Vibration problems at special frequencies of pumps
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The pump experiences excessive vibration over the long term (with radial horizontal vibration levels ranging from 7.3 to 8.4 mm/s), and the vibration frequency is primarily at 71.875 Hz. The vibration of the pump’s foundation is very low, with maximum levels of 0.8 mm/s. The radial horizontal vibration in the outlet pipeline is also high, reaching up to 9.4 mm/s at the outlet check valve and other valves; the vibration frequency in these areas is the same as that of the pump. Vibration levels were also high on the standby pump (which is not in use), at 4.3 mm/s, with the same frequency. What could be the cause of this vibration in the pump?
The frequency of 71.875Hz is not low, and the vibration level is also significant. Normally, bearing failures should not cause such high vibration levels; it might be worth checking whether the vibration is caused by poor fixation of the pipelines.
It should be checked whether the piping was stress-free at that time; it is recommended to measure again to check alignment as well as the stress in the pipes