Over hung fan in an industrial facility.

Editor’s Note: This Blog is authored by Brian Rimmer (Freudenberg) & Stan Riddle (Acoem USA)

Acoem USA recently provided dynamic balancing training for Freudenberg in Durham, NC, using an Acoem Falcon vibration analyzer/balancer they had purchased.  During the class, Acoem was asked to assist in balancing a large primary air fan.


Inspection of the Fan

The fan was inspected before balancing, and personnel reported that:

  • The fan was covered in rust, because it was a carbon steel fan, and it was drawing moist air up from the plant floor.

Rust on fan

  • Several previous attempts had been made to balance the fan.  The fan could be balanced to a tolerable level, but vibration levels would always increase.
    • This is due to:
      • Rust constantly flaking off the fan, changing the mass of the fan, and causing the fan to become unbalanced again.

Deteriorating fan base

      • The grout underneath the fan had deteriorated, causing both looseness and resonance problems, due to inadequate stiffness in the base.  Some of the deterioration of the grout was probably due to excessive vibration, which further impacted the quality of the support.


Recommendations for the Fan

The fan was balanced to a “just barely” acceptable level by Freudenberg and Acoem personnel.  Further recommendations were made to Freudenberg maintenance and engineering to:

  • Clean the fan by wire brushing or blasting, to remove the rust.
  • Coating the fan with an industrial coating, to prevent future rusting.
  • Repairing the fan base, to better support the static and dynamic load of the fan.

During an outage, Freudenberg made the recommended repairs and balanced the fan.  The results speak for themselves. A decrease in vibration at fan running speed from 0.2 IPS to around 0.03 IPS!  This was probably better than when the fan was new!

Vibration Balancing Report

We have said, for years, “You can’t effectively balance a dirty fan!” Here is the proof that you absolutely CAN balance a fan that is clean and well-supported!



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