228 STEAM TURBINES 



is in good order; the oil pump should be looked after, to 

 ascertain whether it is in condition to maintain a continuous 

 supply of oil; and, finally, before the turbine is started, the 

 shaft should be turned over by hand, to insure that the rotor 

 will turn freely in the casing. 



Starting. A steam turbine should be started slowly, and 

 before it is allowed to turn over under steam it should be 

 warmed up. This is accomplished by opening the throttle 

 valve just enough to let steam flow into the turbine. The 

 drains should be kept open until the turbine is well started. 

 The length of time required for warming up depends on the 

 size of the turbine, a large unit requiring more time than a 

 small one. As the warming up proceeds, the throttle may 

 gradually be opened more, and the auxiliary machinery may 

 be started. Once it has been started, the turbine should be 

 brought up to speed slowly. If it is speeded up too rapidly, 

 vibration will result. After the normal running speed has 

 been reached, the load may be thrown on; but this, also, should 

 be done gradually, to prevent a rush of water from the boiler 

 with the steam. 



If superheated steam is used, extra caution must be employed 

 in starting, for during the warming up, with the throttle valve 

 only slightly opened, the passing steam will be cooled consider- 

 ably. But when the valve is opened wider, the greater volume 

 passing will not lose so much of its superheat, and if care is 

 not exercised the turbine will be subjected to sudden expan- 

 sion because of the higher temperature of the steam. The 

 main point in starting is to avoid any sudden changes of 

 temperature in the turbine. If a turbine must be ready to 

 be put in operation at short notice, steam may be allowed to 

 flow through it continually, by means of a by-pass around 

 the throttle valve. It will always be warmed up, then, and 

 can be brought up to speed with less danger and more rapidly. 

 Lubrication of Bearings. The shaft or spindle of a turbine 

 rotates at high speed, and therefore the bearings should be 

 kept well lubricated; for if the oil supply fails, or if a bearing 

 begins to heat because of grit carried into it, the resulting 

 trouble will come very quickly. The presence of a hot bearing 

 will usually be evidenced by the smell of burning oil or by 



