Fan noise and vibration from the bearing, the seat and the housing
A ring turning on the shaft, an outer ring jammed in its housing, loose bolts, poor support and a mixed cap and base.
Is the bearing rotating on the shaft?
Look at the inner ring faces and bore for circumferential scoring. Check the shaft drawings for the fit and geometric tolerances, and the hardness. If an eccentric locking collar is used, check that it was assembled in the right direction for the shaft rotation. Improve the locking: a concentric locking ring system, or an adapter or withdrawal sleeve with a hydraulic nut and controlled drive-up, gives a precisely controlled fit.
Is the outer ring jammed in the housing seat?
A jammed outer ring causes constraint forces, vibration and axial load. First see whether impeller unbalance has caused it and clean or repair the impeller. Then check the extent of wear in the housing seat, and the geometry and flatness of the housing support so the bearing is not pinched by the bore. A different seating fit tolerance may be needed.
Has the housing moved or are the base bolts loose?
- Use the recommended bolt grade and tightening torque, with a torque wrench or a bolt tensioner.
- Align bearing housings after any work on the base.
- Look for damage or rust on the housing support. Support the housing over the whole mounting surface, not just at the bolts; use thicker shims to limit their number and the number of interfaces.
- Make sure cap and base are a matched pair with matching marks.
Could the shaft tolerance be wrong?
Measure the shaft dimensions and roughness. A worn seat can be repaired with a thin sleeve instead of regrinding the shaft.