Weld Requirements for a 3" line coming off of a 10" compressed air lin
Weld Requirements for a 3" line coming off of a 10" compressed air lin
(OP)
At one of our powerplants we have a 10" Schedule 40 carbon steel pipe. It has roughly 1200 psi of air in it. We want to come off of this pipe with a 3 inch pipe for other connections. What is the minimum weld that we have to provide for this connection, and what is the easiest way to figure this out with out purchasing several standards.
Thanks
Rookie Engineer
Thanks
Rookie Engineer





RE: Weld Requirements for a 3" line coming off of a 10" compressed air lin
I want to make sure I've got this right: you're operating a 10", Schedule 40, carbon steel pipe with 1,200 psig of air inside it.
Before I get into the 3" connection you want to make on it, let me cite what my pipe tables tell me:
With A53B or A106B and operating between -20 to 650 oF, I should expect a design stress of 15,000 psi; if I allow 100% joint efficiency for seamless pipe and 0.0 corrosion allowance, I come up with an allowable maximum pressure of 911 psig. This is a pipe with a nominal wall thickness of 0.365" (also considered as "standard"). But if I consider Extra-Strong, (Sched. 60 with 0.500" wall), I still only come up with 1,263 psig max. allowable.
Convince me that I'm wrong or mixed up, because otherwise I wouldn't put any trust on this application. Is your pipe really Schedule 80? Tell me that it's really Sched. 80.
Art Montemayor
Spring, TX
RE: Weld Requirements for a 3" line coming off of a 10" compressed air lin
Lets hope he means 120 psig. If it's 1200 psig I need to know where he is located.
Reminds me when I happened on a 3/8" flexible copper tube about 25'long with 650 steam inside and it was holding.
RE: Weld Requirements for a 3" line coming off of a 10" compressed air lin
I'm really hoping Rookie comes back to us real quick before the night is over. Otherwise, it's going to be a long, long weekend and I don't want to go through this without knowing the facts. I kinda suspect 120 psig also, but like you said about the 3/8" Cu tube - both you and I know in our hearts that the 10" will take the 1,200 psig; the problem is we don't know for how long and under what conditions it currently finds itself!
And I wanted to go see The Passion this weekend....
Art Montemayor
Spring, TX
RE: Weld Requirements for a 3" line coming off of a 10" compressed air lin
Surely he means 120 psig.
rmw
RE: Weld Requirements for a 3" line coming off of a 10" compressed air lin
I think you can rest assured in your belief of a typo...
My experience with many thermal power plants has been that there is no system requiring 1200 psig air and that the machine required to fill a 12" NPS header to that pressure does not exist on any plant I have encountered.
"Rookie Engineer" needs a little background in the subtleties of the ASME B31.1 Power Plant Piping Code. He could also learn about piping specifications, plant modifications etc.... as well as some information about weldolets, sockolets from Bonney Forge
Try www.bonneyforge.com
My opinion only...
MJC
RE: Weld Requirements for a 3" line coming off of a 10" compressed air lin
One has to worry as this type situation is a lot more prevalent than one likes to believe. Anyone with experience has seen too many NEAR HITS.
RE: Weld Requirements for a 3" line coming off of a 10" compressed air lin
there was a typo. The air in the 10 inch line is around 120 psi (plant service air). Thanks for the correction and I look forward to your responses.
UncleSam
RE: Weld Requirements for a 3" line coming off of a 10" compressed air lin
As MJCronin said, the answer is in the Bonney Forge Catalog. Specifically, I recommend you go to:
http://www.bonneyforge.com/specs/branch/weldolet_reduceXS.cfm
And you can see the actual position and dimensions. I recommend this 3" take-off be done at the top of the 10", just as you see it in the illustration.
I had a nervous weekend. But I think we all learned something.
Art Montemayor
Spring, TX
RE: Weld Requirements for a 3" line coming off of a 10" compressed air lin
Appreciated the return and correction.
As Montemayor states such numbers have the capability of causing people concern, myself included. As stated by MJCronin a weldolet is the way to go.
An additional supplier integrally reinforced branch connections is:
www.wfi-int.com
RE: Weld Requirements for a 3" line coming off of a 10" compressed air lin
Hope this helps.
saxon
RE: Weld Requirements for a 3" line coming off of a 10" compressed air lin
Good Luck Sam.
Art Montemayor
Spring, TX
RE: Weld Requirements for a 3" line coming off of a 10" compressed air lin
Does a weldolet satisfy ASME B31.1
RE: Weld Requirements for a 3" line coming off of a 10" compressed air lin
Use MFCronin's link to Bonney Forge as it seems that they have bought out WFI. There is a link to WFI on the Bonney Forge home page.