230 STEAM TURBINES 



Maintenance of Vacuum. As the economy of the steam 

 turbine is dependent so largely on the degree of vacuum carried, 

 it is necessary for the engineer to watch the vacuum gauge 

 closely. With reciprocating engines, the loss of 1 or 2 in. of 

 vacuum may not be of much consequence; but in a turbine 

 plant, where the vacuum is from 27 to 28 in., a loss of 1 or 

 2 in. will result in a considerable increase in the steam con- 

 sumption. Because of the high vacuum employed, the diffi- 

 culty of keeping pipes, valves, and glands from leaking is 

 greater in turbine practice than in engine practice, but the 

 greater economy obtained by keeping everything tight over- 

 balances the increased care and labor. 



Shutting Down. In shutting down a steam turbine, the 

 throttle valve should be closed partly before the load is reduced, 

 so as to prevent any possibility of racing when the load is 

 finally taken off. The load may then be used as a brake to 

 bring the rotor to a stop. When the throttle valve has been 

 closed and the steam supply has been shut off completely, 

 the auxiliary machinery may be stopped. If the load is taken 

 off before the throttle is wholly closed, the turbine may con- 

 tinue to rotate for half an hour, as the rotor is then running 

 in a vacuum and under no load. The speed may be reduced 

 by opening the drains and allowing air to enter the casing. 

 The oil supply to the bearings must be continued until the 

 turbine has come to rest, and the oil pump should be the last 

 auxiliary to be stopped. 



Care of Gears in De Laval Turbines. The De Laval Steam 

 Turbine Company in their directions for operating their tur- 

 bines state that in order to keep the gears in good condition 

 the teeth should be cleaned occasionally when the turbine is 

 not in service. They recommend that a wire brush and 

 kerosene be employed for this purpose. At the same time the 

 gear-case should also be thoroughly cleaned, and after the 

 cleaning the gears should be well lubricated. 



Should an engineer for any reason desire to take the gears 

 out of the case, it is recommended that he secure special 

 directions relating to their removal from the manufacturers. 

 The same statement also applies to the adjustment of the 

 gears, which need to be kept in perfect adjustment. 



