Fan noise and vibration from the impeller
Build-up, loose hubs, worn or broken vanes and the balance that follows them.
Dust and dirt build-up
If the build-up is even, the imbalance is small. When a lump breaks away from the impeller by centrifugal force the imbalance appears suddenly and can be large: a sudden vibration step on a dusty fan is almost always a lump that came off. Clean the impeller regularly and rebalance after repair or cleaning.
Loose impeller or loose blades
Check the impeller attachment (taper bushing, hub, bolts, welds). Measure vibration velocity, enveloped acceleration and bearing temperature and trend them. If bearing trouble recurs, have a vibration specialist find the root cause and refer to a bearing failure handbook for the damage pattern.
Worn, bent, cracked or broken vanes
Repair or renew the impeller, then rebalance. Balance the rotating assembly with an analyser-balancer in its own bearings if possible, and centre the impeller in its casing (centring is part of the balancing job, not an extra).
Quick map
| Symptom | Likely impeller cause | Action |
|---|---|---|
| Sudden rise at 1x shaft speed | Build-up dropped off a blade | Clean, balance |
| Slow rise at 1x over weeks | Progressive build-up or erosion | Clean, trend, repair vanes |
| Rise at 1x with a step at start-up | Loose hub or taper bush | Check attachment, re-tighten or re-fit |
| Noise at blade pass frequency | Impeller off-centre in casing, wrong cut-off | Centre impeller, review cut-off |