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.
[Illustration: 397 Horse-power Babcock & Wilcox Boiler in Course of
Erection at the Plant of the Crocker Wheeler Co., Ampere, N. J.]
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.
[Illustration: 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]
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.
[Illustration: Erie County Electric Co., Erie, Pa., Operating 3082 Horse
Power of Babcock & Wilcox Boilers and Superheaters, Equipped with
Babcock & Wilcox Chain Grate Stokers]
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 statement of the principles which guide
the scientific development of the steam engine. His words are:
"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.
[Illustration: 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]
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.
[Illustration: Copyright by Underwood & Underwood
Woolworth Building, New York City, Operating 2454 Horse Power of
Babcock & Wilcox Boilers]