206 STEAM ENGINES 



be opened, according to circumstances. It will do no harm 

 to allow the steam to condense inside the engine, as the engine 

 will then cool down more gradually, which lessens the danger 

 of cracking the cylinder casting by unequal contraction. All 

 the water of condensation should be drained from the engine 

 before steam is again admitted to it. 



Starting Condensing Slide-Valve Engine. Before the main 

 engine is started, the air pump and circulating pump should 

 be put into operation and a vacuum formed in the condenser; 

 this will materially assist the main engine in starting promptly. 

 Prior to starting the air and circulating pumps, the injection 

 valve should be opened to admit the condensing water into 

 the circulating pump; the delivery valve should also be opened 

 at this time. If an ordinary jet condenser is used, no circu- 

 lating pump is required, the water being forced into the con- 

 denser by the pressure of the atmosphere. If the air pump is 

 operated by the main engine, a vacuum will not be formed 

 in the condenser until after the engine is started and at least 

 one upward stroke of the air pump is made. In this case 

 the injection valve must be opened at the same moment the 

 engine is started; otherwise the condenser will get hot and a 

 mixture of air and steam accumulate in it and prevent the 

 injection water from entering. When this occurs, it is neces- 

 sary to pump cold water into the condenser by one of the 

 auxiliary pumps through a pipe usually fitted for that purpose; 

 if such a pipe has not been provided, it may be found neces- 

 sary to cool the condenser by playing cold water on it through 

 a hose. 



Stopping Condensing Slide-Valve Engine. The operation 

 of stopping a slide-valve surface-condensing engine is precisely 

 similar to that of stopping a non-condensing engine of the same 

 type, with the addition that after the main engine is stopped 

 the air and circulating pumps are also stopped, and in the 

 same way, that is, by closing the throttle, after which the 

 injection valve and the discharge valve should be closed and 

 the drain cocks opened. With a jet condenser, the operation 

 of stopping the engine is the same as the above, with the 

 exception that the injection valve should be closed at the same 

 moment that the engine is stopped. 



