World's First Offshore Use of Adhesively Bonded Mechanically Lined Pipe

Abstract

Abstract The use of Mechanically Lined Pipe (MLP) installed by the reel-lay method is a field proven solution which presents key advantages over other more expensive rigid linepipe and installation methods. Implementing the most commonly used corrosion resistant alloys (CRA) as a thin liner inside a standard carbon steel (CS) pipe has been a differentiator for many projects due to the advantageous procurement lead times and reduced costs over clad pipe made from plates. To prevent the formation of wrinkles on the CRA liner during the reeling process the most reliable method to date was to internally pressurise the pipe with water. This solution, however, can increase the offshore installation time. A solution to prevent liner wrinkling with a standard 3.0mm or even 2.5mm thick liner during reeling without the use of pressurisation has been developed by Butting in the form of the GluBi® lined pipe. Through the liner being adhesively bonded to the outer pipe, its integrity is maintained despite the global plastic strain applied by the installation method. This new linepipe product has been qualified, fabricated and will be installed as a world's first on the AkerBP HOD project in the North Sea in 2022. Following a thorough product technology qualification via DNV, the GluBi® pipe was approved for use on the AkerBP HOD project as the inner pipe of the 12"/16" Pipe-in-Pipe (PiP) production line to be installed by the reel-lay method. As part of the project specific qualification tests, the wrinkling resistance of the liner was demonstrated via full scale reeling simulation testing as well as the full set of Manufacturing Procedure Qualification Tests in line with the project specification. Important areas of the GluBi® pipe design are the pipe ends, particularly the transition between the liner and the weld overlay region. A detailed Finite Element model of the pipe system was created including the PiP centralisers; this allowed a verification of the global and local stresses at the most critical locations including the 3.0mm 316L liner close to the transition liner/overlay. Successful pipe production was run by Butting and the pipes delivered to Subsea7's pipeline fabrication spoolbase in Vigra, Norway, for PiP stalks fabrication using a state-of-the-art mechanised welding solution combining the CMT and PGMAW welding processes. Offshore reel-lay installation with Seven Vega, Subsea 7's most advanced reel-lay vessel, is planned in 2022. This paper will present the project specific product qualification including the mechanical testing of the outer and inner pipes as well as the adhesive material, the detailed finite element analysis (FEA) performed, the production welding activities and offshore installation by reel-lay.