Incident analyses over the last several decades consistently show that outside force is the largest single cause of reportable incidents for the hazardous-liquid- and gas-transmission pipeline systems throughout the world. This paper addresses outside-force incidents due to “acts of man” leading to mechanical damage in the form of dents. As such incidents are significant worldwide, there are worldwide efforts to prevent future incidents, and develop approaches to manage this threat. This paper evaluates the criticality of dents in a more general framework than acceptable dent depth used in codes. This analysis is done with reference to typical line pipe mechanical properties, as well as less know parameters like true -fracture ductility and fracture-initiation toughness. Analyses results characterize severity and rank criticality as a function of dent type in reference to the general PRCI model for mechanical damage. Results are presented that show current code-acceptance criteria for dents are over conservative in general, sometimes significantly, particularly for plain dents. Full-scale test data are introduced to support the analytical results. Results are also presented to assist in evaluating the utility and accuracy of ILI deformation tools, and their calibration with reference to measured field dent size.

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