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VARNISH (STEAM TURBINES)

S servoconalphaMember
ServoCon ALPHA
167 Expo Road
Fishersville, VA 22939
(T) 800-447-7747 (F) 540-337-4901
Website www.servoconalpha.com

AS the EHC system ages, varnish is deposited on the inner walls of the piping, valves, actuators and system components. The varnish is generally a very hard, tenacious deposit that is accumulated over time. Varnish can occur in oils that appear healthy and clean, with no visible signs for concern through normal oil analysis. It cannot be identified by the typical in-service turbine oil tests. Low total acid number (TAN), a low ISO particle count and a high RPVOT does not guarantee that the lubricant is immune from varnish. The varnish deposits that form on machine surfaces cause numerous operational issues by interfering with the reliable performance of the fluid and the machine’s mechanical movements. They can also contribute to wear and corrosion or simply just cling to surfaces.

Other potential problems include: restriction and sticking in moving mechanical parts such as servo or directional valves, servovalve failure, increased component wear due to varnish’s propensity to attract dirt and solid particle contaminants, loss of heat transfer in heat exchangers due to varnish’s insulation effect, catalytic deterioration of the lubricant, plugging of small oil flow orifices and oil strainers, increase of friction, heat and energy because varnish acts as a heat insulator, reduction in filter efficiency and potential filter plugging, damage to mechanical seals, increased maintenance costs due to cleanup and discard of oil.

FLUSHING, CHANGING FLUID AND ELECTROSTATIC PURIFICATION/ IONIC EXCHANGE FILTERING SYSTEMS WILL NOT REMOVE ALL VARNISHING, nor in any way will it help worn parts, such as cylinder piston rings that lead to internal leakage, another contributing factor to varnishing. The only way to remove the varnish from your system in conjunction with proper filtration, fluid monitoring and some of the above ideas is to remove the hydraulic controls such as the cylinders and servovalves from the turbine and have them disassembled, extensively cleaned, re-sealed, worn parts replaced, and machine honed to remove the baked in varnishing, a process that ServoCon ALPHA has perfected. This is normally done during an outage.

While ServoCon ALPHA is disassembling, inspecting, taking photos of as found parts, extensively cleaning, calibrating and testing the control pac assemblies, you should drain old fluid from turbine, thoroughly clean reservoir tank, flush hydraulic lines and hoses and install new filtered/test fluid. It is important to maintain the proper OEM filter recommendations after the units have been re-installed on steam turbine.

Respectfully,
Brian K. Supinger
Account Specialist
Original Post

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J johnmMember
quote:
Originally posted by ServoCon ALPHA:
FLUSHING, CHANGING FLUID AND ELECTROSTATIC PURIFICATION/ IONIC EXCHANGE FILTERING SYSTEMS WILL NOT REMOVE ALL VARNISHING...
Respectfully,
Brian K. Supinger
Account Specialist

It should be added here that your statement MAY be correct only in systems that have been neglected for many years, where varnish ended up being baked on surfaces. In all other scenarios, I beg to differ.

Well, I thought that I know a lot about varnish and techniques for controlling it. But yesterday, members of Portland STLE Section and I, had a rare privilege to listen to Greg Livingston, one of very few folks in the world who devoted years to studying varnish, and see his presentation, where he shared with us his discoveries and solutions in a “down-to-earth” language. Therefore, I am convinced more than ever, that there is a way to “avoid” the situation you described, when one has no other choice but to call ServoCon ALPHA or similar company, and buy new oil. The proper way is to monitor varnish potential in your oil, and make one-time investment in equipment able to control varnish in your oil, by either employing an electrostatic system or a properly designed cellulose-fibers system. Both systems are proven to be effective, and the use of either one will, without a doubt, prolong oil service life and reliability of the equipment, and generate savings by avoiding lengthy and costly downtime needed for disassembling, flushing, and the expense of acquiring new oil.
C ccuserMember
It is good to get another perspective on this topic. Obviously, you are correct that oil conditioning systems will not fix worn parts.

I think that you are confused however with the application. Your topic is varnish in steam turbines, but you discuss EHC systems - the steam turbine hydraulic system. Also, all of the issues that you raise about varnish pertain to mineral oil systems, not EHC systems which use a phosphate ester fluid. The way that deposits form in an EHC system with phosphate ester fluid is significantly different than mineral oil systems.

Obviously, you are trying to push servo-valve rebuilds. Our company has used your services before with success. However, I think that you can give us a sales pitch on your services without bashing other technologies - which are important aspects of minimizing deposit formations.

Also, your write-up of varnish is almost identical to a paper that was recently given to me by a supplier.

Please consider your services complimentary to maintaining good quality oil.
O oilkleenMember
I would like to add to CC USERS post - I agree at first he was talking about steam turbine then EHC...

I would like to add that phosphate ester hydraulic fluid doesnt produce varnish. Its a bad myth going around the industry because it will show up on a colorimetric patch like it has a 100 critical varnish problem. At OILKLEEN we have cleaned numerous EHC systems and even drained these systems and climbed in reservoirs.

In all these systems I have never seen varnish on the reservoir wall. I mean Never!

I have seen this "apple jelly" looking substance on reservoirs like a bath tub ring, but this is NOT VARNISH.

Most of these system which produce the "apple jelly" bathtub ring are using selexsorb or fullers earth filters. These type of filters allow pounds of sub micron material to come off the filter and into the oil. This material is what will show up on a colorimetric patch test and appear to show varnish.

**Remember, a colorimetric patch test will show all insoluble foreign material. This is dirt, oxidation by-products, decomposed addtives, fullers earth material that comes off the filter, and selexsorb material that will come off the filter too.


TO SERVOCON ALPHA
One other thing I would like add is that I dont think its good to bash electrostatic filtration technology when you dont know how it works nor what is really happing in an EHC system. I do take it as a compliment that you would bash electrostatic filtration because soon OILKLEEN has an EHC system we will be launching that should stop servo rebuilds because this OILKLEEN EHC system will be the final solution.

Paul Jarvis
C ccuserMember
I'm not sure what you call varnish, but one of our EHC systems had brown deposits in it that looked exactly like the same kind of deposits that was in my combustion unit's pencil filters. I have pictures of one of the servo valves and it looks like varnish. I still have one of the servo valves on my desk and can send it off for analysis. What tests would indicate that this is varnish or not?

I hope that your EHC unit doesn't leak as badly as your other units.
O oilkleenMember
to CC USER:

Does your EHC system use FYRQUIL? The "apple jelly" bathtub ring in the reservoir is what you see first. Then those "apple jelly" deposits are formed and pressed into filters, and causing them to plug. This matter then allows for dark foreign contamination to stick to it and looks like brown deposits. However, in all the FYRQUIL systems we have seen this, and selexorb or fullers earth was used, this foreign material is not varnish as we know it in Mineral Oil systems.


To answer Andy:

Yes, any time we see the "apple jelly" looking deposits and bath tub rings there is a rise in Al on the Spectro, and now that you mentioned it all systems that the Al increased were using Selexorb and not fullers earth or ion exchange.
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