Paul,
This all depends on the situation. I would expect only one code to apply, be it an ASME, API or whatever other code covers the industry you are dealing with. The relevant code should dictate how welding on the outside of the pipe should be handled. Assuming you are dealing with a serious line due to its pressure or contents, my expectation is the following: 1) The design of the joint must be approved by a competent stress engineer 2) The integrity of the dummy leg weld will most probably be tested with dye penetration or mag particle. They do not seem to trust X or gamma ray on anything other than straight butt welds. 3) The leg MUST be welded on before heat treatment and hydrotest. Welding to tested pipe is generally a no-no. Generally you will be allowed to weld on a longer leg and trim it to length on site, but performing the weld to the pressure pipe after testing is definitely not on.
You need to establish the governing code and go by it.
Gordon Reddek
"Paul Bowers" <pbowers@pipingdesign.com>
16/04/2004 12:29 PM
Please respond to PipingDesign
To: <PipingDesign@yahoogroups.com>
cc:
Subject: Re: [PipingDesign] Horizontal Dummy Leg Question
It's likely a certification issue, given that I don't know how the code(s) cover pressure welding vs. non-pressure welding for this type of thing. Who welds the dummy leg to the pipe? Shop or field? If the assembly was shop-tested, would the elbow's buttweld be affected by welding over it for the dummy leg? As I've mentioned, I don't know enough about it to make an intelligent decision.
Paul
> Paul,
>
> I can not recall seeing that particular detail however it would not
worry
> me to use it. I don't think the stresses generated are likely to be
> greater than those on a dummy leg welded to a 90 degree elbow. I
expect
> you are concerned about the stresses generated at the joint between
the
> elbow and the leg. The bending moment is spread over a much larger
area at
> the contract point in this case compared to the 90 degree elbow case
so I
> would expect the stresses to be less.
>
> Gordon Reddek
>
> "Paul Bowers" <pbowers@pipingdesign.com>
> 16/04/2004 09:50 AM
> Please respond to PipingDesign
>
> To: <PipingDesign@yahoogroups.com>
> cc:
> Subject: [PipingDesign] Horizontal Dummy Leg Question
>
>
> Has anyone ever seen a horizontal dummy leg used on a 45 degree elbow?
>
> Here's a quick sketch:
>
> <a href="http://www.pipingdesign.com/drawings/dummy.jpg">http://www.pipingdesign.com/drawings/dummy.jpg</a>
>
> It is assumed that the non-penetrating weld between the DL and the
elbow
> would overlap, although the sketch doesn't show this.
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[Non-text portions of this message have been removed] Received on Thu Apr 15 22:48:00 2004
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