NPSH is net positive suction head. When the centrifugal pump is working, the liquid will generate vapor at the inlet of the impeller due to a certain vacuum pressure. The vaporized bubbles will ablate the metal surface of the impeller under the impact movement of the liquid particle, thereby destroying the metal such as the impeller. Vaporization pressure, NPSH refers to the excess energy of the unit weight liquid at the pump suction port exceeding the vaporization pressure. The unit is marked with meters and (NPSH)r. The suction stroke is the required NPSH Δh: the vacuum that the pump is allowed to absorb, that is, the allowable installation height of the pump, in meters.
Suction stroke = standard atmospheric pressure (10.33 m) - NPSH - safety (0.5 m) The standard atmospheric pressure energy pipeline vacuum height is 10.33 m.
Calculation formula
What is the NPSH? What is a suction? Respective units of measurement and letters?
Answer: When the pump is working, the liquid will generate liquid vapor at the inlet of the impeller due to a certain vacuum pressure. The vaporized bubbles will peel off on the metal surface such as the impeller under the impact movement of the liquid particle, thereby destroying the metal such as the impeller. Called vaporization pressure, the cavitation allowance refers to the excess energy of the liquid per unit weight at the pump suction port that exceeds the vaporization pressure. The unit is a liquid column and is expressed by (NPSH)r.
The suction stroke is the required NPSH Δ/h: the vacuum at which the pump is allowed to absorb liquid, ie the pump allows geometric installation height. The unit uses meters. Suction stroke = standard atmospheric pressure (10.33 meters) - NPSH - pipeline loss - safety (0.5) standard atmospheric pressure can be pressed on the pipeline vacuum height 10.33 meters
For example: a pump NPSH is 4.0 meters, and the suction range Δh
Solution: Δh=10.33-4.0-0.5=5.83 m
