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Old 07-24-2013, 08:19 PM   #1
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having trouble brazing - not hot enough


How much heat does it take to braze a 3/4 suction line to the service valve?
I've got the valve wrapped in wet cotton, and the same for the line about 6" away. There isn't much distance from the brazing point to the wet rags on the service valve. #0 brazing tip and soft flame got me nowhere.
With a #2 tip I could get a red glow from the line but not the brass fitting on the service valve, and my 15% brazing ring inside the joint isn't flowing.
Do I need more heat, or do I need to get the wet rags farther from the joint, or what am I doing wrong?

I'm trickling CO2 into the shrader fitting on the service valve pretty slowly, but the CO2 is cold. I could try switching to argon if the CO2 is cooling too much. (don't have a N2 tank, just O2, acetylene, CO2 and argon)

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Old 07-24-2013, 09:33 PM   #2
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having trouble brazing - not hot enough


Tried again, put the rag on the line a full foot away, and tried to rewrap the valve without getting wet rag on the tube stub. Kept the #2 tip, but went for a larger flame with more O2 in it. Heated up pretty nice, got braze coming out all around, or so I thought. When it was cool and I inspected it closely, there's a bigger (looks at least 0.008") gap on the back side that didn't fill. I torched it again, concentrating on that spot but no luck. Next step filler rod from the outside of the joint? (I used a sil-fos brazing ring and it looks like it wasn't enough to fill the gap)

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Old 07-24-2013, 10:39 PM   #3
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having trouble brazing - not hot enough


Dumb question number one:

Are you using flux?
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Old 07-24-2013, 10:53 PM   #4
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having trouble brazing - not hot enough


No. I suppose the valve is brass and I should flux?

Quote:
Sil-FosŪ 15
Best alloy for general purpose copper-copper brazing in the Sil-FosŪ family. For copper-to-copper joints the phosphorus in the Sil-FosŪ product serves as the fluxing agent and no seperate flux is necessary. For brass application however, flux is recommended. For use where close fit-ups cannot be maintained Sil-FosŪ 15 works well to "bridge" gaps. Highest joint ductility of the entire Sil-FosŪ family to best withstand the stresses inherent in refrigeration applications. Slow Flow.
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Old 07-25-2013, 04:26 PM   #5
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having trouble brazing - not hot enough


Sounds like that may be your problem.
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Old 07-25-2013, 05:10 PM   #6
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having trouble brazing - not hot enough


you don't need flux as the valve body is copper or brass alloy. not sure what you mean by a filler ring? if the valve body is 3/4 and using 3/4 OD pipe there is not a lot of room for a ring and I surface weld all of them with an oxy acetylene all the time. use a hot sharp small noisy concentrated flame to the point where the wet rag may smoke at the end of the weld. that is normal and the weld is done quick and the valve stays OK. I take a wet rag and throw it on quickly to cool it and have never had problems. if you do it too slow or with a large flame then the heat conducts back down the pipe. not sure about CO2 but you only need 1-2 psi and buy a flow meter from a refrig whlslr if need be. at 1-2 psi it should not be that cold.
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Old 07-25-2013, 05:13 PM   #7
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having trouble brazing - not hot enough


Quote:
not sure what you mean by a filler ring?
New thing for the brazing challenged.

http://www.silfos.com/products/catal...-p-1-c-72.html
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Old 07-25-2013, 05:25 PM   #8
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having trouble brazing - not hot enough


back in 78" we had no such a thing. learned how to braze properly at trade school.

Taxman perhaps you need to get some scrap copper and couplings and practice w/o those rings so you learn how to butt/fill weld a joint. no disrespect intended but it is a skill that needs to be developed under controlled conditions and not easily described over the net.
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Old 07-25-2013, 05:28 PM   #9
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having trouble brazing - not hot enough


I took it apart since the sil-fos ring didn't fill the joint to my satisfaction.
Looked like there was a good joint all around, the braze fillet just didn't make it to the outside everywhere.

The bad news was:
1. I'd taken the joint apart and needed to redo it.
2. There was a hard black film inside the line. Not the flaky crap you see in the 'open air brazing' demonstrations, but nothing I'd want to leave in there. My shield gas was fire extinguisher grade CO2 from a liquid dip tank. I'd trickle it slowly while heating, then open the valve to chill it down after I removed the flame. Maybe I was burning trace oil in the CO2? Or maybe CO2 isn't a perfect shield gas for copper?

I cut back the blackened copper, cleaned out the service valve fitting, and did it again with the argon tank from my MIG welder, Harris Stay-Silv flux, an intense flame and a fresh sil-fos ring. The silver braze came out full circle, but there was still a tiny gap, so I used a 3rd ring like a brazing rod to fill it in. The flux didn't seem to make any difference.

My first beautiful copper brazed joint, and it only took me 2 days to get it right.

Yuri: I'm using the 15% sil-fos rings that you put in the bottom of the fitting, shove the line against it, and heat until it seeps out all around. Figured that was the way to go for my first attempt at brazing copper tubing, I know there's filler in the bottom of the joint, and I can see when there's filler at the top. There seems to be just enough rod in each ring to do a perfect joint, and if the joint is a little loose (if I were a pro I'd have a pipe expander, right?) you come up a bit short on filler. I'm sure my first attempt would have passed a pressure test, but not so sure it would have held for 20 years.
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Old 07-25-2013, 05:32 PM   #10
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having trouble brazing - not hot enough


probably the problem is there is not enough material in that ring and if you do it too slow it runs away. silfoss brazing with a rod is the best way as you have no chance to run out of material.
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Old 07-25-2013, 05:36 PM   #11
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having trouble brazing - not hot enough


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Originally Posted by yuri View Post
back in 78" we had no such a thing. learned how to braze properly at trade school.

Taxman perhaps you need to get some scrap copper and couplings and practice w/o those rings so you learn how to butt/fill weld a joint.
Yeah, I did that years ago with steel and brass filler rod, but since I'm not trying to learn a trade here I wanted to do it the surest way I knew of, with Jim's "filler rings for the brazing challenged". Besides, 25 3/8" rings at $14 and 25 3/4 rings for $24 cost me about the same as a small spool of Stay-Brite 8, or less than a small box of 15% rods.
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Old 07-25-2013, 05:39 PM   #12
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having trouble brazing - not hot enough


as long as it turned out ok then great
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Old 07-26-2013, 09:28 AM   #13
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having trouble brazing - not hot enough


in the future and for other readers . DO NOT use C02 as it has the 2 things we don't want in/while welding. Carbon and Oxygen. that is where that hard black crap came from>> the Carbon. got so hot it became hardened. Nitrogen or Argon are inert gases and displace the oxygen while welding which is what we want.
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Old 07-26-2013, 11:43 AM   #14
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having trouble brazing - not hot enough


I have my students that never even picked up a torch before practice with O percent brazing rod, then move up to 5% and up to 15%. then use 45% silver braze. they learn using a oxy/ace. torches. try taking a piece of 3/4 inch copper and hold in a vise vertical. Then try to braze the end shut without pinching it. this practices torch control. to much heat and it flows inside, too little and it blobs on top. after they pass that test, I put a piece of wood in the vice along with the copper pipe with a coupler a inch away from the wood and they have to braze it with out burning the wood. a lot of schools teach using a "B" tank and it takes forever to heat a pipe, plus the heat travels a lot down the pipe. I tell my students its like having sex, get on and get off quickly. I get laughs with that one. Of course I don't say that if therer are females in the class.
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Old 07-26-2013, 11:57 AM   #15
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having trouble brazing - not hot enough


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Originally Posted by taxmantoo View Post
No. I suppose the valve is brass and I should flux?
I've never heard of not using a flux of some kind when soldering and brazing, but I know from soldering that if you don't it isn't going to go together, the flux is what helps flow the metal out nicely on the surface of the metal.

Even the Sil-Fos mentions the flux it contains, it's included so you don't have to use a separate flux:

Quote:
Best alloy for general purpose copper-copper brazing in the Sil-Fos family. For copper-to-copper joints the phosphorus in the Sil-Fos product serves as the fluxing agent

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