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HYDRAULIC EQUIPMENT 



or where there are pockets formed in the surface of the vanes, pit- 

 ting or corrosion inevitably develops. It has also been demon- 

 strated that where air in large quantities is entrained in the water 

 carried to the turbine corrosion seems to take place very rapidly 

 if the design is not correct. 



"A corroded vane surface has an appearance resembling a 

 sponge, the surface being extremely irregular and the pitted spots 



FIG. 126. Runner for Reaction Turbine. (Built by I. P. Morris Company.) 



often opening holes entirely through the vane. Chemical analysis 

 of the corroded surfaces has brought out the fact that the metal 

 has been oxidized. In runners made of bronze or an alloy, mod- 

 ifications in the composition have been detected in the corroded 

 portions. 



"The theory of corrosion as now generally accepted is that the 

 water in passing over any pocket or depressed surface, or in failing 

 to adhere to the surface of the vane, leaves spaces which are filled 



