Exactly the opposite of what LittleInch said, is what he meant about circ seams and long seams.
I would presume that circumferential joints are not permitted in the manufacture of pipe because if I order a length of pipe, I don't want to receive a series of 3' long pieces from your scrap bin welded together!
I always get those two mixed up. however circumferential butt welds are subject to other stresses in reality so are seen as more important than longitudinal welds.
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"suren12564", Where did you hear or read this statement:"circumferential seam is not allowed in manufacturing of welded pipes?".
Longitudinal Seamed Pipe is purchased in single random lengths, double random lengths and coil lengths.
This pipe is cut to required lengths and then fabricated into configurations called spools for assembly at the jobsite. These configurations contain lots of circumferential weld seams.
Sometimes its possible to do all the right things and still get bad results
pennpiper,
As moltenmetal says "you do not want a random length of pipe being supplied bu welding a number of offcuts". I know pipe may be supplied with a circ weld but from my point of view one circ weld should be the maximum. Fabricated pipe spools are different to pipe from the mill.
There should be no circ welds if supplied from a mill.
If I order a 6 mtr length of pipe I should not receive 2 x 3 mtr lengths welded together.
It is hard enough to get an MTR out of some mills - what do you think the chances are of getting a copy of the WPS (copy of the PQR to support the WPS), copy of the Welder Qualification Certificate and a copy of the NDT report for the circ weld ?
Available lengths from the mill depend on the pipe type, wall thickness and diameter and your mill's capacity to make it. Extruded seamless may be limited to shorter lengths than would be the case if the pipe was made from rolled plate.
API 5lX pipe purchased from the mill is often double ended (circumferentially welded) at the mill to provide longer lengths for transport and minimize field welding.
Precisely. In many cases it is specified in the purchase order what the maximum length of pipes that can be welded together to form a "double jointed length" shall be as well as the minimum, maximum and average length of any finished pipe so joined.
API 5L refers to these as "jointers" and has a number of references to them being allowed "subject to agreement" being 2 or three pieces for a 12m nominal length.
There is even a specific appendix for welded jointers.
Personally I wouldn't agree to it coming from a vendor and have never seen it on a pipeline supply.
Welding DJs in a yard or load out facility yes, from a pipe mill, no.
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Also: If you get a response it's polite to respond to it.
If fluid pressure is the primary load, then the axial stress imposed on a circumferential butt weld is only 50% of the circumferential stress imposed on a longitudinal seam weld. So in that case the butt weld is much stronger and reliable than a seam weld . Further , the seam weld is assumed to have a weld efficiency less than 1.0 . In the creep range ( > 800 F), the seam weld HAZ creep strength is further reduced from the parent metal , so another lower weld creep strength efficiency factor must be applied.
There had been cases where the UT device that was used to confirm correct weld quality was incorrectly calibrated, and a whole batch of seam welded pipe was shipped and used with defective seam welds. And there have been major accidents involving seam welded pipes that failed in the creep regime ( Mohave 1986- 11 deaths) . So there is a reason why some codes do not permit seam welded pipe .
"In this bright future, you can't forget your past..." Bob Marley
I find it funny there's this occasional 'well-posed' question by an (did I say Indian?) newbiw who comes in, posts a very vague question, says thanks (if at all) after a few replies, and leaves, while the debate continues and no one really knows if his not-so-well-posed question is answered satisfactorily.
It's like throwing in a dime in an old jukebox which starts rattling on and on ...
LittleInch,
Makes more sense economically to have the mill make the double end welds and have them radiographed to the appropriate Code. Lower transport, handling and middle man profit costs are achieved as well as potential lowered owner inspection costs. I've done this on cross country pipelines and stainless steel cryogenic pipelines where full inspection was done at the mill by Owner/Engineer.
Ok, but this only works when you can transport true double enders (24m) from the mill to the field. Doesn't happen very often. Each job is different, but there's a reason you don't see many 24m lengths of pipe running around. The right place and the right infrastructure then sure, but most pipelines are in the middle of nowhere and rather difficult for 24m trailers to negotiate.
Welding the joints is an extra activity for the mill and only makes sense if the welder costs are a lot lower than they would be at a pump dump.
XL83NL - Agree with you 100%
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
