What is Cavitation in a Slurry Pump


Published:

Dec 24,2023

According to the statistical analysis of data, about 25% of the overflow parts of the slurry pump are scrapped due to normal wear, and most of the overflow parts are operated under abnormal working conditions and cause early damage, and the difference in life is nearly half. The reason for the large proportion of abnormal damage parts is cavitation, which is divided into true air erosion and gas cavitation.

What is Cavitation in a Slurry Pump

According to the statistical analysis of data, about 25% of the overflow parts of the slurry pump are scrapped due to normal wear, and most of the overflow parts are operated under abnormal working conditions and cause early damage, and the difference in life is nearly half. The reason for the large proportion of abnormal damage parts is cavitation, which is divided into true air erosion and gas cavitation.

Cavitation occurs due to the change in pressure encountered by the liquid as it passes through the pump impeller. As a result of this sudden pressure change, entrained vapor bubbles form and burst. While cavitation is inconsequential in a small area, it can be very damaging to the pump when repeated tens of thousands of times per second.

When the slurry pump cavitation, the bubble in the high-pressure area continues to occur sudden collapse, and accompanied by a strong liquid strike, then the frequency of 600 ~ 25000Hz noise will be generated, the pump can hear the explosion sound, at the same time the unit vibrates, the vibration of the unit will promote more cavitation bubbles to collapse, the two excite each other, when the frequency is close to the natural frequency of the device, the unit will have a strong resonance, called cavitation resonance, when the vibration is violent and the noise is too large, the pump should stop working.

When the slurry pump works under steam (gas) erosion conditions for a long time, under the continuous and strong high-frequency (600~25000Hz) impact (pressure up to 50MPa), there will be pitting on the metal surface in the early stage, and the metal grains will loosen and fall off in the later stage, showing honeycomb, sponge, groove, fish scales and even perforation and fracture.

Practice has proved that the part of vapor (gas) erosion damage is the place where the bubble disappears, so the damage traces are often found at the outlet of the impeller and the inlet of the volute, and also appear on both sides and periphery of the impeller, the front and rear guard plates and the inner wall of the volute.

When cavitation just occurs in the slurry pump, it has little impact on the performance of the pump, and when the cavitation develops to a certain extent, due to the interference and destruction of the energy exchange between the impeller and the liquid, a large number of bubbles will block the flow channel, and the flow, head, efficiency and shaft power curve of the pump will also decrease significantly.

Keyword:

SLURRY PUMP