Q: Tig Root on 3" pipe

Greets all & good morning. would like to preface this by saying I'm not a full-time weldor. Used to do alot more but now I like to pick and choose my work -- 99% of the time its TIG -- typically Al & SS structural -- not a pipe weldor!

close friend of mine is a contract weldor and asked me to lend a hand running tig root pass on a lot contract (he'd follow up behind with a 7018 cap).

welding 3" sch 80 pipe on a bench. These are elbow assemblies made of 1 elbow, an 8" extension on each end, and 2 flanges. I only needed to weld the elbow/extension.. not the flange.

I didn't need to bring anything except gloves and a helmet -- everything else would be provided.

(They supplied an old scratch-start aircooled torch kit wired to the oldest DC machine I've ever seen -- but thats a different story)

anyway, I found 300 of these assemblies already "preped" and ready to weld. each was spot welded and they used 3/8" rounds (with 3/4" mig beads!) in four places around each joint -- every

90 degrees to set the gap -- which meant I could only weld 'round the joint about 1.5" before I'd have to stop and grind that 3/8 round out and fix the bevel that the mig "tack" filled.

man this is getting long winded -- sorry.

bottom line is: is a 3/8" gap pure madness on 3" pipe?

i started welding these flat on the table (1G position) but couldn't get a consistent profile on the inside penetration. (all they had was 3/32" filler and 3/32" tungstens).

Next, I flipped them up on their flanges and welded each joint in a 2G position and I got much more consistent results with a great profile on the inside.

One satisfactory completed piece, with only the root tig weld, on two joints (less than 20" of weld bead) took me exactly 45 mins (including the grind time).

Q: is it my lack of experience with pipe welding? is a 3/8" gap on this size pipe normal? in the end the welds looked good, inside and out -- got a cupwalking ripple pattern even though I had to float it (don't know how to walk) because of the CHASM I had to cross.

there were no prints / specs / etc to follow.. just "here's your pile of stuff -- weld it up for us"

thanks for stick'n through this. :) Tony

Reply to
outofstepper
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We laid a bunch of 3" sch 80 lines, 100% x ray, in a small field and the pipe fitters gaped the joints about 1/8" (1/8" 6010 root and 7018 for hot and cover passes). We didn't use a bent rod, just the "that looks about right" gage system. I would think that TIG would be the same, or even less.

Bruce-in-Bangkok (correct Address is bpaige125atgmaildotcom)

Reply to
Bruce in Bangkok

Thanks Bruce.

These were all beveled by the way -- I was told that ahead of time and thats what I found -- 60 degree with maybe an 1/8" root face -- a bit hit and miss, I think these were ground using a jig and angle grinder.

I expected to find no gap at all..

-Tony

Reply to
outofstepper

I thought you were saying the joints had a 3/8" gap.(which I thought a lot). The pipe we were welding was beveled (generally with an 8" grinder) clamped and down hand welded. I will say that the welder and the pipe fitter were part of the three man team so if the gap "wasn't right" it got changed and I'm sure that they varied from crew to crew but the specs (as far as I can remember) called for 60 degree vee with

1/8" root -- but it was quite a few years ago.

From what you say, you must be spending all your time getting a good looking bead. Is it hourly pay or piece work?

Bruce-in-Bangkok (correct Address is bpaige125atgmaildotcom)

Reply to
Bruce in Bangkok

IIRC, the root opening should be the size of the filler rod as a very general rule of thumb. It is difficult when you have to pick up the next step from someone who obviously doesn't know what you do or how you do it. Since you got in on this late, and didn't get to go to the planning meeting, that makes it bad. If it's all beveled, a 3/8" root sounds excessive.

What's your responsibility in this? If one of these leaks, is it going to be blamed on bad joint design, an excessive root, or YOU? Sounds like you got a bad design, questionable equipment, and not a lot of instructions.

So much for "friends".

Steve

Reply to
SteveB

In fact, thats why I'm posting here and not "working" :) Took a few days to give their inspector a chance to look at them -- apparently he pops in with no real schedule.

Its hourly pay, not piece -- but I wanted to make a good impression.

Wanted to bring my own equip for day 2 but was told not to (guess the pay's always the same and no point putting hours on my own tools?) I did get real used to pulsed TIG -- but with this 4 foot gap I don't think it would've helped me any.

I'm told that these will be "Xray'd to 5%" -- I can't tell you what that means.. maybe 5% of the whole lot?

Thanks for the input so far -- glad to know I'm not alone.

Evening all,

-Tony

Reply to
outofstepper

If I understand your description correctly the 3/8" round stock has been placed IN the gap and forcing you to try to fill the now extremely oversize gap space.

This seems time to call for the old weldor's joke. 'You had better order up some 'range rod' to fill those 'wide open spaces'.

IMHO, a 3/8" gap is "pure madness", (or at least inexperienced fitters).

An excessive gap (and IMHO this is far bigger than just excessive) will lead to poor root weld quality as well as appearance and is likely to result in failure of any QC & x-ray. This will of course be blamed on the weldor. It will also lead to slow welding and the joint will probably be overheating due to the slow forward progression. (It must be very challenging to attempt this work without? a foot control) It will also consume a LOT more rod than necessary. The weldor will also be blamed for being so slow and for the poor weld appearance. The wide gap will also result in the cap being too wide (and probably too high) and also taking too much time and rod.

IMHO, it is up to the weldor to direct the fitter as to what gap/land he requires. A 1/8" gap / 1/8" landing is most common but some (like me) prefer a 3/32" gap / 3/32" landing, it depends on many factors like how good the factory prep is and shipping damage and out of round or hi-low mismatch of pipe or fitting dia.

Round stock is often placed in a pipe bevel so that the tack weld can be placed up on the FACE of the bevel. If the round stock is too small then the tack will spoil the land and if it is too big will spoil the top edge and make for a poor looking cap and easily lead to an undercut cap edge. The correct size 'bridge tack' will use round stock that will allow the tack to be placed in the middle of the bevel so that it can be easily removed without damage to the root land or to the top edge of the bevel. 1/4" or

3/16" is more common for bridge tacks but it depends on the pipe wall thickness and bevel angle and shape.

I do not know of any weldors with your patience. I would have 'dragged up' and made the fitters cut the joints apart and fit them properly. There is no way that I would even attempt to fill a 3/8" gap, especially on 300 bench pieces (600 welds?). In a field repair situation, I would cut the pipe shorter, insert a pup and make two welds.

In this situation I suspect that the flanges are slip on type and if the pipe has already been cut (and especially if welded to the pipe stub) then the final part will now be 1/4" too short, or will have an unacceptable fit inside the flange, (too much setback can cause turbulence and pipe wear). IMHO, the elbow welds should have been made first, then the flange could be fitted for final adjustment of size and square. It seems like the makings of a real problem for somebody as the whole job may now be scrap. IMHO, those experienced pipefitters (and weldors) that were too expensive to hire will be starting to look like a bargain. I would respectfully question whether anyone on this crew has the qualifications or experience for this job.

Good luck, but be sure you don't carry the blame for this FU. IMHO, much better to just drag up and go home.

Just my .02, Usenet advice is worth every penny you paid.

Reply to
Private

Let me get the facts straight. You're not a full time weldor, but are working on a project that is going to be x-rayed. Then are given materials without a lot of directions or explanations.

I'd go to the powers that be and ask exactly what they want you to do, and what the expectations are. No sense spending time and money on something that is going to be unacceptable because of parameters not explained to you. And no sense getting chewed on for not doing something right when you weren't told anything about it in the first place. And maybe not getting paid for pieces you've done that don't meet unstated expectations.

I'd get it all understood before I went any further. It's time to stop and ask.

Steve

Reply to
SteveB

Maybe I left out a critical piece of info --- I'm out here in Europe (Italy) .. going on 6 years now with a long over-due repatriation this summer.

Nothing really works quite 'right' out here -- its bizzarro world.

The kind of place where they hand you a tig torch that needs the backcap duct taped because there aren't any more around.

Maybe the guy before me chewed the back off when he saw what they wanted him to do.

Again, I agree with everyone here -- its day 2 now that I haven't returned to their shop as I'm waiting for answers to just those questions you've asked.

Wonder if my buddy isn't still grinding down that first cap.

Thanks again ... I just wanted to make sure I wasn't the crazy one.

-Tony

Reply to
outofstepper

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