Technical perspective
Grease carries evidence that is difficult to obtain from an oil drain: thickener condition, oil separation, ingress at the seal, wear debris near the contact and the effect of relubrication. It is also difficult to sample well. A small dark mass scraped from an accessible housing edge may describe old stationary residue rather than the grease working in the bearing.
Chem-Tech structures used-grease analysis around the bearing symptom and the comparison available. A representative sample, unused reference grease, equipment details and inspection observations are assessed together. The aim is to support a lubrication, contamination or wear decision—not to force used grease through every new-grease specification test.
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Separate lubricant condition from bearing and sampling effects
Hardening can result from oil loss, oxidation, contamination or prolonged residence. Softening may reflect mixing, excess oil, shear or fluid ingress. Dark colour may be normal product colour, oxidation, wear material or external dirt. Without a reference and a known sampling location, these observations remain ambiguous.
The investigation should document the bearing, load, speed, temperature, relubrication interval and failure symptom. Compare affected and unaffected positions where possible. A paired comparison often provides more useful evidence than a single isolated sample.
- Bearing temperature or vibration rises before the planned relubrication interval.
- Grease purges unusually hard, soft, dry, oily or discoloured material.
- Water, process dust, fibres or metallic sheen is visible near the seal.
- A bearing fails repeatedly even after grease quantity or interval changes.
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Build a comparison set that can answer the failure question
Used-grease results are strongest when compared with the exact unused product and a normal bearing from the same application. The unused reference establishes starting consistency, oil viscosity and formulation markers. The normal used sample shows what the process and interval do without the fault.
Elemental analysis, water, consistency-related observations and base-oil condition may support the diagnosis. Microscopic or debris evidence is selected when wear is suspected. Some new-grease methods require more material than a bearing yields or are not directly interpretable on used grease, so Chem-Tech confirms feasibility before the scope is fixed.
Grease structure
Consistency, oil separation and physical appearance help identify hardening, softening or loss of oil.
Contamination
Water and elemental patterns can support investigation of process ingress, dirt or mixed products.
Wear evidence
Ferrous or microscopic debris evidence can support a bearing-condition investigation when sample quantity permits.
Reference comparison
Unused and normal-used samples prevent product colour or formulation from being mistaken for damage.
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Indicative used-grease analysis packages
Used-grease testing is selected for the sample quantity and failure question. The listed methods may require adaptation, comparison or separate sample portions.
| Package | Use when | Indicative tests and methods | Decision supported |
|---|---|---|---|
| Condition comparison | Routine critical-bearing trend | Appearance; worked penetration — ASTM D217 where sample permits; oil separation — IP 121/ASTM D1742; water — ASTM D95/D1744 | Assess structure and contamination change |
| Bearing wear review | Temperature, vibration or failure concern | Elemental analysis — ASTM D7303; base-oil viscosity — ASTM D445; microscopic debris review by agreed procedure | Support wear-versus-lubrication diagnosis |
| Root-cause comparison | Repeated failure or grease change | Affected, unaffected and unused samples; FTIR/compositional comparison by agreed method; selected corrosion or stability checks | Evaluate product mix, environment and ageing pattern |
Chem-Tech confirms minimum quantity and method suitability before receipt. A result from a small heterogeneous grease sample should be interpreted with the sampling location and bearing inspection.
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Collect grease from the working zone with clean tools
Grease is heterogeneous within a housing. The location, depth and timing of collection must be recorded so subsequent samples can be compared.
- Collect before cleaning, solvent washing or adding fresh grease.
- Use a clean non-reactive spatula or sampling device and a wide-mouth container.
- Identify drive/non-drive end, bearing number and exact collection zone.
- Send the approved unused grease and, where practical, a normal used comparison sample.
- Photograph the housing, seal and purge condition before disturbing the evidence.
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Connect laboratory evidence with the bearing inspection
No grease result replaces inspection of the raceway, rolling elements, cage, seals and fit. A contamination pattern should lead to an ingress-control review; oil loss or hardening should prompt interval, temperature and quantity review; wear debris should be matched with vibration and component evidence.
For critical bearings, establish baseline samples after a controlled grease fill. Trend comparable quantities from the same location and record relubrication events. This converts a one-time post-failure analysis into a condition-monitoring tool.
- Compare the affected bearing with an unused reference and a normal position.
- Review seal condition and purge path when external contamination is detected.
- Reassess grease quantity, interval and operating temperature when structure changes.
- Preserve failed components until laboratory and inspection evidence are reconciled.
Apply this guidance
