The reliability and service life are top priorities for turbine manufacturers. This is especially true for main shaft seals, which are exposed to high forces. In addition, larger shaft diameters have driven the adoption of new, more stringent operating requirements. Freudenberg Sealing Technologies has been successful in the development of a new seal to prevent leakage from the main bearings lubricated with grease, which are used in conjunction with these shafts and at the same time tolerate strong shaft misalignment.
The new sealing solution for wind turbines
Manufacturers continue to increase the size of wind turbines in an effort to generate an ever-increasing supply of clean energy. Larger turbines generate lower material and construction costs than installing multiple smaller turbines. Rotors with a diameter of 180 meters are no longer uncommon. But systems of this size produce enormous forces during operation that impact the main shaft roller bearings and seals, so that require new designs of seals that have been adapted to these conditions. Freudenberg Sealing Technologies has now successfully developed a seal for grease-lubricated bearings on large diameter shafts. The product can be used for the internal and external radial sealing and can even tolerate strong shaft misalignment.
Traditional seals, which produce pretensioning forces on the lip edge by using a helical spring, reach the limits of their capacity when they have to be designed for large diameters. In addition, solutions that provide external radial sealing are difficult or even impossible to implement with this design. The Freudenberg Sealing Technologies“ new shaft seal ”Seventomatic" is designed for shaft diameters starting at 1.5 meters.. It uses a leaf spring to apply the necessary pretensioning forces. The product gets its name from figure “7”: a long sealing leg that is attached to the stationary part of the seal by a flexible joint.
The Seventomatic seal produces constant linear forces and is less susceptible to shaft misalignment than other shaft sealing solutions. In its standard size, the seal tolerates a deflection of ± 4 mm without any decrease in performance. As a result, supports the manufacturing tolerances of the shaft very well. It is made of hydrogenated nitrile butadiene rubber, a material from the Ventoguard family of wind energy solutions.
The basic form of Seventomatic is based on the well-proven Freudenberg Sealing Technologies seals for tunnel boring machines. The aim was to combine the special design of a seal for tunnel boring machines with the advantages of a classic radial shaft seal for the main rotor shaft.
Extensive testing has shown that its elasticity, wear resistance, ability to absorb misalignment and even its superior temperature resistance make it a option to be strongly considered for large diameter rotary sealing solutions (>1500 mm), The company's products are used not only for wind turbines, but also for wind turbine applications in general industry, metallurgy, energy production, etc.
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