Dutch offshore construction specialist Heerema has completed its first turbine installation project, using the dynamically positioned heavy lift vessel Aegir, which it recently converted for this kind of role, to test an innovative way to install units without bolts or grouting.
In April 2018, following a review and commercial evaluation of the market, Heerema Marine Contractors confirmed that it planned to discontinue its offshore pipelay activity as part of a ‘realignment of the company’ relating to unfavourable market conditions and the low level of investment in the offshore oil and gas industry.
Following termination of its pipelay activities the company said it would focus entirely on its core businesses of heavy lift, decommissioning and renewables and convert Aegir, a deepwater construction vessel, to a heavy-lift vessel.
That decision having been taken, Heerema’s successful installation of its first offshore wind turbine on 30 September 2018 is an important milestone as it targets more work in the renewables market.
The project saw Aegir install the Delft Offshore Turbine (DOT) wind turbine on a previously-installed monopile using a slip joint connection. Heerema is a stakeholder of the Slip Joint Offshore Research consortium initiated by DOT BV in late 2016, a consortium that also includes TU Delft, TNO, Van Oord and Sif group, along with Eneco.
The consortium aims to reduce the cost of offshore wind using technology such as slip joints – which eliminate the need for bolts or grouting – and by focusing on transporting and installing wind turbine foundations and turbines.
The DOT wind turbine was installed on Eneco’s Princess Amalia offshore windfarm off the coast of IJmuiden, the Netherlands. The turbine was picked up in a single lift by Aegir, direct from the quayside at Sif Rotterdam and transported to the windfarm.
The fully assembled turbine was installed by the vessel in dynamic positioning mode. Installation was completed in less than an hour, which is significantly quicker than installation using conventional techniques.
A slip joint connection uses friction and the weight of the component being installed to ensure a firm, stable connection. Installation is undertaken by sliding the wind turbine over a monopile, a technique that the consortium said reduces costs by using less material, equipment and personnel and by speeding up the installation process. This was the first time a slip joint connection has been used offshore.
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