HI ALL,
IN OUR POWER PLANT FROM ESP TWO STREAMS ARE THERE-A&B. B STREAM ID FANS GETTING UNBALANCED (1X) REPETEDLY AND AFTER BALANCING VIBRATION LEVELS ARE COMING DOWN TO SATISFACTORY LEVELS.WHAT COULD BE THE REASON FOR GETTING UNBALANCE FOR ONLY B STREAM ID FANS? I THINK ITS NOT WEARING.

hai krishnan,
you already mentioned that there is no wearing problem,i think improper sitting of impeller is one of the reason for imbalancing.you are not mentioned about ID fan cleaning duration between A&B,check for this.Mean while check for any difference between quantity of dust collection in ID fan A&B.

If your ID fans are having aerofoil blades, please check wheather any holes have developed in blades. Dust ingress inside blades through these holes may create unbalance. Otherwise please check for any structural resonance in the fan due to loose packer plates or other nearby sources.