Integrated Toolsets for Rapid Pipeline Girth Weld Reeling ECA Solution

Abstract Welding acceptance criteria derived through engineering critical assessment (ECA) is necessarily performed towards the end of the detailed design phase when design loads are available. The design loads, together with the pipeline and girth weld material testing data, are inputs to ECA and are used to evaluate the pipeline girth weld integrity and criticality of potential weld flaws. With ever-increasing challenging design characteristics (eg deepwater, HP/HT, aggressive fluid composition etc) in oil and gas fields, fatigue damage and fracture failure may limit the post-weld allowable defect size which, in turn, can reduce pipeline production rates. It is therefore essential to develop a robust ECA assessment strategy that can rapidly achieve a practicable post-weld allowable defect size. This paper showcases an innovative response surface (RSM) approach that enables crack driving forces to be determined in an efficient and robust manner. The approach relies on finite element analysis (FEA) automation, using an in-house toolset, which is based on a commercial finite element (FE) software. A case study demonstrates the efficiency and effectiveness of the approach. In the case study, a small diameter carbon steel pipe with thin pipe wall thickness is assumed to be reeled. Material strength mis-match scenarios are considered between the girth weld and the parent pipe material. The weld is assumed to have either at least even-matched or partially over-matched strength. Crack driving force is evaluated from the response surface fitting approach and from a conventional failure assessment diagram (FAD)-based ECA. Recommendations are included in a guideline that addresses the validity of using a FAD-based ECA for partially over-matching girth weld in small diameter pipe with thin wall thickness (WT) in reeling.