TIG Root Pass - High Pressure Pipe (carbon steel) QUESTION

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Ill just get started by giving you guys a brief description on my question.I stareted this new job and we build and maintain extreme high pressure piping systems. I've been welding for 1 year now and pipe for roughly 3 months. In school I always did my tig root with no land, but my employer wants the pipes to all have landings, preferbly 3/32"(2.4mm). Also they want all root passes to be flush, with no sucback (concavity). I went back to my school and asked my teachers what do they see most in their experience 98% TIG root with no landing they say and they like 1/16"-3/32" reinforcement. I was just wondering what type of fit up do you guys prefer.   ex. No land - 3/32" gap.       ex. 3/32" land - 3/32" gapAlso what amount of penetration inside the pipe do you guys think is ideal? I also do the lay wire technique (keep pressure on wire to avoid key hole, I also like to do a slight forward and back motion with my torch, all free handing) What technique do you guys use? For sced 80 4" carbon steel, I use a long pointed tungsten with roughly 1/2" stick out, 92-95 amps, 3/32" ER70S-2 In the 5G position. One more thing, In the 5G from 6o'clock to 8 and 4 on either side im having a problem with suck back, I believer the cause is from going to slow, do you have any opinions on eliminating this problem? Any Help you guys have in this topic is much appreciated. No Landing, 1/16" gapRoot Pass in the 5G position(horizontal pipe) 4" sced. 80 carbon steel, no land, 1/16" gap, 3/32" E3 tungsten, 3/32" ER70S-2
Reply:First off I'm no Tig welder! I like no land, 3/32-inch gap, 1/8-inch filler. To prevent suck back, with the hot pass I won't go up anymore than 10-amps, and switch to 3/32-inch filler. Attached ImagesDon’t pay any attention to meI’m just a hobbyist!CarlDynasty 300V350-Pro w/pulseSG Spool gun1937 IdealArc-300PowerArc 200ST3 SA-200sVantage 400
Reply:My preference? Generally, no land. Tight 1/8 gap ideally. 1/8 filler wire. Your amp range is about right.If you're getting suck back, go faster. This can be done if you set the cup on the bevel and wiggle the torch (similar to a motorcycle throttle) as you move forward. You can go pretty fast that way. Don't go any wider than the filler rod though or you end up washing the metal up on the sides, thus: more suck back. You can also angle the filler rod to around 45 degrees or more so it's at a sharp angle pointing into the gap. Also for the hot pass, turn it up from (let's say) 95 on the root, to 110 or 115, and angle the filler rod in at 45, putting pressure onto the root face with the filler wire as you progress. The pressure from the rod will push on the puddle, and push the root into the opening. If you do this right you'll prevent suck back and (sometimes) add/aid the reinforcement. As far as how much reinforcement... I've always gone by 1/8 is the maximum. I prefer it to look like a wedding band on the root. Between 1/16 and 3/32. Your coupons look flush. I'd take it to the bank.
Reply:Originally Posted by akabadnewsAs far as how much reinforcement... I've always gone by 1/8 is the maximum. I prefer it to look like a wedding band on the root. Between 1/16 and 3/32. Your coupons look flush. I'd take it to the bank.
Reply:I run no land 3/32 gap 3/32 filler, around 80 amps? My machine dial wasn't numbered very well in school.Miller Maxstar 200 SDPiperliner #10 Gold
Reply:1/8" wire is to big in general Imo. I  tig boiler tube all day everyday and I prefer smaller filler as it consumes better. I like a small land and I find that the land is relevant to the wall thickness.  Thinner wall less land for me, reason being the more land the slower your travel speed to insure proper wall breakdown and on thin wall stuff no reason to put anymore heat in tube than necessary by to slow of travel speed. Heavier wall can handle more amps to break down the walls better. The more comfortable feeding filler the better with small filler as you have to cram it in. On carbon in general I'm gonna root at 110-125 amps more if it's heavy wall. Make any sense?  Lol
Reply:Btw going faster typically makes suck back worse,slow down and cram the filler in there. I'll post a link to a thread with some good reading with pictures.Try the link for some good reading on small filler. http://www.millerwelds.com/resources...t-I-do-at-workLast edited by Showdog75; 10-31-2013 at 08:18 PM.
Reply:I use 5/32- 3/16 space and backfeed a 1/8 or 5/32 bead.
Reply:Originally Posted by riflecoI use 5/32- 3/16 space and backfeed a 1/8 or 5/32 bead.
Reply:Showdog what do you think is the beSt way to avoid suck back from 6-8 and 6-4. By pushing more fillet and going slower? Or angling torch different on bottom? I always thought go faster with no isolation. But what do u think about upping Amps and go even faster ?    Let me know what u thinks best way to avoid suck back on bottom?Sent from my iPhone using Tapatalk
Reply:TorontoWelder, I feel it's best to work with a little reinforcement. If it's flush, and you've broken the walls and fused the root in, you are just fine. Generally, in my experience, you want to just be able to feel a slight hump if you run your finger across it on the inside. Though it really depends on what the weld is for. Certain things can work with a lot more build up than others. Some guys on here know more about the metallurgy and code than I do though.I count boilermakers as some of the best tig welders, so I'm going to take your word for it. Most pipe I tig weld is standard, 4-8" with the occasional heavy 2". I've never had an issue going fast, but that doesn't mean issues don't occur. Rifleco... in my experience, unless you've got a jacked to hell fitup, there's no reason for a gap that big. Nor is there a reason to backfeed unless something is in your way. The last time I had to do it was with a 5/32 gap on some stainless and it was such a headache.Showdog, you live anywhere near the Knoxville area? I'm considering moving out that way in a few years but I haven't seen much work.
Reply:TorontoWelder.....Your bottom side question comes up a lot.  You haven't said whether the suckback happens during the root or hot pass.  I've always found a sufficient root buildup is the best defense against suckback.  If your procedure calls for a flat root inside then maybe this isn't for you.You say you use a forward and back motion.  This is what is described in this video.....http://welding-tv.com/2013/06/19/6g-...***-using-tig/ excellent presentation but if you check at the 9 minute to 9:30 second mark you will see the welder has a flat root, perfectly acceptable but no buildup.  I'll offer what works for me.  On a tube that is out in the open, 1/8 filler on a snug 1/8 gap.  If the tube is in a tight spot I'll change down to 3/32 with a 3/32 gap.....little more control but you have to be more confident in your feeding ability.   In either case instead of the front and back motion, I advance steadily with 'W' motion keeping inside the puddle width.  On the bottom only, feed wire at a rate that leaves an obvious convex appearance....with 3/32 filler,  around a 3 or 4 to one ratio of wire to distance.  By the time you get to 4 and 8 o'clock, your exterior should be flattened out.526641[/ATTACH] Attached Images
Reply:Hey guys Im going to post some questions I thought about at work while practicing and writing them down as they came into my head. If you guys can help in any way with any opinions please speak up.- Size of tacks. I find if i put a large tack in for example 1 1/2" / 1 3/4" for my first tack on say 4" pipe my pipe will pull dramaticaly. On one side it will open way up and on the other close tight. What do you guys find is the best way to tack a pipe, size and technique?- What is the best way to start off a tack?  Feathering vs heating up restart and adding filler whats your techniques?- Angle of torch to joint as progessing around the pipe? Do you change angles at different points for different reasons?- Sharpness of Tungsten. Do you find an extremly long point is better when putting in a root?- What do you do if the jam closes tight?  Do you run a thick grinding disk to thin down the walls without cutting right through, or just bump up the heat and take more time breaking down the walls?- Do you guys use a different size wire as you progess around a large diameter pipe? If you start off with a 1/8" gap but as you near the end of closing the root it closes to 3/32" or 1/16" do you guys drop down in wire size, or use a different technique? - Post flow when putting in a root pass. It is extremely important or not important at all?- How to put in a root pass. Do you weld quarters, opposit quarters (9-12,6-3), or halves?- When welding pipe in the 5G position (pipe fixed horizontal), do you start at a top quarter (9-12) to avoid heating up the pipe since heat rises or start at the bottom (6-3)?- Whats your techniques to avoid a pin hole on the interior of your root? - What to do if you touch your tungsten while putting in your root? Do you stop completly and thin down that spot, stop and heat that spot up a little, or do nothing at all? - What is your tollerance/maximum limit for bad pipe fit up (miss-match/high-low)?- Weave vs stringers on hot pass (STICK welding) Im finding when weaving on the bottom half im getting suck back from to much heat and going to slow in one area. What are your techniques for the hot pass? (with STICK welding) - Bevel angle, standard 37.5 degrees. More or less or dead on. What do you guys find works best and for what reason?- Do you find its better to run hotter and faster or colder and slower?- Heat input. In school I was taught if you cant hold the back of your hand over the peice of metal stop until you can. What do you guys find works best for heat input? Any help you guys have with ANY of these questions is much appreciated by me and everyone other pipe welder.  Last edited by TorontoWelder; 11-01-2013 at 06:38 PM.
Reply:That's way too many questions, I'll start with a few, first, the one about pipe in fixed 5G position. I always start at the side and go to the top, then drop down and weld the bottom. That keeps your pipe from pulling out of level so bad.They won't let you TIG the hot pass? if you must stick, use a 3/32 7018 and don't wallow around on the bottom. hi-lo tolerance is probably covered in your welding procedure. we aren't allowed more than a 1/16th where i'm at, but occasionally they may not be able to get that.I'm surprised the fitters let you put a 1-3/4" tack, you must be doing your own fitting, too. Keep your tacks about an inch, that will let you square the fit up without beating on it too much. I always feather my tacks.Pinhole or fish eye inside, feather your puddle out on the bevel. Don't just pull out of a full puddle.I like a long, needle sharp taper on tungsten, points seem to last longer that way, YYMV, that's just the way I've been doing it for 30 years.Hotter and faster, always teetering on the edge. Slow and cold is a recipe for porosity.As for gap, if you're on heavy wall pipe, you need a big gap. Try to soak a bead in heavy wall and you're gonna be doing a lot of grinding.I don't worry about heat input until it gets over the max interpass stated in the WPS(welding procedure).I don't grind a tungsten touch unless a piece breaks off in the puddle.Gap closing up, you can soak a tight gap on top, don't work so great on the bottom. Use a smaller wire, they don't block so much of the heat that you need on the pipe edges.
Reply:Originally Posted by TorontoWelderWhat is your tollerance/maximum limit for bad pipe fit up (miss-match/high-low)?
Reply:Originally Posted by TorontoWelderHey guys Im going to post some questions I thought about at work while practicing and writing them down as they came into my head. If you guys can help in any way with any opinions please speak up.- Size of tacks. I find if i put a large tack in for example 1 1/2" / 1 3/4" for my first tack on say 4" pipe my pipe will pull dramaticaly. On one side it will open way up and on the other close tight. What do you guys find is the best way to tack a pipe, size and technique?That's way too big for a tack. unless you're only putting three in. Which is never advised, but is done a lot more than you'd think. I go 3/4" to 1" maximum. Smaller if it's pipe under 4" OD. - What is the best way to start off a tack?  Feathering vs heating up restart and adding filler whats your techniques?Whichever way works for you. I usually just heat it up and go on stainless. Carbon I feather the edges sometimes.- Angle of torch to joint as progessing around the pipe? Do you change angles at different points for different reasons?The tig torch is designed at a 45 degree angle. So keep it more or less at a 45 all the way around. You will have to move, obviously, to maintain the angle. I just keep my tungsten as close to the puddle as I can get without worrying about sticking. - Sharpness of Tungsten. Do you find an extremly long point is better when putting in a root?I was always warned against long sharp points as it leads to a bigger "cone" shape to the arc. If you keep a short and pointy cone like a center punch you won't ever have a problem. But this is sort of relative.- What do you do if the jam closes tight?  Do you run a thick grinding disk to thin down the walls without cutting right through, or just bump up the heat and take more time breaking down the walls?Get used to NOT using a grinder. I've had plenty of hi-lo but never had an actual gap start to close on me. I figure turn up the heat some.- Do you guys use a different size wire as you progess around a large diameter pipe? If you start off with a 1/8" gap but as you near the end of closing the root it closes to 3/32" or 1/16" do you guys drop down in wire size, or use a different technique? If this were to happen, I'd stop and drop down a size in the filler wire. But this shouldn't happen unless your fit up or bevel is jacked up.- Post flow when putting in a root pass. It is extremely important or not important at all?If you are welding stainless or alloys, post flow is always important. If it's carbon then no. You don't want to contaminate that spot where you finally tie in the root to where you started.- How to put in a root pass. Do you weld quarters, opposit quarters (9-12,6-3), or halves?For tig welding, I weld 6 to 12 in one go. Stick welding I weld quarters. When you tig there's no reason to stop unless you start pulling your side, but if you get it done and move on to the other side you usually won't run into that. Learn how to tig with your left (or right) hand and to go from kneeling to standing while welding. - When welding pipe in the 5G position (pipe fixed horizontal), do you start at a top quarter (9-12) to avoid heating up the pipe since heat rises or start at the bottom (6-3)?6 to 12 all the time. If you weld 9 to 12 you risk opening up the bottom gap a bit, which is going to make the root harder once you get down there. I'd rather if it were to open up, it opens on top where it's on the vert or flat side.- Whats your techniques to avoid a pin hole on the interior of your root? Uh... weld it properly? I haven't had any pinhole issues, except for when I cut off the arc at the top tack. Sometimes if I just snap the torch away, I'll end up with a fisheye and pinhole. I started to break the arc on the bevel or off the filler rod. - What to do if you touch your tungsten while putting in your root? Do you stop completly and thin down that spot, stop and heat that spot up a little, or do nothing at all? I had a weld test that was xray tested, so the entire week I was practicing, if I stuck, I would grind it down. It's not always necessary if your tungsten doesn't break off, but at the same time, it can be hard to tell so it's better to be safe. - What is your tollerance/maximum limit for bad pipe fit up (miss-match/high-low)?I don't have one. I've had the pleasure of fitting my own stuff so I do it right. I would imagine, whichever gap is too small or too big for whatever sort of electrode/filler rod you have to use. - Weave vs stringers on hot pass (STICK welding) Im finding when weaving on the bottom half im getting suck back from to much heat and going to slow in one area. What are your techniques for the hot pass? (with STICK welding) Once that 6010 is in there, it's usually in there. But for a hot pass with stick I always run a slow stringer bead anyway. A slight oscillation to wash in the bevels and flatten out the face. - Bevel angle, standard 37.5 degrees. More or less or dead on. What do you guys find works best and for what reason?I use 30 degree bevels if I cut them myself. If I'm grinding the bevel, I eyeball a 45, then make it a little less. So idk. Doesn't make a difference to me unless it's specified in the WPS one way or the other.- Do you find its better to run hotter and faster or colder and slower?Never run colder and slower. Ever. For anything. Well, maybe 6010 on 2" you run colder than usual, but that's not quite the same.- Heat input. In school I was taught if you cant hold the back of your hand over the peice of metal stop until you can. What do you guys find works best for heat input? Basically. In the field you are going to spend a lot of time waiting for metal to cool down. Especially stainless and the like. Carbide precipitation is a bitch. So that's generally a good rule. If you can't touch it and hold your hand there for 5 seconds it's too hot (with your glove on!!!). Generally I take a break between passes. Root and hot pass, break. Fill passes, break. Cap. Unless the cap is 5 or more beads you'll probably pause for a bit before finishing the last few.Any help you guys have with ANY of these questions is much appreciated by me and everyone other pipe welder.
Reply:Originally Posted by akabadnewsThis is all opinion... you'll eventually learn an answer yourself for every one of them.
Reply:For pipe and walking the cup, I don't feed the wire. I lay it in the groove and walk right over it. I have the wire between 15 and 30 degrees angled into the groove. I hold it about halfway to 3/4 up from the tip that's being melted. I rest it in the groove between my index finger and my thumb and apply pressure with my thumb so the rod stays where it is and doesn't slip around. If you can't picture that.. try this. Make an L with your thumb and index. Place the rod at the corner where the two planes meet (inside corner joint >_>). Now place the tip of the rod in the gap with your palm facing the groove and press down with your thumb. That's usually how I do it for 2G, 5G, and 6G. When I put in a root pass I tend to hold it like a pencil. Pinched between my index and thumb and resting on the tip of my middle finger. That way if I need to feed it, I can without having to stop. I can just shuffle my fingers back on the rod and push it forward.It all depends on you. If I'm doing a bigger pipe and have to go from kneeling to standing I let the rod freeze and stand up and readjust my grip.The thing about doing it the first way, the way I usually do it... if you misjudge how much wire you need you're going to have to stop and let the rod freeze and slide your hand back.Either way. I feel it's better to NOT break the arc. If you have to stop, stop, but be able to do it and continue to weld.CEP, when I was in the ARNG I worked on choppers. When we were in the fab shop, the tolerance was 1/64" on sheet metal parts... we used files because grinders and shears would take too much. I was going to be one of those silly submarine pipe welders for NNS earlier this year but I changed my mind. >_>Last edited by akabadnews; 11-01-2013 at 09:15 PM.
Reply:Originally Posted by akabadnewsCEP, when I was in the ARNG I worked on choppers. When we were in the fab shop, the tolerance was 1/64" on sheet metal parts... we used files because grinders and shears would take too much. I was going to be one of those silly submarine pipe welders for NNS earlier this year but I changed my mind. >_>
Reply:I'll just throw in a few things.....these will apply more in the field than shop work.What do you do if the gap closes tight? Do you run a thick grinding disk to thin down the walls without cutting right through, or just bump up the heat and take more time breaking down the walls?........Not a thick disk.  You can run a zip-cut disk right through and reshape the bevel. - What is the best way to start off a tack? Feathering vs heating up restart?  and - Whats your techniques to avoid a pin hole on the interior of your root?......Feathering is really determined by how heavy your tacks and root are.  When you're all jammed up fighting a butt with clamps and wedges you may only be able to see an inch of the tube.  Last thing you want to risk is a light tack that may crack and pull a chunk of the bevel out.  Got to go heavy.  Got to feather it when it comes time to root out.  Like someone said earlier, proper technique on breakaway is to walk your ark up the bevel to prevent fisheyes.  Thing is that the chance of still leaving a fisheye is so critical that I feather everything to see if I can spot any indication of one.  Also by feathering, even if there is still a fisheye in there, the thinner material should guarantee that you'll burn it out on restart.