What is the impact of too rapid an inlet pressure drop on a centrifugal pump?
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Recently, an issue arose during production: the pressure in the inlet tank of a vertical centrifugal pump dropped rapidly from 530 KPa to 470 KPa due to process operations, which resulted in cavitation in the pump. In normal operation, this pressure is kept at 470–480 KPa, and the pump runs smoothly. I believe that cavitation occurs due to the volatile components in the material being transported, which cause a drop in pressure and resulting flash evaporation; this creates a gas phase that leads to cavitation within the pump. However, I’m not sure how to explain this phenomenon from a theoretical perspective. I would appreciate some guidance from everyone!
The depressurized flashing of the volatile components in the material being transported causes cavitation in the pump. This exists for saturated media.
Pumping cavitation occurs only when the pressure drop is too rapid; a slow decline poses no problem. So what’s going on?
Your question already explains the principle quite clearly. Cavitation is caused by the volatile components in the material being transported undergoing pressure reduction and flash vaporization, which results in a gas phase that induces cavitation within the pump; it is therefore necessary to avoid large fluctuations in inlet pressure.
Cavitation: Cavitation has a significant impact on the damage to pumps, particularly damaging the volute and impeller. Due to the presence of gas at the inlet, this gas is compressed as it passes through the pump. After leaving the impeller, the bubbles expand, causing fluctuations in the fluid flow and leading to collisions with the components of the pump
Increasing the inlet pressure of the pump can eliminate cavitation; for example, by raising the liquid level of the material in the storage tank, lowering the temperature of the material, or increasing the pressure inside the storage tank.
Possible reasons are as follows: 1. A sharp drop in inlet pressure causes fluctuations in outlet pressure, resulting in water hammer in the outlet pipeline and affecting the pump’s operating condition； 2、
If flashing occurs, the temperature at 530 KPa should be high enough. If the temperature is the same in both cases and only the pressure increases, the effect should be the same.