It is very regularly that we receive a call from a client that a fan is vibrating and that we need to send someone out there to balance the fan! A good portion of the time when we arrive, it is indeed a balance issue, where the fan has had a buildup of material on it. Many times this throws off the balance but simply cleaning the fan blades can resolve the issue. Sometimes it can't which is when the actual process of balancing comes into play.
What about the times when its not balancing? Well vibration can be caused by a variety of factors with imbalance being just one of those. Misalignment, structural issues, bearings issues, belt/sheave issues, looseness, motor problems, and many more items can all cause vibration issues with Fans.
I would say the 80/20 rule applies here. 80% of the time we are called out to balance a fan, it is indeed a balance issue. The 20% would account for all of the other items that could be causing the vibration. This is why we always recommend starting a "balance" job with taking vibration measurements including an FFT (Fast Fourier Transform), as commonly referred to as a spectrum. This will allow you to analyze the vibration amplitude versus frequency and diagnose it either as imbalance or another issue. Some issues such as structural issues can be harder to diagnose but there are many proven methods that can be applied for those as well.
So, keep in mind that it may not actually be a balance issue next time your fan vibrations, be sure to have vibration readings taken prior to performing the balance to ensure that you do not waste any time or money on performing an unnecessary task!
HECO - All Systems Go
About the author:
Justin Hatfield is Vice President of Operations at HECO. He is responsible for Electric Motor & Drive Sales, Electric Motor & Generator Repairs, Spare Solutions, and Predictive Services. Justin was instrumental in developing HECO MAPPS (Motor and Powertrain Performance Systems) which focuses on “why” you have a motor problem instead of simply “What” product or service should be recommended. HECO is an EASA Accredited Service Center for Electric Motors as well as a provider of predictive maintenance services and products throughout the United