Regarding replacement of ynthetic oil with mineral oil

We are using Fyrquel L synthetic oil in one of our turbine. Due to frequent degradation and extremely high cost of the oil, we are planning to replace the oil with equivalent viscosity grade and propertires. what are th things to be considered before making any such decision?

Original Post

I'd be very cautious about making that change.  Fyrquel L is a fluid specifically developed to meet the critical needs of certain steam turbine hydraulic control systems.  Additionally, in some machines it can be used as the main lubricant.

The fluid is primarily chosen/recommended for its excellent fire resistance.  I would not make a change to a mineral based fluid without a careful review of why the Fyrquel product was originally recommended.

 Other turbines in your plant are using the same oil without problems ? if YES, then the root cause is not the oil. 

Before making any decision to change the oil type, I recommend to pay close attention to oil temperatures, filters and filtration circuit. Also check oil storage, top up and sampling/condition monitoring practices. 

It would be helpful if you define "degradation"-actual LOA data. In my experience the majority of EHC fluid issues are driven not by the fluid but by the environment. Water intrusion, wrong filter ratings, lack of temperature control etc. All too often plants replace their EHC fluid only to find out that they have not addressed the root cause of the lubricant "failure". With the side stream filters available today it is a rare occurrence where you can't restore your fluid to near new condition. EPRI has studied this issue extensively so if you have access to their material it is well worth the effort to read there recommended maintenance for EHC fluids. If you do decide on a change out be aware that there are suppliers out there that market their products as "fire resistant" when testing has proved otherwise.  

The TAN value is increasing and has gone beyond limit. Also since it is heavier than water, water remains on top and is difficult to remove. Also OEM has not provided any filteration system. This is the first time, we are using synthetic oil for lubrication purpose. Any body aware of moisture removal and filteration system for synthetic oil, pl help.

Absent any LOA data it's hard to pass judgement. I would get Fyrquel involved and talk to one of the formulation engineers as opposed to a salesman. I say this because I've been following an EHC issue for sometime (not Fyrquel fluid) and my standard LOA criteria had it as marginal at best. After talking quite extensively to the product line engineer I found out that the fluid was in every aspect in the "normal" range for the fluid blend and time of service. Boilerplate LOA acceptance criteria needs to be validated for your specific application and fluid type. In the above instance I put off the rental of a filter skid and a scheduled fluid change by talking to the right people. Hope you have the same outcome as I did. 

This is what the maker says...

What is the recommended way to remove water from your fluid? Phosphate ester is a heavier than water fluid and normally has very low miscibility with water which allows for good separation. The best way to remove gross water contamination is to use a “wet vacuum cleaner” to remove the water layer from the top of the fluid level in the reservoir. Removal of water which persists as a second phase but is not in sufficient quantities so as to be efficiently removed via the ‘vacuum cleaner’ method can be removed by a coalescing filter. The best way to remove dissolved water content is by use of water absorbing filter media and using vacuum dehydration for larger fluid fill systems. Contact your Fyrquel® Representative for a recommendation.

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