L51652 Fracture Behavior of Large Diameter Pipeline Girth Welds-Effect of Weld Metal Yield Strength

This is a two-part study. See report L51712 for part two. The integrity of girth weld defects in gas transmission pipelines is ensured by non-destructive inspection procedures. The acceptance level of pipeline girth weld defects revealed by non-destructive testing is commonly based on workmanship quality control. Workmanship defect acceptance levels, however, are based on experience and are, by necessity, both arbitrary and often conservative. An alternative approach of defect acceptance in pipeline girth welds is based on the concept of fitness-for-purpose. This report describes the results of an experimental investigation into the failure behavior of defected girth welds in large diameter line pipes. The focal point of the evaluations was the study of the weld metal yield strength matching effects on weld metal root crack tolerance. The objectives were achieved by testing six girth welds in API5LX65 pipe sections of 916 mm (36 in.) in diameter with a 25,4 mm(1 in.) wall thickness. The girth welds were made with 90 ksi (E9010-G) tensile strength -low toughness- cellulosic electrodes. This electrode was chosen to obtain weld deposit yield strength overmatching.