Net Positive Suction Head Equation - Fluid Flow

Fluid Flow Table of Contents
Hydraulic and Pneumatic Knowledge
Fluid Power Equipment

Net Positive Suction Head

It is possible to ensure that cavitation is avoided during pump operation by monitoring the net positive suction head of the pump. Net positive suction head (NPSH) for a pump is thedifference between the suction pressure and the saturation pressure of the fluid being pumped.NPSH is used to measure how close a fluid is to saturated conditions. Equation 3-19 can be usedto calculate the net positive suction head available for a pump. The units of NPSH are feet of water.

NPSH = Psuction - Psaturation

where:

NPSH = Net Positive Suction Head (m, in)
Psuction = suction pressure of the pump
Psaturation = saturation pressure for the fluid

By maintaining the available NPSH at a level greater than the NPSH required by the pump manufacturer, cavitation can be avoided.