hi buytree. I see you have a parallel thread in engtips.
http://www.eng-tips.com/viewthread.c...=307182&page=1
That's a good place for advice. As mentioned:
- You can't simply use the internal pressure calculations to determine external collapse pressure.
- The ASME BPV code is fairly complex for externally pressurized structures. You'll need to dig into UG-28 through UG-30 yourself to do this analysis.
 Quote by buytree
3. I used the ASME Sec VIII Div 1 mentioned in ASME B 31.3 Sec 304.1.3 to find the thickness due to external pressure. I calculated the factor A and B, but I have a lot of confusion when finding factor B. My duct working temperature is 120 deg c and carbon steel A 515 grade B material. Which chart/table should I use to find factor B?
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Good question, which figure to use for your material? Use CS-2 since if you check ASME B31.3 in the materials section you’ll find A 515 Grade 60 (presume you mean 60, not grade B) has a yield of 32 ksi.
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4. According to step 8 in Sec VIII Div 1, the pressure obtained is much higher than the actual pressure I used as internal pressure. I think I am safe. Comment pl?
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Correct. If you go through the steps in UG-28 and get to step 8 and find your actual pressure is less than the allowable pressure (P
a) then you’re pipe wall thickness is sufficient.
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5. When comparing the minimum thickness formula for internal pressure in ASME B31.3 and the ASME Sec VIII. Div 1 there is a slight variation in formula right?
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Yes, but don’t worry about ASME Sec VIII. Div 1 for internal pressure. Use B31.3 for internal pressure.
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6. How can I determine the stiffener required for the particulaer duct?
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UG-29 covers stiffeners.