longitudinal seam alignment

[spektor]

G'day,
I have come across a problem in the field were a seam welded pipe has been welded end to end ( circumfrential weld) and the seams (longitudinal) are directly apposed to each other on either side of the cicrumfrential weld, I can not find in B31.3 where it states there must be a minimum amount these two longitudinal seams must be separated a certain amount, I have found the clause in AS/NZS 4458, its in our client specification but i can not find it in ASME B31.3, does such clause exist? I'm 99% sure there must be something in there in regards to this, rolled and welded pipe for pressure purposes i imagine would call the same rules as a pressure vessel? but even than i can not find anything in regards to seam locations in conjunction with other welds.
Thanks in advance, im all ears.

 

[LittleInch]

It is basically just good practice and as you say in company specifications normally to reduce the possibility of a seam weld failure turngin into a running fracture going into the next pipe. However this wes more common in the early days of seam welding and low ductility pipe and although still good practise is not actually manadated in any of the major international codes as far as I know. This question comes up time and again and I've never seen a code quote from anyone yet other than some less well used codes like the AS ones.

However if it's in your client spec, make them cut out the weld in question and say at least 1 diameter of pipe and rotate a new spool and weld it in place if you're really concerned about it, but I can't see one joint really casusing you an issue. More than 2 then yes you've got a much higher risk.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[spektor]

it is on an elbow, it goes flange, pup piece 90 degree elbow, pup piece, flange , pup piece is about 300mm long. its on a 750mm gas line, the cut the 300mm pup piece in half to remove some material to achieve alignment of flanges, and welded back together in the same position, no spare material laying about either, only choice i have is to opt for extra NDT can not cut the weld again and rotate because the flange will change axis. this brings me to another question, spec is b31.3, being in australia, i have been under the impresion the job still needs to comply with australian standards as the job is in australia, similar to cars being brought into australia, they must meet australian standards before being registerd.
What are your thoughts?

 

[LittleInch]

I seriously wouldn't worry about a pup piece 300mm long being subject to a running fracture.... So long as you hydrotest it you should be fine, especially if you don't have any spare material lying around. You could rotate the flange so that you move exactly one or two bolt holes round, which is what they should have done when they first cut the pipe, but to be honest, you're more likely to cause more issues with lots of welds in a short distance than any reduction in risk of the seam weld.

AS standards will only apply if they are either mandated by legislation or permissions (unlikely for piping), though this is why the car ones will apply, or specificed in your design basis / scope of work or construction specification (again unlikely, but check).

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[DekDee]

Spektor,
I agree with all of Little Inchs comments.
Couple of additional comments

1 If the fabrication code is B31.3 - forget anything to do with AS codes/standards - they are not applicable.
2 Whoever performed the rework should never have cut a pup piece in half - they should have cut it at the flange/pup piece weld - not only looks like crap but very unprofessional.
3 If the proximity of longitudinal seams is in your clients specification and it doesn't comply it is a cut - out, irrespective of what is in B31.3. Specifications always overrule codes/standards.
Good luck,
Regards,
DD