Circumferential Stress vs Longitudinal Stress 1

[HightyHo]

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!

 

[desertfox]

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

 

[JStephen]

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

 

[eliebl]

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

 

[jte]

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

 

[davefitz]

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.

 

[HightyHo]

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.