CONDITION MONITORING FEATURE
ly not oxidized.
Additive Replenishment: This strat- egy involves slowly adding antioxi- dant concentrates to the in-service oil to maintain desired antioxidant lev- els. It offers economical advantages by conserving base oil, but it requires careful formulation and compatibili- ty testing to prevent undesired reac- tions and deposit formation.
Conclusion Monitoring lubricant oxidation is crucial for ensuring reliable turbine operation and preventing costly failures. Analyti- cal techniques such as RULER, MPC, and RPVOT provide valuable insights into the oxidation condition and the remaining antioxidant levels. By integrating the out- comes of these tests and creating oxida- tion condition models, effective lubricant refreshment strategies can be devised. These strategies, whether through bleed and feed or additive replenishment, con- tribute to extending the lifespan of tur- bine oils and enhancing overall turbine re- liability. While both approaches have their merits and challenges, they collectively underline the significance of meticulous maintenance and monitoring practices in the realm of turbine operation.
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Figure 3. RULER can be quantified by extrapolation in degraded samples. To assess the RULER value better, we
proceeded to perform the extrapolation method. For
this, the complementary
mixtures of new and used oil to cover 0% to 100% refreshments were prepared. After thorough homogenisation, RULER was tested for all samples. Figure 3 shows the RULER outcome. Consider a gas turbine lubricated with
a Group I oil supplemented with a mixed antioxidant package. This system has run for 55,000 operating hours with a 10% re- freshment after 44,000 operating hours. Refreshment plots were performed for this lubricant.
Building an Oxidation Condition Model for Lubricant Refreshment Creating a refreshment model involves analysing the turbine’s oxidation condi-
32
REFERENCES 1. Lubricant Deposit Characterisation. Dave Wooton & Greg Livingstone. Oildoc 2003
tion and proposing a lubricant refresh- ment strategy. By assessing the relation- ship between the actual condition of the lubricant and a hypothetical scenario with a full lubricant change, a compre- hensive model can be constructed. This model guides decisions on the required refreshment percentage to achieve opti- mal oxidation condition for reliable tur- bine operation. Refreshment Strategies Two main
strategies for maintaining high antioxi- dant levels are “bleed and feed” and “ad- ditive replenishment.” Bleed and Feed: This conservative approach involves bleeding a portion of the in-service oil and replenishing it with fresh lubricant. While effec- tive, this method can be costly and wasteful as the bled base oil is usual-
2. Akihiko Yano, Shintaro Watanabe , Yasu- nori Miyazaki, Mitsuyoshi Tsuchiya & Yuji Yamamoto (2004) Study on Sludge For- mation during the Oxidation Process of Turbine Oils, Tribology Transactions, 47:1, 111-122
3. Turbine oil bleed & feed: An expensive option. Greg Livingstone, Turbomachin- ery 2014
4. Bleed & Feed, TMI Staff, Turbomachinery 2014
5. Lubrication Excellence 2007 William Moehle, Vince Gatto, Dave Wooton and Greg Livingstone, “.Practical Approaches to Controlling Sludge and Varnish in Tur- bine Oils”.
6. Norfolk, VA Vincent J. Gatto, William E. Moehle, Tyler W. Cobb, Emily R. Schneller, “Oxidation Fundamentals and its Ap- plication to Turbine Oil Testing” - April 2006 -- JAI Volume 3, Issue 4JAI13498.
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