NPSH: the difference between the total water head of the liquid at the pump inlet and the pressure h
NPSH: the difference between the total water head of the liquid at the pump inlet and the pressure head when the liquid vaporizes
NPSH is expressed in meter (water column)
In most cases, the suction chamber of the pump is under positive pressure, and the pump speed is very low, generally 150-350rpm, so cavitation usually does not occur; However, in order to enhance the operating reliability of the pump under normal conditions and prevent cavitation, the required NPSH of the device must be greater than the effective NPSH of the pump, that is, NPSHA>NPSHR.
If cavitation is possible, the following methods shall be taken to prevent cavitation as far as possible:
? Increase the diameter of the pipeline at the suction end of the pump to reduce the friction loss in the pipeline
? Reduce the length of the pipeline at the suction end of the pump, and minimize the number of valves and elbows to reduce the friction loss in the pipeline
? Try to increase the liquid level at the pump inlet to avoid the pump working under self-priming conditions
? Reduce the necessary NPSH of the pump by reducing the pump speed
? Change the necessary NPSH of the pump by changing the geometry of the stator and rotor