The next Seaway 7 vessel for offshore wind installation.

Redefines heavy lifting

OHT sets new benchmark in heavy offshore transport and installation. The vessel has the ability to perform heavy lift crane operations with the main deck submerged.
17 July 2018
  • The vessel’s capabilities match the future requirements of the offshore wind industry.

Norway based Offshore Heavy Transport (OHT) is set to enter the offshore renewables and installation market with a unique new heavy lift transport and installation vessel, a customised ULSTEIN Alfa Lift design developed by Dutch design company Ulstein Design & Solutions BV (UDSBV) in close cooperation with OHT. The first vessel (with options for up to another 3 units) will be constructed by China Merchant Heavy Industry (CMHI) and available for construction and installation activities from early 2021/2022.

What makes this dynamically-positioned, 48,000 DWT vessel exceptional, is the ability to perform heavy lift crane operations with the main deck submerged. The patent-pending design combines the benefits of a semi-submersible transport vessel with a large, 3,000 mt lifting capacity main crane from Liebherr.

The vessel's capabilities match the future requirements of the offshore wind industry, allowing her to transport and install upto 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.

'We started the development of the ULSTEIN Alfa Lift idea back in 2015 with the driver to increase the safety of submerged operations and at the same time increasing the operability window for subsea installations using a crane,' says Edwin van Leeuwen, managing director at Ulstein Design & Solutions BV.

'It is great to work with such capable people. When we approached Ulstein with our intended strategy to enter the offshore renewables market and the idea of adding crane capacity to a semi-submersible heavy lift transport vessel, UDSBV presented their Alfa Lift solution on the spot', mentions Torgeir E. Ramstad, CEO at OHT. 'That was a direct 'hit', as it allows us to enter the installation market, at the same time expanding on our capabilities in OHT's core market.'

'It is an honour that OHT trusted us to design their first offshore vessel, which we feel is a recognition of our ability to create new, cost effective vessel solutions', continues Van Leeuwen. 'Creating a new design with this combination of functionalities has its own, specific challenges, but it is rewarding our mutual NDA, OHT has contracted a shipyard to build this new vessel type.'

Main dimensions of the vessel are:

Loa 216.3 m

Lpp 204.3 m

Beam (moulded) 56.0 m

Depth (main deck) 12.6 m

Draught (design) 8.0 m

Draught (submerged max.) 27.6 m

Service speed 13 kn

Propulsion thrusters 3 x 5,500 kW

Retractable thruster 1 x 3,000 kW

Tunnel thrusters (fwd) 3 x 3,000 kW

Positioning system DP 2

Class DNV

Deck strength 30 t/m2

Complement 100 persons

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Ulstein Design & Solutions B.V.