Running right through the middle

It’s meant a new look at the overall approach to the technology. “So far, cranes have mostly been used for over the side deployment,” says Jan Kjærstad of Seonics, “but we think there will be a need for towers to launch modules through the moonpool.” Together with Castor Drilling and ICD the venture has developed a framework tower that stands around 12m high and has a capacity of 90 tonnes at depths of 2,000m.

He explains that beyond the ability to run guide wires through the frame and moonpool, there’s other benefits to the layout: “Being in the centre of the ship you have more stability so the placing will be more accurate. There’s also less for the active heave compensation to do so you gain a bigger operational window.”

He explains that although modules will fall within the standard 6.6m diameter range – the limit of most moonpools for reasons of hull integrity – the tower could add to the height of the possible load.

The top of the tower also opens so the vessel gains from being able to take on a parallel lift with the winches also acting alongside the onboard cranes: “This really helps if you have a module with a difficult centre of gravity, or one that has only a single point of attachment,” says Mr Kjærstad.

However, what is quite surprising is that the tower can be lifted on and off the vessel using a harbour’s gantry crane in one operation explains Mr Kjærstad. This means the tower can be used on several vessels, and not just kept to one dedicated ship or indeed lifted off to free up deck space when not in module handling operation.

Although receiving vessels would have to be strengthened to take the 400 tonne tower, actually deploying it on would only take a couple of days. “Since all the equipment is mounted in the tower, you only have to connect up the power supply, so it should be able to be up and running inside two or three days,” he concludes.