Common bearing failure causes include unsuitable lubrication, contamination, mounting or fit problems, excessive or unexpected loads, corrosion and electrical current passing through the bearing. Noise, heat or vibration can alert you to a problem, but they do not identify the cause on their own. Record what happened, preserve the evidence and then assess the damage pattern.
Symptoms, Damage Modes and Root Causes Are Different
“The bearing was noisy” is an operating symptom. “The raceway is spalled” describes damage. The root cause explains how that damage developed. Keeping these statements separate prevents an inspection report from becoming a list of assumptions.
ISO 15243:2017 provides terminology and classifications for rolling bearing damage in service. It helps describe the evidence consistently; it does not make every damaged bearing diagnosable from a photograph. Some investigations need measurements, lubricant testing or laboratory examination.
Common Bearing Damage: What to Check Next
| Observed evidence | Possible contributors | Evidence to collect | Next check |
|---|---|---|---|
| Spalling or flaking | Rolling contact fatigue; lubrication or load conditions may contribute | Damage location, operating hours and load history | Review the load pattern and investigate how the damage started |
| Scoring, smearing or heat distress | Inadequate film, sliding, excessive friction or restricted lubricant supply | Lubricant details, flow records and temperature trends | Check lubricant suitability and delivery before prescribing more grease |
| Dents or abrasive wear | Particles, handling damage or excessive contact loading | Debris, seal condition and photos of the affected surfaces | Look for entry routes and assembly-related damage |
| Rust or etched surfaces | Moisture, process-fluid ingress or unsuitable storage conditions | Lubricant sample, storage history and surrounding leakage | Check sealing, preservation and contamination sources |
| Fretting at ring seats | Small relative movements at the fit | Shaft and housing measurements, seat marks and fit specification | Review fits, support and operating loads together |
| Fine craters or fluting | Electrical erosion is one possible mechanism | Surface examination and machine electrical information | Investigate the current path; do not diagnose from noise alone |
Record the Sequence Before Dismantling
Note when the change first appeared: after installation, after a lubricant change, during a process upset, or after a long period of apparently stable service. Record speed, load, temperature and vibration information that is actually available. Compare trends with the machine’s established behavior rather than applying a universal bearing temperature threshold.
Keep the bearing designation, mounting position and orientation with the records. Photos of the housing, seals, lubricant supply and adjacent components can be as useful as a close-up of the damaged raceway.
For example, a replacement bearing that begins heating immediately after installation warrants a check of the assembly, fit, clearance and lubrication changes. That timing is useful evidence, but it does not prove any one of those caused the problem.
Preserve the Bearing and Lubricant Evidence
Follow the machine manufacturer’s isolation and removal procedure, using qualified personnel where required. Do not continue operating a damaged assembly merely to obtain a clearer symptom. Before cleaning, photograph the as-found condition and arrange appropriate lubricant sampling with the investigator.
Label removed components so their position and orientation remain identifiable. Keep the pieces of a failed assembly together without rubbing damaged surfaces against each other. Avoid polishing away marks or mixing lubricant samples from different positions. Agree handling and preservation with the laboratory if specialized examination is planned.
Choose Preventive Action After the Cause Is Supported
Lubrication checks should cover the specified product, operating viscosity where applicable, quantity, delivery method and contamination control. Adding grease is not a universal remedy for a hot or noisy bearing.
Review mounting and fit measurements against the equipment drawing. Check how installation force was applied, whether the seats were clean and whether the locating arrangement permits the required movement. For clearance questions, see the C3 bearing clearance guide; choosing greater clearance by guesswork can introduce another problem.
If ingress is supported by the evidence, review seals, filtration, storage and handling. If electrical erosion is suspected, involve the appropriate electrical and bearing specialists before selecting a mitigation. A change of bearing material or an insulated execution should follow the machine assessment.
What to Send With a Bearing Failure Enquiry
- Complete bearing marking, equipment position and drawing reference.
- Service time, previous failures and a timeline of the symptoms.
- Known loads, speed, temperature and lubrication details.
- As-found photos of the bearing, seals, seats and surrounding assembly.
- Available measurements, samples and the actions already taken.
When evaluating a replacement, start with the relevant spherical roller bearing or cylindrical roller bearing specification. Matching the size does not resolve an unexplained failure mechanism.
Send ZQM Bearings the designation and available operating details when discussing a replacement enquiry. A confirmed root-cause report may require an independent specialist or laboratory; this checklist is a starting point for collecting useful information.