Drive system checks on a hot or noisy fan
When the bearing is the symptom and the drive is the cause: stroboscope checks, alignment after maintenance, couplings and bolts.
Look at the whole drive
A hot or noisy bearing raises the concern that the drive will fail and stop production. Use a stroboscope, which illuminates the rotating part with a light flashing at the shaft speed, to inspect belts, pulleys, couplings and blades while the fan runs. Wear, cracks, distortion and looseness show up that cannot be seen on a running machine in ordinary light.
Alignment after any work
After impeller cleaning or repair, a belt change or a bearing change, re-check shaft alignment. Dial indicators or simple laser tools are enough on slow fans where a little misalignment is acceptable and the machine is not critical. On fast fans, where a stop is expensive, use precision alignment tools or an expert.
Quick checks
| Check | What it tells you |
|---|---|
| Coupling or belt-pulley alignment | High vibration at shaft speed, heat in the nearest bearing |
| Coupling elements | Damaged rubber or worn, unlubricated metal elements add vibration and load |
| Housing and base bolts | Loose bolts or low torque let the housing move; wrong grade or torque, check with a torque wrench or bolt tensioner |
| Cap and base of split housings | Marks must match: a mixed cap and base distorts the bore |
| Soft foot | Loosen each foot bolt in turn while the others stay tight; if the vibration changes, correct with shims or adjustable chocks |
Training pays
Fans with recurring bearing trouble usually have a handling, mounting or storage cause: nicks, dents and corrosion that happened during transport or in storage show up months later. Train the people who mount and lubricate.