Welding pipe with a HUGE GAP

admin

I am having a little trouble when the gap is too big, on my fit up. I'm welding carbon steel pipe, with a TIG root and hot pass. The schedules vary between 40 and 160. I like a 1/8 rod to just fall through the gap and float the rod in. however when the gap is any bigger than a heavy 1/8 I seem to have trouble , on the bottom half of the pipe. The puddle always starts to droop and ends up on my tungsten. I've tried running between 70 to 90 amps and still have this problem. we recently got in some 5/32 rod but I have never used this for my root, not sure what to run at, or if it will help.These are all x ray welds so they have to be good.  any advice would be greatly appreciated.
Reply:Learn to fit your own pipe. Why do you have such a big gap?? IF you aren't fitting your pipe, get rid of the fiiter that is fitting your pipe, and learn to fit yours. When I encounter gap that is a little wide for one wire, try to lay two wires in there..
Reply:When I work with a fitter , I can get the gap I want.  These joints are already tacked. I'm coming behind to make the root and hot.  I just seem to have a little trouble ,on the bottom, with a big gap. We have 5/32 but I have never run that for my root.. what kind of amperage should I start with. Do I have to be concerned with excessive reinforcement using such a big rod? Also when I use 1/8 why does the puddle drop an end up on my tungsten?  I.E. rod placement or torch angle
Reply:Originally Posted by tiginatorWhen I work with a fitter , I can get the gap I want.  These joints are already tacked. I'm coming behind to make the root and hot.  I just seem to have a little trouble ,on the bottom, with a big gap. We have 5/32 but I have never run that for my root.. what kind of amperage should I start with. Do I have to be concerned with excessive reinforcement using such a big rod? Also when I use 1/8 why does the puddle drop an end up on my tungsten?  I.E. rod placement or torch angle
Reply:On huge gaps I will run a TIG bead on one side and then the other and so on until the gap is small enough for me to fill it in.
Reply:Originally Posted by VPTOn huge gaps I will run a TIG bead on one side and then the other and so on until the gap is small enough for me to fill it in.
Reply:Yeah, I'm not a pipe welder, I am sure they have rules to follow.
Reply:lol ya that wouldnt fly unfortunately in the pressure world. I generally use a 3/32 rod for all my tig roots wether it be stainless, inconel, chrome. I also use a heavy 3/16" gap. Try using your rod and base material as sources of heat control. I free hand my roots and when all the stars align..... which they almost always do because im a FREAK for a perfect fit up i focus my entire arc inside the bevel and kiss each knife edge with a slight weave. you can really move doing it this way. BUT if we encounter a fitup say in the boiler that isnt ideal, ill either play with my heat accordingly or run my weave further up the side of the bevel and spend less time in the center of the joint. When in this situation, i add a good 1/2" of the filler weave down to bottom edge and back up quick, add half inch or so, and weave back down and quickly back up, you kind of turn your hand into a robot.
Reply:when I'm putting the root in the bottom, of the pipe, I hold the rod High up, in the gap, closer to the inside of the pipe. if that makes sense . it just seems that the puddle always wants to droop on to my tungsten. maybe I'm running too hot, I don't know. with a 3/16 gap I run 1/8 rod at about 80 amps. Having trouble with that I don't know why
Reply:I like using a large gap, 5/32 heavy with a land. 1/8'' filler wire and backfeed wire from the inside, helps with bad ''hi-lo'' etc. I use this method on everything from testing, to sch40 pipe to heavy wall high energy pipe, cs,chrome etc.
Reply:Could you elaborate on the backfeeding technique please
Reply:Originally Posted by tiginatorCould you elaborate on the backfeeding technique please
Reply:Originally Posted by tiginatorCould you elaborate on the backfeeding technique please
Reply:Originally Posted by Pressure_Welderlol ya that wouldnt fly unfortunately in the pressure world.
Reply:VPT - this is just my opinion but when doing any sort of pipe work at our power plant we take alot of time to ensure a perfect fitup, because in all reality your trying to eliminate any possibility of weld failure, it severely sucks running a tig root at a set amount of amps having a perfect 3/16" gap your used to turn into 1/4" or even worse shrink up on you to 1/16" ! It starts to get fairly complicated when your dealing with high energy steam piping with a heavy wall that goes through severe heat cycles you have to take that in account for your fitup "expansion and contraction of the pipe" % of elongation allowed etc.
Reply:ot Originally Posted by joelwelderinstead of walking over wire from outside of joint and pushing wire into the molten pool relying on ''surface tension'' your actually sticking wire inside if pipe through the joint, then you just walk over filler metal, or you can dab filler metal into puddle. it enables you to get mad reinforcement on inside of root and takes up for piss poor fitups.
Reply:Originally Posted by tiginatorotOk this sounds similar to how I put a root in. I don't like to soak it in, I float the rod inside the gap and feed a little at the same time. However I'm not feeding from the back. Is this the same thing as backfeeding or do I need to change my filler rod angle?
Reply:like Pressure Welder said, if you puddle starts to drop out on you, you need to carry your puddle farther out on the bevel. Or you might be too hot, also.If you finger the bottom you can back your tungsten out a little to keep the puddle off it when it starts to droop, that makes it easier to wash out wider, too.
Reply:So I tried washing up onto the bevel more and that helped a lot. I tried backfeeding also but no luck with that. Too much reinforcement. Guess I'll have to keep working on that
Reply:Originally Posted by Pressure_WelderVPT - this is just my opinion but when doing any sort of pipe work at our power plant we take alot of time to ensure a perfect fitup, because in all reality your trying to eliminate any possibility of weld failure, it severely sucks running a tig root at a set amount of amps having a perfect 3/16" gap your used to turn into 1/4" or even worse shrink up on you to 1/16" ! It starts to get fairly complicated when your dealing with high energy steam piping with a heavy wall that goes through severe heat cycles you have to take that in account for your fitup "expansion and contraction of the pipe" % of elongation allowed etc.
Reply:Cut the tacks on the wide side, put a jack under the wide side and close up the gap, retack and weld.
Reply:Boiler repairs are quite different then anything you see on pipestands.  Often 10 or more tubes come preassembled in a panel.  It might take a 5 man rigging crew a number of hours to get this panel within an inch of it's mate.  Fitters work their magic and get it close enough to realize what the gap will look like.   Problems such as existing material deformations, bend errors or heaven forbid a fitter mistake can result in uneven or large gaps.  With single tubes it might not be too much of a problem to slip out the tube and hand dress a parallel gap.  With a large panel this could suck up a lot of man hours.  Superstar welders say leave it as it is.  They weld off the roots and they're guaranteed to get on the next shutdown.
Reply:oldsparks is correct! its a whole new world of pipe welding/fitting really no room for error, not to mention everything has to be xray quality. speaking of boilers were currently into unit #5 for a shutdown all waterwall and corner tube inspections this time around and a little bit of primary superheater work, quite alot of soot blow erosion, pad welding corner tubes, one particular wall needs two tubes replaced from the 3rd floor to just below the economizer, big job! lots of fitting.  "gotta love when the operators dont notice a soot blower stuck inside blasting the wall for 36hrs"- walkeri dont agree with your method at all for a number of reasons, your introducing unessecary stress's into the joint before you even start your weldment as your now forcing it into position to make it "weldable" as your making up for a bad fit up. Another key reason is now that you've "jacked" the pipe into a weldable root opening, think of what youve done 10-15-20ft down the line where the next joint or fitting may be? your pipe will most certainly not be true and garunteed your gap will be even worse than the last.
Reply:Try out some way to reduce the huge gap in your pipe. As shortbusWelder said try fitting your own material to the pipe. I believing by placing two wires in the gap, your machine will be able to function appropriately.welding protective clothing