Reasons For Abnormal Vibration And Noise During The Operation Of Centrifugal Pumps

Oct 17, 2024

The causes of abnormal vibration and noise during the operation of centrifugal pumps generally include the following aspects:
1. Cavitation phenomenon occurs.

During the cavitation process, bubbles and bubbles will rupture, causing vibration and noise. If the vibration is caused by cavitation of the chemical pump, it is necessary to change the installation height or increase the system pressure, or even reselect or design the pump.
2. The rotor balance decreases.

When the rotor is unbalanced, the deviation between the center of gravity and the center of rotation of the rotor is too large, resulting in unbalanced force during rotation, especially when the speed is high, the vibration is more obvious. On the one hand, rotor balancing may not meet design requirements during manufacturing or assembly processes; On the other hand, it is possible that after a certain period of operation of the centrifugal pump, the rotor balance accuracy may decrease due to shaft deformation, excessive eccentric wear of parts, and other reasons. In both cases, it is necessary to rebalance the rotor.
3. The centrifugal pump is in the non design operating condition zone.

Chemical centrifugal pumps should operate around the design point and avoid operating in low and high flow areas as much as possible, otherwise the increase in hydraulic shock will cause vibration. When water flows from the outer end of the impeller blades near the guide vanes or volute pump tongue, hydraulic impact is generated, and the degree of impact increases with the increase of the speed and size of the chemical centrifugal pump. When this hydraulic pulse is transmitted to the pipeline system and foundation, it will generate noise and vibration; If the frequency of this hydraulic pulse is similar to the natural frequency of the pump shaft, piping system, or foundation, more severe resonance will occur. In practice, the vibration caused by hydraulic shock can be prevented and reduced through the following methods or measures:
① Appropriately increase the distance between the impeller outer diameter and the pump casing tongue, that is, increase the gap between the impeller outlet.
② Change the profile of the channel to avoid sudden changes in channel area or flow direction, in order to mitigate the adverse effects of hydraulic shock.
③ When assembling multi-stage pumps, the outlet edges of the blades of each impeller should be staggered at a certain distance, and the assembly position of the guide vanes should not overlap with each other, but be arranged in a certain order in a staggered manner. These measures will reduce hydraulic pulses. If changing the resonance frequency of the pipeline system cannot reduce the hydraulic shock of the pump, only by taking measures to reduce the intensity of blade pulses in the hydraulic design of the pump can the problem be fundamentally solved.
4. Impeller flow channel blockage.

When there are foreign objects blocking the impeller flow channel, causing the impeller to become heavy and unevenly stressed, it is necessary to remove the impeller for cleaning.
5. Reasons for bearings.

If the bearing is damaged, in addition to increasing its own operating noise, it will cause the rotor's motion to lose stability, resulting in increased vibration and noise of the pump unit. In addition, excessive radial clearance of the bearing may also cause abnormal noise. At this point, it is necessary to replace the bearings.
6. Reason for installation.

If there is looseness between the centrifugal pump and the base, or between the base and the foundation, or if the coaxiality of the coupling between the motor and the pump is too low, vibration and noise may occur. It is necessary to tighten the connecting bolts again or realign them.