Pump Efficiency
Pump efficiency is the ratio of the hydraulic power delivered to the liquid to the mechanical power supplied at the pump shaft, expressed as a percentage. Hydraulic power is calculated from flow rate, total dynamic head, liquid density and gravitational acceleration; shaft power is often referred to as brake power. Losses arise from hydraulic friction and turbulence, internal leakage across wear rings and clearances (volumetric losses), and mechanical friction in bearings and seals. Efficiency varies with flow and peaks at the best efficiency point; it decreases with increasing liquid viscosity and with wear that opens internal clearances. Overall (wire-to-water) efficiency also includes motor and drive losses. Because energy usually dominates a pump's life-cycle cost, efficiency is a key selection parameter. Test methods for verifying pump performance are given in ISO 9906 and ANSI/HI 14.6.
Examples
- Comparing efficiency of competing pump selections at the duty point
- Energy audit of a water distribution pumping station
- Performance test of a refurbished pump to ISO 9906