Why is My Pump Vibrating?

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Why is My Pump Vibrating?

If you are experiencing excessive vibrations in your pump, it’s generally a good indicator that something is wrong. And if you are reading this article, you may be looking to learn more about what causes pump vibrations, how you can fix them, and how you can prevent them from happening in the future.

Our team at Masterflow has over 20 years of experience delivering high-quality solutions and HVACR services across Australia and New Zealand. We are here to answer any questions you may have. After reading this article, you should have the information you’re looking for to resolve this issue and prevent it from recurring.

Signs your Pump is Vibrating

Whether it is an installation issue or a mechanical problem, there are many reasons why you could be experiencing pump vibrations. This can often occur due to errors like bent shafts from excessive shaft movement, indented bearings, fatigue to components and other things. Here are some of the most common causes of pump vibrations and what you can do about them.

Coupling Misalignment Can Cause Pump Vibrations

Pump vibrations in long coupled pump sets are often caused by coupling misalignment – the extent of which depends on the amount of misalignment and type of coupling used on the pump. Misalignment from the motor to the pump can be damaging to pipes and foundations, causing breakage and cracking.  Whilst alignment will be performed on the pump set during manufacture, transport to site and offloading by forklift or crane will invariably affect the alignment thus making laser alignment after installation essential. Pump manufacturers will not honour the warranty if this is not done.

How can I fix pump vibrations due to coupling misalignment?

Although this issue can be frustrating, fortunately, it is something that can be relatively easy to solve.

To fix the alignment problem, engage a competent technician with the correct laser equipment, to visit the site and perform the alignment. Request an Alignment Report for each pump that is aligned. This report will show both lateral and vertical alignment has been successful.

Close Coupling Can Fix Pump Vibrations due to Coupling Misalignment

Laser alignment only applies to long-coupled pump sets. For this reason, some asset managers prefer to choose a close-coupled pump.

A closed coupled pump is effective at making alignment secure by mounting the motor directly onto the pump.

Pipework Strain Can Cause Pump Vibrations

Pipework strain occurs when pipework approaching a pump inlet is not self-supporting and the installer has forced the pipe into alignment when connecting to the pump flange. This malpractice can also happen during the pump discharge.  When all the flange bolts are tightened on the suction and discharge flanges of the pump, everything will appear to be okay. However, what is happening is excessive strain is bearing on the pump casing which will lead to vibrations and eventually breakage if not corrected. Pipe strain will make laser alignment almost impossible to complete. Pipe straining can be caused by poor design but mostly by poor installation. Pipe strain can lead to other problems in your pump but is something that can be solved.

How can I fix pump vibrations due to pipe strain?

Having a plumber review your pipework is essential if you are experiencing this issue. If your installation has been done recently, the plumber responsible can assess and reinstall his pipework which may require cutting and shortening the pipe. The plumber may also need to reposition the pipe supports to take the weight off the pump casing which removes the strain. It is important to note that both close-coupled and long-coupled pumps will suffer vibration problems if pipe strain is present.

Cavitation can Cause Pump Vibrations

Cavitation can occur when incoming liquid pressure drops below the vapour pressure causing bubbles or voids to form within the fluid. These vapour-filled cavities create shockwaves which are caused by the bubbles collapsing as the liquid enters the high-pressure area. Pitting, a term used to describe pressure waves is when small holes are punched into the internal parts of the pump. These pressure waves can cause vibrations, leading to other problems such as premature bearing failure. If your pump is making strange noises, as if gravel is tumbling inside the casing cavitation could be occurring.

How can I fix pump vibrations due to Cavitation?

If you believe you are having a cavitation issue in your pump, you should have your pump reviewed by a specialist in liquid handling. When reviewing the cavitation issue, the specialist will check for the inlet pressure required by the manufacturer in the pump. The specialist can take a reading of the pump pressure, checking at the discharge port. By gathering information about the different parts of your pump, the specialist can compare this to the manufacturer’s requirements and use it to advise necessary improvements on your pump to put a stop to any issues from continuing or causing more damage. If you cannot have the impeller diameters changed, you may consider reselecting a pump.

Over discharging Can Cause Pump Vibrations

Over discharging is a problem which occurs when the pump is working too far to the right of the best efficiency point (BEP).  Vibration can occur as a pump works operate too far away from the BEP, as this can cause cavitation. The BEP is a point along the pump performance curve and refers to the flow at which the pump operates most optimally depending on its given impeller diameter. Cavitation leads to hydraulic imbalances in the impeller, as bubbles or voids form and create pressure waves which make vibrations in the pump.

How to fix over-discharging causing Pump Vibrations

In order to assess whether your pump is working away from the BEP, you should have your pump reviewed by a specialist. The specialist can check your pumps requirements and do pressure readings on both suction and discharge to see whether your pump is operating according to the pump performance curve. If your pump is found to be operating away from the BEP, the specialist will evaluate the conditions and make suggestions for improvements such as reducing the impeller diameter (trimming) or, in extreme cases, installing a smaller pump.

Harmonic Noise Can Cause Pump Vibrations

Vibrations in a pump can occur due to harmonic noise relating to the speed of the pump and the motor drive system. These vibrations can happen in a frequency range of anywhere between 450 to 60, 000 cpm (7.5 Hz to 1,000 Hz). If you suspect your pump is vibrating due to frequency, you can change the settings on your VSD to make sure that your pump is operating smoothly.

Inertia Base can Solve Pump Vibrations

Concrete inertia bases can be extremely beneficial in reducing vibration in pumps. An inertia base is useful for supporting mechanical equipment by lowering the centre of gravity and reducing excessive movement during start-up and shutdown, thus reducing vibrations. Browse our products for more information or give us a call to ask about what we have to offer.

In this article, you have been introduced to some of the more common causes of vibration noises in pump installations. These problems can be avoided if correct procedures are applied at the design and installation stages. You may find our “Best Practices for Cooling Tower Pump Installations” article helpful. For more information on cavitation refer to our “Cavitation – the How and Why ” article and call us to find out how we can help to solve your problem.

If you feel that your pump needs assessment by a team of trustworthy experts, Masterflow offers service and repairs. Contact us to find out what we can do to help you.

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