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Pharos Offshore Group Completes Diver-less Export Cable Repair for London Array Pharos Offshore Group successfully completed the cable repair and re-burial for London Array Offshore Wind Farm on a section of damaged subsea export cable. Pharos delivered a work package including the rapid mobilisation of engineering, fabrication and operational teams to locate, recover, re-lay and re-bury the power cable off the Kent coast. This is the first diver-less operation to de-bury, retrieve and repair a cable of this size and weight. The 800mm² high voltage export cable has a 218mm diameter and weighs over 50kg/m in water and 86 kg/m in air. Tools for properly handling the large, stiff cable did not exist in the market and standard grapnel operations were not possible due to nearby cable routes. The Pharos team developed multiple operational plans that not only met the client’s tight schedule but allowed for the infield flexibility to deal with as found conditions. Drawing on years of subsea cable operations experience, the Pharos engineering, design and fabrication team designed, built, tested, modified and mobilised subsea equipment controlled
by skilled operators from the surface. Once on site, these tools were able to locate, de-bury, cut, grab and recover the vital export cable in a few days. In addition to the complexities of cable retrieval, the Pharos team also converted a conventional DP-2 telecoms cable ship to accommodate the loading, storage, lay, splicing and safe handling of the product. Pharos has a strong track record of adapting commercially available off-the-shelf (COTS) technology from other markets to meet challenging subsea requirements. Considering the potential operation and maintenance issues due to a nearby foundation, the team was able to reroute the cable away from the original path but still within the planned cable corridors.
Top: Diver-less cable recovery. Bottom: Modified cable tank
The equipment and procedures developed for this repair will work for other repair situations; especially those where increasingly congested cable corridors preclude anchoring and grapnel runs and/or are beyond diver limits.
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18/12/2012 15:53