Dutch company DCN Diving came up with a low cost solution for removing the grouting hoses following installation of transition pieces on top of the monopiles at the Gode Wind 1 & 2 wind farms in Germany.
DCN, which was in charge of cutting off 194 grouting hoses from 97 structures and offloading 58 tons of the grouting hose into containers, deployed a compact version of Saab Seaeye’s Cougar XT remotely operated vehicle (ROV) for a work task typically undertaken by much larger systems and achieved considerable savings in costs by combining a Seaeye hydraulic power pack with a miniBOOSTER and a TNT Rescue ‘Jaws of Life’ hydraulic rescue cutter.
Fred Bosman , ROV operations manager at DCN Diving, explained the technique used: “We first attached an hydraulic clamp on the upper part of the grouting hose, which was connected to both Cougar and vessel crane. Once the clamp was secured to the grouting hose the ROV was pulled back from the clamp so the hose was no longer connected to the ROV but only to the vessel crane.
“Our next step was to cut the hose as close as possible to the lower side of the hose, and the last highest cut just underneath the coupling. At this time the hose was no longer connected to the structure and the vessel crane recovered the hose to the deck where it was stored in an open-top container until off-loaded in port.
“Depending on how close we could position the cutter to the couplings, the remaining hose lengths were about 6m long and weighed about 300kg each.”
The connections between monopiles and transition pieces on Gode Wind 1 and 2 were provided by FoundOcean and BASF, which were contracted by GeoSea for the job.
The last turbine at the Gode Wind site was erected in May. With 97 Siemens 6MW turbines, the project’s total capacity of 582MW will deliver enough green power to cover the consumption of 600,000 Germany households.