Application of instrumented indentation technique for enhanced fitness-for-service assessment of pipeline crack

While most in-field non-destructive technologies for structural integrity diagnosis focus on precise crack detection, a novel instrumented indentation technique for non-destructively determining tensile properties in fields is introduced here. The goal of this work is to apply the newly-developed indentation technique to in-field fitness-for-service (FFS) assessment of linepipe cracks. As one step to verify its applicability, tensile properties in base metal and girth weldement of API-X65-graded linepipe were evaluated by this indentation technique and provided for construction of material-specific failure assessment diagrams (FADs). Results are discussed in terms of the accuracy of the indentation data and how the FAD assessment results are affected by the variation in local tensile properties measured by indenting small target regions such as heat-affected zones (HAZs). Based on the results, we suggest that the indentation technique may be useful for reducing possible difficulties in flaw assessment (arising from the use of incorrect tensile properties) by providing reliably practical data for FAD construction.