Hydraulic Characteristics of Hollow-Jet Valves

For free discharge conditions the hollow-jet valve has proved to be a satisfactory control device for flows through large conduits operating under high heads. Results of field tests with a 96-inch hollow-jet valve have revealed close agreement with hydraulic characteristics predicted from model studies. Piezometric measurements, thrust determinations on the valve needle, and rates of discharge were included in both field and laboratory tests. The prototype valve can be used as a metering device by the employment of model calibration results provided accurate position indicators are used. The only cavitation erosion evident in the prototype valve was caused by local irregularities in the body casting, which have been alleviated in subsequent valves by careful foundry practice and inspection.