What tests are run on in-service lubricating grease samples?
Key tests for in-service grease samples include:
- Appearance – The appearance of in-service grease can tell much about the condition of the equipment from which it was obtained. A small amount of the grease spread thin on a white ceramic tile will allow the analyst to examine it in detail. For example, visible metallic particles or free water may indicate a problem with machine wear or contamination.
- Fourier Transform Infrared (FTIR) Analysis – FTIR Analysis is a well-established and powerful technique for the analysis of in-service grease. It can be used to detect many conditions of in-service grease, such as contamination, oxidation, loss of base oil, etc.
- Metals – Trace amounts of metals in an in-service grease can indicate additive depletion and/or wear metal build-up. ICP, X-ray, and other instrumental techniques are used to measure traces of metals in grease.
- Crackle test for water – The crackle test is a quick and simple way to check for the presence of water in grease. Other techniques such as FTIR Analysis can detect water in grease.
Analysts often compare test data for in-service grease against baseline values for the unused grease. Trends in the test data make it possible to assess the condition of both the lubricant and the machinery being lubricated. Results for trends can be used to make an informed decision about the need for maintenance.