Varnish Removal | Varnish Mitigation | Varnish Solution

By: Environmental & Power Technologies  09-12-2011
Keywords: Gas turbine, Oil analysis

Varnish contamination is the inevitable by-product of many degradation processes in hydraulic and lubrication systems.  The effects of varnish on industrial and manufacturing systems range from the nuisance of minor downtime and routine maintenance to, worst-case scenarios, multi-million dollar catastrophic failures of major capital equipment.

EPT has done more research and testing on lubrication fluid varnish than any company in the world.  EPT has developed a proven, holistic approach to solve varnish by using the most advanced technologies available. Solving varnish related problems will extend fluid life, provide optimum fluid performance, and lower unforeseen costs.

This video shows 2 samples from the same gas turbine lubricant reservoir.  The lubricant is approximately 3 years old and has a MPC ΔE value of 35, which is typical for average gas turbines.  The sample on the left has been treated with ICB, which has removed the oxidation by-products (or varnish pre-cursors), and the sample on the right is as-found.

The solution is maintaining fluid solvency.  Technologies designed to remove particulate debris (electrostatic, agglomeration, or depth filtration systems) can only remove varnish once it has been created and, therefore, cannot prevent varnish formation as demonstrated by the sample on the right in video.  If you do not want the lubricant to release oxidation by-products during shut-down and want to reduce the associated risk of experiencing a fail-to-start condition, you need to remove the soluble contamination during turbine operation.  The only method to do this is by using SVR/ICB technologies.

This plant, operating 7FA turbines in a cycling mode, had extreme varnish problems (as shown in the picture below, left patch).  Last year, this unit had 14 fail-to-start conditions and 3 unit trips that were attributed to varnish.  Their oil analysis indicated a very high varnish potential, yet no actions were taken.  The plant had a small window of time before a shutdown in which they wished to employ EPT technologies and inspect the system for evidence of varnish.  The hope was to visually observe evidence of varnish removal and an improved system after EPT technologies were installed for only 7 days.

Unit

GE 7FA

Duty Cylcle

Peaking

Oil Age

4 years

After Installation of EPT Technologies
As is typical in most cases after the installation of EPT technologies (SVR/ICB), the color and clarity of the fluid improved considerably.  This is due to the removal of soluble degradation (oxidation) products, which are usually dark coloured chromophores (i.e. coloured molecules), making the fluid appear darker in color.

The varnish potential of the fluid went from a Quantitative Spectrophotometric Analysis rating of 92 to 15 in 7 days.

Visual inspection of the reservoir, bearings and hydraulic components revealed that a significant amount of varnish had been removed during the short clean up period.  With the success observed, the plant decided to extend the life of the fluid with EPT technologies.

Keywords: Gas turbine, Oil analysis

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