Post-weld heat treatment with induction
Welding pipe sections together sounds easy enough. But when the pipe is destined for the tough conditions of North Sea oil and gas fields, post-weld heat treatment is essential. For the past nine years, EFD Induction has been helping pipelines survive in one of the world’s harshest environments.
EFD Induction first became involved in the post-weld heat treatment of offshore pipelines in 1997 with a delivery to the Technip Coflexip spool base in Orkanger, Norway. This initial project was followed by a contract for the same customer in the Mexican Gulf. Since then EFD Induction has partnered with Statoil, BP and Exxon on various projects in the North Sea. Current offshore projects include Statoil’s multi-million dollar linking by pipeline of the Skinfaks and Rimfaks satellite oilfields to the large concrete Gullfaks C production platform located 190 km west/north west of Bergen, Norway. The project includes the engineering, fabrication and installation of two parallel 12 km, 10’’ flowlines and a 4.5 km 8’’ flowline in water depths of around 140 m. This part of the work has been awarded by Statoil to Subsea 7, one of the world’s leading subsea engineering contractors.
EFD Induction’s role is to assist with the heat treating of the approximately 2,600 welds involved in the pipelines. Post-weld treatment is needed to relieve stress in the metal caused by the welding, and also to prevent hydrogen cracking in the metal, a common cause of metal failure in subsea environments. The induction system used is a Minac 50 with a closed-loop chiller and a temperature control unit. EFD Induction custom-designed split induction coils for the pipelines, and worked together with the customer on specifying heating cycles.