Casting volute

Bypassing is occurring between volute channels in a double-volute pump casing due to a casting defect or extreme erosion. 

Heavy Duty Volute (150,300 lb. Steel and 125 lb. Cast Iron)... 

The pump casing of a slurry pump often takes the shape of a volute. The best hydraulic design calls for a constant momentum design or a linear increase of the cross-sectional area from the tongue to the throat (Figure 8-19). In reality, the profile of the volute is often simplified to two semicircles. The idea is that hard metals are difficult to cast, and if the shape can be simplified, the casting will flow better during solidification. 

FIGURE 8-21 Casting for the casing and cover plate of a vertical sump pump clearly showing the volute shape—with an integral cast elhow at the discharge. (Courtesy of Mazdak International Inc.)... 

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