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!

 

[nybirdman]

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

Tack up using the 1/8" rod as a gapping tool(bend in a "u"shape.)
As you finish the tacks the joint will shrink slightly giving a perfect gap for 1/8" filler wire.Yes I would "Tig" all the way out,it's only 2-1/2" pipe.
I have done thousands of joints like this over the years,some 100% X-Ray.When you start to weld up if you have everything right you will see a "fish eye",tells you that you have perfect penetration.

 

[Gary Fowler]

All advice is OK if you plan to roll it out. If done in position using an 1/8" rod, you will need to tack up with a larger than 1/8" rod because you have to insert your rod inside the pipe on the bottom and use the rod to hold the puddle up. I would use a 5/32" gap for 2" pipe and for 6" and above you may need to go to 3/16" gap. I have had to use 1/4" gap on 24" and larger and still sometimes have to use a grinder to open up the gap a bit on top. Otherwise you will have a concaved root pass. This is OK for homebrew welding but it wont pass XRAY.

I think a 1/8" gap is fine for TIG on 2" pipe if you can quarter weld it while always having the weld area on the top quarter. You may need to go to a 3/32" filler rod for the last quarter since the gap will be getting pretty small by that time.

 

[Jorville]

Tack up using the 1/8" rod as a gapping tool(bend in a "u"shape.)
As you finish the tacks the joint will shrink slightly giving a perfect gap for 1/8" filler wire.Yes I would "Tig" all the way out,it's only 2-1/2" pipe.
I have done thousands of joints like this over the years,some 100% X-Ray.When you start to weld up if you have everything right you will see a "fish eye",tells you that you have perfect penetration.

Thanks for the tips nybirdman, I know I am rusty at this. Most of my Tig experience is on aluminum. I figure on doing some refresher welding on 3/16" flat bar beveled and open root before I start this. Four of my joints will be 1-1/2" pipe. Many years ago I gas welded pipe and that all looked good. Changing the heat source to something that won"t spit once in awhile should be a big plus.
Where I worked we had a crew come in and weld maybe 1-1/2 " stainless pipe maybe schedule 20 for a 1200 PSI line. That welder did not gap the pipe. It was a tight butt weld with argon purge. I asked him how he got 100% penetration and he said he watched for a fish eye. Could I ask a dumb question, and say what is a fish eye. Or is it too hard to explain?

 

[Jorville]

All advice is OK if you plan to roll it out. If done in position using an 1/8" rod, you will need to tack up with a larger than 1/8" rod because you have to insert your rod inside the pipe on the bottom and use the rod to hold the puddle up. I would use a 5/32" gap for 2" pipe and for 6" and above you may need to go to 3/16" gap. I have had to use 1/4" gap on 24" and larger and still sometimes have to use a grinder to open up the gap a bit on top. Otherwise you will have a concaved root pass. This is OK for homebrew welding but it wont pass XRAY.

I think a 1/8" gap is fine for TIG on 2" pipe if you can quarter weld it while always having the weld area on the top quarter. You may need to go to a 3/32" filler rod for the last quarter since the gap will be getting pretty small by that time.

All this welding will be on the bench. I will be able to position it any way I want. Thanks

 

[LAFarm]

Never had much luck with x-ray on anything without a decent gap. Especially when welding in place on the bottom portion. 6G position with TIG, the gap was critical as need to insert rod through gap and actually "hold" the puddle up with the filler rod so stringer bead did not sag and be below flush. The fish eye you are referring to I suppose is the same thing we called a "keyhole" when running stringer bead on alloys like chrome, inconel, monel and titanium pipe. Basically, you hold the torch where the arc is breaking down the bevels on each side and the rod is fed above this "keyhole" opening whild the weld filler metal flows off of the rod, around the "keyhole" and deposited on the backside of the "keyhole". If you feed too much filler, the "keyhole" closes up and the bevel stops breaking down. Only solution is to stop and grind the gap back open. Stick welding 6G can use tighter gap and when heat set right, pretty much all the "fire" is on the inside of the pipe on stringer bead. Sometimes, TIGing sch 5 stainless, when we could roll them out, would fit tight with minimal land on the bevel and could fuse the joint dragging a 3/32 rod for filler ahead of the puddle allowing just enough extra metal to flow off the end of the rod to flush it out before running a cap. Always use argon purge on alloys or inside of stringer will "sugar". Different metals have different weld characteristics and need different techniques to make x-ray quality welds. Hope this helped a little.

 

[Jorville]

Never had much luck with x-ray on anything without a decent gap. Especially when welding in place on the bottom portion. 6G position with TIG, the gap was critical as need to insert rod through gap and actually "hold" the puddle up with the filler rod so stringer bead did not sag and be below flush. The fish eye you are referring to I suppose is the same thing we called a "keyhole" when running stringer bead on alloys like chrome, inconel, monel and titanium pipe. Basically, you hold the torch where the arc is breaking down the bevels on each side and the rod is fed above this "keyhole" opening whild the weld filler metal flows off of the rod, around the "keyhole" and deposited on the backside of the "keyhole". If you feed too much filler, the "keyhole" closes up and the bevel stops breaking down. Only solution is to stop and grind the gap back open. Stick welding 6G can use tighter gap and when heat set right, pretty much all the "fire" is on the inside of the pipe on stringer bead. Sometimes, TIGing sch 5 stainless, when we could roll them out, would fit tight with minimal land on the bevel and could fuse the joint dragging a 3/32 rod for filler ahead of the puddle allowing just enough extra metal to flow off the end of the rod to flush it out before running a cap. Always use argon purge on alloys or inside of stringer will "sugar". Different metals have different weld characteristics and need different techniques to make x-ray quality welds. Hope this helped a little.

Yes you helped, I did not know fish eye and key hole were one and the same. I had always used the term key hole and thought fish eye was something in the puddle itself. And I never saw any difference in the puddle so I had to ask. Thanks

 

[chuck172]

Yes you helped, I did not know fish eye and key hole were one and the same. I had always used the term key hole and thought fish eye was something in the puddle itself. And I never saw any difference in the puddle so I had to ask. Thanks

Fish eye and keyhole are note the same.

 

[Jorville]

Fish eye and keyhole are note the same.

Did you make a typo? you have NOTE the same. If they are not the same would you be willing to explain the difference, or what is fish eye/

 

[chuck172]

the keyhole is the burning out of the bevel in a round (keyhole) shape. You usually keyhole with stick welding. When you see the keyhole forming on the root pass with usually 6010 rod, you are assured that your penetrating the bevel and land into the ID of the pipe.
The fisheye happens with tig welding. It is a defect, usually a small hole or crator that formed by pulling out of the puddle too quickly, rapid cooling of the molten puddle. This can be fixed by using a foot pedal, or running the puddle out of the weld zone and extinguishing it there.

 

[Tractor Seabee]

I am not a TIG welder but have been around a lot of it and worked as a fitter for TIG welders on SS and other special alloys. In my younger pipefitter days I was a certified ASME pressure piping and pressure vessel welder using both O/A and manual arc. We never saw any advantage to TIG welding mild steel. For production work it is too slow. Up to 4" schd 80 pipe O/A was a one pass weld and arc it was 3 passes for butt welds. I could run circles around arc welders using O/A on pipe up to 4". Socket weld fittings were a PIA with O/A. Over 4" it can be done but it is too hot for me and was a 2 pass job. There were times though when we did O/A on large pipe when it was not feasible to set up for arc on a couple joints. One time I was required to O/A 6 and 8" vertical runs every 10' for 4 stories in position; all horizontal welds which are the hardest position to control the puddle, especially with a #6 Victor short bend tip. To each his own. Glad that is long behind me.

Ron