40 ROUGH-AND-TUMBLE ENGINEERING 



The steam enters the cylinder from the boiler, varying 

 in degrees of heat from 300 to 500. After acting on the 

 piston head, it is exhausted directly into the chamber or 

 hollow bed-plate through which the heater pipes pass. 

 The water, when it enters the heater, is as cold as when 

 it left the tank, but the steam which surrounds the pipes 

 has lost but little of its heat, and by the time the water 

 passes through the^oil of pipes it is heated to nearly the 

 boiling point and can be introduced into the boiler with 

 little tendency to reduce the steam pressure. This use 

 of the exhaust steam is economical, as it saves fuel. Be- 

 sides it is considered injurious to pump cold water di- 

 rectly into a hot boiler. 



If your engine is fitted with both cross head pump and 

 injector, it is better to use the injector for pumping water 

 when the engine is not running. The injector heats the 

 water almost as hot as the heater. If your engine is run- 

 ning and doing no work, use your injector and stop the 

 pump; for, while the engine is running light, the small 

 amount of exhaust steam, is not sufficient to heat the 

 water and the pressure will be reduced rapidly. You will 

 understand, therefore, that the injector is intended prin- 

 cipally for emergency rather than for general use. It 

 should always be kept in order, for, should the pump re- 

 fuse to work, you have only to start your injector and 

 use it until such time as you can remedy the trouble. 



