Welding Duplex pipe

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Hey guys any tips for welding duplex pipe ?  I have to root, fill and cap a 6 inch and 2 inch sch 80.  Not sure of the sch on the 6 inch but told it will take 14 hrs to root, fill and cap.   All this is a job test...   I have no stainless experience either.   They have let me practice for a few days.  Interpass temp has to be kept below 300deg FZeronx 100 is the rod we are using on the root, ER329N is whats being used for the rest..Any advice would be good.  Also how much different is it than welding stainless ?  The foreman who is a boilermaker has told me there isn't much difference...Journeyman / Red Seal Welder (What a useless test)Miller CST 280Miller XMT 350Miller 12vs XtremeEvolution Evo 28 mag drillEvolution 380 Dry Cut saw
Reply:contact Fieldres on youtube. or on here if hes still on he has all his duplex Inconel titanium stainless all the precious metal certs.~1987 Lincoln Sa-200~~1978 Miller Big 40~ (restored) ~and everything inbetween~
Reply:Id love to contact him but he has left his youtube channel and taken down a lot of his videos.  Yea the one on Duplex is gone I checked...   I also don't believe he visits here anymore.   Some guys on here gave him a hard time about his no helmet downhand root pass video and I don't believe he comes here any more either.   Really unfortunate for the people here who actually want to learn..   He is a good guy.  I know a guy here in the Pipefitters union who has worked on the same site as Travis he said he was a good guy...Come on guys there has to be other guys here who have welded Duplex.   Its for the offshore.  Very high pressure im toldJourneyman / Red Seal Welder (What a useless test)Miller CST 280Miller XMT 350Miller 12vs XtremeEvolution Evo 28 mag drillEvolution 380 Dry Cut saw
Reply:I've welded Duplex 2207 alloy before.  It's sluggish like stainless. Severity of warping is about half way between mild steel and stainless.  The fewer passes used to weld it, the better.  But since it doesn't want to wet out, it's a pain to stack a lot of metal successfully.  14 hours sounds a little crazy; but I've only worked with sch 40.  waiting for interpass temp to drop below the max can take a lot of patience. 10 minutes between passes on sch 40 happened occasionally.  Just long enough to get bored, but not quite long enough to get into working on something else.Duplex is even more heat sensitive than stainless.  Too hot is bad(because the joint and HAZ cool too slowly) and too cold is just as bad(rapid quenching of the joint and HAZ).  Standard 2207 should have a max interpass of 250F and no preheat is necessary unless there's condensation on the pipe.  If you get the heat input wrong the duplex won't have the corrosion resistance that it's designed to have.  The joint could look great, but will fail if the service environment is corrosive.  What's the end use for the piping your working on besides being high pressure?Backpurge should be very good with as little O2 contamination as possible.  Using an Oxygen monitor is best; just checking to see if the purge vent gasses will blow out your lighter won't cut it...Super Duplexes are even worse, 200F interpass and tighter control of the back purge O2 content.What are you planning on using for shielding gas and backpurge?  Just straight Argon?Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Originally Posted by A_DAB_will_doI've welded Duplex 2207 alloy before.  It's sluggish like stainless. Severity of warping is about half way between mild steel and stainless.  The fewer passes used to weld it, the better.  But since it doesn't want to wet out, it's a pain to stack a lot of metal successfully.  14 hours sounds a little crazy; but I've only worked with sch 40.  waiting for interpass temp to drop below the max can take a lot of patience. 10 minutes between passes on sch 40 happened occasionally.  Just long enough to get bored, but not quite long enough to get into working on something else.Duplex is even more heat sensitive than stainless.  Too hot is bad(because the joint and HAZ cool too slowly) and too cold is just as bad(rapid quenching of the joint and HAZ).  Standard 2207 should have a max interpass of 250F and no preheat is necessary unless there's condensation on the pipe.  If you get the heat input wrong the duplex won't have the corrosion resistance that it's designed to have.  The joint could look great, but will fail if the service environment is corrosive.  What's the end use for the piping your working on besides being high pressure?Backpurge should be very good with as little O2 contamination as possible.  Using an Oxygen monitor is best; just checking to see if the purge vent gasses will blow out your lighter won't cut it...Super Duplexes are even worse, 200F interpass and tighter control of the back purge O2 content.What are you planning on using for shielding gas and backpurge?  Just straight Argon?
Reply:Interpass temp as per procedure is 300 degrees F.. Straight argon for back purge.  No oxygen monitor,  I asked if they had one and they said to use a lighter..  I know I know...  As for end use I do not know for sure.   All I know is its going offshore and will be under some EXTREME pressures.  There is a 10 inch joint in the shop that has taken 36 hours to weld and it isn't finished....  The wall thickness on the 6 inch for my test is 5/8" to 3/4"..So if I can weld this I shouldn't have any issues welding stainless ??   I have never welded stainless pipe before.  All this is new to me.   But they have been willing to work with me to get me to the point of passing the test so I can work for them....Taz00  what do you mean by avoid a hot pass ?   The guys are running a hot pass.  Procedure states that the root go in at 100-120 amps, next pass at 105-125 and all others 135-155..a 3mm-5mm gap is what is allowed as per procedure.  Im running 1/8 inch gap  3.2mm with a 3/32 rod.Last edited by Newfie_1986; 03-14-2014 at 03:13 PM.Journeyman / Red Seal Welder (What a useless test)Miller CST 280Miller XMT 350Miller 12vs XtremeEvolution Evo 28 mag drillEvolution 380 Dry Cut saw
Reply:This is not a hot pass.A hot pass is what is done eg in pipelines where you start immediately after finishing the root pass and perform the hot pass at high amperage almost remelting the root with the purpose of annealing it and forcing whatever slag inclusions are still there to float to the surface.What you describe is simply a second pass.
Reply:I just saw that you will not have an oxygen monitor. Make sure you have good back purging otherwise you will have problem with the root.Back purging should be maintained for at 2-3 layers.
Reply:Ok so we are on the same page on the hot pass thing.  Not a hot pass unless its being used to burn out issues in the root.  The guys are calling it a hot pass.  Oh well...   Yes I will be back purging until I have about 1/4" of fill put in or a little more...Thanks guysJourneyman / Red Seal Welder (What a useless test)Miller CST 280Miller XMT 350Miller 12vs XtremeEvolution Evo 28 mag drillEvolution 380 Dry Cut saw
Reply:As for fit up on this stuff what do you guys have ?  or prefer ?   What way to you run your roots ?  Dip from the outside ?  Dip from the inside ?  Continuous feed ?Im dipping from the outside,   although I did dip from the inside for a bit but it turned into more of a continuous feed from the inside.  Kept loosing track of the filler metal.On the test I will just dip from the outside it seems to be the way that works best for me now.   But that could change...Journeyman / Red Seal Welder (What a useless test)Miller CST 280Miller XMT 350Miller 12vs XtremeEvolution Evo 28 mag drillEvolution 380 Dry Cut saw
Reply:Good luck on your test.I did a lot of PQR's on duplex pipe a few years back for the Ormen Lange project. Biggest pipe was 18" with a thickness of 70mm.Most was welded using GTAW+SMAW+SAW but a PQR with GTAW and SMAW was made for the places that could not be welded with sub arc. It took A LOT of time. IIRC operating pressure was something like 400bar.I can't find any pics from the duplex but here is pic from some carbon steel fitting on the SAW machine that had almost the same thickness.
Reply:What im welding is tig all the way,  which is why its taking so much time..   That stuff looks huge.   wouldn't want to tig that all the way out...Journeyman / Red Seal Welder (What a useless test)Miller CST 280Miller XMT 350Miller 12vs XtremeEvolution Evo 28 mag drillEvolution 380 Dry Cut saw
Reply:It is not the tig that will slows it down. It the waiting for the test piece to cool down.LOL, tig was used only for the first 2 layers, then a few layers with electrode to bring the thickness to a point we could put it in the submerged arc machine.The duplex pipes were slightly thicker than the one in the photo so you get the idea Don't let the material scare you, do a few test runs and you will figure it out. Do not stay too long in the same place, keep moving like with all stainless steels.
Reply:Well I have it pretty much down now.  Have been running it most of the week getting a feel for it.   It actually isn't too bad to run.  Was just curious how others do it...  And yes it does heat up fast,  which is why it will take so long to weld.   The guys in the shop are only putting on thin passes they have found its easy to get lack of fusion if you try and put too much metal in there.   Is lack of fusion on fill passes really that big of concern on this stuff with tig ?  Im using a dip technique on the fill not a lay wire...Journeyman / Red Seal Welder (What a useless test)Miller CST 280Miller XMT 350Miller 12vs XtremeEvolution Evo 28 mag drillEvolution 380 Dry Cut saw
Reply:Newfie_1986I have nothing to contribute to your inquiry.  In my junior days I did stick/open, and later, TIG, stick,  chill-ring . . .My last pipe episode was: QA root-fit, on 10" S/S, SCH 160, for TIG . . . in '81.Tested at 6000 [400 bar], operated at 3000 [200 bar] on a Hydrogen Sulfide 'Cracker'.There-after I wandered into fabrication.  My experience in pipe & metallurgy is just enough, to follow everything posted; and . . .I would like to thank: All Contributor, for their focus, depth of experience, effort to dialogue, and above all - the substantive information conveyed.  This is the most comprehensive and coherent treads in a long time.  While I cannotweld at your level, you have advanced my understanding of how it is actually done;and this info will benefited, 'those that are learning, and can do'.Kudos to all.OpuspsNewfie_1986 - You are still on the gaff - explain your time-zone?.Last edited by OPUS FERRO; 03-15-2014 at 12:05 AM.Reason: Conformation of 2.5 GMT
Reply:Well I passed the test and im now on the project.   Apparently this pipework is going on the bottom out on the grandbanks to send gas up to the oil rigs.   I asked the engineer with Husky what kind of pressure is on the pipework he told me 10,000 PSI.   All welds get x rayed,  Ut'd and then the pipework gets hydrotested as well, to test the pipe integrity...   Its for the South White Rose Extension Project..Once this is done we will be moving on to fabricate the flare boom for the Hebron GBS,  im told there is lots of regular stainless pipe to be welded for that.   Lots of experience for me :-)Journeyman / Red Seal Welder (What a useless test)Miller CST 280Miller XMT 350Miller 12vs XtremeEvolution Evo 28 mag drillEvolution 380 Dry Cut saw