INDUSTRY FOCUS RENEWABLE ENERGY
OPTIMISING BEARING DESIGN
Wind turbines must operate reliably in a diverse range of environmental conditions - both
onshore and offshore. By optimising the bearing design, lubrication and sealing for wind turbine rotors, blades and tower, reliability and operating life are maximised. Dr Steve Lacey, engineering manager at Schaeffler UK explains more
R
otor, blade and tower bearings are fundamental components of a wind
turbine. The functional reliability of these bearings is critical to the long term, efficient and defect-free operation of the wind turbine installation. The varied and often extreme loads
on a wind turbine require a carefully matched combination of bearing design, lubrication and bearing sealing. This means that a packaged solution for each bearing position is required, which is optimally matched to the specific application.
ALL CONDITIONS Wind turbines are now installed in locations with a wide variety of climatic conditions - both onshore and offshore. The operating temperatures expected of a wind turbine can range from -30°C in Arctic regions to 60°C in sub-tropical climates. Depending on the location, the
installation is exposed to varying levels of ozone, UV light, sand, dust and salt water. In order to ensure maximum availability of a wind turbine, robust, durable bearings are required. This can be achieved, for example, by using seals that protect the system from different weather conditions.
SYSTEM KNOW-HOW The Wind Energy Business Unit at Schaeffler offers a combination of rolling bearing know-how with systems knowledge of wind turbines built up over more than 30 years as both a supplier and development partner.
8 NOVEMBER 2014 | AUTOMATION With assistance from a network of
high performance seal suppliers, bearing seals are now being developed that represent the optimum combination in terms of functional performance, service life and cost. Application development engineers at Schaeffler ensure that the specific details of each customer installation are considered. For example, the change in the seal gap of the rotor bearing arrangement in a 3MW installation can be calculated using design calculation software. In addition to other parameters, the gap dimensions determined for various load cases form the basis of calculating the optimum design of a bearing seal.
ROTOR BEARINGS Rotary shaft seals are the preferred choice for sealing the rotor bearing. The integrated, corrosion resistant steel spring in the sealing element ensures effective sealing over a long operating period. An additional dust lip can be added to provide even greater protection from ambient media. Under the operating conditions, elastomer materials such as HNBR offer outstanding resistance to ozone, debris and ageing. The flexible, fabric reinforced outer part of the rotary shaft seal enables easy mounting and dismounting. The sealing rings can be replaced easily by simply cutting and bonding into place using a special adhesive set during on- site mounting. Moulded, single piece rotary shaft seals can now be produced with shaft diameters up to 3,000mm.
Above: Schaeffler recently introduced a Wind Power Standard (WPOS) for its bearings for wind
power applications
BLADE AND TOWER BEARINGS For blade and tower bearings, double lip type profiled seals are most effective. The inner seal lip retains the lubricant within the bearing, while the outer seal lip prevents the ingress of ambient media. Compared to the rotor bearing design,
seals for blade and tower bearings undergo lower sliding speeds and so are subjected to only minimal thermal strain. In this case, NBR elastomer fulfils the requirements with respect to ozone, debris and ageing resistance over long operating periods. A method for vulcanising the end faces of profiled strands enables the economical production of sealing rings of any diameter required. Advantages of the optimised bearing
seal include extended bearing life, reduced maintenance work, reduced grease leakage and easy replacement.
QUALITY Schaeffler recently introduced a Wind Power Standard (WPOS) for its bearings for wind power applications to ensure the quality and reliability of its bearings. Even during the development process, the requirements for material approval ensure that all components such as greases and seal materials are compatible with one another, the required performance characteristics are reliably achieved and the guidelines relating to prohibited substances are observed.
Schaeffler
www.schaeffler.com T: 0121 313 5870
Enter 201 /AUTOMATION
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