Abstract
Recent incidents outside Canada prompted the Canadian Energy Regulator (CER), the British Columbia Oil & Gas Commission (BCOGC) and the Alberta Energy Regulator (AER) to advise pipeline operators regarding the possibility of girth weld strain-induced failures in high strength pipe. In early 2020, the CER issued a Safety Advisory (SA) relating to the possibility of girth weld strain-induced failures in high strength (Grade X 70 or higher) steel line pipe. There was a concern that similar incidents could occur in Canada, given comparable conditions. Furthermore, the SA stated that.... “The CER expects that regulated companies can demonstrate that longitudinal strains resulting from loadings such as those described in Section 4.2.4 of CSA Z662-19 [essentially external loading over and above typical operating loads] have been accounted for in the design, construction and operation of pipelines where strain could potentially accumulate in under-matched girth welds”.
With respect to the SA, the failure causes were consistently linked to combinations of:
i) high strength pipe with a minimum tensile strength exceeding actual weld strength values,
ii) girth weld HAZ softening as a result of the welding process,
iii) loads applied to the pipeline causing additional longitudinal strain, and
iv) pipes welded with a standard bevel and alignment of approximately 45° between the heat affected zone (HAZ) and the root bead.
Emera New Brunswick (Emera) initiated an assessment of the 30 inch diameter, 145 km long, API 5L Grade X70 Brunswick Pipeline that evaluated:
i) pipeline material, welding and construction records with respect to specified requirements, and
ii) the propensity of the pipeline to external loading via the analysis of repeat inertial measurement unit (IMU) data and a geohazard review of locations exhibiting bending strain to understand the stability of the pipeline in relation to potential external loading.
This paper describes the systematic approach taken to address the potential concerns, the key results and recommendations of the study and how Emera has incorporated those findings into processes within its management system and protection programs.
