The Significance of Embedded Non-planar Defects in Transmission Pipeline Girth Welds: A Literature Review

TWI Industrial Member Report Summary 515/1995

K A Macdonald and P Hopkins (European Pipeline Research Group)

Scope

The workmanship based acceptance criteria for non-planar flaws in girth welds, contained in most standards for pipeline construction, differ widely in specifying flaw sizes to avoid fracture. Furthermore, the standards which allow the use of fracture mechanics - to justify exceedance of these arbitrary criteria - also give rise to wide variations. This report considers the question of which acceptance levels should be adopted through a critical review of the literature. As a result, a three tier approach is proposed to enable the establishment of acceptance criteria for non-planar flaws in pipeline girth welds with respect to fracture and plastic collapse.