Factors Influencing the Severity of The Combined Dent and Gouge Defect – A Comparative Analysis

Abstract

In the USA, Europe, Canada and West Africa, mechanical damage due to third-party interference has been identified to be a leading cause of pipeline failures. This type of damage results in either a dent, a gouge or a combination of both, known as the combined dent and gouge defect. The combined dent and gouge defect is considered a severe form of mechanical damage as it can lead to immediate rupture of the pipeline structure. The severity of the defect has led to the ASME B31.8 design code prescribing a complete cutout and replacement of the defective section. This paper presents the sensitivity of the combined dent and gouge defect on an API 5L X52 pipe grade to critical parameters such as the defect size, orientation, d/t ratio and pipe geometry. Numerical investigations were performed to ascertain the influence of each of these parameters on the severity of the combined dent and gouge defect. The results from the investigation present a qualitative ranking of the defect parameters considered with the view of providing operators and pipeline asset owners a criticality ranking for the defects to aid repairs of defected structures in a manner that ensures the safe operation of their pipeline.