Analysis of the reasons for high vibration in centrifugal pumps (vertical direction)

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This post was last edited by kobeylyl on 2018-10-27 at 09:19. It concerns a centrifugal pump BB2 in a new reprocessing unit – a double-support pump that uses gasoline as the working medium. Since it started operating, the vertical vibration level at the drive end has remained high, reaching up to 6.5 mm/s. There are no issues with the rotor’s dynamic balance, the bearings, or the stresses in the pipelines. Two companies were consulted for online monitoring, and their findings were as follows: 1. According to the spectrum analysis, the vertical vibration at the pump’s coupling end is significant; the dominant vibration frequency is 6X, with additional frequencies of 3X, 4X, 7X, and 9X. The noise level is also high. a) Check the operating conditions and try to run the pump at full load whenever possible； b. Check for any loose fit between components. 2、 a、The vibration of the unit is above the acceptable level; the main components of the vibration in the drive and free ends of the water pump in the horizontal, vertical, and axial directions are multiple harmonics. In the acceleration spectrum, the 3rd harmonic and its higher harmonics are evident. The phenomenon of the inner ring shifting is mainly caused by an excessive clearance between the shaft and the bearing. b. Demodulation analysis of the unit bearings was performed, and no bearing failure characteristics were detected. c. Phase analysis was performed on both ends of the coupling, and the shaft alignment of the unit is good. Could the experts please discuss what the reasons are?