204 STEAM ENGINES 



on the valve chest and the exhaust pipe should be opened, 

 if the engine is non-condensing. If the cylinders are jacketed, 

 steam should be turned into the jackets and the jacket drain 

 cocks should be opened. While the engine is warming up, 

 the oil cups and the sight-feed lubricator may be filled. A 

 little oil may be put into all the small joints and journals that 

 are not fitted with oil cups. The guides should be wiped off 

 with oily waste and oiled. By this time the engine is get- 

 ting warm. If the cylinder is fitted with by-pass valves, they 

 should be used to admit steam to both ends of the cylinder. 

 In general, all cylinders, especially if they are large and intricate 

 castings, should be warmed up slowly, as sudden and violent 

 heating of a cylinder of this character is very liable to crack 

 the casting by unequal expansion. 



An excellent and economical plan for warming up the steam 

 pipe and the engine is to open the stop-valves and throttle 

 valve at the time or soon after the fires are lighted in the 

 boilers, permitting the heated air from the boilers to circulate 

 through the engine, thus warming it up gradually and avoiding 

 the accumulation of a large quantity of water of condensation 

 in the steam pipe and cylinder. When pressure shows on the 

 boiler gauge or steam at the drain pipes of the engine, the stop- 

 valves and throttle may be closed temporarily, but not hard 

 down on their seats. When this method of warming up the 

 engine is adopted, the safety valves should not be opened 

 while steam is being raised. 



Danger of Water Hammer. Stop-valves and throttle valves 

 should never be opened quickly or suddenly and thus permit 

 a large volume of steam to flow into a cold steam pipe or cylin- 

 der. If this is done, the first steam that enters will be con- 

 densed and a partial vacuum will be formed. This will be 

 closely followed by another rush of steam with similar results, 

 and so on until a mass of water will collect, \vhich will rush 

 through the steam pipe and strike the first obstruction, gener- 

 ally the bend in the steam pipe near the cylinder, with great 

 force, and in all probability will carry it away and cause 

 a disaster. This is called -water hammer and has caused many 

 serious accidents. Before turning steam into any pipe line or 

 into a cylinder, all drain valves should be opened. 



