Congratulations,
You are the very first poster to discuss this appendix and it appears as feared you have missed some of the finer points that TG B of B31.3 had for publishing this.
Salient points:
99.9999% of a code stress allowable value complies with the Codes numeric requirements. Any added allowances are at the option of the individual designer and while perhaps warranted for “unknowns” are not a direct code requirement. (Interestingly when discussed by the members of TG B some felt that 99.99% was overstressed, some felt that 101.999% would still be in compliance) Mathematically speaking however 99.99% of an allowable value is less than that value. I suggest you may want to prepare a code inquiry on this for further clarification. Please follow the format as spelled out in Appendix Z
The numeric values in this appendix are approximations of the results from various commercially used pipe stress programs. It was never intended as a “benchmark” See note1 of Table S301.5.1, Table S301.5.2
As stated in S301.7 SE as well as SA has been accounted for in a CAESAR II setup the two distinct OPE cases (T1/P1 vs T2/P2) would be algebraically summated.
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Best Regards,
John C. Luf