Class rules for wind farm service vessels
North Sea Logistics support vessels Endeavour and Enterprise are seen in Ramsgate, where they were used by Vestas during construction of the Thanet Offshore Wind Farm. Photo by Peter Barker
Classification society Det Norske Veritas (DNV) has produced the world’s first class rules which aim to establish uniform standards for the burgeoning fleet of service vessels within the offshore wind farm industry.
The provision of access to the turbines for personnel and equipment during the installation and commissioning phases and thereafter for maintenance and repair activity is an important consideration which continues throughout the life of the wind farm, usually a minimum 20 year period.
Locally based fishing vessels were initially pressed into service but with the increasing scale of projects, the specialist requirement to transfer personnel to a relatively small circular structure and the desirability to do so in all but the worst weather conditions, bespoke craft designed specifically for the task soon emerged.
The vessels gaining most popularity are typically twin hull designs, often with waterjet propulsion configured to ‘slot’ bow first into the corresponding ladder and guide assembly of the turbine tower. Designers are now offering craft over 25m LOA with a cargo capacity of up to 20 tons, including the ability to transfer fuel direct to the tower. Personnel using these ‘buses’ to get to work are particularly well catered for with the latest designs offering accommodation for typically 12 passengers, including suspension seating, galley areas, and WIFI and TV/DVD facilities.
An indication of the scale of the requirement for these vessels is with the recently completed 100 turbine Thanet Offshore Windfarm off the UK’s Kent coast, where around 30 such vessels have been variously employed during the two year construction phase.
They have, however, usually been built and operated to domestic standards and rules applicable to the country where they are employed. This has been problematical when operators wish to transfer vessels to other jurisdictions across Europe. DNV has noted that there is now a demand from within the industry for a more transparent and uniform set of regulations for service vessels. Flag states are also indicating that class will become a mandatory requirement in the near future.
The rules were published on 1 January 2011 but have been used prior to that date, with two new vessels adopting the new DNV rules. The first vessel built to the new class rules is currently under construction at South Boats Medina Shipyard on the UK’s Isle of Wight.
There are two class notations in the rules. Windfarm Service 1 applies to craft trading domestically with up to 12 passengers and Windfarm Service 2 is for craft carrying up to 60 passengers. The Windfarm Service 1 notation is voluntary, aimed at craft involved in domestic operations, and represents a complete technical standard. The notation requirements include the construction, machinery, systems and watertight integrity of the craft as well as stability and lifesaving, fire safety and navigation properties. Windfarm Service 2 applies to vessels typically greater than 24m in length intended to carry up to 60 persons. For these vessels the class and statutory section in the rules may be applied separately to satisfy the requirements of the selected flag state.
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