Resolving fan vibration problems

Are you experiencing increased vibration levels in your facility? Fan rotor unbalance can be the cause and an up-to-date balancer can be the solution to the problem.

Unbalance is the most common cause of increased levels of vibrations. In one example, in-situ balancing of five exhaust and circulation fans was child’s play with the use of a modern balancing instrument, data collector and analyzer.

For several years, the vibration behaviour of these fans had been neglected at a plant that manufactures cartons. No predictive maintenance program was in place, but eventually a new reliability engineer decided to reduce the vibrations in this equipment by getting it analyzed. After performing several diagnostic tasks, the sources of the vibration could easily be detected.

Accumulation of dust and dirt on all the rotor blades led to a 1x vibration peak in the velocity spectrum. In the analysis, the sine waveform and phase analysis confirmed the results. A static unbalance was the reason for the increased vibration.

The balancing procedure was successfully performed on-site during the next shutdown phase of the plant. The balancing instrument was used for the balancing runs, while the results were archived in the related PC software.

Static unbalance requires only a one-plane balancing procedure, which was ideal for these fans. The accelerometers were attached to the non-drive end (NDE) bearing in the horizontal direction. The latest monitoring technology offers a second plane control feature, where the second accelerometer controls any negative influence on the NDE bearing during trim runs. This ensures that the vibration on both bearings will be equally reduced and balanced. The target quality grade of 6.3 (DIN ISO 1940) was easily reached.

The plant went back online a few days later and the operator was extremely satisfied with the result of this service. The manager of the operation later stated: “In the past six years, I have never seen those fans run so smoothly.”

Florian Buder is with Pruftechnik Canada, Laval, QC.

Find the original article on the MRO Website