The servo oil system on our GE steam turbine frequently becomes contaminated with lube oil - Mobil DTE790. We have been unable to determine the source of the contamination.
My question has two parts:
1. Are there any cost effective separation methods to remove lube oil from Fyrquel?
2. Is there a tracer method available (e.g. radioactive) that might help us identify the source of the lube oil?

As far as I know,the only possible source of lube oil into EHC system is wrong oil make-up, such as wrong oil drum, or contaminated transfer vessel. I suggest you check the oil drums carefully. Maybe some lube oil was stored in an empty Fyrquel drum, and mistake happened. Fluid should never added from a suspect drum.

GE's limit of mineral oil contamination in EHC phosphate ester oil is 4%. Althought their density is very different (0.87 to 1.13 roughly), part of mineral oil might become upper layer if settle for a long time, but they have some solubility to each other, not easy to separate mineral oil from phosphate ester oil completely. The best way is to change oil.

One more thing is test method. Some lab use density difference to determime mineral oil content in phosphate ester. Some lab use sulfuric acid method(GE method).But different brand of phosphate ester have different density, range from 1.12 to 1.16. Check the density of virgin phosphate ester is important to confirm mineral oil contamination.

Jack

This message has been edited. Last edited by: Jack Chang,

It depends on the system. Some of our older (BBC / ABB) systems use a 1:1 relay between a control oil (mineral oil) and control fluid (fyrquel) systems. This is a point of possible contamination as the liquids are both present in a common device.

Thanks a lot pepc. I did think about this possibility (lube oil leak into EHC oil through trip system ), and searched in EPRI reports, but didn't find this type of contamination. So I said "only possible" to emphasize the importance of oil drum management. If you have experience with this type of contamination, please let me know. It will be a very helpful information, and I will be more than happy to learn.