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Offshore Wind Journal

Ørsted crew transfer vessels can change-out a turbine gearbox

Tue 19 Mar 2019 by David Foxwell

Ørsted crew transfer vessels can change-out a turbine gearbox
Undertaking a turbine gearbox swap from a CTV requires a stable, well-designed platform

Designer Incat Crowther has confirmed the recent delivery of two multipurpose crew transfer vessels unlike any others built to date.

The 39-m vessels MHO Gurli and MHO Esbjerg were built by PT Bintang Timur Samudera in Indonesia and delivered to MH-O & Co to be operated for Ørsted on the Hornsea Project One offshore windfarm.   

The vessels are the largest crew transfer vessels to enter service to date. They draw on Incat Crowther’s experience with larger offshore fast catamarans operating in the oil and gas industry. 

As highlighted previously by OWJ, operation and maintenance units in the offshore wind industry tend to be categorised as crew transfer or service operation vessels (SOVs), but there is a ‘third way’, said owners of a small but growing number of mid-size units that fit into a niche between the two. As windfarms have been built farther and farther from shore, the need has arisen for larger vessels that can operate in more difficult conditions, remain at sea and provide accommodation for technicians and storage for their equipment.

Mid-size vessels of this type, sitting between a conventional CTV and SOV in terms of capability and cost have been selected for a number of projects, among them the new vessels for MH-O & Co, designed to deliver excellent seakeeping, stability and comfort, while accommodating a highly redundant quad-engine/quad-jet propulsion package. Uniquely, these vessels have continuously rated marine diesel engines installed, offering increased reliability and reduced maintenance costs. 

The 39-m platform is maximised with an aft-mounted superstructure, affording space on the stern for a transverse 20-ft container and an extensive working deck forward.

The result of a collaborative effort between MH-O & Co and Incat Crowther, this layout provides a high level of functionality and accommodates many different load conditions including turbine maintenance operations and a turbine gearbox swap. With turbine gearboxes weighing in at 32 tonnes each, this operation requires a stable and well-designed platform.

Other equipment on the main working deck includes a deck crane, ship’s boat and EU pallet tie-downs, and hard points for task-specific winch installations. In total, 110-ft of containers can be carried on this deck, with mounting feet every 10 ft allowing for flexible combinations.

The vessels are fitted with a quad propulsion package, made up of four Cummins KTA38 main engines coupled to four Kamewa S50-3 waterjets. This package gives MHO Gurli and MHO Esbjerg excellent flexibility and manoeuvrability and redundancy. The top speed is 30 knots and service speed 25 knots, with endurance for 14 days of 24-hour operation, with capacity for 62,000 litres of fuel. 

MHO Gurli has already been approved for transfers in significant wave heights exceeding 2 m.   

The main deck cabin is entered through the wet foyer at the aft end, with lockers, showers, toilets and change facilities for technicians and crew. Forward of this is a crew lounge to port and a crew lounge to starboard. Seating for 24 technicians is provided forward of this, with excellent forward visibility and KAB suspension seats enhancing comfort. 

A set of stairs each side from the main deck cabin lead to the hulls, which house large storage and workshop facilities amidships and resting areas forward. 

Upstairs, the mid-deck houses sleeping quarters for six crew members and two spare cabins, all in single berth cabins. Pairs of cabins share an en suite, while the master and officer cabins have their own en suite bathrooms. 

MHO Gurli and MHO Esbjerg are operated from the third deck, where the wheelhouse and workstations enjoy uninterrupted vision of the turbine tower and surrounding working areas. 

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