Which gas purge is specified for brazing medical-gas copper joints?

• A. Oil-free, dry Nitrogen NF
• B. Any inert gas
• C. Oil-free, dry Argon MD
• D. Oil-less, dry Nitrogen NF

Answer: (A)

Purge gas for brazing medical-gas copper joints must be inert and free of oil and moisture to keep the joint clean and oxidation-free during the heating process. Oil-free, dry nitrogen drawn from NF (National Formulary) standard meets these needs: it provides an inert atmosphere to displace air, and the oil-free, dry condition prevents hydrocarbon contamination and moisture-related oxides or residues that could compromise the joint’s integrity and sterilization compatibility. Nitrogen is also cost-effective and widely available for medical gas systems, making it the practical default.

Using any inert gas isn’t enough if it isn’t guaranteed to be oil-free and dry, and argon, while inert, is typically more expensive without added benefit for this brazing scenario.