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PostPosted: Sat Oct 24, 2009 10:05 am 
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Location: Merkel, Tx
Hi All,

I have been welding for quite a few years. Mostly repairing and fabricating things for my own use. However, I am certainly no expert (in fact I am still a relative newbie to welding). I normally hang on the general discussion forum, but I think this question is more appropriate here.

Can you successfully weld oilfield line pipe with a mig welder? If so, do you need to use any special wire or specialty gas? I have a bunch of old (rusty) 2-3/8 oilfield tubing that is lined with some kind of plastic material (pvc?) that I would like to use for barbed wire fence corner posts. My welder is a Miller 175 mig.

thank you in advance for your kind assistance

Tim

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PostPosted: Sat Oct 24, 2009 11:02 am 
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Joined: Sun Jun 08, 2003 11:52 pm
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Location: NW Indiana. Close to Lake Michigan S. tip
IMHO the 175 will be too light, and will not drive the heavy wire you need. Also the rust if heavy at all will make the job a nightmare.

Mig is best with sheet and new (clean) material, and can run circles around stick for speed and consistancy.

I believe Stick with 7014 or the trademarked 'rustbuster' rod is a better try for heavy fabbing of wellpipe and brackets. We call 7014 farmer rod. it is forgiving in reasonably small amounts of contamination, as is Rustbuster, that will tolerate some surface rust that will escape cleaning.

Best advice is set some things up, and see how a trial goes. 'Hit'em widda hamma' an see what kind of forced destruction it will take. It may serve your purpose, not being too demanding.

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Ignorance can be cured with information. Stupidity is cured by Darwinism.

My computer beat me at chess, it was not so good on Kickboxing.


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PostPosted: Tue Oct 27, 2009 10:18 am 
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Location: Merkel, Tx
Thanks Steamin10,

I was not ignoring you, I was hoping to get some other opinions. Anyway, thank you for your comment.

I have a 250 bobcat that I could use to weld this with some 7014 or 7018 rod, and may resort to that. I went by the welding store yesterday and posed the question. The counterman said the that the 175 should work fine, use the largest wire it will push and since I am working outside, use flux core wire.

I think I will cut some pieces, weld them up and beat the crap out of them with a large hammer. Will see what happens!!

Tim

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PostPosted: Tue Oct 27, 2009 12:09 pm 
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Small mig machines, expecially those used for sheet metal, usually run in short-arc mode. This is where the wire actually touches the workpiece and the spark and current melt off the wire. This usually gives a cold weld that is not very strong. When welding this way, the welding often sounds like a buzzing, popping noise.

What you want to do is run the current up as high as you can to get into a spray arc mode. The wire melts off before it reaches the workpiece and the welding is a smoother noise. You also get base metal melting.

Push it hard and you should do fine.


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 Post subject: fence welding
PostPosted: Fri Oct 30, 2009 6:18 am 
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Location: WV
Depending on the type of joint (butt, tee, miter), I would burn out the plastic on the inside, scrub it with a wire brush, and give a good preheat to the metal which will aid in penetration. Use a self shielded fluxcore wire, as these typically have much better penetration characteristics than solid Mig wire. Spray transfer GMAW requires pure argon, not the typically used CO2 mixes. This isn't a critical weld, so don't worry about the preheat too much. Don't get it red, but around 300 - 400F will extend the thickness range your machine is capable of.


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PostPosted: Sat Oct 31, 2009 10:32 pm 
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Location: Merkel, Tx
Hi all,

I went by the welding store yesterday, ask for some NR-211-MP. They said they don't have it (they are a Lincoln dealer). He sold me some Prostar E71T GS instead. The NR-211-Mp was recommended by another poster on another forum.

This wire worked great. Set the machine on 3 with a feed of 60 (as recommended in the chart in the machine for 1/8" steel) and ran the nicest bead you could ask for. This was on 2-3/8 schedule 40 steel pipe joining another 2-3/8 pipe at a 22.5 degree angle. I did spend some time with the fit-up. I used Tubemiter to create a template for the angle.

I attempted to cut the joint in two with the band saw. It cut about 1/2 way through then just quit cutting. I then attempted to grind through it with an abrasive chop saw. No luck here either. I was able to grind through it enough to see that the weld penetration was very good. No discernible line between the filler and base metals.

I then attempted to beat it apart with a hammer. No luck here either. I think this is going to work just fine.

Thanks,

Tim

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PostPosted: Sun Nov 01, 2009 8:01 pm 
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Location: Merkel, Tx
I fitted and welded this joint yesterday. Figured out photobucket today. Thought I'd send a picture.

Image

Tim

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PostPosted: Mon Nov 02, 2009 8:47 pm 
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Location: NW Indiana. Close to Lake Michigan S. tip
EEGADS! Rusty and crusty pipe! I would hav eground away ALL the rust. But you got a smoooth weld with little spatter. Teh spatter would be a giveaway to rusty metal inclusions blowing the weld up. You dont seem to have many.

You can have my seal of approval if you promise to clean the weld area better.. :lol:

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Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.

Ignorance can be cured with information. Stupidity is cured by Darwinism.

My computer beat me at chess, it was not so good on Kickboxing.


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 Post subject: Rusty pipe
PostPosted: Mon Nov 02, 2009 10:42 pm 
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Joined: Mon Jan 14, 2008 7:49 pm
Posts: 281
Location: Upstate NY
That picture shows really claan pipe by my standard. I'm welding up the breaks in snowmaking pipes that froze and split a few years ago. The splits are about 12 inches long running length wise and the pipe opens maybe 1.5 to 2". I put a chain around the pipe then use the spreader jaw of a porta press plus a sledge hammer to push the pipe back so the slit is mostly closed. 1/8" 6010 rod seems to close the gap inspite of the rust, but I will have to grind that surface and go over it with a stonger rod. Any suggestions are appreciated, as I have lots to do and it is getting cold.

Tom


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PostPosted: Sat Nov 07, 2009 3:31 pm 
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Location: Merkel, Tx
Hi Guys,

A little more on welding oilfield pipe with a mig. I am using this old rusty 2-3/8” oilfield pipe with a Teflon or possibly a Phenolic Epoxy internal coating (thanks Ken). I used a small grinder to cut a groove about 4” back into the mouth of the pipe so I could remove the plastic before cutting. I set up the first piece of pipe (inside the shop) to cut the the saddles on each end. In about 2 seconds the shop filled with a cloud of greasy black stinky and irritating gas.(':shock:') It took me about one second to drop my stuff and get out of there. It took about 3 hours to clear that stink out of the shop with the shop door open and a 3000CFM evaporative cooler blowing. Then I went back to the internet and looked up the MSDS for Teflon (PTFE) and Phenolic Epoxy. I really couldn't tell much from the MSDS sheets except that the fumes from these materials when burned are toxic.

What to Do? Like any good redneck, I set up outside with the evaporative cooler blowing at my back. Also was up wind from the cut. These are pipe sections ranging from 4'-8' long with a saddle on each end. As I am making the first cut, the black smoke is sneaking up on me from behind. It is rolling out of the other end of the pipe which I can't see as I am cutting. I wound up plugging the back end of the pipe with a paper towel to solve that problem. Well, I get all of the saddles cut with no more fume incidents. On the last pipe, I wondered what would happen if I didn't clear away the internal coating before cutting. I knew that with OA, the cut would be horrible as the plastic melted into the cut. But I was using Plasma!! Turns out that the Plasma burns right through the pipe and plastic coating as if the coating wasn't even there (except for the smoke). Also the hot pipe melts the plastic (in a horizontal pipe the plastic runs away from the cut) back about 4-6” from the cut. Hopefully it will be less of an issue when I go to weld all this up.

Conclusions about working with old oilfield pipe lined with a plastic coating (at this point in the project):

Prepare the pipe ends for welding outside in a well ventilated area.

Stand upwind from the cut.

Set up a fan or some other large CFM air source to blow the fumes away from you.

Wear a respirator if you have it (I did not, may modify this conclusion from deathbed).

Using a plasma cutter to make saddles in pipe relieves the need to remove the plastic coating prior to cutting.(':D')

Tim

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