Explosives are substances which, by application of flame, heat, percussion, &c., suddenly assume the gaseous form, thus increasing their bulk many hundred times, usually in a small fraction of a second of time. A second class comprise explosive mixtures of gases, such as hydrogen, and oxygen, carburetted hydrogen, and air. Some attempts have been made to employ explosive substances to drive engines in various ways, but with no permanent success. The second class of explosive mixtures of gases are largely employed in the gas engine, petroleum engine, and their varieties.
Fuels, hydrocarbons, &c., are employed to evaporate water into steam; to expand air or other gases, or convert liquids into gases; and also by vaporisation to supply gas for use in some forms of gas engine.
Section 61.—PUMPING ENGINES, TYPES OF.
VERTICAL ENGINES.
[1114]. Vertical direct-acting, with either ram pump, ram and piston pump, or piston only. See [Section 56].
[1115]. Slot and crank motion, a variety of the last named. Of course any other kind of crank driving can be employed. See [Section 10].
The frame standards are frequently used as air vessels or valve chests.
[1116]. Direct-acting ram pump, with fly-wheel worked off crosshead pin.
[1117]. Direct-acting, with yoke crosshead; much used in the northern counties. The standards form air vessels and valve boxes, and they are made both of the piston and ram types.