Minimum distance between welded branch connections

I seek your help on non-stress topic.

I am searching for some guidelines in any code/standard/paper for minimum distance between two welded branch connections. (effectively min. distance between welding lines.

It would be very helpful if somebody can send link or post some guidelines on this issue.

With Regards,

See clause 304.3.3(e) of ASME B 31.3:2004, PFI Std ES-7 &

http://www.eng-tips.com/viewthread.cfm?qid=25912

regards,

sam

There is no standard available as such but as good engineering practice it is advisable to keep minimum 75mm. It shall never be less than 50mm.

Hello Tushar,

Sam is correct, actually there is a Standard, and it is referenced in B31.3, paragraph 304.3.(e), Multiple Branches - it says "Consult PFI Standard ES-7 for detailed recommendations on spacing of welded nozzles".

You should look for Pipe Fabrication Institute Standard ES-7, ("ES" means "engineering standard"). The title is:

"Minimum Length and Spacing for Welded Nozzles"

and the web site is:

http://www.pfi-institute.org/Product.htm

Look in B31.3 Appendix "E" for Reference Documents and you will find this document listed under "PFI".

Regards, John.

Dear John Sir, sam

Thank you very much for your valuable reply.

Regards,

I got the PFI Standard ES-7 and was very helpful.

I have one more question. Is there any similar specific minimum requirement stated anywhere for "minimum distance between circumferential and longitudinal weldlines on pipes and branch adjacent to it" ?

Regards,

Check out the information at this site.

http://pipingdesigners.com/phpBB/viewtopic.php?t=47

Hello again Tushar,

I had a look at the reference provided by Jop - good discussion.

The minimum distance between circumferential welds will vary as it depends upon the material and other factors. One thing is sure and that is that you would not want to be so close that there was an overlap of the heat affected zones (HAZ's) at the circumferential welds. Also, there would have to be enough distance to allow for the weld preparations at each end. Sometimes you must leave enough room for the preheat and post weld heat treatment coils to be placed (if the material and thickness requires it).

If you are going to make a reinforced (or unreinforced) branch connection, it would be preferable to rotate the "run" pipe during fabrication so that you do not cut through the longitudinal seam (it there is one) to make the connection. Also note that any longitudinal seams in the run pipe or the branch pipe or the reinforcing pad will affect the calculations for the "area replacement” reinforcing pad (if required).

One of my friends in Texas told me: "Do not make the welds so close that they can be covered by one piece of X-ray film. We do not want the radiographs for one weld to show the defects in an existing weld"!!!! I suppose there is a little truth in that

Regards, John.