Session: 04-04-03: Rigid Pipelines III

Submission Number: 157454

Integrated Toolsets for Rapid Pipeline Girth Weld Reeling ECA Solution 

Welding acceptance criteria derived through 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-fitting approach that enables crack driving forces to be determined in an efficient and robust manner.  (Crack tip opening displacement or CTOD is the measure of crack driving force.)  The approach relies on FEA automation, using an in-house toolset, which is based on the commercial 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 even-matched or partially over-matched strength. Crack driving force is evaluated from the response surface fitting approach and from a conventional 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 WT in reeling.   

In summary, integrated toolsets for rapid reeling ECA evaluations based on response surface fitting approach have been developed to address the requirements of challenging ECAs.  A case study for a reeled small diameter thin wall thickness pipe demonstrates the robustness of the approach.  The  validity of using FAD-based ECA is addressed, even when the weld has partially over-matching strength.

Presenting Author: Shiwen Wang Subsea7

Presenting Author Biography: Dr. Shiwen Wang, CEng, MIMechE, ECA Principal Engineer at Subsea7, extensive experience on fracture mechanics and structure integrity assessment on civil nuclear and oil & gas industry, project management, technical delivery and service to clients, including Santos, AkerBP, Total and Petrobras, etc. As an expert on FEA fracture mechanics analyses, Dr. Wang had delivered Santos Barossa ECA scope of work. Previously, Dr. Wang had been working for EDF Energy, UKAEA and ITER. During that period time, Dr. Wang developed integrated toolset for limiting defect size assessment based on EDF Energy R6 procedures. Dr. Wang had successfully delivered an installation lifting procedure to move ITER lower cryostat cylinder from assembly hall to Tokamak pit, which is heavy structure lifting and installation.