Practical answer
Inspect fasteners, coupling, belts, gears, fan and seals before checking lubrication, shaft alignment and bearing fits. Repeating impacts, rubbing or a high-frequency squeal lead to different checks, but sound alone should not be used to declare a bearing failure.
Where possible, record vibration, spectrum and temperature trends at fixed points and compare them with normal historical data. A temporary reduction in noise after adding grease does not by itself prove grease starvation.
On-site checks
- Whether sound changes with speed, load or temperature
- Fasteners, coupling, belts, gears, fan and seals
- Lubrication, alignment and bearing fits
- Vibration and temperature trends at fixed points
Record for enquiry or analysis
- First occurrence and duration of the noise
- Audio or video and the recording position
- Machine speed, load and temperature
- Measurements before and after shutdown inspection
Suffix rules and allowable values vary by manufacturer. Confirm the final selection against current manufacturer documentation and actual machine conditions. Reference entry points:NSK · Schaeffler medias