Long story short I have this project going for a client who owns a large sugar house. We are building Copper manifolds that hold 14, 3/4" pipes and will have about 50psi of steam going through them to heat the sap up. The project is going very well so far but I've ran into a couple snags. To paint the picture for everyone I have bought new copper plate that I have waterjetted and bent to assemble the manifold the copper pipe we are using is older pipe from the early 90's I'm guessing. I have cut the pipe off the old manifolds that were Brazed together and have been using them in the new style manifold being built currently. I'm using a machine with plenty of AMP's so heat isn't an issue. The shielding gas is pure 100% argon, The filler material is deoxidized copper rod I bought from AirGas. the tungsten is E3 (Purple band). This issue is its not becoming air tight for some reason. The welds looks good and the penetration is great. some of the pipes will weld 90% great but then I hit a spot were I get lots of bubbling and it doesn't seem to want to melt together it almost makes an near impossible hold to fill for some reason?? Can anyone help me out with this? I've read some pipe contains oxygen that isn't meant to be welded. Maybe that's the issue?
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Thread: Copper Project
02-02-2014, 12:44 PM #1Junior Member
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- Feb 2014
02-02-2014, 01:23 PM #2
Possible outgasing once pipe is almost completely sealed because the pipe is heating up. Blows away sheilding and molten metal. That's what came to mind. Weld up 90%, allow to completely cool then quickly weld up other 10%. Good luck, hope this helps.
Last edited by ja baudin; 02-02-2014 at 01:29 PM.
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02-02-2014, 01:51 PM #3Senior Member
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- Sep 2009
I wonder if the old pipes are part of the problem. Perhaps there is oxide in there.
I don't typically backpurge copper, but this case might be a good application.
I have not tried to make watertight welds in copper in years. Many years ago I had trouble with it, but I am a better welder now, with better equipment.
For welding, you are theoretically supposed to use 102 alloy, not the common 110 alloy. The 102 has less oxygen. Not sure about pipe alloys, but that could be part of the problem.
The Copper Deveolopment Association says:
Seamless Copper Pipe
Copper pipe is almost pure copper manufactured to the requirements of ASTM B 42 - Standard Specification for Seamless Copper Pipe, Standard Sizes. It may be manufactured from any of five (5) copper alloys (C10200, C10300, C10800, C12000, C12200) that all conform to the chemical composition requirements of alloys containing a minimum of 99.9% Copper (Cu) and a maximum of 0.04% Phosphorous (P).
02-02-2014, 02:42 PM #4Junior Member
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- Feb 2014
To avoid warping I only weld about 1/4 of each pipe at a time to reduce the amount of heat put into the front plate of the manifold. So the heat shouldn't be the issue I wouldn't think since I let everything almost completely cool before doing the next 1/4 of each pipe.
As for backing gas I also thought of this but not really sure how I would seal something off to add a backer. Maybe over the years some of the acids they use to clean the pan each season has affected the pipes. Weird thing is that I had this same problem yesterday when welding a 3/4" elbow to a new pipe even without using filler rod I ran into some problems with bubbling and not being able to melt the material in certain spots even at 270amps which is very hot for K copper pipe.
I'm really thinking it is the oxygen content in the pipes/fittings.
02-03-2014, 06:19 PM #5
It would be easier to make it out of black pipe fittings