We have a fabricator who wants to have 2 longitudinal joints in a shell 1 m in diameter to save on the cost. It is difficult to make him understand that the long seams experience twice stress than the circumferential seams.

Do we have a ruling somewhere that may help?

Can you deliberately increase the number of long seams if you have 100% radiography?

Live and let live! To get 1m diameter they need to buy 6m plate and waste 2.86m, ie 48%. If it's expensive material it's better to make it out of 2m plates and scrap only 0.86m, which is 22%. Additional longitudinal joint cost can still be less than the wasted material. No rule prohibits it. Common sense says that this is the way to go.

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Konrad Anikiel

I think that the stress in the shell does not care if there is one or two welds. When the welds are sound and properly made, they will both hold the pressure.

DK

As far as Code is concern it is silent but at the same time code is not worry about two long seam in one shell that we can feel by UW-9 (d)



""UW-9 DESIGN OF WELDED JOINTS

(d) Except when the longitudinal joints are radiographed
4 in. (100 mm) each side of each circumferential
welded intersection, vessels made up of two or more
courses shall have the centers of the welded longitudinal
joints of adjacent courses staggered or separated by a
distance of at least five times the thickness of the thicker plate.""

Which gives you idea of two L/s in diff. shell for staggering /or keeping away from each other.

So you can not force fully ask fabricator to avoid 2 seams in one shell.yes next time you will have to take care and incorporate this point in your technical specifications.You can ask fabricator to provide more then code requirement.Bcoz code is minimum requirement.[/code]

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Niraj