OK to weld two (2) WN Flanges together at their necks?
OK to weld two (2) WN Flanges together at their necks?
(OP)
Greetings to the Piping Gods:
During one attempt to avoid phone calls, I got out-of-the-office and on-board one of the project LNG carrying vessels that I am assigned to work on. In way of the loading mainfolds I had noticed a set of two 300mm dia 316L flanges welded neck-to-neck (as somewhat-shown below)...
Having made an attempt to enquire-around, nobody I have spoken with thus far has been able to tell me:
1) Is there either a maximum or a minimum limit to the flange sizes that can be utilized in such a configuration?
What about schedule limitations, if any?
2) Why is not a setion of pipe welded to two (2) slip-on flanges used instead of this configuration?
3) Is there either any code requirement, or "sound engineering practice", that frowns upon such a configuration, as that one shown below?
Thanks, in advance, for all of your valuable opinons and direction!
Pete
_____ _____
[_ _] [_ _]
| | | |
| \________ / |
| $ |
|F | F|
|L W|N L|
|A # E|E # A| <<< this is the cheesy,unsophisticated
|N 1 L|C 2 N| representation of the two (2)
|G D|K G| subject, married flanges...
|E | E|
| _____$_____ |
| / \ |
_| |_ _| |_
[_____] [_____]
During one attempt to avoid phone calls, I got out-of-the-office and on-board one of the project LNG carrying vessels that I am assigned to work on. In way of the loading mainfolds I had noticed a set of two 300mm dia 316L flanges welded neck-to-neck (as somewhat-shown below)...
Having made an attempt to enquire-around, nobody I have spoken with thus far has been able to tell me:
1) Is there either a maximum or a minimum limit to the flange sizes that can be utilized in such a configuration?
What about schedule limitations, if any?
2) Why is not a setion of pipe welded to two (2) slip-on flanges used instead of this configuration?
3) Is there either any code requirement, or "sound engineering practice", that frowns upon such a configuration, as that one shown below?
Thanks, in advance, for all of your valuable opinons and direction!
Pete
_____ _____
[_ _] [_ _]
| | | |
| \________ / |
| $ |
|F | F|
|L W|N L|
|A # E|E # A| <<< this is the cheesy,unsophisticated
|N 1 L|C 2 N| representation of the two (2)
|G D|K G| subject, married flanges...
|E | E|
| _____$_____ |
| / \ |
_| |_ _| |_
[_____] [_____]





RE: OK to weld two (2) WN Flanges together at their necks?
Pete
RE: OK to weld two (2) WN Flanges together at their necks?
Can't give you any help on your piping question but I think you problem with your sketch is the window where you type your message uses a proportional font but it is not displayed in the same. However, you could have used the TGML codes to display your post in proportional font as well. Otherwise, for those who are interested, copy MotoGP's sketch and paste it in something like Windows Notepad and use a proportional font to display, it will look much better.
RE: OK to weld two (2) WN Flanges together at their necks?
Why use two WN flanges instead of 2 SO flanges and pipe? Less welding. And if they used WN flanges all the time anyway, less inventory.
Minimum distance between flanges is based more on room to fit up bolts than any stress consideration, I believe.
Flanges like that are undesirable from an economic standpoint, but once there should be no problem. It's always desirable to lay out piping as simply as possible.
RE: OK to weld two (2) WN Flanges together at their necks?
The other method requires me to fitup one flange square with the pipe, that other parallel , and weld them both and keep them properly aligned.
I can see no practical reason to prohibit such a practice other than having enough room for studs.
Gerald Austin
Iuka, Mississippi
http://www.weldinginspectionsvcs.com
RE: OK to weld two (2) WN Flanges together at their necks?
I would consider two butt welded weldneck flanges to be a better design/construction than two slip on flanges with a pup piece between them. As mentioned above, you cut down from four welds to one. One advantage you get with the WN construction is that the seam may be RT'd where the double fillet weld of the SO flanges will require other NDT methods.
jt
RE: OK to weld two (2) WN Flanges together at their necks?
In regards to the weld spacing point raised by JStephen, our corporate standards for welding say 25mm or 4 x thickness of pipe between toes of welds, whichever is larger. This can be waivered providing welding engineer sticks his/her beak with suitable additional requirements.
Cheers
Rob
RE: OK to weld two (2) WN Flanges together at their necks?
You have to fit the flange faces parallel, and live with the resulting variation of space. If you set your space all around to suit the welder you will have the flange surfaces running amock.
JTMcC.
RE: OK to weld two (2) WN Flanges together at their necks?
I may be missing what you say. If I fit two weld neck flanges together with the same gap all the way around, are they not parallel? I've never seen any WN flanges where the welded and was not parallel to the flange.
Straighten me out :)
GA
Gerald Austin
Iuka, Mississippi
http://www.weldinginspectionsvcs.com
RE: OK to weld two (2) WN Flanges together at their necks?
You have to fit the pipe so the faces are parallel, space be damned.
And the shorter the spool, the more critical it becomes.
JTMcC.
RE: OK to weld two (2) WN Flanges together at their necks?
I'm not sure if ANSI B16 addresses this tolerance but I would be pretty confident that the machining would consistent. I may have gotten many freaks .
If someone has a B16 it would be interesting to knowif this is addressed(Flange and Bevel Parallel).
Gerald Austin
Iuka, Mississippi
http://www.weldinginspectionsvcs.com
RE: OK to weld two (2) WN Flanges together at their necks?
The place where you DO set the space to suit, and start welding, is cross country, buried pipelines. And the result are a lot of small but easy to see kinks at the weld joints, but it doesn't matter.
JTMcC.
RE: OK to weld two (2) WN Flanges together at their necks?
RE: OK to weld two (2) WN Flanges together at their necks?
The machined weldneck flanges I have used have always been closer than I could measure with normal fitting tools.
GA
Gerald Austin
Iuka, Mississippi
http://www.weldinginspectionsvcs.com
RE: OK to weld two (2) WN Flanges together at their necks?
JTMcC.
RE: OK to weld two (2) WN Flanges together at their necks?
I never said anything about omitting the step for checking, just that it is easier to do than two slipons. After the tacking starts, things go wild anyway but I can be pretty sure when I fit, if I have the same gap all the way around with two weldnecks, they are close. As the NPS gets smaller this becomes less help since the flangeface diameter is so much larger than the pipe ID at the root.
Have a good one John
GA
Gerald Austin
Iuka, Mississippi
http://www.weldinginspectionsvcs.com
RE: OK to weld two (2) WN Flanges together at their necks?
JTMcC.
RE: OK to weld two (2) WN Flanges together at their necks?
Not to keep beating the dead horse, or the one legged boilermaker, but out of curiosity what size pipe do you normally work with?
That would possibly explain why my take differs so much from yours. We deal with big bore pipe more often than not. We had some 42" .750 wall a couple of weeks ago.
JTMcC.
RE: OK to weld two (2) WN Flanges together at their necks?
I'd like to do some of the bigger stuff sometime. I'd like to get on with a pipeliner sometime even if just as a helper.
Have a good one
GA
Gerald Austin
Iuka, Mississippi
http://www.weldinginspectionsvcs.com