Is external corrosion direct assessment a valid approach for pipeline integrity management?

摘要

ASME B31.8S states that the objective of direct assessment is to determine the integrity of a pipeline. A pipeline requires repair when corrosion features exceed 80% wall thickness or when the length and depth of a feature are such that the line is at risk of rupture. A series of case studies are presented to investigate whether direct assessment can identify such features. The indirect examination phase of Direct Assessment lacks the required precision to identify critical defects. However the pre-assessment phase is critical and plays a key role in the definition of the excavation sites for direct examination.