Fundamental consideration of maximum allowable flaw lengths for limit load evaluation based on flat plates for the ASME Code Section XI

Negyesi, M.*; Hasegawa, Kunio

When flaws are detected in power plant pipes, they are evaluated to determine their impact on component integrity. According to the ASME Code Section XI, the maximum allowable flaw depth should be less than 75% of the pipe wall thickness. The current code maximum allowable flaw length is defined as the length at which through-wall flawed piping fails due to applied stress. Therefore, the current length is irrespective of flaw depth. This paper uses a flat plate model with surface flaws to examine the characteristics of flaw lengths and propose a new methodology for determining the maximum allowable flaw lengths.