The subsea cutting specialist was approached by a major contractor 18 months ahead of the campaign to devise a protocol for cutting a 137 mm diameter studless mooring chain, which was located in an active field with tight restrictions around dropped objects.
The Floating Production System had been towed into place and connected to the mooring system, where it was locked into position with the 137 mm link chain. Three chains on each corner of the platform were then tensioned, leaving 12 loops of loose chain, which were required to be cut and removed by Decom.
Decom Engineering Managing Director, Nick McNally, said: “We had no doubt our C1-16UL Chopsaw was suitable for this project, but the real challenge was in the link retention. We overcame this by developing link retention clamps, which allowed the cut links to be tethered back to the other chain links, ensuring they could not fall to the seabed when cut.
“The retention clamp system was positioned via ROV and tightened with a Class 4 torque tool. The 12 cuts were all completed successfully, with the fastest cut being completed in just 15 minutes.”
The project also had the challenge of being executed on a Jones Act vessel, which meant Decom supplied and trained US personnel to operate the tools on deck, while providing 24-hour onshore support during the cutting phase.
The C1-16UL is the latest development in Aberdeen-based Decom’s highly respected Chopsaw range, specifically engineered to handle the demanding task of cutting flexible risers and mooring chains under tension, Riser Turret Moorings, and Deepwater Tensioned Moorings.
It has been designed to accommodate multiple deployment methodologies, which include via a subsea basket, Decom’s own purpose-built deployment frame, or, as was the case in the Gulf of Mexico project, attached directly to the front of an ROV.
Weighing approximately 270 kg, but only 30 kg in seawater, the ultra-light Chopsaw offers unprecedented maneuverability with ROVs, while maintaining robust and efficient cutting capabilities.
Nick McNally added: “The versatility of the C1-16UL, combined with its lightweight design, opens up entirely new possibilities for subsea intervention work. A focus of our growth strategy is to secure more projects in North and South America, and this successful campaign is another feather in our cap, which strengthens our position as an innovative, trusted, and reliable technology partner.”
