Cavitation, water pump cavitation and the damage of water pump cavitation

Cavitation is an abnormal phenomenon in hydraulic machinery. The cavitation of the water pump is caused by the vaporization of water. The vaporization of water is related to temperature and pressure. At a certain temperature, the critical pressure of water vaporization is called the saturated vaporization pressure at this temperature.

The pump cavitation is when the pump is running, because of some reasons, the pressure of the water in the pump is reduced to the working temperature, the water pressure and the vaporization pressure. The water will vaporize and produce lots of bubbles. A large number of bubbles separated from the water

As the water moves forward flow high pressure part of the impeller, the bubble is squeezed by the fluid surrounding the rapid collapse, and re condenses into water, this phenomenon is called water pump cavitation phenomenon. The most easy to happen cavitation water pump product is all kinds of centrifugal pump products. The principle of centrifugal pump which has low cavitation phenomenon is the self priming pump series, which is included in the vacuum self priming pump, which is the lowest pump product in the pump product of centrifugal pump principle.

The test shows that due to cavitation, the pump generates strong local water hammer, and the impact frequency can reach tens of thousands of times per minute, and it concentrates on tiny metal surface. The instantaneous local pressure can reach tens or even hundreds of MPa. The impeller of the water pump or pump shell wall continuous blow so great pressure in the local transient, metal surface caused by plastic deformation or local hardening, and metal fatigue phenomenon, and cracks and erosion, showing honeycomb like holes in the metal surface, until the impeller is erosion.

The occurrence of cavitation will cause changes in the performance of the pump. This change is different for different types of pumps. The low ns water pump, such as centrifugal pump ns<100, because the pump blade groove strip, cavitation bubble cut at the beginning, occupy the channel area of the head, power and efficiency of the pump started to decline, but had no obvious effect on the normal operation of the pump. When the external conditions make cavitation more serious, the bubbles are generated, blocking the flow channel, causing the continuity of the liquid flow to be damaged, and the flow discontinuity, Q&mdash, H and Q-n curves decline rapidly. For the high ns axial flow pump, the cavitation area is not easy to expand to the whole flow passage since the cavitation begins, since the blade channel is quite wide. Therefore, the performance curve not only decreased slowly, but also does not appear “ &rdquo fracture; damage condition, pump cavitation phenomenon: in the process of pump cavitation, the bubble burst, noise and vibration, strong vibration will make the unit parts and pump structure is destroyed, the noise may also harm management personnel the physical and mental health.

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