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Minimum distance between welds on pressure vessel

thread292-257330

Minimum distance between welds on pressure vessel

Minimum distance between welds on pressure vessel

(OP)
Hi,

Can anyone tell me what the minimum distance is between welds on a pressure vessel.
We have made an error in the placing of a shell seam. This shell seam should now have a lifting lug placed across it.
Is the lifting lug permitted to straddle a seam? Or have I got to ask the client if I can move the lifting lug?
If the lug has to be moved, what is the minimum distance it can be in relation to the seam?

J

RE: Minimum distance between welds on pressure vessel

What Code is the vessel built to? PD5500 does allow attachment welds to cross main seams, if it can't be avoided, but otherwise a minimum separation distance of the smaller of 2t or 40mm. You should discuss with the client though, particularly if they have signed off on drawings that are different to actual fabrication.

Cheers,
John

RE: Minimum distance between welds on pressure vessel

If the Code is ASME VIII (after all this is an ASME Code issues forum), then see UG-82. Attachments can cross pressure retaining welds, either by grinding the weld flush or notching the attachment to clear it. (But still mention to the client what you are doing.)

RE: Minimum distance between welds on pressure vessel

Some company specifications call out minimum spacing of 1" or 4 X the wall thickness, whichever is greater.  This is to separate the Heat Affect Zones of the two welds.  However, as far as I know, this is not a code requirement.

RE: Minimum distance between welds on pressure vessel

Minimum distance between two welds is 2", however some clients ask for more distance (e.g. in my current project that is 100mm or 2t which one is greater). Anyway, if it can't be avoided, the clashes is allowed but you have to do more NDT as required by client.  

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