@Registered Member posted:
1. Its a center hung double suction fan with taper bore anti friction bearings .
2.I am not sure weather they inspected clearances / not .They reluctant to do so ,said every thing good with bearings and clearances .
3.No extra weight added after correction run .Just taken another run to reconfirm the results .
4.No weights are removed , their management want check bearings and clearances once again .
5.If they called , i let you know .
Did you check the closely spaced peaks in the spectrums to confirm their relation to 1x rpm?
A one-third (1/3) running speed sometimes relates to an anti-friction bearing being loose on the shaft, IMO. These being tapered bore bearings, it is a possibility one of the bearings could be loose on the shaft.
Your quote: "Just taken another run to reconfirm the results ." Is this, "another run", when the vibration seems to increase for no apparent reason? Do you mean it looks good after weights are attached, and then you shutdown and restart and vibration goes up again? If so, does the phase shift also?
If you go back later and try the balance again, I know of an "easy" 2-plane setup you might could try.