Audels engineers and mechanics guide ... a progressive illustrated series with questions--answers--calculations, covering modern engineering practice

\^<j^(\jsKji^^JkjX^ ^(OvA/y^

UNIVERSITY OF CALIFORNIA LIBRARY

THIS BOOK IS DUE ON THE LAST DATE
STAMPED BELOW

FC.

AUDELS

ENGINEERS

AND

MECHANICS
GUIDE 5

/K PROGRESSIVE ILLUSTRATED SERIES
WITH QUESTIONS -ANSWERS
CALCULATIONS

COVERING

MODERN
ENGINEERING PRACTICE

SPECIALLY PREPARED FOR ALL ENGINEERS
ALL MECHANICS AND ALL ELECTRICIANS,
A PRACTICAL COURSE OF STUDY AND
REFERENCE FOR ALL STUDENTS AND
WORKERS IN EVERY BRANCH OF THE
ENGINEERING PROFESSION
BY

FRANK D. GRAHAM,B.S.,M.S,M.E.

GRADUATE PRINCETON UNIVERSITY
AND STEVENS INSTITUTE-LICENSED
STATIONARY AND MARINE ENGINEER

THEO. AUDEL 8c GO. • PUBLfSHERs
IZ FIFTH AVE. NEW YORK us.a.

COPYRIGHTED, 1921,

BY

THEO. AUDEL & CO.,
ISTew York

Printed in the United States

NOTE

■■■^■■■■■■■■1

In planning this helpful series of Educators, it has been the
aim of the author and publishers to present step by step a
logical plan of study in General Engineering Practice, taking
the middle ground in making the information readily available and
showing by text, illustration, question and answer, and calcula-
tion, the theories, fundamentals and modern applications, includ-
ing construction in an interesting and easily understandable
form.

Where the question and answer form is used, the plan has
been to give shorty simple and direct answers ^ limited^ to one
paragraph, thus simplifying the more complex matter.

In order to have adequate space for the presentation of the
important matter and not to divert the attention of the reader,
descriptions of machines have been excluded from the main
text, being printed in smaller type under the illustrations.

Leonardo Da Vinci once said:

"Those who give themselves to ready and rapid practice
before they have learned the theory , resemble sailors who go
to sea in a vessel without a rudder"

>»

• — in other words, *'a little knowledge is a dangerous thing
Accordingly the author has endeavored to give as much infor^
mation as possible in the space allotted to each subject.

The author is indebted to the various manufacturers for
their co-operation in furnishing cuts and information relat-
ing to their products.

These books will speak for themselves and will find their
place in the great field of Engineering.

CONTENTS OF GUIDE No. 5

Contents of Guide No. 5

CHAPTER PAGES

54. Heat 1,755 to 1,778

Definition — the three "states" — heat unit — temperature — thermometers
and thermometry — absolute temperature — pyrometers — mechanical
equivalent of heat — expansion and contraction — transfer of heat —
conductivity of absorption of heat — specific heat — TABLES.

55. From Ice to Steam 1,779 to 1,820

Transformation changes — fusion of ice — effect of pressure on melting
point — surfusion — work of fusion — contraction and expansion of the
liquid — STEAM : — erroneous ideas — formation of steam — latent heat —
work of vaporization — sensible heat — internal and external latent heat —
external work of vaporization — total heat of saturated steam — boiling
point — How a Boiler Makes Steam — factors of evaporation — saving
by heating the feed water — superheated steam — caloimeters and calori-
metry.

56. Fuels 1,821 to 1,844

Definition — classification — A. SOLID FUELS — coal — kinds of coal —
heating values of coal — sizes — coke — heat — wood — tan bark — straw —
sawdust — bagarse — tar — B. LIQUID FUELS — comparative evapora-
tion of coal and oil — C. GAESOUS' FUEL — ^natural gas — comparison
of gas and coal — tables.

57. Combustion 1,845 to 1,886

Combustion explained — carbon — hydrogen — sulphur — ignition — com-
bustion— CO 2 — CO — air required — the blow pipe — heating values of
fuels — determination of heating value — ultimate analysis — available,
high, and low heating values — ^heating values of gaseous fuels — proxi-
mate analysis — flame — smoke — ^furnace temperature — ashes — clinker.

58. Fuel Analysis 1,887 to 1,918

Why tests should be made — apparatus required — methods — sampling
coal — proximate analysis — ultimate analysis — calormeter test —
heating value calculation — ash analysis — analysis of liquid fuels.

59. Flue Gas Analysis 1 ,919 to 1 ,938

Waste due to faulty firing — cooling effect of excess air — sampling gases —
flue gas collectors — gas pumps — gas analysis — Orsat three and four
pipette apparatus — pocket CO 2 indicator.

CONTENTS OF GUIDE No. 5

60. GO2 Recorders 1,939 to 1,954

What CO 2 indicates — unreliability of readings — flue gas analyzers z;^. CO 2
recorders — how a recorder works — CO 2 and fuel losses — TABLES.

61. Classification of Boilers 1,955 to 0,000

Various horizontal shell boilers — various vertical boilers — various
water tube 6oi7ers— difference between a tube and flue— tubular
heating surface — various tube arrangements— various furnace and com-
bustion chamber arrangements — various automobile boilers — difference
between a boiler and so-called generator.

62. Characteristics of Boilers .1,973 to 1,984

Best form of heating surface — ^function of grate — grate heating surface
ratios — ratios in common use — gas passages — water space — liberating
surface — importance of rapid circulation — steam space — priming
— proper water level — thin vs. thick plates — Water Tube and Shell
Boilers Compared — quality of the steam with through and submerged
tubes — -comparison of external and internal furnaces.

63. Boiler Materials 1 ,985 to 2,022

1. MATERIALS — copper — brass — brick — cast — malleable and wrought
iron— steel— definitions— 2. PROPERTIES OF MATERIALS— defi-
nitions— copper — iron — malleable iron — steel — brick — boiler coverings
3. TESTS — definitions — Testing Apparatus — calculations — tension,
compression, transverse, shearing, tortional. hardness, cold bending,
homogeneity tests — A»S,M»E, requirements.

64. Shell Boilers .2,023 to 2,056

Classes— 1, EXTERNALLY FIRED— development of the shell
boiler — flue — tube — sheets — evolution of the horizontal return tubular
boiler— 2. INTERNALLY FIRED BOILERS— Trevitheck, Lancashire-
Galloway boilers — vertical boilers — through and submerged tubes —
author's dry pipe — locomotive boilers — marine boilers^— difference
between Clyde and Scotch types — ^Western river construction.

65. Water Tube Boilers 2,057 to 2,098

Classification — arrangement of tubes: a, in series; b, in parallel — essen-
tial parts — early forms — elementary boiler — circulation principles : 1 ,
up flow; 2, down flow; 3, under and over discharge; 4, directed flow —

CONTENTS OF GUIDE No. 5

Water Tube Boilers — Continued

non-sectional and sectional boilers — combustion principles: 1,
direct and baffled draught; 2, down draught — Pipe Boilers — author's
home made series pipe boiler — water grate — curved tubes — Talbot
contra-flow boiler — Mbsher boiler of launch Norwood — automobile
types — closed tube or porcupine boilers — series parallel tube arrange-
ment— up flow and down flow boilers.

66. Special Boilers 2,099 to 2,126

1. FIRE TUBE BOILERS— duplex and triplex types— horizontal
boiler vertically set — vertical extended internal fire box — Manning and
Smith types — radial tube — vertical return tube — modified Clyde type
—extended shell tri-pas— 2. COMBINED FLUE AND FIRE TUBE
BOILERS — Cornish and Lancashire boilers with fire tubes — 3. WATER
TUBE (OR PIPE) BOILERS— types with special fittings— contra flow
—natural baffling— 4. COMBINED FIRE TUBE (OR* FLUE) and
WATER TUBE BOILERS— down draught grade— internal firing
with large water capacity — single and double row of water tubes — 5.
COMBINED SHELL AND WATER TUBE BOILERS— fire engine
boilers— box shell type— 6. COMBINED SHELL, FIRE AND
WATER TUBE BOILERS, with down draught— with Field tubes.

67. Steam Heating Boilers 2,127 to 2,154

Working conditions — heating surface (usually ridiculously small) —
effect of inadequate heating surface — rate of combustion — points of
boilers — division of gases — efficiency of heating surface — short and
long pass — ^fire box proportions — circulation — construction details —
author's home made pipe boiler — tests — steam dome — automatic con-
trol.

68. Details of Strength and Con-

struction 2,155 to 2,262

Construction rules (A,S.M.E, and Marine) — boiler plates — shell —
strength of shell — bursting pressure — factor of safety — working pressure
— thickness of shell — riveted joints — riveted joint calculations —
{A.S^M.E, standard for various joints) — U, S, Marine rules —
heads — tube spacing — area of head to be stayed — riveted socket, and
through stays or stay rods — stay tubes — gusset, palm, crow foot, jaw
and angle stays — crown or roof bars — radial stays — allowable stresses
for stays and stay bolts — boiler opening — steam domes — properties of
boiler tubes— expanders— fire doors— WATER TUBE BOILER
CONSTRUCTION— steam drums— headers and manifolds— /"eed water
heaters — superheaters.

HEAT 1,755

CHAPTER 54
HEAT

Heat may be defined as a form of energy in bodies, consisting
of molecular vibration. When heat is appHed to a substance, the
molecules of which the substance is composed, which are for-
ever moving, move faster. Again, if the substance be cooled,
that is, if some heat be taken away from it, the molecules move
slower.

Oues. What is a molecule?

Ans. The smallest particle in which a substance can exist in
the free or uncombined state.

It is the least part into which a compound can be subdivided and yet
retain its characteristic properties. The molecule of any compound must
contain at least two atoms and generally consists of many more.

Oues. What are the three * 'states" of matter?

Ans. Solid, liquid, and gas.

Oues. With respect to the molecules, how are the
three states distinguished?

Ans. By the character of their motion.

*NOTE. — Sir William Thomson estimated that if a drop of water be magnified to the
size of the earth, the molecules of water would each be less than the size of a baseball and
larger than small shot.

1,756

HEAT

Oues. How do the molecules move in a solid ?

Ans. Back and forth like tiny pendulums.

Oues. How do they move in a liquid?

Ans. They wander all around without any definite path.

Ques. How do they move in a gas?

Ans. In straight lines.

Figs. 3,278 to 3 ,"280. — The three states; solid, liquid, gas, as exemplified by fig. 3,278, a cake
of ice; fig. 3,279, water flowing from a faucet, and fig. 3,280 steam escaping from a safety
valve. In fig. 3,280 it should be noted that the substance is in the state of a gas only at, or
very near the saiety valve, or such portion that is invisible.

*The Unit of Heat. — The present generally accepted heat
unit, called the British thermal unit {B.t.u.), is defined as yw
of the heat required to raise the temperature of water from 32^ to 212°
Fahr.

*NOTE. — The old definition of the heat unit as given by Rankin is: the quantity of heat
required to raise the temperature of 1 pound of water 1° F., at or near its temperature of maximum
density (39.1° F); this unit was the accepted standard up to 1909. Peabody defines it aS
the heat required to raise 1 pound of water from 62° to 63° F, and Marks and Davis as Visa of
the heat reqtiired to raise 1 pound of water from 32° to 212° F. According to Marks and Davis*
definition the heat required to raise 1 pound of water from 32° to 212° is 180 instead of 180.3
units, and the latent heat, 970.4 instead of 969.7 units. Evidently this is the mean heat unit
and the tendency is toward this as a standard. The heat unit represents a definite amount of
heat as distinguished from temperature which represents the intensity of the heat. Thus the
amount of heat so supplied in raising the temperature of 1 pound of water 5° F, or 5 pounds
of water 1° F., is 5 heat units. To raise the temperature of 5 pounds of water 5° F., would
requires 5 X 5=25 heat units, etc.

HEAT 1,757

Temperature. — ^A substance is said to be hot or coW 'according
to its physical or sensible effect when touched* This effect
depends upon the rate of motion of the molecules, that is;*to say,
the faster the molecules mqve, the hotter the substance feels,,
and the slower the motion, the colder the substance. The con-
dition of a substance with respect to its molecular activity
is called its temperature.

Place the hand in a basin of "cold" water. It feels cold; apply heat to-
the water, and it gradually becomes warm, that is its temperature is said
to rise. Again, put a red hot poker into a vessel of water, the poker is.
''cooled" and the water "heated"; that is, heat passes from the poker to
the water, the^temperature of the poker is lowered; and that of the water
increased. In both cases there has been a transfer of heat from one body
to the other, the body from which the heat passes is said to have the higher
temperature.

Oues. Define the term temperature.

Ans. Temperature is the condition of a body on which its
power of communicating heat to, or receiving heat from, other
bodies depend.

Oues. When is a body at a higher temperature than
another body?

Ans. When its molecules move faster than those of the other
body.

Oues. How is temperature measured?

Ans. By a thermometer.

Thermometers. — Experience shows that while an idea of
temperature and of the difference between two temperatures may
be derived from the sense of touch, no accurate knowledge can
be obtained from that source alone.

1,758

HEAT

If a piece of metal and a piece of cloth
which are lying side by side in front of a
fire be touched, the metal will appear
hotter than the flannel, though the two
may be shown by a suitable experiment to
be at the same temperature; again if the
two be very cold, the metal will appear the
colder. From this must be evident that
the sensation does not depend on the tem-
perature alone — it depends also on the
rate at which heat is transferred to or from
the hand and the substance touched.
Accordingly it becomes necessary to
employ an instrument known as a ther-
mometer to accurately measure temper-
ature.

Oues. Upon what principle are
thermometers based?

Ans. The expansion and contrac-
tion of substances due to the effect
of heat.

Oues. What is the substance
generally used in thermometers?

Ans. Mercury.

Pigs. 3,281 and 3,282. — Construction of a mercury thermometer. A bulb A, is blown at one end
of a glass tube of narrow uniform bore. A cup or funnel B, is formed at the other end.
At C, a short distance below the funnel, tube is drawn out by heating it in a blow pipe
flame so as to form a narrow neck for sealing off the thermometer when made. If mercury
be poured into B, it will not run down the tube to fill the bulb because of the narrowness of
the bore. Hence, a small quantity of mercury is placed in B, and the bulb gently heated;
the air expands and some of it bubbles out through the mercury in B. The bulb is then
allowed to cool and the pressure of tht enclosed air falls, thus some of the mercury is forced
down the tube, and, if sufficient air has been expelled, into the bulb. When this takes
place. the mercury in the bulb is boiled, the vapor of mercury forcing most of the air out of
the upper part of the bulb and tube. When the bulb is again cooled the mercury vapor
condenses and more mercury flows in from the reservoir. By repeating the process once or
twice the last traces of air may be removed and the bulb and tube filled with mercury.
Now place the bulb and tube in a bath at a rather higher temperature than the highest at
which the thermometer is to be used. Some of the mercury expands into the funnel; remove
*'-' d allow the thermometer to cool slowly. As the mercury contracts have a blow pipe
knd as the end of the column is just passing the narrow neck C, heat the tube at that
ad draw off the funnel end, thus sealmg the tube. The mercury as it cools contracts,
la space filled only with mercury vapor.

HEAT

1,759

Oues. Describe the contraction of an
ordinary thermometer*

Ans. It consists of a glass tube containing-
mercury. A bulb is blown on one end of the
tube and filled with mercury. When both glass
and mercury are heated, i the mercury expands
more than the glass does, and finds the extra
space needed by rising in the fine capillary bore
of the stem.

The bore is so fine that a very slight change in the
volume of mercury will cause a perceptible change in
the length of the thread of mercury in the stem. The
cylindrical stem acts as a magnifying glass and makes
the thread of mercury look much larger than it is.

Oues. Why is mercury the best liquid
for use in a thermometer?

Ans. 1. It remains liquid through a wide
range of temperature. 2. Its rate of ex-
pansion is nearly constant within ordinary
limits. 3. It transmits or receives heat very
rapidly, and therefore can be rapidly cooled or
heated, and 5, it does not ''wet" the glass in
which it is contained.

Oues. How is the mercury
made to indicate temperature?

Ans. By means of a scale.

column

Fig. 3,283. — Tagliabue thermometer for feed water and condenser use; also for injection water,
inboard delivery, outboard delivery and other marine uses. Straight form type with fixed
thread connection.

1,760

HEAT

Oues. How is the scale graduated?

Ans. By determining the two "fixed points" and then gradu-
ating the distance between them into the proper nvimber of
degrees corresponding to the particular scale used.

Ques. What are the two fixed points?

Ans. The freezing point and the boiling point.

■ 11^' 1 1 1 1 — ^■■^-

FiGS. 3,284 to 3,286. — Tagliabue permanent thermometer connection. Fig. 3,284 fixed;
fig. 3,285, union; fig. 3,286, separable socket. A fixed thread connection (fig. 3,284) is the sim-
plest form and is recommended for a straight form thermometer only. The union connection,
ng. 3,285, allows regular angle and side form thermometers to be attached in a vertical posi-
tion without revolving the scale case, and when applied to straight stems, the thermometer
face may be turned in any direction. A union connection also relieves the thermometer from
all injurious wrenching strains, jars and slips which are likely to occur in attaching. A
separable socket, fig, 3,286, is an additional bulb chamber which exactly fits over the inner
bulb chamber of the thermometer, forming a means of connecting the thermometer to an
apparatus and, after such connection is made, allowing the thermometer itself to be removed
from the socket while the latter remains as a permanent closure of the openihg which was
made in the apparatus to receive the thermometer. This construction is shown in the sectional
illustration at right. D, coupling nut, .revolving on thermometer stem; E, tapered bulb
chamber; F, socket chamber, with inside taper corresponding exactly to outside of E.
Owing to the perfect contact throughout the length of E and F when same are forced to-
gether by means of coupling nut D , the temperature is transmitted through the two chambers
as readily as if they were one solid piece.

HEAT

1,761

FiG.3,289,— Aietnoa or aeiermining the freezing
point Wash some ice, break it small and
pack it around the bulb of the thermometer
in a glass or metal funnel, so that the water
which forms as the ice melts may drain away
into a vessel placed below to receive it. The
ice should be heaped up around the tube until
only the top of the column is visible, and the
thermometer left thus covered for 15 minutes.
Then, with a fine file, make a scratch on the
glass opposite to the top of the column of
mercury which represents the freezing point.

Figs. 3,287 and 3,288.— Tagliabue mercury well /gw^o^'ary thermometer connection and tyije ,
ot thermometer used with same. The mercury well is designed for use with a solid glass
thermometer (fig, 3,287) for test work or for application where only an occasional reading is
required. There is a seating plug provided with a gasket for confining the mercury.

1,762

HEAT

HYP50METER

OR
COPPER COVER-

STEAM

To determine the freezing
point, the thermometer is
packed in melting ice and
allowed to remain until the
mercury comes to rest, when
the height of the liquid is
marked on the scale. The
thermometer is then immersed
in saturated steam at atmos-
pheric pressure, that is, steam
formed under pressure of a
30-inch barometer. The mer-
cury will rise a considerable
distance, and when it comes to
rest its height is located on
the stem.

Thermometer Scale. —

Since the distance or dif-
ference in temperature be-
tween the two fixed points
of a thermometer is con-
siderable, a number of sub-
divisions should be marked
on a scale so that any two
temperatures may be more
closely compared than would
be possible with only the
two fixed points.

Oues. What are these
sub-divisions called?

Ans. Degrees.

Fig. 3,290. — Method of determining the boiling point. Place the thermometerin the saturated
steam issuing from boiling water. The apparatus used for this purpose, called a hyp-
someter is shown in the illustration. It consists of a conical tin or copper cover, with
an inner tube fitting loosely on to a glass flask. A cork passes through the top of the tube
and the thermometer is inserted through a hole in the cork, the bulb being well above the
surface of the water in the flask. As the water boils steam passes around the thermometer
bulb and issues between the flask and the loose cover, flowing down on the outside of the
flask between it and the cover. When the mercury ceases to move in the tube adjust ther-
mometer until the mercury level is just visible above the cork, and after leaving it in this
position a few moments mark the level of the mercury. Before marking the boiling point

Tf^nA 1-\Q-rr>mA+of anA if npppcQflr^r malr** mTTAPf inn for cifnriflarH atmosnhpriC nressure.

HEAT

1,763

Oues. Define a rise of temperature
of one degree.

Ans. It is that rise of temperature which
causes the mercury to expand by some definite
fraction of the total expansion between the
freezing and the boiling points.

Oues. What are the names of the
scales in general use?

Ans. The Fahrenheit, the Centigrade,
and the Reaumur scale.

The Fahrenheit thermometer is generally used
in EngHsh speaking countries, and the Centigrade
or Celsius thermometer in countries that use the
metric system. In many scientific treatises in
EngHsh, however, Centigrade readings are also
used, either with or without their Fahrenheit
equivalents. The Reaumur thermometer is used
to some extent on the continent of Europe.

* The Fahrenheit Scale, — The number of
degrees between the two fixed points is 180. The
freezing point is 32° above zero, hence the boiling
point is 32°+180° =212°.

The Centigrade Scale, — ^The number of
degrees between the two fixed points is 100. The
freezing point is zero, hence the boiling point is
100°.

Fig. 3,291 . — Comparison of thermometer scales, showing relation between values of the F'ahren-
heit, Centigrade, and Reaumur scales.

*NOTE. — The first modern thermometer, in which mercury was used, was the invention
of Gabriel Daniel Fahrenheit, a German natural philosopher, who died September 16, 1736,
at the age of fifty. Fahrenheit was a native of Danzig, and failed as a merchant before he
turned his attention to the making of thermometers. At first he used spirits of wine in the
tubes, but was dissatisfied with the result, and then used mercury with great success. He
opened a shop in Amsterdam , and from there his instruments soon spread throughout the
world. The scale suggested by Fahrenheit is still in general use in a large part of the world,
although the centigrade thermometer of Celsius, of Stockholm, offered a more rational gradua-
tion, and in France Reaumur proposed another graduation, which was adopted in that country.
In England and America, however, Fahrenheit is a household word.

1,764 HEAT

The Reaumur Scale, — The number of degrees between the two fixed
points is 80. The freezing point is zero, and accordingly, the boiHng
point, 80°.

Comparison of Thermometer Scales. — It is often desirable
to find the equivalent reading of one scale on another scale,
because in becoming accustomed to a particular scale, a better
conception of temperature is had than for readings on a less
familiar scale. Accordingly, the following conversion fraction
will be found convenient to obtain equivalent readings.

1 degree Fahrenheit = 5/9 degree Centigrade = 4/9 degree Reaumur

1 " Centigrade = 9/5 " Fahrenheit =4/5

1 " Reaumur = 9/4 " " = 5/4 " Centigrade

Temperature Fahrenheit = 9/5 X temp. C + 32° = 9/4 R + 32°

Centigrade = 5/9 X (temp. Fahr. — 32) = 5/4 R
Reaumur = 4/5 temp. C = 4/9 (Fahr. — 32)

Absolute Temperature. — According to various experiments
that have been made with pure gases [with the rise of air ther-
mometers, it has been found that air expands approximately
459;;2 of i^s volume per degree increase in temperature at zero F .
2731 of its volume at 0° C.) Accordingly, hy cooling the air

*N0TE. — Why Fahrenheit selected 32° (ts the freezing point, Fahrenheit was
living in Danzig at the time of his experiments, and knew from many years' experience just
how cold it is in that city in the coldest weather. He found that he could exactly reproduce
this temperature, anytime, anywhere, by mixing salt with pounded ice. This temperature,
he concluded, was the lowest limit of heat, since neither nature out of doors, nor experiments in
his laboratory, could go any lower. Accordingly, he put some mercury into a tube and bulb,
plunged it into a mixture of salt and ice, and scratched a zero mark on the glass at the top of
the mercury column. This he deemed to be the absolute zero. He then calculated the mercury
volume at that temperature, and found it to be 1,124 parts. Next he placed the same ther-
mometer in a mixture of ice and water. The mercury promptly expanded and occupied
11,156 parts by volume, or 32 parts of an increase over the zero volume. Accordingly, he
scratched the number 32 at this new height of the mercury column, and called it freezing
point of water. Next he placed the thermometer in boiling water. The mercury expanded
to 11,336 parts or 212 parts higher than zero. This he called the boiling point of water. He
divided the scale between 32 and 212 into 180 equal divisions, which he called degrees, and his
scale was complete.

HEAT

1,765

below zero, the reverse process should he true; that is to say, for each
degree F. decrease in temperature, the volume at zero would be
contracted 459:6. It must be evident then, if a volume of a per-
fect gas could be cooled to — 459.2° F. it would cease to exist,
giving the theoretical point known as the absolute zero . However,
all gases assume the liquid form at very low temperature, and
accordingly do not obey the law of contraction of gases at and
near the absolute zero.

ABS. 673'

32" 0
4S3'^59.6"

Fig. 3,292. — Graphical method of determining the absolute zero. It is found by experiment that
when air is heated or cooled under constant pressure, its volume increases or decreases in
such a way that if the volume of the gas at freezing point of water be 1 cu. ft. then its volume
when heated to the boiling point of water, will have expanded to 1 .3654 cu. f t. Or, inversely,
if the volume remain constant, and the pressure exerted by the gas at freezing point
= 1 atmosphere, then the pressure at boiling point of water = 1.3654 atmospheres. These
results jnay be set out in the form of a diagram, as here shown. In construction, draw a
horizontal line to representtemperatures to any scale and mark on it points representing the
freezing point and boiling point of water, marked 32° and 212° respectively. From 32°
set out, at right angles to the line of temperature, a line of pressure AB, = 1 atmosphere to
any scale, and at 212° a line CD = 1.3654 atmospheres to the same scale. Join the ex-
tremities DB, of these lines to intersect the line of temperatures. It is assumed by physicists
that, since the pressures vary regularly per degree of change of temperature between certain
limits within the range of experiment, they vary also at the same rate beyond that range, and,
therefore , that the point of intersection of the straight line DB , produced gives the point at
which the pressure is reduced to zero, this point being known as the absolute zero.

The property of air of changing its volume at constant pressure almost
exactly in proportion to the absolute temperature, gives a starting point
as the basis for all air volume temperattire calculations. If Pq be the pres-
sure and Vo the volume of a gas at 32° Fahr., = 491.6° on the absolute

1,766 HEAT

scale = To; P the pressure and V , the volume of the same quantity of gas
at any other absolute temperature T, then

PV T T + 459.2

PoVo To 491.2

also,

PV _ PoVo

T To

The figure 491.2 is the number of degrees that the absolute zero is below
the melting point of ice by the air thermometer. On the absolute scale,
where division would be indicated by a perfect gas thermometer, the cal-
culated value approximately is 492.66. Thomson considers that — 459.4°
Fahr. ( — 273.1° C) is the most probable value of the absolute zero.

Pyrometers. — Mercury thermometers answer all ordinary
requirements, but are not adapted to the measurements of high
temperatures. For this purpose an instrument known as a
pyrometer, of which there are several types, is used. Among
the various principles upon which pyrometers are constructed,
are:

1. The contraction of clay by heat.

As in the Wedgwood Pyrometer used by potters, the method is not ac-
curate because the contraction varies with the quality of the clay.

2. Expansion of air.

As in the air thermometer, Weborgh's Pyrometer, Uehling and Stein-
hart's Pyrometers, etc.

3. Specific heat of solids.

As in the copper ball, platinum ball, and free clay pyrometer.

4. Relative expansion of two metals or other substances.
As copper and iron as in Brown's and Buckley's pyrometers, etc.

5. Melting parts of metal or other substances.

As in approximate determination of temperature by melting pieces of
zinc, lead, etc.

HEAT

1,767

;er.s°2gs^'ds

X,768

HEAT

6. Measurement of strength of a thermo-electric couple.
As in Le Chatelier's Pyrometer.

7. Changes in electric resistance of platinum.
As in the Siemer's Pyrometer.

8. Mixture of hot and cold air.
As in Hobson^s hot blast pyrometer.

Figs. 3,296 and 3,297. — Brown platinum
rhodium thermo-couples for temperatures
up to 3 ,000° Fahf. The couple is formed
of one wire of chemically pure platinum,
and the other of 90 per cent platinum
and 10 per cent rhodium, the diameter
being .02 under, and the melting point
of the couple being about 3,150° Fahr.
The wires of the thermo-couple are insu-
lated by small porcelain tubes, each
pierced with one hole, through which the
wires are run. The thermo-couple is pro-
tected from the action of gases which

V tend to destroy platinum by either porce-
lain or quartz protecting tubes, both of
which are impervious to gases, and the
thermo-couple has a metal head, fibre
cover and brass binding posts. When
the thermo-couple is heated it generates
a small current of electricity. The
current or millivoltage generated by this
thermo-couple, if suitable alloys be used,
is sufficient to operate an electrical instru-
ment or millivoltmeter. As the tem-
perature of the thermo-couple rises and
falls, the thermo-electric current in-
creases or decreases , and is indicated on
the instrument , in degrees Fahrenheit or
Centigrade, or in millivolts.

9. Time required to heat a weighted quantity of water enclosed
in a vessel.

As in the water pyrometer.

Oues. Describe a simple pyrometer working on the
nrincinle of relative exnansion of two substances.

HEAT

1,769

,^-^,;ir T^-^fV' *-='""!^'.^^!^ -V Q

Fig. 3,298. — ^Fqxboro "pyod" or base metal thermo-couple, one
element of which is a tube the other element being a wire on which
is wound pure asbestos insulation. The two elements are welded
into a junction at one end — the hot end — as shown at the tips of
the sections of the three couples. Pyods are intended for use under
continuous service up to 1,650° or for intermittent service up to
1,800° Fahr. The parts are, C,L, zone box No. 4; W, copper
leads; A, auxiliary couple; P, pyod; DS, double stuffing box; I, iron
or iralume protection pipe .

Pigs. 3,299 to 3,301. — Sectional views of Foxboro "pyod" junctions
showing construction. B , center wire element; D , asbestos insulation;
tubular element; W, weld; CW, cup weld for special use.

NOTE. — Metallic pyrometers used for determining high temperatures must be handled
cautiously owing to the difficulty of exposing the whole of the stem to the current of gas, the
temperature of which is to be determined . Electric pyrometers either of the thermo-couple or
resistance type are satisfactory for this work within their practical limit, which is 1,800°
Fahr. for iron-nickel couples and 3,000° Fahr. for platinum-radium couples or platinum resist-
ance pyrometers. Instruments of this kind can readily be calibrated by comparing them at
low ranges of temperature with a standardized mercurial thermometer, both being placed for
example in a current of hot air the temperature of which is under control. For extremely
high temperatures such as that of a boiler furnace, optical, pneumatic and radiation pyrometers
may be used. The calibration of high-temperature instruments can best be undertaken in a
laboratory especially fitted for the purpose.

1,770

HEAT

Ans. A pyrometer of this type may be constructed by en-
closing a rod of graphite in a tube of iron. The graphite expands
and contracts more than iron, behaving just as the mercury and
glass in a mercury thermometer. There is a limit to the use o
this pyrometer as the very high temperatures met with in furnac(
work will melt the iron and boil the carbon. Carbon has th(
curious property of boiling before it reaches its melting point .

High Temperature Judged by Color. — The temperatur(
of a body can be approximately judged by the experienced ey(
unaided, and M. Pouillet has constructed a table, which has beei
generally accepted, giving the colors and their corresponding
temperature as below:

Incipient red heat . .

Dull red heat

Incipient cherry red

heat

Cherry red heat

Clear cherry red heat

Deg. Deg.
C F

525
700

800

900

1,000

977
1,292

1,472
1,652
1,832

Deg. Deg
C F

Deep orange heat.. 1,100

Clear orange heat . . 1 ,200

White heat 1,300

Bright white heat . . 1 ,400

ri,5oo

Dazzling white heat-j to
il,600

2,02
2,19:
2,37:
2,55:
2,73:
to

2,91:

According to Kent, the results obtained, however, are unsatis
factory, as much depends on the susceptibility of the retina o
the observer to light as well as the degree of illumination unde
which the observation is made.

The Mechanical Equivalent of Heat. — ^Almost everyon
knows that hammering a nail will make it hot, or that the barre
of a bicycle or automobile pump will become heated in pumpin:
up a tire, but comparatively few know that there is a direct nu
merical relationship existing between the amount of work don

HEAT

1,771

and the quantity of heat produced. This relationship is known
as the ''mechanical equivalent of heat,'' and was discovered by
Dr. Joule of Manchester, England, in 1843.

Joule reasoned that if the heat produced by friction, etc., be merely
mechanical energy which has been transferred to the molecules of the heated
body, then the same number of heat units must always be produced by the
disappearance of a given amount of mechanical energy. And this must be
true no matter whether the work be expended in overcoming the friction of
wood on wood, of iron on iron, in percussion, in compression, or in any
other conceivable way. To see whether or not this were so, he caused
mechanical energy to disappear in as many ways as possible, and measured
in every case the amount of heat developed.

Fig. 3,302. — The mechanical equivalent of heat. In 1843 Dr. Joule of Manchester, England,
performed his classic experiment, which revealed to the world the mechanical equivalent of
heat. As shown in the figure, a paddle was made to revolve with as little friction as possible
in a vessel containing a pound of water whose temperature was known. The paddle was
actuated by a known weight falling through a known distance. A pound falling through
a distance of one foot represents a foot pound of work. At the beginning of the experiment
a thermometer was placed in the water, and the temperature noted. The paddle was made
to revolve by the falling weight. When 772 foot pounds of energy had been expended on the
pound of water, the temperature of the latter had risen one degree and the relationship
between heat and mechanical work was found; the value 772 foot pounds is known as Joule's
equivalent. More recent experiments give higher figures, the value 778, is now generally
used but according to Kent 777.62 is probably more nearly correct. Marks and Davis in
their steam tables have used the figure 777.52.

Expansion Due to Heat. — One effect of heat is to cause
substances to expand. This may be explained by saying that
heat is molecular motion. An increase of heat is due to an

1,772

HEAT

increase in the velocity of motion of the molecules. Accordingly
the molecules by their more frequent violent collisions become
separated a little farther from one another, and as a result the
body expands, as shown in the experiments illustrated in the
accompanying cuts. The amount by which, say a rod of metal
increases in length for a moderate use of temperature differs
for different metals, but is in all cases very small. Experi-
ments show that the increase in length is proportional to the

COEFFICIEINT OF EXPANSION = F -5- L

Figs. 3,303 and 3,304. — Coefficient of expansion. If a bar of length L, at temperature n^
Fahr., as in fig. 3,303, be heated to n° +1° Fahr., and expand a distance F, as in fig. 3,304»
then the coefficient of expansion is F ■v* L.

original length and to the change of temperature, careful experi-
ments have been made to find for each substance a factor called
the coefficient of expansion.

Oues. Define the coefficient of linear expansion?

Ans. It is the ratio of the increase in length produced by a rise
of temperature of 1° to the original length.

Oues. What provision must be made on boilers because
of the expansion of the metal due to heat?

Ans. In setting horizontal shell boilers, one end is supported
on rollers to allow expansion and contraction with temperature
changes; the tubes of water tube boilers are arranged so they are

HEAT

1,773

free to expand and contract; steam mains, especially when long
have expansion joints, or the equivalent.

A better method of providing for expansion in boiler shells is to suspend
them by hnks attached to overhead cross beams.

Oues. State some advantages and disadvantages of
expansion and contraction due to heat.

Ans. Boiler plates are fastened with red hot rivets. When
the rivets cool they contract and bind the plates together with

Pig. 3,305. — Radiometer. It consists of a partially exhausted bulb within which is a little
aluminum wheel carrying four vanes blackened on one face and polished on the other.
When the instrument is held in sunlight or before a lamp the vanes rotate in such a way
that the blackened faces always move away from the source of radiation. This is because
the blackened faces absorb ether waves better than do the polished faces, and thus become
hotter. The heated air in contact with these faces then exerts a greater pressure against
them than does the air in contact with the polished faces. The more intense the radiation,
the faster is the rotation.

Pig. 3,306. — Leslie's cube for illustrating Hnes of radiation. It has four polished faces.

great force. Iron tires are first heated and then put onto the
wheel. When the iron cools, the tire contracts and binds the
wheel. A short space must be left between the rails of a railroad
to permit expansion and contraction without injury.

1,774 HEAT

Transfer of Heat. — There are three ways in which heat
may be transferred from one body to another at lower tempera-
ture, as by:

1. Radiation.

2. Conduction.

3. Convection.

These three methods of transfer are clearly illustrated in the operation
of a steam boiler, thus heat from the burning fuel passes to the metal of the
heating surface by radiation; it passes through the metal by conduction,
and is transferred to the water by convection.

When heat is transmitted by radiation, the hot body, as the burning fuel
in the above example, sets up waves in the ether. When the waves fall upon
another body (as the boiler plate) its energy is again converted into heat.
The waves are not heat, hut are caused by heat and may cause heat.

In conduction, heat travels through a body (as the boiler plate) from
molecule to molecule. At points where the temperature is high the mole-
cules are moving faster than at points where the temperature is low. The
molecules communicate the motion to the adjacent molecules, they to
others, and in this way heat passes through the body.

Water and most other liquids are very poor conductors of heat, that is,
heat is not readily transferred to them by conduction. Hence, if an up-
right test tube be filled with water and a flame be applied to its u^per
portion, the water will boil vigorously at the top while no perceptible heat
is felt at the bottom.

Now if the heat be applied at the lowest point, all of the water is quickly
raised to the boiling point. The explanation is that the water next to the
bottom is first heated and caused to expand. Then it rises because of the
buoyant effect of the denser cold liquid. In this way convection currents
are set up which continually raise the warmer water to the top and permit
the cooler water to sink to the bottom. The movement of the water thus
set up is called circulation in boilers, and the successful operation of any
boiler depends upon a proper circulation, so that the heat may be rapidly
transferred to the water by convection.

Conductivity. — On a cold day a piece of metal feels much
colder to the hand than a piece of wood, notwithstanding the
fact that the temperature of the wood must be the same as that
of the metal. On the other hand, if the same two bodies had
been lying in the hot sun in midsummer, the wood might be

HEAT

1,775

handled without discomfort, but the metal would be uncom-
fortably hot. The explanation of this phenomena is found in
the fact that the iron, being a much better conductor than the
wood, imparts heat to the hand much more rapidly in summer,
and removes heat from the hand much more rapidly in winter,
than does the wood. In general, the better 'the conductor, the
hotter it will feel to a hand colder than itself, and the colder to
a hand hotter than itself.

COPPER WIRE

i

Fig. 3,307. — Experiment illustrating the difference in conductivity of metals. Take two wires,
say copper and iron, and stretch them across a flame as shown. Rub the wires back and
forth with a piece of beeswax and at the same time hold a flame beneath the wax. Nunier-
ous beads of the wax will cling to the wires. When cool, let a flame play against the wires
at one point. The wax will melt and flow much farther from the flame on the copper than
on the iron wire. At the point where the flame is applied, the iron will become red-hot
before the copper does, because the heat cannot so readily leave that point on the iron
and also because the capacity of iron for heat is less than that of copper.

All metals are good conductors, though some are much better than
others, silver and copper being the best Any substance that is a good
conductor of electricity is also a good conductor of heat.

Most ordinary liquids and all gases are poor conductors . The experiment
in fig. 3,307 illustrates the difference in conductivity of metals.

The relative conductivity of a number of important substances is given
in the table below:

Silver 1.096

Copper 1.041

Aluminum 344

Zinc 303

Iron 167

Mercury 0152

Marble 005

Glass .0025

Water 0014

Cork 0007

Hydrogen 0004

Air 000056

1,776 HEAT

Absorption of Heat. — Some substances readily absorb the
heat waves which fall upon them. Thus, if a thermometer bulb
be covered with soot or lamp black, it will show a higher tempera-
ture than one near by which is not so heated.

Polished surfaces are poor absorbers and also poor radiators,
while rough surfaces are both good absorbers and radiators.
The radiometer, shown in fig. 3,305, illustrates the absorption of
heat.

Specific Heat. — By experiment upon different substances
it has been determined that it requires different amounts of heat

Fig. 3,308. — Tyndall's specific heat apparatus. It consists of a metal plate, paraffine cake
tripod support and five balls of different metals with holder. In experiment, the balls are
supported on the holder and heated in boiling water. Then, when placed on the paraffine
cake, they will melt their way through it at different rates, depending on their specific heats
The metal plate is used as a mould to form the paraffine cake and also to catch the balls or
their fall.

to change their temperatures one degree. Water is taken as
the standard for specific heat; that is, the specific heat of an^
substance is expressed in terms of the amount of heat required
to raise the temperature of water one degree; thus, by definition
the specific heat of a substance is the ratio of the quantity of heai
needed to raise its temperature one degree to the amount needec

HEAT 1,777

to raise the temperature of the same weight of water one degree;
expressed as a formula,

o -^ 1- ^ B.t.u. required to raise temperature of substance 1°

Specific heat = ■^— -. — -r- : — — — —

B.t.u. required to raise temperature same weight water 1

from this it follows that,

Specific heat = B.t.u. required to heat one lb. of a substance l^F,
One of the simplest methods of determining specific heat is by

mixing the substance with water.

Example. Suppose that six pounds of mercury at 100° C, be poured
into two pounds of water at 0 ° C, and that the resulting temperature of the
"mixture" is 9°. The specific heat S, of the mercury can then be found as
follows:

In falling from 100° to 9° the six pounds of mercury give out
6 X (100 — 9) X S, or 546 S heat units. These have gone to heat two
pounds of water from 0° to 9°, which requires 2X9, or 18 heat units.
Hence, we may write,

546 S = 18
Therefore, S = 18 -- 546 = .033

As given by Rontgen, the specific heat of various substances are as follows:

Specific Heat of Various Substances

Solids

Copper 0951

Wrought iron 1138

Glass. 1937

Cast iron. 1298

Lead 0314

Tin 0562

Q. , f Sott 1165

^^^^^ \Hard 1175

Brass 0939

Pee 504

Liquids
Water 1.

Sulphuric Acid 335

Mercury 0333

Alcohol (nnn) 7

Benzine . . . .95

Ether 5034

1,778

HEAT

Gases

Constant Constant

pressure volume

Air 23751 .16847

Oxygen 21751 .15507

Hydrogen.. 3.409 2.41226

Nitrogen 2438 .17273

Ammonia 508 .299

Alcohol 4534 .399

*NOTE. — Specific heat of gases. Experiments by Mallard and Le Chatelier indic£
a continuous increase in the specific heat at constant volume of steam, carbon dioxide, a;
even the perfect gases, with rise of temperature. The variation is inappreciable at 212° ]
but increases rapidly at the high temperatures of the gas engine cylinder.

FROM ICE TO STEAM 1,779

CHAPTER 55
FROM ICE TO STEAM

In the transformation of a pound of ice into a pound of steam,
by the application of heat, several changes take place, and a
considerable amount of work is done in effecting these changes.
The process may be divided into several stages:

1. Fusion of the ice;

2. Contraction of the water;

3. Expansion of the water;

4. Evaporation of the water.
During this series of changes the substance has existed in three

states, that is,

1. As a solid.

2. As a liquid.

3. As a gas.

Oues. What is a solid?

Ans. A form of matter in which the molecules lie close
together with little freedom of movement, and in which they
cannot be separated, except by the application of a definite
amount of force.

Maxwell defines a solid as a body which can sustain, a longitudinal pres-
sure without being supported by a lateral pressure.

1,780

FROM ICE TO STEAM

Oues. What is a liquid ?

Ans. A body whose molecules move easily among themselves
and yield to the least force impressed.

All liquids are fluids ^ hut not all fluids are liquids. Air and all gases are
fluids, but they are not liquids under ordinary circumstances, though capa-
ble of being reduced to a liquid form by cold and pressure . Water at ordi-
nary temperatures is a liquid.

Fig. 3,309. — Diagram illustrating the triple point, or that Point in which a substance can exist
in all three states (solids liquid^ gas) in equilibrium. For example, there is a certain
temperature and pressure at which water substance may exist partly as ice, partly as
water, and partly as vapor, so that the lower part of a closed vessel containing the mixture
will be filled with water in which ice floats, while the upper part is filled with saturated
vapor, the pressure within the vessel being that of the water vapor at the temperature of
the mixture. The curve of maximum vapor pressure is called the steam line. When the
ice and water are in stable equilibrium, the temperature of the mixture is that at which
the solid melts under the pressure within the containing vessel. This pressure is also
completely determined by the temperature, and the relation connecting this may be
represented graphically by a curve called the ice line. A third curve called the hoar-frost
line* shows graphically the relation between temperature and pressure of a substance when
existing partly in the solid state and partly in the condition of vapor. Evidently a substance
under the condition of temperature and pressure as indicated by F, the point of intersection
of the three curves, or the triple point, can exist in all the three states, that is, as a solid,
liquid, and gas.

*NOTE. — Regnault concluded that in passing from the vapor of the liquid to that of the
solid there is no appreciable change in the vapor pressure curve and that consequently the
hoar-frost line is simply a continuation of the steam line. It was later shown by Kerchoff
that the steam line and hoar-frost line are not continuous, but are distinct curves, intersect-
ing each other at an angle as shown in the figure.

FROM ICE TO STEAM

1,781

Oues. What is a gas?

Ans. A fluid which is elastic and which tends
expand indefinitely.

A gas is in nearly all cases under ordinary conditions .
characterized by great transparency and such extreme tenuity ^ '
as to be imperceptible to touch when at rest .

Fusion of Ice. — In order to transform a pound of
ice into steam, it must pass through two changes of
state, that is to say, 1, from a solid to a liquid, and
2, from a liquid to a gas. Heat is required to effect
each of these changes, being known as
latent heat, and called respectively:

1. Latent heat of fusion.

2. Latent heat of evaporation.

LIQUID

MERCURY

VAPOR OF LIQUID

MENISCU5

Oues. What is understood by the
term "change of state"?

Ans. A substance undergoes a
"change of state" when it changes from
a solid to a liquid, or from a liquid to
a gas.

Fig. 3,310. — Cagniard de La Tour's experiment illustrating critical temperatvre. By defi-
nition the critical temperature is that temperature to which a gas must be cooled before
it can be converted into a liquid by pressure y that is to say, there is a temperature for
all gases such that the substance can be liquified by pressure only if it be below this tem-
perature which is known as the critical temperature. As shown, the apparatus consists of a
bent tube, one end A, containing air to indicate pressure, and the other end B, the liquid to
be experimented upon. The space between A and B, is filled with mercury. If both arms
be graduated the critical pressure and volume may be determined simultaneously. At low
temperatures the vapor pressure may be less than that caused by the air in A, and the col-
umn of mercury. As the temperature of B, is raised the vapor pressure increases, and the
mercury is forced into the other arm compressing the air to some point A. Since the pres-
sure supported by the liquid at any temperature is that of the saturated vapor at that tem-
perature, the formation of bubbles below the surface (boiling) is impossible. Accordingly
evaporation proceeds without boiling till the temperature rises to a certain point, at which a
very striking transformation occurs. The menescus or surface separating the liquid and
vapor grows indistinct and completely disappears, and the substance appears no longer;
to exist in two states. That is, the whole space above the mercury in B, now appears to be
filled with vapor only. On cooling down again a mist suddenly appears about the middle
of the apparently empty space and spreads rapidly throughout the whole interior and sud-
denly vanishes, leaving the lower part of the tube filled with liquid. The critical tempera-
ture of water is 689° Fahr.; ammonia, 266°; carbon dioxide, 88°; air, — ^220°; oxygen, — 182°;
hydrogen, — 389°-

1,782

FROM ICE TO STEAM

Ques. How is a change of state effected ?

Ans. By a transfer of heat to or from the substances, accord-
ing as the change of state is from a solid to a liquid or gas, or from
a gas to a liquid or solid, respectively.

Ques. Is the temperature of the substance raised or
lowered during a change of state?

Ans. No.

VACUUM (NSIOE

riii'iii (li""iiiiil»" nil) '"'llu

Fig. 3,311. — Leslie's experiment showing water freezing as it boils. A small pan containing some
water is placed over a dish filled with sulphuric acid, and the air removed with an air pump.
On removal of the air the water evaporates rapidly and begins to boil, being greatly facili-
tated by the sulphuric acid which absorbs the vapor almost as rapidly as formed. The
temperature of the water is quickly reduced and it finally solidifies, thus the liquid is frozen
while in the act of boiling.

Owes. What is fusion?

Ans. The term * 'fusion** signifies the change of state of a sub-
stance from the solid form to the liquid form. This is popularly
known as melting.

FROM ICE TO STEAM

1,783

Oues. Describe the fusion of one pound of ice.

Ans. If heat be applied to the ice it will gradually melt, but
during the melting process the temperature will remain un-
changed.

Oues. What is the heat called which is required to
melt the ice?

Ans. The latent heat of fusion.

Fig. 3,312 — Experiment illustrating the effect of pressure on tl;e meltingfpoint. A very strong
cylinder fitted with a screw at one end is filled with water and the latter frozen. A metal
ball is placed on top and the cylinder closed by water. The cylinder is then covered with
ice and pressure applied by the screw. The effect of the pressure is to lower the freezmg
point causing the ice to melt within the cylinder, thus permitting the ball to drop to the
bottom. On opening the cylinder, thus reducing the pressure within, the water again
freezes, this re-freezing being known as regelation. By removing the lower cap the ball is
found at the bottom of the cylinder.

The latent heat of fusion may be defined as the heat required inB. t,u.
to convert one pound of a substance from the solid to the liquid state
without change of temperature.

Oues. How much heat is required to melt one pound
of ice at 32°?

Ans. 143.57 heat units.

1,784

FROM ICE TO STEAM

Professor Wood considers 144 heat units {Bj,u.) as the most reliable
value for the latent heat of fusion of ice. Pearson gives 142.65. The
United States Bureau of Standards (1915) gives it as 143.57 Bj.u.

Ques. What name is given to the temperature at which
fusion takes place?

Ans. The melting point.

Ques. Upon what does the melting point depend?

Ans. Upon the pressure.

.^x^

Fig. 3,313. — Familiar operation of making a snowball illustrating regelation. When the snow-
is packed together with the hands, the pressure thus applied lowers the freezing point
and some of the snow melts. On removing the pressure the water formed re-freezes, that is
regelation takes place and the ice firmly binds together the "ball." When the snow is too
cold it will not bind unless very heavy pressure be applied.

Ice melts at 32° P. at ordinary atmospheric pressure, and water freezes
at the same temperature. At higher pressiires the melting point of ice,
or the freezing point of water, is lower, being at the rate of .0133** F.
for each additional atmosphere of pressure.

The lowering of the freezing point of water by pressure or, as it may be
put, the melting of ice under pressure explains many phenomena which
would otherwise be very puzzling. The melting of ice under pressure, and
re-solidification when the pressure is removed, presents itself in many

FROM ICE TO STEAM 1,785.

ordinary occurrences, for instance, the wheel track of a heavy cart in snow
is generally sheeted with a plate of clear ice. The snow, if not too cold,
melts, or partially melts under pressure of the wheel and solidifies again
into transparent ice as soon as the pressure is removed.

The same process takes place in the making of a snowball. If the snow
be near the melting point, the pressure of the hand is sufficient to squeeze
it into a compact partially solidified mass. When the snow is squeezed
between the hands, melting occurs at the points of greatest pressure, and
solidification follows as soon as the resulting liquid is relieved of the pressure.

If the snow be much below the freezing point , however, the pressure of the
hand will not be sufficiently great, and the ball will not "make."

Surf usion. — Some liquids are in an unstable condition at the
freezing point; that is, a liquid which crystallizes in solidifying,
may be carefully and slowly cooled, be reduced to a temperature
much below the freezing point, without solidification taking
place .

If the over cooled liquid be disturbed, or a small piece of the crystalized
solid be placed in contact with it, solidification at once sets in and continues
until the temperature rises to the normal freezing point. This peculiar
behavior which was discovered by Fahrenheit in 1724, is called ''sur-
f usion;" he found that a glass bulb filled with water and hermetically
sealed, remained at a temperature considerably below the freezing
point without solidification taking place, but that on breaking off the
stem, solidification rapidly set in.

Oues. What important change takes place during the
melting of ice?

Ans. It decreases in volume.

The relative volume of ice to water at 32° F. is as 1.0855 to 1; that is,
the space occupied by one pound of ice is 8.55 per cent, greater than that
occupied by one pound of water at the same temperature. Specific gravity
of ice = .922, water at 62° F. being 1.

Oues. Why is this change of volume important?

Ans. Because of the precautions which must be taken with
apparatus in which water is used, to prevent damage in case of
freezing when not in use.

1,786 FROM ICE TO STEAM

When water freezes, the increase in volume will take place against almost
any force however great, as exemplified in the bursting of exposed water
pipes in cold weather. Thus, water pipes burst when the temperature is a
few degrees below 32°, although it requires a pressure of about 14,000
pounds per square inch to burst an ordinary pipe.

The Work of Fusion. — In order to change the state of a
substance work must be done, that is to say, a transfer of heat
must take place. As already stated, it requires 143.6 heat
unit€ to melt one pound of ice **from and at 32° F." One heat
unit has been found by experiments to be equivalent to 777.5
foot pounds of energy, and accordingly the work done during
the fusion of the ice is

777.5X143.6 = 111,649 ft. lbs.

that is to say, 111,649 foot pounds is expended in melting one
pound of ice from and at 32° F. This expenditure of energy
consists of

1. The internal work of fusion;

2. The external work of fusion.

The internal work represents the energy expended in chang-
ing the crystalline structure of the solid to that corresponding to
the liquid state, and in amount is equal to the total work of
fusion minus the external work; that is,

internal work = total work — external work

The external work is the work done by the atmosphere
during the change of volume which takes place during fusion.
It is calculated as follows: 1 cubic foot of water at 32° F.
weighs 32.42 pounds, hence the volume of 1 pound of water at
the same temperature = 1,728 ^ 62.42 = 27.68 cubic inches.
Now the voltmie occupied by 1 pound of ice at 32° F. is as

p:^9Ui JO 2m%voo o^qnop b jo Sui:;sisiioo '\oyp'BC j9%'b/a v jo 5[Dijq
9jg Xq J9q:^x9 p9Sopu9 si pnj Suiujuq 9q:^ J9|ioq ui'B9:^s v uj

9srj Xbui uib9:^s pu^ jq^tb/a p9:^B9i{ gq:). q.Bi{q. os pouxpui wb ui9q; Suxda^:^
*S9qnq. }o J9qumu 9q^ 2uis'B9joui uiojj s:^|ns9J :^U9Ui9A6jduij joxi'^jni' y

:^ou St aqn^ aq:^ jo mo;:;oq sq^ jo ajn^Bjaduia'; aq:^ 9[xqM ao^jjus jaddn st^i ^v jioq uoos hiav
j3:^BAi aqx 'tiMoqs sb do:^ aq:^ %v pa:^Baq sx 'pua jaMo^ aq:^ ui paoB^d aoi jo aoaid v SuiABq
ja^BM. p|oo q^TAv pany aqn:^ :^sa:^ V 'Uoi^oaAuoa Aq Anedpuiid ^^Baq saAiaaaj puB 'joionp
-uoo pBq B sx si%v^ -susjtoq ut uojjvjnoxp'fo aouvjjodiui aq:;Moqso:). ^^uatuuadxa — "828*8 'Oi^

aiQO

a21VM 9Nni09

•p9SB9J0UI SI ^%^I
S^l anq *9UIBS dTl% ST UOI^BpOJp 9X1% JO U0i;09Jip 91IX '93S'g *^9 ^i UMOl{S

SB *9uo JO pB9:^sui sdiuBj 99jq:j. pgoB^d 9q*X'Bui ijoiqM q:^'B9U9q *9uipui Suoi
B o:).ui *g 29J ]'B0xq.*J9A p9:;'B9t[ 9qq. 2uipu9:jx9 Aq 9u6p 9q Avui siqx 's^'Bjjns

2m%V9ll 9q:; 9S'B9J0UI O:; Xj'BSS909U si %l *J9:^S'BJ UI'B9:^S 9:;.'BJ9U92 o% J9pJ0 uj

•y UI J9:;'BM ^^']. wem J9;q2i| qoniu si *g ui
uiB9q.s puB J9:).BAV jo 9Jn:jxiui 9qq. sb p9SB9Joui X^:).b9j2 si uoi:;Bjnojp 9q[i ' g ui
uuoj S9jqqnq uib9:^s U91Im IsS9i OfA% d\i% ui J9:^bai 911:; 'u99M:^9q 9jn^BJ9diU9i

UI 90U9J9jgip 9l{:^ UO 2uipU9d9p 9:^BJ S:^I 'XjMO^S SMOU J9:^BA^. 9qq. ^sjy. Vf

HVHIS 01 HDI WOHd

^C8'X

1,802

FROM ICE TO STEAM

At first the water flows slowly, its rate depending on the difference in
temperature between the water in the two legs; when steam bubbles form
in B , the circulation is greatly increased as the mixture of water and steam
in B, is much lighter than the water in A.

In order to generate steam faster, it is necessary to increase the heating
surface. This may be done by extending the heated vertical leg B, into a
long incline, beneath which may be placed three lamps instead of one, as
shown in fig. 3,325. The direction of the circulation is the same, but its
rate is increased.

BOILING WATER

COLD
WATER

Fig. 3,323. — Experiment to show the importance of circulation in boilers. Water is a bad con-
ductor, and receives heat principally by convection. A test tube filled with cold water
having a piece of ice placed in the lower end, is heated at the top as shown. The water
will soon boil at its upper surface while the temperature of the bottom of the tube is not
appreciably changed.

A further improvement results from increasing the number of tubes,
keeping them all inclined so that the heated water and steam may rise
freely, as shown in fig. 3,326.

In a steam boiler the burning fuel is enclosed either by fire
brick or a water jacket consisting of a double coating of metal

^^ ^I *^ oSC ^'^ ^^} P punod X ^q paidnooo 9uin|0A ^^'x moj^
•s9qoux oiqno ^g- iz = S^'SO ^ 8SZ'l = 9JmBJ9din9:; 9iubs 9i:[:^
:^'B J9:^'BM p punod x Jo 9uin[OA 9i[q. 90U9q 'spunod ^^'^g sqSpM
*iJ oS8 ^^ J9:;ba\ jo :^ooj oiqno x ismo^oj sb p9:^H[uo|H9 sx :n
•uoisnj Suunp 90^1^ S9:^'e']. qoiqM 9mnpA jo 92ubi:[0 0x1% Suunp
9J9qdsoui:^B 9q!; Aq 9uop :>^jom 9q:; si ^^(9/?2 ivuxd^xd atjj^

'sx '\'e\i'^ !>[joM |BUJ9:;x9 9qq. siiuxin uoxsnj
JO ^^JOM ^^(^o:^ 9q:; o:^ ^'Bnb9 sx ^^utxoui'b ux puB *9:^b:^s pxnbxy 9q:^
o:^ 2uxpuods9jJoo :^'Bqq. o:^ PIP^ ^^^ J^ 9jtx:^oxu:^s 9ux^b:^s^jo 9qq. Sui
'^wevp ui p9pu9dx8 A2j9U9 9q:; s:^u9S9jd9J ^^0^ pu^a;ut di{X

•uoxsTXj JO 5fJOM |'BUJ9q.x9 9qx *2
fuoxsnj JO :>[JOM yBUJ9:;ux 9qx "X

JO s:^sxsuoo
X2j9u9 jo 0Jn^xpu9dx9 sxqx 'd[ o2C ^"^ P^'^ uiojj 9ox jo punod
9UO 2up|9tu ux p9pu9dx9 SX spunod ^ooj 6'^9'TIX '-^^^ 0% sx c^-eq:;

•sqi -^^J 6^9*1X1 = 9-g=^IX9ZZZ

sx 90X 9q:^ jo uoxsnj 9q;
Suunp 9uop :5[joAv 9q:^ A^SuxpjoooB pu'B 'A2j9U9 jo spunod :^ooj
9' ILL o^ ;u9|'BAxnb9 9q o:^ s:^U9uixj9dx9 Xq punoj U99q s^q i^xun
;'B9q 9U0 ii'^ oZ2V^ V^'^ "^ojj,, 9ox jo punod 9uo :^pui 0% w\WLXi
:^B9q g-g^x S9Jxnb9J :^x 'p9:^'B:^s XpB9j^'B sy •90B^d ^:\^% :^snm
:^^9q JO j9jsu'bj:^ b 'X-bs o:; sx a'Bq:^ '9uop 9q :^snxu 5[jom 90UB:^sqns
'B JO 9:^b:^s 9q:^ oSu-Bqa o:^ J9pjo uj— -uoTsnj jo ^JJOAV ^HX

•sdid Xj-Buipjo u'B ;sjnq o:^ qoui aj'Btibs jad spunod
000*^1 ;noq^ jo 9jnss9Jd ^ S9Jmb9j :^i qSnoqr^jB ^ggMopq S99jg9p Ai9j
"B SI 9jn:;^J9dui9:^ 9q:^ u9qM ;sjnq S9dxd j9:;bm *snqx •J9ti^'B9M pjoo ux S9dxd
J9;bm p9sodx9 JO 2ux;sjnq 9q!; ux p9gx[dm9X9 sb *:^'B9j2 J9A9Moq 90j6j Aub
;soui]B ;sure2B 90B]d 931'b:^ hF^ 9uih|0A iix gs^joux 9q:^ 's9Z99jj j9:^BAi u^^^

HVHIS 01 HDI NONd 9SL'l

1,800

FROM ICE TO STEAM

the center. This is due to the water being heated most at the
sides, causing it to expand and become lighter. Consequently,
it rises and on reaching the surface is cooled somewhat, which
causes it to contract, and becoming denser it naturally sinks.

The formation of steam takes place in the water directly in
contact with the pot, especially in the lower part where the tem-
perature of the metal is highest.

In the formation of steam, a particle of water in contact with the metal
is heated until it is changed into steam, first appearing as a small bubble,

v("^-

Fig. 3,321. — Circulation of water in boiling. The lower and outer layers are first warmed.
These expand, and becoming less dense, rise to the surface, their place being taken by the
colder and denser layers thus producing convection currents as indicated by the arrows.

which for a time clings to the metal. The size of the bubble gradually
increases by the addition of more steam, formed from the surrounding
water until finally it disengages itself from the. metal. Since it is much
lighter than the water, it quickly rises and bursts on reaching the surface,
allowing the steam to escape into the atmosphere.

In fig. 3,321 the natural circulation of the water with a moderate fire is
up aroimd the sides of the vessel and down in the central part. If the fire
be very hot, steam bubbles will rise from all points at the bottom in such
quantities as to impede the downward flow of the water, in which case the
pot "boils over." This may be prevented if a vessel of somewhat smaller
diameter with a hole in the bottom, be lowered into the pot as shown in

FROM ICE TO STEAM

1,801

fig. 3,322, fastened in such a manner so as to leave a space all around be-
tween it and the pot. The upward currents are then separated from the
downward, and the fire can be forced to a greater extent than before
without boiling over. This simple arrangement is the basis of many
devices for securing free circulation of the water in steam boilers.

The importance of a free circulation is, among other things, to maintain
the boiler at a uniform temperature, so as to prevent unequal expansion in
its various parts, especially in boilers having thick plates, and also to
facilitate the escape of steam from the heating surface as soon as it is
formed.

This is necessary to prevent overheating of the plates, which would occur
unless they be maintained in constant contact with the water.

Fig. 3,322. — ^Why a pot "boils over." A heavy fire applied to the arrangement shown in fig.
3,321 will cause violent agitation at the surface by the unguidcd currents. If an inner vessel
with openings at bottom and top be inserted in the pot, as here shown, it will act as a guide
and separate the ascending and descending currents; the water then will boil more smoothly.

The principle of circulation as applied to the steam boiler is
shown more clearly in fig. 3.324.

A U-shaped tube is connected to a vessel and filled with water. Heat
is applied to one leg, B, and as the water in this leg is warmed, it expands
and hence becomes lighter.

The heavier water in A, consequently sinks and forces the less dense
water in B, up into the vessel at the top. A circulation or flow of water is
thus produced as indicated by the arrows.

1,798

FROM ICE TO STEAM

It should be noted that the sensible heat is said to be in the water and the
total heat in the steam.

The Boiling Point. — Water in an open vessel boils at a tem-
perature of 212° F. when the barometer reads 30 inches. Now,
if the vessel be closed, and the supply of heat be continued,
the pressure of the steam will gradually rise, and the tempera-
ture of the liquid also; that is to say, the boiling point is

i7o.i:

Figs. 3,319 and 3,320. — The boiling point. The temperature at which water boils depends'
upon the pressure. Thus, at atmospheric pressure as in fig. 3 ,319, water boils at 212° Fahr.,
but under say a 17.7 inch vacuum (at 6 pounds absolute pressure) it boils at 170.1°.

elevated above 212° when the pressure is increased above
14.7 pounds, there being a definite temperature or boiling point
corresponding to each value of pressure; in other words, there
is one temperature only for steam at any given pressure; at
any other pressure, the temperature has some other value, but
always fixed for that particular pressure. .

FROM ICE TO STEAM 1,799

Oues. When vaporization takes place in a closed vesoel
what happens if the temperature rise ?

Ans. The pressure rises until equilibrium between tempera-
ture and pressure is re-established.

Ones. If the temperature be lowered, what happens?

Ans. Condensation takes place and the pressure decreases
until equilibrium is re-established between temperature and
pressure.

Ques. What is condensation?

Ans. The change of state of a substance from the gaseous to
the liquid form.

Oues. What causes condensation?

Ans. A reduction of temperature below that corresponding
to the pressure.

Oues. What happens when steam condenses?

Ans. The water from which the steam was formed originally
contained a small percentage of air mechanically mixed with it,
and this air does not re-combine with the water of condensation,
but remains liberated — in the case of a steam heating plant in
the pipes.

Thus the necessity for air relief valves . Again in the case of a condensing
engine, the liberated air must be removed from the condenser in addition
to the condensate to maintain a vacuum.

How a Boiler Makes Steam. — If a pot filled with water, be
placed on an open fire , as shown in fig . 3 ,321 , it will be noticed when
it boils that the water heaves up at the sides and plunges down in

1,796

FROM ICE TO STEAM

STAGE 3

• •*."•

yo'e'

t":'r>::::CM,

•'•. .'*

♦ • *^.

.:.'■: MCM.

*' •'.* V

^:;jp

• V'V-

■;•.•.<

■•■-■■:'§

■••z-

-UJ

>:Q.:

|;»

'..'Ul

.••:q-

•.••2.:

. . Id

■ o-

•.•:':|-

, ' •'.

:•;.-<

*.*••'.*.

:•; a:=

• *•. * • •

■ •■••D

.*,•• '.'•

•.:-.-.H

•*'.*••

r.;s(

* • *. •* •

...:,co

A n

to

<

2

>

O

z
o

21

uJ

>

o

Z

o

a.

-J
<

<

Fig. 3,S18.—Stage 3: the external latent heat, or
heat converted into work by the steam in
making room for itself against the pressure
of the superincumbent atmosphere. The
author does not agree with the generally ac-
cepted calculation for the external work of
vaporization, and holds that it is wrong in
principle. The common method of calcu-
lating this work is to consider the movement
of the piston equal to the distance between the
bottom of the cylinder and the piston or 26.79
feet which would give for the external work

144X14.7X26.79 =56,709.07 ft. lbs.

Motion is purely a relative matter, and ac-
cordingly something must be regarded as being
stationary as a basis for defining motion, hence
the question: Should the movement of the piston
be referred to a stationary water level or to a
receding water level? The author holds that
the movement of the piston referred to a
stationary water level gives the true displace-
ment of the air and is accordingly the proper
basis for calculating the external work. It must
be evident that since the water already existed
at the beginning of vaporization, the atmos-
phere was already displaced to the extent of the
volume occupied by the water, and therefore
this displacement must not be considered as
contributing to_ the external work done by the
steam during its formation. Calculating on
this basis, the external work equals

144X14.7X26.7733 =56,673.72 ft. lbs.

being less than the amount as ordinarily calcu-
lated by

56,709.07 -56,673.72=35.35 ft. lbs.

The amount of error (35.35 ft. lbs.) of the
common calculation, though very small, is an
appreciable amount, especially when expressed
in foot pounds. Its equivalent in heat units is:

35 .35 -^ 777 .52 = .0455 B.t.u.

and the thermal equivalent of the external

work is:

56,673.72 -r 777 .52 =72.89 B.t.u.

FROM ICE TO STEAM 1,797

Now, the volume of one pound of water at 212° (atmospheric pressure)
is 28.88 cubic inches, and, if this water be placed in a long cylinder, as in
fig. 3,317, having a cross sectional area of 144 square inches, it will occupy
a depth of .2 inch or .0167 foot. If a piston (assumed to have no weight
and to move without friction) be placed on top of the water, as in fig.
3,317 and heat be applied, vaporization will begin, and when all the water
has changed into saturated steam, the volume has increased to 26.79
cubic feet, as in fig. 3,318, that is to say, the volume of one pound of
saturated steam at atmospheric pressure is 26.79 cubic feet.

Since the area of the piston is 1 square foot , the linear distance from the
bottom of the cylinder to the piston is 26.79 feet, hut the piston has not
moved this distance. The initial position of the piston being .0167 foot
above the bottom of the cylinder, its actual movement is 26.79 — ■ .0167 =
26.7733 feet.

Accordingly, the external work done by the steam in moving the piston
against the pressure of the atmosphere to make room for itself is,

=area piston X pressure of atmosphere X movement of piston = external work
144sq.ins.X 14.7 lbs. X 26.7733 ft. =56,673.72 ft. lbs.

The Total Heat of Saturated Steam. — In transforming one
pound of water into saturated steam at atmospheric pressure the
amount of heat to be supplied, as already shown, may be tabu-
lated as follows:

Stage 1. — The sensible heat required to raise the temperature

of the water to the boiling point •. 180 B.t.u.

Stage 2. — The internal latent heat absorbed by the water at

212° before a change of state takes place 897.51 " " "

Stage 3, — The external latent heat required for the work to

be done on the atmosphere 72.89 " " "

1,150.4

U ti u

The sum of these three items, is known as the total heat above
2° F., this temperature being taken as the starting point.

Expressed as an equation.
Sensible heat + internal latent heat + external latent heat = total heat
180 + . 897.51 + 72.89 =l,150.4B./.«.

1,794

FROM ICE TO STEAM

STAGE 2

unit may be expressed by the mechanical
equivalent (778 foot pounds) the sensible
heat, or

180 heat units = 180X778 = 140,040 ft. lbs.

STAGE 2— The Latent Heat.— Stages 2
and 3, as given above, comprise the work
corresponding to the latent heat of steam ^ of
which stage 2 is the internal latent heat and
stage 3 the external latent heat.

The Internal Latent Heat.— To under-
stand just what the internal latent heat is,
consider a pound of water at a temperature
of 212° throughout; suppose the water to
be in a beaker and placed over the flame of
a bunsen burner.

The heat now being added to the water
will cause small bubbles of steam to form on
the heating surface, and since these are
formed at a pressure a little greater than
that of the atmosphere (because of the head
of water) the temperature of the steam thus
formed is a little higher than that of the
water.

Each bubble first appears as a very
minute globule, which expands until its
buoyancy overcomes the tension with the
heating surface, when it detaches itself.

Fig. 3,317. — Stage 2; the internal latent heat, or the amount of heat which must be given to
the water at 212° before steam begins to form.

H

<

u

z

o

ul

z

CC.

2i

bJ

b

«*:2

<
-J

^l

-J.

ZbJ

3h:

<

t__ ^

Z

^^

a.

^£

u

1-
z

1^

•■»

a>

00

UJ

z

H

FROM ICE TO STEAM 1,795

During its upward course toward the surface of the water,
the lesser temperature of the water causes it to condense and in
so doing it gives up its latent heat to the mass of water.

This process continues until the water has absorbed 897.6 heat units,
at which time the bubbles of steam begin to break through the surface of
the water and detach themselves therefrom. Up to this point, as stated,
the water has absorbed 897.6 heat units at 212°, known as the internal
latent heat, which is represented in work as

897.6 X 778 = 698,332.8 ft. lbs.

It should be noted at this point , that it requires

698,332.8 ^ 140,040 = 4.96

times as much work or its equivalent in heat units to bring water at 212*
to the critical point where vaporization begins, as it does to heat it from
32 to 212°.

The External Latent Heat. — When vaporization begins,
that is to say, when the liquid has received sufficient heat so
that the steam bubbles formed on the heating surface are able
to reach the upper surface and discharge the contained steam,
work is done in pushing back the atmosphere against its pressure
to make room for the steam. In order to do this work, each
steam bubble must contain a corresponding amount of heat,
which is known as the external latent heat as distinguished from
the internal latent heat.

The work done by the steam in making room for itself against the
pressure of the superincumbent atmosphere (or steam if enclosed in a
vessel) is called the external work of vaporization.

In order to determine the value of the external latent heat, it is necessary
to compute the external work of vaporization, from which the external
latent heat is easily found by means of the mechanical equivalent of heat .

The External Work of Vaporization. — In the formation of
steam, external work must be done in pushing away the atmos-
phere, which exerts a pressure of 14.7 pounds per square inch
upon the water, to make room for the steam.

1,792

FROM ICE TO STEAM

and their sudden collapse sets up vibration in the water which is
communicated to the metal of the containing vessel, causing the
familiar "singing" heard at this stage, and the steam which
composes the bubbles gives up its latent heat, thus warming the
water until the whole mass is at the boiling point .

Fig. 3,315. — The phenomena of vaporization or process of boiling as described in the ac
companying text.

When this stage is reached the steam rises to the surface and escapes
into the atmosphere and the "singing" ceases, that is to say, the water is
boiling,

Oues. Why is the temperature of the steam bubbles,
as they form on the heatmg surface, slightly above 212° F. ?

Ans. Because the pressure at the bottom of the vessel is

FROM ICE TO STEAM

1,793

STAGE 1

greater than the atmospheric pressure, being
equal to the latter plus the pressure due to
the head of water in the boiler.

The Work of Vaporization. — The

amount of work that is done in making one
pound of steam at atmospheric pressure from
one pound of water at a temperature of 32**
F. may be divided into three separate and
distinct stages.

STAGE 1. — The work to raise the tempera-
ture of the water from 32° to 212°.

STAGE 2. — The work required to bring
the water to the point of vaporization.

STAGE 3. — The work required to make room
for the steam against the pressure of the atmos^
phere or surrounding medium.

STAGE 1— The Sensible Heat.— In stage
1 of the preceding paragraph, the work re-
quired to raise the temperature from 32° to
212° is represented by

212^— 32° = 180°, or 180 heat units.

since the amount of water is one pound.
This is called the sensible heat, as dis-
tinguished from the latent heat, because it
is recorded by a thermometer, and is, there-
fore, sensible to the touch. Since a heat

Fig. 3,316. — STAGE 1; the sensible heat. To raise the temperature from 32° to 212° requires
212-32 = 180 heat units.

Hi

3:

»-

idSr

<oZ

<9

!5

o oi

liJ

Z

coo-J

H-Jtio

Ui

<9EcQ

-t

a: ^uJ

ffl

luar

i-i*Jh

(fl

^^o

z

^3^

bJ

u. f^y

(/)

Om^

LU

Z

H

11 lij

CM a.

COS

1 u

cviH

CM

J

P

^-

^:S£

^#1

1,790 FROM ICE TO STEAM

Oues, What is superheated steam?

Ans. Steam having a temperature higher than that corre-
sponding to its pressure.

Owes. What is gaseous steam, or steam gas?

Ans. An objectionable term for highly superheated steam.

The Formation of Steam. — When heat is transferred to
water, at its point of maximum density, it expands as before
stated, and continues to do so as the temperature rises until a
point is reached where there is no further rise of temperature.
This is the temperature at which a second change of state takes
place; that is to say, the original pound of ice, which has already
been changed into water, is now changed into a pound (weight
not pressure) of steam. The temperature at which this change
takes place is called the boiling point,

Ques. Upon what does the boiling point depend?

Ans. Upon the pressure.

Ques. What is the boiling point of water at atmos-
pheric pressure.

Ans. 212° F.

Corresponding to 14.7 lbs. absolute pressure, or 29.92 inches of mercury
{Marks and Davis) .

Ques. What is the pressure of the atmosphere at sea
level?

Ans. 14.75 pounds referred to a 30-inch barometer.

Ques. How does the pressure of the atmosphere vary?

Ans. With the elevation, temperature and humidity.

When the barometer reads 30 inches at sea level, the pressure of the air
is 14.75 pounds per square inch; at M of a mile above sea level it is 14.02

FROM ICE TO STEAM 1,791

pounds; at K mile, 13.33; at % mile, 12.66; at 1 mile, 12.02; at IM mile,
11.42; at 1^ mile, 10.88; and at 2 miles, 9.8 pounds per square inch.

Latent Heat. — When water at atmospheric pressure has been
heated to 212° F., no further expansion takes place while it is in
the liquid state, although the supply of heat be continued.
Moreover, its temperature remains stationary, and considerable
heat must be added to the liquid to transform it into steam, this
is known as the latent heat of vaporization y and may be defined
as the amount of heat necessary to convert one pound of the liquid
at the boiling point into saturated steam of the same temperature.

Vaporization. — This is the change of state of a substance
from the liquid to the gaseous form, which takes place throughout
the mass of the liquid.

Oues. How is the vapor formed?

Ans. Both by evaporation and by boiling.

In the first instance, the change takes place at the surface of the liquid
only, and in the second instance, it proceeds over the heating surface.

Oues. Describe in detail the process of boiling.

Ans. When heat is applied to a liquid such as a quantity of
water in a boiler, the lower layers are first warmed. These
expand and rise to the top, their place being taken by the colder
layers from above, and by this process the mass is warmed
through. The air which is contained in the water expands as
the temperature is raised , and rises to the top . The temperature
of the lower layers in time becomes raised up to slightly above
the atmospheric boiling point, 212° F., and steam is formed,
as bubbles adhering to the heating surface; these bubbles, by expan-
sion, become large enough to detach themselves and rise into the
colder layers above . On reaching the colder layers , they condense

1,788 FROM ICE TO STEAM

done by the atmosphere, or the external work of fusion = (2.387
"-M2) X 14.7 = 2.92 foot pounds.

The internal work = total work — external work = 111,649 —
2.92 = 111,646.08 foot pounds.

Summary — Fusion of one pound of ice from and at 32° F.
Total work of fusion = 777.5X143.6=111,649 ft. lbs.

External work of fusion = (2.387 ^ 12) 14.7 = 2.92 ft. lbs.

Internal work of fusion = 111,646 — 2.92 = 111,649.08 ft. lbs.

Contraction and Expansion of the Liquid. — If additional
heat be applied to the pound of ice which has just been trans-
formed into water at 32° F. its volume will contract until the
temperature has been raised to 39 . 1 ° F .

Ones. What is this point called?

Ans. The point of maximum density.

Ones. What should be noted about this point?

Ans. Water at its point of maximum density (39.1° F.) will
expand as heat is added, and it will also expand slightly as the
temperature falls frona this point.

Oues. How does the water behave on increasing its
temperature above 39.1°?

Ans. It expands as its temperature is raised.

Ones. What is the point of least density?

Ans. The temperature at which steam begins to form.

*NOTE. — These figures show that the external work of fusion is extremely small as com-
pared with the internal work. It should be remembered that in fusion the external work
represents an amount of work done by the atmosphere on the substance undergoing a change of
state, and should be noted that this is just the opposite to what happens in evaporation, in
which case, the external work of evaporation, as will be shown later, represents, an amount
of work done by the substance undergoing a change of state upon the atmosphere.

FROM ICE TO STEAM 1,789

STEAM

The average person has a very vague idea of the meaning

of the word steam. It may be defined as the vapor of water;

the hot invisible vapor given off by water at its boiling point.

The visible white cloud popularly known as steam is not steam,

hut a collection of fine watery particles , formed by the condensation

of steam.

It is important that those who install, or have charge of boilers, should
have some knowledge of the nature of steam, its formation and behavior
under various conditions. This knowledge should be possessed not only
that the plant may be intelligently installed and properly operated, but the
person thus engaged should be sufficiently interested in his occupation that
he be desirous of knowing all about the important medium he has to deal
with.

There are several kinds of steam:

1. Wet steam.

2. Saturated or dry steam.

3. Superheated steam, sometimes called gaseous or steam gas.

Ones. What is wet steam?

Ans. Steam of a temperature corresponding to its pressure
and having intermingled mist or spray.

Oues. What is saturated steam?

Ans. Steam having a temperature corresponding to its pressure.

Oues. What is dry steam?

Ans. Saturated steam, or superheated steam.

The term dry steam is commonly used as the opposite to wet steam,
the term is objectionable in that it does not fully define.

•uoi%TS\noj\o
pid^j S9snB0 'a u^ uuiniOD S9%vja oqi jo it:^TSU9p sq; Suis^gjoap Ait^^9j3 'S9^qqnq uI■B9:^s aq;
90U9U 'v ^Snojqa 3uTdBos9 S9iqqnq m^n^ Au-e s:^u9A9Jd 'ig; }o uonxsod pauipui aqx 'Q ^c[xi%
aioif^n 9tn ui dn puB 'y ^q^^ aioy:uaiop 9q; ui uMop SMoy j9;bm J9p|oo 9q:^ 'uotfouado uj
•sjapoq aqn:^ ja^BM ui so%via jo uo^Bpojio SuiuiB^qo jo poq:^9ui ^qu:^ pawpux — 'fiSS'S *Old

•SA^ojJB 911:; Xq pg^^Boipui s« 9;B|nDjp o:; j9:;bm qx\% Smsn^D snq:; 'y ,.Moy UMop,, 9q:; ui j9;bav
j9iAB9q puB J9p|oo 9q:; .^q p90B|ds'Tp ST 9su9p SS9J S'uTuioo9q puB 'spuBdx9 ^i UI j9:;bav gq:;
*a „J8SW„ JO M^og dn„ ^m o% paiyddB st ^B9q sy 'sj9|Toq ui j9:^ba\ p uot^^bitiojiqI^ — 'fZ2*B '^^d>

/Cq pdtVJ3Ud2 ^vai{ dijt fo ^unoiuv diqvxaptsuoo v Udjtoq fo dUt iux)

eos'T

MVHIS 01 EDI MONd

FROM ICE TO STEAM

1,787

the cylinder to
pressing down
Hence, during

given in fig. 3,314

30.067 cubic
inches, and the
difference in vol-
ume is 30.067 —

27.68 = 2.387
cubic inches; that
is, assuming the
ice to be of a cube
1 square inch in
cross section and
30.067 inches
long, its length
decreases 2.387
inches during
fusion, and the
pressure of the
atmosphere (14.7
pounds per
square inch) has
acted through the
distance, accord-
ingly the work

Fig. 3,314.— The exter-
nal work of fusion.

The volume of 1 pound
of ice at 32 « Fahr. is

30.067 cu. ins., and 1
pound of water at 32°,

27.68 cu. in. Hence, if
placed in a long cylinder
whose cross sectional
area is 1 sq. in., the

— ice and water will fill

. height of 30.067 and 27.68 ins., respectively. Now the pressure of the air
on the ice and water is 14.7 pounds, as represented by the piston and arrows,
fusion of the ice the external work done by the atmosphere is:
(30.067—27.68)

X 14.7 = 2.92 ft. lb

12

qi '%j Z6'z = i-fi X

ST

-pjoooB *oou'B:^sip

SBq (qoui Qj-Bubs
J9d spunod
I'fl) 9J9qdsoui;B
9q:; JO 9jnss9jd
9q:^ puB 'uoisnj:
Suijnp s9qoui

LS2'Z S9S'B9J09p

i:[:^u9| s:^i *2uo];
S9qDui Z,900S

pUB UOip9S SSOJO

m qoui 9j'Bnbs x
9qno "B JO 9q o:^ 90i
OJi']. Suxuinss'B *si
^^'Bqq. !s9i:[0ui oiqno
LS2'Z = 89*ZS
— Z90*08 SI 9mu

-pA UI 90U9J9j^ip

9q:^ pu-B 's9qoui

^iqi^^ Z9008
flS'S •Si;uxu9AiS

(89-ZS— Z90'08)

:si 9Jaqdsom:;B oq^ Xq 9Uop ^^jom jbuj3:^X9 aq:}. 90t 9q:^ jo uoisnj Suijnp '90U9jj
•SMOJJB puB uo:;sTd aq:^ Xq p9!;u9S9Jd9J sb 'spunod I'fi si ja^^BMpuB 9oi 9qi uo UMop 3uTss9jd
JIB aq^ JO 9Jnss9Jd 9q; a\o^ •i^pAi:^09ds9j "sui 89'ZS P^^ Z90'08 P ":^q3i9q o:^ j9puqXo 9q';
tig n!^^ J.d%Te/A puB 9Dt ' *

aq^ '-ui -bs j si "691^
XBuoi:;o9S ssojto asoqAV
oapuqAoSuoi "^ ^^ p9DB^d
ji'9DU9H •ui-no89'ZS
*oS8 *^ J9;bmjo punod
1 puB '-SUI -no ^90-08
s| ^^^^d oS8 i^ 331 P
punod X JO 9uin[OA aqj^
•uoisnj JO moofk jvu

•991 ri7l

ISVl

WVHIS 01 EDI NOHd

FROM ICE TO STEAM

1,803

plates with a space between which is filled with water. On
any type of boiler , a considerable amount of the heat generated by
the fuel is lost.

i^£^i^i^^±^

'Pig. 3,324. — Circulation of water in boilers. As heat is applied to the "up flow" Of **riser'* B,
the water in it expands, and becoming less dense is displaced by the colder and heavier
water in the "down flow" A, thus causing the water to circulate as indicated by the arrows.

•-tA ■■),

Fig. 3,325. — ^Inclined tube method of obtaining circulation of water m water tube boilers.
In operation, the colder water flows down in the down flow tube A, and up m the up flow
tube B . The inclined position of B , prevents any steam bubbles escapmg through A, hence
the steam bubbles, greatly decreasing the density of the water column m B, causes rapid
circulation.

1,804

FROM ICE TO STEAM

r^,". \ s^^L^-^-^lLI B E: RATI NG
TCt^^X;^::;^ SURFACE

PARALUei
CONNECTION

Fig. 3,326. — ^Elementary boiler illustrating parallel connection of the tubes. As constructed ,

■ a boiler contains many up flow tubes B; to divide the water into many small streams and

present considerable heating surface to the fire so as to generate' steam faster. The tubes

are usually inclined 15° to aid the circulation. In the arrangement here shown the tubes

are connected in parallel.

LIBERATING 5URFACL

\\mm\j

v5ERlE5
CONNECTtON

Fig. 3 ,327 . — ^Elementary boiler illustrating aeries connection of the tubes . In the arrangement
the end of one tube is joined to the end of the next, as shown. When thus joined the tubes are
said to be connected in series.

FROM ICE TO STEAM 1,805

Factors of Evaporation. — It takes more coal to generate
steam at high pressure than at low pressures, and accordingly
in the rating of steam boilers some standard of evaporation must
be adopted in order to obtain a true measure of performance.
This involves two items.

1. Temperature of the feed water;

2. Pressure at which the steam is generated.

With respect to the first item, it must be evident that more coal would
be used in generating steam if the feed water were supplied at a low tem-
perature, say 60° F, than at a higher temperature, say 150° F. and no
comparison of the performance of two boilers working under these con-
ditions could be obtained, unless a factor were introduced in the calculation
to allow for the difference in temperature of the feed water. The reason
more heat is required as the pressure of the steam is raised may be less
apparent.

Oues. Why is more coal required to generate steam at
a high pressure than at a low pressure?

Ans. The external work of vaporization is greater.

That is to say, more work is done in the formation of the steam in making
room for itself against a high pressure than against a low pressure.

Oues. How is a standard of vaporization obtained?

Ans. By finding the equivalent vaporization ^'from and at
212'' Fahrr

Oues. What is the meaning of the term *'from and at
212° Fahr.?"

Ans. It signifies the generation of steam at 212° F. from
water at the same temperature.

Ques. Define the term * 'factor of evaporation."

Ans. A factor of evaporation is a quantity which when multi-
plied by the amount of steam generated at a given pressure from

1,806 FROM ICE TO STEAM

water at a given temperature , gives the equivalent evaporation from
and at 212'' Fahr.

Oues. How is the factor of evaporation obtained?

Ans. It is equal to the difference in the heat in the steam at
the pressure generated, and the heat in the water divided by the
latent heat of steam at atmospheric pressure.

Expressed as a formula:

H'-h'

.(1)

in which F = Factor of Evaporation.

if = Heat above 32° Fahr. in the steam at given pressure.
h =Heat above 32° Fahr. in water at given pressure.
H'=Heat above 32° Fahr. in steam at atmospheric pressure.
h'^' =Heat above 32° Fahr. in water at atmospheric pressure.

Formula (1) just given is expressed in the simplest form as

^-97074 * (2)

Here 970.4=^^' -h' =1150.4-180 (see steam table)

Example — What is the factor of evaporation for steam at 200 pounds
pressure when the feed water is delivered to the boiler at a temperature of
ISO ° Fahr . ? From the steam table, the heat H^ in the steam at 200 pounds
pressure = 1,200.2 B.t.u. The heat h, in the feed water above 32° at 150°
Fahr. is 150— 32 = 1185. ^.m. Substituting these values in formula 2

1,199.2-118
^- 970.4 -^-^^^^

The meaning of it is that if a boiler were generating, say 1,000 pounds of
steam per hour at 200 pounds pressure, from feed water at 150° Fahr. it
would absorb the same amount of heat fron; the fire as when generating

1,000X1.1121 =1,112 lbs.

of steam "/row and at 212°'\ that is generating steam at atmospheric
pressure from feed water at 212°.

Oues. How is the calculation of the equivalent evapora-
tion from and at 212° F. facilitated?

FROM ICE TO STEAM

1,807

Ans. By means of a table giving the factors of evaporation
from various pressures and feed water temperatures, such as
is given on page 1,808.

Example. — ^A boiler evaporates 1,000 pounds of steam at 95 pounds
gauge pressure and the feed water is heated to 110**. How much steam
will it evaporate /rom and at 212°?

Referring to the table on page 1,808, the factor of evaporation for
steam at 95 lbs. pressure with feed water at 110°, is 1.145.

95 LBS

,000 L6S. OF 5T£AM
PER HOUR

Fig. 3,328. — Ordinary steam plant illustrating the condition of operation mentioned in the
above example.

If the feed water be heated to 212° and the steam be generated at atmos-
pheric pressure, the boiler will then evaporate

1,000X1.145 = 1,145 lbs. of steam

Saving Due to Heating the Feed Water. — In exhaust stearic
heating installations where only part of the steam from the

1,808

FROM ICE TO STEAM

fc . toMooe>»t' e^t~Mt^M «o-<tOi-i«o oirtoiDO «*<<t>«t«<5>t»< oooooeooo e4t^*Jtoe^ to ^a*

* lo eoMiN<N-H r-iooo505 eooor-t^<o to«ou:!'9<Ti« com(n^^ ooo^woo ooi-t-JbS S55^

40 <N(N<M<NCJ ClC^C^-i.-( r-> -i F-i ^ r-< r-i r-i ^ ^ ri rn ,-.,-. r- ri ri ^S O O O OOOOO OOO

Q

SSggg g212g^ g^55S 'SS^S^^ SS'g^S §S2

f-H-(rH,Hr-« r-^-oli-l r1 i-l r-< rl r1 r-i rt r-l ri M C< M C< <

SSSSg^ SSSSS SSSi:;^ ^^^2:22 JSqSJSi;:? ^S2§2 slo^S 151

Or-C««Oi-i tOt-<tOi-ito 0»no«CO ifOlfWI" OOMOOMOO e^h-<Mr-(M ta^fft—fn <-s.n«A

ISSSS SS^§S SSSSH 2^^^^ S"?^^ Sssii ii|§i iii

a> to •-■ >o o »o o lO o »o <3i»}<<7»i'o> eoooeoooco t^e^i--«^r» i-ito^to^-i iftoirto«n en<«<M

assagj s??s§2 "*^^^ sSs23 J22^'3:q :^22Sg iisii ill

ooirtO'S'O ^ottj<o>^ ooMoo^^oo cir^cir^M corito^co oirto»rto •*o>'«)<o>*< oom-.

PScOCOtNrH ,-.OOa>0» OOQOt-t-tO tOOiOrJ.TJ< «eOJM<M.-. ^ooo^o oot-?SS gSE
(MMe<C>J(N e>l(NC»r-ii-i rH 1-1 ^ r-i r-i ^rH,_i^rH r^ ri r- r- -. r-i r:^ ^^ O O OOOOO S^C

loe^t'^co rHto^to^ irtoooio cs^o»2g; m«moom r-(Mr^(Nt^ .-Oi-ito-H icooo
nenao*^ r-<ooo»OJ ooaoc^t-to ir5u:)'j«»><e<3 coe^eMi-i« oooiOioo oot^r^cSto urK'3<

CMC^C^C^fN e>»<M(N.->^ r-t^'^-><~> rn .-. « rt r-t ,m ,-c -i -■ r-i r-i m o O O OOOOO OOO

• e<5 O •'^ OT "J* o> I* Ci 1" o to 00 w oo o r- e^i t~- c^ t— .HtOi-ito<-i >rtoirtoift OJ'^os'j'Oi Mooto

\fi rfrtOJr-.^ 00050JOO oot-t-toto ioio-a<rjTo eoe^cM^-H oowoiqo ?-^StoSo S'5<-S

W e>»C»C^C>e>» CJC^rHr-jrH r^^,^,-<r^ ^^^,h,-4 r-<^.-J — rH r-jr-jOOO OOOOO OOO

I— 00 « t- e^ t-'c^ r^e^it^ .^to'-'to^ lOOinouj oi'ro>^o> coooeocow t~fot»e><i~- »-itc^

t^C*<fi >-"^ OO050300 OOt-r-tOtO lOlOTfTj-rt C4<NrHriO O Oa 05 00 00 t-t-<OtO«« lO>¥^
CJC^<NMC^ C*C* '-*-*-* ,HrH,-lr^.-; r^.-..-,r-.,-l ,_«^rl.H^ .-"OOOO OOOOO OOO

^

230
227
222
216
211

206
201
196
191
186

ggggs s^^gg

§HS = 2

102
C97
092
087
082

076
071
066
061
056

§11

^^^^^ ^^^^^ ^rH^^^ ,-^--^ ^^^^^ ^^^^^^^^„^^ ^^^

1

1.228
1.225
1.220
1.214
1.209

sssss

g2?2g2S K^yj;???

g?J2::§

%nm%

siS§2

Sis

'-■'- -"^ -^

g §2222 i::^222 22222 Sq:222 SSSoS SoSoo ©So

c«e^c»cie<

woioo^ o>'*0)i'*o> cioonaan t-e^r^c^t~ •-ito-^«o»^ •ooingio o»^o>^o> «go«e
• cicJ'^oo c> OJ 00 00 t- t^totovoui ■^ •«>< CO eo e^ c»i-i^oo oiooooot- otouoiog vrtco

•^t-iNt^ t-< to •-< to <-< »« O lO O »0 OS^O^O!

noooot^ t-toto»ouo «9«»i«eoeoci i-i«ooa

ooirtW'i'OJ -^oitos"* ooeoooMoo «t^Mt-c» <oi-HtOi-ito ouooino •*o>«3<o»«»< «oeo»i
^ ^ X- o o> ci 00 00 1^ t- to to 55 »o 'J" tpcococic^ »-ir-iooo> ^oooot~r- toioini'i' ««co

e>»e>»C^C<-< ,_.^^rtr-> r-"r-i.-i,-<i.H rit-i^i-i»H ri^^^O OOOOO O O C^O O OOO

-<to»^to OUOOiOO ^<3S
o>S«ft'0< •"9'cOMCie^ ^o

30000 OOO

O -< »ft ©' »ft P "S"© "5 0>fO>«5'0» MOOMWCO b-e^r^Mt- »-tO.-itO-< lOCiAO'O 0>1'C<

Sooi* oooot^t-to »oA^"3"W oS(NCMr-i.-i ooggg wgggg g>"S3" <>»e^e^

ajmBjaduidx

■»j<^too«o o«noi«o ^o>^OJg« oQWooeoqp c»t»5?r»M to^to^to 0"0 0»oo i>a>t^
Soo»35a6 o6i>i>toto ic>r»<^eoeo ?S<n-<.-.S ogjojoooo j:r£r5S«SS SSSJSs £?=;=!
eMe;)X<>.4FH ,M^rHi-<»-i i-if-hph^^ ^^^r-i.-i <>40ooo ooooo ooooo ooo

oita^tno «fto>fto«o o>'<»'os^o> nooncon r^Mt-e^t* i-nor-to^ irtomoirt ojm'c*
SaSooS t~t^to*o>a Ti> yi* K eh o* c» rn ,-■ o o o>&>oooot-. t^totoirtuo •^-o'eoMc? ^ -- .-«
S2SS2 Uii-i»->'^-< r-i-<t-i <^. ,-i,-«rt ^rH ooooo ooooo OOOOO ooo

gSSSK 222SSS g????S::i:J 2::§S| iilglligil iiigs sii

iH^^r^rt r^ r^ f-t w4 r-t rH ri ri >.• i-l r^ f-l i-l .-i O OOOOO OOOOO OOOOO OOO

S5SS? §^Ss§ 22SSS S22is iisl| ||||| |li|| §|i

"&??lS§!Sg S?SSge SSSSS S22|g §gg5g ggggg |g|§|J22

FROM ICE TO STEAM , 1,809

engine is used for heating, the unused portion from the engine
and also from the auxiUaries can be used to advantage in heating
the feed water resulting in an approximate saving of 1 per cent,
for each increase of 11° in the temperature of the feed water;
this corresponds to a saving of .0909 per cent, per degree.

The calculation, is made from the following formula:

^ T,f r.

Saving by heating feed water = 77 — r

H—n

in which

iiZ' = total heat in 1 pound of steam at the boiler pressure.

/?= total heat in 1 pound of feed water before entering heater.

/j' = total heat in 1 pound of feed water after passing through heater.

Example. — If the boiler pressure be 80 pounds gauge, initial temperature
of feed water 60°, and final temperature 209° F., what is the saving?
Referring to the Steam Table, the total heat H, above 32° Fahr. in steam
at 80 lbs. gauge is 1,185.4 B.t.u, Substitute the formula:

900 — fin

Example. — What is the saving due to heating the feed water from 60°
to 202°, when the steam pressure is 150 pounds (gauge)?

From the steam table:

Total heat in 1 pound steam at 150 pounds = 1,195
Total heat in 1 pound feed water at 60° = 28.08

also

Heat required to form 1 pound steam 1,166.92

Total heat in 1 pound feed water at 202° = 169.95
Total heat in 1 pound feed water at 60° = 28.08

Heat units saved 141 .87

Since 141.87 heat units are saved, the heat required to generate 1 pound
of steam is

1,166.92-141.87 = 1,025.05

and the percentage is

142.87 4-1,025.05 = 13.84%

1.810

FROM ICE TO STEAM

Superheated Steam. — If a closed vessel containing water
and steam be heated, the pressure of the steam will gradually
rise until all the water has been evaporated. At this point the
further addition of heat will not produce any appreciable in-
crease in pressure but will cause a rise in temperature in which
condition the steam is said to be superheated, hence, superheated
steam is defined as steam heated to a temperature above that due
to its pressure.

Specific Heat of Superfieated Steam, — In Marks & Davis' work the
classical research of Regnault, published in the year 1862, has been con-
sulted.

"Contrary to an assumption sometimes seen in the literature, his work
does not even seem to prove that the specific heat at constant pressure (Cp) of
superheated steam is independent of either the pressure or the temperature,
for he made only four series of experiments, and these were all at atmos-
pheric pressure and covered nearly the same temperature range. He
worked by the method of mixtures, injecting a known weight, first of
slightly superheated steam, and then of highly superheated steam, into a
calorimeter filled with water at room temperature. His computations are
in error because, instead of weighing the cold water in the calorimeter, he
measured it volumetrically in a suitable cast-iron tank. His justification
of this was that although, by reason of the thermal expansion of the water
as compared with that of the tank, there was less water by weight at room
temperature than at 0°C., which was his standard temperature, neverthe-
less, the fact (which he thought to be true at low as well as at high tempera-
tures) , that the specific heat of water increased with the temperature, made
the water in the calorimeter more effective thermally, gram for gram, and
just about made up for neglecting its change of density. But we now know
that at room temperatures the specific heat of water decreases with rising
temperature. His data have, therefore, been recomputed, using his own
value for the expansion coefficient of his sheet iron tanks and modern data f oi
the density and specific heat of water. This slightly reduces each of his
four values of Cp to the following figures:

Temp. Range (C°)

R's Value of Cp

New Value of Cp

Series 1.. .
Series 2...
Series 3...
Series 4...

127.7—231.1
137.7—225.9
124.3—210.4
122.8—216.0

Mean of last three

(.46881)1
.48111
.48080
.47963

(.4655)
.4769
.4736
.4780

.48051

.4762

-From Marks and Davis' Steam Tables,

FROM ICE TO STEAM 1,811

Quality of the Steam. — There is generally more or less
water or moisture carried over in steam from the boiler, depend-
ing on the type, height of the water, and rate at which the boiler
is operated. For comparison, engine and boiler performance
must be reduced to a standard basis of saturated steam, hence
some means is necessary for determining the quality of the steam.
This is done by a device called a calorimeter; there are three
types in general use:

1. The barrel;

2. The throttling;

3. The separating.

The barrel calorimeter was invented by the Alsatian engineer, G. A..
Hine. It is an early form, and though not very accurate, is useful in rough
determinations when there is much water present. With careful operation
it may be relied upon to give results within 2 per cent, of being correct.
An error of ^/lo pound in weighing the combined steam, or an error of
}/2 a degree in "the temperature, will cause an error of over 1 % in the
calculated percentage of moisture.

The throttling calorimeter is most useful and convenient for percentage
of moisture not exceeding 3 per cent.

The separating calorimeter is used when the percentage of moisture is
beyond the range of the throttling type. The calculation with this instru-
ment is quite simple, and tests show the steam discharged from it to be
practically dry.

The Barrel Calorimeter. — This consists of a barrel placed
on weighing scales, as shown in fig. 3,329. The barrel is partly
filled with a certain weight of cold water and its temperature
ascertained. A steam pipe from the boiler is fitted with a valve,
and short length of hose as shown. Steam is blown through the
pipe with hose outside the barrel until thoroughly warmed, when
the hose is suddenly thrust into the water with the valve still
open. An arrangement is fitted to the barrel to stir the water
and so keep the temperature uniform.

1^12

FROM ICE TO STEAM

When the water has reached about 110° the hose is suddenly withdrawn
and the water again weighed.

Then, the heat lost by the steam is

xL-\-w (^3— ts)

and the heat gained by the water is

W (t2-tl)

These two heats must be equal, hence equating and solving for x.

W {U-U)-w (U-U^
x= ^^ .

BARREL ^

Fig. 3,329. — ^The barrel calorimeter. With careful operation results may be obtained within
two per cent of accuracy. The barrel calorimeter is useful in determining the quality of
steam where there is much moisture present.

in the above

X = pounds of dry steam supplied;

w = weight of steam (wet or dry) blown in;

PF = original weight of cold water;

L = latent heat of the steam at given pressure;

ti = temperature of cold water;

t2 = temperature of water after addition of steam;

ta = temperature of the steam.

FROM ICE TO STEAM

1,813

The percentage of moisture = {w—x)-^wy^ 100
Example. — If a barrel or tank contains 200 pounds of water at a tem-
perature of 60° F., and 10 pounds of moist steam be added at a pressure of
85 pounds absolute, thus raising the temperature of the water to 110° F.,
what is the percentage of moisture in the steam? (Latent heat of steam at
85 pounds pressure absolute = 892. Temperature 316 °) .

, = L

Fig .3 ,330 .—Ellison throttling
calorimeter. In principle

its action depends upon the
heat liberated by throttling,
which raises the tempera-
ture of the steam in the cal-
orimeter above that due to its pressure,
the heat liberated being utilized more
or less, according as the steam before
throttling was dry or contained moist-
ure. In construction, the inner cham-
ber, or steam chamber^ is 2 inches in
diameter, 6 inches long. The outer
chamber, or jacket, is 3 inches in di-
ameter and 7 inches long, giving H-inch
space between the chambers .The sampl-
ing nozzles are made in accordance with the form
prescribed by the American Society of Mechanical
Engineers. These nozzles are made of H -inch tub-
ing, closed at the end and perforated with 20 %-
inch holes , equally distributed along and around
their cylindrical surface. Each calorimeter is
packed in a neat case, complete with six sampling
nozzles , one each for 2,3,4,5,6 and 7 inch pipes .
Also valve, thermometer, mercury gauge, dropper
and bottle of mercury. In operation, steam,
entering the sampling pipe , flows to the throttling
plug under full steam pipe pressure without
pockets or up turns in the valve, where it is
throttled into the steam chamber to nearly atmos-
pheric pressure , the throttled steam flowing down
one side and up the other into the exhaust nozzle
at the top, moisture in excess of the throttling
process being separated in the chamber and re-
evaporated by the superheated steam
after a momentary period of excess,
lowering the temperature on the outlet
thermometer in direct proportion,
moisture in excess of both the throttling
and evaporating processes, if any, being
accounted for as separation in the water
glass forming a combined throttling,
separating and evaporating calorimeter
in one chamber, moisture in the up flow falling back and traveling through superheated
steam. The condenser connection is an attachment for connecting the outlet nozzle with
the engine condenser for increasing the evaporating range, steam in the lower regions of
temperature having high capacity for evaporating moisture, 10 pounds below atmosphere
evaporating nearly 2%. It is made of brass, with % in. pipe union, lock nut for nozzle,
copper drain tube with cock for connecting with calorimeter drain, mercury gauge being
replaced with a H in. plug.

__200 (110-60) -10 (316-110)

gc|2~ =8.9 pounds of dry steam

(10-8.9) 4-10X100 = 11 per cent of moisture.

1,814

FROM ICE TO STEAM

The Throttling Calorimeter. — The principle employed in
the throttling calorimeter is that moist steam may be dried and
superheated by throttling, the degree of superheat depending
on the initial condition of the steam, and degree of throttling.
That is, the total 'heat of steam at high pressure is greater than
that at low pressure, and on falling in pressure the excess of heat
is spent in drying, and (if sufficient excess) in superheating the
steam at the lower pressure.

0

SUPPLY

D/SCHARGE

Fig. 3,331. — The throttling calorimeter. Invented in 1888 by Prof. Peabody; its principle of
operation is that moist steam may be dried, and superheated by throttling, the degree of
superheat depending on the condition of the steam before throttling. The range of the
throttling calorimeter is for steam containing from 2 to 3 per cent of moisture.

A throttling calorimeter as shown in fig. 3,331, consists of a chamber
having a reducing tube A, through which the steam enters, a pressure
regulating valve B, thermometer well C, and a cock D, connecting with a
U tube pressure gauge. Steam is throttled through the reducing tube,
which terminates in a He-inch orifice, and enters the chamber. The
pressure here is reduced to nearly that of the atmosphere, but the total
heat in the steam before throttling causes the steam in the chamber to be

FROM ICE TO STEAM 1,815

superheated more or less according to whether the steam before throttHng
was dry or wet. The only observations required are those of the tempera-
ture and pressure of the steam on each side of the orifice.

Example. — The total heat in 1 pound of steam at 100 pounds pressure
absolute is 1,182 B.t.u.y and that in 1 pound of steam at 20 pounds absolute
is 1,151; if the steam were allowed to expand from 100 pounds in the steam
pipe to 20 pounds pressure in vessel C, without doing external work, the
heat units liberated per pound = (1 ,182 — 1 ,151) = 31 , If the steam in vessel
C, be at 20 pounds absolute pressure, its latent heat is 954 units. Weight
of moisture which the excess heat will evaporate will therefore be 31-7-954
= .032 pounds.

If, however, the amount of moisture present were less than this, then the
balance of the excess heat would superheat the remaining steam above its
normal temperature, and the excess would be shown by the thermometer.
In such a case the percentage of moisture may be computed from the
formula given below. If the moisture present be greater than the excess
heat can evaporate, then no superheatmg takes place, and this calorimeter
would not be applicable. It is, however, very accurate within its range;
namely, with steam containing not more than from 2 to 3 per cent, of
moisture, now if:

ti= temperature of steam in main steam-pipe;

t2=temperature in vessel C, into which the steam has been ex-
panded to a lower pressure;
t3 = normal temperature of steam in C, due to its pressure.

then the total heat per pound of steam carried into calorimeter is:

In the calorimeter, the heat in the steam due to its reduced pressure,
when the moisture is just evaporated is:

ha+Ls

and if there be sufficient excess heat to superheat the steam, then the heat
required is

.48 (t2-t3)

Then, hi+xLi=h3+L3+.48 {U-U)

h3-hl+L3+.48 (t2-t3)

or, X = T

The Separating Calorimeter. — For percentages of moisture
beyond the range of the throttling calorimeter, the separating
calorimeter is used, which is simply a separator on a small scale.

1,816

FROM ICE TO STEAM

The construction of the apparatus is shown in fig. 3,332. Steam
from the sampling tube enters the calorimeter through pipe A,
and is discharged downwards into the cup B . The course of the
steam and water is here reversed, with the result that the water
is thrown outward through perforations in the cup and collects

STEAM GAUGE

WATER GAUGE

STPAlvr JACKET

COLLECTING
CHAMBER

ESCAPE ORIFICE

Fig. 3,332. — The separating calorimeter. Invented by Prof. Carpenter; it is used when the
percentages of moisture in the steam is beyond the range of the throttling calorimeter.
The calculations with this instrument are very simple, and tests show the steam discharged
from it to be practically dry.

in the inner chamber C, where it is measured by the gauge
glass D.

The steam passes upward and then downward into the outer chamber,
whence it escapes through a standard orifice E, into the air. The apparatus
is thus jacketed by the escaping steam, which is maintained at a high pres-
sure by the throttUng at E. A gauge at G, shows the pressure of the steam
and the corresponding discharge in pounds per 10 minutes. The calcula-
tions with this instrument are very simple, and tests show the steam dis-
charged from it to be practically dry.

FROM ICE TO STEAM

1,817

^ !r/a >>5 ><I P«^

o ^ O^ (Uf SJ > <i>

a<*^ - 1: ^ ^ o J^ ^

•C"^ c Jj-S <u.S a-^

o g.*^+j "''^ «J O:::^

'^ O c^rC ;3 (U <U rt rj

'.--; <u _, C > o "^
o ^ 0.0 ^ w c -e.o

§1

0)^

s§

o

1—1 ^J
o S

•at

p w

"1 §

>j o
bX)

■2

J=

•O V,

0) O

rH 0)

o o

a

u

:^

(N

ffi

1,818

FROM ICE TO STEAM

The height of the water in the glass D , at the beginning of the test is noted
and marked by the gauge, and the water is again brought to the same level
at the end of the test, by opening cock M, and the amount drained very
carefully weighed. The results may be calculated by the following for-
mula:

W

x = -

and the amount of moisture is

W-\-w

where

l-x

:x:=the quality of the steam, or dryness fraction;
P^= weight of steam discharged through orifice E;
w; = weight in pounds of separated water in C, drained through
cock M.

DIRECTION OF STEIAM FLOW

-^

r-^INCH CALIBRATED NOZZLE.

Fig. 3,337. — Stott and Pigfott sampling nozzle. This was developed due to the lack of experi-
mental data on low pressure steam quality determination. Mr. Pigott says: "The ordinary
standard perforated pipe sampler is absolutely worthless in giving a true sample and it is
vital that the sample be abstracted from the main without changing its direction or velocity
until it is safely within the sample pipe and entirely isolated from the rest of the steam.

12

- 12

'12+1^6 ~ 12.687

= .9459

The moisture then is

1-.9459 = .0541 lb., or 5.41 per cent.

♦NOTE.-;— In connecting a calorimeter, a sampling tube is used, through which a sample
of the steam is taken from the main steam pipe. The usual form of tube is a 3^-inch pipe
extending nearly across the steam pipe, open at the inner end, and perforated with small
holes. The quality of the sarnple of steam will depend somewhat upon the location of these
holes. It is practically impossible according^ to Prof. Jacobus to obtain a true average sample
of the steam flowing in a pipe.

FROM ICE TO STEAM

1,819

Usual Amount of Moisture in Steam Escaping from a
Boiler. — In the common forms of horizontal tubular stationary

boilers, and water tube boilers
with ample horizontal drums,
supplied with water free from
substances likely to cause foam-
ing, the moisture in the steam
usually does not exceed 2%
when not worked above the
rated capacity.

Horizontal tubular boilers without
steam domes should be provided with
a so called dry pipe^ which will de-
liver steam with less moisture.

Vertical tubular boilers with
through tubes will under normal
conditions furnish steam with a
slight degree of superheat, the tube
portion abov§ the water line acting
as a superheater.

SECTION E-F

Fig. 3,330. — Compact form of throttling calorimeter. It consists of two concentric metal
cylinders screwed to a cap containing a thermometer well. The steam pressure is measured
by a gauge placed in the supply pipe or other convenient location. Stearti passes through
the orifice A, and expands to atmospheric pressure, its temperature at this pressure being
measured by a thermometer placed in the cup C. To prevent as far as possible radiation
losses, the annular space between the two cylinders is used as a jacket, steam being supplied
to this space through the hole B. The limits of moisture within which the throttling calo-
rimeter will work are, at sea level, from 2.88 per cent at 50 pounds gauge pressure and 7.17
per cent moisture at 250 pounds pressure.

NOTE. — "The throttling steam calorimeter, first described by Professor Peabody, in
the Transactions, vol. x., page 327, and its modifications by Mr. Barrus, vol. xi., page 790;
vol. xvii., page 617; and by Professor Carpenter, vol. xii., page 840; also the separating calo-
rimeter designed by Professor Carpenter, vol. xvii., page 608; which instruments are used to
determine the moisture existing in a small sample of steam taken from the steam pipe, give
results, when properly handled, which may be accepted as accurate within .5 per cent (this
percentage being computed on the total quantity of the steam) for the sample taken. The
possible error of .5 per cent is the aggregate of the probable error of careful observation and of
the errors due to inaccuracy of the pressure gauges and thermometers, to radiation, and, in
the case of the throttling calorimeter, to the possible inaccuracy of the figure .48 for the specific
heat of superheated steam, in the pipe from which the sample is taken. The practical impossi-
bility of obtaining an accurate sample, especially when the percentage of moisture exceeds
two or three per cent, is shown in the two papers by Professor Jacobus in Transactions ^ vol.
xvi., pages 448, 1,017. _ In trials of the ordinary forms of horizontal shell and of water tube
boilers, m which there is a large disengaging surface, when the water level is carried at least
10 inches below the level of the steam outlet and when the water is not of a character to cause
foaming, and when in the case of water tube boilers the steam outlet is placed in the rear of the
middle of the length of the water drum, the maximum quantity of moisture in the steam rarely,
if ever, exceeds two per cent." — Kent.

1,820

FROM ICE TO STEAM

Sampling Nozzle. — The principle source of error in steam
calorimeter determinations is the failure to obtain an average
sample of the steam delivered by the boiler and it is extremely
doubtful whether such a sample is ever obtained. The two
governing features in the obtaining of such a sample are the type
of sampling nozzle used and its location.

BUTTONHEIAD 80LT5
HtXAGONAL NUTS-A^^g-.^

USE Vs" GASKETS

BETWEEN

FLANGES

5/W 01 A. HOLE

SOLDER HIGH

PRESSURE,
PACKING

'>Sfo" VULCAN IZ
FIBER WASHERS

Fig. 3,339 — Orifice plate for throttling calorimeter.

BRASS
PLATE

\ ASBESTOS
PACKING

The American Society of Mechanical Engineers recommends a sampling
nozzle made of one-half inch iron pipe closed at the inner end and the in-
terior portion perforated with not less than twenty one-eighth inch holes
equally distributed from end to end and preferably drilled in irregular or
spiral rows, with the first hole not less than one-half inch from the wall of
the pipe. Many engineers object to the use of a perforated sampling nipple
because it ordinarily indicates a higher percentage of moisture than is actu-
ally present in the steam. This is due to the fact that if the perforations
come close to the inner surface of the pipe, the moisture, which in many
instances clings to this surface, will flow into the calorimeter and cause a
large error. Where a perforated nipple is used, in general, it may be safe
that the perforations should be at least one inch from the inner pipe surface.

A sampling nipple, open at the inner end and unperf orated, undoubtedly
gives as accurate a measure as can be obtained of the moisture in the steam
passing that end. It would appear that a satisfactory method of obtaining
an average sample of the steam would result from the use of an open end
unperforated nipple passing through a stuffing box which would allow the
end to be placed at any point across the diameter of the steam pipe.

FUELS 1,821

CHAPTER 56
FUELS

By definition, the term fuely broadly speaking, is any substance
which y by its combination with oxygen evolves heat. It is, however,
generally applied, to those substances which are in common
everyday use for heat producing purposes.

The many kinds of fuel used for the generation of steam may
be classified:

1. With respect to character, as:

a. Natural fuels;

Such as wood, coal, crude i>etroleum and natural gas.

h. Prepared fuels;

Such as powdered coal and briquettes.

c. By-products and end-products from industries

Such as bagasse, tan bark, blast furnace gas, coke oven gas, waste gases from cememt
kilns, open hearth furnaces, etc.

2. With respect to their state, as:

Coal

Coke

Peat

Tar

Wood

Tanbark

Sawdtist

a. Solid

Tar, ete.

NOTE. — ^The methods of firing the various fuels here mentioned are explained at length in
later chapters.

1,822 FUELS

b. Liquid

The various liquids of the petroleum group.

r Oac: /Natural gas.
C, Kjas \producer gas.

Of the various fuels here tabulated, coal is by far the most extensively-
used. The use of wood is restricted to special and peculiar processes as the
necessary and increasing demand for its use for structural and other indus-
trial purposes has nearly removed it from any consideration as a fuel.

Special processes and favorable local conditions are necessary before any
competition between either fuel oil or of gases and coal can exist.

A. SOLID FUELS

COAL

The dark brown or black mineral substance known as coal is a
formation from plants that flourished ages ago, oxidation being
prevented by the fact that they fell into swamps and morasses,
and became covered with a protective layer of water. After-
wards they were entombed under billions of tons of sandstone,
limestone and clay'! The resulting pressure and heat caused
the vegetable matter to assume the form of coal.

The store of energy was not reserved during the transformation
period, this being evident from the fact that all plants will burn.

Oues. How do plants receive energy?

Ans. , When a plant is exposed to sunlight it has the power of
chemically combining water with a gas known as carbon mon-
oxide (chemical symbol CO), the same gas that is given off by
animals in breathing. While the plant is able to form the actual

FUELS 1,823

combination of gas and water, the sun does the actual work,
using some of its energy in the operation .

The energy of the sun in helping the plant in its work of chemical com-
bination, is just as much work and of practically the same kind as that put
forth by a laborer in carrying a hod of bricks up a ladder, for as the energy
expended by the laborer remains at the top of the ladder, so does the energy
expended by the sun remain within the wood built up by the plant and
the sun.

When the wood, or the equivalent, coal, is placed under proper conditions
of sufficient heat and abundance of air supply, the wood returns to its origi-
nal components, water and carbonic oxide gas, and the sun's energy that
has been imprisoned within the wood or coal is set free in the form of heat.

Oues. What are the chemical constituents of coal?

Ans. Carbon, hydrogen, oxygen, nitrogen, and inorganic
matter that constitutes the ash. Sulphur in the free state is
sometimes present in coal.

Oues. Explain the terms volatile matter, fixed carbon,
total combustible, and ash?

Ans. In the language of the chemist, that part of coal,
moisture excepted, which is driven off when a sample is subjected
to a temperature up to about 1,750° F. is the volatile matter;
the solid carbon is the fixed carbon; the sum of volatile matter
and fixed carbon is the total combustible, and the part that does
not burn is ash,

Oues. What causes the different heating values of
the mining grades of coal?

Ans. The varying quantities of the chemical constituents
and their combinations.

Oues. Where is coal found?

Ans. It lies in horizontal or inclined layers, being separated
by seams of clay and frequently mixed with iron compounds.

1,824 FUELS

It is found in the geological formation commonly known as
the carboniferous, and it generally lies between primary forma-
tions called Silurian, or sand stone.

Classification of coal. — All coals as already explained are
formed from prehistoric vegetable growths, fossilized by moisture,
heat, pressure and time.*

These deposits vary considerably in age, and distinct species exist which
may be distinguished from one another as well by the physical structure
as by the chemical peculiarities. •

The coal which occurs above the chalk formation is of comparatively
recent origin. This is lignite or brown coal, which frequently contains
almost the entire structure of the vegetable matter from which it was
formed.

That lying below the chalk is known as bituminous coal and in it the vege-
table feature has disappeared excepting in isolated cases. Both differ from
the anthracite or oldest coal, from which almost everything has disappeared
excepting the carbon. The approximate chemical and structural changes
which have taken place are tabulated according to age as follows:

Substance Carbon

Wood fibre 52-53%

Peat 58-60%

Lignite 60-62%

Brown coal 65-70%

Bituminous coal 70-85%

Anthracite coal 85-92%

Owes. Which is the youngest coal?

Ans. Lignite.

{ydrogen

Oxygen

5-55%

40-42%

55-60%

40-42%

50-55%

34-35%

50-55%

25-30%

55-60%

18-20%

4-57%

4-4>^%

*NOTE.— As evidence of the vegetable origin of coal, fossilized trees are found standing
upright and with their roots resting in the seams of coal, also ferns, leaves, boughs, etc., either
wholly or partially fossilized are found in peat bogs. It is stated that several hundred different
species of plant life have been identified in and among coal formations. These evidences
found in the coal measures, by the comparison with existing forms of plant life, testify to the
fact that the climate now existing at those points is materially changed from that which existed
at the time of their growth. All such specimens which have been found indicate that their
natural habitat was in a very warm, moist climate, and that after falling were subjected to
various changes of location due to internal disturbances of the earth, at times being buried
under the water, and at other times, probably by volcanic action, elevated high above the
water.

FUELS 1,825

Ones. Which is the oldest coal?

Ans. Anthracite.

A classification of the great variety of coal, to be compre-
hensive, should be made from several points of view, as:

1. With respect to density, as

a. Soft or so-called bituminous coal
h. Hard or anthracite coal

2. With respect to age, as:

a. Lignite

b. Bituminous

c. Semi-bituminous

d. Semi-anthracite

e. Anthracite

3. With respect to the characteristics of combustion:

a. Caking or non-caking i

6. Long or short flaming
c. "White or red ash

Anthracite Coal. — 'This is said to be the oldest and deepest formation,
and is found principally in the United States . It is also found in the western
part of the South Wales coal fields; in the neighborhood of Swansea; in
some parts of Scotland; to a small extent in France; in the South of Russia;
and in the Osnabriick district of Westphalia, Germany.

Anthracite coal represents the highest quahty of fuel known; that is, it
is the nearest approach to pure carbon combustible. Because of difficulty
in kindling, this coal for years was considered too nearly like a rock to be
burned. It was first used in 1766 for blacksmith work and shortly after-
ward came into considerable use for metallurgical processes, but even as
late as 1812, it was unknown for any large use under boilers.

Today the enormous demand for anthracite coal threatens its extinction
within a few years.

Semi- Anthracite Coal. — In its physical characteristics and appearance

*N0TE. — Bitumirtoas is of Latin origin, meaning containing or resembling bitumen.
Bituminous coals contain no bitumen, the name having been applied because of a misconcepr
tion of their nature, due to the resinous feel of certain kinds. Anthracite is a word of Greek
origin, meaning carbon or coke, the fuel being so named probably because it is that which
contains the largest percentage of fixed carbon.

1,826 FUELS

it closely resembles anthracite. It is represented by what is known as Welsh
anthracite, and by coals from a limited territory in Pennsylvania.

Semi-anthracite coals break with a conchoidal fracture and have a lustrous
surface. They kindle with difficulty, are low in volatile and high in fixed
carbon, but have more ash than the anthracites and somewhat more oxygen.
When handled they soil the hands slightly, and are not of great importance
for power plant use because of the high cost and small supply.

Semi-Bituminous Coal. — Represented chiefly by the Cardiff or Welsh
coals from the enormous fields of South Wales and in the U. S. by the rich
deposits on the slope of the Appalachian Mountains, extending from Clear-
field County, Pa., to the southern boundary of Virginia, the coals in this
belt taking the names of Pocahontas, George's Creek, Clearfield, etc. The
Belgian coal, known as Demigras, is also of this class.

Semi-bituminous coals are among the finest of fuels for steam making,
as they give a high heat value with less difficulty in avoiding smoke than
bituminous coals. In appearance and action they are more like the anthra-
cites than the bituminous coals, but contain more volatile matter than the
anthracites. The better grades, however, are almost free from smoke and
are easier to kindle than the anthracites. The supply of these coals is small
and the resulting high price limits their use for boilers.

Bituminous Coal. — This kind of coal is found almost all over the world.
The largest known fields are in Scotland, England and the U. S. Most
bituminous coals are a dense black, but in some cases vary toward a brown.
The luster is resinous.

The best quality coals are soft and silky to the feel. Caking and non-
caking varieties have distinctly different characteristics. The non-caking
coals are more like lignites, rather hard and brittle and will not melt nor
fuse together in the furnace or when caked. They bum with a yellow smoky
flame and are good for gas producers. Caking coals when thrown into the
furnace swell and fuse into a mass which must be broken up occasionally to
allow the fire to get through it. These are, however, rich in volatile matter
and bum with a long yellow smoky flame which makes it difficult to avoid
making smoke when using them, particularly after green coal has been
thrown on the fire.

Because of the wide variation in the composition of bituminous coals, the
ftunace should be adapted to a particular variety to get the best results.

With bitiiminous coals not only must the furnace be properly designed,
but the firing should be properly done to secure smokeless and efficient
combustion.

FUELS 1,827

Cannel Coal, — This variety of bituminous coal is found in the Midlands
of England, and in the U.S. It is used principally for making illurninating
gas and for domestic purposes. It is a variety of bituminous cdal^ very rich
in hydrogen. '''■'■

In appearance this coal differs from all others. Its structure is more nearly

uniform than others, being a compact mass, varying irorn brown to black

in color, and having usually a dull resinous luster. When brokeii it does not

usually preserve any distinct order of fracture, and is liable to split in any

direction.

Being very rich in hydrocarbons it is well adapted for gas producers, the
preference being in those coals in which hydrogen bears the greatest pro-
portion to the contained oxygen . It readily kindles and bums without melt-
ing, emitting a bright flame like that of a candle, and produces a crackHng
noise in splitting up into fragments when thrown on the fire.

Block CoaL — The peculiarity of this formation from which it derives its
name is the presence of fractures occuring in the coal bed at right angles
or nearly so, and extending from top to bottom of the seam, enabling the
miner to get it out in rectangular blocks.

It is a non-caking bituminous coal occurring in large quantities in Indiana.
It burns well under a heavy load without caking.

The coal is of a dull lusterless black, in thin laminae, separated by fibrous
charcoal partings, very strong across the bedding lines, and is free from
pyrites and calcite. It is largely used for boilers, domestic stoves, grates
and also for blast and puddling 'furnaces.

Lignite, — The principal lignite fields are in France, Italy, Germany -and
Austria, but lignite is also found in the U.S. and in Sweden.

As found in the mines, lignite varies from a brown to a deep black, accord-
ing to its composition, the poorer grades carrying the earthy brown color
and the better grades the black approaching that of bituminous coals.
There are indications of the organic structure in the lower grades.

Lignites are easily ignited because of the softness in texture and high per-
centages of hydrogen and oxygen. They burn with a flame somewhat re-
sembling peat. Lignites absorb water easily, and carry a high percentage of
moisture which cuts down their heating value.

The ash will run from 9 to 58 % and with a lignite which is high both in
ash and moisture, the heating value may be so low as to make it undesirable
for boilers.

Lignites are non-caking and hardly more like anthracite than like bitumi-
nous coals.

1,828 FUELS

A thick fire and strong draught rtiust be carried because of the low heating
value. Lignites are brittle and usually break up when thrown on the fire.
They are also likely to break up when left exposed to the weather.

Culm. — Formerly this was waste product and had no commercial value.
It is fine anthracite coal. Culm banks abound in the anthracite regions of
Pennsylvania and consist of mixed fine coal of many sizes, with a consider-
able proportion of slate and pyrites, requiring careful attention as to
draught, firing and details of grate upon which it is to be burned.

Heating Values of Coal. — The theoretical heating value of
[uel is the heat which it develops when consumed under theo-
retically correct conditions — which are practically only obtained
in the laboratory— and it is expressed in heat units or thermal
units. In England and the United States the British thermal
Linit is adopted; on the Continent of Europe the ''calorie" is
used.

The theoretical heating value of coals varies from about 7,000 to 15,500
Bot.u. per pound, depending largely on the varying amount of uncombustible
matter or ash that the coals contain.

The semi-bituminous coals of the Pocahontas and Cardiff varieties are
the most nearly uniform in this respect, the ash being only 3 to 8 per cent.;
Belgian "Demigras" will run from 5 to 15 per cent., while the residue in
Transvaal coal may reach 25 to 35 per cent.

The anthracite coals, as mined, contain from 15 to 30 per cent, of refuse
or slate. Most of this, however, is usually removed when the coal is pre-
pared for the market, so that anthracite, as sold, may contain as little as
3 per cent. On the other hand, the smaller sizes may run very high in ash,
and cases have been known where 50 per cent, refuse has been found in
boiler tests.

Bituminous coals are extremely variable, running from 5 to 35 per cent,
ash, while the percentage in lignite is usually considerably under 10.

The heating value of the combustible portion of the coal (ash and moisture
deducted) is also quite variable, and depends on the quality of the volatile
matter, which may be either very rich in hydrocarbons, as in semi-bitumi-
nous coals, or comparatively high in oxygen, as in many of the bituminous
coals and lignite. So much, in fact, does the amount of oxygen found in
lignite detract from the heating value of the volatile matter, that the com-
bustible portion of lignite is worth only about three-fourths that of semi-
bituminous coal.

FUELS

1,829

The following table gives a classification of American coals
according to the heating values, being the table prepared by
Kent {Journal A, S. M.E., vol. 36, p. 437, 1917) but arranged
in the order of ascending heating values.

Classification of American Coals

Class

Volatile
matter
in % of

com-
bustible

Oxygen
in com-
bustible
%

B.t.u. per

pounds of

combustible

Sub-bituminous and lignite. . .

Bituminous, low grade

Bituminous, medium grade. . .
Anthracite

27 to 60
32 to 50
32 to 50
less than 10
10 to 15
30 to 45
15 to 30
45 to 60

10 to 33
7 to 14
6 to 14
Ito 4
Ito 5
5 to 14
Ito 6
5 to 8

9,600 to 13,250
12,400 to 14,600
13,800 to 15,100
14,800 to 15,400
15,400 to 15,500

Semi-anthracite

Bituminous, high grade

Semi-bituminous

14,800 to 15,600
15,400 to 16,050
15,700 to 16,200

Eastern cannel

The United States Geological Survey has gone into the matter of proper
grouping or classification of coals very exhaustively. In the report on the
coal testing plant at St. Louis, using various elements and ratios, they

found that the carbon hydrogen ratio _^^ ^hile not perfect, seems to fit

ri

the cases better than any others, and suggest for investigation and discus-
sion the following groups, arbitrarily designated by letters:

Group A (Graphite) 8 to (?)

" B Anthracite (?) to 30 (?)

" C " 30(?)to26(?)

" D Semi- Anthracite 26 (?) to 23 (?)

" E " Bituminous 23 (?) to 20 (?)

" F Bituminous. 20 to 17

" G " 17 to 14.4

" H " 14.4 to 12.5

" I " .12.5 to 11.2

" J Lignite 11.2 to 9.3 (?)

" K Peat 9.3 (?) to (?)

" LWood 7.2

1,830 FUELS

From this report is here quoted the following:

Groups A, B, C, D, and E. As little work was done at this testing
plant on anthracite coal, and as all of the analyses made by the Second
Geological Survey of Pennsylvania were proximate analyses, little material
is available for determining the limits of these groups and the figures given
must be regarded as provisional only, and subject to change when a
greater number of ultimate analyses have been made.

Groups F, G. H, I. — These groups embrace what generally are con-
sidered bituminous coals.

Group F. — Includes Pocahontas coal, the high grade Arkansas coals
west of the Spadra District and New River coals.

Group G. — Includes upper Freeport and Pittsburg coals or Northern
W. Virginia, Kanawha Valley coals, high grade Kentucky coals, and
Alabama coals.

Group H, — Includes all Indian Territory coals, all Kansas coals, high
grade Illinois, Iowa and Missouri coals, and second grade Kentucky coals.

Group I, — Includes the great majority of Iowa, Illinois, and Missouri
coals, Indiana coal and some bituminous coals from Wyoming and Montana.

Group J. — Includes all the lignites, both black and brown that were
tested.

Group K. — Is limited to peat and is based entirely upon one analysis
obtained from outside sources.

Group L. — Is woods, the lowest group in the series.

Coal from every district, indeed from different mines of the same region
vary in their composition. Any table of analyses could therefore only be
of very restricted use, since it is of course impracticable to publish a com-
plete list.

Sizes of Coal. — As taken from the mine, coal varies in size
from lumps to a fine dust.

Oues. What is the effect of size of lumps on coal?

Ans. In general the smaller the size the greater is the amount
of impurities present, the heat value is lower, more coal sifts
through the grate, and other objectionable results are increased.
As a consequence, the larger sizes usually command higher
prices, especially for anthracite.

FUELS

1,831

Oues. How is coal graded into sizes?

Ans. By screening through standard openings which, however,
differ somewhat both as to size and shape in different localities.

The preliminary report of the Committee on Power Tests of the American
Society of Mechanical Engineers (1912) recommends the grading of coal
as follows:

Sizes of Anthracite Coal

Size

Diameter of opening
through or over which coal
will pass, inches

Through

Over

Broken

4^
3J4

%

zyi

Beg

2^A%

r^oo

Stove o 0

iVs

Ohestnut

%

Pea

%

No. 1 Buckwheat

%

No. 2 Buckwheat

^6

No. 3 Buckwheat.

^2

Culm

Sizes of Bituminous Coal — Eastern States

Run of mine coal, — The unscreened coal taken from the mine.

Lump coal — That which passes over a bar screen with openings 134
inches wide.

Nut coal. — That which passes through a bar screen with 1 J^-inch openings
and over one with %-inch openings.

Slack coal. — ^That which passes through a bar screen with J^-inch
openings.

Sizes of Bituminous Coal — Western States

Run of mine coal — The unscreened coal taken from mine.

Lump coal — Divided into 6-inch, 3-inch and IJ^-inch lump according
to the diameter of the circular openings over which the respective grades

1,832 FUELS

pass; also into 6X3 lump and 3X134 l^nip according as the coal passes
through a circular opening of the larger diameter and over one of the
smaller diameter.

Nut coal — Divided into 3-inch steam nut, which passes through a
3-inch circular opening and over a 134-inch; IJ^-inch nut, which passes
through a 1^-inch circular opening and over a %-inch; and %-inch nut,
which passes through a 5€-inch circular opening and over a J^-inch.

Screenings. — That which passes through a 134-inch opening.

Bituminous and semi-bituminous coals usually crumble to powder
when handled, particularly if left exposed to the open air for a time, as
they absorb moisture rapidly and this moisture will not be driven off
except by heating the coal up to 250° F. Such coals are therefore sold as
run of miney which means that lumps and dust and all sizes between are
sold in one mass.

COKE

Ques. What is coke?

Ans. The solid substance remaining after the partial burning
of coal in an oven or after distillation in a retort.

"When the former process is used, the coke is the primary product, and
any other products are considered as by-products, being quite frequently
thrown away, although modern coke making processes save most of them.

In the retort process, however, the coke itself is one of the by-products,
the gases being the object of the operation, although the by-products have
in later years become better revenue producers than the gas itself.

Ques. How is gas retort coke produced?

Ans. It is produced by the application of high temperatures
to the outside of the retort for a short time.

The product is soft, spongy, and of dark grey color, approaching black.
It is not fitted for metallurgical work, and its principal use is for domestic
purposes, and in steam boiler practice, ^

Coke produced in beehive ovens, however, is made under lower tem-
peratures, the process requiring from 48 to 72 hours. It is hard, dense,

FUELS 1,833

and of a light grey color, has a brilliant metallic lustre, and will ring when
struck. The product is especially adapted for heavy metallurgical work,
but its high cost precludes its use for either steam boilers or domestic pur-
poses. This same grade of coke is now extensively produced in closed
ovens in a very much more economical way.

Oues. Does chemical analysis show much difference in
the heating value of different cokes?

Ans. It shows very little difference.

The heating value is roughly considered as being about 14,000 B.^.w. per
pound, and the difference in adaptability is due to the physical differences.
Analyses of twenty-nine samples of coke from six different states give
averages as follows:

Carbon 89.15%; Sulphur .918%, Ash 9.21%

The average weight of solid coke may be taken as 45 pounds per cubic
foot. The average weight of heaped coke may be taken as 30 pounds per
cubic foot. One long ton heaped averages 75 cubic feet.

Under ordinary conditions coke carries from 5% to 10% water, and if
unprotected, will absorb from 15% to 25% of its own weight.

Good coal carefully handled in a beehive oven produces on an average
of about 66% to 663^% coke, which can be marketed as such; about 2%
to 2J^% of breeze or fine coke, and from .75% to 1% ash, there being an
average of about 30% to 31% loss, mostly due to the volatile matters driven
off in the coking process.

PEAT

Ones. What is peat?

Ans. A substance of vegetable origin always found more or
less saturated with water in swamps and bogs.

It consists of roots and fibres in every stage of decomposition, from the
natural wood to vegetable mold. It is valuable as a fuel only after having
been dried out as much as possible. As found in the bog, peat usually
contains 85% to 90% of water, and when air dried still holds at least 15%
moisture.

1,834 FUELS

Oues. What does an analysis of air dried peat of good
quality show?

Ans. About 48% carbon, 4% hydrogen, 27% oxygen, 1%
nitrogen, 15% moisture, 5% ash. 9,000 5. ^w.

The analysis of perfectly dried peat would be about as follows:
58% to 60% carbon, 6% hydrogen, 30% to 31% oxygen, l%to 13^%
nitrogen, 2%% to b% ash. 10,260 B.t.u.

Oues. What is the weight of peat per cubic foot?

Ans. Heaped, it is from 6 pounds to 22}^ pounds, or 33.3
cubic feet to 88.8 cubic feet per ton of 2,000 pounds.

Ques. How is peat prepared as a fuel?

Ans. It is prepared in three forms: 1, as hand or spade peat;
2, as briquetted peat: 3, as machine peat.

1. Spade peat is obtained by cutting out of the bog regularly shaped
blocks, stacking the blocks on the ground to dry. The product is very
commonly friable, will not stand transportation, is not suitable for coking
and is usually quite bulky, although the specific gravity may run from
2 to 1.3.

2. Briquetted peat is produced by compressing dry powdered peat
with heavy machinery into regularly shaped blocks. The briquetted
fuel is clean, and bears transportation fairly well.

3. Machine peat is prepared on the principle that when raw peat con-
taining from 80 to 85% of water is thoroughly mixed and kneaded, it loses
its fibrous structure and on drying, shrinks firmly together into a compact
mass of about one-fifth the original volume.

WOOD

The term wood is generally used to designate the limbs and
trunks of trees as they are felled.

NOTE. — Peat is found in many parts of Europe, and has been used in Ireland for many
years as a domestic fuel. A very valuable deposit exists in Minnesota, where hundreds of
acres of peat several feet deep have been found.

FUELS 1,835

Woods may be divided into two classes: 1. Hard, compact and com-
paratively heavy woods, such as oak, beech, elm and ash. 2, The light-
colored, soft, and comparatively light woods, such as pine, birch, poplar
and willow. When freshly cut, about 45% of the total weight of wood is
water, and when air dried and kept in a dry location, it still retains from
15% to 25% of water.

Oues. What is the relative heating value of wood as
compared with coal ?

Ans. The heating value of thoroughly dried wood is about
40% of that of coal.

Oues. What is the effect of water in wood?

Ans. It causes a loss of economy.

This is shown in the following table, which gives the difference in chemical
composition and heat value between perfectly dried wood and ordinary fire
wood:

Dry wood. Ordinary fire wood.

Carbon 50% 37.5%

Hydrogen 6% 4.5%

Oxygen 41% 30.75%

Nitrogen 1% 0.75%

Ash 2% 1.50%

100% 75.00%

Moisture 25.00%

Total 100.00%

The heat values of the above are as follows:

7,840 5.^.«. 5,880 5.^w.

Equivalent to 8.1 lbs. of water 6.1 lbs. of water

evaporated per pound of fuel from and at 212° F. theoretically.

From the above it will be seen that there is a loss of heating power per
pound of ordinary fire wood of 25%, due to the presence of the hydro-
metric water, and there is a still further loss of 5% due to the fact that
this water must be evaporated.

^ NOTE. — Suppose the wood with its contained water to be fed onto the fire at the
ordinary temperature of 62° F. Each pound of water therefore will require about 1,116.6
B.t.u. to heat it up to 212° F. and evaporate it at this temperature, and as each pound of
wood by above analysis contains M pound of water, this will require 279 heat units to evaporate
it, which is 4.7 per cent of the total heat generated, so that ordinary fire wood has only about
71 per cent of the heat value of perfectly dry wood. The A. S. M. E. have established a value
of wood in its equivalent in coal for the purpose of boiler testing as above stated, viz: 1 pound
of wood = .4 pounds of coal, but in case greater accuracy be desired 1 pound of wood may be
considered as having a heating value equivalent to the evaporation of 6 pounds of water
from and at 212° F,, which is equivalent to 5,794 B.t.u. per pound.

1,836 FUELS

TAN BARK

Tan bark, usually oak bark after having been used in the
process €>f tanning, is frequently burned as fuel. The spent
bark consists of the fibrous portions, and according to M.
Peclet, five parts of oak bark produce four parts of dry tan
the heat value of which is about 6,100 jB./.ti., and this so called
dry tan contains about 15% of ash.

Tan bark in its ordinary state of dryness contains about 30%
water and has a heating value of 4,284 B.t.u. The theoretical
evaporation from and at 212^ F., of 1 pound of spent bark
(equivalent to the heating value just given) is about 4.12 pounds
of water.

Ques. How is wet tan bark burned successfully?

Ans. By burning it in a furnace of sufficient volume to
accommodate a large quantity of wet bark, exposed to the
heated gases coming from the burning bark, which has been
previously dried.

As the wet bark becomes dried, it must be fed down and burned, where
its hot gases in turn assist in drying the newly fed fuel. The rate of com-
bustion is limited by the rapidity of the drying process. If it exceed this,
the dry portion bums up, leaving the wet fuel which will not bum.

STRAW

Straw consists of the stems or stalks of grain, and its principle
use is for plaiting, thatching, paper making, etc., but in certain
localities it is used as a fuel.

Ques. What is the heating value of straw?

FUELS 1,837

Ans. Tests of wheat and barley straw give average of 5,411
Bd.u., out of which 153 B.t.u. must be used in evaporating the
natural water, leaving 5,25SB.t.u. available, which is equivalent
to the evaporation of 5.4 pounds of water per pound of straw
from and at 212'' F,

SAWDUST

The conditions necessary for burning sawdust are that ample
room should be given it in the furnace and sufficient air supplied
on the surface of the mass; the same applies to shavings, refuse,
lumber, etc.

Oues. What is the heating value of sawdust?

Ans. It is naturally the same as that of the wood from which
it is derived, but if allowed to get wet, it is more like spent tan.

Mr. W. S. Hutton gives the following heating values of combustible
refuse:

B.t.u.
per lb. of fuel.

Oak bark, dry , 6,279

Oak bark, in a damp state 3,024

Sawdust from oak or other hard woods, dry 5,912

Sawdust from pine or other soft woods, dry 5,217

Sawdust in moderately dry state, averages 3,961

Wood chips and sawdust, mixed, moderately dry, averages 3,671

Wood chips and green twigs in a damp state, or containing

50 per cent, of moisture, average 1,932

BAGASSE

Oues. What is bagasse?

Ans. The fibrous portion of sugar cane left after the juice
has been extracted.

1,838 FUELS

It consists of woody fibre, water, sucrose, glucose and other solids in
varying proportions, depending upon the quality of the cane and its treat-
ment in the mill.

Ques. What is its heating value?

Ans. Its average heating value when dry is 8,360 B.t.u,

TAR

Coal Tar. — The value of coal tar as a fuel is usually very
much lower than its value for other purposes, but it is at times
used to advantage as a fuel. The yield of coal tar varies with
the kind of coal and with the methods employed, from about
4:}/2 to 63^% of the weight of coal.

It is lower in hydrogen and higher in carbon than crude oil,
and therefore, of a lower calorific value . Tar made from standard
gas coal would have an ultimate analysis about as follows:

Carbon 89.21% Nitrogen 1.05% Sulphur .0.56%

Hydrogen 4.95% Oxygen 4.23% Ash trace

It has a specific gravity of about 1.25; a gallon weighing 10.3 pounds.

Using Dulong*s formula as adopted by the A„ S. Mo E., such fuel
would have about 15,800 B.t.Uo per pound, and a theoretical evaporative
power of about 16.4 pounds of water, from and at 212° F. A series of
calorimetric tests give about 15,700 B.t.u. Coal tar may be burned if
heated and strained, the same as other liquid fuels.

NOTE. — The following are some of the conclusions reached in Louisiana Bulletin No. 117:
"Less excess of air is required with bagasse than with coal, usually 50% or less is sufficient.
The rate of combustion should be at least 100 pounds per square foot of grate surface per hour,
and best results were obtained with rates even higher than this. Not less than 1.5 boiler horse
power should be provided per ton of cane per 24 hours. A good workmg furnace depends
more upon the proportion of heating surface to the grate surface, rate of combustion and other
matters of design and operation than upon the type or form. On account of the large amount
of moisture in bagasse which is converted into steam in the furnace, a volume of gas and steam
much larger than for coal must be provided for in the cumbustion chamber and the passages to
the stack."

FUELS 1,839

Oil Tar. — This is produced in an ordinary gas apparatus, has
a specific gravity of 1.15, is less sticky than coal tar, and can be
transported, handled and burned like other oils. Its analysis
is about as follows:

Carbon 92.7 % Nitrogen .11% Sulphur 37%

Hydrogen 6.13% Oxygen 69% Ash trace

By the Dulong formula the above analysis would give 17,296 B.t.u.,
and its theoretical evaporative power would be about 17.9 pounds of
water from and at 212° F. By the calorimeter such oil gives a value of
17,190 B.t.u,

B. LIQUID FUELS

The many advantages of liquid fuel or fuel oil for use with
steam boilers have been apparent for a long time, and, in localities
where the crude oil or refuse from distillation could be obtained
cheaply (or where coal is very expensive) it has been used with
much satisfaction.

Petroleum is practically the only liquid fuel sufficiently abundant and
cheap to be used for the generation of steam. It possesses many advantages
over coal and is extensively used in many localities.

There are three kinds of petroleum in use, namely those yielding on dis-
tillation: 1st, paraffin; 2nd, asphalt; 3rd, olefine. To the first group
belong the oils of the Appalachian Range and the Middle West of the
United States. These are a dark brown in color with a greenish tinge.
Upon their distillation such a variety of valuable light oils are obtained
that their use as fuel is prohibitive because of price.

To the second group belong the oils found in Texas and California.
These vary in color from a reddish brown to a jet black and are used very
largely as fuel.

The third group comprises the oils from Russia, which, like the second,
are used largely for fuel purposes.

Oues. In general, of what does crude oil consist?

1,840 FUELS

Ans. It consists of carbon and hydrogen, though it also con-
tains varying quantities of moisture, sulphur, nitrogen, arsenic,
phosphorous and silt.

The moisture contained may vary from less than 1 to over 30 per cent,
depending upon the care taken to separate the water from the oil in pumping
from the well. As in any fuel, this moisture affects the available heat of the
oil, and in contracting for the purchase of fuel of this nature it is well to
limit the per cent of moisture it may contain. A large portion of any
contained moisture can be separated by settling and for best results, suffi-
cient storage capacity should be supplied to provide time for such action.

Ques. What is the heating value of petroleum?

Ans. A pound of petroleum usually has a calorific value of
from 18,000 to 22,000 B.tM.

Ques. What are the relative values of oil and coal as
fuels?

Ans. Under favorable conditions 1 pound ot oil will evapo-
rate from 14 to 16 pounds of water Jrom and at 212 deg.; 1 pound
of coal will evaporate from 7 to 10 pounds of water from and at
212 deg,

' The following tables show the comparison in more detail:

Relative Heating Values in Coal and Oil

B.t.u. per pound

Petroleum residuum 19,500

Beaumont crude 18,500

Anthracite coal — East Middle coal field 13,400

Semi-bituminous — Cumberland, Maryland 14,400

Pocahontas, Virgmia 15,070

Bituminous — ^Jackson County, Ohio 13,090

Hocking Valley, Ohio 12,130

Missouri coal 12,230

Alabama coal 13,500

McAUester coal, I. T 12,789

New Mexico 12,000

Texas Lignite 10,000

FUELS

1,841

These calorimeter values are carefully selected averages and furnish a
means of comparing the different coals one with another, but in comparing
liquid fuels with the solid, such as oil with coal, they do not form an accurate
measurement of the relative value of the two kinds of fuel as steam makers,
owing to incomplete combustion due to inefficient firing and other causes.

Comparative Evaporation of Coal and Oil

Taken from the United States Geographical Report on Petroleum

One Pound of Combustible

Pounds of Water

Evaporat's at 212

deg. per pound of

combustible

Barrels of Petro-
leum required to
do same amount of
evaporation as
one ton of coal

Petroleum 18 to 40 deg. Baume

Pittsburg lump and nut, Penna

Pittsburg nut and slack, Penna,

Anthracite, Penna

10.
8.
9.8
9.5

10.
9.7

10.5

10.
9.2
7.3
8.9
7.6
7.6

4.
3.2
3 9

Indiana block

3 8

Georges Creek lump, Maryland

New River, West Virginia

4.

3.8

Pocahontas lump. West Virginia

Cardiff lump, Wales

4.2
4.

Cape Breton, Canada

3.7

Nanaimo, British Columbia

2 9

Co-operative, British Columbia

Greta, Washington

3.6
3.

Carbon Hill, Washington

3.

The U.S. Naval Liquid Fuel Board appointed for the purpose
of thoroughly investigating the problem of using oil as a boiler
fuel, made an exhaustive report to the Navy Department.
Their conclusions are given in full and while relating particularly
to marine practice, there is much that is applicable to land prac-
tice.

NOTE. — The light and easily ignited constituents of petroleum, such as naphtha, gasoline
and kerosene, are oftentimes driven off by a partial distillation , these products being of greater
value for other purposes than for use as fuel. This partial distillation does not decrease the
value of petroletmi as a fuel; in fact, the residuum known in trade as "fuel oil" has a slightly
higher calorific value than petroleum , and because of its higher flash point it may be more safely
handled. Statements made with reference to petroleum apply as well to fuel oil.

1,842 FUELS

Conclusions of the U, S, Naval Liquid Fuel Board.

a. Oil can be burned in a nearly uniform manner.

b. The evaporative efficiency of nearly every kind of oil per pound of
combustible is probably the same. While the crude oil may be rich in
hydrocarbons, it also contains sulphur, so that, after refining, the distilled
oil has probably the same calorific value as the crude product.

c. A marine steam generator can be forced to even as high a degree
with oil as with coal.

d. Up to the present time no ill effects have been shown upon the boiler.

e. The firemen are disposed to favor oil, and therefore no impediment
will be met in this respect.

/. The air requisite for combustion should be heated if possible before
entering the furnace. Such action undoubtedly assists the gasification of
the oil product.

g. The oil should be heated, so that it can be atomized more readily.

C. GASEOUS FUEL

The gaseous fuels used in all steam boilers are natural gas,
waste gas from blast furnaces, coke oven gas and producer gas.
Natural gas, like mineral oil, is chiefly a mixture of hydro-
carbons, but no great complexity exists, as few are gaseous at
ordinary temperatures.

Natural gases contain varying amoimts of CO, CO2 and nitrogen, formed
probably from the action of oxygen on the carbon, the nitrogen accompany-
ing the oxygen. Blast furnace and producer gases contain large percentages
of nitrogen and carbon dioxide, while coke oven gas contains much more
combustible.

FUELS

1,843

Oues. How do gas fuels compare with liquid fuels?

Ans. Gas fuels offer all the advantages of liquid fuels, and
but few of the disadvantages.

Oues. What is the heating value of natural gas?

Ans. It varies from 800 to 1,100 B.t.u. per cubic foot.

1,000 cubic feet of natural gas is approximately equivalent to 57.25
pounds of coal.

Gaseous fuel has so many apparent advantages over any
Dther that it may properly be regarded as the ideal fuel.
Manufacturers who have once realized its advantages, would
gladly welcome some kind of gaseous fuel, provided this can be
nade cheap enough to compete with the local coal.*

The following table shows the relative heat values of a few
^ases, and a comparison of each with soft coal:

Comparison of Gas and Coal.

Variety

Heat Units

per
1000 cu. ft.

Equivalent
pounds
of coal.

Corresponding
price per
1000 cu. ft. -

Natural Gas

1,100,000
755,000
350,000
155,000

81.5

55.9

25.9

11.48

8.15 Cents

Coal Gas

5.59 "

Water Gas

2.59 «

Producer Gas

1 , 148 "

The coal is assumed to cost $2.00 per ton and to have a heat value of
13,500 B.t.u. The efficiency of the two fuels is assumed to -be the same
when burned under a boiler.

The last column shows what price should be paid for the gas in order
to make it economical to use that fuel.

*NOTE. — To answer this demand a number of processes have been invented. The U.S.
Geological Survey in its report on the Mineral Resources of the United States, reports the pro-
duction of natural gas in twenty- two states. In some of these states such quantities are pro-
iuced that immense industrial operations are based on its use.

1,844

FUELS

No account has been taken of the saving resulting from the less attention
needed, the probably higher efficiency, the fact that there are no ashes
to remove, and the greater ease of handling Vhen gas is used.

These factors would make it possible to pay a higher rate for gas depend-
ing on the size of plant and the relative importance of the various items
mentioned.

Cubic Feet of Gas Required per Horse Power Hour

Variety.

100 per cent
efficiency.

80 per cent
efficiency.

70 per cent
efficiency.

60 per cent
efficiency.

Natural Gas

Coal Gas

30.4

44.4

95.6

216.0

38.0

55.5

119.5

270.0

43 5

63.6

136.5

308.6

50.7
74 0

Water Gas /...

Producer Gas

'"9.2
360.0

Water Evaporation on Basis of 75 Per Cent. Boiler Efficiency.

Natural
Gas.

Coal
Gas.

Water
Gas.

Producer
Gas.

Pounds wrter from and at 212°F. per 1000
; cu. ft. Gas.

851

584

270.5

120

COMBUSTION 1,845

CHAPTER 57
COMBUSTION

Ques. What is combustion ?

Ans. Rapid oxidation.

It may further be defined as the rapid chemical combination of oxygen
with any material which is capable of oxidation, the process being accom-
panied by the diffusion of heat and light

Owes. What is the oxygen called?

Ans. The supporter of combustion.

Ques. Where is it obtained?

Ans. In the air.

Pure air is a mechanical mixture of oxygen and nitrogen. The accepted
values for the proportion of oxygen and nitrogen are: by volume, oxygen
20.91%, nitrogen 79.09%; by weight, oxygen 23.15%, nitrogen 76.85%.

Air in nature always contains other constituents in varying amounts,
such as dust, carbon dioxide, ozone and water vapor. Being perfectly
elastic, the density Or weight per unit volume decreases in geometric pro-
gression with the altitude. This fact has a direct bearing in the propor-
tioning of furnaces, flues and stacks at high altitudes. In nature the oxygen
in the air is constantly causing slow combustion, thus iron rusts, various
substances decay, etc.

Owes. What is the material called which is capable of
combustion?

1,846

COMBUSTION

Ans. The combustible.

As used in steam engineering practice, however, the term combustible
is applied to that portion of the material which is dry and free from ash,
thus including oxygen and nitrogen, which may be constituents of the fuel,
material; though not in the true sense of the term combustible.

Oues. What is fuel?

Ans . Any material which serves by combustion for the pro-

0UTERM05T CONE OR MAMTLE
PERFECT COMBUSTION

BRIGHT WHITE LIGHT

ALMOST BLACK
BLUL

INTERMEDIATE CONE
MPERFECT COMBUSTION

NNERM05TC0NE
COMBUSTIBLE GAS

CUP

PERFECT COMBUSTION

Fig. 3,340. — The candle flame. The form of the candle flame is common to all flames which
consist of gas issuing from a small circular jet, like the wick of a candle. The gas issues from
the jet in the form of a cylinder which, however, immediately becomes a diverging cone by
diffusing into the surrounding air. When this cone is kindled, the margin of it, where
interruption with the surrounding air is nearly complete, will be perfectly burned, but the
gases in the interior of the diverging cone cannot burn until they have ascended sufficiently
to meet with fresh air; since these unbumed gases are _ continually diminishing in
quantity, the successive circles of combustion must diminish in diameter resulting in the
conical shape.

duction of fire, as wood, coal, peat, oil, etc.

Combustible is that part of the fuel which burns. Fuel is made up of
the material, and may also contain non-combustible matter.

COMBUSTION

1,847

Ques. What are the principal combustibles in coal and
other fuels?

Ans. Carbon, hydrogen, and sulpfiur.

These occur in varying proportions, car-
bon being by far the most abundant, thus
typical anthracite coals contain:

Carbon 90 to 95 per cent

Hydrogen 1 '^ 3 '' "

Oxygen and nitrogen ... . 1 " 2 " ''

Moisture 1 " 2 " "

Ashes 3 " 5 " "

Carbon. — This is a combustible
element, non-metallic in its nature,
and present in most organic com-
pounds

It forms the base of lamp black and
charcoal and enters largely into min-
eral coals. In its crystallized state, it
constitutes the diamond, the hardest of
known substances, occurring in mon-
ometric crystals like the octahedron,
etc. Another modification is graphite
or black lead, and in this it is soft,
and occurs in hexagonal prisms.

Fig. 3,341. — Davy's safety lamp. This lamp may be carried into a mine where there are explo-
sive gases, and the gas may bum and splutter within the lamp but no explosion will take
place in the mine . The reason for this is because a gas w ill not ignite until its temperature has
been raised to a point called the kindling point, and the wire gauze bemg a good conductor
prevents the temperature rising to the kindling pomt, as illustrated in figs. 3,342 and 3,343.
In construction, the safety lamp is an oil lamp, the flame of which is surrounded by a cage
of iron wire gauze, having 700 or 800 meshes per square inch, and made double at the top,
where the heat of the flame chiefly plays. The cage is protected by stout iron wires attached
to a ring for suspending the lamp. A brass tube passes up through the oil reservoir and in
this there slides, with considerable friction, a wire bent at the top, so that the wick may
be trimmed without taking off the cage. The lower part of the cage is now made of glass,
to afford more light.

1,848

COMBUSTION

|.ssi ^

^ o g «•?

•| §-l 6

E5 O * <o 5
rt ^ a> . ^

CO °-^^ ^

a
■2

^

8|

t 6

i

S8
I

(D O

S *§

O ^

.^ O

^ .&

- I

CD ^

° g

CD (D

^ CD

bjo u

•rH CD

<D +3

^ o

C/3 rill

• rH .+J

S o

p ^

S

o

O

.s

CO _
I. <D

o ^

U

I

§^

I-

O

•Sll

>.5

3 2-c

c3

s

Jh o

COMBUSTION

1,849

Sulphur. — Most coals and some oils contain sulphur. It is
usually present in combined form, either as sulphide of iron or
sulphate of lime; in the latter form it has no heat value.

Its presence in fuel is objectional because of its tendency to aid in the
formation of clinkers, and the gases from its combustion, when in the
presence of moisture, may cause corrosion.

Figs. 3,344 and 3,345. — Experiment with Davy's lamp. If the lamp be stispended in a large jar,
closed at the top with a perforated wooden cover A, and having an opening B , below through
which coal gas is allowed to pass slowly into the jar, the flame will be seen to waver, to
elongate very considerably, and finally to be extinguished, when the wire cage will be filled
with a mixture of coal gas and air burning tranquilly within the gauze which prevents the
flame passing to ignite the explosive atmosphere surrounding the lamp. As proof that the
lamp IS surrounded by an explosive mixture, a lighted taper inserted through the hole C,
will cause an explosion.

Ignition or Kindling Point. — To cause a combustible to unite
with oxygen and combustion take place, its temperature must be

*N0TE . — ^When the Davy lamp is brought into an atrnosphere containing fire damp, a cap^
of blue flame is observed to play above the tip of the illuminating flame. This incipient com-
bustion is more marked when a hydrogen flame is substituted for an oil flame, and the height
of the oil cap furnishes an indication of the quantity of fire damp present. Such a modified
Davy lamp becomes a fire damp indicator.

1,850

COMBUSTION

raised to the ignition or kindling point, and a sufficient time
must be allowed for the complete combustion to take place
before the temperature of the gases is lowered below that point.

According to Stromeyer the approximate ignition tempera-
tures are as given in the following table:

Kindling Temperature of Various Fuels.

Degrees Fahr.

Lignite dust 300

Dried peat 435

Sulphur 470

Anthracite dust 570

Coal 600

Coke red heat

Anthracite red heat, 750

Carbon monoxide red heat, 1211

Hydrogen 1,030 to 1,290

Combustion. — The two principal ele-
ments of coal, carbon and hydrogen, have
an affinity for oxygen. When they unite
chemically heat is produced. The oxygen
having the stronger affinity for hydrogen
unites with it first and sets the carbon free.
A multiplicity of solid particles of carbon
thus scattered in the midst of burning hy-
drogen are raised to a state of incandescence .

Fig. 3,346. — Experiment illustrating the cooling of flame below the igniting temperature. If a thin
copper wire be coiled around into a helix and carefully placed over the wick of a burning
candle, as shown, the heat of the flame will be transmitted along the wire so rapidly that
the temperature will fall below the point at which combustible gases combine with oxygen ,
that is, below the kindling point, and here the flame will be extinguished. If the coil be
heated to redness previously, the flame will not be extinguished. The cooling effect is also
illustrated in the operation of an internal fire box boiler where the heat of the fuel lying next
to the furnace walls is transmitted through the walls to the water so rapidly that the fire
becomes "dead" along the walls.

COMBUSTION

1,851

6 >

•a

cj o

o

TJ u

(D

03 >»

^^ "^

t^.""*

Tt* ;-l

3

^

o

W

.-s

o

is

t^'?^

(<

<"

o

++

I ^ - p ^ ° «

"^W- o

S-^l

^§.2.,
^ C o
■2 rt o

:SS

.2 o
o o

1,852 COMBUSTION

The carbon, in due time, unites with the oxygen forming carbon
dioxide or carbon monoxide.

The light and heat produced by the burning of the coal are due
to the collision of atoms which have been urged together by their
mutual attractions. During the process the hydrogen unites
with the oxygen in the proportion of two atoms of hydrogen to
one atom of oxygen to four of water (H2O) .

An important feature of the process of combustion is the chem-
ical compounds formed by the combinations of carbon and hy-
drogen. These compounds are called hydro-carbons. Those
most necessary to consider are methane or marsh gas (C H4),
having a heat value of 23,616 B.t.u.; ethylene or defiant gas
(C2 H4) having a heat value of 21,344: B.t.u.; acetylene (C2 Hg)
having a heat value of 18,196 B.t.u.; benzole (Ce He) having a
heat value of about 18,000 B.t.u. If these gases be completely
consumed so as to develop the number of heat units given, the
products will be carbon dioxide (C O2) and water (H2 O). The
igniting temperature of these gases varies from 580 degrees to
667 degrees C.

Some of these hydro-carbons, such as marsh gas CH4 and olefiant gas
C2H4, bum without smoke, while others, like benzine CeHe and naphthalene
CioHs, which contain a very large proportion of carbon, undergo partial
combustion, and a considerable quantity of carbon, not meeting with
enough heated oxygen in the vicinity to burn it entirely, escapes in a very
finely divided state as smoke or soot, which is deposited in the chimney,
mixed with a little ammonium carbonate and small quantities of other
products of the distillation of coal.

Figs. 3,347 and 3,348. — Text continued.

If: 1, no air be admitted above the fuel level as in fig. 3,347, the carbon monoxide which
is a combustible gas will pass up the chimney unbumed resulting in a loss, as will be indicated
by inserting a tube in the stack and igniting the escaping carbon monoxide with a match;
2, when air is admitted above the fuel level as in fig. 3,348, the oxygen in the airwill combine
with the carbon monoxide already heated above the igniting temperature, causing complete
combustion that is, burning the carbon monoxide to carbon dioxide, as indicated by attempt-
ing to ignite the gas escaping from the tube. It will not ignite, thus showing that the com-
bustion is complete. Admitting more air than is necessary to secure complete combustion
results in a lo88»

COMBUSTION

1,853

When the gas has been expelled from the
coal there remains a mass of coke or cinder,
which burns with a steady glow until the
whole of its carbon is consumed, and leaves
an ash, consisting of the mineral substances
present in the coal.

The final results of the perfect combustion
of coal would be carbon dioxide, water,
nitrogen, a little sulphur dioxide and ash.

Oues. What other names are
given to carbon dioxide and carbon
monoxide?

Ans. Carbonic acid and carbonic
oxide respectively.

Ques. When is combustion
complete?

B J Ans. When the combustible unites

with the greatest possible amount of
oxygen, as when one atom of carbon
unites with two atoms of oxygen to
form carbon dioxide, whose chemical
symbol is CO2.

V>( V-/2 — This gas is some-
times called carbonic anhydrid.
It is heavy and colorless with a
pungent odor. On account of

Fig. 3,349. — Bunsen Burner. It consists
of a small tube or burner A, which is
placed inside a larger tube B . The latter
has holes CO, a little below the top of the
small tube. The current of gas escaping from the small tube draws the air in through the
holes CC, and produces what is called an induced current of air m the large tube. This air
enters through the holes CC, and is mixed with the gas m the tube B, and the mixture is
burned at D. The flame from such a burner gives hardly any light, but the heat is intense,
as is shown if a metal wire be held in it for a few seconds, it will glow with heat.

1,854

COMBUSTION

its weight, it does not mix readily with other gases or the air, but collects
at lowest levels as near the floor in rooms. It does not support combustion,
nor is it a supporter of respiration.

Formerly it was thought that carbon dioxide was poisonous, but now the
opinion is that it causes death by excluding oxygen. The fact that it is
beneficial to the system if taken into the stomach proves that it is not
poisonous.

Owes. When is combustion incomplete and why?

Fig. 3,350. — Experiment showing that combustion occurs only at the surface of an ordinary
flame. Insert one end A, of a small open tube into the flame. The combustible gas will then
escape at the other end B, and can be lighted with a match.*

Ans . When the combustible does not unite with the maximum
amount of oxygen, as when one atom of carbon unites with one

*NOTE. — It will be found that the flame from a Bunsen burner is considerably more intense
than that of an ordinary candle or gas burner, because since the air is thoroughly mixed with the
gas in a Bunsen burner, combustion takes place throughout instead of only at the surface.

COMBUSTION

1,856

atom of oxygen to form carbon monoxide, whose chemical sym-
bol is CO. The combustion is incomplete because the carbon
monoxide (CO) may be further burned to carbon dioxide (CO2) .

This gas is colorless, without taste and with but little odor. It readily
combines with oxygen to form CO2, and its chief property is its poisonous
nature* It is the deadly constituent of water gas.

HYDROGEN

OXYGEN

Fig. 3,351. — Experiments illustrating that the combustible may become the supporter of combus-
tion, and the supporter of combustion become the combustible. Hydrogen is generally desig-
nated as a combustible and oxygen the supporter of combustion. Hydrogen and oxygen
reservoirs are connected with two bent glass tubes passing through a cork into an ordinary
lamp glass c, upon the upper opening of which wire netting is laid.* The hydrogen being
lighted and the oxygen turned on to about the same extent, the lamp glass is placed over
the cork, where the hydrogen burns steadily. If the oxygen be turned almost off, the flame
will gradually leave the hydrogen tube and come over to the oxygen which will continue
burning in the atmosphere of hydrogen. By again turning on the oxygen, the flame may be
sent over to the hydrogen tube. With a little care the flame may be made to occupy an
intermediate position between the two tubes. The experiment may also be performed with
coal gas and oxygen.

Ones. What causes incomplete combustion?

Ans. Insufficient supply of air.

*NOTE. — In order to prevent the ends of the glass tubes being fused by the burning
gases, little platinum tubes, made by rolling up pieces of platinum foil, are placed in the
orifices, and the glass is melted around them by the blow pipe flame.

1,856 COMBUSTION

If too little air be admitted to the fire there will not he enough oxygen
present to supply two atoms of oxygen to each atom of carbon liberated^ hence
carbon monoxide will he formed having a heating value of only 4,^50 B,t.u.f
instead of carbon dioxide which has a heating value of 14,500 B.t.u.

Thus when CO is formed instead of CO2 because of lack of air supply,
which contains the necessary oxygen, there will be a loss of approximately
69% of the fuel.

Oues. What results when too much air is supplied?

Ans. Since carbon cannot combine with oxygen in any greater
ratio than two atoms of oxygen to one atom of carbon, any
excess air supply simply dilutes the gases and cools the furnace .

Oues. Are steam boilers usually operated with too
much air supply?

Ans. Yes, an excess supply as large as 150% is not uncom-
mon, too much draught being as a rule employed.

Oues. What is the effect of heating the air supply?

Ans. It increases the rate of combustion.

Oues. What are the objectionable effects of the nitro-
gen contained in the air supply?

Ans. In passing through the furnace without change it di-
lutes the air, absorbs heat, reduces the temperature of the
product for combustion, and is the chief source of heat losses in
furnaces.

Oues. What is the useful effect of nitrogen?

Ans. It prevents too rapid combustion.

Without the large proportion of nitrogen in the atmosphere, the latter
would be so rich in oxygen, that the resulting high rate of carbonation would
bum out the grates.

COMBUSTION

1,857

Ques. How much air is required for combustion?

Ans. One pound of carbon requires 2% pounds of oxygen for
its complete combustion to carbon dioxide, or about 12 pounds
of air. When the combustion is not perfect 1 pound of carbon

GA5 BURNING

Fig. 3.352. — Experiment illustrating that the combustible may become the supporter of com-
bustion, and the supporter of combustion become the combustible. Take a flask having
three openings A, B, and C, insert tubes at A, and C, as shown and connect B, with a supply
of coal gas. Turn on the gas at B, and it may be lighted at C. Now if a lighted match be
quickly thrust up the tube A, the air which enters it will take fire and bum inside the globe.

burned to carbon monoxide requires IH pounds of oxygen, or
about 6 pounds of air.

It has been impressed on the engineer's mind that, theoretically, coal
requires 12 pounds of air for its combustion and, in practice, 50 per cent in
excess of this, or 18 pounds. These values are frequently used by teachers,
writers of engineering articles and designers of various apparatus for the

1,858

COMBUSTION

boiler plant. While it is an easily remembered approximate in round num-
bers, the "12 pounds of air per pound of coal" does not hold true, as can
be seen in the first column of the table, since the theoretical amount of
air per pound of coal varies between 7 and a little over 11 poimds.

Air Required for Different Fuels

Fuel

Illinois bituminous, poor quality,
Illinois bituminous, good quality

Anthracite, average

Semibituminous, Pocahontas

Liquid fuel ,

Air theoretically
required per
pound of coal

7.0

9.4

10.2

11.2

14.24

Air theoretically

required per
10,000 B.t.u.,

generated

7.6

7.55

7.65

7.5

7.04

Let the ultimate analysis be as follows:

Per cent

Carbon 74.79

Hydrogen 4.98

Oxygen 6.42

Nitrogen « 1.20

Sulphur 3.24

Water. 1.55

Ash 7.82

100.00

When complete combustion takes place, as already pointed out, the
carbon in the fuel unites with a definite amount of oxygen to form CO2.
The hydrogen, either in a free or combined state, will unite with oxygen
to form water vapor, H2O. Not all of the hydrogen shown in a fuel analysis,
however, is available for the production of heat, as a portion of it is already
united with the oxygen shown by the analysis in the form of water, H2O.
Since the atomic weights and H and O are respectively 1 and 16, the weight
of the combined hydrogen will be J^ of the weight of the oxygen, and the
hydrogen available for combustion will be H — J/g O- Tn complete com-
bustion of the sulphur, sulphur dioxide SO2 is formed, which in solution in
water forms sulphuric acid.

Expressed numerically, the theoretical amount of air for the above analy-
sis is as follows:

COMBUSTION 1,859

.7479 C X 2M =1.9944 O needed
H X 8= .3262 O needed

.0498-:5542\

.0324 S X 1 = .0324 O needed

Total 2.3530 O needed
One pound of oxygen is contained in 4.32 pounds of air.

The total air needed per pound of coal, therefore, will be 2.353 X 4.32 =
10.165.

The weight of combustible per pound of fuel is . 7479 + .0418*+ .0324 -f
.012 = .83 pounds, and the air theoretically required per pound of
combustible is 10.165^.83 = 12.2 pounds.

The above is equivalent to computing the theoretical amounl of air
required per pound of fuel by the formula:

Weight per pound = 11.52 C + 34.56(h — -^ j +4.32 S

(10)

where C, H, O and S, are proportional parts by weight of carbon, hydrogen,
oxygen and sulphur by ultimate analysis.

Ones. Is it possible in practice to obtain perfect com-
bustion with the theoretical amount of air?

Ans. No.

An excess is required, amounting to sometimes double the theoretical
supply, depending upon the nature of the fuel to be burned and the method
of burning it. The reason for this is that it is impossible to bring each
particle of oxygen in the air into intimate contact with the particles in
the fuel that are to be oxidized, due not only to the dilution of the oxygen
in the air by nitrogen, but because of such factors as the irregular thickness
of the fire, the varying resistance to the passage of the air through the
fire in separate parts on account of ash, clinker, etc.

Oues. Is as large an excess of air required for oil as for
coal?

Ans. No.

*NOTE.— Available hydrogen.

1,860

COMBUSTION

Where the difficulties of drawing air uniformly through a fuel bed are
eliminated, as in the case of burning oil fuel or gas, the air supply may be
materially less than would be required for coal.

Experiment has shown that coal will usually require 50 per cent more
than the theoretical net calculated amount of air, or about 18 poimds per
poimd of fuel either under natural or forced draught, though this amount
may vary widely with the type of furnace, the nature of the coal, and the
method of firing.

PLATINUM TIP

Fig. 3,353. — The blow pipe. The pipe is at right angles to the burner as shown. It consists
of a metal tube provided with a platinum tip at one end and an enlargement at the other so
shaped as to cover the lips of the operator who blows through the enlarged end. In opera-
tion, the stream of air should not be propelled from the lungs of the operator (where a great
part of its oxygen would have been consumed) , but from the mouth by the action of the
muscles. The size of the flame, which is non-luminous, is much diminished, and the com-
bustion being concentrated into a smaller space, the temperature must be much higher at
any given point of the flame. Instructions: the blow pipe flame is similar to the ordinary
flame, consisting of three distinct cones: 2, the innermost cone L, is filled with the cool
mixture of air and combustible gas; 2, the second cone A, especially at its point R, is termed '
the reducing flame, because the supply of oxygen at that point is not sufficient to convert
the carbon into carbon dioxide, but leaves it as carbon monoxide, which quickly reduces
almost all metallic oxides placed in that part of the flame to the matalHc state; 3 .the outer-
most cone F, is called the oxidizing flame, because at that point the supply of oxygen from the
atmosphere is unlimited, and any substance which tends to combine with oxygen at a high
temperature is oxidized, when exposed to the action of that part of the flame. The hottest
part of the flames where another fuel or oxygen is in excess, appears to be a very little
in advance of the extremity of the reducing cone A.

COMBUSTION

1,861

If less than this amount of air be supplied, the carbon burns to monoxide
instead of dioxide and its full heat value is not developed.

An excess of air is also a source of waste, as the products of combustion
will be diluted and carry off an excessive amount of heat in the chimney-
gases, or the air will so lower the temperature of the furnace gases as to
delay the combustion to an extent that will cause carbon monoxide to pass
off unbumed from the furnace.

A sufficient amount of carbon monoxide in the gases may cause the
action known as secondary combustion, by igniting or mingling with air
after leaving the furnace or in the flues or stack. Such secondary combus-
tion which takes place either within the setting after leaving the furnace
or in the flues or stack always leads to a loss of efficiency and, in some
instances, leads to overheating of the flues and stack.

Calculated Theoretical Amount of Air Required per pound of
Various Fuels

Fuel

Weight of constituents in one
pound dry fuel

Air required
per pound

Carbon
per cent

Hydrogen
per cent

Oxygen
per cent

of fuel
pounds

Coke.

94.

91.5

87.

70.

50.

85.

5.

5.

6.

13.

'2.6

4.
20.
43.5

1.

10.8

Anthracite coal

11.7

Bituminous coal

11.6

Lignite

8.9

Wood

6.

Oil

14.3

Heating Values of Fuels. — To the engineer the heating
value of any fuel is the amount of water it will evaporate; that
is to say how many pounds of water will one pound of fuel
evaporate. In calculations of this kind the result is brought
down to a comparative basis of evaporation from and at 212
degrees Fahrenheit, and mean atmospheric pressure. Under
this condition one pound of water is turned into steam bv the

1,862

COMBUSTION

I

addition of 970.4 heat units. The quantity of water which
can be evaporated under these conditions by one pound of pure
and dry carbon is 14.94 pounds. As a heat unit is equal to 778
foot pounds, and as a pound of carbon contains about 14,500
heat units, the heat it contains would be equal to 14,500 multi-
plied by 778 = 1,281,000 foot pounds.

In the case of hydrogen, one pound of the fuel would evapo-
rate about 65 pounds of water.

55 6o 65 ■ -70 75 ' So' 85 90 95 ioa
Per Cent of-Eixed Carbon in Combustible

Fig. 3,354. — Curve of relation between heat value per pound of combustibles, and fixed carbon
in combustible as deduced by Kent.

Determination of the Heating Value. — The heating value
of a fuel may be determined either by burning a sample in a
calorimeter or by calculation from a chemical analysis. When
accuracy is desired, the first method should be used, as it is defi-
nitely known that coals having practically the same ultimate
analyses show a difference in thermal value when burned in a
calorimeter. This difference is due to the manner in which the
elementary constituents of the fuel are combined and cannot
be determined by chemical analysis.

COMBUSTION 1,863

"When the heating value is determined by calculation from a chemical
analysis, the calculation should be based on an ultimate analysis, which
reduces the fuel to its elementary constituents of carbon, hydrogen, oxygen,
nitrogen, sulphur, ash and moisture, to secure a reasonable degree of
accuracy.

A proximate analysis, which determines only the percentage of moisr
ttire, fixed carbon, volatile matter and ash, without determining the ulti-
mate composition of the volatile matter, cannot be used for computing
the heat of combustion with the same degree of accuracy as an ultimate
analysis, but estimates may be based on the ultimate analysis that are
fairly correct.

An ultimate analysis requires the services of a competent chemist,
and the methods to be employed in such a determination will be found in
any standard book on engineering chemistry. An ultirtiate analysis, while
resolving the fuel into its elementary constituents, does not reveal how
these may have been combined in the fuel. The manner of their combina-
tion undoubtedly has a direct effect upon their calorific value, as fuels
having almost identical ultimate analyses show a difference in heating
value when tested in a calorimeter. Such a difference, however, is slight,
and very close approximations may be computed from the ultimate analysis.

Ultimate analyses are given on both a moist and a dry fuel basis. Inas-
much as the latter is the basis generally accepted for.th^ comparison of
data, it would appear that it is the best basis on which to report such an
analysis. When an analysis is given on a moist fuel basis it may be readily
converted to a dry basis by dividing the percentages of the various con-
stituents by one minus the percentage of moisture, reporting the moisture
content separately.

Carbon (C)....
Hydrogen (H).

Oxygen (O)

Nitrogen (N). .
Sulphur (S)....
Ash

Moisture.

Moist fuel

Dry fuel

83.95

84.45

4.23

4.25

3.02

3.04

1.27

1.28

.91

.91

6.03

6.07

100.00

.59

.59

100.00

Calculations from an Ultimate Analysis. — The first
formula for the calculation of heating values from the composi-
tion of fuel as determined from an ultimate analysis is due to

1,864 COMBUSTION

Dulong, and this formula, slightly modified, is the most com-
monly used today. Other formulae have been proposed, some
of which are more accurate for certain specific classes of fuel,
but all have their basis in Dulong' s formula, the accepted modi-
fied form of which is:

The heating value per pound of dry fuel is

("-^)

S./.w. = 14,600 C+62,000 I 71-^ I + 4,000 S

where C, H, O and S are the proportionate parts by weight of
carbon, hydrogen, oxygen and sulphur.

Assume a coal of the composition given. Substituting in this
formula (18),

Heating value per pound of dry coal

= 14,600 X .8445+62,000 (.0425 — .:5^)+ 400 X .0091 = 15,093 5./.w.

8

This coal, by a calorimetric test, showed 14,843 B.t.u., and from a
comparison the degree of accuracy of the formula will be noted.

The investigation of Lord and Haas in this country, Mahler in France,
and Bunte in Germany, all show that Dulong' s formula gives results nearly
identical with those obtained from calorimetric tests and may be safely
applied to all solid fuels except cannel coal, lignite, turf and wood, provided
the ultimate analysis be correct. This practically limits its use to coal.

The limiting features are the presence of hydrogen and carbon united
in the form of hydrocarbons. Such hydrocarbons are present in coals in
small quantities, but they have positive and negative heats of combination,
and in coals these appear to offset each other, certainly sufficiently to apply
the formula to such fuels.

*Determination of Air Required for Combustion. — Each
combustible element in fuel will unite with a definite amount of

*NOTE. — From Babcock & Wilcox's book entitled "Steam."

COMBUSTION

1,865

o

Heat

value

perpound

of column

1 B.t.u.

-M-

oooo
o>o>oo

T— 1 rH CO

s

CO

^

05

Gaseous
product
perpound

of
column 1

= 1+

column 8

pounds

(M CO 1>- CO 00 (M
lO t^ TjH »0 (N CO

(N CO CO O 00 ^

,-1 CO irH

00

Air per

pound of

column 1

= 4.32tx

0

pounds

C^COt^cO GO (N
Ot^"^ O (N CO

1-^ CO ^

l>

Nitrogen
perpound

of
column 1
= 332* X

0
pounds

lO CO CO 00 (N
oqTjHCiLQ (N CO

00 -"^ tH CO CO CO

o

Oxygen
perpound

of
column 1

pounds

CO CO »0 00

TJH 1-1

' ^

lO

H

Carbon dioxide. . .
Carbon monoxide.
Carbon dioxide. . .
Watpr

Carbon dioxide

and water . .

Sulphur dioxide.. .

^

II

II II II II ^g II

CO

Atomic
or
com-
bining
weight

(MfMOOi-H CO <N

tHi-HC^ 1-H CO

(N

m

Oogw g m

-

III

O'^ o

1

c

0 P

(X

4

oxygen. With the
ultimate analysis of
the fuel known, in con-
nection with the table
here given, the theo-
retical amount of air
required for combus-
tion may be readily
calculated.

"Available'' Heat-
ing Value. — The heat-
ing value of hydrogen
has been given as in
round numbers, being
62,000 B.t.u. The
exact figures are given
higher or lower by
different authorities,
but the higher figures
seem to have the sanc-
tion of the U. S.
Government in making
coal tests, or 62,032,
the amount given by
Favre and Silberman.

That it will not pay
to decompose the hy-
drogen in water for
the purpose of burning
it as fuel can be clearly

1,866

COMBUSTION

> p. " II :2

is a.

> a

d)

o o ,

:s2S
> ft

s 5=1 s^

O ft^ O

I "si l-a

>

ft^ s

S C g OS ^i; o
^ 2 Q _^ -2

« ;3 ^ a

^2 go
o P<^ >
>

bo rt

5'"

Os8

TjH GO CO i-H CO ^

(M CO Thi 05 Oi <N
i-H LO C<1 CO CO r^
T-H COt-h

iO»0 0(M T-H O
C5 Oi CX) CO tJH CO

oooQ^d

C<l tH i-H T-H TjH (M

OOPwSco

OOgKgco

o) a;
o ?5 2

6^

o'o

^.2

"*^ a
08

^«

o ft

rtcc

perceived by a study
of the process of de-
composition that
takes place.

If nine pounds of
water which would
result from the burn-
ing of one pound of
hydrogen and the giv-
ing off of 62,000 heat
units, the water being
cooled to the temper-
ature of the air, be
passed into a hot
furnace, it will be de-
composed into eight
pounds of oxygen and
one pound of hydro-
gen. The energy con-
sumed in doing this
work will equal
62,000 heat units,
which will be ab-
sorbed from the heat
of the furnace. The
so called available
heating value of it is
obtained as follows:

COMBUSTION 1,867

Example — If one pound of hydrogen to be burned in just enough air
to supply 8 pounds of oxygen, the hydrogen and air be supplied at 62°,
and the products of combustion escape at 212 °F., what is the net
available heating value?

B.t.u. B.t.u.

Total heating value of 1 pound of hydrogen 62,000

Heat lost, latent of 9 pounds of water at 212 °F. =

970.4X9 8,733.6

Nine pounds of water heated from 62°F. to 212°F.. 1,349.3

Nitrogen with 8 pounds oxygen heated from 62 °F.

to212°F. = 8X3. 32 X150X. 2438 (specific heat) . 971 11,053.9

Net available heating value 11,053.9 50,946.1

Example^ — If the air supply be double that required to effect the com-
bustion of the hydrogen, the other conditions being the same as in the
first example, what is the net heating value?

B.t.u.

Net available heating value (from example 1) 50,946.1

Excess air 8X4.32 pounds

B.t.u.
Heat loss due to excess air 4.32* X 150 X. 2375 f = 1,231 1,231

Net heating value (including loss by excess air) 59,715.1

*NOTE. — 4.32 is the proportion of air to oxygen by weight;
tNOTE. — ,2375 is the specific heat of air.

Example — If with double air supply the products of combustion escape
at 562°, what is the total loss and net available heating value?

B.t.u. B.t.u.

Total heating value of 1 pound of hydrogen 62,000

Nine pounds of water heated from 62 °F. to 212 °F. . 1 ,349.3
Latent heat of 9 pounds of water at 212 °F. =

970.4X9 8,733.6

Degrees of superheat = 562—212=350.

Superheated steam, 9X350X .48* 1,512

Nitrogen, 26.56X 350 X .2438 T 3,238

Excess air 34.56 X 350 X .2375 4,104

Total loss 18,936.9 18,936.9

Net available heating value 43,063.1

I

'NOTE. — Specific heat of superheated steam.
tNOTE.— Specific heat of nitrogen.

1,868

COMBUSTION

•|^-s.l§-|l:§l

-d-d.S ^ § S VH .|
c3^ wn »^£ (u

55 5 Si^ o rt g ^ S

(Uh O.-tfT" J?- I> 5 »-«

W^

'all's':: 8 6-2 1

g O £ gp g g o;^ d
U P is ^•^~. <u C (u'o

COMBUSTION 1,869

High and Low Heat Value of Fuels. — In any fuel contain-
ing hydrogen the calorific value as found by the calorimeter is
higher than that obtainable under most working conditions in
boiler practice by an amount equal to the latent heat of the vola-
tilization of water. This heat would reappear when the vapor
was condensed, though in ordinary practice the vapor passes
away uncondensed . This fact gives rise to a division in heat
values into the so-called * 'higher" and 'lower" calorific values.

The higher value, i. e., the one determined by the calorimeter,
is the only scientific unit, is the value which should be used in
boiler testing work, and is the one recommended by the American
Society of Mechanical Engineers.

There is no absolute measure of the lower heat of combustion, and in
view of the wide difference in opinion among physicists as to the deductions
to be made from the higher or absolute unit in this determination, the lower
value must be considered an artificial unit. The lower value entails the
use of an ultimate analysis and involves assumptions that would make the
employment of such a unit impracticable for commercial work. The use
of the low value may also lead to error and is in no way to be recommended
for boiler practice.

An example of its illogical use may be shown by the consideration of a
boiler operated in connection with a special economizer where the vapor
produced by hydrogen is partially condensed by the economizer. If the
low value were used in computing the boiler efficiency, it is obvious that
the total efficiency of the combined boiler and economizer must be in error
. through crediting the combination with the heat imparted in condensing
the vapor and not charging such heat to the heat value of the coal.

Heating Value of Gaseous Fuels. — The method of com-
puting calorific values from an ultimate analysis is particularly
adapted to solid fuels, with the exceptions already noted. The
heating value of gaseous fuels may be calculated by Dulong*s
formula provided another term is added to provide for any car-
bon monoxide present .

Such a method, however, involves the separating of the con-
stituent gases into their elementary gases, which is oftentimes
difficult and liable to simple arithmetical error.

1,870

COMBUSTION

*t:; Qj Jh Wi Qj bo

^ 3 S
O tH w qXJ D*

CJ^

^ o _

3^2^

«+-. ^jO ES r! '^

o <i^ .s C.5_r

O rt'5 rt O ^
• rt tn c3 c n«+^

oL, o o <i> 9i
« ^ ^ C rt P!

. £ ^ be S C!

iC '

• <U-'

Vh »H ™ O Jh "

g^ cts 5 >< fi
.S^ , c o «

'^ P C O -a «-, w

o'o::^ w c: o Qj

M «-i ? O (U»^ ►^

«^ 0+» c g rt

'• ^TJ 5f.2 o «

<0 q i; C -J3 ^ (U

W'3 cj'^ a*' (u

Ph

COMBUSTION

1,871

As the combustible portion of gaseous fuels is ordinarily com-
posed of hydrogen, carbon monoxide and certain hydrocarbons,
a determination of the calorific value is much more readily ob-
tained by a separation into their constituent gases and a compu-
tation of the calorific value from a table of such values of the con-
stituents.

The accompanying table gives the calorific value of the more
common combustible gases, together with the theoretical amount
of air required for their combustion.

Weight and Heating Value of kVarious Gdsses at 32° F. and Atmos-
pheric Pressure with Theoretical Amount of Air Required
for Combustion . '■

Gas

Hydrogen

Carbon monoxide

Methane

Acetylene

defiant gas

Ethane

y

Cubic feet

Cubic feet

B.t.u.

B.t.u.

of air

Symbol

of gas

per

per

required

per pound

pound

cubic
foot

per pound
of gas

H

177.90

62000

349

428.25

CO

12.81

4450

347

30.60

CH4

22.37

23550

1053

214.00

C2H2

13.79

21465

1556

164.87

C2H^

12.80

21440

1675

183.60

cm^

11.94

22230

1862

199.88

Cubic feet

of air

required

per cubic

foot of gas

2.41

2.3

9.57

11.93

14.33

16.74

Example — Assume a blast furnace gas, the analysis of which in per-
centages by weight is, oxygen =2.7, carbon monoxide = 19.5, carbon
dioxide = 18.7, nitrogen =59.1. Here the only combustible gas is the
carbon monoxide, and the heat value will be,

.195 X 4.350 =848.25 5./.W. per pound.

The net volume of air required to burn one pound of this gas will be,
.195 X 30.6=5.967 cubic feet.

1,872

COMBUSTION

Example— A^snme a natural gas, the analysis of which in percentages
bv volume is oxygen = .40, carbon monoxide = .95, carbon dioxide = .34,
olefiant gas (aH^)=.66, ethane {Cm')=SM, marsh gas (CH^) =72.15
and hydrogen =21.95. All but the oxygen and the carbon dioxide are
combustibles, and the heat per cubic foot will be.

I""!" " I'.'. -'..'-■' .l.l.L'TrT-n" 1 1 1 M ! 1 I T 1 1 1 1 M

^^ ■^.-^^^rJr^^r^OLORAOO COAL..

34 .ip ,T,SS-" -- . PITTSBURGH COAL . I

i,*^^-^ - _l_ _|_

21 - - - -y- - ^

^ on -

, '7- + ---:-::: ::;^ = ^ = j±±=±x'?--:j:

y ,-■ .--!' : : " _ " - "

H 13 , ^ -

I ,4 - - - _ _ __

**'•'> " ' ' it

=j '2 _: :

♦: 11 ^ : -_ _ _

< "

o 10 _: : " - "

^ o " ~

m ~~ ' ' ANTHKACME _^ -■;*-*" "

3 -,--.-- - -[- _ _

■____u -.=f.==,p,:==t,^--=^4f|:^

1050 1100 1150

Fig. 3,357. — Percentage curves of volatile matter from different coals at various temperatures.

From CO = .0095 X 339 =3 22

C2H^ = .0066 X 1,675 = 11.05

aw = .0355 X 1,859 = 65.99

CH* = .7215 X 1,050 = 757.58

H = .2195 X 346 = 75.95

B.t.u. per cubic foot 913.79

COMBUSTION

1,873

The net air required for combustion of one cubic foot of the gas will be,

CO =

.0095 X 2.39 = .02

cm' =

.0066 X 14.33 = .09

OH« =

.0355 X 16.74 = .59

CH4 =

.7215 X 9.57 = 6.90

H

.2195 X 2.41 = .53

Total net air per cubic foot 8.13

Proximate Analysis. — The proximate analysis of a fuel gives
its proportions by weight of fixed carbon, volatile combustible
matter, moisture and ash. The following method of making
such an analysis which has been f round to give eminently satis-
factory results:

Figs, 3,358 to 3,360. — Various crucibles. Fig. 3,358 royal Berlin glazed under and outside;
fig. 3,359 Gooch, glazed with perforated bottom; fig. 3,360 normal school. This is a spun
iron crucible for individual use of the laboratory student, or for general experimenting. It
may be used equally well as an open crucible, a closed crucible, or a retort; and being of
thin metal, is easily brought to a red heat in the flame of an ordinary burner. All parts inter-
changeable. Capacity, about IJ^ ounce.

From the coal sample obtained on the boiler trial, an average sample of
approximately 40 grams is broken up and weighed. A good means of
reducing such a sample is passing it through an ordinary coffee mill. This
sample should be placed in a double- walled air bath, which should be kept
at an approximately constant temperature of 105 degrees centigrade, the
sample being weighed at intervals until a minimum is reached. The per-
centage of moisture can be calculated from the loss in such a drying.

For the determination of the remainder of the analysis, and the heating
value of the fuel, a portion of this dried sample should be thoroughly pul-
verized, and if it is to be kept, should be placed in an air-tight receptacle.

One gram of the pulverized sample should be weighed into a porcelain
crucible equipped with a well fitting lid. This crucible should be supported
on a platinum triangle and heated for seven minutes over the full flame of

1,874

COMBUSTION

a Bunsen burner. At the end of such time the
sample should be placed in a desiccator containing
calcium chloride, and when cooled should be
weighed. From the loss the percentage of volatile
combustible rnatter may be readily calculated.

The same sample from which the volatile matter
has been driven should be used in the determination
of the percentage of ash. This percentage is ob-
tained by burning the fixed carbon over a Bunsen
burner or in a mufHe furnace. The burning should
be kept up until a constant weight is secured, and it
may be assisted by stirring with a platinum rod.

The weight of the residue determines the per-
centage of ash, and the percentage of fixed carbon
is easily calculated from the loss during the deter-
mination of ash after the volatile matter has been
driven off.

Proximate analyses may be made and reported
on a moist or dry basis. The dry basis is that
ordinarily accepted. The method of converting
from a moist to a dry basis is the same as described
in the case of an ultimate analysis. A proximate
analysis is easily made, gives information as to the
general characteristics of a fuel and of its relative
heating value.

Fig. 3,361. — The candle flame. It is seen to consist of three
concentric cones. 1 , the innermost around the wick, appear-
ing almost black; 2, the next emitting a bright white light,
and 3, the outermost being so pale as to be scarcely visible
in broad daylight; there is also apparent a bright blue cup
surrounding the base of the flame. 1, The dark innermost
cone consists of the gaseous combustible to which the air
does not penetrate, and which, therefore, is not in a, state of combustion; 2 In the second or
luminous cone combustion is proceeding, but it is by no means perfect, being attended
by the separation of a quantity of carbon, which causes luminosity upon the part of the
flame. The presence of free carbon is. shown by depressing a piece of porcelain upon this
cone when a black film of soot is deposited. The liberation of the carbon is due to the de-
composition of the hydrocarbons by the heat, which separates the carbon from the hydro-
gen, and this latter, undergoing combustion evolves sufficient heat to raise the separated
carbon to a white heat, the supply of air which penetrates into this portion of the flame
being insufficient to affect the combustion of the whole of the carbon; 3, the pale outer-
most cone or mantle of the flame in which the separated carbon is finally consumed may be
termed the cone of perfect combustion, and is much thinner than the luminous cone, the
supply of air to the external shell of flame being unlimited and the combustion therefore
speedily effected; 4, the bright blue cup surrounding the base of the flame is formed by
the perfect combustion (without any separation of carbon) of a small portion of the hydro-
carbons owing to the complete admixture of air at this point.

COMBUSTION 1,875

Flame. — Visible flame consists of combustible gas heated to
an intense heat. If it come in contact with a supply of air in a
chamber where the temperature is sufficiently high , it will burn ,
but if cooled before coming in contact with the air supply it will
escape in an unburned state as gas or smoke. The product of
perfect combustion is invisible. The product of the perfect
combustion of carbon is invisible carbonic acid. The product
of the perfect combustion of hydrogen is invisible water vapor.

As carbon is the principal constituent of coal the state of the
combustion in the furnace is determined very closely by deter-
mining the amount of carbonic acid in the flue gases.

It is considered that when fresh coal is fired into a hot furnace
that the first process which takes place is the evaporation of the
moisture in the coal into steam. This results in the decomposi-
tion of more or less of the steam in contact with the carbon into
hydrogen and carbonic oxide. Also some of the carbonic acid
formed by union of oxygen with coal may be decomposed into
carbonic oxide. These two processes both have a tendency to
cool the furnace. The volatile matter is then distilled off and
burned if the temperature of the furnace be high enough, and
"the air supply be sufficient.

If then the temperature and air supply be maintained, the coal
or coke remaining is consumed except such mineral or earthy
matter in it that is not combustible.

Smoke. — By definition smoke is* a term applied to all the
products of combustion escaping from the furnace whether visible or
invisible. It is popularly and erroneously restricted to the visi-
ble product of combustion.

Oues. What are the black particles in smoke?

Ans. Solid carbon.

1,876 COMBUSTION

Oues. What does colored smoke indicate?

Ans. Imperfect combustion.

Most of the coals used as fuel in boiler furnaces contain substances that
distill at low temperatures and are released when the coal is heated. These
substances are commonly known as volatile matter.

The amount and nature of these distillates vary widely, and upon their
composition depends the amount and nature of the smoke produced.

■

5

1

Figs. 3,362 and 3,363. — Cause of smoke. When the supply of oxygen is insufficient to con-
sume the particles of solid carbon they are set free and then assume the form of soot, the
collection of these minute particles being called smoke. This can be illustrated by cutting a
hole in a card, fig. 3,362, so as to fit over an ordinary gas burner. Now, light the gas and
place a glass chimney over the burner, letting it rest on the card. The flame will at once
begin to smoke, because very little air can then come in contact with the flame, and, there-
fore, when the fine particles of carbon are set free by the combustion of the hydrogen, instead
of being burned, as they would be if the air with its supply of oxygen were not excluded from
the flame by the chimney, they escape unconsumed in the form of black powder or soot. If
the chimney be raised from the card, as in fig. 3,363, so as to permit air to enter space between
them at the bottom of the chimney, as indicated by the arrows, and supply the flame with
oxygen, the smoke will cease, as the particles of carbon are then consumed. The same prin-
ciple is illustrated in an ordinary kerosene lamp. It is well known that without a chimney the
flames of nearly all such lamps smoke intolerably, whereas with a glass chimney and the pecu-
liarly formed deflector which surrounds the wick, the light burns without smoke unless the
wick is turned up high. The effect of the chimney is to produce a draught which is thrown
against the flame by the deflector, and thus a sufficient supply of oxygen is furnishedto con-
sume all the particles of carbon , whereas, without the draught produced by the chimney, the
supply of oxygen is insufficient to ignite all the carbon, which then escapes in the form of
smoke or soot. It must not, however, be hastily assumed that if the flame do not give out
a bright light, therefore the combustion is not complete. As has already been stated, the
light of the gas flame is due to the presence of burning particles of solid carbon, which is
set free by the combustion of the hydrogen with which it is combined. After it is separated
from the hydrogen it immediately assumes a solid form.

COMBUSTION 1,877

The volatile matter (this term does not include the moisture), consists
of hydro-carbons which differ primarily in the temperatures at which they
boil (distill), and in their ignition temperatures.

Furthermore, the lighter volatiles remain in a gaseous state when they
are cooled. The heavier ones such as tar vapors, have a tendency to
dissociate at certain temperatures, liberating the carbon particles. If
sufficiently high temperatures prevail in the combustion chamber, and
these carbon particles come into contact with free oxygen, they bum
completely.

The incandescence of the highly heated carbon particles before their
complete combustion produces the luminosity of the flame. If, however^
oxygen be lacking in the combustion chamber, or if the oxygen do not
come into contact with the carbon particles before the temperature drops
below the ignition point, incomplete combustion takes place and the
unburned carbons pass off as smoke.

Oues. Upon what does the smoke producing tendency
of coals depend?

Ans. Since the various hydrocarbons differ in their readiness
to dissociate, the smoke production of coal depends upon the
nature rather than upon the volume of the volatile content.

Some coals, despite their relatively high percentage of volatile matter,
do not tend to produce smoke as readily as others with less volatile content^
such as lignites.

Oues. Is black smoke an indication of greatly reduced
economy?

Ans. No,

The erroneous opinion prevails that black smoke contains a large amount
of combustible matter and that it is a sign of considerable waste. The
most dense smoke does not commonly contain more than 3^ of 1 per cent
of the combustible fired.

The extreme fineness and the distribution of the carbon particles bestow
upon them a high coloring power. The carbon particles producing visible
smoke are not derived from a lifting of fixed or solid carbon from the
grates, but they are formed from gases during the combustion process.

Oues. How do the losses due to black smoke compare

1,878 COMBUSTION

with those due to incomplete combustion or excessive air,
which generally accompany combustion without visible
smoke?

Ans. They are negligible-

Oues. What is the effect when the air supply does not
thoroughly mix with the gases from the fuel?

Ans. It causes slower combustion, resulting in a longer flame.

For instance, if the glass chimney be removed from the circular burner
of a kerosene lamp a long, smoky flame is produced, but when the chimney
is replaced the flame becomes short and clear. The reason for this is that
the chimney produces a draught. That is, it creates a higher air velocity,
and effects a good mixture of air and combustible gas.

The flame post over the bridge wall in a boiler furnace may be designed
to achieve a similar effect.

Oues. How can the hyrdo-carbon gases be completely
and smokelessly burned?

Ans. By admitting and thoroughly mixing sufficient air before
the gases are cooled below a certain temperature .

Applying these principles to the combustion of volatiles in the boiler
furnace, the following requirements must be met to effect complete and
smokeless combustion.

1. Introduction of the proper amount of air to secure complete com-
bustion.

2. Effective and early admixture of air and volatiles.

3. Sufficiently high temperatures in the combustion zone.

The complete fulfillment of these three cardinal conditions of smokeless
combustion is rather difficult to obtain in the boiler furnace, especially
the second requirement. Undue consideration is generally given to the
maintenance of high temperatures in the combustion space . In the majority
of cases insufficient air and particularly incomplete mixture are the causes
of smoke products. This is especially true where bituminous coals aic
burned.

If care be taken to effect an early and complete mixture of sufficient air
with the combustible gases, satisfactory combustion can be obtained
in furnaces that are completely surrounded by heating surfaces.

COMBUSTION 1,879

Ques. As long as there are combustible gases in the
furnace is a reasonable amount of excess air objectionable?

Ans. No.

The cooling of the flame through moderate air admission above the flame
need not be feared. In fact, air must be provided above the grates to
complete combustion, because generally the amount of air admitted
through the grates is consumed in the fuel bed.

Ones. What is the effect of the heat storing and re-
fractory properties of arches and piers in the combustion
chamber?

Ans. They decrease the efficiency of the furnace and have a
questionable influence upon the completeness of combustion.

The effect of such contrivances must be judged only by their ability to
effect or prevent the thorough mixture of air and combustible gases. To
achieve this, their location must be at the point of origin of flame develop-
ment; that is, at or near the bridge wall.

Taking into consideration the fact that the absorption of heat by a surface
through direct radiation is decidedly greater than the convection of heating
surfaces in contact with the non-illuminant fuel gases, the exposure of the
greatest possible amount of heating surface to the luminous flame is of
prime importance to the economy of the boiler plant. Bearing this in
mind, efforts must be directed to achieve the desired results with as little
refractory brickwork as possible, as otherwise the success in smoke abate-
ment will be gained at the cost of efficiency. This is of greater importance
in the hand fired furnace than in the stoker furnace with continuous feed.

Oues. How should the combustion chamber be pro-
portioned for burning bituminous coals?

Ans. It should be extra large.

Provision must be made to control the air supply above the fuel so as to
supply additional oxygen to complete the combustion.

In admitting air above the fuel, unless it can be supplied at the right
time and place, and in the right quantity, it may prove a worse evil than
the smoke itself by lowering the temperature of the gases in the furnace
to a point below which ignition will not take place.

1,880

COMBUSTION

Ques. How is smoke classified with respect to intensity ?

Ans. By dividing it into several shades, or comparing it
with a smoke chart.

Classification of Smoke. — According to ntmierous authori-
ties, the best scale to adopt seems to be one having five shades:
1. White transparent vapor.

XT
<

X

<

5 2

o

ir I

■

,

V

i

1

■

X

/"

^

/

/

/

/

.

/

/

3.G 3.8 4.0 4.E 4.4 4.6

PER CENT HVDROGEN

4.8

SO

Fig. 3.364. — Ringelmann chart showing how the density of smoke varies with the percentage of
hydrogen in the coal.

2. Light brown smoke.

3. Brownish gray smoke.

4. Dense smoke.

5. Thick black smoke.

The personal equation enters largely into the determination
of the shade of smoke as must be evident.

COMBUSTION

1,881

Furnace Temperature. — The theoretical temperature of a
furnace can be calculated by dividing the heat units produced
by the combustion of the fuel by the weight of the gases multi-
plied by their respective specific heats.

If carbon were burned in the theoretical amount of pure oxygen
necessary for complete combustion and all the heat developed in
raising the temperature of the resulting gases utilized, a tempera-
ture of 18,000° Fahr. would be obtained.

Figs. 3,365 to 3,370. — Ringelmann scale for grading smoke density. It consists ofiour large
sheets ruled with vertical and horizontal lines forming squares as shown. No 1 is ruled with
line 1 mm thick and spaced 9 mm wide; No. 2, 2.3 mm lines, 7.7 mm spaces; No. 3, 3.7 mm
lines, 6.3 mm spaces; No. 4, 5.5 mm lines, 4.5 mm spaces. The cards are placed 50 feet from
the observer in line with the chimney, together with a white and a solid black card. The
observer glances quickly from the chimney to the cards and judges which one corresponds
with the color and density of the smoke. Ringlemann readings are usually taken at 3^ to 1
minute intervals during an hour or more . ^ The readings are plotted in a log which gives a
good general idea of the manner and regularity of smoke emission but is very unsatisfactory
for ordinary stacks.

NOTE. — According to the Am. Soc. of M. E., no wholly satisfactory methods for either
quantitating or qualitating smoke determinations have yet come into use, nor have any reli-
able methods been established for definitely fixing even the relative density of the smokp
issuing from chimneys at different times. One method commonly employed, which answers
the purpose fairly well, is that of making frequent visual observations of the chimney at inter-
vals of one minute or less for a period of one hour and recording the observed charactertistics
according to the degree of blackness and density, and giving to the various degrees of smoke
an arbitrary percentage value rated in some such manner as follows: dense black, 100%;
medium black, 80%; dense gray, 60%; medium gray, 40%; light grey, 20%; very light,
5%; trace, 1 %; clear chimney, 0. The shade and density of smoke depend somewhat on the
character of the sky or other background, and on the air and weather conditions obtaining
when the observation is made, and there should be given due consideration in making com-
parisons .

NOTE. — One of the latest methods for indicating and recording the density of smoke is
one depending on the variations in the electrical conductivity of the metal selenium due to
variations in the intensity of light shining upon it. Openings are provided on either side of
the flue directly opposite each other. The intensity of the light rays falling on the selenium
varies with the density of the smoke. A milli-ampere meter in circuit with the selenium cell
registers the variations.

1,882

COMBUSTION

In burning coal, however, this amount of heat is never attained for
various reasons. There are always losses by radiation and in other ways
and the combustion process is never perfect except in calorimeter tests.

Instead of oxygen,, air is u^ed to support combustion and almost inva-
riably an excess of air over that theoretically required for complete com-
bustion, giving a much larger weight of gases to be heated.

Some of the heat
available, in the
coal is' lost by in-
complete combus-
tion, by radiation
to the exposed sur-
faces to the fuel
bed, by dissociation
of the resulting
gases, by evapor-
ating and super-
heating moisture in
the coal and in the
air supplied and by
heating the ash.

\

^

\

NP

\

Np

\

P

\

'I

20 30 4-0

MINI. PER. HOUR

50 60

Fig. 3,371. — Method of plotting Ringelmann readings as suggested by E. J. Bailey. This method
consists in finding the total time during the day represented by each density, reduce it to
minutes per hour, and add it to the number of minutes corresponding to each higher density.
The totals are plotted against the Ringelmann chart numbers, and the curve represents the
fraction of time during which each given degree of smoke density has been reached or ex-
ceeded, Bailey remarks that Ringelmann chart No. 5 includes all smoke that is opaque.
•Twice as much carbon can be carried at one time as at another, and not affect the density
reading.

For these reasons, the temperature in the furnace of a steam boiler
rarely, if ever, exceeds 3,000°-F. The temperature rise, then, is equal to the
calorific value of the fuel minus the losses due to the foregoing causes
divided by the product of the weight of gases times their specific heat.

NOTE. — Admiral R. T. Hall describes an electrical means of determining the density of
smoke used on the U. S. S. Conyngham. The basic principle is the sensitivity of the metal
selenium to light as affecting the passage of electric current. A selenium disc connected to the
ship lighting circuit was placed on one side of the stack opposite a light on the other. The
intensity of the beam of light striking the disc of course varied with the density of the smoke.
A milliammeter with a suitably graduated scale indicated the changes in current due to the
changes in smoke density.

COMBUSTION 1,883

Oues. How can an increase in the furnace temperature
be obtained?

Ans. 1, By using a coal with a higher heating value; 2, by
decreasing the amount of excess air suppHed, obtaining more
complete combustion; 3, by decreasing the amount of heat radi-
ated from the fuel on the grates, and 4, by preheating the air
admitted for combustion.

Ones. What is the effect of increased furnace tempera-
ture on the heat absorption and efficiency, and why?

Ans. If all the other conditions be maintained constant but
a coal of a higher heating value be substituted, the total heat
absorbed and efficiency will be higher since there will be a greater
amount of heat absorbed by direct radiation.

If the amount of excess air supplied be decreased to secure better com-
bustion, both the heat absorption and efficiency will be increased.

If the amount of heat radiated from the furnace walls be decreased,
both the heat absorption and efficiency are increased, but cut down the
amount of heat radiated to the water heating surface and it wiU be found
that both the heat absorption and efficiency are decreased.

Oues. What is the effect of preheating the air supply ?

Ans. It increases both the heat absorption and efficiency.

Oues. What difficulties are likely to be encountered in
increasing the furnace temperature?

Ans. High furnace temperatures cause increased depreci-
ation of the brickwork and ironwork and is accompanied by the
formation of clinkers.

Coal ash becomes plastic or even liquid at certain temperatures, depend-
ing on its composition. When these temperatures are reached, the ash
will fuse and tend to clog the grates, interfering with the air supply and
decreasing the rate and efficiency of combustion . This tendency is increased

1,884 COMBUSTION

if, in the manipulation of the fire, the ash be raised to the surface of the fue
bed and exposed to the full furnace temperature.

Owes. What determines largely the temperature of
combustion?

Ans. The design of the furnace.

The most important features of the design in this respect are the arrange-
ment of brickwork and heating surface, the volume and length of the com-
bustion space and the type of grate or stoker . These items affect the furnace
temperature because they control the degree of the completeness of com-
bustion, the amount of radiation and to some extent the amount of air
admitted.

Oues. What should be considered in the selection of fire
brick for a furnace?

Ans. They should be chosen to meet the operating condi-
tions of load, furnace temperature, and character of coal particu-
larly with respect to the composition of its ash.

For instance, where there is a steady load and the ash of the coal burned
does not exert an appreciable fluxing action on the brick, any good grade
of fire brick whose fusing temperature is greater than the maximum furnace
temperature obtained would be satisfactory, if properly installed and given
reasonable care.

Where the fine ash carried through the furnace by the gases exerts a
fluxing action on the brick, the brick used in that part of the furnace exposed
to this action should be especially chosen for its ability to resist this influ-
ence.

In many cases the ash in the fuel bed itself exerts a very destructive
effect on the brick work exposed to its influence. Where the load is exceed-
ingly variable and where sudden inrushes of cold air into the furnace cannot
be avoided, heavy stresses are set up in the brick, which call for a brick .
mechanically strong and with a minimum tendency to spall.

Ashes. — By definition the term ashes signifies all the mineral
rmatter left after the complete combustion of fuel.

Every variety of mineral fuel contains more or less incombustible matter
or ashes.

COMBUSTION 1,885

Oues. Why do fuels contain incombustible matter?

Ans. Because the plants of which the coal is formed con-
tained inorganic matter, and because of the earthy matter in the
drift of the coal period.

Ones. What are the principal constituents of ashes?

Ans. Silica, alumina, lime, oxide and bisulphide of iron.

According to Kent the composition of ash approximates that of fine clay>
with the addition of ferric oxide, sulphate of Hme, magnesia, potash, and
phosphoric acid.

White ash coals generally contain less sulphur than the red ash coals ^
which contain iron pyrites.

The analysis of ashes of Pennsylvania anthracite coal by Professor
Johnson yielded:

Silica 53.6

Alumina 36.69

Sesquioxide of iron 5.59

Lime 2.86

Magnesia 1.08

Oxide of magnesia .19

100.01

Ohio bituminous coal, containing 5.95 per cent of ash, yielded upon
analysis:

Silica. 58.75

Alumina 35.3

Sesquioxide of iron 1.2

Magnesia .68

Potash and soda 1 .08

Phosphoric acid .13

Sulphuric acid .24

Sulphur combined .41

Oues. What is clinker?

Ans. A product formed in the furnace by fusing together
impurities in the coal such as oxide of iron, silica, lime, etc.

Oues. Which coals clinker least under high tempera-
ture, as judged from the color of the ashes?

Ans. Those whose ashes are nearly pure white.

1,886 COMBUSTION

Oues. What substance in ashes causes clinker?

Ans. Oxide of iron.

The presence of oxide of iron in any considerable quantity is indicated
by the red color of the ashes. Coals high in sulphur generally give a very
fusible ash, on account of the iron with which the sulphur is in combination.
A double ash tends to form clinker.

Oues. With complete combustion of coal, what per-
centage of ashes remain?

Ans. It varies considerably for different coals, but average
values will be between 5 and 10 per cent.

FUEL ANALYSIS 1,887

CHAPTER 58
FUEL ANALYSIS

Why Tests Should be Made. — The value of coal for the pro-
duction of heat for any given purpose cannot be ascertained from
its appearance. The value is not determined by the locality of
the mine from which it is obtained, nor by the trade name by
which it is placed on the market .

The final value is determined by the results secured when it
is used for the purpose intended. Satisfactory results, however,
depend upon two conditions:

1. The quality and nature of the coal must be suited for the
work intended.

2. The method of firing or using the coal must be correct.

To use fuel intelligently it is necessary to ascertain these two conditions.
The first condition: the determination of the intrinsic quality of the coal, can
be determined only by a laboratory test. The second condition: the
realization of satisfactory operation, is obtained, first, as an outcome of the
first condition, namely:' the obtaining of a fuel with proper constituents;
secondly, its proper method of use as determined by practical operating
experience, modified according to the quality and properties of the coal as
determined by test.

Oues. State the advantages due to testing of fuel.

Ans. 1. It determines its fair purchase price; 2, it locates the
difficulty when results are not satisfactory; and, 3, it is a guide to
better operation.

1,888

FUEL ANALYSIS

Apparatus Required for Fuel Testing

For the Determination of B. T. U.'s, Moisture, Volatile
Mater, Ash and Sulphur.

Sampling and Preparation of
Laboratory Samples

Crusher

Pulverizer

or Ball Mill

Sampler

Sampling Cloth

Brush

Sieves

Analytical Balance

Set of Weights

Sample Bottles 4 oz. with stoppers

Porcelain Capsules with cover

Mason Jars

Spatula

Pellett Press (Optional)

Moisture

Drying Oven
If gas, with burner and thermo-regulator
If electric, Freas or Varsity Electric Oven

Analytical Balance

Set of Weights

Capsules with cover

Dessicator.

Calcium Chloride gran.: for dessicator
Ash

Gas Burner with rubber tubing, also

Tripod with triangle

or Gas Furnace

or Electric Furnace

Dessicator

Calcium Chloride gran. : for dessicator

Analytical Balance

Set of weights

Crucible Tongs

Volatile Matter

Platinum Crucible with coyer, 10 or 20

gram
Tripod with Nichrome Triangle
Meker Burner No. 3
or Electric Furnace
or Gas Furnace

Sulphur

Porcelain Crucibles No, i

Muffle Furnace

or Gas Burner with tripod and triangle

Analytical Balance

Set of Weights.

Funnel Stand

Funnels

Filter Paper, ashless

Drying Oven

Beakers

Eschka Mixture

Bromine

B. T. U/s

Calorimeter

Thermometer

Oxygen

Fusing Point of Coal Ash

"High-Temp" Electric Furnace

or Gas Furnace

Pyrometer

FUEL ANALYSIS 1,889'

Methods of Testing Coal. — The true test of any coal is the
burning of it, but the chemical character and quality of a coal
is a reliable indication of what may be expected from its use.
Coal can be purchased under specifications as to the chemical
content, and knowledge of the chemical content makes it possi-
ble to determine whether the coal specified has been delivered.

In a large manufacturing plant coal and cinder analyses
should be made daily. Coal testing has become standardized
with the following analyses and tests that have been found to
give sufficient information as to the value of a given coal and its.
fitness for a given service.

These analyses and tests are:

1. Proximate analysis; 2, ultimate analysis; 3, sulphur test;
4, heat of combustion (calorimeter) test; 5, ash analysis.

Owes. What is the difference between a proximate and
an ultimate analysis?

Ans. A proximate analysis separates the coal into four parts:
moisture, volatile matter, fixed carbon, and ash; and ultimate
analysis reduces the constituents of the fuel (except the moisture
and ash) to the ultimate chemical elements: carbon, hydrogen^
nitrogen, sulphur, and ash.

Oues. Define fixed carbon.

Ans. Fixed carbon is the carbon remaining after distillation^
It is not the same as the total carbon found by ultimate analysis.

Oues. Define combustible.

Ans. Combustible is that portion oj the coal left after sub-
tracting the ash and moisture.

Oues. What is volatile matter?

1,890

FUEL ANALYSIS

FUEL ANALYSIS

1,891

1

fh.

H

'b>

, 1

^r-^

ill

4

Z.-o^'i^ s^S^-a^ s^^'^.'H-^ g"^ &^«^

• z; o o . u rt-"

00 S.

is &5 is .-s l-e-^P s'.-o . =gs ?•§'= g

o o

0,^.^ 3.^ 3 .

<u c ^j:j t. a; r

»C CO O O OC'C Cu ni rr c«5 ri »-" ^i «^ "JU '■^ '" ro ^^ /v^ r; ""i

J^i^S

S-^ I - si- 2it-2i J^-^ %^ «:cQ e °'e ^i:;

iasbc?*2t'Si2.

CW«-icj*-'0^<U

'il^'.S c: M '^•^■!S w w.S OCX) ••^t^ i^ rt^ rt^ »- 2
^Sf^rt'OW«Co}_,> iS^Tn Q> ^ CIS Oi P^ O ^

'"'^ S'S o S SQf-I3 o^-g^^ .M- 8^ 8<- «

li rt-t^ c!©--

$:5 c 8g-c «ii |8 . > "-3 S IcS ^'^ ^< J I

"5 Js «« 5

5 o o

rt-d wc ^;;;; 0.2 ° oi-[

a2p.sj^s.s-S||,|g|s^.s^s|.£

1,892

FUEL ANALYSIS

Ans. Volatile matter is the total combustible less the fixed
carbon, and includes gases, hydro-carbons, free oxygen and
nitrogen, although the latter two are not combustible.

Ones. What is ash?

Ans. Ash IS the residue remaining after the moisture and
volatile have been driven off and the fixed carbon ignited.

<.." —

Ef-

.'^^ 7,-^.110.^

5i

■=

B^

^~

y^

^^=

tei

§

^^

= ^

ffi

fe H

1^

R=

9^ ^

^ ^

»l

3

Fig. 3.406 to 3,408. — Method used by Bureau of Mines for sealing shipping can with adhesive
tape.

Ques. What is moisture?

Ans. Moisture is the loss in weight of a sample of coal when
dried at a given temperature for a given length of time.

Proximate Analysis. — As stated by Kent, the proximate
analysis is a most valuable means of identifying the general
character of the coal.

FUEL ANALYSIS

1,893

1. The amount of combustible matter, expressed as a percentage of the
combustible, distinguishes between the anthracite, the semi-bituminous,
and the bituminous coals.

2. Among the bituminous coals,, the moisture is an important guide
to the character of the coal.

3. The ash is also a criterion of the coal's value.

4. The sulphur taken in connection with the ash is also an indica-
tor of the value of the fuel, as high sulphur generally is found in a coal
which clinkers badly, and with which it is difficult to obtain the rated
capacity of a boiler.

Ha

Pig. 3,409.— Gaertner analytical balance designed to meet the requirements of educational
laboratories in quantitative analysis, capacity 200 grams, sensibility 1 milligram. The
rider is of aluminum, 1 oxidized block, 7 inches long, divided into fifths of milligrams with
white divisions. The knife edges and planes are of agate; pans of German silver, 2]/^ inches
in diameter; polished mahogany case with counterpoised front door and base fitted with
leveling screws.

Different laboratories use somewhat different methods in making
proximate analysis.

Apparatus Required — For making a proximate analysis the following
apparatus is required: A mill for grinding the coal, chemical scales sensitive
to Viooo of the amount weighed, drying apparatus, including an oven and
a dessicator, a platinum crucible, a Bunsen burner, a blast lamp, and a
supply of oxygen. The Bureau of Mines prefers sulphuric acid to calcium
chloride as a moisture absorbent in the dessicator.

1,894

FUEL ANALYSIS

The U ,S. Bureau of Mines has made a great number of analyses^
and has developed complete and satisfactory methods which agree
very closely with those recommended by the committee on
coal analysis of the American Chemical Society. The tests of
the latter are given to the last detail in the report; they are here"
briefly given in the larger type as follows:

Moisture, — The moisture content is determined by drying the sample
in a suitable oven at a constant temperature of 105° Centigrade for one
hour. Upon being removed from the oven the sample should be cooled
in a dessicator before weighing.

Fig. 3,410. — Eimer and Amend analytical balance weights. The gram weights are of brass
lacquered, the fraction weights of platinum except below 20 milligrams, which are of
aluminum. The set includes riders and forceps in mahogany box, hinged lid lined with
velvet.

Bureau of Mines Method. — Weigh out 1 gram of the pulverized, air dried sample, and
place it in a shallow porcelain capsule, H inch deep and 1^ inches in diameter. Dry for ooe
hour at 105° C. in a constant temperature oven, through which a current of preheated air is
passing at a rate to change the entire volume of air 2 to 4 times per minute. The air is dried
before entering the oven by passing through concentrated sulphuric acid.

After one hour the capsule is removed from the oven, and cooled in the dessicator, the loss
in weight is called the "moisture at 105° C."

Am. Soc. of M, E. Methods: 25. — When the sample lot of coal has been reduced by
quarters to say 100 pounds, a portion weighing say 15 to 25 pounds should be withdrawn for
the purpose of immediate moisture determination. This is placed in a shallow iron pan and
dried in the hot iron boiler flue for at least 12 hours., being weighed before and after drying on
scales reading to quarter ounces.

FUEL ANALYSIS

1,895

26. — The moisture thus determined is approximately reliable for anthracite and semi-
bituminous coal, but not for coal containing much inherent moisture.

For such coal and for all reliable determinations, the following method should be pursued:
Take one of the samples contained in the glass jars, and subject it to a thorough air drying, by
spreading it in a thin layer and exposing it for several hours to the atmosphere of a warm room,
weighing it before and after, thereby determining the quantity of surface moisture it contains.
Then crush the whole of it by running it through an ordinary coffee mill or other suitalole
crusher adjusted so as to produce somew;hat coarse grains (less than Vie inch) , thoroughly mix
the crushed sample, select from it a portion of from 10 to 50 grams, say 3^ ounce to 2 ounces,
weigh it in a balance which will easily show a variation as small as 1 part in 1,000, and dry it
for one hour in an air or sand bath at a temperature between 240 and 280° F.,
(this temperature being necessary with coal which is not powdered) . Weigh it and record the
loss, then heat and weigh again until the minimum weight has been reached. The difference
between the original and the minimum weight is the moisture in the air dried coal. The sum of
the moisture thus found and that of the surface moisture is the total moisture*

Fig. 3411. — Eimer and Amend double wall oven {Bureau of Mines type), designed especially
for determining moisture in coal samples. It consists of a double walled copper cylinder
closed at one end and having a double walled door at the other. The space between the two
walls is for fiUing with a solution of glycerine in water (sp. gr. 1.19) the proportion being
adjusted to maintain 105° C. in the chamber. A copper tube encircles the oven between
the walls, and through it is forced a current of air dried by passing through sulphuric acid,
which IS preheated and forced through the inner chamber, taking up the moisture from the
sample and escaping through a small opening in the door of the oven. The chamber is
provided with openings for thermometer and gas regulator, and is fitted with a sliding
shelf having six holes 1}4 inches in diameter to accommodate crucibles. The oven is mounted
on a rigid support as shown.

Volatile Matter — The volatile test is made in a platinum crucible
with cover. It is accomplished by placing the platinum crucible in a Bunsen
flame of proper dimension in a specific position for a certain period of time,
weighing the crucible and its contents before and after inserting the same
in the flame.

1,896

FUEL ANALYSIS

After removing the platinum crucible from the Bunsen flame, it is cooled
in a dessicator before weighing. This volatile test can be made by placing
the platinum in a furnace, the temperature being gradually raised to 950° C.
and maintained. For this work the electric muffle furnace is rapidly
becoming the preferred medium.

Fig. 3,412. — Gaertner drying oven made of heavy planished copper with tubulation for ther-
mometer and gas regulator, mounted on separate iron support, provided with false bottoms
of sheet iron to protect the copper.

Fig. 3,413.---Eimer and Amend multiple unit and electric muffle furnace for use in deter-
mmmg volatile matter. The units form the heating chamber; they are reversible, however,
for using either the open groove or closed face. The hinged counter weighted door may be
used as a temporary rest for crucibles, etc. The door is reversible for hinging either at
bottom or top. A % inch hole in back provides an escape for fumes, or for the insertion of
a pyrometer couple.

FUEL ANALYSIS

1,897

Bureau of Mines Method.— One gram of the fine coal (that which passes through
a 60 mesh) is weighed into a light, well burnished 10 gram platinum crucible, with a
close fitting capsule cover. It is heated to 950° C. or a platinum or michrome triangle
for 7 minutes in the full flame of a No. 3 Meker burner.

The flame is 16 or 18 centimeters long, and the bottom of the crucible is 2 centimeters
above the top of the burner. A sheet iron chimney is placed around the burner to
prevent draught.

The temperature is measured by a thermocouple where hot junction is buried in
contact with the coal at the bottom of the crucible. After 7 minutes the crucible is
cooled in the dessicator and weighed. The loss in weight is the volatile plus moisture.

Figs. 3,414 to 3,416. — ^Various laboratory burners. Fig. 3,414, meter burner; it requires a
reasonable gas pressure for most economical operation. The whole flame is practically a
homogeneous mass of burning gas, its temperature being nearly uniform throughout ;
fig. 3,415 Chaddock burner, it is being incorrodably made of porcelain and white fire
clay and is specially adapted for use in hoods where metal burners soon corrode. The burner
is supplied with flame spreader, asbestos disc, asbestos ring, and a small chimney for platinum
triangles; fig. 3,416 Parr blast. It yields a flame of high temperature as required for ash

. and volatile matter determinations.

Am.'Soc. of M. E. Method: 274, — Place one gram of the air dried powdered coal
in the crucible and heat in a drying oven to 220° F. for one hour (or longer if necessary
to obtain minimum weight) , cool in a dessicator and weigh.

Cover the crucible with a loose platinum plate. Heat 7 minutes with a Bunsen
burner giving a 6 to 8 inch flame, the crucible being supported 3 inches above the top
of the burner tube and protected from outside air currents by a cylindrical asbestos
chimney 3 inches in diameter.

Cool in a dessicator, remove the cover and weigh. The loss in weight represents the
volatile matter.

1,898

FUEL ANALYSIS

Ash. — Next to the heating value, the ash content is the most important
factor in the commercial valuation of coal. The test is made by burning
a sample to a constant weight over burners or in a suitable furnace until
the ash remaining reaches a constant weight. Chaddock gas burners,
small muffle furnaces or small crucible furnaces, either gas or electrically-
heated, are suitable for this work.

Bureau of Mines Method. — The same sample is used on which the moisture
determination was made. It is left in the capsule and placed in a cool muffle. The
temperature is gradually raised to 750° C, and the ignition is continued, with occa-
sional showing of the ash, until all the carbon particles have disappeared.

The capsule is cooled in a dessicator, weighed, and the ignition repeated until a con-
stant weight has been obtained. A constant weight is assumed to have been obtained
when the difference between successive weighings is .0005 gram.

Fig. 3,417. — ^Weisnegg's muffle furnace for ash determinations, etc. This furnace burns
about 20 cubic feet of gas per hour, and will produce a temperature up to about 700° C.
Accommodates muffle, l^A%X^%X2yi.

The residue in the capsule represents ignited mineral residue or uncorrected ash*

For technical purposes, the uncorrected ash is reported as determined. The principal
use of corrected ash values is in computing the actual coal substance or combustible
matter of coal, for comparing ultimate analysis and heating values on this basis.

Am. Soc. of M. E. Method.— Expose the residue in the crucible to the blast lamp
until it is completely burned, using a stream of oxygen if desired to hasten the process.
The residue left is the ash.

Fixed Carbon, — The fixed carbon in coal is determined by the difference
in weight from the other three factors of the proximate analysis, i. e., the
simi of the percentages of moisture, volatile matter, and ash is deducted
from 100%; the remainder is the percentage of fixed carbon.

FUEL ANALYSIS 1,899

Bureau of Mines Method. — The fixed carbon is determined by subtracting the
sum of the percentages of moisture, ash, and volatile matter from 100.

Am. Soc. of M. E. Method.— The fixed carbon is taken as the difference between
the residue left after the expulsion of the volatile matter and the ash.

Sulphur — The sulphur test is made either by direct determination from
the sample of coal by the Eschka method, or it is determined from the wash-
ings of the bomb calorimeter at the time of making a heat of combustion test.

Bureau of Mines Method. — For the sulphur test use is made of the residue in the
calorinieter after completing combustion in the heat of combustion test. The crucible
is washed out thoroughly and the washings collected in a 250 cubic centimeter breaker.
The washings are titrated with a standard ammonium hydroxide solution to obtain the
acid correction for the heating value. Four cubic centimeters of strong ammonium
hydroxide are added to insure complete precipitation of any metals in solution, and the
solution is heated to the boiling point on the hot plate.

Fig. 3,418. — Scheibler dessicator of Bohemian glass having a ground air tight cover.

The residue mostly ash, is filtered off, and washed five times with hot water, and
5 cubic centimeters of concentrated hydrochloric acid.

A few drops of bromine water are added to the solution which is replaced on the hot
plate and heated to the boiling point. Add 10 cubic centimeters of hot 10% barium
chloride solution and allow the precipitate to settle for at least 2 hours. The super-
natant liquid is decanted and tested with dilute sulphuric acid for an excess of barium
chloride. The precipitated barium chloride is collected on a small filter paper and
washed with hot water till the washings show no reaction for chloride. The filter paper,
with the precipitate, is placed in a crucible, dried, ignited and weighed.

The ignition is in a muffle for 10 minutes. It is covered and cooled in a dessicator.
The precipitate is then brushed onto a balanced watch glass and weighed. The sulphur
in barium sulphate is 32.07-^233.41 = .137 times the weight of the latter.

The percentage of sulphur can be easily determined from the original weight of coal.

Am. Soc. of M. E. Method. — Use is made of Eschkas method described later.

1,900

FUEL ANALYSIS

Eschkas Method. — To deliver sulphur by this method (which is the one commonly
used) a sample of 60 mesh coal weighing 1 .3736 grams is mixed in a 33 cubic centimeter
platinum crucible with about 2 grams of Eschkas mixture (2 pails light calcined mag-
nesium oxide, 1 part anhydrous sodium carbonate), and about 1 gram of the Eschkas
mixture is spread over it as a cover.

The mixture is carefully burned out over a gradually increasing alcohol or natural
gas flame . When all black particles are burned out the crucible is cooled , the contents
digested with hot water, filtered, washed, and the solution heated with salonated
bromine water and hydrechloric acid, boiled, and the sulphur precipitated as barium
sulphate by adding a solution of barium chloride.

For further particulars see Technical Paper No. 8, 1913 of the Bureau of Mines.

Fig. 3,419. — Cla^'^ton and Lambert laboratory blast torch outfit. The adjustable stand permits
the flame to be pointed in any position desired. The tripod is also adjustable and will hold
any ordinary size pan or laboratory vessel; it can be swung out of the way when not in use.

Ultimate Analysis. — The ultimate analysis of coal for its
absolute chemical constituents is a complicated process and one
difficult to be carried out, requiring considerable chemical
apparatus. It should therefore be attempted only by a chemist
or one skilled in making chemical analyses.

NOTE. — A proximate analysis depends upon more or less arbitrary standardized methods
which, if not rigidly followed, give different results for the same coal sample. Thij analysis,
however, is an acceptable indicator of the type of coal.

FUEL ANALYSIS

1,901

In the ultimate analysis, the chemical elements are determined
without regard to their combinations. Greater accuracy of
determination is possible than with the proximate analysis.
The items considered in an ultimate analysis are: moisture,
carbon, hydrogen, oxygen, sulphur, nitrogen and ash.

The ultimate analysis is used in classifying coals, and to cal-
culate the heating value of a coal in the absence of a calorimetric
determination .

Fig. 3,420 and 3,421. — Braun hand power coal grinder fitted with special discs for quickly-
reducing coal and coke samples to the fine mesh required for coal analysis and calorimeter
determinations.

The sulphur determination is made in connection with^ a proximate
analysis and is used to check up coal deliveries with specifications.

An ultimate analysis does not distinguish between carbon and hydrogen
derived from the organic or combustible matter of the coal and the small
proportion of these elements that may be present in an' incombustible form
in the mineral impurities. Since the error is small a correction is not
necessary.

An ultimate analysis includes the hydrogen and oxygen of the moisture
with the hydrogen and oxygen of the dry substance. Usually before
comparisons are made, the ultimate analyses are computed to a dry coal

1,902 FUEL ANALYSIS

basis, thus giving the relative proportions of hydrogen and oxygen in the
coal after the moisture has been eliminated.

Apparatus required. — Mill or grinder for pulverizing the coal; chemical
scales; drying apparatus; combustion apparatus containing a combustion
furnace, glass combustion tube, one end of which is filled with copper oxide
and chromate of lead and the other end with a roll of oxidized copper
gauze; a porcelain boat; set of bulbs containing hydrate of potassium;
a tube filled with chloride of calcium; a supply of pure oxygen and pure
air, together with suitable chemicals and chemical apparatus required for
the various processes.

MOISTURE

The methods employed by the Bureau of Mines and Am. Soc. of M.E. are
the same as described under proximate analysis.

Fig. 3,422. — Crusher plate made of chilled iron with rim, for powdering coal, etc.; with rubber
set in wooden handle.

CARBON AND HYDROGEN

Bureau of Mines Method. — 2 grams of air dried coal is burned in a
25 burner Glaser furnace of Heraeus electric furnace. Complete oxidation
is insured by passing the products of combustion over red hot copper oxide.
A layer of lead chromate follows *the copper oxide to remove the sulphur.

The water vapor and carbon dioxide are absorbed and weighed in pre-
viously weighed calcium chloride and potassium hydroxide solutions
respectively.

No correction is made for the carbon or hydrogen from inorganic matter
in the coal.

Am. Soc. of M. E. Method. — 3^ gram of the pulverized oven dried coal
is placed in a porcelain boat, which is introduced between the copper roll
and the copper oxide within the combustion tube. After the contents
within have been thoroughly dried out by a sufficient preliminary heating,
aided by a current of dry air, the furnace is set to work and the coal burned

FUEL ANALYSIS 1,903

by passing air through the tube, and then finally oxygen, conducting the
products of combustion through the potash bulb and the chloride of calcium
tube.

The carbon dioxide is absorbed by the potash and the water for the
combustion of hydrogen is taken up by the calcium chloride. The quantity
of carbon dioxide, from which the carbon is determined, is ascertained from
the weight of the bulb before and after the absorption.

The quantity of hydrogen is determined by weighing the calcium tube
before and after, which gives the amount of water produced, and, dividing
by 9, the amount of hydrogen.

NITROGEN

Bureau of Mines Method, — For nitrogen determination the Bureau of
Mines uses the Kjeldahl-Grenning method, which is as follows: 1 gram of
air-dried coal is digested with 30 cc. of concentrated sulphuric acid, J^ gram
of metallic mercury and 5 grams of potassium sulphate, until the carbon
has been completely oxidized and nitrogen converted to ammonium sul-
phate. After dilution with water and precipitation of the mercury by the
addition of potassium sulphate, an excess of sodium hydroxide is added,
and the ammonia is determined by distillation.

Am. Soc. of M. E. Method. — Mix a certain weight of coal with stray
sulphuric acid and permanganate of potash and heat until nearly colorless.
This process converts the nitrogen into ammonia and then into sulphate
of ammonia, and the amount of sulphate is determined by making the
solution alkaline and then distilling it . The nitrogen is found by calculation
from the known composition of ammonia. f

SULPHUR

The methods employed by the Bureau of Mines and Am. Soc. of M. E.
are the same as described under proximate analysis.

NOTE . — A complete description of this method is given in the Bureau of Mines Technical
aper No. 8.

tNOTE. — Recent experiments show that the nitrogen thus found in coal is .2 to .3%
)0 low, and that in order to obtain more accurate results it is necessary to add mercury and
Dtassium sulphate. See paper by Fieldner and Taylor in Jour. Ind. and Eng. Chem., Feb..
)15.

1,904

FUEL ANALYSIS

ASH

The same methods are used as described under proximate analyses.

Am. Soc. of M. E. Method. — The ash is found by weighing the refuse lef
in the combustion boat after the coal is completely burned.

OXYGEN

The oxygen is the difference between the sum of the elements previouslj
determined and the original weight of the coal.

Fig. 3,423. — Pellet press for preparing pellets of coal for the calorimeter test.
Fig. 3,424. — Bell shape mortar with pestle.

Heating Value for the Ultimate Analysis. — The heating
value can be obtained from an ultimate analysis by substituting
in Du Longs formula, which is:

Heating value or 5.i.«. ) ^.^^ ^ _^ g2,028 /'h--'\ + 4,050 S
per poimd of coal J * ' * y 8/

in which C, H, O, and S, are respectively the percentages of carbon
hydrogen, oxygen and sulphur in the combustible.

FUEL ANALYSIS

1,905

Ques. Why is this method objectionable?

Ans. 1, the heating value of the several elements have not
been accurately determined; 2, the heating value of the elements
in a free state is not necessarily the same as when they are com-
ponent parts of a chemical compound; 3, the assertion that
all the hydrogen is combined with the oxygen is not correct;
4, the relative accuracy is subject to the uncertainty of the
oxygen determination, and 5, high cost of making an ultimate
analysis.

Fig. 3,425. — ^Jones coal sampler. I,t consists of a hopper set in a four legged support, scoop and
form sampling pans and brush.

For low grade Western coals, in which approximately only two thirds
of the oxygen is in combination with the carbon, Du Long's formula would
give heat values too low by assuring that all the oxygen is in combination
with the hydrogen.

Heat of Combustion of Calorimeter Test. — Since the
amount of water evaporated per pound of coal burned under
1 boiler does not of itself indicate the efficiency of the boiler,
?t is necessary to know the heating value of the coal used.

1,906

FUEL ANALYSIS

For instance, an equivalent evaporation of 8 pounds of water per pound
of dry coal represents an efficiency of 70>^% if the coal contained 11,000
B.t.u. per pound, but the same evaporation with a coal of say 14,500 -B J. «.
heating value would represent only 53}^% efficiency.

Oues. What kind of heating value is obtained by a
calorimeter test?

Ans. The higher heating value .

So called because it is higher than that obtained under boiler conditions

Fig. 3,426. — Mahler calorimeter. It consists of a steel shell B, with cover, capable of with-
standing a pressure 50 atmospheres. The capacity is about 40 cubic inches and the weight
9 pounds. The interior is lined with a coating of enamel to resist corrosion and it is nickel
plated onthe outside. In the cap is a tube with a stop cock, through which runs a well insulated
electrode with a platinum wire on the inner end. The second platinum wire of the circuit
supports a small disc on which the fuel to be burned is placed. The vessel holds about
5 pounds of water and is made of thin brass of size to hold the bomb immersed. A screw-
agitator works outside the bomb to bring all water to the same temperature and a finely-
divided thermometer is placed in the water. Outside the calorimeter shell is a layer of
insulating material and sometimes the whole apparatus is enclosed in another vessel con-'
taining water to absorb radiation.

FUEL ANALYSIS

1,907

by an amount equal to the latent heat of vaporization of the water formed
by the combustion of the hydrogen. The heating value obtained under
boiler conditions is called the lower heating value.

The higher value is the only scientific unit, and its use is recommended by
theA.S.M.E.

Oues. Is there any absolute measure of the lower
heating values?

Ans. No.

r. 3,427. — Sarco calorimeter. In construction, the bomb is of special metal which resists
corrosion and is gold plated on the inside and finished with a coating of platinum. It is
fitted with a cover fastened down by three studs and nuts, the joint between the body of
the bomb and the cover being made with thin lead wire. The cover has a screw valve at-
tached, which regulates the introduction of compressed oxygen from an ordinary gas cylinder.
The electrodes to convey the current are connected by a fine wire which serves to ignite the
fuel, when C9nnected with a battery. One of the electrodes is insulated by a porcelain
collar where it passes through the cover of the bomb.

1,908

FUEL ANALYSIS

It is aTsrtifiekl unit, which involves the ultimate analysis and assu^
tion that make the unit impractical.

Oues. Of what does a standard calorimeter ou<
consist?

HELIX jLAKt^ OF ^
OF WIRE C.P. NAPtHAklNE

IROM
FUSE
WIRE

COMBUSTIBLE

RECESS irJ PLATINUf4
PORCELAIN FUSE WIRE
PIN

mi

5PANNER
FITS IN RECE5!

in recess.

Ans It comprises a platinum lined steel cup or bomb, close
with a screw cap, and fitted with an oxygen ^^^ ' ^j^f ^f^^^^^
electric igniticfa of the charge, a metal can for holdmg distill
water, a mechanical device for stirring the water, a thermomet<

FUEL ANALYSIS

1,909

/hich can be read accurately to .001° C. by means of a cathet-
meter, and a double walled felt lagged metal jacket containing
/ater in which the can containing the bomb fits.

Oues. Describe how a calorimeter test is made.

Ans. Weigh into a platinum tray 1 gram of the coal sample

3,432. — Emerson calorimeter equipped with vacuum walled jacket. By means of this
racuum cup the radiations to and from the calorimeter water are minimized to such an
;xtent that, at the time of a heat of combustion determination in the calorimeter, the heat
eaction is carried out under practically adiabatic condition. This adiabatic condition is
nost nearly realized during a calorimetric test if the temperature of the calorimeter water
)e brought into proximity of the temperature of the surroundings in the same manner as
vith the usual water jacket type of calorimeter. The vacuum wall jacket greatly reduces
he radiations from the calorimeter at any temperature, but if the test be attempted at a
smperature too remote from room temperature, the radiations may become appreciable
nd thereby necessitate the computation of the cooling correction.

1,910

FUEL ANALYSIS

and place it on the support inside of the bomb. Connect a
piece of platinum fine wire to the electrodes and allow it to
dip into the coal. After screwing into place the bomb cap
admit oxygen to a pressure of 350 pounds. The bomb is now

Figs. 3,433 and 3,434. — Parr calorimeter and detail of cartridge. Oxygen under pressure is
not used. In testing, a weighed quantity of coal with the necessary chemicals thoroughly
mixed is put into the cartridge which is then closed and placed in a measured quantity ol
water in the can. After the stirrer has been set in motion and constant temperature obtained
the coal is ignited. Extracting if the heat be complete in from four to five minutes. The
calculation is much in the usual way.

placed in the weighed water, and the temperature of the calori-
meter observed at minute intervals for five minutes; at the
end of the fifth minute the electric current is closed igniting the
coal. The thermometer is now read. The first two readings

FUEL ANALYSIS

1,911

after firing are taken at half minute intervals. Three more
readings are taken at minute intervals. The maximum tempera-
ture will now have been reached and the thermometer is read
for five more minutes.

Ones. How is the heating value of the coal calculated?

Ans. After obtaining the data from the test, connections
must be made for the nitrogen content burned to nitric acid,
and for the sulphur content burned to sulphuric acid. The net

Pig. 3.435.— Eimer and Amend reading lens for reading the divisions on the thermometer.
It maintains the same angle of vision for all points on the scale, thus avoiding errors of the
parallax, while a magnification is provided which augments the comfort as well as the
accuracy of the readmgs.

heating value is obtained by multiplying the rise of temperature
caused by the combustion of the coal by the water value of the
Icalorimeter.

Let w — weight of fuel tested in grams,
r Wi = weight of water in calorimetric vessel in grams.

W2 = water equivalent of calorimeter in grams,
/o = temperature C . of water in calorimeter vessel before combustion .
/i = maximum temperature C. of water in calorimetric vessel after

combustion.
r = correction coefficient for rise of temperature.
X = heat generated in burning the fuse wire.
y = heat due to the formation of aqueous nitric acid.
2 = heat due to the combustion of sulphur to. sulphuric acid.
1.8 = coefficient to convert heat of combustion for kilogram-calories
per kilogram to B.t.u. per pound.
;. Heating value ov B.t.u. \ _ (W1+W2) x {tx—to) r— {x+y-\-z)

per pound of fuel / 2^ Xl.o

1,912 FUEL ANALYSIS

Radiation (r) correction, — Pfaundler's method considered mosi
accurate. It assumes that in starting with an initial rate of radiation anc
ending with a final rate, the rates at intermediate temperatures are propor-
tional to the initial and final rates, that in the rate of radiation at a poini
midway between the temperature of ignition and the temperature at whict
combustion is presumably completed will be the means of the initial anc
final rate. The rate at a point three quarters of the distance on the curvt
between the two temperatures will be the rate at the lower or initial rate
plus three-quarters the difference between the initial and final rate.

^ *Fuse wire (x) correction. — For the fuse wire correction multiply its

Emerson Fuel Calorimeter.
Heat of Combustion.

SAMPLE RUN

November 20, 1912.
Sample No. t28 (air dried.) Run No. 2

Thermometer used. No. 2295.

Weight of tube and coal = 7-937? Room Temp. = 22" C.

Weight of tube = /■0713

Weight of fuel .8666 grams

Weight of water iQoo grams

READINGS OF THERMOMETER

Mme

Temp.

Time Temp.

0

20.348

6 22.600

I

20.352

30 22.900

2

20.358

7 23.100

3

20.362

30 23.150

4

20.368

8 23.194

5

20.376 Firing Temp.

30 23.196 Max. Temp.

30

21.000

9 23.196
30 23.194

/ Calibration \
V Correclion /

rime

Temp.

10

23.194

II

23.182

12

23.174

13

23.166

14

23.158

IS

23.150

Temperature at firing = 20.376 + ( — .011) = 20.365

Temperature at max. == 23.196 + (+ -002) = 23.198

Rise in temperature corrected for errors in the thermometer = 2.833

Rate of change of temperature before firing — 0.0056 = Ri

Rate of change of temperature after maximum temperature = 0.0088 = R2*

Total cooling correction = •

Total cooling correction = tl:^^ y^ (j) + (+ •^>^ (2.5) = .008 (additive)

Total corrected rise in temperature =^ 2.841

Rise per gram of sample = 3.278

The water equivalent of bomb, calorimeter can, stirrer, etc. = 490

Gram calories per gram of coal = (1900 + 490) 3.278 = 7834

British Thermal Units per pound of coal = 7834 X '-S = 14.100

♦ Rate for last five minutes.

Tlie above are Centigrade temperatures.

FUEL ANALYSIS

1,913

weight in milligrams by 1.6, which is the number of calories per milligram.
The result is in given calories.

* Nitric acid (y) correction. — The bomb is carefully washed with water.
The washings are titrated with standard ammonia solution (containing
.00587 grams of NH^ per cc). The correction is 5 gram calories per cc,
of the ammonia solution.

CONDENSER^

.STOP COCK

AB50RPTI0N
BULB

Fig. 3,436. — Apparatus for determination of total carbon for use in connection with Parr
calorimeter. Operation: The fused material is brought into the flask, and dissolved with
the washings from the interior of the bomb. By admitting acid from the funnel, the
carbon dioxide is liberated and carried over into the jacketed burette. In this condition,
also, the temperature may be read by means of the thermometer suspended in the water
surrounding the burette. The gas thus measured, which may also have a small admixture
of air, is conducted over into the absorption bulb, in which is contained a solution of
caustic potash for absorbing the CO2. Upon releasing the residual gas to the burette,
and reading the volume, the dimensions indicates the volume of carbon dioxide present at
the outset. The apparatus permits of boiUng the liquid in the flask in order to expel the dis-
solved gases, and, by means of the condenser, the gas is handled at a constant temperature.

*NOTE. — Detailed instructions for making corrections and calculations are given in
the Bureau of Mines' technical paper No. 8,

*NOTE. — For the derivation of the correction figures and other details, see U. S.Bureau,
of Minci technical paper N9. 8, 1913. '

1,914

FUEL ANALYSIS

* Sulphur (z) correction, — This correction, which is obtained by
precipitation as barium sulphate, is 13 gram calories per .01 gram of sulphur.

Ones. What is the water equivalent of a calorimeter?

Ans . It is the heat capac-
ity of the apparatus referred
to water as unity; that is,
the, sum of the product of
three weights of the parts
by their several specific
• heats.

Methods of obtaining the
water equivalent,

1 . By burning in the calori-
meter a known weight of a
substance, the heating value of
which is accurately known, and
calculating the w^ater equiva-
lent by the heat difference.
This method used by th.eBureau
of Mines because of its con-
venient application.

2. By the method of mix-
tures.

3. By introducing electric-
ally into the calorimeter a
known quantity of heat.

4. By burning in the calori-
meter the same weight of a
given substance but using

Fig. 3,437.— Eimer and Amend sulphur photometer for use in conjunction with Parr calorimeter.
The fusion of coal, coke, petroleum, etc., by means of sodium per-oxide as carried out in
the Parr calorimeter, is made use of for determining sulphur. Operation: Upon removal
of the fused mass, it is dissolved in water and made slightly acid with pure hydrochloric
acid. An aliquot part of this solution is taken and made up to 100 cc. and transferred to an
Erlenmeyer flask. To this, at room temperature is added a large crystal of barium chloride
and at once the flask is shaken vigorously for a short time. The turbid solution is then ready
to read in the photometer. The liquid containing the purely divided precipitate of barium
sulphate is poured into the dropping funnel F, and gradually admitted through the pump
cock C, into the graduated tube A. The lens effect at the bottom of the tube is obtained by
immersing the same in water. By noting the depth at which the light from the flame dis-
appears a reading is obtained directly which indicates the percentage of sulphur in the
sample under examination.

FUEL ANALYSIS

1,915

different amounts of water; these equations may be results involving
two unknown quantities, namely, the water equivalent and the heating
value of the substance.

5. By weighing the parts and adding the products of the weights by
the specific heats.

Ash Analysis. — According to the method employed by the
Bureau of Mines, ash is determined in the residue of dried coal
from the moisture determination the porcelain capsule containing

Pig. 3,438. — Scientia calorimeter. It is of the Berthelpt type. The steel bomb is 21^ inches
in diameter by 3^ inches high; ^-inch wall; porcelain lining on inside. • The cover of the
bomb of the regular outfit has a needle valve with a screw connection for the oxygen inlet
and is also provided with an insulated electrode to which one terminal of the e'ertric circuit
for igniting the charge is connected. The other side of the electric circuit does not require
an insulated electrode, but can be attached to any point on the lid of the bomb. If it be
desired to displace the products of combustion after the test, in order to analyze them for
certain constituents such as CO2 for example, the bomb can be fitted with two needle valves
and screw connections, one of which fitted with a platinum tube running to the bottom
of the bomb. This furnishes a convenient and accurate method for determining the carbon
in the sample tested, and gives an opoprtunity of forcing the air from the bomb before
filling it with compressed oxygen. This calorimeter is also made with vacuum insulation.

this residue is placed in a muffle furnace and slowly heated until
the volatile matter in the coal is driven off.

The object of the slow heating is to avoid coking the sample and thus
making its burning difficult; furthermore, if a coal that is high in volatile
matter be rapidly heated, the gas generated has a tendency to explode
within the capsule and thus carry off mechanically portions of the ash.

1,916

FUEL ANALYSIS

OPEN GLASS GAU6L

U TUBE GAUGE.

SPIRAL rUBE

SMALL CHAMBER

P\H HOLE EXIT

Fig. 3,439. — Carpenter calorimeter. It differs from other calorimeters in that provision is made
in the apparatus for giving the heating value of the fuel almost direct in B.t.u., dispensing
also with some of the objectionable features, such as errors involved in the thermometer, the
determination of the water equivalent, correction for evaporation, radiation, and specific
heats. In principle, the calorimeter in a large thermometer, in the bulb of which combus-
tion takes place, the heat being absorbed by the liquid which is with the bulb. The ab-
sorption of heat is proportional to the height to which a column of liquid rises in the attached
glass tube. In operation, the products of combustion pass upward and downward through
the spiral tube to the small chamber which is connected on the outer end with an open U
tube gauge. The water in the chamber surrounding the combustion cylinder forms a bath
which is connected with an open glass gauge above the water chamber. A diaphragm
above the water is used to adjust the level. From the small chamber, a pin hole exit, serves
to allow the products of combustion to escape slowly. Five pounds of water are placed
in the bath and the charge of fuel used is 2 grams. The asbestos cup is heated to drive off
all organic matter. This cup is then weighed, the sample placed in it and the whole weighed

FUEL ANALYSIS 1,917

The ignition in the muffle is continued at a temperature of about 750°C.,
with occasional stirring of the ash, until all particles of carbon have disap-
peared. The capsule with its contents is then taken from the muffle, cooled
in a desiccator, and weighed, after which it is replaced in the muffle, heated
for half an hour, cooled in a desiccator, and weighed again.

If the change in weight be less than .0005 gram (if the change be greater
than this, the ash is again ignited for 30 minutes and the process is repeated
until the variation in weight between two successive ignitions is .0005
gram or less) , the weight is considered as constant and the weight of the
capsule is deducted from the last weighing.

The weight of the capsule and ash minus the weight of the capsule is taken
as the weight of the ash.

In the case of coals high in iron, some difficulty is often experienced in
ignition to constant weight, because of the oxidation and reduction of iron
oxides.

Ash as determined by this method represents the mineral matter that
remains in coal after ignition.

Analysis of Liquid Fuels. — The determination of carbon
and hydrogen in liquid fuels is made in the same manner as
that concerning the soHd fuels , using special means for preventing
loss in the various processes on account of the volatile character-
istics of the fuel . The ultimate analysis of liquid fuel like that of

Fig. 3,439. — Text continued.

together. The difference gives the weight of the coal used for the test. The cup is then
placed in proper position on the bottom phtg, which is inserted in the combustion cylinder.
Raise the ignition wire above the coal, turn on the current which will, of course, heat the
air in the cylinder and cause the water to rise slightly in the glass tube. As soon as this
commences, turn on the oxygen and pull down the ignition wire to kindle the coal , at the same
instant taking the reading on the glass scale. When combustion has finished as determined
by looking through the observation windows, the scale reading and the time should be
taken. The difference between the first and last readings taken will be the actual scale
reading. This must be corrected for radiation.* _ The amount of ash is determined by
weighing the asbestos cup after combustion. Dividing thQ B.t.u. developed during the test
by the weight of coal burned in pounds gives theB.t.u. per pound. For ordinary everyday
work this is one of the most convenient pieces of apparatus that has been devised, but does
not show quite as accurate results in use as the Mahler.

*NOTE. — To make this correction let the apparatus stand with the oxygen shut off as
long as it took for the combustion to take place, then take the scale reading and the time.
It is assumed that the drop in the scale reading during this time will indicate the amount of
the radiation which took place during the combustion, and should, therefore, be added to the
actual scale reading to give the corrected reading. With each calorimeter is furnished a cali-
bration curve from which by comparison with the corrected scale reading th&B.t.u. developed
during the combustion can be found.

1,918

FUEL ANALYSIS

coal, should only be undertaken by a per-
son familiar with all the necessary details .

Owes. How is the sulphur test
made?

Ans. The oil or other liquid is heated
with nitric acid and barium chloride . The
quantity of sulphate of barium thus pro-
duced is ascertained by filtering and weigh-
ing, and the sulphur calculated from the
known composition of the compound.

Fig. 3,440. — Thompson calorimeter. A simple form for ap-
proximate determination of the heating value. It consistn
of a glass cylinder A, closed at the lower end to contain
water, and a copper vessel B, called the condenser, which is
closed at the upper end with a copper cover having a metal
tube C, with a stop cock at the top. The lower end of B, is
opened and is perforated near the open end by a series of
small holes . D , is a metal base upon which B , is faxed by 3
springs attached to D , and pressing against the internal sur-
face of B . A series of holes is made near the rim of D , to
assist inrnixing the water and allow of easier raising. In-
side B, is a copper cylinder, E, called the furnace, which is.
f. : 5 "Z ^ closed at the lower end only and fits into a metal ring in the

center of D. The weight of water used is 967 times that of
the fuel burned , so that the rise in temperature of the water in degrees Fahrenheit is equal
to the numb.er of pounds of water which 1 pound of the fuel will, theoretically, evaporate
from and at 212° Fahr. Ten per cent is added to this number as a correction for the heats
absorbed by the apparatus itself.*

*N0TE. — In operation 30 grains of finely powdered fuel is mixed with 10 to 12 time
its weight of a perfectly dry mixture of 3 parts chlorate of potash and 1 part niter. This
fuel mixture is carefully pressed into the furnace E, and the end of a slow fuse about .5
inches long is inserted in a small hole made in the top of the mixture. The furnace is placed
on the base D , the fuse lighted and the condenser B , with its stop cock shut is fixed over the
furnace. Previously the cylinder A, has been charged with 29,010 grams of water, the
temperature of which must be recorded. The condenser and base are now quickly placed
in the cylinder and the fuse ignites the fuel mixture. The end of combustion will be shown
by the ceasing of bubbles of gas rising through the water. The stop cock is opened so
that water enters the condenser by the holes at the bottom and by moving condenser up and
down» the water is thoroughly mixed so as to give it a uniform temperature. This is
measured with a thermometer and recorded. By adding 10 per cent to the rise in degrees
Fahrenheit of the temperature of the heating value of the coal is determined approximately.
The heating value in B.i.u. is found by multiplying this by 970.4 (latent heat of steam at
14.7 pounds ab. pressure). The furnace works best with bituminous coal, but coke, anthra-
cite and other more difficult combustibles can be tested by using a wider and shorter furnace
and not pressing the fuel mixture down.

FLUE GAS ANALYSIS 1,919

CHAPTER 59
FLUE GAS ANALYSIS

It has been said that fully one-fourth of the average plant's
fuel supply is wasted. The reason why careful operation can
lead to so much higher boiler efficiency is that this waste is
largely in the heat carried away in the gases passing up the
chimney, the excessive volume of which is usually not realized.

It is possible by means of a chemical analysis of the flue
gases to determine the amount of fuel being wasted, which will
serve as a guide to the fireman as to the efficiency of his firing
methods. If the flue gas analysis show wasteful combustion, it
indicates that some change must be made in one or more of the
following items:

1. Method of firing for the coal in use (coking or spreading
methods) .

2. Condition of fuel surface as to being level to keep it free
of air holes.

3. Depth of fuel.

4. Draught for the thickness of the fuel, and load.

5. Secondary air supply.

6. Condition of setting as to cracks.

Engineers are well acquainted with the term CO2. Measurement CO2 or
carbon dioxide escaping through the chimney is a simple way of measuring
the heat laden gases escaping up the chimney and is the index of combustion
efficiency.

%

1,920

FLUE GAS ANALYSIS

On acceptance tests, with careful firing, testing will show efficiency of
70% to 80%, but in practice with indifferent firing the same results are not
obtained.

If the fuel were pure carbon and all of the oxygen combined
with the carbon as it passed through the fuel bed, the resultant

i^h^i COAL

£^
%^

> u.
a ^

-^

" u
0:0:

UJ uJ
Q-LL

2

>

<
<0

8

!

§

'^

8

1
1-

f

1

f

1

1
f

1

\¥

m\\

— 1

c6

M\

M

s

8

M\

I

VuV

n

UU

W

\\\

uv

^"

W

v\

\\\

\\\

1-

3-

\\

\\

h\

y

\^

^N

^N'

\

\

\\

\^

\\

^

\

\

\i

^>

^

^

\

.\

\

nN

R

^

-^^

\

\

\'

n\

X"

N

<:

^

\

\

\

\

\

N

■\

<^

2:?J

i-

\

k

\,

\

\

X

\
^^^

^

?^

C:

^

^

4^

—

—

—

^

i--^

V'

\

^

^^

v^

^

-<

---

^

— -

N

\

^

^

^

^^

"^«

"^

^

~^c

7 8 9 10

ORIGINAL °/o OF CO2

\Z 13

14

^^i ^,441. — Saving in dollars per year per 100 boiler horse power by increasing the percentage
of CO2, m the flue gases. Suppose for instance, that the original percentage of CO2 be 7,
and with somewhat better firing it be increased to only 8 per cent. Starting at the 7 per cent
mark on the horizontal base line and rising to the C per cent curve then running over hori-
^°^^^^fe *° *^® ^^^*' ^s indicated by dotted line, gives with this measure of CO2 and coal
at $3.00, a yearly saving of $280.00.

products of combustion would be:

21% of CO2
79% of nitrogen

FLUE GAS ANALYSIS

1,921

In practice, however, it is found that excess air has to be introduced to
insure complete combustion of ordinary coals and other fuels. This excess
should be not less than 40% nor more than 60%. This lowers the per-
centage of CO2 in practice to from 13 to 15%, depending upon the nature
of the fuel.

All air which is introduced into the furnace in excess of 40% to 60% cools
heated gases of combustion and is a detriment to furnace efficiency, for
steam is made by virtue of the difference in temperature of the flue gases
and the water in the boiler.

The following table gives the cooling effect due to excess air:
Cooling Effect of Various Percentages of Excess Air

(Based on coal containing C-85%; H-2.5%; N-1%; Ash-7.75%, and 5./.M.- 14.750 per pound
Temperature of external air-o° F.)

Boiler capacity^ IS

Ideal Tempera-

Loss of Tem-

Temperature 0 f

per cent, of ca-

Excess Air in

ture of Com-

perature Due

combustion com-

pacity at 40% ex-

Per Ceivt.

bustion.

to Dilution

pared with that
developedljy Mini-

cess air Flue gas
temperature as-

Degrees

Degrees

mum Quantity of
Air

sumed constant at
600°. Boiler tem-
perature assumed
as 360°F.

0 (or Min.
Quantity)
10% excess

5,132oF
4,710

422

91.8%

20

4,352

780

84.8

. < . .

30

4,044

1,088

78.8

40

3,777

1,355

73.6

166"

50

3,543

1,589

69.0

93.5

60

3,336

1,796

65.0

88.2

70

3,153

1,979

61.4

83.0

80

2,988

2,144

58.2

78.5

90

2,840

2,292

55.3

74.5

100

2,705

2,427

52.7

70

125

2,419

2,713

47.1

63.0

150

2,188

2,944

42.6

56.6

175

1,997

3,135

38.9

51.5

. 200

1,837

3,295 •

35.8

47.0

Excess air also tends to chill the flue gases- If carried to such an extent
that the gases are chilled below the ignition point, carbon (soot) is de-
posited on tha metal surfaces of the boiler and the chimney smokes. Car-
bon which might otherwise have been burned and added to the heat value
of the gases is lost. It also becomes a detriment by preventing the absorp-
tigji of heat by the bpikr surfaces.

1,922 FLUE GAS ANALYSIS

A little increase in the percentage of CO2, obtained in better firing
methods will represent a considerable decrease in excess air carrying heat
away up the chimney.

The curves, fig. 3,441 show, as an example, the dollars saved per 100
boiler horse power operating continuously for one year, for various prices
of coal and various increases in CO2.

The principal constituents of the gases in the flue or chimney are :

1. Oxygen 3. Carbonic dioxide

2. Nitrogen 4. Carbonic nonoxide

The object of the analysis is to determine the percentage of
these gases present, and to deduce therefrom the amount of air
actually entering the furnace, as compared with the air theo-
retically necessary for combustion. If all the air admitted to
the furnace could be brought into such intimate contact with
the fuel that every atom of the oxygen contained in it could
be utilized for the purposes of combustion, the escaping gases
would practically consist of only carbonic acid and nitrogen —
that is, each atom of the carbon of the fuel would unite with two
atoms of oxygen in the air admitted, forming CO2, the nitrogen
passing through unchanged.

Such a result is, however, unattainable, and unless an excess
of air be admitted, the carbon will not be completely consumed,
and CO, consisting of one atom of carbon combined with one
atom of oxygen, will be formed, instead of COg.

The formation of CO results in a very serious loss of heat,
and must therefore be prevented by admitting some excess of
air.

The excess of oxygen required is generally from 6% to 8%
of the volume of the gases. If there be less than 6% of oxygen
there will almost certainly be traces of CO.

There are upon the market a number of instruments for analyzing flue
gases which are not difficult to operate and give results sufficiently accurate
for practical purposes.

FLUE GAS ANALYSIS

1,923

Sampling Gases. — Preliminary to making an analysis a
sample of the flue gases must be obtained and in order for the
analysis to be of any value it is necessary that the sample taken,
represent correctly the average of the flue gases.

There are numerous methods of obtaining 'an average sample
and considerable difference of opinion exists as to which is the
best.

Fig 3,442. — Precision gas collector. It consists of a sub-standard galvanized iron tank with
piping arranged for constantly drawing a sample of gas from the flue. There is a permanent
oil surface for the water in the collector to prevent the absorption of CO2 by the water.

Am. Soc. of M. E, Method, — The sample for flue gas analysis should
be drawn from the region near the center of the main body of escaping
gases using a sampling pipe not larger than J^ inch gas pipe. The point
selected should be one where there is no chance for air leakage into the flue
which could affect the average quality.

In a round or square flue having an area of not more than J^ of the grate

1,924

FLUE GAS ANALYSIS

surface, the sampling pipe may-
be introduced horizontally at
the center line, or preferably a.
little higher than this line, and.
the pipe should contain perfor-
ations extending the whole
length of the part immersed,
pointing toward the current of
gas, the collective area of the
perforations being less than the
area of the pipe. The pipe
should be frequently removed
and cleaned.

It is advisable to take sam-
ples both from the flue and
from the furnace, so as to de-
termine the amount of air leak-
age through the setting and the
changes in the composition of
the gas between the furnace
and the flue.

Bureau of Mines Method.

— ^A water cooled tube or a
quartz tube is preferred to a
plain metal tube.

Fig. 3,443. — Hays automatic gas collec-
tor. In operation, close valve GV,
open gas cock GC, and turn on the
water by opening valve WV. Should
the water overflow through the over-
flow pipe OP, before the tank is full,
remove plug of gas cock GC, and see
that opening is not stopped with grease
or dirt. If there be no stoppage, close valve WV, gradually until overflow ceases. When
the tank has been filled water will overflow through pipe OP. To collect a sample, first
close WV and GC, then open GV. Water will then flow from the Tank T, into flow regu-
lator R, and be discharged through drip DC, the drip cock DC, should be set to just
about fill the tank with gas during the sampling period. Analysis should be made at each
end of each watch. In operating the collector it is necessary to use the valve WV, GV
and cock GC. The sample may be taken from the collector and the tank T, refilled with
water without disturbing DC. To pump gas from the collector set cock of the analyzer
in the open position; hang leveling bottle upon the flange of the case and be sure it is filled
with water. Close GV, open GC, and WV. Water will flow into the back and force gas
out into the analyzer.

NOTE. — Hays objects to the ordinary perforated sampling pipe because: 1, gas will
flow fastest along the lines of least resistance; 2, the nearest hole will furnish more gas than
the next one, etc.; 3, liability of some of the small holes to become stopped up; 4, no means of
knowing when holes are stopped up; 5, the velocity of the gas decreases from the center of the
boiler tewafd the sides, so that even if it wer§ pQShi^le to secure uniformity of gas flow through

FLUE GAS ANALYSIS 1,925

Oues. What determines the location of the sampling
tube?

Ans. The use to be made of the gas analysis.

If the total heat losses be the desired data, the sample should include
all the air leakage into the setting; if the analysis be made as a guide for
controlling the fire, the gas sample should be taken at some point before
they are diluted by leakage through the setting.

Oues. What method of taking the sample is most
desirable?

Ans. It is best to draw a continuous sample, using a suitable
ejector, and provide a branch pipe from which to obtain the test
sample.

The test sample can then be taken either momentarily or
continuously according to requirements. Momentary samples
should be taken every five minutes.

The conditions at the time of taking the sample should be
recorded in order to be able to determine the meaning of the
analysis .

Speed is essential in taking gas samples as conditions may
change from instant to instant.

Flue Gas Collectors. — These are used for holding an average
sample over a given time, obtained by collecting samples every
few minutes. These holders should be of sufficient capacity
to hold 150 to 200 cubic centimeters of gas and may be of the
form shown in fig. 3,443.

The practice of collecting gas over water in collectors is objec-
tionable in that the water may absorb or give up CO2 thus

^OT^.— Continued.
all of the perforations in the tube, the sample derived would not be an ave'-age one; there is no
value of taking a cross sectional sample from side to side unless there be added to this another
cross sectional sample extending longitudinally from baffle to baffle.

1,926

FLUE GAS ANALYSIS

rendering the percentage of CO2 incorrect in the gas sample.
A brine solution will absorb CO2 less readily than will water.

Fig. 3,444. — ^Flue gas collector, capacity 150 to 2Q0 c.c. of gas. The bottle is provided with
a cork through which are passed two tubes , one of which connects through the rubber tube
H, to the water supply, and extends to the bottom of the bottle, the other extends only
through the cork and is provided with a T connection, one branch of which is connected
by means of glass and rubber tubing to the sampling tube, while the other connects to the
suction side of the ejector used to draw the gas. From the bottom of the bottle is a glass
tube with a rubber connection which connects the water to water. In operation, pinch
cock A, is closed and H, opened thus allowing the water to fill the bottle completely. The
pinch cock H, is then closed and J, opened, and the gas drawn through. The T, by the
gas pump in order to remove all air which may remain in the gas connections. After this has
been running for some time the pinch cock A , is opened thus allowing the water in the
bottle to drain out and draw in the flue gas through the tube J, when A, is again closed^
To discharge the gas into the testing apparatus, connect tube to the gas instrunient
and close pinch cock in J; by Qpening pinch cock H, water flows to the bottom of the
bottle and forces the gas into the instrument.

Gas Pumps. — There are three forms of pumps in general use
for drawing the gas into the sampling apparatus:

1. Jet pumps.

2. Fall pumps.

3. Steam pumps.

FLUE GAS ANALYSIS

1,927

An example of the first mentioned type is shown in fig. 3,445, which con-
sists, of a water jet, resembUng very much the common boiler injector with
an air or gas connection and a restricted portion B, with a zigzag tube
C, which is used for breaking up the water into foam.

Oues. What is the principle of a fall pump?

Ans. Its operation depends upon the weight of the water to
maintain a vacuum.

WATER

AIR

Fig. 3,445. — Richards jet pump. In operation, water entering at the top draws the air or
gas through the side connection by forming successive pistons through the restricted passage.

Fig. 3,446. — Bunsen fall pump. It consists of a water connection attached to an enlarged
tube B, and discharges the water through the tube C, which, in order to maintain a perfect
vacuum, should be 34 feet high. In the enlarged tube B, is inserted a smaller glass tube
which extends nearly to the bottom and connects at the other end through G, E and D, to
the gas or air connection. The enlarged portion E, is provided to catch any water which
may be drawn back into the gas connection, and the stop cock H, is used to drain it off.
A scale and mercury U tube is provided in order to ascertain the exact vacuum maintained
in the gas tubes to which it is connected through the tube F . In operation, when it is desired
to draw a sample of the gas, the tube D, is connected to a branch of the rubber tubing
I, shown on the sampling apparatus. The water connection is made through the tube A,
and by the continual falling of the water acting as a series of pistons through B, and C,
gas is drawn from the flue.

1,928

FLUE GAS ANALYSIS

Ques. Describe a steam pump.

Ans. As shown in fig. 3,447, a steam
pump consists of a large tube contracted at
one end into which is inserted a cork B , and
cement C , fitted with a covering D , provided
with a steam tube G, and an air tube E, the
steam tube extending nearly to the end of
the large tubing and held in place by the
washer A.

Gas Analysis. — Carbon dioxide gas is ab-
sorbed by caustic potash. This forms the
basis of operation of all carbon dioxide
instruments . The usual process of measuring
the carbon dioxide in flue gases is that used
by Orsat which form the principle of most
automatic CO2 recorders.

Oues. Describe briefly the usual pro-
cess of gas analysis?

Ans. A sample of the flue gas is taken
and its volume measured. The gas is then
passed through or brought into intimate con-
tact with a solution of caustic potash. As
CO2 is measured by volumetric displacement,
liquid caustic is used. After the CO2 con-
tents have been absorbed, the volume of the
gas is again measured. The difference be-
tween this and the original volume gives the
amount of CO2 in the gas and divided
by the original volume, gives the percentage
of CO2.

FLUE GAS ANALYSIS

1,929

JiAY^ IMPROVED GAS ANALVZEII

1 9*8 MODEL
PAT£NT NO. I.077,J42

Tig. 3,448.— Hays gas analyzer. Size,, 3X7>iXl2^; weight charged, 73^ poaild*^

NOTE. — Care o/ Orsat Apparatus, The- opterator willi Save tinife' and' expfeflse" and;
prevent many troublesome difficulties by taking good care' of the Orsat apparatrus.^ If the'
grotmd glass surfaces of stop cocks be allowed to stand without cleaning, they will' becoffiie-
cemented together by alkaline solutions, and the cocks cannot be operated. The onljy remedy
is to keep the stop cocks free from alkali and lubricated with a thin film of vaseline. If too
much vaseline be used, the openings in the cocks and capillary tubes become stopped' with; tli&-
excess. A properly lubricated stop cock has the appearance of a single piece of thick' glass.
If a solution be accidentally drawn into a stop cock, the cock shbuld be removed at dnce atld
the surfaces wiped clean witTi a cloth or piece of soft paper, and lubricated with a thin film'
of vaseline. If necessary the header should also be removed and washed free from alkali-.
The water in the burette and leveling bottle should be saturated with flue gas and should bfe^'
changed as often as it becomes dirty. If the water become alkaline by solution being drawn-
into the header and washed into the burette, it should be changed at once. If this be not done-
carbon dioxide will be absorbed by tlie alkaline water and the percentage of CO2 indicated by'
the analysis will be low. The joints made with rubber tubing should be examined andj the-
apparatus tested for leaks before wori: is started* Tlais^ is- 6^>edally necessary whea th© Qtsa^
apparatus is not used irequeatly.

1,930

FLUE GAS ANALYSIS

f "\

X -J

h- o

""-^-^^^^

tjj~ O

^£D^$

Z5_

CO

o

-J <

— 1

-I
-J

u-^

lU

CO

i

2

r

CD

? UJ

-J CO

CO

a. <
O

g'cic

si^ e a s «^

o-M li^ J2 y !>

^^L) 5 y fe: «

oj M nj .^:5'2

O f? ^ Vh O ^

05 cS JH ^ ._g

« o o ^7 a;-^
»« a> ■^^ S bo 5^ O

^ ^ 4) C (U »H!S

o C! ^ Q,4J -_^

II If I as

flJ O ^ <U4^

I. S ..-{^-d^-i^
'^'9. u'^ 0) C <u

FLUE GAS ANALYSIS

1,931

'^-p^a§

-2 ".-^-^

iS|-$-^.^^-|o^^g^:g

J +J w ^ c 1^

•SS S S o

t>'^+JCJ-.'-^iiiC-COX<'"ty!> ♦-'3 OCT? w

■43.5 w ^ :3 jrt '=^'5

J ^^ c 4> ^^;::^ o -§ a I r- S 52 P<$S^ « « I «
^Sgo^^S .-g-:^ v^ S^ !^ 5 -o S crxi v.:^ «^

^ o o

o ^

o o

■n

o «s

<N

-d.s-g^

w

S-S-^a

^d

-s-^^'^

d

sg^.-s

m

a^5|

OX! Wo

m

to rt 0 ^

a ^ '^ tJ

H
O

^t3
2 «

o >

a-c; '

If!

p c be

6«S
C3 K O

o a w

o 5,^

H O <U

«-■ fc »-
000

I. fig
W^ fi

oU

1,932.

FLUE GAS ANALYSIS

Oues. Describe the Orsat apparatus for analyzing
flue gases?

Ans. It is a portable instrument contained in a wooden case
with removable sliding doors front and back, and consists
essentially of a measuring tube or burette, three absorbing
bottles or pipettes, and a leveling bottle, together with the

FOURTH

PIPETTE FOR

FINAL WASH

FROM FLUE

Fig. 3,450. — Four pipette Orsat apparatus for accurate analysis. The first pipette B , contains
a solution of caustic potash the second C.an alkaline solution of pyrogallic acid and thft remain-
ing two D , and E , a solution of cuprous chloride . Each pipette contains a number of glass
tubes, to which some of the solution clings, thus facilitating the absorption of the gas. In
the pipettes D , and E , copper wire is placed in these tubes to re-energize the solution as it
becomes weakened. The rear half of each pipette is fitted with a rubber bag, one of which
is shown at K, to protect the solution from the action of the air. The solution in each
pipette should be drawn up to the mark on the capillary tube. The various operationsi
are performed the same as with the three pipette apparatus with the exception that after
the gas has been in pipette D , it is given a final wash in E , and then passed into the pipette
C, to neutralize any hydrochloric acid fumes which may have been given off by the cuproug
chloride solution, which, especially if it be old, may give off such fumes, thus increasing the
volunie of the gases and making the reading on the burette less than the true amount.

FLUE GAS ANALYSIS

1,933

connecting tubes and apparatus. The bottle and measuring
tube contain pure water; the first pipette, sodium potassium
hydrate dissolved in three times its weight of water; the second,
pyrogallic acid dissolved in a like sodium hydrate solution in the
proportion of 5 grams of the acid to 100 cubic centimeters of
the hydrate; and the third cuprous chloride.

Ques. Briefly, how does it work?

Fig. 3,451. — Hempel pipette. It works on the same principle as the simple form of Orsat
apparatus, excepting that the absorption may be hastened by shaking the pipettes bodily
bringing the chemical into more intimate contact with the gas . The illustration shows
a single pipette set; several of these are necessary for the treatment of the different con-
stituent gases. For each process, after absorption the quantity absorbed is determined by
returning the gas into the measuring burette and observing the successive differences.

Ans. After completely drawing out the air contained in the
supply pipe, a sample of the gas is drawn into the measuring
tube by opening the necessary connections and allowing the
water to empty itself from the tube and flow into the bottle.
The quantity of gas drawn in is adjusted to 100 cubic centimeters.

1,934

FLUE GAS ANALYSIS

By opening one by one the connections to the pipettes and
raising and lowering the water bottle, the sample is alternately
admitted to and withdrawn from the pipettes, and the ingredients
one by one absorbed.

Fig. 3,452. — Eliot apparatus. It consists of a measuring tube A, a heating tube B, with
a top connection E , provided with a stop cock F , and a three-way cock J . Pressure bottles
G, and H, are provided with rubber connections to the tubes A, and B , as shown. In opera-
tion, distilled water is put into the tubes and bottles, and the bottles are placed upon the
shelves provided for them, the stop cocks F, and J, being closed. Connection is made to
the gas holder through J, which is turned to open straight from the tube B. By lowering
the bottle, H, the gas is then drawn into the treating tube when J, is turned to connect B,
and E. By opening F, raising H, and lowering G, the gas is drawn into the measuring
tube. A, the water m G, being kept at the same level as in A, by raising or lowering the
bottle, H. The tube. A, is graduated so that the amount of gas it contains can readily be
determined from the scale, and this amount for convenience is usually 100 cubic centimeters.
The stop cock F, is then closed and with J, opened, the bottle H, is raised until all gas is

^•„T^^\\^A •P^^.v, +V,« +.,K^ "D 13,, +,,...»,;♦,„ T 17 :^ ^^^^^rs4-^A +^ tJ 1? ic 4-U^^ ^^^^^^ ^^A +1,^

FLUE GAS ANALYSIS

1,935

The first pipette absorbs car-
bon dioxide CO2, the second,
oxygen O, and the third, car-
bon monoxide CO. The quan-
tity absorbed in each case is
determined by finally return-
ing the sample to the meas-
uring burette and reading the
volume.

The percentage of CO2 is
read directly by the first ab-
sorption. Those of the other
two ingredients are the respec-
tive differences between the
readings taken after successive
absorptions.

Fig. 3,453. — Precision "boiler tester" or
CO2 analysis apparatus. It consists
of a measuring _ burette and a con-
centric glass absorption
pipette filled with five glass
tubes, mounted on a circu-
lar metal stand with stop
cock, and bottle containing
water. The gas passes
through a filter to neutral-
ize the soot before entering
the burette. The burette
is of such form as to be
adapted for use as a draught
gauge and also as a meas-
uring burette for the per-
centage of CO2 having
draught and CO2 scales.
On being connected to the
flue with the water leveled
to the zero of the scale by
the bottle, the draught is
shown on the scale when the cock is opened. Without disconnecting, the bottle is used to
draw in a sample of gas, which is then analyzed and the percentage of CO2 is read off the
other side of scale.

Fig. 3,452. — Text continued.

gas passed into B, for treatment. A 5 per cent, solution of caustic potash is then poured
into the funnel , K , and allowed to drip along the sides of the treating tube until no further
absorption takes place. _ The gas is then passed into A, and measured, its loss in volume,
which was carbon dioxide, being noted. Treatment for oxygen is then proceeded with,
using, instead of the caustic potash, a solution of 5 grams of pyrogallic acid in 15 cubic
centimeters of distilled water, added to 120 grams of caustic potash in 80 cubic centimeters
of water, which is dropped from funnel into B, measuring the gas and noting the loss of
volume due to absorbing the oxygen. Carbon monoxide is then absorbed by a solution
made from 10.3 grams of copper oxide in 100 cubic centimeters of concentrated hydro-
chloric acid. In each case the amount of gas originally drawn being 100 cubic centimeters,
the decrease in volume represents the percentage of the gas which has been absorbed by
the treating solution . The chemicals must be used in the order indicated or the results will
not be correct. Care must be taken when passing back and forth and when letting in
chemicals that no gas escapes and no air enters the apparatus.

1,936

FLUE GAS ANALYSIS

The manipulation of the Orsat apparatus is explained in greater detail
in fig. 3449. Various modifications of the Orsat apparatus have been
developed which enables analysis to be made with greater rapidity than
the form just described.

Oues. How is the volume of air corresponding with
any given volume of oxygen found ?

Ans. As the percentage by volume of oxygen in air is 21.
the volume of air corresponding with any given volume of oxygen

Fig. 3,454. — ^Precision 100 cubic centimeter standard Orsat. The scale divisions on the burette
are divided into tenths.

may be found by multiplying by ^-^y > ^^ 4.762. The volume of
air corresponding to a given volume of CO2, may also be found
by multiplying by the same figures.

FLUE GAS AMALYSiS

1,987

And ex€egs air

^ , COo o

Example. — Analysis shows 13.5% 6%

Th^il air used for combustion = 13.-5X4.762 = 64.3

= 6X4.762 = 28.6

92.9

The percentage of excess air above that which is
necessary for combustion is therefore:

_100X28^;

Ques. What ^reeatftfons

should be observed m

makii^g ^ gas

analysis witfip the

Orsat appa^t^s

,^ (fig. 3,449) ^

Fig. 3,455. — Bacharach pocket CO2 indicator.

Ans. 1. The absorbent should not be forced below the point^
d, or some of the gas may escape and be lost, and, of course,
an incorrect result obtained. 2. The absorbent must be at
exactly the same level in the tube — say at c, when measuring
the volume after the gas has been absorbed as before. 3. Time
must be allowed for the water to drain down the sides of the
tube before taking a reading. The time must be the same on

1,938

FLUE GAS ANALYSIS

each occasion, otherwise more water will drain down at one time
than another, and an incorrect reading result. 4. Much care
should be taken in preparing the cuprous chloride solution and
it must be known to be fresh and capable of absorbing CO,
otherwise no CO will be indicated when CO is present.

Pigs. 3,456 to 3,458. — Manipulation of Bacharach pocket CO2 indicator. After taking the indi-
cator out of the case, the rubber stopper is removed and the two cocks A and B , are put into
their places . The cocks are easily distinguished from each other , cock A , having a bent handle .
The glass jar F, at the lower end is then removed from the metal body G, and filled with the
absorbing solution, after which it is screwed on again. With the pump attached to the open
upper valve D, and the cock A, of the lower valve turned, so that the glass measuring tube
H, in center is open to atmosphere through hole C, the indicator is ready for use. The glass
jar F, having once been filled with KOH (one filling is enough for 200 determinations) , the
open end of the pump is connected to the gas line from which a sample is to be taken. The
gas is now pumped in, at the same time allowing the air to escape to the atmosphere through
hole C. When a fair sample of gas has been collected (about 30 strokes of the pump being
sufficient) the upper cock B, is closed. The lower cock A, is then turned 180° to permit the
gas and KOH to come in contract for chemical action, helping the process by holding it
inclined downward and shaking it. When the solution has been drained back to the glass jar
F, the lower cock A, is closed and the indicator held vertically upsidedown and immersed
in water. The submerged cock B , is opened and the ingoing water, which takes the place of
the absorbed CO2 is leveled with that outside. The cock B, is then closed and the indicator
brought to its base. Opening the cock B, the per cent, of CO2 is read off on the tube at the
water level. Turning the apparatus upside down, the water will run out through the open
cock B, and the instrument is ready for another determination.

COo RECORDERS 1,939

CHAPTER 60

CO2 RECORDERS

What CO2 Indicates. — The CO2 indication answers most
practical purposes . If greater certainty or refinement be desired
after the CO2 has been brought up to the required percentage,
the CO determination must be made. While high CO2 indicates
a small amount of excess air, it does not necessarily mean a
correspondingly good combustion. 1% of CO in the flue gas
would be a negligible indication of the quantity of excess air,
but might mean 4:}/^% loss due to incomplete combustion.

Low CO2 may be caused by excess air, insufficient air (high CO), or
improper mixture of the air and gases, but a surplus of air is the cause in
ahnost every instance. The difference between the CO2 percentage in the
last and the first passes indicates the air leakage in the setting. CO2 is
also affected by the character of the fuel.

The more hydrogen in the fuel, the less CO2 in the flue gases. If the fuel
were all carbon, there would be 21% CO2; if all hydrogen, no CO2 in the
gases.

Unreliability of CO2 Readings Taken Alone. — It is

generally asstmied that high CO2 readings indicate good combus-
tion and hence high efficiency. This is true only in the sense
that such high readings do indicate the small amount of excess
air that usually accompanies good combustion, and for this
reason high CO2 readings alone are not considered entirely
reliable.

1,940

C02 RECORDERS

Fig. 3,459. — Sarco tyi
C, CO2 recorder. F(
description and e:
planation of oper;
tion see page 1,94

C02 RECORDERS 1,941

Oues. Whenever a CO2 recorder is used what should be
done from time to time? '

Ans. Since a CO2 recorder does not give CO readings, it
should be frequently checked with an Orsat or Hempel
apparatus to determine if CO be present.

As the percentage of CO2 in flue gases increases, there is a tendency
toward the presence of CO, which, of course, cannot be shown by a CO2
recorder, and which is often difficult to detect with an Orsat apparatus.*
It is not safe, therefore, to assume without question from a high CO2

*NOTE. — ^As before mentioned, the greatest care should be taken in preparing the cuprous
chloride solution in making analyses and it must be known to be fresh and capable of absorbing
CO.

Fig. 3,459. — Sarco type C, CO2, recorder. Motive power is a fine stream of water with two
foot head. In operation, the water now flows through tube 74 into the power vessel 82:
here it compresses the air above the water level, and this pressure is transmitted to vessel
87 through tube 78. The pressure thus brought to bear on the surface of the liquid with
which vessel 87 is filled (to mark 95), sends this upwards through tubes 91 and 93. Thence
it passes up into vessels 68, 67, 77 and 66, and into tubes 49, 51 and 52. It rises until it
reaches the zero mark 71, which will be found on the narrow neck of vessel 67. ^ At the
moment it reaches this mark the power water, which, simultaneously with rising in vessel
74, has also travelled upwards in syphon 72, will have reached the top of this syphon, which
then commences to operate. Through this syphon 72 a much larger quantity of water is
disposed of than fiows in through injector 9 , so that the power vessels 74 and 82 are rapidly
emptied again. The moment the pressure on vessel 87 is thus released, the liquids return
from their respective tubes into this vessel. Assuming tube 49 to be in connection with a
supply of flue gas, a sample of this is drawn in from the continuous stream which passes
through 43, 45 and 46, as the liquid recedes in 49, by the partial vacuum which is created
by the falling of the fluid. As soon as the liquid has dropped below point 76, which is the
inlet of the flue gas into vessel 67, the gas rushes up into this vessel. As soon as the flow
in the syphon stops, vessel 82 begins to fill again, and the liquids in tubes 91 and 93 rise
afresh. The gas in 67 and 68 is now forced up into tube 50, and caused to bubble right
through a solution of caustic potash {spec. grav. 1.27) with which vessel 94 is filled (to point
64 marked on the outside) . In this process any carbon dioxide (CO2) that may be contained
in the gas is quickly absorbed by the potash. As the gas has to pass through the potash,
the absorption is rapid and complete. The remaining portion of the sample collects in 62,
and passes up through 60 into tubes 57 and 58. (It cannot pass out at 59, as this outlet is
sealed by the liquid in 52.) The gas now passes under the two floats 18 and 26, whereof
the former is constructed larger and lighter and will, therefore, be raised first. By turning
the thumb screws 14 and 15, the stroke of this float is adjusted until just 20 per cent of the
whole of the sample remains to raise float 26, when nothing is absorbed in 94, as would be
the case if air be passed through the Recorder. This float has attached to it pen 36, which
is caused to travel downwards on the chart, when 26 rises. If no CO2 were contained in
the gas, nothing would be absorbed by the potash in 94, and the whole of the 20 per cent
reach float 26. Thus the pen would be caused to travel the whole depth of the chart from
the 20 per cent line at the top to the zero line at the bottom. Any CO2 gas contained in
the sample would be absorbed by the potash, a correspondingly less quantity would reach
float 26, and pen 36 would not travel right down to the bottom of the chart, i.e., the zero
line. Thus any CO2 absorbed will be indicated by a shorter travel of the pen — the actual
percentage being given by the line on which the pen stops. (See flg. 3,460.) On the return
stroke of the liquid, the gas is pushed out from under floats 18 and 26, through tubes 75
and 58, and into tubes 59 and 52. From here it passes out into 66 (as soon as the liquid has
fallen below the outlet of tube 52) , and through tube 51 .

1,942

CO'Z RECORDERS

reading that the combustion, is correspondingly good, and the question of
excess air alone should be distinguished from that of good combustion.

The effect of a small quantity of CO, say one per cent, present in the flue
gases will have a negligible influence on the quantity of excess air, but the
presence of such an amount would mean a loss due to the incomplete com-
bustion of the carbon in the fuel of possibly 4.5 per cent of the total heat
in the fuel burned. When this is considered, the importance of a complete
flue gas analysis is apparent.

Flue Gas Ana-
lyzers vs. CO2 Re-
corders.— In most
boiler plants great
quantities of fuel are
wasted, the chief loss
being due to excess
air. To determine
the loss due to excess
air, hand operated
flue gas analyzers and
CO2 recorders are em-
ployed.

Fig. 3,460. — Bacharach curves for coal fired furnaces, showing that about 40% of excess a.
is necessary to obtain the most efficient combustion. This is indicated by the highest CO2
contents obtained by the amount of air as shown by the two curves. A greater percentage
of excess air reduces the CO2 contents and therefore increases the fuel loss. Thus, for 300%
excess air, the CO2 drops to 5% while the corresponding fuel loss becomes 21%.

...0 2««5e78

» 10 II 12 13 14 IS l« IT

^ - I Vc

r ^^

r

1 1-.

c« H

0

«o - W - —_

J t

4 t

li V

«• I \

500

,0 ^ M - - -4---

»^ A V

S V ± -

^ .

■*" ri - -V \-- — .

? ^. \

, >

£

111 \ \

5.

,- a ^, \^__

- - - _ - »*. 3oa

,0 CO -> Y

|: : :\ >"

---AIR EXCESS

p V \-~^'''''

« £ - --\ N- ":

«* ^v ^v

X N

nv ^

"tX^

^N ,_ 100

^^^

-- ?f EVEMi:WL FUIL.LO^

Ns.^ "■

-yr X T1 — M

'it "±:±t~^

0 ■ TT>*r>.%^ ^*-J-J ,__

ti ii" T 1 ' ■

^2 1 1 iTl^^

• J 3 « 9 « » •

9 10 II 12 13 14

The first ordinarily is an Orsat or one of its modifications; the second,
one of the several different types of recording instruments on the market.

A hand gas analyzer is a useful device, and every boiler plant, no matter
how small, should have one for testing purposes. The instrument is
simple, but as its operation requires considerable time and the information
obtained is not immediately visible to the fireman, its value is reduced.

An automatic recorder shows from 10 to 20 times every hour what quan-
tity of CO2 is in the flue gas, and it operates continuously, thus enabling
the chief engineer to know how careful or careless his firemen were during
the night.

C02 RECORDERS

1,943

How a CO2 Recorder Works. — ^The principle upon which
most recorders work is based upon the absorption of CO2 from
flue gases by a solution of caustic potash.

There are four essential operations to be performed by a
recorder for each CO2 determination.

1. Measuring out a definite quantity of flue gases.

2. Passing the measured sample through the caustic potash
solution which absorbs the CO2, decreasing the volume of the

_%C02 record

Average ior 24 hrs..

Remarks —

^ VD VI

Fig. 3,461. — Sarco type C, CO2 recorder chart. This section of a 24-hour chart shows Suc-
cessively the recorded CO2, in two separate furnaces giving the main flue.

gases in proportion, and recording the decreased volume after
absorption of the CO2 by the caustic potash solution.

3. Exhausting the recorded sample, thus bringing the
apparatus back to its initial condition, ready for the next gas
sample.

NOTE. — It is ordinarily maintained that considerable knowledge is required to under
stand what the CO2 recorder shows. This is not so. Post the CO2 recorder conveniently f9r
the fireman, let him know that the higher the CO2 obtained the better fireman he is, and explain
further that the higher the CO2 the shorter will be the red line drawn by the recorder pen
(or longer, depending upon the type of instrument). This is all that is necessary, except
occasional suggestions on how to handle the fires to obtain a higher percentage of CO2. In
the next few weeks it will be surprising how the CO2 will increase, especially if the firemen are
placed in competition with one another by posting their results conspicuously upon a black-
board. The fireman himself will soon gain confidence, since he will see that when the fires are
bad, the recorder pen strokes upon the chart will be long; when the fires are good, the ink
lines will be short. It is important after he once gains this confidence that the recorders be
kept in good condition and m proper operation; otherwise he will lose faith in the readings.

1,944

C02 RECORDERS

C02 RECORDERS 1,945

Fig. 3,462 shows an elementary apparatus for performing the four-part
cycle just stated, and figs. 3,463 to 3,465, the manner in which the operations
are performed.

The apparatus consists of two vessels, M, and S, suspended by cord from
a pulley and connected with each other by a small rubber tube, as shown.
M, is open at the top and S, is closed on top except for two openings, A^
and B. At A, is a check valve connected by rubber tube to the flue gas
sampling pipe, and at B , is another check valve and rubber tube connecting
with a pipe leading into the gas bell.

The two vessels M, and S, and connections as described form a single
acting pump, the capacity of S, being say 100 cc. As shown S, and the
rubber tub-^ are full of water, but when the pulley is turned counter-clock-
wise (by clock work not shown), S, will be elevated and M, lowered so
that 100 cc. of flue ^ases will be sucked into S, as shown in fig, 3,463.

Now the clock work turns the pulley clockwise till the M, and S, come
back to their original position. The water runs back from M. into S. and
by aid of the check valves forces the measured sample of gas into the gas
bell, which rises as shown m fig. 3,464 and by means of an arm and pencil
records on the drum a line LR, whose length depends upon the amount
of gas that is passed through the caustic potash solution (KOH) in the
containing vessel.

Now if the gases contained no CO2. the same volume of gas would be
admitted to the bell, as was admitted to the measuring vessel S (fig. 3,463),
or 100 cc.f and the recording pen would draw a line of length LF.

Again, if the gases contained say 8% CO2, and this was absorbed in
passing through the caustic potash solution, the volume of gas entering
the bell would be decreased 12%, and the pencil would draw a shorter
line, equal to 100— 12-=88% of LF. That is, calling F, zero and L, 100%,
then the distance FR, not marked by the pencil, represents the per-
centage of CO2, which in this case is 12%.

*NOTE. — In the elementary apparatus just described the longer the line drawn by the
pen the less the percentage of CO2, but it should be noted that in some instruments the longer
the line the greater the percentage of CO^, this being due not to a different principle but to
modified mechanical arrangement.

Figs. 3,462 to 3 AQ5.— Continued.

at beginning of the cycle. First operation: Pulley moves counter-clockwise and 100 cubic
centimeters of the flue gases are taken into S, as m fig. 3,463; second operation, pulley
moves clockwise fig. 3,464 and the measured sample is forced from S, through the caustic
potash into gas bell, absorbing CO2, elevating bell to height corresponding to diminished
volume, and recording on drum the diminished volume; third operation, clockwork opens
exhaust valve fig. 3,465 thus allowing bell to sink to its initial position. Each time the
pulley moves clockwise the ratchet turns down slightly from right to left so that no two pen
rounds will come in the same place on the paper chart attached to drum .

1,946

C02 RECORDERS

Fig. 3,466. — Simmance-Abady CO2 recorder, showing whole of working parts in position
except the clock and pen. Water is put into vessels D and J, and maintained at
correct height by a constant level tank. In operation, water is allowed to flow through
hollow valve stem E, from the small reservoir K, with the safety overflow OO. In syphon
tank A, there is a weighted float B, which is attached by means of a chain E, to the bell D,
of the extractor, and this float rises with the water, allowing the bell D, to fall. At the
top of its stroke, the float B, raises the valve stem E, thus tripping the valve, and momen-
tarily flushing the syphon tank; the water now syphons out of A, through syphon tube
G, and allows the weighted float to fall. As it falls it draws up the water sealed extractor
bell D, in which is created a partial vacuum, and into which, therefore, gas flows from the
flue through P and H . This may be called the beginning of the cycle. Next, the weight of
the water which has flowed from the syphon tube G, into the small pot beneath it, overcornes
the weight of the counter Q, and closes the balance valve H, thereby cutting off a deflnite
sample of the gas. Water is released from the small pot in time to allow the valve to open

C02 RECORDERS 1 ,947

In the gas bell container is an exhaust pipe which runs up to the surface
of the liquid having at the other end a valve under control of an arm
moved by the clock work.

In fig. 3,462 this valve is open so that all the previous sample can be
exhausted into the atmosphere and the gas bell allowed to sink to the level
of the liquid as shown.

In figs. 3,463 and 3,464 this valve is closed so that no gas wiU escape from
the bell until after all the gas has been transferred from S, to the bell, thus
permitting the bell to rise to the proper height and the pen to correctly
record the percentage of CO?-

After the record has been made as in fig. 3,464 the clock work opens the
exhaust valve and the bell sinks to its initial position as in fig. 3,465, the
pen drawing the vertical line FR, thus completing the cycle.

During the cycle each time the pulley moved clockwise the ratchet arm
turns the drum from right to left a very small amount, thus the pen records
are made progressively along a ruled paper card attached to the drum.

By ruling the card horizontally into a CO2 percentage scale and vertically
into a time scale, not only is the same CO2 reading shown, but also the
time at which they were made, assuming that the clockwork is so arranged
that the ratchet will cause the drum to make a complete revolution in
24 hours.

Fig. 3,466.— rg^i continued.

at the proper interval. The stream of water is continually flowing into the tank A, and the
float B, rises again, which allows the extractor bell D, to sink. As it sinks, it will be seen
that the gas in bell D, (which by the closing of the valve H, is now uninfluenced by vacuum
or other conditions in the flue) , is first reduced to atmospheric pressure, and is then actually
under pressure; the volume of the gas is, therefore, forced into vessel M, where it bubbles up
through the caustic solution and CO2 absorbed, and thence into the recorder J, raising
the bell. The boxwood scale N, at the side of the recorder tank is graduated from 100 per
cent, at the bottom to 0 per cent. CO2 at the top, and the capacity of the bell D, is such that
when the apparatus is run on air, containing practically no CO2, the total volume is trans-
ferred to the recorder bell J, which in this case rises to the zero point. When flue gas is
admitted to the apparatus, exactly the same quantity {i.e., enough to send recorder bell
up from 100 to 0) is passed from the extractor bell D, but on the passage of the gas, the
CO2 is absorbed by the caustic potash in iron vessel M, reducing the volume of the gas;
owing to such absorption the recorder bell J, will not rise to its full height, giving line FR. It
automatically rises as far as it will, and a pen then marks on a chart its final position. The
percentage of COz in the gas is thus automatically recorded. This bell J, then vents,
discharging the analyzed gas through the three-way cock, so that it does not mix with or
come in contact with the fresh charge of gas, which is dealt with in exactly the same way,
the whole operation, as well as the continuous drawing forward of the flue gas, taking place
automatically by means of the stream of water. For the purpose of bringing along a constant
supply of gas, below the cock X, is an injector or aspirator, attached to the top of the case;
Pi, is an auxiliary gas connection to the aspirator from the main inlet pipe P. By this means,
gas is continuously exhausted from the pipes connecting recorder to boilers, so
that the successive samples analyzed from the instrument are from the boiler flue, and not
stagnant gases in the connecting pipes. The injector is worked by the small stream of water
(the motive power for the recorder) connected at X, before this enters the top tank of the
Recorder so that no extra water is used for this continuous pump. Two glass bottles are
fixed in connection with the injector as safeguards. A glance at one shows whether the flue
gas pipes are clear of obstructions and the other shows that the stream of gas is being
maintained.

1,948

COo RECORDERS

Fig. 3,467. — Sarco CO2 recorder, type C (see outline diagram on page 1,940). The power
required for operating is derived from a fine stream of water at a head of about 2 ft. The
water flows through tube 74 into the power vessel 82, compressing the air above the water
level and this pressure is transnetitted to vessel 87 through tube 78. The pressure thus cre-
ated in 87 forces the liquid in that vessel upward through tubes 91 and 93 into vessels 66,
67, 68 and 77. It rises until it reaches the O mark 71 on vessel 67, At the moment it
reaches this mark, the power water, which simultaneously has travelled upward in syphon
72, reaches the top of the syphon and empties vessel 82, releasing the pressure in 87. Assum-
ing tube 49 to be in connection with the flue gas, a sample is drawn in from the continuous
stream which passes through 43, 45 and 46 by a partial vacuum created by the falling of the
liquid in 49. As soon as the flow in the syphon stops, vessel 82 begins to fill again and the
liquids in tubes 91 and 93 rise afresh. The gas in 67 and 68 is now forced up into tube 50
and caused to bubble through a solution of caustic potash in vessel 94. The carbon dioxide
is absorbed and the remaining portion of the sample collects in vessel 62 and passes into
tubes 57 and 58; thence it passes under the two floats 18 and 26, displacing same and causing
a movement of the pen on the chart, exactly in proportion to the percentage of CO2 in the
respective gas sample absorbed by the caustic potash. This type of recorder permits of
very rapid analysis of the gas, and up to 30 separate analysis can be recorded per hour.

C02 RECORDERS 1,949

NOTE. — The draught gauge may be employed to great advantage in connection with
the CO2 Recorder. To bum a given quantity of a given coal per square foot of grate per hour
requires a certain draught for each depth of coal on the grates, starting with a minimum draught
just after cleaning fires when the fuel bed is thin and gradually increasing to a maximum when
the fuel bed is thickest, just before the next cleaning period. With a recording draught gauge
of the differential type (that is one to record the drop in pressure of the air in passing through
the fuel bed) installed in connection with a CO2 Recorder, the draught control in the majority
of plants can be readily standardized. Observations should be taken of the draught which is
required for the conditions obtaining at the end of each hour, after cleaning fires, up to the
next cleaning period. The draught should be regulated so that with careful firing, such that
fires are kept well covered, both burnt-out spots and blow holes being prevented, a CO2 re-
corder will indicate about 40% excess air is passing through the furnace. In a comparatively
short time sufficient information will be obtained in most plants to establish a draught line,
starting at a minimum just after a cleaning, and rising steadily to a maximum just before the
next cleaning. Th3 fireman by then holding the draught to this grade line, can regulate his
firing by the CO2 Recorder. He will, of course, have continually to vary the draught above
and below the draught grade line established, according to the fluctuations of load. If the
water level in the boiler be properly maintained and the firing done with regularity, these
variations from the draught grade line, in most plants, will be much smaller than anticipated.
Standardizing the draught control in this manner will very much simplify the fireman's prob-
lems, and will not only increase his efl&ciency, but will decrease the severity of his work.

Fig. 3,467.— rejc/ Continued,

has sealed the lower end of this center tube, exactly 100 cubic centimeters of flue gas are
trapped off in the outer vessel C, and its companion tube, under atmospheric pressure.
As the liquid rises further, the gas is forced through the thin tube and into vessel A, which
is filled with a solution of caustic potash at 1.27 specific gravity. Upon coming into contact
with the potash and the moistened sides of the vessel, the gas is freed from any carbon
dioxide that may be contained in the sample, this being rapidly and completely absorbed
by the potash. The remaining gas gradually displaces the potash solution in A, sending it
up into vessel B. This has an outer jacket, filled with glycerine and supporting a float N.
Through the center of this float reaches a thin tube, through which tke air in B, is kept at
atmospheric pressure. The float is suspended from the pen gear M, by a silk cord and
counter-balanced by the weights X . The rising liquid in B , first forces a portion of the air
therein out through the center tube in the float, and then raises the latter. This causes
the pen lever to swing upwards, carrying pen with it. The mechanism is so calibrated and
adjusted that the pen will travel right to the top, or zero line, on the chart when only atmos-
pheric air is passing through the machine, and nothing is absorbed by the potash in A.
Thus should any carbon dioxide be contained in the gas sample, it would be absorbed by
the potash in A , not so much of this liquid would be forced up into vessel B , and the float
would not cause the pen to travel up so high on the chart, in exact accordance to the amount
of CO2 absorbed. The tops of the vertical lines recorded on the chart, therefore, provide
a continuous curve showing the percentage of CO2 contained in the exit gases from the flues,
on a permanent diagram arranged for 24 hours. When the liquid in C, has reached the
mark on the narrow neck of that tube, the whole of the 100 cubic centimeters have been
forced on to the surface of the potash, one analysis being thus complete. At this moment
the power water, which, simultaneously with rising in tube H, has also traveled upwards
in syphon G, will* have reached the top of this syphon, which then commences to flow.
Through syphon G , a much larger quantity of water is disposed of than flows in through the
cock, so that the power vessel K, is rapidly emptied again. The moment the pressure on
this vessel is released, tne liquid from C, returns into the lower compartment, and float
N, to its original position. As soon as the liquid in C, has fallen below the gas in and outlets
to this vessel , the whole of the remaining gas is rapidly sucked out through E , by the powerful
ejector Q. The vessel F, is provided with a small center tube, open to atmosphere, and this
serves as an indication that the pipe line is clear, the ejector drawing air through the sea.
in the case of stoppage. The instrument, once erected, works entirely automatically, and
requires no attention whatever, beyond changing of the chart and winding of the clock
every 24 hours, and renewal of the potash solution every 14 days to 3 weeks.

1,950

C02 RECORDERS

CO2 and Fuel Losses. — The CO2 percentage indicates the
volume of excess air flowing through the furnace, and the power
of the boiler; it is the ratio between the air that is taken for a
useful purpose in burning the coal and that which is taken to
the wasteful end of cooling the furnace gases. That is all it
does indicate and its indications are only approximations .

STEAM

-GAS INLET

Fig. 3,468. — Diagram illustrating working principle of Uehling CO2 recorder: Measurement
is made by changes in the partial vacuum in chamber C, to which can be connected both indi-
cators and recorders, which may in turn be located where desired. The gas to be analyzed is
drawn through two apertures A, and B, by a constant suction produced by an aspirator.
If the aperture be kept at the same temperature, the suction or partial vacuum in the
chamber between the two apertures will remain constant so long as all the gas passes through
both apertures. If, however, part of the gas be taken away or absorbed in the space between
the two apertures, the vacuum will increase in proportion to the amount of gas absorbed.
It is evident that if a micrometer or light vacuum gauge be connected with this chamber,
the amount of gas absorbed will be indicated by the vacuum reading.

The air excess could be determined much more accurately by finding the
percentage of free oxygen with an analyzer.

The objection to the oxygen analysis is that it takes time and there is
not enough time for it. Speed is essential and some of the data will be

C02 RECORDERS

1,951

lost unless the analyzer be worked about once a minute. It will take five
minutes to determine the oxygen.

When the CO2 percentage has been worked up to 12 or 15 by improving the
firing methods, it will then be time enough to analyze for oxygen and CO.

Numerous charts and tables have been prepared to show the CO ;and
excess air relations and it must be remembered that all such charts and
tables are based upon an assumed set of conditions.

In the accompanying tables the fuel is assumed to be pure carbon,

TO BOILER ROOM INDIC;<TQR

TO RECORDING CAUCE

ABSORPTION CHAMBER

riLTER

WATE^ I
JAR I

Fig. 3,469. — Diagram of the more important parts of Uehling CO2 recorder, showing path
of the gases through the filler, apertures and absorption chamber. The recorder consists
primarily of a filter, dry absorber, two apertures A and B, and a small steam aspirator. Gas
IS drawn from the last pass or uptake of the boiler by means of the aspirator through a pre-
liminary filter located at the boiler, and then through a second filter on the instrument as
shown. Besides these filters, auxiliary filters are supplied before each aperture, which
insure the gas flowing through the apparatus being clean. The clean gas passes through
aperture A, thence through the absorption carton and aperture B, to the aspirator, where
it leaves the instrument with the exhaust steam. Between the two apertures is a carton
containing an absorbent called natron. Each carton will last about a week and may be
replaced by removing cap on carton chamber by unscrewing wing nuts. The column of
water which measures the partial vacuum between apertures A and B , is calibrated directly
in percent, of CO2. This vacuum or per cent. COais also communicated to the recording
gauge and boiler room indicator, both of which can be located at a considerable distance
from the machine proper.

1,952

C02 RECORDERS

and the stack temperatures are assumed to be constant
at 500 °F.; neither of these conditions actually obtain.

The higher the stack temperature, the hotter is the
excess air being heated, and the hotter it is, the greater
the amount of fuel being wasted.

The engineer is not supposed to compute his gains
and losses from the accompanying tables, for the table
applies to pure carbon only. With such fuel the theo-
retical CO2 would be 20.7% by volume, but when a
bituminous coal for instance is burned, the theoretical
CO2 will be less, depending upon the percentage of
hydrogen in the combustible, probably somewhere
between 17% and 19%.

The fuel waste then in any particular plant may be
more or less than the figures given in the table, but they
are sufficiently approximate to serve as a guide for all
practical purposes, and may be used as a basis for a
bonus system for the firemen according to the CO2 results
obtained by them.

Fig. 3,470. — Uehling CO2 machine mounted on central column • If consists of s, csist iron

heading and wrought iron cyHndrical regulator, on which are mounted and properly assembled ,
the necessary filters, absorption chambers and the adjusting cocks, as shown. All connec-
tions are brass and copper tubes.

Figs. 3,471 and 3,472. — Two CO2 charts from a Uehling CO2 recorder installed in a New England
plant. The chart fig. 3,471 was obtained shortly after the installation of the recorder
when the per cent CO2 (as averaged from the chart) was 8.48 per cent and coal consumption
11 tons per day. The second chart fig. 3,472, obtained a iev/ weeks later shows 11.75 per

f>oi-i-f r^(^n oti/^ ■fVio r>nQl *>r>nciimrkfinn txtqc IO i-n-no ■nof Hqt7

C02 RECORDERS

1,953

CO2 and Fuel Losses.

(for pure carbon and 500 °F. stack temperature
According to Hays

Pet. pre- Pet. pre-
ventable ventable

Fuel Pet. Fuel Pet.

Loss CO 2 Loss CO2

Pet. pre-
ventable
Fuel
Loss

i

0

10

5.69

L8

148

9.8

6.04

C.6

305

9.6

6.4

.4

47

9.4

6.78

.2

635

9.2

7.18

808

9

8.8

7.58

.8

99

8.02

.6

1.17

8.6

8.47

.4

1.36

8.4

8.95

.2

1.54

8.2

9.44

1.75

8

9.66

.8

1.95

7.8

10.51

.6

2.16

7.6

11.09

.4

2.38

7.4

11.7

.2

2.6

7.2

12.34

2.84

7

13.02

.8

3.08

6.8

13.74

.6

3.33

6.6

14.49

.4

3.59

6.4

15.3

.2

3.86

6.2

16.16

4.13

6

5.8

17.09

.8

4.43

18.06

.6

4.72

5.6

19.12

.4

5.03

5.4

20.25

.2

5.35

5.2

21.47

5 22.79

4.8 ...24.21

4.6 25.76

4.4 27.44

4.2 29.29

4 31.28

3.8 33.58

3.6 36.08

3.4 38.87

3.2 42.01

3 45.28

2.8 49.64

2.6 54.34

2.4 60.32

2.2 66.3

2 74.

1.8 83.56

1.6 95.45

1.4
1.2
1.

.8

.6

.4

.2

CO2 AND AIR EXCESS

{According to Hays)

Percentage

Percentage

Percentage

Percentage

CO2

air excess

CO2

air excess

15

38

7

158.7

14

47.8

8

195.7

13

59.2

6

245

12

72.5

5

314

11

88.1

4

417

10

107.

3

590

9

130.

2

935

1

1970

1,954

C02 RECORDERS

To determine the percentage of excess air for any given percentage of
CO2, as for example 5.4%, subtract the observed percentage 5.4, from
20.7; divide the remainder by the observed percentage and multiply by
100. This gives the volume of excess air. At 5.4% CO2 the excess air is
283.33%.

Roughly the preventable fuel waste may be computed by allowing 1%
fuel loss for each 12.11% of air excess above 38%. This figure according
to Hays is quite as accurate as the one commonly applied to feed water,
that is, 1% gain per increase of 10 °F. in the temperature of the feed water.

Pig. 3,473. — ^Uehling auxiliary boiler room (CO2) indicator. This permits locating the machine
proper and recorder outside of the boiler room, without depriving the firemen of the benefit
of the equipment,

Pig. 3,474. — ^Uehling CO2 recording gauge. It operates on the hydrostatic principle, by which
all spring levers or joint movements are avoided. The gauge is designed for an 8-inch circular
chart ruled for 0 to 20 per cent CO2 and making two revolutions in 24 hours. The gauge
is connected by drawn copper tubing to the instrument and can be mounted at a distance
from same, as, for instance, in the chief engineer's office .

CLASSIFICATION OF BOILERS 1,955

CHAPTER 61
CLASSIFICATION OF BOILERS

-••#

\-^

The great variety of boilers now in use is due to the many
different kinds of service for which they are intended, the varied
conditions accompanying their use, and the competition among
engineers who have sought to produce, at moderate cost, boilers
that will be safe, durable compact and economical.

Any classification, to be comprehensive, should be made
from numerous points of view. Accordingly, boilers may be
classified:

1 . With respect to service (broadly speaking) , as

a. Stationary l^rwl?"
h. Locomotive
c. Marine

2. With respect to the type of furnace, as

a. Internally fired
h. Externally fired

3. With respect to the character of the heating surface, as

a. Single flue;

h. Two flue, etc.-

c. Galloway tube;

d. Multi- tubular;

e. Pipe.

1,956

CLASSIFICATION OF BOILERS

,2 m3

""Sn'o^i^r l^iT7o^Zl^:'l^^^^-^l:^i^-^;f'''f:i{^'' o^so-caUed Cornish; 3 and 4.

CLASSIFICATION OF BOILERS 1^Q57

4. With respect to the heat absorbing surfaces of the
tubes, as

a. Fire tube;

b. Water tube; ^ ^ u

c. Combination fire and water tube.

5. With respect to special features of the tubes, as

a. Single tube; _. ^ ^ ^ ,

h. Double tube (Field type) ;

c. Through tubes; •

d. Submerged tubes; . ^ ,

e. Radial tubes (porcupme type) .

6. With respect to the shape of the tubes, as

a. Straight;

b. Curved;

c. 'Coiled.

7. 'With respect to the position of the tubes, as

a. Horizontal;

b. Inclined;

c. Vertical.

8. With respect to the grouping of the tubes, as

a. Sectional;

h. Non-sectional.

9. With respect to the liberating surface, as

a. Water level;

b. Semi-flush.

c. Flash.

10. With respect to the flow of the products of combustion, as

a. Single flow;

b. Return flow;

c. Triple flow.

1,958

CLASSIFICATION OF BOILERS

■ * '"

^

■ (cO

jlllH

If!

•ijg2

•CO

S o • - 2
t^ 3.2 o

o ii r

CLASSIFICATION OF BOILERS 1,959

11. With respect to the number and placement of the fur-
naces, as

a. Single;

h. Double, etc.;

c. Single ended;

d. Double ended.

12. With respect to the shape of the furnace

a. Rectangular (stayed);
h. Cylindrical;
c. Corrugated.

13. With respect to the type of combustion chamber, as

a. Water-back (Scotch type);

b. Insulated back {Clyde type).

14. With respect to the shape of the shell, as

a. Haystack or balloon (early type);

b. Plain;

c. Saddle.

15. With respect to the degree of steam pressure, as

a. Low pressure;

b. Medium pressure;

c. High pressure. . '

There are, as can be seen from the classification, a multiplicity
of boiler types, and because of numerous features in common, a
really satisfactory division of the types is difficult.

A classification adopted by Gunsaulus, divides boilers under
two broad heads:

1. According to use.

2. According to form of construction.

This tabulation will be helpful to properly place the various forms.

1,960

CLASSIFICATION OF BOILERS

"WfM

iim^ — ^

%^m

[(&^=^=i==z:=^

n

iiiiiii

Figs. 3,495 to 3,504. — ^Various water tube boilers. 1, Thornycroft; 2, Roberts; 3, Watson;
4, Cook; 5, Seabury; 6, Mosher (double steam drum); 7, Buyer; 8, Normand; 9, Babcock
and Wilcox; 10, Mosher (single steam drum).

CLASSIFICATION OF BOILERS

1,961

CLASSIFICATION OF BOILERS.

1. According to Use.

Stationary

Early forms
Plain cylindrical
Single flue, external flue

r Cornish (single flue)
Flue boilers < Lancashire (two flue)
(, Galloway

Multi-tubular

externally fired
internally fired

Fire box US°af^'

Water tube boiler

Mixed type
Peculiar forms

straight tube
curved tube
horizontal
vertical
sectional
non-sectional "

2. According to form of Construction.
Early Forms

Flue

Cornish ^ (single flue)

Lancashire (two flue)
Galloway

Single flue (externally fired)

Fire Tube

Horizontal (curved form)

Vertical
Return tube
Through tube
Fire box
Peculiar forms

Water Tube

TTr^■riVr^-n+o1 f Straight tubc ( scctional
norizonxai j curved tube ( non-sectional

Vertical {f^fft^e
I Peculiar forms

1,962

CLASSIFICATION OF BOILERS

Pigs 3 505 to 3,512.— Various water tube boilers 1, Marshall-Thornycroft; 2, Berry;
3, Momn's "Climax"; 4, BelviUe; 5, Stirling; 6, Niclausse; 7. Almy; 8, Milne.

CLASSIFICATION OF BOILERS

1,963

Mixed Types

Marine

Locomotive

Early forms (box or rectangular)
Scotch or drum
Return tube
Through tube

r curved tube

Water tube hrcSnir"'

[ non-sectionnl

f Multi-tubular fire box
J Wooten type
1 Corrugated furnace
[ Peculiar forms

SHEET
RIVETED JOINT

FLUE

SMALL DIAMETER
-SHEET

LARGE DIAMETER
SHEET

Figs. 3,513 and 3,514. — Differences between a tube and a flue. The chief differences are sizes
and method of making the joint as by expanding and riveting as shown.

Ques. What is the difference between a tube and a
flue?

Ans. A tube is a lap welded or seamless cylindrical shell
made in small sizes up to and including 6 inches diameter. A flue
is a large cylindrical shell made in sizes from 7 inches to 18 inches
diameter, it may be seamless, lap welded, or riveted.

1,964

CLASSIFICATION OF BOILERS

In England the
term flue is errone-
ously used in the same
sense that tube is used
in America.

Oues. What is
the difference be-
tween a flue and
a tubular boiler?

Ans. A flue boiler
has two or three
flues, whereas a
tubular boiler has a
multiplicity of
tubes.

Oues. Why
have flue boilers
practically gone
out of use?

Ans. Because
considerably more
heating surface can
be provided within
a shell of given size
by using a large
number of tubes
closely spaced, not-
withstanding the
excessively long
length of some flue
boilers .

CLASSIFICATION OF BOILERS

1,965

Oues. What is the difference between a fire tube and
a water tube?

Ans. A fire tube is one in which the products of combustion
pass through the tube which is surrounded by water. A water

Fig. 3,518. — Stanley automobile boiler illustrating the very large amount of heating surface
that can be put in a small shell by using very small tubes. The tubes are *%-inch diameter
by 14 inches long, excepting those in the 26-inch boilers which are 16 inches long. In the
18-inch boilers there are 469 tubes with 66 square feet of heating surface. In the 23-inch
boilers there are 751 tubes with 104 square feet of heating surface. In the 26-inch boilers
there are 999 tubes with 158 square feet of heating surface. Approximate weights
14 inch boiler 112 lbs.; 23 inch 293 lbs., or about 10% of the weight of ordinary vertical shell
boiler of same capacity.

tuDe is surrounded by the products of combustion, the water
being inside the tube.

1,966

CLASSIFICATION OF BOILERS

Figs. 3,519 to 3.524.— Various
tube arrangements as explained
in the accompanying text. 1,
single tube; 2, double tube; 3,
non- sectional; 4, sectional; 5,
submerged tube; 6, through
or flush tube.

CLASSIFICATION OF BOILERS 1,967

Oues. What is a single tube boiler?

Ans. One made up of plain tubes.

Oues. What is a double tube boiler?

Ans. One having an auxiliary tube placed inside each main
tube in order to promote circulation.

Oues. What is a Field tube?

Ans. The term Field tube is another name for a double
tube, so called. because it was invented by Field.

The arrangement consists of two concentric tubes which greatly improves
the circulation and steaming capacity of a vertical boiler, the weight and
cost being also increased.

In operation, the heated water rises in the annulus between the inner
tube and the exterior heating surface, while the cold water circulates down
the inner tube. A Field tube is also called a drop tube because it usually
projects downward from a tube sheet above, although in some cases the
tubes are placed horizontally.

Oues. What is a non-sectional boiler?

Ans. One in which all the tubes are in communication with a
common header at each end.

Oues. What is a sectional boiler?

Ans. One in which the tubes are divided up into groups,
each group communicating with a header at each end making
independent units.

Oues. What is the difference between a through tube
and a submerged tube boiler?

Ans. A through tube extends from the lower tube sheet the
full length of the shell. A submerged tube terminates at its
upper end below the water line.

1,968

CLASSIFICATION OF BOILERS

yf

X1

i

A i;|

: S

B

q

s -

i'

\

P.

i

j

f

Figs. 3,525 to 3,530. — ^Various forms of combustion chamber arrangements as explained in
the accompanying text. 1, vertical cylindrical internally fired; 2, horizontal corrugated
furnace with water Vjack combustion chamber; 3, wet bottom fire box furnace of portable
locomotive type; 4, externally fired furnace, horizontal return tubular; 5, horizontal corru-
gated furnace with water back (Scotch boiler) ; 6, horizontal cylindrical furnace with tubular
section and dry back.

CLASSIFICATION OF BOILERS

1,969

iiS

O ^^^ T>>

I II I ' I [i II II 1 1 II II iiti

cji^ CPC^-^WATER INTAKE-^

jji II iij^i II hie:

ra

uii II I "I h inrr

I [III I ^111 lit!

5P:

i^mj ii

I II rn I

s

X

Itl-llll (

T7^

IJ,ltl

ffiA

5;

HE

f^

n

px

Figs. 3,531 to 3,536. — ^Various automobile boilers. 1. Lane combination flash and shell boiler;

2. (A to G) Serpollet flash generator (fig. A to C, earliest form, figs. D to G, second form);

3. Walker semi-flash generator; 4. Doble flash generator; 5. Geneva combination fire tube,
and water tube boiler; 6. White flash generator. Flash generation of steam should
interest every steam engineer. In flash generators there is but a very small quantity of
water and steam in the generator at any given moment, but the process of making steam
is so rapid that the rate of steam production follows the changes in the intensity of the fire
without any appreciable lapse of time. Tests on the White generator (by Prof. Carpenter)
showed an evaporation of 13 lbs. of water per hour per sq. ft. of heating surface. It re-
mains for some genius to develop the flash system commercially, and considering the many
inherent defects of ordinary boilers it is surprising that so little attention has been given to
the problem of flash steam generation.

1,970 CLASSIFICATION OF BOILERS

Oues. What is a fire box boiler?

Ans. One having the fire within a fire box which, although
external to the shell, is rigidly connected to it.

The fire box is usually made of steel plates instead of brick.

Oues. What is the difference between a Scotch and a
Clyde boiler?

Ans. A Scotch boiler is one in which the combustion chamber
is entirely surrounded by water. A Clyde boiler has, instead of
a water space at the back end of the combustion chamber, a
removable back which is lined with some insulating material
such as asbestos or fire tile.

O^es. What are Galloway tubes ?

Ans. Cross tubes placed in a flue and attached to opening
in the side of the flue to increase the heating surface.

Oues. What is the difference between a Cornish and
a Lancashire boiler?

Ans. These are respectively one, and two flue boilers.

Oues. What is a return tubular boiler?

Ans. One so arranged that the products of combustion after
passing along the length of the shell return in an opposite direc-
tion through the tubes before passing up the stack.

Owes. What is a porcupine boiler?

Ans. One having a vertical central drum into which are
screwed a multiplicity of horizontal short tubes which project
radially and having their outer ends closed and of square section
which enables them to be screwed into the drum with a wrench .

CLASSIFICATION OF BOILERS

1,971

0

C/3

<D

in.

rw

^

U4

+J

o-

^

S

Ih

Ti:^

a

S

o

,.rl

•fH

J^

2

4J

o

^

'd

^

C/3

^

*«

g

^

C)

1

O

>>

s

>»

.9

o

§

03

i

S

^

;3

'M

c;

^

«+-!

•S

-B

1

•s

•s

.s

■^

GO

^
^

•M

^

^

a

cs

a

^

"^

X5

.a

^

o

a

^

S

O

O

GO

•

00

^

O

C/3

o

m ^

P

d

:3

d 'iU

O^

O < -^

1,972 CLASSIFICATION OF BOILERS

Oues. What is the difference between a tube and a pipe i

Ans. The metal of a tube is thin, being proportioned only tc
withstand the steam pressure, whereas a pipe is made of relativel}
thick metal with threaded ends.

Tubes are intended for expanded joints (although in some porcupin<
boilers they are provided with fine threaded joints), whereas pipes ar(
for threaded joints the extra thickness being provided for the rather coarse
Briggs threads.

Oues. What is the difference between a boiler and 2
generator?

Ans. A boiler carries a considerable volume of water ii
proportion to its heating surfaces, and is therefore not ver}
sensitive to sudden changes in the rate of combustion, wherea;
a generator carries no excess volume of water but converts th(
water into steam as it transverses the heating surface pro
gressively from one end to the other; it has no water level aj
indicated by water gauge or gauge cocks.

Ques. Name two types of generator?

Ans. Semi-flash and flash.

A semi-flash generator is a combination of a shell and flash boiler. Ii
consists of a drum or shell holding a body of water and a coil of pipe forming
the heating surface.

A flash generator consists of a long length of tubing formed into a coil
usually water entering at the top and being "flashed" into steam at som(
intermediate point coming out of the lower layer as superheated steam.

The term boiler is frequently used in place of generator.

CHARACTERISTICS OF BOILERS 1,973

CHAPTER 62
CHARACTERISTICS OF BOILERS

Oues. What duty does a boiler perform?

Ans. It transfers heat from the gases of combustion to water
contained in the boiler, and converts the latter into steam
usually under pressure greater than that of the atmosphere.

Oues. What means is provided for the transfer of heat?

Ans. Heating surface.

Oues. What are the essential qualities of the heating
surface?

Ans. It must 1, absorb the heat of the burning gases as
completely as possible, and 2, keep the water and steam from
coming into direct contact with the fire.

Oues. What should be the nature of the material
composing the heating surface?

Ans. It should, 1, be a good conductor, and 2, have ample
strength to retain the steam under pressure even if heated to a
high temperature.

Oues. What material is best adapted to the purpose,
and why?

1,974 CHARACTERISTICS OF BOILERS

Ans. Iron, in general, or in the special form of steel, as it is
a fairly good conductor of heat and has great strength, besides
being obtainable in unlimited quantities at a low price.

Oues. What is the best form for the heating surface,
and why?

Ans. The tubular form, because it gives maximum strength.

That is, it is the form giving the least weight per square foot of heating
surface, lightness being especially desirable in marine practice.

Oues. How long should the gases be in contact with
the heating surface?

Ans. Until cooled to such an extent that active and quick
transmission of heat stops.

This is assumed to occur when the gases have reached a temperature of
from 600 to 800 °F.

Oues. How extensive should the heating surface be?

Ans. It should be large enough to effectually reduce the
temperature of all gases, the size in square feet being regulated
according to the number of pounds of fuel, from which the gases
are developed.

Oues. Where are these gases developed from the fuel?

Ans. On the grate.

Oues. What is the function of the grate?

Ans. Its object is to provide sufficient space for a thin
layer of .the fuel so that the air has easy and uniform access to it,
thus rendering combustion as near perfect as possible.

Oues. What should be the dimensions of the grate to
effect the spreading of the fuel to best advantage?

CHARACTERISTICS OF BOILERS

1,975

.52 .'d
•-• a; C

"5 ^ ^

-. S nJ

lis

CO o c

CO '5 « "
10 & o ai
CO o toU

Ans. The grate should be
wide rather than deep, as this will
allow the fireman to spread the
fuel in nearer uniform thickness,
and keep it in better condition for
complete combustion.

Ones. What determines the
number of pounds of fuel that
can be burned?

Ans. The area of the grate
and the draught.

Oues. How are the heating
surface and the grate area
measured?

Ans. In square feet.

Oues. What is the ratio
between heating surface and
grate area ?

Ans. The number of sq. ft. of
heating surface per sq. ft. of grate
area.

NOTE. — The heating surface of a boiler is
that part of the boiler exposed to the heat generated
by the furnace; it is Cwith respect to the tubes) the
internal surface of fire tubes and the external
surface of water tubes. The area of heating
surface is frequently used to express the horse
power. This is figured from the number of square
feet of boiler and tube surface, exposed to the
action of the fire; the extent of the heating surface
of a boiler depends on the length and diameter of
the shell and the number and size of the tubes or
flues. For the ordinary tubular boiler, fifteen
square feet of heating surface has been held to be
equal to one horse power; it is also customary in
calculating the heating surface of the shell, to
consider that two-thirds of it is exposed to the
action of heat . For internal firebox boilers twelve
square feet heating surface is usually allowed per
horse power.

1,976 CHARACTERISTICS OF BOILERS

The ratio of heating surface to grate area varies widely according to
conditions. With very low rates of combustion it may be say 1 to 20, and
for very high rates as in locomotive practice, as much as 1 to 75 or more.
In general, with ordinary rates of combustion, the ratio of heating surface
to grate area varies usually between 30 to 1 and 40 to 1 , because it has been
found that the heat of the gases produced from the fuel on one square foot
of grate area can be effectively and economically absorbed by from 30 to 40
square feet of heating surface.

Oues. What part of the heating surface is most eflfectire
in the transmission of heat, and why?

3

10 : 1 BADLY DESIGNED HEATING BOILERS

■ I

20 : 1 SMALL VERTICAL BOILERS

I ZZD

30M HORIZONTAL SHELL BOILERS

■ I
50 :1 WATER TUBE BOILERS

■ !
60 :i LOCOMOTIVE BOILERS

Fig. 3,541 to 3,545. — ^Various proportions of grate and heating surface in common use. Where
economy is of any importance, 20:1 is about the lowest rating that should be used. Heating
boilers as made by some manufacturers having only 10 sq. ft heating surface per sq. ft. of
grate will not be accepted by anyone of ordinary intelligence.

Ans. The part of the heating surface nearest the fire,
because at that point the differences in temperature of gases and
water are the greatest, and, therefore, the absorption of heat is
the quickest.

Ques. How is the transmission of heat by the heating
surface measured?

Ans . B y the number of pounds of water evaporated per square
foot of heating surface per hour.

CHARACTERISTICS OF BOILERS 1,977

Oues. What are average rates of evaporation per square
foot of heating surface?

Ans . For natural draught , about three pounds per hour . For
forced draught , up to seven or more pounds of water per square
foot of heating surface per hour.

Oues. How is the efficiency of evaporation affected by
the different rates, and why?

Ans. The efficiency of evaporation is higher at low rates,
because the heat is more completely absorbed .

In practice, however, it is not found profitable to go below average
rates of evaporation, as a boiler, to produce a certain amount of steam,
would have to be much larger and more expensive, if worked with low
rates, than with high rates of evaporation.

Ones. How should the gas passages be arranged?

Ans. They should be so arranged that the whole heating
surface can readily absorb heat of the gases.

Oues. What determines the size of the gas passages?

Ans. The area of the grate.

The ratio between them is usually one square foot of passage for a total
of from seven to nine square feet of grate.

Oues. What is the ratio of the air space area of the grate
to the total area of the grate and to the area of passages?

Ans. The area of the air space is from one-third to one-half
of the total grate area, and one square foot of passage is usually
provided for every 3 to 3.5 square feet of air space of the grate.

Oues. Is the area of the gas passages uniform through-
out its course?

Ans. No.

1,978

CHARACTERISTICS OF BOILERS

The area of the passages decreases, usually toward the funnel, making
the gases travel faster when the heat excess is smaller.

Ques. How should the water space be arranged?

Ans. It should be so designed that the steam evaporated

from the heating surface can, by rapid and undisturbed circula-
tion, be replaced by water.

Ques. Why is rapid circulation
desirable in boilers?

Ans. It is needed to prevent over-
heating of the heating surface; since water
should be kept in contact with the heat-
ing surface in order to absorb sufficient
heat to avoid dangerous temperatures.

Ques. What is the steam space?

Ans. That part of the interior of the
boiler above the water line, in which
steam is stored.

The steaming space, if too small, will cause
undue fluctuation of pressure on sudden demand ,
and if too large will present an unreasonably
large wall area to the relatively cold exterior,
thus causing undue condensation.

Ones. What is the liberating sur-
face?

Ans. The water surface or area
contact between water and steam.

of

It provides for the liberation or escape of the
steam bubbles from the water, hence its name.

Fig. 3,546. — Importance of rapid circulation. Because of the poor circulation in tube L,
the excess steam forming at the bottom of the tube tends to drive the water upward, thus
the metal is left unprotected and quickly becomes overheated by the intense heat from the
furnace. With an inner tube to promote circulation as in tube F, there is a constant flow of
cool water over the metal with the result that the steam is carried off to the liberating surface
as soon as it is formed, thus preventing the metal becoming overheated.

CHARACTERISTICS OF BOILERS

1,979

Ques. What is the result of insufficient liberating
surface?

^^^^<— UN STELA DY PRESSURE.

STEAM 5 PACE.

LIBERATING SURFACE

STEADY
PRESSURE

Figs. 3 ,547 and 3 ,548.— Influence of the size of steam space and liberating surface . The steam
space forms a reservoir for the storage of steam, hence if it be small, as m fig. 3,547, a sudden
and large demand for steam will cause a considerable drop of pressure and the accompanying
violent ebullition to re-establish equilibrium between pressure and temperature will cause
priming, carrying over a large amount pf spray into the steam main. The priming effect
being increased by the small area of liberating surface for the discharge of steam into
the steam space. When the steam space and liberating surface are large as in fig. 3,548, the
opposite conditions obtain.

Ans. It causes priming, on account of the great violence with
which the steam globules break through the water surface.

1,980

CHARACTERISTICS OF BOILERS

Oues. What is priming?

Ans. The carrying of small water particles in dangerous
quantities into the steam rendering it unfit for use in engines.

Oues. How much water should be carried in a boiler?

Ans. There should be enough to cover all the heating
surface subjected to the intense heat of the fire, at least several
inches deep, giving due consideration to inclined positions which
boilers other than stationary may assume, as for instance,
tractors, locomotive or marine boilers.

LOW WATtR LEVEL

WATER MARGIN ABOVE HIGHEST POINT OF
HEATING SURFACE

HORIZONTAL LINE

Fig. 3,549. — Diagram illustrating height of water to be carried in a boiler. There must be
enough water to cover all the heating surface for any position the boiler may assume in
practice. Thus, in the case of a locomotive, if the boiler be tilted to the angle of maxi-
mum grade, evidently the water level should be at the level MS, giving a safe margin of
water R, above the crown sheet. Now, if the boiler be tilted back to its horizontal position,
the water line MS, would assume some position as LF. Hence, the lowest gauge cock should
be located on the line LF.

Owes. What auxiliaries may be added to the heat-
ing surface to more efficiently absorb the heat?

Ans. Feed water heater, super-heater, and economizer.

Feed water heater heats the feed water before it enters the boiler; a super-
heater heats the steam to a temperature greater than that due to its
pressure and an economizer is a supplementary heating surface interposed
between the boiler and chimney to absorb as much of the heat that would
otherwise go up the chimney, as is commercially feasible.

CHARACTERISTICS OF BOILERS

1,981

Oues. In large plants why are several boilers used
instead of one of equivalent capacity?

Ans. 1, for mechanical reasons, especially in the case of
shell boilers the size is limited, 2, in case of accident, only part
of the boiler plant need be shut down during repair; 3, for vari-
able load , the number of boilers in operation may be altered to
suit the demand for steam.

THICK PLAT^

THIN

PLATE

DOES NOT OVERHEAT OVERHEATS AND BURNS

Figs. 3,550 and 3,551. — One reason why very large shell boilers are not used.

Oues. What is the chief difference in behaviour of
water tube and shell boilers ?

Ans. A water tube boiler is more sensitive to changes in
combustion conditions than a shell boiler.

Oues. Why?

Ans. Its response to changes in the rate of combustion is
quicker because it carries less water in proportion to the heating
surface .

1,982

CHARACTERISTICS OF BOILERS

Oues. State some other differences?

Ans. In case of a sudden demand for steam, the pressure
will fall more in a water tube boiler than in a shell boiler, because
the relatively large volume of water in the shell boiler forms a
''reservoir'' for the storage of heat.

The fluctuations in water level are usually greater m water tube boilers,
and because of the relatively small amount of water carried, they require
closer attention than shell boilers.

LARGE

STEAM SPACE-

C STEAM SPACE-

oiviA^i-^i-: (volume op water

imiiiiiifiniiiiiiiiiiiii

iiimiiiiiiiiiiiiiiiiiiiii

Figs. 3,552 and 3 ,553 .—Sensitiveness of shell and water tube boilers. The shell boiler with its
large steam and water spaces is less sensitive to sudden load changes than the water tube
boiler.

Oues. What is the difference between the steam
generated in a horizontal shell boiler and in a vertical
boiler with full length tubes?

Ans. The horizontal boiler usually furnishes steam with
2% or 3% of moisture while the vertical boiler, especially

CHARACTERISTICS OF BOILERS

1,983

MOT

Tubes

3LIGHTLY 5UPEF?HEATEl> 5TEAM

WET STEAM
ZTOSYo

moisture:

Figs. 3,554 and 3,555. — Difference between the steam generated in a horizontal and a through
tube vertical boiler. Ordinarily a horizontal boiler furnishes steam with 2 to 3 per cent
moisture, but in the case of a vertical boiler (especially those of the Manning type) the mul-
tiplicity of hot tubes, a part of whose surface is in the steam space, transmits heat to the
steam and slightly superheats it.

[RADIATION
LOSS

POOR

COMBUSTION

LOSS

Figs. 3 ,556 and 3 ,557. — Characteristics of external and internal furnaces. An external furnace
(fig. 3,556) is subject to loss of heat by radiation, whereas, in an internal furnace (fig. 3,557)
there is a loss due to poor combustion of the fuel in contact with the furnace walls.

1,984 CHARACTERISTICS OF BOILERS

when the water is low in the glass, will produce slightly super-
heated steam.

Ques. How do external and internal furnace boilers
compare?

Ans. An external furnace surrounded by brickwork is subject
to loss by radiation, whereas most of this heat is saved in an
internal furnace boiler, but combustion is not so good near the
cool walls of the internal furnace.

Ones. How does the position of boilers aflfect the
convenience and safety of handling in marine practice?

Ans. The boilers may be placed low in the hold, as in most
sea going ships, or above the water line, as in many river and bay
steamers. The latter position affords a certain convenience
in discharging ashes and handling coal, while the former is the
safer for sea going ships.

In many steamers care must be taken that the heat of the boilers will not
prove injurious to the ship or cargo.

BOILER MATERIALS 1,985

CHAPTER 63

BOILER MATERIALS

In the construction of a steam boiler, a very small variety of
materials are used, yet the subject of boiler materials is of con-
siderable importance both to the designer and operator; it may
be divided into three sections:

1 . Materials

2. Properties

3. Tests

These will now be taken up in the order given.

1. MATERIALS

The substances ordinarily used in boiler construction are:

1 . For the boiler proper

a. Copper.
h. Brass.

^- Il-onfmaneable

d- Steel {^XT

2. For the setting or case

1,986 BOILER MATERIALS

a. Brick.

h. Various insulators { tt'c.^'*°''

In early days copper was used for the furnace sheets and stay bolts in
locomotive boilers and brass for tubes, copper being regarded as the
ideal material for the purposes mentioned because of some of its proper-
ties.

With the gradual increase in steam pressures , copper and cast iron were
found to be unreliable and were discarded in favor of wrought iron and
steel although copper tubes are still employed in special types.

Copper. — The usual method of separating copper from its
ore is by means of heat and is known as smelting. In the
U.S. the ore is smelted to a matte containing 45% or 50% of
copper and then reduced to blister copper in a converter.

In nearly all cases the copper must be refined, usually electrically, so
as to remove those impurities that will not go into the slag, nor be oxidized
like sulphur.

If the matte contain less than 40% of copper, the cost of converting
will be excessive; if more than 70%, it will be difficult to concentrate the
copper.

Coarse ores are treated more rapidly and to better advantage in blast
than in reverberatory furnaces; fine ores are best treated in a reverberatory
furnace.

Both the blast and reverberatory furnaces are the same in principle as
those used in the iron industry.

Brass. — Mixtures of copper and zinc are called brass. Any
mixture of two or more metals is known as an alloy. Seamless
brass tubes are made from ^s inch to 1 inch outside diameter,
varying by He inch, and from l3^ inches to 10 inches outside
diameter, varying by 3^ inch and in all gauges from 2 to 24
A.W.G,

Brick. — The best brick clays are composed of | silica, 3-
alumina, and J- iron, magnesia, soda, potash and water.

BOILER MATERIALS

1,987

Excess alumina over silica causes the brick to crack in burning.
When sand is added to the clay it should be clean, sharp, fusible
and not too fine. The materials of fire brick are generally
fire clays which are hydrated silicates of alumina, containing
from 50% to 65% of silica, 30% to 75% of alumina, and 11% to
15% of water.

Cast Iron. — According to the specifications adopted by the
International Association for Testing Materials cast iron is

Fig. 3,558. — Air furnace for melting iron to be used for malleable castings. A. blast for the
pipe A, passes through the fuel bed B , over the bridge wall C, to the metal on the refractory-
bed D, then over the bridge wall E, into chimney F. The door G, gives access to the fuel
bed and the doors H, to the molten iron, which is drawn off^ through the tap J. Frequently,
air pipes are placed in the first bridge wall C, so as to add air to the flames, slightly improving
the combustion. In the furnace shown the auxiliary air is furnished by a pipe K, running
across the top of the furnace and feeding a number of small pipes L, that supply the air near
the bridge wall so as to obtain the greatest combustion just over the lapping spout. Some-
times the apping spouts are placed at different levels so that the hottest metal can be drawn
off first, thus preventing its burning as well as making the composition of the casting nearer
uniform. The heating of the bath is aided by the arched roof, which deflects the heat toward
the molten metal. The bath should be deepest by the hedge wall C, and slope upward toward
the bridge wall E. To avoid burning the metal here, the metal should be 2 or 3 inches deep
instead of having a feather edge; the coming of slag then will prevent excessive oxidation
of the metal.

defined as iron containing so ntiich carbon that it is not malleable
at any temperature. It consists of a mixture and combination of
iron and carbon, with other substances in varying proportions.

1,988 BOILER MATERIALS

Generally , commercial cast iron has between 3% and 4% of carbon . The
carbon may be present as graphite as in gray cast iron , or in the form of
combined carbon, as in white cast iron.

In most cases the carbon is present in both forms. Besides carbon,
silica, sulphur, manganese, and phosphorus are nearly always present.

Malleable Iron. — The method of producing malleable iron
is to convert the combined carbon of white cast iron into an
amorphous uncombined condition, by heating the white cast
iron to a temperature somewhere between 1,380° and
2,000° F.

The iron (or castings as sometimes called) , is packed in retorts or anneal-
ing pots, together with an oxide of iron (usually hematite ore) . The oxygen
in the ore absorbs the carbon in the iron, giving the latter a steel like nature.

An annealing furnace or oven is used for heating, and the castings are
kept red hot for several days or several weeks, depending upon the pieces.
In order that the process be successful, the iron must have nearly all the
carbon in the combined state, and must be low in sulphur, as the latter
substance is found to greatly increase the time necessary.

Usually only good charcoal melted iron low in sulphur is used, though a
coke melted iron is quite as suitable, provided the proportion of sulphur
be small.

The process is not adapted to very large castings, because they cool
slowly, and usually show a considerable proportion of graphite.

Wrought Iron. — By definition, wrought iron is a slag hearing
malleable iron which contains comparatively little carbon. Nearly
all the wrought iron now used is made by the puddling process.

This process leaves the metal in the condition of a soft plastic ball
saturated with slag. This ball is taken from the furnace and dropped into
a machine which squeezes out most of the slag. It is then passed through
a train of rolls which ejects much of the remaining slag and gives the plastic
mass the form of a bar.

In the making of boiler plates, the muck bar, as it is called, is cut up
into strips; enough strips to produce a sheet of the desired size are bound
into a bundle, the bundle is then brought to a welding heat and passed
through the rolls. Thus it is that a wrought iron plate consists of a series
of welds. This accounts for its laminar structure.

BOILER MATERIALS

1,989

o

The presence of slag in the material con-
tributes largely to its fibrous texture, the rolls
drawing the metal out into a stringy mass, each
fibre of iron being, in fact, the core of a slender
thread of slag.

Wrought iron is graded in several ways, there
being no standard system. It is sometimes
divided into two classes: 1 , charcoal iron , which
is made from charcoal pig and usually refined
and double refined; and 2, common iron^ which
is made from coke pig.

According to another system, it is classed as:
1, charcoal iron; 2, puddle iron; and 3, busheled
scrap iron.

Figs. 3,559 and 3,560. — Puddling furnace capacity usually from 1,000 to 6,000 pounds of iron.
The fireplace is rectangular and is separated from the bath by a low bridge wall . The roof is
arched and slopes toward the flue which causes the flames to beat down upon the metal. The
air supply is regulated by the damper at the top of the stock, forced draught being used. The
bridge work overlaps the tops of the side frames, so as to form a recess for the fettling or fix
with which it is lined. This fettling is a mixture of oxide of iron and sand from the bottom
of the hearth. Under the great heat generated in the furnace, some of this sand melts with
the pig iron and forms what is called a bath in which the puddling process is carried on . The
silica in the sand unites with the iron and makes a slag, which protects the iron from oxidizing
so that large sized puddle balls can be made . A large percentage of slag is worked out in the
further refining which the metal receives.

1,990 BOILER MATERIALS

Steel. — At the present time, steel is the most important
material of construction. Its low price, combined with its
great strength, permits its application to the -largest and most
severely-strained constructive members. It can be forged or
cast in any convenient form, and is readily obtained in form of
plates, bars, and other shapes.

A disadvantage is that it is rather readily influenced by rust and corro-
sion, requiring systematic and careful attention in order to preserve it
against the action of moisture, oxygen and carbonic acid, and insure its
continued usefulness.

It is also attacked by galvanic action, in connection with copper or
brass, upon immersion in a polarizing fluid.

In regard to its percentage of carbon, steel occupies a middle position
between cast iron and wrought iron. In common with the former, it has a
sufficiently low melting point for casting, and, in common with the latter,
a sufficient toughness for forging.

According to their varying percentages of carbon, three kinds
of steel may be recognized:

1. Soft steel.

2. Medium steel.

3. Hard steel.

Soft steel is nearest to wrought iron in carbon percentage and qualities,
being soft, readily forged, and, by careful handling, may also be welded.
It is used in principally the flanged parts, furnace plates, rivets and other
details, which are exposed to alternate heating and cooling, or to severe
treatment by shaping and forming.

Medium steel is harder than soft steel and is used for boiler shells.

Cast Steel has about the same percentage of carbon as soft or medium
steel. It has in addition silicon and manganese which are needed to produce
good castings.

Hard steel comes the nearest to cast iron in carbon percentage, and
possesses, as its most important quality, a decided facility for tempering
and hardening upon sudden cooling in water.

With modem methods, steel is produced by reducing the

BOILER MATERIALS

1,991

carbon percentage of cast iron to the desired amount. This
may take place in two ways by:

1. Bessemer process.

2. Open hearth process.

Bessemer Process. — This process consists in blowing air into a vertical,
pear shaped converter, full of molten cast iron. The air is blown in at the
bottom, and rising through the molten mass burns the carbon. If the air
admission be arrested at the right time a steel of predetermined quality
and hardness may be obtained.

Fig. 3,561. — Bessemer converter. It consists of a large steel shell A, lined' with a refractory
material B , and turning on trunnions C . Air entering through one trunnion passes through
the pipes D, and the tuyere or wired box E, into the converter through the tuyeres F. A re-
fractory bottom K, is fastened to the shell by the key link G, and the lid H, is fastened to
the tuyere box by the key J. As the lining corrodes rapidly around the tuyeres, the bottom is
made easily removable for quick replacement with a new one.

The converter is tripped on trunnions and its contents poured into
moulds.

The ingots coming from these moulds are then rolled into plates or shapes,
or forged out, as required.

1,992

BOILER MATERIALS

Bessemer steel is objected to by some engineers, as not possessing uni-
formity of qualities throughout the material obtained from the same
converter. Further, it is not always possible to determine the exact point
at which to arrest the admission of air, with consequent uncertain results.

Open Hearth Process. — In this method cast iron is deprived of its
surplus carbon in a shallow furnace, where the molten material is exposed,
on a broad surface, to passing currents of air and gases, which burn out the
carbon.

The molten mass can be mixed and stirred, and, by removing a small
amount as a sample, can also be tested. By this means the reduction of

6 J

Figs. 3,562 and 3,563. — Open hearth furnace and plan of regenerative chambers and flues.
Usual capacity 50 to 60 tons. It consists of a rectangular hearth with parts at each and
through which the gas enters and leaves. Two chambers at each end provide means for
heating the air and the gas. ^ The roof of the furnace must be high enough so that it will
not be burned tip by an impinging flame from the parts. The hearth must be of such a
length that there will be complete combustion; its length should be about 2 to 2K times
its width; and its depth sufficient to permit oxidation of the metal, yet shallow enough
to give thorough heating and reasonably quick working of the bath.

carbon can be more accurately adjusted to the desired degree. The open
hearth product is regarded by many engineers as nearer uniform in quali-
ties, and, therefore, preferable for most purposes.

Iron and Steel Definitions. — ^At the Brussels Congress of
the International Association for Testing Materials held in

BOILER MATERIALS 1,993

September, 1906, the following definitions of the most important
forms of iron and steel were adopted:

DEFINITIONS

Alloy cast irons. — Irons which owe their properties chiefly to the pres-
ence of an element other than carbon.

Alloy steels, — Steels which owe theii- properties chiefly to the presence
of an element other than carbon.

Basic pig iron. — Pig iron containing vv little silicon and sulphur that
it is suited for easy conversion into steel by the basic open-hearth process
(restricted to pig iron containing not more than 1.00 per cent of silicon).

Bessemer pig iron.^lron which contains so little phosphorus and sul-
phur that it can be used for conversion into steel by the original or acid
Bessemer process (restricted to pig iron containing not more than -^^
per cent of phosphorus) .

Bessemer steel. — Steel made by the Bessemer process, irrespective of
carbon content.

Blister steel. — ^Steel made by carburizing wrought iron by heating it in
contact with carbonaceous matter.

Cast iron. — Iron containing so much carbon or its equivalent that it is
not malleable at any temperature. The committee recommends drawing
the line between cast iron and steel at 2.2 per cent carbon.

Cast steel. — The same as crucible steel; obsolete, and confusing; the
terms "crucible steel" or "tool steel" are to be preferred.

Converted steel. — The same as blister steel. •

Charcoal hearth cast iron. — Cast iron which has had its silicon and
usually its phosphorus removed in the_ charcoal hearth, but still contains
so much carbon as to be distinctly cast iron.

Crucible steel. — Steel made by the crucible process, irrespective of
its carbon content.

Grfiy pig iron and gray cast iron. — Pig iron and cast iron in the frac-
ture of which the iron itself is nearly or quite concealed by graphite, so
that the fracture has the color of graphite.

1,994 BOILER MATERIALS

Malleable castings. — Castings made from iron which when first made
is in the condition of cast iron, and is made malleable by subsequent
treatpient without fusion.

Malleable iron, — The same as wrought iron.

Malleable pig iron. — An American trade name for the pig iron suitable
for converting into malleable castings through the process of melting,
treating when molten, casting in a brittle state, and then making malleable
without remelting.

Open hearth steel. — Steel made by the open-hearth process irrespective
of its carbon content .

Pig iron. — Cast iron which has been cast into pigs direct from the blast
furnace.

Puddled iron. — Wrought iron made by the puddling process.

Puddled steel. — Steel made by the puddling process, and necessarily
slag-bearing.

Refined cast iron. — Cast iron which has had most of its silicon removed
in the refinery furnace, but still contains so much carbon as to be distinctly
cast iron.

Shear steel. — Steel, usually in the form of bars, made from blister steel
by shearing it into short lengths, piling, and welding these by rolling or
hammering them at a welding heat. If this process of shearing, etc., be
repeated, the product is called "double-shear steel."

Steel. — Iron which is malleable at least in some one range of temperature
and, in addition, is either (1), cast into an initially malleable mass; or (2),
is capable of hardening greatly by sudden cooling; or (3) , is both so cast
and so capable of hardening.

Steel castings. — Unforged and unrolled castings made of Bessemer,
open-hearth, crucible, or any other steel.

Washed metal. — Cast iron from which most of the silicon and phosphor
have been removed by the Bell-Krupp process without removing much of
the carbon, still contains enough carbon to be cast iron.

Weld iron. — The same as wrought iron; obsolete and needless.

White pig iron and white cast iron.—Pig iron and cast iron in the
fracture of which little or no graphite is visible, so that their fracture is
silvery and white.

Wrought iron. — Slag-bearing, malleable iron, which does not harden
materially when suddenly cooled.

BOILER MATERIALS 1,995

2. PROPERTIES
OF MATERIALS

It is essential that anyone engaged in the design, construction,
erection, or operation of a steam boiler should be familiar with
the nature of the various materials entering into its construction.

A material is said to possess certain properties which define
its character or behaviour under various conditions.

The following definitions of terms used to express the properties
of materials entering into boiler construction should be noted:

DEFINITIONS

Brittle. — Breaking easily and suddenly with a comparatively smooth
fracture; not tough or tenacious. This property usually increases with
hardness. The hardest and most highly tempered steel is the most brittle;
white iron is more brittle than grey, and chilled iron than any other. The
brittleness of castings and malleable work is reduced by annealing.

Cold short. — The name given to the metal when it cannot be worked
under the hammer or by rolling, or be bent when cold without cracking
at the edges. Such a metal may be worked or bent when at a great heat,
but not at any temperature which is lower than about that assigned to
dull red.

Cold shut. — In foundry work, when, through cooling, the metal passing
round the two sides of a mould does not properly unite at the point of
meeting.

Ductile. — Easily drawn out; flexible; pliable. Material, as iron, iS
"ductile" when it can be extended by pulling.

Elastic limit. — The greatest strain that a substance will endure and
still completely spring back when the strain is released.

Fusible. — Capable of being melted or liquefied by the action of heat.

1,996 BOILER MATERIALS

Hardness. — The quality or state of being hard in any sense of the word.

Homogeneous. — Of the same kind or nature; hence, homogeneous, as
applied to boiler plates, means even grained. In steel plates there are no
layers of fibers, and the metal is as strong one way as another.

Hot short. — More or less brittle when heated; as hot short iron.

Melting points of solids. — The temperature at which solids become
liquid or gaseous. All metals are liquid, at temperatures more or less ele-
vated, and they probably all turn into gas or vapor at very high tempera-
tures. Their melting points range from 39 degrees below zero of Fahren-
heit's scale, the melting, or rather the freezing point of mercury, up to
more than 3,000 degrees.

Resilience. — The act or quality of elasticity; the property of springing
back or recoiling upon removal of a pressure, as with a spring. Without
special qualifications the term is understood to mean the work given out
by a spring, or piece, strained similarly to a spring, after being strained
to the extreme limit within which it may be strained again and again,
without rupture or receiving permanent set.

Specific gravity. — The weight of a given substance relatively to an
equal hulk of some other substance which is taken as a standard of com-
parison. Water is the standard for liquids and solids, air or hydrogen for
gases. If a certain mass be weighed first in air, then in water, and the
weight in air divided by the loss of weight in water, the result will give
the specific gravity; thus, taking a ten pound piece of cast iron, its weight
suspended from the scale pan in a bucket of water, will be 8.6 pounds,
dividing 10 by the difference 10 — 8.6 or 1 .4, the answer will be 7.14, which is
the specific gravity of cast iron.

Strength. — Power to resist force; solidity or toughness; the quality
of bodies by which they may endure the application of force without
breaking or yielding.

Tenacity. — The attraction which the molecules of a material have for
each other, giving them the power to resist tearing apart. The strength
with which any material opposes rupture, or its tensile strength.

Tough. — 1. Having the quality of flexibility without brittleness; capable
of resisting great strain; able to sustain hard usage; not easily separated
or cut.

2. Material, as iron, is said to be "tough" when it can be bent first in
one direction, then in the other, without fracturing. The greater the angles
it bends through (coupled with the number of times it bends) , the tougher
it is.

Weldable. — A term applied to material; as iron, if it can be united,
when hot , by hammering or pressing together the heated parts . The nearer
the properties of the material, after being welded, are to what they were
before being heated and welded, the more weldable it is.

BOILER MATERIALS

1,997

P
poo

^90

-=-80

1-60
1-SO
1-40
=-30
^20
g-10

LTL

g ;i o CN M <u <u

^13 +» oJ O w y J3
ai ^ 3 <i^ J^ S <^

c't ^ c rt 5 wiS"

^ -^ ^H w o ^ S*«

la- •>dc|'^

o ^ ^ S C rt^^ "
^ bo J2 c3 w 2 "" <"

g >^_ OS > &(_ M

Ill ^"^-!l

(U-Td -M w <u ;3 C3.+J

*S, !:! v^rs ti'5^ ^S-^ 52
.i? 03 S o3"^ o 03 rti cj

C X "U vi OJ C-^ +^
.So3CgC§G+-^

O S <U O w C 0)
• TjM-i <U ^c 03 J5

In addition to these definitions,
others will be found, being terms used
in testing and representing the behav-
iour of material under tests.

Copper. — The strength of copper
decreases rapidly with rise of temper-
ature above 400° F.; between 800° and
900° its strength is reduced about half
that at ordinary temperatures. Cop-
per is not easily welded, but may be
readily braised. At near the melting
point it oxidizes or is burned as it is
called and loses most of its strength,
becoming brittle when cool.

Brass. — ^When zinc is present in
small percentages the color of brass is
nearly red; ordinary brass for piping,
etc., contains from 30% to 40% of
zinc. Brass can be readily cast, rolled
into sheets, or drawn into tubes, rods
and wire of small diameter.

The composition of brass is determined
approximately by its color: Red contains
5% of zinc; bronze color, 10%; light
orange, 15%; greenish yellow, 20%; yellow,
30%; yellowish white, 60%. The so called
low brasses contain 37 to 45% of zinc and
are suitable for hot rolling, and the high
brasses contain from 30 to 40% of zinc,
being suitable for cold rolling.

Cast Iron. — The properties of cast
iron depend chiefly on the proportion

1,998

BOILER MATERIALS

of total carbon, and in the relative proportion of combined
carbon and graphite.

Soft cast iron called gray iron contains a high percentage of
graphite which renders it tough, with low tensile strength;
it breaks with a coarse grained dark or grayish fracture.

Fig. 3,565. — Shore scleroscope outfit consisting of scleroscope (self-contained); plaste
mount vessel; swing arm and post; magnifier hammer (for soft metals only) ; soft and hard
steel replace bars; fifty blank curved charts; carrying case.

NOTE. — The Brinell method of testing hardness consists in pressing a hardened steel ball
into the smooth surface of the metal so as to make an indentation which is then measured by
optical or mechanical means to ascertain the hardness of the material. The Brinell test may be
applied to unfinished material as well as to manufactured goods, such as rails, structural
material, etc.; it will also determine the effects of annealing and hardening of steel and serve
as a basis for calculating the tensile strength directly from the results of the hardness test.

BOILER MATERIALS

1,999

Fig. 3,566. — Olsen universal four-screw testing ma-
chine arranged for long column tests with dial planer
screw beam 100,000 and 200,000 pounds capacity.
The long screws and columns adapt it for long tensUe
and compression tests.

2,000

BOILER MATERIALS

The iron becomes more brittle and harder as the relative percentage of
combined carbon and graphite decreases; its tensile strength increases
somewhat, and the fracture is fine grained or smooth. This grade of iron
is called white iron.

Mottled iron is that grade in which half the carbon is combined and half
separates out as graphite. In casting, when cast iron hardens, it expands,
and then contracts as it cools, the shrinkage being about 3^ inch per foot
in all directions. Hardness and shrinkage increase or decrease together.

In boiler construction cast iron is used for grate bars, furnace
door frames and minor boiler fittings

Figs. 3,567 and 3,568, — Olsen shearing test tool designed for testing 1 inch round specimen
in either single or double shear, and at the same block can, if desired, be provided with
other shearing tools for testing other sizes of specimen. Fig. 3,568, wrench.

Malleable Iron. — In boiler construction malleable iron
finds its chief use for pipe fittings as employed in water tube
boilers of the pipe variety.

The ductility of malleable iron is from four to six times that
of cast iron, or about yV ^^^^ ^^ wrought iron. It may be
welded or forged with proper care and can be case hardened.

BOILER MATERIALS

2,001

Good malleable iron will stand considerable bending and twisting
before breaking.

Steel. — By mixing with steel certain other metals, mainly
manganese, nickel, aluminum, chromium and tungsten, its
strength, hardness or toughness may be increased as desired.

The first essential of boiler plate is a uniform blending of
the physical properties that will enable the material to recover
from the strains induced by the various stresses of operation.

iriNI'0'S"5LSEii

lH£iiiiiiiiill

Fig. 3,569. — Olsen tort ion testing attachment for universal testing machines. The apparatus
is bolted to the lower cross head B, and the torque weighed on testing machine table C.
The specimen is placed at A , and the tortion applied by hand crank I , through worm drive
H, and angular distortion measured from the graduated heads as shown.

^3 . BOILER MATE.

■'Kitnf

.S

The most important

-^-these properties is

tenacity, or ability to

resist a pulling stress.

Carbon possesses no
great strength on its
own account, but when
joined in chemical affin-
ity with iron it develops
strength therein. Cor-
rect proportions must
be maintained , however .
Increasing the carbon
content up to a certain
per cent, conduces to
strength; beyond this
point the strength de-
teriorates.

Fig. 3,571. — Olsen micrometer extensometer.

Mild steel that contains. 1 per cent, of
carbon, for example, has a tensile
strength of about 50,000 pounds per
square inch, while 12 times this quantity,
or 1.2 per cent, increases the tenacity
to nearly 140,000 pounds per square
inch, which is probably the limit for
carbon steel.

Increasing the percentage of carbon
above this figure causes a proportionate
drop in the tenacity of the steel.

Fig. 3,570. — Malysheff method and attachment
for determining elastic limit as used with Olsen
universal testing machines. It is adapted to
determination of elastic limit where threaded
or headed specimens are used and the slip or
give in the grips eliminated. In testing, the
reading of the dial is taken for equal increments of
load and noted and the difference between suc-
cessive readings then plotted on small cross
section paper and cross plotted for which the
elastic limit is noted. The attachment is thrown
in and out of operation by means of hand
wheel shown at B .

m MATERIALS

i(Mi§

With 2 per C(

A further grad
to rapidly acquire

iM

ngtji is about 90,000 pounds.

v^iease of the carbon component causes the material
; characteristics of cast iron.

Phosphorus er"^ nces the strength of steel. It also adds to the hardness
of the plate and thus makes it better able to resist abrasion. These quali-
ties are, however, best secured through the medium of carbon, because
phosphorus tends to make the material brittle. Steel containing much

Fig. 3,572. — Olsen extensometer for tension and compression applicable to all sizesand forms
of specimens within its maximum range IH inches round, square or flat specimens.^ It
forms a ready means of observing elastic limit and yield point when correct determinations
are required . In adjusting this instrument , the two points D ,E , are separated just to straddle
the specimen, and indicator finger C, secured by thumb screw G. In placing instrument on
specimen, bar A, B, is placed horizontal as near as may be observed; indicator finger C, to
point to upper part of dial, as shown in illustration. The spacing bars H, I, by the clamp K,
are placed agamst the instrument's main pivots D, E, and the specimen, and thus holding
the instrument in position. Thumb screw G, is here removed and instrument ready for
the test. As shown in cut, instrument is set for compression test readings, and for tension
or extension readings spacing bars should point up instead of down, as shown in cut. The
instrument is furnished with four verniers, which are marked, the vernier haying the mark
corresponding to the size of the specimen to be used. Spacing bars for 8- inch length of
specimen are furnished, if required, 2-inch, 4-inch, 6-inch, or any other length of si)acing
bars can be supplied. With the clamp K, the instrument is adjusted to zero when in posi-
tion after removing the thumb screw G.

2,004

BOILER MATERIAIS

1 .

phosphorus is particularly weak against shocks uad vibratory strains. On
this account it may be considered the most harmful impurity in steel
boilerplate.

Sulphur increases the brittleness of steel while hot, making it "red
short," and interfering seriously with the shaping and forging of the
material. It should not exceed from .02 to .05 of one per cent.

Manganese increases the
strength, hardness and sound-
ness of the steel. Steel con-
taining a considerable propor-
tion of this element acquires a
peculiar brittleness and hard-
ness that makes it difficult to
cut. Manganese has,. however,
a neutralizing effect on sul-
phur.

Nickel increases both the
strength and toughness of the
steel.

Aluminum acts upon steel
largely in the direction of im-
proving the soundness of ingots
and castings.

The standard rules of
boiler design require the
physical and chemical prop-
erties of the grades of steel
used for plates, stays and
rivets to conform to certain
uniform specifications, as
later given in detail. The
percentage of manganese is
left to the discretion of the
steel maker.

Fig. 3,573. — Olsen duplex micrometer extensometer for round specimens only up to 11^2
inches in diameter, and with proper spacing bars and contact pomt for gauge lengths ot
form 2 to 8 inches. The instrument is graduated to read .0001 to .00001 of an mch for a
length of over 2 inches.

BOILER MATERIALS

2,005

The small quantity of silicon present in boiler plate tends to make the
steel slightly harder than it would otherwise be, but apparently without
diminishing its roughness or ductility, and also without appreciably
affecting its tensile strength.

Brick. — Clay bricks expand or shrink, depending upon the
proportion of siHca to alumina contained in the brick, but most
fire clay brick contain alumina sufficient to show some shrinkage.
A straight 9-inch fire brick weighs 7 pounds, a silica brick

Fig. 3,574.—-01sen extension and compression micrometer. The upper part, or micrometer
proper, remains in the same position, as shown, both for extension and compression tests,
and also whatever length of specimen is operated upon. The lower part, or arm, is adjusted
to the length or kind of test, tensile or compression, that is operated upon. The instrument
is operated on the same principle as an extension rnicrometer with electric contact, only that
no double reading is necessary as this instrument itself gives the mean reading. The read-
ings are to .0001 part of an inch. The instrument, or any part of it, cannot be injured by
breakage of a specimen , and , as it is carried on supports secured to the machine , it may be
left on the machine even if it be not in use , and the machine only used for a test for which
it is not required. ^ It is especially adapted for Olsen four-screw machine, on which it occupies
a place not otherwise used or utilized.

6.2 pounds; a magnesia brick, 9 pounds; a chrome brick, 10
pounds. A silica brick expands about J^ inch per foot when
heated to 2,500° F.

2,006 BOILER MATERIALS

The melting point of the various kinds of brick ranges from 2,800° to
3,900 °F. The chief disadvantage of silicon bricks are brittleness and
liability to "spall" when exposed to sudden changes of temperature.

Compressive strength of ordinary fire brick is from 600 to 1 ,000 pounds
per square inch cold, but some of the best range up to 3,000 pounds cold.

Boiler Coverings or Insulators. — According to Kent

asbestos is one of the poorest insulators. It may be used to

advantage to hold together other incombustible substances, but

the less of it, the better.

Any covering should be not less than one inch thick. A covering should
be kept perfectly dry, because still water conducts heat about eight times
quicker than still air. Some good coverings arranged in order of efficiency
(the most efficient first), are: Rock wool, mineral wool, magnesia, hair
felt, fire felt.

3. TESTS

In boiler design, the importance of properly proportioning
the various parts to withstand the stress due to the steam
pressure can not be over emphasized, for obvious reasons. The
strength of the materials used in construction is best determined
by tests.

Metals are tested for strength in various ways as by taking a
sample of standard shape and subjecting it in testing machines
to tension, compression, bending, sheering stresses. There are
various terms used in testing and the definitions, as here given
should be carefully noted.

DEFINITIONS

Bending stress. — In physics, a force acting upon some member of a
structure tending to deform it by bending or flexure; the effect of this

BOILER MATERIALS 2,007

force causes bending strain on the fibers or molecules of the material of
which the part is composed. An instance of pure bending stress is given
by pulling on the end of a lever, which tends to deflect it while performing
work.

Compression. — To press or push the particles of a member closer
together, as, for instance, the action of the steam pressure in a boiler on
the fire tubes.

Deformation. — Change of shape; disfigurement, as the elongation of a

test piece under tension test.

Factor of safety. — The ratio between the breaking load and what is
selected as the safe working load. Thus, if the breaking load of a bolt be

Fig. 3,575. — Olsen deflection instrument for showing the deflection of transverse specimens.
Deflection magnified ten times.

60,000 pounds per square inchj and the working load be 6,000 pounds per
square inch, then the factor of safety is 60,000 -r- 6,000 = 10.

Force. — That which changes or tends ,to change the state of a body at
rest, or which modifies or tends to modify the course of a body in motion,
as a pull pressure or a push; a force always implies the existence of a
simultaneous equal and opposite force called the reaction.

Load. — The total pressure acting on a surface; thus, if an engine piston
having an area of 200 square inches be subjected to a steam pressure of
150 pounds per square inch, then the load, or total pressure on the piston
is 200 X 150 = 30,000 pounds.

Member. — A part of a structure as a brace, rivet, tube, etc., subject
to stresses.

2,008 BOILER MATERIALS

^ THICKNESS SAME AS BOILER PLATE

L-. *// wl P L-r PARALLEL SECTION ^_ ^

-< 5 >^ ^^ h< NOT LESS THAN 9"" ~ I

— : — M-A ^ L

Fig. 3,576. — A. S. M. E. standard specimen required for all tension tests of plate materiaL

Tension and bend cest specimens shall be taken from the finished rolled material. They
shall be of the full thickness of material as rolled, and shall be machined to the form and
dimensions here shown , except that bend test specimens may be machined with both edges
parallel. One tension, one coldbend, and one quench bend test shall be made from each
plate as rolled. If any test specimen show defeotive machining or develop flaws, it may be
discarded and another specimen substituted. If the percentage of elongation of any tension
test specimen be less than specified in Pars. 28 and 29 below, and any part of the fracture
be outside the middle third of the gauged length, as indicated by the scribe scratches marked
on the specimen before testing, a retest shall be allowed. The thickness of each plate shall
not vary more than .01 inch.

A. S. M. E.—lll PHYSICAL PROPERTIES AND TESTS

28 Tension Tests, a The material shall conform to the following requirements as to ten-
sile properties:

FLANGE FIREBOX

Tensile strength, lb. per sq. in 55,000 — 65,000 55,000—63,000

Yield point, min., lb. per sq. in 5 tens. str. .5 tens. str.

f,500,000 1,500,000
Elongation in 8-in., min., per cent (See Par. 29) •

Tens. str. Tens. str.

b If desired steel of lower tensile strength than the above may be used in an entire boiler,
or part thereof, the desired tensile limits to be specified, having a range of 10,000 lb. per sq. in.
for flange or 8,000 lb. per sq. in. for firebox, the steel to conform in all respects to the other cor-
responding requirements herein specified , and to be stamped with the minimum tensile strength
of the stipulated range.

c The yield point shall be determined by the drop of the beam of the testing machine.

29 Modifications in Elongation, a For material over ^ in. in thickness, a deduction of
.5 from the percentages of elongation specified in Par. 28a, shall be made for each increase of
H in. in thickness above ^ in. , to a minimum of 20 per cent.

h For material K in. or under in thickness, the elongation shall be measured on a gauge
length of 24 times the thickness of the specimen.

30 Bend Tests, a Cold-bend Tests — The test specimen shall bend cold through 180 deg.
without cracking on the outside of the bent portion; as follows: For material 1 in. or under m
thickness, flat on itself; and for material 1 in. in thickness, around a pin the diameter of which is
equal to the thickness of the specimen.

A. S. M. £?.— MINIMUM THICKNESS OF PLATES AND TUBES

17 Thickness of Plates. The minimum thickness of any boiler plate under pressure shall be
J€ in.

18 The minimum thicknesses of shell plates, and dome plates after flanging, shall be as
follows:

WHEN THE DIAMETER OF SHELL IS
36 in. or under Over 36 in. to 54 in. Over 54 in. to 72 in. Over 72 in.

K in. Ke in. ^ in. H in.

BOILER MATERIALS

2,009

2,010

BOILER MATERIALS

^

Fig. 3,578. — Olsen automatic and autographic
testing machine, four-screw type. The auto-
graphic attachment automatically records the
characteristics of the test and produces the
stress strain diagram. An autographic record may be taken of either a tensile com-
pression or transverse test at any point in the travel of the moving crosshead. The
autographic apparatus is mounted on the frame of the machine and is in no_ way supported
by the weighing columns or other parts of the weighing system , thus obtaining the greatest
accuracy and sensitiveness. The screw on the scale beam drives both the weighing poise
and the recording pencil, so that the reading of the load thus recorded must be correct and
correspond to the load weighed. The pencil is arranged with a dotted motion, thus relieving
all the friction from the revolving diagram drum , and the dotting is such as to produce an
even, continuous line as a record of the test. A variable speed cone system is provided,
so that the rate of automatic travel of the weighing poise may be varied quickly to meet
conditions of the test and during the test, so as to produce a regular curve at all times.
The autographic apparatus may be left in contact with the specimen up to the point
of rupture without injury to the apparatus , and thus the curve for the entire test obtained .
Special aluminum clamps, which partly take up for the reduction in area of the specimen
and a special setting apparatus are provided. In operation the pencil scribes the move-
ment of the poise on cross section paper which is placed on the revolving drum, the motion
of which magnifies the elongation or compression of a specimen ten times. To produce the
automatic motion of this recording device, two electric circuits are required; one for opera-
ting the poise on the beam and the other for operating the pencil on the diagram drum.
The scale beam, in rising or falling, makes an electric contact at the top or bottom of the
gate in the front beam stand. This contact produces an electric current which excites a
series of magnets at the back of the scale beam, which in turn, through a friction gear,
operates the screw of the beam, so as to move the poise to balance the beam.

BOILER MATERIALS

2,011

o

D-^-s:

•q^ 5 (U rt oJ

. ': (U-- (D 5 w
£3 g « q; w"^

-< .
|.e2§§i:S

SASH'S 'Sg

o c'5 g a '^ "^
'^ E,c o c '-'

..-S Oi^ c3 fcl ^

^8|

§^^g .O.

^ u<^ '^

O w
^ CD

<U rt 4->
U . '^

«o O

r is

^1

•I

S fi

s .-g

o

« S P
^ a ^

-^ s
^ 8

as

c c

.S'S

rt ^ f^ >

W «^

W

V3 S

pj rH e"^ <i^ o c H
- <^ ^ '•- • 6 t« t^

0 o
o u
<u o

S in <U ^ O -^

*-i .. «^ n cd "H _ rt

o _

0) C

p.g

<D<f^ ^ o 8 2.S S^

o ^

0) fo

O

CD <D

a o

0) ^

cd 3 «

.SS.a

1^ ca oj 4> r^

2,012

BOILER MATERIALS

FIXED END-

'y|ll'^lllllllllllHill\l.|''^allll!l^l||||ll^l

Fig. 3,580. — Tensile teat. The specimen R, is placed in the wedge grips a^b,c,d, thus pulling
it in tension between the fixed end and movable head of the machme. The latter is con-
nected with the scale lever G, upon which slides the weight W, similar to an ordinary weighing
scale. Two center marks L and F, are punched on the specimen at a standard distance A,
apart, in testing, the pull on the specimen is gradually increased by moving W, to the left
and the dimensions A, and B, measured for each increase of load.

^

il

__

1

^ ^

Rf

k

— ♦ .

^

L ^ ^^

H

=

Abh

A

'

^

FRACTURE

Figs. 3,581 and 3,582. — Tensile test specimen before and after rupture showing reduction of
section B', at break. Example, Assume A =2 inches; B=.505 inches then cross area
of specimen before test = .2 square inch; this value is used in calculating elastic limit and
ultimate strength. Now if the loads be 6,250 and 12,160 pounds, then 6,250 -4- .2 =31,250
pounds elastic limit per square inch, and 12,160 4- .2 =60,800 pounds ultimate strength per
square inch. To calculate the percentage of elongation , the broken parts are placed together
and A' measured. Assuming A' =2.55 inches, then 2.55— 2 = .55 m total elongation, and
55-7-2X100=273^ per cent elongation. Again using micrometer, assume B' to measure
.346 inch, then area = .094 inch, and .2 — .094 = .106 square inch total reduction of area from
which .106 4- .2 X 100 =53 per cent reduction of area.

BOILER MATERIALS

2,013

Tensile strength, — The cohesive power by which a material resists an
attempt to pull it apart in the direction of its fibers, tliis bears no relation
to its capacity to resist compression.

Tension, — The stress or force by which a member is ptilled; when thus
pulled, the member is said to be in tension.

Ultimate strength.-

before rupture.

-The maximum imit stress developed at any time

Yield point. — The point at which the stresses and the strains become
equal, so that deformation or permanent set occurs. The point at which
the stresses equal the elasticity of a test piece.

Fig. 3,583. — Compression test. The specimen R, is placed between the two plates M, and
S, and a compression stress of any intensity applied by moving the weight W, on the lever G.
In testing, as the load is gradually increased, the changes in dimensions A , and B , are noted
and result calculated in a manner similar to that explained for the tension test fig. 3,580.

The materials used in the construction of boilers must pass
certain tests, samples or ''specimens''' of the materials having
standard forms being taken for the purpose. The various tests
that should be made are:

1 . Tensile,

2. Compression.

3. Transverse.

4. Shearing.

5 . Tortional

6 . Hardness .

7. Cold bending.

8 . Homogeneity .

2,014

BOILER MATERIALS

These tests are made as here briefly explained, suitable
machines being employed in subjecting the specimens to
the necessary stresses.

Tension Test. — The specimen is placed in the machine and
gripped at each end, then a tension stress is applied gradually
increasing in intensity until rupture, noting its elongation,
contraction of area for various loads, elastic limit, and breaking
load, the results being tabulated thus:

'■M.iu.:,;;:!'i(iiiiiif,i'!i!a!l''[!''''li/l'iliii,ii.'!!!;;ir

Fig. 3,584. — Traverse test. The specimen R, is placed on two supports M, and S, and a load
W, applied at the mid point as shown. The deflection or amount of bending for any load is
indicated with precision by the multiplying gear LF. In testing, the weight W, is gradually
increased and deflections noted till the breaking load is reached.

Specimen: length.

Tensile Test

. . .inches; cross section. . . .inches

shape

Load

Contraction
of area

in%

Elastic limit

Total
in pounds

Povinds
per sq. in.

Tensile strength

BOILER MATERIALS

2,015

Fig. 3,580 illustrates the principles of the test and fig. 3,585 the machine
employed.

Compression Test. — In making this test the specimen is
placed between two plates as in fig. 3,583 and a compression stress
applied gradually increasing in intensity until rupture, noting
its increase of section, decrease in length, elastic limit for various
loads, and its compression strength or load at rupture, the results

Fig. 3,585. — ^Riehle U.S. standard screw power testing machine for tensile specimens, 1 foot
long or less, with 30 per cent, elongation for 1 foot specimens or more for shorter specimens.

2,016

BOILER MATERIALS

being tabulated in a similar measure as indicated under the
tension test.

Transverse Test. — This test is made as shown in fig. 3,584 by
placing the specimen over two supports, loading the bar at a
point midway between the supports , and noting the bending and
breaking loads.

f,ifi/ii/fy^':!:;'^"'''''iiii''':::i'''iiii'.':^^^

Figs. 3,586 and 3,587. — Single and double shear tests. The specimen is placed in the holder
and the stress applied. The cutter shears the metal in a single plane for single shear and in
two planes for double shear-

BOILER MATERIALS

2,017

Shearing Test. — There are two kinds of shearing test accord-
ing as the specimen is in single or double shear, as shown in figs.
3,586 and 3,587. In either case the test is made by cutting
through the specimen and noting the load required for the
operation.

=IXED END

^ELEMENT OF SURFACE BEFORE DEFLECTION

-ELEMENT OF SURFACE AFTER DEFLECTION

SIZE OF SPECIMEN
"USUALLY IINCH IN D!AM; BY 20 INCHES LONG

Fig. 3,588. — Tortion test. The specimen is gripped in the head so that it cannot turn and the
deflector indicator attached; this end free to turn on the support. Tortion is applied by the
weight, which twists the specimen in a clockwise direction, thus an element of its surface
is distorted from a straight line, to a spiral form, the amount of distortion depending
upon the intensity of the tortional force applied and the resisting power of the metal. By
attaching at the deflection end, a suitable scale, the amount of twist can be read in degrees.
The results sought in tortional tests are to determine the tortional elastic limit and ultimate
tortional strength. Since the strain varies over the sectional area, it cannot be expressed as
pounds per square inch, but must be stated as inch pounds. The value is obtained by
multiplying the pull applied by the lever arm by the distance through which it acts. Thus
if the weight be 100 pounds and the lever arm be 30 inches, then the tortional stress
correspondingly is 100X30=3,000 inch-pounds. Again if the indicator register 20° on
a 20-inch specimen the deflection in twist is stated as 20°-r-20 inches = 1° per inch.

Tortional Test. — If one end of a specimen be fixed and a
twisting force be applied to the other end then an element of
the surface which was straight before applying the force will
assume a helical form.

Fig. 3,588 shows the method of making a test of this kind.

2,018

BOILER MATERIALS

HAMMER

DIAMOND POINT
.015 5Q.IN.

GLASS TUBE

Fig. 3,589. — Hardness test — rebound method. A hammer having a diamond point is
placed in a glass tube and elevated 10 inches above the specimen. PYom this position the
hammer is let drop upon the specimen and the rebound noted by aid of the scale. The
higher the rebound the harder the material. This test is adapted for material of the same
kind rather than those of different nature, because in some cases, the softer material will
give a higher rebound.

BOILER MATERIALS

2,019

FLATTENING^

-BEND

Figs. 3,590 and 3,591. — A.S.M.E. cold bending and flattening test for rivets. In the

cold bend test the rivet shank shall bend through 180^ flat upon itself as shown, without crack-
ing on the outside of the bent portion.

A.S.M.E, Tests — Requirements for boiler rivet steel.

44 Tension Tests, a The bars shall conform to the following requirements as to tensile
properties:

Tensile strength, lb. per sq. in 45,000—55,000

Yield point, min., lb. per sq. in 5 tens, str.

Elongation in 8 in., mm., per cent 1,500,000

but need not exceed 30 per cent. Tens. str.

h The yield point shall be determined by the drop of the beam of the testing machine.

45 Bend Tests, a Cold-bend Tests — The test specimen shall bend cold through ISO deg.
flat on itself without cracking on the outside of the bent portion.

b Quench-bend Tests — The test specimen, when heated to a light cherry red as seen in the
dark (not less than 1200 deg. fahr.) , and quenched at once in water the temperature of which is
between 80 deg. and 90 deg. fahr., shall bend through 180 deg. flat on itself without cracking
on the outside of the bent portion.

46 Test Specimens. Tension and bend test specimens shall be of the full-size section of
bars as rolled.

47 Number of Tests, a Two tension, two-cold bend, and two quench-bend tests shall be
made from each melt, each of which shall conform to the requirements specified.

b If any test specimen develop flaws, it may be discarded and another specimen sub-
stituted.

c If the percentage of elongation of any tension test specimen be less than that specified
in Par. 44 and any part of the fracture is outside the middle third of the gaged length, as indi-
cated by scribe scratches marked on the specimen before testing, a retest shall be allowed.

48 Permissible Variations in Gage. The gage of each bar shall not vary more than .01
in. from that specified.

V WORKMANSHIP AND FINISH

49 Workmanship. The finished bars shall be circular within .01 in.

50 Finish. The finished bars shall be free from injurious defects and shall have a work-
manlike finish.

2,020

BOILER MATERIALS

Hardness Test. — There are two methods of testing for
hardness, as by: 1, pressing a hardened steel ball into the
specimen under a fixed pressure, and noting the diameter of the
indentation, and 2, letting a weight fall from a given height on
the specimen, and noting the rebound.

In these tests the hardest material will have the smallest indentation
and cause the highest rebound. Fig. 3,589 illustrates the rebound test.

Cold Bending Test. — The specimen is bent flat (that is

Figs. 3,592 and 3,593. — -A. S. M. E. homogenerty teat. Made by grooving and fracturing
specmen; described in detail in accompanying text.

A. S. M. E. Tests — Requirement for Stayholt Steel.

63 Steel for staybolts shall conform to the requirements for Boiler Rivet Steel specified
in Pars. 40 to 62, except that th^ tensile properties shall be as follows:

Tensile strength, lb. per sq. in 50,000—60,000

Yield point, min., lb. per sq. in 0.5 tens. str.

Elongation in 8 in., min., per cent 1,500,000

Tens. str.

Also with the exception that the permissible variations in gauge shall be as follows:

Permissible Variations inGauge. The bars shall be truly round within 0.01 in. and shall not
vary more than 0.005 in. above, or more than 0.01 in. below the specified size.

BOILER MATERIALS

2,021

through 180°) either on itself or over a pin of given size as in
figs. 3,590 and 3,591 and the condition of the metal at the bend
noted.

Homogeneity Test. — In making this test, the specimen

STANDARD THREAD

Fig. 3,594. — A. S. M. E. standard specimen required for tension tests of gray iron castmfif
material. The quality of the iron going into casting under specification shall be determined
by means of the above specimen, known as the arbitration bar. The tensile test is not recom-
mended, but in case it be called for, the bar as here shown, shall be turned up from any of
the broken pieces from the transverse test. The expense of the tensile test shall fall on the
purchaser.

I PHYSICAL PROPERTIES AND TESTS
A. S. M, E. Tests — Requirements for Rivets.

55 Tension Tests. The rivets, when tested, shall conform to the requirements as to tensile
properties specified in Par. 44, except that the elongation shall be measured on a gauged length
not less than four times the diameter of the rivet.

56 Bend Tests. The rivet shank shall bend cold through 180 deg. flat on itself, as shown
n fig. 2, without cracking on the outside of the bent portion.

57 Flattening Tests. The rivet head shall flatten, while hot, to a diameter 2}4 times the
diameter of the shank, as shown in fig. 3, without cracking at the edges.

58 Number of Tests, a When specified, one tension test shall be made from each size
in each lot of rivets offered for inspection.

b Three bend and three flattening tests shall be made from each size in each lot of rivets
offered for inspection, each of which shall conform to the requirements specified.

II WORKMANSHIP AND FINISH

59 Workmanship . The rivets shall be true to form, concentric, and shall be made in a
workmanlike manner.

60 Finish. The finished rivets shall be free from injurious defects.

Ill INSPECTION AND REJECTION

61 Inspection. The inspector representing the purchaser shall have free entry, at all
times while work on the contract of the purchaser is being performed, to all parts of the manu-
facturer's works which concern the manufacture of the rivets ordered. The manufacturer
shall afford the inspector, free of cost, all reasonable facilities to satisfy him that the rivets are
being furnished in accordance with these specifications. All tests and inspection shall be made
at the place of manufacture prior to shipment, unless otherwise specified, and shall be so con-
ducted as not to interfere unnecessarily with the operation of the works.

62 Rejection. Rivets which show injurious defects subsequent to their acceptance at the
manufacturer's works will be rejected, and the manufacturer shall be notified.

2,022 BOILER MATERIALS

shall be either nicked with a chisel or grooved on a machine,
transversely, about He i^- deep, in three places about 2 in. apart.

The first groove shall be made 2 in. from the square end; each succeeding
groove shall be made on the opposite side from the preceding one. The
specimen shall then be firmly held in a vise, with the first groove about J^
in. above the jaws, and the projecting end broken off by light blows of a
hammer, the bending being away from the groove. The specimen shall
be broken at the other two grooves in the same manner.

The object of this test is to open and render visible to the eye any
seams due to failure to weld or to interposed foreign matter, or any cavities
due togas bubbles in the ingot.

One side of each fracttire shall be examined and the length of the seams
and cavities determined, a pocket lens being used if necessary.

SHELL BOILERS 2,023

CHAPTER 64

SHELL BOILERS

In a shell boiler the water and steam are contained in a vessel
usually of cylindrical form, most of the heating surface being
composed of fire tubes, or flues as distinguished from the com-
bination of drum and water tubes in the water tube boiler.

Oues. What is the difference between a fire tube and
a water tube?

Ans. The hot gases pass inside of fire tubes and outside of
water tubes, the water being outside of fire tubes and inside of
water tubes.

Classes. — There are two great divisions of shell boilers, being
classed with respect to the position of the furnace, according
as it is:

1. Externally fired, or

2. Internally fired.

The multiplicity of types included in these two divisions are
due to varied working conditions encountered. According to
service all boilers may be divided into three classes.

1. Stationary*.

2. Locomotive.

3. Marine.

*NOTE. — The term *'5fa/i>':»<2r^" boilers is purely an American expression, the equivalent
English term being ''land" boilers.

2,024

SHELL BOILERS

Figs. 3,595 and 3,596. — Watt's wagon boiler with split draught. In construction, it consisted
of a cylindrical top, concave sides and a concave bottom. For the larger sizes, the grate was
at one end of the boiler and the gases passed through an internal passage and then split , return-
ing on each side of the boiler to the chimney which was in front. The sides were made con-
cave more readily to form part of the side passages. The form of this boiler was, of course,
not well adapted to withstand high pressures and soon gave way to the cylinder, which is the
ideal form for high pressure work. As shown. A, is the supply pipe terminating in the
cistern at the top of the feed pipe; B , cistern at the top of feed pipe , having a valve fixed at
the bottom; C, the float employed to regulate supply of water to boiler. The water is kept
at the same height by its action upon the valve at the bottom of the feed pipe; thus, when
there is not sufficient water in the boiler, the float sinks, pulls down the arm of the lever a, a,
to which it is attached, and opens the valve, since the counterbalancing weight d, fixed at
the other end of the lever will only support the float when in its proper situation in the boiler
and at the required level of the water. D, is a self acting damper for regulating the con-
sumption of fuel; EE, gauge cocks; G, steam gauge; H, safety valve, regulated by the en-
gineer; I, air valve, or atmospheric safety valve, U, the locked safetj^ valve. A pipe is shown
at the top which leads the steam that escapes into it to the flue or into the air. The steam
passes from the boiler through the steam pipe, a valve, called a throttle valve L, being placed
m it for regulating the amount of steam to the cylinder; M, furnace bars; N, flue; SS,
stays.

NOTE. — The earliest boilers were spherical. These were made of cast iron and set in
brickwork. It was customary to set this type of boiler with the fire underneath and construct
flues in the brickwork to conduct the hot gases around the boiler just below the water level.
The hot gases passed entirely around the boiler before escaping to the chimney.

SHELL BOILERS 2,025

1. EXTERNALLY FIRED
BOILERS

Development of the Shell Boiler. — The early forms of
shell boiler were of the externally fired class, the first of these
being the wagon boiler brought out by James Watt as shown
in figs. 3,595 and 3,596.

At this time the prime object was to get enough steam, no attention
being paid to economy. These boilers were suitable for only very low
pressure and were made of inferior metal.

After some experimenting it became apparent that the shape of the boiler
must be changed to adapt it to higher pressures. To make it more eco-
nomical, the heating surface was divided into smaller sections by inserting
tubes or flues through which the hot gases passed, and later, to increase
the strength, the boiler was made cylindrical.

At first, boilers were spherical, then of various shapes, some resembling
a haystack, and others of more complex forms.

Following these came the plain cylinder, which, in development, was
provided with one or two flues, and as more heating surface was demanded,
the flues were reduced in size and increased in number; then a multiplicity
of tubes were used as in the form commonly used at the present time.

Oues. What is the difference between a flue and a tube?

Ans. A flue is of relatively large diameter and is riveted

at its ends to the sheets. A tube is of relatively small diameter

and is expanded into the sheets.

In tubular boilers sometimes a few heavy tubes are used which are
screwed into the sheets to obtain additional strength. The erroneous use of
the terms flue and tube should be avoided.

Oues. What are the sheets?

Ans. The boiler heads having circular holes for the flues or
tubes and to which they are respectively riveted or expanded.

2,026

SHELL BOILERS

Figs 3,597 to 3,602. — Evolution of the modem * 'horizontal return tubular boiler. '" Fig.
3,597, plain cylinder boiler; fig. 3,598, one flue; fig. 3,599, two flue; ng. 3,600, six flue; fig.
3,601, twelve flue; fig. 3,602, multi-tubular boiler.

SHELL BOILERS

2,027

The Horizontal Return Tubular Boiler. — This type is a
development of the plain cylinder boiler, a shown in figs. 3,597
to 3,602. As shown the flues were first introduced, increased in

Figs. 3,603 and 3,604.— Plain cylinder boiler. It
consists of a cylinder A, formed of^ iron plate
with hemispherical ends BB , set horizontally in
brick work C. The lower part of this cylinder
contains the water, the_ upper part the steam.
The furnace D, is outside the cylinder, being
beneath one end; it consists simply of grate bars
ee, set in the brick work at a convenient distance
below the bottom of the boiler. The sides and
front of the furnace are walls of brick work,
which, being continued upwards support the
end of the cylinder The fuel is thrown on the
bars through the door which is set in the front
brick work. The air enters between the grate
bars from below. The portion below the bars
is called the ash pit. The flame and hot gases,
when formed, first strike on the bottom of the
boiler, and are then carried forward by the
draft, to the so-called bridge wall o, which is a
projecting piece of brick work which counteracts
the area of the passage n and forces all the
products of combustion to keep close to the
bottom of the boiler. Thence the gases pass along the passage n, and return part one side
of the cylinder in the passage m (fig. 3,064) and back again by the other side flue m to the
far end of the boiler, whence they escape up the chimney. This latter is provided with a
door or damper p, which can be closed or opened at will, so as to regulate the draught.
The boiler has the advantages of cheapness, and convenience of cleaning since a man can
get inside and clean and have access to all the interior surface. The large amount of water
carried gives it large reserve capacity It is necessary , however, to obtain adequate heating
surface that it be made very long. It is adapted to bad water and for blast furnace work
when the long flame for the blast furnace has to be utilized. An important defect is that the
temperature in each of the three passages w, w, w, is very different, and consequently that
the metal of which the shell of the boiler is composed expands very unequally in each of the
flues, and cracks are very likely to take place when the effects of the changes of temperature
are most felt. It will be noted that the flames and gases in this earliest type of steam boiler
make three turns before reaching the chimney, and as these boilers were made frequently as
much as 40 feet long it gave the extreme length of 120 feet to the heat products.

2,028

SHELL BOILERS

number and diminished in size, finally a multiplicity of tubes
usually 3 to 4 inches in diameter being used.

The heads above and below the tubes are stayed with diagonal
and through stays.

Some of the tubes are also threaded and fitted with nuts to act as stays.
It is, of course, necessary to provide a brick setting for this type of boiler.

The furnace is located at the front with a bridge wall immediately behind
it and the combustion chamber for the combining of gases beyond.

Fig. 3,605. — Single return flue boiler. To increase the heating surface, flues or internal return
passages were introduced through which the gases should pass to the front of the boiler,
locating*the chimney at the front. This type has great storage capacity and a large increase
of heating surface over the cylinder boiler, but the flues are an element of weakness, as they
are subject to external pressure. The flue boiler is, therefore, not adapted to high pressure
work. The flues act as braces for the heads. It was used for 10 to 60 pounds boiler pressure
and from one to twelve flues were used, these being from 6 to 8 inches on diameter. For
the larger sizes stiffening rings were put around the flues to prevent collapse.

Tubes are fastened to the heads by beading over the ends. The water
line is carried from 3 to 4 inches above the upper tubes so that the amount
which it may vary is comparatively small.

SHELL BOILERS

2,029

The numerous small tubes give a large amount of heating surface, but
the brick setting introduces radiation.

It is rather difficult to clean this type of boiler. A manhole is provided
at the top by which entrance can be had for cleaning and inspection, and
hand holes are provided in the heads below the tubes for introducing scraping
tools and for washing out sediment.

"Figs. 3,606 and 3,607. — Elephant boiler; a type used extensively in France. /* consists of a

tubular boiler placed above and connected by a series of necks to two cylinders or water
"drums" as shown, a steam drum being similarly connected on top. The difficulty vith
this type is in getting good circulation, because the steam formed in the lower water drum
cannot escape to the upper drum only through the necks. Hence where boiler is to be
worked to capacity or forced, a liberal number of necks should be provided.

Sometimes enough of the lower tubes are omitted to furnish space for a
manhole at the bottom. This is a very good feature, especially where
dirty or scale forming water is used.

The tubes are usually arranged in vertical rows to facilitate circulation,
leaving an extra wide space at the middle and next to the shell. In some
designs the tubes are staggered vertically to render the heating surface
more efficient.

The cost of this boiler is of course greater than the flue type, but somewhat
less than the Cornish or Scotch types; this is offset, however, by the expense
of the back setting.

2,030

SHELL BOILERS

Pigs. 3.608 and 3.609. — Front and side sectional views of Western river two shell seven flue boiler showing steam drum, steam
pipe and mud drum. The furnace and forward portion of the gas passages are built of brick. The gases are returned from the
back through the flues to the uptake at the front. The boiler is simple and well adaoted to bad or dirty water.

A.S.M.E. Boiler Code.— Fusible Plugs.

428. Fusible plugs, if used, shall be filled with tin with a melting point between 400 and 500 deg. fahr.

429. . The least diameter of fusible metal shall be not lower than H in., except for maximum allowable working pressures of
over 175 lb. per sq. in. or when it is necessary to place a fusible plug in a tube, in which case the least diameter of fusible metal
shall be not less than % in.

430. Each boiler may have one or more fusible plugs located as follows:

a. In Horizontal Return Tubular Boilers — in the rear head, not less than 2 in. above the upper row of tubes, the measure-
ment to be taken from the line of the upper surf^ace of tubes to the center of the plug, and projecting through the sheet not less
than 1 in.6. In Horizontal Flue Boilers — in the rear head, on a line with the highest part of the boiler exposed to the products
of combustion, and projecting through the sheet not less than 1 in. c. In Traction. Portable or Stationary Boilers of the Loco-
motive Type o» Star Water Tube Boilers — in the highest part of the crown sheet, and projecting through the sheet not less than 1 in.

d. In Vertical Fire-tube Boilers — in an outside tube, not less than one-third the length of the tube above the lower tube sheet.

e. In Vertical Fire-tube Boilers, Corliss Type — in a tube, not less than one-third the length of the tube above the lower tube sheet.
/. In Vertical Submerged Tube Boilers — in the upper tube sheet, and projecting through the sheet not less than 1 in. g. In Water-
tube Boilers. Horizontal Drums. Babcock & Wilcox Type — in the upper drum, not less than 6 in. above the bottom of the drum,
over the first pass of the products of combustion, and projecting through the sheet not less than 1 in. h. In Stirling Boilers,
Standard Tupe — in the front side of the middle drum, not less than 4 in. above the bottom of the drum, and projecting through
the sheet not less than 1 in. «. In Stirling Boilers. Superheater Type — in the front drum, not less than 6 in. above the bottom of
the drum, exposed to the products of combustion, and projecting through the sheet not less than I in. j. Water-tube Boilers,
Heine Type — in the front course of the drum, not less than 6 in. above the bottom of the drum, and projecting through the sheet
not less than 1 in. *. In Robb-Mumford Boilers. Standard Type — in the bottom of the steam and water drum, 24 in. from the
center of the rear neck, and projecting through the sheet not less than 1 in. /. In Water-tube Boilers, Almy Type — in a tube or
fitting exposed to the products of combustion, m. In Vertical Boilers, Climax or Hazelton Type — in a tube or center drum not
less than one-half the height of the shell, measuring from the lowest circumferential seam. n. In Cahall Vertical Water-tube
Bpilers — in th* inner sheet of the top drum, not less than 6 in. above the upper tube sheet, and projecting through the sheet not
less than 1 in. o. In Wickes Vertical Water-tube Boilers — in the shell of the top drum and not less than 6 in. above the upper
tube sheet, and projecting through the sheet not less than 1 in; so located as to be at the front of the boiler and exposed to the
first pass of the products of combustion, p. In Scotch Marine Type Boilers — in the combustion chamber top, and projecting
through the sheet not less than 1 in. <]. In Dry Back Scotch Type Boilers — in the rear head, not less than 2 in. above the upper
row of tubes, and projecting through the sheet not less than 1 in. r. In Economic Type Boilers — in the rear head, above the upper
row of tubes, s. In Cast-iron Sectional Heating Boilers — in a section over and in direct contact with the products of combus-
tion in the primary combustion chamber. /. In Water-tube Boilers. Worthington Type — in the front side of the steam and water
drum, not less than 4 in. above the bottom of the drum, and projecting through the sheet not less than 1 in. u. For other types
and new designs, fusible plugs shall be placed at the lowest permissible water level, in the direct path of the products of combus-
tion, as near the primary combustion chamber as possible.

NOTE. — Fire Engine Boilers are not tisually supplied with fusible plugs. Unless special provision be made to keep the
water above the fire box crown sheet other than by the natural water level, the lowest permissible water level shall be at least
8 in. above the top of the fire box crown sheet.

SHELL BOILERS

2,031

an

^^^

+3 .J^i OJ .^ 5

' ^-^^ J

' 5Pa

" c a3 ^<u S >

! aj o ;3

-^p.|iiili|s|.=

0^+^ S3 g oj ;3

s-s^

1"^^ So oil
r^ a^.S .S 5 SI?

■ CO J-,

1^1

" f^ ^

ft § o ^' «3 C 5

'.rC! a)i^ ^^ r-^O O to >> .r^ <u

. 5 >>-^ '".h:3 ^ o ^ ^ '' "' - '^

05^0 "-so

C^ ;3^ ^^ O O c b,„ ci^ «S C ;5

ft-P 2^ J3 e--^ C 2 S "^ 5-^ ft S «i^
«i!,a Ea w cj+i+Sy:; o a; o ctJ.55 0.23 S

2,032

SHELL BOILERS

Figs. 3,611 and 3,621. — Horizontal return tubular boiler with and without steam dome. Pref-
erable to a steam dome is a dry pipe. This pipe should extend nearly the entire length of
the boiler so as to collect the steam over an extended surface thus avoidinpr as much moisture
as possible. The author's dry pipe for vertical boiler is shown in fig. 3,634.

SHELL BOILERS 2,033

The general features of the horizontal tubular boiler are illustrated in
figs. 3,611 and 3,612, showing boiler with and without dome. The methods
of "setting" the boiler are explained in the chapter on Boiler Settings.

2. INTERNALLY FIRED
BOILERS

The waste by radiation from the externally fired boiler setting
was early observed by Trevithick, a Cornish engineer, who in
order to overcome this adopted the expedient of putting the
furnace inside a large flue, and, as usual ^ instead of receiving
credit for this improvement, it became known as the Cornish
boiler.

Trevithick or So-called Cornish Boilers. — By placing the
furnace inside a large flue running the length of the boiler
Trevithick not only succeeded in reducing the loss by radiation,
but obtained, additional heating surface, thus permitting a
reduction in length as compared with the plain cylinder boiler.

Oliver Evans used this type as early as 1800, and in England
it led to the internally fired flue boilers which are still extensively
used in the small and medium sizes.

The general construction is shown in figs. 3,613 and 3,614. With
increasing pressures it was necessary to support the flat heads, and diagonal
or gusset stays of the type here indicated were used.

2,034

SHELL BOJLERS

The necessity of providing room for the furnace within the boiler shell
also made it necessary to increase the diameter of the boiler and although
the flue acted as a stay for the lower part of the heads, the upper parts
needed support.

Ordinarily the flue is made .6 the diameter of the shell, the space uneler-
neath the flue is about 6 inches, and the length of the iDoiler is five to six

Figs. 3,613 and 3,614. — Trevithick or so called Cornish boiler introduced in Cornwall. It
consists of a cylindrical shell having a large flue running the length of the boiler and in
which is placed the furnace as shown, the grates resting at one end on a brick wall and at the
other on a support riveted to the front of the flue. By this arrangement the sediment was
allowed to faU to the bottom of the boiler where the temperature w?s low so that it did less
harm than in the cylinder type, where it fell on the hottest part. The hot gases pass from
the fire through the flue where they divide and return through the passages M and S,
thence they unite and traverse again the length of the shell through the passage L, which
leads to the chimney. The heads of the boiler are reinforced by gusset stays. To provide
for excess expansion of the flue it was found necessary to build up the flue in sections with
flanges at the ends. The sections being riveted to plain rings, known as Adamson rings,
shown in detail in fig. 0021.

NOTE. — Richard Trevithick, born 1771, died 1833, was a noted English mechanical
engineer. He invented the Trevithick, or so called Cornish, boiler and was the first to apply
steam for drawing loads on railroads. He was especially noted for his inventive genius and
herculean strength. He made various improvements in pumps; invented a double acting
water pressure engine (1800) , a steam road carriage (1801); improved the locomotive for oper-
ating on rails (1808); adapted the steam engine to mining, and made many experiments in
engines for dredging, marine propulsion and other purposes.

NOTE. — Trevithick boiler. — -Diameter usually about Vc of the length; a common pro-
portion is 36 to 40 feet in length and from 6 to 7 feet in diameter. Steam pressure from 15
to- 35 Ibfi.

SHELL BOILERS

2,035

times its diameter. The expansion of the flue, which is greater than that
of the shell, caused trouble, making it necessary to introduce expansion
joints as shown in fig. 3,614.

For very large boilers, the diameter of the flue had to be considerably
increased in order to get sufficient grate surface, which led to the use of
two flues, their arrangement being called the Lancashire boiler.

Lancashire Boiler. — This may be defined as a two furnace
Trevithick boiler. It was constructed to adapt the Trevithick
boiler to larger sizes by providing additional grate area and yet
not increasing the length of the boiler.

Fig. 3,615. — Galloway flue. In construction it has corrugated sides and the conical tubes
are staggered, thus insuring a thorough breaking up of the currents of hot gases. The tubes
are made conical to facilitate removal for repairs. They are more generally riveted than
welded, because the removal of a tube that is welded leaves a large hole in the flue. Other
details of the Galloway boiler are shown in the accompanying cuts.

NOTE. — Cornish boiler. By reason of the large diameter of the flue and its liability
to collapse under a high pressure, the latter was formerly restricted to 45 pounds steam pressure,
but with improved construction these boilers are now made for any ordinary pressure, though
commonly not more than 100 pounds. The principal dimensions of the ordinary sizes used m
England are: diameter of shell, 3 feet 6 inches, 4 feet 3 inches, 5 feet, 5 feet 6 inches, 6 feet;
length, 8 feet, 12 feet, 15 feet, 18 feet, 22 feet; diameter of flue, 2 feet 2 inches, 2 feet 4 inches,
2 feet 9 inches, 3 feet 3 inches, 3 feet 6 inches. A test of a Cornish boiler 6 feet by 28 feet gave
an efficiency of 77% — Barr.

2,036

SHELL BOILERS

«0>

jiH '^ m y, " c a; rt

•^'2 rt^ c^ S)^
o 5-^ <u:S'5 52 o •+^

■P ^ a C3 S SP«' o
w. rt'-^ "'d rt'3 §

boq:^ to O P,42 rt ^+3

When the
shell of a Trev-
ithick boiler
exceeds say six
feet in diam-
eter, the flue
assumes such
large propor-
tions that it
has to be made
very heavy to
secure ade-
quate strength
to prevent col-
lapse. Hence,
as a proper
width of grate
can be secured
by the use of
two smaller
flues without
the risks at-
tending the use
of one large
flue the two
flue arrange-
ment is a bet-
ter construc-
tion. More-
over, better
combustion is
secured be-
cause the alter-
nate method of
firing can be
employed. In
this method,
first one fur-
nace is fired,
then the other
with the result
that the un-
burned gases
issuing from
the fresh fuel
from one fur-
nace are ig-
nited in the ex-
ternal nassaee

SHELL BOILERS

2,037

by the burning gases preceeding from the other furnace. Thus the waste
of fuel due to unburned gases is avoided, if the firing be properly done.

Oues. What are the disadvantages of the Lancashire
boiler?

Ans. 1, Difficulty in the medium sizes, of finding adequate
room for the two furnaces without unduly increasing the diam-
eter of the shell; 2, low furnaces are unfavorable to complete
combustion, the comparatively cold crown plates, when they
are in contact with the water of the boiler, tending to extinguish
the flames from the fuel, when they are just formed; 3, the narrow

Fig. 3,618. — Lancashire
boiler with breeches. In
the older form the two
flues are continued sep-
arate to the end of the shell. In setting, the
furnaces are located at the front end of each
flue and the gases pass downward at the back end into a ^ central passage which runs
under the bottom of the shell to the front where the stream divides and passes through the
two side passages, thence to chimney. Sometimes the flues are arranged so that the gases
pass down the side of the shell before going under the bottom, but this plan does not heat
the water in the lower part of the boiler when raising steam as fast as the former. Char-
acteristics, usual proportions give heating surface ratio 26:1; adapted to dirty and impure
water; slow steam raising, but large reserve capacity; poor circulation; boiler bulky per horse
power rendering it unsuitable for basements of buildings.

Space between the fuel and the crown does not admit the proper
quantity of air being supplied above the fuel to complete the
combustion of the gases, as they arise; 4, danger (in very large
sizes) of collapse of the flues.

Oues. Describe a "breeches flued" Lancashire boiler
and what is the object sought?

2,038

SHELL BOILERS

Ans. In this construction, the
two flues instead of running th(
full 1-ength of the boiler merge
into one large flue which forms
a combustion chamber, and se
cures better combustion.

The combustion chamber or th(
breeches, increases the space, bu
the construction at the junction o
the two flues is weak and has beei
responsible for many explosions.

Figs. 3,619 and 3,620. — Galloway boiler showing breeches and Galloway flues. In th(
breeches are riveted a number of conical water flues, tapering from about 9 inches to 4>^
inches diameter which forms the distinguishing feature of the Galloway boiler. These flue;
which in consequence of the taper form can be easily renewed if required, increase th(
heating surface, and help circulation.

Galloway Boiler. — A third modification of the Trevithici
boiler is the Galloway as shown in the accompanying cuts. The

NOTE.— Both the Trevethick and Lancashire types on account of economy of fuel and
ease of cleaning out have been used extensively in the mining regions of England, where the
water is extremely bad.

NOTE. — The principal dimensions of the three leading sizes of Lancashire boilei
used in England, are, according to Barr: diameter shell, 6 feet, 6 feet 6 inches. 7 feet; length,
20 feet to 28 feet; 20 feet to 30 feet; 21 feet to 30 feet; diameter flues, 2 feet 3 inches. 2 feet

SHELL BOILERS

2,039

object sought in this design was to overcome the defects of the
Lancashire boiler by providing obstruction in the flues.

These obstructions or cross flues, as
shown in fig. 3 ,621 were called Galloway-
flues, and the results obtained by their
use were: 1, multi-deflection of the hot
gases securing a more intimate mixture
of same, giving better combustion; 2>
additional heating surface, and 3, bet-
ter circulation.

The improved circulation reduced
the difference of temperatures in the
upper and lower parts of the boiler,
thus overcoming a serious objection to
the Lancashire boiler.

There are two forms of Galloway
boilers, the one having two distinct
flues, and the other a breeches flued
arrangement similar to the Lancashire
type, but with the breeches perforated
with Galloway flues.

Fig. 3,621. — Galloway flues (so called
"tubes"). As arranged in independent or
through flue. In construction, the Gall-
oway flue is tapered to permit the lower
flange being inserted in the upper opening
to get the flue into place. Many makers
insert cylindrical pipes and weld them to
the flue. Figs. 3,619 and 3,620 show ar-
rangement of Galloway flue in the breeches.

Vertical or "Upright'*
Boiler. — Where floor space is

Figs. 3,622 and 3,623, — Petrie's water pockets introduced into large flues as a precaution
against collapse, in addition to acting as promoters of circulation.

2,040

SHELL BOILERS

C s"

. ^ — ^

S5§

CO §<ou5+^

t/) 2 ;3 „'^

SHELL BOILERS

2,041

valuable and there is sufficient height, a vertical boiler is generally
used. In early times this boiler had only a single flue, and then
additional flues were added gradually increasing the heating
surface until the modern tubular form was reached. In this
form nearly all the members are of cylindrical shape and arranged
vertically, the gases passing direct from the furnace through the
tubes to the stack. Vertical boilers may be divided into two
general types, with respect to the tubes:

1. Through tube

2. Submerged tube.

Oues. Describe a through
tube vertical boiler?

Ans. An outer cylindrical
shell encloses the water and
steam space. Within this
shell is a smaller cylinder
extending about one-third
way up which forms the
furnace and combustion cham-
ber and ash pit. The cylind-
rical furnace is flanged out at

Fig. 3,631. — Bigelow through tube station-
ary vertical boiler as built in sizes from 3
to 100 horse power.

NOTE. — Through tube vertical boiler.

There has been too much a,d verse criticism
of this type of boiler. The trouble is not
with the boiler but with the critics. The
bad reputation of this boiler is due to ignor-
ance in handling and the absence of a steam
collector or dry pipe. To prevent burnt
tube ends, the water should be carried at the
highest practical level. In getting up steam
the boiler should be entirely filled with water
and when steam forms blow down to working
level. The author operated a 6'X9' vertical
marine boiler in this way several seasons and
had no tube trouble whatever. On page
2,406, is shown the author's separating, col-
lecting and drying devices for carrying abnor-
mally high water level in through tube vertical
boilers. Another reason for carrying high
water level is because the heating surface in
contact with the water is more eM^^ient than that
in contact with the steam.

2,042

SHELL BOILERS

the bottom until it meets the outer shell, dispensing in this way
with a lower head. In one side it flanges to the shell to form ar
opening for furnace door; the top is flat and into which an

expanded a multiplicity
of vertical tubes, the up-
per end of which are ex-
panded into a similar flal
surface at the top of the
shell. These flat surfaces
are called respectively the
lower and upper tube
sheets.

The cylindrical furnace is
stayed to the outer shell b>
a proper number of sta;y
bolts, thus strengthening i1
against collapse. The devel-
opment and construction oi
vertical boilers is shown in
the accompanying illustra-
tion.

Oues. What are the
defects of vertical
boilers as ordinarily
constructed?

Ans . Poor circulation ,
liability to foam, tubular
heating surface above
water line inefficient, less
economical than other
types, liability to burn
upper ends of tubes by

Fig. 3.632.-Small ordinary submerged tube ignorant handHng; Small

l^^o sSh^rsIp'^wti. ^'''^'' ^' ^'''^' '"'' "''"' ^'°"' Steam space, lower tube

SHELL BOILERS

2,043

sheet inaccessible for cleaning, greater risk of explosion due to
sediment on lower tube sheet.

Submerged Tubes. — Frequently vertical boilers are con-
structed with submerged tubes, that is the top head of the shell
is riveted to a conical shaped submerging chamber of sufficient
depth that the upper tube sheet attached to its lower flange is
below the water level.

The author objects to this construction because with proper management
it is not necessary and moreover, it complicates the construction and renders
the upper tube sheet less accessible.

Fig. 3,633. — Extreme practice in vertical
boiler construction illustrating the
great amount of heating surface that
can be crowded into a small space,
with very little weight. This boiler as
used on the Stanley steam automobile,
has a shell made of seamless pressed
steel, and reinforced by two layers of
piano wire wound around its exterior
under tension. The upper head is part
of the pressed steel shell. This cut
gives a section through the center show-
ing one row of tubes. An exterior view
of the boiler is shown on page 1,965.
The tubes are usually made of copper
which possesses a superior heat con-
ducting property. The tables below
give dimensions of such boilers as
usually constructed for automobiles
and trucks.

HEAVY TRpCK BOILERS.

AUTOMOBILE BOtLEIia.

(S«amIeM Sb«ns.i

t«nrtb of
luUw Jo.

a

HA
»7A
16A

I6A
18t'.
20A

23W

i-incb boiler* listed above
«re made wuh tubes fourteen, fifteen, sixteen seventeen and eighteen
inches long, which appro ximitely increase* the bpr»e power Jo prpfioruoa
a the tub«s increase lo teosth.

2,044

SHELL BOILERS

If the boiler be full of water in raising steam, and carried at the proper
level during operation there will be no trouble with the tubes, as has been
demonstrated by the author's experience with this type of boiler.

Oues. What should be insisted upon in ordering a
vertical boiler, and why?

Ans. The steam outlet should be provided with a circular
dry pipe extending around the tubes so that the water may be

DRY pipe:

Fig. 3,634. — Author's dry pipe arranged to collect steam around the entire circumference of
shell, thus permitting a high water level to protect the tubes, and increase the efficiency
of the heating surface while insuring dry or practically dry steam and protection for priming
on sudden heavy demand for steam.

carried at proper height to protect the tubes and yet obtain

dry steam.

The water level should be carried high not only to protect the tubes but
to render more of the tube area effective heating surface.

SHELL BOILERS

2,045

Locomotive Boilers. — These boilers are of cylindrical form
through most of the length of the shell, and in the tubes, while
the furnace and forward portion of the shell are constructed in
box form. The tubes are arranged horizontally and the gases
pass directly from the furnace in the front through the tubes to
the rear of the boiler and to the smoke stack. The principal
parts of a locomotive boiler are:

1 . The shell , consisting of
two parts, a cylindrical one
in wake of the tubes and the
front part with rounded top
on a box shaped lower half.

2. The furnace and com-
bustion chamber, with the
grate in the open bottom,
opening through the water
space at the front, with the
furnace door . It is separated
from the shell gnd the heads
by water spaces.^ The sides
and the sometimes flat, some-
times rounded, top require
staying to a large extent.
The sides, at the bottom, are
sometimes flanged to the shell
and heads, and sometimes
connected to them by a solid,
forged ring of the thickness
of the water space .

3. Cylindrical tubes in
large number and relatively
small diameter, which con-
nect the furnace to the rear
he/^d of the shell.

Figs. 3,635 and 3,636. — Edward Field "drop tube" boiler and detail of tube. This is a combina-
tion shell and water tube boiler. In construction, a large number of tubes are expanded
into the tube sheet as shown being closed at the lower end and opening at the upper end
into the water space. Within each tube is another tube open at both ends as shown in fig.
3,636._ It is so suspended that a rapid circulation takes place, the steam and heated water
rising in the outer tube, and the relatively colder (and heavier) water descending in the inner
tube as indicated by the arms. The upper end of the inner tubes are flared to promote
circulation.^ This boiler, according to one maker requires clean feed water, is rather heavy
and expensive, but safe and easily cared for.

2,046

SHELL BOILERS

4. Front and back heads to complete water and steam space; also a
sheet, called the throat sheet, connecting the cylindrical shell at the bottom
to the box portion.

Oues. What are the chief differences in locomotive
boilers?

Ans. They vary mostly in the shape of the furnace and the
location of the grate; they are either straight or wagon top.

Ones. Describe the wagon top construction.

ooooo ooooo

OOOOOO OOOOOO'
OOOOOO OOOOOO
OOOOOO OOOOOO
OOOOOO OOOOOO
.OOOOOO OOOOOO

Figs. 3,637 and 3,638.— Semi-portable locomotive boiler for stationary service. In con-
struction, the fire box is surrounded by a water space of 3 or 4 inches. The use of flat plates
subject to pressure makes it necessary to stay the surfaces of the furnace and this is done at
the sides and back by means of staybolts and on top by crown bars and radial stays which
run to the outer shell. The back end above the tubes is supported by diagonal stays to the
cylindrical shell of the boiler. The space at the sides of the furnace is called the water leg
and in some cases, but not usually, this water space is carried beneath the fire box. On
account of the small space between the water line and the boiler shell, it is usual to place a
dome on the boiler, as the stearn is thus much drier. This boiler requires no setting and is,
therefore, well adapted for semi-, or portable use. It is often used in saw mills and for
temporary installations on excavation work, and while not as economical as a boiler where a
combustion chamber can be used, it gives i airly good economy, with cheap construction.
It has a large amount of heating surface in proportion to the size of the boiler, and the power
is, therefore, large for its weight and for the space occupied.

Ans. The boiler has a cone-shaped portion thus making the
boiler of larger diameter at the furnace end than at the smoke
stack end.

The object of this construction is to give more steam space, but the
increase in size of boilers has raised the top so high above the rails that the
wagon top is not now used as extensively as the straight top.

SHELL BOILERS

2,047

Oues. For what service are locomotive boilers some-
times used other than locomotive work?

Ans. Stationary and marine service.

Considerable additional matter on locomotive boilers wiU be found in
chapter 37 on Locomotives.

Marine Boilers. — There is a multiplicity of types of marine
boiler due to the great variety of steam propelled vessels, the
large range of steam pressures and various kinds of fuel employed .

Stationary and locomotive boilers have been modified in design

Figs. 3,639 and 3,640, — Marine type of locomotive boiler with dry bottom fire box.

and used for marine service as well as the distinctively marine
types.

Of the "borrowed types" the vertical or upright boiler finds its use on
boats of smaller size. It has the advantages of taking up the least floor
space and is cheapest in construction, and the faults of being the least
efficient and having a high center of gravity.

There are, of course, vast differences in the various ways it is manufac-
tured.

The locomotive boiler is advisable in marine work as a good steaming
boiler with forced draught, and as having a low center of gravity, but has

2,048

SHELL BOILERS

the objections of taking up too much room, fore and aft, and bringing the
smoke stack too far forward.

The cylindrical return tubular boiler is the easiest boiler to keep
clean, but on account of the limited grate area and diameter of furnace,
not very efficient for the amount of metal used in its construction.

Where more than one furnace is used the efficiency rises, but even with
three or four, it does not stand comparison with the square base boiler,
taken pound for pound. It is by far the plainest and safest boiler, and
can be made for a steam pressure of 200 pounds or more.

Fig. 3,641. — Through (sometimes called "flush"), tube vertical marine boiler. This boiler, if
built of tested materials, is approved by the government inspectors, for use on all navigable
waters of the United States, excepting on steamers navigating the Red river of the North
and rivers whose water flow into the Gulf of Mexico ana all waters tributary to said waters .
This form of boiler is "borrowed" from the stationary type and by comparing it with fig.
3,631, it will be seen that its diameter has been increased and height lowered, also a much
larger number of tubes are used, thus lowering the center of gravity and increasing the heat-
ing surface per pound weight — two features of importance for marine service . The type
here shown has a corrugated furnace instead of the usual stayed construction.

Oues.
boiler?

What are the distinctive features of a Scotch

SHELL BOILERS

2,049

Ans. It is essentially a high pressure boiler, and has for this
reason, most of the important members in cylindrical shape.
They are all arranged horizontally. The gases pass to the back
and are returned to the front for discharge
The important parts of a Scotch boiler are:

Figs. 3,642 and 3,643. Chas. P. Willard submerged tube vertical marine boiler. Where

boats are to be used in waters under U. S. marine supervision it will be necessary to have
them built in every respect in conformity with U. S. marine laws. These require, among
other things, that vertical boilers used on steamers navigating the Red river of the North,
the Mississippi river and all rivers whose waters flow into the Gulf of Mexico, as well as all
waters tributary to such rivers, must have submerged tubes. This construction enables a
boat to go into any waters, whereas, the through tube design, shown in fig. 3,641, is excluded
from the waters just mentioned.

1. Cylindrical shell, which encloses the steam and water space.

2. 1, 2, 3, or 4 cylindrical furnaces that provide room for the grate.

The grate divides the furnaces into the space for the gases above and into
the ash pit below the grate.

3. Tubes in large number, above and parallel to the furnaces. These

2,050

SHELL BOILERS

SHELL BOILERS

2,051

3 <" 2

•a "

t

^^.2 2

<u be:

I cnt4_i CO
CO «-" <u <u

2,052

SHELL BOILERS

S ^
o u o

a o ^
CO c a;

JS bo <u <u a 3
Sf ^1 ^^

^ u ^

O

(D

S V; § 03:^ ^^ ^

bo rt 2 — * ^3 J.

03

.^ S^ o 5^ o

SHELL BOILERS

2,053

C > o c c

2,054

SHELL BOILERS

Oues. In what
special form is the
Scotch boiler con-
structed?

Ans. It may be
single ended or double
ended. In the latter
case it has combus-
tion chambers com-
mon to either end, or
else separate.

As a usual thing,
Scotch boilers are large
in diameter to accom-
modate furnaces and
return tubes all in one
end; for special uses, as
where head room is
limited, a form known
as the gun boat boiler
is built.

Ones. What is
the difference be-
tween a Clyde and
a Scotch marine
boiler?

Ans. The Clyde
boiler resembles the
Scotch type but has
a removable back
lined with asbestos or
tile instead of a water
space at the back

SHELL BOILERS

2,055

end of the combustion chamber as shown in figs. 3,648 and
3,649.

When properly done this makes a satisfactory arrangement, as it makes
the rear tube sheet very accessible for repairs and cleaning.

Figs. 3,654 to 3,656. — Rees locomotive type marine boiler with mud drum, low design for
western river steamers. Fig. 3,654, longitudinal section; fig. 3,655, cross section through
furnace; fig. 3,656, front end view with smoke door removed showing tubes.

2,C56 SHELL BOILERS

Oues. What are the distinctive features of the leg,
or flue and return tube boiler?

Ans. It is of cylindrical shape in that part of the shell con-
taining the flues and tubes, while the one or more furnaces are
similar to that in "the locomotive boiler.

The one or more combustion chambers are similar to those of
the Scotch boiler. The flues and tubes are arranged horizontally
and the gases pass to the rear, being returned to the front into

Fig. 3,657. — ^Rees western river type flue boiler.

an uptake chamber, frequently built into the boiler. Around this
uptake is often a vertical, cylindrical extension of the steam
space, which acts as a super-heater and steam drier.

The general construction is shown in figs. 3,652 and 3,653.

NOTE. — In the construction of very light draught Western river type boats, the plating
after being shaped and placed is sometimes taken apart and galvanized for better preservation,
and which process is found to considerably increase the life of the hull plating. The practice
of James Rees & Sons Co. provides for double riveting to avoid leakage when in service, and
which adds materially to the strength as well.

WATER TUBE BOILERS

2,057

CHAPTER 65
WATER TUBE BOILERS

The essential difference between a water tube boiler and a
shell or fire tube boiler is that the water
is inside the tubes instead of outside.

In this way, the water is divided into a large
number of columns of small diameter, each en-
tirely surrounded by heating surface, thus the
generation of steam is very rapid.

The circulation is positive, being governed
by the arrangement of the tubes, and the amount
of water contained in the boiler is small as com-
pared to the shell boiler of equal horse power.
These features render the boiler very sensitive
to changes in furnace and load conditions, that
is, it has not so great reserve capacity as the
shell types, and while steam can be raised
quickly, a sudden call for power will often
result in a temporary drop in pressure, while if
the load be suddenly removed, the pressure will
quickly rise and the safety valve blow before
the fires can be checked.

Types of Water Tube Boilers. —

There is a great variety of water

FiG.3,658.— The first water tube
boiler. Built by John Blak-
eley; patented 1766. It con-
sisted of, three water pipes
inclined alternately , con-
nected at the ends by bent
tubes so that the steam
formed in the boiler rises to
the upper part to supply the
engine.

NOTE. — The term tube, is here (because of common usage) loosely used. It should be
understood that the heating surface may be composed either of tubes expanded into headers,
or pipes, with threaded ends.

2,058

WATER TUBE BOILERS

tube boilers adapting them to any kind of service — stationary,
locomotive, and marine.

A classification to be comprehensive should group the boilers
with respect to several points of view. Accordingly, water tube
boilers may be classed:

1. With respect to the grouping of the tubes, as

a. Non-sectional.

b. Sectional.

IN SERIES

Figs. 3,659 and 3,660. — Series connection, showing electric dry cells connected in series and
arrangement of pii)es joined by return bends.

2. With respect to the heating surface, as

a. Tube.

b. Pipe.

3. With respect to the shape of the tubes or pipes

a. Straight.

b. Curved.

c. Coiled.

d. Closed (porcupine).

WATER TUBE BOILERS

2,059

4. With respect to the arrangement or assembly of the heat-
ing surface, as

a. Allin series.*

b. Allin parallel.*

c. Sections in series.

d. Sections in parallel.

e. Sections in series parallel.

■€>-
^
^
^

-^^-jTjr.- •ig:.:B'-^- y » VJSCo:-~ja-0.:o.io-XC,^^

"^"---"3^6 ^,^B^#^^T&3f?sJrdfcoU^dg^-

,z-s.-.os(y:Q:srff%^.

^^^^^^g^©

IN PARALLEL

Figs. 3,661 and 3,662. — Parallel connection, showing electric dry cells connected in parailelt
and similar arrangement of tubes expanded into two headers.

5. With respect to position of the tubes, as

a. Horizontal.

b. Inclined.

c. Vertical.

6. With respect to circulation features, as

^ NOTE. — The terms series and parallel are here used with their electrical significance , thit
is, just as a number of electric cells are connected up to form a battery, a number of pipe
lengths joined end to end like the links of a chain are connected in series; if they be joined to
two headers so that as many separate paths are presented for the flow of the water as there
are pipes they are said to be connected in parallel, as shown in figs. 3,661 and 3,662.

2,060

WATER TUBE BOiLLRL

a. Up flow.

h. Down flow.

c. Over discharge (priming tube) .

d. Under discharge (drowned tube).

e. Directed flow (double tube) .

7. With respect to combustion features

a. Direct draught.

h. Baffled draught.

c. Down draught.

d. Water tube grate

Figs. 3,663 and 3,664. — Gurney's boiler as improved by Dance (1826) showing water grate.
In construction, a number of U shape tubes were laid sidewise and the ends connected to
larger horizontal pipes. These were connected by vertical pipes to permit circulation and
also to vertical cylinders which served as a steam and water reservoir.

Clearly other divisions may be added, as for instance, with
respect to the kind of furnace, jacket, etc., but the above is
ample for a general consideration of the subject.

Essential Parts. — ^Any water tube boiler, no mauter how

WATER TUBE BOILERS

2,061

complex may be its construction,
principal members:

1. Steam and water drum.

2. Down flow tubes.

3. Up flow tubes.

4. Mud drum (or header).

5. Feed water heater.

6. Super-heater.
7' Grate.

is made up of the following

Figs. 3,665 and 3,666. — W. H. James' water tube water grate boiler. In construction, it
consisted of small circular tubes MS, inserted^ into large pipes L, F, as shown. The feed
pipe F, distributes the water uniformily to the circular upflow elements, steam being oUected
in the top pipe L. The boiler was 24 inches in diameter.^ James patented this boiler m 1825.
and may be considered as the first inventor who practically understood what was required
to constitute an efficient boiler.

These are assembled together mto one unit by means of suit-
able fittings and connections, and the assembly placed in an
insulating casing containing the furnace.

Elementary Water Tube Boiler. — The various parts com-
prising a water tube boiler, as just mentioned are shown
assembled in the elementary diagram fig. 3,667.

2,062

WATER TUBE BOILERS

in 0)

"^tCJ

^ "^

§•&

-3

m p

-mJ3

cS-^

o^e

^ti

S-o

^c;

fc5

c3 O

**■£

^'^

M-l g^

^1

yj W

.2

^■^

^•^

u

<U 4^"

1

u

m

1 :3 cj

r.

' ^Si

(A

r^

0*

V. o

3

8^

«

5l8

1

1^1

^T

s.s^

1

t^B

Z

^^.E

E

<U U) C

^

|-ss

a

§

•d^£

0) T*

>»

n

05 >,^

"H

W

1

^

a ^ ^

CO

6

•rj <i^

rf:

Cti (1>

WATER TUBE BOILERS

2,063

The water in the drum D, and down flow pipe E, which is not as hot as
that in the up flow pipes, and therefore denser or heavier, flows by virtue
of its excess weight downward through the down flow pipe to the mud drum
F, thence through the up flow tubes, entering the drum again at H.

As the water traverses the up flow tubes a multiplicity of steam globules
are formed thus greatly increasing the inequality in weight of the ascending
stream in the up flow tubes and the descending stream in the down flow pipe ,
hence a rapid circulation is produced as indicated by the arrows. .Because

Fig. 3,668. — Circulation principles: 1, illustrating up flow.

of this rapid circulation, any impurities in thfe water are deposited by
centrifugal force in the bottom of the mud drum. This force is made
available by suddenly changing the direction of flow at the mud drum.

With scale forming waters, a considerable deposit takes place in the feed
water heater section of the boiler, sometimes these tubes become almost
entirely choked up with scale, necessitating renewal.

At the top of the drum is a dry pipe I , by means of which steam is drawn
from the drum along its entire length rather than in one spot, thus priming
is reduced to a minimum.

There are two outlets to the dry pipe: one J, direct, and the other K^

2,064

WATER TUBE BOILERS

connected to the super-heater L, which terminates at the main outlet M,
of the boiler.

Steam, in passing from the dry pipe, is super-heated to any degree
required as governed by the size and position of the super-heater.

The super-heater being exposed to the hot gases from the furnace,
becomes very hot when there is no demand for steam, dangerously so in
some types, and to prevent overheating, a by pass N , is sometimes arranged,
as shown, so that water mav be admitted from the drum and the super-

FiG. 3,669. — Circulation principles; 2, illustrating aown flow.

heater flooded when the main valve is closed. The super-heater is cleared
of water on resuming operation by means of a bleeder O.

In the diagram (fig. 3,667), the parts are so arranged that all are visible
for clearness , but in practice the elements comprising the boiler are arranged
so that each is placed in such a position relative to the furnace as experience
shows is best, and that will give a compact assembly.

Non- Sectional Boilers. — This type of boiler consists

WATER TUBE BOILERS

2,065

essentially of a mass of tubes expanded in parallel to two headers
which connect with the ends of the drum, as in fig. 3,673.
There are many arrangements , for instance , a transverse drum may

BAFFLE PLATE

OVER DISCHARGE

-WATER LEVEL-
UNDER

IS CHARGE

DROWNLD TUBE

PRIMING TUBES

Figs. 3,670 and 3,671. — Circulation principles: III, illustrating under discharge (drowned
tube) , and over discharge (priming tube) . In the latter method a baffle plate is necessary to
protect the outlet from spray especially in the absence of a dry pipe.

INNER TUBE

CIRCULATION

Fig. 3,672. — Circulation principles: IV, illustrating directed flow (due to Field) . In the Field
drop tube and sometimes in the so called "porcupine" type boiler the heating surface is
composed of tubes closed at one end and the circulation "directed" by means of a smaller
inner tube through which the relatively cold water flows and returns through the larger tube
as shown.

2,066

WATER TUBE BOILERS

be used attached longitudinally to one header (as in the Ward
boiler) and return tubes leading back for the other header shown
in diagram fig. 3,674.

Oues. What are the advantages of these boilers?

Ans. Since all the tubes are accessible for internal cleaning,
they may be used with waters of such degree of impurity as

HEADER OR
WATER LEG

HEADER OR
WATER LEG

Ftg. 3,673. — Elementary non-sectional boiler with longitudinal drum consisting of drum^
two headers or water legs and mass of tubes in parallel.

would preclude the use of other types. Straight tubes are more
easily obtained than the curved variety.

Sectional Boilers. — Instead of connecting all the heating
surface in parallel to two headers as in the non-sectional boiler,

WATER TUBE BOILERS

2,067

it is sometimes divided into a number of sections or units each
consisting of 1, a few tubes expanded in parallel to small headers,
or 2, a few pipes joined in series by return bends. Each of
these sections is joined to a manifold or common passage leading
to the drum. The essential features of each type are shown in
the elementary diagrams, %ures 3,675 and 3,676.

-TRANSVERSE DRUM
/RETURN TUBES

Fig. 3,674. — Elementary non-sectional boiler with transverse drum, and return tubes. Since
only one header is connected to the drum evidently some means of completing the path f of
circulation must be provided, hence the return tubes.

Oues. Mention an important point that should be
noted with respect to boiler tubes in parallel and in series.

Ans. In the parallel arrangement all the tubes are accessible
for cleaning adapting the boiler to the use of impure feed water.

2,068

WATER TUBE BOILERS

Fig. 3,675. — Elementary-
parallel sectional boiler
showing manifolds, and
two tube sections with
their connections in posi-
tion. Note that each tube
is accessible for cleaning
which permits the use of
impure feed water.

SHORT

nipple:

DRUM

ALL TUBES

accessible:
for cleaning

Fig. 3,676.— Ele-
mentary series
sectional boiler
showing mani-
folds and tyvo
pipe sections with
their connections
in position. Note
that the pipes are
not accessible
which precludes the
use of impure
feed water.

INACCESIBie
FORCLtANlNG

WATER TUBE BOILERS

2,069

03

^ s

o ^o

o

a

t/3

(D

Ih

Ti

s

d

>

r)

O

Si

•4^

o

g

CD

CO ^ u/

,/,• <i^ •" S^

0

>
GO

a

^
^

O

2,070

WATER TUBE BOILERS

Ans. The sectional boiler can be more easily transported
than the sectional type over difficult routes because it can be
knocked down into a number of comparative light units. The
sectional construction avoids the use of stay bolts.

Fig. 3.679 — Combustion principles, illustrating down draught. Here, coal is placed on a
supplementary furnace, and air admitted from the top. In operation, the cold air and cool
distilled gases pass together down through the hot coke, and if the air supply be sufficient the
gases will be thoroughly burned and smoke will be prevented. To prevent the burning out
of the grate bars they are made of water tubes, forming part of the heating surface of the
boiler.

Pipe Boilers. — Ordinary wrought iron pipe and malleable
fittings, are extensively used in water tube boiler construction,
bein^ adapted especially to the sectional series arrangement .

'NOTE.— In the selection of a Pipe Boiler, points to be noted are: 1, Accessibility for
repairs e.':*:)ecially the location of the r and / connections which have to be reached to remove
sections; 2, special fittings (these are preferably avoided in design, especially for boilers used
in remote places because of delay in sending to factory for new parts in case of repairs; 3,
provisio 1 for cleaning; 4, construction of casing; 5, mud drum and blow off; 6, lifting ring for
connection to hoist tackle in installing.

WATER TUBE BOILERS

2,071

^MAIN STEAM OUTLET

UPPER CONNECTION TO
WATER COLUMN

UPFLOW L^H.TA PS

FEED COIL CONNECTIONS
'DOWN FLOW OUTLET

Fig. 3,860. — Roberta water tube boiler construction: 1, steam drum. The drum is con-
structed of open hearth steel and the heads riveted in and reinforced by through braces, as
shown. The upper small hole is the top connection for the water column and the lower
ones connect to the feed coils.

ALTERNATE CONNECTIONS IN DRUM FOR
UP FLOWS L.H.TAP5:

Fig. 3 ,861 .^-Roberts water tube boiler construction: 2, steam drum. Lower view showing
two longitudinal rows of holes tapped for connecting nipples to up flow coils. These holes
are spaced alternately for alternate connection with coils leading to the right and left side
pipes.

2,072

WATER TUBE BOILERS

The pipe used is made in sizes according to the Briggs standard
and are listed according to the nominal inside diameter rather
than the actual diameter, there being considerable difference,
especially in the smaller sizes.

The Briggs thread is a taper thread and a tight joint is made by screwing
the pipe into the fitting until a very firm connection is secured.

One of the earliest and at present prominent make of pipe

boiler is the Roberts,
which is a good ex-
ample of pipe boiler.

It is built up in sections,
each section being com-
posed of a few lengths
of pipe connected in series
by return bends. The
lower end of each section
is connected by a right
and left long nipple to a
bottom header or side pipe ,
and the upper end by a
short right and left nipple
to the drum as shown in
fig. 3,684 the left handed
thread connection being
in the side pipe and drum .
The figure shows two sec-
tions in position and the
large connecting pipes
between the side pipes
and drum, the assem-
bling of connecting or down

Fig. 3,682. — Ward Field or double drop tube boiler (round type). D, is a circular drum
into which the "downcomers" are tapped. Into the conical bottom of the drum D, a number
of straight Field tubes are secured, the ends being closed by caps, and the inner ends by
tight fitting plugs in which are two small holes. Into each hole is fitted a small brass tube
open at both ends, one tube extending inside of the hanging tube to within an inch of the
bottom, and the other and shorter one projecting about 4 mches into the drum. Around
the inside 9f the drum, an inclined diaphragm P, is fitted below the openings of the lower
row of vertical tubes. This diaphragm separates the main generating tubes from the down-
comers. By means of the internal feed pipe not shown, the feed water is delivered to the
lower row of tubes, going thence to the manifold and returning to the drum by the tubes
that enter highest. From the drum the water goes down the long brass tube inside T,
where steam is formed which returns to drum through the short brass tube.

WATER TUBE BOILERS

2,073

flow pipes and side pipes also serves as a frame which holds the part rigid
in position.

Fig. 3,685 shows boiler complete without case. As shown the two pipe
sections on either side of the drum form the feed water heater, being con-
nected in parallel series. The siiperheater consists of two sections located
on the sides and extending down to the fire brick.

Oues. What are the features of pipe boilers?

R.&U COUPLINGS

SEPARATING OR
SUPPORT PIPES

Fig. 3,683. — Roberts water tube boiler construction: 4, feed cotls. There are two, one on
each side of the drum (as shown in fig. 3,685). The feed pipe from the pumps or injector
passes through the jacket about on a level with the center of the drum head and enters the
feed tee which connects the feed coils in parallel entering each at the top, the feed water travel-
ing each horizontal layer of pipes progressively from top to bottom of the coils, where it is
delivered into the drum through the discharge feed tee above the water line. It is delivered
above the water line to permit any steam which may form in the coil to rise to the top
of the drum and the water to fall to the water level. The down flow of water through the
coils results in a nearer constant temperature difference between the temperature of the
water and that of the hot gases , than would be the case if the feed entered the lower layer
and flowed upward. Both coils deliver into the head of the drum. The cross pipes are
spacers, to prevent obstruction of the draught. Although these spacers have no water in
them they last for years in practice.

Ans. The material of which they are constructed is cheap
and easily obtained anywhere in case of repairs. They can be
shipped knocked down, facilitating transportation over difficult

2,074

WATER TUBE BOILERS

routes, and are easily assembled by any pipe fitter of ordinary
intelligence; high steam pressure may be safely carried .

Ques. Where are pipe boilers largely used ?

Ans. In marine service.

STEAM a, WATER DRUM

R.a L. NIPPLE

GRATE BAR
SUPPORT
i^LANGE POR CASING
ANGLE-IRON

SEDIMENT POCKET

BLOW-OFF

Fig. 3,684. — Roberts water tube boiler construction: 5, boiler in frame with two up flow
coils and bearing bars (for grate) in position. The holes in the drum and side pipes have
left hand threads, and the coils being connected by r and / nipples any coil may be removed
without disturbing the others. In all boilers over 6 feet in width, these up flow coils only
run to center, the opposite coils meeting same in the center of the boiler.

WATER TUBE BOILERS

2,075

MAIN STEAM OUTLET
FEED INLET 1.^ U| FEED COIL

CASING ANGLE

HEATER

SUPER HEATER
DRAIN

Fig. 3,685. — Roberts water tube boiler construction: 6, boiler complete except jacket or
casing. The angular pipe at the upper rear end leads from the dry pipe, inside the drum,
through the superheater coil (marked "heater" in above illustration); thence through the
riser at the front to a bull head tee (in front of the drum) which-is the niain steam exit and
connects also with the other superheater coil which is on the opposite side of the boiler
similar to the one explained, except it takes the steam from the dry pipe at the front end of
the boiler. The fire brick shown on the sides are not so thick but that they leave sufficient
room for the jacket to enter the angle iron. They are also hollow for lightness, weighing
about }/3 as much as ordinary fire brick of equal size. The tee projecting in front of the drum
head is the feed water inlet. The water column is connected by r and I nipples. The lowest
portion of the down flow pipes are small pockets, each being provided with a blow off valve
as shown.

2,076

WATER TUBE BOILERS

Fig, 3, 686. — Roberts water tube boiler constructions 7 ^ complete boiler with double jacket
or casing, showing main- steam outlet, safety valve, water column cleaning doors, etc.
Every section of the jacket is filled in with magnesia or asbestos 1}4 inches thick. The
vertical rows of tap bolts at each edge of the front are tapped into the ends of the side
sections; the back section is fastened in the same way. By_ taking out these bolts_ after
removing the top, the front and back and two sides may be lifted out. The circulation of
the Roberts Boiler is claimed to be perfect and very rapid, the boiler being so designed that
the hottest waters come in contact with the hottest gases and the tail end gases come in
contact _ with the cold water in the feed coils, resulting in low stack temperatures and very
economical as to fuel.

WATER TUBE BOILERS

2 fin

h^^^.

2 g «« fl'^^w'^.-^

*tr+j M« Site S 2 o
"S O^ a; p o S^cIJ

CJ M CC rt O W ..--H

-B. a-S'^'O rt S <u s

.g ^ <u rt rt wcs^ «
o rt «J a^'^cc^'^

<v w ^ o ^ ' O (0*0
^ «5 3 w ^ ? '^-^ rt

;_j^ WO^ woo g c^

pil^lllll

52 o«

3 tJ wt*

_ X to ►*'^ jj jj . t«4
t> g^C c 5, flj rt ctJ JO O

2,078

WATER TUBE BOILERS

^Tn ?;^!?"^?"S^^^^ non-sectional transverse drum horizontal boiler. This type was develooed
to meet the demand for a high pressure water tube boiler that could beTstllted in bc^ler.

Fig. 3,690.— Casey-Hedges non-sectionm r ,-;:•,; t^ -iLer The hafflp<; r.r<. ^r. nr-^^r.rr^A +v,.^
there are two passes of the hot gases through the tubes and^afbl adjul?erto frlught

WATER TUBE BOILERS

2,079

WATER GRATE

Pig. 3,691. — "Water grate." It consists of a series of pipes connected close together in parallel
to a header at one end and to the up flow elements at the other, thus avoiding sagging or
burning out as experienced with ordinary grates especially when forced. In early times
water grates were tried out by James, see figs. 3,665 and 3,666, Gumey and others. Figs.
3,687 and 3,688 show small boiler with water grate as designed by the author and now under
construction.

Fig. 3,689. — Text Continued.

rooms where ceiling height is limited or where the boiler must be introduced through narrow
passageways or restricted openings. The pressure parts of the boiler are shipped in a knocked
down condition, making it possible to install it without cutting through walls and floors
in locations that would be wholly inaccessible for almost any other type of boiler. _ For
export the cross drum boiler can be handled at much less expense by steamship companies on
account of its reduced bulk in a knocked down condition, and the comparatively small
weight of the heaviest piece; this feature adapts it to remote places where it must be trans-
ported over difficult roads, weak bridges, etc.

Fig. 3,690. — Text Continued.

conditions. The lower row of tubes is completely encased with tile, which forms an incan-
descent reverberatory roof over the furnace, converting it into a Dutch Oven. Thetubes
are divided into two banks, an upper and lower bank. The lower bank is inclined two inches
to the foot. The lower bank of the tubes being the hottest, in consequence the circulation
is most rapid, therefore, the necessity of the increased inclination. The upper row of tubes
and drum are inclined one inch to the foot. The boiler is supported at the front end by a
beam and column suspension. At the rear end it rests on cast iron columns with expansion
plates and rollers. This construction permits the boiler to expand and contract in any
direction without interfering with the brick work. A superheater may be installed between
the upper and lower banks of tubes.

2,080

WATER TUBE BOILERS

Boilers with Curved Tubes.— Owing to the ease and pre-
cision with which tubes may be bent, designers have employed
tubes of various shapes to secure certain advantages in boiler

h'J£^'~^ u''-]"- '''''^ \'^^^^. sectional parallel horizontal boiler wit., .x....... .-.cci incuned

^•^^,Tf V ^^® heating surface is composed of tubes expanded into headers of seSentine or
^y bl eX'rTnHL^d'P^'t'^" ^"^"^ ^^-^ f ^^^f ^^ P°^iti°^ ^^en assembled. The headers
^/fnVi^JJ^^^ as shown or vertical. The sections are attached at their rear lower
SnA°,l*'?''^7'^^^^^ ^^"^ which IS tapped for blow off connection. The boiler is sul-
K^ff P^ ^'''''^^ and rear wrought steel supporting frames independent of the br?ck work to
pennit expansion and contraction without showing either the boiler or brick work^Th^

wiLlassel to "ht"r4Vo¥?hfdn^''T* ^--/l^' ?^T *^^^ Po-t oHntoXction^h^
sectfon? 1mwp?H f L^tfJv ;t, ! ^^^i downward through the rear circulating tubes to the
If^A^!' upward through the tubes of the sections to the front headers and through these
ferf^S ^"""^ ^1°''* circulating tubes again to the drum where such water as ha^ notbeen f ormel
S^^ .1 ?r "'^^f''^^ '^I'^^^i^^ ^^^ ^^^^"^ fo"ned in the passage through th^tubes is Uber-
ated as the water reaches the front of the drum. The steam so formed if stored in th?steam
space above the water line, from which it is drawn through a so-called "dry pjjje"

WATER TUBE BOILERS

2,081

Fig. 3,693. — Wicks non-sec-
tional vertical boiler. It con-
sists o/" cylindrical steam and
water drums, one directly-
over the other connected by
straight tubes. A vertical
baffle extending through a
diameter, about three quarters
the length of the tubes divides
the combustion passages into
two passages which, by virtue
of the temperature difference
in the two passes causes cir-
culation in the direction of
the gases. In construction,
the boiler is supported by
four pressed steel brackets
riveted to the lower drum and
is entirely enclosed in brick

work. On a level with the water line and extending over the tubes In the first compartment
of the upper drum^ is a baffle plate to deflect the water of circulation and prevent splashing
or spraying water into the steam. Ordinarily, feed water is introduced into the steam drum
below the water line and flows downward through the tubes of the second compartment.
The feed water connection may. however, if desired, or conditions so warrant, be made in
the bottom drum. The blow oft is located in the center of the bottom of the lower drum,
and the steam outlet in the center of the top of the steam drum with two safety valves on
either side. In the convex head of the steam drum are placed one manhole and a number of
hand holes, the lower drum being provided with a manhole.

2,082

WATER TUBE BOILERS

Figs. 3,694 to 3,706. — Vanous forms of curved or bent tube as used incurved tube boilers.
They may be classed as: 1, single curve; 2, double curve; 3, triple curve, etc.; 4, circular
form as helix, flat, and cone shaped spirals, etc.

WATER TUBE BOILERS

2,083

construction. The results obtained by the use of bent tubes

are, briefly,

1. Provision for expansion and contraction.

Thus, especially with boilers operated under forced draught, as on fast
vessels there is less trouble with leaking joints.

Fig. 3,707. — Seabury single and double curve bent tube boiler. In construction, there is a
single steam drum connected to two lower or mud drums — one on each side — by two nests
of bent tubes enclosing a large combustion chamber. The tubes are staggered so as to
present the greatest amount of direct heating surface, and are so arranged as to facilitate
their cleaning by means of a steam jet and hose . The feed water heater located on each side
of the steam drum is made of pipe and extra heavy return bends. These boilers are built
in sizes from 3 to 3,000 horse power.

2,084

WATER TUBE BOILERS

the number of these latter tuSs dlolndln^ «nnn f T^^^^^^^ .IfT m ^ "^^^if ^ circulating tubes.

is placed on the top of the center drum TwS^L 5^^ ?^ the boiler. The main steam outlet

WATER TUBE BOILERS

2,085

X ccuJ
23:

^ aj«« wr^ W)^! a> o sj-t^'d'd

*f-) j3 . ro (D Til ro tui r! ?^-t-> il
•g S t'.'d C ^ a)'43 (ui: ai-43 g c

C b rt s o 2 w o^"^ ^ ^tDh

.SS|»-Se.|.»-2|i|ag

^-.a^-

^ ^'^ 2-2.S+21H dnXYloC
-M'^ o-^ o OJ 5r^t^ j:i -2 bo ^1 1^ oJ

,:^ o^*^^^ o c S g-g w 3

2,086

WATER TUBE BOILERS

Fig. 3,710. — Badenhausen water tube boiler and superimposed glass ring with water inside
and heated by a lamp illustrating the circulation. The boiler consists of two water drums,
one steam and water drum, and a steam header, all connected by means of tubes. The
water is fed into drum 3, flows down the rear bank of tubes to drum 1, thence upwardly
over the fire to drum 2, and then backto drum 3. The steam is disengaged from the
water as it enters di*um 3, and, after passing through the roof tubes where it is superheated
from 5 to 10° F., enters the steam header. From there it passes through the steam outlet
to the steam line. The boiler is supported by means of steel framing independent of the
brickwork. Drum 3 rests on beams .^ Drum 2 is suspended from heavy turned bolts
arranged to accommodate any expansion. Drum 1 is suspended from tubes only. The
steam header is supported at both ends on steel angles carried up from the main boiler
frame. Thus it will be seen that each unit of the boiler is free to expand. Asbestos is
placed around the drum ends where they enter the brickwork thus making an expansion
joint to allow for free movement of the drums where the expansion of the unit may dictate.

WATER TUBE BOILERS

2,087

2. Longer tube length.

Thus reducing the number of expanded joints.

3. Flexible disposition of the heating surface.

Thus, in special cases, suitably locating the heating surface without
mechanical difficulties, as to give good circulation.

Fic, 3,711. — Mosher triple curve bent tube double drum, over discharge marine boiler. In
construction, there are two steam drums and two mud drums which are connected by rows
of bent tubing, incHned and connected, above and below, as shown. The two upper drums
are also connected, below the water line, by a length of tubing, thus completing the water cir-
culation . An early design of this boiler was for the fast steam launch Norwood (speed 30 miles
per hour, and famous in its day) , shown in fig. 3, 122, page 1,620. The proportions of this
boiler were: Heating surf ace 1,000 square feet; grate area 26 square feet; center of gravity
very low; tubes 1-inch diameter soHd drawn; weight of boiler 2>^ tons; length 7 feet 3 inches;
breadth 6 feet; height 3 feet 6 inches. The boiler supplied steam to a triple expansion
engine, size 9, 143^, and 22, by 9 in. stroke, about 800 r.p.m.

2,088

WATER TUBE BOILERS

4. In large boilers, one manhole to be removed instead of indi-
vidual tube hand hole plates for cleaning.

This does not apply to all straight tube boilers, there being a number of
makes, as the Vogt, for instance, in which access to the tubes is through
large drums, instead of tube plates.

While, of course it takes longer to remove a multiplicity of hand hole
plates than a manhole, it should be noted that in the former arrangement
the tubes are more accessible for cleaning, and a straight tube is more easily
cleaned than a curved tube, in fact some designs of curve^d tube are so
complex as to practically preclude cleaning. In small boilers cleaning such
tubes is impossible.

Fig. 3,712. — Ofeldt circular form or helix curve bent tube vertical drum automobile type boiler.
This is a true coil, as distinguished from the so called coil boiler in which the "coils" are
made up of straight pipes connected in series by return bends. The Ofeldt boiler consists
of a central vertical drum , surrounded by a number of pipe coils which are connected to the
drum at its extremities. The drum holds a reserve of water, which, when the boiler is in
operation, circulates through the coils absorbing heat from the fire, and re-entering the
drum at the top as water and steam. The amount of water in the drum varies from three
gallons in the smallest size to eight gallons in the 24-inch boiler. Steam is taken from the
top of the drum and passed through a superheater before delivery to engine.

Figs. 3,713 and 3,714. — Ofeldt circular form or helix curve bent tube horizontal drum marine
type boiler and detail of coil. The boiler consists of, two horizontal drums connected on
each side by numerous vertical up flow coils. Between the two series of coils are a set of
down flow coils connected to the two drums. The cooler water in the upper drum flows down
through these coils to the lower drum, thence up through the up flow coils absorbing heat
from the fire and re-entering the upper drum as steam and water.

WATER TUBE BOILERS

2,089

5. Ease oi making repairs depends on the design.

In some boilers, as for instance, the Mosher, any tube may be removed
without disturbing the others, whereas, in some other types it is necessary
to start at the beginning of the row and remove all tubes up to the one
damaged.

6. Curved tubes designed for over-discharge give a large
space above the grate, thus improving the combustion efficiency.

The arrangement is made with only a small increase in the height of
center of gravity, an important point in certain types of vessel.

Ques. Mention one objection to bent tubes.

Fig. 3,715. — The first porcupine boiler. Built in 1804 by Col. John Stevens and operated upon
the Hudson river in a little steam boat 68 feet long by 14 feet beam. The boiler was of the
single parallel tube double bank type and contained 100 tubes 2 inches diameter by 18 inches
long. One end of each tube was fastened to a central water leg, the other end being closed
as shown. The vessel attained a speed of seven miles per hour and was one of the earliest
examples of the use of water tube boilers for marine purposes.

Ans. In the case of repairs, especially in remote regions, they
are not so easily obtained as straight tubes, entailing more or
less vexatious delay with accompanying loss due to shut down oi
plant .

Closed Tube or Porcupine Boilers.— This type of boiler
consists essentially of a tube sheet into which are expanded or
screwed a number of tubes having their exterior ends closed, and
which form the water tubular heating surface.

2,090

WATER TUBE BOILERS

Porcupine boilers may be classed as

1. Parallel tube,

2. Radial tube,

according as the tube sheet is, 1, a flat plate, or 2, a cylindrical drum,
and as

1 . Single tube,

2. Double tube, \

Fig. 3,716, — Shipman single parallel tube porcupine boiler; a widely known and extensively-
used boiler in its day. It was employed on self-contained petroleum burning outfits for small
powers. The boiler consists of tubes about 18 inches long which are screwed into a flat
oblong chamber at one end and closed ^t the Qther, The illustration clearly shows the details
of construction. The large tube seen at the top serves as a steam drum.

according to the absence or presence of inner or Field tubes which serve to
promote circulation.

Figs. 3,716 and 3,717 show respectively the parallel and radial types,
these being single tube boilers, and figs, 3,718 and 3,719 a double tube
boiler of the parallel tube class.

WATER TUBE BOILERS

Boilers with Tubes in Series
Parallel. — By a stretch of the
imagination the term series par-
allel may be appHed to the tube
arrangement found in some of
the multi-drum boilers of very
large capacity, with drums in
common forming a series connec-
tion between two parallel sections
or separate drums connected
by equalizer tubes examples of
the two types being shown in

Fig. 3,717. — Racine single radial tube porcupine
boiler. It consists of, a central column of
heavy hydraulic pipe, into which tubes are
screwed . The vertical drum is extended above
the radial tubular heating surface
to form sufficient space for the steam.
The heads are welded in. The boiler
as shown here is for small power; on
the extended base are seen a feed
water heater and hand pump, the
vacant space being for the engine in
self-contained units.

2,092

WATER TUBE BOILERS

Figs. 3,718 and 3,719. — Niclausse sectional double parallel

tube porcupine boiler, and detail of header connection

to drum. Each tube contains an

inner or Field tube to promote

fApJ^

WATER TUBE BOILERS

2,093

figures 3,720 and 3,721 respectively. The arrangement here
shown lends itself to very large powers, the unit virtually com-
prising several boilers combined into one.

Up Flow and Down Flow Boilers. — ^According to the way

Fig. 3,720. — Bigelow-Hornsby multi-drum boiler with tubes in series parallel by equalizer
tube connectors. The general circulation of this boiler is down the rear sections and up
the front, and in addition to this there is_a rapid circulation in the individual units. The
feed enters the top rear unit drums and mingles with the downward circulating currents in
the rear tubes and then passes up the tubes in the front units. It will be noted that the
rear vertical units (comprising almost half of the heating surface), which are in contact
with the cooler gases of combustion, must be traversed by the feed water before it can
come in contact with the direct heating surface over the furnace.

Fig. 3,718 and 3,719. — Text Continued.

circulation. This is accomplished as shown in fig. 3,719. Here, as indicated by the arrows
the water from the down flow section of the header traverses the inner tube and returns by the
outer tube to the up flow section thus a thin circular film of water is presented to the^ heating
surface rendering it very effective and at the same time producing rapid circulation, but
at the expense of extra weight and complication.

2,094

WATER TUBE BOILERS

in which the water passages are arranged, the circulation may
be directed upward or downward. Although most boilers work
on the upflow principle, Rankine states in favor of downflow
circulation as follows:

Fig. 3,721. — Connelly multi-drum boiler of very large horse power with tubes in series parallel
by drum in common connection; fitted with mechanical stoker and built for sizes ranging
from 1,000 to 4,000 horse power.

WATER TUBE BOILERS

2,095

f n-i S o ri

a ;3;^ ^Q^

?^ "^^ ^ ^ OJ

• 7" S O (5 <U

2,096

WATER TUBE BOILERS

"In a steam boiler it is favorable to economy of fuel that the motion
of the water and steam should, on the whole, be opposite to that of the
flame and hot gas of the furnace, in order that the hottest particles of each
may be in communication with the hotest particles of the other, and that
.the minimum difference of temperature between the adjacent particles of
the two may be the gratest possible. Thus, if there be a feed water heater

=n:

Fig. 3,724. — Diagram of Parker sectional down flow boiler. The drum has separate chambers
for water and for steam, with a valve between to prevent priming. The tubes are arranged
to form continuous passages, termed elements, leading downward from the water chamber,
with direct upcasts from the bottom ends to the steam chamber. A non-return valve at the
top of each element prevents reversal of the flow. The water fed into the drum seeks its
level in the upcast. When heat is applied the water in the upcast is soon discharged into the
drum by the expansion of the steam formed in the lower tube. The water then runs down
from the drum with an effort to retain its level in the upcast, which is frustrated by con-
tmuous evaporation, and the result is a strong and rapid flow, impelled by the gravity head
of water. The flow of water and steam is opposite to the gases, and as the heat transfers
from the latter to the former it is carried back toward the point wheie it was originally
generated. This is an application of the regenerative principle, which has been profitably
used m many of the arts, and its application to boiler practice affords a material
gam m economy. When a drop in pressure occurs, the anti-priming valve closes, and the
difference m pressure created between the two chambers keeps the valve closed while the
drop continues; this effectually prevents priming. In operation, the coolest water passes
through the upper or economizer elements where i*" comes in cor tact with the coolest gases
Steam is delivered direct from the hottest part ot the furnact into the steam chamber

WATER TUBE BOILERS

2,097

Fig. 3,725 to 3,727. — Parker single ended down
flow boiler with superheater showing longi-
tudinal and cross drum types and detail of
tubes . The lower group of tubes m the down
now generating section
and the upper group
feed the water heater.
The superheater con-
sists of U tubes joined
to two headers and
located in the combus-
tion chambers below
the generating tubes.

2,098

WATER TUBE BOILERS

consisting of a set of tubes through which the water passes to be heated
before entering the boiler, that apparatus should be placed near the chimney.
The coolest portions of the water in the boiler should if practicable and
convenient, be contiguous to the coolest part of the furnace; and if there
be apparatus for superheating the steam, that apparatus will be most
efficient if placed in the hottest part of the furnace."

The downfiow principle has been utilized in some flash boilers
and a few water tube boilers. An example of the latter class is
the Parker boiler, the operation of which is shown in figures

'FIELD TUBE GENE-RATINS TUBE-^

Fig. 3,728. — Talbot boiler header and tubes. The header consists of two sets of overlapping
compartments, into one of which is screwed the open end Field tubes and into the other the
generating tubes. The end of each generating tube is welded together so as to close it. These
closed ends are free to expand and are supported in front by perforated sheets of metal.
Both tubes are secured by screwed joints with threads having double the standard pipe thread
taper which makes it easy to remove them, the fit is sufficiently tight for 1,000 lbs. pressure
using standard weight pipe.

3,724 to 3,727. Here the water as it descends with gradual
rise of temperature travels toward the hotter part of the furnace.

A question which naturally presents itself is whether the life of the
lower tubes be shortened because of the more severe conditions due to the
down flow principle.

SPECIAL BOILERS 2,099

CHAPTER 66
SPECIAL BOILERS

There are a few types of boilers, not described in the preceding
chapters, that are of unusual character, and here designated as
special.

Examples of these peculiar boilers are to be found in the various
divisions previously mentioned, that is, classed with respect to
heating surface that may be of the

1. Fire tube.

2. Combined flue and fire tube.

3 . Water tube (or pipe) .

4. Combined fire tube and water tube.

5. Combined shell and water tube.

6. Combined shell, fire and water tubes.

or other special types not included in the above list.

1. FIRE TUBE BOILERS

Duplex and Triplex Fire Tube Boilers. — An inherent defect
in the horizontal return tubular boiler is its limited diameter,
due to the fact that part of the shell being exposed to the intense

2,100

SPECIAL BOILERS

heat of the furnace,
the shell cannot ex-
ceed a certain thick-
ness, otherwise the
outer portion of the
metal especially at
the riveted joint
would become over-
heated. This, and
the constantly in-
creasing size of unit
demanded have re-
sulted in various
modifications,, some
more or less freakish
in their character.
Fig. 3,729 shows
the duplex arrange-
ment, being an at-
tempt to increase
the heating surface
of a shell boiler of
given diameter by
utilizing all the tube
sheet for tubes, and
connecting the shell

:Fig. 3,729. — Duplex horizontal return fire tube boiler consisting of a lower tubulous shell
connected by necks to an upper drum .

»(by short necks) to a steam and water drum as shown.

Although the connecting necks are made as large as possible, the circula-
' tion is poor. The hot gases pass from the furnace underneath and around
the lower shell, thence through the tub-es, and back under the drum.

According to Barr, boilers thus constructed have not sufficient advantages
over the ordinary single shell type to pay for their extra cost.

SPECIAL BOILERS

2,101

O

^ uJi^i

o ^-^ o

<^ ^ c r^

W) ^ 02 O

i

o
bJO •

w C

o -its

s ^

O o

> S

oJ :i

XJi g

CO
CO o

oj :3 *^

^ oj 9^ 0)

'r>^ bJOfp

«-i 03 (1)

o ^ S ^

_^ (D ^ (i>

a. O . >

r5i o H'-'^r^

CO C
t^ o3

""^

t/3 O

bX) a;

OS

^2 ^

bjO

•S ?5

« n y

2,102

SPECIAL BOILERS

tube sheet may be filled with them, thus considerably increasing
the heating surface.

Although the return flow of the hot gases is not obtained in
the vertical setting, the same economic effect is obtained by de-
creasing the diameter of the tubes, thus lowering the stack tem-
perature to the same degree as is obtained with the horizontal

return flow setting; in fact, tests
indicate that the performance of
the vertically set boiler is the
same as the horizontal return
flow setting.

The boiler, as shown, is supported
by an iron collar riveted to the shell
and of proper dimension to support
the boiler in place without bringing
undue strain upon the rivets which
fasten the collar to the shell.

Where floor space is limited and
there is sufficient height, the ver-
tical setting is desirable, provided
the feed water be such as will not
foul the lower sheet.

Vertical Extended Internal
Fire Box Fire Tube Boilers. —

This is a natural development of
the vertically set tubular boiler
just described, in that it elimin-
ates the brick setting, thus

V\G. 3732. — ^Vertical setting for modified horizontal tubular boiler. Since the object of this
arrangement is to secure maximum capacity for a given size shell as well as to economize
floor space, the entire tube sheet area should be utilized for tubes using a large number of
small diameter tubes rather than large tubes, in order that the stack temperature will be
such as gives satisfactory efhciency. The setting should be continued up to within a few
inches of the water level to obtain as much shell heating surface as possible.

SPECIAL BOILERS

2,103

fyiipg

||9|-.«|||||-||

. „ „ipl!|tlll

<D g'^ i50<u^^-i3^ rtj3 c o p g ^

i ^:s^.s g s ^ ° i « ^^ « §

a.SoS-^-2:2^'5'§a;§ac^|
^if^ a:r: (u ^^ 5^'d ^ 2 w J5

rd°t-:S° -§0)0 0^:^8 3^2

||l|ilbril?li

cfl _, u-"
Td rt g *3

^ «S

0) rtt

rt

2S&

^ J-; "'-^

Cfta5w!^'d§S'Q.Qa.S+^^+S

^|&^.tl5g|g-SgS8S

(U 0--2 flU C ctS Jh b ^'Vi rt S O S 4J

2,104

SPECIAL BOILERS

economizing flow space in a
still higher degree.

The design also provides ade-
quate grate area for the very
great amount of heating surface
crowded into a shell of small
diameter. These features
are embodied in the Phoenix-
Manning boiler, figure 3,733,
and with improved construc-
tion in the Smith-Manning
boiler, figure 3,734.

Manning boiler, — As shown
in fig. 3,734, it is very high in
proportion to its diameter in
order, 1, to obtain large capa-
city on small floor space, and 2,
to reduce the stack temperature
to that giving high efficiency.

In order to obtain adequate
grate area for the large amount
of heating surface the shell
diameter is enlarged at the fur-
nace by a doubled flanged ring
as shown, thus the diameter of
the furnace is made equal to or
larger than that of the shell
instead of being reduced as in
the case of the ordinary vertical
boiler.

The tubes are arranged in concen-
tric circles with a space at the center
for circulation. The double flanged
ring also provides for expajision
which, because of the extra length of
the boiler, is an important feature.

Smith boiler. — This is a
modification of the Manning
boiler. In place of the double
flanged ring of the latter, there
is a conical enlargement of the
shell above and around the fur-
nace, and a corresponding en-
largement of the furnace walls
as shown in fig. 3,734. The
objects of this arrangement

Fig. 3,734. — Smith - Manning vertical
tubular boiler. The fire box is conical
permitting a free circulation of water
and the tube sheet is curved for strength .

SPECIAL BOILERS

2,105

are 1, to avoid the ring construction which was an element of weakness^
2, to provide a space around the tubes large enough for a man to walk in
to examine and clean the crown sheet and other interior surfaces, and 3,
to provide additional water space and thus render the boiler less sensitive
to chaiiges in operation.

Vertical Radial Fire Tube
Boilers. — A defect of the verti-
cal fire tube boiler is position of
the lower tube sheet directly
over the fire where scale or sedi-
ment is baked by the intense
heat, and, as usually con-
structed, the impossibility o£
cleaning the tube sheet render-
ing this type of boiler undesir-
able for feed water containing;
impurities. To overcome this
trouble Reynolds conceived the
idea of spacing the tubes in ra-
dial lines, and providing a large
hand hole at the tube sheet
level where these lines converge
thus rendering the spaces be-
tween the radial rows of tubes
accessible for cleaning.

The features of the -design are
shownin figs. 3,735 and 3,736. In fig.
3,735, the space at the left side left
vacant by the tube arrangement is
utilized by an internal stand pipe or
reservoir through which the feed
water passes from the bottom and
overflows at the top.
^ In traversing this reservoir, a con-
siderable portion of the impurities is

Fig. 3,735. — ^Reynolds boiler showing method of introducing the feed water. By raising the
water level in the boiler slightly above the top of the feed column, the latter may be utilized
as a surface blow off to eject scum or light impurities collected on the surface of the water.

2,106

SPECIAL BOILERS

precipitated and caught in the bottom of the reservoir, where it may be
blown off through the lower connection.

Vertical Return Fire Tube Boilers. — An attempt to im-
prove the efficiency of the vertical boiler without increasing its
length and reducing the size of the tubes, resulted in the return
or two pass arrangement shown in figure 3,737. Here the hot
gases after passing through the tubes directly above the furnace

Fig. 3,736. — Detail of crown sheet of Reynolds boiler. The radial tube spacing facilitates
cleaning the .crown sheet.

return downward through the outer circle of tubes, thence to
stack.

In order to avoid the use of stay bolts and permit placing the
outer ring of tubes, a corrugated furnace is used.

To further increase the efficiency the combustion space is of
great height obtained by placing the grate in an extens on ot
brickwork of conical shape directly below the boiler. The wall

SPECIAL BOILERS

2,107

Fig. 3,737. — Webber verti9al
return fire tube boiler with
extended brickwork furnace
and corriLigated combustion
chamber.

Fig. 3,738. — Fitzgibbons combined vertical-horizontal boiler with horizontal fire tubes. As
can be seen the design permits a very roomy combustion chamber which increases the fur-
nace efficiency besides adding very effective heating surface.

2,108

SPECIAL BOILERS

Fig. 3,739. — -Berry vertical boiler with horizontal return fire tubes. It consists of two vertical
cylindrical shells , united at the top by a crowned ring and at the bottom by a conical crown
sheet. These rings do not require bracing, and accommodate any difference in expansion
that may occur. Tubes radiate from the inner to the outer shell, uniting and bracing them
and forming a structure of great strength. A deflecting arch of fire brick is placed in the
internal flue at a point above about two-thirds of the submerged tubes, and a casing or
smoke flue surrounds the boiler on the outside. The boiler is supported on the side walls
of the furnace, which is square and lined throughout with an independent fire brick lining.
The gases rise into the internal combustion chamber, are deflected by the arch, and pass
through the tubes to the outside flue, thence upward and inward through the middle section
of tubes to the internal flue, thence upward and outward through the superheating tubes,
thence upward and inward over the top of the boiler to the stack. The circulation is up the
inside and down the outside. . One-half the area is maintained for circulation on the inside
flue-sheet and three-quarters on the outside sheet. A manhole is provided for entering at
lower shell, which space is unobstructed, and two blow off cocks are provided at base of boiler.
The casing is lined with an insulating material and is mounted on wheels which run upon a
>rack secured to the boiler. The joints are made by a gravel pocket, so that the casing may
bto easily revolved. Doors are provided from top to bottom, which, by revolving the casing,
may be brought opposite any part of the boiler for inspection, cleaning or repairs.

SPECIAL BOILERS

2,109

being perforated as shown by radial holes through which air may
be admitted above the fire to improve combustion.

Modiiaed Clyde Type Boilers. — An objection to the Clyde
and Scotch boilers is the poor circulation because, as usually

Figs. 3,740 and 3,741. — Single flue Clyde type boiler with furnace on side. In this arrange-
ment there being more heating surface on one side than the other, circulation is promoted
and the dead water which collects under the flue on the ordinary type is avoided. Since the
efficiency of the flue heating surface, being on the front pass, is greater than that of the tubes,
, a large number of tubes should be used otherwise the result sought may not be obtained.

Fig. 3,742. — Murray modified Clyde type boiler with short fire tubes at rear of furnace flue,
the object being to promote circulation under the flue.

2,110

SPECIAL BOILERS

constructed, the water lies dead in the bottom of the boiler, the
heat from the furnace not reaching to any degree the bottom of
the boiler. To remedy this defect numerous devices have been
applied.

Fig. 3,742 shows one arrangement in which the furnace instead of extend-
ing the length of the boiler is connected to a number of short tubes. The
effect is to produce rapid upward circulation in that end of the boiler and
draw in that direction the water under the flue.

Fig. 3,743. — Casey-Hedges self-contained two pass fire tube boiler. The furnace or fire box,
which is underneath the cylindrical portion of the boiler, is formed by a metallic jacket
lined with fire brick. The flames and hot gases pass from the furnace back through a nest
of 4-inch tubes to the combustion chamber at the rear end, thence upward, passing back again
to the front end of the boiler through a series of 3-inch tubes, to the smoke stack. The
lower portion at the rear of the boiler affords a large settling chamber for the precipitation
of all impurities, such impurities being away from the direct heat of the boiler, making the
boiler especially adapted for service where the water is heavily charged with mineral sub-
stances. It is accessible for cleaning both externally and internally.

Extended Shell Tri-pass Fire Tube Boilers.— The object
in this arrangement is to obtain an extra long path over the
heating surface for the hot gases, so that the water will absorb
a greater percentage of the heat, thus increasing the Efficiency.

As shown in the diagram figure 3 , 744 the hot gases pass from
the furnace and flow along the lower portion of the shell, thence

SPECIAL BOILERS

2,111

Fig. 3,744. — Diagram showing flov/ of the hot gases in the extended shell tri-pass fire tube
boiler.

Fig. 3,745. — Talbot 150 horse power con-
tra flow water tube boiler being tested
to determine resistance in the various
stages due to circulation. The boiler
consists of a combination of fuel
economizer, water heater, boiler and
steam superheater. The entire unit
is made up of small tubes and a honey
combed header into which the tubes
are secured. Test pressure 1,000 lbs.;
superheater adjusted for temperatures
up to 800 • Fahr . It is claimed that the
rapid circulation prevents scaling of
tubes. The Talbot boiler is further
illustrated and described on pages
2,085 and 2,098,

2,112

SPECIAL BOILERS

3e:ction on ab

Fig. 3,746 and 3,747. — Cornish single flue, fire tube boiler.

iVl

SECTION ON LF

Figs. 3,748 to 3,751. — Lancashire boiler with fire tubes. Fig. 3748, section on line MS; fig.
3,749, elevation; fig. 3,750, section on line LF; fig. 3,761, plan.

NOTE. — Forms of boiler used in different countries. The "power of suggestion"
or local practise of others (no matter how faulty) enters largely into the selection of a boiler.
The following figures by H tiler of the National Boiler Insurance Co. of Manchester, Eng.,
show how largely selection is influenced by local custom.

Per Cent of Boilers of Various Types Used in Europe

United
Kingdom.

France. ^

Germany .

Switzer
land.

Austria .

Lancashire and similar types

Cornish and similar types

Externally fired cylindrical

Externally fired multitubular

Locomotive

Small vertical . . .

38.0
23.7
t6.8

ii'.o

16.6
1.8
2.1

4.7
8.2
57.3
13.4
5.1
3.6
5.7
2.0

35.7

15.3

14.8

5.2

17.3

5.0

4.6

2.1

19.6

40.8

15.5

3.5

5.7

13.5

1.4

*

41.0
7.5

10.5
6.1

Water tube

3.8

Other types

1.4

* Lancashire, Cornish, and similar types, 29.7. f Including "elephant" boilers.

SPECIAL BOILERS

2,113

Ho

5 o c

J-3 -M Q,

h/1 - fli uj *5 P.. .

.2 rt ^§.S oV ^

J - O S t--

o g--^^ a M oj ^

C5 «- fe »2 "iiS.S y 2 o

S M-^ O ?^^ 'S 1^ S "5 (U "*

ii-f^'

S-o^

c^

V ^ o <i> o >

O O CC M ^ o

V. a;§ 5 H-c S<- ^ 8 a> S

_, :3 S »H ftjH j-i o o v-»

2,114

SPECIAL BOILERS

CD
O

CD

-a

;:«
o
u

O

o

172
<D

o

■a

S

D
H

Q

Q

o

ri

O

CD ^

- g

^ 5

xn "+-*

C <D

O ^

o

g 8

C o

H

0)

(D

s

O
o
;^

CD

>

O

fe o

GO

:;5 c
o --^

PQ Pi

<D
<« CD

.b -^

CO >

^ u

CD

SPECIAL BOILERS

2,115

O g W3 O „ V. « r- rt

^-d § ^^ g.s s.s

^^'d J

X a>

"^ d a> «S 5^"^ rt-g
c t^ c C ^J a>-»^-^-^

•*' S^ ^ <u t S <o
u %^-*^^ <u >^ O

oj v^ t^iS y <" 2 ^ p5
^ -^ c.a g o E «

•o'S'd

ja

d ill" ill g

cc M-d-^ H '^^p,a;'d
II'O a ^ § d.tJ ^^"'^
^ oi^ o S-^ <u-- 2 2

2,116

SPECIAL BOILERS

'

u u

an

Figs. 3,757 to 3,759. — Tailor pipe boiler. Fig. 3,757 shows the assembly except for the drum as
shown in fig. 3*,759. The pipes are screwed together as shown in fig. 3,758, the special pro-
cesses in the making of this joint giving one of great durability. Fig. 3,759 shows the assem-
bly of drum, .down flow pipe, bottom or mud pipes and one section in position. The design
of these sections is such that the upper and lower headers form in themselves baffles thus
giving a two pass flow for the products of combustion.

SPECIAL BOILERS 2,117

In order to secure adequate heating surface without an unduly
long boiler, the furnace flues instead of running full length have
been shortened and connected with fire tubes.

Figures 3,746 and 3,747 show a single flue boiler connected in
this manner, and figures 3,748 to 3,751, a two furnace or Lan-
cashire type in which the breeches is shortened, forming a
common combustion chamber with its far side connected to a
mass of fire tubes.

3. WATER TUBE (OR PIPE)
BOILERS

The construction of water tube boilers is so varied that the
distinction between regular and peculiar forms is not so marked
as in the case of fire tube boilers. However, there are a few
examples of unusual construction that may be mentioned.

For instance, the Almy boiler, shown in figures 3,755 and
3,756 does not permit of its being classed as either a vertical or
horizontal boiler. It is, however, sectional and in its construction
some special fittings are employed, the general features being
mentioned under the illustrations.

Another peculiar form is the Taylor boiler, which in a way re-
sembles it, in that it is made up of a large number of pipes
placed in such positions as to make the assembly distinctively
different from the regular types.

The Taylor boiler is sectional, being composed of a number of sections
consisting of a number of vertical pipes connected in parallel by horizontal
headers and in series with the drum and bottom or mud pipes by vertical
connections. The details of construction are shown in figs. 3,757 to 3,759.

2,118

SPECIAL BOILERS

^ 0) •

<y ^^ ^

«- Cd
^^ «

<5^ w

S^f

»H CU O

CO cu ctf

• dJ >

H

h

Q

<

s
.s
§

a;
P.

O O

ctJ a
0) w

O r^

4->

I

0 r-J

5 g

^

SPECIAL BOILERS

2,119

The Fairbain boiler shown in figures 3,760 and 3,761 represents

an early attempt to combine internal firing with large water

capacity and at the same time without having recourse to shells

of large diameter, thus rendering them better adapted to high

pressures.

The principal advantage of this design is that it furnishes a large water
capacity in a space that would not admit of a Lancashire boiler of full
length. As a transition or intermediate type between the fire tube, and
combined fire tube and water tube boilers is the fire tube boiler with water
grate as used in the down draught system of combustion. While the water

"1

Fig. 3,762. — Herbert fire tube boiler with water tube down draught grate. The parts are:
A, fire tube boiler; B, water legs; C, circulating pipes; D, side tubes connecting water legs;
E, water tube grate; F, lower shal^ng grate; G, fire-brick bridge-wall; H, clean-out plugs;
K-L, brass clean- out plugs.

tubes serve primarily as grate bars , they form a very efficient heating surface
and may be considered as such in the classification. Fig. 3 ,762 is an example
of this type.

In operation the flames travel downward through the water tube grate
E, placed the same as the ordinary grate, and on which the coal is fired.
This grate is piped up with the boiler, and water circulates through it
and the piping.

A short distance imder the water tube grate a second common grate is

,120

SPECIAL BOILERS

placed, on which the spent fuel falls as it burns and as the upper fire is
worked. Between these two grates is a furnace of high temperature
in which the fuel, both soHd and gaseous, is consumed before passing to
the boiler. It will be seen that the conditions for the entire combustion of
the coal are thus fully met.

The heat of the gases is made available, thereby saving fuel, while heating
surface is added to the boiler and its natural circulation improved.

In the Lyons combined fire tube and water tube boiler, figure
,763, the water tubes are inserted for a different purpose.

WATER TUBES

^IG. 3,763. — Lyons combined fire tube and water tube boiler with one row of water tubes.
In construction the boiler consists of two main sections: the upper or shell with its contained
fire tubes, and the lower or saddles with their attached water tubes. The front and rear
heads extend below the shell, forming the saddles into which the water tubes are expanded.
The rear saddle extends twelve inches farther beneath the shell than the front saddle, so
that the water tubes incline upward toward the front end of the boiler, this inclination allow-
ing the water to be freely carried to the front end of the boiler and discharged through the
front saddle into the shell. The shell plates are cut away at the point of_ junction with the
saddles, thus giving a free and unobstructed path for the water in its circulation. There

are hand holes in both heads. Tile is suspended from the water tubes directly above the

grate by transverse rods resting on the top of the tubes.

lamely, 1, to improve the circulation, 2, to protect the shell
:rom the direct action of the fire, and 3, by aid of tiles, to pre-
sent the gases of combustion coming in contact with the colder
surfaces of the tubes until complete oxidation, thus obtaining a
sort of Dutch oven furnace effect.

SPECIAL BOILERS

2,121

A further development of this style boiler is shown in figure
3,764, which has two instead of one row of water tubes connecting
to manifolds or headers at the ends of the boiler.

The cut shows plainly both the fire and water tubes. Pile baffles are
placed above each row of water tubes giving the hot gases a tri-pass flow
from the furnace to the chimney.

Fig. 3,764. — ^Hawkes combined fire tube and water tube boiler with two rows of water tubes.

5. COMBINED SHELL AND
WATER TUBE BOILERS

This is a favorite combination used in the design of fire engine

2,122

SPECIAL BOILERS

Fig. 3,765. — Fox combined shell and water tube fire engine boiler. It consists of a simple
annular shell heavily stay-bolted throughout, and constitutes a watei legged fire box and
steam reservoir; the principal heating surface of the boiler consists of an outer and an inner
tube system. The outer system embraces the short manifold sections which completely
encircle the fire-box walls. The top end of each section is screwed and suspended from the
flanged part of the shell, and the lower end is stayed by direct connection with the leg of the
fire-box. The tubes are '"staggered" in their manifolds, thereby exposing the greatest
possible surface to the fire, and filling out the space due to the difference in the width of the
water-leg and steam space of the shell. The direct application of heat to the tubes causes a
natural and active upward current therein, which in turn induces a corresponding downward
movement of the water in the leg of the fire box, and promotes the flow into the feed pipes.
The inner tube system comprises those tube sections which extend to the upper limits of the
boiler, their number and arrangement being such as to completely fill the interior of the shell
above the space required for the combustion of the fuel. The construction of the vertical
inner tube system is simple, and consists of the required number of manifold sections, suit-
ably arranged to conform to the circular space occupied, the flat inner end of each upper
manifold being rigidly bolted to a heavy transverse beam, which in turn is supported in
suitable pockets secured to the upper part of the shell. At the top of the boiler, each sec-
tion has its own connection with the steam space, and it is easy to rehiove either one of the
sections separately without disturbing the others; or the entire inner tube system can he
raised cut of the boiler as a whole, after breaking the proper connections, all of which are
accessible. The current of steam and water carried over through the top connections of the
inner system is generally sufficient to keep the tubes clear of scale; and the point of discharge
and disengagement is brought down low, to prevent its mixture with the drier steam con-
tained in the highest part of the shell.

SPECIAL BOILERS

2,123

°o§oO§pSpg

° Oo^ n o^ o y o °^

•°b-°bPoPo

I

CO

^:^

g ^

2,126

SPECIAL BOILERS

2^V

« bOv-

. -. m

3 ^-=5

tsO .

J.W

d S) cT

^ :3 o

2'q,'-^

^a;g

'-"^ «

: IP

^t^.

d o w

jrj -l-> *

g^-8

^■£-°,

^ g(^

•^ bflir .

1 ^fel

^ cj o

o ^ G

^ -rt

0^8

■ If-S

: ^ fe'^.

"? feO

; p:+» .-

rt^

o^rtd

wh »-i -t^ a>

:^-2s-s

:^ c^ u

^|§5-S

-^ a <uT«

5 c^ a

03 O ;3 cJ

o "■♦^ ^^

^ ^4 <Ui^

:.^-l

-^^H^g

2^"^'^

d Jh P Oj

o <u *2 0<

o G'O w

te-HsSJ

p ■ ... -

^^w>

^ .-.-

W.— -M

-I t-i'rt ■"

* SJ^I

CO O -M c>

- rtJ3

2<;fe2

SPECIAL BOILERS

2,125

Figs. 3,769 and 3,770. — Silsby combined fire tube and (Field drop) water tube fire engine
boiler, and detail (enlarged) of the Field drop tube. In construction, the fire box has
a series of circulating water tubes arranged in concentric circles and securely screwed into
the crown sheet. These drop tubes are closed at their lower ends by means of wrought iron
plugs welded in, and within each of them is placed a much smaller and thinner tube, which
latter is open at both ends. The cooler water in the boiler descends through the inner tube
and is thus brought directly into the hottest part of the furnace, whence, after being for the
most part converted into steam, it ascends through the annular spaces between these inner
and outer tubes. The gases of combustion pass from the fire box to the stack through
fire tubes, the lower ends of which are expanded into the crown sheet, and the upper ends
into the top head of the boiler.

2,126

SPECIAL BOILERS

'^^^

:3 Qi «

^^^ o

a> cj o

o ^ a

TO (U

Si. 2-^ fl

5 ^-^ '='

d O r! C4

C V, O rt

O <L>i ft

^ j:

STEAM HEATING BOILERS 2,127

CHAPTER 67
STEAM HEATING BOILERS

The conditions under which a boiler works in furnishing steam
for heating buildings are quite different from those encountered
in a power plant, hence, as might be expected, the construction
of a heating boiler is quite unlike that of a power boiler.

The chief points to be considered in design are:

1. Very low steam pressure;

2. Low rate of combustion;

3. Long intervals between firing;

4. Automatic draught control;

5. Adequate heating surface.

Accordingly the construction need not be so substantial to re-
sist internal pressure, as for power boilers, thus permitting the
use of cast iron.

Most heating boilers are built in sections of cast iron making a very
durable construction.

By building up a boiler from cast iron sections, the size may be varied
considerably according to the number of sections used, thus a multiplicity
of sizes is obtained without requiring numerous patterns. While this
reduces the cost of manufacture , it results in numerous instances of boilers
not properly proportioned for economy, especially in the vertical types.

2,128

STEAM HEATING BOILERS

25:1

The Heating Surface. — The author after a laborious exami-
nation of about one hundred boiler catalogues found that while
nearly all gave the grate area, very few gave the area of heating
surface (for obvious reasons).

While, for example, he found that in one size of the Vance
boiler 38 square feet of heating surface per square feet of grate is

Fig. 3,772. — Typical round vertical boiler showing general exterior appearance and fixtures.

provided, in another make boiler (the name ought to be printed
in large letters) only 8.3 square feet of heating surface is pro-
vided per square foot of grate. Of course, if coal cost nothing,
or the coal dealers paid for the privilege of delivering it to your
door, such allowance of heating surface might suffice, but

STEAM HEATING BOILERS

2,129

where there is any regard for economy an adequate amount of

heating surface will he provided.

If, instead of closing public buildings, or ordering lightless
nights to conserve the fuel supply, the authorities would pro-
hibit the manufacture of such wasteful apparatus as mentioned
above, a much more intelligent solution of the fuel problem
would be arrived at, and without inconvenience and annoyance

Fig. 3,773. — Sectional view of typical horizontal boiler showing sections and passages for the
now of the hot gases.

of the public. Although the low rate of combustion in a heat-
ing boiler permits a lower ratio of heating surface to grate area
no such ridiculous ratio as 8.3 to 1 should be used.

The usual construction of a vertical sectional boiler comprises
a base section containing the grate, a fire pot with space all
around for the water, and piled up on top of this is one or more

2,130

STEAM HEATING BOILERS

Figs. 3,774 to 3,777. — ^Effect of inadequate heating surface. This may be illustrated by taking
several kitchen hot water kettles of equal capacity, but of different diameters, so that the
area of the bottom or part exposed to the fire (heating surface) will say 8, 15, 20, and 25
square inches. _ Put the same quantity of water into each and place under each a bunsen
burner whose tip has an area of 1 square inch. When the burners are lit (assuming equal
flames) it will be noticed that only a very small portion of the flame will touch the bottom of
kettle Ko. 1, more will come in contact with No. 2, still more with No. 3, and all with
No. 4. The result is that Ko. 4 will begin to boil first, No. 3 next, then No. 2, and last No. 1.
Evidently it takes less fuel to heat No. 4 than any of the others, the waste being about in the
proportion indicated by the arrows. The same thing happens in a house heating boiler.
Don't blame the manufacturers because there are a lot of boilers like kettles Nos. 1 and 2
on the market — it's your fault. If you thought less about first cost, and more about your
coal bills you would buy a boiler like No. 4 kettle, and the cost of coal wouldn't be so high.

'~'^C^'* **' ^^t^

Fig. 3,778. — The principal reason why the tenants get no hot water. It's not the fault of the
manufacturer, he simply builds what the public is wilUng to pay for and does not worry
about the coal bills.

STEAM HEATING BOILERS

2,131

intermediate ''sections," and a

top or dome, thus several sizes

of boilers are listed all having

the same size grate.

Evidently the efficiency of such
apparatus will depend principally
upon the number of sections or
amount -of heating surface piled
up over the furnace and the
arrangement of these sections.
Accordingly if the purchaser be
interested in economy of fuel, he
will select a boiler which has an
adequate amount of heating sur-
face in proportion to the grate
area, and especially in view of the
ever increasing cost of fuel the
ratio of heating surface to grate
area should not be less than 25 to 1 .

Rate of Combustion. — In

steam boilers for power plants
which receive constant atten-
tion, coal is generally burned
at from 10 to 30 pounds per
square foot of grate per hour.
However, in heating boilers,
the conditions are different.
There is no fireman in con-
stant attendance, the practice
being to dump on the grate a
considerable quantity of coal
sufficient to last 6 to 8 hours
at a low rate of combustion.
This requires a deep fire pot
to hold the considerable depth
of fuel.

Fig. 3,779. — International boiler parts show-
ing circulation and travel of the hot gases.

2,132

STEAM HEATING BOILERS

For house heating boilers the standard combustion rate is taken at
4 pounds of coal per square foot of grate per hour, but for larger boilers
such as used for large buildings where the firing is done more frequently
the grates are proportioned for a higher rate.

According to the American Society of Heating and Ventilation Engineers:
*'The grate surface to be provided depends on the rate of combustion
and this, in turn, on the attendance and draught, and on the size of the
boiler. Small boilers are usually adapted for intermittent attention and
a slow rate of combustion. The larger the boiler the more attention is
given to it and the more heating surface is provided per square foot of
grate.'*

DRAFT DOOR

CHAIN f FINGER BAR

GRATE RING GRATE BAR

DRAFT DOOR

BASE, FRONT
FRAME

ASH

^_;,,* X DOOl

DRAFT DOOR
FRAME

^ GRATE ,
CONNECTINS

^^^ / SHAKER

GRATE / CONNECTING
CONNECTING ROD

, COTTER PINS

Pig. 3,780. — National square base with names of parts.

ANGLE

LEVER

6 RATE LOCK

"The following rates of combustion are common for internally fired
heating boilers":

Sq. ft. of grate 4 to *

Lbs. coal per sq. ft. of grate per hour 4

10 to 18 20 to 30
6 10

The following table from Kent gives some proportions and
results that should be obtained:

STEAM HEATING BOILERS

2,133

Proportions and Performance of Heating Boilers

Low

Medium

High

#

boiler

boiler

boiler

1

square foot of grate should burn

3

4

5 pounds coal per
hour

"

" " " " " develop..

30,000

40,000

50,000 B.t.u, per
hour

" " " " will require —

15

20

25 square feet heat-
ing surface

" " " " " supply

120

160

200 square feet ra-
diating surface

Fig. 3,781. — Gas burner and manifolds for square fire pots. The burners are mounted com-
plete with air mixers and orifice spuds. In installing, the burners are placed on top the
grate bars and gas connection made through the grate bars and out through ash pit.

Points on Boilers. — In the selection of a boiler it is well to
examine closely the details of construction. A good design
should embrace the following features:

1. There should be not less than 25 square feet of heating sur-
face per square foot of grate area.

If ma,nuf acturers would stop talking so much about "prime" or direct
and indirect heating surface, and state the total amount of heating surface
provided per square foot of grate, and its arrangement, the purchaser

2,134

STEAM HEATING BOILERS

would be more enlightened, especially the better informed, and less printer's
ink and paper would be wasted.

2. The passages through which the hot gases traverse the
heating surface should be so arranged that they have the proper

'MONO DIVISION

SMALL DIVISION

MULTI DIVISION

length of travel (guided by baffles or
equivalent) and come in contact with
all the heating surface, that is, short
circuiting should be avoided.

The proper length ®f travel will depend on the
arrangement of the heating surface. There are

Figs. 3,782 to 3,784. — Division of the hot gases. For equal
travel of the gases over the heating svirface the mono-
divisional arrangement of fig. 3,782 is very wasteful.

As the gases are spUt up into more divisions as in figs.
3,783 and 3,784 each being surrounded by heating sur-
faces, evidently (assuming adequate combustion
chamber) more heat is absorbed and the stack temper-
ature reduced , because the gases come into contact with
a larger amount of heating surface per foot of travel.
It follows then that the less the division of the gases,
the longer must be the travel of the gases, for equal
efficiency.

STEAM HEATING BOILERS

2,135

three cases, 1, non-division^ small division, and mult i- division of the
gases, as shown in figs. 3,785 to 3,787. Evidently the first arrangement
requires numeruos passes for the gas to travel for proper absorption of heat,^
whereas with the second or third arrangement a short travel will suffice,
the length of travel depending on the degree of division of the gases as
shown in the figures.

SMALL DIVISION

rffffiifffi

mtiiffffviif

ffffffMffflMf

Figs. 3,785 to 3,787. — The efficiency of the heating surface does not depend on the length of
travel, but on the ratio of the cross sectional area of the passage to its length and the arrange--
ment or disposition of the surface with respect to the hot gases. In a vertical tubular
boiler for instance there may be only one large and long tube as in fig. 3,785, and the tem-
perature of the gases escaping at the end of the tube will assume a certain value depending
upon the rate of combustion and the efficiency will depend on these values. The single tube
of fig. 3,785 may be replaced by several smaller and shorter tybes as in fig. 3,786, or a still
larger number of very small and very short tubes as in fig. 3,787, the ratio of length to diam-
eter (or cross sectional area) being the same in each case, and there will not be any loss of
ftfficiency. That is by properly proportioning the size and number of the tubes. Any
length tube may be used without increasing the stack temperature.

3. For a given length of travel of the hot gases the efficiency
of the heating surface decreases with the number of turns, as in
figures 3,788 and 3,789.

2,136

STEAM HEATING BOILERS

3u.

QUI a.

5<

''in

.--sS^K

ill "?s -m^^^^

3 o H

sa^Nboo a:3iin3HiD x«ohs

STEAM HEATING BOILERS

2,137

Whenever the direc-
tion of flow is changed,
centrifugal force causes
the steam of hot gases to
leave one surface and pile
up on the other, short
circuiting the abrupt
corners.

4 . The combustion
chamber or fire pot
should be large so as to
obtain good combus-
tion.

This involves for equal
grate areas, and equal
intervals between firings,
a larger fire pot for high
than for low combustion
rates, in order to provide
space for the larger charge
of fuel at each firing.

5. The fire box
should be proportioned
according to the rate
of combustion, and in
the smaller sizes should
have considerable
depth below the firp
door in order to hold
sufficient charge for
from 6 to 8 hours
operation without at-
tention.

Pig. 3,791. — Williamson underfeed boiler. In construction^ there is connecting with the coal
chute a funnel shaped hopper, with its feed opening outside of the boiler proper. By means
of a piston, which slides in this coal chute, and a light, wooden lever, which operates the
plunger, coal which has been placed in the hopper is easily pumped through the chute,
up onto the grate and underneath the body of burning coal. The fire is pushed upward
and outward, and the fresh coal is thus surrounded on all sides and the top by fire.

2,138

STEAM HEATING BOILERS

3 Lb. RATE

4 LB. RATE

5 LB. RATE

Figs. 3,792 to 3,794. — The depth of the fire pot should increase with the rate of combustion in
order not to reduce the size of the combustion chamber. The figures show the relative
amounts of coal thrown into the furnace at each firing for the 3- , 4- and 5- pound combustion
rates with equal intervals between firings and equal grate area. Hence, for different atings
on one size grate, the higher the rating the deeper should the fire pot be, to avoid decreasing
the size of the combustion chamber.

CHECK
DAMPER

INTERMEDIATE
SECTION (TOR)

DOME

(TOP section)

INTERMEDIATE ,
SECTION (BOTTOM)

CONNECTION

FIRE POT

Figs. 3,795 to 3,800. — Parts of Magee boiler above the base showing fire pot interrnediate
sections, dome, damper, and ^ush nipple. In construction, the corner sheet is cast
integral with the fire pot whose interior sides are corrugated to increase the heating surface.
The parts are joined together by push nipples.

STEAM HEATING BOILERS

2,139

Fig. 3,801. — United States "Capitol" horizontal boiler showing mixing chamber and ignition
wall. In operation, the volatile gases pass from the furnace into a mixing chamber through
two horizontal openings at the top and in the back or bridge wall of the furnace. This
mixing chamber back of the furnace is formed by the bridge wall at the front and an ignition
wall of fire brick at the rear of the mixing chamber. Because of the continuous volume of
burning gases pouring from the furnace through the bridge wall and against this ignition
wall it is constantly m?intained at a temperature of approximately 1,600 degrees or about
400 degrees above the ignition point, the temperature at which these gases burn. All the
gases from the furnace must pass through this mixing chamber, and while they enter the
mixing chamber through two horizontal openings, their escape. from the mixing chamber
to the combustion chamber at the rear of the boiler is through a long vertical opening in
the ignition wall, the area of which is slightly less than the area of the two horizontal openings
into the mixmg chamber. It is claimed that the effect of this arrangement ia a congestion
and intermixture of burning gases within the mixing chamber in contact constantly with the
ignition wall, which is maintained at a temperature above the ignition point of the gases.

Fig. 3,802. — Push nipple used to join together sections of cast iron boilers. The nipple is
accurately machined and has a slight taper so that when forced into the opening in the
sections, by drawing the sections together by means of a rod a tight joint is obtained.

Fig. 3,803. — Gilt edge water back attachment for hot water supply.

2,140

STEAM HEATING BOILERS

6. There should be a wide door at the level of the grate and
just high enough to permit removing clinkers; it is called the
slice door.

7. The grate should be of the shaking and dumping type,
easily accessible for repairs, and of a standard make so that
duplicate parts may be obtained.

8. The ash pit should be large and deep so that it will hold a
large quantity of ashes.

SURNED OUT
GRATE BARS

Fig. 3,804. — Usual condition of the ash pit when the owner cannot put off taking up the ashes
any longer. Note the burned out grate bars due to letting ashes accumulate in the ash
pit. The illustration does not show the new grate just ordered from the plumber, but it is
on the way.

With the inferior and careless attention (or rather non-attention) usually
given to house heating boilers, ashes are allowed to accumulate until they
are flush with the grate bars and are then only removed because, they
interfere with the draught. Of course, where the owner does his own firing
and can stand the expense of frequent grate renewals, he may adopt this
method of handling the ashes.

STEAM HEATING BOILERS

2,141

8. There should be a positive circulation of water and suffi-
cient liberating surface and steam space provided to prevent
priming or unsteady water level.

9. The ratings of heating boilers as given in manufacturers*
catalogues may be as a rule safely accepted, but the efficiency
of the apparatus should be seriously questioned.

The amount and arrangement of the heating surface, size of combustion
chamber and grate area should be thoroughly investigated.

Fig. 3,805. — Gorton arop tube magazine feed vertical boiler, designed especially for soft coaL
In construction, the boiler is made in two parts, the tubular part, or boiler shell, is directly
over the fire, and the lower part, or the water leg, surrounds the fire. They are connected
together by the two circulation pipes, one in the front and one in the back of the boiler. The
lower part of the shell extends down into the upper part of the water leg, and the space
between the shell and the water leg is used for the coal reservoir and coking chambers.
Ihe reservoir is divided into four compartments, which form the coking chambers, in which
the coal IS C9ked. The fire pot is so constructed that sufficient additional air is drawn
through the ring at the lower edge of the coking chambers to ignite the gases arising from the
coking process, giving good combustion.

2-142

STEAM HEATING BOILERS

Figs. 3,806 to3, 812. — Method of assembling a horizontal boiler. First comesthe base, fig. 3,806.
It is in four main pieces which are bolted together; fig. 3,807, the grate bars are dropped
into their sockets; fig. 3,808, after fastening grate shaker connections, the grate is tested

STEAM HEATING BOILERS

2,143

Construction Details. — A large proportion of the small and
medium size boilers are made of cast iron. This material not
only being very durable, but lends itself to flexibility of design,
the sectional method of construction permitting boilers to be
shipped knocked down and carried through narrow openings in
buildings.

Figs. 3,806 to Z, ^12. —Continued.

by shaking, the back half is being operated fig. 3,808; the first section is lifted on and slid
into place fig. 3,809; push nipples are inserted and another section placed in position fig.
3,810; the four short tie bolts are then tightened; in the last section is being put in position
fig. 3,811, and boiler erected is shown in fig. 3,812.

2,144

STEAM HEATING BOILERS

Fig. 3,813 .—Monitor coil boiler.
In type, this is a combined
shell and water tube boiler.
The cut shows plainly the
general construction , thus re-
quiring no description. The
form of heating surface is
very efficient.

Figs. 3,814 to
3,818. — Inter-
national base,
ash pit door,
drop frame ,
grate gears and
shaker.

STEAM HEATING BOILERS

2,145

J?ase.— This acts as a support for the fire pot and heating sections of
the boiler. It should be so proportioned as to form a deep, commodious
ash pit with a large ash door.

Usually a draught door is placed in the middle of the ash door, but in
some designs, it is found on the side. This draught door should be balanced
so accurately and work with such ease that it will open and close with the
slightest variation of the steam pressure acting on the regulator.

2,146

STEAM HEATING BOILERS

The grate is located in the top of the base and is an important part of
the apparatus. It should permit of both shaking and dumping, be easily
accessible for repairs or renewal. Figs. 3,814 to 3,832 shows a typical base
with ash and draught doors as constructed for a round, vertical boiler.

Fire Pot, — This is a most vital part of the boiler because, especially

on account of the inadequate
heating surface usually pro-
vided and the fact that the
fire pot heating surface is more
efficient than that further re-
moved from the fire, the larger
the fire pot heating surface
and its coal capacity, together
with proper combustion space
and ample water passages, the
more satisfactory will be the
boiler's performance.

The fire pot in vertical
boilers is usually made in a
single casting, corrugations
sometimes being provided to
increase the heating surface.

Fig. 3,833. — Spencer double tube magazine feed
horizontal boiler showing general construction.

Fig. 3,834. — Ga^-, and u. U i Ua\cl m Spencer double
tube boiler, showing water divided into annular
streams between the outer and inner tubes with
heating surface on both sides. This arrangement
renders the heating surface very efficient.

In horizontal boilers it is
built up from the sections, and
also in some vertical boilers
the fire pot is in several pieces.
In the side openings are pro-
vided for the fuel and slice
doors, the bottom of the slice
door being on a level with the
grate.

Intermediate Sections. —

Superposed on top of the fire
pot of vertical boilers are one
or more intermediate sections
(sometimes more), consisting
of hollow castings containing
the water to be heated, and
whose exterior forms heating
surface.

Flue passages of proper area
are provided through these
castings, being staggered in
adjacent sections so as to lead

STEAM HEATING BOILERS

2,147

the gases in a roundabout way in traversing the heating surface, thus avoids
ing more or less short circuiting.

The practice of listing several sizes of boiler according to the number
of intermediate sections piled up on the fire pot, all having the same size
grate cannot be too strongly condemned; that is, by assuming different
rates of combustion and adding a little extra heating surface, the rated radia-
tion capacity is increased 50% or more. As a matter of fact, for house

n

FK'- .."'■■ fl3,836. — ^'Half sections of Ideal horizontal heater showing 1
and circulation (fig. 3,836).

.3,835),

heating boilers there is in general a particular rate of combustion (depend-
ing upon the intervals between firing, available draught, kind of coal,
etc.), that will give the best all round satisfaction. If this rate of com-
bustion be say 4 pounds per square foot of grate per hour and the capacity
of fire pot be proportioned for 8 hour intervals between firings, evidently
a different rate of combustion would be required for increased radiation
capacity, or else a larger grate.

2,148

STEAM HEATING BOILERS

i ^ o '

:^?s:l:^^^a:

» •

I •
I I

•^•;*:'Vt--^';'^.t.--.-j;;^::sv:d

Zee
<o

CCQ

■S^ixfe^ir^

E^:

?^ o ? o -- 05

j'Q o g
w 5 (U .4:!_^
g (U w wi3

'0.0 5:J:S^ }r?

G< 0) Q. O 1>
• to «>. J3 fli

^ 5^ S I' cCQ

.D0+-> C ^N O

•fill I 8

r< ^O o t'S ^

" *-« cx-C h

g (DIM IN -_5

^ o a e ti-S

^ -,-> p, 0) <U w ?^

STEAM HEATING BOILERS

2,149

Fig. 3,839. — Gurney down draught boiler. Features: Separate half sections connected
to top and side drums, cast iron sections in place of the usual one-piece castings, effective
heating surface, accessibility for cleaning, steady water line, smoke consuming.

Fig. 3,840. — Gurney sectionai uuncr ciiuwing ucaLing bunaue, luug hic iravel and horizontal
arrangement of water tubes. Cut also shows method of dividing each section into half
sections — a construction which insures freedom from breakage through sudden expansion,
or contraction.

2,150 STEAM HEATING BOILERS

Increased capacity with the same size grate, means, not only a higher
rate of combustion, but in order not to decrease the 8-hour interval between
firings, a larger quantity of coal must be put on at each firing and this
means a deeper fire pot to hold the excess coal, and a higher available
draught in order 1, to maintain the increased rate of combustion, and 2, to
force the air through the greater depth of fuel.

In the selection of a heater these items should be considered, also that
whereas cast iron heaters are more durable than wrought iron heaters,
wrought iron is a better conductor of heat than cast iron, thus for equal
efficiency more heating surface should be provided for cast iron than for
wrought iron.

Fig. 3,841. — Gumey sectional boiler with bridge wall section and combustion chamber.

In the case of a vertical cast iron boiler, the author would recommend a
high boiler consisting of several intermediate sections in preference to a
low boiler without these sections, because the ratio of heating surface to
'grate area is increased. In support of this advice it is only necessary to
quote the results obtained from tests (as given in one manufacturer's
catalogue), several cast iron boilers all having the same size grate, but with
different number of sections:

STEAM HEATING BOILERS

2,151

Steam Heating Boiler Tests

Fuel

Area

Number

Steam

Number

anthracite

of

of

produced

8 hour

of

pounds per

grate

sections

per pound

rating

boiler

square foot

square

including

of

square feet

of grate

feet

dome

coal

0

4.39

1.23

1

7.5

200

1

5.12

1.23

2

8.

250

IV2

5.28

1.23

3

8.5

275

2

5.44

1.23

4

9.

300

Fig. 3,842. — International steam dome showing water gauge, gauge cocks, steam gauge,
damper, safety valve, automatic diaphragm regulator, and clean out door.

Since the number of sections as listed includes the top or dome, boiler O,
had no intermediate sections. It will he noted that the evaporation in
this boiler was only 7.5 pounds per pound, of coal, and that even with the
rate of combustion increased with the addition of intermediate sections,
the evaporation increased from 7.5 to 9 pounds. It is simply a question

2,152 STEAM HEATING BOILERS

of whether the purchaser prefers a cheap boiler and big coal bill, or an
expensive boiler and small coal bill — that is for him to decide.

The ratio of heating surface to grate, according to Kent is given for low,
medium and high boilers, as 15, 20 and 25 to 1 , where the rate of combustion
is respectively 4 and 5 pounds of coal per square foot of grate per hour.

The author believes that in no case should there be less than 25 square
feet of heating surface per square foot of grate, in order:

1. To obtain high efficiency under normal operation.

2. To permit forcing in extreme cold weather without material loss of
efficiency.

3. To obtain quicker response especially in starting the fire.

U

Fig. 3,843. — Ideal syphon steam regulator.

Steam Dome. — This section is placed on top of the inter-
mediate sections in a vertical boiler and acts as a cover with an
outlet to smoke stack and enclosed space for steam and water.
In some designs the dome is really two sections cast in one
piece that is two water spaces with a smoke space between.

The dome is usually made of larger diameter than the water section to
increase the extent of the liberating surface and provide ample space for
the steam so as to avoid priming.

Automatic Control. — In order that steam may be main-
tained at a constant pressure during the long intervals when the
boiler is unattended, some method of automatic control of the

STEAM HEATING BOILERS

2,153

Fig. 3,844. — National boiler, sectional view showing interior construction and location of
nipples.

2,154 STEAM HEATING BOILERS

fire is essential. This is accomplished by means of a diaphragm
regulator as shown in figure 3 ,805 .

In construction, two oval shaped castings form the case of the regulator,
the upper one inverted and bolted to the lower one with a rubber diaphragm
between. The lower casting is connected to the boiler (preferably below
the water line), so that the steam pressure acts on the lower side of the
diaphragm.

The upper casting has an opening in the center through which is placed
a small plunger, whose lower end rests on the diaphragm and the upper end
is bolted and pivoted to a long lever as shown. One end of the lever
is connected by chains to the draught door and the other to a damper
in the stack.

An adjustable weight is adjusted so that when there is no steam on the
boiler it will push down the diaphragm and elevate the end connected to
the draught door, which opens this door wide.

Fig. 3,845. — Three piece fire pot of National boiler showing corrugated walls to augment
heating surface.

DETAILS AND STRENGTH OF CONSTRUCTION 2,155

CHAPTER 68
DETAILS AND STRENGTH OF CONSTRUCTION

Construction Rules. — Manufacturers, engineers and steam
users in general have devoted a vast amount of time and attention
to the study of steam boilers. Much has been written and
discussion upon the subject is frequently taking place among
engineering societies, especially with reference to the strength of
parts.

Formerly there has been a great lack of uniformity in the rules by
different writers and by legislation.

In marine practice, boilers for merchant vessels must be constructed ac-
cording to the rules and regulations prescribed hy the Board of Supervising
. Inspectors of steam vessels; in the U.S. Navy, according to rules of the
navy department, and in some cases according to special acts of Congress.

In some states such as Massachusetts and Ohio, and in some cities, for
instance, Philadelphia, the construction must conform to local laws, but
in many places there are no laws, the matter being left to the individual
engineers and boiler makers.

Lately there has been a great effort toward standardizing
construction, due to the activity of the American Boiler Manu-
facturers Association, American Society for Testing Materials,
and chiefly to the work of the American Society of Mechanical
Engineers, which in 1915 issued its boiler code, containing rules
of construction and which is now the generally accepted standard,
a digest of these rules being given in this chapter.

2,156 DETAILS AND STRENGTH OF CONSTRUCTION

Boil'er Plates. — This term was formerly used to denote supe-
rior qualities or brands of wrought iron rolled out into sheets,
suitable for constructing shells or drums of steam boilers, but
at present mild steel is the standard material.

A disadvantage of iron is that the plates were much shorter and narrower
than can now be had in mild steel, because steel plates have no grain or
fibre, but are of uniform character, and can accordingly be rolled lengthwise
or crosswise as may be most conveniently done in the rolling mill. The
advantage of this is a reduction of the number of plates and riveted joints
comprising a shell.

The A.S.M.E. Code requirements for boiler plate are given in the
chapter on boiler materials:

Marine Rules — Boiler Plate.

Rule I, 1. — Every iron or steel plate intended for the construction or repairs of boilers to
be used on steam vessels shall be stamped by the manufacturer in the following manner:

At two diagonal corners, at a distance of about 8 inches from the edges, and at or near the
center of the plate, with the name of the manufacturer, place where manufactured, and the
number of pounds tensile stress it will bear to the sectional square inch, expressed in thousands.

Every iron or steel plate to be used in the construction or repairs of boilers for steamers
navigated under the provisions of Title LII, Revised Statutes, which will be subject to tensile
strain in said boilers shall be tested and inspected by an inspector duly authorized under the
provisions of said title, and such plates shall not be stamped until they have been tested by the
inspector, and each of such plates shall then be stamped by the manufacturer in the presence
of the inspector with the minimum number of thousand pounds tensile stress it will bear to the
sectional square inch.

All plates which conform to the physical, chemical, and other requirements prescribed by
these rules shall be stamped by the inspector near the manufacturer's stamp, with the official
stamp of the United States Steamboat-Inspection Service, and with the initials of his name and
a serial number. (Sec. 4430, R. S.)

Rule I, 2. — Plates may be tested and inspected at the mills for repairs to marine boilers
or to be carried in stock, the report of such test to be in duplicate, one copy to be furnished
through the supervising inspector to the local inspectors in the district where the purchaser
of such material is located, and the ether to the purchaser, who shall deliver a copy of the
same to the parties using the material, who, in turn, shall submit the same to the local inspectors
in the district where the material is to be used, before being assembled in the boiler. Steamers
carrying such repair material to be used in emergencies shall carry the record of each sheet of
such material on board. (Sees. 4430, 4431 , R. S.)

Rule I, 3. — Boilers built since February 28, 1872, of material stamped and tested according
to the requirements of section 4430, Revised Statutes, and having a record thereof in the office
of the local inspectors in the district where the boiler was built or intended to be used , may be
used for marine purposes, notwithstanding that such boilers may have been used for other
purposes, if in the judgment of the local inspectors they are deemed safe. (Sec. 4430, R. S.)

Rule I, 4. — Steel plates shall be made by the open-hearth process, except that steel for
plates to be used in the manufacture of boiler tubes may be made by the Bessemer process .

Open-hearth steel shall contain not more than .04 per cent of phosphorus nor more than
.04 per cent of sulphur.

The manufacturer shall furnish the inspector, with each order tested, a certificate stating
the process by which the steel was manufactured and a copy of the analysis of each melt.

DETAILS AND STRENGTH OF CONSTRUCTION 2,157

The Shell.— Although the heat transmitting power of steel
plate even of considerable thickness, when perfectly clean is
beyond anything demanded in boiler practice, it is a fact that
a very thin film of grease, or a coating of scale of many varieties
in composition covering a plate so retards the rate of flow of heat
through the plate as to cause its temperature to rise to the point
at which its tensile strength has become greatly lowered. This
results in burning or serious distortion from form, often pro-
ducing blisters, bulging and sometimes complete failure.

>

Marine Rules. — Boiler Plate. — Continued

The analysis may, if deemed expedient by the Supervising Inspector General, be verified at
the expense of the manufacturer. (Sees. 4405, 4430, R. S.)

Rule I, 5. — When the tensile strength determined by the test is less than 63,000 pounds,
the minimum elongation shall be 25 per cent for plates three-fourths inch and under in thickness
and 22 per cent for plates over three-fourths inch in thickness. The quench bend specimen shall
bend through 180° around a curve the radius of which is three-fourths the thickness of the speci-
men. When the tensile strength determined by the test is 63,000 pounds or greater the mini-
mum elongation shall be 22 per cent for plates three-fourths inch and under in thickness, and
20 per cent for plates over three-fourths inch in thickness. The quench bend specimen shall
bend through 180° around a curve the radius of which is one and one-half times the thickness of
the specimen. (Sec. 4430, R. S.)

Rule I, 6. — The tensile strength shall be not less than 45,000 pounds per square inch. The
elongation shall be not less than 15 per cent. The reduction of area shall be not less than 15
per cent for 45,000 pounds tensile strength, and for each increase of 1 ,000 pounds tensile strength
up to 55,000 pounds, an addition of 1 shall be made to the required percentage of reduction of
area. The bend test specimen shall bend cold through 90° around a curve, the radius of which is
not greater than one and one-half times the thickness of the specimen. (Sec. 4430, R. S.)

Rule I, 7. — Tension test specimens shall be milled with the following dimensions: Length
at least 16 inches, ends from 1>^ to 33^ inches wide by about 3 inches in length, and parallel
section at center 1 to 1 3^ inches wide by 9 inches in length. The percentage of elongation shall
be measured in a gauge length of 8 inches.

Where specimens are to be tested on the testing machines of the Steamboat-Inspection
Service, they shall be 1 inch wide at parallel section in center, and shall not exceed 2 inches in
width on the ends.

Bend test specimens shall be at least 12 inches in length and from 1 to 3^^ inches in width,
and the full thickness as rolled. The edges may be planed. The corners shall not be rounded,
but the sharpness may be removed with a fine file. After bending, the specimens shall show no
cracks or flaws on the outside of the bent portion.

Bend test specimens for steel plates, before bending, shall be heated to a cherry red as seen
in the dark, and quenched in water the temperature of which is about 82° F.

Two tension and two quench bend tests shall be made from each plate as first rolled from
the billet, slab, or ingot.

The tension test specimens shall be cut from diagonal corners and the bend test specimens
shall be cut from the other diagonal corners.

The finished material shall be free from all injurious defects, and shall have a good and work-
manlike finish.

All measurements of test specimens and material shall be made by any standard American
gauge, and record of tests shall be submitted on Form 934. (Sees. 4405, 4430, R. S.)

2,158 DETAILS AND STRENGTH OF CONSTRUCTION

o-^ rt o S

W O "^ JL? <u

c/2 p o 43 a »H

c ^^ m '^ ^

. p

4f <1>

> a

9 4J HH

So w ., t

' s^^

^
^ c

>. rt

CD

o ^

^2 IS

C/3

o;

;-. u

^H rCl^ t3 -^ «-<

e ?i

o o

o c

^ ^.

tuO,

'^ bJO+^. 5^ c^

^ 5.^

c^

0) r^

o -Si

o;*^.^ C "^ '"

a

O »H-^

«^-

COT?

DETAILS AND STRENGTH OF CONSTRUCTION 2,159

boilers is narrowly limited. For boilers with shells exposed to the fire,
experience has set 3^ inch in thickness as a maximum where good water is
available, but for general practice ^/le inch in thickness is undoubtedly safer
and better.

Having adopted this limit of thickness in the shell of such boilers, calcu-
lation at once shows that either the diameter of the boiler must be small,
if moderately high pressures be desired, or in the presence of large diameters,
that low pressures must be carried. It further becomes evident that, being
limited in diameter for a desired pressure, the size of the tmit must also
be limited.

Courses. — The quality of the metal having been selected, the number
of courses or sections which is to make up the shell and the manner of riveting
these courses together must have thorough consideration.

Experience has demonstrated that it is always better to use one plate or
sheet for each circumferential course, thus enabling the bringing of the
longitudinal joint well up above the fire line in place of using one plate under
the entire length of the boiler, which necessitates, owing to its limit in size,
bringing the longitudinal joints down into the gas passage.

In earlier times, the number of courses of which a boiler was made, as
previously mentioned, was Umited by the power of the mills to produce large
plates. As the mills have grown, larger and larger plates have been made
and used. Experience enough has now been gained with large plates to
show that to preserve stiffness, courses should not exceed nine feet in
length and some designers prefer that a foot shorter be the limit.

Strength of the Shell. — To determine the strength of the
shell it is necessary to consider:

1. Steam pressure.

2. Diameter of shell.

3. Thickness of shell.

4. Efficiency of the joint.

In making the calculation, a section of the shell one inch long is taken and
its diameter is expressed in inches because the steam pressure, as indicated
by the steam gauge, means the pressure acting on each square inch. The
thickness of the shell is expressed as a fraction of an inch.

Now consider a one-inch section of a shell 10 inches in, diameter and
suppose the lower half to be filled with concrete and the upper half subjected
to a steam pressure of 50 pounds per square inch,- as in fig. 3,846.

Since the shell is 10 inches in diameter and one inch long, evidently the
area of the concrete surface exposed to the steam pressure is lOX 1=10
square inches, and as there is 50 pounds steam pressure acting on each square
inch, the total pressure on the concrete is
50X10 = 500 pounds

2,160 DETAILS AND STRENGTH OF CONSTRUCTION

This total pressure is plainly carried by the metal of the shell at A, and B ,
hence half of it is carried by A, and half by B.

For clearness, imagine half of the
shell to be cut away and the lower
half supported by two spring scales
as in fig. 3,847. Now, substituting
for the steam pressure 50-pound
weights, one placed on each square
inch of the concrete, evidently each
scale will indicate a pull of 250
pounds, that is, the metal of the
shell at A, is subjected to a force of
250 pounds tending to pull it apart ,
the same conditions existing at B ,
also. This force must be expressed
in pounds per square inch because
the tensile strength of the metal is
taken in pounds per square inch.

Now if the shell were one inch
thick there would be one square
inch area of metal in section A, of
the shell, hence the stress in the
shell would be 250 pounds per
square inch.

If, however, the shell be, say,
only }/s inch thick, the area of sec-
tion A, would be J^X 1 = 3^ square
inch, and the total pressure of 250
pounds would be carried by only 3^
square inch of metal, hence the
stress would be increased 8 times,
that is, the metal would be sub-
jected to a stress of

250-^3^ = 250X8=2,000 pounds
per square inch

Oues. What important
point remains to be con-
sidered ?

Ans. The riveted joint.

Fig. 3.848.— Half section of shell, illustrating
efficiency of the joint.

Oues. Why?

Ans. Because the strength of the joint is always less than
the strength of the plate.

DETAILS AND STRENGTH OF CONSTRUCTION 2,161

Oues. What is the ratio of the strength of the joint
to the strength of the plate?

Ans. The efficiency of the joint.

Evidently, from figs. 3,846 and 3,847, it is only necessary to consider
half of the shell to determine its strength , as shown in fig. 3 ,848 .

In boiler construction the ends of the plates are joined together usually
by riveting instead of welding. This seam or joint is necessarily weaker
than the solid plate because part of the metal of the plate is cut away for
holes for the rivets, hence the importance of considering this part of the
shell.

From figs 3,846 and 3,847 it is evident that only a half longitudinal
section of the shell need be considered in calculating the strength. Let
fig. 3,848 represent such section, and imagine that the thickness of the
plate end be reduced so that section J , will represent the strength of the
joint as compared with full section P, which represents the strength of the
solid plate. The efficiency of the joint then will equal area J -r-area P.
That is if the thickness of the plate be 3€ inch at P, and J's inch at J , the
respective areas are .25 and .125 square inches, and the efficiency of the
joint is .125 -T- 25 = .5, or 50 per cent. /

Example. — If the efficiency of the joint in fig. 3,848 be 50 per cent, and
the plate be 14 irich thick at section P, what is the stress on the metal at
. the joint?

The total pressure coming on the full plate section is 250 pounds and
since the plate is ^ inch thick, the stress on section P, is

250 -^ 34 square inch = 1 ,000 pounds

The efficiency of the joint being 50 per cent, the area of section J, will
be one half of P, or 3^ of 34 = 3^ square inch, hence

stress along the joint =250 -^ 3^ =2,000 pounds

The same result is obtained by dividing the stress on the solid plate by
the efficiency of the joint, that is, 1,000 -^ .5 = 2,000 pounds.

From the foregoing explanations the following rules must be
self evident .

1 . To find the total pressure to be carried by the shell

RULE. — Multiply the gauge steam pressure in pounds per square
inch by the radius of the shell expressed in inches.

2,162 DETAILS AND STRENGTH OF CONSTRUCTION

2. To find the stress coining on the shell

Rule. — Divide the total pressure {as found in 1) hy the area of the solid
plate per inch length of longitudinal section, and hy the efficiency of the
joint.

Expressed as a formula

stress in shell =

steam pressureXradius of shell

thickness of solid plate *X efficiency of joint

my'-

■•••:' ?co N CRETE v: ;- > V:

m-

%^:^;mm^:

%

;.;.-v^;=>V(-/---y:V::

^H

-' o V -•'**• •^'.•, • . • '!• '

^

^

BL.'-' -v : •■••'>"\ •••;-••:

^k.'=v-':^:-.:i^...:'.:

^^^^'i^^.o:--::*;:^;

BOILER

^^""^ ^^^^^^JL " '

SHELL

Bursting Pressure. — The

determination of the bursting
pressure is a ver}^ important
calculation, for upon this de-
pends the maximum pressure
to be allowed in operation.
The bursting pressure depends
upon:

1. Tensile strength of the
shell.

2. Thickness of the shell.

3. Radius of the shell.

4. Efficiency of the joint.

Considering a half section as in
fig. 3,849, evidently if the internal
pressure acting on the shell indi-
cated by the weights be sufficient
to bring a stress in the metal equal
to its tensile strength, the shell will
be pulled apart or ruptured as
shown, the rupture taking place at
the weakest section of the joint.

Now if the thickness of the
solid plate be 34 inch and the

Fig. 3,849.— Half section c^ shell, illustrating *NOTE—Smce one mch length of shell is

bursting pressure. The concrete indicates being considered, the thickness of plate and

uniform distribution of pressure due to the area of longitudinal sections are numerically

weights. the same.

DETAILS AND STRENGTH OF CONSTRUCTION 2,163

efficiency of the joint be 50 per cent, then the equivalent thickness of
solid metal where strength is equal to that of the joint is 50 per cent of
H = y8 inch.

If the tensile strength of the metal be 60,000 pounds per square inch^
y^ of this would be the corresponding force necessary to rupture joint, or

Vs of 60,000 = 7,500 pounds

That is, the total pressure necessary to burst the boiler is 7,500 pounds ^
acting on the half section, and since this pressure is distributed over an
area of 5 square inches, the equivalent steam pressure per square inch is

7 ,500 ^ 5 = 1 ,500 poimds

Accordingly, the following rule

1. To determine the bursting pressure

RULE. — Multiply the thickness of the shell (expressed in inches or
fraction of an inch), by the efficiency of the joint and by the tensile
strength of the metal. Divide the product by the radius of the shell and
the result will be the bursting pressure in pounds per square inch.

Factor of Safety. — Because of the disastrous consequences
which attend boiler explosions it is necessary that boilers be of
sufficient strength to withstand several times the maximum pres-
sure of operation or working pressure"^ .

The ratio of the bursting pressure to the working pressure is
called the factor of safety, that is

factor of safety = bursting pressure-r- working pressure

The Working Pressure. — The maximum pressure to be
allowed at which it is considered safe to operate a boiler depends
on:

1. Tensile strength.

♦NOTE. — The working pressure is the maximum pressure safe to carry on a boiler con-
sistent with the factor of safety employed in the design; it should not be confused with the
running pressure, that is, with the pressure ordinarily carried in running the engine. The
safety valve is usually set to blow off at the working pressure, hence, the running pressure
of necessity must be lower. If the working pressure of a boiler be 100 pounds and the
bursting pressure be 600 pounds, then the factor of safety is, 600-t-IOO =6.

2,164 DETAILS AND STRENGTH OF CONSTRUCTION

2. Thickness of the shell.

3. Radius of shell.

4. Efficiency of the joint.

5. Factor of safety.

Example, — What is the maximum allowable working pressure to be
carried on a boiler 50 inches in diameter, tensile strength 60,000 pounds,
plates ^ inch thick, efficiency of joint 87 per cent, factor of safety 5.

MAX. LOAD AT J . feo,000 X^j X 87% ^ 3^^^^ ^^3_

—25 INSr

WORKING PRESSURE

3,915-25 = 156.6 LB5

Fig. 3,850. — Half section of shell, illustrating method of determining the working pressure.

A tensile strength of 60,000 pounds corresponds to a stress of

60 ,000X % = 22 ,500 pounds

in a ^-inch plate per inch length of section, and for a factor of safety of 5
the maximum load allowable on the solid metal of the shell is

22,500-7-5=4,500 pounds

Considering the efficiency of 87 per cent of the joint, this load must
be reduced to

87 per cent of 4,500 = 3,915 pounds

not pounds per square inch, but the maximum allowable force tending

DETAILS AND STRENGTH OF CONSTRUCTION 2,165

to pull the metal of the shell apart. Since this force is distributed over
the radius of the shell or 50 -j- 2 = 25 inches (that is, 25 square inches, consid-
ering 1 inch length of shell) , the maximum allowable working pressure is

3,915 -^25 = 1563^ pounds

Expressed as a formula the problem becomes

., tensile strengthX thickness of plateX efficiency of joint
working pressure = radius of shellXfactor of safety

or using the usual symbols

«7 1 . T^ TXtXE

Working Pressure = j^^p

in which

T = ultimate tensile strength stamped on shell plates, pounds per
square inch.

t=minimimi thickness of shell plates in weakest course, inches.

E = efficiency of longitudinal joint or of ligaments between tube holes
(whichever is the least) .

R= inside radius of the weakest course of the shell or drum, inches.

F=factor of safety, or the ratio of the ultimate strength of the
material to the allowable stress.

Thickness of the Shell. — After figuring the size of a boiler
for a given ( apa.dty, about the first problem that confronts the
designer is to determine the proper thickness necessary for safety.
This' depends on:

1. Working steam pressure.

2. Radius ot the shell.

3. Efficiency of the joint.

4. Tensile strength of the plate.

5. Factor of safety.

The following example will serve to illustrate the method of
solving the problem.

2,166 DETAILS AND STRENGTH OF CONSTRUCTION

Example. — ^What thickness of shell is required for a 50-inch boiler suit-
able for 125 pounds working pressure, if the tensile strength of the plates
be 60,000 pounds, efficiency of joint 82 per cent, factor of safety 5.

The total pressure to be carried by the shell is equal to

radiusX working pressure = 25X 125 = 3 , 125 pounds

Since the factor is 5, the shell must be strong enough to withstand 5
times this load or

5X3,125 = 15,625 pounds

TOTAL PRESSURE = 25X125 = 3125

TENSILE STRENGTH
60,000 LBS.

Fig. 3,851. — Half section of shell, illustrating method of determining thickness of shell.

If the efficiency of the joint were 100 per cent, and with 60,000 pounds
•tensile strength, the thickness of shell would be

$
15,625 -^60,000 = .26 inch

Now, since the efficiency of the joint is only 82 per cent, the thickness of
the shell is

,26-7- .82 = .317 or say ^^e inches

According to the A. S. M.E. Code, the minimum thickness of boiler shell
plates, and dome plates after flanging, shall be as follows:

DETAILS AND STRENGTH OF CONSTRUCTION 2,167

Minimum Thickness for Boiler Plate (A.S.M.E. Boiler Code)

Diameter of Boiler

36

inches
or under

36

to

54 inches

54

to
72 inches

Over

72
72 inches

Minimum thickness of plates.

J^ inch

S/fg inch

^inch

3^ inch

Thus the calculated thickness comes within the limit of the table.

Riveted Joints. — The ends of the plate or plates forming a
course or band section of the shell are joined together by rivets,
and since part of the metal must be cut out of the plate to provide
holes for the rivets, the strength of the joint is always less than
that of the solid plate, though by the use of the more complicated
forms -of riveted joint, the strength of the latter can be made
almost equal to that of the solid plate.

The various forms of riveted joint have become well standard-
ized during the advance in the art of boiler making, and these
various forms may be classified as:

f single riveted
1 . Lap joints i double riveted
[ with cover plate

2. Butt and double strap

' double riveted
i triple riveted
i quadruple riveted
^ quintuple riveted

Oues. What is the difEerence between a lap and a butt
joint?

Ans. The plate ends overlap to form a lap joint and register
with each other to form a butt joint as shown respectively in
figs. 3,852 and 3,853.

NOTE. — The likelihood of failure by shearing of rivets and by tearing of the plate will
be equalized when the shearing strength of the rivets is equal to the tearing strength of the
plate between rivet holes. In the case of a lap joint the rivet will shear at only one section.

2,168 DETAILS AND STRENGTH OF CONSTRUCTION

0

Oues. What is the ob-
jection to a lap joint?

Ans. The plate end,
through which the rivets passs
being in different planes, the
pull is not direct, but tends to
twist the plates, frequently
causing them to bend as
shown in fig. 3,859, and
sometimes resulting in an
explosion.

The Hartford Steam Boiler In-
surance Co. criticise the lap joint
as follows:

"The fearful boiler explosion
at Brockton, Mass., was due to
an undiscoverable defect known
as a lap joint crack'. Although
there is nothing new about this
defect, which has been known
and recognized for many years
among boiler experts, yet the
terrible Brockton disaster has
attracted greater attention to it,
and the general interest that is
felt is well shown by the many
letters that we have received and
also by the numerous articles
that have appeared in periodi-
cals, both technical and general."

For the girth or circumferential
seam which runs around the
boiler there is no great objection
to the lap joint, but for a longi-
tudinal seam where the disposi-
tion of the metal is not such as
to resist so effectively the twist-
ing action, only the butt and
double strap joint should be used
on boilers for moderate or high
pressures.

DETAILS AND STRENGTH OF CONSTRUCTION 2,169

Ques. In designing a riveted joint what is the chief
object in view?

Figs. 3,854 and 3855.— Butt joint with two covers.

Figs. 3,856 and 3,857. — Lap joint with cover plate or offset strap. It is safer than the plain
lap joint but not as good as the butt joint with double strap .

Ans. To so proportion it that it will be equally strong against
failure by all possible ways of breaking.

2,170 DETAILS AND STRENGTH OF CONSTRUCTION

These are: 1, shearing of the rivets, 2,
tearing apart of the plate along the last row of
rivet holes, 3, crushing down of the metal in
front of the rivets, or the rivet itself, 4, shearing
of the metal between a rivet and the edge of
the plate (this is possible only in case of single
riveted joint), 6, a combination of any of these
items just mentioned.

Oues. What is the distance
between centers of adjacent rivets in
the same row called ?

Ans . The pitch , as shown in fig . 3 ,860 .

Oues. What is diagonal pitch?

Ans. It is, where there are two or
more rows of rivets, the distance between
the centers of diagonally Mjacent rivets,
as shown in fig. 3,860.

Ques. What is back pitch?

Ans . The distance between the center
lines of any two adjacent rows of rivets
measured at right angles to the direction
of the joint as shown in fig. 3,860.

Ones. What is the difference be-
tween single and double shear ?

Ans . Single shear occurs in one plane
as in a lap joint, and double shear in
two planes as in a butt and double strap
joint.

Ones. What is the advantage of
double shear ?

DETAILS AND STRENGTH OF CONSTRUCTION 2,171

Ans. The force necessary to shear a rivet in one plane as in
single shear is equal to the cross-sectional area of the rivet multi-
plied by its shearing strength, hence if it shear in two planes as
in double shear, the force necessary to shear the rivet is doubled.

In practice it is taken at 1^ to allow for imperfection of construction
whereby more force may be exerted on the rivet by one strap than by the
other.

Fig. 3,860. — Double riveted butt joint, illustrating pitch, diagonal pitch and hack pitch.

Oues, What is the efficiency of a riveted joint?

Ans. The ratio which the strength of a unit length of a riveted
joint has to the same unit length of the solid plate.

NOTE. — The e fficiency increases as the rivet diameter and pitch is increased; there is,
however, a practical limit to the increase of the diameter due to the difficulty of heading up
very large rivets, and a limit to the increase of the pitch due to the necessity of guarding against
eakage.

DETAILS AND STRENGTH OF CONSTRUCTION

Oues. How is the strength of
a riveted joint determined?

Ans. It depends on whether the
plate or the rivets be the stronger
of the two.

Theoretically in a properly designed
joint , the strength of the plate and that of
the rivets should be equal so that there
will be no more chance of failure in one
way than the other. However, in practice
since corrosion usually affects the plate
only, it is often considered good practice to
make the plate slightly stronger, so that
even after some wasting by corrosion the
joint may still be in fair proportion as to
the relative strength of plate and rivets.

How to Calculate a Riveted
Joint. — In determining the strength
of any form of riveted joint a unit
length or element of the joint is taken,
the length considered depending upon
the arrangement of the rivets and is
equal to the greatest pitch.

Evidently no further section need
be considered because the entire
seam is composed of similar elements
having the same symmetrical ar-
rangement of rivets and plate metal.

In calculating any riveted joint
there are these three things to be
determined:

NOTE. — "The investigation of the strength of
riveted joints by any simple theory is necessarily quite
imperfect, because we do not know in just what way
the stress is distributed through the remaining part of
the plate, nor through the section of the rivet, nor what
allowance to make for the f rictional grip of the joint."
— Durand.

DETAILS AND STRENGTH OF CONSTRUCTION 2,173

1 . Strength of the plate .

2. Strength of the rivet or rivets.

3. Efficiency of the joint.

The method of calculating the various riveted joints will now
be given.

Single Lap Joint. — This is the simplest and most inefficient

Fig. 3,863. — Single riveted lap joint, illustrating element of the seam to be considered in
determining the strength of the joint. The shaded portion ABCD is the element; its equ val-
ient A B C D' may also be considered as an element .

joint, and is made by lapping the plate ends a proper distance
and securing with a single row of rivets.

In fig. 3,863, ABCD, is the element of the joint to be considered. Evi-
dently, since R, has been cut out of the plate for the rivet, the solid metal
of the plate left to resist the pull is M+S, or since M+R+S is equal to the
pitch.

Strength of plate = thicknessX (pitch — Jmm. of rivet)X tensile strength;

or, as expressed with the usual symbols

Strength of plate = ^ (F—d) T (1)

2,174 DETAILS AND STRENGTH OF CONSTRUCTION

in which /= thickness of plate; P= pitch; (i = diameter of rivet, and T =
tensile strength.

Similarly

strength of rivet =^ section area of rivetX shearing strength
or expressed as a formula:

strength of rivet = .7854 d^XS (2)

in which .7854 </2= section area of rivet, and S = shearing strength.

Now, if the tensile strength of the plate be say 60,000 lbs. per sq. in.
of section, and say, 40,000 lbs. per sq. in. of section for the rivet, then

Shearing strength of rivet = ' tensile strength of plate, or

that is Q

S=|t (3)

Hence, substituting this value for S, in equation (2)

Strength of rivet = .7854 J^x? T = .524 d'' T (4)

o

Now, for equal strength of plate and rivet the values obtained in (1)
and (4) for strength of plate and rivet must be equal, that is

t (P—d) T = .524 d^ T
or (5)

t (P—d) = .524 c/2

The strength of the solid plate must be considered to determine the ef-
ficiency of the joint. Evidently

Strength of solid plate = thicknessXpitchXtensile strength =t PT (6)

Now, since efficiency of the joint = strength of joint -^ strength of solid
plate, and since strength of plate at the joint = strength of the rivet, then
form equations (1), (4) and (6).

^^ . t (P— ^) T = .524 d^ T

Efficiency^ ^ ^^ . -^p^

or reduced to lowest terms

^ „ . P—d 524 J2

Efficiency = -p- = -—^ (7)

DETAILS AND STRENGTH OF CONSTRUCTION 2,175

One item not considered in the calculations just given is the
strength of the plate against shearing between rivet and edge of
plate as shown in fig. 3,865.

This is guarded against by placing the rivet hole at a proper distance
from the edge of the plate, which by experience, is found to be about one
diameter solid metal, that is, 13^ diameters from edge of plate to center
of rivet hole.

Figs. 3,864 and 3,865. — Failures of riveted joints; fig. 3,864, fracture between rivets; fig. 3,865
split and double sheer between rivets and edge of plate. The first is caused by the rivets
being too close together, that is, not enough metal in the plate between rivet holes, and
the second is due to insufficient metal between rivet holes and edge of the plate.

In practice, the diameter of the rivet is taken at from 1.5 to 2.5 times the
thickness of the plate, the lower values being more commonly employed
with very thick plates on account of the difficulty of heading up excessively
large rivets, and the necessity of a moderate pitch to allow proper calking
to prevent leakage. In order, furthermore, to guard against danger of
rupture by crushing the upper limit, 2.5, should not be exceeded.

2,176 DETAILS AND STRENGTH OF CONSTRUCTION

The foregoing calculations are intended to illustrate the prin-
ciples involved, and if thoroughly understood there should be nc
difficulty in applying them to the more complicated joints.

The American Society of Mechanical Engineers has made an
exhaustive study of the subject and in its boiler code have
formulated rules for calculating the various forms of joint,
which will now be given.

^]

RIVETED JOINTS

According to

A.S.M.E. Boiler Code

EfiEiciency of Riveted Joints. — The ratio which the strength
of a unit length of a riveted joint has to the same unit length of
the solid plate is known as the efficiency of the joint and shall be
calculated by the general method illustrated in the examples
which follow:

In the examples the following notation is used:

r5 = tensile strength stamped on plate, lb. per sq. in.
< = thickness of plate, in.
&= thickness of butt strap, in.

P= pitch of rivets, in., on row having greatest pitch
d = diameter of rivet after driving , in . = diameter of rivet hole
a = cross-sectional area of rivet after driving, sq. in.
5 = shearing strength of rivet in single shear, lb. per sq. in., as given
in Par. 16, page 2,177

DETAILS AND STRENGTH OF CONSTRUCTION 2,177

S = shearing strength of rivet in double shear, lb. per sq. in., as given

in Par. 16
c = crushing strength of mild steel, lb. per sq. in., as given in Par. 15»
n = number of rivets in single shear in a unit length of joint
N = number of rivets in double shear in a unit length of joint.

Example 1. — Lap joint, longitudinal or circumferential, single-riveted
(fig. 3,866).

A = strength of solid plate = PX/Xr5

5 = strength of plate between rivet holes = (P — d)tXTS

C = shearing strength of one rivet in single sh.ea.T = nXsXa

Fig. 3,866. — Example of lap joint, longitudinally, and circumferentially single riveted.

A.S.M.E. Boiler Code. — Ultimate strength of materials used in computing joints.

12 Cast iron shall not be used for boiler and superheater mountings, such as nozzles,
connecting pipes, fittings, valves and their bonnets, for steam temperatures of over 450 deg.
Fahr.

14 Tensile Strength of Steel Plate. The tensile strength used in the computations for steel
plates shall be that stamped on the plates as herein provided, which is the minimum of the
stipulated range, or 55,000 lbs. per sq. in. for all steel plates, except for special grades having a
lower tensile strength.

15 Crushing Strength of Steel Plate. The resistance to crushing of steel plate shall be
taken at 95,000 lb. per sq. in. of cross-sectional area.

16 Strength of Rivets in Shear. In computing the ultimate strength of rivets in shear, the
following values in pounds per square inch of the cross-sectional area of the rivet shank shall be
used:

Iron rivets in single shear 38,000

Iron rivets in double shear 76,000

Steel rivets in single shear 44,000

Steel rivets in double shear 88,000

The cross-sectional area used in the computations shall be that of the rivet shank after
driving.

2,178 DETAILS AND STRENGTH OF CONSTRUCTION

P = crushing strength of plate in front of one rivet =</X/Xc

Divide By Cor D (whichever is the least) by A , and the quotient will be the
efficiency of a single-riveted lap joint as shown in fig. 3,866.

r5 =55,000 lb. per sq. in.
/=34 in. =.25 in.
F=l^ in. =1.625 in.
d="/f6in.=.6875in.
C=.3712 sq, in.
^-44,0001b. persq. in.

12,890 {B)
22,343 (A)

.c =95,000 lb. per sq. in.

A =1.625X.25X55,000 =22,343

5 =(1.625— .6875) .25X55,000=12,890

C = 1X44,000X.3712 =16,332

D = .6875X .25X95,000 = 16,328

= .576 = efficiency of joint

Fig. 3,867. — Example of lap joint, longitudinally and circumferentially double riveted.

Example 2, — Lap joint, longitudinal or circumferential, double-
riveted (fig. 3,867).

A = strength of solid plate = PX^Xr5

5 = strength of plate between rivet holes = {P — d) tXTS

C = shearing strength of two rivets in single shear = wX5Xa

Z) = crushing strength of plate in front of two rivets = wX^X/Xc

Divided, C, or D (whichever is the least) by A , and the quotient will be the

efficiency of a double-riveted lap joint, as shown in fig. 3,867.

DETAILS AND STRENGTH OF CONSTRUCTION 2,179

TS =55,000 lb. Tier sq. in.
/ =546 in. =.3125 in.
P =2% in. =2.875 in.
J=M in. =.75 in.
a =.4418 sq. in.
s =44,000 lb. per sq. in.

36.523 {B)

49,414 (A)

c =95,000 lb. per sq. in.
A =2.875X0.3125X55,000 =49,414 *
B =(2.875— .75) .3125X55,000 =36,523
C =2X44 ,000X .4418 =38,878
D =2X.75X. 3125X95,000 =44,531

= .739 = efficiency of joint

Example 3. — Butt and double-strap joint, double-riveted (fig. 3,

i n «i

Fig. 3,868. — Example of butt and double strap joint, double riveted.

A = strength of solid plate = PXtXTS

5 = strength of plate between rivet holes in the outer row = (P — d) tXTS

C = shearing strength of two rivets in double shear, plus the shearing
strength of one rivet in single shear = NXSXa-\-nXsXa

i) = strength of plate between rivet holes in the second row, plus the shear-
ing strength of one rivet in single shear in the outer row = (P — 2d)
tXTS+nXsXa

2,180 DETAILS AND STRENGTH OF CONSTRUCTION

£ = strength of plate between rivet holes in the second row, plus the crush-
ing strength of butt strap in front of one rivet in the outer row =
{P—2d) tXTS+dXbXc

7^ = crushing strength of plate in front of two rivets, plus the crushing
strength of butt strap in front of one rivet = NXdXtXc -\-nXdXbXc

G = crushing strength of plate in front of two rivets, plus the shearing
strength of one rivet in single shear = NXdXtXc-\-nXsXa

fi' = strength of butt straps between rivet holes in the inner row = (P — 2d)
2bXTS. This method of failure is not possible for thicknesses of
butt straps required by these rules and the computation need
only be made for old boilers in which thin butt straps have
been used. For this reason this method of failure will not be con-
sidered in other joints.

Divide J5, C, D,E, F,G or H (whichever is the least) by A , and the quo-
tient will be the efficiency of a butt and double strap joint, double-
riveted, as shown in fig. 3,868.

TS =55,000 lb. per sq. in. a = .6013 sq. in.

/ = ^in. =.375 in. 5 =44,000 lb. per sq. in.

6=5/i6in. =.3125in. - 5=88,000 lb. per sq. in.

P =VA in. =4.875 in. c =95,000 lb. per sq. in.
d=:^ in. =.875 in.

Number of rivets in single shear in a unit length of joint =1,
Number of rivets in double shear in a unit length of joint =2.

A =4.875X .375X55,000 =100,547

-B =(4.875— .875) .375X55,000 =82,500

C=2X88.000X.6013+1X44,000X. 6013 =132,286

D =(4.875— 2X. 875) .375X55,000+ 1X44.000X .6013 =90,910

£ =(4.875— 2X. 875) .375X55,000-f.875X .3125X95,000 =90,429

F =2X.875X.375X95.000+.875X.3125X95,000 =88,320

G=2X.875X.375X95,000+1X44,000X .6013 =88.800

82.500 (B) CO «; • t • ■ .

- = .82 = efficiency of jomt

100,547 (A)

Example 4, — Butt and double strap joint, triple-riveted (fig. 3,869).

A = strength of solid plate = PXtXTS

jB = strength of plate between rivet holes in the outer row = (P — d) tX TS

C = shearing strength of four rivets in double shear, plus the shearing
strength of one rivet in single shesiT = NXSXa^-nXsXa

D = strength of plate between rivet holes in the«second row, plus the shearing

DETAILS AND STRENGTH OF CONSTRUCTION 2,181

strength of one rivet in single shear in the outer row = (P — 2d)
tXTS+nXsXa

£ = strength of plate between rivet holes in the second row, plus the crush-
ing strength of butt strap in front of rivet in the outer row = ( P — 2d) t
XTS+dXbXc

p = crushing strength of plate in front of four rivets, plus the crushing
strength of butt strap in front of one rivet = NX dXtXc-{-nX dXbXc

C = crushing strength of plate in front of four rivets, plus the shearing
strength of one rivet in single shear = iVX^X^Xc+wX.^Xa

Divide B, C, D^E^ F or G (whichever is the least) by A , and the quotient
will be the efficiency of a butt and double strap joint, triple-riveted, as
shown in fig. 3,869.

IG. 3,869. — Example of butt and double strap joint, triple riveted.

TS =55,000 lb. per sq. in.
/ = H in. =.375 in.
& =5^5 in. =.3125 in.
P =6}^ in. =6.5 in.

J=i3/i-'gin. =.8125in.

a =.5185 sq. in.
J =44,000 lb. persq. in.
5 =88,000 lb. per sq. in.
c =95,000 lb. per sq. in.

Number of rivets in single shear in a unit length of joint = 1 .
Number of rivets in double shear in a unit length of joint =4.

2,182 DETAILS AND STRENGTH OF CONSTRUCTION

A =6.5X.375X55.000 =134,062
5 = (6.5— .8125) .375X55,000 = 117,304
C=4X88,000X.5185+1X44,000X .5185 =205,326
Z> = (6.5— 2X. 8125) .375X55,000+1X44,OOOX.5185 =123,360
£ =(6.5— 2X. 8125) .375X55,000-1- .8125X.3125X95,000 =124,667
F=4X.8125X.375X95,OOOH-1X.8125X.3125X95,000 =139,902
G=4X.8125X.375X95,000-|-1X44,OOOX.5185 =138.595
117,304 iB)

134,062 (A)

= .875 = efficiency of joint

Fig. 3,870. — Example of butt and double strap joint, quadruple riveted.

Example 5. — Butt and double strap joint, quadruple riveted (fig. 3,870.)

A = strength of solid plate = PX/Xr5

^ = strength of plate between rivet holes in the outer row = (P — d)tXTS

C = shearing strength of eight rivets in double shear, plus the shearing
strength of three rivets in single shear

D

--NXSXa+nXsXa

strength of plate between rivet holes in the second row, plus the shear-
ing strength of one rivet in single shear in the outer row = (P — 2d)
tXTS+lXsXa

DETAILS AND STRENGTH OF CONSTRUCTION 2,183

£ = strength of plate between rivet holes in the third row, plus the shearing
strength of two rivets in the second row in single shear and one rivet
in single shear in the outer row= (P — ^d)V><^TS-{-nXsy,a

F = strength of plate between rivet holes in the second row, plus the crushing
strength of butt strap in front of one rivet in the outer row = (P — 2d)
tXTS+dXbXc

G= strength of plate between rivet holes in the third row, plus the crushing
strength of butt strap in front of two rivets in the second row and one
rivet in the outer row = (P— 4f/) tXTS+nXdXbXc

JZ" = crushing strength of plate in front of eight rivets, plus the crushing
strength of butt strap in front of three rivets = NXdXtXc+nXdXbXc

7 = crushing strength of plate in front of eight rivets, plus the shearing
strength of two rivets in the second row and one rivet in the outer
row, in single shear = NXdXtXc+nXsXa

Divided, C, D, E, F, G, H or I (whichever is the least), by A, and the
quotient will be the efficiency of a butt and double strap joint quadruple-
riveted, as shown in fig. 3,870.

TS =55,000 lb. per sq. in.
< = 3^ in. =.5 in.
6 =1^6 in. =.4375 in.
P = 15in.
rf = i5^6in.=.9375in.

a =.6903 sq. in.
5 =44,000 lb. per sq. in.
5 =88,000 lb. per sq. in.
c =95,000 lb. per sq. in.

Number of rivets in single shear in a unit length of joint =3.
Number of rivets in double shear in a unit length of joint =8.

A.S.M.E. Boiler Code. — Riveting and Calking.

253 Riveting. Rivet holes, except for attaching stays or angle bars to heads, shall be
drilled full size with plates, butt straps and heads bolted in position; or they may be punched
not to exceed \i in. less than full diameter for plates over ^ in. in thickness, and y^ in. less
than full diameter for plates not exceeding i^ in. in thickness, and then drilled or reamed to
full diameter with plates, butt straps and heads bolted in position.

254 After drilling rivet holes, the plates and butt straps shall be separated and the burrs
removed.

255 Rivets. Rivets shall be of sufficient length to completely fill the rivet holes and form
heads at least equal in strength to the bodies of the rivets.

256 Rivets shall be machine driven wherever possible, with sufficient pressure to fill the
rivet holes, and shall be allowed to cool and shrink under pressure.

CA ULKING

257 Caulking. The caulking edges of plates, butt straps and heads shall be beveled. Every
portion of the caulking edges of plates, butt straps and heads shall be planed, milled or chipped
to a depth of not less than K in. Caulking shall be done with a round-nosed tool.

2,184 DETAILS AND STRENGTH OF CONSTRUCTION

A =15X.5X55,000 =412,500
^ = (15— .9375) .5X55,000=386,718
C =8X88,000X. 6903+3 X44,000X.6903 =577,090
^=(15— 2X. 9375) .5X55, 000+ 1X44.000X. 6903 =391,310
£=(15— 4X. 9375) .5X55,000+3X44,000X.6903 =400,494
2? =(15— 2X. 9375) .5X55 ,000+ .9375X.4375X95,000 =399,902
G = (15-^X.9375) .5X55,000+3X.9375X.4375X95,000=426,2(
H =8X.9375X.5X95.000+3X.9375X.4375X95,000 =473,145
1 =8X.9375X.5X95 .000+3X44 .OOOX. 6903 =447,369'

386,718 W)
412,500 (A) ''

.937 = efficiency of joint

©

Fig. 3,871. — Example of butt and double strap joint, quintuple riveted.

Example 6. — Butt and double strap joint, quintuple-riveted (figs. 3,871
and 3,872).

A = strength of solid plate = PX/Xr,5

B = strength of plate between rivet holes in the outer row = (P — d) tXTS

DETAILS AND STRENGTH OF CONSTRUCTION 2,185

C = shearing strength of 16 rivets in double shear, plus the shearing strength
of seven rivets in single shear =A^X'SXa-t-wX5Xa

D = strength of plate between rivet holes in the second row, plus the shearing
strength of one rivet in single shear in the outer row = (P — 2d) tXT5
+ lXsXa

£ = strength of plate between rivet holes in the third row, plus the shearing
strenglfi of two rivets in the second row in single shear and one rivet
in single shear in the outer row = (P — 4d) tXTS-\-SXsXa

© © d
i) © ©

© © (i

© © a
© © © ©

©

©

§.J

Fig. 3,872. — Example of butt and double strap joint, quintuple riveted.

F = strength of plate between rivet holes in the fourth row, plus the shearing
strength of four rivets in the third row , two rivets in the second row
and one rivet in the outer row in single shear = (P — Sd) tX TS-\-nXsXa

G = strength of plate between rivet holes in the second row, plus the crushing
strength of butt strap in front of one rivet in the outer row = (P — 2d) t
XTS+dXbXc

2,186 DETAILS AND STRENGTH OF CONSTRUCTION

77 = strength of plate between rivet holes in the third row, plus the crushing
strength of butt strap in front of two rivets in the second row and one
rivet in the outer row = (P— 4c?) tXTS+'SXdXbXc

I — strength of plate between rivet holes in the fourth row, plus the crushing
strength of butt strap in front of four rivets in the third row, two
rivets in the second row and one rivet in the outer row = (P — 8<i) tX
TS+nXdXbXc

/s= crushing strength of plate in front of 16 rivets, plus the crushing strength
of butt strap in front of seven rivets = NX dXtXc-\-nXdXbXc

Figs. 3,873 and 3,874. — ^Illustration of butt and double strap joint with straps of eqtml width.

K = crushing strength of plate in front of 16 rivets, plus the shearing strength
- of four rivets in the third row, two rivets in the second row and one
rivet in the outer row in single shesiv = NXdXtXc-\'nXsXa

Divided, C, D, E, F, G, H, I,JotK (whichever is the least), by A , and
the quotient will be the efficiency of a butt and double strap joint, quintuple-
riveted, as shown in fig. 3,871 or fig. 3,872.

TS =55,000 lb. per sq. in.
t=%in. =0.75 in.
6 =H iu. =0.5 in.

a =1.3529 sq. in.

J =44,000 lb. per sq. in.

5 =88,000 lb. per sq. in.

DETAILS AND STRENGTH OF CONSTRUCTION 2,187

P=36in. 5 = 44,000 lb. per sq. in.

rf =15^5 in. =1.3125 in. 5 = 88,000 lb. per sq. in.

a = 1.3529 sq. in. c =95,000 lb. per sq. in.

Number or rivets in single shear in a unit length of joint =7.

Number of rivets in double shear in a unit length of joint =16.
A =36X.75X55,000 =1,485.000
25 = (36—1 .3125) .75X55,000=1,430,860
C =16X88,000X1.3529+7X44,000X1.3529 =2,321,576
Z) =(36— 2X1.3125) .75X55,000+1X44,000X1.3529 =1,436,246
£ =(36— 4X1.3125) .75X55,000+3X44,000X1.3529 =1,447,020
F =(36—8X1.3125) .75X55,000+7X44,000X1.3529 =1,468,568

Figs. 3,875 and 3,876. — Illustration of butt and double strap joint of the saw tooth type.

G = (36—2X1.3125) .75X55,000+ 1.3125X. 5X95,000 =1,439,064
/? = (36^X1.3125) .75X55,000+3X1.3125X.5X95,000 =1.455,472
7 =(36—8X1.3125) .75X55,000+7X1.3125X.5X95,000 =1,488,141
J =16X1.3125X.75X95,000+7X1.3125X. 5X95,000 =1,932,266
K =16X1.3125X.75X95,000+7X44,O00X1.3529 =1,912,943

1,430,860 (B) ^_ „ . ...

1.485.000 (^) = -^^^ ^efficiency of jomt

Figs. 3,873 to 3,876 illustrate other joints that may be used. The

2,188 DETAILS AND STRENGTH OF CONSTRUCTION

butt and double strap joint with straps of equal width shown in figs. 3,873
and 3,874 may be so designed that it will have an efficiency of 82 to 84 per
cent and the saw tooth joint (figs. 3,875 and 3,876), an efficiency of from
92 to 94 per cent.

The following tables give details of riveted joints for different
thicknesses of plate as recommended by the Wickes Boiler Co.

Lap Joints

c""

u

Center of

Hole to Edpe

of Plate

Inches

Sinpfle Riveted

Double Riveted

^1

■ 5-1

ft

it
1
1

it!

If

I'

2\
2^\

2fV.

3

3rV

3^.

57.1

56.6
56.2
55.8
55.5
56.4
54.0

h

-I
1'

2|

2\\

3^

1

3|

3/.
4|
5
5

5<^

2t\
2^
2[
2i

72.7
72.3
72.0
71.1
70.3
71.4
70.6

Triple

Riveted

Butt Strap Jo

int

^ 4) ^

III

aj i> 05
I'll

a, iij c

III

■Hat;

00,2

?! <" V!

go"

3=^
•::2fi
...

03 ♦^ 0

t\

ii

3^x6}

91

14

2^

H

88

ii

i^

3|x6A

9{

14

^

2^

u

88.5

1

32x6|

14j

Tif

21'.

U\

87.9

if

f

3^x7

9|

14i

/.

'^r

h\

88.4

I'l

11

3^x7^

9?

15,

1 •

ih

87.9

i

3|x7^

10^

151

H

2?^

lil

87.5

i

I

3Jx7^

101

15^

tV

2,

IB

87.8

Quadruple Riveted Butt Strap Joint

f

1

7j X 14|

9 J

20|

A

2t\

1/^

94.4

W

1

7gx 14^

91

20 1

tV

2tV

ItV

94.5

tV

it

7^x 15

9|

22

t

2^

ItV

94.2

il

7

1

8x 16

lOi

221

if

2i

ni

94.1

i

8x 16

10^

22|

fff

2|

iH

94.1

A.S.M.E. Boiler Code. — Specifications for boiler rivet steel.

51. Marking. Rivet bars shall, when loaded for shipment, be properly separated and
marked with the name or brand of the manufacturer and the melt number for identification .
The melt number shall be legibly marked on each test specimen.

DETAILS AND STRENGTH OF CONSTRUCTION 2,189

U.S. Marine Rules. — Riveted joints .

9. The diameter of rivets, rivet holes, distance between centers of rivets, and distance
from centers of rivets to edge of lap for different thicknesses of plates for single and double
riveting shall be determined by the following rules.

The following formulas, equivalent to those of the British Board of Trade, are given for
the determination of the pitch, distance between rows of rivets, diagonal pitch, maximum
pitch, and distance from centers of rivets to edge of lap of single and double riveted lap joints,
for both iron and steel boilers:

Letp =greatest pitch of rivets in inches,
n =number of rivets in one pitch,
pd = diagonal pitch in inches,
d = diameter of rivets in inches.
T =thickness of plate in inches.
V = distance between rows of rivets in inches.
E = distance from edge of plate to center of rivet in inches.

TO DETERMINE THE PITCH
Iron plates and iron rivets:

d^ X .7854Xn , .
P= ^ 4-d.

Example, first, for single-riveted joint: Given, thickness of plate (T) =}4 inch, diameter of
rivet (d) = J^ inch. In this case n =1. Required the pitch.

Substituting in formula, and performing operation indicated,

T3-^ t, (K)^X .7854X1 ,7 or^T-T- 1-
Pitch = — ho =2.077 inches

>2 o

Example for double-riveted joint: Given, t =3^ inch and d =iVi6 inch. In this case n =2.
Then —

Pitoh = l!Ml><;^i><?+|_3 2.886 inche..
V2 16

For sltel plates and steel rivets:

_ 23Xd^X.7854Xn
^ 28XT

+d.

Example for single-riveted joint: Given, thickness of plate =>^ inch, diameter of rivet
« 15^6 inch. In this case n = 1 .

T3;.^u-23X(V6)'X.78o4Xl , 15 ^ _^ . ^
Pitch 28>0^ +16 =2-071 inches

Example for double-riveted joint: Given thickness of plate =H inch, diameter of rivet.
= >^ inch. n=2. Then —

T3;.^u_23X(K)^X.7854X2 ,7 „ ^_ . ^^
^'^^^ 28>C^ +8=2.80 mbhes.

FOR DISTANCE FROM CENTER OF RIVET TO EDGE OF LAP.

Example: Given, diameter of rivet (d) = K mch; required the distance from center of rivet
to edge of plate.

E = — ^ — =1.312 inches, for single or double riveted lap joint.

2,190 DETAILS AND STRENGTH OF CONSTRUCTION

U.S. Afarine Rules. — Riveted Joints. — Continued.

FOR DISTANCE BETWEEN ROWS OF RIVETS.

The distance between lines of centers of rows of rivets for double, chain-riveted joints (V)
shall not be less than twice the diameter of rivet, but it is more desirable that V should not be
less than

4d+l
2 •
Example under latter formula: Given, diameter of rivet =J4 inch. Then —

"-f*><^>+' =2.25 inches.

2

For ordinary, double, zigzag riveted joints:

V^ V(llp+4d) (p+4d)
10
Example: Given, pitch =2.85 inches, and diameter of rivet =J4 inch. Then —

V^ V11X2.85+4XK) (2.85+4XK),,,3,.^^^^3,

DIAGONAL PITCH.
For double, zigzag riveted lap joint. Iron and steel:

6p+4d

P^=-io-

Example: Given, pitch =2.85 inches, and d = J^ inch. Then—
pa =^^X"-^^>+^^X^> =2.06 inches.

MAXIMUM PITCHES FOR RIVETED LAP JOINTS.
For single-riveted lap joints:

Maximum pitch =(1.31XT)H-1^.
For double-riveted lap joints:

Maximum pitch = (2 .62 X T) -fl 5^ .
Example: Given, a thickness of plate = 14 inch, required the maximum pitch allowable.
For single- riveted lap joint: '

Maximum pitch =(1.31 XM)+1^ =2.28 inches.
For double-riveted lap joint:

Maximum pitch =(2.62X3^)+!^ =2.935 inches.

To determine the pitch of rivets from the above formulae, use the diameter and area of the
rivet holes. The diameter of the rivets is the diameter of the driven rivet.

Any riveted joint shall be allowed when it is constructed so as to give an equal percentage
of strength to that obtained by the use of the formula given. (Sees. 4418, 4433, R. S.)

BUTT STRAPS.

10. Where butt straps are used in the construction of marine boilers, the straps for single
butt strapping shall m no case be less than the thickness of the shell plates; and where dotible
butt straps are used, the thickness of each shall in no case be less than five-eigjiths the thick-
ness of the shell plates. (Sec. 4418, R. S.)

DETAILS AND STRENGTH OF CONSTRUCTION 2,191

A.S.M.E. Boiler Code— Boiler Joints.

181 Eficiency of a Joint. The efficiency of a joint is the ratio which the strength of the
iointbear^ to the strength of the solid plate. In the case of a riveted joint this is determined
bTcaSting the breaking strength of a unit section of the joint, fo^sidenng each possib^
mode of failure separately, and dividing the lowest result by the breaking strength of the solid
plate of a length equal to that of the section considered.

182 The distance between the center lines of any two adjacent rows of n vets, or the back
pitch'' measured at right angles to the direction of the joint, shall be at least twice the diameter
of the rivets and shall also meet the following requirements:

a Where each rivet in the inner row comes midway between two rivets in the outer row,
the sum of the two diagonal sections of the plate between the inner rivet and the
two outer rivets shall be at least 20 per. cent greater than the section of the plate
between the two rivets in the outer row. . x • ^i. 4. ^^ +1,^ o,,^

b Where two rivets in the inner row come between two rivets in the outer row the sum
of the two diagonal sections of the plate between the two inner rivets and the two
rivets in the outer row shall be at least 20 per cent greater than the difference in
the section of the plate between the two rivets in the outer row and the two rivets
in the inner row.

Fig. 3.877. — ^A.S.M.B. circumferential joint for thick plates of horizontal return tubular
boilers.

183 On longitudinal joints, the distance from the centers of rivet holes to the edges of
the plates, except rivet holes in the ends of butt straps, shall be not less than one and one-half
times the diameter of the rivet holes.

184 a Circumferential Joints. The strength of circumferential joints of boilers, the heads
of which are not stayed by tubes or through braces shall be at least 50 per cent of that of the
longitudinal joints of the same structure.

b When 50 per cent or more of the load which would act on an unstayed solid head of the
same diameter as the shell, is relieved by the effect of tubes or through stays, in consequence
of the reduction of the area acted on by the pressure and the holding power of the tubes and
stays, the strength of the circumferential joints in the shell shall be at least 35 per cent that
of the longitudinal joints.

185 When shell plates exceed ^/{^ inch in thickness in horizontal return tubular boilers,
the portion of the plates forming the laps of the circumferential joints, where exposed to the
fire or products of combustion, shall be planed or milled down as shown in fig. 3,877, to H inch
in thickness, provided the requirement m par. 184 is complied with.

186 Welded Joints. The ultimate tensile strength of a longitudinal joint which has been
properly welded by the forcing process, shall be taken as 28,500 pounds per square inch, with
steel plates having a range in tensile strength of 47,000 to 55,000 pounds per square inch.

187_ Longituainal Joints. The longitudinal joints of a shell or drum which exceeds 36
inches in diameter, shall be of butt and double-strap construction.

188 The longitudinal joints of a shell or drum which does not exceed 36 inches in diameter,
may be of lap-riveted construction; but the maximum allowable working pressure shall not
exceed 100 pounds per square inch.

2,192 DETAILS AND STRENGTH OF CONSTRUCTION

Boiler Heads. — These serve two purposes, 1, to close the
ends of the boiler, and in the case of fire tube boilers to hold the
ends of the tubes. There are two general classes of head as,

1. Flat.

2. Dished.

Examples belonging to the two classes are shown in figs. 3,878

m

Figs. 3,878 to 3,881._— Types of boiler head. Pig. 3,178, flat head with through stay; fig.
3,879, flat head without through stay; fig. 3,180, dished head with convex external side;
fig 3,881, dished head with concave external side.

to 3,881. In drums for water tube boilers, the flat form shown
in figs. 3,878 and 3,879 is generally used,

The dished form has greater strength and avoids the use of
stays.

A.S.M.E. Boiler Code. — Boiler Joints. — Continued.

189 The longitudinal joints of horizontal return tubular boilers shall be located above
the fire-line of the setting.

190 A horizontal return tubular boiler on which a longitudinal lap joint is permitted shall
not have a course over 12 feet in length. With butt and double-strap construction, longitudinal
joints of any length may be used provided th^ plates are tested transversely to the direction of
rolling, which tests shall show the standards prescribed under the Specification ot Boiler Plate
steel.

191 Butt straps and the ends of shell plates forming the longitudinal joints shall be rolled
or formed by pressure, not blows, to the proper curvature.

DETAILS AND STRENGTH OF CONSTRUCTION 2,193

The fiat flanged head is the type used in tubular boilers . Usu-
ally the flange 'of the head is placed inside the shell.

Tube Spacing. — The many causes of dangerous accumulation of sedi-
ment, scale and foreign matter which inspection brings out, makes it clear

Tube Spacing 48 to 60 inch Boilers

BOILER 48" IN DIAMETER
34 TUBESSJ-'OIA.

BOILER 48" IN DIAMETER
46 TUBES 3'D1A.

Figs. 3,882 to 3,890. — ^Wickes standard layout of tubes and braces for horizontal tubular
boilers with manhole in head, for 48'inch to 60-inch boilers.

2,194 DETAILS AND STRENGTH OF CONSTRUCTION

that it is wiser that fewer tubes be used than was formerly the custom.
Ample space should be left between the tubes and between the tubes and
the shell and under the tubes for access at all times for the removal of foreign
matter collected.

Tube spacing 66 to 78 inch Boilers

BOtCER 66*tN DIAMETER
72 TUBES 3 J-' DIA.

eOiLER 66* IN OlAMETEft
88TueES3'0lA.

Figs. 3,891 to 3,899. — ^Wickes standard layout of tubes and braces for horizontal tubular

DETAILS AND STRENGTH OF CONSTRUCTION 2,195

Figs 3,882 to 3,899 are examples of tube spacing for boilers ranging in
size from 48 to 78 inches in diameter.

Ligaments. — ^When a head is drilled for tubes, a good deal of the metal
is cut away, hence the efficiency of the metal between the tube holes or
ligament must be considered.

There are two cases, according to the arrangement of the tubes.

5 V-

-.- 5 V-

■<- 5^

S\"

LONGITUDINAL LINE! ►

Fig. 3,900. — Example of tube spacing, with pitch of holes equal in every row, illustrating
efficiency of ligament.

(D .(Dd)

•fcV—

6 V

,2/

d) o

oo oo o

*- feH"

LONGITUDINAL LINEL- p^

Fig. 3,901.— Example of tube spacing with pitch of holes unequal in every second row. illus-
tratmg efficiency of ligament,

1. Holes drilled in line parallel to the axis of the shell (figs. 3,900
to 3,902.)

A. Pitch of the tube holes in every row equal.

B. Pitch of the tube holes in any one row unequal.

2. Holes drilled in a line diagonal with the axis of the shell
(fig. 3,903).

2,196 DETAILS AND STRENGTH OF CONSTRUCTION

The methods of determining the efficiency of the ligament
for the several cases are, according to the A.S.M.E. Boiler Code

as follows:

A. Pitch of the tube holes in every row equal as shown in fig. 3,900.
efficiency of ligament = —

u S P^ pitch of tube holes in inches
wnere ^ j _ diameter of tube holes in inches

LONGITUDINAL LINE — ^

Fig. 3,902. — Example of tube spacing with pitch of holes varying in every second and third row^
illustrating efficiency of ligament.

Example. — If the pitch of tube holes, in the head shown in fig. 3,900 be
514: inches, diameter of tubes 334 inches, tube holes 3^2 inches, what is
the efficiency of the ligament?

efficiency of ligament =

p—d 5M— 3% _ 5. 25— 3.281

534

5.25

= .375

B. Pitch of tube holes in any one row unequal, as shown in figs. 3 901
and 3,902.

NOTE. — The Hartford Boiler Insurance Co. says, in regard to tube spacing: "In our
experience we have found great difficulty with this arrangement of tubes (speaking of tubes
closely put in) , particularly when used with bad water. It gives a greater area of tube surface,
but considerable portion of the surface so gained is useless, and worse than useless, from the
fact that the water space is unduly taken up by the superfluous tubes.'

DETAILS AND STRENGTH OF CONSTRUCTION 2,197

efficiency of ligament = ^— ^ —
P

f /) = unit length of ligament in inches
where i n = number of tube holes in length p
[ d = diameter of tube holes in inches

Example, — If the diameter of tube holes be 3^, and the spacing be as
shown in fig, 3,901, what is the efficiency of the ligament?

efficiency of ligament ■

p—nd_ 12—2X3.281

P

12

= .453

Example.— 'What is the efficiency of ligament for the spacing shown in
fig. 3,902, and 3%^-inch holes?

o ^ o ^ o ^ n
o o n ^

o

(R^O O

-5t~

LONGITUDINAL LINEl-

FiG. 3,903. — Example of tube spacing with tube holes on diagonal lines, illustrating efficiency
of ligament.

2. Holes drilled in a line diagonal with the axes of the shell as

shown in fig. 3,903.

For this arrangement of tube holes the efficiency of the

ligament shall be determined by the following methods and

the lowest value used.

.95(/?i— J)

efficiency of ligament =

Pi

2,198 DETAILS AND STRENGTH OF CONSTRUCTION

( pi = diagonal pitch of tube holes in inches
where j d = diameter of tube holes in inches

1 p = longitudinal pitch of tube holes or distance between center of
[ tubes in a longitudinal row in inches

The constant .95 in the formula a applies provided pi-i-d be 1.5 or over.

E::ample, — Diagonal pitch of tube holes, as shown in fig. 3,903=6.42
inches, diameter of holes, 4}^2 inches, longitudinal pitch of holes, 113^ inches.

.95(6.42-4.031)
a. ^^ =.353

. 11.5—4.031 ...
h, — jy:^— =649

Taking the least value determined by formulae a and h, the efficiency of
ligament is .355.

Area of Head to Be Stavpd. — Where fiat heads are used, it
is necessary to provide stays or braces for that part unsupported
by the tubes. For the water space the bracing afforded by the
tubes is sufficient, although sometimes a few stay tubes with
screw threads and lock nuts are provided to increase the bracing
power; for the rest of the head it is necessary to provide sufficient
bracing to resist the pressure .

A problem which presents itself is to find the area of the seg-
ment of the head to be braced, and it should be noted that this
is a quest ior. often asked on examination papers for engineer's
license.

A.S.M.E. Boiler Code. — Tubes.

248 Tube Holes and Ends. Tube holes shall be drilled full size from the solid plate, or
they may be punched at least H inch smaller in diameter than full size, and then drilled, reamed
or finished full size with a rotating cutter.

249 The sharp edges of tube holes shall be taken off on both sides of the plate with a file
or other tool . '

250 A fire-tube boiler shall have the ends of the tubes substantially rolled and beaded,
or welded at the firebox or combustion chamber end.

251 The ends of all tubes, suspension tubes and nipples shall be flared not less than
H in. over the diameter of the tube hole on all water-tube boilers and superheaters, or they
may be beaded.

252 The ends of all tubes, suspension tubes and nipples of water-tube boilers and super-
heaters shall project through the tube sheets or headers not less than )^ inch nor more than
3^ inch before flaring.

DETAILS AND STRENGTH OF CONSTRUCTION 2,199

Oues. What portion of the head not occupied by tubes
must be stayed?

Ans. According to the A. S. M. E. Boiler Code the area of a
^gment of a head to be stayed shall be the area enclosed by lines

U.S. Marine Rules — Heads.

REQUIREMENTS FOR HEADS.

3. All plates used as heads, when new and made to practically true circles, and as described
below, shall be allowed a steam pressure in accordance with the following formula:

CONVEX HEADS.

TXS
R

Where P =steam pressure allowable in pounds.
T = thickness of plate in inches.
S = one-fifth of the tensile strength.
R = one-half of the radius to which the head is bumped.

CONCAVE HEADS.

For concave heads the pressure allowable shall be eight- tenths times the pressure allowable
for convex heads.

NOTE. — To find the radius of a sphere of which the bumped head forms a part, square
the radius of head, divide this by the height of bump required; to the result add height of bump,
which will equal diameter of sphere, one-half of which will be the required radius.

Example.

Required, the working pressure of a convex head of a 54-inch radius; material, 60,000'
pounds tensile strength and one-half of an inch thick. Substituting values and solving, we have

P=-5X|:550 ^222 pounds.

The pressure allowable on a concave head of the same dimensions would be 222X.8 =177
pounds.

To avoid grooving the flanging shall be well rounded at the bend.

Bumped heads may contain a manhole opening flanged inwardly, when such flange is^
turned to a depth of three times the thickness of material in the head.

Material used in the construction of all bumped heads shall possess the physical and chem-
ical qualities prescribed by the Board of Supervising Inspectors for all plates subject to tensile
strain, as required by section 4430, Revised Statutes.

FLAT HEADS OF WROUGHT-IRON OR STEEL PLATE.

Where flat heads do not exceed 20 inches in diameter they may be used without being
stayed, and the steam pressure allowable shall be determined by the following formula:

p^CXT2
A

2,200 DETAILS AND STRENGTH OF CONSTRUCTION

drawn 3 inches from the shell and 2 inches from the tubes as
shown in fig. 3,904 and 3,905.

The net area to be stayed in a segment of a head may be determined by
the following formula: #

^ 4(H— 5)^ V2(R--3) . u

area oj segment = ^ — ^ square inches

o H — 5

in which H= distance from tubes to shell, and R = radius of boiler head
both in inches.

When the portion of the head below the tubes (lower segment), in a

Fig. 3,904. — Upper segment of head to be stayed.

U. S. Marine Rules, — Heads — Continued,
Where P = steam pressure allowable in pounds.

T = thickness of material in sixteenths of an inch.
A = one-half the area of head in inches.
C =112 for plates seven-sixteenths of an inch and under.
C =120 for plates over seven-sixteenths of an inch.
Provided, The flanges are made to an inside radius of at least 114 inches.

Example.

Required the working pressure of a flat head 20 inches in diameter and three-fourths of
an inch thick. Substituting values, we have

^ 120X144 ,,„ , •

P = — Tv;= — =110 pounds.
157

DETAILS AND STRENGTH OF CONSTRUCTION 2,201

horizontal return tubular boiler is provided with manhole opening, the
flange of which is formed from the solid plate and turned inward to a depth
of not less than three times the thickness of the head, measured from the
outside, the area to be stayed as shown in fig. 3,905, may be reduced by 100
square inches. The surface around the manhole shall be supported by
through stays with nuts inside and outside at the front head {A.S.M.E.
Boiler Code),

Reinforcement of Flat Surfaces. — ^All fiat surfaces in boilers
must be stiffened or supported, otherwise the internal pressure
of the steam would bulge them outward and tend to make them

oo

Fig. 3,905.— Lower segment of head to be stayed.

A.S.M.E, Boiler Code. — Braced and Stayed Surfaces.

199 The maximum allowable working pressure for various thicknesses of braced and
stayed flat plates and those which by these Rules require staying as flat surfaces with braces
or staybolts of uniform diameter symmetrically spaced, shall be calculated by the formula:

where

P = maximum allowable working pressure, pounds per square inch.
/ = thickness of plate in sixteenths of an inch

P = maximum pitch measured between straight lines passing through the centers of
the staybolts in the different rows, which lines may be horizontal, vertical or
inclined, inches
C =112 for stays screwed through plates not over T^e inch thick with ends riveted over
C =120 for stays screwed through plates over Ke inch thick with ends riveted over
C = 135 for stays screwed through plates and fitted with single nuts outside of plate
C = 175 for stays fitted with inside and outside nuts and outside washers where the diam-
eter of washers is not less than Ap and thickness not less than /.
If flat plates not less than V^ inch thick are strengthened with doublmg plates securely riveted
thereto and having a thickness of not less than % t, nor more than t, then the value of t in the
formula shall be % of the combined thickness of the plates and the values of C given above
may also be increased 15 per cent.

2,202 DETAILS AND STRENGTH OF CONSTRUCTION

Spherical or cylindrical in shape. This reinforcement is obtained
by means of stays and braces.

By common usage, the difference between stays and braces
seems to be chiefly one of size, that is, a brace is a large stay.*

Oues. Into what two classes may all of reinforcing
members be divided ?

Ans. They may be classed as independent and connecting
fastenings.

Pig. 3,906. — Stay bolt, consisting of a threaded length of rod with a nut at each end, or a
forged head at one end and a nut at the other end.

Stay Bolts. — The term "bolt" is defined as a metallic pin or
rody used to hold objects together and generally having screw threads
cut at one end, and sometimes at both, to receive a nut.

The author regards a nut as forming part of a bolt and therefore restricts
the term stay holt to the type of stay shown in fig. 3,906.

It consists of a rod having a thread its entire length and a nut on each end .
This kind of stay is used in making repairs but owing to the extra amount of
metal in the nut is not so well adapted to the intense heat in the firebox as
the riveted stays shown in figs. 3,915 and 3,916. It is suitable for less severe
conditions as for staying the steam jacketed uptake in marine leg boilers.

*N0TE. — The author objects to the use of the term brace because by definition a brace
is a rigid piece, as of timber, to hold something, as parts of a frame in place, expecially 1, a
framed diagonal piece in an angle, 2, a strut, and 3. lateral support acting in compression.
The general conception of a brace is that it is a stiff member designee to resist both tension and
compression. Accordingly, the author uses the term stay rather than brace.

DETAILS AND STRENGTH OF CONSTRUCTION 2,203

d

o

o

^

^

-*j

o

s

o

Vh

<t)

d

^

g

1

a

»

tuO

a

£

t^

<i;

t

C3

+J

'E

o

.c

c« .

1
1

II

O CD

bo

cd J:j

C

t^TJ

t

Ss^

s ^

3

W)'r=l

.';3

C^

'O «>

•S o

1|

c^fe

"^'i^

^S:

-^^

rt ^

XX

t^ c

be S

^^"ti

.^ f^

•H^

?i1 o

^ c;J

a.is

J

si

^ o

^ Wi

1^

0) <i>

>.«

12

1"-

g ^

?!

:^

|i

s^

«JS

H"C

l^f^

u

^

2,204 DETAILS AND STRENGTH OF CONSTRUCTION

g

>>

C3

^

GO

Ul

o

4-^

VN

o

Jan.,

«)

'o 'S

5 53

'2 2

5:

+- A

_. ^J

2i

CsJ

0*

"OX)

+>

•;->

{§

^ a.

•5

0 5

CO ^

'■♦3

-ss

S

P, 0

J3

Sj3

1

2-1

•fj

^ ^

'o

s s

>>

<^ ^

cJ

1-H C3

t^

0.3,

1

S3-C

-O

^ ^

|i

^

-^ 0

0 ^

2

C3 '^

^

1

^ .^

-**
5i

1 2

CO

05

o

+J

. >>

o
co"

it

0 5^

o

;h

fe

CL

DETAILS AND STRENGTH OF CONSTRUCTION 2,205

Ans. By the use of a long or stay bolt tap which threads
both plates in one operation.

Oues. What thread is used for stay bolt taps ?

Ans. All sizes of stay bolt taps have 12 threads to the inch,
the approved form being the U. S. standard, though the '*V'^
thread is sometimes used.

Ques. What diameter of a screwed stay is taken in
calculating its strength ?

Ans. The least diameter.

Fig. 3,915. — Riveted screw stay or so-called stay bolt. _ The standard sizes vary from % to
\y^ inches in diameter, and all have twelve threads per inch.

Fig. 3,916. — Hollow or drilled riveted screw stay.

For a continuous thread this is at the bottom of the thread, and at the
middle section of turned stays.

Riveted Stays. — The usual form of riveted stay used for carry-
ing the pressure on the sides of the fire box in vertical and loco-
motive boilers consists of a rod threaded at the ends and turned
down along the middle section to a diameter slightly less than
that of the root of the threads as shown in fig. 3,915.

2,206 DETAILS AND STRENGTH OF CONSTRUCTION

OS 03 -^'o "^

o ?f 6 ^2*

The approved form of riv-
eted stay is shown in fig.
3,916. In this stay a ?^ in.
hole is drilled in each end as
shown, extending J^ inch or
more beyond the inside of the
plate.

Owes. What is the ob-
ject of drilling holes in the
ends of screwed stays?

Ans. To show by a leak
through the drilled holes
where the stay has broken,
as in fig. 3,917.

The break is most likely to oc-
cur near the plate and inspection
in parts of boilers which must be
stayed in this manner is in most
cases impossible. Sometimes the
drilled hole extends the length of
the stay.

Oues. Why do screwed
stays sometimes break?

Ans . Owing to unequal ex-
pansion between the outer
and inner plates, the stays
are bent back and forth each
time this occurs, as shown in
figs. 3,917.

DETAILS AND STRENGTH OF CONSTRUCTION 2,207

cs'd t^

a
rt

^

4J

'^*o

^H

<D

a

^Jd ^

^

^53 i2

S

•4->

^

II .1

'rt

<U.S,-ii Q.

u

r^

(D

(X>

reade
main
two t
f the

t

re th
ively
thei
its 0

.^

^

ce

•+J

fd

T3

ed spindle. The taps ai
e tap to the other is posit
■ a continuous thread in
anything within the lire

^

*&

S

0)

xn
w

•fH

Pi

03

^

1

o
'd

4->

taps with threadi
y of lead from om
es the tapping of
e sheets may be

^

U

3
8

fij

Q>

C/3

3

-a-^5:2

it.

;h

T^

CO

;tay-bo
contint
;ion ins
itween

t

1

1

£

o

0

a

.—Pratt and Whitney spindle j
ain definite relationship so that
tween the taps. This construct
0 be located. The distance be

CO

O

o

S3

s

^

CD

^

CO

;3

g
P

<D

05

.918
cert
:ebe
, is t

4^

g

CD

s

p

''IG. 3
in a
tanc
bolt

O

o

V3

Q)

(1)

•

f

^

w

o

i

O
^

1
fc

1

^

?^

o

o
o

c»

4->

^

^

4^

-)J

O

["■?

;:s

a;

'd

u

^

o

^

CD

o

eg

IS

^

t/3

ctJ

73

H

■4^

2,208 DETAILS AND STRENGTH OF CONSTRUCTION

of a rod and socket. The socket is placed between the plates to
be stayed and the rod passed through the plates and socket and
riveted in place as shown in fig. 3,919.

Stay Rods or Through Stays. — These are used chiefly in
marine shell boiler^ of the Scotch and Clyde types. These
boilers being short and of large diameter, the considerable
amount of flat surface in the heads not reinforced by the tubes is
conveniently stayed with through stays without rendering the

COPPER WASHERS

Fig. 3,920. — Stay-rod or through-stay, especially adapted to short boilers of large diameter.
The most common and simple form is a plain rod threaded at the ends. The rod passes through
the steam space and the ends are fastened to the heads. The length is adjusted in various
ways, the simplest being by nut and washers as here shown. The copper washers prevent
abrasion of the plates by the nuts and act as packing in securing a tight joint. In place
of the nuts the rod is sometimes bolted to angle irons which are riveted to the heads. In
this case, turn buckles are used for adjusting the length.

interior inaccessible. These stays are usually plain rods 1J4 to
23^ inches in diameter. The ends are fastened to the plates by
nuts and washers as shown in figs. 3,920. The large washers are
used to secure a larger heating surface.

These stays being in the steam space should be at least 14 inches apart
so that a man can pass between them. The threads at the ends may be cut
on the plain rod or the ends may be forged larger and the threads cut on
the enlarged part.

DETAILS AND STRENGTH OF CONSTRUCTION 2,209

Stay Tubes. — Although the holding power of the ordinary
tubes expanded into the heads is considerable and in most cases
is sufficient for the sheet area covered, sometimes a few stay
tubes are inserted, especially where the tube pitch is large.

Fig. 3,921. — Turnbuckle used for adjusting the length of stay rods or through stays when
the latter are bolted to internal angle irons instead of passing through the shell as in fig. 3 ,920 .

These tubes are of the same outside diameter as the ordinary
tubes, but are thicker, being usually ^--inch thick, and are pro-
vided with threads on the ends.

Frequently the threads are cut at both ends; both tube plates are tapped
and the tubes screwed in. When both ends are threaded one end must be

Figs. 3,922 and 3,923.— Stay tube ends; fig. 3,922 upset end, fig. 3,923 plain end. It must be
evident that where both ends are threaded one end must be of larger diameter than the other
to allow inserting the tube.

smaller than the other so that it may be slipped through the hole, as shown
in figs. 3,922 and 3,923. The back end is beaded over or nutted and the
front end fastened with shallow nuts. Sometimes two nuts are placed on
the front end; one inside and one outside of the boiler plate.

Stay tubes are not used now as extensively as they were formerly. They
were very common at a time when the holding power of expanded tubes had

2,210 DETAILS AND STRENGTH OF CONSTRUCTION

been experimented on but little. It is now apparent from numerous tests
that the holding power of expanded tubes is more than is necessary to support
the pressure coming on the spaces between the tubes of an ordinary tube
sheet .

Pigs. 3,924 and 3,925. — Luken's diagonal stay bent to form from a flat steel plate.

Fig. 3,926. — Diagonal stay with eye ends. It is attached to the boiler angle irons and pins.

Pig. 3,927 and 3,928. — Diagonal stay with forged ends.

A.S.M.E. Boiler Code.— Stay Tubes.

232. When stay tubes are used in multi-tubular boilers to give support to the tube plates,
the sectional area of such stay tubes may be determined as follows:

Total section of stay tubes , square inches = -

a) P

where

A =area of that portion of the tube plate containing the tubes, sq. in.
a = aggregate area of holes in the tube plate, sq. in.
F= maximum allowable working pressure, pounds per sq. in.
T = working tensile stress allowed in the tubes not to exceed 7,000 lbs. per sq. in.

DETAILS AND STRENGTH OF CONSTRUCTION 2,211

Gusset Stays. — The flat ends of cylindrical boilers (especially
marine boilers) are stayed to the round portions of triangular
plates of iron called gusset stays. These are simply pieces of
plate iron secured to the boiler front or back, near the top or
bottom, by means of two pieces of angle iron, then carried to the
shell plating, and again secured by other pieces of angle bar,
as shown in fig. 3,929.

Sometimes only one angle iron is used at each end, the plate itself being
flanged to form the other side of the T.

Fig. 3,929. — Gusset stay consisting of a flat piece attached diagonally to the shell and head by
angle irons. Because of the character of the stress coming on a gusset stay it should be
proportioned for a larger factor of safety than for ordinary diagonal stays.

A.S.M.E. Boiler Code. — Stay Tubes. — Continued.

r=working tensile stress allowed in the tubes, not to exceed 7,000 pounds per square
inch

233 The pitch of stay tubes shall conform to the formula given in par. 199, using the values
of C as given in Table 6.

Table 6. Values of Cfor Determining Pitch of Stay Tubes. .

Pitch of Stay Tubes in the Bounding Rows

When tubes

have no Nuts

Outside of Plates

When tubes

are Fitted with

Nuts Outside

of Plates

Where there are two plain tubes between each stay tube

Where there is one plain tube between each stay tube . . .

Where every tube in the bounding rows is a stay tube and

each alternate tube has a nut

120
140

130
150

170

2,212 DETAILS AND STRENGTH OF CONSTRUCTION

Oues. How is the stress distributed in a Gusset stay?

Ans. The tension is not uniform, but is greater near one edge.

Palm Stays. — These are often used in the same position as a

Figs. 3,930 and 3,931.— Crow-foot stay, consisting of a rod with forked end, attached by a pin
to a V-shaped end with palms or so-called crow foot, the palms of which are riveted to the
flat plate to be stayed .

A.S.M.E. Boiler Code,— Stay Tubes.— Continued.

When the* ends of tubes are not shielded from the action of flame or radiant heat, the values
of C snail be reduced 20 per cent. The tubes shall project about K inch at each end and be
slightly flared. Stay tubes when threaded shall not be less than Ife inch thick at bottom of
thread; nuts on stay tubes are not advised* For a nest of tubes C shall be taken as 140 and 5
as the mean pitch of stay tubes. For spaces between nests of ttibes 5 shall be taken as the hori-
zontal distance from center to center of the bounding rows of tubes and C as given in Table 6.

U.S. Marine Rules. — Diagonal and Gusset Stays.

II — 16. Multiply the area of a direct stay required to support the surface by the slant
or diagonal length of the stay; divide this product by the length of a line drawn at right angles
to surface supported to center of palm of diagonal stay. The quotient shall be the, required
area of the diagonal stay.

DETAILS AND STRENGTH OF CONSTRUCTION 2,213

Gusset stay; that is, from the back or front end of the boiler to

the shell plates; they are sometimes used to stay the curved tops

of combustion chambers.

As shown in fig. 3,932, the stay consists of a round rod having forged on
one end a plate or "palm" and a thread and nut connection at the other end.

Crow Foot Stays. — These are virtually double palm stays,

V77r^r/////^/////////A/^/^y^^^/y^^//^^

Fig. 3,932. — Palm stay, so-called because it has a palm-like plate forged at the end. Since
the threaded end passes through the head obliquely, two diagonally cut washers are used
as connectors between the nuts and plate.

Figs. 3,933 and 3,934. — ^Jaw stay. This type of stay is used in connection with T irons.

riveted to the head.

two palms being connected together into a so-called crow foot,

which is attached by a bolt to the forked end of a long bar.

This type is suited for long stays as it gives convenience for removal and
repair of the long bolts without disturbing the crowfoot.

Jaw Stays. — This type of stay is shown in figs. 3 ,933 and 3 ,934

2,214 DETAILS AND STRENGTH OF CONSTRUCTION

and consists of a round bar having jaws forged at one end and a
flat plate at the other inclined at the proper angle for riveting to
the boiler shell. The jaw end is attached by a pin to a T iron
which is rivetecrto the head.

Steel Angle Stays. — When the shell of a boiler does not
exceed 36 inches in diameter and is designed for a pressure of not
over 100 pounds, the segment of heads above the tubes may be
stayed by steel angles as shown in figs. 3,935 and 3,936.

The following table from the A.S.M.E. Boiler Code gives the approved

dimensions for steel angle stays.

Table 5. Sizes of Angles Required for Staying Segments of Head

With the short legs of the angles attached to the head of the boiler

30-Inch Boiler

34-Inch Boiler

36-Inch Boiler

Height

segment,
dimension

Bin
Fig. 3,936

Angle

32XJ

In.

Angle

3§X3

In.

Angle
4X3
In.

Angle

3iX3

In.

Angle

4X3

In.

Angle

5X3

In.

Angle

4X3

In.

Angle
5X3
In.

Angle

6X3i

In.

Di-
men-
sion
A in

Thick-
ness,
In.

Thick-
ness,
In.

Thick-
ness,
In.

Thick-
ness,
In.

Thick-
ness,
In.

Thick-
ness,
In.

Thick-
ness,
In.

Thick-
ness,
In.

Thick-
ness,
In.

Fig.
3,936

10
11
12
13
14
15
16

i

1

i

6J^

7

7H
8

8M
9

9K

Crown or Roof Bars. — For supporting the fiat tops of fire
boxes and combustion chambers, especially in locomotive and
marine boilers a bridge or girder form of stay is often used . These

DETAILS AND STRENGTH OF CONSTRUCTION 2,215

bars extend across the flat surfaces and the ends rest on the
side plates.

Bolts properly spaced connect the flat surface to the bar. The
latter may be a solid bar or may be made up of two plates welded
together at the ends and having a depth of about 4 to 6 inches
and proper thickness to support the load coming on it.

Either bolts or rivets may be used to keep the plates which form
the girder from spreading.

Figs. 3,935 and 3,936. — Staying of head in tubular boiler with steel angles. The approved
dimensions of these angles is given in tho accompanying table from the A. S. M. E. Boiler
Code. The legs attached to the heads may vary in depth K inch above or below the dimen-
sions specified in the table. When this form of bracing is to be placed on a boiler, the
diameter of which is intermediate to or below the diameters given in Table 5, the tabular
values for the next higher diameter shall govern. Rivets of the same diameter as used
in the longitudinal seams of the boiler shall be used to attach the angles to the head and to
connect the outstanding legs. The rivets attaching angles to heads shall be spaced not over
4 inches apart. The centers of the end rivets shall be not over 3 inches from the ends of the
angle. The rivets through the outstanding legs shall be spaced not over 8 inches apart;
the centers of the end rivets shall be not more than 4 inches from the ends of the angles.
The ends of the angles shall be considered those of the outstanding legs and the lengths
shall be such that their ends overlap a circle 3 inches inside the inner surface of the shell
as shown. The distance from the center of the angles to the shell of the boiler, marked A,
shall not exceed the values given in the table, but in no case shall the leg attached to the
head on the lower angle come closer than 2 inches to the top of the tubes. When the seg-
ments are beyond the range of the table the heads shall be braced or stayed in accordance
with the requirements in these rules.

AXD STRENGTH OF COSSTRLCT

1 T

-I -_ SECTION L-F

fidi pimfei

DETAILS as:

Oy 2^17

Radial Stays. — These are used ci:at::Ly in kxxxnofdve boiers,
in which the fire box down sheet is arched. The stays are ar-
ranged radially to the curvative of the two plates, ¥diidi ^MCf
conaect, as shown in fig. 3,^1.

Fig. ZMl.—Y^'.^ w

I (

N,

_^B 1

^^

H) I

©

©

0 \

©

©

©

flT 1

©

fl) /

© 1

®

w

■^

, •

■--i

-x^fcuuis at oomer a

sorTcsaiaes.

^. s. Jr. JL i

418. t^e^mble loads bMed oa the set
pitches is panossibfe. ThefaaagDlafarthe

a£ sfeV9' ^''bI'^. ''■■^ ^

r qC stay boit over «e threMdIs, m
rof ataiybotetliiittjiiaf Arewte»i
Where U. S. kneads ue wed, tite fm— !■ Tii r riMii

2,218 DETAILS AND STRENGTH OF CONSTRUCTION

DETAILS AND STRENGTH OF CONSTRUCTION 2,219

A. S. M. E. Boiler Code — Stay Bolts.

200 The ends of screwed staybolts shall be riveted over or upset by equivalent process.
The outside ends of such staybolts shall be drilled with a hole at least ys inch diameter to a
depth extending H inch beyond the inside of the plates , except on boilers having a grate area
not exceeding 15 square feet, where the drilling of the staybolts is optional.

201 * When channel irons o^ other members are securely riveted to the boiler heads for
attaching through stays the transverse stress on such members shall not exceed 12,500 pounds
per square inch. In computing the stress, the section modulus of the member shall be used
without addition for the strength of the plate. The spacing of the rivets over the supported
surface shall be in conformity with that specified for staybolts.

202 The ends of stays fitted with nuts shall not be exposed to the direct radiant heat of
the fire.

203 The maximum spacing between centers of rivets attaching the crowfeet of braces to
the braced surface, shall be determined by the formula in par. 199, using 135 for value of C.

The maximum spacing between the inner surface of the shell and lines parallel to the surface
of the shell passing through the centers of the rivets attaching the crowfeet of braces to the head,
shall be determined by the formula in par. 199, using 160 for the value of C.

Table 3. Maximum Allowable Pitch, in Inches, of Screwed Stay-
bolts, Ends Riveted Over

Thickness of Plate, Inches

Pressure
Pounds per
Square Inch

A

^•8

ii

3^

A

H

li

Maximum Pitch of Staybolts, Inches

100

6M
5

4M

4J^
4M
4^
4

6^
6

&%
5

4J4
4M
4

1%
7

6M
6

4J^

110

8

6%
5

120

125

130

140

8^
8

7M
7j|
7^

7H

7

6M

150

160

170
180
190
200
225
250
300

7M
7M

6M

8}^
8

7%
7

204 The formula in par. 199 was used in computing Table 3. Where values for screwed
stays with ends riveted over are required for conditions not given in Table 3, they may be com-
puted from the formula and used, provided the pitch does not exceed 83^ inches.

2,220 DETAILS AND STRENGTH OF CONSTRUCTION

A,S.M.E. Boiler Code. — Stay Bolts .^Continued .

205 The distance from the edge of a staybolt hole to a straight line tangent to the edges of
the rivet holes may be substituted for p for staybolts adjacent to the riveted edges bounding a
stayed surface. When the edge of a stayed plate is flanged, p shall be n^sured from the inner
surface of the flange, at about the line of rivets to the edge of the stayb»iv^ or to the projected
edge of the staybolts.

206 The distance between the edges of the staybolt holes may be substituted for p for
staybolts adjacent to a furnace door or other boiler fitting, tube hole, hand hole or other opening.

207 In water leg boilers, the staybolts may be spaced at greater distances between the rows
than indicated in Table 3, provided the portions of the sheet which come between the rows of
staybolts have the proper transverse strength to give a factor of safety of at least 5 at the maxi-
mum allowable working pressure.

208 The diameter of a screw stay shall be taken at the bottom of the thread, provided
this is the least diameter.

209 The least cross-sectional area of a stay shall be taken in calculating the allowable
stress, except that when the stays are welded and have a larger cross-sectional area at the
weld than at some other point, in which case the strength at the weld shall be computed as
well as in the solid part and the lower value used.

210 Holes for screw stays shall be drilled full size or punched not to exceed J^ inch less
than full diameter of the hole for plates over ^ inch in thickness, and ^ inch less than the
full diameter of the hole for plates not exceeding r^ inch in thickness, and then drilled or
reamed to the full diameter. The holes shall be tapped fair and true, with a full thread.

211 The ends of steel stays upset for threading, shall be thoroughly annealed.

212 An internal cylindrical furnace which requires staying shall be stayed as a fiat surface
as indicated in Table 3.

213 Staying Segments cf Heads. A segment of a head shall be stayed by head to head ,
through, diagonal, crowfoot or gusset stays, except that a horizontal return tubular boiler,
may be stayed as provided in Pars. 225 to 229 (see Boiler Code.)

214 Areas oj Segments of Heads to he Stayed. The area of a segment of a head to be stayed
shall be the area enclosed by lines drawn 3 inches from the shell and 2 inches from the tubes,
as shown in figs. 3,904 and 3,905.

215 In water tube boilers, the tubes of which are connected to drum heads, the area to be
stayed shall be taken as the total area of the head less a 5 inch annular ring, measured from the
inner circumference of the drum shell.

When such drum heads are 30 inches or less in diameter and the tube plate is stiffened by
flanged ribs or gussets, no stays need by used if a hydrostatic test to destruction of a boiler or
unit section built in accordance with the construction, shows that the factor of safetj'^ is at
least 5.

216 In a fire tube boiler, stays shall be used in the tube sheets if the distances between the
edges of the tube holes exceed the maximum pitch of staybolts given in Table 3. That part of
the tube sheet which comes between the tubes and the shell , need not be stayed when thedis-
tance from the inside of the shell to the outer surface of the tubes does not exceed that given
by the formula in par. 199, (page 2,201) using 160 for the value of C.

217 The net area to be stayed in a segment of a head may be determined by the following
formula:

-o)\ \2 (R—3]
^-4/ iH-5:

±AH 5) ^ /2 (^ 3) _ gQg ^^^^^ ^^ ^^ ^^^y^^^ ^^_ .^^
-5)

where

// = distance from tubes to shell, in.
R = radius of boiler head, in.
218 When the portion of the head below the tubes in a horizontal return tubular boiler is
provided with a manhole opening, the flange of which is formed from the solid plate and turned
inward to a depth of not less than three times the thickness of the head, measured from the
outside, the area to be stayed as indicated in fig. 3,905, may be reduced by 100 sq. in. The
surface around the manhole shall be supported by through stays with nuts inside and outside
at the front head.

DETAILS AND STRENGTH OF CONSTRUCTION 2,221

Fig. 3,952. — ^Radial T bars for fastening stays to heads.

Boiler Code. — Slay Bolts — Continued.

Table 4. Maximum Allowable Stresses for Stays and Staybolts

Stresses, pounds per square inch

Description of stays

For lengths

between supports

not exceeding

120 diameters

For lengths

between supports

exceeding

120 diameters

a Unwelded stays less than twenty di-
ameters long screwed through
plates with ends riveted over

h Unwelded stays and unwelded por-
tions of welded stays, except as
specified in line a

7,500

9,500
6,000

8,500

c Welded portions of stays

6,000

219 When stay rods are screwed through the sheets and riveted over, they shall be sup-
ported at intervals not exceeding 6 feet. In boilers without manholes, stay rods over 6 feet in
length may be screwed through the sheets and fitted with nuts and washers on the outside .

220 The maximum allowable stress per square inch net cross sectional area of stays and
staybolts shall be as given in Table 4.

The length of the stay between supports shall be measured from the inner faces of the stayed
plates. The stresses are based on tension only. For computing stresses in diagonal stays, see
pars. 221 and 222.

2,222 DETAILS AND STRENGTH OF CONSTRUCTION

x:

angle: bar

//'im:

o

0

o

#:°

:#>:

:#:

0

:#>\\

' S-CHANNEL BARS ^

/ °#vl=

■#0

»#

0 0 r:^ 0 0

► 0 0 o(|ft)o 0 0^

0 0 ^^^ C J

i

»oVo<g)o ^

000000000000000

Fig. 3,953. — ^Angle and channel bars for through stay connections.

A,S,M.E. Boiler Code — Stresses in Diagonal and Gusset Stays

221 Multiply the area of a direct stay required to support the surface by the slant or
diagonal length of the stay; divide this product by the length of a line drawn at right angles
to surface supported to center of palm of diagonal stay. The quotient will be the required area
of the diagonal stay.

, aXL

where

A = sectional area of diagonal stay, sq. in.
a = sectional area of direct stay, sq. in.
L =length of diagonal stay, in.

/ = length of line drawn at right angles to boiler head or surface supported to center of
palm of diagonal stay, in.
Given diameter of direct stay =1 in., a =0.7854, L =60 in.,
/ =48 inches; substituting and solving:
^ = .7854X60

48

= .981 sectional area, sq. in.

Diameter =1.11 inches = 1 ^ in .
^ 222 For staying segments of tube sheets such as horizontal return tubular boilers, where
L is not more than 1.15 times / for any brace, the stays may be calculated as direct stays,
allowing 90 per cent, of the stress given in Table 4 (page 2,221) .

A.S.M.E. Boiler Code. — Diameter of pins and area of rivets in brace.

223 The sectional area of pins to resist double shear and bending when secured in crow-
foot, sling, and similar stays shall be at least equal to three-fourths of the required cross-
sectional area of the brace. Ihe combined cross section of the eye at the sides of the pin shall
be at least 25 per cent, greater than the required cross-sectional area of the brace.

The cross-sectional area of the rivets attaching a brace to the shell or head shall be not less
than one and one quarter times the required sectional area of the brace. Each branch of a
crowfoot shall be designed to carry two-thirds of the total load on the brace. The net sectional
areas through the sides of the crowfeet, tee irons or similar fastenings at the rivet holes shall

DETAILS AND STRENGTH OF CONSTRUCTION 2,223

A.S.M.E. Boiler Code. — Diameter of pins and area of rivets in braces. — Continued.

be at least equal to the required rivet section. All rivet holes shall be drilled and burrs removed,
and the pins shall be made a neat fit.

224 Gusset stays when constructed of triangular right-angled web plates secured to single
or double angle bars along the two sides at right angles shall have a cross-sectional area (in a
plane at right angles to the longest side and passing through the intersection of the two shorter
sides) not less than 10 per cent, greater than would be required for a diagonal stay to support
the same surface, figured by the formula in par. 221, assuming the diagonal stay is at the same
angle as the longest side of the gusset plate .

A.S.M.E. Boiler Code. — Crown bars and girder stays.

230 Crown bars and girder stays for tops of combustion chambers and back connections,
or wherever used, shall be proportioned to conform to the following formula:

cy.d'y.T

Maximum allowable working pressure = t

(W—P)XDXW
where

W= extreme distance between supports, in.
P=pitch of supporting bolts , in.

D = distance between girders from center to center, in.
d = depth of girder, in.
T= thickness of girder, in.

C =7,000 when the girder is fitted with one supporting bolt
C = 10,000 when the girder is fitted with two or three supportmg bolts
C = 11,000 when the gird«r is fitted with four or five supporting bolts
C = 11,500 when the girder is fitted with six or seven supporting bolts
C = 12,000 when the girder is fitted with eight or more supporting bolts

Example: Given W = 34 in., P = 7.5 in., D = 7.75 in., d = 7.5 in., T =2 in.; three
stays per girder, C = 10,000; then substituting in formula:

Maximum allowable working pressure =

10,000X7.5X7.5X2 ,^, , ,^
(34-7.5)X7.75X34=^^^-^ lb. per sq. m.

U.S. Marine Rules. — Stays.

The maximum working pressure in pounds allowable per square inch of cross-
sectional area for stays used in the construction of marine boilers where same are accurately
fitted normal to supported surfaces and properly secured shall be ascertained by the following
formula:

Where P = working pressure in pounds.

A =least cross-sectional area of stay in inches.

a =area of surface supported by one stay in inches.

C =a constant.

C =9,000 for tested steel stays 1 inch and upward in diameter when such stays are
not forged or welded. The ends may be upset to a sufficient diameter to
allow for the depth of the thread . The diameter shall be taken at the bottom
of the thread, provided it is the least diameter of the stay. All such stays
after being upset shall be thoroughly annealed.

C =8,000 for a tested Huston or similar type of brace, the cross-sectional area of
which exceeds 5 square inches.

C =7,000 for such tested braces when the cross-sectional area is not less than 1.227

2,224 DETAILS AND STRENGTH OF CONSTRUCTION

^ .

U.S. Marine Rules. — Stays. — Continued

and not more than 5 square inches, provided such braces are prepared at one
heat from a solid piece of plate without welds.
C =7,500 for wrought iron stays 1 inch and upward in diameter when made of the
best quality of refined iron. The ends may be upset to allow for the depth
of the thread. The diameter shall be taken at the bottom of the thread,
provided it is the least diameter of the stay. Such stays may be welded.

Where C =6,000 for welded crowfoot stays when made of best quality of refined wrought iron,
and for all stays not otherwise provided for when made of the best quality of
refined iron or steel without welds.

Example. — Required the working pressure of a stay 1 inch in diameter, pitched 6 inches
by 6 inches center to center.

w 1- (1X1X.7854)X 6,000 ,^^^

Workmg pressure = ^-— ^ = 130.9 pounds.

oXo

Stay bolts and stays made of the best quality of refined wrought iron may be welded.
The lengthening of steel stays by welding shall not be allowed.

U.S. Marine Rules. — Screw Stays.

The diameter of a screw stay shall be taken at the bottom of the thread, provided it is
the least diameter of the stay.

For all stays the least sectional area shall be taken in calculating the stress allowable.

All screw stay bolts shall be drilled at the ends with a three-sixteenths-inch hole to at
least a depth of one-half inch beyond the inside surface of the sheet . Stays through laps or butt
straps may be drilled with larger hole to a depth so that the inner end of said larger hole shall
not be nearer than the thickness of the boiler plates from the inner surface of the boiler.
Hollow-rolled screw stay bolts may be used.

Flexible stay bolts that are made with a ball in socket on one end, the socket screwed into
the outside sheet and covered with a removable cap and bolt screwed into the inside sheet and
riveted over, may be used for staying flat surfaces without being drilled with a telltale hole.

Such screw stay bolts, with or without sockets, may be used in the construction of marine
boilers where fresh water is used for generating steam: Provided, however, That screw stay
bolts of a greater length than 24 inches will not be allowed in any instance , unless the ends of
said bolts are fitted with nuts. Water used from a surface condenser shall be deemed fresh
water.

Holes for screw stays shall be tapped fair and true, and full thread.

The ends of stays which are upset to include the depth of thread shall be thoroughly
annealed after being upset.

U.S. Marine Rules. — Pins and Rivets.

The sectional area of pins to resist double shear and bending, accurately fitted and secured
in crowfeet, sling, and similar stays, shall be at least equal to eight-tenths of the required
sectional area of the brace. Breadth across each side and depth to crown of eye shall not be
less than .35 of diameter of pin. In order to compensate for inaccurate distribution the forks
shall be proportioned to support two- thirds of the load, thickness of forks to be not less than
.66 of the diameter of pin.

The combined sectional area of rivets used in securing tee irons and crowfeet to shell,
said rivets being in tension, shall be not less than the required sectional area of brace. To insure
a well proportioned rivet point, rivets shall be of sufficient length to completely fill the rivet
holes and form a head equal in strength to the body of the rivet. All rivet holes shall be drilled.
Distance from center of rivet hole to edge of tee irons, crowfeet, and similar fastenings, shall
be so proportioned that the net sectional areas through sides at rivet holes shall equal the
required rivet section. Rivet holes shall be slightly countersunk in order to form a fillet at
pomt and head.

DETAILS AND STRENGTH OF CONSTRUCTION 2,225

Boiler Openings. — There are numerous openings into the
water and steam space of the boiler which are necessary for proper
operation and care. They may be divided into classes:

1. The major openings.

U.S. Marine Rules. — Pins and rivets. — Continued .

When sling stays are connected by pins to angles secured to shell, said angles shall be of
sufficient depth to resist shear. Section to resist shear shall be of sufficient depth to resist
shear. Section to resist shear shall be determined by the following formula:

A=DX2T

Where A = sectional area of pin.

D = depth from edge of pinhole to end of leg.
2T = thickness of two angles.

Example.

Diameter of sling stay, 2 inches. Diameter of pin, 1.6 inches. Thickness of angle, seven-
eighths of an inch. Required the depth from edge of pinhole to end of leg.
Substituting values and solving:

^ .7854X1.6X1.6 , _ . ,
^= 2X:875 =l-15mches.

Minimum diameter of rivets shall be found as follows:
Minimum diameter = -J_

.7854 X 12, 000 XN
where N equals number of rivets. Rivets shall be staggered in each leaf.

U.S. Marine Rules. — Tests of Bars for Stays and Braces.

All steel bars to be used as stays or braces in marine boilers and allowed a stress of 7,000,
8,000, or 9,000 pounds per square inch of section, tested by the United States assistant inspec-
tors at the mills where the material is manufactured, shall be tested in the following manner:
There shall be taken from each heat two pieces for tensile tests and two pieces for bending
tests. The full-size bars within the capacity of the testing machine may be used for tensile
tests. Where the full size of the bar is too large for the capacity of the testing machine, the
bar may be reduced in size to meet such capacity. To facilitate and insure accurate tests, all
bars for tensile and bending tests may be reduced in size. The minimum tensile strength df
each test piece shall be not less than 58,000 pounds per square inch of section and each test
piece that has been reduced in size shall show an elongation of at least 28 per cent, in 2 inches.
Where the full size of the bar has been used for testing, the test piece shall show an elongation
of at least 25 per cent, in 8 inches. When the tensile strength of the test piece is more than
63,000 pounds per square inch of section, each test piece that has been reduced in size shall
show an elongation of at least 26 per cent, in 2 inches. Where the full size of the bar has been
used for testing, each test piece shall show an elongation of at least 22 per cent, in 8 inches.
The pieces for the bend test shall be bent cold to a curve, the inner radius of which is equal to
one and one-half times the diameter of the bar without flaws or cracks. Should any such test
JDar fail in either the tensile or bending test, no bars from such heat shall be allowed to be used
in the construction of any marine boiler. Where a heat of steel bars has been passed by an
inspector, separate lots of bars from such heat may be furnished to different boiler manufac-
turers upon a certificate from the mill that the bars were made from such accepted heat.

2,226 DETAILS AND STRENGTH OF CONSTRUCTION

a. Hand hole

b. Manhole

2. The minor openings.

a. Steam

h. Water

main outlet
outlet for safety valve
outlets for auxiliary steam
outlet for injector

outlets for gauge cocks
outlets for water gauge
outlet for blow off valve
outlet for scum cock
inlet for feed water

Pigs, 3,954 to 3,958. — ^Hand hole and man hole construction.

Hand Holes and Man Holes. — These are placed in such position that
accumulations of sediment can be removed and that tools can be inserted
for cleaning boiler tubes and shell and so that entrance can be had for the
examination and replacing of stays, braces, tubes and pipe connections.
The man hole for a horizontal tubular boiler is usually placed in the top of
the shell or, for large boilers, in the head above the water line. In water-
tube boilers the man hole is placed in the end of the steam drum and for

DETAILS AND STRENGTH OF CONSTRUCTION 2,227

large sizes a manhole is placed in the end of the mud drum as well. For
smaller sizes a large hand hole is used in the rnud drum in place of the
man hole.

In horizontal tubular boilers, the hand hole is placed in each head below
the tubes and for vertical boilers hand holes are placed opposite the crown
sheet and at the bottom of the water leg . The man hole is usually made 11X15
inches, the longer diameter being placed at right angles to the axis of the
shell. The opening is made elliptical, and since the removal of the section
of the shell reduces its strength, reinforcement must be used, either by flang-
ing over the shell or by riveting on a collar around the opening.

The sectional area of the reinforcing rings should be not less than that of
the plate removed measured on the line parallel to the axis of the shell.

F:iG. 3.959. — Eclipse man-hole construction.

Many builders of boilers use a special form of man hole head called the
' Eclipse." In this the strengthening of the shell is secured by flanging the
boiler head around the opening and a steam tight joint is formed by using
a tongue and groove joint, as shown in fig. 3,959.

^ The accompanying table shows the area of hand and man holes in square
mches, and will be found useful in calculating the total pressure upon the
hand and man hole plates.

A.S.M.E, Boiler Code,~Man holes.

_ 258. An elliptical manhole opening shall be not less than 11 X 15" inches or 10 X 16
inches m size. A circular manhole opening shall be not less than 15 inches in diameter.

259. A manhole reinforcing ring when used, shall be of steel or wrought iron, and shall
be at least as thick as the shell plate.

260. Manhole frames on shells or drums when used, shall have the proper curvature,
and on boilers over 48 inches in 'diameter shall be riveted to the shell or drum with two rows
of rivets, which may be pitched as shown on page 2,215. The strength of the rivets in shear
on manhole frames and reinforcing rings shall be at least equal to the tensile strength of that
part of the shell plate removed, on a line parallel to the axis of the shell, through the center of
the manhole, or other opening.

2,228 DETAILS AND STRENGTH OF CONSTRUCTION

Area of Hand Holes and Man Holes

Long diameter

Short
diameter

6

8

10

12

12^

13

14

14M

15

Area in square inches

4

4^

5

5^

6

6}^

7

7J^

8

9

10

11

18.85

21.2

23.56

31.41
34.55
37.69
40.84
43.98

47.12
51.04
54.97
58.90
62.83
66.75

61.62
65.97
70.68
75.39
80.13
84.82
89.53
94.24

68.72
73.59
78.54
83.64
88.36
93.3
98.17
103.08

71.47

76.57

81.68

86.78

91.89

96.99

102.10

107.20

112.31

87.96
93.46
99.06
104.45
109.95
115.45
120.95

97.23
102.49
108.18
113.88
119.61
125.27

111.91
117.81
123.70
129.59

A,S.M.E. Boiler Code., — Man holes .-^ontiftued ,

261. The proportions of manhole frames and other reinforcing rings to conform to the
■above specifications may be determined by the use of the following formulee, which are based
on the assumption that the rings shall have the same tensile strength per square inch of section
^s, and be of not less thickness than, the shell plate removed.

For a single-riveted ring:

2 xr

For a double-riveted ring: W=,r—^-{-2d
For two single-riveted rings: W = tt7,+^

Where

For two double-riveted rings: ^^"JV/"^^^

W =least width of reinforcing ring, in.

DETAILS AND STRENGTH OF CONSTRUCTION 2,229.

Oues. How is the area of an elliptical hand or man holei
plate calculated?

Ans. The area of an ellipse is equal to the product of its semi-
axesX3.1416, or = product of its axesX .7854.

Oues. Why is only one or two bolts sufficient for secur-
ing a hand or man hold cover to the boiler?

Ans. Because the pressure of the steam does not come on the
bolts but on the boiler plate, the bolts serving merely to hold the
cover in place when there is no internal pressure on the boiler.

A.S.M.E. — Boiler Code. — Man holes. — Continued.

/i = thickness of shell plate, in.
d = diameter of rivet when driven, in.

/ = thickness of reinforcing ring — not less than thickness of the shell plate, m.
T = tensile strength of the ring, pounds per sq. in. of section
a =net section of one side of the ring or rings, sq. in.

5 = shearing strength of rivet, pounds per sq. in. of section (see par. 16, page 2,177.)
I = length of opening in shell in direction parallel to axis of shell, in.
N = number of rivets
To find the number of rivets for a single or double reinforcing ring:

5.ixrxa

iV + =-

SXd'-

262. Man hole plates shall be of wrought steel or shall be steel castings.

263. The minimum width of bearing surface, for a gasket on a manhole opening shall
be K inch. No gasket for use on a man hole or hand hole of any boiler shall have a thickness
greater than 34 inch.

264. A man hole shall be located in the front head, below the tubes, 9f a horizontal return
tubular boiler 48 inches or over in diameter. Smaller boilers shall have either a man hole or a
hand hole below the tubes. There shall be a man hole in the upper part of the shell or head of a
fire- tube boiler over 40 inches in diameter, except a vertical fire- tube boiler, or except on
internally fired boilers not over 48 inches in diameter. The man hole may be placed in the head
of the dome. Smaller boilers shall have either a man hole or a hand hole above the tubes.

A.S.M.E. Boiler Code. — Washout Holes.

265. A traction, portable or stationary boiler of the locomotive type shall have not less
than six hand holes, or washout plugs, located as follows: one in the rear head below the tubes;
one in the front head at or about the line of the crown sheet; four in the lower part of the
water leg; also, where possible, one near the throat sheet.

266. A vertical fire-tube boiler, except the boiler of a steam fire-engine, shall have not
less than seven hand holes, located as follows: three in the shell at or about the line of the crown
sheet; one in the shell at or about the line of the fusible plug when used; three in the shell at
the lower part of the water leg. A vertical fire-tube boiler, submerged tube type, shall have two
or more hand holes in the shell, in line with the upper tube sheet.

267. A vertical fire-tube boiler of a steam fire-engine shall have at least three brass wash-
out plugs of not less than 1-inch iron pipe size, screwed into the shell and located as follows: one
at or about the line of the crown sheet; two at the lower part of the water leg.

2,230 DETAILS AND STRENGTH OF CONSTRUCTION

Oues. When a man hole is cut in a shell how is the
shell reinforced ?

Ans. By a forged steel ring fitted about the hole as shown in
figs. 3,960 and 3,961.

Oues. How is a tight joint secured on a hand or man
hole?

Ans. By means of a gasket.

Figs. 3,960 and 3,961. — Man-hole and shell construction, showing reinforcing ring and other
details.

U. S. Marine Rules. — Manholes, Handholes, and Holes for Pipe Connections.

4. All boilers built on and after August 1, 1914, shall have a manhole opening above the
flues or tubes of not less than 10 by 16 inches, 11 by 15 inches, or of an equal area, in the
clear, and shall have such other manhole openings in other parts of the boiler as may be required
by local inspectors when considering blue prints or tracings submitted to them for approval, of
sufficient dimensions to allow easy access to the interior of the boiler for the purpose of inspec-
tion and examination.

When holes exceeding 6 inches in diameter are cut in boilers for pipe connections, manhole
and handhole plates, such holes shallbe reinforced, either on the inside or outside of boiler,
with reinforcing wrought-iron or steel rings, which shall be securely riveted or properly fas-
tened to the boiler, such reinforcing material to be rings of sufficient width and thickness of
material to fully compensate for 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 reinforcincr

DETAILS AND STRENGTH OF CONSTRUCTION 2,231

Fig. 3,962. — Method of riveting man-hole frames to shells or drums with two rows of rivets.

Fig. 3,963.— Cahill swinging
man-hole cover. It is hinged
to the boiler, thus permitting
it to be moved back from^ its
closed position and yet kept
in position for immediate re-
placement . This insures that
the cover will always come
back_ to exactly the same
position, so that the gasket
will fit in the same place each
time.

U.S. Marine Rules. — Man holes, hand holes and holes for pipe connections. — Contimied

ring shall have a sectional area equal to at least one-half of the sectional area of the 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

2,232 DETAILS AND STRENGTH OF CONSTRUCTION

Steam Domes. — The use of steam domes is practically a thing
of the past except on locomotive and some special boilers.

Formerly it was thought that
nearly dry steam could not be
obtained without the use of a
dome, but it has since been found
out that practically the same
results can be obtained without
a dome by means of a properly
designed so called dry pipe,
collecting the steam along the
entire length of the boiler. This
avoids the extra expense of a
dome and the objection that it
tends to weaken the she'l.

Oues. What is neces-
sary to obtain ^ood re-
sults with either a steam
dome or a dry pipe?

Pig. 3,964. — Steam dome with, cast iron head arranged for man-hole on ocomotive boiler.

U* S, Marine Rules. — Manholes, handholes and holes for pipe connections. — Continued

flanged inwardly to a depth of not less than 1}4 inches, measuring from the outer surface, the
reinforcement rings may be dispensed with.

When reinforcing rings as described above are made of wrought iron or steel, the material
shall not be required to be tested.

Seamless forged steel nozzles may be used for reinforcing holes cut in boilers when the
amount of material in the flange of the saddle that is secured to the boiler is equal to the amount
of material removed from the boiler.

No connection between shell of boiler and mud drum shall exceed 9 inches in diameter, and
the flange of the mud-drum leg shall consist of an equal amount of material to that cut out of
the shell of boiler. (Sec. 4418. R, S.)

DETAILS AND STRENGTH OF CONSTRUCTION 2,233

Ans. There should be an adequate amount of liberating sur-
face, and the boiler not operated beyond a reasonable overload
capacity.

Oues. What size opening is cut in tlie shell to com-
municate with the dome?

Ans. Some makers place the upper man hole in the dome
instead of the boiler head, while others make the opening just-
large enough to pass the steam at the proper velocity.

Fig. 3,965. — Steam dome with diagonal bracing and having steam and drain opening in shell-

For man hole construction the large opening is reinforced by flanging
the shell into the dome, as in fig. 3,964, and sometimes further strengthened
by riveting around it a heavy ring. Where the opening serves solely as a
steam outlet small drain holes should be dulled at the lowest point on each
side.

A.S.M,E, Boiler Code — Domes.

194 The longitudinal joint of a dome 24 in. or over in diameter shall be of butt and
double-strap construction, and its flange shall be double riveted to the boiler shell when the
maximum allowable working pressure exceeds 100 lb. per sq. in.

The longitudinal joint of a dome less than 24 in. in diameter may be of the lap type, and
its flange may be single riveted to the boiler shell provided the maximum allowable working
pressure on such a dome is computed with a factor of safety of not less than 8.

The dome may be located on the barrel or over the fire-box on traction, portable or station-
ary boilers of the locomotive type up to and including 48 in, barrel diameter. Fqr larger
barrel diameters, the dome shall be placed on the barrel.

2,234 DETAILS AND STRENGTH OF CONSTRUCTION

Oues. What is the usual proportion of a steam dome?

Ans. The diameter and height is usually about one-half the
diameter of the boiler.

The usual proportions for various size boilers are given in the following
table:

Proportions of Steam Domes

For 100 pounds pressure

Thickness

Thickness

Diameter of

Diameter of

Height of

of dome

of dome

boiler

dome

dome

shell

head

36

20

22

M

5f6

38

20

22

H

^/fe

40

22

24

K

Hi

42

22

24

H

Hi

44

24

26

H

Hi

46

24

26

H

Hi

48

26

28

K

Hi

50

26

28

'Ae

%

52

28

30

^i6

Vs

54

28

30

'4^

%

56

30

32

• %

%

58

30

32

He

%

60

32

34

H,

%

62

32

34

He

H

64

34

36

He

y%

66

34

36

%

Vm ■

68

36

38

Vs

Hi

70

36

38

Vs

Hi

72

36

40

Vs '

Hi

The Minor Openings. — The ordinary horizontal tubular
boiler should be provided with:

1 . Two main outlets for steam (one being for main steam sup-
ply and the other for supply to auxiliaries) .

2. An independent outlet for injector only.

DETAILS AND STRENGTH OF CONSTRUCTION 2,235

3. Two outlets for water column connections.

4. Opening for fusible plug.

5. Inlet for feed water.

6. Outlet for scum cock.

7. Outlet to blow off cock.

On vertical boilers the water column fixtures are usually connected direct
to the shell, thus there will be in addition to the above, three openings for
gauge cocks, two for water gauge, one for steam gauge. There is usually
only one main steam outlet, the safety valve being attached to a branch
connection from the outlet. On all boilers there should be a separate out-
let for the injector, and steam should not he taken for any other purpose
from this outlet .

Figs. 3,973 to 3,975 show the minor openings for horizontal and vertical
boilers.

The following table gives the usual proportions for the
minor openings:

A.S.M.E. Boiler Code. — Threaded openings.

268 An opening in a boiler for a threaded p _
have not less than the number of threads given in Table 7.

268 An opening in a boiler for a threaded pipe connection 1 in . in diameter or over shall

Table 7. Minimum Number of Pipe Threads for Connections

to Boilers

Size of pipe connec-
tion , m

1 and IM

1}4 and 2

23^ to 4
inclusive

4Mto6
inclusive

7 and 8

9 and 10

12

Number of threads
per in

IIH

113^

8

8

8

8

8

Minimum number of
threads required in
opening

4

5

7

8

10

12

13

Minimum thickness
of material re-
quired to give
above number of

* threads , in

0.348

0.435

0.875

1

1.25

1.5

1.625

If the thickness of the material in the boiler be not sufficient to give such number of threads,
there shall be a pressed steel flange, bronze composition flange, steel-cast flange 9r steel plate,
so as to give the required number of threads , constructed and riveted to the boiler in accordance
with methods given in par. 261 (page 2,228). A steam main or safety valve opening may-
be fitted with either a steel cast, wrought-steel or bronze composition nozzle. A feed-
pipe connection may be fitted with a brass or steel boiler bushing.

2,236 DETAILS AND STRENGTH OF CONSTRUCTION

Minor Openings in Horizontal Tubular Boilers

Horse Power

Diameter of shell

Length of shell

Size of main outlet

Size of auxiliary outlet

Size of blow off outlet. ....
Size of water column outlet
Size of feed water inlet ....

45

50

60 70

75 100

125

150

175 200 225

48

12

3

48

14

3

i

54

14

3

2K

2M

54
16

2K

13^

60
14

3

2K

IH
IK

60

16

5

3K
2K

72
16

5

4

23^2
IM
VA

72
18

5

4

23^
IM
13^

78

18

6

43^2

23^

13^

78
20

6

5

21^2

IM

2

84
20

6

5

23^

IH

2

Pigs. 3,966 to 3,972. — Bigelow pressed steel boiler parts. Such parts as lugs, hangers, man hole
saddles, man hole plates, nozzles and mouldings for the fronts are made of pressed steel
instead of cast iron. The advantage of this construction over cast iron must be apparent.

Oues. What are nozzles?

Ans. Short flanged nipples riveted to the main steam outlets.

Oues. Of what material should nozzles be made?

Ans. Of pressed steel.

DETAILS AND STRENGTH OF CONSTRUCTION 2,237

Fig. 3,975. — Minor openings in a vertical
boiler. In this type boiler the fusible
plug is tapped into one of the fire tubes,
being reached through a hand hole at the
low water level.

2,238 DETAILS AND STRENGTH OF CONSTRUCTION

Weight
Peri
Foot

PouNtts

00 ^ «0 0\ <N O ro Tt< lO -H »-■ CN fS 00 CN <^^ Tf« b- to O Ov oo o^ 1

1-1 1^ CN t^ fO 00 00 t^ vo »-< fO «0 fO Tf< -O 00 "^ O »0 ^ <S 00 ^0 ■

•^^^^c4<NfOfO'*Tj5.'TiI'r5<5 t>; O <N fD* vd 1-1 uS 00 ^ i I

Length

of Tube

Containing

One Cu.

Ft

1

279.449

163.178

106.839

75.340

55.965

43.205

35.208

28 599

23.690

20.237

17.252

14.882

13.164

10.237

8.^286

5.703

4.121

3.117

2.456

1.992

1.644

i.376

r:i69

II

1

vO'*<vOO\0"*r}<0\fOO\«NOO-«tfO rv» tJ< C/) 00 P>J 00 C^ i-* «0
^O'^-rt<»^i0t>*Ot^Ot^00CNO'-it^t^0\rlH0\v0P0O
t>vOO\'!j<^OOvO»OfOeN— iOOO\OOvO»O.Tl<Tjicr)cr)rofO

■^ CO es CN es »h' ,-<*,-<' .r.^ ,-1 ^Vi ,.4

1

Ovovo<^oooooov<^»r>-^o\»oa\-*t^ot>»'<^p^t^oo'<i«

esiiOTj.00'-'C>CM00t^t^O\«-'iOTfVOfO-^I^Cvj00rJ<T-.O\

oooio»-«0\vo»of0.rgi-iooo\oot^vo«OTjiT^c*5focccs
fC to <S <N i-i »-i »H th i-I »-I ^* T-i

1

c

1

0»0 0\-*0\«00\r*<OOTj<oflt>.00*OiOfO'-*0000-HOOiM
t^ TT r^ O^^OTJ^■e^OO^OOt^^OCNfOtO<MTt•vO OOrJ^ to SO •«i'
CM fO T** -^ »0 NO 00 0\ 0\ Ti CS fO vO 00 C^ O »0 O 0\ rsl rfi rf< lO

^r-<T-<»-l.»H<NfOfO^Tt<VOt^00Ov

c

II

lOr^00»-lP0f0Ov00NV0t~-l^0\'OO\av<Mrt»0\tN<M0\O

^oo^-Ht^foo\rot^»-iTt«t^<r)vot^'*-*ocNO\ooesc\

I.- OOrOOMOCOOOO'-ifOvOOOfOr^OvCNVOCNtOVO'^

*-i rH CS oo.'^l* »0 vO t^ 00 On O ■*'*>* lO-^vdoocst^rffO

c

p

iOr^t>»iO«NOO\00\NO'-flOO^iO'*tO«Ot^OfOf^eN

OOC^OOrfit^O'^OONCVjTtOOrO^-OOO'^rJicoONfO.
t^CMt^rJi»-iONO\ONOCNvOOiOO\vOCNrf>CNNO>OOOt^

i-.TH(NfOfO'rt*iOt^OOa\'-iCvjiOOvOOOOOfOOOiOfO«N
^^^_CNPO>^Ot^ON'-^fO

c
S

'0

c

2

c

1

to o lo ^ o <N CMo o o cvj x^ ^ to 00 «r) ■<* o po o lo o lo

rffO^Ooot^OtO'*'iOT»«rv]rviON»^— <iOONTj«Ti«t^vO'^
^Of0»-lO^N0^'-<0Nt^Tt<CNOf-*CN^-»00O\O'-|'-•'-leN^0

<Nrorr^fcONOf^t^OOONO«-<'-<POrj<J^O"5ft^OfOOO\

U

1
1

3.142
3.927
4.712
5.498
6.283
7 069
7.854
8.639
9.425
10.210
10.996
11.781
12.566
14.137
15.708
18.850
21.991
25.133
28.274
31.416
34.558
"37.699
40.481

1

CQ

rO'OrorO<^PO<N<»<-s.T-^ — OOavOOOOOOt>-NOlO •««<

1

lOlOtOtOlOlOO^O^O^OOO':l•■*OOtOl>:)lOO^OC^OO
ggggggOOOCNr^rvjcor^^N^NOOO^gCN^J^cq

5

c

1

1

1

OOOfOtOOOOCNtOt^OtN'OI^^CNr'.NOOONOtOtotOlO

««„,-itStNCSCS*O«O'0'0Tl«^«ONOt^00OvO'H<M

o

U

1

c

^^.,-.^c^es<N<Mco«*5POfO'«f«*<tONOt^ooa^»-«-*-

^^

rt O

If
is

•si

u ^

3 cu

a> ^
U ^

^ o

"^ t/j

-^ ^
i^

ft dj
«^ ^

0) CO
4f (D

S cu
^ o

oj •-

JS|
§B§

■" '-'.S

p <u w
<i) p, w

^ w q

^ d n
1^2

^ o

^ 1 t5

^ ^ ^

:S :^ CD

^ .^ 2

.^ o ^

^^ ^

2 O <D

(D

7< "^ U

.-g

CT3 r^ r^

'^ ^ >.
H Pi S

nS ^ .^
^ 2 .&

DETAILS AND STRENGTH OF CONSTRUCTION 2,239

The table on page 2,238 gives the ''properties" of stationary
and marine boiler tubes.

A.S.M.E. Boiler Code. — Tubes.

21 Tubes for Water Tube Boilers. The miiiimum thickness of tubes used in water tube
boilers measured by Birmingham wire gauge, for maximum allowable working pressures not
exceeding 165 lb. per sq. in., shall be as follows:

Diameters less than 3 in ^ No. 12 B.W.G.

Diameter 3 in. or over, but less than 4 in • No. 11 B.W.G.

Diameter 4 in. or over, but less than 5 in No. 10 B.W.G,

Diameter 5 in No. 9 B.W.G.

The above thicknesses shall be increased for maximum allowable working pressures higher
than 165 lb. per sq. in. as follows:

Over 165 lb. but not exceeding 235 lb 1 gauge

Over 235 lb. but not exceeding 285 lb 2 gauges

Over 285 lb. but not exceeding 400 lb 3 gauges

Tubes over 4-in. diameter shall not be used for maximum allowable working pressures
above 285 lb. per sq. in.

22 Tubes for Fire Tube Boilers. The minimum thicknesses of tubes used in fire tube
boilers measured by Birmingham wire gauge, for maximum allowable working pressures not
exceeding 175 lb. per sq. in., shall be as follows:

Diameters less than 23^ in No. 13 B.W.G.

Diameter 2% in. or over, but less than 3M in No. 12 B.W.G.

Diameter 3>^ in. or over, but less than 4 in No. 11 B.W.G.

Diameter 4 in. or over, but less than 5 in No. 10 B.W.G,

Diameter 5 in No. 9 B.W.G.

_ For higher maximum allowable working pressures than given above the thicknesses shall
be increased one gauge.

164 Process, a Lapwelded tubes shall be made of open-hearth steel or knobbled ham-
mered charcoal iron.

b Seamless tubes shall be made of open- hearth steel.

169 Hydrostatic Tests. Tubes under 5 in. in diameter shall stand an internal hydrostatic
pressure of 1,000 lb. per sq. in. and tubes 5 in. in diameter or over, an internal hydrostatic
pressure o^ 800 lb. per sq. in. Lapwelded tubes shall be struck near both ends, while under
pressure, with a two-pound hand hammer or the equivalent.

U.S. Marine Rules. — Tubes.

11-15 Lapwelded and seamless tubes, used in boilers whose construction was commenced^
after June 30, 1910, having a thickness of material according to their respective diameters,
shall be allowed a working pressure as prescribed in the following table, provided they are
deemed safe by the inspectors. Any length of tube is allowable.

Outside

Thickess

Maximum

Outside

Thickness

Maximum

diameter.

of Material

pressure
allowed

diameter.

of material.

pressure
allowed.

Inches.

Inch.

Pounds.

Inches.

Inch.

Pounds.

2

.095

427

SH

.120

308

2M

.095

380

3M

.120

282

2^

.109

392

4

.134

303

2M

.109

356

4M

.134

238

3

.109

327

5

.148

235

3M

.120

332

6

.165

199

2,240 DETAILS AND STRENGTH OF CONSTRUCTION

Another difference between boiler tubes and wrought pipe
consists in the fact that the outside of boiler tubes is smooth and
even, while wrought pipe is left comparatively rough and uneven.

Boiler tubes were formerly most commonly made of charcoal iron and lap
welded, but the present tendency is to use seamless and lap welded steel
tubes. In the formation of the lap of a lap welded tube, the plate i| upset,

Fig. 3,976. — ^Roller tube expander. It consists of a, set of rolls placed in a cage and in contact
with a central tapered pin . In operation the rolls are faced against the inside of the tube
by driving in the turning and forcing in the taper pin. The rolls rotate with the pin and
gradually expand the tube against the tube sheet.

then bent around until the thickened edges lap suflQciently. It is then
heated progressively about 8 inches at a time, and welded over a mandrel,
consisting, of a cast iron arm, with a slightly convex top over which the
tube is placed.

Seamless tubes are manufactured from solid billets by passing the
billet heated white hot through a piercing mill. The billet is forced over a
stationary piercing point of malleable iron by the forwarding and revolving
action of heavy rotary discs, enormous power being applied to displace the
metal from the center of the hot billet.

Holding Power of Boiler Tubes, — Experiments by Yarrow 8t Co., on
steel tubes 2 to 23^ inches in diameter, expanded into tube sheets gave
varying results, ranging from 7,900 to 41,715 pounds, the majority ranging

Fig. 3,977. — ^Prosser segment tube expander. It consists of a number of segments and a
taper pin. The segments are held in place by a spring. The outside surface of the segments
have the form to be given to the expanded tube, and the inside is a straight hollow cone
into which the steel taper pin fits. In operation the segments are forced apart in expanding
the tube by hammering on the steel pin. This type of expander requires careful handling
in order not to injure the tube. The hammering should be done gradually and the expander
turned frequently.

DETAILS AND STRENGTH OF CONSTRUCTION 2,241

from 20,000 to 30,000 pounds. In 15 experiments on 4 and 5-inch tubes the
strain ranged from 20,720 to 68,040 pounds. Beading the tube does not
necessarily give increased resistance, as some of the lower figures were
obtained with beaded tubes.

Ques. How are boiler tubes fastened to the heads or
tube sheets?

Ans. By expanding the metal of the tube against the tube
plate with a tube expander and then beading over the ends with
a beading tool.

Figs. 3,976 and 3,977 show two forms of tube expanders in general use,
and fig. 3,978 a beading tool.

U.S. Marine Rules. — Tubes.- — Continued
LAP WELDED BOILER TUBE UP TO AND INCLUDING 4 INS. IN DIAMETER.

All lap welded tubes shall be made of charcoal iron or mild steel made by any process.

Each tube shall stand an internal hydrostatic pressure of 1,000 pounds per square inch
and shall be struck near both ends while under pressure with a 2-pound hammer or its equiva-
ent without showing signs of weakness or defects.

All steel tubes, except those made of open- hearth steel, shall have the ends properly an-
nealed by the manufacturer before shipment.

All steel tubes shall stand expanding flanging over on the tube plate, and beading with-
out flaws cracks , or opening at the weld .

All lap welded boiler tubes over 4 inches in diameter, up to and including 30 inches in
diameter, shall be made of wrought iron or mild steel made by any process.

LAP WELDED BOILER TUBES OVER 4 INCHES UP TO AND INCLUDING
30 INCHES IN DIAMETER.
Each tube shall stand an internal hydrostatic pressure of 800 pounds per square inch and
shall be struck near both ends while under pressure with a '2-pound hammer or its equivalent
without showing signs of weakness or defects.

All steel tubes except those made of open-hearth steel shall have ends properly annealed
by the manufacturer before shipment.

SEAMLESS STEEL BOILER TUBES.
All steel tubes shall stand drilling, riveting, and culking and work necessary to install
them into the tube head without showing any weakness or defects .

No tube increased in thickness by welding one tube inside of another shall be allowed ior
use, but the ends of boiler tubes may be welded on for the purpose of making repairs or new
tubes may be welded for the purpose of making seamless steel boiler tubes them longer.

All seamless steel boiler tubes shall be made of open hearth steel.

Each tube shall be subjected to an internal hydrostatic pressure of 1,000 pounds per
square inch without showing signs of weakness or defects.

All tubes shall stand expanding, flanging over on the tube plate, and beading without
flaw or crack.

2,242 DETAILS AND STRENGTH OF CONSTRUCTION

Fire Doors. — In the case of vertical boilers, it is necessary to
provide an opening through both furnace and outer shell for
firing. The constructions of this opening are shown in figs.
3,979 to 3,982.

The simplest is the use of the ring indicated in fig. 3,979,
and perhaps the most common is that indicated in fig. 3,982.
In all cases the plates are riveted together or against the ring
and caulked to give a tight joint.

Figs. 3,983 to 3,985 show special construction of fire door
openings.

Doors are made of cast iron and should be sufficiently large to permit of

3D

Fig. 3,978. — ^Beading tool.

;$fe^^

<

^^

W///^

2^ .^K

_
I"

Figs. 3,979 to 3,982. — Various fire-door openings for vertical boilers.

^

NOTE. — Speller izing. — This is a method of treating metal which consists in subjecting
the heated bloom to the action of rolls having regularly shaped projections on their working
surfaces, then to the action of smooth faced rolls, and repeating the operation, whereby the
surface of the metal is worked so as to produce a uniformly dense texture, better adapted to

DETAILS AND STRENGTH OF CONSTRUCTION 2,243

Fig. 3,983 to 3,985. — Special constructions of fire-door openings.

0<o>0 OC O O C o<^
OCOOOOOOOO

ooooococoo

OCOOOOOOOO

oocooooooo
oooooooooo

o<^o OOO O O O<o>

Figs. 3,986 to 3,988. — ^Views of ordinary fire door, showing damper and baffle plate.

Figs. 3,989 and 3,990, — Balanced fire door as used on the sterling boiler.

2,244 DETAILS AND STRENGTH OF CONSTRUCTION

the convenient handling of shovel, slice bar and hoe to the back of the fire.
The opening is usually at least 12 inches high by 10 inches wide and runs
from this to 16 X20. For wide grates two small doors are preferable to one
large one.

The door proper is protected on the inside by a lining plate of cast iron
which should be perforated so that air entering the damper of the door will
be divided into fine streams. These plates must be made renewable, as
they are likely to be warpt and cracked by the heat.

Two forms of fire doors are shown in figs. 3,986 to 3,990, one in particular
showing the balanced doors used by the Stirling Boiler Co., which is opened
and closed up by a push on the counterweight which is outside the boiler.
In some plants the doors are covered with an asbestos coating on the out-
side and in others are given a coat of white paint to lessen the radiation and
discomfort to the fireman.

WATER TUBE BOILER
CONSTRUCTION

Steam Drums. — The great variety of ways in which the water
tube principle can be applied in the design of a water tube boiler
gives rise to a multiplicity of drum types. These may be classi-
fied:

1. With respect to position, as

a. Longitudinal.
h. Transverse.

2. With respect to function as

a. Steam.
h. Water.
c. Mud.

3. With respect to mechanical arrangement as

a. Tapped.
hm Header.
c. Manifold.

DETAILS AND STRENGTH OF CONSTRUCTION 2,245

4 . With respect to circulation as

a.
h.

Over or dry discharge.
Under or wet discharge.

Most boilers have longitudinal drums, because this gives a
longer drum, thus obtaining greater liberating surface.

Transverse drums are used on some marine boilers and others
where there is little head room, necessitating a low boiler.

TUBES

Fig. 3,991. — Ladd transverse steam drum with holes for expanded tubes. In construction
the drums are of one or two sheets without circumferential sheet seanis. The longitudinal
seams are above the roof tile, the head seams being protected by the side walls. The man-
hole covers are of the un-swinging type, and all flanges and connections are of wrought metal.

On boilers of small and medium size there is usually only one
drum for the steam and water (called the steam drum) , the water
line coming about the center of the drum, separate drums for
water and steam represent additional complication which is not
necessary.

On very large boilers there may be several drums. In fact,
the water tube principle lends itself to a very flexible construc-
tion, that is, boilers may be designed for practically any capa-
city, and also to fit almost any shaped volume.

2,246 DETAILS AND STRENGTH OF CONSTRUCTION

DISHED HEAD

Fig. 3,992. — Babcock and Wilcox marine transverse drum with holes bored for tubes leading
to the upflow and down flow headers. These are expanded joints for tubes as distinguished
from tapped or screwed joints -is used in pipe boilers.

Fig. 3,993. — Edge Moor longitudinal header drum connection with header on two drum boiler,
showing part of header and arrangement of stays.

DETAILS AND STRENGTH OF CONSTRUCTION 2,247

Tapped Drums. — Fig. 3,992 shows a typical drum of this type which is
tapped on each side along its length for connection with the pipe section
ends. Where tubes are used instead of pipes they are expanded into the
drum instead of connected by threaded joints.

Header Drums, — On boilers in which the tubes are expanded into head-
ers, the drums instead of having rows of holes for the upflows, have a large
opening at each end, each connecting with a leader. In some designs the
entire drum end is riveted to the header as shown in fig. 3,993. The first
mentioned construction is shown in fig. 3,994, in which only part of the
drum end is on communication with the header.

Fig. 3,994. — ^Union Iron Works longitudinal header drum end showing connection with header
and method of feed water delivery. The lettered parts are: A, front diaphragm; B, rear
diaphragm; G, feed water pipe; D, sediment blow off; E, water level; F, corrugated connec-
tion. The feed water is brought in at the front end of the drum, carried through to the
rear of the drum in an internal feed pipe which liberates the water into the purifying chamber.
The water when liberated is at the boiling point and precipitation of the solids and other
impurities takes place readily. These deposits settle in the bottom of the chamber and are
blown off by blow off pipe D . Baffles A and B show the method of isolating purifier and
conducting water from same down the rear header connection without obstructing the cir-
culation from the front to the rear of the drum. Special provision can be made to prevent
deposits in the feed pipe, where water is highly saturated with lime, magnesia or other solid
matter.

2,248 DETAILS AND STRENGTH OF CONSTRUCTION

Manifold Drums. — These, instead of being connected to a header at
each end, are provided with cross boxes which have a number of tapped
holes for connection to manifolds or small headers. Figs. 3,995 and 3,996
show one of the cross boxes, the drum construction in other respects being
similar to the header drum previously described.

Over and Under Discharge Drums. — ^According to the requirements
of the service for which a boiler is designed, the upflow tubes may be ar-
ranged to discharge into the drum either below or above the water level.
The first type is sometimes called drowned tube, because the tubes are always
covered with water. Fig. 3,997 shows this type as built for marine service,
and fig. 3,998, an over discharge or dry tube in which all the upflow tubes

o e o o o

Figs. 3,995 and 3,996. — ^Views of Babcock and Wilcox cross box which forms a connection
between the drum and the numerous manifolds or small sectional headers. The box is made
of forged steel.

discharge above the water. The object of the arrangement, as must be
evident is to obtain a low center of gravity.

Water and Mud Drums. — The Vogt boiler will serve to illustrate the
destruction between these drums and in fact it shows all three kinds of
drums as classified. In the "parallel series" arrangement of the tubes in

DETAILS AND STRENGTH OF CONSTRUCTION 2,249

^ si

'^3S

^'S'^

■^i^

^^|.S

S'!"

■*^ rt rt 1

U^^ M

(U

.'S.iS'^.S

o^ ^-S

o

.s

'S^iS

g C C5 yj

7i"B - ^

«)

^s^-s^

Of

.1

discha

vity is
connec
tubing

'C

h *S'd<*-.

gbo|o
5 <i> ^ «

s

2,250 DETAILS AND STRENGTH OF CONSTRUCTION

a; «

w • .2

^ biO g

4J ^H O

Ci5
^■^

0) .

mh o
w o

(U

03

13

1

biO

o

•3

o
P.

i

^ w

bo

s

S

^ «

Cli

C ••H

2g

1.1

w 8

•s

1

•i^.52

w ^

1?)

.2

S.<i^

g^

'^

^ w

d

O.J2

, 4->

rO

rOr^

^.^

4^

^ O

"Sd w^"

•a-^

^

si

^

£

5*^

^

DETAILS AND STRENGTH OF CONSTRUCTION 2,251

^

■+->

^

^"^

rO

a

0

CD

■^

^

(D

O

^

?.

j3

■+J

<D

.2

%

'3

CD

u

B

0

<D

03

o

x^

<D

M-1

^

X/1

.s

^

<D

"5

•S

a

a

O

o

rt

'■+J

o

CD

§

^

-2^

^

0

«

Q<

^

0

g*

-4J

£

$

ctJ

O

^

o

t/2

S-l

<D

3

O

*.

-^J

•3

^

H

CD

Q

^

S

.

1

,

^

s

OD

'rt

u

s

2

>

-^

>.

rt

o

S

^

a

1

^

;^

i

«

i

C3

C/2

>

>

'S

C/2

"a;
Q

'I

p

^

1

O

1

8

S3

p

2,252 DETAILS AND STRENGTH OF CONSTRUCTION

M^np^XapiS

m

€

UJ

<
UJ

X

Fig. 4.003.— Edge
Moor saddle type ol
support for rear
headers.

Figs. 4,004 to 4,010.-
Parts of Edge Moor
header showing ellip-
tical hand holes, tube
holes and holes for
stays, also the end
and side pieces, mar
hole and drum plates

p'k> <9

<»

iiiillla ^/k^r\

,,ilL •.

'Illii

»\\

u\\ll^\

fi9 O

,^

,„....

,^///#^7f

DETAILS AND STRENGTH OF CONSTRUCTION 2,253

where the tubes are divided up into groups as in ''sectional"
water tube boilers, in place of one large header at each end,
there are a number of small headers or manifolds.

Figs. 4,011 to 4,013.— Construction of
Edge Moor header hand hole plate.
Fig. 4,011, elliptical holes are first
punched in the blank plate by means of a
combined punch and spacing mechanism;
fig. 4,012, the plate is then heated to a
cherry red and the holes are forged to
shape between multiple dies; fig. 4,013,
a multiple spindle machine faces the
edges and automatically spaces and drills
the holes for the stays.

Figs. 4,004 to 4,010 show the parts of an Edge Moor header, and fig.
4,022 a portion of the header assembled. Figs. 4,014 to 4,021 show typical
manifold sectional header construction.

2,254 DETAILS AND STRENGTH OF CONSTRUCTION

Figs. 4,014 to 4,019. — ^Babcock and Wilcox sectional headers or manifolds. Fig. 4,014 and
4,015, wrought steel vertical header; figs. 4,016 and 4,017, wrought steel inclined header;
figs. 4,018 and 4,019 cast iron header. For pressures up to 160 pounds, cast iron headers
are used. The headers, as shown, may be either vertical or inclined. Opposite each tube
end in the headers is placed a hand hole of sufficient size to permit the cleaning, removal or
renewal of a tube. These openings in the wrought-steel vertical headers are elliptical in
shape, machine faced, and milled to a true back from the edge a sufficient distance to make
a seat. The openings are closed by inside fitting forged plates, shouldered to center in the
opening, their flanged seats milled to a true plane. These plates are held in position by studs
and forged steel binders and nuts, the joints between plates and manifolds are made with a
thin gasket, In the wrought steel inclined manifolds the handhole openings are either
circular or elliptical, the former being ordinarily supplied. The circular openings have a
raised seat milled to a true plane. _ The openings are closed on the outside by forged steel
caps, milled and ground true, held in position by forged steel safety clamps and secured by
ball headed bolts to assure correct alignment. With this style of fitting, joints are made
tight , metal to metal , without packing of any kind . Where elliptical hand holes are furnished
they are faced inside, closed by inside fitting forged steel plates, held to their seats by studs
and secured by forged steel binders and nuts. The joints between plates and manifolds are
made with a thin gasket. The vertical cast iron manifolds have elliptical hand holes with
raised seats milled to a true plane. These are closed on the outside by cast iron caps milled
true, held in position by forged steel safety clamps, which close the openings from the inside
and which are secured by ball headed bolts to assure proper alignment . All joints are made
tight, metal to metal, without packing of any kind.

DETAILS AND STRENGTH OF CONSTRUCTION 2,255

Figs 4,020 and 4,021. — Hand hole fittings. Fig. 4,020 inside hand hole fitting for wrough
steel vertical manifold; 4,021 outside hand hole fitting for wrought steel inclined manifold

Fig. 4,022. — ^Portion of Edge Moor header assembled showing elliptical hand holes. The
elliptical hand holes make it possible to pass every cover through its own handhole instead
of from one hole to another. The covers bear against the inside of the header plate. No
special make of gasket is required. The edges of the hand hole plate are flanged inward,
the upturned edges being faced in a special machine.

2,256 DETAILS AND STRENGTH OF CONSTRUCTION

Feed Water Heaters. — One of the component parts of some
types of water tube boilers, especially those intended for marine
service, is a feed water heater placed within the casing, compris-
ing about 20 to 30 per cent, of the total heating surface.

The feed water after passing through the heater and its temperature raised
to the boiling point, enters the boiler proper. Fig. 3,685 page (2,075) shows
one section or so-called "feed coils" of a typical heater as used on the Roberts
boiler. In assembling, one of these coils is placed on each side of the drum
above the main heating surface, and the two connected in series, parallel^
to feed line and drum as shown on page 2,075.

Figs. 4,023 to 4,026. — ^Unlon Iron Works component parts of hand hole plate complete with
both nut and yoke for same. These plates are made of steel, fit on the inside (9r pressure
side) of header plate and withdraw through the hole they cover. The bolt is securely
riveted to the plate in a hydraulic riveter and the yoke is of unique construction, permitting
its quick removal by simply loosening the nut a few turns, leaving the nut on the stud, thus
eliminating losses of same.

Superheaters. — Nearly all water tube boilers are provided
with superheaters, the great saving due to superheating now being
fully recognized. Steam, when first formed as in a boiler is known
as saturated steam, the temperature of which depends on the
pressure. To add more heat to a boiler in which water is present
would merely result in the production of more saturated steam
"wrifh i-nr>-r<=»oc<:^ r»f •nrf^ccurp' A diiryprhf^atf^r sprves to sp.narate thft

DETAILS AND STRENGTH OE CONSTRUCTION 2,257

steam from the presence of the water and expose it to the heat
of furnace gases, which results in superheat.

The amount of heat which may be added to steam in a super-
heater is independent of the pressure and is limited only by the
ability of the metal to withstand the high temperature .

This amount reaches the practical limit with ordinary materials of

Fig. 4,027.-
baffling.

-Foster superheater assembled for use in horizontal water tube boiler with vertical

A.S.M.E. Boiler Code. — Superheaters.

252 The ends of tubes, suspension tubes and nipples shall project through the headers
not less than 34 in., nor more than 3^ inch before flaring.

288 Every superheater shall have one or more safety valves near the outlet. The dis-
charge capacity of the safety valve or valves on an attached superheater may be included in
determining the number and sizes of the safety valves for the boiler, provided there are no in-
tervening valves between the superheater safety valve and the boiler.

289 Every safety valve used on a superheater, discharging superheated steam, shall have
a steel body with a flanged inlet connection and shall have the seat and disc of nickel composi-
tion or equivalent material, and the spring fully exposed outside of the valve casing so that it
shall be protected from contact with the escaping steam.

306 Each superheater shall be fitted with a drain.

2,258 DETAILS AND STRENGTH OF CONSTRUCTION

construction at, approximately, 1,000° Fahrenheit as a final temperature,
which represents, as superheat, the difference between the temperature of
saturated steam at the pressure under consideration, and 1,000°.
Fig. 4,027 show an approved form of superheater extensively used in both
water tube and fire tube boilers.

♦Location of Superheater. — ^A much used location for a superheater
is inside the boiler setting at a point in a water tube boiler between the tubes
and the shell. With the arrangement the steam is passed from the boiler,
through the superheater into the steam main to the engines.

Fig. 4,028. — Construction detail of Foster superheater element. In assembling, groups of
U-shaped elements, as shown, are joined in parallel to manifolds or connecting headers.
Series of cast iron annular gills or flanges, placed close to each other, are carefully fitted to
the outside of the tube so as to be practically integral therewith, thus exposing an external
surface of cast iron , to contact with the heated gases. The rings or annular gills are carefully
bored to gauge and shrunk on the tubes. Once being in position, the rings and tubes act
practically as a unit. As the coefficient of expansion of steel is a trifle greater than that of
cast iron, the rings grip the tubes even tighter when the temperature is increased as is the
case when the superheater is in service. The mass of metal in the tubes and covering acts as
a reservoir for heat. Inside the elements are placed closed tubes of smaller diameter, cen-
trally supported on kncbs to form a thin annular passage for steam between the inner and
•uter tubes , thus dividing the steam flow into three annular streams . The joints at the ends
of the elements are made by expanding the steel tubes into wrought steel headers.

*NOTE. — The question as to the proper location in which to place the superheating de-
vice has received a good deal of attention and been the subject of a great deal of experiment,
but still remains perhaps a matter of discussion. First there is the possible location of the
superheater in the main flue where it is exposed to the gases of combustion after they have left
the boiler and are to be allowed to escape. At first thought this location seems attractive
from the fact that any heat obtained in this way is a direct saving and that the superheating
would cost nothing. Further consideration, however, shows that in a properly designed and
operated plant practically no superheating at this point is possible for the reason that with a
boiler operating under 150 lbs. pressure good practice would call for a release of the combustion
gases at a temperature not much exceeding 500 °F., which temperature is necessary to maintain
a natural chimney draught sufficiently strong to burn a common grade of bituminous coal.
Again it will be found that while existing conditions may be such as to make it possible to
install the superheater in the flue and show a small increase in economy due to the increase in
temperature, yet, by placing an economizer in the same location, through which the feed water
may be passed on its way to the boiler, a much greater gain would result. The reason for this
is that the transfer of heat depends upon the difference of temperatures. This difTerence in
the case of an attempt to superheat the steam would be only 100 °F., to 200 °F., while in the
case of feed water it would be from 200 °F. to 400 °F., so that the saving due to an economizer
would be several times greater than could possibly result from the use of the superheater.

DETAILS AND STRENGTH OF CONSTRUCTION 2,259

Ones. What must be done in starting up a cold boiler
with a superheater located as just described?

Ans. The superheater being exposed to a very high tempera-
ture, must be flooded with water until the boiler is generating
steam freely.

Oues. What ill effect results from this flooding?

Figs. 4,029 and 4,030. — Cast iron corrugated rings forming the external protective covering
of Foster superheater elements.

Ans. It causes a deposit of scale at a location where, in some
types of superheater it is impossible to remove.

The flooding and draining of a superheater is in no sense a difficult
operation , but still it is one more operation to be performed when cutting
a boiler into and out of service and is best avoided if possible.

Another plan of locating the superheater is to place it higher

2,260 DETAILS AND STRENGTH OF CONSTRUCTION

**-! a; 03 rf 5^ o;
•o be S ^ -H o

Miff'

0) ^.S'O

rt c) S a « — o .'

to ,2

•S E lZt-% ?^<S| I SI'S »'«-5g| &^

g||!fj^!ei|ill^ll||ii

,D ^ S^Ts'S <r>-S a3"+H5 ^ 3 <l^ S t-i ► w 9:^ O) «

bo

) vh^ +3 5

, -e rt ?i o i:^ ?;4J--''rt c: F, CD „-i^ o

-73 C o a^ ,
--53^-MH:.^ jH OS t« o; O ^£ '

«4-i C^ ^U r-. ^ rs d ^S,'^:3<U^ S^ri

, p ;3 +

- - O "t^ <1>

tG ^, (D C >>i^-'-'J3

rt-g O fe S O 0) "^
C (U a; aS.t! >< rt

DETAILS AND STRENGTH OF CONSTRUCTION 2,261

up, but still within the boiler setting and entirely separated from

the main gas passages.

A small quantity of hot gas is conducted from the furnace or combustion
chamber through a small duct in the walls, to the superheater chamber
where it is brought into intimate contact with the superheating surfaces
after discharging into the main passage.

A . B^Uf^ERHEATER

Fig. 4,032. — Heine superheater setting. A small flue in the side walls passes some of the hot
gases direct from furnace to superheater chamber, where they make two passes around the
superheater tubes. ^ The flow of these gases is controlled by means of a damper at the outlet.
When closed the circulation is stopped, and as soon as the heat from the gases is absorbed,
only saturated steam will be delivered. By opening the damper various degrees the flpw
of gases can be regulated so as to give any desired degree of superheat up to the capacity
of the apparatus. Since the hot gases do not come into contact with the damper until
after passing through the superheater, there is no danger of overheating it. In the Heine
bulletin "Superheater Logic" page 30, cross- sectional views on lines AA and BB are shown,
illustrating in further detail the superheater chamber and passage leading thereto.

By manipulating a damper the flow of gas is controlled to suit the degree
of superheat desired, and by using thermostatic control a nearer uniform
superheating effect may be obtained than in any other way except possibly

2,262 DETAILS AND STRENGTH OF CONSTRUCTION

with the separately fired plan. The steam connection may or may not be
arranged to by pass the superheater.

Still another practice, and one for which there are many argu-
ments, is to place the superheater outside the boiler entirely and
over a separately fired furnace, passing either the whole or only
a portion of the steam through it.

In a large installation where the superheater would be of sufficient size
to warrant separate attention, the independently fired superheater will give
good economy, but in a plant consisting of only one or two boilers, the
superheater would necessarily be quite -small and might require more care
than would be justified for its operation, as it would be necessary to watch
it very closely.

Either gas or oil should be used for fuel since they may be quickly and
accurately controlled. Unless so handled it is quite uncertain whether the
total efficiency of the steam plant would be increased at all and if such a
superheater were placed where it would receive only average attention, it
is probable that its use would be unsatisfactory.

Oues. What are the main requisites for a satisfactory
superheater?

Ans. 1. proper location; 2, accessibility for cleaning and
repairs; 3, safety, and 4, durability.

INDEX OF GUIDE No, 5

READY REFERENCE

INDEX

Absolute, temperature, def., 1,764.
value, 1,766.
zero, determining, ills., 1,765.
Absorption of heat, 1,776.

rate, 1,776.
Acetylene, heating valve, 1,852".
Acid, nitric, fuel analysis, 1,913.
Air, absolute zero, ills., 1,765.

combustion, amount required, 1,857.
necessary amount, theoretical, cal-
culation, table, 1,861.
composition, 1,845.
constituents, 1,845.
corresponding volume oxygen, finding

volume, 1,936.
dried peet, analysis, 1,834.
excess, and CO2, table, 1,953.
effects, 1,879.

on combustion, 1,856.
flue gas, analysis, cooling effects,
table, 1,921.
furnace, steam boiler materials, ills.,

1,987.
heating, effects, 1,856.
nitrogen effects, 1,856.
oxygen, from, 1,845.
perfect combustion, actual amount,

1,859.
per pound fuel, theoretical amount,

computing, 1,859.
required for, combustion at 32° and 29.92
ins., table, 1,865.
combustion, determination, 1,864.
various fuels, 1,858.
supply, fuel gases, non-mixing, effects,
1,878.
pre-heating effects, 1,883.
volumetric analysis, 1,845.
weight analysis, 1,845.
Alloy, cast iron, steam boiler materials,
def., 1,993.
steels, steam boiler materials, def., 1 ,993 .
Almy series parallel pipe boiler, ills., 2,095,

2,115.
Aluminum steel, steam boiler material, use,
2.004.

American coals, classification, 1,829.
Analysis of, air, 1,845.
air dried peet, 1,834.
candle flame, diag., 1,846,
coke, 1,833.
flue gas, 1,919-1,938.
fuel, 1,887-1,918.
liquid, 1,917.
proximate, see Proximate analysis,
ultimate, see Ultimate analysis.
Analytical balance, Gaertner, ills., 1,893.

weights, Eimer & Amend, ills., 1,894.
Andrews vertical tubular steam heating

boiler, ills., 2,136.
Angle, bar, steam boiler construction, ills.,
2,222.
corner, ills., 2,217.
stays, steel, 2,214.
Anthracite coal, des., 1,825.
semi-, des., 1,825.
sizes, 1,831.
Apparatus, Eliot, flue gas analysis, ills.,
1,934.
fuel analysis, 1913.
necessary for fuel testing, 1,888.
Orsat, four pipette, ills., 1,932.
chemical reagents used, 1,931.
flue gas analysis, care of, 1,929.
Area, gas passage, steam boiler, 1,977.
hand hole(s) , plate, calc, 2,229.

table, 2,228.
head to be stayed, des., ills., 2,198-2,201.
man hole, table, 2,228.
plate, 2,229.
Ashes, analysis, 1,823, 1,915.

combustion, constituents, 1,883, 1,886.
def., 1,884.

determination, fuel analysis, 1,915.
fuel analysis, 1,892, 1,904.

testing for, 1,898.
iron oxide, effects of, in, 1,886.
A. S. M. E», method of determining carbon,
hydrogen and nitrogen, fuel
analysis, 1,902, 1,903.
obtaining average flue gas sample,
1,923.
riveted joints, Boiler Code, 2,176-2,188,

2,191.
testing steam boiler material code, 2,008.
Asphalt, des., 1,839.

II

INDEX OF GUIDE No. 5

Atmospheric pressure at sea level, 1,790.
Automatic, control, steam heating boiler,
2,152.

flue gas, collector. Hays, 1,924.

testing machine, steam boiler material,
Olsen, ills., 2,010.
Automobile boiler, Ofeldt, ills*, 2,088.

Stanley, ills., 1,965.

various, ills., 1,960.
Auxiliary, apparatus, 1,923.

B

Babcock & Wilcox, cross box construction,
ills., 2,248.
marine transverse drum, boiler construc-
tion, ills., 2,246.
sectional y headers, steam boiler cons.,
_ ills., 2,254.
horizontal water tube boiler, ills.,
2,080.
Bacharach pocket CO2 recorder, 1,937, 1,938.
Back rivet pitch, 2,170, 2,171.
Bagasse, des., 1,837.

heating value, 1,837.
Balance, analytical, Gaertner, ills., 1,843.
weights, fuel analysis, analytical, Eimer
& Amend, ills., 1,894.
Bar, crown, steam boiler construction, 2,214.
steam boiler construction, angle, ills.,
2,222.
Barrel calorimeter, des., 1,811, 1,812.
Base, steam heating boiler^ International, ills.,
2,144, 2.145.
square. National, parts, ills., 2,132.
Badenhausen water tubs boiler, ills., 2,033.
Bell mortar, fuel analysis, ills., 1,904.
Bending, cold, testing steam boiler materials,
diag., 2,019.
stress, def., 2,096.
Bent tube(s) water tube boiler, objection,
2,089.
Seabury, ills., 2,083.
Stirling, ills., 2,084.
various forms, ills., 2,082.
Benzole, heating value, 1,852.
Berry vertical fire tube boiler, ills., 2,108.
Bessemer, converter, ills., 1,991.

gas, steam heating boiler, ills., 2,133.
pig iron, def., 1,993.
■ process, steel production, 1,991-1,993.
Bigelow-Hornsby multi-drum water tube

boiler, ills., 2,093.
Bigelow upright shell boiler, ills., 2,041.
Bituminous, def., 1,825.

coal, combustion chamber, proportions,

1,879.
des., 1,826.
size, des., 1,826.
semi-, eastern states, 1,831.
western states, 1,831.
Block coal, des., 1,827.

particles in smoke, 1,875.

Block coal, — Continued

smoke, indication, 1,877.
Blakeley water tube boiler, ills., 2,057.
Blast tank, laboratory, Clayton & Lambert,

ills., 1,900.
Blow pipe, combustion, ills., 1,860.
operation, 1,860.
parts, 1,860.

using, instructions, 1,860.
Boiler(s), apparatus, auxiliary, 1,980.
automobile, Stanley, ills., 1,965.

various, ills., 1,969.
baffled, draught, ill?., 2,067.
bolts, 2,202.
braces, 2,202.
breeches flue{s), 2,037.

Calloway, ills., 2,038.

Lancashire, des., 2,037.
cast steel, carbon, 1,990.
characteristics, 1,973-1984.

air space ratio, 1,977.

circulation, 1,978.

gas passages, 1,977.

grate dimensions, 1 ,975.

heat transmission, 1,976.

heating sjirf age, 1,973-1,977, 1,980.

liberating surface, 1,978, 1,979.

position of boilers, 1,984.

priming, 1,980.

steam space, 1,978, 1,979.

various kindsiof boilers, 1,981-1,984.

water, height'of, ills., 1,980.

space, anangement, 1,978.
circulation experiment, ills., 1,802.
classification, 1,955-1,927.

externally fired, 1,§71.

furnace arrangements, various, ills.,
1.968.

internally fired, 1,971

shell, various, ills., 1,956.

steam generator, diff., ills., 1,971.

vertical, various, ills., 1,958.

water tube, various- ills., 1,960,
1,962.
Clyde, ills., 2,057.

Code, A.S.M.E., braced and stayed sur-
faces, 2,201.
coil, Monitor, ills., 2,144.
combined shell and water tube, ills.,

2,124-2,126.
Cornish, des., 2,033.

dimensions, 2,035.

Lancashire, diff., 1,970.

per cent, used, 2,112.
crown sheet, Reynolds, ills., 2,106.
coverings, 2,006.
difference between generator and boiler,

1,971, 1,972.
direct draught, ills., 2,067.
dome, ills., 2,232.
double tube, 1,967.
down draught, ills., 2,070, 2,119, 2,124,

2,126.
draught, ills., 2,067, 2,070.
drop tube. Field, ills., 2,045.

single, ills., 1,958.

INDEX OF GUIDE No. 5

III

Boiler (s) , — Continued
duty, 1,973.

elementary f parallel connection, ills.,
1,804.
series connection, ills., 1,804.
elephant, per cent used, 2,112.
evaporation, rates, 1,977.
expansion provision, 1,772.
externally fired, 1,971, 1,984.

per cent used, 2,112.
Fairbain, advantage of, 2,119.
Field tube, 1,967.

operation, 1,967.
Ward, ills., 2,072.
fire box, 1 970.
j$rciM&e(5), 2,099-2,117.

combined, Fitzgibbons, ills., 2,107.

shell, ills., 2124-2126.
crown sheet, Reynolds, ills., 2106.
duplex and triplex, des., 2,099.
internal fire box, vertical, 2,102.
horizontal, vertically set, 2,101.
radial, vertical, 2,105.
return, horizontal, duplex, ills., 2,100.
triplex, ills., 2,101.
object, 2,106.

vertical, Webber, ills., 2,107.
single flue, ills., 2,112.
tri-pass, extended shell, object,

2,110.
two-pass, Casey-Hedges, ills., 2,110,
vertical. Berry, ills., 2,108.
Reynolds, ills., 2,105.
setting, ills., 2,102.
water tube, diff., 1,965.
Hawkes, 2,121.
Silsby, ills., 2,125.
fiue and fire tube, Burnham, ills., 2,114.
fine, and tubular, 1,964.
disadvantage, 1,964.
Galloway, breeches and flues, cons.,

2,035, ills., 2,038.
tube, diff., ills., 1,963.
Western river typ3, Rees, 2,056.
fuel economy, conditions, 2,031.
furnace is), arrangements, ills., 1,968.
classification, 1,955-1,959.
internal, external, comparison,

1,984.
shape, classification, 1,959.
Galloway, des., 2,03 ^.
Graham, ste-m heating boiler, ills., 2, 148.

water tube boiler, ills., 2,077.
Graham, ills., 2,077, 2,148.
Gumey, ills., 2,060.
Gansaulus', classification, 1,959.
gas passage, area, 1,977.
arrangement, 1,977.
size, 1,977.
generator and boiler, diff., 1,972.
grate, dimensions, 1,974.
function, 1,974.
surface, 2,113.

various proportions, diag., 1,976.
headier), hand hole plate, ills., 2,253.
ills., 2,230,

Boiler(s), head(er), — Continued

staying, ills., 2,201.
hard steel, carbon, percentage, 1,990.
heat absorbing, class, 1,957.
heating surface, classification, 1,955.

essential qualities, 1,973.

extensiveness, 1,974.

form, 1,974.

tubular, characteristic, diag., 1,964..
heat transmission, measurement, 1,976.
horizontal, openings, ills., 2,237.

shell, steam generation, 1,982.

tube, ills., 1,958.

vertical, steam, difference, 1,982,
ills., 1,983.
insulators, 2,006.
internally fit ed, 1,971. 1,984.

Fairbain, 2,119. '
iron, use, 1,974.
Lancashire, ills., 2,035.

breeches, fluid, dc., 2,037.

dimensions, 2,038.

disadvantages, 2,037.
liberating surface, 1,978.

classification, 1,957.

insufficient, results,, 1,979.
locomotive, 2,045.

class, 1,963.

horse power, 2,113.

per cent used, 2,112.
marine, class, 1,963.

Clyde and Scotch, difference, 2,054.

des., ills., 2,047.

horse power, 2,113.

le^, ills., 2,054.

over discharge, Mosher, ills., 2,249.

position of, 1,984.

under discharge. Yarrow, ills.,.
2,249.

vertical, through tube, ills., 2,048.
mixed types, class., 1,963.
modern high pressure Scotch, ills.,

2,050.
modified Manning const., ills., 1,958.
moisture, amount, 1,819.
multi-tube, ills.. Manning, 1,958.
non-sectional, ills., 2,067, 1,967, 2,067.
one furnace, ills., 2,052.
openings, classification, 2,225.
pipe, 2,070, 2,117.

features, 2,073.

use, 2,074.

Taylor, ills., 2,116.

use, 2,074.
plate, silicon, effect, 2,005.

marine requirements, 2,156.
porcupine, 1,970.

tubes in, 1,972.
position, effect, 1,984.
pressure, classification, 1,959.
primary, 1,980.
rapid circulation, desirability, des.,

diag., 1,978.
return tube, features, 2,056,
Scotch, Clyde, diff., 1.970.

features, 2,048,

IV

INDEX OF GUIDE No. 5

Boiler(s), Scotch — Continued
form, 2,054.

modern high pressure, ills., 2,050. .
sectional, 1,967.

series pipe, ills., 2,077._
used in various countries, 2,112,
service, classification, 1,955.
setting, Lancashire, ills., 2,037.

materials used in, 1,985.
shell, 2,023.

classes, 2,023.

Clyde, Marine Iron Works, ills.,

2.052.

removable, ills., 2,051.
Cornish, ills., 2,034.

parts, 2,034.
development, 2,025.
elephant, ills.. 2,029.
flue, tube, difference, 2,025.

Galloway, ills., 2,035, 2,038,

2,039.

western river type, Rees, ills.,
2,056.
horizontal return tubular, ills., 2,026.

des., 2,027.
internally fired, 2,033.
Lancashire, breeches fiued, des.»2,037.

des., 2.035.

dimensions, 2,038.

disadvantages, 2,037.

without breeches, ills., 2,036.
large, disadvantage, diag., 1,981.
locomotive, 2,045.

differences, 2,046.

wagon top, cons., 2,046.

semi-portable, ills., 2,046.
marine, des., ills., 2,047.

locomotive type, Rees, ills.,
2,055.

Marine Iron Works, special,
ills., 2,053.

leg, ills., 2,054.
plain cylinder, ills., 2,027.
return tube, features, 2,056.,
Scotch, features, 2,048.

form, 2.054.

modern high pressure, ills.,
2,050.

parts, 2,049.

single furnace, ills., 2 051.
service classification, 2,023.
shape, classification, 1,959.
sheets, des., 2.025.
single return flue, ills., 2,028.
submerged tube, 1.958, 2.043.

Marine Iron Works, ills., 2.049.
Trevithick, dimensions, 2.034.

ills., 2,034.
tube flue, diff., 2,025.
tubular, threerpass, adv., 2,031.

horizontal return, ills., 2,032.

three-pass, ills., 2.031.
upright, Bigelow, ills., 2.041.

dry pipe, Graham, ills., 2,044.

evolution, diag., 2,040.

submerged tube, ills., 2.042.

Boiler(s), upright, — Continued

through tube, ills., 2,048.
types, 2,041.
various, ills., 1,956.
wagon. Watts', ills., 2,024.
water, level, proper, 2,044.

pockets, Petrie's, ills.. 2,039.
water tube, 2,121.

Fox, ills., 2,122.
Harrisburg, ills., 2,123.
sensitiveness, diag., 1.982.
use, 2,121.

Western river, ills., 2,030.
single tube, 1,967.

soft steel, carbon, percentage, 1,990.
steam formation, 1,799.
steam space, 1,978.

Clyde, modified, 2,109.

type, Murray, ills., 2,109..
single flue, ills., 2,109.
internal fire box, vertically extended,

2,102.
Kingsford, ills., 2,113.
Lyons, combined, adv., 2,120.
Smith- Manning, des., 2,104.
tube feature, class., 1,957.
steam generator, ills., 1,971.
steel, carbon, percentage, 1,990.

rust, effects, 1,990.
superheater, flooding, object, 2,259.
transfer of heat, method, 1,973.
Trevithick, des., 2,033.
tubes, see Tubes.

vertical, steam generating, 1,982.
through tube, ills., 1,958, 1,967.
water, 1,790.
water, fire, diff., 2.023.
tubular return, 1,970.
U. S. Marine rules, manholes, hand

holes, 2,232.
vertical, non-sectional, ills., 2,031.
openings, ills., 2.237.
per cent used, 2,112.
various, ills., 1,950.
submerged tube, ills., 2,042.
through tubes, various, ills., 1,958.
water, circulating, inclined tube method,
ills., 1,803.
grate, ills., 2.061.
height, diag., 1.980. ^

pockets, Petrie's, ills., 2.039. *
space, arrangement, 1.978.
special, classification, 2.099.
water tube, 2,117.

advantages, 1,981.
automobile, Ofeldt, ills., 2,088.
Badenhausen, ills., 2,086.
bent, objection, 2,089.
Seabury, ills., 2,083.
Stirling, ills., 2,084.
Blakeley, ills., 2,057.
circulation, directed flow, ills.,
2065.

feature classification, 2,059.
ills., 1,803.
over discharge, ills., 2,085.

INDEX OF GUIDE No. 5

V

Boiler(s), water tube, circulation, — Con.

under discharge, ills., 2,065.
closed, 2,089.
combustion feature classification,

2,060.
combustion principles, ills., 2,069.
curved, 2,080.
def., 2,057.
down flow, circulation, ills., 2,064.

sectional, Parker, diag., 2,096.

single ended, Parker, types,
ills., 2.097.
draught, down, ills., 2,070.
elementary, des., 2,061, ills., 2,062.

operation, 2,062.
field. Ward, ills., 2,072.
Graham, ills., 2,144.
Gumey's, ills., 2,060.
heating surface classification, 2,058,

2,059.

James', ills., 2,061.

load effects, 2,057.

multi-drum, Bigelow-Homsby, ills.,

2,093.

Connelly, ills., 2,094.
non-sectional, advantages, 2,066.

des., 2,064.

elementary, longitudinal drum,
ills., 2,061.

horizontal, Casey-Hedges, ills.,
2,078.

Keeler, ills., 2,078.

water tube,

vertical. Wicks, ills., 2,081.
operation, 2,062.

parallel, arrangement, accessibility,
2,067, ills., 2,068.

connection, ills., 2,059.

sectional, elementary, ills.,
2,068.
parts, 2,060.

ills., 2,060-2,062.
pipe, Almy, ills., 2,115,
per cent used, 2,112.
Porcupine, 2,089.

class., 2,090.

Niclausse, ills., 2,092.

Racine, ills., 2,091.

Shipman, ills., 2,090.
Roberts, cons., ills., 2,171-2,076.
sectional, horizontal, Babcock &

Wilcox, ills., 2,080.

parts, 2,066.
sensitiveness, ills., 1,982.
series, connection, ills., 2,058.

parallel, 2,091.

sectional, ills., 2,068.
special, 2,117-2,126.
tuhe{s), grouping classification,

2,058.

bent, various forms, ills., 2,082,
transverse drum, ills., 2,250.
triple tube, over discharge, Mosher

marine, ills., 2,087.
types, 2,057.
up flow, circulation, ills., 2,063.

Boiler(s), water tube, up flow, — Con.
down flow, 2,093.
Vogt, ills., 2,250.
water, grate, ills., 2,079.
level, 1,980.
Boiler construction, 2,155-2,262.
angle, bar, ills., 2,222.
comer, ills., 2,217.
bolt, stay, tap thread, 2,205.
brass, gauges used, 1,985.
brick, specifications, 1,985.
bursting pressure, des., diag., 2,162.
cast iron, use, 2,000.
copper, smelting methods, 1,985.
cross box, Babcock & Wilcox, 2,248.
crown bar, 2,214.
dome, tracing, diagonal, ills., 2,233.

proportions, 2,234.
drum, end. Union Iron Works, ills., 2,247.
longitudinal header. Edge Moor,

ills., 2,246.
marine transverse, Babcock &

Wilcox, ills., 2,246.
class, 2,244.

steam and water, Vogt, ""Is., 2,251.
Edge Moor, ills., 2,253.
factor of safety, 2,163.
fire door, des., ills., 2,242-2,243.
flat surfaces, reinforcement, 2,201.
gasket, use, 2,230.
hand hole, area, table, 2,228.
des., ills., 2,226.
fittings, ills., 2,255.
plate, area, calc, 2,229.

Union Iron Works, parts,
ills., 2,256.
header, 2,251.

classes, des., ills., 2,192.

Edge Moor, ills., 2,255.

sectional, Babcock & Wilcox, ills.,

2,254.
stayed area, des., ills., 2,198-2,201.
staying, ills., 2,215.
heater, feed water, 2,256.
^oint(s), butt, 2,179, 2.181, 2,182, 2.184.
butt, straps, equal, ills., 2,186.

ills., 2.169.
circumferential, ills., 2,191.
efficiency, diag., 2,160.
lap, butt, diff., ills., 2,167,. 2,168.
ills., 2,169, 2,177, 2,178.
single, 2.173.
riveted, efficiency, 2,171.
pull, effects, diag., 2.170.
riveted, strength, 2,160.

U, S. Marine Rules, 2,189-
2,190.

Wicks, table, 2,188.
ligament, efficiency, diags., 2,196.
malleable iron, use, 2,000.
man hole, area, table, 2,228.

cover, swinging, Cahill, ills., 2^231.
des., ills., 2,226.
Eclipse, ills., 2,227.
frame, riveting, ills., 2,231.
plate, area, calc, 2,229.

VI

INDEX OF GUIDE No. 5

Boiler construction, man hole, — Continued

reinforcement ring, ills., 2,230.
manifold, 2,251.
parts, 1,985.

pipe threads, number, minimum, 2,235.
plate, 2,156.

radial T bars, ills., 2,221.
reinforcements, types, 2,202.
rivet{s)f fracture between, ills., 2,175.

pitch, 2170, ills., 2.171.
riveted joints, calc, 2,172.
rivets, split and double shear, ills., 2,175.
rules, 2,155.

seam, element, ills., 2,173.
shear, single, double, difl., 2,170.
shell, 2,157.

course, 2,159.

strength, calc, 2,159.

thickness, 2,165.
ills., 2,166.

total pressure, diag., 2,158.
side plates, ills., 2,216.
sling straps, ills., 2,216.
stay angle, steel, 2,214.
stay bolt, screwed, maximum, pitch, 2,219.

tap, ills., 2,203.
stay is), breaks, 2,207.

crow foot, des., 2,213, ills., 2,212.

diagonal, types, ills., 2,210.

fastening, methods, ills., 2,218.

gusset, des., ills., 2,211.
stress, 2,212.

hollow, ills., 2,205.

jaw, des., ills., 2,213.

palm, des., 2,212, ills., 2,213.

radial, des., ills., 2,217.

riveted, des., ills., 2,205.

rod, des., ills., 2,208.

screwed, diameter, 2,205.

drilled holes, object, 2,206.
flaws, des., ills., 2,206.

socket, des., ills., 2,207.

stress, minimum, 2,221.

tube, 2,209.

ends, ills., 2,209.
pitch, 2,211.
•steam drum, Ladd, ills., 2,245.
steel, application, 1,990.
superheater, 2,256.

elements, ills., 2,259.

Foster, ills., 2,257, 2,258, 2,259.

Heine, ills., 2,260, 2,261.

location, 2,258.
thread stripping, prevention, 2,204.
tubeis), 2,238.

expander, segment, Prosser, ills.,
2,240.
roller, ills., 2,240.

fastening, 2,241.

des., ills., 2,193-2,198.
turnbuckle, ills., 2,209.
working pressure, des., 2,163, 2,164.
BoilerC) heating, 2,127-2,154.
automatic control, 2,152.
base. International, ills., 2,145.

square. National, parts* ills.» 2,132.

Boiler(,) heating, — Continued
capacity, table, 2,151.
coil. Monitor, ills., 2,144.
combination, rate, 2,131.
construction details, 2,143-2,152.
drop tube, Gorton, ills., 2,141.
fire pot, National, ills., 2,154.
gas, burner, ills., 2,133.

travel, diag., 2,134.
heating surface, 2,128.

efficiency, diag., 2,135.

inadequate, effect, ills., 2,130.
horizontal, assembling, ills., 2,142-2,143.

Capitol, ills., 2,139.

circulation. Ideal, ills., 2,147.

Graham home made water tube,
ills., 2,148.
International, parts, ills., 2,131.^
long pass, short pass, characteristics,

ills., 2,136.
Mayer, parts, ills., 2,138.
not cleaning, result, ills., 2,140.
performance, 2,133.
"points," 2,133.
proportions, 2,133.
push nipple, ills., 2,137.
section. National, ills., 2,153.
sectional, Gurney, ills., 2,149, 2,150.
steam dome, 2,152.

International, ills., 2,151.
syphon steam regulator. Ideal, ills.,

2,152.
underfeed, Williamson, ills., 2,137.
vertical, round, ills., 2,128.

tubular, Andrews, ills., 2,136.
water back. Gilt edge, ills., 2,139.
Boiler material (s), 1,985-2,022.
alloy, cast iron, def., 1,993.

steels, def., 1,993.
Bessemer, process, ills., 1,991.^

pig iron, def., 1,993.

steel, def., 1,993.
boiler, plate, silicon, effect, 2,005.
brass, physical properties, 1,997.
bricks, expansion, 2,005.

melting points, 2,006.

weight 2,005.
brittle, def., 1,995.
cast iron, 1,987.

def., 1,993.

physical properties, 1,997.
cast steel, def., 1,993.
charcoal hearth cast iron, def., 1,993.
coldshort, def., 1.995.
converted steel, def., 1,993.
copper, physical properties, 1,997.
crucible steel, def., 1,993.
ductile, def., 1,995.
elastic limit, def., 1.995.
fusible, def., 1,995.
grey cast iron, def., 1,993.
hardness, def., 1.996.

testing, Brinnell method, 1,998.
homogeneous, def., 1,996.
hot short, def., 1,996.

INDEX OF GUIDE No. 5

vir

Boiler material (s,) — Continued
malleable, castings, def., 1,994.

producing niethods, 1,988.
melting point of solids, def., 1,996.
open hearth steel, def., 1,994.
pig iron, def., 1,994.
puddled, iron, def., 1,994.

steel, def., 1,994.
refined cast iron, def., 1,994.
resilience, def., 1,996.
sheer steel, def., 1,994.
specific gravity, def., 1,996.
steel, aluminum, use, 2,004.

carbon, percentage, 2,002.

castings, def., 1 ,994.

def., 1,994.

manganese, use, 2,004.

nickel, use, 2,004.

phosphorus, use, 2,003.

physical properties, 2,001.

productiori, Bessemer process, 1,991.
open hearth process, 1,992.

sulphur, use, 2,004.
strength, def., 1,996.
tensity, def., 1,996.
tough, def,, 1,996.
used, 1,985.

washed metal, def., 1,994.
weldable, def., 1,996.
weld iron, def., 1,994.
white, cast iron, def., 1,994.

pig iron, def., 1,994.
wrought iron, def., 1,988, 1,994*.

Puddling, furnace, ills., 1,989.
process, 1.988.
Boiler materialsC) testing, 1,997-2,022.
A.S.M.E. Boiler Code, 2,008.
bending stress, def., 2,006.
casting, specimen, ills., 2,021.
cold bending, diag., 2,011.

test, 2,020.
compression, 2,007.

diag., 2,013, des., 2,015.
deflection instrument, Olsen, ills., 2,007.
deformation, 2,007.
elastic limit, Malyshoff method, diag.,

2,002.
factor of safety, 2,007.
flattening test, diag., 2,019.
force, 2,007.
hardness, ills., 2,018.

test, 2,020.
homogenity test, ills., 2,020, des.,

2,021.
cad, 2,007.
machine, automatic, Olsen, ills., 2,010.

Olsen, four-screw, ills., 1,999.
micrometer, ills., 2,005.
modulus of elasticity, 2,009.

of rupture, 2,009.
object, 2,006.
Olsen micrometer extensometer, ills.,

2,002-2,004.
permanent set, 2,009.
resilience, 2,011.
Riehle machine, ills., 2,015.

Boiler inaterials(,) — Continued
scleroscope, 1,997, 1,998.
shear, 2,011.
shearing test, 2,017.
single, double shear, ills., 2,016.
specimen holder, Riehle, ills., 2,011.
standard specimen, diag., 2,008.
strain, 2,011.
stress, 2,011.
tensile, diag., 2,012.

specimen, ills., 2,012.
tension, 2,014.

tortional test, des., ills., 2,017.
traverse, ills., 2,014, des., 2,016.
universal machine, tortion attachment^

Olsen, ills., 2,001.
weight beam, Riehle, ills., 2,009.
yield point, 2,013.
Boiling water, circulation, ills., 1,800.
importance, ills., 1,802.
free circulation, importance, 1,801.
higher temperature of steam, causes,

1,792.
pot, action in, 1,779.

inner bend in, effect, ills., 1,801.
U tube, circulation, 1,801.
Bolt(s), stay, boiler, 2,202.

boiler construction, ills., 2,202, 2,203.
tap, thread, 2,205.
Brace, boiler, 2,202.
Bracing, dome, steam boiler construction,

diagonal, ills., 2,233.
Brass gauges used, 1,986.

materials, physical properties, 1,997.
Braun hand power coal grinder, fuel analysis,.

ills., 1.901.
Breaking stay bolts, steam boiler construc-
tion, 2,207.
Breeches, flue boiler, 2,037.

Galloway boiler, ills., 2,038.
Bricks, compressive strength, 2,006.

boiler materials and specifications, 1,986.

expansion, 2,005.

fire, furnace, selection, consideration,

1,884.
melting points, 2,006.
weight, 2,005.
Brinnell method of testing, hardness of boiler

materials, 1,998.
Briquetted peat, des., 1,834.
British Thermal Unit, def., 1,756.
Brown platinum-rhodium thermo-couples^

ills., 1,768.
Bunsen, burner, operation, 1,853.
parts, ills., 1,853.
fall pump, flue gas analysis ills., 1,927.
Bureau of Mines, determining, carbon, fuel
analysis, 1,902.
hydrogen, 1,902.
nitrogen, 1,903.

method of, obtaining average flue gas
sample, 1,924.
sealing shipping cams, ills.,
1.892.
Bumham flue and fire tube boiler, ills.,
2,114.

VIII

INDEX OF GUIDE No. 5

Bursting pressure, steam boiler construction,

diag., des., 2,162.
Butt joint (s), steam boiler construction,

ills., 2,169, 2,179, 2,181, 2,182,

2,184, 2196.

Calorimeter, barrel, des., 1,811, 1,812.

combustion, double valve type, Emer-

^ son, ills., 1,870.
connections, wrong, diag., 1,817.
Carpenter, ills., 1,916.
operation, 1,916.
principles, 1,916.
fuse wire, correction, 1,912.
heat radiation, correction, 1,912.
ignition wiring, methods, Emerson, ills.,

1,908.
Mahler, ills., 1,906.
radiation correction, Pfaundler's method,

1,912.
readings, erroneous, ills., 1,817.
sampling nozzle^ 1,820.

Stott and Pigott, ills., 1,818.
Sarco, ills., 1,907.
Scientia, ills., 1,915.
separating, des., 1,815.

error, percentage, 1,811.
operation, 1,816.
sulphur correction, fuel analysis, 1,914.
test, des., 1.909.

fuel analysis, heat of, combustion,
1,905.
Thompson, ills, 1,918.
throttling, compact, ills., 1,819.
Ellison, construction, 1,813.
ills., 1,813.
operation, 1,813.
error, percentage, 1,811.
ills., 1,814.

ice to steam, ills., origin plate, 1,820.
types, 1,811.
uses, 1,811.
vacuum walled jacket, Emerson, ills.,

1.909.
water equivalent, 1,914.

methods of obtaining, 1,914.
Calorific values combustible gases, 1.871.
Can, shipping, sealing method, U. S. Bureau

of Mines, ills., 1,892.
Candle flame, analysis, diag., 1,846, 1.874.
Cannel coal, des., 1,827.
Capacity, flue gas collectors, 1.925.

table steam heating boilers, 2,151.
Capitol horizontal steam heating boiler,

ills., 2,1^9.
Carbon, apparatus for determining, ills.,
1,913.
cast steel, percentage, 1,990.
des., 1,847.

dioxide, physical properties, 1,853.
fixed, 1,823, 1,889, 1,898.

Cairhon.,— Continued

fuel analysis, A.S.M.E. method of de-
termining, 1,902.
Bureau of Mines, method of de-
termining, 1,902.
hard steel, carbon percentage, 1,990
hydrogen ratio, coal classification, use,

1,829.
steel, percentage, 1,990, 2.002.

steam boiler materials, uses, 2,002
Carpenter calorimeter, 1,916.
Cartridge details. Parr calorimeter, ills.,

1,910.
Casey-Hedges non-sectional horizontal water
tube boiler, ills., 2,078.
two pass fire tube boiler, ills., 2,110.
Cast iron, steam boiler material, 1,987.
alloy, def., 1,993.
charcoal hearth, def., 1,993.
grey, def., 1,993.
open hearth process, ills., 1,992.
physical properties, 1,997.
refined, def., 1,994.
use, 2.000.
white, def., 1.994.
Cast steel, carbon percentage, 1,990.
def., 1.993.
malleable, def., 1,994.
steel, def., 1,994.
Centigrade thermometer scale, 1,763.
Chamber combustion, bituminous coal,
proportions, 1,879.
h'eat storing, effects, 1,879.
refractory properties, effects, 1,879,
"Change of state," def., 1,781.
how effected, 1,782.
temperature, 1,782.
Charcoal hearth cast iron def., 1,993.
Chart(s), CO2 recorder, Sarco, ills., 1,943.
smoke, Ringelmann, diag., 1,880.
Uehling CO2 recorder, diag., 1,952.
Circulation, features, classification, water
tube boiler, 2,059.
Ideal horizontal steam heating boiler,

ills., 2,147.
in boilers, importance, ills., 1,802.
of water, in boiling, ills., 1,800.

in boilers, ills., 1,803.
rapid, steam boiler desirability, des.,

diag., 1,978.
water in boilers, inclined tube method,

ills., 1,803.
water tube boiler {s), directed flow, ills.,
2,064, 2,065.
Circumferential joint, steam boiler construc-
tion, ills., 2,191.
Clayton & Lambert, laboratory blast torch,

ills., 1,900.
Clinkers, cause, 1,883.

def., 1,885.
Closed, vessel, vaporization, effects, 1,779.
temperature, lowering, effects,
1,799.
water tube boilers, 2,089.
Clyde, & Scotch marine boilers, difference,
2.054.

INDEX OF GUIDE No. 5

IX

Clyde, — Continued.

boiler, Marine Iron Works, ills., 2,052.
type, special boiler, modified, 2.109.
Murray, ills., 2,109.
single flue, ills., 2,109.
water back, removable, ills., 2,051.
Coal, age, classification, 1,825.

American, classification, 1829.
losses, table, 1,953.
anthracite^ des., 1,825.

sizes, 1,831.
ash, des., 1,823.
bituminous, des., 1,826.
semi-, des., 1,826.
size, eastern states, 1,831.
western states, 1,831.
block, des., 1,827.
cannel, des., 1,827.
carbon hydrogen ratio, classification,

use, 1,829.
chemical J composition, 1,824.

constituents, 1.823.
classification, 1,824, 1,825.
combustible, total, des., 1,823.
combustion, air required for, 1,861.

characteristics, 1,825.
composition of, 1,876.
culm, des., 1,828.
density, classification, 1,825.
fixed carbon, des., 1,823.
fuel analysis, heating value, calc,

1,911.
gas, comparison, table, 1,843.
grinder, fuel analysis, hand power,

Braun, ills., 1,901.
heating values, 1,828.

different causes, 1,823.
lignite, des., 1,824, 1,827.
location, 1,823.
lumps, 1,830.
oil, evaporation, comparative, 1,841.

fuel value, relative, 1,840.
properties of, 1,822.
5am^/e(5), grots, preparing, ills., 1,890-91.

Jones, ills., 1,905.
sizes, 1,830, 1,831.
Coal tar, composition, chemical, 1,838.
des., 1,838.
heating value, 1,838.
vs. oil tar, 1,839.
testing, 1,889.
, vegetable origin, evidence, 1,824.
volatile matter, des., 1,823.

percentage curves, 1,872.
wood, heating values, comparative,
1,835.
Cochrane boiler, ills., 1,938.
Coefficient of, expansion, diag., 1,772.

linear expansion, def., 1,772.
Coke, analysis, 1,833.

combustion, air required for, 1,861.
des., 1,832.

gas retort, production, 1,832.
heating value, 1,833.
physical properties, 1,832.
Coil boiler. Monitor, ills., 2,144.

Cold, bending, test, diag., 2,019, 2,020.
effects, 1,755.

molecular vibration, influence, 1,755.
short, def., 1,995.
shut, def., 1,995.
Collector, j^M« gas, automatic. Hays, 1,924.
capacity, 1,925.
ills., 1.926.
operation, 1,926.
over water, objection, 1,925.
sample. Hays automatic flue gas
collector, 1,924.
Colored smoke, indication, 1,876.
Combined fire tube boiler, Fitzgibbons, ills..

2,107.
Combustible, def., 1,889.
principle{s,) 1,847.

variation, 1,847.
total, des., 1,823.
Combustion, actual, resultant, 1,921.
air, excess, effects, 1,879.
heating, effects, 1,856.
necessary amount, theoretical, cal-
culated, table, 1,861.
nitrogen, effects, 1,856.

effect, useful, 1,856.
supply, pre-heating, effects, 1,883.
analysis, ultimate, 1,858.
ashes, def., 1,884.

iron oxide, effects of in, 1,886.
principle constituents, 1,885.
blow pipe, ills., 1,860.
operation, 1,860.
parts, 1,860.

using, instructions, 1,860.
calorimeter, double valve type, Emerson,

ills., 1,870.
candle flame, analysis, diag., 1,846.
carbon, des., 1,847.

dioxide, physical properties, 1,853.
chamber, bituminous coal, 1,879.
heat storing, effects, 1,879.
refractory properties, effects, 1,879.
character ot coal classification, 1,825.
clinker {s), def., 1,885.

cause, 1,883.
coal, volatile matter, percentage curves,

1,872.
complete, 1,851, 1,853.

ashes, percentage, 1,886.
hydro-carbon gases, how obtained,

1.878.
oxygen, amount necessary, 1,854.
crucibles, various, ills., 1,873.
Davy's lamp, experiment with, ills.,

1,849.
def., !,845.

Dulong's formula, 1,864.
elements, 1,850.
excess air, effects, 1,856.
feature classification, water tube boiler,

2,060.
flame, candle, 1,874.

cooling ignition temperature, ills.,

1,850.
visible, 1,875.

INDEX OF GUIDE No. 5

Combustion, — Continued
fuel, def., 1,846.

dry, heating value, formulae, 1,864.
gaseous, heating valve, 1,869. _
gases, air supply, non-mixing,

effects, 1,878.
heating value, available^ 1,865.
determination, 1,862, 1,863.
high and low, 1,869.
incombustible matter, 1,885.
kindling temperature, 1,850.
smoke causes, 1,877.
various, air required, 1,858.
Jurnace, design, poor, effects, 1,884.
fire brick, selection, 1,884.
temperature, calculating, 1,881.
increasing, 1,883.
gases, calorfic valves, 1,871.
heat of, calorimeter, fuel analysis, table,
1,912.
calorimeter test, 1,905.
■hydro-carbon, acetylene, heating valve,
1,852.
benzole, heating value, 1,852.
heating valve, 1,852.
marsh gas, heating value, 1,852.
methane, heating value, 1,852.
defiant gas, heating value, 1,852.
hydrogen, des., 1,848.

density, 1,848.
ignition point, 1,849.
imperfect, how indicated, 1,876.
incomplete, 1,855.

ills., 1,851.
kindling point, 1,849.
J>erfect, air, actual amount, 1,859.
invisibility, 1,875.
products,, resultant, 1,920.
results, 1,853.
principles, water tube boiler, ills., 2,069.
proximate analysis, 1,873.
rates, steam heating boiler, ills., 2,138.
Ringlemann's readings, plotting, diag.,

1,882.
secondary, causes, 1,861.
smoke, black, indications, 1,877.
black particles, 1,875. ,

•causes, ills., 1,876.
chart, Ringelmann, diag., 1,880.
classification, 1,880.
colored, indication, 1,876.
density, determining, electrical
method, 1,882.
grading, 1,881.
neating boiler, rate, 2,131,
sulphur, des., 1,849.
supporter of, ills., 1,855, 1,857.
surface of flame, ills., 1,854.
ultimate analysis, 1,863.
throttling, calorimeter, ills., 1,819.
■Compression test, 2,007, 2,013, 2,0l5.

steam boiler materials, diag.
Compressive strength, bricks, 2,006.
Condensation, causes, 1,799.
Conductivity of heat, in metals, ills., 1,775.

Connelly multi-drum water tube boiler, ills.,

2,094.
Cooling, effects due to excess air, table, 1:921.
of flame below ignition temperature, ills.,
1.850.
Copper, smelting methods, 1,986.

physical properties, 1,997.
Corner angles, steam boiler const., ills., 2,217.
Couple, thermo-, Fox bars, com., ills., 1,769.
Courses, shell, boiler construction, 2,159.
Cover, man hole, steam boiler construction,

swinging, Cahill, ills., 2,231.
Coverings, steam boiler, 2,006.
Cornish boiler, des., 2,033.
dimension, 2,035.
parts, 2,034.
Cornish, Lancashire steam boiler, diff., 1,970.
CO2 recorder, air excess, table, 1,953.

auxiliary boiler room, Uehling, ills.,

1,954.
Bacharach pocket, ills., 1,937.
chart, sarcq, ills., 1,943.
checking CO2, 1,914.
draught gauge, 1,949.
elementary, operation cycle, 1,944.
flue gas analysis, Bacharach pocket,

manipulation, diag., 1,938.
fuel losses, table, 1,953.
gauge, Uehling, ills., 1,954.
machine, Uehling, ills., 1,952.
operation, principles, 1,943.
readings, taken alone, unreliability,

1,939.
Sarco, 1,948.

operation, 1,941.
parts, ills., 1,940.
Uehling, charts, diag., 1,952.

important parts, diag., 1,951.
working principles, diag., 1,950.
what CO2 indicates, 1,939.
Critical temperature, diag., 1,781.
Cross box, steam boiler construction, Bab-
cock & Wilcox, ills., 2,248.
Crow foot stay, 2,213, ills., 2,212.
Crown, bar, steam boiler construction, 2,214.

sheet, Reynolds, boiler, ills., 2,106.
Crucible (s), combustion, various, ills., 1,873.
steel steam boiler, material, def., 1,993.
Crude oil, des., 1,839.
Crusher plate, fuel analysis, ills., 1,902.
Cube, Leshe, ills., 1,773.
Culm, des., 1,828.
Curved water tube boilers, 2,080.
Curves, volatile matter, coats, percentage,

1,872.
Cycle, operation, cog recorder, 1,944.

Davy's safety lamp, cams, 1,847.
experiment with, ills., 1,849.
ills., 1,847.
principles, ills., 1,848.

INDEX OF GUIDE No. 5

xr

Deformation test, steam boiler materials,

2,007.
Density, liquid, point, 1,788.
maximum, liquid, 1,788.

volumetric changes, 1,788.
of, coal, classification, 1,825.

hydrogen, 1,848.
smoke, determining, electrical method,
1,882..
grading, 1,881.

Ringelmann sc!ale, ills., 1,881.
Design, furnace, poor, effects, 1,884.
Dessicator, fuel analysis, Scheibler, ills., 1,899,
Diagonal, bracing, steam dome, ills., 2,233.
rivet pitch, 2,170, ills., 2.171.
stay, types, ills., 2,210.
Diameter, screwed stay, 2,205.
Diox;ide, carbon, physical properties, 1,853.
Directed flow, water tube boiler, ills., 2,065.
Distillates in coal, 1,876.
Dome steam boiler, bracing, ills., 2,233.
International, ills., 2,151.
proportions, 2,234.
Doors, fire, des., ills., 2,242-2,243.
Down, draught steam heating boiler, ills.,
2,149.
water tube boiler, ills., 2,070.
flow, water tube boilers, ills., 2,064,
2,070, 2,096. 2,097.
Draught gauge, CO2 recorders, 1,949.
Drop tube boiler. Field, ills., 2,045.

heating boiler, Gorton, ills., 2,141.
Drum, see boiler (s), drum, 2,245.
Dry, fuel, heating value, formulae, 1,864.
pipe, upright shell boiler, Graham, ills.,

2,044.
steam, 1,789.
Drying oven, Gaertner, ills., 1,896.
Ductile, def., 1,995.
Dulong's formula, oil tar, 1,839, 1,864.
Duplex, and triplex fire tube boilers, des.,
2,099.
horizontal return fire tube boiler, ills.,
2,100.

Eastern States bituminous coal, 1,831.
Eclipse manhole construction, ills., 2,227.
Edge Moor, header, ills., 2,255.

longitudinal header drum, boiler cons-
truction, ills., 2,246.

steam boiler construction, ills., 2,253.
Eimer & Amend, analytical balance weights,
ills., 1,894.

double wall oven, ills., 1,895.

muffle furnace, fuel analysis, ills., 1,896.

readmglens, ills., 1,911.

sulphur photometer, ills., 1,914.
Elastic limit, Malysheff method, determining,
diag., 2,002.

steam boiler materials, def., 1,995.

Elasticity, modulus of, 2,009.
Electric, muffle furnace, ills., 1,896.

method of determining smoke density,
1,882.
Elementary, CO 2 recorder, operation cycle,
1,944.
non-sectional water tube boiler, longi-
tudinal drum, ills., 2,066.
parallel sectional water tube boiler, ills.,

2,068.
series sectional water tube boiler, ills.,,

2,068.
steam boiler, parallel connection, ills.,
1,804.
series connection, ills., 1,804.
water tube boiler, des., 2,061, ills., 2,062.
Elephant boiler, ills., 2,029.
Eliot apparatus, flue gas analysis, ills., 1,934,
Ellison throttling calorimeter, 1,813.
Emerson, calorimeter, ignition wiring, meth-
ods, ills., 1,908.
vacuum walled jacket, ills., 1,909.
double valve type calorimeter, ills., 1,870
Energy, row plants receive, 1,822.
Engine, fire boiler, fire tube water tube,
Silsby, ills., 2,125.
shell water tube. Fox, ills., 2,122.
Equivalent, of heat, mechanical, 1,770.

water, calorimeter, 1,914.
Eschkas method, fuel analysis, 1,900.
Ethelyne, heating valve, 1,852.
Evaporation, /aciors o/, 1,803, 1,805, 1,806.
table, 1,807, 1,808.
latent heat, 1,781.
of coal and oil, comparative, 1,841.
rates, steam, boiler, 1,977.
standard, 1,805.
water, fuel, table, 1,844.
Evolution of, horizontal return tubular
boiler, ills., 2,026.
upright boiler, diag., 2,040.
Excess air, and C02, table, 1,953.
combustion, effects, 1,856.
flue gas analysis, table, 1,921.
Expander, tube, roller, ills., 2,240.

segment, Prosser, ills., 2,240.
Expansion, coefficient of, diag., 1,772.
due to heat, 1,771.

advantages, 1,773.
linear, coefficient of, def., 1,772.
liquid, 1,788.
of bricks, 2,005.
provision in boilers, 1,772.
Extended shell tri-pass fire tube boiler, 2,110.
Extension and compression micrometer,

Olsen, ills., 2,005.
Extensometer, micrometer, Oken, 2,002-

2,004.
External, latent heat, 1,795.

diag., 1,796.
External, work of fusion, 1,786.
diag., 1,787.
formula, 1,787.
work of vaporization 1,795.
Externally fired boiler, 1,971, 1,984..

XII

INDEX OF GUIDE No. 5

Factor (s) of evaporation, 1,805.
how obtained, 1,803.
table, 1,808.
use, 1,807.
Factor of safety, steam boiler, 2,163.
test, steam boiler materials, 2,007.
Fahrenheit, surfusion, 1 785.

thermometer, scale, 1,763.
Fall pump, Bunsen, ills., 1,927.
Feed water heaters, boiler construction, 2,256.
Field drop tube boiler, ills., 2,045, 2,072.
operation, 1,967.
Ward, ills., 2,072.
Fire, box, boiler, 1,970.

bricks, furnace, selection, consideration,

1,884.
doors, steam, des., ills., 2,242-2,243.
engine boiler, fire tube water tube,
Silsby, ills., 2,125.
shell, water tube. Fox, ills.,
2,121.
pot, steam heating boiler. National,

ills., 2,154.
tube and water tube boiler, diff., 1,965.
Fire tube boiler, see Boiler(s) fire tube.
Firing, grate shape, boiler characteristics,
effect, diag., 1,975.
proper, eondition necessary, 1,887.
Fittings, header hand hole, ills., 2,255.
Fitzgibbons combined fire tube boiler, ills.,

2,107.
Fixed carbon, des., 1,823.
def., 1,889.

fuel analysis, testing for, 1,898.
Fixed points, thermometer scale, 1,760.
Flame, candle, analysis, diag., 1,846.
ills., 1,874.
parts, ills., 1,874.
cooling, ignition temperature, ills., 1,850.
surface, only complete combustion, ills.,

1,854.
visible, 1,875.
Flattening test, diag., 2,019.
Flooding superheater, object, 2,259.

results, 2,259.
Flue, and fire tube boiler, Bumham, ills., 2,114.
object, 2,114.
and tube, diff., 2,025.
and tubular steam boiler, 1,964.
boiler, disadvantages, 1,964.

Western river type, Rees, ills., 2,056.
Galloway, ills., 2,039.
Flue gas analysis, 1 ,9 19-1 ,938.

basis chemical reaction, 1,928.
CO2, increased saving due to, 1,920.
CO2 recorder, Bacharach pocket, ills.,

1,937, 1,938.
Ehot apparatus, ills., 1,934.
excess air, cooling effects, table, 1,921.
fall pump, Bunsen, ills., 1,927.
jet pump, Richards, ills., 1.927.

Flue gas analysis, — Continued

Or sat apparatus, care of, 1,929.
chemical reagents used, 1,931.
des. 1,932.

four pipette, ills., 1,932.
precision 100 cc. standard, ills. ,1,936.
three pipette, connection, ills., 1,930.
pipette, Hempel, ills., 1,933.
precision ''Boiler tester," ills., 1,935.

parts, 1,935.
process, des., 1,928.
resultant products perfect combustion,

1,920.
results, 1,919.

sampling tube, location, 1,925.
steam pump, des., 1,928.
Flue gas, collecting over water, objection,
1,925.
collector, automatic. Hays, collecting
sample, 1,924. 1,925, 1,926,
precision, ills., 1,923.
pumps, types, 1,926.
sample average, obtaining, A.S.M.E.
method, 1,923.
obtaining. Bureau of Mines meth-
od, 1,924.
sample, taking, best method, 1,925.
sampling, 1,923.
Flue, shell boiler, Galloway, cons., 2,035.
Foster superheater, elements, ills., 2,259.

ills., 2,257, 2,258.
Four, pipette Orsat apparatus, ills., 1,932.

screw testing machine, Olsen, ills., 1,999.
Foxboro thermo-couple, cons., ills., 1,769.
Fox shell water tube fire engine boiler, ills.,

2,122.
Frame, man hole, riveting, ills., 2,231.
Free circulation of water, importance,

1,801.
Freezing, point thermometers, method of
determining, ills., 1,761.
water, as it boils, Leslie's experiment,
diag., 1,782.
volumetric change, 1,785.
"From and at 212° F," def., 1,805.
Fuel, amount, boiler characteristics, deter-
mination, 1,975.
Fuel analysis, 1,887-1,918.

analytical balance, Gaertner, ills., 1,893.
approximate analysis, 1,892.
apparatus required, 1,893.
ultimate difference, 1,889.
ash, 1,892.

analysis, 1898, 1.915.
balance weights, analytical, Eimer &

Amend, ills., 1,894.
bell motors, ills., 1,904.
calorimeter, see Calorimeter.
carbon, A.S.M.E., determining, 1,902.
Bureau of Mines, determining,

1,902.
fixed, def., 1,884.

testing for, 1,898.
coal, grinder, hand power, Braun, ills.,
1.901.

INDEX OF GUIDE No. 5

XIII

Fuel analysis, coal, — Continued
heating value, calc, 1,911.
sample t gross, preparing, ills.,
1,890-1,891.
Jones, ills., 1,905.
combustible, def., 1,889.
crusher plate, ills., 1,902.
dessicator, Scheibler, ills., 1,899.
furnace^ electric muffle, Eimer & Amend ,
ills., 1,896.
muffle, Weisnegg's, ills., 1,898.
heating value, see Heating value.
hydrogen^ A.S.M.E. and Bureau of

Mines f determining, 1,902.
laboratory, blast torch, Clayton & Lam-
bert, ills., 1,900.
burners, various, ills., 1,897.
lens, reading, Eimer & Amend, ills.,

1,911.
liquid, 1,917.

sulphur test, 1,918.
ultimate, 1,917.
moisture f 1,892.

determining, 1,902.
testing, methods, 1,894.
necessity of, 1,887.
nitric acid correction, 1,913.
nitrogen^ A.S.M.E. and Bureau of

Mines, determining, 1,903.
oven, double wall, Eimer & Amend,

ills., 1,895.
oxygen determination, 1,904.
pellet press, ills., 1,904.
shipping cans, method of sealing, U. S.
Bureau of Mines, ills., 1,892.
sulphur, correction, 1,914.
determining, 1,903.
photometer, Eimer & Amend, ills.,

1,914.
testing, 1,899.

Eschbach's method, 1,908.
total carbon determination apparatus,

ills., 1,913.
ultimate, analyses, 1,900.

apparatus required, 1,902.

heating value, 1,904.

heat value, determining, objection

to, 1,905.
items, considered, 1,901.
proximate, difference, 1,889.
volatile matter, 1,889, 1,895.
Fuel(s), bagasse, des., 1,837.
heating value, 1,837.
character, classification, 1,821.
clinker, def., 1,885.
coalf gas, comparison, table, .1,843.
heating values, 1,828.
oil, evaporation, comparative, 1*841 .

fuel value, relative, 1,840.
sizes, 1,830.

testing, methods, 1,889.
coke, des., various kinds, 1,825 1,828.

gas retort, production, 1,832.
combustion, see Combustion

Fuel(s), combustion, -^Continued

heating value, available, 1,865.

determining, ultimate analysis,
method, 1,863.
incombustible matter, 1,885. *

^ndling temperature, 1,850.
crude oil, composition, 1,839.
•definition, 1,821, 1,846.
dry, heating value, formula, 1,864.
economy condition, steam boiler, 2,031.
gas, amount per H. P. required, 1,844.
coal, comparison, table, 1,843.
liquid fuel, comparison, 1,843.
natural, heating value, 1,843.
gaseous, composition, 1,842.

heating value, 1,869.
gases, air supply, non-mixing, effects,

1,878.
heating value, see Heating value.
liquid, 1,839-1,842.

crude oil, composition, 1,839.
gas fuel, comparison, 1,843.
oil, U. S. Navy report, 1,841.
petroleum, heating value, 1,840.
losses and CO2, table, 1,953.

represented by CO2, 1,950.
oil, advantages, 1,839.

coal, evaporation, comparative,

1.841.
coal, fuel value, relative, 1,840.
U, S. Navy report, 1,841.
peet, 1,833, 1,834.
petroleum, heating value, 1,840.

kinds, 1,839.
sawdust, conditions necessary for, 1,837.

heating value, 1,837.
smoke, causes, 1,877.
state, classification, 1,821.
straw, composition, 1,836.

heating, 1,836.
tan bark, use, 1,836.

wet, proper use, 1,836.
tar, coal, composition, chemical, 1,838.
des., 1,838.
heating value, 1,838.
oil, composition, 1,839.
heating value, 1,839.
testing, apparatus, necessary, 1,888.
use of, knowledge necessary, 1,887.
value of coal and oil, relative, 1,840.
various, air required, 1,858.
water evaporation, tables, 1,844.
wood, kinds of, 1,835.
term, 1,834.
water, effect, 1,835.
Furnace (s), air, steam boiler materials, ills.,
1,987.
arrangements, steam boiler, various,

ills., 1,968.
classification, steam boiler, 1,955, 1,959.
combustion, temperature, calculating,

1.881.
design, poor, effects, 1,884.
fire brick, selection, consideration, 1,884.

XIV

INDEX OF GUIDE No. 5

FurnaceCs), — Continued

electric muffle, Eimer & Amend, ills.,
1,896.
muffle, Weisnegg's, ills., 1,898.
open hearth, steel production, ills., 1,992.
puddling, wrought iron, ills., 1,989.
shape classification, 1,959.
internal, external, comparison, 1,984.
temperature, increasing, 1,883.
Fuse wire correction, calorimeter, 1,912.
Fusible, def., 1,995.
Fusion, 1,788.

description, 1,782.

external work, 1,786, 1,787.

^'ormula, 1,787.
heat, latent, def., 1,783.
internal work, 1 ,786.

formula, 1,786.
latent heat, of, 1,781.

use of, 1,783.
of ice, changes necessary, 1,781.
work of, 1,786.

Gaertner, analytical balance, ills., 1,893.
drying oven, fuel analysis, ills., 1,896.
Galloway, boiler, des., 2,038.

boiler showing breeches and Galloway

flues, ills., 2,038.
flue, ills., 2,039.
cons., 2,035.
tubes, steam boiler, 1,970.
Galvanic action on steel, effects, 1,990.
Gas(es), and liquid fuels, comparison,
1,843.
burner, steam heating boiler, ills., 2,133.
coal, comparison table, 1,843.
combustion, calorific values, 1,871.
description, 1,781.
flow. Ideal horizontal steam heating

boiler, ills., 2,147.
flue analysis, see Flue gas analysis.
Gas, hydro-carbon, complete combustion,
how obtained, 1,878.
marsh, heating value, 1,852.
molecular movements, 1,756.
natural, heating value, 1,843.
defiant, heating, value, 1,852.
passage, steam boiler, area, 1,977.
required per H. P., fuels, amount, 1,844.
retort coke, production, 1,832.
specific heat variation, 1,778.
travel, steam heating boiler, diag.,
2,134.
Gaseous fuels, composition, 1,842.

heating value, 1,869.
Gaseous steam, 1,790.
Gases, specific heat, table, 1,778.
Gasket, steam boiler construction, use,

2,230.
Generator, difference between boiler and,
ills., 1,971, 1.972.
types, 1,972.

Gilt edge water back, steam heating boiler.

ills., 2,139.
Gorton drop tube steam heating boiler, ills.,

2.141.
Graham, dry pipe for upright shell boilers,
ills., 2,044.
steam heating boiler, ills., 2,148
water tube boiler, ills., 2,148.
Grate dimensions, 1,974.
function, 1,974.
surface, boiler, 2,113.
various proportions, diag., 1,976.
water tube boiler, water, ills., 2,079.
width, boiler characteristics, 1,975.
Gravity, specific, def., 1,996.
Gray, pig iron, def., 1,993.

cast iron, def., 1,993.
Gauge, CO2 recorder, Uehling, lis., 1,954.

draught, CO2 recorder, 1,949.
Gunsaulus steam boiler classification, 1,959.
Gurney's boiler, ills., 2,060.

down draught steam heating boiler, ills.,

2,149.
sectional steam heating boiler, ills.,
2,149, 2,150.
Gusset stay, des., ills., 2,211. stress, 2,212.

H

Hand, hole, plate, area, calc, 2,229.
fittings, ills., 2,255.
plate. Union Iron Works, parts,

ills., 2,256.
table, 2,228.
power coal grinder, Braun, ills., 1,901.
Hard steel, carbon percentage, 1,990.
Hardness, def., 1,996.

testing, Brinnell method, 1,998.

boiler materials, 2,020, iils., 2,018.
Harrisburg shell water tube boiler, ills., 2,123.
Hawkes fire tube, water tube boiler, ills.,

2,121.
Hays, automatic flue gas collector, ills., 1,924.
Head, area stayed, des., ills., 2,198-2,201.
Header(s), See Boiler construction, header(s)»
Heat, absorption, 1,776.

conductivity, des., 1,774.

in metals, ills., 1,775.
definition, 1,755.
effects, 1,755.
expansion, advantages due to, 1,773.

due to, 1,771.
latent, des., ills., 1,794.
evaporation, 1,781.
external, 1,795.

diag., 1,796.
fusion, 1,781.
internal, 1,794.

heat units, 1,795.
mechanical equivalent, 1,770, 1,771.
• molecular vibration, influence, 1,755.
of combustion, fuel analysis, table, 1,912.
of fusion, latent, def., 1,783.
of vaporization, latent, def., 1,791.

INDEX OF GUIDE No. 5

XV

Heat, — Continued

radiation of calorimeter, 1,912.
relative conductivity, table, 1,775.
required to melt ice, 1,783.
saturated steam, total, 1,797.
sensible, des., ills., 1,793.
specific^ 1,776.

apparatus, Tyndall's, ills., 1,776.

example, 1,777.

gases, table, 1,778.

liquids and solids, table, 1,777.

standard, 1,776.

superheated steam, 1,810.
transfer, def., 1,757.

method, 1,774-1,973.

rate of, 1,758.
transmission, 1,976.
unit(s), 1,756.

in internal latent heat, 1,795.

in sensible heat, 1,793.

old def., 1,756.
zero, absolute, diag., 1,765.
Heaters, feed water, 2.256.
Heating boiler, see Boiler(s), heating.
Heating surface, measurement, 1,975.
classification, steam boiler, 1,955.
essential qualities, 1,973.
extensiveness, 1,974.
form, 1,974.
material, nature, 1,973.
Heating surface, steam heating boilers, in-
adequate,
ills., 2,128, 2,130.
tubular, characteristics, diag., 1,964.
water tube boiler classification, 2,058.
Heating value, bagasse, 1,837.

coalf fuel analysis, calc, 1,911.

tar, 1,838.'
dry fuel, formula, 1,864.
fuel, available, 1,865.

determining, ultimate analysis,
method, 1,863.

high, 1,869.

natural gas, 1,843.
of acetylene, 1,852.
of benzole, 1,852.
of coal, 1,828.

different, causes, 1,823.
of coke, 1,833.
of ethylene, 1,852.
of gaseous fuels, 1,869.
of marsh gas, 1,852.
of methane, 1,852.
defiant gas, 1,852.
of straw, 1,836.
of tan bark, 1,836.

of wood and coal, comparative, 1,835.
oil tar, 1,839.
petroleum, 1,840.
sawdust, 1,837.
ultimate analysis, 1,904.
Heine superheater, ills., 2,260, 2,261.
Hempel pipette, flue gas analysis, ills., 1,933.
High, heating value of fuels, 1,869.

pressure,Scotch boiler, m6dern,ills.,2,050.
temperature, colors, 1,770.

Hoar frost line, 1,780.

Hollow stay, boiler construction, ills., 2,205.
Homogeneity, ills., 2,200, des., 2,021.
Homogeneous, def., 1,996.
Horizontal, fire tube boiler vertically set,
2,101.
return fire tube boiler, triplex, ills., 2,101.
des., 2,027.
evolution, ills., 2,026.
ills., 2,032.
steam heating boiler, assembling, ills.,
2,142-2,143.
Capitol, ills., 2,139.
ills., 2,129.
^ circulation. Ideal, ills., 2,147.

•water tube boiler, non-sectional, Casey-
Hedges, ills., 2,078.
non-sectional, Keeler, ills., 2,078.
Horse power of, locomotive boilers, 2,113.

marine boilers, 2,113.
Hot short, def., 1,996.

Hydro-carbon (s) acetylene, heating value
1,852.
benzole, heating value, 1,852.
ethylene, heating value, 1,852.
gases, complete combustion, how ob-
tained, 1,878.
marsh gas, heating value, 1,852.
methane, heating value, 1,852.
olefiant gas, heating value, 1,852.
Hydrogen, des., 1,848.

I

Ice, fusion of, changes, necessary, 1,781.
heat required to melt, 1,783.
melting, effects of pressure on, ills., 1,783.
point, 1,784.
volumetric change, 1,785.
. regelation, effects of, ills., 1,783, 1,784.
specific gravity of, 1,788.
Ideal horizontal steam heating boiler, circula-
tion, ills., 2,147.
gas flow. Ideal, ills., 2,147.
Ideal syphon steam regulator, steam heating

boiler, ills., 2,152.
Ignition, point, combustion, 1,849.

wiring, Emerson calorimeter, methods,
ills., 1,908.
Inclined tube, method of circulating water in

boiler, ills., 1,803.
Incombustible matter in fuels, 1,885.
Influence of cold on molecular vibration,

1.755.
Insulation, steam boiler, 2,006.
Intensity, smoke, 1,880.

Internal, external furnaces, steam boiler,
, comparison, 1,984.

fire box, fire tube boilers, vertical, 2,102.
latent heat, 1,794, 1,795.
work of fusion, 1,786.
Internally fired boiler, 1,971, 1.984, 2.033.

XVI

INDEX OF GUIDE Nc. 5

International, base^ steam heating boiler,
ills., 2.145.
steam heating boiler, ills., 2,144.
steam heating boiler, parts, ills., 2,131.
steam dome, steam heating boiler, ills.,
2.151.
Iron, cast, see Cast iron.

J

James' water tube boiler, ills., 2,061.

Jaw stay, steam boiler construction, des., ills.,

2,213.
Jet pump, flue gas analysis, Richards, ills.,

1,927.
Joint (s), boiler construction, butt, straps,
equal, ills., 2,186.
objection, 2,168.
butt, 2,179, 2,181, 2,182, 2,184.
efficiency, diag., 2,160.
ills., 2.169.

circumferential, ills., 2,191.
lap, butt, diff., 2,167, ills., 2,168.
ills., 2,177, 2,178.
single, 2.173.
pull, effect, diag., 2.170.
riveted A.S.M.E, Boiler Code, 2,176-
2.188, 2,191.
calculation, 2,172.
classes, 2,167.
efficiency, 2,171.
strength, 2,160.
U. S. Marine rules, 2,189-2,
Wicks, table, 2,188.
coal samples, fuel analysis, ills.,
1,905.

Jones

K

tube

Keeler non- sectional horizontal' water

boiler, ills., 2,078.
Kindling, point, combustion, 1,849.

temperatures fuels, 1,850.
Kingsford special boiler, ills., 2,113.

Ladd steam drum, steam boiler construction,

ills., 2.245.
Lamp, Davy's, experiment with, ills., 1,849.
ills., 1,847.

principles, ills., 1,848.
Lancashire boiler, breeches flued, des., 2,037,
2 038.
without breeches, ills., 2,036.
Lap and butt joints, steam boiler con-
struction, 2,167, ills., 2,168.

Lap joint, steam boiler construction, ills.
2,169.

ills., 2,177, 2,178.

objections, 2,168.

single, 2,173.
Latent heat, des., ills., 1,794, 1,796.

effusion, 1,781, 1.783.

of vaporization, def., 1.791.
Leslie's, cube, ills., 1,773.

experiment of freezing water, as it boils,
diag., 1,782.
Leg marine boiler, ills., 2,054.
Liberating surface, insufficient, results, diag.f

des., 1,979.
Ligament, efficiency, diag., 2.196.
Lignite, coal, des., 1,827.

combustion, air required for, 1,861.

youngest coal, 1,824.
Linear expansion, coefficient, def., 1.772.
Liquid, and gas fuels, comparison, 1,843.

def., 1,780.

expansion, 1,788.
Liquid fuel, 1,839-1,842.

advantages, 1,839.

analysis, 1,917.

sulphur test, 1,918.
ultimate, 1,917.

crude oil, composition, 1,839.

gas fuel, comparison, 1,843.

oil, U. S. Navy report, 1,841.

Petroletitn, heating value, 1,840.
kinds, 1.839.
Liquid (s), least density, point, 1,788.

maximum density, 1,788.

volumetric changes, 1,788.

molecular movements, 1,756.

specific heat, table, 1,777.
Load, effects on water tube boilers, 2,057.

test, steam boiler material, 2,007.
Locomotive boiler (s), 2,045.

classification, 1,963.

horse power, 2,113.

differences, 2.046.

semi-portable, ills., 2.046.

wagon top, com., 2.046.
Locomotive type marine boiler, Rees, ills.,

2.055.
Long pass, short pass, steam heating boiler,

characteristic, ills., 2,136.
Longitudinal, _ drum, elementary _ non-sec-
tional water tube boiler, ills.,
2,066.

header drum, ills., 2,246.
Luken diagonal stay, ills., 2,210.
Lyons combined boilers, aid v., 2,120.

Magee steam heating boiler, parts, ills.,

2,138.
Mahler calorimeter, parts, ills., 1,906.
Malleable, castings, 1,994.

iron, production, methods, 1,988.

INDEX OF GUIDE No. 5

XVII

Malleable, iron, — Continued

steam boiler construction, 2.000.
pig iron steam boiler, materials, 1.994.
Malysheff method determining elastic limits,

diag., 2,002.
Manhole, see Boiler(s) construction, man-
hole.
Manifold, steam boiler construction, 2,251.
Manning, boiler, ills., 1,958.

special boiler, des., 2,104.
Marine boiler (s), Clyde & Scotch, difference,
2,054.
des., ills., 2,047.

Graham, dry pipe for vertical boiler of
steamer Stor noway 11 1 ills., 2,044.
horse power, 2,113.
leg, ills., 2,054.

over discharge^ Mosher, ills., 2,249.
triple tube, Mosher, ills., 2,087.
position of, 1,984.
plate requirements, 2,156.
under discharge. Yarrow, ills., 2,249.
vertical, through tube, ills., 2,048.
Marine Iron Works, Clyde boiler, ills., 2,052.
special marine shell boiler, ills., 2,053.
submerged tube shell boiler, ills., 2,049.
Marine, shell boiler, locomotive type, ills.,
2,055.
Marine Iron Works, ills., 2,053.
steam boiler classification, 1,963.
transverse drum, boiler construction,
Babcock & Wilcox, ills., 2,246.
Marsh gas, heating value, 1,852.
Matter, gas, molecular, mo verts, 1,756.
liquid, molecular movements, 1,756.
solid, molecular movement, 1,756.
three states of , 1,755,1,756.
volatile, des., 1,823.
Maxim.um, density, 1,788.
liquid, 1,788.
volumetric changes, 1,788.
pitch, screwed staybolts, 2,21S.
Maxwell's definition of a solid, 1,779.
Mechanical equivalent of heat, 1,770.

ills., 1,771.
Melting, ice, heat required 1,783.
volumetric change, 1,785.
point, of bricks, 2,006.
ice, 1,784.

of solids, def., 1,996.
Mercury, thermometers, advantages of using,
1.759.
cons., ills., 1,758.
well, temporary thermometer connec-
tion, Tagliabue, ills., 1,761.
Metallic, pyrometer, calibrating, 1,769.
handling, precautions, 1,769.
Metals, heat, conductivity, ills., 1,775.
Methane, heating value, 1,852.
Micrometer, 2,002-2,005.
Modified Clyde type, special boiler, 2,109.
Modulus of, elasticity, testing 2,009.

rupture, 2,009.
Molecule, def., 1,755.
Molecular, movements, gases, 1,756.
temperature on, 1,757.

Molecular, — Continued

vibration, cold, influence on, 1,755.
Monitor coil boiler, ills., 2,144.
Mortar, fuel analysis, bell, ills., 1,904.
Mosher, over discharge marine boiler, ills.,
2,249.
triple tube over discharge marine boiler,
ills., 2,087.

N

National steam heating boiler, fire pot, ills.,
2,154.
parts, ills., 2,132.
section, ills., 2,153.
Natural gas, heating value, 1,843.
Nickel, steel, use, 2,004.
Niclausse porcupine boiler, ills., 2,092.
Nipple, push, steam heating boiler, ills.,

2,139.
Nitrogen, air, effects, 1,856.
Non-sectional boiler, 1,967.

horizontal water tube latter, Casey-
Hedges, ills., 2,078.
Keeler, ills., 2,078.
Wicks, ills., 2,081.
water tube boiler, des., 2,064.

elementary, longitudinal drum, ills.,
2,066.

transverse drum, ills., 2,067.
Nozzle, calorimeter, sampling, Stott &
Pigott, ills., 1,818.
sampling, calorimeter, 1,820.

Ofeldt automobile boiler, ills, 2,088.
Oil, coal, evaporation, comparative, 1,841.
fuel value, relative, 1,840.
combustion, air required for, 1,861.
crude, composition, 1,839.
fuel, 1,839-1,842.

advantages, 1,839.
U. S. Navy report, 1,841.
tar, 1,839.

composition, chemical, 1,839.
defiant gas, heating value, 1,852.
Olefin, des., 1,839.

Olsen, automatic testing machine, ills., 2,010,
deflection instrument, ills., 2,007.
extension and compression micrometer,

ills., 2,005.
four screw testing machine, ills., 1,999.
micrometer extensometer, ills., 2,002-

2,004.
securing test tool, ills., 2,000.
tortion attachment, universal testing
machine, ills., 2,001.
Open hearth, process, cast iron, ills., 1,992.

_ steel, def., 1,994.
Orifice plate, throttling calorimeter, 1,820,

XVIII

INDEX OF GUIDE No. 5

Orsat apparatus, care of, 1,929.
chemical reagents used, 1,931.
four pipette, ills., 1,932.
precision 100 cc. standard, ills., 1,936.
three pipette connection, ills., 1,930.
Over discharge, marine boileVy Mosher, ills.,
2,249.
triple tube, Mosher, ills., 2,087.
water tube boiler, ills., 2,065.
Oven, double wall, fuel analysis, Eimer &
Amend, ills., 1,895.
drying, Gaertner, ills., 1,896.
Oxide, iron, effects of, in ashes, 1,886.
Oxygen, determination of, 1,904.

necessary for complete combustion,

amount, 1,854.
required for combustion, table, 1,865.
supporter of combustion, 1,845.
volume, finding corresponding volume

air, 1,936.
where obtained, 1,845.

Palm stay, des., 2,212, ills., 2,213.
Paraffin, des., 1,839.

Parallel, arrangement, water tube boiler,
accessibility, 2,067, ills., 2,068.
connection^ elementary steam boiler,
ills., 1,804.
water tube boiler, ills., 2,059.
elementary, ills., 2,068.
Parker, water tube boiler, 2,096, 2,097.
Parr calorimeter, apparatus for use with,
ills., 1,913.
cartridge details, ills., 1,910.
Passage (s), gas, stem boiler, 1,977.
Peet, 1,833, 1.834.

machine, des., 1,834.
Pellet press, fuel analysis, ills., 1,904.
Petrie's water pockets, ills., 2,039.
Petroleum, advantages, 1,839.

heating value, 1,840.
Pfaundler's method for radiation correction,

calorimeter, 1,912.
Phoenix- Manning vertical boiler, ills., 2,103.
Phosphorous steel, boiler materials, use,

2,003.
Photometer, sulphur, fuel analysis, Eimer

& Amend, ills., 1.914.
Pig iron, 1.993, 1,994.
Pipe, blow, combustion, ills., 1,860.
Pipe boiler(s), 2,117.
des., 2,070.
features, 2.073.
Taylor, ills., 2,116.
use, 2,074.
Pipe, difference between tube and, 1,972.
threads, number, minimum, 2,235.
water tube boiler, ills., 2,095.
Pitch, of stay, tube, 2,211.
rivets, 2,170, ills., 2,171.

diagonal, 2,170, ills., 2,171.

Pitch, rivets, — Continued
maximum, 2,219.
Plain cylinder, shell boiler, ills., 2,027.
Plate (s) boiler, marine requirements, 2,156.
silicon, effect, 2,005.
crusher, fuel analysis, ills., 1,902.
orifice, throttling calorimeter, ills., 1.820.
steam boiler construction, 2,156.
side, boiler construction, ills., 2,216.
Platinum-rhodium thermo-couple. Brown,

ills., 1,768.
Pocket CO2 recorder, Bacharach, ills., 1,937.

manipulation, diag., 1,938.
Pockets, water, shell boiler, Petrie, ills.,

2,039.
Point, boiling, thermometer, method of
determining, ills., 1,762.
fixed, thermometer scale, 1,760.
kindling, combustion, 1.849.
melting, ice, 1,784.
Porcupine, boiler, 2,089.
classification, 2,090.
Niclausse, ills., 2,092.
Racine, ills., 2,091.
Shipman, ills., 2,090.
tubes in, 1,972.

Ward, Field or double drop tube 2,072.
Pratt & Whitney stay bolt taps, ills., 2,204,

2,207.
Precision, Boiler tester, flue gas analysis, ills.,
1,935.
flue gas collector, ills., 1,923.
Preheating air supply, combustion, effects,

1,883.
Pressure, atmospheric, sea level, 1,790.
variations, 1,790.
melting ice by, 1,785.
on boiling point, effect, 1,790.
on melting ice, effects of, ills., 1,783,
on melting point, effect, 1,784.
^ steam boiler, bursting, diag., 2,162.
working, des., 2,163, 2,164.
Priming, steam boiler, 1,980.
Prosser segment tube expander, ills., 2,240.
Proximate analysis, coal, 1,889.

combustion, 1,873.
Puddled, iron, def., 1,994.

steel, steam boiler, materials, def., 1,994.
Puddhng, furnaces, ills., 1,989.

process, wrought iron, 1,988.
Pull, joints, effect, diag., 2,170.
Push nipple, steam heating boiler, ills., 2,139.
Pyrometer(s), metallic, calibrating, 1.769.
precaution necessary, 1,769.
principles, 1,766.
simple, working, 1,768.
types, 1,766,

Racine porcupine water tube boiler, ills.,

2,091.
Radial, fire tube boiler, vertical, 2,105.
stay, des., ills., 2.217.

INDEX OF GUIDE No. 5

XIX

Radial, — Continued

T Bars, ills.,. 2.221.
Radiation, calorimeter, heat, correction,

1,912.
Radiometer, ills., 1,773.
Rapid circulation, steam boiler, desirability,
des., diag., 1,978.
evaportcHon, steam boiler, 1,977.
Reaumur thermometer scale, 1,764.
Recorder CO2, see CO2 recorder.
Rees, locomotive type marine boiler, ills.,
2,055.
Western river type flue boileuj ills., :4056.
Refined cast iron, def., 1,994.
Regelation, effects of, ills., 1,783, 1,784.
Regulator steam heating boiler, syphon

steam. Ideal, ills., 2,152.
Relative, conductivity of heat, table, 1,775.

fuel value of coal and oil, 1,840.
Report, of U. S. Navy on oil fuel, 1,841.
Resilience, steam boiler materials, def., 1,996.

test, steam boiler materials, 2,011.
Return, fire tube boilers, horizontal, duplex,
ihs., 2.100.
horizontal, triplex, ills., 2,101.
object, 2,106.

vertical, Webber, ills., 2,107.
flue boiler, single, ills., 2,028.
tube boiler, features, 2,056.
tubular boiler y 1,970.
des., 2,027.

evolution, ills., 2,026. ills., 2,032.
Reynolds, boiler, crown sheet, ills., 2,106.

vertical fire tube boiler, ills., 2,105.
Richards jet pump, ills., 1,927.

flue gas analysis, operation, 1.927.
Riehle, specimen holders, diag., 2,011.
testing machine, ills., 2,015.
weighing beam, ills., 2,009.
Ringlemann's, readings, plotting, diag., 1,802
scale for grading smoke density, ills.,

1.881.
smoke chart, diag., 1.880.
Rivet, steam boiler construction, 2,170,
diagonal, 2,170, ills., 2,171.
pitch, ills., 2,171.
Riveted joint (s), A.S.M.E. Boiler Code,
2,176-2,1^, 2,191.
calculation., 2,172.
classes, 2,167.
efficiency, 2,171.
straight, 2,160.
strength, 2.172.

U. S. Marine Rules, 2,189-2,190.
Wicks, table, 2,188.
Rivet pitch, 2.170, ills., 2,171.
Riveted stay, des., ills., 2,209.
Riveting man hole irames, ills., 2,231
Rivets, fracture between, ills., 2,175. 5.
split and double shear, ills., 2,175.
Roberts water tube boiler construction, ills.,

2,071-2,076.
Roller tube expander, ills., 2,240.
Round vertical steam heating boiler, ills.,

2,128.
Rules, construction, steam boiler, 2,155.

Rupture, modulus, 2,009.
Rust, effect on steel, 1,990.

Safety, factor of, 2,007.

lamp, Davy's cons., 1^847.
principle, ilL., 1,848.
steam boiler comstruction, factor, 2,163.
Sample (s), coal, preparing, ills., 1,890-91.
Jones, ills., 1,905.
flue gases, 1,923.

Hays, automatic flue gas collector,
collecting, 1,924.
Sampling, nozzle, calorimeter, 1,820.
Stott & Pigott, ills., 1,818.
tube, flue gas analysis, location, 1,925.
Sarco, calorimeter, fuel analysis, ills., 1,907.
CO2 recorder, 1,940, 1,941, 1,943, 1.948.
Saturated steam, def., 1,789.

total heat, 1,797.
Sawdttst, fuel, condition, necessary, 1,837.
Scale (s), for grading smoke density, Ringel-
mann, ills., 1,831.
scleroscope, 1,997.
thermometer, centigrade, 1,760, 1,763.
comparison, 1,763, 1 ,764.
des., 1,762.

Fahrenheit, 1,760. 1,763.
Reaumur, 1,764.
subdivision, 1,762.
types, 1,763.
use, 1,759.
Scleroscope, ills., 1,997, 1,998.
Scheibler, dessicator, ills., 1,899.
Scientia calorimeter, ills., 1,915.
Scotch boiler, features, 2,048.
Clyde, diff., 1,970.
form, 2,054.

modern, high pressure, ills., 2,050.
shell boiler, parts, 2,049.

single furnace, ills., 2,051.
Screwea stays, 2,205, 2,206, 2,217.
Sea level, atmospheric pressure, 1,790.
Seabury bent water tube boiler, ills., 1,960.
Seam, steam boiler construction, element,

ills., 2,173.
Sectional, boiler, Graham, ills., 2,077.

down flow water tube boiler, Parker,

diag., 2,096.
headers, ills., 2,254.
horizontal water tube boiler, Babcock

& Wilcox, ills., 2,080.
steam, boiler, 1,967.

heating boilers, Gumey, ills., 2,149,
2,150.
view, National steam heating boiler,

ills., 2.153.
water tube boilers, adv., 2,069.

parallel, elementary, ills., 2,068.
parts, 2,066.

series, elementary, ills., 2.068.
Segment tube expander, steam boiler con-
struction, Prosser, ills., 2,240.

XX

INDEX OF GUIDE No. 5

Semi-anthracite coal, des., 1,825.
Semi-bituminous coal, des., 1,826.
Semi-portable locomotive shell boiler, ills.,

2,046.
Sensible heat, des., ills., 1,793.
Separating calorimeter, des., 1,815.
error, percentage, 1,811.
operation, 1,816.
Series, connectors, elementary steam boiler,
ills., 1,804.
water tube boiler, ills., 2,058.
Parallel f pipe boiler, Almy, ills., 2,095.

water tube boiler, 2,091.
sectional water tube boiler, elementary,
ills., 2,068.
Setting, steam boiler, materials used in, 1,985.
Shear, single, double, diff., 2,170.

testing, single and double, ills., 2,016.
test, steam boiler materials, 2,011.
Shearing, ills., 2,172.

testf steam boiler materials, kinds, 2,017.
tool, Olsen, ills., 2,000.
Sheet, crown, Reynolds, boiler, ills., 2,106.

des., 2,025.
Shell and water tube boiler, sensitiveness,

diag., 1,982.
Shell boiler, see Boiler(s), shell.
Shipman porcupine boiler, ills., 2,090.
Shore sceleroscope outfit, ills., 1,998.
Short, cold, def., 1,995.

hot, 1,996.
Silicon in boiler plate, effect, 2,005.
Silsby fire tube water tube fire engine boiler,

ills., 2,125.
Simmance-Abady CO2 recorder, working

parts, ills., 1,946.
Single, and double shear test, ills., 2,016.
double shear, 2,170.
flue Clyde type boilers, ills., 2,109.
furnace Scotch shell boiler, ills., 2,051.
lap joint, 2,173.
return flue boiler, ills., 2.028.
tube boiler, 1,967.
Sling straps, boiler construction, ills., 2,216.
Smelting copper, methods, 1,985.
Smith-Manning special boiler, ills., 2,104.
Smoke, black, indication, 1,877.
particles, 1,875.
cause of, 1,876, 1,877.
chart, Ringelmann, diag., 1,880.
colored, indication, 1,876.
combustion, classification, 1,880.
def., 1,875.

density, determining, electrical method,
1,882.
grading, 1,881.

Ringelmann scale, ills., 1,881.
Socket stays, des., ills., 2,207.
Soft steel, carbon percentage, 1,990.
Solid(s), des., 1,779.

Maxwell's, def., 1,779.

molecular movement, melting point def.

1,756, 1.996.
specific heat, table, 1.777.
Soot, cause of, ills., 1.876.
Spade peet, des., 1,834.

vSpecial boiler(s), see Boilers special.
Specific gravity, of ice, 1,785.

def., 1,996.
Specific heat, 1,776, 1,777.

apparatus, Tyndall's, ills., 1,776.

def., 1,776.

gas variations, 1,778.

liquids, table, 1,777.

of gases, table, 1,778.

of solids, table, 1,777.

of super-heated steam, 1,810.

standard, 1,776.
Stanley automobile boiler, ills., 1,965.
States of matter, 1,755.
Stay, boiler construction, hollow, ills., 2,205.

screwed, drilled holes, object, 2,206.
flaws, des., ills., 2,206.
Stay bolts, screwed, pitch, maximum, 2,219.

des., ills., 2,202.

breaking, 2,207.

top, ills., 2,203.
thread, 2,205.
ills., 2,204.
Stay, gusset, stress, 2.212.

jaw, ills., 2,213.

palm, ills., 2,212, 2,213.

riveted, boiler des., ills., 2,205.

rods, steam boiler, des., ills., 2,208.

screwed, diameter, 2,205.

crow foot, des., 2,213, ills., 2,212.

diagonal, Luken, ills., 2,210.
types, ills., 2,210.

fastening, methods, ills., 2,218.

gusset, des., ills., 2,211.

jaw, des., ills., 2,213.

palm, des., 2,212, ills., 2,213.

radial, des., ills., 2,217.

socket, des., ills., 2,207.

stress, minimum, 2,221.

tube, ends, ills., 2,209.
pitch, 2,211.
Staying boilei head, ills., 2.215.
Steam, boilers, see Boilers.

calorimeter, see Calorimeter.

circulation of water in boilers, ills.,
1,803.

condensation, causes, 1,799.

definition, 1,789.

dome, steam heating boiler, 2,152.
International, ills., 2,151.

drum, Vogt, ills., 2.251.
class., 2,244.
Ladd, ills., 2.245.

dry, 1,789.

engine, fire, boiler, fire tube, water tube,
Silsby, ills., 2,125.
shell water tube. Fox, ills., 2,122.

evaporation factor, see Evaporation
factor.

formation, 1,790, 1,800.

gas, 1,790.

gaseous, 1,790.

generator (s), boiler, diff., 1,972.
types, 1,972.

heating boiler, see Boiler, heating

ice to, 1,779-1,820.

INDEX OF GUIDE No. 5

XXI

Steam, — Continued

latent heat, des., ills., 1,794.

external, 1,795.
parallel connection, elementary boiler,

ills., 1,804.
pressure, classification steam boilers,

1,959.
pump, flue gas, analysis, des., 1,928.

operation, 1,928.
quality, 1,811.
regulator, steam heating boiler, syphon,

2,152.
space, steam boiler, 1,978.
superheated, 1,790,

ice to steam, 1,810.
specific heat, 1,810.
wet, des., 1,789.
Steamer, Norwood, boiler, ills., 2,087.
Steel, angle stays, 2,214.
aluminum, use, 2,004.
application to boiler construction, 1,990.
Bessemer, qualities, 1,992.
def., 1.993.
process, 1,992.
carbon, percentage, 2,002.

carbon, uses, 2,002.
cast, carbon, percentage, 1,990.

def., 1,993.
castings, def., 1,994.
converted, def., 1,993.
crucible, def., 1,993.
def., 1,994.

manganese, use, 2,004.
nickel, use, 2,004.
open hearth, def., 1,994.
phosphorus, use, 2,003.
physical properties, 2,001.
puddled, def., 1,994.
rust; effects, 1,990.
sheer, def., 1,994.
soft, carbon, percentage, 1,990.
steam boiler materials, 1,993.
sulphur, use, 2,004.
Stirling bent water tube boiler, ills., 2,084.
Stott & Pigott sampling nozzle, calorimeter,

ills., 1,818.
Straps, sling, ills., 2,216.
Straw, composition, 1,836.

heating value, 1,836.
Strength (of) riveted joint, 2,160, 2,172.
steam boiler, shell, calculating, 2,159.
. materials, def., 1,996.
Stress, bending, def., 2,006.
gusset stay, 2,212.
test, 2,011.
Submerged tubes, shell boiler, 2,043.

shell boiler. Marine Iron Works, ills.,

2,049.
vertical boiler, ills., 2,042.
Sulphur, combustion, des., 1,849.
correction, calorimeter, 1,914.
fuel analysis, determining, 1,903.
photometer, fuel analysis, Eimer &

Amend, ills., 1,914.
steel, steam boiler material, use, 2,004.
testing for, 1,899.

Sulphur, — Continued

test liquid fuel analysis, 1,918.
testing, Eschkas method, 1,900.
Superheated steam, 1,790.

specific heat, 1,810.
Superheaters, boiler construction, 2,256.
elements, Foster, ills., 2,259.
flooding, object, 2,259.
Foster, ills., 2,257, 2,258.
Heine, ills., 2,260, 2,261.
location, 2,258.
Surface (s), flat, reinforcement, 2,201.
grate, boiler, 2,113.
heating, measurement, 1,975.
form, 1,974.

tubular, characteristic, diag., 1,964.
steam heating boiler^ efficiency, diag.,
2,135.
extensiveness, 1,974.
inadequate, effect, ills., 2,130.
liberating, 1,978.

insufficient, results, diag.,des., 1,979.
Surfusion, 1,785.

unstable condition, 1,785.
temperature change, 1,785.
Syphon steam regulator, steam heating
boiler. Ideal, ills., 2,152.

Table (of), comparison of gas and coal,
1,843.
air required for combustion at 1,865.

1,861.
CO2 and excess air, 1,953.
factors of evaporation, 1,807, 1,808.
heat of combustion, fuel analysis, 1,912.
relative conductivity of heat, 1,775.
riveted joints. Wicks Boiler Co., 2,188.
specific heat, of gases, 1,778.
of liquids, 1.777.
of solids, 1,777.
water evaporation, fuels, 1,844.
Tagliabue, mercury well, 1,761.

thermometer, ills., 1,759, 1,760.
Tailor pipe boiler, ills., 2,116.
Talbot boiler, water tube, ills., 2,077, 2,111.
Tan bark, composition, 1,836.
fuel, wet, proper use, 1,836.
heat value, 1,836.
use of, 1,836.
Tap(s), stay bolt, ills., 2,203.
ills., 2,204.

thread, 2,205.
Tar, coal, composition, chemical, 1.838.
heating value, 1,838.
oil, 1,839.

composition, chemical, 1,839.
heating value, 1,839.
Temperature, 1,757-1,770.
absolute, 1,764.
value, 1,766.
zero, ills., 1,765.
change in surfusion, 1,785.

XXII

INDEX OF GUIDE No. 5

Temperature, — Continued
critical, diag., 1,781.
during change of state, 1,782.
furnace t combustion, calculating, 1,881.

increasing, 1,883.
high, colors of, 1,770.
lowering, closed vessel, effects, 1,799.
measurement, 1,757.
molecular movement,' influence on,

1,757.
of one degree, rise, def., 1,763.
Tensile, strength, 2,013.

test, boiler materials, ilL., 2,012, 2,015.
ills., 2,012.
Tension test, 2,014, 2,013,
Tenacity, steam boiler materials, def., 1,996.
Test, calorimeter, des., 1,909.
cold bending, des., 2,020.
hardness, 2,020.

homogeneity, ills., 2,020, des., 2,021.
sulphur, liquid fuel analysis, 1,918.
tensile, ills., 2,012, 2,015.
Testing, fuel, see Fuel analysis

machine f automatic, Olsen, ills., 2,010.
Olsen four screw, ills., 1,999
Universal tortion attachment, Ol-
sen, ills., 2,001
steam boiler materials, see Boiler mater-
ials, testing.
Thermal unit, British, definition, 1,756.
Thermo-couple, Foxboro, ills., 1,769.

platinum-rhodium. Brown, ills., 1,768.
Thermometer (s), boiling point, method of
^ determining, ills., 1,762.
connections, Tagliabue, permanent, ills.,

1,760.
freezing point, ills., 1,761.
mercury, advantages of using, 1,759.
cons, ills., 1,758.
use of, 1,758.
ordinary, contraction, 1,759.
principles, basic, 1,758.
scale, see Scale,
Tagliabue, ills., 1,759, 1,761.
temporary connection, mercury well,
use of, 1,757.
Thompson calorimeter, fuel analysis, 1,918.
Thread (s), pipe, steam boiler construction,
number, minimum, 2,235.
stay bolt tap, boiler construction, 2,205 .
stripping, steam boiler construction,
prevention, 2,204.
Three pass tubular shell boiler, adv., 2,031.
Three pipette Orsat apparatus, ills., 1,930.

states of matter, ills., 1755, 1,756.
Throttling calorimeter, compact, 1,814, ills.,
1,819.
Ellison, construction, 1,813.

operation, 1,813.
error, percentage, 1,811.
ice to steam, orifice, plate, ills., 1,820.
Through tube, 1,967.

vertical marine boiler, ills., 2,048.
Tools taps, stay bolt, thread, 2,205.
ills., 2,203.
Pratt «& Whitney, ills., 2,204, 2,207.

Torch, blast, laboratory, Clayton & Lambert,

ills., 1,900.
Tortion attachment, Olsen, ills., 2,001
Tortional test, testing, des., ills., 2,017.
Towering temperature enclosed vessel, 1,799.
Transfer of heat, def., 1,757.
methods, 1,774. 1,973.
rate of, 1,758.
Transmission of heat, 1,976.
Transverse drum, elementary non-sectional
water tube boiler, ills., 2,067.
test, ills., 2,014, des., 2,016.
Travel, gas, steam heating boiler, diag.,

2,134.
Trevithick shell boiler, 2,033, 2,034.

ills, 2,034.
Tri-pass fire tube boiler, extended shell,

object, 2,110.
Triple, point, ice to steam, diag., 1,780.

tube over discharge marine boiler,
Mosher, ills., 2,087.
Triplex horizontal return fire tube boiler, ills.,

2,101.
Tube(s), arrangements, steam boiler, various,
ills., 1,966.
difference between pipe and, 1,972.
double, 1,967.
ends, stay, ills., 2,209.
expander. Roller, ills., 2,240.

segment, Prosser, ills., 2,240.
Field, 1,967.

fire and water, diff., 2,023.
flue, difference, 2,025. -

steam boilers, diff., des., ills*. 1,963.
Galloway, 1,970.
grouping, steam boiler, 1,957.
water tube boiler, 2,058.
parallel and series, 2,067.
pipe, steam boiler, diff., 1,972.
position, water tube boiler, 2,059.

steam boiler classification, 1,957.
sampling, location, 1,925.
spacing, des., ills., 2,193-2,198.
stay, 2,209.

pitch, 2,211.
steam, fastening, 2,241.
single, 1,967.

submerged, shell boiler, 2,043.
U, boiling water, circulating in, 1,801.
various, ills., 1,960, 1,962.
water, Graham boiler, ills., 2,144.
water tube boilers, bent, various, 2,082.
Tubular, boiler, horizontal returns, 2,027.
heating surface, characteristic, 1,964.
shell boiler, horizontal return, ills., 2,032.
three pass, adv., 2,031.
Tumbuckle, ills., 2,209.
Two pass fire tube boiler, Casey-Hedges, ills.,

2,110.
Tyndall's specific heat apparatus, ills., 1,776.
auxiliary boiler room CO2 recorder, ills.,

1.754.
VehlingC02 recorder, charts, diag., 1,952,
1,950.

INDEX OF GUIDE No. 5

XXIII

u

Ultimate analysis, coal, 1,889, 1,900.
combustion^ 1,858.

calculation from, 1,863.
heating value, 1,903, 1,904.
Ultimate, liquid fuel analysis, 1,917.

strength, 2,013.
Under discharge, marine boiler. Yarrow,
ills., 2,249.
water tube boiler, ills., 2,065.
Underfeed steam heating boiler, Williamson,

ills., 2,137.
Union Iron Works, drum end, steam boiler
construction, ills., 2,247.
hand hole plate parts, ills., 2,256.
Unit(s), British thermal, def., 1,756.
heatf internal latent heat, 1,795.
old def., 1,756.
sensible heat, 1,793.
Universal testing machine, Olsen, ills., 2,001.
Up flow, circulation, water tube boiler, ills.,
2,063.
down flow water tube boilers, 2,093.
Upright boiler, Bigelow, ills., 2,041.
des., 2,039.

dry pipe, Graham, ills., 2,044.
evolution, diag., 2,040. '
types, 2,041, des., 2,041.
water level, proper, 2,044.
U, S. Navy report on oil fuel, 1,841.
U tube, boiling water circulating in, 1,801.

Vacuum, calorimeter, Emerson, ills., 1,909.
Vapor formation, 1,791.
Vaporization, des., 1,791.

external work, 1,795.

in a closed vessel, effects, 1,799.

latent heat, def., 1,791.

phenomena, ills., 1,792.

work of, stages, 1,793.
Vegetable origin of coal, evidence, 1,824.
Vertical boiler (s), des., 2,039.

Berry, ills., 2,108.

defects, 2,042.

Reynolds, ills., 2,105.

submerged tube, ills., 2,042.

various, ills., 1,958.
Vertical, internal fire box, fire tube boilers,
2,102.

marine boiler, through tube, ills., 2,048.

radial fire tube boiler, 2,105.

return fire tube boiler, Webber, 2,107.

setting, fire tube boiler, ills., 2,102.

steam heating boiler, round, ills., 2,128.

tubular steam heating boiler, Andrews,
ills., 2,136.

Vessel, closed, vaporization, effects, 1,799.
Visible flame, 1,875.
Volatile matter, 1,889, 1,895

des., 1,823.

coals, percentage curves, 1,872.
Volumetric, analysis of air, 1,845.

change (s), of freezing water, 1,785.
with maximum density, 1,788.
Vogt, steam drum, ills., 2,251.

watevt drum ills., 2,251.

tube boiler, ills., 2,250.

W

Wagon, boiler. Watts, ills., 2,024.

top, locomotive boiler, cons., 2,046.
Ward drop Field tube boiler, ills., 2,072.
Waste heat vertical boiler. Phoenix- Man-
ning, ills., 2,103.
Water, back, Clyde shell boiler, removable,
ills., 2,051.
steam heating boiler, gilt edge,
ills., 2,139.

boiler, circulation, ills., 1,803.

boiling, 1,792, 1,799 1,800-1,802

circulation in boilers, experiment, ills.,
1,807.

contraction and expansion, 1,788.

drum, Vogt, ills., 2,251.

equivalent, calorimeter, 1,914.

evaporation^ determining heating value
of fuel, 1,861.
evaporation, fuels, table, 1,844.

feed, heating, saving, 1,807.

fire, tubes, diff., 2,023.

freezing, volumetric change, 1,785.

grate, water tube boiler, ills., 2,079.

height, steam boiler, diag., 1,980.

in wood, effect, 1,835.

level, upright shell boiler, proper, 2,044.

maximum density, 1,788.

pockets, shell boiler, Petrie's, ills., 2,039.

relative volume to ice, 1,785.

space, steam boiler, arrangement, 1,978.
Water, steam boiler, amount in, 1,980.

tube boiler, see Boilers, water tube
Watts wagon boiler, ills., 2,024.
Webber vertical return fire tube boiler, ills.,

2,107.
Weighing beam, testing Riehle, ills., 2,009.
Weight (s), analysis of air, 1,845.

balance, Eimer & Amend, ills., 1,894.
Weisnegg's muffle furnace, ills., 1,898.
Weld iron, steam boiler material, def., 1,994.
Weldable, def., 1,996.
Western, river shell boiler, ills., 2,030.

state size of bituminous coal, 1,831.
Wet, steam, des., 1,789.
White, cast iron, def., 1,994.

pig iron, def., 1,994.

XXIV

INDEX OF GUIDE No. 5

Wicks Boiler Co., table of riveted joints,
2,188.
non-sectional vertical water tube boiler,
ills., 2,081.
Williamson underfeed steam heating boiler,

ills., 2,137.
Wood, classes, 1,834, 1,835.

coal, heating values, comparative, 1,835.
combustion, air required for, 1,861.
water, heat units, loss due to, 1,835.
Wrought iron, def., 1,988. process, 1,988.
steam boiler materials, def., 1,994.

Yarrow under discharge marine boiler, ills.,

2,249.
Yield point, testing steam boiler materials,

2,013.

Zero, absolute, determining, ills., 1,765c

HAWKINS' MECHANICAL

DICTIONARY $2

This volume is the most useful book in Mechanical
Literature. If constantly referred to will enable the

student to acquire
a correct knowl-
edge of the
words, terms
and phrases
in use in
Mechanical
Engineering
and its vari-
ous branches.
Its great-
est value lies
in this: that
no man rep-
resenting -the
mechanical
profession
can find ex-
cuse for not
knowing the
use and
meaning of
the terms
used in his
work.

Hawkins'
Mechanical
Dictionary
explains and de-
fines in plain language
the use of words and
terms now used or heretofore
used in the Mechanic Arts, Trades
and Sciences.
It is an unequaled reference work, and is the one
book of permanent value no student or expert should
dispense with. Complete from A to Z. Highly en-
dorsed. Price, $2. postpaid.

6,0^3

I of I

3 O c C
o -« rt

g5So

"^ <u m o

rt

ly c«

,Si o <y «

^ rj W
> C M p c«

ft) rt o ll o
"^ -o.S

'That's Just what I Need

9f

TIT ERE IS a set of books that no man in the ELEC-
"■■ •*• TRICAL FIELD should do without. This is the
ELECTRICAL AGE in which we live; ELECTRIC-
ITY now controls more trades, directs more men,
offers more opportunities than any other power that
man has yet discovered. Do you wish to know the
underlying principles of MODERN ELECTRICAL
PRACTICE?

If so, HAWKINS ELECTRICAL GUIDES will give
you the information. In reality they are a school
within themselves, containing a complete study course
with QUESTIONS, ANSWERS AND ILLUSTRA-
TIONS, written in plain everyday language so that a
practical man can understand the "HOW, WHEN
AND WHY" OF ELECTRICITY.

Read over the titles shown on the back of each volume, and
mote the scope of each book. They are handsomely bound in
flexible black cloth with gold edges and will readily go in the
pocket. THEY ARE NOT ONLY THE BEST, BUT THE
CHEAPEST WORKS PUBLISHED ON ELECTRICITY.

Each book is complete in itself and will be supplied fi.oo pel"
copy, but we believe that the complete set is the best bargain.

The books can speak for themselves and a careful examination,
page by page, and illustration by illustration, will convince yoa
of their big value.

If you will fill out the following coupon g-iving all the informa-
tion requested, WE WILL SUBMIT THE TEN VOLUMES
FOR EXAMINATION ON CONDITIONS NAMED.

FREE E^TAMINATION OFFER

THEO. AUDEL & CO.,

72 5th Ave., NEW YORK.

Please submit me for examination
HAWKINS ELECTRICAL GUIDES (Price $i each.)

Ship at once, prepaid, the lo numbers; if satisfactory I agree to
«end you $i within seven days and to further mail you $i each
month until paid.

Signature.! ,

Occupation

Business Address ..
JLeiidence

Lilt.

A NEW Up-to-Date GUIDE For

MARINE ENGINEERS

Giving Just the Needed Information

WITH A

uestions and iVnswers

on the following subjects

Q

850

■ Pages

600

Illustrationis

Flexible Covers
Pocket Size
Large Typo

PRICE $3 POST

PAID

How to Figure (with
examples) .

Safety Valve Rules.

Horse Power Rules.

Theory and Elements of
Engineering.

Steam Tables.

Marine Boilers.

Oil Burners.

Marine Engines.

Tiirbines.

Pumps and Condensers.

Injectors and Heaters.

Steering Engines.

Pipes and Piping.

Auxiliary Machines^

General Care an^
Management, with
Suggestions.

Breakdowns and Re-
pairs at Sea.

Overhauling and Lay-
ing Up.

Gasoline Engines.

Gas Producers.

Heavy Oil Engines.

Piesel Engines.

Dynamos and Motors.

ElectricShipPropulsion.

Refrigerating.

Machinery.

Government Rules and
Regulations Relating
to Engineers* Certifi-
cates and Many Use-
ful Questions and
Answers Covering
Practical, Modem
and Approved Marine
Practice.

THIS BOOK WILL HELP YOU

AUDELS ENGI NEERS ^Att,

MECHANICS GUIDES

A Progressive, Illustrated Series with Questions , Answers and Calculations
covering Modern Engineering Practice, SPECIALL Y prepared for all Engine
eers, all Mechanics , all Electricians , and as a practical course of study for all
students and reference for instructors in every branch of the Engineering
professions. By Frank D. Graham, B.S., M.S., M.E.

Engineers* and Mechanics* Guide No, 1, price $1.50 — contains 470 pages — 847 illus-

Itrations covering fully the Theory , Practice and Operation oi all Steam Engines — all
Valve Motons — Valve Setting, with complete and practical information on all the
various engines and pumps.

Engineer^ and Mechanics' Guide No. 2, price $1.50 — contains 500 pages — 997 illus-

2trations — divided into 23 chapters, starting with the CORLISS ENGINE and covering
theTheory, Construction and Operation of all Steam Engines, including UNIFLOW,
and POPPET VALVE ENGINES, LOCOMOBILES.

Engineers* and Mechanics' Guide No. 3, price $1.50 — contains 375 pages — 793 illus-

3trations covering fully the Locomotive — Marine Engines — Turbines — Rotary
Engines—the Indicator — Lubricants and Lubrications — PRACTICAL MANAGE-
MENT — Instructions on how to use the Indicator.

Engineers* and Mechanics* Guide, No. 4, price $1.50 — contains 475 pages — 640 illus-

4trations covering fully GAS, GASOLINE, OIL, SEMI- and FULL DIESEL EN-
GINES—Aeroplanes and Aviation^HOW TO SELECT AN ENGINE— Complete
working instructons and drawings on STEAM ENGINE DESIGN, including rules

and formulae in general use.

Engineers' and Mechanics* Guide No. 5, price $1.50 — contains 525 pages — 755 illus-

5trations covering fully the Theory and Construction of all types of Steam Boilers
including: Heat — Combustion — Fuel and Flue Gas Analysis — CO2 recorders — Char-
acteristics of Boilers — Materials — Construction of all types of Boilers, (LATEST
PRACTICE.)

Engineers* and Mechanics' Guide No. 6, price $1.50 — contains 575 pages — 999 illus-
trations covering fully Boiler Construction — Mechanical Stokers — OIL BURNERS
6— Settings— Chimneys— Mechanical Draught— HOW TO SELECT A BOILER—
Complete instructions and drawings on BOILER DESIGN based on A.S.M.E.
BOILER CODE— OPERATION, including installation, FIRING, care and repair
of Steam Boilers.

Engineers' and Mechanics* Guide No. 7, price $1.50 — contains 550 pages — 1,071 illus-

7trations covering fully Pipes, Fittings and Pipe Fitting — Heating and Ventilation —
Refrigeration — Cooling Towers — Condensers — Distilling Apparatus — Elevators —
Cranes and Hoisting Machinery — Ropes and Cables — Splicing, etc.

Engineers' and Mechanics' Guide No. 8, price $3.00 — contains 1,000 pages — 2,648

8illlustrations. This is the latest, complete handbook on electric wiring in all branches
and a compendium of practical electrical engineering as an aid for engineers and elec-
tricians in obtaining a license — 57 chapters — ready reference index — ^pocket size — a
regular giant covering the entire field of Modem Electricity,

for the complete series post paid^ or sup-
plied separately — eight numbers — flexible
pocket size — 147 chapters-^, 400 pages
— 8,750 illustrations — numerous tables
— complete ready reference indexes.
Satisfaction guaranteed.

Price $12

THEO. AUDEL & CO., Publishers, ffrw

72 FIFTH AVENUE
YORK

THIS BOOK IS DUE ON THE LAST DATE
STAMPED BELOW

BOOKS REQUESTED BY ANOTHER BORROWER
ARE SUBJECT TO IMMEDIATE RECALL

UCD LIBRARY
AUG 27 1981 Ua

LIBRARY, UNIVERSITY OF CALIFORNIA, DAVIS

Book Slip— Series 458

506
Graham

Audels engineers and

TJ151
S67

mechanics g-iiae.

V.5

UNIVERSITY OF CALIFORNIA LIBRARY