Oiling up turbines is big business these days as natural gas-fired and combined cycle units have become the go-to power source for generating electricity. The tipping point happened in 2015, as natural gas surpassed coal as the United States most popular fuel, according to the U.S. Energy Information Administration.
Turbines are used for base load power, meaning they run constantly; peakers, which come online for two or three hours a day during peak loads; and as standby units that are only used during super-hot summer days. Peaking units that are constantly cycled on and off are especially susceptible to accumulating varnish, which has become a huge headache for the industry.
Trade-offs
The move to API Group II base oils for turbine lubes has offered improved oxidative and thermal stability, but the downsides have been reduced solubility of additives and increased varnish formation.
Keeping varnish away while dealing with other mechanical and lube-related issues is especially important in the energy sector, as utility companies can be fined thousands of dollars an hour for outages. Taking a turbine offline for maintenance is also an expensive proposition. With a national average price of $38 per megawatt hour in 2017, per EIA data, one turbine could produce $228,000 to $760,000 worth of electricity a day.
Lube problems in turbines are not uncommon and account for 20 percent of all unplanned outages, according to additive maker Afton Chemical.
The lubes used in some turbine-powered systems are asked to pull double duty, as they also serve as the hydraulic fluid used in the units control systems. Other systems circulate the lube through the gearbox thats used to step down shaft speeds.
Original equipment manufacturers are squeezing design parameters to increase efficiency, which is making things harder for the lubes business. Operating temperatures are going up as reservoir volumes are coming down. Flow rates are increasing and dwell times in the reservoirs have become shorter, leaving less time for cooling and for air to leave the lubricant. These changes in design necessitate a constant push for better antioxidant performance from turbine oils.
Oxidation brings the challenge back to fighting varnish. Varnish is created when molecules of waste dissolved in hot lube settle into thin coats of contamination on metal surfaces as the lube cools. Varnish can be thwarted by using base stocks that resist oxidation, including antioxidant additives and ion exchange programs.
None of these varnish prevention methods are easy, inexpensive or foolproof, leaving some experts in the lube business wishing that turbine OEMs would go back to the drawing board.
Peter Dufresne, executive vice president of EPT based in Calgary, Alberta, told LubesnGreases, If we could start all over, I would design the mechanical systems differently. In a perfect world you would not combine lube oil and hydraulics into one common system. You would increase reservoir sizes, keep return lines below the oil surfaces and increase the surface area of filters. You would also eliminate stagnant oil lines and try to maintain more uniform temperatures throughout the mechanical system.
Whose Specs?
Because of the splintered international nature of the petroleum industry, turbine oil formulators are forced into an alphabet soup of specifications and standards that are required to gain access to various country or regional markets. In addition to the American Gear Manufacturers Association and the U.S. military, OEMs like Siemens and GE all have their own sets of specifications.
In order for new lubes to make it onto the approved list they have to be tested. Popular tests include the Rotating Pressurized Vessel Oxidation Test (RPVOT) and the Turbine Oxidation Stability Test (TOST), which has several variations. Theres also the Thermal Stability Test A, the Remaining Useful Life Evaluation Routine (RULER) and many others. The tests themselves raise issues as even the testers admit that what happens in the controlled environment of a lab may not translate to field operation.
According to a report that Barclays PLC released in May, Mitsubishi Hitachi Power Systems received more than half of all global orders for gas-fueled turbines in the first quarter of 2018, the companys best-ever performance in a market that has seen traditional gas turbine manufacturers struggle in recent months.
Mitsubishi attributes its recent success to the rollout of its new J-class turbine, which the firm says can produce electricity 30 percent cheaper than its F-class turbine technology from the 1980s.
The Barclays report also notes that Siemens AG had 26 percent of global orders in the first quarter of 2018, with General Electric, long the leader in worldwide turbine sales, seeing its share drop to 14 percent. GEs problems have been well documented with no bottom in sight as its stock price recently fell below $10 a share, which has not happened since 2009.
As renewable energy sources in the U.S. sip away at the natural gas- and steam-powered turbine business, overseas markets are still expanding. The London-based consulting firm Technavio says the Asia-Pacific region is still hot for turbines and is expected to become the largest revenue-contributing region in the market by 2020 and projected to occupy more than 49 percent of the overall market share. The firm attributes this demand to rising economic development in the region and the growing need to replace coal-fired plants.
Companies including Phillips 66 are responding to the need for more high-performance turbine oils for all kinds of equipment. In this Spotlight, the company describes its latest turbine oil product.
Next Generation Turbine Oils
Phillips 66 Lubricants, the third-largest finished lubricants supplier in the U.S., has developed the next generation of turbine oils.These turbine oils, which include the companys mainline turbine oil and best-in-class Diamond Class Turbine Oil, have been re-engineered with hydrocracked base oils and proprietary additives. These new fluids address the increasing performance demands on modern steam, gas and combined-cycle turbines, providinga proactive solution to oxidation and varnish/sludge control.
The Next Generation Diamond Class Turbine Oil has been tested and proven to be superior to other leading turbine oils currently on the market. Extensive in-house testing, including the use of the Mitsubishi Heavy Industries (MHI) Dry TOST test, was used to show that the Next Generation Diamond Class Turbine Oil dramatically outperformed competitors turbine oils in RPVOT retention (Rotary Pressure Vessel Oxidation Test) and sludge/varnish control.
Industry-wide issues with RPVOT retention and sludge/varnish control led Phillips 66 Lubricants to significantly upgrade their turbine oil product line. Many years of operating data collected from the companys power generation customers, along with expertise in turbine oil development, provided Phillips 66 Lubricants with the knowledge needed to formulate its new, improved turbine oils.
Phillips 66 Next Generation Turbine Oils set industry-leading standards including excellent oxidative life suited for steam and gas turbines, reduced varnish and sludge due to improved additive solvency, improved water separation, improved foam/entrained air release, excellent rust and corrosion inhibition, and effective lubrication of journal/thrust bearings.
Long, trouble-free turbine life depends onproperly maintained equipment andthe use of high-quality turbine oils capable of dealingwith water, particle contamination, heat, andcontinuous operations insteam turbines and cyclic operations with gas turbines.
For more information regarding Phillips 66 Next Generation Turbine Oils, or to learn how the expert technicians at Phillips 66 can support your ongoing operations, call the Phillips 66 Technical Services Hotline at 877-445-9198.