NPSH (Net Positive Suction Head) - Net hydraulic head (cavitation head). It is measured by the height of the liquid column at the pump suction and has the dimension "m liquid column", or for water "m water column - m water column". It is extremely important to consider this parameter when installing the pump in the centrifugal pump system.


Pb = atmospheric pressure, in metres;
Vp = Saturated vapour pressure of the liquid at the maximum operating temperature of the liquid, in metres;
P = Pressure at the surface of the liquid in a closed container, in metres;
Ls = Maximum suction height, in metres;
Lh = Maximum height of the support, in metres;
Hf = Friction loss in the suction pipe at the required pump capacity, in metres. The available head NPSHa must exceed NPSHr. Preferably by 0.5 m (recommended margin). In an actual system, the NPSHa is determined by means of a pressure gauge installed on the suction side of the pump.