In our power plant, I take oil sample from oil tank. While it is hot, it is transparent. You can see background clearly. However, after a while oil cool down to room temperature and oil becomes cloudy. It is not transparent any more. I check that whether it contains water or not. But there is no indication of water. What can be the result.

You have not mentioned the type of the oil sample.Is it synthetic oil or mineral based one.Such problems can be seen in some types of synthetic oil due to improper mixing of additives.

Actually, i don't want to mention oil brand. But it is a mineral based turbine oil. Also, i am filtering oil by means of 1 micron element. Sample (aprox. 75 C)after filtration is clear and becomes cloudy after cooling down to room temperature. After waiting for one week, Oil seems cloudy again in addition that cloud becomes denser and darkend suspended in the mid level first. Then gradually that dark cloud subside.

Can it be some sort of oxydation (reacting with oxygen)?

See this article !

Oxidation is possible. Since the journal bearing is sealed by means of extraction air from air compressor. Its temp. is approx. 200 C. But how can i remove the oxidation effect. Oxidation products are submicron particles. Conventional filtration is not solution.

We notice the same with Turbo CC32, anyone else?

Andy

My oil is also Turbo CC 32. (The situation may resulted from improper composition of oil or more popular oil oxidation-varnish-sludge etc) Can you share your symptom and diagnosis?
I take sample regularly and lab analyse the oil. Viscosity and TAN seems ok (there is no significant increase).Lab is not capable of identifying the situation. There are some test methods but analyst can not interpret the the situation wrt results although they have FTIR, colorimetric analyser etc.

Sounds like you have either a.) incompatibility issue (if you added make up oil to you in-service oil), or b.) the original blending issue. My suggestion for case "a": grab a quart of old oil and quart of the new oil (make up oil), and send them to a lab for compatibility testing. In case "b": Fill a glass beaker with your unused oil (hopefully you have a sample of your oil that you took at the point of delivery and stored it for reference), and observe it when it cools down. If you see cloudiness and separation of phases, then you have a product that has been screwed when it was originally blended.

Neoidea
You have a symptom called auto-degradation. It is the automatic generation of insoluble material in a static body of oil. This is very common in gas turbine applications, especially frame 7/9 units. Auto-degradation occurs because of a combination of physical reactions, (precipitation, condensation, agglomeration) and chemical reactions (auto-oxidation). Auto-oxidation occurs when there is an overabundance of free radicals in the oil and insufficient antioxidant levels. This phenomenon can be measured by taking a sample and performing on-site colorimetric tests every day. You'll notice the patch become considerably darker and then stabilize after 4-7 days. If you have really extreme auto-degradation, you'll notice significant darkening of the patches in several hours.

The antioxidant chemistry that is most beneficial to preventing this form of degradation are phenols. Turbo CC is an amine-only additive system. This problem does occur in turbine oil chemistries with mixed antioxidant systems, but not usually until the phenols are 20-30% of new. (Obviously, this percentage also depends upon the actual volume of phenolic antioxidants formulated into the turbine oil.)

You need an electrostatic separation unit (1-micron filters, including depth media cellulose filters, are ineffective at removing soft contaminants in an operating gas turbine lube system). You also need to sweeten your additive system by bleed & feed (not a big bang for your buck), drain & refill or additive replenishment (usually without the support of your lubricant supplier).

When you eventually replace the oil, you may consider purchasing a turbine oil with a mixed antioxidant system. Shell has some.

Bottom line - the same phenomenon that you are seeing in the sample bottle is also occuring in low flow areas of your system and forming varnish. In a gas turbine, this is often the IGV line and explains why peaking/cycling units have the Monday morning blues. (Fail-to-start conditions due to IGV va**e sticking when you go to fire the unit and it has been on turning gear for the weekend.) I have a paper on this if you'd like further information. gregjlivingstone@yahoo.com

This message has been edited. Last edited by: Greg Livingstone,

water can disso**e in oil .When the water content reaches the saturation point of the oil, it separates out and free water is formed as a solution and the oil looks cloudy. The solubility of water in oil depends on temperature and it encreases as the temperature rises. So at high temperature you have clear oil with water disso**ed in it and with cold oil you can see the water in oil that is already saturated
Regards
Reuven Sasson
ihsil@hotmail.com, Israel

Good point Reuven. Based on the initial comments "no indication of water in it" probably means that a crackle test was done. The saturation point of turbine oil can be as low as 200ppm at room temperature - lower than the detection limits of the crackle test. Be sure to run water by KF.

Has the Oil been analyzed by means of an FT-IR

You lab may have an unit available which should be able to tell if the problem maybe water or oxidation has occurred. They could even determine the possibility of cross contamination with various other lubricants.

This cloudy oil is a continuing issue here in the USA and although it is a good idea to check the basics first, water, Contamination, Pollen, other things through FTIR, the issue may be sludge or varnish. We are increasingly seeing some turbine oil which used to be pure mineral oils swinging formulation to a higher percentage of Group II base stock. Some of these oils have a higher sludging tendency. If you contact a good lab and request a full turbine lube ascessment including varnishing potential you may get to the problem sooner rather than later.

Take the advice of either Greg or andy. they both know what they are doing.

Labs see http://www.analystsinc.com
another http://www.bentlytribology.com
or http://www.focuslab.co.th

There are many others jus as qualified, but these are a few that we know.