From "Machinery Oil Analysis"

The color of a lubricant provides no direct indication of its lubricating properties; however, a change in color does signify a change in chemistry or the presence of a contaminant. Lubricant color assessment is normally based on transmitted light, and the common color scales used for color interpretation are based on this principle. The basic assumption of the color test is that oil color can be related to deterioration or degree of refining and that any color change is due to deterioration or contamination.

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QUESTION: What are common properties of engine oil that blotter spot testing evaluates?

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"We recently experienced a massive water leak in our steam turbine. We removed most of the water using a vacuum dehydrator but I am worried we may have destroyed the oil. What tests can I perform, and what should I be looking for? We are using an ISO 68 mineral oil."

With large amounts of water, there are several problems that can occur with both the base oil and additives. For the base oil, your main concern should be excessive oxidation caused by the catalytic effects of water. To test for this, you may want to run either an acid number or FTIR oxidation test to determine to what extent the base oil has oxidized. Remember to run these two tests on both the used oil and a fresh new oil sample to allow a differential comparison of the test results.

As for additives, your main focus should be on the corrosion and oxidation inhibitors and the demulsifying additives. To test the corrosion prevention characteristics of the oil, you may want to run the ASTM rust inhibition test (ASTM D665) as well as the copper strip corrosion test (ASTM D130) to test for yellow metal corrosivity. The antioxidant additives can be tested using the RPVOT test (ASTM D2272) used to measure the oxidation stability of steam turbine oil. A low RPVOT value relative to the new oil may indicate significant antioxidant depletion.

To determine if the demulsifying additive has been appreciably destroyed, you may want to run the standard test method to determine the demulsibility characteristics of the oil (ASTM D1401), which seeks to determine how quickly the oil will shed water at elevated temperatures. Good luck!

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