TURBINES 



231 



(Figs. 124 and 125). The thrust bearing is occasionally located 

 between the generator and the turbine, and supported by the 

 latter, but it is usually and preferably placed on top of the 

 generator, and supported by a spider mounted on the generator 



FIG. 123. Single-runner Vertical Turbine with Volute Casing and Draft 

 Tube Molded in the Concrete Substructure. 



frame. The gate mechanism is of the exposed type, no parts 

 being in the water except the gates themselves, and all bearings 

 and pin connections are accessible for lubrication. 



Runners: The runners are mostly made in one piece (Fig. 126), 

 except for very large sizes where it becomes preferable to make 

 them in sections on account of shipping limitations and so as to 

 assure sound castings. While bronze was used previously to a 

 very great extent so as to prevent corrosion, experience has proved 

 that this effect is primarily due to defective designs. For this 

 reason cast iron is now used to a much greater extent for runners 



