ASME B31.3 - Longitudinal Seam weld

[Mustakim]

Hi All expert,

Would like to clarify if there are any provision within ASME B31.3 that allows welded pipe to have two longitudinal seam? We have ordered pipe base on ASTM A358 EFW TYP304 CLASS 1,30" NPS 1" thick. The manufacturer (from India) produces the pipe with 2 plates, resulting in 2 longitudinal seam. Their argument was, nowhere is A358 it mention two seam cannot be used, obviously a flawed argument. I am trying to counter with B31.3 or A358, just dont know the right clause to refer to that specifically address the issue. I am well aware on the joint efficiency factor etc.

 

[Dhurjati Sen]

Dear Mustakim,

The pipes are as per API 5L, ASTM equivalent. You need to prove they are not ASTM equivalent.

Regards.

DHURJATI SEN

 

[LittleInch]

We did something similar before

https://www.eng-tips.com/viewthread.cfm?qid=377792

Upshot was that it wasn't a flawed argument, it was a valid argument and in bigger sizes and with thicker plate, two welds were to be expected.

Only thing I could possibly find is that B31.3 definitions for pipe types state "a" weld seam, not "weld seam(s)", but if you use that I think you're clutching at straws a bit....

There may well be no code or technical reason why two seams are prohibited.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[racookpe1978]

Class 1, 30 inch dia with a 1 inch wall thickness, right?

 

[Mustakim]

Thanks everyone for the feedback so far.

Dhurjati Sen;
After we received the pipe with the 2 seam yes we did find provision for double seam in API 5L, its just that its coverage seem to be for larger diameter. So far we have yet to purchase any pipe with double seam according to API 5L.

LittleInch
Thanks for the thread, it is an almost similar case with us. I also did not specify the number of seam, and the fabricator proceeded to use two plate (without informing us) as they did not have plate large enough, you need about 2.5m width plate for a 30" Dia pipe (the one they eventually used was a 1.25m width).

Agree with you on relying to B31.3 wording "seam" is not really a strong argument. If we look at the wall thickness calculation, my assumption is the factor E, joint efficiency factor, will hold true with one weld joint. How does that impact the calculation when there are more than 1 seam, wouldn't it mean the joint efficiency now is less as there are 2 joints instead of 1? Assuming the pipe is made weaker due to one additional seam. Referring to the code diagram/figure etc, it seem only to address 1 seam weld. In our case the Class 1 requires 100% RT therefore E=1, so maybe OK even if there are 2 seam. But when its less than 1 (no RT, or spot RT) I am a bit confuse.

racookpe1978
Yes, you are right. Its used for a Natural Gas line in an LNG plant, operating at 60+ barg. Ambient temp.

 

[KevinNZ]

Two seams does not change the join efficiency. The seam on one side does not effect the strength of the seam on the other side.
I section through a large spiral welded pipe with have two seams.

 

[EdStainless]

In general plate wider than 8'is difficult to source, so anything over 22" should be expected to have two long seams.
The other side of this is that if they cut the plates the other direction you lengths would only be 8' long, which can drive fab costs up significantly.
With 3m plate you can get to 36" with one seam, but almost no one has the ability to form these.

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