r should be started lightly; the feed being gradually increased so as not to cause any decrease of steam pressure.
36. Q. What is the purpose of a safety valve on a locomotive boiler? Why are more than one used?
A. A safety valve is used to limit the maximum pressure in the boiler by opening and allowing steam to escape. More than one safety valve are used as additional protection against excessive pressure; one is set at the maximum pressure and the others are set at two or three pounds above the maximum pressure.
37. Q. What is usually the reason for steam being wasted from the safety valve? What can be done to prevent this waste?
A. Careless firing, careless running. Both engineer and fireman work in harmony to obtain the best results.
38. Q. What is the estimated waste of coal for each minute the safety valve is open?
A. About fifteen pounds. The estimated waste of steam when an engine pops equals every second all the heat obtained from a quarter pound of coal. Sa