TPT July 2007

Technology Update

Orbital welding increases longevity for underwater umbilicals

All tubes and other elements (power and fibre) in the umbilical are laid up, armoured and finally protected by a PE-sheeting. The umbilical itself varies in size from 75mm to 300mm OD. There is no room for planned obsolescence. Once buried underwater, sometimes as deep as 2,000m, these umbilicals are difficult to repair. The quality must be impeccable and both the customer and the manufacturer must have the utmost confidence in the manufacturing process. Nexans begins its process with 12m to 40m lengths of super duplex tubing, welding them into lengths up to 20,000m or more, the capacity of its enormous reels. The umbilicals are used to control sub- sea offshore equipment from a platform, production ships or directly from onshore. The company is currently producing the Ormen Lange 1 umbilical for Norsk Hydro, which will reach 120km from shore in Norway to the sub-sea field, and will contain seven super duplex tubes. The umbilical, one of two, will contain approximately

Nexans Norway, part of the Nexans worldwide group of cable manufactures, specialises in the production of sub-sea power cables and umbilicals, and has already delivered approximately one hundred umbilicals. Modern umbilical cables are not simply thousands of metres of assorted wires within a waterproof outer wrapping or container. The umbilicals, manufactured by Nexans at its Halden plant, normally contain between three and twenty super duplex tubes which contain various fluids. Each tube is fabricated in up to 20km or more.

› PC transistorised power source with numeric control

37,000 welds, and will supply hydraulic fluid, electrical power and control signals (via integrated fibre optics) from the onshore gas processing facility at Nyhamna on the west coast of Norway to the sub-sea production systems. Ormen Lange is the largest gas field under development on the Norwegian continental shelf, and is located 100km off the northwest coast of Norway at a water depth of 850 to 1,100m. The gas from this field is transported to shore for processing and

fi A Nexans production line

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J uly /A ugust 2007