Dear David, Dear Richard, Dear piping engineers,

I have a question on the High Pressure Part of B31.3: Chapter IX
According K 302.3.2 "Bases for allowable stresses" one should use 2/3 of the yield strength at design / operating temperature.
I am astonished that there is no further limitation as in the main part of B31.3, especially not the 1/3 of tensile strength limitation. For me it seems to be unlogical, that for high pressure pipes should be lower limitation as for normal piping ?
In other words: Can the regulations of Chapter IX be seen as "on the top" or "instead" of the main part of B31.3 ?
If you can not answer that exactly, where could I find information to clarify that point ?

Thanks in advance & Kind Regards
Peter