A place to put the wire
As anyone who’s been involved in a wiring project knows there may well be the odd bit of cable left over.
But when the project is as vast as the Nordergründe windfarm, you can be looking at a couple of thousand tonnes of bulk that can’t be left lying around the deployment facility.
Something had to be done, but rather than just rent storage Stemat and Visser & Smit Marine Contracting decided that a barge mounted carousel would provide a safe place for this rather costly resource while at the same time allowing it to be at hand when required. So, Blue Offshore Marine Services and Caley Ocean Systems were given the job of designing and building barge-fitted basket type carousel.
Putting together the 5.5m high, 18m diameter and 9,000 tonne basket was carried out against a very tight timeframe – only 10 weeks from order to delivery. However, on the side of speed was Caley’s pre-existing pattern and the fact that most of the components were already in stock.
There are a number of features to the design which made it particularly useful for this kind of storage; for example the carousel’s inner hub is 6.0m diameter which mean’s the cable is kept in good shape and the basket carousel can be fitted with inner and outer partitions to separate different kinds of cabling.
But operations needs to be flexible, so one part of the specification was for a ‘portable’ solution, able to be installed or demounted by cranes: the answer lies in the base grillage which will allow lifting the complete carousel with up to 1,500 tonnes of wire already spooled. Further the carousel’s three hydraulic motors – which can get up to 1.5 rev per minute speed inside 20 seconds – are integrated into this base to make mobilisation easier. There’s flexibility in the type of cable too, the tensioners can handle a product range between 30mm and 350mm diameter and the system includes a 5m bend radius overboarding chute.
At present the 2,200 tonne capacity basket carousel is mounted rather neatly onto Stemat 91 giving the companies a mobile ‘knitting basket’ that can be called up very quickly when there’s a job to be done.
By Stevie Knight
