Seeking answer to technical welding question please

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I've seen on a video or two, two weldors utilizing two independent welding machines on the same piece (ie pipe, beam, or whatever...). Or, perhaps it was one machine utilized with two "stingers" and one shared ground clamp.  I'm not sure what I saw exactly.  Anyway, is there any special precaution(s) needed to keep the independent welding circuits from causing any trouble from occurring between the two machines?   I don't know electrical theory very well, so please forgive my ignorance.  Why doesn't (or does it?) the flow of electrons through one machine (machine-A) travel through the other machine's (Machine-B) ground clamp, through the machine itself and out the burning  electrode, thus adversely affecting  the performance of the other or both machines while both running simultaneously?  I hope that made sense.  Is there a simple explanation or necessary precaution to take before lighting off both machines on the same work piece?   Second question, can machine-A run on "AC" while machine-B runs "DC" current?  Or do both machines need to run on the same polarity for simultaneous operation?Thanks in advance.Lincoln Power Mig 216Lincoln AC/DC-225/125Miller  625 X-Treme PlasmaMiller 211 Forney 95FI-A 301HF 91110Victor Journeyman O/PMilwaukee DaytonMakita  Baileigh NRA Life Member
Reply:I am no electrical engineer but its common to have a welder hooked electrode positive running stick and another welder hooked up electrode negative running innershied with no problems. The only way I could see an AC machine hooked up would be an AC TIG with high frequency hooked up and a DC source say running a spoolgun on an aluminum frame and that would not be good because of the high frequency waves would raise hell with the electrics on the other machine.Miller xmt304,  Miller S22 p12, Miier Maxstar SD, Miller 252 w 30A, Miller super32p12, Lincoln Ranger 9, Thermal Arc 181I with spoolgun, Hypertherm 10000 ,Smith torches. Esab 161lts miniarc.
Reply:It is done all the time with no problems, as long as the machines are in good working order and hooked up properly. The reason that power does not flow from one machine to the other is that the output terminals of the machines are isolated from the primary and from earth ground. Remember that even though the work connections of welders are erroneously called "ground", they are not supposed to be connected to the earth ground.Other than incorrectly wired equipment, there is a potential hazard if one machine is connected DCEN and the other is connected DCEP. In that case, the voltage between the two stingers will be twice the voltage of one machine. This rarely happens in practice, however.JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:You guys have me scared to death. Here is some inverter on inverter violence.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:http://weldingweb.com/vbb/showthread.php...ltiple-weldersEd Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:She doesn't get "Sun Burn" I got a pretty good burn just using my little 120v Lincoln wear short sleeves one day.Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Originally Posted by Broccoli1She doesn't get "Sun Burn" I got a pretty good burn just using my little 120v Lincoln wear short sleeves one day.
Reply:Originally Posted by 7A749Slowhand said it was only happening with certain combinations of certain machines. He had said his XMT conversion had a rough time when a Miller Pipe Pro inverter based machine was on the other side of the pipe from him. It was over my head, but he had some significant issues with his arc because of it IIRC.
Reply:Originally Posted by 7A749Slowhand said it was only happening with certain combinations of certain machines. He had said his XMT conversion had a rough time when a Miller Pipe Pro inverter based machine was on the other side of the pipe from him. It was over my head, but he had some significant issues with his arc because of it IIRC.
Reply:Originally Posted by Silicon-based.................................. Remember that even though the work connections of welders are erroneously called "ground", they are not supposed to be connected to the earth ground..........John
Reply:Originally Posted by gnm109Please clarify this statement. I just looked at my Syncrowave 200 Technical Manual in the electrical diagram area. The ground clearly shows a ground path connection from the unit's cable to earth. The Millermatic 252 manual shows the same configuration. The electrical in my barn shop was wired professionally to code about 35 years ago. It has a dedicated 70 amp welding circuit that has never had a problem. It's wired so that the welding machines are connected to the panel ground. There is also a neutral in the panel but that's only used for 120 VAC circuits and doesn't connect to the welders. Since the machine's ground is a safety ground, I was under the impression that it would have to be connected to the earth ground. I'm just curious - not taking issue.  Thanks in advance.
Reply:Originally Posted by Broccoli1The WORK clamp is attached to the work- people call it Ground but it is not the Ground wire or grounding you are thinking about that the machine uses for Input power.
Reply:One time I found myself on 36" x70 .375wt xray pipe for texas eastern across the pipe from a rectified a/c machine.  Think it was a commander 300.  I had a stock 200d that was almost new.  Mine welded good until he would start welding then my arc would start blowing most of its molten metal off the pipe down my shirt collar.  Those machines didn't work well together.  Haha.I call it cross feed.
Reply:Two old generator Lincoln's will pretty much equal out.  One will gain while the hotter one will loose. But its only noticeable to a certain extent. I guess it depends on just how crossed up all those cables are, the condition of the cables, and probably the condition of each of the machine.  I'll also say it depends on the heat you are running.  The hotter, and the shorter arc length, then the more noticeable it is.  More time also shows it more, least it does to meThrow in two completely different technologies then what.  Probably real noticeable.  Lol.  It probably takes less heat, less of being all  crossing up, and less time to notice it.  Least thats how I see it anyway.I have welded with guys that has told me (besides me seeing it too) that because my machine was across the pipe that it helped their arc. (their voltage I would tell them). Of course I could feel them in there with me. Who couldn't. Parasite. HahaThis is all old school stuff.  You didn't cross leads all up in the day.... unless you wanted to fight.  Some of them I'd say knew why, but,  some I'd say, did not.....With my xmt-200d machine I use on pipeline today I don't cross leads.  And if I do allow a cross lead then I haft to like you. Haha.  If I don't kinda like you the answer is probably going to be no.  I'm going to run my big knob kinda on the low side and if you got an electronic dig controlled machine too then Im going to request that you do the same too.  If you refuse and tune in something like 280 and 80 on the dig then I might just flat out refuse to weld with you.  I'd probably try a couple joints, but I'd bet I stop all the madness....  Unless..... its tearing u up worse than it is me!!!!  Then I might be doing just fine over here. :HahaAs for answering the o.p.  The arc completes the circuit through the material back to the machine.  The arc characters are in the other half,  the machine half.  The pipe is just a dumb piece of meta. It cant think, l.  We are holding one of the wires.  The other half, the controlling half, is up there. In the machine.  We drawing through in reverse polarity, like most of us use.  But no matter which it is, the heat is on the other end  .  Of that wire. The machine.Last edited by slowhand; 02-15-2014 at 03:34 PM.
Reply:I ran into problems when the ground clamp on the DC welding machine fell off.  The welding current was travelling back through the AC machine.  These were old machines being used for tack welding.  It had me scratching my head wondering where all the welding heat had gone.  I could still run a bead though.
Reply:"This is all old school stuff. You didn't cross leads all up in the day.... unless you wanted to fight"Reminded me of when I was in old school, literally.Back in welding school, all the welders were situated in a row along the front wall of the class room in a group.  Every welder work lead was connected to a common conductor welding table about 50 or 60 feet long.  Only curtains and panels divided the table into individual booths.  All of our trees (where we mounted our welding plates) where based on that table.  But the electrode conductors ran overhead above the curtains and traveled to the respective booth that specific welder was powering.The overhead conductors were solid steel bars about 3/4" dia and were supported by insulator cradles, but the bars themselves were not insulated or covered.The classes were done on a continually "refreshing and graduating" system where you would have students about to graduate welding in the same room as newbies.  The "upper classmen" would all "gang bang" a newbie by putting him in the booth farthest down the line and then when the newbie struck an arc, the older students would reach up in unison and touch their electrode tips to the bar that was feeding the newbie's booth.  The resultant flash and melt in the newbie's booth was quite impressive.  And of course, just seconds later, every student in the room was just a weldin' away on their lessons as innocent as can be (if you can weld while stifling a laugh).
Reply:I was running a 16" gas main line through the rafters of a light bulb plant one time (up on scaffolding) and found my heat was really reduced for some strange reason. I was using that contractors lincoln 250 ac/dc box and i had that thing really cranked up man. (any pipeliner can imagine my frame of mind). The owner heard me gripping about my lack of heat and stopped me from welding. He wanted to know if i was trying to blow up his welding machine or what. The ground clamp wasn't even hooked up. I was grounding through the electric cord. Hahaha.  It welded, but man was it cold. Last edited by slowhand; 02-16-2014 at 04:20 PM.
Reply:Originally Posted by slowhandI was running a 16" gas main line through the rafters of a light bulb plant one time (up on scaffolding) and found my heat was really reduced for some strange reason. I was using that contractors lincoln 250 ac/dc box and i had that thing really cranked up man.  The owner heard me gripping about my lack of heat and stopped me from welding. He wanted to know if i was trying to blow up his welding machine or what. The ground clamp wasn't even hooked up. I was grounding through the electric cord. Hahaha.  It welded, but man was it cold.
Reply:Years ago in the winter time it wasn't all that uncommon to get a call out for a frozen water line from someone that knew you had a SA200 generator welder on your rig. Some of my friends did but I always turned them down because I knew it would probably hurt my machine and that thing was my living.You had two holes in the ground where u hooked your leads up at.  Ground on one end and the stinger on the other. Then u were supposed to tune in something like 150 and 25 then let her cackle.  It's gonna take awhile.... Those windings are gonna cook man.... The heat is in between those 2 wires, and we're holding one of them.   We are arcing that electricity across. There's the heat. Right there.  Yea, the flow could heat up the base material, like the water line deal,   but... prob not much cause we ain't on a dead short, we have voltage so we need less amps.   So the flow rate should be decent and the heating ? nothing.I can't explain to the op how the electricity finds its way back to that one certain machine when many are welding at the same time on one piece, but this,  we got one of the wires in our hand and if we touch the base metal with it we are completing an electrical circuit. A circuit that starts up there in the machine.  The one we are ahold of. Last edited by slowhand; 02-17-2014 at 04:19 PM.
Reply:The electrons are like ants.  Though their paths may cross another colony's paths in their wanderings, the ants only return to the colony they went out from.How's that?