Lithium complex (LiCX) greases have been widely used in the wind power industry for years. They have become popular because of their properties suited to the unique requirements of bearing lubrication in wind turbines. LiCX greases provide strong mechanical stability and good water resistance; their soap structure behaves well under vibrations and release a sufficient amount of oil to protect bearings efficiently against wear and corrosion. This is why LiCX greases have been the prime choice of turbine-makers to ensure trouble-free operations.
By a twist of fate, renewable energy intermittency has encouraged new developments in energy storage capacities based on lithium-ion batteries. Alongside the upcoming demand for electric vehicles, it has put high pressure on lithium prices: the silvery metal’s contract price has jumped from $6,000 to $14,000 a ton, which was a record in 2017, according to Londonbased Benchmark Mineral Intelligence. This trend can negatively affect maintenance costs while companies in the wind sector strive to improve competitiveness.
Rethinking grease strategy and offering the wind industry a reputable lithium-free technology is Total’s response to the speculative road to ‘lithium Eldorado’.
Meeting manufacturers’ requirements
Selecting proper lubrication is essential to ensuring the highest reliability of rolling bearings. Since the early 1990s, Total has been researching calcium sulphonate complex grease technology as a means of delivering optimum performance in demanding bearing applications. The technology, called CERAN – a registered trademark – surpasses the marketleading LiCX greases used in wind energy.
Whatever the design – geared or direct drive – a wind turbine’s main shaft arrangement must withstand axial and radial loads and operate under harsh, continually changing conditions. Oscillations and vibrations occurring at low speeds have a considerable effect on the structure of the grease, which must remain stable and consistent in every circumstance.
Calcite particles contained in CERAN thickener can reach high extreme pressure levels without extra additives. With 4mg wear only, CERAN delivers stellar performance on tapered roller bearings subject to modified FE8 wear test – 500 hours at 7.5rpm/127kN/80°C. With a controlled oil release, the grease delivers excellent lubricating capability. The synthetic base oil combined with the latest calcium sulphonate complex technology makes CERAN appropriate for extreme cold and fluctuating temperatures while keeping a very high level of pumpability.
Giving a new dimension
CERAN has been used for more than 20 years on large bearings operating under heavy loads, low speed and contaminated process waters. In industries such as steel and paper, it has delivered unrivalled performance on massive spherical roller bearings, and has earned its reputation as a prime product among leading bearing manufacturers.
The inherent extreme pressure and anti-wear properties of CERAN soap stand out from lithium ones. The calcite particles that form the soap build a ‘wafer network’ structure on the bearing’s raceway while insulating shear planes on the metal surfaces. Under mechanical stress, the rolling elements will shear away the protective calcite layer more than the metal, dramatically reducing wear.
Additionally, its unique micelle structure entraps water while keeping performances at a high level. Even with 20% water admixed, the lubricating ability and consistency of the grease remain unchanged. CERAN has already proved effective in main shaft bearings of onshore wind turbines. The natural protection of CERAN thickener against salt corrosion also makes it the perfect grease for offshore giants.
A last piece of good news for wind farm operators and maintenance providers is that CERAN is compatible with the LiCX greases that are currently used in wind turbines, thereby facilitating product-switch in the field.
Innovation in the design of wind turbine components continues to be critical to achieving better performance and cost-efficiency. In a fast-changing energy landscape, CERAN grease technology is best suited to help the wind industry reach new levels of robustness and competitiveness. Its unique features have been making the difference in bearing applications for years.
