TPi November 2015

through use of the same type of equipment, from continuous manufacturing of spooled tubing to final umbilical construction and subsequent connection. All welding procedures are transposable and ensure traceability. Polysoude safeguards the methodology by harmonising welding procedure development. Polysoude offshore welding solutions Polysoude has been a TIG (tungsten inert gas) welding specialist since 1992. In 99 per cent of applications relating to umbilical cable production, the cold wire TIG process is used. However, it has been demonstrated that a clear gain in terms of productivity and quality can be achieved with hot wire TIG installations, depending on the diameter-to-thickness ratio. As the energy input required to melt the wire is lower, the ferrite rate is also lower than is the case with cold wire technology. The materials used can also result in a number of constraints that are all successfully handled by Polysoude. For example, duplex and super-duplex steels can lose their mechanical and physical properties as the ferrite content increases. The energy level must therefore be kept as low as possible to ensure the lowest ferrite level. Polysoude equipment is fully compliant to manage such requirements. Hyper-duplex offers good weldability with a high level of austenite reformation in the heat-affected zone. This produces a weld seam with good hardness and excellent mechanical and corrosion resistance.

Productivity level between cold wire/hot wire processes

A specific filler wire is required to guarantee optimum mechanical strength and corrosion resistance properties.

TIG welding is strongly recommended, and the welding procedure must include a heat input of 0.2 to 1kJ/mm and an interpass temperature not exceeding 100°C. Argon, either pure or with a nitrogen or helium content, must be used as the shielding gas. Pre- and post-heating are not necessary. References Sandvik: Umbilical tubing in Super-Duplex and Hyper-Duplex steel – Sandvik Materials Technology Nexans Norway AS: Polysoude interview in 2010 with Truls Nordahl, welding manager, Halden (Norway) and photographs Technip: photograph and information from website www.technip. com, and article published in L’Usine Nouvelle on 29 May 2014, www. usinenouvelle.com Aker Solutions: photographs and information from website www. akersolutions.com Oceaneering: information from video www.oceaneering.com/ oceanmedia/subseaproducts/multiflex-pc-fullvideo.html

Cold wire TIG welding principle

Polysoude SAS – France info@polysoude.com www.polysoude.com

Hot wire TIG welding principle

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Tube Products International November 2015

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