eJournals International Colloquium Tribology 23/1

International Colloquium Tribology
ict
expert verlag Tübingen
125
2022
231

Longer Lifetime of Wind Turbine Bearings and Gears Using Phyllosolicate-Additives

125
2022
Stefan Bill
REWITEC, as a part of Croda Int Plc, is a developer and manufacturer of an innovative particle-based surface treatment Phyllosilicate-technology for increasing the reliability and lifetime of wind turbine gears and bearings. The active particles are compatible to all common oils and greases and use lubricants as a carrier to build through their adsorption a protective and repairing phyllosilicate-based coating on the surface. The modified surface has a significantly lower surface roughness, which ensures a better load distribution, lower local pressure and lower tribological stress. Additionally, due to the special layered material structure the particles can be sheared in the tribological contact, which leads to a reduction in friction. All in all, when applying the products systems can run better with reduced friction, wear, surface roughness and temperature. These effects lead to great reliability and longer lifetime and reduce costs. In this presentation we would like to show our new scientific study about the lifetime calculation of a grease-lubricated wind turbine bearing (1.5 MW) with and without the technology application. The project is a cooperation between Croda and Sentient Science who performs lifetime calculations using digital clone method based on real friction coefficient and surface roughness data. The project includes data generation using MTM test bench, in a wind turbine bearing and subsequent simulation based on this data and bearing geometry. The simulation shows that with REWITEC the probability for a bearing failure significantly decreases which leads to a lifetime extension of up to 17.3 years.
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23rd International Colloquium Tribology - January 2022 133 Longer Lifetime of Wind Turbine Bearings and Gears Using Phyllosilicate-Additives Stefan Bill REWITEC GmbH, Lahnau, Germany stefan.bill@croda.com Abstract REWITEC, as a part of Croda Int Plc, is a developer and manufacturer of an innovative particle-based surface treatment Phyllosilicate-technology for increasing the reliability and lifetime of wind turbine gears and bearings. The active particles are compatible to all common oils and greases and use lubricants as a carrier to build through their adsorption a protective and repairing phyllosilicate-based coating on the surface. The modified surface has a significantly lower surface roughness, which ensures a better load distribution, lower local pressure and lower tribological stress. Additionally, due to the special layered material structure the particles can be sheared in the tribological contact, which leads to a reduction in friction. All in all, when applying the products systems can run better with reduced friction, wear, surface roughness and temperature. These effects lead to great reliability and longer lifetime and reduce costs. In this presentation we would like to show our new scientific study about the lifetime calculation of a grease-lubricated wind turbine bearing (1.5 MW) with and without the technology application. The project is a cooperation between Croda and Sentient Science who performs lifetime calculations using digital clone method based on real friction coefficient and surface roughness data. The project includes data generation using MTM test bench, in a wind turbine bearing and subsequent simulation based on this data and bearing geometry. The simulation shows that with REWITEC the probability for a bearing failure significantly decreases which leads to a lifetime extension of up to 17.3 years. 1. Introduction While wind power is enjoying significant growth, it is also important to understand its limitations. Multiple studies have confirmed that wind turbines suffer from reliability issues: The EU’s RELIAWIND study aimed to examine current reliability of large wind turbines. The study found that electrical systems accounted for the highest failure rate, but gearbox failures accounted for the highest amount of downtime (14 days) [1]. Another study, by the National Renewable Energy laboratory (NREL) also found that gearbox failures contributed the greatest amount of downtime of any single wind turbine component, while the majority of wind turbine gearbox failures (76.2%) are caused by bearings. Gears were the second leading cause of failures (17.3%) [2,3,4]. A later review by [5] also suggested that reliability of gearboxes has not improved over time and that drivetrain technology has not yet fully matured. Figure 1 displays the annual failure rate and downtime per failure by component. For offshore wind turbines, reliability is even more critical, with marine operations costing significantly more than onshore. Efforts have been made to remove the gearbox from offshore wind turbine designs completely, with Siemens Gamesa announcing in 2017 that all offshore wind turbines will be direct drive in the future [6]. The market leader, Vestas, however, has committed to offshore wind turbines with gearboxes, with one source suggesting up to a 10% increase in material costs for a direct drive vs wind turbine with gearbox [7]. A review by [8] revealed that gearbox failures for offshore wind turbines happens at about three times the onshore rate. Maintenance of wind turbines is essential to prevent and mitigate failures. However, ongoing operation and maintenance (O&M) is costly, representing around 25% of the total cost of the wind turbine over its lifetime [10]. 134 23rd International Colloquium Tribology - January 2022 Longer Lifetime of Wind Turbine Bearings and Gears Using Phyllosilicate-Additives 2. Friction reduction in bearings The following MTM test shows the friction performance in a common grease with and without PHYLLOSILI- CATE-ADDITIVE at different rolling/ sliding ratios. Following test parameters were used: load 70 N, temperature 23°C, velocity 700 mm/ s, time 172 s. The diagram shows that the friction coefficient can be significantly reduced for all bearing relevant (0 to 40%) rolling/ sliding combinations by up to a maximum 38 %. Figure 2: Coefficient of friction at different rolling/ sliding ratios in grease Mobil SHC 681 without (blue) and with (green) PHYLLOSILICATE-ADDITIVE. Figure 1: Annual failure rate and downtime per failure by component, adapted from [9]. 3. Conclusion PHYLLOSILICATE-ADDITIVE technology helps to significantly reduce or even prevent the damage, whereby an application is recommended for both new and already damaged systems. The technology is an innovative lubricant additive with a protective and repairing effect, which mainly consists of phyllosilicates in the form of micro and nanoparticles. The particles use lubricant as a carrier to reach the rubbing metal surfaces and to coat damaged areas them by adsorption. The new, modified surface is optimized and protected from a tribological point of view, so that surface roughness, friction, wear, and temperature in the system are reduced. This leads to a significant improvement in efficiency and lifespan. The tests confirmed the expected improvements in friction and wear with all common experimental methods. Beside the classical friction and wear reduction, PHYLLOSIL- ICATE-ADDITIVE technology can repair partly damaged surfaces, which increases the lifetime enormously. Overall, utilizing the PHYLLOSILICATE-ADDITIVE leads to higher efficiency, higher reliability, and longer lifetime. References [1] Final Publishable Summary of Results of Project ReliaWind, ReliaWind Project Nr 212966 [2] https: / / grd.nrel.gov/ #/ stats [3] Wind Turbine Drivetrain Condition Monitoring During GRC Phase 1 and Phase 2 Testing S. Sheng, H. Link, W. LaCava, J. van Dam, B. McNiff, P. Veers, and J. Keller [4] National Renewable Energy Laboratory S. Butterfield and F. Oyague Boulder Wind Power 23rd International Colloquium Tribology - January 2022 135 Longer Lifetime of Wind Turbine Bearings and Gears Using Phyllosilicate-Additives [5] Wind turbine reliability data review and impacts on levelized cost of energy Cuong Dao | Behzad Kazemtabrizi Christopher Crabtree [6] Wind turbine reliability: A comprehensive review towards effective condition monitoring development Estefania Artigaoa, Sergio Martín-Martíneza,b, Andrés Honrubia-Escribanoa,b, Emilio Gómez-Lázaroa,b,* [7] https: / / www.siemensgamesa.com/ en-int/ newsroom/ 2017/ 11/ sgre-launches-new-wind-power-solutions-new-geared-turbine [8] https: / / www.reuters.com/ article/ us-vestas-windresults-gearbox/ vestas-bets-on-geared-turbines-topropel-it-to-margin-goal-idUSKBN1FS2X0 [9] Wind turbine reliability data review and impacts on levelized cost of energy Cuong Dao | Behzad Kazemtabrizi Christopher Crabtree [10] Chizhik et al., Wear 426-427 (2019) 835-844