Weld Requirements for a 3" line coming off of a 10" compressed air lin 2

[UncleSam]

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

 

[Montemayor]

UncleSam:

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

 

[unclesyd]

Montemayor,
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.

 

[Montemayor]

unclesyd:

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

 

[rmw]

I want to know how he got there, if, in fact, it is 1200 psi. I would address that compressor as "sir". (although, I have seen just such gadgets, they just weren't small.)

Surely he means 120 psig.

rmw

 

[MJCronin]

Montemayor, et al....

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

http://www.bonneyforge.com

My opinion only...


MJC

 

[unclesyd]

I wish UncleSam would come back and straightened this bunch out. MJCronin has provided the answer, so all you have to say everything is OK.

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.

 

[UncleSam]

Sorry folks,

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

 

[Montemayor]

Sam:

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

 

[unclesyd]

UncleSam,

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:

http://www.wfi-int.com

 

[saxon]

UncleSam, A weldolet that matches the piping spec. would be the way to go. But, before you take this route, get a copy of the compressed air piping specification used in your facility. This should give you all the information you need, including allowable branch connections, in order to make an informed decision.

Hope this helps.
saxon

 

[Montemayor]

Good point, saxon! Initially, we've only addressed the basic query; but there has to be a scope of work and some underpinnings to the 3" installation. It falls right into the MOC arena: Management of Change. And, as such, should be preceded and documented with a carefull study and investigation of what the change will bring about - positive and negative. A Hazop, albeit short and informal, is still a basic requirement where I come from.

Good Luck Sam.

Art Montemayor
Spring, TX

 

[robert7350139]

I would like to install a 10" weldolet in a 20" schedule 40 pipe. the operating pressure is 150 PSI hot water at 185 degree f.

Does a weldolet satisfy ASME B31.1

 

[unclesyd]

Yes, if the installed as per the manufacturers recommendations.

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.