Seal addresses lubrication needs of wind turbine bearings

The wind industry has evolved into a sophisticated, viable resource. With an additional 54 GW (gigawatts) of wind power added in 2016, nearly 500 GW of installed power worldwide and a projected annual growth rate of 11% in coming years, wind plant operators are becoming a leading source of clean, renewable energy for countries throughout the world.

With this growth comes an increase in size and performance demands of wind turbines and related components. Rotors with 180-meter diameters are no longer a rarity. Recently a Danish manufacturer upgraded its largest 8 MW turbine to 9.5 MW. Thus, the industry is constantly entering new territory at the level of components with increasing dimensions and loads.

Real size test stands can ensure reliable data and reduce the time required for certification and validation. There are only a few of them so far, so most testing still takes place directly in the gondola of the turbine.

The change to larger diameters is creating a challenge to bearing lubrication. The challenge is caused when the consistency of grease changes during the operation of large bearings. When this grease gets pasty, firmer areas slide below the sealing lip causing the lip to float and the irreversible process of leakage begins. To prevent this, the sealing lip must be pre-tensioned in a defined manner. Paradoxically, even the strongest of the used ring springs typically no longer help. The radial force component of such springs, which is required for the pre-stressing, goes towards zero as the diameter grows.

The Merkel Seventomatic seal addresses these concerns. It combines the special design of a seal for tunnel boring machines with the advantages of a classic radial shaft seal. Time-intensive tests can be eliminated through the use of innovative tools, robust design and the company’s own validation methods.

The seal allows variant sealing towards the outside, enabling new design options for windpower applications.

As the ever-increasing requirements of the windpower industry continue to evolve, Freudenberg recognizes the importance of optimally sealing grease-lubricated large bearings. Leak-free performance through a uniform pressure force of the sealing lip, with the help of a vulcanized-in meander spring (and the simple cutting and joining of the new seal on site in the event of maintenance), meet the wind industry’s needs for reliability and planning security.

Freudenberg Sealing Technologies

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