20. February 2018

NPSH value of a pump, minimum pre-pressure

A calculation of the pump pre-pressure "H" is recommended

A calculation of the pump pre-pressure "H" is recommended:

  1. at high media temperatures
  2. if the flow rate is significantly higher than the nominal flow rate of the pump
  3. when the fluid is pumped from great depth
  4. when feeding the pumped medium over long pipes
  5. in poor feed conditions. To avoid cavitation, make sure that there is always a minimum pressure on the suction side of the pump


The maximum suction height "H" in m can be calculated as follows:

  • H = (Pb x 10,2) - NPSH - Hf - Hv - Hs



NPSH value of a pump


If a positive value is determined for "H", the pump can be operated at a suction height of at most "H" m. 
If a negative value is determined for "H", an inlet pressure of at least "H" m is required.



Note: To prevent cavitation from occurring, never select a pump whose operating point is too far to the right of the NPSH characteristic.

The NPSH value of the pump must always be determined for the highest possible delivery rate.


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