Liquid ring vacuum pump noise

Causes of noise in vacuum pump, solutions to noise in vacuum pump

The normal sound of the liquid ring vacuum pump is caused by the eddy current of the liquid ring. When the pump exceeds the critical compression ratio, the air pressure discharged from the vacuum pump can not withstand the air pressure at the exhaust port, resulting in the increase of the back pressure of the air in the vacuum pump, which is transmitted to the liquid ring and slows down the flow rate. At first, only the outer part of the liquid ring close to the pump body between the suction hole and the exhaust hole forms vortex. Then, with the further increase of the back pressure of the exhaust hole, the scope of the vortex also expands, gradually reducing the volume of the suction space and the effective section of the suction hole, resulting in the decrease of the air child.

The vortex of liquid ring formed when the compression ratio exceeds the critical value makes the gas pressure and gas volume in the vacuum pump pulsate periodically, which causes the sound of the vacuum pump. The sound increases with the increase of compression ratio (but the shaft power does not rise much). When the maximum compression ratio is reached, the gas flow is zero, and the whole liquid ring from the suction hole to the exhaust hole forms eddy current, which makes the gas flow fluctuation and noise level reach the maximum value. This noise is related to the peripheral speed of vacuum pump, suction pressure, wall thickness of vacuum pump, structure of air-water separator and water supply basin. For the running vacuum pump, if the water supply is adjusted properly, or a small valve is installed on the air inlet pipe to discharge the air into the vacuum pump body, the sound may be reduced.

During the operation of liquid ring vacuum pump, if the sound is not caused by the above normal hydrodynamics phenomenon, but one of the following three conditions occurs, it means that there is a fault in the pump.

(1) At any compression ratio, the pump makes noise.

(2) There is obvious metal friction sound or impact sound.

(3) The shaft power increases obviously (observe the voltmeter and ammeter of the motor).

Causes of noise in liquid ring vacuum pump: the abnormal noise may be caused by the metal friction sound caused by the eccentric wear between the side cover of vacuum pump and the end face of impeller, or by the sundries in the vacuum pump, or even the impeller blades are broken. At this time, the pump shall be shut down for inspection.


Liquid ring vacuum pump noise

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