Grease Mixing and Compatibility Studies
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The document discusses the risks and issues related to mixing greases and the inadequacies of compatibility charts. It emphasizes the importance of conducting compatibility studies to evaluate grease mixtures before mixing is unavoidable, as incompatibilities can lead to machine failures. The proposed methods for compatibility testing, including ASTM D6185, are detailed to guide proper grease evaluation and ensure effective lubrication.
Grease Mixing and Compatibility Studies
- 1. Grease Compatibility Studies – Can Your Next Grease Change Cause Issues
- 2. Today’s Topics Why mixing greases is a bad idea Why using Compatibility Charts is an EVEN WORSE idea What should I do if I can't avoid the mixing What is REALLY in ASTM D6185? Why is it being changed? How can I work greases like the REAL WORLD? Demonstration of the Grease Thief Test Stand How to interpret Grease Compatibility results
- 3. Mixing greases Grease gets runny Grease gets hard Leaks out Failure to lubricate Hard as a rock Unable to pump Machine failure
- 4. Compatibility Charts – BAD IDEA
- 5. Compatibility Charts – BAD IDEA
- 6. Compatibility Charts – BAD IDEA Charts do not agree Do not reference testing that was used to create them Do not account for base oil differences Do not account for additive differences
- 7. Why run a Compatibility Study? When grease mixing cannot be avoided When its too late, the mixing has already occurred When getting all the old grease out is impossible or impractical Even if greases are made with the same base oil and thickener type they may be incompatible Evaluating grease mixtures can prevent issues when supply or formulation changes have happened If the greases are incompatible, mixing them during use could lead to significant changes in grease flow characteristics and shear behavior which would result in inadequate lubrication
- 8. Advantages of a Compatibility Study Allows for evaluation of mixtures without risk to equipment or affecting uptime Can provide data to support the ability to mix greases slowly or if maintenance needs to be scheduled to change out greases Assess risks and costs of available alternatives
- 9. Compatibility Study– per D6185 Primary testing using three standards to evaluate grease mixtures (10:90, 50:50 and 90:10) – Dropping point by D566/D2265 – Shear stability by D217 – Storage stability by D217 If all mixtures pass primary testing or if an application requires specific evaluation secondary compatibility tests can be used for further evaluation
- 10. Working the mixtures ASTM D6185 Proposed Change: Test Stand Mix & Work 10,000 Double Strokes in Grease Worker 72 Hours in Bearing Simulator 9 balls rotating at 1795 rpm 3.6x Ball Pass frequency Equivalent to 93 seconds of working in a typical electric motor bearing Total mixing/working events: 28,000,000
- 11. MRG Compatibility Study– added steps The baselines and 10:90, 50:50 and 90:10 mixtures and mixed and verified using FTIR and RDE The baselines and mixtures and packed and worked on test stand simulator for 72 hours Using D7718 samples are pulled, and rheological properties are evaluated for changes Formulations are compared for additive dilution, function Baseline formulations are compared
- 12. Prep for Compatibility Study
- 13. Interpreting Results To pass the mixtures need to have responses that are between the two baseline greases Changes outside of this can cause the grease mixture to perform differently than expected