244 



HYDRAULIC EQUIPMENT 



Arrangement of Runners. The two principal runner arrange- 

 ments are the single-overhung and the double-overhung. In 

 addition there is also the self-contained type. The first-named is 

 mounted on an overhung extension to the generator shaft (Figs. 

 116 and 134), no extra outboard bearings being provided, and the 

 second type comprises simply two single-overhung wheels, one 

 being mounted on a shaft extension at each end of the generator. 

 This is the ideal construction for large units and is extensively 

 used. With the double-overhung type it is possible to make a 



FIG. 134. Single Overhung Impulse Turbine, Governor Regulated by Jet 

 Deflector. (Built by Pelton Water Wheel Company.) 



prime mover of double the power output, maintaining the same 

 speed of rotation with the same conditions of water pressure. 

 For very large units, two wheels on each side of the generator may 

 be used, making four wheels per unit. This usually requires four 

 bearings, the generator rotor being mounted between the two main 

 bearings, with an outboard bearing at each end, two wheels being 

 located between one main bearing and one outboard bearing. The 

 self-contained type has its own shaft, bearing, base and housing, 

 one or more runners being mounted on the same shaft and in the 

 same housing. It is mainly used for small capacity units. 



