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Reasons For Large Vibration Of Vertical Pump Motor
TIME：2024-06-11 Author：admin Views：
Problems of vertical pump motors
Generally, there are insufficient balance accuracy, bearing installation problems, motor installation problems, structural resonance problems. As for electrical problems, in the dry test state, they are generally not reflected due to insufficient current, and can generally be eliminated first.
(1) Vertical pump motor balance accuracy is not enough
This problem is actually rare. The reason why it is listed is because when the cylinder support and the overall stiffness of the motor are relatively weak, a small imbalance can easily cause larger vertical pump motor vibrations, which often reduces the imbalance. Vibration requirements can be met.
Generally, the balance standard for this type of motor is G2.5, which means the vibration is about 15 μm (p-p). As long as it meets this standard, balance problems can be eliminated. You can refer to the factory balance report, or go directly to the test platform for a dry test.
If the vibration is above 30μm, it can be rebalanced, which should have a more significant effect. Generally, this problem will occur on newly installed vertical pump motors.
(2) Bearing installation problems
In large vertical pump motors, the upper bearing is generally stressed, and the lower shaft plays a supporting and guiding role. The rotor is in a suspended state. Therefore, in vertical pump motors, the upper bearing is often damaged first.
However, if the lower bearing is stressed due to bearing installation problems, a "shaking head and head shaking" phenomenon will occur between the top of the vertical pump motor. This type of phenomenon is relatively common on site.
If the bearing capacity of the lower shaft is relatively large, it is easy to rule out the problem, because the "shaking head and head shaking" phenomenon is more serious during the empty test on the test platform. However, when the force is not large, it may occur during the empty test on the test platform. It is not obvious, but after being installed on the cylinder support, the vibration will be amplified (when the overall stiffness is weak), so the recommended method is to check the stress of the two bearings. This type of problem usually occurs after the vertical pump motor is repaired or the motor is replaced.
(3) Motor installation issues
This kind of failure is usually caused by insufficient vertical installation of the motor or insufficient tightening force of the connecting bolts with the support cylinder. You can use a level to measure the connecting bolts and retighten them. This kind of failure usually occurs after the pump rotor is connected, and the vibration problem is particularly prominent.
(4) Structural resonance problem
The structural frequency of some motors is lower than the frequency of the rated speed, and is very low, especially variable frequency motors. This is the design that was later implemented by the motor factory. After testing, the influence range of the resonance frequency actually reached plus or minus 160 revolutions, and some actually affected the rated speed. It is a frequency conversion motor.
When the structural frequency is lower than the rated speed, a speed test can be performed to determine whether there is resonance. If it is a frequency conversion motor or the structural frequency is higher than the rated speed, start the machine for analysis and observe the amplitude and phase. Determine if you are affected by resonance. This problem usually occurs when a new installation starts production. The general solution on site is to improve the balance accuracy.
Generally, there are insufficient balance accuracy, bearing installation problems, motor installation problems, structural resonance problems. As for electrical problems, in the dry test state, they are generally not reflected due to insufficient current, and can generally be eliminated first.
(1) Vertical pump motor balance accuracy is not enough
This problem is actually rare. The reason why it is listed is because when the cylinder support and the overall stiffness of the motor are relatively weak, a small imbalance can easily cause larger vertical pump motor vibrations, which often reduces the imbalance. Vibration requirements can be met.
Generally, the balance standard for this type of motor is G2.5, which means the vibration is about 15 μm (p-p). As long as it meets this standard, balance problems can be eliminated. You can refer to the factory balance report, or go directly to the test platform for a dry test.
If the vibration is above 30μm, it can be rebalanced, which should have a more significant effect. Generally, this problem will occur on newly installed vertical pump motors.
(2) Bearing installation problems
In large vertical pump motors, the upper bearing is generally stressed, and the lower shaft plays a supporting and guiding role. The rotor is in a suspended state. Therefore, in vertical pump motors, the upper bearing is often damaged first.
However, if the lower bearing is stressed due to bearing installation problems, a "shaking head and head shaking" phenomenon will occur between the top of the vertical pump motor. This type of phenomenon is relatively common on site.
If the bearing capacity of the lower shaft is relatively large, it is easy to rule out the problem, because the "shaking head and head shaking" phenomenon is more serious during the empty test on the test platform. However, when the force is not large, it may occur during the empty test on the test platform. It is not obvious, but after being installed on the cylinder support, the vibration will be amplified (when the overall stiffness is weak), so the recommended method is to check the stress of the two bearings. This type of problem usually occurs after the vertical pump motor is repaired or the motor is replaced.
(3) Motor installation issues
This kind of failure is usually caused by insufficient vertical installation of the motor or insufficient tightening force of the connecting bolts with the support cylinder. You can use a level to measure the connecting bolts and retighten them. This kind of failure usually occurs after the pump rotor is connected, and the vibration problem is particularly prominent.
(4) Structural resonance problem
The structural frequency of some motors is lower than the frequency of the rated speed, and is very low, especially variable frequency motors. This is the design that was later implemented by the motor factory. After testing, the influence range of the resonance frequency actually reached plus or minus 160 revolutions, and some actually affected the rated speed. It is a frequency conversion motor.
When the structural frequency is lower than the rated speed, a speed test can be performed to determine whether there is resonance. If it is a frequency conversion motor or the structural frequency is higher than the rated speed, start the machine for analysis and observe the amplitude and phase. Determine if you are affected by resonance. This problem usually occurs when a new installation starts production. The general solution on site is to improve the balance accuracy.
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