Abstract: The pump system provides for a more efficient operation of multistage centrifugal pumps operating at less than designed capacity. The system includes a flow meter located in the inlet conduit to the pump, a control valve is located in a discharge conduit that extends from the discharge of the first stage of the pump to the inlet conduit, and a connection between the flow meter and control valve whereby the control valve will open to bypass liquid from the first stage discharge to assure that flow through the first stage is greater than the value wherein the internal recirculation occurs. Thus, the pump is capable of circulating a substantially greater amount of liquid through the first stage of the pump when the demand volume at the pump discharge is substantially less than the design value.

Abstract: A flushing liquid system for an improved wearing ring in a centrifugal pump which wearing ring has spaced flushing liquid inlet and outlet chambers, has a first control assembly for supplying flushing liquid to the flushing liquid inlet chamber and a second control assembly for returning or draining at least a portion of the flushing liquid through the flushing liquid outlet chamber, with respective first and second control assemblies either having a predetermined setting or operatively responsive to signals from sensory devices for sensing at least one or more operating conditions of the centrifugal pump so that the operation of the first and second control devices can act to minimize flushing liquid requirements of the wearing ring and minimize dilution by the flushing liquid of the process fluid or mixture being pumped by the centrifugal pump.