
rope sheave, and consists of a nut that travels on the shaft as the
latter revolves. At both sides of the screw there are projection
cases upon the inclosing frame, which are struck by the traveling
nut when it comes near enough to either end. When the nut
strikes the projection, the hand rope sheave is revolved with the
shaft and thus the machine is stopped. To understand this ac-
tion it must be remembered that the hand rope sheave does not
revolve except when turned by the pull on the hand rope or by
the action of the slack cable stop or the traveling nut.
The controller box on top of the motor contains the starting
resistance, the starting and reversing switch, and also a magnet
to actuate a switch that gradually cuts out the starting resistance.
The way in which the switches act to start and stop the motor
can be readily explained by the aid of the diagram Fig. 327.
This shows the circuit connections in the simplest possible
734
HANDBOOK ON ENGINEERING.
form. In this diagram all the wires whose presence would make
t
SArETY MAGNET FOR
BRAKE ON MA CHINE
SHUNT FILLD
Fig. 327. Diagram of controller box and wiring.
the drawing confusing have been removed, but the manner in
HANDBOOK ON ENGINEERING. 735
which they are connected will be readily understood from the
following explanation : —
The main switch, which connects the motor circuits with the
line, is located at the upper left hand corner of the diagram, the
main line wires being marked-}- and — . When this switch is
closed, the motor circuits are connected with the line, but the
motor circuit itself is not closed so long as the switch M remains
in the position shown. When this switch is turned about one
quarter of a revolution in either direction, one end will ride over
the upper contact and the other one over the lower contact.
The reversing drum and switch M are mounted on the same
spindle and move together. They are located within the con-
troller box, on top of the motor, and are moved by the horizontal
bar ; see Fig. 326. The shaded portions of the drum, on which the
brushes h and i rest are made of insulating material so that when
switch M and the reversing drum are in the position shown the
motor circuit is open at two points. This is the position of these
parts when the machine is stopped.
The starting resistance is shown above the reversing drum,
and in the machine it occupies the space at the back of the con-
troller box, shown on top of the motor in Fig. 326. The segment
R is a series of contacts that are connected with the resist-
ance in the resistance box; No. 2 contact being con-
nected with point 2 on the resistance and so on for all the other
numbers. The switch arm JVis moved over the contacts R by a
magnet that is represented by the spiral L. The motor arma-
ture and the shunt and series field coils are shown at the bottom
of the diagram. The motor is compound wound, it being made
so for the purpose of keeping the starting current as low as possi-
ble. The path of the current through the wires is as follows : Sup-
pose the reversing drum andtheJtf switch are revolved in the direc-
tion in which the hands of a clock move, then brushes # and i will
rest on one segment, and h and Jc will rest on the other segment.
736 HANDBOOK ON ENGINEERING.
As switch M will now be closed, the current will flow to brush
g and through the reversing drum segment to brush i; then it
will follow the wire to the right side / of the armature and pass-
ing through the latter will reach wire E and thus brush h, from
which it will pass to brush Jc. From this brush the current will
go to and through magnet L and by wire C ' and switch N will
reach contact No. 10. As this contact is connected with point
10 of the resistance the current will reach the latter and will pass
through the whole of it, coming out at the opposite end C. This
end is connected with contact (7, so that from this segment the
current can flow through wire 0 to the end F of the series field
coils, and passing through these to end H, will find its way to
wire /, and thus return to the opposite side of the main line.
From this explanation it will be seen that the current will pass
through the motor armature, and then through the whole of the
resistance in the resistance box, and then through the series field
coils, and finally reach the other side of the main line. From
the switch M another current will branch off and run to binding
post .D, and thence through the shunt field coil . to binding post
.fiT and thus to wire/, and through the latter to the opposite of
the main line.
The switch lever N is in some cases arranged so that the mag-
net L acts to hold it upon contact 10 and a spring acts to carry
it forward toward contact^.; in other cases the magnet is wound
with two coils, one of which pulls N in one direction and the
other pulls it in the opposite direction, the two coils being so pro-
portioned that N moves gradually from contact 10 toward con-
tact A. If we take the spring arrangement, then magnet L will
pull N back toward contact 10, and the spring will pull it forward.
As the starting current is very strong, ^Twill be held on contact
10, but as the current weakens, the spring will begin to overpower
the magnet, and N will slide over contact 9 and then 8 and 7 and
so on to contact A. As contact 9 is connected with the point 9
HANDBOOK ON ENGINEERING. 737
of the resistance, when JV reaches it, the section of the resistance
between points 10 and 9 will be cut out. When N reaches con-
tact 7 the resistance between points 10 and 7 will be cut out for
the latter point is connected with contact 7. As all the contacts
are connected with the corresponding points of the resistance,
when N reaches contact (7, all the resistance in the resistance box
will be cut out of the circuit. As will be noticed, contact B is
connected with the center point G of the series field coil so that
when N reaches contact B one-half of the series coils will be cut
out in addition to the whole of the resistance box. When N
reaches contact^ the current will pass directly to wire/, and thus
cut out all the series field coils and then the motor will run as a
plain shunt-wound machine, and its speed will be the highest it
can attain.
If the reversing drum and switch M are now revolved to the
position shown in the diagram, the circuit through the motor will
be broken and the machine will come to a state of rest. If the
reversing drum and M are now revolved in the opposite direction,
that is, contrary to the movement of the hands of a clock, the
brushes g and h will rest on one of the revolving drum segments,
and i and k on the other segment. If the path of the current is
now traced it will be found that it will enter the armature through
wire E, and the left side, instead of through wire 7, as in the pre-
vious case. It will also be found, however, that 'the current after
passing through the armature will reach the series field coils
through Fj which is the same path as before, so that the direction
of the current has been reversed through the armature only,
which is what is required to reverse the direction of rotation of
the motor. Whichever way the switch M and the reversing drum
are turned, the direction of the currents through the series field
coils and the shunt field coil will be the same, and only the arma-
ture current will be reversed.
Cutting out the series field coils not only increases the speed
47
738 HANDBOOK ON ENGINEERING.
of the motor, but obviates the danger of the car attaining a dan-
gerously high speed if the load is being lowered. A shunt wound
motor will run as a motor up to a certain speed, but if the veloc-
ity is forced above this point by driving the machine by the ap-
plication of external power, then the motor will begin to act as a
generator, and as it takes power to run a generator the motor will
begin to hold back. Now if an elevator car is running down
with a heavy load, the load will draw the car down, and unless a
resistance of some kind is interposed, the speed will become
preater and greater as the car descends, and by the time it
reaches the bottom of the shaft it may be running at a velocity
almost equal to that attained by a free fall. The power required
to drive the motor when acting as a generator serves to hold the
car back, for the current developed increases very rapidly with
increase of speed, so that an increase of speed of ten or fifteen
per cent above the normal running velocity will be about as much
as can be reached even with an extra heavy load.
Although the motor will act as a generator and hold the car so
that it cannot attain a dangerous speed when descending under
the influence of a heavy load, it will only accomplish this result
when the circuit is closed ; for if the circuit is open there will be
no power generated ; hence, no power will be absorbed by the
motor. As can be readily seen, it is possible for the circuit out-
side of the motor to become broken by the melting of a fuse or
some other cause, and if this occurs when the car is coming down
with a heavy load there might be a serious accident. To obviate
such mishaps the main switch is made with a magnet &, which
holds the switch closed so long as current passes through it, but
allows the switch to swing open if the line current disappears.
This switch on this account is called a potential switch, because
it is arranged to be actuated by the difference of potential be-
tween the two sides of the line. When the line current fails, and
the potential switch opens, the blade m comes into contact with w
HANDBOOK ON ENGINEERING. 739
and thus the circuit for the motor armature is closed through the
resistance wire s, which is connected with contact 7. This con-
nection short circuits the armature through a resistance sufficient
to keep it from being burned out, but not enough to prevent the
motor from acting as a brake and holding the car down to a safe
speed.
The wire c c, which runs from magnet b of the potental switch
it will be noticed, connects with a coil marked safety brake mag-
net. This magnet acts normally to hold the brake off when the
machine is running, but if the current passing through it dies out,
then it acts to put the brake on. Now, as has already been ex-
plained, when the current is flowing in the main line, there is a
current passing through coil b of the potential switch ; hence,
there is a current passing through the coil of the safety magnet for
the brake ; but if the line current fails the current through the
brake magnet will also fail and the brake will go on ; so that the
car will be doubly protected, one protection being the short cir-
cuiting of the motor circuit through wire s, and the other the ap-
plying of the brake by reason of the failure of the current to flow
through the safety brake magnet.
As to directions for the proper care of these machines, very
little need be said, as they are simple and substantial in con-
struction and give very little trouble. The motor proper requires
the same attention as is given to any stationary -motor, that is,
the commutator and all other parts must be kept as clean as pos-
sible and the brushes must be properly set. As to the other
parts, all that need be said is that the bearings must be well lubri-
cated and free from grit. They must be tight enough to not al-
low the parts to play, but at the same time care must be taken
that they are not so tight as to heat up or cut. All bolts and
nuts must be regularly examined and kept tight, so that they
may not work loose or out of place. The most important point
to observe, however, is not to undertake under any circumstances
740 HANDBOOK ON ENGINEERING.
to tinker with the sheave wheel and the gears that connect it with
the horizontal bar that operates the brake and controller
switches. Neither must the brake or the switches be disturbed.
All that is to be done to the latter is to keep the contacts bright
and clean. If any of these parts, from the sheave wheel to the
controller switches, get out of set, so that the machine will not
run satisfactorily, do not undertake to readjust them, but send
for an expert from the elevator company. If any of these parts
are removed or shifted there is danger of their not being put
back in their proper position, and if they are misplaced a very
serious accident may be the result. If the proper adjustment of
these parts is destroyed, the elevator will not stop automatically
at the top and bottom landings, but will run too far at one end
and stop short of the mark at the other ; hence, the car may
either strike violently against the floor or ran at full speed into
the overhead beams, and in either case the results might be very
serious. Even elevator experts have to go cautiously in adjust-
ing the position of the sheave wheel and the parts connected
with it.
The fact that those not thoroughly posted in the operation of
these elevators should not tamper with the hand rope sheave and
its connections, is not at all unfortunate, for it is next to impos-
sible for them to get out of place ; but special caution is advised
at this point, because there are many men who are apt to take it
for granted that if the machine runs poorly from some trifling
cause that they have not been able to locate, the trouble must be
due to some defect in the adjustment of the several parts of the
operating sheave and its connections. They will then proceed to
pull the machine apart, and when they put it together again they
are very liable to get it connected wrong, and if such should be
the case the first trip made by the elevator might end seriously.
Although the machine described in the foregoing works in an
entirely satisfactory manner, it has been superseded almost en-
HANDBOOK ON ENGINEERING.
741
tirely in first-class installations of recent date by machines that
are controlled by means of a small switch in the car instead of
the hand rope. There are several types of such elevators made
by the Otis company, one of the latest designs being shown in
Fig. 328.
w
Fig. 328. Latest design of direct connected machine.
As will be noticed at once, this machine is different in several
respects from" the hand rope control machine shown in Fig. 326 . As
the machine is controlled by the movement of a switch in the car,
the brake cannot very well be actuated mechanically, hence a
magnetic brake is provided, the magnet being seen at the top of
-the stand to the right of the motor. The automatic stopping de-
vices and the slack cable stop are also arranged so as to act upon
742
HANDBOOK ON ENGINEERING.
switches, which are contained within the casings seen at the front
end of the hoisting drum. The controller for this type of
machine is not placed on top of the motor, generally, for since it
CAff
Fig. 329. Diagram of wiring connections for controller.
is not connected mechanically with any of the moving parts of the
machine, it can be located at any convenient point, and is then
connected with the motor armature, field coils and with the brake
HANDBOOK ON ENGINEERING. 743
magnet and automatic stop switches by means of copper wires.
The controller used with this type of machine is arranged after
the fashion of a switchboard, the switches being located on the
front, and the connecting wires, together with the starting resist-
ance, being at the back. The switches are actuated by means of
electromagnets, and on that account the device is called a magnet
controller. The diagram of the wiring connections with this con-
troller is more complicated than that for the hand rope controller,
but for the purpose of simplifying the drawing as much as pos-
sible we have removed all the connections that are not actually
necessary for a proper understanding of the general arrangement
of the circuits. This simplified diagram is shown in Fig. 329.
The front of the controller is shown in Fig. 330, and the back
of same in Fig. 331, the starting resistance being removed in this
illustration so as to afford a clear view of the wire connections.
The side of the starting resistance can be seen in Fig. 330. In
this last named illustration, all the switches are in the position
they take when the elevator is stopped. The two large switches
on either side at the bottom of the board are the starting switches,
one acting to run the car up and the other one to run it down.
The two smaller switches occupying the center of the bottom
panel of the board and the two switches in the upper corner are
for the purpose of accelerating the velocity of the motor when it
is started. When the motor starts, there is a resistance in the
armature circuit, and the current after passing through the arma-
ture is passed through series field coils. After the motor has
started, the starting resistance is cut out, and then the series field
coils are cut out, so that when the full speed is attained, the
motor is a simple shunt- wound machine. In this respect the
arrangement of the motor circuits is the same as in the hand rope
controller machine.
When it is desired to start the car, a small switch in the latter
is moved toward the right or left, according to the direction in
744
HANDBOOK ON ENGINEERING.
which the car is to move. To run the car up, the car switch is
turned to the left, and this movement sends a current through the
magnet of the lower right side magnet on the controller board.
Fig. 330. Showing front of controller.
This magnet then lifts its plunger and the two discs mounted upon
the latter come into contact with the stationary connectors located
just above them, and then the current can find its way through
HANDBOOK ON ENGINEERING „
745
the motor circuits in the proper direction to produce the upward
motion. The four small switch magnets on the controller board
are connected in separate circuits that are in parallel with each
Fig. 881. Back ot controller.
other, and in shunt relation to the armature of the motor. When
the motor first starts, the counter electromotive force developed
by the armature is not as great as when it is running at full speed,
746 HANDBOOK ON ENGINEERING,,
HANDBOOK ON ENGINEERING. 74?
ping the motor, if the car reaches either end of its travel without
being stopped by the operator, or the action of the stop motion
switch. This switch is closed under ordinary conditions, so that
the current in wire C can flow all the way to the lower contact a
of the car switch. If it is desired to run the car down, the car
switch is turned to the right, and then wire G is connected with
wires D ' and FD. The stop motion switch is normally in the
position shown so that the current in wire D ' can pass to D0 and
following this wire it will reach contact DO which is under the
lower disc of the right side starting switch. Through the disc
this contact is connected with the corresponding contact on the
other side of the disc, and this latter contact is connected with a
wire that carries the current to the magnet of the left side starting
switch. Considering now the main current in the + line it can
be seen that it can flow down to the line near the bottom of the
controller portion of the diagram, and which terminated in the
-f- contacts of both the starting switches, but can go no further
so long as the discs on the plungers of the magnets are in the
lower position. As soon, however, as the current coming from
the car switch passes through the magnet of the left side switch,
as just explained, the plunger will be lifted, and then the disc will
connect the + contact with the S2 contact, and also with a
smaller contact B. When this connection is made, the main cur-
rent can flow from contact S2 to contact 82 of the right side
switch, and thence through the connecting disc to contact I which
is connected by wire to binding post I; the latter being con-
nected with the right side armature terminal I. After passing
through the armature the main current reaches binding post E
and through the connecting wire the contact E at the top of the
left side starting switch, and as the plunger of this switch is in
the raised position, the current can pass to contact R and thus
reach the upper end R of the starting resistance in the resistance
box.
748 HANDBOOK ON ENGINEERING.
HANDBOOK ON ENGINEERING. 749
Thus it will be seen that the four switches, 1,2, 3 and 4, will
act one after the other. This same operation is repeated if the
car switch is moved to the right, so as to run the elevator down,
the only difference being that the starting switch at the right side
of the board will be lifted, but the action of the four smaller
switches will be the same.
In addition to the operating circuits described in the foregoing
there are wires that connect the slack cable switch with the motor
circuits and other connections by means of which the elevator may
be run from the controller board whenever desired. These con-
nections are not shown in Fig. 329, as they would complicate the
drawing, and it is not thought advisable to complicate the explan-
ation of the main part of the system for the sake of introducing
the minor details.
This type of electric control is used for elevator machines in-
stalled in office buildings , and others placed where the car is oper-
ated by a regular attendant. For private house elevators and for
dumb waiters it is necessary to modify the controlling system so
that the car may be operated not only from within, but also from
any of the floors of the building. It is further necessary that
the circuit connections be such that if the car is operated from
any floor, it will run to that floor, whether above or below it, and
further, so that if it is being operated by a person within the car
it cannot be operated by any one else from any of the landings.
It must also be arranged so that if the car is set in motion from
any floor it cannot be stopped or interfered with in any way by
a person at another floor. For the purpose of safety the system
must also be arranged so that the car cannot move away from any
floor until the landing door is closed. This feature is necessary
to guard against people falling through the open doorway into the
elevator shaft. Although it would appear difficult to accomplish
all these results without resorting to great complications, as a
matter of fact the system used by the Otis company is decidedly
750
HANDBOOK ON ENGINEERING.
HANDBOOK ON ENGINEERING. 751
simple. At each floor of the building a push button is placed,
and by pressing this for an instant the car is set in motion wher-
ever it may be, providing it is not being used by some other per-
son, and when it reaches the floor from which it has been operated
it will stop automatically. If the elevator is operated from the
car, a button is pushed that corresponds to the floor at which it
is desired to stop, the car will then begin to move, and when the
floor is reached it will stop. If the passenger after stepping out
of the car forgets to close the landing door, the elevator cannot
be moved away from the landing by the manipulation of any of
the push buttons on the various floors or within the car. The
way in which all these results are accomplished can be made
clear by the aid of Fig. 332, which is a simplified diagram of the
wiring.
In this diagram most of the parts are marked with their full
name. The floor controller is a drum, which is revolved by the
elevator machine, and its office is to shift the connections of the
wires 11, 22, 33, 44, from one side of the circuit DU to the
other as the car ascends and descends in the elevator shaft. This
shifting of these connections is necessary to cause the car to run
down if above the landing from which it is operated, and to run
up if it is below the landing. The actual position of the floor con-
troller with reference to the elevator machine can be seen in Fig.
333 in which the floor controller is located back of the motor and is
driven from the drum shaft by means of a chain and sprocket wheel.
In the diagram Fig. 332 it will be noticed that the drum surface is
divided into two segments and upon one rests the brush of wire
D while upon the other rests the brush of wire U. The twelve
contacts shown at G form the operating switch. The center row
marked m n o p are movable, and the four contacts above them
as well as the four below are stationary. The center row of con-
tacts m n o p are moved upward by a magnet represented by the
coil D and they are moved downward by another magnet repre-
752 HANDBOOK ON ENGINEERING.
sented by the coil V. From this it will be seen that if a current
comes from the floor controller through wire D the movable con-
tacts of G will be lifted and will connect with the top row, while
if the current comes from the floor controller through wire (7, the
movable contacts will be depressed and will make connections with
the lower row of contacts.
The main switch that connects the motor circuits with the
main line is shown at S. As will be noticed, a wire marked d + H
runs from the + wire to the right side of the diagram, where the
landing and the car push buttons and their connections are shown.
This wire runs from top to bottom of the elevator shaft and is con-
nected with switches that are closed when the landing doors are
closed, and open when the doors are open. These switches are
indicated by the four circles marked door contacts, the diagram
being for a building four stories high. If the door contacts are
closed, the current can pass as far as the wire marked -f- which
runs through the flexible cable to the car. In the car there is a
switch in this wire and further on a gate contact, which is closed
when the car door is closed. If these switches are closed, the
current can return from the car through wire A and run as far as
the center of the diagram under the main switch S. The floor
controller is shown in the position corresponding to the car at the
bottom of the shaft. Suppose now that the landing push button
I is pressed for a second, then the wires B and I will be connected,
and the current in wire A will pass to wire B and through the
push button to wire I and thence to wire II. The coil between
wire I and wire II is a magnet, and as soon as the current passes
through it, it draws the contact to the right and thus provides a
path for the current direct from wire A to wire ZZ, so that the push
button may be raised without opening the circuit. The current
in wire II will pass through the floor controller to wire £7 and thus
through magnet U of the operating switch G. This magnet will
then draw down the movable contacts m n o p, and the main line
HANDBOOK ON ENGINEERING.
753
current from the -f- wire will pass from contact m to wire m' and
through wire m' to point zo, hence through wire wr to the acceler-
ating, or starting resistance, and to wire F which leads to tha
series field coils. Returning from these coils through wire H to
Eaagnet switch 2 and thence wire n' to contact n, and as this con-
Fig?. 333. Direct connected eleyator with floor controller.
tact is pressing against the one directly below it, the current will
flow through the connection to wire E and thus to the armature ;
returning from the latter through wire I and wire o' to the contact
below o and thus to o and through the permanent connection to
contact p and to the lower right hand contact, which is connected
48
754 HANDBOOK ON ENGINEERING.
with wire r, which runs to the — side of the main switch. The
shunt field current is derived from wire m' and returns to contact
p and thus to wire r through wire p* ', as can be clearly traced.
The brake magnet current starts from the left side contact of G
through wire + B and returns directly to the lower end of
wire r.
The magnet switches 1 and 2 act in the same manner as those
in diagram Fig. 329, that is, by the increase in the counter electro-
motive force of the armature which causes the current that passes
through them to increase in strength. When magnet I closes its
switch, the current passes from wire w9 to wire F and thus the
accelerating resistance is cut out. When magnet 2 closes its
switch the current passes from wire m" directly to n' and thus to
the armature without going through the series field coils ; thus
the latter are cut out.
Returning now to the operation of the floor controller it will be
seen that as the current is flowing through wire II the circuit will
be broken if the controller is rotated until the gap at the top
comes under the brush of wire II. Now the floor controller
drum begins to turn as soon as the elevator machine moves, and
it is so geared to the elevator drum that when the car comes op-
posite the first floor the brush of wire II will be over the upper
gap, and then the circuit will be open and the magnet U will be
de-energized and allow switch G to move back to the stop position.
If button No. 4 is pressed instead of No. 1 the car will not
stop until the gap at the top of the floor controller drum comes
under the brush wire 44, for the circuit between this wire and
wire U will be closed until that position is reached.
If the car is run up to the fourth floor, as the gap at the top
of the floor controller drum will then be under the brush of wire
44, the brushes of wire 11, 22 and 33 will rest upon the same
segment as the brush of wire D; therefore, if with the car at
the top floor a button is pressed at any one of the lower floors
HANDBOOK ON ENGINEERING. 755
the current will pass from its corresponding wire to wire D and
thus through magnet coil D and to wire / and wire r. The cur-
rent passing through magnet D will draw the movable contacts of
the operating switch 6 upward, and thus set the elevator machine
in motion in the opposite direction from that in which it runs ,
when the IT magnet is energized.
In tracing out the circuits from the floor push buttons as just
explained it will be noticed that if any one of them is depressed,
the current in wire A will flow through wire B to the button de-
pressed, and then enter the wire returning from that button.
When the car buttons are depressed the current in wire A will
pass to wire C and then through the button in the car to the
proper return wire ; that is, to one or the other of the wires
1, 2, 3, 4. After entering one of these four wires the current
follows the same path as it does when one of the floor buttons
is depressed. The magnet B' in the B wire, and the
magnet C' in the C wire, are for the purpose of preventing in-
terference between a person operating the elevator from within
the car and another one at one of the landings. The B' switch is
actuated by a magnet that is wound with two coils that act in
opposition to each other. These coils are shown to the left of B' '.
When the elevator is operated from one of the floor push buttons
the current in wire A passes through both the coils on the magnet
of switch Bf and as one coil counteracts the other the switch
is left closed and the current passes directly to wire B. If the
elevator is operated from within the car the current from wire A
in passing to wire C passes through one of the coils of the mag-
net that actuates switch B' ', hence this switch is opened and the
connection with wire B is broken, so that if now any one of the
floor buttons is pressed it will have no effect as the circuit is
opened at switch B'. The current flowing through wire C passes
through a magnet that acts to close the switch C' and thus allow
a portion of the current to pass directly to wire r. This current
756 HANDBOOK ON ENGINEERING.
will continue to flow even after the car has stopped at the landing,
providing the door is not opened. As soon as the door in the
car, or the landing door, is opened the circuit is broken either in
wire Hor in wire A, and then the car cannot be moved until the
doors are closed. If it were not for switch (7 it would be possi-
ble for a person at one end of the landings to move the car if he
pressed the button during the short interval of time between the
stopping of the car and the opening of the landing door. The
opening of the door would stop the car, but by this time it might
be a foot or two away from the floor level. The current that
passes from switch C" to wire r is kept down to a small amount
by passing it through a high resistance which in the diagram is
marked 700 w.
The electrical portion of the Otis electric elevators has been
supplied for many years to four or five of the leading companies,
which were controlled by the Otis, and during the last two or
three years it has been supplied to practically all the prom-
inent makers, as these are now part and parcel of this
company ; hence the descriptions given in the foregoing
are more than likely to cover any case met with in
practice, for although there are numerous small manufacturers,
the sum total of their elevators in use is comparatively small.
The only electric elevators in addition to those described in the
foregoing that have come into extensive use are those made by the
Sprague Electric Co.
These machines are of two different types, one being the ordi-
nary drum design, and the other the screw machine. The drum
machine is similar in its main features to the same type of ma-
chine of other makers, and it is only in the minor details of con-
struction that any radical difference can be noted. In the means
employed for controlling the motion of the motor, however, there
is a decided difference. In all the Sprague elevators the car is
controlled electrically, hand rope control not being used in any
HANDBOOK ON ENGINEERING.
757
3
<yf
8
I
"»
758 HANDBOOK ON ENGINEERING.
HANDBOOK ON ENGINEERING.
759
Fig. 335. Elevator controller board.
760 HAND BOOK ON ENGINEERING.
The nut carried by the traveling cross- head is so arranged that
when the latter reaches the end of its travels at either end of the
screw, the nut is released and then rotates with the screw with-
out moving the cross -head. This forms a perfect top and bottom
limit stop, for even if the motor continues to run, the car cannot
be carried beyond the positions corresponding to the points at
which the nut slips around in the cross-head.
The brake for holding the machine is mounted upon the outer
end of the armature shaft, ancj. can be seen at Fig. 334 at the ex-
treme right hand side. This brake is actuated by a magnet that
releases it, and a spring that throws it on. When the current is
on, the brake is lifted and when the current is off the brake goes
on. In this respect, the action is the same as in all other electric
elevators.
The operation of the motor is controlled by a small switch in
the car, which is connected with the motor circuits by means of
wires contained in a flexible cable, just like the Otis electrically
controlled machines. The controller consists of a main switch,
which is moved by a small motor called a pilot motor, and a num-
ber of smaller magnetic switches whose action will be presently
explained. All these parts are mounted upon a switchboard, and
present the appearance shown in Fig. 335. The pilot motor and
main switch are located at the top of the board, and the magnet
switches cover the space below, while the starting and regulating
resistance is mounted on the back of the board.
The complete wiring diagrams for these machines is decidedly
complicated owing to the fact that there are numerous switches
and devices whose office is to afford additional safety, or to ren-
der the control more perfect. When all the parts that are not
actually necessary to illustrate the system are removed, however,
the diagram becomes quite simple and can be readily understood.
Such a diagram is shown in Fig. 336. This diagram shows the
motor together with the screw and sheaves, the elevator car, the
HANDBOOK ON ENGINEERING. 761
counterbalance, and the operating switches. The wires marked +
and — are connected with the main line. The switch in the car
is connected with the controller by means of four wires, marked
c b d and s. The lower one of these wires, marked s, is connected
with the stud around which the car switch swings. When the
car switch is moved onto the upper contact, it connects wire s
with wire c and then the car runs up. When the car switch is
moved down onto the lower contact, wire s is connected with wire
d, and then the car runs down. When the car switch is placed in
the central position wire s is connected with wire b and then the
elevator stops. The two switches marked " up limit," " down
limit," are for stopping the car automatically at the top and bot-
tom landings. Normally the up limit switch is closed and the
down limit switch is open. With these switches in this position,
which is the position in which they are shown in the diagram, the
current from the + wire can pass through the up limit switch to
wire fc, and thence through wire I to the armature of the motor,
and then through the field coils, and reach wire m. It cannot go
beyond this point until the switch C is moved. This is the main
operating switch, which in Fig. 335 is seen at the top of the board,
the contacts being arranged in two circles. The pilot motor that
rotates the arm of this switch, which is clearly shown in Fig. 335, is
represented in this diagram, Fig. 336, at A. As will be seen in
this diagram, this motor has a field provided with two magnetizing
coils, one for the up motion, and one for the down motion, and in
addition it is provided with a brake to stop it quickly and hold it
when not in use. The portion of the diagram marked B is the
reversing switch.
Let us suppose now that the car switch is moved upward, so as
to cause the elevator to ascend, then wire s will be connected with
wire c. From the + wire a current will pass through wire a to s
and thus to c, and through magnet e of switch ^, thus closing this
switch so as to connect wires li and i. The current in wire c will
762
HANDBOOK ON ENGINEERING.
pass to B and through the connecting plate u will reach the end
of the up field coil of the pilot motor, and then pass through the
armature of this motor, and finally through the magnet that re-
leases the brake. The pilot motor will now rotate the reversing
switch B so that the contact plates will move toward the left.
This movement will bring plate w under the ends of wires s and t,
thus permitting a current from s to pass to tf, and as switch g is
Fig. 886. Diagram of elevator controller board.
closed this current will reach wire h and thus the magnet J,
thereby lifting the plunger switch that closes the gap between
wire q and the — wire. As the arm of the main switch 0
moves with the reversing switch _B, this arm will ride over the
contacts on the right side, marked" up res." and thus the current
from wire m will be able to reach wire q after passing through the
up resistance.
HANDBOOK ON ENGINEERING. 763
If sthe car switch is left on the upper contact, the pilot motor
will continue to rotate until the arm of switch C reaches the top
of the resistance contacts, marked Full Up. When this point is
reached, the contact plate u of the reversing switch B will pass
from under wire c and the terminal of the up field of the pilot
motor, and then this motor will stop rotating.
If the car switch is not kept on the upper contact very long,
the pilot motor can be stopped with the. arm of switch G at some
intermediate point on the resistance contacts, thus by the time
during which the car switch is kept upon the upper contact, the
amount of resistance cut out of the motor circuit can be con-
trolled and thereby the speed of the car can be controlled.
In this operation it will be noticed that the motor is connected
with the main line and that the current enters through the + wire
and passes out through the — wire. If now we turn the car
switch downward, the s wire will be connected with the d wire and
by following the latter to the reversing switch B it will be seen
that through connecting plate v it is connected with wire z which
leads to the end of the down field of the pilot motor, thus setting
the latter in motion in the opposite direction so as to shift the
contact plates of B toward the right, and at the same time rotate
the arm of the main switch C to the left, thereby making contact
with the contacts of the down resistance. With the arm of G in
this position, it will be seen that the current in wire I can flow
through the motor armature and field and through wire m to the
arm of switch G and through the down resistance to wire n and
thus back to wire Z, thereby forming a closed circuit within the
motor wires and connections, and disconnected from the main line
except on the side of the + wire. The rotation of B causes the
connecting plate x to ride upon the terminals of wires s and £, and
thus a current is sent through the brake magnet so as to lift the
brake, and allow the elevator machine to run. When the pilot
motor moves the arm of C so far as to reach the top of the down
764 HANDBOOK ON ENGINEERING.
resistance, the contact plate v of the reversing switch B will pass
beyond the terminals of wires d and z, thus breaking the circuit
of the pilot motor and bringing the latter to a stop.
When the reversing; switch B is in the stop position, as shown
in the diagram, the terminal of wire b does not rest upon a con-
necting plate but when the switch is rotated for the up motion, the
terminal of b rests on plate v so that if the car switch is turned
to the stop position, the current from wire b will pass to wire
z and thus reverse the direction of rotation of the pilot
motor, and return the switches to the stop position. If
the car is running down, when the car switch is turned
to the stop position, the current from wire b will pass to
wire z and thus reverse the direction of rotation of the pilot
motor, and return the switches to the stop position. If the car
is running down, when the car switch is turned to the stop posi-
tion, the wire b will ride over the plate u and thus the current
will pass through the pilot motor through the up field and thus
rotate the switches back to the stop position. In each case, as
will be noticed, whenever the current flows through wire b it ene
gizes coil / and thus opens switch g. When the car is running
up the current for the brake magnet passes from wire i through
the switch which is energized by the main current flowing in wire q.
When the car runs too far down, and closes the down limit switch,
the motor circuit becomes closed through wires j), r and &, thus
giving another path for the current generated by the motor arma-
ture and thereby increasing the resistance to rotation.
The controller for the Sprague drum machines is very similar
to the one just described. It is operated by a pilot motor, and
in so far as the controller switchboard is concerned looks the
same. The only difference is that rendered necessary by the
fact that in lowering as well as in raising the load, the motor is
connected with the line. This requires a slight change in some
of the wire connections.
HANDBOOK ON ENGINEERING. 765
The electrical parts of the Sprague elevators require very little
attention other than to keep them clean and all the contacts bright
and in proper adjustment, so that when moved a good contact
may be made. Of the mechanical portion, the drum machines
require about the same attention as other machines of this type.
As to the screw machines, the part that requires most attention is
the screw and the nut. As can be readily understood, if the nut
were solid, the friction against the screw would be very great ;
therefore, to reduce this friction, the nut is made so as to carry a
large number of friction balls. These run in a groove cut in the
side of a thread and roll between the thread and the screw and
the thread in the nut. A tube is attached to the nut to provide a
path through which the friction balls can pass from the end of the
thread to the beginning, thus making an endless path in which
they move. As these friction balls are subjected to a heavy pres-
sure, there is more or less danger of their giving trouble and on
that account the thread on the screw should be carefully examined
and kept as clean and free from grit as possible. Under favorable
conditions these screws run very well, the wear being trifling, but
in some instances they are liable to cut badly, hence they should
be closely watched.
DIRECTIONS FOR THE CARE AND OPERATION OF THE
ELECTRIC ELEVATOR.
Whenever the attendant wishes to handle the machine to clean,
adjust, repair or oil it, he should see that the current is shut off
at the switch, and thus prevent all possibility of accident.
Cleaning. — Keep the entire machine clean. Clean the com-
mutator and other contacts and brushes carefully with a clean
cloth and keep them free from grease and dirt. If the face of the
rheostat on which the rheostat arm brushes work becomes burnt,
clean with a piece of fine sand-paper (No. 0), or if necessary use
HANDBOOK ON ENGINEERING.
HANDBOOK ON ENGINEERING. 767
resistance is cut out of the armature circuit by slightly easing off
the weight, which acts in opposition to the core of the small
solenoid. This solenoid controls a valve in the dash-pot and
thereby regulates its speed in proportion to the current passing.
If a governor starter is used and the current is admitted too
rapidly, tighten the governor spring on the armature shaft, or
close the vent in air dash-pot. If the car refuses to ascend
with a heavy load, immediately throw the lever to the center
and reduce the load, as in all probability it is greater than
the capacity of the elevator. If it refuses to ascend with
a light load, throw the lever to the center and have the
fusible strip examined. If, in descending, the car should
stop, throw the lever to the center and examine safeties,
fusible strip and machine, and before starting, be sure that the
cables have not jumped from their right grooves. If the car
refuses to move in either direction, throw the lever on the center
and have the fusible strips examined. Never leave the car with-
out throwing the lever to the center. If the car should be stalled
between floors, it can be either raised or lowered by raising the
brake and running it by turning the brake-wheel by hand. Such
a stoppage might be caused by the current being shut off at the
station, undue friction in the machine, too heavy a load, fuses
burnt out, or a bad contact of the switches, binding posts or elec-
trical connections. If the car by any derangement of cables or
switch cannot be stopped, let it make its full trip, as the auto-
matic stop will take care of it at either end of the travel. The
bearings should be examined occasionally to insure no heating
and proper lubrication.
General directions* — Have the machine examined occasionally
by someone well posted in electric motors and elevators. The
attendant should inspect the machine often. All brushes and
switches should be sufficiently tight to give a good contact, but
no tighter. None of the brushes should spark when in their
768 HANDBOOK ON ENGINEERING.
normal position. When the brushes become burnt dress witn
sandpaper or file, or, if necessary, replace with new ones. If
brushes spark, dress with sandpaper or file to a good bearing,
and, if necessary, set up springs, but do not make the ten-
sion such as to interfere with their ready movement. Adjust
commutator brushes gradually for least sparking. These should
be close to the central position. Contacts and brushes should
be kept clean and smooth and lubricated sparingly. While
replacing a fusible strip, be sure that main switch is open, and be
careful not to touch the other wire with your tool or otherwise, as
such contact would be dangerous. Never put in a larger fuse
than the one burnt. Inspect the worm and worm-wheel occasion-
ally through hand-holes in casing, to see that they are well lubri-
cated, and that no grit gets into the oil. They should show no
wear. The stuffing-box on the worm shaft should be only tight
enough to keep the oil from leaking out of the worm chamber.
Be sure that all parts are properly lubricated, and that none of
the bearings heat. To make sure that the car and machinery run
freely, lift brake lever and then rotate worm shaft by pulling on
the brake wheel. The empty car should ascend without any exer-
tion. Keep operating cables properly adjusted. Open main
switch when the elevator is not in service.
The Lever.
Relative Position of Power, Weight and Fulcrum in :
Lever of the first class Power. Fulcrum. Weight.
Lever of the second class Power. Weight. Fulcrum.
Lever of the third class Weight. Power. Fulcrum.
Power X power-arm Power V power-arm
"— = Weight. Weight -- = Weight-arm.
Weight X weight-arm Weight X weight-arm
Power-arm ~ - Power' Power = Powei"arm-
Weight
power = ratio of, or proportion of, power-arm to weight-arm.
Power-arm
Weight-arm = ratio of> or Pr°PortiO11 of ; weight to power.
HANDBOOK ON ENGINEERING. 769
CHAPTER XXVI.
ELECTRIC ELEVATORS.
Electric elevators of the drum type while very satisfactory for
buildings of moderate height, are not well adapted to office build-
ings of many floors, where the run is from 200 to 300 feet. The
objection to them for such cases is that the drum has to be of such
large dimensions that frequently space near the elevator well can-
not be had for it. As can be easily seen the drum must be of
such diameter and length that all .the rope required to lift the car
to the top of the building can be wound upon it. If the diameter
of the drum is enlarged so as to provide the requisite surface,
there is difficulty in obtaining the desired car speed, because the
worm gear has to be increased proportionately with the drum, so
that the pressure in the teeth may be not so great as to cause them to
cut. If the worm gear is large the motor must make a greater
number of revolutions for each turn of the drum, hence, although
the car will travel further per turn of drum, the increase in this
direction is not as great as the increase in the ratio between the
speed of the motor and that of the drum. The motor speed can
be reduced considerably by using a worm with double thread, but
even then high motor speed is required for high car speed, higher
than with elevators running to a moderate height. If the re-
quired drum surface is obtained by increasing the length of the
drum, then the machine is liable to become so wide that it cannot
be placed In the opening at the side of the elevator well provided
for it. If there is space enough for the machine, the spread of
the ropes when they are unwinding from the sides of the drum
may be greater than the width of the elevator well.
770 HANDBOOK ON ENGINEERING,
It was to overcome the above difficulties that the Sprague screw
Fig. S37. Diagram of Frazer Duplex Elevator*
machine was devised, bat this machine has not withstood the test
HANDBOOK ON ENGINEERING. 771
of time and is no longer manufactured. Another machine that
overcomes the objections to the drum machine for high buildings
is the Frazer Duplex Motor Elevator.
The general arrangement and principle of operation of the
Frazer elevator can be made clear by the aid of the diagram Fig.
337. As will be seen in this diagram there are two motors
placed one on top of the other. On the ends of the amature
shafts are mounted grooved sheaves, and under these sheaves run
endless cables in the manner clearly shown. The elevator car is
suspended from the frame of one of the traveling sheaves around
which the cables pass, and a counter-balance weight is suspended
from the frame of the other travelling sheave. The two motors
are arranged to rotate in opposite directions, as indicated by the
arrows. In the operation of the elevator the motors never re-
verse, but always run in the same direction. The motors are of
the variable speed type, and the running of the elevator car in
either direction is effected simply by changing the velocity of the
motors. Looking at the diagram it can be seen that if both
motors are running at the same speed, the top one will run the
cables out to the right just as fast as the lower one will run them
to the left, hence, the travelling sheaves will not move, and the
car will stand still. Now suppose the top motor runs faster than
the lower one, then the top ropes will run out to the right faster
than the lower ones will run out to the left, and as a result the
right side travelling sheave will move up, and the other one will
move down, thus causing the car to rise, and the counterbalance
to descend. If the motor velocities are reversed, that is, the top
one reduced to a speed lower than the lower one, then the top
one will not run the cables out to the right as fast as the lower
one will run them to the left, and as a result the left side travel-
ling sheave will rise, thus causing the car to run down and the
counterbalance to run up. By varying the speed of the two
772
HANDBOOK ON 'ENGINEERING.
motors any desired velocity of the car can be obtained from zero
to the maximum running in either direction.
Fig. 3B7a. Duplex Motor.
The motors used are made so that their speed can be varied
from 280 to 520 revolutions per minute, the. average velocity
being 400. When both motors are running at 400 the car stands
still, and when the top motor runs 280 and the bottom one 520
HANDBOOK ON ENGINEERING. 773
the maximum car speed is obtained with the car on the up trip.
The sheaves on the shafts of the. motor armatures are about 19
inches in diameter, so that with the speeds above named, the car
travels about 600 feet per minute.
Although the car should stand still when the two motors are
running at the same speed, in practice this result cannot be
obtained, as slight variations in velocity will occur, and these
fluctuations will cause the car to shake. To overcome this
trouble a brake is provided to hold the top sheave over which the
car lifting ropes pass, as clearly shown in the diagram. Gener-
ally the motors are stopped when the elevator is stopped.
This elevator is the most perfect in operation of any electric
elevator that has been devised, its velocity can be varied at the
will of the car operator from zero to the maximum speed, and it
can be stopped and reversed when running at full speed without
producing the slightest jolt ; but it possesses undesirable features
that tend to offset its fine running qualities. The main objection
is that the driving sheaves mounted on the ends of the armature
shaft have to be of very small diameter, so as to not impart too
high a velocity to the driving ropes. As these sheaves are only
19 inches in diameter, steel ropes cannot be used, in their stead
hemp ropes with a steel core are used, and while these may be
just as safe as steel cables, they do not inspire the same amount
of confidence.
• As there is very little friction about the Frazer elevator, it
would naturally be inferred that it will require less current to do
the same work, but actual practice seems to show that it ia not
any more economical than the drum machine.
The duplex motor of the Frazer elevator is shown in Fig. 337a,
and is so simple as to require no explanation, being in fact noth-
ing but two motors mounted one on top of the other.
The way in which the Frazer elevator is controlled can be ex-
plained in connection with the wiring diagram Fig. 338. The
774
HANDBOOK ON ENGINEERING.
s
I
s
g
ft
s-
OJ
2
bo
upper part of the diagram represents the car switch, a photo-
graphic view of which is shown in Fig. 338a. The car switch is
HANDBOOK ON ENGINEERING.
775
Fig. 338a. Frazer Car Controller.
provided with resistances that can be connected in parallel with
the field coils of either motor, so as to vary the velocity. The
parts marked U limit, and D limit are automatic stopping switches
that are located in the elevator well near the top and bottom, and
in such position that they may be moved by the elevator car when
it reaches either end of its travel. These limit switches stop the
car gradually by cutting in the resistance in the manner clearly
indicated in the diagram. A photographic view of the D limit
switch is given in Fig 338b. The U limit switch is substantially
the same in construction and appearance. As will be seen the
switch lever is actuated by a rod that carries a roller at its end,
this roller being placed in a position where it will be struck by an
inclined plane attached to the elevator car, so as to gradually
776 HANDBOOK ON ENGINEERING.
cut the resistance into the circuit. The lower part of the dia-
gram constitutes the controller and the several switches of which
it is composed are assembled on a slate panel in the manner
shown in Fig. 338o, which is a photographic view of the con-
troller front.
The operation of the controller is as follows : — The potential
switch is jlosed by hand, but is arranged like a circuit breaker,
so that it will open whenever the potential of the current dies out.
To start the motors, the car switch D is closed, and then a cur-
Fig. 338b. Frazer Limit Switch.
rent starting from A will pass through D and thence through the
magnet of S and following the path indicated by the arrow heads
will reach wire E and thus return to the lower side of the potent-
ial switch. As soon as the magnet of S is energized, the contact
plates will be raised so as to close the main circuit, and then the
current will flow through the starting series field and thence
through the armatures of the two motors and back to lower side
of potential switch. From the end of the series field a current
will branch off through the magnet of AS' and through the magnets
HANDBOOK ON ENGINEERING.
777
of the switches that cut out the series field. The shunt fields of
the two motors are connected in series and to the left side contact
at top of switch S' and to the lower right side contact of $. To
Fig. 338c. Front of Frazer Controller.
make the car run in either direction it is necessary to change the
speed of the motors, and this is done by moving the contact B in
the car switch, by means of the operating lever, to one side or the
778 HANDBOOK ON ENGINEERING.
other. Let B be moved to the left, then current coming up from
A will pass through B to the lever of the U limit and thence fol-
low the arrow heads to point C between the shunt field coils of
the two motors. In this way the resistance in the car switch is
connected in parallel with the field coil on the right of (7, hence,
the field of this motor, will receive less current than, the field of
the other motor, and as a result its amature will run faster.
If B is moved to the right, then current will flow from point C in
the opposite direction, as indicated by the arrows a, and reaching
the D limit will pass through the lever and thence through the car
switch resistance, through B and thence through wire E will
reach points F. In this case all the field current will pass
through the right side field but at C it will divide part going
through the left side field and the remainder following the path of
arrows a to point F. Thus by swinging the lever of the car
switch to one side or the other, one or the other of the motors can
be made to run faster and the direction of the car can be reversed,
while the speed can be varied as may be desired.
THE TRACTION TYPE OF ELECTRIC ELEVATOR.
Another form of electric elevator designed to overcome the
disadvantages of drum machines for high runs is what is known as
the traction type, and is illustrated diagrammatically in Fig. 339
on the left side. In this construction only one motor is used and
on the end of its armature shaft is mounted a sheave much larger
than those used on the Frazer machine. The size of the sheave
is large enough to permit the use of regular steel wire cables.
These cables pass over two travelling sheaves, in the manner
clearly shown in the diagram, and the ends are anchored to suit-
able supports as shown. The car is suspended from ropes that
pass over a sheave at tlie top of the elevator well and run down to
the frame of one of the travelling sheaves. The counterbalance
is similarly connected with the other sheave frame.
HANDBOOK ON ENGINEERING. 779
From an inspection of the diagram it will be seen that this ma-
MODIFIED FORM'
Fig. 389. Traction Types of Electric Elevator.
chine is geared two to one, that is, the car speed is one-half the
780 HANDBOOK ON ENGINEERING.
velocity of the circumference of the driving sheave on the motor
shaft. In the Frazer machine the car is ran in either direction
while the motors always run in the same direction, and the car
can be stopped without stopping the motors, simply by bringing
the two to the same speed. In the traction system this cannot
be done, the motor must be stopped to stop the car, and it must
be reversed to reverse the direction of the car. For these reasons
the control is not so perfect as in the Frazer machine, but the
difference is slight in practice, in fact hardly worth noticing ; but
as an offset we have the fact that a sheave of standard size can be
placed on the motor shaft and, therefore, regular steel ropes can
be used instead of hemp ropes with a steel centre.
In looking at the diagram this arrangement of elevator appears
to be as simple as anything can be, but the actual apparatus is
not as simple as the diagram. The traveling sheaves have to run
in guides and these must extend something more than half the
height of the elevator well. Such guides are expensive, and in
addition take up a considerable amount of space, which in office
buildings in large cities is very valuable. Now it can be easily
seen that if a motor can be made that will drive an elevator by
being geared two to one as in the diagram, it is only necessary to
make the motor so as to pull twice as hard and then it can be
connected directly with the elevator. To do this the size of the
motor must be increased, but as an offset we have the fact that
all the expense of the traveling sheaves can be used to cover the
additional cost of the motor, and the space occupied by the sheave
is saved, which is so much clear gain, in addition to which the
greater simplicity must be taken account of. An elevator of this
type is shown in the diagram at the right of Fig. 339, and it is
known as one to one cable drive elevator.
This elevator which has been developed by the Otis Elevator
Company is now being introduced for high speed elevators in
large office and other buildings. The principle of operation is
HANDBOOK ON ENGINEERING.
781
the same as that used in cable railroads. The motor carries on
the end of the amature shaft a grooved sheave about 36 inches in
diameter, and an idle sheave is placed directly above the motor
sheave. The lifting ropes pass over the upper sheave once,
and under the motor sheave twice. This double wrap around the
the driving sheave has been found by many trials to give all the
Fig. 340. Cable Drive Elevator Machine.
adhesion required to lift the heaviest loads the elevator can carry.
A side view of the motor is shown in the centre of diagram Fig.
339, from which the relative position of the driving and the idle
782 HANDBOOK ON ENGINEERING.
sheave can be understood. The construction is still better shown
in Fig. 340 which is a photographic view of the motor. The
brake on the motor is located between the field frame and the
bearing at the driving sheave end, and is actuated by powerful
springs. A magnet is used to pull the brake off when the motor
is running. As soon as the current stops the magnet releases the
brake and the springs apply it with all the force necessary to pre-
vent the shaft from rotating even with ithe heaviest load in the
car. The counterbalance weight used with these elevators weighs
as much as the car and one-half the maximum load that it is in-
tended to lift, from which it will be seen that the break does not
have to be so powerful as might appear at a first glance.
In some cases these elevator machines are placed at the top of
the elevator well, and then the idle sheave is placed under the
motor, and is secured to overhead framing provided for the
the purpose. Such a construction is shown in Fig. 340a which is
a perspective view of a complete elevator, broken away at two
places so as to shorten the picture.
The elevator machine has no safety appliances attached to it
other than the break, as none are required upon it. The auto-
matic stops are arranged^in the elevator well mear the top and bot-
tom landings, in a manner that will be explained presently. The
break on the motor is arranged so that normally it acts with a
moderate pressure, but if the occasion requires it the breaking
force can be instantly increased by simply moving the operating
switch in the car to the central position. The connections of the
motor with the controller are such that in stopping the motor is
converted into a generator, and thus has to be driven by the force
of the descending weight.
As will be seen in Fig. 340a there is a small governor located
by the side of the moter, this is the regular Otis safety governor
that is arranged so as to stop the car if it attains an excessive
velocity from any cause. In this machine this governor has an
HANDBOOK ON ENGINEERING.
783
Fig. 340a.
additional appliance consisting of a switch that acts to stop the
784
HANDBOOK ON ENGINEERING.
motor whenever the governor throws the car safeties into action,
thus preventing the lifting ropes from becoming slack.
HANDBOOK ON ENGINEERING.
785
This cable drive elevator is arranged so as to run at different
speeds, the result being accomplished by the movement of the arc
switch handle to different positions. The change in the velocity
of the motor is effected in different ways. In one arrangement
w
CJ
1
•2
s
I
§
if
5
of the controlling devices, the speed variation is obtained by vary-
ing the strength of the current passing through the field of the
motor; in another it is obtained by introducing resistance in the
armature circuit, and by sending more or less current through a
78(5 HANDBOOK ON ENGINEERING.
by pass around the armature. In another arrangement both these
methods are combined. The wiring diagram, Fig. 341, illus-
trates the latter arrangement. The appearance of the controller
to which this diagram corresponds is shown in Fig. 34 la.
In the wiring diagram, Fig. 341, the heavy lines indicate wires
through which the strong armature current passes, the fine lines
are wires through which the field current, and the switch magnet
currents pass. A complete explanation of this diagram would be
very lengthy, and to avoid this we have placed arrow heads on all
the lines which will greatly facilitate the understanding of the
condensed explanation that follows : —
The line wires are connected with the two pole switch at the
right of the diagram. From this switch connections run to a
potential switch directly to the left. The accelerating magnet
cuts out the resistance shown above it, from the armature circuit,
when the highest velocity is desired. Directly to the left of the
accelerating magnet are shown a number of magnetic switches,
that act to cut resistance out of the armature circuit, and to in-
crease the resistance in a circuit that shunts the armature, and
finally to open this circuit. These switches are operated from
the car switch, which is shown at the left side of the diagram.
The circle marked A represents the motor armature, and at the
bottom of the diagram is shown the shunt field coils. The motor
is of the plain shunt type. Following the wire starting from A it
will be seen that it passes through the field coils of the motor and
ends at B. The circuit from A through the potential switch can
be easily traced to (7, and from here the fine wire runs through
switch 5, to and through E, and from here to switch 1 and to the
lower up contact of the car switch. E is the magnet coil of one
of the starting switches E' ', and if the car switch is turned so as
to cover the first contact, the current after reaching this, will re-
turn through the centre wire from the car and reach the point 0'
on the potential switch. The current will then flow through the
HANDBOOK ON ENGINEERING. 787
motor by way of switch E' in the way indicated by the arrow
heads. As the car switch is advanced it covers in succession the
contacts from which lead wires that pass through the roller
switches, 1, 2, 2, 3, 5, and thence to the magnets of the switches
that cut the resistances A' into the circuit that shunts the arma-
ture, and cut out the resistances directly above, that are in series
with the armature. In this way the motor speed is increased.
When the accelerating magnet cuts out all its resistance it also
closes the circuit of F and then resistance F' is cut into the
shunt field circuit, and the motor speed further increased. The
roller switches 1, 2, 3, 4, 5, are limit switches to stop the car
automatically at the top floor, if the operator fails to turn the car
switch to the stop position. Similar limit switches are shown in
the wires running from the do.wn side of the car switch. In Fig.
340a two of these switches can be seen at the side of the guide
near the bottom of the well. The two roller switches seen at the
right of the diagram are final limit switches that are actuated if
the car overruns the limits. When one of these switches is
moved, the motor is disconnected from the circuit, the brake
goes on with full force, the armature generates a strong current
and the motor stops at once.
788 HANDBOOK ON ENGINEERING.
CHAPTER XXVII.
THE DRIVING POWER OF BELTS.
The average strain or tension at which belting should be run
is claimed to be 55 pounds for every inch in width of a single belt,
and the estimated grip is one-half pound for every square inch of
contact with pulley, when touching one-half of the circumference
of the pulley. For instance a belt running around a 36-inch pul-
ley would come in contact with one-half its circumference, or 56£
inches, and allowing a half-pound per inch, would have a grip 28£
pounds for each inch of width of belt.
MECHANICAL PROBLEMS AND RULES.
Problem 1. To find the circumference of a circle or a
pulley : —
Solution. Multiply the diameter by 3.1416 ; or, as 7 is to 22
so is the diameter to the circumference.
Problem 2. To compute the diameter of a circle or pulley : —
Solution. Divide the circumference by 3.1416; or multiply
the circumference by .3183 ; or as 22 is to 7, so is the circumfer-
ence to the diameter, equally applicable to a train of pulleys, the
given elements being the diameter and the circumference.
Problem 3. To find the number of revolutions of driven pulley,
the revolution of.driver, and diameter of driver and driven being
given : —
Solution. Multiply the revolutions of driver by its diameter,
and divide the product by the diameter of driven.
HANDBOOK ON ENGINEERING. 789
Problem 4. To compute the diameter of driven pulley for any
desired number of revolutions, the size and velocity of driver
being known : —
Solution. Multiply the velocity of driver by its diameter and
divide the product by the number of revolutions it is desired the
driven shall make.
Problem 5. To ascertain diameter of driving pulley : —
Solution. Multiply the diameter of driven by the number of
revolutions it is desired it shall make, and divide the product by
the number of revolutions of the driver.
6. Rule for finding; length of belt wanted: Add the diame-
ters of the two pulleys together, divide the result by two, and
multiply the quotient by 3 1/7. Add the product to twice the
distance between the centers of the shafts, and we have the
length required.
FOR CALCULATING THE NUMBER OF HORSE-POWER WHICH A BELT
WILL TRANSMIT, ITS VELOCITY AND THE NUMBER OF SQUARE INCHES
IN CONTACT WITH THE PULLEY BEING KNOWN.
Divide the number of square inches of belt in contact with the
pulley by two, multiply this quotient by velocity of the belt in
feet per minute and divide the product by 33,000 ; the quotient is
the number of horse-power.
Example. — A 20-inch belt is being moved with a velocity of
2,000 feet per minute, with six feet of its length in contact
with the circumference of a four-foot drum ; desired its horse-
power. 20 x 72 equal 1,440, divided by two, equals 720, x 2,000
equal 1,440,000, divided by 33,000 equals 43| horse-power.
Rule for finding width of belt, when speed of belt in feet per
minute and horse-power wanted are given : —
For single belts* — Divide the speed of belt by 800. The horse-
power wanted divided by this quotient, will give the width of
belt required.
790 HANDBOOK ON ENGINEERING.
Example. — Required the width of single belt to transmit 100
horse-power. Engine pulley 72" in diameter. Speed of engine,
. 220 revolutions per minute.
800) 4146 (speed of belt per minute).
5.18)100.00 (horse-power wanted).
19" width of belt required.
For doable belts* — Divide the speed of belt in feet per minute
by 560. Divide the horse-power wanted by this quotient for the
width of belt required.
Example. — Required the width of double belt to transmit 500
horse-power. Engine pulley 72" in diameter. Speed of engine,
220 revolutions per minute.
560)4146 (speed of belt per minute).
7.4)500.00 (horse-power wanted).
67J" width of belt required.
NOTES ON BELTS.
PRINCIPLES GOVERNING BELTS.
Although there is not near as much known in general about
the power of transmitting agencies as there should be, still it
seems that almost any other method or means is better understood
than belts.
One of the chief difficulties in the way of a better knowledge of
the belting problem, is the relation that belts and pulleys bear to
each other. The general supposition, and one that leads to many
errors, is that the larger in diameter a pulley is, the greater its
holding capacity — the belt will not slip "so easily, is the belief.
But it is merely a belief, and has nothing to sustain it, unless it
be faith, and faith without work is an uncertain factor. It is very
HANDBOOK ON ENGINEERING. 791
desirable to impress upon the minds of all interested, the folio wing
immutable principles or law : —
1. The adhesion of the belt to the pulley is the same — the arc
or number of degrees of contact, aggregate tension or weight
being the same — without reference to width of belt or diameter
of pulley.
2. A belt will slip just as readily on a pulley four feet in diam-
eter, as it will on a pulley two feet in diameter, provided the
conditions of the faces of the pulleys, the arc of contact, the ten-
sion, and the number of feet the belt travels per minute are the
same in both cases.
3. A belt of a given width and making two thousand, or any
other given number of feet per minute, will transmit as much
power running on pulleys two feet in diameter as it will on
pulleys four feet in diameter, provided the arc of contact, tension
and conditions of pulley faces all be the same in both cases.
It must be remembered, in reference to the first rule, that when
speaking of tensions, that aggregate tension is never meant unless
so specified. A belt six inches wide, with the same tension, or
as taut as a belt one inch wide, would have six times the aggre-
gate tension of the one inch belt. Or it would take six times
the force to slip the six inch belt as it would the one inch. It
is well to induce readers to become practical students and to be
able to learn for themselves. Information obtained in that way
is far more valuable, and liable to last much longer.
In order that the reader may more fully understand whether
or not a large pulley will hold better than a small one, let him
provide a short, stout shaft, say three or four feet long and two
inches in diameter. To this shaft firmly fasten a pulley, say
12 in. in diameter, or any other size small pulley that may be
convenient. The shaft must then be raised a few feet from the
floor and firmly fastened, either in vises, or by some other means,
so that it will not turn. It would be better, of course, to have
792 HANDBOOK ON ENGINEERING.
a smooth-faced iron pulley, as such are most generally used. So
far as the experiment is concerned, it would make no difference
what kind of a pulley was used, provided all the pulleys experi-
mented with be of the same kind, and have the same kind of face
finish. When the shaft and pulleys are fixed in place, procure a
new leather belt and throw it over the pulley. To one end of the
belt attach a weight, equal, say, to forty pounds — or heavier, if
desired — for each inch in width of belt used ; let the weight
rest on the floor. To the other end of the belt attach another
weight, and keep adding to it until the belt slips and raises the
first weight from the floor. After the experimenter is satisfied
with playing with the 12 in. pulley, he can take it off the
shaft and put on a 24 in., a 36 in., or any other size he may
wish ; or, what is better, he can have all on the shaft at the
same time. The belt can then be thrown over the large pulley
and the experiment repeated. It will then be found if pulley
faces are alike, that the weight which slipped the belt on the
small pulley will also slip it on the large one. The method
shows the adhesion of a belt with 180 degrees contact, but as the
contact varies greatly in practice, it is well enough to understand
what may be accomplished with other arcs of contact. But, after
all, many are probably at a loss how to account for some obser-
vations previously made. They have noticed that when a belt at
actual work slipped, an increase in the size (diameter) of the
pulleys remedied the difficulty and prevented the slipping.
A belt has been known to refuse to do the work allotted to it,
and continue to slip over pulleys two feet in diameter, but from
the moment pulleys were changed to three feet in diameter there
was no further trouble. These observed facts seem to be at
variance with and to contradict the results of the experiments
that have been made. All, however, may rest assured that it is
only apparent, not real.
The resistance to slippage is simply a unit of useful effect (or
HANDBOOK ON ENGINEERING. 793
that which can be converted into useful effect). The magnitude
of the unit is in proportion to the tension of the belt. The sum
total of useful effect depends upon the number of times the unit
is multiplied. A belt 6 inches wide and having a tension equal
to 40 Ibs. per inch in width, and traveling at the rate of 1 foot
per minute, will raise a weight of 240 Ibs. 1 foot high per minute.
If the speed of the belt be increased to 136.5 feet per minute, it
will raise a weight of 33,000 Ibs. per minute, or be transmitting
1 horse-power. The unit of power transmitted by a belt is rather
more than its tension, but to take it at its measured tension is at
all times safe, and 40 to 45 Ibs. of a continuous working strain is
as much, perhaps, as a single belt should be subjected to. A
little reflection will now convince the reader that a belt transmits
power in proportion to its lineal speed, without reference to the
diameter of the pulleys. Having arrived at that conclusion, it is
then easy to understand why it is that a belt working over 36-inch
pulley will do its work easy, when it refused to do it and slipped
on 24-inch pulleys. If the belt traveled 800 feet per minute on
the 24-inch pulleys, on the 36-inch it would travel 1,200 feet,
thus giving it one-half more transmitting power. If, in the first
instance, it was able to transmit but 8 horse-power, in the second
instance it will transmit 12 horse-power. All of which is due to
the increase in the speed of the belt and not to the increase in the
size of the pulleys ; because, as has been shown, the co-efficient
of friction, or resistance to slippage, is the same on all pulleys
with the same arc of belt contact.
There is no occasion for elaborate and perplexing formulas and
intricate rules. They serve no useful purpose, but tend only to
mystify and puzzle the brain of all who are not familiar with the
higher branches of mathematics, — and it is the fewest number
of our every-day practical mechanics who are so familiar. In all,
or nearly all treatises on belting, the statement is made that at
600, 800 or 1,000 feet per minute, as the case may be, a belt one
794 HANDBOOK ON ENGINEERING.
inch wide, will transmit one horse-power ; and yet, when we come
to apply these rules in practice, no such results can be obtained
one time in ten. The rules are just as liable to make the belt
travel 400, 1,000 or 1,600 per minute per horse-power as the
number of feet they may give as indicating a horse-power.
All .of the following simple calculations are based upon the
assumption that a belt traveling 800 feet per minute, and running
over pulleys, both of which are the same diameters, will easily
transmit one horse-power for each inch in width of belt. A belt
under such circumstances would have 180 degrees of contact on
both pulleys without the interposition of idlers or tighteners.
The last proposition being accepted as true and the basis cor-
rect, the whole matter resolves itself into a very simple problem,
so far as a belt with 180 degrees contact is concerned. It is
simply this : If a belt traveling 800 feet per minute transmit one
horse-power, at 1,600 feet, it will transmit two horse-power ; or
if 2,400 feet, three horse-power, and so on. It is no trouble for
any one to understand that, if he understands simple multiplica-
tion or division.
It is not, however, always the case that both pulleys are the
same size, and as soon as the relative sizes of the pulleys change,
the transmitting power of the belt changes ; and that is the rea-
son why no general rule has ever, or ever will be made for ascer-
taining the transmitting capacity of belts under all circumstances.
When the pulleys differ in size, the larger of the two is lost sight
of — it no longer figures in the calculations — the small pulley,
only, must be considered. To get at it, the number of degrees
of belt contact on the small pulley must be ascertained as nearly
as possible and use for a guide, for getting at the transmitting
power, the next established basis given. Of course, the experi-
menter can make a rule for every degree of variation, but it would
require a great many, and is not necessary. Five divisions are
used, as follows: —
HANDBOOK ON ENGINEERING. 795
For 180 degrees useful effect .... 100
For 157| " " " 92
For 135 " " ' " 84
For 112i u 44 fi 76
For 90 " " " 64
The experimenters may find that the figures are under obtained
results, which is exactly what they are intended to be, more
especially on the 90 degree basis. Always make ample allow-
ance.
To ascertain the power a belt will transmit under the first-named
conditions : Divide the speed of the belt in feet per minute by
800, multiply by its width in inches and by 100. For the second,
divide by 800, multiply by width in inches and by .92. Third
place, divide by 800, multiply by width in inches and by .84.
Fourth place, divide by 800, multiply by width in inches and by
.76. Fifth place, divide by 800, multiply by width in inches and
by .64. As an example: What would be the transmitting power
of a 16-inch belt traveling 2,500 feet per minute by each of the
above rules?
1st: 2,500 divided by 800 equal 3.125 x 16 x 100 equal 50 h. p.
2d: 2,500 " 800 " 3.125 x 16 x .92 equal 46 "
3d: 2,500 " 800 " 3.125 x 16 x .84 equal 42 "
4th: 2,500 " 800 " 3.125 x 16 x .76 equal 38 "
5th: 2,500 " 800 " 3.125 x 16 x .64 equal 32 "
As stated, when the degrees of contact come between the
divisions named above, in order to be on the safe side, calculate
from the first rule below it, or make it approximate as desired.
If the above rule is studied well and strictly used, there can
be no excuse for any mechanic putting in a belt too small for the
work it has to do, provided he knows how much there is to do,
which he ought, somewhere near at least.
796
HANDBOOK ON ENGINEERING.
HORSE-POWER TRANSMITTED BY LEATHER
BELTS.
DRIVING POWER OF SINGLE BELTS.
Speed in
Feet per
Minute.
Width of Belt in Inches.
2
3
4
5
6
8
10
12
14
H. P.
H. P.
H. P.
H. P.
H. P.
H. P.
H. P.
H. P
H. P.
400
1
Ij
1
2
2^
3
4
5
6
7
* 600
H
I
3
31
41
6
71
9
101
800
2
3
4
5
6
8
10
12
14
1,000
21
31
5
64
71
10
"I
15
171
1,200
3
4,
7
71
9
12
15
18
21
1,500
1,800
31
41
6
6;
92
92
H4
st
15
18
221
221-
27
261
311
2,000
5
7-
10
121
15
20
25
30
35
2,400
6
9'
12
15
18
24
30
36
42
2,800
7
10-
I
14
171
21
28
35
42
49
3,000
71
11:
(
15
181
221
30
371
45
52£
3,500
81
13
171
22
26
35
44
52 £
61
4,000
10
15
20
25
30
40
50
60
70
4,500
114
17
22J
28
34
45
57
69
78
5,000
121
19
26
31
371
50
621
75
87
DRIVING POWER OF DOUBLE BELTS.
Speed in
Feet per
Minute.
Width of Belts in Inches.
6
8
10
12
14
16
18
20
24
H. P.
H. P.
H. P.
H. P
H. P.
H. P.
H. P.
H. P
H. P.
400
44
51
74
84
10
H4
13
144
174
600
61
81
11
13
15
174
194
22
26
800
«!
Hi
141
174
204
23
26
29
344
1,000
11
14J
184
214
254
29
324
36
434
1,200
13
171
22
26
304
344
39
44
524
1,500
164
211
274
324
38
434
49
544
654
1,800
191
26
321
39
454
52
59
654
784
2,000
2l|
29
361
434
504
58
654
724
87
2,400
26
341
44
524
604
694
784
88
105
2,800
801
401
51
61
71
81
914
102
122
3.000
32 L
431
541
654
76
874
98
108
131
3,500
38
501
634
76
89
101
114
127
153
4,000
43^
584
721
87
101
116
131
145
174
4,500
49
65
82
98
114
131
147
163
196
5,000
54£
72|
91
109
127
145
163
182
218
HANDBOOK ON ENGINEERING. 797
Example. — Required the width of a single belt, the velocity of
which is to be 1,500 feet per minute ; it has to transmit 10 horse-
power, the diameter of the smaller drum being four feet with five
feet of its circumference in contact with the belt.
33,000 x 10 equal 330,000, divided by 1,500 equal 220, divided
by 5 equal 44, divided by 6 equal 1\ inches, the required width of
belt.
Directions for calculating the number of horse power which a
belt will transmit. Divide the number of square inches of belt in
contact with the pulley by two ; multiply this quotient by the
velocity of the belt in feet per minute ; again we divide the total
by 33,000 and the quotient is the number of horse-power.
Explanations. — The early division by two is to obtain the
number of pounds raised one foot high per minute, half a pound
being allowed to each square inch of belting in contact with the
pulley.
Example. — A six-inch single belt is being moved with a
velocity of 1,200 feet per minute, with four feet of its length in
contact with a three-foot drum. Required the horse-power.
6x48 equal 288, divided by 2 equal 144 x 1,200 equal 172,-
800, divided by 33,000 equal, say, 5J horse-power.
It is safe to reckon that a double belt will do half as much
work again as a single one.
Hints to users of belts. — 1. Horizontal, inclined and long
belts give a much better effect than vertical and short belts.
2. Short belts require to be tighter than long ones. A long
belt working horizontally increases the grip by its own weight.
3. If there is too great a distance between the pulleys, the
weight of the belt will produce a heavy sag, drawing so hard on
the shaft as to cause great friction at the bearings ; while, at the
same time, the belt will have an unsteady motion, injurious to
itself and to the machinery.
4. Care should be taken to let the belts run free and easy, so
798 HANDBOOK ON ENGINEERING.
as to prevent the tearing out of the lace holes at the lap ; it also
prevents the rapid wear of the metal bearings.
5. It is asserted that the grain side of a belt put next to the
pulley will drive 30 per cent more than the flesh side.
6. To obtain a greater amount of power from the belts the pul-
leys may be covered with leather ; this will allow the belts to run
very slack and give 25 per cent more durability.
7. Leather belts should be well protected against water, oil and
even steam and other moisture.
8. In putting on a belt, be sure that the joints run with the
pulleys, and not against them out.
9. In punching a belt for lacing, it is desirable to use an oval
punch, the larger diameter of the punch being, parallel with the
belt, so as to cut out as little of the effective section of the leather
as possible.
10. Begin to lace in the center of the belt and take care to keep
the ends exactly in line and to lace both sides with equal tight-
ness. The lacing should not be crossed on the side of the belt that
runs next the pulley. Thin but strong laces only should be used.
11. It is desirable to locate the shafting and machinery so that
belts shall run off from each other in opposite directions, as this
arrangement will relieve the bearings from the friction that would
result where the belts all pull one way on the shaft.
12. If possible, the machinery should be so planned that the
direction of the belt motion shall be from the top of the driving to
the top of the driven pulley.
13. Never overload a belt.
14. A careful attention will make a belt last many years which
through neglect might not last one.
DIRECTIONS FOR ADSUSTINd BELTING.
In lacing-, cut the ends perfectly square, else the belt will
stretch unevenly. Make two rows of holes in each end ; put the
HANDBOOK ON ENGINEERING.
799
ends together and lace with lace leather, as shown in Figs. 342
and 343. For wide belts, in addition, put a thin piece of leather or
Figs 342 and 843. Showing laced joint.
rubber on the back to strengthen the joint, equal in length to the
width of the belt, and sew or rivet it to the belt. In putting on
belting, it should be stretched as, tight as possible, and with wide
belts, this can be done best by the use of belt clamps.
HORSE POWER OF BELTING.
To ascertain horse-power which belts will transmit, multiply
width of 'belt ,by diameter of pulley in inches, by revolutions
of pulley per minute, by number in table corresponding to the
pull the belt can exert per inch of width.
Example. — 10" single horizontal belt, 36" pulley, 200 revolu-
tions, pull taken at501bs.
10" x 36" x 200 x 0.0004 = 28.8 horse-power.
The pulls which belts 1" witle will transmit are as follows : —
Constant.
Single horizontal belts (pulley same diameter) 50 Ibs. .0004
Double tfc " ' " ' " " 100 kt .0008
Single vertical " " " " 40 ' .00032
Double " " " " " 60 4 .0005
Single belts (large to very small pulleys) . 10 ' .0001
Double " *« '" " . 15 4 .00012
Quarter twist, single belts . . . 0 . . 25 ' .0002
" " double " • „ 40 ' -00032
800 HANDBOOK ON ENGINEERING.
CHAPTER XXVIII.
CAPACITY OF AIR COHPRESSORS.
To ascertain the capacity of an air compressor in cubic feet of
free air per minute, the common practice is to multiply the area
of the intake cylinder by the feet of piston travel per minute.
The free air capacity of the compressor, divided by the number
of atmospheres, will give the volume of compressed air per
minute. To ascertain the number of atmospheres at any given
pressure, add 15 Ibs. to the gauge pressure ; divide this sum by
15 and the result will be the number of atmospheres. The above
method of calculation, however, is only theoretical and these
results are never obtained in actual practice, even with com-
pressors of the very best design working under the most favor-
able conditions obtainable. Allowances should be made for
losses of various kinds, the principal losses being due to clear-
ance spaces, but in machines of poor design and construction
other losses occur through imperfect cooling, leakages past the
piston and through the discharge valves, insufficient area and
improper working of inlet valves, etc. In practice there are com-
pressors where losses through imperfections and improper working
conditions range from 15 to 25 per cent, while und-er favorable
conditions and with the average compressor, the loss averages
from 8 to 12 per cent. So that to get sufficiently accurate
results in finding capacity of the compressor, subtract 12 per
cent from above computation, which gives nearly accurate
figures. The following table will be found useful for quickly
ascertaining the capacity of an air compressor, also to find the
cubical contents of any cylinder, receiver, etc. The first column
HANDBOOK ON ENGINEERING.
801
is the diam. of cylinder in inches. The second shows the contents
in cubic feet, for each foot in length.
Contents of a Cylinder in Cubic Feet for Each Foot
in Length.
Diam.
Inches.
Cubic
Contents.
Diam.
Inches.
Cubic
Contents.
Diam.
Inches.
Cubic
Contents.
• OQ
g CD
I A
51
Cubic
Contents.
Diam.
Inches
Cubic
Contents.
1
.0055
6
.1963
11
.6600
20
2.182
36
7.069
«
.0085
«
.2130
Hi
.6903
204
2.292
37
7.468
ij
.0123
6i
.2305
U4
.7213
21
2.405
38
7.886
1|
.0168
.61
.2485
ill
.7530
214
2.521
39
8.296
2
.0218
7
.2673
12
.7854
22
2.640
40
8.728
2i
.0276
7*
.2868
12*
.8523
224
2.761
41
9.168
2*
.0341
74
.3068
13
.9218
23
2.885
42
9.620
2|
.0413
7|
.3275
13J
.9940
234
2.885
43
10.084
3
.0401
8
.3490
14
1.069
24
3.012
44
10.560
8*
.0576
8*
.3713
i«
1.147
25
3.142
45
11.044
3£
.0668
84
.3940
15
1.227
26
3.400
46
11.540
8}
.0767
8|
.4175
15J
1.310
27
3.687
47
12.048
4
.0873
9
.4418
16
.396
28
3.976
48
12.566
«
.0985
9*
.4668
164
.485
29
4.587
f
*l
.1105
n
.4923
17
.576
30
4.909
4|
.1231
9|
.5185
174
.670
31
5.241
5
.1364
10
.5455
18
.767
32
5.585
-5i
.1503
IQi
.5730
184
.867
33
5.940
*S
.1650
10£
.6013
19
.969
34
6.305
5|
.1803
lOf
.6303
19^
2.074
35
5.681
To find the capacity of an air-cylinder, multiply the figures in
the second column by the piston travel in feet per minute. This
applies to double-acting air cylinders. In the case of single-
acting air cylinders, the result should be divided by 2.
•
THE McKIERMAN DRILL COMPANY'S AIR COMPRESSOR.
The air -cylinder and water-jacket are one complete casting.
The heads are made with hoods and provision made for cool air
in-take. "
51
802
HANDBOOK ON ENGINEERING.
The atmosphere valves ste bronze, of poppet form. There-
fore, there is no vacuum and the cylinder fills absolutely with free
air. The valves are closed by mechanical means.
The discharge valves are self-acting, are made of bronze. All
of them are free to inspection without removal or disturbance of
other parts.
The cooling apparatus, or heat-preventing device, is extremely
effective. Water jacket completely surrounds the cylinder, water
Fig. 344. Horizontal single stage compressor.
is forced to wash the walls and is kept in rapid motion from bot-
tom to top, from end to end, absorbing heat rapidly. It enters
the jacket at bottom, flows from end to end, around partitions,
back and forth and up. Follows natural laws in absorbing,
retaining and dispelling the heat of air.
Regulation of pressure and speed is entirely automatic. The
regulating device is one of those in which the air weighs the
steam admitted to tte cylinder. Throttle may be thrown wide
open at start, then the regulator takes absolute control, governing
the speed from highest to lowest rate, varying the speed for
HANDBOOK ON ENGINEERING.
803
variable amounts of air which may be required and in such man-
ner as to keep the pressure constant.
D ui SBCTKM. A<«-CiiiHUi»-ENo ELE.ATIO*.
> SuovfiMi Y*iv«».
Fig. 345. The Bennett automatic air compressor.
Fig. 346. Iiigersoll-Sergeaiit air compressor.
804
HANDBOOK ON ENGINEERING.
INGERSOLL-SERGEANT AIR COMPRESSOR.
This engine, illustrated in Fig. 346, is fitted with Inger-
soll-Sergeant air compressor cylinders, and in connection with
the Pohle air lift system, has double the supply of water,
using only one-half the fuel previously required. The steam
cylinders are of the duplex Corliss condensing type and con-
nected tandem, and on each side are two Ingersoll-Sergeant air
cylinders and two Conover water cylinders. When the engine
Fig. 347. Sectional view of air cylinder with vertical lift valves,
class "E" and "F" compressors.
is in operation, the air cylinders raise the water by the Pohle air
lift system, from the wells to a tank at the surface, and from
there it is taken by the water cylinders and forced to the stand-
pipe. The cost of this combination compares favorably with the
old plan of using separate compressors and water pumps, each
with their own steam cylinders, and the saving in attendance,
friction and foundation commends its use. The engines run at a
fixed moderate speed and the regulation of the air and water is
effected by passing the water from suction to discharge when the
tank is too low, and by mechanically unloading the air cylinders
HANDBOOK ON ENGINEERING. 805
with a pressure regulator when the tank is too full. The regula-
tion is done mechanically, with floats at the top and bottom of the
receiving tank. This combination can also be furnished with
straight line compressors ; the advantage of the duplex is that
should it be necessary, the one side of the engine can be discon-
nected and the other side made to do the work.
As will be seen, the inlet valves, which are on the lower side of
the cylinder are offset, thus preventing their being sucked into
the cylinder and wrecking the compressor. They are made out
of a solid piece of steel and are extremely durable, because they
are placed vertically, work in a bath of oil and do not slide on
their seats. Both the inlet and discharge valves, being in
the cylinder, allow the heads to be thoroughly water- jacketed,
and .this is an important feature when it is remembered that
the heat of compression is greatest at the end of the stroke.
The cylinder is, therefore, completely water- jacketed. The
valves are arranged so that the air can be taken from outside of
the engine room, which increases the efficiency of the machine 8
to 15 per cent, and are easily accessible.
The two inlet valves are located in the piston, and, with
the tube, are carried back and forth with the piston. The valve
on that face of the piston which is toward the direction of move-
ment is closed, while the one on the other face is open. This is
exactly as it should be in order to force out the compressed air
from one end of the cylinder while taking in the free air at the
other ; when the piston has reached the end of its travel there is,
of course, a complete stop while the engine is passing the center,
and an immediate start in the other direction. The valve which
was open immediately closes „ There is no reason for its remain-
ing open any longer, and it closes at exactly the right time, its
own weight being all that is necessary to move it. The valve
on the other side is left behind by the piston and the free air
is admitted to that end of the cylinder for compression on the
806
HANDBOOK ON ENGINEERING.
return stroke. No springs are used, and there is none of the
throttling of the incoming air, and none of the clattering or
hammering so noticeable with poppet-valves. As there is nothing
to make the valve move faster than the piston, it stays behind until
the piston stops, leaving the port wide open for the admission
DETAILS OF PISTON INLET AIR CYLINDER.
A.— CircuTatfng Water Jnlet, D.— Oil Hole for Automatic Oil Cup. G.— Piston Inlet Vair
B.—Circulating Water Outlet. K— Air In let (through piston in let pipe). H.— Discharge Valve,
C.-Wat6r Jacket Drain Pipe. F.— Air Discharge (showi&g flange); }.— Water Jacket.
Fig. 348. Sectional view of Ingersoll-Sargeant single
compressor.
of air. It is well known that while the fly-wheel and, of course,
the crank, rotate at a uniform speed, the movement of the piston
is not uniform, but gradually increases in speed from the start
till the crank has reached half -stroke, when it gradually slows up
till the crank is on the center, and at this moment of full stop
the valve gently slides to its seat.
HANDBOOK ON ENGINEERING.
807
Fig. 349. The Pohle air lift system.
808 HANDBOOK ON ENGINEERING.
The illustrations on page 807 show the method of pumping
water by air. A compressor in connection with the air-lift sys-
tem pumps the water by direct air pressure. The pump con-
sists of a water pipe and an air pipe, the latter discharging the
air into the former at its bottom, through a specially designed
foot-piece. The natural levity of the air compared with the
water, causes it to rise and, in rising, to carry the water with it
in the form of successive pistons, following one another. This
system of pumping has found a large range of application and is
of peculiar service in connection with deep well pumping. For
this purpose, the absence of mechanical parts many feet below
the surface, offers a commanding advantage. Method No. 1 and
No. 2 are almost alike, consisting in placing the air and water
pipes alongside of one another in the well, connecting them at
the bottom with an end piece. Method No. 3 consists in placing
a water discharge pipe into the well ; the air passing down into
the well through the annular space between the well casing and
the water pipe. Method No. 4 consists in using {he well casing
as the water discharge pipe, and simply putting an air pipe down
into the well, with a specially designed foot-piece attached at the
bottom through which the air escapes.
Air Lift Formulas.
Height of Lift
For maximum economy ^ s^mersioiT should eQual °-5
125 X Cu. Ft. Free Air
Gallons of water raised per Mm. = -
Cubic feet of free air per Min. =
Lift in feet above water level =
Lift in Feet
Gals, raised per Min. X Lift
125
125 X Cu. Ft. Free Air
Gals, per Min.
Air press, required to start lift = Submersion + Lift X -*34 4- 5
Ratio of areas of water pipe to air pipe = 6 to 1
HANDBOOK ON ENGINEERING. 809
CHAPTER XXVIII. — CONTINUED.
THE METRIC SYSTEM.
It frequently happens that an engineer, in reading books and
papers devoted to steam engineering, is confronted with terms
taken from the metric system, which he does not understand.
We present a few of the metric system terms most commonly
used, with their values in feet and inches, also, gallons, quarts,
pounds, tons, etc.
A French meter is 39.37079 inches long, or a little less than
39| inches. It is generally taken, — for convenience in fig
uring, — at 39.37 inches.
1 decimeter is -^ of a meter, or, 3.937 inches nearly.
1 centimeter is T^ " " " .3937 " "
1 millimeter is ^fa " " " .03937 " "
ALSO.
1 decameter equals 10 meters, or, 32.80 feet nearly.
1 hectometer " 100 " " 328 " "
1 kilometer " 1000 " " 3280 " "
APPLICATION.
1. An engine shaft is 5 meters long, what is its length in feet
and inches? Ans. 16 ft. 4£ ins. nearly.
qq 07 \s K
Operation J °"'°'* ° = 16.4 ft. nearly.
MM
2. An engine cylinder is 10.3 decimeters in diameter, ho^i
much is this in inches? Ans. 40J ins. nearly
Operation: 3.937 X 10.3 = 40.55 ins. nearly.
810 HANDBOOK ON ENGINEERING.
3. A piston-rod is 8.7 centimeters in diameter, how much is
this in inches? Ans. 3| ins. nearly.
Operation : -3937 X 8.7 .= 3.42 ins. nearly.
4. A chimney is 5.1 decameters tall, how much is this in feet
and inches? Ans. 167 ft. 3 ins. nearly.
Operation : 32.80 X 5.1 = 167.28 ft.
5. How many miles are there in 30.2 kilometers?
Ans. 18-j?^ miles nearly.
Operation : There are 5280 ft. in a mile.
Then, 828° X 80'2 =, 18.7 miles.
5280
6. A valve has 2 millimeters lead, how much is this in frac-
tional parts of an inch? Ans. -f-^ in. nearly.
Operation: .03937 X 2 = .07874.
And, .07874 X 64 = /¥ nearly.
7. How many square feet in a circle whose diameter is one
meter? Ans. 8£ nearly.
n 39,37 X 39.37 X .7854
Operation : — — = 8.45.
144
8. The cylinder clearance is 1.1 cubic decimeter, how many
cubic inches in the clearance? Ans. 67 nearly.
Operation: 3.937 X 3.937 X 3.937 X 1.1 = 67.12+
ALSO.
1 gramme equals 15.433 grains, or 1 ounce nearly.
1 kilogramme equals 2.2047 pounds avoirdupois.
1 tonne equals 1.1024 tons of 2000 Ibs.
ALSO.
1 litre equals 1.0566 quarts.
HANDBOOK ON ENGINEERING. 811
CONSEQUENTLY,
1 U. S. gallon equals 3.79 litres nearly.
1 U. S. pint equals .4732 litres nearly.
1. A main shaft weighs 800 kilogrammes, how much is this in
avoirdupois pounds? Ans. 1763J Ibs. nearly.
Operation : 2.2047 X 800 = 1763.76.
2. An engine weighs 12 tonnes, how much is this in U. S. tons
of 2000 Ibs. each? Ans. 13 J tons nearly.
Operation: 1.1024 X 12 = 13.2288.
3. A tank contains 9000 litres of water, how much is this in
U. S. gallons? Ans. 2377.35 galls.
1.0566 X 9000
Operation: T~ — Because 4 quarts equal 1 gallon.
THERMOMETERS.
In the U« S* the Fahrenheit scale is the one in most common
use, although in our laboratories and for scientific purposes it is
displaced by the Reaumer and Centigrade scales. Fahrenheit's
scale marks the boiling point by 212 degrees, and the freezing
point by 32 degrees above zero.
The Reaumer scale marks the boiling point by 80 degrees, and
the freezing point by zero.
The Centigrade, or Celsius scale, marks the boiling point by
100 degrees, and the freezing point by zero. So that, reckoning
from the freezing point of Fahrenheit, 180 degrees Fah. equal
80 degrees Reaumer, and 100 degrees Centigrade. Bearing in
mind that Fahrenheit's zero is 32 degrees below the freezing point,
one scale may readily be converted into another.
To convert degs. of Reaumer into those of Fah.
Rule* — Multiply by 9, divide by 4, and add 32.
812 HANDBOOK ON ENGINEERING.
Example: 80 degs. Reaumer equals how many degs. Fah?
Ans. 212.
Operation: 80 X 9 = 720.
720
And, 1— — 180. Then, 180 + 32 =212.
4
To convert the degs. of Centigrade into those of Fahrenheit.
Rule* — Multiply by 9, divide by 5, and add 32.
Example: 100 degs. Centigrade equal how many degs. Fah.?
Ans. 212.
Operation: 100X9 =
And, 180.
o
Then, 180+32 = 212.
So, also, 3 degs. Centigrade equal 37.2 degs. Fahrenheit.
Thus; 3X9 = 27. And, £i =5.2. Then, 5.2 + 32 =37.2.
ROPE TRANSMISSION.
There are two systems of rope transmission, the English,
or multiple-rope system, and the American or continuous wound
rope system in which the necessary adhesion of rope to sheave is
obtained by a tension carriage. We will treat of the American sys-
tem only, as it is almost universally used in this country to the
exclusion of the other. One of the most common mistakes is to
lead the rope to the tension carriage from the tight or pulling
side of the drive, and putting on an abnormal amount of tension
weight in a vain endeavor to take out the slack. Under the enor-
mous strain of such an arrangement the rope wears out very rap-
idly, and more frequently parts at the splice. It is desirable in
all cases of rope transmission to so arrange the drive that the
slack side of the rope shall be on the upper part of the pulley
HANDBOOK ON ENGINEERING.
813
thus increasing the arc of contact, as the two sides will then
approach each other when in motion. The working strain in
pounds on a rope should not exceed 200 times the square of the
diameter of the rope. The speed of the rope should not exceed
5500 feet per minute, and this speed gives the best results in
H. P. The practical limit to the number of ropes for one sheave
cannot be definitely named. The only limiting condition is the
ability of the tension carriage to keep up the slack and when the
number of ropes exceeds the capacity of one carriage, a second
may be added and the drive made double. Diameters of sheaves
should not be less than 40 diameters of the rope, and 50 to 60
diameters are advisable, being justified by greater length of life
of the rope.
HORSE POWER TRANSfllTTED BY ROPES.
The following table gives the horse-power transmitted by a
single manila rope when the arc of contact is not less than 165
degrees, and the tension not greater than 200 times the square of
the diameter of the rope.
Velocity
Diameter of Rope.
of Kope in
Feet per
Minute.
5Is"
3/4"
1"
ir
IV
11"
2"
1000
1.24
2.25
3.57
5.59
8.02
10.85
14.20
2000
2.70
3.84
6.84
10.68
15.39
20.93
27.36
2500
3.30
4.71
8.38
13.10
18.86
25.66
33.54
3000
3.83
5.46
9.80
15.39
21.87
29.74
38.88
3500
4.30
6.23
11.09
17.33
24.94
34.03
44.35
4000
4.74
6.83
12.15
18.98
27.33
37.17
48.59
4500
5.01
7.24
12.89
20.15
29.00
39.45
51.57
5000
5.20
7.47
13.29
20.76
29.89
40.65
53.15
5500
5.29
7.60
13.53
21.14
30.43
41.39
54.11
6000
5.08
7.32
13.10
20.36
29.32
39.77
52.12
6500
4.74
6.83
12.13
19.00
27.34
37.21
48.63
7000
4.12
5.93
10.54
16.47
23.72
32.26
42.18
7500
3.25
4.67
8.32
13.00
18.73
25.42
33.23
814
HANDBOOK ON ENGINEERING.
TO TEST THE PURITY OF ROPE.
A simple test for the purity of manila or sisal rope is as fol-
lows : —
Take some of the loose fiber and roll it into balls and burn
them completely to ashes, and, if the rope is pure manila, the ash
will be a dull grayish black. If the rope be made from sisal the
ash will be a whitish gray, and if the rope is made from a com-
bination of manila and sisal the ash will be of a mixed color.
WIRE ROPE DATA.
HOISTING ROPE.
PATENT FLATTENED STRAND.
1
H
4
l|
2
2*
HERCU-
LES.
13.5
22.5
32
40.5
56
67
84
124
168
211
260
CRUCI-
BLE.
I!
5-2
24
30
50"
59J
86
121
144
182
9
15
21
29
38
47
56
81
109
140
176
4
6
9
13
17
21
28
40
54
66
75
19 WIRE ROUND STRAND.
03
HEKCU-
LES.
CKUCI- |
BLE.
IRON.
w
•Q
oo
Dd
O
fl
0
fl .
o
fl .
0
**'
^£
£5
o .
22
£ fl
M
»s
5 go
AS
•2 a-
&•§
fl"s
B
ga
SI
IP
1"
IP"
03 *
IH
cu
IP
1
16J
"5
12.5
20
11
14
8.8
13 6
8
12
6
1
30
29
18
19.4
16
9
1
39
36
23
26
20
13
1
a
50
60
30
38
34
42
26
33
17
21
ij
71
77
46
50
40
25
Ji
103
113
66
72
57
36
11
147
157
93
96
80
48
2
172
191
111
124
92
62
2*
218
238 1
142
156
117
74
HANDBOOK ON ENGINEERING. 815
ALTERNATING CURRENT MACHINERY.
CHAPTER XXIX.
THE PRINCIPLES OF ALTERNATING CURRENTS.
The actions of alternating currents are not so easily under-
stood as those of continuous currents and to most men not
familiar with the subject they appear to be a mystery that can
only be fathomed by those who are well versed in the higher
branches of mathematics. As a matter of fact, when we once
get on the right track, alternating current actions present no more
difficulty to the man of fair mental ability, who is willing to work
to learn, than the more simple continuous current actions. What
makes alternating currents difficult to understand is, that in con-
sequence of the ever-changing strength of the current, inductive
actions are developed that react upon the current itself so that it
becomes impossible to determine the magnitude of the current,
the e.m.f . or the energy flowing in the circuit by the simple rules
used for continuous currents. As the strength of an alternating
current is constantly changing the magnitude of the inductive
actions is constantly changing, and this fact further increases
the difficulty of the subject.
In studying the principles of continuous currents we learn that
when a conductor is moved across a magnetic field an e.m.f. is
developed in it ; arid thus we understand the operation of a gen-
erator, as we know that when the armature revolves, it carries
the conductors upon its surface through the magnetic flux that
issued from the poles of the field. We further learn that inas-
816 HANDBOOK ON ENGINEERING.
much as the magnitude of the e.m.f . is increased by increasing
the strength of the magnetic flux, or the number of conductors
on the armature or the velocity of rotation', that one or all these
factors must be increased to increase the voltage. Thus we come
to consider that to induce a high e.m.f. we must have a strong
magnetic field. Now one of the first things that the student of
alternating currents finds out is that in an alternating current
circuit, the strongest e.m.f. induced by the action of the current
itself, comes at the very time when the magnetic field is the
weakest, and this appears to him to completely upset all the
principles of continuous currents ; but in reality it does not.
To be able to get over this stumbling block successfully it is
necessary to realize that the magnitude of the e.m.f. induced in
a conductor that is moved through a magnetic field is not depend-
ent upon the strength of the magnetic field, but upon the rate,
or rapidity with which the conductor cuts the magnetic flux.
Now it so happens that in a continuous current generator, the
rapidity with which the conductors cut the magnetic flux increases
with increase in the strength of the magnetic field, or the velocity
of rotation, and thus it comes about that in this case, the increase
in the induced e.m.f. appears to be due to increase in armature
velocity or field strength when in reality it is due to increase in
the rate at which the conductors cut through the magnetic flux.
The magnetic flux developed by an alternating current alternates
precisely as the current does, and, as will be clearly explained
presently, this magnetic flux cuts through any conductors in its
path, and the rate at which it cuts them is the greatest at the in-
stant when the direction of the flux is changing, and this is the
instant when the flux is nothing, so that the e.m.f. induced by
the magnetic flux developed by an alternating current is the
greatest at the very instant when the magnetic field has a zero
strength. The foregoing facts can be made more clear by refer-
ence to diagrams.
HANDBOOK ON ENGINEERING.
817
Fig-* 350 is a simple diagram that can be taken to represent a gen-
erator, either of continuous or alternating currents. The dark circles
A A, B B and G G represent the sides of three loops of wire
which may be regarded as wound upon the surface of an armature.
Figs. 350 and 851. Principle of electric generator.
The vertical lines represent a magnetic flux passing between the
field poles Pand N. If the armature upon which the three loops
are mounted is rotated, e.m.fs., will be induced in each one of
the loops, but the magnitude of these e.m.fs. will not be the
same. If we take the instant when the loops are in the position
shown, the e.m.f . in A A will be zero, while that in G G will be
the highest and that in B B will be seven-tenths of that in G G.
Now all these coils rotate at the same velocity being mounted upon
the same armature, and all move through a magnetic field of the
same strength, yet, in A A no e.m.f. is developed while in B B the
e.m.f. is only seven-tenths of that developed in G (7. The
question is, why this difference? The answer is, that while loops
A A move just as fast as G G they do not cut the magnetic flux
52
818 HANDBOOK ON ENGINEERING.
because they are moving in a direction parallel with the lines of
force, the vertical lines, hence, the rate at which the magnetic
flux is cut by them is zero, therefore the e.m.f . developed is zero.
In B B the e.m.f. is seven-tenths of that developed in G (7,
because the sides of this loop are moving in a direction that is
not directly across the magnetic flux, but forms an angle of 45
degrees with it, so that their actual velocity in a direction parallel
with A A is seven-tenths of the velocity of G 0 in. this same
direction.
From the foregoing it will be seen that when we get down to
a close examination of Fig. 350 we find that the magnitude of
the e.m.f. developed in the several loops is directly proportional
to the rate at which the sides of the loop cut through the
magnetic flux.
Let us now consider Fig. 35 1. In this diagram, circle A repre-
sents a wire, seen end on, through which an alternating current is
flowing. An alternating current is one that flows first in one
direction, and then in the opposite direction, and continues
changing the direction in which it flows at regular intervals of
time. Now it is self-evident that if a current flows through a
wire in alternate directions, it must stop flowing in one direction
before it can flow in the opposite direction, that is at the instant
when the direction of flow is changing, there can be no current.
Such being the case, when the current begins to flow in either
direction, it must increase in strength gradually up to a certain
point, and then begin to decrease, so as to reduce to nothing at
the instant when the direction of flow changes. As is explained
in the section on continuous currents, when a current of elec-
tricity flows through a wire, a magnetic flux is developed around
the wire and this can be represented by lines of force drawn in
the form of circles, as in Fig. 351. If there is no current flowing
through the wire there is no magnetic flux, therefore, if we
consider the instant when a current begins to flow, we can imagine
HANDBOOK ON ENGINEERING. . 819
that at this instant the magnetic flux begins to expand outward
from the wire, and since the circular lines are drawn to represent
this flux we can assume that these expand outward, like the rip-
ples on the surface of a pond when a pebble is thrown into the
water. So long as the current flowing through the wire increases
in strength, just so long will the magnetic circles of force expand,
but when the current reaches its greatest strength the circular
lines of force will become stationary, and will remain so if the
current remains at its maximum strength ; but if the current
begins to reduce in strength as soon as it reaches its maximum,
then the circular lines of force will begin to contract immediately
after they stop expanding, just as a swing will begin to move
backward the instant it stops swinging forward.
If the circles B and G in Fig. 351 represent two wires parallel
with A, it is evident that the magnetic circles of force when they
move outward from A will cut through B and C in one direction,
and when they contract back upon A they will cut through these
two wires in the opposite direction. When these circular lines
of force cut through the wires B G they will induces. m.fs. in the
latter, and if these e.m.fs. are positive when the lines of force ex-
pand, they will be negative when the lines contract. When the
current reaches its maximum strength and the circular lines of
force become stationary for an instant, they will not cut the wires
B and C and at this instant there will be no e.m.f. induced in
these wires. Now the circular lines of force become stationary
at the very instant when the current flowing through the wire
reaches its greatest strength and is on the point of reducing, so
that at this instant the e.m.f. induced in the wires B and C is zero
The highest e.m.f. induced in B and C occurs at the instant
when the current flowing through A is changing its direction, or, in
other words, at the instant when there is no current. Just
before the current reduces to zero, the circular lines of force
are contracting upon wire A, and the instant after the cur-
820 HANDBOOK ON ENGINEERING.
rent reduces to zero and changes its direction, tlKse lin?s
of force will be expanding so that in the first case the lines
of force will sweep over wires B and 0 in a direction toward
A, and in the second case they will sweep over these wires in a
direction away from A. From this fact it might be inferred that
the e.m.f. induced in the two cases would be in opposite direc-
tions, but this is not so, owing to the fact that the lines of force
change in direction when the current changes, so that if while
contracting they are directed clockwise, as soon as they begin to
expand they will be directed counter clockwise. As a result of
this change in the direction of the lines of force when they change
from contracting to expanding, the e.m.fs. induced in B and C
are in the same direction before the lines stop contracting and
after they begin to expand. The circular lines of force stop con-
tracting and begin to expand at the same instant, so that the
inductive action developed by the contracting lines is followed up
without a break by the expanding lines. In alternating currents
such as are actually used in practice, the rate at which the
strength of the current changes is the greatest when it is just
beginning to grow, and when it is reduced almost to zero, and on
this account the highest e.m.f. induced in wires B and G occurs
at the instant when the direction of the current is changing, that
is, when the current is zero. Alternating currents can be de-
veloped in which the rate of change in the current is not the
greatest just when they begin to grow and when they are reduced
nearly to zero and with such currents the highest e.m.f. induced
in wires B and 0 would not come at the instant when the current
is zero, but would come at the instants when the change in the
current is the most rapid.
In every kind of alternating current, however, the instant when
the e.m.f. induced in B and C is zero is the instant when the
current reaches the maximum value, and begins to decrease,
for this is the only instant when the circular lines of force are
HANDBOOK ON ENGINEERING.
821
immovable ; it being the instant when they are about to change
from expanding to contracting, while still flowing in the same
direction. When the current becomes zero, the lines of force
change from contracting to expanding but at this instant they
also change their direction so that the new expanding circular
lines of force take up the work if inducing an e.m.f. in the wires
B and (7 at the very point where the contracting lines leave off.
The circular lines of force developed by the current flowing
in A, cut through this wire as well as through B and (7, hence,
they induce an e.m.f. in A; that is an alternating current induces
an e.m.f. in its own circuit as well as in adjoining circuits. The
action upon adjoining wires is called mutual induction, and that
upon its own wire is called self-induction. These e.m.fs. act in
a direction opposite to that of the current that induces them.
The relations between alternating currents and e.m.fs. can be
shown by means of diagrams, the simplest of which are con*
Fig. 352. Relation between current and electro- motive force*
structed in the manner shown in Fig. 352. In diagrams of this
type the line 0 T represents time, thus if a point is assumed to
move from 0 in the direction of T at a uniform velocity of say
one foot per second, then a length of one inch will represent an
interval of time of one-twelfth of a second. Distances measured
in the vertical direction, along 0 S represent the magnitude of
822 HANDBOOK ON ENGINEERING.
the current or e.m.f. Positive currents and e.m.f. are indicated
above the time line 0 T and negative currents and e.m.fs. below
this line. Thus the wave line A A A can represent an alternating
current or e.m.f. or an alternating magnetic flax. This curve it
will be seen is above 0 T from 0 to 6, and below 0 Tfrom b
to d, being again above from d to T. The two sections of the
curve from 0 to d constitute one cycle, or two alternations. The
portions between the lines 0 a, a 6, b c, c d are called quarter
cycles or quarter periods. The time from O to d is called one
period, and if this is equal to one-tenth of the distance that
represents one second, then there are ten periods to one second.
This fact is indicated by saying that the periodicity of the current
is ten, or that its frequency is ten. The frequency of alternating
currents in common use ranges between 20 and 130.
The curve A A in Fig. 352 represents a current or e.m.f. that
increases or decreases at a certain rate, but for a current varying
at some other rate it would be necessary to use a curve of differ-
ent shape to correctly represent it. Thus if the current does not
increase so fast when rising from the zero value, but increases
faster when nearing its maximum value we will require a modifica-
tion of the curve such as is indicated by B, in which the slope is
more gradual on the start, and near the middle becomes more
steep. If on the other hand the current increases more rapidly
on the start, and less rapidly as it approaches the maximum value,
we will have to use a curve something like C which is steeper at
the ends and flatter at the middle.
The actual form of curve required to correctly represent an
alternating current depends upon the rate at which the current
varies, and this rate depends upon the construction of the machine
in which it is generated. For the purpose of simplifying calcula-
tions it is necessary to assume that the rate of variation of a cur-
rent is such that it can be represented in a diagram such as Fig*
352 by some form of curve that can be drawn in accordance with
HANDBOOK ON ENGINEERING.
823
some fixed rule. The curve A A is of circular form, but there
are few alternating current generators that develop currents that
such a curve can properly represent.
If a current alternates in equal intervals of time, and the rate
of variation is the same when it is flowing negatively as when it is
flowing positively, then it can be represented by a curve that is
of symmetrical construction, such as A A in which the intervals of
time 0 &, b d are equal and the curves above the line 0 T are of
the same shape as those below it. Such a current is called a
symmetrical periodic current, and it is the only kind with which we
have to do in practice. It can be readily understood, however,
that the current can be far from regular, that is, the time during
which it flows positively can be more or less than the time during
which it flows negatively, and the rate of variation in the two
0
&
Fig. 353. Irregular periodic curve.
instances can be different. The curves in Figs 353 and 354 illus-
trate currents of this kind. In Fig. 353 the positive impulses of
the current are longer than the negative, as is shown by the greater
length of lines 0 a, b c as compared with a b. It will also be
seen that the rate of variation is different as is indicated by the
difference in the form of the portions A A and B B of the
curve. In Fig. 354 the irregularity is still greater, as all the time
intervals Oa, a &, & c, c d, are different, as are also the portions
A B C D E of the curve.
824
HANDBOOK ON ENGINEERING.
The alternating currents developed by alternating current
generators have such a rate of variation that they can be repre-
sented in diagrams by means of what is known as a sine curve.
s
Tig. 354. Showing still greater irregularity.
Tnis curve is not a perfectly true representation of practical
alternating currents, but it comes so near to it that calculations
I M,sed upon the assumption that the sine curve represents the actual
a a,
ff
\
Fig. 355. Construction of sine curve.
variation, do not depart from the truth by more than two or three
per cent, and in some cases less than that. As the sine curve is
commonly used to represent alternating currents we will show
HANDBOOK ON ENGINEERING. 825
how it is constructed by the aid of Fig. 355. In this diagram dia-
metrical lines a b c are drawn on the circle B, dividing it into
any desired number of equal parts. A distance 0 T on the hor-
izontal line is divided into an equ^l number of equal parts and
perpendicular lines a a are drawn at these divisions. From the
points where the lines a b c cut the circle lines are drawn parallel
with 0 T as shown at e f g and the points where these cut the
corresponding perpendicular lines a a form points of the sine
curve A A. The distance O T can be made anything desired
without affecting the character of the curve, the only difference
being that if it is short the curve will be more pointed than if it
is long.
One reason why it is assumed that alternating currents vary
in accordance with a sine curve is that if the variation is at this
rate the e.m.f . induced by the magnetic flux developed by the
current will also vary in accordance with the sine curve, so that
the current, the magnetization and the induced e.m.f. can be rep-
resented by sine curves, and thus the process of calculating the
effect of the induced e.m.f. upon the strength of the current can
be greatly simplified.
By looking at Fig. 350 it can be seen at once that if the
loop A A is revolved at a uniform velocity, and the
magnetic field between the poles P and N is of uniform
strength at every point, the e.m.f. induced in A A will
vary in strict accordance with the variations of the sine
curve A A of Fig. 355, for in the position A A the e.m.f. will be
zero, and in position G C it will be the maximum, while in any in-
termediate position such as B B it will be equal to the actual velocity
of the sides of the loop measured in the direction parallel with
AA , and this velocity is equal to the distance of the side of the
loop from the horizontal line A A. Now the height of the sine
curve A A in Fig. 355 at any point is also equal to the distance from
the end of the corresponding line in circle B from the horizontal
826
HANDBOOK ON ENGINEERING.
line, that is, the distrance e e' from the horizontal line to the curve
is the same as the distance e e on the circle.
The complete sine curve from 0 to T is traced by following the
rotation of the radius of the circle through one complete revolu-
tion. On that account this distance 0 T is taken to represent one
revolution, and is divided into 360 degrees, the same as the
circle. Half the distance, or 0 d, is equal to 180 degrees, and
one-quarter the distance is 90. The vertical lines a a in Fig. 355
are 30 degrees apart.
The way in which sine curves are used to represent alternat-
ing currents and e.m.fs. is shown in Fig. 356. In this diagram,
a
Fig. 356. Manner of indicating alternating currents.
let the curve A represent an alternating current flowing through a
wire. As is fully explained in the foregoing, this current will
develop an alternating magnetic flux, and this flux will increase
and decrease as the current increases and decreases, that is, it
will keep in time with the current, or in step with it, as it is com-
monly expressed. Such being the case, the curve A can be used
to represent the magnetic flux as well as the current, providing
we assume a proper scale for both. Looking at the half circle to
the left of the figure, it will be seen that curve A is described by
HANDBOOK ON ENGINEERING. 827
a radius rotating around the middle circle. Remembering what was
said in connection with Fig. 351 as to the time relation between the
magnetic flux and the e.m.f . induced thereby, we will realize that
at the instant 0 when the flux is zero, the induced e.m.f. must
be at the maximum value, and it will act in opposition to the
e.m.f. that drives the current through the wire, hence, in the
diagram, it will have to be drawn below line 0 T. Let the maxi-
mum value of this induced e.m.f. be equal to 0 c, then for all
other values it will be correctly represented by the sine curve .B,
which is traced by the rotation of the radius of the inner circle.
At the instant of time 0, the magnetic flux is zero, hence the
radius of the middle circle from which curved is traced must be
in the direction of line 0 T. At this same instant the induced
e.m.f. is at the maximum value hence the radius that traces
curve B must be in the vertical position parallel with O c. From
this we see that in relation to time the curves A and B that repre-
sent the magnetic flux and the induced e.m.f. are one-quarter of
a cycle apart, that is the induced e.m.f. is 90 degrees behind the
magnetization, and also 90 degrees behind the current that flows
through, the wire.
No kind of electric current, whether continuous or alternating,
can flow through a circuit unless there is an e.m.f. to drive it,
and this e.m.f. must be sufficient to impel the current against
all resistances of any kind that it may encounter. The e.m.f.
that impels a current through an alternating current circuit is
called the impressed e.m.f. In Fig. 356 it is evident that the
impressed e.m.f. must be sufficient not only to overcome the
actual resistance that opposes the flow of the current represented
by curve -4, but also sufficient to overcome the opposing action of
the induced e.m.f. represented by curve B. Now the e.m.f.
required to overcome the resistance that opposed the flow of the
current can be represented by the curve -4, in precisely the same
828 HANDBOOK ON ENGINEERING.
way as this curve represents the magnetization ; hence, the curve
G which represents the impressed e.m.f. must at every point be
equal, in height, from the line 0 T, to the sum of the heights of the
curves A and B, when these two curves are on opposite sides
of 0 T, or to their difference when they are on the same side. At
the instant 0 it is clear that as the current is zero, the impressed
e.m.f. C must be of the value 0 c' to balance the induced e.m.f.
B for if it were not, there would be a current flowing negatively
under the influence of e.m.f. B. At any instant between O and
d, the impressed e.m.f. C must be equal to the sum A and B, that
is, the distance from G to the time line 0 T must be equal to the
distance between the curves ^4 B measured on the same vertical line.
At the instant d the induced e.m.f. is zero, hence the impressed
e.m.f. is equal to the distance of curve A above line 0 T. For
any interval of time between d and e, the impressed and the in-
duced e.m.fs. are acting together, so that the first named, that is,
curve (7, need only be equal to the difference between A and B.
By studying the diagram Fig. 356 it will be seen that the curve
(7, which represents the impressed e.m.f., is described by the
rotation of the radius of the outer circle at Z), and in order that
this e.m.f. may have the value of 0 cf at the instant 0, it is nec-
essary for the describing radius at this instant to be in the posi-
tion b. From this it will be seen that the impressed e.m.f. is not
in time with the current but in advance of it by a time interval
that is equal to the angle formed by the radius b with the line
0 T.
If two alternating currents, e.m.f. or magnetic fluxes are
in time with each other they are said to be in phase, but if they
are not in time they are out of phase. In Fig. 356 the current, the
impressed e.m.f. and the induced e.m.f. are out of phase with each
other. The impressed e.m.f. leads the current, and the latter
leads the induced e.m.f. This relation is also expressed by say
HANDBOOK ON ENGINEERING.
829
ing that the current lags behind the im-
pressed e.m.f. and the induced e.m.f.
lags behind the current. The current
and the impressed e.m.f. can never be
out of phase by an angle as great as 90
degrees, but the phase difference can be
any angle less than this. The induced
e.m.f. is always 90 degrees out of phase
with the current. The induced e.m.f.
in the circuit in which the current flows
is called the self-induction.
The relations between the impressed
e.m.f., the current and the self-induc-
tion both in magnitude and phase are
clearly shown in Fig. 357, which is
simply an enlarged view of the left side
of Fig. 356. The radius A of the outer
circle is the impressed e.m.f. The
radius B of the middle circle is the cur-
Fig. 357. Enlarged Yiew
of Fig. 356. rent, and the radius C of the inner
circle is the self-induction. The magnitude of any one of these
three quantities at any instant of time is equal to the distance
from the end of the line to the horizontal line. The radius B
which represents the current is on the horizontal line, hence the
current at the instant represented by the diagram is zero. The
self-induction C has a value at this instant equal to. the length of
the line, that is, it is at the maximum value, and as it is below
the horizontal line it is negative. The impressed e.m.f. A, has
the value of a a, and being above the horizontal line, it is positive.
The phase relation and also the magnitude of these quantities is
also shown in Fig. 358, which is constructed from Fig. 357 by remov-
ing the self-induction to the position of line a a. From Fig. 358 it
830
HANDBOOK ON ENGINEERING.
CURRENT.
can be seen that if we know two
of the quantities we can always
determine the other one by sim-
ply constructing a right angle
triangle.
The self-induction acts to
oppose the flow of current,
hence it is equivalent to the
addition to a certain amount of
resistance to the circuit, but as
can be seen from the diagrams
it cannot be added directly,
after the fashion in which
numbers are added. To add it
properly it must be placed at
right angles to the resistance.
If the self-induction is divided
by the strength of the current,
we get a quantity that can be
compared with the resistance,
and this quantity is called the
RESISTANCE.
Figs. 858 and 859. Illustrating
resistance, reactance and
impedance.
reactance and is measured in ohms precisely as the resistance is.
The flow of current in a continuous current circuit is opposed
by the resistance only, but in an alternating current circuit it is
opposed by the resistance and the reactance and the combined
effect of these two is called the impedance of the circuit.
The relation between resistance, reactance and impedance is
the same as that between impressed e.m.f., current and self-
induction, and is shown in Fig. 359.
The reactance multiplied by the current gives the self -induction.
The impedance multiplied by the current gives the impressed
e.m.f.
HANDBOOK ON ENGINEERING.
831
The resistance multiplied by the current gives the e.m.f. in
phase with the current, which is also called the active e.m.f.
A sine curve diagram, such as is shown in Fig.
356, serves very well to enable the learner to under-
stand the relation between the current and e.m.fs. but
when this relation has been fully mastered, what is known
as a clock dial diagram becomes more convenient, especially
if we desire to represent several currents arid their e.m.fs. Fig. 357
is virtually one-half of a clock dial diagram. A regular clock
dial diagram to represent a single alternating current is shown
in Figs. 360 to 362. The radius A represents the current, and is
Figs. 360, 361 and 362. Clock dial diagrams.
supposed to rotate at a velocity equal to the frequency of the
current. The strength of the current for any instant of time is
obtained, by measuring the distance from the horizontal line S S
to the end of the radius at that particular instant as indicated by
line a a in Fig. 361. If A is above the line S S the current is
positive, and if it is below S S the current is negative. At the
instant when A is in the vertical position, as in Fig. 362, the
current is at its maximum value, and when A is horizontal as in
Fig. 360 the current is zero. If we -desire to find the relation
between the current and impressed e.m.f. or the self-induction,
we draw radial lines of the proper length to represent these
e.m.fs. and in the proper angular position with reference to the
current and then assume them to be locked together when they
832
HANDBOOK ON ENGINEERING.
are rotating so that the distances from the ends of each one to
the line JS S at any instant gives the values of the quantities at
this instant.
Diagrams of this type are specially valuable for the represen-
tation of polyphase currents. Currents of this type are commonly
spoken of as a two-phase current, or a three-phase current, or a
polyphase current. Now there are no multiplephase currents.
What is improperly called a two-phase current is a combination
or two simple alternating currents so timed that they are out
of phase with each other by one quarter of a period, or revolu-
tion. This constitutes a system of two-phase currents. Three
simple alternating currents so timed as to be out of phase with
each other by one-third of a period, constitute a system of three
phase currents. In the first case we have two currents, and in
the second we have three currents. These currents in either
system are connected so as to act together in the same system
of circuits. If the phase relations are not such as given above,
they cannot constitute true, two or three-phase systems.
Pigs. 363, 364 and 365. Phase relations for two-phase system.
The phase relations for the two-phase system are shown in Fig.
363 and for the three-phase system in Fig. 366. The two currents
A B in Fig. 363 are at right angles with each other, and the three
currents in Fig. 366 are 120 degrees apart, or one-third of a
period, or cycle. To obtain the values of the two currents in
HANDBOOK ON ENGINEERING.
833
Fig. 363 at any particular instant, they are rotated together as is in-
dicated in Figs. 364 and 365. The values will be equal to the lines
a a and b b. In the same way the values of the three currents in
a three-phase system are obtained for any instant as is illustrated
in Figs. 367 and 368.
For the transmission of the currents of a two-phase system,
three or four wires can be used. In the three-phase system, if
the three currents are equal, three wires are sufficient, but if these
currents are not equal a fourth wire is required to carry the surplus
a
Figs. 366, 367 and 368. Phase relations for three-phase system.
current as it may be called. When the three currents of a three,
phase system are equal it is called a balance system, but if they
are not equal the system is unbalanced. In Figs. 366 to 368 the
three currents are drawn of equal length and it will be found that
in every position in which the lines can be placed the sum of the
two currents on one side of line S S will be just equal to the cur-
rent on the other side, so that if the current is flowing away from
the generator through one wire, it will divide up and return
through the other two, and provide for each wire just the amount
of current required. Thus in Fig. 366 the current flowing in A is
zero, and the positive current in B is equal to the negative current
in (7. In Fig. 367 the two positive currents a a and b b in lines
A J5, are just equal to the one negative current in (7, and this
is also the case in Fig. 368.
834 HANDBOOK ON ENGINEERING.
HANDBOOK ON ENGINEERING. 835
tive e.m.f . in the circuit and thus retard the current, so that the
actual amount of current flowing will be less than it would be in
a continuous current circuit acted upon by an impressed e.m.f. of
the same magnitude. As will be noticed, the direction of the flux
at (7 and D is such that they oppose each other, that is the lines
C and D flow through the space between the two sides of the loop
A A in opposite directions, and on that account the lines G can
only extend to the center of the space, while lines D will occupy
the upper half. This being the case it is evident that if the cir-
cuit wires are brought closer together as indicated by the lines
B JB, the magnitude of the magnetic flux that will surround each
wire will be correspondingly reduced as is indicated by the lines a a.
The self -inductive e.m.f. developed in the circuit will be propor-
tionaHo the magnitude of the flux that surrounds the wire, hence
the nearer the two sides are brought to each other the less the
self-induction, and if the two wires could be placed side by side
the inductive effect would be practically nothing. From this it
'£^xD
•* <MT
m
. ~-, -^
Fig. 369. Inductive action in alternating current circuits.
will be seen that if an alternating current is transmitted to a dis-
tance the nearer the line wires to each other the smaller the self-
induction developed in them.
In an alternating current circuit the self-induction developed in
every portion is not the same, and the total effect is equal to the
sum of the several effects. For example in Fig. 370 let A A A
represent a circuit that is fed by a generator at G. The self-
836
HANDBOOK ON ENGINEERING.
induction on the line A will be small, specially if the wires
are placed near each other. If a number of incandes-
cent lamps are connected at C the self-induction of these
will be practically nothing. If at B we place some kind of
device that is provided with wire in the form of coils, then at this
point a large self-induction will be developed, for then the
magnetic flux from each turn of wire in the coil will be able to cut
Fig. 370. Illustrating alternating current circuit.
through many other turns, and thus greatly increase the inductive
action. To determine the total amount of inductive action in
this circuit, so as to ascertain the amount of current that
will flow through it, we will have to find the total impedance
of the circuit, and this we do by finding the impedance of each
part and then adding these impedances, but all this operation is
carried out not in the way in which we add figures, but in the
manner shown in Fig. 359. The diagram Fig. 371 illustrates the
operation. By actual measurement we can find the resistance of
the line A in ohms and we can mark it down on the diagram as
o a. By calculation, we find the reactance of line A and mark it
down as a a', thus we obtain the impedance of oa' of the line.
Next, we find the resistance of the lamps 0 which we mark down
at a' &, and from b draw b bf equal to the reactance of the lamps,
thus obtaining the impedance a' &', of the lamps. We now draw
b' c equal to the resistance of B and c c' equal to the reactance of
HANDBOOK ON ENGINEERING. 837
B and thereby obtain the impedance b' c' of B. We now join o
Fig. 371. Determining total inductive action.
with c' and obtain the line G which is the total impedance of the
circuit, and line B, which is the total reactance, while line A is
the total resistance. A glance at the diagram will show that the
total impedance C is less than the sum o a' a' b' and b' c' if these
were added in the ordinary way, so that the total impedance of a
circuit can be less than the direct sum of the impedances of its
several parts.
Fig. 872. Showing e.m.f. and current in phase.
The angle of lag between the current and impressed e.m.f.
in an alternating circuit plays a very important part in determin-
ing the actual amount of energy that is transmitted. In a
continuous current circuit the energy is always equal to the
838
HANDBOOK ON ENGINEERING.
product of the volts by the amperes but in an alternating circuit
it may be equal to this product and it may not be as much
as one per cent of this product. What proportion of the product
of the volts by the amperes will represent the actual energy trans-
mitted will depend upon the angle of lag between the current
and the impressed e.m,f., the greater this angle the less the en-
ergy. The way in which the angle of lag affects the amount of
energy flowing in the circuit can be made clear by means of Figs.
372 to 374. In these figures, curve A represents the impressed
e.m.f. and curve B is the current, while the shaded curves repre-
sent the energy. In Fig. 372 the impressed e.m.f. and the current
Fig. 373. Angle of lag affects energy in circuit.
are shown in phase with each other, and as a result the curves (7,
which represent the energy are drawn above line 0 T, thus show-
ing that all the energy is positive, and it is equal to the direct
product of the volts by the amperes. In Fig. 373 the current and
impressed e.m.f. are drawn out of phase 90 degrees. Starting
from 0, the e.m.f. is positive while the current is negative, curve
B being below line 0 T. This means that the current and e.m.f.
act against each other hence the energy represented is negative.
After the first quarter of a period, the current becomes positive
HANDBOOK ON ENGINEERING.
839
and then the energy is positive. Thus for the first half period we
have two energy curves, D negative, and C positive, both of these
are equal and, therefore, just offset each other, so that the net
energy flowing in the circuit during this time is zero. As will be
seen, during the following half periods, the same operation is re-
peated, so that the actual result is that energy is put into the circuit
during one quarter period, and during the next quarter it is taken
Fig. 374. Energy in circuit affected by lag.
out, and the actual energy flowing through the circuit is nothing.
The action is the same as when a swing is set in motion, during
the first half of each swing energy is .accumulated by the descent
of the weight, but during the next half it is all absorbed in lifting
the same weight, and unless we supply from outside enough en-
ergy to overcome the friction the swing will soon come to a
standstill. In an alternating current circuit, if the impressed
e.m.f. and the current were out of phase 90 degrees no energy
would be introduced into the circuit, hence, no current at all
could flow, but if the angle is a trifle less than 90, say 89, a suf-
ficient amount of energy can be put into the circuit to overcome
the resistance loss, and then a strong current will sway back and
forth that is not capable of doing any work. A current of this
840 HANDBOOK ON ENGINEERING.
•
kind is called a wattless current as it carries no energy. The rea-
son why it carries no energy is that the self-induction very nearly
balances the impressed e.m.f. so that the effective e.m.f . is very
small, in fact it is just enough to force the current against the
resistance of the circuit.
In Fig* 374 the current and impressed e.m.f. are shown out of
phase by an angle of 45 degrees, and as will be seen the shaded
curves C which represent positive energy, are much larger than
those below line 0 T, which represent negative energy. The
difference between these two is the actual energy flowing in the
circuit. It can be clearly seen that the smaller the angle of lag
between the current and impressed e.m.f. the larger the shaded
curves above line 0 T and the smaller those below the line ;
hence, the greater the energy flowing in the circuit.
By the use of condensers, the effect of self-induction can be
counteracted, and in that way the lag of the current can be re-
duced and thus the energy in the circuit can be increased. A
condenser is a device that is so constructed as to be able to re-
ceive a very large electriostatic charge. To explain the nature
of electrostatic charges so that they may be understood we may
say that bodies arranged so as to hold a charge will carry this
charge upon their surface. Thus we can picture to the mind's
eye the charge as flowing over the surface until it completely
covers it. When a condenser is used in an alternating current
circuit, it is charged and discharged each time the current
alternates, and the time relation of the charging and discharging
currents is such as to be directly opposite to the current that would
flow under the effect of the self-induction, or, to put it in another
way, the e.m.f of the condenser current is 180 degrees out of
phase with the self-induction. Now, by properly proportioning
the condenser it can be made to just balance the self-induction,
and then we get the relations illustrated in Fig. 3 75 in which curve B
represents the self -induction, curve C the condenser e.m.f. which
HANDBOOK OK ENGINEERING.
841
is directly opposite and of equal magnitude. Curve A represents
the impressed e.m.f . as well as the current, both being in phase
with each other.
The general principle of construction of a condenser is illus-
trated in Fig. 376, in which the plates A B represent the condenser,
Fig. 375. Self-induction and condenser e.m.f.
and G the generator that provides the current, the connecting
wires being S S. A device of this kind, if placed in a continuous
8
B
Fig. 876. Principle of the condenser.
current circuit, will simply prevent the flow of current ; but when
connected in an alternating current circuit, if of the proper pro-
portions, will act as if it did not break the circuit. This is because
842
HANDBOOK OK ENGINEERING.
the large surfaces on the plates A B act as reservoirs and accumu-
late all the current that flows into them during the short time each
impulse lasts. When the current reverses, the charge in the con-
denser runs out together with the generator current. We
can thus consider that if a positive impulse of the current fills
plate A and empties plate B, a negative impulse will reverse the
operation.
Mutual induction* — In connection with Fig. 351 it was shown
that when an alternating current flows through a wire, the alter-
Fig. 377. Illustrating mutual induction.
nating magnetic flux that surrounds the wire, if it cuts through
any other wires running parallel with it will induce e.m.fs. in
them. The direction and phase of these e.m.fs. will be the same
as that of the self-induction in the wire carrying the current. If
we have two wires running parallel with each other and alternat-
ing currents flow through, then the action of wire No. 1 upon
wire No. 2 will be the same as that of No. 2 upon No. 1. This
action is called mutual induction, and it is made use of in the
HANDBOOK ON ENGINEERING.
843
construction of an apparatus used for transforming alternating
currents which is commonly called a transformer.
By the aid of Fig. 377 the principles of mutual induction can be
made quite clear. In this diagram suppose that the circle A rep-
resents one wire through which an alternating current is flowing,
and circle B represents another wire carrying an alternating cur-
rent. If these two wires are some distance apart, it is clear that
a considerable portion of the magnetic flux of A will not cut
through 5, and in like manner that a considerable portion of
the flux of B will not cut though A, as is indicated by
Fig. 378. Inductive effect of wires upon each other.
the dotted circles at a a a. In any case, however, some
of the flux of one wire will cut through the other. From
this it follows that the effect of the current in each wire
upon the other wire will be less than that upon itself,
but the closer the wires are to each other the nearer equal
the effects will be. When it is desired to avoid the effects of
mutual induction as far as possible the wires must be separated
to the greatest distance, and when we desire to make the mutual
inductive effect the greatest, we must bring the wires as close
844 HANDBOOK ON ENGINEERING.
together as possible. The inductive effect of wires upon each
other in some cases produces very objectionable results, for
example when telephone wires are run side by side for any
distance the inductive action of one wire upon the other serves
to render the conversation indistinct. Why this is so it can be
appreciated at once from an inspection of Fig. 378, which shows
a pole carrying four wires. Telephone currents are not alter-
nating but they pulsate and thus produce the same effect as if
they were alternating. In Fig. 378 the circles drawn around
each one of the wires as will be seen cut through all the other
wires. If the two upper wires belong to one circuit and the two
lower ones to another, then if one set of wires are crossed at every
three or four poles so that the wire running on the right side
for a certain distance will then be changed over to the left side,
the inductive actions will be counteracted to a very great extent
and this method is followed in stringing telephone wires. It is
also used in regular alternating current circuits when interference
between different circuits is to be avoided.
With regards to the two wires belonging to the same
circuit, it is advantageous to string them as close together as
possible, for in this case, the effect of mutual induction is to
neutralize the effect of self-induction. Referring to Fig. 369 it
can be seen at once that if the magnetic flux at 0 develops a self-
induction in lower A toward the right, it will develop an induc-
tion in upper A also towards the right, but with reference to the
wire itself this induction will be just opposite to that in the lower
side so that the two will counteract each other. Thus to reduce
the reactance of the line, the two sides of the circuit must be
placed as near together as is practicable.
Transformers* — A transformer is an apparatus in which the
principle of mutual induction is utilized for the purpose of gener-
ating a second current by the inductive action of a primary
current. Referring to Fig. 377 it can be seen that if wire B is
HANDBOOK ON ENGINEERING.
845
closed upon itself the e.m.f. induced in it by the magnetic flux
issuing from A will cause a current to flow and then this current,
which is brought into existence by the inductive action of the
current in A, will in turn develop a magnetic flux that will react
upon wire A in precisely the same manner as if the current were
not induced in J5, but it came from an independent source. In a
transformer, the wire is wound in the form of compact coils, and
one of these coils, which is called the primary, is connected with
an alternating current circuit. The current flowing through this
coil induces a current in the other coil which is called the second-
ary. The general construction of a transformer can be under-
,''~~f~l- ^a
f I s^~ - -Uu V \
I ' r^ N. . \
-H-
m
Fig. 370. Priiiciple of the transformer.
stood from Fig. 379. An iron core G is provided upon which are
wound two coils marked A and B. The coil A which is the prim-
ary, is connected with an alternating current circuit, and thus the
iron coreO is strongly magnetized. The presence of the iron core
G serves to greatly increase the magnetic flux but does not in any
way interfere with its alternating properties, so that it increases
and decreases and changes its direction in precisely the same
manner as the flux that surrounds a single wire. The flux de-
846 HANDBOOK ON ENGINEERING.
veloped by A, swells out as indicated by the lines a a a and cuts
through the side of the secondary coil B. If the circuit through
this coil is close an alternating current will be generated in it,
and this current will develop a magnetic flux that will swell out
and cut the side of the primary coil A. The e.m.f. induced in
A by the flux of B will be in opposition to the self-induction de-
veloped by its own flux, hence, if the circuit through B is open,
the current flowing through A will be small because the self-
induction will counteract the impressed e m.f . so as to leave but
a small effective e.m.f. As soon as the circuit through B is
closed, the inductive action of this coil upon A will offset to a
certain extent the self-induction and thus assist the impressed
e.m.f. in forcing more current through A. The more the current
through B is increased, the stronger its action upon A and as a
result the more the self-induction of A will be neutralized and the
stronger the primary current will become. This action, which
occurs in a perfectly natural manner, serves to make the trans-
former a self -regulating apparatus, so that if a strong current is
required in the secondary circuit, a strong current passes through
the primary so as to furnish the energy necessary to develop the
strong secondary current. If no current is drawn from the
secondary, the primary current is reduced to nearly nothing.
To explain fully the action in a transformer would require a
rather lengthy discussion of the principles involved, but the
action, in a general way, can be made clear without going deeply
into the theory. In explaining the phase relation of the current,
the self-induction and the impressed e.mafs. in connection with
Fig. 357 it was shown that theangle between the self-induction and
the current is 90 degrees, and that the angle between the current
and the impressed e.m.f. can be anything from zero up to nearly
90 degrees. If the current is passed through transformers or
other inductive devices, the current will lag considerably.
Suppose it lags 10 degrees, then the total angle between the im-
HANDBOOK ON 'ENGINEERING. 847
pressed e.m.f. and the self-induction will be 100 degrees. Now
in a transformer the e.m.f. induced in the secondary coil is in
phase with the self-induction in the primary coil, hence, with the
above angles it would be 100 degrees behind the impressed e.m.f.
in the primary coil. Now if the secondary current lags as much
as the primary, it will be 110 degrees behind the primary im-
pressed e.m.f. and the magnetic flux developed by this current
will induce an e.m.f. in the primary coil 90 degrees behind
itself or 200 degrees behind f_ie primary impressed e.m.f.
This e.m.f. induced in the primary coil by the action of the sec-
ondary current not only counteracts the self-induction in the
primary coil, but in addition changes the phase relation between
the primary current and its impressed e.m.f., making the angle
smaller. This change in the phase relation between the current
and impressed e.m.f. results, in turn, in a change of the phase
relation of the secondary current, and this change in the phase of
the secondary makes a corresponding change in the phase of the
primary. If we were to trace up the action back and forth from
primary to secondary currents we would finally arrive at
the true phase relation of the currents and e.m.fs. in both circuits
but this is a complicated and unnecessary process of reasoning.
We can easily see that the current induced in the secondary coil
will have a certain phase relation with respect to the primary
current, and we can further see that the combined magnetizing
effect of the two currents, the primary and secondary, is the
same as that of a single current having a phase intermediate
between the phases of these two. Following this course of
reasoning we have only one inductive action to deal with and this
is in such a phase relation that as it increases it decreases the self-
inductive e.m.f. in the primary and thus permits more current to
pass through this coil, and this increase in current in the primary
causes a corresponding increase in the secondary current. When
the secondary current is very small the self-induction in the
848 HANDBOOK ON ENGINEERING.
primary is very great and as a result the lag of the primary
current is increased and its strength is decreased. As the sec-
ondary current increases, the self-induction in the primary
decreases, and the lag of the primary current reduces while
the current strength increases. The strength of the secondary
current is varied by varying the resistance in the secondary
circuit ; if this resistance is reduced the current is increased.
To make a transformer as perfect as possible it is necessary to
place the primary and secondary coils in such a position that
the mutual induction between them may be the greatest pos-
sible, that is so that all the magnetic flux developed by
the primary coil may cut through the secondary and all
the flux of the secondary may cut through the primary.
If the coils, are arranged as in Fig. 379 it can be seen at once that
all the flux of A will not cut through B and in like manner all the
flux of B will not cut through A. It is not possible to arrange
the coils so that all the flux of one coil will pass through all the
turns of wire on the other coil, but this condition can be very
nearly realized. If one-half of coil A is wound on each side of
the core G and then the B coil is wound in two parts directly
over the A coils the chance for the flux of one coil to not pass
through the other coil will be greatly reduced.
The flux that does not pass through the opposite coil is called a
leakage flux, thus in Fig. 379 the lines a that pass through coil
A but not through B constitute the leakage from coil A and in
like manner the flux oH coil B that does not pass through A is
the leakage of B. The leakage flux represents just so much mag-
netism thrown away, hence the effort of the designer is to arrange
the coils so as to reduce it to the smallest amount possible. If
the two coils were wound together, that is, if we took the wires
and wound them side by side forming a single coil, the leakage
would be practically nothing, but this construction cannot be used
as with it there would be great danger of the insulation between
HANDBOOK ON ENGINEERING.
849
the coils giving away, and this would destroy the transformer.
This form of winding can be approximated to by winding each
coil in many sections and placing these in sandwich fashion upon
Fig. 380. Position of transformer coils on iron core.
the iron core as is shown in Fig. 380 in which the sections forming
one coil are shaded, and those of the other coil are not. This is
the construction that is followed generally in large transformers.
In the majority of designs, however, the primary and secondary
coils are wound one over the other.
Transformers are used for the purpose of changing the voltage
of the current. The name transformer is misleading, as it creates
the impression that the device transforms the current, when as
shown in the foregoing it does nothing of the kind, it simply
generates a secondary current, which is in no way connected with
the primary. When electric energy is transmitted to a consider-
able distance by means of alternating currents, the voltage used
is much higher than is required for the operation of lamps
or motors, hence, at the receiving end of the line this cur-
rent is passed through transformers and secondary currents are
generated in these that are of the voltage desired. The voltage
850 HANDBOOK ON ENGINEERING.
of the secondary current is controlled by the number of turns of
wire placed upon the secondary coils. Roughly speaking, if
the primary coil has ten times as many turns as the secondary
the voltage of the secondary current will be one-tenth of that of
the primary. If the primary voltage is 2000 and the secondary
is 100 the primary coil will have twenty times as many turns of
wire as the secondary.
Transformers that deliver a secondary current of lower volt-
age than the primary are called lowering transformers, while
those that deliver a secondary of higher voltage are called raising
transformers. For distributing current to consumers, lowering
transformers are used. But in long distance transmission plants,
where the current in the transmission line has ane.m.f. of any-
where from 10,000 to 30,000 volts, raising transformers are
used at the power house, and these take the current from the
generators, which may be of 1,000 or 2,000 volts and deliver to
the line a secondary current of 10,000 or more volts.
Transformers cannot be used with continuous currents for the
simple reason that as these currents do not fluctuate the magnetic
flux developed by them remains stationary and, therefore, there
is no inductive action.
A medium size transformer is shown in Fig. 381. The com-
plete transformer is seen at the right side of the illustration. In
the center is shown the lower part of the iron core, with the wire
removed from one leg, this wire being shown on the left. The
iron plates at the bottom of the figure form the upper part of the
iron core.
The iron core of a transformer is built up out of sheet iron.
It could not be made a solid mass, for, if it were, secondary cur-
rents would be induced in it, and thus the energy in the primary
current would be used up in developing useless currents in the iron
core. The sheet iron laminations are insulated from each other,
so as to prevent the development of currents in the core.
HANDBOOK ON ENGINEERING.
851
As can be seen from the illustration, the wire wound on each
leg of the core belongs in part to the primary and in part to the
secondary circuit. If the primary wire is proportioned so that it
is proper for a 1,000-volt current when the parts on the two legs
are connected in series, then it can be made proper for 500 volts
j
Fig. 381. Showing outer coyering of transformer.
by connecting the two parts in parallel. If the secondary coils
will develop a voltage of 100 when both parts are connected in
series, they will develop 50 volts if both parts are connected in
parallel, but in this case the current will be doubled.
The transformer as shown to the right in Fig. 381, is complete,
but for the purpose of protecting the wire an outer casing is pro-
852 HANDBOOK ON ENGINEERING.
vided. For high voltage transformers, this casing is made water
tight and is filled with oil so as to improve the insulation of the
apparatus. Very large transformers are provided with means for
cooling them. In some, air is forced through the coils and iron
core. In others, coils of pipe are placed within the casing and
water circulates through these.
Alternating current generators. In alternating current gen-
erators the field is magnetized permanently by means of a con-
tinuous current. This current is obtained, generally, from a small
continuous current generator that is called an exciter. Some alter-
nators, as a rule of small capacity, are provided with a commu-
tator to rectify a portion of the current the machine generates so
as to provide a continuous current to magnetize the field. An
alternating current cannot be used to magnetize the field because
the field magnetism must remain unchanged.
Alternators are also arranged so that the field is magnetized
by the combined action of the two continuous currents above
mentioned, that is, by the current from a separate exciter and
the current derived from the armature. Alternators excited in
this manner are called compound machines and are the counter-
part of the continuous current generator. Alternators that are
excited by the current from a separate exciter alone are the coun-
terpart of the plain shunt wound continuous current generator.
There are several other ways in which the field can be magnet-
ized to make an alternator of the compound type, and the most
important of these will be found fully explained under the head-
ing of "Compensated Generators."
The object of compound winding in alternators is the same as
In continuous current generators, that is, to keep the voltage con-
stant and not allow it to drop as the current strength increases.
Large alternators used in central stations are always of the com-
pound type.
The way in which alternating current generators act can be
HANDBOOK ON ENGINEERING.
853
understood from the diagrams Figs. 382 to 386. In Fig. 382 P
and N represent the poles of the field magnet of a two-pole
machine. The armature is provided • with a single coil of wire
marked a. When this coil is in the position shown, no e.m.f.
will be induced in it, but as it begins to rotate from this position
an e.m.f. will begin to be induced, and this will increase in mag-
nitude until one -quarter of a revolution has been made, when it
will be at the maximum value. During the next quarter revolu-
tion the e.m.f. will gradually reduce, becoming zero when the
half turn is completed. During the next half turn the e.m.f. will
again rise to a maximum and fall to zero, but it will be oppositely
Figs. 382, 383 and 384. Generating current in alternator.
directed, so that if during the first half turn the e.m.f. is posi-
tive, during the next half it will be negative, and this operation
will be repeated for each revolution of the armature. Thus it
will be seen that if the armature revolves ten times in a second,
the frequency of the current generated will be ten, and in any
case the frequency will be equal to the number of revolutions the
armature makes in a second. This is true for a two-pole machine,
if the generator has four poles the frequency of the current will
be equal to twice the number of revolutions per second and for
any greater number of poles the frequency will be equal to the
number of revolutions of the armature per second multiplied by
half the number of poles. Alternating current generators are
always made with a large number of poles so that the frequency
required may be obtained without running the armature at too
great a speed.
854 HANDBOOK ON ENGINEEKING.
The diagram Fig. 382 illustrates a simple alternating current
generator, or what is called a single-phase generator. A single-
phase machine is one that has one coil on the armature for each
pair of poles in the fields and generates one alternating current.
Fig. 383 illustrates diagrammatically a two-phase generator. A
two-phase generator is an alternating current generator that gene-
rates two alternating currents that are out of phase with each
other by one-quarter of a period, that is, by 90 degrees. Such a
generator is provided with two coils or sets of coils for each pair
of poles and these are placed at right angles to each other in a
two-pole machine, and so that the sides of one set come opposite
the centers of the other set, in multipolar machines.
In Fig. 383 it will be seen that coil a is in the same position as
the coil in Fig. 382, hence no e.m.f. is being induced in it. Coil
&, however, is in the position in which the induced e.m.f. is of the
maximum value, thus it will be seen that as the armature revolves
the e.m.f. in one coil will rise toward the maximum while that in
the other coil will be decreasing toward zero.
Fig. 384 illustrates a three-phase generator. A three-phase
generator is a machine that generates three alternating currents
that are out of phase with each other by an angle of 120 der
grees, or one-third of a period. Such a machine has three coils
or sets of coils for each pair of field poles.
In Fig. 384 it will be seen that coil a is in the position in which
no e.m.f. is generated, and if we assume that the armature is re-
volving in the direction of the hands of a clock, then the
e.m.f. induced in coil b is very near the maximum value, but is
still increasing, and will become the maximum when the coil
reaches the horizontal position. In coil c the e.m.f. has passed
the maximum and is reducing toward zero, which value it will
reach when the coil reaches the vertical position, or the position
in which a now is.
If an alternator is of the multipolar type the coils will be dis-
HANDBOOK ON ENGINEERING.
855
posed in the manner shown in Fig. 385. If it is a single-phase
machine it will have one set of coils only, those marked A. If it
is a two-phase generator it will have two sets of coils, the addi-
Fig. 385. Arrangement of coils in multipolar alternator.
tional set being placed in the position shown in broken lines and
marked B. In this construction the machine appears to have as
many A coils as there are poles and the same number of B coils,
which is in contradiction to the statement made above that a single-
phase machine has one coil for each pair of poles. The truth,
Fig. 386. Arrangement of coils in three-phase generator.
however, is that each coil in Fig. 385 is virtually one-half of a
coil. Fig. 386 shows the way in which the coils are arranged in a
three-phase generator of the multipolar type, the three sets of
coils being marked ABC. In monocyclic generators the coils
856
HANDBOOK ON ENGINEERING.
are arranged as in Fig. 385, but they differ from the two-phase
winding in that the B coils are one-quarter the size of the A coils.
In actual generators the armature coils are seldom given the form
shown in these diagrams, but whatever the form may be the prin-
ciple of winding is the same.
In an alternator the armature coils forming one set are connected
in series with each other, and the entering end of the first coil and
the leaving end of the last coil are connected with collector rings
mounted upon the armature shaft, and the current is taken from
these by means of brushes similar to the commutator brushes of
Fig. 387. Revolving field alternator.
continuous current machines. In monocyclic generators one end
of the B set of coils is connected with the middle point of the
A set, and the three remaining ends are connected with col-
lector rings. This is the arrangement with generators of
what is known as the revolving armature type, which is the
HANDBOOK ON ENGINEERING. 857
one illustrated in Fig. 382 to 386. There is another type in
which the outer part, which is stationary, is the armature, and the
revolving part is the field. Machines of this kind are called re-
volving field alternators. The principle of operation is the same
in both types, but the revolving field type has the ad vantage that,
as the armature is stationary, no collector rings and brushes are
required to take off the current. All that is necessary is to pro-
vide binding posts to which the ends of the armature coils are con-
nected, and from these the external circuit wires are run off.
A revolving field alternator is shown in Fig. 387. In machines
of this type, the field magnetizing coils are mounted on the
periphery of the revolving part, hence the current that traverses
them must pass through collector rings mounted upon the shaft.
These rings are clearly shown in the illustration, the collector
brushes being held, insulated from each other, by the stand
located in front of the rings. Thus it will be seen that this type
of machine requires collector rings, just the same as the revolving
armature type, but the difference between the two is that in the
latter the whole armature current passes through the collector
rings, and on that account they must be made very large, while
in the revolving field machines they can be made small, as only the
field current passes through them, and this is only from one to
two per cent of the armature current.
There is still another type of alternating current generator in
which the wire on the field as well as the armature is held station-
ary. Such machines are called inductor generators. The revolv-
ing portion of such generators is simply a mass of iron formed
like a very large pinion with correspondingly large teeth. When
this part revolves the ends of the teeth sweep over the armature
coils, running as close to them as they can without touching. The
magnetic flux developed by the field coil issues from the ends of
the teeth and cuts through the armature coils thus inducing e.m.fs.
in them. It will be seen that the difference between this type of
858
HANDBOOK ON ENGINEERING.
generators and the revolving armature type is that instead of re-
volving the armature coils through the stationary field flux, the
latter is revolved and the armature coils are held stationary. The
Fig. 888. Inductor alternator.
difference between the inductor generator and the revolving field
type is that in the latter the field is magnetized by a number of
coils and these are rotated together with the field poles, while in
the inductor machine there is a single field magnetizing coil and
this remains stationary, the part that revolves being what might
be called the poles.
An inductor alternator is shown in Fig. 388. The small
machine mounted on the right side of the base is the exciter that
HANDBOOK ON ENGINEERING. 859
furnishes the field magnetizing current. The outer casing of the
machine holds a ring built up of sheet iron laminations, which
constitutes the armature and supports the armature coils. The
large teeth, or polar projections, which are well shown in the
illustration, are carried by the revolving part, and when rotating
cause the magnetic flux to sweep over the armature coils. The
field coil is placed back of these polar projections.
Alternating current generators are run singly, or they may be
connected in parallel, but they cannot be run in series. If an
attempt is made to run them in series, one of the machines will
act as a motor and will be driven by the current generated by the
other. When alternators are connected in parallel it is necessary
that they run at exactly the same velocity, if they are identical
in construction. If the generators are not of the same construe^
tion then their velocities will depend upon the number of poles
each one has. Machines of different size and even design, can be
connected in parallel, providing the frequency of the currents
they generate are the same. To make the frequency the same it
is necessary that the velocity of each machine multiplied by the
number of poles it has be equal to the same number. Thus if
one machine has twice as many poles as the other, it must run at
one-half the velocity. The velocity of alternators connected in
parallel must be equal, absolutely, and not practically so ; that
is, if two machines are alike, and one runs at 1000 revolutions
per minute, the other must run at 1000 and it cannot run at 999
or 1001. Since such extreme accuracy in speed is necessary it
might be inferred that it is practically impossible to run alter-
nators in parallel unless their shafts are coupled together, or they
are connected through spur gearing with the same driving shaft.
As a matter of fact, however, alternators can be run in parallel
even if one is driven by a steam engine and the other by a water
wheel, and they may be side by side or several miles apart. The
reason why this is the case is that when the machines are in oper-
860 HANDBOOK ON ENGINEERING.
ation, the current holds them in step. If several generators are
feeding into the same circuit, and one machine tends to lag
behind the others, its current reduces and thus the speed in-
creases as less power is required to drive it. If the tendency to
lag increases, the machine begins to act as a motor, and is driven
by the current from the other machines.
While it is possible to run alternators in parallel under almost
any conditions providing they are speeded so as to generate cur-
rents of the same frequency and nearly the same voltage, entirely
satisfactory results cannot be obtained unless the angular motion
is uniform, that is, unless the velocity of rotation is the same at
all points of the revolution. If a steam engine has a light fly-
wheel the velocity of the shaft will not be the same at all
points of the revolution, but will be the slowest when the
crank is passing the center, and the fastest when at half stroke.
This fact is clearly shown by the irregular motion of the
paddle-wheels of river boats driven by a single engine.
If two alternators are driven by two engines whose rotative
motion is not uniform and the engines are so timed that one
is on the center when the other is at half -stroke, then the
action of the two alternators will be irregular, for when one
machine is rotating at the highest velocity the other will be ro-
tating at the lowest. This uneven action of the alternators may
be compared with the work of two horses hitched to a wagon and
pulling unevenly. If both horses pull together all the time the
whiffle-tree will remain straight and the wagon will be drawn
along smoothly ; but as soon as the horses begin to pull unevenly
the whiffle-tree will be jerked back and forth and the motion of
the wagon will be irregular. In this case the horses soon tire
out because they work against each other part of the time. The
action between two alternators that do not rotate with uniform
velocities is practically the same as that of two horses that do
not work together ; the machine that runs ahead not only sends a
HANDBOOK ON ENGINEERING. 861
current into the main circuit, but in addition backs up a cur-
rent through the other generator, thus wasting energy by
causing a strong current to flow back and forth between the two
machines. To overcome this difficulty engines made to drive
alternators are provided with extra heavy flywheels, so that the
momentum may be sufficient to keep the speed up to the normal
point while the crank is passing the center.
With small alternators that have only a few poles and are
driven by high-speed engines, the affect of irregular motion is not
so great as in large machines having many poles, hence the large
slow-speed engines used to drive alternators having a large num-
ber of poles, must be provided with excessively large flywheels to
run in a satisfactory manner.
The reason why alternators with a large number of poles require
greater regularity in motion to give satisfactory results, can be
easily understood. Suppose we have a pair of two-pole machines
driven by engines whose flywheels are 25 ft. in circumference.
Suppose, further, that the irregularity in motion is such that each
engine when running at the faster velocity, gets three injches ahead
of the other. Then the advance in position will be one per cent,
and consequently the currents of the two generators will run
ahead and behind each other one per cent at each quarter of a
revolution. Now, if these same two engines drive two twenty-
pole alternators, then the irregularity in motion will be multiplied
ten times, because one-tenth of a revolution will give one cycle of
current, and the current of each machine will run ahead and fall
behind the other ten per cent, instead of one per cent.
Starting" alternators connected in parallel : — In starting con-
tinuous current generators that are connected in parallel all we
have to do is to set one machine in operation and then after the
second one is running up to full speed, we adjust its field regu-
lator until the voltage is the same as that of the first machine, or
one or two volts higher. We then throw the switch and connect
862 HANDBOOK ON ENGINEERING.
it with the switchboard. In starting alternators that are con-
nected in parallel we have to do more than this, we must not only
adjust the second machine so that its voltage is the same as that
of the first, but we must bring it up to the proper speed and get its
current in phase with that of the first generator before we connect
it with the switchboard. To accomplish all this with certainty,
devices are used that are called synchronizers, or phase indicators.
These devices consist generally of a couple of small transformers
one of which is connected with the circuit of each generator. The
secondary wires of these transformers are connected with each
other and one or two incandescent lamps are connected in this
circuit. When the second machine is started up, as its speed is
much lower than that of the generator already in operation the
frequency of the secondary current of its transformer will be much
lower than that of the first machine, and as a result the lamps in
the circuit of the two transformers will flicker rapidly. As the
second machine builds up its speed the flickering of the lamps
will become slower. When the two generators are running at
nearly the same speed the flickering will be replaced by rather
long periods of darkness and light. During the periods when the
lamps are lighted the current generated by one of the transformers
is in such a direction as to act in series with the current of the
other and thus draw the current through the lamp. When the
lamps are dark it is because the currents of the two transformers
are in opposition to each other and thus no current passes through
the lamps. The second generator is connected with the switch-
board during one of the periods of darkness or brightness, de-
pending upon the way in which the transformers are connected.
The second generator will not be running at exactly the proper
speed when it is connected with the switchboard, but as soon as
it is connected the currents of the two machines acting upon each
other will at once draw the second machine into step with the
first one, and they will continue to run in step even if the power
HANDBOOK ON ENGINEERING.
863
driving one of the machines should fail. In the latter case, the
first machine would not only furnish current for the main cir-
cuit, but would in addition drive the second machine as a motor.
The way in which synchronizing lamps are connected in single
or polyphase circuits is clearly illustrated in the diagram Fig. 389-
To Bus Bars.
Sy nchr oni zing
"To GeneraCor.
Fig. 389. Showing arrangement of synchronizing lamps.
The three upper lines are connected with the main bus-bars on
the switchboard and the lower lines run to the generator that is to
be synchronized. The left side of the diagram shows the connec-
tions for synchronizing a single-phase generator. In such a case,
the middle wire running to the bus-bars and to the generator would
not be used. The synchronizing transformers would have their
primary coils connected with the side wires in the manner shown
by lines //and g g. When the generator current is in synchro-
nism with that in the bus-bars, the primary currents in the two
synchronizing transformers will flow in the direction of the arrows
a a, and the secondary currents will be in the direction of arrows
c, that is, in opposition to each other, so that no current will pass
through the synchronizing lamps. If the connections of one of
864 HANDBOOK ON ENGINEERING.
the transformers are reversed, either in the primary or secondary,
the two secondary currents will flow through the lamps in the same
direction as indicated by the arrows d on the right side of the
diagram. Thus it will be seen that the synchronizing lamps can
be arranged so that they will light up when the generator current
is in phase with the bus-bar current, or they may be arranged so
as to be dark at this instant. Generally they are arranged so as
to be bright when the current is in phase and the switch connect-
ing the generator with the switchboard is closed at the instant
when the lamps appear to be brighter.
When two and three-phase generators are started up the first
time a temporary synchronizing arrangement is connected in the
manner shown on the right side of Fig. 389. The synchronizing
lamps on the left side will show that the current flowing in the
two side wires is in synchronism, but this does not show that
the other currents also synchronize. To make sure that the
temporary transformer is properly connected the connections e
are made first, and if the lamps on both sides of the diagram
become dark and bright together, the' connections are correct.
The connections are then broken and are transferred to the middle
wire ; then when all the currents are synchronized, all the lights
will light up together. Generally the internal connections of
synchronizing transformers are properly made, and the correct
connection of the terminal wires is clearly indicated so that mis-
takes in making connections are not very liable.
Compensating and compounding alternators* — Continuous
current generators are provided with a compound field winding
for the purpose of maintaining the voltage uniform as the arma-
ture current increases. Alternating current generators are
compounded for the same purpose. If the field of an alternator
is excited by a current derived from an exciter the voltage of
the machine will drop as the strength of the current generated in
the armature increases. A part of the drop is due to the fact
HANDBOOK ON ENGINEERING. 865
that the increased current absorbs more voltage in passing through
the armature coils. The balance of the drop is produced by
the reaction of the armature current upon the field. As the
current of the exciter that magnetizes the field remains constant,
the magnetization produced .by it remains constant. The cur-
rent flowing in the alternator armature acts to demagnetize the
field, and, as its action increases as the strength increases it
follows that the stronger the current becomes the weaker the
field will be, and, as a result, the lower the voltage of the cur-
rent generated in the alternator armature.
If a portion of the current of the alternator armature is recti-
fied by being passed through a commutator and is used to assist
the exciter current to magnetize the field then the field magnetism
will increase as the armature current increases, because the
action of the rectified current will increase. Thus by the com-
pound action of the exciter current and the rectified armature
current, the magnetism of the field of the alternator can be made
to increase as the armature current increases, and in this way the
voltage is increased so as to compensate for the greater drop of
voltage on the armature coils, the result being that the voltage
impressed upon the wire remains practically the same for all
strengths of current.
The above results can be obtained providing the phase relation
between the current and the impressed, or line e.m.f. does not
change ; but if the phase relation is continually changing such
perfect regulation cannot be realized. The reason why changes
in the phase of the current interfere with the regulation is that
the same strength of armature current will produce different de-
grees of reaction on the field magnetism with different phase
relations. .If the lag of the current is increased the reaction upon
the field will be increased, and in like manner a decrease in the
lag will reduce the reaction upon the field. Several arrangements
are used for obtaining field magnetizing currents that will com-
55
866 HANDBOOK ON ENGINEERING.
•
pensate for variations in the lag of the current as well as for va-
riations in strength. Alternators provided with such arrange-
ments are called " Compensated Generators." The way in which
a field magnetizing current is obtained v that will compensate for
variations in lag as well as in current strength is by using a por-
tion of the armature current to vary the strength of the current
generated by an exciter, the exciter being provided with coils
through which the current taken from the armature is passed.
These coils are so disposed that their governing action upon the
exciter is proportional to the lag of the current as well as its
strength, hence the current that the exciter sends through the
field coils of the alternator is at all times sufficient to compensate
for variations in the strength and phase of the armature current.
If an alternator is single-phase, one commutator is sufficient to
rectify the portion of the armature current and to magnetize the
field. For a two-phase machine, two commutators are required
and for a three-phase, three commutators. To obviate using
two and three commutators in polyphase generators, trans-
formers are employed, two transformers for two-phase and
three transformers for three-phase. The recording currents
of these transformers are combined into one, and this com-
bined current is passed through a single commutator to be recti-
fied. In some cases only one of the currents of a two or three-
phase generator is rectified, but with most machines, if they are
connected in parallel, care must be taken to have the circuits
from which the rectified current is taken properly connected with
each other ; if not, one armature will short circuit the other.
This is due to the fact that when alternators are run in parallel
the rectified currents for the field coils are connected with each
other through equalizer wires, in a manner similar to that used
with continuous current generators.
The ordinary connections for two generator's in parallel are
shown in the diagram Fig. 390.
HANDBOOK ON ENGINEERING.
867
As will be seen, the field-magetizing currents derived from the
commutators are connected with each other through the equalizer
switches, hence, to avoid short circuiting the armature through the
equalizer connections, if the commutator rectify one current only,
Commutator
Fig. 890. Connections of composite field alternating generators
for running: in parallel.
the two rectified currents must be in phase with each other. The
rheostats shown in each field circuit are for the purpose of
adjusting the voltage of each generator independently.
The use of transformers to transform the portion of the arma-
ture current that is rectified is no objection against polyphase
machines, because, even with single phases, the armature voltage
is generally so high that a transformer is used so as to obtain a
secondary current of low voltage to pass through the field coils.
Alternating current motors* — From the foregoing it can be
understood that an alternating current generator can be used as
a motor providing it is supplied with the same kind of currents,
868 HANDBOOK ON ENGINEERING.
that is, with a continuous current to magnetize the field, and with
an alternating current for the armature. A single-phase alter-
nator will run as a motor if connected in a single-phase circuit.
Two-phase generators will act as two-phase motors, and three-
phase generators will act as three-phase motors. With either one
of these three types of machines a continuous current will
be required to magnetize the field. Two and three-phase ma-
chines can be run with a single alternating current, by connect-
ing one of the armature circuits only, or all the circuits may be
used if they are connected in parallel.
When an alternator is used as a motor it is called a synchro-
nous motor, because it runs in synchronism with the generator
that supplies the current. A simple alternator (single-phase ma-
chine) becomes a single-phase synchronous motor, and a two
or three-phase generator becomes a two or three-phase syn-
chronous motor.
A single-phase synchronous motor will not start up of its own
accord, but must be set in motion and run up to nearly its full
speed before it will begin to act as a motor. If it is started up
without a load when it comes rather near to its full speed it will
give a sudden jump and swing into step with the current and then
continue to run at this velocity. If it is started with a full load
it will not fall into step with the current until its speed is very
nearly up to the proper point. Synchronous motors are never
started under load, they are always started light.
Two and three-phase synchronous motors can be started with-
out outside assistance. Synchronous motors are generally pro-
vided with a self -starting motor, to set them in motion, or else
they are arranged so as to be self -starting by being converted,
in the act of starting, into some form of motor that is self-
starting.
Fig* 39 \ shows a synchronous motor of large size provided
with an induction motor of much smaller capacity to start it.
HANDBOOK ON ENGINEERING.
869
This motor is of .the revolving field type, and, as will be seen, is
precisely the same as the same type of generator.
Fiff. 391. 1000 h. p. two-phase revolving field synchronous motor.
Owing to the fact that synchronous motors are not self -starting,
they are generally used only where large power is required, unless
they happen to be made so as to be self -starting, then they are
used in small sizes.
A synchronous motor, when running, will keep in step with the
current, no matter how much the load may vary, provided it is
not made greater than the capacity of the machine. If the load
is made so great that the motor cannot carry it, the armature
will be pulled out of step with the current and will imme-
diately come to a stop. On this account, motors of the
synchronous type are not well adapted to operate cranes or similar
machines in which there is a liability of greatly overloading the
machine occasionally.
870 HANDBOOK ON ENGINEERING.
The current developed by an alternating current generator will
lag behind the impressed e.m.f. as has been fully explained in the
foregoing. If this current is passed through a second machine, that
acts as a motor, the latter will tend to generate a current that flows
in opposition to that of the generator ; hence, in this current the lag
will be in the opposite direction of that of the current that drives
it. That is when the machine acts as a motor its whole action as
a generator is reversed. Owing to this fact, if a synchronous
motor is placed at one end of a circuit, and a generator at the
other, the motor will act to neutralize the self-induction of the
generator, and thus to bring the current in the circuit, and the
impressed e.m.f . into phase with each other. Thus, a synchro-
nous motor can be made to act in the same way as a condenser,
to reduce the lag of the current.
Power factor* — In an alternating current circuit, it is very
important to reduce the lag of the current as far as possible
because the actual amount of energy carried by the current depends
upon the angle of lag, as was fully explained in connection with
Figs. 372 to 374. In a continuous current circuit the power is
always equal to the product of the volts by the amperes,
but in an alternating current circuit this product is not a
measure of the power. It is called the apparent power, or the
volt-amperes. The actual power is equal to the amperes multi-
plied by the e.m.f. in phase with the current, or the active voltage,
as it is called. The ratio between the true power and the volt-
amperes is called the power factor. The power factor can be
obtained by dividing the true power by the volt-amperes, and it
may range from 100 per cent when the current and impressed
e.m.f. are in phase down to five or ten per cent when the angle of
lag is nearly 90 per cent. In actual working circuits the power
factor ranges between about 95 and 75 per cent. Any kind of
device that has a low reactance, as, for example, incandescent
lamps, acts to keep the angle of lag of the current small, and thus
HANDBOOK ON ENGINEERING. 871
the power factor high. Devices having large reactance, such as
transformers, and induction motors act to increase the angle of
lag of the current, and thus to reduce the power factor. Devices
that develop a negative reactance, that is, which cause the current
to lead the impressed e.m.f., such as condensers and synchronous
motors, can be used in circuits in which transformers and similar
devices are operated so as to counteract these and thereby keep
up the percentage of the power factor.
Induction and other types of motors* — In addition to the
synchronous motors just explained, the only type of machine that
requires notice here is the induction motor. This is by far the
most extensively used of all alternating current motors, and from
the manner in which it acts it has a greater range of adaptability
than any other type. It may be well to mention here, however,
that a plain motor, such as those used with continuous currents,
can be made to operate with alternating currents providing the
field cores are made laminated, instead of solid castings. If the
field is solid the motor will not run if connected in an alternating
current circuit because the large mass of iron constituting the field
cannot be magnetized and demagnetized as fast as the current
alternates. If we take hold of a freight car and try to shake it
we will fail in the effort, simply because the bulk is too great to
be set in motion rapidly. If, however, we take hold of the side
of a light buggy and shake it we will be able to produce a very
vigorous movement, simply because the bulk is light. In the
same way, if we attempt to alternate the magnetic polarity of
large masses of iron >re fail because the bulk is too great, but if
we divide the mass up into many thin sheets we will have no diffi-
culty in causing its polarity to change rapidly. Alternating cur-
rent motors of this kind which are called commutator motors,
have been made, but they are not used or manufactured for com-
mercial purposes at the present time, because they are far inferior
to other types. They are open to two objections, one of which
872
HANDBOOK ON ENGINEERING.
is that they spark considerably and the other is that they will not
give much more than one-third the power that the same machine
will develop if supplied with a continuous current. The reason
why they give such small power is that on account of the many
turns of wire on the field the inductive action is very great, hence
the reactance is very high, and as a result the current lags exces-
sively so that the power factor is very low, therefore, although the
current is strong, the actual energy carried by it is comparatively
small. Several other types of alternating current motors have
been devised, but they have never got beyond the experimental
stage.
Principle of the induction motor- — Induction motors are
made for single and polyphase currents. When in operation the
392 and 393. Principle of induction motor.
principle of action is the same in all, but in the act of starting the
single-phase machine is different from the others. Single-phase
induction motors will not start of their own accord unless provided
with special starting arrangements. The most common way of
arranging a single-phase induction motor so as to be self-starting
is to provide a set of starting coils that virtually convert it into a
HANDBOOK ON ENGINEERING. 873
two-phase machine in the act of starting. When the motor is
underway the starting coils are cut out, although in some cases
they are left in circuit all the time. The principle of the induc-
tion motor can be explained by the aid of the diagrams Figs.
392 to 395. These diagrams illustrate the action in a two-phase
machine, which is the one most easily understood. The
single-phase induction motor is the most difficult one to ex-
plain or to understand, so we will leave it for the
last. In an induction motor, the stationary part, which is
called the stator, and sometimes the field, is provided with coils
that are connected with the operating circuits. The rotating part,
which is called the rotor, and sometimes the armature, is provided
with coils that are short circuited upon themselves and are not
connected with the operating circuits. The principle of operation
generally stated is that the currents in the stator develop an in-
ductive action upon the coils of the rotor thus developing currents
in these, the action being substantially the same as that in a
transformer. On that account the stator is also called the
primary member, while the rotor or armature is commonly called
the secondary member. The primary currents passing through
the coils of the stator, develop a magnetic flux and the secondary
currents induced in the coils of the rotor also develop a magnetic
flux, these two fluxes are at an angle with each other, and, hence,
there is a strong attraction exerted between them, the magnetism
of the rotor making an effort to place itself parallel with that of
the stator. The magnetism of the stator rotates, on account of
being developed by alternating currents, and the magnetism of
the rotor in trying to place itself parallel with that of the stator
also rotates, chasing the latter around the circle but never
overtaking it.
In Fig. 392 let A A represent two coils connected in one of the
circuits of a two-phase system, and let B B represent two other
coils connected in the other circuit of this same system. Suppose
874
HANDBOOK ON ENGINEERING.
we consider the instant of time when the current flowing through
the A A coils is at its maximum value, then at this very same instant
the current in the B B coils will be zero. The current in the A A
coils is then the only magnetizing current acting upon the ring at
this instant. Suppose the direction of the current through A A
is such as to develop a magnetic flux that will traverse the space
in the center of the ring in the direction of arrow C. As the
current in the A A coils begins to decrease, that flowing in the
B B coils will begin to increase. Let the direction of the current
in the B B coils be such as to send a magnetic flux through the
center of the ring in the direction of arrow C in Fig. 394. This
magnetization will act upon that developed by the current in the
A A coils and will have a tendency to twist it around into the
direction of arrow C in Fig. 393. When the current in the .4 A
coils has reduced and the current in the B B coils has increased
until they are both equal, then each one will act with equal force
Figs. 394: and 395. Illustrating operation of induction motor.
to establish a magnetization in its own direction, and the result
will be that the actual direction of the magnetic flux will be as
indicated by arrow C in Fig. 393. Thus we see that by the
decrease in the strength of the current in the A A coils and the
HANDBOOK ON ENGINEERING. 875
increase in the strength of the current in the B B coils until they
are both equal, the magnetic flux has been rotated from the
position of arrow C in Fig. 392 to its position in Fig. 393. Now
as the variation in the currents progresses, and that in A A
becomes weaker, while that in B B becomes stronger, the
direction of the magnetic flux will be still further rotated so that
when the current in B B reaches the maximum value, and that in
A A becomes zero, the direction of the flux will be that of arrow
C in Fig. 394. As we advance beyond this instant of time, the
current in B B will begin to reduce, while that in A A will begin
to increase, but its direction will be the opposite of what it was
iii Fig. 392, so that when the currents in the two sets of coils
become equal again, the direction of the magnetic flux will be
that of arrow 0 in Fig. 395. When the current in the A A coils
reaches the maximum and that in B B becomes zero, the flux will
have rotated through one-half of a revolution and arrow G will
be in the vertical position but pointing downward.
If we follow the action of the currents further we will find that
as a result of the continuous increasing and decreasing and
changing of direction, the magnetic flux indicated by arrow C
will continuously rotate keeping time with the frequency of the
currents. Now if we suppose that an armature upon which a
number of coils are wound in a diametrical position, is placed
. within the field ring, and is held stationary, we will see at once
that the rotating magnetic flux will cut through its coils and
develop e.m.fs. in them. The currents developed in these coils
on the stationary armature will be alternating, hence, they will
develop a magnetic flux in the armature that will rotate, and
keep time with the rotating flux developed by the field coils.
Both these fluxes act inductively upon the field and armature
coils, their combined effect being equal to that of a single flux
located 90 degrees in advance of the e.m.f. induced in the
armature coils, hence, somewhat more than 90 degrees ahead of
876 HANDBOOK ON ENGINEERING.
•
the armature current. If we hold the armature by means of a
brake, and free this slightly, so that the armature may revolve
slowly, it will at once follow around after the rotating field, but
as its magnetization is developed by currents that are induced by
the action of the field magnetism, it will matter little how fast
the armature may revolve, its magnetization will never be able to
overtake that of the field.
As can be judged from the foregoing explanation, an induction
motor is not a synchronous machine, and its armature can never at-
tain a velocity equal to that of the rotating field. If the resistance
of the armature coils is made very low, it may reach a velocity
very near to that of the rotating flux. The difference between the
velocity of the rotating flux and that of the rotating armature is
called the slip of the motor.
If the motor is designed for constant speed, the resistance of
the armature coils is made very low, and then when the machine is
running free, the speed of the armature may run up to 99 or 99£
per cent of the speed of the rotating field, and when the maximum
load is put on it may not drop lower than 94 or 95 per cent. If
a motor is designed in this way the pull of the armature when it
starts up will be small and will gradually increase until the speed
is about nine-tenths of the maximum when it will again begin to
decrease.
If it is desired to make a motor that will give a strong pull
when it starts up, its armature coils must have more resistance,
and then it will pull harder on the start, but as fast as the speed
builds up the pull will reduce. From this it will be seen that in-
duction motors that are made so as to run at nearly a constant
speed, say to vary five or six per cent between full load and run-
ning free, will not give a strong pull in the act of starting, hence
they will have to be started without a load. If a motor is to be
made to start under a full load it must be proportioned so that it
will not run at a constant speed, but will gradually reduce its
velocity as the load is increased.
HANDBOOK ON ENGINEERING. 877
Induction motors, if very small, are started by connecting
them directly with the operating circuits, but if they are of any
capacity they must be provided with some kind of starting resist-
ance so as to keep the starting current down within safe limits.
One way of starting is to introduce resistance into the primary
circuits, but this results in reducing the strength of the
field, and thus the pull of the armature. Another way is to intro-
duce resistance into the armature coil circuit. This is the best
method, because it enables the motor to start up with a strong
pull.
Three-phase induction motors act in precisely the same way as
the two-phase, the only difference being that the rotation of the
field flux is produced by the increase and decrease in the strength
of three currents flowing through three sets of coils equally
spaced around the circle instead of by the increase and decrease
in two currents flowing in two sets of coils equally spaced around
the circle.
In the single-phase induction motor, the magnetic flux developed
by the single alternating current traversing a single set of coils on
the field combines with the magnetic flux developed by the armature
current, to develop a rotating field and this acting upon the armature
coils produces rotation in precisely the same way as in the two-
phase machine. This is the action that takes place after the
armature is set in motion, but if the load is increased and the
armature speed is reduced the rotating field begins to become
irregular, and by the time the armature velocity is reduced to
about one-half, the rotating flux becomes so irregular in its move-
ment, that the armature pull begins to reduce very rapidly, and
the machine comes to a standstill. Owing to this fact single-
phase induction motors cannot be used in cases where it is de-
sired to start with a strong pull, or where a wide range of speed
variation is desired.
To make a single-phase induction motor self -starting, it is wound
878 HANDBOOK ON ENGINEERING.
with two sets of coils, like the diagrams Figs. 392 to 395, and the
current from the single-phase circuit is passed through these two
sets of coils in parallel branches, and in one of the branches the
reactance is greatly increased, so as to make the current in this
branch lag much more than in the other. In this way a phase
displacement is obtained between the two currents, and this pro-
duces a corresponding displacement in the magnetic fluxes devel-
oped by the two sets of coils, so that their combined action
develops a rotating field. This field does not rotate at a uniform
rate, like the field of a two-phase motor, but it is uniform enough
for the purpose of setting the machine in motion. To increase
the reactance in the auxiliary starting coils, all that is necessary
is to wind them with many turns of fine wire, and this is an
arrangement very commonly employed, but, in some cases, sep-
arate coils are placed in the auxiliary circuit to obtain the required
reactance.
There are other ways in which single-phase induction motors
are made self -star ting, but they are not very extensively used.
While induction motors are very satisfactory machines, being
adapted to every kind of work, even to the operation of railway
cars, they have the objection of being highly inductive devices
that act to greatly increase the lag of the current, and thereby to
reduce the power factor. On this account they are often used in
connection with synchronous motors so that the latter may coun-
teract their inductive effect, and thus keep the power factor high.
The small motor shown in Fig. 391, is an induction motor.
Induction motors are made in many different designs, and as
large as 300 to 400 H. P., but as a rule they are confined to much
smaller capacities ; synchronous motors being used for the larger
sizes.
Rotary transformers and rotary converters* — A rotary
transformer is a machine by means of which a continuous current
may be obtained from an alternating current. A rotary con-
HANDBOOK ON ENGINEERING.
879
verier is a machine for accomplishing the same result. The
essential difference between the two is that the first is driven by
an alternating current and generates a continuous current, while
the second changes an alternating into a continuous current. As
a result of this difference the rotary transformer can be used to
obtain a continuous current of any desired voltage from an
alternating current of any given voltage ; but in the rotary con-
verter, as the action is to convert the alternating into a con-
tinuous current, the voltage relation is fixed so that for a given
alternating current voltage we will get a corresponding contin-
uous current voltage. Both these machines can be used in the
reverse order, that is to transform or convert a continuous into an
alternating current.
B
Fig. 396. Principle of the rotary transformer.
Principle of the rotary transformer* — The principle of the
rotary transformer is illustrated in Fig. 396. In this diagram A
represents a continuous current armature, and B is an alternating
current armature. If both these are provided with suitable
magnetic fields then if continuous current is passed through A it
will become a motor and will drive B and generate therein a
single alternating current or a number of them according to the
way in which the armature is wound. Thus B may become a
single or a polyphase generator. It can further be seen that the
880
HANDBOOK ON ENGINEERING.
voltage of the currents generated by B is in no way connected
with the voltage of the current that drives A, and depends wholly
upon the way in which B is wound. If B is connected with an
alternating current circuit, then it will run as a synchronous
motor and drive A and the latter will generate a continuous
current. This machine if driven by a continuous current will be
self -starting, but if driven by an alternating current it will have
to be started. If driven by an alternating current its speed will
be controlled by the frequency of the current, but if driven by a
continuous current its speed will vary with the magnitude of the
load placed upon it.
b
0
/
c
5 C
Ml
C
A
/
y /*
u\
Us l*>
Figs. 397 and 398. Principle of the rotary converter.
Figs. 397 and 398 illustrate the principle of operation and the
construction of a rotary converter. The armature A is of the
continuous current type, having a commutator C. If it is a two-
pole machine, then if wires are connected with diametrically
opposite segments of the commutator as is indicated in Fig. 398
by the arrows, and these are connected with the collector rings
a a, brushes c c placed on these rings, will take of a true alter-
nating current if the armature is placed in a suitable field and is
driven. While alternating current can be taken from the brashes
C c, a continuous current can also be taken from the brushes b &,
HANDBOOK OK ENGINEERING. 881
jyhich bear upon the commutator C. Thus, this machine, if
driven, becomes a combination generator which will deliver a
continuous and an alternating current at the same time.
Machines of this type are constructed and are called double
current generators.
If the brushes c c are connected with a single-phase circuit,
and the armature is placed in a suitable field, it will rotate and
from the b b brushes of the commutator a continuous current
can be drawn. If the brushes b b are connected with a continu-
ous current circuit, an alternating current will be delivered
through the brushes c c.
If four wires are connected with four commutator segments one
quarter of the circumference apart, and these are connected with
four collector rings, then from these rings two alternating cur-
rents 90 degrees out of phase can be obtained. Thus, with four
connections with the commutator segments the machine can
convert two -phase currents into one continuous current, or one
continuous current into two-phase currents, that is into two alter-
nating currents 90 degrees out of phase.
If wires are connected with three commutator segments one-
third of the circumference apart, and these are connected with
three collector rings, then the machine will become a three-phase
converter, and if connected with a three-phase system will deliver
one continuous current or if connected with a continuous current
circuit will deliver the three currents of a three-phase system.
The rotary converter, as will be seen from the foregoing,
actually changes a continuous current into one or more alternat-
ing currents, or one or more alternating currents into one con-
tinuous current, and in every case there is a direct electrical con-
nection between the continuous and the alternating current cir-
cuits. As this type of machine simply converts the current of
one type into current of the other type it is quite evident that
there must be a fixed relation between the strength of the alternat-
56
882 HANDBOOK ON ENGINEERING.
ing and continuous currents and also between the voltages. An
alternating current if of the sine type, will have an effective value
of 70.7 per cent of its maximum value, for the amperes as well as
the volts. So that if we have a continuous current of 70.7
amperes and 70.7 volts, we must have an alternating current of
100 amperes maximum value and 100 volts maximum value to be
equal to it, and if the energy is also to be equal, the current in
the alternating current circuit must be in phase with it e.m.f.,
that is the power factor must be 100.
In a rotary converter the voltage of the continuous current is
equal to the maximum voltage of the alternating current and the
strength of the continuous current is equal to one-half the maxi-
mum strength of the alternating current. Thus if the maximum
voltage of the alternating current is 1,000 volts, the voltage of the
continuous current will be 1,000, and if the maximum strength of
the alternating current is 100 amperes the strength of the contin-
uous current will be 50 amperes. This arises from the fact that
the rotary converter does not develop energy, as it drives itself,
hence, the energy in the continuous current cannot be more than
that in the alternating, in fact it will be a trifle less owing to the
energy absorbed in driving the machine. Now if the alternating
e.m.f. and current have the maximum values of 1,000 volts and
100 amperes, their effective values will be 707 volts and 70.7
amperes, and the product of these two will be the energy in watts.
Thus 707 X 70.7 = 50,000 watts. Now if the voltage of the
continuous current is 1,000, its strength must be 50 amperes, less
the amount absorbed in overcoming the friction of the machine.
Fig. 399 shows a rotary converter of large size.
Alternating current distributions* — The principal advantage
of alternating over continuous currents is that they can be used
for transmitting energy to much greater distances, owing to the
fact that a high voltage can be used to transmit the main current
over the wire, and at the receiving end this current can be passed
HANDBOOK ON ENGINEERING.
883
through transformers, from which secondary currents of low volt-
age may be obtained. In a few instances, low voltage alternating
Fig. 399. Rotary converter.
currents are used for distributing current over small areas. The
general arrangement of circuits and. apparatus for a three-phase
system of this kind is illustrated in the diagram Fig. 400.
B
Fig. 400. General arrangement of three-phase system.
The generator is shown at the extreme left. At A an induction
motor is connected with the circuit. At B an " arc " light is
corrected in the secondary circuit of a small transformer. At G
884
HANDBOOK ON ENGINEERING.
a number of incandescent lamps are connected. At D the circuit
is used to drive a rotary transformer, which develops a continuous
current to charge storage batteries at E. The three solid line
wires constitute the main circuit and all the apparatus is
connected with them. The broken line above these is the
neutral wire and is connected with the incandescent lamps
only. If the number of these lamps in each circuit is the
same, as is shown on the diagram, no current will pass to the
neutral wire, but if in one of the circuits there are more lamps
t,han in the other, the excess of current will pass to or from the
,ieutral wire. Systems of this type are operated at voltages rang-
ing between 200 and 600.
Fig, 401. Arrangement for distances up to four miles.
The diagram, Fig. 401, shows the way in which the circuits are
arranged when the distance of transmission is from one to three
or four miles. For such cases, the voltage generally used is
2300. The generator at the left develops currents that pass
directly to the main line. At A an induction motor is connected
directly to the main line. At B transformers are used to develop
secondary currents of low voltage to supply the circuit wires C
from which the motor D and incandescent lamps E are fed. At F
a series transformer is used to develop a secondary current of
constant strength to operate the arc lamps G. The difference be-
tween a series transformer and the ordinary type is that the
former is provided with a mechanical regulator, actuated by the
current which maintains the secondary current of constant
strength and varies the voltage in accordance with the number of
HANDBOOK ON ENGINEERING.
885
lamps in service. At H another set of transformers are used to
develop low voltage secondary currents, which pass through a
rotary converter /, and are converted into a continuous current
to feed the incandescent lamps at J.
Fig. 402 illustrates the arrangement of circuits and appara-
tus for long distance transmissions, which may range all the
way from five or six miles up to one hundred or more, the
greatest distance covered up to date being 145 miles. To trans-
mit current to great distances with a small loss in the trans-
mission lines, it is necessary to use very high voltages, ranging
from 10,000 to 60,000, and as it is not advisable to construct
Fig. 402. Arrangement for long distances.
generators to develop such high pressures, raising transformers
are employed to develop the line current. These transformers are
shown in Fig. 402 at A. The generator develops currents at 1,000
volts, and this passing through the primary coils of the trans-
formers at A induces secondary currents which may have any
voltage desired, say, 20,000. These secondary currents pass to
the transmission lines B B, which may extend a distance of ten,
twenty or more miles and may deliver all their energy at the end
of the line or drop part of it at intermediate points. The trans-
formers at C and also those at L develop secondary currents of
any lower voltage that may be required ; thus, those at C develop
secondary currents for the circuits 7), which may be of, say, 1,000
volts. The motor E is shown connected directly with Z), but
886 HANDBOOK ON ENGINEERING.
motor G and lamps J, K require a still lower voltage, hence the
currents in D are passed through a second set of transformers at
jP, Hsiud J. The three transformers at L develop secondary cur-
rents of sufficiently low voltage to be passed through the rotary
converter M , and thus provide a continuous current for the trolley
road as shown.
STARTING.
When the armature is turning, see that the oil rings in the
bearings are in motion. When the machine is up to speed and all
switches are open, lower the brushes on the commutator and col-
lector, making sure that each bears evenly and squarely on the
surface. Turn the rheostat until all resistance is in, then close
the switch in the exciter circuit. Set the exciter brushes properly
and adjust the voltage of the exciter to the proper point.
The alternator rheostat may then be turned gradually over until
the proper alternating voltage is indicated. The main circuit of
the machine may now be closed. The commutator brushes should
be adjusted at a non-sparking position. If there is any load the
voltage should increase slightly. If it decreases, it shows that
the series coils and the separately excited coils are opposing each
other, unless this decrease is caused by a drop in speed. If it is
found that the coils are opposing each other, unclamp the brush-
holder yoke of the alternator and move its commutator brushes
backward or forward one and one-half segments in a three-phase
machine, and one segment in a two-phase machine. A position
giving maximum voltage will be found from which any motion,
forward or backward, diminishes the voltage. Having once de-
termined the correct setting of the brushes, they may generally
remain unchanged, unless the generator is subject to great varia-
tion of load when in some machines, slight movements may be
found desirable.
HANDBOOK ON ENGINEERING. 887
PARALLEL RUNNING OF ALTERNATORS.
TYPES SUITABLE FOR PARALLEL OPERATION.
If the speeds are exactly adjusted, any two alternators of the
same frequency will operate together in parallel. The maximum
angular displacement that may take place between two machines
in parallel without causing objectionable phase difference decreases
with increased number of poles. For this reason high frequen-
cies are, generally speaking, less favorable to parallel operation
than lower frequencies. Machines of the highest frequencies
ordinarily used can, however, be successfully run in parallel if
the mechanical arrangements are suitable.
DIVISION OF LOAD.
Machines to operate in parallel must run at such speeds as will
give exact equality of frequency. If the prime mover running
one machine tends to produce a lower frequency than that run-
ning the other, the machines cannot carry equal loads.
When two alternators operate in parallel, each must carry an
amount of load proportionate to the power received from its prime
mover. If one engine or water-wheel governs in such a manner
as to give more power than the other, this machine must carry more
load, no matter what the field excitation may be. If under such
conditions the field excitations are correct, both machines will de-
liver current to the line in approximately the proportions in which
they receive power from their prime movers. If the field adjust-
ments are incorrect, there will be idle currents between the machines
in addition to the currents which go to the line.
COMPOUND ALTERNATORS.
When compound alternators are operated in parallel, equalizer
connections should be used so that the rectified alternating
888 HANDBOOK ON ENGINEERING..
current can properly distribute itself into the fields of all the
machines. Without equalizers, an unstable condition may exist
which will render parallel operation unsatisfactory. This
applies particularly in the case of machines driven from the
same source of power. The greater the amount of compounding,
the greater will be the tendency to instability.
BELTED MACHINES.
If two machines are belted to separate prime movers, their
parallel operation is dependent upon the governing of the prime
movers. If they are belted to the same source of power, their
parallel operation depends upon the proportions of pulleys and
belts, and upon the tension and friction of the latter. Under
such conditions the pulleys and belts must be adjusted with great
nicety, so that both machines will tend, with proper belt tension,
to run at exactly the same frequency. Even where pulleys are of
exactly the correct dimensions, a slight difference in the thick-
ness of belts may cause considerable cross currents or unequal
division of load.
DIRECT COUPLED MACHINES.
With such machines, engines must not only be adjusted to
run at synchronous speed, but must also be provided with fly-
wheels large enough to prevent appreciable variations of fre-
quency within each revolution. Inequalities of speed, due to
insufficient fly-wheel effect, will cause periodic cross currents
between dynamos, or will entirely prevent their operation in
parallel. The greater the number of poles in a direct coupled
machine, the less the angular speed variation necessary to cause
trouble.
High speeds are much more desirable with direct coupled alter-
nators than low speeds, and low frequencies present less diffi-
HANDBOOK ON ENGINEERING.
culties than high. The desirabilty of high speeds with direct
coupled alternators cannot be too strongly stated. While an
increase of fly-wheel effect will equalize the angular irregularities
of an engine's motion, it cannot bring about such good results
as would be brought about by a similar reduction of angular
error effected through an increase of speed. While the large fly-
wheel steadies the motion, it may tend to prevent correction of
the angular error through the effect of the cross currents. Cross
currents, which flow in machines having light fly-wheels may have
an effective tendency to hold them together ; while machines with
very heavy fly-wheels may tend to act independently of each
other as far as angular variations are concerned.
These matters should be carefully considered in installing
direct connected alternators. Where engines operate at the same
speed and have the same number of cranks, this trouble can
sometimes be overcome by synchronizing the engines themselves so
that the impulse in both come together. When the fly-wheel
effect is insufficient, the frequency will fluctuate and this fluctua-
tion may cause serious trouble if synchronous motors or rotary
converters are connected to the circuit. When the cranks of two
engines coupled to alternators are synchronized, any fluctuation of
frequency which is due to lack of fly-wheel effect will still exist,
although it may not affect parallel runnkig.
Where alternators have to be operated in parallel by engines to
which they are directly coupled, it is generally desirable to use
engines having as many cranks as possible, so that the crank
efforts will be well distributed throughout the revolution, and
will not tend to produce an irregularity of motion.
'
STARTING.
When a machine driven by a separate engine is thrown in
parallel with others which are carrying load, the throttle should
be partly closed so that it can just run at synchronous speed with-
890 HANDBOOK ON ENGINEERING.
out carrying load. After it is in step with the other machines,
load can gradually be taken on by giving it more steam. If this
is carefully done the voltage on the circuit is not disturbed by the
addition of the new machine.
When a belted machine is to be thrown into parallel with others
driven by the same shaft, its belt tension should first be reduced,
which will tend to admit enough slip to bring it into step with
the loaded machines. After it is thrown in it will gradually take
load as the belt is tightened.
SHUTTING DOWN.
In shutting down machines operating singly, both the gener-
ator and exciter field resistance should be cut in by turning the
rheostat before the line switch is opened.
When two or more generators are running in parallel on the
bus-bars, one may be shut down at any time. The equalizer
switch should be opened first, then the load reduced by throttling
the engine or by slacking the belt. As soon as the load is prac-
tically off, open the main switch.
CAKE OF MACHINES.
With high voltage machines it is absolutely essential that they
be kept scrupulously clean. Small particles of copper or carbon
dust, may be sufficient to start a disastrous arc.
The commutator collector should receive careful attention and
be wiped thoroughly every day.
From time to time the machine should be thoroughly over-
hauled and given a coating of air-drying japan after cleaning.
Machines of the rotary field type are so constructed that it is a
comparatively easy matter to get at every part of the armature
coils. In a large station it is recommended that an air compres-
sor be installed so that a hose can be led to the machine and the
dust thoroughly blown out.
HANDBOOK ON ENGINEERING. 891
It is advisable to have rubber mats in front of high tension
switchboards and on the floor at the commutator-collector end of
the generator. If it is necessary to adjust the brushes while the
machine is in operation, the attendant should stand on the mat
and it is also recommended that he wear rubber gloves.
Both commutator and collector rings require a very slight
amount of vaseline. In applying it a dry stick with a little
chamois leather tied to one end may be used, so that there will be
no danger of coming in contact with the brushes.
With the brushes properly set and all screws firmly tightened
into place, the generators should require very little attention
while running. It is well to note from time to time whether the
oil rings are working properly.
Electrical Formulas.
Volts X Volts
Watts = Amperes X Volts. Watts = olrnS —
Watts == Amperes X Amperes X Ohms.
Volts
Volts — Amperes X Ohms. Amperes = QJ- —
Volts
Ohms:= Amperes Heat Units per Sec* = Amp* X AmP- X OhmsX Sees.
X 0.24
Watts
Electrical Horsepower = -,„ »
TT "P N.
H. P. lost in conductor = 16.6538 X (initial Volts) X length in miles.
2150 X Watts per lamp
Area of cond. in circular mils = x x % Qf drQp X no. of
lamps X dist. to center of distribution in miles, or
. 2150 X dist. to center of distribution X Amperes
$Tof Drop X Volts
Distance in miles X Distance in miles
Weight of copper = — — XT lx
Volts X volts -5- 100
100 — % of line loss ./ 0/»ft -
H. P.del.verec. to motor X -% of „„„ logs
Energy Required to Produce 1 Candle Power.
Watts. Watts. Watts.
Tallow 124 Mineral oils 80 Cannel gas 48
Wax 94 Vegetable oils 57 Incandescent lamp.... 15
Spermaceti 86 Coal gas 68 Arc lamp , 3
892
HANDBOOK ON ENGINEERING.
CHAPTER XXX
A CHAPTER OF TABLES.
TABLE NO. 1.- HYPERBOLIC LOGARITHMS.
1
«
t*
3
0
I
It
3
o
tf
I
0
i
M
o
3
£
I
!
0
o
«
be
3
0
ti
5
1.00
.0000
2.45
.8961
3 90
1.3610
5.35
.6771
6 80
1.9169
8.25
2.1102
9.70
2.2721
1.05
.0488
2.50
.9163
3 95
1.3737
5 40
.6864
6.85
9242
8.30
2.1163
9.75
2.2773
10
.0953
2 55
.9361
4 00
1.3863
5 45
.6956
6.90
.9315
8.35
2 1223
9 80
2.2824
15
.1398
2 60
.9555
4 05
1 3987
5 50
.7047
6 95
.9387
8 40
2 1282
9.85
2.2875
.20
.1823
2 65
.9746
4.10
1.4110
5.55
.7138
7.00
.9459
8.45
2.1342
9.90
2 2925
25
.2231
2 70
• 9933
4.15
1.4231
5.60
.7228
7.05
.9530
8.50
2.1401
9.95
2 '2976
30
.2624
2.75
1.0116
4 20
1.4351
5.65
.7317
7.10
.9601
8.55
2 1459
10.00
2.30J6
.35
.3001
2.80
1.0296
4 25
.4469
5 70
.7405
7.15
.9671
8 60
2.1518
.40
.3365
2 85
1.0473
4.30
4586
5.75
.7402
7 20
.9741
8 65
2.1576
.45
.3716
2 90
1 0647
4 35
4702
5.80
.7579
7 25
1.9810
8.70
2.1633
50
.4055
2.95
1.0818
4 40
.4816
5.85
.7664
7.30
1.9879
8.75
2.1691
55
.4383
3.00
1.0986
4.45
4929
5 90
.7750
7.3'.
1.9947
8.80
2.1748
60
.4700
3.05
1.1151
4 50
.5041
5 95
.7834
7 40
2.0015
8.85
2.1804
65
.5008
3.10
1 1314
4.55
.5151
6.00
7918
7 45
2 0082
8 90
2.1861
70
.5306
3.15
1.1474
4.60
5261
605
8001
7.50
2.0149
8.95
2.1917
.75
.5596
3 20
1.1632
4 65
.5369
6.10
.8083
7.55
2.0215
9.00
2.1972
80
.5878
3 25
1.1787
4.70
.5476
6.15
.8165
7.60
2 0281
9 05
2.2028
.85
.6152
3.30
1.1939
4 75
.5581
6.20
.8245
7.65
2.0347
9.10
2 2083
1.90
.6419
3.35
1.2090
4 80
.5686
6.25
.8326
7.70
2.0412
9.15
2.2138
1.95
.6678
3.40
1 2238
4.85
5790
6.30
.8405
7.75
2.0477
9.20
2 2192
2 00
.6931
3.45
1.2384
4 90
.5892
6.35
.8485
7.80
2.0541
9 25
2.2246
2 05
.7178
3 50
1.2528
4.95
.6994
6.40
.8563
7 85
2 0605
9 30
2 2300
2.10
.7419
3 55
1 2669
5 00
.6094
6.45
.8641
7.90
2.0669
9.35
2.2354
2.15
.7655
3 60
1 2809
5.05
6194
6 50
.8718
7.95
2.0732
9 40
2.2407
2.20
.7885
3.65
1 2947
5.10
6292
6.55
1.8795
8.00
2.0794
9.45
2.2460
2.25
.8109
3.70
1 3083
5 15
.6390
6.60
1.8871
8.05
2.0857
9 50
2.2513
2 30
.8329
3 75
1.3218
5 20
.6487
6 65
1 8946
8 10
2 0919
9.55
2 2565
2.35
.8544
3 80
1.3350
5 25
.6582
6 70
1.9021
8 15
2.0980
9 60
2.2618
2.40
.8755
3.85
1.3481
5.30
6677
6 75
1.9095
8.20
2.1041
9.65
2.2670
To find the hyperbolic logarithm of a ratio which is ten times any ratio given in
the table, find the ratio in the table which is one-tenth of the giren ratio and add
2.3026 to the corresponding logarithm; the sum will be the required logarithm.
Example: What is the hyperbolic logarithm of 155? 155 is ten times 1.55. The
logarithm of 1.55 is .4383, and ,4383 + 2.3026 =* 2.7409 which is the hyperbolic logar-
ithm of 16.5.
HANDBOOK ON ENGINEERING.
TABLE NO. 2.
893
DTJPI/EX STEAM PUMPS.
For Water Pressure Not Exceeding 150 Ibs. Speed from 50 to
100 feet per Minute.
i
«
H
tf
JM
O
•s! 6
JsU
!*rf
£
£
2
c 2 ?
Jc ^ c3 Oa"
.£ u g>3 a;
£1
°2
•a
l|s
1111*3
•S Oi +» o
t.s
e^
W 3
43
i
l|§
SL-S J5 o 6
C . 4J» to CO
«u
ctf PH
P
S*fT*!5
O C PH fe ^ w
»j-j f^jQ "Jrt Q
S
5
3
S °
0<
0
3
2
3
.04
100 to 250
8 to 20
4%
2%
4
.10
100 to 200
20 to 40
5%
3%
5
.20
100 to 200
40 to 80
6
4
6
.33
100 to 150
70 to 100
7%
4%
6
.42
100 to 150
85 to 125
7%
5
6
.51
100 to 150
100 to 150
7%
4%
10
.69
75 to 125
100 to 170
9
10
.93
75 to 125
135 to 230
10
6 *
10
1.22
75 to 125
180 to 300
10
7
10
1.66
75 to 125
245 to 410
12
7
10
1.66
75 to 125
245 to 410
14
7
10
1.66
75 to 125
245 to 410
12
8%
10
2.45
75 to 125
365 to 610
14
8%
10
2.45,
75 to 125
365 to 610
16
8%
10
2.451
75 to 125
365 to 610
18%
8%
10
2.45
75 to 125
365 to 610
20
8%
10
2.45
75 to 125
365 to 610
12
flo
3.57
75 to 125
530 to 890
14
10%i
tio
3.57
75 to 125
530 to 890
16
10%
10
3.57
75 to 125
530 to 890
18%
10%;
10
3.57
75 to 125
530 to 890
20
10%
10
3.57
75 to 125
530 to 890
14
12
10
4.89
75 to 125
730 to 1220
16
12
10
4.89
75 to 125
730 to 1220
18%
12
10
4.89
75 to 125
730 to 1220
20
12
10
4.89
75 to 125
730 to 1220
18%
14
10
6.66
75 to 125
990 to 1660
20
14
10
6.66
75 to 125
990 to 1660
17
10
15
5.10
50 to 100
510 to 1020
20
12
15)
7.34
50 to 100
730 to 1460
20
fcfc
15'
11.47
50 to 100
1145 to 2290
25
15
15!
11.47
50 to 100
1145 to 2290
894
HANDBOOK ON ENGINEERING.
TABLE NO. 3
Tank or Light Service Pumps.
These pumps are principally used at railroad water stations, gas and
oil works, -bleacheries, tanneries, refineries, plantations, distilleries, etc. A
variety of valves are used adapted for pumping hot, cold, thick, thin, alka-
line or other liquids.
For quarries and clay pits, also for coffer dams, tunnels, foundation
pits, ore beds, sewerage and irrigating purposes, these pumps are. especially
adapted, having large water passages and valve openings. •
SIZES AND CAPACITIES.
c
' 0)
m
I
I
1
5..
1
I
0>
1.
Sl
Capacity per minute at
ordinary speed.
H*
i
•&
£
fs
aj
i
*s» •
§3
ery pipe,
bes.
Floor Space
Required.
Inches.
8*0
0) O
X
o g
03 o
ts 13
> o
P
I*
1
3S
•
A a
o a
cJ
is
GO
£
03
O
00
fir"
CO
Q
""Ik
3&
4
.15
125 Strokes, .18 gals.
4.
*
14
154
28 xlO
4
4
5
.27
125 33
4
X
2
14
34 xll
5
4
7
.39
125 •• 49
K
24
2
44 x!2
54
54
7
.72
125 " 90
B
3
24
44 xl34
6
f>%
7
.72
125 " 90
i
3
24
44 x'134
6
6
12
1.47
100 •• 147
i
4
4
66^x19 '
6
7
12
2.00
100 " 200
x
5
5
662£xl9
74
7
10
1.66
100 •• 166
54
5
5
56J4xiy
74
74
10
1.91
100 " 191
34
5
5
564x19
8
6
12
1.47
100 " 147
iff
4
4
66^x19
8
7
12
2.00
100 •' 200
134
5
5
665^x19
8
8
12
2.61
100 " 261
1J4
5
5
662ix20
8
9
12
3,30
100 " 330
tM
6
6
66^x214
8
10
12
4.08
100 »• (408
154
6
6
66^x214
10
10
12
4.08
100 " 408
15<
14
6
6
66^x214
10
10
16
5.44
75 " 408
1J4
14
6
6
78^x21>/3
10
12
12
5.87
100 " 587
1M
14
8
•6
66%x23>4
10
12
16
7.83
75 " 587
134
8
6
78/8x23'4
12
10
12
4.08
100 " 408
2
gi/
6
6
66^x214
12
10
16
5.44
75 " 408
2
24
6
6
78^x214
12
12
12
5.87
100. • 587
2
24
8
6
66^x23^
12
19
16
7.83
75 ' 587
2
24
8
6
784x23«£
14
12
12
5.87
100 ' 587
2
24
8
6
(56^x235^
14
12
16
7.83
'75 < 587
2
24
8
6
784x23^
14
14
16
10.66
75' '• -800
2
24
10
8
784x27
14
14
24
16.00
£0 *, 800
24
3
10
8
108 x27
14
16
16
14.92
75. ' 1020
24
3
12
10
80 x354
14
16
24
20.88
50, ' 1044
24
3
12
10
108 X35J4
16
14
16
10.66
75 • 800
24
3
10
8
784x27
16
14
24
16.00
60 ' 800
24
3
10
8
108 x27
16
16
16
14.92
75 ' 1020
24
3
12
10
80 x354
16
16
24
20.88
50 " 1044
24
3
12
10
108 x354
16
18
24
26.44
50 •• 1322
24
3
12
10
108 x38
16
20
24
32.64
50 " 1632
24
3
14
12
108 x40
18
16
24
20.88
50 " 1044
34
4
12
10
110 x354
18
18
24
26.44
50 < 1322
34
12
10
110 x38
18
20
24
32.61
50 ' 1632
34
14
12
110 x40
18
22
24
39.50
50 ' 1975
34
14
14
110 x42
20
18
24
26.44
50 ' 1322
34
12
10
118 x38
20
20
24
32.64
50 ' 1622
34
14
12
118 X40
20
22
24
39.50
60 ' 1975
34
14
14
118 x42
20
24
24
47.00
60 • 2350 •
q*
4
16
16
118 £44
HANDBOOK ON ENGINEERING.
895
TABLE NO. 4.
DIAMETERS, AREAS AND CIRCUMFERENCES
OF CIRCLES.
•w
4
' d
|s
I
c"3'
f«5
•d
§fl
3X3
a>M
§J3
t<
5«
*s
s§
•o5
$
«S
5*
<$
«s
.b a
1
3.14159
'0.78540
4
12.5664
12.566
8
25.1327
50.265
A
3.33794
0.88064
i
12.7627
12.962
H
25 5224
51.84.9
8
3.53429
0.99402
^8
12.9591
13.364
25.9181
53.456
1
3.73064
3.92699
1.1075
1.2272
ft
13.1554
13.3518
13.772
14.186
$
26.3108
26.7035
55.088
56.745
4.12334
1.3530
A
13.5481
14.607
%
27.0962
58.426
rt
4.31969
1.4*49
\l
13.7445
15.033
%
27.4889
60.133
/a
4.51604
1.6230
13.. 9408
15.466
%
27.8816
61.862
fc
4.71239
1.7671
H
14.1372
15.904
9
28.2743
63.617
i9<f
4.90874
1.9175
14.3335
16.349
H
28.6670
65.397
£l
5.10509
2.0739
/8
14.5299
KU'OO
H
29.0597
67.201
ri
5.30144
2.2365
11
14.7262
17.257
96
29.4524
69.029
5.49779
2.4053
%
14.9226
17.721
J£
29.8451
70.882
13
5.69414
2.5802
13
15.1189
18.190
%
30,2378
'72.760
%
5.89049
2.7612
/8
15.3153
18.665
'£
30.6305
74.662
h
6.08684
2.9483
i1 3
15.5116
19.147
31.0232
76.589
2
6.28319
3.1416
r>
15.7080
19.635
10
31.4159
78.540
>\j
6.47953
3.3410
15.9043
20.129
32.2013
82.516
M
6.67588
3.5466
/Q
16.1007
20.629
l/2
32.9867
86.690
6.87223
3.7583
1\
16.2970
21.135
% -
33.7721
90.763
5*
7.06858
3.9761
y±
16.4934
21.4348
11
34.5575
95.033
5
7.26493
4.2000
8
10.0897
22.166
35.3429
99.402
%
7.46128
4.4301
%
10.8861
22.691
H
36.1283
103.87
I7*
7.65763
4.6664
I7H
17.0824
23.221
X
30.9137
108.43
H
7.85398
4,9087
54
17.2788
23.758
12
37.6991
113.10
8.05033
5.1572
*&
17.4751
24.301
14
38.4845
117.86.
ft
8.24668
5.4119
%
17.6715
24.850
r|
39.2699
122.72
ti
8.44303
5.0727
n
17.8678
25,406
5^
40.0553
127.68
3^
8.63938
5.9390
%
18.0642
25.967
13
40.840>
132.73 v
jn
8.83573
6.2126
li
18.2605
20.535
41.6261
137.89
«
9.03208
0.4918
%
18.4569
27.109
16
42.4115
143.14
II
0.22843
6.7771
IS
18.6532
27.688
k
43.1969
148.49
3^
9.42418
7.06S6
6
18.8496
28.274
14
43.9823
153.94
11.62115)
7.3662
Vs
19.2423
29.465
H
44.767r
159.48
•8
9.81748
7.6699
14
19.6350
30.680
45.5531
165.13
ino
10.0138
7.9798
H
20.0277
31.919
%
46.3385
170.87
l'\
10.2102
8.2958
Yz
20.4204
33.183
15
47.1239
176.71,
J5fl
10.4065
8.6179
20.8131
34.472
47.9093
182.65.
U£
10.^029
8.9462
%
21.2058
35.785
Vz
48.694"
188.69
l'7rt
10.7992
9.2800
ft
21.5984
37.122
%
49.4801
194.83.
i^
10.9950
9.0211
7
21.9911
38.485
16
50.2655
201.061
jjjj
11.1919
9.9678
22.3838
39.871
|4
51.0509
207. 39V
11.3S83
10.321
^
22.7765
41.282
51.8363
213.82-
io
1L5846
10.080
?»
23.1692
42.718
%
52.621"
220.35
3a
11.7810
11.045
Va
23.5619
44.179
17
53.4071
226.98-
3
11.977;.'
11.418
?8
23.9546
45.664
W
54.192:
233. 7t
x
12.1737
11.793
3/
24.3473
47.173
ll
54.9779
24o 53
is
12.3700
12.177
3
24.7400
4S.707
05.7030
247. 4&.
896
HANDBOOK ON ENGINEERING.
Diameters, Areas and Circumferences of Circles.— Con.
Diam. II
Inches.
Circumf.
Inches.
s
Diam.
Inches.
Circumf.
Inches.
gs
l|
Circumf.
Inches.
fi
18
56.5487
254.47
32
100.531
804.25
46
144.513
1661.0
54
57.3341
2t<1.59
54
101.316
816.86
H
145.299
1680.0
58.1195
268 80
3
102.102
829.58
B
146.0.S4
1698.2
3£
68.9049
276.12
1H2.887
842.39
146.869
716.5
19
59.6903
283.53
33*
103.673
855.30
47'4
147.65;-.
734.9
54
60.4757
291.04
104.458
fc'68.31
54
148.440
753.5
H
61.2611
2-J8.65
Vi
105.243
881.41
149.226
772. J
62.0465
306.35
%
106.029
894.62
94
150.011
75>0.8
20
62.8319
314.16
34
106.814
907.92
48
150.796
1809 6
54
63.6173
3^2.06
54
107.600
921.32
H
151.582
1828.5
H
64.4026
330.00
H
108.385
934.82
152.367
1847.5
66.1880
338.16
109.170
•948.42
3
153. 15H
1866.5
21 *
65.9734
346.36
354
109.956
962.11
49
133.938
1885.7
54
66.7588
354.66
54
110.741
975.91
154.723
1905.0
V*
67.5442
363.05
H
111. 627
989.80
y
155.509
1924.2
68.329H
371.54
112.312
1003.8
&
156.294
1943.9
224
69.1150
380.13
36 4
113.097
1017.9
50
157.080
1963.5
54
69.9004
388.82
54
113.883
1032.1
54
157.865
1983.2
H
70.6858
397.61
%
114.668
1046.3
K
158.650
2003.0
71 4712
406.49
115.454
J060.7
159.436
2022.8
23
72.2566
415.48
37 4
116,239
1075.2
51 4
160.221
2042.8
54
73 .'0420
424.56
54
117.024
1089.8
161.007
2062.9
y*
73.8274
433.74
H
117.810
1104.5
H
161.792
2083.1
%
74.6128
443.01
118.596
1119.2
162.577
2103.3
24
75.3982
452.39
384
119.381
1134.1
52/4
163.363
2123.7
5-4
76.1836
461.86
H
120.166
1149.1
M
164.148
2144.2
H
76.9690
471.44
H
120.951
1164.2
H
164.934
2164.8
*
77.7544
481.11
121.737
1179.3
165.719
2185.4
25
78.5398
490.87
39 4
122.522
1194.6
534
166.504
2206.2
54
79.3252
500.74
123.308
1210.0
54
167.290
2227.0
n
80.1106
510.71
Vi
124.093
1225.4
168.075
2248.0
%
80.8960
520.77
94
124.878
1241.0
94
168.861
2269.1
20
81.6814
530.93
40
125.664
1256.6
54
169.646
2290.3
54
82.4668
541.19
K
126.449
1272.4
54
170.431
2311.5
K
83.2522
551.55
127.235
1288.2
171.217
2332. »
84.0376
562.00
9£
128.020
1304.2
94
172.002
2354.3
27*
84.8230
572.56
41
128.805
1320.3
55^
172.788
2375.8
54
85.6084
583.21
54
129.591
1336.4
173.573
2397.5
86.3938
593.96
130.376
1352.7
y
174.358
2419.2
9s£
87,1792
604.81
94
131.161
1369.0
%
175.144
2441.1
~H
87.9646
615.75
42
131.947
1385.4
56
175.929
2463.0
54
88.7500
626.80
54
132. 732
1402.0
176.715
2485.0
H
89.5354
90.3208
637,94
649.18
y*
133.518
134,303
1418.6
1435.4
&
177.500
178.285
2507.2
2529.4
so'4 .
91.1062
660.52
434
135,088
1452.2
57
179.071
2551.8
54'
91.8916
671. 9d
54
1469.1
179.856
2574.2
'/a
92.67-50
683.49
Vi
136 1659
1486.2
H
180.642
2596.7
?£
93.4624
695.13
137.445
1503.3
9i
181 .427
2619.4
BO
94.2478
706.86
44*
138.230
1520,5
58
182.212
XJ642.1
H
95.0332
718.69
54
139.015
1537.9
182.998
2664.9
H
95.8186
730.62
/4
139.801
1555.3
y
183.783
2687.8
*j
96.6040
742.64
a'
110.586
1572.8
%t
184.569
2710.9
81
97.3894
754.77
45'
141.372
1590.4
59
185.ar>4
2734.0
fe
98. 1748
766. 9j)
54
142.157
1608.2
186.139
2757.2
H
98.9602
779.31
H
142.942
1626.0
y
186.925
2780.5
~*»
99.7456
791.73
143.728
1643.0
%
187.710
2803.9
HANDBOOK ON ENGINEERING.
897
Diameters, Areas and Circumferences of Circles. — Con.
Diam. !|
Inches..
Circumf.
Inches.
SM
%
Diam.
Inches.
Circumf,
Inches.
f
*&
Diam.
Inches.
Circumf.
Inches.
II
.60
188.496
2827.4
74
232.478
4300.8
88
276.460
6082.1
189.281
2851.0
h
233.263
4329.9
k
277.246
6116.7
y*
190.066
2874.8
l/2
234.049
4359.2
i?
278.031
6151.4
%
190.852
2898.6
%
334.834
4388.5
H
278.816
6186.2
61
191.637
2922.5
75
235.619
4417.9
,89
279.602
6221.1
' J4
192.423
2946/5
&
236.405
4447.4
H
2«0.387
6256.1
5?
193'. 208
2970.6
Yz
237.190
4477.0
l/2
281.173
6291.2
%
193.993
2994.8
%
237.976
4506.7
u
281.958
6:£H'.4
62
194.779
3019.1
76
^38.761
4536.5
901/
282.743
6361.7
&
195.564
8048.5
!/4
239.546
4566.4
283.529
6397.1
H
196.350
3068.0
tt
2i0.332
4596.3
H
284.314
6432.6
%
197.135
3092.6
%
241.117
4626.4
' %
285.100
6468.2
63
197.920
3117.2
77
241.903
4656.6
91
285.885
6503.9
1A
198.706
3142.0
&
242.688
4086.9
H
286.670
6539.7
4
199.491
3166.9
H
243.473
4717.3
M
287.456
6575 5
%
200.277
3191.9
*
244.259
4747.8
%
238.241
6611.5
64
201.062
3217.0
78
245.044
4778.4
$2
289.027
66-17.6
H
201.847
3242.2
K
245.830
4809.0
K
289.812
(5683.8
H
202.633
3267.5
H
246.615
4839.8
• l/2
390.597
6720.1
%
203.418
3292.8
it
247.400
4870.7
%
291.383
6756.4
66
204.204
3318.3
79
248.186
4901.7
88
202.168
6792.9
/4
204.989
3343.9
K
248.971
4932.7
H
292.954
6829.5
y$
205.774
3369.6
%
249.757
4963.9
'/2
293.739
6866.1
%
206.560
3395.3
%
250.542
4995.2
• %
294.524
6902.9
66
207.345
3421.2
80
251.327
5026.5
9;4
295.310
6939.8
34
208.131
3447.2
k
252.113
5058.0
r?H
296.095
6976.7
H
208.916
3473.2
*
252.898
5089.6
'/2
296.881
7013.8
V
209.701
3199.4
%
253.684
5121.2
'%
297.666
7051.0
67
210.487
3525.7
81
254.469
5153.0
95
398.451
7088.2
fc
211.272
3552.0
y*
255.254
5184.9
'H
399.237
7125.6
l/2
-412.058
3578.5
K
256.040
5216.8
' l/2
300.022
7163.0
%
212.843
3605.0
x
256.825
5248.9
^ %
300.807
7200.6
68
213.628
3631.7
82
257.611
5281.0
96
301.593
7238.2
K
214.414
3658.4
y\
258.396
5313.3
H
302.378
7276.0
3
215.199
3685.3
y*
259.181
6345.6
3
303.164
7313.8
%
215.984
3712.2
%•
359.967
5378.1
1i
303.949
7351.8
«9
216.770
3739.3
83
260.752
5410.6
97
304.734
7389.8
14
217.555
3766.4
y±
261.538
5443.3
M
305.520
742S-.0
y*
218.341
3793.7
1A
262.323
5476.0
v H
306.305
7466.2
u
219.126
3821.0
%
263.108
5508.8
• %
307.091
7504.5
70
219.911
3848.5
84
263.394
5541.8
98
307.876
7543.0
tt
220.697
3876.0
\i
264.679
5574.8
H
308.661
7581.5
l/i
221.482
3903.6
H
265.465
5607.9
y*
309.447
7620.1
94"
222.268
3931.4
3^
266.250
5641.2
%
310.232
7658.9
71
223.053
3959.2
55
267.035
5674.5
"i
311.018
7697.7
H
223.838
3987.1
!/i
267.821
5707.9
311.803
7736.6
3
224.624
4015.2
H
268.606
5741.5
H
312.588
7775.6
%
225.409
4043.3
^
269.392
5775.1
%
313.374
7814.8
72
226.195
4011.5
86
270.177
5808.8
100
314.159
7854.0
H
226.980
4099.8
H
270.962
5842.6
Vi
227.765
4128.2
%
271.748
5876.5
%
228.551
4156. 8
%
272.533
5910.6
-73
229.336
4185.4
87
273.319
5944.7
230.122
4214.1
H
274.104
5978.9
H
230.907
4242.9
3
274.889
6013.2
3rf
281.^2
4271.8
y
2T6.R75
6017.0
898
HANDBOOK ON ENGINEERING.
TABLE NO. 5.
CUBIC FEET OF AMMONIA GAS "PER MINUTE TO
PRODUCE ONE^TON OF REFRIGERATION PER DAY.
CONDENSER.
P
P
103
"5
127
139
153
168 185
200
218
t ; 65°
70°
75°
80°
85°
90°j '95°
100
105°
*
r A 2O°
7 I o
5.84
5-9
5.96
6.03
6.06
6.16
6.23
6.30
6.43
o
0
^o:
5.35
5-4
5.46
5-52
5.58
5-64
5.70
5-77
h
9
— 10 j
4.66
4-73
4.76
4.81
4.86
4.91
4-97
5-°5
5-oS
w
13
~" 0
4.09
4.12
4.17
4.21
4.25
4.3°
4-35
4.40
4.44
o
16
° \
3.59
3-63
3-66
3-70
3-74
3.78
3.83
3.87
2
20
5 \
3-2C
3.24
3-27
3.30
3-34
3.38
3-41
3.45
3-49
w
Jo
10°
2.87
2.9
2-93
2.96
2.99
3.02
3.06
3-°9
3.12
28
'5
2.59
261
2.65
2.68
2.71
2-73
2.76
2.80
2.82
!.
aj
20
2.31
2-34
2.36
2.38
2.41
2-44
2.46
2.49
2.51
39
25*
2.06
2.08
2.10
2.12
2.» 5
2.17
2. 2O
2. -2 2
2.24
«
3°
1.85
1.87
1.89
I.9I
1-93
1.95
1.97
2.00
2.OI
3i>
1.70
1.72
1.74
1.76
1.77
1.79
1.81
1.83
1.85
TABLE KG. 6.
PROPERTIES OF SULPHUR DIOXIDE.
t
. P
H
h
L
V
\\
V
. 22
T"1*
—4
S.S^
7-23
9.27
157.43
158.64
159.84
^19-56
—16.30
— »3-°5
176.99
•174.95
172.89
I3.I7
10.27
8.12
.076
.097
.123
.4041
.3914
•3791
5
«4
23
11.76
14.74
18.31
161.03
162.20
163.66
—9.79
-6.53
—3.27
170.82
168.73
166.63
6.50
5.25
4.29
•153
.190
.232
•3673
•3559
•3449
32
4<
5°
«.53
27.48
33-25
164.51
165.65
166.78
o.oo
3-27
6.55
164.5 r
162.38
160.23
3.54
2.93
2.45
.282
•340
.406
•3344
.3241
.3M2
59
68
77
39 33
47-61
56.39
167.90
168.99
170.09
9.83
13."
16.39
158.07
155-89
153-7°
2.07
i-75
1.49
•483
•570
.669
.3046
.2952
.2861
86
95
104
66.36
77.64
90.31
171.17
172.54
1 73.30
19.69
22.98
26.28
15L49
149.26
147.02
1.27
1.09
.91
.780
.906
1.046
.2774
.2689
.2607
HANDBOOK ON ENGINEERING.
899
TABLE NO. 7.
PROPERTIES OF AMMONIA.
t
*4
A.
B
t
*=4
A
B
—40
1.3802
.0000
.0000
60
•9959
.2136
.1707
— 35
1.3569
.0118
.0115
65
.9803
.2231
.1768
1-3343
.0236
.0224
70
.9651
.2326
.1825
— 25
1.3119
.0351
.0332
75
.9500
.2420
.1881
—20
1.2902
.0465
.0435
80
•9353
•2513
•1936
—15
1.2689
.0578
•0535
85
.9207
.2605
.1990
— 10
1.2481
.0690
.0631
90
.9065
.2696
.2042
— 5
1.2276
.0800
.0726
95
.8922
.2787
.2093
* 0
1.2076
.0910
.0816
100
.8788
.2877
.2140
+5
1. 1880
.1018
.0904
105
.8650
.2966
.2186
10
1.1688
.1125
.0989
no
.8516
•3054
.2232
15
1.1500
.1230
.1072
115
•8385
.2276
20-
1.1315
• 1335
.1152
120
.8255 .3228
-2319
1.1134
.1439
,1229
125
.8129
•33i3
.2360
30
1.0957
.1541
.1304
130
.8002
.3398
.2402
35
1.0783
.1643
.1376
US
.7878
•3483
.2441
40
1.0613
.1743
.1446
140
•7756
•3567
.2479-
45
1-0445
.1843
.1514
145
.7636
•3650
.2516
5°
1.0280
.1941
.1581
150
.7518
•3732
•255*
55
1.0118
.2039
.1645
,7402
.3814
.2586
— logeli.
In this table :
AA — A 2 = c loge lj ; where c is the specific heat of
liquid ammonia, c is assumed equal to 1; if any other
value is taken the numbers in the table must be multiplied
by that value..
^-63 = 9s -
Examples of use of table :
(1) Per cent, of liquid in wet compression to prevent
superheating = (Bj-B2)/^2.
(2) Superheating above condenser with dry compres-.
sion = ,0a,(7Bi7BB;lTB^
(3) Work to compress, i pound of ammonia = 788
(T\ - T2) 9>2 ;— i cubic foot = 788 (T, — T2) <P2 W8.
(4) Mean pressure = «f (T, - T2) <P2 W2.
(5) Equation of adiabatic A9 + «3^2 = Al + »,9r
900
HANDBOOK ON ENGINEERING.
TABLE NO. 8.
PROPERTIES OF CARBONIC ACID.
f |
P
H
h L
v
w
0
i
_ .-
_
.
— ,
. ,
— 22
210
98.35
—37.80 136.15
.4138
! 2.321 «
.3108
— 13
249
99.14
—32.51
131.65
•3459
j 2:759
.2945
— 4
292
99.88
26.91 126.79
.2901
3-265
.2785
1
j
5 ;
342 100.58
^—20.92
121.50
.2438
1 3.853
.2613
14
396
IOI.2I
— 14.49 I!5-7°
.2042
, 4.535
.2441
23
457
IOI.8I
—7.56 ' 109.37
.1711
!' 5.331
I
.2262
32
525
102.35
o.oo
102.35
.1426
•: 6.265
*• .2080
41
599
IO2.84
8.32
94-52
.1177
7-374
.1887
5°
680
103.24
17 60 85.64
.0960
' 8.708
•'679,
i
1
59
768
103.59
28.22
75-37
.0763
i 10.356
.1452
68
864 j 103.84
40.86
62.98
•0577
j 12.480
77
968
10395
57.06 46.89
.0391
:i5475
.0873
86
1.080
10372
84.44 ' 19-28
.0147
21.519
.0353
1 i
TABLE NO. 9.
PROPERTIES OF BRINE SOLUTIO'N.
(Common Salt.)
1
•ifc
Wo
!-
i
1.
[1
i
ific Gravity
it 60° F.
1
:ific heat.
I .
11
i
li
^"3,
"? e
1
f
I*
F
1
*
I
I
So
&
r
^
o
0
0
X.
i.
8.35
0.
62.4
32.
I
r-4
i
1.007
0.992
8-4
0.084
62.8
5
; [20
5
-037
0.96
8.65
0.432
64.7
25.4
10
40
10
.073
0.892
8-95
0.895
66.95
18.6
15
60
15
.H5
0-855
9-3
1-395
69.57
12.2
20
80
'9
0,829
9-6
1.92
71.76
6.86
35
IOO
23
.191
0.783
9-94
2.485
74,26
1.00
HANDBOOK ON ENGINEERING.
901
00
0
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902
HANDBOOK ON ENGINEERING.
tf
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1
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to
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t^ 00 M
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to
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k.H
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HANDBOOK ON ENGINEERING.
903
TABLE NO. 12.
Reaumufj Fahrenheit, and Celsius
Thermometers Compared.
R.
F.
C.
-Hnn
E-+210-E
75--
E- 205-E
E- 200-E
--95
E4- 195-E
--90
70--
65--
E- 190-E
— —
j o er
Q tf
•~ 155
-
E- iso-E
E- 175-E
55
--80
60--
E- 170- E:
E- 165-E
75
55--
50--
45--
E- 160-E
E- 155-E
:- 150- =
:-70
E- 145- E
R A
: 140- _
E- 135-E
e; K
-- 13Q-:
40--
35--
E- 125-E
- j o A
:-«»
E- U5-E
y| •£
E- uo-E
-----
32l
1-105-1
1-40
R
R
C.
+32- -
30--
-+104 i
— loo-E
- 35
--30
25--
E— 90~E
E— 85-E
20--
E- so-E
--25
15--
E— TO -E
_ OA
E — 65 -E
E- eo-E
-- 15
10--
5--
E— 55-E
J A
: 50 r
—
:_ 4Q-E
-- 5
o--
E— 35-E
E- 30-E
-- 0
-5--
E— 25- E
E-.20-E
-— 5
E— 15-E
— 10
10--
15-
E- IO-E
— 4R
-
:- 0-
_
904
HANDBOOK ON ENGINEERING.
3.
O
to
H
PQ
a
•JN3JL
905
HANDBOOK ON ENGINEERING.
TABLE NO. 14.
Weight of Rivets and Round Headed Bolts Without
Per 100.
LENGTH FROM UNDER HEAD. ONE CUBIC FOOT WEIGHING 480 LBS^
LENGTH
INCHES.
3/8"
DIAM.
y2"
DIAM.
%"
DIAM.
w
DIAM.
%"
DIAM.
1"
DIAM.
I'/s"
DIAM.
1U"
DIAM.
U4
5.4
12.6
21.5
28.7
43.1
65.3
91.5
123.
1%
6.2
13.9
23.7
31.8
47.3
707
98.4
133.
i%
6.9
15.3
25.8
34.9
51.4
76.2
105.
142.
2
7.7
16.6
27.9
37.9
55.6
81.6
112.
150.
2*4
8.5
18.0
30.0
41.0
59.8
87.1
119.
159.
2Y2
9.2
19.4
32.2
44.1
63.0
92.5
126.
167.
23^
10.0
20.7
34.3
47.1
68.1
98.0
133.
176.
3
10.8
22.1
36,4
50.2
72.3
103.
140.
184.
3^4
11.5
23.5
38.6
53.3
76.5
109.
147.
193.
3V3
12.3
24.8
40.7
56.4
80.7
114.
154.
201.
3%
13.1
26.2
42.8
59.4
84.8
120.
161.
210.
4
13.8
27.5
45.0
62.5
89.0
125.
167.
218,
4H
14.6
28.9
47.1
65.6
93.2
131.
174.
227.
4V2
15.4
30.3
49.2
68.6
97.4
136.
181.
236.
43/4
16.2
31.6
51.4
71.7
102.
142.
188.
244.
5
16.9
33.0
53.5
74.8
106.
147.
195.
253.
6H
17.7
34.4
55.6
77.8
110.
153.
202.
261.
5V2
18.4
35.7
57.7
80.9
114..
158.-
209.
270.
534
19.2
37.1
59.9
84.0
118.
163.
216.
278.
6
20.0
38.5
62.0
87.0
122.
16.9.
223.
287.
6V3
21.5
41.2
66.3
93.2
131.
180.
236.
304.
7
23.0
43.9
70.5
99.3
139.
191.
250.
321.
7Va
24.6
46.6
74.8
106.
147.
202.
264.
338.
8
26.1
49.4
79.0
112.
156.
213.
278.
355,
8Va
27.6
52.1
83.3
118.
164.
223.
292.
372.
9
29.2
54.8
87.6
124.
173.
234.
306.
389.
9Va
30.7
57.6
9i.8
130.
181.
245.
319.
406;
10
32.2
60.3
96.1
136.
189.
256.
333.
423.
lOVa
33.8
63.0
101.
142.
198.
267.
347.
440.
11
35.3
65.7
105.
14S.
206.
278.
361.
457.
11 Va
36.8
68.5
109.
155.*
214.
289.
375.
474.
12
38.4
71.2
113.
161.
223.
3QQ.
388,
491.
Heads.
1,8
5.7
10.9
13.4
22.2
38,0
'57.0
82;0
HANDBOOK ON ENGINEERING.
TABLE NO. 15.
Weight and Strength of Iron Bolts.
ENDS ENLARGED OR UPSET.
ENDS NOT EN-
LARGED.
ENDS ENLARGED OR. UPSET.
ENDS NOT EN-
LARGED.
8
|;
8
*g
fe
tfx
O
* fc
By
*g
fc 5
P5 .
g .
fr «
oS
rt
"g
El
B§
'Eg
i.S
B H'
w K
ng
5 g
62
gg
JS_
°0
r
H
3 *
£
3 S
p
2o
r
§a
i1
Ine.
Pounds.
Tons.
2340 Ibs.
Ins.
Lbs.
Ins.
Lbs,
Tons
2240 Ibs.
Ins.
Lbs.
V/L
.0414
.245
1%
8.10
45.7
2.14
12«0
&
.093
.553
If!
8.69
49.0
2.22
12.9
I 6
.165
.983
.35
.321
•*• 1 6
1%
9.30
52.5
2.30
13.8
JL
.258
1.53
-43
.452
9.93
56.0
2.38
,14.7
%
.372
2.21
.50
.654
216
10.6
59.7
2.45
f!5.7
ft
.506
3.00
.58
. .897
oys
12.0
63.8
2.59
17-5
V*
.661
3,93
.66
' 1.14
2Vi
13.4
71.6
2.73
19.5
ft
.837
4.97
.73
1.41
2%
14.9
79.7
2.88
,21.6
%
1.03
6.14
.80
1.67
2Vfc
16.5
88.4
3.02
'23.9
li
1.25
7.42
.88
2.03
2%
18.2
97.4
3.16
26.1
1.49
8.83
.96
2.41
2%
20.0
106.9
3.30
28.5
1*
1.75
10.4
1.04
2.81
21.9
116.8
3.45
31.1
2.03
12.0
1.12
3.26
3
23.8
127.2
3.60
[33.9
M
2.33
13.8
1.20
3.77
3V4
27.9
141.0
3.86
39.1
i
2'.65
15.7
1.27
4.27
32.4
163.6
4.12
44.4
ift
2.99
16,8
1.35
4.77
3%
37.2
187.7
'4.41
51.0
1%
3.35
18.9
1.42
5.28
4
42.3
213.6
4.70
57.8
1ft
3.73
21.1
1.49
5.81
4Vi
47.8
227.0
4.98
65.2
1%
4*13
23.3
1.55
6.39
53.6
254.5
5.25
72.9
1ft
4.56
25.7
1.64
7.04
4«I
59.7
283.5
5.53
'80.5
1%
5.00
28.2
1.72
7,74
5
66.1
314.2
5.80
88.1
1ft
~5.47
30.8
1.80
8.48
5^4
72.9
324.7
6.08
97.0
5.95
33,6
1.87
9.20
51/2
80.0
356.4
6.36
106.
1ft
6.46
36.4
1.94
9.88
534
87.5
389.5
6.63
116.
1%
6.99
394
2.00
10.6 '
6
95.2
424.1
6.90
126.
JJi
,7.53
42.5
2.07
11.3
For square Jbarslncrease the breaking strains Vi part.
A long upset rod is no'strpngcr than one not upset, against slowly ap*
plied loads or strains.' Therefore in such cases the column of kireate'st diam-
eter in the table should be used.
HANDBOOK ON ENGINEERING.
907
TABLE NO. 16.
Boiling: Point* of Various Substances.
At Atmospheric Pressure at Sea Level.
Substance.
Degrees
Fahr.
Substance.
Degrees
Fahr.
Alcohol
173
Sulphur
670
Ammonia. ...
28
Sulphuric Acid, s. g 1.848
590
Benzine
176
Sulphuric Acid, s. g. 1 3
240
Coal Tar
325
Sulphuric Ether . . ... .
100
Linseed Oil
597
315
Mercury
648
Water
212
Naptha...
186
Water, Sea
213.2
Nitric Acid, s. g. 1.42. . . .
248
Water, Saturated Brine
226
Nitric Acid, s. g. 1 5.
210
Wood Spirit
150
Petroleum Rectified
316
TABLE
Melting Points of Metals.
From D. K. C.
NO. 17.
Melting: Points of Various Solids.
From D. K. C. and H.
Metal.
Degrees
Fahr.
Substance.
Degrees
Fahr.
Aluminum
Full Red
Heat.
1150
507
1690
1996
2156
2282
2012
( 1922
] to
C 2012
.2912
617
—39
1873
( 2372
< to
( 2552
442
773
Carbonic Acid
-108
2377
32
95
45
112
91
606
120
( 109
to
( 120
239
92
14
142
154
Antimony
Glass
Bismuth
Bronze
Lard
Copper
Nitro-Glycerine
Gold, Standard.
Gold, Pure
Pitch
Iron, Cast, Gray
Saltpetre
Iron, Cast, White
Iron, Wrought
Lead
Mercury ... ...
Tallow
Silver . .
Steel
Wax, Bleached
Tin
Zinc
Melting: Points of Fusible Plugs.
From D. K. 0.
Softens at
Melts at
Softens at
Melts at
2 Tin, 2 Lead
365
372
2 Tin, 7 Lead
377J
S88
Tin, 6 Lead
372
383
2 Tin, 8 Lead
3954
408
908
HANDBOOK ON ENGINEERING.
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SSISSSSSi
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HANDBOOK ON ENGINEERING.
909
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iJlO HANDBOOK ON ENGINEERING.
TABLE NO. 20.
Capacity of Reservoirs in Gallons.
NOTE — The columns headed Length and Width denote the length and width
in feet; the columns headed Gallons denote the capacity In U. S. gallons for one
foot In depth.
Length
and
Width
Gallons.
Length
aud
Width.
Gallons.
Length
and
Width.
Gallon*.
Length
and
Width.
Gallons,
1x1
2x 1
7.481
14.961
15 x 7
16 x 7
785.455
837.818
23x10
24 x 10
1720.519
1795.325
13x13
14x13
1264.208
1361.454
3X 1
22.442
17 x 7
890.182
25x10
1870.130
15x13
1458.701
2X 2
29.922
18 x 7
942.545
26x10
1944.935
16x13
1555.948
3x 2
44.883
19 x 7
994.909
27x10
2019.740
17x13
1653.195
4x 2
59.844
20x 7
1047.273
28x10
2094.545
18x13
1750.442
6x 2
74.805
21 X 7
1099.636
29X10
2169.351
19x13
1847.688
6x 2
89.766
8x 8
478.753
30X10
2244.156
20x13
1944.935
8x3
67.325
9X 8
538.597
11X11
905.143
21x13
2042.182
4x3
89.766
10 x 8
598.442
12X11
987.429
22x13
2139.429
6x 3
112.208
11x8
658.286
13X.11
1069.714 .
23x13
2236.675
6x 3
134.649
12 x 8
718.130
14X11
1152.000
24 x 13
2333.922
7X 3
157.091
13 x 8
777.974
15X11
1234.286
25 x 13
2431.169
8x 3
179.532
14 X 8
837.818
16X11
1316.571
26x13
2528.416
9x 3
201.974
15 x 8
897.662
17X11
1398.857
27x13
2625.662
4X4
119.688
16 x 8
957.507
18X11
1481.143
28 x 13
2722.909
6x 4
149.610
17 x 8
1017.351
19x11
1563-429
29x 13
2820.156
6x 4
179.532
18 x 8
1077.195
20X11
1645.714
30 x 13
2917.403
7x 4
209.455
19 x 8
1137.039
21X11
1728.000
31 x 13
3014.649
8x 4
239.377
20x 8
1196.883
22x11
1810.286
32 x 13
3111.896
fix 4
269.299
21 x 8
1256.727
23x11
1892.571
33 x 13
3309.143
10 x 4
299.221
22x 8
1316.571
24x11
1974.857
34X 13
3306.390
11 X 4
329.143
23x 8
1376.416
25X11
2057. 143
35 x 13
3403.636
12 X 4
359.065
24X 8
1436.260
26x11
2139.428
36 x 13
3500.883
6x 5
187.013
9x 9
605.922
27X11
2221.714
37x13
3598:130
6x 5
224.416
10 x 9
673.247
28x11
2304.000
38x13
3695.377
7x 6
261.818
11 x 9
740.571
29x11
2386.286
39x13
3792.623
8x 5
299.221
12 x 9
807.896
30 x 11
2468.571
14 x 14
1466.182
9x 5
336.623
13 x 9
875.221
31x11
2550.857
15x14
1570.909
10 x 6
374.026
14" x 9
942.545
32x11
2633.143
16x14
1675.636
11 x 5
411.429
15 x 9
1009.870
33 x 11
2715.429
17 x 14
1780.363
12 x 5
448.831
16 x 9
1077.195
12x12
1077.195
18 it 14
1885.091
13 x 6
486.234
17 x 9
1144.519
13x12
1166.961
19x14
1989.818
14 X 5
623.636
18 x 9
1211.844
14 x 12
1256.727
20x 14
2094.545
15 x 5
561.039
19 x 9
1279.169
15 x 12
1346.493
21 XI4
2199.263
ex 6
269.299
20x 9
1346.493
16x12
1436.260
22x14
2304.000
7x 6
314.182
21 x 9
1413.818
17x12
1526.026
23 x 14
2408.727
8x 6
359.065
22x 9
1481.143
18x12
1615.792
24 x 14
2513.454
Ox 6
403.948
23x 9
1548.467
19x12
1705.558
25 x 14
2018.182
10 x 6
448.831
24 x 9
1615.792
20 x 12
1795.325
•26 X 14
2722.909
U x 6
•493.714
25x 9
1683.117
21x12
1885.091
27 x 14
2827.636
12 x 6
538.597
26 x 9
1750.442
22 x 12
1974.857
28x14
2932.364
13 x 6
583.480
27x 9
1817.766
23x12
2064.623
29x14
3037.091
14 x 6
628.364
10 x 10
748.052
24x18
2154390
30X14
3141.818
15 x 6
673.247
11 x 10
822.857
25 x 12
2244.156
31 X14
3246.545
16 x 6
718.130
12 x 10
897.662
26x12
2333.922
32x14
3.351.273
17 x 6
763.013
13 x 10
972.467
27 x 12
2423.688
33x14
3456.000
18 x 6
807.896
14x10
1047.273
28 x 12
2513.455
34x14
3560.727
7x 7
366.545
15 x 10
1122.078
29 x 13
2603.221
35x14
3665.454
8x 7
418.909
16x10
1196.883
30 x 12
2692.987
*36 X 14
3770.182
9x 7
471.273
17 x 10
1271.688
31 x 12
2782.753
37x14
3874.U09
10 x 7
523.636
18 x 10
1346.493
33s 12
2872.520
38.x 14
3/79.636
11 x J
576.000
19 x 10
1421.299
33 x 13
2962.386
,'J9 x 14
4084.364
12 x 7
628.364
20 x 10
1496.104
34 x 12
3052.052
40 x 14-x
4189.091
13 X 7
680.727
21 x 10
1570.909
35x12
3141.818
41x14
4393.818
14X 7
733.091
22X10
1645.714
36 XW
3231.585
42x14
4398.545
HANDBOOK ON ENGINEERING.
TABLE NO. 21.
Oapaoity of Reservoirs in Gallons. — Continued.
911
Length
Length
Length
Length
and
Gallons.
and
Gallons.
and
Gallons
and
Gallons.
Width
Width.
Width.
Width.
15 x 15
16 x 15
1683.117
1795.326
28X17
29X17
3560.727
3687.896
33x80
34 x20
4937 143
5086.753
52x28
54 x28
"ioSi'ese
11310.545
17 x 15
1907.532
80X17
3815.065
35x20
5236.364
56 x 28
11729.454
18 x 15
2019.740
81X17
3942.234
36x20
5385.974
30 x30
6733.467
10 x 15
2131.948
82x17
4069.403
37 x20
5535584
32x30
7181.299
20X15
2244.156
33X17
4196.571
38x20
5685 195
34 x30
7630130
21 X 15
2356.364
34 x 17
4323.740
39x20
5834.805
36 X30
8078.961
82X-15
2468.571
18 X 18
2423.688
40x20
5984.416
38x30
8527.792
23X15
2580.779
19X18
2558338
'23x22
3620 571
40x30
8976.623
24X15
2692.987
20X18
2692.987
24x22
3949 714
42x30
9425.454
25X15
2805.195
21X18
2827.636
26x22
4278.857
44 x30
9874.286
26X15
2917.403
22X18
. 2962.286
28x22
4608.000
46X30
10323.117
27X15
8029.610
23X18
3096.935
30x22
4937 143
48x30
10771.948
28X15
3141.818
24X18
3231.584
32x22
5266.286
50 x30
11220.770
29X15
3254.026
25X18
3366.234
34x22
5595.429
52x30
11669.610
30X15
3366.234
26X18
3500.883
36 x22
5924.571
54 X30
12118.442 .
31 X15
3478.442
27X18
3635.532
38x22,
6258.714
56x30
125H7.273 «
32X15
3590.649
28X18
3770.183
40x22
6582.857
58x30
13016.104
33 X 15
3702.857
29X18
3904.831
43x32
6912.000
60x30
13464. y35 •
34X15
3815.065
30X18
4039.480
44x22
7241.143
32x32
7660.052
35X15
3927.273
31X18
4174.130
24x24
4308.779
34x33
8138.805
86X15
4039.480
32X.18
4308.779
26x24
4667.844
36 x 32
n 8617.558
37X15
4151.688
33X18
4443.429
28x24
5026.909
38x32
9098.312.
88X15
4263.896
34X18
4578.078
30x34
5385.974
40 x 32
9575.065
39 X 15
4376.104
35X18
4712.727
32x24
5745.039
42 X 32
10053.818
40X15
4488.312
36X18
4847.377
34x24
6r04.104
44 x33
10532.571
41X15
4600.519
19 x 19
2700.467
36x24
6463.169
46x32
11011.325
43X15
4718.727
20 X 19
2842.597
38x24
6822.234
48 x 32
11490.078
43X15
4824.935
21 xi9
2984.727
40x24
7181 299
50x32
11968.831
44X15
4937 143
22 x 19
3126.857
42 x 24
7540.364
52x33
\ 2447. 584
45X15
5049.351
. 23 x |9
3268.987
44x34
7899.429
54x32
12926.338
16x16
1915.013
24 X 19
3411.117
46x24
8258.493
56 x 32
13405.091
17X16
2034.701
25 x 19
3553.247
48 x 24
8617.558
58x33
13883.844
18X16
2154.390
26 X 19
3695.377
26^26
5056.831
60x32
143C2.597
19x16
2274.078
27 X 19
3837.506
28x26
5445.818
62x32
,14841.351
20x16
2393.766
28 X 19
3979.636
30x26
5834.805
64x34
1 15320. 104
21X16
2513.454
29X19
4121.766
32x26
6223.792
34x34
8647.480
22X16
2633.143
30X19
4263.896
34x36
6612.779
36x34
0156.156
23X16
2753.831
31 X19
4406.026
86x26
7001.766
38x34
0664.831
24X16
2872.519
32 x 19
4548.156
38x26
7390.753
40x34
10173.506
25X16
2992.208
33X19
4690.286
40x26
7779.740
4*x34
10682.182
26X16
3111.896
34X19
4832.416
42x26
8168.727
44x34
11190.857
27 x 16
3231 584
35X19
4974.545
44 x26
&557.714
46x34
11699.532
28X16
3351.273
36 x 19
5116.675
46x26
8946.701
4»x34
12208.308
29 x 16
3470.961
87 x 19
5258.805
48x26
9835.688
50x34
12716.883
80 x 16
3590649
38 x 19 -
5400.935
50x26
9724.675
62x34
13225.558
81 X 16
3710.338
20x20
2992.208
52x26
10113.662
54x34
13734.231 .
82 x 16
3830.026
21 x20
3141.818
28x28
5864.727
56x34
14242.900
17 x 17
2161.870
22x20
3291.429
30x28
6283.636
58x34
14751.584
18 x 17
2289.039
23x20
3441.039
32x28
6702.545
60x34
15260.260
19 x 17
2416.208
24x20
3590.649
34x28
7121.454
62 x 34
15768.935
20 x 17
2543.377
25x20
3740.260
36x28.
7540.364
64x34
16377.610
21 X 17
2670.545
26x20
3889.870
38x28
7959.273
66x34 ,
16786.286
22 x 17
2797.714
27 X20
4039.480
;40x28
8378. 182
68x34
17394.961
23 x 17
2924.883
28x20
4189.091 ,
142 x 28
8797.091
36x36
9694,753
24 x 17
3052.062
29.x 20
4338.701
f 44 x 28
9216.000
38 x 36
10233.351
25x 17
3179.221
80 x20
, 4488.312
46x28
9634.909
40x36
10771.948
26 x 17
3306.390
31 X 20
4637.922
48x28
10053.818
43x36
11310.545
27 x 17
3433.558
82x20
4787.532
50x38
10472.727
44x36
11849.143
The United States inspection laws allow 20 per cent more pressure to b<|
carried on boilers with double -riveted longitudinal seams, than on single rlveteU
ooilera.
912
HANDBOOK ON ENGINEERING.
w
PQ
p,
GO
O
I
tf
s
CO
o
O
W
tf
"T
rH
T
1
§
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C^CMCM^rO^^^^iOOvOt'-OOOOO^OcMrO^^DCJOOrHcF
^ is" s"
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8 SSI
rH CM CMC
338S
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in c^- Q CM in jj- c
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r^rHi^COCMOOCQtOiOrO'^^riOLOvOOC^-OOC75C"i— iCM^mS
. r-4 1-( rH i— I f-t
J8S
HANDBOOK ON ENGINEERING.
913
TABLE NO. 23.
Properties of Saturated Steam.
Pressure
per Square
Inch.
Pressure
Above
Zero.
Temperature.
Latent Heat.
Total Heat
Above Lero.
Weight of
One
CubicFoot
Inches of
Mercury.
Pounds
per Square
Inch.
Fahr. Deg.
B. T. U.
Fahr., B. T. U.
Pounds.
2.04
1
102 00
1042 96
1145 05
0030
4 07
2
126 26
1026 01
1152 45
.0058
6.11
3
141.62
1015 25
1157 13
.0085
8 14
4
153 07
1007 22
1160 62
0112
10 18
5
1K2.23
1000 72
1163.44
0137
12 22
6
170 12
995.24
1165 82
.0163
14 25
7
176.91 .
990 47
1167 89
0189
16.29
8
182.91
986.24
1169.72
0214
18 32
9
188 31
9*2.43
1171 37
.0239
20 36
10
193 24
978 95
1172 87
.0264
22 39
11
197 76
975 76
1174 25
0289
24 43
12
201.96
972.80
1175.53
.0313
'26 46
13
205 88
970 02
1176 73
.0337
28 51
14
209 56
967.42
1177 85
0362
Gauge Press.
14 7
212 00
965 7
1178.10
.0380
3
15
213.02
964 97
1178.91
.0387
1 3
16
216.29
962.65
1179.90
0413
2 3
17
219 41
960 45
1180 85
.0437
3 3
18
222 37
958 34
1181 76
.0462
4.3
19
225.20
956 34
1182.61
.0487
6.3
20
227.91
954.41
1183 45
.0511
6.3
21
230 51
952 57
1184.24
.0536
7 3
22
233.01
950 79
1185.00
.0561
83
2.5
235.43
949 07
118>.74
.0585
93
24
237.75
947 42
1186 45
.0610
10.3
25
240.00
945 82
1167.13
.0634
11 3
26
242.17
944.27
1187 80
.0658
12 3
27
244 28
942 77
1188 44
0683
is. a
28
246 32
941 32
1189.06
0707
14 3
29
248.31
939 90
1189 67
0731
15.3
30
250 24
938 92
1190 26
.0755
16 3
31
252 12
937 18
1190 83
.0779
17 3
32
253.95
935 88
1191 39
0803
18.8
38
255.73
934.60
1191 93
0827
19 3
34
257 47
933 36
1192 46
.0851
20.3
35
259.17
932 15
1192 98
.0875
21 3
36
260.83
930 96
1193 49
.0899
22.3
87
262 .
929 80
1193.98
.092-
23 3
38
264 04
928.67
1194 47
.0946
24 3
89
265 59
927.56
1194.94
0970
25 3
40
267.12
926.47
1195.41
.0994
26 1
41
268.61
925.40
1195 86
.1017
27 3
42
270.07
924 35
1196 31
.1041
58
914
HANDBOOK ON ENGINEERING.
TABLE NO. 24.
Properties of Saturated Steam— Continued.
Gauge
Pressure.
Pressure
Above
Zero.
Temperature.
Latent Heat.
Total Heat.
Above Zero.
Weight ot
one
Cubic Foot
Pounds
Pounds
per Square
per Square
Fahr. Deg.
B. T. U.
Fahr.,B.T.U.
Pounds.
Inch.
Inch.
28.3
43
271 50
923.33
1196.74
.1064
29 8
44
272 91
922.32
1197.17
.1088
30.3
45
274.29
921 33
1197.WO
.1111
31 8
46
275 65
920.36
1198 01
.1184
32.3
47
276 98
919.40
1198.42
.1158
38 3
48
278 29
918 46
1198 82
.1181
34.3
49
279 58
917.54
1199.21
.1^04
35. 8
60
280.85
916.63
1199.60
.1227
36.3
61
282.09
915.73
1199 98
.1251
37.8
62
283 32
914.85
1200.35
. 1274
38 3
53
284.53
913 98
1200 72
. 1297
39 3
54
285.72
913.13
1201.08
.1320
40.3
65
236.89
912 29
1201 44
.1343
41.3
56
2S8.05
911 46
1201.79
1366
42.3
57
289 11
910.64
1202.14
1388
43 8
68
290 31
909.83
1202.48
.1411
44.3
69
291 42
909.03
1202.82
1434
45.3
60
292 52
908.24
1203 15
.1457
46.3
61
293 59
907 47
1203 48
.1479
47.3
62
294.66
906.70
1203.81
.1502
48.8
63
295.71
90.3.94
1204.13
.1524
49 8
64
296.75
905.20
1204.44
.1347
60.3
65
297.77
904 46
1-204.76
.1569
61 3
66
298.78
903.73
1205.07
.1592
62 8
67
299.78
903.01
12U5 37
.1614
53 3
68
800 77
902.29
1205 67
.1637
54.3
69
301.75
901.59
1205.97
.1659
55.3
70
802.71
900.89
1206.26
.1681
66.3
71
303.67
900 21
1206 56
.1708
67.3
78
304 61
899.52
1200 84
.1725
68.8
73
805 55
898 85
1207.13
.1748
59.8
74
306.47
898 18
1207 41
.1770
60.8
75
307 88
897 52
1207 69
1792
61 8
76
308.29
896.87
1207.96
1814
62.3
77
309.18
896 23
1208.24
.1836
68.8
78
310.^6
895 69
1208 51
.1857
64.8
79
310. i,4
894.95
1208 77
.1879
65 3
80
314.81
894 33
1209 04
.1901
66 3
81
312.67
893 70
1209 30
.1923
67-8
82
313 52
893 09
1209 56
.1945
68 3
83
314.36
892 48
1209 82
.1967
69.3
84
315.19
891 88
1210.07
.1988
70 3
85
316 02
891 28
1210.32
.2010
71.8
86
316.83
890 . 69
1210.57
.2082
72.8
87
317.65
890.10
1210 82
.2053
HANDBOOK ON ENGINEERING.
915
TABLE NO. 25.
Properties of Saturated Steam — Continued.
Gauge
Pressure.
Pressure
Above
Zero.
Temperature
Latent Heat.
Total Heat.
Above Zero.
Weight of
One
CubicFoot.
Pounds
Pounds
per Square
per Square
Fahr. Deg.
B. T. U.
Fahr.,B.T.U.
Pounds.
Inch.
Inch.
73.8
88
318 45
889.52
1211.06
.2075
74 8
89
319.24
888.94
1211.81
.2097
75 3
90
320.03
888.37
1211.55
.2118
76.3
91
820.82
837 80
1211.79
.2130
77.3
92
321 59
887.24
1212 02
.2160
78.3
93
322 36
886 68
1212.26
.2182
79.8
94
323 12
886.13
1212.49
.2204
80 3
95
323 88
885.58
1212.73 .
.2224
81.3
96
824 63
885.04
1212.95
.2245
82.3
97
325.37
884.50
1213.18
2266
88 3
98
326 11
883 97
1213.40
.2288
84.3
99
326.84
883 44
1213 62
.2309
85.8
100
327 57
882.91
1213.84
.2330
86.3
101
328 29
882 39
1214.06
.2301
87 3
102
329 00
881 87
1214.28
2371
88.3
103
829 71
881-35
1214.50
.2392
89.8
104
330.41
880 84
1214.71
.2418
90 3
105
331.11
880.34
1214.92
.2434
91.3
106
381.80
879.84
1215.14
.2454
92.8
107
332 49
879 34
1215.35
.2475
93.3
108
333 17
878 84
1215.56
.2496
94.3
109
333.86
878 35
1215.76
.2616
95.8
110
834.52
877 86
1215 97
.2537
96.3
111
335 19
877 37
1216.17
.2558
97 .3
112
335 85
876.89
1216.37
.2578
98 3
113
336.51
876 41
1216.57
.2599
99.3
114
337 16
875 94
1216.77
.2619
100 3
115
337.81
875.47
1216 97
.2640
101.3
116
838 45
875 40
1217.17
.2661
102 3
117
339.10
874.53
1217.36
.2681
103 3
118
339 73
874.07
1217 66
.2702
104 3
119
340 36
873 61
1217 75
2722
105 8
120
340.99
873 15
1217 94
.2742
106 H
121
311 61
872 70
1218.13
.2762
107 3
122
342.23
872 25
1218.32
.2782
108.8
123
342 85
871 80
1218.51
.2802
109 3
124
343 46
871 35
1218.69
.2822
110 3
125
344 07
870 91
1218.88
.2842
111.3
126
344 67
870 47
121906
.2862
112 8
127
845 27
870 03
1219.27
.2882
113.3
128
345 87
869.59
. 121943
.2902
114.3
129
346.45
869 16
1219.61
2922
115.3
130
347.05
868.73
1219 79
.3942
116 8
131
347.64
868.30
1219.97
2961
916
HANDBOOK ON ENGINEERING.
TABLE NO. 26.
Properties of Saturated Steam — Continued.
Gauge
Pressure.
Pressure
Above
Zero.
Temperature.
Latent Heat.
Total Heat.
Above Zero.
Weight of
One
CublcFoot.
Pounds
Pounds
per Square
per Square
Fahr. Deg.
B. T. U.
Fahr., B. T. U
Pounds.
Inch.
Inch.
117.3
13-2
348 22
867.88
1220 15
.2981
118 3
133
348.80
867 46
1^0 32
.3001
119.3
134
349.38
867.03
It'iU 50
.3020
120 3
135
349.95
866 62
U<0 67
. 3u»()
121 3
136
350.52
866 20
12-/0 85
.3u60
122.3
137
351.08
866 79
1221 02
3u79
123 3
138
351.75
865.38
1-^1 19
3u99
124.3
139
352 21
864 97
12.51 36
.31i8
125.3 "
ito
352.76
864 56
1221 53
.3138
126.3
141
363.31
864.16
1221 70
.3158
127 3
142
358.86
863.76
12-21 87
.3178
128.3
143
354.41
863.36
1222 03
.3199
129.3
144
354.96
86-2.96
1222.20
3219
130 3
145
355 50
862 56
1222 36
.3*39
131.3
146
356 03
862 17
1222.53
.3209
132.3
147
,85657
861.78
1*2-2 69
.3'/79
133.3
148
357.10
861 39
1222.85
3299
134 3
149
357 63
861 00
1223 01
.3319
135.3
150
358 16
860.62
1223.18
.3340
136 3
151
358 68
860 23
1223 33
.3358
137 3
152
359 20
859.85
1223 49
.3376
138 3
153
359 72
859 47
1223 65
3394
139.3
154
360.28
859 10
12-23 81
.3412
140.8
155
360.74
858.72
1223.97
.3430
141.3
156
361.26
858 35
1224.12
.3448
142.3
157
361.76
857 98
1224 28
.3466
143 3
158
362.27
857.61
1224.43
.3484
144 3
159
362.77
857 24
1224 58
.3502
145.3
160
363.27
856.87
1224.74
.3520
146.3
161
363 77
856 50
1224 89
.3539
147.3
162
364.27
856.14
1225.04
.3558
148.3
163
364 76
855.78
1225.19
.3577
149. 3
164
365 25
855 42
1225 34
3596
150.3
165
365.74
855 06
1225.49
.3614
151.3
166
366 23
854 70
12-25 64
.3633
153.3
167
366.71
854 35
1225.78
3652
153 3
168
367.19
853 99
1225.93
.3671 •
154.3
169
367 68
853.64
1226 08
.8690
155.3
170
368.15
853.29
1226.22
.3709
156.3
171
368.63
852 94
1226.37
.3727
157.3
172'
369.10
852 59
1226.51
.3745
158.3
173 •
369.57
852.25
1226 66
3763
159.3
174
870.04
851.90
1226 80
3781
160.3
175
370 51
851.56
1226.94
.3791)
161 3
176
370.97
851 22
1227.08
.3817
HANDBOOK ON ENGINEERING.
917
TABLE NO. 27.
Properties of Saturated Steam — Continued.
Gauge
Pressure.
Pressure
Above
Zero.
Temperature.
Latent Heat.
Total Heat.
Above Zero.
Weight of
One
Cubic Foot.
Pounds
Pounds
per Square
Inch.
per Square
Inch.
Fahr. Dcg
B. T. U.
Fabr., B. T. U.
Pounds.
162 3
177
371.44
850.88
1227 32
.3835
163 3
178
371 bO
850 54
1227-37
.3853
164.3
179
372 36
850 20
12-27.61
.3871
165.3
180
372.82
849 86
1227 65
.3889
166 3
181
373 27
849 53
1227 78
.3907
167.3
182
373 73
849 20
1227 92
.3925
168.3
183
374 18
848 86
1228.06
.3944
169 3
184
374 63
848 53
1228 20
3962
170.3
185
375 08
848 20
1228.33
.3980
171 3
186
375.52
847.88
1228.47
.3999
172 3
187
375 97
847,55
1228 61
.4017
173 3
188
376 .4-1
847 22
1228 74
.4035
174.3
189
376.85
846 90
1228 87
.4063
175.3
190
377 29
846 58
1229.01
.4072
176.3
191
377.72
846.23
1229.14
.4089
177 3
192
378 16
845.91
1229.27
.4107
178.3
193
378 59
845 62
1229.41
.4125
179 3
194
379 02
845 30
1229.54
.4143
180.3
195
379 45
844.99
1229.67
.4160
181.3
196
379 97
844 68
1229.80
.4178
182 3
197
380.30
844 36
1229.93
.4196
183.3
198
380 72
84* 05
1230.06
.4214
184.3
199
381.15
843 74
1230 19
.4231
185 3
200
381.57
843 43
1230.31
.4249
186.3
201
381 99
84? 12
1230 44
.4266
187.3
202
382.41
84° 81
1230 67
.4283
188 3
203
382 82
8*? 50
1230.70
.4300
189 3
204
383 24
8'? 20
1230 82
.4318
190 3
205
383.65
841 89
1230 95
.4335
191.3
206
384.06
8*1 59
1231 07
.4352
192 3
207
384.47
8' 1.29
1231.20
.4369
193 3
208
384.88
840.99
1231 32
.4386
194 3
209
385.28
8^0.69
1231 45
.4403
195.3
210
385 67
840.39
1231 57
.4421
918
HANDBOOK ON ENGINEERING.
TABLE NO. 28.
SWEDES IRON TRANSMIS-
CRUCIBLE CAST STEEL
SION OR HAULAGE
TRANSMISSION OR
ROPES.
HAULAGE ROPES.
7 Wires ta the Strand. Hemp
7 Wires to the Strand. Hemp
Centre.
Centre.
d
d®
bflOQ
.«,
d
bo OD
• .
^
Diameter in
Inches.
i Price per Foot 1
t Cents.
Breaking Strai
in Tons of 2.0C
Pounds.
Proper Workln
Load in Ton
of 2,000 Lbs.
ised for Derricki
Ferries, Trang
Average Weigh
per Foot.
Minimum Size
of Drums or
Sheaves in Ft
Diameter in
Inches.
Price per Foot
in Cents.
Breaking Strai
in Tons of
2,000 Pounds.
Proper Workm
Load in Tons
of 2,000 Pound
sed for Derrick*
jrries, Transmie
Average Weigh
per Foot.
Minimum Size
of Drums or
Sheaves in Ft.
9-32
5-16
3|
1.4
17
i
aS
"5 "So
a, be .;
.15
li
J*
9-32
5-16
4^
2|
3
I
s£
.15
3
!7-16
4|
6i
2 4
3 3
i
£*~y o
§«*
.22
.30
2
2|
7!6
if
5
63
1
figs
.22
.30
P
9-16
|
8
10
4 2
5.3
6.6
1
m
SSI
.39
.50
.64
|
9-16
|
1\
9
11
83
io|
13
2
|2|
.39
.50
.64
1
Tl-16
12
7.9
i
«*gpL,
.75
4
11-16
13i
16
3
SJi ij
.75
6*
If
14
23
29
86
9.3
12.
16.
20.
24.
! 2-5
; 1-5
4-5
CD 08«_,
Hj
.89
1.20
1.58
2 00
2.45
1
it
16
22
28
36
43
19
24
32
40
48
?
10
e Ropes
s, Steam
L of Powe
.89
1.20
1.58
2.00
2 45
1
]•
43
29.
5 4-5
J5s
3 00
8
if
51
58
12
y> rtQ
3.00
JIT
H •
51
34.
7
H
8 55
84
if
60
68
14
go-s
3 55
13
•
HANDBOOK ON ENGINEERING.
919
TABLE NO. 29.
CRUCIBLE CAST STEEL
SWEDES IRON PLIABLE
PL LE HOISTING
HOISTING ROPES.
ROPES.
19 Wires to the Strand. Hemp
ires to the Strand. Hemp
Centre.
Centre.
a
||
§1
beg
44
bo
,j
a
a
*1
bo
O QQ
1
«H
I
I
fa
£c*
»*
o o1
§• ^
N «*
«25
.9
I
L|
03 O1
EH .
l|*
Ij
(4
) 0)
if
i1"1
\ Price per
| Cents.
Breaking
in Tons <
Pounds.
III
ll?
o o
g£
Minimum
of Drumi
Sheaves
Diameter
Inches.
Price per
Cents.
Breaking
in Tons <
2,000 Pou
Diam. of
Rope of
Strength
cL^cT
£3*
||
Minimum
Drums o
Sheaves
>16
9
3
?
i!
;i
. .10
.15
.22
u
5-16
i
P
11.20
1.70
2.50
9-16
1
.10
15
.22
1
-16
10
7
li
1 2-5
.30
2*
7-16
7*
3.40
1
K
.30
•i
t
11
9
it
1 4-5
.39
8
4.40
1$
1
.39
ii
-16
12
11
i 9-16
2 1-5
.50
2§
9-16
10
5.60
1 5-16
1 1-10
.50
2
14
14
1|
24-5
.64
34
12
6 80
1*
If
.64
24
18
20
21
4
.89
4
s
16
9.70
if
4
.89
3
23
26
2|
5 1-5
1.20
4i
V
20
13.
2
2 3-5
1 20
3'i
30
38
34
42
3
3|
6 4-5
8 2-5
1 58
2.00
i*
I
26
38
17.
21.
P
3 2-5
4 15
1.58
2 00
*I
46
52
3|
10
2.45
61
]1
40
25.
5
2.45
56
63
4
12
3.00
7
]a
48
31.
U
6 1-5
3.00
6
66
74
93
77
86
106
1
15
17
20
3.55
4.15
5.25
I
ii
57
63
80
36.
42.
48.
4
41
7 1-5
8 2-5
9 3-5
3.55
4 15
5.25
64
111
125
25
6.30
12
2
92
62.
4}
12 2-5
6.30
9*
I
142
160
32
8 00
13
2*
117
78.
5i
15 3-5
8 00
10
920
HANDBOOK ON ENGINEERING.
TABLE NO. 30.
19 Wires to the Strand. Hemp
Centre.
WIRE ROPE FOR INCLINED
PLANES.
For the benefit of those desiring to
use wire rope on slopes, inclined
Planes, etc , a table by which the strain
produced by any load may be readily
ascertained.
This table gives only the strain pro-
duced on a rope by a load of one ton of
two thousand pounds, an allowance for
rolling friction being made. An addi-
tional allowance for the weight of the
rope will have to be made.
Example: For an inclination of 100
feet in 100 feet, corresponding to an
angle of 45°, a load of 2,000 pounds will
produce a strain on the rope of 1,419
pounds, and for a load of 9,000 pounds
the strain on the rope will be
Inches.
Price per Foot,
in Cents.
Breaking Strain
in Tons of
2,000 Pounds.
Proper Working
Load in Tons
of 2,000 Lbs.
Average Weight
per Foot.
Minimum Size
of Drums or
Sheaves in Ft.
r-16
i-,6
k
14
15
17
19
22
28
35
45
54
65
80
95
112
136
160
220
8
10
13
15
20
30
40
50
63
76
95
115
130
160
220
235
2^
P
1
13
16
19
22
25
33
40
.22
.30
.39
.50
.64
.89
1.20
1.58
2 00
2 45
3.00
3.55
4.15
5.25
6 30
8.00
2
2*
P
4
5
6
7
8
9
10
11
12
13
14
15
>uuu
Elevation in •
100 Feet.
bo
Boa
•CM 3
"fl «'g
evation in
DO Feet.
bo
fl -
•OM S
&CJ- £
*g
1*1.
S§«2
7 Wires to the Strand. Hemp
Centre.
31"1
5
10
1ft
20
25
30
35
40
45
50
65
60
65
70
75
80
85
90
11 1-5
144
19 1-5
21 5-6
24i
28 5-6
31
33 1-12
35
37
38f
40i
42
112
211
308
404
497
586
673
754
832
905
975
1,040
1,100
1,156
1,210
1,260
1,304
1,347
95
100
105
110
115
120
125
130
135
140
145
IftO
155
160
165
170
176
455
46*
tTf
49
50;
5L
52i
53i
54l-
55i-
56
57;
68
68 4-5
59J
60i
1,385
1,419
1,457
1,487
1,516
1,544
1,570
1,592
1,614
1,633
1,653
1,671
1,689
1,703
1,717
1,729
1,742
h6
15
18
25
38
42
63
64
76
92
11
14
18
28
36
48
60
72
82
100
2
!»
6
7
11
18
16
20
.39
.60
.64
.89
1.20
1 58
2 00
2 45
3.00
3 55
3
4
6
7
8
9
10
11
12
A factor of safety of five to seven
times should be taken; that is, the
working load on the rope should only
be one-fifth to one- seventh of its break-
ing strength. As a rule, ropes for
shafts should have a factor of safety of
five, and on inclined planes, where the
wear is much greater, the factor of
safety should be seven.
HANDBOOK ON ENGINEERING.
921
TABLE NO. 81.
Table of Transmission of Power by Wire Ropes.
This table is based upon scientific calculations, careful observations and expert*
ence, and can be relied upon when the distance exceeds 100 feet. We also find by
experience that it is best to run the wire rope transmission at the medium number
of revolutions indicated in the table, as it makes the best and smoothest running
transmission. If more power is needed than is indicated at 80 to 100 revolutions,
choose a larger diameter of sheave.
Diameter of
Sheave in ft.
I
Number of
Revolutions.
Diameter of
Rope.
Horse-Power.
Diameter of
Sheave in Ft.
Number of
Revolutions.
^
Horse- Power.
3
80
i
8
. 7
140
9-16
35
3
100
3|
8
80
i
26
3
120
I
4
8
100
32
3
4
140
80
I
Ji
8
8
120
140
39
45
4
100
i
5
9
80
.
47
48
4
120
1
6
9
100
9-16|
58
' 60
4
140
1
7
9
120
9 16§
69
73
5
80
7-16
9
9
140
9 16$
82
84
5
100
7-16
11
10
80
g 11 16
64
68
5
120
7-16
13
10
100
f 11-16
•*
80
85
5
140
7 16
15
10
120
S 11-16
96
102
6
80
*
14
10
140
i 11-16
i 112
1 119
6
100
i
17
12
80
j 11 16}
93
99
6
120
i
20
12
100
11 16|
! 124
140
6
140
}
23
12
120
11-16J
149
7
80
9-16
20
12
140
i
173
141
7
100
9-16
25
14
80
Hi
148
176
7
1-20
9-16
80
14
100
1 1*
185
922
HANDBOOK ON ENGINEERING.
§|ssz
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8|«
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tl
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ts a
22
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ss»l!
l°!.1£^
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at
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HANDBOOK ON ENGINEERING.
923
TABLE NO. 33.
Percentage of Power Gained by Adding a Condenser, the Speed
and Point of Cut-Off Remaining the Same.*
VACUUM •== 24.5 INCHES.
Per Cent
Per Cent
Per Cent
Per Cent
M. K. P.
of Power
M. B. P.
of Power
M. E. P.
of Power
M. E. P.
of Power
Gained.
Gained.
Gained.
Gained.
5
250
17
70.5
38
31,6
62
19.8
6
200
18
66.6
40
30
64
18.7
7
171.4
19
63.1
42
28.5
66
18.1
8
150
20
60
44
27.2
68
17.6
9
133.3
22
54.5
46
26.08
70
17.1
10
120
24
50
48
25
72
16.6
11
109
26
46.1
50
24
74
16. S
12
100
28
44.3
52
23.07
76
15.7
13
92.3
30
40
54
22.2
78
15.9
14
85.7
32
37.5
56
21.4
80
15
15
80
34
35.2
58
20.6
82
14.63
16
76
36
33.3
60
20
85
14.12
Calculated gain due to vacuum, friction not considered.
TABLE NO. 34.
glies of Cylinders Usually Furnished for Compound Pumps, and
Corresponding Ratios of Expansion.
Diameter
High Pressure
Cylinder.
Diameter
Low Pressure
Cylinder.
Ratio
of
Expansion.
6
10
2.78
7
12
2.94
8
12
2.25
9
14
2.42
10
16
2.56
12
18
2.25
14
20
2.04
16
24
2.25
18
30
2.77
924
HANDBOOK ON ENGINEERING.
TABLE NO. 35.
Indicated Horse-power for One Pound of Mean Pressure.
Diameter of
Cylinder in
Inches.
SPEED ov PISTON IN FEET PER MINUTE.
240
300
350
400
450
500
550
600
6
0-205
0-256
0-299
0-342
0-385
0-428
0-471
0-513
;y
0-279
0-348
0-408
0-466
0-524
0-583
0641
0-699
8
0-365
0-456
0-532
0-608
0-685
0-761
0-837
0-912
9
0-462
0-577
0-674
0-770
0866
0-963
1154
10
0-571
0-714
0-833
0-952
1-071
1-190
1 \ A)§
1-428
11
0-691
0-864
1*008
1-153
1-296
1-44
1-584
1-728
12
0-820
1-025
1-195
1-366
1-540
1-708
1-880
2-050
13
0-964
1-206
1-407
1-608
1-809
2-01
1-211
2-412
14
1-119
1-398
1-631
1-864
2-097
2-331
2-564
2-797
15
1-285
1-606
1-873
2131
2-409
2-677
2-945
3-212
16
1-461
1-827
2-131
2-436
2-741
3-045
3-349
3-654
17
1-643
2-054
2*396
2-739
3-081
3-424
3-V66
4-108
18
1-849
2-312
2-697
3-083
3-468
3-854
4-239
4-624
19
2-061
2-577
3-006
3-436
3-865
4-297
4-724
5-154
20-
2-292
2-855
3-331
3-807
4-285
4-759
5-234
5-731
^21
2-518
3148
3-672
4-197
4-722
5-247
5-771
6-296
22
2-764
3-455
4-031
4-607
5-183
5-759
6-334
6-911
25
3-021
3-776
4-405
5-035
5-664
6-294
6-923
24
3-289
4-111
4-797
5-482
6167
6-^3
7-538
8*223
25
3-569
4-461
5-105
5-948
6-692
7-436
8173
8-923
26
3-861
4-826
5-630
6-435
7-239
8-044
8-848
9-652
27
4-159
5-199
6-066
6-932
7-799
8-666
9-532
10-399
28 ,
4-477
5-596
6-529
7'462
8-395
9-328
10261
11-193
29
4-805
6-006
7-007
8-008
9-009*
10-01
11-011
12-012
30
5-141
6-426
7-497
8-568
9-639
10-71
11-781
12-852
31
5-486
6-865
8-001
9-144
10-237
11-43
12-573
13-716
32
5-846
7-308
8-526.
9-744
10-962
12-18
13--398
14616
33
6-216
7-770
9-065
10-360
11-655
12-959
14.-245
15-54
34
6-59
8-238
9-611
10-984
12-357
13-73
15103
16;476
35
6-993
8-742
10-199
11-656
13-113
14-57
16-027
17-434
36
"7-401
9-252
10-734
12-336
13-878
15-42
16-962.
18-50}
37
7-819
9-774
11-403
13-032
14-861
16-29
17-519
19-543
33
8-246
1(7-508
12-026
13-744
15-462
17'18
18-898
20-61.6
39
8-618
10-86
12-67
14-48
16-29
18-1
19-91
21-61 .
40
9-139
11-424
13-323
15-232.
17-136
19-04
20-94.4
22-843
41
9-604
12-006
14-007
16-008
18-009
20-00
22-011
24-012
42
10-065
12-594
14-693
16-792
18-901
20-99
23-089
25-188
43
10-56
13-20
15 :4
17-6
19-8
22-00
242
26-4
44
11-046
13-818
16-121
18-424
20-727
23-03
25-333
27-636
45
11-563
14-454
16-863
19-272
21-681
24-09
26S399
28-908
46
12-086
15128
17«626
20-144
22-662
25-18
27-698
30<216
47
12-614
15-768
18-396
21024
23-652
26-28
28-908
31-536
48
12-816
16-446
19-187
21-928
24-669
27-41
30-151
32-152
49
12-933
17-142
19-999
22-856
25-713
28-57
33-427
34-2B4
60
14-28
17-85
20-825
23-8
26-775
29-75
32-725
35'7
NOTE. — Mean effective pressure =^Mean prewure minus the back preasur*
HANDBOOK ON ENGINEERING.
925
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HANDBOOK ON ENGINEERING.
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HANDBOOK ON ENGINEERING.
927
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HANDBOOK ON ENGINEERING.
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HANDBOOK ON ENGINEERING.
929
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HANDBOOK ON ENGINEERING.
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HANDBOOK ON ENGINEERING.
931
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HANDBOOK ON ENGINEERING.
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HANDBOOK ON ENGINEERING.
933
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934
HANDBOOK ON ENGINEERING.
TABLE NO. 40.
ROCK DRILLS.
Factor lor Deter mi nine: Free Air Per Minute Required for Rock BYills
at 30, 7O, 80, 00, 1OO Pounds Pressure, and Altitudes frditu Sea
Level to 10,000 Feet Above.
i
FACTOR OF MULTIPLICATION.
ALTITUDE IN
ATMOSPHERIC
PRESSURE AT DRILL
FEET ABoVB
PRESSURE LBS.
SEA LEVEL.
FEU SQlt. IN
60 Ibs.
70 Ibs.
80 Ibs.
90 Ibs.
100 Ibs.
0
14.7
.00
.133
2P.
.40
.535
600
14.46
.015
.15
.28
.4-25
.663
1,000
14.12
.03 „
.17
31
43
59
1,500
13 92
048
19
.33
,48
62
2,000
13.61
06
.21
.35
.50
.645
3,000
13.10
10
.25
.40
.55
70
4,000
12.61
131
.287
.443
60
755
5,000
12 15
17
33
4J6
:652
81
6,000
11 75
.20
37
.537
.705
1.87
7,000
11 27
.24
42
69
.76
1.935.
8,000
10 85
.282
1.4H6
.<45
.825
2.00
9,010
10 45
1 32
1 51
1 70
1.90
2 07
10,000
10.10
1 365
1 56
1.755
1.963
2.143
.
TABLE NO. 47.
Oubic Feet of Air Per Minute Required to Operate a Small Number of
Rand Drills of Various Sizes at 60 Pounds Air Pressure at Sea
Level.
No. OK NAME.
KID.
No. 1
Xo 2
No. 3
No. 3$
No. 4
No. 6.
No. 7
DIam of Cylinder
in Inches.
JJin.
2iin
2|ln.
3J in.
3J In.
3| In.
4*ln.
5 In.
Number of Drills.
1
35
53
64
95
103
112
132
164
2
61
93
112
166
180
196
231
.270
3
88
133
160
238
258
280
330
385
Otf ENGINEERING. 93S
TABLE 47.
TABLE OF THE ARRAS OF CIRCULAR SKGMKNTS FOR DIAMETKR = 1.
Height
Area.
Height.
Area 1
Height |
Area.
Height
Area
.001
000 042
.064
.021 168
1-27
.Oo7 991
.190
103 900
.002
.000 119
oes
021 660
128
058 658
.191
.104 6f>-
.003
.000 219
.066
022 155
129
.059 328
.192
105 472'
.004
.000 337
.067
.022 653
.130
.059 999
.193
.10»; 261
.005
.000 471
.068
.023 155
.131
.OhO 673
.194
.107 OM
.006
.000 619
.069
.023 660
132
.061 349
.195
.107 843
.007
.000 779
.070
.024 168
.133
06-2 027
.196
.108 636
.008
.000 952
.071
.024 680
134
0«2' 707
.197
.109 4X1
.009
.001 136
.072
025 1%
.135
063 389
.198
110 227
.010
.001 329
.073
.023 714
.136
064 074
.199
.111 025
.011
.001 533
.074
.026 236
.137
.064 761
.200
111 824
.012
.001 746
.075
.026 761
138
.065 449
.201
.112 625
.013
.001 969
076
.027 290
.139
066 140
.202
.113 427
.014
.002 199
077
.027 821
.140
.066 833
.203
.114 231
.016
.002 438
.078
.028 35H
.141
.«67 528
.204
.115 036
.016
.002 685
.079
.028 894
.142
.068 225
.205
.115 842
.017
.002 940
.080
.029 436
.143
068 924
.206
.116 651
.018
.003 202
.081
.029 979
.144
.069 626
.207
.117 460
.019
.003 472
.082
.030 526
.145
.070 329
.208
.118 271
.020
OOS 749
.083
.031 077
.146
.071 034
.209
.119 084
.021
.004 032
.084
.031 630
.147
.071 741
.210
.119 898
.022
.004 322
.086
.032 186
.148
.072 460
.211
.120 713
.023
.004 619
.086
.032 746
.149
.073 162
212
.121 530
.024
.004 922
.087
,033 308
.150
.073 875
.213
.122 348
.0-25
.005 231
.088
.033 «73
.151
.074 590
.214
.123 167
.026
.005 546
.089
.034 441
.152
.075 307
.215
.123 988
.027
.005 «67
.090
.035 012
.153
.076 026
.216
.124 811
.028
.006 194
.091
.035 586
.154
.076 747
.217
.125 634
.029
.006 527
.092
.036 162
,.155
.077 470
.218
1-26 459
.030
008 866
.093
.036 742
.156
.078 194
.219
.127 286
.031
.007 209
.094
.037 324
.167
.078 921
.220
.128 114
.032
007 559
.09->
.037 909
Jf»8
.079 650
.221
.128 943
.033
.007 913
.096
.038 497
.159
.080 380
.222
.129 773
.034
.008 27.i
.097
.039 087
.160
.081 112
.223
.130 605
.035
.008 638
.098
.039 681
.161
.081 847
.224
.131 438
.036
.009 008
.099
.040 277
.162
.082 582
!225
.132 273
.037
.009 383
.100
040 875
.163
.083 320
.226
.133 10(1
.038
009 764
.101
.041 477
164
.084 060
.227
.133 946
.039
.010 148
.102
.042 081
,165
.084 801
228
.134 784
.040
.010 538
.103
.042 687
?166
.085 545
.229
.135 624
.041
.010 932
.104
.043 296
167
.086 290
.230
.136 465
.042
.011 331
.105
.043 908
168
.087 037
.231
.137 »07
.043
.011 734
.106
.044 523
.169
.087 785
.232
.138 151
.044
.012 142
.107
.045 140
.170
.088 53IJ
.233
.138 996
.045
012 555
.108
.045 759
.171
.089 -288
.234
.139 842
.046
.012 971
.109
.046 381
.172
.090 042
.235
.140 689
.047
.013 393
.110
.047 006
.173
.090 797
.236
.141 -538
.048
.013 818
.111
.047 633
.174
.091 555
.237
.142 388
.049
.014 248
.112
.048 262
.175
.092 314
.238
.143 239
.050
.014 681
.113
.048 894
176
.093 074
.239
.144 o'.U
.051
.015 119
.114
.049 529
.177
.093 837
.240
144 945
.052
.015 561
.115
.050 165
.178
.094 601
.241
.145 800
.053
.016 008
.116
.050 805
.179
.095 367
..242
.146 656
.054
.016 458
.117
.051 446
180
.096 135
.243
.147 513
.055
.016 912
.118
.052 090
.181
096 904 '
.244
.148 371
.056
.017 369
.119
.062 737
.182
097 675
.245
.149 231
.057
.017 831
.120
.053 385
.183
.098 447
.246
.150 091
.058
.018 297
.121
.054 037 i
.184
.099 221
.247
.150 95 3
.059
.018 766
.122
.054 690
.1S5
.099 997
.248
.151 816
.060
.019 239
.123
.055 346
.186
100 774
.249
.152 681
.061
.019 716
.124
.056 004
.187
.101 553
.250
.153 546
.062
.020 197
.125
056 664
.188
.102 334
,063
.020 6S1
.126
.057 327
.189
.103 116
936 SAKdBddS Off ENGINEERING.
TABLE 47. - COM tinned.
TABLE OF THE AREAS OF CIRCULAR SEGMENTS FOft DtAMKffe ft S= I.
Height
Area
Height
Area.
[Height
Area.
Height
Area.
.251
.154 413
.314
.'.Ill 083
.377
.270 951
.440
.332 S4*
.262
.165 281
.315
.212 Oil
.378
.271 921
.441
*333 836
.953
.156 149
.316
.212 941
. .379
.272 891
.442
.334 829
.254
.167 019
.317
.213 871
.380
.273 861
.443
.335 823
.266
.W7 €91
.318
.214 802
.381
.274 832
.444
.336 816
.266
.158 763
.319
.215 734
.382
.275 804
.445
.337 810
.267
.159 636
.320
.2 IK 666
.383
.276 776
.446
.338 809
.2*8
.160 511
.321
.217 600
.384
.277 748
.447
.339 799
.269
.161 386
.322
.218 534
.385
.278 721
.448
.340 793
.260
.162 263
.323
.219 469
.386
.279 695
.449
.341 788
.261
.163 141
.324
.220 404
.3S7
.280 669
.450
.342 783
//2
.164 020
.325
.221 341
.388
.281 643
.451
.343 778
.263
.164 900
.326
.222 278
.389
,282 618
.452
.344 773
,264
.165 781
.327
.223 216
,390
.283 593
.453
.345 768
.265
.166 663
.328
.224 154
' .391
284 569
.454
.346 764
,.266
.167 546
.329
.225 094
.392
.285 545
.455
.347 760
.267
.168 431
.330
.226 034
.893
.286 521
.456
.348 756
.268
.169 316
,3ol
.226 974
.394
.'267 499
.457
.349. 752
.269
.170 22
.332
.227 916
.395
.288 476
.458
.360 749
,270
.171 OHO
.333
223 858
.396
.289 454
.459
.351 745
271
.171 978
.334
.229 801
.397
.290 43-2
.460
.352 74»
.272
.172 868
.335
.230 745
.398
.291 411
.461
.353 739
.278
.1?3 758
.336
.231 689
.399
292 390
.462
.354 736
,274
.174 650
.337
.232 634
.400
.293 370
.463
.355 733
,275
.175 542
.338
.2*3 580*
.401
.294 350
.464
.356 730
.276
.176 436
.339
.234 526
.402
.295 350
.465
.357 7-28
;277
.177 330
.340
.235 473
.403
.296 311
.466
.358 725
.278
.178 226
.341
.236 421
.404
.297 292
.467
.3.9 723
.279
.179 122
.342
.237 369
.405
.298 274
.468
.360 721
,280
.180 020
.343
.238 319
.406
.299 256
.469
.361 719
.281
.180 918
.344
.239 268
.407
.300 238
.470
.362 717
,282
.181 818
.345
.240 219
.408
.301 221
.471
.363 715
.'/83
.182 718
.346
.241 170
.409
.302 204
.472
.364 714
.284
.183 619
.347
.242 122
.410
.303 187
.473
.365 712
w285
.184 622
.348
.243 074
.411
.304 171
.474
.366 711
*286
.1*5 426
.349
.244 027
.412
.306 156
.475
.367 710
,287
.186 329
'.650
.244 980
.413
.3<>6 140
.476
.368 708
.288
.187 235
.351
.245 935
.414
.307 125
.477
.369 707
*289
.188 141
'.352
.246 890
.416
.308 110
.478
.370 7ufi
'.290
.189 048
;353
.247 845
.416
.309 096
.479
.871 705
.291
.189 956
.354
.248 801
.417
.310 082
.480
.372 704
.292
.190 865
.355
.249 758
.418
.311 068
.481
.373 704
>293
.191 774
.356
.250 715
.419
.312 065
.482
.374 703
/.294
.192 685
.357
.251 673
.420
.313 042
.483
.376 7o2
',295
.193 597
.368
.252 632
.421
.314 029
.484
.376 702
»296
.194 509
.359
.253 691
.422
.316 017
.485
.377 701
,297
.195 423
.360
.254 551
.423
.316 OG5
.486
.378 701
:298
.196 337
.361
.256 511
.424
.316 993
.487
.379 701
,299
.197. 252
.362
.256 472
.425
.317 981
.488
.380 700
.300
.198 168
.363
.257 433
.426
.318 970
.489
.381 700
301
.199 085
.364
.258 395
.427
.319 959
.490
.382 700
..302
.200 003
.365
.259 358
.428
.320 949
.491
.383 700
^303
.200 922
.366
.260 321
.429
.321 938
.492
.384 699
.304
.201 841
.367
.261 285
.430
.322 928
.493
.385 699
,305
.202 762
.368
.262 249
.431
.323 919
.494
.386 699
.,306
.203 683
.3«9
.263 214
.432
.324 909
.495
.387 699
.307
.204 605
.370
.264 179
.433
.325 900
.496
.388 6<)9
.308
.206 528
.371
.265 145
.434
.326 891
.497
.3S9 6«.«9
.309
.206 452
.372
.266 111
.435
.327 883
.498
.390 699
.810
.207 376
.373
.267 078
.436
.328 874
.499
.391 tt'.'9
.an
.208 302
.374
.268 046
.437
.329 866
.600
.392 699
,312
.209 228
.375
.269 014
.438
.330 868
.313
.210 155
..376 1
.269 982
.439
.331 851
HANDBOOK ON ENGINEERING.
937
HARTFORD SPECIFICATIONS;
The following are the specffications, for steel plate, of the Hartford Steam
Boiler Inspection and Insurance Co.
OPEN HEARTH FIRE BOX STEEL
To have a tensile strength of. not less than 55,000 lbs.,nor more than 62,000
IDS. per square inch of section, with not less than 56% of ductility as indicated
by contraction of area at point of fracture under test and by an elongation
of 25£ in a length of 8 inches.
HE ADS- To be made of best Open Hearth Flange Steel, 60,000 T. S. All
plates, both of shell and heads, must be plainly stamped with name of
maker, brand and tensile strength; brands so located that they may be seen
on each plate after bolter is finished. Each shell plate must bear a coupon
which shall be sheared off, finished up and tested by the maker of ihe
boiler, at his own expense. Each coupon must fill the above requirements
as to strength and ductility, and must also stand bending down double
when cold, when red hot and after being heated red hot and quenched in
cold water, without SILTS of fracture. All plates failing to pass these tests
will be rejected. All tests and inspections of material shall be made at the
place of manufacture prior, to shipment.
TABLE No. 48.
Showing details of rivet laps for different thicknesses of boiler plate as ad-
vocated by the Hartford Steam Boiler Inspection and Insurance Co. for
DOUBLE RIVETED BUTT JOINTS.
2*4X4*
ofi
if
4V» in
il"
9 in
1014 •'
11J4 "
H in
ft::
ir
ill-
IK in2K In
. - -
2H'
2M
2^
TABLE No. 48.— Continued.
TRIPLE RIVETED BUTT JOINTS.
Thicknes
Plate.
iame
Riv
Pitch of Riv
in inches.
Width o
Outside B
Strap.
idth of
ide Bu
Strap.
Thickne
Coveri
Stra
sg.
Ill
&
n
si
53
s~
J°s
^3s
O S3 «>*
C3*3 *
®O <»CC
&D >•
|w
i
y
3|x6|
3ix7
11§ in
ij
p
2il
23
11 in
87.5^
86%
88%
88%
87.59J
87.6^
86.6%
For detailed drawings of above laps, tee pages 946 to 951 inclusive.
938
HANDBOOK ON ENGINEERING.
STAYING BOILER HEADS.
In the return tubular boiler the tubes occupy a considerable
portion of the boiler head, usually amounting to about two-thirds
of the entire area of the head, as shown by Figure 403. There
•V*
o
_ J
ooooo
ooooo
ooooo
ooooo
oooo
o
ooooo
ooooo
ooooo
ooooo
oooo
o
Fig. 403.
Showing No. of stays in a well proportioned boiler of 60 in. in diameter
is very little surface, comparatively speaking, between the tubes
for pressure to act upon, and as the tubes serve as stays to a con-
HANDBOOK ON ENGINEERING. 939
siderable extent, it is, therefore unnecessary to introduce stays
between them. The remaining flat surface above and below the
tubes is exposed to full boiler pressure, and would tend to bulge
outward, and thus loosen the tube ends if not properly secured
in position. The upper part of the head can be held in position
by means of rods connected to both heads, or by means of stays
connected to the head and boiler shell. When the area above
the tubes is secured by means of rods connected to both heads,
the rods are called direct, or through stays, and when the
rods run from the head to the shell, they are called diagonal
stays.
There is no necessity for using direct or head-to-head stays in
the return tubular boiler, because the shell possesses a surplus of
strength in the direction of its length, which is sufficient to resist
all the pressure that can be brought to bear on the area of the
head above and below the tubes. The ability of the shell to aid
in strengthening the head can be made use of by putting in the
proper number of diagonal stays. The advantages offered by
the latter style of stay are that the stays occupy comparatively
little space in the steam room of the boiler, thus permitting the
interior, both above and below the tubes, to be thoroughly in-
spected and cleaned, and the stays being shorter, the effects of
expansion are less noticeable upon the boiler heads, and the ten-
dency of the sta}Ts to work loose is correspondingly reduced.
When calculating the number of stays required in a boiler
head, it is not necessary to include the entire area above the
tubes, because it has been found by experiment that the flange
of the head imparts sufficient strength to a distance of 3 inches
from the flange, and that the tubes tend to stay the head to a
distance of 2 inches above the tops of the upper row of tubes.
It will be seen, therefore, that the actual area to be stayed ex-
tends to within 3 inches of the shell, and to within 2 inches of
the top of the tube. The area to be stayed is contained within
940
HANDBOOK ON ENGINEERING.
the dotted lines shown in Fig. 404, and is in the form of a seg-
ment of a circle.
In order to find the total pressure or stress on this area it is
first necessery to find the area of the segment formed by the
dotted lines. It will be seen that the top of this segment is an
i
oooo
Fig. 404.
Showing the area to be stayed.
arc of a circle which is smaller than the boiler head. If we take
off 3 inches from the diameter of the head at both top and bot-
tom it will give the diameter of the circle of which the segment is
HANDBOOK ON ENGINEERING. 941
a part, and the diameter will be found to be 6 inches less than
the diameter of the boiler head. The distance, H, Fig. 404, is
called the height of the segment. The area of the segment
multiplied by the steam pressure gives the total stress to be re-
sisted by the stays, and the total stress divided by the stress
which one stay will hold gives the number of stays required .•
To illustrate the method of finding the number of stays re-
quired, suppose the stays in a 60-inch and a 72-inch boiler head
are to be determined. In a well proportioned boiler head th<*
distance from the bottom of the shell to the top of the upper row
of tubes is about 60 per cent of the diameter of the head, and
60 per cent of 60 inches is 36 inches, which is the distance, A,
Fig. 404. The distaace from the top of the tubes to the top of
the boiler head is 60 — 36 = 24 inches. According to the rule
previously given we must subtract the width of the space, D,
which is three inches, and also the width of the space, E, which is 2
inches thus making the height of the segment equal to 24 — (3+2)
= 19 inches, which is the height, H, Fig. 404. Divide the
height, H, by the diameter, d, of the circle of which the segment
is a part. In the table of areas of segments of circles on
page 935, find the quotient in the column headed, Height,
and multiply the corresponding decimal in the column headed
area, by the square of the diameter of the circle of which
the segment is a part ; the product will be the area of the
segment included within the dotted lines. Thus, the diam-
eter of the circle of which the segment is a part is 60 — 6
= 54 inches, and 19 -f- 54 = .351. In the column headed
Height, we find .351 and opposite we find the decimal .2459
which, when multiplied by the square of the diameter of the
circle, gives .2459 X (54 X 54) = 717 square inches, the area
of the segment. If the boiler pressure is to be 100 pounds
on each square inch the total pressure will be 717 X 100 =
71,700 pounds, which is the stress to be borne by all the stays.
When stays are not subjected to the action of water they may be
942
HANDBOOK ON ENGINEERING.
allowed a stress of 7,500 pounds per square inch of section, but
when subjected to the action of the water in the boiler the stress
should not exceed 6,000 pounds.
Now stays in horizontal tubular boilers are generally made of 1
inch round bars and as a bar of this size has an area of .7854 of
a square inch each bar or stay will stand a stress of 7,500 X
.7854 = 5890 pounds, and the number of stays required is
71,700 ~ 5890 =33 12 stays, as shown in Fig. 403.
J K
Gr
\i
Fig. 405.
Method of connecting a diagonal stay.
The stress on diagonal stays is a little greater than on direct
stays running from head to head, so that the area of the 12 stays
must be increased in proportion to the increased stress. The
minimum length of stay allowable is 3J feet, and the stress
on the diagonal stay is as much greater than the stress on the
direct stay as the length of the stay FG, Fig. 405, is greater
than the distance JK. Suppose the distance, JK, is 45 inches,
and the length of the stay, FG, 48 inches, then the stress on the
diagonal stay is 48 -=- 45 = lTJo- times the stress on the direct
stay and consequently the area of the stay must be 1T^ times the
area calculated or .7854 X ITTFTF = -^ °* a S(luare inch, which
corresponds to a diameter of l^ inches. Thus the 60-inch boiler
requires 12 stays each 1T^ inches in diameter, as shown in Fig. 403.
HANDBOOK ON ENGINEERING. 943
The number of stays required in the 72-inch boiler is found in
the same manner. Thus, the diameter of the circle of which the
segment to be braced is a part, is 72 — 6 = 66 inches. The dis-
tance from the bottom of the shell to the top of the tubes is 60
per cent of 72 inches, or 43 inches, and the distance from the top
of the tubes to the top of the shell is 72 —43—29 inches. From
this is to be subtracted 3 inches measured from the shell, and 2
inches measured from the tubes, making 5 inches in all, thus leav-
ing 29 — 5 — 24 inches, which is the height, H, of the segment
represented by the dotted lines. Dividing the height of the seg-
ment by the diameter of the circle of which the segment is a part, we
have 24-r-66=.363. In the table of areas of segments of circles
find .363 in the column headed, Height, and opposite we find the
decimal .2574, which, when multiplied by the square of the
diameter of the circle of which the segment is a part, gives
.2574 X ( 66 X 66 ) = 1121 square inches area of segment.
Assume the pressure to be 110 pounds per square inch. The
total stress to be borne by all the stays is 1121 X HO = 123,310
pounds. If the stays are to be of 1 inch rods, which is the
smallest size used for boilers above 44 inches in diameter, the
area of each rod or stay will be .7854 of a square inch, and it
will be capable of resisting a stress of 7,500 X .7854 = 5890
pounds.
The number of 1 inch stays required, therefore, is 123,310 -5-
5890=21 stays.
Now, if the distance, J K, Fig. 405, in this case is 48 inches,
and the length of the stay 52 inches, the stress on the diagonal
stay will be 52 ~- 48 = 1T§ ^ times what it would be on a direct
stay, and consequently the area of the stay must be lyf^ times
greater, or .7854 X 1.08 = .85 square inch, which corresponds
to a diameter of l^ inches, therefore the 72-inch boiler will
require 2 1 stays 1-^ inches in diameter.
It sometimes happens that the maximum pressure employed
944
HANDBOOK ON ENGINEERING.
when calculating stays call for a certain number which it is found
difficult to properly distribute over the boiler head. In this case
the number of stays must be changed, but the combined area of
the stays must necessarily remain the same. To illustrate, sup-
oooooo
ocoooo
oooooo
oooooo
oooooo
ooooo
00
oooooo
oooooo
oooooo
oooooo
oooooo
ooooo
oo
Fig* 406.
No. of stays in a well proportioned boiler of 72 in. in diameter.
pose 21 stays could not be distributed to advantage on the
72-inch head, and it is desired to use, say, 18 stays. Now, the
21 stays have a combined area of .85 X 21 = 17J square inches,
and this area divided among 18 stays would give each an area of
HANDBOOK ON ENGINEERING. 945
17| -f- 18 = 1 square inch, which corresponds to a diameter of
1| inches, therefore the 72-inch boiler will require 18 stays 1£
inches in diameter.
The same method is used when finding the number and size of
the stays below the tubes. It is seldom practicable, with the
usual arrangement of tubes and man -hole, to use more than two
stays below the tubes so that the area is made sufficient to enable
two stays to carry the stress.
When finding the size and number of screw stays or stay
bolts, such are used in the water-legs of locomotive boilers and
in the headers of water tube boilers where the bolts are subjected
to the action of the water, the maximum stress allowable per
square inch of net section, which is the area of the bolt measured
at the bottom of the threads, is 6,000 pounds. For instance,
what is the diameter, number and stress on the stay bolts required
in the water-leg of a locomotive boiler, the flat surface measuring
40 X 54 inches, and the maximum pressure 125 pounds? The
total area is found to be 40 X 54 = 2,160 square inches, and the
total pressure to be resisted by the stay bolts is 2,160 X 125 =
270,000 pounds, For pressures exceeding 100 pounds per
square inch, the pitch of staybolts in stationary boilers should
not exceed 4J inches. . The area supported by each bolt is
4J X 4J = 18 square inches and the stress on each bolt is
18 X 125 = 2,250 pounds. The total stress is 270, 000 pounds,
consequently 270,000 divided by 2,250 will give the number of
bolts which is 270,000 -~ 2,250 = 120. The stress allowed per
square inch of net sectional area is 6,000 pounds, and as each
bolt must sustain a stress of 2,250 pounds the net area of each
bolt is 2,250 -f- 6,000 = .375 or f of a square inch measured at
the bottom of the threads, which corresponds to a bolt f inch in
diameter measured to outside of threads. This surface, there-
fore, requires 120 staybolts -if inch in diameter, spaced 4J inches
between centers for a working pressure of 125 pounds.
946
HANDBOOK ON ENGINEERING.
DOUBLE RIVETED LAP AND GIRTH JOINT'S
Longitudinally Riveted.)
This construction is based on a tensile strength of 60,000 Ibs. for plata
.and a shearing strength of 38,000 Ibs. for rivets.
LAP JOINT.
GIRTH JOINT.
-23-
• plates, double riveted; holes, %•; rivets, J|". (Efficiency ,
LAP JOINT.
GIRTH JOINT.
plates, double riveted; holes. U',' rivets, fc% (Efficiency,
59
HANDBOOK ON ENGINEERING.
947
Double Riveted Lap and Girth Joints.
LAP JOIKT. GIRTH JOIHT.
-34*
• plate*, doable riveted ; holes, }}• i rivets, £ -. (Efficiency . TO*. )
GIKTH JOINT.
•ai-
' plates, double riveted; hole* I'; rlrets, H*- (Efficiency, TOjt)
OIBTB JOINT.
(I* plat** double rtreted) hol««, 1 A' » rtvet* 1 ' (Efficiency,
948
HANDBOOK
Triple fciveted Lap and Girth Joints.
(Longitudinally Riveted )
This construction is based on a tensile strength of 60.000 Ibs, for plate
ittfra shearing strength of 88,000 Ibs. for rivets.
IiAP JOINT..
GIRTH JOINT.
' plates, triple riveted) holes, }j-i rivets, %•. (Efficiency. 77i.)
LAP JOINT.
k — 3k* —
GIRTH JOINT.
CM
i*o
b* plmtes. triple riveted; holes, % * $ rivets. 14-. (Efficiency, 76*.)
HANDBOOK ON ENGINEERING.
rtAP~ JOINT. GIRTH JOIKT.
K 3*'-
' plates, triple riveted ; holes, {|* ; rivets 2£ '. (Efficiency, 755?.)
LAP JOIKT.
GIRTH JOINT.
1»
«SJ
f
' plates, triple riveted; boles, 18'; rivets, %•» (Efficiency .75*.)
GIRTH JOINT.
I — a*:-
plates, triple riveted ; holes, I • ; rivets, if
949
950
HANDBOOK ON ENGINEERING,
Triple Riveted Butt Joints.
nt for &• plates; holes, &'; rivets, ||». (Efficiency, 88*.)
i
^
0
•^>
f^
ffl
feutt joint for %• plates; holes, y ; rivets, &'. (Efficiency.
Butt joint f or /e • plates; holes, 53 ; • rlvete, %'. (Efficiency, 86*.)
HANDBOOK ON ENGINEERING.
TRIPLE RIVETER BUTT JOINTS-CContinued.)
ck.
Butt joint for Vs" plates; holes, 1"; rivets, Jg' (Efficiency, 86.65?.)
i
Butt joint for ft* plates; holes, 1^' ; rivets, 1% (Efficiency, 66£)
Butt Joint tor-K* nl»tew t»J««. I.A' ri»et» f. (Efficiency. 8C*.}
951
952
HANDBOOK ON ENGINEERING.
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HANDBOOK ON ENGINEERING.
953
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954 HANDBOOK ON ENGINEERING.
CHAPTER XXXI.
HYDRAULIC ELEVATORS.
The purpose of these pages is to furnish such instruction and
information as will be of use to engineers in the care of elevator
machinery. To accomplish this end, cuts and sectional views
of cylinders and valves of the different types of elevator ma-
chinery made by the different elevator companies, are herein pro-
duced, so as to make the different elevators plain to the engineer.
It must be borne in mind that the one point of paramount im-
portance for the successful operation of an elevator is proper
care and management ; a lack of thorough knowledge of the ma-
chine and lack of attention in this respect shortens the life of the
machine and often makes extensive repairs necessary.
Hydraulic elevators are designated as horizontal or vertical
according to the position in which the lifting cylinder is placed.
Horizontal machines are generally placed in buildings where
there is ample floor space, while vertical elevators are used in
buildings standing on small lots. Vertical elevators are made so
as to lift the elevator by means of ropes, and are geared up so
that the travel of the piston is considerably less than that of the
car, and they are also made so that the piston, or plunger, pushes
directly against the bottom of the car and lifts it to the top of
the building. This type of elevator, which is now being intro-
dued on an extensive scale, is known as the direct plunger, or
simply plunger elevator.
Horizontal hydraulic elevators are designated as pushing or
pulling machines according to the way in which the power is ap-
plied. In pulling machines, the water under pressure is admit-
HANDBOOK ON ENGINEERING.
955
ted between the piston and the front end of the cylinder, and
the piston rods pull a set of movable sheaves toward the cylin-
'/* /
/
Fig. 407. Horizontal Hydraulic Elevator. Pushing Type.
956 HANDBOOK ON ENGINEERING.
der, aud thus lift the car. In pushing machines the water is
admitted to the back end of the cylinder and the piston rod pushes
the movable sheaves away from the cylinder to lift the elevator
car.
The general arrangement of a horizontal hydraulic elevator of
the pushing type is shown in Fig. 407. This is an Otis machine.
The lifting cylinder is at A, B being the piston rod, C the set of
movable sheaves and D a set of stationary sheaves. The lifting
ropes pass around these two sets of sheaves several times, block
and tackle fashion, and then run up and over an overhead sheave
E and down to the top of the elevator car. Another set of ropes
run up over the sheave F and down to a counterbalance weight G.
The number of times that the lifting ropes wind around the
sheaves determines the gear of the machine. The gear is always
the ratio between the distance traveled by the car and the stroke
of the piston. If the car runs ten times the stroke of the piston,
the gear is ten to one, and so on for any other ratio. Horizontal
machines are geared from six up to 14 to one, the average being
about 10 and 12.
The valve for operating the elevator is at jET, and is of the same
design as that used by the same makers for their vertical ma.
chines and is explained in connection with the latter machines.
Another valve is located at / and its office is to stop the elevator
automatically at the top and bottom landings, if the operator fails
to move the operating lever. This valve is actuated by the chain
J which is moved by an arm K attached to the movable sheave
frame. This arm strikes stop balls that are secured to J at the
proper points to cause the car to stop even with the top and bot-
tom landings of the building.
This illustration shows an actuating lever L in the car, which
acts through a system of rope connections to move the valve H.
This arrangement is used for high speed passenger elevators, but
HANDBOOK ON ENGINEERING.
957
slow speed freight machines are generally arranged so that a
hand rope passes through the car and the valve is moved by
pulling on this rope. The rope connections between the lever L
Fig. 408. Horizontal Hydraulic Elevator Machine.
and the valve are generally arranged on one of two different sys-
tems, which are designated as the running rope and the standing
rope. In the former the ends of the ropes are fastened to the
ends of a cross-lever located on the back end of the shaft that
carries L and therefore run when the car runs. In the standing
rope system the ends of the ropes are secured to the top and the
bottom of the elevator well and therefore stand still when the car
runs. In Fig. 407 it will be seen that there are small sheaves n',
ft, at top and bottom of the elevator well, the latter being mounted
on the side of a larger sheave over which runs a rope 0. This
rope passes around a sheave P located on the valve casing, and
by its rotation the valve is actuated in a manner fully explained
in connection with vertical elevators. The lever L is connected
with the sheaves ri ', ?i, by the ropes m, and by rocking i, to
one side or the other, these ropes are drawn up on one side and
let out on the other so as to cause one of the n sheaves to rise
and the other to fall and thus to rotate the large sheave, am}
through rope 0 the valve sheave P.
958
HANDBOOK ON ENGINEERING.
HANBBOOK ON ENGINEERING. 959
Another design of pushing machine is shown in perspective in
Fig. 408. This is a Crane machine, and canbe more fully under-
stood from Figs. 409-410 the first being a side elevation and the
second a plan. Fig. 409 also serves to make clearer the operation
of the running rope connection between the car lever and the
valve. When the operating valve is moved by means of a car
lever, it cannot be moved directly, because the lever swings
through a small distance only and on that account the force re-
quired to move it would be more than the operator could exert
for any considerable length of time. When the valve is operated
by a hand rope passing through the car, a small force is required
to pull the rope because it is pulled through several feet, which is
four or five times the distance through which the lever is moved.
To make the lever move freely a small valve is provided, called a
pilot valve, and this is what is moved by the car lever. The pi-
lot valve permits water to flow in or out of the main valve in such
a way as to move it in the desired direction. In Fig. 409 the pilot
valve is at M, and the main valve is inside of the chamber L L.
The automatic stop valve is within K, and is actuated through
rod J by means of the two arm lever H G and the frame F. This
frame has attached to it a rod upon which are fastened stops G
D and these are struck by an arm E projecting from the movable
sheave frame, see Fig. 410. In this way valve Kis moved auto-
matically at the top and bottom landings to stop the elevator.
The operation of the main and pilot valves can be understood
from Fig. 411 which is a vertical sectional view. The shaft 8 is
rotated by the carlever as shown in Fig. 409. If the movement is
such as to swing A to the left, the pilot valve at M will be moved
in the same direction and water will pass from space B at the
large end of the main valve to the discharge pipe C. This will
force the valve to the left and thus connect the supply pipe E
with the cylinder inlet D through the movement to the left of pis-
ton Go The water passing into the cylinder will force the piston
960
HANDBOOK ON ENGINEERING.
m
be
HANDBOOK ON ENGINEERING.
961
out and thus lift the elevator. It will be seen that as soon as the
main valve moves to the left, it carries lever / with it, and as this
ever swings around J the pilot valve is moved back to the stop
position. It can also be seen that the further the pilot valve is
moved by the swing of A, the further the main valve must move
to swing I far enough to return the pilot to the stop position ;
that is, the further the arm is moved, the wider the main valve is
opened. Thus the extent to which the main valve is opened is
dependent upon the angle through which A swings, and this
angle is dependent on the angle through which the car lever L is
M
Fig. 411. Take of Fig. 408 Machine.
moved ; hence, the operator has as perfect control of the move-
ment of the main valve as if he moved it by pulling directly upon
a hand rope.
Fig* 4f 2 is a photographic view of the Morse & Williams hori-
zontal pushing machine. This is what is called a double decked
machine and is a construction commonly resorted to when floor
space is limited. Each machine operates a different elevator.
The valve of this machine is arranged to be operated by a hand
rope, the latter being passed around the large sheave wheel A.
On the shaft of this wheel is mounted a small pinion that meshes
into a rack attached to the end of the valve stem. This construc-
tion will be seen illustrated fully and explained in connection with
HANDBOOK ON ENGINEERING.
HANDBOOK ON ENGINEERING. 963
the vertical elevator machines. The automatic stop valve is op*
erated by means of the rope seen at the side of the machine that
passes around sheaves J3, (7, the latter acting to close the valve.
HORIZONTAL HYDRAULIC ELEVATORS, PULLING TYPE.
In Fig. 413 is shown a horizontal machine of the pulling type.
This is the design made by the Whittier Elevator Company. The
stationary set of sheaves is located at the front, and the travel-
ling sheaves are between it and the end of the cylinder. The op-
erating valve is on top of the cylinder at the front end, the pilot
valve being on top of the main valve. The automatic stop valve
is just below the main valve and is operated by means of a rope
passing over sheaves and provided with stop balls, all of which is
clearly shown. The arrangement of the valve and pilot valve can
be understood from Figs. 414-415, the first being a plan and the
second a vertical section. The pilot valve is moved by lever E
which is connected with the actuating ropes A A that run to the
car lever. The lever E is pivoted at F so that when it swings in
either direction it moves the pilot valve through rod C. The oper-
ation of this valve and pilot valve is the same as that of Fig, 411
that is, the movement of the pilot valve to either side of the cen-
tral position acts to connect the end Koi the main valve cylinder,
either with the pressure pipe P or the exhaust It, thus moving
the main valve in one direction or the other. If .ZT is connected
with the pressure pipe, the valve is moved to the left and the
cylinder is connected with the discharge pipe and the elevator
runs down. The movement of the pilot valve in the opposite di-
rection will connect K with the discharge and then the main valve
will move to the right and the cylinder will be connected with the
pressure pipe and the elevater will go up. In either case, the
pilot valve is first moved in the same direction in which the main
valve is moved immediately after, and the movement of the main
964
HANDBOOK ON ENGINEERING.
HANDBOOK ON ENGINEERING.
965
valve acts to return the pilot to the stop position through the
lever D and rod C.
The automatic stop valve is shown in Figs. 416-417, the two
drawings being taken at right angles to each other. This valve
consists of two parts, the valve proper B and a cylindrical car-
rier A. The weight shown in Fig. 413 acts to swing A with B into
the position shown in Fig. 417, and the automatic stops act to
swing these parts so as to cover either one of the ports (7, D. If
the car is going up the automatic stop rotates A in a clockwise
direction so as to cover port C, and if coming down the rotation
Fig. 414. Valve of Whittle r Machine. Top View.
s opposite, so that A is moved over D. The valve B is held
against A by the tension of a spring, and also by the water pres-
sure, when the elevator is being stopped ; but when it is started
again, by reversing the position of the main valve, the pressure
acts to lift B from its seat against A and permit water to leak
through slowly and thus allow the car to start up gradually. As
soon as the car begins to move, the stop ball is drawn out of the
way and the weight acting on A draws it into the position of Fig.
417 so as to open the valve wide and permit the car to attain full
speed.
966
HANDBOOK ON ENGINEERING.
VERTICAL HYDRAULIC ELEVATORS.
The construction of a vertical elevator machine, Otis type, can
be understood from Fig. 418 which is a vertical elevation of the
lifting cylinder and operating valve in section. At A the valve
is in the position it takes when the elevator is at rest. At B the
position of the valve is that corresponding to the up motion of
the car, while at G the position of the valve for the down motion
is showno The pipe seen at the side of the cylinder is called a
circulating pipe, and its office is to permit the water in the upper
end of the cylinder to pass to the lower end, or circulate, while
the elevator is running down. As can be clearly seen the easiest
Fig. 415. Talve of Whittier Machine. Side Elevation.
way in which to make a vertical cylinder elevator would be to
have the lower end permanently open, and to let water into the
upper end to force the piston down and the elevator car up, and
to let this water out of the cylinder to permit the piston to run up
and the car to run down. A little reflection, however, will show
that with this arrangement, simple as it is, the force acting to
force the piston down when the latter is at the top of the cylinder
would be the pressure of the water only, while when the piston is
At the bottom of the cylinder the force would be the pressure plus
HANDBOOK ON ENGINEERING.
967
the weight of water above the cylinder. Now if the cylinder is,
say, thirty feet long this water would increase the pressure near-
ly 14 pounds, hence, when the car is at the top of the well there
would be a greater force than when at the bottom, and the load
in all probability would be less. If the circulating pipe is used,
the force acting on the piston is the same at every point in the
stroke, because the water under the piston is drawn up by the
vacuum that tends to form ; therefore, the force of the vacuum act-
ing to draw down the piston is just as great as the force due to
the weight of the water pressing on top of the piston, and as one
Fig. 416. Fig. 417.
Automatic Stop Valve for Whittier Machine.
increases as fast as the other decreases, the two balance each
other at all times and the force acting on the piston remains un-
changed.
The valve shown in Fig. 417 is of the kind used with a hand
rope passing through the car to operate it. The hand rope is
wound around the sheave 13, and when it is pulled it turns the
sheave, the direction of rotation of the latter depending on the di-
rection in which the rope is moved. The connection of the rope
with the hand sheave is made such that if the car is going up the
rope must be pulled up to stop, and if coming down the rope
968
HANDBOOK ON ENGINEERING.
SECTION OF ELEVATOR CYLINDER
VALVE SHOWING WORK ING 'PARTS]
c
Fig. 418. Otis Vertical Elevator. .
HANDBOOK ON ENGINEERING.
969
must be pulled down to stop. The rotation of the sheave turns
the pinion, seen in Fig. 418, and thus through the rack on the
valve stem the valve is shifted.
r
Fig. 419. Otis Vertical Elevator System.
With the valve in the position A of Fig. 418 the piston cannot
move because the water below it cannot escape. If the valve is
raised to the position of JB, the water under the piston can escape
970
HANDBOOK ON ENGINEERING.
to the discharge tank, and then the piston can move down, that
is, if it is in any position above the lowest. If the valve is
lowered to the position C then the water in the upper end of the
cylinder can pass through the valve chamber to the lower end,
and the pressure being equalized, the piston will move upward,
Fig. 419 is an illustration that serves to show how a complete
Fig. 420. Otis Valye.
vertical elevator system is arranged, although in practice few
installations are arranged in this way ; generally the distance be-
tween the tanks, and between these and the pump and elevator
cylinder, is greater than here shown. In this illustration, the
pressure tank is shown directly above the discharge tank, and
the steam pump that supplies the water is located at the side of
HANDBOOK ON ENGINEERING. 971
the discharge tank. The pump draws the water from the dis-
charge tank and delivers it into the pressure tank. The elevator
cylinder draws its supply from the pressure tank and discharges
it into the lower tank.
VALVE CONSTRUCTION.
The construction of the valve in Fig. 418 can be understood
more fully from Fig. 42 00 It will be seen that the valve pistons
are provided with cup packings, the cup in E being set so as to
hold pressure acting from below, and F having packings to hold
pressure from above. The valve casing opposite F has a brass
lining which is perforated with numerous holes about one-quarter
of an inch diameter. This construction is used in all hydraulic
elevator valves, with the exception of very small pilot valves
which are in some cases made solid and ground to a perfect fit.
This is done so as to reduce the friction and make them move
more freely. The perforated brass lining for the valve chamber
is used so as to prevent the cup packing from dropping into the
port holes as it passes them. The main pistons of hydraulic
lifting cylinders are made so as to be packed with leather cups,
also with hemp packing, and in some cases have a combination of
cup and hemp packing ; but the latter alone is as good as any-
thing, provided it is not pressed up too tight by the follower.
Cases have been known where the cylinder has been burst by
having the packing pressed up too tight.
The vertical elevator shown in Fig. 418 is provided with a valve
that is actuated by the direct pull of a hand rope. This con-
struction which was used exclusively in former days, is now em-
ployed only for freight elevators, or passenger machines that run
at a low speed. For first class service, such as the elevators of
modern office buildings, a pilot valve is provided so that the op-
erator may be able to control the movement of the car with cer-
972
HANDBOOK ON ENGINEERING.
Fig. 421. Otis Tertical Elevator with Pilot; VaJv« r«nt™i_
HANDBOOK ON ENGINEERING.
973
tainty even at the highest speed. An Otis vertical elevator for
first class service, provided with a pilot valve is shown in Fig. 421
This machine is geared four to one. The main valve is similar to
Fig. 422. Otis Vertical Elevator, showing method of operating
Pilot Valre.
that of Fig. 418, the only difference being that it has added to its
upper end a larger piston, the office of which is to move the valve.
In the simple arrangement of Fig. 418 the car is stopped automat-
974
HANDBOOK ON ENGINEERING.
ically at the top and bottom landings by simply placing stop balls
on the hand rope is such position that they will be struck by the
car at the proper time. This construction cannot be used with
the pilot valve system because the operating ropes are held by the
lever in the car, and are not free to move. Owing to this fact, a
separate automatic stop valve is added and is connected between
the main valve and the cylinder, as clearly shown in Fig. 421.
Fig. 423. Otis Vertical Elevator. Main Valve Used with
Pilot Valve Control.
This stop valve is operated by means of a cable that passes
around a sheave on the valve spindle, and another sheave near
the top of the building. On this cable there are stop balls and
these are struck by an arm projecting from the traveling sheave
frame, the action being the same as in the horizontal machines.
The way in which the valve is actuated by the movement of the
oar lever is clearly shown in Fig. 421, but the operation of the
HANDBOOK ON ENGINEERING.
975
valves can be made clearer by the aid of Fig. 422. When through
the movement of the car lever L, the sheaves P and P* are ro-
tated, the pilot valve at h is either raised or depressed. If it is
depressed, the pressure pipe is connected with the space T above
the large valve piston, through the pipes g and/. The pressure
in T forces the valve down so that the water in the upper end of
Fig. 424. Details of Otis Pilot Valve.
the lifting cylinder can circulate through pipe G to the lower end
of the cylinder and permit the piston to go up and the car to de-
scend. If the pilot valve is raised, the space T is connected with
the discharge through pipe/ and/ and the water escapes, and as
the pressure above the large valve piston is removed, the valve
rises and thus the lower end of the cylinder is connected with the
97() HANDBOOK ON ENGINEERING.
discharge, and the water runs out, while the pressure water
passes through port Vio the circulating pipe G and thus to the
upper end of the cylinder.
The construction of the main valve can be clearly understood
from the drawing Fig. 423 which is a vertical section. As will be
seen the only difference between it and the valve Fig. 420 is that
it is provided with the additional motor piston G which is in the
position occupied by the rack and pinion in the latter drawing,
The pilot valve can be understood from Fig. 424 in which the pipe
outlets are marked to correspond with Fig. 422.
Additional light can be thrown upon the operation of the pilot
and main valves by the aid of Fig. 425 which is a vertical eleva-
tion of the valve gear the same as that shown in Fig. 422, but on
a larger scale, and divested of the complication due to the pipe
connections. The sheave 31 is rotated by the movement of the
car lever, and the crank upon shaft 32 moves the lever 17 through
the connecting rod 18. As the pilot valve moves easier than the
main valve, this movement of 17 shifts the pilot valve, through
rod 19. If the pilot valve is depressed, pressure water entering
through ports 24 passes out through ports 26 and enters the space
at top of main valve chamber, above motor piston 8. The pres-
sure forces the main valve down and the upper end 11 of valve 13
uncovers the ports at 12 so that the water in the upper end of the
cylinder can pass through the valve to the lower end and the pis-
ton can go up, and the car come down. If the pilot valve is
raised, ports 26 are connected with the lower end of pilot valve
chamber, and the water above piston 8 can escape, so that the
main valve may move up and connect ports 12 with the discharge
pipe. It will be noticed that for either movement of the pilot
valve, the following movement of the main valve acts through
lever 17 to return the pilot to the stop position, and the further
the latter is moved by the rotation of 31, the further the main
valve will have to travel to return the pilot to the stop position ;
HANDBOOK ON ENGINEERING.
977
Fig, 425. Otis Differential
and Pilot Valve*
978
HANDBOOK ON ENGINEERING.
thus the extent to which the main valve is moved is in direct pro
portion to the extent to which 31 is rotated, and this is in pro
portion to the extent to which the car lever is moved.
Fig. 426. Otis Main Valve with Magnetically Operated Pilot Yalre.
Sometimes hydraulic elevators are installed in private houses,
or are used to operate dumb waiters, and in either case an opera=
HANDBOOK ON ENGINEERING.
979
tor to run the car is not required. As a rule elevators of this
kind are operated by electric machines, but when hydraulic ma-
chines are so used, they are arranged in the same way, that is,
so that they may be operated by means of push buttons at the
several floors and in the car. To make the hydraulic valve gear
so as to be electrically operated, all that is necessary is to pro-
vide magnets that will move lever 17 in the same way as it is
moved by the rotation of sheave 31. A valve gear provided with
SUPPLY
Fig. 427. Pipe Connections for Fig. 426.
such magnets is shown in Fig. 426, in which M M' are electro-
magnets, and A A' iron armatures attached to the lever B. If
current is turned onto the magnet M , armature A is drawn down
and through rod 0 lever D is pushed up carrying the pilot valve
with it. If current is turned onto magnet JfcP, armature A' is
drawn down and then G pulls D down and with it the pilot valve.
The action of the main and pilot valves is the same as in Fig. 425,
980
HANDBOOK ON ENGINEERING.
The pilot valve for this magnet control is made so as to fit tight
by grinding, so as to get rid of the friction of the cup packings.
The way in which the pilot valve is connected with the main
valve chamber, and the supply and discharge pipes is shown in
Fig. 427. Two strainers are placed in the supply connection, so
that by means of the three-way cocks shown either one may be
Fig. 428. Photographic Yiew of Fig. 427.
disconnected whenever it is desired to clean it. Fig. 428 is a
photographic view of this type of magnetic valve gear.
With this arrangement of magnets, the current for operating
them is drawn from an incandescent lighting circuit. It is
necessary sometimes, however, to arrange the apparatus so that
it may be operated by current obtained from primary batteries,
HANDBOOK ON ENGINEERING.
981
a lighting circuit not being available. As the current from
primary batteries is weak, and expensive, it becomes necessary to
modify the magnetic devices so that they may be actuated with
Fig. 429. Otis Main Valve with Magnet Control Adapted to Operate
with Battery Current.
smaller currents. This is accomplished by the arrangement
shown in Fig. 429. In this construction, the magnets M M' move
982
HANDBOOK ON ENGINEERING.
a pilot valve B that is much smaller than that used in Fig. 426,
and works correspondingly easier. This secondary pilot controls
the flow of water into a motor cylinder 7), and the piston in this
3 WAY
&URPLV PIPE
Fig. 480. Pipe Connections for Fig. 429.
cylinder acting through rod E moves the lever P in the same way
as it is moved by the magnets in Fig. 426. As valve B is much
smaller than the main pilot valve R the power required to move
HANDBOOK ON ENGINEERING.
983
it is much less than that required for the construction of Fig. 426.
From Fig. 430, which shows the pipe connections of this double
pilot valve construction, the operation of the valves can be more
fully understood. The actual appearance of the valve gear is
shown in the photographic view Fig. 431.
A complete diagram of a hydraulic elevator arranged for push
Fig. 431. Photographic Yiew of Fig. 430.
button operation is shown in Fig. 432. At C is located a de-
vice calld a floor controller, and its office is to change the
circuit connections so that by pressing the same button at any
floor, the car may be caused to run up, if it is below that
floor, or to run down if it is above the floor. A photo-
graphic view of the floor controller is shown in Fig. 433.
984
HANDBOOK ON ENGINEERING.
J.
Fig. 432. Otis Private House Elevator, Push Button Control.
HANDBOOK ON ENGINEERING.
985
This floor controller is driven by chain E which is moved
by the arm F, of the traveling sheave. The chain rotates
a shaft that carries a worm that meshed into gear D and
thus rotates C. The controller C has mounted on its surface
two metallic strips that are connected with the opposite sides
of the circuit. Contact brushes rest on these strips, there being
one for each floor. The contact strips are set spirally on the
face of the drum of 0, and the drum travels on a thread that is
the same pitch as this spiral so that the brushes may always rest
on the strips. When the elevator car is below a given floor, the
Fig. 483. Floor Controller for Otis Fash Button System. Fig. 433a.
brush corresponding to that floor rests on one of the metallic
strips forming the spiral, but when the car is above this floor the
brush rests upon the other strip. In this way the circuit con-
nections are changed, so that if the car is above the floor, press-
ing the button causes the car to run down, and if it is below the
floor, pressing the same button causes it to run up. The way in
which all this is accomplished is made clear by the wiring dia-
gram, Fig. 434.
Two operating batteries are shown, and either one can be used
986 HANDBOOK ON ENGINEERING.
by turning the switch in the proper direction. If the switch is
turned to close the circuit the current will flow into the + wire all
the way to the car and back to wire A, and through coils a b to c
and to wire B which connects with all the floor and car push but-
tons. The coils a b and contacts c represent a magnetic switch
with the two coils wound in opposition to each other, so that if
current passes through both, contacts c remain closed. If any
one of the push buttons is depressed the current will pass through
it to the corresponding wire of the set 1, 2, 3, etc., and through
the corresponding coil 11, 22, 33, etc., to a corresponding floor
controller brush, and then through wire n and the upper magnets
back;to the battery. The coils 11, 22, 33, etc., represent mag-
netic switches that close the contacts seen to the right of them
when a current passes. As soon as the contacts are closed, cur-
rent flows through wire m from the junction of coils a b and then
the coil b being cut out, the circuit with B is broken at c, so that
after this instant, no one can interfere with the movement of the
car by pressing another button because there is no current in B.
Thus it will be seen that as soon as the car is started from any
floor, or from the car itself, all the push buttons are cut out until
the trip is completed. The circles seen in the upper part of the +
wire represent door switches at the landings, that are open when
the door is opened, so that unless the landing door is closed the
car cannot move. As soon as the car begins to move, the floor
controller begins to rotate, and when the car reaches the floor
corresponding to the button pushed, the controller brush through
which the current is passing passes onto the break between the
segments n' and p' and the circuit through the magnets is broken
and the ear stops. If the controller brush connected with the
wire through which the current comes is resting onp', insteadof n'
the current will flow through the lower valve magnets, and the di
rection of the car will be reversed. In Fig. 434 the floor control-
ler is shown with the segments eovering less than half a circle, so
HANDBOOK ON ENGINEERING.
987
as to simplify the diagram, but in the actual controller they are
arranged in a spiral line as shown in Fig. 433, so as to give more
space between the brushes.
Fig. 434. Wiring Diagram for Otis Push Button System.
DOUBLE POWER HYDRAULIC ELEVATORS.
Hydraulic elevators of the types so far explained have one de-
fect, and that is that it requires just as much power to run the
14
988 HANDBOOK ON ENGINEERING.
car up empty as if fully loaded. This is so from the fact that in
either case a cylinder full of water must be used. To obviate
this loss of power, the Otis Company make what is called the
double power system. The difference between this and the ma-
chines so far described is that water at two different pressures is
used, the low pressure being about half as much as the high ; gen-
erally the low pressure is 100 and the high 180 to 200 pounds.
The valves are so arranged that for small loads only low pressure
water is used the high pressure being reserved for heavy loads.
The valves of the double pressure system are shown in Fig. 435,
and as will be seen are substantially the same as those already
shown, the actual difference being that the piston F is added so
as to control the flow of high pressure water. The pilot valve is
made so that its first movement causes motor piston E to
move far enough to let on the low pressure water only. If this
is not sufficient to move the car, the operator moves the lever
further, and then the pilot valve moves far enough to lift valve F
above the lower edge of port i so that high pressure water may
flow into the cylinder. In practice it is found that there is an in-
jector effect produced which draws low pressure water in together
with the high pressure, so that if the load in the car is more than
the low pressure can lift, but less than the maximum capacity of
the high pressure, then water is drawn from both sources, and
the amount drawn from each one is nearly in proportion to the
load.
HIGH PRESSURE HYDRAULIC ELEVATORS.
As low pressure elevators take up a considerable room, on ac-
count of the large size of the lifting cylinders, the connecting
pipes and the tanks, high pressure machines are frequently in-
stalled in large office buildings, specially if these occupy small
floor space. High pressure machines are made horizontal as
well as vertical, but more are made of the latter type. A high
HANDBOOK ON ENGINEERING.
989
Fi?. 435. Otis Double Pressure Eleyator,
990 HANDBOOK ON ENGINEERING.
HANDBOOK ON ENGINEERING.
991
S3
•c
I
$
992 HANDBOOK ON ENGINEERING.
as the pilot valve is operated with low pressure water. The con-
struction of the valves is shown in Fig. 438, in which the pilot is
on the left, and is moved by the connecting rod E, which in
turn is moved by L through rod D. The motor cylinder is in
the center, and the main valve on the right. The pilot valve con-
trols the flow of water into the motor cylinder, and when the
piston Amoves, the piston rod Cr, through the connecting arms
J and P, moves the main valve ; and also through lever JT, which
swings around the upper end of D, moves the pilot valve back to
the stop position. The pilot valve is operated with low pressure
water because it would not be practical to use high pressure
on account of the smallness of the ports. In fact the first ma-
chines of this type were made with high pressure to operate the
pilot valves, but they gave a great deal of trouble on account of
the wearing out of the ports and valves. The sheave that moves
the pilot valve is attached to the disc S, or to the shaft on which
this disc is mounted.
In Fig, 437 the automatic stop valve is located near the main
valve, at the lower end of the guides for the traveling sheave, and
is actuated by levers that extend in the path of the sheave frame,
so as to be struck by it at the proper time. The valve is also
placed just below the lower end of the lifting cylinder, and is
actuated by a chain that passes round a sheave mounted on its
spindle and runs by the side of the traveling sheave frame to
the lower end where it passes around a carried sheave. In this
construction the chain has stop balls placed on it at both ends,
and these are struck by a projecting arm on the sheave frame at
the proper time to stop the car at the upper and lower floors.
The valve used with this arrangement is shown in Figs. 439-440,
441 and 442. The sprocket wheel around which the chain passes
is at A, and when the arm on the traveling sheave frame strikes
one of the stop balls, A is rotated and with it the valve #, Fig.
4:4:2. The shaft of A carries a pinion that meshes into a gear on
HANDBOOK ON ENGINEERING .
993
Fig* 437t HigU Pressure Hydraulic Elevator System witli Inverted
Plunger,
994 HANDBOOK ON ENGINEERING.
the valve shaft, Fig. 440, so that A turns through several revo-
lutions to close the valve G. The wheel C is provided to return
the v-'tlve to the central position. A strap, to which a weight is
attached, is secured to G and passes between the small wheels
D 7), Fig. 440. The weight is heavy enough to rotate C.
The movement of A is geared down so as to produce a slow
closing of the stop valve and thus prevent violent stopping of the
elevator. The valve G is made so as not to fit perfectly, and is
held against the seat in stopping by the pressure of the water,
but when the pilot valve is turned to run the car in the opposite
direction, the current of water through G changes its direction
and the valve is lifted from its seat so that water can leak through
fast enough to give the car a smooth start. As soon as the car
moves, the arm that struck the stop balls moves out of the way,
and then the weight suspended from G rotates the latter and
returns the valve to the central position.
Fig. 443 shows two views of a valve not shown in Fig. 437.
This valve is simply a speed governor. In high office buildings
elevators run at very high speed, 500 to 600 feet per minute, and
with such velocities it is possible for a car to run away if the
load is light and the operator opens the valve too wide. The
object of Fig. 443 is to prevent such run aways by checking
the flow of water. In the sectional view of this valve it will be
seen that the pipes are connected with the outlets C and D.
Now the water to pass from one to the other has to flow
through the valve piston B. This piston has small holes E
for the water to flow through, and some pressure is lost by the
passage of the water through these holes, the amount of pres-
sure increasing as the velocity of the water increases. The
spring JTact8 to hold piston B in the central position, and is ad-
justed so as to hold against the pressure developed by the high-
est velocity at which it is desired that the water should flow. If
+,m's velocity is exceeded, the pressure due to the loss of head in
HANDBOOK ON ENGINEERING.
995
Fig. 438. YalYesUsedinFir.437.
996
HANDBOOK ON ENGINEERING.
passing through holes E will increase, and then B will be carried
to one side of the center and some of the holes in sleeve F will
be covered, thus reducing the opening through which the water
can pass, and thereby checking the speed of the elevator.
Figs. 444 and 445 are two views of the accumulator. An ac-
cumulator is simply a hydraulic cylinder standing upright and
provided with a plunger that is loaded with iron weights until
the desired pressure of water is obtained. In the illustrations, K
Fig. 439. Fig. 440.
Automatic Stop Valve Used in Fig. 437.
is the cylinder and L the plunger, which is provided with a cross-
head at the top, from which depend rods M M that hold the
weights A. These weights are made with a hole in the center
large enough to clear the cylinder, so that when the water is
all out, the weights envelop the cylinder. This construction is
used in cases where it is desired to economize head room ; in
other cases the weights are set directly on top of the plunger.
To prevent pumping enough water into the accumulator to force
the plunger out the top. and also to prevent drawing out so
HANDBOOK ON ENGINEERING.
997
much as to empty the cylinder and allow the plunger to strike the
bottom, automatic stops are provided to control the pump, and
also the flow of water from the accumulator. The rope to which
the weight B is attached runs to the valve of the pump, and
when the accumulator is full this weight B is lifted by shelf Q
and then the pump valve is closed. The flow of water in or out
of the accumulator is controlled by valve D. This valve is moved
by an arm on the weights A striking the stop balls 2^ on the
chain E. When the water is at the low limit, the lower F is
struck and this closes valve D so that while water can flow in
none can pass out. If the accumulator is full, the upper F is
Fig. 441. Fig. 442.
Automatic Stop Valve Used in Fig. 437.
struck and then D is reversed, so that no more water can be
pumped in, but water can flow out freely.
Valve D is shown in Figs. 446 and 447. In the first drawing,
the arrows A indicate the course of the water flowing into the ac-
cumulator, and the outgoing path is indicated by the dotted ar-
rows. The check valve in the outlet passage E opens upward,
and check valve in the inlet passage F opens downward. If
valve D is in the central position, water can pass through it in
either direction, but if rotated in one direction it will stop the flow
through E and if rotated in the opposite direction it will stop the
flow through F. The passages E and F surround valve D, as
998
HANDBOOK ON ENGINEERING.
seen in Fig. 447 but the ports in the valve D as well as the valve
chamber, are so shaped that E &ndF can be connected separately
with B but not directly with each other.
Fig. 443. Speed Controller Used in Fig. 437.
PLUNGER ELEVATORS.
In plunger elevators, the lifting cylinder is placed in a hole
bored down in the ground directly under the centre of the car.
HANDBOOK ON ENGINEERING
999
The plunger pushes the car to the top of the building; therefore,
the plunger and cylinder both have to be made a few feet longer
than the height to which the elevator is raised. The cylinder is
Fig. 444. Fiff. 445.
Accumulator Used in Fig. 437.
made of steel pipe, as many lengths as may be necessary bei&g
joined together by means of sleeve couplings. The ends of the
pipe sections are turned square with the axis of the pipe, and the
1000
HANDBOOK ON ENGINEERING.
threads are cut true so that when the several lengths are joined
they may form a straight cylinder. The plunger is also made of
lengths of steel pipe which are joined by internal sleeves. These
sleeves are made extra long so as to give the plunger just as
much strength at the joints as at other points. The pipes form-
ing the plunger are turned true and made smooth so as to 'slide
through the stuffing box with as little friction as possible, and
also so as to make a tight joint at the box. The top of the cyl-
inder consists of a casting provided with an outlet for the water
Fig. 446.
Fig. 447.
Valve for Accumulator, Figs. 444 & 445.
pipe to attach to, and a stuffing box at the top ; the latter is in
some cases made separate and bolted to the main casting.
The plunger is made from six to seven inches in diameter, and
the cylinder is about two inches larger, so that only the top cast-"
ing has to be finished to fit the plunger. The lower end of the
plunger is finished off with a casting, The hole in the ground is
made about 13 inches in diameter, and when the cylinder is in
place, the space between it and the sides of the hole is filled with
sand.
HANDBOOK ON ENGINEERING. 1001
Plunger elevators have been made for years for short runs, but
it is only within the past few years that they have been installed
for high buildings and for all classes of service. While there are
probably many concerns that make plunger machines for side-
walk elevators, and other low runs, there are only two companies
that make them for high speed passenger service in high office
buildings. These concerns are, The Plunger Elevator Company
and The Standard Plunger Elevator Company, both of which
have their works in Worcester, Mass.
The general arrangement of the elevator made by the Standard
Company is shown in the half tone Fig. 448, and the elevator of
the Plunger Company is shown in half tone Fig. 449. From both
these illustrations it will be seen that ropes pass from the top of
the car over an overhead sheave and down to a counterbalance
weight. If the building is high, say from 150 to 300 feet, the
plunger will weigh so much that a part of it will have to be
counterbalanced, so that the counterbalance weight will be
heavier than the car proper, and will actually lift the upper end
of the plunger. Owing to this fact, the plunger has to be firmly
secured to the bottom of the car so that there may be no dan-
ger of its pulling away.
The fact that the counterbalance weight is heavier than the
car serves to increase the stiffness of the plunger for the reason
that the upper end is subject to a tension, instead of compression,
and the tendency to buckle is confined to the lower end. On this
account the plungers do not buckle even when 200 to 300 feet
long, notwithstanding that the diameter is between six and seven
inches. Sometimes when making a quick stop coming down
the plunger may spring slightly, but it at once returns to the
straight position.
In the Standard Elevator Fig. 448 the main valve is at A, the
pilot valve being at the extreme right side end, and is moved by
the car lever through the rope connection as clearly shown. The
1002
HANDBOOK ON ENGINEERING*
I
HANDBOOK ON ENGINEERING. 1003
automatic stop valves to stop the car at the top and bottom land-
ings are located below the main valve at B, the lower limit valve
being at L and the top valve at Lf. These limit valves are act-
uated by the ropes E and F. The first being attached to the
bottom of the car on the left side. This rope runs over a small
sheave and down and around the sheave on the end of the lever
L, thence to the top of the elevator well, over a sheave and down
to the top of the car where it is fastened on the right side. The
other rope starts from the left side of the top of the car, and run-
ning over a sheave at the top of the well runs down and around
the sheave on the end of L'9 and thence up to the bottom of the
car on the right side. Each one of these ropes is given a sharp
bend when the elevator reaches its end of the well, and in that
way the lever of the corresponding limit valve is raised, and the
valve is closed so as to stop the car. The water from the pressure
tank enters through pipe S to the main valve chamber, and
passing down through the limit valve chamber reaches the cylin-
der. In escaping from the cylinder the water passes through the
limit valve to the main valve and thence to the discharge pipe D.
The operation of the valves will be explained further on.
In Fig. 449 the limit valves are actuated in substantially the
same manner as in Fig. 448, but the ropes are stationary, their
upper ends being fastened to the framing at the top of the eleva-
tor well and the lower ends to the valve levers. In this elevator,
the main valve is connected between the cylinder and the limit
valves, which is just the opposite of the arrangement in Fig. 448.
The details of construction of the cylinder and plunger of the
Standard machine are shown in the line drawings, Figs. 450 and
451, the first being a vertical elevation in section, and the
other an outside view taken at right angles to Fig. 450. In the
last named drawing, the long sleeve couplings inside of the
plunger can be clearly seen, also the construction of the top
36
1004
HANDBOOK ON ENGINEERING.
Fig. 449. Is Plunger Elevator of the Plnnerer Elevator C&.
HANDBOOK ON ENGINEERING. 1005
cylinder casting, with the water pipe opening A. Within the
plunger there is a strong steel cable B that is secured to the floor
framing of the car, and runs down to the bottom of the plunger
where it is firmly secured. This is an extra safeguard to hold
the plunger if from any cause it should break away from the un-
derside of the car floor. The bottom of the plunger terminates
in a brass casting (7, which is made of brass so that that portion
of it that does not pass through the stuffing box when the car
reaches the top floor, may not become rough by rusting. This
casting carries at its lower end three copper wire brushes d which
serve to prevent the lower end of the plunger from hitting the
sides of the cylinder, and also will permit water to run out of
the top of the cylinder if for any reason the car should run above
the top limit. This is a safety arrangement provided so that the
car cannot run into the overhead beams.
The valves of the Standard Plunger Elevator are shown in Fig.
452. The supply pipe is at £, and the discharge pipe at E.
When the car runs up the main valve is moved to the right carry-
ing E fast enough to permit water from S to pass S' '. W7hen run-
ning up, valve Fisto the left of the position shown, so that from
S' the water can pass to D and to the cylinder. In coming
down, the main valve is moved to the left far enough for T to
connect E with E' and then the water in the cylinder can pass
out through D to E' and through the main valve chamber to E.
The pilot valve is located at the right of the main valve, JV
being its stem. The lever K is moved by the car lever through
the running rope gear as shown in Fig. 448. If K is raised, the
rod L lifts the shaft that carries pinion P, and thus the pilot
valve is raised, so that the water from the supply pipe /Scan pass
through A to the pilot valve chamber and come out through
pipe C to pipe P and thence to space M back of the motor piston
Q of the main valve. This water will move the main valve to
the right and cause the elevator to ascend. At the same time
1006
HANDBOOK ON ENGINEERING.
DETAILS OF PLUNGER ELEVATOR PARTS AND CONNECTION
Fig. 450. For Standard Plunger Elerator. Fig. 45
HANDBOOK ON ENGINEERING.
1007
the movement of rack U will rotate pinion P and cause it to run
down on the thread in L and thus lower the pilot valve to the
central position. In going down the lever K is depressed and
the movement of the pilot valve is in the opposite direction so
that pipe P is connected through the lower end of the pilot valve
chamber with the pipe leading to the discharge, and in this way
end Q of motor cylinder is emptied and the main valve moves to
the left. From the foregoing it will be seen that the action of
Fig. 452. Pilot Controlling Valve for Standard Plunger Elevator
and Automatic Stopping Yalve for End of Bun.
the pilot and main valves in this construction is substantially the
same as in other types of elevators, in fact all hydraulic elevator
pilot valve gears act upon the same principle, and only differ in
construction. The action of the limit valve is not clearly seen
from Fig. 452, because in this drawing the end levers are in an in-
rerted position, this being done so as to contract-the drawing by
shortening the connections S' E'. If it is kept in mind that the
end levers are reversed, as shown in Fig. 448, then it can be seen
1008 HANDBOOK ON ENG1NUE1UNG.
that when W is raised, Yis closed, and that the same is true of
Z and F. The valves G G at the inner ends of ]Tand Z are for
the purpose of stopping the ports from S' and E' if the ropes that
operate the limit valves should break or run off the sheaves. It
will be noticed that at the lower end of the shaft of pinion P
there are two spiral cams, and a stationary cam is located be-
tween them. These cams are for the purpose of preventing a
too sudden stop of the car, by an instantaneous closing of the
main valve. If the main valve is closed instantly, when the car
is running up, the headway will keep the car moving up some
distance and as water cannot flow into the cylinder, the plunger
will leave the top of the water. The headway of the car will
then soon stop and its weight will bring it back and cause the
plunger to strike the top of the water in the cylinder, and pro-
duce an uncomfortable jolt. If the sudden stop is effected when
the car is going down the plunger will buckle to some extent to
relieve the jar. The cams below P prevent these sudden stops
because L cannot move P vertically any faster than the cams
turn around so that even if K is moved ' to the stop position in-
stantly, the pilot valve will not move any faster than is per-
missible.
The main and pilot valves of the Elevator made by the Plunger
Co., Fig. 449 are shown in Fig. 453. The pilot valve is moved by
lever H. There are two valves used to perform the pilot work,
L the pilot valve proper, and JT, which is called a throttle. If H
is lifted, the lever I will swing arouud its upper end and move L
to the left. The supply pipe is at E, and is connected with
chamber 1 by port 0, and 1 is connected with 2, so that when 1
is moved to the left, water can pass from 1 to 2 thence through
3 to 4 and through pilot valve to passage 6 and to the back end
of motor piston- cylinder, and force the main valve to the right,
BO that water from E may pass to F and to the lifting cylinder.
The movement of the main valve to the right will cause K to
HANDBOOK ON ENOINEERING.
1009
1010 HANDBOOK ON ENGINEERING.
move to the left, and L to the right, thus bringing the pilot valve
back to the stop position, just as in all other pilot valve arrange-
ments. The movement of K to the left closes the opening be-
tween d and / at e so that the only way for water to pass from
one space to the other is through the opening opposite the end
of screw N. This construction is for the same purpose as the
cams on the shaft of pinion P in Fig, 452, that is, to prevent too
sudden a stoppage of the elevator. The operation is as follows :
Suppose the operator moves the car lever rapidly to the stop posi-
tion, then lever H swings down rapidly, and carries the pilot valve
with it, but the water in the back of the motor cylinder, to
reach the discharge pipe must follow the path indicated by 6
&, c, djf, and g to G. Now as we have shown, the opening be-
tween d and / through K has been closed , so that the water has
to pass through the hole opposite screw N and by properly ad.
justing the position of this screw the passage can be made as
small as desired, and the time required for the water to pass can
be as much as may be necessary to prevent the main valve from
closing too rapidly.
The operation of this valve in going down is the reverse of that
above explained. On the down trip the pilot valve water is dis-
charged in stopping through spaces 2, 4, and passes through
opening opposite screw M , and is adjusted by this screw.
The operation of the limit valves in Fig. 449 can be easily under-
stood from the line drawing Fig. 454. The pipes A and B con-
necting the limit valves with the pilot valve chamber are for the
purpose of giving a direct connection between the supply and
discharge and the pilot valve. The main valve shown in Fig.
454 is not a duplicate of that in Fig. 453, the principal difference
between them, however, is that in the latter all the connections
are made by passages cast in the valve casing, while in the former
these connections are made by outside piping.
Fig* 455 shows in outline a simplified form of plunger elevator
HANDBOOK ON ENGINEERING.
ion
Fig. 454. Fine Illustration of the Plunger Elevator Company's
Elevator for Pilot Valve Control.
made by the Plunger Co, for freight service. In this arrange-
ment the valve is actuated by a hand rope, and, therefore, is of
]012 HANDBOOK ON ENGINEERING.
simple construction, without a pilot valve. The limit valves
are also dispensed with as their office is filled by the stop balls
attached to the hand rope. The valve used in Fig. 455 is shown
in Fig. 456 and is so simple as to require no explanation. It
may be well to mention, however, that it shows the exhaust pipe
connection on the side of the valve chamber, instead of at the
end. This construction is for the purpose of effecting a more
perfect balancing of the end thrust by the use of an additional
piston C. It can be seen that with the addition of 0 it makes
little difference where the discharge tank is placed, either above
or below the valve, for if there is any back pressure it will act
equally upon B and (7, but if C were removed it would act against
B only. When the discharge tank can be placed on a level with
the valve, nothing is gained by adding piston C.
HOW TO PACK HYDRAULIC VERTICAL CYLINDER
ELEVATORS.
Packing Otis Vertical Piston from bottom* — Remove the
top stop-button on hand rope and run the car up until the pis-
ton strikes the bottom head in cylinder. Secure the car in this
position by passing a strong rope under the girdle or cross-
head and over the sheave timbers. When secured, close the
gate valve in the supply pipe, open the air cock at the head of
the cylinder, and throw the operating valve for the car to go up.
Also open the valve in the drain pipe from the side of the cylin-
der, and from the lower head of the cylinder, thus allowing the
water to drain out of the cylinder. When the cylinder is empty,
throw the valve for the car to descend in order to drain the wa-
ter from the circulating pipe. In case of tank pressure, where
level of water in lower tank is above the bottom of the
cylinder, the gate valve in the discharge pipe will have to be
closed as soon as the water in the cylinder is on a level with that
HANDBOOK ON ENGINEP:RING.
1013
Fig. 155. Plunger Elevator with Hand Rope Control*
1014
HANDBOOK ON ENGINEERING.
of the tank, allowing the rest to pass through the drain pipe to
the sewer. When the water is all drained off, remove the lower
head of the cylinder, and the piston will be accessible. Remove
the bolts in the piston follower by means of the socket wrench,
which is furnished for that purpose. Before removing the piston
head, mark its exact position, then there will be no difficulty in
replacing it ; also be careful and not let the piston get turned in
the cylinder, so as to twist the piston rods. On removing the
piston follower, you will find a leather cup turned upwards, with
coils of |-inch square duckpacking on the outside. This you will
remove and clean out the dirt ; also clean out the holes in the
Fig. 456. Valve for Plunger Elevator with Hand Rope Control.
piston, through which the water acts upon the cups. If the
leather cup is in good condition, replace it, and on the outside
place three new coils of |-inch square duck packing, being careful
that they break joints and also that the thickness of the three coils
up and down does not fill the space by J inch, as in such case
the water might swell the packing sufficiently to cramp it in this
space, thus destroying its power to expand. If too tight, strip
off a few thicknesses of canvas. Replace the piston follower and
cylinder head, and the cylinder is ready to refill. Close the
valves in the drain pipes, leave the air cock open at the head of
the cylinder and the operating valve in the position to descend,
and open gate valve in the discharge. Slowly open the gate valve
HANDBOOK ON ENGINEERING. 1015
in the supply pipe, allowing the cylinder to fill gradually and the
air to escape at the head of the cylinder. When the cylinder is
I full of water, leave the air cock open and put the operating valve
on the center. The car can then be untied, the stop button can
be reset, and the elevator is ready to use. Make a few trips be-
fore closing the air valve.
Packing vertical cylinder piston from top* — Run the car to
the bottom and close the gate valve in the supply pipe. Open
the air cock at the head of the cylinder, and also keep open the
valve in the drain pipe from the side of the cylinder long enough
to drain the water in the cylinder down to the level of the top
of the piston. Now remove the top head of the cylinder, slipping
it and the piston rods up out of the way, and fasten there. If
the piston is not near enough to the top of the cylinder to be
accessible, attach a rope or small tackle to the main cables
(not the counter-balance cables) a few feet above the car, and
draw them down sufficiently to bring the piston within reach.
Remove the bolts in the piston follower by means of the socket
wrench furnished for that purpose. Mark the exact position
of the piston follower before removing it, so that there will be
no difficulty in replacing it. On removing the piston follower
you will find a leather cup turned upwards, with coils of |-inch
square duck packing on the outside. This you will remove and
clean out the dirt ; also clean out the holes in the piston through
which the water acts upon the cup. If the leather cup is in
good condition, replace it, and on the outside place three new
coils of |-inch square duck packing, being careful that they
break joints, and also that the thickness of the three coils up
and down does not fill ths space by £ inch, as in such case the
water might swell the packing sufficiently to cramp it in this
space, thus destroying its power to expand. If too tight, strip
off a few thicknesses of canvas. Replace the piston follower and
let the piston down to its right position. Replace the cylinder
1016 HANDBOOK ON ENGINEERING.
head and gradually open the gate valve in the supply pipe, first
being sure that the operating valve is on the down stroke or it is
so the car is coming down. As soon as the air has escaped be-
fore closing the air cock to make sure the air is all out of the
cylinder, make a few trips, and the elevator is ready to run.
Packing the vertical cylinder valves. — To pack the valve,
run the car to the bottom and close the gate valve in the supply
pipe. Then throw the operating valve for the car to go up, open
the air cock at the head of the cylinder and the valve in the drain
pipe at the bottom, and the water will drain out of the cylinder.
When the cylinder is empty, reverse the valve for the car to run
down so as to let the water out of the circulating pipe. In cases
of tank pressure, where the level of the water in the lower tank is
above the bottom of the cylinder, the gate valve in the discharge
pipe will have to be closed as soon as the water in the cylinder is
on a level with that in the tank, allowing the rest to pass through
the drain pipe to the sewer. As soon as the water has all drained
off, take off the valve cap and remove the pinion shaft and sheave,
marking the position of the sheave and the relation which the
teeth on the pinion bear to the teeth on the rack before removing.
You can now take out the valve plunger and put the new cup
leather packings on in the same position as you find the old ones.
Replace all the parts as first found. Before refilling the cylinder,
close the valves in the drain pipes, but leave the air cock at the
head of the cylinder open and be careful that the operating valve
is in position for the car to go down. Gradually open the gate
valve in the supply pipe. When the cylinder has filled with water
and the air has escaped, close the air cock and open the gate
valve in the discharge pipe.
Packing piston rods* — Close the gate valve in the supply
pipe. Remove the followers and glands to the stuffing boxes
and clean out the old packing. Repack with about eight turns of
HANDBOOK ON ENGINEERING. 1017
J-inch flax packing to each rod, and replace glands and followers..
Screw down the followers only tight enough to prevent leaking.
If traveling or auxiliary sheave bushing is worn so that sheave
binds, or the bushing is nearly worn through, turn it half round,
and thus obtain a new bearing. If it has been once turned put
in a new bushing. See that the piston rods draw alike. If they
do not, it can be discerned by trying to turn the rods with the
hand, or by a groaning noise in the cylinder. However, this
groaning may also be caused by the packing being worn out, in
which case the car would not stand stationary. See that all sup-
ports remain secure and in good condition.
WATER FOR USE IN HYDRAULIC ELEVATORS.
In hydraulic elevator service little heed is usually given to the
quality of water, with which the system is operated. Much loss
of power by friction and many dollars spent annually in repairs
can be avoided by a little thought and action on this subject. In
order to prove the truth of this statement, one has only to obtain
two samples of water, one of soft water and the other of what
is commonly known as hard water. For example, take rain
water as the first sample and water from the well as the second.
Now rub your hands briskly together while holding them im-
mersed in one, and then in the other of these samples. You
will instantly realize that the quality of water used in elevator
service has much to do with the efficiency of the hydraulic ma-
chinery. Water from the service pipes of the oity water-works
always contains more or less sand and other gritty substances
in suspension, and this grit acts much the same 'on the packing
and metal parts of the apparatus as does a sand blast. Some
engineers, having realized the evil effects of water in the state
that is generally used have attempted to remedy the matter by
replacing the water which is lost by leakage or evaporation by the
1018 HANDBOOK ON ENGINEERING.
addition of the water which is discharged from the steam traps of
the plant; and as this has been distilled, it is almost chemically
pure — thus the man who uses distilled water in an elevator sys-
tem instead of the water containing grit, is simply getting out of
one difficulty into another.
It is a well-known fact in chemistry that pure water is a solvent
for every known substance, and will especially attack iron to a
large degree. Whenever it is practicable, the water for elevator
use should be passed through a filter to remove grit before being
allowed to pass into the surge tank. In many cases, however, it
would be difficult for the engineer to convince the owner of the
advisability of buying and installing a filter for this purpose. A
simple and somewhat inexpensive remedy is within reach of all —
the plentiful use of soap will obviate many of the evil effects of
hardness of the water, will double the life of the packing, will
reduce the loss by friction, and will, to a large extent, prevent
the chattering of the pistons, making the elevators run much
smoother. In laboratory practice, the degree of hardness or
softness of water is determined by the amount of pure soap that
is necessary to mix with the water to form a lather, or to precip-
itate a certain quantity of carbonate of lime and other substances.
This same action, on a larger scale, takes place when soap is in-
troduced into an elevator tank, and while the oily portion of the
soap forms an emulsion with the water, of great lubricating
properties, the gritty matter is precipitated and can be gotten rid
of through means of a blow-off in the bottom of the tank. The
cheapest and most convenient form in which to obtain soap for
this purpose, is. the soap powder extensively manufactured by
various firms and which can be purchased for about four cents
per pound. In a plant of six elevators, with usually a strong
capacity of some 8,000 gallons, it is a good practice to use about
twenty pounds of this soap each week. The soap should be at
first? dissolved in about ten times its weight of boiling water, and
HANDBOOK ON ENGINEERING. 1019
when cold it will form a stiff soft soap. The practice of putting
in the refuse oil collected from the drip pans is of little value ; it
will not mix with the water, but floats on the surface. It rarely
gets low enough to enter the suction pipes of the pumps, and has
little or no tendency to precipitate the solid matter that is held in
suspension in the water.
If car settles, the most probable cause is that the valve or pis-
ton needs repacking. If packing is all right, then the air valve
in the piston does not properly seat. If the car springs up and
down when stopping, there is air in the cylinder. When there is
not much air, it can often be let out by opening the air cock and
running a few trips, but when there is considerable air, run the
car to near the bottom, placing a block underneath for it to rest
upon, then place the valve for the car to descend. While in this
position, openthe air cock and allow the air to escape. This may
have to be repeated several times before the air is all removed.
Keep the cylinder and connections protected from frost.
Where exposed, the easiest way to protect the cylinder is by an
air-tight box, open at the bottom, to which point keep a gas jet
burning during cold weather. Where there is steam in the build-
ing, run a coil near the cylinder. Keep stop buttons on hand
cable properly adjusted, so that the car will stop at a few inches
beyond either landing, before the piston strikes the head of the
cylinder. Regulate the speed desired for the car by adjusting
the back stop buttons, so that the valve can only be opened
either way sufficiently to give this speed. Occasionally try the
governor to see that it works properly. Keep the machinery
clean and in good order.
ELEVATOR INCLOSURES AND THEIR CARE.
Elevator inclosures, while intended for protection to passen-
gers, are often carelessly neglected and are often a source of
1020 HANDBOOK ON ENGINEERING.
danger, unless looked after and taken care of in a proper manner.
It is of the utmost importance that no projection of any kind
shall extend into the doorways for clothing of passengers to
catch on, thus endangering their lives. The doors should move
freely to* insure their action at the touch of the operator. See
that all bolts and screws are tight, and replace at once all that
fall out, otherwise, the doors and panels may swing into the path
of the elevator cage and be torn off, and probably injure some
one, thus placing the owner liable to damages. Elevator doors
that are automatic in their closing are the best, but all operators
should be held strictly responsible for accidents occurring from
the carelessness of leaving doors open. All inclosures should be
equipped with aprons above the doors to the ceiling and as close
to the cage as possible, to prevent passengers from falling out or
extending their person through to be caught by ceilings or beams
in the elevator shaft. As a rule, proprietors of buildings take a
pride in keeping their inclosures and cars in a neat condition, as
they are considered an ornament to the building for the purpose
for which they are intended, and no expense is spared in the
line of art ; so it is recommended that they be kept free from
dampness. Dust with a feather duster and use soft rags for
cleaning. Never use any gritty substance, soaps or oils. II
they become damaged, have the maker repair and relacquer them.
HANDBOOK ON ENGINEERING.
1021
STANDARD HOISTING ROPE WITH 19 WIRES
TO THE STRAND.
IRON.
0
fc
0)
I
Diameter.
Circumfer-
ence
in inches.
Weight per
foot in Ibs.
of rope
with hemp
center.
Breaking
strain in
tons of
2000 Ibs.
f
Proper
working
load in tons
of
2000 Ibs.
Circumfer-
ence of new
Manilla
rope of
equal
strength.
Minimum
size of
drum or
sheave in
feet.
1
24
61
8.00
74
15
14
13
2
2
6
6.30
65
13
13
12
3
11
54
5.25
54
11
12
10
4
II
5
4.10
44
9
11
84
5
14
41
3.65
39
8
10
74
54
U
«
3.00
33
64
9*
7
6
14
4
2.50
27
54
84
64
7
H
34
2.00
20
4
74
6
8
i
3*
1.58
16
3
64
5J
9
i
21
1.20
11-50
24
54
44
10
1
24
0.88
8.64
U
41
4
104
i
2
0.66
5.13
14
31
34
10£
ft
If
0.44
4.27
1
34
21
101
4
14
0-35
3.48
4
3
24
lOa
ft
U
0.29
3.00
I
21
2
10i
14
0.26
2.50
4
24
14
1
Operating Cable or Tiller Rope, 1 in. diam.; | in. diam.; £ in. diam.;
| in. diam.
Cables, and how to care for them. — Wire and hemp ropes
of same strength are equally pliable. Experience has demonstrated
that the wear of wire cables increases with the speed. Hoisting
ropes are manufactured with hemp centers to make them more
pliable. Durability is thereby increased where short bending
occurs. All twisting and kinking of wire rope should be avoided.
Wire rope should be run off by rolling a coil over the ground
like a wheel. In no case should galvanized rope be used for
hoisting purposes. The coating of zinc wears off very quickly
1022 HANDBOOK ON ENGINEERING.
and corrosion proceeds with great rapidity. Hoisting cables
should not be spliced under any circumstances. All fastenings
at the ends of rope should be made very carefully, using only
the best babbitt. All clevises and clips should fit the rope
perfectly. Metal fastenings, where babbitt is used, should be
warmed before pouring, to prevent chilling. Examine wire ropes
frequently for broken wires. Wire hoisting ropes should be con-
demned when the wires (not strands) commence cracking. Keep
the tension on all cables alike. Adjust with draw-bars and turn-
buckles provided.
Leather cup packings for valves* — Leather for cups should
be of the best quality, of an even thickness, free from blemish
and treated with a water-proof dressing. The cups should be
of sufficient stiffness to be self-sustaining when passing over per-
forated valve lining. When ordering cups, the pressure of water
carried should be specified, aa the stiff cups intended for high-
pressure would not set out against the valve lining when low
pressure is used.
Water* — Water for use in hydraulic elevators should be per-
fectly clear and free from sediment. A strainer should be placed
on the supply pipe and water changed every three months, and
the system washed and flushed.
Closing down elevators* — If an elevator is to be shut down
for an indefinite period, run the car to the bottom and drain off
the water from all parts of the machine ; otherwise, a freeze is
likely to burst some part of the machinery. If the machine is of
the horizontal type, grease the cylinder with a heavy grease ; if
vertical, the rods should be greased. Oil cables with raw linseed
oil.
HANDBOOK ON ENGINEERING. 1023
LUBRICATION FOR HYDRAULIC ELEVATORS.
The most effectual method of lubricating the internal parts of
hydraulic elevator plants where pump and tanks are used, is to
carry the exhaust steam drips from the foot of the pump exhaust
pipe to the discharge tank, thus saving the distilled water and
cylinder oil. This system is invaluable when, water holding in
solution minerals is used, as these minerals greatly increase cor-
rosion. Horizontal machines operated by city pressure are best
lubricated with a heavy grease applied either mechanically or by
means of a piece of waste on the end of a pole. The former
method serves as a constant lubricator, while in the latter case,
greasing is often neglected, and in consequence packing lasts but
a short time.
Lubrication of cables* — A good compound for preservation
and lubrication of cables is composed of the following : Cylinder
oil, graphite, tallow and vegetable tar, heated and thoroughly
mixed. Apply with a piece of sheepskin with wool inside. To
prevent wire rope from rusting, apply raw linseed oil.
Lubrication of guides* — Steel guides should be greased with
good cylinder oil. Grease wood strips with No. 3 Albany grease
or lard oil. Clean guides twice a month to prevent gumming.
Lubrication of over head sheave boxes* — In summer use a
heavy grease. In winter add cylinder oil as required.
USEFUL INFORMATION.
To find leaks in elevator pressure tanks in which air is con-
fined, paint round the rivet heads with a solution of soap and the
leak will be found wherever a bubble or suds appear. To ascer-
tain the number of gallons in cylinders and round tanks, multi-
ply the square of diameters in inches by the height in inches
and the product by .0034=gallons. Weight of round wrought
1024
HANDBOOK ON ENGINEERING.
iron : Multiply the diameter by 4, square the product and, divide
by 6=the weight in pounds per foot. To find the weight of a
casting from the weight of a pine pattern, multiply one pound of
pattern by 16.7, for cast-iron, and by 19 for brass. Ordinary
gray iron castings = about 4 cubic inches to the pound.
"Water* — A gallon of water (U. S. Standard) contains 231
cu. in. and weighs 8^ Ibs. A cubic foot of water contains 7£ gal.
or 1728 cu. in. and weighs 62.425 Ibs. A " Miner's inch " is a
measure for the flow of water and is the amount discharged
through an opening 1 inch square in a plank 2 in. in thickness,
under a head of 6 in. to the upper edge of the opening ; and this
is equal to 11.625 U. S. gal. per minute. The height of a
column of fresh water, equal to a pressure of 1 Ib. per sq. in., is
2.304 feet. A column of water 1 ft. high exerts a pressure of .433
Ibs. per sq. in. The capacity of a cylinder in gallons is equal to
the length in inches multiplied by the area in inches, divided by
231 (the cubical contents of one U. S. gal. in inches). The
velocity in feet per minute, necessary to discharge a given volume
of water in a given time, is found by multiplying the number of
cu. ft. of water by 144 and dividing the product by the area of
the pipe in inches.
Decimal Equivalents of an Inch.
1-16
1-8
3-16
1-4
5-16
3-8
7-16
1-2
.0625
.125
.1875
.25
.3125
.375
.4375
.5
9-16
5-8
11-16
3-4
13-16
7-8
15-16
.6625
.625
.6875
.75
.8125
.875
.9375
HANDBOOK ON ENGINEERING. 1025
ELEVATOR SAFETIES.
All types of elevators in which the car ia lifted by cables are
provided with means for arresting the movement of the car if it
attains a dangerously high speed through the breaking of the
lifting ropes or the disarrangement of any part of the hoisting
apparatus. The direct plunger elevators are not provided with
safety appliances, it being considered that the plunger on which
the car is lifted will prevent the latter from dropping, as it cannot
be crushed by the load, nor caused to run down any faster than
the water can escape from the cylinder.
In the early days of elevators, when the car speed was low, the
safety devices consisted of racks attached to the faces of the
guides, and dogs carried by the car, these dogs being held out of
action so long as the ropes did not break. With the gradual in-
crease in height of buildings, the car speed was increased and
then it was realized that the rack and dog devices were not adapt-
ed to do the work, as they would stop the car so suddenly as to
give the passengers nearly as bad a shaking up as they would re-
ceive if the car went to the bottom of the well. For the purpose
of producing a more gradual stoppage of the car, wedge safety
devices were introduced. . These safeties act by forcing a wedge
between the guides on which the car runs and strong iron jaws
carried by the car, and as the wedges are tightened slowly, the
car can run some distance before it is' stopped, thus producing a
gradual stop. The jaws that hold the clamping wedge are
fastened to the ends of a massive hard wood plank, and for this
reason the apparatus was called a " Safety Plank, " and is known
by that name at the present time.
A wedge safety plank, of the type used by the Otis elevator Co. ,
is shown in Figs. 457, 458, 459, the last two illustrations only
show one end of the apparatus. This device is used in connec-
1026
HANDBOOK ON ENGINEERING.
tion with four lifting cables two of which are secured to the ends
A B of a rocker (7, 'the other two being similarly connected with
a rocker at the other end. The rocker G has projections that
move levers mounted on shaft H, and one of these levers, marked
HANDBOOK ON ENGINEERING. 1027
5, when raised strikes wedge ^and forces it up between the jaw?
of the safety plank and the guide M. The end of b is sharp and
long enough to reach the guide and cut into it, thus helping to
force the wedge up tight enough to hold the car. If one of the
lifting cables attached to the ends A B of rocker C should break,
that end of C will drop and then shaft H will be rotated so as to
swing b upward and force the wedge JVinto action. The rocker
C has two projections, one on each side of H so that no matter
which way C is tilted, b will be moved upward.
If elevators dropped only when the ropes break, the safety as
explained would be sufficient, but as a matter of fact, they can-
not very well drop in this way, because all the cables will not
break at the same time. In, nearly every case, the elevator does
not actually drop, but through some disarrangement of the ma-
chinery it attains a dangerously high speed, that is, it runs away.
Owing to this fact it is necessary to arrange the safeties so that
they will act if the car speed becomes too great, regardless of
what the cause may be. This is accomplished by providing a
governor, similar to those used on engines, that is driven by the
car, and when the speed becomes too great it throws the safety
into action. The safety governor of the Otis Co., is shown in
Fig. 460. It is driven by a rope that passes over sheave A and
runs down in the elevator well to the bottom where it passes under
another sheave. This rope is fastened to the end ytoi lever G,
Fig. 458, and through lever Jc acts to rotate shaft H. The spring
S wound on H is stiff enough to. drive the governor and prevent
If from turning, but if the car speed becomes too great, the rod
D, Fig. 460, will lift the crank jVand thus throw in a clamp that
will hold the rope fast. When this occurs, the downward move-
ment of the car will cause lever G to rotate shaft H and thus 6
will force the safety wedge N into position to stop the car.
There are many modifications of the wedge safety, but as they
do not work with certainty on iron guides they are now practical-
1028
HANDBOOK ON ENGINEERING.
ly out of date, as wooden guides are not used except in the few
cases where they are permitted by the insurance regulations, or
where a cheap construction is desired. In large fireproof build-
ings they are not allowed.
Tig. 460. Otis Safety Governors Single Acting.
A modification of the wedge safety that was used to some ex-
tent a few years ago is shown in Figs. 461 and 462, the first giving
the position of the parts when out of action, and the second the
position when in action. This is known as the roller safety. The
HANDBOOK ON ENGINEERING.
1029
roller a, when drawn up by the lifting rod, wedges between the
iron guide and the jaw of the safety plank and then rolls up
until it binds tight enough to stop the car. The objection to
this device is that it grips too soon, in fact it is liable to stop
HANDBOOK ON ENGINEERING.
the; car in two or three inches, so that if the speed is high, the
passengers will get a serious shaking up. The lifting rod is
operated by a safety governor, the connections with the latter
being indicated in Figs. 463 and 464, the first showing the actual
Fig. 403. Governor Rope Connection for Roller Safely.
connection with the governor rope, and the second, the levers, in
the top framing of the car, to transmit the movement to the op-
posite side so that both rollers may be thrown into action at the
HANDBOOK ON ENGINEERING.
1031
same time. It will be noticed in Fig. 464 that the lifting cables
are permanently secured to the car framing, and not to any part
of the safety, so that if one or two of them should break, the
safety would not go into action. This, however, does not make
the device any the less effective, because the car could not drop
unless all the ropes broke at the same time, and if this occurred,
f^
1
V
n
r-
— r
-J
/.
i
,'T
ij, p
• I
^^ ^
>%^ 222
k
a
j©^D
e j^b
Iff
^^&
JA
^1L
Fit?. 464. Lifting Rope Connections for Roller Safety. '*
the speed would at once increase, and then the safety governor
would come into action and throw the rollers up, just the same
as if the speed had increased from some other cause. This type
of safety is not used now because it stops the car too suddenly.
A safety to be satisfactory must be so arranged that it will
produce a gradual stop, if it comes into action, This result is
1032
HANDBOOK ON ENGINEERING.
accomplished in the type of safety commonly known as the brake
or clamp safety. It consists of strong brake shoes arranged to
press against the sides of the guides on which the car runs, with
a continuously increasing pressure until the breaking action be-
comes sufficient to actually stop the car. It can be easily seen
that with such an arrangement, the effect is to first reduce the
car velocity and then gradually bring it to an actual stop, the
time, or distance in which the car is stopped depending on the
rapidity with which the braking force is increased. Two views
of the Otis clamp safety are given in Figs 465 and 466, the first
HANDBOOK ON ENGINEERING. 1033
being a side elevation in section, and the second a plan. The
Fig. 4C7.
Governor Rope Connection for Brake Safety*
rope that winds around the actuating drum, Fig. 465, ia attached
1034 HANDBOOK ON ENGINEERING.
to the governor rope, in the way clearly shown in Fig. 467. If
the car speed becomes too great, the governor acts, and clarnps
the rope, then the drum rope unwinds, and thus rotates the
drum, and the latter by turning the right and left hand nuts
forces the screws out and thus spreads the toggle links B B Fig.
466, and applies the brakes to the guide. It is evident that the
further the car runs after the safety governor has gripped the
rope, the further the actuating drum will be rotated, and as a
result the more the safety brake jaws will be forced against the
guides. By this arrangement the motion of the car is gradually
arrested, and the passengers are not seriously jolted. If the
load in the car is light, and the guides are not properly lubricated,
it is possible for this device to grip suddenly, but it can never act
as suddenly as the roller safety.
There are several different designs of these brake safeties, but
they are all substantially alike. The Morse and Williams design
is shown in Figs. 468 and 469. As will be seen the diff erencebe-
tween this and the Otis safety is principally in the details of con-
struction of the clamping jaws. In the Otis design a lever C is
provided that can be moved by the operator in the car, so as to
either put on the brake, or release it after it has caught. In the
Morse and Williams design this same result is accomplished
through the beveLgears shown, in, Fig. 469, the end M being
squared so as to receive a wrench.
Another type of clamp safety is shown in Figsl 470-471-472
This is known ais the " Pratt safety." This device has a strong
spring M in addition to the parts used in the two previously ex-
plained designs* When the safety is out of action, this spring is
held compressed by a catch 'JT, ' as in Fig. 470. When the device
goes into action, the first rotation of the drum and its shaft D
acts to move ,7 to one side and releasethe catch K thus permit-
ting spring M to throw the levers into the position of Fig. 471
and thereby to apply the brake shoes with all the force due to
HANDBOOK ON ENGINEERING,
1035
the tension of the spring. This force is not enough to stop the
car suddenly, even if lightly loaded, but it will retard the velocity
decidedly. The continued rotation of the drum compresses spring
M and thus increases the pressure on the brake shoes until the
car comes to rest, and the safety assumes the position shown in
Fig. 472.
Fig. 468.
Fig. 469. Morse & Williams Brake Safety
The clamp safety is the only one suitable for electric eleva-
tors because it can be easily arranged so as to act on the up
as well as the down trip of the car. Electric elevators are almost
always arranged so that the counterbalance weighs more than the
car. As a rule the counterbalance weighs as much a,s thie car
and one half of the maximum load, hence, if the car runs up with*
1036
HANDBOOK ON ENGINEERING.
a light load, and it runs away the counterbalance will run down
and send the car up to the top of the building at a high velocity.
jp
Fig. 470. Fiff. 471. Ffe. 472.
Pratt-Brake Safety.
If the car has a full load, then it will weigh more than the coun-
terbalance, and as a result will run down to the bottom of the
HANDBOOK ON ENGINEERING. 1037
well at a high velocity. On this account a safety to be of any
value on an electric elevator must be able to act for either direc-
tion of motion of the car. By looking at Fig. 467 it can be seen
that to make the clamp safety act in both directions, all that is
necessary is to place another sheave directly under A so as to
hold the drum rope in position when the governor rope pulls
down as well as when it pulls up. This is the way in which the
safety is arranged when used with electric elevators. The safety
governor in such cases is made double acting, which is accom-
plished by providing rope clamping devices on both sides as
shown in Fig. 473, which is the double acting Otis safety governor.
This governor will clamp the rope regardless of which direction
it is running. The levers shown on the clamping devices of the
governor are for the purpose of releasing it after it comes into
action.
In addition to the safeties explained in the foregoing, all
elevators, hydraulic and electric, are provided with automatic
stopping devices that will stop the car automatically at the top
and bottom landings, providing they are properly adjusted, and
kept in running order, and unless a car attains a very high vel-
ocity in running away, these automatic stops will check its speed
at the end of its travel. Experience, however, shows that these
stops are often allowed to get out of adjustment so that they
fail to act properly when called upon. This is also true of the
safeties herein explained. If you want to avoid accidents, make
sure that the safeties and safety governor, and the automatic
stops are properly adjusted, and in perfect working order.
Never use a governor or automatic safety rope that looks at all
worn, for when called into action it may break, and then an
accident will follow.
As can be seen, if the governor rope is not strong, it may snap
off when the clamp grips it, and if this occurs, the safety will
not act. The ropes used to operate the hydraulic automatic
1038
HANDBOOK ON ENGINEERING.
stops are not so. likely to break because they come into action
very often, hence, they are more likely to show when they are
Fig-. 473.
Otis Double Acting Safety Governor.
worn out ; but the automatic stops should be kept in perfect
adjustment all the time.
As the safeties seldom come into action, they are liable to rust
up and stick, unless often examined, oiled up and well cleaned,,
HANDBOOK?
1039
PIPES AOT ITAffKS.
CONTENTS^IN CUBIC FEET AND IN UVS. GALLONS,
(FROM TRAUTWINE)
Of 231 cubic inches (or 7.4805 gallons to a cnblc foot); and for one foot of length off
the cylinder. For the contents for a greater diameter than any in the table lake.
quantity opposite one-half said diameter, and multiply it by 4. Thus, the number
.oi cobic feet in one foot length of a pipe 80 inches in diameter is equal t$
18.728X4=34.912 cubic feet. So also with gallons and areas.
8*^
For 1 foot in
For 1 foot in
o
For 1 foot in
jfl
>-<M
length.
£ j:
s-r o' '
length.
c
"£ oj
length.
:2®
*? o
«.£3
o
®J
-S:-
0
«J
So
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ill
1
2$3
Iff
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.5625| .2485
1 859
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583
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7.
.58331 .267$
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2074
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2.182
18.32
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.0078
1
.6250
.3068
2.295
I
.708
3.292
17.15
•0417J .0014
.0102
.6458
.3275
2 450
21
750
2 405
1799.
9-16
.0469 .0017
.0129
8.*
6667 .3490
2 611
i
.792
2.521
18 Sii.
ft
.0521
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.0159
i
.6875
.3713
2 777
22
833
2.640
19.751
(11-16
.0573
.0026
;0193
j
.7083
.3940
2 948
i-
875
2.761
20.(£
• 0625
.0031
.0230
.7292 .4175
3 125
23
1.917
2 886
22.5S\
113-16
.0677 .0031
.0270
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1
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3.976
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.0918
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.5730
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.6013
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4 587
31 3*
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.1667
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.1632
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5.633
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2.833
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47.171
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65.29
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9.180
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3.416
9.168
68.58
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1.292
1.310
9.801
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9.620
71.96
i
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1.124
1.333
1.396
10.44
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3.583
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1963
1.469
1.458
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3.833
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12.566
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.-- — ' -
4 • •'•• ' ~ ^
'„.„,., *
1040 HANDBOOK ON ENGINEERING.
CHAPTER XXXII.
FRICTION AND LUBRICATION.
BY WILLIAM M. DAVIS.
Friction has been aptly described as the " Highway robber of
mechanical energy," levying tribute on all matter in motion, ex-
erting a retarding influence and requiring power to overcome it.
When one realizes that if it were not for the thin film or layer
of oil between the surface of the journals and their bearings and
the constant supply of oil to maintain this film, the largest loco-
motive could not start a heavy train or keep it in motion, or the
most powerful marine engine could not drive the ship a mile
without heating of the bearings, one readily understands that a
knowledge of lubrication and friction and of the laws relating to
friction is a very important part of the training of an engineer.
LAWS OF FRICTION.
Friction is defined as the resistance caused by the motion of a
body when in contact ivith another body that does not partake of its
motion.
There are five commonly accepted and fundamental laws re-
lating to the friction of plane surfaces in contact.
First. — Friction will vary in proportion to the pressure on the
surfaces. That is, increasing the pressure increases the friction.
Second. — Friction is independent of the areas of the contact
surfaces when the pressure and speed remain constant. But
distributing the pressure or friction over a larger area renders the
liability of heating and abrasion less than if the friction had been
concentrated on a smaller area.
Third. — Friction increases with the roughness of the surfaces
and decreases *<» the surfaces become smoother.
Fourth. — Friction is greatest at the beginning of motion. In
the effort to move a body greater force is required to overcome
HANDBOOK ON ENGINEERING. 1041
the friction at the instant of starting than after motion has com-
menced.
Fifth. — Friction is greater between soft bodies than between
hard bodies.
These rules hold good within certain limits but will fluctuate
under varying conditions of load and lubricant, and condition and
composition of the contact surfaces.
Friction is always a resisting and a retarding force, tending to
bring everything in motion to a state of rest, and in doing so re-
sults in the conversion of energy into heat, it has been calculated
that one horse power or 33,000 foot pounds exerted in over-com-
ing friction results in the conversion of energy into 43 British
Thermal Units of heat.
In the case of machinery in motion the surfaces moving in con-
tact have a tendency to adhere to each other ; the minute pro-
jections which exist on all surfaces to a greater or less extent
(depending upon the hardness and smoothness of the surfaces)
have a tendency to cling to each other and in order to operate
machinery without undue friction the surfaces must be kept
apart, something must be used that will flow or spread out over
the surfaces and cover up these projections and prevent the sur-
faces from coming in direct contact, for which purpose lubricants
of various grades are used.
USES OF FRICTION.
Yet, friction in mechanics has its uses ; it is the friction, or
adhesion (as it is sometimes called) of the driving wheels to the
rails that enables a locomotive to start and keep in motion a
heavy train, it is the friction of the brake shoes on the wheels as
applied by the air brakes that stops the train, it is the friction of
the belt on the pulley that enables power to be transmitted from
one piece of mechanism to another.
Friction as it occurs in mechanics is what is known as friction
1042
HANDBOOK ON ENGINEERING.
of solids and friction of fluids ; friction of solids may be divided
into two classes, namely: rolling friction, such as a car wheel
rolling on a rail or balls in a ball bearing ; and sliding
friction, such as a cross-head on the guide bars.
CO-EFFICIENT OF FRICTION.
The relation that thepoiver required to move a body bears to the
weight or pressure on the body is known as the co-efficient offrictwn,
or, to put it in another form, the co-efficient of friction is the
ratio between the resistance to motion and the perpendicular
pressure, and is determined by dividing the amount of the former
by the latter.
One of the simplest methods of demon strati ng graphically the
simple laws of friction of plane surfaces and the determination of
the co-efficient of friction is by drawing a block of iron or other
metal across a table or an iron plate by means of weights sus-
pended to a cord which is attached to the block as shown in
Figs. 1 and 2.
L*"'
Fig. 1. Illustrating Laws of Friction.
It is noticed that the block is flat on one side, and on the other
side are four small projections or legs, each one square inch in
area, the size of the block is 12 inches long, 8 inches wide and 2
inches thick, and weighs 50 pounds. If we lay the block with
its largest surface down it will have a surface contact with the
HANDBOOK ON ENGINEERING.
1043
table of 96 square inches and placing weights on the cord until
the block commences to move we find that it requires a weight of
7 pounds to pull it across the table ; now if the block be turned
upside down so that it rests on the four legs it will be found that
it requires exactly the same amount of force to move the block
that it had before.
As we have found by experiment that to move the weight of 50
pounds required a force or pull of 7 pounds, the co-efficient of
friction in this case will be found by dividing the pull by the
weight, 7-r-50= .14, or, to put it in another form, it will require
.14 of a pound of force to move 1 pound of weight.
Fig. 2. Illustrating Laws of Friction.
The second law states that friction is independent of the areas
of the surfaces, it has been found by experiment that it required
a pull of 7 pounds to move the block no matter which side it
stood on.
Let us prove this.
The block when on its largest side had a surface contact of
8"xl2", or 96 square inches and exerted a pressure due to its
weight of 50 Ibs., or .52 of a pound per square inch of area.
The co-efficient has been found to be .14, then the pull per square
inch of surface would be .52 x. 14 = .0729, which multiplied by
the total area, 96 sq. in., will be found to be 6.9888, or practically
7 pounds.
1044 HANDBOOK ON ENGINEERING.
Now, when the block was reversed and stood on the four legs
of 1 sq. in. each, the total contact was only 4 sq. inches, but
the pressure (50 pounds), remained the same, 50 -i- 4 =12. 5
pounds per square inch, which multiplied by the co-efficient .14
equals 1.75, then again multiplying this result by 4 sq. in, again
gives a total of 7 pounds.
Thus it will be seen that the extent of surfaces has no influence
on the friction as long as the pressure of weight is constant, but
in machine design increasing the area of surface contact allows
the total pressure to be distributed over a greater area and re-
duces the liability of heating and abrading, or in other words,
while the total pressure remains the same the pressure per square
inch will be less.
Fig. 3. Laws of Friction.
Another method of determining the co-efficient of friction, or,
as it is usually termed, the angle of friction, can be illustrated by
means of a weight on an inclined plane.
Place a weight on a board or other plane surface and raise one
end slowly as in Fig. 3 until the weight commences to slide ; the
angle "a " between the position of the plane surface when the
weight commenced to move and the horizontal is the angle of
friction, and will vary with the smoothness of the surfaces and
the weight or pressure.
The angle of friction indicates the point where the attraction
of gravitation just overcomes the friction between the surfaces.
To find the amount of power absorbed by friction multiply the
weight by the co-efficient of friction, multiply the result by the
velocity in feet per minute and divide that by 33,000.
HANDBOOK ON ENGINEERING. 1045
For instance, a shaft and fly wheel weighs 8,000 pounds, sur-
face travel of journals is 300 feet per minute, the co-efficient of
friction is taken as being .04.
What would be the horse power required to run the shaft?
8,000 x. 04x300
-=2.&09 H. P.
33,000
While the co-efficient of friction must always be taken into
consideration when designing and constructing machinery, it is
not always practicable to calculate it with any degree of accuracy,
in fact it can only be determined absolutely by experiment.
THEORY OF LUBRICATION.
Lubrication as it is considered in mechanics is the application
or introduction of a smooth fluid substance, preferably an oil,
between two hard moving surfaces that will keep them from com-
ing in direct contact.
Unless the surfaces are kept apart by some medium the asper-
ities and irregularities which exist on all surfaces no matter how
hard or smooth, will interlock, and the friction caused in tearing
them apart and wearing them down will generate heat.
The action of a lubricant is to flow between the close-fitting
surfaces, filling up the interstices and covering up the high spots,
acting as a cushion and taking up whatever heat may be gener-
ated and carrying it off instead of allowing it to be absorbed by
the wearing surfaces.
To do this properly, a lubricant should have certain properties,
it should be of a fluid nature so that it will flow readily between
surfaces that are close-fitting and under heavy pressure. It
should possess a certain amount of cohesiveness, or viscosity, as
it is usually called.
By cohesiveness is meant the Clinging together of the molecules
its own particles.
1046 HANDBOOK ON ENGINEERING.
Oil should have good adhesive properties in order that it will
cling well to metallic surfaces.
By adhesion is meant the tendency of a substance to cling to other
substances
It should be high in flash test in order that whatever heat it is
subjected to will not cause it to give off an inflammable vapor.
It should have a cold test of such degree that it will remain fluid
at low temperatures.
The above requirements will be found embodied to the greatest
degree in the various kinds of vegetable, animal and petroleum
oils.
The first oils used in the lubrication of machinery were vegeta-
ble oils, such as castor oil, palm oil, and olive oil ; and animal oil
such as lard, neats-foot, tallow and sperm oils.
All these oils, while in many respects excellent lubricants are
not now used to any extent since the introduction of petroleum or
mineral oils, for the following reasons : First. — On account of
their higher price as compared with petroleum oils. In recent
years the processes of refining petroleum have been brought to
such a state of perfection that they have almost entirely driven
the animal and vegetable oils from the market as lubricants for
machinery. Second. — Being of organic origin they absorb
oxygen from the atmosphere, and, in time, become rancid, thick
and gummy. These oils are of very poor cold test, congealing at
a comparatively high temperature, thus making them inconvenient
for use in cold weather.
Petroleum oils have many advantages as lubricants over ani-
mal or vegetable oils. First. — Is their cheapness. Second. — •
Being of non-organic origin they do not change their condition,
do not become rancid, thick or gummy by constant exposure to
the air, and have no corrosive action on metals. Third. — By
what is known, as fractional distillation they can be separated into
a great many different grades, from the lightest spindle oils to
HANDBOOK ON ENGINEERING. 1047
the dense heavy cylinder oils. Fourth. — They are of lower cold
test and there is not the liability of spontaneous combustion as
with animal oils.
The engineer in charge of a plant will find on the market a
wide range of petroleum lubricants to choose from to meet the
various conditions which will arise in the proper lubrication of
his machinery.
The conditions which produce the greatest differences in ordi-
nary lubrication are the nature and quality of the lubricant, the
nature and condition of the wearing surfaces, the speed and
pressure and the temperature.
Variations of friction of lubricated surfaces occur with every
change of condition of either the bearing or journal surfaces, or
of the lubricant applied to them.
The ordinary facilities of the engine room do not usually afford
means to make elaborate tests of the co-efficient of friction of
various oils, nor would such tests be of any practical value to an
engineer, as they can only be made with any degree of accuracy
on expensive testing machines built expressly for this purpose,
which are very little used except in the laboratories of the techni-
cal schools and the testing rooms of a few of the large railroad
companies and manufacturers of oils.
But an engineer can often make valuable comparative tests of
different grades of oil on the ordinary machinery of the engine
room ; for instance, a difference between two oils of several de-
grees in the temperature of a bearing of an engine or a dynamo
may be detected by means of a thermometer placed in the bear-
ing, with the bulb resting on the shaft or immersed in the oil
chamber.
In tests of this kind care must be taken that the rate of oil
feed, the belt tension, the pressure on the bearings and the speed
remain constant ; an allowance should also be made for any dif-
ference in the temperature of the room during the tests.
1048 HANDBOOK ON ENGINEERING.
Some day, engine builders will equip the main bearings of
their engines with thermometers so that the temperature can be
noted, the engineer will then be able to see at a glance whether
the temperature is above the normal or not, in the same way as
he notes the temperature of his feed water by means of a ther-
mometer in the boiler feed pipe ; of course, an engine bearing
from lack of oil, stoppage of the oil cups or other cause, can be-
come overheated to such a degree as to ignite the oil in some
particular spot before the rise in temperature would be indicated
on a thermometer a few inches away.
But a thermometer in a bearing would indicate from day to
day, any difference in the condition of either the lubricant or the
bearing — for instance, an engineer on taking up the lost motion
of a main bearing notices that the temperature rises 10 to 20
degrees above what it had previously been, this warns him that
this bearing must be carefully watched to see that it does not get
too hot.
One of the essential points in lubrication is that the lubricant
be made to reach every part of the contact surfaces, and in con-
nection with lubrication one may assume an oil to have the nature
of a mass of globular molecules or atoms, which roll on each
other and the wearing surfaces and are carried or flow between
the close-fitting surfaces and form an elastic coating to the metal,
becoming thinner as the pressure increases or the temperature
rises, and thicker as the pressure decreases, or the temperature
falls, and absorbing whatever heat may be generated and carrying
it off.
The best lubricant for a bearing under normal conditions may
not do so well after heating commences, a thick viscous oil which
under ordinary conditions on high speed machinery would be
comparatively wasteful of power is often an excellent lubricant
for a hot bearing, and for the following reason : an engineer on
finding a bearing heating up will apply the ordinary oil freely
HANDBOOK ON ENGINEERING. 1049
and at the same time loosen up the bolts so as to allow for in-
creased expansion and free flow of oil, if the heating continues,
and the engine or machinery must be kept in operation at all haz-
ards, he will turn to his cylinder oil, apply it freely, and often
with good results. The reason of this is that the cylinder oil,
owing to its high fire test, (from 550 to 600), became thin and
limpid without burning, and flowed freely between the close-
fitting surfaces and kept them apart, and at the same time, ab-
sorbed the heat that would otherwise have gone into the metal
and carried it away, while the engine oil, being of lower flash test,
vaporized, and if the bearing got hot enough, caught fire.
The theory of a heating bearing is as follows : If for any rea-
son the oil is prevented from reaching every part of a bearing,
the surfaces will come in direct metallic contact, excessive friction
is set up and heat is generated ; if the pressure be not great and
the bearing area is ample the heat may be absorbed by the metel
and radiated out into the air and nothing serious occur. But if
the pressure is heavy and the speed high, the heat may be gener-
ated faster than the metal can carry it away ; the original dry
spot may not have been over J or J of a square inch in area but
sufficient heat may have been generated at this point to cause the
adjacent oil to evaporate and shrink away, thus increasing the
area of dry surface, as the heat increases the metal expands
causing the surfaces to fit tighter and thus creating more friction
until the temperature reaches such a point that it ignites and
burns. As a good engine oil will have a flash test of about 400
degrees the temperature of a metal must rise above that in order
to ignite the oil.
CYLINDER AND VALVE LUBRICATION.
In the lubrication of the interior wearing surfaces of the valves
and cylinders of steam engines conditions will be met which are
1050 HANDBOOK ON ENGINEERING.
altogether different from those encountered in the lubrication of
bearings and journals.
In the latter case, the working and comparing of one oil with
another, and the results obtained, can be easily determined by
noting the changes of temperature, etc., but in internal lubrica-
tion the conditions are altogether different.
In the case of journals and bearings, the oil can be applied
directly to the surface to be lubricated ; in cylinder lubrication
one must depend upon the flow of steam to convey the oil to the
parts of wearing surfaces requiring lubrication.
The points that govern the conditions of interior lubrication
are: The conditions of the surfaces, the steam pressure, the
amount of moisture in the steam, the piston speed, weight and fit
of the moving parts, and the make or type of the engine.
An automatic cut-off engine with balanced or piston valves will
usually require less oil. than an engine with a heavy unbalanced
valve.
A large cylinder whose piston is supported b}^ a " tail-rod " is
more easily lubricated than one whose heavy piston drags back
and forth over the bottom of the cylinder.
The dryness of the steam is a very important factor in cylinder
lubrication, engines which take their steam supply from foaming
or priming boilers, or through long uncovered steam pipes usually
require more oil than an engine supplied with dry steam.
Wet steam is the greatest cause for complaint in the lubrica-
tion of valves and cylinder surfaces with which an engineer has
to contend, but some grades of cylinder oil will give better results
in connection with wet steam than others ; they will stick to the
moist surfaces better.
An engineer who desires to secure the best results and reduce
the friction loss to the minimum must study the various condi-
tions which exist in the machinery in his charge ; always bearing
in mind that friction costs more than oil, and that a small quan-
HANDBOOK ON ENGINEERING. 1051
tity of good oil properly used will be more economical than any
quantity of poor oil.
An oil to be used as a cylinder lubricant in order to give good
results must possess certain essential properties.
It must be of high flash test, so that it will not volatilize or
vaporize when in contact with the hot steam ; it must have good
viscosity or body when in contact with the hot surfaces, and
should adhere to, and form a coating of oil so as to prevent wear
and reduce as much as possible the friction of the moving parts.
Some of the essentials to be desired in a cylinder lubricant are
obtained to the greatest degree in the heavier or more dense and
viscid of the petroleum oils, but there is one element in which a
pure petroleum oil is usually lacking as a cylinder lubricant and
that is its inability to adhere to a wet surface, and for that reason
it is necessary that it be combined with some one or more of the
various vegetable or animal oils.
There is always a certain amount of moisture present in the
valve chambers and cylinders of a steam engine, due partly to
condensation of the steam in the pipe on its way from the boilers
to the engine and partly to the expansion which takes place in the
cylinders.
A petroleum oil, while it may possess the proper viscosity and
flash test, will not of -itself mix with or form an emulsion with
water and consequently will not stick to the moist surfaces, but
will be easily washed out by the action of the steam ; but animal
and vegetable oils, while not so viscid 'as the petroleum oil, will
combine with it and emulsify freely with water and when com-
pounded in the proper proportions with a heavy petroleum pro-
duce a cylinder oil that is suitable for interior lubrication.
While the quality of a cylinder oil as shown by the use of
testing instruments will give one a general idea of its lubricating
value, the engineer who is studying the question cf cylinder lub-
rication can determine more accurately its exact value by experi-
1052 HANDBOOK ON ENGINEERING.
meriting on his engines and pumps and under the conditions
peculiar to his own plant.
Any engineer in charge of a steam plant knows that nearly
every engine will indicate either audibly or otherwise perceptibly,
any lack of lubrication.
A Corliss type of engine will usually indicate need of more
cylinder oil by a slight groaning of the valves, if not loud enough
to be heard, it can be detected by feeling of the valve stem, or by
the vibration or trembling of the valve and eccentric rods.
Buckeye, Russell, Porter- Allen and other makes of engines
with balanced valves will usually indicate a lack of oil by a rattling
noise in the steam chest, rocker-arms and the eccentric and
governor connections.
For instance, an engineer has submitted to him for trial three
sample lots of cylinder oil, and he wishes to determine which is
the most suitable and economical oil for him to use ; he may
notice after starting with the first sample that the valves work
free and smooth on say, eight (8) drops a minute; he then re-
duces the oil feed gradually to four (4) drops, and then notices
a slight tremor in the eccentric rods, and later, if a Corliss engine,
he may detect a decided groaning sound in one or more of the
valves.
If the oil feed is then increased to six (6) or seven (7) drops
per minute and the valves begin to work freely again and when
the oil feed is reduced to five (5) drops and the valves commence
to work hard again, and 'the results are the same after repeated
trials, the engineer can determine just how much of this particu-
lar brand of oil is required to keep the valves working smoothly
and quietly.
The next thing in order is to remove the cylinder head or steam
chest cover, or if a Corliss engine, draw out one of the valves and
examine the wearing surfaces ; if well lubricated they will present
HANDBOOK ON ENGINEERING. 1053
a dark glossy appearance, and a good coating of oil all over the
interior surfaces.
The most reliable test of the condition of the surfaces is to
wipe over them with a piece of soft white paper, such as a piece
of ordinary newspaper ; if a decided stain of oil is seen on the
paper it is an indication of good lubrication. Another method is
to wipe over the surface with several thicknesses of tissue paper
and note the number of thicknesses that the oil has saturated
through.
But if no stain of oil can be seen upon the paper and the sur-
faces have a dull appearance, and with traces of metallic wear it
is a positive evidence that the oil is not lubricating properly.
Then, if another sample of oil is tried and it is found to require
from ten (10) to twelve (12) drops per minute to keep the valves
quiet, and the surfaces when examined showed little or no signs
of oil, it would prove conclusively that it is a very poor lub-
ricant, and would be a most expensive oil no matter how cheap
in price per gallon.
But, if after trying the third sample it will be found that the
oil feed can be reduced to one (1), two (2), or three (3) drops
per minute, or, perhaps one (1) drop every two minutes, and
kept at that rate for hours, without showing any evidence of lack
of perfect lubrication, and the surfaces after standing cold for
several hours still show a good coating of oil and no rust or
" raw spots," and these results hold good on all the engines and
pumps in the plant, it would prove conclusively that this oil will
be the cheapest to use no matter what the price per gallon may be
and regardless of all laboratory tests.
LUBRICATION OF REFRIGERATING MACHINERY.
In the operation of refrigerating machinery certain conditions
exist which require that the oil used for lubrication shall be of
1054 HANDBOOK ON ENGINEERING.
such a nature that it can be subjected to quite a high temperature
and to a very low temperature without congealing.
In the manufacture of artificial ice, or to speak more correctly,
in mechanical refrigeration, the anhydrous ammonia gas is com-
pressed in the compression cylinders to about 120 to 200 pounds
pressure per square inch, according to the class of work done,
and the requirements of the plant. It is then allowed to expand
down to about 15 pounds in the expansion coils. In some types
of machines oil is used to lubricate the ammonia cylinders and
pistons and to fill the clearance space and to reduce the heat of
compression, for in compressing the ammonia gas to the required
pressure its temperature is raised to about 180 to 200 degrees.
And the oil for this purpose must have a flash point so high as to
not give off any great amount of vapor.
After the ammonia has been compressed to the proper extent
it is allowed to flow through the expansion coils and thus pro-
duce the refrigerative effect.
All refrigerating plants are provided with a separator in the
ammonia discharge pipe which is supposed to, and does to a cer-
tain extent, separate the oil and other foreign matter from the
ammonia ; but a certain quantity of oil will always go past the
separator in the form of vapor and collect in the condensing coils,
so that it is very essential that the oil be of such a nature that it
will remain in a fluid state when subjected to low temperatures.
If the oil be of poor cold test it will congeal and form a coating
on the inside of the coils and tend to lower the efficiency of the
system and eventually clog up the pipes.
An oil for this work should be of 30 gravity, of about 300 to
325 flash test, and stand a temperature of 5 degrees above zero
without congealing.
Different makes of refrigerating machines have different re-
quirements as to the use of oil. The De La Vergne machine is
what is known as the double-acting type, and oil is used to fill
HANDBOOK ON ENGINEERING. 1055
the clearance space as well as to lubricate the cylinders and pis-
tons. On some makes of machines the oil is only used in the
space in the stuffing boxes on the piston rods, and none is fed
into the compression cylinders ; but no matter how tight the
packing is kept some of the oil will work through into the cylin^
ders and pass out with the ammonia gas ; and notwithstanding
the fact that the discharge pipes are provided with separators,
some of the oil will pass through into the system.
In the lubrication of the steam cylinders of a refrigerating
plant, especially where ice is made, certain points must be
looked after that are not essential in any other class of engine.
It is customary in the manufacture of ice to condense the ex-
haust steam and purify it, and use it to make ice of ; and for this
reason the oil used for lubricating the valves and surfaces of the
steam cylinders should be of pure petroleum or very nearly so ;
and it is well for the engineer in charge of a. refrigerating plant
to go on the theory that the less oil used in the cylinders the less
there will be to separate from the condensed water. The steam
cylinders of refrigerating machines are not as a rule very large,
and the piston speed does not as a rule exceed 400 to 600 feet
per minute, so that if a first class quality of oil is used very little
will be required to give good lubrication.
In the process of making ice the exhaust steam first passes
through a separator where the steam is relieved of some of the
oil ; from there it passes to a feed water heater, where it im-
parts some of its heat to the boiler feed water, then it goes to the
condenser and is condensed and the water of condensation is
pumped to a re-boiler and skimmer ; and any oil that has not been
removed in the preceding processes is taken off, the water passes
through the cooling coils and on to the bone dust or charcoal
filters, where it is still further cleaned of its impurities, from
there it passes to the settling or sweet water tank, as it is
1056 HANDBOOK ON ENGINEERING,
called, and it is finally drawn off through a sponge filter on its
way to the freezing cans.
From this it will be seen how important it is that the water
be kept as free from oil as possible. If the oil contains any
great amount of animal fats in its composition it will form a white
milky looking emulsion with the water that will be very difficult
to remove.
The presence of a yellow or reddish color in the ice is often
attributed to the cylinder oil getting in the ice. This may some-
times happen when the oil is used too freely, or the filters are out
of order ; but as a general thing the stain is due to the presence
of rust in the water. Condensed water has a very active effect
on iron when combined with oxygen, and when the plant is shut
down and the pipes are empty the action of the air on the moist
pipes soon causes them to rust, and when the plant is started
again, unless care is taken to prevent it, the rust will be de-
posited in the freezing cans.
INDEX.
AIR, composition of, 651.
f( compressor, Bennett, auto-
matic, 803.
" compressor, capacity of, 800.
" compressor, effect of fly wheel,
806.
" compressor, horizontal, 802.
" compressor, Ingersoll - Sar-
gent, 804.
" compressor, McKierman Drill
Co.'s, 801.
" lift, construction of, 808.
" " formulas, 808.
" " required for combustion,
484.
" volume per pound of coal, 651.
Arc lighting apparatus, 103.
Atmosphere, pressure of, 560.
Atmospheres, number of, to find,
806.
Atmospheric pressure, 233, 661.
Auxiliary injection, 259.
BANKING fires, 531.
Belts, adjusting, 798.
arc of contact, 795, 799.
driving power of, 788.
effect of size of pulley, 791.
effect of speed, 793.
grain side of, 768.
horizontal, 797.
horsepower of, 789, 793, 799.
inclined, 797. %
lacing, 798.
laws relating to, 791.
length required, 789.
long, effect of, 787.
making joints, 799.
proper direction to run, 798.
pull on, 795.
punching for lacing, 798.
resistance to slippage, 792.
short, effect of, 797.
Belts, slippage, cause of, 791.
" speed of, 793.
" testing adhesive qualities,
792.
<e to increase power of, 798.
" width of, 789, 797.
Bevel wheels, 707.
Biowoff cocks, 435.
Boiler, area of head to be stayed,
938.
" blowing out, frequency of,
435.
" calking leaks, 535.
" capacity, to heat water in
tank, 479.
" capacity to heat swimming
pool, 479.
" care and management, 433.
" cause affecting strength, 450.
" cleaning, 533.
" compound, how to use, 655.
" cooling down and filling,
534.
(l definitions applied to, 415.
" efficiency, on what it de-
pends, 664.
" foaming and priming, 535.
" furnaces, 432.
" hammer test for, 447.
" heating surface in square
feet, 501.
" heating surface required,
327.
" height of fire line, 669.
u horsepower, A. S. M. E.
rating, 406.
" horsepower of, 663.
" horizontal, how to set, 671.
" " specifications,
for, 524-527.
(f importance of circulation,
421, 423.
(1057)
1058
INDEX.
Boiler, inspection of, 328.
" instruction for attendant,
532.
laying up, 649.
leaving at night, 650.
low water, what to do, 325.
materials, definitions, ap-
plied to, 415.
operating valves on, 535.
plain vertical tubular, 514.
plate, characteristics of, 662.
t( manufacture and use
of, 460.
" " strength between rivet
holes, 537.
" " strength of solid,
537.
" proper point for closing in,
520.
" raising steam in, 324.
(e rating by weight of feed
water, 676.
" reinforcing ring, size of,
541.
" selection of, 422.
" stayed surfaces, strength
of, 473.
" starting and stopping, 532.
" staying heads, 938.
ie stays, 474.
" the Heine safety, 507.
" the O'Brien, 503.
" to manage with low water,
649.
" trimmings 426.
" water tube, sectional, 502.
Boilers, blister, cause of, 444.
t( cheap, not economical, 453.
" common types of, 402.
<f corrosion in, 445.
" defects in construction,
" 457.
" design of, 454.
u deterioration, cause of, 451,
(f energy stored in, 400, 448.
" firebox, when recom-
mended, 425.
" forms of, 456.
" hard patch for, 444.
Boilers, heating surface required,
403.
(e horsepower of, 402.
" what it is, 405.
" improvements in, 459.
te inspection of, 445.
i( material required for set-
ting, 522.
" method of comparing, 403.
" patching, 444.
" preventing corrosion, 443.
" leaks, 443.
u proportions of joints, 467-
472, 946.
f< pulsation in, 487.
" rating of, 404.
'• riveted seams, strength of;
461.
" rules relating to, 536.
t( safe working pressure, 516-
519.
" settings for, 456.
" single and double riveted
seams, 462.
" soft patch, 444.
" special high pressure, 401.
" stayed and flat surfaces,
473.
" steel for use in, 425.
" strength of, on what it de-
pends, 455.
" submerged tubes, 521.
" testing of, 447.
te tests, rules for conducting,
407.
" tubular, when recom-
mened, 425.
fc use and abuse of, 449»
et use of zinc, 442.
" vertical, when recom-
mended, 425.
et working beyond rated
capacity, 451.
" working capacity of, 405.
British thermal unit, what it is, 401.
" " " mech. equiva-
lent, 688.
CARBONATE of lime, 440.
Centigrade thermometer, 811.
INDEX.
1059
Centrifugal force, 501.
Changing from non-condensing tc
condensing 238.
Chimney, 688.
" cause of draft, 670.
" horsepower of, 692.
te stacks, 692.
Cisterns, capacity of, 585.
Cleaning tubes, 436.
Clearance, definition of, 653, 659.
Coal, composition of, 651.
" horsepower for 1 pound, 420.
" required to heat water by
steam, 479.
" value of, per pound, 404.
Combustion, air required for, 419.
Compound engine, 253.
Compressing, adjusting valves for,
212.
Condenser, 235.
" auxiliary injection, 259.
t( device for breaking
vacuum, 247.
" distance will raise
water, 249, 250.
" gain by using, 654.
" jet, 246.
" jet, method of connect-
ing, 248.
safety device for, 248.
siphon, 249.
" and starting
valve, 251.
t( cc method, of con-
necting, 252.
" speed of, 254.
starting the, 258.
surface, 243.
" " efficiency of,
661.
type^ of, 242.
" water required for,
237, 258, 670.
Condensing to noncondensing, 238.
Connecting rod brasses, 189.
1 " effect on cutoff,
671.
" • " to find length of,
667.
te
if
tc
u
Copper staybolt, grip of, 474.
Corliss engine, double eccentric,
215.
" " long range cutoff,
215.
" " steam distribu-
tion, 219.
" " governor, adjust-
ing, 214.
Crankpins, 188.
Cutoff, equilizing, 213, 267.
Cylinder, capacity in cu. ft., 801.
" lubrication, 309.
Dead center, to find, 195.
Decimal equivalents of an inch,
1024.
Double eccentric valve gear, 215-
222.
Do you do these things, 388.
Draft, effect of bad, on economy,
327.
Dynamos and motors, care of, 80.
EBULLITION, 439.
Eccentric diagrams, 361.
" effect of shifting, 361.
" " of moving, 319.
out of place, 360.
rod, length of, 668.
" " with link
motion, 317.
straps, 192.
throw, 390.
Electrical: —
Alternating and direct currents, 18.
A.C. E.M.F., 821.
" generators, armature circuits,
106.
belted, 888.
Brush arc, 104.
care of, 890.
commutators, 866.
compensating and
compounding,|864.
generators, compound, 887.
a compounding, 85?.
" connecting to
switchboard, 862.
" direct coupled, 888.
1060
INDEX.
(C
u
Electrical : — •
A. C. generators, division of load,
887.
u exciter, use of, 864.
" how run, 859.
" inductor, type of,
857.
<» operation, 110.
t( " regular speed for,
861.
•« ' regulator, 108.
" " revolving field, 857.
€i u running in parallel,
861, 887.
" lt setting brushes,
110.
" " shutting down, 890.
" " starting a, 889.
" " two and three-
phase, 854.
" " voltage of, 106.
Ammeter and voltmeter, construc-
tion of, 60.
Ammeter where placed, 50.
Ampere, turns required, 46.
" what it is, 73.
Angle of lag, 837.
Arc lamp, enclosed, A.C., 103.
r< " constant current circuits,
127.
" " Fort Wayne systems,
126, 150.
" " series system, 112, 118.
" " series system, regulat-
ors, 120, 124.
" ft series system, switch-
boards, 114, 117, 118.
" " series systems trans-
formers, 113, 120.
" " carbons, 156.
'• (* carbons, diam., length
and quality, 157.
ft " carbons, for D.C. and
A.C., 136.
" " frequency of, 159.
" " life of, 157.
" " polarity of, 158.
Arc lamps, 128, 132, 147, 159.
" (t carbon holders, 135.
Electrical: —
Arc lamps, care of gas check, 158.
" " clutches, 133, 158.
" (- condition of globes, 159.
" •' connection to upper
carbon. 135.
" " constant potential, 146e
" " current consumption,
154, 156.
" " cut out for, 145.
" " dashpot, 158.
" " direct current, 136, 145.
f< " directions for care, 156.
" t( enclosed, 103, 151, 156,
159.
" <e Excello, 153, 155.
u " flaming arc type, 152,
156.
" " for power circuits, 141.
" " Fort Wayne, 131, 134,
135, 139,142,147,151.
" " frequency of alternat-
ing, 159.
" " General Electric, 128,
136, 137, 144, 149,
155, 156.
" " how to install, 159.
" " how to trim, 157.
" " inner globes, 158.
" " inspecting mechanism
159.
" " life of carbons, 155.
" " multiple series, 141.
" " use of oil, 159.
a " Western Electric, 132,
134, 135.
" " Westinghouse, 129, 134,
139, 144, 148.
Arc lighting, A.C.., 104.
s( apparatus, 103.
" " constant current
circuits, 127.
<f " constant potential,
136, 146.
" " direct current, 136.
" " Fort Wayne street,
150.
te tc power circuits, 141.
te <e series system, 112.
INDEX.
1061
Electrical: —
Arc lighting, coils, connections of.
30.
Armature, cores, construction of,
23.
effect of displacement^,
flow of current in, 84.
method of raising, 75.
principle of, 16.
pull of, 63.
ring, 27.
Balance, effect of distributing, 96.
Batteries, 81.
Brushes, connection to, 40.
" number of, 39.
« position of, 36, 85.
Candle power, measurement of, 73,
Circuit breakers, principle of, 62.
Collector rings, arrangement of,17.
Commutator, care of, 76, 88.
lf construction of, 18.
Condenser, use of, 840.
Conductors and non-conductors,
14.
Constant current machines, 34.
Construction of bipolar machine,
22.
Current, how generated, 12.
" measure of strength, 73.
Cylinder controller, 72.
Direction of rotation, effect of, 15.
Distributing boards, 59.
circuits, 47.
Distributions, A. C. 882.
Drum and barrel windings, 45.
" armature, 29.
Dynamos, switching into circuit,
78.
Effect of current on needle, 8.
" u direction of current on
conductor, 11, 19.
" " number of armature
coils, 25.
" " number of poles, 39.
" " turns of wire, 20.
Electro-magnetic induction, 14.
Electromotive force, how deter-
mined, 15.
Elevators, 716, 769.
Electrical: —
Elevators, belt driven, 717.
" cable-drive machine,
781.
car switch, 748.
" controller for, 728, 775,
777, 785.
" diagram of wiring, 774.
784.
" diagrams of traction
types, 779.
direct, driven, 730.
duplex motor, 772.
Frazer duplex, 770.
" limit of drum type, 769.
" limit switch, 776.
'• machines, care of, 739-
765.
•' machines, Otis .direct
connected, 741.
" machines, types of, 756.
if method of controlling,
773.
motor, care of, 726.
" plants, installation of,
726.
" traction type, 778.
Equalizing connections from gen-
erator, 63.
Field coils of multipolar machines,
45.
Fluctuation of current, 24.
Form of curve, 823.
Formulas, 891.
Fuses, location of, 60.
Generator and motor, installing, 74.
" " " running in par-
allel, 79, 80.
" Brush arc, 103-110.
" compound, connections,
53.
" " operation, 34.
" " wound, start
ing, 55.
" constant potential, 34.
" heating in, 93.
" multipolar, 38,
" noise in, 91.
" principle of, 7.
1062
INDEX.
Electrical:—
Generator, series and shunt, 81.
" starting a, 77.
Impedance, diagram, 837.
Impressed, E. M. F., 838.
Inductive action, 834.
Instruments required in circuit, 49.
Lap winding, 42.
Light and power systems for build-
ing, 58.
Lightning arrester, loca ion, 49.
Lines of force around conductors, 9.
« « « direction of, 5.
Live and dead side of coil, 29.
Long shunt, 32.
Magnetic field, 10.
tf flux through armature, 63.
" force, how measured, 13.
Magnetization of field, 32.
Magnet, lifting capacity of, 13.
tl needle, 3.
Motor, compound, 35.
" current required by, 57.
" effect of overloading, 65.
4< field, regulating strength,69.
11 heating in, 93.
" induction, 871.
" induction, three-phase, 877.
" principle of, 11.
" principle of synchronous,
867.
t( reversing the direction of,
70.
" shunt and compound, 33.
•' shunt, varying speed of, 71.
<e single phase synchronous,
70.
" starting switch, 65.
" to start, 68.
te two and three-phase, 70.
" variable speed, 68.
Motors, 64.
Mutual induction, 842.
Ohm, definition, 73.
Panel boards, 59.
Permanent magnet, 1.
Personal safety, 129.
Phase, meaning of, 828.
Polyphase, 832.
Electrical: —
Power factor, 870.
Principles of A. C., 870.
Reactance, 830.
Resistance of conductor, 15.
" regulator, 48.
" to magnetic force, 21.
Rotary converter, 886.
Rotary converter for St. Ry., 885.
" transformers and convert-
ers, 878.
" transformers connection of
brushes, 881.
Self-induction, 829.
Sine curve, 824.
" " diagram, 831.
Soldering fluid, 101.
Strength of current, how measured,
15.
" " field, effect on speed,
12.
Switchboard for three- wire system,
57.
" for two generators, 51.
<e general arrangement,
50.
Switchboards and instruments, 47.
Synchronizer or phase indicator,
862.
Synchronizing lamps, 861.
Transformers, kinds of, 850.
fC principle of, 844.
fe use of, 849.
Two and three-phase systems, 883
Two and three-wire systems, 56.
Two-bar magnets, 3.
Voltage, effect on number of lamps,
56.
Watt, what it is, 73.
Wave winding, 43.
Winding for four-pole machine, 39.
" " multipolar armatures,
40.
Why commutators spark, 82.
Elevator safeties, 1025.
" <f brake or clamp,,
type, 1031-1034.
4i ee cable connections,
1031.
INDEX.
1063
Elevator safeties, miscellaneous de-
vices, 1037.
f< ee proper care of,
1037.
(C ft requirements of,
1027.
" •' roller type, 1028-
1030.
" " speed governors
for, 1027.
" {f type used with
electric eleva-
tors, 1035-1037.
" " wedge type, 1025.
" " wedge type, mod-
ification of, 1027.
tf " wedge type, Otis,
1025.
Engine, Armlngton and Sims, 290.
u automatic, 376.
" care and management, 185.
" compound, 222.
" " adjusting gov-
ernor, 232,
te <c equalizing load,
230.
" " horsepower, 232.
" " mean effective
pressure, 232.
" " points of cutoff,
231.
•f u proportion of
cylinders, 227.
" te reheater, 255.
" " starting, 257.
" " starting and
running, 253.
" " total no. of ex-
pansions, 228.
<l " types of, 224.
" condensing, 232.
" " advantage of,
234.
" connecting piston rod and
crosshead, 190.
" Corliss, adjustment of
valves, 206.
41 Corliss, double eccentric,
669.
Engine, effect of cut off and speed,
380.
" formulas, 203.
<e foundation, 182.
f< high speed, 179.
" horsepower, 649.
" how to line, 199.
" Ideal, 298.
" length of stroke, to find, 273
" location of, 181.
" low speed, advantage of.
179.
<s performance of non-con-
densing, 183.
** repairs for, 191.
u running ^over' and
< under,' 668.
" selecting oil for, 187.
" selection of, 177.
" sett ug up and running Cor-
liss, 205.
" the most economical, 182.
" throttling, 376, 379.
" to increase horsepower of,
383, 385.
te to increase speed of 381.
" to line with direct shaft-
ing, 387.
" to line with line shafting,
385.
" triple expansion, 653.
Engines, automatic, 194.
^ « cutoff, 339.
" clearance spaces, 276.
" gene al proportions, 275.
" regular expansion, 338.
" slide valve, 337.
" steam used by, 403.
•c water required by small,
676.
" weights of, 273
" f< per rated horse-
power, 276.
Engineer, the first duty of, 323,
325, 656.
Evaporation, factor of, 539.
" highest average, 327.
Exhaust pipes, 275.
Expansion curve, locating true, 354.
1064
INDEX.
Expansion gain by, 183, 336.
" to find number, 226.
FAHRENHEIT thermometer, 809.
Fairburn's experiments, 473.
Feed water, gain by heating, 680.
" heater open, 681.
" heaters, 678.
Firebrick, 433.
Fly-wheel, 184.
weights of, 276.
" why used, 655.
Foaming and priming, 436.
Friction and lubrication, 1040.
u coefficient of, 1042.
" laws of, 1040.
" uses of, 1041.
Fuel, utilization of, 327.
Furnace boiler, 431, 513, 525.
" down draft, 522.
" grates, how set, 670.
Fusible plug, 533.
" plugs, care of, 435.
GEARING, construction of, 706.
Governor, 183.
" adjustment for riding
cutoff, 268.
" the Gardner, 341.
" throttling, 666.
to block up, 669.
Gauge cocks, location and care,
429, 434, 521.
" glass, location and care,
434.
" steam, connections and care
430, 434, 489.
HARRIS BURG engine, 291.
Heat and steam, 416.
" in water between 32° and 212°,
604.
" latent, 583, 652.
" measurement of, 419.
" mechanical equivalent, 420.
(e of combustion, 418, 484.
" radiation of, 421.
" sensible, definition, 657.
" utilization in boiler, 417.
Heater, capacity for heating water,
482.
Heating surface, definition, 663.
Heating surface, per horsepower
648.
Horsepower, 185, 275.
" definition of, 653.
indicated, 353.
<e of gears, 695.
" of shafting, 697.
Hydraulic elevators, 954.
Hyd. Elev. accumulators, 996.
" " " construc-
tion of,
996.
" te " operation
of, 997.
" " cables, care of, 1021.
" " " lubrication,
1023.
" " car, settling of, 1019.
" " circulatingpipe, 967.
" " closing down, 1022.
se " controllers, circuit
connections, 986.
" " controllers, eleotric
floor, 985.
<e " controllers, operation,
986.
" " Crane, 959.
" " cylinder and plunger,
1005.
" " double power type,
987.
u enclosures, 1019.
" gear of, 956.
" operating, 956.
" " guides, lubrication,
1023.
(t " hand rope operation,
967.
" " high pressure type,
988.
" " horizontal, 954.
" " " high pres-
sure, 990.
" " leaks, how to find,
1023.
" " lubrication, 102.3.
tf u Morse and Williams
design, 961.
" " Otis vertical, 966.
"
INDEX.
1065
Hyd. Elev. piston, packing Otis
vertical, 1014.
" fe piston, rods, packing,
Otis, 1016.
" " plunger, balancing of,
1001.
" " " construction,
1000.
" " " Plunger Elev.
Co.'s, 1001.
" " " Standard Plun-
ger Elev.
Co.'s, 1001.
« type, 998.
tf u pulling machines,
horiz., 963.
" 'f pushing machines,
horiz., 956.
" se ropes, standard, hoist-
ing, 1021.
" " sheaves, lubrication,
1023.
" " sheaves, traveling,
1007.
" " stop balls for hand
rope, 1019.
" " types of, 954.
" " valve construction,
971.
" " " hand rope type,
1013.
" " " Otis, main, 976.
" <l " pilot, 976, 1005.
" " " " battery
type. 981. 1
ndic*
control, I
ndic*
971.
floor con-
<
troller,
(
push but-
(
ton, 985.
t
for verti-
cal, 990.
i
magnet
t
control,
979.
it
push but-
ton con-
a
trol, 983.
Hyd. Elev. valve running and
standing rope,
957.
" " " speed governing,
994.
" " " Standard Plunger
Co.'s, 1007.
'•' " a stop for accumu-
lators, 997.
" " valves, action of limit,
1007.
" " (t automatic stop,
973-1003.
" " t( cup packing
for, 1022.
" " " for double
power, 988.
" " " limit, 1012.
" " " main and pilot,
959, 975, 978,
1008, 1010.
" " " plunger type,
limit stop,
1003.
" " vertical high pressure,
990.
" " " type, 966.
" " water for, 1017.
a K Whittier design, 963.
Hyperbolic curve, to draw, 355.
IGNITION point of various sub-
stances, 589.
Inches in decimals of a foot, 714.
Incrustation, 682.
Indicating Ideal engines, 306.
Indicator, applying pencil to card,
367.
attaching the card, 366.
benefit from use of, 364.
combined diagram, 362.
connecting to cylinder,
346.
construction of, 345.
diagram analysis, 347,
377.
" ammonia
pump, 373.
" Ball engine,
374.
106G
INDEX.
Indicator diagram condensing
engine, 352.
Dickson en-
gine, 376.
Eclipse refrig.
mach., 371.
" Harrisburg
Ideal, 369.
H Harrisburg
Standard,
370.
measuring,
346.
" Russell en-
gine, 367.
eccentric card,
362.
" effect of changing valve
stem, 364.
lf " leakage, 363.
of what use, 649.
operation of, 346.
selecting spring, 366.
springs, 346.
" attention re-
quired, 366.
steam chest cards, 359.
stroke cards, 358.
" tension of drum spring,
366.
" to take a diagram, 365.
Injector, and inspirator, 591.
" capacity, horsepower,
etc., 601.
height of lift, 671.
piping an, 594.
selection of, 428.
starting pressure, 597.
the Peuberthy, 600.
the World, 593.
to discern cause of diffi-
culties, 599.
" to test for leaks, 601.
Injection, auxiliary, 259.
Inspirator, the Hancock, 597.
" to clean, 598.
Iron, weight of square and round,
488.
JOURNALS, heating of, 193.
1C
it
KNOCKING in engines, 189, 119
LAP, definition of, 654.
Lead, adjusting the, 319.
" definition of, 653.
" inside, 666.
" with link motion, 318.
Lever, the, 768.
Liquids, friction of, 564.
Lost motion, taking up, 652.
Low water, 436.
Lubrication, 186.
adhesion 1046.
cohesiveness, 1045.
cylinder And valve,
1049.
" essent als of cylinder,
1051
" number of drops of
oil, 1052.
" of refrigerating ma-
chinery, 1053.
" petroleum oils, 1046.
(t reliable test, 1053.
" theory of, 1045.
" to detect insufficient,
1052.
te wet steam, effect of,
1050.
lubricators, automatic, 310.
" sight feed, 312.
MAIN bearing, care of, 190, 192.
Mclntosh and Seymour engine,
29o.
Mechanical refrigeration, 619, 635.
Melting points of metals, 687.
Metric system, 809.
Momentum, 671.
Mud drum, 648.
PETROLEUM in boilers, 442.
Pipe, blowoff, 429.
cutting to order, 675.
dry, what it is, 431.
expansion of wrought iron,
485.
feed, area of, 427.
length required to condense
steam, 47£.
Pipes. looa,iiori of steam, 428.
" capacities of, 485, 1039.
INDEX.
1067
Pipes, contents in gallons, 1039.
" sizes of mai s and branches,
485.
" steam, 785.
" " connecting up, 429.
Piping, simplicity in steam, 674.
Piston, area, to find, 564.
" leaking, to tell from dia-
gram, 655.
" rings, 187.
" speed, 275.
" for pumps, 654.
" testing for leakage, 669.
Pitch for wheels, 704.
Pohle, air lift system, 807.
Porter- Allen engine, 281, 288.
Power, definition of, 274.
if rope transmission of^ 712.
Pressure, absolute, 398.
" excessive, effect of, 452.
u in receiver, 256.
t( mean effective, 349, 351.
" test for boilers, 447.
tf total average, 275.
Priming, effects of, 329.
Pump, arranging pipe connections,
569.
" Blake, 555.
calculating boiler for, 580.
Cameron, 548.
Deane, direct acting, 546.
duplex, operation of, 569.
formulas, 618.
Hooker, 553.
Knowles, 550.
Lost motion, in, 567.
miscellaneous questions,
550-567, 571-580.
<e setting valves on duplex,
567.
" taking care of, 575.
" Worthington compound, 544.
QUESTIONS asked when applying
for license, 648-671.
REAUiMER thermometer, 811.
Receiver pressure, 256.
Refrigeration, 619-640.
" air in system, 628.
" brine system, 622,
Refrigeration, cold easily regu-
lated, 622.
<{ condenser, 626.
" " pressure,
624.
" direct expansion,
623.
lf, effect of ammonia on
pipes, 633.
" expansion coils, 634.
tc function of pump,
621.
tf instructions for oper-
ating plant, 624.
leaks in pipes, 625.
" lubrication of ma-
chine, 632.
" oil in the system, 627.
" operation of appar-
atus, 620.
" principles of opera-
ation, 620.
ce process of, 635.
" pump and condenser,
621,636.
" rating of machine,
623.
" reboilers, 628.
" selection of oils, 633.
" shutting down ma-
chine, 625.
te starting machine, 624.
(t steam condensers,
627.
ff suction pressure, 625.
" test for compressor,
626.
" testing for water, 631.
fe to charge system,
634.
" utilizing the cold,
622.
f< valves, location of,
624
" what does the work,
621.
Rocker shaft, influence of, 273, 319.
Rope, hoisting, 814.
" horsepower transmitted, 813,
1068
INDEX.
Rope, proper diam. of sheaves, 813,
" speed of, 813.
" to test purity of, 814.
" transmission, systems of, 812.
" working strain, 813.
Ropes, limit to number, 813.
Rules: —
air cylinder, capacity of, 801.
ampere turns required, 46.
amperes, to find, 166.
area of safety valves, 427.
armature pall, 63.
belt, length required, 789.
" width required, 789.
boiler, distance between rows of
rivets, 465.
boiler, maximum pitches of riv-
ets, 466.
boiler, pitch, diagonal, 464, 456.
" safe working pressure,
477.
centrifugal force, 501.
chimney, stability of, 693.
chorda! pitch, 699.
circle circumference, 788.
circular mils, 166.
circumference of gear, 700.
cylinder, capacity, 565.
engine, duty of pumping, 615.
" to increase p >wer, 383.
s( to increase speed, 381.
factor of evaporation, 539.
gears, depth of tooth, 709.
" distance between centers,
711.
" horsepower of, 695, 710.
" speed of, 7LO.
" velocity of, 695.
heating surface in square feet,
539.
heating surface of water tube
boilers, 461.
horsepower, boiler pump will
supply, 617.
horsepower, of compound en-
gine, 392.
horsepower of noncondensing
engine, 392.
horsepower of pumping engine,
616.
linear expansion of pipe, 394.
magnet, lifting capacity, 13.
magnetic flux in maxwells, 63.
number of expansions, 226.
pinion, diameter of, 700.
pulley, diameter of driven, 789.
" effect of arc of contact,
791, 795.
" effect of distance be-
tween, 797.
" effect of size, 790.
" revolution of driver, 788.
" speed of driven, 788.
" velocity of driver, 788.
pump, capacity to feed boiler,
616.
" discharge nozzle, 607.
u maximum lift, 618.
' ' pressure can work against,
604.
" size to feed boiler, 613.
" suction pipe, size of, 608.
" to find diameter of piston,
605.
" to find horsepower of
boiler required, 606.
" to find horsepower re-
quired in a, 605.
" to find steam pressure re-
quired, 604.
proportional radius of gears,
700.
reinforcing ring, width of, 541.
relative velocity of pinion, 700.
revolutions of wheel or pinion,
700.»
rivets, shearing strength, 537.
safe stress for tooth, 705.
" working pressure, 536.
« " " " A.S.M.E.
rule, 537.
shafting, horsepower of, 697.
steam and water pistons, sizes,
603.
gteam pipe size required, 394.
" u §ed with steam jets, 542
INDEX.
1069
Rules: —
Steam, weight discharged, 540.
strain allowed on stay, 475.
strength of boiler joint, 537.
strength of diagonal stays, 476.
" of stayed flat surfaces,
thickness of plate for shell, 463.
train of wheels and pinions, 699.
valves, safety, center of gravity
of lever, 499.
valves, safety, pressure to raise
weight, 498.
valves, safety, U. S. Gov. rule,
427.
valves, safety, weight required,
497.
volts lost, to find, 166.
water, area for given discharge,
611.
" consumption of engine,
395.
" discharge under head, 609.
" elevated per minute, 565.
" flow in pipe, 611.
" gallons delivered per min-
ute, 603.
" given press, to find dis-
charge, 610.
" head, in feet corresp. to
friction, 613.
lt horsepower required to
elevate, 563.
" pounds per horsepower
for boiler, 618..
" velocity for given dis-
charge, 609.
" weight of column, 565.
weight of fly-wheels, 276.
wheel, diameter of, 699.
t( il for given pitch,
703.
" number of teeth, 697.
" pitch of, 698.
" proportional velocity of,
701.
wire, size of, 166.
Russell engine, setting single valve,
277.
SAFETY at high pressure, 401.
Scale, effect of, 440.
" how to remove, 655.
Screw-cutting, 713.
Shafting, lining up, 672.
Sheet iron, weight, 712.
Slide valve, changing cutoff, 666.
" " fitting, 191.
Smoke, 419.
Soda, carbonate, 441.
Something for nothing, 688.
Staybolt, grip, of copper, 474.
Steam coils, 480,481.
Steam, consumption in practice,
180.
" u of an engine,
834.
" dome, 430.
" effect of compression, 399.
" generating, 332.
" gage, what it indicates, 399.
tf high pressure, 332.
" method of condensing, 233.
" pipe for heating water, 478.
" pipes, loss of heat irom, 391.
" size of, 275.
" plants, economy in, 327.
" power plant, operating a,
325.
" " " taking charge
of, 323.
" pressure of, 400.
" properties of saturated, 330.
" pump, the, 544.
" temperature and pressure,
684.
" used with steam jets, 542.
" using full stroke, 335.
" velocity in engine, 394.
" " of escape, 496.
€( water required to condense,
236.
'.' weight condensed in heating
water, 479.
" " discharged per second,
540.
" where the force comes from,
398.
" why valuable, 652.
Steel stacks, weight of, 694.
1070
INDEX.
Stufflngboxes, 188.
Sulphate of lime, 441.
Tables: —
actual ratios of expansion, 928.
air required for rock drills, 933,
934.
ammonia compressor, 902.
" gas for one ton refri-
geration, 898.
t( horsepower to compress
one cu. ft. 901.
" properties of, 899.
amperes, per lamp* 173.
amperes, per motor, 169, 170.
arcs of contact, useful effect,
795.
areas of circular segments, 935,
936.
area of safety valve, 495.
boiler, energy stored in, 448.
boiling points of various sub-
stances, 907.
brick required for boiler setting,
522.
brine solution, properties of,
900.
capacity and horsepower of in-
jector, 601.
" of reservoirs in gal-
lons, 910.
" of square cistern in
gallons, 585.
" of tanks in gallons,
584.
carbonic acid, properties of, 900.
carrying capacities of wires, 99-
102.
coal, per sq. ft. of grate, 908.
condenser, power gained by ad-
ding a, 923.
" water required for,
237.
contents of cylinder for one foot
length, 801.
te of pipes and tanks, 1039.
Corliss engines, sizes and dimen-
sions, 926.
cost of coal per annum, 909.
Tables:—
cost of water per 1000 gallons
587.
decimal equivalent of an inch,
583.
diameters, circumferences, and
areas of circles, 895.
dimensions of steam, gas and
water pipe, 486.
electric light conductors, 176.
feed water required by small
engines, 676.
flues, safe pressure for, 952.
fusible plugs, melting points,
907.
heating surface in square feet,
501.
f( tf per horsepower,
403.
heat in water between 32° and
212°, 602.
hoisting rope, strength and price,
812,919.
horsepower for one pound
M.E.P., 924.
" of slide valve en-
gines, 922.
ft per ton of refrigera-
tion, 904
" " " of belts, 796.
" " « of gear
wheels,
696.
•' " " of manilla,
rope,
712,
813.
•' " " of shafting
697.
t€ " f( of wire rope
715.
hyperbolic logarithms, 892.
ignition points of various sub-
stances, 589.
incandescent wiring, 161, 162.
latent heat of liquids, 583.
loss by friction in water pipes,
588.
INDEX.
1071
Tables:—
Loss, from uncovered pipes, 391.
mean absolute pressures, 925.
melting points of metals and
solids, 687-907.
piston speed ft. per min., 912.
pipes and tanks, cap'y, 1039.
pitch of wheels, 706, 704.
pneumatic tools, 933.
pressure in boilers built since
1872, 516-519.
" of water due to height,
582.
" required to start injector,
597.
properties of saturated steam,
330, 913.
proportions of boiler joints, 467-
472, 946.
ff of parts of engines,
275.
pull of belt one inch wide, 799.
pump, boiler feed, 397.
pumps, capacity of duplex, 893.
" " of low pres-
sure, 894.
<f sizes of cylinders for
compound, 923, 927.
speed and capacity of
centrifugal, 927.
rise of safety valve, 494.
riveted seams, measurement of,
944-951.
{( specifications for,
937.
ropes for inclined planes, 920.
" iron and steel transmis-
sion, 918.
ft transmission of power, by,
921.
•aving by heating feed water,
680.
showing how water may be
wasted, 589.
sizes of chimneys, 692.
Bteam consumption in N C. en-
gines, 183.
•ulphur dioxide, properties of,
898.
Tables:—
thermometers, 903.
total heat in steam, 677.
tubular boilers, 930, 931, 932.
U. 8. gallons in given number of
cu. ft., 586.
volts, lost for per cent of drop,
171, 172.
wages, table of, 929.
weight and strength of iron bolts,
906.
weight of engine, 273.
" " rivets and bolts, 905.
' " round iron, per foot, 488.
e " steel smoke stacks, 694.
< " water, 585.
' per square foot of sheet iron.
712.
weights of feed water and of steam,
677.
wire gages, difference between,
175.
" u for 110-volt lamps, 37.
<f " weight and meas. of
water proof, 174.
Tanks, capacity of, 584.
Tannate of soda, 442.
Teeth of wheels, 705, 709.
Theoretical curve, 353.
Thermometers, 811.
Tubes or flues, materials for, 481.
lf " " seamless, 482.
" '* " sizes, 482.
USEFUL INFORMATION, 1023.
VACUUM, effect on economy, 233.
" how maintained, 653.
" in condenser, 236. *
Valve, check, 429.
" cutoff, setting, 266.
" flat riding cutoff, 268.
" gear, double eccentric, 215,
222.
" leaking, how to discover,
655.
" motion, direct and indirect,
668.
" plain slide, function of, 320.
" piston, riding cutoff, 263.
« " type, setting, 261.
1072
INDEX.
Valve, safety, 426, 491, 499.
" " area of, 495.
(t proportion of lever, 670.
" rise of, 494.
" setting for engineers, 318.
" " plain slide, 318,, 320.
" " riding cutoff with
governor, 272.
" " slide with link-mo-
tion, 313.
" slide, to set in a hurry, 388.
" spindle, adjusting length,
319.
'* stem, length of, 668.
Ventilation, data relating to, 484.
Water, 681, 1024.
" columns, 489, 515.
»< cost of, 587.
" distilled for boilers, 439.
" evaporated per pound of
coal, 650.
tf for use in boilers, 438.
(l height of column for given
press, 580.
Water, how may be wasted, 589.
" kinds of impurities, 438.
" loss by friction in pipes,
588.
" maximum evaporat on,
421.
tf meter^ the Worthington,
681.'
" pressure due to height,
582, 585.
te " of column, 565.
" required by boiler, 565.
" steam required to heat,
478.
" weight of, 564, 585.
Westinghouse compound engine,
307.
Wheel gearing, 698.
Wire rope, transmission of
power, 715.
Wood, weight equal to coal, 651.
Work, definition of, 274.
Worm screw, 708.
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LIBRARY. BRANCH OF THE COLLEGE OF AGRICULTURE
137
Tulley
TJ151
Handbook
on
T8
engineer!!*
5*
1907
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