Rotary Pumps NPIP (Net Positive Inlet Pressure)

Positive displacement or rotary pump people do not use the term “head”, they use the term “pressure” instead, so NPSHR would not be an appropriate term.

Rotary pumps are often selected to move liquids with a low vapor pressure point, or fluids with a lot of entrained bubbles.

This means that NPIP required (NPSH in centrifugal pumps) is difficult to test. The Hydraulic Institute establishes the point at the first indication of any of the following.

  • Cavitation noise is heard.
  • A 5% reduction in capacity at constant differential pressure and speed
  • A 5% reduction in power consumption at constant differential pressure and speed



  • On February 16, 2018