Is there any direct relationship between TAN Value and Oil viscosity.

NO

Dear A.S.Pal

This depends of the type of oil. For example for turbine oil in steam turbine application, yoy can find an increase in the TAN value, and the viscosity remains in the permised level. This is commented in the ASTM D-4378.

For gas turbines, in some cases appears a relation between color and viscosity.

For other applications, it could occur that you find a correlation between both parameters.

What application do you refer?

Regards

Dear Mr.Pal,

Are you talking about used oil?

Mr. Menon
Yes, I am talking about used or in service lubricants.

Mr. Ing. Cristian Schmid.
Can you please elaborate your comment. Well I want to know about this relationship for Gear Oils, Hydraulic Oils, Turbine Oils, Engine Oils.

Thanks

I would have to agree with John that NO is technically the correct answer.

The only observation I can add is that typically as oxidation and the age of the oil increases so does your TAN and viscosity - however this is not always noticable nor always the case.

quote:

Originally posted by Andrew:
...The only observation I can add is that typically as oxidation and the age of the oil increases so does your TAN and viscosity - however this is not always noticable nor always the case.

Correct! Depending on the operating conditions of certain application, even the same oil (e.g. R&O turbine oil) would have different TAN-Viscosity ratio during and at the end of service life. For example, turbine oils used in steam and gas powerplants at the end of their service life usually have increased TAN and the viscosity, while the same oil, if used in hydropower application, would end up having elevated TAN and decreased viscosity. It might be possible to tentatively establish such ratio for a certain type of oil (containing the same type of base oil and additives), and associated equipment. However, if the type of base oil (e.g. naphthenic, paraffinic, PAO, vegetable, or synthetic base oils) or the additives are changed in any way, such ratio would be invalid. Considering how highly complicated process in establishing such delicate, but fragile, ratios could be, and the negative consequences for the equipment welfare that may occur if such ratios are taken for granted without regularly scrutinizing mentioned factors, I would not suggest that taking steps any further would be wise.