High-performance Seals for Wind Power Facilities
Press release -Increasingly large facilities and ever more extreme locations are placing greater demands on seals in wind turbines. They must not only withstand severe fluctuations in temperatures but above all must be resistant to the lubricants used in their drive units. Freudenberg Sealing Technologies has developed the “Ventoguard” material family to reliably seal the bearings of wind power plants. The seals manufactured from this material stand out for their special longevity. Especially in high seas, expensive maintenance work should be kept to a minimum during the 20-year lifespan that these facilities require.
As wind power continues to expand, the demands on facilities and components are rising. While most wind turbines were previously designed for an output up to 2 megawatts, they now produce a rated output of up to 6 megawatts in large offshore wind parks. This increase in performance can only be achieved with larger rotors. In most cases, the dimensions of the main bearing increase along with the rotor diameter. For generators directly driven by the rotor, the main bearings now reach a diameter of up to 4 meters. That poses disadvantages for maintenance, however. For example, it can take several days to replace a main bearing seal due to its sheer dimensions and the difficult access to gondolas at height of more than 100 meters. That is why seal durability has moved to the center of operators’ concerns. The designed lifetime of a seal for a main bearing must correspond to the facility’s service life, which is at least 20 years.
That is why Freudenberg Sealing Technologies has developed seals for the main bearings of wind turbines that meet extremely stringent requirements. Depending on the location and the time of year, temperatures in the gondola can vary greatly; they fluctuate between -40°C and more than 40°C. In the area of the sealing point, the seal lip must even withstand far higher temperatures. The grease and additives used to lubricate the drive unit are still more stresses that can damage the material. The seals developed by Freudenberg Sealing Technologies for wind turbines belong to the “Ventoguard” family, which encompasses various solutions for a wide range of applications. The seals are made of nitrile butadiene rubber (NBR), a high-performance synthetic rubber. It not only exhibits especially high resistance to grease, oils and hydrocarbons but is also insensitive to temperature fluctuations. It exhibits a favorable aging behavior and low abrasive wear. For one thing, these qualities make it possible for the main bearing seals to permanently keep lubricants from leaking from the bearing. For another, they ensure that dirt particles, sand and water condensation do not penetrate the bearing from the exterior and damage it. The world market leader in sealing technology benefits from decades of experience with large sealing systems, for example, for the sealing of drive gondolas in ships.
Since the requirements vary greatly depending on the location and the facility, Freudenberg Sealing Technologies has developed a computer program for experts that harmonizes the precise material qualities, the seal geometry and the lubricant to the manufacturer’s particular facility concept. The material developers at our Hamburg facility can turn to various mixtures within the Ventoguard material family to achieve the optimal resistance to aging and media as well as a high level of wear resistance. The material can also be selected based on the desired temperature and relaxation behavior. Moreover, the option of coordinating the sealing material with lubricants from Klüber, which has been part of the Freudenberg Group since 1966, is a special advantage – making it possible for the main bearing in wind turbines can fulfill its task over an entire lifetime.
