Longitudinal weld seam on piping.

By jon20013 (*****)

Date 09-19-2005 09:37

I am speaking strictly from memory here, but every B31.3 job I've worked on had mandatory staggering of the longitudinal seams. I think there is a code requirement for it, but I don't have a B31.3 to verify, I may just be remembering project specifications.

By NDTIII

Date 09-19-2005 09:48

I looked in B31.3 and the interpretations and could not find any requirement for staggering Longseams. The only reference I could find for alignment was in Paragraph 328.4.3, which gives the same alignment requirements as circumferential welds.
It seems that the code is more interested in internal alignment than they are in longseam staggering.
My experience tells me that our Engineering Standards always told us to try to stagger longseams. This was done in the event a longseam failed during service, the failure would be stopped at the first intersecting circumferential weld. If you could not stagger them, then you would perform NDT on the circ weld.
Sometimes it is not possible to stagger Longseams. Especially on pipelines where you may run into a bend or sag or you may have to try to evenly distribute the out-of-roundness.

By JTMcC

Date 09-20-2005 04:31

Just as an interesting (to me) aside, I've seen (and repaired) a lot of pipe failures under hydro, and I've never seen the tear cross a circumferential weld. The pipe rips open longitudinally until the tear comes to about 2" or 3" from the weld and then makes a 90 degree turn and tears parallel to the weld seam for another foot or so.
I'm always suprised to see it as I would think the failure would be progressing with enought velocity and ferocity to continue right through the weld without even noticing.

JTMcC.

By NDTIII

Date 09-20-2005 05:34

Yes Jim. I agree but please keep in mind, there is a big difference between a hydrotest failure and a high pressure gas pipeline failure. There can be enough velocity and ferocity to tear through anything in its path including a circ weld. Why do you think they prefer to stagger them? Another thing they try to do on pipelines is try to place the longseams in the bottom half of the line in case of an explosion, the blast will go downwards.

By JTMcC

Date 09-20-2005 15:09

Did you miss the part about "an interesting aside?"

My name is not Jim. My initials are J. T. McC.

"High pressure gas line failures" are a very, very rare occurance.

Pipelines are where I make my living so I'm somewhat familiar.

just my four remarks,
JTMcC.

By JTMcC

Date 09-20-2005 17:05

I recieved email concerning my comment so to clarify, It's a given that one reason why line pipe seams are staggered is so a failure in one joint of pipe isn't encouraged to rip right on down the line. I'm not disputing that.
I just pointed out an interesting thing I've seen on dozens of line pipe failures under hydro, at least interesting to me. Like I said, an interesting aside, not disputing anybody's post, except for the one calling me Jim ; )
Another aside, those failures I've seen under hydro rarely started in the manufacturers weld seam. And, these were in old pipe, past it's designated lifespan.

JTMcC.

By JTMcC

Date 09-20-2005 21:33

Ok, I continue to recieve beligerant email so I will make one last effort make my position clear.
I have not disagreed with any post made in this thread.
I have not "attacked" anyone who has posted on this thread.
I am not playing "games" with anyone who has posted on this thread.
I'm in total agreement that one of the reasons factory seams are offset when welding pipelines is to avoid failure in one joint of pipe from extending into multiple joints.
I posted my somewhat related anectdotal observations because I find it interesting, and think that others posting on the original topic might as well.
To denegrate my welding ability, and the ability of my little company to complete a job, based on the fact that I've made multiple repairs to a pipeline that was laid while I was attending the 3rd grade almost 1200 miles away (and in defense of the old timers who DID weld that line, none of those failures were weld failures, they were worn out pipe failures) is illogical.
So, Ed Trotter or NDTIII or whoever you are, do me a favor and stop emailing me.

JTMcC.

By G.S.Crisi (****)

Date 09-19-2005 14:43

Jon and NDTIII are right. Even if the Code says nothing, it's good engineering practice to stagger the longitudinal welds in welded pipes (API 5L for example).
An analogy would be a storage tank or a pressure vessel, where the longitudinal welds are staggered, and in these cases the appplicable codes (ASME VIII for pressure vessels, API 650 for oil storage, AWWA D100 for water storage), say the must be staggered.
Giovanni S. Crisi]
Sao Paulo - Brazil

By jon20013 (*****)

Date 09-19-2005 15:09

I just asked Mr. Walter Sperko to have a look for me. Mr. Sperko is Vice Chair of ASME IX and has authored numerous articles on the subject of B31.3 as well as many other articles for the Welding Journal. There are no requirements within B31.3, contrary to my faulty memory.

I agree whole-heartedly with Giovanni however in his statement about good practice. Most of the Codes we work with have some verbiage explaining that it is simply not possible for the codes/standards to address every conceivable scenario so good engineering practice should always be employed even where the codes/standard is mute on a particular subject.

By JCaprarulo (**)

Date 09-25-2005 15:44

Thanks,I think your answer is the exact synthesis for all the responses.
Thanks a lot to everybody.