A note from the developer of the pipe stress analysis software for ASME B31.1, B31.3, and EN 13480 code authors
Alex Matveev
DEVELOPER of Pipe Stress Analysis Software (PASS/START-PROF) passuite.com/start
A note from the developer of the pipe stress analysis software for ASME B31.1 and ASME B31.3 code authors. I don't know how to contact them, so just publish it here. Maybe someone can pass this to the right people.
The hoop stress should not be multiplied by the axial stress intensification factor Ia. If we do so, we will receive the silly results. We found this issue when calculated the SIF using finite element method in integrated solution of PASS/START-PROF for pipe stress analysis plus PASS/NOZZLE-FEM for piping component finite element analysis (learn more) which was demonstrated live in this webinar.
The axial stress intensification factor (Ia) is calculated using finite element method from the external load Fa excluding the internal pressure. Therefore the axial pressure thrust stress PDo/4tn should not be multipied by Ia.
Just imagine if we have a tee with a high pressure, but with the caps on all three sides. The F, Mi, Mo, Mt are zeroes and Ia=10. We will receive the SL=10*PDo/4tn. The tee will fail the sustained stress analysis, SL is several times greater than allowable Sh. But FEA analysis with only pressure load (we tested with PASS/NOZZLE-FEM) shows that the tee satisfies the code requirements.
ASME B31.1-2022 Proposal
ASME B31.1-2022 equations 15 and 16 should be modified as following:
Remark: Fa should not include the pressure thrust stress PDo/4tn
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ASME B31.3-2022 Proposal
It is not so obvious, but the ASME B31.3-2022 has the same issue.
The equation 23d should be modified like this:
EN 13480
EN 13480?3:2017+A1:2021 also has this issue. I will not explain how to solve it, I think it's easy to do following the idea explained for ASME B31.1 and B31.3
Conclusion
Before piping component finite element analysis software was integrated with pipe stress analysis software this problem did not come up. But now PASS/NOZZLE-FEM and PASS/START-PROF are fully integrated and this issue becomes very important. Now we have the more applicable data, every tee, bend, trunnion and other elements now have the axial stress intensification factors greater than 1.0 and calculated using FEA.
Hope this will help to improve the code, thank you.
Piping Engineer at JGC Algeria | Layout | Stress analysis | Oil & Gas .
1 年ahmed A.
WinPIPE programmer
1 年Alex, I have not got B31.1-2022 yet. But B31.1-2020 has what you have proposed above, and it is more accurate than yours since the yellow part should be included in absolute form. I'll comment on "Ia" later.
Consultant - Species Analytics FZ-LLC
1 年Alex - You should contact Becht Engineering as the are highly authoritative and on the ASME B31.1/B31.3 Commitee - Chuck Becht is the CEO
Pipeline Consultant, PMP, API 1169, GPI, NACE Corrosion Technologist, CIP 1, CP 3, Concrete and Utility Inspector (Self-employed)
1 年This information is highly informative. Thank you very much! I am interested in documents showing the results for PASS/Nozzle FEM and PASS/Start Prof Integration to combine applicable data for axial stress intensification factors. As well as the software utilized?