Acceptance Standards in Section XI of the ASME Boiler and Pressure Vessel Code have an important role as the first step in the flaw evaluation procedure. When a flaw size is within the allowable flaw size in the Acceptance Standard, the flaw is acceptable and analytical evaluation is not required. Although ASME Section XI has Acceptance Standards for Class 1 piping in IWB-3500, there are no Acceptance Standards for Class 2 and 3 piping. Furthermore, the development of the current Acceptance Standards for Class 1 piping was based on flaw detectability by ultrasonic inspection and consideration of fracture mechanics. In this paper, the development of proposed new Acceptance Standards for Class 2 and 3 piping, as well as for Class 1 piping, is described. The development methodology is based on a fracture mechanics approach. For Class 1 piping with high fracture toughness, the allowable flaw sizes were determined by limit load solution. For Class 1 piping, the intent was to maintain overall consistency with the current Acceptance Standards. Proposed Acceptance Standards for Class 2 and 3 austenitic piping were also developed by the methodology used to develop the proposed new Acceptance Standards for Class 1 piping. Allowable flaw sizes for both surface flaws and subsurface flaws for preservice and inservice examinations were developed.
Technical Basis of Proposed New Acceptance Standards for Class 1, 2 and 3 Piping
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Miyazaki, K, Hasegawa, K, Miura, N, Kashima, K, & Scarth, DA. "Technical Basis of Proposed New Acceptance Standards for Class 1, 2 and 3 Piping." Proceedings of the ASME 2007 Pressure Vessels and Piping Conference. Volume 1: Codes and Standards. San Antonio, Texas, USA. July 22–26, 2007. pp. 3-15. ASME. https://doi.org/10.1115/PVP2007-26124
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