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A structured bearing failure analysis checklist covers five stages: secure the failed bearing, record operating conditions, inspect visually against ISO 15243 failure modes, examine lubrication and contamination evidence, and compile a documented failure report with photos and root-cause conclusions. Following this sequence helps maintenance and reliability teams avoid repeat failures, support warranty or supplier claims, and plan corrective action with measurable, traceable evidence.
When a bearing fails unexpectedly, guesswork is expensive. A repeat failure without a proper investigation can cost a plant days of downtime and thousands of dollars in unplanned maintenance. This is where a consistent bearing failure analysis checklist becomes essential for industrial maintenance and reliability teams.
This guide walks through a practical, step-by-step process for diagnosing, documenting, and reporting a failed bearing, aligned with the ISO 15243 failure-mode classification used across the bearing industry. Whether the bearing is from a cement plant, a steel mill, a fleet workshop, or a marine application, the same disciplined approach applies.
Table of Contents
- What Is Bearing Failure Analysis?
- Why Does a Structured Diagnosis Process Matter?
- What Do You Need Before You Start?
- Step-by-Step Bearing Failure Analysis Checklist
- What Are the 6 ISO 15243 Failure Modes to Check Against?
- How Do You Document a Bearing Failure Correctly?
- How Do You Write a Bearing Failure Report?
- What Mistakes Should You Avoid During Bearing Failure Analysis?
- How Does KG International Support Bearing Failure Analysis?
- Frequently Asked Questions
- Conclusion
- Disclaimers
What Is Bearing Failure Analysis?
Bearing failure analysis is the structured process of inspecting a failed or degraded bearing to identify the failure mode, trace the root cause, and recommend corrective action. It typically combines visual inspection, operating-condition review, lubrication assessment, and comparison against recognised failure-mode standards such as ISO 15243. The goal is not just to confirm that a bearing failed, but to understand why, so the same failure does not repeat the replacement bearing.
Why Does a Structured Diagnosis Process Matter?
Without a checklist, failure investigations tend to stop at the first visible clue, such as a spalled raceway or discoloured grease. This often leads to the wrong corrective action, for example replacing the bearing without fixing a misalignment or contamination source that caused the original failure. A consistent process:
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Reduces the chance of repeat failures on the same asset. -
Creates a documented record for warranty, insurance, or supplier discussions. -
Builds a failure-history database that supports future maintenance planning. -
Helps distinguish a manufacturing or product issue from an application or maintenance issue.
What Do You Need Before You Start?
Gather the following before beginning the inspection so the investigation is not interrupted partway through:
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The failed bearing, removed with care to avoid adding new damage marks. -
The mating shaft, housing, or adapter sleeve if accessible. -
A camera or smartphone for close-up photographs. -
Basic cleaning materials (lint-free cloth, solvent) to remove surface grease without disturbing wear marks. -
Operating data: load, speed, temperature, running hours, and lubrication schedule. -
The original bearing designation, part number, and installation date, if known.
Step-by-Step Bearing Failure Analysis Checklist
Use this sequence for every bearing failure analysis case to keep the investigation consistent across sites, shifts, and teams.
Step 1: Secure and Label the Failed Bearing
Remove the bearing without further disassembly where possible, and tag it immediately with the asset ID, date, and location. Do not wash away grease residue, debris, or discolouration before photographing, since this evidence is often the first clue to the failure mode.
Step 2: Record Operating Conditions and History
Note the running speed, radial and axial load, ambient and operating temperature, lubrication type and interval, and total running hours since installation. Cross-check this against the bearing designation to confirm it was correctly selected for the application in the first place.
Step 3: Perform an External Visual Inspection
Examine the outer ring, seals, and housing fit for signs of overheating (bluish or brownish discolouration), leakage, or physical damage from handling. Check for fretting corrosion on the housing seat, which often points to a loose fit rather than a bearing defect.
Step 4: Inspect the Internal Components
Open the bearing carefully and examine the rolling elements, cage, and raceways. Look for spalling, flaking, scoring, indentation (denting), discolouration, or cracking. Compare the pattern and location of damage against the ISO 15243 failure-mode categories in the next section.
Step 5: Assess the Lubricant Condition
Check grease colour, consistency, and odour. Milky or discoloured grease often signals water contamination; gritty texture suggests particulate contamination; burnt or hardened grease points to overheating or insufficient replenishment. Where lubrication is the suspected cause, this is also the point to reference correct grease selection, such as KG Ultra Grease, for the replacement bearing.
Step 6: Check for Contamination and Sealing Failure
Identify whether contaminants entered through a damaged seal, an open housing, or an inadequate sealing arrangement for the operating environment. Dust, coolant, or water ingress is one of the most common and preventable causes of premature bearing failure in cement, mining, and steel applications.
Step 7: Evaluate Fit, Alignment, and Load Path
Measure or visually assess whether the bearing was correctly fitted onto the shaft and into the housing. Uneven wear across the raceway width usually indicates misalignment, while damage concentrated on one side of the rolling elements can indicate excessive axial load.
Step 8: Match Findings to a Root-Cause Category
Group the observed evidence into one of the recognised root-cause categories: lubrication failure, contamination, misalignment, overloading, incorrect fit, electrical erosion, or normal fatigue at end of rated life. Most field failures trace back to lubrication or contamination rather than a manufacturing defect.
Step 9: Photograph and Document Every Stage
Take clear, well-lit photographs of the bearing before cleaning, during disassembly, and of each identified defect. Label each image with the inspection step it corresponds to for the final report.
Step 10: Compile the Bearing Failure Report
Summarise the operating data, visual findings, lubricant assessment, root-cause conclusion, and recommended corrective action in a single report, following the format outlined later in this guide.
What Are the 6 ISO 15243 Failure Modes to Check Against?
ISO 15243 classifies rolling bearing damage into six primary failure modes. Matching your inspection findings against this table speeds up the bearing failure analysis process and keeps terminology consistent across sites and suppliers.
| Failure Mode | Typical Visual Evidence | Common Root Cause |
|---|---|---|
| Fatigue | Spalling or flaking on raceways/rolling elements | Normal end of rated life, or overload accelerating fatigue |
| Wear | Gradual material loss, smooth worn surfaces | Contamination, inadequate lubrication, abrasive particles |
| Corrosion | Rust, etching, dark pitting on surfaces | Moisture ingress, chemical exposure, poor storage |
| Electrical Erosion | Fluting, small craters on raceway surfaces | Stray electrical current passing through the bearing |
| Plastic Deformation | Indentations, dents matching rolling-element spacing | Shock loads, impact during handling or installation |
| Fracture and Cracking | Cracks, chipped rings, broken cage | Overload, improper fitting, mishandling, excessive force |
Source: ISO 15243 bearing damage classification (Schaeffler Group)
How Do You Document a Bearing Failure Correctly?
Documentation quality determines whether the investigation is useful six months later, when the same failure mode shows up on a different asset. A consistent documentation format should capture:
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Asset ID, location, and bearing designation (part number and brand, if known). -
Installation date and total running hours at the time of failure. -
Operating conditions: load, speed, temperature, and lubrication type. -
Photographs at each inspection stage, labelled and dated. -
Observed failure mode, matched to the ISO 15243 category. -
Suspected root cause and supporting evidence. -
Recommended corrective action and any parts replaced.
Pro Tip: Keep a running failure log by asset. A single failure report is useful, but a log across 12 to 24 months reveals recurring patterns, such as a specific pump consistently failing from misalignment rather than a one-off bearing defect.
How Do You Write a Bearing Failure Report?
A bearing failure report should be short enough for a plant manager to review in minutes, but detailed enough for a reliability engineer to act on. Structure it in five parts: a summary of the failure and its impact, the operating and lubrication data, the visual findings mapped to an ISO 15243 failure mode, the root-cause conclusion, and a corrective action plan with an owner and target date.
What Mistakes Should You Avoid During Bearing Failure Analysis?
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Cleaning the bearing before photographing it. Washing off grease or debris removes evidence needed to identify contamination or lubrication failure. -
Stopping the investigation at the first visible defect. A spalled raceway may be the result of an earlier, undocumented misalignment or contamination event, not the root cause itself. -
Skipping the operating-data review. Without load, speed, and temperature data, it is difficult to confirm whether the bearing was correctly selected for the application. -
Not comparing findings against a recognised standard. Inconsistent terminology across sites makes it harder to spot repeat failure patterns over time. -
Failing to close the loop with corrective action. Diagnosing the cause without implementing a fix, such as improving sealing or correcting alignment, allows the failure to repeat.
How Does KG International Support Bearing Failure Analysis?
KG International supports industrial maintenance and reliability teams throughout the bearing failure analysis process through KG Smart Support, which includes online and offline condition monitoring, remote failure analysis, and the KG Maintenance Assessment. These services are designed to help maintenance teams identify the root cause of equipment failure and reduce the chance of it recurring on the same asset.
For teams sourcing a replacement bearing after a failure investigation, the KG product range spans deep groove ball, tapered roller, spherical roller, and cylindrical roller bearings under the KG Ultra brand, engineered for demanding industrial applications. If the investigation points to lubrication as the root cause, review correct grease selection with KG Ultra Grease guidance before reinstalling the replacement bearing.
Maintenance teams working across cement, mining, or steel applications can also review sector-specific guidance on durable bearings for steel and metallurgy applications, which outlines common bearing types used in high-load, high-contamination environments.
For background on the most frequent causes behind bearing wear and corrosion, see the related KG International technical article on understanding industrial bearing failure and the causes of bearing corrosion.
Have a failed bearing that needs a professional assessment? Contact KG International to speak with the team, or explore the e-catalog for replacement bearing options.
Frequently Asked Questions
Conclusion
A repeatable bearing failure analysis checklist, from securing the bearing and recording operating conditions through to matching evidence against ISO 15243 failure modes and compiling a clear report, turns a single breakdown into a learning opportunity that prevents the next one. Consistency in inspection, documentation, and root-cause reporting is what separates a one-off repair from a genuine reliability improvement program.
Ready to investigate a failed bearing or source a replacement? Request a quote from KG International, or connect with the KG Smart Support team for a maintenance assessment.
Disclaimers
Technical Advice: This content is for general informational purposes only. Product selection, installation, maintenance, and safety decisions should be made by qualified professionals using official technical documentation and application-specific requirements.
Compatibility: Compatibility references are provided for identification and sourcing support only. Final fitment should be confirmed using official part numbers, application data, and technical guidance before purchase or installation.
Trademark: All third-party brand names, logos, and trademarks referenced are the property of their respective owners. Their use is for identification and reference purposes only and does not imply ownership, endorsement, or affiliation unless explicitly stated.
