The floating DP3 heavy lift and installation vessel Green Jade will be equipped with a Huisman crane. Belgian offshore contractor DEME is building the ship with its Taiwanese partner CSBC. The Offshore Mast Crane is to have a lifting capacity of 4000 metric tonnes.

The crane will be built at the production facility of Huisman in China and is scheduled for delivery in 2022. The joint venture CSBC-DEME Wind Energy (CDWE), consisting of DEME and CSBC shipbuilding group, will deploy the vessel in the Taiwanese offshore wind market.

With a lifting capacity of 4000 metric tonnes at 125 metres above deck, and outfitted with specific auxiliary systems for handling tall structures, this Offshore Mast Crane (OMC) enables Green Jade to install the next generation of foundations and giant wind turbines. The crane is prepared for a super fly jib with significant lifting capacity and a whiphoist, which allows lifting of smaller components up to a height of 185 metres above deck.

In addition to the main crane, Huisman will deliver a 65-metric-tonne Knuckleboom Crane for general lifting purposes. Both cranes will be installed and commissioned at the CSBC shipyard.

Offshore Mast Crane

The OMC is highly suitable for the installation of wind turbine foundations. It combines a very large lifting height with a small footprint on deck. A large capacity for dynamic loads is required for high workability of the vessel continuously operating in diverse weather conditions.

The small footprint comes with a small minimum radius, which leaves a maximum amount of space for project cargo. A crane with such lifting height impacts the vessel’s stability because of the large weight of the crane and the high centre of gravity. This impact is minimised by the Mast Crane concept, whereby the winches are located at deck level instead of at the level of the slew platform.

Floating installation concept

DEME has another floating installation vessel under construction, the Orion, which somewhat resembles the Green Jade. The similarity is that they both work with DP and are not jacked up, as is usual when installing wind turbines at sea. The difference is that the Green Jade is designed to install foundations for wind turbines and that the Orion also has to install the hundreds of tonnes of heavy generator houses (nacelles) from water level at altitudes far above one hundred meters.

DEME is the only one so far to have opted for the floating installation concept, in which the ship is held in place by an advanced DP system. Because even a small movement of the ship can lead to a considerable sway of the enormous crane arm, extreme demands are placed on the accuracy and reliability of this DP system.

Delivery of the Orion has been delayed, however, after the hook of its 5000-tonne Liebherr crane broke during load tests, causing severe damage to the crane and ship. An investigation into the precise cause of this accident is still ongoing. It is as yet unclear when the Orion will be ready for deployment.

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