Next-generation fracture prediction models for pipes with localized corrosion defects

Abstract

This study presents a novel concept and a guide for developing the next generation of fracture prediction models for corroded metallic pipelines. Based on this new concept, the first 3D burst capacity models are developed herein. These models combine simplicity and accuracy through the use of a new parameter, volume of the defect, to measure the burst pressure of corroded pipes with localized defects of complex morphology. The past 50 years has seen the development of numerous 2D burst capacity models, which have focused only on the longitudinal-section area of the corrosion defect and have become increasingly more complicated and less practical in an attempt to increase their relatively low accuracy and stability. Unlike these earlier models, the 3D models presented herein do not require definition of the exact defect profile; despite this, they are significantly more accurate and more stable than the well-known conventional models. Thus, they can significantly reduce the life-cycle costs of pipelines through eliminating or substantially reducing the unnecessary repair or replacement of corroded pipelines. The 3D models have been developed from two sets of computational models that were validated against full-scale burst capacity tests on API-5L pipes with localized complex-shaped defects. In addition, high-speed imaging of the fracture was used to determine the location of ductile crack initiation and the corresponding internal pressure.