Hi
Is there any limitation about the distance between 2 weld line in pipe line welding, specially according to B31.4 or B31.8 ?
I listened "at least 3 times of OD" but i cant find it in standards !
Thanks in advance, friends
Vahid
Pipeline Welding
Re: Pipeline Welding
Lotra,
In case I understood your point correctly, 3 times OD could be a serious anomaly. You wouldn't have a 6 foot separation between two 24-inch dia pipes.
I still assume though that apparently you are referring to the "Root Opening" between two pipes. If so, then standards do not specify any specific distance or formula to determine that distance as far as I have understood.
It is experience-based with the focus on finding the fine balance between ensuring adequate penetration and allowing sufficient room for the weld/filler metal to shrink when cooling down (hence depends on the linear thermal expansion coefficient of the filler metal).
Kamran
In case I understood your point correctly, 3 times OD could be a serious anomaly. You wouldn't have a 6 foot separation between two 24-inch dia pipes.
I still assume though that apparently you are referring to the "Root Opening" between two pipes. If so, then standards do not specify any specific distance or formula to determine that distance as far as I have understood.
It is experience-based with the focus on finding the fine balance between ensuring adequate penetration and allowing sufficient room for the weld/filler metal to shrink when cooling down (hence depends on the linear thermal expansion coefficient of the filler metal).
Kamran
Re: Pipeline Welding
Further to my earlier post (or posts since they ended up getting posted twice), you might want to note that most experienced welders determine their root opening on the basis of the filler metal rod. The diameter of the filler metal rod, according to many, is just big enough to prevent it from falling through the root opening.
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ashfaqanwer
- Site Moderator
- Posts: 434
- Joined: 16 Mar 2010, 03:36
Re: Pipeline Welding
Lotra,
The topic you have initiated has always been very popular in discussions.
To exactly answer your query, I confirm you that you would not be finding anything specific regarding proximity of welds in any of ASME, AWS or API. Yes but in some British and Australian piping standards, you would be finding specific guidelines regarding distance between the welds.
Now coming to the requirement of minimum distance between the welds, you need to be sure of three major things that is:
1. Heat affected zones of the two nearby welds shall not be overlapped.
2. Stress concentrations shall be minimized by having the welds at a suitable distance.
3. NDT can be easily performed on the welds after completion. Just in case of performing UT, you need a certain distance to run TOFD probes or other AUT techniques.
Having said all that I recommend spacing between the welds greater of 4" or 4 times the thickness of the pipe. You would also be finding many others rules of thumbs also used by many experts.
But if you consider above three factors and then decide the spacing, even what you mentioned that is 3 times OD would serve the purpose.
The topic you have initiated has always been very popular in discussions.
To exactly answer your query, I confirm you that you would not be finding anything specific regarding proximity of welds in any of ASME, AWS or API. Yes but in some British and Australian piping standards, you would be finding specific guidelines regarding distance between the welds.
Now coming to the requirement of minimum distance between the welds, you need to be sure of three major things that is:
1. Heat affected zones of the two nearby welds shall not be overlapped.
2. Stress concentrations shall be minimized by having the welds at a suitable distance.
3. NDT can be easily performed on the welds after completion. Just in case of performing UT, you need a certain distance to run TOFD probes or other AUT techniques.
Having said all that I recommend spacing between the welds greater of 4" or 4 times the thickness of the pipe. You would also be finding many others rules of thumbs also used by many experts.
But if you consider above three factors and then decide the spacing, even what you mentioned that is 3 times OD would serve the purpose.
Ashfaq Anwer
-thepetrostreet.com
-thepetrostreet.com
Re: Pipeline Welding
I have always set this distance not less than 500 mm for piping in sizes above 8". This can be minimized considering the overlapped HAZ area of the weld.
In one questionnaire of piping design, I found this:
"The rule of thumb is that the minimum distance between adjacent butt welds is 1D. If
not, it is never closer than 1-1/2". This is supposedly to prevent the overlap of HAZs.
Minimum spacing of circumferential welds between centrelines shall not be less than 4
times the pipe wall thickness or 25 mm whichever is greater."
In one questionnaire of piping design, I found this:
"The rule of thumb is that the minimum distance between adjacent butt welds is 1D. If
not, it is never closer than 1-1/2". This is supposedly to prevent the overlap of HAZs.
Minimum spacing of circumferential welds between centrelines shall not be less than 4
times the pipe wall thickness or 25 mm whichever is greater."
Re: Pipeline Welding
Hi friends
Thanks for your useful replies
regards
Vahid
Thanks for your useful replies
regards
Vahid