Subsea 7's New Semi-Submersible Vessel Equipped for XXL Offshore Wind Foundations En Route to Europe

Credit: Subsea 7
Credit: Subsea 7

Subsea 7's recently delivered Seaway Alfa Lift offshore wind foundation installation vessel is in transit to Europe and is expected to join Subsea 7's fleet in the third quarter of 2023.

The semi-submersible heavy installation vessel, designed by Ulstein, will be used to install the next-generation XXL offshore wind foundations.

The newbuild heavy lift crane vessel Seaway Alfa Lift (CMHI-207), was originally ordered in 2018 by OHT on speculation. OHT eventually became part of Subsea 7's Seaway 7 branch.

The vessel itself was floated out from drydock at the China Merchants Heavy Industry (CMHI) shipyard in Jiangsu, China in February 2021, and had been scheduled for delivery during the same year, and for debut in the UK offshore wind sector in 2022, installing wind turbine foundations at the Dogger Bank wind farm.

However, an October 2021 crane incident delayed the delivery, and Subsea 7 then said that the Seaway Strashnov vessel would be deployed on what was supposed to be Alfa Lift's project for a full 2023 campaign.

The vessel earlier this month left China following its delivery from China Merchants Heavy Industry (CMHI).

According to information shared by Ulstein, the mission equipment for monopile handling remains the critical path to the vessel being operational for foundation monopile installation. Credit: OHT (File image)

"The main elements of this equipment commenced transport from China at the end of 2022. Seaway Alfa Lift will head to Europe, where the mission equipment will be completed and commissioned," Ulstein said.

The semi-submersible vessel features a large, 3,000 mt lifting capacity main crane, and can perform heavy lift crane operations with the main deck submerged.

The vessel will be able to transport and install up to 10 x 1,500t ultra-large jacket foundations or 11 x 2,000t XXL monopiles plus transition pieces for the largest anticipated wind turbine generators.

The vessel’s crane has a maximum lifting capacity of 3,000 tonnes at 30 meters and 1,000 tonnes at 76 meters outreach. The 216.3-meter vessel will also have a 10,000+ m² “smart deck” that can carry up to 14 giant monopiles per trip and will be fully submersible to a depth of 14.66 meters.

In a statement on Wednesday, Subsea 7 said: "Seaway Alfa Lift is currently in transit to Europe and will join the fleet in Q3 2023. 

AIS data from VesselFinder shows that the vessel had made a port call in Sri Lanka, and departed on July 22. Its next stop is Port of As Suways / Suez Port in Egypt, where it is expected to arrive on August 7

Subsea 7 also shared what the Seaway's Alfa Lift would be, once it reaches the Dogger Bank site: "The vessel is planned to be deployed on transition piece installation on Dogger Bank A & B and C from 2023 to 2025, while monopile installation will continue throughout the period with Seaway Strashnov. 

"This revised plan is being developed with our client and, although subject to final approvals, provides confidence in our financial estimates for the project. The construction of Seaway Ventus, a heavy-duty jack-up suitable for turbine and monopile installation, remains on track.

Dogger Bank

The Dogger Bank offshore wind farm in the UK is being developed in three phases by Equinor, SSE and Vårgrønn, and will, once fully developed be the world's largest offshore wind farm with a capacity of 3.6GW.

Equinor said Wednesday that the first turbine components were being loaded for installation at Dogger Bank project, with first power expected during summer. Full commercial production for Dogger Bank A is expected in the third quarter of 2024, and the whole project is expected to be completed in 2026.

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