Evaluation of Girth Weld Defect Acceptance Criteria

摘要

This report assesses several proposed girth weld defect acceptance criteria as presented in industry report appendices: the British Standards Institution PD 6493 and BS 4515; American Petroleum Institute API 1104; Canadian Standards Association CSA 2184; and the National Bureau of Standards. While criteria are based on fracture mechanics, their specific defect acceptance procedures are distinct. Assessments were based on identification of in-service loadings to which transmission, pipelines are subjected and resulting stresses at girth welds, and application of the proposed standards to hypothetical girth weld defect cases and available full-scale test data on defective girth welds. Critical assessments are made on each proposed girth weld defect tolerance criteria, considering both range of applicability and level of conservativism. Aspects of the criteria which require alteration are discussed, and improvements are recommended.