For the sixth edition, this chapter has been updated with revised Code requirements and Code Cases from the 2017 Code and 2019 Code Editions. The important areas of revised requirements and procedures include flaw proximity rules in IWA-3300, change in the yield strength limits from 50 ksi to 90 ksi for selected grades of SA-508 and SA-533, addition of stress intensity factor equations for circumferential OD surface flaws in Appendix A, A-3000, revised procedures for pipe flaw evaluation in Appendix C, C-4000 and C-5300, and an updated glossary terminology/definitions. Several new and revised Code Cases are also discussed to include N-513-5 (temporary acceptance of flaws in moderate energy piping systems), N-705-1 (temporary acceptance of flaws in moderate energy vessels and tanks), N-806-1 (evaluation of wall loss in buried pipe), N-848-1 (proximity rules for quasi-laminar flaws), N-869 (extension of N-513 to higher pressures for Class 2 and 3 piping systems), N-877 (characterization of multiple subsurface radially oriented planar flaws), N-889 (new reference curves for irradiated-assisted stress corrosion cracking growth for austenitic stainless steels), N-899 (weld residual stress reference curves for dissimilar metal welds), and N-890 (materials exempted from Appendix G, G-2110(b) requirements). It is important to note that additional proposal changes are being developed by the committees, some of which are discussed in 30.11.