Analysis of the causes of centrifugal pump failures
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Recently, a 100AYⅡ-120*2 atmospheric bottom pump was kept in normal standby. When attempting to start it, the motor tripped as soon as it started up, preventing the pump from operating. After disconnecting the coupling between the motor and the pump, rotating the pump was easy, with no uneven areas. Subsequently, the electrical and mechanical teams inspected and repaired the motors and pumps, after which the fault was resolved. Without specifying which faults are being ruled out, let’s all discuss how your organization coordinates electrical and mechanical maintenance teams when such fault symptoms occur. Also, what could be the possible causes of these faults?
First, contact the electrical team for an inspection to confirm that there are no issues with the electrical system; after that, the machine repair technician will handle it by checking the pump itself as well as ensuring proper alignment between the pump and the motor. I don’t know where the problem lies; let’s learn about it.*
Reply to 1# linigood: First, test the vibration and listen to the operating sound; if something is abnormal, inform the mechanic； If everything is normal, inform the electrician to check the current to see if it is too high or if there is a missing phase ； The current is excessively high; the coupling disengages, and the motor is tested individually ； In the case of a missing phase, repair the motor directly. If all aspects of the motor are normal, the maintenance team will work with the process engineering staff to check whether there are any changes in the viscosity, temperature, or other properties of the process medium
First, the machine repair fitter inspects the pump; if it operates smoothly, then the electrician is asked to check the electrical protection devices. I’ve learned it.*
The analysis is as follows: 1. One of the electrical connections for the motor is missing; 2. The lock nut of the impeller has fallen off, causing the impeller to get stuck; 3. Screws or other objects have entered the pump inlet and caused the impeller to get stuck
The electric fitter also went to the site to inspect the motor and the pump body, continuing until the problem was identified and resolved; they could leave only after a successful test run. Your pump is likely having an electrical issue
After the above fault occurred, both electricians and fitters went to the site; they first disconnected the coupling, then turned the pump – it moved easily, and they also turned the motor, which moved just as easily. At the same time, the individual test run of the motor showed no issues. Since removing the pump was rather troublesome, I checked the soft starter in the power distribution room again, suspecting that there might be a problem with it. I then replaced the soft starter from another pump with one for this pump, but the same fault symptoms persisted. There was no other choice; the fitter began to disassemble the pump. Once it was disassembled, a problem was discovered: the back of the impeller was loose, the impeller was moving axially, and rubbing occurred between the impeller and the casing. After the back is tightened and the sweat is gone, the problem is solved.
It might be a electrical short circuit; I encountered this problem while working on a plasma cutter before!
Reply to 7# linigood: Haha, this issue can be detected by hearing a difference in sound the moment the pump starts; an experienced maintenance technician should be able to identify it. Additionally, the steps for testing should be as follows: 1. Initiate a preliminary start-up and listen to the sound; 2. Check the alignment as well as the bolts used for alignment, depending on the type of coupling you have; 3. Disconnect the motor and conduct a ‘no-load test’ of the motor; 4. If everything is fine, then start the pump for further testing. Haha
Reply to 9# zxf760718: Well, in theory, static and kinetic friction should produce abnormal noises, but the environment at the site was noisy, and it only took a little over 10 seconds from when the pump started to when it stopped working; therefore, it was not possible to determine the fault based on sounds :)
I need to think more about this issue; it’s definitely a mechanical problem. If the motor works fine when tested separately, then it’s certainly a mechanical issue