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I am currently in a steam turbine turn around; prior to the shutdown we were fighting a servo hydraulic leak which was contaminating the turbine hydraulic system, resulting in the active thrust bearing thrusting and tripping the turbine. I have heard that some utilities are replacing Fyrquel with lube oil. What specifically has to happen to accomplish this change?
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First you are trying to fix a mechanical problem with a product solution. The real problem in this situation is a servo valve leak. It is extremely difficult to flush out a phosphate ester based product like FYRQUEL or Shell TURBO DR and replace it with a mineral oil based turbine oil that is NOT COMPATIBLE at all. Not to mention a company that would perform such flushing procedure would charge a very high rate because of the liability if the flushing was not 100% perfect.

I would suggest using less downtime than a flush and fixing the leaking servo valve or install some type of drip pan to catch and collect the leaks.

Paul Jarvis
Shell Lubricants
If the Frquel (or Fire resistant Hydraulic Fluid) was used, it must be there for a very good reason. Servo valves are high precision direction equipment and have very very fine clearances . Consequently, they require super clean fluids (NAS 6 – 5). Many of the servo valves manufacturers recommend use Phophate Ester High Resistivity FR fluids, a product I have come across in India is Castrol Anvol PE 46 HR.

Phosphate Ester’s are very sensitive to moisture, and break down to corrosive acids in the presence of moisture/water. In a super heated steam environment the probability of condensate forming is also high. It is imperative, that your arrest the leakage immediately, then deal with other issues. Also re-check composition of seals and gaskets, they must be viton or other synthetic rubbers only.

In conclusion you cannot change FR Fluid in Servo valves with general lube oil.

M Hussam Adeni
i very much agree with MR.Adeni.

Fire resistant Hydraulic Fluid are used very purposely. high precision control at elaved temp without any hazad is must.

NAS4-7 is really a super claen oil. and can be achieved by electrostatic filtering machine.

i amnot expert in this subject but being a end user i have tried this in various applications in plant.
Turbine, To start off i would stay away going to mineral oil from Fyrquel. First Paul mineral oil is not compatible with Fyrquel at all. I would go a different route and use another synthetic fluid that is compatible. That product is called EcoSafe EHC,it is totally compatible with Fyrquel and is a PAG based chemistry. You can top off Fyrquel with EcoSafe EHC or just drain and fill a flush is not neccessary. I know of plenty of powergen plant that have done this with no side effects to the systems. Plus it is a nontoxic(worker friendly) fluid and is inert to water (no gels,sludge or varnish)
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