Fan troubleshooting
Poor airflow and fan system problems that mimic bearing trouble
Impeller direction, centring, duct size, blockage, running far from the best efficiency point and standing waves.
Impeller related
- Check the impeller orientation and direction of rotation. If it turns the wrong way, check the supply connections to the motor.
- Impeller not centred in its housing, bearing housings out of line, wrong shaft centring.
- Incorrect vane design or missing cut-off.
System problems
| Problem | What it looks like |
|---|---|
| Duct too large | Pulsations of the air column in the ductwork |
| Air flow obstructed in the pipework | Low flow, high power, noise and vibration from stalled operation |
| Running far from the best efficiency point | High vibration, noise and bearing loads, low efficiency |
| Resonant pulsations (standing waves) | Noise and vibration at blade pass frequency in the duct |
Before taking the bearing apart
If the fan runs far from its design point or the ducting is wrong, the bearing is only reporting what the system is doing. Check the operating point against the fan curve first.
Takeaway. A fan running off its curve shakes its bearings. Check the system before you replace anything.
Put it to work in the tool