Accumulation of dust and dirt on all rotor blades leads to a 1x vibration peak in the velocity spectrum. 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. VIBXPERT II and OMNITREND® software were used for the balancing runs. The static unbalance requires only a one-plane balancing procedure which was ideal for those fans. The accelerometers were attached to the non-drive end (NDE) bearing in the horizontal direction. VIBXPERT 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 according to DIN ISO 1940 was easily reached.
The plant went back online a few days later and the customer was extremely satisfied with the result of this service, he later stated:
“In the last 6 years, I have never seen those fans run so smooth.”
Special thanks to PRUEFTECHNIK Canada for sharing this success story with us.