An Integral Balance Piston For Centrifugal Pump Impellers

Abstract

Axial thrust balancing of pressure forces in centrifugal pumps has long been a design challenge for pump engineers. This becomes particularly important in sealless pumps, due to their lack of thrust bearing capacity, and an increasingly difficult in high speed pumps, as stage pressure rise is increased. Many thrust balancing configurations have been used including devices such as balance pistons which can compensate for variable conditions. Separate balancing devices, however, add significant disc friction power and require excessive leakage flow, both of which reduce efficiency. A unique thrust balancing device has been developed which integrates the balance piston with the impeller shrouds. This patented device achieves self-compensating thrust balance in addition to minimizing overall leakage and disc friction power. A detailed description of the integral balance piston is presented. Technical features and performance calculations are supported by development test results and operating field experience.