Condition monitoring
Setting up bearing vibration measurements: sensor, interval and alarms
Where to put the sensor, how often to measure and how to set alarms that people act on.
Sensor and mounting
| Choice | Guidance |
|---|---|
| Location | On the bearing housing, as close as possible to the load zone, in the radial direction |
| Mounting | A stud mount is best. A magnet is acceptable for periodic readings. Hand-held readings vary the most. |
| Direction | Measure radial. Add axial on bearings that carry thrust. |
| Repeatability | Mark the point. A shift of a few centimetres can change the reading. |
How often
| Machine | Typical interval |
|---|---|
| Critical, fast failing | Online, every few hours |
| Important | Weekly to monthly |
| General | Monthly to quarterly |
| After any sign of a fault | Shorten to days until the trend is clear |
Alarm levels
- Overall velocity zones from the ISO 10816 and 20816 family are a start for the machine class, but they are for overall condition, not for early bearing faults.
- Set a second alarm on the fault line itself, or on the envelope level, and trend it.
- Set an alert on a rate of change, such as doubling within two weeks.
- Review each alarm at teardown and adjust the limits.
Record with every reading
- Speed and load.
- Sensor position and type.
- Measure used (peak, RMS, harmonic sum).
- Temperature of the bearing.
Takeaway. A good point, a fixed method and a trend of the fault line itself beat a perfect alarm level.
Put it to work in the tool