Lengthening of LWN Flange

[teokal]

Dear all,
We need LWN flanges with L=250mm, while we have available a lot of the required diameter and rating but with L=200mm. Is it allowed to lengthen the flange by welding a 2" piece of pipe and then perform NDT? The new weld - if acceptable - will be too close to the circumferential flange neck-to-shell weld; ASME VIII is not clear about the distances of adjacent welds, is there any knowledge on these two questions?
Please refer to the relative sketch, attached.
Thank you.

Only best result in absolutely necessary time

 

[austsa]

What pipe will you use for the extension? A 2" 300# LWN has a 3.31"OD x 2"ID neck. The closest pipe I can see is a 3" Sch XXH pipe, but it has a 2.3"ID. This I believe is the issue here.

If close proximity of the welds is your only concern (which I believe is not a serious issue), you can cut the LWN neck shorter and add in a longer extension.

austsa

 

[teokal]

@ austsa:
No my friend, the issue is not the size of the additional material, this is easy, although it should be a consideration whether I use the same material (SA350 LF2) or pipe (SA106 GrB); the issue is whether it is permitted or not to lengthen a LWN by welding, adding a small piece. And later, the new weld (did you see my sketch?) how much close can it be to the shell to LWN weld. From the second part of your answer, I assume that lengthening is permitted...(?)

Only best result in absolutely necessary time

 

[Bobfromoh]

I have seen LWN nozzles made longer. The vendor bought extra LWN's and cut off from one what was needed and welded to the other LWN to get the correct projection.

 

[austsa]

teokal,
Codes allow welds that are close together or even overlap (eg reinf pad overlapping a seam weld). It's not good engineering practice. Try to avoid it if you can. Refer to previous discussions in this forum.
Regarding welding an extension piece to a LWN, code doesn't prohibited it.
austsa