The Magazine for Underwater Professionals
DCN Diving comes up with a low cost solution for removing the grouting hoses following installation of transition pieces on top of Godewind monopiles
Cutting off 194 grouting hoses from 97 structures in 24 days, DCN Diving, the Netherlands, deployed a compact version of a Saab Seaeye, UK, Cougar XT ROV, measuring just 1.3 metres by 0.78 metres, for a work task typically undertaken by much larger systems – with considerable savings in costs.
The success of the project came from incorporating a tooling package created by DCN Diving into its Cougar XT Compact, a robotic system specially designed for handling strong currents around wind farms with its six-thruster power and low profile structure.
DCN’s low-cost solution for removing the grouting hoses following installation of transition pieces on top of the monopiles at the Godewind 1 and 2 wind farms came from combining a Seaeye hydraulic power pack with a miniBOOSTER and a TNT Rescue, USA, ‘Jaws of Life’ hydraulic rescue cutter to create a uniquely powerful and effective system.
The task for the compact Cougar also included offloading 58 tonnes of the grouting hose into containers.
The result was a task completed on time, within budget and to the full satisfaction of the customer, says Fred Bosman, ROV operations manager at DCN Diving.
Bosman explains 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 six metres long and weighed about 300 kilograms each.”