This paper describes the safety factors used for fracture assessments of pipes having circumferential surface flaws. The “Fitness-For-Services Codes (the FFS Codes)” of the Japan Society of Mechanical Engineers (JSME) restrict the depths of flaws according to their angles to prevent pipes with flaws from being fracture. Past restrictions were determined based on deterministic evaluations. In fracture assessments of pipes having flaws, however, the effects of measurement errors in flaw dimensions and of variations on material strength must be taken into account. Thus, we evaluated the effects of such variations on fracture assessments of pipes having flaws, and examined safety factors for giving failure probability (or reliability) equal, irrespective of the cracking angles. We found out that failure probability is heavily dependent on the measurement accuracy of flaw depths and material strength (flow stress). In view of this finding, we examined and proposed a simple approach which meets the target reliability without conducting complex evaluations by the Monte Carlo method and reliability evaluation methods (e.g., first-order second-moment method (FOSM)).
Safety Factor for Flaw Evaluation of a Pipe Having a Circumferential Surface Flaw
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Machida, H, & Arakawa, M. "Safety Factor for Flaw Evaluation of a Pipe Having a Circumferential Surface Flaw." Proceedings of the ASME 2015 Pressure Vessels and Piping Conference. Volume 1A: Codes and Standards. Boston, Massachusetts, USA. July 19–23, 2015. V01AT01A051. ASME. https://doi.org/10.1115/PVP2015-45730
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