Maintenance-free BobTail® fastening system selected for use in German wind turbine construction
Following a successful test project, Huck LockBolts manufactured by Alcoa Fastening Systems (AFS) have been selected for use by renowned German steel construction specialist Butzkies GmbH in the production of three new wind turbine towers.
At a height of 100m, each of the towers will be built using the maintenance-free Huck® BobTail system with the aim of providing durability and 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. 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."
As part of the tower monitoring pilot test, set up as a collaborative research project with the Rostock Applications Centre for Large Structures in Production Engineering of the Fraunhofer-Gesellschaft and the Business Development and Technology Transfer Corporation of Schleswig-Holstein (WTSH), it quickly emerged that using the BobTail Lockbolts offered key advantages.
To ensure the idea was subject to the appropriate rigorous tests, Butzkies GmbH constructed a special 61.5 metre tower. The entire structure was fitted with a total of 4,360 Huck BobTail Lockbolts. The initial advantages of the system emerged during construction of the tower, which was erected on site in record time. The Huck BobTail fastener can be installed about 75 per cent 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.
"We are delighted that our Lockbolts from the Huck BobTail series are now also used for construction of wind farms," comments Alexander Petri, key account sales manager at AFS. "Our solution enables us to offer a convincing alternative to an important industry of the future. The operators of wind farms are assured the necessary safety over the longer term and reliable operation of their power plants, while we can simultaneously contribute to significant cost savings."
BobTail Video: AFS Industrial YouTube Channel
Contact AFS: 00 44 1952 290011
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