Almost everyone that has worked in the reliability field has either experienced or heard about a lubrication problem brought on by combining incompatible lubricants. Sometimes this is accidental, such as a leaking hydraulic line dripping onto a gearbox. Other causes are intentional, i.e. the plant wants to consolidate the number of lubricants in use; the current product is discontinued or there are supply chain issues. In any case, compatibility testing is required.
Eurofins TestOil Vice President Sales and Marketing Michael Barrett advises testing before any lubricant switch, “Whenever you switch lubricants, you will never completely remove all of the old lubricant and even a small quantity mixing with the new can be detrimental.”
Problems with compatibility include excessive foaming, precipitate or deposit formation, and loss of essential performance traits such water separability. Compatibility testing is critical for heading off these and other serious issues. It’s also important to remember that “equivalent” or “comparable” lubricants are not the same as compatible lubricants.
Selecting Appropriate Compatibility Tests
There are several considerations for determining the best compatibility test or slate (Eurofins TestOil’s experts can help with this). Two of these considerations include:
- Decide if you will test your current in-use fluid with the replacement fluid(s). If you have one lubricant system that’s transitioning to a new oil, it’s a good idea to test the used fluid with the replacement fluid. This will detect any possible incompatibilities between the used oil and new oil. If you have multiple systems that will be changing to the new oil then comparing a new oil sample of the fluid currently in use in the machines to a new oil sample of the replacement fluid will provide a basic determination of compatibility. Alternatively, a used oil sample from each of the systems can be tested with the replacement fluid.
- Determine which mixtures you would like tested. ASTM D7155 calls for at least one mixture in the ratio of 50:50. Additional mixtures can be added if appropriate. If you are doing a complete change out, but some residual fluid may be present in the system and could mix with the new fluid then adding a 90% new oil to 10% used oil mixture is recommended. If the replacement fluid will be gradually added to the existing fluid, then three mixtures are recommended, either 90:10, 50:50, and 10:90 or 25:75, 50:50, and 75:25.
Eurofins TestOil’s Compatibility Studies are based on ASTM D7155 Standard Practice for Evaluating Compatibility of Mixtures of Turbine Lubricating Oils as the guideline for compatibility testing. These tests are categorized into four tiers; the first two tiers are required for accurate results, the 2nd two tiers are optional.
Tier I: Visual Inspection: calls for heating the mixtures along with neat samples of the constituent oils for a period of time, then incubating at room temperature, with visual assessments of the mixtures for clarity and development of precipitates after both the heating and room temperature incubation. If no signs of incompatibility are observed during Tier I, then Tier II, Tier III and Tier IV testing should be considered.
Tier II: Interfacial Properties, tests include:
- Demulsibility ASTM D1401
- Foam ASTM D892
- MPC ASTM D7843
- Air Release ASTM D3427
Tier III: Physical and Chemical Properties, tests include:
- V40 ASTM D445
- V100 ASTM D445
- Viscosity Index ASTM D2270
- Color ASTM D1500
- Acid Number ASTM D974
- Additive Metals ASTM D5185
- Water Content ASTM D6304
Tier IV: Specific Performance Properties, tests include:
- RPVOT ASTM D2272
- Rust ASTM D665
- Copper Corrosion ASTM D130
Compatibility testing will identify incompatible lubricants before they are mixed in equipment and cause operational issues. Alternative choices can then be evaluated so that a suitable replacement can be selected. While, lubricant compatibility testing cannot guarantee compatibility, it can predict compatibility.
Eurofins TestOil offers standard and customizable compatibility test packages. For more information visit: https://testoil.com/services/lubricant-compatibility-analysis/
About Eurofins TestOil
With more than 30 years of experience in the oil analysis industry, Eurofins TestOil focuses exclusively on assisting industrial facilities with reducing maintenance costs and avoiding unexpected downtime through oil and fuel analysis program implementation. As industry experts in diagnosing oil-related issues in equipment such as turbines, hydraulics, gearboxes, pumps, compressors and diesel generators, Eurofins TestOil provides customers with same-day turnaround on routine oil analysis testing. For more information on partnering with Eurofins TestOil on oil analysis programs or training opportunities visit https://testoil.com. Contact: Michael Barrett 216-251-2510; email@example.com.
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