The vibration levels during pump testing were above the acceptable range; it is suspected that vibration in the outlet pipeline is the cause

Is the pump secured with its foundation screws properly? What is the degree of concentricity between the motor and the pump? If the outlet pressure of the pump is high, the outlet pipeline needs to be fixed.

Is there a problem with the alignment of the pump and motor? Is there any blockage in the inlet? Is the pump suffering from cavitation? Has the impeller drawn in foreign objects? Is the impeller dynamically balanced properly? Are the anchor bolts loose?

Since it’s in the trial phase, it’s still in the factory’s workshop. Suggestions: 1. Disconnect the flanges connecting the pump’s inlet and outlet separately to check for any stress. 2. The vibration level is too high – how many mm/s is it? It is recommended to use a spectrometer to measure the vibration components. It’s possible that it’s not a pipeline issue, but rather caused by factors such as misalignment or imbalance.

Disconnect the flanges of the inlet and outlet pipelines to check for misalignment with the pump flange. If the misalignment is large, the piping needs to be redrilled to eliminate it or flexible connections should be used. If no misalignment is found during the inspection, proceed to check the alignment of the coupler, and verify that the diaphragm or hexagonal gasket is in good condition. If there are still no problems, then issues with the impeller and bearings need to be suspected.

I encountered a case recently where trying to place a layer of gauze on the surface where the pump meets its base should help reduce the issue a bit

Excessive stress on pipes and pumps can cause vibration, but wear on the pump bearings, shaft, and impeller, as well as misalignment, can also be factors. If the motor and pump are connected by a coupling, alignment also affects vibration.

There are various reasons for excessive pump vibration. Regarding the pipelines alone, it is necessary to check whether there is stress on the flanges connecting the inlet and outlet pipelines to the pump. The flange bolts can be removed to verify whether there are any misalignments or gaps between the pipeline flanges and the pump’s inlet and outlet flanges. The distance between the flanges should not exceed 0.5 mm more than the thickness of the gasket. The flange bolts should move freely when passing through the mating flanges; there should be no obstruction, nor should the bolts be forced through the holes using a hammer. Specific requirements regarding misalignment and gaps in mating flanges are specified in relevant standards. Furthermore, when tightening the inlet and outlet pipelines of the pump as well as the flange bolts, a alignment gauge should be placed on the coupling (the coupling must be in a loose state; it cannot be tightened). While tightening the flange bolts, the deviation indicated by the alignment gauge must not exceed a certain value. There should also be pipeline supports at the first elbow of the inlet and outlet pipelines to support them. If in operation, due to the simultaneous operation of several pumps, the process pipelines affect one another, resulting in excessive vibration in the pipelines and pumps. If the pump vibration is above the acceptable level, there are many possible causes; each specific case needs to be analyzed individually.

OP, have you figured out what the cause was later on?

This post was last edited by 3983596_FPPZ on 2018-9-23 09:38. We are currently working on fabricating the appropriate pressure-taking pipelines and fixing the pipeline fittings; the work is not yet complete. The flow channels within the pump body have been polished, the position of the partition lip has been adjusted, and the impeller is undergoing dynamic balancing. If that doesn’t work, we will use a closed-frame testing setup to eliminate the impact of pipeline vibration. I will keep you updated on the progress :)