I need some advice regarding vibration of the motor in a centrifugal pump! ! !
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There is a centrifugal pump equipped with a 110KW motor of grade 4. Recently, it was observed that the motor end experiences significant vibration, with a amplitude of around 9 MM/S; there is almost no vibration at the pump end. Additionally, during operation, there are intermittent sounds similar to friction coming from the motor side. The alignment of the motor and pump couplings has been adjusted, but the problem persists. I would like to know whether this issue is caused by a problem with the bearings or an internal fault in the motor (the three-phase currents are not very different: 190, 191, 180)
This post was last edited by sifangok on 2016-11-20 01:29. You have already checked the reasons to a large extent; now look for any defects in the motor’s structure as well as issues with its installation. Such faults are mainly manifested as an elliptical shape of the shaft journal, bending of the rotating shaft, excessive or insufficient clearance between the shaft and the bearing shells, insufficient stiffness in certain parts of the bearing housing, base plate, or foundation – or even in the entire motor mounting foundation. The motor may not be securely fixed to the base plate, the foot bolts may be loose, and there may be looseness between the bearing housing and the base plate. An excessive or insufficient gap between the shaft and the bearing bush can not only cause vibration but also lead to abnormalities in the lubrication and temperature of the bearing bush. No problems can be found; it’s best to contact the manufacturer. Pumps of this high power generally come with good after-sales service
The possible reasons are: 1. There is a problem with the motor’s bearings； 2. The shaft of the motor is not rounded ； 3. The internal balance of the motor is not proper; please have the motor manufacturer handle it.
A few days ago, there was a topic on the forum titled 【Fault Analysis of Pump Vibration】; in your case, the vibration originates from inside the motor.
Check if there is anything wrong with the motor fan; if there is a problem with it, it can also affect the motor’s dynamic balance. If the motor bearing temperature and other parameters are all normal, then it indicates a problem with the motor’s dynamic balance ； If the motor’s dynamic balance was fine originally, the problem arose later on. Check the motor fan and things like that
There is a high likelihood that there is a problem with the motor bearings. This issue arose once 4 years ago at Sichuan Petrochemical; a certain type of imported compressor supplied by us was installed on site and waited for a year before being tested. The project owner failed to carry out regular shaft rotation inspections as required, and it was not possible for me to go to the site. After ruling out all other possibilities, it was finally determined that the bearing at the motor shaft end had been damaged due to prolonged stress. Fortunately, Nanyang Motor had a resident representative on site, and the problem was resolved after replacing the bearing. Upon cleaning the replaced bearing, minor dents could be seen……
Check the bearing clearance and retainer wear, as well as the fit between the bearing and the shaft and the fit between the bearing and the housing bore
It’s simple: disconnect the coupling, test the motor individually, and use a sound detector and vibration meter for testing； If the data is normal, the issue lies on the pump side ； If the data is poor, it’s quite easy to tell from listening whether the bearings are functioning properly; of course, those who are not in the maintenance industry would likely find it difficult to make such a judgment ； The single-test data isn’t good yet; remove the motor and check the bearings
It is best to use the relevant instruments for fault diagnosis, by examining the vibration spectrum, before making further judgments
It’s probably a problem with the motor itself