Commentary on Class 2/3 Piping Rules

Much of the piping in a nuclear plant is designed to the ASME Boiler and Pressure Vessel Code, Section III, Class 2 or 3 requirements. The Code rules are given in NC/ND-3600 of Section III. These rules were developed from the B31.1 rules, and incorporated into Section III 1971 for nuclear components. However, the Class 2/3 piping Code requirements have changed significantly since that time. There is not a criteria document available from ASME that describes the Class 2/3 piping rules. The purpose of this paper is to provide background information and a discussion of the Code stress limits so that the piping analyst can properly interpret the meaning of the Code requirements.