Pump net positive suction head issue
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A certain centrifugal pump in the oil depot indicates a NPSH of 4.5 meters. So how should I control my inlet pressure? I asked an experienced employee who has been to the pump manufacturer, and he said that it’s possible to reach around -0.059 Mpa. However, while I was operating it, after the inlet pressure dropped to -0.002 Mpa, other senior employees said that the pump had gone vacuum.
At that time, the medium was water, and the liquid level in the tank was around 0.7 meters; the installation height of the pump should be roughly at the same level as the bottom of the tank
Single-stage double-suction centrifugal pump TSY500-400-895: flow rate of 2200, head of 90, NPSH of 4.5.
This is not cavitation; it’s evacuated!
Under normal calculations, cavitation should only occur when the inlet pressure is above 0.05 MPa (G) (absolute pressure). If cavitation occurs prematurely, it is either because the pump’s net positive suction head value is inaccurate, or there is an obstruction at the inlet that results in insufficient liquid supply
But the manufacturer says that -0.0569 Mpa can be achieved; it is likely necessary to take into account both atmospheric pressure and the saturated vapor pressure of water
Do you mean by \"finding some time\" that the water has already vaporized?
-0.0596MPA is pretty much the same as my absolute pressure of 0.05MPA as well
The length of the inlet line, the opening degree of the inlet valve, and whether there is a filter at the inlet (i.e., the level of cleanliness) are all factors that influence this situation (the possibility of high water temperature inside the tank is not considered for now~~)~~
The water has not reached the vaporization stage; it is due to insufficient water supply, which is a different concept from cavitation. Having water but being unable to pump it up due to low pressure (vaporization) is cavitation.
Only consider the pump inlet pressure P1 ≥ (1+4.5)*density*g + Pv, where Pv is the saturated vapor pressure of the operating liquid