SYNCHRONOUS GENERATORS 



337 



operated with surface pressures of 400 to 500 pounds per square 

 inch. A considerable excess of area must be provided, however, 

 to take care of the starting and stopping conditions which are 

 much more severe than the running conditions. 



The spring-thrust bearing (Figs. 198 and 199), automatically 

 adjusts itself to unequal loading due to inaccuracies in workman- 

 ship or in alignment. This is of the utmost importance as, while a 

 bearing may be properly adjusted when installed, a distinctive 

 feature of the spring-supported bearing is that it will automatically 

 adjust 'tself while in operation if there is a loss of alignment due to a 

 settling of foundation or to other causes. 



As seen from the illustrations, the thrust collar is keyed to the 



Retaining Ring 



FIG. 199. Spring Thrust Bearing. 



shaft and transmits the weight of the revolving parts to the 

 rotating ring of the bearing. This ring has a smooth rubbing 

 surface and is so designed that a rapid circulation of oil is main- 

 tained. The upper surface of the stationary ring is the stationary 

 rubbing surface of the bearing. The ring rests on springs held in 

 position by means of center pins, while dowel pins are provided to 

 keep the stationary ring from revolving. 



The rubbing surfaces are in a bath of oil, the quantity of oil 

 circulated from an outside source depending on the losses and the 

 cooling conditions. Water cooling coils may be installed in the 

 bearing housing which will reduce the amount of oil, and for 

 smaller bearings, at low speed, no circulation of oil from a source 

 outside the bearing housing is required. 



