Designed on the basis of the knowledge and experience gained from installing over 800 turbines and more than 400 foundations, A2SEA’s SEA INSTALLER is one of the offshore wind industry’s most sophisticated installation vessels. To find out what makes the SEA INSTALLER so special, we talked to Hans Peter Johannsen, Head of Engineering and Senior Project Manager at A2SEA.

Setting high standards for second-generation design

A second-generation, purpose-built installation vessel, the SEA INSTALLER is designed to transport and install up to eight 3.6MW turbines. With a reinforced deck as long as a football pitch, she’s made to carry large, heavy loads. “The deck is designed to support 15 tonnes per square metre, which makes her one of the strongest vessels in the business,” says Hans Peter.

The new second-generation vessels have either a four or six-leg configuration. With her four legs, the SEA INSTALLER has less payload than a six-legged vessel, but a more feasible distribution over the entire deck area. “In our experience, the middle legs of the six-legged vessels often get in the way, which can be a major problem when operating in shallow water. The crane has much better clearance and manoeuvrability with the four-leg configuration,” explains Hans Peter.

The crane itself is attached to one of the rear legs. “Because the crane pedestal is wrapped around one of the legs, it can slew 360 degrees without anything getting in the way. The crane operator actually sits in front of the fourth leg, so with only three legs to negotiate, it makes his job easier. And of course it’s a big advantage in shallow ports and waters where the legs can be a major obstacle,” adds Hans Peter.

Instant reaction

Equipped with a DP2-class type dynamic positioning system and a Voith Schneider propulsion system, the SEA INSTALLER can change direction in an instant. Much faster than conventional systems with one shaft and a rudder, the SEA INSTALLER’s propulsion system consists of three pivotable, vertical blades on a rotating circular plate, and three bow thrusters, which makes the vessel very stable and manoeuvrable, even under extreme conditions with high currents and wind speeds.

Fully booked for the next two years, the SEA INSTALLER sat sail for the Gunfleet Sands 3 project in the UK with two 6MW Siemens turbines on the 7 January. With its instant manoeuvrability, a deck built to withstand massive loads, and a crane that can slew 360 degrees, extend 100 metres and lift 900 tonnes, the SEA INSTALLER is one of the most impressive installation vessels currently in operation. Keep an eye out for her – she’s well worth a look.

 

(The photo above shows SEA INSTALLER loading 6MW test turbines at the Port of Esbjerg for Gunfleet Sands 3. Photo by Paul Langrock.)

 

 

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