Copper line brazing/soldering

I have a oxygen/acet torch and a little hand held torch.

Should I use a certain kind of solder.

I was afraid of what I would hear when asking this question but that is how it goes.

I feel I could clean and braze the tubing but I am not prepared to flush the system with Co2 or dry nitrogen while welding. Never thought about contamination of the inside of the tube while welding.

Purge the system of all refrigerant.

Clean the pipe ends with 80grit emery paper and the pipe fittings with a fitting wire brush. NO acid/flux is required provided your joints are precleaned as described as above and using 15% Ag solder. Harris makes a great brand, about $30lb.

Use Oxy/Acet torch with a "O" size brazing tip with using a slightly reducing flame. Don't use more heat than required. It should take about 3min of preheating to get 15% to start running, any sooner then your using too hot of flame.

Use Co2 or dry nitrogen as a purge gas as you weld as this keeps acid scale from forming on the inside. The acid scale will break off and plug your expansion valve or capillary tubes. Use just enough pruge gas flow from the high side to the low side, exit low side, to just feel on your hand at the exit point. You do not want pressure on the system while brazing.

Heat the joint with a medium flame until the solder will flow, then move the flame towards the rear of the joint thus sucking in the liquid solder thru out the joint. Add enough solder until a slight solder dimple forms at the bottom of the joint seam, then stop as the joint is full.

I like dry nitrogen as I then pressure test the system at 150psi for leaks and the nitrogen will remove moisture where Co2 will not.

Nitrogen is a stable gas at temperature so it's very easy to see any leaks in the system on your gauges.

Use a mixture 50% liquid dish soap and 50% water to test joints for leaks.

After the pressure test, you then need to do a blow down of two charges of nitrogen, then vacuum pump for 1hr to 29.25hg. This assures that you have a dry system without any leaks. If you don't use the two charge nitrogen blow down then you will need to pump the system for about 4hrs to remove all mositure. At 29.25hg then the system contains no water.

The system is now ready for recharge.

T_Bone

I've used StayBrite flux before with excellant results but never any of there solders.

About 30yrs ago I went to the refrigeration parts house and bought a sample of all the popular brands and solder mixs. I then tested each one on the same type of joint.

Some came close to the Harris 15% Ag solder but none could match it for all around use both in quailty and being easy to use.

Alot of refrigeration compressors viberate alot along with 400psi and that will quicky fail a weak braze joint. In 35yrs of refrigeration repair, I never had to return to a job for the same leak that I had repaired. Kinda hard not to use what works.

However I'm not saying that other brands and mixs can't be used for a different type of joint and work very well.

I'm a die hard Chemtron 7018 man but under the right conditions, joint design and position, I would grab the Lincoln 7024 and put my 7018 to shame.

T_Bone

The Copper Tube Handbook published by the Cooper Development Association is the best reference available for all aspects of designing and working with copper tubing. Scroll down to section VII, Brazed Joints.
You might want to download the entire handbook for easy future reference - 7MB total.

Rod

• Welding refrigerant tubing