A failed bearing can leave the machine with two jobs still open. One is to restore production safely. The other is to understand why the bearing came out.
The replacement may close the first job. A quick wash of the old part can make the second much harder.
Cleaning may reveal damage on a raceway. It also removes lubricant and deposits from the places where they were found. For an early, repeated or unexplained failure, those locations may matter as much as the damaged surface. Before the part reaches the solvent tray, decide what the next person will need to know.
Give the repair and the investigation different endings
“Bearing replaced, machine running” is a repair outcome. It is not a cause of failure.
Keeping those two statements separate takes pressure off the technician to produce an instant diagnosis. The machine can follow the site's return-to-service process while the investigation retains an owner, a question and the material needed to answer it.
For a planned removal, agree preservation with the receiving laboratory or bearing specialist before the work begins. Site isolation, stored-energy and lifting procedures come first. Plan photography and sampling around safe work.
The useful handover is simple: what was found, what was changed and what remains unresolved? A person on the next shift should be able to follow it without needing the person who removed the bearing to retell the job from memory.
Keep the location with the material
Imagine receiving a jar labelled “bearing grease”. The label names the material, but it may leave the most useful question unanswered: where, exactly, was it collected?
Grease beside a seal and material inside a bearing are different collection locations. Mixing them into one jar removes that distinction. Keep them separate and link both specimens to the bearing position, photographs and investigation reference.
One bearing. More than one collection location.
Separate specimensPreserve each collection location.
Shared referenceLink parts, photographs and history.
Start the visual record before removal, wherever the arrangement is safely accessible. Record the asset, bearing position and designation, then photograph the parts as they are exposed. Agree any orientation marks with the examiner and keep them away from surfaces to be studied.
Identify the lubricant product and recent additions or changes. Ask the receiving specialist about specimen quantity, containers and preservation. Do not add solvent to ease collection or mix locations to make a larger sample.
JTEKT's inspection guidance places the condition record and lubricant retention before cleaning. SKF's failure-analysis guidance adds separate labelled specimens, mounting references and protection from contamination and moisture. The point is to preserve the original relationships before examination changes them.
Tell the examiner what the tools changed
A puller can leave a mark. Cutting, heating or striking can change a component. An unprotected part can acquire contamination on the bench. If those events are missing from the record, the examiner must decide whether a feature belongs to the failure or to the work that followed it.
SKF's collection checklist calls for recording unavoidable removal damage. Write down what was done and why while the work is fresh. “Ring cut during removal” is useful history; a photograph of a cut without that history leaves a question open.
First seen does not mean first formed.
Use these records to narrow the possibilities.
Build the photographs from wide view to detail. Show the arrangement, then the component, then the feature. Keep the work-order reference readable and place a scale beside the feature without touching the examination surface. Check focus and glare before the arrangement changes.
Retain the original files. Cropped or annotated copies can help discussion, but should remain linked to the originals. A circle around a mark tells someone where to look. It does not identify the mechanism.
Write the observation before the explanation
The words on the work order can either open the investigation or steer everyone toward a conclusion that the evidence has not earned.
Consider this training exercise. Neither note describes a customer case.
At the handover
Which note gives the next person something to investigate?
A cause asserted
“Water caused the bearing failure.”
No observation, retained item or next check is identified.
An observation preserved
“Discoloured areas near the seal side. Bearing, seal and separate lubricant specimens retained. Check the lubricant and possible entry route.”
The finding, retained evidence and open question stay distinct.
Discolouration alone does not establish water ingress or its role in a failure. The second note is better because it can be tested, not because it proves the proposed mechanism.
Damage guides help people describe features consistently. They do not turn one photograph into a verdict. NTN notes that interrelated factors can make the real cause difficult to establish, and asks reviewers to consider installation, operating conditions and the surrounding arrangement.
The public scope of ISO 15243:2017 also separates visible damage classification from further investigation that may be needed to resolve cause. “Feature described; two explanations still open” can be a useful intermediate finding. “Poor lubrication” written because a washed bearing looked dry cannot recover the condition before washing.
Send the parts with a question someone can answer
The examiner needs the component and the service record to tell the same story. Give the physical items, photographs, lubricant specimens and work history a common reference. Agree packaging, preservation treatment, hazardous-residue handling and examination scope with the specialist, then record who receives the items.
Include the first reported symptom, operating conditions, monitoring trend and recent lubrication or maintenance changes. State what is still uncertain. For example: what evidence supports or weakens the proposed contamination mechanism, and what machine check would distinguish it from another explanation?
That invites an examination of the evidence. Asking the specialist to “confirm water damage” after already recording water as the cause narrows the question too soon.
Prepare the next removal while there is time
Choose one completed bearing-replacement work order. Could someone from another shift identify the bearing position, the last lubrication intervention and what happened during removal?
Use the missing details to prepare the next job: labelled containers, a photograph sequence, an owner for the retained parts and a receiving specialist. Do not fill gaps from memory and treat the old record as complete.
Cleaning can be part of a careful examination. The decision is about sequence: preserve the evidence first, then clean under the method agreed with the examiner. The bearing may have stopped turning. Its useful history should not stop at the edge of the bench.
Use one old work order as a team exercise
Separate what was observed, what was inferred and what was left untested. Then make those distinctions part of the next removal plan.
Explore lubrication trainingReferences
This article concerns evidence from bearings removed for investigation. It is not a procedure for teardown, routine cleaning, bearing reuse or machine release.
- SKF: Bearing damage and failure analysis, Appendix D, Collecting information. Printed page 98.
- JTEKT: Maintenance and inspection of bearings. Section 15-6-1.
- NTN: Inspection of bearings after operation.
- ISO 15243:2017: Rolling bearings, damage and failures. Public scope consulted.
Continue reading
Why Bearings Run Hot After Greasing follows the evidence while the bearing is still in service. Water in Oil: Read the Report Before You Blame the Cooler separates a reported finding from the proposed cause.
