236 



HYDRAULIC EQUIPMENT 



type of gate mechanism, is much superior to the older types in 

 which the moving parts are more or less submerged. The exposed 

 type, as applied to spiral casing turbines for high heads, is the 

 ideal arrangement in that all bearings may be lubricated and the 

 gate-stem packings may be arranged to exclude water and grit. 

 The exposed mechanism has a further advantage in that it per- 

 mits a more direct connection between the operating ring, to which 

 the gate-stem levers are connected, and the regulating cylinders 



FIG. 128. Vertical Reaction Turbine, Showing the Gate-operating Mechanism 

 and Speed Ring. (Built by I. P. Morris Company.) 



or " servo-motors " of the governor system. When the operating 

 ring is outside the wheel casing, it may frequently be directly 

 attached to the connecting rod of the regulating cylinder. Large 

 units should have two regulating cylinders connected to the ring 

 at diametrically opposite points, so as to insure a balanced con- 

 dition. 



The wicket gates, or movable guide vanes, are mostly made of 

 cast steel. They are subjected to rough usage on account of ice, 

 stones and rubbish in the water, and cast iron is too brittle for 

 such service. In very large units, the gate stems or fulcrums 



