High vibration in the rear bearing of a multi-stage centrifugal pump?
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Our facility uses large multi-stage centrifugal pumps of the 125D-25×8 model manufactured by Zhejiang Pump Factory. We have now observed that the vibration of the rear bearing is as high as 15 mm/s. A bearing was replaced during maintenance today, but the old bearing removed showed no obvious defects. After re-aligning it, the vibration level when the pump was started was still 10.5 mm/s – the problem has not been resolved. Could the experts please shed some light on this?
Is there a vibration spectrum? Is the gap normal? Could the vibration of the rear bearing shell be caused by the thrust bearing receiving excessive axial force? Consider it from the perspective of reducing axial force. You wrote it too simply.
The dynamic balance of the impeller is also one of the causes of vibration; it is best to conduct a thorough inspection
Regarding vibration, it is necessary to measure the spectrum; a high speed value alone does not necessarily indicate a bearing problem.
Re-align it to check whether the motor and the pump are at different heights!
Does an increase in axial backlash increase bearing vibration? Will it be more noticeable on the front axle or the rear axle!
Perform static balancing on the impeller; in this type of multi-stage pump, the shaft is flexible, and even a small amount of imbalance can cause severe vibration
Check the spacers between each stage of the impeller, and reinspect aspects such as clearance and material.