四, must NPSH and NPSH effectively

NPSH is effective in overcoming pressure head on the surface of the liquid into a container in the suction pipe installation flow losses, and increase the water to the corresponding height, after more than vaporization pressure energy of the head.

Effective NPSH is determined by the device characteristics of intake system, has nothing to do with the performance of the pump itself.

(1) when the flow rate increases, the flow in the suction line loss increase, effective NPSH, the possibility of cavitation.

(2) the pump the liquid temperature is higher, corresponding to the evaporation pressure, the greater the effective NPSH is smaller, the greater the possibility of cavitation.

(3) effective NPSH, the greater the pump, the smaller the possibility of cavitation.

Must be NPSH is liquid from the pump inlet pressure drop to the lowest pressure point inside pump, has nothing to do with the device of suction system, determined by the cavitation performance of the pump itself. Must be NPSH is smaller, the better pump cavitation resistance.