Steam, Its Generation and Use | Page 4

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