Innovative Wind Lattice Towers with Maintenance-Free Fastening System
Safe: Lockbolts from Alcoa Fastening Systems guarantee long-term stability at low cost
Maintenance-free: Huck® BobTail® fastening system – reliable and durable high vibration resistance
The innovative Lockbolts from the global manufacturer of fastening systems, Alcoa Fastening Systems (AFS), are now also used in the construction of lattice towers for wind farms, offering durability and stability at a reduced “joint” lifetime cost in comparison to conventional threaded fasteners. The fastening systems from the Huck BobTail range, which are certified as “maintenance-free”, were selected by Butzkies GmbH for a special wind lattice tower. Based on the convincing results of a pilot project, the renowned steel construction specialist will use the Huck BobTail Lockbolts for the series production of its innovative wind lattice towers.
In an initial phase, three towers (each at hub height of 100 m) will be built using the Huck BobTail system.
In wind power plants, mechanical anchoring and fastening elements are particularly exposed to extremely high vibration. The tension on the wind lattice tower increases significantly at higher hub heights, even up to the level that wind gusts could cause the entire structure to start swaying. Detlef Bengs, Managing Director of Butzkies Stahlbau GmbH explains this as follows:
“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 lattice 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 a ‘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.
Pilot plant successfully tested
To ensure their idea was put through rigorous tests, Butzkies GmbH constructed a special wind lattice tower at a hub height of 61.5 metres. The entire structure was fitted with a total of 4,360 Huck BobTail Lockbolts. The initial advantages of this innovative system already clearly emerged upon construction of the tower: the Butzkies tower was erected on site in record time because the Huck BobTail fastener can be installed about 75 per cent faster than comparable conventional threaded fasteners. This saved approximately 14 hours just in the special case of the prototype. Additionally, the clamp force of the Huck BobTail system is very high, predictable and extremely reliable.
But the decisive added value is eliminating time-consuming and high-cost maintenance work that can mean annual costs of about 15,000 Euros for a large wind lattice tower at 130 metres hub height. This is the reason that the Huck BobTail system – an unrivalled solution worldwide – is completely maintenance-free. The Deutsches Institut für Bautechnik, DIBt also confirmed this special attribute by issuing the ‘National technical approval’ (Number Z-14.4-591). By contrast, regular maintenance work is mandatory for standard conventional threaded fasteners on tower structures.
“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 Alcoa. “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.”
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