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Offshore Wind Journal

Offshore Wind Journal

In-service experience feeds into SOV operations and design

Tue 25 Apr 2017

In-service experience feeds into SOV operations and design
The most recent generation of SOVs is purpose-designed with wind turbine technicians and their work in mind

The concept of a service operation vessel is still a relatively new one in the offshore sector, and concepts of operation and the design of these specialised vessels is evolving steadily

 

Early examples of service operation vessels (SOVs) were often based on existing offshore vessel designs. Later, purpose-designed units began to enter service, usually intended for operation on a specific windfarm.

Now, however, with a couple of years of experience operating SOVs on offshore windfarms, Siemens is looking at ways to reduce the cost of operations, fully utilise the vessels it has on charter and enable them to provide O&M services on more than one windfarm.

René Cornelis Wigmans, head of maritime and aviation solutions at Siemens Wind Power, said “We were the first OEM to offer these so called ‘floating warehouses’ for far-from-shore windfarms. Now, after months spent familiarising ourselves with this new concept, we are looking at new ideas to enhance utilisation of SOVs through vessel sharing.”

Traditionally, vessel sharing involves an agreement between partners in a consortium to operate a liner service along a specified route, using a specified number of vessels. Now, it seems, Siemens is looking at doing something similar and has initiated a project to determine how a fleet of SOVs could be shared between multiple offshore windfarms to maximise vessel utilisation.

Mr Wigmans says that, since SOV operations got started two years ago, SOV performance has been higher than expected. “This means that the SOVs assigned to specific sites are not being fully utilised to their full potential,” he says, which opens up a raft of options to make even better use of them.

“We are running a project to develop a roadmap to increase the utilisation rate of SOVs,” he explained. Siemens believes that sharing ships between windfarms would help reduce the cost of doing so to each. Currently, the project is focusing on shared charters for SOVs between windfarms off the coast of Sylt in northern Germany, where a couple of projects are in operation. “In layman’s terms,” he said, “the project aims to increase SOV utilisation to its full potential, reduce costs associated with offshore logistics and increase SOV flexibility to promote a ‘multifarm’ setup.”

In the past, SOVs were designed for use on specific offshore windfarms, but Mr Wigmans and his colleagues believe that relatively small design changes could be used to adapt vessels to meet the demands of multiple windfarms.

The kind of design changes he has in mind include adaptations in respect of the height of monopiles on different windfarms, tidal variations and the ability to carry tools and spare parts for more than one type of wind turbine, should the need arise.

“The unique design and structure of SOVs would need to be modified to a more open approach,” Mr Wigmans said, noting that – at the moment – the scope for using first-generation SOVs on more than one windfarm is limited because they are of windfarm-specific design.

To be able to service more than one windfarm, SOVs would need to have more flexible equipment such as gangways so that a vessel could service turbines with different types of monopiles or jackets and cope with tidal variations across windfarms.

“Increased SOV utilisation has its risks,” said Mr Wigmans. “It might put pressure on resource allocation and on service technicians and materials if a vessel was put to more than one use. If utilisation increased, room for further improvement may be difficult to achieve if vessels are already working at full capability. Nevertheless,” he said, “opportunities for SOV sharing are definitely there.”

Concepts of operations for SOVs are not the only thing that is changing, however. As Håkong Vevang, chartering manager at Østensjø Rederi in Norway explained, owners such as Østensjø have invested in offshore wind-specific vessels, which are designed from scratch for their role. “They used to be based on modified platform supply vessels (PSVs),” he told OWJ. “We have taken a very different approach that enables safe, stepless transfer of windfarm personnel. Windfarm technicians on our vessels walk straight from the workshop on board onto a turbine. The flow of personnel and equipment is optimised in a way it wasn’t before on designs that had PSVs as their basis.

“Working closely with Rolls-Royce, we produced a design that keeps distances short and reduces the amount of climbing technicians need to do. Technicians can roll trolleys with their equipment to work. There are no ‘thresholds’. The elevators they use to take them up to the access system (which is being supplied by Uptime in Norway) are dimensioned, and their capacity is specific to the requirement. The way the vessel is designed also ensures that windfarm technicians live in a productive, low-noise environment. The vessels have more than enough workshop space, and there is plenty of space on deck for containers.” Looking ahead, Mr Vevang said he anticipates that walk-to-work systems will become more thoroughly integrated into vessel systems, such as dynamic positioning and control – in fact, this is already happening with the latest offshore access systems. “Servicing multiple windfarms would not be a problem for our vessels,” he concluded.

Bibby Marine Services’ SOV Bibby WaveMaster 1 was launched at Damen Shipyards Galați in Romania on 24 March. Primarily intended for the offshore wind industry, it can also work in the oil and gas market and is another example of a vessel that was designed from the outset for the offshore wind industry, despite other potential uses. When completed, Bibby Marine Services Ltd, part of Bibby Line Group, will deploy the vessel to support forthcoming offshore wind construction and O&M projects in the North Sea.

Stephen Blaikie, chief executive officer at Bibby Marine Services Ltd, said “This is an important key milestone in the delivery of the vessel. Sea trials will start soon, and we will take delivery in August. We are very impressed with the quality of the build, and the whole process has gone smoothly.”

Peter Robert, director business development and market intelligence at Damen, said “Carrying out the integrated hardware in the loop simulator analyses of the vessel plus DP system plus gangway in a time domain simulation with the actual controllers connected to it proves, in real-life conditions, safe operations in the 2.5 m significant wave height , as required by the tenders. Based on this, the shipowner can guarantee site-specific vessel performance and safe operations.”

Bibby WaveMaster 1 was designed and built specifically for the transfer and accommodation of offshore personnel and aims to maximise working time, technician comfort and safety. With a DYNPOS (AUTR) DP2 system, the 90 m vessel has a motion compensated access system for walk-to-work transfers.

Although primarily designed with offshore wind in mind, the vessel is capable of a much wider scope of work in a variety of offshore industries. A range of options are available including an additional deck crane with up to a 24-tonne capacity, tanks arrangements suited to liquids such as glycols and low-flashpoint liquids with separate delivery intakes and facilities for diving support and ROV operations.

Bernhard Schulte’s second SOV, Windea Leibnitz, is to start work on behalf of Siemens Wind Power Service in April. Bernhard Schulte and ICBC Leasing held a naming ceremony for the vessel this week. The naming ceremony was held in Ulsteinvik, Norway, at Ulstein Verft where the vessel was built. The vessel was designed by Ulstein Design & Solutions AS. Starting in April, the vessel was due to begin work on the Sandbank windfarm in the German Bight, transporting windfarm technicians to service the 72 wind turbines installed there. Windea Leibnitz and sister vessel Windea la Cour are co-owned with Chinese company ICBC Leasing.

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