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Circumferential Stress vs Longitudinal Stress

Circumferential Stress vs Longitudinal Stress

Circumferential Stress vs Longitudinal Stress

(OP)
For use in Sect VIII UG-27.  I have always used the formula for Circumferential Stress (long seams) to determine my MAWP and minimum required thickness for pressure vessels under internal pressure.  When would I use the longitudinal stress formula?  How do I know if longitudinal stresses are the governing factor?  Thank you in advance for any advise!

RE: Circumferential Stress vs Longitudinal Stress

Hi Highty

You may use the longnitudual stress formula if your tank or vessel is subject to expansion and you need to consider
buckling, or to allow for a suitable expansion joint.


regards

desertfox

RE: Circumferential Stress vs Longitudinal Stress

You may have wind, seismic, or saddle loads that add to the longitudinal stresses.

RE: Circumferential Stress vs Longitudinal Stress

The longitudinal stress calculation would be governing if the joint efficiency of the circumferential seams is less than half of the joint efficiency for the longitudinal joints or the UG-22 loads result in an increase in the longitudinal stresses.  

I reviewed over 3000 designs when I was employed with an AIA and I don't recall a single time where the longitudinal stresses goverend.

EJL

RE: Circumferential Stress vs Longitudinal Stress

Just to be clear, it would be quite unusual for a longitudinal tensile stress to govern. Not at all unusual for a longitudinal compressive stress to govern the lower shell courses in a tower or the top part of a horizontal vessel in between the saddles.

jt

RE: Circumferential Stress vs Longitudinal Stress

longitudinal stress may govern if the component operates at elevated temperatures (1100-1200 F) , has a butt weld, and the weld creep strength reduction factor is close to 0.5 , as with sa 335 P 122.

RE: Circumferential Stress vs Longitudinal Stress

(OP)
Thank you all for your insight.  This is what i thought but was just making sure that the formulas i am using were correct again.

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