Before entering the boiler, water is heated in a heater by exhaust steam. This heater consists of a vessel filled with brass tubes. Steam passing through or around the tubes causes the temperature of the water to be raised. This process prevents steam from condensing in the boiler as it would if cold water entered. Moreover, the salts are deposited in the boiler instead of in the heater. An economizer is a device consisting of iron or steel tubes through which feed water passes while the products of combustion circulate around the tubes. A steam separator is used to remove moisture from steam before entering the engine cylinder. A steam trap is a device to remove condensed steam from steam pipes without allowing any of the live steam to escape.

A damper regulator is an apparatus for regulating the damper and controlling the draughts by the pressure of steam on the boiler. This regulator has the power to move the damper or dampers in both directions by water pressure, and will close or open them on a variation of one pound of steam. It makes a partial stroke and stands at any point; that is, it will move from the open position to one-quarter, one-half, three-quarters, or fractions thereof, and come to and remain indefinitely at a state of rest, and then return to the open position, thereby making the only true and proper movement of the damper.

Fig. 168.   Injector.

Fig. 168. - Injector.