value of the joints coefficients from the B31.1?

Are you referring to the flexibility factor k and stress intensification factor j in Table D-300 in B31.3 and in Table D-1 in B31.1? If so, the numerical values for these factors are not all the same for similar piping fittings or geometry.

JTHEVENET-

If you are referring to the Weld Joint Efficiency Factors referred to in B31.1 102.4.3 and Table 102.4.3 then the answer is "Close, but not quite the same." The E factors for B31.1 "... are included in the allowable stress values given in Appendix A." The "SE" term in 104.1.2 is one variable.

B31.3 on the other hand, expects the designer to use an allowable stress which the designer must multiply by a joint efficiency E found in Table A-1B. These factors can be increased with additional inspection per 302.3.4(b) and Table 302.3.4. The "SE" term in 304.1.2 is two variables.

The values given for "E" are close, but different for the two codes. You'll have to get a copy of B31.3 to compare the values of E directly with B31.1, and be sure also to use an allowable stress consistent with the code which you are using.

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