RPVOT test Results

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WE have recently conducted RPVOT test on VG32 Mineral Oil - Fresh and Used. The used oil is in service for one year only. following are the test results.
Fresh oil - 342 minutes
Used Oil - 135 minutes.
The test result indicates 60% depletion of Anti-Oxidant within one year. is it Ok or abnormal?
The steam turbine driven compressor oil capacity is 70 drums and oil inlet and outlet temperatures are 45 and 60 Deg respectively.Average bearing pad(load pad)temperatures on the machine train is 97 Deg(+-5 Deg).

4/5/0510:29 PM

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andysittonMember

What brand of the new oil?

Andy Sitton

4/6/052:54 AM

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johnmMember

I would not call it normal, but I would not panic either. It is known that original RBOT (or better RPVOT) value often drops after the oil is in use, and than stabilize. In you case, this drop is maybe too drastic. However, you might re-test it more often, and test and track AN. As long as the AN is low, the oil is fine. Next time you take a sample make sure the oil is clean and dry before you send it to a lab, because contaminants can interfere with the test and yield a false negative result. I have seen this happen.

4/6/053:20 AM

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nnkmenonMember

Please do the other tests also like viscosity,TAN etc...If these are within limits.
I don't see any problem for you to continue with the same oil.But you have to monitor the oil frequently.

4/6/054:32 AM

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billjacobyanskyMember

This seems like a heck of a drop to me. Turbine oil is expected to last a long time. The fact that 60% of the life may be gone after one year would have me questioning the brand and type of oil that is being used in the application. There is a significant cost in replacing all of that oil every two years as opposed to every five. As everyone else has said continue to sample and establish a trend. This should be a concern and you should watch this closely.

4/7/059:33 AM

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