Brazing and Tubing Practice
Making clean, leak free refrigerant joints with nitrogen flowing, and working safely with heat.
Procedure
Technician
#procedure#brazing#refrigeration#safetySafety
Confirm the system is recovered and at zero pressure before applying heat. Use a nitrogen regulator, never heat a sealed tube, wear eye protection and ventilate.
What it is
Brazing joins copper tubing using a filler metal that melts above roughly 840 degrees Fahrenheit, drawn into the joint by capillary action. The base metal is not melted. Joint quality depends on cleanliness, clearance, heat control and flowing nitrogen.
Procedure
- 1Cut the tubing square with a tubing cutter and deburr it.
- 2Clean the tube end and the fitting socket until bright.
- 3Assemble with the correct clearance and support the joint so it cannot move.
- 4Set a low flow of dry nitrogen through the tubing, a few cubic feet per hour, with an open exit path.
- 5Heat the joint evenly, working the flame around the fitting rather than holding it on the filler.
- 6Add filler at the joint edge and let capillary action draw it in when the base metal is hot enough.
- 7Let the joint cool naturally, then wipe it and inspect all the way around.
- 8Pressure test with dry nitrogen before evacuating.
Nitrogen purge is what separates good work from callbacks
Brazing without flowing nitrogen forms copper oxide scale inside the tube. That scale breaks loose later and plugs the metering device or filter drier, producing a restriction fault months after the job.
Safety
Heat, pressure and fumes
Always use a regulator on nitrogen and never leave a tube capped while heating, since trapped pressure can burst the joint. Recover refrigerant and confirm the system is at zero pressure before applying heat, because heating refrigerant produces toxic decomposition products. Wear eye protection and gloves, keep a fire extinguisher and heat shield at hand, protect combustibles nearby, and ventilate the work area. Follow any hot work permit requirements that apply.
Common faults
- Overheating, which burns the flux and produces a weak or leaking joint.
- Insufficient heat, leaving the filler sitting on the surface instead of drawn into the joint.
- Dirty or oxidized surfaces preventing flow.
- No nitrogen, producing internal scale.
- Moving the joint before it solidifies.
- Skipping the nitrogen pressure test and discovering the leak after charging.
Local Code Notice
Hot work permits, fire watch requirements and cylinder storage rules vary by jurisdiction and the site where the work is performed.
Practice & Mastery
- Questions1
- Brazing and Tubing Practice Troubleshooting Scenarios2
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