Turbine oil acid number

I would claim that TAN value of 0.10 is just fine (Depending on oil type of course). I have a reference sample from Regal oil R&O 68 giving 0.07 (after ASTM D-664).

Note: TAN does not always give good enough confirmation of oxidation problems in turbine oils. You should look into FT-IR analysis (peaks at 1630 & 1714 cm-1), Gravimetric analysis and Ultracentrifuge test (RPVOT). Also regular particle counts are recommended.

It would be in your best intrest to do a complete analysis of your "used" oil and compare it with the same test results from a drum of "new" oil. That way you will know where you stand and can tailor your test slate to suit. Spend you $$$ on what's important.

viscosity change and water content are important but Tan is good.

water content is also important

quote:

Originally posted by mr. Hughes:
Note: TAN does not always give good enough confirmation of oxidation problems in turbine oils. You should look into FT-IR analysis (peaks at 1630 & 1714 cm-1), Gravimetric analysis and Ultracentrifuge test (RPVOT). Also regular particle counts are recommended.

Just for clarification to readers, RPVOT is not and never has been the "Ultracentrifuge test", as could be easily miss-understood from the above quote.

A tan of 0.1 is not bad. but it is important to note that the absolute value is not good indicator, the evolution(variation on the time) of the characteistic is more important and can indicate lot of things. you can send a sample of a new oil for analysis and used the result as a reference.

I agree, we use a General Guideline of 0.10 for unknown turbine oils and unknown OEM (why do people send in samples with no info and data???) Anyway, look for a doubling of that TAN value to 0.20 as a critcal limit, again,this a GENERAL GUIDELINE. And remember,that the TAN test has accuracy and repeatability issues at this low level (makes it even more fun) so, you would be best to back up the TAN with a RULER and FTIR tests.