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Offshore Wind Journal

Offshore Wind Journal

New SOV uses boats, not gangway, to transfer personnel

Mon 22 Jan 2018

New SOV uses boats, not gangway, to transfer personnel
Esvagt Mercator does not have a motion-compensated gangway like many SOVs and will use boats to transfer personnel to turbines

As highlighted before in OWJ, service operation vessel design has evolved rapidly in recent years – the latest delivery to Esvagt, one of the leading operators in this field, is a customised unit that uses boats to transfer personnel to turbines rather than a gangway


Esvagt’s latest service operation vessel (SOV) Esvagt Mercator was formally named at Port of Ostend in Belgium in December 2017 and has been chartered by MHI Vestas Offshore Wind.

The 58 m ship was designed for the highest possible level of efficiency and low fuel consumption and will operate from the port at which it was named, providing a base for 36 windfarm technicians for up to two weeks at sea. MHI Vestas has an operations and maintenance base in Ostend with 65 people in permanent employment. Esvagt Mercator will support 50 turbines on the Nobelwind offshore windfarm and 55 turbines on the Belwind 1 project. Both windfarms have turbines from MHI Vestas.

The ship is equipped with three safe transfer boats (STBs) designed for safe and efficient transfer of personnel from Esvagt Mercator to turbines.

Esvagt Mercator is significantly smaller than other SOVs, and it is not equipped in quite the same way as most units of this type. Unlike other SOVs, it will transfer technicians to turbines using the STBs rather than using a motion compensated gangway of the type found on almost every other SOV.

The vessel is the first of two Havyard 831 SOVs for the Danish shipowner. The second vessel, for which a contract was signed earlier this year, is scheduled for completion by August 2019.

The SOV is of Havyard 831 SOV design and was developed in close co-operation between Havyard Design & Solutions and Esvagt. It was built by Turkish shipyard Cemre.

The Havyard 831 SOV is 58.50 m overall with a beam of 16.60 m and draught of 5.50 m. It has a service speed of approximately 12 knots and will have two safe transfer boats, an STB 7B and an STB 12A.

The owner was looking for a fuel-efficient design with a particularly high level of manoeuvrability, given its role working in windfarms. It has a passive anti-roll system to reduce motions and ensure that the technicians housed on board are always in good shape to undertake their work.

The STBs will be fitted out inhouse by Esvagt in order to give the company’s personnel the greatest possible insight into their design and operation.

The company sees the STBs as a game-changer in SOV operations on offshore windfarms. The concept has not been employed elsewhere by other SOV owners, and the concept behind the STBs is based on Esvagt’s many years of experience building and operating fast rescue boats (FRBs). It said that, over the many years that it has operated FRBs – primarily in the offshore oil and gas industry, where it has long provided emergency response and rescue vessels to safeguard personnel on rigs in the event of an incident – it has continually refined their design based on its experience.

“This is how Esvagt incorporates its seafaring experience into continual product improvement,” the company said. “It is also one of the reasons why Esvagt has chosen to fit out STB 7 numbers 4 and 5 itself.” The two boats are now on board Esvagt Mercator.

“We have gained valuable experience from STB operations for MHI Vestas on Esvagt Supporter (an older vessel rebuilt in 2001, which has served in the offshore oil and gas industry) that we can incorporate into the design. We know how the STBs work, and we understand the tasks they need to perform. This means that we can be even sharper at matching the needs that they must fulfil,” said Esvagt.

In addition to implementing experience gained, keeping development inhouse is also important for the company. “No one knows STBs better than we do because we designed them and built them ourselves. And when the STBs need a yearly survey, it will be done in our workshop. This is why there is a valuable synergy to be gained by fitting and equipping them ourselves.”

MHI Vestas Offshore Wind has been active awarding contracts to other owners too and has awarded Vroon Offshore a contract for its vessel VOS Start to support the commissioning phase of the Borkum Riffgrund II offshore windfarm.

Vroon said the contract, which will come into effect in early 2018, “underlines the strong relationship between Vroon and MHI Vestas and is recognition of the service quality being delivered by VOS Start and its crew to the MHI Vestas team in the context of the commissioning of the Walney Extension offshore windfarm since August 2017.”

VOS Start is a subsea support/walk-to-work vessel with a 50-tonne active heave compensated crane, Barge Master motion compensated gangway for personnel transfers and high-spec accommodation and office facilities for 60 people.

VOS Start was Vroon’s first walk-to-work vessel and was purpose built to support offshore operations in the renewable energy industry and walk-to-work projects in the offshore oil and gas industry. A sister vessel, VOS Stone, has also been delivered to the company and outfitted in the Netherlands.

The outfitting at Damen Shiprepair Oranjewerf followed construction of the ship at Fujian Southeast Shipbuilding in China, an arrangement that was also followed for VOS Start, which was completed by Oranjewerf in mid-2017.

The eight-week programme for VOS Stone involved a wide range of activities, including installation of a 50-tonne active heave compensated, knuckleboom crane, along with a tautwire system, RadaScan and Hipap from Kongsberg for the vessel’s positioning system, a boat landing and system for fuelling crew transfer vessels from the ship.

Like VOS Start, VOS Stone was purpose built to support offshore operations in the renewable energy industry and walk-to-work projects in the offshore oil and gas industry. Shortly before it was completed, Vroon was awarded a contract for the ship by VBMS, a subsidiary of Royal Boskalis Westminster, to support inter-array cabling operations on the Arkona offshore windfarm in the Baltic. The vessel is also due to undertake operations for E.ON later this year, working on commissioning of the wind turbines at the same windfarm.

Another SOV due to enter service shortly is Acta Auriga, a newbuild DP2 walk-to-work/construction support vessel that will also be capable of undertaking work in the offshore oil and gas and offshore wind industries. At the time of writing, the vessel was at Ulstein shipyard in Norway where it is being completed.

The hull of the Ulstein SX195 vessel arrived at Ulstein towards the end of 2017 having been built by Ulstein’s partner yard in Poland. Outfitting and completion of the vessel will include the installation of a motion compensated gangway and 3D crane from SMST in the Netherlands.

Describing the offshore access system it is providing for the vessel, SMST Designers and Constructors in the Netherlands – which is also providing a 3D motion compensated crane for the ship – described the system as “the first of its kind” and said it offers “a complete solution for offshore logistics”.

The gangway will be mounted on an integrated tower with height adjustment and a lift for personnel and cargo. It will provide a complete package with an elevator and access bridge trolley system. The trolley system will allow pallets carrying cargo to be transported onto the elevator, which can stop at different levels to optimise the performance of the vessel. The 3D motion compensated crane will have a lifting capacity of 6 tonnes.

Capable of working over both sides of the vessel, the gangway and tower will enable personnel from different deck levels to make their way to it without exposing them to the weather. The gangway is also capable of lifting cargo up to 1 tonne with motion compensation and will be able to handle trolleys and euro pallets of up to 300 kg.

SMST describes the combination of the access system and crane as “a modular setup that maximises utilisation and performance whilst focusing on safety and efficient transfer of cargo and personnel”. In offshore mode, the crane will be capable of lifting 10 tonnes without compensation and 6 tonnes with compensation. At maximum draught, it will have a lifting height above water level of 26 m.

On delivery, which was anticipated to take place by the end of Q1 2018, Acta Auriga will join Acta Orion, a near sister vessel, and be tendered for walk-to-work, offshore logistics and accommodation services in the offshore renewable and offshore oil and gas industries.

Acta Auriga offers clients safe, stepless transfer of people and cargo using the motion compensated gangway in significant wave heights of up to Hs 3.0 m. The vessel also has a sophisticated 3D motion compensated knuckleboom crane for up to 6 tonnes of cargo that is capable of operation in up to Hs 2.5 m. The vessel has an optimised hullform that incorporates the Ulstein X-BOW and X-STERN in order to enhance workability in adverse weather conditions.

Thanks to the combined X-BOW and X-STERN configuration, the vessel will have a particularly high level of operational flexibility when operating at an offshore windfarm or an offshore oil and gas installation. In particular, the yard/designer claims, the X-STERN will allow for astern operations more than 70% of the time, significantly enhancing stationkeeping and manoeuvrability around turbines. The hullform will also experience substantially less slamming and hence lower levels of noise and vibrations and increased crew comfort.

It also provides accommodation facilities for up to 120 people and 1,000 m2 of deck space for cargo.

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