Our generating plants would like us to begin to look in to testing for varnish potential in their turbine lube oils and EHC fluids. We would be able to use our FTIR and look at the Nirate region around 1630 cm. However I have not been able to find any info or index at what level or percent increase in abs. would you consider an action level or critical level. Has anyone had any experience with this method? Thanks.

Last ASTM meeting D02 in Norfolk had a symposium on turbine oil oxidation and varnish potential. Imagine proceedings should be available in near future - check ASTM website. Trending of antioxidants, especially aromatic amine type, and filtration method to isolate insolubles were discussed with regard to remaining oxidation stability and varnish formation/potential
In Industrial Lubrication subject on this NORIA site - 1st page about half way down "turbine oil varnishing" is a subject with several replies
Don't believe any of this relates to EHC fluids. Some discussion under Filtration and Contamination Control subject

Do you know about the patch colorimetric test? does it give any info about the varnishing potential.

What do you think about the electrostatic filtration methods?

You will spend a lot of time to find out FTIR will only be good at telling the type of varnish problem that you have, whether it is oxidative or thermal degradation.

The best way to measure the trend of varnish production (note I did say the amount, but the trend) is with colorimetric patch analysis. We have our own VPI test, others have a test called VPR.