Remotely Operated Underwater Thermal Cutting Processes for the Decommissioning of Large North Sea Platforms

A study has demonstrated the automation of underwater thermal cutting processes for remote decommissioning operations. The first phase of cutting trials evaluated five cutting processes underwater (air plasma, oxy-hydrogen, flux-cored arc, oxy-petrol and Kerrie cable systems). In the second phase, three manual cutting systems (oxy-petrol, “Broco” type system and Kerrie cable) were adapted for operation by a manipulator arm of the type commonly used offshore on Remotely Operated Vehicles. This manipulator, which usually requires a human operator, was interfaced to computer simulation and control software. The results of underwater cuts on steel plate using these systems are discussed, with applicability to offshore decommissioning. Ongoing work using other novel thermal cutting processes is also described.