A NEW TITAN FOR OFFSHORE WIND SECTOR

Incorporating diesel-electric power and propulsion and specified to DP2 dynamic positioning standard, the vessel is of semi-submersible type, equipped with a 3,000t-capacity, foldable crane, geared principally to handling next-generation substructures, and also topside and subsea modules.

According to Norwegian contractual owner Offshore Heavy Transport (OHT), payload capabilities include up to 14 ultra-large monopiles, or 12 jackets, per voyage. At the offshore location, it will be possible to submerge the main deck to a depth of nearly 15m.

Float-out of the newbuild was effected on February 28 at the Jiangsu premises of China Merchants Heavy Industry(CMHI), where the production schedule calls for completion by early 2022 in readiness for the ship’s assignment to the Dogger Bank Wind Farm development in the North Sea. Key elements of the HLC 15000-type main crane have been manufactured by Liebherr at its Rostock plant in Germany. The slewing column and A-frame were shipped this month, to be followed by the boom.

The vessel design is the outcome of cooperation between the owner and Norwegian company Ulstein Design & Solutions, with input from Liebherr and DNV.

Over 10,500m² of cargo deck area is provided by way of the main deck(8,100m²) and raised forecastle deck(2,470m²), which also mounts the crane, bridge and accommodation for up to 100 personnel.

The main, submersible deck will be fully mechanised, equipped with skidding tracks for moving foundations during load-out and installation. Monopile lifting, skidding and transfer will be undertaken using an up-ending tool and motion-compensated gripper frame. The integrated pile gripper allows offshore placement of monopoles in DP2 mode, in keeping with the newbuild project emphasis on speeding the whole process of offshore windfarm construction. The arrangements are the product of technical collaboration between MacGregor and Kongsberg Maritime.

The power plant of the Alfa Lift is based on four principal gensets, each driven by a 12-cylinder V32/44CR medium-speed diesel from MAN Energy Solutions, individually rated at 7,200kW, for a total maximum output of 28,800kW.

The extensive Kongsberg outfit embraces the three 5,500kW propulsion thrusters, single 3,000kW retractable thruster and three 3,000kW bow tunnel thrusters, besides K-Pos dual-redundant DP system, K-Chief automation and K-Power products related to the main switchboard, generators and drives.

Alfa Lift is committed to the handling of all monopole foundations and transitions pieces for each of the two 1.2GW phases of the Dogger Bank project between 2022 and 2024. The wind farm is being developed by SSE Renewables and Equinor, with first power expected in 2023. The versatile nature of the design lends the vessel to other applications and markets within heavy transportation, installation and decommissioning.

OHT currently owns and operates five open-deck, semi-submersible heavy transport vessels. The company has also booked two self-propelled, wind turbine installation ships of jack-up type from CMHI, and holds an option there on a further newbuild of the Alfa Lift class.