Code Case N-513 provides evaluation rules and criteria for temporary acceptance of flaws, including through-wall flaws, in moderate energy piping. The application of the Code Case is restricted to Class 2 and 3 systems, so that safety issues regarding short-term system operation are minimized. The first version of the Code Case was published in 1997. Since then, there have been five revisions to the Code Case that have been published by ASME. The Code Case has been used numerous times by utilities to avoid unscheduled shutdowns without impacting plant safety.

Recent revisions of Code Case N-513 continue to expand its scope to piping components including elbows, reducers, branch tees and gate valve body ends. This paper provides three application examples of the Code Case implementation based on US plant operating experience. Specifically, detailed evaluations of through-wall leakage in straight pipe, a piping elbow and gate valve body end are provided. These examples will help facilitate Code Case implementation by future users.

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