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user-deleted-1103
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Join Date: Jun 2007
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Minimum distance between welds

09/28/2007 4:52 PM

Hi All,

I want to remove a welded expansion joint on a cryogenic pipe and replace it with a similar joint which also needs to be welded into place. What is the requirement of ASME B31.3 regarding the minimum distance between welds on cryogenic piping? I looked but can't seem to find it and any help will be really appreciated.

Neville
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Anonymous Poster
#1

Re: Minimum distance between welds

09/29/2007 12:26 AM

according to IBR rule Minimum distance of 4" Between Two pipes.
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user-deleted-1103
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#5
In reply to #1

Re: Minimum distance between welds

10/02/2007 8:37 AM

Thank you for your comment.
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TexasCharley
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#9
In reply to #1

Re: Minimum distance between welds

10/02/2007 1:59 PM

can you cite that please.

Thanks

CR3

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Anonymous Poster
#2

Re: Minimum distance between welds

09/29/2007 12:35 AM

there no code rule persay if this is cryo what is material ss?

if so make sure they do not overlap as the second weld joint may cause metalurgical changes that could reduce impact toughness of material.
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user-deleted-1103
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#6
In reply to #2

Re: Minimum distance between welds

10/02/2007 8:38 AM

Thank you for your comment.
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Abdel Halim Galala
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Engineering Fields - Piping Design Engineering - New Member Egypt - Member - Member since 02/18/2007

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#3

Re: Minimum distance between welds

09/29/2007 5:01 AM

A lot of engineers and specialists used to ask that question.

I'd like to say that there is no code rule -such as ASME, AWS, API- determining that min. distance between welds, whatever is it cryogenic piping system or not.

But we do our best to avoid welding near the existing welds to avoid problems of HAZ, because repeated overheating can cause metallurgical faults in both base metal and weld metal.

From my experience, I recommend that distance m to be not less 2.5" or 2.5 t whichever is larger (where t is the nominal pipe wall thickness and m is the clear distance between welds, not from center-to-center).

And a UT and hardness tests are required to be carried out at the HAZ before and after applying the new weld.

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user-deleted-1103
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#7
In reply to #3

Re: Minimum distance between welds

10/02/2007 8:38 AM

Thank you for your comment.
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hakr5
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Join Date: Feb 2010
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#10
In reply to #3

Re: Minimum distance between welds

06/12/2010 2:36 PM

Dear Sir

If we are applying PWHT, whether there is any such restriction for adjacent weld distance?

Regards

Harikrishnan N S
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PennPiper
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Engineering Fields - Piping Design Engineering - Retired Piper

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#11
In reply to #10

Re: Minimum distance between welds

06/12/2010 3:14 PM

No!

If you are applying PWHT (Post Weld Heat Treating) anyway then there is no minimum. The PWHT normalizes the "HAZ" (Heat Affected Zone). Just follow your weld procedure.

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TexasCharley
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#4

Re: Minimum distance between welds

09/29/2007 9:00 PM

Abdel has it right.

In high purity applications we like to see nothing closer than 2 pipe diameters. This is for what is typically 1/4" to 4" diameters 316L SS 5Ra .035' wall to .098" respectively.

cr3

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user-deleted-1103
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#8
In reply to #4

Re: Minimum distance between welds

10/02/2007 8:38 AM

Thank you for your comment.
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Users who posted comments:

Abdel Halim Galala (1); Anonymous Poster (2); hakr5 (1); PennPiper (1); TexasCharley (2); user-deleted-1103 (4)

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