Modelling 3D interaction limits of inclined stress corrosion cracking in pressurised gas pipelines

Assessment of high pH stress corrosion cracking in field inspections frequently involves using the Canadian Energy Pipeline Association (CEPA) interaction guidelines to determine whether two cracks could be interacting. These guidelines were created under the assumption of traditional SCC that propagates perpendicular to the applied stress. Recently in both Canada and Australia, X65 pipelines have presented stress corrosion cracking that instead grows at an angle from the perpendicular. This presents a case for crack interaction which could fall outside the scope of the initial assumptions of the CEPA guidelines. This case is investigated in this paper by developing a model that tests a series of worst case possibilities of inclined crack interaction based on previous field surveys of crack parameters. Results show that the CEPA guidelines could be breached by some crack configurations, but all of those geometries are proven unattainable due to shielding effects found through finite element analysis.