C1 Wedge Connections

As Turbines Get Bigger, Leading Offshore Wind Players Gather Around Alternative to Bolted L-Flange Connections

A consortium comprising some of the world’s leading offshore wind developers and Tier 1 suppliers have initiated a joint industry project that aims to commercialise a new foundation connection technology developed by the Netherlands-based company C1 Connections.

“With the increasing size of wind turbines, the traditional L-flange design has reached a point where in cases it cannot provide the required capacity anymore. The C1 Wedge Connection™ has been developed to overcome this issue,” C1 Connections states in a press release issued on 3 July.

The Wedge Connection joint industry project (JIP) gathers BP, TotalEnergies, RWE, Vattenfall, EnBW, Iberdrola, Ocean Winds, Ørsted, Equinor, Siemens Gamesa Renewable Energy, Vestas, GE Vernova and C1 Connections.

Within the project, the consortium will focus on bringing the C1 Wedge Connection solution to commercial scale implementation in offshore wind projects for both monopile-to-transition piece and foundation-to-tower connections.

“The goal of this JIP is to create a new standard for offshore wind connections. The feedback from all participating companies is that an alternative solution to the traditional bolted L-flange is highly needed to allow this industry to scale up further,” said Coen van Ruitenburg, Business Development Manager at C1 Connections.

The technology was already tested offshore. In 2022, Heerema Marine Contractors and C1 Connections performed an installation of a tower on board the vessel Thialf as part of the preparations for the offshore wind turbine installation at Arcadis Ost in Germany.

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According to Heerema, the C1 Wedge Connection enabled a safe disconnection of the tower from a grillage on a barge, with the alignment and quick connection of the tower performed without any personnel below the suspended load.

The solution features pre-installed fasteners and only lightweight tools were needed to finalise the connection, Heerema noted in 2022.

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The Dutch foundation connection technology developer says that the C1 Wedge Connection can deliver a significantly higher ultimate resistance and fatigue resistance than conventional bolted flange connections and is also expected to allow both faster and safer installation of connections offshore.

The now-initiated project will provide the participants with insight into the full production supply chain from flange manufacturing to the welding the flanges to can sections. The JIP will also provide knowledge and first hand experience on all installation aspects, including installation speed, pile driving and sealing of the C1 Wedge Connection.

Image source: C1 Connections

In the JIP, full-scale flanges will be manufactured by GRI and Shandong Iraeta and welded to can sections by EEW.

The development of the C1 Wedge Connection started in early 2017 in close collaboration with Delft University of Technology (TU Delft). The technology also received support from the Netherlands Enterprise Agency (RVO).

In 2021, the technology was introduced in the first 14 MW wind turbine, at that time the largest wind turbine in the world, installed in northern Denmark, according to information on C1 Connections’ website. While the Dutch company does not specify the turbine model and its manufacturer, the 14 MW model installed in the North Denmark Region at that time was Siemens Gamesa’s SG 14-222 DD prototype at the test centre in Østerild.

Last year, C1 Connections’ technology also received an A-level component certificate from DNV. Since then, several more connections have been installed, according to the company.


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