Colossal carousel for wind farm barge

Therefore it should come as no surprise that the carousel recently built by Fraser Hydraulic Power (FHP) to be fitted onto Explorer, a cable deployment barge owned by Global Marine Systems, was truly massive, reaching 26m across the 30m wide deck and standing 5m high.

But the entire system to be installed went well beyond the carousel. FHP also built a suite of equipment to complete a fully functional offshore lay system, with the other main elements including a loading tower, a 20 ton tensioner, and two control cabs; the first being placed on top of an 8m superstructure and the second on deck. Both of these are electronically linked with a pendant radio control that can be used from the carousel’s basket. Other parts of the system include a 20 ton track engine and three pairs of linear cable engines.

Peter Fraser of FHP explained that there is approximately 700 tons of steel in the whole system. However, because of this weight, the barge’s deck had to be strengthened from underneath by stools supporting the carousel plate area, a modification taken on by the barge’s owners before the arrival of the carousel.

Mr Fraser explained that the carousel is not just designed to transport 7,000 tons of cable, it is designed to carry it in storm conditions. ‘If you could keep to calm water the system could have been designed to be a lot lighter, but it has to be able to take on significant amounts of stress caused by heel’, he said.

He added that the necessary stress calculations are by no means simple and called for the utilisation of a finite element analysis application particularly relevant to structural mechanics. Happily, the final design was DNV approved.

Mr Fraser also pointed out that the carousel basket is supported on 178 rollers which are located on the base plate, but the main centre bearing takes most of the load of the carousel when the unit is rolling at sea and is both the largest individual component and one of the most stressed parts of the installation. Therefore, the king post and bearing assembly weighs some 52 tons.

The superstructure of the barge has been changed in a dramatic way to accommodate the new loading tower, arm and the carousel. This gives Explorer an unmistakable profile, and the capacity to take on its new mission to help link up the latest round of wind farms.