How To Outsmart Varnish and Avoid Unexpected Downtime

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The lubricating oil in gas turbines and hydraulic systems is increasingly subject to the ravages of varnish. The debilitating effects of varnish are well documented and the complexities associated with detecting varnish potential render routine oil analysis ineffective in reporting varnish. However, there are a number of technologies, although seldom used, which have been successful in reporting incipient varnish potential. In this webinar you will learn what lube oil varnish is and what causes lube oil varnish in your systems. You will also learn about the proper tools to detect varnish potential and how to read varnish potential analysis test results. Sign up for the Webinar September 10, 2013
http://forms.testoil.com/acton/form/4748/0015:d-0002/0/index.htm

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How To Outsmart Varnish and Avoid Unexpected Downtime

  1. 1. How To Outsmart Varnish and Avoid Unexpected Downtime
  2. 2. Presentation Overview
  3. 3. What is Varnish?
  4. 4. What is Varnish? • Varnish can be defined as: • A thin, hard, lustrous, oil- insoluble deposit. • Composed primarily of organic residue, and most readily definable by color intensity. • It is not easily removed by wiping with a clean, dry, soft, lint-free wiping material and is resistant to saturated solvents. • Its color may vary, but it usually appears in gray, brown, or amber hues. Ref: ASTM D.02 C.01 Bath tub rings in a reservoir.
  5. 5. Turbine Oils Overview • Turbine Oils are formulated differently today compared to a decade ago • In general, they have superior performance but require different maintenance strategies: – Degradation is not linear, requiring different condition monitoring tests – May be more prone to deposits & varnish
  6. 6. Antioxidants are like an Apple’s skin
  7. 7. Antioxidants are like an Apple’s skin When the antioxidant depletes, the lubricant fails quickly.
  8. 8. There are many ways for oils to Degrade Varnish
  9. 9. SO WHY IS VARNISH SO SERIOUS ANYWAY?
  10. 10. Valve Sticking in the Power Generation Market is the highest profile problem Varnish on bore of Gas Turbine IGV Valve Typical Cost of a full load trip: $20,000 - $100,000 Typical Cost of a Fail-to-Start Condition $10,000 - $25,000 Typical Cost of a full load trip: $20,000 - $100,000 Typical Cost of a Fail-to-Start Condition $10,000 - $25,000
  11. 11. Other Varnish Related Problems Premature bearing wear and elevated temperatures on a gas turbine. Accelerated wear from deposits in a load gear Journal bearing deposits are a common place for deposits Deposits on heat exchangers result in the inability to maintain low temperatures Premature filter life due to deposits. Spark discharge often contributes to deposits.
  12. 12. Testing for Varnish Potential • Ultra Centrifuge • Membrane Patch Colorimetry • Particle Count Differential • RULER
  13. 13. Ultra Centrifuge • A portion of the oil sample is placed in a centrifuge tube and spun at 17,000 rpm in an ultra centrifuge • Soft contaminants are forced to the bottom of the tube and deposited
  14. 14. Ultra Centrifuge The amount of material deposited in the centrifuge tube is visually compared to a rating scale and a numerical rating is assigned.
  15. 15. Ultra Centrifuge Samples that are rated five or higher are considered to show the presence of significant amounts of contaminants.
  16. 16. Ultra Centrifuge What factors can affect this test? • Particle count • Presence of water • Fluid type
  17. 17. Membrane Patch Colorimetry • A portion of the oil sample is diluted with a non-polar solvent • The diluted sample is passed through a .45 micron Millipore patch • Large, polar soft contaminants are deposited on the patch
  18. 18. Membrane Patch Colorimetry • These contaminants are colored, and the color is measured using a spectrophotometer to give an indication of the level of contaminants present
  19. 19. Membrane Patch Colorimetry
  20. 20. Membrane Patch Colorimetry What factors can affect this test? Particle count Presence of water
  21. 21. Particle Count • Two types of particle count testing commonly used: – Optical particle count: a portion of the sample is passed through a laser or light beam. Interruptions of the laser or light are counted as particles
  22. 22. Particle Count – Pore blockage: a portion of the sample is passed through a calibrated metal mesh screen. As the pores in the mesh become blocked with particles the flow through the screen decreases. The instrument uses the decay in flow rate to calculate a particle count.
  23. 23. Particle Count • Optical particle counters will count air bubbles, water droplets and soft contaminants as particles. • Pore blockage will not count air bubbles, water droplets or soft contaminants – they pass right through the screen without decreasing the flow rate. • Significant differences between results from the two methods may indicate the presence of soft contaminants.
  24. 24. Particle Count • What factors can affect these results? – Procedures for testing water contaminated oil with an optical particle counter call for the addition of solvents to make the water dissolve in the oil. The addition of these solvents may also cause soft contaminants to be dissolved, and therefore not counted by the optical counter.
  25. 25. RULER • Tests for the presence of antioxidants in the oil using linear sweep voltammetry.
  26. 26. RULER • Levels of antioxidants present in in-use oil are compared to the levels in a virgin sample of that specific oil type.
  27. 27. RULER • Each antioxidant produces a peak on the graph • The area under each peak is calculated • The areas for the in- use oil are compared to the areas for the new oil to generate percent remaining values
  28. 28. RULER • Antioxidants protect oil from oxidation – varnish can be comprised of by-products of oxidized oil. Low levels of remaining antioxidants mean less protection from oxidation and higher risk of varnish. • Varnish can also be comprised of degraded antioxidants. Low levels of remaining active antioxidants mean higher levels of spent antioxidants and a greater potential for varnish formation.
  29. 29. RULER • What factors can affect RULER analysis? – Lubricant identification. Each oil type has different types and amounts of antioxidants. It is important to compare in-use oil to the same type of virgin oil to obtain accurate percent remaining values.
  30. 30. RULER – Variations in formulations. Whenever possible, use a retain sample from the original fill of the turbine as the baseline.
  31. 31. RULER – Mixed oils. If the oil in use is a mixture, accurate percent remaining values will not be obtainable. However, this test can still produce valuable trend data if the same virgin sample is used for each analysis. Test results will also give a general picture of the amount of antioxidants present.
  32. 32. SOLVING VARNISH Understanding Fluid Parameters
  33. 33. Factors to Consider When Selecting Technologies
  34. 34. Chemistry of Deposits
  35. 35. The fluid temperature determines solubility 25o C 50o C
  36. 36. SOLVING VARNISH What Technology to Use, When
  37. 37. Varnish Removal Technologies Technologies that can remove soft contaminants under the right conditions.
  38. 38. Depth Media Filtration Pros Cons 1. Simple and economical to operate 2. High dirt holding capacity and efficiently filters to as low as 3mm. 3. Adsorbs soft contaminants 4. Adsorbs moisture 1. Only removes soluble soft contaminants that are in suspension. For varnish removal, ideally suited for reservoirs operating <40C. Source: CC Jensen,
  39. 39. Electrostatic Oil Cleaning Pros Cons 1. Efficiently removes all suspended contaminants down to 0.01mm in size. 2. Successfully removes inorganic, insoluble degradation products (i.e. depleted ZnDDP) 3. Removes soot-type carbonaceous particles 1. Only removes soluble soft contaminants that are in suspension. For varnish removal, ideally suited for reservoirs operating <40C. 2. Sensitive to water and other conductive contaminants/fluids 3. Complex controls can be sensitive Source: Kleentek
  40. 40. Charged Agglomeration Pros Cons 1. Efficiently removes all suspended contaminants including sub-micron particles 2. Product does not “trip off” in the presence of moisture 3. Through agglomeration, allows conventional micro-fiberglass filters to remove soft contaminants 1. Only removes soluble soft contaminants that are in suspension. For varnish removal, ideally suited for reservoirs operating <40C. 2. Does not work in conductive or moist fluids Source: ISOPur
  41. 41. Chemical Filtration Media Pros Cons 1. Removes soft contaminants that are both in suspension and in solution 2. Has a wide range of temperature effectiveness from 10o C – 70o C. 3. Simple design allows for easy operation 1. Only removes organic soft contaminants. Has no impact on other hard contaminants or inorganic soft contaminants. Source: Livingstone, Wooton
  42. 42. Will Varnish Technologies Clean a System? • It is often claimed that varnish mitigation technologies will clean the fluid, allowing the fluid to be a cleaner and to remove sludge and varnish deposits through the system. True or False? • Dependent upon the chemistry, location and age of the deposit • Sometimes, the system becomes cleaner as a result of these technologies, other times there is no deposit removal
  43. 43. Avoiding Varnish requires a holistic perspective
  44. 44. www.testoil.com 216-251-2510 kwilliams@testoil.com

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