What is cavitation? What causes cavitation problem in the pump?

What is cavitation? What causes cavitation problem in the pump?

Let’s briefly define what cavitation means. Cavitation is caused by the formation of vapor-filled bubbles and their sudden bursting. The cavitation problem usually occurs as a result of the pressure in the pump falling below the vapor pressure of the pumped fluid. Cavitation damage is a threat to the pump. To prevent cavitation, there must be a minimum pressure at the suction port, defined as the positive suction head (NPSH), so that the liquid does not boil or evaporate. Thanks to this minimum pressure, cavitation formation can be prevented. The pressure applied at the suction port must be higher than the vapor pressure of the fluid. If there is cavitation damage in the pump, it may be necessary to throttle the control valve located on the pressure side. It is possible to reduce the flow rate and the NPSH value required by the pump by throttling the control valve. The important point here is to ensure that the residual flow is high enough to cool the pump. As a result of the cavitation problem, small gas bubbles form in the liquid. These reduce the capacity of the pump over time and thus shorten the life of the pump. It also causes the pump to run noisy, which is one of the most disturbing situations. Cavitation occurs as a result of rapid movement of any substance in a fluid. We can also call cavitation a kind of phase change event.

What are the negative effects of cavitation?

Cavitation is valid for all systems with pressure and velocity changes, which is possible even in the human body. Joint problems are common. Cavitation is directly proportional to the ambient temperature. With the decrease of the evaporation temperature, a cold boiling occurs in the system with water vapor and air bubbles, and this event leads to cavitation. The lowest pressure in pumps occurs at the inlet of the impeller, so it can be said that cavitation in pumps is usually collected at the inlet of this impeller.

If we examine the effects of cavitation under a few headings, we come across the following items.
• Cavitation is dependent on the pressure drop, but it is a preventable problem by controlling the pressure drop.
• Since it occurs in the liquid phase, it is unlikely to be observed in the solid and gas phases.
• It shortens the life of the pump, causes noise in the pump and causes abrasive and corrosive effects.