Steam, Its Generation and Use

by Babcock & Wilcox Company

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 When steam formed and raised the piston, the heat was withdrawn and the piston did work on its down stroke under pressure of the atmosphere.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.
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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: