From Table A-1 (B31.3) for the material A312-TP321 (page 172) There are two material selection (with different allowables) one is pipe smls >3/8 in. thk. and the other is =< 3/8 in. thk. & wld..What does thk. stands for? Is this the pipe thickness?


Does CAESAR II automatically selects this material as per thk...?

Thanks in advance....

CAESAR II will not make any automatic selections. We would have only put one of these materials in the database, usually the thinner one.

The yield and tensile strength of the Code materials are subject to the thickness of pipe, heat treatment, welding, and others, and the Code allowable stress is subject to the yield/tensile strength ,as well as material itself.
Generally the yield/tensile strength of ticker pipe/plate is lower than thinner ones. Hence, piping stress engineer should be careful of the selection of proper allowable stress per the ASME B31.3. The pipes listed below will have different allowable values for each thinner and thicker pipe in the oil&gas and petrochemical projects typically.

-321 grade austenitic stainless pipe for high temp./press. hydrocarbon service
-P91 low alloy pipe for high temp./press. power/steam piping

Also the allowable stress for bolting material(bolt & nuts) are subject to the bolt diameter similarly.

I wonder how many will take a look into the B31.3 to check this issue. Maybe is not a bad idea to update the database. I have now some lines that will be subject to some modifications, several times analyzed in the past and in all calculations the allowable was the higher value. I had some doubts an I checked also in B31.3 and surprise.
I will check also the piping spec thicknesses, who knows.

Regards,