Phillips 66® next-generation turbine oils have been re-formulated for superior protection against oxidation, sludge and varnish. This was achieved with premium base stocks and a proprietary additive system specifically engineered for steam, gas and combined-cycle turbine applications operating under severe conditions. The result is a premium product line designed to improve rotating pressure vessel oxidation test (RPVOT) retention, water separation, varnish and sludge formation, rust and corrosion protection, as well as foam and entrained air release.

Evolving turbine trends

Evolving plant operations, with a focus on efficiency, require modern power turbines to operate under severe conditions marked by high energy output, increased cycle times and high operating temperatures. These design and operating parameters introduce more thermal stress on the lubricant, demanding increased performance against oxidation, sludge and varnish formation. Phillips 66 has effectively re-engineered its turbine oil line to meet these performance challenges in steam and combined-cycle turbine systems, and particularly for the expanding gas-turbine market.

Turbine oils must be formulated to minimize component wear while maintaining smooth control system operation. This is accomplished by preventing the buildup of sludge and varnish in the lubrication system of the turbine. The new line of Phillips 66 turbine oil products uses a proprietary formulation with properly balanced additive chemistry, reducing unplanned downtime previously caused by varnish buildup within the hydraulic control systems of the turbine.

The engineering of turbine oil

To design a premium-quality turbine oil that meets these requirements, Phillips 66 chemists sought the optimal base oils, antioxidants, rust inhibitors and other additives, which interact favorably to improve oxidation resistance, sludge and varnish control and water separation. The reformulated oils also offer improved RPVOT retention, rust and corrosion protection, and promote rapid foam and entrained air release.

Figure 1: Dry TOST data show that next-generation Phillips 66 turbine oils outperform the competition in terms of RPVOT retention and sludge/varnish control. Source: Phillips 66Figure 1: Dry TOST data show that next-generation Phillips 66 turbine oils outperform the competition in terms of RPVOT retention and sludge/varnish control. Source: Phillips 66

The effectiveness of the reformulated product line was confirmed by dry turbine oil oxidation stability test (TOST) data. The assay developed by Mitsubishi is deemed a better predictor of oil service life and sludge and varnish formation relative to previously used methods. Dry TOST testing demonstrated 270% and 220% improvements in next-gen Diamond Class and mainline turbine oil RPVOT retention, respectively. For sludge and varnish control, a 200% improvement was documented for Diamond Class Turbine Oil and a 190% gain was recorded for mainline turbine oil.

Dry TOST data also shows that the next-generation Phillips 66 turbine oils outperform the competition — Shell Turbo T turbine oil, Chevron GST and Mobil DTE 700 series — in terms of RPVOT retention and sludge and varnish control.

Field test performance

Field testing has been ongoing since March 2017 in a GE Frame 7 gas turbine with Diamond Class Turbine Oil 32. Results to date indicate 85% RPVOT retention relative to 65% for older-technology turbine oil formulations over the same timeframe. For reference, current industry recommendations do not suggest action until the in-service oil reaches 25% RPVOT retention.

Figure 2: After two years of testing, MPC data show that sludge varnish potential remains virtually flat, indicating no need to increase the monitoring frequency of next-generation Phillips 66 turbine oils. Source: Phillips 66Figure 2: After two years of testing, MPC data show that sludge varnish potential remains virtually flat, indicating no need to increase the monitoring frequency of next-generation Phillips 66 turbine oils. Source: Phillips 66

Membrane patch colorimetry (MPC) is a test method that quantifies the current amount of varnish precursors present in in-service turbine oil. As MPC values increase, so does the propensity for varnish to form in the hydraulic control system of the turbine. After two years in-service, the MPC values for Diamond Class Turbine Oil continue to trend flat, between values of 5 and 10, and well within the normal range for this method.

By starting with quality base oils and combining them with a select balance of additives, Phillips 66 next-gen turbine oils are among the highest-performing turbine oils in the power generation industry, with Phillips 66 Diamond Class Turbine Oil outperforming the leading competitors by more than 60% in RPVOT retention. The product provides long service life and significant cost savings by minimizing the formation of harmful sludge and varnish deposits, particularly in the hydraulic control circuits of gas turbines subject to the severe operating conditions present in modern power generation stations.

Contact one of our technical experts and learn more about Phillips 66 Diamond Class Turbine Oil improvements that maximize RPVOT retention and minimize sludge and varnish formation.