pipe welding

[Jorville]

I want to make a hot water heating manifold using 2-1/2 inch pipe for part of it. I have bought 2-1/2" butt weld caps and butt weld reducing couplings. The butt weld fittings are already beveled and have a nose on them. I plan on beveling the pipe to match. I am planning on Tig welding the root pass (open root) then using 3/32" 7018 on the final pass. I have never tig welded pipe before. When I was allowed to weld pipe I always put the root pass in with 1/8" 6010, cover passes with 3/32" 7018. But that was always with 4" and larger pipe.

I am thinking or guessing that I can gap the butt joint 1/8" and tack it in 4 places and put that root weld in with no filler rod. Am I on track or is done differently?

 

[Shield Arc]

I am thinking or guessing that I can gap the butt joint 1/8" and tack it in 4 places and put that root weld in with no filler rod.

Boy you are light years ahead of me if you can do that with out filler!:thumbsup:

For open root Tig welding like a 37 1/2 degree bevel. About 1/32 inch land. With 3/32 inch gap. I use 1/8 inch filler, at around 95 to 100 amps.

 

[nybirdman]

Your set-up is perfect;I would TIG all the way out;root pass with 1/8" and the rest of the way out.

 

[Jorville]

Boy you are light years ahead of me if you can do that with out filler!:thumbsup:

For open root Tig welding like a 37 1/2 degree bevel. About 1/32 inch land. With 3/32 inch gap. I use 1/8 inch filler, at around 95 to 100 amps.

Give me a brake Shield Arc, I said I have never done it before and was guessing or thinking. The land on my fittings look like 1/16" and 1/8" gap is definitely a little strong for that. Back in the early 70's in welding school I saw a 6 inch pipe set up and a partial weld put in with a tig machine. Same a you mentioned 37 degree bevel and with 6 inch most likely a 1/8 inch land. The gap could have been 1/8', don't remember. The weld I saw on that pipe joint was perfect, same height same width, ripples same distance apart, did not appear to have had any filler applied. Sort of looked like he might have walked the cup. And that is why I thought it was possible to do as I thought. Might be kind of hard to walk the cup with a joint so narrow as I will have. Now I am thinking a 3/32" gap, or maybe a 1/16" gap. I am still thinking and guessing. I will have a couple of practice joints made up for heat setting and a little practice. Maybe I will get a couple more suggestions.

 

[Jorville]

Your set-up is perfect;I would TIG all the way out;root pass with 1/8" and the rest of the way out.

Are you saying 1/8" gap or 1/8"filler as Shield arc suggested? And Tig the entire joint?

 

[Shield Arc]

I wouldn't go with anything less than 3/32 inch gap. Reason being, the gap will close up on you as you weld. When it closes up you have to take a zip disk to open the gap up. Or you will not get any penetration.

99.9 % of the time I walk the cup on the root, with the lay wire technique. The hot pass, and fill I free hand and dip the filler.

With 37 1/2 degree bevel a number 7 cup rides perfect in the joint. I also take a mil file and knock off the sharp edge on the outside of the bevel so the cup will walk real nice.

 

[Jorville]

I wouldn't go with anything less than 3/32 inch gap. Reason being, the gap will close up on you as you weld. When it closes up you have to take a zip disk to open the gap up. Or you will not get any penetration.

99.9 % of the time I walk the cup on the root, with the lay wire technique. The hot pass, and fill I free hand and dip the filler.

With 37 1/2 degree bevel a number 7 cup rides perfect in the joint. I also take a mil file and knock off the sharp edge on the outside of the bevel so the cup will walk real nice.

Thanks for the tips Shield Arc

 

[Shield Arc]

You may want to practice this a few times. There are easier welds, than open root pipe with Tig.

 

[chuck172]

I like a 1/8" gap, feathered. 1/8" filler rod. I walk the cup.
Then a tig hot pass, then stick it out.
This is really advanced pipe welding.

 

[Shield Arc]

This is really advanced pipe welding.

Just being an X structural hand, it is really hard for me. Especially 6-G! When you have to be able to weld with both hands!