Maintenance-free BobTail used in wind turbines 29 August 2013

Lockbolts manufactured by Alcoa Fastening Systems (AFS) have been selected for use by German steel construction specialist Butzkies GmbH in the production of three new wind turbine towers.

At a height of 100m each the towers will be built using the maintenance-free Huck® BobTail system with the aim of providing durability, stability and a reduced lifetime cost in comparison to conventional threaded fasteners.

Mechanical anchoring and fastening elements are particularly exposed to extremely high vibration in wind power plants. The tension on the wind turbine tower increases significantly the taller it is, even to the point where gusts of wind could cause the entire structure to start swaying.

Picture, (l-r) Alexander Petri, key account sales manager, Alcoa Fastening Systems and Detlef Bengs, managing director of Butzkies Stahlbau GmbH

Detlef Bengs, managing director of Butzkies Stahlbau GmbH, explains: “No conventional threaded fastener is permanently resistant to extreme mechanical tension or vibration. Threaded fasteners loosen over time which can culminate in considerable problems with a wind turbine tower. To fully comply with the regulations for operational stability, the threaded fasteners must be repeatedly checked, re-tightened and, if required, replaced. This can cost the operator large sums of money over the years. From the start, we wanted to avoid this problem with our tower construction. This is why we took a deliberate decision not to use conventional threaded fasteners and alternatively to build our test plant by fitting the Huck BobTail Lockbolts from Alcoa Fastening Systems.”

To ensure the idea was subject to the appropriate rigorous tests, Butzkies GmbH constructed a special 61.5m tower, which was fitted with a total of 4,360 Huck BobTail Lockbolts. Alcoa says its Huck BobTail fastener can be installed approximately 75% faster than comparable conventional threaded fasteners and as a result reduced the prototype’s construction time by approximately 14 hours. In addition, the clamp force of the Huck BobTail system is very high, predictable and extremely reliable.

This added value eliminates time-consuming and high-cost maintenance work, currently 15,000 euros per annum for a large wind turbine tower at 130 metres high.

Claire Aldridge Deputy Editor t: +44 (0) 1727 743 889

Having spent a decade in the fastener industry experiencing every facet – from steel mills, fastener manufacturers, wholesalers, distributors, as well as machinery builders and plating + coating companies, Claire has developed an in-depth knowledge of all things fasteners.

Alongside visiting numerous companies, exhibitions and conferences around the world, Claire has also interviewed high profile figures – focusing on key topics impacting the sector and making sure readers stay up to date with the latest developments within the industry.