When the liquid ring vacuum pump is working, at a certain temperature, when the liquid pressure at the low pressure is lower than the vaporization pressure (that is, the saturated vapor pressure) at the temperature, the liquid begins to vaporize to generate bubbles, and when the liquid enters the high pressure area, the bubbles are formed. When broken, the surrounding liquid quickly fills the original bubble cavity, resulting in hydraulic shock. This phenomenon of bubble generation, development and collapse is called cavitation.

During the working process of the liquid ring vacuum pump, the absolute pressure of the suction area is consistent with the absolute pressure of the pumped system. That is, the higher the vacuum skin of the pumped system, the higher the vacuum in the suction area.

Liquid ring vacuum pumps require liquid as the working medium. Each liquid has a corresponding saturated vapor pressure at a certain temperature. When the absolute pressure of the suction zone area is closer to the saturated vapor pressure of the liquid, the liquid is closer to the boiling voltaic state. At this time, a large number of bubbles will be generated on the surface of the working fluid in the suction area. Since the working fluid vapor generated by the liquid in the working chamber will occupy part of the space of the working chamber, the external suction capacity of the pump will be reduced. When the pressure in the suction area reaches the saturated vapor pressure of the working fluid, it can be considered that the working chamber is completely filled with the working fluid vapor. At this time, the external suction capacity of the pump is close to 0, and the cavitation phenomenon of the pump is also serious at this time. .

If the working fluid is water, the higher the water temperature, the more the pumping performance of the pump decreases.

The cavitation damage of the liquid ring pump is the same as that of the centrifugal pump. It is in the place where the bubbles are generated and ruptured. The metal surface has cavitation, and serious honeycomb damage will occur. If the vacuum pump impeller has a large residual stress in the cavitation part, it will also cause stress release and cracks.

Due to the sudden bursting of bubbles in the high pressure area during pump cavitation, and the accompanying strong water hammer, noise and vibration are generated on the surface. A crackling sound like popping beans can be heard. The measured results show that the vibration frequency range caused by cavitation is 600~25000Hz, and the pressure is 49MPa.

If the above-mentioned bubbles burst on the metal surface, the metal surface will be subjected to continuous and strong water hammer, pitting will appear, and the metal grains will be loosened and peeled off into a honeycomb shape, or even perforated. In addition to mechanical effects, cavitation damage is accompanied by various complex effects such as electrolysis and chemical corrosion. The actual damage situation shows that the part where the cavitation damage of the pump flow parts is destroyed is the place where the bubbles disappear.