USA pipeline girth weld failures: an alternative metallurgical analysis of the literature

Following reports of pipeline girth weld failures in the USA, Australian Pipeline & Gas Association (APGA) convened a workshop to discuss the technical requirements and structural integrity of their pipeline network. The USA failures were claimed to be mostly grade X70 pipe welded with cellulosic consumables, E6010/E8010, and USA code compliant. This paper details the information compiled and presented during the APGA workshop. It is based on a detailed literature review and a careful metallurgical analysis based on published information of the USA failures, along with advanced numerical modelling in an attempt to provide some clarity as to the root cause. The literature review revealed that two waves of girth weld failures occurred in quick succession in the USA. The first wave was identified as hydrogen-assisted cold cracking (HACC) while the second wave exhibited a number of failures with similar characteristics. Moreover, the second wave contained five (5) tie-in welds, with one identified as HACC. The metallurgical analysis of the published information and detailed modelling provided strong circumstantial evidence that the combination of external loading in the presence of what appears to be weld defects had exacerbated the weld strength undermatching in these failures. In addition, significant differences in weld procedure requirements between the Australian and American pipeline codes, potentially indicating insufficient controls, may have contributed to the reported girth weld failures in the USA.