The Importance of Flowing Nitrogen While Brazing

The Importance of Flowing Nitrogen While Brazing: Enhancing Quality & Reducing Callbacks 

Why We Started This Practice

After facing numerous warranty calls due to restricted TXVs and pistons, we decided to investigate the root cause rather than attributing the issues to "Manufacturer's Defect."

I had always heard about the practice of flowing nitrogen while brazing but dismissed it as overkill. Given our circumstances, I decided to look into it further.

To my surprise, it made sense. Despite initial resistance from our technicians, I invested in multiple purge tools and revamped our brazing procedures.

One year later, we observed a significant reduction in callbacks related to failed TXVs, clogged pistons, and refrigerant restrictions.

This proved that the practice of flowing nitrogen while brazing is not only necessary for providing a quality product but also saved us time, money, and our reputation.

No customer wants their new HVAC system to break down shortly after installation.

Why Is It Needed?

When copper is heated during brazing, it reacts with oxygen, forming copper oxide (black soot).

This black soot forms on both the outside and inside of the pipe, leading to a contaminated refrigerant system.

By flowing nitrogen through the pipes during brazing, you displace the oxygen, preventing copper oxide from forming.

This ensures a clean joint and prevents contamination of the system.

How Is It Done?

1. Get the Correct Nitrogen Regulator:
   • We recommend the Uniweld Nitrovue Flow Indicator.
   • Check it out here: Uniweld Nitrovue Flow Indicator
2. Set Up Your Equipment:
   • Connect a nitrogen tank and flow regulator.
   • Set the delivery pressure to 60 PSI to control the nitrogen gas pressure.
3. Purge the Copper Lines:
   • Set the nitrogen flow rate to 20+ SCFH to purge the lines.
4. Adjust for Brazing:
   • Reduce the flow rate to 3-5 SCFH for the brazing process.
   • Use the flow regulator to control this low flow of nitrogen.
5. Monitor the Flow:
   • Continuously check the flow meter to ensure nitrogen is flowing. If the meter indicates no flow, oxygen is not being displaced.
6. Prevent Oxidation and Scale:
   • Ensure nitrogen is flowing throughout the brazing process to displace oxygen inside the tubing, preventing internal oxidation and resulting scale.
7. Safety Features:
   • Use equipment with safety features, such as a resettable safety blow-off valve, to protect from overpressure.

Conclusion 

As HVAC technicians, our primary goal should be to deliver the highest quality service to our customers, even if it involves a little extra work.

Initially, flowing nitrogen while brazing may seem like an extra step, but with practice, it becomes second nature.

In the end, this practice can save you time, money, and your company’s reputation.