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JACK-UP VESSELS


FEATURE SPONSOR


THE FIRST INSTALLATION VESSEL WITH PRE-LOADED KNOW-HOW


In its 13-year history offshore wind installation specialists A2SEA has been involved in the installation of over 1,000 turbines and more than 400 foundations. The Danish company (part-owned by majority shareholder DONG Energy alongside Siemens Wind Power) has built up formidable experience in the sector and recently took its own step towards realising the needs of an industrialised offshore wind sector with the arrival of Sea Installer, an installation vessel purpose-built for the offshore wind industry.


WEST OF DUDDON SANDS Sea Installer, delivered to Denmark in December 2012, is currently working out of Belfast on the West of Duddon Sands offshore wind site. A ‘second-generation’ vessel was designed to operate in the more challenging conditions found in deeper waters further from shore that will be witnessed in Round Three zones.


CAPACITY


The vessel is equipped to transport and install up to eight 3.6MW turbines (with built-in adaptability to accommodate 6, 7, or 8 MW models as larger turbines become standard). She features a reinforced deck capable of supporting 15 tonnes per square metre and an 800 tonne crane that can slew 360 degrees.


The crane is described as the vessel’s workhorse and its lifting capacity has been optimised for large-scale offshore wind projects. In addition to the main Gusto GLC-800 crane, the vessel also has five smaller cranes for other lifting tasks.


OPERATION


The vessel uses a four-leg configuration that offers better clearance and manoeuvrability for her cranes than a six-leg configuration and can operate in water depths in excess of 45 metres and continue to carry out installations through challenging weather conditions. Her jacking system can raise the fully loaded vessel at a speed of approximately 1 metre per minute – twice as fast as standard jacking systems used in the sector.


The vessel can accommodate up to 60 people on board and features excellent crew facilities including the mess, a cinema, gym and ‘The Comfort Zone’ where crew shower and change from their work clothes into their leisure clothes.


She is equipped with a DP2-class type dynamic positioning system and a Voith Schneider propulsion system that allows her to change direction very swiftly. The vessel’s propulsion system comprises three pivotable vertical blades on a rotatable circular plate and is considerably faster than conventional systems, even under extreme conditions with high currents and wind speeds.


SECOND GENERATION


“SEA INSTALLER is an example of what is called a ‘second generation’ vessel,” comments A2SEA Project Manager Søren Grøn. “This means that it is a purpose-built vessel for the renewables industry. Before her arrival we had two self-propelled vessels and two barges – all were revamped vessels. We are now dealing with a purpose-built vessel; that’s the key difference.”


Grøn explains that designing the vessel was not simply a matter of increasing the size of an existing vessel, to fulfil its purpose the craft needed to be tailored to the requirements of the offshore wind industry. “The vessel was designed with UK Round Three zones in mind,” he says. “It can take more components that a simple scale increase might slow because it has been purpose built to take particular offshore wind components.”


“The main design criteria for the vessel was turbine installation,” Grøn continues. “When design was started it was designed for ten Siemens 3.6MW turbines, but now, some six years later, with the development within the turbine industry we are down to eight turbines, mainly because the weight of all the components has gone up.”


“The vessel can also accommodate piles for foundation installation. The thought behind the design was to carry components, including blades tower and nacelle, for all eight turbines,” he adds.


TWIN SISTER VESSEL


In 2014 Sea Installer will get a twin sister when A2SEA takes delivery of Sea Challenger. This vessel is to be almost identical in specification to Sea Installer, but will feature a larger crane capable of lifting up to 900 tonnes (that’s a 100 tonne improvement on her sister vessel). The increased lifting capacity will meet the trend for the installation of larger and larger turbines in offshore wind developments.


A2SEA www.a2sea.com


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www.windenergynetwork.co.uk


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