TPT July 2007

Technology Update

further to the United Kingdom in a sub-sea pipe called Lange-Led. This gas will cover approximately 20 per cent of the UK’s gas consumption. During the past decade, Nexans has developed a new generation of umbilicals for controlling sub-sea systems that carry energy, telecommunications, fluids, methane, fibre-optics, and chemicals via super duplex tubes. In the Norwegian ‘Snow White’ project for Statoil, a single 146km umbilical of this design transfers all wellhead control functions to shore, eliminating costly platform facilities. In another current project, umbilicals are being installed in the Gulf of Mexico beyond 2,000m water depths. Nexans Norway started manufacturing umbilical cables in 1991. From the beginning, orbital welding was

As the welded tube advances out of a weld station, each weld is X-rayed. If a defect is revealed, the weld is cut out and re-welded. The welded lengths are then collected on a large reel, with an outside diameter of approximately 4m. Each reel can hold more than 20,000m of ½" tubing. The tubes on the reel are then filled with water and pressure tested, usually with 1.5x normal working pressure, in a special pressure testing room. In the umbilical lay-up machine there may be as many as a dozen large reels containing stainless steel tubing with various IDs and ODs. The actual lay-up point is placed approximately 12m above the large rotating turntable. Each reel feeds its contents upwards to the lay-up standing point where the super duplex tubes are spiralled around a larger centre tube, forming the interior of an umbilical cable. The cable can then go to the armouring operation first, or be wrapped in a plastic material to hold it together, prior to the PE sheet extruding operation.

recognised as the only way to manufacture these lengthy tube assemblies, and to obtain perfect welds in a repetitive and precise manner. In a welding plant which is approximately 150m in length, nearly 120m of plant floor are devoted to the production process for the three orbital welding lines. Bundles of super duplex tubes with IDs from ½" to 2½", in lengths of 12m to 40m, are brought into the factory, unwrapped, and lifted to a sorting station on a dispensing platform at one

When contents of one of the tube- feeding reels comes to an end, the lay-up process halts while the empty reel is replaced.

A welder will then use the Polysoude orbital welding equipment to weld the new reel’s tube to the end of the previous reel’s tube. is performed on a platform approximately 10m above the plant floor. A special This welding

› Full function welding head, Type MU

end of the factory. Tubes are dispensed automatically to each of the welding stations which is manned by one operator. The three orbital welding stations each employ Polysoude PC systems. The welding station equipment is on tracks, and can be moved to accommodate welding tube lengths from 14m to 40m. Polysoude orbital welding equipment has been used for umbilical production by Nexans since 1994. In 2005, 1.6 million metres of tubing were welded, using 75,000 welds. Nexans uses open weld heads having AVC and oscillation features with wire feed (cold wire TIG). The cycle time from the beginning of setup to the beginning of the next setup at a weld station is dependent upon the tube diameter. A diameter of ¾" may take one minute to weld (diameters referenced are always ID, since various ODs are used.)

extension cable has been constructed by Polysoude to permit the welding machine to remain on the floor below. When the welding is complete, the lay-up process continues. The umbilical is produced to an outside turntable measuring more than 35m across, with a capacity more than 7,000t. The completed umbilicals are loaded onto ships at the plant’s quay-side.

Article supplied with input from Mr Truls Nordahl, welding coordinator, Nexans Norway AS

Polysoude SAS – France Fax : +33 2 4068 1188 Email : info@polysoude.com Website : www.polysoude.com Nexans – France Fax : +33 15669 8484 Website : www.nexans.com

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J uly /A ugust 2007