A Constraint-Based FAD Procedure for Defect Assessments of Pipelines

This study explores applications of the failure assessment diagram methodology to predict the failure pressure for high pressure pipelines with planar defects having different geometries (i.e., crack depth and crack length). One purpose of this investigation is to assess the capability of FAD procedures in integrity analyses of high pressure pipelines with varying crack configurations. Another is to address the effectiveness of constraint-corrected FADs to predict burst pressure of low-constraint cracked pipelines. The FAD curves are corrected for effects of constraint based on the Lr-Q trajectories for pin-loaded SE(T) specimens. Full scale burst testing of end-capped pipe specimens with axial surface flaws provides the data needed to compare the failure predictions derived from the FAD procedures. The analyses reveal that the degree of agreement between predicted pressures and experimentally measured values depends rather markedly on the crack size for the tested pipes. Moreover, the analyses also show a potential weak dependence of the predicted pressures on the constraint-based correction scheme. Overall, the results validate the use of FAD-based methodologies for defect assessments of axially cracked pipelines.Copyright © 2006 by ASME