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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?
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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
Last edited by jackchang
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.
I have heard of this problem with a Westinghouse system and there the problem was that the turbine oil was used as make-up in the Steam Generator PORV reservoirs. Determine what procedures are in place to prevent mistakes. Dedicated containers can help as would signage on the equipment to use only phosphate esters. Too much mineral oil affect the fire resistance, can affect EPR seals and can affect fluid life.

A possible contributing factor is that Fyrquel fluid is normally only in drums and typically the only drum for make-up is down near the ST control system reservoir and might require an Operator to operate the drum pump or fill cart. Having phosphate ester fluid in suitable pails or other containers might help. Do not use PVC, or galvanized containers.

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