ASME B31.3 Appendix V

[rhino27]

I am currently trying to understand B31.3 Appendix V Allowable Variations in Elevated Temperature Service. I am hoping to gain some insight on the example given in this appendix. I understand everything until the point where the Stress due to sustained loads is calculated in accordance with para. 320.2. The example comes up with values of 3.0 ksi, 3.0 ksi, and 3.7 ksi. The information in the example does not list any weight or length of the pipe, nor does it give information on the fluid or pipe insulation type or thickness. Without this additional information, how would one calculate the sustained load per para. 320.2? My Sa term comes out to be 2,195.1 psi based off of the 250 psig internal pressure and 2,897.6 psi based off of the 330 psi internal pressure. Does anyone know or understand how the example is coming up with the Sb (sustained due to bending) term and St (Sustained due to Torsion) terms? I feel that a pipe routing and Caesar analysis would need to be performed to get these terms; however, the example does not mention an analysis. If anyone could shed some light on this area for me, it would be greatly appreciated.

If my understanding of Appendix V is correct, my company could implement it in order to design our Incoloy 800HT piping system with a thinner wall thickness and higher allowable stresses which would save quite a bit on the overall cost. However, I want to ensure that I am completely understanding the example before I present this option.

Thanks for your help,

 

[XL83NL]

Good question. Ive never really used app. V though it seems an interesting feature for the scope of work we do. I definitely need to review app V and am curious to hear an answer to your question.

 

[rhino27]

Well, I think I figured it out myself. You can put the model in Caesar and get all of the sustained load cases. Using appendix V instead of using B31.3 straight criteria allowed us to use a 6" schedule 160 pipe versus a 6" special mill run pipe with 0.913" wall thickness. Only one thing to point out is that "owner approval is required" to use appendix V. However, if you run design life of 10-15 years most owners should not have an issue approving this considering the overall upfront cost that it will save.

Hope this helps.