Chapter 2 FAILURE ANALYSIS OF A STRESS-BASED PIPELINE UNDER PLASTIC STRAIN

Strain based design concept have been extensively used for pipelines experience expectable plastic strain for both installation and service, meanwhile most transmission pipelines are designed by hoop stress induced by internal pressure, and maximum longitudinal stress which is typically limited by 90% specific minimum yield strength of pipe. However, some stress-based designed pipelines have experienced unforeseen plastic strain in past decade that resulted in failure. Strain criteria including the strain demand from ground movement and strain capacity of the girth weld are often used in strain based design. In the paper, the failure causes of rupture of a girth weld of 32 inches API 5L X80 SAWH gas pipeline are present for demonstration of the failure analysis.