Relaxation of Welding Residual Stress in CRA-lined Pipes during Reel-lay Installation

摘要

Mechanically Corrosion Resistant Alloy (CRA)-lined pipes have beenincreasingly used and the reel-lay installation method has beenconsidered as an efficient way in installation of the CRA-lined pipe. Apipe can be subjected to multiple reeling cycles of up to 2% axial strainand a realistic treatment of welding residual stress during reel-lay iscrucial for reeling engineering critical assessment (ECA). In this paper,a comprehensive testing program was conducted for measurement ofthe welding residual stresses at a CRA pipe girth weld. Weldingresidual stresses were measured during the pre-reeling and post-reelingstages and it demonstrates that the reel-lay installation relaxes thewelding residual stresses. Welding numerical simulation was alsoperformed and this provides a self-balanced residual stress profile in thegirth weld and seal weld of the CRA-lined pipe. The residual stressprofiles are compared between the finite element (FE) analysis andmeasurement. The implementation of welding residual stressdistributions into the FE-based reeling ECA is described.