When testing rotodynamic pump efficiency, what is the standard method for testing?
Pump efficiency tests are performed to verify the efficiency of pumps and their conformance to any standards as applicable. The Energy Conservation Standard for Certain Clean Water Pumps, recently implemented by the United States Department of Energy, is a requirement for efficiency testing.
This standard incorporates by reference HI 40.6 Methods for Rotodynamic Pump Efficiency Testing. A pump efficiency test consists of measurement of flow, head and pump power input. Pump efficiency is a dependent variable that is calculated from these measured independent variables.
Uncertainty must be considered, as is the case with all tests. The uncertainty of a measurement depends on the residual uncertainty of the measurement device and on the method of measurement used.
After all known errors have been removed by zero adjustment, calibration, careful measurement of dimensions, proper installation, etc., there remains a value of uncertainty that never disappears. Methods for calculating uncertainty are also provided in the standard.
To determine the overall (wire-to-water) efficiency of a motor pump unit or a complete pump (i.e., bare pump, drive mechanical, driver and drive coupled together and treated as an integral unit), the driver or control power input and the pump power output are measured with the drive working under test conditions.
The ratio between pump power output and driver or control power input yields the overall efficiency. The driver or control power input is measured at the input terminals of the motor or control, if present on the pump under test. If the tested pump efficiency and the efficiency of all pump components are known, the product of the pump and all component efficiencies may be used to calculate overall efficiency.
For more information about estimating and testing pump efficiency, refer to ANSI/HI 20.3 Rotodynamic Pumps Guideline for Efficiency Prediction and HI 40.6 Methods for Rotodynamic Pump Efficiency Testing at www.pumps.org.