As the number of offshore wind turbines increases, so too does the need for cost-effective and efficient installation solutions. IHC Engineering Business (IHC EB), part of the IHC Merwede group, has risen to the challenge and developed a self-propelled trenching solution for the inter array power cables used to connect turbines on offshore wind farms. Their new ITAT and ITAT-HG trenchers will be launched at RenewableUK 2010 on stand 121.
The spread has been designed specifically for this work and to maximise functional operability, speed of trenching and ease of mobilisation. For the first time IHC EB is intending making the trenching spread available for rental as well as for purchase.
"Trenchers have very definite appeal to developers who would rather see them used than ploughs for inter array work close to the turbines. As they are self-propelled there is no necessity for the cable lay vessel to come too close to the turbines," explains Robbie Blakeman, Special Projects Manager at IHC EB. "We are very much looking forward to explaining the features of the new spread to developers and contractors at RenewableUK 2010.
"The ITAT uses trenching and jetting techniques - for which we have partnered with Pharos Offshore Group Ltd on this development; while the ITAT-HG, for use in harder soils than the ITAT, is based on our successful i-Trencher design - in effect, a 'mini-i-Trencher. We are therefore working with known technology to ensure a cost-effective and efficient solution to a major challenge. Both the ITAT and ITAT-HG can be launched and recovered by means of a common launch and recovery system (EM-LARS), making mobilisation simpler and quicker, while also reducing the overall cost.
Ease of mobilisation is key
"Ease of mobilisation is all important," Blakeman adds. "We have designed for a single lift mobilisation of the A-frame, winch and all necessary control and monitoring systems, on a common structural grillage. This grillage also serves to distribute loads into the vessel deck, removing the requirement for dedicated under-deck reinforcement."
The ITAT is seen as the 'tool of choice' due to the predominantly sandy soil conditions evident in the majority of wind farm sites, however, when survey data highlights the presence of harder clays or gravels which are not readily jettable, the ITAT-HG can be quickly deployed to mechanically trench the problem section. Through the use of a common umbilical and subsea pod with quick release mounts and a single control system, the two machines can be rapidly interchanged, launched and recovered, giving flexibility when working offshore where the reality may not be as predicted by survey data.
"It makes sense for us to work on a joint venture basis with Pharos, so that we can provide a tried and tested ROV-based solution - a departure from our more normal tractor-type vehicles. We will be manufacturing and supplying the ITAT as a fully integrated unit," says Robbie Blakeman. "Both vehicles have a number of features built into them to reflect a dedicated use in inter array work, such as low profile buoyancy for reduced susceptibility to cross currents and large tracks for operation in very soft soils.
"The ITAT and ITAT-HG have a common control and power system which ensures that deck space and costs can be kept at a minimum. We firmly believe this is an elegant and highly cost effective solution, and foresee much demand in the coming years on the UK's Round 2 and Round 3 sites and on offshore wind farms around the world."
IHC EB's Port of Tyne manufacturing and support base provides a range of mobilisation, commissioning and storage services for contractors looking to utilise a flexible trenching solution that is available as and when they require it, throughout the construction season.
The IHC EB stand will also feature their cable ploughs which continue to do sterling work in the offshore wind business on the Thanet, Walney 2 and Greater Gabbard wind farms, and are used by contractors including Subocean Group, Visser and Smit Marine Contracting and Pharos Offshore Group.
Further information on the ITAT and ITAT-HG is available from IHC EB on their stand at RenewableUK 2010 and from IHC Engineering Business Ltd, Broomhaugh House, Riding Mill, Northumberland NE44 6EG, UK. Tel: +44 (0)1434 682 800; Fax: +44 (0)1434 682 801; Email: firstname.lastname@example.org; and www.engb.com