The horizontal vibration of the motor in a horizontal centrifugal pump is above the acceptable level, and resonance is occurring; how to resolve this issue?
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There is a horizontal double-suction centrifugal pump on site, with a variable-frequency motor. The vibration of the pump during operation is within acceptable limits, but the horizontal vibration of the motor exceeds the specified limits. Measurements revealed that resonance is present in the motor. I would like to ask how the inherent frequency of a motor can be increased by modifying its base structure and design. Have any of you encountered similar experiences?
Check whether the motor base is deformed, and alternately loosen the motor’s foot bolts to see if the vibration improves.
Strengthening the entire water pump unit is necessary to have a fundamental impact.
Add buffer shims to the fixing nut, and also check whether the base is securely fixed.
The motor is an inverter-driven motor, so its speed varies; resonance may occur only when the speed reaches a certain value. It is recommended to install fixed supports on the motor, preferably by welding. Change its natural frequency
Strengthening its bottom plate can change that! If reinforcement is carried out by welding, care must be taken to prevent deformation!
Upstairs, there is basically no correct solution, as the vibration occurs in the horizontal direction rather than the vertical one. Strengthening the platform can only reduce the stiffness in the vertical direction; it does not help to alleviate vibrations in the horizontal direction. It is recommended to have the manufacturer handle it.
1. If horizontal vibration is high only within a certain speed range, resonance can be confirmed； 2. Even if resonance is confirmed, it cannot be determined whether it is rotor resonance or foundation resonance; the proper approach is to carry out a tapping test to identify it ； 3. If the conditions are not met, base resonance is the common scenario in practice; horizontal stiffness can be increased by measures such as widening the base or adding lateral reinforcement bars, in order to raise its natural frequency.
Loosen the nut of the motor’s foot bolts, start the motor, and check the vibration levels in both horizontal and vertical directions to determine whether they are within acceptable limits. If they are not, it is necessary to contact the manufacturer or have the motor repaired. If the limit is not exceeded, use a dial indicator to check for soft feet on the motor and eliminate them.
We have conducted numerous experiments on-site. It has been determined that the motor is subject to an excitation force at twice the frequency of the power grid; during the frequency increase process, 2x resonance occurs when this force approaches the system’s horizontal natural frequency. The natural frequency of the motor system is currently 65, and it wants to be increased to above 110 in order to avoid resonance. I would like to ask if anyone has any relevant practices, calculations, or models that can achieve the goal by modifying the scaffold structure. Welding brackets with support ribs has been tried, but the effect was not significant.
Consider strengthening the machine structure and adding shock-absorbing rubber rings……