Gene Vogel
EASA Pump and Vibration Specialist

When motors are installed on top of vertical pumps, high vibration is a common problem. The source of the problem can be a mechanical issue with the pump, motor or coupling, or it can be hydraulic forces from the pump. Often structural issues involving resonance amplify the vibration. An understanding of the nature of this style pump and the various forces is essential to diagnosing and correcting vibration problems on vertical pump motors.

There are quite a number of configurations of vertical pumps. Submersible pumps fall into this general category. This discussion, however, will omit submersibles and focus on those pumps that are surface mounted where the motor is bolted to a pedestal on top of the pump. See Figure 1. This is the style that most commonly exhibits high vibration conditions. An important contributing condition is resonance, and specifically “reed frequency” resonance. But an understanding of the vibratory forces is important also.

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