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i35 9 



INTERNATIONAL 
LIBRARY OF TECHNOLOGY 



A SERIES OF TEXTBOOKS FOR PERSONS ENGAGED IN THE ENGINEERING 

PROFESSIONS AND TRADES OR FOR THOSE WHO DESIRE 

INFORMATION CONCERNING THEM. FULLY ILLUSTRATED 

AND CONTAINING NUMEROUS PRACTICAL 

EXAMPLES AND THEIR SOLUTIONS 



TYPES OF MARINE BOILERS 

MARINE-BOILER DETAILS 

MARINE-BOILER ACCESSORIES 

ECONOMIC CPMJayST.iON 

MARINE-BOILER FEEDJNG 
MARI N E-BOI LE R- MANAGEMENT 

MARINE-BOILER REPAIRS 
MARINE-BOILER INSPECTION 

PROPULSION OF VESSELS 
REFRIGERATION 



'^^'"^ 



"t -; *^ O '-. V' 



SCRANTON: 
INTERNATIONAL TEXTBOOK COMPANY 

9B 



the:: 17/ ypy 

PUBLIC LIBRARY 

ATTO*. LCMCX AtfD 

R ^•'^ . L 



OfifyrUiht, IWI7. Iiy Ihtbitwatiowal Tbxtbook CowFAjrr- 

'I >!»*«• '»f MNrirM lloiU'f* Oipyriicht, IWJ^. by Iktevkation^l Text»c-:k C/:mp%xt. 
KiiUiriMt Mt HUiii'/fM-rft' iUli. I>/nd//n. 

Mufliiii lloilt'r Oi-tMtU O/fiyrsKht, 1904. by Inteitkational TextboT'K Compaxt. 
KnU'riMl Ml Hliiti'/iM'm' Mftll. Um'Vin. 

Mfiilfti* ll»ill«'r A''i*»v/fi«-» (lottyhi(hi, 11106. by ]ktebkatiokal Teztbook Compaxy. 
lCht«'r««l Ml t>tufi'/riir»' Kail, I>/nM'/n. 

I'lllHM ro|iy»JHlit, l«00, by IwiEHWATiOKAL Tex7IK>ok Companv. Entcwd at 
)U««tl<ftii>r«' Hull, I^ifiMon, 

KiiifiMiiili CiiinbiiMion' r^#i»yri«hi, 1906. by Inters* atiokal Textbook Company. 
JChlcfril Ht, Hiuiunii'rn' Mall. I^/nMon. 

MniIim' IImIIit rrrrlifiK' Otjiyriuht, IHTW. by I.vternational Textbwjk Company. 

Mftiliii* HuIIki Mii/tfO^^")*'^** ("M'Vrvini.* lOQf^C-tj^ Iktbrkational Textbook Com- 
I'AWv. KiilMrM lit SiJilioncru' HalI.*L«7rfrfoh. • 

• • r 1 •••• •,•• 

Mmliin 111. Hit KrjwirK: <>3i*y HiM. 3^0^^. ^y Inter.vatiokal Textbook Company. 
KiHi'IimI nl Hulioni'fV*ltiilU3^All2l'4ri.* I 

MmiImi* HmIIim liiH|M"tVm* J*t''ii/V'rij:tij^»>^07. Iry International Textbook Company. 

ICiiIimimI III HtiiiioiV'rh;'fUlj;LUAfil^ft; ; • 

• • • • • • • ••!•,,; 

|*iti|MiUI<in (ff VcMcU: (!(JifynKht. 1006. by International Textbook Company. 
Kiitrri'il 111 Stutidiicrii' Hall. hantUnx, 

Hpir\u«*rniUii\: C(i\tynu\M, \WH\, by International Textbook Company. Entered 
Hi Hlntloiirm' Httll, I^mdim. 

All riKltttt reserved. 



Printed in tub United States 

10718 




I 



The International Library of Technology is the outgrowth 

of a large and increasing demand that has arisen for the 
Reference Libraries of the International Correspondence 
Schools on the part of those who are not students of the 
Schools. As the volumes composing this Library are all 
printed from the same plates used in printing the Reference 
Libraries above mentioned, a few words are necessary 
regarding the scope and purpose of the instruction imparted 
to the students of — and the class of students taught by — 
these Schools, in order to afford a clear understanding of 
their salient and unique fe-if^res. 

The only requirement f6r iymisMonlo sny'<5f the courses 
offered by the International CoTespondencfc Schools, is that 
the applicant shall be able to rciKl^-^he' English language and 
to write it sufficiently well *o ttlnV.b his written answers to 
the questions asked him infeiriJrible. Each* course is com- 
plete in itself, and no textbooks are required other than 
those prepared by the Schools for the particular course 
selected. The students themselves are from every class. 
trade, and profession and from every country; they are, 
almost without exception, busily engaged in some vocation, 
and can spare but little time for study, and that usually 
outside of their regular working hours. The information 
desired is such as can be immediately applied in practice, so 
that the student may be enabled to exchange his present 
vocation for a more congenial one, or to rise to a higher level 
in the one he now pursues. Furthermore, he wishes to 
obtain a good working knowledge of the subjects treated in 
the shortest lime and in the most direct manner possible. 



iv PREFACE 

In meeting: these requirements, we have produced a set of 
books that in many respects, and particularly in the g:eneral 
plan followed, are absolutely unique. In the majority of 
subjects treated the knowledg^e of mathematics required is 
limited to the simplest principles of arithmetic and mensu- 
ration, and in no case is any greater knowledg:e of mathe- 
matics needed than the simplest elementary principles of 
alg:ebra, geometry, and trigonometry, with a thorough, 
practical acquaintance with the use of the logarithmic table. 
To effect this result, derivations of rules and formulas are 
omitted, but thorough and complete instructions are given 
regarding how, when, and under what circumstances any 
particular rule, formula, or process should be applied; and 
whenever possible one or more examples, such as would be 
likely to arise in actual practice — together with their solu- 
tions — are given to illustrate and explain its application. 

In preparing these textbooks, it has been our constant 
endeavor to view the matter from the student's standpoint, 
and to try and anticipate everything that would cause him 
trouble. The. utmpst.p^iiQS. have ^been taken to avoid and 
correct any^a|id^lJambig]TUUS*^^ressions — both those due 
to faulty rhetorig^and tho3ls* jiyp ^o* insufficiency of statement 
or explanation. • ^ As ^I4^:bcst way to make a statement, 
explanation, ot.Tie;^Q]cip^<>P:¥lear is to give a picture or a 
diagram in coitnecjtion ."A^CI^ {(^illustrations have been used 
almost without limit. The illustrations have in all cases 
been adapted to the requirements of the text, and projec- 
tions and sections or outline, partially shaded, or full-shaded 
perspectives have been used, according to which will best 
produce the desired results. Half-tones have been used 
rather sparingly, except in those cases where the general 
effect is desired rather than the actual details. 

It is obvious that books prepared along the lines men- 
tioned must not only be clear and concise beyond anything 
heretofore attempted, but they must also possess unequaled 
value for reference purposes. They not only give the maxi- 
mum of information in a minimum space, but this infor- 
mation is so ingeniously arranged and correlated, and the 



PREFACE 



indexes are so full and complete, that it can at once be 
made available to the reader. The numerous examples and 
explanatory remarks, together with the absence of long 
demonstrations and abstruse, mathematical calculations, are 
of great assistance in helping one select the proper for- 
mula, method, or process and in teaching him how and 
when it should be used. 

The first part of this volume treats on the construction, 
care, and management of marine boilers and their acces- 
sories, the usual methods of firing, and the principles under- 
lying the economic combustion of coal. Special attention 
has been given to the subject of marine-boiler inspection 
tmder United States laws, the rules of the Canadian Board 
rpf Steamboat Inspection, and the rules of the British 
Imperial Board of Trade, as a good knowledge of this subject 
is necessary for a candidate for a marine engineer's license. 
Following the treatment of boilers is a section on the elements 
of propulsion of vessels, followed by a section on the theory 
of refrigeration; these two sections will prove of great value 
to chief engineers and others interested. The aim through- 
out has been to present matter that will be of special value 
to the operating marine engineer rather than to the designer 
of marine machinery, with a view of giving a fundamental 
education that will enable persons having the legal practical 
experience to easily pass examinations for a marine engi- 
neer's license. 

The method of numbering the pages, cuts, articles, etc. is 
such that each subject or part, when the subject is divided 
into two or more pans, is complete in itself: hence, in order 
to make the index intelligible, it was necessary to give each 
subject or part a number. This number is placed at the top 
of each page, on the headline, opposite the page number; 
and to distiiiguish it from the page number it is preceded by 
the printer's section mark (§). Consequently, a reference 
such as § 16, page 26, will be readily found by looking along 
the inside edges of the headlines until § 16 is found, and 
then through £^ 16 until page 26 is found. 

International Textbook Companv 



CONTENTS 



Types of Marine Boilers Section Page 

Definitions 9 1 

Fire-Tube Boilers 9 10 

Water-Tube Boilers 9 32 

Sectional Pipe Boilers 9 46 

Comparisons 9 54 

Marine-Boiler Details 

Shell 10 1 

Riveted Joints 10 3 

Heads 10 13 

Openings ^ 10 17 

Appurtenances 10 21 

Staying 10 23 

Furnaces 10 32 

Combustion Chambers 10 42 

Passages for Gases of Combustion ... 10 48 

Marine-Boiler Accessories 

Safety Valves 11 1 

Steam Gauges and Water Gauges .... 11 18 

Blow-Off Apparatus 11 36 

Pipe Fittings -11 39 

Miscellaneous Accessories 11 46 

Firing 

Theory of Combustion 12 1 

Fuels and Their Combustion 12 11 

Combustion of Coal 12 15 

Combustion of Oil 12 23 

Draft 12 30 

iH 



iv CONTENTS 

Economic Combustion Sutton Page 

Principles of Combustion 13 1 

Smoke 13 7 

Air Supply to Furnace 13 11 

Furnace and Combustion Chamber . . ■ 13 16 

Heat Losses and Their Prevention ... 13 19 

Marine-Boiler Feeding 

Feed- Apparatus Arrangement 14 1 

Feed-Apparatus Construction 14 6 

Feedwater Purification . 14 32 

Feedwater Heating 14 50 

Loss of Feedwater 15 1 

Salt Measurement and Reeulatioo .... 15 10 

Heat Transfer to Water 15 21 

Marine-Boiler Management 

Getting Ready for Sea 16 1 

Leaving Port, at Sea, and Coming to - - 16 7 

Cleaning, Overhauling, and Laying Up - - 16 23 

Inspection 16 28 

Marine-Boiler Rep.\irs 

Wear and Tear 17 1 

Boiler Explosions 17 6 

Repairs at Sea 17 7 

Repairs in Port 17 21 

Marine-Boiler Inspection 

Speciacations for Materials 18 1 

Cylindrical Shells 18 10 

Riveted Joints 18 23 

Openings in Boilers 18 43 

Flat Surfaces and Staying 18 4-5 

Furnace Flues, Smoke Flues, and Tubes . 18 70 

Boiler Heads and Untmheads 18 80 

Pipes and Safety Valves 18 85 

Propvlsion- Of Vessels 

Introauctton 19 I 

Paddle Wheels 19 11 



CONTENTS V 

Propulsion of Vessels — Continiied Section Page 

Screw Propellers 19 21 

Thrust 19 31 

Speed of Vessels 19 39 

Refrigeration 

Fundamental Principles 20 1 

Adiabatic-Expansion Refrigeration ... 20 6 

Latent-Heat Refrigeration 20 12 

Application of Refrigeration 20 25 

Running Refrigerating Machines .... 20 28 






TYPES OF MARINE BOILERS 

INTRODUCTION 



DEFINITIONS 



GENERAI. NAUTICAL TERMS 

1. There are numerous terms and phrases used on board 
'ship with which people living on land are not familiar; hence, 
the meaning of those terms that are apt to be used by the 
marine engineer will be explained. 

Fig. 1 represents a plan view of a vessel. The forward 
lart of the vessel is called the bo^v; the rear part, the stern, 




oard Watt 




•he forward extremity a of the vessel is known as the siom. 
An observer standing so as to be looking toward the bow 
^lULS on his right the starboard side of the vessel, and on 
his left the port side. Anything located near the center of 
the vessel, as at .-J, is said to be anildshlp; any object 
located near the bow, as at B, forward; if located near the 
stern, as at S, it is said to be aft. Any object placed so that 

aHmgklia bt /mlernatianal Ttiltoot CBrnfant. Enltral at Slaliantrt' Hall. Umdom 



2 TYPES OF MARINE BOILERS §9 

its direction is parallel to the line a^ is said to be placed 
fore and aft; any object placed so that its direction is at 
ris^ht ang^les to the line a b^ as the line c d, is said to have an 
athwartslilp direction. The width of a vessel is called 
its beam. The perpendicular distance from the lowest 
point of the vessel below the water-line to the surface of the 
water is known as the draft; it is expressed in feet and 
inches in Eng^lish-speakins: countries. The platforms divi- 
ding: ^ vessel into horizontal spaces, forming the ceiling of 
one space and the floor of the next space above it, are called 
decks. Those parts of the sides of a vessel that project 
above, and surround the upper deck are called the bul- 
^rarks, or rails. Looking from either rail toward the 
center line a ^ of the vessel is called looking Inboard; look- 
ing from the center line a ^ of the vessel toward either rail 
is called looking outboard. Any object outside of a vessel 
that is in line with the athwartship line cd \s said to be 
abeam or abreast of the vessel. When two objects on 
board of a vessel are in line with each other fore and aft, 
the one nearer the stem is said to be abaft the other one; 
for example, the engines are abaft the boilers. An object 
behind the ship is said to be astern, and one in front of 
the vessel is said to be ahead. 

Beneath the deck is belo^r. Ascending from below is 
going on deck. Descending from the deck is going beloxv. 

Pitching: is the alternate up-and-down motion of the bow 
and stem of a vessel in a rough sea. Rolling: is the athwart- 
ship motion of the vessel in a rough sea. 

Wlndi^vard is the direction from which the wind is blow- 
ing, licei^vard (pronounced lee-ard) is the direction toward 
which the wind is blowing. When the wind is blowing 
toward a shore, the latter is known as a lee shore; when the 
wind is blowing in an opposite direction, it is said to be 
blowing off shore. Under the lee means being on the leeward 
side of an elevated object — high land, for instance. 

Way is the motion of the vessel through the water. 

liceway is the drift or sidewise motion of the vessel to 
leeward, driven in that direction by the wind. Sternway 



TYPES OF MARINE BOILERS 3 

is the motion of a vessel when the engines are backing, that 
is, the going backwards of a vessel. Under ^vay is the for- 
ward motion of a vessel when running on its course. Gelling 
under way is the operation of hoisting anchor or casting off 
the lines from the wharf and starting the engines. 
The hold is the cargo or stowage space below deck, 

tA hatchway is an opening in the deck to receive and 
IsL'harge cargo or stores to and from the hold. 
CoRl bunkers are the spaces devoted to the stowing 
E coal. TrlmralnK the bunkers is the operation of 
;owine the coal. Bunker scuttles are circular openings 
I the deck through which the coal is put into the bunkers. 
Coaling shtp is taking coal on board and stowing it in 
the bunkers. 

An ash chute is an inclined trough through the bulwarks 
gifarough which the ashes are dumped overboard. 

A hatch is the cover that is placed over a hatchway when 

vessel is at sea. A eotnpanlun^^ay is a hatchway for 

Ihe ship's company and passengers to descend from or 

ascend to the deck by means of ladders or stairs. 

ShtppluK fi sea is the breaking of a wave over the 

^H^lu-arks, thus flooding the deck. 

^^H A hatch coinblnK >s a bulwark around a hatchway to 
^^Brevcnt the water from going below when a sea is shipped, 
^^Br while washing the deck. 

^^H Waterways are small channels or gutters, around the 
^^Bsck at ihe base of the bulwarks, to carry off the water. 
^^B Scuppers are small openings through the base of the 
^^Bnlwarks to permit the water to flow overboard from Ihe 
^HPlaterways. 

Overboard is outside of Ihe vessel, in the sea. 
The spaces under the engines, boilers, storerooms, floor 
plates, etc, are the bilges; pumping bilges is the operation 
of pumping out the water collected in the bilges. 

Coming lo is the act of bringing the vessel to anchor or 
alongside the wharf. Ijuyiug to is stopping a vessel while 
she is on her course to speak another vessel, pick up a pilot. 
When speaking of a vessel, it is always considered as 






4 TYPES OF MARINE BOILERS 5 9 

having the feminine gender; thus, she is under war. she is 
laying to, etc. 

When a vessel is canght in a violent gale and rongh sea. 
it is sometixnes necessary to slow the enginei^ down to 
Ateers^pe wmy, which means to just speed enough to cause 
the nxdder to act on the water sufficiently to control the 
movements of the vessel and head the vessel into the gale; 
this is called hemvinn^ to. 

Shoald a vessel arrive off her port of destination late in 
the evening, after dark, or during the night and no pilot 
is obtainable, it is customary to run the vessel slowly back 
and forth to and from the entrance to the harbor until day- 
light; this is called layini^ off and on. Making Cast is 
the operation of securing a vessel to a wharf or buoy with 
hawHen or cables. 

r.)perating the engines in answer to signals is called 
vrf>rklnK to bells. 

When a screw vessel is pitching violently, the stem rises 
and lifts the screw propeller out of the water more or Iess» 
which causes a sudden increase in the speed of the engine; 
this is called racing. 

When a vessel lying in the stream is made ^t at both 
ends, that U. bow and stem, to two buoys or anchors, one 
ahead and the other astern, she is said to be mooretl. 

When a vessel is riding to a single anchor and the ride 
cnms she revolves around a semicircle the center of which is 
Che anchor. This is called swinging to the ti«ie« or just 
tfrwinglng. 

The engineer on duty in the engine room is the engineer 
of tHe' wratch. 

That port of a vessel or that part of an object on board of 
a vessel nearest the bow. is called the forward part: and 
that part nearest the stem is called the after port, for 
example, the forward part of the fireroom: the after part of 
Che iirerootr.: the forward boiler the after boiTer. 

The InmA wmter-llne is an imaginary line ^-i::no the oc:r- 
side of Che hull of a vessel that co:nc:v^:< w:ch tire wirer-Irre 
when she is fully loaded wizh cargo. co«iI. store:?, ecc. Wben 



§9 TYPES OF MARINE BOILERS 5 

the load water-line, forward, is below the surface of the 
Lwater, the vessel is said to be down by the beutl. When 
Ethe load water-line, aft. is below the surface of the water, the 
' vessel is said to be down by the stem- 
When a vessel is immersed in the water more on one side 

than on the other, she is said to be listed to port or lifted 

fto i^tarboai-d, as the case may be. When a vessel is 
ftoimersed in the water equally on both sides, she is said to 
Be on an even beam. When a vessel is listed, the act 
of slowing the cargo or using the coal from the bunkers so 
that she will be brought to an even beam is called trlm- 
DiiuK the ship. 

A tarpaulin is a piece of heavy canvas 8 or 10 feet 
square coated with tar or painted to make it waterproof. In 
rough weather the hatchways are covered with tarpaulins 
secured to the hatch combings; this is called battening: 
ilowu hatohcs. 

Biilklioads are the partitions in the vessel dividing it into 
compartments. IValer-tighl bulkheads are tight bulkheads 
ilaced in the hull of a vessel, dividing it into water-tight 

impartments, no two of which are large enough to hold 
Bufiicient water, in case of a serious leak, to sink the ship. 

When a vessel has a hole knocked in her bottom, she is 
said to be stove. 

YeDtilutorM are large sheet-metal pipes, with trumpet 
mouths placed at right angles with the upright part. They 
lead from above the deck to the fireroom. hold, etc. to 
supply these spaces with air. Wind sails are large canvas 
pipes or tubes, with outstretched wings at their tops, lead- 
ing from above the deck down through the hatchways into 
ilhe hold to ventilate the ship below decks. When the trum- 

it mouths of the ventilators or the opening of the wind 
point to windward they are said to be trimmed to 
iiu wind. 

When a vessel is in port and there is no steam on the 
Iwilers, the smokestack is often covered with a sheei-metal 
or canvas covering to keep out the rain; this covering is 
called the sniokcstut-k hood. 



^ C01 



6 • TYPES OF. MARINE BOILERS §9 

A clinometer is an instrument, usually a pendulum, 
suspended on a bulkhead, hatch combing;, or other con- 
venient place, to desig^nate the number of degrees the 
ship rolls. 

To enlist in the merchant service or in the navy is 
to ship. 

An object floating helplessly in the water is said to be 
adrift. 

The speed of a vessel is usually measured by means of an 
instrument called a log:. This consists of a triangular piece 
of wood weighted at one side to keep it upright in the water, 
and called the log: chip. To the log chip the log: line is 
attached, which is coiled on a reel and has pieces of cord 
tied to it at equal distances apart. To measure the speed 
of a ship, the log chip is thrown overboard and the log line 
is allowed to pay out, that is, unreel, until the first knot 
reaches the observer*s hand. He then calls out for a second 
observer to turn over a sand glass, timed to run either 28 or 
30 seconds, and at the moment the glass is turned over, lets 
the log line pay out again, noting the number of knots that 
pass through the hand while the glass is running. Then the 
number of knots and fraction thereof counted represent the 
rate of advance of the vessel either in nautical or in statute 
miles per hour. Thus, if 12a knots slip through the observ- 
er's hand, the speed of the vessel is said to be 12t knots, 
which corresponds to 12a nautical or statute miles per hotu*, 
depending on what mile the log line is divided for. 

The nautical mile is in practice taken as 6080 feet, which 
value has been assigned to it by the British Admiralty, and 
which has been universally adopted. The statute mile is 
5280 feet in length. 

For a 28-second glass the knots in the log line are 47.29 
feet apart for the nautical mile and 41.06 feet for the statute 
mile; for a 30-second glass the knots are 50.6 feet apart for 
the nautical mile and 44 feet for the statute mile. 

The nautical mile is used as the unit of distance in ocean 
navigation, and the statute mile in river, lake, and inland 
navigation in general. 



i TYPES OF MARINE BOILERS 7 

Landsmen often erroneously speak of the speed of a vessel 

being so many knots per hour; as has been explained, the 

imi knot defines the rate of speed, bill not the distance 

■aversed in one hour. This should be expressed distinctly 

nautical or statute miles. 

The displace itient of a vessel is equal to the weight of 
Ihe water it displaces, and is usually expressed in tons of 
2,240 pounds. It will vary with the draft, for the deeper 
the vessel is in the water, the more water will it displace. 
The tonnngo of a vesse! is its entire internal cubic capacity, 
measured in the United States in tons of 100 cubic feet each, 
in a manner prescribed by law. Tonnage should not be 

i confounded with displacement. 
' SPECIAL NATAL TEBMS 

■ 2. There are certain phrases used in the navy that are 
not commonly used in the merchant service. The captain's 
quarters is called the eabln. The cabin on board a naval 
vessel is located aft. The commissioned officers' quarters is 
called the w^aril i-ooin, which is usually located just forward 
of. or underneath the cabin, according to the construction of 
the vessel. Just forward of Ihe ward room is the ateera^', 
where the warrant and appointed officers and midshipmen 
are quartered. The crew is quartered on the berth deck, 
which is located forward of the engines and boilers. The hos- 
pital of the ship is called the sick bay, and is usually located 
forward of the berth deck at the bow. The ship's prison is 
called the lirl^. The quarter deck is the starboard side of 
the main deck abaft the mainmast when the vessel is in port, 
and the windward side at sea. It is only occupied by the cap- 

ttain. the executive officer, and the officer of the deck. Every- 
body else is supposed to keep off unless they have business 
with one of the officers mentioned, and after Ihe business is 
transacted they are expected to depart immediately for 
"tiieir own part of the deck. All persons on entering on the 
quarter deck are required to touch their caps with the fingers 
of the right band; this is called saluting Ihe quarter deek. 




8 TYPES OF MARINE BOILERS §9 

At the bow, there is often a small deck elevated above 
the main deck, and called the topgrallant forecastle (pro- 
nounced t-g:allant-fo-cassel); on this, in fine weather, the 
crew congregate during recreation hours to smoke. During 
foul weather, they smoke under the topgallant forecastle deck. 
The i^valsts of the ship are the passageways between the 
bulwarks and the hatch combings, on each side of the deck. 
That on the port side is called the port waist; that on the 
starboard side is called the starboard waist. The icanign'vays 
are openings cut in the bulwarks of the vessel for the 
entrance to and exit of persons from the deck, to or from 
boats or the wharf. 

The ^rarrant machinists in the United States navy now 
act as assistant engineers. They operate the engines and 
have charge of a watch. There is another position in the 
engineer's force of a man-of-war, called the engrlneer^s 
yeoman. He has charge of the tools and stores (supplies), 
and serves them out when they are needed. He also copies 
the log, writes the reports, and keeps the expenditure book, 
and acts, in general, as the chief engineer's clerk. This posi- 
tion seldom, if ever, exists in the merchant service, the nearest 
approach to it being that of storekeeper, or man in charge 
of the stores and tools. 

OENEBAIi DESCRIPTION OF A BOILER 



ESSENTIAL PARTS 

3. A steam boiler is an apparatus for the generation of 
steam from water for various industrial purposes, such as the 
production of mechanical power to operate machinery or pro- 
pel vessels through the agency of the steam engine, and for 
heating and drying purposes. A boiler must contain three 
essential parts, which are: (1) a place for the fire, (2) a place 
for the water, and (3) a division or partition between them. 

A steam boiler consists of a vessel containing water, which 
is converted into steam by the application of heat. The heat 
is generated by the combustion of some fuel, such as coal, 



■be 
tact 
Bte£ 



TYPES OF MARINE BOILERS 9 

jvood, pelroleum, etc.. in the rurnace. To carry away the 
^oducts of combustion and to create a rtraTt, that is, to 
inpply the burning fuel with air, the furnace is connected 
nth the siitokcstack, sometimes called the funnel. The 
water used for the generation of steam is supplied to the 
boiler by the fetd-apparatus, and enters the boiier through 
the feedpipe. The steam generated in the boiler is con- 
veyed to its destination by the steam pipe. 

When any portion of a boiler, such as a plate or tube, is in 
contact with the fire or hot gases on one side and water on 
the other, the surface in contact with the fire and hot gases 
5 called a hentiiig surraco. The sum of all such surfaces 
|_is called the total healing surfaces. Such surface as is in con- 
tact with fire or hot gases of combustion on one side and 
^team on the other side is called a superheating siirlate. 

The furnace is provided with a grate, on which the fuel is 

placed to be burned. The grate usually consists of a series 

of cast-iron bars with spaces between them for the admission 

^■_of air to the burning fuel. The area of the grate, expressed 

^^Bn square feet, is called the ^ra/f surface. 

^^B It is imperative that a steam boiler should only be partly 

^Vfilled with water when ready for service. As 1 cubic inch of 

^H water occupies nearly 1 cubic foot of space when converted 

^P into steam at the atmospheric pressure (hut less at higher 

pressures), a very considerable portion of the space within a 

boiler must be reserved as a receptacle or reservoir for the 

steam; this is called the steam space, and, as a matter of 

course, it is located at the highest part of the boiler above 

the water-line. That portion of a boiler occupied by the 

water is called the water space. 

r[ CLASSIFICATION 

4. Steam boilers may be divided into four distinct classes 
or types, namely: stationary, portable, locomotive, and marine 
boilers. The first three classes may be grouped under the 
general head of land boilers to distinguish them from those 
used on vessels, which are termed marine boilers. 



10 TYPES OF MARINE BOILERS §9 

Marine boilers are divided into two distinct types: fire- 
tube boilers^ and water-tube^ or tubulouSy boilers. Their distin- 
guishing^ features are: In fire-tube boilers, the flame and 
gases of combustion pass through tubes or flues which are 
surrounded by water; whereas, in Tvater-tube boilers, the 
water circulates through the tubes and the flame and gases 
of combustion surround them. Another distinguishing 
feature is that in fire-tube boilers the tubes and flues are 
enclosed in a shell, which must be strong enough to sustain 
the steam pressure within it, while the tubes of the water- 
tube boilers are enclosed in a casing of light sheet-iron lined 
with some refractory and non-heat-conducting substance, 
such as asbestos, magnesia, mineral wool, etc. This casing 
is not called on to sustain any pressure, that duty being per- 
formed by the tubes, steam drums, and mud-drums, which, 
being of small diameter compared with the shell of tubular 
or flue boilers, may be made of much thinner plates, and 
consequently lighter, than the shell of fire-tube boilers. 



CONSTRUCTION OF MARINE BOILERS 



FIRB-TUBE BOILERS 



FLUE BOILERS 

5. Externally Fired Flue Boilers. — The simplest 
form of marine boiler, as used at the present time, is the 
flue boiler, shown in Fig. 2. This type of boiler is still 
in extensive use on Western-river steamboats. It consists 
essentially of a long cylinder a, called the shell, made of 
iron or steel plates riveted together. The ends of the boiler 
are closed by flat or hemispherical plates b, b, called the 
heads of the boiler. Two or more flues c^Cy in some 
instances as many as six, are fixed to the front and rear 
heads. To the front of the boiler a sheet-iron casing d, 
known as the front connection, is secured; the upper part 
of this leads to the smokestack e. To give access to the 



n TYPES OP MARINE BOILERS §9 

flues, doors / are provided. When two boilers are placed in 
one setting, as shown in the figure, they are usually con- 
nected to a steam drum ^, the object of this drum being 
to furnish dry steam. Fitted to the steam drum is the stop- 
valve ^'', by means of which communication between the 
boilers and the engines may be shut off. Connected to the 
stop-valve is the steam pipe ^^ that conveys the steam to 
the engines. Attached to the top of the steam drum is the 
safety valve ^', which prevents the steam pressure from 
exceeding the safe working pressure of the boiler. To 
indicate the steam pressure, a steam ^iraiigre / is attached to 
each set of boilers. To indicate the water level within the 
boiler, g^augre-cocks / are fitted to the front heads. A 
manhole s, which is simply a hole cut in the shell and 
closed by a suitable cover, gives access to the inside of the 
boiler. To provide a quiet place for the settlement of the 
foreign matter held in suspension in the water used for feed- 
ing the boiler, a mud-drum A, connected to the shell by 
the nozzle h\ is provided. Attached to the mud-drum is a 
blow-off pipe A'' provided with a stop-cock, not shown in the 
figure, by means of which the sediment may be drawn off, 
or the boiler emptied. A similar drum k is attached to the 
rear of the boilers to receive the feedwater, which passes 
thence into the boilers. The pipe k^ leads to the feed-pump. 
As usually set, the front ends of the boilers are supported 
in a cast-iron front A resting on the deck. The rear ends 
are supported by cast-iron brackets B placed underneath the 
feed-drum and secured to the deck. Brickwork, lined with 
firebrick, forms the sides and top of the boiler setting. The 
bottom of the setting that forms the lower smoke flue m 
is made of wrought-iron plates «, n lined with firebrick. 
The furnace C is placed under the front end of the boiler 
shell. The fuel is thrown in through the furnace doors 
OyO and burns on the jarrate /*, the ashes falling through 
the grate into the ash-pit D, which is provid^ with 
doors D\ Behind the furnace is built the firebrick brragre r. 
It serves to keep the hot gases in close contact with 
the imder side of the shell. The gases arising from the 






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ck/fed br a Kihicbjt: cxrrt^-. s:rres acygrss 10 liie inside of tbe 
V>Ser- To ^vnot a gs^ct place fee ihe sefrrlrmpia of ihe 
icif ea;{:33 sjctrer btSc ia »2spensicm id ibe wazer izsed sor feed- 
iz>z t3oe t»2jeT. a idim1-^j-«^ il. cozmected to ibe sbeH by 
libKt SKXEzJie 4r^ i» prcnridesd. Anached 10 the mnd-drmn is a 
Uf/w^jH yt^ k" proTided with a siojxsixi, i>ot sbovn in tbe 
hxm^, hy means of vbidi tbe sediment may be drawn off« 
or tJae hoiltr emptied- A similar drum k is attarhed to tbe 
rear of tbe boilers to reoeive tbe feedwater. wbicfa insses 
tbitaiot inUj tbe boikrs. Tbe pipe i*' leads to tbe feed-pomp. 
As nsnally set, tbe front ends of tbe bouers are supported 
in a cavt'iron front A resting on tbe deck. Tbe rear ends 
are t^xpp^/TUid by cast-iron brackets B plsuced trndemeatb the 
feed-drum and secured to tbe deck. Brickwork, lined witb 
firebrick* forms tbe sides and top of the boDer setting. Tbe 
boll</m of tbe setting: that forms tbe lower smoke fine m 
i% made of wronght-iron plates w, n lined with firebrick. 
Ilie furnace C is placed under the front end of the boiler 
%he\L Tbe fuel is thrown in throug^h the furnace doors 
0,0 and bams on the fprate P, the ashes falling: throug:h 
the j^rate into the ash-pit D, which is provided with 
do*/n> />'. Behind the furnace is built the firebrick bnogre r. 
It Mrrves to keep the hot g:ases in close contact with 
tbe under side of the shell. The gases arising from the 



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TYPES OF MARINE BOILERS 13 

combustion of the fuel pass from the furnace C over the 
bridge r into the smoke flue m, Ihence into the cylindrical 
boiler flues c.c, whence they pass into the front connection 
d and up the smokestack, which is provided with a damper, 
shown at f". 

It will be seen, by referring to Fig. 2. that the brickwork 
of the setting covers the upper portion of the boiler shell in 
such a manner as to prevent the hot gases from coming in 
contact with the shell above the water-line IK The part 
of the boiler shell above the brickwork, the steam drum, 
and the steam pipe are covered with some non-conducting 
material to prevent the radiation of heat. 

In the flue boiler, the heating surface, according to the 
definition, consists of the part of the shell that is over the 
furnace, the rear head (both to be measured up lo the under 
side of the top of the setting), the inside of the flues, and 
the front head. The front head is usually omitted in calcu- 
lating the heating surface. 



loc 



€. A typical modem Western-river steamboat boiler 
shown in Fig. 3. Fig. 3 (a) is a front elevation, 
looking aft. Fig. 3 (d) is a side elevation, looking from 
port to starboard. Fig. 3 (f) is a plan view, a section being 
taken through the port boiler along its horizontal center line 
in order to show the flues and the inside of the setting. 
Fig. 3 ((/) is a rear view of the boilers and setting, part of 
the setting being broken away around the starboard boiler, 
through which a vertical section has been taken in order to 
show the location of the flues. The three boilers W, B , andC 
are of the flue type, containing five flues. The location of 
the flues is shown in Fig. 3 (c) and (</). There is one wide 
grate common to all boilers: when there are more than three 
boilers in a battery, there may be two or more furnaces. 
The breeching, or front connection, D.D is common to all 
boilers, and is provided with doors, as shown, to allow the 
flues, etc. to be examined and cleaned. The boilers are 
:tenially fired, and the gases of combustion surround about 
ro-tbirds of the shell. They pass to the rear of the boiler. 



14 TYPES OF MARINE BOILERS §9 

and then through the flues forwards again into the breeching, 
whence they pass up the two stacks Ey E. The use of two 
stacks is common on all Western-river steamers, as it gives 
the pilot an unobstructed view forward and aft. When only 
one stack is used, as is sometimes done in the smaller 
vessels, it is usually set on one side of the boat, so as not to 
obstruct the view of the pilot. Each boiler is provided with 
its own safety valve; the nozzles to which the valves are 
attached are shown at a, by and c. Occasionally two safety 
valves are used, one of them being a lock-up safety valve, 
set by the boiler inspector to the steam pressure allowed, 
and the other a common safety valve. The three boilers are 
connected by suitable flanged nozzles to the steam drum /% 
forming a steam reservoir. The main steam pipe leading to 
the engines is connected to the nozzle /. All other steam 
pipes, such as those for the whistle, steering gear, feed- 
apparatus, capstan, etc., are also connected to the steam 
drum at suitable places. The bottoms of the three boilers 
are connected together by two mud-drums, or stand pipes, 
as they are often called; the rear mud-drum is shown at G 
and the forward mud-drum at H. These mud-drums are 
supposed to provide a quiet place for the collection of mud 
and sediment held in mechanical suspension in the feedwater. 
Each drum is provided with two nozzles to which the mud- 
valves or blow-off valves are attached. Suitable pipes lead 
the water overboard. The nozzles gyg of the rear mud-drum 
are attached to the lower part of the drum and point aft. 
The nozzles on the forward drum are attached to the lower 
part of the two heads. One of these nozzles is shown at h. 
The nozzle / in the center of the rear mud-drum is for the 
donkey feed-pipe. Each boiler has its own main feedpipe 
and check-valve; the water is introduced through the rear 
head, and passing through a coil of pipe is delivered in the 
steam space near the front of the boilers. The gauge cocks / 
are in the rear head of the boiler, as are also the float water 
gauges 0, The purpose of placing the gauges in the rear 
head of the boilers is to allow the engineer to see the height 
of water in the boilers without leaving the engine room. 



TYPES OF MARINE BOILERS 



;i 1 1 1 '1 iV ^-^C^- 




16 TYPES OF MARINE BOILERS §1 

Suitable manholes and handholes are provided to allov 
examination and repair of the boilers, mud-drums, and stean 
drums. The front of the boiler settin£: is of cast iron; th< 
sides, rear, bottom, and top of sheet iron. Every part o 
the setting that is exposed to the fire is lined with firebrick 
The boilers and setting are secured to the deck by the tie 
rods Uy n, 

7. Internally Fired Flue Boiler. — The flue boilen 
shown in Figs. 2 and 3 have the furnace outside of the boiler 
and hence are called externally fired boilers. The desire 
for more compact and self-contained boilers, that is, foi 
boilers requiring no brick setting, led to the development ol 
Internally fired boilers, in which the furnace is contained 
within the boiler itself. A boiler of this class, known as a 
firebox flue boiler, is illustrated in Fig. 4. The shell oi 
the boiler is composed of two diflEerently shaped parts riveted 
together. The rear part of the boiler is cylindrical; the front 
part is of a rectangular cross-section with vertical sides and 
a semicircular top. There are one or more furnaces A (two 
in this case), with vertical sides and a round top. A space 
is left between the two furnaces as well as between the fur- 
naces and the sides of the boiler; these spaces, shown at a, a, 
are filled with water, and are known as the water leKs- 
From the furnaces, the large flues CyCyC lead to the combus- 
tion chamber, or back connection, B common to both fur- 
naces. Two nests of tubes T' connect the combustion cham- 
ber with the front connection, or uptake, C. It will be noticed 
that the uptake is inside the boiler and surrounded by water 
at the lower end and by steam at the upper end. Such an 
uptake is called a -wet uptake to distinguish it from the 
form of an uptake placed entirely outside of the boiler, and 
known as a dry uptake. Access to the front and back 
connections is provided by means of the doors Z>, D', The 
upper part of the uptake opens directly into the smokestack 5, 
which is provided with a damper F. The steam drum E is 
connected to the shell by the nozzles e,€y as shown. The 
manhole is shown at G. Handholes h,h,h are provided to 



TYPES OF MARINE BOILERS 17 

^ facilitate the cleaning out of the water legs. The boiler is 
supported at the rear by the cast-iron saddle H, lo which 
it is firmly bolted, the saddle in turn being securely attached 

I to the timbers or framing of the bottom of the vessel. The 
front part of the boiler is fastened to a cast-iron frame, 
piown at J. This frame is bolted to the framing, and also 
ferras the asb-pil A', Since the flat sides of the furnaces and 
■hells would bulge on account of the pressure, ihey must be 
braced or stayed; this is accomplished by the screw stays s, s. 
Similar screw stays are employed to connect the combustion 
chamber with the rear head, strengthening them both against 
bulging; this kind of stay is also used between the combus- 

tlion chamber and the outer shell except at the lop. which is 
(trengthened by the girder stays w supported by the sling 
ptays g,q. The top of the furnace is stayed by the toggle 
braces /, /, attached to rings, shown at r,r, made of angle 
iron and riveted to the shell. Toggle braces p are used 
lo stay the flat surfaces of the rear head and of the uptake. 
At A', the steam pipe is attached; at /,, Ihe safety valve; 
the furnace door is shown at P; the grate at M. The 
gases of combustion pass from the furnaces A through the 
flues f to the combustion chamber B, whence they pass 
through ihe lubes T to the front connection C and up the 
smokestack S. As shown in this figure, Ihe water legs only 
extend a Utile below the grate, the ash-pil being formed by 
the frame J. Sometimes there is a water space below the 
ash-pit; that is, the furnace and asb-pit are entirely sur- 

I rounded by water; a boiler constructed in this manner is 
known as a wet- bottomed boiler. The type illustrated in 
Fig. 4 is called a dry- bottomed boiler, 
In the firebox boiler shown, the heating surface is formed 
P^ the inside of the furnaces above the grate, the inside of 
l^e flues c, the sides, top, and bottom of the combustion 
<!bamber, deducting, of course, the spaces taken up by the 
flues cf and the door /?', the inside of the lubes, and ihe 
sides and bottom of the uptake. Only in case of a wet 
uptake is lis surface to be taken as heating surface, and then 
k-onty up lo the water-line. 



18 TYPES OF MARINE BOILERS §9 



FIREBOX TUBULAR BOILERS 

8. Wet-Bottomed Firebox Tubular Boiler. — By 

extending the principle of the flue boiler, that is, reducing 
the size and increasing the number of flues, the tubular 
boiler is evolved. This boiler, which gives a greater heat- 
ing surface than the flue boiler, is constructed in various 
forms, varying chiefly in small details. A pair of -wet- 
bottomed firebox tubular boilers is shown in Fig. 5. 
Boilers of this kind are used to some extent on steamboats 
navigating the Western rivers of the United States of 
America, and in similar service. Fig. 5 («) is a front view 
looking forwards, and Fig. 5 (d) a vertical fore-and-aft sec- 
tion through the starboard boiler. Each boiler is composed 
of two parts, the forward part being cylindrical and the after 
part approximately rectangular with a semicircular top. 
There are two furnaces in each boiler, each furnace having 
its own nest of tubes leading to the front connection A, 
which is common to both furnaces. The steam generated 
in the boilers passes through the nozzles a and d into the 
steam drum B. The main steam pipe is connected at c to 
the steam drum. The auxiliary steam pipes are also con- 
nected to this drum. The water space of both boilers is 
connected by the mud-drum C. In this design, each boiler 
has its own front connection and smokestack, although more 
than one boiler may be connected to one stack. Each boiler 
has its own safety valve, which is attached at d, A manhole 
is shown at / and some handholes at /; these are placed in 
various parts of the boiler to allow it to be examined and 
cleaned. Suitable manholes and handholes are also pro- 
vided for the steam drum and mud-drum. As shown in the 
figure, the furnaces are surrounded entirely by water, hence 
this boiler belongs to the wet-bottomed type. The flat sur- 
faces of the boiler are stayed by the screw stays / and the 
diagonal braces w. The crown sheets of the furnaces are 
stayed by the crown bars o made of T iron, which are riveted 
to the crown sheets by numerous rivets. Distance pieces or 
thimbles are placed between the top of the crown sheet and 





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20 TYPES OF MARINE BOILERS §9 

the bottom of the crown bars. The crown bars are con- 
nected to the top of the boiler by the toggle braces «, which 
are cottered to the crown bars and riveted to the shell. In 
the particular design of boiler shown, a bridge wall E is 
built in each furnace. However, firebox boilers are fre- 
quently built without a bridge wall. The smokestacks are 
supported by the stanchions shown. The boilers are secured 
to the deck by tie-rods, not shown in the illustration. This 
style of boiler being internally fired, there is no elaborate 
setting required for them. 

9. Dry-Bottomed Firebox Tubular Boiler. — Fig. 6 
illustrates a form of a firebox tubular boiler that is con- 
structed with a dry bottom to the ash-pit, and from its 
resemblance to the boiler of a locomotive is often called a 
locomotive boiler. This type of boiler is principally used 
in river and similar service. The boiler consists of two dif- 
ferently shaped parts riveted together. The forward part 
is cylindrical; the cross-section of the after part is rectangu- 
lar with a semicircular top. It has one large furnace, which 
is surrounded by water on the sides and top, but open at the 
bottom, thus making it a dry-bottomed boiler. It is pro- 
vided with a steam drum A^ the heads of which in the larger 
sizes are stayed by through stayrods a, a provided with nuts 
on the inside and outside of the heads. The ash-pit is 
entirely separate from the boiler proper, the grate being 
placed at the bottom of the furnace. The flat surfaces of 
the furnace and also the crown sheet are stayed by screw 
stays screwed into the sheets and riveted over. That part 
of the rear head which is not stayed to the furnace plate is 
stayed by diagonal stays by b, similar stays being employed 
for the front head. The bottom of the water legs, as the 
spaces surrounding the furnace are often called, is closed by 
a cast-iron or wrought-iron mud-ring c. The water legs are 
provided with handholes in suitable locations; one of these 
handholes is shown at e. At / a manhole is shown. The 
safety valve is attached at g. The gases of combustion 
traverse a nest of tubes extending from the rear tube sheet 



Hwa 



^^e 



TYPES OF MARINE liOILERS 21 

) the front head, and are discharged into the front connec- 
ion h, whence ihey pass up the stack. The main steam pipe 
% connected to the nozzle / on the side of the steam drum; 
jt curved pipe takes the steam from the lop of the drum. 



SCOTCH BUII.EitS 

Single-Ended Scotcli Boiler. — For seagoing 
vessels a type of internally fired tubular boiler has 
■t>ecn gradually developed that is known commonly as the 
Hcoleh boiler, and is occasionally spoken of as the drum 
tKtller. This type of boiler is used in the service mentioned 
practically to the exclusion of all other types of fire-tube 
ilers, and it is only within recent years that hollers of the 
rater-tube type have to a considerable extent taken its place. 
A sluslc-cnded Scotcli boiler is shown in Fig. 7. By 
ingle-ended is meant that the boiler has furnaces at one end 
mly. It has a cylindrical shell with flat heads. The diam- 
of these boilers may vary from 10 to 15 or even 20 feet; 
le length may vary from 7 to H feet. The boiler is pro- 
led with two, three, or four large corrugated furnace 
les At A. The one shown in the figure has four. The rear 
end of each furnace flue opens into a combustion cliani- 
ber B. Usually each flue has its own combustion chamber, 
but in some cases two or more flues open into a common 
chamber. Nests of tubes 7", 7" extend from the front plate 
of the combustion chamber to the front head of the shell. 
These tubes place the combustion chambers B, B in commu- 
nication with the large smoke chamber E, commonly known 
as the front connection. The upper part of this chamber 
forms the uptake, which in turn leads directly to the smoke- 
stack. The flat heads of the shell are kept from bulging by 
the heavy stayrods R, R, and further by the diagonal braces, 
or palm stays, H.H. About one-third of the tubes (those 
marked with a cross in the figure) are threaded and provided 
with nuts, and thus act as stayrods for the flat surfaces 
lOGcupied by the tubes. The flat sides of the combustion 
ibers are stayed to each other and to the rear head by 



§9 TYPES OF MARINE BOILERS 23 

Ihe staybolts S, S. The flat tops of the combustion cham- 
bers, called the crown slieftn, are strengthened by the 
glriler stays, or (logs, C, C. The manholes M, M give 
access to the various parts of Ihe boiler. The various fit- 
lings are not shown in the figure, but are attached in 
convenient places. The furnaces are placed within the cor- 
rugated flues A, A. As shown, the grate G is made in three 
sections, supported by the cross-bars A'. K. Below the grate 
is the ash-pit D. At the rear end of the grate is placed a 
firebrick plate P for the purpose of preventing cold air from 
sweeping through the ash-pit into the combustion chamber 
without first passing through the grate. The gases arising 
from the combustion of the coal pass into the combustion 
chamber B, where they undergo further combustion in con- 
tact with the air that passes through the grate. The hot 
products of combustion then pass through the tubes to the 
front connection E. and out through the smokestack. The 
flues and tubes are completely surrounded by water; like- 
wise, the combustion chambers. 

11. In Art. 3, it was stated that the heating surface of a 
boiler is the surface that is in contact with the fire or hot 
gases of combustion, the other surface of the plate, etc. 
being in contact with the water. In Fig, 7, the water is 
shown covering the tubes 7". 7" to a depth of several inches. 
Hence, from the foregoing definition, the heating surface of 
a Scotch boiler consists of the following; (1) The part of 
the furnace flues above the grate; (2) the back, sides, and top 
of the combustion chamber; (3) the front plate of the com- 
bustion chamber, known as the back tiilje-sheet; (4) the 
inner surface of the tubes; (5) the part of the front head 
pierced by the tubes, known as the front tube-sheet. As 
the front tube-sheet does not form a very efficient heating 
surface, it is customary not to consider it as such in com- 
puting the healing surface of a boiler. 

12. Uoublo-Kntled St'otch Boiler. — In Fig. 8 is shown 
b section of a iloublo-<>iido(l Scott'li bollt?r. At the left 

I of the figure, the section is taken through one of the 



24 



TYPES OF MARINE BOILERS 



lower flues, and at the right end through one of the upp* 
flues. The furnace flues are placed in each end of tbel 
boiler, the combustion chambers being near the center.j 
Each chamber is connected with the nearest head by a r 
of lubes leading to the uptakes H, II. The flat surfaces ar« 
stayed and braced as just described in the case of the single- 
ended boiler shown in Fig, 7. The process of combustion ■* 
and the path of the gases are the same as for the single- 
ended boiler. The plates P, P prevent air from passing 
from the ash-pit to the combustion chamber. The steam a 
dome, or drum, is attached at D. 




13. It will be observed that a double-ended boiler i 
practically two single-ended boilers with their back 1 
removed and the shells placed back to back and joined, 
avoiding the use of the two back heads, a large saving e 
weight is effected, and the cost of construction is 1< 
Therefore, a double-ended boiler is lighler, cheaper, ; 
occupies somewhat less space in length than two single 
ended boilers of the same aggregate steaming capacity. 

To still furiher lighten double-ended boilers, commonj 
combustion chambers for corresponding furnaces at the twelj 
ends have been used. Such a form of double-ended boilei 



§9 



TYPES OF MARINE BOILERS 



25 



is shown in Fig. 9, The furnace flues are placed in each end 
of the shell, but each opposite pair opens into a common 
combnstion chamber C. Each of these combustion chambers 
has two nests of tubes, one nest connecting it with one head, 
the other nest with the other head. The gases from two 
opposite furnaces mix together in the common combustion 
chamber and then pass through the two nests of tubes, one- 
half to one smoke flue, the other half to the other. In other 
respects, the construction of the boiler is similar to that 
shown in Fig, 8. The steam dome is attached at 5, 




114. Clyde Boiler. — A modification of Ihe Scotch' boiler, 
d, in outward appearance, resembling it. is shown in 
Fig. 10. The difference between the two boilers is in the 
construction of the combustion chambers. In the Scotch 
boiler, the combustion chamber is surrounded by water; 
while, in the boiler shown in Fig. 10. the combustion chamber 
is not surrounded by water and is simply attached to its rear 
^^bead. For this reason, it is often called a dry-buck Scotcli 
^Htoller, although most engineers refer to it as the Clyde 
^nmller. presumably because this type was originally designed 
in the shipyards on the river Clyde. Scotl.ind. The object 
of this modification is to reduce the weight and cost of 




o 




26 



I 



TYPES OF MARINE BOILERS 27 

instruction. It provides a light and inexpensive boiler for 
lall and moderate-size vessels, lugs, and like craft. 
[ A boiler of this type consists of a large cylindrical shell a, 
fihe ends of which are closed by the flat heads i, b. A large 
irnace flue c of the type known technically as the Morlsou 
spension fiirunce flue, extends clear through the boiler 
and is securely riveted to the two heads, which are flanged 
inwards for this purpose. Above and beside the furnace flue, 
and parallel thereto and below the water-line, is a nest of 
tubes li that extend from head to head. The front ends of 
lese tubes open into an uptake e that connects with the 
limney or stack /. The flat heads are stayed by through 
itayrods g.g in the steam space, which prevent deflection of 
the heads. The remaining parts of the flat heads are sup- 
irted by the tubes, which are expanded and beaded over, 
id by the furnace flue. The furnace is placed within the 
'furnace flue, and, as usual, consists of the grate h. the ash- 
and the bridge k. The gases of combustion flow to the 
lar into the combustion chamber / and then pass through 
le tubes to the front and into the uptake. The combustion 
lamber is formed by a thin cylindrical shell attached to the 
:ar end of the boiler, and is lined with firebrick or thick 
ibestos millboard, which is light and is not affected by 
itense heat. The back plate is removable, giving access to 
the rear ends of the tubes. A door /' gives access to the 
combustion chamber for the removal of ashes and soot and 
for the purpose of examination and repair. The feedwater 
enters the boiler at m and. passing through the internal per 
forated feedpipe n, is discharged downwards alongside the 
shell in small streams. The various fittings are not shown 
Id the illustration. The steam gauge and water column 
would naturally be located close to the front end of the boiler; 
the safety valve is intended to be bolted to the outlet o* and 
the steam pipe to the outlet o" of the nozzle o. The steam 
is collected by the dry pipe /, which is perforated with numer- 
ous slots on top. The dry pipe is fairly effective in freeing 
the steam from any water that may be mixed with it. The 
manhole is at q and two handholes at r. The blow-otT is 




TVPES OV MARINE HOILERS 



§3 




attached at s. The boiler 
is entirely self-contained, 
that is, it does not require 
any brickwork setting. It 
is simply bolted to three 
saddles that rest on and 
are fastened to the framing 
of the vessel. 

\5.- Gunboat Bollor. 

A modification of the 
Scotch boiler, made for 
the purpose of providing 
a boiler of small diameter 
that can be placed in gun- 
boats and other small 
light-draught vessels not 
having space enough 
below the deck for the 
regulation Scotch boiler, 
is the i^unboat boUer, 
shown in Fig. 11. The 
peculiarity of this boiler is 
that the tubes, instead of 
being placed above and 
around the furnace flues, 
are placed in the rear and 
in line with them. By this 
arrangement of the parts, 
the boiler is greatly 
reduced in diameter, but 
its length is doubled. The 
reduced diameter enables 
the shell to be made of 
thinner plates. This boiler 
consists of the cylindrical 
shell a with flat heads 6, h. 
The corrugated furnace 




S9 TYPES OF MARINE BOILERS 29 

flues f,e are similar to those used in the ordinary Scotch 
boiler, and. as usual, contain the grates. The combustion 
chamber d is made twice the depth of the combustion cham- 
ber of a Scotch boiler of the same capacity, to compensate 
for its reduced height. The tubes e extend from the rear 
wall of the combustion chamber to the rear head of the 
boiler. The uptake or smokebox (not shown in the illus- 
tration) leading to the smokestack is atiached to the rear 
head of the boiler. The combustion chamber is provided 
with the vertical tapering tubes /",/,/. These connect the 
upper and lower parts of the waler space together, promote 
circulation, add considerably to the heating surface, and 
assist in staying and strengthening the flat top of the com- 
bustion chamber. They are made tapering to enable the 
flange at the lower or smaller end of the tube to be passed 
through the opening in the top sheet of the combustion 
chamber while the boiler is under construction. The taper- 
ing form, with the large end uppermost, also facilitates the 
release and discharge of the steam that is generated within 
the lubes, which are called Giilloway tubes. The heads 
are braced by the tubes e, the furnace flues c, c, the longitu- 
dinal braces g, and the diagonal braces or palm stays li./i. 
The palm stays are made of round bar iron or steel with flat 
pieces welded to them. In some cases, they have a palm / 
at each end, which are riveted to the shell and the head of 
the boiler; in other cases, they have a palm at one end only 
and are threaded at the other end. When they are made in 
this way, the palm end is riveted to the shell of the boiler 
and the threaded end passes through the head, with a nut on 
each side of the plate, as shown at J. The flat top of the 
combustion chamber is braced by the sling stays *. k. The 
sides and bottom of the combustion chamber are secured to 
the shell of the boiler by the staybolts /, /. 






16. Combustion Chambers of Sc-otoli Bollere. — The 

jations of each type of Scotch boiler are usually in their 
combustion chambers, the single-ended variations being 
as follows: (1) each furnace has a separate combustion 



30 TYPES OF MARINE BOILERS §9 

chamber; (2) two or more furnaces have a common com- 
bustion chamber. Double-ended variations are: (1) each 
furnace has a separate combustion chamber; (2) two or more 
furnaces in one end of the boiler have a common combustion 
chamber; (3) two or more furnaces in line with each other 
in opposite ends of the boiler have a common combustion 
chamber. 

The relative merits of each of these variations are still in 
dispute, but practice seems to show that a separate combus- 
tion chamber for each furnace is the best arrangement. The 
separate combustion chamber variation is the one adopted 
by most of the builders of large boilers in the United States 
of America. The advantages of having a separate combustion 
chamber for each furnace are: (1) the circulation of the 
water is much improved, and the boiler, in consequence, is 
kept at a more uniform temperature; (2) repairing and over- 
hauling can be performed more easily in the separate nests 
of tubes; (3) if forced draft is used, it is more efficient and 
better combustion is insured; (4) working on one fire does 
not cool down the others or interfere with the draft; (5) the 
boiler is stronger when made from this design than if the 
combustion chamber is common to several furnaces. 
h About the only disadvantages of this method of construc- 
tion are that the boiler is heavier and costs more to build. 



VERTICAL MARINE BOILERS 

17. Purpose. — Although vertical boilers are becom- 
ing obsolete for marine purposes, there are still many of 
them in use in steam launches, and in larger vessels as 
auxiliary or donkey boilers. They are not economical in 
the use of fuel, as, on account of the short passage of the 
gases of combustion from the furnace to the stack, a con- 
siderable amount of the heat of combustion escapes up the 
smokestack and is lost. These boilers are, however, gener- 
ally made in small sizes, in which economy of fuel is not 
of so much importance as in larger boilers. Unless they are 
built very low, they are top heavy, which raises the center 



§9 



TYPES OF MARINE BOILERS 



31 



of gravity of small craft, making them unstable. On the 
other hand, they should not be too low, else the tubes will 
be too short and the passage of the gases from furnace to 
smokestack will be reduced to such an extent that most of 
the heat will go up the smokestack. In the latter case, 
spiral baffles placed in the tubes will improve matters some- 
what. Vertical boilers answer very well as donkey boilers 
in mo derate- sized vessels. They occupy very little floor 
space, and it is usually not a difficult matter to find a place for 
them in almost any vessel, either in the fireroom or on deck. 
As donkey boilers are used only when there is no steam on 
the main boilers, their duration of service is usually short; 
therefore, the little extra coal they burn does not amount to 
much. Vertical boilers that 
are intended to be used as 
donkey boilers on board 
ship need not be built as 
low as those for launches: 
consequently, the tubes may 
be longer, by which a higher 
efficiency is obtained. 

There are two types of 
vertical boilers, designated 
as the flush-lube boiler and 
■ the submerged-lube boiler. 

H 18. Construction.— A 
'vertical section of a riusli- 

tube boiler is shown in 

Fig. 12. It will be observed 

that the upper ends of the 

tubes a. a project above the 

water-line b and are s 

rounded by steam, while all Pio. n 

the remaining parts of the tubes are surrounded by water. 

If the fire is forced, there is some danger of overheating the 

upper ends of the tubes, but under moderate steaming they 

have a tendency to dry the steam. 





32 TYPES OF MARINE BOILERS §9 

19. A siilimet-tct^'il-tiibe boiler is illustrated in Fig. 13, 
The shell a, the firebox b, and the uptake c are shown in sec- 
tion. The water-line is 
about at the center of 
the uptake; therefore, 
all the tubes d are en- 
tirely covered by water. 
This obviates the 
danger of burning the 
upper ends of the tubes. 
The firebox and uptake 
are secured to the shell 
by a large number of 
socket staybolts e,f, 
etc., and the heads are 
braced by the diagonal 
braces f,f. Hand- 
holes g;g are provided 
for the purpose of clean- 
ing mud and sediment 
out of the water space 
of the boiler, but the 
tubes are not readily 
accessible for scaling. 
Therefore, pure feedwater should be used in these boilers. 



WATER-TUBB BOIIiERS 



CI-ASSIFICATION 

20. There is such a variety of water-tube boilers on the 
market that it is difficult to rigidly classify them. Nearly 
every conceivable aggregation and arrangement of tubes and 
pipes have been employed to produce water-tube boilers; 
thus, considerably over two hundred styles of this type of 
boiler have been approved up to 1903 by the Board of United 
States Supervising Inspectors of Steam Vessels, and author- 
ized to be installed on vessels plying on United States waters. 




§9 TVPES OF MARINE BOILERS 33 

In general, the different varieties of water-tube boilers are 
designated by the size and arrangement of their lubes or 
pipes, namely: straight-tube and bent-tube boilers; large- 
tube and small-tube boilers; horizontal-tube, vertical-tube, 
and inclined-tube boilers; pipe and coil boilers, There is 
also another designation known as sectional and non-sec- 
lional boilers. There are also various combinations of the 
above-mentioned types forming other types, but they all 
follow the same general principle of the water circulating 
through the tubes and the products of combustion surround- 
ing thera. For the sake of convenience, the boilers described 
have been divided into straight-tube, bent-tube, and sectional 
pipe boilers. The boilers illustrated have been selected as 
illustrating to the best advantage the salient features of each 
type; the fact of their being described is not intended to prove 
them superior to others on the market, nor is the omission 
of other boilers to be construed as a mark of inferiority on 
their part. 



fc 



IIT-TDHE BOILERS 

21. Babcock & Wlleox Bollor.— A boiler of the large 
■aighl-tube type is illustrated in Fig. 14. From the name 
of the firm manufacturing it, it is known as the Babcock & 
Wilcox luarliic bollpr. As illustrated, the principal pres- 
sure parts are the steam and water drum a, the front headers b, 
the rear headers c, ihe generating tubes d,d, the horizontal 
connecting tubes e, and Ihe cross-boxes (,g. The upper ends 
of the front headers are connected to the steam and water 
dmm by nipples, one of which is shown at h. and the lower 
ends are connected with the forged steel cross-box g by short 
nipples, one of which is shown at /. The upper ends of the 
rear headers are connected to the forged-steel cross-box / by 
nipples. The tubes d.d forming the heating surface are 
arranged in vertical sections, and. to insure a continuous cir- 
culation in one direction, are placed on an inclination of 15° 
with the horizontal. As shown in Fig. 1.5, the two forged- 
ijeel headers a,b and the tubes e,c connecting the headers 
:ether constitute one section. A number of these sections 



34 



TYPES OF MARINE BOILERS 



%i 



placed side by side form a boiler. The sections are in com- 
munication with one another through the cross-boxes f.gi 
Fig. 14, and the drum a. The tubes of each section a« 
expanded at their ends into the headers, which, being sinuoiu 
in form, permit the tubes to be placed staggered. The ctuv 
rents of hot gases are therefore completely broken up in their 




passage across the heating surface, and the too free esc^ 
of the products of combustion is also prevented. By dividioj 
the heating surface into sectional elements, the injurious 
effects of unequal expansion cfue to raising steam quickly, or 
unequal contraction caused by sudden cooling, are obvi- 
ated, each element being thus free to expand and coatrac| 



U 




TYPES OF MARINE BOILERS 



independently of the others. The side sections are continued 
down to the level of the grate, the tubes being replaced by 
forged-steel boxes of square cross-section at the sides of the 
furnaces. These boxes are placed one above the other at the 
same angle as the tubes; they take the place of brickwork, 
insure a cool side casing, prevent the adherence of clinkers, 
and are of sufficient thickness to withstand the wear and tear 
of the firing tools. 
The square boxes are 
technically called 
water-tube sides, and are 
shown at j\j. Fig. 14. 
As mentioned before. 
the upper end of each 
front header is directly 
connected with the 
drum, white the upper 
end of each rear header 
is first connected lo the 
cross-box / and then to 
the drum by a horizon- 
tal tube e; hence, each 
section is provided 
with an independent 

Mnlet and outlet for 

Jpater and steam. 

Pt The cross-box ^ is 
located at the lowest 
part of the bank of 
tubes and forms a mud- 
drum for the collection of sediment; the boiler may also be 
drained through it. All tubes are constructed of seamless 
steel and are extra heavy. The generating tubes d.d are 
2 inches outside diameter. Opposite the ends of the tubes 
are openings, or handholes d.d. Fig. 15, in the headers 
through which the tubes may be examined, cleaned, plugged, 
r renewed. In some cases, the handholes are 4 inches in 
meter, and they are closed by forged-steel plates into 




36 TYPES OF MARINE BOILERS §9 

which are riveted 1-inch studs. These plates are faced, and 
are drawn to faced seats by forged-steel bridges and nuts, 
the joints being made on the inside of the header, by means 
of thin gaskets. When the 4-inch handhole is adopted, a 
group of four of the 2-inch generating tubes may be taken 
care of through one handhole. In other cases, as shown 
at k, ky Fig. 14, each tube is provided with a separate 
opening in the header just large enough in the clear for 
the tube to be passed through. These holes are closed with 
screw plugs. Should a tube be found defective, it may be 
renewed or plugged, as both ends are accessible. 

The lower row of the bank of generating tubes generally 
consists of 4-inch tubes / instead of groups of four 2-inch 
tubes.* The upper tubes m of the water-tube furnace sides 
are also 4-inch. The boiler is enclosed in a sheet-metal casing 
lined with some refractory non-heat-conducting substance 
such as asbestos, magnesia, etc. Openings are made in the 
casing for the front and rear tube doors o and /, Fig. 14, 
respectively, which provide access to the ends of the tubes. 
One of the furnace doors is shown at ^, in this case under- 
neath the lower end of the bank of tubes and cross-box^. 

The location of the steam and water drum is at the front 
of the boiler immediately overhead. Vertical baffles r, r, in 
connection with the roof s of light fire-tiles placed on the 
lower row of tubes, compel the gases to follow the circuitous 
route shown, crossing the heating surface three times before 
their exit, thus causing them to impart the greatest possible 
amount of their heat to the water in the tubes. 

As the furnace increases in height as it approaches the 
firebrick bridge wall /, a combustion chamber of ample size 
is thereby provided, and the gases have both space and time 
in which to thoroughly mix and bum before entering the 
spaces between the tubes. The gases evolved from the 
combustion of the fuel are compelled to flow toward the rear 
of the furnace by the roof s of fire-tiles, which causes them 
to pass over the incandescent bed of coal and under the hot 
tile roof. By this arrangement, a high furnace temperature 
is maintained, which is an essential requirement of boiler 



38 TYPES OF MARINE BOILERS §9 

economy. The distance traveled by the products of com- 
bustion in contact with the heating surface is about 16 feet; 
hence, good economy is maintained with high rates of com- 
bustion, and a low uptake temperature is assured. 

The location of the drum in front of the boiler renders all 
valves and fittings accessible and tends to shorten steam- 
pipe connections. The main stop-valve and safety valves, 
feed stop-valve and feed check-valve for both main and 
auxiliary feeds, and the glass water gauges are flanged 
directly to nozzles provided with counterbored seats and 
fastened to the drum shell or heads. 

A perspective exterior view of a Babcock & Wilcox boiler, 
with one pair of tube doors and part of the side casing 
removed, is given in Fig. 16. The boiler here illustrated 
differs in some minor details of construction from that shown 
in Fig. 14, but serves to show the general appearance. 

22. The operation of the boiler is as follows: The boiler 
being filled with water until ih6 steam and water drum is 
half full, the fires are then started. The water in the 
inclined tubes becomes heated first, owing to the tubes 
being exposed to the most intense heat of the fire; it then 
expands and flows up to and through the rear headers and 
through the horizontal tubes into the drum. Cooler water 
flows from the bottom of the drum into the front headers 
and also into the cross-box £-, Fig. 14, which acts as the 
mud-drum. This water, in turn, becomes heated and flows 
up the inclined tubes as before, circulation being thus main- 
tained. On entering the drum, the steam and circulating 
water are directed against the baffle plate «, which causes 
the water to be thrown downwards, while the steam is 
liberated from the water and passes around the ends of the 
baffle plate to the steam space. To insure dry steam, a dry 
pipe V is fitted inside of the drum; it is suspended in the 
upper part of the drum by hangers. The main and auxiliary 
steam pipes take steam through this dry pipe. 

Zinc slabs w, w are suspended in the steam and water 
drum just below the water level to arrest corrosion caused 



§9 TYPES OF MARINE BOILERS 39 

by galvanic action. The pan x is placed underneath the 
slabs to catch the pieces of zinc that fall from the slabs 
when they disintegrate by the action of the galvanic current. 
The surface blow-off pipe is attached to the lower part of one 
of the drum heads; it extends inwards for a short distance 
and then bends upwards, as shown at j-, where it terminates 
in the scum pan z, which collects the scutn and other foreign 
matter floating on the surface of the water and allows it to 
be blown out through the surface blow-off pipe. 



23. See Boiler. — A boiler of the straight inclined-tube 
type, which differs considerably from the Babcock & Wilcox 
boiler, is shown in Fig. 17. It is known, from the name of 
its designer, as the See bollei-. The boiler consists of the 
steam drum a, the two water or mud-drums d, b and the two 
I nests of tubes c,c. This illustration shows only the pressure 




Its without the casing. Like all boilers of this class, it 
tas a large heating surface and makes steam rapidly. The 

tabes, being straight and accessible, can be cleaned of scale — 

a most important feature in any boiler. 
A sectional view of the mud-drum, showing its method of 
instruction, is given in Fig. 18, and an exterior view of the 




40 



TYPES OF MARINE BOILERS 



§91 



complete boiler is given in Fig. 19, An imporlant feature 
of this boiler is that the weight of the steam-generating part, 
cont)ibting of the drums and tubes, 
IS supported from the steam 
\ drum and not on the mud-drums, 
is the usual custom with boilers 
of this type. This permits the 
tubes to expand and contract freely 
without bringing undue strain on 
them. The mud-dnims are kept 
spreading by the hinged brackets a, a, Fig. 19. The 




I 



from ! 




safety valve ^, gauge glass c, and steam gauge d are attached 
to ibe front end of the steam drum. 



§9 TYPES OF MARINE BOILERS 41 

The operation of the boiler is as follows: It is filled with 
water lo about the middle of the steam drum, and the fire is 
started. The inside tubes of each nest being most exposed 
to the intense heat of the fire, the water in them expands 
and rises to the steam drum. The outside tubes being 
located in a relatively cool place, water flows down them 
to the mud-drums to take the place of that flowing up the 
inside tubes. A steady and rapid circulation of the water is 
ihus established, 

^ BENT-TUBE BOILERS 

24. Seabnry Boiler. — The boiler shown in Fig, 20 is 
an example of the bent-tube type, and belongs to the class 
having but one bend in each tube, as shown. It is known 
as the Senbury boiler, and is applicable to yachts, torpedo 
boats, and other small craft. This boiler has large grate 
and heating surfaces for its size and weight, and makes 
steam rapidly when clean. 

Its essential features are the steam drum o, the water 
drums b. b, and the tubes c In common with all boilers of 
this class, the tubes connect the steam drums and water 
drums together and afford passages for the water to circulate. 
The water drums are semicircular in section, the tube-sheet a. 
Fig. 21. forming the flat side of the drum. The curved 
part b of ihe drum is made by welding a head in each end of 
a piece of lap-welded iron or steel pipe, dividing it into 
halves through the center lengthwise and planing the 
edges c,e to fit the grooves e,e in the under side of the 
tube-sheet. The joint is made tight by placing asbestos 
gaskets in the grooves e.e. The curved part of the drum is 
held in place by straps / and screw bolts g. The heads of 
bolts are countersunk on the top side of the tube sheet, 
Wliich makes a flush surface, so that ashes, etc, may be easily 
cleaned off. The bolts are provided with cap nuts h.A that 
protect Ihe threads from corrosion. The straps and bolts 
are also shown at i/and e. Fig. 20. The boiler is supported 
by the tube-sheets of the water drums resting on the angle 
', which are bolted to the bunker bulkheads k, k. 



TYPES OP MARINE BOILERS 



43 



Pig. 20. The tubes are expanded into the steiim drum and 
[linto the tube-sheets of the water drums. The front head of 
|. the steara drum is provided with a manhole to give access 
to the interior for examination, cleaning, and repairs. In 
the small sizes of boilers, the steam drums are made of steel 
pipe, and the heads are bolted on at each end. Each water 

tdnim has a handhole in its front head. A feedwater heater 
or economizer is located in the uptake, through which heater 
Ihe feedwater passes before entering the steam-generating 
part of the boiler, whereby considerable heat is saved that 




would otherwise be lost through the smokestack. This 
apparatus consists of a bank of lap-welded iron pipe and 
and malleable-iron return bends. It is shown at /. Fig. 20. 
Firebrick bafRe plates, one of which is shown at w, are 
placed over the inner row of tubes for the purpose of direct- 
ing the flow of the hot gases of combustion amongst the 
lower ends of the tubes. When the fire is burning fiercely, 
the firebricks become very hot, and the heat thus absorbed 
is given off again when the furnace is cooled down by 
— pntting fresh coal on the fire. 

25, The circulation of the water in this boiler is accom- 
Kplisfaed in the following manner: The boiler being filled 
■ with water up to the center of the steam drum, the lire is 



44 TYPES OF MARINE BOILERS §9 

lighted. The hot gases of combustion will come in contact 
with the inner row of tubes first, which will cause in those 
tubes an upward movement of the water toward the steam 
drum. As the heat increases, the water in the other tubes 
will be affected in a similar manner and will also rise to the 
steam drum. By the time the hot gases have reached the 
outer row of tubes, they have surrendered a large part of 
their heat to the water in those tubes with which they have 
been in contact; consequently, the outer row of tubes will be 
much cooler than the others. The rapid upward movement of 
the mixed water and steam in the hotter tubes causes the solid 
water to flow into the lower end of those tubes from the 
water drums, and, necessarily, the cooler water must flow 
down through the outer row of tubes from the steam drum 
to supply the place of that which has been taken from the 
water drums. Thus, a continuous circulation is maintained. 

26, The tubes have sufficient bend to enable them to 
expand and contract without distortion or straining the joints 
at their ends. Perforated steam pipes, with the openings 
opposite the spaces between the tubes and pointing across 
the tube-sheets and upwards amongst the tubes, are placed 
between the outer row of tubes and the casing for blowing 
the soot and ashes oft the tube-sheets and lower ends of the 
tubes. These can be put into operation at any time, even 
while steaming. The feedwater heater and the upper parts 
of the tubes can be cleaned of soot by inserting the per- 
forated nozzle of a steam hose through properly located 
doors provided for this purpose in the casing. This is a very 
valuable feature, as it renders it possible to keep the heating 
surface clean at all times. Although it is possible to clean 
the insides of the tubes by removing the lower parts of the 
water drums and passing a chain with a wire brush attached 
through each tube from the steam drum, it is by no means 
an easy operation and it is hence preferable to use pure 
feedwater in this boiler and also in all other boilers of the 
bent- tube type, and thereby keep the impurities out of 
them entirely. 



46 TYPES OF MARINE BOILERS §9 

27, Mississippi Boiler. — A boiler of the bent-tube type 
in which each tube has several bends, and belon^g to a 
class of which there are numerous examples in existence, is 
the Mississippi boiler, shown in Fig. 22. In order to 
show the construction clearly, the boiler is shown in several 
stages of its erection, Fig. 22 (a) showing one set of gen- 
erating tubes in position; Fig. 22 (^), two sets; Fig. 22 (c), 
all the tubes; and Fig. 22 (d), the boiler completed. It is 
principally adapted for yachts, torpedo boats, and small 
craft generally, and is a rapid steam generator that will 
stand considerable forcing without distortion, as the tubes 
are so crooked to begin with that a little more bending will 
do no harm. Like all boilers of this class, the generating 
tubes connect the steam drum with the water drums and 
provide an upward passage for the water and steam. 

Referring to Fig. 22 (a), a is the steam drum, d,d are the 
water drums, and r, c are the downtake pipes for returning 
the water from the steam drums to the water drums, thereby 
maintaining a constant circulation. These elements form 
the framework of the boiler. The ends of the tubes are 
secured to the steam drums and water drums by right-and- 
left threaded steel bushings, as it will be observed that the 
drums are too small for a man to enter to expand the tubes 
in the ordinary way. 

By referring to Fig. 22 (^), it will be seen that the down- 
flow pipes are located outside of the casing, and hence are 
comparatively cool, as they are not exposed to the radiant 
heat of the fire. The circulation of the water is upwards 
from the mud-drums in all the generating tubes; water from 
the steam drum flows downwards through the large and cool 
down-flow pipes to the mud-drums to take the place of that 
ascending in the generating tubes. 



SECTIONAL. PIPE BOILERS 

28. Roberts Boiler. — Boilers made up of pipe and the 
usual forms of pipe fittings, with all or most joints made 
with screw threads, are generally classified as pipe boilers 



48 



TYPES OF MARINE BOILERS 



and are usually sectional, that is, the generating tubes 
separate sets or sections. The Roberts boiler, shown id 
Pig. 23, belongs to this class, and has a combination of 
vertical and slightly inclined horizontal generating tubes. 
Although the tubes are straight, it cannot be classed as a 
strictly straight-tube boiler, because the straight sections of 
pipe are connected together by elbows, thus preventing 
access to the interior of the tubes for cleaning; hence, pure 
water only should be used in this boiler, as otherwise the 
tubes will soon become coated with scale, greatly diminishiug 
its efficiency and shortening its period of usefulness. 
The construction of the boiler is as follows: A cyli 
steam drum W forms a receptacle for a small body of water, 
the space above the water forming the steam space; it is 
made of a steel or iron plate, and closed by tlanged heads 
riveted to the shell, having the heads stayed by the stayrods 
shown at m. Two side pipes B (only one is shown in the 
figure) are connected to the front and back of the steam drum 
by means of the down-flow pipes C, C, the angular down-flow 
pipes B' , and the cross-pipes B. It will be noticed that on 
each of the T's ZJ.ZJ is a flange, to which are bolted the 
angle irons carrying the jacke| G, G. A plate, on which the 
ends of the grate bars A', as well as the firebrick lining L', 
are supported, extends across the furnace in the front and 
rear, the plates being bolted to the flanges of the bottom T's. 
The grate is composed of two lengths of grate bars, whidi' 
are held up at the center of the furnace by the bearing 
bars x,x, which in turn are supported by studs screwed into 
the bottom of the side pipes. The firebrick lining L rests 
on the side pipes. Connected to the lop of the side pipes 
are the up-flow coils c and (/; only two are shown in full, the 
rest being shown broken off; they start alternately from the 
right and left side pipes. These coils are composed of pipes 
and return bends, with the return bends tapped "on a spread"; 
that is, so as to give all the pipes an upward inclination. 
This is shown in the front elevation, which also shows ate* 
the point at which the up-ilow coil c enters the steam drum. 
The coil (I enters the steam drum at a similar point at the 



ine _ 

can 

;er, ■ 
s 
s 
s 

e 

n 

a 

^1 




§9 TYPES OF MARINE BOILERS 49 

opposite side. Two feed-coils h,v are placed one on each 
side of the drum, and are supported on the small pipes p,o. 
Superheating coils »,»' are placed one on each side of the 
furnace, outside of the up-flow coils. The boiler is enclosed 
at the four sides and the top by a sheet-iron jacket G, G, 
lined with some non-heat-conducting material. An opening 
is provided in the top of the jacket, through which the smoke- 
stack y comiects with the space inside the jacket forming the 
combustion chamber, the space directly over the grate X 
being the furnace. At IV, the water column, mounted with 
a glass water gauge and three gauge-cocks, is shown. The 
steam gauge is shown at S, the furnace door at A', and the 
ash-pit al V. 

The feedwater enters at s, and is divided into two streams 
by a partition cast with the T's. One stream passes through 
the pipe r into the feed-coil k; the second stream passes 
through a similar pipe into the feed-coil v. The feedwater 
is heated to a high temperature before leaving the coils. 
On leaving them, the water passing through the coil « enters 
the steam drum at w', and the water passing through v 
enters at w. In operation, the entering feedwater is dis- 
charged above the water-line to allow the steam that may 
have formed in the feed-coils to rise to the top of the drum. 
and the water to fall to the water level. The horizontal 
layers of the feed-coils are separated by cross-pipes e, which 
are placed there to prevent sagging of the free ends of each 
layer of pipe composing the coils. In order to show the 
coil It more clearly, these cross-pipes have been omitted in 
the front view. There is no water in these cross-pipes. 



29. The boiler being filled with water until the steam 
drum is about one-cjuarter full vertically, and the fire started. 
the water expands and becomes lighter much faster in the 
up-flow coils c, (/ than in the down-flow pipes C, C; this is due 
both to the fact of the small pipes absorbing a greater 
amount of heat, owing to their being directly over the fire, 
and also to their being of a smaller diameter, because there 
is more heating surface for a given volume of water in the 



50 TYPES OF MARINE BOILERS 31 

pipes. The result is that the water at once commences UN 
rise in the small up-flow coils and to fall in the large dowiu 
flow pipes. As soon as steam bubbles commence to formJ 
this movement of the water becomes more rapid, as wated 
holding these bubbles is much lighter than solid water, evem 
if their temperatures are the same. To assist the upward flo«| 
of the water, the pipes c, d are given an upward inclinatioa. 
The up-flow coils now begin to throw currents of water 
mixed with steam bubbles into the drum. The steam bubbles 
break, the steam rises to the top of the drum, and the solid 
water flows out of each end into the cross-pipes leading to 
the down-flow pipes. The lower pari of the bottom 1 D oi 
each down-flow pipe forms a mud, or sediment, pocket; thai 
is. it provides a quiet place for the deposit of foreign matter 
held in suspension in the feedwater. This deposit may be 
drawn off by means of the cocks g,g. Just above the mud- 
pockets, the downward currents make a turn at riuht anglei 
into the side pipes, part of the water flowing inlo the up-flo»^ 
coils as it passes along underneath them. The two currenli 
one from each end of each side pipe, meet in the center 
the side pipes and there form an eddy, the only non-circula- 
ting water in the boiler excepting that in the mud-pockets. 
The steam at the top of the drum passes into a spray pipe, 
or dry pipe, a. running from one head to the other, and 
drilled full of small holes on top for about half its length in 
the center. By locating the holes near the center, no wateCi 
can enter the dry pipe when the vessel is pitching. Thol 
superheating coil n' is connected to one end of the dry pipe 
by the pipe b', and the superheating coil w to the other end by 
the pipe b. The steam flows inlo Ihe lop of ihe coils and 
passes downwards to Ihe bottom, rising upwards again 
within the pipes i.j that unite at k, whence the steam passes. 
into the pipe /. To the upper end of this pipe a T is attached, 
to one outlet of which the safety valve is fitted, while to Ihe 
other outlet the steam pipe leading Ihe steam to the engine 
is connected. These connections, for want of room, are not 
shown. The superheating coils «, «' answer the double pur- 
pose of drying the steam and of protecting the jacket from 



oe 
id- 

i 

I 

1 




TYPES OF MARINE BOILERS 



51 



■brai 



the action of the fire. The object of the angular down-flow 
pipes B' is to prevent any part of the down-flow system (the 
pipes B.B'.C) from being thrown above the water-line by 
a listing o! the vessel, which would greatly interfere with 
the circulation. 

30. The Roberts boiler is an example of one of the two 
general types into which water-tube boilers are sometimes 
divided, viz., drowned-ttibe boilers, or boilers in which the 
upper ends of the tubes are submerged in water, and dry-tube 
boilers, or boilers in which the upper ends of the tubes are 
filled with steam only, or such water as is carried up by the 
violent ebullition of the water within the lower part of the 
tubes. From the construction of the Roberts boiler, it 
follows that it belongs to the drowued-tobe type. 

31. Alniy Boiler. — An example of the dry-tube sec- 
loal-pipe boiler is shown in Fig. 24. It is composed of 

ight pipes, part of them being nearly horizontal and part 
of them vertical, and connected together by elbows, return 
bends, and Y fittings. From its designer, it is known as the 
Alnty boiler. The interior of the tubes are inaccessible 
for cleaning; hence, pure feedwater only should be used in 
it, as well as in all pipe and bent-tube boilers. 

The construction of the boiler is as follows: A continuous 
manifold c, which forms the base of the boiler, extends along 
the sides and across the back of the boiler. At the lop is a 
similar manifold a, which extends along the sides and across 
the front of the boiler. To form the heating surface, a series 
of up-flow coils 0,i/, made up of pipes connected together 
by elbows, return bends, and four-way Y fittings, are con- 
nected to the top and bottom manifolds and with each other 
by means of unions. The coils D at the sides of the boiler 
rise from the manifold to a proper height to form the top of 
the furnace: they then extend half way across the furnace 
and return to the sides; thence up. connecting to the side 
pipes of the top manifold a. The coils d that form the back 
furnace rise from the back manifold to a heighl sufE- 
it to cross over above and at a right angle tu those forming 




^9 TYPES OF MARINE ItOlLERS 53 

the top of the furnace; Ihey then pass to the front and connect 
to the manifold extending across the front at the top. A 
feed-coil E, serving to heat the feedwater. and consisting of 
two layers of pipe connected together by return bends, thus 
forming a continuous pipe, rests on the top manifold. The 
feedwater enters this coil at v, and after passing through, 
leaves it by means of the pipe q connected to the bottom of 
the horizontal water reservoir C, which extends across the 
front of the boiler. The top manifold a is attached by means 
of the nozzle g to the vertical separator F placed on top of 
the horizontal water reservoir. A jacket /, /, lined on the 
inside with some non-heat-conducting material, encloses the 
boiler on the four sides and at the top. To the ring H, on 
top of the jacket, the smokestack is attached. The grate is 
composed of square iron bars o, a that are supported by the 
bearing bars f>,/>. To prevent any entrance of air to the 
furnace, otherwise than through the grate, bafHe plates s 
extend around the sides and back of the furnace. At the 
front, the dead plate s serves the same purpose. The boiler 
is provided with a water column IV. mounted with a glass 
water gauge and three gauge-cocks, and which also carries 
the steam gauge 5. At .-/, the furnace door is shown. /J. B 
are doors in the jacket to allow inspection, etc. of the inside, 
and K is the ash-pit. In the center of the bottom back mani- 
fold, a mud or sediment pocket b is located, whence the sedi- 
ment may be drawn off or the boiler emptied through the 
pipe i. Both the separator and the water reservoir, as well 
as the down-flow pipes G, G, which are connected to the water 
reser\'oir and extend down to the manifold at each side of 
the furnace, are outside the jacket, and hence in a cool place. 

32. The operation of the boiler is as follows: The boiler 
being filled with water until the reservoir C is about half full 
vertically, the fire is started. The water in the coils D,d 
expanding, and hence becoming lighter, rises to the top 
manifold, carrying the steam bubbles with it; cooler water, 
coming from the reservoir C through the down-flow pipes C, 
constantly takes its place, and in turn becomes heated and 





54 TYPES OP MARINE BOILERS §9 

rises. On reachins: the top manifold, the steam babbles 
burst, the steam and entrained water rising to the top; the 
water thrown into the top manifold by the violent ebollition 
within the tubes, after flowing: alon^ the bottom, falls through 
the opening r in the horizontal water reservoir to the water 
level. The steam and entrained water pass into the sepa- 
rator /% where, by curved partitions, the steam is con- 
strained to move in a spiral path; that is, it passes from g 
into j\ thence into r, thence into the passage /, whence it 
passes into / and out of the separator at », entering there the 
bottom of the steam pipe k. By giving the steam a whirling 
motion, the particles of entrained water are, by the action 
of centrifugal force, thrown against the curved partitions; the 
water drips down these partitions and flows back into the 
reservoir C through an opening in the base of the separator 
(not shown in the figure) and through the holes shown at /. 
To the top of the T shown at iw , the safety valve is attached. 



COMPARISONS 



ADVANTAGES AND DISADVANTAGES OF SCOTCH BOILARS 

33. Until recent years, the Scotch boiler has been 
installed almost universally in ocean-going steam vessels of 
the world, both in the merchant service and in the various 
navies. For numerous reasons, it has been the most efficient 
marine boiler in use up to a recent period, and, although it 
has been superseded by the water-tube boiler on the larger 
high-speed vessels of the merchant service and navies, it 
still continues to be the favorite boiler for other vessels. 
The principal meritorious features of this boiler are as fol- 
lows: It is durable under rough usage, and easy to take 
care of and repair. The tubes being straight and of standard 
sizes, they can be procured in any port of commercial con- 
sequence in the world. Being straight, the tubes can easily 
be cleaned of soot, and while steaming if necessary. A 
leaky tube can be plugged without blowing oflE the pressure 



§9 TYPES OF MARINE BOILERS 55 

from the boiler, and a new lube can be put in easily: to do 
this however, the boiler, of course, must be blown down to 
a point below the defective tube. The evaporation results, 
that is, the number of pounds of water evaporated per pound 
of coal, are satisfactory, and experience has shown that it is 
no more liable to leakage than other shell boilers. 

B 34. The Scotch boiler possesses serious disadvantages, 
Ramely: 

1. Excessive Weight. — Thus, a modern eight-furnace 
double-ended boiler suitable to generate steam for a 3.300- 
horsepower engine will weigh, when filled, about 110 tons. 
A water-tube boiler of the same capacity and of a heavy type 
will weigh only about 80 tons; and if of light type running 
under forced draft, as low as .'iO tons. 

2. Limit of Pressure Caused by Conslruclive /Reasons. — This 
limit, for large boilers, may be placed in the neighborhood 
of 200 pounds per square inch, when the shell plates become 
so thick as to present serious difficulties in their working 
and handling. 

3. Bad Effects of Unequal Expansion and Contraction. 
Owing to the rapid expansion of those parts of a Scotch 
boiler that are directly in contact with the burning gases — 
notably the furnace flues and combustion chambers — and the 
comparatively slow expansion of the other parts, great 
strains occur between the hot and cooler parts that will 
sooner or later entirely destroy the boiler if precautions are 
not taken to prevent it by heating the boiler up very slowly 
and gradually in order to equalize the expansion as much 
as possible. This requires considerable time, from 4 to 
10 hours, the latter, and even more time being preferable, 
and the same length of time should be allowed the boiler to 
cool down; otherwise, contraction will act on them in a 
similar manner to unequal expansion. This loss of time 
in getting up sieara and cooling down is a serious detriment 
to vessels in which the exigencies of their service frequently 

^demand a rapid getting under way or short stays in port. 





56 TYPES OF MARINE BOILERS §9 



COMPARISON OF WATER-TUBE BOILER TYPES 

35. Second in importance only to having a boiler strong 
enough to stand the pressure of steam carried, is its accessi- 
bility for cleaning and repairs. A water-tube boiler may 
produce most excellent results as a steam generator when 
new and clean both inside and outside, but if it cannot be 
cleaned and repaired its high efficiency will be of short 
duration. Unless pure feed water is used, scale will soon 
form on the inside of the tubes, which will retard the heat of 
combustion entering the water, and some of it will go up the 
smokestack instead. Thick scale on the inside of a tube 
and a coating of soot on the outside renders the tube nearly 
valueless as a heat transmitter, and if these deposits cannot 
be removed, the boiler will in a short time become of very 
little use as a steam generator. 

The claim is made that the circulation of water in a water- 
tube boiler is so rapid that the impurities in the water are 
swept through the tubes so quickly that they have not time 
to adhere to the tubes. While this is true so far as the mud 
and other foreign matter held in mechanical suspension in 
the water is concerned, it does not hold good in regard to 
the impurities held in solution by the water, which are 
precipitated by the heat and adhere very tenaciously to the 
hot metal of the tubes. 

Manifestly, then, the water-tube boiler that can most easily 
be cleaned and repaired, other things being equal, is the 
best boiler. 

36. Straight-tube boilers possess some advantages over 
bent-tube boilers. The most important one is that, if the 
tubes are properly arranged, a scaling tool can be passed 
through them and the scale removed, which cannot be done 
with most bent-tube boilers under any circumstances. 
Another advantage is that it is comparatively an easy job to 
cut out a defective tube and replace it with a new one in a 
straight-tube boiler, whereas in most of those of the bent- 
tube type, a faulty tube, especially if it is in one of the inner 



§9 TYPES OF MARINE BOILERS 57 

rows of a nest of tubes, as it is very apt to be, is very diffi- 
cult of access, and it is usually necessary to cut out a num- 
ber of sound tubes to reach the one that is defective. 
Again, the straight tube provides a more direct passage for 
the circulation of the water and with less friction. Yet 
another important advantage in favor of the straight tubes 
is that they are of standard sizes and do not have to be bent 
into special shapes by special machines; hence, they can be 
obtained in any commercial port in the world, and as every 
lube will fit into any pair of holes opposite each other, they 
are interchangeable, and a large number of differently shaped 
tubes will not have to be carried, as would be the case with 
bent-tube boilers. 

Bent-tube boilers are usually more compact and lighter 
ihan the straight-tube type for the space occupied; hence, 
Ihey are almost indispensable for torpedo boats and racing 
yachts, where lightness and compactness are of primary 
importance, and a very high speed must be maintained for 
a limited time even if it results in the ruination of the boiler. 
Moreover, bent tubes are less liable to injury from excessive 
expansion due to the severe forcing of the fires that is 
occasionally necessary, or from raising steam quickly in a 
cold boiler, than are straight tubes. This is due to the fact 
that each tube can spring and take care of its own expan- 
sion independently of the others. 

37. The merits and demerits of large-tube and small- 
tube boilers very nearly balance each other, and it is a 
much-mooted question among engineers as to which is the 
better. This matter is generally determined by the size of 
the boiler, however, the larger boilers being fitted with large 
tubes and the smalfer boilers with small tubes. Tubes in 
marine boilers vary in diameter from 1 inch to 4 inches. 
Large tubes require fewer joints for a given amount of heat- 
ing surface, and they may be made thicker without materi- 
ally affecting their internal capacity. They are not so liable 
IJtO have all the water in them suddenly converted into steam 
nder extreme forcing conditions, and leave the tube exposed 



58 TYPES OF MARINE BOILERS §9 

to overheating, as mig:ht be the case with small tubes. They 
have the following: disadvantages, however: Should a large 
tube be ruptured, a much larger volume of steam and water 
would be discharged and more damage would likely be done 
than if a small tube should burst. Should it be necessary to 
plug a large tube, a larger amount of heating surface would 
be rendered inefiEective than would be the case if a small 
tube is plugged. It will also take longer to raise steam 
in a large-tube boiler, on account of the large volume of 
water in comparison with the amount of heating surface. 

38. The tubes of water-tube boilers are placed at all 
possible angles, from horizontal to vertical; yet there is con- 
siderable diflEerence in the efficiency of the boiler, depending 
on how the tubes are arranged in this respect. When the 
tubes are placed at an angle less than 15° from the horizontal, 
the steam is delivered spasmodically, in gulps, from both 
ends of the tubes, which produces foaming; and when the 
fires are forced, this action may at times leave the tubes 
unprotected by the water, which invites overheating of the 
tubes. The deposits of scale and soot will be greater on 
horizontal or nearly horizontal tubes than on those that are 
placed at a considerable angle, which renders them more 
liable to injury from the fierce heat of the fire. The water 
does not circulate as freely through horizontal tubes as 
through those placed at an angle, owing to the fact that the 
heated water and steam have a strong tendency to rise, and 
this tendency is resisted by the horizontal position of the 
tubes; consequently, the steam and water are compelled to 
struggle along to the ends of the tube. 

There are also certain objections to placing the tubes 
vertically, especially if they are connected directly with the 
steam drum. In this case, the water will be forced out of 
the tops of the tubes in jets and fill the drum with a mixture 
Aji steam and water. As this action will be violent and con- 
tiguous, the water will have no chance to settle to its true 
level and much of it will be carried into the steam main with 
the bteam, under which conditions dry steam will be an 



§9 TYPES OF MARINE BOILERS 59 

impossibility. This objectionable action is intensitied when 
the tubes are short and of small diameter, and when the fires 
are forced; moreover, when the water is violently shot out 
of the tops of the tubes, they will be left dry at times and be 
burnt, as the water will not be able lo flow into the lower 
ends of the tubes as fast as it is projected out of their upper 
ends. However, if the upper ends of the tubes are connected 
to cross-boxes and the cross-boxes connected with the steam 
drum by horizontal or nearly horizontal tubes, this bad action 
will, to a considerable extent, be arrested. 

39. Although pipe boilers are used extensively on board 
yachts and similar small craft, they possess some objection- 
able features. Pipe boilers are usually made of ordinary 
lap-welded pipe and cast-iron or casl-sleel fittings with screw 
joints — a combination not very durable when exposed to 
tierce heat. Lap-welded pipe is very liable to split under 
high pressure, and the chief object of water-tube boilers is 
to furnish high pressures; consequently, it would be an 
improvement if lap-welded pipe was discarded in these 
boilers and solid-drawn tubes substituted. The fittings, as 
stated, are made of cast metal^a material that cannot be 
depended on when exposed to the intense heat of the fur- 
nace. The multiplicity of screw joints exposed to the tire is 
another very objectionable feature, as they are sure to leak 
sooner or later. Boilers of this type should have the joints 
and fittings protected from the fire in some way. or else 
they should be placed outside of the heated parts of the 
boiler. These boilers, as a rule, cannot be cleaned of scale; 
therefore, it is absolutely necessary for their preservation 
that pure feedwater only should be used in them. It is 
almost impossible to repair a pipe boiler without taking it 
almost entirely apart, which operation will destroy a large 
part of it if the tubes are much worn and the screw joints 
are stuck fast. 

40. Sectional boilers are those that are made up of sec- 
tions that consist of groups of tubes put together in the 
shop and the sections assembled on board the vessel to 




«C6()ivi 



60 TYPES OP MARINE BOILERS §9 

constitute a complete boiler. This is a great convenience in 
reboilering a vessel, as the sections can be lowered into the 
fireroom through the hatchways, and the necessity of cutting 
a large opening in the deck is obviated. For a new vessel, 
however, the advantage of this method of placing the boiler 
is not so great. A boiler can be more conveniently put 
together in the shop, in which there is more room to work 
and more light than in the hold of the vessel. 

41. It is to be understood that the foregoing is merely a 
criticism of water-tube boilers in general. There being such 
a vast number of designs of these boilers, it is impracticable 
to deal with each individually and the points presented may 
not apply strictly to individual boilers of the different 
varieties. 

ADVANTAGES AND DISADVANTAGES OF WATER-TUBE 

BOILERS 

42. Properly designed and constructed water-tube boilers 
possess numerous advantages for marine purposes over shell 
boilers, one of the most important advantages being that a 
disastrous explosion cannot occur with them. The worst 
that can happen in the form of a rupture is the bursting of 
one of the tubes, which will liberate a comparatively small 
volume of steam and hot water without doing serious dam- 
age to the vessel. Owing to the small diameter of the tubes 
and other pressure parts, they are capable of sustaining with 
absolute safety a much higher pressure than a shell boiler. 
They can be forced to almost any extent, or steam may be 
raised in the shortest possible time, without injury, as sudden 
and excessive expansion of their various parts will not pro- 
duce undue strains. They occupy less space, have larger 
areas of grate and heating surfaces for the space occupied, 
and are much lighter than shell boilers. This latter attribute 
is owing largely to the fact that they carry much less water 
than shell boilers, and that the elements composing their 
pressure parts being smaller they may be made of thinner 
metal. The saving in weight is an important feature in 
modem high-speed ocean steamers and cruisers. 



§ 9 TYPES OF MARINE BOILERS 61 

A well-designed water-tube boiler is easily cleaned and 
repaired, all parts being generally accessible from the out- 
side; this cannot be said, however, of all water-tube boilers, 
or of shell boilers either. A defective tube can be cut out 
and a new one inserted, or it may be plugged as a temporary 
expedient; and as all these operations are simple they can 
be performed by the regular engineer's force of the vessel. 

43. There are no serious disadvantages of a properly 
designed water-tube boiler, except, perhaps, the cost. They 
are more expensive to build than shell boilers, but they are 
worth the difference in their greater economy of operation, 
smaller space occupied, and lesser weight. 



MARINE-BOILER DETAILS 



WATER AND STEAM SPACES 



FORMING THE SUEI.L 



The Shell 
rge water-tube boilers are b 
iron or steel, technically known 
plates are a product of the rolling 



of fire-tube and flue boilers and the drams 

s boilers are built up of curved plates of 

boiler plates. These 

11, where they are manu- 



factured by passing very highly heated iron blooms or steel 
ingots between rolls operated by a powerful engine. Boiler 
plates vary in thickness from A inch to 2 inches, the latter 
being about the maximum thickness that has been attained. 
Plates less than A inch are sometimes called sheets, but 
these are not used in the construction of the pressure parts 
of a boiler. They are, however, used in the construction of 
smokestacks, front and back connections of fire-tube and flue 
boilers, and in the casings of water-tube boilers. Plates that 
are intended for marine boilers are usually sheared at the 
rolling mill to the sizes ordered by the boiler manufacturer. 
After the arrival of the plates at the boiler works, their 
edges are planed, usually on a slight bevel, in a planing 
machine. They are then passed between large rolls, three 
in number, and bent to a cylindrical form. The rivet holes 
are then marked off and enough of them are drilled to enable 
the different plates to be bolted together to form the complete 

Ci^nflMJ by Intmaliimttl Ttjitoot Cirmfaty. Enttrid at Slaliontts' Hall, Umdim 




2 MARINE-BOILER DETAILS §10 

shell. If butt joints are to be used, the cover-plates are 
prepared meanwhile; a few holes are drilled in them and 
they are bolted in their places, after which the rest of the 
holes are drilled through the cover-plates and the shell plates. 
After all the holes are drilled, the plates are taken apart 
and the burrs removed; then they are bolted together again 
and the riveting is commenced. The circumferential seams 
in the shell of a Scotch boiler are usually lap jointed and the 
longitudinal seams butt jointed. 



ASSEMBLING THE BOILER 

2. While the shell is under construction, the heads are 
being flanged, and, if the boiler is of the Scotch type, the 
combustion chambers are being erected and the furnace flues, 
if they are of the built-up type, are being made; but, if they 
are of the corrugated type, they have been ordered from the 
makers. After all the riveting on the shell is completed, 
the heads are fitted to their places, the rivet holes are 
marked and drilled, and the burrs removed, after taking the 
head out. The combustion chambers and furnace flues are 
next riveted to the front head, which is then placed in the 
boiler and riveted. Then the rear head is put in and 
riveted. Next, in order, are the tubes, which are inserted 
and expanded in the holes prepared for them in the front 
head and front sheet of the combustion chambers. The 
crown bars are now put into place on the top sheets of the 
combustion chambers; the diagonal braces, if any are used, 
are fitted to stay the heads, and finally the longitudinal braces 
are put into place; then, after calking the seams, the boiler is 
ready for its setting. 

In the construction of the firebox or locomotive boiler, the 
firebox is built up and introduced before the front head is 
put on. SHng stays are also used in connection with the 
crown bars in this boiler to provide additional support for 
the flat top of the firebox. 

In assembling the parts of a flue boiler, the flues are placed 
in their proper positions inside of the boiler and temporarily 



§10 



MARINE-BOILER DETAILS 



RIVETED JOINTS 



secured there while the heads are being fitted and riveted in. 
In this case, the furnace is outside the boiler, it being 
externally fired, while the Scotch and firebox boilers are 

t internally fired. 

I RIVETS 

3. Common forms of rivets are shown in Figs, 1 to 5. 
In Figs. 1 and 2 are shown examples of hand riveling; in 
Fig. 1 , the head is hammered down to a cone, while in Fig. 2 
the rivet has a cup, or snap, head. This form of head is 
produced by first hammering the rivet down roughly and 
then finishing the head by a cup-shaped die called the button 

r: 





The dotted lines in the figure show the shape of the 
hvet shank before being upset by the hammer. The rivets 
shown in Figs. 3 and 4 are examples of machine riveting. 
The rivet is placed between two dies that are forced 
together by heavy steam or hydraulic pressure. The most 
important advantages of machine riveting are the following: 
On account of the force with which the plates can be held 
together while the head is being formed, a tighter joint can 
be made; the heavy pressure used to upset the rivet and 
form the head causes it to expand and fill the hole more 
sompletely than it will when headed by the blows of a ham- 
when a large number of rivets is to be driven, 




MARINE-BOILER DETAILS 



iio ' 



machine riveting is cheaper than hand riveting. A rivet ] 
with countersuak head is shown in Pig. 5. Such riveting is , 
sometimes necessary where a smooth surface is needed for ■ 
the attachment of boiler mountings. In Figs. 4 and 5, the 
holes in the plates are countersunk slightly under the rivet 
beads. This provides for an increase in the size of the rivet 




» 



Just under tbe head and makes the rivet much stronger than 
i« the case «rber« the coonection between the head and the 
riwt forms a sharp angle, as in Figs. 1. 2. and 3. 

As shown in tbe ficmvs, the rivets, before being headed, 
ar« stlKbtly smaller than the hole, so that they may be 
luwrted easily. It is the general mle to malce the rivet 
holtt \^ inch larger than the rivet. When the work is prop- 
erly done, the upsetting action 
r , j of heading the rivets causes 

I h**4H 'S them to fill the holes when 

, beaded down. The proportions 
usually given to the rivet heads, 
i and the distance the rivet shank 
projects from the plate before 
beading, are given in terms of 
the rivet diameter, when driven, 
"•■• that is, in terms of the rivet 

W»h>s *« i*v^wn in F>8S. 1 to 6- Thus, in Fig. 1, the diameter 
sa (h» wt>*wr hiNttl is KJ^TO as SJ; when d. the diameter of 
IIm (iwl Ikv)*, ix tA inches, tbe diameter of the upper 




-AW 




5 10 



MARINE-BOILER DETAILS 



5 



4. The rules prescribed by the Board of United States 

Supervising Inspectors of Steam Vessels provide that all rivet 

holes and holes for staybolls must be drilled fairly. This 

I rule applies to all boilers coming under their jurisdiction. 



FORMS OF RIVETED JOINTS 

5. Hlveted Joints of different forms are shown in Figs. 6 
When one plate overlaps the other and the two are 



m. 



^p- 



I 



joined with one or more lines of rivets, as shown in Figs. 6 

and 7, the joint is said to be lap rlveteil. When, however. 

I the plates are placed edge to edge, as in Figs. 8 and 9, and 




■ the joint is covered with one or two plates, the joint is called 
a butt Joint. 

Fig. 6 represents a single-riveted lap Joint, that is, the 
plates are overlapped and joined with one row of rivets. 
The distance p from center to center of the rivet holes is 




MARINE-ROILER DETAILS 



§10 



called the pitch of the rivets. The distance / from the 

center line of the rivet hole is usually made li times the 
diameter d of the rivet hole. The distance that the two plates 
overlap, that is, the dis- 



1 



mmm 



®®®(f 



tance from the edge of 
one plate to the edge of 
I the other plate and at 
the joint, is called the 
lap. 

Fig. 7 shows a <lou- 
l>le-rlTeteil lap 
Joint. The rivets may 
be 8ta^g;ered , as shown 
''""° in the figure, which 

method is commonly called ssiszag rtvetlng, or placed one 
behind the other, as shown in Fig. 8. In the latter case ihe 
joint i.s chain riveted. In a zigzag riveted joint, the dis- 
tance from the center of one rivet to the center of the next 



(®) # # (I 

(S) '3) W' v^ 



# (®) ® 
% # ®> 



H«l in the other row is called the diagonal pitch. It is 
fjulie cuitomary in boiler construction to single rivet the 
glrlh wamK and double rivet the longitudinal seams, since 
(he atreis on the latter is twice that on the former. 



\ 




MARINE-BOILER DETAILS 



A butt joint with a. single cover-plate is shown in Fig. 8, 
while a butt joint with two cover-plales is shown in Fig, 9. 
Either may be riveted with one, two. or more rows of rivets. 



1 


® ;•-' 


'-•/ 






(•) ;•:■ ;•; ;'•; 


(®; 


#) (•'-■ 


-•'' 


] 



Fig. 9 shows an example of chain-riveting. A well -de signed 

buit joint with two plates will be stronger than one with a 

Bgle plate. Butt joints are generally used for plates over 



1 


''*' 




'®' 


',*'■ 


{• 


:» 


;• 


e • 










di; 




fe; 


* 


1 



i inch thick and are taking the place of lap joints for longi- 
tudinal seams in good designs of smaller work. When one 
cover-plate is used on a butt joint, its thickness should not 
be less than li times the thickness of the plate; when two 




8 



MARINE-BOILER DETAILS 



§10 



cover-plates are used, the thickness of each should not be less 
than about, five-eighths of the plate thickness. 

It is sometimes the case that the cover-plates of double- 
strap butt joints are made unequal in width, the wider 
cover-plate being placed inside of the boiler. Two examples 
of a joint of this character are illustrated in Figs. 10 and 11. 
The joint shown in Fig. 10 is double zigzag riveted; the one 
shown in Fig. 11 is triple zigzag riveted. The cover-plates 
of a butt joint are also called butt straps. 

6. Attempts have been made to weld the longitudinal 
seapis in the shells, as well as the seams of the internal 
parts of Scotch boilers, but this method has not yet passed 
the experimental stage. Should this process be satisfactorily 
accomplished in the future, the labor of drilling the rivet 
holes, the riveting, calking, and some of the flanging will 
be saved. 



ARRANGEMENT OF JOINTS 

7. The plates of externally fired boilers should be 
arranged so that the riveted joints are as far as possible 




Pio. 12 



from the fire. This may be accomplished by using extra 
large plates for the fiurnace end of the shell. 



§10 



MARINE-BOILER DETAILS 



Wherever a girth seam occurs, the Jongitudinal seams 
should break joint, as shown in Fig. 12. In order to make 
a tight joint where three plates come together, the inner 
plate of a longitudinal lap joint must be hammered thin at 
the edge, as shown in Fig. 13. 

^^n In the construction of both vertical and horizontal shells, 
it is customary to have the inside lap facing downwards, 
since, if it faces upwards, a ledge is formed on which sedi- 
ment may be deposited. 

Since wrought-iron plates are stronger in the direction 
of the fiber, they should be arranged so that the fiber runs 



rcomfereniially around the shell; that is, in the direction of 
ibe girth seams. 
8. Different methods of connecting plates at right 
jles are shown in Figs. H to 17. In Fig. 14, the two 
Utes are riveted to an angle iron. This constructioo was 





10 



MARrNE-BOILER DETAILS 



§101 



formerly used for connecting the heads of a boiler to ths 
shell, but since high steam pressures have come into use, this 
method has been abandoned as unsalisfactory. As shown ia 
Figs. 15 and 16, the head is flanged and riveted to the shell, 
while in Fig. 17 the head and shell are 
connected by a flanged ring. The meth- 
ods of connection shown in Figs. 15 and 
16 are generally considered preferable to 
those that are shown in Figs. 14 and 17, 
since in the latter methods there are two 
joints to be kept tight, while in the former 
there is but one. 

Iron or steel for flanging should be of 
the best quality. The radius of the curve 
to which the head is flanged should be at 
least four times the thickness of the plate. 





H me 



Some makers of large boilers prefer to flange the end 
plates of the shell to receive the head, which is, consequently, 
a flat disk. 

In Figs. IS to 24 is shown the usual construction of the 
water legs and furnace doors of vertical and firebox boilers.. 
Fig. 18 shows the door constructed by flanging the furnace' 
sheet W and the front sheet B of the boiler. In the figure, 
the joint is single riveted, although it is frequently double 
riveted. An enlarged view of this construction is shown in 



r«io 



MARINE-BOILER DETAILS 



11 



Fig. 19, The door C is generally made of cast iron and is 
hinged to a cast-iron frame that is usually held in position 
by four studs. Sometimes the frame is omitted and the 
door is made of wrought iron; the door is then held in posi- 
tion by riveting the hinges to the boiler. 

Around the tower ends of the water legs, or around the 

bottom of the furnace, and between the inside and outside 

plates is riveted a wrought-iron ring D\ in 

cheap boilers, this ring is frequently made 

of cast iron. Instead of flanging both 

sheets, as shown in Figs. 18 and 19, the 

furnace opening is sometimes constructed 

I as shown in Figs. 20 and 21. A hole is 

I cut in the outer sheet C, and the furnace 

sheet A is flanged. The flanged ring li 

is then riveted to the plates A and C, and 

forms the opening for the door. An 

enlarged view of this construction is 

shown in Fig. 21. A flanged ring/?, Fig, 

20, is sometimes used at the bottom of the 





rftter leg in place of a wrought-iron ring D, Fig. 18, one of 
' the flanges being riveted to the furnace plate and the other 
to the shell, as shown. An enlarged view of this con- 
struction is shown in Fig. 22. In Fig. 23 is shown another 
caethod of constructing the opening for the furnace door and 
bottom of the water leg. In this construction, the 




MARINE-BOILER DETAILS 



wroughl-iron ring .-J is placed between the furnace plate B \ 
and the shell C of the boiler, and riveted to them. An J 
enlarged view of this construction is shown in Fig. 24. 




the boitom of the water leg, the furnace plate i: 
riveted lo the shell, as shown. 



CALKING 



0. An upsetting process applied to a riveted joint, 
lOfdcr to make it steam-tight, is known as calktnir. The 
ojwrufon is shown in Fig. 25. A round-nose calking tool ia 



§10 



MARINE-BOILER DETAILS 



13 




10. 



FLAT BEADS 

The heads of Scotch boilers are formed of one, 



driven against ihe beveled edge of the upper plate, forcing 
the metal into close contact with the lower plate, thus effec- 
tually closing the seam. A tool with a sharp edge should 
never be used, as it is liable to score the under plate, and 
thus lead to grooving. 
Although the calking of 
boiler seams was formerly 
done entirely by hand, it 
is now largely performed 
by the pneumatic calking 
hammer. 

When the edges of the pj^.k 

plates have not previously been planed, it is necessary to 
chip them before calking. Formerly, this was done by hand; 
it is now performed by the pneumatic chipping hammer. 

I 

^Hwo, or three sheets, according to the diameter of the boiler. 

^^ffhe plates having been sheared and planed to the proper 

^Bozes and shapes, their curved edges are fianged over at 

^^ieht angles, as shown at a, a, Fig. 26 {a}. After heating 

the plate in a furnace or forge at the edge to be flanged, the 

flange is turned over by either a hydraulic flanging press, a 

steam hammer, or. up to a certain thickness, by hand with large 

wooden mauls, the plate meanwhile resting on a cast-iron 

mold block of the required shape of the flange. The flanges 

are made oE sufficient width to provide space for a single 

row of rivets in heads for boilers of small diameters, and for 

a double row of rivets in heads intended for boilers of large 

diameters. When the head consists of more than one sheet, 

the several sheets are joined by riveted lap joints, or seams, 

as shown at d.i-. Fig. 26 id). After the sheets, or plates, have 

Ken shaped, flanged, and fitted, the rivet holes for the hori- 
Qtal seams are marked off and enough of them are drilled 



14 



JViARiNE-BOILER DETAILS 



§10 



to permit the sheets to be firmly bolted together, care being 
taken to drill the holes in the two adjoining sheets so that 
they will come fair with each other. After the sheets are 
bolted together, the rest of the rivet holes are drilled, either 
by a power drill or by hand. Of course, in all well-equipped 
boiler shops, all work that can be properly done by machin- 
ery is so performed in preference to hand work, and since 
the introduction of portable pneumatic tools much of the 




work on boilers that was formerly done by hand is now 
accomplished mechanically by such tools. 

At the ends of the lap joints in the head where the two 
flanges overlap, the flange of the under plate is forged taper- 
ing in order to make the joint at those points steam- and 
water-tight, as shown at c,c. Fig. 26 (^). In some cases, 
the overlapping flanges at the ends of the horizontal seams 
are welded together, as shown at d,d. Fig. 26 (^). This 
method insures a tight joint and a good fit of the head in the 



^10 



MARINE-BOILER DETAILS 



15 



shell, but it is objectionable owing to the uncertainty of 
making a reliable weld. 

1 1 . An elevation and a sectional view of the front head of 
either a single-ended or a double-ended boiler are illustrated 
in Fig. 27. The course of procedure of flanging, drilling, 




riveting, etc. in constructing this head is similar to that 
employed in the construction of the rear head, as just 
described. In addition thereto, the openings a, a for the 
furnace flues are cut out and flanged, as shown at i, b. The 
tube holes c,c are also drilled in the tube-sheet rf, and 
the manholes e.e and handholes /./are cut out. The man- 
holes are reenforced by riveting a ring of boiler plate around 
ihem, as shown at g,j^. All of these operations are per- 
formed before the plates are riveted together. The plates 
pare also annealed before being riveted up. 

12. Forming the front heads of a Scotch boiler is one 
[ the most difficult operations attending its construction. 
Iiis is owing to the deformation of the plates that takes 



MARINE-BOILER DETAILS 



BUMPED OR DISHED HEADS 

15. Cylindrical flue boilers of small diameters, such as 
are in service on the Red River of the North, North America, 
and rivers whose waters flow into the Gulf of Mexico, and 
steam, water, and mud-drums of all boilers, are usually fitted 
with bumped or dished heads. They may be either con- 
vexed or concaved; the radius of the curve to which they 
are bumped is usually equal to the diameter of the boiler or 
dnun for which they are made. 

Bumped heads are illustrated in Fig. 28, the one shown 
in Fig. 28 (a) being ; 
convened head and that 
shown in Fig. 28 {/<) , 
being a concaved head. . 
They are flanged and I 
riveted in the shell, as I 
shown in the figure, I 
These heads require no ] 
bracing, because they 
are bumped to the shape 
[hey would naturally M <»> 

assume underpressure; P'c^ 

hence, they are self-supporting. 

Bumped heads may have a manhole opening flanged 
inwardly when such flange has a sufficient depth and thick- 
ness to furnish as many cubic inches of material as was 
("imoved from the head to form the opening. 
MASUULES 
16. For the purposes of allowing the inside of the boiler 
to be inspected, cleaned, and repaired, holes closed by 
suitable covers are cut into the heads and shell. When they 
are of sufficient size to admit a man, they are called tiiaa- 
koles; otherwise, handholes. 




OPENINGS 





18 



MARINE-BOILER DETAILS 



§10 



A common form of construction of a manhole and ifs 
cover is shown in Fig. 29. An elliptic hole is cut into Ihe 
head or the shell of the boiler, A wrou^ht-iron or steel 
t reentorcing ring, is riveted to the plate /*, 



ring R, called 




I 



generally on the outside, for the purpose of strengthening 
the plate, whii^h is weakened considerably by the cutting of 
such a large hole through it. A cover A' made of wrought 
iron or steel is fitted to the hole, inside of the boiler, and is 
provided with two studs Y, Y riveted to it. This cover is 
flanged and overlaps the edges of the plate about 1 inch c 
more all aroundJts perimeter, A yoke M is slipped i 
each stud, its two extremities resting on the reenforcio 
ring. A ring G. or gasket, as it is commonly called, madi 
of sheet rubber or any other pliable waterproof material, ii 
placed between the plate and the cover and serves to make | 
water -tight joint, 

17. Of late years, it has become quite generally the 
practice to flange the head inwards and face its edge, thus 
doing away with the 
necessity for the rcen- 
forcing ring. When the 
manhole is in the shell. 
P'o * in Ihe best modern 

practice, a flanged reentorcing ring is riveted to the inside 
of the shell, as shown in Fig. 30. In this design, the edges 
of the ring and cover are faced and carefully fitted to each 



§10 



MARINE-BOILER DETAILS 



19 



other, thus making a metallic joint. Owing to the practical 
difficulty of making such a joint perfectly water-tight, most 
engineers prefer to place a gasket, either fibrous or metallic, 
between the cover and its seat, even when both are faced 
and fitted to each other. The rules and regulations of the 
United States Board of Supervising Inspectors provide that 
all manholes for the shells of boilers over 40 inches in diam- 
eter shall have an opening not less than 11 inches by 15 
inches in the clear, except that boilers with 40 inches diam- 
eter of shell or under shall have a clear opening in the man- 
holes of not less than 9 inches by 15 inches. A manhole 
openiDg in the front head of externally fired boilers and 
under the flues must measure not less than 8 inches by 12 
inches in the clear. 






nAJ>'DUOL.KS 

18. Bandboles are placed in boilers whose construction 
les not permit the entrance of a man, as, for example, in 

vertical boilers. They are also placed in other boilers in 
convenient positions; thus, in boilers of the locomotive type, 
they are usually placed in the corners of the water legs, and 
in Scotch boilers Ihey are placed above the crowns of the 
furnace flues. The handhole is a convenient place to rake 
out sediment and scale and to admit a hose for the purpose 
of washing out the boiler. The handhole and its cover are 
constnicted very much like a manhole and cover; the hand- 
hole, being smaller, requires but one yoke and bolt to secure 
the cover. 

Manholes and handholes are made elliptic to allow the 
cover to be passed through the hole. The smallest diameter 
of the cover is somewhat less than the largest diameter of 
the manhole, and thus allows the cover to pass freely through 
the manhole. It is then turned one-quarter around inside the 
boiler, the gasket placed on the flange, and put in position. 

19. When using sheet rubber or other fibrous gaskets, it 
( advisable to give them a good coaling of plumbago on 
K>th sides. This will prevent their sticking to the cover and 




20 MARINE-BOILER DETAILS §10 

seat, thus allowing them to be readily removed* It is rarely 
advisable to use the same gasket again when replacing the 
cover; it will usually have become carbonized by the heat 
and thus be too hard to make a tight joint, no matter how 
hard the nuts are screwed up. When the cover has been 
replaced with a new fibrous gasket, it is well to examine it 
again after steam has been raised, and tighten the nnts once 
more. A plentiful supply of graphite (plumbago) smeared 
on the threads of the bolts before the cover is replaced will 
allow the nut to be readily removed at the next examination. 

When a manhole or handhole gasket blows out, as will 
happen if the work of replacing the cover has been carelessly 
done or the gasket has been cut too large, about the only 
thing that can be done is to haul the fire, blow out the 
boiler after the steam has gone down, and make the joint 
over again. 

Before taking off a manhole or handhole cover, imme- 
diately after the boiler has cooled down, it is advisable to 
raise the safety valve or open a valve or gauge-cock so as to 
break the vacuum that may have been formed by the con- 
densation of the steam remaining in the boiler. If this pre- 
caution is neglected, it may result in serious injury. While 
it cannot be truthfully stated that a vacuum will always form, 
instances are on record where this has happened and the 
cover forced inwards by the external air pressure. 



MISCEL.LJLNEOUS OPENINGS 

20. Openings, other than manholes and handholes, are 
cut into the shells, heads, steam drums, and other parts of 
boilers to provide passages for steam or water to flow into 
or out of the boiler. Pipes and suitable valves are attached 
at the openings, either by screw threads or by flanged joints. 
Valves and cocks up to li inches in diameter can be secured 
by tapping the hole in the boiler with a pipe thread and 
screwing in these fittings; larger valves and cocks must be 
attached with flanges. Feedpipes and steam pipes up to 
1 inch in diameter, if attached to a plate less than i inch thick, 



»^' 



§10 MARINE-BOILER DETAILS 21 

must be screwed into a bushing threaded inside and outside 
and screwed into the plate up to a shoulder provided on the 
bushing, which should preferably be secured with a jam nut 
placed on the water or steam side of the plate. Feedpipes 
and steam pipes up to 2 inches in diameter can be screwed 
directly into plates if ibey are a inch or more in thickness. 
AH pipes over 3 inches in diameter must be attached to the 
boiler or its parts by flanges. All holes over 6 inches in 
diameter cut into a boiler must be reenforced with a reenfor- 
cing ring, except when such holes are cut into a flat surface. 
in which case the plate may be flanged inwards to a depth 
of not less than li inches and the reenforcing ring dispensed 
with. On boilers carrying a steam pressure of not over 
75 pounds per square inch, a flanged cast-iron stop-valve 
placed over an opening more than 6 inches in diameter may 
be used as a reenforcement. Openings serving as a connec- 
tion between the shell of a boiler and a mud-drum must 
not exceed 9 inches in diameter. 

t DOMES AND STEAM DRUMS 

!1. Domes are placed on cylindrical boilers for the pur- 
^i^se of increasing the steam space, and also for the purpose 

of drying the steam, the supposition being that the steam 
will be dried on account of its being farther removed from 
the water. The hole cut into the shell to give communication 
between the boiler and the dome should be made only large 
enough to allow a man to pass through, since a large hole 
materially weakens the shell. The edge of the plate around 
the hole should be reenforced by a wrought-iron ring riveted 
to it. The flat top of the dome must be stayed by diagonal 
braces. Steam domes usually have a diameter equal to one- 
half the diameter of the boiler, and a height equal to about 
nine-sixteenths the diameter of the boiler. 

22. Shell boilers are often fitted with a steam liriim 
|Btead of a dome. The steam drum is simply a cylindrical 



APPURTENANCES 




22 MARINE-BOILER DETAILS §10 

vessel connected to the shell. When several boilers are set 
so as to form a battery, they are often connected to one 
drum common to all boilers. When each boiler has its own 
furnace, there should be a stop- valve between each boiler 
and the drum to allow the boiler to be taken out of service 
when required. When the boilers in battery have one fur- 
nace common to all of them, no stop- valve should ever be 
placed in the pipe connections between each boiler and the 
drum. Where boilers are in battery with separate furnaces, 
each boiler must have its own safety valve, which should 
always be so fitted that it cannot be cut oflE from the boiler 
under any circumstances. Scotch boilers are rarely fitted 
with steam drums; they are frequently used, however, in 
connection with the boilers installed on Western-river steam- 
boats. Nearly all designs of water-tube boilers require a 
combined steam and water drum. 

23. Some boilermakers, when fitting: a longfitudinal 
steam drum to a shell boiler, will attach it by two nozzles. 
Many engineers object to this method, since with an unequal 
expansion of the boiler and drum, which is quite likely to 
occur, the joints of the nozzles will become leaky, owing to 
the strains to which they are subjected. It is now the rule, 
in good work, to use one nozzle only. When the steam 
drum is used for a single boiler, its diameter may be made 
equal to one-half the diameter of the boiler, and its length 
equal to the diameter of the boiler. Where one steam drum 
is common to several boilers, its diameter is usually made 
equal to half the diameter of one of the boilers, and its length 
equal to the horizontal outside-to-outside measurement over 
the several boiler shells. 

The strength of steam drums may be determined by the 
rules governing the strength of boiler shells. They require 
just as rigid inspection as the boiler itself. 



MARINE-BOILER DETAILS 



MUD-nnuMS 

24. Mad-drums are occasionally attached to boilers for 
the purpose of providing a quiet place for the collection of 
mud and sediment in mechanical suspension in the feedwater, 
which is introduced into the mud-drum. In shell boilers the 
mud-drum is located underneath the boiler and at the rear 
end, being connected to the boiler by a suitable nozzle. 
When several boilers are set in battery, they are sometimes 
connected to a common mud-drum. This practice is per- 
missible when the whole battery is used at once. When so 
fitted, none of the boilers can be temporarily taken out of 
service unless each nozzle is provided with a slop-valve. 
Owing to the difficulty of protecting the valve from the heat 
of the fire, this is rarely if ever done. This consideration 
limits the use of a common mud-drum to cases where all 
the boilers are worked together. When a mud-drum is 
fitted, the blow-off should be attached to it and the sedi- 
ment collected in'lhe drum should frequently be blown out. 

Mud-drums for shell boilers are not used to any extent 
outside of Western-river steamboats and vessels engaged 
in similar service. Practically all marine water-tube boilers 
have one or more mud-drums or the equivalent thereof, 
their desigrn generally requiring this. 



STATING 



Ir PURPOSE AND CLASSIFICATION 

I- 25. The surfaces of boiler shells are, in general, either 
cylindrical, hemispherical, or fiat. A cylinder or sphere sub- 
jected to an internal steam pressure is sell-stipporling; that 
is, the steam pressure tends to maintain the cylindrical or 
spherical form of the vessel, and hinders distortion instead 
of producing it. If, on the contrary, the vessel is composed 
of flat surfaces, the steam pressure tends to distort it and 
_ give it an approximately spherical form. Hence, flat surfaces 
—are not self-supporting, and must be braced or stayed. 




MARINE-BOILER DETAILS 



The flat surfaces commonly found in boiler construe lion 
are the flat heads of Scotch boilers and the sides, back, and 
top of the combustion chambers; in firebox boilers, the sides, 
back, and top of the combustion chambers, the crown of the 
furnace, the water legs, and the flat heads. 

The appliances used for bracing steam boilers may 1 
divided into direct stays, diagonal stays, and girder stays. 

A direct stay may be defined as one in tension, in whii 
the load is applied directly in line with the axis of the stay 

A diugoiial stay is a tension member in which the loi 
acts at an inclination to the stay; in other words, it is a sta] 
that is not placed at right angles to tlie surfaces it support*. 

A KlnliT stny is a slay in the form of a girder, and i 
subjected to bending stresses produced by the load. 

PIHKCT STAYS 

2G. Screw Stnys. — The most common form of a «crei 
stay used in firebox boilers is shown in Fig. 31. The sta 



\'"\ 



MliMM 



is threaded the entire length. It is screwed into place and tj 
ends are headed over by hammering. A much better for 
is shown in Fig. 32. The thread is turned off in the center, 




which increases the durability of the bolt, for the reason that 
a smooth surface is not so readily attacked by corrosion as \ 
threaded surface. 




§ 10 MARINE-BOILER DETAILS 2,5 

27. Stiiy bolts.— Fig. 33 shows a staybolt of the con- 
struction usually met with in Scotch boilers, used for staying 
the sides and back of the combustion chambers. It consists 



P>f 



ttf a wrought-iron or steel bolt a, screwed into the two plates 
6,6. and secured by a nut at each end. An enlarged section 
of the nut is shown at c. Fig. 33. The face of the nut is 
recessed, the recess being filled with red-lead putty mixed 
wiih iron filings. The putty serves to make a steam-tight 
and water-tight joint. 

All screw stays and staybolts for boilers using fresh water 
that are constructed in the United States after July 1, 1899, 
must be drilled on both ends with a central hole, as a, Fig. 32, 
having a diameter of not less than i inch and a depth suffi- 
cient to extend at least i inch beyond the inside surface of 
the sheet. Should a stay break, water will issue from this 
hole, thus giving notice of the break. 

tA socket stoybolt is shown in Fig. 34. The 

socket consists of a tube expanded into the sheets b and f. 

A bolt li fitting closely the inside of the tube a is passed 
^through and secured by a nut. The ends of the socket pro- 
Hjkct from the sheets and are beaded over. Sometimes the 





MARINE-BOILER DETAILS 



staybolt shown in Fig. 31 is protected by a socket. If sail 
water is used for the Eencration of steam, all screw stay- 
bolts must be provided with sockets to protect them from 
the corrosive effect of the sea-water. Water from a surface 
coodenser is deemed fresh water by the Usited States 
Inspectors of Steam Vessels. 

29. Stayrods. — A rod that is chiefly used for siayini 
the heads of Scotch boilers, and passes through from hes 




to head, is known 
shown in Figs. 35, 



a stayrod. Examples of stayrods are 
37, 38, and 39. The end of the stay- 
rod B, Fig. 35, is enlarged 
and threaded and passes 
through the plate A. Two 
nuts and washers are pro- 
vided. The larger washer J 
is on the outside and i^ 
riveted to the plate; it t 
serves to distribute the sup-l 
porting effect of the rod. 
Sometimes, instead of the washer, a stifEeniug plate isfl 
used, covering the whole area to be braced, and 
either inside or outside of the boiler. By means of the nuts 





Ho 



MARINE-BOILER DETAILS 



27 



ihe tension of the stayrod may be adjusted, the nuts on the 
inside serving to lock the rod in position. 

Sometimes siayrods without washers, as shown in Fig. 36, 
are employed. The nuts in this case are recessed, the same 
as those illustrated in Fig. 33. Occasionally, two small 
washers are used, as shown at a and l>. Fig. 37. A some- 



I 



I 



D 



Q 


Q~^ 


- 





Q 


Q 




what different form of a stayrod is shown in Fig. 38. Two 
angle irons a, a are riveted to the plate. The end of the 
stayrod is enlarged and made square in cross-section. It 
is tapped to receive a bolt c passing through the plate and 
between the angle irons. A leaf d is placed on the outside 
and helps to support the plate. 

f The diameters of through siayrods vary from 1} to 2} 
, according to the ste.im pressure. 



MARINE-BOILER DETAILS 




Another method of connecting the ends of stayrods to the J 
plate is shown in Fig, 39- Here the end of the siayrod A,{ 
instead of bei ngl 
threaded, is forked to 
receive the connec- 
tion B B, which is 
riveted to the sheet 
to be stayed, am 
joined to the stayroi 
by a bolt C The 
combined effective 
area of the two leggj 
of the connection BB 
should exceed tha 
area of the stayrod. 
This connection is often used to support the lower part of 
the rear tube-sheets of Scotch boilers. 



DIAGONAL STAYS 

30. Palm Stays and Uiisset Htays. — A palm stay ii 

shown in Fig. 40. The end B is flattened and riveted to thi 

shell. The other end ,/ is threaded and supplied with a no 

and taper washer on each side of the head, the washert 

having such a taper that, 

when one of the faces is 

against the head.tbe 

other is parallel to the 

face of the nut. The 

hole through which the 

stay passes is not 

threaded, but is made sufficiently large to allow the stay taJ 

pass through. In some instances, the end A is bent, so as tap 

pass through the plate at a right angle to it. This is don^ 

to obviate the need of taper washers. 

Palm stays, or dlivKonal stays, as they are sotnetJmef 
called, are used in locations prohibiting the use of a throuj^ 
stayrod. In Scotch boilers, they are usually found supportia^l 




^10 



MARINE-BOILER DETAILS 



29 



the lower part of the heads between the furnaces. The 
combined area of the rivets attaching the stay to the shell 
should at least equal the area of the rod. The angle that a 
diagonal Stay mates with the shell should not exceed 3^, 

and should be as much smaller as possible. 



This stay cod- 




31. In Fig. 41 is shown a K^^set stiif, 
sists o( a wrought-iron or 
steel plate A, secured lo 
tl)e head and shell by either 
aogle or T irons /J, j5. 
Gusset stays are some- 
times used for the same 
purpose as palm stays. 

32. Crowfoot Brn- 
ct's. — The flat heads of boilers are sometimes supported by 
crowfoot brac-eht, which are securely riveted to the head 

and the shell. The crow- 
foot brace is shown in 
Fig. 42 (a). In this style 
of brace, the crowfoot, or 
part that is riveted lo the 
head, is formed by weld- 
ing flat bars to a cylindri- 
cal stem. The strap end, 
or pari that is riveted to 
the shell, is also welded to 
the stem. An improved 
form of crowfoot brace is 
the McGrcKor brace, 
shown in Fig. 42 (*). This 
brace is formed by a piece 
vi<^>2 of sheet steel, hent in one 

heat as shown. Being weldless, it may naturally be assumed, 
and the assumption has been borne out by experiments, that, 
for equal cross-sectional areas, it will bear a much greater 

fain than the welded crowfoot brace. It will be observed 
It the crowfoot of the McGregor brace is formed by 




tSS> 



30 



MARINE-BOILER DETAILS 



SlOl 



Splitting the sheet and bending it at a right angle. In t 
Huston improved crowfoot brace, shown in Fig. 42 (c). the 
crowfoot is formed by flanging the plate of which the brace is 
formed, thus giving probably the strongest form of crowfoot 
that can be devised. 

GiRDER STAYS 

33. The tops of the combustion chambers of Scotch 
boilers are usually supported by girder stays, the construc- 
tion of which is shown in Fig. 43. Two girders A, A' are held 



\ 



fnrtt 


m 


,ip 


r-n 


i<n^ 


-f 


L&-i — 


==v^ 


J 




apart by two distance pieces <i,a'. Staybolts, similar to the 
one shown in Fig. .33, are supported by the girders. To pre- 
vent spreading of the girders, washers d. d provided with 
lugs b, b are used. To give access to the plate and to prevent 
local overheating of the plate, which would likely occur if 
the girders touched the whole length of the plate, a space c, 
generally about 2 inches in depth, is left between the girder 
and the plate. To prevent buckling of the plate by setting 
the staybolt loo tight, a thimble or socket B is sometimes 
placed over the staybolt between the girders and the plate. 
34. The upper plates or crown sheets of the furnaces of 
internally fired boilers of the locomotive type are supported^ 
by girder slays, or crown bars, as they are usually called 
when applied to a firebox boiler. These are sometimes 



\ 




SlO 



MARINE-BOILER DETAILS 



31 



further supported by sliu^ stays, wbich consist of brace 
rods running from the crown bars to an angle bar riveted to 
the shell of the boiler above the crown bars. 

Referring to Fig. 44, A is the crown bar, B, B are the side 



rQQQQQQQnQQQQpV 
OOOPOQOOOOOO 

sheets of the iirebox, C is the crown sheet, D, D are the pins 
that secure the crown bar to the crown sheet, E, E are the sling 
stays, and E is the angle bar. The latter is bent to the shape 
of the boiler shell and securely riveted to it, as shown in the 




illustration. The lower ends of the sling stays have single 
eyes forged in them that are secured between the two mem- 
bers of the crown bar by bolts or split pins. The upper ends of 
the sling stays are forked and have two eyes that straddle the 
flange of the angle bar and are secured to it by bolls or pins. 



32 MARINE-BOILER DETAILS § Itti 

35. The lower part of the combustion chambers of Scotch 
boilers is often strengthened by several hoops made of angle 
iron and riveted to the plate. This arrangement is shown 
in Fig. 45, in which a is the lower part of the combustion 
chamber and b, b are the angle-bar hoops. 



FIKE AND COMBUSTION SPACES 



FURNACES 



INTRODUCTION 

36. Furnaocs of marine boilers may be divided into 
two distinct classes, namely, inUmal furnaces and trxternat 
furnaces. The Interuitl furnaces of cylindrical or shell 
boilers of the Scotch, firebox, locomotive, and vertical 
types are parts of the apparatus, being built into the 
boilers during their construction, and of similar material 
to that used in the other parts of the boilers. The fur- 
naces of these boilers are portions of the pressure parts 
and are surrounded, or partly surrounded, by the water 
the boiler. They are therefore built strong enough 
sustain the same pressure to which the boiler shell : 
other pressure parts of the boiler are subjected. 

Cylindrical marine boilers, such as are used on Western*^ 
river steamboats, have externa! furnaces, and they are 
usually constructed of firebrick under the front end of tlie 
boiler. Brick furnaces are not suitable, however, for the 
boilers of sea-going vessels. The brick walls are too heavy 
and occupy too much space, and the working of the ship in 
a seaway would cause them to crack and eventually fall. 

The furnaces of marine water-tube boilers like the Babcock 
& Wilcox, Almy. Roberts, and other steam generators of this 
type may be properly called internal furnaces, as they are 
surrounded on their sides by water tubes that form a part 
of the heating surface, and are in communication 



ur- 
rtg J 

i 



that form a part ^H 
ucation with the ^| 



§10 MARINE-BOILER DETAILS 33 

steam space. The generating tubes of water-tube boilers 
are enclosed in a casing of sheet iron or steel, lined with 
some refractory substance, such as asbestos, magnesia, etc. 



* 



FURNACE FLCKS 

37. The furnaces of Scotch boilers are cylindrical in form, 
and are known as furnace flues. The longitudinal seams 
of furnace flues may be either welded or riveted, the latter 
method being now obsolete. When furnace flues with riveted 
longitudinal seams are used, they are fitted into the boiler so 
that the seams are below the grate bars, in order that the 
fierce heat of the fire may not injure the seams. Furnace 
flues are either p/ain or corrugated. 

38, Plain furnace flues may be made in different ways, 
as shown in Fig. 46. The flue shown at A, Fig. 46, is made 
in sections of not more than S feet in length. Each section 
is flanged to a depth of not less than 1\ inches, and the sec- 
tions are riveted together with a wroiight-iron ring (shown 
at a) between the flanges. The thickness of the ring must 
not be less than i inch nor its width less than 21 inches. 

A diflferent construction is shown at 5, Fig. 46. Angle- 




iron rings, as a. are employed, serving to stiffen the flue. 
The thickness of the material of the ring must not be less 
than double that of the flues, and the depth must not be less 
than 2t inches, The rings are held in position by rivets 
passing through wrought-iron thimbles b, b, placed between 




34 



MARINE-BOILER DETAILS 



§10 



the inner surface of the strengthening ring and the outer 
surface of the flue. The length of tlie thimbles must not be 
more than 2 inches, nor the diameter of the rivets less than 
Ij times the thickness of material in the flue. The pitch of 
the rivets, measured at the outer surface of the flue, is not to 
be more than 6 inches. 

At C, Fig. 46, the strengthening ring shown at a is made 
of half-round iron. The proper area of the ring may be 
found by multiplying the thickness of the flue in decimals of 
an inch by the constant 9.6; the product will be the area, in 
square inches. The ring is held in position by rivets passing 
through wrought-iron thimbles b not more than 2 inches in 
height. If rivets » inch diameter and over are used, the 
pitch must not exceed 8 inches; for rivets J inch diameter, 6 
inches; or for rivets i inch diameter, 4 inches; the pitch to be 
measured at the outer surface of the flue. No rivets smaller 
than I inch are to be used for securing strengthening rings. 

The distance from center to center of flanges or strength- 
ening rings is to be taken as the length of the flue in com- 
puting the working pressure allowable. 




I 



39. CorriiRated lurnace flues are used extensively 
for Scotch boilers, the corrugation serving to strengthen 
the flue considerably, and they also permit the flue to 
expand and contract freely in the direction of its length with- 
out subjecting the combustion chamber and the front head 
of the boiler to undue strain, as is the case with the plain 
furnace. The corrugations open and close by expansion and 
contraction like the bellows of an accordion, but. of course, to 
a much less degree. The longitudinal seams of corrugated 



Uo 



MARINE-BOILER DETAILS 



ftirnaces are invariably welded. In Fig. 47, a common con- 
stXTjction of such a flue is shown. The end A is cylindrical 
s'^tJ is attached, by rivets, to the head of the boiler, which is 
fl^Oged either inwardly or outwardly to fit closely over the 



rUtaiatMiMMbi 



tp'ljndrica] part of the furnace flue. The other end of the flue 
ii flanged in the manner shown: the back tube sheet is riveted 
o the flange C, and the plates forming the sides of the com- 
bustion chamber are riveted to the flanges D,£). The dis- 
tance from center to center of corrugations is 8 inches; the 
plain part at the ends must be not more than 9 inches, and 
the thickness not less than -fs inch. The radius of the outer 
corrugation must be not more than half that of the reverse 
r suspension curve, 

A Piirves ribbed rtirnace flue is shown in Fig. 48. 
the height of the ribs is made Iff inches, the distance from 




ibter to center of ribs 9 inches. The thickness of the flue 
: not be less than -^ inch, and the length of the plain 
t at the ends must not exceed 9 inches. 



MARINE-BOILER DETAILS 



§101 



Both corrugated and ribbed flues may be used for the ' 
uptakes of boilers having a wet uptake. 

41. A Morlaou suspension fiiruace flue is shown in 
Fig. 49. This flue somewhat resembles the corrugated flue 
shown in Fig. 47. The outer corrugations, as a, a. Fig. 49, 
are made to a small radius, and are joined by a curve o£ 
large radius. 

FDBNACK FITTINGS 

42. General Arrangement. — The ttirnaee flttingrs 



of a Scotch boiler 
made of cast 



shown in Fig. 50. A furnace front A, 
i fitted to the front of the furnace. It is 




held in position by studs screwed into the head of the boiler. 
A furnace door B is fitted to the furnace front. It is generally 
made of the shape shown, and is about IS inches by 15 inches 
in size. A baffle plate b is attached to the door by means 
of long bolts, distance pieces b' made of iron pipe serving 
to keep the plate in place. This baflle plate increases the 
durability of the furnace door and prevents, to some extent, 
the radiation of heat, as it absorbs most of the radiant heat 
of the burning fuel, and thus prevents its coming in contact 
with the door. The furnace door is often provided with 
a small hinged door B' to allow the slice bar to be pushed^ 
into the furnace and the fire sliced without opening the t 
nace door. The inrush of cold air that always accompanies 
the opening of the door proper is thus avoided. Means for 
admitting air above the grate are often provided. The fur- 
nace door may be perforated and supplied with a suitable 
arrangement by which the admission of air may be 



'ith 
ledj 

liesl 



4M. 



e re£ulated.,J 



\%K 



MARINE-BOILER DETAILS 



37 



I Baffle plate 6 may also be perforated to aid in distributitiE 
the air. The lower end of the furnace front forms what is 
known as the dead plate, extending clear across the furnace. 

43. Grate. — The grate, which is generally made in two 
sections, as C C. Fig. 50, is composed of cast-iron grate 
bars supported by a bearing bar D in the center of the 
furnace and by the dead plate and the bridge bar E. 

The grate bars are generally made from 3 feet to 3 feet 
6 inches in length, a greater length being awkward to handle. 
' In order to facilitate the access of air, the fall of ashes, and 
the cleaning of the fire from below, they are made somewhat 
thinner at the bottom. They are provided with distance 
pieces cast with the bar at both ends, and sometimes also 
in the center. These keep the bars apart. 

Grate bars for marine boilers are often cast with two ribs, 
and when so made are called double bars. Single bars, with 
one rib, are used only to fill out a row of bars when there 

ifs not space enough to insert a double bar. A double grate 
bar is illustrated in Fig. 61. The grooves a,a are cast along 
Ifee top edges of the ribs. These grooves soon become 

filled with ashes or clinkers, which protect the top of the bar 
from being burnt. In order to allow grate bars to expand 
freely in the direction of their lengths, one end of each bar. 
where it rests on the dead plate or bridge-wall plate, is 
made slanting at an angle of about 45°. as shown at b. 
Fig. 51. The slanting end of the bar is in contact with a 
similar slant in the dead plate or bridge-wall plate. This 
permits the slanting ends of the bars to slide up when 
expanded. If both ends of the bar were made square, there 
would be no room for the bar to expand and it would soon 
become bent out of shape. Even if spaces were left betweeo 





38 MARINE-BOILER DETAILS §1 

the ends of square bars and the dead plate or bridge-wal 'M 
plate, they would soon become filled with ashes and theiz' 
object thereby defeated. End motion of the bar is prevented, 
by notching the end of the grate bar that rests on the centei" 
bearing bar, as shown at c. Fig. 51. The grate is usually 
placed lower at the back of the furnace, the inclination beings 
about i inch for each foot of length of the grate. This per- 
mits free access of air to the back of the grate. 

44. The width of the air space and hence the thickness 
of the grate bar depend largely on the character of the fuel 
burned. For the larger sizes of anthracite and bituminous 
coals, the air space may be from i to i inch wide, and the 
grate bar may have the same width. For pea and nut coal, 
the air space may be from f to i inch, and for finely divided 
fuel, like buckwheat coal, rice coal, birdseye coal, culm, and 
slack, air spaces from A to f inch may be used. When 
these small air spaces are used, the grate, if made of bars 
like that shown in Fig. 51, must have the ribs so thin in 
proportion to their length that they will warp and twist, and 
a large number of the bars will soon break, especially when 
the rate of combustion is high. To overcome this objection- 
able feature, the grate bar shown in Fig. 52, and known as 




Fig. 52 

the herring-bone fin*ate bar, was designed, and where the 
small sizes of coal are used, it has almost entirely superseded 
the ordinary grate bar. Owing to the shape of the supports 
for the fire, they are free to expand and contract; being quite 
short and of small depth in comparison to the ordinary grate 
bar, there is very little danger of excessive warping of the 
supports. In consequence, they will usually far outlast a set 
of ordinary grate bars. Since there are only a few large bars 
for the grate, it is also easier to replace a broken bar. 



I 



§10 MARINE-BOILER DETAILS 39 

"^tTJng-bone grate bars can be obtained in a great variety 

°' Styles and with different widths of air spaces. 

■45. In general, a grate bar that is suited for the kind of 
''^el that is to be burned should be selected. Thus, if finely 
'divided coal is to be burned, a grate bar having small air 
spaces and supports should be selected, since otherwise a 
Urge percentage of the fuel will fall into the ash-pit. On 
the other hand, for the large sizes of coal, select bars having 
large air spaces, using the largest air space when caking 
coals are to be burned. Some varieties of bituminous coal 
will cal-g, that is, fuse together to a considerable degree, and 
Ihe ashes and clinkers formed will be of such size that a 
large part of them cannot pass through the air spaces unless 
these are ample; the grate thus becomes clogged, shutting off 
the air from the fire. This reduces the rate of combustion 
and evaporation. 

46. Brlilere and Asb-PIt. — Referring again to Fig. 50, 
the bridge f is built up of firebrick on a bearing bar of the 
cross-section shown. Its object is to retard the escape of 
the gases from the furnace, and thus promote a more perfect 
combustion. The distance from the top of the bridge to the 
lop of the furnace varies from 13 inches to IG inches. The 
best height is determined by actual trial, as it depends on 
the intensity of the draft, Ihe thickness of the fire, the kind 
of coal used, and the quantity of air admitted. Generally 
speaking, the area over the bridge is equal to one-sixth the 
area of the grate. The cast-iron bar on which the bridge is 
built is attached to brackets made of angle iron riveted or 
secured by studs to the side plates of the combustion cham- 
ber. The lower half of the furnace flue, that is, the part 
below the grate that forms the ash-pit, is usually lined 
with sheet iron. Sometimes a thin coating of cement is 
applied. A baffle plate G is secured by tap bolts to the bridge 
bar ^'and prevents the free access of air to the combustion 
chamber. Sometimes this plate is perforated, as in some 
cases it is of advantage to admit air behind the bridge. If 
■insufScient oxygen is mixed with the fuel, incomplete 



40 MARINE-BOILER DETAILS §10 

combustion will result. But, by mixing: oxygen with the prod- 
ucts of combustion, after they have left the furnace proper, 
and while they are still in a red-hot state, complete combus- 
tion can be obtained. Sheet-iron ash-pit doors are usually 
provided for the furnaces. They are not attached to the 
furnace, but are kept in a convenient place until required, 
when they are merely placed in position, two hooks riveted 
to the door serving to keep it in place. 

47. Liazy Bar. — A wrought-iron bar H, Fig. 50, extends 
across the furnace, about 12 inches below the dead plate. 
This bar serves as a rest for the fire-tools when clean- 
ing the ash-pit, and a support for the pricker bar while 
pricking the fire from below, and is called a lazy bar by 
firemen. There is another form of lazy bar that is placed 
across the furnace-door opening as a support for the hoe 
and devil's claw while cleaning, banking, or hauling the 
fires. This lazy bar consists simply of a bar a of li-inch 
round iron bent to the shape shown in Fig. 53, in which 

b represents the furnace-door 
opening, c, c are the hinge lugs 
attached to the furnace front, 
and d the catch of the door 
latch. It will be observed that 
one end of the bar rests on the 
upper hinge lug, while the other 
^'°*^ end is supported by the catch 

of the door latch, the furnace door, of course, being open 
while the bar is in position for use. The latch end of 
the bar may be flattened so that it will fit into the notch 
of the latch catch and at the same time form a shoulder that 
will prevent the bar from sliding endwise. This may also 
be accomplished by forming the hinge end of the bar into 
a hook that will grip the hinge lug. This simple arrange- 
ment enables the fireman to clean the fires more quickly 
and get the furnace doors shut sooner than without it, so 
that the rush of cold air into the furnace will be stopped 
earlier. It also lightens the labor of the fireman very 




MARINE-BOILER DETAILS 




considerably, especially 
if very heavy firing 
tools are used. 

48. Furnace Door. 
The Morison furnace 

door illustrated in Fig. 
54, is intended to over- 
come some of the de- 
fects that are inherent 
to the usual type of fur- 
nace doors in use on 
marine boilers. In the 
illustration, the door is 
shown closed at (a) and 
open at (/>); a sectional 
view through the door 
and furnace front is 
given at (c). The pri- 
mary object in con- 
structing the door in 
this manner is to pre- 
vent the undue accumu- 
lation of fuel on the 
front end of the grate, 
which causes overheat- 
ing and uhiniate des- 
truction of the furnace 
door and its attach- 
ments; in consequence 
of the freedom from 
obstruction in the front 
end of the furnace, very 
much better facilities 
are aflorded for prop- 
erly working the fire. 

To accomplish this, 
a portion of the dead 



42 MARINE-BOILER DETAILS §10 

plate immediately inside of the furnace door is cut away at a 
so as to leave a recess. The door is provided with an exten- 
sion, which, when the door is closed, fills the recess in the 
dead plate. This extension, and also the vertical portion of 
the door, may be perforated for the admission of air into the 
furnace. The furnace front b is made of a plate of pressed 
steel worked to the shape indicated in the illustration; the 
furnace door is protected from the fire by the perforated 
liner c. This furnace door is arranged to open upwards, and 
is so counterbalanced by the weights d^ d as to remain open 
while the furnace is being stoked. This is an advantageous 
feature in a marine boiler, as it does away with the necessity 
of catches or other devices for preventing the door from 
being closed by the motion of the ship. 



COMBUSTION CHAMBERS 



PURPOSE 

49. The combustion chamber of a steam boiler is an 
enclosed space, usually located back of the bridge wall, pro- 
viding a place for the unconsumed gases to be thoroughly 
mixed with air and thus effect their complete combustion. 
In some cases, a small quantity of air is admitted into the 
chamber from the ash-pit through small openings in the 
bridge wall or in the diaphragm below the bridge wall. In 
other cases, the air is admitted through small perforations 
in the furnace door. Sometimes, the excess of air that 
passes through the grates is depended on to produce the 
complete combustion of the gases in the combustion 
chamber; or, small openings may be made in the sides of 
the combustion chamber through which the air may enter. 
In all cases, however, provision should be made to rec^late 
the quantity of air admitted, as more air is required to com- 
pletely consume the gases under some conditions than under 
others. When bituminous coals are used, a large quantity 
of air will be required; while with the hard anthracite much 
less air will be needed. The lowest temperature at which 



§10 MARINE-BOILER DETAILS 43 

ignition of the gases can take place is about 1,800° P.; it is, 
therefore, evident that, if the gases are cooled below the 
point of ignition by too much air or otherwise, they will be 
carried to the smokestack unconsumed. It follows that the 
furnace must either be of sufficient height to provide a space 
in which the great volume of gas can burn before being 
cooled, or else there must be a combustion chamber adjacent 
to the furnace in which the gases can burn. No set rule can 
be made in regard to the right quantity of air to admit to the 
combustion chamber; it depends on the experience, skill, and 
attention of the firemen to obtain the best results. 



CONBTHUCTION 

50. The combustion chambers of internally fired marine 
boilers are constructed of similar material, and the plates are 
joined together by riveted seams in a similar manner to that 
employed in the construction of the shells and heads of 
boilers of that class. They are built into the boilers and 
are designed to sustain safely the steam pressures that are 
carried in the boilers to which they belong. 

The shape of a combustion chamber depends on the form 
of the boiler of which it is a part, and as to whether or not 
it is internal or external. Internal combustion chambers are 
usually made circular at their lower ends to conform to the 
curve of the boiler shells, and concentric with them. The 
upper parts are usually rectangular with flat or arched tops. 
External combustion chambers are usually rectangular or 
nearly so. 

51. A transverse section of the longitudinal section given 
in Fig. 55 (a), of two of the combustion chambers of a four- 
furnace, single-ended, Scotch boiler is shown in Fig. 55 (^). 
The sectional view given in Fig. 55 la) is taken through the 
center of the combustion chamber a. Fig. 55 (A). By the 
method of construction shown, each furnace is provided with 
its own combustion chamber, which arrangement is preferable 
to having one combustion chamber common to two or more 
furnaces, though more expensive to build. The front sheet 



44 



MARINE-BOILER DETAILS 



§10 



of the combustion chamber, which is also the lube-sheet, i 
shown at b. and the rear sheet at c; d is the furnace flue, 
The tube-sheet and rear sheet are flanged inwardly, as shown 
at e,e, to which flanges the side and top sheets /.fare riv- 
eted. A circular opening is cut in the lower part of the 
tube-sheet to receive the rear end of the furnace flue, the 




two being firmly riveted together, as shown at £^.g^. 
bustion chambers of Scotch boilers are secured lo the s 
and rear head of the boiler and to each other by stayboH" 
as A, h. The bridge wall /, which is constructed of firebrick, 
is built on the cast-iron bearing bar j. The brickwork 
extends across the floor of the combustion chamber and 
up the rear sheet of the same for some distance above 



^ 



§10 



MARINE-BOILER DETAILS 



45 



the lop of the furnace flue, as shown at i- and /, lo pro- 
tect the metal at those points from the intense heat of the 
flame, which otherwise would impinge directly against it, 
accomplishing its early destruction. 

52. Combustion chambers are sometimes constructed 
with rounded or arched backs, as shown at a, Fig. 56. The 



r rr ^ii 





purpose of this is to facilii 
tale the flow of the gases 
of combustion into llie 
tubes, the curved top of the 
combustion chamber act- 
ing as a deflector for the 
gases. 

S3. The combustion 
chambers of firebox boilers 
of the locomotive type are 
constructed as shown in 
Fig. 57. It will be ob- 
served that ill this boiler the combustion chamber a is an 
extension of the furnace b and is separated from it by the 
bridge wall r; also, that the back sheet of the combustion 



46 



MARINE-BOILER DETAILS 



chamber is the front lube-sheet. The side sheets are secured I 
to the shell of the boiler by the staybolts f, ^, and to the | 
lube-sheet and firebox by the flanges /, /. 

54. The combustion chamber of a firebox boiler of the 
flue and retum-lubular type is shown at a. Fig. 58, It is con- 
structed and secured in the boiler in very much the same way 
as those just described, with this difference, however: it is 
located at the rear end of the flues b, b, at some distance I 




from the furnace c; hence, there is a greater opportunity tov\ 
the unconsumed gases to cool below the temperature oVu 
ignition before they reach the combustion chamber, byl 
coming in contact with the walls of the comparatively cool | 
flues, than if the combustion chamber were located immedi- 1 
ately adjoining the furnace. The door d is provided toj 
afford access to the interior of the combustion chamber for| 
cleaning, inspection, and repairs. 

55. The combustion chamber of a return-flue boiler is ' 
illustrated at a. Fig. 59, This is an externally fired boiler in 
which ihe construction of the combustion chamber differs .^ 
radically from those of internally fired boilers. In this c 



uo 



MARINE-BOILER DETAILS 



47 




it is formed of firebricks. This method of construction has . 
its peculiar advantage. The combustion chamber being 
located at a considerable distance from the furnace b, the 
unconsumed gases would be cooled below the temperature of 
ignition if it were not for the fact that the bricks of which 
the combustion chamber g « 

and the smoke flue c are 
constructed become highly 
heated and the heat given 
olT from them assists in 
keeping the temperature of 
the gases up to the point 
of ignition. The combus- 
tion of the gases is also in 
progress during their pas- 
sage through the smoke 
flue. The doorway d is 
constructed in the rear wall Pm m 

of the combustion chamber to afford access to its interior for 
examination, cleaning, and repairs. 

56, The construction of the form of furnace commonly 
used with water-tube boilers of the Babcock & Wilcox type 
is such that there is little opportunity for combustion to take 
place after the gases leave the firebox. The gases rise 
nearly vertically from the fuel bed and pass from the firebox 
immediately into contact with the tubes; the narrow spaces 
between the tubes divide the gases into thin sheets that are 
rapidly cooled below the temperature of ignition. The vertical 
direction of the current of gases in the furnace makes it diffi- 
cult to secure any considerable admixture of air from the 
fire-door; the chief dependence for the air supply must, there- 
fore, be on the air that rises through the grates and passes 
upwards through the bed of fuel. These conditions make it 
essential that, for complete and economical combustion, a 
sufficient supply of air be admitted through the grate itself 
and that the supply be well distributed over the whole grate 
area so that it may become mixed with the gases almost as 




4S 



MARINE-BOILER DETAILS 



§10 



soon as they are formed. It is also important that the grate 
be placed far enough below the tubes to peniiit of a thorough 
mixture of the gases and air and of complete combustion of 
the gases before they enter the spaces between the tubes. 
The distance from the grate to the tubes should be regulated 
in accordance with the volatile contents of the coal; for 
anthracite or coke, the minimum distance is about 24 inches; 
for coals containing large quantities of volatile matter and 
burning with a long flame, a distance of 36 inches or more is 
often needed. 

PASSAGES FOR GASES OF COMBUSTION 



BOILER FLUES 

57. The longitudinal seams of boiler flues may be either 
riveted or lap welded. Riveted flues are usually made as 
shown in Fig. 60, They are made in sections, the ends of 
the sections being fitted one into the other and substantially 



I 




riveted. Lap-welded flues above 6 inches in diameter j 
not exceeding 16 inches diameter need not be made in se< 
tions, provided that the steam pressure does not exceed 
60 pound« per square inch or the length of the flue 18 feet. . 
If the pressure is over 60 pounds and not exceeding 120 
pounds, such flues may be made in sections not exceeding j 
5 feet in length. 



UHKS 

58. Hntcrlals and Sizes. — The principal purpose i 
boiler tubes is to increase the heating surface of the boild 
and thereby increase its steaming capacity. The tubes alsflrS 
divide the water and heated gases into small bodies, tbe^eb)^1 



L^.^^ .^w- *-4 



S!0 



MARINE-BOILER DETAILS 



49 



t;reatly facilitating the transmission of the heat from the 

^■ases to the water. 

Boiler tubes are made of iron, steel, and brass, and until 
recently were all lap welded. Lately, however, cold-drawn, 
seamless, steel tubes have come into extensive use for first- 
cbss work. Brass tubes were formerly much used in the 
.Vdvy, but they have been superseded by steel tubes. Seam- 
iess copper or brass tubes not exceeding J inch in diameter 
Jie allowed in the construction of water-tube pipe boilers or 
generators in which liquid fuel is used. 

59. The sizes of tubes and flues are designated by their 
outside diameters to distinguish them from pipes, which are 
designated by their inside diameters. Tubes more than 6 
inches in diameter are usually called flues. The thicknesses of 

SIZES OF BOILEB TUBES 



Outside 


Thickness 


Thickness 


Outside 


ThicknesB 


Tbichness 


Diameter 


Fractions 


byB.W.G. 


Diameter 


Fractions 


byB.W.G. 


Inches 


of an Inch 


Number 


Inches 


of an Inch 




, 


.072 




4* 


-134 


10 


b ■* 


.072 




S 




148 


9 


m •* 


.083 




6 




'fis 


8 


m '* 


■09S 




7 




165 


8 


■ ' 


■095 




8 




165 


8 


W '^ 


.095 




9 




180 


7 


W 'i 


,109 
.tog 


12 


II 




203 

220 


6 

5 




.log 




12 




229 




- '■ 


.120 




13 




23« 


4 


& '» 


.120 




M 




248 




■ ,i 


.120 




IS 




2S9 


3 


W . 


.134 




16 




270 





tubes are expressed in fractions of an inch, and also by wire- 
tauge numbers. There are numerous wire gauges in use, but 
lUe one geaerally accepted as the standard is the Birmingham 




50 



MARINE-BOILER DETAILS 



9 to 



wire gauge, which is usually designated by the capital letters 
B. W. G. 

The thicknesses of boiler tubes and flues, as required by 
the Board of United States Supervising Inspectors of Steam 
Vessels, are given in the table in this article. 

The table gives the minimum thickness of boiler tubes and 
flues up to 6 inches in diameter, and of any required length, 
to carry a working pressure not to exceed 225 pounds per 
square inch, if deemed safe by the inspectors. Lap-welded 
flues over 6 inches in diameter and not over 16 inches in diam- 
eter, of the thicknesses given in Table I, are allowed a pres- 
sure of GO pounds per square inch if their lengths are not 
greater than IS feet. Lap-welded and riveted flues over 
6 inches in diameter and not over 16 inches in diameter, and 
not longer than 18 feet, are allowed a pressure of 120 pounds 
per square inch if made in sections not over 5 feet long that | 
are properly fitted into each other and substantially rivetec 



60. Securlngr Tubes. — The method of securing the 
tubes of Scotch boilers is illustrated in Fig. 61, in which a 
is the tube, b the front 
tube-sheet, and c th^ back i 
tube-sheet. The tubes a 
inserted from the froi 
of the boiler and driven ' 
through both tube-sheets 
until they project about 
i inch into the back t 
nections, their length^ 
I being such tfaat about 1 1 
i inch will be left outside ' 
of the front tube-sheet. 
The ends of the tubes are expanded in the lube-sheets by 
means of a tool called a lube expander, this serving to make ■ 
the joints tight. After being expanded, the ends of the tubt 
projecting into the combustion chamber are peened over witt 
a ball-faced hammer and then beaded over the tube-sheet, i 
shown at d. Fig. 61, by a beading tool, commonly called i 



thata 

the" 
ich d 
ront 
back H 

teoJf 

-iven * 
Gets 

!OUl 

m 



§10 MARINE-BOILER DETAILS 51 

Iwot-tool, made as shown in Fig. 62, The front ends of the 
tubes are sometimes merely expanded, so that the tubes may 
be driven inwardly a little and expanded and beaded anew 



I 




should they leak, but more often they are peened over 
slightly, as shown at e, Fig. 61. 

61. The Dudgeon roller-tube expander, shown in 
Fig. 63, is most commonly used for expanding boiler tubes. 
It consists of a body A provided with three slots for the recep- 
tion of the rollers a. a, a. A plate B, fastened to the body by 
the three screws r, c, c, prevents any longitudinal movement 
of the rollers. The rollers are forced outwards and rotated 
by the taper pin C, which is provided with a head perforated 




with two holes at right angles to each other. To make the 
expander adjustable for different thicknesses of tube-sheets, 
the hood D may be moved longitudinally and may be locked 
in any desired position by means of a small taper pin d, which 
is driven inwards to lock the hood. The operation of the 
expander is as follows: The expander is pushed into the 
tube, the projections /?', D" limiting the depth to which 
the tool may be inserted. A sharp blow with a copper 
hammer is struck on the head of the pin C, fordng it inwards, 
and heace the rollers outwards. Next, a bar is inserted into 



52 



MARINE-BOILER DETAILS 




one of the holes in the head and the pin rotated; the frictioal 
between the pin and the rollers causes the latter, and ( 
sequentty the whole tool, to rotate; this operation expands! 
the tube. 

62. The ends of boiler tubes should be annealed befonfl 
they are expanded; otherwise, they will be hard and brittleJ 

and liable to splitf 
while being expaad-j" 
ed. The process of" 
annealing the tubes 
is as follows: The 
ends of the tubes are 
heated to a red heat 
in a furnace or forge, 
and the tubes are then 
stood on their heated 
ends in a box con- 
taining a mixture of fine charcoal and air-slacked lime, in 
equal parts, to a depth of 5 or 6 inches, and there allowed'fl 
to cool. This renders them soft and ductile, which enabieq 
them to be expanded without danger of splitting. 

Tubes or flues above 5 inches in diameter are commonl7.| 
riveted to the heads, which are flanged to receive them. 

63. 8t(ij--tubcs are used to stay the tube-sheets, and ar«| 
tubes of greater thicknesses than the ordinary tubes. 
ends are enlarged and threaded, and 
the tube is screwed into the front 
and rear tube-sheets. They are 
secured either by a nut on the outside 
of the sheet, as shown in Fig. 64, or 
beaded over, as illustrated in Fig. 6"). 
Sometimes a nut on each side of the 
sheet is used. From one-third to one- 
fourth of the tubes in a Scotch boiler 
are stay- tubes. 

A sectional view of a wrench that is very convenient forfl 
screwing and unscrewing stay-tubes is shown in Fig, 66. Iti 




§ 10 MARINE-BOILER DETAILS 53 

consists of the spindle or mandrel a, which is just large 
enough to enter the tube. Two semicircular grooves i, i 
are cut into the sides of the spindle, into which are fitted two 
short pieces of tool steel c,c, of the section shown, and held 
there by any convenient means. Their outer edges being 
roughened, they grip the inside of the tube whichever way 
it may be turned. 

64. Tubes of water-tube boilers of the Babcock & 
Wilcox type are secured in a similar manner to those of the 
fire-lube boiler. The tubes of water-tube boilers of the 
See and Seabury types are expanded into the steam and 
water drums, the operation being similar to that practiced 
with large tubes. 

The tubes of the Mississippi boiler are secured in the 
steam and water drums by screw ferrules. These ferrules 
are threaded both inside and outside; the inside thread 
receives the end of the tube, while the outside thread is 
screwed into the drum. Pipe boilers of the Almy and 
Roberts types are put together with ordinary threaded pipe 
tittings. 

65. Serve Tube, — A sectional view of a boiler tube 
that is now being used to a considerable extent in the boilers 
of modern steamships is illustrated in 
Fig. 67. It is known as the Serve tube 
and its special feature is that its interior 
surface is largely composed of a number i 
of longitudinal ribs, as shown at ■: 
The object of these ribs is to increase ' 
the amount of surface of the tube that 
is in contact with the hot gases, and 
thereby extract a larger amount of heat 
from them, which is transmitted to the water through the 
ribs and walls of the tube, thus increasing the efficiency of 
the boiler. 

66. 8plral Retarder. — It is sometimes the case that in 
fire-tube boilers with very strong natural draft, or when using 
forced draft, the gases of combustion enter the stack at a 



le extent in the boilers 

:0 





54 



MARINE-BOILER DETAILS 



^in 



very high temperature, and much of the heat they contain, 
which should have been absorbed by the water to make 
steam, is lost. In order to overcome this difficulty and cause 
the gases to be retained in contact with the heating surface 
of the tubes for a longer period of time, and thus utilize 
more of their heat, an arrangement called a spiral retarder 
is inserted into each tube. The reiarder is illustrated in 




Fig. 68, in which a is the tube and d the retarder, which 
consists simply of a strip of thin (say, i inch thick) sheet 
iron or steel, the width of which is just equal lo the inside 
diameter of the tube. This metal strip is twisted lo a spiral 
form, very similar to a carpenter's auger, and placed in the 
tube, wherein it is a loose fit. This spiral strip causes the 
current of hot gases to take a spiral course through the 
tube, thereby increasing the distance they have to travel, 
and keeping them in contact with the walls of the tube a 
longer period of time, which gives the heat a better oppor- 
tunity to enter the water. 

By gripping the end of the retarder with a pair of black- 
smith's longs, it may be turned around and around, thus 
loosening any soot or other foreign matter that may have 
become incriisted on the inside of the tube, after which the 
retarder can be withdrawn and the loosened incrustation 
blown from the tube by a steam jet. 




MARINE-BOILER ACCESSORIES 



CONSTRUCTION, USE, AND CARE 



SAFETY VAIiVES 



CONSTRUCTION 

1. A ftafety valve is a device used to prevent the steam 
within the boiler from exceeding a certain pressure. This is 
accomplished by the steam overcoming the downward force 
on the valve and opening a passage for the steam to escape 
into the atmosphere. The valve remains open for some 
time, reducing the steam to a somewhat lower pressure, and 
relieving the boiler, 

2. A common lever safety valve, as applied to boilers 
of steam vessels, is shown in Fig. 1. The lower end of the 
casing A communicates with the boiler and is bored out to 
receive the gun-metal bushing j9. This bushing is secured 
to the casing, its upper edge d being chamfered and forming 
the seat for the valve K Four arms on the inside of the 
bushing support the boss />', which is bored out central with 
the seat, and forms a guide for the lug on the lower face 
of the valve. Attached to the upper end of the valve is 
the stem S, which passes through a gun-metal bushing in the 
bonnet A' and is guided at its upper end by a bushing in the 
yoke y. The stem is slotted below the yoke and above 

Cc^Tighlld br ImUrnaliimal Tiilbook Comfant. Enlirtd at Smluxtt't' Hall. Ij-mten 
111 



HARIXE-BOILER ACCESSORIES 



Sll 



the boDoet. and is prorided with knife-edee bearings for the 
lever L, which has its folcnun at the iqiper end of the link / 
pivoted at a. A weieht Wis placed a "t*"" distance from 
the folcmm; this wetght acts on the valve stem, and conse- 
qoently presses Uie valve to its seat, foiming the resistance, 
or downward force, that the sieam actiiiE on the nader side 
of the valve has to overcome. On the steam pressnre reach- 
ing a certain point, it will balance the ilownward force, and a 
slight increase of the steam pressnre will canse the valve to 
lift from its seat, thus forming an anntilaip opening through 
which the steam escapes into the passage P and thence 
tbroneh a pipe (not shown tn the figure) into the atmos- 
phere. As the steam pressure becomes less, a point is soon 




reached at which the downward force balances the steam 
pressore, and on the pressure being still further reduced, 
the valve closes. A small drain pipe should be fitted to the 
casing just above the valve seat, to carry away any water 
that may collect, and which, by its weight, would add to the 
external load on the valve. Lever safety valves are today 
practically obsolete in sea-going vessels, but are used to 
some extent on river steamers. 

3. A deaU-welftht safety valve is shown in Fig. 2, 
In this construction, the external load on the valve is formed 
by cast-iron or leaden weights W. W piled on a plate P 
attached to the valve stem. The action of this valve, under 
pressure, is the same as thai of the valve jast described. 



HI 



MARINE-BOILER ACCESSORIES 



ICi© 



A crown cap, or hood /?, provided with two rings cast on it 
and also with a handle, is attached to the upper end of the 
valve stem 5, by means of the cotter C, and fits the 
stem loosely. The depth of the slot in the stem S, which 
works in a bushing F fixed in the cover, is such that the 
valve can move upwards a 
certain distance without lift- 
ing the hood D, while the 
hood cannot be raised with- 
out raising the valve with 
I At. By means of the forked 
lever L, the valve can be 
lifted and its freedom of 
action tested. The handle 
attached to the hood is for 
the purpose of turning the 

live around on its seat 3 
asionally, thus crushinj; 
any scale or other sediment 
that may lodge on it. 

The dead-weight safety 
valve is the earliest form of 

fety valve, but is now obso- 

ite in American practice. 

4, A sprtuft-loadod sHfcty valve is illustrated in 
The external load is the force required to compress 
9ie coiled spring T. By means of the threaded bushing (7, the 
of the .lipring can be regulated by screwing the bush- 
ing up or down, thus providing a simple method of adjusting 
' the downward force to the pressure at which the valve is 
to open. The hood D, which fits loosely on the upper part 
of the bonnet or casing ff, is keyed to the valve stem 5" by 
t'lneans of the cotter C, in which is the padlock hole d. 
"he hood, and consequently the valve, may be lifted by 
i of the lever /,. At the same time, the valve is at 
lerty to open without lifting the lever. The bushing C. 
^bich is provided with a locknut d', forms a guide for the 





MARINE-BOILER ACCESSORIES 



111 




I 



upper end of the valve stem. When the steam pressure lifts 
the vnlve off its seat, the spring is compressed; this increases 
the rosiMtancc of the spring and so increases the force acting 
downwards on the valve. This prevents the valve froi 
liftinc nn^ higher, and gives but a limited area for the stei 
Id cscnpc. 

5. To overcome thJ 
increasing resistance of 
spring mentioned in Art. 

so-called pop safety 
'I* To) ^ol^*^ has been designed, 
and has now superseded 
all other forms of spring- 
loaded safety valves; in fact, 
this type of safety valve is 
used for most marine boilers. 
A pop-val\~e is shown in 
Fig, 4, A gun-metal bnsh- 
— c /» is fitted to the lower 
of the valve casing A. 
. bashing is threaded and 
; « -'.h a movable ring Ji 
' >5-scctioa shown 
^ _r«. A threaded 
— „^,^^ with a 
~ .: a snide 
> is nsed 



it<»titait'.- 



tte iMft WKSIIfit 



1 



HI 



MARINE-BOILER ACCESSORIES 



steam to escape freely. This additional pressure can be 
adjusled by raising or lowering the ring /?, thus reducing or 
increasing the area of the passage bb. The smaller the area 
of this passage, the 
faster the pressure 
will accumulate and 
the higher the valve 
will lift; conversely. 
the larger the area 
of the passage, the 
slower will the pres- 
sure accumulate, and 
the longer will be 
the time required for 
the full opening of the 
valve, A pop-valve 
closes very promptly, 
thus preventing an 
II nndue loss of steam. 

L 

■ 6. A safety valve 

'Ik 18 intended to relieve 
a boiler of all the 
surplus sieam gener- 
ated. To accom- 
plish this object, this 
valve must have a 
certain area of open- 
ing: this area is fixed '" * 
by the rules and regulations of the Board of Supervising 
Inspectors of Steam Vessels to be, for lever safety valves, 
at least 1 square inch to every 2 square feet of grate surface 
of the boiler to which the valve is attached. For spring- 

I loaded safety valves constructed so as to give an increased 
■i^ by the operation of steam after being raised from their 



ZE AMD ARRA^'G 





6 MARINE-BOILER ACCESSORIES §11 

ftcatft, or any tpriDs:-loaded safety valve constructed in any 
other manner to as to s:ive an effective area equal to the first- 
mentioned ftprins:-loaded valve, the area of opening must be 
At least 1 square inch to every 3 square feet of srrate surface. 

All spring-loaded safety valves for water-tube, coil, and 
sectional boilers required to carry a steam pressure exceed- 
ing 176 pounds per square inch must have an area of not less 
than 1 sciuare inch to every 6 square feet of grate surface of 
the boiler. 

The term area of opening refers to the area corresponding 
to the internal diameter of the valve. The term elective area 
always refers to the area of the annular opening between the 
valve and its seat, through which the steam escapes when 
the valve is raised. 

7» The safety valves of a battery of boilers must be 
arranged in such a manner that each boiler shall have one 
separate safety valve, unless the arrangement is such as to 
prt^chule the possibility of shutting off the communication 
oC any binler with the safety valve or valves employed. This 
also applies to safety valves provided with an attachment 
prt^venting any but an authorised person to increase the 
vUnvnwanI force on the valve. A valve constructed in such 
a iwann<?r i?i known as a luck«up safety valve. Referring 
U^ Fig*. S ami 4» if a ^vadlock were attached to the cotter C 
at ^s th<^ c^^tlt^r c\nild not be withdrawn unless the padlock 
w^tt^ reinovtM) tirst: ami. as the hood D covering the adjust- 
ing bushing CiAUUol be remv^ved without withdrawing the cot- 
ter, uv^ one but the per^ou having the key of the padlock can 
4Kl>u^t the wwp'^sf^^^ v>i the spring. 



S^ All ^xrtug^lvx*vVf\! :wttetY vgLlves: most be pcovided 
d levev thjtt will r^isie :be vi^ve from its seat a dxstance of 
^»v^t le*:5i tb^i^t oue-ei^^tb the ^.liaajeter ot the valve opening. 
rthi' se^it* s^: Jt•,^Y :^ie or saf^cy vxve *^sed oa a marine boiler 
^f^usc >ave .tii x:i^;c vK v'-v-vratioc f,* the center T^^^e of 45". 
l>c -tr^^t or Ovvw*.:-*^ o: :<K* sVfjiievM::ctt Irecweea tihe safety 
v.i \c a:n* :v>c Vi'et -j^ucsx l^e it leas^ ^uul ia area to the 
i;ex» ,*i VJ^- ^al\v. 



Ml 



MARINE-BOILER ACCESSORIES 



9. Very often, one lijck-up safety valve is provided for 
every common safety valve. The valves (two or more in 
number) are usually placed on a separate fitting, shown at 
A. Fig. 5. This fit- 
ting may be attached 
to the shell of the 
boiler or the shell 
of the steam drum. 
It avoids the neces- 
sity of cutting a 
separate hole in the 
shell for each valve. 
In the illustration, B 
and C are the safety 
valves, and 6 and c 
their respective 
escape pipes lead- ''"'■ ^ 

ing the steam blown off to the main escape pipe. The 
drain pipes />', c' prevent the accumulation of water in the 
valve casing. 




CALCULATIONS 

10. Lever Safety Valves. — No safety valve can open 
without a slight increase of pressure above that for which it 
is set; since, in order to lift the valve, the pressure on the 
under side of the valve, which may be called the inlerttal, or 
upward, force, must exceed the external, or dmi'Tin-ard, force 
on the valve plus the friction of the mechanism of the valve. 
If the internal and the external forces on the valve are equal, 
the valve will be in equilibrium (balanced), and an increase 
of the internal force will cause it to open. A safety valve 
will not close until the pressure has been reduced somewhat 
below the pressure at which the valve opened. 

11. The point at which a safety valve will blow off 
depends on the external force on the valve. To be in equi- 

^wlibrium. the external load exerting a downward pressure on 
^■Ae valve must be equal to the internal force exerting an 



8 MARINE-BOILER ACCESSORIES §11 

upward pressure on the under face of the valve. Evidently, 
the upward pressure is equal to the area of the valve multi- 
plied by the pressure per unit of area. 

Whenever the word pressure is used in relation to calcu- 
lations pertaining to safety valves, the fi^ug^e pressure is 
meant, unless otherwise stated. By the area of a safety valve 
is meant the area of that part which is exposed to the steam 
pressure when the valve is seated. 

12. Suppose that a dead-weight safety valve, as shown 

in Fig. 2, has a diameter of 4 inches and an external load or 

force, consisting of the valve and stem, the supporting plate 

and the weights, equal to 815.8 pounds. It is desired to 

know the pressure at which the valve will open. Since the 

internal and external forces must balance, it is evident that 

815.8 = 4' X .7854 X steam pressure, in pounds per square 

815 8 
inch. Then, — ;[— — = 65 pounds per square inch, nearly, 

the pressure at which the valve is about to open. 

13. In the lever safety valve shown in Fig. 1, the 
external load depends on the position of the weight Won 
the lover A. Here the same general law holds good; the 
external and the internal forces must be equal before the 
valve is alx>ut to open. The internal force, as stated 
iKforo, is the area of the valve times the steam pressure. 
The downward force on the valve may be found as follows: 
Supi>ose that a weight P, Fig. 6, weighing 100 pounds is 




e 



Pt^.f 



^ 



placcil directly on the top of the valve stem C; evidently, the 
dowmvAix^ toroo is iv>\v cq«Al to the weight of the weight P. 
Suppose, i^ow, th,it the wcijiht is removed to the position 
showii in the t^jjure, the weij^ht's instance d from the fulcrum 



§11 MARINE-BOILER ACCESSORIES 9 

being six times greater than the distance a from the ful- 
crum lo the center line of the valve. Evidenlly, the effect 
of the weight on the valve stem will now be six times greater; 
that is, the downward force will be 6 X 100 = 600 pounds. 
Hence, to find the downward force, divide the distance (/by 
the distance a and multiply the quotient by the weight of the 
weight P. 

As the valve and stem have a certain weight, the external 
force is increased an amount equal to that of the weight of 
the valve and stem, in pounds. Furthermore, the lever has 
a certain weight, and this, acting at the center of gravity 
of the lever, adds a certain amount to the downward force. 
This amount is equal to the product of the distance from the 
fulcrum of the lever to its center of gravity and the weight 
of the lever, divided by the distance from the fulcrum to the 
center line of the valve. 

The distance to the center of gravity of the lever may be 
mnd by balancing the lever on a knife edge and measuring 
the distance from the center of the fulcrum to the knife 
edge. If this should not be feasible, the center of gravity 
must be found by calculation. In engineers' examinations, 
the lever is usually given as straight and parallel, in which 
case the distance from the fulcrum to the center of gravity 
of the lever should be taken as equal to one-half the length 
of the lever. 

The amount of the downward force on the valve due to 
the weight of the lever may be found directly by attaching 
a spring balance by a cord to the lever at the point at which 
it acts on the valve stem. The spring balance will indicate 
the correct doi\-nward force, in pounds. 

Now, to have the valve balance, the area of the valve 
times the steam pressure (the upward force) must equal the 
weight times the distance from the fulcrum to the weight 
divided by the distance from the fulcrum to the center line 
of the valve; to this downward force must be added the 
additional downward force due to the weight of the valve, 
stem, and lever, the sum of these two downward forces con- 
stitutine tli6 external force. 



^ ii,. 



10 



MARINE.BOILER ACCESSORIES 



811 



14. How to find the pressure per square inch at which 
a safety valve is about to blow off, may best be explained 
by the following example; Suppose that a safety valve has 
the following dimensions; The area of the valve is 12,566 
square inches; the distance from the fulcrum to the center 
line of the valve is 4 inches; the weight is 135.2 pounds; the 
length of the lever, between fulcrum and weight, is 36 inches; 
the weight of the valve and stem. 9.2 pounds, and the down- 
ward force due to the weight of the lever, as found by one 
of the three methods previously described, 150 pounds. 
From what has been explained, it should be clear that the 
valve balances, or is in equilibrium, if the steam pressure X 
12.566 = 135.2 X 36 -f- 4 + 9.2 + 150. That is, the steam 
pressure X 12.566 = 1,376. Then the steam pressure 
1.376 
12.666 



109.5 pounds per square inch. 



Let A = area of valve, in square inches; 

D = distance from center line of valve to fulcrui 

in inches; 
Z, = distance of weight from fulcrum, in inches; 
P = steam pressure, in pounds per square inch; 
IV = weight, in pounds, of load or weight on lever; 
w = weight of valve and stem, in pounds, plus 
ward pressure due to weight of lever. 

Rule. — To find the pressure at which a safety valve is abt 
to blow off, multiply the weight by the length of the lever a. 
divide this prodiul by the distatue from the fukrum to the cem 
line of the valve. To the quotitni, add the downward press* 
on the valve due to the weight of the valve, stem, and lever, m 
divide the sum by the area of the valve. 



WL , 



Or. 



Example,— The area of a lever safety valve Is II square inches; t 
distance from the center line of valve to the fuLcniiu, i\ inches; t 
distance of the weight, which weighs 125 pounds, from the fulcnul 
35 inches; the weight of valve and stem plus the downward pro 



MARINE-BOILER ACCESSORIES 



due tA the weight oi (he lever equals 137 pounds. PInd the pressure 
per square inch at which the valve is about to open. 



Solution.— Applying the rule just stven, 

P =» '—r- = 100.84 lb. per sq. i 






15. To explain how to find where a. given weight must 
be placed on the lever in order that the safety valve may be 
about to blow off at a given pressure, consider the first para- 
graph in Art. 14. In the case cited, the pressure was found 
to be 109.5 pounds per square inch; hence, the total upward 
force is 109.5 x 12MG = 1,375.977, say 1,376 pounds. This 
force is partially balanced by the weight of the valve and 
stem, and the downward force due to the weight of the lever. 
Consequently, the total upward force = 1.376 ~ (150 + 9.2) 
— 1,216.8 pounds, is to be balanced by the downward force. 
As the downward force is the weight times the length of the 
lever divided by the distance from the fulcrum to the center 
line of the valve, it should be plain that the valve will be in 

.,.. . ■ -( 1 010 o 135.2 X the length of lever 
equilibnum agam if 1,216,8 = ■ — —^ . 

That is, 1,216.8 = 33.8 X the length of lever, since 135.2 -r- 4 

= 33.8. Hence, the lever = ^g^^- = 36 inches. Or, if 

1.216.8 = 135.2 Xlen gthgLI_ever ^2l&.Sx4 = 135.2xlength 



of lever, and length of lever = 



1.216.8 X 4 
136.2 



= 36 inches. 



■ Bale. — To find the distance from the fulcrum to the point at 

' which the weight must act. in order lo have the valve bloui off at 

a given pressure, subtract the downward force due to the weight 

of the valve, stem, and lever frotn the product of the area and the 

steam pressure. Afultiply the remainder by the distance from 

e fvfcrum to the tenter lineol tfu valve and divide this product 

f the weight. 



( AP-w)/y 



I 



12 MARINE-BOILER ACCESSORIES §ll 

Example. — At what distance from the fulcmm must a weight of 
150 pounds act in order that the valve may be about to blow off at 
100 pounds per square inch pressure; the diameter of the valve is 3} 
inches; the distance from the fulcrum to the center line of the valve is 
4i inches, and the downward force due to the weight of valve, stem, 
and lever is 125 pounds? 

Solution.— Area of valve = (3})* X .7854 = 11.01 sq. in. Applying 
the rule just given, 

^^.{lL0Oii00-J25)XJL6_ 29.37 in. Ans. 

16. Suppose it is desired to find the weight that must 
be placed on a lever to have the valve blow off at a given 
pressure. Using the example given in Art. 15, the unbal- 
anced upward force, as previously found, is 1,216.8 pounds. 

The valve then will balance if 1,216.8 = wdght X 36 . ^^^ .^^ 

4 

if 1,216.8 X 4 = weight X 36; whence, the weight 

1,216.8X4 1.216.8 .oi^o ^ 

= — — ^^ = -^— - — = 135.2 pounds. 

36 •" 9 ^ 

Rule. — To find the weight thai must act on a lever at a given 
distance from the fulcfum so that the valve is about to blow ofi 
at a given pressure^ subtract the downward force due to the 
weight of the valve ^ stem^ and lever from the product of ike area 
and the steam pressure. Multiply the reinainder by the distance 
from the fulcrum to the center line of the valve ^ and divide this 
product by the distafue from the fulcrum at which the weight is 
to act. 

Or. W = iAP.-p>l^ 

Example. — A safety valve has the following dimensions: Area of the 
valve, 15.7 square inches; distance of weight from fulcrum, 48 inches; 
distance from fulcrum to center line of the valve, 5 inches; the down- 
ward force due to the weight of the valve, stem, and lever is 182 pounds. 
Find the weight to blow off at 04 pounds per square inch. 

Solution. — Applying the rule just given, 

... (15.7 X ^A - 182) X 5 _ _ ,. . 
W = -^ ^ ■ = 85. /I lb. Ans. 

17. Some inspectors of the United States Steamboat 
Inspection Service prefer to have the lever safety-valve 



^Pll MARINE-BOILER ACCESSORIES 13 

7 P''ob!enis worked out by rules I. II, and III, which follow. 
These rules will give exactly the same results as the cor- 
responding rules given in Arts. 14, 15, and 16. Their 
(ierivalions. since it involves a knowledge of algebra, is not 
given. Rules 1 and II are colloquially known among Ameri- 
can marine engineers as "Roper's rules." When a candi- 
date for marine engineer's license knows that the examining 
inspector prefers Roper's rules, the candidate is advised to 
use them. 

I In the formulas following the rules, 
Let A = area of valve, in square inches; 
D = distance from center line of valve to fulcrum, 
in inches; 
L = distance of weight from fulcrum, in inches; 
P = steam pressure, in pounds per square inch; 
W = weight of load or weight on lever, in pounds; 
y = weight of valve and stem, in pounds; 
w = weight of lever, in pounds; 
/ = distance from fulcrum to center of gravity of 
lever, in inches, 
The distance from the fulcrum to the weight is usually 
called the len^h of the lever, but on account of confusing 
the length from end to end of the lever with this term, it is 
not used here. 

Knle 1. — To finii the pressure at which a lever safety valve 
is abaut to blgw off, multiply the weight of the weight by Ike 
distance of the weight from the fulcrum. Multiply the weight 
of the lever by oiu-half ils length, if the lever is straight and 
parallel, or by i/ie distance from the fulcrum to the center of 
gravity, if the lever is tapered. Multiply the weight of valve 
and stem by the dislatue from the center line of tfie valve to the 
fulcrum. Add tticse three products together and divide the sum 
by the product obtained by multiplying the area of the valve by 
the distance of the center line of Ifie valve from the fulcrum. 



Or, 



WL + wl->rVD 
AD 



14 MARINE-BOILER ACCESSORIES §11 

Example 1. — At what pressure will a safety valve having a diameter 
of 4 inches blow off, when the weight of the valve and stem is 10 
pounds; of the lever, 20 pounds; and of the ball, 120 pounds? The 
total length of the lever, which is straight, is 44 inches; the weight is 
40 inches from the fulcrum, and the distance from the center line of 
the valve to the fulcrum is 4 inches. 

Solution.— The area of the valve = 4* X .7854. As the lever is 
straight, its distance from the fulcrum to the center of g^vity is taken 
as one-half its length, or V- Applying the rule, 

_ 120 X 40 -h 20 X V + 10X4 ._ .. • , a 

P = 4«'v~7ft54~vT ~ P^*" *^' *°'* nearly. Ans. 

Rule II. — To find the weight necessary to put on a safety- 
valve lever, multiply the area of the valve by the steam Pressure 
and nmltiply this prodiut by the distance between the center line 
of the valve and the fulcrum. Multiply the weight of the lever 
by one-half its length, if straight arid Parallel, or by the distance 
between the cciiter of gravity and the fulcrum, if tapered. 
Multiply the weight of the valve and stem by the distance 
between the center line of the valve arid the fulcrum. Add the 
last two Products together and subtract their sum from the first 
Product, Divide the remainder by the distance the weight is 
from the fulcrum. 

Or, W = APD-iwl+VD ) 

Example 2. — With a safety valve having the dimensions given in 
example 1, what weight is necessary to have the valve about to blow 
off at a steam pressure of 100 pounds per square inch? 

Solution.— Applying rule II, 

Rule III. — To find at what distance from the fulcrum to 
place the weight of a lever safety valve, multiply the area of the 
valve by the steam pressure, and multiply this product by the 
distance beturcfi the center line of the valine and the fulcrum. 
Multiply the weight of the lever by one-half its length, if 
straight and parallel, or by the distance of its center of gravity 
from the fulcrum, if tapered. Multiply the weight of valve and 
stem by the d/stanre bctzvcen the center line of the valve and the 
fulcrum. Add the last two products together and subtract their 



rill MARINK-BOILER ACCESSORIES 16 

In '» liom the lirst product. Divide the remaifidef by the weight 
'■t llie zffight. 
nr / _ APJ}-W> 1+ VD) 

Example 3.— A safety valve has an area of 11 square inches; the 
distance from the center line oE the valve to the fulcrum is 3 inches; 
(he steam pressure, 40 pounds per square inch;' the weight weighs 
.iO pounds; the lever is straight and parallel. 32 inches long, and 
weighs 1>5 pounds; the valve and stem weigh U pounds. How far 
[rom the fulcrum must the weight be placed^ 



Solution. — Applying rule 111, 



11 



;40x 



- (1 5XV + 6X 3) . 



60 



21.24 ii 






18. A candidate for American marine engineer's license 
should thoroughly familiarize himself with the calculations 
pertaining to a lever safety valve, as a candidate for a 
marine engineer's license must be rejected by the examining 
inspectors if he fails to solve safety-valve problems similar 
to those given in the examples. 

19. spring Safety Valves. — The question often arises, 
what pressure is a safety-valve steel spring intended for? 
When mac!e with 13 complete turns, the standard prescribed, 
the question can be answered by an application of the rule 

^_pf the Board of Trade, Great Britain, governing this problem. 

^B'Snle. — To find the steam pressure for which a spritig is 

^Bitiended, cube the diameter, in ittches, of the wire, if round, or 

the side of square, if square, and multiply by 8,000 for round 

wire and 11.000 for sgitarc wire. Divide the product by tite 

product of the diameter of the spring, in inches, measured from 

to center of the wire, and the area of the safety valve. 

P = ''--^, 
DA 

\ P = steam pressure, in pounds per square inch; 

d = diameter, or side of square, of wire, in inches; 

c = 8.000 for round wire and 11,000 for square wire; 

D s diameter of spring from center to center of wire; 

A = area of safety valve, in square inches. 



16 MARINE-BOILER ACCESSORIES §11 

Example.— For what pressure is a spring made of square wire 
measuring i inch and 3 inches in diameter intended, if the. valve has 
an area of 6 square inches? 

Solution.— Applying the rule given, 

-, .6» X 11,000 -^ - ,. -A 

P = i,-" „ = 76.4 — lb. per sq. m. Ans. 

«J X o 

• 

Spring-loaded and pop safety valves are finally adjusted 
under pressure by comparison with an accurate steam gauge, 
increasing or diminishing the tension of the spring until the 
valve opens at the desired pressure. The rule given will 
Hhow about what pressure the spring can be used for. 



EXAMPL.ES FOR PRACTICE 

1 . A dead-weight safety valve having an area of 12 square inches 
JM to be on the point of blowing off at 75 pounds per square inch 
preRsurc, absolute; find the weight. Ans. 723.6 lb. 

2. What area of safety-valve opening is required for a water-tube 
boiler carr>*ing steam at 180 pounds per square inch pressure, the 
grnte surface being 48 square feet.^ Ans. 8 sq. in. 

3. At what pressure will a safety valve of the following dimensions 
blow off: Area of valve, 10 square inches; distance from the valve to 
the fulcrum, 8 inches; length of lever (the distance from the fulcrum 
to the point where the weight acts), 90 inches; weight of the weight, 
S:M pi>unds; weight of valve and stem, 5 pounds; weight of lever, 
12 (vninds; total length of lever, 32 inches? The lever is straight and 
parallel. Ans. 90 lb. per sq. in. 

4 . Suppi'kse all the quantities to remain the same as in example 3, 
except that the valve is to blow off at 75 pounds per square inch pres- 
sure; at what distance fix^m the fulcrum must the weight be placed? 

Ans. 24.58 in. 

5. All quantities rem.'iining ^he same as in example 3, except that 
the valx'e is to blow off at S2 pl^unds per square inch pressure, find 
the weight that must bo plavx^l on the lever. Ans. 75.1 lb. 

6. If the spring of a popva]\x is made of wire i inch in diameter 
and has a oontcrto-oentcr diamorer of ,>J inches, what pressure is it 
intende*1 for if used with a vaix-c having an area of 12 square inches? 

Ans. 50 lb. per sq. in., nearly 



MARIN'E-BOILER ACCESSORIES 



USR AND CABE OF SAFETY VALVES 

20. See that the safely valve is attached directly to the 
boiler. If there is a stop-valve between the valve and 
boiler, have it removed or arranged so that it cannot be 
shut under any circumstances. Take care that the valve 
does not become corroded and stick fast to its seat. It is a 
good plan to frequently lift the valve from the seat and see 
whether or not it works freely. Do not overload the valve 
or increase the tension of the spring, and take care that it is 
not done by others. 

In practice, the position of the weight on the lever is 
nsually found by trial in preference to finding it by calcula- 
tion. Most safety-valve levers are notched and have figures 
stamped below the notch, which are supposed to represent 
the pressure per square inch at which the valve will blow off 
when the weight rests in the notch. However, since it may 
be possible that the notches have not been correctly located, 
it is good practice to check the graduation by an actual trial. 
To do so, get up steam on the boiler, and as soon as the 
steam gauge shows the blow-off pressure, shift the weight 
until the valve just commences to blow off. Then fasten or 
lock the weight, if possible, so that it may not be shifted 
accidentally. Before adjusting the position of the weight, 
make sure that all parts of the valve work freely and that 
the steam gauge is correct. 

After adjustment, the valve should occasionally be tested 
by comparing its blowing-off point with the. pressure shown 
by the steam gauge. If the steam gauge indicates a higher 
pressure, it shows one of two things: either the steam gauge 
has become impaired or the valve is out of order. If there 
is reason to suspect the steam gauge, have it tested. At 
any rate, however, in order to be on the safe side, the 
steam gauge may be assumed to be correct and the valve 
examined to see if everything works freely. If found so, 
and the weight of a lever safety valve is still at the same 
mark, it is reasonable to conclude that the gauge is out 
of order. 



18 MARINE-BOILER ACCESSORIES §11 

It is common practice to connect a pipe to the blow-off 
side of the safety valve for the purpose of carrying the 
steam blown oflE out of the fireroom. Such an escape pipe, 
while harmless enough when of sufficient area and kept well 
drained, may become a source of danger if no provision is 
made for draining it constantly. Instances are not rare when, 
owing to the absence of a drain pipe, the escape pipe has 
become filled with water, thus adding greatly to the external 
force on the valve and rendering it inoperative for the blow- 
oflE pressure for which it was set. When an escape pipe is 
used, it should not be of smaller diameter than the valve, 
and should have a drain pipe of ample size at its lowest point. 
No cock or valve should under any circumstances be placed 
in this drain pipe. 

STEAM GAUGES AND WATER GAUGES 



STEAM GAUGES 

21. Constrnctioii. — The steam graugre indicates the 
pressure of the steam contained in the boiler. The most 
common form is the Bourdon pressure graug^e, shown in 
Fig. 7. It consists of a tube a, of elliptic cross-section, that 
is filled with water and connected at b with a pipe leading to 
the boiler. The two ends, at c, are closed and are attached 
to a link ^, which is, in turn, connected with a rack g. This 
rack gears with a pinion / on the index pointer g. When the 
water contained in the elliptic tube is subjected to pressure, 
the tube tends to take a circular form, and the tube, as a whole, 
straightens out, throwing the free ends out a distance pro- 
portional to the pressure. The movement of the free ends 
is transmitted to the pointer by the link, rack, and pinion, 
and the pressure is thus recorded on the graduated dial. 

Mercurial gaugres, in which a column of mercury was 
forced into a closed glass tube by the steam pressure com- 
pressing the air above the mercury, were formerly used, but 
were superseded by a gauge of the construction shown in 
Fig. 7, and which is called a metallic, or dial, gaug^e. 



K 



MARINE-BOILER ACCESSORIES 



19 



22. Steam gauges are placed where they are immediately 
within sight of ihe water tender, but out of reach of rough 
usage. The steam pipe for the gauge is generally connected 
to the top of the boiler, sometimes to the steam drum, and, 
in some instances, the gauge is placed on top of a so-called 
water column. A siphon should be placed directly under the 
gauge. This siphon is formed by carrying the steam pipe 
to a lower level than the gauge and then bending it upwards, 
thus forming a U that is filled with water to prevent the heat 
of the steam from injuring the spring and the other mechan- 




ism of the gauge, or distortmg tts action by the expansion 
of its parts. A small drip cock, shown at rf, Fig. 8, is fitted 
to the lowest point of the siphon and serves to let the water 
out of the leg of the siphon connected witll the boiler. If 
no cock were fitted, the water accumulating in this leg by 
the condensation of the sleam would, by its weight, cause 
the gauge to indicate a higher pressure than that due to the 
sleam. Care should be taken not to locate the steam-gauge 
pipe near the main steam outlet of the boiler, since this may 
cause the gauge to indicate a lower pressure than really exists. 




20 



MARINE-BOILER ACCESSORIES 



§11 




23. Pressure gauges for indicating steam pressure are, 
in English-speaking countries, invariably graduated to indi- 
cate pressure above that of the atmosphere, in pounds per 

square inch, and show how much the pres- 
sure has been increased above the atmos- 
pheric pressure. When pressure gauges 
are used for indicating the pressure in 
the condenser, they are called vacuum 
g:aug:es, and are invariably graduated to 
show, in inches of mercury, how much the 
pressure has been decreased below that of 
the atmosphere. Then, to find the absolute 
pressure, the vacuum-gauge reading must 
be subtracted from 30, and the pressure will 
be given in inches of mercury. To obtain 
the absolute pressure in pounds per square 
inch, multiply the diflEerence between 30 
and the gauge reading by .49. Thus, if 
the vacuum gauge indicates 25 inches, the 
absolute pressure in the condenser is 
(30 — 25) X .49 = 2.45 pounds per square inch. The direc- 
tions just given are entirely correct for normal atmos- 
pheric conditions at sea level. Since the pressure of the 
atmosphere is not constant, but varies between certain 
limits, it is better, if accuracy is desired, to use the fol- 
lowing general rule: 

Rule. — 71? find the absolute pressure shown by a vacuum 
gaugey subtract the vacuum-gauge reading from the reading oi 
the barometer and multiply the difference by .49, 

Example. — What is the absolute pressure if the vacuum gauge 
indicates 19 inches, while the barometer stands at 28 inches? 

Solution. — Applying the rule just given, 

Absolute pressure = (29 - 19) X .49 = 4.9 lb. Ans. 

24. Compound steam f^au^es are occasionally met 
with, in which the left-hand part of the dial indicates vacuum 
iji inches of mercury and the right-hand part indicates pounds 
per square inch above the atmospheric pressure. They are 



Pio. 8 



MARINE-BOILER ACCESSORIES 



Usually found attached to the receivers of multiple-expansion 
ondensing engines. 



25. Use and Care ol Steam Gnnst^s. — While the 
■engine is running, it will often be noticed that the pointer 
mot the gauge vibrates so much that the pressure cannot be 
^ead. This can be prevented by partially closing the cock a. 
The greatest of care must be taken, however, to 
^prevent an entire closing of the cock. The pointer of a 

■ steam gauge will stick occasionally; hence, experienced 
engineers always jar the gauge a little, in order to dislodge 
any foreign matter that may be preventing movement of the 

1 pointer, before they accept its indication as correct. 

w Steam gauges will lose their accuracy after they have been 

pin use for some time, owing to the spring losing its elasticity 

' or taking a permanent set. In this case, the gauge will indi- 
cate a pressure higher than the actual pressure in the boiler. 
This can usually be discovered by the pointer failing to 
return to the zero mark when there is no pressure in the 
boiler. If the pressure apparently indicated when there is 
no pressure be subtracted from the pressure indicated when 
the boiler is under steam, the correct pressure will be given 
approximately. However, when a gauge shows a wrong 
pressure, a new one should be immediately substituted and 

I the old one discarded or sent to the maker for repair. When 
inspecting boilers, the boiler inspector usually tests all steam 
{gauges on board by comparison with an accurate test gauge. 

f The gauge to be tested and the test gauge are both attached 
vessel in which the pressure is raised by means of a 

I small force pump, and the readings of the two gauges are 

tcompared at different pressures. 

As previously explained, the accuracy of the safety valve 

1 be checked by means of the steam gauge when the latter 

i known to be accurate. Conversely, when the safety valve 

Bis known to be set correctly, the steam gauge can be checked 

■ lor the blow-off pressure by watching its indication when the 
I'Valve just blows off. If a steam gauge shows an erro"- of 
f more than 5 pounds, it will be condemned by most boiler 



22 MARINE-BOILER ACCESSORIES §11 

inspectors. Steam s^auges should be taken off at least once 
a month and the connectin^^ pipe cleared by blowing steam 
through it. When the gauge is off, see that the hole in the 
nipple is perfectly clear. 

Good practice demands that one steam gauge should be 
attached to each boiler when more than one boiler is 
used. On some vessels, however, it is not uncommon to see 
one steam gauge do duty for a whole battery of boilers. 
This is permissible where several boilers are set in a battery, 
that is, have a common furnace and are connected by drums 
at the top and bottom. An arrangement of this kind is 
never found in sea-going vessels, but is common in vessels 
navigating the western rivers of the United States of America 
and many South American rivers. 

With some kinds of water, the spring of the steam gauge 
will corrode. Under no circumstances attempt to fix a 
corroded spring by soldering up the hole or holes. Instead 
of this, send the gauge to the maker to have a new spring 
fitted and adjusted. When replacing the gauge after taking 
it off, make sure that the valve in the steam-gauge pipe is 
opened before going further, and then make sure that the 
gauge is operative. It has happened in numerous instances, 
in putting up the piping with unions, that the gasket placed 
between the two parts of the union has been so large that in 
tightening the nut it has been squeezed out so as to com- 
pletely stop the hole in the pipe, thus preventing the gauge 
from showing the pressure. 



WATER GAUGES 

2(>. (iaiiffe-Cooks. — A special form of valve or cock 
attached to the boiler for the purpose of testing the level of 
the water is known as a jiniup:e-cock. The cocks, usually 
three in number, are placed either on the head or shell or 
they are attached to the water column. Three gauge- 
cocks a, d,r are shown in Fig. 9, screwed into the front head 
of a Scotch boiler. The middle gauge-cock d is at the 
proper water level, generally about 8 or 9 inches above the 



§11 



MARINE-BOILER ACCESSORIES 



23 



top o£ the combustion chamber. The lower giiuge-cock c is 
about 5 inches below the middle cock, and the lop gauge- 
cock a is 5 inches above it. Should the top gauge-cock be 
opened while the boiler is steaming, steam will issue from 
it. On opening the middle gauge-cock, a mixture of water 
and steam will issue, and solid water will come out of the 
lowest cock. When gauge-cocks are fitted in the position 
shown in the figure, a drip pan D is fitted below the cocks to 
prevent the water from the cocks coming in contact with the 
head of the boiler and corroding and soiling it. The nozzles 
of the cocks are pointed in such a direction that the jet of 
steam or water issuing from one cock cannot strike the one 
below it and scald the attendant. Gauge-cocks are often 
placed on a separate fitting, consisting of a tube with its 




I ends connecting with the steam and water spaces of the 
■boiler, sufficiently below and above the water level to be out 
of reach of the violent ebullition going on at the surface of 
the water. If the cocks are connected directly to the bead 
or the side of the boiler, this violent ebullition may cause 
the gauge-cocks to indicate a wrong water level. 

27. Gauge-cocks are made in a great variety of forms, 
md it is largely a matter of choice which to adopt. Those 

jcks shown at a,b,(, Fig. 9. belong to a type that is used 

j^xtensively. It consists of a threaded spindle or stem having 

. small conical disk valve on its inside end, which fits a 

leat inside the cock body, and has a crank-shaped handle 

I its outside end. The cock is opened by re 




volving the ^k 



MARINE-BOILER ACCESSORIES 



§11 



firerooin floor. When they s 

- T " • 



crank-shaped handle about a quarter of a turn. This cock is 

suitable for boilers of large diameters on which the cocks are 

placed too high to be conveniently reached by hand from the 
so placed, they are usually 
operated by a rod having a - 
hand grip at one end and 
an eye made to fit over the 
handle of the cock at the 
other end. 

Another form of gauge- 
cock is shown in Fig. 10. 
It consists of the body a, 

the stem A, to which the valve is attached, and the nozzle (. 

This cock is similar in construction to the one just described, 

with the exception that instead of having a crank-shaped 

handle, it has a disk of hardwood for turning the valve. 

The wood, being a non-conductor of heat, prevents the 

hand from being burned. This cock is suitable for small 

boilers only, on which the cocks can be reached by the 

hand of the operator, 

A form of gauge-cock that has come into extensive use is 

shown in Fig. 11. Itis known to the 

trade as the trgisler pattern gauge- 

cotk and consists of the body a and 

a nozzle, which consitutes the valve 

seat, The weighted handle b. called 

the ball, is secured to the body of 

the cock by the pivot <-. A strip of 

sheet rubber d is inserted in a slot 

in the base of the handle, which 

makes a water-tight joint on the 

nozzle when the cock is closed. 

The cock is kept closed by the 

weight of the ball. To open the 

cock, it is only necessary to lift the ball, and it will close 

itself when the ball is released. When the vessel gives a 

sudden lurch, this cock is liable to spring open for an instant 

and blow out some hot water on the heads of the boiler 



4 




ill 



MARINE-BOILER ACCESSORIES 



25 



\ 



attendants; this is a serious disadvantage, but not serious 
enough to warrant the exclusion of this kind of cock from 
marine work. 

Still another gauge-cock is illustrated in Fig. 12, It is 



I 

enc 
spa 



known as the Mlsslsslpjtl tn^iiKc-cock and consists of the 

body a and the rod or spindle 6. This rod has the valve c 

on one end and the push handle d on the other end. The 

valve fits into a seal at the end of the cock body. The steam 

or water flows out through the orifice e into 

the atmosphere when the gauge is opened. 

This is done by pushing against the handle 

with the hand, and on the handle being 

released, the pressure of the steam or water 

€)n the back of the valve closes it and keeps 

it closed until opened again. 

The above-described cocks are either 
screwed directly into the head of the boiler 
or else into a separate fitting. 

28. Glass Water Uaiiee. — A glass tube 

lose lower end communicates with the 

water space of the boiler and whose upper 

end is in communication with the steam 

Space, is known as a glass water |i:a.uf>;f . 

;ll in good order, the level of the water in 

auge will be the same as in the boiler, 

liters, in good practice, are provided with 

th cocks and gauges. Fig. 13 shows a '■if- ■■' 

common form of gauge-glass connection. The lower fitting 

connects with the water space, and the upper fitting with 

le steam space, of the boiler. A drip cock is placed at the 

twer end of the glass for the purpose of draining it. The 




MARINE-BOILER ACCESSORIES 



§11 



fittings may be screwed directly into ihe boiler head. The 
gauge should be so located that the water will show in 
the middle of Uie gauge glass when at its proper level in the 
boiler. The fittiugs are provided with valves for the par- 
pose of shutting off the gauge from the boiler when a glass 
tube breaks and it becomes necessary to put in a new one. 
The valves are also used for blowing 
out and testing the working of the gauge. 

29. It frequently happens that the 
glass tubes of water gauges are broken. 
This is usually the result of improper 
fitting of the tube; thus, the tube may 
be too long, so that when expanded by 
Ihe heat it will be crashed between the 
fittings. Being improperly packed is 
also a fruitful source of the breakage of . 
glass tubes. They may be packed too i 
tightly or not properly centered at the I 
ends. When the glass tube of a water 
gauge breaks, a, considerable amount of | 
steam and hot water is blown from it I 
and the water showered about the fire- I 
room. To obviate this in a measure, the 1 
quick-closing water gauge, illustrated in I 
Fig. 14, was introduced. The two valves J 
are provided with yokes that are con- 
nected together by chains, the bights of I 
which hang down into the fircroom. One I 
pull on the chain will close both valves, j 
This may be done very quickly, but even I 
then a man may be severely scalded] 
^"^ " before he can pull the chain. 

30. To overcome the difficulty referred to in Art- 29, 
self-closing glass water gauges were designed, one form o( I 
which is illustrated in Fig. 1.1. The principal feature is 
two balls in the steam and water passages, as shown in the ' 
sectional portion of the figure. These balls are enclosed in | 




§11 



MARINE-BOILER ACCESSORIES 



27 



conical chambers provided for them m the upper and lower 
connections of the gauge to the boiler. Under normal con- 
ditions, the balls He passively in the large ends of the cham- 
bers, there being sufficient space between the balls and the 
walls of the chambers for the steam and water to flow to the 
glass tube unobstructed and without creating enough current 
to move the balls. But, should the glass tube break, there 
will be a sudden rush of steam or water through the passages, 
which will force the balls into the small ends of the chambers 
and close the openings communicating with the glass tube. 
After the balls close the openings, 
the pressure of steam and water 
behind them would hold them in 
these positions until the pressure in 
the boiler was blown off if some 
means were not provided to force 
them away from the openings after 
they have served their purpose. 
This is accomplished by having a 
small projection, or teat, on the under 
side of the valve, which pushes ihe 
ball from the opening when the valve 
is screwed shut; the ball will then 
roll, by gravity, to the large end of 
the conical chamber, where it will 
remain until it is required for ser- 
vice again by the breaking of another 
glass tube. The balls are prevented '^" ' 

from rolling back into ihc boiler by wire pins driven across 
the passages behind the balls. To preserve the self-closing 
feature of this gauge, the valves should be screwed back as 
far as they will go while the steam pressure is on, so as to 
allow the balls to act promptly when occasion requires. 

31. A glass water-gauge tube may be cut to the proper 
length by the small tool illustrated in Fig. 16, and called a 
fllass-tube cuitpi-. It consists of the metal rod a having 
the thumb and finger handle 6 at one end and Ibe revolving 





MARINE-BOILER ACCESSORIES 



Sul 



disk or wheel c at the other end. The wheel is made of 
hardened tool steel and is provided with a knife edge. The 
guide d regulates the amount of the lube to be cut off and 
is held by the thumbscrew e. The proper length of the tube 
is found by measuring the distance between the fittings, 
allowing a small margin for expansion. The guide is then 
slid to the proper position to cut the tube the required length, 
and is secured there by the thumbscrew. The tool is now 
inserted into the tube with the cutting edge of the wheel 
against the inside surface of the tube and turned around by 
the thumb and fingers. By so doing, the wheel will score the 
inside of the tube, after which the tool is removed from 
the tube and the edge of the part of the tube to be detached 
is inserted into the slot /; then, by a sharp downward move- 
ment of the handle end of the tool, the tube will be broken 
oS squarely where scored. If a cutting tool is not at hand. 



I 



a glass tube may be cut by filing a groove around it with 
sharp-edged file and then tapping it sharply with the file. 
tittle turpentine applied to the file will facilitate the filinj 
operation. Another way to cut a glass tube is to tie a tum- 
or two of lamp wicking or soft string, saturated with turpen- 
tine or other inflammable liquid, around the tube at the place 
where it is desired to cut it, and set the wicking or string on 
fire; then, while it is hot, strike the end of the tube a quick, 
sharp blow with a piece of metal, when the tube will gener- 
ally break at the place where it was heated by the burning 
string. 

32. Water Columns. — Gauge-cocks and glass waterfl 
gauges connected directly to the boiler head are open to thoV 
objection that the violent ebullition at the surface of tbof 
water will cause them to indicate a wrong water level, 
overcome this objection, they are frequently placed on i 
separate fitting known as a water column, which consists 



MARINE-BOILER ACCESSORIES 



29 



811 

of a large tube with its ends connected to the steam and 
water spaces of the boiler far enough above and below the 
water level to be out of reach of the violent ebullition of the 
surface of the water. 

A water column is shown in Fig, 17. The top and bottom 
ends of the column A, which 
is simply a east-iron tube, are 
connected to the steam and 
water spaces of the boiler by 
the pipes B and C, respectively. 
The gauge-cocks (I, (I, n and the 
steam gauge 5 are fitted to this 
column. It will be noticed that 
a coit siphon is used below the 
steam gauge. No drip cock 
needs to be fitted to this kind 
of siphon, as no water can 
collect and disturb the indica- 
tion of the gauge. The con- 
struction of the glass water 
gauge is as follows: Two fit- 
tings />, b, which are provided 
with cocks e, r, are screwed 
into the water column. These 
fittings connect with the top 
and bottom of a glass tube / 
open at both ends. Each fit- 
ting is provided with a stuff- 
ingbox d to make a steam- and C 
water-tight joint between the 
fitting and the glass tube. To 
the lower fitting, a drain cock.f . 
provided with a waste pipe, is fir, it 

attached; this cock is used to empty the glass tube. The 
water column is attached to the boiler at such a height that 
the water, when at its proper level, will show in the middle 
of the glass tube. It will be seen that the water level in this 
case is self-indicating, and always in plain sight of the 




30 



MARINE-BOILER ACCESSORIES 



§11 



attendant. The communtcalions of the tube with the steam 
and water may be shut off by means of the cocks e,e in case 
the tube breaks. 

Another form of water column is illustrated in Fig. IS. 
This column is more extensively used in America than the 
one just described. The principles governing both, however, 
are the same, the difference being only in the details. The 
body of the column is shown at a, the upper and lower glass- 
gauge fittings at b.b. the gauge-cocks at c,c,c, and the drip 
pipe, containing a valve, at d. It 
will be observed that screw plugs 
are fitted opposite the ends of the 
pipes connecting the column with 
the boiler, for the purpose of clean- 
ing out those pipes with a wire 
should they become choked. There 
is also a drip cock placed below the 
glass tube. 




33. I'ao and Care of Glass 
WaltT Guu(i;es and Water Col- 
umns. ^Too much reliance must 
not be placed on the gauge glass. 
If the water is muddy or contains 
soda, it is liable to foam, and the 
glass cannot give the true water 
level. Again, the connections be- 
tween the glass and boiler may 
become so filled with incrustation 
"^""^ that scarcely any water can enter 

the gauge. To prevent this, the glass should be blown out 
frequently. The water gauge and water column should be 
tested at least once each watch; i.e.. every 4 hours. When 
the water gauge is attached directly to the head, open the _ 
drain cock to blow out the glass. Observe if the watq 
returns immediately to its former level when the drain co< 
is closed. If it fails to do so. this indicates that the lowfl^ 
fitting is choked with sediment or scale. Should the watt 



§11 MARINE-BOILER ACCESSORIES 31 

fail to leave the glass, or leave it very slowly, it indicates thai 
the upper fitting is choked. When this test shows the gauge 
to be out of order, it should be repaired at the first possihle 
opportunity, running in the meantime by the gauge-cocks. 
To remove all temptation to look at the glass, cover it with 
any material handy. While this may seem an unnecessary 
precaution, it may be the means of preventing an explosion. 

3-1. When water columns are used, they usually have a 
valve in each connecting pipe. To test both the gauge and 
the column connecting pipes at the same lime, double ihut off 
one connection and see if the proper fluid comes through 
both drain cocks. That is, to test the water connection, shut 
the upper valve of the gauge glass and the valve in the steam 
connection. Then open, successively, the drain cocks of the 
glass water gauge and water column. If water issues in a 
constant stream from both, the water connection is clear. 
Now open the upper valve of the gauge glass and the valve 
in the steam connection and close the lower gauge-glass 
valve and the valve in the water connection. If steam flows 
freely from both the gauge-glass and the water-column drain 
cocks, the steam passages and the column itself are clear. 
Close the drain cocks again and open all valves. 

This method of testing is commonly expressed iri a some- 

^vhaX ungrammaiical form as follows: Double shut off what 

^Hmk get, and see if you get the other. 

^^p85. When the gauge-cocks and glass water gauge are 
^attached to a water column, a test of the glass water gauge 
may show it to be unreliable. Then, in order to run by the 
gauge-cocks, it is first necessary to test and prove that the 
water column is in good order. To test the water column, 
shut off the glass water gauge on top and bottom; then shut 
the valve in the steam connection and open the water-column 
drain, from which water should flow in a full stream, the 
valves in the water connection being open. Now close the 
valve in the water connection and open the valve in the steam 
mnection, when steam should issue freely from the water- 
Uuinn draia. 



32 MARINE-BOILER ACCESSORIES §11 

36. When the water column has no valves in its steam 
and water connections, it cannot be properly tested. Open- 
ing the drain cock of the column will merely prove the water 
connection to be clear, by water issuing: in a solid stream, but 
will not prove either the steam connection or the column to 
be clear. Hence, it is advisable to have valves in the steam 
and water connections of the column. If these valves are not 
fitted, the g^lass water g:aug:e should be tested as thoug^h it were 
directly attached to the boiler; if the gauge does not prove 
right, it is best to assume that both the water column and the 
glass water gauge are out of order, and to shut down until they 
can be repaired, unless gauge-cocks are fitted separately to 
the boiler, by which to run until repairs can be effected. 

37. The practice of testing the water column only cannot 
be too severely condemned, because the testing of the column 
does not prove the glass water gauge to be correct. When 
possible, test the glass water gauge and the column sepa- 
rately and prove both to be correct. To prevent the water 
column from choking up, drain it frequently, and do the same 
with the glass water gauge. Always supplement the draining 
by the test given. The water gauges are the most important 
accessories to a steam boiler, and too much care cannot be 
bestowed on having them absolutely reliable. 

38. The pipes for the water column should run as 
straight as possible and connect directly to the boiler. 
Under no circumstances whatsover should these connecting 
pipes be used for any other purpose or have any other pipe 
connection. When observing the water gauge while the 
boiler is under steam, note particularly whether the water 
showing in the glass is stationary or not. If the water level 
does not fluctuate, or pulsate up and down, as it were, it is 
an infallible sign that the glass water gauge or the water 
column is out of order. Immediately test the glass water 
gauge and water column, and if draining fails to clear them, 
shut down the boiler until they can be cleared, unless the 
boiler has gauge-cocks directly attached by which to run 
until repairs can be made. 



§11 



MARINE-BOILER ACCESSORIES 



33 



39. Float Water Gauice. — The teedwater used in the 
boilers of vessels navigating the western and southern 
rivers of the United States of America is usually quite 
muddy, and as the boilers are forced considerably, a good 
deal of foaming is produced. The ordinary glass water 
gauge and gauge-cocks will not show the true water level 
when the boiler is foaming, and as this is taking place more 
or less all the time with the bad feedwater used and the high 
rate of evaporation, it is very desirable to have a water-level 
indicator that will not be affected by foaming. Hence, the 
riout water gauge has been designed, and is, in variously 
modified forms, in common use on the boilers of river 




steamers, taking the place of the glass water gauge. Fig. 19 
is an illustration of such a gauge; a is a hollow copper 
sphere, or float, fastened to one end of the lever 6, which 
is rigidly fastened to a spindle free to turn in the dial stem c. 
This stem carries a large dial if, graduated as shown. A 
pointer is fastened to the spindle, and moving in front of 
the dial, indicates on it the height of the water in the boiler. 
Now, as the float cannot float on foam, this gauge will not 
be affected by foaming, but will always indicate the true 
water level, provided that the spindle moves freely. To 
lake a steam-tight joint between the spindle and boiler, a 
ingbox and gland is employed, and great care must be 



U MARINE-601LER ACCESSORIES §11 

takeo, in packing it, not to pack it too tight. The float must 
be free to move with any variation of the water level; if the 
spindle is packed too tight, it may stick and indicate plenty of 
water in the boiler when the water really is dangerously low. 

40. Fusible Plagrs. — A safety device having a part that 
fuses at a low temperature, and is known as a taalble plu^, 
is attached to most marine boilers. The purpose of a fusible 
plug is to give warning in case the water in a boiler should 
become low. The plug consists of a bronze casing, as 
shown in Fig. 20, hollowed out, tapering, and threaded on the 
outside to screw into the boiler plate or tube. The hollowed- 
out portion of the plug must be filled with Banca tin, which 
melts at a temperature of about 443° P. As long as the 
plug is well covered with water, the fusible metal is kept 
from melting by the comparative coolness of the water; but 
should the water sink low enough to uncover 
the top of the plug, the filling quickly melts 
and allows the steam to rush out, thus giving 
warning of the shortness of water. The plug 
shown has a conical tilling, the larger end of 
the filling receiving the steam pressure. The 
conical form of the filling prevents its being blown out by 
the steam pressure. 

The rules' and regulations of the United States Board of 
Supervising Inspectors of Steam Vessels require that all 
steamers plying on United States waters or sailing from 
United States ports shall have inserted in their boilers plugs 
of Banca tin at least i inch in diameter at the smallest end 
of the internal opening, in the following manner: Cylindrical 
boilers with flues shall have one plug inserted in one flue of 
each boiler; and also one plug inserted in the shell of each 
boiler from the inside immediately below the &re-line, and 
not less than 4 feet from the forward end of the boiler. All 
firebox boilers shall have one plug inserted in the crown of 
the back connection or in the highest fire-service of the boiler. 
All upright tubular boilers used for marine purposes shall 
have a fusible plug inserted in one of the tubes at a point 




Ill 



MARINE-BOILER ACCESSORIES 



35 



■ at least 2 inches below the lower gauge-cock, and said plug 
may be placed in the upper head-sheet when deemed advisable 
by the local inspectors. The bronze casing o( all fusible 
plugs, unless otherwise provided, shall have an external 
diameter of not less than that of a ?-inch gas- or steam-pjpe 
screw tap: except, when such plugs shall be used in the tubes 
of upright boilers, plugs may be used with an external diam- 
eter of not less than that of a f-inch gas- or steam-pipe screw 
tap, and having the smallest end of the opening in the plug 
at least i inch in diameter. 

■II. As with other safety devices, dependence can only 
be placed on a fusible plug when it is given intelligent and 
reasonable care. It should be removed frequently and 
examined to see that the filling is not covered by hard scale. 
Instances are not rare when the filling has melted out and 
the steam been prevented from issning by a heavy covering 
of scale. The filling should be renewed at least once a year. 
Before screwing the plug home, smear a liberal supply of 
plumbago ( graphite) on the threads; this will allow the plug 
to be easily removed. Do not use any oil; this will become 
carburized, owing to the high temperature, and will make it 
pile difficult to remove the plug. 

' For the filling of fusible plugs for American marine boilers, 
:a tin must be used. This can be procured almost 
bywhere, although, in general, it is cheaper to keep a small 
ppply of plugs on hand, and simply replace the plug with a 
IT one, instead of refilling it. 

"hen taking charge o£ an old boiler, it is well to examine 
e ftisible plug to see if it really is what it is supposed to be. 
bstances are not rare when ignorant persons have either 
replaced the fusible plug by a solid gas ping or stopped up 
the hole in the plug by driving wood or iron into it after the 
filling bad melted out. 




MARINE-BOILER ACCESSORIES 



§1JI 



BLOW-OFF APPAKATUS 



BOTTOM BLOW-OFF 

42, In order that a boiler may be emptied either partiall; 
or entirely, a cock called the bottom blow-off cocb is 

attached by a short pipe to the lowest point of the boiler 
and is connected with a waste pipe discharging; overboard. 
Fig. 21 shows the manner in which this cock is often con-- 
structed. The shell ^ of the cock t 
provided with two rectangular pass 
sages B, D' , and has fitted to it i 
taper plug P, pierced by the trap« 
zoidal hole b. The upper end i 
this plug is cylindrical and somewhaC 
smaller in diameter than the shell,! 
thus leaving a space for the insertion'! 
of packing. With the plug in the p 
tion shown, communication between 
the passages B and B' is shut off; but 
on the cock being given a quarter turn, 
the hole b in the plug will be brought 
in line with the passages B and ff, 
thus allowing the steam or liquid in., 
one passage to pass to the other, anf ■ 
from thence to its destination. A cocks' 
in which ihe passages are directly opfl 
posite, Hke in the one shown, is called 
"''"■ ^ a strulRlitway cock. If the pas- 

sages are at an angle to each other, the cock is called i 
anfcle cock. The upper end of the gland G forms a capifl 
which is bored out large enough to admit the body of theil 
spanner, or key, A', and is provided with a slot 5, shown in ' 
the plan view, in such a position that in removing the 
spanner from the square end of the plug, the tongue / of 
the spanner cannot pass through the slot 5" unless the cock , 
is fully closed. It is the custom in American s 




erican steam vessels H 

.mm 



§11 



MARINE-BOILER ACCESSORIES 



37 



to put this spanner in the care of the engineer on watch or 
in charge, thus preventing any person but himself, or a 
person authorized by him, from opening the blow-off cock. 
After closing the cock, the spanner is removed and returned 
to the engineer. Blowing off with the bottom blow is some- 
times called blowing down. 

Although globe valves are extensively used on blow-off 
pipes, they are objectionable for the reason that, though 
tightly screwed down, the valve may not be properly closed 
on account of a piece of scale or similar matter getting 
between the valve and its seat. As a result, the water may 
leak out of the boiler unperceived. Formerly, brass plug 
cocks were used almost entirely, which, owing to their stick- 
ing tightly, were superseded by globe valves and gate valves. 
Within the last few years plug cocks packed with asbestos 
have been placed in the market, the asbestos packing 
removing the objectionable features of the plug cock. Many 
engineers now insist on the use of these cocks for the blow- 
off pipe. Gate valves are also, to some extent, open to the 
same objection as globe valves. 

The waste pipe, or blow-off pipe, connects with an angle 
cock attached to the side of the vessel. The construction of 
this cock is similar to the one attached to the boiler. When 
it is desired to blow off the boiler, this cock is opened first, 
and then the cock attached to the boiler; this operation is 
reversed when the boiler has been emptied or blown out 
sufficiently. Should the waste pipe break while the boiler is 
blowing off, or at any other time, the water from the sea 
would flow into the ship if no cock were fitted to the ship's 
side. It will thus be seen that the fitting of this cock is 
merely a precautionary measure. 



SURFACE BLOW-OFF 

43. Marine boilers usually have a pipe and cock or valve 
attached near the water level, the pipe extending inside of 
the boiler and terminating in a scoop or ladle, called a scum 
pan, placed about 3 inches below the water level. The 



38 



MARINE-BOILER ACCESSORIES 



§11 



cock itself is known as the surface blcw-off cock, or 
scum cock, and has a waste pipe connected usually with 
the bottom blow-oflE pipe, between the bottom blow-oflE cock 
and the cock on the side of the vessel. 

The surface blow-ofiE cock is used to remove the gjease 
and oil and other impurities floating: on the surface of the 
water. The ladle at the end of the pipe serves merely as a 
funnel for the collection of these impurities. Sometimes a 
trough is fitted, running across or from the front to the back 
of the boilers, having the surface blow-o£E connected to the 
bottom of the trough. 




Pig. 22 



The ordinary arrangement of the blow-off apparatus for a 
Scotch boiler is shown in Fig. 22. At A, the surface blow- 
off cock is shown; its waste pipe B connects to the waste pipe C 
of the bottom blow-off cock D, The water discharges over- 
board through the cock E, The internal surface blow-ofi 
pipe is shown at /% and scum pan at G. 

44. After either blow-off has been used for the purpose 
of partially emptying the boiler of water, the greatest care 
should be used to make sure that the cocks or valves are 



Sii 



MARINE-BOILER ACCESSORIES 



completely closed. If there is a leak, it may be discovered 
by feeling the blow-off pipe at some distance from the boiler. 
If the pipe is very hot, it is an indication that the blow-off 

I valves or cocks are leaking, provided that the test is made 
long enough after the blowing down to give the pipe a 
Bbance to cool. 
Uli 



PIPE FITTINGS 



VAI.\'Ea 

45. For the purpose of controlling the flow of fluids 
Uirough pipes, valves and cocks are universally used. 
Talves that allow the fluid to flow through Ihem in either 
direction are divided into two general classes, viz., g/olif 
valves and gale valves. 

46. Globe valves are made in a variety of forms, follow- 
ig the same general idea of construction. A common form 



( I ._ 1 ^ 




shown in Fig. 23. The fluid enters at A and flows out 

B. The opening in the valve seat is closed by a flat 

movable disk, which may be renewed when worn so as 

I leak. Another common construction is shown in Fig. 24. 



MARINE-noILER ACCESSORIES 



%1» 



This style of valve is used at the junction of two pipes at a 
right angle, and hence is termed an aa^ie valve. The seat 
of the particular valve shown is beveled; when worn, it may 
be made tight again by grinding it in. Globe valves should 
be attached to the pipes in such a manner that the valve will 
close against the pressure. This will allow the valve stem 
to be packed without blowing off the steam from the boilers. 

47. The steam generated in the boiler is carried to it« 



destination by the steam pipe. 



This pipe is provided with a 
stop-valve, which, for large 
sizes of pipes, is a modifica- 
tion of the globe angle valve i 
shown in Fig. 24. The usual! 
construction of a large stop-^ 
valve is illustrated in Fig. 25. 
A cast-iron casing or body A 
is bolted to a nozzle riveted 
to the boiler or steam drum. 
The lower part of the casing 
is fitted with the gun-metal 
ring B, forming the seat for 
the valve K, which is guided 
by wings, as shown in the 
figure. The hand wheel li 
is fixed on the end of the 
valve stem S, which works 
inside a brass nut screwed 
"^' into the yoke of the bonnet 

or cover C; the valve stem passes through the stuffing- 
box (with its gland and neck ring as shown), and is so 
attached to the valve V that the latter can be raised or 
lowered without turning around when the valve stem is 
revolved by the wheel //. To prevent any movement of the 
brass nut in the yoke, it is locked in position by means of a 
small pin shown at D, which passes through the yoke and 
nut. The steam pipe is bolted to the flange /^ Whea 
the valve is raised, the steam flows through 




; flange /•. Whea h 
irough the annulaf.fl 



^11 



MARINE-BOILER ACCESSORIES 



^^=^ 



opening between the valve and the seat, and thence into 
the steam pipe. 

48. The waterway through a globe valve is so contorted 
that it obstructs the flow of a fluid through the valve to some 
extent. To overcome this objection, icate valves have 
been designed, a common form of which is shown in Fig. 26. 
By tiiniing the stem B, the wedge-shaped disks A. A, are 
moved across the seats c, c, and 
the orifice is opened or closed [ 
gradually. The disk A, has cast 
on its lower side a projection D 
that rests on a corresponding pro- 
jection £ that is cast with the 
valve body. These two projec- 
tions form a stop for the disk .-J,; 
when it has come to a stop, a fur- 
ther turning of the stem wedges 
the two disks apart, pressing 
them tightly against the seats. 
A gate valve may be put on to 
receive the pressure on either 
side. 

49. Chect-valvos are valves 
designed to permit the flow of 
fluids in one direction only and to 
positively prevent any return flow 
The most common form of chei-k 
valve is that known as a tclobo 
check. It is shown in Fig 27 ' 

The valve .-f is a solid disk of metal ground lo the beveled 
seat B. It is guided by the wings C and E above and below 
the seat. The fluid passes in the direction of the arrows. 

An improved form of check-valve, known as a switig check, 
is shown in Fig. 2S. The valve disk is attached to an arm 
that swings on a pin, as shown. The passage of the fluid 
through this valve is more direct than in the globe check. 
The fluid passes through the check in the direction shown 




by Ihe arrows, that is, from A toward B. In case of a rapi( 
flow, the projection C on the end of the arm to whit.h thi 
valve is attached strikes against the bottom of the screw D, 
and is thus kept from going too far. 

The two kinds of check-valves illustrated are not very weB' 
adapted for working in any other except a horizontal posi* 



i 




tion. If a check-valve must be used in a vertical pipe, om 
made especially for this purpose should be obtained. 

In marine work, when several boilers are fed by a com^ 
mon apparatus, it is customary to fit each boiler with a 
check-valve having an adjustable lift, and to use this valve 
for regulating the amount of feedwater entering each boiler. 



60. For controlling the flow of liquids, cocks are often 
used. In marine work, they are chiefly used on blow-otf 
pipes, tor the water service of the engine room and fireroora,' 
and on the pipe lines used for fire-service. Ordinary waters 
cocks made with a brass body and a brass plug ground int» 
it are not well adapted for blow-off cocks; special blow-oS 
cocks are made and can be obtained from all reputable 
makers. The objection to the ordinary plug cock is its 
tendency to leak around the bottom and the difficulty of 
moving the plug after the cock has been closed for some 
time. To overcome this difficulty, asbestos -packed plug 



.^>e^. 



11 



MARINE-BOILER ACCESSORIES 



43 



ocks have been designed and are gradually coming into 
xtensive use. These cocks have dovetail grooves cast into 
he body, into which asbestos is lightly driven. The 
isbestos, being slightly elastic, lits snugly against the plug, 
hus making a tight joint; at the same time, owing to the 
imall amount of friction, it allows the plug to be turned 
easily. Since the asbestos is not affected by heat or mois- 
:ure. it is quite durable. 

The use of ground plug cocks should be avoided as much 
IS possible in marine work; especially the use of large-sized 
;ocks of this pattern. They cannot be kept tight for any 
length of time if used much, are difficult to repair, and are 
liable to stick fast in the body when only used occasionally. 
f\.n attempt to move ihem when stuck will often result in 
twisting off the plug end. They answer fairly well in very 
small pipe lines, say up to J-inch nominal pipe diameter, but 
for all larger pipes, valves or asbestos-packed cocks are to 
be preferred. As a general rule, they should not be used 
lor steam pipes, although their use is customary on indicator 
piping and steam-gauge piping. 



EXPANSION .lOINTS 



TBI. Where more than one boiler is used on a steam ves- 
sel, all boilers are connected by short branch steam pipes to 
one large pipe called the main steam pifx. Each boiler is 
provided with a stop-valve, by means of which the commu- 
nication of the boiler with the main steam pipe may be shut 
afT, if desired. The main steam pipe is also provided with a 
stop-valve close to the engine, for the purpose of shutting 
3ff all communication of the steam with the engine. As the 
leat of the steam expands the metal of which the main steam 
pipe is composed, and consequently increases its length, 
neans must be provided by which this increase in length 
■nay be taken care of. This is usually accomplished by 
ueans of eipansion joints, one form of which, known 
:>oth as a packed expauslon Joint and a slip Joint, is 





44 



MARINE-BOILER ACCESSORIES 



Sill 



shown in Fig. 29. It has a body A into which the brass 
bushing B is forced. Into the latter is fitted a shding tube C 
Packing is placed in the stuffingbox D, and is held in posi- 
tion by the gland E, the gland being screwed down by meaiis- 
of bolts, one of which is shown in dotted lines. The packiOiT 
is put in to prevent the leakage of steam. Studs F, F. filleii 
with nuts and check-nuts, limit the amount of movement uF 
the sliding tube C These studs, or other means of prevenl- 
ing the joint being forced entirely apart by the steam pres- 
sure, are extremely importanl, many very disastrous and. 
fatal accidents having been caused by their absence. The 
flanges G and //are bolted to the flanges of the pipe: con- 
sequently, when the pipe expands, the body A of the espaor' 
sion joint is forced to the left, and the sliding tube C to 



P^ 



\^ 



/»5!«W f— 



BP= 



^^^* 



]1 

ipo^ 



right, and when the pipe contracts, they are forced in op] 
site directions. A small drain pipe, not shown in the figure, 
is usually fitted to the lowest point of the body A, and is 
provided with a stop-cock. This pipe is used to drain the 
water formed by condensation of the steam from the joint. 
If no provision is made for carrying off this water, it will 
soon corrode the body, unless it be made of brass or 
metal, as is sometimes the case. 



i^l|| 



52, Slip joints are used where the expansion of a straij 
line of large pipe has to be provided for. In a great many 
instances, expansion may be provided for by bending the 
pipes in the manner shown in Fig. 30, the figure illustrating 
the arrangement of the steam pipes of the steamship Yumuri. 
There are six Scotch boilers standing athwartship, provided 




46 MARINE-BOILER ACCESSORIES §11 

with steam drums. Attached to the top of the drums are 
the stop-valves A^ Ax, A^, etc. The steam pipes B, B^ are 
bent to the shape shown, and increase in leng^th by merely 
bending the pipes. Expansion between A^ and ^„ and A^ 
and A^ is provided for by slip joints C, G. Each battery has 
a separate main steam stop-valve, shown at D and Dx. The 
two branch mains join at E, whence the main steam pipe F 
leads to the engine. Fig. 30 also shows the general arrange- 
ment of the safety-valve escape pipes. At a, b, Cy dy e, and /, 
the safety valves are shown, a\ d\ f', d\ ^, and f being their 
respective escape pipes, which deliver into the main escape 
pipe A. Steam pipes were formerly, but are rarely today, 
made of copper, each section being provided with flanges, 
by means of which the different sections were bolted 
together. Wrought-iron pipes are sometimes employed for 
the smaller sizes, and, lately, welded-steel pipes have been 
used, especially in naval vessels. Copper pipes are some- 
times strengthened by winding them with one or more layers 
of square steel wire, their weak spots generally being the 
brazed joints. Cast iron was at one time very extensively 
used for steam pipes, but, owing to numerous accidents due 
to the treacherous nature of the metal, it has been super- 
seded by copper, wrought iron, and steel. Steam pipes are 
generally covered with some non-heat-conducting material. 



MISCELLANEOUS ACCESSORIES 



WHlSTLtES A:N1) SIRENS 

53« Every steam vessel is provided with a ^wUstle or a 
slrou for signaling purposes. Two of the most common 
constructions are shown in Figs. 31 and 32. Referring to 
Fiv;:. 31, the belK or upper portion, is a hollow cylinder closed 
at the top ami open at the bottom, and is held in position by 
a stud that passes throug:h the center and is secured at the 
upper end by means of a screw and jam nut. The hollow 
base has a narrow annular orifice that communicates with 



§11 MARINE-BCILER ACCESSORIES 47 

the steam pipe and valve. As the steam rushes out of the 
orifice in an upward direction, toward the mouth of the bel), 
it slifibtly compresses the air contained in the bell. The air 
being elastic will not retain a fixed or stationary position. 
but will slightly spring back toward the inrushing steam, 
when it is again forced back in a compressed state, causing 
a vibration of the air and steam. These vibrations continue 
as long as steam is permitted to flow, and are communicated 
to the surrounding atmosphere, thus producing sound. 

The tone may be changed to a higher pitch by lowering, or 
to a lower pitch by raising, the bell. This may be done by 
loosening the jam nut and 
turning the bell up or down, 
after which the nut should be 
tightened. 

Whistles are also con- 
structed to produce two or 
more tones of different pilch 
simultaneously by dividing the 
bell into two or more cell-like 
parts, as shown in Fig. 32. 
Each apartment produces 
different lone, and when these 
tones chord perfectly, the 
effect is quite pleasing. ''"'*" '■"'■™ 

In large steam vessels, the whistle is usually located at a 
considerable distance above the boilers. In order to prevent 
Ihe long whistle pipe becoming filled with water, it is advisa- 
ble to fit a small drain pipe and valve directly above the 
stop-valve in the whistle pipe, which is placed close to the 
boiler. When not in use, the steam may be shut off from 
the whistle, if deemed advisable, and the drain valve opened. 
When no separate valve is fitted to the whistle to shut 
myS the steam, the blowing of the whistle, due to an acci- 
BBent to the whistle valve, may be stopped by pushing a 
^kick into the bell; if this is not feasible, due to the con- 
^■ruction of the whistle, stuff cotton waste into the bell, using 
He long stick. I 





55. As the donker boiler is used only when the vessel 
ii in port, the sieam required lo work tbe atuiliary iDa<:fatD- 
ery at sea mast be taken from tbe main boiler or boilere, 
and this is dose by connecting one of the main boilers, when 
several are nsed, with the main steam pipe leading to the 
anxiliary machinery. Tbe pipe coimeciing the boiler with 
tbif steam pipe is provided with a stop-val^-e known as the 
donkey valve. Its construction does not present any 
Special features; in fact, any ordinary globe valve or gate 
valve may be used. 



MARINE-BOILER ACCESSORIES 



FIRE-APPARATUS 

56. Connected to the main steam pipe or to one of the 
main boilers is a pipe with branches leading to the different 
compartments of the vessel, each branch having a separate 
stop-valve. Usually, all the branches are connected to one 
fiUing, called a manilold. as shown in iPig. 34. In case of 
ftre in any of the compartments of the vessel, the compart- 
ment is closed, and steam from the boilers is led to the 
burning compartment by the pipes mentioned, the steam 
driving out the air and thus smothering the tire. 




I 



The rules and regulations of the Board of Supervising 
Inspectors of Steam Vessels provide that these pipes shall 
not be less than li inches in diameter, except on steamers 
employed on western rivers, where the branch pipes must 
not be less than J inch in diameter. Each branch pipe must 
be supplied with a stop-valve, the handle of which must be 
marked to indicate the compartment or part of the vessel 
it leads to, and, if feasible, the whole arrangement is to be 
enclosed in a suitable box and plainly marked "Fire 
Apparatus.' ' 



FRONT CONNECTION AND SMOKESTACK 



57. In Scotch boilers and modifications thereof, the 
products of combustion, after leaving the furnace, pass 
through the combustion chamber into the tubes and thence 
into the front connection. This is made of suitable shape, 
for instance as shown in Fig. 35, and is built up of sheet 



60 



MARINE-BOILER ACCESSORIES 



§11 



iron about A inch thick. It is provided with a large door A 
that is fitted with a baffle plate B to prevent radiation. This 
door gives access to the tubes and front tube sheet. The front 
connection is usually attached to angle irons C C bent to the 
required shape and secured to the head of the boiler either 
by studs or by riveting. The front connection, the uptake, and 
the smokestack are usually made with an air casing around 




Fig. 35 



them; that is, they are made double, leaving an air space of 
about 3 inches or more between the inner and the outer 
plates. The lower end of the smokestack is steadied by a 
cast- or wrought-iron ring secured to the upper deck of the 
vessel. The top of the smokestack is steadied by guys, 
usually wire ropes, which may be tightened by means of 
turnbuckles. The area of the uptake should not be less than 
the combined area of all the tubes discharging into it. 



§11 MARINE-BOILER ACCESSORIES 61 

DAMPER 

58. A da»nper is occasionally filled in the smokestack. 
The simplest construction of a damper is shown in Fig. 36. 
A shaft A carried in two bearings, one at each side of the 
slack, has riveted to it a flat wroughl-iron plate B, elliptic 
in shape, fitting loosely into the stack. A lever Cis keyed 
to one end of the shaft, and provided with an endless chain 
leading to the engine room, by means of which it may be 
opened or closed, thus increasing or decreasing the area of 




LOpening of ihe stack, and hence regulating the draft. The 
chain passes over rollers ^, F, C, and //, and is connected to 
a lever O, working on a stud d. A sector /, provided with 
holes, serves to keep the lever in position, a pin -4 being 
inserted inlo a hole in the lever and a hole in the sector. 
With this arrangement, the damper is not affected by ihe 
rolling or pitching of the vessel. 



MARINE-BOILER ACCESSORIES 



§11 



8DPBRHBATBRS 

59. Steam may be superheated in a separate vessel, 
called a superheater, utilizing the heat of the waste gases. 
The use of superheaters in connection with iire-tube boilers 
was quite common in marine work up to the year 1880, but 
since then their use has been gradually abandoned, as the 
practical difficulties incidental to the use of superheated steam 
are considered to overbalance the advantages. The diffi- 
culties encountered are the rapid deterioration of the super- 
heaters, and the carburizing of the lubricant for the engine 




cylinders. There are many old vessels fitted with super- 
heaters, however, and for this reason two forms are here 
described. 

60. A superheater at one time largely used in British 
ships is shown in Fig. 37. It consists of a cylindrical shell 5 
having a number of large tubes T passing through it. It 
is usually fitted into the uptake or the base of the smoke- 
stack, and is provided with a safety valve, shown at B, and 
braced in the same manner as a boiler. It is used for drying 
the steam on its passage from the boilers to the engine. 



ni 



MARINE-BOILER ACCESSORIES 



53 



This is done by the hot gases of combustion passing through 
the tubes and around the shell, thus heating the steam in the 
superheater above the temperature due to its pressure. A 
drain pipe C is provided. The steam enters the super- 
heater through the pipe A and leaves it through the pipe A'. 
The connection to the boiler is made in the following 
manner: The steam pipes A, A', Fig. 38, leading from 
the several boilers are all joined to the pipe .-/"connected to 
the bottom of the superheater. The steam enters the super- 
heater / through this pipe and passes out at the top in the 
main steam pipe G. Should it be desired to dispense with 
the use of the superheater, it may be done by opening the 
valve C on the by-pass pipe D, and closing the valves E 
and F. By means of these valves, the superheated and the 




saturated steam may be mixed, if so desired. This is done 
by opening the three valves, when part of the steam will 
pass through the by-pass pipe and part through the super- 
heater, the superheated and saturated steam mixing in the 
main steam pipe. The superheated steam will have a tem- 
perature but little less than that of the gases of combustion, 
say about 650° F., and this high temperature will soon dry 
out the packing used about the engine and carbonize the oil 
used for lubricating the cylinder. To avoid this, the super- 
heated and saturated steam are often mixed in the manner 
just described, the superheated steam expending part of 'its 
heat in drying the saturated steam. The temperature of the 
mixture will thus he reduced considerably, and drier steam 
furnished to the engine. The ratio of the beating surface o£ 



54 



MARINE-BOILER ACCESSORIES 



§11 



the superheater to the heating surface of the boilers is gen- 
erally made about 1 : 10. 

61. Superheaters of the design shown in Fig. 37 have 
not found much favor in the United States. The steam 
ehlmnoy, shown in Fig. 39, is used instead. This, in effect, is 

nothing but a jacket 
surrounding the 
smokestack at its 
base. The steam 
enters the steam 
chimney through the 
stop-valve A, is su- 
perheated by coming 
in contact with the in- 
ner lining of the 
steam chimney, 
2 which is heated by 
the hot gases of com- 
bustion, and passes 
to its destination 
through the main 
steam pipe B, As 
usually arranged, the 
steam chimney can- 
not be shut off, but 
all the steam on its 
passage to the engine 
must pass through it. 
Thd jjlt-iiiu i'hinuiey is braced by stay-bolts of suitable size 
uimI pilili, ami must be provided with its own safety valve, 
^liiiii III rilmwii at C\ also, a drain, shown at a, by means of 
wliii li II tn.tv lu' rmptied of all the water formed by the con- 
lU.iib.dh'ii i»t llir steam. To allow of inspection and repair, 
lilt. :>ii..tiii ihimnry is provided with one or more manholes, 
.!«.« liiiliiii' ^' iIk'. siio, one of which is shown at m. 




Kio. S9 



§11 MAKINE-BOILEK ACCESSORIES 



STEAM nRlIM ANII JIRV PIPE 

62, A steam ilruin is a cylindrical vessel connected to 
the boiler by one or more passages, and placed on lop of the 
boiler to increase the steam space and also to prevent 
primiitg. It is supposed that by taking the sieam from 
the boiler at a considerable height above the water level, 
the steam will be drier. Where steam drums are used, the 
steam pipe is connected to the drum, and often the safety 
valves are placed on top of the latter. 

Lately, the use of steam drums has been almost abandoned 
in favor of a so-called dry plpo. This is a pipe provided 
with a number of slots, or perforations, shown at a, a. etc., 
Fig. 40. U is placed inside the boiler at the highest point. 



I 




and is supported at the ends by iron straps h, b bolted to the 
boiler shell. The dry pipe is connected to the steam pipe in 
such a manner that the steam can only enter the steam pipe 
by passing through the slots, the ends of the pipe being 
closed. The combined area of the slots, or perforations, 
in the dry pipe is usually made equal to that of the steam 
pipe connected to ii. A small hole should be drilled into 
the bottom of the pipe to allow the dry pipe to drain. 



\ 



STEAM SEl'ARATOBS 

63. A Brpnrntof is an apparatus designed to remove 
the entrained water, or the oil, dirt, or other impurities from 
a current of steam flowing through a pipe. When the sepa- 
rator is intended simply to free the steam from water, it is 
placed on the main pipe leading from the boiler to the engine. 



and as close as possible to the latter, ^V'heQ il is desired to 
remove the grease and dirt from the exhaust steam before 
condensing it and feeding it back into the boiler, the separa- 
tor is placed in the exhaust pipe leading from the engine to 
the condenser. 

The Stratton separator is shown in Fig. 41, It consists 
'f a chamber with a steam inlet and 
utlel.and containing a vertical pipeii. 
The steam enters by the inlet r, and is 
deflected by a curved partition, which 
gives it a spiral motion about thsj 
pipe a. The particles of steam at 
thrown off by centrifugal action, 
run down the walls to the bottoi 
of the chamber. The steam passefl 
through the pipe a and out the out- 
let rf in a practically dry condition. 
The separator is provided with a drip 
pipe h for the removal of the water, 
and a gauge glass g. The wings b, 
are four in number, and are for the! 
purpose of destroying the centrifugal 
effect of the steam after it has reacht 
the bottom of the separator. Thej 
likewise offer additional surface ft 
the water particles to adhere 
Were il not for these wings, 
steam would keep up its rotatiw 
motion while passing up the pipe t\ 
■* and thus necessarily carry some oi 
^'^ *• the entrained water with it. 

There are many other makes of separators, all, however^ 
operating on practically the same principle. What is requirt 
of a separator is to abruptly change the direction of the cur- 
rent. The particles of water will continue in the original 
direction of the current by reason of their inertia, while the 
dry steam passes otT in another direction. 





MARINE-BOILER ACCESSORIES 



■ BOILER SADDLES 

V64. The usual method of setting a Scotch boiler when it is 
placed athwartship is illustrated in Fig. 42 {(t) arid (A). Two 
saddles, or cradles, of wrought- iron or steel plate a, a and 
angle bars b,6 bent to conform lo the shape of the boiler 
shell are firmly secured to the framing of the vessel by 
means of the angle bars 6', 6'. The boiler rests in these 
saddles and is secured to them, if the boiler is small, by 
straps passing around it. As the weight of the boiler and 
the water it contains would throw a heavy bending stress on 
the saddles when the vessel is rolling, the saddles must be 
stiffened in an athwartship direction. To do this, gusset 
braces c,e of iron or steel plate are secured by means of 
the angle-bar clips d.d to the saddles and to plates firmly 
riveted to the reversed frames e,e. The diagonal edges of 
the gusset braces are stiffened by the angle bars /, / riveted 
to them. The lower corners of the gusset-brace plates are 
cut off lo clear the angle bars 6'. b'. Large boilers are 
secured to the saddles by means of tap bolts, with the heads 
on the inside of the boiler. The bolls are screwed into the 
shell of the boiler from the inside and pass through boles pro- 
vided for Ihem in the flanges of the saddle angle bars b, b; nuts 
are screwed on the bolts outside the flanges of the angle bars. 
The holes through the flanges of the angle bars are drilled 
larger than the bolts, in order to provide room for adjustment. 
These holes are drilled, after the saddle is permanently 
secured in its place, from a templet taken from the boiler. 
Washers are placed under the heads and nuts of these bolts. 
It will be observed that the saddle plate is cut away at^,^, 
and that the angle bars are benl to conform to the shape of 
these spaces, in order lo let the saddle clear the butt straps h, k 
thai cover the joints in the boiler shell. 

H^6. The setting of a Scotch boiler when it is placed fore and 
Br is illustrated in Fig. 43((7 ) and (^ ) . The saddles are shown al 
fl.fl, there being five of them in this case. They are constructed 
in a similar manner lo those described in conjunction with 



58 MARINE-BOILER ACCESSORIES §J 





MARINE-BOILER ACCESSORIES 



Fiy. 42, with the exceptions that they are shaped to conform to 
the curve of the reversed frames b. b, />. etc. and that lightening 
holes c, c are cut in them to reduce weight. To brace the boiler 




*oen the vessel is pitching, the brackets d, d are secured to 
•"6 framing of the vessel and to the ends of the boiler by the 
*f>8le bars e, e. The bracket consists of a triangular-shaped 
piece of iron or steel plate, strengthened by angle bars. 




i 



FIRING 



COMBUSTION 



THEOHY OF COMBUSTION 



LAWS OP CHEMICAL COMBINATIONS 

1. Klenieuts and Compounds. — Every mass of matter 
is an elemenl, a compound, or a mixture. Iron, silver, sul- 
phur, and oxygen are elements; water, wood, lime, and car- 
twnic acid are compounds. 

2. A compound may be decomposed or divided into 
separate substances. For example, if an electric current is 
passed through water, the water slowly disappears and two 
Bases are formed. These gases are entirely unlike, and 
neither resembles the water from which it is produced. 
Likewise, lime can be divided into two other substances — 
calcium and oxygen. Any substance that can thus be decom- 
posed or divided into other substances is called a compound. 

3. There are substances that have never been decom- 
posed into other substances. By no known process can 
sulphur be separated into other substances; so with iron, 
Eold, arsenic, and many other substances. Substances that 
■"Sve never been decomposed are called elements. 

The elements that will be considered are: hydrogen, H\ 
''^ygen, O; nitrogen, N; carbon. C; sulphur, 5. 

In referring to an element, it is customary to use only 
?^ symbol, which is usually the first letter of the name. 
\, H stands for hydrogen, C for carbon, etc. 



2 FIRING §12 

4. Chemical Combination. — When two or more ele- 
ments are brought into contact under favorable circum- 
stances, they will combine and form a new substance that 
is unlike either of the elements. Of course, the new sub- 
stance will be a compound. Thus, if carbon and oxygen are 
brought together at a high temperature, they will combine 
and form carbon dioxide. Hydrogen and oxygen combine 
to form water. Hydrogen, nitrogen, and oxygen, when 
combined in certain proportions, form nitric acid. A given 
volume of nitrogen and three times that volume of hydrogen 
combine and form ammonia — a gas that difiEers greatly from 
both nitrogen and hydrogen. 

5. It is supposed that each molecule of an element, such 
as hydrogen or oxygen, is composed of two atoms. It is 
further supposed, by chemists, that at a given pressure and 
temperature equal volumes of all gases, whether simple or 
compound, contain the same number of molecules. Thus, a 
cubic foot of hydrogen, a cubic foot of air, a cubic foot of 
steam, all contain the same number of molecules at the same 
temperature and pressure. 

Suppose, now, that a cubic foot of hydrogen gas is allowed 
to come into contact with a cubic foot of chlorine gas 
(symbol, C/). The mixture is exposed to heat or light, and 
the gases combine. The process of combination is explained 
as follows: There is a certain attraction or affinity between 
the hydrogen atoms and the chlorine atoms. Under the 
influence of heat or light, this attraction becomes so strong 
that the two atoms composing the molecule of hydrogen are 
torn apart. Likewise, the atoms composing a molecule of 
chlorine separate. Each atom of chlorine seizes on an atom 
of hydrogen and forms a molecule of an entirely new gas, 
viz., hydrochloric-acid gas. Since each atom of chlorine 
takes i>//r atom of hydrogen, it is plain that the number of 
molecules of each gas must be the same. In other words, 
1 cubic foot of chlorine requires 1 cubic foot of hydrogen 
to combine with it: these gases cannot be made to combine 
iu any other proportion. For example, if 3 cubic feet of 



chlorine were placed in contact with 2 cubic feet of hydro- 
gen, 4 cubic feet of hydro chloric- acid gas would be formed, 
and the extra cubic foot of chlorine would still remain 
chlorine. The symbol for hydrochloric-acid gas is HCl. 

Suppose, now, that hydrogen and oxygen are placed in 
contact and heated. They will combine and form steam (or 
water); but it will be found that each atom of oxygen seizes 
Iwo atoms of hydrogen to form a molecule of water, and 
(heretore the volume of hydrogen must be double the volume 
of the oxygen with which it combines. This is shown by 
the symbol for water, which is H,0; that is, a molecule of 
water is composed of two atoms of hydrogen to one of 
oxygen. Similarly, the symbol for ammonia is NH,\ that 
is, three atoms of hydrogen to one of nitrogen. Again, 
hydrogen and carbon form a compound; each atom of carbon 
seizes four atoms of hydrogen and forms a molecule of 
marsh gas. The symbol for marsh gas is, therefore, CH.. 

6. The symbol of any compound indicates how the 
atoms of the elements combine to form the compound. 
Thus, the symbol for water. H,0, shows that two atoms of 
hydrogen and one of oxygen unite to form a molecule of 
water. The symbol H.SO, (sulphuric acid) shows that one 
molecule of the sulphuric acid contains two atoms of hydro- 
Een, one of sulphur, and four of oxygen. 

7. Comblnntton by Weight. — One cubic foot of hydro- 
gen combines with just 1 cubic foot of chlorine. But on 
"■eighing each gas it is found that the cubic foot of chlorine 
*eighs 3,5.6 times as much as the cubic foot of hydrogen. 
A cubic foot of oxygen weighs 16 times as much as a cubic 
foot of hydrogen. 

At a given pressure and temperature, equal volumes of 
eases contain the same number of molecules; therefore, 
' cubic foot of oxygen must contain the same number of 
sioms as I cubic foot of hydrogen. Now. since the former 
"■eighs 16 times as much as the latter, it follows that an 
atom of oxygen weighs IfJ times as much as an atom of 
hydrogen. Similarly, an atom of chlorine weighs 35.5 times 




% 



4 FIRING §12 

as much as an atom of hydrogen. This ratio between the 
weight of an atom of any element and the weight of an atom 
of hydrogen is called the atomic weifirlit of the element. 
The atomic weight of any element may be found by divi- 
ding the weight of a given volume, say 1 cubic foot of the 
element when in a gaseous state, by the weight of 1 cubic foot 
of hydrogen when both are at the same temperature and pres- 
sure. The atomic weight is, therefore, much the same thing 
as specific gravity, except that the weight of hydrogen is used 
as the standard of comparison instead of the weight of water. 

8. The atomic weights of the elements named are: 
Hydrogen, H^ 1; oxygen, O, 16; nitrogen, N^ 14; car- 
bon, C 12; sulphur, 5, 32. 

By the aid of these atomic weights, the composition of any 
substance, by weight, known as the molecular >veigrht, caxi 
be found when its symbol is known. The molecular weiglit 
may be defined as the ratio of the weight of a molecule of a 
substance to the weight of an atom of hydrogen, the weight 
of the latter being taken as 1. Take water, symbol H^0\ that 
is, there are two atoms of H to one of O, Multiply the num- 
ber of atoms of each by the atomic weight of the atom. Thus, 

2x1= 2 parts by weight of hydrogen 
1 X 16 = 16 parts by weight of oxygen 

18 parts by weight of water 

2 
Hence, the water is composed of t^ = .1111 = 11.11 per 

Ifi 
cent, of hydrogen and — = .8889 = 88.89 per cent, of 

18 

oxygen. 
As another example, take carbon dioxide, CO,. Then, 

1 atom of C X atomic weight, 12 = 12 parts by weight of C 

2 atoms of O X atomic weight, 16 = 32 parts by weight of 

44 parts by weight of CO, 

12 
Hence, COt contains - - = .2727 = 27.27 per cent, carbon, 

44 

QO 

and ''7 = .7273 = 72.73 per cent, oxygen. From these 
44 



Ui FIRING 5 

. examples, il is plain that the molecular weight o£ water is 18 
tod of carbon dioxide 44. 

9, Mixtures. — Two or more substances, either elements 
I 01 compounds, may be mixed together and yet not combine 
lo form a new substance. They are then said to form a 
mixture. The mixture has tlie properties of the substances 
composing it. The most familiar example of a mixture is 
"rdinary air. It is composed of oxygen and nitrogen, 23 
parts, by weight, of the former to T7 parts, by weight, of the 
'after. The two gases are not combined chemically; they 
^^ simply mixed. 

ELEMENTS OF COMBUSTION 

10. Definitions. — Combustion is a very rapid chemi- 
^1 combination. The atoms of some of the elements have a 
very great affinity or attraction for those of other elements, 
'fid when they combine they rush together with such rapidity 
^ncj force that heat and light are produced. Oxygen, for 
^Jsample, has a great attraction for nearly all the other ele- 
"^ents. An atom of oxygen is ready to combine with almost 
'^ny substance with which it comes in contact. For carbon, 
•^Sygen has a particular liking, and whenever these two 
elements come in contact at a sufficiently high temperature, 
^hey combine with great rapidity. The combustion of coal 
'n the furnace of a boiler is of this nature. The temperature 
Of the furnace is raised by kindling the tire, and then the 
Carbon of the coal begins to combine with oxygen taken 
from the air. The combination is so rapid and violent that 
a great quantity of beat is given out. 

The elements that enter into combustion are oxygen and, 
usually, either carbon or hydrogen. Coal, wood, and other 
fuels are composed almost entirely of these three elements. 
Combustion is, therefore, a rapid chemical combination of 
oxygen with either carbon or hydrogen, or both. 

11. When carbon and oxygen combine they form CO., 
or carbon dioxide; when hydrogen and oxygen combine 
they form water, //,0. These are called the products of 



e FIRING § 12 

combustion. When, as is ordinarily the case, the oxygen 
is obtained from the air, the nitrogen of the air passes into the 
furnace with the oxygen. It takes no part in the combustion, 
but passes through the furnace and up the smokestack wKh 
the C(9, without any change in its nature; it is, however, 
usually called a product of combustion in air, 

12. Weig^ht and Volume of Air Required for Com- 
bustion. — Carbon dioxide, CO,, is composed by weight of 
12 parts of carbon and 32 parts of oxygen. Hence, to bum a 

pound of carbon requires -— = 2f pounds of oxygen. If 

the oxygen is taken from the air, it will take 2f -r .23 
= 11.6 pounds of air to supply the 2f pounds of oxygen. 
This is because only 23 per cent, of air is oxygen. The com- 
bustion of a pound of carbon may be represented as follows: 

Elements Products 

1.0 pound carbon . 1.00 pound carbon . 1 « «»» .i ^r^ 

t n o'j A t 3.67 pounds CO, 

-- ^ , . f 2.67 pounds oxygen . J *^ 

' ^ * ' * 1 8.93 pounds nitrogen 8.93 pounds nitrogen 

1276 1^60 12.60 

That is, 1 pound of carbon requires 11.6 pounds of air for 
complete combustion. Of this air, 2.67 pounds is oxygen, 
which combines with the pound of carbon, forming 3.67 pounds 
of carbon dioxide. The 8.93 poimds of nitrogen contained in 
the air passes off with the CO^ as a product of combustion. 

Take, next, the complete combustion of 1 pound of hydro- 
gen. The product of the combustion is water, H^O, which 
is composed, by weight, of 2 parts hydrog t<^ 16 parts 

oxygen. Hence, 1 pound of H requires - 8 pounds of 

to unite with it. The air required to furnish 8 pounds of 
is 8 -T- .23 = 34.8 pounds. The process of combustion is, 
therefore, as follows: 

Elements Products 

1 pound hydrogen 1 pound hydrogen 1 ^ po«nds water (^.O) 

o. Q A • J ^ pounds oxygen } ^ 

34.8 pounds air . . . < „_ „ ' , ./° o^ o a 

^ [26.8 pounds nitrogen 26.8 pounds nitrogen 

35^8 35^ 35i8 



§12 



FIRING 



13. There is one other case that may occur; the com- 
bustion of carbon may not be complete. If insufficient air 
or oxygen is supplied to the burning carbon, it is possible 
fjf the carbon and oxygen to form another gas, carboo 
monoxide, CO, instead of carbon dioxide, (70,. 

The combustion of 1 pound of carbon to form CO, of 
course, requires only one-half the oxygen that would be 
necessary to form CO,. This is because in CO gas one atom 
of carbon seizes one atom of oxygen instead of two atoms. 
To burn 1 pound of carbon to CO, requires 11.6 pounds of 
air; to burn it to CO will, therefore, require but 5.8 pounds 
of air. 

14. The quantities of air required for combustion are 
shown in the following scheme: 

I Pound Ajb at 62° 



Hydrogen . . 
Carbon burned 

to CC, . . . 
Carbon burned 

to CO . . . 



34.8 pounds, c 
11,6 pounds, c 
6.S pounds, c 



152 cubic feet 



pHonuCT OF 
Combustion 

f Waler 

1 Nitrogen 

(Carbon dioxide 
Nitrogen 

{Carbon monoxide 
Nitrogen 



15. The fuels in common use are composed chiefly of 
carbon, with sometimes a small percentage of hydrogen, 
oxygen, and incombustible matter called ash. When the 
percentages of carbon and hydrogen are known, the air 
required for the combustion of 1 pound of the fuel is easily 
found. For example, suppose that a certain coal is 91 per 
cent, cariio-.- 'Jid 9 per cent, hydrogen. To bum the carbon 
requin-s 152,. ■'- = 138.32 cubic feet of air; to bum the 
hydrogen requir^^: 457 X -09 = 41.13 cubic feet of air. 
Hence, to burn 1 pound of the fuel requires 138.32 + 41.13 
= 179.45 cubic feet of air. 

From this the following rule is derived: 

Rule. — To find, in ettbie feel, (he quantity of air at 62° F, 
Ttquired to bum 1 pound of a given fuel, multiply the percentage 
of carbon by 152, and tAe percentage of hydrogen by 457. Add 
the two products. 




8 FIRING §12 

Or. ^ = 152 C+ 457^ 

where A = air, in cubic feet; 

C = percentage of carbon, expressed decimally; 
H = percentage of hydrogen, expressed decimally. 

Example 1. — How many cnbic feet of air are required to bum 
1 pound of coal containing 84 per cent, carbon, 5 per cent, hydrogen, 
7 per cent, oxygen, and 4 per cent, ash? 

Solution. — Applying the rule, 

A = 152 X .84 -h 457 X .06 = 150.53 cu. ft. Ans. 

Example 2. — How many cubic feet of air are required to bum 
1 pound of coal oil containing 88 per cent, carbon, 11 per cent, hydro- 
gen, and 1 per cent, oxygen? 

Solution. — Applying the rule. 

A = 152 X .88 + 457 X .11 = 184.03 cu. ft. Ans. 

When the fuel already contains oxygen, a little less air 
than given by the rule is required to bum it; if it contains 
sulphur, a little more air will be required. In either case, 
the difference is very slight. It will be found that 1 pound 
of coal requires practically the same amount of air, whether 
it be anthracite or bituminous. Roughly speaking, it requires 
about 12 pounds, or 160 cubic feet, of air to bum 1 pound of 
carbon or coal. If less air is supplied, the combustion is 
imperfect; that is, the carbon bums to CO instead of CO,. 

16. Heat of Combustion. — The quantity of heat devel- 
oped by the complete combustion of a pound of fuel is known 
as its heat of combustion, and also as its heating value ^ 
heating power^ calorific power ^ or calorific value. The quanti- 
ties of heat produced by the complete combustion of the ele- 
ments composing the fuels have been found by experiment. 
They are: Hydrogen, 62,000 British thermal units per 
pound; carbon burned to COt, 14,600 British thermal units 
per pound; carbon burned to CO, 4,400 British thermal 
units per pound: sulphur, 4,000 British thermal units per 
pound. When a fuel contains oxygen, the oxygen during 
combustion will unite with one-eighth its weight of hydrogen 
and form water. H,0, thus reducing the heat of combustion 
of the hydrog:en. Suppose a fuel contains, by weight, 85 per 
cent, carbon, 4 per cent, oxygen, 6 per cent, hydrogen, 1 per 



§12 FIRING 9 

cent, sulphur, and 4 per cent. ash. The total heal of com- 
bustion of a pound of this fuel is found thus; The heat of 
combustion of the carbon is 14.600 X. 85= 12,410 British 
thermal units. The heat of combustion of the hydrogen, 
rememberine Ihat the oxygen present combines with one- 



eighth of its weight of hydrogen, is 62,00(1 X (.06 - ■^\ 

= 3,410 British thermal units. The heat of combustion of 
the sulphur is 4,000 X .01 = 40 British thermal units. Then, 
the total heat of combustion is 12,410 + 3,410 + 40 = 1.5,860 
Brilish thermal units. Expressing this in the form of a rule, 
Outung's rule is obtained, which is as follows: 

Rule. — To tind the heat of combustion of a pound of a given 
fuel, multiply 11, 600 by the percentage of carbon; divide the per- 
centage of oxygen by S, subtract the quotient from the percentage 
of hydrogen, and multiply 112,000 by the remainder; multiply 
4,000 by tfte percentage of sulpliur, and add the l/tree products. 

I. Or, A' = 14,600 r-l- 62,000 (j¥-^) +4,000 5 
trhere X = heat of combustion per pound, in British thermal 
. units; 

1 C = percentage of carbon, expressed decimally; 

1 // = percentage of hydrogen, expressed decimally; 

I O = percentage of oxygen, expressed decimally; 

5 = percentage of sulphur, expressed decimally. 
Example. — What is the heat of corabusiion of a pound of fuel con- 
taining 66 per cent, carbon, a per cent, oxygen, 8 per cent, hydrogen, 
2 per cent, sulphur, and 1<I per cent. ashP 
SOLUnos.— Applying the rule, 

tX = 14,(iOOX .60 4-ti2,<X« [.08- -^] + 4,000 X ,02 
= H.aWB.T.U. Ans. 
17. Maximum Evnporutlon.— It requires 966.1 British 
.thermal units to evaporate 1 pound of water at 212** F. into 
steam of the same temperature and corresponding pressure. 

I Then, the greatest weight of water, that is, the theoretical 
weight, that can be evaporated from and at 212° F. by a 



10 FIRING § 12 

pound of a grfven fuel is found by dividing its heat of com- 
bustion per pound by 966.1. 

Example. — How many poands of water can be evaporated, theo- 
retically, by a pound of coal whose heat of combustion is 13,897 British 
thermal units? 

SoLCTiox. — Evaporation = oiivi- = H.38 lb. Ans. 

18, Temperature of Conibastton. — Making no allow- 
ance for losses of heat, and supposing that just enough air is 
furnished for the combustion, burning carbon should have a 
temperature of about 4,940° F. above zero; burning hydrogen 
should have a temperature of about 5,800° F. above zero. 
In practice, these temperatures are never attained, on account 
of the losses of heat. Usually, the quantity of air admitted 
to the furnace is from 50 to 100 per cent, more than is theo- 
retically necessary for the combustion. This extra quantity 
of air enters at a temperature of 60° F. or 70° F., and escapes 
up the smokestack at a temperature of from 400° F. to 600° F. 
A large quantity of heat is thus wasted and the temperature 
of the fire is greatly lowered. When the fire is outside the 
boiler and the furnace is surrounded by brickwork, the furnace 
temperature may be 2,500^ F. or 3,000° F., but when the 
furnace is inside the boiler and is surrounded on all sides by 
water, the temperature rarely rises above 2,000° F., and is 
usually less. A high temperature is desirable, since the water 
of the boiler will take up heat much faster at high furnace 
temperatures than at low furnace temperatures; combustion 
is also more perfect at high temperatures. 



EXAMPLES FOB PRACTICK 

Ix How many pounds of air will be required for the perfect com- 
bustion of 7 (>ouuds of cartK>n? Ans. 81.2 lb. 

-. A fuel :s S8 per v.>fut. carbon and 12 per cent, hydrogen; how 
triany cubic feet of air are required for the complete combustion of 
I pound ot :he fuel? Ans. 188.6 cu. ft. 

*.v ' y< How rrrany Br :ish thermal units would the combustion of the 

rx^v.-^v! ot :i:el or exarjple *i v:*.ve out? { ^ •■ How manypounds of water at 

21--" F. woulJ. I poucd ot :h:s fuel evaporate? 

, f(<*) 30.288 B. T.U. 

'^\i*) 21 lb. 



§12 FIRING 11 

(4) The chemical symbol o( the product of combuslion o( sulphur 
wiih oxygen is SO, (sulphurous oxide}; what is the composition of this 
gas by weight? f Sulphur, 50percent, 

' lOxygen, 50 per cent. 

(5) Assume that, with ordinary draft, double the theoretical quan- 
tity of air is used to bum a fuel; how many cubic feet of air will be 
required to burn 115 pounds of coal, the chemical composition being 

_ //, 5 parts; C, 90 parts; O, 3 parts; and ash, 2 parts; total. 100 parts. 
L Ans. 36.719.5 cu. ft, 

Kom) 

r 1 



What is the heat of combustion of a pound of coal having the 
mposition mentioned in example 5? Ans. Hi,0U7.6 B. T. U. 



FUELS AND TIIEIK COMBUSTION 



KINDS OF FCEL8 

19. Conl. — The fuels ordinarily used in marine work in 
the generation of steam are coal, wood, and oil. A promi- 
nent authority, Mr. William Kenl, divides coal into four 
leading varieties, as follows: 

1. Anthraeile, which contains from 92.31 to 100 per cent, 
of fixed carbon and from to 7.69 per cent, of volatile hydro- 
carbons. 

2. Semianlhracile, which contains from 87.5 to 92.31 per 
cent, of fixed carbon and from 7.69 to 12.5 per cent, of volatile 
hydrocarbons, 

3. Semibituminous coal, which contains from 75 to 87,5 
per cent, of fixed carbon and from 12.5 to 25 per cent, of 
volatile hydrocarbons. 

4. Bilutninous coal, which contains from to 75 per cent. 
of fixed carbon and from 25 to 100 per cent, of volatile 
hydrocarbons. 

20. Anthracite is rather hard to ignite and requires a 
I'ltrong draft to burn it. This coal is quite hard and shiny. 

In color, it is a grayish black, and bums with almost no 
imoke; this fact gives it a peculiar value in places where 
-imoke is objectionable. 

Anthracite is known to the trade by different names, 
^Recording to the size into which the lumps are broken. 



12 FIRING §12 

These names, with the generally accepted dimensions of the 
screens over and through which the lumps of coal will pass, 
are: 

Culm passes through A-inch round mesh. 

Rice passes over -A-inch mesh and through f-inch square 
mesh. 

Buckwheat passes over |-inch mesh and through i-inch 
square mesh. 

Pea passes over i-inch mesh and through J-inch square 
mesh. 

Chestnut passes over J-inch mesh and through If-inch 
square mesh. 

Stove passes over It-inch mesh and through 2-inch square 
mesh. 

/C<r passes over 2-inch mesh and through 24-inch square 
mesh. 

Bwken passes over 2j-inch mesh and through 3a-inch 
square mesh. 

Steamboat passes over 3i-inch mesh and out of screen. 

Lump passes over bars set from 3i to 5 inches apart. 

21. Sonilauthraolte kindles easily and bums more 
freely than the true anthracite; hence, it is highly esteemed 
as a fuel. It crumbles readily, and may be distinguished 
from anthracite by the fact that when just fractured it will 
soil the hand, while anthracite will not. It bums with very 
little smoke. Semianthracite is broken into different sizes 
for the market; these sizes are the same, and are known by the 
s^ume trade names, as the corresponding sizes of anthracite. 

22. 8on\lbltunilnou$ coal differs from semianthracite 
only in having a smaller perc^entage of fixed carbon and more 
xx^Uiile hydfivarbons. Its physical properties are practi- 
cally the same, and s^inoe it bonis without the smoke and 
Svx^t emitted by bituminous cv>aU it is a valuable steam fuel. 

t!^l« lUf uiuUioiis oiMil may be hrvvadly divided into three 

1, v<*c.»;c i'^v,\ — This nATTje i:? driven to coals that, when 
bun^ts: xu the tun^j^c^e. ^iixx^'ll aao fuse together, forming a 



912 



FIRING 



13 



spongy mass that may cover the whole surface of the grate. 
These coals are difficult to burn, since the fusing prevents 
the air passing freely through the bed of burning fuel; when 
caking coals are burned, the spongy mass must be frequently 
broken up with the slice bar, in order to admit the air needed 
for its combustion. 

2. Free- Burning Co<7/.— This is often called non-caking 
(oal, from the fact that it has no tendency to fuse together 
when burned in a furnace. 

3. Cannel Coal. — This is a grade of bituminous coal that 
is very rich in hydrocarbons. The large percentage of vola- 
tile matter makes it valuable for gas making, but it is little 

leased for the generation of steam, except near the places 
nrbere it is mined. 

Bituminous and semibituminous coals are known to the 
trade by the following names: 

mp. which includes all coal passing over screen bars 
|ti inches apart. 

Nut, which passes over bars i inch apart and through bars 
^1 inches apart. 

Pea, which passes over bars 3 inch apart and through bars 
( inch apart. 

< Stack, which includes all coal passing through bars \ inch 
ipart. 

24. lilffnlte may be classified as coming under the 
general head of bituminous coal. Properly speaking, lignite 
occupies a position between peat and bituminous coal, being 
probably of a later origin than the latter. It has an uneven 
fractiu-e and a dull luster. The value of lignite as a steam 
fuel is limited, since it will easily break in transportation. 
Exposure to the weather causes lignite to absorb moisture 
rapidly, when it will crumble quite readily. Lignite is non- 
caking and yields but a moderate heal, and is in this respect 
r to even the poorer grades of bituminous coal. 

5. The heat of combustion of coal depends entirely 

i chemical composition, and as this varies between 

: limits, the heat of combustion also varies between 




J 



14 FIRING § 12 

corresponding limits. Thus, a sample of Arkansas lig^nite 
had a value of 9,215 British thermal tmits per potmd; a 
sample of Kentucky cannel coal, 15,198 British thermal units 
per pound; a sample of Pennsylvania coal from Monongahela, 
14,130 British thermal units per poimd. 

26. Wood. — Steamers navigating rivers flowing through 
localities where wood is abundant and coal either very scarce, 
unobtainable, or very high priced, often use wood for steam 
making. The heating value of the different woods varies 
but little when dried; 1 pound of wood may be estimated to 
be equal in steam-making capacity to about .4 poimd of 
ordinary coal. Naturally the heating value of wood varies 
considerably with its condition; thus, when full of sap, as 
when a live tree has just been cut up, its heating value is 
much less than when the largest part of the moisture has 
been driven off by seasoning the wood or artificially drying it. 

27, Mineral Oil. — The mineral oil known as i)etroleuin 
is occasionally used in marine work as a fuel, and as such 
has many advantages over coal. The universal use of oil, 
however, is prevented chiefly by the limited supply, and to 
some extent by its high price, except under especially favor- 
able conditions. The advantages of oil as a fuel in marine 
work are as follows: Reduced weight and space per horse- 
power; decreased number of firemen; reduction in time 
required for raising steam; instantaneous lighting and 
extinguishment of the fire; ready adjustment of the fire to 
suit the demand for steam; absence of ashes and smoke. 
The disadvantages are: Loss of fuel by evaporation; danger 
of explosion; unpleasant odors; difficulty of obtaining a 
supply everywhere; comparatively high price. 

The chemical composition of oil, like that of coal, varies 
through a considerable range, but the following may be con- 
sidered as average: carbon, 84 to 88 per cent.; hydrogen, 
11 to 14 per cent.; and oxygen, .1 to 1.5 per cent. The 
specific gravity at 32^ F. is approximately .9, and the 
average calorific value, or heating power, may be taken at 
20,000 British thermal units per pound of oil. If it is 



§12 FIRING 15 

assumed that good coal on an average will develop 14.000 
British thermal uuits per pound, it is plain that 1 pound of 
. ' . — 1 J nnnnfic^ ocarly, of coal in 

heating value. There are features of oil burning that modify 
the above relative value and often turn the balance in favor 
of the use of coal, but so far as the actual quantity of heat 
produced is concerned, it may be safely stated that oil yields 
about 40 per cent, more than an equal weight of coal. 



ec< 



COMBUSTION OF COAL 

28. Systems of FlrliiK- — The management of the fire 
or fires used in generating steam is known as firing. The 
style of firing to be adopted in any given case depends 
largely on the conditions present, such as the kind of fuel 
used, the intensity of the draft, the demand for steam, etc. 

There are three methods of hand firing, known as coking 
firitig, spreading firing, and aHeniale Uring, in common use. 
Each of these methods has advantages peculiar to itself, and 
none is applicable to all cases and all conditions, that is, if 
economy in the generation of steam is an object, 

29. The coking system of firing is especially adapted 
bituminous coals that are rich in volatile matter. The 

coal is first piled on the dead plate near the door and there 
allowed to coke. After coking from 20 to 30 minutes, the 
hydrocarbons, that is. the volatile constituents of the coal 
that can be distilled or driven oflE by heat, will have been 
driven off. The coke is then pushed toward the bridge and 
distributed evenly over the fire. A new charge of coal is 
immediately heaped on the dead plate. 

This is one of the most economical methods of burning 
bituminous coal; if properly managed, it will give excellent 
results in regard to the prevention of smoke. In order to 
get good results, the furnace door should be perforated and 
a suitable damper fitted for opening and closing the per- 
forations. The air admitted in jets through the openings 
lixes intimately with the gases formed; the mixture passes 




in 



16 FIRING §12 

to the rear over the bed of burning coke on the gjate, where 
the temperature is high enough to secure their ignition and 
complete the combustion before they are chilled by contact 
with the cold surfaces of the boiler and tubes. To secure 
success with this method, the coal should be charged in 
small quantities and allowed to remain on the dead plate 
until it is as thoroughly coked as possible; 30 minutes will, 
in general, be sufficient. As a matter of course, actual trial 
in each and every case will have to determine the proper 
length of time. Large lumps that will coke slowly must be 
broken up; if the coal cakes badly in coking, the crust thus 
formed must be broken with the slice bar from time to time, 
so as to secure the complete removal of the hydrocarbons. 
The size of the grate and the intensity of the draft should be 
such that the coke will be burned at as high a rate of com- 
bustion, per square foot of grate surface, as the conditions 
will permit. This results in a high furnace temperature, 
which promotes complete combustion of the gases. 

Coking firing is best adapted for cases where the demand 
for steam is moderately regular, since with coking firing 
it is somewhat difficult to force the boiler when there is a 
sudden and heavy demand for steam. Coking firing should 
never be adopted for anthracite. 

30. The spreading system of firing consists of covering 
the whole of the grate evenly with the fresh charge of coal, 
and is the system in most common use. While good results 
can be obtained by it, if the firing is done skilfully, the spread- 
ing system is not particularly to be recommended either for 
economical or for smokeless combustion. Best results will 
be obtained from the spreading system by firing light charges 
at frequent intervals. The habit of covering the incandescent 
coke on the grate with a thick layer of fresh coal naturally 
results in a lowering of the furnace temperature far below 
the ignition point of the hydrocarbons driven off. In conse- 
quence, there is an enormous waste of heat, and with* bitumi- 
nous coal, vast quantities of black smoke are produced. To 
prevent this heat loss, the firing must be light and frequent. 



§12 



FIRING 



17 



The spreading system is best adapted to anthracite in sizes 
larger than pea. 

31. In the alternate system of firing, the coal is thrown 
alternately on each side of the furnace; at one firing one side 
of the grate is spread with coal, and at the next firing the 
other side receives the charge. This method is preferable to 
the spreading system in that the whole of the furnace is not 
cooled off at once by the fresh fuel. While it keeps a bright 
bed of fuel in one side of the furnace and tends to keep the 
average temperature of the furnace nearly constant, it cannot 
be recommended as being the best method for securing com- 
plete combustion of the hydrocarbons that form a valuable 
constituent of bituminous coal. The gases from the freshly 
fired coal, instead of being passed over the bright bed of fuel 
on the other side of the furnace, are likely to pass directly to 
the smokestack without being sufficiently heated to secure 
their ignition and complele combustion. For both bitumi- 
nous and anthracite coals, the alternate system of firing is 
preferable to the spreading system, however, since gas 
explosions in the furnace are not as likely to occur as when 
the latter system is used. 

^33. Ons Explosions. — Explosions of the gases in the 
amace, commonly catted back draft, occur usually with small 
oal and are the result of careless firing. When the smaller 
sizes of anthracite or bituminous coal are burned with the 
spreading system, and when a heavy charge is put into the 

E*- — lace. it frequently happens that an explosive mixture of 
and gas is formed, which needs but a spark to ignite it. 
ing to the interstices between the pieces of coal being 
ill and tortuous, especially with the smaller coals, the 
hydrocarbons driven off from the heavy charge are not ignited 
as rapidly as formed, and hence collect and mix with the air 
^bove the grate, forming an explosive mixture if the con- 
EUtions are favorable. All danger of a gas explosion is 
pbviated if the firing is done very lightly, or if the alternate 
lystem is adopied, or if some part of the fire is left uncovered 
Ifhen putting in fresh coal, thus igniting the hydrocarbons as 




13 



FIRING 



M 



quickly as they are distilled off. The smaller the size of t 
coal, the greater is the liability of a gas explosion, with: 
a heavy charge fired spreading. With coals of sizes larges 
than pea, there is little danger of an explosion when I 
spreading, except when fired thick instead of light. 



33. Thickness of Fire. — The thickness of the fire io 

furnace depends to a large extent on the draft, the nature 
and the quality of the fuel, the size of the grate, and the rate 
of combustion required. As a general rule, the stronger the 
draft, the thicker the fire can be. Where a high rate of com- 
bustion is required with ordinary natural draft, it may often 
be attained by a thin fire and frequent, light charges of fresh 
coal. It is claimed that this is not the most economical wa; 
of firing, because the cold air rushing into the furnace when- 
ever the fire-door is open for charging the fire reduces the 
temperature of the furnace and of the gases in combustion. 
and consequently reduces the evaporation. For instance, let 
10 pounds of coal be burned per square foot of grate surface 
per hour, evaporating 100 pounds of water. Then, if 
20 pounds of coal be burned on the same area in the same 
time, instead of evaporating twice the amount of water, that 
is, 200 pounds, the actual evaporation will probably be about 
170 or 180 pounds. The average thickness of the fire varies 
from 8 to 14 inches. 

34. Flrc-Tools. — The special tools used in working the 
fires are shown in Fig. 1, The slice bar, shown at W. is 
made of 1-inch or li-inch round iron, about S feet long, one 
end of it being flattened and a handle formed at the other 
end. This tool is employed for breaking up the crust formed 
at the surface of the fire when bituniinotls coal is used. The 
heat of the fire fuses the fresh charge of coal in a short 
time, thus keeping a sufficient supply of air from passing 
through the grate. About ten minutes after charging the 
fire, the slice bar is run into the fire on the surface of the 
grate, and, by depressing the end of the bar outside the txir- 
nace, the Sre is broken up. This operation is called i/icisi 
the fire. 



IS called slums 



FIRING 



n 



The T bar. shown at R, is a slice bar with a broad, flat 
Point, and is used, when liring anthracite, for breaking up 
the clinkers and cinders lying on the grate. It is merely 
niQ along the top of the grate the whole length, tliis opera- 
tion facilitating the admission of air to the fire. 

The hoe, made of H-inch bar iron, is shown at C: generally 
two are used—a heavy hoe with a broad end, and a lighter 
one. The lighter one is used for leveling the fire; the 
heavier one in cleaning the fire and ash-pit. 

The usual construction of the i>okt>r is shown at D. A 
handle is formed at one end; the other end is enlarged and 
is rectangular in cross-section. !i is provided with a slot 




for the insertion of the blade, which is shown enlarged at E. 
These blades are usually A inch thick by U inches wide, 
and about S inches long, and are forged to the shape 
shown at F. A number of these blades are carried in 
stock, and are inserted when required by driving out the 
taper key, thus allowing the old blade to be removed and 

lew one inserted: the key is then driven home, locking 
the blade in position. This tool is used for cleaning the 
space between the grate bars from below, should it become 
choked. 

In some localities, a so-called devil's claw is added to 
the equipment. This is simply a three-pronged rake used 
for drawing large clinkers out of the fire, but as this can 



i 



, well, the devil's claw has 



be done with a hoe just about i 
not come into very extensive use, 

35. Cleaning Fires. — Two methods of cleaning a 6re 
are in use. In the first method, the burning fuel, or the Iht 
coal, as it is termed, is pushed to one side of the furnace 
while the other side is being cleaned. The live coal is then 
distributed evenly all over the grate and covered with a ligtii 
charge of fresh fuel. 

In the second method, the live coal is pushed back againsi 
the bridge, and the cinders and clinkers covering the frt 
of the grate are pulled out. The live coal is then pulled 
the front of the furnace, and the cinders, etc. on the badT 
part of the grate are pulled over the top of the live coal, afier 
which the latter is spread evenly over the grate, and covered 
with a tight charge of fresh coal. 

It is well to allow the fire to burn down somewhat before 
cleaning, as it will then be easier to clean. The dampei 
should be partially closed, to prevent cold air from rushing 
into the furnace and cooling the furnace plates above the fire. 
For this reason, and also to prevent loss of steam pressure, 
the cleaning should be done quickly. In cleaning a fire, 
special attention should be devoted to cleaning out the cor- 
ners near the door; being somewhat inaccessible, they are 
apt to be neglected, to the detriment of the fire. 

36, BaiikliiK rires. — Should it be desirable to have 
boiler lying idle, with steam up and the fires ready to gei 
ate steam to the full capacity of the boiler at short notice; 
the fires are banked. This is done by first cleaning the fire, 
and then either pushing the live coal against the bridge or 
pulling it to the front and covering it with fresh fuel. The 
fire will lie smoldering, the air supply being regulated, by 
the damper, the fire-door, and the ash-pit damper, to keep 
the fire burning sufficiently to keep up the steam pressure. 
When it is desired to start the fires again, some of the fuel 
covering the live coal is skimmed off, and the live coal is 
spread over the grate. The fire-door is then closed, the ash- 
pit and smokestack dampers are opened, and the fire allowed 



:iie« 




lo burn up, for 2 or 3 minutes, perhaps, when it is covered 
wiih a light charge of fresh fuel. 

37. Hauling Fires. — When the demand for steam sud- 
- deoly ceases, as, for instance, in case of a breakage necessi- 
tating stoppage of the engine for a considerable period, the 
burning fuel has to be drawn from the furnace. The hard 
labor entailed ia hauling the fire, as it is termed, may be 
reduced considerably by allowing the fire to bum low, if the 
circumstances permit it. When it becomes necessary to haul 
the fire, in case of the water gelling low in the boiler, it is 
considered the best practice to deaden the fire before hauling 
by spreading over it a heavy charge of fresh fuel or ashes. 

38. Llghtlus Fires.— To start a fire, the grate is 
lightly covered with coal. Wood ia piled evenly on top of 
il and covered with some coal. Greasy waste is put in front 
of the wood. This, when lighted, will soon ignite the wood, 
the fire gradually working toward the bridge; the layer of 
coal below the burning wood protects the grate bars from 
the heat and thus prevents warping of the bars. As soon as 
the wood is burning freely, more coal is put on. The fire- 
door should be kept open while the wood is burning, and the 
ash-pit damper shut. The fire should burn very slowly at 
first, so as not lo injure the boiler by the unequal expansion 
of its various parts. The rate at which the fire burns may 

R regulated by the smokestack damper. 
89. Practical Hints on Firing.— As it is usually desir- 
le to keep the steam at an even pressure, the following 
points ought to be observed. Two fires in the same boiler 
should never be cleaned at once. When putting a fresh 
charge of fuel into the furnace, do it as rapidly as possible 
to avoid the inrush of cold air, which will injure the furnace 
plates and also reduce the temperature of the gases of com- 
bustion. Two furnaces in the same boiler should not be 
charged at once, as the fresh charge deadens the fire and 
reduces the generation of steam, The usual method of 
— nanaging the fire is as follows: Let A and B be two singie- 
■■Ided Scotch boilers with two furnaces each, numbered as in 

L 




22 FIRING §12 

Fig, 2, and suppose that bituminous coal is used. Furnace 1 
is charged with fresh fuel; the fire in furnace 2 is leveled off 
with the hoe; the fire in furnace 3 sliced, and, next, the grate 
of furnace 4 is cleaned from below; furnace 2 is now charged 
with fuel, and 3 is leveled, 4 sliced, and the grate of 1 
cleaned; furnace 3 is charged, 4 leveled, 1 sliced, and the 
grate of 2 cleaned; furnace 4 is charged, 1 leveled, 2 sliced, 
and the grate of furnace 3 cleaned. 

It will thus be seen that the same operation is not repeated 
at the same time in one boiler, and, furthermore, that each 
operation is performed in the numerical order of the fur- 
naces. Thus, if the first fire sliced were in furnace 5, the 
next one to be sliced would be in furnace 4, the next one in 

furnace 1, and the next 
one in furnace 2. 

The furnaces numbered 
with the even numbers are 
in one boiler; those with 
the odd numbers are in 
the other boiler. 
^'°- ^ This system of firing is 

in vogue in sea-going steamers, or wherever the engineer in 
charge believes in doing work systematically. Of course, 
the system may be changed to suit varying conditions, the 
arrangement of the operations as described being intended 
to furnish an idea as to a systematic way of firing. The 
same system may be and is followed in cleaning fires. The 
length of time a fire will burn without needing cleaning 
depends on the amount of coal burned and the quality of the 
coal. When consuming about 15 pounds of coal per square 
foot of grate surface per hour, with average coal, the fire 
will burn about 12 hours before it must be cleaned. 

40. Lumps of coal should not be thrown into the fire, 
but should be broken into pieces about the size of a man's 
fist. The fresh charge of fuel should be spread evenly over 
the fire. With irregular-sized coal, leveling with the hoe 
has to be resorted to some time before a fresh charge of 




§12 FIRING 23 

fuel is put into the furnace. Should it he noticed, while 
charging, that the fire has burned out in one spot, owing to 
clinkers having formed on the grate and prevented admission 
of air to the fuel above it, or to the burning away of the fuel, 
the grate at that spot should be cleaned and the open spot 
filled with live coal before a fresh supply of fuel is put into 
the furnace. The back of the grate should not be allowed 
to become bare, as the inrushing cold air will cool the hot 
gases of combustion and greatly reduce the amount of 
steam generated. The ash-pit should be kept clean, as 
ashes accumulating therein will prevent the free access of 
air to the furnace. The length of time that air is admitted 
above the fire, and the amount of it, depends on the quantity 
and quality of the coal. For coal rich in hydrocarbons, a 
longer time will be required than for other coal. But in no 
case should air be admitted after the hydrocarbons are 
expelled from the coal, which, with anthracite, will be in 2 
or 3 minutes after charging. By watching the steam gauge, 
the condition of the fires can be told, and a look at the 
burning fuel will show whether fresh fuel is needed, or the 
fires require slicing, or the air supply is insufficient, either by 
reason of the damper being closed or the grate clogged up. 

Before cleaning fires, it is often advisable to increase the 
feed and to work up the steam pressure, and to reduce the 
feed while cleaning. A certain quantity of heat is stored up 
in the extra water fed into the boiler, which is liberated when 
the feed is reduced, and tends to keep up the steam pressure. 

An anthracite fire does not need to be sliced, as no crust 
is formed on the surface of the fire. Slicing will merely mix 
the cinders and clinkers with the live coal and deaden the 
fire. The T bar should be run in under the tire to break up 
the cinders. 

COMBl'STION OF OIL 

41. Since the first attempt to use petroleum for fuel, 

early in the history of the oil industry, down to the present 

I time, the principal problem to be solved has been the 

■ nethod of burning. Naturally, the first attempts to bum 



24 FIRING §12 

oil were by lighting: the surface of a mass of oil as it lay in 
vessels or pans. The amount of combustion that it was 
possible to obtain with this method was limited because ni 
the limited surface of oil that could be exposed to the flame. 
Attempts were made to increase this surface by causing the 
oil to run over plates and broken brickwork, but the ^reai 
difficulty of supplying air to the entire surface of the oil and 
the interior of the flame soon caused this method to be given 
up. Next, attempts were made to gasify the oil and then 
burn the gas. Part of the heat of combustion was utilized 
in converting additional oil into gas, and thus it was hoped 
to render the process continuous. Because of their exposure 
to the intense heat of the furnace, these various arrange- 
ments rapidly deteriorated; also, a carbonized residue of 
soot and tar was found to clog the pipes and passages. The 
difficulties of this method were early seen to preclude the 
possibility of success along this line, and the attention 
engineers was turned to the spraying method, with resull 
that leave little to be desired. 



lufl 



42. The spraying method of burning oil consists of 
introducing the oil into the furnace in a very finely divided 
state by means of a jet of air or steam and causing the 
combustion of the oil while in the spray form. The most 
obvious method in a boiler room of producing a spray of oil 
is by means of a jet of steam, and consequently it is found 
that a very large class of oil burners depend on this spraying 
agent. The method by which spraying is caused to take 
place varies slightly in different types of burners, but. in 
general, it may be stated that the oil and steam are caused 
to mingle within the passages of the burner, and the high 
velocity of the steam blows the oil into the furnace in a very 
finely divided slate. 

A burner that utilizes steam as the spraying agent is 
shown in cross-section in Fig. 3. It consists of a cylinder a 
having one end closed by means of a cap 6 and the other end 
by a stuffingbox. Extending axially Ihrough this cylinder is 
a pipe f having one end pointed and making a steam-tight 



Sl2 



FIRING 



25 



joint in a conically shaped orifice in the cap b. The other 
end of this pipe is closed with a plug f^. A tapered open- 
ing through this plug is closed by means of a needle 
valve e. The pipe e can be moved in or out of the cylinder a 
by means of the hand wheel /, thus closing or opening the 
conical orifice in the cap b. A hood g is cast in one with 
the cap b and serves to protect the end of the burner from the 
intense heat of the furnace. Oil under pressure enters 
the burner through the pipe h, passes through the needle 




valve e into the pipe c, and out through a small opening in 
the end into the furnace. Steam from the boiler enters 
through the pipe k, surrounds the pipe c, and passes through 
the interior of a into and out of the conical opening around 
the end of c into the furnace. The supply of oil is regulated 
by the valve e, and the supply of steam is controlled by 
turning the hand wheel /. The oil mingling with the steam 
as it passes out of the burner into the furnace is converted 
into spray, and combustion is readily caused to take place 
L^thin the furnace. 

■ 43. All oil burner that uses air instead of steam as the 
' vaporizing agent does not differ materially from the burner 
just described. As in the burner using steam, the oil enters 
a smalt inner pipe, and Ihe atomizing agent, that is, the air. 
is supplied through the outer shell of the burner to the tip 
or cap on the furnace end, where the oil and air mingle and 
pass into the furnace. The relative efficiency of steam and 
r has not as yet been definitely determined, hut there can 
e no question that, with air, the mixture of the combustible 




26 FIRING § 12 

elements of the oil and the oxys^en of the air is mnch more 
intimate at the beginning^ of combustion than conld possibly 
be the case with steam and oil. Another advantage that air 
has over steam in oil bomers is that there is no loss of 
steam and consequently of fresh water. This is of great 
importance aboard ship, where fresh water is very valuable. 
The United States Navy Department found, as the result of 
experiments with liquid fuel, that the water consumption of a 
steam-operated burner is between 4 and 5 per cent, of the 
total evaporation. Another advantage of the air is that it 
can be stored under great pressure in tanks, and thus the 
oil burners can be utilized in getting up steam when all 
the boilers in the battery are cold. With a steam-operated 
burner, a coal fire must be started under one boiler in order 
to get steam to operate the oil-burning devices. The prin- 
cipal disadvantage of the use of air is the necessity of the 
installation of an air compressor or blower, and the conse- 
quent increase in weight. 

44, Attempts have been made to produce a burner that 
is a combination of the two classes and that uses both steam 
and air for atomizing purposes. Extended tests by the 
United States Navy show that a burner of this class requires 
several times as much steam for successful operation as 
does a burner using steam alone. This class of burner 
is much more complicated in design, more costly to manu- 
facture, and requires much more skill in operation than 
burners using either air or steam alone. The Naval Board 
unqualifiedly condemned burners using both air and steam 
as the spraying agent. 

45. The steam that is used in spraying the oil does not 
in any manner increase the temperature of the flame, if, 
indeed, it does not actually decrease it. The water forming 
the steam is undoubtedly decomposed by the high temper-^ 
ature that obtains in the furnace, thus setting free the 
hydrog:en and oxygen, of which the water is composed. 
Farther back in the furnace, where the temperature is lower 
than that necessary for the disassociation of the elements of 



§12 



FIRING 



27 



water, the hydrogen burns and water is again formed. When 
water is broken up into its elements by exposure to high tem- 
perature, exactly the same amount of heat is absorbed as is 
given out when the resulting free hydrogen is again burned. 
The water thus formed passes off as steam with the other 
products of combustion. One effect of the use of steam under 
pressure is undoubtedly beneficial, in that its action tends to 
produce a more even distribution of heat in the furnace, and 
transfers heat from the point where it is greatest to the back 
I of the furnace and to the tubes, where it is less. A source 
[ loss due to the presence of steam is that it undoubtedly 
asses up the smokestack at a considerably higher tempera- 
ire than that with which it enters the burner; the additional 
le&t being, of course, taken directly from the furnace. 



46. The accessories that should accompany an oil-burn- 
ing installation are: oil pumps arranged in duplicate for 
pumping the oil from the storage tanks and supplying it to 
the burner under pressure; heating tanks for heating the oil 
a high temperature by means of a steam coil; strainers 
It removing all dirt and grit; and when air is used as the 
Momizing agent, an air compressor or fan. It is highly 
important that the oil pumps should be in duplicate, as a 
breakdown might cause a stoppage of the entire plant. 
Insurance companies prohibit feeding the oil by the gravity 
system, owing to the danger of fire. It is also desirable to 
have the strainers arranged in pairs, as the opening in the 
burner for the discharge of the oil into the furnace is very 
small, and very little dirt or grit will materially affect the 
operation of the burner. It has been found advantageous 
to arrange for heating the air used in the combustion of the 
Ail. This is usually accomplished by forcing the air over 
peated surfaces or through pipes that are more or less 
exposed to the heat of the furnace. Heating the air does 
not increase the heat of the flame, but tends to promote 
combustion. It is conducive to the best working of the 
burner to raise the temperature of the oil to the ignition 
possible after it leaves the tip of the burner, 






^Moint as soon as pos 



28 FIRING gii 

and this result ts fouad to be much hastened by heating tlie 
air supply to as high a lemperatore as practicable, 
pressure of the steam used in the burners may vary between 
the limits of 20 and 70 pounds per square inch. There hav 
been no tests made public to show the most economica! 
pressure, but the results of the oil-fuel tests of the United 
States Navy Department show that the higher the pressure 
the greater the amount of water that was evaporated, and< 
also that the efficiency of the burner slightly increasi 
Increasing the pressure of the oil and steam had the disad- 
vantage of increasing the steam consumption of the burner. 
When air is used, the pressure is much lower, varying from 
less than 1 pound with an ordinary fan blower up to about 
20 pounds with an air compressor. 

47. It is usually found advisable to make the steam 
pressure in the burner a certain proportion of the pressure 
in the boiler, as oil burners are most efficient when the steam 
used as the atomizing agent is superheated. The cheapest 
means of superheating, where a superheater is not installed, is 
by means of free expansion of the steam in a reducing valve; 
the steam pressure in the burner should be about 25 per cent, 
of the pressure in the boiler. As any change in the pressure 
of the air, steam, or oil makes a readjustment of all valves 
necessary, care should be taken that the pressures in an oil 
burner be kept as nearly constant as possible when once the 
burner is in operation. Too much stress cannot be laid on this 
point. It is advisable to have the steam supply of the burners 
so arranged that any boiler can furnish steam to any burner. 

48. In the following description of the method of raising 
steam on a battery of boilers having an oil-burning installa- 
tion using steam as an atomizing agent, it is assumed that 
there is steam in one boiler for operating the burners. If 
there is not, steam must be raised by means of a coal f5re 
under one boiler for that purpose. 

Steam is first turned on to a burner, and any accumwlation 
of water in the steam pipes is thus blown out. Next, the 
oil valve is slowly opened, and the oil spray that is thus 



§12 FIRING 29 

formed is ignited by means of oily waste or, preferably, by 
a short-handled torch. The supply of steam and oil should 
now be regulated until the furnace is completely filled with 
a flame that is steady, white or bluish white, and that gives 
off little or no smoke at the top of the smokestack. Much 
smoke is a certain indication of a poorly adjusted burner. 
As the experience of the fireman increases, he will be 
enabled to judge of the efficiency of combustion by the 
sound that is emitted from the furnace. If, for any reason, 
the flame is extinguished at any burner, the oil supply 
should be immediately shut off, or the accumulation of oil 
vapor in the furnace will cause a more or less violent explo- 
sion when the burner is relighted. When steam is used as 
the atomizing agent, and a burner is extinguished, it is 
advisable to shut off at once both steam and oil; but when 
air is used, and a burner is extinguished, it is well to shut 
off the oil only. When the air is also shut off, the com- 
pressor or fan causes a larger quantity to pass through the 
other burners, and, as this disturbs the proper relation 
between the quantities of oil and air, much smoke is pro- 
duced and a readjustment of the valves on all the burners is 
thus made necessary. All this is obviated by permitting the 
lir to blow through the idle burner until it is expedient to 
ilight it. Care should be exercised that the oil is not 
)})eated in the oil heater to so high a temperature that vola- 
tile gases are driven off and caused to accumulate in any 
l^f the pipes. This gas, if it is forced through the burner, 
interrupts the steady flow of oil, and thus will often extin- 
guish the burner. If air becomes mixed with this gas, as it 
may in some forms of oil heaters, the gas and air will bum 
within the pipes and necessitate a shut down. Burners have 
been known lo gel red hot from combustion within the oil 
passages. The strainers, arranged in duplicate, should be 
regularly cleaned out at stated intervals, instead of waiting 
until one is completely choked and the supply of oil is 
thereby diminished. There should not be any oil allowed 
appear on the floor of the fireroom. Firing vnlh oil does 
It require bodily strength, nor experience with firing coal. 



E' 



DRAFT 

49. Natural Draft.— The difference between the weigbl 
of a column of hot gases contained within a smokestack and 
the weight of an equal column of cold air results in an 
upward motion of the hot gases within the stack, which 
motion is called natural draft. It is well known that any 
gas, when heated, is lighter, bulk for bulk, than when cool. 
Now, when the hot gases pass into the smokestack they 
have a temperature of 400° F. or 500'* F., while the air out- 
side the smokestack has a temperature of from 40° F. to 
90° F. Roughly speaking, the air weighs twice as much. 
bulk for bulk, as the hot gases. Naturally, then, the pres- 
sure in the smokestack is a little less than the pressure of 
the outside air. Consequently, the air will flow from the 
place of higher pressure to the place of lower pressure; thai 
is, into the smokestack through the furnace. As an example. 
suppose that a smokestack is 150 feet high and that the tem- 
perature of the hot gases is 500°. A column of gas at this 
lemperature, 150 feet high, and of I square foot cross-section, 
weighs about 6i pounds. A column of air at 60°, of the 
same length and cross-section, weighs about Hi pounds. 
Hence, the difference in pressure at the bottom of the chim- 
ney is Hi — 6j = 5 pounds per square foot. This difiterence 
in pressure is spoken of as the draft pressure. ■ 



drJ 

\TetV 



SO. It is customary to express the pressure of the dra 
in inches of water. It has been shown that the pressure o 
the atmosphere, 14.7 pounds per square inch, supports a col- 
umn of water 34 feet high. 34 feet of water = 14.7 pounds 
per square inch; or. 34 X 12 = 408 inches of water = U.J^ 
pounds per square inch; = 2,116.8 pounds per square foi 
Therefore, 1 inch of water = — ■'- = 



inch; : 



pound per squai 
5.2 pounds per square toot. 



2.H6.8 

408 
The draft pressure, or intensity of the draft, 
by means of a water gauge, one form of which is shown 4 





FIRING 



31 



Fig, 4. As inspection shows, it is a glass tube open at both 
ends, bent to the shape of the letter U: the left leg communi- 
taies with the smokestack; the air outside the smokestack, 
being heavier, presses on the surface of the water in the 
nghi leg and forces some of it up the left leg; the difference 
1)1 the two water levels // and Z in the legs represents the 
iniensity of the draft and ia expressed in inches of water. 

The draft pressure required depends on the kind of fuel 
used, Wood requires but little draft, say i inch or less; 
bituminous coal generally requires less draft than anthracite. 
To burn anthracite, slack, or culm, the draft pres- 
sure should be li inches of water, 

51. The area of the smokestack must be such • 
that the gases of combustion may be discharged 
freely. Experience has shown that an area of 
1 square foot of smokestack to every 8 square 
feet of grate surface is a fair ratio, representing 
the practice of some of the best builders. The 
iniensity of the draft depends on the height of the 
smokestack; hence, the amount of coal that may be 
burned per square foot of grate surface per hour 
may be roughly estimated from the height of the 
smokestack, provided that the area of the smoke- 
stack is of the required size. The height of the 
smokestack is to be taken as the perpendicular 
distance between its top and the grate. Owing to coals of the 
Hmc kind varying in chemical composition, and between wide 
HlpBils, the quantity of coal burned with a given smokestack 
^P^ grate area cannot be estimated with any great exactness; 
Bihis must be borne in mind when applying the rales given. 
The probable maximum rales of combustion attainable 
"Oder natural draft are given by the following rules, which 

I nave been deduced from the experiments of Isherwood, 
nited States Navy, 
here W = weight, in pounds, of coal burned per square 
foot of graie area per hour; 
// = height of smokestack, in feet. 



82 FIRING §12 

Rule I. — To find the amount of anthracite that may be- 
bunieii per sgiiare foot of grate surface per hour under the niosf 
favorable conditions, subtract 1 from twice (lie square root of Ifir 
height of the smokestack. ■ 

Or, W=2<H-l ■ 

Rnlc II. — For anthracite burning wider ordinary conditions-^ 
sublracl 1 from otie and one-half limes the square root of the 
height of the smokestack. 

Or, W= 1.5^-1 

Rule III. — For best semianthracite atid bituminous coal, mitl— 
lipiy the square root of the height of the smokestack by 2.25, 

Or, IV=2.^<H 

Bulo IV. — For ordinary soft coals, multiply the square root 
of the height of the smokestack by 3. 1 

Or. W =Z<H I 

The maximum rate of combustion is thus fixed by th<f 
height of the smokestack; the minimum rate may be any- 
thing less. 

Example. — What is the raaxirauni coal consumption per hour of a 

vessel filled with six boilers with two furnaces each, the length of the 

grate being S feet, the nidth 3 feet tt inches, and the height of Ibe 

smokestack 65 feetP Ordinary soft coal is being used. 

Solution.— Using rule IV, 

(f = 3^66 = 24.IS7 lb. per sq. (t. of grate area per hr. 

The total grate area = 6 X 2 X 6 X 3.5 = 2S2 sq. ft. Hence, tiff 

maximum coal consumption = 252x2-1.187 = 6,095.12 lb per hr. 

Ans 

52. Mechanical I>rart. — As previously explained, 
natural draft is caused by the upward flow of heated air. 
The force of the draft depends a great deal on various con- 
ditions, such as the direction and force of the wind, the tem- 
perature of the air, the height of the smokestack, the thick- 
ness of the fire, etc. To make the draft independent of any 
of these conditions, various mechanical arrangements may 
be used and a draft thus created mechanically. In that case 



"I 



§12 



FIRING 



the draft is spoken of as mechanical draft. In marine 
work, mechanical draft is applied in one of three ways: 
Either the air is forced by a fan into an air-tight fireroom, 
when the system is called the closed fireroom system, or the 
air is forced by suitable mechanism into air-tight ash-pits, 
when the system is called the closed ash-pit system. Both of 
these systems are spoken of as forced-draft systems. In the 
third application of mechanical draft, a partial vacuum is 
created in the uptake or base of the smokestack by fans or 
sleam jets; this system is spoken of as an indtued-draft system. 
In naval vessels, the closed fireroom system of forced draft 
is extensively used. All openings from the fireroom are 
closed air-tight, and air forced in until the desired pressure 
has been reached. This system has not found much favor in 
the mercantile service, and the closed ash-pit system has 
been adopted instead. 



S3. lloTvden's closed ash-pit system, in which hot 
air under pressure is delivered into the ash-pits and furnaces, 
is shown in Fig. 5. By means of a blower located in a suit- 
able pJace, cold air is forced through the pipe H into a 
closed air chamber located in the uptake immediately above 
the doors of the front connection. The gases of combustion 
pass through numerous vertical tubes, shown at .4, contained 
in the air chamber, thus heating the air surrounding the tubes. 
The heated air passes into an air-tight reservoir B, attached 
to the front end of the boiler and surrounding the furnaces, 
as well as the front connection G. This reservoir, projecting 
about 10 inches from the front of the boiler, receives the air 
under pressure. The air admitted above the fire enters 
through the valve C into a space between the outer and 
inner furnace doors, both of them swinging on one hinge. 
The inner door is perforated, and is provided with a per- 
forated air-distributing bos D, the outer door serving to 
retain the air pressure. The air passing through the valve C, 
besides filling the spaces between the doors, also fills the 
space around the furnace door, whence it passes into a per- 
forated air-distributing box E. covering the whole surface of 



FIRING 



36 



i 



;e furnace front inside the furnace. Part of the air passes 
through the perforated dead piate into the ash-pit, which is 
closed by hinged doors. The rate of admission of air to the 
i-pit is regulated by means of the valves F. 
In operation, the rate of combustion of the fuel is gov- 
led by the valves F regulating the air pressure. The 
valves Care adjusted at the beginning of the trip to suit the 
character of the fuel used. The jets of highly heated air 
admitted by these valves above the fire tend to promote com- 
plete combustion. 
In some closed ash- 
[Ht systems, cold air 
is delivered under 
pressure into the 
ash-pit, 

54, Theapplica- 
iiim of a fan to the 
base of a smoke- 
staclc, in order to in- 
duce draft, is shown 
in Fig. 6. A pair of 
fans A, A are lo- 
cated at the base of 
the smokestack, one 
in each side. Both 
fans are mounted 
oo the same shaft, 
which passes through the smokestack. The shaft is belted 
to a steam engine, not shown in the figure. In operation, 
the damper B is closed while using the exhaust draft. 
The rapidly revolving fans exhaust the air in the uptake, 
thus reducing the pressure in the tubes and furnaces, and 
thereby producing a more rapid current of air through the 
furnaces, both below and above the grate. No alteration 
of the arrangement of the furnace fittings is necessary. 
system can be applied very cheaply to steamers already 




36 FIRING Si! 

55. In the Ellis &. Eaves ioduced-drart system, , 

fan is placed outside the uptake: the fan inlet is below 
and the fan outlet is above the smokestack damper. This 
arrangement allows either natural or mechanical draft i 
be used at will. The air entering the furnace is healed b 
passing around nests of tubes through which the gases oi 
combustion pass before reaching the fan; the furnaces a 
closed off from the fireroom by air-tight furnace doors and 
ash-pit doors, and suitable mechanism is provided for admit- 
ting air either above or below the grate, as may be required. 



56. Induced draft bjr means of a steam jet is to be 
found m many American steamships, and has much in 
recommend it The chief points in favor of the steam ji;i 
are the e^se with which it can be applied to existing boilers, 
its low first cost and the reliability of its action; besides, 
being located inside the smokestack, 
it does not occupy valuable space. 
While its steam consumption is 
greater than that of the fan engine 
used in mechanical -draft installations, 
it affords a ready means of increasing 
the evaporative power of a boiler or 
boiler plant. Whether it will increase 
the efficiency of the boiler, that is, 
increase the number of pounds of 
water evaporated per pound of coal, 
is somewhat doubtful. 

In installing a steam jet, it must 
not be overlooked thai the steam 
used is lost, while with a fan engine 
the steam can be, and usually is, 
exhausted into the condenser, thus saving the fresh water. 
This consideration limits the steam jet chiefly to vessels run- 
ning in fresh water, and to such other vessels in which the 
saving of the fresh water is not essential. 

The construction of a BlooinsburK steam Jet is shown 
in Fig. 7. It consists of a casing a having a central nozzle i 





at iis lower end. Steam from ihe boiler enters the cham- 
ber c formed by the lower part of the casing and the nozzle, 
and flows through the annular opening at e. The steam 
issues from this opening at a high velocity and thus induces 
a I'urrent of air to flow in the same direction as the steam. 
A number of these small jets are attached to a spider, which 
consists of a central casting with radiating steam pipes, the 
enils of each steam pipe carrying a jet. 
Its arrangement in the smokestack is 
shown in Fig. 8. A steam gauge is 
attached to the system of jets, showing 
the steam pressure in the jets. To 
start the induced draft, simply turn on 
the steam; to regulate the intensity of 
the draft, open or close the valve. 

57. With non-condensing engines, 
the exhaust from the engine may be 
'nroed into the smokestack in order 
li) induce draft; this arrangement is 
quite common on steamers navigating 
the western rivers of the United States 
of America and on those engaged in 
similar service elsewhere. In that 
case, it is usual to provide a valve 
hy means of which the exhaust can he 
discharged either directly into the at- 
mosphere or into the smokestack. 

58. Air may be forced into a 
closed ash-pit by means of a steam 
jet, which is similar to the device 
described in Art. 56. While this 
application of forced draft is quite common 
practice, it is very uncommon in 




Pio. B 



I stationary 
: work. However, 
it has an advantage in the case of coal that must be used 
continuously and that is liable to clinker badly, adhering 
firmly to the grale bars and sides of the furnace. In this 
particular case, it seems to be the consensus of opinion 



S8 FIRING § 12 

amons: engrineers that the admission of steam into the ash- 
pit, incidental to the employment of the steam jet, has a 
tendency to alleviate the clinkering and subsequent sticking 
of the clinkers to the bars. 



ECONOMIC COMBUSTION 



ECONOMIC COMBUSTION OF COAL 



PRINCIPLES OF COMBUSTION 



" CONSTITIJBNT8 OP COAL 

1. Introcliictloii. — Since fuel, chiefly in the form of 
coal, is the source of all the energy made available by the 
steam engine, a study of the principles governing the eco- 
nomical generation of power by means of the steam engine 
must begin with a study of the combustion of fuel, and of 
the means of preventing waste of heat by guarding against 
those conditions that tend toward incomplete combustion. 
Heat lost by imperfect combustion cannot be recovered; no 
arrangement of elaborate and economical machinery in the 
engine room will utilize the energy wasted in the fireroom 
through ignorance or carelessness on the part of the fireman, 

2. Derinltlous antl Clnssiricatlon. — Bituminous coal 
is composed largely of various compounds of carbon and 
hydrogen called hydrocarbons. When the coal is heated, 
these compounds are driven off, partly in the form of perma- 
nent gases and partly as vapors that may easily be condensed 
or changed to a liquid form. The process of separating the 
gases and vapors from the part of the coal that cannot be 
vaporized by the mere action of heat is called distillation; 
the sxibstances driven off from the coal by heat are called 
volntile substances; while the portion remaining forms 

CtttritMnl »r Inlpnatiimal Tixlbooi Companj. EnUrid al Slalitnirs' Hall. L. 
Ill 




a 



2 ECONOMIC COMBUSTION §13 

coke, which is composed chiefly of carbon. This carbon is 
called the fixed carbon of the coal. 

The volatile substances may be divided into two classes, 
viz., non-combtistibU and combustible substances. The first 
class consists mostly of water, free oxygen, and nitrogen; 
these are driven off when the coal is heated — the water as 
steam and the gases in their free state. The second class 
consists of the hydrocarbons, which comprise numerous 
compounds of hydrogen and carbon. When the coal is 
heated, a part of the hydrocarbons is driven off in a gaseous 
form and a part as vapors. 

The principal gases in the volatile combustible are car- 
bureted liydrogreii, or marsh g^as (consisting of 1 atom 
of carbon and 4 atoms of hydrogen, as shown by its sym- 
bol, C//4), and olefiant sras, C,//«. With many coals, free 
hydrogen is given off in considerable quantities; small 
quantities of other less important gases also are generally 
present. 

The vapors are mostly coal tar and naphtha, with small 
quantities of sulphur. Their presence can be detected by 
inserting a cold iron bar into the yellow gases rising from 
a fresh charge; a sticky coating, consisting mostly of the 
condensed tar, will form on the cold metal. 

The proportion of the volatile matter in coal depends on 
its composition. Anthracite consists almost entirely of fixed 
carbon and ash; in some bituminous coals, the greater part 
is volatile. The relative proportions of fixed gases and con- 
densable vapors in the volatile parts of coal also vary with 
the composition of coal. In some cases, the volatile matter 
contains considerable quantities of the tarry vapors and 
heavy hydrocarbon gases, as C//«, while in others it consists 
largely of the light marsh gas, C//«, and free hydrogen. 

The quantity and composition of the volatile matter 
depend not only on the composition of the coal itself, but 
also on the conditions under which distillation takes place, a 
difference in the temperature and the presence or absence of 
air or steam modifying the composition of the vapor and 
gases to a very great extent. Irregular firing and draft 



§13 



ECONOMIC COMBUSTION 



result in a great difference in the quantity and composition 
of the gas burned in the furnace at different periods. 

With few exceptions, coal contains small quantities of 
sulphur, usually in combination with some other element; 
one of the most common compounds is that of sulphur and 
iron, known as Iron pyrites. When the coal is heated, the 
sulphur is separated from the iron and burns to sulphur 
dioxide. SO,. The heat derived from the combustion of the 
sulphur found in coal is small, but the sulphur dioxide 
formed, in combination with the moisture in the gases, cor- 
rodes iron very rapidly; any relatively cold metal exposed 
to the gases from coal rich in sulphur is rapidly corroded 

^(^ld destroyed. 
[ COMBUSTIOK OF CONSTITUENTS OF COAL 
3. Combustion ot Volntlle Constituents. — At the 
tcmperalure generally existing in a boiler furnace, the tar 
and other liquids vaporize and mix with the gases; this 
gaseous mixture is readily burned under proper conditions 
of air supply and temperature. The conditions involved in 
the combustion of the gases and vapors may readily be 
studied by the aid of the flame of a common tallow candle. 
The tallow forms a supply of solid hydrocarbon that, under 
the action of the heat of the flame, is liquefied; then, by 
capillary attraction, it is drawn up 
into the wick lo a point where the 
heat is sufficient to vaporize it. A 
process of distillation here goes on, 
and a blue, transparent, cone-shaped 
mass of vapor and gas, shown al c, 
in Fig. 1, is formed. The heat of the 
flame causes a current of air to ap- 
proach from all sides and provides 
a supply of oxygen that comes in 
contact with the surface of the hot ' 

cone of vapor. The air that reaches 

this part of the flame, however, is not sufficient for the com- 
■plete combustion of the vapor, and since the hydrogen in 





Ihe hot cone has a greater affinity for oxygen than it has fi 
carbon, the hydrogen combines with all the available oxygi 
and burns to water, H,0. The carbon is left in the form o 
minute solid particles that become highly heated and j 
this part of the Hame its bright yellow color. As t 
particles of carbon rise, they come id contact with the inw 
current of air, which furnishes oxygen sufficient to bum 
them to CO,. The gas so produced, mixed with the H,0 
from the luminous portion b of the flame, forms the nearly 
colorless outer and upper section a that gradually mixes with 
the surrounding air. cools, and becomes wholly invisible. 

If the end of a glass tube is inserted into the inner cone of 
the flame, as shown in Fig. 2, a part of the gas that has 
- not yet received a supply of air 
may be drawn oft. In passing 
through the tube, this gas is 
cooled below the temperature 
at which it will burn and issues 
from the tube into the air with- 
out igniting. By applying a 
lighted match to this gas and 
heating it, it may be lighted 
and burned. This simple ex- 
periment illustrates two of the 
most important principles 
involved in the economical com- 
bustion of the gases in a boiler 
fiu'nace. It shows: (1) that the 
gas that has been cooled below 
''■" ' Ihe temperature of ignition can- 

not be burned merely by furnishing a supply of air; (2) 
th»t when the gas is supplied with air, it can be burned if its 
tcmjiorature is raised to the igniting point. 




4, iKitttloii Tt'inpernture. — In order to bum the fixed 
ciirlKm thai is in the coal, a high temperature is needed i- 
cause the iitom* of carbon to combine with the oxygen sup- 
plied by the air. The igniting temperature of the fixed 



3 13 



ECONOMIC COMBUSTION 



carbon, and of the volatile substances also, is estimated to be 
about 1,800° F. Since the maximum temperature in the 
furnace rarely exceeds 2, .500° F., and is ordinarily several 
hundred decrees less, it is seen that, on account of the rela- 
tively small difference between the igniting temperatures of 
the carbon and gases and the maximum temperature in the 
furnace, constant care is needed to prevent the temperature 
in the furnace falling below 1,800° F. The temperature in 
the furnace can be judged quite accurately by the appearance 
or color of the fire, in accordance with the relation between 
color and temperature given in the accompanyinE table. 

When the supply of air is sufficient and the temperature 
high enough, the carbon burns to carbon dioxide, CO., which, 
being the product of complete combustion, is incombustible. 
With a high temperature and a deficient air supply, carbon 
monoxide, CO, is formed. Since this gas is the product of 
incomplete combustion, it can be burned to CO, by bringing 
it into intimate contact with air while highly heated. 
TABLE I 
COLOR AND TEHPEBATURE OF FIRE 



Temperft- 

■DcRreeB 

Pahrea- 

beJI 


Appearance 


Tempera- 

Degrees 
Fahren- 
heit 


Appearance 


980 
1,290 

1,470 
1.657 
1,830 


Red— just visible 

Dull red 

Dull cherry red 

Full cheny red 

Bright red 


2, 190 

2.370 
2.550 
2,740 


Dull orange 

Bright orange 

White heat 

White, welding heat 

White, dazzling heat 



5. Combustion ot Bolld Carbon. — When solid carbon 
bums on a grate, the chemical changes or reactions are about 
as follows; Some of the oxygen of the air that rises through 
the grate combines with the first layers of hot carbon in the 
proportion of two atoms of oxygen to one atom of carbon, 
Mod carbon dioxide, CO., is formed. As the gases rise 



6 ECONOMIC COMBUSTION §13 

through the fire, more of the oxygen combines with carbon, 
and as long as the supply of air is sufficient and well dis- 
tributed, the combination is mostly in the proportion that 
produces CO^, With a thick bed of fuel, however, or an 
arrangement of the fuel that does not permit of a proper 
distribution of the air, there will be some portions of the fire 
in which the supply of oxygen is not great enough to furnish 
the two atoms for the production of C(9.; only one atom of 
oxygen will be available for combination with some of the 
carbon atoms burned, and the product will be CO. Further, 
when a molecule of CO. comes into close contact with the 
hot carbon, the attraction of the carbon for oxygen is so 
great that one atom of the oxygen leaves the CO^ and com- 
bines with an atom of carbon; two molecules of CO are thus 
formed, one by the separation of one of the oxygen atoms 
from the molecules of CO., and the other by the combination 
with an atom of carbon of the oxygen atom so released. 
The separation of a given weight of CO, into CO and O 
absorbs as much heat as was developed when the CO com- 
bined with oxygen to form the CO,; the net production of 
heat is the same, whether a certain amount of carbon is 
burned to CO directly and passes off in that form, or a part 
of it is first burned to CO^ and this gas is then decomposed, 
with the production of CO and of oxygen that combines with 
the remainder of the carbon to form CO. The carbon mon- 
oxide formed in the fuel bed passes into the fiimace, and if 
there is not sufficient oxygen present, or if the temperature 
is not high enough, it will pass away unbumed. If suf- 
ficient oxygen is present and the furnace temperature is 
high enough, each molecule of CO will combine with 
another atom of oxygen and thus burn to CO^. 

6. Summary. — A careful study of the outlines of the 
processes involved shows that economical combustion, both 
of the volatile matter and of the solid carbon, involves 
the following essential conditions: (1) there must be a 
supply of air sufficient to furnish the oxygen required for 
complete combustion; (2) this air must be so distributed as 



§13 ECONOMIC COMBUSTION 7 

to bring the oxygen into intimate contact with all parts of 
the fuel; (3) the temperature must be high enough to bring 
about the combustion. With any of these essentials lack- 
ing, there will be incomplete combustion anti a loss of heat. 






BHOKE FORMATION 

7. The smoke arising from an ordinary coal fire may 
properly be divided into two classes: (I) the partly con- 
densed tarry vapors produced by the distillation of the fuel; 
(2) the minute particles of solid carbon left when the hydro- 
carbons are but partially burned. Smoke of the second class 
is so objectionable that some steamships, in order to pro- 
mote the comfort of passengers, burn only arthracite, which 
burns practically without smoke. 

8. When hydrocarbons are heated in the presence of atr, 
the affinity of the hydrogen for oxygen is great enough to 
cause it to separate from the carbon and combine with the 
oxygen. If the supply of air is sufficient and the tempera- 
ture is sufficiently high, the carbon set tree will bum and 
practically no smoke will be produced. If, however, there 
is a limited supply of air or too low a temperature for their 
combination with oxygen, the carbon atoms will combine 
with each other and form molecules of carbon that collect 
into minute particles of solid carbon. It is the presence of 
these heated carbon particles that gives color to the flame 
of an ordinary lamp or fire. If they can be supplied with 
oxygen at a high enough temperature, they will burn, as in 
the fiame of the candle. Fig. 1. Under unfavorable condi- 
tions, however, these solid particles of carbon do not burn, 
but are deposited as soot or are carried out of the furnace 
with the gases as smoke. The nature of these unfavorable 
conditions can well be studied by considering the action of 
an ordinary kerosene lamp. With a good chimney, a flame 
not too high, and a clean burner, the lamp burns with a 



8 ECONOMIC COMBUSTION §13 

bright, steady flame and oo smoke. The bright flame indi- 
cates a high temperature, and the absence of smoke shows 
that the air supply is ample and well distributed. Insert a 
cold iron rod into the flame from the top of the chimney; a 
deposit of soot — unbumed carbon — collects on the rod, and 
the gas that rises along the sides of the rod is cooled so 
much that a part of the carbon is not burned and considerable 
smoke is formed. Interfere with the air supply by partly 
closing the top of the chimney or the holes in the burner; 
a cloud of smoke is formed. Remove the chimney, so as to 
interfere with the distribution of the air to the lower part of 
the flame while a large volume of cold air meets the upper 
part, and a condition obtains in which the carbon is cooled 
by the action of an excessive supply of cold air imperfectly 
distributed. Turn the wick too high, and the formation of 
the gases is too rapid in comparison with the supply of air; 
hence, part of the gases cools below the temperature 
required for perfect combustion. 



8MOKE PREVENTION 

9. It is seldom that the supply of air to a boiler furnace 
is not great enough to burn the carbon and prevent the 
formation of smoke; in fact, it is often found that large 
volumes of smoke are accompanied by a liberal supply of 
oxygen. The more common condition when smoke is 
formed is too low a temperature of the fire or a distribution 
of the air that prevents oxygen from reaching the carbon 
before it is cooled by contact with the boiler plates. Heavy 
firing, by means of which large volumes of gas are formed 
and the furnace greatly cooled, is one of the most prolific 
causes of smoke production. Owing to the high ignition 
temperature of solid carbon, smoke, when once formed, is 
extremely difficult to burn. With properly constructed fur- 
naces, good draft, and careful management, smoke pre- 
vention is possible; smoke cmi sumption, however, may be 
said to be practically impossible under any of the conditions 
existing in the furnace of a steam boiler. 



? 13 ECONOMIC COMBUSTION 9 

10. If Ihe bed of burning fuel is thick and the draft 
sluggish, carbon nionoxide will rise from the surface of the 
lire, and if it is not burned to carbon dioxide by mingling 
with air admitted above the fire, it will pass through the 
flues and cause a great loss of heat — about 10.100 British 
thermal units for each pound of carbon. 

Two remedies for this type of toss are available: (1} the 
fuel bed may be made so thin that sufficient air can enter 
through the grate, either to prevent the formation of carbon 
monoxide or to burn it to carbon dioxide as soon as it is 
formed; (2) suiKcienl air to burn the carbon monoxide that 
rises from the coal may be admitted into the furnace above 
the fire. If there is a brisk fire and a consequent high tem- 
perature in the furnace, the carbon monoxide can be easily 
burned by either of the two methods given, a short, pale 
bine Hame being produced near the surface of the fuel. 
With a slow, dull fire, the temperature in the furnace may 
be loo low to ignite Ihe escaping gas, which will pass out 
with any air that may be present, no combination taking 
place. There is. thus, a double loss; heat is wasted not 
only by the escape of carbon monoxide, but also by the heat- 
ing of the excess of air. 

1 1 . The presence of unconsumed carbon monoxide is not 
easily detected by mere observation, owing to the gas being 
colorless. By regulating the fire, however, so that a high 
temperature is maintained in the furnace, and by watching 
the surface of the burning fuel to see that sufficient air is 
present to produce the pale blue flame previously mentioned, 
it is possible to make reasonably sure that the amount of 
unconsumed carbon monoxide will be exceedingly small. 

With a large grate area and a very low rate of combustion, 
there is usually formed a considerable quantity of uncon- 
sumed CO, owing to the relatively low temperature in the 
furnace. In the case of a single boiler, the remedy is to 
restrict the grate area by bricking up with one or more 
courses of firebrick, so as to secure a higher rate of combus- 
tion and the consequent high temperature. In the case of 



10 ECONOMIC COMBUSTION §13 

several boilers, one or more may be cut out of service when 
conditions permit in order to secure a higher combustion 
rate and temperature in the furnaces of the boilers in ser- 
vice. Simply admitting more air when there is a very low 
rate of combustion is liable to aggravate the heat losses, 
since it will result in still further lowering the temperature 
of the furnace. 

The escape of unconsumed hydrocarbon, with its attendant 
loss of heat, is more readily detected by direct observation 
of the fire than carbon monoxide, especially when the loss 
from this source is large. The yellowish vapors that rise 
from freshly * fired coal are familiar to all firemen and 
are an evidence of unconsumed hydrocarbons. When the 
heavier hydrocarbons are contained in the smoke in consid- 
erable quantities, the smoke from the smokestack is yellowish 
in color and has a tarry odor. 

12. The conditions required for the complete combustion 
of the hydrocarbons are the same as for the fixed carbon of 
the fuel; that is, a sufficient air supply, an intimate mixture 
of the air with the gases, and a high temperature. In prac- 
tice, it seldom happens that a large part of the carbon in the 
volatile matter escapes unburned, even when a great deal of 
black smoke is produced. Owing to its finely divided state, 
a small quantity of carbon will give a high color to a large 
volume of gas coming from a chimney, and there will appear 
to be a serious waste when the actual heat loss is really 
comparatively small. 

Numerous careful tests in stationary steam-engineering 
practice have shown that the production of black smoke does 
not necessarily represent a great loss in efficiency. In many 
cases, it has even been found that a reduction of efficiency 
accompanied the use of furnace arrangements that were suc- 
cessful in preventing smoke. The reason for this appears 
to be that the gases were burned with a large excess of air, 
which, while so controlled as to bum the carbon to CO or Cft, 
thus rendering it invisible, carried much more heat from the 
furnace than was developed by the comparatively small 



weijiht of carbon that would have appeared in the smoke. 
The losses due to solid carbon falling into the ash-pit, tbe 
escape of unburned hydrocarbons, incomplete combustion of 
the fixed carbon on the grate, and a needless excess of air 
are always much more serious than tbe loss due to the forma- 
tion of black smoke. 

AUhough smoke in itself represents no serious loss of 
heat, its production in large quantities is often the result of 
conditions that produce imperfect combustion of the carbon 
monoxide and the hydrocarbons. A low furnace tempera- 
ture, the piling of coal on the fire in such large quantities 
that an excessive volume of combustible gas is given off, 
while, at the same time, the furnace temperature is lowered 
by the heat absorbed in the process of distilling the volatile 
matter from the freshly fired coal, and also the admission of 
large volumes of cold air, tend to producS black smoke, and, 
besides, represent serious and unnecessary heat losses. 



AIR SUrPLY TO FURNACE 



AIR SUPPLY BELOW URATB 

It has been shown that the complete and economical 
nbustion of coal and the prevention of smoke depend pri- 
marily on a sufBcient air supply being brought, under proper 
conditions, into intimate contact with the iixed carbon and 
volatile combustibles. Without the proper distribution of 
the air supply, the high temperature necessary for complete 
combustion cannot be maintained. One of the best methods 
of supplying the air is that in which the fire is thin and open 
enough to permit sufficient air to rise through the grate and 
fuel bed. The advantages of this method are as follows: 

The air, in rising through the fuel bed, becomes highly 
heated. If a clean, even fire is maintained, the air supply is 
well distributed and comes in intimate contact with the gases 
almost as soon as they are formed; the air and gases are 
thus thoroughly mixed in the vicinity of the hottest part of 



12 ECONOMIC COMBUSTION §13 

the furnace, and complete combustion follows. The danger 
of chilling the boiler plates by a current of cold air is less 
than when the air is admitted at any point above the gjates. 

With this method of air supply, the firing must be care- 
fully done; the fire must be maintained at a moderate and 
even thickness, the gjates must be kept clean, and each air 
space must be kept as free from clinkers as possible. No 
bare spots should be allowed to form, ^d, finally, the coal 
should be supplied in small quantities and often, each 
shovelful being spread over as much surface as possible. 
Large lumps should always be broken before beings fired, and 
in no case should a thick mass of freshly fired coal be allowed 
to collect in any part of the furnace. Such a method of 
firing demands care and close attention on the part of the 
fireman, but if it is carefully followed, the coal will be burned 
in a very economical manner and without the formation of 
black smoke. The reduction in the amount of coal that must 
be handled will, in a great degree, make up for the apparent 
increase in labor connected with such a system of firing. 

The thickness of the bed of fuel to be used with this sys- 
tem of firing depends on the quality of the fuel and the 
intensity of the draft. In general, it may be stated that the 
best results will be obtained with a good strong draft that 
will permit of a fuel bed, with reasonably good bituminous 
coal, of from 7 to 12 inches in thickness. The thickness 
can best be determined by actual trials and carefully watch- 
ing the results. 

AIR SUPPLY ABOVE GRATE 

14. In a great many cases, it is impracticable, or at least 
difficult, to regulate the fire so carefully as to secure a proper 
supply of air through the grates. For example, in Western 
river and similar service, where the demand for steam and 
the intensity of the draft are very irregular, it is found to be 
practically impossible to maintain a depth of fire that will 
conform to the irregularity in the conditions of running. 
The heavy currents of air drawn through the thin bed of fuel 
by the irregular action of the exhaust tear holes in the fire if 



§13 



ECONOMIC COMBUSTION 



13 



it is kept too thin, thus allowing large quantities of cold air 
to enter at one place; these currents of cold air, in addition to 
their evil effects on the combustion of the gases and their 
chilling effect on the boiler, often carry considerable quanti- 
ties of solid fuel into the flues. 

It is seldom that the conditions are as unfavorable in sea- 
going service as In Western-river service, but there are many 
cases in which the irregularity of the draft, or of the demand 
for steam, is considerable; the quality of the fuel may also 
make it very difficult to keep a clean, open tire that will 
permit the steady supply of air demanded; it is, therefore, 
often essential that means be provided for furnishing, 
through openings above the grate, at least a part of the air 
required to burn the gases. Of the methods used for this 
purpose, the one most commonly found is, perhaps, either 
a partly opened fire-door or some special arrangement of 
openings through the (ire-door that will serve as an inlet 
for the air and distribute it over the fire in a more or 
less satisfactory manner, 

A partly opened door must be regarded as one of the 
most unsatisfactory means of getting air into the furnace 
that could be devised. The air enters in a large stream that 
is more likely to cool the small proportion of the gas that it 
reaches below its ignition temperature than it is to promote 
its combustion; further, the concentrated current of cold air 
is almost sure to strike a limited section of the furnace, 
which section becomes chilled; this, in turn, produces severe 
stresses in the boiler plates. Much more satisfactory results 
are obtained when the door is provided with special openings 
that serve to divide the entering current of air and distribute 
it over a considerable part of the grate. The perforated inner 
door is particularly useful in this respect; it serves the com- 
bined purpose of protecting the outer door from the heat 
radiated from the fire and of dividing the entering current of 
air into a large number of small jets, which are considerably 
heated in their passage over its surface, and are then distrib- 
nied to the fire through the perforations and around the 
edges of the plate. 




9 



14 ECONOMIC COMBUSTION §13 

15. With a lar^e furnace working under natnral draft, it 
may be difficult either to admit sufficient air through the 
perforated door to supply all parts of the furnace or to 
properly distribute the air so admitted. To remedy this 
defect, recourse is had, in marine practice, to admitting: the 
air above the grate under pressure, as is done in the How- 
den and also in the Ellis & Eaves mechanical-draft systems. 
In firebox and locomotive-tjrpe marine boilers working under 
natural draft, a few rows of hollow staybolts may be used 
just above the surface of the fire; these admit air in small 
jets that enter that part of the furnace least likely to be 
reached by air from the door, at right angles to the current 
of the gases, and the air is thus more easily mixed with the 
gas than would be the case if the currents were parallel. A 
point that would seem to be unfavorable to the ultimate 
success of any attempt to introduce air through the sides of 
the furnace in this manner is the difficulty of controlling the 
quantity so introduced in accordance with the varying con- 
ditions of draft and fuel supply. 

16. The admission of air through properly constructed 
openings in the bridge wall and above the fire has been 
shown, by experiment, to produce economical results when 
a bituminous coal rich in volatile matter and producing a 
long, smoky flame is used. The openings through the bridge 
wall should be so arranged as to discharge the air in a 
number of jets at a right angle to the direction of flow of 
the gases. The space back of the bridge should then be 
large enough to form a combustion chamber in which there 
will be a thorough mixture and complete combustion before 
the air and gas are chilled by entering the tubes. A large 
space produces a relatively moderate velocity of flow of 
the gases, which is favorable to the intimate mixture of the 
air and gas. 

HEATED-AIR SUPPLY 

17. While it would be an advantage to have the air 
enter at a high temperature, no means have yet been devised 
that will accomplish this in an economical manner with 



§13 



ECONOMIC COMBUSTION 



15 



natural draft. Of course, the temperature of the air is raised 
to a slight degree in its passage through the ash-pit, or the 
openings in the setting leading to the bridge, and in passing 
through the bridge to the openings through which it is dis- 
charged, but the actual gain by this means is relatively 
unimportant, even when rather elaborate systems of pas- 
sages are used. Some of the difficulties attendant on this 
method are the following: In order to prevent loss from 
too much or too little air, the passages must be controlled 
by dampers that should be regulated according lo the con- 
dition of the fire and the rate of combustion; this demands 
close attention and intelligent care on the part of the fire- 
man, who must either maintain nearly constant conditions 
in the furnace or change the dampers as often as there is 
a material change in the condition of the fire. The pas- 
sages through the bridge wall may give trouble by becoming 
clogged with ashes and clinkers that have been pushed back 
from the fire during cleaning or carried back by the draft, 
and so become useless. The method is limited in its appli- 
cation to furnaces so constructed that there is room for a 
combustion chamber of considerable size, in which mixture 
and combustion may take place before the gases are cooled. 
The difficulties just mentioned are minimized in mechan- 
tcal*draft systems, like the Howden and the Ellis & Eaves 
systems, where the heated air is discharged, under pressure, 
where it will do the most good, and where there is an 
absence of passages likely to give trouble by becoming 
choked with ashes and refuse. The proper control of the 
supply of heated air above and below the grate demands 
intelligent supervision, however, in both of these systems. 




1 



16 ECONOMIC COMBUSTION §13 



FURNACE AND COMBUSTION CHAMBER 



SHAPE AND SIZE OF FURNACE 

18. The lowest temperature at which ig^nition of the 
gases can take place is about 1,800 F. By reference to the 
Steam Tables, in Heat and Steam ^ it is seen that the tempera- 
ture of the water in the boiler, even under a pressure of 200 
pounds per square inch, is less chan 400^ F.; this is practi- 
cally the temperature of the surface of the boiler. It is 
therefore evident that any gas that comes into close contact 
with the boiler before being burned will be cooled below the 
point of ignition, and, unless subsequently heated, will be 
carried to the smokestack unconsumed. With coals contain- 
ing large quantities of volatile matter and burning with a 
long smoky flame, it follows -that the firebox must be of 
ample depth to provide a space in which the great volume 
of gas can bum before being cooled; or that there must be a 
combustion chamber in which the gas can bum after leaving 
the firebox. 

The danger of loss from cooling the gases too suddenly is 
greatest in intemally fired boilers of the vertical, locomotive, 
and firebox types. Unless the crown sheet is unusually high 
above the grate, vertical boilers are especially unfitted for 
the use of rich bituminous coals. Locomotive-type and fire- 
box boilers, if properly managed, are better; by the use 
of the coking system of firing, the gas must pass through 
the length of the firebox and over the hot bed of coke, thus 
giving it considerable time to burn before entering the tubes, 
the heat radiated from the coke helping to keep it at a tem- 
perature at which combustion is possible. 

Firebox and locomotive-type marine boilers may be fitted 
with firebrick arches that extend from the tube sheet toward 
the door and force the gases to take a path, first toward the 
door and then back above the arch to the tubes. The arch 
becomes highly heated, thus preventing the cooling of the 
gases before they become mixed with the air, and the path 



S 13 ECONOMIC COMBUSTION 17 

of the gases is lengthened sufficiently to enable them to burn 
before entering the tubes. It also increases the life of the 
flues by preventing the entrance of large volumes of cold 
air when the door is opened, and thus aids in maintaining a 
more even temperature. 

The opinion of railroad men, almost without exception, is 

in favor of the firebrick arch for locomotives burning bitu- 

■ minous coals, and there is no doubt that the principle 

involved in its use can be employed to great advantage in 

marine work for similar boilers. 



ADMISSION OP STEAM INTO POBNACB 

19. When steam is admitted into the furnace through 
the ash-pit. or otherwise, it is decomposed by the heat into 
its constituents, hydrogen and oxygen. This process, how- 
ever, absorbs as much heat as can possibly be developed by 
the combustion of the hydrogen thus formed. From this it 
follows that there can be no possible gain in heat from intro- 
I'idticing steam. In fact, there are several features that may 
Vcaitse the use of steam to result in an actual loss of heat; 
there is danger that much of the hydrogen liberated by the 
decomposition of the steam may escape unburned owing to 
the reduction of temperature of the fuel bed produced by 
the decomposition of the steam. Also, the steam enters the 
n.ash-pit at a temperature seldom above 212° F. and passes 
Bfato the chimney at the temperature of the flue gases, which 
[is rarely below 400° F. It thus carries more heat into the 
himney than it introduces into the furnace. 
The use of a steam jet for forcing air into the ash-pit, and 
hbe admission of steam through a small pipe to the ash-pit 
P»re quite common in stationary practice, but very uncommon 
marine work. There are cases, however, where either 
toethod may be advantageously employed in marine work, 
irbich occur when coals that tend to clinker badly and stick 
J the grate bars must be used. With such coals, the effect 
W the steam is to prevent the clinkering to a considerable 
V^tent; this enables the fireman to keep the grate cleaner, 



18 ECONOMIC COMBUSTION §13 

prevents the destruction of the grate, and, on account of the 
improved condition of the fire, permits of a better distribu- 
tion of air and more complete and economical combustion. 
In the case of a steam jet forcing air into the ash-pit, or a 
steam jet in the smokestack, using live steam, there is often 
an increased economy in the use of the coal over that Which 
is obtained by natural draft; the gain, however, must be 
ascribed solely to the improved air supply, and not to the . 
fact that steam is used. A similar improvement in the draft 
by means of a higher smokestack or by some mechanical- 
draft appliance will generally give even better results than 
can be obtained by the use of steam. 



COMBUSTION CHAMBER 

20. In internally fired boilers of the Scotch marine and 
similar types, having large fiu'nace flues that open into a 
chamber in the rear, the gases that are cooled by contact 
with the walls of the flue and pass through it unconsumed 
sometimes bum in the rear chamber, which, for this reason, 
is given the name combustion chamber. With exter- 
nally fired boilers of the flue type, the space back of the 
bridge serves the purpose of a combustion chamber to a 
certain extent. The gases, however, tend to rise and flow 
along the cold surface of the boiler; it is, therefore, difficult 
to prevent a considerable body from thus becoming cooled 
below the ignition temperature and passing unconsumed into 
the tubes. 

Water-tube marine boilers generally have no distinct com- 
bustion chamber, unless the term be applied to the upper 
space within the jacket surrounding the boiler. The gases 
rise nearly vertically from the fuel bed and pass from the 
firebox immediately into contact with the tubes; the narrow 
spaces between the tubes divide the gases into thin sheets 
that are rapidly cooled below the temperature of ignition. 

The vertical direction of the current of gases in the furnace 
makes it difficult to secure any considerable admixture of air 
from the fire-door; the chief dependence for the air supply 



§ 13 ECONOMIC COMBUSTION 19 

must therefore be on the air that rises through the grates 
and passes upwards through the bed of fuel. These condi- 
tions make it essential, for complete and economical com- 
bustion, that a sufficient supply of air be admitted through 
the grate itself, and that the supply be well distributed over 
the whole grate area, so that it may become mixed with the 
gases almost as soon as they are formed. It is also impor- 
tant that the grate be placed far enough below the tubes to 
permit of a thorough mixture of the gas and air and of 
complete combustion of the gas before it enters the space 
between the tubes. 

HEAT L08BE8 AND TIIEIU PREVENTION 



MISCELLANEOUS HEAT L099ES 

21< A portion of the heat generated in the furnace is 
usefully expended in evaporating water, but a large percentage 
of the heat is often wasted. Some of these heat losses are 
unavoidable, while others are due to poor management or poor 
design of the boiler. 

The heat losses due to incomplete combustion of the car- 
bon and hydrocarbons, the formation of smoke, excessive 
air supply, etc. have already been pointed out, and the 
methods of preventing them have been explained. In addi- 
tion to these losses, there is the loss of heat inseparable 
from the use of natural draft. Since the draft depends 
entirely on the difference in density between the gases 
within the smokestack and the air surrounding the smoke- 
stack, it follows that the heat recjuired to produce the differ- 
ence in density (that is, to produce the draft), while not 
available for the generation of steam, is essential to the 
operation of a boiler; while the heat thus expended may be 
called a heat loss, it is nevertheless an unavoidable loss. 

Some heat is lost by radiation from the boiler itself and 
some from the connections. This loss, while it cannot be 
prevented entirely, can be minimized by covering the exposed 
■parts with some good non-conducting material. 



20 ECONOMIC COMBUSTION § 13 



MOISTURE AND DISTILI^TION HEAT LOSSES 

22. There are processes accompanying the combustion 
of coal in the boiler furnace that in themselves absorb great 
quantities of heat and, in consequence, have an important 
bearing on the question of complete and economical combus- 
tion. All moisture that enters the furnace with the coal must 
be evaporated at the expense of the heat developed by the 
combustion of the coal; the vapor thus formed passes out of 
the smokestack at a temperature seldom less than 400° F. 
Assuming that the moisture enters the furnace at a tempera- 
ture of 70° F. and leaves at 400° F., 1,200 British thermal 
units, nearly, will be lost for each pound of moisture in the 
coal. Moisture in coal can only be driven off by heating it 
above ordinary temperatures, but it will be readily absorbed 
at ordinary temperatures; hence, it is important that coal 
when stored is not exposed to rain — it should always be stored 
under cover. In some cases, it may be advantageous to wet 
bituminous coal; when wet, especially if the coal is fine, it 
cokes better, and hence there is less waste from coal falling 
into the ash-pit. Wetting is recommended only for bitumi- 
nous slack and anthracite culm, and should be as moderate 
as will secure the results desired. It would be much better, 
however, when the draft is moderate, to use grates having 
smaller openings. When the draft is exceptionally strong 
and very fine coal is burned, wetting becomes almost a neces- 
sity. If not done, the strong draft will actually carry a large 
percentage of the fine coal up the smokestack. 

The distillation of the volatile matter is a process that, 
with all bituminous coals, and to a lesser degree with anthra- 
cite, absorbs a great deal of heat, as is shown by the drop 
in the steam pressure when a large quantity of fresh coal 
is thrown on the fire; this drop is largely due to the lower- 
ing of the furnace temperature through the heat absorbed by 
the distillation of the volatile matter. While the absorption 
of heat is necessary to drive off the volatile combustible, 
the losses attendant upon a lowering of the furnace tempera- 
ture can be minimized by frequent light charges of coal. 



fc 



ECONOMIC COMBUSTION 



lan-TBMPERATrRE nSAT LOSSES IN SMOKESTACKa 

i3. In many cases, there is a large amount of heat pass- 
ing out of the smokestack in excess of that required to 
produce the necessary intensity of draft. In practice, it has 
been found that, when the temperature of the escaping gases 
has been lowered to about 500° F., the draft will be ample. 
If their temperature is in excess of this, it usually indicates 
a serious heat loss. The high temperature may be due to 
several causes, either singly or combined, among which may 
be mentioned insufficient heating surface, inefficient heating 
surface, and poor water circulation. 

It is rather hard to decide where to place the blame in 
case' the temperature of the escaping gases is excessive. In 
general, the trouble is that the efficiency of the heating sur- 
faces has become impaired by reason of the collection of 
soot and condensable tarry vapors on the fire side, and the 
deposit of scale on the water side. The obvious remedy is 
to clean the surfaces, and to clean them thereafter at such 
intervals as will keep thera in a state of high efficiency. 

If the heating surfaces are clean and the temperature of 
the escaping gases is excessive, the trouble, with fire-tube 
boilers, may be due to poor circulation. It is difficult to stale 
just exactly what should be done to improve the natural cir- 
culation, since boilers vary so much in design. In general, 
it is cheapest to use some suitable apparatus designed to 
give a forced circulation. In flue boilers and water-lube 
boilers, the circulation is usually free and strong; an exces- 
sive temperature of the escaping gases with these types of 
boilers is usually due to dirty or insufficient heating surfaces. 

Insufficiency of heating surface is generally found in cases 
where, due to the exigencies of service, boilers are forced 
beyond the steam-making capacity for which they were 
installed. This calls for an increased combustion rate per 
square foot of grate surface, in consequence whereof an 
increased volume of gas passes through the tubes and over 
the beating surface at a higher velocity. Since the transfer 
■M heat from the heated gases to the water depends to a 



22 ECONOMIC COMBUSTION § IS I 

large extent on the time during which they are in contact 4 
with the heating surfaces, a proportionately smaller amount I 
of heat per pound of gases is transferred to the \ 
A partial remedy for loss due to this cause is to lengthen 1 
the time the gases are kept in contact with the heating sur-l 
faces, as may be done by using spiral retarders in the tubea-J 
of fire-tube boilers; or, if feasible, by fitting suitable bafflftj 
plates between the tubes of water-tube boilers, in ordei 
to lengthen the path of the gases. Another partial remedy 
is a feedwater heater placed in the path of the waste gases ' 
before they pass out of the smokestack. 



BUUeS FOR BUILER BFFICIENCT 

24. The efficiency of a boiler is the ratio of the differ- 
ence between the heat in the steam delivered by the boiler 
and the heat in the feedwater to the heat that would be 
developed by the perfect combustion of the fuel, and is 
expressed by dividing the former quantity by the latter. 
Thus, if a test shows a total supply of heat of 270.187.000 
British thermal units, and a useful application of 186.429,030 
British thermal units to the evaporation of water into dry 
186.429.030 



steam, the efficiency of the boiler is ' -'--rrr = .69. 

Boiler efficiency thus determined consists of two factors 
not readily separable — the eiKciency of the furnace as a heal 
producer and the efficiency of the boiler as a heat absorber. 
It is possible to have a furnace so well constructed and 
managed that the combustion is nearly perfect, and still 
have a low efficiency of the boiler as a whole, owing 
to inefficient healing surfaces, large radiation losses, etc 
In order to secure a high eiificiency of the boiler, as a wholCj 
it is necessary to pay strict attention to each and every 
detail and to keep it in the most perfect condition possible. 

25. Having seen that complete, i. e., economical, com^ 
bustion depends on a sufficient air supply intimately mixec 
with the combustibles, and a high furnace- and combustioni 







§ 13 ECONOMIC COMBUSTION 23 

chamber temperature to insure ignition, the following rules 
will be self-evident: 

1. Fire light and often. 

2. Keep the fire as thin as circumstances will permit. 

3. Keep the fire clean. 

4. Keep the space between the grate bars clear. 

5. Keep the ash-pit clear. 

6. When using bituminous coal, use the coking firing 
system, if possible. 

7. Regulate the draft so that it will be strongest when a 
fresh charge of coal is put into the furnace. 

8. Do not let the fire bum out in spots. 

9. Do not let the fire bum too low before charging. 

10. If possible, fire at regular intervals and in regular 
charges. 



L MARINE-BOILER FEEDING 



FEED-APPAKATUS 



ARRANGEMENT 



INTRODUCTION 

1. The feed-apparutus of marine boilers comprises 
Suitable machinery for forcing the water into the boiler. 
piping for conveying it to the boiler and deliverinE it therein 
at the desired place, and suitable valves for regulating the 
liow of the feedwater. Auxiliary devices often used in con- 
nection with the feed-apparatus are feedwater heaters, feed- 
water purifiers, and circulation-improving devices intended 
to better the transfer of heat from the burning fuel to the 
water in the boiler; and in cases where the steam used in 
the engine is condensed and returned to the boilers without 
being mingled with the water used for condensing it, there 
must be some means of making up for the loss of feedwater 
caused by leakage. 

The machinery used for forcing the water into the boiler 
consists either of pumps or of injectors, the former being 
either driven directly by the propelling machinery or inde- 
pendent steam pumps. Usually, two independent sets of 
feed- apparatus are fitted to marine boilers, both of which 
may have pumps or injectors, or one set may comprise 
pumps and one set injectors. 

In practice, the feedwater for marine boilers is obtained 
either by using the surrounding water, which method is 

Ctpyrtglnti in /Hltrmtunal Ttiltoak Comttmy. Enirted at Sfofiowrj' //all, lemtbm 




2 MARINE-BOILER FEEDING §14 

today used ordinarily only by vessels navigating fresh 
water, or by condensing the steam used in the engine and, 
without mingling it with the water used for condensing, 
returning it to the boiler, which method is used by prac- 
tically all ocean-going vessels. 

2. There are two methods of condensing the steam used 
by the engine. In the first method, the steam is condensed 
by being brought in direct contact with a spray of cold water 
in a vessel called a Jet conclenser. The condensing water 
usually flows to the condenser by gravity and atmospheric 
pressure. The mingled condensing water and condensed 
steam are drawn from the condenser, together with any air 
present, by the air pump; as much of this water as is 
required for the boilers is supplied to the feed-pumps, the 
remainder being discharged overboard by the air* pump. It 
is obvious that by this method the impurities contained in the 
condensing water are carried into the boiler. In the second 
method, the steam is condensed by being brought into contact 
with metallic surfaces kept cold by water pumped over them, 
which are contained within a vessel called a surface eon- 
denser. The condensed steam, vapor, and any air present 
is removed from the condenser by the air pump and delivered 
into a vessel called a hotwell, from which the condensed 
steam is taken by the feed-pump and returned to the boilers. 
The condensing water is pumped through the condenser by 
the circnlatin{^ pump. In a surface condenser, the con- 
densed steam and the condensing water do not mingle, and 
hence the water taken from the hotwell, unless contami- 
nated by leakage or the deliberate admixture of sea-water, 
is pure distilled water, generally free from harmful ingredi- 
ents, except oil or grease. The grease or oil in the feed- 
water is usually extracted by filtering, although in some 
cases attempts are made to remove it from the exhaust 
steam before condensation. 

3. It is of the utmost importance that the feed-apparatus 
of a marine boiler shall be as perfect as possible, not only 
in regard to its capacity to supply the boiler with all the 



§14 MARINE-BOILER FEEDING 3 

water it may require, even in case of a heavy leak, but also 
that the possibility of its becoming inoperative shall be 
reduced to a minimum. The pipes should be nm as straight 
as convenience will permit, avoiding all unnecessary bends 
and turns, and they should be so located that they may be 
readily traced from end to end. Although it is sometimes 
necessary to place some of the pipes under the engine-room 
and fireroom floors, it is better to avoid this whenever pos- 
sible; but when it must be done, the floor plates over them 
should be laid so that they can easily he taken up and thus 
access be gained to the pipes underneath, particularly at 
those points where valves are located. 



* 



INST AUCTION 

4. In sea-going steam vessels, every pump in the ship is 
usually provided with the pipe connections necessary to 
allow it to be used for feeding the boilers. Fig. 1 illustrates 
one way in which the feedpipes may be connected; for the 
sake of clearness, only the pipes relating to the feed-appara- 
tus are shown. The boiler is shown at C, the engine at D, 
the condenser at £', the air pump at /^ and the circulating 
pump at G. The plunger feed-pumps A, A' are worked by 
the engine, taking their water supply through the suction 
pipes o.i/ from the hotwell B, and discharging the water 

■ough the main feedpipe b into the feed check-valve C 
rhence it passes through the stop-valve /y into the boiler. 

le feed check-valve is a device that permits the feedwater 

flow into the boiler, but automatically prevents water in 
le boiler flowing into the feedpipe. 

The piping just described constitutes the main feed. On 
all marine boilers, a bronze or brass-seated stop-valve must 
be attached between the boiler and each feed check-valve to 
facilitate access to the check-valves while the boiler is under 
steam, and also as an additional safeguard to keep the water 
in the boiler, Check-vaives will sometimes fail to seat 
properly, allowing the water in the boiler to leak past them 
while the pump is stopped, the water passing through the 



MARINE-BOILER FEEDING §1( 




§H 



MARINE-BOILER FEEDING 



the main feedpipe into one of the other hoilers in which Ihe 
pressure may be somewhat less, thus allowing the water to 
become dangerously low in the first boiler. By closing the 
Slop-valve in the feedpipe this is prevented. The duplex 
sleam pump E and the single-acting pump H are connected 
to [he hotwell B by the suction pipes / and c. The pump E 
is provided with branch suction pipes d and e leading, 
respectively, to the sea and to the fresh-water ballast tank, 
Similar suction pipes (/, and e, are fitted to the pump //, and 
other branch suction pipes leading to other available sources 
of water supply may be fitted to each pump, as required. 
The pump E delivers through the pipe {. and the pump H 
Ihruugb the pipe /', into the donkey feedpipe, or auxiliary 
feedpipe g, whence the water passes through the donkey 
check-valve /■"' and the stop-valve G' into the boiler. The 
'wo feed-arrangements just described constitute the donkey 
feed, also called the auxiliary leed. 

It has been shown that in the arrangement described there 
are three ways of feeding the boiler, each independent of 
the others. The main feed-arrangement may be used, or, 
ii desired, either of the other two arrangements. Hence, the 
Possibility of being unable to supply the boiler with feed- 
Water is very remote. 



5. The point at which the feeder enters the boiler varies 
With different builders. In shell boilers, some take the feed 
through Ihe front head of the boiler, some through the rear 
head, and some through the shell. The common practice is 
to lead the feedwater to the coolest part of the boiler. This 
is done by a pipe secured to the inside of the boiler shell. 
When a large body of comparatively cool water is discharged 
on to a hot plate, severe local strains are set up in the plate, 
due to the contracting of the part cooled by the entering 
feedwater. These strains soon destroy the plate; to obviate 
ihis, the end of the internal feedpipe is often closed and 
the entering feedwater distributed over a large area by 
numerous holes drilled into ihe pipe in such a position 
that the water will issue in a direction away from the 




6 MARINE-BOILER FEEDING §U 

plates composing the boiler. In Scotch boilers, in the best 
modem practice, the feedwater is discharged by a pipe 
lying on a level with the top row of tubes, the pipe being 
perforated and discharging downwards between two nests 
of tubes. 

CONSTRUCTION 



h 



PUMPS 

6. Kinds of Pumps Used. — The pumps employed 
regularly for pumping feedwater into the boilers are usually 
of the plunger pattern, and may be either single-acting or 
double-acting. They are either driven directly by the main 
engine, in which case it is the usual practice to employ sin- 
gle-acting pumps, or they are independent, in which case 
they are frequently duplex and double-acting — ^by duplex 
being meant that there are two separate pump mechanisms 
combined to form one pump. Independent single or duplex 
direct-acting steam feed-pumps are made either vertical or 
horizontal, the choice of pattern usually depending on the 
room available. In steamboats navigating the western rivers 
of the United States of America, a special form of independ- 
ent steam pump is largely used, in which the pumps are 
operated by a beam rocked back and forth by a steam engine. 

7. single- Acting Plunger Feed-Pump. — One form 
of construction of the type of plunger feed-pump generally 
used in connection with vertical marine engines and driven 
from one of the crossheads through a rocking beam giving 
the plunger a to-and-fro motion, is shown in Fig. 2, in which 
A is the plunger, made of Muntz metal. It is cored out to 
lighten it, and it passes through a stuffingbox and gland lined 
with white metal. The pump chamber B is bolted to the 
side of the air pump. A valve chamber C containing the 
suction valve D and delivery valve E is bolted to the pump 
chamber. These valves work in gun-metal bushings fitted 
to the valve chamber. Above each valve is a yoke d, e that 
prevents the valve from rising too high, A ^tua,ll petcock K 



MARINE-BOILER FEEDING 7 

itted between the suction and delivery valves; this may 
used to test the working of the pump and also to admit 
to the air chamber. The air in the air chamber will 
lier or later be absorbed by the water, in which case the 




Ves will seat with a considerable shock. Opening the pet- 
;k will admit air on the up stroke of the plunger. On the 
iva stroke, water will issue if the pump is working prop- 
In some cases, no petcock is fitted. When the valves 
frheavily, or s/am, as it is called, 4oosening the gland of 



MARINE-BOILER FEEDING 



§14 



the plunger will admit some air and cure the slammiog 
Rolled to the bottom of the valve chamber is the suction 
pipe F, which connects with the holwell, and is providcL! 
with a stop-valve, not shown in the figure. For the purpose 
of examination, the valve chamber is provided with a remov- 
abfe cover, not shown in the figure. An air chamber H is 
fitted to the top of the valve chamber, and attached to this 
air chamber is the feedpipe G leading to the boiler. 

8. The plunger pump A, Fig. 2, is working as long as 
the engine is running, and, consequently, is feeding the boiler 
or boilers continually. When two or more boilers are sup- 
plied from the same main feedpipe, the amount of feedwater 
entering each boiler is regulated by adjusting the lift of th 
feed check-valves. If one boiler gets less than its prope 
amount of feed, as may be found by watching the wate 
gauge, the amount may be increased by giving a higher 111 
to the check-valve, thus increasing the area of the passag 
to the boiler. Conversely, reducing the lift of the valv 
reduces the feed. When an independent pump is used fo 
feeding one boiler, the feed may be regulated by varying th 
speed of the pump; but. with attached pumps having a con 
stant speed, the check-valve must be used for that purpon 

9. Doctor. — The feed-pumps and heaters of a westen) 
river steamer are shown in Fig. 3. This combination \ 
known as a doctor, is in common use, and is located a 
deck and hence above the water level. The doctor consist 
essentially of a beam engine, with crank and flywheel. ■ 
ting four pumps, two on each side. The lifting pumps A, i 
are single-acting; they draw the water from the river an 
discharge it into the open heaters D,B'. Here the water is 
heated by being brought in direct contact with the exhaust 
steam, the exhaust from each engine passing through its own 
heater. The force pumps on the other side take the watern 
from the heaters and force it into the boilers; one of thes 
pumps is shown at C . The base plate D on which the d 
tor is erected contains the various passageways forming ( 
water connections between the pumps, the passages beio 




10 MARINE-BOILER FEEDING §14 

cored in the casting. The suction pipe to the river connects 
directly with the vacuum chamber E^ so called since a partial 
vacuum is necessarily maintained therein. The object of 
this vacuum chamber is to prevent shocks and to steady the 
flow of water in the suction pipe. The lifting pumps being 
single-acting, the column of water ascending the suction pipe 
would, if such chamber were not provided, be suddenly 
brought to rest by the closing of the suction valve of the 
pump. The kinetic energy of the moving body of water 
would be given up suddenly, and be expended in a violent 
blow or shock; but with a vacuum chamber the column of 
water, with the exception of that comparatively small por- 
tion of it between the piston and the chamber, is not sud- 
denly checked, but continues to move during the down stroke 
of the piunp plunger, compressing the rarefied air in the 
vacuum chamber. Shocks are thus obviated and the inflow 
of water steadied. A cored passage in the base connects 
the vacuum chamber with the suction end of the two lifting 
pumps. The water is delivered through the delivery casings 
a, a', which contain the delivery valves, into passages in 
the base plate that connect with the hollow columns F and 
/^, the column /^communicating with a and the coltunn F 
with a\ The water does not pass straight up the columns, 
however, but is led through the valves G, G\ and then back 
into the columns, and thence to the heaters. When the 
doctor is stopped for the purpose of opening and examining 
the valves of the lifting pumps, valves G, G' are closed and 
serve to retain the water in the heaters. The heaters con- 
sist of wrought-iron shells with cast-iron heads; the exhaust 
from each engine enters its own heater through one head 
and leaves it through the other head. The exhaust comes 
in contact with a coil H of copper pipe near the bottom of 
each heater; the lifting pumps force the water through this 
coil and discharge it at the bottom of the heater below the 
diaphragm L. While this diaphragm does not in any way 
prevent the exhaust steam from coming in contact with the 
water, it acts as a baftle plate, preventing violent agitation 
of the surface of the water in the heater, and at the same 



MARINE-BOILER FEEDING 

time provides a quiet spot for the collection of floating 
impurities. An overflow pipe is attached to the heater at or 
about the level of this diaphragm, which not only prevents 
the flooding of the heater, but also serves to carry off the 
oil and other light impurities floating on the siu^face of the 
water. The heated water flows by gravity down hollow 
columns opposite /"and F' to the suction side of the force 
pumps, which are single-acting plunger pumps. It now 
"passes through the delivery chambers, one of which is shown 
at c, into two pipes that unite to form the main feedpipe. 
The exhaust pipes from each heater are usually united to 
form one main exhaust pipe, extending from near the heaters 
to near the back end of the boilers. Here this pipe forms 
two branches, each branch leading to one of the smokestacks. 
Provision is usually made for turning the exhaust either 
into the smokestack for the purpose of increasing the draft 
or directly into the almosphere by dividing the pipe into 
two branches and placing a rotary valve at the junction. 
The main feedpipe passes through a stutfingbox into the 
after end of the Y fitting at the after junction of the two 
exhaust pipes; it then passes through the whole length of 
the main exhaust pipe and emerges through a stuffiiighox at 
the forward end, where the exhaust is again divided. The 
main feedpipe then leads downwards and branches ofl to 
each boiler. By passing the feedwater through the heaters 
and exhaust pipe, it is heated to a high temperature. 

The pumps are all attached to the walking beam A', con- 
nected to a steam cylinder O at one end and to a crank and 
flywheel /"at the other end. The slide valve of the engine 
is operated by a small crank, or occasionally an eccentric, on 
the end of a flywheel shaft. To allow the cylinder to be readily 
warmed up when starting, and also to facilitate the starting 
of the doctor, the eccentric rod Q is hooked over a pin of 
the bell-crank K. When the rod is unhooked from this pin, 
the slide valve can be operated by hand. 

10. While the doctor may appear complex at first sight, 
it is really a very simple machine, in which the working parts 



12 



MARINE.BOILER FEEDING 



a 



are simple in construction and very accessible. In western- 
river service, where the water is frequently very muddy and 
must always be pumped against very high pressures, the 
doctor has proved economical and efficient, and has held its 
own against direct-acting steam pumps and injectors. The 
general demand for lightness and simplicity in machinery is 
well met by the manner in which the frame is made use of 
in providing the water passages, and in the design illustrated 
by making the steam pipe and exhaust pipe of the steam 
cylinder serve as crosshead guides. 



4 



FEED-VALVES 

11. The check-valve fitted to the main feedpipe is called 
the main check-valve, and the one fitted to the auxiliary 
feedpipe is called the auxiliary, or tloukey, checl*-valve. 
The donkey check-valve does not differ in any respect from 
the main check-valve; it is 
merely so named from its 
location. 

A common construction 
of a feed check-valve is 
shown in Fig. 4. It con- 
sists of a body or casing .-J 
bored out at the lower end 
to receive the gun-metal 
bushing /i forming the 
seat, and a guide for the 
valve I', which is provided 
with four wings, as shown. 
The feedpipe is bolted to 
the flange shown at C. 
while the passage Z? con- 
nects with the boiler. 
When water flows through the feedpipe into the passage C. 
it raises the valve and flows through the annular opening 
between the valve and seat into passage /), and thent 
through a stop-valve (not shown in the figure) into 1 





§14 MARINE-BOILER FEEDING 13 

boiler. The valve f-' allows the water to pass only in one 
direction; should the ilirection of the flow of the water be 
reversed, the valve will return to its seal and shut off com- 
munication with the passage C. By means of the screw S, 
the height of the lift of the valve can be regulated, thus 
increasing or diminishing the quantity of water passing 
through the valve. The screw S is commonly made of 
Muntz metal, to prevent corrosion. 

13. Should either the check-valve C or stop-valve ly. 
Fig. 1, be closed for some reason while the pump A is 
working, either the pump or the feedpipe will burst. To 
prevent this, a relief valve that will open and allow the water 
to escape in case the pressure on the pipe exceeds the pres- 
sure on the boiler by, say, 15 pounds per square Inch is fitted 
either to the pump chamber or to the air chamber. The 
usual construction of a relief valve is shown at /, Fig. 2. 
The area of this valve is equal to that of the feedpipe. 
Relief valves are sometimes called safety feed-valves. 
The valve is kept to its seat by the spring shown, which 
abuts against a yoke fitted over two studs provided with 
nuts, by means of which the tension of the spring can be 
adjusted to the desired pressure. 



INJECTOlta 

13. Action. — The Injector is an apparatus for forcing 
the feedwater into a steam boiler. It was invented in 1858 
by an eminent French scientist, Henri Giflard, and was 
introduced into the United States in 1860 by William Sellers 
& Co.. of Philadelphia. 

On investigating the action of the injector, it will be found 
that dry steam at a given pressure enters the apparatus, 
passes through several contracted passages, raises several 
check-valves, and then forces water into the boiler against a 
pressure equal to that which the steam had when it first 
began the operation. The steam, in forcing the water 
through the injector and into the boiler, gives up its heat 
and performs actual mechanical work as truly as though the 




steam acted on a piston and moved a pump plunger with it. 
Before the action of an actual injector can be studied prop- 
erly, it is necessary to have a clear understanding of the 
fundamental principle on which its action is based. This 
may be stated thu.s: A current of any kind, be it steam, air. 
water, or other matter, by reason of friction has a tendency 
to induce a movement in the same direction of any body 
with which it may come in contact. The steam entering a 
injector and moving with an extremely high velocity first: 
carries the air inside the injector with it and thus creates i 
partial vacuum, causing the water to flow into it. The steant 
then imparts a portion of its velocity to the water and givei 
it sutRcienl momentum to throw open the check-valves and. 
enter the boiler. By striking the cold mass of water. th« 
heat and velocity of the steam will be greatly reduced, and 
it will be condensed at the same time. 




14. The essential parts of an injector are shown i 
Fig. 5, which does not represent a practical injector, bt 
serves to illustrate the combination of the essential parts b 
means of which the injector performs its function. Steal 
is admitted from the boiler through the steam pipe a; tbt, 
chamber /> connects to the water supply through the nozzle fj 
The tube rf is called the combining tube; the space e is thS 
overflow space: the overflow is carried away by a pipe attached 
to the overflow nozzle g. The water passes through th« 
check-valve / into the discharge pipe A and thence into tho 
boiler. The check-valve may not be part of the inject* 
itself, but it is an essential part of the installatioa. 



The action of the instrument is as follows: Steam is 
admitted through a and flows through the nozzle with a high 
velocity, passes through the combining tube d and out 
through the overflow e and nozzle^. This current of steam 
carries the air in the chamber b with it, thus forming a par- 
tial vacuum; the pressure of the atmosphere then forces 
water from the supply into the chamber and into the com- 
bining tube d. In rf the steam and water are combined, with 
the result that the steam imparts a great deal of its velocity 
to the water and at the same time is condensed. This forms 
a jet of water that flows from the combining tube d with such 
a high velocity that it passes over the overflow e and into the 
discharge pipe /;, the energy in the water being great enough 
to overcome the pressure in the boiler. The water thus 
flows past the check-valve ( into the boiler. When the 
injector is working properly, all the steam that is used to 
give the water its high velocity is condensed, thus leaving a 
steady, unbroken jet of water that flows across the space 
between the combining tube and the discharge pipe. If the 
water is too hot to condense the steam, or if there is so 
much steam that it is not all condensed in the combining 
tube, the steam, owing to its lightness, will not be carried 
into the boiler, but will flow out into the overflow space e 
and be discharged from the overflow nozzle g. This esca- 
ping steam breaks the jet of water and interferes with the 
action of the instrument so much as to stop the flow into 
the boiler, and serves to show the engineer when there is too 
much steam admitted for the water that is used. When the 
supply of steam is too small, the velocity of the jet of water 
flowing from the nozzle is so small that its momentum is not 
sufficient to carry it into the discharge pipe against the pres- 
sure in the boiler, and the water is therefore discharged 
through e and out of the overflow nozzle^. This shows the 
ngineer that the supply of steam is too small. 



! 16. The temperature at which water will be delivered by 
D injector to the boiler depends on the steam pressure and on 
! quantity of water being delivered per pound of steani, 




16 MARINE-BOILER FEEDING §14 

the feedwater temperature remaining: constant. Thus, if an 
injector is worked at its maximum capacity with a steam 
pressure of 30 pounds, the temperature of the water deliv- 
ered to the boiler will be about 114° F.; if the pressure is 
200 pounds, the temperature of the injected water will be 
about 154° F. The temperature of the water delivered will 
increase as the delivery of the injector is cut down from its 
maximum to its minimum. Thus, under 140 pounds steam 
pressure, and working^ at its maximum capacity, an injector 
may deliver water at about 135° F.; while if the injector is cut 
down to its minimum delivery, the water will be delivered at 
about 250° F. Under ordinary working conditions, the water is 
probably delivered at a temperature between 160° and 200° F. 
The highest temperature at which an injector will lift the feed- 
water decreases as the steam pressure under which the injector 
is working is increased. At low steam pressures, the injec- 
tor may raise water at 125° or 130° F.; while at 140 pounds and 
upwards, it is not safe to have the water much above 110° F. 

16. The number of pounds of water delivered per pound 
of steam decreases as the steam pressure is increased. At 
30 pounds steam pressure, an injector may deliver from 
20 to 25 pounds of water per pound of steam; while at 
140 pounds pressure, it will deliver only about 13 pounds, 
and at 180, only about 11 pounds. 

17, The term range, when applied to an injector, refers 
to the steam pressure at which it will start and the steam 
pressure at which it ceases to work. The range of an injector 
decreases with any increase in the distance that the water 
must be lifted, and also decreases with any increase in the 
temperature of the water supply. This is clearly shown in 
the following table published by the American Injector 
Company and referring to an injector manufactured by it. 

The steam pressure at which injectors of different makes 
will start varies somewhat, but the range between the start- 
ing and stopping pressures with different injectors is practi- 
cally the same. Most injectors will start on 25 pounds steam 
pressure, but some are made to start on 15 pounds. 



U4 



MARINE-BOILER FEEDING 



17 



18. Construction. — Injectors may be divided into two 
genera! classes — non-lifling and lilting injectors. They dif- 
fer from each other, as implied by the name, in that the one 
class is capable of lifting the water from a level lower than 
its own, while the other class cannot. 

Non-lirtln£c Injectors are intended for use where there 
is a head of water available; consequently, they must be 
TABLE 1 

RANGE OF INJECTORS 





Feedwater at to- 


Feedwater at 75° 


Feedwater at too" 


Vertical 

Lift 

Feet 


Starting 
Pressure 


Stopping 
Pressure 


Starting 
Pressure 


Stopping 
Pressure 


Starting 'stopping 
Pressure (Pressure 


Pounds 


Pounds 


Pounds 


Pounds 


Pounds 


Pounds 


per 
Square 
Inch 


Inch 


per 

?ncir 


per 

Square 
Inch 


per 
Square 
Inch 


per 
Square 
Inch 


2 


IS 


I5S 


IS 


MS 


20 


120 


4 


|8 


i";o 


18 


140 






6 


2o 


142 










8 


25 


135 


25 


125 






10 


30 


125 


30 


115 


35 


90 


12 


35 
40 


118 










'5 






50 


85 


45 


70 


i6 


■IS 


102 










|8 


SO 


90 










30 


55 


«5 


55 


75 






22 


55 


75 











placed below the water level. Non-lifting injectors resemble 
the lifting injector so much in their action that no description 
if them will be given, 

IIiHtlnK Injeetors are of two types — aulomalic and 
wilive injectors. Since positive injectors generally have 
sets of tubes, they are frequently called doubk-htbe 
Ktors. 




18 



MARINE-BOILER FEEDING 



§li 



Automatic IuJp<-tors are so called from the fact that they 
will automatically start again in case the jet of water is brokesV 
by jarrine or other means. They are simpler in construction 
than double-tube injectors, and they answer very well forjd 
moderate temperature of feed-water supply and not too g 
a range in steam variation. 

Positive, or <loublc-tube, Injectors are provided nitlll 
two sets of tubes, one set of which is used fur lifting tbe | 
water, while the other set forces the water delivered to it by J 




the first set into the boiler. A positive injector has a wider 
range than an automatic injector and will handle a hotter 
feed-water supply. It will also lift water to a greater 
tical height than the automatic injector. 

19. The construction of the Penbertliy automatl 
Injector is shown in Fig. G. Steam from the boiler enters 
the nipple ('and passes into the nozzle R and then into the 
conical combining tube S. In rushing past the annular open- 
ing between R and S. it creates a partial vacuum and caui 



ler 

tit* 




m iMARINE-BOILER FEEDING 19 

water to flow through P. filling the space surroumiing the 
lower end of i¥ and the upper end of 5". The nipple /*, which 
is shown at the right-hand side, is really situated in the rear. 
At first, the mingled steam and water, by reason of the water 
not having acquired sufficient momentum, do not flow to the 
boiler; but after the tube I', the space surrounding it, and 
the feed-delivery pipe attached to the nipple Z are filled, the 
mingled steam and water force the swing check-valve Q and 
pass through the overflow T. As soon as the jet of water 
passing tlirough the combining tube has acquired sufficient 
momentum, the boiler check-valve is forced open and the 
water commences to enter the boiler. In consequence, no 
more water will enter the space around the iower end of 5 
and the upper end of )', and there being no pressure in this 
space, the overflow valve Q will close. The overflow valve 
is kept closed by the atmospheric pressure on top of it, for, 
while the injector is working steadily, there will be a partial 
"aeuum in the space around 5 and V. 

To start the injector, all that is required is to turn on the 
Weam and water. If the steam supply is loo great, steam 
*in issue from the overflow; if the water supply is too great, 
''ater will issue. Should the jet of water be broken, J. e., 
'*il to enter the boiler, the overflow valve will lift and the 
"lingled water and steam will come out of the overflow until 
we jet has acquired sufficient momentum to enter the boiler 
Mtain, when the overflow valve will close for the reasons 
Sveo. 

' The automatically closing overflow valve is the distin- 
taishing feature of the automatic injector, and in some form 
IT other is found in all instruments of this class. 

0. Fig. 7 is a sectional view of the Buffalo aiitomattc 
itjeetor, which differs considerably in its construction from 
: Penberthy, but which operates in practically the same 
ler- This injector needs no valves on the steam and 
r pipes, the steam-admission valve being controlled by 
a placed on the valve stem d. With the valve and 
1 ID the position shown, the injector is working. Steam 



MARINE-BOILER FEEDING 



21 



fs through c into a chamber surrouading the steam 
e d and through openings in the rear end of t!ie nozzle 
the latter. In rushing into the suction jet e, it carries 
lir in / with it. creating a partial vacuum there and 
ng water to flow through g. This water, combined 
the sieam, enters the combining tube h and fills the 
r feedpipe, which is connected to the nipple /. At first, 
Set has not sufficient momentum to force the boiler 
[-valve, and consequently the water flows through the 
lar opening between e and h and. after lifting the over- 
valve k, out of the overflow /. The speed of the jet 
tally increases, and as soon as its momentum is suflS- 
, the jet forces the boiler check-valve and enters the 
r. The overflow valve k then closes automatically and 
ijector is working. 

the jet should break from any cause, the water will lift 
iverflow valve and come out of the overflow, but as 

as the momentum is sufficient again, the water will 

the boiler once more and the overflow valve will close 

|)ttticalty. 

'atop the injector, the handle a is turned so as to .screw 

iBlve stem inwards. The steam nozzle rf, which is 

ble longitudinally, remaining at rest, the valve at the 

f b first closes the central opening in the nozzle; then, as 

K>tion of the handle continues, the nozzle and valve stem 

forwards together until the conical seat on the nozzle 
□ the steam-jet guide m, when steam is completely shut 
;ni] the steam nozzle. To start the injector, the valve 

is slowly turned by means of the handle a, which first 
( the central opening of the nozzle, and then, as the 
\ moves backwards with the valve stem, the other open- 
■A the nozzle also admit steam and the injector starts. 

» Fig. 8 shows the Hancock Inspirator, which is 
{ the earliest types of a double-tube injector. The term 
jator is merely a trade name. Steam from the boiler 
i through the pipe a and flows through the steam 
% n into the combining nozzle o, thereby causing water 




I 



MARINE-BOILER FEEDING 



Sill 



to flow up the pipe b into the lifting side of the inslnimenl. 
The water then passes in the direction of the arrows to lie 
forcing side of the instrument, entering at the top of li 
forcing tube s, where it is met by a jet of steam flowinn 
through the forcing steam noszle r, and is further heated anil 
given an increased 
velocity. It then 
passes through ibe 
pipe c to the boilei. 
In order to siait 
the instrument, Ihe 
valve I' musl be 
closed and the over- 
flow valves (. :. 
opened. Nest, the 
water valve d and 
then the steam valve 
c are opened, when 
the steam will rush 
through M.o, /, anda* 
I and out of the over- 
w until it creates 
a suflicient vacuum 
on the left, or lift- 
ing, side to cause 
the water to tjow up, 
which will then dis- 
charge out of tlM 
overflow. As s< 
as the water appe! 
the valve / must 
^'^^ * closed and the val' 

II opened. Immediately thereafter the overflow valve jv is 
be closed, when the inspirator will be working, To stop the 
injector, the valves f and v must be closed and / and n> opened. 




dis- 
ttie ■ 

i 



23. The Kortlng; nntversnl doiible-ttilie Injeirtor is 

shown in elevation in Fig. i) («) and in section in Fig. 9 (b). 




24 MARINE-BOILER FEEDING §14 

This injector, in common with the majority of double-tube 
injectors, contains a mechanically operated overflow valve, 
which is closed by the act of startin^^ the injector to feed 
the boiler. In this injector, the lower nozzles constitute the 
lifting: apparatus that delivers the water to the upper noz- 
zles, where it is given sufficient velocity to enter the boiler. 
Steam enters at a and the water enters at b\ the overflow d 
is closed by the valves on the stem r, and the water passes 
to the boiler through e. The steam nozzles /and^ are closed 
by valves connected by means of the yoke bar h to the start- 
ing shaft 2. 

The operation of the injector is as follows: The starting 
handle k being in the position shown, the overflow valves 
are wide open, but the nozzles / and g are closed by their 
respective valves. The steam- and water-admission valves 
are now open and the handle k is pulled over gently toward 
the position shown in dotted lines. This causes the starting 
shaft i and the yoke bar h to move in the same direction as 
the handle, and consequently the valves closing the nozzles 
/ and ^ are opened. At the same time, the overflow valves 
are closed slightly, the starting shaft being comiected to the 
overflow-valve stem by links /, bell-cranks iw, and links n. 
The bell-cranks have their fulcrum at o. The steam rushing 
through the lower nozzle g creates a partial vacuum in the 
water-supply pipe and causes the water to flow up, which is 
then delivered into the chamber p and passes out of the 
overflow. Some of the water in p will pass to the nozzle / 
and will deliver into the chamber g and thence into the over- 
flow. In a very short time, the water will be flowing freely 
from the overflow, and the handle is then pulled over as far 
as it will go, this operation opening the steam-nozzle valves 
to their full extent and at the same time closing the overflow 
openings of the chambers p and g. The injector is now 
working, the check-valve r being forced open. 

Since the overflow outlet is positively closed, the effects 
of too much steam or water cannot manifest themselves by 
either fluid coming from the overflow. The effect of too 
much water will be the stopping of the injector, which can 



§14 



MARINE-BOILER FEEDING 



25 



be told by the absence of vibration in the feedpipe and the 
comparatively low temperature of the injector. Too much 
steam manifests itself by the heating of the injector and 
failure to work; the remedy is either to reduce the steam sup- 
ply or to increase the water supply, as the healing shows that 
the steam is not being condensed. These statements apply 
to all injectors having positively closed overflows, i, e., over- 
flow valves so constructed that they cannot lift automatically 
when the injector fai!s to force the water into the boiler. 

23. The Moiiltor lirtlntE Injector, shown in Pig. 10, 
occupies an intermediate position between the single-tabe 




3 double-tube injectors, for while it has two sots of tubes, 
the one set is used in starting the injector, but is thrown out 
of action as soon as the injector is working. Steam enters 
the injector at F; the water enters at P and passes to the 
boiler through the nipple A'; the overflow is at O, 

The operation is as follows: The water-admission valve B 
is first opened by turning the hand wheel IV; the primer 
valve /f is then opened by the handle J, thus permit- 
ting steam to flow through the passage £ and a connec- 
tion, not shown in the figure, to the nozzle u. From u, 
the steam rushes into tlie overflow nozzle O, this nozzle, 



26 MARINE-BOILER FEEDING §14 

in conjunction with the nozzle », forming the lifting^ part 
of a double-tube injector. A passage connects the chamber 
surrounding: u with the space above the overflow valve L 
The jet of steam rushing from u through O carries with it 
some of the air in the chamber to which O is connected, thus 
forming a partial vacuum in the space above the overflow 
valve, which opens and thus allows the air in Z7, C, G, H, K, 
T, and P to be exhausted. The pressure of the atmosphere 
now forces the water into the injector, and it finally appears 
at the overflow. As soon as this happens, the valve R is 
closed, which throws the priming part of the injector out of 
action. The steam valve A is now opened by turning the 
wheel Sy which admits steam to the nozzles of the injector 
proper. At first, the water will come out of the overflow, 
but as soon as the velocity has become high enough, it will 
enter the boiler, the overflow valve L closing automatically. 

24, Size of Injectors. — The capacity of an injector 
cannot be calculated by any simple rules; furthermore, there 
is no standard method followed by all injector makers of 
designating the capacity of their instruments by numbers or 
other designations. Hence, an injector must be selected 
from the lists of capacities published by the makers, select- 
ing one. having a delivery per hour at least one-half greater 
than the evaporation per hour of the boiler to which it is 
applied, in order to have some reserve capacity. 

25. Installation. — An injector must always be placed 
in the position recommended by the maker, for the reason 
that some injectors will work well only in one position. 
There must always be a stop-valve in the steam-supply pipe 
to the injector, which should, for convenience, be placed as 
close to the injector as is possible. While lifting injectors, 
when working as such, scarcely need a stop- valve in the 
suction pipe, it is advisable to supply it. When the water 
flows to the injector under pressure, a stop- valve in the 
water-supply pipe is a necessity. A stop-valve and check- 
valve must be placed in the feed-delivery pipe, with the 
stop-valve next to the boiler. The check-valve should never 



)14 MARINE-BOILER FEEDING 27 

le omitted, even though the injector itself is supplied with 
>ne. No valve should ever be placed in the overflow pipe, 
lor should the overflow be connected directly to the over- 
flow pipe, but a funnel should be placed on the latter so that 
ibe water can be seen. This direction does not apply to the 
inspirator or to any other injector that has a hand-operated, 
separate overflow valve. In the inspirator, the overflow 
pipe is connected directly to the overflow, but the end of the 
pipe must be open to the air. In general, where the injector 
lifts water, it is not advisable to have a fool-valve in the 
saclioD pipe, as it is desirable that the injector and pipe 
drain themselves when not in use. It is a good idea to 
place a strainer on the end of the suction pipe. 

The steam for the injector must be taken from the highest 
part of the boiler, as it is essential to the successful worldng 
of the injector that it be supplied with dry steam. Under no 
consideration should the steam be taken from another steam 
pipe; the injector should always have its own independent 
steam-supply pipe. The suction pipe should be as straight 
as possible and must be absolutely air-tight. A very impor- 
tant consideration in connecting up an injector is to have the 
pipes cleaned by blowing them out with steam before making 
ihe connection, since quite a small bit of dirt getting into 
the injector will interfere seriously with its working. It is 
recommended to always so locate the injector that the steam 
pipe, suction pipe, and feed-delivery pipe will be as straight 
and as short as possible. With boilers that are forced very 
much and hence generate wet steam, it is advisable to use a 
so-called supplementary dome, which is simply a vertical piece 
of, say. 2-inch pipe about 12 to IS inches long; the injector 
steam pipe is then connected to the top of this supplemen- 
tary dome. 

26. Tronbles and Remedies. — In discussing the diffi- 
culties experienced with injectors, the suction pipe, strainer, 
feed-delivery pipe, and check-valve are considered as parts of 
the injector, since a disorder in any of these affects the work 
of the injector itself. In searching for the cause of a trouble. 



28 MARINE-BOILER FEEDING §14 

therefore, the suction and delivery pipes should be carefully 
inspected, as well as the injector. 

27. The causes that prevent an injector raisinsT water are: 

1. Suction Pipe Stopped Up. — This is due, generally, to a 
cloggfed strainer or to the pipe itself beinsf stopped up at 
some point. This prevents water from coming: through and 
is probably the most frequent cause of an injector not priming. 
In case the suction pipe is clogged, blow steam back through 
the pipe to force out the obstruction. 

2. Leaks in Suction Pipe. — When this is the case, air 
enters and prevents the injector forming the vacuum required 
to raise the water. To test the suction pipe for air leaks, 
plug the end and turn the full steam pressure on the pipe. 
The presence of leaks will be revealed by the steam issuing 
therefrom. To get steam into the suction pipe, the overflow 
valve must be held to its seat in some convenient way, or the 
overflow must be closed tight in some manner. It is advis- 
able to have the suction pipe full of water before steam is 
turned on, since the presence of small leaks will be revealed 
better by water than by steam. After testing, do not forget 
to clear the overflow and the end of the suction pipe. 

3. Water in the Suction Pipe Too Hot. — In case the feed- 
water supply is taken from a tank and the supply is cool 
under normal conditions, a leaky steam valve or leaky 
boiler check-valve and leaky injector check-valve may be 
the cause of hot water or steam entering the source of sup- 
ply and heating the water so hot that the injector refuses to 
handle it. 

The reason that hot water in the suction pipe affects the 
operation of the injector is as follows: The temperature at 
which water boils depends on the pressure to which it is 
subjected. It has been determined, by experiment, that 
water will boil at about 380° F. under a gauge pressure of 
180 pounds; at 212° F. when subjected to an atmospheric 
pressure of about 14.7 pounds per square inch; and at about 
190° F. when in 10 inches of vacuum. This shows that 
decreasing the pressure on the water lowers its boiling point. 



Sl4 MARINE-BOILER FEEDING 29 

Now, when the lifting jet of an injector is turned on, a 
vacuum is formed in the suction pipe; and if the water there 
is at a temperature of 160° to 175° F,, it gives off vapor, 
which fills the suction pipe and destroys the vacuum. 

In case the water is too hot, cool it in any convenient 
manner and at the first opportunity trace out the cause and 
remove it. When the water in the suction pipe is very hot, 
but the water in the source of supply is cool, hold the over- 
flow valve to its seat in any convenient manner or plug the 
overflow and open the steam valve. The steam pressure 
will then force the hot water out of the suction pipe. Open 
the overflow valve or overflow as soon as this has been done; 
the cool water entering the suction pipe should now be raised 
easily. Hot water in the suction pipe only is most likely 
due to a choked overflow. 

4. Obstruction in Tubes. — There may be an obstruction in 
the lifting or combining tubes, or the spills (or openings) 
in the tubes through which the steam and water escape to 
the overflow may be clogged up. In either case, the free 
passage of the steam to the overflow will be interfered with, 
and, consequently, a steam pressure instead of a vacuum will 
be formed in the suction pipe, the extent of the pressure 
depending on the amount of obstruction. 

28. In some cases an injector will lift water, but will not 
force it into the boiler; or it may force part of it into the 
boiler and the rest out of the overflow. When it fails to 
force, the trouble may be due to one or the other of the fol- 
lowing causes; 

1. Choked Suctiffn Pipe or Strainer. — If the suction pipd 
or the strainer is partially choked, the injector, in either 
case, will be prevented from lifting sufScient water to con- 
dense all the steam issuing from the steam valve. The 
uncondensed steam, therefore, will gradually decrease the 
vacuum in [he combining tube until it is reduced so much 
that the injector will break. It is to be remembered that 
when the injector is operating, it is tlie vacuum in the com- 
bining tube that causes the water to be raised. The remedy. 



L 



30 MARINE-BOILEK FEEDING §14 

in case the supply valve is partially closed, is obvious. In 
the case of choked suction pipe, blow out the obstruction. 

2. Siulion Pipe Leaking. — The leak may not be sufficient 
to entirely prevent the injector lifting water, but the quantity 
lifted may be insufficient to condense all the steam, which, 
therefore, destroys the vacuum in the combining tube. 
A slight leak may exist that will simply cut down the 
capacity of the injector. In such a case, an automatic 
injector will work noisily, on account of the overflow valve 
seating and unseating itself as the pressure in the combinine 
tube varies, due to the leak. 

3. Boiler Check-l'alve Stuck Shut. — If completely closed, 
the injector may or may not continue to raise water and 
force it out of the overflow: it depends on the design of th» 
injector. If the boiler check is partly open, the injector wiB 
force some of the water into the boiler and the remainder' 
out of the overflow. In case the check-valve cannot 
opened wide, water may be saved by throttling both steam 
and water until the overflow diminishes, or, if possiblet 
ceases. The steam should be throttled at the valve in the 
boiler steam connection, however, and not at the steam 
valve of the injector, as throttling tends to superheat thtt> 
steam, and an injector will not work as satisfactorily witll 
superheated steam as with saturated steam. By throttlia* 
the steam at the boiler, the excess of heat due to this 
throtthng will be lost before the steam reaches the injector;i 

If a check-valve sticks, it can sometimes be made to woil 
again by lapping lightly on the cap or on the bottom of t 
valve case. 

4. Obslnulion in Delivery Tube. — Any obstruction in t 
delivery tube, such as cotton waste, scale, or coal, will c 
a heavy waste of water from the overflow. To remedy tbia^ 
the tube will probably have to be removed and cleaned. 

5. Leaky Overflow I'alve. — This not only diminishes tbq 
capacity of the injector, but allows air to be drawn into 
the boiler; and if the leak is sufficiently great, it will destroy 
the vacuum in the combining lube and prevent the injecto] 
operating. A leaky overflow valve is indicated by the boilei 




■14 



MARINE-BOILER FEEDING 



31 



I 



leck chatterine on its seat. To remedy this defect, grind 
le valve on its seat until it forms a tight joint. 

Injeetor Choked With LiMe.^H is essential to the 
)roper working of an injector that the interior of the tubes 
should he perfectly smooth and of the proper bore. When 
'the injector handles water containing scale-forming impuri- 
ties, such as are found in river and lake waters, which are 
chiefly sulphate of lime and carbonate of lime, the tubes, in 
course of time, become covered with a deposit of lime and 
the capacity of the injector decreases until, finally, it refuses 
to work at all. If the water used is very bad, it becomes 
necessary to frequently cleanse the tubes of the accumulated 
lime. This may be accomplished by putting the parts in an 
acid bath, allowing the acid to remove the scale. The bath 
should consist of one part of muriatic acid to ten parts of 
water. The tubes should be removed from it as soon as the 
gas bubbles cease to be given off. The acid combines with 
the lime and forms a gas, and as long as there is lime to 
combine with, it will not attack the copper in the tubes. 
After the lime has all combined, however, the acid will 
attack the tubes, with the result that the inner surface will 
become pitted and rough, which will affect the working of 
the injector. 

29< AdvantaBes and DlsadvantHKes. — The advan- 
tages of the injector as a boiler-feeding apparatus are its 
cheapness as compared with a pump of equal capacity; it 
occupies but little space; the repair bills are low, owing to 
the absence of moving parts; no exhaust piping is required, 
as with a steam pump; it delivers hot water to the boiler. 
The disadvantages of the Injector are that it will not start 
with a steam pressure less than that for which it is designed, 
and that it will stand but little abuse, being poorly adapted 
(or handling water containing grit or other matter liable to 
cut the nozzles- 
Such economy as is derived from the use of an injector is 
not chargeable to its economy in the use of steam, for it 
uses as much steam as a fairly good steam pump, but rather 



32 MARINE-BOILER FEEDING §14 

to the fact of the use of an injector insuring the delivery of 
hot feedwater to the boiler. The introduction of hot feed- 
water has a marked effect on the repair bills and tends to 
increase the life of a boiler by diminishing^ the stresses 
incidental to expansion and contraction. 



FEEDWATER PURIFICATION AND 

HEATING 



FEEDWATER PURIFICATION 



IMPURITIES 

30. The solid matter contained in sea-water consists 
chiefly of chloride of sodium (common salt), sulphate of 
lime (plaster of Paris), carbonate of lime (limestone or 
marble), chloride of magnesium, and traces of various other 
substances. River and lake waters, if fresh, as is usually the 
case, are liable to contain carbonate of lime, sulphate of lime, 
carbonate of magnesia, sulphate of magnesia, organic matter, 
earthy matter, and occasionally acids. Fresh water from a 
surface condenser or the water drawn from a jet condenser 
usually contains the oil or grease used for lubricating the 
engine cylinders, which is carried into the condenser by the 
exhaust steam. 

Carbonate of lime will not dissolve in pure water, but will 
dissolve in water that contains carbonic-acid gas. It 
becomes insoluble and is precipitated in the solid form when 
the water is heated to about 212°, the carbonic-acid gas 
being- driven off by the heat. 

Sulphate of lime dissolves readily in cold water, but not in 
hot water. It precipitates in the solid form when the water 
is heated to about 290°, corresponding to a gauge pressure 
of 45 pounds. 

Chloride of sodium will not be precipitated by the action of 
heat unless the water contains large quantities of it. Since it 



§ 14 MARINE-BOILER FEEDING 

is generally present in but very small quantities in fresh water. 
it will lake a very long time before it causes trouble in the 
l>oiler; and if the boiler is blown out at the usual intervals, 
there will be little danger of the water becoming saturated 
with it. Consequently, it is one of the least troublesome 
Kcale-forming substances contained in fresh water. In sea- 
waler. however, it is present in such a large proportion 
thai the use of sea-water for boiler feeding, except in emer- 
gencies, is precluded. 
1 Chloride of magnesium is one of the worst impurities in 

■ waier intended for boilers, for while not dangerous as long 
\ as the water is cold, it renders the water corrosive when 
^b heated, and dangerously corrosive when it is present in large 
^H [JUantities; in such a case the metal of the boiler is rapidly 
'ff corroded. 

"} Carbonate of magnesia and sulphate of magnesia are not very 

''■oublesome constituents of feedwater. 

Organic mailer by itself may or may not cause the water 
''* become corrosive, but will often cause foaming; when it 
'■* present in small quantities in water containing carbonate 
"^ sulphate of lime, or both, it usually serves to keep the 
deposits from becoming hard. 

-Earthy mailer, like organic matter, is not dissolved in the 

'^"^ter, but is in mechanical suspension. It is very objeclion- 

''■*ile, especially in the form of clay; and when other scale- 

'■^rming substances are present, a hard scale resembling 

Cirtland cement is likely to result. 

Acids, such as sulphuric acid, nitric acid, tannic acid, and 

**ietic acid, are sometimes present in feedwater taken from 

*"ivers. The sulphuric acid is the most dangerous of these 

**tids. attacking the metal of which the boiler is composed 

^t]d corroding it very rapidly. The other acids, while, not 

^^j violent in their action as the sulphuric acid, are also dan- 

t£erous, and water containing them should be neutralized 

^vhen it must be used. 

Oil, or grease, in the feedwater. when carried into the boiler, 

is liable to do much harm; it seems to combine mechanically 

l^th certain impurities, forming a loose, spongy mass, or 




34 MARINE-BOILER FEEDING §14 

deposits by itself, on the plates. In either case, it greatly 
hinders the transfer of heat from the plate to the water, and 
hence has been in numerous instances the cause of over- 
heated plates and collapsed furnace flues. Too great care 
cannot be exercised to keep oil or grease out of boilers. 



METHODS OF PURIFICATION 

31. The impurities contained in the feedwater of marine 
boilers may be removed or rendered harmless in several 
ways: 

1. By Filtration. — This method will remove floating 
impurities, such as oil or grease mixed with the feedwater of 
a condensing engine. It will also quite effectually remove 
all matter in mechanical suspension, such as earthy matter. 
Filtration pure and simple will not remove matter in solution. 

2. By Gravity Separation, — This method relies on the 
difference in specific gravity between oil or grease and water 
for a separation. It will not separate matter in solution 
from the feedwater. 

3. By Heat, — This method will precipitate carbonate of 
lime, sulphate of lime, and chloride of sodium, the three 
scale-forming substances held in solution. The carbonate 
of lime and the sulphate of lime precipitate as soon as the 
water is heated to about 290° F. Hence, if the feedwater 
be heated in a separate vessel to that temperature, the 
impurities will deposit there instead of in the boiler. Chlo- 
ride of sodium (salt) will not be precipitated by heating the 
water, unless the water is saturated with it. Chloride of 
magnesium cannot be removed from the water by heating:. 

4. By Chemical Means, — This method will render harm- 
less the choloride of magnesium contained in solution in sea- 
water. When water containing chloride of magnesium in a 
proportion of more than about 200 grains to the gallon is 
heated to a high temperature, the water will, under certain 
conditions, particularly if corrosion has already begun in the 
boiler, become acid, and hence highly corrosive. Chemical 
means will also render harmless fatty acids due to vegetable 



Or animal oils, or adulterated mineral oils that have beeo 
decomposed by heat. In marine work, it is extremely rare 
to attempt to purify fresh feedwater by chemical means. 



32. 



PTTRIFriNG BY FILTRATION 

A cheap, easily installed, and quite efficient way of 



removing oil or grease and other floating impurities from feed- 
water is to pass the water through an open wooden box filled 
with hay. The suction pipe of the feed-pump is connected 
to the bottom of this box, the end of the suction pipe being 
covered with a perforated plate called a strahur, to prevent 
any hay from entering the pump. The oil and grease con- 
tained in the water will deposit on the hay, which is renewed 
occasionaliy. The box is usually divided by wooden parti- 
tions into several compartments, the passage of the water 
being as follows: It enters at the bottom of one compart- 
ment, flows upwards through the hay therein, and then enters 
the top of the next compartment through a hole near the top. 
or over the top. of the partition. It then flows downwards 
into the second compartment and enters the third at the bottom, 
and so on, leaving finally at the bottom. Sometimes burlap 
(ordinary coarse bagging) is placed in the first compartment 
for the water to percolate through. In doing so, it deposits 
most of the impurities on the burlap, which must be cleaned 
and renewed frequently. 

33. A Rose feedwater Tllter, designed to remove oil 
and grease from the feedwater of a surface condensing 
engine, is shown in Fig. 11. The water coming from the 
feed-pump enters at a and passes into the filtering cham- 
ber b. It cannot leave this filtering chamber without passing 
through the filter c. which consists of light circular bronze 
sections of open latticework held together by long bolts and 
covered by toweling. This material is technically known as 
"linen terry," and popularly as "Turkish toweling." The 
toweling is made up in the shape of a bag somewhat larger 
Ihan the spider; it is drawn over the filter and down between 
each of the sections by a string wound around it, The 



1 



3C MARINE-BOILER FEEDING gl* 

feedwater slowly passes through the filtering material into 
the interior of the filter; it then goes through the left-hand 
opening of the filtering chamber and through the valve 
into the feedpipe again, and thence to the boiler. The foreipi 
matter fiiiered from the water accumulates on the filterinE, 
material, and in course of time oflers considerable resistanct 
to the passage of the water. This resistance is shown bytt 
difference in reading of two pressure gauges. One of the! 
is connected to the chamber b and the other to the left-haaft< 
passage. When this difference amounts to 3 pounds, the 
filter is in need of dean-" 
ing. To clean the filter, 
close valves d,e and open 
the drain at /. Now open 
valve (■ a little. A current 
of water will then flow 
around the filter and out 
of the drain, washing the 
outside of the toweJioE. 
Next, close valve e 
open valve d. Then, 
drain being open , a currt 
of water will flow thron| 
the filler in a direction 
posite to that in which the' 
water passes through it 
whenfiltering. Thewater, 
flowing in a reverse direc- 
tion, tends to loosen the foreign matter adhering to the outside 
of the filter. To start the filter again, open valves d and t and 
close the drain. Should it be found that the washing of the 
filter as explained above is insufficient to clean it. new towel- 
ing must be inserted. To do this, close valves d and e and 
open the drain. The water from the feed-pump will now pass 
directly to the boiler, the screwing down of the valve e 
close the opening to the filter chamber opening a by-pass, 
shown. The covers can now be removed and new towelii 
inserted. 





1 14 



MARINE-BOILER FEEDING 



37 1 



34. An Edmistoii feedwater filter is shown in Fig. 12. 
lit consists of a vessel a divided into two chambers by per- 
Kibraied plates b, b covered with coarsely woven cioth. The 
leedwater is admitted to the chamber «', and cannot reach 
tte chamber a" except by passing through the filtering cloth. 
■ The oil and other floating impurities rise into the scum 
I diaraber c. whence they are removed, periodically, by opening 
I the hlow-off d. The heavier impurities settle into the pocket e. 




which is provided with a blow-off cock. A pressure gauge is 
attached to the chamber; when this gauge indicates more 
than 5 pounds pressure in the chamber in excess of that in 
the boiler, it shows that the strainer is clogged and must 
be cleaned. This is done by closing the valves l,g and 
opening the by-pass valve h, thus cutting the filter out of the 
feedpipe. The soda cup / is now filled with soda, and steam 
turned on, thus boiling out the filter. The soda dissolves 
the crease and the matter in the filler can be blown out. 




MARINE-BOILER FEEDING 



!ul 



If boiling out fails lo clear the filter, the filtering cloths 
must be removed and new ones substituted. To do \hh, 
first cut the filter out of the feedpipe, letting the feedwsier 
go through the by-pass. Then loosen the setscrew k. Hi 
open the hinged door /. The plates or diaphragms c; 
then be readily removed. 

35. The feedwater filter that is illustrated in Figs. 13, 
14, and 15 is known to the trade as the Reflex feedwai«r 
filter and is manufactured by the Blackburn-Smith Co., oi 




New York City. This filter consists mainly of the cast-iron 
vessel or chest a. Fig. 13, having a removable cover 6, and 
containing a number of what are termed cartridges e.c.c. 
One of these cartridges is illustrated in detail in Fig. li- 
lt consists of two tubes, one inside of (he other; Fig. H {a) 
represents the Inner tube and Fig. 14 (i^) the outer lube. 
TheiO tubes are cylindrical vessels of sheet metal, closed at 
Ihoir tops and perforated with large rectangular boles; io j 
fact, they are merely light frames for the support of I 







MARINE-BOILER FEEDING 



fiilering material. The lower end of the inner tube is perma- 
nenily expanded in the plate d. Figs. 13 and 14 (u). which 
separates the filter chest from the pure-water chamber e. 




: outer tube, Fie. H ib), is removable; its upper end 

I by the flanged stopper f, which is riveted in. A 

»ped hole g is provided in the center of the stopper to 

xvve the threaded part of the handle and cloth cramp h. 



40 MARINE-BOILER FEEDING §14 

Fig:. 14 (r). The filtering: material consists of a bag: made 
of linen or cotton special Turkish toweling, left open at the 
top end. The leng:th of the bag: is a little more than the 
combined lengths of the inner and outer tubes, and it is of 
the proper size to fit snugly over the outside of the outer 
tube. The bag is drawn over the outer tube until it extends 
i inch above the top of the tube. It is then turned in as 
shown at /, Fig. 14 ((/), and the handle h is screwed in 
place, thereby cramping the cloth effectually at that end. 
The loose end of the bag, which is closed and extends 
beyond the lower end of the outer tube, is shoved inside, as 
shown at y. Fig. 14 ((/), by any convenient rod or stick. 
The outer tube is then placed over the inner tube telescop- 
ically, as shown in Fig. 14 (^) , which completes the cartridge. 

36. The filtration of the water is effected as follows: 
The water from the feed-pump enters the filtering chamber k, 
Fig. 13» through the pipe / and surrounds the cartridges c,c,c. 
The water is imder sufficient pressure to force it through the 
outer , covering of filtering cloth shown at i«. Fig. 14 [e]. 
It now enters the annular space n between the inner and 
vuiter tubes of the cartridge, whence it passes through 
another thickness of the filtering cloth into the inside of the 
inu^r tube and out through the lower end of it into the pure* 
Welter chamber r» Fig. 13, and thence through the pipe o and 
v»lK*»iu^ P to the boilers. The lower parts of the filtering 
clv»lhH arv cut away in Fig. 13 in order to partly show the 
^\ui!itvuctk>u c>f the cartridges. The number of cartridges 
Vi4nvJi itivm I to 19, according to the capacity of the filter, and 
i« HiKii^ Ht^t oi bags, which should always be kept clean, is 
H^vi^^^^t with each filter. The foul bags can be removed 
(UkI ihpu wA:^eU out in boiling water and soda. Thus a 
siWs\\\ xvt v>f bags is always ready for insertion at any 
uiv'iiiv^ut. 'l^« advantages claimed for these cartridges are 
H4uii4\cUy. «^str of removal, large filtering surface in a small 
HiKKV* ^i^ilwtivcuess due to double filtration, saving of 
\\v'i)i£ht. .ukI th^ rapidity with which the filtering bags can be 



§14 



MARINE-BOILER FEEDING 



41 



37. The valves and other details of the Reflex filter are 
illustrated in Fig. 15. The inlet, outlet, and by-pass valves 
are operated by a single stem a. While the filter is in use, 
the valve stem is screwed up as far as it will go. This 
opens the inlet valve b and the outlet valve c simultaneously. 



^ 




At the same time, the upper edge d of the outlet valve closes 
Ihe by-pass passage. To clean the filter, the valve stem is 
screwed down hard, thereby closing the inlet and outlet 
valves and opening the by-pass valve. This allows the 
boilers to steadily receive their normal amount of feedwater. 
Aside from the fact that with a single stem weight is saved 




ti 



MARINE-BOILER FEEDING 



SI 



and simplicity is gained, the most important feature of ibis 
arrangement is that it is impossible to fracture the feed- 
pump or feedpipe by closing the inlet valve before opening 
the by-pass valve, which might be the case if three distinct 
valves were used. 

38. Filters of over 150-h or se power capacity are fitted 
with two pressure gauges, one on the inlet side e and one on 
the outlet side / of the chest. The difference of pressure 
shown by these two gauges indicates the actual pressure on 
the filtering cloths. To obtain the best results from the 
filter, the pressure difference should be kept under 30 pounds 
per square inch; if the difference of the gauges indicates moiC 
than this, the filter is in need of cleaning. The drain and 
sludge valve j is placed at the lowest point of the filter 
chest, through which the oil and dirt can be blown out. The 
steam-cleaning valve A, which is attached to the pure-water 
chamber, is provided to temporarily clean the filter without j 
removing the cartridges. This is effected by by-passing tbea 
feedwater and then opening the steam-cleaning and draiq^ 
valves. The steam flows in the reverse direction to the fl 
of water and blows a large portion of the grease and sec 
ment through the drain valve. 

39. When it is desirable to provide for constant filtration 
in preference to by-passing the greasy water into the boilers 
while the filter is being cleaned, the duplex filter meets the 
requirement. This consists simply of a pair of duplicate 
filters connected up by means of the necessary piping and 
ordinary cross and angle stop-valves, so arranged thai either 
filter can be entirely shut oil for cleaning, while the other, fof.J 
the time being, does the work of both. These fillers t 
tested to 300 pounds hydrostatic pressure per square inch. 



PURIFTING BT GRAVITT S&PARATION 

40. A Wass grea»e extractor, as made by Crai 
& Co., is illustrated in Fig. 16. It consists of a closed caa 
iron vessel placed between the feed-pump and the boiln 
The feedwater enters at A and passes over and under tl 



§14 



MARINE-BOILER FEEDING 



43 



slteroate partitions B, B. leaving the extractor at C. The 
E''ease. on account of its lower specific gravity, rises to the 
surface in each of the compartments formed by the parti- 
•ions, and since the level of the water is above the top of the 
"igher partilions, the tendency of the grease on the surface 
IS to flow toward the outlet end of the apparatus, where the 
i outlet pipe D is located. The pressure exerted by 
' COD fined between the surface of the liquid and the 




■bver forces out the grease on opening the valve in the 
TJipe D. This is done at intervals varying with the amount 
of grease carried in. A plate E at the outlet end prevents 
the mixture of the outflowing grease and feedwater. A float 
valve /"allows the air lo escape from the extractor when it 
is first filled. The valve is closed by means of the float, on 
the water reaching a certain height, and the air remaining 
■ compressed. By means of the drain-cock G, the extractor 
iRy be emptied for the purpose of examination or repair, 



44 MARINE-BOILER FEEDING §14 

the different compartments communicating with each othet 
by a small hole g at the bottom of each partition. This 
style of extractor is extensively used in sea-goiog steam 
vessels having surface condensers. The pipe connections 
are made so that the extractor may be cut out, if desired, 
and the feedwater passed directly to the boiler. 



PURIFYING BT HIAT 

4 1 . Heat causes the precipitation of several scale-forming 
substances. If the water be heated in a separate vessel, and 
if a large, quiet chamber be provided for the reception of the 
heated water, a considerable quantity of matter in mechanical 
suspension will settle at the bottom of the chamber, in addi- 
tion to the matter precipitated by becoming insoluble. Puri- 
fication by heat is especially adapted to river and lake waters. 

42. A Buffulo feedwater heater and purifier, which 
can be applied to any boiler, is shown in Fig. 17, The feed- 
pumps deliver their water through the pipe e and check-valve f 
into the lop of the heater. The entering feedwater strikes 
against the top head; the solid stream of water is thus broken 
up. It now flows in a zigzag course over the edges of ihe 
spray disks g, g. being thus spread out into large, thin sheets, 
which readily absorb the heat of the live steam with which 
the spray chamber is filled and which is admitted through d. 
The highly heated water falls to the bottom, and passing 
around Ihe division plate / and deflector plate m, rises in the 
settling chamber a. Thence it passes into the feedpipe <-. 
The feedwater being heated to almost the same temperature 
as that in the boiler, the scale-forming substances precipitate 
and collect at the bottom of the settling chamber, whence 
they can be removed by opening the blow-oflE valve ;. 
Nearly all foreign matter in mechanical suspension also 
collects in this settling chamber, and is removed with the 
scale-forming substances. The impurities that have a smaller 
specific gravity than water rise to the top of the settling 
chamber and float on the water. By extending the equali- 
zing pipe (', which forms the feed-outlet from the heater, 



1 14 



MARINE-BOILER FEEDING 



Iwlow the surface of the water, the floating impurities are 
prevented from entering the feed-outlet. The heater should 
be placed above the boilers; the water will then flow into the 
boilers by gravity. To prevent the water in the boilers from 
hacking up into the heater when the blow-off of the heater 
is opened, an automatic shut-ofi valve, which is simply a 




wcial form of check-valve, is supplied. This valve is 

"placed in the feedpipe between the heater and the boilers. 

Under ordinary working conditions, it is sufficient to blow 

out the heater once every 6 hours. Siphonage through < is 

^K |tteveated by the equalizing tube i, which is open on top, and I 

Hfasures equal pressures inside of c and the heater at all times. I 



MARINE-BOILER FEEDING |14 ] 



PCRIPVINd BT CUKMICAL MEAXS 

43. When sea-water is mixed with the feedwater of sur- 
face condensing engines, the corrosive effect of the chleiride 
of magnesium thus admitted can be neutralized by using the 
ordinary unslaked lime of commerce. The lime converti 
the chloride of magnesium into magnesia and chloride oi 
calcium, neither of which is corrosive. 

When starting with new boilers, it is recommended that 
10 pounds of lime be placed in the boilers for every thousand 
indicated horsepower on the first day. For the next 6 days' 
continuous steaming, use about .i pounds of lime for everj 
thousand indicated horsepower. When the boilers are exam- 
ined at the expiration of this lime, they should have a thin 
coating of lime scale all over the inside. If this is not the 
case, the use of lime should be continued. Mix the finely pow- 
dered lime in the proportion of 1 pound of lime to a gall< 
water, thus making the so-called "milk of lime." Introduce it 
into the hotwell in any convenient manner in small quantities. 

It is a good plan to use lime continuously to prevent cor« 
rosion. About 1 pound of lime per day for each thousand 
horsepower is usually sufficient. 

44. Feedwater taken from rivers and lakes often contains; 
much carbonate of lime or sulphate of lime, or both. Water 
containing carbonate of lime may be treated with caustic soda, 
which precipitates the carbonate of lime and leaves carbonate 
of soda, which is harmless. For every 100 grains of carbott- 
ate of lime 80 grains of caustic soda should be added. 

45. Sal ammoniac is sometimes added to water contain- 
ing carbonate of lime and will cause the latter to precipitate. 
Its use is not advisable, however, on account of the danger 
of the formation of hydrochloric acid, which will attack tho 
boiler. The formation of this acid is due to an excessive 
quantity of sal ammoniac having been used, 

46. While slaked lime will precipitate carbonate ot 
liinc, it will have no effect on sulphate of lime, and wate^ 
containing the latter, either alone or in conjunction wil 




1 14 MARINE-BOILER FEEDING 47 

carbonate of lime, must be treated with other chemicals. The 
TOOsl available ones for water containing both are carbonate 
of soda and caustic soda. These are often fed into the 

I boiler and will precipitate the carbonate of lime and sulphate 
of lime there, requiring the sediment to be blown out or 
Otherwise removed periodically. 
47. The action of caustic soda on carbonate of lime and 
sulphate of lime in water containing both these ingredients 
is as follows: The soda precipitates the carbonate of lime, 
and in so doing carbonate of soda is formed, which, in turn, 
combines with the sulphate of lime, precipitating it in the 
form of carbonate of lime, and in so doing forming sulphate 
f>f soda, which is very soluble and harmless and may long 
! neglected. 

48. When treating water containing carbonate of lime 

^ftod sulphate of lime, caustic soda may be used either by 

Mtself or in combination with carbonate of soda, depending 

' on the relative proportions of carbonate of lime and sulphate 

of lime present in the water. The amount of caustic soda 

or carbonate of soda to be used per gallon of feedwater, of 

231 cubic inches, can be found as follows: 

Rule I. — Multiply the number of grains of carbonate of ItPte 

per gallon by 1.36. If this prodtut is greater tlian the number of 

fwraim of sulphate of lime Per gallon, only caustic soda is to be used, 

W7o find lAe guantily of caustic soda required per gallon, mulli' 

y.piy the number of grains of carbonate of lime in a gallon by .8. 

Rule II. — Multiply the nu?nber of graitts of carbonate ol 

lime per gal Imi by 1.36. If this prodtict is less than the number 

of graitis of sulphate of lime per gallon, lake the difference and 

multiply it by .78 to obtain the nu^nber of grains of carbonate of 

soda required per gallon. To find the amount of caustic soda 

required per gallon, multiply the number of grains of carbonate 

of lime in a gallon by .8. 

Example.'— A quantitative analysis of a certain feedwater shows it 
to contain '23 grains of sulphate of lime and 14 grains of carbonate of 
t |iine per galloaj how much caustic soda and carbonate of soda should 
' e nsed per gallon to precipitate the scale- forming substances? 





48 MARINE-BOILER FEEDING §14 

SoLmoN.— By rule 1, 14 X 1^ » 19 gr. Since this product is lea 
than the number of grains ci sulphate of lime per gallon, rule n is to 
be used. Applying rule 11, it is found that (23 — 19) X .78 - 3.12 gr. 
of carbonate of soda, and 14 X .8 = 11.2 gr. of .caustic soda ire 
required. Ans. 

49. Water containing sulphate of lime, bat no carbonate 
of lime, may be treated with carbonate of soda. The 
amonnt of the latter that is required per gallon to precipi- 
tate the sulphate of lime is fomid by multiplying the number 
of grains per gallon by .78. 

50. When using soda, it is well to keep in mind that it 
will not remove deposited lime from the inside of a boiler. 
All that the soda can do is to facilitate the separating of the 
lime; i. e., cause it to deposit in a soft state. This sediment 
must be removed periodically. 

51. For decomposing sulphate of lime, tribasic sodium 
phosphate, more commonly known as trisodium phosphate, 
is often used. This is claimed to act on the sulphate of 
lime, forming sulphate of sodium and phosphate of lime, 
the former of which remains soluble and is harmless, while 
the latter is a loose, easily removed deposit. Trisodium 
phosphate also acts on carbonate of lime and carbonate of 
magnesia, forming phosphate of lime and phosphate of 
magnesia, at the same time neutralizing the carbonic acid 
released from the carbonate of lime and magnesia, and the 
sulphuric acid released from the sulphates. 

52. Acid water can be neutralized by means of an alkali, 
soda probably being the best one. The amount of soda to 
be used can best be found by trial, adding soda until the 
water will turn red litmus paper blue. 



TKSTI>'G WATER 

53. A quantitative analysis of feedwater can be made 
only by an expert chemist having a well-appointed laboratory 
and the proper apparatus: a qualitative analysis for the most 
common impurities can be easily made, however, with the 
aid of chemicals procurable in almost any drug store. Such 



Sl4 



MARINE-BOILER FEEDING 



49 



an analysis will show what kinds of impurities are present, 
but will not show the amounts. 

It is a good plan to test the feedwater and also the water 
in the boiler occasionally for corrosiveness. This may be 
done by placing a small quantity in a glass tumbler and 
adding a few drops of methyl orange. If the sample of 
water is acid, and hence corrosive, it will turn pink. If it is 
alkaline, and hence harmless, it will be yellow, The acidity 
may also be tested by dipping a strip of blue litmus paper 
into the water. If it tiirns red, the water is acid. This 
method is not as sensitive as the previous one, which should 
be used in preference. If litmus paper is kept in stock, it 
should be kept in a bottle with a glass stopper, as exposure 
'o the atmosphere will deteriorate the paper. If the water 
in the boilers has become corrosive and corrosion has set in, 
the water in the gauge glass will show red or even black. 
As soon as the color is beyond a dirty gray or straw color, 
'I is advisable to introduce lime or soda to neutralize the acid. 

To test for carbonate of lime, pour some of the water to 
be tested into an ordinary tumbler. Add a little ammonia 
and ammonium oxalate; then heat to the boiling point. If 
carbonate of lime is present, a precipitate will be formed. 

When testing for sulphate of lime, pour some of the feed- 
water into a tumbler and add a few drops of hydrochloric 
acid. Add a small quantity of a solution of barium chloride 
and slowly heat the mixture. If a white precipitate is 
formed that will not redissolve when a little nitric acid is 
added, sulphate of lime is present. 

When making a test for organic matter, add a few drops 
of pure sulphuric acid to the sample of water. To this add 
enough of a pink-colored solution of potassium permanga- 
nate to make the whole mixture a faint rose color. If the 
solution retains its color after standing a few hours, no 
organic substances are present. 

Matter in mechanical suspension may be tested for by 
keeping a tumblerful of the feedwater in a quiet place for a 
day. If sediment is present in the tumbler, there is mechan- 
ically suspended matter in the water. 




i 



50 MARINEBOILER FEEDING §14 



FKBDWAT£R HEATING 



KCONOMT 

54. It is important that the feedwater should be intro- 
duced into the boiler at as hi^h a temperature as possible. 
The advantages of hot feedwater are: (1) The avoidance of 
the strains produced by the unequal expansion of the plates 
of the boiler by the introduction of cold feedwater; (2) the 
saving of fuel effected by the higher temperature of the feed- 
water. In order that there will be a direct saving of fuel, it 
is necessary that the heat used for heating the feedwater be 
taken from some source of waste; the principal ones being the 
waste furnace gases and the exhaust steam from the engine. 
When the feedwater is heated in an apparatus that utilizes the 
heat from the exhaust steam, or from live steam, it is called 
a ffc^^^ivater tieater« which may be installed either in the 
engine room or fireroom. as most convenient. When the feed- 
water is heated by waste gases from the furnaces, the heater 
is called an economizer* and it is placed in the flue between 
the boilers acd the stack. Economizers have not been sac- 
cessiully applied to marine boilers as jret, except in connec- 
tion with some of the pipe boflers, their great weight, the 
space occupied by them, and the cost of up^keep being greater 
c:sad\*actages than the benedts derived from their use. 

Fee^iwjter heaters as used with condensing engines utilize 
sorr:e or the heat in the exhaust steam from the auxiliary 
engines, steam psircps^ etc. only; the exhaust steam from 
:he main engine going to the condenser. On modem ocean 
siejLir.ersi. the auxilijiry engines, steam pumps, etc. will fnr- 
c:>h x:: ar.:ple supply of exhaust steam to heat the feedwater 
to r^eiT the K^iMng point. Feeidwater heaters applied to 
r.or.-cvr.v:er.>ir:^ engines nnlise some of the heat of the 
exb.Aus: stejin: from the main eagines, whidi would other- 
wise ^v :o \Yis:e. 

55. The eoorr.^nty of n$in^ hoc feedwater may be shown 
by i ^luivle cjl-culiiicn. Sc:ppc;>e that a tioiler is required to 



|Sh marine-boiler feeding 51 

furnish steam at 145 pounds gauge pressure (160 pounds, 
B^lute) and that the feedwateris introduced into the boiler 
from a condenser at a temperature of 100° F. The number 
of British thermal units required to change a pound of water 
ai 100° F- into steam at 145 pounds gauge pressure is, from 
"Je Steam Table, about 1,125. Now, suppose that the feed- 
^3ter was passed through a heater and its temperature raised 
to 210° F., at which temperature it enters the boiler, instead 
t 100° F., as before. Then the number of British ther- 
"^al units gained thereby are 210 - 100 = 110, and the gain 
" per cent, is y\^- = .978 = 9.78 per cent. Every increase 

ot 10° p. in the temperature of feedwater effects a saving of 
approximately 1 per cent, of fuel. 



CONSTRUCTION OF FEEDWATER HEATERS 

, 56. A Blake marine feedwater heater is illustrated 
Ui Fig. 18. It is constructed on what is known as the jet 
System. This heater consists of two sections a and 6, 
designated as the upper chamber and the receiver. The 
feedwater and the exhaust steam from the auxiliary engines, 
steam pumps, etc. are brought together in the upper cham- 
ber by means of the spray cone f, which is adjustable 
from the outside by the hand wheels d, d'. In the upper 
chamber, the heat of the steam is quickly absorbed by ihe 
feedwater. The water then falls to the receiver below, 
where it is allowed to accumulate only in sufficient quantity to 
operate the float e, which, by means of the levers, rods, etc. 
shown, controls the steam throttle valve / that supplies steam 
to the feed-pump. This valve is balanced and regulates the 
speed of the pump in a positive manner. The feedwater is 
pumped up from the hotwell tank into Ihe upper chamber 
of the heater through the feedwater inlet g, the water 
spraying through the adjustable cone into the dome of the 
heater. After passing through the spray nozzle in the form 
of a thin sheet, the water is still further atomized by two per- 
forated baffle plates. The exhaust steam from the auxiliary 



J 



MARINE-BOILER FEEDING 



engines, steam pumps, etc. enters the heater by the sieam- 
exhauat inlet nozzle k through the automatic check -v aU^e i. 




This check-valve is provided with a dashpot / on its upp* 
side. The amount of cushion for the dasbpot is adjustaU 



[4 



MARINE-BOILER FEEDING 



53 



3m the outside by means of the hand wheels k, k'. This 
:ater is also provided with the air valve / for allowing the 
r and uncondensed vapors to pass from the lop of the heater 
the surface condenser. The safety valve w, also located 

I the top of the heater, can be set at any pressure desired — 
lualiy the pressure carried in the low-pressure receiver of 
le main engine. The usual practice is to have a branch pipe 
>iinecting the heater with the receiver of the low-pressure 
'lioder of the engine, so that any surplus exhaust steam from 
le auxiliaries not condensed by the feedwater will pass to 
le engine — or vice versa. The heater is also provided with 
earn- and water-pressure gauges, shown at n and n'. The 
ass water gauge o shows clearly the level of the water in 
e receiver. The feedwater outlet to the pump is shown at ^ 
le balanced steam throttle valve / is shown as being placed 
>ngside of the heater, but It is very desirable to have this 
Ive located as near the feed-pump as possible and con- 
cted to the ball-float lever by suitable rods, etc. 

The advantage claimed for this heater is the presence of the 
;eiving chamber referred to. This receiver acts as a reser- 
ir, in which the water comes to rest, frees itself from vapors, 
d maintains a steady, even level, so that the ball float gov- 
line the speed of the feed-pump moves slowly and with the 
tst oscillating movemenl. thus avoiding the uneven motion 
which other forms of heaters are liable. The feed-pump is, 
irefore, prevented from entirely draining the heater. The 

II float is counterbalanced by the counterweight q. and, 
'ing to its being in a horizontal chamber, it has a radius of 
tion not possible in a vertical cylinder of reasonable size, 

57. The heaters shown in connection with the doctor, 
ustrated in Fig. 3, are known as open heaters, from the fact 
at the part of the heater which contains the feedwater is 
«n to the atmosphere through the exhaust pipe. Such 
len heaters, used only with non-condensing engines, are 
ijected to by some engineers on the ground that the oil 
ed in the cylinders is carried into the heaters by the exhaust 
>am, and that consequently at least some of it mixes with 





MARINE-BOILER FEEDING 




K. 



MARINE-BOILER FEEDING 55 



— dwater and is carried into the boilers, where it deposits 

. ~™-^^ plates. It cannot be denied that this is true to some 

'^■*- "^p but since river water is usually very muddy, the boilers 

^^ "be frequently cleaned on account of the mud deposited; 

^J"^-* 3] carried in is then removed with the mud. 

^^^^^wever. to overcome this objection, closed feedwaler 

^^' rs have been designed. In these the feedwater passes 

^^-^'Vngh a closed system of pipes under pressure, is not 

^^^^^sed to the atmosphere at all during its passage from the 

taon pipe of the pump to the boilers, and does not come 

^^^ontact with the exhaust steam. Hence, in the closed 

^^^3water heater no oil can mix with the water. 

^S8. One design of a closed feedwater heater for non- 

■-^^^^densing engines, as used frequently on steamboats navi- 

^*-ting the western rivers of the United States of America, 

^ shown in Fig. 19. The heater consists of a cylindrical 

^^^^cughi-iron or sleel shell a, to the ends of which angle-iron 

~^*^£s are riveted. The lube sheets b, b' and cast-iron heads 

~ » «* are bolted to these rings. Tubes d, d are expanded into 

^**-e tube sheets so as to form steam-tight and water-tight 

■^^^ints. The exhaust steam from the engine enters the 

^*^7.zle e and leaves the heater through Ihe nozzle /. It sur- 

*"^unds the tubes and heats the feedwater, which enters 

^krough g and leaves at //. The plate / serves to distribute 

'^ie entering feedwater. Any condensed exhaust steam is 

'Srarried off through the pipe * attached to the bottom of the 

Veater; the water side of the heater can be emplied through 

a pipe attached at /. This style of heater is not adapted to 

a doctor of the description given, a pump that will simply 

force the water through the heater being all that is required. 

This pump handles cold water only, inasmuch as the water 

is heated after it leaves the delivery side of the pump. 

The rules of Ihe Board of Supervising Inspectors provide 
that the feedwater for a boiler used in connection with a 
non-condensing engine shall not be admitted at a lower tem- 
perature than ISO" F. Hence, the necessity of employing a 
heater on river steamers will be apparent. 




k MARINE-BOILER FEEDING 
(PART 2) 




PEEDWATER 



liOSS OF FEED WATER 



ORDIN&Ry HEAI49 OF MAKING UP LOSS 

1. When a surface condenser is used, a certain amount 
of water is evaporated into steam in the boiler, turned into 
Water again in the condenser, taken from there to the 
boiler and reconverted into steam, used once more in the 
engine, again exhausted into the condenser, and so on. It 
will be seen that, if there were no loss through leakage and 
in other ways, the same water could be used over and over 
again, no further supply being needed. But, as a matter of 
course, there is always a certain amount of leakage going on, 
in the piping conveying the steam to the engines, in the 
engines themselves (at the glands, etc.), and in the feed- 
pumps and piping. Besides this, there is the loss due to 
blowing the whistle and to steam used in the various auxiliary 
engines that do not exhaust into a condenser. All these 
losses must be made good. This loss of water may be 
discovered by watching the water gauge of the boiler. 
Should the water gradually become less in the boiler, with 
the feed-pumps operating properly, it shows that there is a 
deficiency of water in the hotwell. 
The most common way of making up for the loss consists 
. in connecting the water end of the condenser with the steam 

KOftiTitliUd tf /HltrmHumal Tta-liooi.Cemfanr. Enltrtd at Slaliooeri- Hall. Ijmdim 




2 MARINE-BOILER FEEDING §15 

end of the condenser by means of a U-shaped pipe. This 
pipe has a valve or cock in it, which is opened whenever an 
additional amount of feedwater is required, and is allowed 
to remain open for a certain leng^th of time. Some of the 
cooling water will flow into the steam side of the condenser 
and mingle with the condensed steam. The arrangement 
described is known as the salt feed. 

When a ship is fitted with ballast tanks filled with fresh 
water, a small pipe provided with a stop-valve may connect 
the inside of the condenser with the tanks. In this case, 
when the stop-valve is opened, the pressure of the air forces 
the water in the tanks into the condenser, there being a partial 
vacuum within it. 

EVAPORATORS 

2. Purpose. — In modern sea-going vessels, especially 
if intended for long runs, the loss of feedwater is usually 
made up by means of an apparatus called an evaporator, 
which converts sea-water into fresh water by evaporating it 
and condensing the steam. Since the solid matter contained 
in sea-water cannot be vaporized at the same temperatures 
at which water can be transformed into steam, the condensed 
steam from sea-water is pure if condensed in a separate ves- 
sel, as the impurities are left in the vessel in which the sea- 
water is evaporated. While the water from an evaporator is 
pure or fresh, it is not well adapted for drinking purposes, 
except in an emergency, it having a peculiarly flat and bitter 
taste. It is eminently suitable, however, for boiler feeding. 

3. Construction. — Three views of one form of the 
Baird evaporator, which is largely used in American sea- 
going steamships, are shown in Fig. 1. Like reference 
letters refer to like parts in the several views. The construc- 
tion of this evaporator is as follows: The vertical cylindri- 
cal vessel fl, closed at both ends, is provided with a coil i, 
made up of a number of boiler tubes bent into U shape and 
with their ends expanded into the tube-sheet c. There are 
two nests of these tubes, one above the other. The dished 



MARINE-BOILER FEEDING 

cover, or bonnet, d is bolted over the tube-sheet, and has 
partitions in it, causing the steam that enters the space e 
through the steam pipe /. which is provided with a stop- 
valve g, to flow through the coil in the zigzag path indicated 
by the arrow x. The steam condensed in the coil leavei 
through the pipe h pravided with a globe valve. The sea- 
water admission pipe i. provided with a globe valve f, may 
be connected either at k or k', the unused opening being 
closed by a plug. The sea-water entering through / passes 
into a pipe / provided with a cross and two short pieces o( 
pipe m, m, closed at their ends and perforated at the bottom, 
through which perforations the water passes to the boiloni 
of the inside of the shell a. A blow-off pipe leading over- 
board, and serving to empty the shell «, may be attached to 
nozzle n or n', as may be most convenient. A steam gauge o 
is connected with the coil h. and a combined steam and vacuum 
gauged connects to the inside of the shell a. A glass water 
gauge g shows the water level in the shell. A large vapor 
pipe r. fitted with a rose i, connects the inside of the shell 
with the condenser; it is provided with a stop-valve /. The 
nests of tubes can be removed bodily for cleaning by unscrew- 
ing the nuts on the studs holding the tube-sheet c and 
net d in place, and then withdrawing the nest from the sheO. 

4. The operation of the evaporator is as follows: ThB 

stop-valve t is opened, thus connecting the inside of (ha 
evaporator with the steam side o£ the condenser, and hence; 
forming a vacuum inside the shell a. The salt-water admifr 
sion valve / is now opened and sea-water is allowed to floWi 
into the shell until the coil b is covered to a depth of seven 
inches, as indicated by the glass water gauge g. when ;'i 
closed. Live steam is now admitted to the coil by openinf 
the valve g. and the valve in the drain pipe A, which i)i[ 
leads to a device that permits the condensed steam to drai 
from the coil b, but prevents the passing of steam. The Ui 
steam heats and evaporates the sea-water surrounding "& 
coil, the vapor passing to the condenser. Since the water 
the evaporator is subjected to a very low pressure, by reasi 




MARINE-BOILER FEEDING 

of the shell being connected to the condenser, slightly less 
heal is required to evaporate the sea-water than would be 
the case otherwise. This, however, is merely an incidental 
advantage of connecting the evaporator to the condenser, 
the main object of the connection being the condensation of 
the vaporized sea-water without a separate apparatus. The 
rate of evaporation is regulated by the stop-valve g, partly 
closing it to reduce the pressure of the steam and hence its 
temperature, whereby the evaporation rate is reduced. The 
pressure in the coil is indicated by the steam gauge o. When 
the water gauge q shows that most of the sea-water has been 
evaporated, more, is admitted by opening the stop-valve /. 
Owing to the salt and the other scale-making impurities con- 
tained in sea-water, the density of the water in the evapo- 
rator will quickly increase, and hence the evaporator must be 
blown ofi frequently. This is done by first closing the stop- 
valve /. which causes some of the sea-water to be evaporated 
into steam; the pressure soon begins to rise, as shown by the 
gauge p. The stop-valve of the blow-off pipe n is opened 
when a sufficient steam pressure has been reached, and the 
dense water in the evaporator is blown out. The evaporator 
is now ready for a fresh charge of sea-water, and the oper- 
ation may be repeated. 

5. During the process of evaporating the sea-water, a 
large proportion of the scale-making impurities in the water 
will be precipitated by the heat and will adhere tenaciously 
to the outside of the tubes in the form of scale. This scale, 
being a non-conductor of heat, decreases the efficiency of the 
evaporator as it accumulates on the tubes, and hence arises 
the necessity of occasionally removing Jt from the tubes. 
The salt will remain in solution in the water until the water 
becomes saturated with it, after which it will deposit in the 
form of solid salt on the bottom of the evaporator; and if the 
process were allowed to continue under these conditions it 
would eventually fill up the evaporator solid with salt. 
rendering the apparatus useless; hence, it is necessary to 
blow out the water before it becomes saturated. 





MARINE-BOILER FEEDING 



§lfr 



It will be observed that there are two sources of fresh- 
water supply from this evaporator: (1) the water of coo- 
densation from the steam coil i; (2) the condensation of the 
vapor from the sea-water that passes into the condenser 
through the pipe r. The water from both sources eventually 
flows to the hotwell or feed-tank, whence it is pumped into 
the boilers as make-up feedwaler. 

6. An important part of the evaporator is a device called 
a steam tritp. This device permits the water formed by 
the condensation of the steam in the coil d, Pig. I, to drain 




into the hotwell, but it prevents the escape of steam, thus 
holding the pressure and temperature inside the coil, and, 
consequently, utilizing the latent heat of the steam in vapor- 
izing sea-water fed to the evaporator. The construction o£ 
one form of trap is shown in Fig, 2. Inside a cast-iron 
chamber is a lever F, pivoted at //, and working in a forked 
guide £. Attached rigidly to the lever F, is a hollow copper 
ball D, known as a float. A piston valve 1/ is attached by 
the link C to the lever F. The valve is provided with four 
ports, all of which, at a certain position of the valve, com- 
municate with the passage in the valve chamber A', leadiag; 




Sl5 MARINE-BOILER FEEDING 



I hotweU^ 



to the drain pipe /.which communicates with the 1 
The inlet pipe G is connected to the drain pipe ol the 
evaporator. When steam is admitted to the evaporator, it 
flows ihrouEh the coil into the drain pipe, thence into the 
steam trap, where fnrther escape is prevented, since the out- 
let to the drain pipe / is shut off by the valve U, the ball D 
being in the position shown. The steam in the coil and the 
trap gradually condenses, the water gradually collects and 
rises in the trap and lifts the ball D until, by means of the 
connections shown, the valve U is opened, when the pressure 
of the steam will blow a certain quantity of the water through 
the four passages of the valve into the valve chamber, and 
thence into the drain pipe /. The ball D sinks as fast as the 
water leaves the trap, until the communication to the drain is 
shut off. when the water will again collect in the trap and the 
operation will be repeated. By means of the adjusting 
screw A, which limits the drop of the bali, the quantity of 
water discharged may be regulated. The screw B. forming 
a stop for lever F, is used for regulating the amount of 
opening of the valve. 

Steam traps are made in a variety of forms; they are often 
used on the return pipes of the steam-heating systems of 
steam vessels and serve the same purpose as the one used 
in connection with the evaporator. 

7. The QalKtrln evaporator is illustrated in Fig. 3. 
Securely bolted to the inside of the vertical steel shell a, in the 
lower portion, are two annular, composition manifolds b,l/, 
of proper thickness to withstand the usual boiler pressure. 
Connected to these manifolds, in a vertical position, are the 
spiral-shaped tinned-copper heating coils c.c. The coils are 
interchangeable, and can be disconnected in a few minutes. 
when required. Owing lo their inherent elasticity, it is difB- 
cult for them to leak, being unaffected by irregular expansion 
and contraction. If. by any mishap, the feed should be 
stopped, the coils will not be damaged by becoming exposed, 
and no harmful results to the evaporator can arise from inat- 
tention to the feed or from overheating the coils. Riveted ■ 



MARINE-BOILER FEEDING 



1 15 



to the shell are two manhole frames, oc a large door with » 
frame, so located as to afford ready access to the inicriot fot 
cleaning purposes, or for disconnecting the coils, which ci 
be done by means of an ordinary wrench. Fitted to the shcK 



is a suitable plate of rolled 



of proper area, for takinj 
up galvanic actiota 
The shell being i 
the vertical type, ac 
having an abundance 
of vapor space in tl 
upper portion, p; 
raing is avoided. 

The coils f.r inthei 
lower part of the shell 
receive the steam 
from the main boilers, 
or from the inter- 
mediate-pressure re* 
ceiver of the engine, 
through the upper 
manifold b. These 
coils are covered to t 
certain height by sei- ■ 
water, which is fed 
into the evaporator 
by means of a small 
feed or donkey pnmp, 
set to supply thA 
amount of water 
evaporated and t 
maintain a unifonQ 
feed-level of water il 
the evaporator. Thll 
pump takes its suction from the discharged circulatinj 
water, thereby getting the benefit of the heat that i 
been given up by the exhaust steam in condensing. 1 
steam in passing through the coils gradually gives up ll 
heat to the water surrounding them, and converts it ini 




Us MARINE-BOILER FEEDING 9 

""Vapor. By the time the steam reaches the bottom manifold i'. 
" has given up all its heat above the temperature due to the 
Pressure carried in the shell, and has been condensed to 
Water, and in this form it flows to an automatic steam trap, 
•^hencc to the feed-tank for the boilers. The vapor arising 
^^om the surface of the water comes in contact with the upper 
Part of the coils and is thoroughly dried, and any spray or 
Priming that might rise through too violent ebullition is thus 
Prevented from passing over with the vapor through the 
Valve d to the receiving tank, the condenser, or the low- 
Pressure receiver. 

The constant evaporation of the water, which leaves all 
the solids behind, necessarily causes an accumulation of 
Scale on the heating surfaces, thus gradually reducing their 
efficiency. In this evaporator, the nature of the heating sur- 
face insures the cracking off of most of the scale as fast as 
formed, owing to the expansion and contraction of the spiral 
coils {the tubing of which has a crescent-shaped cross-section) 
that is always going on. The scale accumulates in the bottom 
of the shell and is readily taken out through the lower man- 
hole, If any of the scale has hardened and still remains on the 
coil, it can be removed by blowing off the hot water and then 
turning on steam to the coils, thus causing a sudden expansion 
and breaking off of the scale; it can also be removed by stri- 
king the coils gently with a stick or hammer handle. 

This evaporator will work practically automatically, and 
only requires attention to be given to the blowing ofi, and 
an occasional look at the feed-pump to see that it is not 
giving too much feed. It is nearly useless to blow out for 
the removal of sulphate of lime scale. This will form any- 
how, and the more water blown out the more must be fed in. 
But, if the density is allowed to become too high, there will 
be a deposit of common salt. Blowing out will prevent this. 
Experience has shown that a density of A may be safely 
carried. A higher density risks the deposit of salt, and a 
lower one means greater loss of heat. 
H When the evaporator is required for making up boiler feed 
Buily, it can be connected to the main exhaust pipe by means 



10 MARINE-BOILER FEEDING §16 

of a springy regulating valve, which is supplied for the pur- 
pose by the manufacturer. 

The evaporator is fitted with all the valves, gauges, and 
fittings necessary for its efficient operation. These comprise 
the vapor-outlet valve dy the steam-inlet valve e^ the drain 
valve /, and the blow-off valve g. It is also provided with 
the safety valve A, a pressure gauge, and a glass water gauge 
(not shown in figure). 

SAIiT MEASUREMENT AND REGUIiATION 



MEASUREMENT 

8. Saturation. — Ordinary sea-water contains on an 
average 1 pound of solid matter, about one-quarter of which 
is salt, in every 32 pounds of water. If sea-water is evapo- 
rated, the solid matter held in solution in the water remains; 
that is, if 32 pounds of sea-water is evaporated, 31 pounds 
of steam is formed and 1 pound of solid matter remains. 
Should but part of the 32 pounds be evaporated, say 
16 pounds, there will remain 16 pounds of salt water con- 
taining 1 pound of solid matter. Again, if one-half of this is 
evaporated, the 1 pound of solid matter will still be contained 
in the remaining 8 pounds of salt water. Suppose that a 
vessel contains 32 pounds of sea-water, and that 16 pounds 
of water is evaporated, and there remains in the vessel 
16 pounds of water containing 1 pound of solid matter. 
Another 32 pounds of sea-water is put into the vessel, and 
the same number of pounds are evaporated. It is evident 
that there is now 2 pounds of solid matter contained in the 
16 pounds of water that is left in the vessel. This shows 
that the more sea-water is added and evaporated, the more 
solid matter will be contained in the water remaining in the 
\*essel. This is exactly what takes place in a marine boiler 
usiniT seA-water, and it is evident that, in order that the 
oont;\ineil solid matter may not exceed a certain amoimt, a 
'jV^rtion ot the water must be occasionally drawn off from the 
l\>:U"r. This is done by means of either the bottom or the 
surtaci: blow-off cock, and is termed bloivrins off. 



MARINE-BOILER FEEDING 



II 



115 

The term satnratlon is used to denote the number of 
pouods of solid matter in every 32 pounds of water, and is 
usually expressed in the form of a fraction. Many engineers 
ose the term density instead of saturation. For instance. 
A saturation means that there is 3 pounds of solid matter 
in 32 pounds of water. Fresh water at sea level boils at 
212° F., but if solid matter is added, the temperature of the 
boiling point will be raised. In Table t, the boiling points of 
Sea-water at different degrees of saturation are given. As 
Water will boil at a temperature varying with Ihe pressure 
of the atmosphere, the boiling points given in the table are 
Correct for but one pressure, namely, 30 inches of mercury. 

TABLE I 

BOIl.tMO POINTS OF HSA-WATKR 



Saturation 


Boiling Point 
Degrees F. 


Saturation 


Boiling Point 
Degrees P. 


A 




•h 


220.3 


A 


2'3 


2 


A 


22 1. S 


A 


214 


4 


A 


222.7 


A 


2'S 


S 


is 


223.8 


A 


2l6 


7 


ii 


225.0 


A 


217 


9 


ii 


236.1 


A 


219 









At H saturation, the water becomes saturated; that is, it 
will not dissolve any more solid matter. 

9. Flndlnic Baturntlon hy Thermometer. — It will be 
seen, by referring to Table I, that the boiling point rises 
about 1.2° F. for every poimd of solid matter added. It has 
been determined that, for every tenth of an inch variation in 
the height of the barometer, the boiling point of the water 
varies .16° F. If the height of the barometer is less than 
30 inches, the water will boil at a lower temperature than 
given in Table I. For instance, if the height of the barom- 
eter is 29 inches, water containing A solid matter will boil 




A 



12 



MARINE-BOILER FEEDING 



Sii 



at 214.4 - 10 X .16 = 212.8°. Conversely, if the height o( 
the barometer is 30.4 inches, the same water will boil ai 
214.4 +4 X'.16 = 215.04° F. 

Should it be desired to find the saturation of the water 
the boiler, some water is drawn from it into an open vesset] 
and is then heated to the boiling point. The temperature 
which it boils is ascertained by means of a thermometer, and 
the boiling point with the barometer standing at 30 inches 
is calculated. The saturation is found by the approxiniaii 
rule given below: 

Rule. — To find the degree of saturation by means of 
thermometer, subtract 212° from the corrected boiling point of II 
water tested and divide tie remainder by 1.2. 

Or, 5 = -^i-f---M 

where S = saturation; 

A - boiling point of water tested; 

B = product of number of tenths of an inch variation 

in height of barometer and ,16, this product \o 

be subtracted when barometer is above 30 

inches, and to be added when below 30 inches. 

ExAMPLB.— A sample of water boils at 215.2" F., the height of tht 

barometer being 30.5 Inches. What is the saturation of the water? 

Solution. — Since the barometer reading is above 30 in., the v«l"' 
of B must be subtracted from that of A. Substiluling values, 
_ (215 .2 -5 X .16] -212 



all? 



1.2 



- <=2lb.oEsotid matter,or A 



A». 



10. FlndltiK Saturation by Hydrometer, — It is 

evident that as the density of water increases, the more 
solid matter there is dissolved in Ji, and consequently, by 
measuring the density of the water, the amount of solid mat- 
ter may be readily found. This is done by means of > 
hyilronietur, shown in Fig. 4. This instrument is often 
called a Halinomotcr; that is, a salt measurer, as it is use<l 
for measiuing the quantity of salt contained in Water. Ii 
consists of a glass tube, near the bottom of which are two 
bulbs. The lower and smaller bulb is loaded with mercurj^ 
or shot, so as to cause the instrument to remain in a 




MARINE-BOILER FEEDING 



13 



irien placed in the water. The upper bulb is filled 
and its volume is such that the whole instrument is 
an an equal volume of water. Most salinometers 
lated to read off the density when the water has a 
are of 200° F,; some of these instruments, however, 
e scales, one each for 190° F.. 200° F., and 210° F. 

^ salinometer is graduated by trial, placing it first 
valer having the temperature at, say, 200° F. The 
which the instrument sinks in the water is marked on 

tube. It is then placed in water having the same 
lire and containing aV part of salt. The depth to 
: instrument now sinks is the sea-water mark, and 

marked on the tube. This operation is 
with water containing A, A, and so on 
part of salt, always taking care that the 
are of the water is exactly 200° F. The 

the tube are transferred to a paper scale, 
jasted to the inside of the tube in exactly 

position as the marks on the tube. The 

between the marks are usually divided 
es, quarters, and eighths. If the sali- 
ts to give a correct reading at 190° F. 
F., the process of graduating must, of 
e carried out at the desired temperature 
ut. Knowing the process of graduation, 
neter can be improvised out of a piece of thin 

tall and slender bottle, etc. 

f the hydrometer is placed in a vessel containing 
er drawn from the boiler and having a temperature 
hat at which the instrument was graduated, it will 
depth corresponding to the density of the water, 
saturation may be read off on the scale. For 
if the hydrometer sinks to the 2b graduation on the 
means that there is 2i pounds of solid matter in 
pounds of water. 

the temperature of the water under test vary from 
;rature at which the hydrometer was graduated, the 



Pio. 1 



b. 



i 



14 



MARrNE-BOILER FEEDING 



!li 



.-^ 



indication of the hydrometer will not be correct. This is " 
due to the difference in density of water at differcDt tem- 
peratures. Allowance may be made for this error in tbc 
following manner: The indication of the hydrometer wUl d 
vary A part of 1 pound of solid matter for every degree tlM'l 
temperature of the water varies from the temperature at whi 
the hydrometer scale was marked, 

Thus, if the temperature is 205° F., 
a hydrometer ^aduated at 200° F. wiH I 
show /o part of 1 pound of solid mat- 
ter less than there really is in (bt 
water. For instance, the temperalnre 
of the water being 206° F., and ihe 
hydrometer indicating liS pounds oi 
salt, the actual amount of salt will be 
A of 1 pound more, and as A = i*!. 
iH + V« = 2 pounds will be the actual 
saturation. Also, if the temperature 
of the water is less, the indication of 
the hydrometer will be too high. For 
example, the temperature of the water 
being 180° F., and the hydrometer 
indicating 2i pounds, the indicalion 
will be 3S pound too high. Subirad- 
ing IS = i from 21, 2 pounds is found 
to be the true amount of solid matter 
in every 32 pounds of the water drawn 
from the boiler. 

13. For convenience, a flallnom- 
^'»-6 eter pot, shown in Fig. 6. is com- 

monly used. It is attached to the boiler, or, should there 
be several boilers, it is put up in the engine room and 
connected by branch pipes with each boiler. The pot con- 
sists of two cylindrical brass vessels, one of larger diam- 
eter than the other, communicating with each other by 
a passage P in the base of the instrument. A removable 
cover C is fitted to the larger vessel. The pipe A conaecls 




S MARINE-BOILER FEEDING 

th the water space of the holler. On opening the stop- ' 
Ive fl, water flows into the smaller vessel and through the 
ssage P into the larger one. The water is prevented from 
erilowing by the overflow pipe 0, which empties below 
! drain valve d into the drain pipe D. A thermometer T 
licates the temperature of the water. If the temperature 
the water is too low, the stop-valve a is opened until the 
sired temperature is reached; if too high, the water is 
owed to cool. To prevent the water admitted to the pot 
ing upwards and scalding the attendant, the admission 
le A' is turned downwards, as shown. Any vapor formed 
y escape through the perforated top B. When the water 
the larger vessel is at the proper temperature, the density 
iscertained by means of the hydrometer, and then the pot 
Irained by opening the drain valve d. 



^^^^ REGUI^TION ^ 

4. It is evident that, to keep the water in the boiler at 
trtain degree of saturation, the solid matter carried with 
feedwater into the boiler in a stated time must be 
loved from the boiler in the same length of time; that is, 
number of pounds of feedwater multiplied by the amount 
iolid matter in 1 pound, must equal the number of pounds 
vater blown oS multiplied by the amount of solid matter 
I pound. 

a rules I and II, the quantity of water may be taken in 
nds, tons, gallons, cubic feet, etc., but it is absolutely 
essary to use the same denomiaalion throughout the cal- 
Ltion. 
.et A = quantity of water blown off; m 

B = saturation of .-/; '■ 

C = quantity of feedwater; I 

D = saturation of C; 

A = quantity of water evaporated, corresponding to C. 
Uile I. — To find the qttaniiiy ol water to be iloivu oil in a 
ed time, divide tlie product ol the quantity of feedwater 



16 MARtNE-BOlLER FEEDING Sl5 

admitted in that time and its saturation t>y the saturation of tk 
water to be blown off. 

Example 1. — 2,000 pounds of feedwater enters a boiler every hoar 
at a saturation of i%\ how much water must be blown off every hour to 
keep the saturation at A? 

Solution. — Applying rule I, 

A = ^'QQQX* = 1,000 lb. Ans. 

Example 2. — How much water must be blown off every hoar to 
keep the saturation at i^, when 48,000 gallons of sea- water, at a satu- 
ration of A, is fed to the boiler in 24 hours? 

Solution.— The water fed per hour = ^W^ = 2,000 gal. Apply- 
ing rule I, 

A = ^'Q^X A ^ gg^ g^ ^^3 

Rule II. — To find the quantity of water evaporated into steam 
for a given quantity of water blown off^ divide the saturaim 
of the water blown off by the saturation of the feedwater^ sub- 
tract 1 from this quotient and multiply the remainder by the 
quantity of water blown off. 






Or, 



-(!-) 



Example 3. — The saturation of the feedwater being A, how much 
water is evaporated into steam for 1 pound of water blown off at 
A saturation, the saturation to be kept constant? 

Solution. — Applying rule II, 



£^ = 1 X (x - l) = ^ 1*^- Ans. 



Rule III. — 71? find the quantity of water blown off for a 
given quantity evaporated, divide the saturation of the water 
blown off by the saturation of the feedwater, and subtract 1 from 
the quotient. Divide the quaritity of water evaporated by the 

remainder, 

E 



Or, A = - 



I-' 



■ l5 MARINE-BOILER FEEDING 17 ] 

Example 4.— The saturation of the boiler being kept at A and the 
^^(Iwaier being at A. how much water must be blown off for every 
P»^tiiid of water evaporated? 

Solution.— Applying role III, 

A — -f = i lb. Ans. 

s- 

The total feed obviously must be the sum of the water 
evaporated and the water blown off, in order to keep a steady 
■boiler water level. Thus, if the evaporation is 6,000 pounds 
per hour, the feedwater at sV, and the boiler worked at A satu- 

6,000 

- 1 
sir 
= 2,000 pounds, and the total feed is 6,000 + 2,000 = 8,000 
pounds per hour. 

15. It was formerly the practice not to let the satura- 
tion of the water in the boilers exceed A. This limit to 
saturation has, however, been gradually raised to A, as less 
scale-forming matter is carried into the boiler at that density 
than at the lower one. Furthermore, with the water in the 
boiler at jV. there is sufficient ditierence between the specific 
gravity of the oil or grease carried in by the feedwater, even 
when combined with some of the carbonate of lime, and that 
of the boiler water to insure the grease and oil floating on 
top. whence it can largely be removed by a frequent use of 
the surface blow-off. Since much less scale-forming material 
is carried into the boiler at a high density, there is propor- 
tionately less scale formation. 

The reason that less scale-forming material is carried into 
the boiler when the water is at a high density is that less 
water requires to be blown off and replaced. Besides this, 
there is the additional advantage in a high saturation of less 
waste of heat. 

16. A simple calculation will show that less solid matter 
is carried in at a high saturation than at a low one. Suppose 
that a boiler contains 100,000 pounds of sea-water at its 
steaming level, and evaporates 50,000 pounds of water per 




18 MARINE-BOILER FEEDING §15 

hour. Let sea-water at ih be used for boiler feeding^, let die 
saturation be kept at A, and let the steaming: period be 
6 days of 24 haurs each. 

At the beginning, the boiler contains ^ ^88^^ = 3,125 pounds 
of solid matter. To bring the saturation to A, 100,000 pounds 
of water must have been evaporated and replaced, thus 
bringing in 3,125 pounds more of solid matter. The time 
required to bring the saturation to A is WAV = 2 hours, 
at the end of which period the boiler contains 3,125 + 3,125 
= 6,250 pounds of solid matter. By rule III, Art. 14, the 

quantity blown oflE per hour is -^ = 50,000 pounds, 

giving a total feed per hour of 50,000 + 50,000 = 100,000 
pounds, which brings in -^f*^ = 3,125 pounds of solid 
matter. In 6 days there is 6 X 24 = 144 hours, of which 
2 hours was consumed in bringing the saturation to iht leav- 
ing 144 - 2 = 142 hours, during which 142 X 3,125 = 443,750 
pounds of solid matter is carried in. The total solid matter 
carried in during 144 hours is 443,750 + 6,250 = 450,000 
pounds, under the assumed conditions. 

Now consider the same boiler with the saturation kept 
at A. To bring the saturation to "A", the water has to be 
changed four times; that is, 100,000 X 4 = 400,000 pounds 
must be fed in and evaporated, leaving behind *^8S^^ = 12,500 
pounds of solid matter. With the first filling, 3,125 pounds 
was carried in. The time required to evaporate 400,000 
pounds of water is WoW = 8 hours, at the end of which 
period the boiler contains 3,125 + 12,500 = 15,625 pounds 
of solid matter. By rule III, Art. 14, the quantity blown 

50 000 
off per hour is -^ = 12,500 pounds, giving a total feed 

per hour of 50,000 + 12,500 = 62,500 pounds, which 
brings in *W^ = 1,953.125 pounds of solid matter. This 
amount is carried in during 144 — 8 = 136 hours, during 
which time 136 X 1,953.125 = 265,625 pounds of solid 
matter is carried in, making a total for 144 hours of 



MARINE-BOILER FEEDING 



19 



§15 

265.625 + 15.625 = 281.250 pounds, against 450.000 pounds 
carried in when the saturation is kept at ^. 

17. By drawing hot water from the boiler and making 
up the deficiency with colder water, a certain amount of heat 
is lost. The amount is equal to the difference in tempera- 
ture between that of the water in the boiler and that of the 
feedwater. For instance, if the temperature of the water 
in the boiler is 320°, and that of the feedwater 180°, then 
320° - 180° = 140° will be the amount of heat lost. This 
represents the number of British thermal units lost for each 
pound of water blown off and replaced with a pound of 
cooler water. Knowing this, the difference in the loss of 
heat due to blowing off at different densities can be found. 
To keep the density at -^i by rule III, Art. 14, for each 

pound of water evaporated there must be blown off -»- 

^-1 

-hi 

= 1 pound of water, the density of the feedwater being sV. 
If the feedwater temperature is 160°, and the temperature 
in the boiler 300°, the loss of heat per pound of water 
evaporated is 300 - 160 = 140 British thermal units. All 
conditions remaining the same as before except that the 
saturation in the boiler is kept at s^f , the water blown off for 



each pound evaporated is 



i pound, and the loss of 



heat per pound of water evaporated is 140 X i = 35 British 
thermal units. This shows that the heat lost by blowing off 
is reduced by carrying a high density. 

18. The percentage of loss of heat due to blowing off 
is found as follows: 

Rule. — To find the percentage of loss of heal due to blowing 
off, divide the number of British thermal units lost in blowing 
off 1 Pound of water by the sum of the total heat (above the tem- 
perature of the feedwater) imparted to the amount of water con- 
verted into steam for 1 pound of water blown off, and the number 
of British thermal units lost in bloifing off J pound ol water. 




20 MARINE-BOILER FEEDING §15 



Or, L = 



A^- B 
where L = percentage of heat lost; 

A = total heat (reckoned above temperature of feed) 
imparted to amount of water converted into 
steam for 1 pound of water blown off; 
B = number of British thermal units lost in blowins: 
off 1 pound of water. 

ExAMPLB. — The saturation of the water in a certain boiler is to be 
kept at A; the temperature of the feedwater being 160^ P., its satura- 
tion A, and the steam pressure 90 pounds, absolute, what will be the 
percentage of loss due to blowing off? 

Solution.— The sensible heat of steam at 90 lb. pressure is 
320.094° P.; 320.094^-160°= 160.094°, represents the difference of 
temperature, and the number of B. T. U. lost in each pound of water 
blown off. In order to find the total heat mentioned in the rule, the 
amount of water converted into steam for 1 pound of water blown off 
has first to be found from rule II, Art. 14. This amount is found 
to be 2 lb. The total heat above 32° P. of a pound of steam at 90 lb. 
pressure is 1,179.569 B. T. U., and above 160° P. it is 1,179.569 
-(160-32) = 1,051.569 B.T.U. Consequently, for 2 lb. the total heat 
is 1,051.569 X 2 = 2,103.138 B. T. U. Por each pound of water blown 
off, 1 lb. will have to be fed into the boiler, in addition to the amount 
evaporated, and the amount of heat carried into the boiler by this 
pound of feedwater must be added to the total heat. Now, substi- 
tuting the values, 

160 004 
^ = 2,103.138 + 1 60:094 = '^^^^ = ^'^^ P^" ^^°*- °^^y- ^°"- 



EXAMPLES FOR PRACTICE 

1. The height of the barometer being 30.4 inches, find the boiling 
point of water having a saturation of A- Ans. 218.54° F. 

2. A sample of water boils at 216.7° P., the height of the barometer 
being 30.3 inches; find the saturation. Ans. ^^ 

3. A salinometer graduated for 200° P. immersed in water having 
a temperature of 208° P. indicates 3 pounds of salt; correct the read- 
ing. Ans. 3.1 lb. 

4. How much water at A saturation will have to be blown off to 
keep the saturation constant, the saturation of the feedwater being A> 
and 5,000 pounds entering the boiler every hour? Ans. 1,666.67 lb. 

5. How much water at ^ is evaporated for every 120 gallons of 
water blown off at ff? Ans. 240 gal. 



§15 



MARINE-BOILER FEEDING 



21 



HKAT TRAN8PKB TO WATER 



6. Fiiiil the percentftge of heat lost in blowing off water a.t A. 'he 
steam pressure beiag lUO pounds, absolute, the temperature of the 
feedwater 190" P., and its saturation Jf. Take the total heat of 
1 pound of steam at 100 pounds pressure, absolute and above H\l P°, as 

I118I.H<i£ British thermal units, and its seasible heat as 327.625° F. 
Ads. 1.29 per cent., nearly. 
F NATURAL CIRCOtATION 

[ 19. The transfer of heat from the furnace to the water 
tn the boiler is accompHshed by radiation, conduction, and 
convection. It is estimated that when the fire is burning 
brightly, about one-half of the heat received from the furnace 
by the boiler is radiated. The transfer of heat through the 
water is due to convection, since liquids are poor conductors 
of heat. The particles of water next to the shell or plate 
become heated, and immediately rise into the main body of 
water, giving place to fresh particles of cold water. This 
setting up of a current by the action of heat is called circu- 
lation. The rapidity with which heat will be absorbed by 
convection depends on the effectiveness of the water circu- 
lation in the boiler, and on the extent and conductivity of 
the heating surfaces. The transfer of heat through the shell 
and furnace plates takes place by conduction. It has been 
proved, experimentally, that the quality or thickness of the 
material has little influence, thick iron tubes working prac- 
tically as well as thin brass ones. Very thick plates are, 
however, liable to be injured by burning when exposed to 
the direct action of the fire. 

20. Water circulation is essential to the efficient opera- 
|tion of a boiler. It has just been stated that the rapidity of 
^e transfer of heat by convection depends on the rapidity 
tof circulation. Besides this, the circulation is useful in 
preventing, in some degree, the deposit of sediment that 
iccumulates from the feedwater. Again, a rapid circulation 
teeps the parts of the boiler at a uniform temperature. 




MARINE.BOILER FEEDING 



§15 



21, Fig. 6 shows the circulation of the water in an 
externally fired cylindrical boiler. The heated currents rise 
from the hottest part of the shell directly over the furnace, 
and carry the bubbles of steam to the surface. The cooler 
water rushes in to tike their place over the furnace and thus 
the circuHtiDn ib maintained As shown in the figure there 
are two currents, one carrying the cold water from rear to 




front, and the other carrying it down the outside of the s 
and up through the center. It will also be noticed that 1 
circulation is in a direction contrary to that of the furnacj 
gases. Since in all cylindrical boilers the water is not coijfl 
tained in a solid mass, but is broken by flues or tubes, t 
circulation is more or less interfered with by opposin 
currents. 

22. Fig. 7 illustrates the circulation of the water i 
Scotch boiler. The water directly over the top of 
furnaces is healed first; it rises between the tubes and a 
side each nest of tubes, cooler water coming down betwei 
the nests and alongside the shell. The circulation i 




MARINE-BOILER FEEDING 

lower half of the boiler is very feeble; some of the water 
passes upwards alongside the furnaces, where the downward 
currents meet it and almost neutralize its motion. It will 




thus be seen that the circulation is greatly interfered with by 
opposing currents, and as a consequence the lower half of 
the boiler is considerably cooler than the upper half; the 
difference in tempera- 
ture between different 
parts of the sheets sets 
up severe strains in the 
material, thus tending 
to shorten the life of the 
boiler. The circulation 
is more rapid and ef- 
fective if the water is 
constrained to follow a 
particular path. To ac- 
complish this object, 
thin sheet-iron plates 
are sometimes fitted in 
Scotch boilers in such a 

position that the upward and downward currents cannot inter- 
fere with each other. The arrangement of the plates is shown 
in Fig. 8. The thin iron plates /'./'enclose each separate nest 





4^1 



24 



MARINE-BOILER FEEDING 



hi 



of lubes, extending very nearly the whole length, and down- 
wards to the lowest tubes of each nest. The upper ends of 
the plates enclosing each nest are inclined toward each 
other, and are carried up a short distance above the v 
level. The water is lifted through the opening between the 
two plates by the ebullition on the surface of the water, and, 
after parting with the particles of steam suspended within it, 
flows down the upper inclined surfaces of the plates and 
augments the downward current. These plates will acceler- 
ate the circulation in a direction at right angles to the axis 
of the boiler, but do not influence any current in an axial 
direction. The arrows show the direction of the currents. 
This arrangement helps the circulation somewhat, but still 
leaves much to be desired. 



■-Ck 




23. It is one of the strong points of the water-tube 
boilers that the water must pass in one direction throagh t 
series of tubes; hence, the circulation is strong and uninter- 
rupted. Of course, this statement refers only to properly 
designed water-tube boilers. In the earlier designs, th^ 
circulation of the water had either not been provided for a 
alt, or but indifferently. For this reason the first water-tub* 
boilers placed in a steamship were failures; but since then, 
the importance of providing for a rapid circulation has beett 



recognized and the boilers designed accordingly, so that at 

«"e present day the statement made holds good for nearly 

*" Water-tube boilers used in steam vessels. Tlie difference 

^^tWeen the cylindrical and water-tube boilers in this respect 

, ^y be illustrated as follows: The cylindrical boiler wiih 

^^ contained mass of water may be compared to an ordinary 

^ttle in the process of boiling (see Fig. 9). The water rises 

^pidly around the outer edges and flows downwards in the 

^^oter. If, however, the fire is quickened, the upward and 

'iownward currents interfere with each other, and the kettle 

wils over. The water-tube boiler should be identical in 

principle with a U lube hanging from a vessel filled with 

water, and with the heat applied to one leg (see Fig. 10). 

The circulation is set up immediately, and proceeds quietly, 

no matter how fierce the fire may be. 

FOBCEI3 CIRCULATION 

24. Of late years, much attention has been paid to the 
improvement of the circijlalion of the water in the fire-tube 
marine boilers, and today a great many of them are fitted 
with some apparatus for improving the circulation. This 
may be done by a small pump connected to the bottom of 
the boiler, drawing the cold water from the lower half and 
discharging it through a perforated pipe near the water level 
downwards between the nests of tubes. 

25. The Crulfc licaMnfc iind circulating appariitiis 
is shown in Figs, 11 and 12. In general design and principle 
of operation, it greatly resembles an injector. In Fig. 11, 
the feedwater enters through the pipe /., passing through the 
check-valve Cinto the nozz.Ie B; thence through .•/ into the feed 
check-valve M, and tlirough the stop-valve R into the boiler. 
The water passing through 5 at a high velocity induces a 
current of water to pass through the induction pipe A' con- 
nected to the bottom of the boiler, the water passing through 
the check-valve E into D, thence through the annular open- 
ing between the nozzles /"and G into F^. whence it passes 
into A. mingling with the feedwater. To heat the water, a 




MARINE-BOILER FEEDING 



Sic 



jet of live steam is admitted by the valve A' and nozzle G. 
The steam pipe P, bolted to the valve A', leads to the donkey 
boiler. When it is desired to equalize the temperature and 
circulate the water while getling up steam in a boiler fitted 
with the apparatus, steam from the donkey boiler is admitted 
by the valve A". The steam flowing through G into A at a 
high velocity acts the same as an injector, inducing a flow oi 
water through JV, £, D, F, A, M, and R into the boiler, and 




delivering the water at a high temperature. The cbec 
valve C prevents auy of the water from entering the fei 
pipe L. When the boiler is under steam, the apparatus | 
used lo circulate and heal the feedwater. the circulation bein 
induced by the feedwater flowing through B with a I 
velocity and inducing a current of water to pass up throng 
N,E,D,F, and/', into .-/, and thence into the boiler. ~ 
feedwater is heated by mingling with the hot water comid^ 
from the bottom of the boiler. 



MARINE-BOILER FEEDING 



27 



In Fig. 12, the apparatus is shown applied to a Scotch 
oiler. At A^,, the internal induction pipe is shown. This 
, a perforated pipe running in the direction of the length of 
le boiler, and is connected to the external induction pipe A', 
rovided with a slop-valve n. The feedpipe L is provided 
■itb a slop-valve /. At M the feed check-valve is shown. 




'hence the water passes through the stop-valve J? into the 
ilernal feedpipe ,)/,. thence into the perforated distributing 
ipe Af„ discharging the water downwards between the nests 
f tubes. P is the steam pipe leading to the donkey boiler, 
"his pipe is provided with a stop-valve A'. To circulate 
le water while running, the valve w is opened, when the 
:edwater itself will maintain the circulation. To heat and 



28 



MARINE-BOILER FEEDING 



Si.i 



circulate the water before fires are lighted, the valve / is i 
closed, the valves M and n are opened, and steam from theri 
donkey boiler is admitted to the apparatus, the steam, in tha-J 
manner previously explained, heating and circulating thel 
water, thus bringing alt the parts of the boiler to a unifonal 
temperature, and thereby greatly reducing the local straina:B 
in the material of the boiler due to starting a fire in the fi 
naces. The apparatus may be connected by suitable pipingB 
to serve for the main feed as well as for the donkey feed. 

27. Bloomsbiirfi's equlllbrliiin circulator is shown 

in Fig. 13, and its application to a marine boiler in FJg. 14. 

Referring to Fig. 13. the feedwaler enters at n in a solid 

body, and in flowiog 

through the annular 

opening b assumes 

a tubular shape. The 

whole device being 

immersed in water, tie 

friction of the annular 

jet issuing at a high velocity 

causes the surrounding 

water to move in the direction o£ 

and with the jet, thus inducing S 

current of water to flow through / into d and out at e. 

In Fig. 14. the device is shown applied to a Scotch boiler. 
In this figure, a represents the circulator. The suction pipe; 
is connected to / (see Fig. 13). This suction pipe has twu 
branch suction pipes, taking the water from the coolest part 
of the boiler. The water is discharged through h above tW 
tubes. The main feedpipe i and auxiliary feedpipe j ; 
both connected to the circulator (at a in Fig. 13). Fronf 
the foregoing it is seen that as long as the feed-pumpt 
are working this device will automatically improve thfr 
circulation. 

In order to improve the circulation while getting up steam, 
and also in order to heat the water in the boiler, a jet simiUC 
to that shown in Fig. 13 is sometimes placed at the junction 




§15 



MARINE-BOILER FEEDING 



29 



of the main and branch suction pipes, the jet pointing 
upwards into the main suction pipe. By means of a suitable 
pipe connection and valve, live steam from the donkey boiler 
or one of the main boilers can be turned into the jet, thus 
inducing a current of heated water to flow upwards. By 
means of this supplementary device, circulation can be kept 
up and improved when the feed-pumps are not working, or 
it can be used in conjunction with the circulator if desired. 




28. Many Scotch boilers are equipped with the so-called 
hydroklnoter, which is a circulation-improving device simi- 
lar to those previously described, and which is placed inside 
the boiler. It consists of several cone-shaped nozzles placed 
in line with one another; a jet of steam is admitted axially 
to the nozzles from a boiler in service, and this induces a 
current, the water flowing in through the large open end of 
the nozzles and out of the small part. The hydrokineter is 
used chiefly in getting up steam in a cold boiler, giving a 
forced circulation. 



Harine-boiler management 

MANAGEMENT WHEN STEAMING 
GETTING READY FOR SEA 



GENERAI. INSTRUCTIONS 

1. Examlnatlouof Rollers ami Fittings. — The Rules 

^nd Regulations of the United States Steamboat Inspection 
Service state as follows: "It shall be the duty of an engi- 
tieer. when he assumes charge of the boilers and machinery 
of a steamer, to forthwith thoroughly examine the same, 
and if he finds any part thereof in bad condition, caused by 
neglect or inattention on the part of his predecessor, he shall 
immediately report the facts to the local inspectors of the 
district, who shall thereupon investigate the matter; and if 
the former engineer has been culpably derelict of duty, they 
shall suspend or revoke his license." 

2. In making the required examination of the boilers, on 
assuming charge, the engineer should i;ispect them both 
internally and externally. Before entering a boiler that has 
just been opened, it should be tested for foul air by holding 
a lighted lamp or candle inside of it and noting the effect on 
the flame. If the flame burns brightly, it will be safe to 
enter the boiler; but if it burns dimly and finally goes out, 
the boiler should not be entered until it has been thoroughly 
ventilated. If the donkey boiler, or any other boiler on 
board, has steam in it at the time the examination is being 
made and there is a steam connection between it and the 

CopyrifhM b> /mlernalwital rr-iltmak Comtany. Enlrtcd at SlalKmrti' /<i.!l. Londn 



2 MARINE-BOILER MANAGEMENT §16 

boiler undergoing inspection, the stop-valve in that connec- 
tion should be tightly closed and secured so that it cannot 
be opened by mistake, thus preventing the possibility of 
scalding the man making the inspection. 

The principal defects to look for are bulges^ cracks, blisters, 
and thin and burnt places in the plates composing the heating 
surfaces. The first defect named is revealed by an ocular 
inspection; the others can be discovered easiest by tapping: 
the plates with a light hammer and listening for any differ- 
ence in sound. The seams, rivets, staybolts, and tubes 
should be examined for leaks. The stayrods should 
be calipered to ascertain if they have been reduced in 
thickness, to any great extent, by corrosion; their ends 
should be examined to see if they are properly secured. 
The fusible plugs should also receive atteption. The thick- 
ness of the scale on the tubes and on the plates composing 
the heating surfaces should be noted, and whether there are 
any large flakes of rust peeling off them; also, note if there 
is much mud or other sediment in the boilers. Examine the 
crown bars. Look at all openings to pipes, gauges, safety 
valves, etc. to see that they are clear. Look the dry pipe 
over and see that the perforations or slits are clear. Examine 
the zinc protectors and see that they are properly placed 
and connected, and that the baskets are in good condition. 
Look very carefully for oil and grease on the heating sur- 
faces, especially on the crown sheets and the top sheets of 
the combustion chambers; if any is found, be sure to have it 
removed before the boiler is closed up. Before coming out 
of the boiler, look for lamps, oil cans, bunches of waste, 
tools, and other foreign matter liable to be left there by the 
workmen. 

After completing the examination in the steam and water 
space, the heat space should be entered and inspected with 
the same degree of care and thoroughness that was given to 
the water space and steam space. Such defects as bulges, 
cracks, blisters, thin and burnt places in the plates, and leaks 
in seams, rivets, staybolts, and tubes can best be detected 
from the fire side of the plates. Leaks will generally be 



H6 



MARINE-BOILER MANAGEMENT 



revealed by having more or less salt or rust around them, 
or by bare spots where the soot has been b!own away by 
jets of steam or water squirting through the leaks. The 
crown sheets and the back sheets of the combustion chambers 
should receive special attention, as it is on these sheets 
that the flames impinge, and no part of a boiler is exposed 
to more intense beat and greater strains. While inside the 
heat spaces, examine the bridge walls, grate-bar beams and 
their lugs, and also the dead plates, The exteriors of the 
boilers and front connections should now receive attention. 
Examine the boiler coverings and note if there are any leaks 
in. or rusty spots on. the shells. Look over all the pipes 
thai are connected to the boilers, especially the feedpipes, 
back to the source of the feedwater supply, inclusive of the 
feed-pump and all cocks and valves in the feedpipes, as well 
as those in all the other pipes. Try the dampers, safety 
valves, gauge-cocks, cocks in glass water gauge, and water- 
column connections. Examine the salinometer pots and con- 
necting pipes; also, all drain pipes, and try their cocks. 

If any defects are found during the examination, they 
should be remedied at once; and if the boilers require 
cleaning and scaling, there should be no delay in having 
these operations performed. If any rusty places are found on 
the shell of the boilers, the rust should be scraped off and 
the bare spots painted with red-lead paint. Pack all valve 
stems that need it; in fact, put everything in good order so 
as to be in readiness to raise steam whenever required to do so. 

3. Flreroom Force. — On an ocean steamer, the fire- 
m force consists of the water tenders, firemen, and coal 

issers. There is usually one fireman and one coal passer 
to every 100 or 125 square feet of grate surface in the boilers. 
In the United States Navy, the men on duty in the fireroom 
are under the immediate chaige of the water tender, who 
also regulates the feedwater supply, the steam pressure, etc. 
In the merchant service, these duties are usually performed 
by an engineer; and on small vessels, the engineer of the 

ratch attends to them. The fireroom force is usually divided 




4 MARINE-BOILER MANAGEMENT §16 

into three divisions, called ^^atches, each division taking its 
turn and being on duty 4 hours and off duty 8 hours. This 
rotation goes on continuously day and night while the vessel 
is und.er way. In vessels plying regularly between ports 
only a short distance apart, there are often but two watches, 
of 6 hours each; and in vessels making very short runs, there 
is usually but one watch. 

4. Coaling: Ship. — Before taking in coal, the bunkers 
should be examined; and if any of the braces have been 
removed to facilitate taking out coal during the last run they 
should be replaced; all rubbish should be removed from the 
bunkers and the doors closed. On vessels in which coaling 
ports are not provided, the scuttle plates on deck should be 
taken off and the chutes rigged. The required number of 
shovels, slice bars, coal mauis, and bunker lamps for stowing 
the bunkers should be sent on deck; also, if considered 
necessary, a weighing scale for weighing the coal. A com- 
petent man should be detailed to run the winch, and other 
men to tally ^ that is, count, the tubs or baskets of coal as 
they come on board. Men should also be detailed to stow 
the coal and trim the bunkers. After the coaling has com- 
menced, a sufficient number of tubs or baskets of coal should 
be weighed to get their average net weight, and after the 
coaling has been completed the number of tubs or baskets of 
coal put into the bunkers multiplied by their average net 
weight will give the total amount of coal received. When 
the bunkers are nearly full, the stowing of the coal should be 
carefully attended to, so that there will be no empty spaces 
left in the bunkers. After the bunkers are filled, the chutes 
are unrigged and stowed away, the scuttle plates put on, the 
shovels and other tools are collected and sent below. The 
winch engine is wiped off and drained, and the cover put on, 
if one is provided. 

GETTING UP STEAM 

5. General Preparations. — Clean off manhole and 
handhole cover-plates and their seats and renew gaskets 
wherever necessary. Replace the grate bars. See that the 



MARINE-BOILER MANAGEMENT 

blow-off cocks, the drain cocks, and valves in pumping-out 
pipes are closed. Ease off the main and auxiliary stop- 
valves and seat them gentlj-. Open cocks in connections to 
water columns, glass water gauges, and steam gauges. 
Close cocks in the pipes to the salinometer pots. Open feed 
stop-valves. Remove smokestack hood. Slack off the 
smokestack guys. Open the damper. Examine the valves 
of the auxiliary feed-pump, and overhaul the putnp if it 
requires it. Try the ash hoist. 

6. Closing Boilers. — When the engineer of the watch 
receives orders to get up steam, he immediately summons to 
the fireroom the division of men whose turn it is to go on 
watch and assigns to each fireman the furnaces he is to take 
care of and details a coal passer to supply him with coal. 

On the arrival of the men in the fireroom, they proceed at 
once to close up the boilers by putting on the manhole and 
handhole cover-plates, A thin coaling of black lead (graph- 
ite) and tallow mixed together should be spread over the 
gaskets if they are of sheet rubber or asbestos. If corru- 
gated copper gaskets are used, the black lead and tallow 
may be dispensed with. 

T, FIllliiK Boilers. ^If the vessel is lying in fresh and 
pure water, it is only necessary to open the bottom blow 
cocks and let the water flow in to its proper level from over- 
board, the safety valves" having previously been opened to 
permit the escape of air as the water flows in, Should the 
boilers be so located in the vessel that the water from over- 
board will not rise to the required level, the amount lacking 
must be pumped into them. If the vessel is lying in impure, 
very muddy, or salt water, the boilers should be filled from 
some other source. If the vessel is lying at a wharf, the 
boilers may be filled by a hose attached to the water pipes on 
shore. If the boilers are not fitted with nozzles for the pur- 
pose of attaching the hose, the upper manhole plate of each 
boiler should be left off and the hose inserted through the 
manholes. If the vessel is lying in the stream, it will be 
necessary to get the water supply from a water boat. 



6 MARINE-BOILER MANAGEMENT §16 

8. starting: Fires. — While the water is running into the 
boilers, the furnaces may be charged. The rear halves of 
the grates are covered with a thin layer of coal and the front 
halves with split cord wood. Some of the wood should be 
broken into kindling, which is placed under and amongst the 
front ends of the sticks of cord wood just inside the furnace 
doors; then a bunch of oily waste, or shavings, if any are on 
hand, is put amongst the kindling and ignited. When the 
wood is burning freely, coal is thrown on top of the wood, a 
little at a time. By the time the wood is all consumed, there 
will be thin beds of live coals all over the grates. The fires 
are then built up gradually by throwing thin layers of coal 
on top of the burning coal until the fuel bed reaches the 
required thickness. 

9. RaisiiiK Steam. — When getting up steam, the fires 
should not be forced, but should be allowed to burn up grad- 
ually, thus giving the boiler an opportunity to expand more 
uniformly under the influence of the increasing heat. By 
forcing the fires, the plates or tubes that are nearest the fires 
are subjected to extreme expansion, while those parts that 
are remote from the fire are still cold; under such conditions, 
the seams and rivets, and also the tube ends, are liable to be 
severely strained, and possibly permanently injured. 

It is not desirable to raise steam in an internally fired 
fire-tube marine boiler in less than from 3 to 5 hours, 
while from 7 to 9 hours, and even more, would be better. 
Externally fired fire- tube boilers are not subjected to the 
strains due to expansion to such an excessive degree as 
the internally fired type, and water- tube boilers are still less 
affected by unequal expansion- and contraction; therefore 
steam may be raised in such boilers without serious injury 
in less time than in internally fired boilers. 

Assuming that the pressure at which the boilers are to 
operate has been reached, before connecting them with the 
engine, all the cocks and valves should be tried under pres- 
sure. The safety valves should be raised for a moment and 
their action noted; the water columns should be blown 



5 16 MARINE-BOILER MANAGEMENT 7 

through and tbe gauge-cocks tested; the feed stop-valves 
should be opened and the feed-apparatus tried; and it should 
be particularly noted whether the check-valves seat properly. 
The blow-oflE cocks should also be tried and their condition 
Doted. Everything being found in good condition, the 
boilers will be ready for service, 

lO. Smokestacb: Uuys. — While in port, the smoke- 
stack guys may either be cast off at their lower ends and 
the slack coiled down on the fireroom-hatch gratings near 
the pipe, or they may be kept in their places and hauled 
taut. If the latter method is practiced, the guys should be 
slacked off before getting up steam, and in either case, after 
the smokestack has expanded to its full height, the guys 
should be hauled taut and the ends firmly secured, so that 
they will support the smokestack when the ship rolls and 
pitches at sea. 

LEAVING PORT, AT SEA, ANJJ COMING TO 

li — 

^^H GETTING UNDEB WAT 

l'^^. When the signal to get ready to start the engines is 
received in the engine room, the boiler attendant should 
be notified at once; he should then immediately open the 
damper, if closed, close the furnace door and connection 
doors, if any of them are open, and if the boilers are fitted 
with lever safety valves, and they are open, he should close 
them. The stop-valves in the main feedpipes should now be 
opened and those on the auxiliary feedpipes closed. When 
the steam pressure in the various boilers has risen to wi 
aay, 10 pounds of the usual working pressure, the boilers 
are connected by opening their stop-valves. Before connect- 
ing, great care must be exercised to have the steam pres- 
sures in the several boilers practically equal. The stop- 
valves, in fact any valve that is subjected to great pressure, 
should be opened very slowly to prevent too sudden a 
change in the temperature and expansion of the piping 
through which tbe steam flows, and to prevent ujolet 




8 MARINE-BOILER MANAGEMENT §16 

hammer. The latter is caused by larg^e bodies of condensed 
steam being driven violently forwards by the out-nishing 
steam, due to opening a valve too quickly. Water hammer 
is liable to prove disastrous to the piping, the heavy blow 
due to the momentum of the body of condensed steam mov- 
ing with high velocity being likely to cause a leaking of the 
joints, if not a bursting of the pipe. To prevent the accumula- 
tion of water, the steam-pipe drains should be kept open mitil 
the pipe is thoroughly warmed up; that is, until nothing but 
steam issues from the drains. In large vessels, with many 
boilers and long steam mains, it requires considerable time 
to thoroughly warm these pipes by a slow circulation of 
steam, and not until then should the boiler stop- valves be 
opened wide. 

It is the practice of some engineers to open the main 
stop-valve entirely before warming up the steam piping; 
others warm up the piping as far as the main stop-valve and 
fully connect the boilers before, very slowly and by degrees, 
opening the main stop-valve. In the latter case, this valve 
should be very slightly moved from its seat before the boiler 
stop-valves are opened, in order that expansion may not 
jam it so hard that it cannot be opened. Neither practice 
possesses any great advantage over the other. 

As soon as the steam pressure at the throttle has risen to 
the desired point, the engineer will commence to warm up the 
engines. Care must be exercised in the boiler room not to 
let the steam pressure run up high enough to lift the safety 
valves; this involves a careful watching of the steam gauges 
and subsequent regulation of the fires, checking a too rapid 
steam generation by putting the ash-pit dampers in place, 
.by the main damper, and, as a last resort, by opening the 
furnace doors and finally the front-connection doors. 



WORKING THE FIRES 

12. The fuel bed should be kept at an even thickness. 
As a general rule, this should be about 8 or 10 inches, though 
this thickness may have to be varied to suit the different 
kinds and grades of coal used and the intensity of the draft. 



SlG MARINE-BOILER MANAGEMENT 9 

The surface of the fire shouid be kept level and only enough 
coal should be put on at one lime to fairly but thinly cover 
the entire surface of the glowing coals. No lumps of coal 
larger than a man's fist should be put on a fire if the best 
results are expected. Care should be taken to prevent holes 
being burned in the fuel bed. If there are any thin spots in 
the fire or if the surface is uneven it should be leveled off 
before coaling. 

13. After a fire has been burning a certain length of 
time, it will require cleaning, as all varieties of coal contain 
more or less clinker-making material. The time and method 
of cleaning a fire depend principally on the nature of the 
fuel used and the rapidity with which it is consumed. 

14. When a fire is permitted, by carelessness or other- 
wise, to get so low that it will no longer make steam, the 
best way to build it up is to draw all the live coals to the front 
end of the furnace, haul out all ashes, clinhers, and dead 
coal, and cover the grate bars back of the live coals with 
fresh coal. If soft coal is used, the fire will soon work its 
way back through the fresh coal and ignite it; but if anthra- 
cite is used there will be more difficulty experienced in build- 
ing up a low fire. If an anthracite fire should get very low, 
the best method is to haul it and start a new fire with wood, 
or with live coals from one of the other fires. It is useless 
to throw wood on top of a nearly burned-out anthracite fire, 
as that course will make matters worse. 

15. The best course to pursue to hold the steam pres- 
sure in check when the engines are stopped temporarily is to 
close the damper and ash-pit doors. If the pressure still 
continues to rise, the bleeder may be used to work off the. 
surplus steam. The bleeder is a pipe of fairly large size 
connecting the main steam pipe directly with the condenser, 
permitting the surplus steam to be condensed, and also pre- 
venting the noise that the safety valves would make when 
discharging. This pipe is generally fitted in naval vessels, 
where condensers with independent air pumps and circulating 
pumps are the rule. If the stoppage of the engines is 



10 MARINB-BOILER MANAGEMENT §16 

prolonged beyond a few minutes some of the fires may be 
pushed back from the front, uncovering the grates for a short 
distance, thus checking the formation of steam. The following 
should be avoided, if possible, as they are all objectionable or 
detrimental to the boilers: blowing off with the safety valves; 
pumping in'cold water and blowing with the blow-off cocks; 
opening the furnace doors and connection doors. When the 
engines are started again, the damper should be opened, 
the bleeder shut off, and if the fires have been pushed back, 
they should be spread out again as quickly as possible. 

16. It is necessary to systematically remove the ashes 
from the ash-pits and to dispose of them, as well as of the 
refuse drawn from the furnaces in cleaning fires, in a suitable 
manner. In vessels where the fireroom force is divided into 
watches, it is the usual custom to clear the ash-pits and fire- 
rooms of all ashes and clinkers near the end of each watch. 
When the ashes have to be hoisted from the fireroom, they 
are usually wetted down to prevent excessive dust. In wet- 
ting down ashes, they should not be deluged with water from 
a hose or buckets, on account of the cloud of fine ashes that 
arises when so treated, which afterwards settles on every- 
thing within its reach. The proper way to wet down ashes 
is by means of a spray nozzle on the ash hose. If the vessel 
is provided with an ash ejector, the ashes may be ejected 
overboard whenever convenient to do so, and much ti'ouble 
and annoyance may thereby be obviated. 

17. In ships navigating the high seas, ashes are dis- 
posed of by throwing them overboard; in harbor and river 
navigation, regulations generally prohibit the throwing over- 
board of ashes and other refuse. Ashes must then be collected 
in suitable iron cans and removed from the ship at suitable 
intervals by ash and garbage collectors, who dispose of them in 
such a manner as the municipal or other regulations demand. 
As this service must be paid for, it is the practice in ships 
navigating the high seas to throw overboard all ashes and 
other refuse just before entering the harbor limits, thereby 
reducing the expense of ash and garbage removal. 



I IG MARINE-BOILER MANAGEMENT 11 

L PRIMING AMD FOAMING 

^Pw> Priming. — Priming in a steam boiler is analogous 
S'the boiling over of tbe water in a teakettle. On the appli- 
cation of intense heat, the water in contact with the bottom 
af the kettle or the heating surfaces of a steam boiler will be 
rapidly converted into steam, which will rise to the surface 
with considerable force, carrying the water with it until it 
averflows the kettle, or, in the case of a boiler, carrying the 
water into the steam pipe and thence into the engine cylin- 
ders, where it is liable to do considerable damage if it is not 
checked in time. There are several causes for priming, of 
which tbe most common are the following: (!) insufficient 
boiler power; (2) defective design of [he boiler; (3) water 
level carried too high; (4) irregular firing; (5) sudden open- 
ing of stop-valves. 

When the boiler power is insufficient, the boilers must be 
forced in order to furnish enough steam for the engine, and, 
consequently, the sleam bubbles will rise through the water 
with such speed that they will carry particles of water with 
them by friction and cohesion. Tbe best remedy for this 
cause of priming is to install larger boilers or more of them; 
[he nest best course to pursue is to put in a steam separator, 
which, obviously, will only prevent the entrained water from 
reaching the engines; it will not stop the priming. 

Defective design in boilers generally consists of too smalt 
steam space, or of an imperfect arrangement of tubes, which 
may be spaced so close together in an effort to obtain greater 
healing surface as to seriously interfere with the circulation 
of the water. In some cases, a small steam space can be 
increased by the addition of a steam drum; or the top row of 
tubes may be taken out to advantage, which will admit of 
carrying a lower water level and thus increase the steam 
space. Defective water circulation is difficult to detect and 
to remedy; it may be due to too close spacing of the tubes, 
a marked improvement having occasionally been effected by 
the removal of one or two vertical rows of tubes. Thin 
sbeel-iron plates are sometimes fitted in Scotch builers in 




12 MARINE-BOILER MANAGEMENT §16 

such a position that the upward and downward currents of 
water cannot interfere with each other. Mechanical circu- 
lators are now largely appHed to marine boilers with benefi- 
cial results. 

The remedy for too high a water level is obvious— carry 
the water at a lower level. With irregular firing, especially 
when the draft is strong, the rate of evaporation will be so 
high at times that the steam bubbles will rise at such speed 
as to carry the water with them, just as in the case of insuffi- 
cient boiler power. 

The sudden opening of a stop-valve or the throttle valve 
causes a momentary local lowering of the pressure near the 
steam outlet of the boiler; consequently, some of the water 
in the other parts of the boiler will, by the greater pressure, 
be thrown toward the outlet and mix with the steam that is 
rushing from the boiler. 

19. Priming manifests itself by a peculiar cracking 
sound in the cylinders of the engines, due to the water 
being thrown violently against the heads. In cases of very 
violent priming, the water will rise several inches in the 
glass gauge, thus showing a false water level. Wheii priming 
takes place, one method of checking it temporarily is as fol- 
lows: Close the damper and ash-pit doors, thereby checking 
the fires until the water has quieted down. The throttle or 
the maim stop-valve should also be partly closed to check the 
onrush of water from the boilers and also to increase the 
pressure on the surface of the water, which tends to keep it 
from rising. After the priming is checked, observe if the 
water level drops in the glass water gauge, as it probably 
will; if it does, more feedwater will be required. To prevent 
damage to the engines, the drains in the steam pipe and 
cylinders should be opened. Regular and even firing tends 
to prevent priming by maintaining a steady pressure. Pri- 
ming may also be produced by the main steam pipe being 
attached to the boiler too close to the water surface, or the 
absence of a dry pipe may offer an inducement for water to 
enter the steam pipe. 



§16 MARINE-nOILRR MANAGEMENT 13 

20. FunmliiK- — The chatiging of a body of water, vary- 
ing in depth, at the normal steaming level of a boiler into 
foam is called foutnlnjf- This phenomenon shows itself in 
the water gauge glass by a violent and abnormal agitation 
and the absence of a well-defined water-line. It is extremely 
difficult to draw a sharp line of demarkation between foaming 
and priming, as the causes that produce priming may also 
produce foaming, and the same remedies will stop it in most 
cases. Foaming, may, however be caused by an excess of 
soda introduced in the boiler, by dirty or greasy water, and 
also by running from salt to fresh water, or vice versa, pro- 
vided that the make-up feedwater is taken from overboard. 
If the engines are suddenly stopped while the boilers are 
foaming, the safety valves or bleeder should be immediately 
opened so as to keep the water foaming, otherwise, when the 
water level falls, some portions of heating surfaces may be 
uncovered and burnt. When foaming is caused by dirty or 
greasy water, much of the dirt and grease may be got rid of 

_l)y blowing it out through the surface blow. 

K GENERAI. BOILEIt MANAUEMENT AT SEA 

21. Feedwater Kef; n la t Ion. — Each marine boiler is 
supplied with feed check-valves and feed stop-valves for the 
main feed and for the auxiliary. As a general rule, the 
chegk-valves are of the adjustable-lift type; in that case, 
the amount of water entering each boiler is regulated by 
varying the lift of the check-valve. If the check-valves are 
non-adjustable, the feed stop-valve is used for regulating the 
water supply. In practically all sea-going vessels, feed- 
pumps are run so as to keep the water level in the hotwell 
constant, and consequently they deliver practically the cor- 
rect quantity of water required for the boilers. This fact 
permits the water tender to so adjust, by trial, the feed-valves 
that the water level in all the boilers will remain practically 
constant. When the water level in al! the boilers is gradu- 
ally dropping while that in the hotwell remains constant, it 
shows the need of additional feedwater, which is taken from 




14 MARINE-BOILER MANAGEMENT §!« 

the salt feed, fresh-water tanks, or evaporator, accordine to 

circumstances. A gradual rising of the water level in all 
the boilers indicates that an undue quantity of water is enlei- 
ing the hotwell, most likely through the salt feed being 
partly open, or through burst condenser tubes. 

22. Saturation Reg:iilatlon. — With surface condensing 
engines in perfect order, very little, if any, salt water need 
ever enter the boilers, if the ship is fitted with an evaporatot 
or ample fresh-water tanks. In this case, there is little need 
of testing the saturation of the water in the boiiers more 
than once or perhaps twice a day, as at least once every 
four hours the engineer on watch should test, by tasting, the 
water in the hotwell to discover if any sea-water reaches 
the steam side of the condenser. When this is found to be 
the case, and it cannot be remedied before reaching port, the 
saturation will have to be tested quite frequently to note the 
rate at which it increases and thus enable the engineer in 
charge to determine whether blowing off will have to be 
resorted to before making port. Generally speaking, it is 
not necessary to blow off until the saturation reaches ■^ or 'A- 
In blowing off, only a relatively small amount of water can 
be blown off at a time, as the water level must not fall below 
the highest point in contact with the gases of combustion; 
the water level must then be restored by pumping, and the 
process of blowing off and pumping ts repeated until the 
saturation has been sufficiently lowered. The greatest vigi- 
lance must be exercised by the person having charge of the 
blowing off to see that the blow-off cocks are fully clo) 
after each blowing down. 

23. Trlinnilns Ventilators. — Ventilators are provti 
on board ship for the double purpose of conveying 
furnaces and ventilating the fireroom, and it is imporl 
that they should be kept trimmed to the wind, while runnin^r 
to supply the necessary amount of air. The tops or cowls 
of ventilators are made so that they may be turned toward 
the direction from which the wind is blowing, and they caa 
usually be operated from the fireroom. If the vessel chanj 



i 

mtr ■ 




Sl6 



MARINE-BOILER MANAGEMENT 



15 



its course or the wind shifts, the cowles are turned so that 
the wind will blow into them. 

24. Fln<lln)e Water Level. — The only safe and reliable 
method of testiny the height of the water in a boiler is by 
means of the gauge-cocks. The glass gauge is merely a 
convenience, and it is not intended that it should be depended 
on exclusively, as it is very liable to become stopped up with 
dirt or scale and thereby show a false water level in the boiler. 
The glass gauges should be blown through frequently and 
their use should be supplemented by the frequent opening 
of the gauge-cocks. 

25. Care of Safety Valves. — To test the freedom of 
working of safety valves, they should be lifted by means of 
the hand gear at least once a day. Should any safety valve 
be found to be stuck fast, the boiler to which it is attached 
should at once be cut out of service and the repairs made, 
unless the boiler is fitted with a second safety valve of suffi- 
cient capacity and in good order, in which case repairs can 
usually be deferred until the vessel reaches pqrt. 

Safety valves will occasionally leak, and thus waste fresh 
water, through a chip of scale or some Other foreign sub- 
stance lodging on the valve seal. This can usually be dis- 
lodged by lifting the valve, when the steam will blow the 
obstruction away. A leaky safety valve should be repaired 
by scraping and grinding at the earliest opportunity, as it not 
only wastes steam, which means fresh water, but is also a 
great annoyance owing to the noise it causes. 

26. Care of Coal Bunkers. — A careful watch should 
be kept on the temperature of the coal bunkers. Coals that 
contain sulphur, especially when wet, are very liable to ignite 
from spontaneous combustion. If the temperature of a 
bunker should rise suddenly, it is an indication that spon- 
taneous combustion is in progress, and the bimker should be 
carefully examined. If the coal is found to be on fire, it 
may be extinguished by the fire apparatus, or by steam, if 
pipes are fitted for that purpose, as is the case on board 
modem seagoing vessels. Coal bunkers should be ventilated 



16 MARINE-BOILER MANAGEMENT §16 

whenever the weather conditions on deck will admit of this 
being done without getting water into the bunkers. Wet 
coal should never be stowed in a ship's bunkers. Bituminous 
and semibituminous coals are more susceptible to spon- 
taneous combustion than is anthracite. 

27. Ijow Water in Boilers. — There is no more impor- 
tant duty connected with the management of boilers than to 
guard against letting the water get dangerously low in any of 
the boilers. The principal causes of low water in boilers arc: 
insufficient feedwater, priming, leaky boilers, improper regiF 
lation of the check-valves, irregular firing, and sudden stop- 
ping of the engines. 

Insufficient feedwater is the result of shortness in the supply 
of make-up feedwater, and the remedy is to increase that 
supply, whether it be from overboard, from tanks, or from 
an evaporator. 

Low water caused by priming is the result of the water 
being carried over into the engines, the remedy being to 
check the priming and increase the feed. 

Leaks in boilers may cause low water if they are numerous 
or extensive. When low water results from this cause, put 
on all the feed that is necessary to keep the water in sight in 
the glass gauge, and stop the leaks at the earliest oppor- 
tunity. 

If the check-valves are not properly adjusted, obviously 
the remedy is to regulate them so that each boiler will get 
the amount of water that it requires. 

Irregular firing will cause a boiler to require more feed- 
water at one time than another; this will necessitate frequent 
adjustment of the check-valves, which if not carefully attended 
to will result in that boiler getting too much feedwater at one 
time and not enough at another time. 

When the main engines are running at full speed, the water 
level in the boilers is usually higher than when the engines 
are at rest; and when the engines are suddenly stopped, the 
water-line almost instantly falls to its true level, which may 
be below the gauge cocks. When this occurs, the safety 



Slti MARINE-BOILER MANAGEMENT 17 

valve or bleeder, or both if necessary, should be opened so 
as to keep the water lifting until the water level is pumped 
up above the danger point. 

When the water level in a boiler drops below the gauge 
cocks or out of sight in the gauge glass, its exact location is 
unknown. Some portion of the heating surface may be 
uncovered and become very hot. If auch be the case, it will 
be unsafe to put on the feed, as thai act might result in the 
explosion of the boiler; the fires should be deadened as 
quickly as possible by throwing wet ashes or fresh coal on 
them, the boiler cut out of service, and then allowed to cool. 
The fires may be hauled after they have been thoroughly 
deadened. After the boiler is cool enough to be entered, a 
thorough examination should be made of it, noticing partic- 
ularly the high parts of the heating surface. If the boiler is 
not seriously damaged, the fires may be started again, steam 
raised, and the boiler put into service. Bui if any serious 
injury, such as the cracking or burning of any of the plates, 
has been sustained, the boiler must remain out of service 
until it is repaired. 

28. Importance of Carryinff a Uolfornx Pressure. 

In order to obtain the best results from the engines and 
boilers for the amount of coai burned, it is necessary that 
the engines he kept running at a steady speed. This requires 
a uniform pressure, which can be maintained only by regular 
firing and a steady, continuous feed. A certain proportion 
of the fires should be kept in the best possible condition to 
make steam while the other fires are being worked. Two 
fires in the same boiler should not be worked at the same 
time. A routine of firing, or a system of working the fires 
by which, each fire will be worked at regular intervals in its 
lum, should be inaugurated. 

29. SweeploK Tubes While Under Way.— When the 
coal used is very fine and dry and of a variety that does not 
coke, large quantities of soot and coal dust collect in the 
lubes of fire-tuhe boilers, which reduce the draft area, 
thereby affecting the draft unfavorably. Besides, soot is a 



IS 



MARINE-BOILER MANAGEMENT 



SUl 



non-conductor of heat, and a coating of it on the heating ' 
surfaces of a boiler will retard the passage of the heat tDic 
the water and permit a large part of the heat to escape uf 
the smokestack and thus be lost. When this occurs, 
necessary to sweep the soot out of the tubes to get the best ' 
results for the coal burned. The method usually employed 
in sweeping the tubes is to use the sUam tube cleaner, which 
consists of a length of steam hose one inch or more in 
diameter, one end of which is attached to any conveniem 
steam connection, with a nozzle on the other end. The notilt _ 
is inserted into the front end of the tube and the steam turn 
on, the jet of steam blowing the soot into the back c 
tions. If the soot has become incrusted in the tubes, a :i 
lube hrush or a lube scraper will be required to remove it. As 
the connection doors must be open while sweeping tubes, the 
operation should be performed as quickly as possible and the 
doors then closed. Only one nest of tubes should be swept 
at a time. 



I 



30. Cutting Out a Boiler. — Emergencies frequently 
arise whereby it is necessary to quickly cut a boiler out of 
service for the purpose of making temporary repairs, or to 
prevent damage or interference in working the fires from 
escaping steam or scalding water. Such casualties, for 
instance, as the collapsing of a tube, the blowing out of »^ 
manhole or handhole gasket, or a serious leak developia 
anywhere about a boiler will necessitate such a cours 
When it becomes necessary to cut out a disabled boiler. 1 
fires should be quickly covered with wet ashes and the stei 
worked oflE by the engines until the pressure commences | 
fall; then the stop-valve of the disabled boiler should I 
closed and its safety valve opened. When the pressure has 
fallen to a point considerably below the normal, the fires 
may be hauled, care being taken that enough pressure is 
retained to blow the water level below the leak, in case it 
should be necessary to do so. If the leak is below the 
norma! water level, the feed should be kept on full until^ 
after the fires are hauled so that the heating surfaces will l 




§16 MARINE-BOILER MANAGEMENT 19 

protected while hauling the fires; then shut off the feed and 
open the bottom blow cock and blow the water level below 
the leak. After the boiler has cooled sufficiently proceed 
to repair the leak. If the boilers are filled with dumping 
grates, the fires may be dropped into the ash-pits instead of 
being covered with ashes; or if the furnaces are provided 
with spray nozzles, they may, in case of a great emergency, 
be used for extinguishing the fires. 

31. Malu Feed-Piinip Broken Dow^n. — Should the 
main feed-pump become inoperative, one or more of the 
auxiliary pumps should be immediately put into operation 
to supply the boilers with water. The main feed-pump 
should then be examined to ascertain the trouble. It may 
be that a valve is caught up or broken; the piston or 
plunger packing may be blown out, or leaking to such an 
extent that the pump can neither take nor throw water. 
The feedwater may be so hot that vapor has been formed 
in the pump barrel and prevents the water flowing into it. 
If the derangement is in the valves, they should be repaired 
or new ones inserted. If the piston or plunger packing is 
the cause of the trouble, it should be renewed. If the feed- 
water is too hot, its temperature should be lowered by giving 
the condenser more injection water, 

32. BeltevlDK Wiitcht's. — The men on duty at a given 
time in the fireroom and engine room, that is, the watch, are 
changed every four or six hours, as a general rule. The 
watch coming on duty to relieve the outgoing watch must 
not only be prompt, but must also be satisfied by proper and 
careful examination that the fires, ash-pits. etc. are all right, 
that the boilers contain plenty of water, that the feed check- 
valves are not stuck, that the steam pressure is not unduly 
low, that no blow-off cock has been left partly open, that all 
ashes have been disposed of, etc. before relieving. Whoever 
is in charge of the incoming fireroom watch must bear in mind 
that by relieving the outgoing watch he at once assumes 
full and undivided responsibility for all existing conditions 
in his department, and cannot shift this responsibility by 




20 MARINE-BOILER MANAGEMENT §16 

the plea of lack of knowledge. He is supposed not to 
assume responsibility until he knows that everything is in 
good and proper condition, and to refuse to relieve until 
matters that are wrong have been righted. 



COMING TO 

33. As a vessel approaches her port of destination, the 
fires should be allowed to burn down gradually, so that 
they will be nearly burned out by the time the vessel is 
secured to the dock or at anchor. The object of this is to 
save coal and to obviate the waste and noise of blowing ofi 
the surplus steam through the safety valves; it also saves 
the labor of hauling or banking heavy fires. The exact time 
to stop firing depends on the kind and quality of the coal 
burned, the type of boilers used, and a knowledge of the 
harbor, or on definite information as to the time the vessel 
will be brought to. Even then good judgment is essential, 
else the fires may burn out before the vessel is secured, 
which might result disastrously in a harbor crowded with 
shipping or on encountering an unusually strong ebb tide. 

34. As the fires burn down, the steam pressure should 
also be allowed to drop considerably below the normal, but 
not below the point required to work the engines properly. 
The object of this is to keep the steam pressure under con- 
trol and obviate blowing off steam through the safety valves 
or opening the furnace doors and connection doors while the 
engines are being worked to signals. If the pressure should 
rise to the blowing-off point, the excess of steam may be 
disposed of by using the bleeder. When the signal to. slow 
down the engines is received from deck, the blowers should 
be stopped, if forced draft is used, and the damper closed. 
If the pressure has been allowed to fall sufficiently, nothing 
else need be done for the time being but to stand by for the 
next signal from deck. This will probably be to stop the 
engines, followed by a series of signals to back, stop, and go- 
ahead, which is called workinj3^ the engines to sigyiais, and 
is for the purpose of bringing the ship to her berth. During 



§16 MARINE-BOILER MANAGEMENT 21 

this time the blowers, damper, feed stop-valve, and bleeder 
should be operated as circumstances require, for which no set 
roles can be laid down, as the conditions will vary with each 
case. The main object is to keep the pressure under control 
and avoid blowing oil steam or opening the furnace and con- 
nection doors if possible, but should the necessity of doing 
so arise there should he no hesitancy in resorting to these 
methods of reducing the pressure. 

35. If one of the main boilers is to be used as the donkey 
boiler, the fires should be kept in it, and, after the ship has 
been secured, all communication between it and the other 
boilers should be closed, and the auxiliary steam and feed- 
systems to it should be opened. If the vessel is provided 
with a separate donkey boiler, the fire may be started in it 
with live coals from the main boilers, 

36. After the vessel is secured in her berth, the notifi- 
cation "through with the engines" will be received from 
deck. The engineer of the watch will then give orders as to 
what shall be done with the fires^whether hauled, banked, 
or allowed to die out. Hauling fires is not good practice, as 
it allows the boilers to cool down too rapidly; the modem 
and best method is to let the fires die out. This is done 
by closing all the doors and the damper for the purpose of 
excluding the air from the fires. The common practice is 
to keep the boilers closed until the next morning after com- 
ing to, when they will be cool enough to enter for the pur- 
pose of cleaning them. While the boilers are being closed 
up, the boiler stop-valves should be closed, also the feed 
stop-valves, the steam should be shut off the steering engine, 
and the drain cocks on the shut-off steam pipes opened. 

If the vessel is to remain in port a few hours only, the 
fires are usually banked. In this case, the boiler slop-valves 
are allowed to remain open, but the main-engine stop-valves 
■ are closed, 

37. If the boilers require examination and subsequent 
overhauling they must be emptied by blowing down or other- 
wise. The method of procedure depends on the location of 



82 MARINE-BOILER MANAGEMENT §16 

the boilers, the time the vessel will be in port, and the facil- 
ities provided for emptying the boilers. 

If conditions permit, it is best to allow the boilers to cool 
down and to pump the water from them, if located below the 
water-line of the vessel, or to let the water run out through 
the bottom blow-off cocks if the boilers are located above the 
water-line, as is common in river steamboats. If this practice 
is adopted, none of the impurities in the boilers will be baked 
on the plates, tubes, etc. Either a manhole or handhole 
above the water-line of the boilers should be opened, or the 
safety valves should be blocked open, to admit air to the 
boilers, before attempting to empty them. 

When the boilers are located below the water-line of the 
vessel and cannot readily be pumped out, either for lack of 
time or facilities, they must be blown down under steam pres- 
sure. This should be allowed to fall to, say, 20 pounds per 
square inch, and the blow-off cocks opened gradually and not 
too much in order to keep down the vibrations of the hull 
caused by blowing the hot boiler water into the cold water 
surrounding the vessel. Care must be taken to close the 
blow-off cocks promptly when the boilers are empty. 



¥ 



MARINE-BOILER MANAGEMENT 



MANAGEMENT IN PORT 



CLEANING, OVERHAULING, AND LAYING UP 

CLEANING AND SCALING BOILEHS 

38. After a vessel has arrived in port, and as soon as 
Uie boilers have cooled ofE, the furnace doors, ash-pit doors, 
and connection doors are opened, the boilers are emptied by 
whatever method is most convenient, and the manhole and 
hanJhole cover-plates are taken ofT. The tubes are then 
swept, and the boilers cleaned out and scaled. The scale is 
removed by means of scaling hammers, steel scrapers, and 
chisel bars. Especial care should be taken not to force the 
edges of the chisel bars into the seams and thereby cause 
leaks. All grease should be carefully removed from the 
water side of the heating surfaces. After all the scale has 
been loosened and swept into the water bottoms, it may 
be drawn out through the lower handholes by a small long- 
handled hoe. A strong stream of water from a hose directed 
through the upper manhole of a boiler will assist very 
materially in dislodging loosened scale and dirt and washing 
them into the water bottom. The stream of water may 
then be directed into the water legs and water bottc 
wash them out. If any evidence of leaks is discovered 
during the process of cleaning and scaling, the location of 
the leaks should be marked with white chalk, so that they 
Itoay afterwards be readily found for calking. 

After the boilers have been cleaned, scaled, and washed 
out, the engineer in charge of the work should make a 
thorough inspection of them. It is assumed that he has 
Jcept a list of all defeirts that have developed during the last 
and it is now his duty to closely examine those defects 





24 MARINE-BOILER MANAGEMENT §16 

and determine how they shall be treated. After entering 
a boiler, the engineer should note if it has been properly 
cleaned and scaled; he should caliper the braces to ascertain 
if they have been thinned by corrosion to any extent; also, 
he should examine the ends of the braces or stayrods to ascer- 
tain if the fastenings are in good condition, tapping the 
braces lightly with a hammer to learn if any are loose. He 
should look at the gauge and other pipe-connection open- 
ings, and at the fusible plugs, examine the leaks that were 
marked with chalk while the boilers were being cleaned, 
and any other leaks that may be on his list, look through 
the tubes and examine the tube ends, inspect the dry pipe, look 
for blisters, bulges, and cracks in the plates and, if any are 
found, ascertain their extent and determine how they shall 
be treated. If any plates are found that show extensive cor- 
rosion, they should be drilled and their thickness measured. 
After the engineer has made a thorough inspection of all the 
boilers, he should at once commence work on the repairs. 



OVERHAULING 

39. Overhauling boilers consists principally of calking 
the leaks, reexpanding or renewing leaky, corroded, or split 
tubes, cutting out and renewing those rivets and staybolts 
that leak too much to be calked effectively, replacing soft 
patches by hard patches, and treating cracks, bulges, and 
blisters in plates, if any are found, according to the neces- 
sities of each case. After the repairs in the interiors of the 
boilers are completed, remove from the boilers all tools, 
lamps, pieces of waste, etc., and clean all oil and grease ofE 
the water side of the heating surfaces very thoroughly. 
Paint the exteriors of the boilers, if they require it, and 
repair the boiler coverings. Make new joints in pipes, 
and renew split pipes and pipe coverings wherever needed. 
Overhaul all cocks and valves in the fireroom and grind in 
or pack all those that leak. Examine and clean out all drain 
pipes. Clean off all manhole and handhole cover-plates 
and their seats and renew all defective gaskets. Repair 



bridge walls. Examine and renew all defective grate bars 
and bearing bars. Test liteam gauges if they have shown 
any derangement. After all these instructions have been 
carried out, the boilers may be reported ready for service. 

liATIMO UP BOILERS 

40. When a vessel is to be laid up for an indefinite 
length of time the boilers should receive the closest atten- 
tion, as no part of the equipment of a steam vessel will 
deteriorate more rapidly when not in use than the boilers, 
situated, as they are, in the hold of the vessel where, in 
laid-up ships, the atmosphere is always damp. If the boilers 
are not properly laid up and well cared for afterwards, it is 
very probable that they will be found to be so much corroded 
when the vessel is again put into commission that they will 
require exleusive repairs or else be entirely useless as steam 
generators, thus entailing great expense to repair or renew 
them and causing serious delay in the use of the vessel at a 
time when her services may be greatly needed. The tubes 
are particularly susceptible to deterioration when exposed to 
dampness. Under these conditions, they soon become pitted, 
and it is merely a question of time when they will become 
corroded through in places, which will necessitate an entire 
new set of tubes. The metal of the boilers in a laid-up 
vessel's hold is usually several degrees colder than the sur- 
rounding atmosphere, and if there is much moisture in the 
air, as there will be whenever the weather is damp, the 
boilers will sweat; that is, the moislure in the air will be 
condensed on the boiler plates in the form of beads or drops, 
which will trickle down the surfaces of the plates, leaving wet 
streaks, producing the best possible condition for corrosion. 

41. When a vessel is about to be laid up, two points 
regarding the boilers must be taken into consideration: 
whether the vessel is to be laid up with the intention of 
thoroughly overhauling and repairing her before putting her 
into active service again, or whether she has been over- 
hauled and repaired before being laid up. so as to be in 



I 






26 MARINE-BOILER MANAGEMENT §18 

readiness for immediate service when needed. In ihe firsl 
case, the boilers need to be simply cleaned of dirt and loose 
scale and ihorouehly dried inside and outside preparatory tc 
being laid up. The scale that adheres to the plates need no' 
be removed, as it will act, to a certain extent, as a protectior 
against corrosion. But in the second case, the boilers shoulc3 
be thoroughly cleaned, scaled, repaired, and paioted before 
being laid up. and greater care should be taken of thei 
afterwards, in order that they may be in the best possible 
condition when the vessel is put into active ser\'ice- 

43. Two methods of laying up boilers are practiced; 
namely, the dry method and the aW melhod. Which method 
to adopt will depend on the care that will be given the 
boilers while they are laid up; but whichever method ir' 
adopted they must be properly cared for, meanwhile, if Ihef 
are expected to escape the destructive effects of corrosimi' 
and be found in good condition when they are required fo 
service. Laying up the boilers properly will not alone b 
sufficient for their best preservation; they must be kepi 
under constant observation, and all deterioratioQ must bt 
checked as soon as discovered. 

43. The dry method of laying up boilers is to tboi^ 
oughly dry all parts of the boilers, particularly tbe i 
bottoms and water legs, before laying them up; and keqi 
them perfectly dry while they are laid up. To accomplisl 
this, all the manhole and handhole cover-plates should b< 
taken off to afford a circulation of air through the boilers^ 
and they should be examined at least once every day, par 
ticularly during damp weather, and if any moisture appeal 
on the plates, light fires of shavings should be started in t] 
furnaces and the tires kept up until all moisture has disap 
pcared. Or, better still, one or more large coal stovt 
should be set up in the fireroom and fires started in thai 
whenever any moisture appears on the plates. To carry oi 
this method properly, the furnace, connection, and asb-p 
doors and the damper should be opened and the smokesuc^ 
hood should either be taken off or else raised a short distant 



§J6 MARINE-BOILER MANAGEMENT 27 

3bove the top of the pipe, so that there will be a cirailation 
"^ Warm air through the fire sides of the boilers. As an 
^aditional precaution, the boilers should be occasionally 
'^Spected by an experienced marine engineer and his sug- 
gestions and recommendations in regard to their preserva- 
*^*on should be closely followed. The cost of carrying out 
*-his method of preserving the boilers of a laid-up vessel will 
be trifling compared with the loss by deterioration if they 
^re neglected. 

44. Another dry method of laying up a ship's boilers that 
is sometimes practiced is as follows: After the interiors of 
the boilers have been thoroughly dried, pans of chloride of 
lime are placed inside of the water spaces and the manhole 
and handhole cover-plates are put on to exclude the outside 
air. The chloride of lime, having a great affinity for the 
vapor of water, will attract and absorb the moisture from the 
air inside the boilers, and thus prevent it condensing on the 
plates. But this is only a half-way measure, so to speak, and 
it is not to be recommended, because the water sides of the 
plates only are protected, while their fire sides and the out- 
side surfaces of the shells are left to take care of themselves. 

45. The wet method of laying up boilers is as follows: 
After the boilers have been cleaned out, the manhole and 
handhole cover-plates are put on and screwed up water-tight; 
the stop-valves, and all other valves on the boilers, are lightly 
closed. The boilers are then entirely filled, up to the safety 
valves, with water, and they are thus allowed to remain until 
the vessel is again required for service. The idea underly- 
ing this method is that since the air is excluded from contact 
with the metal by the water, oxidation of the metal, that is, 
corrosion, is prevented. There are several very grave objec- 
tions to this method, however. In the first place, the sur- 
faces of the steam spaces and water spaces are the only parts 
that are protected by the water, and all the other parts of the 
boiler are exposed to the effects of corrosion. Moreover, it 
is hardly possible that a boiler, while cold, will be entirely 
Iree from small leaks through which water will find its way 




28 MARINE-BOILER MANAGEMENT §16 

and trickle down over the plates, leaving streaks of dampness 
in their wakes. The damp streaks will quickly corrode, and 
if unchecked, the process of decay will progress rapidly. 
If this state of affairs is permitted to continue without 
hindrance for a considerable length of time, the boilers will 
be found to be in a deplorable condition when the time arrives 
to put them into service, and the necessity of a general over- 
hauling will be the result. It is, therefore, plain that, unless 
the boilers are entirely free of leaks, the wet method of 
laying them up is attended with considerable risk. 

46. It seems to be the consensus of opinion among 
marine engineers that the dry method is the better method 
of laying up marine boilers, if it is properly carried out, for 
the reasons that all parts of the boilers are open to observa- 
tion, and if any deteriorating influences arise they may be 
detected and checked in their early stages. In summing np 
the evidence on all sides, the conclusion may be reached that 
the preservation of laid-up boilers will depend principally on 
their being kept free from moisture. 



INSPECTION 



OCULAR INSPECTION 

47. Inspection of boilers is one of the most important 
duties of an engineer, because on this depends largely their 
safety and good condition. Owing to the several deterio- 
rating agents that tend to weaken and shorten the life of a 
boiler if their effects are neglected, it is important that 
inspections should be held periodically and notes made of the 
general condition from time to time. An engineer should 
not depend entirely on the report of a government inspector 
on the condition of his boiler, but should make inspections 
himself and actually see the condition of the boiler, the idea 
being that very valuable knowledge can thus be gained. 

Every part, both external and internal, should be thoroughly 
examined. Corrosion and its progress should be noted and 



§16 MARINE-BOILER MANAGEMENT 29 

action taken to entirely stop it or at least to limit it in extent. 
Leaks should be looked for and stopped immediately. The 
internal surfaces of the plates should be examined at the 
water-line for pitting and at the junction of the plates -in 
the seams for grooving. The condition of slays and braces, 
and whether they are tight, should be noted. Should the 
staying be found loose, it must be tightened by whatever 
means are available. 

HAMMER AND BTDR09TATIC TESTS 

48. The ocular inspection should be accompanied by 
striking the plates, stays, and tubes with a hammer to deter- 
mine their soundness; this is called a hammer test. Sound 
plates and tubes when struck with a hammer emit a clear, 
bell-like ring, while those that are thin or defective give 
forth a dul! sound, similar to that of a piece of cracked pot- 
tery. A broken stay gives a peculiar sound that cannot be 
described by words. 

49. The lijdrostatlc test (filling the boiler with water 
and applying a pressure by means of a pump or otherwise) 
is valuable only in showing leaks and to determine the 
ability of the boiler to withstand a prescribed pressure. It 
will not reveal weak places, unless such places are so \yeak 
as not to be able to stand the required pressure. But it 
frequently happens that thin places do stand the pressure to 
an astonishing degree, although they are in a dangerous 
condition; hence, the hydrostatic test should always be sup- 
plemented by an ocular inspection and a hammer test. 

An objection to the hydrostatic test is that there is 
danger of straining the plates beyond the elastic limit and 
that thereby a boiler may be permanently injured which 
would have been safe at the working steam pressure. 
The inspectors in most cases depend on the hammer test 
and on ocular inspection, but use the hydrostatic test for 
new boilers, old boilers that have just been extensively 
repaired, and all boilers that cannot be examined thoroughly 
inside and outside. 



30 MARINE-BOILER MANAGEMENT §1(1 

When applying the hydrostatic test, the escape of air from ' 
the boiler while filliiiE with water should be provided for, 
leaving some valve or cock open until the water is forced 
out in a solid stream. The valve or other opening used fct 
the escape of air must be located as high as. possible, so thai 
practically little or no air remains in the boiler when it ;; 
closed. The necessity of this precaution is obvious when )i 
is considered that, should the boiler burst under pressure 
while still containing air, the parts, by reason of the expan- 
sion of the air. are liable to fly with great force, perhaps 
injuring some one in their flight. A boiler, from which all 
air has escaped, bursting under the hydrostatic test will not 
do any serious damage. 

When there are two or more boilers connected by piping, 
the inlercommunication being broken only by a valve, it will 
be necessary to place a blank flange between the valve and 
the boiler that is to be tested, thus completely isolating tbt 
boiler from those in operation. This is done as a measure 
of safety, which the valve alone is not capable of insuring. 

50. In making the hydrostatic test, the pressure mnsl 
be applied very slowly and carefully, and the gauge must be 
watched for any drop of pressure that would denote a yield- 
ing of some part of the boiler. New boilers are tested by 
hydrostatic pressure to reveal leaky joints or rivets. When 
the seams or rivets are not tight, water trickles out in 
drops or spins out in a stream. Such places are marked 
with chalk and afterwards recalked. 

The rules of the United States Board of Supervising 
Inspectors of Steam Vessels, of the British Board of Trade, 
and of the Canadian Inspection Service provide that the 
hydrostatic test pressure shall be li limes the working pres- 
sure, while Lloyd's rules and those of the Bureau Veritas 
demand a hydrostatic test pressure of double the working 
pressure. 

61. A method of applying the hydrostatic test that is 
used by many engineers is to fill the boiler full of cold water 
and build a gentle fire in the furnace. As the temperalore 





§ 16 MARINE-BOILER MANAGEMENT 31 

of the water rises, it expands, and thus subjects the boiler to 
pressure. It is urged in favor of this method that the pres- 
sure is raised steadily, and that the boiler is not so liable to 
injury as it is when subjected to sudden and jerky rises of 
pressure due to the working of a pump. The temperature 
of the water should in no case be made to rise above 212^, 
since, if a rupture should take place, the pressure of the 
water would lower to that of the atmosphere, and the tem- 
perature of the water being above the boiling point at atmos- 
pheric pressure, a quantity of the water might suddenly 
become steam and cause an explosion. 

The inspection of steam boilers should begin at the place 
where the plates are manufactured and continue as long as 
the boiler is in use. 



I 



MARINE-BOILER REPAIRS 

INTRODUCTION 



WEAR ANU TEAR 



C0RB08I0N 

1. Definitions. — Corrosion in boilers may be defined 
as the eating away or wasting of the plates due to the 
chemical action of impure water, or due to moisture. Il is 
probably the most destructive of the various forces thai tend 
to shorten the life of a boiler. Corrosion is of two forms — 
infernal and external. Internal corrosion may present 
itself as: uniiortn corrosion, pilling or honeycombing, grooving. 

2. Internal Corrosion. — In cases of uniform corro- 
sion, large areas of plate are attacked and eaten away. 
There is no sharp line of division between the corroded 
part and the sound plate, and oftentimes the only way of 
detecting the corrosion is by testing the suspected plate with 
a hammer and then drilling a hole through it to ascertain its 
thickness. Corrosion often attacks the slaybolts and rivet 
heads. 

3. PUtlng or honej'comblnff is easily perceived. 
The plates are, in spots, indented with holes from A" to 
i inch deep. The appearance of a pitted plate is shown in 
Fig. 1. On the first appearance of pitting, the affected 
surface should be thoroughly cleaned and a good coating 
of thick paint made of red lead and boiled linseed oil applied. 

Coty'tMid iy InltinaliBial Terltook Cnmpair. EnUitd al Slaliontti' Hall, Lonacn 

ii7 



2 MARINE-BOILER REPAIRS 

This treatment should be given from time to time to insuie , 
protection to the metal. 

4. Grooving; is generally caused by the buckling aclion^ 
of the plates when under pressure. Thus, the ordinary lap 

joint of a boiler distorts the shell slightly from a truly cylin- 
drical form, and the steam pressure tends to bend the plates 
at the joint. This bending action is liable to start a small 




fracture along the lap. which, being acted on by the corr 
sive agents in the water, soon deepens the groove, as 
in Fig. 2. The score made along the seam by a sharp calti 
ing toot, when used by careless worltmen, is almost certai 

to lead to grooving, 

5. To prevent internal corrosion, the feedwater shoid 
be as free as possible from corrosive impurities. When fc 
water must be used, the corrosive impurities should be 
neutralized by adding alkaline substances, such as caustic 
soda or soda ash. Zinc is much used to arrest corrosion in 
marine boilers. It is believed by some that corrosion is due, 
in some measure, to galvanic action between the non-homo- 
geneous portions of the iron and steel plates. By placioi 
the plates in connection with slabs of zinc, a galvanic actii 




§17 MARINE-BOILER REPAIRS 3 

is set up between the iron and zinc, which destroys the latter 
and leaves the former untouched. 

6. Exterual Corrosion of Flre-Tnbe Boilers. — Exter- 
nal corrosion frequently attacks marine boilers, particularly 
when they are neglected or laid up. The causes of external 
corrosion are dampness caused by leakage from joints, 
by moisture arising from drain pipes, blow-off pipes, damp 
atmosphere, etc. When leakage occurs in a joint that is 
hidden by the boiler covering, the plates may be corroded 
very seriously before being discovered. External corrosion 
should be prevented by keeping the boiler shell free from 
moisture and by repairing all leaks as soon as they appear. 
Joints and seams should be in positions where they may be 
inspected for leaks. Leakage at the seams may be caused 
by delivering cold feedwater against hot plates; another cause 
is the practice of emptying the boiler while hot and then 
refilling with cold water before it has cooled off. The leak- 
age in both cases may be traced to sudden contraction of the 
plates due to sudden cooling. In any case, abrupt changes 
in the temperature of the shell should be avoided. The rush 
of cold air into the furnaces of a boiler when the doors are 
opened is a fruitful source of leakage and fracture. For this 
reason, a boiler should, if possible, be so constructed that 
none of the seams comes in contact with the fire. 

7. External Corrosion of Water-Tube Boilers. — In 
water-tube boilers of the inclined-tube type, external corro- 
sion principally attacks the ends of the tubes close up to the 
headers into which they are expanded, and especially at the 
back ends. This is caused by the combined action of leakage 
and the gases of combustion, which rapidly destroys the tubes. 
This corrosion usually extends to from 4 to 8 inches from 
the headers, and soon small pinholes appear, manifesting 
themselves by threadlike streams of water while under pres- 

In the course of time, the tubes will leak around the 

ixpanded portion in the headers, though unless the leak is a 

Barge one its presence may not even be suspected. In this 

ype of boilers, a small leak around a tube is difficult to 




4 MARINE-BOILER REPAIRS §17 

locate, unless the tube is in one of the top or bottom rows. 
Hence, such leaks continue for a considerable length of time, 
partly obscured by the accumulation of soot, until the tube 
becomes eaten away, as described before. When, on exsun- 
ination, it is found that a leak exists in a tube near the 
center row, though the particular tube cannot be exactly 
located, it is advisable to expand all the tubes in the imme- 
diate vicinity of the one that leaks, so as to make sure of 
expanding the right one. This, of course, involves more 
labor, but when in doubt as to the exact tube it pays to 
do it. 

OVSRHEATINO AND LAMINATIONS 

8. Overheating: may be caused by low water or by 
incrustation. When a plate is covered by a heavy scale, the 
heat is not carried away by the water fast enough to pre- 
vent a rise of temperature, the plate becomes red hot and 
soft, and yields to the steam pressure, forming a bulge as 
shown at A in Fig. 3. If the bulge is not discovered and 
repaired, it will stretch until the material becomes too thin 



to withstand the pressure, when the bulge bursts and an 
explosion follows. The vegetable or animal oils carried into 
the boiler from a surface condenser are particularly liable to 
cause the formation of bulges and, in Scotch boilers, the 
collapse of the furnaces; consequently, the greatest care 
should be exercised not only to keep oil out of the boilers, 
but also to remove frequently and thoroughly any grease 
that, in spite of this care, may have found its way into the 
boilers. 



in 



MARINE-BOILER REPAIRS 



9. T^mliiiitlons in a plate are sometimes developed by 
the action of the fire, causing a bag or blister to appear. 
Laminations are due to slag and other impurities in the 
metal, which become flattened out when the plates are rolled, 
as shown at a, a. Fig. 4. Under the action of heat, the part 
exposed to the fire will form a blister, as shown in the figure. 



which may finally open at the point b or c , depending on the 
position of the slag in the plate. The laminated portion of 
the plate may be very small; in that case a hard patch may 
be put on. If there are a number of laminations in the same 
plate, it is advisable lo put in a new plate. When a lami- 
nated or an otherwise aflected portion of a plate has to be 
cut out, the form of the piece cut out should be as nearly 
circular as possible. In any case, no sharp corners should 
be made, because of the tendency of cracks to start at such 
places. _^ 

BOILER EXPLOSIONS 



CAUSES 

10. Boiler explosions can be caused only by weakness 
of the boiler or by overpressure of steam. Either the boiler 
is not strong enough to carry its ordinary working pressure or 
else, for some reason, the pressure has risen above the usual 
point. A boiler may be too weak to sustain the required 
pressure for any of the following reasons: It may be improp- 
erly designed; the material or workmanship may be faulty; 
it may have become weakened by corrosion or by care- 
less or reckless management, such as letting cold water 
come in contact with hot plates, or blowing off the boiler 
while hot, and then quickly filling it with cold water. When 
the pressure rises above the point for which the safety 
valve is supposed to be set, the fault is probably due to the 



I 



6 MARINE-BOILER REPAIRS §17 

sticking fast or overweighting of the safety valve. Several 
very disastrous explosions have been caused by closing a 
stop-valve between the safety valve and the boiler while clean- 
ing or repairing the latter, and then forgetting to open the 
stop- valve. The placing of a stop- valve between the boiler 
and the safety valve cannot be too strongly condemned; if 
one is there, it should be so secured that it cannot be shut. 

It was formerly believed that, if the water level in a boiler 
fell low enough to uncover the heating surface, thus per- 
mitting the plates to become very hot, and the feedwater 
was then turned on, an explosion was inevitable. This 
hypothesis, however, has been proved by extensive experi- 
ments to be not strictly correct, but it has not yet been 
established under what particular or peculiar conditions a 
boiler will or will not explode from this cause. Therefore, 
the safest plan, for the present at least, is to refrain from 
turning on the feedwater when the exact location of the 
water level is unknown or uncertain. 

Experiments conducted by the United States government 
have shown that it is possible to explode a boiler by a very 
sudden opening of the stop-valve. This may be accounted 
for thus: The sudden rush of steam from the boiler reduces 
the pressure materially for an instant; as the water in the 
boiler retains the temperature corresponding to the former 
pressure, part of the water flashes into steam, thus suddenly 
raising the pressure again and straining the boiler to the 
point of rupture. 

PREVENTION 

11. Boiler explosions may be prevented by observinsf 

the following directions: 

1. Inspect the boiler frequently and thoroughly, both 
inside and outside. Do not rely entirely on the annual 
inspection by government and insurance inspectors; while 
this is usually quite thorough, the time elapsing between 
inspections of this kind is so long that the boiler may have 
become dangerously deteriorated long before it is time for 
the next inspection. 



817 MARINE-BOILER REPAIRS 7 

2. Use all possible care to prevent internal and external 
corrosion and do not permit any oE the plates to become 
dangerously weak before renewing them. 

3. Do not strain the boiler by subjecting it to too great 
and sudden changes of temperature; that is. do not blow it 
oft while hot and quickly fill it up with cold water; do not 
deluge red-hot plates with cold water; and do not admit 
more cold air through the furnace doors than is absolutely 
necessary. 

4. Do not overload the safety valves, or let them become 
corroded fast to their seals, or let the stems corrode fast to 
the bonnets. 

6. Be careful not to let the water level become danger- 
ously low. 

6. Open the stop-valves slowly. 

7. Do not attempt to use a worn-out boiler; replace it 
with a new one. 

8. In selecting new boilers, adopt a type in which the 
danger of a disastrous explosion is reduced to a minimum. 



» REPAIRS AT SEA AND IN PORT 
REPAIRS AT SEA 
H1BCELLANEOU8 BEPAtRS AT SEA 
12. Grate bars burn out sometimes, especially when 
forced draft is used. When this occurs, the live coals are 
first cleared from the space made vacant by the burnt bar; 
then the blade of a slice bar is thrust into the space between 
the two members of a new grate bar. which is turned on its 
side and pushed into the furnace with the slice bar. when, by 
a dexterous movement, the grate bar is dropped into its 
place and the fire leveled. 

13. The breaking of glass water-gauge tubes is of 
f jrequent occurrence, when it becomes necessary to put in 
lew ones. When a glass tube breaks, the gauge should 




8 MARiNE-fiOiLER REPAIRS §17 

be immediately shut off from the boiler; then unscrew the 
packing glands and remove the packing and remains of the 
broken tube, insert the new tube, repack the ends, and screw 
up the glands. Be sure that the tube is properly centered at 
both ends, that the glands are not screwed up too tightly, 
and that the shut-off valves are opened again. 

14. Cracks and bulges in the internal plates of boilers 
are generally the result of shortness of water, deposits of 
scale and grease, or defective circulation. They may also 
be due to the weakening of the plates by corrosion and wear. 
Blisters are caused by laminations, which are the result of 
imperfect rolling. The plates that are the most liable to 
become cracked or bulged are those that are exposed to the 
most intense heat, such as the back sheets of the combustion 
chambers, the back tube sheets, and the crown sheets of the 
furnaces. These plates are also favorably located for the 
accumulation on them of scale or grease, and they are 
usually difficult of access for cleaning, all of which renders 
them particularly liable to become cracked or bulged. Other 
possible causes of plates cracking are cooling off the boiler^ 
suddenly, or admitting large volumes of cold air into it by 
opening the furnace and connection doors while running. 
Bulges that are caused by scale or grease are liable to crack; 
therefore, when a bulge is discovered in a boiler, that boiler 
should be cut out of service, the water level lowered to a 
point below the bulge, and the deposit of scale or grease 
removed; after this a careful examination of the bulge should 
be made. If it is found that the part that has bulged is 
not cracked or greatly reduced in thickness or seriously 
burned, the removal of the scale or grease will be all that is 
necessary to be done at that time, as absolutely necessary 
repairs only are expected to be made at sea. It is not 
customary, as a rule, to make any attempt to reduce a bulge 
while the vessel is at sea, as this would be a difficult opera- 
tion to perform under the circumstances; moreover, it is 
hardly probable that the necessary appliances for this pur- 
pose would be found on board, whereas temporary repairs 



Sl7 MARINE-BOILER REPAIRS 9 

that will enable the vessel to reach port can usually be made. 
Should the bulged part be considerably reduced in thick- 
ness, a staybolt or brace, reaching to and connected with the 
most convenient point on the shell, should be fitted at the 
center of the bulge. If the metal is cracked or badly burned, 
it should be covered with a soft patch. 

15. A soft patch consists of a piece of boiler plate 
large enough to cover the defective portion of the plate to 
be patched, allowing sufficient margin to insure enough solid 
metal around the defect for the bolt holes. A templet of 
the patch is first made of a piece of sheet lead thick enough 
to hold its shape while being handled, which is cut out 
to approximately the size and shape the patch is to be; it is 
then fitted by trimming and bending to the place where the 
patch is to go. If the templet is very crooked or uneven 
after being fitted, it will have to be flattened out again for 
the purpose of marking off the shape of the patch on the 
plate from it. The templet is then again fitted and bent 
to the form the patch is to be, and the patch is cut out and 
bent, at the forge, to conform exactly to the shape of the 
templet. A thin shallow lip, not more than i inch in depth, 
is turned inwards all around the patch, after which the bolt 
holes are drilled, or punched if it is .1 hurried job. The bolt 
holes are then marked off on the defective plate from the 
patch, and the holes drilled. A stiff putty, composed of 
red lead, white lead, and some fine ca.stiron borings well 
mixed together is now made and applied to the inside surface 
of the patch to a thickness a little greater than the depth 
of the lip. The patch is then bolted to its place by through 
bolts and nuts, using washers and grommeis. A Kromniet 
consists of a piece of cotton lamp wicking, 10 or 12 inches 
long, saturated and covered with moist white lead. This 
strand of wicking is wound tightly around the bolt, one piece 
under the head and another under the nut. When the nut is 
screwed up tight, the grommets are squeezed into the crevices 

I between the washers and the bolt, sealing the joints, and 
Itetidering them waterproof. The excess of white lead that 



10 MARINE-BOILER REPAIRS §17 

has been squeezed out during: the process of screwing: up the 
nuts is then scraped off, and the lip of the patch is calked up 
tig:ht against the boiler plate. In places where throug:h bolts 
and nuts cannot be used, tap bolts must be substituted for 
them. In that case, the holes in the boiler plate must be 
drilled smaller than the holes in the patch, to permit tapping. 
A soft patch is a temporary expedient only, but it is 
usually sufficient to enable the vessel to reach port, when 
more permanent repairs should be made. 

16. There are three methods of treating: simple cracks 
in boiler plates; which method to use depends on the extent 
of the crack. A crack may be closed by calking, by a row 
of screw riveiSy or by patching. 

If the crack is a small one, calking: will g:enerally stop the 
leak; the end of the crack should be first drilled out and a 
screw rivet put in to prevent the crack extending^ farther 
into the plate. 

A screw rivet is made by screwing a threaded piece of 
iron rod, slightly longer than the plate is thick, into a 
threaded hole in the plate and then riveting over both ends. 
If calking will not close the crack, a row of screw rivets 
may be put in, close together, throughout the entire length 
of the crack, and their ends calked over each other; this 
method will usually be effective. But if the crack is too 
extensive, either in length or in breadth of opening, to be 
closed by either of these methods, it should be soft-patched. 
In all cases in which cracks occur in the plates forming the 
heating surfaces of a boiler, the inside of the plate should 
be thoroughly cleared of all scale, grease, or sediment in 
order to prevent further development of the crack. 

17. Cracks in tube sheets usually extend from one tube 
hole to an adjacent tube hole. If calking will not close th^ 
crack, it should be patched. The customary way to do this 
is to fit a patch around the holes at each end of the crack 
and secure the patch to the tube sheet by square-headed 
tap bolts, and afterwards calk around the edge of the patch. 
If the crack extends through several tube holes, the patch 



§17 MARINE-BOILER REPAIRS 11 

should, of course, be made large enough to entirely cover 
the crack. Cracks are sometimes, but not often, found in the 
shell plates. The treatment of such cracks may be similar 
to that given to cracks in the internal sheets. 

18. When blisters are dJstovered on the internal plates 
of a boiler, they should be carefully examined by sounding 
with a hammer, or by chipping and drilling to ascertain 
their extent and thickness. The blistered portion should be 
cut away, in most cases, as corrosion may be in progress on 
the internal surfaces. If a blister is thin and of small area, 
all that will be necessary to do for the time being is to 
remove it by chipping; but if it is very deep and extends 
over a large area, the plate containing it should be addi- 
tionally stayed or braced after the blister has been removed; 
or else the pressure should be reduced until the vessel 
reaches port, when a more permanent repair should be made. 

REPAIR OP ORDINARY LEAKS 

19. L-eak; Boiler Tubes. — In old fire-tube boilers, 
especially, leaking of boiler tubes is a very common occur- 
rence. The leaks may be found around the ends of tubes that 
have not been properly expanded in the tube sheet, or that 
have become thin by frequent reexpauding. The bead at the 
rear end of a tube may be burned or corroded off and cause 
a leak. The tubes may be split or cracked at an imperfect 
weld or, after long use or exposure to moisture while not 
in use, they may become pitted by corrosion, which will 
ultimately cause numerous holes to develop in them. When 
a leak occurs around the end of a tube, if the tube is sound, 
the leak can usually be stopped by reexpauding the lube; but 
if the bead is burned or corroded off, it will he necessary to 
drive the tube back slightly from the front connection end 
and then reexpand and rebead the rear end. If the tube is 
too short to admit of being driven back, the leak may he 
slopped by driving a cap ferrule, specially made for this pur- 
pose, into the end of the tube. This ferrule is illustrated in 
Fig. 5, in which a is the tube, d, b are the tube sheets, and c 



MARINE-BOILER REPAIRS 



§i: 



is the ferrule. This ferrule is known as the A(liulruU> 
imttcrii cap fomile and is extensively used in the British 
navy. 



20. Leaks arising from split or corroded tubes are 
stopped by a device called a tube stopper, of which sevetiil 
types are in common use. One of the most simple is illus- 
trated in Fig. 6, in which a is the tube, d.d are Ihe tube 
sheets, and <-, c are casi-iron plugs with cupped flanges, one 
plug being placed in each end of the leaky tube. These plugs 




1Z 



IT 



are held in place by the rod rf, which is threaded at its ends 
and fitted with nuts and washers as shown. By screwing up^ 
the nuts, the edges of the cupped flanges c,e are brought 
close contact with the lube sheet and firmly held there, 
preventing the water from running out of the tube. 



i 



21. Another tube stopper is illustrated in Fig. 
stopper is similar to the one shown in Fig. 6, except that 
cupped washers a, a are substituted for the cast-iron plugs 
Fig. 6, The stoppers shown in Figs. 6 and 7 will answer 
the double purpose of stopping leaks at the tube ends as well 
as leaks inside the tubes, but they put the tube out of service 
in either case. 




§17 MARINE-BOILER REPAIRS 13 

32. Yet another form of tube stopper that is used to stop 
leaks inside of lubes is illustrated in Fig. 8, The advantaife 
of this stopper is that it can be inserted into a tube without 




having to draw the fires. Referring to Fig. 8, it will be seen 
that the washers A, B, having the rubber ring /between them, 
are placed on each end of the tie-rod C. This rod is threaded 
at both ends and fitted with nuts and washers. The sleeve D, 
made of ordinary steam pipe, is placed between the two pair 
of washers. The distance L is about 1 inch less than the 
length of the tube. To stop a leak in a tube with this stopper. 




it is inserted from the front connection end of the tube and 
the nut £"is screwed up, the rod being held by a wrench on 
the square end F to prevent it from turning. Screwing up 
on the nut £" draws the washers A and ff together, which 
compresses the rubber ring /, causing its edge to press against 
the side of the tube, making a water-tight joint. The washers 
placed under the nuts should he of soft copper, in order that 
a water-tight joint may be made. 

23. Another tube stopper of the same class as that illus- 
trated in Fig. 8 is shown in Fig. 9. It consists of an iron 
tie-rod ir. threaded at both ends and fitted with nuts and 
washers. Four large metal washers i>. b, just slightly less in 




14 



MARINE-BOILER REPAIRS 



ilT 



diameter than the inside of the tube, are fitted on the rod in 
pairs; between each pair of these washers are the thick rub- 
ber washers r, c. which are made to closelj' fit both the tube 
and the rod. The sleeve li, made of ordinary steam piping, 
is for the purpose of holding the group of washers at each 
end of the rod in place while the nut e is beine screwed up, 
the rod being held by a wrench pat on the square end /of 
the rod to prevent it from turning. To stop a leak inside of 
a lube with this stopper, the nut e is first slacked off, then 
the stopper is inserted into the front end of the tube and 
pushed into its place; the nut e is then screwed up tight; this 
compresses the rubber washers and squeezes their edges 
against the inside of the tube and also against the rod, 
making water-tight joints that stop the leak very effectnally. 
This stopper is to be preferred to the one shown in Fig. ^•, 
moreover, it can be made on board ship from materia 
usually carried in store. 




24. When a tube gives out from either a split or corrq 
ston and there are uo tube stoppers on board, or it is W 
convenient to make the stopper described in Fig. 9, woodi 
plugs, made preferably of white pine, may be driven iol 
each end of the disabled tube. The water will cause the pit 
to swell and the tube will fill up with salt, which will effe 
tually stop the leak. With this method, however, it willl 
necessary to haul the fires and blow off the pressure from d 
boiler containing the leaky tube. A very simple and effe< 
ive method of stopping an internal leak in a tube is to drii 
a snugly fitting plug of soft wood into the leaky tube 
the front end, forcing the plug back beyond the leak, 
then to close up the front end of the tube with another 



§17 MARINE-BOILER REPAIRS 15 

plug: or, for a boiler carrying high pressure, take a soft-wood 
plug, cut it down in the middle as shown in Fig. 10, and drive 
it into the tube so that the leak a will be opposite the smaller 
portion of the plug. The pressure cannot blow out this tube 
stopper as it might do if separate plugs are used. 



I 



\\^Ml\ 



25. Another method of plugging a leaky tube is by intro- 
ducing a split sleeve or ferrule made as shown in Fig. II, 
which also shows its method of application. The sleeve may 
be made of a piece of old boiler tube and may be given a 
length of from li to 2 diameters. The piece of tube is split 
lengthwise into two pieces, which are bent slightly to conform 
to the inside of the leaky lube. The piece should be split at 
an inclination of about i inch to the foot and the edges filed 
smooth and true. After smearing the inside of the leaky 
tube with red-lead putty, one half of the sleeve is put in flush 
with the tube end; the other half 
is placed on top, as shown in 
Fig. 11, and then driven home 
flush with the end of the tube. 
By reason of the edges being 

in a plane inclined to the axis, the two halves of the sleeve 
are firmly wedged against the inside of the leaky tube when 
the second half is driven home. The sleeves must be neatly 
fitted; in that condition they have been used with good suc- 
cess, effectually stopping a leak and obviating the necessity 

_.of withdrawing the tube or losing its service. 

IV 26. An easily made tube stopper is illustrated in Fig. 12. 

lot consists of two tapering pine plugs having a central hole 
through which a rod. made of S-inch round iron, is passed. 
This rod is provided with nuts and washers at each end, by 




MARINE-BOILER REPAIRS 



§17 



means of which the plugs can be drawn home. This tube 
stopper is quite effectual so far as stopping the leak is con- 
cerned, but it is open to the objection that a man must enter 
the back connection in order to place the plug in the rear enj 
in position and in order to put the nut and washer on the rod 



27. The stoppers illustrated in Figs. 8, 9, 10, and 11, and 
the wooden plugs driven into a tube from its front end. can 

be inserted without hauling the fires, but they can be used 
only when the tubes are reasonably free from hardeaed sooi 
and salt. When a tube is nearly filled with incrustatioD. as 
leaky tubes are very liable to be, it will be impossible to 
insert the stoppers into a tube until the incruslatioo is 
removed. This is not an easy task, as the mixture of salt 
and soot in the tube will be baked about as bard as graniie 
by the intense heat to which it is exposed, and a steel chisd 
bar will be required to remove il; an ordinary tube scraper 
will have no effect on it. Now, if the tube is in an 
advanced stage of corrosion, the blows of the chisel bar on 
the hard incrustation will be very liable to break more holes 
in the tube, and probably almost wholly destroy it; therefore, 
it is not always advisable to undertake to clear out a choked 
lube; this should never be attempted with pressure on the 
boiler, for the man handling the chisel bar may be badly 
Hcnlded. When a tube is choked with incrustation, it is pref- 
erable to use either of the stoppers illustrated in Figs. 6 and 7, 
or cNe clean the scale out of the ends of the tube and dti\ 
In wooden plugs. 

28. To insert the Admiralty ferrule, or the stoppers illi 
Irated in Figs. 6, 7, and ]'2, into a tube, it will be necessary 
to firm haul ihe fire from the boiler having the leaky tube, 
close the stnp-valve, and blow off the pressure. It may also 
be necessary, if the leak is a large one. to run the water level 



d7. 

] 



|17 MARINE-BOILER REPAIRS 17 

'below the leaky tube to enable a man to safely go into the 
back connections to adjust the rear end of the stopper or to 
insert the ferrule. Although cases are known in which men 
have performed this operation while the pressure was on the 
boiler, it is a dangerous practice and is not recommended. 

29. The stoppers illustrated in Figs. 7, 9, 10, 11, and 12 
have the merit of being easily made on board ship of mate- 
rials usually carried in store. The rubber washers c,c, 
Fig. 9, should be made of pure gum; an old, soft-rubber, air- 
pump or circulating-pump valve will answer very well for 
this purpose. 

The Admiralty ferrule will stop a leak at the ends of a 
tube only. The stoppers illustrated in Figs. 6 and 7 will stop 
leaks both inside and around the ends of the tubes, while the 
stoppers illustrated in Figs. 8 to 12, and the wooden plugs 
mentioned, will stop internal leaks only. It will thus be seen 
that each class of stoppers has its own sphere of usefulness, 
and in fitting out an engine department of a vessel some of 
each class, or materials to make them, should be provided. 
The dimensions of the ferrules or stoppers and their different 
members' will, of course, depend on the sizes of the tubes in 
which they are to be used. There are a number of other 
tube stoppers and ferrules in use, but those described above 
are examples of the representative types. 

30. Plugging leaky tubes is only a temporary expedient, 
and, therefore, as a matter of course, those plugged tubes 
that are too far gone to be reexpanded should be cut out 
and new ones inserted on the vessel's arrival in port. 
When several tubes give out on account of corrosion, it is 
strong evidence that all the other tubes are in verj- nearly 
the same condition, and the safest plan, in that case, will be 
to entirely retube the boiler while in port. When tubes 
begin to give out from corrosion, they are apt to go one 
after another in rapid succession, and if a vessel goes to sea 
in that condition she may become disabled at a critical time. 
The condition of those tubes that are cut out will be a 
standard to judge the others by; if they are in an advanced 




MARINE-BOILER REPAIRS 



§1? 



stage of corrosion, all the others are probably in a simJlaij 
condition. H 

31. Leaky RlTets, BtayboltB, and Beams. — Lealu^ 

frequently occur at rivets, staybolts, and seams, but ther 
are usually very small at first and do not require any 
immediate treatment. Small trickling leaks will frequently 
oalt up in time; that is, the water that oozes through tbe 
leak will be evaporated, leaving such impurities as it coo- 
tains in a hard mass around and over the leak, which closes 
it effectually. If, however, the water squirts out of the 
leak in jets, it is not probable that the leak will salt up; 
on the contrary, it is apt to increase. Leaks of this kind 
should be closely watched, and if they increase to such an 
extent, before reaching port, that they interfere with the 
fires, tbey should be repaired. This will necessitate cutting 
out of service the boiler containing the leak and allowing ii 
to cool down sufficiently to work in. Usually, leaks of this 
character can be stopped temporarily by calking, but in the 
cases of leaky rivets and staybolts. especially if they have 
been calked several times before, the leak cannot always be 
stopped in this manner. It will then be necessary to cut 
out the defective rivet or staybolt and insert bolts and nuts 
in their places, or lap bolts, if the location is inaccessible 
for pulling in a bolt and nut. Extra large cupped washers 
should be put under the heads and nuls of these bolts, the 
cupped part of the washer being filled with a stiff putty com- 
posed of a mixture of white and red lead and a small quan- 
tity of fine cast-iron borings. To further insure against 
leakage around the bolt, grommets should be placed under 
the head of the bolt and under the nut. 

32. If the leaky staybolt is of the socket type, either the 
new bolt or a mandrel should be pushed into the hole and 
through the socket as the old bolt is being withdrawn, in 
order to prevent the socket, in case it should happen to be 
loose, dropping into the water bottom of the boiler, from 
whence it might be troublesome to recover it. If the staya 
bolt to be cut out is of the screw type, aod it is desired a 




1 17 



MARINE-BOILER REPAIRS 



necessary to replace it with a socliet bolt, and if its location 
in the boiler is such that it cannot be reached by the arm or 
tongs, a very good plan to get the socket into its place is to 
pass a string through both holes and secure the ends, drop- 
ping the center and hauling the bight through a handhole; 
then cut the string, pass one of the ends through the socket, 
join the ends of the string together again, and haul the 
socket to its place. In fitting sockets, it is important that 
their lengths should equal the exact distance between the 
sheets, and that the ends should be filed square, otherwise 
Ithe sheets may be drawn out of shape. 

33. Leaks in seams at the junction of three plates are 
often very troublesome to slop. No amount of calking. 

ngly. will close them. Sometimes, a small steel pin 
or wedge may be driven into the leak and the plate may be 
calked over the pin or wedge; this will be effective in stop- 
ping such a leak. 

34. Leaky Manholes and BandholeB. — When leaks 
occur at manholes and handholes, they should be stopped at 
once, or the gasket may be blown out and the boiler tem- 
porarily disabled. If the gasket is sound and the leak is 
attended to as soon as discovered, it may be stopped by 

wing up the nuts on the studs or holts of the plate. 
'This is an operation that requires care and should be per- 
formed only by a man experienced in that kind of work, as 
otherwise a stud might be twisted off. which would be apt to 
let the plate spring away from its seat sui^iciently to allow 
the gasket to be blown out with disastrous results. The 
nuts should not be screwed up beyond hand taut with a mod- 
erate-sized wrench; a sledge hammer should never be used 
to drive up the wrench in a case of this kind. Should a 
gasket be blown out, the only course to pursue is to cut out 
that boiler, blow the water level below the leak, and make a 
new joint with a new gasket. A supply of spare gaskets 
should always be carried for such emergencies, 

35. Leaky Blow-Orr Cocks.— Should it be found diflfi- 
it to maintain the water level at its proper height in any 




J 



20 MARINE-BOILER REPAIRS §17 

of the boilers when the feed is on full, it is strong: evidence 
that some of the water is leaking out of th'e boiler. After 
establishing: the facts that the proper amount of water is 
going: into the boiler, and that the drain cock is closed, both 
the surface and bottom blow cocks should be examined to 
ascertain if they leak or are partly open. This inspection 
may be made by feeling the pipes outside the cocks with 
the hand. If the pipe is quite hot, it indicates that water 
from the boiler is leaking through the cock, or that the cock 
is not entirely closed, or that the plug of the cock is slack 
or considerably worn. It is plain what should be done in 
the first two instances; namely, entirely close the cock or 
tighten the plug. In the other case, close the outboard 
valve of the blow-off pipe and keep it closed while the blow- 
off cocks are not in use, and tighten up or grind in the plug 
at the first opportunity. If the plug is too much worn to 
be groimd in successfully, put in a new cock. 

36. Leaky Pipes. — Both steam pipes and water pipes 
are liable to leak from several causes, one of the most com- 
mon being defective joints. Joints in pipes are of two 
kinds; namely, screw joints in small pipes and flanged joints 
in large pipes. Other sources of leaks in pipes are cracks 
and pinholes. A pinhole in a steam pipe will increase in 
size very rapidly, as the jet of steam issuing therefrom will 
cut away the metal around the hole considerably in a very 
short time. In the cases of leaks occurring at a screw joint 
or on account of a crack or pinhole, temporary repairs can 
be made by wrapping the pipe at the leak, and for some dis- 
tance each side of it, with a strip of coarse canvas with a thin 
layer of white lead spread on it. After the canvas has been 
wrapped tightly around the pipe, it is secured by being sewed 
with marline or annealed wire, which is wound around the 
pipe in close coils, hauled taut, and the end securely stopped. 
Iron clamps may also be used for this purpose, if they are at 
hand. In the case of a leak occurring in a flanged joint, it 
can usually be stopped by setting up on the joint bolts, pro- 
vided that this is done in time; but if the leak is permitted 



REPAIRS IN PORT 



§17 MARINE-BOILER REPAIRS 21 

to continue for some time, the chances are that the gasket 
will be blown out, in which event it will be necessary to cut 
that pipe out of service and make a new joint with a new gas- 
ket. Should a gasket be blown out of a joint in the main 
steam pipe, it will necessitate shutting down the main engines 
for a considerable length of time to make repairs. As it is 
not an easy matter to make a new joint in a large pipe at sea, 
especially in rough weather, the importance of promptly stop- 
ping a leak in a joint in the main steam pipe is apparent. 

» INTRODUCTORY REMARKS 

37. After a steam vessel has been in active service for 
^ome time, the boilers will require general, and sometimes 
extensive repairs. Boilers that have been properly cared 
for. that is, kept clean and free from corrosion and not heated 
up and cooled down suddenly, will run much longer without 
extensive repairs than if these precautions had not been 
taken. When general repairs are to be made on boilers, the 
services of experienced boilermakers and the facilities of a 
boiler shop are required; hence, when a vessel is to be laid 
up for such repairs, she must be taken to a port where these 
facilities may be obtained. This work is usually let by con- 
tract to the lowest bidder, if there is competition, or if the 
company to which the vessel belongs has no shop in the 
vicinity; therefore, it will be necessary for the engineers of 
the vessel to carefully inspect the boilers to ascertain what 
repairs are required, and lo make a list of them for the com- 
peting boilermakers to bid on. 

The lesser repairs, such, for example, as expanding lubes, 
cutting out and putting in tubes and sleeves, calking leaky 
seams, rivets, staybolts, etc. may be done by the fireroom 
force. But when the cutting out of sheets or the portions of 
sheets to be patched, the driving of rivets, and similar work 

, are to be undertaken, it is generally advisable that none but 

■boilermakers should attempt it. 






22 MARINE-BOILER REPAIRS 

PI^TK REPAIRS 

38. Wben a defect in a boiler plate necessitates bard 
patcbing, the defective part is cut out and a templet of the 
patch is made of sheet lead and fitted over the cut 
part, taking care to make the templet large enough to leai 
sul^cient lap for the rivets. The templet is then taken 
the boiler shop and a boiler-plate patch of the exact size and 
shape of the lead templet is made, and the rivet holes are 
drilled. The patch is then taken on board ship and the rivet 
holes marked off from the patch on the plate where it is to 
be secured, and the holes are drilled. The patch is next held 
in place by a few bolts and nuts, after which it is riveted on. 
If the location of the patch is such that rivets cannot be 
driven, bolts and nuts or tap bolts must be used instead of 
rivets. After the patch is secured, it should be calked, both 
around the edge of the patch and around the edge of the 
hole. Patches should be put on the pressure side of the 
plates wherever their locations are accessible for that 
purpose. 

39. When an entire plate is condemned, it should be cut 
out and a new one inserted. To remove the defective plate, 
the rivet heads are cut off by means of a boilermaker's cold 
chisel and a sledge hammer; the rivets are then backed out 
by a drift. After the plate is released from the surrounding 
plates it is taken to the shop, where a new plate is made the 
exact shape of it and the rivet holes are marked off and 
drilled; the new plate is then taken on board the vessel and 
riveted in its place and its edges calked. If any stavboll 
holes are required in the new plate, care should he exercised 
in marking them off, so that they will come fair with the holefl 
in the opposite plate. The same care should be observed it 
marking off the rivet holes. 

40. If a bulge is quite shallow, that is, not more thatq 
say, 2 inches in depth, and the metal is neither burned o 
cracked, it may be reduced by first heating it in a portabl 
furnace and then forcing it back with a hydraulic jack. 




if the bulge is of greater depth than about 2 inches, or if the 
metal of the bulge is stretched, it cannot be put back by that 
means. In this case, it must be driven back by round-faced 
sledge hammers. It is necessary to apply forced draft to 
the portable furnace to produce heat enough to drive the 
bulge back with hammers or force it back with a jack. If a 
[ bulge is cracked or badly burned, it should be cut out and 
be plate hard-patched. ^__^^_ 

TUBE REPAIRS 

41. In cutting out old fire-tube-boiler tubes, the rear ends 
BIpf the tubes are split for about I or 2 inches with a narrow-edge 
rcape chisel, after which the ends are bent inwards toward 




Idle center of the tube; this releases the tube from the rear 
tnbe sheet. Then, by striking the rear end of the tube with 
a light sledge hammer and driving it forwards, the tube will 
be released from the front tube sheet, when it may be drawn 
out into the fireroom, provided that the coating of scale on 
the tube is not too thick, in which case the scale must be 
removed before the tubes can be drawn through the holes in 
the front sheet; or the lubes must be cut in two inside the 
boilers and the pieces taken out through the manhole. 

42. A tool called a ripper, and shown in Fig. 13 {a), is 
I sometimes used instead of a cape chise! for cutting out old 
(boiler tubes. Fig. 13 {6) shows how it is applied and 




24 ' MARINE-BOILER REPAIRS §17 

Fig. 13 ic) shows an end view of the tube after it has been 
cut. By means of the ripper, a slit about i inch wide and 
extending about 1 inch beyond the inside of the sheet is cut; 
the end of the tube can then readily be squeezed together so 
that the tube will pass through the hole. With reasonable 
care, there is little danger of cutting into the tube sheet. 
In splitting the end of a tube, care should be exercised not 
to turn a chip of the metal down inside the tube sheet, or the 
tube will be very troublesome to remove. 

43. The ends of new boiler tubes should .be annealed, 
that is, softened by heating them to a cherry red and allowing 
them to cool slowly, before being expanded. The length of 
the tubes should be about i inch greater than the distance 
between the rear surface of the back tube sheet and the front 
surface of the front tube sheet. When the tube is in its 
proper position, it should project into the combustion 
chamber about i inch. A man with a tube expander should 
be stationed at each end of the tube. The expanders should 
be inserted into each end of the tube and rolled until the tube 
is firmly secured in the tube sheet. Care should be exer- 
cised to roll the tubes enough, but not too much, less they 
be split or otherwise injured. After the tubes have been 
expanded into the tube sheets, the ends that project into the 
combustion chamber are turned over with a peening ham- 
mer and afterwards beaded with a boot tool. The stay-tubes 
are extra heavy, usually about twice the thickness of ordinary 
tubes; their ends are reenforced by welding ferrules 3 or 4 
inches long to them, after which the ends are threaded. The 
stay-tubes are screwed into the tube sheets from the front, 
nuts being screwed on the ends outside of the tube sheets. 



STAY REPAIRS 

44. There is only one sure remedy for a leaky staybolt 
or rivet, and that is to cut it out and put in a new one. 
Should the holes of the defective rivets or staybolts be much 
enlarged by corrosion, they should be reamed out until solid 
metal is reached and rivets or staybolts of larger sizes than 



il7 MARINE-BOILER REPAIRS 25 

tine original ones put in. If a large number of new and larger 
i are put into a joint, there is a strong presumption 
that the safe working strength of the joint is reduced thereby; 
if this should be the case, the working pressure on the boiler 
will have to be reduced below the former pressure allowed. 
Should any of the stayrods, staybolts, gusset stays, palm 
Stays, etc. show a considerable reduction in size or be found 
broken, Ihey should be removed and new ones substituted, 
taking care that these new stays are made of the correct 
S^gth. 

FURNACE REPAIRS 

45. Dead plates being constructed of cast iron and 
.exposed to extreme heat and rough usage, it is probable 
that some of them will be found cracked or broken. These 
should be renewed, as a general rule, as they are extremely 
difficult to repair. Furthermore, the cost of a new dead 
plate will usually be less than the cost of repairs. 

46. It is to be expected that the bridge walls will be 
found in a rather dilapidated condition. Many of the bricks 
will probably be missing, while others will be loose or broken. 
All such should be removed, and only those that are held 
firmly in their places should fcie retained. Whatever remains 
of the wall after removing the loose and broken bricks should 
ibe thoroughly cleaned off and sprinkled with water before 
[the new bricks are laid. Firebricks only should be used in 
building or repairing bridge walls; common bricks will not 
answer for this purpose, as they are unable to stand the heat 
to which they are exposed. Fireclay, mixed quite thin with 
water, should be used as the mortar for bridge walls. Each 
brick should be dipped in water just before laying it to cause 
the mortar to adhere to it. The bricks should be carefully 
laid with their edges flush on the sides and top of the walls, 
'and then plastered over with fireclay. 

47. Grate bars and bearing bars are exposed to great 
jat and rough usage; consequently, their life is compara- 

short and they require frequent renewal. While general 



26 



MARINE-BOILER REPAIRS 



tepairs are going on, these bars should be overhauW; 
that is, the good bars sorted out from the bad and the laiter 
sent ashore. The bearing-bar brackets should also be 
examined and any defects found in thera remedied. The 
supply of spare grate and bearing bars should oow be 
brought up to its standard quantity of one-eighlh of a com- 
plete set for all furnaces, for a sea-going vessel. 

48. Furnace fronts, being made of cast iron and exposed 
to considerable changes of temperature, are liable to crack, h 
any such cracked fronts exist, they should be removed, Th(!_ 
linings of the furnace doors will probably be burnt, crackf 
and warped; these should be removed. Furnace doors fre^ 
quently become sagged so that they cannot be closed tightl 
all such should be straightened and put in good condition. 

MISCELI.AMEOUS REPAIRS IN PORT 

49. It is to be expected that the zinc boiler protectoi 
will require renewal occasionally. The straps for holdin 
the zinc plates should be filed bright where they come in contac 
with the zinc and with the boiler braces. After the strapl 
are boiled in place, the joints should be made water-tight byl 
cement. There should be 1 square foot of exposed zinc sur- 
face, exclusive of edges, for each 1.30 square feet of healing 
surface in a boiler. In the British navy, zinc slabs 12 inches 
by 6 inches and i inch thick are attached to the boiler brace 
there being one slab to every 20 horsepower. These s 
eaten up and renewed, when the boilers are in use, 
fiO to 90 days. The baskets or troughs for catching the di» 
integrated zinc should be examined and, if needed, pat ■ 
good order. 

50. Rain and sulphurous gases from the coal have i 
destructive effect on the metal of the uptakes and smolU 
stack; therefore, in course of lime, they will become i 
roded to such an extent that they must be renewed. Thosj 
sheets that are most exposed to dampness and corrosion wifl 
be the first to give out. These should be examined auiJ 
renewed, if necessary. 



i 



MARINE-BOILER REPAIRS 



27 



51. Before painting; the boilers, their shells should be 
thoroughly cleared of rust, Hakes of old paint, and other 
foreigD substances that may be adhering to them. A good 
paint is a mixture of red lead and boiled linseed oil. The 
bottoms of the boilers and those parts that are not pro- 
tected by the coverings should receive two coats of paint. 

After the paint on the shelves of the boilers is thoroughly 
dry, the coverings should be replaced. So much of the old 
covering as may be in good condition should be utilized 
and the deficiency be made iip with new material. If the 
coverings of any of the steam pipes were removed or injured 
while repairing, they should now be replaced or repaired. 

52. Boiler fittings are subjected to corrosion and wear 
and they are also exposed to accidents; therefore, they 
require overhauling occasionally, and the proper time to put 
them in order is while the ship is laid up for repairs. 

53. When a vessel is laid up for repairs, advantage is 
taken of the opportunity to put her into dry dock and clean 
and paint the hull below the water-line. This gives the 
engineers a chance to examine and overhaul the outboard 
valves and strainers, and it is very important that this oppor- 
tunity should not be neglected. The Kingston valves, the 
outboard delivery valve, the outboard blow valves, and the 
injection valve should be examined and put in perfect order. 
The flanges of valves that are secured directly to the outer 
hull plating should be bolted to strengthening rings by steel 
studs with composition nuts, care having been taken not to 
drill the stud holes entirely through the rings. A zinc pro- 
tecting ring is fitted in each opening in the outer skin in such 
a manner as to be easily renewed. In vessels with double 
bottoms, all sea valves over the double bottoms are inside 
the inner skin and are connected to the outer skin by a pipe. 
The valve chamber is bolted to a flange on the upper end 
of the pipe, there being a zinc protecting ring near the upper 
end of the pipe, or secured to the lower flange of the valve 
chamber. These rings should be made accessible for 
renewal. 




28 MARINE-BOILER REPAIRS §17 

54. All copper suction and discharge pipes designed to 
convey salt water should be fitted, at intervals of from 10 to 
15 feet, with cast composition boxes, with fianges matching 
flanges on pipes. These boxes are placed on horizontal 
sections of the pipes. The zinc protecting rings on the sea 
suction valves may be regarded as one of the zinc boxes in 
spacing the remainder. Each pump discharge pipe designed 
to convey salt water should have a zinc box as near the 
pump as is practicable, after which they should be spaced as 
specified above. The design of the zinc boxes should be 
such as to leave the pipe unobstructed. The box should 
have the general form of the body of a gate valve, there 
being a bonnet and a faced opening for inserting the zinc, 
which should be of U shape, bent from a rolled slab i inch 
thick. 

The perforations in the strainers over the pipe openings in 
the hull plating should be cleaned out and the strainer fast- 
enings examined, and renewed if necessary. 



MARINE-BOILER INSPECTION 

(PART 1) 



AMERICAN, BRITISH, AND CANADIAN 
RULES 



SPECIFICATIONS FOR MATERIALS 



INTRODUCTION 

1. Practically all civilized countries have passed laws 
providing not only for the licensing of marine engineers, but 
also for the inspection of steam vessels and their machinery. 
In the United States of America, the inspection of steam 
vessels and licensing of engineers is performed by The Steam- 
boat-Inspection Service, IJepartment of Commerce and Labor, 
with headquarters at Washington, District of Columbia. In 
Great Britain, The Imperial Board of Trade performs a sim- 
iliar function; in Canada, The Department of Marine and 
Fisheries, through its Board of Steamboat Inspection, inspects 
steam vessels and examines marine engineers. These various 
bodies are governed in their action by rules and regulations, 
which of course are amended and added to from time to time. 
Obviously, marine boilers, in order to pass inspection, must 
conform to the rules and regulations in force in the country 
in which they are built. In addition, various marine under- 
writers, such as Lloyd's and the Bureau Veritas, have their 
own rules and regulations, which must be complied with if 
the boilers are to be insured in these societies. 

CotYTiiHttd by fiUmalmnal Ttilboali Comfatr. Emitrtil at Slalioiuri' Hall, limdm 



2 MARINE-BOILER INSPECTION §18 

The title of the American regulations is **General Rules 
and Regulations Prescribed by The Board of Supervising 
Inspectors, Steamboat-Inspection Service"; they will be 
referred to hereafter as ''American rules" for short. These 
can be obtained by applying to the Supervising Inspector- 
General, Steamboat-Inspection Service, Department of Com- 
merce and Labor, Washington, District of Columbia. The 
British Imperial Board of Trade rules are entitled ** Regula- 
tions and Suggestions as to the Survey of the Hull, Equip- 
ments, and Machinery of Steam Ships Carrying Passengers"; 
their price is six pence, and they can be purchased from 
Wyman & Sons, Ltd., Fetter Lane, E. C, London, England, 
or Oliver & Boyd, Edinburg, Scotland, or E. Ponsonby, 
116 Grafton Street, Dublin, Ireland. The Canadian rules, 
which are very nearly the same as the British Board of Trade 
rules, can be obtained by applying to the Minister of Marine 
and Fisheries, Ottawa, Canada; their title is "Rules for the 
Inspection of Steamboats and for the Examination of Engi- 
neers of Steamboats." 

* 

2. The Canadian rules are divided into two parts, each 
cov^ering virtually the same ground. Part I is normally used 
by the Canadian inspectors; Part II is headed thus: Regula- 
tions governing the inspection and testing of boilers now in 
existence and of boilers now or hereafter to be manufactured, 
in Canada, for the use of steamboats, whenever in the 
opinion of the Inspector the regulations contained in Part 
One of these Regulations, on account of the make of such 
boilers, or for some other reason, are not capable of applica- 
tion in the testing thereof; provided that in every such case 
the Inspector shall issue his certificate, in which he shall 
state that his inspection has been made under Part Two of 
this Order. 

3. The American rules here quoted are taken from the 
edition of August 8, 1906; the Canadian rules are from the 
1904 edition; and Board of Trade rules, from the 1905 
edition; these editions in every case were the latest at the 

date of writing. 



§18 MARINE-BOILER INSPECTION 



4. Plates. ^The American rules provide that every 
iron or steel plate intended for a marine boiler must be 
stamped with the tensile stress per square inch of section 
it will bear; the tenacity must not be less ihan 45,000 pounds 
per square inch for iron plate and 50,000 pounds per square 
inch for steel plate. 

5. Steel plates, under the American rules, must be made 
by the basic or acid open-hearth processes, if intended for 
use in boilers; plates used for making tubes may be made 
by the Bessemer process. 

Plates made by the basic process must not contain more 
than .04 per cent, of phosphorus and .04 per cent, of sulphur; 
when made by the acid process, they must not exceed .06 per 
cent, of phosphorus and .04 per cent, of sulphur. 

The tested sample must have a tensile strength of not 
less than 50,000 nor more than 70,000 pounds per square 
inch; it must show an elongation of at least 25 per cent, in 
a length of 2 inches for a thickness up to J inch, inclusive; 
for plates between i and -^g inch, inclusive, the length is 
4 inches; for plates over -ns inch, the length is 6 inches. 
The sample must also show a reduction of sectional area as 
follows: At least 50 per cent, for a thickness up to i inch, 
inclusive; 45 per cent, for a thickness over i and up to J inch, 
inclusive; 32.5 per cent, for a thickness above i inch. 

Steel plates must also be subjected to a quenching and 
bending test. The test piece for this must be at least 
12 inches long and from 1 to 34 inches wide; it must he 
heated to a cherry red (as seen in a dark place) and then 
plunged into water at a temperature of about S2° F. The 
sample thus prepared must stand bending, without cracks 
or flaws, to a curve the inner radius of which is not greater 
than li times the thickness, and the ends must be parallel 
after bending. 

Steel used in the construction of furnaces must have a 
tensile strength of not less than 58,000 nor more than 67,000 




.^ 



4 MARINE-BOILER INSPECTION §18 

pounds per square inch, with a minimum elongation of 20 
per cent, in a length of 8 inches. 

6. The American rules provide that a sample taken from 
an iron plate must show, when tested, a tensile strength not 
lower than 45,000 nor higher than 60,000 pounds per square 
inch. The elongation in a length of 8 inches must be at 
least 15 per cent. The reduction in area must be as follows: 
For samples showing 45,000 pounds tensile strength, 15 per 
cent.,, and for each additional 1,000 pounds 1 per cent. more. 
Samples testing over 55,000 up to 60,000 pounds tensile 
strength need not show a greater reduction in area than 
25 per cent. 

All iron plate must be subjected to a bending test, using 
a test piece at least 12 inches long and from 1 to 3i inches 
wide. This sample must stand bending cold, without cracks 
or flaws, to an angle of 90° to a curve the inner radius of 
which is not less than li times the thickness. 

7» The Board of Trade rules specify that steel must be 
of a general quality that has been found suitable for marine 
boilers. Each plate must be stamped, giving its tensile 
strength, and also its elongation. The elongation should be 
about 25 per cent, in a length of 10 inches, and must not be 
less than 18 per cent.; when the plate has been annealed, the 
elongation must not be less than 20 per cent. Plates not 
exposed to flame must pass a bending test; plates exposed to 
flame must pass a bending and quenching test, quenching in 
water at about 80° F. and bending cold until the sides are 
parallel and at a distance from each other of not more than 
three times the thickness. The test strip must be abont 
2 inches wide and 10 inches long. The tensile strength, for 
plates not exposed to flame, must not be less than 27 gross 
tons nor more than 32 gross tons per square inch. The ten- 
sile strength of furnace, flanging, and combustion box plates 
must range between 26 gross tons and 30 gross tons per 
square inch. In calculations, the Board of Trade surveyor is 
enjoined by the rules to take the tensile strength of approved 
steel plates as 27 gross tons per square inch imless all the 



§18 



MARINE-BOILER INSPECTION 



plates for a given boiler have been tested in his presence, in 
which case he may use the actual tensile strength found. 
The Canadian rules for steel plates are the same as the 
Board of Trade rules on the whole; they differ in Part II, 
where it is slated that in calculations made under the rules 
given in that Part the tensile strength of best quality steel 
plate is to be taken as 60,000 pounds per square inch, 

8. Both the Board of Trade and Part I of the Canadian 

rules specify that the tensile strength of iron plates is. to be 
taken as 47,000 pounds per square inch with the grain of the 
iron and as 40,000 pounds across the grain. Part II of the 
Canadian rules specifies that the tensile strength of iron plates 
made of the best material is to be taken as 4S,000 pounds per 
square inch with the grain and 42,000 pounds per square inch 
across the grain. The Board of Trade rules further provide 
that in calculating the working pressure the actual tensile 
strength of tested iron plates may be used with a factor of 
safety of 4.5 in case the elongation in a length of 10 inches is 
not less than 14 per cent, with the grain and 8 per cent, across 
the grain, if the surveyor is satisfied as to the quality of the 
plates. 

When iron plates are used in superheaters, the Board of 
Trade and Canadian rviles specify that their tensile strength in 
calculations is to be taken as 30,000 pounds per square inch, 
unless the flame impinges at, or nearly at, right angles to the 
plate, when 22, 400 pounds per square inch is to be taken as 
the tensile strength. The use of steel plates in superheaters 
is discouraged in all cases by the Board of Trade and the 
Canadian rules. 

9. Rivets.— The Board of Trade rules prescribe that the 
tensile strength of the bars from which rivets are made must 
not be less than 26 gross tons nor more than 30 gross tons 
per square inch, and that the elongation must not be less than 
25 per cent, in a length of 10 inches. The tensile strength 
of the finished rivets must not be less than 27 gross tons 
nor more than 32 gross tons per square inch, and they 
must show a reduction of area of at least 60 per cent. The 



MARINE-BOILER INSPECTION 



hi 



Canadian rules specify the same tensile strength and eloDja- 
lion for rivet bars and finished rivets as the Board of Trade 
rules; the American rules do not prescribe any test for riveis. 

10. Stays. — The American rules specify that steel bars 
to be used for stays or braces must pass a cold bending test; 
the sample is to be bent cold to a curve the inner radius of 
which is equal to one and one-half times the diameter or 
thickness of the bar, and must stand this bending without 
showing flaws or cracks. 

The Board of Trade and Canadian rules specify that tbe 
tensile strength of steel stay-bars must not be less tbsn 
27 gross tons nor more than 32 gross tons per square inch; 
the elongation should be about 25 per cent, and must not be 
less than 20 per cent,, in a length of 10 inches. The use of 
welded steel stays is forbidden by the American, Board of 
Trade, and Canadian rules. 

11. Stny-Tubcs. — The tensile strength of stay-tubes, 
according to the Board of Trade and Canadian rules, mnst 
not be less than 26 gross tons nor more than 30 gross tons; 
the material should show an elongation of about 25 per cent, 
in 10 inches and must never be less than 20 per cent. The 
rules demand a minimum net thickness of i inch. 



12. Boiler Tubes. — The American rules provide that 
lap-welded boiler tubes may be made of charcoal iron, or 
of mild steel made by any process, and must be free from 
defective welds, cracks, blisters, scale pits, and sand marks. 
All tubes up to and including 30 inches in diameter must 
stand the following test: A test piece 2 inches in length cut 
from a lube must stand being flattened by hammering until 
the sides are brought parallel, with the curve on the inside at 
the ends not greater than three times the thickness of (he 
metal, without showing cracks or flaws, with bend at o 
being in the weld. Tubes 4 inches in diameter and under-a 
must pass a flanging test in addition, consisting of flangi 
the tube at right angles to ihe body and to a width of j int 
These tests are made on cold tubes. All lap-welded boiler* 
tubes must be tested hydrostatically to an internal pressure 



undeE;^ 
iDgiiMH 
HncUl 
hoilep" 




518 



MARINE-BOILER INSPECTION 



of 500 pounds per square inch, and under this pressure show 
no signs of weakness or defects. 

13. Seamless steel boiler tubes, under the American 
rules, must be made by the open-hearth process, must be 
free from all surface defects, and must have been annealed if 
cold-drawn. 

A test piece 3 inches long cut from a tube must stand 
being flattened by hammering until the sides are brought 
parallel, with a curve on the inside at the ends not greater 
(ban three times the thickness of the metal, without showing 
cracks or fJaws. In addition, the tubes must stand flanging 
all around the end to a width of S inch beyond the outside 
body of the tube. 

Both of these tests must be made on cold tubing. Each 
seamless steel boiler tube must be sybjected to an internal 
hydrostatic pressure of 1,000 pounds per square inch without 
showing signs of weakness or defects. 

14. The Board of Trade rules state; "Steel tubes made 
by the Mannesman process need not be objected to for use 
in boilers, provided the material and the tests comply in all 
respects with the Board's usual requirements," The Rules 
do not specify what these requirements are. 

15. Welded Stonni and Water Pipes. — The American 
rules state that welded pipe may be made of wrought iron 
or mild steel, and must be smooth, straight, and free from 
defects. The use of threaded pipe of standard thickness is 
discouraged and absolutely prohibited if the pipe is above 
5 inches, nominal diameter. 

Welded pipe up to and including 3i inches, nominal diam- 
eter, must be tested by an internal hydrostatic pressure to 
600 pounds per square inch. 

Welded pipe from 4 inches to 30 inches, nominal diameter, 
if made from iron must have a minimum tensile strength of 
44,000 pounds per square inch and a minimum elongation of 
12 per cent, in 8 inches. Welded steel pipe must have a. 
tensile strength of not less than 50,000 pounds per square 
inch, and a minimum elongation of 20 per cent. All pipe 




« 



8 MARINE-BOILER INSPECTION §18 

must be tested to at least 500 pounds per square inch by 
internal hydrostatic pressure. In addition to these require- 
ments, a test piece 2 inches long must stand being flattened 
by hammering until the sides are brought parallel, with the 
curve on the inside at the ends not greater than 3 times the 
thickness of the metal, without showing cracks or flaws, 
with the bend at one side being in the weld. 

16. Seamless Steel Steam and Water Pipes. — The 

American rules provide that the material for seamless steel 
pipe must be made by the open-hearth process, and that 
the pipe must be smooth and straight, and inside and outside 
be free from all surface defects that would materially weaken 
it or form starting points for corrosion. The tensile strength 
must not be less than 48,000 pounds per square inch, and 
the elongation not less than 12 per cent, in 8 inches. A test 
piece 2 inches long must stand, without showing cracks or 
flaws, being flattened by hammering until the sides are 
brought parallel, with the curve on the inside at the ends 
not greater than 3 times the thickness of the metal. 



SPSCIFICATIONS AND TESTS FOR CASTINGS 

17. Cast Iron. — Regarding the use of cast iron, the 
American rules state: **No cast iron subject to pressure 
shall be allowed to be used in boilers or the pipes connected 
thereto, except as described as follows: Cast iron may be 
used in the construction of manhole and handhole plates, 
valves and cocks, water columns, flanges, saddles, ells, tees, 
crosses, or manifolds when such flanges, saddles, ells, tees, 
crosses, valves and cocks, or manifolds are bolted or riveted 
directly to the boiler and the valves or cocks; also casings of 
slip joints in pipes; provided, however, that the material shall 
be of the best grade and of suitable thickness and uniform 
section for the pressure allowed on boilers." 

18. The Board of Trade rules state: "In all boilers in 
which the surveyors find that cast iron is employed in such a 
manner as to be subjected to the pressure of steam and 



Mis MARINE-BOILER INSPECTION 

water, they should report the circumstances to the Board of 
Trade. Cast-iron stand pipes or cocks intended for the pas- 
sage through them of hot brine should not be passed. Sur- 
veyors should also discourage the use of cast-iron chucks 
and saddles for boilers," 

19. The Canadian rules state: "Cast iron must not be 
used for stays, and inspectors should also discourage the use 
of cast iron for chucks and saddles for boilers." The same 
rules also prohibit the use of cast iron for stays, pipes, or 
elbows in water-tube boilers. 

20. Steel Castings. — Neither the Board of Trade nor 
the Canadian rules contain any special clause in regard to the 
use of steel castings; the American rules state: "Flowed 
steel castings shall possess a tensile strength of not less than 
62.000 pounds, an elastic limit of not less than 30,000 pounds 
to the square inch, reduction of area of not less than 35 per 
cent., elongation of not less than 23 per cent., and contain 
not more than .04 per cent, of phosphorus, and not more than 
.OS per cent, of sulphur. Each of such castings shall be dis- 
tinctly marked with name of manufacturer. Manufacturers 
shall furnish report of test to supervising inspector of district 
where castings are to be used. All steel castings shall be 
thoroughly annealed. Castings of steel possessing the fore- 
going characteristics may be used for the necks or nozzles 
connecting the steam drum, or dome, and the boiler, and for 
the fittings of boilers, and fittings of steam, feed, and water 
pipes: Provided, that nozzles made of cast steel shall not be 
used in connecting shells of externally fired boilers to mud- 
drums, when said nozzles are exposed to the direct action of 
the flame." 

21. Malleable-Iron Castings. — The American rules 
state: "The use of malieable-iron or cast-steel manifolds, 
tees, return bends, or elbows in the construction of pipe 
generators shall be allowefl." 



k 




10 MARINE-BOILER INSPECTION §18 



CYIilNDRICAIi SHEIiliS 



STRESSES ON CYLINDERS 

22. If the cylindrical shell shown in Fig. 1 is subjected 
to an internal pressure, there will be two forces tending to 
rupture it. One force, indicated by the arrows A, A, acting 
in the direction of the length, tends to tear the shell in a 
transverse plane, as BB^. The other force, indicated by the 
arrows C, C, acting perpendicular to the axis, tends to rupture 




the boiler in a longitudinal plane passing through the 
axis, as DDx.DnD^. These two forces are opposed by the 
tenacity of the material of which the shell is composed. 

The magnitude of the force tending to rupture the shell in 
a transverse plane is equal to the area of the head in square 
inches times the steam pressure per square inch. As this 
force is resisted by the tenacity of the material, the magni- 
tude of the tenacity being measured by the sectional area, the 
Htress per square inch of section of the material is 

• area of the head X pressure 
area of section 
The magnitude of the force tending to rupture the shell in 
Kig. 1 in a longitudinal plane is equal to the internal diam- 
eter times the length times the pressure. This force is 
reHiHted by the combined sectional area of the material of the 
two Hides of the shell. Hence, the stress per square inch of 
beet ion equals 

the internal d iameter X the length X the pressure 

combined sectional area 



us 



MARINE-BOILER INSPECTION 



U 



23. Consider a plain cylindrical shell constructed of any 
convenient material. Let the inside diameter be 36 inches, 
the length 120 inches, the thickness of the shell i inch, and 
the internal pressure to which it is subjected 100 pounds per 
square inch. The pressure on the head and. consequently, 
the maEnitude of the force acting in the direction of the 
length is 

36' X .7854 X 100 = 101,787.8 pounds 

This force' is resisted by the tenacity of 
36.5' X .7854 - 36' X .7854 = 28.471 square inches of material 

Hence, the stress per square inch of section is 101,787.8 
-§- 28.471 = 3,575.14 pounds. The magnitude of the force 
acting perpendicular to the axis equals 36 X 120 X 100 
= 432,000 pounds. The area of the material resisting this 
force equals 120 X .25 X 2 = 60 square inches; hence, the 
unit stress is 432,000 -;- 60 = 7,200 pounds per square inch. 
This shows that there is 7,200 -h 3,575.14 = 2.01, say about 
twice as much resistance to transverse rupture as there is to 
rupture in a longitudinal plane. Hence, it follows that if the 
material is proportioned to withstand the force perpendicular 
to the axis, it will possess ample strength in the other direc- 
tion. For convenience in calculation, the length of the shell 
is taken as I inch. If a boiler is constructed of plates vary- 
ing in thickness and tensile strength, the least thickness and 
the lowest tensile strength must be used in calculating the 
strength of the boiler. 



, AND TEST PRESSURES 

24. FiiiMlaniental Itules, — In a seamless cylinder that 
is on the point of bursting, the resistance of the material to 
rupture must be equal to the force tending to cause rupture. 
Hence, such a cylinder is on the point of bursting if the 
product of the diameter and pressure equals the product of 
twice the thickness of the cylinder and the ultimate tensile 
strength of the material of which it is composed. From 
this, it follows that the bursting pressure equals 

twice the thickness X the u ltimate tensile strength 
diameter 




JC 



12 MARINE-BOILER INSPECTION §18 

This may be simplified by using the radius of the cylinder 
instead of the diameter. Then, as the radius is one-half 
the diameter, the bursting pressure will be 

the thickness X the ultimate tensile strengt h 

radius 

Rule. — To find the bursting pressure of a seamless cylinder, 
in pounds Per square ifuh^ divide the Product of its thicktusSy in 
inches y and the ultimate tensile strength , in Pounds Per squart 
inch^ by the internal radius ^ in inches. 

or. />. = ^ 

in which T = thickness of shell of cylinder, in inches; 
R = internal radius, in inches; 
S = ultimate tensile strength of material, in 

pounds per square inch; 
Ft = bursting pressure, in pounds per square inch. 

ExAMPLB.— A cylinder 48 inches in internal diameter and .375 inch 
thick is made of wrought iron having a tensile strength of 50,000 ponnds 
per square inch; what is its bursting pressure? 

Solution. — The internal radius is 48 4- 2 = 24 in. Appl3nng the 
rule, 

Pi = '^'^ X 5 0jg0 ^ ^gj 2^ j^ p^^ ^^ j^ ^^ 

25. When a cylinder has a longitudinal seam or joint, its 
bursting strength is diminished. It is usual to express the 
efficiency of a seam or joint in per cent, of the solid plate. 

Rule. — 71? find the bursting strength, in pounds per square 
iyich, of a cylinder having a longitudinal seam or joint, divide 
the product of the thickftess, in inches, the tensile strength of the 
material, in Pounds per square inch, and the efficiency of the 
seam or joint expressed decimally, by the internal radius, in 
inches. 

Or P - ^^^ 

in which E is the efficiency of the joint, expressed decimally, 
and the other letters have the same meaning as in the 
formula given in Art. 24. 



§IS MARINE-BOILER INSPECTION IS 

EsAMPi.H.— A boiler shell 60 inches in diameter is constructed of 
material having a tensite strength of 60, IKK) pound)! per square inch 
and .5 inch thick. It has a single-riveted longitudinal joint having an 
efficieticy of 56 per cent.; at what pressure will the shell burst? 

Solution. — The internal radius is 60 + 2 = 30 inches. Applying 
the rule, 

.S X 60 .000 X .56 
^*" 30 



lb. per sq. in. Ans. 



f 



26. The fundamental rules given in Arts. 24 and 25 are 
Bsed in the Board of Trade. Canadian, and American rules 
as a basis for determining the safe working pressure on 
boiler shells and pipes subjected to internal pressure, either 
by introducing a factor of safety or a coefficient combining a 
factor of safety with the efficiency of the longitudinai seam 
or jotnl- A factor of eafoty, when referring to boilers, 
may be defined as the ratio between the safe working and 
the bursting pressure. 

27. American Rule for WorkltiR Pressure on Boiler 
eticll. — The American rules provide that the working pres- 
sure allowable on a boiler shell shall be ascertained as follows: 

Rule. — Multiply one-sixlk of Ihe lowesl tensile strength found 
stamped on any plate in the cylindrical shell by the thickness, in 
inches, of the thinnest plate in the shell and divide by the radius, 
in inches; Ihe quotient will be the Pressure allowable Per square 
inch for single riveting, to which add 20 per cent, for double 
riveting, whai all the rivet holes in the shell of such a boiler 
have been ^'fairly drilled" and no part of such holes has been 
punched. 

Or, for single -rive ted longitudinal joints, 

P. = ^ 

and for double -riveted longitudinal joints, 
P = 1-2 T t ^ Tt_ 
6 A' hR 

in which P., = working pressure, in pounds per square inch; 
T = tensile strength, in pounds per square inch; 
/ = thickness, in inches; 
R = radius, in inches. 



14 MARINE-BOILER INSPECTION §18 

The factors 5 and 6 appearing^ in the formulas are not 
factors of safety, but coefficients; making allowance for the 
weakening effect of the seams, these coefficients usually 
represent factors of safety of 3.5 and 3.4, approximately. 

ExAMPLB 1. — A boiler 48 inches in diameter, with single-riveted 
seams, is constructed of material f inch thick and having a tensile 
strength of 50,000 pounds per square inch; what working pressure will 
be allowed on the boiler shell? 



Solution. — Applying the rule, 

}X 50,000 



^» ^ Q ^ AA ~ ^ 130.2 lb. per sq. in. Ans. 



ExAMPLB 2. — A Scotch boiler is 14 feet 2 inches in diameter; the 
shell plates are of steel having a tensile strength of 62,000 pounds 
per square inch and are 1 inch thick. The longitudinal seams are 
triple riveted, with inner and outer butt straps, and in the American 
rules are considered as equivalent, for the purpose of calculation, to 
double-riveted seams. What working pressure will be allowed on the 
shell .^ 

Solution.— 14 ft. 2 in. » 170 in. The radios is 170 ^ 2 = 85 in. 
Applying the rule, 

„ 62.000X1 ,-c«,K 1 A 

/» = — e Qg - =» 145.91b. persq. m., nearly.^ Ans. 

28. Board of Trade and Canadian Rales for Work- 
ins: Pressure on Boiler Shell. — Both parts of the 
Canadian rules, and also the Board of Trade rules provide 
that the allowable working pressure on a boiler shell is to 
be ascertained as follows: 

Rule. — Multiply ike tensile strength of the material, in 
fhyunds per square inch^ hy the least efficiency of the longitu- 
dinal joint y in per cent, expressed decimally^ by 2, and by the 
plate tkickncsSs in inches. Divide the product by the product oi 
the factor of safety and inside diamuter of the boiler^ in inches. 
The quotient 7till be the all^ntable pressure^ in pounds per square 
ifuhs OH the boiler shell. 

Or. B = ^*2_7- 

FD 
in which B — working pressure, in pounds per square inch; 
S = tensile strength, in pounds per square inch; 



§18 MARINE-BOILER INSPECTION 16 



% = least efficiency of longitudinal joint, in per 

cent., expressed decimally; 
T = thickness of plate, in inches; 
D = diameter of boiler, in inches; 
F = factor of safety. 



LHPLB. — What working pressure is allowable on a boiler shell 
2 inches in diameter, 1 j inches thick, coaslructed of sleel plates 
having a teosile strength of 60.000 pounds per square inch, and a joint 
efficiency of 80 per cent., using a factor of safely of 4.8? 
Solution. — 14 ft, 2 in, = 170 in. Applying the rule, 

»„ 60.000 X .80 X 2 X 1.25 , ,- ,. . , . 

B = — 48"xl70~" ' ^ ^^ ^'^' '"" ■'^^"y' ■"°'- 

29. It is to be noted in regard to the tensile strength of 
the material that the surveyor or inspector is enjoined by the 
Rules to use the actual tensile strength of iron or steel plate 
only in case all the plates have been actually tested; in all 
other cases, both in the Board of Trade rules and those in 
Part I of the Canadian rules, iron plates are to be assumed 
to have a tensile strength of 47,000 pounds per square inch 
(48,000 pounds in Part II, Canadian rules) with the grain, 
and 40,000 pounds per square inch (42,000 pounds in Part II, 
Canadian rules) across the grain. Steel plates under the 
same conditions are assumed to have a tensile strength of 
27 gross tons per square inch; their actual tensile strength 
may be used only in case the surveyor or inspector has 
personally witnessed the testing of all the plates. 

30. The Board of Trade rules state: "When the cylin- 
drical shells of boilers are made of best material with all the 
rivet holes drilled in place and all the seams fitted with double 
butt straps each of at least five-eighths the thickness of the 
plates they cover, and all the seams at least double riveted 
with rivets having an allowance of not more than 75 per 
cent, over the single shear, and provided that the boilers 
have been open to inspection during the whole period of 
inspection, then 5 may be taken as the factor of safely." 

"If, however, the iron be tested and the elongation meas- 
ured in a length of 10 inches is not less than 14 per cent, 
with, and 8 per cent, across, the grain, and the surveyors are 





16 



MARINE-BOILER INSPECTION 



§18 



TABIiE I 
ADDITIONS TO FACTOR OF SAFETY ON BOILJCB SHELLS 



Identification 
Letter 



At 



Bt 



D 



E* 



Gt 



H 



/t 



J* 



K 



M 




.15 



.75 



.1 



.15 



15 



.2 



.2 



.2 



.1 



Condition 



To be added when all the holes are fair and 

good in the longitudinal seams, bnt drilled 

out of place after bending. 
To be added when all the holes are fair and 

good in the longitudinal seams, but drilled 

before bending. 
To be added when all the holes are fair 

and good in the longitudinal seams, bat 

punched after bending. 
To be added when all the holes are fair 

and good in the longitudinal seams, but 

punched before bending. 
To be added when all the holes are not fair 

and good in the longitudinal seams. 
To be added if the holes are all fair and 

good in the circumferential seams, but 

drilled out of place after bending. 
To be added if the holes are fair and good 

in the circumferential seams, but drilled 

before bending. 
To be added if the holes are fair and good in 

the circumferential seams, but punched 

after bending. 
To be added if the holes are fair and good in 

the circumferential seams, but punched 

before bending. 
To be added if the holes are not fair and 

good in the circumferential seams. 
To be added if double butt straps are not 

fitted to the longitudinal seams and the 

said seams are lapped and double riveted. 
To be added if double butt straps are not 

fitted to the longitudinal seams, and the 

said seams are lapped and treble riveted. 
To be added if only single butt straps are 

fitted to the longitudinal seams, and the 

said seams are double riveted. 



§18 MARINE-BOILER INSPECTION 17 1 


TABLE I — Co7itiniied | 


Me«,H.a„o„ 


AUd 


CoDdllloq 






To be added i£ only single butt straps are 


A- 


■ IS 


litted to the toagttudinal seams, and the 
said seams are treble riveted. 


O 


I.O 


To be added when any description of joint 




io the lougitudinal seams is single riveted. 






To be added if Ihe circumferential seams 


P** 


■' 


are fitted with single butl straps and are 
double riveted. 


e- 


■" 


lilted with single butt straps and are single 
riveted. 
To be added if the cireumferealial seams 


R" 


.1 


are fitted with double butt straps and are 






single riveted. 


s**x 




To be added if the circumferential seams are 


'' 


lapped and double riveted. 


T 




To be added if the circumferential seams are 


■* 


lapped and single riveted. 






To be added when the circumferential seams 


U 


.25 


are lapped and the strakes of plates are 


#■ 




not entirely under or over. 
To be added when the boiler is of such a 
length as to fire from both ends, or is of 
unusual length, as in the caiie of Hue 


VX 




boilers, and the circumferential seams 


■^ 


fitted as described opposite P, A", and S\ 






but when the circu inferential seams are as 






described opposite Q and T, .4 should be 






added. 


w* 




To be added if the longitudinal seams are 


.4 


not properly crossed. 






To be added when the iron is in any way 


X' 


■4 


doubtful and the surveyor (inspector) is not 






satisfied that it is of the best quahly. 
To be added if the boiler is not open to 


YXX 


..6s 


construction. 
Part II. Canadian rules; To be added If the 


YXt 


1.0 


boiler is not open to inspection daring the 
whole period of its construction. 


1^^ J 



18 MARINE-BOILER INSPECTION 

Notes is Rbcard to Taslb I 

1 Board of Trade, but not Canadian, mies: "When the holes are 
(o be rimered or bored out in place the case should be submitted lo the 
Board as to the reduction or omission of A, B, C, and /." 

•Board of Trade and both parts of Canadian rules: "The facir;, 
may be increased still further if the workiuanship or material is suih 
as in the surveyor's (iaspector's) judgment renders such increa-y; 
aeeessary." 

"Both parts of Canadian, but not Board of Trade, rules: "Shi 
not apply lo the end or circumferential seams if such seams are sutli 
ciently stayed by through bolts; nor to the seatriE between the squait 
and round part of the shell, in cylindrical boilers with square furnaces, 
when such seams are double riveted." 

J Board of Trade, but not Canadian, rules: "When the middle cir- 
cumferential seams are double strapped and double riveted or lappeij 
and treble riveted, and Ihe calculated slrength not less than 65 per 
cent, of the solid plate, S and V may be omitted. Tbe end circum- 
ferential seams in such cases should be at least double riveted." 

IJBoth parts of Canadian, and Board of Trade, rules: "When 
surveying (inspecting) boilers that have not been open to inspectioa 
during construction, the ca^e should be submitted to the Board (Chair- 
man, Board of Steamboat Inspection, in Canada) as to the factors to 
be used." 

otherwise satisfied as to the quality of the plates and rivets, 
4.5 may be used as the factor of safety instead of 5. in which 
case the minimum actual tensile strength of the plates 
should be used in calculating the working pressure." 

The Canadian rules prevent the use of untested boiler 
plates; Part I establishes 4.5 as the factor of safety and 
Part II names 4. 

Both parts of the Canadian rules and also the Board of 
Trade rules state: "When the above conditions are not com- 
plied with, the additions in the following scale should be 
made to the factor of safely, according to the circum stances 
of each case." 

The object of these additions to the factor of safety is ti 
promote good workmanship and design. 

EiAMPLK.— What pressure would a Board of Trade surveyor a 
on the shell of a Scotch boiler having a diameter of 12 feet, a tl 
of 1 inch, and entirely made of inspected iron plate having a ti 
strength of 50, (KK) pounds per square inch? The longitudinal s 
lapped and double riveted, with iron rivets \-^ inch diameter a 
A-^ inch pilch, have an efficiency of 66, fi per cent., and the r 
boles have been punched fair and good after bending. The c 
ferentlol seams are lapped, (air and well punched after bending, i 




§18 MARINE-BOILER INSPECTION 19 

are single riveted. The boiler has been open to inspection and the 
surveyor is satisfied with the quality of the material. 

Solution. — According to Art. 30, the factor of safety, the plate 
having been tested, is 4,5. This is Co be increased, for lap joints and 
double riveting, by .2 (see A'. Table I); and by .3 for punching in the 
longitudinal seams alter bending (see C, Table I): and by .2 for cir- 
cumferential seams lapped and single riveted (see 7", Table I); and by 
.15 for punching the holes in the circumferential seams (see//, Table 1). 
This makes the factor of safety 

4.5 + .3+ .3 + .2 + .15 = 5.35 

Applying the rule in Art. 28, 

„ 50,000 X .666 X 2 X 1 oa ^s .u ■ a 

^ 5:35-xl2l^l2— = "-*^"'P" '"'■"'■ *"'■ 

31. In regard to steel boiler shells, the Board of Trade 
rules state: "When the minimum tensile strength of the 
shell plates is S tons and full allowance is wished, the 
rivet section, if iron, in the longitudinal seams of cylindrical 
shells should, when those seams are lapped, be at least ' - 
the net plate section, and if steel rivets are used their section 



tensile strength of the rivets is not less than 27 tons (gross) 
and not more than 32 tons (gross) per square inch. In cal- 
culating the working pressure, the percentage strength of the 
rivets may be found in the usual way by the Board's rules, 
but in dealing with iron rivets the percentages found should 

be divided by — --, and in the case of steel rivets by --, the 

results being the percentages required. If the percentage 
strength of the rivets is found by calculation to be less than 
the calculated percentage strength of the plate, the working 
pressure should be calculated by both percentages. When 
using the percentage strength of the plate 4.5 plus the addi- 
tions suitable for the method of construction as by the Board's 
rules for iron boilers, may be used as the nominal factor of 
safety, but when using the percentage strength of the rivets 
4.0 may be used as the factor of safety. The less of the two 
pressures so found is the working pressure to be allowed for 
the cylindrical portion of the shell." 




MARINE-BOILER INSPECTION 

32. Tbe Canadian rules state in regard to steel boiler 
shells: "The rivet section.if of tron.in the longitudinal seams 
of cylindrical shells, where lapped and at least doable riveted, 
should not be less than V times the net plate section; bnt if 
steel rivets are used, their section should be at least K of the 
net section of the plate if tbe tensile strength of tbe riretit 
not less than 27 tons gross and not more ihao 32 tons groii 
per square inch. Therefore, in calculating the working pres- 
sure, the percentage strength of the rivets may be found -2 
the usual way by the rules, but in the case of iroo rivets the 
percentages found should be divided by \^. and in the caseoi 
steel rivets by H. the result being the percentages requirec. 
If the percentage strength of the rivets by calculations is 
less than the calculated percentage strength of the plate, 
calculate the working pressure by both percentages. When 
using the percentage strength of the plate, 4.25 plus the 
additions suitable for the method of construction as by the 
rules for irou boilers may be used as the nominal factor of 
safety, but when using the percentage strength of the rivets, 
4.25 may be used as the factor of safety. The less of the 
two pressures so found is the working pressure to be allowed 
for the cylindrical portion of the shell, or otherwise in accord- 
ance with the formulas in the appendix." 

The formulas referred to are given under the heading 
Riveted Joints. 

33. The working pressure allowable on the shell of cylin- 
drical superheaters, under the Board of Trade and Canadian 
rules, is to be calculated in the same manner as for a boiler 
flhcll, except that, as previously stated, the tensile strength 
of the iron must be taken as 30,000 pounds per square inch, 
unless the heat or flame impinges at, or nearly at. right 
angles to the plate, when 22,400 pounds per square inch is to 
be used as the tensile strength. 

34. The working pressure of the shells of steam drums 
and mud-drums, except those of water-tube boilers, is 
calculated by the same rules governing that of the boiler ■ 
nhcll, 




35. WorklnR Prfssiire Allowable on Briiius of 
Water-Tube Boilers.— The Board of Trade rules do not 
contain any specifications in regard to water-tube boilers; the 
Canadian rules specify that the working pressure on water- 
tube boiler drums exposed to the fire is to be found by the 
rule given in Art, 28, taking the strength of the plate as 
30,000 pounds per square inch and the factor of safety as 5, 
making additions thereto, if necessary, as specified in Art. 30 
and Table I. and calculating the efficiency of the joint and also 
the percentage of plate left by the line of holes where the 
water tubes are attached, using the lowest percentage found. 

When the drum of a water-tube boiler is not exposed to 
flame, under Canadian rules, the calculation is made in the 
same manner as for a boiler shell, using 5 as the factor of 
safety, with additions such as the conditions specified in 
Art, 30 require, and making allowance for the weakening 
due to the holes receiving the water tubes. 

36. The American rules state that the working pressure 
allowable on the shell of a drum forming part of a water-tube 
or coil boiler, when such shell has a row or rows of pipes or 
tubes inserted therein, shall be determined as follows: 

Biilc. — From the distance, in inches, between the tube or pipe 
centers, in a line from head to head, subtract Ike diameter of the 
Uibe hole, in inehes. Multiply the remainder by the thickness of 
the plate, in inches, and by one-sixth of its tensile strength. 
Divide the product by the Product of the distance, in inches, 
befween the lube or pipe centers in a line from head to head, and 
the radius of the shell, in incites. The quotient will be the 
allowable working pressure, in pounds per square inch, on the 
shell of a water-tube boiler drum. 

(D-d )TS 
DR 
■■ allowable working pressure, in pounds per 
square inch; 

- distance between tube or pipe centers in a 
line from head to head, in inches; 

- diameter of hole, in inches; 




d 



22 



MARINE-BOILER INSPECTION 



T = thickness of plate, in inches; 
5 = one-sixth of tensile strength; 
R = radius of shell, in inches. 
ExAUPLB. — The drum o( a water-lube boiler has a di&meler 3 
S4 inches, is \ inch thick, and is constructed of steel having a 
strength of 60,000 pounds per square inch. The water tubes iit J 
1| inches outside diameter and spaced 3 inches center to cetitcr. WtutJ 
working pressure is allowable on the shell under American rules? 

Soi.«TiON.— S = 60.000 -^ 6 = 10,000. * = M -{- 2 - 12. App^ 
ing the rule. 

- li)X .5X lO.OOO 



P~ = 



- = 166.26 lb, per sq. in. Ans. 



2X 12 

37. Hydrostattc Test Preasures. — The America 
rules provide that fire-tube boilers must be subjected to j 
hydrostatic test of li limes the working pressure, andwateP 
tube boilers must be tested to twice the working pressure. 

The Canadian rules specify the same tests as the Aroericaa 
rules. 

The Board of Trade rules state that all boilers shall be 
subjected to a hydrostatic lest of twice the working pres- 
sure, and that no hydrostatic test shall be considered good 
in which the boiler has not borne satisfactorily the intended 
test pressure for at least 10 consecutive minutes. 



EXAMPLES FOR PRACTICE 

What is the bursting pregsure of a seamless steel tube 10 it 



r and i inch thick if the tensile strength is 6.'i,D00 poui 
per square inch? Ans. 3.250 lb. per sq. i 

2. A boiler shell 48 inches in diameter and i Inch thick has a 
sile strength of 66,000 pounds per square inch. The efficiency of tl 
joint being 70 per cent., at what pressure would the shell burst' 

Ans. (iOl.56 lb. per sq. in." 
8. What working pressure, under American rules, will be allowed 
- on a 4S-iach boiler shell f inch thick, double riveted, and having « 
tensile strength of 50,000 pounds per square inch? 

Ans. 156.26 lb. per SI 
4. Under Board of Trade rules, what working pressure vrill t 
allowed on the boiler shell in example 3 if the factor of safety i) 
the efficiency of the joint TO per ci 




S18 MARINE-BOILER INSPECTION 23 

5. A water-tube boiler has a drum 20 inches in diameter and -^ incli 
thick, the plale having a tensile strength of 60,000 pounds per square 
inch. The water tubes have an outside diameter of 2 inches and are 
spaced 4 inches center to center. What working pressure will be 
allowed under American rules? Ans. 218.75 lb. per sq. in. 

6. A water-lube boiler is to be worked at 200 pounds per square 
iocb; what must the hydrostatic test pressure be under American rules? 

Ans. 400 lb. per sq. in. 

BIVBTED JOINTS 



GENERAl. HEGUI'ATIONS 

38. The American rules state: "All boilers for i 
purposes shall be required to have the rivet holes in the 
shells, heads, and flanges of same, steam and mud-drums, 
and holes for stay-bolts and tubes fairly drilled, and no part 
of such holes shall be punched." 

The Board of Trade and Canadian rules permit the punch- 
ing of holes, penalizing this method, however, by requiring 
a higher factor of safety to be used. See Table I. 

According to the Board of Trade and Canadian rules, 
rivets in double shear are considered as having 1.75 times 
the shearing strength of rivets in single shear. 

Rivets, before riveting, are usually about -,^e inch smaller 
in diameter than the rivet hole, to permit easy insertion; 
when riveted they fill the hole. In all rules and formulas 
involving the use of either the diameter or area of rivets, 
the diameter or area after riveting is referred to. 

The Board of Trade and Canadian rules specify that when 
plates, including butt straps, have been drilled in place, the 
plates must be taken apart after drilling, the burr taken oS, 
and the holes slightly countersunk from the outside. 

BUTT STRAPS 

39. Under American rules, single butt straps must not 
be thinner than the plate; double butt straps must be at least 
five-eighths the plate thickness. The Board of Trade and 
Canadian rules demand single butt straps to be at least one 




24 MARINE-BOILER INSPECTION §18 

and one-eighth the plate thickness; double butt straps must 
be at least five-eighths the plate Jthickness. ^he same rules 
specify that butt straps must be cut from plates, be of as 
good quality as the shell plates, and those for the longi- 
tudinal seams should be cut across the fiber. Both the 
Board of Trade and Canadian rules specify that when the 
joint has double the number of rivets in the inner than in 
the outer row, that is, when every alternate rivet in the outer 
row has been omitted, the least thickness of the butt straps 
must be found as follows: 

Rule I. — To find the least thickness of a single butt strap 
with a joint having every alternate rivet omitted in the outer 
row^ multiply 9 by the plate thickness, in inches ^ and by the 
difference between the pitch and the rivet diameter. Divide the 
product by 8 times the difference between the greatest pitch and 
twice the rivet diameter. 

Or r = ^^(P-d) (1) 

in which Tx = thickness of butt strap, in inches; 
T = thickness of plate, in inches; 
p = greatest pitch of rivets, in inches; 
d = diameter of rivet, in inches. 

Rule II. — To find the least thickness of double butt straps 
with a joint having every alternate rivet omitted in the outer 
row, multiply 5 by the plate thickness, in inches, and by the 
difference between the pitch and the rivet diameter. Divide the 
product by 8. times the difference between the pitch and twice 
the rivet diameter. 

^- - W^) <"' 

in which the letters have the same meaning as in formula 1. 

Example 1.— A single-butt-strap joint is triple riveted, the pitch of 
the rivets in the outer row being 9 inches and in the inner rows 
4 ^ inches; the plate is 1 } inches thick and the rivets are 1^ inches in 
diameter. What is the least thickness of the butt strap? 

Solution.— Applying rule I, 

_ 9 XUX(9-Ii) 



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§18 MARINE-BOILER INSPECTION 25 

ExAMPLB 2.— In a triple-riveted double-butt-strap joint, the rivets 
are Ij^ iQclies in diaitieter and tiave a pitch of 8 inches in the outer 
row and 4 inches in the inner rows. The plate being 1 inch thick, 
what should be the least thickness u£ the butt strapsf 

Solution. — Applying rule II, 

8X(8-2XlJ) 



EXAMPLES FOB PRACTICE 

1. Under Canadian rules, in a double-butt-strap triple-riveted 
joint having every alternate rivet omitted in the outer row. what is 
tbe least thickness of the butt straps? The plate is | inch thick; the 
rivets are 1^ inches in diameter and pitched 7 inches in the outer row. 

Ans. .666 in. 

3. Under American mies, wbat iS the least thickness of the butt 

strap in a double-butt-strap joint for a plate thickness of l\ inches? 

Ans. e in- 



PROPORTIONB OF JOINTS 

40. Introductory. — The American rules only contain 
formulas for the proportions of single-riveted and double- 
riveted lap joints; the Board of Trade and Canadian rules 
give formulas for butt joints as well. The usual joints met 
with in marine boilers are given in Fig. 2. 

In the formulas given here, the letters have the following 
meaning: 

I' = distance between rows of rivets, in inches; 
Ki = distance between inner and middle row of rivets, in 
inches, in triple-riveted butt joints having alternate 
rivets omitted in the outer row; 
rf = diameter of rivets, in inches; 
J^ = factor of safety for shell plates; 
n = number of rivets in one pitch; 
pj — diagonal pitch, in inches; 

J'd = diagonal pitch, in inches, between inner and middle 
row of rivets in triple-zigzag-riveted butt joints 
having every aUcmate rivet omitted in the outer 
row; 




i 



MARINE-BOILER INSPECTION 

p = greatest pitch of rivels. in inches; 

S, = tensile strength of plate, in tons of 2,240 pounds; 
T = thickness of plate, in inches. 

The number « of rivets in one pitch is an expression ' 
requiring an explanation. Conceive the joint to be divided 
by lines at right angles to itself into equal strips having a 
width equal to the greatest pitch of the rivets. Then, the 
number of rivets in one of these strips is the number 
referred. In case of butt joints, the number of rivets at 
one side of the joint is taken. 

In a singie-riveled lap or butt joint n = 1; in a double- 
riveted lap or butt joint, either chain or zigzag riveted,, 
n = 2; in a triple- rive ted lap or butt joint, either chain ot 
zigzag riveted, w = 3; in a quadruple-riveted lap joint, either. 
chain or zigzag riveted, « = 4; in a double-riveted butt joint,, 
either chain or zigzag riveted, with every alternate rivet 
omitted in the outer row, w = 3; in a triple-riveted lap joint,. 
either chain or zigzag riveted, with every alternate i 
omitted in the two outer rows, Ji = 4; in a triple-riveted butt 
joint, either chain or zigzag riveted, where every alternate 
rivet has been omitted in the inner and outer rows, n = ^ 
in a triple-riveted butt joint, either chain or zigzag riveted, 
where every alternate rivet has been omitted in the outCT 
row, n = 5. 

41. Rules for Pitch of Rivets. — Under American rules, 

to find the pilch of rivets in single-riveted or double-riveted 
lap joints, either chain or zigzag riveted, for iron plates and 
iron rivets, proceed as follows: 

Rule. — S</uare the dianieUr of the rivet, in inches, 
by .7831, and also by the number of rivels in one pilch. Divit 
Ike product by the thickness of Ike plate, in inches, and la tkg^ 
quotient add the diameter of the rivet. 

Or, ^-d•■^*!>i«, 

Example.— 

rivets H 'H'-'l' 
plftte and the r 




s the pilch for a double-riveted lap joint bavingl 
neter. the plate iKiDg \ icch thick? Both tlM| 



MARINE-BOILER INSPECTION 



Solution.— Applving the rul 
P = - - - ■ 



■ + +5 = 3. no in. Ans. 



\ 

42. For steel plate and steel rivets, the pitch, under the 
American rules, is found as follows for single-riveted or 
double-riveted lap joints: 

Rule. — Multiply 23 by the square of the rivet diameter, in 

inches, and by .7S5i and by the number of rivels in one pitch. 

Divide the product by 2li limes the thickness of the plate, in 

inches, and to tlie quotient add the rivet diameter. 

^ 23 rf* .7854 71 , 

28 /■ 

NoTH. — This formula reduces to the simpler form pi'— \- d\ 

examiners of mariue engineers usually prefer candidates to work 
CKamples by the formulas priatecl in the Rules of their various Boards, 
which formulas for tbis reason are here given as they appear ip the 
American, Board of Trade, and Canadian rules. Many of these 
formulas can be reduced mathematically to a simpler form. 

Example.— Find the pitch of steel rivets | inch in diameter for a 
single -riveted lap joint, with steel plate -j^inch thick. 
Solution. — Applying the rule, 
< tS)' X .7864 X 



Or. 



- + d 



P = - 



SXtV 



- + I = 2.0(H in. Ans. 



I 



43. To prevent choosing a rivet diameter larger in pro- 
portion to the thickness of the plate than experience has 
shown to be warranted, the American rules provide that in 
single-riveted lap joints the pitch of the rivets must never 
be greater than 1.31 times the plate thickness plus it inches. 
For double-riveted lap joints, the pitch must not exceed 
2.62 times the plate thickness plus IS inches. 

44. The Board of Trade and Canadian rules for finding 
the greatest pitch of rivets in ordinary chain or zigzag-riveted 
lap or butt joints for iron plates with iron rivets are alike. 

Rule. — Multiply the square of the rivet diameter by .781)4 
and by the number of rivets in one pitch, and by 1.75 if the 
rivets are in double shear. Divide the product by the plate 
thickness and to the quotient add the rivet diameter. 




^\ 



28 MARINE-BOILER INSPECTION §18 

Or, for single shear, 

and for double shear, 

. d\nbA n\.lb . ^ 
P = J. rd 

Example. — What is the greatest pitch of the rivets in an ordinary 
triple-riveted, double-butt-strap joint where the plate is 1 inch thick 
and the rivets are l^V inches in diameter, both plate and rivets 
being of iron? 

Solution. — In this case ir » 3; see Art. 40. The rivets are in 
double shear. Applying the rule, 

(ItV)'X. 7854X3X1.75 . , , 
P = = h iVy = 5.717 m. Ans. 

45. The Board of Trade and Canadian rules for finding 
the greatest pitch of rivets in ordinary chain or zigzag-riveted 
lap or butt joints for steel plates with steel rivets are almost 
alike, differing slightly in the numerical value of one of the 
factors. 

Bole. — Multiply 23 by ike square of the diameter of the 
rivets in inches^ and by .7854, and the number of rivets in one 
pitch, and by 1,75 if the rivets are in double shear, and by the 
factor of safety for shell plates. Divide the Product by the product 
of 4.5 (4.25 under Canadian rules) and the tensile strength of 
the plate, in gross tons, and the thickness of the plate, in inches. 
To the quotient add the diameter of the rivet, in inches. 

Or, for single shear (Board of Trade), 

, ^ 23 d' .7854 nF . 
^ 4.55.7- 

and for double shear (Board of Trade), 

23d\78b4nl.75F . 
^ 4.55.7- 

and for single shear (Canada), 

^ 4.25 S^T 

and for double shear (Canada), 

23 rf* .7854;! 1.75/^ , 
^ 4.25 S,T 



§18 



MARINE-BOILER INSPECTION 



29 



ExAMFLB, — Under Board o£ Trade rules, what is the greatest pitch 
of rivets in a double- butt-strap joint, double chain riveted with l-inch 
rivets, if the plate is } inch thick, has a tensile strength of 28 gross 
tons, and the factor of safety corresponding to the constrnction is 6.3? 
Plate and rivets are steel. 



- -|- 1 = 4,65 in., nearly. Ans. 

46. To prevent the choice of a diameter of rivet so large 
as to be badly out of proportion to the thickness of the plate, 
both the Board of Trade and Canadian rules fix a maximum 
pilch that must never be exceeded. 

Hule. — To find the maximum pilch of rivets, multiply the 
constant taken from Table II by the tfiickness of the plate, in 
inches, and add li inches. 

Or, p = CT-^n 

in which C = constant taken from Table II. 

TABLE II 
CONSTANTS FOR FINDING MAXIMITM PITCH OF RIVETS 



It will be plain that the pitch of rivets should be calculated 
by the proper one of the preceding rules and then checked 

by applying the rule given in this article. 

Example. — Referring to the example in Art. 45, Hod if the pitch 
there calculated will be passed. 



SoLtrriON.— By Table II, (he 



<|-(-lt = J.a-i it 
This shows (hat the pitch previously calculated i) 
inspection. Ans. 



s3.5. Applying the rule, 




30 



MARINE-BOILER INSPECTION 



iu 



47. Rtilos for Diameter of Rivet. — The Americ 
rules present a table of proportions of single- and doubl 
riveted lap joints, from which it appears that for 
riveted lap joints and iron plates and iron rivets the rivel 
diameter is equal to the plate thickness plus | inch. For 
double-riveted lap joints and iron plates and iron rivets, the 
rivet diameter is equal to the plate thickness plus n^ inch. 
For single-riveted lap joints and steel plates and steel rivets, 
the rivet diameter is equal to the plate thickness plus i^ inch. 
For double-riveted lap joints and steel plates and steel rivets, 
the rivet diameter is equal to the plate thickness plus I inch. 

The Board of Trade and Canadian rules stale that the rivet 
diameter should never be less than the thickness of the plate. 

48. Rules for Dletnuce From Center of Rivet t9 
Edfte of Plate. — The American, Board of Trade, and Cana- 
dian rules all state that the distance from the center of the 
rivet to the edge of the plate must never be less tbao 
li times the rivet diameter. 

49. Rules for Distance Betvpeen Ro-vva of RIvetB. 
The American, Board of Trade, and Canadian rules specify 
that the distance between the rows of rivets in all ordinary 
chain-riveted joints {the American rules only cover double- 
chain-riveted lap joints) shall not be less than twice the rivet 
diameter, and should preferably be twice the rivet diamettt 
plus i inch. 

50. For double-zigzag-riveted lap joints, the Americas 
rules specify that the distance between the rows of rivets 
must be that given by applying the rule in this article. The 
Canadian and Board of Trade rules prescribe the same rale 
for all ordinary zigzag-riveted lap and butt joints. 

Rule. — Multiply the sum of 11 limes the pitch and 4 tim 
the rivet diameter by the sum of the pilch and 4 times the t 
diameter. Extract the square root of the guotienl and divHt 
the root by 10. 



Or, 



<{np + \d) (.p + Ad) 

10 




§18 



MARINE-BOILER INSPECTION 



31 



Example.— Wilh rivets having a diameter of J inch and a pitch of 
2i inches, what should be the distance between the rows ol rivets, the 
joint being double zigzag riveted? 

Solution.— Applying the rule. 



P 



K = 



V(n X 2H 



<?)X(gi + 4Xi) 



10 



1.2E 



Ans. 



51. The Board of Trade and Canadian rules provide 
that for chain-riveted joints having each alternate rivet 
omitted in the outer tow, or in the inner and outer rows, 
the distance between those rows of rivets having the larger 
and smaller number of rivets should be calculated by the rule 
given in the previous article. If the calculated value is less 
than twice the rivet diameter, the distance between the rows 
of rivets must be made at least twice the rivet diameter, and 
preferably i inch more. It is to be observed that the greatest 
pitch is to be used in applying the rule referred to. 

52. For a triple-chain-riveted butt joint in which every 
alternate rivet is omitted in the outer row, the distance 
between the inner and middle row of rivets, according to the 
Board of Trade and Canadian rules, must not be less than 
twice the rivet diameter, and preferably should be a inch more. 

53. For a triple-zigzag-riveted butt joint in which every 
alternate rivet is omitted in the outer row, the distance 
between the inner and middle row of rivets, under Board of 
Trade and Canadian rules, is found as follows: 

Rule. — Multiply the sum of 11 limes the pitch and 8 limes the 
rivel diameter by the sum of the pitch and 8 times the rivet diatn- 
eter. Extract the square root of Ihe product and divide the root 
by 20. 

Or, 

EsAMFLB. — What should t>e the distance between the inner and 
middle row of rivets in a tri pi e-iigzag- riveted butt joint in which every 
alternate rivet is omitted in the outer row, it the rivets are Ij iochcB 
in diameter and have a pilch of 9 inches in the outer row? 

SoLimoN. — Applying the rule, 



y_ ^ ■<{np + 8d)ip + &d) 




MARINE-BOILER INSPECTION 

54. In a Oouble-zigzag-riveted butt joint with every alter- 
nate rivet omitted in the outer row, and in a triple-zigzag- 
riveted lap joint and butt joint with every alternate rivei 
omitted in the inner and outer rows, the distance between the 
rows of rivets, according to the Board of Trade and Canadian 
rules, is to be found by the rule given in this article. The 
same rule is also used for finding the distance between the 
middle and outer rows of rivets in a triple-zigzag-riveted bui: 
joint where every alternate rivet in the outer row has been 
omitted. 

Knle. — Multiply the sum of \h times the greatest pitch and 
the rivet diameter by the sum of A times the greatest pilch 
and the rivet diameter. Extract the square root of the produet. 

Or, V = VrnZ-t- lYMpVd) 

EXAMPta. — In a triple-riveted lap joint having' every alternat* 
rivet omitted in the inner and outer rows, the greatest pitcb of Ihs 
rivets is S inches and their diameter 1^ inches; what stioold tx Ibe 
distance between the rows of rivets? 

Solution.— Applying the rule, 

y = -VtH X B + li) X (sV X 8 -I- U) = 3.06 in. Ans. 

55. Rules tor Diagonal Pitch. — The American rules 
specify for double-zigzag-riveted tap joints, and the Board of 
Trade and Canadian rules, in addition to this kind of joint, 
specify for triple-zigzag-riveted and quadruple- zigzag-rive led 
lap joints, and for double-zigzag-riveted and triple-zigzag- 
riveted butt joints, it being understood that joints in which 
alternate rivets are omitted in any row are not refetred to, 
that the diagonal pitch of the rivets is to be found as follows: 

Knle. — To 6 times the pitch add 4 times the rivet diameter. 
Divide the sutn by 10, 

Or, p,= ^-P±A^ 

'^ 10 

ExAHPLB. — In Adouble-sjgzag-riveted lap joint tfae rivets are }iiic)i 
in diameter and have a pitch of 2^ inches; what should the diagooot 
pitch be? 

Solution.— Applying the rule, 
6 X 2^ -t- 4 > 




» 



§18 MARINE-BOILER INSPECTION 33 

56. For triple-zigzag-riveted lap joints having every 
alternate rivet omitted in the outer rows, and butt joints 
having alternate rivets omitted in the inner and outer rows, 
and for a double-zigzag-riveled butt joint having every alter- 
nate rivet omitted in the outer row, the Board of Trade and 
Canadian rules give the rule presented in this article for 
finding the diagonal pitch. The same rule is also applied to 
finding the diagonal pitch between the middle and outer rows 
of rivets in a triple -zigzag-rive ted butt joint having every 
alternate rivet omitted in the outer row. 

Rule. — To Vo times the greatest pitch add the diameter of 
the rivet. 

Or, pi = -hp + d 

EXAUPLE.— la a triple- zigzag- riveted butt joint in whicb every alter- 
nate rivet has been omitted in the outer row, the rivets are \\ inches 
in diameter and the pitch in the outer row is "i inches. Find the 
diagonal pitch between the middle and outer rows o( rivets. 

So h;tion.— Applying the rule, 

pd = A X 7J -I- 1-i = 3.6 in. Ans. 

57. The Board of Trade and Canadian rules specify that 
the diagonal pitch between the inner and middle row of 
rivets in a triple-zigzag-riveted butt joint having every alter- 
nate rivet omitted in the outer row, shall be found as follows: 

Bule. — To 3 times the greatest pitch add 4 times the rivet 
'.meter and divide Hit sum by 10. 



a, Bule 
m^amete 

^ Or, 



10 



'ExAUPLB. — Using the values given in the example in Art. 56, what 

■hould be the diagonat pitch between the inner and middle row 

_ ■©£ rivets? 

SotDTION.— p = ^3 in,; rf = ij in. Applying the rule, 
3 X 7i + 4 X li 




34 MARINE-BOILER INSPECTION §18 



EXAMPLES FOR PRACTICE 

1. Under American rules, what should be the pitch of the rivets in 
a double-zigzag-riveted lap joint, iron plate and iron rivets, if the 
rivets are 1 inch in diameter and the plate is |-^ inch thick? 

Ans. 3.285 in. 

2. Under American rules, what should be the pitch of the rivets in 
a double-chain-riveted lap joint, steel plate and steel rivets, if the 
rivets are 1 inch in diameter and the plate is f inch thick? 

Ans. 3.064 in. 

3. Under American rules, what is the maximum pitch permissible 
in the joint in example 2? Ans. 3.26 in. 

4. Under Board of Trade and Canadian rules, what is the pitch of 
the rivets in a triple-riveted lap joint, iron plate and iron rivets, the 
plate being } inch thick and the rivets 1 inch in diameter? 

Ans. 4.14 in. 

5. Under Board of Trade and Canadian rules, what is the maxi- 
mum pitch permissible in the joint in example 4? Ans. 4.227 in. 

6. Under American rules, what will be the rivet diameter for a 
steel plate ^i inch thick, double-riveted lap joint, the rivets being 
steel? Ans. l-j^jin. 

7. If the rivets are 1^ inches in diameter, how far must their center 
be from the edge of the plate? Ans. 2i^ in. 

8. What should be the distance between the rows of rivets in a 
double-zigzag- riveted lap joint if the rivets are 1 inch in diameter and 
the pitch is 3 inches? Ans. 1.609 in. 

9. In a triple-zigzag-riveted butt joint having every alternate rivet 
omitted in the outer row, what should be the distance between the 
middle and inner row of rivets if the rivets are 1 inch in diameter and 
have a pitch of 6 inches in the outer row? Ans. 1.609 in. 

10. What should be the distance between the middle and outer 
rows of rivets in the joint in example 9? Ans. 2.3&4 in. 

11. What should be the diagonal pitch in an ordinary double- 
zigzag-riveted lap joint if the rivets are 1 inch in diameter and the 
pitch is 3 inches? Ans. 2.2 in. 

12. In a double-zigzag-riveted butt joint every alternate rivet is 
omitted in the outer row; tl^e pitch in the outer row being 5 inches 
and the rivets j^ inch in diameter, what should the diagonal pitch be.^ 

Ans. 2^ in. 



§18 MARINE-BOILER INSPECTION 

1.1, Find the diagonal pitcb between the inner and middle row 
of rivets in a triple-zigzag-riveted butt joint having every alternate 
rivet omitted in the outer row, the rivets being If inches in diameter 
and 8 inches pitch in the outer row. Ans, 2.95 in. 



EFFICIENCY OF RIVETED JOINTS 

58, The ratio between the strength of the plate and the 
strength of the joint is called the emdency of the Joint, 
and is expressed as a percentage of the strength of the solid 
plate. 

In order to determine the efficiency of the joint, its resist- 
ance must be computed for each of the diiTerent ways in 
which it may fail; the lowest efficiency found will be the 
efficiency of the joint. 

A riveted joint may fail in several ways: (!) The plate 
may break along the rivet holes. (2) The rivets may shear 
off. (3) The plate may shear out in front of the rivet. 
(4) The plate may crush in front of the rivet. (5) In zig- 
zag-riveted joints, the plate may break diagonally between 
the rivet boles. With joints having the proportions given 
by the Board of Trade, Canadian, and American rules, the 
liability of a joint failing in the way described under (3), 
(4), and (5) is extremely retnote. 

69. The American rules do not contain any formula for 
finding the efficiency of a joint; the Board of Trade and 
Canadian rules present the formulas here given. In these 
_,iormulas, 

p = greatest pilch of rivets, in inches; 
' d = diameter of rivet, in inches; 
T = thickness of plate, in inches; 
Sx = tensile strength of steel plate, in gross tons (2,240 

pounds); 
K = number of rivets in one pitch; 
r = percentage of plate left between holes in greatest 

pitch; 
R = percentage of value of rivet section; 

- percentage of combined plate and rivet section. 



60. For failure of the joint by breaking of the plate, iot 
iron plate and iron rivets or steel plate and steel or iron 
rivets, the Board of Trade and Canadian rules state that ibe 
efficiency is to be calculated as follows, calling it the per- 
ceutage of plate left between holes In greatest plU^U; 

Ktile. — Multiply 100 by the dUkreme between the greattst 
pitch and the rivet diameter, in inehes. Divide the prodwd i§ 
the greaieii pilch, in inches. 

Or, r = ^MAPszJX 

P 

EXAMFLH.— What is the efficiency of a double- riveled lap joint, plait 
and rivets being steel, calculated for failure by breaking of Ihe plaic, 
when the pitch of the rivets is 3 inches and their diameter is I iuch? 
Solution. — Applying the rule, 

r = i*2<J3zLii = 66.67 per cent, Aos. 

61. For failure of the joint by shearing of the rivets, for 
iron plates and iron rivets, the Board of Trade and Canadian 
rules state that the efficiency is to be calculated as follows. 
calling the efficiency the percentage of value of rivet 
section; 

Rule. — Multiply 100 by the square of the rivet diameter, by 
.785-1, by the number of rivets in one pitch, and by 1.75 if the 
rivets are in double shear. Divide the product by the product al 
the greatest pitch and plate thickness, in inches. 

Or, for single shear, 



i 



R » 



100 d- .7854 » 
PT 



and for double shear, 

„ 100 d- .7854 n 1.76 
''- JT 

The rule just given assumes that the shearing strength 
and tensile strength of wrought iron are equal. This 
assumption is incorrect, as the shearing strength of wrought 
iron is in reality somewhat less than its tensile strength. 
The rule must be used, however, by candidates for marine, 
engineer's license. 







§18 



MARINE-BOILER INSPECTION 



37 



EXAMP1.B. — Given a double -rive ted lap joint, iron plale nnd iron 
rivets, the plate being i inch chick, the rivets l-jV inches in diameter, 
and the pitch 3.42t> inches; what is the efficiency calculated Eor failure 
by shearing of the rivets? 

Solution.— « = 2. Applying the rule, remembering that the 
ri'-ets are in single shear, 

_ 100 X (1 -iV) ' X ,7854 X 2 _ 
3.426 X} 



/{ = - 



= 69 per cent., nearly. Ans. 



P 



62. For failure by shearing of the rivets, with steel 
plates and steel rivets, the Board of Trade prescribes the 
rule given in this article. The Canadian rule differs slightly 
in the value of one of the factors. The result is called the 
percentage of value of rivet section. 

Rule.~Aful/ifi/y 100 by 23, by the square of the rivet 
diameter, by .7854, by the number of rivets in me pilch, by 
J. 75 ('/ the rivets are itt double shear, and by the factor of 
safety demanded by the eonstruclion of the joint. Divide the 
product by the prodiul of 4.5 {4.25 under Canadian fiules) and 
the tensile strength of the plate, in gross tons, and the greatest 
pitch, in inches, and the plate thickness, in inches. 
Or, for single shear (Board of Trade), 

„ ^ 100x23rf'.7854«F 
4.5 S,pT 
and for double shear (Board of Trade), _ 

J. ^ 100 X 23 d' .7854 n 1.75 F 
4.5 S,pT 
and for single shear (Canada), 

R = 1™>123 d' .7 854 nF 
4.25 5. p T 
and for double shear (Canada), 

p = 10Qx23fl " .7854 « 1.75 f 
4.25 S.pT 
Example.— In a triple-riveted, double-butt-strap joint having alter- 
nate rivets omitted in the outer row, the rivets are lj inches in diam- 
eter and pitched T^ inches in the outer row and 3j inches in the 
middle and inner rows. The plate is 1 inch thick and has a tensile 
strength ot 30 gross tons per square inch of section. The factor of 
safety beiijg 5, under Board of Trade rules, what is the efficiency of 




38 MARINE-BOILER INSPECTION §18 

the joint calculated for failure by shearing of the rivets? Plate and 
rivets are steel. 

Solution. — In this case, » ~ 5. Applying the rule, remembermg 
that the rivets are in double shear, 

^ 100 X 23 X(li)*X. 7864X6X1.75X5 ^ ^^ 

R = -, I ^^ — —. ; « »8.79 per cent. Ans. 

4.5 X 30 X 7i X 1 ^ 

63. The Board of Trade rules, for failure by shearing of 
the rivets, with iron rivets and steel plate, specify that the cal- 
culation for efficiency is to be made as follows, calling the 
efficiency the percentage of value of rivet section: 

Rule. — Multiply 100 by 17,5^ by the square of the rivet 
diameter^ in inches , by .7854 , by the number of rivets in one 
pitchy by 1,75 if the rivets are in double shear ^ and by the factor 
of safety demanded by the construction. Divide the Product by 
the Product of 4.5 ^ the tensile strength of the plate ^ in gross tons^ 
the greatest pitch of the rivets ^ and the plate thickness^ in inches. 

Or, for single shear, 

^ ^ 100 X 17.5^'.7854,«/^ 

A.bS.pT 
and for double shear, 

^ ^ 100 X 17.5 ^' .7854 « 1.75/^ 

A.bS.pT 

Example. — In a double-riveted lap joint, the steel plate is ^ inch 
thick and has a tensile strength of 28 gross tons. The iron rivets are 
\^ inch diameter and have a pitch of 2.9 inches. The factor of safety 
being 5.2, what is the efficiency of the joint calculated for failure by 
shearing of the rivets? 

Solution. — In this case, « = 2. Remembering that the rivets are 
in single shear, and applying the rule, 

^ 100X17.5X (H)"X. 7854X2X5.2 ^^ ^^ 

^ = T-^ — -^ — TTz, i « 68.76 per cent. Ans. 

4.5 X 28 X 2.9 X i *^ 

64. The Canadian rules, for failure by shearing: of the 
rivets, with iron rivets and steel plates, specify that the calcu- 
lation for efficiency is to be made as follows, calling the 
efficiency the percentage of value of rivet section: 

Rule. — Multiply 100 by 8, by the square of the rivet diam- 
eter, by ,7854 y by the number of rivets in oru pitchy by 1.75 if 



H« 



MARINE-BOILER INSPECTION 



the rivets are in double shear, and by the factor ol safety demanded 
by the covstruction. Divide the product by the product ol 4.25, 
and 13, and the greatest pitch, in inches, and the plate thickness, 
in inches. 

Or, for single shear, 

100X8t/'.7854«^ 



R = 

and for double shear, 



4.25 X 13^ T 
100x8rf'.7854« \.1hF 



4.25 X \Zp T 
Example. — Taking the example given in Art. 63, calculate the 
efficiency of the joint by the Canadian rule. 
I SotCiTioN,— Applying the rule, 

100X8X {\%y X .7854 X 2 X 5.2 



JT •>- 



- = 71. ft 



perci 






¥ 



3 X 2.9 X i 

65. Riveted joints in which every alternate rivet has 
been omitted in the outer row, or in the inner and outer 
rows, may fail by breaking of the plate in the row or rows 
having the greatest number of rivets and the shearing of 
rivets. For this manner of failure, the Board of Trade and 
Canadian rules state that the efficiency is to be calculated as 
follows, calling it the perceutaffe of combined plate and 
rivet section: 

Rule. — Multiply 100 by the difference between the greatest 
pilch and twice the rivet diameter. Divide the product by the 
greatest pitch. To the quotient add the quotient obtained by 
dividing the efficiency ol the joint calculated for failure by 
shearing of the rivets, by the number of rivets in one pitch. 
lQ0(p-2d) R 



Or. 



R. =- 



Example, — In a tri pie- ligzag- rive led joint having double butt 
straps, every alternate rivet is omitted in the outer row. The rivets are 
\\ inches in diameter and pitched Tj inches in the outer row. Plate 
and rivets are steel, the plate being t inch thick and having a tensile 
strength of 28 gross tons. The factor of safety, under Board of Trade 
rules, is 5. Calculate the percentage of combined plate and rivet section. 

Cercentage of value of the rivet section hat to be 
r the case given, the rule in Art. B2 applies. 




40 MARINE-BOILER INSPECTION §18 

Remembering that » = 5, and that the rivets are in doable shear, 

„ lOOX 23 X(li)*X. 7854X5X1.75X5 ,^ ^^ 

R = —^ — — — —. = 105.84 per cent. 

4.5 X 28 X 7i X 1 

Applying the rule in this article, 

100X(7j-2Xli) 105.84 ^, ^^ 

R^ = ^ * . 4- —z — = 91.17 per cent. Ans. 

7^ 5 

66. The application of the rules will now be shown. 

Example 1. — Calculate the efficiency of a doable-chain-riveted bntt 
joint with single butt strap, plate and rivets wrought iron; the plate is 
\ \ inch thick, the rivets are 1 inch diameter, and the pitch is Z\ inches. 

Solution. — For the joint given, « = 2. The rivets are in single 

shear. Applying the rule in Art. 60, 

100 X (3i - 1) ^ ^ 
r = -r = 69.23 per cent. 

Applying the rule in Art. 61, 

^ = ^^^1? if ^' -70.3 per cent. 
3i X It *^ 

Then, efficiency of joint is 69.23 per cent. Ans. 

Example 2. — Calculate the efficiency of a single-riveted lap joint, 
plate and rivets of steel; the plate is -^ inch thick and has a tensile 
strength of 28 gross tons. The rivets are 1 inch in diameter and have 
a pitch of 2\ inches. Use Board of Trade rules and a factor of safety 
of 5.5. 

Solution. — For this case, « = 1; the rivets are in single shear. 
Applying the rule in Art. 60, 

r = -J- = 52.94 per cent. 

28 

Applying the rule in Art. 62, 

^ 100 X 23 X 1" X .7854 X 1 X 5.5 ^- ^ 

R = — -- — —, s = 65.93 per cent. 

4.5 X 28 X 2i X 1^ ^ 

Efficiency of joint is 52.94 per cent. Ans. 

Example 3. — Calculate the efficiency of a triple-riveted, double- 
butt-strap joint in which every alternate rivet has been omitted in the 
outer row. Plate and rivets are steel. The plate is 1 inch thick and 
has a tensile strength of 30 gross tons. The rivets are 1\ inches in 
diameter and are pitched 7f inches in the outer row and 3| inches in 
the inner row. The factor of safety is 5. Use Canadian rules. 

Solution. — For this case, « = 5; the rivets are in donble shear. 
Applying the rule in Art. 60, 

100 X (7| - l\) 



7i 



= 83.87 per cent. 



MARINE-BOILER INSPECTION 



Applying the rule in Art. 63, 
„ 100X23X(U)"X.7854> 



I 






4.25 X30x7f X I - ■ K- 

Applying: the rule in Art. G5, 

^ _ 10.X(7}-2XU) ^ 12^7 _ ^ .^ ^^^ ^^^, 

7J 6 

EfBciency of joint Is 83.87 per cent. Ans. 

ExAUPLs i. — Calculate, by Canadian rules, the efficiency of a 
triple -riveted, single-butc-strap joint in which the plate is of steel and 
^ inch thick. The iron rivets are | inch in diameter and 3j inches 
pitch. The faclor of safety Is 1.9. 

Solution. — For this case, n = 3; the rivets are in single shear. 
Applying the rule in Art. 6U, 

100 X {Si - I) 
r = — i — — = 73.08 per cent. 

Applying the rule in Art. 64, 

„ 100 X 8 X {h' X .7854 X 3 X 4.9 .. 

Ji = ~ — , ; => 78.76 per cent. 

4.25X13x3ixi ' 

Efficiency of joint is 73.08 per cent. Ans. 

EXAMPLES FOR PRACTICE 

1. What is the percentage of plate left between the rivets in the 
greatest pilch in a double- rive led, douhle-bult-strap joint having 
rivets } inch in diameter and 2.8 Inches pilch? Ans. 73.21 per cent. 

2. What is the percentage of value of the rivet section of the joint 
in example 1. plate and rivets being iron and the plate being^ inch 
thick? Ans. 98.17 per cent. 

3. Given a triple-itigiag- riveted lap joint, steel plate and steel 
rivets. The plate is i inch thick, and has a tensile strength of 
28 gross tons. The rivets areji inch in diameter and their pitch is 
3.3 inches. The factor of safety being 5, find the percentage of value 
of the rivet section nnder Canadian rules. Ans. 91.1 per cent. 

4. If the rivets in example 3 were wrought iron, what would the 
percentage of value of the rivet section be under Canadian rules, 
assuming them to be J inch in diameter? Ans. TS.IS per cent. 

5. In a triple-chain-riveted, double-butt-strap joint, alternate 
rivets are omilled in the inner and outer rows. The rivets are 1 J inches 
in diameter and pitched 7i inches in the inner and outer rows, Plate 
and rivets are steel, the plate being ^ inch thick and having a 
tensile strength of 27 gross tons. The factor of safety being 5.2, 

mbined plate and rivet section under 
Ans. 96.84 per cent. 



I 





MARINE-BOILER INSPECTION 

(PART 2) 



AMERICAN, BRITISH, AND CANADIAN 
RULKS 



OPENINGS IN BOILERS 



MANII 

1. The American rules state: "All manholes for the 
shell of boilers over 40 inches in diameter, when practicable 
for use, shall have an opening not less than 10 by 16 or H 
by 15 inches in the clear, except that boilers 40 inches 
diameter of shell and under shall have an opening of not 
less than 9 by 15 inches in the clear in manholes: Provided, 
That manhole opening in front head of externally fired 
boilers, under the flues, so required by section 4434. Revised 
Statutes of the United States, shall be of dimensions not 
less than S by 12 inches in the clear," 

2. Neither the Board of Trade nor the Canadian rules 
specify a minimum size of manholes; both specify that man- 
hole and handhole openings in the shell of cylindrical boilers 
should have their shorter axes placed longitudinally. The 
Board of Trade rules prohibit the use of cast-iron manhole 
plates; the American rules permit cast iron to be used for 
this purpose, stating: "Provided, however, that the material 
shall be of the best grade and of suitable thickness and 
uniform section for the pressure allowed on boilers." 

Co>>r»(*ttrf ty litttnalioHal Trzllmik Comtanr. Enltrtd at Slaliunfi' Hall. Lotidim 
lU 




44 MARINE-BOILER INSPECTION §18 



REINFORCEMENT OF OPENINGS 

3. The American rules state: **When holes exceeding 
6 inches in diameter are cut in boilers for pipe connections, 
man- and handhole plates, such holes shall be reinforced, 
either on the inside or outside of boiler, with reinforcing 
plates, which shall be securely riveted or properly fastened 
to the boiler, such reinforcing material to be ring^s of the 
same kind and quality as the material reinforced, and of 
sufficient width and thickness of material to equal the amount 
of material cut from such boilers, in flat surfaces; and where 
such opening is made in the circumferential plates of such 

* boilers, the reinforcing ring shall have an area of at least 
one-half the area of material there would be in a line drawn 
across such opening parallel with the longitudinal seams of 
such portion of the boiler. On boilers carrying 75 pounds 
or less steam pressure, a cast-iron stop-valve, properly flanged, 
may be used as a reinforcement to such opening. When 
holes are cut in any flat surface of such boilers and such holes 
are flanged inwardly to a depth of not less than li inches, 
measuring from the outer surface, the reinforcement rings 
may be dispensed with. 

4. The Board of Trade rules state: ''Compensating rings 
of at least the same sectional area as the plate cut out, 
should be fitted around all manholes and openings, and in 
no case should the rings be less in thickness than the plates 
to which they are attached. 

**It is very desirable that the compensating rings around 
openings in flat surfaces should be made of L or T iron." 



5. The Canadian rules state: Manhole openings must 
be stiffened with compensating plates or rings of at least 
the same effective sectional area as the plate cut out, and in 
no case shall such plates or rings be of less thickness than 
the plate to which they are attached, nor the attachment of 
less strength than the plate or ring. All openings in the 
shells of boilers should have their short axis placed longi- 
tudinally, and if not so placed must have compensating 



118 



MARINE-BOILER INSPECTION 



45 



plates or rings, and attachments, equal to twice the effective 
sectional area of the plate cut out," 

When cast-iron frames are fastened around manholes in 
steamboat boilers, a compensating ring in addition must be 
provided. 

Mud-holes or handholes should not be placed in boiler 
shells of a greater short diameter than 5 inches, unless pro- 
vided with reinforcine plates, and if on the cylindrical shell 
of a boiler, their short diameter should be in a line with the 
axis of the shell. 

FLAT SURFACES AND STATING 



STRENGTH OF FLAT SCRFACES 

6. The American rules provide that the working pres- 
sure on flat surfaces supported by stays shall be determined 
by the rule given in this article, defining as a flat surface 
any stayed surface formed to a curve having a radius over 
21 inches. 

Rule. — Multiply ike constant corresponding lo the conditions 
by the sguate of the plale thickness, in sixteenths ol an inch, 
and divide (he product by the square ol the greatest pilch of the 
stays, in inches. 



Or. 
in which P^ 



P. 



P' 



working pressure, in pounds per square inch; 

T = thickness of plate, in sixteenths of an inch; 

P = greatest pitch of stays; 

C = 112 for ordinary riveted screw stays and 
plates -h inch thick or under; 

C = 120 for ordinary riveted screw stays and 
plates over I's inch thick; 

C = 140 for plates fitted with stays having one 
nut on ihe inside and one nut on the out- 
side of the plate; 



i6 MARINE-BOILER INSPECTION §18 

C = 160 for plates fitted with washers having at 
least half of the thickness of the plate and 
a diameter of at least half of the greatest 
pitch of the stays, riveted to the outside 
of the plates, and having: one nut inside 
of the plate and one nut outside of the 
washer: T will then equal 80 per cent, of 
the combined thickness of the plate and 
washer; 
C = 200 for plates fitted with doubling plates 
which have a thickness equal to at least 
half of the thickness of the plate reinforced 
and covering: the full area braced (up to the 
curvature of the flang:e, if any), riveted to 
either the inside or outside of the plate, and 
stays having one nut outside and oneinside 
of the plates: provided, that the washers 
or doubling plates are riveted to the plates 
with rivets spaced and of suflScient sec- 
tional area as provided for stays and fiat 
surfaces, the pitch to be determined by 
the thickness of the washer or doubling 
plate: T will then equal 80 per cent, of the 
combined thickness of the two plates; 
C = 200 for plates fitted with tees or angle bars 
having a thickness of at least two-thirds 
the thickness of plate and depth of webs 
at least one-quarter the greatest pitch of 
the stays, and riveted on the inside of the 
plates, and stays, having one nut inside 
bearing on washers fitted to the edges of 
the webs that are at right angles to the 
plate: T' will then equal 80 per cent, of the 
combined thickness of web and plate. 
For the cases where C = 160 and 200, T'may be found as 
follows: Assume that the combined thickness is li inches. 
Then, 80 per cent, of this is li X .8 = .9 inch. This value 
must be expressed in sixteenths, which may be found by 



§18 



MARINE-BOILER INSPECTION 



multiplying (he value {expressed decimally) by 16. Thus, 
.9 inth = .9 X 16 = 14.4 sixteenths of an inch. 

Example 1,— What working pressure will be allowed on a Hal plate 
I inch ihick, fitted with screw slays having a pitch of T inches one 
way and Oj inches the other way? 

SoLr-noN.— Since | = A. 7"=" 8. For this case, C = H2. Apply- 
ing the rule, 

/>» = ^^' = 82.20 lb. per sq. in. Ans. 

ExAUPLB 2.— A plate j inch thick is supported by screw stays 
having a pitch of 10 inches; what working pressure will be allowed on 
this plate? 

SoLimoN.— Since f = H,T=- 12. For this case. C = 120. Apply- 
ing the rule, 

P. = "~^ = 172.8 lb. per sq. in. Ans. 

Example 3.— What working pressure will be allowed oo a plate 
}-f inch thick that is supported by stayrods 14 inches from center to 
center, the stayrods being filled with one nut on the inside and one 
nut on the outside of the plate? 

T =• 13. For this c 



SOLDTION.- 



140 > 



140. Applying Ihe rule, 
— = 120.71 lb. per sq, in. Ans. 

Example 4. — A plate ^ inch thick is braced by stayrods spaced 
14 inches center to center and is reinforced by washers 8 inches in 
diameter and J inch thick, properly riveted: Che stayrods have one nut 
inside the plate and one nut outside the washer. What working 
pressure will be allowed on the plate? 

Solution.— J -|- g = 1 in. 80 per cent, of this is 1 X .8 = .8 in. 
Reduced to sixteenths, this is .3 X IIJ = 12.8. For this case, C = 160. 
Applying the rule, 

160 X 12.6' 



/"- = - 



14" 



- = 133.75 1b. persq. i 






Example 5.— A plate J inch thick is reinforced with a doubling 
plate J inch thick and properly riveted; Ihe plate is braced by stay- 
rods spaced 15 inches center to center and each is supplied with a nut 
on the inside and outside of the plate. Find the allowable working 

SOLUTION.- I -t- i - 1}- 80 per cent, of this is ij x .8 = 1 in., 
whence T = lii. For this case, C = 200. Applying the rule, 
200X16- 



i-.-- 




- B 227.5fj lb. persq. i 






48 MARINE-BOILER INSPECTION §18 

7. The American rules provide that the maximum pitch 
of stays, measured from center to center, must not exceed 
IO2 inches when the plates are exposed to the impact of the 
heat or flame, and 18 inches in all other cases. 

• 

8. In applying: any one of the rules relating to the 
strength of fiat surfaces it must be remembered that it pre- 
supposes that the stress per square inch of section does not 
exceed the lawful limit. Should the stress be more, the pres- 
sure must be reduced to suit the size of the stays. 

9. The Board of Trade, and also the Canadian, rule for 
the working pressure allowable on flat surfaces is as follows: 

Rule. — Multiply the constant corresponding to the circum- 
stances by the square of the sum of the plate thickness^ in six- 
teenths of an inchy and 1, Divide the product by the difference 
between the number of square inches of surface supported and 6, 

Or, B = C( 7>1).- 

5-6 
in which B = working pressure, in pounds per square inch; 

T = nuhierator of fraction expressing plate thick- 
ness, in sixteenths of an inch; 

5 = surface supported, in square inches; 

C = 192 under Board of Trade and 160 under Cana- 
dian rules, when the plates are not exposed 
to the impact of heat or flame, and the stays 
are fitted with nuts on both sides of the plates 
and doubling strips not less in width than 
two-thirds the pitch of the stays and of the 
thickness of the plates, are securely riveted 
to the outside of the plates they cover; 

C = 168 under Board of Trade and 150 under Cana- 
dian rules, when the plates are not exposed 
to the impact of heat or flame, and the stays 
are fitted with nuts on both sides of the plates, 
and with washers not less in diameter than 
two-thirds the pitch of the stays and of the 
same thickness as the plates, securely riveted 
to the outside of the plates they cover; 



ii8 



MARINE-nOILER INSPECTION 



49 



C - 132 under Board of Trade and 100 under 
Canadian rules, when the plates are not 
exposed to the impact of heat or flame, and 
the stays are fitted with nuts on both sides 
of the plates, and with washers outside the 
plates at least three times the diameter of 
the stay, and two-thirds the thickness of the 
plates they cover; 

C = 120 under Board of Trade and 90 under 
Canadian rules, when the plates are not 
exposed to the impact of heat or flame, and 
the stays are fitted with nuts on both sides 
of the plates; 

C = 90 under Board of Trade rules, when tube 
plates are not exposed to the direct impact 
of heat or flame, and the stays are fitted 
with nuts; 

C = 70 under Board of Trade rules, when tube 
plates are not exposed to the direct impact 
of heat or flame, and the stay-tubes are 
screwed and expanded; 

C = 70 under both Board of Trade and Canadian 
rules, when the plates are not exposed to 
the impact of heat or flame, and the stays 
are screwed into the plates and riveted over; 

C = 60 under both Board of Trade and Canadian 
rules, when the plates are exposed to the 
impact of heat or flame, with steam in con- 
tact with the plates, and the stays are fitted 
with nuts and washers, the latter being at 
least three times the diameter of the stay, 
and two-thirds the thickness of the plates 
they cover; 

C = 54 under both Board of Trade and Canadian 
rules, when the plates are exposed to the 
impact of heat or flame, with steam in con- 
tact with the plates, and the stays are fitted 
with nuts only; 





50 



MARINE-BOILER INSPECTION 



§1! 



C = 80 under both Board of Trade and Canadian 
rules, when the plates are exposed to the 
impact of heat or flame, with water yi con- 
tact with the plates, and the stays are 
screwed into the plates and fitted with nots; 
C = 60 under both Board of Trade and CauadUa 
rules, when the plates are exposed to the 
impact of heat or flame, with water in con- 
tact with the plates, and the stays are 
screwed into the plates, and have the ends 
riveted over to form substantial beads; 
C = 36 under both Board of Trade and Canadian 
rules, when the plates are exposed to the 
impact of heat or flame, with steam in con- 
tact with the plates, with the staj'S screwed 
into the plates, and having the ends riveted 
over to form substantial heads. 
Both the Board of Trade and Canadian rules state; "When 
the riveted ends of screwed stays are much worn, or when 
the nuts are burned, the constants should be reduced, but the 
surveyor (inspector, in Canada) must act according to the 
circumstances that present themselves at the time of the sur- 
vey (inspection, in Canada), and it is expected that in cases 
where the riveted ends of screwed stays in the combustion 
boxes and furnaces are found in this state it will be often 
necessary to reduce the constant 60 to about 36." 

All the values of C given in this article are for iron boilers. 
For steel boilers in which the material complies with the 
specifications, both the Board of Trade and Canadian rules 
state: "If flanged plates and plates exposed to flame comply 
with the foregoing conditions, the constants in the Rules (or 
iron boilers may be increased as follows: 

"The constants for flat surfaces when they are supported, 
by stays screwed into the plate and riveted, 10 per cent. 

"The constants for flat surfaces when they are supported 
by stays screwed into the plate and nutted, or when the stays 
are nutted in the steam space, 25 per cent. This is also, 
applicable to the constants for flat surfaces stiffened by 



MARINE-BOILER INSPECTION 



jpported by nutted 



riveted washers or doubling strips, and s 
slays." 

Example 1.— What working pressure, under Canadian rules, will 
be allowed on a com bust ion -oh amber back plale ^ inch thick, made ot 
wrought iron, and stayed by screwed staybolts having a pitch of 
6i inches and fitted with ntit&i 

Solution.— f = |S, or T = 10. 

5 = 6j X 6i = 42,2.5 sq. in. 

The plate being in contact with water and exposed to the direct 
impact of the flame, and the screwed staybolts having nuts, C = SO. 
Applying the rule, 



_<_(IO+l|^ 
42.25 - 6 



7 lb. per sq. i 






Example 2.— What working pressure, under Board of Trade rules, 
will be allowed on the back head of a single-ended Scotch boiler built 
of wrought iron, the head being 1 inch thick, and the stayrods having 
a pitch of 15 inches and being fitted with auts on each side of the 
plate, but no washers? 

Solution,— 1 - fj. or T = 16. 

5 = 15 X 15 = 226 sq. in. 

The back head of a single-ended Scotch boiler not being in contact 
with flame, C = 120 for this case. Applying the rule, 
< (16+ n- 



" - 225^ 
EXAMPL8 3.— If the boiler ii 

passed inspection, what pressur 
Solution. —In this case, 1 

26 per cent. Then, 



= 158.31 









120 may be increased 



hi)' 



5 lb. per sq. i 



10. When plates not exposed to the impact of the heat 
or flame are reinforced by doubling plates riveted to them, 
said doubling plates covering the whole of the flat surface, 
the working pressure, according to the Board of Trade rules, 
is to be found as follows: 

'RuXe.^Multiply the cmistant applicable to the case (as givm 
in Art. O) by the square of the sum of the plate thickness, in 
sixteenths of an inch, and 1. .4dd to the product, the product of 
the constant and the square of Ike sum of the doubling-plate 




52 MARINE-BOILER INSPECTION §18 

thickness^ in sixteenths of an inch^ and 1, Divide the sum by 
the number of square inches of surface supported diminished by 6, 

Or B = ^(7^+1)'+ C(7; + l)' 

in which Zi is the numerator of the fraction expressing the 

thickness of the doubling: plate, in sixteenths of an inch, and 

the other letters have the same meaning: &s in Art. 9. 

ExAMPLB 1. — The front head of a firebox boiler is of wrought iron 
^ inch thick and reinforced with a doubling plate f inch thick; it is 
stayed with stayrods having nuts inside and outside, and having a 
pitch of 14 inches. What working pressure will be allowed? 

Solution.— ^ = ^, or T' = 8. | = A, or 7; = 6. 

5 = 14 X 14 = 196 
By Art. 9, C = 120. Applying the rule. 

/? 120X(8-f D'-f 120X(6-f 1)' _ „o 1 1h rw.r en In A„c 

If = iQfi — R • P®^ ^^' *°" Ans. 

Example 2. — If the boiler in example 1 were built of steel, what 
working pressure would be allowed on the head? 

Solution. — The constant 120, by Art. 9, can be increased 25 per 

cent. Then, 

C = 120 X 1.25 = 150 

Applying the rule in Art. lO, 

^ 150X(8-f D' -f 150X(6-f 1)' inoftQiK • a 

^ ^ J — 102.63 lb. per sq. m. Ans. 

lyb — o 

II. The Canadian rules state that when doubling plates 
cover the whole of the fiat surfaces, and have a thickness of 
not less than two-thirds or more than the thickness of the 
plate covered, and are substantially riveted, the working pres- 
Mure on such reinforced surfaces is to be found as follows: 

Uulo. — Multiply the constant 140 for iron, or 175 for steel 
by the square of the sum of the plate thickness and one-half the 
doubliNX'Plate thickness, both expressed in sixteenths of an inch, 
f)iviile the product by the number of sgtmre inches supported. 

i4o(r+0' 

( )r. for iron. B = ^ ' 

175(r+0* 
i4iMt for steel, B = ^^-3; — — 




MARINE-BOILER INSPECTION 



in which / is Ilie numerator of the fraction expressing the 
thickness of the doubling plate, in sixteenths of an inch, and 
the other letters have the same meaning as in Art, 9. 

Example. — The front head of a firebox boiler made of steel is 
i inch thick and reinforced by a doubling plate J inch thick riveted 
to it; the stayrods being placed 15 iaches center to center, what 
working pressure would be allowed? ,^^_ 



SoLtnioN.- 



Applyiog the rule, 

„ 1-5X(10 + J)' 



= 10. 



: 162.'14 lb. per sq, ii 



Ans.1 



13. The Board of Trade rules state that when doubling 
plates do not cover the whole of the flat surfaces but are 
fitted between the rows of supporting stays, the working 
pressure allowed on such flat surfaces should be only two- 
thirds of that which would be allowed for similar doubling 
plates extending beyond and embracing the supporting stays, 
as found by the rule in Art. 10. 

13. The Canadian rules give the following rule for find- 
ing the working pressure on flat steel plates that are in no 
way exposed to the action of the fire or hot gases and are 
supported by stays having nuts, and washers equal in diam- 
eter to at least one-third of the pitch of the slays and a 
thickness of one-half the thickness of the plate: 

Rale.— Multiply 48,000 by the square of (he plate thickness, 
in inches, and diviJc the product by the square of the greatest 
pitch of the stays, in inches. 

t, 48,000 r- 



Or, 
in which 



T = thickness of plate, in inches; ^H 

P = greatest pitch of stays, in inches; ^J 

/*. = working pressure, in pounds per square inch. 



ExAJiPLB, — A Steel plate not exposed to fire or hot gases is 1 inch 
thick and is supported by slayrods having a pitch of H inches, the 
stayrods being fitted witti washers f inch thick and 5 inches in diam- 
eter; what working pressure will he allowed? 



MARINE-BOILER INSPECTION 



Solution. — Applying the n 
48.000 X r 



/■. = 



2*4.9 lb. persq. i 



14. When tube plates are not reinforced by doublini 
plates between the nesis of tubes, the working pressure 
ailowable on the part of the tube plates between the nests oi 
tubes is, under Board of Trade rules, to be calculated by ihe 
rule in Art. 9, and when doubling plates are fitted, by the 
rule in Art. 10. The value of 5 in those rules is to k 
taken as one-half the sum of the square of the horizontal 
pitch of the stay-tubes and the square of the vertical pitch 
of the stay-tubes, both pitches being in inches. The pitches 
are to he measured from center to center of the stay-tubes, 
and no deduction is permitted for any tubes in the surface 
included in the rectangle formed by Hoes joining the centers 
of the stay-tubes nearest the space between the nests. 

Example. — The back tube sheet of a. three-furnace Scotch boiler ii 
I inch thick, and made of steel; the stay-tubes, which are iittcd with 
nuts in the bounding rows of the nests of tubes, are placed 15 iacbfi 
center to center horiioti tally and 9j inches verticaliy. What working 
pressure will be allowed on the part of Ihe tube-sheet tietween the 
□esls of tubes? The boiler has one large combustion chamber. 



SoinnoN.- 



15" 



5= - 



K9i)' 



160 sq. in. nearly 
which may be increased 35 per c 



By Art. 9, C = 8 
that is, for this case 

C= MX 1.25 = 
As no doubting plate is Rtted, the rale 
T s> 14. Applying the rule, 
„ 100X114-1-1) ^ 



. in. nearly ^M 

eased 35 per cent, for sIm|^| 

100 H 

lArl, 9 applies. J = H.« 

persq, in. Ans. ^M 

iratiTp nn th*» nart rtf th^^* 



= 146.1 lb. persq, i 

15. The working pressure allowable on the part of the 
tube sheet that receives the tubes is found, under Board of 
Trade rules, by the rule given in Art. 9. The value of 5 in 
that rule is found for this case by multiplying together the 
horizontal and the vertical pitch of the stay-tubes, in inches, 
and subtracting therefrom the aggregate area, in square 
inches, of the tubes in the space bounded by four stay-tui 
plus the area of one stay-tube. 




§18 MARINE-BOILER INSPECTION 55 

EXAMPLH. — What working pressure, under Board of Trade rules, is 
allowable on that part of a steel tube-sheet that contains the nest tubes 
if the sheet is J inch thick; the stay-lubes have a horiKontal pitch of 
7 inches and a vertical pitch of »jf inches; there are five ordinary 
tubes 2^ inches in outside diameter in the space bounded by four stay- 
tubes, and the stay-tubes are 2j inches in outside diameter? 

Solution.— I = \i. or T = 14. 

C= HOX 1.25 = 100 

S is found as follows: Area of rectangle formed by lines drawn from 
center to center of four stay-tubes is 7 X 9} = 68.25 sq. in. Area of 
stay-tube is (23)' X .7S64 = 5,iM sq. in. Area of ordinary tubes is 
5 X (2i)* X .7854 = 24.54 sq. in. Then, 

5 = 68.35 - (24,54 4- 5.94) = 37.77 

Applying the rule in Art. 9, 

B - ^^-77~V" " ™ '*'■ P^"" ^^- '"■• "^'■'y' '*°^- 
16. The Canadian rules do not contain any rules for 
finding the working pressure on the flat surface of tube 
plates of iron boilers, prescribing rules for steel tube plates, 
however. The working pressure on the part of the tube- 
sheet that contains the tubes is to be found as follows: 

Rule. — Multiply 140 by the square of the plate thickness, in 
sixteenths of an inch, and divide the product by the square of the 
mean pilch of the stay-tubes, measured from center to center. 

Or, P. - »»-r 

in which P,, = working pressure, in pounds per square inch; 

T = numerator of fraction expressing plate thick- 
ness, in sixteenths of an inch; 
P = mean pitch of stay-tubes, 
ExAMPLB.— In a steel tube-sheet I inch thick, the stay-tubes are 
Lced 7 inches center to center horizontally and 9^ inches center to 
rrtically; what working pressure will be allowed under 
Canadian rales? 



^W" 



Solution.— i = H. or T = 14. 




i 



I 



56 MARINE-BOILER INSPECTION §18 

17, Under Canadian rules, the working pressure on that 
part of a steel tube-sheet that lies between the nests of tubes, 
if this part is not covered by a doubling: plate, is to be found 
as follows: 

Rule. — Multiply the constant corresponding to the conditiom 
by the square of the tube^ plate thickness^ in sixteenths of an inch, 
and divide the Product by the square of the center-to^enkr 
distafue^ in inches^ of the bounding rows of tubes. 

Or. /V = ^ 

in which Pw = working pressure, in pounds per square inch; 
T = numerator of fraction expressing thickness 
of tube plate, in sixteenths of an inch; 



P = horizontal distance from center to center of 
the bounding row of tubes; 

C = 120 where the stay-tubes in the bounding 
rows are pitched with two plain tubes 
between them and are not fitted with nuts 
outside the plates; 

C = 130 if the stay-tubes are fitted with nuts out- 
side the plates and there are two plain 
tubes between the stay-tubes in the bound- 
ing rows; 

C = 140 if each alternate tube in the bounding 
rows is a stay-tube and not fitted with nuts 
outside the plates; 

C = 150 if each alternate tube in the bounding 
rows is a stay-tube aud fitted with nuts 
outside the plates; 

C = 160 if every tube in the bounding rows is a 
stay-tube but not fitted with nuts outside 
the plates; 

C = 170 if every tube in the bounding rows is a 
stay-tube and each alternate stay-tube is 
fitted with nuts outside the plates. 

Example. — A tube-sheet is } inch thick and made of steel. In the 
two vertical rows of tubes bounding two nests, each third tut)e is a 



MARINE-BOILER INSPECTION 

slay-luhe, the stay-lubes befog fitted with nuts outside the lube-sheet, 
r distance of the stay-tubes in the bound- 
hat working pressure will be ailowud, 
that part of the tube-sheet situated between 



The homontal c 


enler-to-ce 


ing rows being 


13 inches. 


under Canadian 


rules, on I 


the nests? 




Solution.— 


i = il.o 


ing the rule, 




„ 


_ 130 X 12 



;, C = 130, Apply- 



7 lb. per sq. i 



18. When the part of a steel tube-sheet that lies between 
the nests of tubes is reinforced by a doubling plate securely 
riveted thereto and having a thickness of at least two-thirds 
of the tube-sheet thickness, the Canadian rules specify that 
the working pressure allowable on this part shall be found 
as follows: 

Biile. — Multiply (he coiislant corresponding to the ease {^iven 
in Art. 17) by the square of the sum ol the lube-skeei thickness 
and half Ifie doubling-plate thickness, in sixteenths of an inek. 
Divide the product by the horizontal distance from center to 
center between the bounding rows of tubes. 



C[T^'-\ 



Or. 



A = 



in which / is the numerator of the fraction expressing the 
thickness of the doubling plate, in sixteenths of an inch, and 
the other letters have the same meaning and C the same 
values as in Art. 17. 

Example.— A steel tube plate % inch in thickness is reinforced by 
a doubling plate J inch thick; the tubes in the bounding rows are 
13 inches center to center horizontally, and each alternate tube is a 
stay-lube filled with nuts outside the plates. What working pressure, 
under Canadian rules, will be allowed on the part between the nests 
of tubes? 

Solution — | = iS[. or T = 10. \ = -j^j. or / = 8. C. by 
Art. 17, = 160. Applying the rule, 
<(10-!-|)' 



/". = - 



13' 



> 173.96 lb. per sq, in. Ans. 



19. The tube-sheet that forms part of a firebox tfr com- 
bustion chamber is subjected to a crushing stress. The 




A 



MARINE-BOILER INSPECTION 



magnitude of this stress ia limited by the rule ^iven in tl 
article, which appears in the American, Board of Trade, and 
Canadian rules. 

Rule.— From the least horizontal distance between tuheeenttrs, 
in inches, subtract the inside diameter of the tubes, in inches. 
Afultiply the retnainder by the thickness of the tube plate, in 
inches, and the required cotistani. Divide the product by the 
product of the extreme width [measured in the direction of the 
length of the boiler) of the firebox or combustion chamber and 
the least horizontal distance between tube centers, both in inchet,^ 



Or. 
in which B 



{D-d) rc 

WD 



working pressure, in pounds per square indiJ: 
D = least horizontal distance between tube centers, 

in inches; 

d = inside diameter of ordinary tubes, in inche^J 

T = tube-sheet thickness, in inches; 

W = width of firebox or combustion chamber, iii 

inches, or distance between tube-sheets in 

double-ended boilers in case the combusci 

chamber is common to the furnaces at both 

ends; 

C = 28,000 for steel under American, Board o£ 

Trade, and Canadian rules; 

C = 18,000 for iron under Canadian rules; 

C = 22,000 for iron under Board of Trade rules. 

RxAMi'i.B. — What working pressure, calculated for crushing and 

uniUr Americon rules, will be allowed aa a steel back tube-sheet oF i 

Scotch boiler i( the sheet is J inch thick, the tubes are 2j inches in 

lUHlde diameter and spaced 3^ inches center lo center horizontally, 

and the ccrabustion chamber is 25 inches wide? 



I 



Soil 



N,— C = 28,000. Applying the rnle, 
(3i - 2i) X i X 28,000 





MARINE-BOILER INSPECTION 



EXAMPLES FOB PRACTICE 

1. Under Aioeri can rules, what pressure will be allowed on the inner 
side plates of the firebox of a firebox boiler if the plates are ^ inch 
thick and stayed by ordinary riveted screw staybolts having a pitch 
of 6 inches? Ans. 213.3 lb. per sq. in. 

2. The front head of a Scotch boiler is stayed by rods 14 inches 
center to center that are each fitted with a washer of proper diameter 
riveted to the outside of the head and one nut inside the head and one 
nut outside the washer. The head is -j-J inch thick; the washers are 
i inch thick. What working pressure will be allowed , under American 
rules? Ans. 150,98 lb, per sq. in. 

3. Under Board of Trade rules, what pressure will be allowed on 
the outer firebox plates, which are not exposed to heal or dame, o( a 
firebox boiler if the plates are of steel ^ inch thick and the screw 
staybolts, which are riveted over, have a pitch of 6 inches? Take C 
as 77. Ana. 1W.27 lb. per sq. in. 

4. The back head of a single-ended Scotch boiler made of steel 
is ^ inch and reinforced by a doubling plate ^ inch thick; the stayrods 
have nuts inside and outside the plates, and are pitched Iti inches 
center to center. What working pressure will be allowed, under 
Hoard of Trade rules? Take Cas 150. Ans. 1.50 lb. per sq. in. 

a. What working pressure will be allowed, under Canadian rules, 
OD the head of example 4? Ans. 175 lb. per sq. in. 

6. A flat steel plate J inch thick and not exposed to the lire in any 
way is supported bystayrods having a pitch of 13 inches; the stayrods 
are 5tted with ants and washers, the washers being ^ inch thick and 
4i inches in diameter. What working pressure will be allowed on this 
plate, under Canadian rules? Ans. I,i9.76 lb, per sq. in. 

7. A double-ended Scotch boiler has a single combustion chamber 
common to all furnaces. The combustion-chamber tube-sheets con- 
tain three nests of tubes and are f inch thick, and made of steel. The 
stay-tubes in the bounding rows of tubes are pitched 9j inches verti- 
cally and 12 inches horizontally, and are fitted with nuts. What 
working pressure, under Board of Trade rules, will be allowed on the 
parts of the tube plates that are situated between the nests of lubes? 
Take Cas 100, Ans. 152,1 lb, per sq. in, 

8. What pressure will be allowed on the tube-sheets in example 7, 
under Canadian rules? There are two plain tubes between each two 
stay-lubes, Ans, 130 lb. per sq, in. 

9. A steel tube plate i inch thick is reinforced by a doubling 
^V^late I inch thick riveted to the part between the nests of tubes. In 



60 



MARINE-BOILER INSPECTION 



§18 



the bounding rows, each second tube is a stay-tube fitted with nuts; 
the horizontal center-to-center distance of the stay-tubes in the 
bounding rows is 11 inrhes. Under Canadian rules, what working 
pressure will be allowed on the reinforced part of the tut>e-sheet? 

Ans. 150 lb. per sq. in. 

10. What pressure, calculated for crushing and under Board of 
Trade rules, may be carried on an iron back tube-sheet -^ inch thick 
containing tubes having an inside diameter of 2^ inches and spaced 
4 inches . center to center, the combustion chamt>er being 22 inches 
wide? Ans. 187.5 lb. per sq. in. 

STRENGTH OF STAYS 

20, The area supported by one stay is found by multi- 
plying the distance from center to center of stays in one 
direction by the distance from center to center in the other 




Fig. 1 

direction. The center-to-center distance is known as the 
pitch of the stays. In Fig. 1, the stays being spaced equi- 
distant in both directions, the area supported by each stay 
is a X a = fl*. If the pitch is 7 inches and 6 inches, 
respectively, the area supported by each stay will be 7 X 6 
= 42 square inches. If extreme accuracy is required, the 



lis 



MARINE-BOILER INSPECTION 



61 



\ 



area of the stayboll should be subtracted from the area 
found by multiplying the pitch in one direction by the pitch 
in the other direction. Thus, in the example, assnmine the 
area of the staybolt to be 1 square inch, the area supported 
by the bolt will be 42 — 1 = 41 square inches. This is a 
refinement of calculation rarely used in practice, but it is the 
ithematically correct way of calculating the area. Now, 
tea supported by each slay, in square inches, multi- 
by the gauge pressure in pounds, constitutes the load 
by each stay. To bear the load safely, the stay must 
have a certain minimum area, which depends on the maxi- 
mum stress allowable per square inch of cross-section. 

By "area of a stay" is always meant the smallest cross- 
sectional area of the stay. In the case of a screw stay, the 
smallest cross-sectional area is that corresponding to the 
diameter over the bottom of the thread, unless some other 
part has a smaller diameter. 

21. Under American rules, the maximum stress allow- 
able on stays is as follows: Tested steel stays above 
2i inches, 9,000 pounds per square inch; tested steel stays 
li inches and not exceeding 23 inches, when such stays have 
neither been forged nor welded, excepting upsetting of the 
ends and subsequent annealing, 8,000 pounds per square 
inch; tested Huston or similar type of brace having a cross- 
sectional area exceeding 5 square inches, 8,000 pounds per 
square inch; tested Huston or similar type of brace having a 
cross-sectional area of not less than 1.227 and more than 
S square inches, provided the braces are prepared at one 
heat from a solid piece of plate without welds, 7,000 pounds 
per square inch; all stays not otherwise provided for, 
6,000 pounds per square inch. 

23. The Board of Trade rules, in case of new boilers. 
,fix the maximum stress on stays as follows: Solid iron 
.■crew stays, 7,000 pounds per square inch when the stays 
!bave not been welded: if iron stays have been welded, 
[6,000 pounds per square inch; iron slay-tubes having a net 
thickness of at least i inch, 6,000 pounds per square inch; 





MARINE-BOILER INSPECTION §13 



solid steel screw stays, tested and not welded, 9,000 pounds 
per square inch; tested steel stay-tubes having a net thick- 
ness of at least i inch. 7,500 pounds per square inch; stays 
for convex heads thick enough for the pressure not to 
require staying. 14,000 pounds per square inch when not 
welded and 10.000 pounds per square inch when welded. 

23. The Canadian rules, in case of new boilers, specify 
the maximum stress on stays as follows: Solid i 
stays, unwelded or worked in the fire, 7,000 pounds per 
square inch; solid iron screw stays which have been welded 
or worked in the fire. 6,000 pounds per square inch; tested 
solid steel screw slays, unwelded, 9,000 pounds per square 
inch; tested steel stayrods exceeding li inches in diaroetef^ 
10,000 pounds per square inch: tested steel stay-tubes having 
a net thickness of at least i inch, 7,500 pounds per square 
inch. 

For water-tube boilers, the allowable stress on solid iron 
screw stays, not welded, when supporting flat surfaces, mnst 
not exceed 5,000 pounds per square inch; when such stays 
have been welded the stress must not exceed 4,000 pounds 
per square inch, ttlien stays are used under conditions 
similar to those in fire-tube boilers, the stress may be 
6.000 pounds per square inch. When slays are used for 
supporting heads of steam drums, the heads being bumped 
and heavy enough to pass without staying, a stress of 
10,000 pounds per square inch is allowed. 

24. The rules given in this article and relating to stays; 
and staying should be very carefully studied and memorized^ 
especially by candidates for an American marine engineer's 
license, as the Examining Board is enjoined by law I 
reject candidates who cannot solve problems similar I 
those given in connection with the various rules. 

Let W = area, in square inches, supported by a screw stay, 

Slayboll. or siayrod; 

B = cross-sectional area of stay, in square inches; 

P = working steam pressure, in pounds per squaW 

inch; 



er', 





^is 



MARINE-BOILER INSPECTION 



/, — load on stay, in pounds; 

S = stress per square inch of cross-section of stay; 

S, — total allowable stress in a stay; 

Af = lawful stress per square inch of cross-section of 

stay; 
j4, — total area to be supported, in square inches; 
A^ = number of stays. 
Rale I. — To iiiid the load on a stay, vtulliply the area sup' 
ported by the slay, in square inches, by the gauge pressure of the 
steam, in pounds per square inch . 

Or. L = AP (1) 

ExAUPLE I. — Find the load on a staybolt, the pitch of Che stayboltB 
beioi; 8 inches either way and the steain pressure 65 pounds. 
Solution.— Applying the rule, 

i = 8" X 86 = 5,440 lb. Ana. 

Rule W.^To find the stress per square inch of cross-section 
in a stay, divide the load on the slay, in pounds, by ilte area of 
the stay, in square imkes. 

AP 



Or, 



3 = "^- 



(2) 



Example 2.— SCaybolts l] inches in diameter are placed Sj^ inches 
from cenler to center; the steam pressure Iwing 100 pounds, what is 
Che stress per square inch in Che stay? 

Soi.rTioN,— Theareaof ChestayboltiE(li)* X .7854 = 1.22T2sq.ia. 
Applying rule II, 

(8ir__ 

1.2272 



5= - 



i^s— = 6,887.39 lb. Ads. 



Riile m. — To find the total allowable stress in a stay, mul- 
tiply the area of the stay, in square inches, by the lawful stress 
per square imh. 

Or. S, = BM (3) 

Example 3. — Under Canadian rules, what stress can be allowed on 
_ ■ steel stayrod 2^ inches in dlaraeter? 

M Solution.— By Art. 23, M ■> 10.000. Applying the rale, 
H 5, = (2i)' X .7854 X 10.000 = 49.087 lb. Ans. 

t 



Rnle IV. — To find the working steam pressure allowable on 
slay, in pounds per square inch, multiply the area of Ike stay. 



64 MARINE-BOILER INSPECTION §18 

171 square inches^ by the stress corresponding to the diameter and 
material of the stay^ in pounds per square inch. Divide this 
prodiut by the area supported by the stay, in square inches. 

Or. ^=-5 (4) 

A 

Example 4. — Steel stayrods 2 inches in diameter are placed 14 inches 
from center to center; what working steam pressure would be allowed 
for these stays, under American rules? 

Solution.— By Art. 21, M = 8.000. Applying the rule, 

-, 2* X .78 54 X 8,000 ,00 oo ik a 
P = ^- ,, = 128.23 lb. Ans. 

Rule V. — To find the number of stays required, multiply the 
area of ike sheet to be stayed, in square inches, by the steam pres- 
sure^ in pounds per square inch, and divide by tfie total stress 
allowable in the given size of stay, in pounds. 

Or. N=^ (5) 

ExAMFLK 5. — Under Canadian rules, how many l|^-inch round iron 
stayt>oIts are required for a plate 40 inches by 50 inches to cany 
W pounds per square inch working pressure? The stay bolts have 
Ihs^q wv>rked iu the fire. 

SiXLinnoN.— By Art. 23, M = 6.000. Then, by rule III, 

wS » Kl^V X .7854 X 6,000 = 5,9W lb., nearly 

Applying rule V. 

.. 40X50X90 «^„ ^, ^ . 

*N « - - o*ti ~ = ^-2. say 31 stays. Ans. 

UuW Vl» — To find the area of a direct stay, in square inches, 
mh^tiply the area supported by the stay, in square inches, by the 
\U%im pi^fssmrr^ in pounds per square inch. Divide tfie product 
by th^ liMwful stress per square inch of cross-section. 

Or. ^ = 4^ (6) 

kCwNH^tic <^.'— Wrought'iron screw stays that have not been welded 
.41V |MWhi^.l 7 iucb«s center to center; the working pressure desired 
Uviui; U"^) (H^uttds per square inch, what should the area of each stay 
llv^ MiivW* Hv^^ixl of 'l>ade rules? 

H\a V'VU*.N Hv Art. 22, M = 7,000. Applying rule VI, 

ik — -, .^;r-. =1.26 sq. in. Ans. 

4 ilNAI 



us 



MARINE-BUILER INSPECTION 



66 



25. While the load on all direct stays is equal to the 
total pressure on the area supported by the stay, it is greater 
for palm stays. 

Let fi = length, in inches, of a line drawn at right angles 
to surface supported to end of diagonal stay, 
that is, distance, in inches, from boiler head to 
intersection of center line of stay with shell, in 
the usual case of head beiug at right angles to 
shell; 
/ = length of palm stay, in inches, measured between 
head and shell along center line of stay; 
A P = total pressure, in pounds, on area supported by 
stay; 
L = load on stay, in pounds. 

Rnle I. — To find the load, in pounds, on a palm stay, divide 
the length of the palm slay, in inches, by the distance from Ike 
head to the intersection of the center tine of the palm stay with 
the shell, in inches. Multiply the quotient by the total pressure, 
in pounds. 



Or, 



'AP 



(1) 



Example 1.— The palm stay of a boiler is 78 inches long; the dis- 
lauce from the head to the point of iaiersectioa o( the center line of the 
stay with the shell is 72 inches, if the area supported by the stay is 
100 square inches and the steam pressure 80 pounds, what is the load 
on the stay? 

Solution.— The total steam pressure is 100 X 80 = 8,000 lb. Then, 
I applying the rule, 

I i = =n X 8.000 = 8.666.67 lb. Ans. 

The stress per square inch of cross-section is found for a 
palm stay in the same manner as for any other stay, that is, 
by rule 11, Art. 24. 

Example S. — What is the stress per square inch if the stay in the 
previous example is 1| inches in diameter.' 

Solution. — Applying rule II. Art. 24, 



h 



S = -r. 



H,6tl6,67 



(lg)'X.7854 



= 4,178.92 lb. Am. 



66 MARINE-BOILER INSPECTION 

The load for a given supported area ot plate and steam.' 
pressure being greater for palm stays than for stajrods, tht 
allowable working pressure is conversely smaller. 

Rule II. — To find Ihe working steam pressure allowable on m 
palm slay, multiply the result obtained by rule IV, Art. 24, 
by ihe guolient obtained by dividing the dislaiue front ike head 
to the intersection, of the center line of the stay with the shell by 
the length, both in inches. 



Or, 



P- • 



I 



(2) 



in which B,Af,A, and P have the same meaning 
Art. 24. 

ExAMPLB 3.— What working steam pressure will be allowed for tb* 
pnlm stay having the same dimensions as given in the last example, 
made oC iron, and allowed b. stress of 6.00U pounds per square 

Solution.— Applying rule II, 
„ (]|)'X.7854x 



100 



*^78 ' 



114.86 11). Ads. 



Rule III. — To find the area of a palm stay, find the ana of 

a direct slay required to support ihe surface [by rule I'/.Art. '44): 
multiply this area by Ihe length of the palm stay, in inches, and 
divide the product by Ihe length of a line drawn at right attgia 
to the surface supported to l/ie end of Ihe palm stay. 



Or, 



(3) 
, /", and A/ have tlie same ; 



nmg as i 



in which . 
Art. 24. 

ExAMPLB 4.— Find the diameter of a wrought-iron palm stay, ' 
the [out welded on. which supports aa area of 140 square inches 
is to be strong enough to stand a working pressure of ItlO pounds ptf'fl 
square inch; the length of the stay is 60 inches, a.nd the length of ■! 
line at right angles to ttie boiler head to the end of Ihe slay is fiO inchM. | 
Take Ihe permissible stress per square inch as 5.000 pounds, i 
scrilied by the Board of Trade rules. 

Solution.— Applying the rule, 
1 40 X li" 
5,000 



^ = -^onfr-Xfln-*'^«''<l-i 



Then, d 






-' \:7! 



2,605 ii 



MARINE-BOILER INSPECTION 

larger commercial siz« of round iron would be used. This is either 
2-^ or 2^ in. , depending; on the practice of the mill from which the iron 
is purchased. Ans. 

26. The American, Board of Trade, and Canadian rules , 
al] give the same rule for the working pressure allowable on 
solid rectangular girder stays, sometimes called crown bars, 
and used for supporting the lop sheet of combustion cham- 
bers and fireboxes, differing on!y in the value of the constant 
employed. The American rules provide that when the pres- 
sure exceeds 160 pounds per square inch, girder stays must 
be suspended from the top of the shell by braces having each 
a sectional area at least twice the sectional area of each of 
the staybolts suspending the top sheet from the girder. 

Rule. — Multiply the constant corresponding to conditions by 
the square of the depth of the girder, in inches, and ike thick- 
ness of the girder, in inches. Divide this product by the differ- 
ence belaieen the width of the combustion box, in inches (measured 
in the direction the girder is applied) and the pitch of the stay- 
bolts, multiplied by the distance between girders from center to 
center, in inches, and the length of the girder, in feet. 

in which B = pressure, in pounds per square inch; 
d = depth of girder, in inches; 
T = thickness of girder, in inches; 
W = width of combustion box, in inches; 
P = pitch of staybolts, in inches; 
D = distance between girders, in inches, measured 

from center to center; 
Z. = length of girder, in feet; 
A'' = number of supporting bolts; 
C = 550, American rules, when the girder is fitted 

with one staybolt; 
C = 825, American rules, when the girder is fitted 

with two or three staybolts; 
C = 935, American rules, when the girder is fitted 
with four staybolts; 



68 MARINE-BOILER INSPECTION SlS 

C = — — -^ , Board of Trade rules, when the num- 

N-{- 1 

ber of staybolts is odd and the girder stays 

are iron; 

C = ,^ * ■ X 1.1, Board of Trade rules, when the 
A^-h 1 

number of staybolts is odd and the g:irder 
stays are steel; 

C = - — "•" * , Board of Trade rules, when 

the number of staybolts is even and the 
girder stays are iron; 

C = ^^t/^ i ~ X 1.1, Board of Trade rules, 
A^-j- 2 

when the number of staybolts is even and 

the girder stays are steel; 

C = ' -, Canadian rules, when the number of 

staybolts is odd and the girder stays are iron; 

C = —r—--- X 1.1, Canadian rules, when the num- 
jV-\- 1 

ber of staybolts is odd and the girder stays 

are steel; 

^ (A^+ 1) 1,000 ^ J. , ,. t_ 

C = -^ T^S,- — , Canadian rules, when the num- 

A^-j- 2 
ber of staybolts is even and the girder stays 
are iron; 

C = ^^t/^ o'^^ X 1.1, Canadian rules, when 
A^+ 2 

the number of staybolts is even and the 

girder stays are steel. 

KxAMPLB I. — Under American rules, what working pressure will be 
MlldWtid on a solid rectangular steel girder 7 inches deep and 2 inches 
thick, Htted with three staybolts, and 2.5 feet long? The girders are 
k|ii4('td 7 inches center to center, the pitch of the staybolts is 7.5 inches, 
Hud (ht> combustion chamber is 30 inches wide. 

Hdi-U'iioN.— For this case, C = 825. Applying the rule, 
^ - (30 -"7.6rx 7"ir2:5 = 205.3 lb. per sq. m. Ans 



us 



MARINE-BOILER INSPECTION 



Example 2. — What working pressure will be allowed under Board 
of Trade rules on tbe girder in example li 
Solution.— For this case, 

__ 3Xl.ac 



Applying the rule, 



< 1.1 ^ 



-— jj = 246.4 lb. per sq. : 






(30-7.5)x7X2.5 " 
EXAUPLB 3. — What working pressure will be allowed under 
'aaadian rules on the girder in example IP 
Solution.— For this case. 



C = -o- 



+ 1 



Applying the rule, 

(30 - 7.6) X 



EXAMPLES FOR PRACTICE 

Find tbe load on a staybolt. the pitch being 6^ inches a 



1 the 



sleaia pressure 125 pounds per square inch. Ans. 5,381.25 lb. 

2. Find the stress per square inch of section o£ a staybolt 1 inch 
in diameter, the pitch being 5| inches and the stearo pressure 
120 pounds. Ans. 4,621. S5 lb. per sq. in. 

3. Under Board of Trade rules, what stress can be allowed on an 
iron stayrod 2 inches in diameter and not welded? Ans. 21,991.2 lb. 

4. Under American rules, what working pressure will be allowed 
on Ij-inch steel staybolts pitched Sj inches center to center? Tbe 
slaybolts have not been forged or welded. Ans, 135.88 lb. per sq. in. 

5. The lop sheet of the middle combustion chamber of a Scotch 
double-ended boiler is 34 inches by 24 inches and is stayed by 1 J-'lnch 
steel staybolts: how many solid steel slayboHs will be required for 
KiO pounds per square inch working pressure, under Board of Trade 
roles? Ans. 12 

6. Wrought-iron screw stays pitched 8 inches center to center sup- 
port the plates of a Hrebox; what should be the area of each for a 
working pressure of 160 pounds per square inch, tinder Araerican 
rules? Ans. 1.707 sq. in. 



palm stay 



T. What is the stress per square inch of sect 
7 feet 6 inches long? The diameter of the stay i; 
supported by the stay is l^'ili square inches, and the steam pressui 



^ 



70 MARINE-BOILER INSPECTION §18 

130 pounds. The distance from the head to the point of intersection 
of the center Kne of the stny with the shell is 6 feet 9 inches. 

Ans. 6.620.831b. 

8. What working pressure, nnder Canadian rules, will be allowed 
on a welded wroogfat-iron palm stay 2^ inches in diameter, if the stay 
is 76 inches long and supports a surface of 140 square inches; the 
length of a line at right angles to the boiler head and to the end of 
the stay is 68 inches? Ans. 152.47 lb. per sq. in. 

9. Find the area of a wrought-iron palm stay, with the foot welded 
on. that is to support an area of 164 sqnare inches against a steam 
pressure of ISO pounds per square inch. The palm stay is 62 inches 
k>ng. and the length of a tine at right angles to the boiler head to the 
end of the stay is 57 inches. Inspection is under Board of Trade rules. 

Ans. 6.422 sq. in. 

10. Under American rules, what working pressure will be per- 
mitted on a girder stay fitted with four staybolts having a pitch of 
7 inches* the girder stay l>eing 2^ inches thick, having a depth of 
i^ inches, and a length of 3.9 feet? The girder stays are placed 7 inches 
center to center and the combustion chamber is 35 inches wide. 

Ans. 263.19 lb. per sq. in. 

FVRNACS FI«U£8, SMOKE FliUES, AND TUBES 



FURNACE FLUES 

37« The American, Board of Trade, and Canadian rules 
prescribe the same general rule for finding the permissible 
external working pressure on corrugated and similar furnace 
Aues« differing somewhat, however, in the value of the 
vxmstant forming a factor in the rule. 

Hul«s» — Multi^y ike amstani corresponding to the case by the 
ikiiJtfit^ss i^ tke iurmmce fluey in inches, and divide the product by 
the meiAH diameter^ im inches. 

iu which /^ ' working pressure, in pounds per square inch; 
T » thickness of furnace, in inches; 
/> s mean diameter, in inches; 
C « liXOOO for corrugated iron furnace flues, 
Canadian rules; 



§18 MARINE-BOILER INSPECTION 71 

C = 15,000 for bulb-type furnace flues made by 
the Leeds Forge Company, Board of Trade 
rules;' 
^L C = 15,600 for Morison furnace flues, American 

^t rules; 

^^P C = 14,000 for Morison furnace flues, under Board 

^^^^^^_ of Trade and Canadian rules, and for 

^^^^^^^H Purves, Pox, and Brown furnace flues under 

H^^H^^K American, Board of Trade, and Canadian 

" rules. 

Under American rules, the mean diameter of Morison 
furnace flues is the least inside diameter plus 2 inches; 
under Board of Trade and Canadian rules, it is the outside 
diameter at the bottom of the corruEalions. For ordinary 
corrugated (Fox) furnace flues, the mean diameter, under 
all rules, is the outside diameter at the bottom of the corru- 
gations. For Furves and Brown furnace flues, under all 
rules, the mean diameter is the least outside diameter, that 
is, the diameter of the plain parts. For Leeds Forge Com- 
pany furnace flues, under Board of Trade rules, the mean 
diameter is the outside diameter at the middle of the plain 
parts. 

Example 1. — What working pressure will be allowed, under 
Canadian rules, on an iron corrugated furnace flue 40 inches in 
mean diameter and \ inch thick? 

Solution.— C = 10.000. Applying the rule, 

10.000 X i 

P = jy— ' = 125 lb, per sq. in. Ans. 

Example 2. — What working pressure will be allowed on a Purves 
furnace Hue 36 inches in mean diameter and S inch thick? 
SoLDTiON. — C = 14,000. Applying the rule, 

14,000 X k 

P = — ^ = 1*5.83 lb. per sq. in. Ans. 

28. A type of furnace flue is used to some extent which 
is built up of short sections fitted into each other and riveted 
together, each section having one corrugation 2v inches deep, 
and the corrugations being 18 inches center to center. The 
plain parts at the end do not exceed 12 inches in length, and 




72 MARINE-BOILER INSPECTION §18 

the thickness is not less than i^ inch. For such a furnace, 
the American rules prescribe that the working pressure be 
found by the rule in Art. 27, making C = 10,000. 

29. Plain horizontal furnace flues made up of flanged 
sections riveted together with a ring between the flanges 
are known as the Adamson type of furnace flue. Under the 
latest American rules, the sections must not be shorter than 

23 inches nor longer than 54 inches, nor less than i^ inch 
thick. The flanges must have a depth of not less than three 
times the rivet-hole diameter plus the radius of the furnace 
wall (measured from the inside of the furnace flue); the radii 
of the flanges on the fire-side should be not less than three 
times the plate thickness. The distance from the edge of 
the rivet hole to the edge of the flange must not be less than 
the diameter of the rivet hole; the rivet diameter before 
riveting must be at least i inch more than the plate thick- 
ness. The rings must be at least i inch thick and have a 
depth of not less than three times the rivet-hole diameter; 
the fire-edge of the ring must terminate at or about the 
point of tangency to the curve of the flange. 

Rule. — Divide 51,5 by the outside diameter of the fumaa 
flue, in inches. Multiply the quotient by the difference between 
18,75 times the plate thickness ^ in sixteenths of an inch^ and the 
product of the length of the furnace flue section^ in inches, 
and 1.03, 

Or, /> = §^ [18.75 T^ {LX 1.03)] 

in which P = working pressure, in pounds per square inch; 
D = outside diameter of furnace flue, in inches; 
T = numerator of fraction expressing plate thick- 
ness, in sixteenths of an inch; 
L = length of furnace section, in inches. 

Example. — An Adamson type of furnace flue is made of sections 

24 inches long and ^^ inch thick; the diameter being 40 inches, what 
working pressure will be allowed under American rules? 

Sol iTiON. — 7* = 7. Applying the rule, 
r -^ ^^^ \ [1S.75 X 7 - (24 X 1.03)] = 137,16 lb. per sq. in. Ans. 



|18 MARINE-BOILER INSPECTION 73 

30. For horizontal steel furnace flues of the Adamson 
"pe, the Board of Trade and Canadian rules prescribe the 
■following rule for finding the working pressure: 

Rule. — Multiply 9,900 by the plate thickness, in inches, and 
divide the product by three times the outside diameter of Ike 
furnace Hue, in inches. Multiply the quotient by the difference 
between 5 and the guolient obtained by dividing the sum of l/te 
length between centers of flanges, in inches, and 12 by sixty 
limes the plate thickness, in inches. 

r 

T 
120 



Or, B -- 

3D \ GOT / 

1 which B = working pressure, in pounds per square inch; 
T = plate thickness, in inches; 
D = outside diameter of furnace flue, in inches; 
L = length of section between center of flanges, 
in inches. 

The rules provide that L must be never greater than 
~I20 T- 12. 



Kk AMPLE.— What working pressure will be allowed, under Board 
ot Trade and Canadian rules, od the furnace flue mentioned in the 
example in Art. 3U? 

Solution. — Applying the rule, 
„_ 9,900 X^^ 



3 X 40 



- X 5-_^ "^ ."-) = 130.97 1b. persq. ; 



>31. The working pressure allowable on plain cylindrical 
furnace flues, under American rules, is found by the rule 
^ven in Art, 29, taking L as the center-to -center distance 
of the strengthening rings. 
32. The Board of Trade and Canadian rules prescribe 
flie same rules for finding the working pressure allowable on 
plain cylindrical furnace flues, taking as a standard a furnace 
with longitudinal joints welded, or made with a single butt 
strap double riveted, or double butt straps single riveted, 
rivet holes drilled. Such furnaces are allowed the highest 
working pressure, determined in part by the constant 90,000 
H^in rule I, this article; for furnaces constructed in a different 
■teuiner than just specified, the constant is reduced. The 



^ 



74 



MARINE-BOILER INSPECTION 



S18 



working pressure is to be calculated both by rule I and by 
rule II; it will be the smaller of the two values. The rules 
given apply to iron furnace fines; for steel furnace fluei 
multiply the results of the two rules by 1.1 under Board of 
Trade rules; under Canadian rules multiply the result of 
rule I by 1.1, and in rule II substitute the constant 10,000 
for 9,000 in case the furnace flue is made of steel. 

Itnle l.^Multifily the conslanl 90,000 or suek other eonslant 
as the case demands by the square o! the plnte thickness, in in 
Divide the product by the product obtained by multiplying tht 
sum ot the length of tke furnace flue, in feet, and 1 by Ike 
diameter, in inches. 



Or, 



90,000 T' 



Rule U.—Afultifily 9.000 by the plate thickness, in inches, 
:d divide the product by the diameter, i?t inches. 
„ _ 9,000 T 



Or, 



D 



(2) 



^ 



In the rules given, let 

B — working pressure, in pounds per square inch; 

T = plate thickness, in inches; 

L = length, in feet, measured from center to center o( 
strengthening rings if such are fitted; 

D = outside diameter of furnace, in inches. 

The constants to be used in place of 90.000, are as follows, 
the joints referred to being the longitudinal joints: 
80,000 for single-butt-strap joints single riveted, drilled 

rivet holes; 
85,000 for single-butt-strap joints double riveted, punched 

rivet holes; 
75,000 for single-butt-strap joints single riveted, punched 

rivet holes; 
85,000 for double-butt-strap joints single riveted, punched 

rivet holes; 
80.000 for double-riveted lap joints, beveled, drilled rivet 

boles; 



>2 



MARINE-BOILER INSPECTION 

75,000 for double-rive led lap joints, not beveled, drilled 

rivet holes; 
70,000 for single-riveted lap joints, beveled, drilled rivet holes; 
65,000 for single-riveted lap joints, not beveled, drilled rivet 

holes; 
75,000 for double-riveted lap joints, beveled, punched rivet 

holes; 
70,000 for double-riveted lap joints, not beveled, punched 

rivet holes; 
65,000 for single-riveted lap joints, beveled, punched rivet 

boles; 

,000 for single-riveted lap joints, not beveled, punched 

rivet holes. 

ExAUPLB 1.— What working pressure will be allowed on a plain 
cylindrical furnace flue 42 inches in diameter, i inch thick, made of 
steel with welded longitudinal joint, fllted with strengthening rings 
2 feet apart, under Board of Trade rules? 

Solution.— In this case, the consiant is 90,000. Applying rule I, 
and multiplying by 1.1 on account of the furnace flue t)eing Bteel, 
90,000 X(i)' 
= !■>+ II V 41 X ' ■! = '^''-l^ lb. per sq. in 

Applying rule II and multiplying by I.I 
9.000 X k 
B = ■ — - --' X 1.1 = 117.86 1b. persq. in. 

The result of rule II being the smaller, it is the working pressure. 

Example 2. — Under Canadian rules, what working pressure will 
be allowed on a plain cylindrical steel furnace flue 40 inches in dianj- 
eter having the longitudinal seam fltled with a siagle-riveted single butt 
strap, drilled rivet holes, plate i inch thick, and strengthening rings 
placed 3^ (eel center to center? 

Solution.— For this case, the constant is 80.000. Applying rule 1 
and multiplying by I.l, 

~ [3i + l')x"40^ 
Under Canadian rules, the constant 9,000 in rule II becomes 10,000 
for steel. Applying the rule. 

10,000 xj _ 



1 = 122.22 1b. persq. i 



^^-^ = 126 1b. persq. in, 

s the working pressure 




76 MARINE-BOILER INSPECTION §18 

33. When plain cylindrical flues are used for furnaces of 
vertical fire-tube boilers, the working pressure allowable on 
them is, under American rules, found by the rule in Art; 27, 
making C = 10,677. The length of the furnace flue must 
not exceed 42 inches, however, measuring from the center of 
the rivet holes in the head to the center of the rivet holes in 
the leg. If the diameter of the ftu-nace flue for a vertical 
boiler exceeds 42 inches, it is considered to be a flat surface 
and must be braced by stays. 

34. Under Board of Trade and Canadian rules, the work- 
ing pressure allowable on plain cylindrical furnace flues used 
as furnaces for vertical fire-tube boilers is to be found by 
applying the two rules given in Art. 32, reducing the con- 
stant corresponding to the construction 10 per cent., that is, 
multiplying it by .9. 

35. Vertical fire-tube boilers are often fitted with a cone- 
shaped combustion chamber at the top. Under American 
rules, the working pressure is found by the rule in Art. 27, 
making C = 10,153. D is taken as the outside diameter at 
the middle of the height, and must not exceed 42 inches. 
When larger, the cone must be stayed as a flat surface. 
The height must not exceed 42 inches, measured from, the 
center of the rivet holes in the top head to the center of the 
rivet holes in the upper tube-sheet. 



SMOKE FLUBS 

36. Under American rules, the Morison, Fox, Brown, 
Purves, and Adamson types of furnace flues may be used as 
smoke flues for steam chimneys (superheaters). These 
types are almost invariably made of steel, and when used as 
smoke flues of superheaters their working pressure is ascer- 
tained by the rule in Art. 27, making C = 12,000, provided 
the conditions here given are complied with. 

Flues under 30 inches in diameter must be at least i^ inch 
thick and be supported by angle rings at least 2i inches by 
21 inches. 



Bis 



MARINE-BOILER INSPECTION 



77 



Flues 30 inches and under 45 inches in diameter must be 
at least e inch thick and be supported by angle rings at least 
21 inches by 2J inches. 

Flues 45 inches and under 55 inches in diameter must be 
at least A inch thick and be supported by angle rings at 
least 3 inches by i! inches. 

Flues 55 inches and under 65 inches in diameter must be 
at least : inch thick and be supported by angle rings at least 
3 inches by 3 inches. 

Flues 65 inches and under 75 inches in diameter must be 
at least Mt inch thick and be supported by angle rings at least 
3s inches by Sh inches. 

Flues 7.5 inches and under 85 inches in diameter must be 
at least h inch thick and be supported by angle rings at least 
3j inches by 3i inches. 

Flues 85 inches in diameter must be at least ii inch thick 
and be supported by angle rings at least 4 inches by 4 inches. 

For flues over 85 inches in diameter, add -,'i inch to I i inch 
for every 10 inches increase in the diameter. 
[ The center-to-cenler distance between the angle rings, or 
I the distance from the center of an angle ring to the center 
of the rivets in the heads must never exceed 2a feet, The 
angle rings must be accurately fitted to the ilues and sub- 
stantially riveted thereto, and must be connected to the outer 
shell by braces not more than 20 inches center to center on 
the flue. 

When the flues are made in sections not exceeding 2^ feet 
in length and united by Adamson flanged joints, the bracing 
may be dispensed with. 

Plain cylindrical flues may be used for superheaters if their 
length does not exceed 8 feet, and they have a minimum 
thickness of » inch when under 32 inches in diameter and 
a inch when over 32 inches and under 46 Inches in diameter. 
When these conditions are complied with, the constant Cin 
I flie rule in Art. 27 is 8,000. 



37. The Board of Trade and Canadian rules discourage 
I the use of steel for superheaters, Both provide that when 



78 MARINE-BOILER INSPECTION §18 

iron furnace flues are used as smoke flues for superheaters, 
the constants given in Art. 32 should be multiplied by { 
before applying the two rules in Art. 32; the smaller of the 
two pressures will then be the allowable working pressure. 

38. Under American rules, the working pressure on 
ordinary riveted or lap-welded smoke flues made in sections, 
as used in externally fired flue boilers, is found by the rule ii 
Art. 27, the constant C for this case being S.OOO. The fol- 
lowing conditions must be complied with: Greatest length 
of section for flues over 6 and not over 10 inches in diameter, 
60 inches; (or flues over 10 and not over 23 inches, 36 inches; 
for flues over 23 and not over 40 inches, 30 inches. Mini- 
mum thickness to be as follows: Flues over fi and not over 
7 inches, .18 inch; flues over 7 and not over 8 inches, ,2 inch; 
flues over 8 and not over 10 inches, .21 inch; flues over lO 
and not over 12 inches, .22 inch; for every inch increase ii 
diameter over 12 inches, the minimum thickness is to btf 
increased .01 inch over .22 inch. 

Example.— Find Ihe minimum thickness of a smoke flue 24 it 
in diameter, mode of sections properly riveted, and find ttie working; 
pressure allowed [hereon. 

Solution. — Minimum thickness is 

.22 -f [(24 - 12) X .01] = .34 inch. Ana. 

Applying the rule in Art. 27, and making C = 8,000, 



24 



■ >= 113.33 lb, per sq. In. Ans. 



39. Formerly, lap-welded flues over 6 inches and nol 

over 16 inches in diameter could be made as long as 18 ferf 
and were then allowed an external working pressure ot 
60 pounds per square inch under American rules; when made 
in sections not over 5 feet long, these flues were allowed a 
working pressure of 120 pounds per square inch. This hai 
been changed, however, and in all marine boilers made in thd 
United States of America after June 30, 1905, flues ovet 
6 inches in external diameter must conform to the conditioni 
stated in Art. 38. 




Sis MARINE-BOILER INSPECTION 



t 



BOILER TUBES 

40. Under AmericaQ rules, lap-welded boiler tubes from 
1 inch in diameter up to and including 6 inches in diameter 
and of standard thickness for the diameter, may be of any 
length and be allowed an external working pressure up to 
and including 225 pounds per square inch, if they are deemed 
safe by the inspectors. With each shipment of tubes, the 
manufacturers must furnish an affidavit certifying that the 
tubes have been properly tested. 

Neither the Board of Trade nor the Canadian rules contain 
any clause fixing the external working pressure to be allowed 
on boiler tubes. _^___ 

EXAMPLES FOR PRACTICE 

t. What workiDg pressure will be allowed, under Americaa rules, 
on a Morison furnace flue 38 inches in mean diarneler and i inch 
thick? Ans. 205.26 lb, per sq. in. 

2. A furnace flue 3fl inches in mean diameter is built up from sec- 
tions 18 inches long, each section having one corrugation 2i inches 
deep. The plate being ^ inch thick, what working pressure will be 
allowed, under American rules^ Ans. 13H.89 lb. per aq. in. 

.^. An Adamson type furnace Rue is made in sections 30 inches long 
and -^ inch thick; the outside diameter being 42 inches, what working 
pressure will be allowed, under American rules? 

Ans. 169.03 lb. per sq, in. 

4. What working presstire will be allowed, under Board of Trade 
rules, on the furnace flue in example .f? Ans. Iti5.98 lb. per sq. in. 

5. What working pressure will be allowed, under Canadian rules, 
on a plain circular (urnace flue made of iron i inch thick having a 
single-rive led, single-butt-strap longitudinal joint, an outside diameter 
of 38 inches, and a length of 4 feet? The rivet holes are drilled. 

Ans. lO.'i.SSlb. persq. in. 

6. Under American rules, what working pressure will be allowed 
on a plain cylindrical flue used for the furnace of a vertical boiler if its 
diameter is 36 inches and its thickness f inch? 

Ans. 110.18 1b. persq. in. 

7. A plain cyhndrical furnace flue 2^ feet long, with a welded 
longitudinal joint, made of iron -j^ inch thick, has an outside diameter 
of 30 inches and is used for the furnace of a vertical boiler; what 





80 MARINE-BOILER INSPECTION §18 

working pressure will be allowed on it under Board of Trade rules? 

Ans. 118.13 lb. per sq. in. 

8. The cone-shaped upper combustion chamber of a vertical boiler 
has a mean diameter of 36 inches and is f inch thick; what working 
pressure will be allowed on it, under American rules? 

Ans. 105.76 lb. per sq. in. 

9. A plain cylindrical furnace flue 30 inches in diameter and f inch 
thick is used as a smoke flue for a superheater; what working pressure 
will be allowed on it, under American rules? 

Ans. 166.67 lb. per sq. in. 

10. A plain cylindrical iron furnace flue 32 inches in diameter, 
f inch thick, and 48 inches long, with a welded longitudinal joint, is 
used as a smoke flue for a superheater; what working pressure will be 
allowed on it under Board of Trade rules? Ans. 112.2 lb. per sq. in. 

11. Under American rules, what is the minimum thickness of a 
smoke flue 30 inches in diameter? Ans. .4 in. 

12. Under American rules, what working pressure will be allowed 
on a properly made smoke flue .42 inch in thickness and 30 inches in 
external diameter? Ans. 112 lb. per sq. in. 

BOIIiEB HEADS AND DRUMHEADS 



BOILER HEADS 

41. The American rules state in regard to boiler heads: 
**A11 heads employed in the construction of cylindrical exter- 
nally fired boilers for steamers navigating the Red River of 
the North and rivers whose waters flow into the Gulf of 
Mexico, shall have a thickness of material as follows: 

For boilers having a diameter: 
Over 32 inches and not over 36 inches, not less than i inch. 
Over 36 inches and not over 40 inches, not less than A inch. 
Over 40 inches and not over 48 inches, not less than f inch. 
Over 48 inches, not less than f inch." 

42. In practically all fire-tube boilers, the heads are 
supported by stays, and the working pressure allowable on 
the heads is calculated by the rules in Arts. 6 to 18, which 
assume proper staying. When the staying is weaker, the 
working pressure must be reduced until the stress on the 
stays comes within the legal limit. 



MARINE-BOILER INSPECTION 



43. 



DRUMHEADS 

The heads of steam, water, and mud-drums are 



either flat, convex (bumped), or concave (dished). 

Under American rules, flat drumheads, unstayed, must 
not exceed 20 inches in diameter; the heads of steam and 
mud-drums of cylindrical externally fired boilers for steamers 
navigating the Red River of the North and rivers whose 
waters flow into the Gulf of Mexico must not be less than 
i inch thick; the flangfes of all unstayed flat heads must be 
made to an inside radius of at least 1' inches. When the 
heads exceed 20 inches in diameter, they must be stayed, 
and their working pressure is determined by the rule for 
flat surfaces in Art. 6. For unstayed f!at heads, the 
American rule for finding the working pressure is as 
follows: 

Rule. — Multiply the (onslant corresponding to the thickness 
by the square of the thickness of (lie material, in sixteenths of 
an inch, and divide the product by one-hall the area of the head, 
in square inches. 

Or, />=^ 

in which P — working pressure, in pounds per square inch; 

C = 112 for plates t^it inch and under; 
C = 120 for plates over t'o inch; 
T = numerator of fraction denoting plate thick- 
ness, in sixteenths of an inch; 
A = one-halt the area of the head, in square inches. 
ExAKPLB.— What working pressure will be allowed on a i 
unstayed steam drumlieai! J inch thick and 18 inches in diameter? 
Solution.— } = W, ot T = 12. 

. 18* X .78M ,.,, „ 
A =■ 2 = 127.2 sq. ID, 

= 120. Applying the rule, 

P = -^,^-.1— = 135.85 lb. per sq. in. Ans. 

Neither the Board of Trade nor the Canadian rules make 
provision for unstayed flat heads of steam or mud-drums. 



J 



MARINE-BOILER INSPECTION 

44. The Canadian rules slate thai in water-tube boikrs, 
drumheads must not be less than i inch thick. When stayed 
by a number of stays, the working pressure on a fiat drum- 
head is found by the rule presented in Art. 9, both under 
Board of Trade and Canadian rules. 

For the common case where the flat heads of a drum of a 
water-tube boiler are stayed by a single stayrod in the 
center of the heads, the Canadian rules specify that the work- 
ing pressure is to be found as follows, provided the plates 
of the drum are exposed to the impact of heat or flame (as in 
the Roberts boiler) and the stayrod is screwed into the 
heads and fitted with nuts, or well riveted over to form a 
good head, and the boiler is new: 

Rule. — AfuHiply 80 by Ihe square of the sum of the ifikknea 
of Ike head, in sixteenths of an inch, and 1. Divide the prodmi 
by the square of the difference between one-half Hie inside diam\ 
eler of Ihe dnimliead, in inches, and 1, diminished by 6. 

„_ mir+rr 



Or, 



in which P = working pressure, in pounds per square in( 
T = numerator of fraction denoting the Ihickm 

of the head, in sixteenths of an inch; 
d = inside diameter of the drumhead, in inches^ 
Example.— The Bat head of a sleara drum 24 inches inside diom- 
eler is stayed by a sinyrod in the cenler and is } inch thick; what 
working pressure will be allowed on it, under Canadian mles? 
Solution.— } = H, or T = 12. Applying the rule, 

P =. ^-^~^~ = 117.57 lb. per sq. in. Am. 



45. For unstayed convex heads, that is, heads receivia) 

the steam pressure on their concave side, the American r 
prescribe the following rule; 

Rule. — Aftiltifi/y the thickness of the plate, in inches, by i 
sixth of the tensile strength and divide the product by one-h 
the radius to which the head is bumped. Tfu quotient will 4j 



'11114 

1 

]es,H 




§18 MARINE-BOtLER INSPFXTION 83 

the working pressure if Ike head is single riveted lo the drum. 
When the head is double riveted to the drum, add 20 per cent.; 
that is, multiply by 1.2. 
Or. for single rivetine, 

--¥ 

and for double rivetinc, 

p =T^X 1.2 

in which P — working pressure, in pounds per square inch; 
T = thickness of head, in inches; 
.S = one-sixth of the tensile strength, in pounds 

per square inch; 
R = one-half the radius to which the head Is 
bumped. 
To find the radius to which the head is bumped, square 
one-haif the diameter of the head and divide by the height 
of the bump; to the quotient add the height of the bump and 
divide the sum by 2. 

EsAMPLH.— The head of a steam drum is convex, bumped to a 
radius of 36 iacbes. is ^ inch thick, and ha.s a tensile strength of 
55,000 pounds per square inch; what working pressure will be allowed 
on this head; (a) if single riveted? {b) if double riveted? 
Solution.— (a) Applying the rule, 

^" ^r^^ = 2W.83 lb, persq. in. Ans. 

(6) Applying the rule, 

P = 5 j^ — X 1.2 = 305.56 lb. per sq. in. Ans. 

46. The Board of Trade rules state: "If dished ends 
(convex heads) are not equal to the pressure needed when 
considered as portions of spheres, they should be stayed as 
flat surfaces." 

The general rule for finding the working pressure on a 
jointless sphere, or a portion of a jointless sphere, is as 
follows: 

Rule. — Multiply twice the tensile strength of Ike material, in 
pounds per square inch, by its thickness, in inches; divide the 




i 



84 MARINE-BOILER INSPECTION §18 

product by the product of the radius of the sphere^ in inches, and 
the factor of safety. 

Or. B = 2|-j: 

RF 

in which B = working pressure, in pounds per square inch; 

C = tensile strength, in pounds per square inch; 

R = radius of sphere, in inches; 

F = factor of safety. 

The Board of Trade rules do not give the factor of safety 

to be used in case of convex heads; they imply that it will 

be 4.5 if the material is tested. 

Example. — What working pressure will be allowed on a convex 
steel head \ inch thick, having a tensile strength of 60,000 pounds per 
square inch, and bumped to a radius of 30 inches, using a factor of 
safety of 4.5? 

Solution. — ^Applying the rule, 

^ 2 X 60,000 X i 
~ — any 4 5 — ~ 444.44 lb. per sq. in. Ans. 

47. Under Canadian rules, the working pressure on con- 
vex heads of steam drums, when not exposed to the impact 
of heat or flame, is found by the rule in Art. 46, makin^^ 
F = A when the heads are pressed into shape by a machine 
and subsequently annealed, and making F = 5 when the 
heads are worked into shape by hand and subsequently 
annealed. When a greater pressure is desired than given by 
the rule, the heads must be stayed as flat surfaces. 

48. Neither the Board of Trade nor the Canadian rules 
make any provision for concave heads, that is, heads that 
receive the steam pressure on their convex side. The 
American rules permit a working pressure of .6 that per- 
mitted on the same head when used as a convex head; there- 
fore, to find the working pressure on a concave head, apply 
the rule in Art. 45 and multiply the result by .6. 



KXAMP1.E8 FOR PRACTICE 

1. Under American mles, what working pressure will be allowed 
on a a AX unstayed head of a mud-dmm if the head is ^ inch thick and 
10 inches in diameter? Ans. 195.57 lb. per sq. in. 



§18 



MARINE-BOILER INSPECTION 



its 



2. What workiog pressure will be allowed, uniier Canadian rules, 
on a flat drumhead 20 inches in diameter and \^ inch thick, properly 
stayed by one stayrod In its center, and used (or a water-tube boiler? 

Ans. Ii09 lb. per sq. in., Dearly 

3. A convex head is bumped to a radius of 30 inches, is S 'Qch 
thick, and has a tensile strength of (iO.OOO pounds per square inch; the 
head being single riveted to the shell, what working pressure will the 
American rules allow on this head? Ans. 250 lb. per sq. in. 



it? 



1. what pressure wo 
Ans. 150 lb. per sq. 



lid 



6. A convex head for the steam drum of a lire-lube boiler is 
buraped to a radius of 24 Inches and is worked into shape by hand; it 
is made of wrought iron having a tensile strength ot 50,000 pounds per 
square inch, and is ^ inch thick. What working pressure will be 
allowed on this head under Canadian rules? Ans. 312.5 lb. per sq. in. 



PIPES AND SAFETY VALVES 



49. Under American rules, the workine pressure allow- 
able on wrought-ircn or steel pipes is found as follows: 

ItuXe.—Afulliply 10,000 by the thickness of the pipe, in 
inches, diminished by .125, and divide the product by the inside 
diameter, in inches. 

p _ 10.000 (T- .125) 



Or, 



D 



in which P = working pressure, in pounds per square inch; 
T = thickness of pipe, in inches; 
D = inside diameter, in inches. 
Example.— What working pressure will be allowed on a main 
steam pipe 12 inches in inside diameter and ^ inch thick, under 
American rules? 



So LOTION.— Applying Ihe rule, 
IO.OOO X (\- .125) _ 



208.331b. persq.ii 



60. The Canadian rules do not prescribe any formula 
for finding the working pressure allowable on wrought-iroD 




M 



M MARiNE-BOlLfiR INSPECTION §l8 

or steel pipes; tinder Board of Trade rules, it is found as 
follows: 

^VLle.— Multiply 6,000 by the thickness of the pipe, in 
inches, and divide the product by the inside diameter^ in inches, 

nr P- 6,000 r 

ur, /- ~ ^ 

in which the letters have the same meaning^ as in Art. 49. 

Example. — Under Board of Trade rules, what working pressure 
will be allowed on a wrought-iron steam pipe 12 inches in inside diam- 
eter and i inch thick? 

Solution.— Applying the rale, 

6,000 X i 
P = Tg = 187.5 lb. per sq. in. Ans. 

51. The Canadian rules do not contain a rule for finding; 
the working pressure allowable on copper pipes; the Ameri- 
can and Board of Trade rules give the same rule, differing: 
only in the value of the constant. 

Rule. — Multiply 8,000 (under American rules) or 6,000 
(under Board of Trade rules) by the thickness of the pipe 
diminished by iV inch. Divide the product by the inside diam- 
eter of the pipe. 

Or, American rules, 

p^ 8,000 (r-iV) 
D 
and, Board of Trade rules, 

p^ 6,000 (r- A ) 
D 
in which the letters have the same meaning as in Art. 49. 

Example. — A copper feedpipe -^^ inch thick has a diameter of 
4 inches; what working pressure will it be allowed, under American 

rules? 

Solution.— Applying the rale, 

^ 8,000 X (A - A) _,. . ^ 

P = -z = 250 lb. per sq. m. Ans. 



§18 MARINE-BOILER INSPECTION 87 

SAFETY-VALVE AREA 

52. Under American rules, ihe area of a safety valve, in 
square inches per square foot of grate surface, is to be found 
by the rule in this article. Obviously, the result of the rule 
must be multiplied by the number of square feet of grate 
surface of the boiler in order to obtain the area of the safety 
valve required. When the diameter exceeds 6 inches, it is 
customary to use two valves whose combined area will equal 
that calculated. If the calculation gives an odd size of safety 
valve, the next larger standard size is chosen. 

Rule.^ — Multiply (he constant .2074 by the nnmbfr of pounds 
of water evaporated per hour per square foot of grate surface. 
Divide the product by the absolute boiler pressure, taken as the 
gauge pressure plus 15. 

Or, , = .^"^i? 

in which a — area of safety valve, in square inches, per 

^ square foot of grate surface; 

W = pounds of water evaporated per square foot 
of grate surface per hour; 
P = working pressure, in pounds per square inch, 
+ 15. 
ExAMPLB.— A boiler is esiimaled to burn 12 pounds of coal per 
square Coot of grate surface per hour, and to evaporate II pounds of 
water per pound of coal; the boiler having 30 square feet of grate 
surface, what area should ihe safety valve have, under American 
rules? The boiler pressure is 150 pounds per square inch. 
Solution.— H' =. 12 X 9 = 108, /> = l.'K) + 15 = i&5. Applying 

.2074 X 108 ,_„ 
fl = —^— = . 1358 sq.m. 

Then, area of safety valve for the boiler is 

.13o8 X 30 = 4,074 sq. in. Ans. 

Under American rules prior to June 1, 1904, lever safety 

valves were required to have an area of 1 square inch for 

^ every 2 square feet of grate surface, and spring-loaded safety 

^L valves, 1 square inch for every 3 square feet of grate surface. 



\ 



i._ 



88 MARINE-BOILER INSPECTION 8 18 

For water-tube, coil, and sectional boilers carrying a pressure 
in excess of 175 pounds per square inch, the requirements 
were 1 square inch of safety-valve area for every 6 square 
feet of grate surface. 

53. The Canadian rules prohibit the use of a safety valve 
smaller than 1 inch diameter; under Board of Trade rules, 
the diameter must not be less than 2 inches. 

Under both Board of Trade and Canadian rules, the area of 
a safety valve, in square inches per square foot of grate 
surface, for boilers worked under natural draft, is found by 
the rule given in this article. Obviously, the result of the 
rule must be multiplied by the number of square feet of 
grate surface of the boiler to find the safety-valve area for 
that boiler. 

Rule. — Divide 37,5 by the absolute bailer pressure^ taken as 
the sum of the gauge pressure and 15. 

o. 37.5 

Or, ""^ ~p' 

in which the letters have the same meaning as in Art. 52. 

Example. — What area of safety valve is required, under Canadian 
and Board of Trade rules, for a boiler worked under natural draft at 
a g:auge pressure of 150 pounds per square inch, the boiler having 
30 square feet of grate surface. 

Solution. — Applying the rule, 

37.5 ,^^ 

" = 150+16 ' -^ ^'J- "*• 
Then, area of safety valve is 

.227 X 30 = 6.81 sq. in. Ans. ' 

54. For boilers worked under forced draft, the safety- 
valve area, in square inches per square foot of grate surface, 
is found as follows, under Board of Trade rules: 

Rule. — Multiply the area of safety valve per square foot 
of grate surface calculated for natural draft {by the rule in 
Art, 53) by the estimated coal consumption per square foot oi 
grate surface per hour, in pounds, and divide the product by 20. 

Or. A = l^ 

20 



§ 18 MARINE-BOILER INSPECTION 89 

in which A = area of safety valve per square foot of grate 

surface for forced draft, in square inches; 

a = area of safety valve per square foot of grate 

surface for natural draft, ip square inches; 

C = coal consumption, in pounds per hour per 

square foot of grate surface. 

EzAUPLE. — Under Board of Trade rules, what area of safely valve 
will be required for a boiler having a grate surface of 42 square feet, 
burning -W pounds of coal per square foot of grate surface per hour 
□ Dder forced draft, and carrying a steam pressure o( ISO pounds per 

Solution.— Applying the rule in Art. 53, 
Applying the rule in Art. 54, 
Then, area of safely valve is 



EXAMPLES FOR PRACTICE 

1. Under American rules, what working pressure will he allowed 
on a wroughl-iron Eteam pipe } inch thick and 7 inches in inside 
diamelerf Ans. 178.57 lb. per sq. in. 

2. What working pressure will be allowed, under Board of Trade 
rules, on the pipe in example IP Ans, ^14.29 lb. per sq, in. 

"A. A copper pipe 6 inches in inside diameter has a thickness 
of ) inch; what working pressure will be allowed ou it: (a) under 
American rules? {b) under Board of Trade rules? 



4. A boiler is estimated to evaporate ISO pounds oE water per hour 
per square foot of grate surface, which measures 00 square feet; what 
area of safety valve is required for the boiler, under American rules, 

'if the working pressure is to be 105 pounds per square inch by 
the gauge? Ads. 12.4-1 sq. in. 

5. A boiler having BO square feet of grate surface is to be worked 
at a gauge pressure ot 160 pounds per square inch under natural 
draft: what area of safety valve is required, under Canadian rules> 

Ans, 17.14 sq. in. 




90 MARINE-BOILER INSPECTION §18 

6. Under Board of Trade rules, what safety-valve area is required 
for a boiler burning 36 pounds of coal per square foot of grate surface 
per hour under forced draft, the boiler pressure being 185 pounds per 
square inch by the gauge, and the grate surface 60 square feet? 

Ans. 20.25 sq. in. 



PROPULSION OF VESSELS 



PROPELLING INSTRUMENTS 



INTBODUCTION 



HBTUODS OF PHOPUL8ION 

1. A steam vessel may be propelled either by a stream 
of water, caused by suitable means to flow in a direction 
opposite to that in which it is desired to propel the vessel; 
or it may be pulled along a stationary chain or cable lying 
on the bottom of the river, the chain passing around a drum 
situated within the vessel and actuated by suilable machinery. 
Chain propulsion is used to some extent in Europe, but since 
it does not possess any special features calling for a descrip- 
tion of the system, it will not be treated here. In the first 
method of propulsion mentioned, the stream of water pro- 
jected from the vessel propels the vessel by its reaction. 

In practice, a stream of water may be projected from a 
vessel in three ways: (1) By means of one or more paddle 
wheels; when there is only one wheel, it is usually situated 
at the stem of the vessel; when there are two, they are placed 
amidships, or nearly so. (2) By means of one or more 
screws situated either at the stern or at both the bow and 
the stern. (3) By means of a pump placed within the vessel. 

In the last case, a stream of water is led to the pump by 
suitable piping, and is ejected under pressure from orifices 
located in the sides of the vessel. A vessel propelled in this 
manner is known as a jel propeller. Owing to practical diffi- 
culties, jet propulsion has never come into general use, and, 
|_ hence, will not be treated here. 

iKltrmUimal Tiilbook Comfanr. Entirti al Statumtri- Hall. Lamion 




2 PROPULSION OF VESSELS §1^ 

SLIP 

2. Action ot Propelling Instrument. — When a pad- 
dle wheel or screw serving as a propelling instrument is 
revolved, it tends to force backwards a certain quantity of 
water; the inertia of the water opposes this effort, and, by 
virtue of the reaction thus created, the vessel is propelled. 
When the engines are first started, the propelling instrument 
revolves for a certain time before the inertia of the vessel is 
overcome, and during this short space of time the water thai 
is driven backwards has nearly the same velocity with respect 
to the main body of water that it has to the ship. Suppose 
after the ship is under way. that the instrument maintains the 
same speed of revolution and the speed of the ship gradually 
increases; then, as the stream of water forced back tnaintains 
a constant velocity relative to the ship, it is seen that its 
velocity relative to the main body of water is eradually 
decreasing. 

The speed of the ship will gradually increase up to a certain 
point, due to the force of propulsion, and then remain 
that speed — that is. provided the velocity of the issu; 
stream remains the same. The whole of the propelling 
effort is now absorbed in overcoming the resistance of thi 
air, skin friction, inertia of the water, etc. 

3. Mensurement ot Ship's Bpeed. — The speed of sl 
vessel may be measured in two ways — by its motion I 
through water and by its motion over ground. The latter, ' 
which is the actual speed in reference to a fixed point on | 
land, is obtained from the former by allowing for the motion I 
of the water in which the vessel floats. There may be a 
decided difference in speed measured in the two ways men- 
tioned, as the following consideration will show. Let the 
distance between two ports be 1,000 miles, and let the ship ■ 
cover this distance in 100 hours. Then, its speed in relattoa J 
to a fixed point of the earth (the port of departure) 13 1 
VnV = 10 miles per hour. Now, assume that the vessel 1 
is again leaving the same port of departure bound for the I 



I 




I 



§19 PROPULSION OF VESSELS 3 

same port of destination and over the same route, but that 
on leaving port it enters a current setting in the same direc- 
tion as the ship is advancing, and running 2 miles per hour. 
Then, in order to reach the port of destination in the same 
time as before, that is, in 100 hours, its speed per hour in 
regard to the point of departure must be 10 miles; but, owing 
to being in a current advancing the vessel 2 miles per hour, 
its speed through the surrounding water must be 10 — 2 = 8 
miles per hour. This shows that there may be a difference 
between the speed of a ship through the surrounding water, 
that is, the speed with which the surrounding water may be 
conceived to move past the ship, and the speed of a ship 
relative to a hxed point of the earth. It is of the utmost 
importance, that this be kept in mind. In considering the 
speed of a vessel from the propulsion point of view, its 
speed Id respect to the surrounding water must be taken. 

4. Wake. — By reason of friction, a moving vessel will 
drag with it some water, which forms a casing, as it were, 
the different parts of which have different velocities. Thus, 
the water directly in contact with the part of the vessel 
below the water-line will have a velocity probably nearly 
equal to that of the ship, while particles of water several 
inches from the ship will have a much lower velocity, and 
so on, until, finally, those some distance from the vessel 
will have no motion in relation to the surrounding water. 
The water thus dragged along, with its velocity modified by 
other conditions, will collect near the stern of the vessel in 
the form of a stream moving in the same direction as the 
vessel; this stream is called the wako. When standing at 
the stem of a ship and looking at the wake, it appears to 
recede from the ship; this, of course, is due to the fact that 
tiie vessel moves forwards faster than the wake. If the 
vess-sl could be instantly brought to rest, the wake would 
flow toward the ship; in other words, its motion in relation 
to the ship is always forwards. The velocity of the wake, in 
relation to the surrounding water and the ship, is greatly 
influenced by the form of the vessel below the water-line, 



I 



¥ 



4 PROPTLSIOX OF VESSELS |:> 

one With a bhmt stern impartsn^ a greater Teuccarr n is 
wake than one with a fine after body. It is reaajr sbsl 
that the creation of a wake reduces the f ofce a:i:s£is^i}e ±x 
g'trinz speed to the vesseU as a considerable port ^ se 
total force exerted by the engine is expedOed m dncC3x^ 
the water forming the wake. 



5« True 81lp. — In considering the speed of a 
projected by a propelling instrument from a 
motion, it must be borne in mind that while the streaz: is 
propelled astern the vessel is advancing. Since the strean 
must move astern faster than the vessel advances, tbe 
rearward speed of the stream in relation to a fixed point c: 
the water some distance astern of the ship, as a floatzz^ 
piece of wood, will be the difference between the speed of 
the vessel in relation to the piece of wood and the rearward 
speed of the stream in relation to the vessel. If the pro- 
pelling instrument, as for instance the paddle wheels of a 
side-wheel steamer, does not work in a wake, the speed of 
the vessel, in relation to a fixed point of the water astern, 
may be conceived to be the average speed with which the 
water is fed to the propelling instrument. When the pro- 
peller works in a wake, however, which, as previously stated, 
has a forward motion, the speed with which water is fed to 
the propelling instrument is reduced thereby and it becomes 
cciual to the difference between the forward speed of the 
vessel in relation to a fixed point of the water clear of the 
wake and the wake velocity. Thus, if the speed of the ship 
is 15 miles per hour and a wake that has a forward velocity 
of l\ miles per hour collects at the stem, the speed with which 
the water is fed to a screw propeller is 15 — 3 = 12 miles 
per hour. The difference between the speed with which 
water is fed to the propelling instrument and the speed with 
which it is projected astern, both speeds being measured in 
relation to the vessel, is called the true slip, and also the 
roal Hlip, of the stream. 

(>. Assume that a vessel whose propelling instrument 
is working in water clear of the wake is descending a river, 



§19 



PROPULSION OF VESSELS 



5 



which means that it floats in a favoring current. The speed 
of the ship in relation to its port of departure will be increased 
by the current; that is. the speed of the ship through the 
water remaining the same, the advance of the ship in relation 
to the port of departure will be the sum of the speed through 
the water and the speed of the current in relation to the port 
of departure. Letting a denote the speed of the ship through 
the water and c the speed of the current, the speed of the 
ship in relation to the port of departure is « + c. Likewise, 
if d denotes the speed of the ship in relation to the port of 
departure, its speed through the water will be d — c = a. 
If ii denotes the speed of the stream projected from the 
vessel, measured in relation to the vessel, the true slip, 
measured in relation to the port of departure, is ^ — (rf — c), 
which is the same as i — a. 

Suppose that the vessel is moving through still water, 
but that a wake is following the ship and that the propel- 
ling instrument is working in this wake. This wake can be 
likened to the current previously mentioned, and hence its 
forward speed can be denoted by c. Then, if d denotes the 
advance (the speed) of the ship in relation to a fixed point in 
the water in which it floats (this point is the port of depar- 
ture of the previous case), the true slip, as before, is 
6—ld — c); or if a denotes the advance of the vessel in 
relation to a fixed point of the wake, the true slip is b — a. 

7. A force must act continuously to propel a vessel 
through the water; this force is the reaction of the stream 
projected astern by the propelling instrument and is propor- 
tional to the true slip, the cross-sectional area of the stream 
remaining the same. From this statement, it follows that 
without true slip there can be no reaction, that is, no propul- 
sive force; in other words, propulsion of a vessel without 
real slip is an impossibility. 

8. Apparent Slip. — In practice, it is very inconvenient 
and exceedingly difficult to measure either the wake velocity 
or the speed of the ship in relation to the wake, but it is a very 
simple matter to measure the speed of the vessel in relation 




PROPULSION OF VESSELS 



I 



to a Rxed point in the water clear of the walce by means of 
an instrument called a lofj. This instrument consists of 
three parts: the log chip, the iog line, and the log glass. 
The chip, which is a triangular piece of light wood attached 
to the line, is thrown overboard; as it strikes the water it 
soon virtually ceases to partake of the ship's onward motion 
and becomes stationary; the distance of this stationary object 
from the ship is then measured after a certain interval of 
time has passed and from this the approximate rate of speed 
is ascertained, the log glass defining the interval of time. 
The difference between the speed of the stream projected 
by the propelling instrument and the speed of the ship 
thus found, that is, b — d. Art. 6, is taken as the slip. When 
calculated in this manner it obviously is not the same as 
the true slip; it is called the apparent slip. Conditions 
are possible under which the true slip and apparent slip 
may have the same numerical value; this, however, does 
not change the fact that they are separate quantities. 

9. Negative 61tp. — It is perfectly possible for a i 
pelling instrument to have an apparent slip of zero, 
under certain conditions calculation may even show 
apparent slip to be less than zero; it is then called nc^^tlvt 
sitp. This arises from failing to take into account eith 
the wake velocity or the velocity of the vessel aided by ■! 
favorable wind, in case the speed of the vessel is measured, 
as it should be in considering propulsion problems, in refer- 
ence to a fixed point of the water clear of the wake. When 
the speed of the vessel is measured in respect to a fixed 
point of the earth, as its port of departure, the existence of a 
favoring current is an additional cause that may produce a _ 
negative apparent slip, either by itself or in conjunction « 
the wake velocity and wind effect. 

10. In algebra, a number greater than zero is called 3 
five number, and a number less than zero is called a lugaiiii 
number. It is not possible to arithmetically subtract a positiW 
subtrahend from a smaller positive minuend; this is easily doi 
algebraically, however, with the aid of the following rule. 




US) 



PROPULSION OF VESSELS 



Rule. — To algebraically subtract one positive number horn a 
smaller positive number, subtract Ike smaller number from the 
larger one and prefix the minus sign to the difference to indi- 
cate that it is negative. 

Example 1.— Subtract IS from 8. 

SOLCTIOS.— 12 



-4 Ans. 

A negative number can be divided by a positive number 
as in arithmetic; a minus sign is prefixed to the quotient to 
indicate that the dividend was a negative number. 

ExAUPi^ 2. — Divide —144 by ft. 

Solution. — 6) —144 ( —24 Ana. 



24 

11. Assume a side-wheel steamer to be descending a 
river whose current is running 5 miles per hour, that its 
speed through the water is 10 miles per hour, as shown by 
the log, and that the paddle wheels project streams to the 
rear at the rate of 12 miles per hour. In a side-wheel 
steamer, the propelling instruments are practically clear of 
the wake, so that the problem under consideration is not 
complicated by having to take a wake velocity into account. 
The speed with which the ship advances in respect to the 
port of departure is 10 + 5 = 15 miles per hour; the real, or 
true, slip is 12 — 10 = 2 miles per hour, but the apparent ■ 
slip is 12 — 15 = —3 miles per hour; that is, apparently, the 
ship is moving faster than the stream projected by the pro- 
pelling instrument. Obviously, the presence of negative 
slip, in this particular case, is due to taking the ship's speed 
in relation to the port of departure instead of in reference 
to the water in which the paddle wheels work. Taking 
the ship's speed in reference to the water, the apparent slip 
for this case 12 — 10 = 2 miles per hour, or the same as 
the true slip, as here the wake velocity does not enter the 
problem. 




PROPULSION OF VESSELS 




i 



12. The influence of the wake velocity on the appareot 
slip when the ship's speed is taken from the log is similar 
to that of a favorable current in that case where the speed 
of a ship is reckoned from its' advance irom the port of 
departure. The log does not show the ship's speed in 
relation to the wake, but in relation to a fixed point in the 
water clear of the wake {the port of departure in case of the 
paddle-wheel steamer mentioned in Art. 11), and hence 
shows a higher speed in relation to the water in which the 
propelling instrument works than really exists. Consa- 
quently, when the propelling instrument works in wal 
having a high forward velocity, a neglect to take this ft 
ward velocity, or wake, into account may result in 
extremely small or even negative apparent slip. 

13. The apparent slip can be reduced, or even mi 
negative, by a wind helping the vessel along. Thus, if 
vessel advances 15 miles per hour, as shown by the li 
which means in relation to a fixed point of the water cli 
of the wake, of which speed 13i miles per hour is due to 1 
propelling instrument and 1 i miles per hour due to the wii 
and if the propelling instrument projects a stream at the ral 
of Hi miles per hour, the apparent slip is Mi — 16 = — 
that is, negative. Taking into consideration the speed pi 
(luced by the wind, however, the apparent slip would ' 
14i — (16 — Ij) = 1 mile per hour. 

14. When a calculation for apparent slip — where ti 
■ ship's velocity is taken in relation to the water throoj 

which it advances, that is, from a fixed point clear of tl 
wnke — shows an extremely small apparent slip, or even 
negative slip, it proves usually that one or both of two c 
ditions exist. These are an abnormatly high wake velociq 
and an increase in the speed of the ship by the action of 
favorable wind. An abnormally high apparent slip denote 
(hat the propelling instrument is unsuitable for the com 
tions under which the vessel is propelled at the time fo 
whii'h the calculation was made; if the apparent slip I 
become abnormally high in comparison to that usual 




119 



PROPULSION OF VESSELS 



existing, it tends to show that the resistance of the ship has 
been increased in some manner, as by a head-wind or head- 
sea or by a foul bottom, or that the efficiency of the pro- 
pelling instrument has suddenly been decreased, as by the 
breaking of one or more blades of a screw propeller. 

15. Negative apparent slip is often found in stem- 
wheel steamers and in screw steamers having a blunt stem. 
Negative slip due to a high wake velocity is not observed 
in side-wheel steamers, as the paddle wheels are located 
clear of the wake; these steamers can show a negative slip 
due to a favorable current or wind action, however. The 
former, as is also the case with stern-wheel and screw 
steamers, can occur when the speed of the ship is taken in 
reference to a fixed point of the ground instead of in refer- 
ence to the water in which the ship floats, as it should be; 
a negative apparent slip can also occur when the speed of 
the ship is properly taken in reference to the water in which 
it floats, but no allowance is made for the increase of speed 
due to the wind. The same remarks also apply to an 
abnormally low apparent slip. 

16. The existence of negative apparent slip, when 
traced to a high wake velocity, shows a poor efficiency of 
propulsion for the existing conditions, as measured by the 
horsepower developed for the speed. The fitting of a pro- 
pelling instrument giving a positive apparent slip will gen- 
erally greatly improve the efficiency of propulsion. 

17. Rules for Slip, — It is customary to express slip 
in per cent, of the velocity of the stream projected by the 
propelling instrument. This may be done by the followiD£ 
rules: 

Rnle I. — To iind the true slip, from ike velocity of the stnatn 
projected by ihe Propelling inslrumetit subtratt the velocity with 
ivhich the water is fed to the propelling insirument. both velocities 
being expressed in any convenient, but the same, measure of lime 
and distance. Divide the difference by ilu velocity of the stream 
projected by the propelling instrument. 




10 PROPULSION OF VESSELS §19 

Or. & = -^^^ 

where 5/ = true slip in per cent., expressed decimally; 

V = velocity of stream projected by propelling instru- 

ment, in relation to vessel; 
Vt = velocity of water fed to propelling instrument; 
that is, speed of vessel in relation to the sur- 
rounding water diminished by the wake veloc- 
ity at the point where the propelling instru- 
ment is located, for a vessel under way. 

Example 1. — Find the true slip when the speed of the vessel, by the 
log, is 12 miles per hour; the wake velocity 3 miles per hour; and the 
stream is projected by the propelling instrument at 13 miles per honr. 

Solution. — Applying rule I, 

St = ^^ " 13^ "" ^^ = -3077 = 30.77 per cent. Ans. 

Rule II. — To find the apparent slip in reference to the skip's 
motion through the water ^ from the velocity of ike stream pro- 
jected by the propelling instrument subtract the speed of the vessel 
in relation to the water. Divide the difference by the velocity of 
the stream projected by the propelling instrument. The velocities 
may be expressed in any convenient measure of time and distance^ 
but the same measure must be used for both. 

Or. ^. = ^- 

where Sm = apparent slip in reference to the ship's motion 

through the water, expressed decimally and 
in per cent.; 

V = velocity of stream projected by the propelling 

instrument; 
F, = speed of vessel in relation to the water, as 
shown by the log. 

Example 2. — Find the apparent slip for the vessel in example 1. 
Solution. — Applying rule II, 

13 — 12 
Sa = — Jo — = .0769 = 7.69 per cent. Ans. 

18. Apparent slip when calculated properly, that is, in 
reference to a fixed point of the water clear of the wake, 



§10 PROPULSION OP VESSELS 11 

is a measure of the efficiency of propulsion of that vessel 
when considered in conjimction with the true slip. It should 
never be construed to be a measure of the efficiency of pro- 
pulsion if considered only by itself. Experience has shown 
that a very low apparent slip by itself may be an indication 
of poor efficiency; in that case, it will be combined with a 
high true slip. A low apparent slip coupled with a low true 
slip, however, indicates a high efficiency, while a high appa- 
rent slip and high true slip indicate a poor efficiency for the 
existing conditions. Likewise, a high apparent slip and a 
low true slip indicate a poor efficiency of propulsion for the 
existing conditions. This fact is illustrated by considering 
a vessel moored to the dock, with the engine working ahead. 
As the vessel does not advance at all, the apparent slip is 
100 per cent.; the true slip, as measured by the difference in 
velocity of the stream projected by the propeller and the 
speed of the water fed to it, may be extremely low, say 1 per 
cent. Then, for this case, the efficiency of propulsion, if per- 
fection is taken as 1, is 1 — 1 = 0; while the efficiency of 
the propeller is 1 - .01 = .99. 

19. It is customary among writers on marine propulsion 
to refer to apparent slip simply as slip; when the true slip 
is meant, it is usual to qualify the term slip by prefixing the 
word true or real, that is, to call it distinctly the true slip or 
the real slip. 

PADDLE WHEELS 



DEnXlTIONS 

20. The paddle wheel, in its simplest form, consists 
of two rings, concentric with the axis of the shaft and lying 
in planes perpendicular to it, that are secured, by arms, to a 
hub keyed to the shaft. At the outer edges of the rings, 
and placed between them, are the buckets (sometimes called 
floats), which are either flat wooden boards, generally elm, 
or iron plates; they are situated at equal distances apart, in 
planes passing through the axis of the shaft. A paddle 




12 



PROPULSION OF VESSELS 



§19 



wheel with the buckets placed thus is known as a radial 
wheel. The wheel, or wheels, is attached to the vessel in 
such a position that the lower part is immersed in water to a 
certain depth, which is usually spoken of as the dip of the 
wheel. The vertical distance from the inner edge of \ht 
buckets to the surface of the water, is called the Immersion 
of the buckets. 

BLIP OP PADDI.E WHBBL 

21. In order to find the velocity at which a stream 
water is projected by a paddle wheel, it is necessary to Gi 
find that point of the wheel at which its whole action on tl 
water may be assumed to be concentrated. This point 
known as the center ol pressure, often called the centi 
of action of the wheel; and twice the distance of this poi 
from.the outer edge of the buckets subtracted from the dial 
eter of the wheel (the diameter to be measured from ont 
edge to outer edge of backets) constitutes the eflectli 
diameter of tite wh«e1. 

The effective diameter may be determined approximate 
by the follonine mte: 

VtnW.—Multipif tmHkird tAt mmm Apfk oi the btuh 
whglly imm tt n td hf the tnamher 0/ bmckets u immerted. To U 
fndmtl, mdd the pnAxt tttmt-ikird the mean depth of the ttukt 
pmrlly imwened mnd their mmmher. Divide the smm of I 
ht* Pntdmts h 'he mumiier tt the buckets paHly and whU 
The fuetitml tt4U he the dittmme et the center 
Pnssuwr fnm the mOtr e4gr tl the hmchets. The effeeHre dim 
eter fmn thm he fmmi kg iwhtrmfH9g twice the distance of I 
anter ti pmsmme iwmm ilk mder eelet »t the hnckeU from then 
Side dimmehir tt the vhed. 



D. = D-^X 



3(* + rf) 



vtefc P ^ dwtinwr oloeateroi l ae s s ur e bum ooter ed 
buckets, in aches; 
1 depth o( tacfats irikoOr immersed* 




PROPULSION OF VESSELS 



13 



K 



b = number of buckets wholly immersed; 

e = mean depth of buckets, partly immersed, in 

inches; 
d = number of buckets partly immersed; 
D = diameter of wheel, measured over outer edge of 

buckets; 
D, = effective diameter. 
To find the mean depth of the buckets, and also the num- 
ber of buckets wholly and partly immersed, draw the 
wheel to any convenient scale, taking care to draw the buckets 
in their true positions. Also, draw a line representing the 
surface of the water, at a distance from the outer edge of the 
lowest bucket equal to the dip. Then the number of buckets 
wholly and partly immersed will be seen at a glance. To 
find the mean depth of the buckets, measure the depth of 
each bucket wholly immersed (not the depth to which each 
bucket is immersed) to the same scale the wheel was drawn, 
and perpendicular to the surface of the water. Add the 
depths of the diilerent buckets together, and divide the sum 
by the number of buckets wholly immersed. For those 
partly immersed, which hardly ever will be more than two. 
measure the perpendicular distance between the lower edge 
of the bucket and the surface of the water. Add the dis- 
tances together, and divide by the number of buckets. 

Example.— A paddle wheel 3fi feel in diameter has, at a certain 
dip. seven buckets of a mean depth of 24 inches wholly immersed, 
and one bucket immersed to a depth oE IS inches; (ind the effective 
diameter of the wheel. 

SOLUTIOK. — Applying the rule, 

7 + 15 X 1 



A ="36XI2-2X- 



3(7 + 1) 



= 416.75 ii 






Having determined the effective diameter, to determine 
the theoretical velocity of the stream projected by the wheel, 
find the velocity of a point on the circle having a diameter 
•-equal to the effective diameter of the wheel, expressing its 
■ velocity in the same terms in which the speed of the vessel 
Fis expressed. For example, taking the wheel in the above 
lexample, its circumference will be 3.1416 X 416.75 = 1,309.26 



14 



PROPULSION OF VESSELS 



§19 



inches. Assumins: the revolutions to be 20 per minnte, the 
speed of a point on the effective diameter circle will be, io 

feet per second, ^'^'^^i^^ = 36.37 feet. This is, theo 

retically, the velocity of the stream projected by the wheel; 
and, knowing the velocity of the vessel, the slip may be 
foimd by rule I or rule II, Art. 17. 



RADLAX PADDI^ TVHlSlSIi 

22. In Fig. 1, a radial paddle wlieel is shown io 
diagrammatic form, where A represents the shaft; B^Bx^B 



» 




Pig. 1 



etc. represent the buckets. Assume the wheel to revolve 
in the direction of the arrow x\ also, assume the line CD to 



§19 



PROPULSION OF VESSELS 



15 



represent the surface of the water. Then, the direction In 
which the vessel moves, which is evidently parallel to the 
surface of the water, is shown by the arrow d. It will be 
seen that the bucket 5,, just entering the water, enters at an 
angle, shown by the arc a, with the surface. This angle is 
known as the angle of Incidence. The effect of this is 
that the bucket, instead of driving a body of water straight 
astern, drives it in a direction perpendicular to the surface 
of the bucket, as indicated by the arrow c\ in other words, 
the bucket depresses the water. The power consumed in 
depressing the water is wasted. Evidently, the stream of 
water projected by the propelling instrument will have the 
maximum propelling effect if projected straight astern, in a 
direction parallel to the surface of the water. This is proved 
by the following simple experiment: Place some heavy 
weight, weighing, say, ahout 100 pounds, on the floor. Try 
to slide it along the floor by pushing against the end of a 
board placed against the weight, and held at an angle of 
about 45° with the floor. The chances are that it will not 
be possible to move it. Depress that end of the board 
against which the push is exerted, and push just as hard as 
in the first place. It will now be found possible to move 

I the weight, and it will also be found that the more the free 
end of the board is depressed, the less will be the power 
required to move the weight. This proves that the nearer 
the direction of a force is to the direction in which a weight 
(as the vessel) is to be moved, the less will be the amount 
of power required. From this, it follows that the nearer 
the angle of incidence is to 90°, the more efficiently will the 
power be applied. By reference to Fig. 1, it will be seen 
that it is not alone through the action of the bucket B, that 
power is lost, but also that a further loss of power is due 
to the oblique action of the buckets B, and B,. The only 
bucket that is acting at its maximum efficiency is B^, the 
surface of which is perpendicular to the direction in which 
the vessel moves. It will be observed that the buckets B,. B„ 
and B, tend to elevate a body of water; this causes a loss 
of power equal to that caused by the action of the buckets 



Ik 



PROPULSION OF VESSELS 

Bt, B„ and B,. The sum of the two losses is called the 
iosi of effect due to oblique action of Ifte buckets, and is a defect 
inseparable from the employment of a radial paddle wheeL 
Assume the vessel to be loaded until the surface of the 
water is at C D'. It will be seen that the angle of incidence 
b is less than it was previously; hence, more power will be 
uselessly expended. From the foregoing explanations, the 
following conclusion is drawn: The greater the dtp of s 
paddle wheel, the greater will be the loss of power due to 
oblique action of the buckets. 

FKATIIERING PADDLE WHEEL 

23. In order to prevent the toss of power incidental to 
the use of radial buckets, a paddle wheel in which, by 
suitable mechanism, the buckets are forced to enter d 
water perpendicularly, or nearly so, is often used. Such 
wheel, which is known as a reutherlns paddle wheel, 

shown in Fig. 2. The buckets B, B B,, turn on pins 

fixed in brackets a attached to the arms A of the wheel; they 
are free to move on axes parallel to the axis of the shaft. 
To the outboard end of each bucket, a lever L is rigidl] 
attached; in order to control the buckets, the extremity of 
each lever is connected to the eccentric strap Fhy means of 
a radius rod r, which is pivoted to the strap as well as to the. 
lever. An eccentric pin c is placed at a distance d ahead of- 
the shaft. The eccentric pin is stationary, but the eccentric 
strap is free to revolve on the pin. The pin is supported by 
means of the bracket E. which, in turn, is bolted to the spon- 
son beam G. To give motion to the eccentric strap, it U 
attached to one of the bucket levers by means of the king- 
rod H. The kingrod, which is rigidly fastened to the 
eccentric strap, is pivoted to the bucket lever. As the wheel 
revolves, each bucket in its turn, on entering the water, 
assumes the position in which the bucket B is shown, and, in 
passing around with the wheel, assumes the positions of the' 
buckets B,. B B.. 

It will be seen at a glance that, for wheels of equal diam- 
eter and equal dip, the angle of incidence is much larger 



I 




18 PROPULSION OF VESSELS §19 

with the feathering than with the radial paddle wheel. Hence, 
a larger proportion of the power applied to the wheel is 
expended in propelling the vessel. 



ROLLING CIRCLE 

24. The circle concentric with the paddle wheel, any 
point on the circumference of which has a velocity equal to 
the velocity of the vessel is called the rolling: circle of the 
paddle wlieel. Its diameter may be found by the follow- 
ing rule: 

Rule. — To find the diameter^ in feei^ of the rolling circle of 
a paddle wheels divide the distance moved by the vessel in a 
given timCy in feet^ by 3.1416 times the number of revolutions of 
the wheel in the same time. 

Or, D = ^ 



3.1416^ 

where S = distance moved by vessel, in feet; 
R = number of revolutions of wheel; 
D = diameter of rolling circle, in feet. 

The term rolling circle of the paddle wheel is an expression 
of no particular value, although considerably used. The true 
and apparent slips may be determined if the effective diam- 
eter and the diameter of the rolling circle are known. The 
difference in the two diameters, expressed in per cent, of the 
effective diameter, will be the percentage of true or apparent 
slip, and will be found to be the same, all data remaining the 
same, as that found by the rules given in Art. 17. 

Example. — A vessel advances 1,570.8 feet in 1 minute, as shown by 
the log, during which time the paddle wheels make 25 revolutions; if 
the effective diameter of the wheels is 25 feet, what is the percentage 
of slip? 

Solution. — Applying the rule given in this article, 

_ 1.570.8 ^ 20 f t 
^""3.1416X25 -^"•' 
the diameter of the rolling circle. The difference in diameters is 
25 — 20 = 5 ft.; and this, in per cent, of the effective diameter equals 
A = .2 = 20 per cent., the apparent slip. Ans. 



519 



PROPULSION OF VESSELS 



The velocity ot the stream projected by the wheels is 25 
X 3.1416 = 1,963.5 ft. Substituting values in rule 11, Art. 17, 
_ 1,963.6 - 1 .670.S 
l.m.b 



= 20 per CI 



t., the same as above. 



SIZE OF PADDLE WHEELS 

25. Diameter, — The efFective diameter of a paddle 
wheel is found by the rule below. In order to apply this 
rule, an apparent slip has to be assamed, and the velocity of 
the ship in relation to the water it floats in, as well as the 
number of revolutions, has to be known. The apparent slip 
for a radial wheel varies from 15 to 30 per cent., the lower 
value occurring with buckets of ample area, and averages 
about 25 per cent.; the apparent slip of a feathering paddle 
wheel averages 16 per cent. 

Rule. — To find Ihe effective diameter of a paddle wheel, in 
/eel, multiply l/ie difference between 1 and the percentage of 
apparent slip, expressed decimally, by lite proposed number of 
revolutions per minute and by 3.1416. Divide the speed of the 
ship per minute in relation to the water by Ikis product. 



Or, 



V, 



diameter of the 



(1 -5.) 3.1416 A^ 
where D, = effective diameter, in feet; 
5. = apparent slip, in per cent.; 
V, = velocity of ship, in feet per minute; 
A' = number of revolutions per minute. 
ExAUPLE. — A vessel is to make 10 statute miles per hour through 
the water when Ihe wheels make 30 revolutions per minute; assuming 
a stip of 2h per cent., what should be the eSectii 
paddle wheels? 

Solution.— 10 statute mi. per hr. 
Applying the rule given. 

^•- (1-,^.)^.H16X 30 -■"■'"'■ *»■ 
26. Area and Number of Buckets. — For radial and 
I feathering paddle wheels, when the ship is a side-wheel 
\ Steamer, Seaton recommends that the area, in square feet, 
I of one bucket and the number be as follows: 



_ 10X6,2! 



20 PROPULSION OF VESSELS §19 

Rule. — To find the area of one bucket for the paddle wheels 
of a side-wheel steamer^ divide the indicated horsepower of the 
propelling machinery by the effective diameter of the wheels in 
feet. For a radial paddle wheels multiply the quotient by .25 
for slow boats, and by .175 for fast-running light steamers, 
choosing a value between the two given as judgment indicates it 
should be varied. For a feathering paddle wheel, multiply the 
quotient by .32. For a radial paddle wheel there should be one 
bucket for each foot of effective diameter; to find the num^ber of 
buckets for a feathering paddle wheel, add 2 to the effective 
diameter, in feet, and divide the sum by 2. 

Or. A 

n = De for radial paddle wheels 

Z? 4- 2 
n = * ^ for feathering: paddle wheels 

where A = area of one bucket, in square feet; 
L H. P = indicated horsepower; 

C = a constant varjring between .175 and .25 for 
radial wheels, and taken as .32 for feathering 
wheels; 
Dt = effective diameter, in feet; 
n = number of buckets. 

If the side wheels are driven by separate eng^ines, their 
combined horsepower is to be used. For a stem-wheel 
steamer, the area of the bucket may be about twice that 
given by the rule. For side-wheel steamers, the depth of 
the buckets is usually made about one-fourth their width. 

Example. — Find the area of each backet and their number for a 
side- wheel steamer fitted with feathering paddle wheels 25 feet in 
effective diameter, each wheel being driven by a separate engine of 
500 indicated horsepower. 

SoLtTTiON.— Applying the rule given, 

. (500 -f 500 ) X .%> ... ^ 
--f = — = 12.8 sq. ft. 

25 + 2 
and n = "—;,-— = 13.5 = 14. Ans. 



§19 



PROPULSION OF VESSELS 



SCREW PROPELLERS 



DEFINITIONS 

27. If a point be caused to rotate at a uniform distance 
from and about an axis, and if the point at the same time be 
caused to advance at a uniform rate in the direction of axis, its' 
path will be a helix. If the point, when moving away from the 
observer, moves in the direction of the hands of a watch, the 
helix will be right-handed; if in an opposite direction, Ml- 
handed. The distance the point advances in one complete 
revolution is known as the pilch. If a line passing through 
the axis be caused to rotate about the axis, and to pass along 
the path of the point mentioned above, its path will be the 
surface of a true screw, provided the angle that the line 
makes with the axis remains constant. From this, it follows 
that a true screw is one in which the advance of any point, 
in the direction of the axis, at any distance from it. for 
any part of a revolution, but the same in each case, is the 
same. By causing lines making equal angles with each other 
and the axis to rotate about the axis in a helical path, a 
multiple-threaded true screw will be generated, having the 
same pitch as a single-threaded true screw generated by a 
line following the same helical path. 

28. Consider a four-threaded, right-handed screw, gen- 
erated by the lines OA, OB, OC, and O D, Fig. 3. These 
lines represent the intersections of the four helical surfaces 
with a plane EF perpendicular to the axis. Assume the 
helical surfaces to be cut by a plane, as G H. parallel to the 
first and intersecting the axis at another point. Then. 
O.IA'Cy. OBR'a, OrC'C.andOZJj9'0'will be the hel- 
ical surfaces of the blades of a four-bfaded, right-handed 
screw propeller. If pieces of metal be shaped to conform 
to these helical surfaces and if these pieces of metal, which 
are called blades, be fastened to a hub. which in turn is 

, keyed to a shaft rotated by an engine, the scro^v propeller 
^In its simplest form is obtained. If the screw propeller is 



22 



PROPULSION OF VESSELS 



§19 



revolving in the direction of the arrow, that portion of the 
blade that strikes the water first, which will be near the plane 
G Hy is known as the anterior portion of the blade; and 
the portion that is near the plane EF^ as the posterior 
portion. That part of the blade that is near the periphery 
A A* is known as the tip. In practice, screw propellers arc 
hardly ever made of the shape shown in Fig. 3. Generally 
the anterior portion of the blade is rounded off toward the 

B O 




Pio. 3 

tip, as shown by the dotted line on the blade OAA'C/. 
The posterior portion is also slightly rounded. Very often 
part of the anterior portion near the hub is also cut away. 

29. Sometimes the surfaces of the blades are not truly 
helical; as usually found, the pitch near the tip is greater 
than the pitch near the hub. Such a propeller is said to 
have a radially expanded pitch. The reason for constructing 
the blade in this manner is this: Since the part of the blade 
near the hub strikes the water at nearly a right angle, it acts 
chiefly to churn the water, and since the water near the 



Il9 PROPULSION OF VESSELS 23 

periphery is thereby disturbed, the tip of the blade acts on 
water in motion. By increasing the pitch at the tip. it is 
supposed thai the resistance at all parts of the blade is more 
nearly equalized. 

The blades are sometimes constructed in such a manner 
that the anterior porrion of the blade has a finer pitch than 
(he posterior portion. Such a blade is said to have an 
expanding or axially expanded pitch. The object to be 
attained by it is as follows: The anterior portion of the 
blade, striking on water at rest and encountering the resist- 
ance due to a solid body moving through water at rest, 
sets the water in motion, driving it astern. Therefore, 
the posterior portion acts on water in motion. By expand- 
ing the pitch to the same extent, further motion is given to 
the water by the posterior portion, and it is supposed that the 
resistance at all parts of the blade is thereby equalized, the 
same as with radially expanded pitch blades. 

From the explanations given it follows that, while radially 
expanded pitch blades are supposed to equalize the resistance 
at different parts of the blade at varying distances from the 
axis, expanding pitch blades are supposed to equalize the 
resistance at different parts of the blade at the same distance 
from the axis. 

Neither radially expanded nor expanding pitch screw 
propellers seem to have met with the success claimed for 
them by their advocates, and, although at one time they 
obtained great favor, at present most vessels are fitted with 
propellers having blades forming helical surfaces. 

30. The actual area of the surface on the driving side of 
a propeller blade is known by various names, as the developed 
blade area, the lielicoidal blade area, or simply the blade area. 
When referring to the total blade area, it is usually spoken 
of as the developed propeller area, the lielicoidal propeller area. 
or simply, the propeller area. The area of a blade projected 
on a plane at right angles to the propeller shaft is called its 
Projected area; the projected area of all the blades is the ^ro- 
jected propeller area. The area of the circle described by the 





24 



PROPULSION OF VESSELS 



§19 



tips of the blades is the disk area of the propeller. The 
pitch ratio is the ratio of the pitch of the propeller to its 
diameter; it is usually expressed by giving its value; that is, 
the quotient obtained by dividing the pitch by the diameter. 



MEASUREMENT OF PITCH 

31. As stated in Art. 27, the distance that a point mov- 
ing in a helical path advances in the direction of the axis in 
one complete revolution is the pitch. Since the screw pro- 
peller blade, however, contains but a small portion of the 
line generated by a point moving in a helical path when the 
shaft makes one revolution, the pitch must be calculated by 
first finding the distance that a point, at a uniform distance 




Fio. 4 



from the axis, advances for that part of a helix that can be 
represented on the propeller blade; by the rules of propor- 
tion, the distance that a point would advance if the helical sur- 
face were continuous can then be found. In practice, the 
pitch of a propeller may be found quite closely in the manner 
illusUrated in Fig. 4. Take a piece of joist or lath D^ which 



Sl9 PROPULSION OF VESSELS 25 

should be as straight as possible, and place it so as to touch 
one of the blades at any distance, as b, from the axis A B, 
taking care to hold it parallel to the axis. Next take a 
carpenter's square, shown at E, and place it on the lath and 
against the blade, so that the point at which the square touches 
the blade will be the same distance from the axis as is the 
lath. Measure the distances a, b, and c; a being the distance 
from the square to the point at which the lath touches the 
blade, and c the distance from the point at which the square 
touches the blade to the lath. The distances a and c may be 
obtained in a different manner, if considered more convenient, 
thus: Place the screw propeller so that one blade is horizon- 
tal. To a piece of string about 10 feet, or more, in length 
tie two nuts; place the string over the blade, with the nuts 
hanging down, at the distance from the shaft axis at which it 
is desired to find the pitch, taking care to so place the string 
that both parts hanging down are the same distance from 
the axis. The distance the two parts are apart is the dis- 
tance (I, Fig. 4. To find c, hold a lath against the blade and 
both vertical parts of the string; while holding the lath 
parallel to the shaft axis the distance c can be measured. 

In a third method, which is a favorite with English marine 
engineers, the distance a is found by measuring with a lath 
from the after face of the stern post, or bracket, or using a 
string with two nuts. The width of the face of the blade, at 
the points the distance a was taken, is then measured, and the 
distance c is calculated by extracting the square root of the dif- 
ference between the square of the width of the face of the 
blade and the square of the depth of the blade (the distance a. 
Fig. 4). Since, in the first and second methods given, the dis- 
tance e is measured directly, these methods are preferable. 

Having obtained the three measurements required, the pitch 
may be found very closely from the following proportion: 

c : circumference of circle having radius b = a : pitch 
whence, pitch = ^^^, where 2:r = 2x3.1416 = 6.2832. 

The directions given for finding the pitch may be stated in 
the form of a rule, thus: 




26 PROPULSION OF VESSELS §19 

Rule. — To find the pitch of a given screw propeller y at a 
given distance from the center of the shafts mecLSure the depth of 
the blade at that distance and parallel to the shaft; measure the 
width of the blade at right angles to the shaft and at the same 
distance. Multiply the depth of the blade by the distance from 
the ceriter of the shaft and by 6.2832/ divide the product by the 
width of the blade. All dimensions are to be taken in inches. 

Qj. p ^ 6.2832 b a 

c 

where P — pitch of screw propeller; 
a — depth of blade; 
b — distance from center of shaft where width and 

depth of blade is measured; 
c = width of blade. 

Example. — If a screw propeller blade 6 feet from the center of the 
shaft is 22 inches deep and 41 inches in width, at right angles to the 
shaft, what is the pitch? 

Solution. — Applying the rule given, 

P = g^M2<|f X 6.2832 ^ 242.746 in. 
41 

Or, ?i?^1? = 20 ft. 2.746 in. Ans. 

32. In practice, it is advisable to take the measure- 
ments a and r, Fig. 4, at three or four distances from the 
axis, and calculate the pitch separately for each set of 
measurements. If the calculated pitches agree within a 
small percentage of error, the propeller will be either a true 
screw or one having expanding pitch blades. If the differ- 
ence in the calculated pitches be considerable, it will show 
the propeller to be of radially expanded pitch; in that case, 
add the pitches together and divide by the number of them 
to obtain the mean or average pitch. 

To find whether a propeller is constructed with expanding 
pitch or as a true screw, proceed as follows: Let Fig. 5 be 
a section through the blade at any convenient distance from 
the axis; the full lines show the outline of an expanding 
pitch blade, the dotted lines the outline of a blade forming 
part of a true screw. 



H9 



PROPULSION OF VESSELS 



27 




ih^it. 



Measure the distances a and d on the posterior portion. 
and the distances c and d on the anterior portion; also the 
distance from the axis at which the measurements are taken. 
Calculate the pitches for the anterior and posterior portions 
separately. If the pitches agree very closely, say within an 
error of 1 per cent., the blade is 
part of a true screw; if otherwise, 
the screw has an expanding pitch. 
If found to be the latter, add the ' 
two together and divide by 2 to 
get the mean pitch. If greater 
accuracy is required, the pitch may 
be calculated for any convenient 
number of portions of the blade, 
and the mean pitch found as above. 

The measurements for pitch 
should always be taken on the side 
of the blade that strikes the water ''"^•^ 

when propelling the vessel ahead. In Fig. 5, which is the 
blade of a riglii-handed propeller, the surface e is the proper 
one on which to make the measurements. 

The directions given may, in other words, be stated as 
follows: 

To determine whether a screw propeller is a true screw, 
two or more measurements of the pitch should be taken on 
different parts of the blade at the same distance from the axis. 
Another set of measurements should be taken at some other 
distance from the axis. If the pitches calculated from these 
measurements agree closely, the propeller is a true screw. 

To determine whether the pitch of the screw is radially 
expanded, calculate the pitch at two or more distances from 
the axis; if the pitch increases toward the tip of the blade, 
the screw propeller is of radially expanded pitch. 

To determine whether the screw has an expanding pitch, 
the pitch must be calculated for the anterior and posterior 
portions of the blade. The pitch for the posterior portion 
should be the coarser; and, if calculated for any distance 
from the axis, the pitches of the anterior portion, as well 




28 



PROPULSION OP VESSELS 



as those of the posterior portion of the blade, should agree 
provided that the axial measurements are taken in the same 
planes passing through the axis. 

33. Screw propellers, the blades of which form practically 
no screw at all, are sometimes fomid. To determine their 
pitch, a set of measurements should be taken at equidistant 
intervals from the axis, both for the anterior and posterior 
portions of the blade; the pitches calculated are added 
together, and the sum divided by the number of pitches in 
order to find the mean pitch. 

In measuring a screw propeller for the pitch, it is well to 
remember that it is only necessary to measure one blade, 
no matter what the number of blades may be. ^1 



SI.II' or SCKEW PROPGI,I.KR ' 

34. The blades of a screw propeller drive a stream of 
water astern by their oblique action on the water when the 
instrument is revolved. The velocity of the stream thus 
projected is taken as that found by multiplying the pitch, in 
feet, by the number of revolutions in a given time. If the 
speed of the vessel in relation to the surrounding water clear 
of the wake be known, the apparent slip is calculated by 
rule II. Art. 17. The true slip is calculated by rule I. 
Art. 17. The apparent slip of a screw propeller will 
average about 10 per cent., except in freight steamers run- 
ning at low speed and having a full under-waler body, where 
the slip usually averages about 6 per cent. 



SIZE OF 8CHEW PROPELXER 

35. Pltoli. — The pitch required for a screw propeller 
found by the following rule: 

Rule. — To find tke pilck of a proposed screw propelU 
mbiraet the percenlage of apparent slip, expressed decimally, from 
1 and multiply the remainder by the number of rex-olutiims per 
minute. Divide the desired speed of the vessel, in refererue to ti 
■water clear of the wake, in feet per minute, by this Product. 



\ 

111. 




I Sl9 



PROPULSION OF VESSELS 



Or, 



(1-5.) A' 
where P = pitch, in feet; 

y, = speed of ship, in feet per minute, shown by log; 
S. = apparent slip, in per cent., expressed decimally; 
/^ = revolutions per minute. 
Example. — Find the pilch for a vessel to make 12 knots* at 60 revo- 
lutions with 10 per cent. slip. 
Solution.— 12 knots = 
the rule given, 

1.216 



" (I- 



1)X6( 



= 22.5 ft., nearly. Ans. 



36. Diameter. — For the diameter of a screw propeller, 
Seaton gives the following rule; 

Rale. — To iind the diameter of a screw propeller, divide the 
indicated horsepower by the cube of the product of the pitch, in 
feet, and the revolutions per minute. Extract the square root oi 
the quotient and multiply it by a constant ranging from 17,000 
lor slow freight steamers to 25,000 /or fast-running light 
steamers, as torpedo boats and fast steam launches. 

Or. 

where D = diameter of screw propeller, in feet; 
L H. P. = indicated horsepower; 

P = pitch of screw propeller, in feet; 
N = revolutions per minute; 

C = a constant ranging between 17,000 and 25,000. 

ExAMPLB, — Find the diameter of a screw propeller (or a steam 

laqnch with an engine of !0 horsepower, the screw having a pitch of 

4 feet and making 200 revolutions per mi 

Solution.— Applying the rule given, 



D = 25,000 



/~io ~ 

\(4 X 20i 



= 3.5 ft. Ans. 



200)" ■ 

When the rule gives a diameter that is impossible for the 
' conditions, either P or N, or both, must be varied. Making 
I either or both of these values larger will give a smaller 
I "A knot is 1 nautical mile per hour; it is not a distance 



30 PROPULSION OF VESSELS §19 

• 

diameter of screw; conversely, making either or both of 
these values smaller gives a larger diameter of screw. The 
rule is intended for screw propellers with four blades; if three 
blades are to be used, the diameter should be increased about 
10 per cent.; and if two blades are to be used, about 20 per 

cent. The pitch ratio ( ,,^' ^ — ) varies in practice between 

Vdiameter/ 

1.1 and 1.6. 

37. Blade Area. — The total actual blade area of screw 
propellers, according to Prof. W. F. Durand, for four-bladed 
screw propellers is made from 35 to 45 per cent, of the disk 
area. For a three-bladed screw, the total blade area varies 
between 27 and 33 per cent, of the disk area; and for two- 
bladed screws, between 20 and 25 per cent, of the disk area. 
The value to be chosen should vary with the pitch ratio, 
using a low total blade area for a low pitch ratio and 
increasing the value as the pitch ratio is made greater. The 
same authority states that ordinarily nothing is to be gained 
by making the total blade area more than 48 per cent, of the 
disk area. 

38. Summary. — With the present imperfect knowledge 
of the action of screw propellers, no exact rules can be given 
for predetermining the pitch, diameter, and blade area, and 
also, no rules based on purely theoretical considerations that 
will at the same time conform with actual practice are pos- 
sible at present. The rules given are empirical to a large 
extent; they are not intended to supersede good judgment 
based on actual experience with the action of screw propel- 
lers, but will furnish a guide tending to prevent judgment 
from going far astray. 

EXAMPLES FOR PRACTICE 

1. If a vessel is descending a river running 3 miles per hour, and 
at the expiration of 12 hours is 140 miljs from the port of departure, 
what is: (a) its speed in relation to the port of departure? (d) its speed 
through the water? Express the speed in miles per hour. 

Anc /('') 11.67 mi. per hr. 
^°^\(^) 8.67 mi. perhr. 



p 



§19 PROPULSION OF VESSELS 31 

2. A screw propeller has a. pitch of 20 feet aad makes 70 revolulioas 
per minute when it drives the ship at the rate of 12 knots; if the wake 
velocity is 2 knots, wbal is: (a) the true slip? {b) the apparent slipf 

An= I'"! 27,62 per cent., nearly 
*°^-\(6) 13.14 per cent., nearly 

3. Assuming' the diameter of the rolling circle of a paddle wheel to 
be IS feet, what is the percentage of apparent slip if its effective 
diameter is 23 feet? Ans, 21.74 per cent. 

4. The diameter of the rolling circle being 20 feet, and the revolu- 
tions 30 per minute, what is the speed of the vessel, in miles per hour, 
counting 5,280 feet lo the mile? Ans. 14.28 mi. per hr. 

6. What should be the effective diameter of a stern wheel for a 
vessel lo make 15 statute miles per hour at 25 revolutions per minute, 
allowing a slip of 20 per cent.? Ans. 21 ft. 

6. What should be the pitch of a screw propeller to drive a ship 
15 knots at 80 revolutions per minnte with an apparent slip of 
10 per cent.? Ans. 21.1 fl. 

PROPULSION CALCULATIONS 



TDEORETICAI., ACTUAL, AND INDlCATftD THRUST 

39. A stream of water projected from a vessel propels 
the vessel by its reaction. According to Newton's third law 
of motion, there is always to every action an equal and 
opposite reaction, Hence, if the magnitude of the action 
Is calculated, the magnitude of the reaction is known, since 
both are equal. The reaction of the stream of water pro- 
jected from a vessel is known as the tlirust, and is equal 
to the force required to project it. The magnitude of this 
force, and, hence, of the thrust, may be calculated hy the 
following rule: 

Rule. — To find the magnitude of the theoretical tknist, 
multiply togt-ther the weight of the stream projected from the 
vessel, in pounds per second, and its velocity in regard to the 



32 PROPULSION OF VESSELS §19 

surrounding water^ in feet per second^ that is, the true slip. 
Divide the product by 32.16, 

Or, T^^ 

where W = weight of stream projected from vessel, in 

pounds per second; 
V = its velocity in regard to surrounding water, in 

feet per second; 
g = acceleration due to gravity, taken as 32.16; 
T = theoretical thrust. 

The rule just given is general; that is, it may be applied 
to any case, whether the vessel is propelled by paddle wheels, 
screw propeller, or a jet. The thrust found is the theoret- 
ical thrust. In practice, however, it cannot be calculated 
exactly, as only an approximation to the actual weight of the 
water projected in 1 second, and to its velocity in regard to 
the surrounding water, can be obtained. In thrust calcula- 
tions, the weight of a cubic foot of sea-water is taken as 
64.1 pounds, and the weight of a cubic foot of fresh water 
as 62.5 pounds. 

The actual thrust is the real measure of the propelling 
force, and is always equal to the resistance of the vessel, 
in pounds. It cannot be calculated, but must be found by 
means of an instrument commonly known as a dynamometer. 

Example. — A paddle-wheel steamer, fitted with wheels having an 
effective diameter of 25 feet, makes 16 knots. If the revolutions per 
minute are 26, the width of the buckets 8 feet, and their depth 2 feet, 
what is the theoretical thrust in sea- water? 

Solution. — The velocity with which the paddle wheels project the 
stream is ^x = 34 ft. per sec. The velocity of the vessel, 

Ift V ft OATI 

in feet per second, taking the knot as 6,080 ft., 's— ^^r— ^^^ = 27 ft. 

Then, the velocity of the stream, in relation to the surrounding water, 
is 34 — 27 = 7 ft. The cross-sectional area of the stream is equal to 
the area of the buckets; that is, 8 X 2 = 16 sq. ft., and as there are two 
wheels, and, hence, two streams, the total area is 2 X 16 = 32 sq. ft. 
As the streams are projected at a velocity of 34 ft. per sec, their com- 
bined cubical contents are 32 X 34 = 1,088 cu. ft., and since the weight 



[519 



PROPULSION OF VESSELS 

I, U. of sea-water is 64.1 lb., the combined weight o( tlie t 
3 is 1,088 X W.l = (19,740.8 lb. Applying the rule given, 

69,740.8 X 



r=^ 



^ 1.5,179.9 1b. Ans. 



40. To find the weight of the stream projected by a screw 
propeller, the diameter and pitch of screw, the diameter of 
the hub, and the number of revolutions per second must be 
known. The following example shows how, from these data, 
the theoretical thrust may be calculated: 

EXAMPLB. — A vessel, filled with a screw propeller 14 feet in diam- 
eter and 18 feet pitch, makes 14 knots when the engine is making 
90 revolutions a minute. The diameter ol the hub is 3 feet. Find Ihe 
theoretical thrust in sea-waier, neglecting Ihe wake velocity. 

Solution.— First, the cross-seclional area of ihe stream projected 
by Ihe propeller must be found. This is assumed to be equal in area 
to the difference in areas between two circles havinf; diameters equal 
to Ihe screw and hub, respectively. The difference in area = 14' 
X .78r>4 - 3" X .7854 = IQS.iKW - 7.0(!9 = H6.S69sq, ft. Thevelocityof 
1 relalion to the vessel, is - ^^- = 27 ft. per sec. The 



60 



velocity of the vessel per sec. i 



14 X 6.01 



00X60 --^W-.^t^arty. Hence, 
the velocity of the stream, in regard to Ihe surrounding water, is 
27 - 23,(14 = 3-36 ft. a sec. The weight of the stream projected in 
1 sec, is 27 X 146.869 X 64.1 => 254,166.18 lb. Applying the rule given 
in Art. 3&, 

_ 2S4, 186.18 X 



32.16 



6,556.77 lb. Ana. 



41. The term Indicated thrust may be defined as the 
measure of the total force exerted by the propelling mecha- 
nism. It derives its name from the fact that it is calculated 
from the indicated horsepower of the engine. The indicated 
thrust should not be confounded with the actual thrust; the 
latter is the value of the net force actually propelling Ihe 
vessel, while the former is the sum of the net force usefully 
applied to propelling the vessel and the force lost in over- 
coming all the frictional and other resistances. 

A horsepower is 33.000 pounds raised 1 foot in 1 minute. 
The total work done by the engine, in foot-pounds per 
mintite, is 33,000 X the indicated horsepower. Since work 



^ 



34 PROPULSION OP VESSELS §19 

is the product of force and distance, the magnitude of the 
force, whose reaction is the indicated thrust, may be found 
if the distance through which the force acts in 1 minute is 
known. This distance is found by multiplying the pitch of 
the screw propeller, in feet, by the number of revolutions 
per minute. 

Rule. — To find the indicated thrust of a screw propeller, 

divide 33,000 times the indicated horsepower of the engine by the 

prodtut of the pitch, in feet^ and the number of revolutions i>er 

minute, 

f^ 0j^ uujOOU Jti 

Or, t; - — ^— 

where H = indicated horsepower of engine; 

P = pitch of screw propeller, in feet; 

R = revolutions per minute; 

Ti = indicated thrust. 

Example. — Find the indicated thrust when the pitch is 22 feet, and 
the indicated horsepower developed by the engine, when making 
94 revolutions, is 1,034. 

Solution. — Applying the rule given, 

y, = ^'^^l^ = 16,500 lb. Ans. 

42. By reasoning similar to that from which the rule in 
Art. 41 is deduced, a rule for finding the indicated thrust of 
a paddle wheel may be obtained. The work done, as in the 
former case, is 33,000 X the indicated horsepower. The 
distance through which the force acts is equal to the speed, 
in feet per minute, of a point on the effective diameter circle. 

Rule. — To find the indicated thrust of a Paddle-wheel 
steamer, divide 33,000 times the indicated horsepower of the 
engine by the product of 3.1416 times the effective diameter of the 
wheel, in feet, times the number of revolutions Per minute, 

^ >j^ 33,000 ri 

' ~ 3.1416 dTR 

where D, is the effective diameter of the paddle wheel, in 
feet; the other letters denote the same values as in the 
formula given in Art. 41, 



PROPULSION OF VESSELS 



Example. — Find the intlicated thrust when the effective diameter 
of paddle wheels is 26 feet and the indicated horsepower developed by 



Solution.— Applying the rule given, 
^ 3 3,000 X ! 
' 3.14iax2« 



12.120.2 lb. Ans. 



I 



In applying the rule just given, it should be borne in mind 
that the total thrust is calculated. In case two wheels are 
driven by one engine, the thrust of each wheel is one-half 
the calculated thrust. In case of each wheel having a sepa- 
rate engine, as in some Western-river steamboats, the horse- 
power of the engine driving the wheel should be used to find 
the thrust of that wheel. If one wheel is driven by two 
engines, as in stern-wheel steamers, the combined horse- 
power of the two engines should be used. 

THRUST BEABINOS 

43. The thrust of the paddle wheels is taken by the 
bearings in which the paddle-wheel shaft is supported. The 
outboard bearings are usually bolted to a bracket securely 
attached to the side of the vessel; against these bearings, 
the whole of the thrust is exerted. The bearings may be 




. of any suitable form, provided that they are strong enough 
to withstand the thrust. 

With a screw propeller, a special form of bearing is 
necessary. The simplest form of such a bearing is shown 
in Fig. 6. The thrust of the screw propeller tends to force 
the propeller shaft either inboards or outboards, according 




36 PROPULSION OF VESSELS §19 

to the direction in which the vessel is propelled- To resist 
this tendency, a number of collars c are forged on the thrust 
shaft A\ these collars bear against semicircular bronze thrust 
rings a, by placed within recesses formed in the cap B and 
base C, respectively. To prevent any rotation of the thrust 
rings, a tongue e is placed between the cap and base at each 
side of the shaft. To prevent any longitudinal movement 
of the cap, it is fitted carefully between lugs /, / cast solid 
with the base; it is also bolted to the latter. Both the cap 
and base are cored out, as shown at B' and C'\ they are 
usually fitted with inlet and outlet pipes, by means of which 
water may be circulated through the cored chambers in 
order to prevent or alleviate any heating of the thrust rings 
that may occur while running. The whole arrangement, 
which is called a thrust block, is bolted to a pedestal P 
that is securely attached to the framing of the vessel. The 
thrust block may be adjusted to a limited extent in an axial 
direction by inserting a thin liner at p and removing one of 
the same thickness at ^, or vice versa. To allow such an 
adjustment to be made, the holes in the base through which 
the holding-down bolts s, s pass are made oblong. To pro- 
vide for a constant lubrication of the collars, a reservoir o is 
formed in the lower part of the base. This is filled with a 
mixture of oil and soapy water. The collars dip into this 
mixture and carry it around with them, thus providing an 
automatic lubrication. The reservoir may be emptied by 
means of the petcock r. It is of the greatest importance 
that the thrust should be evenly distributed over all the 
collars and thrust rings; for, assuming the whole thrust to 
be exerted against but one or two rings, the pressure would 
be so great as to prevent lubrication. In the thrust block 
shown in Fig. 6, the thrust rings cannot be adjusted very 
readily; therefore, this style, which is known as a soh'd thrust 
block, is gradually going out of use. 

44. The sectional, or horseshoe, thrust blacky shown in 
Fig. 7, is taking the place of the solid thrust block. In this, 
each thrust ring may be adjusted very readily to a nicety. 



PROPULSION OF VESSELS 




38 PROPULSION OF VESSELS §19 

independently of the others, or all rings may be adjusted at 
once, if required. In the figure, A is the thrust shaft; B, the 
base; and C, C^ the bearings placed at each end of the thrust 
block in order to support the thrust shaft. The thrust rings j 
are made in the form of a horseshoe, as shown in detail at 
Ay Fig. 7. The wearing surfaces f, ^ are usually formed of 
bronze for wrought-iron shafts, and of Babbitt, or any other 
white metal, for steel shafts. They are usually made sepa- 
rate from the thrust rings, which, in this case, are steel cast- 
ings, and are either hung on steady pins driven into the thrust 
rings, or inserted into recesses formed in the thrust rings. 
Large screws E, E' are placed on each side of the block and 
pass through holes in the bearings C, C'\ they are secured 
by nuts situated on the forward and after sides of each bear- 
ing. The thrust rings are placed over these screws and may 
be adjusted as well as locked, when in position, by means of 
nuts, as e^e!. The thrust rings, as well as the base, are cored 
out and provided with suitable piping, by means of which 
water may be circulated through them. The lower part of 
the base forms a reservoir for the lubricant. 

45. The thrust block is usually located close to the 
engine, it being the common practice to make the thrust 
shaft the first length of shafting abaft of the engine. Thrust 
blocks of the horseshoe type are frequently bolted directly 
to the bedplate of the engine. If located there, they can be 
given the attention their importance demands. If heating 
and subsequent cutting of the thrust rings occur, which 
entail a very rapid wearing away of the rings, the whole line 
of shafting is thrown forwards an amount equal to their wear. 
Should the crank-shaft and line-shaft journals be grooved to 
any extent, their heating and subsequent cutting are very 
liable to occur as soon as the thrust block heats. Since the 
shafting and bearing may be seriously damaged by means of 
this, it is of great importance that all possible attention be 
given to the thrust block. 



PROPULSION UF VESSELS 



SPEED UF V&SBEI.S 



POWERING OF VESSELS 

46. The exact amount of power required to propel a 
vessel at a given speed cannot be deduced very readily from 
the elementary principles of mechanics. Instead, empirical 
rules based on the actual performance of vessels are usually 
relied on. The conditions that influence the relation between 
power and speed are many, but only a few of the more 
important ones will be enumerated here. For instance, the 
area of the blades of the screw propeller may not be suffi- 
cient for high speed, owing to a churning of the water 
when the propeller is revolved beyond a certain speed; 
and, although the power expended in revolving the propeller 
faster may be considerable, the increase of the speed of the 
vessel may be very slight. A similar state of aiTairs may 
occur if the area of the buckets of a paddle wheel is too 
small. It may be amply sufficient for a low rate of speed, 
and still be entirely too small for a higher rate, thus show- 

I ing, probably, a high efficiency of the propelling instrument 
a low speed, and a very poor one at a higher rate. Again, 

I the efficiency of the engine may vary greatly for different 
powers developed by the same engine. Therefore, no hard 
and fast rule can be laid down that will express the relation 
between power and speed under all conditions. 

47. The rule most frequently used in the powering of 
vessels is known as the Admiralty rule. It involves the 
selection of a proper constant based on actual experience; 
when this constant, a number of which are given in Table I, 
due to Mr. Sealon, is properly selected, the results of the 
rule will be found to agree very closely with the actual per- 
formance of vessels powered by the rule, at least under 
ordinary conditions and for ordinary efficiencies of the pro- 
pelling apparatus. 

Kiile. — To find the indicated horsepower required to propel a 
^L vessel al a givett speed, multiply together the cube of the sPeed 



40 



PROPULSION OF VESSELS 



§19 



a7id the cube root ot the square of the displacement. Divide this 
product by the constant corresponding to the lengthy speedy and 
shape of the vessel^ as given in Table I, 



Or, 



H = 



where // = indicated horsepower; 

IV = displacement of vessel, in tons of 2,240 pounds; 
k = B. constant (see Table I); 
5" = speed, in knots. 

TABLE I 

VALUES OF k IN ADMIRALTY RULE 



Description of Vessel 


Speed 
Knots 


k 


Under 200 feet, fair 

Under 200 feet, fine 

Under 200 feet, fine 

Under 200 feet, fine 

From 200 to 250 feet, fair 

From 200 to 250 feet, fine 

From 200 to 250 feet, fine 

From 250 to 300 feet, fair ' 

From 250 to 300 feet, fair 

From 250 to 300 feet, fine 

From 250 to 300 feet, fine 

From 250 to 300 feet, fine 

From 300 to 400 feet, fair 

From 300 to 400 feet, fair 

From 300 to 400 feet, fine 

From 300 to 400 feet, fine 

From 300 to 400 feet, fine 

Above 400 feet, fine 


9 to 10 
9 to 10 

10 to II 

11 to 12 
9 to II 
9 to II 

II to 12 

9 to II 

II to 13 

9 to II 

II to 13 

13 to 15 

9 to II 

II to 13 
II to 13 
13 to 15 
15 to 17 
15 to 17 


200 

230 

210 
200 
220 
240 
220 
250 
220 
260 
240 
200 
260 
240 
260 
240 
190 
240 



48. To determine whether a vessel is fair or fine, it is 
usual to compare its displacement, in cubic feet, with the 
volume of a rectangular box having a length equal to the 



§19 PROPULSION OF VESSELS 41 

length of the vessel on the water-line, a width equal to 
the beam, and a depth equal to the mean draft of the vessel 
diminished by the depth of the keel. If the displacement is 
.55 of Ihe volume of the box, or less, the vessel is fine; if 
above .r>5 and less than .70, fair. The quotient obtained by 
dividing the displacement by the contents of the imaginary 
bos is called the coelHcieni of fineness. 

ExAMFLB.~A vessel, '2U0 feet loug and finely shaped, having a dm- 
placement of 1,000 tons, is to have a speed of lb knots; what should 
be Ihe indicated horsepower of the engine? 

SomrroN.— From the table, k = 200. Applying the rule given, 

200 



H = '-^LJ^X.— - = 1.S87.5 I. H. P. 



49. The selection of a proper value of fc calls tor the 
exercise of considerable judgment, based on personal knowl- 
edge of the actual performance of similar vessels. Gener- 
ally speaking, the value of k is influenced by the length, 
speed, and shape of the vessel. The value of k should be 
greater with an increased length of the vessel in propor- 
tion to the width, and also with a finer under-water body; 
conversely, its value should be less as the ratio of length 
to width becomes smaller, and as the form becomes fuller. 
Furthermore, the value of k should be smaller for rela- 
tively high speeds than tor low speeds, for vessels of the 
same form and displacement. Prof. W. F, Durand states that 
a speed may be considered as relatively high or low if the 
speed exceeds the numerical value of the square root of the 
length of the vessel in feet, or falls below it. Thus, if a 
vessel is 64 feet long, V64 = 8, a speed of 10 knots would 
be considered as relatively high, while a speed of 5 knots 
would be considered as relatively low. For small boats, if 
the speed is given in statute miles per hour, the values of k 
range between 150 and 225, and for speeds given in knots, 
between 100 and 150. according to Prof. W. F. Durand, in an 
article contributed to "Marine Engineering." 

ExAMi-LR 1. — A boat 70 feet long and 7 feet tieara is to make 10 knots; 
its displacement is 30 tons, and Ihe vesiiel bas fair lines, haviug a coeffi- 
cient of (iueness of ,65. What horsepower is required^ 



42 PROPULSION OF VESSELS §19 

Solution. — As the speed is relatively high, it will be well to select 
a rather low value of k, say 120. Applying the rule given in Art. 47, 

^ = foA^^ = 80.46, say 81, I. H. P. Ans- 

ExAMPLB 2.— A boat 00 feet long and 8 feet beam is to make 
9 knots; its displacement is 30 tons, and it has fair lines. What horse- 
power is required? 

Solution. — As the speed is relatively high, a low valneof k should 
be selected on this account. Furthermore, as the ratio of length to 
width is small, the value of k should be decreased on this account also. 
Selecting a value of 110, by the rule given in Art. 47, 

//=^^j^ = WI. H.P., nearly. Ans. 

Example 3.— A boat 50 feet long and 7 feet beam is to make 
6 knots; its displacement is 25 tons and it has fine lines. What horse- 
power is required? 

Solution. — The speed being relatively low, and the lines fine, a 
rather high value of k, say 140, can be selected. Applying the rule 
given in Art. 47, 

H = ^^^ = 13.2 I. H. P., neariy. Ans. 



KNGrWE 8PKED AND SHIP'S 8PKED 

50. Very often, the question as to the speed at which 
the engine must be run to drive the vessel at a certain 
velocity, confronts the marine engineer. If the revolutions 
per minute of the engine for a certain speed of the vessel 
are known, the question may be readily answered. Assuming 
the percentage of slip to remain constant, doubling the 
velocity of the stream projected by the propelling instrument, 
that is, doubling the revolutions of the engine, and, hence, of 
the screw propeller or paddle wheels, doubles the speed of 
the vessel; in other words, the speed is directly proportional 
to the revolutions of the engine. In actual practice, the per- 
centage of slip varies somewhat at different speeds and under 
different conditions; hence, the following rule, which is based 
on the assumption of a constant percentage of slip, does not 
give the exact number of revolutions per minute required, 
which can be found only by actual trial. However, the rule 
will give a very fair approximation. 



H'J 



PROPULSION OF VESSELS 



Rule. — To find the revoUttions per minute at which to run the 
engine in order to give the required speed, divide the product oi 
the revolutions producing any given speed and the required speed 
by the given speed. 



Or, 



R. = ^ 



1 speed; 



where R = revolutions per minute for a givi 
S = given speed; 
R, = required revolutions; 
5> = required speed. 
Example.— If a vessel is propelled at the rate of 16 knots when the 
engine is raakitig 32 revolutions per miuule, what should be the revotu- 
lions per minute to give it a speed of 14 knots? 
SoLouON. — Applying the rule given, 

Rv =• ^^^ = 28 rev. per min. Ans. 

51. On taking charge of a steatner, the number of revo- 
lutions at which to run the propelling instrument to produce 
a given speed, when none of the data called for in the rule 
given in Art, 50 are available, is often desired. In that 
case, the pitch of the screw, or the effective diameter of the 
paddle wheel (taking the effective diameter for this purpose 
from center to center of buckets) must be measured and a 
fair slip value assumed. The revolutions can then be found 
by the following rule: 

Kule. — To find the revolutions per minute required to pro- 
duce a given speed Per hour, multiply the pitch of a screw propel- 
ler, or the circumference of the effective diameter circle of a 
Paddle wheel, by 60 and by the difference between 1 and the 
assumed apparent slip, expressed decimally. Divide the speed of 
the ship in feet per hour through the water by this product. 



Or, 



60 Z> ( 1 - 5.) 
R = revolutions per minute; 
5 = speed, in feet per hour; 
D = pitch of screw propeller, or effective diameter 

X 3.1416 in case of a paddle wheel; 
St — apparent slip, expressed decimally in per cent. 



44 PROPULSION OF VESSELS §1^ 

ExAMTUt. — Tbe pftcii c4 a screw propeller » IS fiect; Ibov masr 
rtr^otifMA per mrfrate most ie maiEe to drrte tike sfcfp at the ate of 
10 kooCft* tbe ^ppart^i sHp tMsof: wrtmafrd at 10 per cent ? 

SoLcmrwf.— Apptyiogf the rale g:hrco. 

At as s 70.37 mr. Her ^uxt. Aos. 

52. The probable speed of a ship with a gixen number 
of rerolations of the propellioc^ instrnmeiit can be fonnd 
as follows: 

Rale. — Tff find the probable speed of a steam vessel ^ in miles 
Per hour, multiply 60 by Ike revoluticns Per minute and the 
pilch ^ in feel, of a screw propeller^ or Ike circumference of the 
effcclive diameter circle of a paddle wkeelj and by ike differena 
between J and the per cent, of apparent slip expressed decimally. 
Divide the product by 5^80 or by 6,060, auarding to whether 
the speed is to be expressed in statute miles or nautical miles. 

Or, S = 60^^(1--S:) 

where / is the number of feet per statute or nautical mile; 
the other letters have the same meanin^^ as in the formula 
given in Art. 51. 

Example.— A propeller of 20 feet pitch makes 70 revolutions per 
roinute; with an assumed slip of 12 per cent., what wiU be the speed 
of the ship in knots? 

Solution.— Applying the rule just given, 

,, 60X20X 70 X (1 - .12) ,« lii u * a 

S = ^-7iZ/» = 12.16 knots. Ans. 

6,080 



RELATION BETWEEN HORSEPOWER AND REVOLUTIONS 

53. The speed of a ship fully under way is about directly 
proportional to the number of revolutions made by the 
engine. But the power required to turn the propelling 
instrument varies as the cube of the number of revolutions, 
or (which is the same thing) as the cube of the speed. 
Assume some body (the shape of it is immaterial) to be 
moved through water at a uniform speed of 1,100 feet per 
minute, and assume that a constant propelling force of 
16,500 pounds is required to maintain that rate of speed. 



§19 PROPULSION OF VESSELS 45 

Since work is the product of force into distance, the work 

done per minute is 1,100 X 16.500 = 18,150,000 foot-pounds. 

Since a horsepower is 33,000 foot-pounds of work per 

minute, the horsepower required to move the body at the 

given speed is 'V^u'oo*^ = 550 horsepower. Suppose that 

the same body is moved through the water at the uniform 

speed of 2,200 feet per minute, that is, twice as fast as before. 

Now, the resistance to a body moving through water varies 

as the square of the velocity; hence, the force required to 

move the body at double the speed will be 2" X 16,500 

= 66.000 pounds. But, since the body will move the same 

distance as in the first case considered, i. e., 1,100 feet in 

one-half the time, or 30 seconds, the power required will be 

66,000 X 1.100 X 60 . i^n t, 
— .,„-™- „„- — = 4,400 horsepower. 
33,000 X 30 

This shows that to double the speed the power had to 
be increased 2x2x2 = 8 times; that is, it varies as the 
cube of the speed. Had the calculation been made for any 
other speed, say 1.5 times the original speed, the power 
required would have been found to be 1.5 X 1-5 x 1.5 = 
3.375 times as much. Likewise, for a speed treble that first 
considered, the power would have been 3 X 3 X 3 = 27 times 
as much. From this the following rule is derived: 

Rule. — To find, approximately- the power developed by an 
engine for any given number of revolutions per minute, any other 
horsepower and the corresponding revolutions per minute being 
known, multiply together the cube of the revolutions at the 
required horsepower and the given horsepower. Divide the prod- 
uct by the cube of the revolutions corresponding to the given power. 

Or, H. = ^'^^ 

where /f, ~ required indicated horsepower; 

R, — revolutions at required power; 

H = given indicated horsepower; 

R — revolutions corresponding to it, 
ExAHFt.K.— A IiiK eagine develops TO indicated horsepower at 100 
revolutions; wbat power would it probably develop at GO revolutions? 



u 



I 



46 PROPULSION OF VESSELS 

Solution, — Applying ihe rule given, 

H, = ^T^,— = 15.12 1 H, P. Acs. 

In practice, the horsepower calculated by this rule will not 
always correspond to that actually used, as found by I 
indicator diagram. This is due to the fact that the efficienei 
of the machinery is not necessarily the same at all speed: 
As a general rule, the engine will be at its maximum i 
ciency at some certain speed, and will have a lower efficiencyfl 
at a higher or lower speed. The speed at which the engtn 
is at its best efficiency can be found only by actual trial. 

BEUUCTION OF UOR8EPOWER WHEN TOWINO 

54. It is a well-known fact among marine engineers that 
an engine will develop a lower horsepower with a given 
boiler pressure, throttle position, and cut-off when lowing or 
having the resistance of ihe vessel increased by other means, 
as by a head-wind, a head-sea, or an adverse current, than 
will be developed under the same engine conditions but run- 
ning free. The reason for this is explained in the following 
discussion, in which for the sake of simplicity two convenient 
assumptions have been made that are not absolutely cor- 
rect in practice. These assumptions are that the borsepowefl 
of an engine varies directly as the first power of the numb< 
of revolutions, the mean effective pressure remaining I 
same, and that the speed of the vessel varies directly i 
the first power of the number of revolutions. 

Consider a paddle-wheel steamer running free, with its" 
engine developing its greatest horsepower possible. Since 
the turning effort of the engine depends only on the mean 
effective pressure in the cylinders, it is independent of ihe i 
revolution so long as the throttle position, boiler pressured 
and cut-off remain the same. This turning effort, wheifl 
exerted at the circumference of the effective diameter circle 
tangentially to the same and parallel to the surface of the water, 
is the total force tending to propel Ihe vessel forwards, and 
is resisted by an opposing force, which is the resistance qlf 
the vessel. Let the engine be started and assume that it I 



ntent 
cor-^H 
owef^l 

mber^l 

: tfaofl 

ly «^ 

^ its^ 

an 
he H 




PROPULSION OF VESSELS 



47 



f §19 

making its greatest turning effort. The resistance being less 
than the forward force, the vessel moves forwards under the 
influence of a forward accelerating force equal to the differ- 
ence between the total forward force and the resistance. 
As the vessel gathers headway, the resistance increases; 
this means that the difference between the forward and the 
resisting force, that is, the accelerating force, decreases 
until the total forward force and total resistance have become 
equal, when the vessel continues at a uniform speed. Let 
the resistance be increased either by the vessel picking up a 
tow, by a head-wind or head-sea, by encountering an adverse 
current, or by a combination of these circumstances. The 
conditions remaining the same as before at the engine, the 
turning effort, that is, the total forward force is the same; 
but, as the initial resistance is increased, the initial difference 
between the total forward force and the total resistance is 
smaller than in the first case. This means that a smaller 
accelerating force is available with an increased resistance, 
and consequently the total forward force and total resistance 
become equal at a lower speed of the vessel, which then 
continues under way at a uniform, but lower speed. Now, 
the horsepower of an engine varies (theoretically) directly 
as the first power of the number of revolutions, the mean 
effective pressure remaining constant. It has been shown 
that the speed of the vessel has been lowered; from this 
it follows that the revolutions and consequently the horse- 
power must be less when the resistance has been increased. 
By adding to the resistance of the vessel, a condition is 
finally reached similar to that of a vessel moored to a dock; 
the forward force and resistance are equal and the vessel, as 
no accelerating force is available, remains stationary. In 
this condition, the number of revolutions, and, hence, the 
horsepower, has dropped to the lowest limit. 

RELATION OF COAL CONSUMPTION TO SPEED 

55. The fuel consumption may he said to vary directly 
i»s the horsepower developed (this is not exactly true, but 
r-oaly approximately). The horsepower varies about directly 




48 PROPULSION OF VESSELS §19 

as the cube of the speed, whence it follows that the fuel con- 
sumption will also vary as the cube of the speed (approxi- 
mately). From this, the following rules have been deduced. 

Rule I. — To find the Probable coal consumption for a speed 

different from a known speedy multiply the cube of the new speed, 

in miles Per hour or knots ^ by the coal consumption y in tons^ at 

the known speed. Divide the Product by the cube of the known 

speedy expressed in the same terms cls the new speed; the quotient 

will be the coal consumption expressed in the same terms as the 
known one. 

Or. '^^ ^^^ 

where c = coal consumption, in tons, at the new speed; 
s = new speed; 
5* =. known speed; 
C = coal consumption, in tons, at the known speed. 

Example 1. — A steamer consumes 80 tons of coal per day at a 
speed of 12 knots; suppose that the speed is to be reduced to 10 knots, 
what will be the fuel consumption per day at that rate of speed? . 

Solution. — Applying rule I, 

c = — Y6i — ^ ^-3 1*- P®^ ^^-i nearly. Ans. 

Rule II. — To find approximately the speed of steaming for a 
new coal coftsumption, multiply the new coal consumption by the 
cube of the known speedy divide the prodiut by the coal consump- 
tion at the known speedy and extract the cube root of the quodcni. 
The coal consumption is to be expressed in the same terms in both 
cases, and the new speed will be in tJie same terms as the old speed. 



Or. ' = <H'' ^^^ 



where the letters have the same meaning as in formula 1. 

Example 2. — A steamer consumes 100 tons of coal per day at a 
speed of 10 knots; what should be the speed in order to cut the coal 
consumption down to 50 tons per day? 

Solution. — Applying rule II, 

, .'M) X 10* ., ^ O 1 . I A 

J = < ( ^ ^ — = /.9, or 8 knots, nearly. Ans. 



> 



( 



519 PROPULSION OF VESSELS 49 

Example 8.— IC a. steamer consumes 15 tons of coal per day tu 
produce a speed oF 9 knots, how many knots would she steam if 
the coal vonsuroption were reduced to 12 tons per day? 

SoLOTiov.— Applying rule II, 

J = \^ - = 8.35 knots, nearly. Ans. 

56. At sea, owing to an accident, it often occurs that it 
is desired lo know what speed lo maintain in order to reach a 
given port with the amount of coal on hand. This problem 
is readily solved by trial and by application of rule I, Art. 55. 
In practice, a good margin of coal shotild be shown by the 
calculations as left over, for the reason thai the actual coal 
consumption at the reduced speed will, as a general rule, be 
in excess of the calculated consumption, by reason of the 
decrease in economy of the engine induced by reducing the 
developed horsepower. 

ExAUPLB. — A steamer consumes 20 tons of coat per day at a nor- 
mal Kpeed nf 10 knots; the distance to the nearest port wher« coal 
had Is tlOO miles, and the estimated quantity of coal in the 
bunkers is but 35 tons. Fiud what speed should be maintained in 
order to reach the coaling station with the coal supply on hand. 
Solution.— The best way to proceed in a case of this kind is to 
isume a lower speed, say 8 knots, and calculate the new coal con- 
lanmption for that speed; thus, £ = ^^,- = 10.24 T. per da., or .43 T. 
per hr, The time required to carer a distance of l!00 mi. at a speed 
of 8 knots is 'S* = 75 hr,. and at a coal consumption of .W T. 
per hr. the total quantity of coal required at thai speed is 'B x .43 
= 32.25 T. Hence, if a speed of H knots is maintained, the supply 
.of coal on hand (35 T.) will suffice to reach the coaling station under 
.'Ordinary weather conditions. Ans. 



EXAMPLES FOR PRACTICE 

1. If a stream of water weighing 32,t(i0 pounds be projected per 
•econd from a ve.ssel, what will be the theoretical thrust, assuming the 
iitme slip to be 2 feet per second P Ans. 2.U0U lb. 

Find the indicated thrust when the pitch of screw propeller is 
90 feet; revolutions per minute, tJO; indicated horsepower developed, 
1,000. Ans. -Il/MO lb. 




60 PROPULSION OP VESSELS §19 

3. The effective diameter of a stem wheel is 15 feet; what is the 
indicated thrust corresponding to 100 indicated horsepower at 30 revo- 
lutions? Ans. 2,334.27 lb. 

4. Find the indicated horsepower for a vessel 190 feet long, having 
a displacement of 1,000 tons, a coefficient of fineness of .53, and a 
speed of 12 knots. Ans. 864 1. H. P. 

5. At what number of revolutions should a screw propeller turn to 
drive a vessel at 15 knots, if at 60 revolutions it made 12 knots? 

Ans. 75 rev. 

6. If a screw propeller has a pitch of 14 feet, and its apparent slip 
is known from a trial-trip record to be 15 per cent., how many revolti- 
tions per minute must it make to drive the ship 12 statute miles per 
hour against a current running 2 miles per hour? 

Ans. 103.5 rev., nearly 

7. About what speed may be expected from a stem-wheel steamer 
if the wheel has an effective diameter of 17 feet and makes 32 revolu- 
tions per minute? The speed is desired in knots, and the apparent 
slip is estimated at 20 per cent. Ans. 13.5 knots, nearly 

8. If a marine engine develops 100 indicated horsepower at 90 revo- 
lutions, what will it develop at 100 revolutions? Ans. 137.17 I. H. P. 

9. A steamer consumes 20 tons of coal per day at a speed of 7 knots; 
what is the probable coal consumption at 11 knots? 

Ans. 77.6 T. per da. 

10. At what speed must a steamer proceed to cut the coal consump- 
tion down to 40 tons per day when at 60 tons per day itmakes 18 knots? 

Ans. 15.7 knots, nearly 




REFRIGERATING MACHINERY 



FUNDAMENTAL PKINCIPIiES 



ISTBODUCTION 

1. Frocesses ol ProdtictntJ Cold. — The act of lower- 
ing: the temperature of a body, or of keeping its temperature 
below that of the atmosphere, is spoken of as refrigera- 
tion. It may be produced by one of the following processes: 

1. A transfer of heat from a warmer to a colder body. 

2. A chemical action, as exemplified by the so-called 
freezing mixtures. 

3. The adiabatic expansion of a gas. 

4. The evaporation of liquids having a low boiling point. 
Heat will pass from a warmer to a colder body. Drop a 

hot piece of iron into a vessel of cold water; the water will 
absorb heat from the iron until both the iron and the water 
are at the same temperature; that is, the heat of the warm 
body (the hot piece of iron) passes to the cold body (the 
coo! water). 

In actual practice, ice-making and refrigerating machines 
employ either of the last two processes in combination with 
the first. The second process has no practical applicability 
at present in commercial work. 

In order to change a liquid into a vapor, a certain quantity 
of heat, called the latent heal ol vaporization, must be added 

Cotyrigkttd by Inlrrualioinl Tulboot Company. Bnlrtid al Slalionirs' /fall, London 
130 



2 REFRIGERATION §20 

to the liquid. When this process of vaporization or evapo- 
ration is taking place in the presence of other warmer bodies, 
the heat required for it is drawn from these bodies, and they 
are thereby cooled. From this, it follows that, with a liquid 
having the boiling point below the freezing point of water, 
water can be frozen by allowing the liquid to absorb the heat 
contained in the water, and thus acquire the heat required 
for its own evaporation. 

2. Adiabatic and Isothermal Expansion and Com- 
pression. — Let a given volume of any gas be confined under ' 
pressure in a cylinder, like that of a steam engine; the gas 
will then tend to move the piston, that is, it will tend to 
overcome resistance. If the pressure is sufficient to over- 
come the resistance, the piston will move and the gas, in 
expanding, will be doing work. Now, if a thermometer is 
inserted in the cylinder, it will be found that as the gas 
expands its temperature is lowered. As is well known, it is 
not the steam itself that does work in a steam engine, but it 
is the heat contained in the steam. This statement applies 
to all other gases as well. Then, as heat must be given up 
in order to do work, it follows that if no heat is supplied 
from outside sources, a gas, in expanding, cannot do work 
without its temperature being lowered. The expansion of a 
gas not accompanied by a transfer of heat from another body, 
is kno>K*n as adlabatle expansion. The word "adiabatic'' 
is derived from the Greek word adiabatos (a, not; diabainchiy 
to pass through), and is descriptive of a process in which 
there is no transfer of heat from or to a body operated on 
to or from another body. Conversely, if a given volume of 
a gas be compressed, its temperature is raised if no heat is 
abstracted from it during compression. That the tempera- 
ture must become higher can be seen when it is considered 
that it is impossible to compress the gas into a smaller 
vohmie without doing work. The process of compression 
chancres this work into heat: that is, heat is added to the gas, 
ami consequently its temperature is increased. The com- 
pression y>i a i;as. accompanied by an increase of temperature 



REFRIGERATION 



proportional to the conversion of the work done in com- 
pressing it into heat, is known as atllnbnttc compression. 
In other words, a gas is said to expand or to be compressed 
ndiabatlcallj' when no heat is added to it from an outside 
source during expansion or abstracted by any medium while 
the gas is compressed. 

3. Let a given volume of gas under pressure expand and 
do work. As previously explained, it cannot do work with- 
out parting with an equivalent amount of heat. Let this 
same amount of heat be added from some outside source. 
Then, the gas, in expanding and doing work, will remain at a 
constant temperature, and it is now said to expand isolher- 
mally. The term "isothermal," which is derived from the 
Oreek {t'sos. equal; tkernif, heat), simply means at a constant 
temperature. Conversely, if a given volume of gas at a 
given temperature be compressed, and the amount of work 
converted into heat in compressing it be abstracted by some 
means, its temperature will remain the same. This process 
is known as tsotbcriiial compression. In other words, a 
gas is said to expand or to be compressed Isotherinally 
when heat is added during expansion or abstracted during 
compression, to keep the temperature constant, 

4. Suppose that a certain volume of gas at a given 
pressure is allowed lo expand without doing any work. 
Then, assuming the vessel in which expansion is taking 
place to be a perfect non-conductor of heat, so that no heat 
can be added or abstracted by any outside means, the tem- 
perature of the gas during expansion will remain constant; 
that is. the expansion is adiabatic and isothermal at the 
same time. 

5. The third method mentioned in Art. 1 suggests a 
mechanical process of refrigeration. Let a certain volume 
of any gas be confined in a cylinder and let it be compressed 
adiabatically by doing work on it. When compressed to 
the smallest volume feasible, reduce the temperature by 
allowing the heat due to the conversion of work into heat 
during compression to pass into a colder body, say cool 



4 REFRIGERATION §20 

water. The gas having been cooled to the original tempera- 
ture, or nearly to it, can be made to do work, expanding 
adiabatically. But in doing work, the pressure and tem- 
perature of the given quantity of the gas fall rapidly, and the 
temperature soon falls far below that of the atmosphere sur- 
roimding the machine in which expansion is taking place. 
Then, as heat will readily pass from a warmer to a colder 
body, the expanded gas, which is very cold, will, on being 
brought near a warmer body, absorb some of its heat, that 
is, cool it. 

CAPACITY OF REFRIGERATING ICACHIlfES 

6. The capacity of a refrigerating machine is the meas- 
ure of its ability to abstract heat. The unit of refri^eratinic 
or ice-melting capacity is the quantity of heat required to 
melt 1 ton (2,000 pounds) of ice at 32° F. to water at 32° F. 
The latent heat of fusion of water being 144 British thermal 
units, the unit of refrigerating capacity is equal to 144 X 2,000 
= 288,000 British thermal units. 

It is the practice of some British writers to use the long 
ton (2,240 pounds); on this basis, the unit of refrigerating 
capacity is equal to 144 X 2,240 = 322,560 British thermal 
imits- This value is virtually obsolete at present, however. 

Rule. — To find the refrigerating capacity of an ice machine^ 
divide the number of British thermal units abstracted in 24 hours 

by 288,000. 

^* " 288,000 

where F = refrigerating capacity, in tons; 

/f = number of British thermal units abstracted per 
day of 24 hours. 

Example. — A refrigerating machine abstracts 2,375,241 British 
thermal units in 20 hours; what is its refrigerating capacity? 

e rr.u U . '. V. . . A ' A 2.375,241 X 24 

Solution.— The heat units abstracted m a day are -^^ 

B. T. U. Applying the rule just given, 

^ = -^"1^^- = »•'»■• ^y ^« T. Ans. 



§20 REFRIGERATION 5 

7. The ice-making capacity is the number of tons of ice 
that a machine is capable of producing in 24 hours. As the 
temperature of the water from which the machine makes the 
ice varies from 50° to 95°, and as it is necessary to coo! this 
water to 32^ before any ice can be made, it will be seen that 
the ice-making capacity is variable and is largely afEected by 
the conditions under which the machine operates. Owing 
to the necessity of cooling the water from which the ice is 
made from its initial temperature to a temperature below the 
freezing point, and owing to other losses, such as radiation, 
etc., the ice-making capacity is only about 50 or 60 per cent, 
of the ice-melting capacity. 

8. A refrigerating machine is generally driven by a steam 
engine; therefore, the energy delivered to the machine is 
contained primarily in the fuel fed to the furnace, usually 
coal. For this reason, it is customary in commercial work 
to measure the commercial efficiency, or the economy of a 
refrigerating machine, by the pounds of ice-melting effect 
per pound of coal used. For every pound of coal consumed 
in the boiler to produce steam to operate the refrigerating 
machine, a quantity of heat is abstracted from the cold body 
sufficient to melt a definite number of pounds of ice at 32° F. 
into water at 32° F. This quantity of ice is a measure of 
the commercial efficiency of the machine. 

Example, — A refrigerating machine having an actual ice-melting 
capacity of 23.5 tons requires 4,360 pounds of coal per '2i hours to 
operate it; what is the efficiency, expressed in ice. per pound of coal^ 

SoLUTtoN.— 23-5 T = 47,000 lb.; 47.000 -^ 4,350 = lO.M; or, 10.8 lb. 
of Ice is melted per pound of coal burned. Aqs. 

L ADIABATIC-EXPANSION REFRlGEirATlON 



\ t FREE-AIR REFRIGERATING MACHINES 

9. Air being the cheapest and most readily obtained gas, 
is for that reason used to some extent for the production 
of artificial cold. The machines in which it is used are 
aiown as atr-reri-ti;eratlug luat-liliie^. 



REFRICfiRATION 



They utilize the fall of temperature that occurs when cont 
pressed air expands adiabatically and performs work, aS' 
staled in Art. 5. 

The general arrangement of an air-refrigerating macfainr 
is shown in Fig. 1. The machine consists essentially of a 
compression cylinder W, an expansion cylinder B, a coB> 
denser R, and a cooler, or refrigerator box, D. The piston 
of the cylinder A is provided with suction valves K J'open- 
ing inwards, a discharge valve f, and a water-jaclcet J. 
The diameter of the cylinder B is slightly less than that of A 



tralerOHtM. 




The piston is solid, but the cylinder head is provided witf 
two valves, an inlet valve 5" and an outlet valve S. which are 
operated by the eccentrics C and C. The pistons are 
nected to cranks set at 180°. The condenser A" is a surface 
condenser and receives a current of cold water from tbt 
water-jacket J oi the compression cylinder W. A receiver^ 
is connected with the condenser and also communicates wid 
the inlet valve S of the expansion cylinder B, 

The air at ordinary pressure is taken into the cylinder 
through the valves V, V. and is compressed adiabatically 
until the pressure becomes sufficient to open the valve f"J 
The air then passes into the condenser R, where it comes ii 
contact with the cold surfaces of that vessel. The adiabatt< 
compression has raised the temperature of the air; but ii 
passing through the condenser, some of the heat cuntaini 



S20 REFRIGERATION 

in the air is given up to the cold water circulating through 
the condenser, and the temperature is lowered nearly to that 
of the surrounding air, During this time, the valve 5 of the 
expansion cylinder B opens and permits an amount of air 
equal in weight to that expelled from A to pass from the 
receiver R' into the cylinder. The valve 5 closes and the 
air in the cylinder B expands, forcing the piston forwards 
and doing a certain amount of work. This expansion of the 
air in the cylinder B and the performance of work in forcing 
the piston forwards is at the expense of the energy stored in 
the air. The air therefore gives up sufficient heat to do the 
mechanical work, and as a result its temperature falls. As 
the air on entering B was at a normal temperature, the 
expansion brings the temperature below that of the surround- 
ing objects. In other words, the air is cooled. 

When the piston in B reaches the upper limit of its stroke, 
the valve S' opens; and as the piston descends, the cooled 
air escapes by means of the pipe 7" into the refrigerator 
box D. 

The difference between the work done on the air in the 
compression cylinder and that done by the air in the expan- 
sion cylinder, and, in addition, the work required to over- 
come the friction of the entire machine, must be supplied by 
a steam engine or other motor. 

10. Air at any ordinary temperature can hold a certain 
amount of water vapor in suspension. The limit, or point 
of saturation, that is. the point at which the air can bold no 
more water vapor, is called the (le\v point. When this point 
is reached, the excess of moisture above that which the air is 
able to hold is precipitated in the form of dew. The weight 
of moisture contained in a given volume of air at the dew 
point is not the same for all temperatures; in fact, air will 
hold in suspension four times the weight of moisture at 72° 
that it will at 82°. Assume that the air on entering the 
expansion cylinder B. Fig. 1, is at a temperature of 7'2° and 
is saturated with moisture. As the temperature falls during 
expansion, the water is gradually precipitated and condenses 



8 



REFRIGERATION 



S20 



on the walls of the cylinder. This water cools as the expan- 
sion goes on until it reaches 32°, when it freezes. The con- 
densation, cooling, and freezing of the water greatly decrease 
the useful effect of the machine. Besides, the snow, which 
is the result of freezing the moisture, often gives trouble by 
clogging the valves. 

11. The Haslam Foundry and Engineering Company, 
Derby, England, makes what is known as a dry-air system. 
They place a drier in the suction pipe from the condenser to 
the expansion cylinder. The compression cylinder A, Fig. 2, 




Fig. 2 

takes the cold air from the refrigerator box D; on its way to 
A, this cold air passes through the pipes of the drier M. The 
cold strikes through these pipes and cools the air surrounding 
the pipes on its way from the receiver R to the expansion 
cylinder B. The air gives up a large percentage of its' mois- 
ture in the drier, and the frosting in the cylinder B is much 
diminished. 



ALLEN DENSE-AIR REFRIGERATING MACHINE 

12. The air-refrigerating machines described in Arts. 9 
and 1 1 take in air from the surrounding atmosphere at every 
stroke; in the Allen dense-air maclilne, however, air is 
used under an initial pressure of about 60 pounds per square 
inch and the same air is used over and over again. 

A small supplementary pump attached to the machine 
charges the system and machine with air at the given 



§20 



REFRIGERATION 



pressure, and serves to make up any loss due to leakage. The 
advantage of uaing air under pressure is as follows: The 
amount of heat that a given volume of air can abstract from 
a warmer body varies directly as the weight of the given 
volume. That is, if a given volume of air weighs 5 pounds, 
it can abstract five times the quantity of heat from the warmer 
body that can be abstracted by an equal volume weighing 
only 1 pound. This allows a smaller conveying pipe to be 
used, and also allows the machine to be placed at some 
distance from the refrigerating box or ice-making tank. 
Naturally, the smaller the pipe conveying the cold air to the 
refrigerating box, the less surface there is for the absorption 
of heat from the surrounding air and consequent warming of 
the cold air; hence, with the small pipe used in this machine, 
the cold air can be conveyed farther for a given rise of 
temperature. 

13. A general perspective view of one form of the Allen 
dense-air machine is given in Pig. 3, and a diagrammatic 




illustration of a plant employing that machine is shown in 
Fig. 4. The machine consists of the following parts: a steam 
cylinder^, an air compressor B, an air expander D, a cooler C, 



§20 REFRIGERATION 11 

a water pump F. which supplies the cooling water to the 
cooler, a primer pump ^7 for charging the machine with com- 
pressed air. and a trap H^ in which the initial charge of air 
parts with nearly all of its moisture. The steam piston, air- 
compressor piston, and expander piston are coupled to the 
same crank-shaft. 

14. The operation of the machine is as follows: On 
starting up, the primer pump charges the system with air 
taken from the surrounding atmosphere, compressing it to 
a pressure of from 60 to 65 pounds. This air, heated by the 
compression, is discharged into the trap H. where it is cooled 
by coming in contact with the cold head of the cooler C. On 
cooling, it deposits most of its moisture in this trap. The 
primer pump runs continually, and thus keeps up the initial 
pressure; any excess of air beyond that required is discharged 
through a small safety valve. From the trap, the compressed 
and cooled air passes into the double-acting air compressor B, 
where the initial charge is compressed to a pressure of from 
210 to 22.5 pounds. The heat is abstracted from the air 
by passing it through a copper coil inside the cooler C. 
through which the cooling water is constantly circulated by 
the pump F. The air under high pressure is here cooled to 
nearly the temperature of the cooling water, and passes from 
the cooler to the expander cylinder, where it is cut ofl at 
one-third of the stroke, and in expanding does work. Its 
temperature is thus lowered to from 35° to 55° F. below 
zero. The expanded cold air, which is now at a pressure of 
from 60 to 65 pounds, then passes into an oil trap F, where 
it parts with most, if not all, of the lubricating oil used in 
the compressor and expander. All snow, due to unremoved 
moisture in the air, is gathered here. This trap is steam- 
jacketed; the steam is turned on, however, only when it is 
desired to move the oil and the snow from the trap. The 
air now passes through coils of pipe in the ice box T and 
refrigerating room A'; the coils of the refrigerating room are 
shown at L. From there it passes through the drinking- 
^»water butt M and returns to the compressor inlet. By 



12 REFRIGERATION §20 

passing the cold air through coils, a large heat-absorbing sur- 
face is provided; in its passage through these coils, the cold 
air absorbs the heat of the warmer air surrounding the coils, 
and thus cools it. Naturally, the cold air becomes warmer. 
In some instances, the return air, which is still quite cold, 
is passed through a special cooler, where it cools the highly 
compressed air coming from the cooler C, thiis furnishing 
the expander cylinder with cooler air than could be obtained 
otherwise. If this is done, the builder claims that a tem- 
perature of from 70° to 90° F. below zero is obtained. 



EXAMPLES FOR PRACTICE 

1. A refrigerating machine produces the refrigerating effect of 
the melting of 15 tons of ice in 24 hours; how many British thermal 
units does it abstract? Ans. 4,320,000 B. T. U. 

2. A refrigerating machine producing the refrigerating effect of 
the melting of 20 tons of ice requires 5,000 pounds of coal in 24 hours 
to operate it; how many pounds of ice, in ice-melting effect, is this 
equivalent to, per pound of coal? Ans. 8 lb. 

3. In example 2, if the coal cost $5 per ton, what will be the cost, 
per ton of ice, in the ice-melting effect produced? Ans. $.625 per T. 

4. The ice-making capacity of the refrigerating machine mentioned 
in examples 2 and 3 is 60 per cent, of its refrigerating capacity; what 
will be the cost per ton of the ice made by it? Ans. $1.04 per T. 



liATENT-HEAT REFRIGERATION 



REFRIGERATING AGENTS 

16. Requirements. — The air-refrigerating machine 
produces its refrigerating effect by means of the fall of 
temperature incident to adiabatic expansion. In all other 
refrigerating machines, the abstraction of heat is brought 
about by the vaporization of some liquid having a low boil- 
ing point. Such machines may be classed as latent-beat 
ri^rrlf^cratinpT machines. Theoretically, any volatile 
li(iuid may be used as a, working fluid in a latent-heat 
machine; there are, however, various considerations of a 



§20 



REFRIGERATION 



13 



P 



practical nature that govern the choice of the liquid. The 
chief requisites of the fluid used are: (1) It should vaporize 
at a low temperature when at ordinary atmospheric pres- 
sure; (2) it should have a high latent heat. The fluids that 
have been used in compression machines are ether, sulphur 
dioxide, Pittet fluid, carbon dioxiik, and anhydrous ammonia. 

16, Table I gives the boiling points, latent heats, and 
specific heats of various liquids at atmospheric pressure, 
14.7 pounds per square inch. 

TABLK I 
PROPERTIES OF RBFRIGSRATINO AGENTS 



I 



Kitric acid . . 

Saturated brine 
Water .... 
Alcohol . . . 
Chloroform 
Eiher. Sulphurous 
Ether, Methyl . . 
Sulphur dioxide 
Anhydrous ammonia 
Carbon dioxide . . 



Temperature 

of Boiling 

Point 

Degrees Fah- 



.4100 
1.0058 
■9950 



17. Ether. — Early in the history of ice-making and 
refrigerating machines, etber was almost universally used 

on account of its high condensing temperature and consequent 
low condensing pressure. This low condensing pressure 
made it possible to use compression pumps of ordinary con- 
struction, very much after the style and pattern of air pumps. 
However, the disadvantages of the use of ether were found 
to be very great; Ihus, the first cost of ether is considerable, 
it is very inflammable, and liable to explode when mixed with 




14 REFRIGERATION §20 

air. Furthermore, owing to the density of the vapor at the 
required working pressure, the compression cylinder must be 
very large, viz., six times larger than for sulphur dioxide and 
seventeen times larger than for ammonia. 

18. Salpliur Dioxide. — The objections to ether led to 
further investigation. Sulphur dioxide was found to be 
more efficient than ether, for though it required a higher 
condensing pressure, it did not require to be evaporated 
under a vacuum. Consequently, the compression pumps 
were made somewhat smaller for a given capacity, but were 
built stronger and more attention was given to the elimina- 
tion of clearance spaces. The temperatures produced with 
sulphur dioxide, though lower than those obtained with 
ether, were not sufficiently low. 

19. Pictet Fluid. — It was found by Professor Pictet, a 
Swiss physicist, that a mixture of 97 per cent, of sulphur 
dioxide and 3 per cent- carbon dioxide, commonly known as 
carbonic-acid gas, gives a boiling point 14° F. lower than 
pure sulphur dioxide. This liquid has been since known as 
Pictet fluid. Its latent heat has never been closely deter- 
mined, but is probably nearly the same as that of pure 
sulphur dioxide. 

20. Carbon Dioxide. — The lowest boiling point of any 
of the liquids employed at present in refrigeration is pos- 
sessed by carbon dioxide. Under a gauge pressure of 
200 pounds per square inch, it will boil at a temperature of 
about — 22° F. Its condensing pressure is correspondingly 
high, being about 900 pounds per square inch for a water 
temperature of 70° F. 

21. Ammonia. — One atom of nitrogen combines with 
three atoms of hydrogen to form one molecule of ammonia; 
this is the only combination of these two elements. The 
ordinary ammonia of commerce is a solution of ammonia 
gas in water, and is properly known as aqua ammonia. * The 
gas that passes off from the aqua ammonia is the ammonia 
formed by the combination of nitrogen and hydrogen. When 



fg20 REFRIGERATION 15 

this gas is entirely free from vapor of water it is called 
auliydrous-amnioula K>i8. 

Ammonia gas, when liquelied under a high pressure and 
allowed to evaporate under atmospheric pressure, gives a 
temperature of 28.5° F. below zero. Liquid anhydrous 
ammonia, when subjected to a temperature of — 115'^ F., 
freezes and forms a solid; in this state, it is almost odorless 
and is heavier than the liquid for a given volume. 

Ammonia has no effect on either iron or steel, but rapidly 
corrodes copper and brass. It is therefore necessary to make 
the parts of ammonia machines out of the former metals. 
At a temperature of 900° F. the gas is resolved into its con- 
Atituent elements. But is is probable that this dissociation 
'occurs to a limited degree at much lower temperatures. 

Ammonia is not inflammable at ordinary temperatures. 
The liquid will not explode, but when run into drums or 
flasks, room should be left for expansion. Like almost all 
liquids, ammonia expands when heated, and if sufficient 
space is not left the flask is likely to burst if exposed to a 
lligh temperature. 

22. Aqua ammonia, known also as ammonia liquor, is 
B solution of ammonia gas in water. At 32° F. and under 
atmospheric pressure, water will absorb 1.140 times itg vol- 
iime of ammonia gas. The amount of gas held in solution 
%Sects the specific gravity of the solution; the more gas 
absorbed, the less is the density. The amount of ammonia 
that can be absorbed by water is governed by the tempera- 
ture of the water and the pressure of the gas. The colder 
the water and greater the pressure, the greater is the quantity 
of ammonia taken up. 

The strength of a solution of ammonia gas in water is 
measured by a hydrometer. When this instrument is placed 
in a liquid, it is evident that it will sink deeper the less is the 
density of the liquid; hence, the density will be indicated by 
the mark on the scale at the level of the liquid. For liquids 
lighter than water, the point to which the instrument sinks 
iWhen placed in a solution of ten parts of salt to ninety of 



16 



REFRIGERATION 



§20 



water is marked 0°, and the point to which it sinks in dis- 
tilled water is marked 10°. The space between the two 
marks is divided into ten parts and the division is continued 
to the top of the stem. The hydrometer thus graduated is . 

TABLE II 
STRENGTH OF AMMONIA LIQUOR 



Percentage of 

Ammonia by 

Weight 


Specific Gravity 


Degrees on 


Hydrometer 


Water 10° 


Water 0° 


o 


1. 000 


lO.O 


0.0 


I 


.993 


II.O 


I.O 


2 


.986 


12.0 


2.0 


4 


.979 


13.0 


3.0 


6 


.972 


14.0 


4.0 


8 


.966 


15.0 


5.0 


ID 


.960 


16.0 


6.0 


12 


.953 


17.I 


7.0 


M 


.945 


18.3 


8.2 


i6 


.938 


19.5 


9.2 


i8 


.931 


20.7 


10.3 


20 


.925 


21.7 


II. 2 


22 


.919 


22.8 


12.3 


24 


.913 


23.9 


13-2 


26 


.907 


24.8 


14.3 


28 


.902 


25.7 


15.2 


30 


.897 


26.6 


16.2 


32 


.892 


27.5 


17.3 


34 


.888 


28.4 


18.2 


36 


.884 


29.3 


19. 1 


38 


.880 


30.2 


20.0 



generally used for ammonia solutions, though there is 
another graduation in which the reading for pure water is 0° 
instead of 10°. 

The specific gravity of aqua ammonia and the percentage 
of ammonia gas, corresponding to a given hydrometer 



REFRIGERATION 



17 



reading on either of the graduations mentioned, are given in 
Table II. Iq this table, the first column gives the number 
of parts of ammonia gas in one hundred parts of the solution; 
the second cohinin gives the specific gravity of the solution; 
and the third column gives the corresponding reading on the 
hydrometer. For example, if the hydrometer reading is 16°, 
the solution consists of ten parts, by weight, of ammonia to 
ninety parts of water, and the specific gravity of the solution 
is .960, the point to which the hydrometer sinks in distilled 
water being marked 10°, 

23. All chemical actions, as well as solutions and 
absorptions, are accompanied by an increase or decrease in 
the temperature of the mixture. This is especially true of 
absorptions. In the case of ammonia absorbed in water, 925.7 
British thermal units is given up for each pound of ammonia 
gas absorbed under atmospheric pressure. Though no very 
exhaustive experiments have been made on this subject, 
results deduced from the practical running of refrigerating 
machines show that this figure is practically constant. Since 
heat is given up when ammonia gas is absorbed, heat will be 
absorbed when the gas is again liberated from the water. 
The quantity of heat necessary to liberate 1 pound of anhy- 
drous gas is 92.5,7 British thermal units, the same amount 
that is given out by the liquid when the gas is being absorbed. 

I S4. If it is desired to test the purity of liquid anhydrous 
lammonia, draw some into a fiask having a cork with a bent 
jttibe inserted in it. Wrap the flask in dry waste or cloth 
(before drawing oft the ammonia, or the fingers may be frozen 
fast to the -flask. The liquid ammonia evaporates slowly, the 
gas passing out of the bent tube. If an accurate low-tem- 
.perature thermometer is immersed in the boiling liquid, it 
•hould indicate a temperature of —2^.5° F., with normal 
barometric pressure. If the liquid is pure anhydrous 
ammonia, there should be no residue left in the fiask; a 
deposit of oil or water indicates impure ammonia. 

To detect a leak in piping, in case the odor does not 
stray it, hold a glass rod moistened with muriatic acid near 




18 REFRIGERATION §20 

the supposed leak; a white fume rising from the rod indi- 
cates an escape of ammonia. 

To detect ammonia leaks in piping under water or brine, 
add to a sample of the suspected liquid a few drops of 
NessUr's reagent; a yellow coloring indicates traces of 
ammonia, but if the quantity of ammonia is large^ the color 
changes to a dark brown. To prepare Nessler's reagent, 
dissolve i ounce of mercuric chloride in about IO9 ounces of 
distilled water; dissolve 1} ounces of potassium iodide in 
3i otmces of water; add the former solution to the latter, 
with constant stirring, until a slight permanent red precipi- 
tate is produced. Next, dissolve 41 oimces of potassium 
hydrate in about 7 ounces of water; allow the solution to 
cool; add it to the above solution, and make up with water 
to Sdi ounces, then add mercuric-chloride solution tmtil a< 
permanent precipitate again forms; allow it to stand until 
settled, and decant off the clear solution for use; keep it in 
glass-stoppered blue bottles, and set away in a dark place to 
keep it from decomposing. 

25. Coolinf? Effects of Various Refrlfceratlni? 
Aleuts. — The density of the gas at the evaporating tem- 
perature and the latent heat of the liquid determine the size 
of the compression cylinder necessary for any required 
capacity. The same machine working between 5° and 64.4° 
will give the following cooling effects per cubic foot of 
compressor-piston displacement tmder theoretically perfect 

conditions: 

British Thbrmal 
Units 

Carbon dioxide 248.18 

Ammonia 62.75 

Sulphur dioxide 22.88 

Sulphuric ether 3.68 



AMMOSIA-COMPRESSION SYSTEM 

26. General Deseriptlon. — Suppose that a flask or 
ordinary bottle /?, Fig. 5, supplied with a cork having a bent 
tube G inserted, is partly filled with anhydrous ammonia. 



§20 



REFRIGERATION 



This can be done easily, as the evaporation o£ the ai 
is comparatively slow, owing to its high latent heat. As the 
ammonia enters the flask, frost will begin to gather on the 
outside. If this flask is now placed in a pail A partly 
filled with water C, in a short time ice D will begin to gather 
on the outside of the flask. This is tlie simplest form of ice 
machine, but in this form the liquid ammonia, when it evap- 
orates, passes out of the flask and is lost. 

As with all volatile vapors, the temperature at which vapo- 
rization (or condensation) occurs rises as the pressure of the 
vapor increases. To prove this, insert a thermometer into 
the flask so that the bulb is immersed in the boiling ammonia. 
The temperature will fall rapidly, and, if the thermometer is 
correct, should register 28.5° below 
zero. Take a piece of pipe; weld or 
plug one end and fit the other with a 
cap B. Fig. 6. Arrange a stuflFingbox 
C about the thermometer f in the 
cap. Also provide an opening i.on 
necting with the pressure gauge P 
Unscrew the cap and pour the con 
tents of the flask into the pipe -i and 
screw on the cap B. If the gauge 
points to zero, the thermometer 
should still read -28.5° F. Watch the ''"'■ ^ 

gauge and thermometer carefully. The ammonia evapora- 
ting in the pipe liberates gas. As this gas cannot escape, it 
creates a pressure in the pipe, which will be shown on the 
gauge, and a corresponding increase in the temperature of the 
boiling ammonia will become apparent. This will continue 
until the temperature of the liquid will be identical with the 
surrounding objects. Assume this temperature to be about 
70° F.; the gauge should then show a pressure of 130 pounds 
per square inch. If, therefore, the temperaiure of the pipe 
is kept at 70° by immersing it in water at that temperature, 
and a pressure slightly in excess of KiO pounds per square 
inch is kept in the pipe, no further evaporation will take place, 
and the remaining liquid ammonia will lie quietly in the pipe. 





20 



REFRIGERATION 



27. It is apparent that if some meaDS be devised * 
taking the evaporating gas as it leaves the flask in Pig. | 
and transferring it into the pipe of Fig. 6, it will be possiU 
to save the gas. In plate of a short piece of pipe A, Fig, ( 
submerge a large coil of pipe A, Fig. 7, in a tank of water C 
The water enters by means of the pipe F. and overflows t 
the pipe F'; the continuous flow 
tends to keep the temperature of 
the coil A constant. Replace the 
flask B, Fig. 5, with a coil of 
pipe ff. Fig. 7. immersed in a 
water tank D. Provide a pump 
capable of working against a high 
pressure, and connect the suction 
of the pump with the coil B, and 
the discharge with the coil A. 
Also provide pressure gauges C, 
G on each line. Connect the 
bottom of the two coils together, 
and place a valve E in the line. 
I'arlly fill the coil A with anhy- 
drous ammonia. If the tempera- 
lure of the water in C is about 
70'^. the gauge G' will show a 
pressure of 130 pounds. Open 
the valve F slightly, and leave it 
open. The pressure denoted by 
the gauge G will gradually rise. 
and ice will begin to form on the 
lower pipes of ff. When the 
pressure shown by G has reached 
16 pounds, start the pump P. which will draw the gas out of 
the coil B. compress it, and deliver it to the coil A. The gas 
entering A, which has been heated by the compressions 
comes in contact with the cold pipe surface, and is fini 
cooled until its temperature is but little above that of theo 
densing water flowing out through F'. The gas llien coi 
denses and falls to the bottom of the coil in the form t 





§20 REFRIGERATION 

liquid anhydrous ammonia. As the valve £" is open, the coil 

A is prevented from filling up. The withdrawal of a quan- 
tity of the gas in the coil B tends to decrease the pressure 
in that coil; however, a quantity of the liquid passes from 





t to B, through the expansion valve £. vaporizes, and sup- 

|dies an amount of gas equal to (hat withdrawn by the pump. 

8. Dry Comiiresslon, Wet Compression, and OH 

" Injection. ^If ammonia vapor is compressed adiabaticaUy, 
it will be superheated, as the work done on the vapor by 
the piston is stored in the vapor in the form of heat. This 
heat must be got rid of during the period of compression, 
since otherwise it must be absorbed by the condensine water 
before the vapor can be condensed. It is most economi- 
cal to remove the heat, as far as possible, as fast as it is 
generated, and to keep the temperature of the cylinder 
comparatively low throughout the compression. In fact, 
it is absolutely necessary to employ some method of 
keeping the cylinder cool, otherwise the excessive heat 
developed in compression will soon become so great that 
the gas will enter the cylinder in a greatly superheated 
state, which will lessen its density. This decrease in density 
will naturally cause a corresponding decrease in (he weight 

nof gas pumped in a given time, thus affecting both capacity 
nd economy. 



22 REFRIGERATION §20 

29. Various expedients are resorted to for the purpose 
of abstracting the heat of compression. The simplest of 
these is jacketing the cylinder with water; this method is 
known as the dry-compression system. The gas enters 
the cylinder in a nearly saturated state; the instant that com- 
pression begins, the vapor would become immediately super- 
heated if the heat were not carried off by the cold water 
surrounding the cylinder. 

The majority of compressors built in the Upited States 
are of the water-jacketed, dry -compression type. In the 
case of vertical compressors, the water-jackets are merely 
small tanks enclosing the walls of the cylinder, and are 
sufficiently high, so that the top head of the cylinder is 
also immersed. They are open at the top and the water 
passes off by gravity. Horizontal compressors are usually 
water-jacketed on the cylinder walls only, the heads being 
unjacketed. 

30. In the wet-compression system, the cylinder is 
not jacketed, but a certain amount of liquid anhydrous 
ammonia is allowed to enter the cylinder with each stroke 
of the compressor; the mixture of vapor and liquid remains 
saturated while it is compressed, since the heat equivalent 
of the work of compression is taken up by the vaporiza- 
tion of a part of the liquid, and the vapor remains at the 
temperature due to the pressure. 

The injection of a small quantity of anhydrous ammonia 
to cool, by its evaporation, the walls of the cylinder was the 
invention of Prof. C. P. G. Linde, of Munich, Germany. 
The machines built under this system bear his name and are 
of the horizontal, double-acting type. The temperature of 
the gas leaving the compressor in case of the Linde machine 
is much lower than that in the dry-compression system, and 
the theoretical economy is somewhat higher. 

31. A third method of removing the heat of compression 
is employed in the so-called oll-lnjectlon system, which is 
a modification of the wet-compression system, and is used 
by the De La Vergne Refrigerating-Machine Company, of 



§20 REFRIGERATION 23 

New York. Instead of permitting anhydrous ainmonia to 
enter the cylinder, a certain quantity of oil is injected during 
the stroke; the oil cools the gas during compression, seals 
the valves, and cuts down the clearance space. 

In the earlier machines, a small quantity of oil was admitted 
into the compression cylinA;r during suction and was expelled 
at compression. The mixture of oil and gas at a somewhat 
high temperature passed to the oil separator, where the oil 
was separated from the ammonia gas. The gas passed on 
to the condenser in its regular cycle; the oil was taken from 
the separator, passed through a cooling coil immersed in 
running water, and was then allowed to run into a receiver, 
from which it again passed into the suction pipe. As by this 
method a certain quantity of oil was allowed to enter with 
the gas, the volume of the gas entering the cylinder at each 
stroke was decreased in proportion to the amount of oil 
injected; in case a considerable quantity of oil was fed in, 
this would cut down the capacity appreciably. In order to 
obviate this difficulty, the De La Vergne Refrigerating- 
Machine Company, in its new compressors, injects oil by 
means of a small pump after the work of compression has 

|«et in, and not during suction as formerly. This also per- 
mits the oil to be kept fully charged with ammonia. 
I AMMONIA-ABSORPTION SYSTEM 

' 32. The action of a refrigerating system of the absorp- 
'feon type is based on the affinity of a vapor, usually ammonia 
vapor, for water. If heat be applied to a strong aqua- 
ammonia solution, the ammonia gas or vapor will be driven 
o£E at a relatively high pressure, and when passed through a 
condensing coil will condense to the liquid state. The liquid 
can now. just as in the compression system, be admitted to 
refrigerating coil through an expansion valve. In this coil, 
will vaporize and withdraw heat from the surrounding 
ijects. The vapor may now be again absorbed by water, 
'ftns regaining its original state and closing the cycle of 
operations. 



hi 



34 



REFRIGERATION 



!» 



33. The essential features of the absorption system are 
shown in Fig. 8. Steam is admitted, at a gauge pressure of 
al>out 40 pounds per square inch, to a coil B submerged in a 
strong solution of aqua ammonia contained in the vessel A. 
The temperatnre of the 
solution will be rateed 
nearly to that of the in- 
coming steam, say to 
about 270° F.. and the 
heat absorbed will 
cause the ammonia gas 
to be driven off at a 
pressure of, say, 160 
pounds per square inch. 
As the temperature 
of the solution is below 
the boiling point of 
water for this pressore, 
no water will evaporate, 
and only ammonia gas 
will pass over into the 
condenser C. The cold 
water Sowing over the 
condensing coils ab- 
sorbs heat from the 
gas, and the combined 
effect of the high pres- 
sure and the cooling 
action of the water 
liquefies the gas. 

As the ammonia liq- 
uid passes through the 
expansion valve to the 
expansion coils, the 
* pressure is reduced, 

re evaporation begins in the expansion coils, and heat 
is absorbed from the brine or other substance in the 
tank D. 




REFRIGERATION 



25 



In the compression system, the ammonia pump draw3 the 
gas from the expansion coils; but in the absorption system, 
the removal of the gas is effected by allowing the gas irom 
the expansion coils to mingle with the weak solution of 
ammonia from which the gas was expelled in the still, or 
generator, ,-/. 

During the process of generating the ammonia gas in the 
still A, the strong solution rises to the top on account of its 
smaller specific gravity, and the weaker solution settles to 
the bottom and flows through a pipe to the vessel £, called 
the absorber. Here it meets the gas as it comes from the 
expansion coil and absorbs it. Since a low temperature is 
required for efficient absorption, the weak liquor on its way 
to the absorber passes through a coil IV that is cooled by 
running water. The absorber E is also provided with a water 
coil /^ A small pump P takes the strong liquid from near 
the top of the absorber and forces it back into the generator; 
this completes the cycle of operations. 



APPLICATION OP REFRIGERATION 



RBFHIGERATINO SYSTEMS 

34. There are two widely used systems of refrigeration, 
viz., the drine and the direrf expansion. In the former sys- 
tem, the expansion coils are immersed in a tank of brine: 
this brine, which is a non-freezing solution, gives up its heat 
to the ammonia evaporating in the coils or to the cold air 
passing through them; it is then pumped through coils of 
J. pipe placed on the sides or ceiling of the room to be cooled. 
E circulating brine thus continually absorbs heat from the 
Jold room and gives it to the ammonia or air. 

In the dtrect-expniiston amnionta, or all*, system, 
2ie ammonia or air is admitted directly into the coils in the 
rooms to be refrigerated. The heat of the cold room is 
tiaken up by the ammonia or air directly, and the intermedi- 
ite agent, brine, is not employed. The difference between 
Ehe two systems may be explained as follows: In Pig. 7, 



26 REFRIGERATION §20 

suppose the expansion coil i9 to be a comparatively short or 
compact coil, and let the vessel D he a. tank containing 
brine; this arrangement constitutes the brine system. On 
the other hand suppose the vessel D to represent the room 
or rooms to be cooled, and suppose the expansion coil ^ to be 
a long coil divided into many branches and located on the 
ceilings or sides of the rooms; this arrangement consticntes 
a direct-expansion system. 

In another direct-expansion air system, the cold air is led 
through suitable chutes to the rooms to be cooled, and is 
discharged directly into the room. The air compressor 
draws its air supply from these rooms. 

The proper temperatures for the refrigerating rooms 
depend on the nature of the article to be preserved. They 
are about as follows: fish, meat, and poultry, 20° F.; tmii 
and vegetables, about 35° F. 



BRINE 

35. There are two salts in common use for making the 
brine used in brine circulation. The first is Liverpool salt 
(chloride of sodium), which forms the ordinary brine capable 
of withstanding a temperature of about 0° F. This sail is 
cheap in first cost, but has a corrosive action on iron. 

The other salt is the chloride of calcium. It has no 
corrosive action on iron, which makes it imnecessary lo 
have the brine pump lined with brass. It is oily in narrire. 
and for that reason has a strong tendency to leak :f ihe 
piping is in any way imperfect; care should therefore re 
exercised in the pipework of a chloride-of-calcium bri::e 
circulation. It is possible to obtain much lower tempera- 
tures by the use of chloride of calcium than with chloriie 
of sodium. 

The cost of chloride of calcium is about double that cf 
salt. The quality is extremely variable; insist on having 
///j/'^y chloride of calcium. The salt is excessively de!:q::e>- 
cent, that is, it is capable of absorbing a large quaci:*y :: 
water; for this reason it is often used as a drier. This ^ne^: 
avidity of calcium chloride for water renders adulteratioc ry 



§20 



REFRIGERATION 



the absorption of water very easy. Even the fused salt 
contains as much as 20 per cent, of water, whereas the 
unfused salt, though still in solid form, contains upwards of 
50 per cent, of water. Care should, therefore, be used in 
selecting the salt. 

When it is desired to purchase chloride of calcium, request 
samples. Dissolve a certain weight of each sample of the 
salt in the same quantity of water; take a hydrometer read- 
ing of each of the samples after the salt is thoroughly dis- 
solved; the one giving the highest reading is the best sample. 

To make chloride-of-calcium brine, use about equal weights 
of water and chloride of calcium. Whenever it is observed 
that the brine commences to freeze, add a little chloride of 
calcium, stirring it well into the brine. 



» 



ICE MAKING 

36. There are now two systems in use for making ice, 
viz.. the can syslfin and the plate system. The can system is 
the more common of the two, being cheaper in first cost and 
requiring less attention in manipulation. The plate system, 
however, has the advantage of giving a clearer ice. 

The apparatus used in the eun sj-Bteiii consists of a large 
rectangular wood or iron tank containing the expansion coils 
or pipes. Galvaiiized-iron cans are placed between the rows 
of expansion coils. These cans are filled with distilled 
water, and when the brine is chilled below the freezing point 
of distilled water, the water in the cans freezes. If the 
temperature of the brine is not allowed to fall below 25° and 
ordinary well water is used in the cans, the ice produced will 
be comparatively clear on the outside and rather snowy 
in the center. If, however, the brine temperature is allowed 
to fa_;i to about 15°, the ice will be entirely opaque. 

In the plate systpin. the refrigerating fluid is circulated 
through vertical cast-iron or wTought-iron hollow plates, set 
'On edge in a tank of water. Ice begins to form on the plates 

id gradually extends out into the tank. If the temperature 

the plates is kept comparatively high at the start until 2 or 3 



28 REFRIGERATION S^O 

inches of ice is formed, and then gradually reduced as the 
ice formation increases, a clear cake or plate of ice will be 
formed on each side of the plates. The refrigerating fluid 
is then drained from the plates, and warm water is intro- 
duced, which thaws the ice adhering to the sides. As soon 
as the ice is detached, it floats to the surface of the water in 
the tank. 

RUNNING REFRIGERATING MACHINES 



RUNNING AN ALLEN DENSE-AIR MACHINE 

37. Warm up the steam engine. Open the suction valve 
and discharge valve of the circulating pump. See that the 
two valves in the main pipes are open, and that the valve of 
the by-pass pipe connecting the retum-air pipe with the cold- 
air pipe is closed. Open the blow valves of the expander 
cylinder and the petcocks of the traps. Start the machine; 
when no more grease or water discharges from the various 
petcocks, close them. Be sure that the circulating water 
is in motion. 

During running, open the petcocks of the water trap H 
frequently enough to allow the water collected there not to 
fill it more than half full. Once or twice a day the machine 
should be cleaned by heating it and blowing out all oil and 
deposits; this is done as follows: First open the valve in 
the by-pass pipe. Then close the two valves of the main 
pipes. Open the valves in the hot-air pipe leading from the 
valve chest of the compressor to the expander cylinder and 
partly close the valve of the expander inlet pipe. Turn 
the live steam on the jacket of the oil trap, opening the 
outlet of the jacket just enough to drain off the condensed 
steam. Run in this manner for about \ hour, and during 
this time frequently open the blow-off valves of the oil trap 
and expander, until the trap and expander are clear. Then 
shut off the steam from the jacket of the trap, drain the con- 
nections, close the valves in the hot-air pipe leading from 
the compressor to the expander, close all petcocks, open the 



Sao 



REFRIGERATION 



29 



valves of the main pipes, and close the by-pass valve. The 
machine will now generate cold as usual. When a pressure 
of from 60 to 65 pounds cannot be retained in the system. It 
indicates a leakage of air somewhere. It is usually found 
at the stufBngboxes, which should then be tightened or 
repacked. If the compressor does not keep up its usual 
pressure in relation to the initial pressure, it shows that 
J there is either a leak from the high-pressure to the low- 
pressure part of the system or to the atmosphere, or it may 
be due to the cup-leather packing of the compressor and 
expander cylinder having given out. The failure to main- 
tain the high pressure will result in a higher cold-air tem- 
perature. The cup leathers should be made of white-oak 
tanned leather well soaked in castor oil. They will last 
from 1 to 2 months in steady use. The sight-feed lubrica- 
tors for the compressor and expander cylinders should be 
filled with a light, pure mineral machine oil from which all 
paraffin has been removed. Use about three drops of oil 
per minute in the compressor and two drops in the expander. 
The makers of this machine recommend Leonard & Ellis 
extra machine oil for this purpose. 

Whenever the pipes of the manifolds in the refrigerating 
room, ice tank, etc., are thawed out, drain them. Never 
omit to do this when the opportunity presents itself. 



reed fl 



RtTNNING AN AMMONIA-COMPRESSION MACIIINB 

38. The brine having been prepared, the machine charged 
' with ammonia, and all connections tested, the apparatus is 
ready for service. Before any cooling is possible in the 
refrigerating room, it is necessary to cool the brine charge 
below the freezing point of water. The brine pump being 
stopped, the water pump is started and water is run over the 
condensers and through the waler-jacket of the compressor. 
As the temperature of the brine is probably in the neighbor- 
hood of 55°, a comparatively high back pressure can be kept 
in the expansion coils. As the compressor is started when 
the pressure in the expansion coils is comparatively high 



30 REFRIGERATION §20 

— 100 to 150 pounds — it is necessary to reduce this pressure 
to 30 or 40 pounds before the brine shows any perceptible 
cooling. The main suction and discharge valves are opened, 
the by-pass valves are closed, and the compressor is started. 
The back-pressure gauge will begin to indicate less and less 
pressure. When a pressure of 30 pounds is reached, the 
expansion valve is slightly opened, and care is taken to 
regulate it so as to keep the back pressure between 30 and 
35 pounds. After some time, the brine temperature will 
have fallen to about 25*^. 

The brine pump can now be started. This will start the 
circulation in the refrigerating room and also that in the 
brine tank, which will help to cool the brine more rapidly. 
The expansion valve can be closed a little, so that the back 
pressure will drop gradually as the temperature of the brine 
falls. The machine is now in full operation. 

If at any time the compressor cylinder begins to groan, 
some oil should be pumped into the suction pipe. Care 
should also be taken that the piston-rod packing is well lubri- 
cated; if it begins to heat, the gland on the stuffingbox should 
be slackened and some oil pumped in. *This will cool the rod. 
It is better to have the piston rod leak a little the first day 
or two than to have the packing so tight as to cut the rod. 

39. When the brine has cooled to a temperature of 15°, 
an inspection of the charge should indicate at least 6 inches 
of liquid anhydrous ammonia in the receiver of the con- 
denser and a back pressure of 20 to 25 pounds. If, however, 
the back pressure is lower and there is a small quantity of 
anhydrous ammonia in the receiver, a drum containing liquid 
anhydrous ammonia should be connected up and its contents 
pumped into the machine. There is usually one main expan- 
sion valve and a number of feed-valves, one on each coil, for 
the purpose of regulating the amount of anhydrous ammonia 
being fed to the separate coils. These valves should be 
adjusted so as to proportion the amount of anhydrous 
ammonia supplied to each coil; then they should be left alone. 
The total amount of anhydrous ammonia expanded should be 



REFRIGERATION 



regulated by the main expansion valve. If the compressor 
is working properly, the whole action of the machine hinges 
on the proper manipulation of the expansion valve. A low 
back pressure is detrimental to the economical working of 
a compression machine. Therefore, care should be taken to 
carry as high a back pressure as possible, and at the same 
lime avoid overfeeding. The best indication of overfeeding 
is a heavy frost on the suction pipe of the compressor. Not 
all the liquid anhydrous ammonia is evaporated in the expan- 
sion coils, and. consequently, some of it passes over to the 
compressor. The evaporation in the suction end of the 
cylinder causes the packing of the piston rod to freeze, and 
it is liable to leak as soon as it thaws out again. The great- 
est danger from overfeeding, however, arises from liquid 
ammonia or oil entering the cylinder of the compressor. 
The liquid being incompressible, its presence may result in 
the breakage of a cylinder head or of a shaft, or the derange- 
ment of some part of the compressor. 

40. To shut down a compression machine, the main 
throttle valve of the steam engine is closed, care being taken 
that the compressor does not stop on a dead center. The 
valve on the oil feed is then closed, together with the main 
suction and delivery valves and the expansion valve; the 
other valves may be left open. The water pump is then 
stopped and all the drips arc opened; the same is done with 
the brine pump. The refrigerating plant is now shut downj 
—and the steam plant may be shut down as in ordinary practice. 



W RUNNING AN AMMONIA-ABSORPTION MACHINE 

41. After the air and other gases have been expelled 
from the absorber, the ammonia pump is started, and the 
Steam is gradually turned on the generator. When a pres- 
sure of 120 or 130 pounds has been reached, the valve 
leading lo the condenser is opened and the water is turned 
on the condenser and absorber. This valve should be 
opened slightly, so as not to create too strong a current 
between the condenser and the generator, as the difference 



32 REFRIGERATION § 20 

between the pressures in these two vessels may be consider- 
able. The generator pressure now extends to all the bis:h- 
pressure parts of the machine. The expansion valve is then 
opened a very little until the gauge indicates 15 to 20 pounds. 
As soon as the liquor is seen in the gauge glass of the 
absorber, the suction valve and the delivery valve of the 
ammonia pump are opened and the ammonia pump is 
started. The pump is run at such a rate as to keep the 
liquor in the gauge glass on the absorber at a constant 
level. The machine is now doing regular work, cooling the 
brine in the brine tank. 



INDEX 



NoTB. — ^An items in this index refer first to the section and then to the page of the 
section. Thtis. "Abaft. (9. p2," means that abaft will be found on page 2 of section 9. 



Abaft, S9. p2. 
Abreast, $9, p2. 
Absorber, (20. p25. 

Absorption refrigerating machine. Running 
an ammonia. $20, p31. 

refrigeration system. Ammonia, (20, p23. 
Accessories. Marine-boiler, ill, pi. 
Acid in feedwater. il4, p33. 
Action, Center of, il9, pl2. 

of injector, {14, pl3. 

of propelling instruments. {19, p2. 
Actiial thrust. $19, pp31. 32. 
Adiabatic compression, $20. pp2. 3. 

expansion. $20, p2. 

-expansion refrigeration, $20, p5. 
Admiralty pattern cap ferrule. $17. pl2. 
Admission of steam into furnace, $13, pi 7. 
Adrift, $9, p6. 
Advantages of injectors. $14, p31. 

of Scotch boilers. $9. p54. 

of water- tube boilers, $9, p60. 
Aft, $9, pi. 

Agents, Q>ollng effects of refrigerating, $20, 
pl8. 

Refrigerating, $20, pl2. 
Air pump $14, p2. 

refrigerating machine, Allen dense, $20, p8. 

refrigerating machine. Running an Allen 
dense. $20, p28. 

refrigerating machines. Free. $20. i>5. 

required for combustion, Weight and vol- 
ume of, $12, p6. 

supply above grate. $13, pl2. 

supply below grate. $13. pll. 

supply. Heated. $13. pl4. 

supply to furnace, $13. pll. 
Allen dense-air refrigerating machine. $20. p8. 

dense-air refrigerating machine. Running 
an, $20, p28. 



Almy boiler, $9, p51. 

Alternate firing, $12. pl7. 

American rule for working pressure on boilei 

shell, $18. pl3. 
Amidship, $9, pi. 
Ammonia, $20. pl4. 

-absorption refrigerating machine, Rtmning 
an. $20. p31. 

-absorption refrigeration system, $20, 
p23. 

Aqua. $20. pl4. 

-compression refrigerating machine. Run- 
ning an, $20, p29. 

-compression refrigeration system. $20, 
Pl8. 

gas. Anhydrous, $20. pl5. 

liquor. Strength of, $20, pl6. 
Angle cock. $11. p36. 

of incidence. $19. pl5. 
Anhydrous-ammonia gas. $20, pl5. 
Anthrticite, $12. pll. 
Apparent slip, $19. p5. 
Aqu^ ammonia, $20. ppl4. 15. 
Area. Blade, $19, p23. 

Helicoidal blade. $19. p23. 

Helicoidal propeller, $19. p23. 

of propeller. Disk. $19. p24. 

Propeller, $19. p23. 

Rules for safety-valve, $18, p87. 
Arrangement of riveted joints, $10, p8. 

of safety valves, $11, i>5. 
Ash chute, $9. p3. 

-pit. $9. pl2; $10. p39. 
Astern, $9. p2. 
Athwartship. $9. p2. 
Atomic weight, $12, p4. 
Automatic injectors, $14, pl8. 
Auxiliary check- valve, $14, pl2. 

feed. $14. p5. 
Axially expanded pitch, $19, p23. 



VU 



mu 



INDEX 



Babcock & Wilcox boiler. {9. p33. 
Back connection, 19. pl6. 

draft, §12. pl7. 

tube-sheet. {9. p23. 
Baird evaporator. il5. p2. 
Banking fires, il2. p20. 
Bar. Crown. §10. p30. 
Battening down hatches, f 9, p5. 
Bay, Sick. f9. p7. 
Beam. {9. p2. 

On an even. {9, p5. 
Bearings. Thrust. il9, p35. 
Below. 19. p2. 
Bent- tube boilers. 19, p41. 
Berth deck. 19. p7. 
Bilge. i9. p3. 

Bituminous coal, il2, pl2. 
Blade area, {19. p23. 

of screw propeller. §19. p21. 
Blake marine feedwatcr heater, (14, p51. 
Bleeder. {16, p9. 
Block, Horseshoe thrust. il9. p36. 

Sectional thrust. il9. p36. 

Solid thrust. §19. p35. 
Bloomsburg steam jet. il2. p36. 
Bloomsbuig's equilibrium circulator, f 15. p28. 
Blow-off apparatus, fll. p36. 

-oflf cock. Bottom. §11, p36. 

-off cock, Surface. §11, 1x38. 

-off cocks. Leaky. §17. pl9. 
Blowng off. 515. plO. 

off, Loss of heat by. §15, pl9. 
Board of Trade and Canadian rules for work- 
ing pressure on boiler shell. {18. pl4. 
Boiler accessories. Marine. $11. pi. 

Almy. §9, p51. 

Babcock & Wilcox. §9, p33. 

Qyde, J9, p25. 

Cutting out a. $16. pl8. 

details. Marine, §10, pi. 

Double-ended Scotch, $9, p23. 

Drum. J9. p21. 

Dr>'-back S<^-otch. $9. p25. 

Dr>'-bottomed, J9. pl7. 

Dry-bottomed firebox tubular, §9, p20. 

efficiency. Rules for, §13. p22. 

explosions, $17, p5. 

Firebox flue. §9, pl6. 

flues. §10, 1)48. 

Flush-tube. §9. p31. 

Gunbt^at. §9. p28. 

head. §0. plO; §10. pl3. 

heads. Flat. §10. pl3. 

inspection. §16. p28. 

inspection. Marine. §18, pi. 

inspection. Ocular. §16, p28. 



Boiler — (Continued) 

leaks. Repairing. §17. pll. 

Locomotive. $9. p20. 

management at sea. General, f 16 pl3. 

management in port, f 16. p23. 

management. Marine. §16. pi. 

management when steaming. $16, pi. 

materials. Specifications for. f 18. pi. 

Mississippi. f9, p46. 

plate, $10. pi. 

-plate repairs. $17. p22. 

piates. Specifications and tests for, $18, pi 

repairs at sea, $17. p7. 

repairs in port. $17. p21. 

repairs. Marine. $17. pi. 

repairs. Miscellaneous, f 17. p26. 

Roberts. $9. p46. 

saddles, $11. p57. 

Seabury, $9. p41. 

See, $9, p39. 

sheU. $9, plO; $10, pi. 

shell. American rule for working pressure oo; 
$18. pl3. 

shell. Board of Trade and Canadian ruks 
for working pressure on. $18, pl4. 

Single-ended Scotch. $9. p21. 

stay repairs, $17, p24. 

Steam. $9, p8. 

tests. Hammer and hydrostatic. $16. p29. 

-tube repairs. $17, p23. 

tubes. $18. p79; $10. p48. 

tubes. Leaky, $17, pll. 

tubes. Securing. $10. p50. 

tubes, Specifications and tests for, §18. p6. 

Wet-bottomed, $9, pl7. 

Wet-bottomed firebox tubtilar, §9, pl8. 
Boilers, Advantages of Scotch, §9, p54. 

Advantages of water-tube. $9, iiQO. 

and fittings. Examination of. §16. pi. 

Bent- tube. $9. p41. 

Qeaning and scaling. $16. p23. 

Qosing, $16. p5. 

Combustion chambers of Scotch, $9, p29. 

Comparison of, $9, p54. 

Comparison of water-tube, $9. p56. 

Construction of marine, $0. plO. 

Drowned-tube. $9, p51. 

Dry-tube. $9. p51. 

External corrosion of, $17, p3. 

Externally fired flue, $9, plO. 

Filling, $16, p5. 

Firebox tubtilar. $9, pl8. 

Fire-tube. $9, plO. 

Flue, $9, plO. 

Internally fired flue, $9, pl6. 

La\-ing up, $16, p25. 

Low water in, $16, pl6. 





INDEX 


1 

ix 


knlen— (Dnittntwd) 








OvertMuling. HB. p2*. 




dioxide, |20. pl4i |12. pfi. 




Scotch, 10, p2l. 




FiMd. 113, p2. 




Sediunat pipe, |S, i>4fi. 




monoxide, |12, p7. 




Stmighl-tube. IB. p33. 




Carbonate of lime, 114. p32. 








of magnesiB. |14. pSS. 




Types of murine. (9, pi. 




Carbuieied hydrogen. 113. p3. 




Verti™l marim. 19. p30. 




Care and use of atety valve*. lU, pl7; 


(IB.- 


Wnwr-w!-. IB. I^a, 




pis. 




Wear uid tear of, |17. pi. 




and u« of >ieam gauges, HI, pZl. 






on drums of 


ofeoalbunker^. lie, pis. 




waieT-lulB. 118, p21. 




Cut iron, SpeciRcations for. f IS. p8. 




ioilins pnintB of bu water. (10 


plL 


Castings. Gpecilications and te&U For 


ned. 


k«rt-i™l. 110. p51. 




118. p9. 




Jottom Wow-off eock. HI, p.TB 




Spe<:i(ications (or malleable-inm. |18 


P». 


Bourdon pnssuTT gBuge. |1I, plS. 










Center of actioo, 119. pl2. 




Bn«. Huston. HO. p30. 




of pressufe. iia. pl2. 




UrGngor, |10. pBg. 




Chain ni-eting. f 10. pS. 




BncM, Cruw.fcxit, |10, pZB. 




Chamber. Comhu«tion, [9. pZl ; |13. pl8 




Bridge, le. pia. 




Purpose of combustion. |10, p4a. 








Rule for cDi>e-<hBped (.-ombustion. 


(ta. 


Bris. 19. p7. 




p76. 




Brine, lao. p2a. 






HO. 






p43. 




Broken-down main feed-pump. 


16, plB. 


of Stolch boUets. Combustion, |9, pSB 




Bnish, Wire lube, IIB. pis. 




Check. Globe. Ill, p41. 




Bueket. 119. pll. 




Swing. Ill, p4I. 




Bucket). Immenion of the, fl 


.pl2. 


-valve. Auxiliary. |I4, pl2. 






plB. 


■valve. Donkey. H4, pl2. 




feedwater heater and purifle 


114. pM 


-valve. Main, 114.^12. 




Bulkhead, [9, p5. 




-valves. 111. p41. 




Bulvrark, 19, p2. 








Bumped head!, (10. pl7. 








Bunker. Coal, 19, p3. 




menns, Purifying feedwater by. (14, p4e. ■ 


KutUe, 19, p3. 




Chimney. Steam, HI, p51- 








Chip, Log. 19. p6- 




Bursting, working, and te=[ p 


reaurss, 118, 


Chloridc of mBtmesium, |U, p33. 








of sodium, lU. P32. 




Buttjoinl, 110, pp5, 7. 




Chute. Ai*. IB. p3. 




■ itnp, 110, p8: lis, p23. 




Cinle of paddle wheel. Rolling, 119. plS 




m Button «t, no, p3. 




Circulating apparatus. Craig heating and 


HS. 


I 




p25. 




m C«bin. IB. p7. 








■ CalL-ulBCions, Lever Hfety valve 


llI.pT. 


ariulation of water. Forced. 116. p25. 








of water. Natural. (16, pZI. 




Calking, 110. pIZ. 






(IB. 


Calonfic power. 112, pS. 




p28. 




value, lia, 08- 




Claw. Devil's. |13. plO. 




m C«n syiteni of ice makiOB. JM, 


pa7, 


Cleaner. Steam tube. |18. pI8. 




L CMUid<an tulo for working prr 


mrronboUer 


aeuiing and scaling boilert. ilfi, p!3. 




■ shell. Board of Trs.le and. 


US, pl4. 


fires, |1Z. p20. 




^Opaeily. lee-niaking. 120, p5. 








■ Ice-melling, 120, p4. 








p4- 


Kowden's. |I2. |>3.1. 




Unit of relrigcratmK. |20, p* 








Cap ferrule, Admiralty patu-m. 


117. pl2. 


ausing boilers, 116, |>S, 


J 



INDEX 



Qyde boiler. |9. i>25. 
Coal. (12. pll. 

Bituminous, $12. pl2. 

bunker. 19. p3. 

bunkers. Care of. $16, pl5. 

Combustion of. $12, pl5. 

Combustion of constituents of. $13. p3. 

Constituents of, $13. pi. 

consumption to speed. Relation of, $19. p47. 

Economic combustion of. $13, pi. 

Li>fnite. $12. pl3. 

Semibituminous. $12. pl2. 
CoaUng ship. $9. p3; $16, p4. 
Cock. Angle. $11, p36. 

Bottom blow-off, $11. p36. 

Scum. $11. p38. 

Straight- way. $11. p36. 

Surface blow-off, $11. p38. 
Cocks. $11. p42. 

Leaky blow-off. $17. pl9. 
Coefficient of fineness, $19, p41. 
Coke. $13. p2. 
Coking firing. $12. pl5. 
Cold. Processes of producing. $20. pi. 
Color and temperature of fire, $13, p5. 
Column. Water, $11, p28. 
Columns, Testing water gauges and water, 

$11. p30. 
Combination. Chemical, $12. p2. 
Combinations. Laws of chemical. $12. pi. 
Combined plate and rivet section. Percentage 

of. $18. p39. 
Combing. Hatch. $9, p3. 
Combustible substances. $13. p2. 
Combustion chamber. $9. p21; $13. pl8. 

chamber. Purpose of, $10, p42. 

chamber, Rule for cone-shaped, $18, p76. 

chanilx*rs. Construction of. $10. p43. 

chaml)ors of Scotch boilers. $9. p29. 

Elements of. $12. p5. 

Fuels and their. $12. pll. 

Hcati>f. $12. p8. 

of c«>al. $12. pl5. 

of coal. Economic. $13, pi. 

of constituents of coal, $13, p3. 

of v>il. $12. p23. 

of solid oarlxin, $13. p5. 

of volatile sul>stanccs. $13, p3. 

Principles «»f. J 13. pi. 

Pn>durts t>f. $12. p5. 

s|MUV, J 10, i>32. 

T<'miH*rat\jrr of. $12, plO. 

Thot)rv of. J 12. pi. 

\Vri«ht anti vohmie of air required for, $12. 

dmwwti to. JO. |v3: Jlrt. p20. 
('omi»<»i»i"nwny, §0, \\i. 



Comparison of boilers. $9. p5i. 

of water- tube boilers, $9. p56. 
Compound steam gauge, $11, p20. 
Compotinds. Elements and. $12. pL 
Compression. Adiabatic, $20, p2. 

Dry, $20. p21. 

Isothermal. $20. p2. 

refrigerating machine. Running an acuQO 
nia, $20. p29. 

refrigeration system. Ammonia, $20. pl8. 

systems. $20. p22. 

Wet. $20. p21. 
Condenser, Jet, $14, x>2. 

Surface. $14. p2. 
Cone-shaped combustion chamber. Rule (at 

$18. p76. 
Connection. Back. $9. pl6. 

Construction of front. $11, p49. 

Front. $9. plO. 
Constituents of coal. $13, pi. 

of coal. Combustion of. $13. p3. 
Construction of bridge. $10, p39. • 

of combustion chambers. $10, i>43. 

of evaporators, $15. p2. 

of feed-apparatus, $14. p6. 

of feedwater heaters. $14, p51. 

of front connection, $11, p49. 

of grate. $10. p37. 

of injectors, $14. pl7. 

of marine boilers. $9. plO. 

of steam gauges, $11, pi 8. 
Consumption to speed. Relation of coal. |19, 

p47. 
Cooling effects of refrigeration agents. |20, 

pl8. 
Corrosion. Internal, §17, pi. 

of boilers. External, $17, p3 

Uniform. $17, pi. 
Corrugated furnace flues, $10, p34. 
Cover-plate, $10, p7. 
Craig heating and circulating apparatus, |15. 

p25. 
Crow-foot braces, $10, p29. 
Crovm bar. $10, p30. 

sheet, $9, p23. 
Cutter. Glass- tube. $11. p27. 
Cutting out a boiler, $16, pl8. 
Cylinders, Strength of. $18, pll. 

Stresses on, $18, plO. 

D 

Damper, $9. pl3; $11. p51. 
Dead plate. $10. p37. 

-weight safety \'alve. $11, p2. 
Deck. $9. p2. 

Berth. $9. p7. 

Quarter, $9, p7. 



INDEX 



Tns relating to screw propellers, il9, 

ir refrigerating machine, Allen, f20, 

refrigerating machine. Running an 
:n. f20. p28. 
.§15. pll. 

Marinie- boiler, flO, pi. 
led blade area. (19. p23. 
llerarea, il9. p23. 
daw. (12, pl9. 
int. 520, p7. 
a pitch, §10, p6. 
of rivets. Rules for. |18, p32L 

ilO. p28. 
am gauge, §11. pl8. 
;r of paddle wheel. Effective, §19, pl2. 
et. Rules for. §18. p30. 
. Carbon, §20. pl4. §12. p6. 
\ir, §20. pl4. 
). pl2. 

xpansion refrigerating eystem, f20, 
). 
tays. §10. p24. 

Rules fur. §18. p62. 
.ntages of injectors, §14, p31. 
)tch boilers, §9, p54. 
ter-tube boilers, §9, p60. 
heads, §10, pl7. 
» of propeller. §19. p24. 
;ment, §9. p7. 

e between rows of rivets. Rules for. 
. p30. 
center of rivet to edge of plate. Rule 

§18. p30. 
ion, §13, pi. 

osses, Moisture and. §13. p20. 
§14, p8. 
.p23. 
Steam. §10. p21. 

check- valve, §14, pl2. 
§14, p5. 
.§11. p48. 
umace, §9, pl2. 
on furnace, §10, p41. 
ended SciJtch boiler, §9, p23. 
grate bars, §10, p37. 
ed lap joint. §10, p6. 
injector, Korting universal, §14, p22. 
injectors. §14, pl8. 
y the head, §9. p5. 
e stem, §9, p5. 
9. p2: §9. p9. 

§12. pl7. 
& Eaves system of induced, §12. p36. 
len's closed ash-pit system of mechan- 
. §12. p33. 



Draft — (Continued) 

Mechanical. §12 p32. 

Natural. §12. p30. 

pressure. §12, p30. 

water gauge, §12. p30. 
Drowned-tube boilers. f9, i>51. 
Drum boiler. §9, p21. 

Mud. §9. pl2. 

Steam. §9, pl2; §10. p21: §11. p55. 
Drumheads, Rules for, §18, p81. 
Drums of water-tube boilers. Worldng preS' 

sure allowable on. §18. p21. 
Dry-back Scotch boiler. §9. p25. 

-bottomed boiler, §9, pl7. 

-bottomed firebox tubular boiler, §9. p20. 
Dry compression. §20, p21. 

-compression s>'stem. §20. p22. 

pipe, §11, p65. 

-tube boilers, §9, p51. 

uptake, §9, pl6. 
Dudgeon roller tube expander, §10, pSl. 

Earthy matter in feedwater, §14, p33. 
Economic combustion of coal, §13. pi. 
Economizer^ §14, p50. 
Edmiston feedwater filter. §14, p37. 
Effective diameter of paddle wheel, §19, pl2. 
Effects of refrigerating agents. Cooling. §20, 

pl8. 
Efficiency of riveted joints, §18, p35. 

Rtiles for boiler. §13. p22. 
Elements -and compotuids, §12. pi. 

of combustion, §12. p5. 
Ellis & Eaves system of induced draft. §12, 

p36. 
Engine speed and ship's speed, §19, p42. 
Equilibrium circulator, Bloomsbuig's, §15. 

p28. 
Ether, §20. pl3. 

Evaporation, Maximum, §12. p9. 
Evaporator, Baird, §15, p2. 

O^iggin, §15, p7. 
Evaporators. §15. p2. 
Even beam. On an. §9. jvS. 
Examination of boilers and fittings. §16. pi. 
Expanded pitch. Axially, §19, p23. 

pitch. Radially. §19, p22. 
Expander, Dudgeon roller tube, §10, p51. 

Tube. §10. p50. 
Expanding pitch, §19, p23. 
Expansion, Adialiatic. §20, p2. 

Istithermal, §20. p2. 

joint, Packed. §11. p43. 

joints, §11. p43. 

refrigeration, Adiabatic. §20, p5. 

refrigerating system. Direct. §20. p25. 



xu 



INDEX 



Explosions, Boiler. $17, p5. 

Gas. J12. pl7. 
External corrosion of boilers, $17, p3. 

furnaces, $10, p32. 
Externally fired flue boilers. $9. plO. 
Extractor, Wass grease, $14, p42. 



Factor of safety. $18. pl3. 
Feathering paddle wheel, $19, pi 6. 
Feed. Auxiliary. $14. p5. 

-apparatus, $9. p9; $14. pi. 

•apparatus. Construction of, $14. p6. 

-apparatus installation, $14, p3. 

Donkey, $14, p5. 

Main, $14.)>3. 

-pump broken down. Main, $16. pl9. 

•pump. Single-acting plunger, $14, p6. 

-pumps, $14, p6. 

relief valve. $14. pl3. 

-valve. Safetyt $14, pl3. 

-valves, $14. pl2. 
Feeding, Marine-boiler, $14, pi; $15. pi. 
Feedpipe. $9, p9. 
Feedwatcr, Acid in, $14, p33. 

by chemical means. Purif>'ing. $14, p46. 

by filtration. Purifying. $14, p35. 

by gravity separation. Purifj-ing, $14, 
p42. 

by heat, Purif>'ing. $14, p44. 

Earthy matter in, $14. p33. 

filU'r. Edmiston. $14. p37. 

fiUiT. Reflex. $14. 1)58. 

filtfr. Ross. $14. p35. 

Tm-aw in, $14. p33. 

heator. $14. pSO. 

hratvr and purifier. Buffalo, $14, p44. 

hcatrr. Blake marine. $14. p51. 

h«*at«*n(, OiJscd. $14, p55. 

hrrttt-n*. Tonstruction of, $14, p51. 

hfAtns. Open. $14, p53. 

tu-atm^'. $14, iO(). 

liii|iuittt4'H in, $14, i>32. 

liitw ot. $U^, pi. 

Mikkiii>; \tp losN itf. $15. pi. 

Ml iti.iil; «>i puritvtng, $14, p34. 

Oil lit |i r \<Mi. 

iii»..tiii. iii.iiti*! in. $14, i^. 

|. ill nil .((loll. 11 1. Wi2. 

ii-i-.ul.iu -11 |UV. )>Ui. 

ti blur i I t \*^^- 
I'. II. ill \<ii.iiialt\ |v.atem cap. $17, pl2. 
I'jiiiii.t i<"iii to 4 hv |0. 
liii . r. iiiii,i->ii ifi'tlwator, $14. p37. 

l« iti .. l« i •l>«>tlii . |14. iviS. 

It ■ . . i< i..i.«aii.i $11, iCC>. 
iiu. .ii.u k'uiU^iiiij UviUuti'r by,$14. p35. 



Finding saturation by hydrometer. $15, p]l 

saturation by thermometer, $15, pll. 

water level. $16, pl5. 
Fineness. Coefficient of, §19, i>41. 
Fire-apparatus, $11. p49. 
Fire, Color and temperature of, $13, p5. 

-space, $10, p32. 

-tools, $12, pl8. 

•tube boilers. $19. plO. 

-tube boilers. External corrosion of, |17,p3. 
Firebox flue boiler. $9. pl6. 

tubular boilers. $9, pplS, 20. 
Fires. Banking. $12. p20. 

Qeaning. $12. p20. 

Hauling, $12, p21. 

Lighting. $12. p21. 

SUrting, $16. p6. 

Working the, $16, p8. 
Firing, $12, pi. 

Alternate, $12. pl7. 

Coking. $12, pl5. 

Practical hints on. $12, p21. 

Spreading. $12. pl6. 

Systems of. §12. pl5. 
Fittings, Examination of boilers and, $16. 
pi. 

Furnace, $10, p36. 

Pipe. $11. p39. 
Fixed carbon, $13, p2. 
Flat boiler heads. $10. pl3. 

surfaces. Rules for, $18. p45. 

surfaces. Strength of, $18. p45. 
Float. $19. pll. 

water gauge, $11, p33. 
Flue, $9. plO. 

boiler, Firebox. $9, pl6. 

boilers, $9. pplO. 16. 

Morison suspension furnace. $10. p36. 

Purves ribbed furnace, $10. p35. 
Flues, Boiler. $10. p48. 

Corrugated furnace. $10, p34. 

Plain furnace. $10. p33. 

Rules for ftunace. $18, p70. 

Rules for smoke, $18. p76. 
Fluid. Pictet. $20. pl4. 
Flush-tube boiler. $9. p31. 
Foaming, $16, pl3. 
Fore and aft. $9, p2. 
Forced circulation of water, $15. p25. 
Forecastle, Topgallant. $9, p8. 
Formation, Smoke, $13. p7. 
Forms of riveted joints, $10, p5. 
Forward, $9, pi. 

Free-air refrigerating machines. $20, p5. 
Front connection, $9, plO. 

connection. Construction of. $11, p49. 

tube-sheet, $9. p23. 



INDEX 



xiii 



Fuels and their combtistion, $12. pll. 

Kinds of. il2. pll. 
Fundamental principles of refri^ration, (20. 

Pl. 
Funnel. $9. p9- . 
Furnace. i9, p9. 

Admission of steam into, (13. pl7. 

Air supply to. {13, pll. 

door. i9. pl2. 

door, Monson. $10. p41. 

fittings. $10. p36. 

flue. Morison suspension, $10, p36. 

flue, Purves ribbed, $10, p35. 

flues. Corrugated, $10, p34. 

flues. Plain. $10. p32. 

flues, Rtdes fur. $18, p70. 

repairs, $17, p25. 

Shape and size of, $13, pl6. 
Furnaces, $10, p32. 
Fusible plug. $11, p34. 



Galloway tube. $9. p29. 

Gangway, $9, p8. 

Gas. Anhydrous-ammonia, $20. pl5. 

explosions, $12, pl7. 

Marsh, $13, p2. 

Oleflant, $13, p2. 
Gasket, $10. pl8. 
Gate valves. $11. p41. 
Gauge. Bourdon pressure, $11. pl8. 

-cock. $9. pl2. 

-cock. Mississippi, $11, p25. 

-cock. Register pattern, $11, p24. 

-cocks, $11, p22. 

Compound steam, $11, p20. 

Dial steam, $11, pl8. 

Draft water, $12. p80. 

Float water, $11, p33. 

Glass water, $11, p25. 

Mercurial steam, $11. pl8. 

Metallic steam. $11, pl8. 

Steam, $9, pl2. 

Vacuum, $11. p20. 
Gauges and water columns. Testing water, 
$11. p30. 

Construction of steam. $11, pl8. 

Use and care uf steam, $11, p21. 

Water, $11. p22. 
General boiler management at sea, $16, pl3. 
Getting ready for sea. $16. pl. 

under way. $16. p7. 

up steam. $16, p4. 
Girder sUys, $9, p23; $10, p30. 

stays, Rule for, $18, p67. 
Glass- tube cutter. $11. p27. 

water gauge. $11. p25. 



Globe check. $11. p41. 

valves. $11. p39. 
Grate, $9. p9; $9. pl2. 

Air supply above. $13, pl2. 

Air supply below. $13, pll. 

bars. Double. $10. p37. 

bars. Herring- bone. $10. p38. 

bars. Single. $10. p37. 

Construction of, $10. p37. 

surface, $9, p9. 
Gravity separation. Purifying feedwater by, 

$14, p42. 
Grease extractor, Wass. $14,.p42. 

in feedwater, $14. p33. 
Grommet, $17, p9. 
Grooving. $17, p2. 
Gunboat boiler. $9, p28. 
Gusset sUy. $10. p29. 
Guys. Smokestack, $16, p7. 

• H 

Hammer and hydrostatic boiler tests, $16. 
p29. 

Water, $16. p7. 
Hancock inspirator, $14, p21. 
Handholes, $10. pl9. 

Leaky. $17. pl9. 
Hatch. $9. p3. 

combing. $9. p3. 
Hatches. Battening down. $9. p5. 
Hatchway. $9. p3. 
Hauling fires. $12. p21. 
Head. Boiler. $9. plO. 

Down by the. $9, p5. 
Heads, Boiler, $10, pl3. 

Bumped, $10. pl7. 

Dished. $10. pl7. 

Flat boiler, $10, pl3. 

Rtdes for boiler, $18. p80. 
Heat by blowing off. Loss of. $15, pl9. 

losses and their prevention. $13. pl9. 

losses in smokestacks. High-temperature. 
$13. p21. 

losses. Miscellaneous. $13. pl9. 

losses. Moisture and distillation. $13, 
p20. 

of combustion. $12. p8. 

of vaporization, Latent, $20. pl. 

Purifx-ing feedwater by. $14. p44. 

transfer to water. $15, p21. 
Heated-air supply, $13, pl4. 
Heater and purifler, Buffalo feedwater, $14, 
p44. 

Blake marine feedwater, $14, j>51. 

Feedwater. $14, p,50. 
Heaters, Closed feedwater. $14, i)55. 

Open feedwater. $14. p53. 



XIV 



INDEX 



Heating and circulating apparatus, Craig, f 15. 
p25. 

Feed water. §14. p50. 

power, $12. p8. 

surface, (9. p9. 

value, (12. p8. 
Heaving to, $9, p4. 
Helicoidal blade area. $19. p23. 

propeller area, f 19. p23. 
Herring-bone grate bars. §10, p38. 
High-temperature heat losses in smokestacks. 

§13. p21. 
Hints on firing. Practical, $12. p21. 
Hoe. $12, pl9. 
Hold. $9. p3. 
Honeycombing, $17, pi. 
Hood. Smokestack. $9. p5. 
Horsepower and revolutions. Relation be- 
tween. $19, p44. 

when towing. Reduction of, ^19. p46. 
Horseshoe thrust block. $19, p36. 
HotweU. $14. p2. 
Howden's closed ash-pit system of mechanical 

draft. $12. p33. 
Huston brace, $10. p30. 
Hydrocarbons, $13. pi. 
Hydrogen. Carbureted, $13. p2. 
Hydrokineter, $15, p29. 
Hydrometer. $15, pl2. 

Finding saturation by, $15. pi 2. 
Hydrostatic boiler tests. Hammer and. $16, 
p29. 

test pressures. $18, p22. 



Ice making. Can system of. $20. p27. 

-making capacity. $20. p5. 

making. Plate system of. $20. p27. 

-melting capacity. $20. p4. 
Ignition temperature, $13. p4. 
Imniersion of the buckets. $19. pl2. 
Impurities in fccdwater. $14. p32. 
Inbtiard. $9. p2. 
Incidence, Angle of. $19. pl5. 
Indiratcd thrust. $19. pp31, 33. 
Induced draft. Ellis & Eaves system of, $12. 

Inicaion. Oil. §20. p21. 

-systt'in. Oil. §20. p22. 
Inirct'»r. Action of. §14. pl3. 

Buffalo automatic. §14. pl9. 

Korting universal double-tube, $14, p22. 

Monitor liftini;. §14. i>2o. 

IVnU-rthy aut'»mati«-. §14. pl8. 

triMibli'S and rcnu'ilit'*;. §14. p27. 
Inifit-T^;. Advantages of. §14. j^l. 

Automatic. §14, pl8. 



Injectom — (Continued) 

Construction of. $14. pi 7. 

Double-tube, $14. pig. 

Installation of. $14. p26. 

Lifting. $14. pl7. , 

Non-lifting, $14, pi 7. 

Positive. $14. pl8. 

Range of. $14. pl6. 

Size of. $14. p26. 
Inspection. Boiler. $16, p28. 

Marine-boiler. $18. ppl. 43. 

Ocular boiler. $16, p28. 
Inspirator, Hancock, $14, p21. 
Installation, Peed-apparatus. $14, p3. 

of injectors. $14. p26. 
Instruments. Propelling, $19. pi. 
Internal corrosion. $17, pi. 

ftimaces. $10. p32. 
Internally fired flue boilers. |9. pl6. 
Iron and steel. Specifications and tests for 
wrought. $18. p3. 

castings. Specifications for malleable. §18. 
p9. 

p>'rites, $13, p3. 

Specifications for cast, f 18. p8. 
Isothermal compression, f20. p2. 

expansion. $20. p2. 

J 

Jet. Bloomsburg steam. |12. p36. 

c*ondenser. $14. p2. 

joint. Butt. $10, p5. 

Double-riveted lap, $10, p6. 

Packed expansion, $11. p43. 

Single-riveted lap, $10. p5. 

S'ip. $11, p43. 
Joints, Arrangement of riveted. $10. p8. 

Butt, $10. p7. 

Efliciency of riveted. §18. p35. 

Expansion, $11. p43. 

Forms of riveted. $10, i>5. 

Proportions of riveted, §18, p25. 

Riveted. $10. p3; $18. p23. 

K 

Kindsof fuels. $12, pU. 
Korting tiniversal double- tube injector, §14. 
p22. 



Laminations, $17, p5. 
Lap. §10. p6. 

joint. Double-riveted, $10, p6. 

joint. Single-riveted, §10, p5. 
Latent heat of vaporisation. $20. pi. 

-heat refrigeration, $20, pi 2. 

-heat refrigerating machines, $20, pl2. 



Hp 


INDEX 


XV -^H 








^1 


Laying qH and on, 19, p4. 




Free-air refrigerating, (20, pG, 




W, 19, p3- 








uuboilcra. 110. p2S. 




Running refrigerating. (20, p28. 




, Lar.y >»t. 110, p40. 




Magnesia. Carbonate al. (14. p33. 




Le-ks, Rcpairiaa builM, |17, pll. 




Sulphate of. f 14, p33. 




Leaky blow-tpff cocka. |17, plU. 








b..i1<r lube.. 117, pll. 




Main check-valve, (U. pl2. 








feed, 114, p3. 




manholt.. |17. pl9. 




fced-punip broken down, (16, plB. 




pip«, 117. p20. 




MaldoB fast, IB. p4. 




rivets. 117, pis. 




uplosaoffeedwater. il5, pi. 




Beams. |17. pta. 




Malleablc-iroo castings, Specifications 


^1 


ctaybdU, |17. plS. 




(18. p9. 




Lee shore. [9. p2. 




Management at sea, General boiler. (IS 


■ 


Under the. (B. pZ. 




Marine-boiler, (le, pi. 




La ward, tO, pS. 




. when ateaming, BoQer. (IG. pi. 




Leeway. IH, pi. 








Lea. Water. fS. pI8. 




Leaky. (17. plB- 




Level, Finding water, (IS. plG. 




Marine-boiler accessories. (11. pi. 




Uversafety valve, JU, pi. 




-boiler details. (10, pi. 




lafcly-valve calcmations. Ill.p7. 




-boiler feeding. (14, pi ; US. pi. 




Liftinij injector. Mi>niliir, 114. p25. 




-boiler inspection. (18, ppl. 43. 




injcrtors, IH. pl7. 




•boiler management, (lB.pl. 




Lishling fires. 112, p21. 




-boiler repairs, J17.pl, 




Lignite coal, |1Z, pl3. 




Marine boUcra, Construction of. (9. pIO 




Unie, Carbonate of. |14, p32. 




boilers. Types of, (9, pi. 




Sulphate of. IU.P32. 




boilcn, VertiaJ. (0. p30. 




Line. Log, tO. pS. 




feedwatei heater. Blake, |14, pSL 








Marsh gas. |13, p2. 




Lilted. iS. p5. 

Load ™ter-li™.. |9, p4. 

Lock-up «fety valve. m.pO. 




Materials. Specificationii for boiler, f IS, 


^H 




McGreftar brace, (ID, pZ9. 


^1 


Ltn-omotive btriler. |9. pZO. 




Mcflsurement of ship's speed. (IB. p2. 




Log. IB, p6^ HIB. J*. 




Salt, lis, plO. 




chip, 19, p6. 






p24. H 


line. (9, p6. 




Mechanical draft. 112. p32. 




LoH of feedwater, |15, pi. 




dimn, Ho«den-i dosed ash-pit lyite 


■« ^M 


of heat by blo«ng olT. (15, plB- 




(12. p33. 






(13. 


Melting capacity, loe, (20, p4. 




pW. 




Menmrial sle«m gauge, (11. p28. 








Metallic steam gauge, (11. pl8. 




113. pZl. 








Hii«lUneoi>theB[. 113, pig. 




of purift-ing feedwaCer. |14. p34. 




Moisture and distiUation heat, |13, p20. 


Mineraloa, (12, pi*. 




Low water in boilers. (IB. plO. 
M 




heat losses. (13. pl9. 


■ 


Machine. AHeil dense-air refrigerating 


120, 


(lauge-cock, lll.p25. 




pB. 




Mi^tunrs. |12, pS. 




Rtmnlng an Allen dense-air rvbieen 




Mobture and distillation heat losses 


(13 ■ 


130. pZ8. 




p20. 






Mdecular weight. |1Z. p4. 




«ng, 120, p31. 




Monitor lifting injector, (14. p2fl. 




Running an ammonia-compresMon refrig- 


Mooring, IB, p4. 




eratinH, (20, pSB. 




Moriion furnace door, 110. p41 






■ 




J 



xvi 



INDEX 



Mud-drum. §9. pl2; f 10. p23. 
-valve. 59, pl4. 

N 

Natural circulation of water, f 15. p21. 

draft. il2. p30. 
Nautical terms, 19, pi. 
Negative slip, (19, p6. 
Nessler's reagent, 120, pl8. 
Non-combustible substances. (13, p2. 

-lifting injectors, §14, pl7. 

O 

Ocular boiler inspection. $16. p28. 

Off shore. {9, p2. 

Oil, Combustion of, §12, p23. 

in feed water, il4, p33. 

injection, $20, p21. 

-injection system, $20, p22^ 

Mineral, $12. pl4. 
Olefiant gas, $13, p2. 
On an even beam. $9, p5. 
Open feed water heaters, $14, p53. 
Openings, Reinforcement of. $18. p44. 
Organic matter in feed water. $14. p33. 
Oiitboard. $9, p2. 
Overboard, $9, p3. 
Overhauling boilers, $16. p24. 
Overheating $17. pA. 



Packed expansion joint. $11. p43. 

Paddle wheel, Effective diameter of, $19, pl2. 

wheel, Featherin«. $19, pl6. 

wheel, Radial, $19. pl4. 

wheel. Rolling circle of. $19, pl8. 

wheel. Slip of, $19, pl2. 

wheels, $19, pll. 

wheels. Size of, $19, pl9. 
Palm stay. $9, p21, $10, p28. 
• stays. Rules for. $18, pC5. 
Pan. Scum. $11, p37. 
Patch. Soft, $17, p9. 
Penberthy automatic injector, $14. pl8. 
Percentage of combined plate and rivet sec- 
tion. $18. p39. 

nf plate l)Ct\vcen holes. $18. p36. 

of value of rivet section. $18, p36. 
Pictct fluid. §20. pl4. 
Pijw boilers, Sectional, $9. p46. 

Dry §11. p5r>. 

fittintrs, §11, p39. 

Stand. §9 pl4. 

Steam. §0. p9. 
Pipes, Leaky §17, p20. 

Rules for §18. p«rj. 

SpeHfications and tests for seamless steel 
steam and water. §18. p8. 



Pipes — (Continued) 

Specifications and tests for wdded steam 
and water. $18. p7. 
Pitch. $10, p6. 

Axially expanded, $19, p23. 

Diagonal, $10. p6. 

Expanding. $19, p23. 

of rivets, Rtiles for, $18. p26. 

of rivets. Rules for diagonal, $18, p32. 

of screw propeller, $19, p21. 

of screw propeller. Measuring. $19. p24. 

of stays, $18, p60. 

Radially expanded, $19, p22. 

ratio of propeller. $19. p24. 
Ktching, $9, p2. 
Pitting. $17. pi. 
Plain furnace flues. $10, p33. 
Plate and rivet section. Percentage of com- 
bined, $18. p39. 

Boiler. $10, pi. 

Dead, $10, p37. 

repairs. Boiler, $17, p22. 

system of ice making, $20, p27. 
Plates. Rules for tube, $18, p54. 

Specifications and tests for boiler. $18, 
p3. 
Plug. Fusible, $11. p34. 
Plunger feed-pump. Single-acting, $14. p6. 
Point. Dew, $20. p7. 
Poker. $12, pl9. 
Pop safety valve. $11, p4. 
Port, $9, pi. 

Boiler management in, $16. p23. 

Boiler repairs in, §17. p21. 

waist, $9. p8. 
Positive injectors, §14. pi 8. 
Pot. Salinometer, §15. pl4. 
Powering of vessels, §19, p39. * 
Practical hints on firing. §12, p21. 
Pressure allowable on drums of water-tube 
boilers. Working. §18, p21. 

allowable on shell of superheaters. Working. 
§18. p20. 

Center of. §19. pl2. 

Draft. §12. p30. 

gauge. Bourdon. §11. pl8. 

on bi>iler shell, American rule for working. 
§18. pl3. 

on boiler shell. Board of Trade and Cana- 
dian rules for working. §18. pl4. 
Pressures, Bursting, working, and test. §18. 
pll. 

Hydrostatic test. $18. p22. 
Prevention. Heat losses and their, $13,pr9. 

of boiler explosions, $17, p6. 

Smoke. $13. p8. 
Priming, $16, pll. 



INDEX 



xvii 



Principles of combustion, §13, pi. 

of refrigeration. Fundamental. §20, pi. 
Producing cold. Processes of, §20, pi. 
Products of combustion, $12, p5. 
Projected blade area, §19, p23. 

propeller area, $19, p23. 
Propeller area, Developed, §19, p23. 

area. Helicoidal, (19. p23. 

area. Projected, §19, p23. 

Blade of screw, §19, p21. 

Disk area of, $19. p24. 

Measuring pitch of screw, 519, p24. 

Pitch of screw, §19, p21. 

Pitch ratio of, $19, p24. 

Size of screw, §19, p28. 

Slip of screw, §19. p28. 
Propellers, Definitions relating to screw, 

J19. p21. 
Propelling instruments, §19, pi. 
Properties of refrigerating agents. §20, pl3. 
Proportions of riveted joints, J 18, p25. 
Propvilsion calculations, (19, p31. 

of vessels. §19, pi. 
Pump, Air, §14, p2. 

Circulating, §14, p2. 
Pumps. Feed, §14, p6. 
Purification, Feed water, §14, p32. 
Purifier. Buffalo feed water heater and, §14, 

p44. 
Purifying feedwater by chemical means, §14, 
p46. 

feedwater by filtration, §14. p35. 

feedwater by "gravity separation, §14, 
p42. 

feedwater by heat, §14, p44. 

feedwater, Methods of, §14, p34. 
Purpose of combustion chamber, §10, p42. 

of evaporators, §15, p2. 
Purves ribbed furnace flue, §10, p35. 
Pyrites, Iron, §13, p3. 



Quarter deck, §9, p7. 
Quiggin evaporator, §15, p7. 

R 

Racing. §9. p4. 

Radial paddle wheel. §19, pl4. 
Radially expanded pitch, §19, p22. 
Rail. §9. p2. 
Raising steam. §16, p6. 
Range of injectors, §14. ppl6, 17. 
Ratio of propeller. Pitch. $19, p24. 
Reagent. Nessler's. §20. pi 8. 
Real slip. §19. p4. 

Reduction of horsepower when towing, §19, 
p46. 



Reflex feedwater filter, §14. p38. 
Refrigerating agents, §20. pl2. 

agents. Cooling effects of, §20, pl8. 

agents. Properties of, §20, pl3. 

capacity. Unit of §20, p4. 

machine, Allen dense-air, §20, p8. 

machine. Running an Allen dense-air, §20, 
p28. 

machine, Running an ammonia-absorption. 
§20. p31. 

machine. Running an ammonia-compres- 
sion, §20. p29. 

machines. Capacity of, §20. p4. 

machines. Free-air, §20, p5. 

machines, Latent-heat, §20, pl2. 

machines. Running, §20, p28. 

system. Brine, §20. p25. 

s>'stem. Direct-expansion. §20, p25. 
Refrigeration, §20, pi. 

Adiabatic-expansion, §20, p5. 

Fundamental principles of, §20. pi. 

Latent-heat, §20, pl2. 

system. Ammonia-absorption, §20, p23. 

system. Ammonia-compression, §20. pl8. 
Register pattern gauge-cock, §11, p24. 
Regulation, Feedwater, §16, pl3. 

Salt. §15. pl5. 

Saturation. §16, pl4. 
Reinforcement of openings, §18, p44. 
Relation between horsepower and revolution-, 
§19, p44. 

of coal consumption to speed, §19, p47. 
Relief valve. Feed, §14. pl3. 
Relieving watches, §16, pl9. 
Remedies, Injector troubles and, §14, p27. 
Repairing boiler leaks, §17, pll. 
Repairs at sea. Boiler. §17, p7. 

Boiler-plate, §17, p22. 

Boiler-stey, §17, p24. 

Boiler-tube, §17, p23. 

Furnace, §17, p25. 

in port. Boiler, §17, p21. 

Marine-boiler, §17, pi. 

Miscellaneous boiler, §17, p26. 
Retardcr. Spiral. §10. p53. 
Revolutions. Relation betw^een horsepower 

and, §19, p44. 
Ribbed furnace flue, Purves, §10, p35. 
Ripper, §17. p23. 
Rivet, Rules for diameter of, §15. p30. 

Screw, §17. plO. 

section. Percentage of combined plate and, 
§18. p39. 

section, Percentage of value of, §18, p36. 

to edge of plate. Rule for distance from cen- 
ter of , §18, p30. 
Riveted joints. §10, p3; §18, p23. 



xvm 



INDEX 



Riveted — (Continaed) 

joints. Arrangement of. (10. p6. 

joints. Efficiency of. f 18. p35. 

joints. Poims of. f 10, p6. 

joints. Proportions <^, f 18, p2S. 
Riveting, Chain. flO. p6. 

Staggered. {10. p6. 

Zigzag. SIO. p6. 
Rivets. (10. p3. 

Leaky, f 17. pl8. 

Rules for diagonal pitch of. (18, x>32. 

Rules for 'distance between rows <^, f 18, 
p30. 

Rules for pitch of. (18. p26. 

Specifications and tests for, |,18, p5. 
Roberts boiler, (9. p46. 
RoUer tube expander. Dudgeon. (10. p51. 
Rolling. (9. p2. 

circle of paddle wheel. (19, pl8. 
Ross feed water filter, (14, p35. 
Rows of rivets. Rides for distance between, 

(18. p30. 
Rule for cone-shaped combustion chamber, 
(18. p76. 

for distance from center of rivet to edge of 
plate. (18. p30. 

for girder stays, (18, p67. 

for safety-valve steel spring, (11, pl5. 

for working pressure on boiler shell. Ameri- 
can, (18. pl3. 
Rules for boiler efficiency, (13, p22. 

for boiler heads, (18. p80. 

for diagonal pitch of rivets. (18, p32. 

for diameter of rivet, (18, p30. 

for direct stays. (18, p62. 

for distance between rows of rivets, (18. 
p30. 

for drumheads, (18, p81. 

for flat surfaces. (18, p45. 

for furnace flues, (18, p70. 

for palm stays, (18, p65. 

for pipes, (18, p85. 

for pitch of rivets, (18. p26. 

for safety-valve area, (18, p87. 

for slip. (19. p9. 

for smoke flues, (18, p76. 

for tube plates, (18. p54. 

for tube-sheets, (18, p54. 

for working pressure on boiler sheU, Board 
of Trade and Canadian, (18, pl4. 
Running an Allen dense-air refrigerating 
machine. (20, p28. 

an ammonia -absorption refrigerating 
machine, (20, p31. 

an ammonia-compression refrigeration 
machine, (20. p29. 

refrigerating machines, (20. p28. 



Saddles, Boiler, (11, p57. 
Safety, Factor of, (18. pl3. 

feed- valve, (14. pl3. 

valve. (9, pl2. 

-valve area, Rides for (18. p67. 

-valve calctUations. Le\-er. (11. p7. 

valve. Dead- weight. (11. p2. 

valve. Lever. (11. pi. 

valve. Lock-up. (11. p6. 

valve. Pop, (11. p4. 

valve. Size of. (11. p5. 

valve. Spring-loaded. (11. p3. 

-valve steel spring. Rule for, (11. pl5. 

valves. (11, pi. 

valves. Arrangement of, (11. p5. 

valves. Use and care of. (11. pl7; (16. pl5k 
Sail. Wind. (9. p5. 
Salinometer. (15. pl2. 

pot, (15. pl4. 
Salt feed. (15. p2. 

measurement, (15. plO. 

regulation. (15, pl5. 
Saturation. (15. plO. 

by hydrometer. Finding, (15, pl2. 

by thermometer. Finding. (15. pll. 

regulation. (16. pl4. 
Scaling boilers. Cleaning and. (16. p23. 
Scotch boDer. Double-ended. (9. p23. 

boiler. Dry-back. (9, p25. 

boiler. Single-ended. (9. p21. 

boilers. (9. p21. 

boilers. Advantages of, (9. p54. 

boilers. Combustion chambers of, (9, p29. 
Scraper. Tube, (16, pl8. 
Screw propeller. Blade of, (19. p21. 

propeller. Measuring pitch of. (19. p24. 

propeller. Pitch of. (19, p21. 

propeller, Size of, (19, p28. 

propeller. Slip of. (19. p28. 

propellers. Definitions relating to. (19. p21. 

rivet, (17. plO. 

stay. (10. p24. 
Scum cock, (11, p38. 

pan, (11. p37. 
Scupper, (9, p3. 
Scuttle, Bunker, (9. p3. 
Sea, Boiler repairs at, (17. p7. 

General boiler management at, (16, pl3. 

Getting ready for, (16. pi. 

-water. Boiling points of. (15, pll. 
Seabury- boiler, (9, p41. 
Seamless steel steam and water pipes. Specifi 

cations and tests for, (18, p8. 
Seams, Leaky, (17, pl8. 
Sectional pipe boilers, (9, i>46. 

thrust block, (19, p36. 



INDEX 



XIX 



Securing boiler tubes, (10, p50. 

See boiler. iO. p39. 

Semianthracite, (12, pl2. 

Semibituminous coal, $12, pl2. 

Separation, Purifying feed water by gravity, 

§14. p42. 
Separator, Steam, $11, p55. 
Stratton steam, $11, p56. 
Serve tube. $10, p53. 
Shape and size of ftimace, $13, pl6. 
Sheet. Crown. $9, p23. 

Shell. American rule for working pressure on 
boiler. $18. pl3. 

Board of Trade and Canadian rules for 
working pressure on boiler, $18, pl4. 

Boiler, $9. plO; $10. pi. 

of superheaters. Working pressure allow- 
able on. $13. p20. 
Ship. Coaling, $9. p3; $16, p4. 

Trimming the, $9. p5. 
Ship's speed and engine speed. $19, p42. 

speed, Measurement of, $19, p2. 
Shore, Lee. $9, p2. 

Off, $9. p2. 
Sick bay. $9, p7. 
Single-acting plunger feed-pump, $14, p6. 

-ended Scotch boiler. $9, p21. 
Single grate bars. $10. p37. 

-riveted lap joint. $10. p5. 
Siren. Steam. $11. p48. 
Size of furnace. Shape and. $13, pl6. 

of injectors, $14, p26. 

of paddle wheels. $19. pl9. 

of safety valve, $11, p5. 

of screw propeller, $19, p28. 
Slice bar. $12, pl8. 
Sling stay. $10. p31. 
Slip. $19. p2. 
* Apparent. $19, p5. 

joint, $11. p43. 

Negative, $19, p6. 

of paddle wheel. $19. pl2. 

of screw propeller, $19, i>28. 

Real. $19. p4. 

Rules for. $19. p9. 

True. $19, p4. 
Smoke flues. Rules for, $lf , p76. 

formation. $13. p7. 

prevention. $13. p8. 
Smokestack, $9. p9. 

guys. $16, p7. 

hood, $9, p5. 
Smokestacks, High-temperature heat losses 

in. $13. p21. 
Socket staybolt. $10. p25. 
Sodium. Chloride of. $14. p32. 
Soft patch, $17, p9. 



Solid carbon. Combustion of, $13. p5. 

thrust block. $19. p35. 
Space, Combustion, $10, p32. 

Fire, $10. p32. 

Steam, $9, p9; $10, pi. 

Water. $9, p9: $10, pi. 
Speed, Engine speed and ship's, $19, p42. 

Measurement of ship's. $19, p2. 

of vessels, $19, p39. 

Relation of coal consumption to. $19, p47. 
Specifications and tests for boiler plates* 
$18. p3. 

and tests for boiler tubes. $1S, p6. 

and tests for rivets, $18. p5. 

and tests for seamless steel steam and water 
pipes, $18. p8. 

and tests for stays. $18, p6. 

and tests for stay«tubes. $18, p6. 

and tests for steel castings, $18, p9. 

and tests for welded steam and water pipes, 
$18, p7. 

and tests for wrought iron and steel. $18, p3^ 

for boiler materials. $18. pi. 

for cast iron. $18. p8. 

for malleable-iron castings, $18, p9. 
Spiral reterder, $10. p53. 
Spreading firing. $12. pl6. 
Spring-loaded safety valve, $11, p3. 

Rule for safety-valve steel, $11, pl5. 
Staggered riveting, $10, p6. 
Stand pipe. $9, pl4. 
Starboard. $9. pi. 

waist, $9. p8. 
Starting fires. $16. p6. 
Stay. Girder. $9. p23. 

Gusset. $10. p29. 

Palm. $9. p21; $10. p28, 

repairs, Boiler, $17, p24. 

Screw. $10. p24. 

Sling. $10. pl3. 

-tubes. $10. p52. 

-tubes, Specifications and tests for, $18. p6 
Staybolt. $10. p25. 

Socket. $10. p25. 
SUy bolts. Leaky. $17, pl8. 
Staying. $10. p23. 
Ste>Tod. $10, p26. 
Stays. Diagonal, $10, p28. 

Direct. $10. p24. 

Girder, $10. p30. 

Pitch of. $18. p60. 

Rule for girder. $18, p67. 

Rules for direct. $18. p62. 

Rules for palm. $18. p65. 

Specifications and tests for. $18, p6. 

Strength of. $18. p60. 

Stress allowable on, $18, p61. 



XX 



INDEX 



Steam and water pipes. Specifications and 
tests for seamless steel. §18. p8. 

and water pipes. Specifications and tests 
for welded, §18, p7. 

boiler. §9. p8. 

chimney, 511, p54. 

dome. ilO. p21. 

drum. (9. pl2: $11. p55. 

drums, (10, p21. 

gauge. (9, pl2. 

gauge. Compound. $11* p20. 

gauge. Dial. §11, pl8. 

gauge. Mercurial, $11, pl8. 

gauge. Metallic, fll. pl8. 

gauges. Construction of. $11. pl8. 

gauges. Use and care of, $11, p21. 

Getting up. $16. p4. 

into furnace. Admission of. $13, pl7. 

jet, Bloomsburg, $12, p36. 

pipe. $9. p9. 

Raising. $16, p6. 

separator. $11. p55. 

separator, Stratton. $11, p56. 

siren. $11. p48. 

space. $9. p9; $10. pi. 

trap, $15, p6. 

tube cleaner. $16. pl8. 

whistle, $11. p46. 
Steaming. Boiler management when. $16, pi. 
Steel castings. Specifications and tests for. 
$18. p9. 

Specifications and tests for wrought-iron 
and. $18. p3. 

steam water pipes. Specifications and tests 
for seamless. $18, p>8. 
Steerage. $9, p7. 

way. $9. p4. 
Stem. $9. pi. 
Stem. $9. pi. 

Down by the. $9, p5. 
Stemway, $9. p2. 
Stopper, Tube, $17, pl2. 
Straight-tube boilers, $9, p33. 

-way cock, $11, p36. 
Straps. Butt. $10. p8; $18. p23. 
Gtratton steam separator, $11, p56. 
Stress allowable on stays. $18, p61. 
Stresses on cylinders. $18, plO. 
Strength of ammonia liquor, $20. pl6. 

of cylinders, $18, pll. 

of flat surfaces, $18, p45. 

of stays. §18, p60. 
Submerged-tube boiler, $9. p32. 
Substances, Combustible. §13. p2. 

Combustion of volatile, §13, p3. 

Non-combustible, §13, p2. 

Volatile, §13, pi. 



Sulphate of lime, §14. p32. 

of magnesia, $14, p33. 
Sulphur dioxide. $20, pl4. 
Surface blow-off cock, $11, p38. 

condenser. $14, p2. 

Orate. $9, p9. 

Heating. $9. p9. 

Superheating, $9, p9. 
Surfaces, Rules for flat. §18. p45. 

Strength of fiat. $18. p45. 
Superheaters. $11, p52. 

Working pressure allowable on shell of. §18l 
p20. 
Superheating stirfaoe, $9. p9. 
Suspension furnace flue. Morison, $10. p36. 
Sweeping tubes while under way, $16, pl7. 
Swing check. $11. jAl. 
Swinging to the tide, $9. p4- 
System, Ammonia-absorption refrigeration, 
$20. p23. 

Ammonia-compression refrigeration. $20, 
pl8. 

Brine refrigerating. $20, p25. 

Direct-expansion refrigerating. $20, p25. 

Dry-compression. $20. p22. 

of ice making. Can. §20, p27. 

of ice making. Plate. §20. p27. 

Oil -injection, $20. p22. 

Wet-compression, $20. p21. 
Systems of firing. $12, pl5. 



Tbar. $12. pl9. 
Tarpaulin. $9. p5. 
Temperature. Ignition, $13. p4. 
of combustion. $12. plO. 
of fire. Color and, $13, p5. 
Terms. Nautical. $9. pi. 

Test pressures. Bursting, working, and. §18. 
pll. 
pressures. Hydrostatic. §18. p22. 
Testing feed water. §14. p48. 

water gauges and water columns, §11, p30. 
Tests for boiler plates. Specifications and. §18. 
p3. 
for boiler tubes. Specifications and. §18. p6. 
for rivets. Specifications and, §18. p5. 
for seamless steel steam and water pipes. 

Specifications and. §18. p8. 
for stay- tubes. Specifications and. §18. p6. 
for stays. Specifications and. §18. p6. 
for steel castings, Specifications and. §18. 

p9. 
for welded steam and water pipes. Specifi- 
cations and. §18, p7. 
for wrought iron and steel. Specifications 
and. $18. p3. 



INDEX 



XXI 



Testa — (Continued) 

Hammer and hydrostatic boiler. (16, p29. 
Theoretical thrust. §19, p31. 
Theory of combustion, (12, pi. 
Thermometer. Finding saturation by, (15, 

pll. 
Thickness of fire, (12, pl8. 
Thrust, Actual, (19, p31. 

bearings, (19, p35. 

block. Horseshoe. (19, p36. 

block. Sectional, (19, p36. 

block. Solid. (19. 35. 

Indicated, (19, pp31, 33. 

Theoretical, (19, pp31, 32. 
Tide, Swinging to the, (9, x)4. 
Tonnage, (9, p7. 
Topgallant forecastle. (9. p8. 
Towing, Reduction of horsepower when, (19. 

p6. 
Transfer to water. Heat. (15. p21. 
Trap. Steam. (15. p6. 
Trimming the ship. (9, p5. 

ventilators. (16, pl4. 
Troubles and remedies. Injector. (14, p27 
True sHp, (19. p4. 
Tube brush. Wire, (16, pl8. 

cleaner. Steam. (16, pl8. 

expander. (10, p50. 

expander. Dudgeon roller, ilO, ))61. 

Galloway. (9. p29. 

plates. Rules for. (18, p54. 

repairs. Boiler, (17. p23. 

scraper, (16, pl8. 

Serve, (10, p53. 

-sheets, (9, p23. 

-sheets. Rules for, (18, p54 

stopper, (17, pl2. 
Tubes, Boiler, (10, p48: (18, p79. 

Leaky boiler, (17. pll. 
. Securing boiler. (10, p50. 

Specifications and tests for boiler. fl8, p6. 

while tmder way, Sweeping, (16. pl7. 
Tubular boiler. Dry-bottomed firebox. (9, 
p20. 

boiler, Wet-bottomed firebox, (9. pl8. 

boilers, Firebox. (9, pl8. 
Types of marine boilers, (9, pi. 

U 

Under way, (9, p3. • 

way, Getting. (16, p7. 

way. Sweeping tubes while, (16, pl7. 
Uniform corrosion, (17, pi. 
Unit of refrigerating capacity, (20, p4. 
Universal double-tube injectoi, Korting, (14, 

p22. 
Uptake. (9. pl6. 



Use and care of safety valves. (11, pi 7. 
and care of steam gauges. (11. p21. 



Vacuum gauge, (11, p20. 

Value of rivet section. Percentage of, (18, p36. 

Valve calculations. Lever safety, (11, p7. 

Dead- weight safety, (11. p2. 

Donkey. (11, p48. 

Feed-relief. (14. pl3. 

Lever safety. (11, pi. 

Lock-up safety, (11, p6. 

Mud. (9. pl4. 

Pop safety. (11, p4. 

Safety. (9, pl2. ' 

Size of safety, (11, p5. 

Spring-loaded safety, (11, p3. 
Valves, Arrangement of safety. (11, p6. 

Gate. (11, p41. 

Globe, (11. p39. 

Safety, (11. pi. 

Use and care of safety, (11, pl7; (16. pl5. 
Vaporization, Latent heat of, (20, pi. 
Ventilator. (9, p5. 
Ventilators, Trimming, (16, pl4. 
Vertical marine boilers, (9, p30. 
Vessels, Powering of, (19, p39. 

Propulsion of, (19. pi. 

Speed of. (19. p39. 
Volatile substances. (13. pi. 

substances. Combustion of, (13, p3. 
Volume of air reqtiired for combustion. 
Weight and. (12, p6. ' 

W 

Waist. Port. (9. p8. 

Surboard. (9. p8. 
Wake. (19. p3. 
Ward room, (9, p7. 
Wass grease extractor, (14, p42. 
Watch, (16, p4. 
Watches, Relieving. (16, pl9. 
Water column, (11, p28. 

columns. Testing water gauges and, (11 
p30. 

Forced circulation of, (15, p25. 

gauge. Draft. (12, p30. 

gauge. Float. (11, p33. 

gauge, Glass. (11. p25. 

gatigcs. (11, p22. 

gauges and water columns. Testing, (il 
p30. 

hammer, (16, p7. 

Heat transfer to. (15, p21. 

in boilers, Low, (16. pl6. 

leg, (9. pl6. 

level. Finding. (16, pl6. 



XXI! 



INDEX 



Water— f C..ntimKd) 
-line. Load. f9. pi. 
Natural circulation of. f 15. p21. 
pipes. Specifications and test for seamless 

steel steam and. |18. p8. 
pipes. Specifications and tests for welded 

steam and, f 18. p7. 
-tube boilers, |9. p32. 
-tube bijilers, Advantai;es of. f9. p60. 
-tube boilers. Comparison of, f9. p56. 
-tube boilers. External corrosion of. (17, 

p3. 
-tube boilers. Working pressure allowaUe 

on drums of. |I8. p2I. 
space, {9. p9: |I0, pi. 
Waterway. §9. p3. 
Way. J9. p2. 

Getting under. |16. p7. 
Steerage. Jl», p4. 

Sweeping tubes while under, f 16, pl7. 
Under, §9. p3. 
Wear and tear of boilers, f 17. pi. 
Weight and volume of air required for com- 
bustion. §12. p6. 
Atomic. §12. p4. 
Molecular. §12. p4. 
Welded steam and water pipes. Specifications 

and tests for, §18. p7. 
Wet-bottomed boiler, §9, pl7. 

-bottomed firebox tubular boiler, §9, pl8. 



Wet — ^Continued) 

compression. §20. p21. 
-compression system, f20. p22. 
uptake. §9. pl6. 
Wheel. Effective diameter of paddle. §19. pl2. 
Feathering paddle, §19. pl6. 
Radial paddle. §19. pi 4. 
Rolling circle o: r>addle. §19. pi 8. 
SUp of paddle. §19. pl2. 
Wheels. Paddle. §19. pll. 

Size oi paddle. §19. pl9. 
Whistle. Steam. §11. p46. 
Wind sail. §9. po. 
Windward. §9. p2. 
Wire tube brush, §16. pl8. 
Wood. §12. pl4. 

Working and test pressures. Bursting. §16. 
pll. 
pressure allowable on drurr^ of -n-ater-tube 

boilers. §18. p21. 
pressure allowable cm sheO of superheaters. 

§18. p20. 
pressure on boiler shell. American rule fc-r, 

§18. pI3. 
pressure on boiler shell. Board of Trade and 

Canadian rules for. §18. pi 4. 
the fires. §16. p8. 
to bells. §9, p4. 

Z 

Zigzag ri\'eting, §10. p6. 



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