Vibration problems in centrifugal pumps
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We have one centrifugal pump. In May, the horizontal vibration of the thrust bearing was 8.0 mm/s. After opening it, it was found that the bearing was slipping out of its housing; it was taken for repair, but the results were not satisfactory, so an original manufacturer’s bearing housing was ordered. However, after replacing the bearing housing, it was found that the vibration had decreased, but it was still at 5.5 mm/s. The shaft has also been timed. The motor vibration is not high. The coupling is fine too. The amplitude of the 6th harmonic in the spectral analysis is high. Could some expert help me analyze the reason?
The one who tied the knot must be the one to untie it. Why not let the manufacturer handle it? This is either a problem with the part coming from the factory, or an issue with the precision of installation. There are many factors that cause vibration, and they need to be checked one by one. Whether the prestress in the foundation and its connecting elements is uniform, as well as the levelness ； Levelness of the rotor, alignment, coupling clearance ； Dynamic balance of the rotor, bearing clearance, and interference fit. If the thrust bearing is damaged, levelness could be one of the contributing factors. For reference.
It’s difficult to make an accurate judgment just by looking at the spectrum. Check the number of blades on the impeller; if it’s also 6, consider whether it’s the frequency at which the impeller operates. There isn’t enough information, so I can only guess based on possibilities.
If the frequency of rotation of the impeller is high, what factors cause this? Thank you
By looking at the spectrum, the pump’s rotation speed should be 3000, driven by a synchronous motor; the vibration levels at 1x, 2x, and 3x are also considerable. If 6x corresponds to the blade passage frequency, this is something that typically occurs in high-head single-stage pumps. Check the inlet and outlet piping systems to see if there are any design issues, and also refer to the provisions in API610 regarding vibration caused by blade passage frequency to determine whether everything is in compliance