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Title: Steam, Its Generation and Use

Author: Babcock & Wilcox Company

Release date: September 18, 2007 [eBook #22657]
Most recently updated: June 29, 2021

Language: English

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*** START OF THE PROJECT GUTENBERG EBOOK STEAM, ITS
GENERATION AND USE ***

Steam: its Generation and Use

TRANSCRIBER'S TABLE OF CONTENTS—CHAPTERS
Chapter
LIST OF ILLUSTRATIONS
TITLE PAGE
The Early History of the Generation and Use of Steam
Brief History of Water-tube Boilers
Requirements of Steam Boilers
Evolution of the Babcock & Wilcox Water-tube Boiler
The Babcock & Wilcox Boiler
Advantages of the Babcock & Wilcox Boiler
Heat and its Measurement
The Theory of Steam Making
Properties of Water
Boiler Feed Water
Feed Water Heating and Methods of Feeding
Steam
Moisture in Steam
Superheated Steam
Properties of Air
Combustion
Analysis of Flue Gases
Classification of Fuels
The Determination of Heating Values of Fuels
Combustion of Coal
Solid Fuels other than Coal and their Combustion
Liquid Fuels and their Combustion
Gaseous Fuels and their Combustion
Utilization of Waste Heat
Chimneys and Draft
Efficiency and Capacity of Boilers

The Selection of Boilers with a Consideration of the Factors Determining
such Selection
Operation and Care of Boilers
Brickwork Boiler Settings
Boiler Room Piping
Flow of Steam through Pipes and Orifices
Heat Transfer
INDEX

TRANSCRIBER'S LIST OF
ILLUSTRATIONS
Illustration
Works at Bayonne
Works at Barberton
Works at Renfrew
Fonderies et Ateliers
Longitudinal Drum Boiler
Boiler at Ampere
Boilers and Superheaters in Chicago
Erie County Electric Co.
Boilers and Superheaters at Blue Island
Woolworth Building
Boilers in Philadelphia
Boilers in Boston
Boilers and Superheaters in South Boston
Boilers in Johnstown
Boilers and Superheaters in South Boston
Boilers in Pittsburgh
Longitudinal Drum Boiler
Cross Drum Boiler
Longitudinal Drum Boiler
Longitudinal Drum Boiler
Longitudinal Drum Boiler
Cross Drum Boiler

Boilers in Boston
McAlpin Hotel
Northwest Station Chicago
Vertical Header Boiler
Boilers in Raritan
Boilers in Pittsburgh
Ninety-sixth Street Station in New York
Boiler in Boston
Boilers and Superheaters in Chicago
Boilers and Superheaters in Washington
Boilers and Superheaters in Passaic
Boilers and Superheaters in Washington
Boilers in Newark
Boilers in Louisville
Superheater
Boilers and Superheaters in Atlanta
Boilers and Superheaters in Chicago
Boilers and Superheaters in New York City
Boilers and Superheaters in Pittsburgh
Boilers and Superheaters in Washington
Chain Grate Stoker
Boilers in Portland
Boiler and Superheater in Quincy
Boilers in San Francisco
Boiler with Oil Furnace
Boilers in Bethlehem
Boiler and Superheaters in Underwood
Boilers and Superheaters in Chicago
Boilers in Washington
Boilers in Chicago
Boilers in Northumberland
Boilers in Chicago
Boilers in Chicago
Boilers in Chicago

Boilers in Minneapolis
Boilers in Billings
Boilers and Superheaters in East Pittsburgh
Boilers and Superheaters in Long Island City
Boilers in Chicago
Boiler Casing
Boilers and Superheaters in Louisville
Bankers Trust Building
Vesta Coal Co.
Iron City Brewery

[Pg 1]

STEAM
ITS GENERATION AND USE

THE BABCOCK & WILCOX CO.

NEW YORK
Pg 2]

Thirty-fifth Edition

4th Issue

Copyright, 1919, by The Babcock & Wilcox Co.

Bartlett Orr Press

New York

[Pg 3]

THE BABCOCK & WILCOX CO.
85 LIBERTY STREET, NEW YORK, U. S. A.

Works

BAYONNE NEW JERSEY
BARBERTON OHIO

Officers

W. D. HOXIE, President
E. H. WELLS, Chairman of the Board
A. G. PRATT, Vice-President

Branch Offices

ATLANTA Candler Building
BOSTON 35 Federal Street
CHICAGO Marquette Building
CINCINNATI Traction Building
CLEVELAND New Guardian Building
DENVER 435 Seventeenth Street
HAVANA, CUBA 104 Calle de Aguiar
HOUSTON Southern Pacific Building
LOS ANGELES I. N. Van Nuy’s Building
NEW ORLEANS Shubert Arcade
PHILADELPHIA North American Building
PITTSBURGH Farmers’ Deposit Bank Building
SALT LAKE CITY Kearns Building

SAN FRANCISCO Sheldon Building
SEATTLE L. C. Smith Building
TUCSON, ARIZ. Santa Rita Hotel Building
SAN JUAN, PORTO RICO Royal Bank Building

Export Department, New York: Alberto de Verastegni, Director

TELEGRAPHIC ADDRESS: FOR NEW YORK,
“GLOVEBOXES”

FOR HAVANA, “BABCOCK”

[Pg 4]

Works of The Babcock & Wilcox Co., at Bayonne, New Jersey

[Pg 5]

[Pg 6]

Works of The Babcock & Wilcox Co., at Barberton, Ohio

[Pg 7]

[Pg 8]

Works of Babcock & Wilcox, Limited, Renfrew, SCOTLAND

[Pg 9]

BABCOCK & WILCOX Limited
ORIEL HOUSE, FARRINGDON STREET, LONDON, E. C.

WORKS: RENFREW, SCOTLAND

Directors

JOHN DEWRANCE, Chairman CHARLES A. KNIGHT
ARTHUR T. SIMPSON J. H. R. KEMNAL
WILLIAM D. HOXIE Managing Director
E. H. WELLS WALTER COLLS, Secretary

Branch Offices in Great Britain

GLASGOW: 29 St. Vincent Place MANCHESTER: 30 Cross Street
MIDDLESBROUGH: The
BIRMINGHAM: Winchester House
Exchange
CARDIFF: 129 Bute Street NEWCASTLE: 42 Westgate Road
BELFAST: Ocean Buildings, Donegal SHEFFIELD: 14 Bank Chambers,
Square, E. Fargate

Offices Abroad

BOMBAY: Wheeler’s Building, Hornby MELBOURNE: 9 William
Road, Fort Street
BRUSSELS: 187 Rue Royal MEXICO: 22-23 Tiburcio
MILAN: 22 Via Principe
BILBAO: 1 Plaza de Albia
Umberto
MONTREAL: College Street,
CALCUTTA: Clive Building
St. Henry

JOHANNESBURG: Consolidated
NAPLES: 107 Via Santa Lucia
Buildings
LIMA: Peru SHANGHAI: 1a Jinkee Road
SYDNEY: 427-429 Sussex
LISBON: 84-86 Rua do Commercio
Street
MADRID: Ventura de la Vega TOKYO: Japan
TORONTO: Traders’ Bank Building

Representatives and Licensees in

ADELAIDE, South
CAIRO, Egypt MOSCOW, Russia
Australia
CHILE, Valparaiso, So. PERTH, Western
ATHENS, Greece
America Australia
AUCKLAND, New
CHRISTIANIA, Norway POLAND, Berlin
Zealand
BAHIA, Brazil COLOMBO, Ceylon RANGOON, Burma
COPENHAGEN, RIO DE JANEIRO,
BANGKOK, Siam
Denmark Brazil
SMYRNA, Asia
BARCELONA, Spain ESKILSTUNA, Sweden
Minor
BRUNN, Austria GIJON, Spain SOURABAYA, Java
BUCHAREST, HELSINGFORS, ST. PETERSBURG,
Roumania Finland Russia
TAMMERFORS,
BUDAPEST, Hungary HENGELO, Holland
Finland
BUENOS AYRES, KIMBERLEY, South THE HAGUE,
Argentine Rep. Africa Holland

TELEGRAPHIC ADDRESS FOR ALL OFFICES EXCEPT BOMBAY
AND CALCUTTA: “BABCOCK”
FOR BOMBAY AND CALCUTTA: “BOILER”

[Pg 10]

Fonderies et Ateliers de la Courneuve, Chaudières Babcock & Wilcox,
Paris, France

[Pg 11]

FONDERIES ET ATELIERS DE LA COURNEUVE
CHAUDIÈRES

BABCOCK & WILCOX
6 RUE LAFERRIÈRE, PARIS

WORKS: SEINE—LA COURNEUVE

Directors

EDMOND DUPUIS J. H. R. KEMNAL
ETIENNE BESSON IRÉNÉE CHAVANNE
CHARLES A. KNIGHT JULES LEMAIRE

Branch Offices

BORDEAUX: 30 Boulevard Antoine Gautier
LILLE: 23 Rue Faidherbe
LYON: 28 Quai de la Guillotier
MARSEILLE: 21 Cours Devilliers
MONTPELLIER: 1 Rue Boussairolles
NANCY: 2 Rue de Lorraine
ST. ETIENNE: 13 Rue de la Bourse

REPRESENTATIVE FOR SWITZERLAND: SPOERRI & CIE,
ZURICH

TELEGRAPHIC ADDRESS: “BABCOCK-PARIS”

[Pg 12]

Wrought-steel Vertical Header Longitudinal Drum Babcock & Wilcox
Boiler, Equipped with Babcock & Wilcox Superheater and Babcock &
Wilcox Chain Grate Stoker

[Pg 13]

THE EARLY HISTORY OF THE GENERATION
AND USE OF STEAM
While the time of man’s first knowledge and use of the expansive force of
the vapor of water is unknown, records show that such knowledge existed
earlier than 150 B. C. In a treatise of about that time entitled “Pneumatica”,
Hero, of Alexander, described not only existing devices of his predecessors
and contemporaries but also an invention of his own which utilized the
expansive force of steam for raising water above its natural level. He clearly
describes three methods in which steam might be used directly as a motive
of power; raising water by its elasticity, elevating a weight by its expansive
power and producing a rotary motion by its reaction on the atmosphere. The
third method, which is known as “Hero’s engine”, is described as a hollow
sphere supported over a caldron or boiler by two trunnions, one of which
was hollow, and connected the interior of the sphere with the steam space of
the caldron. Two pipes, open at the ends and bent at right angles, were
inserted at opposite poles of the sphere, forming a connection between the
caldron and the atmosphere. Heat being applied to the caldron, the steam
generated passed through the hollow trunnion to the sphere and thence into
the atmosphere through the two pipes. By the reaction incidental to its
escape through these pipes, the sphere was caused to rotate and here is the
primitive steam reaction turbine.

Hero makes no suggestions as to application of any of the devices he
describes to a useful purpose. From the time of Hero until the late sixteenth
and early seventeenth centuries, there is no record of progress, though
evidence is found that such devices as were described by Hero were
sometimes used for trivial purposes, the blowing of an organ or the turning
of a skillet.

Mathesius, the German author, in 1571; Besson, a philosopher and
mathematician at Orleans; Ramelli, in 1588; Battista Delia Porta, a
Neapolitan mathematician and philosopher, in 1601; Decause, the French
engineer and architect, in 1615; and Branca, an Italian architect, in 1629, all
published treatises bearing on the subject of the generation of steam.

To the next contributor, Edward Somerset, second Marquis of Worcester, is
apparently due the credit of proposing, if not of making, the first useful
steam engine. In the “Century of Scantlings and Inventions”, published in
London in 1663, he describes devices showing that he had in mind the
raising of water not only by forcing it from two receivers by direct steam
pressure but also for some sort of reciprocating piston actuating one end of a
lever, the other operating a pump. His descriptions are rather obscure and no
drawings are extant so that it is difficult to say whether there were any
distinctly novel features to his devices aside from the double action. While
there is no direct authentic record that any of the devices he described were
actually constructed, it is claimed by many that he really built and operated a
steam engine containing pistons.

In 1675, Sir Samuel Moreland was decorated by King Charles II, for a
demonstration of “a certain powerful machine to raise water.” Though there
appears to be no record of the design of this machine, the mathematical
dictionary, published in 1822, credits Moreland with the first account of a
steam engine, on which subject he wrote a treatise that is still preserved in
the British Museum.
[Pg 14]

397 Horse-power Babcock & Wilcox Boiler in Course of Erection at the
Plant of the Crocker Wheeler Co., Ampere, N. J.

[Pg 15] Dr. Denys Papin, an ingenious Frenchman, invented in 1680 “a steam
digester for extracting marrowy, nourishing juices from bones by enclosing
them in a boiler under heavy pressure,” and finding danger from explosion,
added a contrivance which is the first safety valve on record.

The steam engine first became commercially successful with Thomas
Savery. In 1699, Savery exhibited before the Royal Society of England (Sir
Isaac Newton was President at the time), a model engine which consisted of
two copper receivers alternately connected by a three-way hand-operated
valve, with a boiler and a source of water supply. When the water in one
receiver had been driven out by the steam, cold water was poured over its
outside surface, creating a vacuum through condensation and causing it to
fill again while the water in the other reservoir was being forced out. A
number of machines were built on this principle and placed in actual use as
mine pumps.

The serious difficulty encountered in the use of Savery’s engine was the fact
that the height to which it could lift water was limited by the pressure the
boiler and vessels could bear. Before Savery’s engine was entirely displaced
by its successor, Newcomen’s, it was considerably improved by Desaguliers,
who applied the Papin safety valve to the boiler and substituted condensation
by a jet within the vessel for Savery’s surface condensation.

In 1690, Papin suggested that the condensation of steam should be employed
to make a vacuum beneath a cylinder which had previously been raised by
the expansion of steam. This was the earliest cylinder and piston steam
engine and his plan took practical shape in Newcomen’s atmospheric engine.
Papin’s first engine was unworkable owing to the fact that he used the same
vessel for both boiler and cylinder. A small quantity of water was placed in
the bottom of the vessel and heat was applied. When steam formed and
raised the piston, the heat was withdrawn and the piston did work on its
down stroke under pressure of the atmosphere. After hearing of Savery’s
engine, Papin developed an improved form. Papin’s engine of 1705
consisted of a displacement chamber in which a floating diaphragm or piston
on top of the water kept the steam and water from direct contact. The water

delivered by the downward movement of the piston under pressure, to a
closed tank, flowed in a continuous stream against the vanes of a water
wheel. When the steam in the displacement chamber had expanded, it was
exhausted to the atmosphere through a valve instead of being condensed.
The engine was, in fact, a non-condensing, single action steam pump with
the steam and pump cylinders in one. A curious feature of this engine was a
heater placed in the diaphragm. This was a mass of heated metal for the
purpose of keeping the steam dry or preventing condensation during
expansion. This device might be called the first superheater.

Among the various inventions attributed to Papin was a boiler with an
internal fire box, the earliest record of such construction.

While Papin had neglected his earlier suggestion of a steam and piston
engine to work on Savery’s ideas, Thomas Newcomen, with his assistant,
John Cawley, put into practical form Papin’s suggestion of 1690. Steam
admitted from the boiler to a cylinder raised a piston by its expansion,
assisted by a counter-weight on the other end of a beam actuated by the
piston. The steam valve was then shut and the steam condensed by a jet of
cold water. The piston was then forced downward by atmospheric pressure
and did work on the pump. The condensed water in the cylinder was
expelled through an escapement valve by the next entry of steam. This
engine used steam having pressure but little, if any, above that of the
atmosphere.
[Pg 16]

Two Units of 8128 Horse Power of Babcock & Wilcox Boilers and
Superheaters at the Fisk Street Station of the Commonwealth Edison
Co., Chicago, Ill., 50,400 Horse Power being Installed in this Station.
The Commonwealth Edison Co. Operates in its Various Stations a Total
of 86,000 Horse Power of Babcock & Wilcox Boilers, all Fitted with
Babcock & Wilcox Superheaters and Equipped with Babcock & Wilcox
Chain Grate Stokers

[Pg 17] In 1711, this engine was introduced into mines for pumping purposes.
Whether its action was originally automatic or whether dependent upon the
hand operation of the valves is a question of doubt. The story commonly
believed is that a boy, Humphrey Potter, in 1713, whose duty it was to open
and shut such valves of an engine he attended, by suitable cords and catches
attached to the beam, caused the engine to automatically manipulate these
valves. This device was simplified in 1718 by Henry Beighton, who
suspended from the bottom, a rod called the plug-tree, which actuated the
valve by tappets. By 1725, this engine was in common use in the collieries
and was changed but little for a matter of sixty or seventy years. Compared
with Savery’s engine, from the aspect of a pumping engine, Newcomen’s
was a distinct advance, in that the pressure in the pumps was in no manner

dependent upon the steam pressure. In common with Savery’s engine, the
losses from the alternate heating and cooling of the steam cylinder were
enormous. Though obviously this engine might have been modified to serve
many purposes, its use seems to have been limited almost entirely to the
pumping of water.

The rivalry between Savery and Papin appears to have stimulated attention
to the question of fuel saving. Dr. John Allen, in 1730, called attention to the
fact that owing to the short length of time of the contact between the gases
and the heating surfaces of the boiler, nearly half of the heat of the fire was
lost. With a view to overcoming this loss at least partially, he used an
internal furnace with a smoke flue winding through the water in the form of
a worm in a still. In order that the length of passage of the gases might not
act as a damper on the fire, Dr. Allen recommended the use of a pair of
bellows for forcing the sluggish vapor through the flue. This is probably the
first suggested use of forced draft. In forming an estimate of the quantity of
fuel lost up the stack, Dr. Allen probably made the first boiler test.

Toward the end of the period of use of Newcomen’s atmospheric engine,
John Smeaton, who, about 1770, built and installed a number of large
engines of this type, greatly improved the design in its mechanical details.

The improvement in boiler and engine design of Smeaton, Newcomen and
their contemporaries, were followed by those of the great engineer, James
Watt, an instrument maker of Glasgow. In 1763, while repairing a model of
Newcomen’s engine, he was impressed by the great waste of steam to which
the alternating cooling and heating of the engine gave rise. His remedy was
the maintaining of the cylinder as hot as the entering steam and with this in
view he added a vessel separate from the cylinder, into which the steam
should pass from the cylinder and be there condensed either by the
application of cold water outside or by a jet from within. To preserve a
vacuum in his condenser, he added an air pump which should serve to
remove the water of condensation and air brought in with the injection water
or due to leakage. As the cylinder no longer acted as a condenser, he could
maintain it at a high temperature by covering it with non-conducting
material and, in particular, by the use of a steam jacket. Further and with the
same object in view, he covered the top of the cylinder and introduced steam
above the piston to do the work previously accomplished by atmospheric

pressure. After several trials with an experimental apparatus based on these
ideas, Watt patented his improvements in 1769. Aside from their historical
importance, Watt’s improvements, as described in his specification, are to
this day a [Pg 18]
[Pg 19] statement of the principles which guide the scientific development of
the steam engine. His words are:

Erie County Electric Co., Erie, Pa., Operating 3082 Horse Power of
Babcock & Wilcox Boilers and Superheaters, Equipped with Babcock &
Wilcox Chain Grate Stokers

“My method of lessening the consumption of steam, and consequently
fuel, in fire engines, consists of the following principles:

“First, That vessel in which the powers of steam are to be employed to
work the engine, which is called the cylinder in common fire engines,
and which I call the steam vessel, must, during the whole time the
engine is at work, be kept as hot as the steam that enters it; first, by
enclosing it in a case of wood, or any other materials that transmit heat
slowly; secondly, by surrounding it with steam or other heated bodies;
and, thirdly, by suffering neither water nor any other substance colder
than the steam to enter or touch it during that time.

“Secondly, In engines that are to be worked wholly or partially by
condensation of steam, the steam is to be condensed in vessels distinct
from the steam vessels or cylinders, although occasionally
communicating with them; these vessels I call condensers; and, whilst
the engines are working, these condensers ought at least to be kept as
cold as the air in the neighborhood of the engines, by application of
water or other cold bodies.

“Thirdly, Whatever air or other elastic vapor is not condensed by the
cold of the condenser, and may impede the working of the engine, is to
be drawn out of the steam vessels or condensers by means of pumps,
wrought by the engines themselves, or otherwise.

“Fourthly, I intend in many cases to employ the expansive force of
steam to press on the pistons, or whatever may be used instead of them,
in the same manner in which the pressure of the atmosphere is now
employed in common fire engines. In cases where cold water cannot be
had in plenty, the engines may be wrought by this force of steam only,
by discharging the steam into the air after it has done its office….

“Sixthly, I intend in some cases to apply a degree of cold not capable of
reducing the steam to water, but of contracting it considerably, so that
the engines shall be worked by the alternate expansion and contraction
of the steam.

“Lastly, Instead of using water to render the pistons and other parts of
the engine air and steam tight, I employ oils, wax, resinous bodies, fat
of animals, quick-silver and other metals in their fluid state.”

The fifth claim was for a rotary engine, and need not be quoted here.

The early efforts of Watt are typical of those of the poor inventor struggling
with insufficient resources to gain recognition and it was not until he became
associated with the wealthy manufacturer, Mattheu Boulton of Birmingham,
that he met with the success upon which his present fame is based. In
partnership with Boulton, the business of the manufacture and the sale of his
engines were highly successful in spite of vigorous attacks on the validity of
his patents.

Though the fourth claim of Watt’s patent describes a non-condensing engine
which would require high pressures, his aversion to such practice was
strong. Notwithstanding his entire knowledge of the advantages through
added expansion under high pressure, he continued to use pressures not
above 7 pounds per square inch above the atmosphere. To overcome such
pressures, his boilers were fed through a stand-pipe of sufficient height to
have the column of water offset the pressure within the boiler. Watt’s attitude
toward high pressure made his influence felt long after his patents had
expired.
[Pg 20]

Portion of 9600 Horse-power Installation of Babcock & Wilcox Boilers
and Superheaters, Equipped with Babcock & Wilcox Chain Grate
Stokers at the Blue Island, Ill., Plant of the Public Service Co. of
Northern Illinois. This Company Operates 14,580 Horse Power of
Babcock & Wilcox Boilers and Superheaters in its Various Stations

[Pg 21] In 1782, Watt patented two other features which he had invented as
early as 1769. These were the double acting engine, that is, the use of steam
on both sides of the piston and the use of steam expansively, that is, the
shutting off of steam from the cylinder when the piston had made but a
portion of its stroke, the power for the completion of the stroke being
supplied by the expansive force of the steam already admitted.

He further added a throttle valve for the regulation of steam admission,
invented the automatic governor and the steam indicator, a mercury steam
gauge and a glass water column.

It has been the object of this brief history of the early developments in the
use of steam to cover such developments only through the time of James
Watt. The progress of the steam engine from this time through the stages of
higher pressures, combining of cylinders, the application of steam vehicles

and steamboats, the adding of third and fourth cylinders, to the invention of
the turbine with its development and the accompanying development of the
reciprocating engine to hold its place, is one long attribute to the inventive
genius of man.

While little is said in the biographies of Watt as to the improvement of steam
boilers, all the evidence indicates that Boulton and Watt introduced the first
“wagon boiler”, so called because of its shape. In 1785, Watt took out a
number of patents for variations in furnace construction, many of which
contain the basic principles of some of the modern smoke preventing
furnaces. Until the early part of the nineteenth century, the low steam
pressures used caused but little attention to be given to the form of the boiler
operated in connection with the engines above described. About 1800,
Richard Trevithick, in England, and Oliver Evans, in America, introduced
non-condensing, and for that time, high pressure steam engines. To the
initiative of Evans may be attributed the general use of high pressure steam
in the United States, a feature which for many years distinguished American
from European practice. The demand for light weight and economy of space
following the beginning of steam navigation and the invention of the
locomotive required boilers designed and constructed to withstand heavier
pressures and forced the adoption of the cylindrical form of boiler. There are
in use to-day many examples of every step in the development of steam
boilers from the first plain cylindrical boiler to the most modern type of
multi-tubular locomotive boiler, which stands as the highest type of fire-tube
boiler construction.

The early attempts to utilize water-tube boilers were few. A brief history of
the development of the boilers, in which this principle was employed, is
given in the following chapter. From this history it will be clearly indicated
that the first commercially successful utilization of water tubes in a steam
generator is properly attributed to George H. Babcock and Stephen Wilcox.
[Pg 22]

Copyright by Underwood & Underwood

Woolworth Building, New York City, Operating 2454 Horse Power of
Babcock & Wilcox Boilers

[Pg 23]

BRIEF HISTORY OF WATER-TUBE
BOILERS[1]
As stated in the previous chapter, the first water-tube boiler
was built by John Blakey and was patented by him in
1766. Several tubes alternately inclined at opposite angles
were arranged in the furnaces, the adjacent tube ends being
connected by small pipes. The first successful user of
water-tube boilers, however, was James Rumsey, an
American inventor, celebrated for his early experiments in
steam navigation, and it is he who may be truly classed as
the originator of the water-tube boiler. In 1788 he patented,
in England, several forms of boilers, some of which were
of the water-tube type. One had a fire box with flat top and Blakey, 1766
sides, with horizontal tubes across the fire box connecting
the water spaces. Another had a cylindrical fire box
surrounded by an annular water space and a coiled tube was placed within
the box connecting at its two ends with the water space. This was the first of
the “coil boilers”. Another form in the same patent was the vertical tubular
boiler, practically as made at the present time.

The first boiler made of a
combination of small tubes,
connected at one end to a reservoir,
was the invention of another
American, John Stevens, in 1804.
This boiler was actually employed
to generate steam for running a
steamboat on the Hudson River, but
John Stevens, 1804 like all the “porcupine” boilers, of
which type it was the first, it did not
have the elements of a continued
success.

Another form of water tube was patented in
1805 by John Cox Stevens, a son of John
Stevens. This boiler consisted of twenty
vertical tubes, 1¼ inches internal diameter and
40½ inches long, arranged in a circle, the
outside diameter of which was approximately
12 inches, connecting a water chamber at the
bottom with a steam chamber at the top. The
steam and water chambers were annular spaces
of small cross section and contained
approximately 33 cubic inches. The illustration
shows the cap of the steam chamber secured by
bolts. The steam outlet pipe “A” is a pipe of John Cox Stevens, 1805
one inch diameter, the water entering through a
similar aperture at the bottom. One of these
boilers was for a long time at the Stevens Institute of Technology at
Hoboken, and is now in the Smithsonian Institute at Washington.

About the same time, Jacob Woolf built a boiler of large horizontal tubes,
extending across the furnace and connected at the ends to a longitudinal
drum above. The first purely sectional [Pg 24] water-tube boiler was built by
Julius Griffith, in 1821. In this boiler, a number of horizontal water tubes
were connected to vertical side pipes, the side pipes were connected to
horizontal gathering pipes, and these latter in turn to a steam drum.

In 1822, Jacob Perkins
constructed a flash boiler
for carrying what was then
considered a high pressure.
A number of cast-iron bars
having 1½ inches annular
holes through them and
connected at their outer
ends by a series of bent
pipes, outside of the furnace
walls, were arranged in
three tiers over the fire. The
water was fed slowly to the

Joseph Eve, 1825 upper tier by a force pump
and steam in the
superheated state was
discharged to the lower tiers into a chamber from which it was taken to the
engine.

The first sectional water-tube boiler, with a well-defined circulation, was
built by Joseph Eve, in 1825. The sections were composed of small tubes
with a slight double curve, but being practically vertical, fixed in horizontal
headers, which headers were in turn connected to a steam space above and a
water space below formed of larger pipes. The steam and water spaces were
connected by outside pipes to secure a circulation of the water up through
the sections and down through the external pipes. In the same year, John
M’Curdy of New York, built a “Duplex Steam Generator” of “tubes of
wrought or cast iron or other material” arranged in several horizontal rows,
connected together alternately at the front and rear by return bends. In the
tubes below the water line were placed interior circular vessels closed at the
ends in order to expose a thin sheet of water to the action of the fire.

In 1826, Goldsworthy Gurney
built a number of boilers,
which he used on his steam
carriages. A number of small
tubes were bent into the shape
of a “U” laid [Pg 25] sidewise
and the ends were connected
with larger horizontal pipes.
These were connected by
vertical pipes to permit of
circulation and also to a
vertical cylinder which served Gurney, 1826
as a steam and water reservoir.
In 1828, Paul Steenstrup made
the first shell boiler with vertical water tubes in the large flues, similar to the
boiler known as the “Martin” and suggesting the “Galloway”.

The first water-tube boiler having fire tubes within water tubes was built in
1830, by Summers & Ogle. Horizontal connections at the top and bottom

were connected by a series of vertical water tubes, through which were fire
tubes extending through the horizontal connections, the fire tubes being held
in place by nuts, which also served to make the joint.

Stephen Wilcox, in 1856, was the
first to use inclined water tubes
connecting water spaces at the front
and rear with a steam space above.
The first to make such inclined
tubes into a sectional form was
Twibill, in 1865. He used wrought-
iron tubes connected at the front and
Stephen Wilcox, 1856 rear with standpipes through
intermediate connections. These
standpipes carried the system to a
horizontal cross drum at the top, the entrained water being carried to the rear.

Clarke, Moore, McDowell, Alban and others worked on the problem of
constructing water-tube boilers, but because of difficulties of construction
involved, met with no practical success.

It may be asked why
water-tube boilers did
not come into more
general use at an early
date, that is, why the
number of water-tube
boilers built was so
small in comparison to
the number of shell
boilers. The reason for
this is found in the
difficulties involved in
Twibill, 1865
the design and
construction of water-
tube boilers, which
design and construction required a high class of engineering and
workmanship, while the plain cylindrical boiler is comparatively easy to

build. The greater skill required to make a water-tube boiler successful is
readily shown in the great number of failures in the attempts to make them.

[Pg 26]

Partial View of 7000 Horse-power Installation of Babcock & Wilcox
Boilers at the Philadelphia, Pa., Plant of the Baldwin Locomotive
Works. This Company Operates in its Various Plants a Total of 9280
Horse Power of Babcock & Wilcox Boilers

FOOTNOTES
[1] See discussion by George H. Babcock, of Stirling’s paper on “Water-tube and
Shell Boilers”, in Transactions, American Society of Mechanical Engineers,
Volume VI., Page 601.

[Pg 27]

REQUIREMENTS OF STEAM BOILERS
Since the first appearance in “Steam” of the following “Requirements of a
Perfect Steam Boiler”, the list has been copied many times either word for
word or clothed in different language and applied to some specific type of
boiler design or construction. In most cases, although full compliance with
one or more of the requirements was structurally impossible, the reader was
left to infer that the boiler under consideration possessed all the desirable
features. It is noteworthy that this list of requirements, as prepared by
George H. Babcock and Stephen Wilcox, in 1875, represents the best
practice of to-day. Moreover, coupled with the boiler itself, which is used in
the largest and most important steam generating plants throughout the world,
the list forms a fitting monument to the foresight and genius of the inventors.

REQUIREMENTS OF A PERFECT STEAM BOILER

1st. Proper workmanship and simple construction, using materials which
experience has shown to be the best, thus avoiding the necessity of early
repairs.

2nd. A mud drum to receive all impurities deposited from the water, and so
placed as to be removed from the action of the fire.

3rd. A steam and water capacity sufficient to prevent any fluctuation in
steam pressure or water level.

4th. A water surface for the disengagement of the steam from the water, of
sufficient extent to prevent foaming.

5th. A constant and thorough circulation of water throughout the boiler, so as
to maintain all parts at the same temperature.

6th. The water space divided into sections so arranged that, should any
section fail, no general explosion can occur and the destructive effects will

be confined to the escape of the contents. Large and free passages between
the different sections to equalize the water line and pressure in all.

7th. A great excess of strength over any legitimate strain, the boiler being so
constructed as to be free from strains due to unequal expansion, and, if
possible, to avoid joints exposed to the direct action of the fire.

8th. A combustion chamber so arranged that the combustion of the gases
started in the furnace may be completed before the gases escape to the
chimney.

9th. The heating surface as nearly as possible at right angles to the currents
of heated gases, so as to break up the currents and extract the entire available
heat from the gases.

10th. All parts readily accessible for cleaning and repairs. This is a point of
the greatest importance as regards safety and economy.

11th. Proportioned for the work to be done, and capable of working to its full
rated capacity with the highest economy.

12th. Equipped with the very best gauges, safety valves and other fixtures.

[Pg 28]

The exhaustive study made of each one of these requirements is shown by
the following extract from a lecture delivered by Mr. Geo. H. Babcock at
Cornell University in 1890 upon the subject:

THE CIRCULATION OF WATER IN STEAM BOILERS

You have all noticed a kettle of water boiling over the fire, the fluid rising
somewhat tumultuously around the edges of the vessel, and tumbling toward
the center, where it descends. Similar currents are in action while the water
is simply being heated, but they are not perceptible unless there are floating
particles in the liquid. These currents are caused by the joint action of the
added temperature and two or more qualities which the water possesses.

1st. Water, in common with most other substances, expands when heated; a
statement, however, strictly true only when referred to a temperature above
39 degrees F. or 4 degrees C., but as in the making of steam we rarely have
to do with temperatures so low as that, we may, for our present purposes,
ignore that exception.

2nd. Water is practically a non-conductor of heat, though not entirely so. If
ice-cold water was kept boiling at the surface the heat would not penetrate
sufficiently to begin melting ice at a depth of 3 inches in less than about two
hours. As, therefore, the heated water cannot impart its heat to its
neighboring particles, it remains expanded and rises by its levity, while
colder portions come to be heated in turn, thus setting up currents in the
fluid.

Now, when all the water has been heated to the
boiling point corresponding to the pressure to which it
is subjected, each added unit of heat converts a
portion, about 7 grains in weight, into vapor, greatly
increasing its volume; and the mingled steam and
water rises more rapidly still, producing ebullition
such as we have noticed in the kettle. So long as the
quantity of heat added to the contents of the kettle
continues practically constant, the conditions remain
Fig. 1 similar to those we noticed at first, a tumultuous
lifting of the water around the edges, flowing toward
the center and thence downward; if, however, the fire
be quickened, the upward currents interfere with the downward and the
kettle boils over (Fig. 1).

If now we put in the kettle a vessel somewhat
smaller (Fig. 2) with a hole in the bottom and
supported at a proper distance from the side so as to
separate the upward from the downward currents,
we can force the fires to a very much greater extent
without causing the kettle to boil over, and when we
place a deflecting plate so as to guide the rising
column toward the center it will be almost
impossible to produce that effect. This is the

invention of Perkins in 1831 and forms the basis of Fig. 2
very many of the arrangements for producing free
circulation of the water in boilers which have been
made since that time. It consists in dividing the currents so that they will not
interfere each with the other.

[Pg 29]

But what is the object of facilitating the circulation of water in
boilers? Why may we not safely leave this to the unassisted
action of nature as we do in culinary operations? We may, if we
do not care for the three most important aims in steam-boiler
construction, namely, efficiency, durability, and safety, each of
which is more or less dependent upon a proper circulation of
the water. As for efficiency, we have seen one proof in our
kettle. When we provided means to preserve the circulation, we
found that we could carry a hotter fire and boil away the water
Fig. 3 much more rapidly than before. It is the same in a steam boiler.
And we also noticed that when there was nothing but the
unassisted circulation, the rising steam carried away so much
water in the form of foam that the kettle boiled over, but when the currents
were separated and an unimpeded circuit was established, this ceased, and a
much larger supply of steam was delivered in a comparatively dry state.
Thus, circulation increases the efficiency in two ways: it adds to the ability
to take up the heat, and decreases the liability to waste that heat by what is
technically known as priming. There is yet another way in which,
incidentally, circulation increases efficiency of surface, and that is by
preventing in a greater or less degree the formation of deposits thereon. Most
waters contain some impurity which, when the water is evaporated, remains
to incrust the surface of the vessel. This incrustation becomes very serious
sometimes, so much so as to almost entirely prevent the transmission of heat
from the metal to the water. It is said that an incrustation of only one-eighth
inch will cause a loss of 25 per cent in efficiency, and this is probably within
the truth in many cases. Circulation of water will not prevent incrustation
altogether, but it lessens the amount in all waters, and almost entirely so in
some, thus adding greatly to the efficiency of the surface.

A second advantage to be obtained through circulation
is durability of the boiler. This it secures mainly by
keeping all parts at a nearly uniform temperature. The
way to secure the greatest freedom from unequal
strains in a boiler is to provide for such a circulation of
the water as will insure the same temperature in all
parts.

3rd. Safety follows in the wake of durability, because a
boiler which is not subject to unequal strains of Fig. 4
expansion and contraction is not only less liable to
ordinary repairs, but also to rupture and disastrous
explosion. By far the most prolific cause of explosions is this same strain
from unequal expansions.

Having thus briefly looked at the advantages of circulation of water in steam
boilers, let us see what are the best means of securing it under the most
efficient conditions We have seen in our kettle that one essential point was
that the currents should be kept from interfering with each other. If we could
look into an ordinary return tubular boiler when steaming, we should see a
curious commotion of currents rushing hither and thither, and shifting
continually as one or the other contending force gained a momentary
mastery. The principal upward currents would be found at the two ends, one
over the fire and the other over the first foot or so of the tubes. Between
these, the downward currents struggle [Pg 30]
[Pg 31] against the rising currents of steam and water. At a sudden demand for
steam, or on the lifting of the safety valve, the pressure being slightly
reduced, the water jumps up in jets at every portion of the surface, being
lifted by the sudden generation of steam throughout the body of water. You
have seen the effect of this sudden generation of steam in the well-known
experiment with a Florence flask, to which a cold application is made while
boiling water under pressure is within. You have also witnessed the geyser-
like action when water is boiled in a test tube held vertically over a lamp
(Fig. 3).

386 Horse-power Installation of Babcock & Wilcox Boilers at B. F.
Keith’s Theatre, Boston, Mass.

If now we take a U-tube depending from a vessel of
water (Fig. 4) and apply the lamp to one leg a
circulation is at once set up within it, and no such
spasmodic action can be produced. Thus U-tube is the
representative of the true method of circulation within a
water-tube boiler properly constructed. We can, for the
Fig. 5 purpose of securing more heating surface, extend the
heated leg into a long incline (Fig. 5), when we have
the well-known inclined-tube generator. Now, by
adding other tubes, we may further increase the heating
surface (Fig. 6), while it will still be the U-tube in effect and action. In such
a construction the circulation is a function of the difference in density of the
two columns. Its velocity is measured by the well-known Torricellian
formula, V = (2gh)½, or, approximately V = 8(h)½, h being measured in
terms of the lighter fluid. This velocity will increase until the rising column
becomes all steam, but the quantity or weight circulated will attain a
maximum when the density of the mingled steam and water in the rising

column becomes one-half that of the solid water in the descending column
which is nearly coincident with the condition of half steam and half water,
the weight of the steam being very slight compared to that of the water.

It becomes easy by this rule to determine the circulation in any given boiler
built on this principle, provided the construction is such as to permit a free
flow of the water. Of course, every bend detracts a little and something is
lost in getting up the velocity, but when the boiler is well arranged and
proportioned these retardations are slight.

Let us take for example one of the 240 horse-
power Babcock & Wilcox boilers here in the
University. The height of the columns may be
taken as 4½ feet, measuring from the surface
of the water to about the center of the bundle
of tubes over the fire, and the head would be
equal to this height at the maximum of
circulation. We should, therefore, have a
velocity of 8(4½)½ = 16.97, say 17 feet per
second. There are in this boiler fourteen Fig. 6
sections, each having a 4-inch tube opening
into the drum, the area of which (inside) is 11
square inches, the fourteen aggregating 154 square inches, or 1.07 square
feet. This multiplied by the velocity, 16.97 feet, gives 18.16 cubic feet
mingled steam and water discharged per second, one-half of which, or 9.08
cubic feet, is steam. Assuming this steam to be at 100 pounds gauge
pressure, it will weigh 0.258 pound per cubic foot. Hence, 2.34 pounds of
steam will be [Pg 32]
[Pg 33] discharged per second, and 8,433 pounds per hour. Dividing this by
30, the number of pounds representing a boiler horse power, we get 281.1
horse power, about 17 per cent, in excess of the rated power of the boiler.
The water at the temperature of steam at 100 pounds pressure weighs 56
pounds per cubic foot, and the steam 0.258 pound, so that the steam forms
but 1⁄218 part of the mixture by weight, and consequently each particle of
water will make 218 circuits before being evaporated when working at this
capacity, and circulating the maximum weight of water through the tubes.

A Portion of 9600 Horse-power Installation of Babcock & Wilcox
Boilers and Superheaters Being Erected at the South Boston, Mass.,
Station of the Boston Elevated Railway Co. This Company Operates in
its Various Stations a Total of 46,400 Horse Power of Babcock & Wilcox
Boilers

It is evident that at the highest possible velocity of exit
from the generating tubes, nothing but steam will be
delivered and there will be no circulation of water
except to supply the place of that evaporated. Let us see
at what rate of steaming this would occur with the
boiler under consideration. We shall have a column of
steam, say 4 feet high on one side and an equal column
of water on the other. Assuming, as before, the steam at
100 pounds and the water at same temperature, we will Fig. 7
have a head of 866 feet of steam and an issuing
velocity of 235.5 feet per second. This multiplied by
1.07 square feet of opening by 3,600 seconds in an hour, and by 0.258 gives
234,043 pounds of steam, which, though only one-eighth the weight of
mingled steam and water delivered at the maximum, gives us 7,801 horse

power, or 32 times the rated power of the boiler. Of course, this is far beyond
any possibility of attainment, so that it may be set down as certain that this
boiler cannot be forced to a point where there will not be an efficient
circulation of the water. By the same method of calculation it may be shown
that when forced to double its rated power, a point rarely expected to be
reached in practice, about two-thirds the volume of mixture of steam and
water delivered into the drum will be steam, and that the water will make
110 circuits while being evaporated. Also that when worked at only about
one-quarter its rated capacity, one-fifth of the volume will be steam and the
water will make the rounds 870 times before it becomes steam. You will thus
see that in the proportions adopted in this boiler there is provision for perfect
circulation under all the possible conditions of practice.

In designing boilers of this style
it is necessary to guard against
having the uptake at the upper
end of the tubes too large, for if
sufficiently large to allow
downward currents therein, the
whole effect of the rising
column in increasing the
circulation in the tubes is
nullified (Fig. 7). This will
Fig. 8 [Developed to show Circulation] readily be seen if we consider
the uptake very large when the
only head producing circulation
in the tubes will be that due to the inclination of each tube taken by itself.
This objection is only overcome when the uptake is so small as to be entirely
filled with the ascending current of mingled steam and water. It is also
necessary that this uptake should be practically direct, and it should not be
composed of frequent enlargements and [Pg 34]
[Pg 35] contractions. Take, for instance, a boiler well known in Europe, copied
and sold here under another name. It is made up of inclined tubes secured by
pairs into boxes at the ends, which boxes are made to communicate with
each other by return bends opposite the ends of the tubes. These boxes and
return bends form an irregular uptake, whereby the steam is expected to rise
to a reservoir above. You will notice (Fig. 8) that the upward current of
steam and water in the return bend meets and directly antagonizes the

upward current in the adjoining tube. Only one result can follow. If their
velocities are equal, the momentum of both will be neutralized and all
circulation stopped, or, if one be stronger, it will cause a back flow in the
other by the amount of difference in force, with practically the same result.

4880 Horse-power Installation of Babcock & Wilcox Boilers at the Open
Hearth Plant of the Cambria Steel Co., Johnstown, Pa. This Company
Operates a Total of 52,000 Horse Power of Babcock & Wilcox Boilers

In a well-known boiler, many of which were sold, but of which none are
now made and a very few are still in use, the inventor claimed that the return
bends and small openings against the tubes were for the purpose of
“restricting the circulation” and no doubt they performed well that office;
but excepting for the smallness of the openings they were not as efficient for
that purpose as the arrangement shown in Fig. 8.

Another form of boiler, first invented by Clarke or Crawford, and lately
revived, has the uptake made of boxes into which a number, generally from
two to four tubes, are expanded, the boxes being connected together by
nipples (Fig. 9). It is a well-known fact that where a fluid flows through a

conduit which enlarges and then contracts, the
velocity is lost to a greater or less extent at the
enlargements, and has to be gotten up again at the
contractions each time, with a corresponding loss of
head. The same thing occurs in the construction
shown in Fig. 9. The enlargements and contractions
quite destroy the head and practically overcome the
tendency of the water to circulate.

Fig. 9 A horizontal tube stopped at
one end, as shown in Fig.
10, can have no proper
circulation within it. If moderately driven, the
water may struggle in against the issuing steam
sufficiently to keep the surface covered, but a
slight degree of forcing will cause it to act like the
test tube in Fig. 3, and the more there are of them
in a given boiler the more spasmodic will be its
working. Fig. 10

The experiment with our kettle (Fig. 2) gives the
clue to the best means of promoting circulation in ordinary shell boilers.
Steenstrup or “Martin” and “Galloway” water tubes placed in such boilers
also assist in directing the circulation therein, but it is almost impossible to
produce in shell boilers, by any means the circulation of all the water in one
continuous round, such as marks the well-constructed water-tube boiler.

As I have before remarked, provision for a proper circulation of water has
been almost universally ignored in designing steam boilers, sometimes to the
great damage of the owner, but oftener to the jeopardy of the lives of those
who are employed to run them. The noted case of the Montana and her sister
ship, where some $300,000 [Pg 36] was thrown away in trying an experiment
which a proper consideration of this subject would have avoided, is a case in
point; but who shall count the cost of life and treasure not, perhaps, directly
traceable to, but, nevertheless, due entirely to such neglect in design and
construction of the thousands of boilers in which this necessary element has
been ignored?

In the light of the performance of the exacting conditions of present day
power-plant practice, a review of this lecture and of the foregoing list of
requirements reveals the insight of the inventors of the Babcock & Wilcox
boiler into the fundamental principles of steam generator design and
construction.

Since the Babcock & Wilcox boiler became thoroughly established as a
durable and efficient steam generator, many types of water-tube boilers have
appeared on the market. Most of them, failing to meet enough of the
requirements of a perfect boiler, have fallen by the wayside, while a few
failing to meet all of the requirements, have only a limited field of
usefulness. None have been superior, and in the most cases the most ardent
admirers of other boilers have been satisfied in looking up to the Babcock &
Wilcox boiler as a standard and in claiming that the newer boilers were “just
as good.”

Records of recent performances under the most severe conditions of services
on land and sea, show that the Babcock & Wilcox boiler can be run
continually and regularly at higher overloads, with higher efficiency, and
lower upkeep cost than any other boiler on the market. It is especially
adapted for power-plant work where it is necessary to use a boiler in which
steam can be raised quickly and the boiler placed on the line either from a
cold state or from a banked fire in the shortest possible time, and with which
the capacity, with clean feed water, will be largely limited by the amount of
coal that can be burned in the furnace.

The distribution of the circulation through the separate headers and sections
and the action of the headers in forcing a maximum and continuous
circulation in the lower tubes, permit the operation of the Babcock & Wilcox
boiler without objectionable priming, with a higher degree of concentration
of salts in the water than is possible in any other type of boiler.

Repeated daily performances at overloads have demonstrated beyond a
doubt the correctness of Mr. Babcock’s computation regarding the
circulating tube and header area required for most efficient circulation. They
also have proved that enlargement of the area of headers and circulating
tubes beyond a certain point diminishes the head available for causing

circulation and consequently limits the ability of the boiler to respond to
demands for overloads.

In this lecture Mr. Babcock made the prediction that with the circulating tube
area proportioned in accordance with the principles laid down, the Babcock
& Wilcox boiler could be continuously run at double its nominal rating,
which at that time was based on 12 square feet of heating surface per horse
power. This prediction is being fulfilled daily in all the large and prominent
power plants in this country and abroad, and it has been repeatedly
demonstrated that with clean water and clean tube surfaces it is possible to
safely operate at over 300 per cent of the nominal rating.

In the development of electrical power stations it becomes more and more
apparent that it is economical to run a boiler at high ratings during the times
of peak loads, as by so doing the lay-over losses are diminished and the
economy of the plant as a whole is increased.

[Pg 37]

The number and importance of the large electric lighting and power stations
constructed during the last ten years that are equipped with Babcock &
Wilcox boilers, is a most gratifying demonstration of the merit of the
apparatus, especially in view of their satisfactory operation under conditions
which are perhaps more exacting than those of any other service.

Time, the test of all, results with boilers as with other things, in the survival
of the fittest. When judged on this basis the Babcock & Wilcox boiler stands
pre-eminent in its ability to cover the whole field of steam generation with
the highest commercial efficiency obtainable. Year after year the Babcock &
Wilcox boiler has become more firmly established as the standard of
excellence in the boiler making art.

South Boston Station of the Boston Elevated Ry. Co., Boston, Mass. 9600
Horse Power of Babcock & Wilcox Boilers and Superheaters Installed
in this Station

[Pg 38]

3600 Horse-power Installation of Babcock & Wilcox Boilers at the
Phipps Power House of the Duquesne Light Company, Pittsburgh, Pa.

[Pg 39]

EVOLUTION OF THE BABCOCK & WILCOX
WATER-TUBE BOILER
Quite as much may be learned from the records of failures as from those of
success. Where a device has been once fairly tried and found to be imperfect
or impracticable, the knowledge of that trial is of advantage in further
investigation. Regardless of the lesson taught by failure, however, it is an
almost every-day occurrence that some device or construction which has been
tried and found wanting, if not worthless, is again introduced as a great
improvement upon a device which has shown by its survival to be the fittest.

The success of the Babcock & Wilcox boiler is due to many years of constant
adherence to one line of research, in which an endeavor has been made to
introduce improvements with the view to producing a boiler which would
most effectively meet the demands of the times. During the periods that this
boiler has been built, other companies have placed on the market more than
thirty water-tube or sectional water-tube boilers, most of which, though they
may have attained some distinction and sale, have now entirely disappeared.
The following incomplete list will serve to recall the names of some of the
boilers that have had a vogue at various times, but which are now practically
unknown: Dimpfel, Howard, Griffith & Wundrum, Dinsmore, Miller “Fire
Box”, Miller “American”, Miller “Internal Tube”, Miller “Inclined Tube”,
Phleger, Weigant, the Lady Verner, the Allen, the Kelly, the Anderson, the
Rogers & Black, the Eclipse or Kilgore, the Moore, the Baker & Smith, the
Renshaw, the Shackleton, the “Duplex”, the Pond & Bradford, the
Whittingham, the Bee, the Hazleton or “Common Sense”, the Reynolds, the
Suplee or Luder, the Babbit, the Reed, the Smith, the Standard, etc., etc.

It is with the object of protecting our customers and friends from loss through
purchasing discarded ideas that there is given on the following pages a brief
history of the development of the Babcock & Wilcox boiler as it is built to-
day. The illustrations and brief descriptions indicate clearly the various
designs and constructions that have been used and that have been replaced, as
experience has shown in what way improvement might be made. They serve
as a history of the experimental steps in the development of the present

Babcock & Wilcox boiler, the value and success of which, as a steam
generator, is evidenced by the fact that the largest and most discriminating
users continue to purchase them after years of experience in their operation.

No. 1. The original Babcock &
Wilcox boiler was patented in 1867.
The main idea in its design was
safety, to which all other features
were sacrificed wherever they
conflicted. The boiler consisted of a
nest of horizontal tubes, serving as a
steam and water reservoir, placed
above and connected at each end by
bolted [Pg 40] joints to a second nest of
inclined heating tubes filled with No. 1
water. The tubes were placed one
above the other in vertical rows, each
row and its connecting end forming a single casting. Hand-holes were placed
at each end for cleaning. Internal tubes were placed within the inclined tubes
with a view to aiding circulation.

No. 2. This boiler was the same as No. 1, except that the internal circulating
tubes were omitted as they were found to hinder rather than help the
circulation.

Nos. 1 and 2 were found to be faulty in both material and design, cast metal
proving unfit for heating surfaces placed directly over the fire, as it cracked as
soon as any scale formed.

No. 3. Wrought-iron tubes were substituted for the cast-iron heating tubes, the
ends being brightened, laid in moulds, and the headers cast on.

The steam and water capacity in this design were insufficient to secure
regularity of action, there being no reserve upon which to draw during firing
or when the water was fed intermittently. The attempt to dry the steam by
superheating it in the nest of tubes forming the steam space was found to be
impracticable. The steam delivered was either wet, dry or superheated,
according to the rate at which it was being drawn from the boiler. Sediment

was found to lodge in the lowermost point of the boiler at the rear end and the
exposed portions cracked off at this point when subjected to the furnace heat.

No. 4. A plain cylinder, carrying the
water line at its center and leaving
the upper half for steam space, was
substituted for the nest of tubes
forming the steam and water space in
Nos. 1, 2 and 3. The sections were
made as in No. 3 and a mud drum
added to the rear end of the sections
No. 4 at the point that was lowest and
farthest removed from the fire. The
gases were made to pass off at one
side and did not come into contact with the mud drum. Dry steam was
obtained through the increase of separating surface and steam space and the
added water capacity furnished a storage for heat to tide over irregularities of
firing and feeding. By the addition of the drum, the boiler became a
serviceable and practical design, retaining all of the features of safety. As the
drum was removed from the direct action of the fire, it was not subjected to
excessive strain due to unequal expansion, and its diameter, if large in
comparison with that of the tubes formerly used, was small when compared
with that of cylindrical boilers. Difficulties were encountered in this boiler in
securing reliable joints between the wrought-iron tubes and the cast-iron
headers.

No. 5. In this design, wrought-iron
water legs were substituted for the
cast-iron headers, the tubes being
expanded into the inside sheets and a
large [Pg 41] cover placed opposite the
front end of the tubes for cleaning.
The tubes were staggered one above
the other, an arrangement found to be
more efficient in the absorption of No. 5
heat than where they were placed in
vertical rows. In other respects, the
boiler was similar to No. 4, except that it had lost the important element of

safety through the introduction of the very objectionable feature of flat stayed
surfaces. The large doors for access to the tubes were also a cause of
weakness.

An installation of these boilers was made at the plant of the Calvert Sugar
Refinery in Baltimore, and while they were satisfactory in their operation,
were never duplicated.

No. 6. This was a modification of
No. 5 in which longer tubes were
used and over which the gases were
caused to make three passes with a
view of better economy. In addition,
some of the stayed surfaces were
omitted and handholes substituted
for the large access doors. A number
of boilers of this design were built
No. 6
but their excessive first cost, the lack
of adjustability of the structure
under varying temperatures, and the
inconvenience of transportation, led to No. 7.

No. 7. In this boiler, the headers and water
legs were replaced by T-heads screwed to
the ends of the inclined tubes. The faces of
these Ts were milled and the tubes placed
one above the other with the milled faces
metal to metal. Long bolts passed through
each vertical section of the T-heads and
through connecting boxes on the heads of
the drums holding the whole together. A
large number of boilers of this design were No. 7
built and many were in successful
operation for over twenty years. In most
instances, however, they were altered to later types.

No . 8 No. 9

[Pg 42]

Nos. 8 and 9. These boilers were known as the Griffith & Wundrum type, the
concern which built them being later merged in The Babcock & Wilcox Co.
Experiments were made with this design with four passages of the gases
across the tubes and the downward circulation of the water at the rear of the
boiler was carried to the bottom row of tubes. In No. 9 an attempt was made
to increase the safety and reduce the cost by reducing the amount of steam
and water capacity. A drum at right angles to the line of tubes was used but as
there was no provision made to secure dry steam, the results were not
satisfactory. The next move in the direction of safety was the employment of
several drums of small diameter instead of a single drum.

This is shown in No. 10. A nest of
small horizontal drums, 15 inches in
diameter, was used in place of the
single drum of larger diameter. A set
of circulation tubes was placed at an
intermediate angle between the main
bank of heating tubes and the
horizontal drums forming the steam
No. 10 reservoir. These circulators were to
return to the rear end of the circulating
tubes the water carried up by the
circulation, and in this way were to allow only steam to be delivered to the

small drums above. There was no improvement in the action of this boiler
over that of No. 9.

The four passages of the gas over the tubes tried in Nos. 8, 9 and 10 were not
found to add to the economy of the boiler.

No. 11. A trial was next made of a box coil
system, in which the water was made to
transverse the furnace several times before being
delivered to the drum above. The tendency here,
as in all similar boilers, was to form steam in the
middle of the coil and blow the water from each
end, leaving the tubes practically dry until the
steam found an outlet and the water returned.
This boiler had, in addition to a defective No. 11
circulation, a decidedly geyser-like action and
produced wet steam.

All of the types mentioned, with
the exception of Nos. 5 and 6, had
between their several parts a large
number of bolted joints which
were subjected to the action [Pg 43]
of the fire. When these boilers
were placed in operation it was
demonstrated that as soon as any
scale formed on the heating
surfaces, leaks were caused due to
unequal expansion.

No. 12. With this boiler, an
No. 12 attempt was made to remove the
joints from the fire and to increase
the heating surface in a given
space. Water tubes were expanded into both sides of wrought-iron boxes,
openings being made for the admission of water and the exit of steam. Fire
tubes were placed inside the water tubes to increase the heating surface. This
design was abandoned because of the rapid stopping up of the tubes by scale
and the impossibility of cleaning them.

No. 13. Vertical straight line headers of
cast iron, each containing two rows of
tubes, were bolted to a connection leading
to the steam and water drum above.

N
o.
14
.A
wr
ou
gh
t- No. 13
iro
n
box was substituted for the double
cast-iron headers. In this design, stays
No. 14 were necessary and were found, as
always, to be an element to be avoided
wherever possible. The boiler was an
improvement on No. 6, however. A slanting bridge wall was introduced
underneath the drum to throw a larger portion of its heating surface into the
combustion chamber under the bank of tubes.

This bridge wall was found to be difficult to keep in repair and was of no
particular benefit.

No. 15. Each row of tubes was expanded at each end into a continuous
header, cast of car wheel metal. The headers had a sinuous form so that they
would lie close together and admit of a staggered position of the tubes when
assembled. While other designs of header form were tried later, experience
with Nos. 14 and 15 showed that the style here adopted was the best for all
[Pg 44] purposes and it has not been changed materially since. The drum in this
design was supported by girders resting on the brickwork. Bolted joints were
discarded, with the exception of those connecting the headers to the front and
rear ends of the drums and the bottom of the rear headers to the mud drum.
Even such joints, however, were found objectionable and were superseded in
subsequent construction by short lengths of tubes expanded into bored holes.

No. 15

No. 16

No. 16. In this design, headers were tried which were made in the form of
triangular boxes, in each of which there were three tubes expanded. These
boxes were alternately reversed and connected by short lengths of expanded
tubes, being connected to the drum by tubes bent in a manner to allow them
to enter the shell normally. The joints between headers introduced an element
of weakness and the connections to the drum were insufficient to give
adequate circulation.

No. 17

No. 17. Straight horizontal headers were next tried, alternately shifted right
and left to allow a staggering of tubes. These headers were connected to each
other [Pg 45] and to the drums by expanded nipples. The objections to this
boiler were almost the same as those to No. 16.

No. 18 No. 19

Nos. 18 and 19. These boilers were designed primarily for fire protection
purposes, the requirements demanding a small, compact boiler with ability to
raise steam quickly. These both served the purpose admirably but, as in No. 9,
the only provision made for the securing of dry steam was the use of the
steam dome, shown in the illustration. This dome was found inadequate and
has since been abandoned in nearly all forms of boiler construction. No other
remedy being suggested at the time, these boilers were not considered as
desirable for general use as Nos. 21 and 22. In Europe, however, where small

size units were more in demand, No. 18 was modified somewhat and used
largely with excellent results. These experiments, as they may now be called,
although many boilers of some of the designs were built, clearly
demonstrated that the best construction and efficiency required adherence to
the following elements of design:

1st. Sinuous headers for each vertical row of tubes.

2nd. A separate and independent connection with the drum, both front and
rear, for each vertical row of tubes.

[Pg 46]

3rd. All joints between parts of the boiler proper to be made without bolts or
screw plates.

4th. No surfaces to be used which necessitate the use of stays.

5th. The boiler supported independently of the brickwork so as to allow
freedom for expansion and contraction as it is heated or cooled.

6th. Ample diameter of steam and water drums, these not to be less than 30
inches except for small size units.

7th. Every part accessible for cleaning and repairs.

No. 20A No. 20B

With these points having been determined, No. 20 was designed. This boiler
had all the desirable features just enumerated, together with a number of
improvements as to detail of construction. The general form of No. 15 was
adhered to but the bolted connections between sections and drum and sections
and mud drum were discarded in favor of connections made by short lengths
of boiler tubes expanded into the adjacent parts. This boiler was suspended
from girders, like No. 15, but these in turn were carried on vertical supports,
leaving the pressure parts entirely free from the brickwork, the mutually
deteriorating strains present where one was supported by the other being in
this way overcome. Hundreds of thousands of horse power of this design
were built, giving great satisfaction. The boiler was known as the “C. I. F.”
(cast-iron front) style, an ornamental cast-iron front having been usually
furnished.

The next step, and the one which
connects the boilers as described
above to the boiler as it is built to-
day, was the design illustrated in
No. 21. These boilers were known
as the “W. I. F.” style, the fronts
furnished as part of the equipment
being constructed largely of
wrought iron. The cast-iron
drumheads used in No. 20 were
replaced by wrought-steel flanged
No. 21 and “bumped” heads. The drums
were made longer and the sections
connected to wrought-steel cross
boxes riveted to the bottom of the drums. The boilers were supported by
girders and columns as in No. 20.

[Pg 47]

No. 22. This boiler, which is designated as the “Vertical Header” type, has the
same general features of construction as No. 21, except that the tube sheet
side of the headers is “stepped” to allow the headers to be placed vertically
and at right angles to the drum and still maintain the tubes at the angle used in
Nos. 20 and 21.

No. 22

No. 23, or the cross drum design
of boiler, is a development of the
Babcock & Wilcox marine
boiler, in which the cross drum is
used exclusively. The experience
of the Glasgow Works of The
Babcock & Wilcox, Ltd., with
No. 18 proved that proper
attention to details of
No. 23 construction would make it a
most desirable form of boiler
where headroom was limited. A
large number of this design have been successfully installed and are giving
satisfactory results under widely varying conditions. The cross drum boiler is
also built in a vertical header design.

Boilers Nos. 21, 22 and 23, with a few modifications, are now the standard
forms. These designs are illustrated, as they are constructed to-day, on pages
48, 52, 54, 58 and 60.

The last step in the development of the water-tube boiler, beyond which it
seems almost impossible for science and skill to advance, consists in the
making of all pressure parts of the boiler of wrought steel, including sinuous
headers, cross boxes, nozzles, and the like. This construction was the result of
the demands of certain Continental laws that are coming into general vogue in

this country. The Babcock & Wilcox Co. have at the present time a plant
producing steel forgings that have been pronounced by the London Engineer
to be “a perfect triumph of the forgers’ art”.

The various designs of this all wrought-steel boiler are fully illustrated in the
following pages.
[Pg 48]

Wrought-steel Vertical Header Longitudinal Drum Babcock & Wilcox
Boiler, Equipped with Babcock & Wilcox Superheater and Babcock &
Wilcox Chain Grate Stoker

[Pg 49]

THE BABCOCK & WILCOX BOILER
The following brief description of the Babcock & Wilcox boiler will clearly
indicate the manner in which it fulfills the requirements of the perfect steam
boiler already enumerated.

The Babcock & Wilcox boiler is built in two general classes, the longitudinal
drum type and the cross drum type. Either of these designs may be
constructed with vertical or inclined headers, and the headers in turn may be
of wrought steel or cast iron dependent upon the working pressure for which
the boiler is constructed. The headers may be of different lengths, that is,
may connect different numbers of tubes, and it is by a change in the number
of tubes in height per section and the number of sections in width that the
size of the boiler is varied.

The longitudinal drum boiler is the generally accepted standard of Babcock
& Wilcox construction. The cross drum boiler, though originally designed to
meet certain conditions of headroom, has become popular for numerous
classes of work where low headroom is not a requirement which must be
met.

LONGITUDINAL DRUM CONSTRUCTION
—The heating surface of this type of boiler is
made up of a drum or drums, depending upon
the width of the boiler extending longitudinally
over the other pressure parts. To the drum or
drums there are connected through cross boxes
at either end the sections, which are made up
of headers and tubes. At the lower end of the
sections there is a mud drum extending
entirely across the setting and connected to all
Forged-steel Drumhead sections. The connections between all parts are
with Manhole Plate by short lengths of tubes expanded into bored
in Position seats.

The drums are of three sheets, of such
thickness as to give the required factor of
safety under the maximum pressure for which
the boiler is constructed. The circular seams
are ordinarily single lap riveted though these
may be double lap riveted to meet certain
requirements of pressure or of specifications.
The longitudinal seams are properly
proportioned butt and strap or lap riveted joints
dependent upon the pressure for which the
boilers are built. Where butt strap joints are Forged-steel Drumhead
used the straps are bent to the proper radius in Interior
an hydraulic press. The courses are built
independently to template and are assembled
by an hydraulic forcing press. All riveted holes are punched one-quarter inch
smaller than the size of rivets as driven and are reamed to full size after the
plates are assembled. All rivets are driven by hydraulic pressure and held
until black.

The drumheads are hydraulic forged at a single heat, the manhole opening
and stiffening ring being forged in position. Flat raised seats for water
column and feed connections are formed in the forging.

[Pg 50]

All heads are provided with manholes, the edges of which are turned true.
The manhole plates are of forged steel and turned to fit manhole opening.
These plates are held in position by forged-steel guards and bolts.

The drum nozzles are of forged steel, faced,
and fitted with taper thread stud bolts.

Cross boxes by means of which the
sections are attached to the drums, are of
Forged-steel Drum Nozzle forged steel, made from a single sheet.

Where two or more drums are used in one boiler they are connected by a
cross pipe having a flanged outlet for the steam connection.

The
sectio
ns are
built
of 4-
inch
hot
finishe Forged-steel Cross Box
d
seaml
ess open-hearth steel tubes of No. 10 B. W. G. where the boilers are built for
working pressures up to 210 pounds. Where the working pressure is to be
above this and below 260 pounds, No. 9 B. W. G. tubes are supplied.

The tubes are
expanded into headers
of serpentine or
sinuous form, which
dispose the tubes in a
staggered position
Inside Handhole Fittings when assembled as a
Wrought-steel complete boiler. These
Vertical Header headers are of wrought
steel or of cast iron,
the latter being
ordinarily supplied where the working pressure is not
to exceed 160 pounds. The headers may be either
vertical or inclined as shown in the various
illustrations of assembled boilers.

Opposite each tube end in the headers there is placed
a handhole of sufficient size to permit the cleaning, Wrought-steel
removal or renewal of a tube. These openings in the Vertical Header
wrought steel vertical headers are elliptical in shape,
machine faced, and milled to a true plane 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 [Pg 51] binders and nuts. The joints between plates and headers
are made with a thin gasket.

In the wrought-steel
inclined headers the
handhole openings are
either circular or
elliptical, the former
being ordinarily
supplied. The circular
openings have a raised Inside Handhole Fitting
seat milled to a true Wrought-steel
plane. The openings are Inclined Header
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.
Wrought-steel
Inclined Header Where elliptical handholes 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 header are made with a thin gasket.

The vertical cast-iron headers have elliptical handholes 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.

The mud drum to which the sections are attached at the lower end of the rear
headers, is a forged-steel box 7¼ inches square, and of such length as to be
connected to all headers by means of wrought nipples expanded into

counterbored seats. The mud drum is
furnished with handholes for cleaning,
these being closed from the inside by
forged-steel plates with studs, and secured
on a faced seat in the mud drum by forged-
steel binders and nuts. The joints between
the plates and the drum are made with thin
gaskets. The mud drum is tapped for blow-
off connection.

All connections between drums and
sections and between sections and mud
drum are of hot finished seamless open-
hearth steel tubes of No. 9 B. W. G.

Boilers of the longitudinal drum type are
suspended front and rear from wrought-
steel supporting frames entirely Cast-iron Vertical Header
independent of the brickwork. This allows
for [Pg 52]
[Pg 53] expansion and contraction of the pressure parts without straining
either the boiler or the brickwork, and also allows of brickwork repair or
renewal without in any way disturbing the boiler or its connections.

Babcock & Wilcox Wrought-steel Vertical Header Cross Drum Boiler

CROSS DRUM CONSTRUCTION—The cross drum type of boilers differs
from the longitudinal only in drum construction and method of support. The
drum in this type is placed transversely across the rear of the boiler and is
connected to the sections by means of circulating tubes expanded into bored
seats.

The drums for all pressures are of two sheets of sufficient thickness to give
the required factor of safety. The longitudinal seams are double riveted butt
strapped, the straps being bent to the proper radius in an hydraulic press. The
circulating tubes are expanded into the drums at the seams, the butt straps
serving as tube seats.

The drumheads, drum fittings and features of riveting are the same in the
cross drum as in the longitudinal types. The sections and mud drum are also

the same for the two types.

Cross drum boilers are supported at the rear on the mud drum which rests on
cast-iron foundation plates. They are suspended at the front from a wrought-
iron supporting frame, each section being suspended independently from the
cross members by hook suspension bolts. This method of support is such as
to allow for expansion and contraction without straining either the boiler or
the brickwork and permits of repair or renewal of the latter without in any
way disturbing the boiler or its connections.

The following features of design
and of attachments supplied are
the same for all types.

FRONTS—Ornamental fronts are
fitted to the front supporting
frame. These have large doors for
access to the front headers and
panels above the fire fronts. The
fire fronts where furnished have
independent frames for fire doors
which are bolted on, and ashpit
doors fitted with blast catches. The
lugs on door frames and on doors
are cast solid. The faces of doors
and of frames are planed and the
lugs milled. The doors and frames Cross Drum Boiler Front
are placed in their final relative
position, clamped, and the holes
for hinge pins drilled while thus held. A perfect alignment of door and frame
is thus assured and the method is representative of the care taken in small
details of manufacture.

The front as a whole is so arranged that any stoker may be applied with but
slight modification wherever boilers are set with sufficient furnace height.

In the vertical header boilers large wrought-iron doors, which give access to
the rear headers, are attached to the rear supporting frame. [Pg 54]

Wrought-steel Inclined Header Longitudinal Drum Babcock & Wilcox
Boiler, Equipped with Babcock & Wilcox Superheater

[Pg 55] FITTINGS—Each boiler is provided with the following fittings as part
of the standard equipment:

Blow-off connections and valves attached to the mud drum.

Safety valves placed on nozzles on the steam drums.

A water column connected to the front of the drum.

A steam gauge attached to the boiler front.

Feed water connection
and valves. A flanged
stop and check valve of
heavy pattern is attached
directly to each
drumhead, closing
automatically in case of a
Automatic Drumhead Stop and Check Valve rupture in the feed line.

All valves and fittings
are substantially built and are of designs which by their successful service
for many years have become standard with The Babcock & Wilcox Co.

The fixtures that are supplied with the boilers consist of:

Dead plates and supports, the plates arranged for a fire brick lining.

A full set of grate bars and bearers, the latter fitted with expansion sockets
for side walls.

Flame bridge plates with necessary fastenings, and special fire brick for
lining same.

Bridge wall girder for hanging bridge wall with expansion sockets for side
walls.

A full set of access and cleaning doors through which all portions of the
pressure parts may be reached.

A swing damper and frame with damper operating rig.

There are also supplied with each boiler a wrench for handhole nuts, a water-
driven turbine tube cleaner, a set of fire tools and a metal steam hose and
cleaning pipe equipped with a special nozzle for blowing dust and soot from
the tubes.

Aside from the details of design and construction as covered in the foregoing
description, a study of the illustrations will make clear the features of the
boiler as a whole which have led to its success.

The method of supporting the boiler has been described. This allows it to be
hung at any height that may be necessary to properly handle the fuel to be
burned or to accommodate the stoker to be installed. The height of the nest
of tubes which forms the roof of the furnace is thus the controlling feature in
determining the furnace height, or the distance from the front headers to the
floor line. The sides and front of the furnace are formed by the side and front
boiler walls. The rear wall of the furnace consists of a bridge wall built from
the bottom of the ashpit to the lower row of tubes. The location of this wall
may be adjusted within limits to give the depth of furnace demanded by the
fuel used. Ordinarily the bridge wall is the determining feature in the
locating of the front baffle. Where a great depth of furnace is necessary, in
which case, if the front baffle were placed at the bridge wall the front pass of
the boiler would be relatively too long, a patented construction is used which
maintains the baffle in what may be considered its normal position, and a
connection made between the baffle and the bridge wall by means of a tile
roof. Such furnace construction is known as a “Webster” furnace. [Pg 56]

[Pg 57] A consideration of this furnace will clearly indicate its adaptability, by
reason of its flexibility, for any fuel and any design of stoker. The boiler
lends itself readily to installation with an extension or Dutch oven furnace if
this be demanded by the fuel to be used, and in general it may be stated that
a satisfactory furnace arrangement may be made in connection with a
Babcock & Wilcox boiler for burning any fuel, solid, liquid or gaseous.

Longitudinal Drum Boiler—Front View

The gases of combustion evolved in the furnace above described are led over
the heating surfaces by two baffles. These are formed of cast-iron baffle
plates lined with special fire brick and held in position by tube clamps. The
front baffle leads the gases through the forward portion of the tubes to a
chamber beneath the drum or drums. It is in this chamber that a superheater
is installed where such an apparatus is desired. The gases make a turn over
the front baffle, are led downward through the central portion of the tubes,
called the second pass, by means of a hanging bridge wall of brick and the
second baffle, around which they make a second turn upward, pass through
the rear portion of the tubes and are led to the stack or flue through a damper
box in the rear wall, or around the drums to a damper box placed overhead.

The space beneath the tubes between the
bridge wall and the rear boiler wall forms a
pocket into which much of the soot from the
gases in their downward passage through the
second pass will be deposited and from
which it may be readily cleaned through
doors furnished for the purpose.

The gas passages are ample and are so
proportioned that the resistance offered to
the gases is only such as will assure the
proper abstraction of heat from the gases
without causing undue friction, requiring
excessive draft.

The method in which the feed water is
introduced through the front drumhead of
the boiler is clearly seen by reference to the
illustration. From this point of introduction
the water passes to the rear of the drum, Partial Vertical Section
downward through the rear circulating tubes Showing Method of
to the sections, upward through the tubes of Introducing Feed Water
the sections to the front headers and through
these headers and front circulating tubes
again to the drum where such water as has not been formed into steam
retraces its course. The steam formed in the passage through the tubes is
liberated as the water reaches the front of the drum. The steam so formed is
stored in the steam space above the water line, from which it is drawn
through a so-called “dry pipe.” The dry pipe in the Babcock & Wilcox boiler
is misnamed, as in reality it fulfills none of the functions ordinarily
attributed to such a device. This function is [Pg 58]
[Pg 59] usually to restrict the flow of steam from a boiler with a view to avoid
priming. In the Babcock & Wilcox boiler its function is simply that of a
collecting pipe, and as the aggregate area of the holes in it is greatly in
excess of the area of the steam outlet from the drum, it is plain that there can
be no restriction through this collecting pipe. It extends nearly the length of
the drum, and draws steam evenly from the whole length of the steam space.

Cast-iron Vertical Header Longitudinal Drum Babcock & Wilcox Boiler

The large tube doors through which access is had to the front headers and the
doors giving such access to the rear headers in boilers of the vertical header
type have already been described and are shown clearly by the illustrations
on pages 56 and 74. In boilers of the inclined header type, access to the rear
headers is secured through the chamber formed by the headers and the rear
boiler wall. Large doors in the sides of the setting give full access to all parts
for inspection and for removal of accumulations of soot. Small dusting doors
are supplied for the side walls through which all of the heating surfaces may
be cleaned by means of a steam dusting lance. These side dusting doors are a
patented feature and the shutters are self closing. In wide boilers additional
cleaning doors are supplied at the top of the setting to insure ease in reaching
all portions of the heating surface.

The drums are accessible for inspection
through the manhole openings. The
removal of the handhole plates makes
possible the inspection of each tube for
its full length and gives the assurance
that no defect can exist that cannot be
actually seen. This is particularly
advantageous when inspecting for the
presence of scale.

The materials entering into the
construction of the Babcock & Wilcox
boiler are the best obtainable for the
special purpose for which they are used
and are subjected to rigid inspection and
tests.

The boilers are manufactured by means
Closed Open of the most modern shop equipment and
appliances in the hands of an old and
well-tried organization of skilled
Patented Side Dusting Doors mechanics under the supervision of
experienced engineers. [Pg 60]

Cast-iron Vertical Header Cross Drum Babcock & Wilcox Boiler

[Pg 61]

ADVANTAGES OF THE BABCOCK & WILCOX
BOILER
The advantages of the Babcock & Wilcox boiler may perhaps be most
clearly set forth by a consideration, 1st, of water-tube boilers as a class as
compared with shell and fire-tube boilers; and 2nd, of the Babcock &
Wilcox boiler specifically as compared with other designs of water-tube
boilers.

WATER-TUBE VERSUS FIRE-TUBE BOILERS

Safety—The most important requirement of a steam boiler is that it shall be
safe in so far as danger from explosion is concerned. If the energy in a large
shell boiler under pressure is considered, the thought of the destruction
possible in the case of an explosion is appalling. The late Dr. Robert H.
Thurston, Dean of Sibley College, Cornell University, and past president of
the American Society of Mechanical Engineers, estimated that there is
sufficient energy stored in a plain cylinder boiler under 100 pounds steam
pressure to project it in case of an explosion to a height of over 3½ miles; a
locomotive boiler at 125 pounds pressure from one-half to one-third of a
mile; and a 60 horse-power return tubular boiler under 75 pounds pressure
somewhat over a mile. To quote: “A cubic foot of heated water under a
pressure of from 60 to 70 pounds per square inch has about the same energy
as one pound of gunpowder.” From such a consideration, it may be readily
appreciated how the advent of high pressure steam was one of the strongest
factors in forcing the adoption of water-tube boilers. A consideration of the
thickness of material necessary for cylinders of various diameters under a
steam pressure of 200 pounds and assuming an allowable stress of 12,000
pounds per square inch, will perhaps best illustrate this point. Table 1 gives
such thicknesses for various diameters of cylinders not taking into
consideration the weakening effect of any joints which may be necessary.
The rapidity with which the plate thickness increases with the diameter is
apparent and in practice, due to the fact that riveted joints must be used, the

thicknesses as given in the table, with the exception of the first, must be
increased from 30 to 40 per cent.

In a water-tube boiler the drums seldom exceed 48 inches in diameter and
the thickness of plate required, therefore, is never excessive. The thinner
metal can be rolled to a more uniform quality, the seams admit of better
proportioning, and the joints can be more easily and perfectly fitted than is
the case where thicker plates are necessary. All of these points contribute
toward making the drums of water-tube boilers better able to withstand the
stress which they will be called upon to endure.

The essential constructive difference between water-tube and fire-tube
boilers lies in the fact that the former is composed of parts of relatively small
diameter as against the large diameters necessary in the latter.

The factor of safety of the boiler parts which come in contact with the most
intense heat in water-tube boilers can be made much higher than would be
practicable in a shell boiler. Under the assumptions considered above in
connection with the thickness of plates required, a number 10 gauge tube
(0.134 inch), which is standard in Babcock & Wilcox boilers for pressures
up to 210 pounds under the same allowable stress as was used in computing
Table 1, the safe working pressure for the tubes is 870 pounds per square
inch, indicating the very large margin of safety of such tubes as compared
with that possible with the shell of a boiler.

[Pg 62]

TABLE 1 A further advantage in the
water-tube boiler as a class is
PLATE THICKNESS REQUIRED FOR the elimination of all
VARIOUS CYLINDER DIAMETERS compressive stresses.
Cylinders subjected to
ALLOWABLE STRESS, 12000 external pressures, such as
POUNDS fire tubes or the internally
PER SQUARE INCH, 200 POUNDS fired furnaces of certain types
GAUGE PRESSURE, NO JOINTS of boilers, will collapse under
Diameter Thickness Diameter Thickness a pressure much lower than
Inches Inches Inches Inches that which they could

4 0.033 72 0.600 withstand if it were applied
36 0.300 108 0.900 internally. This is due to the
48 0.400 120 1.000 fact that if there exists any
60 0.500 144 1.200 initial distortion from its true
shape, the external pressure
will tend to increase such distortion and collapse the cylinder, while an
internal pressure tends to restore the cylinder to its original shape.

Stresses due to unequal expansion have been a fruitful source of trouble in
fire-tube boilers.

In boilers of the shell type, the riveted joints of the shell, with their
consequent double thickness of metal exposed to the fire, gives rise to
serious difficulties. Upon these points are concentrated all strains of unequal
expansion, giving rise to frequent leaks and oftentimes to actual ruptures.
Moreover, in the case of such rupture, the whole body of contained water is
liberated instantaneously and a disastrous and usually fatal explosion results.

Further, unequal strains result in shell or fire-tube boilers due to the
difference in temperature of the various parts. This difference in temperature
results from the lack of positive well defined circulation. While such a
circulation does not necessarily accompany all water-tube designs, in
general, the circulation in water-tube boilers is much more defined than in
fire-tube or shell boilers.

A positive and efficient circulation assures that all portions of the pressure
parts will be at approximately the same temperature and in this way strains
resulting from unequal temperatures are obviated.

If a shell or fire-tubular boiler explodes, the apparatus as a whole is
destroyed. In the case of water-tube boilers, the drums are ordinarily so
located that they are protected from intense heat and any rupture is usually in
the case of a tube. Tube failures, resulting from blisters or burning, are not
serious in their nature. Where a tube ruptures because of a flaw in the metal,
the result may be more severe, but there cannot be the disastrous explosion
such as would occur in the case of the explosion of a shell boiler.

To quote Dr. Thurston, relative to the greater safety of the water-tube boiler:
“The stored available energy is usually less than that of any of the other
stationary boilers and not very far from the amount stored, pound for pound,
in the plain tubular boiler. It is evident that their admitted safety from
destructive explosion does not come from this relation, however, but from
the division of the contents into small portions and especially from those
details of construction which make it tolerably certain that any rupture shall
be local. A violent explosion can only come from the general disruption of a
boiler and the liberation at once of large masses of steam and water.”

Economy—The requirement probably next in importance to safety in a steam
boiler is economy in the use of fuel. To fulfill such a requirement, the three
items, of [Pg 63] proper grate for the class of fuel to be burned, a combustion
chamber permitting complete combustion of gases before their escape to the
stack, and the heating surface of such a character and arrangement that the
maximum amount of available heat may be extracted, must be co-ordinated.

Fire-tube boilers from the nature of their design do not permit the variety of
combinations of grate surface, heating surface, and combustion space
possible in practically any water-tube boiler.

In securing the best results in fuel economy, the draft area in a boiler is an
important consideration. In fire-tube boilers this area is limited to the cross
sectional area of the fire tubes, a condition further aggravated in a horizontal
boiler by the tendency of the hot gases to pass through the upper rows of
tubes instead of through all of the tubes alike. In water-tube boilers the draft
area is that of the space outside of the tubes and is hence much greater than
the cross sectional area of the tubes.

Capacity—Due to the generally more efficient circulation found in water-
tube than in fire-tube boilers, rates of evaporation are possible with water-
tube boilers that cannot be approached where fire-tube boilers are employed.

Quick Steaming—Another important result of the better circulation
ordinarily found in water-tube boilers is in their ability to raise steam rapidly
in starting and to meet the sudden demands that may be thrown on them.

In a properly designed water-tube boiler steam may be raised from a cold
boiler to 200 pounds pressure in less than one-half hour.

For the sake of comparison with the figure above, it may be stated that in the
U. S. Government Service the shortest time allowed for getting up steam in
Scotch marine boilers is 6 hours and the time ordinarily allowed is 12 hours.
In large double-ended Scotch boilers, such as are generally used in Trans-
Atlantic service, the fires are usually started 24 hours before the time set for
getting under way. This length of time is necessary for such boilers in order
to eliminate as far as possible excessive strains resulting from the sudden
application of heat to the surfaces.

Accessibility—In the “Requirements of a Perfect Steam Boiler”, as stated
by Mr. Babcock, he demonstrates the necessity for complete accessibility to
all portions of the boiler for cleaning, inspection and repair.

Cleaning—When the great difference is realized in performance, both as to
economy and capacity of a clean boiler and one in which the heating
surfaces have been allowed to become fouled, it may be appreciated that the
ability to keep heating surfaces clean internally and externally is a factor of
the highest importance.

Such results can be accomplished only by the use of a design in boiler
construction which gives complete accessibility to all portions. In fire-tube
boilers the tubes are frequently nested together with a space between them
often less than 1¼ inches and, as a consequence, nearly the entire tube
surface is inaccessible. When scale forms upon such tubes it is impossible to
remove it completely from the inside of the boiler and if it is removed by a
turbine hammer, there is no way of knowing how thorough a job has been
done. With the formation of such scale there is danger through overheating
and frequent tube renewals are necessary.

In Scotch marine boilers, even with the engines operating condensing,
complete tube renewals at intervals of six or seven years are required, while
large replacements are often necessary in less than one year. In return tubular
boilers operated with bad feed water, complete tube renewals annually are
not uncommon. In this type of boiler [Pg 64]
[Pg 65] much sediment falls on the bottom sheets where the intense heat to

which they are subjected bakes it to such an excessive hardness that the only
method of removing it is to chisel it out. This can be done only by omitting
tubes enough to leave a space into which a man can crawl and the
discomforts under which he must work are apparent. Unless such a deposit is
removed, a burned and buckled plate will invariably result, and if neglected
too long an explosion will follow.

Portion of 29,000 Horse-power Installation of Babcock & Wilcox Boilers
in the L Street Station of the Edison Electric Illuminating Co. of Boston,
Mass. This Company Operates in its Various Stations a Total of 39,000
Horse Power of Babcock & Wilcox Boilers

In vertical fire-tube boilers using a water leg construction, a deposit of mud
in such legs is an active agent in causing corrosion and the difficulty of
removing such deposit through handholes is well known. A complete
removal is practically impossible and as a last resort to obviate corrosion in
certain designs, the bottom of the water legs in some cases have been made
of copper. A thick layer of mud and scale is also liable to accumulate on the
crown sheet of such boilers and may cause the sheet to crack and lead to an
explosion.

The soot and fine coal swept along with the gases by the draft will settle in
fire tubes and unless removed promptly, must be cut out with a special form
of scraper. It is not unusual where soft coal is used to find tubes half filled
with soot, which renders useless a large portion of the heating surface and so
restricts the draft as to make it difficult to burn sufficient coal to develop the
required power from such heating surface as is not covered by soot.

Water-tube boilers in general are from the nature of their design more readily
accessible for cleaning than are fire-tube boilers.

Inspection—The objections given above in the consideration of the inability
to properly clean fire-tube boilers hold as well for the inspection of such
boilers.

Repairs—The lack of accessibility in fire-tube boilers further leads to
difficulties where repairs are required.

In fire-tube boilers tube renewals are a serious undertaking. The
accumulation of hard deposit on the exterior of the surfaces so enlarges the
tubes that it is oftentimes difficult, if not impossible, to draw them through
the tube sheets and it is usually necessary to cut out such tubes as will allow
access to the one which has failed and remove them through the manhole.

When a tube sheet blisters, the defective part must be cut out by hand-tapped
holes drilled by ratchets and as it is frequently impossible to get space in
which to drive rivets, a “soft patch” is necessary. This is but a makeshift at
best and usually results in either a reduction of the safe working pressure or
in the necessity for a new plate. If the latter course is followed, the old plate
must be cut out, a new one scribed to place to locate rivet holes and in order
to obtain room for driving rivets, the boiler will have to be re-tubed.

The setting must, of course, be at least partially torn out and replaced.

In case of repairs, of such nature in fire-tube boilers, the working pressure of
such repaired boilers will frequently be lowered by the insurance companies
when the boiler is again placed in service.

In the case of a rupture in a water-tube boiler, the loss will ordinarily be
limited to one or two tubes which can be readily replaced. The fire-tube

boiler will be so completely demolished that the question of repairs will be
shifted from the boiler to the surrounding property, the damage to which will
usually exceed many times the cost of a boiler of a type which would have
eliminated the possibility of a disastrous explosion. In considering the proper
repair cost of the two types of boilers, the fact [Pg 66] should not be
overlooked that it is poor economy to invest large sums in equipment that,
through a possible accident to the boiler may be wholly destroyed or so
damaged that the cost of repairs, together with the loss of time while such
repairs are being made, would purchase boilers of absolute safety and leave
a large margin beside. The possibility of loss of human life should also be
considered, though this may seem a far cry from the question of repair costs.

TABLE 2 Space Occupied—
The space required
COMPARATIVE APPROXIMATE FLOOR for the boilers in a
SPACE OCCUPIED BY BABCOCK & WILCOX plant often exceeds
AND H. R. T. BOILERS the requirements for
Size of unit Babcock & Wilcox H. R. T. the remainder of the
Horse Power Feet and Inches Feet and Inches plant equipment.
100 7 3 × 19 9 10 0 × 20 0 Any saving of space
150 7 10 × 19 9 10 0 × 22 6 in a boiler room will
be a large factor in
200 9 0 × 19 9 11 6 × 23 10
reducing the cost of
250 9 0 × 19 9 11 6 × 23 10 real estate and of the
300 10 2 × 19 9 12 0 × 25 0 building. Even when
the boiler plant is
comparatively small, the saving in space frequently will amount to a
considerable percentage of the cost of the boilers. Table 2 shows the
difference in floor space occupied by fire-tube boilers and Babcock &
Wilcox boilers of the same capacity, the latter being taken as representing
the water-tube class. This saving in space will increase with the size of the
plant for the reason that large size boiler units while common in water-tube
practice are impracticable in fire-tube practice.

BABCOCK & WILCOX BOILERS AS COMPARED WITH
OTHER WATER-TUBE DESIGNS

It must be borne in mind that the simple fact that a boiler is of the water-tube
design does not as a necessity indicate that it is a good or safe boiler.

Safety—Many of the water-tube boilers on the market are as lacking as are
fire-tube boilers in the positive circulation which, as has been demonstrated
by Mr. Babcock’s lecture, is so necessary in the requirements of the perfect
steam boiler. In boilers using water-leg construction, there is danger of
defective circulation, leaks are common, and unsuspected corrosion may be
going on in portions of the boiler that cannot be inspected. Stresses due to
unequal expansion of the metal cannot be well avoided but they may be
minimized by maintaining at the same temperature all pressure parts of the
boiler. The result is to be secured only by means of a well defined
circulation.

The main feature to which the Babcock & Wilcox boiler owes its safety is
the construction made possible by the use of headers, by which the water in
each vertical row of tubes is separated from that in the adjacent rows. This
construction results in the very efficient circulation produced through the
breaking up of the steam and water in the front headers, the effect of these
headers in producing such a positive circulation having been clearly
demonstrated in Mr. Babcock’s lecture. The use of a number of sections,
thus composed of headers and tubes, has a distinct advantage over the use of
a common chamber at the outlet ends of the tubes. In the former case the
circulation of water in one vertical row of tubes cannot interfere with that in
the other rows, [Pg 67] while in the latter construction there will be downward
as well as upward currents and such downward currents tend to neutralize
any good effect there might be through the diminution of the density of the
water column by the steam.

Further, the circulation results directly from the design of the boiler and
requires no assistance from “retarders”, check valves and the like, within the
boiler. All such mechanical devices in the interior of a boiler serve only to
complicate the design and should not be used.

This positive and efficient circulation assures that all portions of the pressure
parts of the Babcock & Wilcox boiler will be at approximately the same
temperature and in this way strains resulting from unequal temperatures are
obviated.

Where the water throughout the boiler is at the temperature of the steam
contained, a condition to be secured only by proper circulation, danger from
internal pitting is minimized, or at least limited only to effects of the water
fed the boiler. Where the water in any portion of the boiler is lower than the
temperature of the steam corresponding to the pressure carried, whether the
fact that such lower temperatures exist as a result of lack of circulation, or
because of intentional design, internal pitting or corrosion will almost
invariably result.

Dr. Thurston has already been quoted to the effect that the admitted safety of
a water-tube boiler is the result of the division of its contents into small
portions. In boilers using a water-leg construction, while the danger from
explosion will be largely limited to the tubes, there is the danger, however,
that such legs may explode due to the deterioration of their stays, and such
an explosion might be almost as disastrous as that of a shell boiler. The
headers in a Babcock & Wilcox boiler are practically free from any danger
of explosion. Were such an explosion to occur, it would still be localized to a
much larger extent than in the case of a water-leg boiler and the header
construction thus almost absolutely localizes any danger from such a cause.

Staybolts are admittedly an undesirable element of construction in any
boiler. They are wholly objectionable and the only reason for the presence of
staybolts in a boiler is to enable a cheaper form of construction to be used
than if they were eliminated.

In boilers utilizing in their design flat-stayed surfaces, or staybolt
construction under pressure, corrosion and wear and tear in service tends to
weaken some single part subject to continual strain, the result being an
increased strain on other parts greatly in excess of that for which an
allowance can be made by any reasonable factor of safety. Where the
construction is such that the weakening of a single part will produce a
marked decrease in the safety and reliability of the whole, it follows of
necessity, that there will be a corresponding decrease in the working pressure
which may be safely carried.

In water-leg boilers, the use of such flat-stayed surfaces under pressure
presents difficulties that are practically unsurmountable. Such surfaces
exposed to the heat of the fire are subject to unequal expansion, distortion,

leakage and corrosion, or in general, to many of the objections that have
already been advanced against the fire-tube boilers in the consideration of
water-tube boilers as a class in comparison with fire-tube boilers.

Aside from the difficulties that may arise in actual service due to the failure
of staybolts, or in general, due to the use of flat-stayed surfaces,
constructional features are encountered in the actual manufacture of such
boilers that make it difficult if not [Pg 68]
[Pg 69] impossible to produce a first-class mechanical job. It is practically
impossible in the building of such a boiler to so design and place the
staybolts that all will be under equal strain. Such unequal strains, resulting
from constructional difficulties, will be greatly multiplied when such a boiler
is placed in service. Much of the riveting in boilers of this design must of
necessity be hand work, which is never the equal of machine riveting. The
use of water-leg construction ordinarily requires the flanging of large plates,
which is difficult, and because of the number of heats necessary and the
continual working of the material, may lead to the weakening of such plates.

McAlpin Hotel, New York City, Operating 2360 Horse Power of
Babcock & Wilcox Boilers

In vertical or semi-vertical water-tube boilers utilizing flat-stayed surfaces
under pressure, these surfaces are ordinarily so located as to offer a
convenient lodging place for flue dust, which fuses into a hard mass, is
difficult of removal and under which corrosion may be going on with no
possibility of detection.

Where stayed surfaces or water legs are features in the design of a water-
tube boiler, the factor of safety of such parts must be most carefully

considered. In such parts too, is the determination of the factor most
difficult, and because of the “rule-of-thumb” determination frequently
necessary, the factor of safety becomes in reality a factor of ignorance. As
opposed to such indeterminate factors of safety, in the Babcock & Wilcox
boiler, when the factor of safety for the drum or drums has been determined,
and such a factor may be determined accurately, the factors for all other
portions of the pressure parts are greatly in excess of that of the drum. All
Babcock & Wilcox boilers are built with a factor of safety of at least five,
and inasmuch as the factor of the safety of the tubes and headers is greatly in
excess of this figure, it applies specifically to the drum or drums. This factor
represents a greater degree of safety than a considerably higher factor
applied to a boiler in which the shell or any riveted portion is acted upon
directly by the fire, or the same factor applied to a boiler utilizing flat-stayed
surface construction, where the accurate determination of the limiting factor
of safety is difficult, if not impossible.

That the factor of safety of stayed surfaces is questionable may perhaps be
best realized from a consideration of the severe requirements as to such
factor called for by the rules and regulations of the Board of Supervising
Inspectors, U. S. Government.

In view of the above, the absence of any stayed surfaces in the Babcock &
Wilcox boiler is obviously a distinguishing advantage where safety is a
factor. It is of interest to note, in the article on the evolution of the Babcock
& Wilcox boiler, that staybolt construction was used in several designs,
found unsatisfactory and unsafe, and discarded.

Another feature in the design of the Babcock & Wilcox boiler tending
toward added safety is its manner of suspension. This has been indicated in
the previous chapter and is of such nature that all of the pressure parts are
free to expand or contract under variations of temperature without in any
way interfering with any part of the boiler setting. The sectional nature of the
boiler allows a flexibility under varying temperature changes that practically
obviates internal strain.

In boilers utilizing water-leg construction, on the other hand, the
construction is rigid, giving rise to serious internal strains and the method of
support ordinarily made necessary by the boiler design is not only

unmechanical but frequently dangerous, due to the fact that proper provision
is not made for expansion and contraction under temperature variations.

[Pg 70]

Boilers utilizing water-leg construction are not ordinarily provided with mud
drums. This is a serious defect in that it allows impurities and sediment to
collect in a portion of the boiler not easily inspected, and corrosion may
result.

Economy—That the water-tube boiler as a class lends itself more readily
than does the fire-tube boiler to a variation in the relation of grate surface,
heating surface and combustion space has been already pointed out. In
economy again, the construction made possible by the use of headers in
Babcock & Wilcox boilers appears as a distinct advantage. Because of this
construction, there is a flexibility possible, in an unlimited variety of heights
and widths that will satisfactorily meet the special requirements of the fuel to
be burned in individual cases.

An extended experience in the design of furnaces best suited for a wide
variety of fuels has made The Babcock & Wilcox Co. leaders in the field of
economy. Furnaces have been built and are in successful operation for
burning anthracite and bituminous coals, lignite, crude oil, gas-house tar,
wood, sawdust and shavings, bagasse, tan bark, natural gas, blast furnace
gas, by-product coke oven gas and for the utilization of waste heat from
commercial processes. The great number of Babcock & Wilcox boilers now
in satisfactory operation under such a wide range of fuel conditions
constitutes an unimpeachable testimonial to the ability to meet all of the
many conditions of service.

The limitations in the draft area of fire-tube boilers as affecting economy
have been pointed out. That a greater draft area is possible in water-tube
boilers does not of necessity indicate that proper advantage of this fact is
taken in all boilers of the water-tube class. In the Babcock & Wilcox boiler,
the large draft area taken in connection with the effective baffling allows the
gases to be brought into intimate contact with all portions of the heating
surfaces and renders such surfaces highly efficient.

In certain designs of water-tube boilers the baffling is such as to render
ineffective certain portions of the heating surface, due to the tendency of
soot and dirt to collect on or behind baffles, in this way causing the
interposition of a layer of non-conducting material between the hot gases
and the heating surfaces.

In Babcock & Wilcox boilers the standard baffle arrangement is such as to
allow the installation of a superheater without in any way altering the path of
the gases from furnace to stack, or requiring a change in the boiler design. In
certain water-tube boilers the baffle arrangement is such that if a superheater
is to be installed a complete change in the ordinary baffle design is
necessary. Frequently to insure sufficiently hot gas striking the heating
surfaces, a portion is by-passed directly from the furnace to the superheater
chamber without passing over any of the boiler heating surfaces. Any such
arrangement will lead to a decrease in economy and the use of boilers
requiring it should be avoided.

Capacity—Babcock & Wilcox boilers are run successfully in every-day
practice at higher ratings than any other boilers in practical service. The
capacities thus obtainable are due directly to the efficient circulation already
pointed out. Inasmuch as the construction utilizing headers has a direct
bearing in producing such circulation, it is also connected with the high
capacities obtainable with this apparatus.

Where intelligently handled and kept properly cleaned, Babcock & Wilcox
boilers are operated in many plants at from 200 to 225 per cent of their rated
evaporative capacity and it is not unusual for them to be operated at 300 per
cent of such rated capacity during periods of peak load.

[Pg 71]

Dry Steam—In the list of the requirements of the perfect steam boiler, the
necessity that dry steam be generated has been pointed out. The Babcock &
Wilcox boiler will deliver dry steam under higher capacities and poorer
conditions of feed water than any other boiler now manufactured. Certain
boilers will, when operated at ordinary ratings, handle poor feed water and
deliver steam in which the moisture content is not objectionable. When these
same boilers are driven at high overloads, there will be a direct tendency to

prime and the percentage of moisture in the steam delivered will be high.
This tendency is the result of the lack of proper circulation and once more
there is seen the advantage of the headers of the Babcock & Wilcox boiler,
resulting as it does in the securing of a positive circulation.

In the design of the Babcock & Wilcox boiler sufficient space is provided
between the steam outlet and the disengaging point to insure the steam
passing from the boiler in a dry state without entraining or again picking up
any particles of water in its passage even at high rates of evaporation. Ample
time is given for a complete separation of steam from the water at the
disengaging surface before the steam is carried from the boiler. These two
features, which are additional causes for the ability of the Babcock & Wilcox
boiler to deliver dry steam, result from the proper proportioning of the steam
and water space of the boiler. From the history of the development of the
boiler, it is evident that the cubical capacity per horse power of the steam
and water space has been adopted after numerous experiments.

That the “dry pipe” serves in no way the generally understood function of
such device has been pointed out. As stated, the function of the “dry pipe” in
a Babcock & Wilcox boiler is simply that of a collecting pipe and this
statement holds true regardless of the rate of operation of the boiler.

In certain boilers, “superheating surface” is provided to “dry the steam,” or
to remove the moisture due to priming or foaming. Such surface is
invariably a source of trouble unless the steam is initially dry and a boiler
which will deliver dry steam is obviously to be preferred to one in which
surface must be supplied especially for such purpose. Where superheaters
are installed with Babcock & Wilcox boilers, they are in every sense of the
word superheaters and not driers, the steam being delivered to them in a dry
state.

The question has been raised in connection with the cross drum design of the
Babcock & Wilcox boiler as to its ability to deliver dry steam. Experience
has shown the absolute lack of basis for any such objection. The Babcock &
Wilcox Company at its Bayonne Works some time ago made a series of
experiments to see in what manner the steam generated was separated from
the water either in the drum or in its passage to the drum. Glass peepholes
were installed in each end of a drum in a boiler of the marine design, at the

point midway between that at which the horizontal circulating tubes entered
the drum and the drum baffle plate. By holding a light at one of these
peepholes the action in the drum was clearly seen through the other. It was
found that with the boiler operated under three-quarter inch ashpit pressure,
which, with the fuel used would be equivalent to approximately 185 per cent
of rating for stationary boiler practice, that each tube was delivering with
great velocity a stream of solid water, which filled the tube for half its cross
sectional area. There was no spray or mist accompanying such delivery,
clearly indicating that the steam had entirely separated from the water in its
passage through the horizontal circulating tubes, which in the boiler in
question were but 50 inches long. [Pg 72]

Northwest Station of the Commonwealth Edison Co., Chicago, Ill. This
Installation Consists of 11,360 Horse Power of Babcock & Wilcox
Boilers and Superheaters, Equipped with Babcock & Wilcox Chain
Grate Stokers

[Pg 73] These experiments proved conclusively that the size of the steam
drums in the cross drum design has no appreciable effect in determining the
amount of liberating surface, and that sufficient liberating surface is

provided in the circulating tubes alone. If further proof of the ability of this
design of boiler to deliver dry steam is required, such proof is perhaps best
seen in the continued use of the Babcock & Wilcox marine boiler, in which
the cross drum is used exclusively, and with which rates of evaporation are
obtained far in excess of those secured in ordinary practice.

Quick Steaming—The advantages of water-tube boilers as a class over fire-
tube boilers in ability to raise steam quickly have been indicated.

Due to the constant and thorough circulation resulting from the sectional
nature of the Babcock & Wilcox boiler, steam may be raised more rapidly
than in practically any other water-tube design.

In starting up a cold Babcock & Wilcox boiler with either coal or oil fuel,
where a proper furnace arrangement is supplied, steam may be raised to a
pressure of 200 pounds in less than half an hour. With a Babcock & Wilcox
boiler in a test where forced draft was available, steam was raised from an
initial temperature of the boiler and its contained water of 72 degrees to a
pressure of 200 pounds, in 12½ minutes after lighting the fire. The boiler
also responds quickly in starting from banked fires, especially where forced
draft is available.

In Babcock & Wilcox boilers the water is divided into many small streams
which circulate without undue frictional resistance in thin envelopes passing
through the hottest part of the furnace, the steam being carried rapidly to the
disengaging surface. There is no part of the boiler exposed to the heat of the
fire that is not in contact with water internally, and as a result there is no
danger of overheating on starting up quickly nor can leaks occur from
unequal expansion such as might be the case where an attempt is made to
raise steam rapidly in boilers using water leg construction.

Storage Capacity for Steam and Water—Where sufficient steam and water
capacity are not provided in a boiler, its action will be irregular, the steam
pressure varying over wide limits and the water level being subject to
frequent and rapid fluctuation.

Owing to the small relative weight of steam, water capacity is of greater
importance in this respect than steam space. With a gauge pressure of 180

pounds per square inch, 8 cubic feet of steam, which is equivalent to one-
half cubic foot of water space, are required to supply one boiler horse power
for one minute and if no heat be supplied to the boiler during such an
interval, the pressure will drop to 150 pounds per square inch. The volume
of steam space, therefore, may be over rated, but if this be too small, the
steam passing off will carry water with it in the form of spray. Too great a
water space results in slow steaming and waste of fuel in starting up; while
too much steam space adds to the radiating surface and increases the losses
from that cause.

That the steam and water space of the Babcock & Wilcox boiler are the
result of numerous experiments has previously been pointed out.

Accessibility—Cleaning. That water-tube boilers are more accessible as a
class than are fire-tube boilers has been indicated. All water-tube boilers,
however, are not equally accessible. In certain designs, due to the
arrangement of baffling used it is practically impossible to remove all
deposits of soot and dirt. Frequently, in order to cheapen the product,
sufficient cleaning and access doors are not supplied as part [Pg 74]
[Pg 75] of the boiler equipment. The tendency of soot to collect on the crown
sheets of certain vertical water-tube boilers has been noted. Such deposits
are difficult to remove and if corrosion goes on beneath such a covering the
sheet may crack and an explosion result.

Rear View—Longitudinal Drum Vertical Header Boiler, Showing Access
Doors to Rear Headers

It is almost impossible to thoroughly clean water legs internally, and in such
places also is there a tendency to unsuspected corrosion under deposits that
cannot be removed.

In Babcock & Wilcox boilers every portion of the interior of the heating
surfaces can be reached and kept clean, while any soot deposited on the
exterior surfaces can be blown off while the boiler is under pressure.

Inspection—The accessibility which makes possible the thorough cleaning
of all portions of the Babcock & Wilcox boiler also provides a means for a

thorough inspection.

Drums are accessible for internal inspection by the removal of the manhole
plates. Front headers may be inspected through large doors furnished for the
purpose. Rear headers in the inclined header designs may be inspected from
the chamber formed by such headers and the rear wall of the boiler. In the
vertical header designs rear tube doors are furnished, as has been stated. In
certain designs of water-tube boilers in order to assure accessibility for
inspection of the rear ends of the tubes, the rear portion of the boiler is
exposed to the atmosphere with resulting excessive radiation losses. In other
designs the means of access to the rear ends of the tubes are of a makeshift
and unworkmanlike character.

By the removal of handhole plates, all tubes in a Babcock & Wilcox boiler
may be inspected for their full length either for the presence of scale or for
suspected corrosion.

Repairs—In Babcock & Wilcox boilers the possession of great strength, the
elimination of stresses due to uneven temperatures and of the resulting
danger of leaks and corrosion, the protection of the drums from the intense
heat of the fire, and the decreased liability of the scale forming matter to
lodge on the hottest tube surfaces, all tend to minimize the necessity for
repairs. The tubes of the Babcock & Wilcox boiler are practically the only
part which may need renewal and these only at infrequent intervals When
necessary, such renewals may be made cheaply and quickly. A small stock of
tubes, 4 inches in diameter, of sufficient length for the boiler used, is all that
need be carried to make renewals.

Repairs in water-leg boilers are difficult at best and frequently unsatisfactory
when completed. When staybolt replacements are necessary, in order to get
at the inner sheet of the water leg, several tubes must in some cases be cut
out. Not infrequently a replacement of an entire water leg is necessary and
this is difficult and requires a lengthy shutdown. With the Babcock &
Wilcox boiler, on the other hand, even if it is necessary to replace a section,
this may be done in a few hours after the boiler is cool.

In the case of certain staybolt failures the working pressure of a repaired
boiler utilizing such construction will frequently be lowered by the insurance

companies when the boiler is again placed in service. The sectional nature of
the Babcock & Wilcox boiler enables it to maintain its original working
pressure over long periods of time, almost regardless of the nature of any
repair that may be required.

Durability—Babcock & Wilcox boilers are being operated in every-day
service with entirely satisfactory results and under the same steam pressure
as that for which [Pg 76]
[Pg 77] they were originally sold that have been operated from thirty to thirty-
five years. It is interesting to note in considering the life of a boiler that the
length of life of a Babcock & Wilcox boiler must be taken as the criterion of
what length of life is possible. This is due to the fact that there are Babcock
& Wilcox boilers in operation to-day that have been in service from a time
that antedates by a considerable margin that at which the manufacturer of
any other water-tube boiler now on the market was started.

1456 Horse-power Installation of Babcock & Wilcox Boilers at the
Raritan Woolen Mills, Raritan, N. J. The First of These Boilers were
Installed in 1878 and 1881 and are still Operated at 80 Pounds Pressure

Probably the very best evidence of the value of the Babcock & Wilcox boiler
as a steam generator and of the reliability of the apparatus, is seen in the
sales of the company. Since the company was formed, there have been sold
throughout the world over 9,900,000 horse power.

A feature that cannot be overlooked in the consideration of the advantages of
the Babcock & Wilcox boiler is the fact that as a part of the organization
back of the boiler, there is a body of engineers of recognized ability, ready at
all times to assist its customers in every possible way.
[Pg 78]

2400 Horse-power Installation of Babcock & Wilcox Boilers in the
Union Station Power House of the Pennsylvania Railroad Co.,
Pittsburgh, Pa. This Company has a Total of 28,500 Horse Power of
Babcock & Wilcox Boilers Installed

[Pg 79]

HEAT AND ITS MEASUREMENT
The usual conception of heat is that it is a form of energy produced by the vibratory motion of
the minute particles or molecules of a body. All bodies are assumed to be composed of these
molecules, which are held together by mutual cohesion and yet are in a state of continual
vibration. The hotter a body or the more heat added to it, the more vigorous will be the
vibrations of the molecules.

As is well known, the effect of heat on a body may be to change its temperature, its volume, or
its state, that is, from solid to liquid or from liquid to gaseous. Where water is melted from ice
and evaporated into steam, the various changes are admirably described in the lecture by Mr.
Babcock on “The Theory of Steam Making”, given in the next chapter.

The change in temperature of a body is
ordinarily measured by thermometers, though
for very high temperatures so-called
pyrometers are used. The latter are dealt with
under the heading “High Temperature
Measurements” at the end of this chapter.

By reason of the uniform expansion of
mercury and its great sensitiveness to heat, it
is the fluid most commonly used in the
construction of thermometers. In all
thermometers the freezing point and the
boiling point of water, under mean or average
atmospheric pressure at sea level, are assumed
as two fixed points, but the division of the
scale between these two points varies in
different countries. The freezing point is
determined by the use of melting ice and for
this reason is often called the melting point.
There are in use three thermometer scales
known as the Fahrenheit, the Centigrade or
Celsius, and the Réaumur. As shown in Fig.
11, in the Fahrenheit scale, the space between
the two fixed points is divided into 180 parts;
Fig. 11
the boiling point is marked 212, and the
freezing point is marked 32, and zero is a
temperature which, at the time this
thermometer was invented, was incorrectly imagined to be the lowest temperature attainable. In
the centigrade and the Réaumur scales, the distance between the two fixed points is divided into
100 and 80 parts, respectively. In each of these two scales the freezing point is marked zero, and

the boiling point is marked 100 in the centigrade and 80 in the Réaumur. Each of the 180, 100
or 80 divisions in the respective thermometers is called a degree.

Table 3 and appended formulae are useful for converting from one scale to another.

In the United States the bulbs of high-grade thermometers are usually made of either Jena 58 III
borosilicate thermometer glass or Jena 16 III glass, the stems being made of ordinary glass. The
Jena 16 III glass is not suitable for use at temperatures much above 850 degrees Fahrenheit and
the harder Jena 59 III should be used in thermometers for temperatures higher than this.

Below the boiling point, the hydrogen-gas thermometer is the almost universal standard with
which mercurial thermometers may be compared, while above this point [Pg 80] the nitrogen-gas
thermometer is used. In both of these standards the change in temperature is measured by the
change in pressure of a constant volume of the gas.

In graduating a mercurial thermometer for the Fahrenheit scale, ordinarily a degree is
represented as 1 ⁄ 180 part of the volume of the stem between the readings at the melting point of
ice and the boiling point of water. For temperatures above the latter, the scale is extended in
degrees of the same volume. For very accurate work, however, the thermometer may be
graduated to read true-gas-scale temperatures by comparing it with the gas thermometer and
marking the temperatures at 25 or 50 degree intervals. Each degree is then 1 ⁄ 25 or 1 ⁄ 50 of the
volume of the stem in each interval.

Every thermometer, especially if intended for use above the boiling point, should be suitably
annealed before it is used. If this is not done, the true melting point and also the “fundamental
interval”, that is, the interval between the melting and the boiling points, may change
considerably. After continued use at the higher temperatures also, the melting point will change,
so that the thermometer must be calibrated occasionally to insure accurate readings.

TABLE 3

COMPARISON OF THERMOMETER SCALES
Fahrenheit Centigrade Réaumur Fahrenheit Centigrade Réaumur
Absolute Zero -459.64 -273.13 -218.50 50 10.00 8.00
0.00 -17.78 -14.22 75 23.89 19.11
10.00 -12.22 -9.78 100 37.78 30.22
20.00 -6.67 -5.33 200 93.33 74.67
Boiling
30.00 -1.11 -0.89 212 100.00 80.00
Point
Freezing Point 32.00 0.00 0.00 250 121.11 96.89
Maximum 300 148.89 119.11
Density
of Water 39.10 3.94 3.15 350 176.67 141.33
F = 9 ⁄ 5 C+32° = 9 ⁄ 4 R+32° C = 5 ⁄ 9 (F-32°) = 5 ⁄ 4 R R = 4 ⁄ 9 (F-32°) = 4 ⁄ 5 C

As a general rule thermometers are graduated to read correctly for total immersion, that is, with
bulb and stem of the thermometer at the same temperature, and they should be used in this way
when compared with a standard thermometer. If the stem emerges into space either hotter or
colder than that in which the bulb is placed, a “stem correction” must be applied to the observed
temperature in addition to any correction that may be found in the comparison with the
standard. For instance, for a particular thermometer, comparison with the standard with both
fully immersed made necessary the following corrections:

Temperature Correction Temperature Correction
40°F 0.0 300°F +2.5
100°F 0.0 400°F -0.5
200°F 0.0 500°F -2.5

When the sign of the correction is positive (+) it must be added to the observed reading, and
when the sign is a negative (-) the correction must be subtracted. The formula for the stem
correction is as follows:

Stem correction = 0.000085 × n (T- t )

[Pg 81] in which T is the observed temperature, t is the mean temperature of the emergent
column, n is the number of degrees of mercury column emergent, and 0.000085 is the
difference between the coefficient of expansion of the mercury and that in the glass in the stem.

Suppose the observed temperature is 400 degrees and the thermometer is immersed to the 200
degrees mark, so that 200 degrees of the mercury column project into the air. The mean
temperature of the emergent column may be found by tying another thermometer on the stem
with the bulb at the middle of the emergent mercury column as in Fig. 12. Suppose this mean
temperature is 85 degrees, then

Stem correction = 0.000085 × 200 × (400 - 85) = 5.3 degrees.

As the stem is at a lower temperature than the bulb, the thermometer will evidently read too
low, so that this correction must be added to the observed reading to find the reading
corresponding to total immersion. The corrected reading will therefore be 405.3 degrees. If this
thermometer is to be corrected in accordance with the calibrated corrections given above, we
note that a further correction of 0.5 must be applied to the observed reading at this temperature,
so that the correct temperature is 405.3 - 0.5 = 404.8 degrees or 405 degrees.

Fig. 12 shows how a stem correction can be obtained for the case just described.

Fig. 13 affords an opportunity for comparing the scale of a thermometer correct for total
immersion with one which will read correctly when submerged to the 300 degrees mark, the
stem being exposed at a mean temperature of 110 degrees Fahrenheit, a temperature often
prevailing when thermometers are used for measuring temperatures in steam mains.

Absolute Zero —Experiments show that at 32 degrees Fahrenheit a perfect gas expands 1 ⁄
491.64 part of its volume if its pressure remains constant and its temperature is increased one

degree. Thus if gas at 32 degrees Fahrenheit
occupies 100 cubic feet and its temperature
is increased one degree, its volume will be
increased to 100 + 100 ⁄ 491.64 = 100.203
cubic feet. For a rise of two degrees the
volume would be 100 + (100 × 2) / 491.64 =
100.406 cubic feet. If this rate of expansion
per one degree held good at all temperatures,
and experiment shows that it does above the
freezing point, the gas, if its pressure
remained the same, would double its
volume, if raised to a temperature of 32 +
491.64 = 523.64 degrees Fahrenheit, while
under a diminution of temperature it would
shrink and finally disappear at a temperature
of 491.64 - 32 = 459.64 degrees below zero
Fahrenheit. While undoubtedly some change
in the law would take place before the lower
temperature could be reached, there is no
reason why the law may not be used within
the range of temperature where it is known
to hold good. From this explanation it is
evident that under a constant pressure the
Fig. 12 volume of a gas will vary as the number of Fig. 13
degrees between its temperature and the
temperature of -459.64 degrees Fahrenheit.
To simplify the [Pg 82]
[Pg 83] application of the law, a new thermometric scale is constructed as follows: the point
corresponding to -460 degrees Fahrenheit, is taken as the zero point on the new scale, and the
degrees are identical in magnitude with those on the Fahrenheit scale. Temperatures referred to
this new scale are called absolute temperatures and the point -460 degrees Fahrenheit (= -273
degrees centigrade) is called the absolute zero. To convert any temperature Fahrenheit to
absolute temperature, add 460 degrees to the temperature on the Fahrenheit scale: thus 54
degrees Fahrenheit will be 54 + 460 = 514 degrees absolute temperature; 113 degrees
Fahrenheit will likewise be equal to 113 + 460 = 573 degrees absolute temperature. If one
pound of gas is at a temperature of 54 degrees Fahrenheit and another pound is at a temperature
of 114 degrees Fahrenheit the respective volumes at a given pressure would be in the ratio of
514 to 573.

Ninety-sixth Street Station of the New York Railways Co., New York City, Operating
20,000 Horse Power of Babcock & Wilcox Boilers. This Company and its Allied
Companies Operate a Total of 100,000 Horse Power of Babcock & Wilcox Boilers

British Thermal Unit —The quantitative measure of heat is the British thermal unit, ordinarily
written B. t. u. This is the quantity of heat required to raise the temperature of one pound of
pure water one degree at 62 degrees Fahrenheit; that is, from 62 degrees to 63 degrees. In the
metric system this unit is the calorie and is the heat necessary to raise the temperature of one
kilogram of pure water from 15 degrees to 16 degrees centigrade. These two definitions lead to
a discrepancy of 0.03 of 1 per cent, which is insignificant for engineering purposes, and in the
following the B. t. u. is taken with this discrepancy ignored. The discrepancy is due to the fact
that there is a slight difference in the specific heat of water at 15 degrees centigrade and 62
degrees Fahrenheit. The two units may be compared thus:

1 Calorie = 3.968 B. t. u. 1 B. t. u. = 0.252 Calories.
Unit Water Temperature Rise
1 B. t. u. 1 Pound 1 Degree Fahrenheit
1 Calorie 1 Kilogram 1 Degree centigrade

But 1 kilogram = 2.2046 pounds and 1 degree centigrade = 9 ⁄ 5 degree Fahrenheit.

Hence 1 calorie = (2.2046 × 9 ⁄ 5 ) = 3.968 B. t. u.

The heat values in B. t. u. are ordinarily given per pound, and the heat values in calories per
kilogram, in which case the B. t. u. per pound are approximately equivalent to 9 ⁄ 5 the calories

per kilogram.

As determined by Joule, heat energy has a certain definite relation to work, one British thermal
unit being equivalent from his determinations to 772 foot pounds. Rowland, a later investigator,
found that 778 foot pounds were a more exact equivalent. Still later investigations indicate that
the correct value for a B. t. u. is 777.52 foot pounds or approximately 778. The relation of heat
energy to work as determined is a demonstration of the first law of thermo-dynamics, namely,
that heat and mechanical energy are mutually convertible in the ratio of 778 foot pounds for one
British thermal unit. This law, algebraically expressed, is W = JH; W being the work done in
foot pounds, H being the heat in B. t. u., and J being Joules equivalent. Thus 1000 B. t. u.’s
would be capable of doing 1000 × 778 = 778000 foot pounds of work.

Specific Heat —The specific heat of a substance is the quantity of heat expressed in thermal
units required to raise or lower the temperature of a unit weight of any substance at a given
temperature one degree. This quantity will vary for different substances For example, it requires
about 16 B. t. u. to raise the temperature of one [Pg 84] pound of ice 32 degrees or 0.5 B. t. u. to
raise it one degree, while it requires approximately 180 B. t. u. to raise the temperature of one
pound of water 180 degrees or one B. t. u. for one degree.

If then, a pound of water be considered as a standard, the ratio of the amount of heat required to
raise a similar unit of any other substance one degree, to the amount required to raise a pound
of water one degree is known as the specific heat of that substance. Thus since one pound of
water required one B. t. u. to raise its temperature one degree, and one pound of ice requires
about 0.5 degrees to raise its temperature one degree, the ratio is 0.5 which is the specific heat
of ice. To be exact, the specific heat of ice is 0.504, hence 32 degrees × 0.504 = 16.128 B. t. u.
would be required to raise the temperature of one pound of ice from 0 to 32 degrees. For solids,
at ordinary temperatures, the specific heat may be considered a constant for each individual
substance, although it is variable for high temperatures. In the case of gases a distinction must
be made between specific heat at constant volume, and at constant pressure.

Where specific heat is stated alone, specific heat at ordinary temperature is implied, and mean
specific heat refers to the average value of this quantity between the temperatures named.

The specific heat of a mixture of gases is obtained by multiplying the specific heat of each
constituent gas by the percentage by weight of that gas in the mixture, and dividing the sum of
the products by 100. The specific heat of a gas whose composition by weight is CO 2 , 13 per
cent; CO, 0.4 per cent; O, 8 per cent; N, 78.6 per cent, is found as follows:

CO 2 13.0 × 0.2170 = 2.82100
CO 0.4 × 0.2479 = 0.09916
O 8.0 × 0.2175 = 1.74000
N 78.6 × 0.2438 = 19.16268
–––– –––––––
100.0 = 23.82284

and 23.8228 ÷ 100 = 0.238 = specific heat of the gas.

The specific heats of various solids, liquids and gases are given in Table 4 .

Sensible Heat —The heat utilized in raising the temperature of a body, as that in raising the
temperature of water from 32 degrees up to the boiling point, is termed sensible heat. In the
case of water, the sensible heat required to raise its temperature from the freezing point to the
boiling point corresponding to the pressure under which ebullition occurs, is termed the heat of
the liquid.

Latent Heat —Latent heat is the heat which apparently disappears in producing some change
in the condition of a body without increasing its temperature If heat be added to ice at freezing
temperature, the ice will melt but its temperature will not be raised. The heat so utilized in
changing the condition of the ice is the latent heat and in this particular case is known as the
latent heat of fusion. If heat be added to water at 212 degrees under atmospheric pressure, the
water will not become hotter but will be evaporated into steam, the temperature of which will
also be 212 degrees. The heat so utilized is called the latent heat of evaporation and is the heat
which apparently disappears in causing the substance to pass from a liquid to a gaseous state.

[Pg 85]

TABLE 4

SPECIFIC HEATS OF VARIOUS SUBSTANCES
SOLIDS
Temperature Temperature
[2] [2]
Specific Heat Specific Heat
Degrees Degrees
Fahrenheit Fahrenheit
Glass
(normal
Copper 59 –460 .0951 66 – 212 .1988
ther. 16 III
)
Gold 32 –212 .0316 Lead 59 .0299
Wrought
59 –212 .1152 Platinum 32 – 212 .0323
Iron
Cast Iron 68 –212 .1189 Silver 32 – 212 .0559
Steel (soft) 68 –208 .1175 Tin -105 – 64 .0518
Steel (hard) 68 –208 .1165 Ice .5040
Sulphur
Zinc 32 –212 .0935 (newly .2025
fused)
Brass
32 .0883
(yellow)
LIQUIDS
Temperature Specific Heat Temperature Specific Heat
[2] [2]

Degrees Degrees
Fahrenheit Fahrenheit
Sulphur
Water [3] 59 1.00000 246 – 297 .23500
(melted)
Tin
Alcohol 32 .54750 .06370
(melted)
Sea Water
176 .76940 (sp. gr. 64 .98000
1.0043)
Sea Water
Mercury 32 .03346 (sp. gr. 64 .90300
1.0463)
Oil of
Benzol 50 .40660 32 .41100
Turpentine
122 .45020 Petroleum 64 – 210 .49800
Sulphuric
Glycerine 59 –102 .57600 68 – 133 .33630
Acid
Lead
to 360 .04100
(Melted)
GASES
Temperature Specific Specific Temperature Specific Specific
[2] Heat at Heat at [2] Heat at Heat at
Degrees Constant Constant Degrees Constant Constant
Fahrenheit Pressure Volume Fahrenheit Pressure Volume
Carbon
Air 32 –392 .2375 .1693 41 – 208 .2425 .1728
Monoxide
Carbon
Oxygen 44 –405 .2175 .1553 52 – 417 .2169 .1535
Dioxide
Nitrogen 32 –392 .2438 .1729 Methane 64 – 406 .5929 .4505
Blast Fur.
Hydrogen 54 –388 3.4090 2.4141 Gas ... .2277 …
(approx.)
Superheated Flue gas
See table 25 ... .2400 …
Steam (approx.)

Latent heat is not lost, but reappears whenever the substances pass through a reverse cycle,
from a gaseous to a liquid, or from a liquid to a solid state. It may, therefore, be defined as
stated, as the heat which apparently disappears, or is lost to thermometric measurement, when
the molecular constitution of a body is being changed. Latent heat is expended in performing
the work of overcoming the molecular cohesion of the particles of the substance and in
overcoming the resistance of external pressure to change of volume of the heated body. Latent
heat of evaporation, therefore, may be said to consist of internal and external heat, the former
being [Pg 86] utilized in overcoming the molecular resistance of the water in changing to steam,
while the latter is expended in overcoming any resistance to the increase of its volume during
formation. In evaporating a pound of water at 212 degrees to steam at 212 degrees, 897.6 B. t.

u. are expended as internal latent heat and 72.8 B. t. u. as external latent heat. For a more
detailed description of the changes brought about in water by sensible and latent heat, the
reader is again referred to the chapter on “The Theory of Steam Making”.

TABLE 5 Ebullition —The temperature of
ebullition of any liquid, or its boiling
BOILING POINTS AT ATMOSPHERIC point, may be defined as the
PRESSURE temperature which exists where the
Degrees Degrees addition of heat to the liquid no
Fahrenheit Fahrenheit longer increases its temperature, the
Ammonia 140 Water 212 heat added being absorbed or utilized
Bromine 145 Average Sea Water 213.2 in converting the liquid into vapor.
This temperature is dependent upon
Alcohol 173 Saturated Brine 226
the pressure under which the liquid is
Benzine 212 Mercury 680 evaporated, being higher as the
pressure is greater.

Total Heat of Evaporation —The quantity of heat required to raise a unit of any liquid from
the freezing point to any given temperature, and to entirely evaporate it at that temperature, is
the total heat of evaporation of the liquid for that temperature. It is the sum of the heat of the
liquid and the latent heat of evaporation.

To recapitulate, the heat added to a body is divided as follows:

Total heat = Heat to change the temperature + heat to overcome the molecular cohesion + heat
to overcome the external pressure resisting an increase of volume of the body.

Where water is converted into steam, this total heat is divided as follows:

Total heat = Heat to change the temperature of the water + heat to separate the molecules of the
water + heat to overcome resistance to increase in volume of the steam,
= Heat of the liquid + internal latent heat + external latent heat,
= Heat of the liquid + total latent heat of steam,
= Total heat of evaporation.

The steam tables given on pages 122 to 127 give the heat of the liquid and the total latent heat
through a wide range of temperatures.

Gases —When heat is added to gases there is no internal work done; hence the total heat is that
required to change the temperature plus that required to do the external work. If the gas is not
allowed to expand but is preserved at constant volume, the entire heat added is that required to
change the temperature only.

Linear Expansion of Substances by Heat —To find the increase in the length of a bar of any
material due to an increase of temperature, multiply the number of degrees of increase in
temperature by the coefficient of expansion for one degree and by the length of the bar. Where
the coefficient of expansion is given for 100 degrees, as in Table 6 , the result should be divided

by 100. The expansion of metals [Pg 87] per one degree rise of temperature increases slightly as
high temperatures are reached, but for all practical purposes it may be assumed to be constant
for a given metal.

TABLE 6

LINEAL EXPANSION OF SOLIDS AT ORDINARY TEMPERATURES

(Tabular values represent increase per foot per 100 degrees increase in temperature, Fahrenheit
or centigrade)
Coefficient per Coefficient per
Temperature Conditions 100 100
[4] Degrees Degrees
Substance Degrees Fahrenheit Fahrenheit Centigrade
Brass (cast) 32 to 212 .001042 .001875
Brass (wire) 32 to 212 .001072 .001930
Copper 32 to 212 .000926 .001666
Glass (English flint) 32 to 212 .000451 .000812
Glass (French flint) 32 to 212 .000484 .000872
Gold 32 to 212 .000816 .001470
Granite (average) 32 to 212 .000482 .000868
Iron (cast) 104 .000589 .001061
Iron (soft forged) 0 to 212 .000634 .001141
Iron (wire) 32 to 212 .000800 .001440
Lead 32 to 212 .001505 .002709
Mercury 32 to 212 .009984 [5] .017971
Platinum 104 .000499 .000899
Limestone 32 to 212 .000139 .000251
Silver 104 .001067 .001921
Steel (Bessemer rolled,
0 to 212 .00056 .00101
hard)
Steel (Bessemer rolled,
0 to 212 .00063 .00117
soft)
Steel (cast, French) 104 .000734 .001322
Steel (cast annealed,
104 .000608 .001095
English)

High Temperature Measurements —The temperatures to be dealt with in steam-boiler practice
range from those of ordinary air and steam to the temperatures of burning fuel. The gases of
combustion, originally at the temperature of the furnace, cool as they pass through each
successive bank of tubes in the boiler, to nearly the temperature of the steam, resulting in a wide
range of temperatures through which definite measurements are sometimes required.

Of the different methods devised for ascertaining these temperatures, some of the most
important are as follows:

1st. Mercurial pyrometers for temperatures up to 1000 degrees Fahrenheit.

2nd. Expansion pyrometers for temperatures up to 1500 degrees Fahrenheit.

3rd. Calorimetry for temperatures up to 2000 degrees Fahrenheit.

4th. Thermo-electric pyrometers for temperatures up to 2900 degrees Fahrenheit.

5th. Melting points of metal which flow at various temperatures up to the melting point of
platinum 3227 degrees Fahrenheit.

6th. Radiation pyrometers for temperatures up to 3600 degrees Fahrenheit.

7th. Optical pyrometers capable of measuring temperatures up to 12,600 degrees
Fahrenheit. [6] For ordinary boiler practice however, their range is 1600 to 3600 degrees
Fahrenheit. [Pg 88]

228 Horse-power Babcock & Wilcox Boiler, Installed at the Wentworth Institute, Boston,
Mass.

[Pg 89] Table 7 gives the degree of accuracy of high temperature measurements.

Mercurial Pyrometers —At atmospheric TABLE 7
pressure mercury boils at 676 degrees
Fahrenheit and even at lower ACCURACY OF HIGH TEMPERATURE
temperatures the mercury in MEASUREMENTS [7]
thermometers will be distilled and will Centigrade Fahrenheit
collect in the upper part of the stem. Accuracy Accuracy
Therefore, for temperatures much above Temperature Plus or Temperature Plus or
400 degrees Fahrenheit, some inert gas, Range Minus Range Minus
such as nitrogen or carbon dioxide, must Degrees Degrees
be forced under pressure into the upper 200– 500 0.5 392– 932 0.9
part of the thermometer stem. The
500– 800 2.0 932– 1472 3.6
pressure at 600 degrees Fahrenheit is
about 15 pounds, or slightly above that of 800– 1100 3.0 1472– 2012 5.4
the atmosphere, at 850 degrees about 70 1100 – 1600 15.0 2012– 2912 27.0
pounds, and at 1000 degrees about 300 1600– 2000 25.0 2912– 3632 45.0
pounds.

Flue-gas temperatures are nearly always taken with mercurial thermometers as they are the
most accurate and are easy to read and manipulate. Care must be taken that the bulb of the
instrument projects into the path of the moving gases in order that the temperature may truly
represent the flue gas temperature. No readings should be considered until the thermometer has
been in place long enough to heat it up to the full temperature of the gases.

Expansion Pyrometers —Brass expands about 50 per cent more than iron and in both brass and
iron the expansion is nearly proportional to the increase in temperature. This phenomenon is
utilized in expansion pyrometers by enclosing a brass rod in an iron pipe, one end of the rod
being rigidly attached to a cap at the end of the pipe, while the other is connected by a
multiplying gear to a pointer moving around a graduated dial. The whole length of the
expansion piece must be at a uniform temperature before a correct reading can be obtained.
This fact, together with the lost motion which is likely to exist in the mechanism connected to
the pointer, makes the expansion pyrometer unreliable; it should be used only when its
limitations are thoroughly understood and it should be carefully calibrated. Unless the brass and
iron are known to be of the same temperature, its action will be anomalous: for instance, if it be
allowed to cool after being exposed to a high temperature, the needle will rise before it begins
to fall. Similarly, a rise in temperature is first shown by the instrument as a fall. The explanation
is that the iron, being on the outside, heats or cools more quickly than the brass.

Calorimetry —This method derives its name from the fact that the process is the same as the
determination of the specific heat of a substance by the water calorimeter, except that in one
case the temperature is known and the specific heat is required, while in the other the specific
heat is known and the temperature is required. The temperature is found as follows:

A given weight of some substance such as iron, nickel or fire brick, is heated to the unknown
temperature and then plunged into water and the rise in temperature noted.

[Pg 90]

If X = temperature to be measured, w = weight of heated body in pounds, W = weight of water
in pounds, T = final temperature of water, t = difference between initial and final temperatures
of water, s = known specific heat of body. Then X = T + W t ÷ w s

Any temperatures secured by this method are affected by so many sources of error that the
results are very approximate.

Thermo-electric Pyrometers —When wires of two different metals are joined at one end and
heated, an electromotive force will be set up between the free ends of the wires. Its amount will
depend upon the composition of the wires and the difference in temperature between the two. If
a delicate galvanometer of high resistance be connected to the “thermal couple”, as it is called,
the deflection of the needle, after a careful calibration, will indicate the temperature very
accurately.

In the thermo-electric pyrometer of Le Chatelier, the wires used are platinum and a 10 per cent
alloy of platinum and rhodium, enclosed in porcelain tubes to protect them from the oxidizing
influence of the furnace gases. The couple with its protecting tubes is called an “element”. The
elements are made in different lengths to suit conditions.

It is not necessary for accuracy to expose the whole length of the element to the temperature to
be measured, as the electromotive force depends only upon the temperature of the juncture at
the closed end of the protecting tube and that of the cold end of the element. The galvanometer
can be located at any convenient point, since the length of the wires leading to it simply alter
the resistance of the circuit, for which allowance may be made.

The advantages of the thermo-electric pyrometer are accuracy over a wide range of
temperatures, continuity of readings, and the ease with which observations can be taken. Its
disadvantages are high first cost and, in some cases, extreme delicacy.

Melting Points of Metals —The approximate temperature of a furnace or flue may be
determined, if so desired, by introducing certain metals of which the melting points are known.
The more common metals form a series in which the respective melting points differ by 100 to
200 degrees Fahrenheit, and by using these in order, the temperature can be fixed between the
melting points of some two of them. This method lacks accuracy, but it suffices for
determinations where approximate readings are satisfactory.

The approximate melting points of certain metals that may be used for determinations of this
nature are given in Table 8 .

Radiation Pyrometers —These are similar to thermo-electric pyrometers in that a thermo-
couple is employed. The heat rays given out by the hot body fall on a concave mirror and are
brought to a focus at a point at which is placed the junction of a thermo-couple. The
temperature readings are obtained from an indicator similar to that used with thermo-electric
pyrometers.

Optical Pyrometers —Of the optical pyrometers the Wanner is perhaps the most reliable. The
principle on which this instrument is constructed is that of comparing the quantity of light
emanating from the heated body with a constant source of light, in this case a two-volt osmium

lamp. The lamp is placed at one end of an optical tube, while at the other an eyepiece is
provided and a scale. A battery of cells furnishes the current for the lamp. On looking through
the pyrometer, a circle [Pg 91] of red light appears, divided into distinct halves of different
intensities. Adjustment may be made so that the two halves appear alike and a reading is then
taken from the scale. The temperatures are obtained from a table of temperatures corresponding
to scale readings. For standardizing the osmium lamp, an amylacetate lamp, is provided with a
stand for holding the optical tube.

TABLE 8

APPROXIMATE MELTING POINTS OF METALS [8]
Temperature Temperature
Metal Metal
Degrees Fahrenheit Degrees Fahrenheit
Wrought Iron 2737 Lead 621
Pig Iron (gray) 2190-2327 Bismuth 498
Cast Iron (white) 2075 Tin 449
Steel 2460-2550 Platinum 3191
Steel (cast) 2500 Gold 1946
Copper 1981 Silver 1762
Zinc 786 Aluminum 1216
Antimony 1166

Determination of Temperature from Character of Emitted Light —As a further means of
determining approximately the temperature of a furnace, Table 9 , compiled by Messrs. White
& Taylor, may be of service. The color at a given temperature is approximately the same for all
kinds of combustibles under similar conditions.

TABLE 9

CHARACTER OF EMITTED LIGHT AND CORRESPONDING
APPROXIMATE TEMPERATURE [9]
Temperature Temperature
Character of Emitted Light Degrees Character of Emitted Light Degrees
Fahrenheit Fahrenheit
Dark red, blood red, low red 1050 Light orange 1725
Dark cherry red 1175 Yellow 1825
Cherry, full red 1375 Light yellow 1975
Light cherry, bright cherry, light red 1550 White 2200
Orange 1650

FOOTNOTES
[2] When one temperature alone is given the “true” specific heat is given; otherwise the value is the
“mean” specific heat for the range of temperature given.

[3] For variation, see Table 13 .

[4] Where range of temperature is given, coefficient is mean over range.

[5] Coefficient of cubical expansion.

[6] Le Chatelier’s Investigations.

[7] Burgess-Le Chatelier.

[8] For accuracy of high temperature measurements, see Table 7 .

[9] Messrs. White & Taylor Trans. A. S. M. E., Vol. XXI, 1900.

[Pg 92]

THE THEORY OF STEAM MAKING
[Extracts from a Lecture delivered by George H. Babcock, at Cornell
University, 1887[10]]

The chemical compound known as H2O exists in three states or conditions
—ice, water and steam; the only difference between these states or
conditions is in the presence or absence of a quantity of energy exhibited
partly in the form of heat and partly in molecular activity, which, for want
of a better name, we are accustomed to call “latent heat”; and to transform it
from one state to another we have only to supply or extract heat. For
instance, if we take a quantity of ice, say one pound, at absolute zero[11] and
supply heat, the first effect is to raise its temperature until it arrives at a
point 492 Fahrenheit degrees above the starting point. Here it stops growing
warmer, though we keep on adding heat. It, however, changes from ice to
water, and when we have added sufficient heat to have made it, had it
remained ice, 283 degrees hotter or a temperature of 315 degrees
Fahrenheit’s thermometer, it has all become water, at the same temperature
at which it commenced to change, namely, 492 degrees above absolute zero,
or 32 degrees by Fahrenheit’s scale. Let us still continue to add heat, and it
will now grow warmer again, though at a slower rate—that is, it now takes
about double the quantity of heat to raise the pound one degree that it did
before—until it reaches a temperature of 212 degrees Fahrenheit, or 672
degrees absolute (assuming that we are at the level of the sea). Here we find
another critical point. However much more heat we may apply, the water, as
water, at that pressure, cannot be heated any hotter, but changes on the
addition of heat to steam; and it is not until we have added heat enough to
have raised the temperature of the water 966 degrees, or to 1,178 degrees by
Fahrenheit’s thermometer (presuming for the moment that its specific heat
has not changed since it became water), that it has all become steam, which
steam, nevertheless, is at the temperature of 212 degrees, at which the water
began to change. Thus over four-fifths of the heat which has been added to
the water has disappeared, or become insensible in the steam to any of our
instruments.

It follows that if we could reduce steam at atmospheric pressure to water,
without loss of heat, the heat stored within it would cause the water to be
red hot; and if we could further change it to a solid, like ice, without loss of
heat, the solid would be white hot, or hotter than melted steel—it being
assumed, of course, that the specific heat of the water and ice remain
normal, or the same as they respectively are at the freezing point.

After steam has been formed, a further addition of heat increases the
temperature again at a much faster ratio to the quantity of heat added, which
ratio also varies according as we maintain a constant pressure or a constant
volume; and I am not aware that any other critical point exists where this
will cease to be the fact until we arrive at that very high temperature, known
as the point of dissociation, at which it becomes resolved into its original
gases.

The heat which has been absorbed by one pound of water to convert it into
a pound of steam at atmospheric pressure is sufficient to have melted 3
pounds of steel or 13 pounds of gold. This has been transformed into
something besides heat; [Pg 93] stored up to reappear as heat when the
process is reversed. That condition is what we are pleased to call latent heat,
and in it resides mainly the ability of the steam to do work.

The diagram shows graphically the relation of heat to temperature, the
horizontal scale being quantity of heat in British thermal units, and the
vertical temperature in Fahrenheit degrees, both reckoned from absolute
zero and by the usual scale. The dotted lines for ice and water show the
temperature which would have been obtained if the conditions had not
changed. The lines marked “gold” and “steel” show the relation to heat and
temperature and the melting points of these metals. All the inclined lines
would be slightly curved if attention had been paid to the changing specific
heat, but the curvature would be small. It is worth noting that, with one or
two exceptions, the curves of all substances lie between the vertical and that
for water. That is to say, that water has a greater capacity for heat than all
other substances except two, hydrogen and bromine.

In order to generate steam, then, only two steps are required: 1st, procure
the heat, and 2nd, transfer it to the water. Now, you have it laid down as an
axiom that when a body has been transferred or transformed from one place

or state into another, the
same work has been
done and the same
energy expended,
whatever may have been
the intermediate steps or
conditions, or whatever
the apparatus. Therefore,
when a given quantity of
water at a given
temperature has been
made into steam at a
given temperature, a
certain definite work has
been done, and a certain
amount of energy
expended, from
whatever the heat may
have been obtained, or
whatever boiler may
have been employed for
the purpose.

A pound of coal or any
other fuel has a definite
heat producing capacity, and is capable of evaporating a definite quantity of
water under given conditions. That is the limit beyond which even
perfection cannot go, and yet I have known, and doubtless you have heard
of, cases where inventors have claimed, and so-called engineers have
certified to, much higher results.

The first step in generating steam is in burning the fuel to the best
advantage. A pound of carbon will generate 14,500 British thermal units,
during combustion into carbonic dioxide, and this will be the same,
whatever the temperature or the rapidity at which the combustion may take
place. If possible, we might oxidize it at as slow a rate as that with which
iron rusts or wood rots in the open air, or we might burn it [Pg 94] with the

rapidity of gunpowder, a ton in a second, yet the total heat generated would
be precisely the same. Again, we may keep the temperature down to the
lowest point at which combustion can take place, by bringing large bodies
of air in contact with it, or otherwise, or we may supply it with just the right
quantity of pure oxygen, and burn it at a temperature approaching that of
dissociation, and still the heat units given off will be neither more nor less.
It follows, therefore, that great latitude in the manner or rapidity of
combustion may be taken without affecting the quantity of heat generated.

But in practice it is found that other considerations limit this latitude, and
that there are certain conditions necessary in order to get the most available
heat from a pound of coal. There are three ways, and only three, in which
the heat developed by the combustion of coal in a steam boiler furnace may
be expended.

1st, and principally. It should be conveyed to the water in the boiler, and be
utilized in the production of steam. To be perfect, a boiler should so utilize
all the heat of combustion, but there are no perfect boilers.

2nd. A portion of the heat of combustion is conveyed up the chimney in the
waste gases. This is in proportion to the weight of the gases, and the
difference between their temperature and that of the air and coal before they
entered the fire.

3rd. Another portion is dissipated by radiation from the sides of the furnace.
In a stove the heat is all used in these latter two ways, either it goes off
through the chimney or is radiated into the surrounding space. It is one of
the principal problems of boiler engineering to render the amount of heat
thus lost as small as possible.

The loss from radiation is in proportion to the amount of surface, its nature,
its temperature, and the time it is exposed. This loss can be almost entirely
eliminated by thick walls and a smooth white or polished surface, but its
amount is ordinarily so small that these extraordinary precautions do not
pay in practice.

It is evident that the temperature of the escaping gases cannot be brought
below that of the absorbing surfaces, while it may be much greater even to

that of the fire. This is supposing that all of the escaping gases have passed
through the fire. In case air is allowed to leak into the flues, and mingle
with the gases after they have left the heating surfaces, the temperature may
be brought down to almost any point above that of the atmosphere, but
without any reduction in the amount of heat wasted. It is in this way that
those low chimney temperatures are sometimes attained which pass for
proof of economy with the unobserving. All surplus air admitted to the fire,
or to the gases before they leave the heating surfaces, increases the losses.

We are now prepared to see why and how the temperature and the rapidity
of combustion in the boiler furnace affect the economy, and that though the
amount of heat developed may be the same, the heat available for the
generation of steam may be much less with one rate or temperature of
combustion than another.

Assuming that there is no air passing up the chimney other than that which
has passed through the fire, the higher the temperature of the fire and the
lower that of the escaping gases the better the economy, for the losses by
the chimney gases will bear the same proportion to the heat generated by
the combustion as the temperature of those gases bears to the temperature
of the fire. That is to say, if the temperature of the fire is 2500 degrees and
that of the chimney gases 500 degrees above that of the atmosphere, the
loss by the chimney will be 500⁄2500 = 20 per cent. Therefore, as the escaping
gases cannot be brought below the temperature of the absorbing surface,
[Pg 95] which is practically a fixed quantity, the temperature of the fire must
be high in order to secure good economy.

The losses by radiation being practically proportioned to the time occupied,
the more coal burned in a given furnace in a given time, the less will be the
proportionate loss from that cause.

It therefore follows that we should burn our coal rapidly and at a high
temperature to secure the best available economy.

Portion of 9880 Horse-power Installation of Babcock & Wilcox Boilers
and Superheaters, Equipped with Babcock & Wilcox Chain Grate
Stokers at the South Side Elevated Ry. Co., Chicago, Ill.

FOOTNOTES
[10] See Scientific American Supplement, 624, 625, December, 1887.

[11] 460 degrees below the zero of Fahrenheit. This is the nearest approximation
in whole degrees to the latest determinations of the absolute zero of temperature

[Pg 96]

PROPERTIES OF WATER
Pure water is a chemical compound of one volume of oxygen and two volumes of hydrogen, its chemical
symbol being H 2 O.

The weight of water depends upon its temperature. Its weight at four temperatures, much used in physical
calculations, is given in Table 10 .

TABLE 10 While authorities differ as to the weight of water, the
range of values given for 62 degrees Fahrenheit (the
WEIGHT OF WATER AT TEMPERATURES standard temperature ordinarily taken) being from
USED IN PHYSICAL CALCULATIONS 62.291 pounds to 62.360 pounds per cubic foot, the
Weight per Weight per value 62.355 is generally accepted as the most
Temperature Degrees accurate.
Cubic Foot Cubic Inch
Fahrenheit
Pounds Pounds
A United States standard gallon holds 231 cubic
At 32 degrees or freezing
point at sea level 62.418 0.03612 inches and weighs, at 62 degrees Fahrenheit,
approximately 8 1 ⁄ 3 pounds.
At 39.2 degrees or point of
maximum density 62.427 0.03613 A British Imperial gallon holds 277.42 cubic inches
At 62 degrees or standard and weighs, at 62 degrees Fahrenheit, 10 pounds.
temperature 62.355 0.03608
At 212 degrees or boiling The above are the true weights corrected for the effect
point at sea level 59.846 0.03469 of the buoyancy of the air, or the weight in vacuo . If
water is weighed in air in the ordinary way, there is a
correction of about one-eighth of one per cent which is usually negligible.

TABLE 11

VOLUME AND WEIGHT OF DISTILLED WATER AT VARIOUS TEMPERATURES [12]
Temper- Relative Weight Temper- Relative Weight Temper- Relative Weight Temper- Relative Weight
ature Volume per ature Volume per ature Volume per ature Volume per
Degrees Water Cubic Degrees Water Cubic Degrees Water Cubic Degrees Water Cubic
Fahren- at 39.2° Foot Fahren- at 39.2° Foot Fahren- at 39.2° Foot Fahren- at 39.2° Foot
heit = 1.000 Pounds heit = 1.000 Pounds heit = 1.000 Pounds heit = 1.000 Pounds
32 1.000176 62.42 160 1.02337 61.00 290 1.0830 57.65 430 1.197 52.2
39.2 1.000000 62.43 170 1.02682 60.80 300 1.0890 57.33 440 1.208 51.7
40 1.000004 62.43 180 1.03047 60.58 310 1.0953 57.00 450 1.220 51.2
50 1.00027 62.42 190 1.03431 60.36 320 1.1019 56.66 460 1.232 50.7
60 1.00096 62.37 200 1.03835 60.12 330 1.1088 56.30 470 1.244 50.2
70 1.00201 62.30 210 1.04256 59.88 340 1.1160 55.94 480 1.256 49.7
80 1.00338 62.22 212 1.04343 59.83 350 1.1235 55.57 490 1.269 49.2
90 1.00504 62.11 220 1.0469 59.63 360 1.1313 55.18 500 1.283 48.7
100 1.00698 62.00 230 1.0515 59.37 370 1.1396 54.78 510 1.297 48.1
110 1.00915 61.86 240 1.0562 59.11 380 1.1483 54.36 520 1.312 47.6
120 1.01157 61.71 250 1.0611 58.83 390 1.1573 53.94 530 1.329 47.0
130 1.01420 61.55 260 1.0662 58.55 400 1.167 53.5 540 1.35 46.3
140 1.01705 61.38 270 1.0715 58.26 410 1.177 53.0 550 1.37 45.6
150 1.02011 61.20 280 1.0771 57.96 420 1.187 52.6 560 1.39 44.9

[Pg 97]

Water is but slightly compressible and for all practical purposes may be considered non-compressible. The
coefficient of compressibility ranges from 0.000040 to 0.000051 per atmosphere at ordinary temperatures, this
coefficient decreasing as the temperature increases.

Table 11 gives the weight in vacuo and the relative volume of a cubic foot of distilled water at various
temperatures.

The weight of water at the standard temperature being taken as 62.355 pounds per cubic foot, the pressure
exerted by the column of water of any stated height, and conversely the height of any column required to
produce a stated pressure, may be computed as follows:

The pressure in pounds per square foot = 62.355 × height of column in feet.

The pressure in pounds per square inch = 0.433 × height of column in feet.

Height of column in feet = pressure in pounds per square foot ÷ 62.355.

Height of column in feet = pressure in pounds per square inch ÷ 0.433.

Height of column in inches = pressure in pounds per square inch × 27.71.

Height of column in inches = pressure in ounces per square inch × 1.73.

By a change in the weights given above, the pressure exerted and height of column may be computed for
temperatures other than 62 degrees.

A pressure of one pound per square inch is exerted by a column of water 2.3093 feet or 27.71 inches high at 62
degrees Fahrenheit.

Water in its natural state is never found absolutely pure. In solvent power water has a greater range than any
other liquid. For common salt, this is approximately a constant at all temperatures, while with such impurities
as magnesium and sodium sulphates, this solvent power increases with an increase in temperature.

TABLE 12

BOILING POINT OF WATER AT VARIOUS ALTITUDES
Boiling Altitude Atmospheric Barometer Boiling Altitude Atmospheric Barometer
Point Above Pressure Reduced to Point Above Pressure Reduced to
Degrees Sea Level Pounds per 32 Degrees Degrees Sea Level Pounds per 32 Degrees
Fahrenheit Feet Square Inch Inches Fahrenheit Feet Square Inch Inches
184 15221 8.20 16.70 199 6843 11.29 22.99
185 14649 8.38 17.06 200 6304 11.52 23.47
186 14075 8.57 17.45 201 5764 11.76 23.95
187 13498 8.76 17.83 202 5225 12.01 24.45
188 12934 8.95 18.22 203 4697 12.26 24.96
189 12367 9.14 18.61 204 4169 12.51 25.48
190 11799 9.34 19.02 205 3642 12.77 26.00
191 11243 9.54 19.43 206 3115 13.03 26.53
192 10685 9.74 19.85 207 2589 13.30 27.08
193 10127 9.95 20.27 208 2063 13.57 27.63
194 9579 10.17 20.71 209 1539 13.85 28.19
195 9031 10.39 21.15 210 1025 14.13 28.76

196 8481 10.61 21.60 211 512 14.41 29.33
197 7932 10.83 22.05 212 Sea Level 14.70 29.92
198 7381 11.06 22.52

Sea water contains on an average approximately 3.125 per cent of its weight of solid matter or a thirty-second
part of the weight of the water and salt held in solution. [Pg 98]
[Pg 99] The approximate composition of this solid matter will be: sodium chloride 76 per cent, magnesium
chloride 10 per cent, magnesium sulphate 6 per cent, calcium sulphate 5 per cent, calcium carbonate 0.5 per
cent, other substances 2.5 per cent.

7200 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters at the Capital Traction
Co., Washington, D. C.

The boiling point of water decreases as the altitude above sea level increases. Table 12 gives the variation in
the boiling point with the altitude.

Water has a greater specific heat or heat-absorbing capacity than any other known substance (bromine and
hydrogen excepted) and its specific heat is the basis for measurement of the capacity of heat absorption of all
other substances. From the definition, the specific heat of water is the number of British thermal units required
to raise one pound of water one degree. This specific heat varies with the temperature of the water. The
generally accepted values are given in Table 13 , which indicates the values as determined by Messrs. Marks
and Davis and Mr. Peabody.

TABLE 13

SPECIFIC HEAT OF WATER AT VARIOUS TEMPERATURES
MARKS AND DAVIS PEABODY
From Values of Barnes and Dieterici From Values of Barnes and Regnault
Temperature Temperature Temperature Temperature
Specific Specific Specific Specific
Degrees Degrees Degrees Degrees Degrees Degrees
Heat Heat Heat Heat
Fahrenheit Fahrenheit Centigrade Fahrenheit Centigrade Fahrenheit
30 1.0098 130 0.9979 0 32 1.0094 50 122 0.9980

40 1.0045 140 0.9986 5 41 1.0053 55 131 0.9985
50 1.0012 150 0.9994 10 50 1.0023 60 140 0.9994
55 1.0000 160 1.0002 15 59 1.0003 65 149 1.0004
60 0.9990 170 1.0010 16.11 61 1.0000 70 158 1.0015
70 0.9977 180 1.0019 20 68 0.9990 75 167 1.0028
80 0.9970 190 1.0029 25 77 0.9981 80 176 1.0042
90 0.9967 200 1.0039 30 86 0.9976 85 185 1.0056
100 0.9967 210 1.0052 35 95 0.9974 90 194 1.0071
110 0.9970 220 1.007 40 104 0.9974 95 203 1.0086
120 0.9974 230 1.009 45 113 0.9976 100 212 1.0101

In consequence of this variation in specific heat, the variation in the heat of the liquid of the water at different
temperatures is not a constant. Table 22 [13] gives the heat of the liquid in a pound of water at temperatures
ranging from 32 to 340 degrees Fahrenheit.

The specific heat of ice at 32 degrees is 0.463. The specific heat of saturated steam (ice and saturated steam
representing the other forms in which water may exist), is something that is difficult to define in any way
which will not be misleading. When no liquid is present the specific heat of saturated steam is negative. [14]
The use of the value of the specific heat of steam is practically limited to instances where superheat is present,
and the specific heat of superheated steam is covered later in the book.

FOOTNOTES
[12] Marks and Davis

[13] See page 120 .

[14] See Trans., A. S. M. E., Vol. XIV., Page 79.

[Pg 100]

BOILER FEED WATER
All natural waters contain some impurities which, when introduced into a
boiler, may appear as solids. In view of the apparent present-day tendency
toward large size boiler units and high overloads, the importance of the use
of pure water for boiler feed purposes cannot be over-estimated.

Ordinarily, when water of sufficient purity for such use is not at hand, the
supply available may be rendered suitable by some process of treatment.
Against the cost of such treatment, there are many factors to be considered.
With water in which there is a marked tendency toward scale formation, the
interest and depreciation on the added boiler units necessary to allow for the
systematic cleaning of certain units must be taken into consideration. Again
there is a considerable loss in taking boilers off for cleaning and replacing
them on the line. On the other hand, the decrease in capacity and efficiency
accompanying an increased incrustation of boilers in use has been too
generally discussed to need repetition here. Many experiments have been
made and actual figures reported as to this decrease, but in general, such
figures apply only to the particular set of conditions found in the plant where
the boiler in question was tested. So many factors enter into the effect of
scale on capacity and economy that it is impossible to give any accurate
figures on such decrease that will serve all cases, but that it is large has been
thoroughly proven.

While it is almost invariably true that practically any cost of treatment will
pay a return on the investment of the apparatus, the fact must not be
overlooked that there are certain waters which should never be used for
boiler feed purposes and which no treatment can render suitable for such
purpose. In such cases, the only remedy is the securing of other feed supply
or the employment of evaporators for distilling the feed water as in marine
service.

TABLE 14

APPROXIMATE CLASSIFICATION OF IMPURITIES FOUND IN FEED

WATERS
THEIR EFFECT AND ORDINARY METHODS OF RELIEF
Difficulty Resulting Nature of Ordinary Method of
from Presence of Difficulty Overcoming or Relieving
Sediment, Mud, etc. Incrustation Settling tanks, filtration, blowing
down.
Readily Soluble Salts Incrustation Blowing down.
Bicarbonates of Lime, Incrustation Heating feed.
Magnesia, etc. Treatment by addition of lime or
of lime and soda.
Barium carbonate.
Sulphate of Lime Incrustation Treatment by addition of soda.
Barium carbonate.
Chloride and Sulphate of Corrosion Treatment by addition of
Magnesium carbonate of soda.
Acid Corrosion Alkali.
Dissolved Carbonic Acid Corrosion Heating feed. Keeping air from
and Oxygen feed.
Addition of caustic soda or
slacked lime.
Grease Corrosion Filter. Iron alum as coagulent.
Neutralization by carbonate of
soda.
Use of best hydrocarbon oils.
Organic Matter Corrosion Filter. Use of coagulent.
Organic Matter (Sewage) Priming Settling tanks. Filter in connection
with coagulent.
Carbonate of Soda in large Priming Barium carbonate. New feed
quantities supply.
If from treatment, change.

[Pg 101]

It is evident that the whole subject of boiler feed waters and their treatment
is one for the chemist rather than for the engineer. A brief outline of the
difficulties that may be experienced from the use of poor feed water and a

suggestion as to a method of overcoming certain of these difficulties is all
that will be attempted here. Such a brief outline of the subject, however, will
indicate the necessity for a chemical analysis of any water before a treatment
is tried and the necessity of adapting the treatment in each case to the nature
of the difficulties that may be experienced.

Table 14 gives a list of impurities which may be found in boiler feed water,
grouped according to their effect on boiler operation and giving the
customary method used for overcoming difficulty to which they lead.

Scale—Scale is formed on boiler heating surfaces by the depositing of
impurities in the feed water in the form of a more or less hard adherent crust.
Such deposits are due to the fact that water loses its soluble power at high
temperatures or because the concentration becomes so high, due to
evaporation, that the impurities crystallize and adhere to the boiler surfaces.
The opportunity for formation of scale in a boiler will be apparent when it is
realized that during a month’s operation of a 100 horse-power boiler, 300
pounds of solid matter may be deposited from water containing only 7 grains
per gallon, while some spring and well waters contain sufficient to cause a
deposit of as high as 2000 pounds.

TABLE 15 The salts
usually
SOLUBILITY OF MINERAL SALTS IN WATER responsibl
(SPARKS) e for such
IN GRAINS PER U. S. GALLON (58,381 GRAINS), incrustatio
EXCEPT AS NOTED n are the
Temperature Degrees Fahrenheit 60 Degrees 212 Degrees carbonates
and
Calcium Carbonate 2.5 1.5
sulphates
Calcium Sulphate 140.0 125.0
of lime
Magnesium Carbonate 1.0 1.8 and
Magnesium Sulphate 3.0 pounds 12.0 pounds magnesia,
Sodium Chloride 3.5 pounds 4.0 pounds and boiler
Sodium Sulphate 1.1 pounds 5.0 pounds feed
treatment
in general deals with the getting rid of these salts more or less completely.

Table 15 gives the solubility of these mineral salts in water at various
temperatures in grains per U. S. gallon (58,381 grains). It will be seen from
this table that the carbonates of lime and magnesium are not soluble above
212 degrees, and calcium sulphate while somewhat insoluble above 212
degrees becomes more greatly so as the temperature increases.

Scale is also formed by the settling of mud and sediment carried in
suspension in water. This may bake or be cemented to a hard scale when
mixed with other scale-forming ingredients.

CALCIUM SULPHATE AT TEMPERATURE ABOVE Corrosio
212 DEGREES (CHRISTIE) n—

Temperature degrees Fahrenheit 284 329 347-365 464 482 Corrosion
, or a
Corresponding gauge pressure 38 87 115-149 469 561
chemical
Grains per gallon 45.5 32.7 15.7 10.5 9.3
action
leading to
the actual destruction of the boiler metal, is due to the solvent or oxidizing
properties of the feed water. It [Pg 102] results from the presence of acid,
either free or developed[15] in the feed, the admixture of air with the feed
water, or as a result of a galvanic action. In boilers it takes several forms:

1st. Pitting, which consists of isolated spots of active corrosion which does
not attack the boiler as a whole.

2nd. General corrosion, produced by naturally acid waters and where the
amount is so even and continuous that no accurate estimate of the metal
eaten away may be made.

3rd. Grooving, which, while largely a mechanical action which may occur in
neutral waters, is intensified by acidity.

Foaming—This phenomenon, which ordinarily occurs with waters
contaminated with sewage or organic growths, is due to the fact that the
suspended particles collect on the surface of the water in the boiler and
render difficult the liberation of steam bubbles arising to that surface. It
sometimes occurs with water containing carbonates in solution in which a
light flocculent precipitate will be formed on the surface of the water. Again,

it is the result of an excess of sodium carbonate used in treatment for some
other difficulty where animal or vegetable oil finds its way into the boiler.

Priming—Priming, or the passing off of steam from a boiler in belches, is
caused by the concentration of sodium carbonate, sodium sulphate or sodium
chloride in solution. Sodium sulphate is found in many southern waters and
also where calcium or magnesium sulphate is precipitated with soda ash.

Treatment of Feed Water—For scale formation. The treatment of feed
water, carrying scale-forming ingredients, is along two main lines: 1st, by
chemical means by which such impurities as are carried by the water are
caused to precipitate; and 2nd, by the means of heat, which results in the
reduction of the power of water to hold certain salts in solution. The latter
method alone is sufficient in the case of certain temporarily hard waters, but
the heat treatment, in general, is used in connection with a chemical
treatment to assist the latter.

Before going further into detail as to the treatment of water, it may be well to
define certain terms used.

Hardness, which is the most widely known evidence of the presence in water
of scale-forming matter, is that quality, the variation of which makes it more
difficult to obtain a lather or suds from soap in one water than in another.
This action is made use of in the soap test for hardness described later.
Hardness is ordinarily classed as either temporary or permanent.
Temporarily hard waters are those containing carbonates of lime and
magnesium, which may be precipitated by boiling at 212 degrees and which,
if they contain no other scale-forming ingredients, become “soft” under such
treatment. Permanently hard waters are those containing mainly calcium
sulphate, which is only precipitated at the high temperatures found in the
boiler itself, 300 degrees Fahrenheit or more. The scale of hardness is an
arbitrary one, based on the number of grains of solids per gallon and waters
may be classed on such a basis as follows: 1-10 grain per gallon, soft water;
10-20 grain per gallon, moderately hard water; above 25 grains per gallon,
very hard water.

[Pg 103]

Alkalinity is a general term used for waters containing compounds with the
power of neutralizing acids.

Causticity, as used in water treatment, is a term coined by A. McGill,
indicating the presence of an excess of lime added during treatment. Though
such presence would also indicate alkalinity, the term is arbitrarily used to
apply to those hydrates whose presence is indicated by phenolphthalein.

Of the chemical methods of water treatment, there are three general
processes:

1st. Lime Process. The lime process is used for waters containing
bicarbonates of lime and magnesia. Slacked lime in solution, as lime water,
is the reagent used. This combines with the carbonic acid which is present,
either free or as carbonates, to form an insoluble monocarbonate of lime.
The soluble bicarbonates of lime and magnesia, losing their carbonic acid,
thereby become insoluble and precipitate.

2nd. Soda Process. The soda process is used for waters containing sulphates
of lime and magnesia. Carbonate of soda and hydrate of soda (caustic soda)
are used either alone or together as the reagents. Carbonate of soda, added to
water containing little or no carbonic acid or bicarbonates, decomposes the
sulphates to form insoluble carbonate of lime or magnesia which precipitate,
the neutral soda remaining in solution. If free carbonic acid or bicarbonates
are present, bicarbonate of lime is formed and remains in solution, though
under the action of heat, the carbon dioxide will be driven off and insoluble
monocarbonates will be formed. Caustic soda used in this process causes a
more energetic action, it being presumed that the caustic soda absorbs the
carbonic acid, becomes carbonate of soda and acts as above.

3rd. Lime and Soda Process. This process, which is the combination of the
first two, is by far the most generally used in water purification. Such a
method is used where sulphates of lime and magnesia are contained in the
water, together with such quantity of carbonic acid or bicarbonates as to
impair the action of the soda. Sufficient soda is used to break down the
sulphates of lime and magnesia and as much lime added as is required to
absorb the carbonic acid not taken up in the soda reaction.

All of the apparatus for effecting such treatment of feed waters is
approximately the same in its chemical action, the numerous systems
differing in the methods of introduction and handling of the reagents.

The methods of testing water treated by an apparatus of this description
follow.

When properly treated, alkalinity, hardness and causticity should be in the
approximate relation of 6, 5 and 4. When too much lime is used in the
treatment, the causticity in the purified water, as indicated by the acid test,
will be nearly equal to the alkalinity. If too little lime is used, the causticity
will fall to approximately half the alkalinity. The hardness should not be in
excess of two points less than the alkalinity. Where too great a quantity of
soda is used, the hardness is lowered and the alkalinity raised. If too little
soda, the hardness is raised and the alkalinity lowered.

Alkalinity and causticity are tested with a standard solution of sulphuric
acid. A standard soap solution is used for testing for hardness and a silver
nitrate solution may also be used for determining whether an excess of lime
has been used in the treatment.

Alkalinity: To 50 cubic centimeters of treated water, to which there has been
added sufficient methylorange to color it, add the acid solution, drop by
drop, until the mixture is on the point of turning red. As the acid solution is
first added, the red color, which shows quickly, disappears on shaking the
mixture, and this color [Pg 104]
[Pg 105] disappears more slowly as the critical point is approached. One-tenth
cubic centimeter of the standard acid solution corresponds to one degree of
alkalinity.

2640 Horse-power Installation of Babcock & Wilcox Boilers at the
Botany Worsted Mills, Passaic, N. J.

Causticity: To 50 cubic centimeters of treated water, to which there has been
added one drop of phenolphthalein dissolved in alcohol to give the water a
pinkish color, add the acid solution, drop by drop, shaking after each
addition, until the color entirely disappears. One-tenth cubic centimeter of
acid solution corresponds to one degree of causticity.

The alkalinity may be determined from the same sample tested for causticity
by the coloring with methylorange and adding the acid until the sample is on
the point of turning red. The total acid added in determining both causticity
and alkalinity in this case is the measure of the alkalinity.

Hardness: 100 cubic centimeters of the treated water is used for this test, one
cubic centimeter of the soap solution corresponding to one degree of
hardness. The soap solution is added a very little at a time and the whole
violently shaken. Enough of the solution must be added to make a permanent
lather or foam, that is, the soap bubbles must not disappear after the shaking
is stopped.

Excess of lime as determined by nitrate of silver: If there is an excess of lime
used in the treatment, a sample will become a dark brown by the addition of
a small quantity of silver nitrate, otherwise a milky white solution will be
formed.

Combined Heat and Chemical Treatment: Heat is used in many systems of
feed treatment apparatus as an adjunct to the chemical process. Heat alone
will remove temporary hardness by the precipitation of carbonates of lime
and magnesia and, when used in connection with the chemical process,
leaves only the permanent hardness or the sulphates of lime to be taken care
of by chemical treatment.

TABLE 16

REAGENTS REQUIRED IN LIME AND SODA PROCESS
FOR TREATING 1000 U. S. GALLONS OF WATER
PER GRAIN PER GALLON OF CONTAINED IMPURITIES[16]
Lime[17] Soda[18] Lime[17] Soda[18]
Pounds Pounds Pounds Pounds
Calcium Carbonate 0.098 … Ferrous Carbonate 0.169 …
Calcium Sulphate … 0.124 Ferrous Sulphate 0.070 0.110
Calcium Chloride … 0.151 Ferric Sulphate 0.074 0.126
Aluminum
Calcium Nitrate … 0.104 0.087 0.147
Sulphate
Magnesium Free Sulphuric
0.234 … 0.100 0.171
Carbonate Acid
Magnesium
0.079 0.141 Sodium Carbonate 0.093 …
Sulphate
Magnesium Free Carbon
0.103 0.177 0.223 …
Chloride Dioxide
Magnesium Nitrate 0.067 0.115 Hydrogen Sulphite 0.288 …

The chemicals used in the ordinary lime and soda process of feed water
treatment are common lime and soda. The efficiency of such apparatus will
depend wholly upon the amount and character of the impurities in the water
to be treated. Table 16 gives the amount of lime and soda required per 1000
gallons for each grain per gallon of the various impurities found in the water.

This table is based on lime containing 90 per cent calcium oxide and soda
containing 58 per cent sodium oxide, [Pg 106] which correspond to the
commercial quality ordinarily purchasable. From this table and the cost of
the lime and soda, the cost of treating any water per 1000 gallons may be
readily computed.

Less Usual Reagents—Barium hydrate is sometimes used to reduce
permanent hardness or the calcium sulphate component. Until recently, the
high cost of barium hydrate has rendered its use prohibitive but at the
present it is obtained as a by-product in cement manufacture and it may be
purchased at a more reasonable figure than heretofore. It acts directly on the
soluble sulphates to form barium sulphate which is insoluble and may be
precipitated. Where this reagent is used, it is desirable that the reaction be
allowed to take place outside of the boiler, though there are certain cases
where its internal use is permissible.

Barium carbonate is sometimes used in removing calcium sulphate, the
products of the reaction being barium sulphate and calcium carbonate, both
of which are insoluble and may be precipitated. As barium carbonate in itself
is insoluble, it cannot be added to water as a solution and its use should,
therefore, be confined to treatment outside of the boiler.

Silicate of soda will precipitate calcium carbonate with the formation of a
gelatinous silicate of lime and carbonate of soda. If calcium sulphate is also
present, carbonate of soda is formed in the above reaction, which in turn will
break down the sulphate.

Oxalate of soda is an expensive but efficient reagent which forms a
precipitate of calcium oxalate of a particularly insoluble nature.

Alum and iron alum will act as efficient coagulents where organic matter is
present in the water. Iron alum has not only this property but also that of
reducing oil discharged from surface condensers to a condition in which it
may be readily removed by filtration.

Corrosion—Where there is a corrosive action because of the presence of
acid in the water or of oil containing fatty acids which will decompose and
cause pitting wherever the sludge can find a resting place, it may be

overcome by the neutralization of the water by carbonate of soda. Such
neutralization should be carried to the point where the water will just turn
red litmus paper blue. As a preventative of such action arising from the
presence of the oil, only the highest grades of hydrocarbon oils should be
used.

Acidity will occur where sea water is present in a boiler. There is the
possibility of such an occurrence in marine practice and in stationary plants
using sea water for condensing, due to leaky condenser tubes, priming in the
evaporators, etc. Such acidity is caused through the dissociation of
magnesium chloride into hydrochloride acid and magnesia under high
temperatures. The acid in contact with the metal forms an iron salt which
immediately upon its formation is neutralized by the free magnesia in the
water, thereby precipitating iron oxide and reforming magnesium chloride.
The preventive for corrosion arising from such acidity is the keeping tight of
the condenser. Where it is unavoidable that some sea water should find its
way into a boiler, the acidity resulting should be neutralized by soda ash.
This will convert the magnesium chloride into magnesium carbonate and
sodium chloride, neither of which is corrosive but both of which are scale-
forming.

The presence of air in the feed water which is sucked in by the feed pump is
a well recognized cause of corrosion. Air bubbles form below the water line
and attack [Pg 107] the metal of the boiler, the oxygen of the air causing
oxidization of the boiler metal and the formation of rust. The particle of rust
thus formed is swept away by the circulation or is dislodged by expansion
and the minute pit thus left forms an ideal resting place for other air bubbles
and the continuation of the oxidization process. The prevention is, of course,
the removing of the air from the feed water. In marine practice, where there
has been experienced the most difficulty from this source, it has been found
to be advantageous to pump the water from the hot well to a filter tank
placed above the feed pump suction valves. In this way the air is liberated
from the surface of the tank and a head is assured for the suction end of the
pump. In this same class of work, the corrosive action of air is reduced by
introducing the feed through a spray nozzle into the steam space above the
water line.

Galvanic action, resulting in the eating away of the boiler metal through
electrolysis was formerly considered practically the sole cause of corrosion.
But little is known of such action aside from the fact that it does take place
in certain instances. The means adopted as a remedy is usually the
installation of zinc plates within the boiler, which must have positive
metallic contact with the boiler metal. In this way, local electrolytic effects
are overcome by a still greater electrolytic action at the expense of the more
positive zinc. The positive contact necessary is difficult to maintain and it is
questionable just what efficacy such plates have except for a short period
after their installation when the contact is known to be positive. Aside from
protection from such electrolytic action, however, the zinc plates have a
distinct use where there is the liability of air in the feed, as they offer a
substance much more readily oxidized by such air than the metal of the
boiler.

Foaming—Where foaming is caused by organic matter in suspension, it may
be largely overcome by filtration or by the use of a coagulent in connection
with filtration, the latter combination having come recently into considerable
favor. Alum, or potash alum, and iron alum, which in reality contains no
alumina and should rather be called potassia-ferric, are the coagulents
generally used in connection with filtration. Such matter as is not removed
by filtration may, under certain conditions, be handled by surface blowing.
In some instances, settling tanks are used for the removal of matter in
suspension, but where large quantities of water are required, filtration is
ordinarily substituted on account of the time element and the large area
necessary in settling tanks.

Where foaming occurs as the result of overtreatment of the feed water, the
obvious remedy is a change in such treatment.

Priming—Where priming is caused by excessive concentration of salts
within a boiler, it may be overcome largely by frequent blowing down. The
degree of concentration allowable before priming will take place varies
widely with conditions of operation and may be definitely determined only
by experience with each individual set of conditions. It is the presence of the
salts that cause priming that may result in the absolute unfitness of water for
boiler feed purposes. Where these salts exist in such quantities that the
amount of blowing down necessary to keep the degree of concentration

below the priming point results in excessive losses, the only remedy is the
securing of another supply of feed, and the results will warrant the change
almost regardless of the expense. In some few instances, the impurities may
be taken care of by some method of water treatment but such water should
be submitted to an authority on the subject before any treatment apparatus is
installed.
[Pg 108]

[Pg 109] Boiler Compounds—The method of treatment of feed water by far
the most generally used is by the use of some of the so-called boiler
compounds. There are many reliable concerns handling such compounds
who unquestionably secure the promised results, but there is a great
tendency toward looking on the compound as a “cure all” for any water
difficulties and care should be taken to deal only with reputable concerns.

3000 Horse-power Installation of Cross Drum Babcock & Wilcox
Boilers and Superheaters Equipped with Babcock & Wilcox Chain
Grate Stokers at the Washington Terminal Co., Washington, D. C.

The composition of these compounds is almost invariably based on soda
with certain tannic substances and in some instances a gelatinous substance
which is presumed to encircle scale particles and prevent their adhering to
the boiler surfaces. The action of these compounds is ordinarily to reduce the
calcium sulphate in the water by means of carbonate of soda and to
precipitate it as a muddy form of calcium carbonate which may be blown
off. The tannic compounds are used in connection with the soda with the

idea of introducing organic matter into any scale already formed. When it
has penetrated to the boiler metal, decomposition of the scale sets in, causing
a disruptive effect which breaks the scale from the metal sometimes in large
slabs. It is this effect of boiler compounds that is to be most carefully
guarded against or inevitable trouble will result from the presence of loose
scale with the consequent danger of tube losses through burning.

When proper care is taken to suit the compound to the water in use, the
results secured are fairly effective. In general, however, the use of
compounds may only be recommended for the prevention of scale rather
than with the view to removing scale which has already formed, that is, the
compounds should be introduced with the feed water only when the boiler
has been thoroughly cleaned.

FOOTNOTES
[15] Some waters, not naturally acid, become so at high temperatures, as when
chloride of magnesia decomposes with the formation of free hydrochloride acid;
such phenomena become more serious with an increase in pressure and
temperature.

[16] L. M. Booth Company.

[17] Based on lime containing 90 per cent calcium oxide.

[18] Based on soda containing 58 per cent sodium oxide.

[Pg 110]

FEED WATER HEATING AND METHODS OF
FEEDING
Before water fed into a boiler can be converted into steam, it must be first heated to a
temperature corresponding to the pressure within the boiler. Steam at 160 pounds gauge
pressure has a temperature of approximately 371 degrees Fahrenheit. If water is fed to
the boiler at 60 degrees Fahrenheit, each pound must have 311 B. t. u. added to it to
increase its temperature 371 degrees, which increase must take place before the water
can be converted into steam. As it requires 1167.8 B. t. u. to raise one pound of water
from 60 to 371 degrees and to convert it into steam at 160 pounds gauge pressure, the
311 degrees required simply to raise the temperature of the water from 60 to 371
degrees will be approximately 27 per cent of the total. If, therefore, the temperature of
the water can be increased from 60 to 371 degrees before it is introduced into a boiler
by the utilization of heat from some source that would otherwise be wasted, there will
be a saving in the fuel required of 311 ÷ 1167.8 = 27 per cent, and there will be a net
saving, provided the cost of maintaining and operating the apparatus for securing this
saving is less than the value of the heat thus saved.

The saving in the fuel due to the heating of feed water by means of heat that would
otherwise be wasted may be computed from the formula:

100 (t − ti)
Fuel saving per cent = –––––––––––––––––– (1)
H + 32 − ti

where, t = temperature of feed water after heating, ti = temperature of feed water before
heating, and H = total heat above 32 degrees per pound of steam at the boiler pressure.
Values of H may be found in Table 23. Table 17 has been computed from this formula
to show the fuel saving under the conditions assumed with the boiler operating at 180
pounds gauge pressure.

TABLE 17

SAVING IN FUEL, IN PER CENT, BY HEATING FEED WATER
GAUGE PRESSURE 180 POUNDS
Init’l Final Temperature—Degrees Init’l Final Temperature—Degrees
Temp. Fahrenheit Temp. Fahrenheit
° °
Fahr. 120 140 160 180 200 250 300 Fahr. 120 140 160 180 200 250 300

32 7.359.02 10.69 12.36 14.0418.20 22.38 95 2.203.975.73 7.499.25 13.6618.07
35 7.128.79 10.46 12.14 13.8218.00 22.18 100 1.773.545.31 7.088.85 13.2817.70
40 6.728.41 10.09 11.77 13.4517.65 21.86 110 .892.684.47 6.258.04 12.5016.97
45 6.338.02 9.71 11.40 13.0817.30 21.52 120 .001.803.61 5.417.21 11.71 16.22
50 5.937.63 9.32 11.02 12.7216.95 21.19 130 .912.73 4.556.37 10.9115.46
55 5.537.24 8.94 10.64 12.3416.60 20.86 140 .001.84 3.675.51 10.0914.68
60 5.136.84 8.55 10.27 11.97 16.24 20.52 150 .93 2.784.63 9.2613.89
65 4.726.44 8.16 9.87 11.59 15.88 20.18 160 .00 1.873.74 8.4113.09
70 4.316.04 7.77 9.48 11.21 15.52 19.83 170 .942.83 7.5512.27
75 3.905.64 7.36 9.09 10.8215.16 19.48 180 .001.91 6.67 11.43
80 3.485.22 6.96 8.70 10.4414.79 19.13 190 .96 5.7710.58
85 3.064.80 6.55 8.30 10.0514.41 18.78 200 .00 4.86 9.71
90 2.634.39 6.14 7.89 9.6514.04 18.43 210 3.92 8.82

[Pg 111]

Besides the saving in fuel effected by the use of feed water heaters, other advantages
are secured. The time required for the conversion of water into steam is diminished and
the steam capacity of the boiler thereby increased. Further, the feeding of cold water
into a boiler has a tendency toward the setting up of temperature strains, which are
diminished in proportion as the temperature of the feed approaches that of the steam.
An important additional advantage of heating feed water is that in certain types of
heaters a large portion of the scale forming ingredients are precipitated before entering
the boiler, with a consequent saving in cleaning and losses through decreased efficiency
and capacity.

In general, feed water heaters may be divided into closed heaters, open heaters and
economizers; the first two depend for their heat upon exhaust, or in some cases live
steam, while the last class utilizes the heat of the waste flue gases to secure the same
result. The question of the type of apparatus to be installed is dependent upon the
conditions attached to each individual case.

In closed heaters the feed water and the exhaust steam do not come into actual contact
with each other. Either the steam or the water passes through tubes surrounded by the
other medium, as the heater is of the steam-tube or water-tube type. A closed heater is
best suited for water free from scale-forming matter, as such matter soon clogs the
passages. Cleaning such heaters is costly and the efficiency drops off rapidly as scale
forms. A closed heater is not advisable where the engines work intermittently, as is the
case with mine hoisting engines. In this class of work the frequent coolings between
operating periods and the sudden heatings when operation commences will tend to
loosen the tubes or even pull them apart. For this reason, an open heater, or economizer,
will give more satisfactory service with intermittently operating apparatus.

Open heaters are best suited for waters containing scale-forming matter. Much of the
temporary hardness may be precipitated in the heater and the sediment easily removed.
Such heaters are frequently used with a reagent for precipitating permanent hardness in
the combined heat and chemical treatment of feed water. The so-called live steam
purifiers are open heaters, the water being raised to the boiling temperature and the
carbonates and a portion of the sulphates being precipitated. The disadvantage of this
class of apparatus is that some of the sulphates remain in solution to be precipitated as
scale when concentrated in the boiler. Sufficient concentration to have such an effect,
however, may often be prevented by frequent blowing down.

Economizers find their largest field where the design of the boiler is such that the
maximum possible amount of heat is not extracted from the gases of combustion. The
more wasteful the boiler, the greater the saving effected by the use of the economizer,
and it is sometimes possible to raise the temperature of the feed water to that of high
pressure steam by the installation of such an apparatus, the saving amounting in some
cases to as much as 20 per cent. The fuel used bears directly on the question of the
advisability of an economizer installation, for when oil is the fuel a boiler efficiency of
80 per cent or over is frequently realized, an efficiency which would leave a small
opportunity for a commercial gain through the addition of an economizer.

From the standpoint of space requirements, economizers are at a disadvantage in that
they are bulky and require a considerable increase over space occupied by a heater of
the exhaust type. They also require additional brickwork or a metal casing, which
[Pg 112] increases the cost. Sometimes, too, the frictional resistance of the gases through
an economizer make its adaptability questionable because of the draft conditions. When
figuring the net return on economizer investment, all of these factors must be
considered.

When the feed water is such that scale will quickly encrust the economizer and throw it
out of service for cleaning during an excessive portion of the time, it will be necessary
to purify water before introducing it into an economizer to make it earn a profit on the
investment.

From the foregoing, it is clearly indicated that it is impossible to make a definite
statement as to the relative saving by heating feed water in any of the three types. Each
case must be worked out independently and a decision can be reached only after an
exhaustive study of all the conditions affecting the case, including the time the plant
will be in service and probable growth of the plant. When, as a result of such study, the
possible methods for handling the problem have been determined, the solution of the
best apparatus can be made easily by the balancing of the saving possible by each
method against its first cost, depreciation, maintenance and cost of operation.

Feeding of Water—The choice of methods to be used in introducing feed water into a
boiler lies between an injector and a pump. In most plants, an injector would not be
economical, as the water fed by such means must be cold, a fact which makes
impossible the use of a heater before the water enters the injector. Such a heater might
be installed between the injector and the boiler but as heat is added to the water in the
injector, the heater could not properly fulfill its function.

TABLE 18 The
inje
COMPARISON OF PUMPS AND INJECTORS ctor,
Method of Supplying cons
Relative amount of ider
Feed-water to Boiler.
coal required per Saving of fuel over ed
Temperature of feed-water
unit of time, the the amount required only
as delivered to the pump,
amount for a when the boiler in
or to injector,
direct-acting pump, is fed by a the
60 degrees Fahrenheit.
feeding water at direct-acting pump light
Rate of evaporation of
60 degrees without heater of a
boiler, to pounds of water
without a heater, Per Cent com
per pound of coal from and
being taken as unity bine
at 212 degrees Fahrenheit
Direct-acting Pump feeding water d
at 60 degrees without a heater 1.000 .0 heat
er
Injector feeding water at 150
and
degrees without a heater .985 1.5
pum
Injector feeding through p, is
a heater in which the water is clai
heated from 150 to 200 degrees .938 6.2 med
Direct-acting Pump feeding to
water through a heater in which it hav
is heated from 60 to 200 degrees .879 12.1 ea
Geared Pump run from the ther
engine, feeding water through a mal
heater in which it is heated effic
from 60 to 200 degrees .868 13.2 ienc
y of
100 per cent, since all of the heat in the steam used is returned to the boiler with the
water. This claim leads to an erroneous idea. If a pump is used in feeding the water to a
boiler and the heat in the exhaust from the pump is imparted to the feed water, the
pump has as high a thermal efficiency as the injector. The pump has the further
advantage that it uses so much less steam for the forcing of a given quantity [Pg 113] of
water into the boiler that it makes possible a greater saving through the use of the

exhaust from other auxiliaries for heating the feed, which exhaust, if an injector were
used, would be wasted, as has been pointed out.

In locomotive practice, injectors are used because there is no exhaust steam available
for heating the feed, this being utilized in producing a forced draft, and because of
space requirements. In power plant work, however, pumps are universally used for
regular operation, though injectors are sometimes installed as an auxiliary method of
feeding.

Table 18 shows the relative value of injectors, direct-acting steam pumps and pumps
driven from the engine, the data having been obtained from actual experiment. It will
be noted that when feeding cold water direct to the boilers, the injector has a slightly
greater economy but when feeding through a heater, the pump is by far the more
economical.

Auxiliaries—It is the general impression that auxiliaries will take less steam if the
exhaust is turned into the condensers, in this way reducing the back pressure. As a
matter of fact, vacuum is rarely registered on an indicator card taken from the cylinders
of certain types of auxiliaries unless the exhaust connection is short and without bends,
as long pipes and many angles offset the effect of the condenser. On the other hand, if
the exhaust steam from the auxiliaries can be used for heating the feed water, all of the
latent heat less only the loss due to radiation is returned to the boiler and is saved
instead of being lost in the condensing water or wasted with the free exhaust. Taking
into consideration the plant as a whole, it would appear that the auxiliary machinery,
under such conditions, is more efficient than the main engines. [Pg 114]

Portion of 4160 Horse-power Installation of Babcock & Wilcox Boilers at the
Prudential Life Insurance Co. Building, Newark, N. J.

[Pg 115]

STEAM
When a given weight of a perfect gas is compressed or expanded at a constant temperature, the product of the
pressure and volume is a constant. Vapors, which are liquids in aeriform condition, on the other hand, can exist
only at a definite pressure corresponding to each temperature if in the saturated state, that is, the pressure is a
function of the temperature only. Steam is water vapor, and at a pressure of, say, 150 pounds absolute per square
inch saturated steam can exist only at a temperature 358 degrees Fahrenheit. Hence if the pressure of saturated
steam be fixed, its temperature is also fixed, and vice versa .

Saturated steam is water vapor in the condition in which it is generated from water with which it is in contact. Or it
is steam which is at the maximum pressure and density possible at its temperature. If any change be made in the
temperature or pressure of steam, there will be a corresponding change in its condition. If the pressure be increased
or the temperature decreased, a portion of the steam will be condensed. If the temperature be increased or the
pressure decreased, a portion of the water with which the steam is in contact will be evaporated into steam. Steam
will remain saturated just so long as it is of the same pressure and temperature as the water with which it can
remain in contact without a gain or loss of heat. Moreover, saturated steam cannot have its temperature lowered
without a lowering of its pressure, any loss of heat being made up by the latent heat of such portion as will be
condensed. Nor can the temperature of saturated steam be increased except when accompanied by a corresponding
increase in pressure, any added heat being expended in the evaporation into steam of a portion of the water with
which it is in contact.

Dry saturated steam contains no water. In some cases, saturated steam is accompanied by water which is carried
along with it, either in the form of a spray or is blown along the surface of the piping, and the steam is then said to
be wet. The percentage weight of the steam in a mixture of steam and water is called the quality of the steam.
Thus, if in a mixture of 100 pounds of steam and water there is three-quarters of a pound of water, the quality of
the steam will be 99.25.

Heat may be added to steam not in contact with water, such an addition of heat resulting in an increase of
temperature and pressure if the volume be kept constant, or an increase in temperature and volume if the pressure
remain constant. Steam whose temperature thus exceeds that of saturated steam at a corresponding pressure is said
to be superheated and its properties approximate those of a perfect gas.

As pointed out in the chapter on heat, the heat necessary to raise one pound of water from 32 degrees Fahrenheit to
the point of ebullition is called the heat of the liquid . The heat absorbed during ebullition consists of that
necessary to dissociate the molecules, or the inner latent heat , and that necessary to overcome the resistance to the
increase in volume, or the outer latent heat . These two make up the latent heat of evaporation and the sum of this
latent heat of evaporation and the heat of the liquid make the total heat of the steam. These values for various
pressures are given in the steam tables , pages 122 to 127 .

The specific volume of saturated steam at any pressure is the volume in cubic feet of one pound of steam at that
pressure.

The density of saturated steam, that is, its weight per cubic foot, is obviously the reciprocal of the specific volume.
This density varies as the 16 ⁄ 17 power over the [Pg 116] ordinary range of pressures used in steam boiler work and
may be found by the formula, D = .003027 p .941 , which is correct within 0.15 per cent up to 250 pounds pressure.

The relative volume of steam is the ratio of the volume of a given weight to the volume of the same weight of
water at 39.2 degrees Fahrenheit and is equal to the specific volume times 62.427.

As vapors are liquids in their gaseous form and the boiling point is the point of change in this condition, it is clear
that this point is dependent upon the pressure under which the liquid exists. This fact is of great practical
importance in steam condenser work and in many operations involving boiling in an open vessel, since in the latter
case its altitude will have considerable influence. The relation between altitude and boiling point of water is shown
in Table 12 .

The conditions of feed temperature and steam pressure in boiler tests, fuel performances and the like, will be found
to vary widely in different trials. In order to secure a means for comparison of different trials, it is necessary to
reduce all results to some common basis. The method which has been adopted for the reduction to a comparable
basis is to transform the evaporation under actual conditions of steam pressure and feed temperature which exist in
the trial to an equivalent evaporation under a set of standard conditions. These standard conditions presuppose a
feed water temperature of 212 degrees Fahrenheit and a steam pressure equal to the normal atmospheric pressure at
sea level, 14.7 pounds absolute. Under such conditions steam would be generated at a temperature of 212 degrees,
the temperature corresponding to atmospheric pressure at sea level, from water at 212 degrees. The weight of water
which would be evaporated under the assumed standard conditions by exactly the amount of heat absorbed by the
boiler under actual conditions existing in the trial, is, therefore, called the equivalent evaporation “from and at 212
degrees.”

The factor for reducing the weight of water actually converted into steam from the temperature of the feed, at the
steam pressure existing in the trial, to the equivalent evaporation under standard conditions is called the factor of
evaporation. This factor is the ratio of the total heat added to one pound of steam under the standard conditions to
the heat added to each pound of steam in heating the water from the temperature of the feed in the trial to the
temperature corresponding to the pressure existing in the trial. This heat added is obviously the difference between
the total heat of evaporation of the steam at the pressure existing in the trial and the heat of the liquid in the water
at the temperature at which it was fed in the trial. To illustrate by an example:

In a boiler trial the temperature of the feed water is 60 degrees Fahrenheit and the pressure under which steam is
delivered is 160.3 pounds gauge pressure or 175 pounds absolute pressure. The total heat of one pound of steam at
175 pounds pressure is 1195.9 B. t. u. measured above the standard temperature of 32 degrees Fahrenheit. But the
water fed to the boiler contained 28.08 B. t. u. as the heat of the liquid measured above 32 degrees Fahrenheit.
Therefore, to each pound of steam there has been added 1167.82 B. t. u. To evaporate one pound of water under
standard conditions would, on the other hand, have required but 970.4 B. t. u., which, as described, is the latent
heat of evaporation at 212 degrees Fahrenheit. Expressed differently, the total heat of one pound of steam at the
pressure corresponding to a temperature of 212 degrees is 1150.4 B. t. u. One pound of water at 212 degrees
[Pg 117] contains 180 B. t. u. of sensible heat above 32 degrees Fahrenheit. Hence, under standard conditions, 1150.4
- 180 = 970.4 B. t. u. is added in the changing of one pound of water into steam at atmospheric pressure and a
temperature of 212 degrees. This is in effect the definition of the latent heat of evaporation.

Hence, if conditions of the trial had been standard, only 970.4 B. t. u. would be required and the ratio of 1167.82 to
970.4 B. t. u. is the ratio determining the factor of evaporation. The factor in the assumed case is 1167.82 ÷ 970.4 =
1.2034 and if the same amount of heat had been absorbed under standard conditions as was absorbed in the trial
condition, 1.2034 times the amount of steam would have been generated. Expressed as a formula for use with any
set of conditions, the factor is,

H−h
F = –––––––––– (2)
970.4
Where H = the total heat of steam above 32 degrees Fahrenheit from steam tables,
h = sensible heat of feed water above 32 degrees Fahrenheit from Table 22 .

In the form above, the factor may be determined with either saturated or superheated steam, provided that in the
latter case values of H are available for varying degrees of superheat and pressures.

Where such values are not available, the form becomes,

H − h + s ( t sup − t sat )
F= (3)
––––––––––––––––––––––––––––––––––

970.4
Where s = mean specific heat of superheated steam at the pressure existing in the trial from saturated steam
to the temperature existing in the trial,
t sup = final temperature of steam,

t sat = temperature of saturated steam, corresponding to pressure existing,
( t sup − t sat ) = degrees of superheat.

The specific heat of superheated steam will be taken up later.

Table 19 gives factors of evaporation for saturated steam boiler trials to cover a large range of conditions. Except
for the most refined work, intermediate values may be determined by interpolation.

Steam gauges indicate the pressure above the atmosphere. As has been pointed out, the atmospheric pressure
changes according to the altitude and the variation in the barometer. Hence, calculations involving the properties of
steam are based on absolute pressures, which are equal to the gauge pressure plus the atmospheric pressure in
pounds to the square inch. This latter is generally assumed to be 14.7 pounds per square inch at sea level, but for
other levels it must be determined from the barometric reading at that place.

Vacuum gauges indicate the difference, expressed in inches of mercury, between atmospheric pressure and the
pressure within the vessel to which the gauge is attached. For approximate purposes, 2.04 inches height of mercury
may be considered equal to a pressure of one pound per square inch at the ordinary temperatures at which mercury
gauges are used. Hence for any reading of the vacuum gauge in inches, G, the absolute pressure for any barometer
reading in inches, B, will be (B - G) ÷ 2.04. If the barometer is 30 inches measured at ordinary temperatures and
not corrected to 32 degrees Fahrenheit and the vacuum gauge 24 inches, the absolute pressure will be (30 - 24) ÷
2.04 = 2.9 pounds per square inch.

[Pg 118]

TABLE 19

FACTORS OF EVAPORATION
CALCULATED FROM MARKS AND DAVIS TABLES
Feed
Temp- Steam Pressure by Gauge
erature
Degrees
Fahren- 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240
heit
32 1.2143 1.2170 1.2194 1.2215 1.2233 1.2233 1.2265 1.2280 1.2292 1.2304 1.2314 1.2323 1.2333 1.2342 1.2350 1.2357 1.2364 1.2372 1.2378 1.2384 1
40 1.2060 1.2087 1.2111 1.2131 1.2150 1.2168 1.2181 1.2196 1.2209 1.2221 1.2231 1.2241 1.2250 1.2259 1.2267 1.2274 1.2282 1.2289 1.2295 1.2301 1
50 1.1957 1.1984 1.2008 1.2028 1.2047 1.2065 1.2079 1.2093 1.2106 1.2117 1.2128 1.2137 1.2147 1.2156 1.2164 1.2171 1.2178 1.2186 1.2192 1.2198 1
60 1.1854 1.1881 1.1905 1.1925 1.1944 1.1961 1.1976 1.1990 1.2003 1.2014 1.2025 1.2034 1.2044 1.2053 1.2061 1.2068 1.2075 1.2083 1.2089 1.2095 1
70 1.1750 1.1778 1.1802 1.1822 1.1841 1.1859 1.1873 1.1887 1.1900 1.1911 1.1922 1.1931 1.1941 1.1950 1.1958 1.1965 1.1972 1.1980 1.1986 1.1992 1
80 1.1649 1.1675 1.1699 1.1720 1.1738 1.1756 1.1770 1.1785 1.1797 1.1809 1.1819 1.1828 1.1838 1.1847 1.1855 1.1863 1.1869 1.1877 1.1883 1.1889 1
90 1.1545 1.1572 1.1596 1.1617 1.1636 1.1653 1.1668 1.1682 1.1695 1.1706 1.1717 1.1725 1.1735 1.1744 1.1750 1.1760 1.1766 1.1774 1.1780 1.1786 1
100 1.1443 1.1470 1.1493 1.1514 1.1533 1.1550 1.1565 1.1579 1.1592 1.1603 1.1614 1.1623 1.1633 1.1642 1.1650 1.1657 1.1664 1.1671 1.1678 1.1684 1
110 1.1340 1.1367 1.1391 1.1411 1.1430 1.1448 1.1462 1.1477 1.1489 1.1500 1.1511 1.1520 1.1530 1.1539 1.1547 1.1554 1.1562 1.1569 1.1575 1.1581 1
120 1.1237 1.1264 1.1288 1.1309 1.1327 1.1345 1.1359 1.1374 1.1386 1.1398 1.1408 1.1418 1.1427 1.1436 1.1444 1.1452 1.1459 1.1466 1.1472 1.1478 1
130 1.1134 1.1161 1.1185 1.1206 1.1225 1.1242 1.1257 1.1271 1.1284 1.1295 1.1305 1.1315 1.1324 1.1333 1.1341 1.1349 1.1356 1.1363 1.1369 1.1375 1
140 1.1031 1.1058 1.1082 1.1103 1.1122 1.1139 1.1154 1.1168 1.1181 1.1192 1.1203 1.1212 1.1221 1.1230 1.1239 1.1246 1.1253 1.1260 1.1266 1.1272 1
150 1.0928 1.0955 1.0979 1.1000 1.1019 1.1036 1.1051 1.1065 1.1078 1.1089 1.1099 1.1109 1.1118 1.1127 1.1136 1.1143 1.1150 1.1157 1.1163 1.1169 1
160 1.0825 1.0852 1.0876 1.0897 1.0916 1.0933 1.0948 1.0962 1.0975 1.0986 1.0997 1.1006 1.1015 1.1024 1.1033 1.1040 1.1047 1.1054 1.1060 1.1066 1
170 1.0722 1.0749 1.0773 1.0794 1.0813 1.0830 1.0845 1.0859 1.0872 1.0883 1.0893 1.0903 1.0912 1.0921 1.0930 1.0937 1.0944 1.0951 1.0957 1.0963 1
180 1.0619 1.0646 1.0670 1.0691 1.0709 1.0727 1.0741 1.0756 1.0768 1.0780 1.0790 1.0800 1.0809 1.0818 1.0826 1.0834 1.0841 1.0848 1.0854 1.0860 1
190 1.0516 1.0543 1.0567 1.0587 1.0606 1.0624 1.0638 1.0653 1.0665 1.0676 1.0687 1.0696 1.0706 1.0715 1.0723 1.0730 1.0737 1.0745 1.0751 1.0757 1
200 1.0412 1.0439 1.0463 1.0484 1.0503 1.0520 1.0535 1.0549 1.0562 1.0573 1.0584 1.0593 1.0602 1.0611 1.0620 1.0627 1.0634 1.0641 1.0647 1.0653 1
210 1.0309 1.0336 1.0360 1.0380 1.0399 1.0417 1.0432 1.0446 1.0458 1.0469 1.0480 1.0489 1.0499 1.0508 1.0516 1.0523 1.0530 1.0538 1.0544 1.0550 1

[Pg 119]

The temperature, pressure and other properties of steam for varying amounts of vacuum and the pressure above
vacuum corresponding to each inch of reading of the vacuum gauge are given in Table 20 .

TABLE 20

PROPERTIES OF SATURATED STEAM FOR VARYING AMOUNTS OF VACUUM
CALCULATED FROM MARKS AND DAVIS TABLE
Absolute Temperature Heat of the Liquid Latent Heat Total Heat Density or Weight
Vacuum
Pressure Degrees Above 32 Degrees Above 32 Degrees Above 32 Degrees per Cubic Foot
Ins. Hg.
Pounds Fahrenheit B. t. u. B. t. u. B. t. u. Pounds
29.5 .207 54.1 22.18 1061.0 1083.2 0.000678
29 .452 76.6 44.64 1048.7 1093.3 0.001415
28.5 .698 90.1 58.09 1041.1 1099.2 0.002137
28 .944 99.9 67.87 1035.6 1103.5 0.002843
27 1.44 112.5 80.4 1028.6 1109.0 0.00421
26 1.93 124.5 92.3 1022.0 1114.3 0.00577
25 2.42 132.6 100.5 1017.3 1117.8 0.00689
24 2.91 140.1 108.0 1013.1 1121.1 0.00821
22 3.89 151.7 119.6 1006.4 1126.0 0.01078
20 4.87 161.1 128.9 1001.0 1129.9 0.01331
18 5.86 168.9 136.8 996.4 1133.2 0.01581
16 6.84 175.8 143.6 992.4 1136.0 0.01827
14 7.82 181.8 149.7 988.8 1138.5 0.02070
12 8.80 187.2 155.1 985.6 1140.7 0.02312
10 9.79 192.2 160.1 982.6 1142.7 0.02554
5 12.24 202.9 170.8 976.0 1146.8 0.03148

From the steam tables , the condensed Table 21 of the properties of steam at different pressures may be
constructed. From such a table there may be drawn the following conclusions.

TABLE 21 As the pressure and temperature increase, the latent heat
decreases. This decrease, however, is less rapid than the
VARIATION IN PROPERTIES OF corresponding increase in the heat of the liquid and hence the
SATURATED STEAM WITH PRESSURE total heat increases with an increase in the pressure and
Pressure Temperature Heat of Latent Total temperature. The percentage increase in the total heat is small,
Pounds Degrees Liquid Heat Heat being 0.5, 3.1, and 4.7 per cent for 20, 100, and 300 pounds
Absolute Fahrenheit B. t. u. B. t. u. B. t. u. absolute pressure respectively above the total heat in one pound
14.7 212.0 180.0 970.4 1150.4 of steam at 14.7 pounds absolute. The temperatures, on the
20.0 228.0 196.1 960.0 1156.2 other hand, increase at the rates of 7.5, 54.6, and 96.9 per cent.
The efficiency of a perfect steam engine is proportional to the
100.0 327.8 298.3 888.0 1186.3
expression ( t - t 1 )/ t in which t and t 1 are the absolute
300.0 417.5 392.7 811.3 1204.1 temperatures of the saturated steam at admission and exhaust
respectively. While actual engines only approximate the ideal
engine in efficiency, yet they follow the same general law. Since the exhaust temperature cannot be lowered
beyond present practice, it follows that the only available method of increasing the efficiency is by an increase in
the temperature of the steam at admission. How this may be [Pg 120] accomplished by an increase of pressure is
clearly shown, for the increase of fuel necessary to increase the pressure is negligible, as shown by the total heat,
while the increase in economy, due to the higher pressure, will result directly from the rapid increase of the
corresponding temperature.

TABLE 22

HEAT UNITS PER POUND AND WEIGHT PER CUBIC FOOT OF WATER
BETWEEN 32 DEGREES FAHRENHEIT AND 340 DEGREES FAHRENHEIT
Temp- Temp- Temp- Temp-
Heat Weight Heat Weight Heat Weight Heat Weight
erature erature erature erature
Units per Units per Units per Units per
Degrees Degrees Degrees Degrees
per Cubic per Cubic per Cubic per Cubic
Fahren- Fahren- Fahren- Fahren-
Pound Foot Pound Foot Pound Foot Pound Foot
heit heit heit heit

32 0.00 62.42 89 57.00 62.13 146 113.86 61.27 203 170.95 60.05
33 1.01 62.42 90 58.00 62.12 147 114.86 61.25 204 171.96 60.02
34 2.01 62.42 91 59.00 62.11 148 115.86 61.24 205 172.96 60.00
35 3.02 62.43 92 60.00 62.09 149 116.86 61.22 206 173.97 59.98
36 4.03 62.43 93 60.99 62.08 150 117.86 61.20 207 174.97 59.95
37 5.04 62.43 94 61.99 62.07 151 118.86 61.18 208 175.98 59.93
38 6.04 62.43 95 62.99 62.06 152 119.86 61.16 209 176.98 59.90
39 7.05 62.43 96 63.98 62.05 153 120.86 61.14 210 177.99 59.88
40 8.05 62.43 97 64.98 62.04 154 121.86 61.12 211 178.99 59.85
41 9.05 62.43 98 65.98 62.03 155 122.86 61.10 212 180.00 59.83
42 10.06 62.43 99 66.97 62.02 156 123.86 61.08 213 181.0 59.80
43 11.06 62.43 100 67.97 62.00 157 124.86 61.06 214 182.0 59.78
44 12.06 62.43 101 68.97 61.99 158 125.86 61.04 215 183.0 59.75
45 13.07 62.42 102 69.96 61.98 159 126.86 61.02 216 184.0 59.73
46 14.07 62.42 103 70.96 61.97 160 127.86 61.00 217 185.0 59.70
47 15.07 62.42 104 71.96 61.95 161 128.86 60.98 218 186.1 59.68
48 16.07 62.42 105 72.95 61.94 162 129.86 60.96 219 187.1 59.65
49 17.08 62.42 106 73.95 61.93 163 130.86 60.94 220 188.1 59.63
50 18.08 62.42 107 74.95 61.91 164 131.86 60.92 221 189.1 59.60
Temp- Temp- Temp- Temp-
Heat Weight Heat Weight Heat Weight Heat Weight
erature erature erature erature
Units per Units per Units per Units per
Degrees Degrees Degrees Degrees
per Cubic per Cubic per Cubic per Cubic
Fahren- Fahren- Fahren- Fahren-
Pound Foot Pound Foot Pound Foot Pound Foot
heit heit heit heit
51 19.08 62.41 108 75.95 61.90 165 132.86 60.90 222 190.1 59.58
52 20.08 62.41 109 76.94 61.88 166 133.86 60.88 223 191.1 59.55
53 21.08 62.41 110 77.94 61.86 167 134.86 60.86 224 192.1 59.53
54 22.08 62.40 111 78.94 61.85 168 135.86 60.84 225 193.1 59.50
55 23.08 62.40 112 79.93 61.83 169 136.86 60.82 226 194.1 59.48
56 24.08 62.39 113 80.93 61.82 170 137.87 60.80 227 195.2 59.45
57 25.08 62.39 114 81.93 61.80 171 138.87 60.78 228 196.2 59.42
58 26.08 62.38 115 82.92 61.79 172 139.87 60.76 229 197.2 59.40
59 27.08 62.37 116 83.92 61.77 173 140.87 60.73 230 198.2 59.37
60 28.08 62.37 117 84.92 61.75 174 141.87 60.71 231 199.2 59.34
61 29.08 62.36 118 85.92 61.74 175 142.87 60.69 232 200.2 59.32
62 30.08 62.36 119 86.91 61.72 176 143.87 60.67 233 201.2 59.29
63 31.07 62.35 120 87.91 61.71 177 144.88 60.65 234 202.2 59.27
64 32.07 62.35 121 88.91 61.69 178 145.88 60.62 235 203.2 59.24
65 33.07 62.34 122 89.91 61.68 179 146.88 60.60 236 204.2 59.21
66 34.07 62.33 123 90.90 61.66 180 147.88 60.58 237 205.3 59.19
67 35.07 62.33 124 91.90 61.65 181 148.88 60.56 238 206.3 59.16
68 36.07 62.32 125 92.90 61.63 182 149.89 60.53 239 207.3 59.14
69 37.06 62.31 126 93.90 61.61 183 150.89 60.51 240 208.3 59.11
Temp- Temp- Temp- Temp-
Heat Weight Heat Weight Heat Weight Heat Weight
erature erature erature erature
Units per Units per Units per Units per
Degrees Degrees Degrees Degrees
per Cubic per Cubic per Cubic per Cubic
Fahren- Fahren- Fahren- Fahren-
Pound Foot Pound Foot Pound Foot Pound Foot
heit heit heit heit
70 38.06 62.30 127 94.89 61.59 184 151.89 60.49 241 209.3 59.08
71 39.06 62.30 128 95.89 61.58 185 152.89 60.47 242 210.3 59.05
72 40.05 62.29 129 96.89 61.56 186 153.89 60.45 243 211.4 59.03
73 41.05 62.28 130 97.89 61.55 187 154.90 60.42 244 212.4 59.00

74 42.05 62.27 131 98.89 61.53 188 155.90 60.40 245 213.4 58.97
75 42.05 62.26 132 99.88 61.52 189 156.90 60.38 246 214.4 58.94
76 44.04 62.26 133 100.88 61.50 190 157.91 60.36 247 215.4 58.91
77 45.04 62.25 134 101.88 61.49 191 158.91 60.33 248 216.4 58.89
78 46.04 62.24 135 102.88 61.47 192 159.91 60.31 249 217.4 58.86
79 47.04 62.23 136 103.88 61.45 193 160.91 60.29 250 218.5 58.83
80 48.03 62.22 137 104.87 61.43 194 161.92 60.27 260 228.6 58.55
81 49.03 62.21 138 105.87 61.41 195 162.92 60.24 270 238.8 58.26
82 50.03 62.20 139 106.87 61.40 196 163.92 60.22 280 249.0 57.96
83 51.02 62.19 140 107.87 61.38 197 164.93 60.19 290 259.3 57.65
84 52.02 62.18 141 108.87 61.36 198 165.93 60.17 300 269.6 57.33
85 53.02 62.17 142 109.87 61.34 199 166.94 60.15 310 279.9 57.00
86 54.01 62.16 143 110.87 61.33 200 167.94 60.12 320 290.2 56.66
87 55.01 62.15 144 111.87 61.31 201 168.94 60.10 330 300.6 56.30
88 56.01 62.14 145 112.86 61.29 202 169.95 60.07 340 311.0 55.94

[Pg 121]

The gain due to superheat cannot be predicted from the formula for the efficiency of a perfect steam engine given
on page 119 . This formula is not applicable in cases where superheat is present since only a relatively small
amount of the heat in the steam is imparted at the maximum or superheated temperature.

The advantage of the use of high pressure steam may be also indicated by considering the question from the aspect
of volume. With an increase of pressure comes a decrease in volume, thus one pound of saturated steam at 100
pounds absolute pressure occupies 4.43 cubic feet, while at 200 pounds pressure it occupies 2.29 cubic feet. If
then, in separate cylinders of the same dimensions, one pound of steam at 100 pounds absolute pressure and one
pound at 200 pounds absolute pressure enter and are allowed to expand to the full volume of each cylinder, the
high-pressure steam, having more room and a greater range for expansion than the low-pressure steam, will thus
do more work. This increase in the amount of work, as was the increase in temperature, is large relative to the
additional fuel required as indicated by the total heat. In general, it may be stated that the fuel required to impart a
given amount of heat to a boiler is practically independent of the steam pressure, since the temperature of the fire
is so high as compared with the steam temperature that a variation in the steam temperature does not produce an
appreciable effect.

The formulae for the algebraic expression of the relation between saturated steam pressures, temperatures and
steam volumes have been up to the present time empirical. These relations have, however, been determined by
experiment and, from the experimental data, tables have been computed which render unnecessary the use of
empirical formulae. Such formulae may be found in any standard work of thermo-dynamics. The following tables
cover all practical cases.

Table 22 gives the heat units contained in water above 32 degrees Fahrenheit at different temperatures.

Table 23 gives the properties of saturated steam for various pressures.

Table 24 gives the properties of superheated steam at various pressures and temperatures.

These tables are based on those computed by Lionel S. Marks and Harvey N. Davis, these being generally
accepted as being the most correct.

[Pg 122]

TABLE 23

PROPERTIES OF SATURATED STEAM REPRODUCED BY PERMISSION FROM
MARKS AND DAVIS “STEAM TABLES AND DIAGRAMS”
(Copyright, 1909, by Longmans, Green & Co.)

Pressure, Temperature Specific Volume Heat of the Latent Heat of Total Heat of
Pounds Absolute Degrees F. Cu. Ft. per Pound Liquid, B. t. u. Evap., B. t. u. Steam, B. t. u.
1 101.83 333.0 69.8 1034.6 1104.4
2 126.15 173.5 94.0 1021.0 1115.0
3 141.52 118.5 109.4 1012.3 1121.6
4 153.01 90.5 120.9 1005.7 1126.5
5 162.28 73.33 130.1 1000.3 1130.5
6 170.06 61.89 137.9 995.8 1133.7
7 176.85 53.56 144.7 991.8 1136.5
8 182.86 47.27 150.8 988.2 1139.0
9 188.27 42.36 156.2 985.0 1141.1
10 193.22 38.38 161.1 982.0 1143.1
11 197.75 35.10 165.7 979.2 1144.9
12 201.96 32.36 169.9 976.6 1146.5
13 205.87 30.03 173.8 974.2 1148.0
14 209.55 28.02 177.5 971.9 1149.4
15 213.0 26.27 181.0 969.7 1150.7
16 216.3 24.79 184.4 967.6 1152.0
17 219.4 23.38 187.5 965.6 1153.1
18 222.4 22.16 190.5 963.7 1154.2
19 225.2 21.07 193.4 961.8 1155.2
20 228.0 20.08 196.1 960.0 1156.2
22 233.1 18.37 201.3 956.7 1158.0
24 237.8 16.93 206.1 953.5 1159.6
26 242.2 15.72 210.6 950.6 1161.2
28 246.4 14.67 214.8 947.8 1162.6
30 250.3 13.74 218.8 945.1 1163.9
32 254.1 12.93 222.6 942.5 1165.1
34 257.6 12.22 226.2 940.1 1166.3
36 261.0 11.58 229.6 937.7 1167.3
38 264.2 11.01 232.9 935.5 1168.4
40 267.3 10.49 236.1 933.3 1169.4
42 270.2 10.02 239.1 931.2 1170.3
44 273.1 9.59 242.0 929.2 1171.2
46 275.8 9.20 244.8 927.2 1172.0
48 278.5 8.84 247.5 925.3 1172.8
50 281.0 8.51 250.1 923.5 1173.6
52 283.5 8.20 252.6 921.7 1174.3
Pressure, Temperature Specific Volume Heat of the Latent Heat of Total Heat of
Pounds Absolute Degrees F. Cu. Ft. per Pound Liquid, B. t. u. Evap., B. t. u. Steam, B. t. u.
54 285.9 7.91 255.1 919.9 1175.0
56 288.2 7.65 257.5 918.2 1175.7
58 290.5 7.40 259.8 916.5 1176.4
60 292.7 7.17 262.1 914.9 1177.0
62 294.9 6.95 264.3 913.3 1177.6
64 297.0 6.75 266.4 911.8 1178.2
66 299.0 6.56 268.5 910.2 1178.8
68 301.0 6.38 270.6 908.7 1179.3
70 302.9 6.20 272.6 907.2 1179.8 [Pg 123]
72 304.8 6.04 274.5 905.8 1180.4
74 306.7 5.89 276.5 904.4 1180.9

76 308.5 5.74 278.3 903.0 1181.4
78 310.3 5.60 280.2 901.7 1181.8
80 312.0 5.47 282.0 900.3 1182.3
82 313.8 5.34 283.8 899.0 1182.8
84 315.4 5.22 285.5 897.7 1183.2
86 317.1 5.10 287.2 896.4 1183.6
88 318.7 5.00 288.9 895.2 1184.0
90 320.3 4.89 290.5 893.9 1184.4
92 321.8 4.79 292.1 892.7 1184.8
94 323.4 4.69 293.7 891.5 1185.2
96 324.9 4.60 295.3 890.3 1185.6
98 326.4 4.51 296.8 889.2 1186.0
100 327.8 4.429 298.3 888.0 1186.3
105 331.4 4.230 302.0 885.2 1187.2
110 334.8 4.047 305.5 882.5 1188.0
115 338.1 3.880 309.0 879.8 1188.8
120 341.3 3.726 312.3 877.2 1189.6
125 344.4 3.583 315.5 874.7 1190.3
130 347.4 3.452 318.6 872.3 1191.0
135 350.3 3.331 321.7 869.9 1191.6
140 353.1 3.219 324.6 867.6 1192.2
145 355.8 3.112 327.4 865.4 1192.8
150 358.5 3.012 330.2 863.2 1193.4
155 361.0 2.920 332.9 861.0 1194.0
160 363.6 2.834 335.6 858.8 1194.5
Pressure, Temperature Specific Volume Heat of the Latent Heat of Total Heat of
Pounds Absolute Degrees F. Cu. Ft. per Pound Liquid, B. t. u. Evap., B. t. u. Steam, B. t. u.
165 366.0 2.753 338.2 856.8 1195.0
170 368.5 2.675 340.7 854.7 1195.4
175 370.8 2.602 343.2 852.7 1195.9
180 373.1 2.533 345.6 850.8 1196.4
185 375.4 2.468 348.0 848.8 1196.8
190 377.6 2.406 350.4 846.9 1197.3
195 379.8 2.346 352.7 845.0 1197.7
200 381.9 2.290 354.9 843.2 1198.1
205 384.0 2.237 357.1 841.4 1198.5
210 386.0 2.187 359.2 839.6 1198.8
215 388.0 2.138 361.4 837.9 1199.2
220 389.9 2.091 363.4 836.2 1199.6
225 391.9 2.046 365.5 834.4 1199.9
230 393.8 2.004 367.5 832.8 1200.2
235 395.6 1.964 369.4 831.1 1200.6
240 397.4 1.924 371.4 829.5 1200.9
245 399.3 1.887 373.3 827.9 1201.2
250 401.1 1.850 375.2 826.3 1201.5 [Pg 124]

Portion of 6100 Horse-power Installation of Babcock & Wilcox Boilers Equipped with Babcock & Wilcox
Chain Grate Stokers at the Campbell Street Plant of the Louisville Railway Co., Louisville, Ky. This
Company Operates a Total of 14,000 Horse Power of Babcock & Wilcox Boilers

[Pg 125]

TABLE 24

PROPERTIES OF SATURATED STEAM REPRODUCED BY
PERMISSION FROM
MARKS AND DAVIS “STEAM TABLES AND DIAGRAMS”
(Copyright, 1909, by Longmans, Green & Co.)
Degrees of Superheat
Pressure
Saturated
Pounds 50 100 150 200 250 300
Steam
Absolute
t 162.3 212.3 262.3 312.3 362.3 412.3 462.3
5v 73.3 79.7 85.7 91.8 97.8 103.8 109.8
h 1130.5 1153.5 1176.4 1199.5 1222.5 1245.6 1268.7
t 193.2 243.2 293.2 343.2 393.2 443.2 493.2
10 v 38.4 41.5 44.6 47.7 50.7 53.7 56.7
h 1143.1 1166.3 1189.5 1212.7 1236.0 1259.3 1282.5
t 213.0 263.0 313.0 363.0 413.0 463.0 513.0
15 v 26.27 28.40 30.46 32.50 34.53 36.56 38.58
h 1150.7 1174.2 1197.6 1221.0 1244.4 1267.7 1291.1
t 228.0 278.0 328.0 378.0 428.0 478.0 528.0
20 v 20.08 21.69 23.25 24.80 26.33 27.85 29.37
h 1156.2 1179.9 1203.5 1227.1 1250.6 1274.1 1297.6
t 240.1 290.1 340.1 390.1 440.1 490.1 540.1
25 v 16.30 17.60 18.86 20.10 21.32 22.55 23.77
h 1160.4 1184.4 1208.2 1231.9 1255.6 1279.2 1302.8
t 250.4 300.4 350.4 400.4 450.4 500.4 550.4
30 v 13.74 14.83 15.89 16.93 17.97 18.99 20.00
h 1163.9 1188.1 1212.1 1236.0 1259.7 1283.4 1307.1

t 259.3 309.3 359.3 409.3 459.3 509.3 559.3
35 v 11.89 12.85 13.75 14.65 15.54 16.42 17.30
h 1166.8 1191.3 1215.4 1239.4 1263.3 1287.1 1310.8
t 267.3 317.3 367.3 417.3 467.3 517.3 567.3
40 v 10.49 11.33 12.13 12.93 13.70 14.48 15.25
h 1169.4 1194.0 1218.4 1242.4 1266.4 1290.3 1314.1
t 274.5 324.5 374.5 424.5 474.5 524.5 574.5
45 v 9.39 10.14 10.86 11.57 12.27 12.96 13.65
h 1171.6 1196.6 1221.0 1245.2 1269.3 1293.2 1317.0
t 281.0 331.0 381.0 431.0 481.0 531.0 581.0
50 v 8.51 9.19 9.84 10.48 11.11 11.74 12.36
h 1173.6 1198.8 1223.4 1247.7 1271.8 1295.8 1319.7
t 287.1 337.1 387.1 437.1 487.1 537.1 587.1
60 v 7.78 8.40 9.00 9.59 10.16 10.73 11.30
h 1175.4 1200.8 1225.6 1250.0 1274.2 1298.1 1322.0
Degrees of Superheat
Pressure
Saturated
Pounds 50 100 150 200 250 300
Steam
Absolute
t 292.7 342.7 392.7 442.7 492.7 542.7 592.7
60 v 7.17 7.75 8.30 8.84 9.36 9.89 10.41
h 1177.0 1202.6 1227.6 1252.1 1276.4 1300.4 1324.3
t 298.0 348.0 398.0 448.0 498.0 548.0 598.0
65 v 6.65 7.20 7.70 8.20 8.69 9.17 9.65
h 1178.5 1204.4 1229.5 1254.0 1278.4 1302.4 1326.4
t 302.9 352.9 402.9 452.9 502.9 552.9 602.9
70 v 6.20 6.71 7.18 7.65 8.11 8.56 9.01
h 1179.8 1205.9 1231.2 1255.8 1280.2 1304.3 1328.3
t 307.6 357.6 407.6 457.6 507.6 557.6 607.6
75 v 5.81 6.28 6.73 7.17 7.60 8.02 8.44
h 1181.1 1207.5 1232.8 1257.5 1282.0 1306.1 1330.1
t 312.0 362.0 412.0 462.0 512.0 562.0 612.0
80 v 5.47 5.92 6.34 6.75 7.17 7.56 7.95
h 1182.3 1208.8 1234.3 1259.0 1283.6 1307.8 1331.9
t 316.3 366.3 416.3 466.3 516.3 566.3 616.3
85 v 5.16 5.59 6.99 6.38 6.76 7.14 7.51
h 1183.4 1210.2 1235.8 1260.6 1285.2 1309.4 1333.5
t 320.3 370.3 420.3 470.3 520.3 570.3 620.3 [Pg 126]
90 v 4.89 5.29 5.67 6.04 6.40 6.76 7.11
h 1184.4 1211.4 1237.2 1262.0 1286.6 1310.8 1334.9
t 324.1 374.1 424.1 474.1 524.1 574.1 624.1
95 v 4.65 5.03 5.39 5.74 6.09 6.43 6.76
h 1185.4 1212.6 1238.4 1263.4 1288.1 1312.3 1336.4
t 327.8 377.8 427.8 477.8 527.8 577.8 627.8
100 v 4.43 4.79 5.14 5.47 5.80 6.12 6.44
h 1186.3 1213.8 1239.7 1264.7 1289.4 1313.6 1337.8
t 331.4 381.4 431.4 481.4 531.4 581.4 631.4
105 v 4.23 4.58 4.91 5.23 5.54 5.85 6.15
h 1187.2 1214.9 1240.8 1265.9 1290.6 1314.9 1339.1
t 334.8 384.8 434.8 484.8 534.8 584.8 634.8
110 v 4.05 4.38 4.70 5.01 5.31 5.61 5.90
h 1188.0 1215.9 1242.0 1267.1 1291.9 1316.2 1340.4
Degrees of Superheat

Pressure
Saturated
Pounds 50 100 150 200 250 300
Steam
Absolute
t 338.1 388.1 438.1 488.1 538.1 588.1 638.1
115 v 3.88 4.20 4.51 4.81 5.09 5.38 5.66
h 1188.8 1216.9 1243.1 1268.2 1293.0 1317.3 1341.5
t 341.3 391.3 441.3 491.3 541.3 591.3 641.3
120 v 3.73 4.04 4.33 4.62 4.89 5.17 5.44
h 1189.6 1217.9 1244.1 1269.3 1294.1 1318.4 1342.7
t 344.4 394.4 444.4 494.4 544.4 594.4 644.4
125 v 3.58 3.88 4.17 4.45 4.71 4.97 5.23
h 1190.3 1218.8 1245.1 1270.4 1295.2 1319.5 1343.8
t 347.4 397.4 447.4 497.4 547.4 597.4 647.4
130 v 3.45 3.74 4.02 4.28 4.54 4.80 5.05
h 1191.0 1219.7 1246.1 1271.4 1296.2 1320.6 1344.9
t 350.3 400.3 450.3 500.3 550.3 600.3 650.3
135 v 3.33 3.61 3.88 4.14 4.38 4.63 4.87
h 1191.6 1220.6 1247.0 1272.3 1297.2 1321.6 1345.9
t 353.1 403.1 453.1 503.1 553.1 603.1 653.1
140 v 3.22 3.49 3.75 4.00 4.24 4.48 4.71
h 1192.2 1221.4 1248.0 1273.3 1298.2 1322.6 1346.9
t 355.8 405.8 455.8 505.8 555.8 605.8 655.8
145 v 3.12 3.38 3.63 3.87 4.10 4.33 4.56
h 1192.8 1222.2 1248.8 1274.2 1299.1 1323.6 1347.9
t 358.5 408.5 458.5 508.5 558.5 608.5 658.5
150 v 3.01 3.27 3.50 3.75 3.97 4.19 4.41
h 1193.4 1223.0 1249.6 1275.1 1300.0 1324.5 1348.8
t 361.0 411.0 461.0 511.0 561.0 611.0 661.0
155 v 2.92 3.17 3.41 3.63 3.85 4.06 4.28
h 1194.0 1223.6 1250.5 1276.0 1300.8 1325.3 1349.7
t 363.6 413.6 463.6 513.6 563.6 613.6 663.6
160 v 2.83 3.07 3.30 3.53 3.74 3.95 4.15
h 1194.5 1224.5 1251.3 1276.8 1301.7 1326.2 1350.6
t 366.0 416.0 466.0 516.0 566.0 616.0 666.0
165 v 2.75 2.99 3.21 3.43 3.64 3.84 4.04
h 1195.0 1225.2 1252.0 1277.6 1302.5 1327.1 1351.5
Degrees of Superheat
Pressure
Saturated
Pounds 50 100 150 200 250 300
Steam
Absolute
t 368.5 418.5 468.5 518.5 568.5 618.5 668.5
170 v 2.68 2.91 3.12 3.34 3.54 3.73 3.92
h 1195.4 1225.9 1252.8 1278.4 1303.3 1327.9 1352.3
t 370.8 420.8 470.8 520.8 570.8 620.8 670.8 [Pg 127]
175 v 2.60 2.83 3.04 3.24 3.44 3.63 3.82
h 1195.9 1226.6 1253.6 1279.1 1304.1 1328.7 1353.2
t 373.1 423.1 473.1 523.1 573.1 623.1 673.1
180 v 2.53 2.75 2.96 3.16 3.35 3.54 3.72
h 1196.4 1227.2 1254.3 1279.9 1304.8 1329.5 1353.9
t 375.4 425.4 475.4 525.4 575.4 625.4 675.4
185 v 2.47 2.68 2.89 3.08 3.27 3.45 3.63
h 1196.8 1227.9 1255.0 1280.6 1305.6 1330.2 1354.7
190 t 377.6 427.6 477.6 527.6 577.6 627.6 677.6
v 2.41 2.62 2.81 3.00 3.19 3.37 3.55

h 1197.3 1228.6 1255.7 1281.3 1306.3 1330.9 1355.5
t 379.8 429.8 479.8 529.8 579.8 629.8 679.8
195 v 2.35 2.55 2.75 2.93 3.11 3.29 3.46
h 1197.7 1229.2 1256.4 1282.0 1307.0 1331.6 1356.2
t 381.9 431.9 481.9 531.9 581.9 631.9 681.9
200 v 2.29 2.49 2.68 2.86 3.04 3.21 3.38
h 1198.1 1229.8 1257.1 1282.6 1307.7 1332.4 1357.0
t 384.0 434.0 484.0 534.0 584.0 634.0 684.0
205 v 2.24 2.44 2.62 2.80 2.97 3.14 3.30
h 1198.5 1230.4 1257.7 1283.3 1308.3 1333.0 1357.7
t 386.0 436.0 486.0 536.0 586.0 636.0 686.0
210 v 2.19 2.38 2.56 2.74 2.91 3.07 3.23
h 1198.8 1231.0 1258.4 1284.0 1309.0 1333.7 1358.4
t 388.0 438.0 488.0 538.0 588.0 638.0 688.0
215 v 2.14 2.33 2.51 2.68 2.84 3.00 3.16
h 1199.2 1231.6 1259.0 1284.6 1309.7 1334.4 1359.1
t 389.9 439.9 489.9 539.9 589.9 639.9 689.9
220 v 2.09 2.28 2.45 2.62 2.78 2.94 3.10
h 1199.6 1232.2 1259.6 1285.2 1310.3 1335.1 1359.8
Degrees of Superheat
Pressure
Saturated
Pounds 50 100 150 200 250 300
Steam
Absolute
t 391.9 441.9 491.9 541.9 591.9 641.9 691.9
225 v 2.05 2.23 2.40 2.57 2.72 2.88 3.03
h 1199.9 1232.7 1260.2 1285.9 1310.9 1335.7 1360.3
t 393.8 443.8 493.8 543.8 593.8 643.8 693.8
230 v 2.00 2.18 2.35 2.51 2.67 2.82 2.97
h 1200.2 1233.2 1260.7 1286.5 1311.6 1336.3 1361.0
t 395.6 445.6 495.6 545.6 595.6 645.6 695.6
235 v 1.96 2.14 2.30 2.46 2.62 2.77 2.91
h 1200.6 1233.8 1261.4 1287.1 1312.2 1337.0 1361.7
t 397.4 447.4 497.4 547.4 597.4 647.4 697.4
240 v 1.92 2.09 2.26 2.42 2.57 2.71 2.85
h 1200.9 1234.3 1261.9 1287.6 1312.8 1337.6 1362.3
t 399.3 449.3 499.3 549.3 599.3 649.3 699.3
245 v 1.89 2.05 2.22 2.37 2.52 2.66 2.80
h 1201.2 1234.8 1262.5 1288.2 1313.3 1338.2 1362.9
t 401.0 451.0 501.0 551.0 601.0 651.0 701.0
250 v 1.85 2.02 2.17 2.33 2.47 2.61 2.75
h 1201.5 1235.4 1263.0 1288.8 1313.9 1338.8 1363.5
t 402.8 452.8 502.8 552.8 602.8 652.8 702.8
255 v 1.81 1.98 2.14 2.28 2.43 2.56 2.70
h 1201.8 1235.9 1263.6 1289.3 1314.5 1339.3 1364.1
t = Temperature, degrees Fahrenheit.
v = Specific volume, in cubic feet, per pound.
h = Total heat from water at 32 degrees, B. t. u.

[Pg 128]

Fig. 15. Graphic Method of Determining Moisture Contained in Steam from Calorimeter Readings

[Pg 129]

MOISTURE IN STEAM
The presence of moisture in steam causes a loss, not only in the practical
waste of the heat utilized to raise this moisture from the temperature of the
feed water to the temperature of the steam, but also through the increased
initial condensation in an engine cylinder and through friction and other
actions in a steam turbine. The presence of such moisture also interferes
with proper cylinder lubrication, causes a knocking in the engine and a
water hammer in the steam pipes. In steam turbines it will cause erosion of
the blades.

The percentage by weight of steam in a mixture of steam and water is called
the quality of the steam.

The apparatus used to determine the moisture content of steam is called a
calorimeter though since it may not measure the heat in the steam, the name
is not descriptive of the function of the apparatus. The first form used was
the “barrel calorimeter”, but the liability of error was so great that its use
was abandoned. Modern calorimeters are in general of either the throttling
or separator type.

Throttling Calorimeter—Fig. 14 shows a typical form of throttling
calorimeter. Steam is drawn from a vertical main through the sampling
nipple, passes around the first thermometer cup, then through a one-eighth
inch orifice in a disk between two flanges, and lastly around the second
thermometer cup and to the atmosphere. Thermometers are inserted in the
wells, which should be filled with mercury or heavy cylinder oil.

The instrument and all pipes and fittings leading to it should be thoroughly
insulated to diminish radiation losses. Care must be taken to prevent the
orifice from becoming choked with dirt and to see that no leaks occur. The
exhaust pipe should be short to prevent back pressure below the disk.

When steam passes through an orifice from a higher to a lower pressure, as
is the case with the throttling calorimeter, no external work has to be done

in overcoming a resistance. Hence,
if there is no loss from radiation, the
quantity of heat in the steam will be
exactly the same after passing the
orifice as before passing. If the
higher steam pressure is 160 pounds
gauge and the lower pressure that of
the atmosphere, the total heat in a
pound of dry steam at the former
pressure is 1195.9 B. t. u. and at the
latter pressure 1150.4 B. t. u., a
difference of 45.4 B. t. u. As this
Fig. 14. Throttling Calorimeter heat will still exist in the steam at
and Sampling Nozzle the lower pressure, since there is no
external work done, its effect must
be to superheat the steam. Assuming
the specific heat of superheated steam to be 0.47, each pound passing
through will be superheated 45.4⁄0.47 = 96.6 degrees. If, however, the steam
had contained one per cent of moisture, it would have contained less heat
units per pound than if it were dry. Since the latent heat of steam at 160
[Pg 130] pounds gauge pressure is 852.8 B. t. u., it follows that the one per
cent of moisture would have required 8.5 B. t. u. to evaporate it, leaving
only 45.4 - 8.5 = 36.9 B. t. u. available for superheating; hence, the
superheat would be 36.9⁄0.47 = 78.5 degrees, as against 96.6 degrees for dry
steam. In a similar manner, the degree of superheat for other percentages of
moisture may be determined. The action of the throttling calorimeter is
based upon the foregoing facts, as shown below.

Let H = total heat of one pound of steam at boiler pressure,
L = latent heat of steam at boiler pressure,
h = total heat of steam at reduced pressure after passing orifice,
t1 = temperature of saturated steam at the reduced pressure,
t2 temperature of steam after expanding through the orifice in the
=
disc,
0.47 = the specific heat of saturated steam at atmospheric pressure,
x = proportion by weight of moisture in steam.

The difference in B. t. u. in a pound of steam at the boiler pressure and after
passing the orifice is the heat available for evaporating the moisture content
and superheating the steam. Therefore,

H - h = xL + 0.47(t2 - t1)
H - h - 0.47(t2 - t1)
or x = –––––––––––––––––––––––––––––––– (4)
L

Almost invariably the lower pressure is taken as that of the atmosphere.
Under such conditions, h = 1150.4 and t1 = 212 degrees. The formula thus
becomes:

H - 1150.4 - 0.47(t2 - 212)
x= –––––––––––––––––––––––––––––––––––––––––––– (5)
L

For practical work it is more convenient to dispense with the upper
thermometer in the calorimeter and to measure the pressure in the steam
main by an accurate steam pressure gauge.

A chart may be used for determining the value of x for approximate work
without the necessity for computation. Such a chart is shown in Fig. 15 and
its use is as follows: Assume a gauge pressure of 180 pounds and a
thermometer reading of 295 degrees. The intersection of the vertical line
from the scale of temperatures as shown by the calorimeter thermometer
and the horizontal line from the scale of gauge pressures will indicate
directly the per cent of moisture in the steam as read from the diagonal
scale. In the present instance, this per cent is 1.0.

Sources of Error in the Apparatus—A slight error may arise from the
value, 0.47, used as the specific heat of superheated steam at atmospheric
pressure. This value, however is very nearly correct and any error resulting
from its use will be negligible.

There is ordinarily a larger source of error due to the fact that the stem of
the thermometer is not heated to its full length, to an initial error in the

thermometer and to radiation losses.

With an ordinary thermometer immersed in the well to the 100 degrees
mark, the error when registering 300 degrees would be about 3 degrees and
the true temperature be 303 degrees.[19]

The steam is evidently losing heat through radiation from the moment it
enters the sampling nipple. The heat available for evaporating moisture and
superheating [Pg 131] steam after it has passed through the orifice into the
lower pressure will be diminished by just the amount lost through radiation
and the value of t2, as shown by the calorimeter thermometer, will,
therefore, be lower than if there were no such loss. The method of
correcting for the thermometer and radiation error recommended by the
Power Test Committee of the American Society of Mechanical Engineers is
by referring the readings as found on the boiler trial to a “normal” reading
of the thermometer. This normal reading is the reading of the lower
calorimeter thermometer for dry saturated steam, and should be determined
by attaching the instrument to a horizontal steam pipe in such a way that the
sampling nozzle projects upward to near the top of the pipe, there being no
perforations in the nozzle and the steam taken only through its open upper
end. The test should be made with the steam in a quiescent state and with
the steam pressure maintained as nearly as possible at the pressure observed
in the main trial, the calorimeter thermometer to be the same as was used on
the trial or one exactly similar.

With a normal reading thus obtained for a pressure approximately the same
as existed in the trial, the true percentage of moisture in the steam, that is,
with the proper correction made for radiation, may be calculated as follows:

Let T denote the normal reading for the conditions existing in the trial. The
effect of radiation from the instrument as pointed out will be to lower the
temperature of the steam at the lower pressure. Let x1 represent the
proportion of water in the steam which will lower its temperature an
amount equal to the loss by radiation. Then,

x1 = H - h - 0.47(T - t1)
––––––––––––––––––––––––––––––

L

This amount of moisture, x1 was not in the steam originally but is the result
of condensation in the instrument through radiation. Hence, the true amount
of moisture in the steam represented by X is the difference between the
amount as determined in the trial and that resulting from condensation, or,

X = x - x1
H - h - 0.47(t2 - t1) H - h - 0.47(T - t1)
X = ––––––––––––––––––––––––––––––– - –––––––––––––––––––––––––––––––
L L
0.47(T - t2)
X = –––––––––––––––––––– (6)
L

As T and t2 are taken with the same thermometer under the same set of
conditions, any error in the reading of the thermometers will be
approximately the same for the temperatures T and t2 and the above method
therefore corrects for both the radiation and thermometer errors. The
theoretical readings for dry steam, where there are no losses due to
radiation, are obtainable from formula (5) by letting x = 0 and solving for t2.
The difference between the theoretical reading and the normal reading for
no moisture will be the thermometer and radiation correction to be applied
in order that the correct reading of t2 may be obtained.

For any calorimeter within the range of its ordinary use, such a thermometer
and radiation correction taken from one normal reading is approximately
correct for any conditions with the same or a duplicate thermometer.

The percentage of moisture in the steam, corrected for thermometer error
and radiation and the correction to be applied to the particular calorimeter
used, would be [Pg 132] determined as follows: Assume a gauge pressure in
the trial to be 180 pounds and the thermometer reading to be 295 degrees. A
normal reading, taken in the manner described, gives a value of T = 303
degrees; then, the percentage of moisture corrected for thermometer error
and radiation is,

0.47(303 - 295)
x= ––––––––––––––––––––––––––

845.0
x = 0.45 per cent.

The theoretical reading for dry steam will be,

1197.7 - 1150.4 - 0.47(t2 - 212)
0= ––––––––––––––––––––––––––––––––––––––––––––––––––––

845.0
t2 = 313 degrees.

The thermometer and radiation correction to be applied to the instrument
used, therefore over the ordinary range of pressure is

Correction = 313 - 303 = 10 degrees

The chart may be used in the determination of the correct reading of
moisture percentage and the permanent radiation correction for the
instrument used without computation as follows: Assume the same trial
pressure, feed temperature and normal reading as above. If the normal
reading is found to be 303 degrees, the correction for thermometer and
radiation will be the theoretical reading for dry steam as found from the
chart, less this normal reading, or 10 degrees correction. The correct
temperature for the trial in question is, therefore, 305 degrees. The moisture
corresponding to this temperature and 180 pounds gauge pressure will be
found from the chart to be 0.45 per cent.

There are many forms of throttling calorimeter, all of which work upon the
same principle. The simplest one is probably that shown in Fig. 14. An
extremely convenient and compact design is shown in Fig. 16. This
calorimeter 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. Steam 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 calorimeter 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.

Separating Calorimeter—The
separating calorimeter mechanically
separates the entrained water from the
steam and collects it in a reservoir, where
its amount is [Pg 133] either indicated by a
Fig. 16. Compact Throttling gauge glass or is drained off and
Calorimeter weighed. Fig. 17 shows a calorimeter of
this type. The steam passes out of the
calorimeter through an orifice of known
size so that its total amount can be calculated or it can be weighed. A gauge
is ordinarily provided with this type of calorimeter, which shows the
pressure in its inner chamber and the flow of steam for a given period, this
latter scale being graduated by trial.

The instrument, like a throttling calorimeter, should be well insulated to
prevent losses from radiation.

While theoretically the separating calorimeter is not limited in capacity, it is
well in cases where the percentage of moisture present in the steam is
known to be high, to attach a throttling calorimeter to its exhaust. This, in
effect, is the using of the separating calorimeter as a small separator
between the sampling nozzle and the throttling instrument, and is necessary
to insure the determination of the full percentage of moisture in the steam.
The sum of the percentages shown by the two instruments is the moisture
content of the steam.

The steam passing through a separating calorimeter may be calculated by
Napier’s formula, the size of the orifice being known. There are objections

to such a calculation, however, in
that it is difficult to accurately
determine the areas of such small
orifices. Further, small orifices have
a tendency to become partly closed
by sediment that may be carried by
the steam. The more accurate method
of determining the amount of steam
passing through the instrument is as
follows:

A hose should be attached to the
separator outlet leading to a vessel of
water on a platform scale graduated
to 1⁄100 of a pound. The steam outlet
should be connected to another
vessel of water resting on a second
scale. In each case, the weight of
each vessel and its contents should be
noted. When ready for an
Fig. 17. Separating Calorimeter
observation, the instrument should be
blown out thoroughly so that there
will be no water within the separator.
The separator drip should then be closed and the steam hose inserted into
the vessel of water at the same instant. When the separator has accumulated
a sufficient quantity of water, the valve of the instrument should be closed
and the hose removed from the vessel of water. The separator should be
emptied into the vessel on its scale. The final weight of each vessel and its
contents are to be noted and the differences between the final and original
weights will represent the weight of moisture collected by the separator and
the weight of steam from which the moisture has been taken. The
proportion of moisture can then be calculated from the following formula:

100 w
x = ––––––––––– (7)
W-w

Where x=
per cent moisture in steam,
[Pg 134]
W = weight of steam condensed,
w = weight of moisture as taken out by the separating
calorimeter.

Sampling Nipple—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.

The American Society of Mechanical Engineers recommends a sampling
nozzle made of one-half inch iron pipe closed at the inner end and the
interior 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
actually 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 said that
the perforations should be at least one inch from the inner pipe surface.

A sampling nipple, open at the inner end and unperforated, 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.

Incidental to a test of a 15,000 K. W. steam
engine turbine unit, Mr. H. G. Stott and Mr.
R. G. S. Pigott, finding no experimental data
bearing on the subject of low pressure steam
quality determinations, made a investigation

Fig. 18. Stott and Pigott of the subject and the sampling nozzle
Sampling Nozzle illustrated in Fig. 18 was developed. In
speaking of sampling nozzles in the
determination of the moisture content of low
pressure steam, 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.”

It would appear that the nozzle illustrated is undoubtedly the best that has
been developed for use in the determination of the moisture content of
steam, not only in the case of low, but also in high pressure steam.

Location of Sampling Nozzle—The calorimeter should be located as near
as possible to the point from which the steam is taken and the sampling
nipple should be placed in a section of the main pipe near the boiler and
where there is no chance of moisture pocketing in the pipe. The American
Society of Mechanical Engineers recommends that a sampling nipple, of
which a description has been given, should be located in a vertical main,
rising from the boiler with its closed end extending nearly [Pg 135] across the
pipe. Where non-return valves are used, or where there are horizontal
connections leading from the boiler to a vertical outlet, water may collect at
the lower end of the uptake pipe and be blown upward in a spray which will
not be carried away by the steam owing to a lack of velocity. A sample
taken from the lower part of this pipe will show a greater amount of
moisture than a true sample. With goose-neck connections a small amount
of water may collect on the bottom of the pipe near the upper end where the
inclination is such that the tendency to flow backward is ordinarily
counterbalanced by the flow of steam forward over its surface; but when the
velocity momentarily decreases the water flows back to the lower end of the
goose-neck and increases the moisture at that point, making it an
undesirable location for sampling. In any case, it should be borne in mind
that with low velocities the tendency is for drops of entrained water to settle
to the bottom of the pipe, and to be temporarily broken up into spray
whenever an abrupt bend or other disturbance is met.

Fig. 19. Illustrating the Manner in which Erroneous Calorimeter
Readings may be Obtained
due to Improper Location of Sampling Nozzle

Case 1—Horizontal pipe. Water flows at bottom. If perforations in nozzle are too near
bottom of pipe, water piles against nozzle, flows into calorimeter and gives false reading.
Case 2—If nozzle located too near junction of two horizontal runs, as at a, condensation
from vertical pipe which collects at this point will be thrown against the nozzle by the
velocity of the steam, resulting in a false reading. Nozzle should be located far enough
above junction to be removed from water kept in motion by the steam velocity, as at b.
Case 3—Condensation in bend will be held by velocity of the steam as shown. When
velocity is diminished during firing intervals and the like moisture flows back against
nozzle, a, and false reading is obtained. A true reading will be obtained at b provided
condensation is not blown over on nozzle. Case 4—Where non-return valve is placed
before a bend, condensation will collect on steam line side and water will be swept by
steam velocity against nozzle and false readings result.

Fig. 19 indicates certain locations of sampling nozzles from which
erroneous results will be obtained, the reasons being obvious from a study
of the cuts.

Before taking any calorimeter reading, steam should be allowed to flow
through the instrument freely until it is thoroughly heated. The method of
using a throttling calorimeter is evident from the description of the
instrument given and the principle upon which it works.
[Pg 136]

Babcock & Wilcox Superheater

FOOTNOTES
[19] See Stem Correction, page 80.

[Pg 137]

SUPERHEATED STEAM
Superheated steam, as already stated, is steam the temperature of which exceeds that of
saturated steam at the same pressure. It is produced by the addition of heat to saturated steam
which has been removed from contact with the water from which it was generated. The
properties of superheated steam approximate those of a perfect gas rather than of a vapor.
Saturated steam cannot be superheated when it is in contact with water which is also heated,
neither can superheated steam condense without first being reduced to the temperature of
saturated steam. Just so long as its temperature is above that of saturated steam at a
corresponding pressure it is superheated, and before condensation can take place that
superheat must first be lost through radiation or some other means. Table 24[20] gives such
properties of superheated steam for varying pressures as are necessary for use in ordinary
engineering practice.

Specific Heat of Superheated Steam—The specific heat of superheated steam at atmospheric
pressure and near saturation point was determined by Regnault, in 1862, who gives it the
value of 0.48. Regnault’s value was based on four series of experiments, all at atmospheric
pressure and with about the same temperature range, the maximum of which was 231.1
degrees centigrade. For fifty years after Regnault’s determination, this value was accepted
and applied to higher pressures and temperatures as well as to the range of his experiments.
More recent investigations have shown that the specific heat is not a constant and varies with
both pressure and the temperature. A number of experiments have been made by various
investigators and, up to the present, the most reliable appear to be those of Knoblauch and
Jacob. Messrs. Marks and Davis have used the values as determined by Knoblauch and Jacob
with slight modifications. The first consists in a varying of the curves at low pressures close
to saturation because of thermodynamic evidence and in view of Regnault’s determination at
atmospheric pressure. The second modification is at high degrees of superheat to follow
Holborn’s and Henning’s curve, which is accepted as authentic.

For the sake of convenience, the mean specific heat of superheated steam at various
pressures and temperatures is given in tabulated form in Table 25. These values have been
calculated from Marks and Davis Steam Tables by deducting from the total heat of one
pound of steam at any pressure for any degree of superheat the total heat of one pound of
saturated steam at the same pressure and dividing the difference by the number of degrees of
superheat and, therefore, represent the average specific heat starting from that at saturation to
the value at the particular pressure and temperature.[21] Expressed as a formula this
calculation is represented by

Hsup - Hsat
Sp. Ht. = –––––––––––––––––––– (8)
Ssup - Ssat
Where Hsup = total heat of one pound of superheated steam at any pressure and temperature,

Hsat = total heat of one pound of saturated steam at same pressure, [Pg 138]
Ssup = temperature of superheated steam taken,
Ssat = temperature of saturated steam corresponding to the pressure taken.
TABLE 25

MEAN SPECIFIC HEAT OF SUPERHEATED STEAM
CALCULATED FROM MARKS AND DAVIS TABLES
Gauge Degree of Superheat
Pressure 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 225 250
50 .518.517 .514 .513 .511 .510 .508 .507 .505.504 .503 .502.501 .500.500 .499 .497.496
60 .528.525 .523 .521 .519 .517 .515 .513 .512 .511 .509 .508.507 .506.504 .504 .502.500
70 .536.534 .531 .529 .527 .524 .522 .520 .518.516 .515 .513.512 .511 .510 .509 .506.504
80 .544.542 .539 .535 .532 .530 .528 .526 .524.522 .520 .518.516 .515.514 .513 .511 .508
90 .553.550 .546 .543 .539 .536 .534 .532 .529.527 .525 .523.521 .519.518 .517 .514.510
100 .562.557 .553 .549 .544 .542 .539 .536 .533.531 .529 .527.525 .523.522 .521 .517.513
110 .570.565 .560 .556 .552 .548 .545 .542 .539.536 .534 .532.529 .528.526 .525 .520.517
120 .578.573 .567 .561 .557 .554 .550 .546 .543.540 .537 .535.533 .531.529 .528 .523.519
130 .586.580 .574 .569 .564 .560 .555 .552 .548.545 .542 .539.537 .535.533 .531 .527.523
140 .594.588 .581 .575 .570 .565 .561 .557 .553.550 .547 .544.541 .539.536 .534 .530.526
150 .604.595 .587 .581 .576 .570 .566 .561 .557.554 .550 .547.544 .542.539 .537 .533.529
160 .612.603 .596 .589 .582 .576 .571 .566 .562.558 .554 .551.548 .545.543 .541 .536.531
170 .620.612 .603 .595 .588 .582 .576 .571 .566.562 .558 .555.552 .549.546 .544 .538.533
180 .628.618 .610 .601 .593 .587 .581 .575 .570.566 .561 .558.555 .552.549 .546 .540.536
190 .638.627 .617 .608 .599 .592 .585 .579 .574.569 .565 .562.558 .555.552 .549 .543.538
200 .648.635 .624 .614 .605 .597 .590 .584 .578.574 .569 .566.562 .558.555 .552 .546.541
210 .656.643 .631 .620 .611 .602 .595 .588 .583.578 .573 .569.565 .561.558 .555 .549.543
220 .664.650 .637 .626 .616 .607 .600 .592 .586.581 .577 .572.568 .564.561 .558 .551.545
230 .672.658 .644 .633 .622 .613 .605 .597 .591.585 .580 .575.572 .567.564 .561 .554.548
240 .684.668 .653 .640 .629 .619 .610 .602 .595.589 .584 .579.575 .571.567 .564 .556.550
250 .692.675 .659 .645 .633 .623 .614 .606 .599.593 .587 .582.577 .574.570 .567 .559.553

Factor of Evaporation with Superheated Steam—When superheat is present in the steam
during a boiler trial, where superheated steam tables are available, the formula for
determining the factor of evaporation is that already given, (2),[22] namely,

H-h
Factor of evaporation = ––––––––––
L

Here H = total heat in one pound of superheated steam from the table, h and L having the
same values as in (2).

Where no such tables are available but the specific heat of superheat is known, the formula
becomes:

H - h + Sp. Ht.(T - t)
Factor of evaporation = ––––––––––––––––––––––––––––––––––

L
Where H = total heat in one pound of saturated steam at pressure existing in trial,
h = sensible heat above 32 degrees in one pound of water at the temperature entering
the boiler,
tsat = temperature of saturated steam, corresponding to pressure existing,
T = temperature of superheated steam as determined in the trial, [Pg 139]
t = temperature of saturated steam corresponding to the boiler pressure,
Sp. Ht. = mean specific heat of superheated steam at the pressure and temperature as
found in the trial,
L = latent heat of one pound of saturated steam at atmospheric pressure.

Advantages of the Use of Superheated Steam—In considering the saving possible by the
use of superheated steam, it is too often assumed that there is only a saving in the prime
movers, a saving which is at least partially offset by an increase in the fuel consumption of
the boilers generating steam. This misconception is due to the fact that the fuel consumption
of the boiler is only considered in connection with a definite weight of steam. It is true that
where such a definite weight is to be superheated, an added amount of fuel must be burned.
With a properly designed superheater where the combined efficiency of the boiler and
superheater will be at least as high as of a boiler alone, the approximate increase in coal
consumption for producing a given weight of steam will be as follows:

Superheat Added Fuel Superheat Added Fuel
Degrees Per Cent Degrees Per Cent
25 1.59 100 5.69
50 3.07 150 8.19
75 4.38 200 0.58

These figures represent the added fuel necessary for superheating a definite weight of steam
to the number of degrees as given. The standard basis, however, of boiler evaporation is one
of heat units and, considered from such a standpoint, again providing the efficiency of the
boiler and superheater is as high, as of a boiler alone, there is no additional fuel required to
generate steam containing a definite number of heat units whether such units be due to
superheat or saturation. That is, if 6 per cent more fuel is required to generate and superheat
to 100 degrees, a definite weight of steam, over what would be required to produce the same
weight of saturated steam, that steam when superheated, will contain 6 per cent more heat
units above the fuel water temperature than if saturated. This holds true if the efficiency of
the boiler and superheater combined is the same as of the boiler alone. As a matter of fact,
the efficiency of a boiler and superheater, where the latter is properly designed and located,
will be slightly higher for the same set of furnace conditions than would the efficiency of a

boiler in which no superheater were installed. A superheater, properly placed within the
boiler setting in such way that products of combustion for generating saturated steam are
utilized as well for superheating that steam, will not in any way alter furnace conditions.
With a given set of such furnace conditions for a given amount of coal burned, the fact that
additional surface, whether as boiler heating or superheating surface, is placed in such a
manner that the gases must sweep over it, will tend to lower the temperature of the exit
gases. It is such a lowering of exit gas temperatures that is the ultimate indication of added
efficiency. Though the amount of this added efficiency is difficult to determine by test, that
there is an increase is unquestionable.

Where a properly designed superheater is installed in a boiler the heating surface of the
boiler proper, in the generation of a definite number of heat units, is relieved of a portion of
the work which would be required were these heat units delivered in saturated steam. Such a
superheater needs practically no attention, is not subject to a large upkeep cost or
depreciation, and performs its function without in any way [Pg 140] interfering with the
operation of the boiler. Its use, therefore from the standpoint of the boiler room, results in a
saving in wear and tear due to the lower ratings at which the boiler may be run, or its use will
lead to the possibility of obtaining the same number of boiler horse power from a smaller
number of boilers, with the boiler heating surface doing exactly the same amount of work as
if the superheaters were not installed. The saving due to the added boiler efficiency that will
be obtained is obvious.

Following the course of the steam in a plant, the next advantage of the use of superheated
steam is the absence of water in the steam pipes. The thermal conductivity of superheated
steam, that is, its power to give up its heat to surrounding bodies, is much lower than that of
saturated steam and its heat, therefore, will not be transmitted so rapidly to the walls of the
pipes as when saturated steam is flowing through the pipes. The loss of heat radiated from a
steam pipe, assuming no loss in pressure, represents the equivalent condensation when the
pipe is carrying saturated steam. In well-covered steam mains, the heat lost by radiation
when carrying superheated steam is accompanied only by a reduction of the superheat which,
if it be sufficiently high at the boiler, will enable a considerable amount of heat to be radiated
and still deliver dry or superheated steam to the prime movers.

It is in the prime movers that the advantages of the use of superheated steam are most clearly
seen.

In an engine, steam is admitted into a space that has been cooled by the steam exhausted
during the previous stroke. The heat necessary to warm the cylinder walls from the
temperature of the exhaust to that of the entering steam can be supplied only by the entering
steam. If this steam be saturated, such an adding of heat to the walls at the expense of the
heat of the entering steam results in the condensation of a portion. This initial condensation
is seldom less than from 20 to 30 per cent of the total weight of steam entering the cylinder.
It is obvious that if the steam entering be superheated, it must be reduced to the temperature
of saturated steam at the corresponding pressure before any condensation can take place. If
the steam be superheated sufficiently to allow a reduction in temperature equivalent to the
quantity of heat that must be imparted to the cylinder walls and still remain superheated, it is

clear that initial condensation is avoided. For example: assume one pound of saturated steam
at 200 pounds gauge pressure to enter a cylinder which has been cooled by the exhaust.
Assume the initial condensation to be 20 per cent. The latent heat of the steam is given up in
condensation; hence, .20 × 838 = 167.6 B. t. u. are given up by the steam. If one pound of
superheated steam enters the same cylinder, it would have to be superheated to a point where
its total heat is 1199 + 168 = 1367 B. t. u. or, at 200 pounds gauge pressure, superheated
approximately 325 degrees if the heat given up to the cylinder walls were the same as for the
saturated steam. As superheated steam conducts heat less rapidly than saturated steam, the
amount of heat imparted will be less than for the saturated steam and consequently the
amount of superheat required to prevent condensation will be less than the above figure.
This, of course, is the extreme case of a simple engine with the range of temperature change
a maximum. As cylinders are added, the range in each is decreased and the condensation is
proportionate.

The true economy of the use of superheated steam is best shown in a comparison of the “heat
consumption” of an engine. This is the number of heat units required [Pg 141] in developing
one indicated horse power and the measure of the relative performance of two engines is
based on a comparison of their heat consumption as the measure of a boiler is based on its
evaporation from and at 212 degrees. The water consumption of an engine in pounds per
indicated horse power is in no sense a true indication of its efficiency. The initial pressures
and corresponding temperatures may differ widely and thus make a difference in the
temperature of the exhaust and hence in the temperature of the condensed steam returned to
the boiler. For example: suppose a certain weight of steam at 150 pounds absolute pressure
and 358 degrees be expanded to atmospheric pressure, the temperature then being 212
degrees. If the same weight of steam be expanded from an initial pressure of 125 pounds
absolute and 344 degrees, to enable it to do the same amount of work, that is, to give up the
same amount of heat, expansion then must be carried to a point below atmospheric pressure
to, say, 13 pounds absolute, the final temperature of the steam then being 206 degrees. In
actual practice, it has been observed that the water consumption of a compound piston
engine running on 26-inch vacuum and returning the condensed steam at 140 degrees was
approximately the same as when running on 28-inch vacuum and returning water at 90
degrees. With an equal water consumption for the two sets of conditions, the economy in the
former case would be greater than in the latter, since it would be necessary to add less heat to
the water returned to the boiler to raise it to the steam temperature.

The lower the heat consumption of an engine per indicated horse power, the higher its
economy and the less the number of heat units must be imparted to the steam generated. This
in turn leads to the lowering of the amount of fuel that must be burned per indicated horse
power.

With the saving in fuel by the reduction of heat consumption of an engine indicated, it
remains to be shown the effect of the use of superheated steam on such heat consumption. As
already explained, the use of superheated steam reduces condensation not only in the mains
but especially in the steam cylinder, leaving a greater quantity of steam available to do the
work. Furthermore, a portion of the saturated steam introduced into a cylinder will condense
during adiabatic expansion, this condensation increasing as expansion progresses. Since

superheated steam cannot condense until it becomes saturated, not only is initial
condensation prevented by its use but also such condensation as would occur during
expansion. When superheated sufficiently, steam delivered by the exhaust will still be dry. In
the avoidance of such condensation, there is a direct saving in the heat consumption of an
engine, the heat given up being utilized in the developing of power and not in changing the
condition of the working fluid. That is, while the number of heat units lost in overcoming
condensation effects would be the same in either case, when saturated steam is condensed
the water of condensation has no power to do work while the superheated steam, even after it
has lost a like number of heat units, still has the power of expansion. The saving through the
use of superheated steam in the heat consumption of an engine decreases demands on the
boiler and hence the fuel consumption per unit of power.

Superheated Steam for Steam Turbines—Experience in using superheated steam in
connection with steam turbines has shown that it leads to economy and that it undoubtedly
pays to use superheated steam in place of saturated steam. This is so well established that it
is standard practice to use superheated steam in connection [Pg 142] with steam turbines. Aside
from the economy secured through using superheated steam, there is an important advantage
arising through the fact that it materially reduces the erosion of the turbine blades by the
action of water that would be carried by saturated steam. In using saturated steam in a steam
turbine or piston engine, the work done on expanding the steam causes condensation of a
portion of the steam, so that even were the steam dry on entering the turbine, it would
contain water on leaving the turbine. By superheating the steam the water that exists in the
low pressure stages of the turbine may be reduced to an amount that will not cause trouble.

Again, if saturated steam contains moisture, the effect of this moisture on the economy of a
steam turbine is to reduce the economy to a greater extent than the proportion by weight of
water, one per cent of water causing approximately a falling off of 2 per cent in the economy.

The water rate of a large economical steam turbine with superheated steam is reduced about
one per cent, for every 12 degrees of superheat up to 200 degrees Fahrenheit of superheat. To
superheat one pound of steam 12 degrees requires about 7 B. t. u. and if 1050 B. t. u. are
required at the boiler to evaporate one pound of the saturated steam from the temperature of
the feed water, the heat required for the superheated steam would be 1057 degrees. One per
cent of saving, therefore, in the water consumption would correspond to a net saving of
about one-third of one per cent in the coal consumption. On this basis 100 degrees of
superheat with an economical steam turbine would result in somewhat over 3 per cent of
saving in the coal for equal boiler efficiencies. As a boiler with a properly designed
superheater placed within the setting is more economical for a given capacity than a boiler
without a superheater, the minimum gain in the coal consumption would be, say, 4 or 5 per
cent as compared to a plant with the same boilers without superheaters.

The above estimates are on the basis of a thoroughly dry saturated steam or steam just at the
point of being superheated or containing a few degrees of superheat. If the saturated steam is
moist, the saving due to superheat is more and ordinarily the gain in economy due to
superheated steam, for equal boiler efficiencies, as compared with commercially dry steam
is, say, 5 per cent for each 100 degrees of superheat. Aside from this gain, as already stated,

superheated steam prevents erosion of the turbine buckets that would be caused by water in
the steam, and for the reasons enumerated it is standard practice to use superheated steam for
turbine work. The less economical the steam motor, the more the gain due to superheated
steam, and where there are a number of auxiliaries that are run with superheated steam, the
percentage of gain will be greater than the figures given above, which are the minimum and
are for the most economical type of large steam turbines.

An example from actual practice will perhaps best illustrate and emphasize the foregoing
facts. In October 1909, a series of comparable tests were conducted by The Babcock &
Wilcox Co. on the steam yacht “Idalia” to determine the steam consumption both with
saturated and superheated steam of the main engine on that yacht, including as well the feed
pump, circulating pump and air pump. These tests are more representative than are most tests
of like character in that the saving in the steam consumption of the auxiliaries, which were
much more wasteful than the main engine, formed an important factor. A résumé of these
tests was published in the Journal of the Society of Naval Engineers, November 1909.

[Pg 143]

The main engines of the “Idalia” are four cylinder, triple expansion, 111⁄2 × 19 inches by
2211⁄16 × 18 inches stroke. Steam is supplied by a Babcock & Wilcox marine boiler having
2500 square feet of boiler heating surface, 340 square feet of superheating surface and 65
square feet of grate surface.

The auxiliaries consist of a feed pump 6 × 4 × 6 inches, an independent air pump 6 × 12 × 8
inches, and a centrifugal pump driven by a reciprocating engine 57⁄16 × 5 inches. Under
ordinary operating conditions the superheat existing is about 100 degrees Fahrenheit.

Tests were made with various degrees of superheat, the amount being varied by by-passing
the gases and in the tests with the lower amounts of superheat by passing a portion of the
steam from the boiler to the steam main without passing it through the superheater. Steam
temperature readings were taken at the engine throttle. In the tests with saturated steam, the
superheater was completely cut out of the system. Careful calorimeter measurements were
taken, showing that the saturated steam delivered to the superheater was dry.

The weight of steam used was determined from the weight of the condensed steam discharge
from the surface condenser, the water being pumped from the hot well into a tank mounted
on platform scales. The same indicators, thermometers and gauges were used in all the tests,
so that the results are directly comparable. The indicators used were of the outside spring
type so that there was no effect of the temperature of the steam. All tests were of sufficient
duration to show a uniformity of results by hours. A summary of the results secured is given
in Table 26, which shows the water rate per indicated horse power and the heat consumption.
The latter figures are computed on the basis of the heat imparted to the steam above the
actual temperature of the feed water and, as stated, these are the results that are directly
comparable.

TABLE 26

RESULTS OF “IDALIA” TESTS
Oct. Oct. Oct. Oct.
Date 1909 Oct. 11
14 14 12 13
Degrees of superheat Fahrenheit 0 7 88 96 105
Pressures, pounds per Throttle 190 196 201 198 203
square inch above First Receiver 68.4 66.0 64.3 61.9 63.0
Atmospheric Pressure Second Receiver 9.7 9.2 8.7 7.8 8.4
Vacuum, inches 25.5 25.9 25.9 25.4 25.2
Temperature, Degrees Feed 201 206 205 202 200
Fahrenheit Hot Well 116 109.5 115 111.5 111
Air Pump 57 56 53 54 45
Circulating
Revolutions per minute 196 198 196 198 197
Pump
Main Engine 194.3 191.5 195.1 191.5 193.1
Indicated Horse Power, Main Engine 512.3 495.2 521.1 498.3 502.2
Water per hour, total pounds 9397 8430 8234 7902 7790
Water per indicated Horse Power, pounds 18.3 17.0 15.8 15.8 15.5
B. t. u. per minute per indicated Horse Power 314 300 284 286 283
Per cent Saving of Steam … 7.1 13.7 13.7 15.3
Percent Saving of Fuel (computed) … 4.4 9.5 8.9 9.9

The table shows that the saving in steam consumption with 105 degrees of superheat was
15.3 per cent and in heat consumption about 10 per cent. This may be [Pg 144] safely stated to
be a conservative representation of the saving that may be accomplished by the use of
superheated steam in a plant as a whole, where superheated steam is furnished not only to the
main engine but also to the auxiliaries. The figures may be taken as conservative for the
reason that in addition to the saving as shown in the table, there would be in an ordinary
plant a saving much greater than is generally realized in the drips, where the loss with
saturated steam is greatly in excess of that with superheated steam.

The most conclusive and most practical evidence that a saving is possible through the use of
superheated steam is in the fact that in the largest and most economical plants it is used
almost without exception. Regardless of any such evidence, however, there is a deep rooted
conviction in the minds of certain engineers that the use of superheated steam will involve
operating difficulties which, with additional first cost, will more than offset any fuel saving.
There are, of course, conditions under which the installation of superheaters would in no way
be advisable. With a poorly designed superheater, no gain would result. In general, it may be
stated that in a new plant, properly designed, with a boiler and superheater which will have
an efficiency at least as high as a boiler without a superheater, a gain is certain.

Such a gain is dependent upon the class of engine and the power plant equipment in general.
In determining the advisability of making a superheater installation, all of the factors

entering into each individual case should be considered and balanced, with a view to
determining the saving in relation to cost, maintenance, depreciation etc.

In highly economical plants, where the water consumption for an indicated horse power is
low, the gain will be less than would result from the use of superheated steam in less
economical plants where the water consumption is higher. It is impossible to make an
accurate statement as to the saving possible but, broadly, it may vary from 3 to 5 per cent for
100 degrees of superheat in the large and economical plants using turbines or steam engines,
in which there is a large ratio of expansion, to from 10 to 25 per cent for 100 degrees of
superheat for the less economical steam motors.

Though a properly designed superheater will tend to raise rather than to decrease the boiler
efficiency, it does not follow that all superheaters are efficient, for if the gases in passing
over the superheater do not follow the path they would ordinarily take in passing over the
boiler heating surface, a loss may result. This is noticeably true where part of the gases are
passed over the superheater and are allowed to pass over only a part or in some cases none of
the boiler heating surface.

With moderate degrees of superheat, from 100 to 200 degrees, where the piping is properly
installed, there will be no greater operating difficulties than with saturated steam. Engine and
turbine builders guarantee satisfactory operation with superheated steam. With high degrees
of superheat, say, over 250 degrees, apparatus of a special nature must be used and it is
questionable whether the additional care and liability to operating difficulties will offset any
fuel saving accomplished. It is well established, however, that the operating difficulties, with
the degrees of superheat to which this article is limited, have been entirely overcome.

The use of cast-iron fittings with superheated steam has been widely discussed. It is an
undoubted fact that while in some instances superheated steam has caused deterioration of
such fittings, in others cast-iron fittings have been used with 150 degrees of superheat
without the least difficulty. The quality of the cast iron used in [Pg 145] such fittings has
doubtless a large bearing on the life of such fittings for this service. The difficulties that have
been encountered are an increase in the size of the fittings and eventually a deterioration
great enough to lead to serious breakage, the development of cracks, and when flanges are
drawn up too tightly, the breaking of a flange from the body of the fitting. The latter
difficulty is undoubtedly due, in certain instances, to the form of flange in which the strain of
the connecting bolts tended to distort the metal.

The Babcock & Wilcox Co. have used steel castings in superheated steam work over a long
period and experience has shown that this metal is suitable for the service. There seems to be
a general tendency toward the use of steel fittings. In European practice, until recently, cast
iron was used with apparently satisfactory results. The claim of European engineers was to
the effect that their cast iron was of better quality than that found in this country and thus
explained the results secured. Recently, however, certain difficulties have been encountered
with such fittings and European engineers are leaning toward the use of steel for this work.

The degree of superheat produced by a superheater placed within the boiler setting will vary
according to the class of fuel used, the form of furnace, the condition of the fire and the rate
at which the boiler is being operated. This is necessarily true of any superheater swept by the
main body of the products of combustion and is a fact that should be appreciated by the
prospective user of superheated steam. With a properly designed superheater, however, such
fluctuations would not be excessive, provided the boilers are properly operated. As a matter
of fact the point to be guarded against in the use of superheated steam is that a maximum
should not be exceeded. While, as stated, there may be a considerable fluctuation in the
temperature of the steam as delivered from individual superheaters, where there are a number
of boilers on a line the temperature of the combined flow of steam in the main will be found
to be practically a constant, resulting from the offsetting of various furnace conditions of one
boiler by another.
[Pg 146]

8400 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters at the
Butler Street Plant of the Georgia Railway and Power Co., Atlanta, Ga. This Company
Operates a Total of 15,200 Horse Power of Babcock & Wilcox Boilers

FOOTNOTES

[20] See pages 125 to 127.

[21] The actual specific heat at a particular temperature and pressure is that corresponding to a
change of one degree one way or the other and differs considerably from the average value for the
particular temperature and pressure given in the table. The mean values given in the table give
correct results when employed to determine the factor of evaporation whereas the actual values at
the particular temperatures and pressures would not.

[22] See page 117.

[Pg 147]

PROPERTIES OF AIR
Pure air is a mechanical mixture of oxygen and nitrogen. While different authorities give slightly
varying values for the proportion of oxygen and nitrogen contained, the generally accepted values are:

By volume, oxygen 20.91 per cent, nitrogen 79.09 per cent.
By weight, oxygen 23.15 per cent, nitrogen 76.85 per cent.

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 of volume decreases in geometric progression
with the altitude. This fact has a direct bearing in the proportioning of furnaces, flues and stacks at
high altitudes, as will be shown later in the discussion of these subjects. The atmospheric pressures
corresponding to various altitudes are given in Table 12 .

The weight and volume of air depend upon the pressure and the temperature, as expressed by the
formula:

P v = 53.33 T (9)
Where P = the absolute pressure in pounds per square foot,
v = the volume in cubic feet of one pound of air,
T = the absolute temperature of the air in degrees Fahrenheit,
53.33 = a constant for air derived from the ratio of pressure, volume and temperature of a perfect
gas.

The weight of one cubic foot of air will obviously be the reciprocal of its volume, that is, 1/ v pounds.

TABLE 27

VOLUME AND WEIGHT OF AIR
AT ATMOSPHERIC PRESSURE AT VARIOUS TEMPERATURES
Volume Weight Volume Weight Volume Weight
One One One One One One
Temperature Temperature Temperature
Pound Cubic Pound Cubic Pound Cubic
Degrees Degrees Degrees
in Foot in Foot in Foot
Fahrenheit Fahrenheit Fahrenheit
Cubic in Cubic in Cubic in
Feet Pounds Feet Pounds Feet Pounds
32 12.390 .080710 160 15.615 .064041 340 20.151 .049625
50 12.843 .077863 170 15.867 .063024 360 20.655 .048414
55 12.969 .077107 180 16.119 .062039 380 21.159 .047261
60 13.095 .076365 190 16.371 .061084 400 21.663 .046162
65 13.221 .075637 200 16.623 .060158 425 22.293 .044857
70 13.347 .074923 210 16.875 .059259 450 22.923 .043624
75 13.473 .074223 212 16.925 .059084 475 23.554 .042456
80 13.599 .073535 220 17.127 .058388 500 24.184 .041350

85 13.725 .072860 230 17.379 .057541 525 24.814 .040300
90 13.851 .072197 240 17.631 .056718 550 25.444 .039302
95 13.977 .071546 250 17.883 .055919 575 26.074 .038352
100 14.103 .070907 260 18.135 .055142 600 26.704 .037448
110 14.355 .069662 270 18.387 .054386 650 27.964 .035760
120 14.607 .068460 280 18.639 .053651 700 29.224 .034219
130 14.859 .067299 290 18.891 .052935 750 30.484 .032804
140 15.111 .066177 300 19.143 .052238 800 31.744 .031502
150 15.363 .065092 320 19.647 .050898 850 33.004 .030299

[Pg 148]

Example: Required the volume of air in cubic feet under 60.3 pounds gauge pressure per square inch at
115 degrees Fahrenheit.

P = 144 (14.7 + 60.3) = 10,800.
T = 115 + 460 = 575 degrees.
53.33 × 575
Hence v = –––––––––––––––––––– = 2.84 cubic feet, and
10,800
1 1
Weight per cubic foot = –––– = –––––––– = 0.352 pounds.
v 2.84

Table 27 gives the weights and volumes of air under atmospheric pressure at varying temperatures.

Formula ( 9 ) holds good for other gases with the change in the value of the constant as follows:

For oxygen 48.24, nitrogen 54.97, hydrogen 765.71.

The specific heat of air at constant pressure varies with its temperature. A number of determinations of
this value have been made and certain of those ordinarily accepted as most authentic are given in Table
28 .

TABLE 28

SPECIFIC HEAT OF AIR
AT CONSTANT PRESSURE AND VARIOUS TEMPERATURES
Temperature Range
Specific Heat Authority
Degrees Centigrade Degrees Fahrenheit
-30– 10 -22– 50 0.2377 Regnault
0–100 32– 212 0.2374 Regnault
0–200 32– 392 0.2375 Regnault
20–440 68– 824 0.2366 Holborn and Curtis
20–630 68–1166 0.2429 Holborn and Curtis
20–800 68–1472 0.2430 Holborn and Curtis
0–200 32– 392 0.2389 Wiedemann

This value is of particular importance in waste heat work and it is regrettable that there is such a
variation in the different experiments. Mallard and Le Chatelier determined values considerably higher
than any given in Table 28 . All things considered in view of the discrepancy of the values given, there
appears to be as much ground for the use of a constant value for the specific heat of air at any
temperature as for a variable value. Where this value is used throughout this book, it has been taken as
0.24.

Air may carry a considerable quantity of water vapor, which is frequently 3 per cent of the total
weight. This fact is of importance in problems relating to heating drying and the compressing of air.
Table 29 gives the amount of vapor required to saturate air at different temperatures, its weight,
expansive force, etc., and contains sufficient information for solving practically all problems of this
sort that may arise.

[Pg 149]

TABLE 29

WEIGHTS OF AIR, VAPOR OF WATER, AND SATURATED MIXTURES OF AIR AND VAPOR
AT DIFFERENT TEMPERATURES,
UNDER THE ORDINARY ATMOSPHERIC PRESSURE OF 29.921 INCHES OF MERCURY
Mixtures of Air Saturated with Vapor Cubic
Feet of
Volume Weight of Cubic Foot Weight Vapor
of Dry Elastic of the Mixture of Air Weight of Dry from
of
Air at Force of and Vapor Air One
Different Weight the Air Vapor Pound
Mixed
Mixed
Temper- of Cubic in the with of
atures, Foot of Mixture with Water
Total One One
the Dry Air Elastic of Air Weight Weight Weight Pound at its
Temper- Volume at the Force of and of the Pound own
of the of of
Vapor of Air,
ature at 32 Different Vapor in Vapor in Air in Mixture in Vapor, Pressure
Degrees Degrees Temper- Inches of Inches Pounds in in Pounds in in
Fahr- being atures Mercury of Pounds Pounds Column
Pounds
enheit 1.000 Pounds (Regnault) Mercury 4
1 2 3 4 5 6 7 8 9 10 11
0 .935 .0864 .044 29.877 .0863 .000079 .086379 .000921092.4 …
12 .960 .0842 .074 29.849 .0840 .000130 .084130 .00155 646.1 …
22 .980 .0824 .118 29.803 .0821 .000202 .082302 .00245 406.4 …
32 1.000 .0807 .181 29.740 .0802 .000304 .080504 .00379 263.81 3289
42 1.020 .0791 .267 29.654 .0784 .000440 .078840 .00561 178.18 2252
52 1.041 .0776 .388 29.533 .0766 .000627 .077227 .00810 122.17 1595
62 1.061 .0761 .556 29.365 .0747 .000881 .075581 .01179 84.79 1135
72 1.082 .0747 .785 29.136 .0727 .001221 .073921 .01680 59.54 819
82 1.102 .0733 1.092 28.829 .0706 .001667 .072267 .02361 42.35 600
92 1.122 .0720 1.501 28.420 .0684 .002250 .070717 .03289 30.40 444
102 1.143 .0707 2.036 27.885 .0659 .002997 .068897 .04547 21.98 334
112 1.163 .0694 2.731 27.190 .0631 .003946 .067046 .06253 15.99 253
122 1.184 .0682 3.621 26.300 .0599 .005142 .065042 .08584 11.65 194
132 1.204 .0671 4.752 25.169 .0564 .006639 .063039 .11771 8.49 151

142 1.224 .0660 6.165 23.756 .0524 .008473 .060873 .16170 6.18 118
152 1.245 .0649 7.930 21.991 .0477 .010716 .058416 .22465 4.45 93.3
162 1.265 .0638 10.099 19.822 .0423 .013415 .055715 .31713 3.15 74.5
172 1.285 .0628 12.758 17.163 .0360 .016682 .052682 .46338 2.16 59.2
182 1.306 .0618 15.960 13.961 .0288 .020536 .049336 .71300 1.402 48.6
192 1.326 .0609 19.828 10.093 .0205 .025142 .045642 1.22643 .815 39.8
202 1.347 .0600 24.450 5.471 .0109 .030545 .041445 2.80230 .357 32.7
212 1.367 .0591 29.921 0.000 .0000 .036820 .036820 Infinite .000 27.1

Column 5 = barometer pressure of 29.921, minus the proportion of this due to vapor pressure from
column 4.

[Pg 150]

COMBUSTION
Combustion may be defined as the rapid chemical combination of oxygen with carbon, hydrogen and sulphur,
accompanied by the diffusion of heat and light. That portion of the substance thus combined with the oxygen is
called combustible. As used in steam engineering practice, however, the term combustible is applied to that portion
of the fuel which is dry and free from ash, thus including both oxygen and nitrogen which may be constituents of
the fuel, though not in the true sense of the term combustible.

Combustion is perfect 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, CO2. The combustion is imperfect when
complete oxidation of the combustible does not occur, or where the combustible does not unite with the maximum
amount of oxygen, as when one atom of carbon unites with one atom of oxygen to form carbon monoxide, CO,
which may be further burned to carbon dioxide.

Kindling Point—Before a combustible can unite with oxygen and combustion takes place, its temperature must
first be raised to the ignition or kindling point, and a sufficient time must be allowed for the completion of the
combustion before the temperature of the gases is lowered below that point. Table 30, by Stromeyer, gives the
approximate kindling temperatures of different fuels.

TABLE 30 Combustibles—The principal combustibles in coal and other fuels are
carbon, hydrogen and sulphur, occurring in varying proportions and
KINDLING TEMPERATURE OF combinations.
VARIOUS FUELS
Degrees Carbon is by far the most abundant as is indicated in the chapters on fuels.
Fahrenheit
Hydrogen in a free state occurs in small quantities in some fuels, but is
Lignite Dust 300
usually found in combination with carbon, in the form of hydrocarbons. The
Dried Peat 435 density of hydrogen is 0.0696 (Air = 1) and its weight per cubic foot, at 32
Sulphur 470 degrees Fahrenheit and under atmospheric pressure, is 0.005621 pounds.
Anthracite Dust 570
Coal 600 Sulphur is found in most coals and some oils. It is usually present in
Coke Red Heat combined form, either as sulphide of iron or sulphate of lime; in the latter
Anthracite Red Heat, 750 form it has no heat value. Its presence in fuel is objectionable because of its
Carbon MonoxideRed Heat, 1211 tendency to aid in the formation of clinkers, and the gases from its
Hydrogen 1030 or 1290 combustion, when in the presence of moisture, may cause corrosion.

Nitrogen is drawn into the furnace with the air. Its density is 0.9673 (Air =
1); its weight, at 32 degrees Fahrenheit and under atmospheric pressure, is 0.07829 pounds per cubic foot; each
pound of air at atmospheric pressure contains 0.7685 pounds of nitrogen, and one pound of nitrogen is contained in
1.301 pounds of air.

Nitrogen performs no useful office in combustion and passes through the furnace without change. It dilutes the air,
absorbs heat, reduces the temperature of the products of combustion, and is the chief source of heat losses in
furnaces.

[Pg 151]

Calorific Value—Each combustible element of gas will combine with oxygen in certain definite proportions and
will generate a definite amount of heat, measured in B. t. u. This definite amount of heat per pound liberated by
perfect combustion is termed the calorific value of that substance. Table 31, gives certain data on the reactions and
results of combustion for elementary combustibles and several compounds.

TABLE 31

OXYGEN AND AIR REQUIRED FOR COMBUSTION
AT 32 DEGREES AND 29.92 INCHES
BY WEIGHT
1 2 3 4 5 6 7 8 9 10
Nitrogen Gaseous
Oxygen per Air per Product per Hea
Oxidizable per Pound of Pound of Pound of Value
Substance Atomic or Pound of Column 1. Column 1. Column 1[25] Pound
or Chemical Combining Chemical Product of Column 1 3.32[23] × 4.32[24] × + Column 8 Colum
Combustible Symbol Weight Reaction Combustion Pounds O Pounds O Pounds Pounds B. t.
C+2O = Carbon
Carbon C 12 2.667 8.85 11.52 12.52 1460
CO2 Dioxide
Carbon
Carbon C 12 C+O = CO 1.333 4.43 5.76 6.76 445
Monoxide
Carbon CO+O = Carbon
CO 28 .571 1.90 2.47 3.47 1015
Monoxide CO2 Dioxide
H+O =
Hydrogen H 12 Water 8 26.56 34.56 35.56 6200
H 2O
Carbon
CH4+4O =
Methane CH4 16 Dioxide and 4 13.28 17.28 18.28 2355
CO2+2H2O
Water
S+2O = Sulphur
Sulphur S 32 1 3.32 4.32 5.32 405
SO2 Dioxide
BY VOLUME
1 2 11 12 13 14 15 16 17 18
Volume Volume
per Volume Volume of Gas p
Pound of of Volume of Nitrogen pound
Volumes of Column 1 Oxygen Products of per Pound Colum
Volumes of Oxygen Volumes in per Combustion of =
Oxidizable Column 1 Combining of Gaseous Pound of per Pound Column 1. Column
Substance Entering with Product Form Column 1 of 3.782[26] × ÷
or Chemical Combination Column 11 Formed Cubic Cubic Column 1 Column 15 Column
Combustible Symbol Volume Volume Volume Feet Feet Cubic Feet Cubic Feet Cubic F
Carbon C 1C 2 2CO2 14.95 29.89 29.89 112.98 142.8
Carbon C 1C 1 2CO 14.95 14.95 29.89 56.49 86.3
Carbon
CO 2CO 1 2CO2 12.80 6.40 12.80 24.20 37.0
Monoxide
Hydrogen H 2H 1 2H2O 179.32 89.66 179.32 339.09 518.4
1CO2
Methane CH4 1C4H 4 22.41 44.83 67.34 169.55 236.8
2H2O
Sulphur S 1S 2 1SO2 5.60 11.21 11.21 42.39 53.6

It will be seen from this table that a pound of carbon will unite with 22⁄3 pounds of oxygen to form carbon dioxide,
and will evolve 14,600 B. t. u. As an intermediate step, a pound of carbon may unite with 11⁄3 pounds of oxygen to
form carbon monoxide and evolve 4450 B. t. u., but in its further conversion to CO2 it would unite with an
additional 11⁄3 times its weight of oxygen and evolve the remaining 10,150 B. t. u. [Pg 152] When a pound of CO
burns to CO2, however, only 4350 B. t. u. are evolved since the pound of CO contains but 3⁄7 pound carbon.

Air Required for Combustion—It has already been shown that each combustible element in fuel will unite with a
definite amount of oxygen. With the ultimate analysis of the fuel known, in connection with Table 31, the
theoretical amount of air required for combustion may be readily calculated.

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 of H and O are respectively 1 and 16, the weight of the combined hydrogen will be 1⁄8 of the weight of the
oxygen, and the hydrogen available for combustion will be H - 1⁄8 O. In complete combustion 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 analysis is as follows:

0.7479 C × 22⁄3 = 1.9944 O needed
0.0642
( )
0.0498 - –––––––––––– H × 8 = 0.3262 O needed
8
0.0324 S × 1 = 0.0324 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 × 4.32 = 10.165.

The weight of combustible per pound of fuel is .7479 + .0418[27] + .0324 + .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 amount of air required per pound of fuel by the formula:

O
(
Weight per pound = 11.52 C + 34.56 H - –––– + 4.32 S
8
) (10)

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

[Pg 153]

In practice it is impossible to obtain perfect combustion with the theoretical amount of air, and an excess may be
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. 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 pounds per pound of fuel
either under natural or forced draft, though this amount may vary widely with the type of furnace, the nature of the
coal, and the method of firing. If less than this amount of air is supplied, the carbon burns to monoxide instead of
dioxide and its full heat value is not developed.

TABLE 32 An excess of air is also a source of waste, as
the products of combustion will be diluted
CALCULATED THEORETICAL AMOUNT OF AIR and carry off an excessive amount of heat in
REQUIRED PER POUND OF VARIOUS FUELS the chimney gases, or the air will so lower the
Weight of Constituents in One Air Required temperature of the furnace gases as to delay
Pound Dry Fuel per Pound the combustion to an extent that will cause
Fuel carbon monoxide to pass off unburned from
Carbon Hydrogen Oxygen of Fuel
Per Cent Per Cent Per Cent Pounds the furnace. A sufficient amount of carbon
Coke 94.0 … … 10.8 monoxide in the gases may cause the action
known as secondary combustion, by igniting
Anthracite Coal 91.5 3.5 2.6 11.7
or mingling with air after leaving the furnace
Bituminous Coal 87.0 5.0 4.0 11.6 or in the flues or stack. Such secondary
Lignite 70.0 5.0 20.0 8.9 combustion which takes place either within
Wood 50.0 6.0 43.5 6.0 the setting after leaving the furnace or in the
Oil 85.0 3.0 1.0 14.3 flues or stack always leads to a loss of
efficiency and, in some instances, leads to
overheating of the flues and stack.

Table 32 gives the theoretical amount of air required for various fuels calculated from formula (10) assuming the
analyses of the fuels given in the table.

The process of combustion of different fuels and the effect of variation in the air supply for their combustion is
treated in detail in the chapters dealing with the various fuels.
[Pg 154]

4064 HORSE-POWER Installation of Babcock & Wilcox Boilers and Superheaters, Equipped with Babcock
& Wilcox Chain Grate Stokers, at the Cosmopolitan Electric Co., Chicago, Ill.

FOOTNOTES

[23] Ratio by weight of O to N in air.

[24] 4.32 pounds of air contains one pound of O.

[25] Per pound of C in the CO.

[26] Ratio by volume of O to N in air.

[27] Available hydrogen.

[Pg 155]

ANALYSIS OF FLUE GASES
The object of a flue gas analysis is the determination of the completeness of
the combustion of the carbon in the fuel, and the amount and distribution of
the heat losses due to incomplete combustion. The quantities actually
determined by an analysis are the relative proportions by volume, of carbon
dioxide (CO 2 ), oxygen (O), and carbon monoxide (CO), the determinations
being made in this order.

The variations of the percentages of these gases in an analysis is best
illustrated in the consideration of the complete combustion of pure carbon, a
pound of which requires 2.67 pounds of oxygen, [28] or 32 cubic feet at 60
degrees Fahrenheit. The gaseous product of such combustion will occupy,
when cooled, the same volume as the oxygen, namely, 32 cubic feet. The air
supplied for the combustion is made up of 20.91 per cent oxygen and 79.09
per cent nitrogen by volume. The carbon united with the oxygen in the form
of carbon dioxide will have the same volume as the oxygen in the air
originally supplied. The volume of the nitrogen when cooled will be the
same as in the air supplied, as it undergoes no change. Hence for complete
combustion of one pound of carbon, where no excess of air is supplied, an
analysis of the products of combustion will show the following percentages
by volume:

Actual Volume
Per Cent
for One Pound Carbon
by Volume
Cubic Feet
Carbon Dioxide 32 = 20.91
Oxygen 0 = 0.00
Nitrogen 121 = 79.09
–––––– –––––––––––

Air required for one pound Carbon 153 = 100.00

For 50 per cent excess air the volume will be as follows:

153 × 1½ = 229.5 cubic feet of air per pound of carbon.

Actual Volume
Per Cent
for One Pound
by
Carbon
Volume
Cubic Feet
Carbon Dioxide 32 = 13.91
Oxygen 16 = 7.00 } = 20.91
cent
per

Nitrogen 181.5 = 79.09
–––––––––– –––––––––––

Air required for one pound
229.5 = 100.00
Carbon

For 100 per cent excess air the volume will be as follows:

153 × 2 = 306 cubic feet of air per pound of carbon.
Actual Volume
Per Cent
for One Pound
by
Carbon
Volume
Cubic Feet
Carbon Dioxide 32 = 10.45 20.91 per
Oxygen 32 = 10.45
= }
cent
Nitrogen 242 = 79.09
–––––– –––––––––––

Air required for one pound
306 = 100.00
Carbon

In each case the volume of oxygen which combines with the carbon is equal
to (cubic feet of air × 20.91 per cent)—32 cubic feet.

[Pg 156]

It will be seen that no matter what the excess of air supplied, the actual
amount of carbon dioxide per pound of carbon remains the same, while the
percentage by volume decreases as the excess of air increases. The actual
volume of oxygen and the percentage by volume increases with the excess of
air, and the percentage of oxygen is, therefore, an indication of the amount
of excess air. In each case the sum of the percentages of CO 2 and O is the
same, 20.9. Although the volume of nitrogen increases with the excess of air,

its percentage by volume remains the same as it undergoes no change while
combustion takes place; its percentage for any amount of air excess,
therefore, will be the same after combustion as before, if cooled to the same
temperature. It must be borne in mind that the above conditions hold only for
the perfect combustion of a pound of pure carbon.

Carbon monoxide (CO) produced by the imperfect combustion of carbon,
will occupy twice the volume of the oxygen entering into its composition
and will increase the volume of the flue gases over that of the air supplied
for combustion in the proportion of

100 + ½ the per cent CO
1 to –––––––––––––––––––––––––––––––––––––––

100

When pure carbon is the fuel, the sum of the percentages by volume of
carbon dioxide, oxygen and one-half of the carbon monoxide, must be in the
same ratio to the nitrogen in the flue gases as is the oxygen to the nitrogen in
the air supplied, that is, 20.91 to 79.09. When burning coal, however, the
percentage of nitrogen is obtained by subtracting the sum of the percentages
by volume of the other gases from 100. Thus if an analysis shows 12.5 per
cent CO 2 , 6.5 per cent O, and 0.6 per cent CO, the percentage of nitrogen
which ordinarily is the only other constituent of the gas which need be
considered, is found as follows:

100 - (12.5 + 6.5 + 0.6) = 80.4 per cent.

The action of the hydrogen in the volatile constituents of the fuel is to
increase the apparent percentage of the nitrogen in the flue gases. This is due
to the fact that the water vapor formed by the combustion of the hydrogen
will condense at a temperature at which the analysis is made, while the
nitrogen which accompanied the oxygen with which the hydrogen originally
combined maintains its gaseous form and passes into the sampling apparatus
with the other gases. For this reason coals containing high percentages of
volatile matter will produce a larger quantity of water vapor, and thus
increase the apparent percentage of nitrogen.

Air Required and Supplied —When the ultimate analysis of a fuel is known,
the air required for complete combustion with no excess can be found as
shown in the chapter on combustion, or from the following approximate
formula:

C O S
Pounds of air required per - (
pound of fuel
= 34.56 ( 3 + (H 8 ) + 8 )
–––– –––– ––––
[29]
11 )

where C, H and O equal the percentage by weight of carbon, hydrogen and
oxygen in the fuel divided by 100.

[Pg 157]

When the flue gas analysis is known, the total, amount of air supplied is:

N
Pounds of air supplied per ( 12
pound of fuel
= 3.036 ( CO + ) × C
–––––––––––––––––

2
[30]
)
CO

where N, CO 2 and CO are the percentages by volume of nitrogen, carbon
dioxide and carbon monoxide in the flue gases, and C the percentage by
weight of carbon which is burned from the fuel and passes up the stack as
flue gas. This percentage of C which is burned must be distinguished from
the percentage of C as found by an ultimate analysis of the fuel. To find the
percentage of C which is burned, deduct from the total percentage of carbon
as found in the ultimate analysis, the percentage of unconsumed carbon
found in the ash. This latter quantity is the difference between the percentage
of ash found by an analysis and that as determined by a boiler test. It is
usually assumed that the entire combustible element in the ash is carbon,
which assumption is practically correct. Thus if the ash in a boiler test were
16 per cent and by an analysis contained 25 per cent of carbon, the
percentage of unconsumed carbon would be 16 × .25 = 4 per cent of the total
coal burned. If the coal contained by ultimate analysis 80 per cent of carbon
the percentage burned, and of which the products of combustion pass up the
chimney would be 80 - 4 = 76 per cent, which is the correct figure to use in
calculating the total amount of air supplied by formula ( 12 ).

The weight of flue gases resulting from the combustion of a pound of dry
coal will be the sum of the weights of the air per pound of coal and the
combustible per pound of coal, the latter being equal to one minus the
percentage of ash as found in the boiler test. The weight of flue gases per
pound of dry fuel may, however, be computed directly from the analyses, as
shown later, and the direct computation is that ordinarily used.

The ratio of the air actually supplied per pound of fuel to that theoretically
required to burn it is:

N
3.036 ( CO + CO ) × C
–––––––––––––––––

2
––––––––––––––––––––––––––––––––––––––––––––– ( 13 )
C O
34.56 (3 + H - 8)
––– –––

in which the letters have the same significance as in formulae ( 11 ) and ( 12
).

The ratio of the air supplied per pound of combustible to the amount
theoretically required is:

N
–––––––––––––––––––––––––––––––––– ( 14 )
N - 3.782(O - ½CO)

which is derived as follows:

The N in the flue gas is the content of nitrogen in the whole amount of air
supplied. The oxygen in the flue gas is that contained in the air supplied and
which was not utilized in combustion. This oxygen was accompanied by
3.782 times its volume of nitrogen. The total amount of excess oxygen in the
flue gases is (O - ½CO); hence N - 3.782(O - ½CO) represents the nitrogen
content in the air actually required for combustion and N ÷ (N - 3.782[O -

½CO]) is the [Pg 158] ratio of the air supplied to that required. This ratio
minus one will be the proportion of excess air.

The heat lost in the flue gases is L = 0.24 W (T - t ) ( 15 )

Where L = B. t. u. lost per pound of fuel,
W = weight of flue gases in pounds per pound of dry coal,
T = temperature of flue gases,
t = temperature of atmosphere,
0.24 = specific heat of the flue gases.

The weight of flue gases, W, per pound of carbon can be computed directly
from the flue gas analysis from the formula:

11 CO 2 + 8 O + 7 (CO + N)
––––––––––––––––––––––––––––––––––––––––––––– ( 16 )
3 (CO 2 + CO)

where CO 2 , O, CO, and N are the percentages by volume as determined by
the flue gas analysis of carbon dioxide, oxygen, carbon monoxide and
nitrogen.

The weight of flue gas per pound of dry coal will be the weight determined
by this formula multiplied by the percentage of carbon in the coal from an
ultimate analysis.

Fig. 20. Loss Due to Heat Carried Away by Chimney Gases for Varying
Percentages of Carbon Dioxide.
Based on Boiler Room Temperature = 80 Degrees Fahrenheit.
Nitrogen in Flue Gas = 80.5 Per Cent. Carbon Monoxide in Flue Gas =
0. Per Cent

Fig. 20 represents graphically the loss due to heat carried away by dry
chimney gases for varying percentages of CO 2 , and different temperatures
of exit gases.

[Pg 159]

The heat lost, due to the fact that the carbon in the fuel is not completely
burned and carbon monoxide is present in the flue gases, in B. t. u. per
pound of fuel burned is:

CO
L' = 10,150 × ( CO + CO )
–––––––––––––––––

2
( 17 )

where, as before, CO and CO 2 are the percentages by volume in the flue
gases and C is the proportion by weight of carbon which is burned and
passes up the stack.

Fig. 21 represents graphically the loss due to such carbon in the fuel as is not
completely burned but escapes up the stack in the form of carbon monoxide.

Fig. 21. Loss Due to Unconsumed Carbon Contained in the CO in the
Flue Gases

Apparatus for Flue Gas Analysis —The Orsat apparatus, illustrated in Fig.
22, is generally used for analyzing flue gases. The burette A is graduated in
cubic centimeters up to 100, and is surrounded by a water jacket to prevent
any change in temperature from affecting the density of the gas being
analyzed.

For accurate work it is advisable to use four pipettes, B , C , D , E , the first
containing a solution of caustic potash for the absorption of carbon dioxide,
the second an alkaline solution of pyrogallol for the absorption of oxygen,
and the remaining two an acid solution of cuprous chloride for absorbing the
carbon monoxide. Each pipette contains a number of glass tubes, to which
some of the solution clings, thus facilitating [Pg 160] 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 gas is drawn into the burette through the U-tube H , which is filled with
spun glass, or similar material, to clean the gas. To discharge any air or gas
in the apparatus, the cock G is opened to the air and the bottle F is raised
until the water in the burette reaches the 100 cubic centimeters mark. The
cock G is then turned so as to close the air opening and allow gas to be
drawn through H , the bottle F being lowered for this purpose. The gas is
drawn into the burette to a point below the zero mark, the cock G then being
opened to the air and the excess gas expelled until the level of the water in F
and in A are at the zero mark. This operation is necessary in order to obtain
the zero reading at atmospheric pressure.

The apparatus should be carefully tested for leakage as well as all
connections leading thereto. Simple tests can be made; for example: If after
the cock G is closed, the bottle F is placed on top of the frame for a short
time and again brought to the zero mark, the level of the water in A is above
the zero mark, a leak is indicated.

Before taking a final sample for analysis, the
burette A should be filled with gas and
emptied once or twice, to make sure that all
the apparatus is filled with the new gas. The
cock G is then closed and the cock I in the
pipette B is opened and the gas driven over
into B by raising the bottle F . The gas is
drawn back into A by lowering F and when the
solution in B has reached the mark in the
capillary tube, the cock I is closed and a
reading is taken on the burette, the level of the
water in the bottle F being brought to the same
level as the water in A . The operation is
repeated until a constant reading is obtained,
the number of cubic centimeters being the
Fig. 22. Orsat Apparatus percentage of CO 2 in the flue gases.

The gas is then driven over into the pipette C
and a similar operation is carried out. The difference between the resulting
reading and the first reading gives the percentage of oxygen in the flue
gases.

The next operation is to drive the gas into the pipette D , the gas being 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 cuprous
chloride solution, which, especially if it be old, may give off such fumes,
thus increasing the volume of the gases and making the reading on the
burette less than the true amount.

The process must be carried out in the order named, as the pyrogallol
solution will also absorb carbon dioxide, while the cuprous chloride solution
will also absorb oxygen.

[Pg 161]

As the pressure of the gases in the flue is less than the atmospheric pressure,
they will not of themselves flow through the pipe connecting the flue to the
apparatus. The gas may be drawn into the pipe in the way already described

for filling the apparatus, but this is a tedious method. For rapid work a
rubber bulb aspirator connected to the air outlet of the cock G will enable a
new supply of gas to be drawn into the pipe, the apparatus then being filled
as already described. Another form of aspirator draws the gas from the flue
in a constant stream, thus insuring a fresh supply for each sample.

The analysis made by the Orsat apparatus is volumetric; if the analysis by
weight is required, it can be found from the volumetric analysis as follows:

Multiply the percentages by volume by either the densities or the molecular
weight of each gas, and divide the products by the sum of all the products;
the quotients will be the percentages by weight. For most work sufficient
accuracy is secured by using the even values of the molecular weights.

The even values of the molecular weights of the gases appearing in an
analysis by an Orsat are:

Carbon Dioxide 44
Carbon Monoxide 28
Oxygen 32
Nitrogen 28

Table 33 indicates the method of converting a volumetric flue gas analysis
into an analysis by weight.

TABLE 33

CONVERSION OF A FLUE GAS ANALYSIS BY VOLUME TO ONE BY
WEIGHT
Volume
Analysis by Analysis by
Molecular times
Gas Volume Weight
Weight Molecular
Per Cent Per Cent
Weight
536.8
Carbon CO
12.2 12+(2×16) 536.8 ––––––––––– = 17.7
Dioxide 2 3022.8
Carbon CO .4 12+16 11.2 11.2 = .4
Monoxide –––––––––––

3022.8
220.8
Oxygen O 6.9 2×16 220.8 ––––––––––– = 7.3
3022.8
2254.0
Nitrogen N 80.5 2×14 2254.0 ––––––––––– = 74.6
3022.8

Total 100.0 3022.8 100.0

Application of Formulae and Rules —Pocahontas coal is burned in the
furnace, a partial ultimate analysis being:

Per Cent
Carbon 82.1
Hydrogen 4.25
Oxygen 2.6
Sulphur 1.6
Ash 6.0
B. t. u., per pound dry 14500

[Pg 162]

The flue gas analysis shows:

Per Cent
CO 2 10.7
O 9.0
CO 0.0
N (by difference) 80.3

Determine: The flue gas analysis by weight (see Table 33 ), the amount of air
required for perfect combustion, the actual weight of air per pound of fuel,
the weight of flue gas per pound of coal, the heat lost in the chimney gases if
the temperature of these is 500 degrees Fahrenheit, and the ratio of the air
supplied to that theoretically required.

Solution: The theoretical weight of air required for perfect combustion, per
pound of fuel, from formula ( 11 ) will be,

.821 .026 .016
W = 34.56 ( 3 + ( .0425 - 8 ) + 8 ) = 10.88 pounds.
––––––– ––––––– –––––––

If the amount of carbon which is burned and passes away as flue gas is 80
per cent, which would allow for 2.1 per cent of unburned carbon in terms of
the total weight of dry fuel burned, the weight of dry gas per pound of
carbon burned will be from formula ( 16 ):

11 × 10.7 + 8 × 9.0 + 7(0 + 80.3)
W= ––––––––––––––––––––––––––––––––––––––––––––––––––––– = 23.42 pounds
3 (10.7 + 0)

and the weight of flue gas per pound of coal burned will be .80 × 23.42 =
18.74 pounds.

The heat lost in the flue gases per pound of coal burned will be from formula
( 15 ) and the value 18.74 just determined.

Loss = .24 × 18.74 × (500 - 60) = 1979 B. t. u.

The percentage of heat lost in the flue gases will be 1979 ÷ 14500 = 13.6 per
cent.

The ratio of air supplied per pound of coal to that theoretically required will
be 18.74 ÷ 10.88 = 1.72 per cent.

The ratio of air supplied per pound of combustible to that required will be
from formula ( 14 ):

.803
––––––––––––––––––––––––––––––––––––––– = 1.73
.803 - 3.782(.09 - ½ × 0)

The ratio based on combustible will be greater than the ratio based on fuel if
there is unconsumed carbon in the ash.

Unreliability of CO 2 Readings Taken Alone —It is generally assumed that
high CO 2 readings are indicative of good combustion and hence of 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 CO 2 readings alone are not considered entirely
reliable. Wherever an automatic CO 2 recorder is used, it should be checked
from time to time and the analysis carried further with a view to ascertaining
whether there is CO present. As the percentage of CO 2 in these gases
increases, there is a tendency toward the presence of CO, which, of course,
cannot be shown by a CO 2 recorder, and which is often difficult to detect
with an Orsat apparatus. 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. [Pg 163] In one instance that came to our
attention, in using an Orsat apparatus where the cuprous chloride solution
was believed to be fresh, no CO was indicated in the flue gases but on
passing the same sample into a Hempel apparatus, a considerable percentage
was found. It is not safe, therefore, to assume without question from a high
CO 2 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
combustion 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.

Table 34 gives the densities of various gases together with other data that
will be of service in gas analysis work.

TABLE 34

DENSITY OF GASES AT 32 DEGREES FAHRENHEIT AND
ATMOSPHERIC PRESSURE
ADAPTED FROM SMITHSONIAN TABLES

Weight Volume
of of Relative Density,
Specific Hydrogen = 1
Chemical One One
Gas Gravity
Symbol Cubic Pound
Air=1
Foot Cubic
Exact Approximate
Pounds Feet
Oxygen O 1.053 .08922 11.208 15.87 16
Nitrogen N 0.9673 .07829 12.773 13.92 14
Hydrogen H 0.0696 .005621 177.90 1.00 1
Carbon
CO 2 1.5291 .12269 8.151 21.83 22
Dioxide
Carbon
CO 0.9672 .07807 12.809 13.89 14
Monoxide
Methane CH 4 0.5576 .04470 22.371 7.95 8
Ethane C 2 H 6 1.075 .08379 11.935 14.91 15
Acetylene C 2 H 2 0.920 .07254 13.785 12.91 13
Sulphur
SO 2 2.2639 .17862 5.598 31.96 32
Dioxide
…
Air … 1.0000 .08071 12.390 …
[Pg 164]

1942 Horse-power Installation of Babcock & Wilcox Boilers and
Superheaters in the Singer Building, New York City

FOOTNOTES
[28] See Table 31 , page 151 .

[29] This formula is equivalent to ( 10 ) given in chapter on combustion . 34.56 =
theoretical air required for combustion of one pound of H (see Table 31 ).

[30] For degree of accuracy of this formula, see Transactions, A. S. M. E., Volume
XXI, 1900, page 94.

[31] For loss per pound of coal multiply by per cent of carbon in coal by ultimate
analysis.

[32] For loss per pound of coal multiply by per cent of carbon in coal by ultimate
analysis.

[Pg 165]

CLASSIFICATION OF FUELS
(WITH PARTICULAR REFERENCE TO COAL)

Fuels for steam boilers may be classified as solid, liquid or gaseous. Of the
solid fuels, anthracite and bituminous coals are the most common, but in this
class must also be included lignite, peat, wood, bagasse and the refuse from
certain industrial processes such as sawdust, shavings, tan bark and the like.
Straw, corn and coffee husks are utilized in isolated cases.

The class of liquid fuels is represented chiefly by petroleum, though coal tar
and water-gas tar are used to a limited extent.

Gaseous fuels are limited to natural gas, blast furnace gas and coke oven gas,
the first being a natural product and the two latter by-products from
industrial processes. Though waste gases from certain processes may be
considered as gaseous fuels, inasmuch as the question of combustion does
not enter, the methods of utilizing them differ from that for combustible
gaseous fuel, and the question will be dealt with separately.

Since coal is by far the most generally used of all fuels, this chapter will be
devoted entirely to the formation, composition and distribution of the
various grades, from anthracite to peat. The other fuels will be discussed in
succeeding chapters and their combustion dealt with in connection with their
composition.

TABLE 35 Formation of Coal
—All coals are of
APPROXIMATE CHEMICAL CHANGES vegetable origin and
FROM WOOD are the remains of
FIBER TO ANTHRACITE COAL prehistoric forests.
Substance Carbon Hydrogen Oxygen Destructive
Wood Fiber 52.65 5.25 42.10 distillation due to
Peat 59.57 5.96 34.47 great pressures and
temperatures, has
Lignite 66.04 5.27 28.69

Earthy Brown Coal 73.18 5.68 21.14 resolved the organic
Bituminous Coal 75.06 5.84 19.10 matter into its
Semi-bituminous Coal 89.29 5.05 5.66 invariable ultimate
Anthracite Coal 91.58 3.96 4.46 constituents, carbon,
hydrogen, oxygen
and other substances, in varying proportions. The factors of time, depth of
beds, disturbance of beds and the intrusion of mineral matter resulting from
such disturbances have produced the variation in the degree of evolution
from vegetable fiber to hard coal. This variation is shown chiefly in the
content of carbon, and Table 35 shows the steps of such variation.

Composition of Coal—The uncombined carbon in coal is known as fixed
carbon. Some of the carbon constituent is combined with hydrogen and this,
together with other gaseous substances driven off by the application of heat,
form that portion of the coal known as volatile matter. The fixed carbon and
the volatile matter constitute the combustible. The oxygen and nitrogen
contained in the volatile matter are not combustible, but custom has applied
this term to that portion of the coal which is dry and free from ash, thus
including the oxygen and nitrogen.

The other important substances entering into the composition of coal are
moisture and the refractory earths which form the ash. The ash varies in
different coals from 3 to 30 per cent and the moisture from 0.75 to 45 per
cent of the total weight of the [Pg 166] coal, depending upon the grade and the
locality in which it is mined. A large percentage of ash is undesirable as it
not only reduces the calorific value of the fuel, but chokes up the air
passages in the furnace and through the fuel bed, thus preventing the rapid
combustion necessary to high efficiency. If the coal contains an excessive
quantity of sulphur, trouble will result from its harmful action on the metal
of the boiler where moisture is present, and because it unites with the ash to
form a fusible slag or clinker which will choke up the grate bars and form a
solid mass in which large quantities of unconsumed carbon may be
imbedded.

Moisture in coal may be more detrimental than ash in reducing the
temperature of a furnace, as it is non-combustible, absorbs heat both in being
evaporated and superheated to the temperature of the furnace gases. In some
instances, however, a certain amount of moisture in a bituminous coal

produces a mechanical action that assists in the combustion and makes it
possible to develop higher capacities than with dry coal.

Classification of Coal—Custom has classified coals in accordance with the
varying content of carbon and volatile matter in the combustible. Table 36
gives the approximate percentages of these constituents for the general
classes of coals with the corresponding heat values per pound of
combustible.

TABLE 36

APPROXIMATE COMPOSITION AND CALORIFIC VALUE
OF GENERAL GRADES OF COAL ON BASIS OF
COMBUSTIBLE
Per Cent of Combustible B. t. u.
Kind of Coal Per Pound of
Fixed Carbon Volatile Matter Combustible
Anthracite 97.0 to 92.5 3.0 to 7.5 14600 to 14800
Semi-anthracite 92.5 to 87.5 7.5 to 12.5 14700 to 15500
Semi-bituminous 87.5 to 75.0 12.5 to 25.0 15500 to 16000
Bituminous—Eastern 75.0 to 60.0 25.0 to 40.0 14800 to 15300
Bituminous—Western 65.0 to 50.0 35.0 to 50.0 13500 to 14800
Lignite Under 50 Over 50 11000 to 13500

Anthracite—The name anthracite, or hard coal, is applied to those dry coals
containing from 3 to 7 per cent volatile matter and which do not swell when
burned. True anthracite is hard, compact, lustrous and sometimes iridescent,
and is characterized by few joints and clefts. Its specific gravity varies from
1.4 to 1.8. In burning, it kindles slowly and with difficulty, is hard to keep
alight, and burns with a short, almost colorless flame, without smoke.

Semi-anthracite coal has less density, hardness and luster than true
anthracite, and can be distinguished from it by the fact that when newly
fractured it will soot the hands. Its specific gravity is ordinarily about 1.4. It
kindles quite readily and burns more freely than the true anthracites.

Semi-bituminous coal is softer than anthracite, contains more volatile
hydrocarbons, kindles more easily and burns more rapidly. It is ordinarily
free burning, has a high calorific value and is of the highest order for steam
generating purposes.

[Pg 167]

Bituminous coals are still softer than those described and contain still more
volatile hydrocarbons. The difference between the semi-bituminous and the
bituminous coals is an important one, economically. The former have an
average heating value per pound of combustible about 6 per cent higher than
the latter, and they burn with much less smoke in ordinary furnaces. The
distinctive characteristic of the bituminous coals is the emission of yellow
flame and smoke when burning. In color they range from pitch black to dark
brown, having a resinous luster in the most compact specimens, and a silky
luster in such specimens as show traces of vegetable fiber. The specific
gravity is ordinarily about 1.3.

Bituminous coals are either of the caking or non-caking class. The former,
when heated, fuse and swell in size; the latter burn freely, do not fuse, and
are commonly known as free burning coals. Caking coals are rich in volatile
hydrocarbons and are valuable in gas manufacture.

Bituminous coals absorb moisture from the atmosphere. The surface
moisture can be removed by ordinary drying, but a portion of the water can
be removed only by heating the coal to a temperature of about 250 degrees
Fahrenheit.

Cannel coal is a variety of bituminous coal, rich in hydrogen and
hydrocarbons, and is exceedingly valuable as a gas coal. It has a dull
resinous luster and burns with a bright flame without fusing. Cannel coal is
seldom used for steam coal, though it is sometimes mixed with semi-
bituminous coal where an increased economy at high rates of combustion is
desired. The composition of cannel coal is approximately as follows: fixed
carbon, 26 to 55 per cent; volatile matter, 42 to 64 per cent; earthy matter, 2
to 14 per cent. Its specific gravity is approximately 1.24.

Lignite is organic matter in the earlier stages of its conversion into coal, and
includes all varieties which are intermediate between peat and coal of the
older formation. Its specific gravity is low, being 1.2 to 1.23, and when
freshly mined it may contain as high as 50 per cent of moisture. Its
appearance varies from a light brown, showing a distinctly woody structure,
in the poorer varieties, to a black, with a pitchy luster resembling hard coal,
in the best varieties. It is non-caking and burns with a bright but slightly
smoky flame with moderate heat. It is easily broken, will not stand much
handling in transportation, and if exposed to the weather will rapidly
disintegrate, which will increase the difficulty of burning it.

Its composition varies over wide limits. The ash may run as low as one per
cent and as high as 50 per cent. Its high content of moisture and the large
quantity of air necessary for its combustion cause large stack losses. It is
distinctly a low-grade fuel and is used almost entirely in the districts where
mined, due to its cheapness.

Peat is organic matter in the first stages of its conversion into coal and is
found in bogs and similar places. Its moisture content when cut is extremely
high, averaging 75 or 80 per cent. It is unsuitable for fuel until dried and
even then will contain as much as 30 per cent moisture. Its ash content when
dry varies from 3 to 12 per cent. In this country, though large deposits of
peat have been found, it has not as yet been found practicable to utilize it for
steam generating purposes in competition with coal. In some European
countries, however, the peat industry is common.

Distribution—The anthracite coals are, with some unimportant exceptions,
confined to five small fields in Eastern Pennsylvania, as shown in the
following list. These fields are given in the order of their hardness.

Lehigh or Eastern Middle Field
Wyoming or Northern Field
[Pg 168]
Green Mountain District Continued
Black Creek District Pittston District
Hazelton District Wilkesbarre District
Beaver Meadow District Plymouth District
Panther Creek District[33] Schuylkill or Southern Field

Mahanoy or Western Field[34] East Schuylkill District
East Mahanoy District West Schuylkill District
West Mahanoy District Louberry District
Lykens Valley or Southwestern
Wyoming or Northern Field
Field
Carbondale District Lykens Valley District
Scranton District Shamokin District[35]

Anthracite is also found in Pulaski and Wythe Counties, Virginia; along the
border of Little Walker Mountain, and in Gunnison County, Colorado. The
areas in Virginia are limited, however, while in Colorado the quality varies
greatly in neighboring beds and even in the same bed. An anthracite bed in
New Mexico was described in 1870 by Dr. R. W. Raymond, formerly United
States Mining Commissioner.

Semi-anthracite coals are found in a few small areas in the western part of
the anthracite field. The largest of these beds is the Bernice in Sullivan
County, Pennsylvania. Mr. William Kent, in his “Steam Boiler Economy”,
describes this as follows: “The Bernice semi-anthracite coal basin lies
between Beech Creek on the north and Loyalsock Creek on the south. It is
six miles long, east and west, and hardly a third of a mile across. An 8-foot
vein of coal lies in a bed of 12 feet of coal and slate. The coal of this bed is
the dividing line between anthracite and semi-anthracite, and is similar to the
coal of the Lykens Valley District. Mine analyses give a range as follows:
moisture, 0.65 to 1.97; volatile matter, 3.56 to 9.40; fixed carbon, 82.52 to
89.39; ash, 3.27 to 9.34; sulphur, 0.24 to 1.04.”

Semi-bituminous coals are found on the eastern edge of the great
Appalachian Field. Starting with Tioga and Bradford Counties of northern
Pennsylvania, the bed runs southwest through Lycoming, Clearfield, Centre,
Huntingdon, Cambria, Somerset and Fulton Counties, Pennsylvania;
Allegheny County, Maryland; Buchannan, Dickinson, Lee, Russell, Scott,
Tazewell and Wise Counties, Virginia; Mercer, McDowell, Fayette, Raleigh
and Mineral Counties, West Virginia; and ending in northeastern Tennessee,
where a small amount of semi-bituminous is mined.

The largest of the bituminous fields is the Appalachian. Beginning near the
northern boundary of Pennsylvania, in the western portion of the State, it
extends southwestward through West Virginia, touching Maryland and
Virginia on their western borders, passing through southeastern Ohio,
eastern Kentucky and central Tennessee, and ending in western Alabama,
900 miles from its northern extremity.

The next bituminous coal producing region to the west is the Northern Field,
in north central Michigan. Still further to the west, and second in importance
to the [Pg 169] Appalachian Field, is the Eastern Interior Field. This covers,
with the exception of the upper northern portion, nearly the entire State of
Illinois, southwest Indiana and the western portion of Kentucky.

The Western Field extends through central and southern Iowa, western
Missouri, southwestern Kansas, eastern Oklahoma and the west central
portion of Arkansas. The Southwestern Field is confined entirely to the north
central portion of Texas, in which State there are also two small isolated
fields along the Rio Grande River.

The remaining bituminous fields are scattered through what may be termed
the Rocky Mountain Region, extending from Montana to New Orleans. A
partial list of these fields and their location follows:

Judith Basin Central Montana
Bull Mountain Field Central Montana
Yellowstone Region Southwestern Montana
Big Horn Basin Region Southern Montana
Big Horn Basin Region Northern Wyoming
Black Hills Region Northeastern Wyoming
Hanna Field Southern Wyoming
Green River Region Southwestern Wyoming
Yampa Field Northwestern Colorado
North Park Field Northern Colorado
Denver Region North Central Colorado
Uinta Region Western Colorado
Uinta Region Eastern Utah

Southwestern Region Southwestern Utah
Raton Mountain Region Southern Colorado
Raton Mountain Region Northern New Mexico
San Juan River Region Northwestern New Mexico
Capitan Field Southern New Mexico

Along the Pacific Coast a few small fields are scattered in western
California, southwestern Oregon, western and northwestern Washington.

Most of the coals in the above fields are on the border line between
bituminous and lignite. They are really a low grade of bituminous coal and
are known as sub-bituminous or black lignites.

Lignites—These resemble the brown coals of Europe and are found in the
western states, Wyoming, New Mexico, Arizona, Utah, Montana, North
Dakota, Nevada, California, Oregon and Washington. Many of the fields
given as those containing bituminous coals in the western states also contain
true lignite. Lignite is also found in the eastern part of Texas and in
Oklahoma.

Alaska Coals—Coal has been found in Alaska and undoubtedly is of great
value, though the extent and character of the fields have probably been
exaggerated. Great quantities of lignite are known to exist, and in quality the
coal ranges in character from lignite to anthracite. There are at present,
however, only two fields of high-grade coals known, these being the Bering
River Field, near Controllers Bay, and the Matanuska Field, at the head of
Cooks Inlet. Both of these fields are known to contain both anthracite and
high-grade bituminous coals, though as yet they cannot be said to have been
opened up.

Weathering of Coal—The storage of coal has become within the last few
years to a certain extent a necessity due to market conditions, danger of labor
difficulties at the mines and in the railroads, and the crowding of
transportation facilities. [Pg 170] The first cause is probably the most
important, and this is particularly true of anthracite coals where a sliding
scale of prices is used according to the season of the year. While market
conditions serve as one of the principal reasons for coal storage, most power

plants and manufacturing plants feel compelled to protect their coal supply
from the danger of strikes, car shortages and the like, and it is customary for
large power plants, railroads and coal companies themselves, to store
bituminous coal. Naval coaling stations are also an example of what is done
along these lines.

Anthracite is the nearest approach to the ideal coal for storing. It is not
subject to spontaneous ignition, and for this reason is unlimited in the
amount that may be stored in one pile. With bituminous coals, however, the
case is different. Most bituminous coals will ignite if placed in large enough
piles and all suffer more or less from disintegration. Coal producers only
store such coals as are least liable to ignite, and which will stand rehandling
for shipment.

The changes which take place in stored coal are of two kinds: 1st, the
oxidization of the inorganic matter such as pyrites; and 2nd, the direct
oxidization of the organic matter of the actual coal.

The first change will result in an increased volume of the coal, and
sometimes in an increased weight, and a marked disintegration. The changes
due to direct oxidization of the coal substances usually cannot be detected by
the eye, but as they involve the oxidization of the carbon and available
hydrogen and the absorption of the oxygen by unsaturated hydrocarbons,
they are the chief cause of the weathering losses in heat value. Numerous
experiments have led to the conclusion that this is also the cause for
spontaneous combustion.

Experiments to show loss in calorific heat values due to weathering indicate
that such loss may be as high as 10 per cent when the coal is stored in the air,
and 8.75 per cent when stored under water. It would appear that the higher
the volatile content of the coal, the greater will be the loss in calorific value
and the more subject to spontaneous ignition.

Some experiments made by Messrs. S. W. Parr and W. F. Wheeler, published
in 1909 by the Experiment Station of the University of Illinois, indicate that
coals of the nature found in Illinois and neighboring states are not affected
seriously during storage from the standpoint of weight and heating value, the
latter loss averaging about 3½ per cent for the first year of storage. They

found that the losses due to disintegration and to spontaneous ignition were
of greater importance. Their conclusions agree with those deduced from the
other experiments, viz., that the storing of a larger size coal than that which
is to be used, will overcome to a certain extent the objection to
disintegration, and that the larger sizes, besides being advantageous in
respect to disintegration, are less liable to spontaneous ignition. Storage
under water will, of course, entirely prevent any fire loss and, to a great
extent, will stop disintegration and reduce the calorific losses to a minimum.

To minimize the danger of spontaneous ignition in storing coal, the piles
should be thoroughly ventilated.

Pulverized Fuels—Considerable experimental work has been done with
pulverized coal, utilizing either coal dust or pulverizing such coal as is too
small to be burned in other ways. If satisfactorily fed to the furnace, it would
appear to have several advantages. The dust burned in suspension would be
more completely consumed than is the case with the solid coals, the
production of smoke would be [Pg 171] minimized, and the process would
admit of an adjustment of the air supply to a point very close to the amount
theoretically required. This is due to the fact that in burning there is an
intimate mixture of the air and fuel. The principal objections have been in
the inability to introduce the pulverized fuel into the furnace uniformly, the
difficulty of reducing the fuel to the same degree of fineness, liability of
explosion in the furnace due to improper mixture with the air, and the
decreased capacity and efficiency resulting from the difficulty of keeping
tube surfaces clean.

Pressed Fuels—In this class are those composed of the dust of some suitable
combustible, pressed and cemented together by a substance possessing
binding and in most cases inflammable properties. Such fuels, known as
briquettes, are extensively used in foreign countries and consist of carbon or
soft coal, too small to be burned in the ordinary way, mixed usually with
pitch or coal tar. Much experimenting has been done in this country in
briquetting fuels, the government having taken an active interest in the
question, but as yet this class of fuel has not come into common use as the
cost and difficulty of manufacture and handling have made it impossible to
place it in the market at a price to successfully compete with coal.

Coke is a porous product consisting almost entirely of carbon remaining
after certain manufacturing processes have distilled off the hydrocarbon
gases of the fuel used. It is produced, first, from gas coal distilled in gas
retorts; second, from gas or ordinary bituminous coals burned in special
furnaces called coke ovens; and third, from petroleum by carrying the
distillation of the residuum to a red heat.

Coke is a smokeless fuel. It readily absorbs moisture from the atmosphere
and if not kept under cover its moisture content may be as much as 20 per
cent of its own weight.

Gas-house coke is generally softer and more porous than oven coke, ignites
more readily, and requires less draft for its combustion.
[Pg 172]

16,000 Horse-power Installation of Babcock & Wilcox Boilers and
Superheaters at the Brunot’s Island Plant of the Duquesne Light Co.,
Pittsburgh, Pa.

FOOTNOTES

[33] The Panther Creek District forms a part of what is known as the Southern
Field; in the matter of hardness, however, these coals are more nearly akin to
Lehigh coals.

[34] Sometimes called Western Middle or Northern Schuylkill Field.

[35] Geographically, the Shamokin District is part of the Western Middle
Mahanoy Field, but the coals found in this section resemble more closely those of
the Wyoming Field.

[Pg 173]

THE DETERMINATION OF HEATING VALUES OF
FUELS
The heating value of a fuel may be determined either by a calculation from a chemical
analysis or by burning a sample in a calorimeter.

In the former method 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 moisture, fixed carbon, volatile matter
and ash, without determining the ultimate 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 ultimate 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
combination 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. Inasmuch as the latter is
the basis generally accepted for the 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
constituents by one minus the percentage of moisture, reporting the moisture content
separately.

Moist Fuel Dry Fuel
C 83.95 84.45
H 4.23 4.25
O 3.02 3.04
N 1.27 1.28
S .91 .91
Ash 6.03 6.07
–––––––––––

100.00

Moisture .59 .59
–––––––––––

100.00

Calculations from an Ultimate Analysis—The first formula for the calculation of heating
values from the composition of a fuel as determined from an ultimate analysis is due to
Dulong, and this formula, slightly modified, is the most commonly used to-day. 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 modified form of which
is:

Heat units in B. t. u. per pound of dry fuel =

O
(
14,600 C + 62,000 H - ––––
8
) + 4000 S (18)

[Pg 174]

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

.0304
= 14,600 × .8445 + 62,000( .0425 - ––––––––– ) + 4000 × .0091 = 14,765 B. t. u.
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, Mabler 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 is 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.

High and Low Heat Value of Fuels—In any fuel containing 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 volatilization 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 distinction 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 computing 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 carbon monoxide present. Such a method,
however, involves the separating of the constituent gases into their elementary gases,
which is oftentimes difficult and liable to simple arithmetical error. As the combustible
portion of gaseous fuels is ordinarily composed of hydrogen, carbon [Pg 175] monoxide and
certain hydrocarbons, a determination of the calorific value is much more readily obtained
by a separation into their constituent gases and a computation of the calorific value from a
table of such values of the constituents. Table 37 gives the calorific value of the more
common combustible gases, together with the theoretical amount of air required for their
combustion.

TABLE 37

WEIGHT AND CALORIFIC VALUE OF VARIOUS GASES
AT 32 DEGREES FAHRENHEIT AND ATMOSPHERIC PRESSURE
WITH THEORETICAL AMOUNT OF AIR REQUIRED FOR COMBUSTION
Gas Symbol Cubic Feet B. t. u. B. t. u. Cubic Feet Cubic Feet of
of per per of Air Required
Pound Air Per Cubic

Gas per Cubic Required Foot
Pound Foot per Pound of Gas
of
Gas
Hydrogen H 177.90 62000 349 428.25 2.41
Carbon
CO 2.81 4450 347 30.60 2.39
Monoxide
Methane CH4 22.37 23550 1053 214.00 9.57
Acetylene C2H2 13.79 21465 1556 164.87 11.93
Olefiant Gas C2H4 12.80 21440 1675 183.60 14.33
Ethane C2H6 11.94 22230 1862 199.88 16.74

In applying this table, as gas analyses may be reported either by weight or volume, there is
given in Table 33[36] a method of changing from volumetric analysis to analysis by weight.

Examples:

1st. Assume a blast furnace gas, the analysis of which in percentages 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,

0.195 × 4450 = 867.75 B. t. u. per pound.

The net volume of air required to burn one pound of this gas will be,

0.195 × 30.6 = 5.967 cubic feet.

2nd. Assume a natural gas, the analysis of which in percentages by volume is oxygen =
0.40, carbon monoxide = 0.95, carbon dioxide = 0.34, olefiant gas (C2H4) = 0.66, ethane
(C2H6) = 3.55, marsh gas (CH4) = 72.15 and hydrogen = 21.95. All but the oxygen and the
carbon dioxide are combustibles, and the heat per cubic foot will be,

From CO = 0.0095 × 347 = 3.30
C2H4 = 0.0066 × 1675 = 11.05
C2H6 = 0.0355 × 1862 = 66.10
CH4 = 0.7215 × 1050 = 757.58
H = 0.2195 × 349 = 76.61
–––––––––––

B. t. u. per cubic foot = 914.64

[Pg 176]

The net air required for combustion of one cubic foot of the gas will be,

CO = 0.0095 × 2.39 = 0.02
C2H4 = 0.0066 × 14.33 = 0.09
C2H6 = 0.0355 × 16.74 = 0.59
CH4 = 0.7215 × 9.57 = 6.90
H = 0.2195 × 2.41 = 0.53
–––––––

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. A method of making such an
analysis which has been found to give eminently satisfactory results is described below.

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 percentage 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 pulverized, 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 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 matter 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 obtained by burning the fixed
carbon over a Bunsen burner or in a muffle 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 percentage of ash, and the percentage of fixed carbon
is easily calculated from the loss during the determination 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, and this is the basis adopted throughout this book. 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.

Table 38 gives the proximate analysis and calorific value of a number of representative
coals found in the United States.

[Pg 177]

TABLE 38

APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF CERTAIN TYPICAL
AMERICAN COALS
B. t.
Proximate Analysis (Dry
u.
Coal)
Field, Bed Per
State County Mine Size Authority
or Vein Pound
Volatile Fixed
Moisture Ash Dry
Matter Carbon
Coal
ANTHRACITES
Beaver
Pa. Carbon Lehigh 1.50 2.41 90.30 7.29 Gale
Meadow
Pa. Dauphin Schuylkill Buckwheat 2.15 12.88 78.23 8.89 13137 Whitham
No. 2
Pa. Lackawanna Wyoming Belleview 8.29 7.81 77.19 15.00 12341 Sadtler
Buck.
Pa. Lackawanna Wyoming Johnson Culm. 13.90 11.16 65.96 22.88 10591 B. & W. Co.
No. 2
Pa. Luzerne Wyoming Pittston 3.66 4.40 78.96 16.64 12865 B. & W. Co.
Buck.
Pa. Luzerne Wyoming Mammoth Large 4.00 3.44 90.59 5.97 13720 Carpenter
Pa. Luzerne Wyoming Exeter Rice 0.25 8.18 79.61 12.21 12400 B. & W. Co.
Pa. Northumberland Schuylkill Treverton 0.84 6.73 86.39 6.88 Isherwood
Buck
Pa. Schuylkill Schuylkill 3.17 92.41 4.42 14220 Carpenter
Mountain
Pa. Schuylkill York Farm Buckwheat 0.81 5.51 75.90 18.59 11430
Pa. Victoria Buckwheat 4.30 0.55 86.73 12.72 12642 B. & W. Co.
Lehigh & Buck. &
Pa. Carbon Lehigh 1.57 6.27 66.53 27.20 12848 B. & W. Co.
Wilkes C. Co. Pea
Pa. Carbon Lehigh Buckwheat 5.00 81.00 14.00 11800 Carpenter
Del. & Hud. No. 1
Pa. Lackawanna 6.20 11.60 12100 Denton
Co. Buck.
SEMI-ANTHRACITES
Pa. Lycoming Loyalsock 1.30 8.72 84.44 6.84
Pa. Sullivan Lopez 5.48 7.53 81.00 11.47 13547 B. & W. Co.
Pa. Sullivan Bernice 1.29 8.21 84.43 7.36
SEMI-BITUMINOUS
Big Vein,
Md. Alleghany 3.50 21.33 72.47 6.20 14682 B. & W. Co.
George's Crk.
George's
Md. Alleghany 3.63 16.27 76.93 6.80 14695 B. & W. Co.
Creek
George's
Md. Alleghany 2.28 19.43 77.44 6.13 14793 B. & W. Co.
Creek
George's
Md. Alleghany Ocean No. 7 Mine run 1.13 14451 B. & W. Co.
Creek
Md. Alleghany Cumberland 1.50 17.26 76.65 6.09 14700
Washington U. S. Geo. S.
Md. Garrett Mine run 2.33 14.38 74.93 10.49 14033
No. 3 [37]
Pa. Bradford Long Valley 1.55 20.33 68.38 11.29 12965
Pa. Tioga Antrim 2.19 18.43 71.87 9.70 13500
Soriman Shaft
Pa. Cambria "B" or Miller 3.40 20.70 71.84 7.46 14484 N. Y. Ed. Co.
C. Co.
Pa. Cambria "B" or Miller Henrietta 1.23 18.37 75.28 6.45 14770 So. Eng. Co.

Pa. Cambria "B" or Miller Penker 3.64 21.34 70.48 8.18 14401 B. & W. Co.
Pa. Cambria "B" or Miller Lancashire 4.38 21.20 70.27 8.53 14453 B. & W. Co.
Lower Penn. C. & C.
Pa. Cambria Mine run 3.51 17.43 75.69 6.88 14279 U. S. Geo. S.
Kittanning Co. No. 3
Upper
Pa. Cambria Valley Mine run 3.40 14.89 75.03 10.08 14152 B. & W. Co.
Kittanning
Lower
Pa. Clearfield Eureka Mine run 5.90 16.71 77.22 6.07 14843 U. S. Geo. S.
Kittanning
Pa. Clearfield Ghem Mine run 3.43 17.53 69.67 12.80 13744 B. & W. Co.
Pa. Clearfield Osceola 1.24 25.43 68.56 6.01 13589 B. & W. Co.
Pa. Clearfield Reynoldsville 2.91 21.55 69.03 9.42 14685 B. & W. Co.
Atlantic-
Pa. Clearfield Mine run 1.55 23.36 71.15 5.94 13963 Whitham
Clearfield
Barnet &
Pa. Huntington Carbon Mine run 4.50 18.34 73.06 8.60 13770 B. & W. Co.
Fulton
Pa. Huntington Rock Hill Mine run 5.91 17.58 73.44 8.99 14105 B. & W. Co.
Lower
Pa. Somerset Kimmelton Mine run 3.09 17.84 70.47 11.69 13424 U. S. Geo. S.
Kittanning
"C" Prime
Pa. Somerset Jenner Mine run 9.37 16.47 75.76 7.77 14507 P. R. R.
Vein
U. S. Geo. S.
W. Va. Fayette New River Rush Run Mine run 2.14 22.87 71.56 5.57 14959
[Pg 178]
W. Va. Fayette New River Loup Creek 0.55 19.36 78.48 2.16 14975 Hill
W. Va. Fayette New River Slack 6.66 20.94 73.16 5.90 14412 B. & W. Co.
W. Va. Fayette New River Mine run 2.16 17.82 75.66 6.52 14786 B. & W. Co.
W. Va. Fayette New River Rush Run Mine run 0.94 22.16 75.85 1.99 15007 B. & W. Co.
Pocahontas
W. Va. McDowell Zenith Mine run 4.85 17.14 76.54 6.32 14480 U. S. Geo. S.
No. 3
W. Va. McDowell Tug River Big Sandy Mine run 1.58 18.55 76.44 4.91 15170 U. S. Geo. S.
W. Va. Mercer Pocahontas Mora Lump 1.74 18.55 75.15 6.30 15015 U. S. Geo. S.
W. Va. Mineral Elk Garden 2.10 15.70 75.40 8.90 14195 B. & W. Co.
W. Va. McDowell Pocahontas Flat Top Mine run 0.52 24.02 74.59 1.39 14490 B. & W. Co.
W. Va. McDowell Pocahontas Flat Top Slack 3.24 15.33 77.60 7.07 14653 B. & W. Co.
W. Va. McDowell Pocahontas Flat Top Lump 3.63 16.03 78.04 5.93 14956 B. & W. Co.
B. t.
Proximate Analysis (Dry
u.
Coal)
Field, Bed Per
State County Mine Size Authority
or Vein Pound
Volatile Fixed
Moisture Ash Dry
Matter Carbon
Coal
BITUMINOUS
Ala. Bibb Cahaba Hill Creek Mine run 6.19 28.58 55.60 15.82 12576 B. & W. Co.
Ala. Jefferson Pratt Pratt No. 13 4.29 25.78 67.68 6.54 14482 B. & W. Co.
Ala. Jefferson Pratt Warner Mine run 2.51 27.80 61.50 10.70 13628 U. S. Geo. S.
Ala. Jefferson Coalburg Mine run 0.94 31.34 65.65 3.01 14513 B. & W. Co.
Ivy C. & I.
Ala. Walker Horse Creek Nut 2.56 31.82 53.89 14.29 12937 U. S. Geo. S.
Co. No. 8
Galloway C.
Ala. Walker Jagger Mine run 4.83 34.65 51.12 14.03 12976 U. S. Geo. S.
Co. No. 5
Ark. Franklin Denning Western No. 4 Nut 2.22 12.83 75.35 11.82 U. S. Geo. S.
Ark. Sebastian Jenny Lind Mine No. 12 Lump 1.07 17.04 74.45 8.51 14252 U. S. Geo. S.
Ark. Sebastian Huntington Cherokee Mine run 0.97 19.87 70.30 9.83 14159 U. S. Geo. S.
Col. Boulder South Platte Lafayette Mine run 19.48 38.80 49.00 12.20 11939 B. & W. Co.
Col. Boulder Laramie Simson Mine run 19.78 44.69 48.62 6.69 12577 U. S. Geo. S.

Nut and
Col. Fremont Canon City Chandler 9.37 38.10 51.75 10.15 11850 B. & W. Co.
Slack
Col. Las Animas Trinidad Hastings Nut 2.15 31.07 53.40 15.53 12547 B. & W. Co.
Col. Las Animas Trinidad Moreley Slack 1.88 28.47 55.58 15.95 12703 B. & W. Co.
Col. Routt Yampa Oak Creek 6.67 42.91 55.64 1.45 Hill
Ill. Christian Pana Penwell Col. Lump 8.05 43.67 49.97 6.36 10900 Jones
Ill. Franklin No. 6 Benton Egg 8.31 34.52 54.05 11.43 11727 U. S. Geo. S.
Ill. Franklin Big Muddy Zeigler ¾ inch 13.28 31.97 57.37 10.66 12857 U. S. Geo. S.
Ill. Jackson Big Muddy 4.85 31.55 62.19 6.26 11466 Breckenridge
Ill. La Salle Streator 8.40 41.76 51.42 6.82 11727 Breckenridge
Ill. La Salle Streator Marseilles Mine run 12.98 43.73 49.13 7.14 10899 B. & W. Co.
Ill. Macoupin Nilwood Mine No. 2 Screenings 13.34 34.75 44.55 20.70 10781 B. & W. Co.
Ill. Macoupin Mt. Olive Mine No. 2 Mine run 13.54 41.28 46.30 12.42 10807 U. S. Geo. S.
Ill. Madison Belleville Donk Bros. Lump 13.47 38.69 48.07 13.24 12427 U. S. Geo. S.
Ill. Madison Glen Carbon Mine run 9.78 38.18 51.52 10.30 11672 Bryan
Ill. Marion Odin Lump 6.20 42.91 49.06 8.03 11880 Breckenridge
Ill. Mercer Gilchrist Screenings 8.50 36.17 41.64 22.19 10497 Breckenridge
Ill. Montgomery Pana or No. 5 Coffeen Mine run 11.93 34.05 49.85 16.10 10303 U. S. Geo. S.
Ill. Peoria No. 5 Empire 17.64 31.91 46.17 21.92 10705 B. & W. Co.
Ill. Perry Du Quoin Number 1 Screenings 9.81 33.67 48.36 17.97 11229 B. & W. Co.
U. S. Geo. S.
Ill. Perry Du Quoin Willis Mine run 7.22 33.06 53.97 12.97 11352
[Pg 179]
Ill. Sangamon Pawnee Slack 4.81 41.53 39.62 18.85 10220 Jones
Nigger
Ill. St. Glair Standard Mine run 14.39 32.90 44.84 22.26 11059 B. & W. Co.
Hollow
Ill. St. Clair Standard Maryville Mine run 15.71 38.10 41.10 20.80 10999 B. & W. Co.
Ill. Williamson Big Muddy Daws Mine run 8.17 34.33 52.50 13.17 12643 U. S. Geo. S.
Carterville or
Ill. Williamson Carterville 4.66 35.65 56.86 7.49 12286 Univ. of Ill.
No. 7
Carterville or Nut, Pea
Ill. Williamson Burr 11.91 33.70 55.90 10.40 12932 B. & W. Co.
No. 7 and Slack
Ind. Brazil Brazil Gartside Block 2.83 40.03 51.97 8.00 13375 Stillman
Ind. Clay Louise Block 0.83 39.70 52.28 8.02 13248 Jones
Ind. Green Island City Mine run 6.17 35.42 53.55 11.03 11916 Dearborn
Ind. Knox Vein No. 5 Tecumseh Mine run 10.73 35.75 54.46 9.79 12911 B. & W. Co.
Parke Coal
Ind. Parke Vein No. 6 Lump 10.72 44.02 46.33 9.65 11767 U. S. Geo. S.
Co.
Ind. Sullivan Sullivan No. 6 Mildred Washed 16.59 42.17 48.44 9.59 13377 U. S. Geo. S.
Ind. Vigo Number 6 Fontanet Mine run 2.28 34.95 50.50 14.55 11920 Dearborn
B. t.
Proximate Analysis (Dry
u.
Coal)
Field, Bed Per
State County Mine Size Authority
or Vein Pound
Volatile Fixed
Moisture Ash Dry
Matter Carbon
Coal
Ind. Vigo Number 7 Red Bird Mine run 11.62 41.17 46.76 12.07 12740 U. S. Geo. S.
Iowa Appanoose Mystic Mine No. 3 Lump 13.48 39.40 43.09 17.51 11678 U. S. Geo. S.
Iowa Lucas Lucas Inland No. 1 Mine run 16.01 37.82 46.24 15.94 11963 U. S. Geo. S.
Iowa Marion Big Vein Liberty No. 5 Mine run 14.88 41.53 39.63 18.84 11443 U. S. Geo. S.
Iowa Polk Third Seam Altoona No. 4 Lump 12.44 41.27 40.86 17.87 11671 U. S. Geo. S.
Iowa Wapello Wapello Lump 8.69 36.23 43.68 20.09 11443 U. S. Geo. S.
Weir Southwestern
Kan. Cherokee Lump 4.31 33.88 53.67 12.45 13144 U. S. Geo. S.
Pittsburgh Dev. Co.
Kan. Cherokee Cherokee Screenings 6.16 35.56 46.90 17.54 10175 Jones
Kan. Cherokee Cherokee Lump 1.81 34.77 52.77 12.46 12557 Jones