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TransCanada Corporation operates pipelines across North America, and must consider applicable codes and standards in Canada, United States, and Mexico when developing welding procedures. The North American standards pertaining to pipelines, Canadian Standards Association (CSA) Standard Z662 鈥淥il and gas pipeline systems鈥� and the American Petroleum Institute (API) Standard 1104 鈥淲elding of Pipelines and Related Facilities鈥�, which are of relevance to this study, contain alternative defect acceptance criteria based on fracture mechanics principles.

Acceptability criteria for given welds are determined on the basis of the specific weld and heat-affected zone (HAZ) properties for a project. Fracture properties are measured using the crack tip opening displacement (CTOD) test. HAZ CTOD is strongly influenced by thermal cycling from welding.