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Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/23/2012 4:56 PM

I'm going to guess that it's against code, but if so... exactly why is that? I need an inline reducing tee in a steam system that has considerably less than 150 psi. Ideally, I need the main line to be 1/2" steel pipe that has butt welded tee fittings. But the side pipe needs to have a female 1/4" NPT port. If I could just butt weld a threaded reducing tee, that would solve my problem. But that doesn't sound legal.

So my questions are: 1) Why would that be unsafe, if in fact it is, and 2) What configuration of fittings would give me a 1/4" female NPT side port within a line of butt welded 1/2" sch 40 pipe? This is carbon steel, not stainless.

I'm making a header. Yes I know the easy answer is to use all threaded connections, but let's say that isn't the preferred method at this point. I could also weld a small cover plate across the third opening of a standard butt weld tee, and tap a 1/4" NPT hole in it... but again, I don't know the code regarding that.

Suggestions? For some reason I'm drawing a blank on this one, but I suspect there is a simple solution that I can't recall.
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Pathfinder Tags: butt weld pipe pipe fittings thread-o-let threaded pipe outlet threadolet
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Doorman
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#1

Re: Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/23/2012 5:04 PM

Does it need to have a fitting? How about a Threadolet?

I'll let someone else discuss the sched 40 pipe.

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#2
In reply to #1

Re: Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/23/2012 5:07 PM

Aha! Yes, I thought of that, but I was mispronouncing it and googling the word "threadlette". Yes, that could be exactly what I need, if they are still available. haven't used one in twenty years.

That's a good start Doorman. Thanx.
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#5
In reply to #1

Re: Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/24/2012 3:25 AM

Kosher. GA.

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#3

Re: Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/23/2012 11:34 PM

If it's against code to butt weld a threaded fitting as you suggested then it's logical to assume that welding a "threadolet" would also be against code. Think about it. Mechanically speaking, there is no difference in the joint connection when comparing your threaded fitting and that "threadolet" because you would prep your threaded fitting the same way before welding anyway. No?
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#4

Re: Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/23/2012 11:55 PM

Bonney Forge is one manufacturer; I don't know if they are made that small, though.

Another possibility could be a 1/2" socket weld tee, with a female threaded insert for the 1/4" branch. (In socket weld fittings, an insert is basically the same as a bushing.)

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#7
In reply to #4

Re: Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/24/2012 9:01 AM

Your solution might be easier and neater!

At least you dont need to prepare the 1/2" pipe for the threadolet.

GA
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#8
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Re: Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/24/2012 9:07 AM

Thanx. I've just made an inquiry at Bonney Forge.

Right, a bushing is what I'd use if I could weld the threaded T inline. I didn't know there was a comparable fitting for weld fittings. I haven't seen one, anyway. I'll have to keep looking for a 1/2" to 1/4" welded insert.

If I can find such small threadolets, I think it would be a toss up as to which is easier. With threadolets I could use just a single straight pipe with 6 threadolets spaced along it. With a fitting, I wouldn't have to drill the pipe, but I would have to assemble 6 T's.

You all are very helpful. Thank you again.
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-A-
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#6

Re: Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/24/2012 8:21 AM

Thread-O-Let looks like the way to go.

The reason butt welding a threaded fitting is not allowed:

The minimum cross section area thickness is less on a threaded fitting as opposed to a butt weld fitting, because the threads are cut in from the "back" side. The outside appearance may be the same but there is less metal there.

Back welding a threaded fitting is allowed but only to seal the connection. This in no way is allowed to improve the strength calculations.

Someone please let me know if I am in error.

-A-

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#9
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Re: Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/24/2012 9:21 AM

Ok, so you've confirmed that it is, in fact, not allowed... as I thought.

As a side note, the steam pressure in this system will never exceed 30 psi. And, it is a machine that is going to India.

I wonder if any of our Indian friends here have any insight on this particular code over there.
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#10
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Re: Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/24/2012 10:01 AM

Well in that case . . . you can count on the steam containing 10% caustic vapors, having 20% saturation, being held at 1.5X MAWP, ZERO PMQC, and an assumed 200 years MTBF. Oh, and it will be installed with hammers. No problem.

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#11

Re: Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/24/2012 12:15 PM

This is what you are looking for.

http://www.mcmaster.com/#cadinlnord/4587k51/=izmyb5

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#12
In reply to #11

Re: Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/24/2012 1:11 PM

By George, that is precisely what I'm looking for! I'd looked in McMaster, of course... but was not using the correct terminology. Thank you ronseto, and everybody else. Problem solved. Ordering a dozen right now.
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#13

Re: Is it Allowable to Butt Weld Threaded Pipe Fittings?

08/25/2012 7:58 PM

i don't think i would unless your sure it can with-stand years of vibration, temp changes, pressure changes, ect
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