The Effects of Radial Thrust on Centrifugal Pumps
April 20, 2021

Vertical Pumps and Vibration

All equipment has a natural frequency in which it should vibrate. A common occurrence in vertical pumps that are near to each other is for them to have excessive vibration. The pump may be deemed to have a resonant condition when vibrations excite the natural frequency of the pump’s structure. It all depends on the pump’s mass, damping, and stiffness – with only the mass being a constant factor. As a result, vibration outside the allowable parameters can happen for any number of reasons. Below, we will help you understand more on vertical pumps and vibration.

How to Diagnose a Vertical Pump’s Vibration

You may notice your pump’s excessive vibration via many means. These include excessive sound, movement of the pumps, poor performance, excessive power use, and many other factors. It is important to immediately and correctly diagnose a pump when it shows these or other high vibration characteristics. Incorrect diagnosis lead to incorrect fixes as well as lost time and funds. You need the correct instruments and know-how to accurately measure the frequency and amplitude of the pump’s vibration along with the correct operating parameters. It may also be useful to look at the pump’s vibration phase angle.

We at HDS mainly advise one or more of the below tests for vertical pump vibration diagnosis:

  1. Perform a test on the pump’s vibration frequency. It should match the rotation speed. However, many issues can cause the vibration to be off. These include but are not limited to flow turbulence, cavitation, damaged bearings or seals, and other related issues.
  2. Perform a bump test on the pump. A bump test is used to determine the natural frequency of the pump. It can be used to identify damping, modal stiffness, mode shapes, modal mass, and isolation efficiency.
  3. Operating Deflection Shapes test to analyze the vibration’s mode shape at rotating speed. The ODS test also helps with where to add stiffness to increase the natural frequency over the rotating speed.
  4. Modal analysis to go beyond the traditional bump test. It is useful when the pump is off and utilizing an external force like a shaker or mallet.

Your pump’s alleged vibration may also be caused by resonance. It can be marked by a relatively low exciting force that generates a high amplitude vibration. For example, it can be a misaligned coupling or slight residual pump unbalance.

In many instances, a vertical pump with high vibration that was just installed is often diagnosed as unbalanced when the actual issue is resonance. Be sure to test for resonance in these instances before moving on to the motor or pump

Houston Dynamic Supply Vertical Pumps and Vibration

HDS has over 30 years of experience working with vertical pumps in many industrial applications. We have one of the largest testing and diagnosing facilities in the Gulf Coast area and pride ourselves in accurately diagnosing the cause of vertical pump vibration and other issues. Our team has the ability to repair pumps and their components. We work in many industries from manufacturing to refineries and many more. In addition to expert testing, we provide precision machining, visual inspections, non-destructive testing, disassembly, and much more for your vertical pumps and other rotating equipment. Contact us today to learn more.