What causes the abnormal noise in the centrifugal pump casing?

Aug. 17, 2021

the pump casing

pump casing

The causes of abnormal vibration and noise of the centrifugal pump can be divided into two aspects.

The first reason is mechanical.

1. The rotating parts are unbalanced. In addition to the unqualified rotor dynamic balance after manufacturing or welding repairs, local corrosion, wear or siltation of the impeller may also cause it to lose its balance.

2. The pump base is not good. For example, the anchor bolts are loose, the rigidity of the base is insufficient to resonate with the pump, or the base sinks to make the axis misaligned.

3. Moving and static parts rub against each other. This may be caused by the bending of the pump shaft, bearing wear, etc., or the failure of the axial thrust balance device, which causes the impeller to move axially and touch the pump casing.

4. The prime mover itself vibrates, and the coupling can be detached for operation inspection.

5. Poor coupling or improper installation of the piping caused the pump shaft to be misaligned.

The second reason is liquid.

Cavitation phenomenon. The vibration and noise caused by this phenomenon are usually generated when the flow rate is large, and the frequency is high (600~25000HZ). You can check whether the suction vacuum is too large to help judge. It can usually be eliminated by reducing the flow rate (such as closing the discharge valve or reducing the speed), lowering the liquid temperature, or increasing the injection height.


What are the hazards of cavitation in centrifugal pumps?

1. The performance of the centrifugal pump is degraded. The flow rate, pressure head, and efficiency of the pump are all reduced. If a large number of bubbles are generated, air binding may occur, forcing the centrifugal pump to stop working.

2. Produce noise and vibration, which affect the normal working environment of the pump.

3. The materials of the pump casing and impeller are damaged, which reduces the service life of the pump.


Causes of cavitation

It is caused by the static pressure near the suction port of the impeller being lower than a certain value. There are many reasons for the low static pressure, such as the installation height of the pump exceeding the allowable value, the temperature of the pumped liquid is too high, and the local resistance of the suction pipe is too large. To avoid cavitation, try to ensure that the pressure near the inlet of the impeller is lower than the saturated vapor pressure of the liquid at the conveying temperature. Generally, according to the anti-cavitation performance of the pump, reasonably determining the installation height of the pump is an effective measure to prevent the occurrence of cavitation.


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