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Demulsibility

ASTM method - D1401

This test measures a lubricant's ability to separate from water.

Operating Principle

Equal portions of water and oil are blended together at a set temperature for a predetermined amount of time to produce an emulsion. The mixture is then allowed to separate. The amount of oil, water and emulsion is recorded at 5 minute intervals. A result of 3 mL or less emulsion within 30 minutes for oils with viscosities less than 90 cSt or within 60 minutes for oils with viscosities greater than 90 cSt is considered acceptable. Results are reported in the format: mL oil / mL water / mL emulsion (time in minutes).

The results are reported as such: [40-40-0 (60)]

After 60 minutes this sample passed. It contained 40 ml of oil, 40 ml of water and 0 emulsion. This sample separates water and therefore, has good demulsibility.

Significance

This test is crucial for critical equipment that may be at risk for water contamination. The inability of a lubricant to separate from water will result in fluid degradation, corrosion of components, and potential failure due to improper lubrication.

Applications

This test is commonly used for lubricants from systems which have a risk of frequent or large scale water contamination to ensure adequate ability to separate from water. A minimum of 80 ml of sample is needed to perform this test.