B31.1 Close welds

[anolan23]

This unit shall be built to ASME B31.1. See the picture that shows the spool piece . The small flange is a socketweld and the larger one is a blind flange. There is an intermediate small pipe. I want to know if the distance between welds is an issue. If the closeness of the welds is an issue, does filling the space between help at all? Thank you

 

[pennpiper]

anolan23,
You wrote "I want to know if the distance between welds is an issue?"
It depends. That little piece of pipe there is referred to as a "Pup" piece. Some people say that Pup must be any where between one to three pipe diameters between welds. Other allow as little as two or three times the wall thickness of the Pup/pipe.

The best thing to do is talk to a qualified Weld Inspector (in your Company) and then get the Approval of the proper authority on the Client's side.

If you are interested, I am one of the 3XT school for the minimum length of a Pup.
You should also do a Search on this site for Threads for "Pups"

 

[DSB123]

pennpiper,
By what you say using 3XT pup length. So for a 12"nb pipe Sch STD you beleive a pup piece of 3x0.375" = 1.125" (28.575mm) is acceptable? Wow this means that with a backing fillet of say 6mm the toe edges would only be 28.575 - 12 = 16.575mm apart - way too close.

BS 2633 which is for class 1 pipework states that the minimum distance between the toes of adjacent butt welds welds should be 4xT apart.

 

[anolan23]

Thanks for your expertise

 

[MickMc]

I believe Pennpiper was referring to the distance between edge of welds, I have seen the same criteria used along with rule of thumb 50mm depending on client and it is all related to Heat affected Zone (HAZ).

 

[KevinNZ]

The age old question.

Some codes do not have a requirement. There is even a B31.1 code case (B31.3 1987 interpretation 7-02) to say there is no requirement.

http://www.twi-global.com/technical...ndard-requirements-on-the-proximity-of-welds/