Tig backfeeding

[Kevin Morris]

Guys, I've got a question for you on backfeeding carbon steel pipe. I'm doing 3" schedule 80 running an 1/8" gap with 3/32" filler wire at 110 amps. I'm feeding off of the bottoms of my 3:00 and 9:00 tacks backfeeding. My problem is that everything goes really smooth until I get close to tying into my 3:00 and 9:00 tacks. At this point I loose my wire no matter how much I feed. Like the bead doesn't want to tie into the tack. I've feathered the tacks and tried about all I can think of. Any help would be appreciated.

[shovelon]

Sounds like you are loosing your arc to the tack side. Can you jump over to the tack side and weld conventionally and push the weld into the root and tie in the weld? Are you using an amptrol to increase the amps at all on demand?

[Kevin Morris]

No sir no amptrol. I can come out and face feed and make it. Sometimes I go to a dip method from the outside right at the tack. I guess the problem is that the tack is cold so keeping that continuous feed up onto the tack makes it difficult. I'm thinking that maybe feathering the tack sharper may help. Thanks for your reply. I really appreciate any help.

[Noel]

Guys, I've got a question for you on backfeeding carbon steel pipe. I'm doing 3" schedule 80 running an 1/8" gap with 3/32" filler wire at 110 amps. I'm feeding off of the bottoms of my 3:00 and 9:00 tacks backfeeding. My problem is that everything goes really smooth until I get close to tying into my 3:00 and 9:00 tacks. At this point I loose my wire no matter how much I feed. Like the bead doesn't want to tie into the tack. I've feathered the tacks and tried about all I can think of. Any help would be appreciated.

Well Kevin, if we could see through your eyes...?

I'm going to offer up some advice.

Keep in mind I'm no expert, I'm good, just no expert.

But without being there... watching...it's kind of hard.

I do a bit of over thinking so hear me out. Remember the process leads itself to basically one of two approaches, both require seeing clearly, and some understanding of what are some basic principles.

1) Take a flash light and hold it at varying distances to a wall. That's to represent your tungsten and your heat spread profile. In out tilted this way or that...Depending on how you tilt the torch it changes. That's affecting heat input to the surface and the filler rod. And yes, that's a whole new level of science.

2) Blow through a straw into a glass of water. Vary that distance and straw size. That's voltage and deeper stuff then you probably don't want me to discuss. Getting the puddle more liquid then mush makes it harder to control, and it takes longer to solidify.

3) Heat sink. Material and it's ability to absorb heat. Bevel and land. How hot's the pipe when you tie in? 3/32 rod size only chills so much,

and how smooth you feed the rod to help control filling and chilling.

Of course the rods tip surface and angle pays a role in controlling heat along with torch inclination to the surface. Ideally, you want the rod to flow and fill but depending how far in or out of the groove it's placed will effect root build up.

4) Amperage. It's better to develop patience when your young . What I'm getting at is it's about controlling heat to get the metal to flow. There is a difference between a flow and a run. Think of an egg yolk.

Also...

Your heating three surfaces in a solid state too a point of liquid mush and controlling how they flow together, or blend into each other by controlling the temperature to maintain it.

Your doing it by understanding and applying the principles of what the process allows through process variables, it's not about burn it in there.

The filler rod should be small enough to melt easily, yet large enough to be used to control the heat building in the puddle. I'm sure things are good with that fit up but a 5/32 gap and 1/8 rod? Just curious, you can't use bridge tacks?

4) Remember that heat input changes based on Tungsten profile 3:1/6:1

, arc length, stick out, nozzle size and gas flow.

As well, with out a visual of what you, your body type, positioning, torch inclination, ability to feed rod, your movements, It's a guess if any of this will help?But it all comes into play in solving a guys issues, whether it's that location of a joint, or any other spots on a pipes circumference that gives a guy trouble.

Because I'm not 100% on what you describe, If I get it wrong please offer corrections.

If your feeding from the back off the tack, progressing in a vertical motion and as you progress find you are leaving the tack tied in improperly, I would suggest a few reasons why.

1) Not getting a clear picture from the top of the build up melting when tying in?

2) Suck back from over heating pulling off the tack? Lower heat, travel slow, push slightly more or less?

3) Poor torch angle and heating an elliptical puddle? Is the rod end melting into a droplet?

4) Poor body position too the joint limiting torch angle over comfort, does your torch angle remain consistent?

So...When you weld do you melt droplets and dab dab dab? Or do you watch a continued stream slowly flow and blend off the rods end?

Oh yea...one last thing. you mention 110 Amps. At some point ask your self, Why not 105? 95? What's your hurry?

Anyways...good luck with that action. Not saying it makes sense, just saying.

[Kevin Morris]

Thanks Noel. I'm trying a few different approaches. I'm feeding off of the bottom side of the 3:00 tack in my scenario and having a hard time running up onto the tack with a continuous flow instead of having to drip weld the last 1/4" but I know it's hard to advise me without seeing what I'm doing. Thank you for your time .