Manual welding of narrow groove pipe

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Has anyone here had any experience with manual GTAW of narrow groove pipe (particularly 3"+ wall thickness)?With our extended J prep, we're looking at about .560 diameter to move around in, with a cup size of .4375" OD.  We can fit a WP-125L torch down in there, but are concerned primarily about gas coverage with the 5/16" ID cup.  We're wondering whether the confined joint space and backpurge will shield adequately.  If it doesn't, we need to find a supplementary shielding gas setup, which will be difficult yet again due to the confined joint space.  These joints are typically welded orbitally, but we're looking to develop a manual procedure for certain high/low mismatches, tacks, and repairs.  We're willing to give it a shot, but we don't think its ever been done before at the thicknesses we're exploring.
Reply:Have you got a photo?  I'm having trouble picturing this in my head.I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.
Reply:I can't see any reason why it won't work.  The groove will actually HELP your shielding.  I'm thinking it should be easy...just time consuming.
Reply:I'm wondering what kind of torch restrictions you're dealing with by calling it a confined joint ? Since you're an old chassis welder I'm not even going to guess since you're used to tight spots. I keep a WP-25 on the shelf for tight work...it's essentially a flexible pencil torch and I normally have a #5 nozzle on it (13N09). That little sucker has saved me a few times !!Last edited by olddad; 08-07-2008 at 09:10 PM.Reason: spellingAnything worth doing is worth doing RIGHT
Reply:It's an extended J-prep.  .25 radius at the bottom, and it tapers up two to the top of the material, which on our P91 steel is up to 5" wall.  Picture the image on the right with virtually no root opening, and a 2 degree bevel on each side.There is virtually no room to manipulate the torch, other than moving it down the length of the groove, just a few thousandths on each side.  That's why we needed the tiniest head we can find, with a 5" neck on the torch itself just to fit in the joint.  Nobody makes a ceramic cup long enough to reach the bottom of the joint, and standard torches won't come close to fitting down in there.
Reply:Sorry, I've never seen anything that would be narrow enough to go beyond 2 - 3 inches.You could make a gas tube for each top side of the wall but that still wouldn't help with torch manipulation. Someone has to make a special purpose torch that would work, might just have to spend a couple days on the phone ??Anything worth doing is worth doing RIGHT
Reply:We've got a torch that would fit, its just a matter of whether we can get it to work.  Normal trailing shields aren't an option because A) they won't fit, and B) if we made one that would fit, it would obstruct the welder's view even more.  If need be, we may get a camera to snake through a gamma plug and let the welder see the backside of the root.  It's also coming into question whether or not the equipment and the weldor can take the heat.  5" wall pipe and 400 degree minimum preheat is a lot of radiant heat for a guy to take in, and these torches are made typically for fine detail work, not root passes.
Reply:Supe,obviously you already know much about narrow groove welds, but are you crazy, or just overly optimistic, or just way more skilled than I can imagine?.   I don't tolerated being told that something cannot be done, but I've got to question your logic here.I have not done narrow groove welds myself, but have seen several live demonstrations with orbital equipement at the AWS annual conference.  For people who have never seen it, here is a link to an ArcMachines video of narrow groove TIG and other nice orbital welds. http://www.arcmachines.com/videoOnline/index.html  This was recorded with very $ophisticated video camera and welded with a very $ophisticated weld head which has the coolest little oscillating tungsten electrode mechanism to achieve sidewall fusion.  I hate to guess what the entire system would CO$T!  I am guessing that getting good shielding is only the first problem that leads to many other problems for manual deep groove TIG.  In machine welding of a deep groove it is difficult to oscillate the arc to the sidewalls to achieve sidewall fusion, and ArcMachines has a good solution.  This is much more diffiucult to do manually with gas nozzle that barely fits into the grrove.  Add on top of that, trying to feed wire into the puddle when you can barel see the puddle, arc, sidewalls, and filler because the goove is deep and the nozzle is in the way.I am picturing a torch with a gas lens and stubby nozzle outside the joint, the tunsten stuck out 3" or whatever to get into the joint, another guy holding a long narrow nozzle down in the joint connected to a gas lens,  An I'm picturing a big mess, hitting the tunsten on the sidewalls, hitting the tunsten with the wire, lack of fusion, so forth and so on.You might just spend $50,000 (just a wild guess) on the ArcMachines camera system, and have a nice clear magnified image of the weld on a monitor, while you attempt to manually manipulate the torch, filler, and shield setup, but that would be crazy.Sorry, but IMHO this is unfortunately a very expensive job for a very special orbital machine like the ArcMachines unit.
Reply:Pulser, thank you for the link. Amazing welding process and machine. If I win the lottery, I'll get one so we can play with it!!!And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Pulser - We've actually got a torch coming from Weldcraft on Monday.  5" neck, and the entire cup fits down in the joint.  We're not worried about sidewall fusion, as it will only be used for root passes on that J prep with a very thin land, mostly.  I was able to get ahold of a few other engineers whose companies have successfully welded narrow groove roots manually.  Hot and fill passes were where they had nightmare RT issues.  By the way, we have four of those fancy ArcMachines hotwire orbital units already   We've got even more standard ArcMachines orbital units, as well as Magnatech flux core orbitals.  The company has a 16 billion dollar work backlog right now.  We're definitely not doing the manual thing out on a whim.Just to give you an idea of why we're attempting this, our last powerplant project was non-union.  2 orbital welds out of 1400 needed repairs, and that ain't bad.  Fast forward to one of our current projects, this time a union job.  What do you know, 7 out of 7 orbital welds need repairs.  They had a max .020 high/low, we ran roots in our test facility PERFECTLY with a .080 mismatch!  That was over a full lands width offset.  Orbital welding, faster production, less need for manpower/hours on a union job... I think you can see what's going on here.Basically, if we can get a manual setup to work JUST for root repairs, it will save us a LOT of time and money over sending one of our really good orbital guys out to the jobsite to try and do an orbital repair on the fly.
Reply:You may not even need to manipulate the torch side to side much.  You may be able to depend on the heat to spread the puddle.If you can't get a torch in there, and you can't manipulate it well enough to get a good weld, you may just need to make a wider bevel.Perhaps you can work a repair procedure that allows a wider groove than the original weld procedure.
Reply:Engloid - That's what we're hoping, and are looking into pulsing in the repair to get a higher peak amperage in so we don't chance a lack of root fusion.Unfortunately making the groove wider isn't a viable option either.  The narrow groove was chosen not just for increased deposition rates, but also for certain heat input requirements (ASME Section IX).  Not only would we have to go and qualify a number of different WPQ's, but it's also virtually impossible to manually open up a narrow groove bevel face, as there is just no way to fit anything other than a large diameter wafer wheel in there.  The time it would take to try and do that, especially on our 5" wall thicknesses, we would be better off splicing in a new section of pipe with newly machined preps.
Reply:Originally Posted by SupeEngloid - That's what we're hoping, and are looking into pulsing in the repair to get a higher peak amperage in so we don't chance a lack of root fusion.
Reply:Originally Posted by pulserSupe,obviously you already know much about narrow groove welds, but are you crazy, or just overly optimistic, or just way more skilled than I can imagine?.   I don't tolerated being told that something cannot be done, but I've got to question your logic here.I have not done narrow groove welds myself, but have seen several live demonstrations with orbital equipement at the AWS annual conference.  For people who have never seen it, here is a link to an ArcMachines video of narrow groove TIG and other nice orbital welds. http://www.arcmachines.com/videoOnline/index.html  This was recorded with very  video camera and welded with a very  weld head which has the coolest little oscillating tungsten electrode mechanism to achieve sidewall fusion.  I hate to guess what the entire system would CO!  I am guessing that getting good shielding is only the first problem that leads to many other problems for manual deep groove TIG.  In machine welding of a deep groove it is difficult to oscillate the arc to the sidewalls to achieve sidewall fusion, and ArcMachines has a good solution.  This is much more diffiucult to do manually with gas nozzle that barely fits into the grrove.  Add on top of that, trying to feed wire into the puddle when you can barel see the puddle, arc, sidewalls, and filler because the goove is deep and the nozzle is in the way.I am picturing a torch with a gas lens and stubby nozzle outside the joint, the tunsten stuck out 3" or whatever to get into the joint, another guy holding a long narrow nozzle down in the joint connected to a gas lens,  An I'm picturing a big mess, hitting the tunsten on the sidewalls, hitting the tunsten with the wire, lack of fusion, so forth and so on.You might just spend $50,000 (just a wild guess) on the ArcMachines camera system, and have a nice clear magnified image of the weld on a monitor, while you attempt to manually manipulate the torch, filler, and shield setup, but that would be crazy.Sorry, but IMHO this is unfortunately a very expensive job for a very special orbital machine like the ArcMachines unit.
Reply:Engloid - Point noted on the pulse.My mistake on wording it as deposition rate, you got what I meant.I will have to double check, but I believe our PQR's pertaining to Section IX for  P91 specifies heat input limits in joules.  I'm not sure if changing to a wider bevel would affect this.For removing material from the root, we have large diameter, narrow abrasive wheels, as well as specialty burrs that can reach down in the groove.It just boils down to saving a LOT of time and money if we can get by making small repairs manually.
Reply:P91,  do I take it that that is carbon?What is the size of the repairs generally?I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.
Reply:P91 is 9 1/4 chrome.  It is subject to more code requirements and heavily controlled PWHT and bakeout temperatures than carbon steel.  Repair length depends on the portion of the root that did not have adequate penetration/did not completely consume the land, but typically are no more than a few inches in length on large diameter pipe.
Reply:So that will rule out the O/A then Obviously there's enough money kicking around to look at some options.A good sized purge box with a nice big window for the welder to see through so then no shroud needed so there's room to move the arc around.Cheap option, use a more standard setup and run a blunt tungsten so you get extra coverage (make a bigger weld pool)  an extra purge hose running along the weld pushing argon toward the area it's needed in because of the long stick out. Hell I'd love to be able to have a crack at something like this I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.