Figure 3: Ruler graph comparison.
Consistency testing in accordance with ASTM D7918 measured by Die Extrusion Index, compares the grease consistency of an in-service grease to baseline grease to view the difference in force load. Consistency indicates whether the grease is losing the base oil charge due to vibration, elevated temperature or age. This may increase the wear rate due to the equipment not being lubricated enough. If more force is required, then the baseline of your grease is thickening up. If the force is less than the baseline, this could indicate possible churning. Churning occurs when the soap structure breaks down causing the grease to thin out and results in higher temperatures and failure.
How to read grease analysis report Testing should take the guesswork out of the knowing the condition of the in-service grease. An expert analysis of all test results will help determine equipment health and the grease’s overall health to determine when maintenance actions are required. An analysis report should include the severity or condition of the overall results with an indication of the severity for the type of concerns identified. The analyst comments will provide recommendations and actions if needed to correct concerns identified.
Grease Analysis Report
Example 3: Die Extrusion Coupon.
Figure 5: Example Analysis Report. Comments, data and images are advisory only and assume sample data submitted is valid.
No warranty expressed or implied. Conclusion Figure 4: Consistency graph.
Microbial contamination for grease testing will indicate microbial growth by testing cellular Adenosine Triphosphate (ATP) by use of ASTM D7463. All living cells contain ATP regardless of whether they are bacteria, fungi or any other type of microbe. The measurement is a direct indication of the microbiological content in your sample.
In conclusion, industries are starting to successfully monitor in-service grease analysis to not only identify wear conditions and prevent failures and downtime, but they are also using it to successfully determine lubrication schedules for grease replenishment to lower cost, improve reliability and increase safety. The old run-to-failure reactive model for maintenance for grease has now evolved to a more effective predictive maintenance model. To leave with a question, where are you in testing grease?
polarislabs.com
LUBE MAGAZINE NO.174 APRIL 2023
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