WINNING WITH WASHERS

The creation of an innovative wedge-locking washer kit is eliminating costly repair issues in the maintenance of wind turbine towers

Wind turbine towers, while built to be extremely strong and sturdy, are also designed to flex and bend in order to help dissipate the significant forces exerted upon them during operation. This flexing and bending, however, had been causing a major North American power company dangerous and expensive­to­repair failures in the bolts that hold up the Yaw and Saddle decks inside its towers. Naturally, this was a major problem for the company which has some 6,000 towers of this design. On a wider scale, it is estimated there are up to 35,000 wind turbine towers of this type across the whole of North America. The wind turbine OEM attempted several in­house fixes, such as putting stronger bolts in the L­angle deck brackets. This was a complex and costly endeavour, involving maintenance crews working over shutdowns of more than 24 hours at a time, and still didn’t solve the problem.

After several years of struggling with this issue, one of the company’s engineers concluded that its was not the bolts that were the problem, but the bracket. After recognising that the answer most likely lay in the form of an articulating joint, he scanned the market for the right parts, but no suitable off­theshelf hardware was readily available. This led him to approach his local Fastenal store to search for possible equipment that could replace the OEM bracket.

Designing the fix

After discussions between the engineer and Fastenal’s technical experts, the partners came up with a simple solution based on an articulating joint secured with wedge­locking washers from bolting solutions manufacturer Nord­Lock. The new bracket design was assembled and installed on two of the company’s wind towers to test their effectiveness.

Nord­Lock’s original wedge­locking technology secures bolted joints, even when exposed to severe vibration and dynamic loads. Due to the wedge created underneath the bolt head and nut, it is impossible for products to loosen unintentionally under stress.

The washers were essential to the success of the design, preventing the bolts in the articulating joints from coming loose and holding the decks securely in place during operation – something that previous fixes had failed to do. The design allows the decks to move slightly in multiple directions when the tower deforms under wind forces.

The Deck Bracket Replacement Kit

After studying the condition of twenty of these test brackets installed for over a year in the Yaw and Saddle decks of the power company’s operating wind turbines, the partners confirmed no signs of wear. The positive results of these tests prompted the partners to create a simple Deck Bracket Replacement Kit for wind turbine towers of this design.

Developed to be available for shipment to wind turbine sites for replacement work, the kit consists of five articulating joints and the associated bolts, as well as the Nord­lock wedge­locking washers. Besides offering a permanent solution to the repair and maintenance issue, the articulating joint is also much faster to install than previous solutions, taking between three and four hours.

The kit also provides wind tower OEMs with the additional benefits of revenue generation, improved safety of personnel, reduced maintenance costs and financial payback over the long run.

www.nord-lock.com