Oxidation of Heat Transfer Fluid

Many commercial, thermal fluids have additives and impurities that would condense out as a solid. Hard to say what it would be. Best to have a sample tested; most labs would charge you fifteen hundred bucks (or more cause' you're in Oakville) but at least you would know for sure.

I would send the oil to Wearcheck for testing. I beleive they are in Ontario.

I would recommend the use of a better fluid. I sell a product that has a temperature limit of almost twice the 170 C. At the low temperature you are describing, my fluid should last 3-5 years before needing replacement.

Do you have filters in the system? They are very important. Your goal should be to reduce the micron rating to at least 10.

Prior to using your current fluid, did you clean the system?

The nitrogen blanket will help considerably.

Please e-mail me if you are interested in my product @ lubricants@rgreenwald.com

Instead of N2, you might want to consider Argon as your shielding gas. It is heavier than air and will not tend to be displaced or diluted as easily as N2.

You also might want to give these guys a call. They have a number of products that would be better fit for this application.

http://www.paratherm.com/heat_transfer_fluids.asp