A lack of grid capacity, strong fluctuations in grid voltage, constantly changing wind conditions, spinning operation and the intermittent operation of components: Wind turbines are extremely susceptible to faults. High gearbox wear combined with frequent gearbox changes are the result. 1 - 2 gearbox replacements per year are not uncommon for wind turbines. The negative consequences of this are machine downtime, a poorer energy balance, high maintenance costs and an extended energy-related service life. Preventive measures against premature gearbox wear therefore definitely pay off.
The main causes of gearbox failures in wind turbines are damage caused by friction, such as grey spotting, roughness and pitting (link to corresponding blog article). As soon as it is possible to reduce the frictional forces and the associated wear, the number of gearbox replacements required also decreases significantly. An extremely effective approach against wear damage is offered by so-called surface passivation through enrichment with silicon atoms, which form a smooth and wear-resistant metal-ceramic layer during the friction process. The significantly smoother surfaces drastically reduce friction and wear, and the wind turbine gearbox runs much more efficiently and with less vibration. At first glance, this sounds like a rather complex protective measure, but at second glance it is quite simple thanks to the use of an innovative oil additive. The oil additive DuraGear® W100 (link on landing page), which was specially developed for wind turbines, is added to the lubricant of the wind turbine gearbox during operation and uses it to transport the active ingredient to damaged areas - without affecting the lubricant itself in any way.
Windkraft Simonsberg, one of Austria's largest wind power producers, made a conscious decision to increase the performance and maintenance of its wind turbine gearboxes by using DuraGear® W100 and contacted the Lahnau-based manufacturer REWITEC®. The primary objectives of the application were to improve the condition of the gearbox and extend its service life. The tooth flank load-bearing capacity was also to be optimised and the previous damage condition frozen. During an on-site visit to the Vestas V80 wind turbine in Steinberg-Prinzendorf, the wind turbine gearbox was inspected by REWITEC® engineers prior to the DuraGear® W100 application. Running marks were found on the tooth flanks and so-called run-through, as well as rust-like discolouration in the base area. The surfaces were rough, and an electrical resistance measurement revealed a value of up to 20 ohms. For a before/after comparison, high-precision surface impressions (resolution accuracy 0.1μm) were taken from a previously marked tooth flank and then analysed microscopically. The Hansen gearbox of the wind turbine was then treated with the tribological coating concentrate DuraGear® W100. The results after seven months of running with DuraGear® W100 were remarkable. A detailed examination of the gearbox revealed a slight reduction in rust-like deposits and a reduction in surface running marks, so that the surfaces felt much smoother. The electrical resistance had increased to up to 200 ohms. Analyses using a laser scanning microscope (type "Keyence VK8700") showed an improvement in the roughness values from Rz 8.899 to Rz 7.036μm and Ra 0.595 to Ra 0.411μm. The bearing surface had increased from 46.402% to 58.702%. CMS analyses showed that the trend of the measured vibrations had decreased significantly after the application.
Marxen Bauträger has been using DuraGear® W100 since mid-2010 and regularly treats the gearboxes of all 25 wind turbines with the innovative oil additive. Since then, no further gearbox failures have been reported. Before the application, an average of 1-2 gearbox replacements were recorded annually. The savings over 5 years for 25 wind turbines amount to an impressive €562,500.
Turbulent regions with high wind speeds generally deliver the best wind harvest. However, the frequently changing wind conditions and often very unstable network structures have a rather unfavourable effect on the maintenance of the gearboxes. Due to the intermittent drive of the mechanical components, the tribological wear is significantly higher than in regions with more stable wind conditions. Many wind farm operators therefore deliberately forego a higher wind harvest in favour of a better grid connection and more constant wind conditions. Surface passivation with DuraGear® W100 reduces the mechanical "stress" acting on the gearbox, even under unfavourable conditions, so that wind turbine operators will be able to operate wind turbines in high-wind regions in the future without an increased risk of repair and failure.
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