Last year my facility began performing oil analysis on several large rotary screw air compressors filled with "Sullube" fluid. Sullube is a PAG/POE synthetic oil which is made by Dow Chemical and is rated for 8,000 hours service life. After only 6,000 hours, Dow condemned the fluid of one compressor sighting low fluid pH (4.40) when the fluid TAN was fine (0.61). Dow explained that low pH (when all other indicators are normal) is an indication the compressor has ingested air containing acidic gases. I'd like to hear from anyone who has had similar problems or even heard of this before. And, does anyone know of any oil purification products available that will remove acids from the oil? At close to $60/gallon, I hate the thought of having to change our oil prematurely.

years ago was a "pickle" plant and the acid in the air made the condensate from the compressor
acidic and it ate through a copper heat exschanger. so the air intake will make a difference.
bruce

Sounds like a common problem with Rotary Screw's on Synthetics.....

Joe, There is a compressor oil purifier product by Fluid Metrics LLC that is ideally suited for controlling acidic and oxidizing gas contamination of rotary screw compressor fluids. This product increases the service life of synthetic and mineral based compressor oils by using ion exchange technology to remove acids from the oil. This will help control both fluid TAN and pH. Ion exchange technology, which has been in use for more than a decade with phosphate ester oils in turbine EHC systems, was developed and endorsed by Dow Chemical for air compressor applications. The purifier also increases the service life of compressor bearings, separators and coolers by removing ultra-fine solids down to 3 microns absolute. Go to fluidmetrics.com to download their brochure.