Which of the following filler metals shall be used to braze copper-to-copper joints in medical gas/vacuum distribution piping?

• A. BAg series
• B. BAu series
• C. BCuP series
• D. BNi series

Answer: (C)

In medical gas/vacuum piping, the joint fill metal for copper-to-copper brazing must wet copper well, flow reliably into tight spaces, and produce a strong, clean joint without contaminating the gas. Copper-phosphorus brazing filler metals are designed exactly for this scenario. Their phosphorus content promotes excellent wetting of copper and strong capillary flow, enabling a smooth, leak-tight joint in thin-walled copper tubing common in gas systems. They braze at a practical temperature for copper piping and yield a durable joint with minimal risk of outgassing or impurity migration into the medical gas stream. That makes the copper-phosphorus filler metal series the best choice for copper-to-copper joints in medical gas and vacuum distribution.

Silver-based fillers, gold-based fillers, or nickel-based fillers exist for other applications, but they are not as well suited for standard copper-to-copper joints in medical gas piping due to cost, potential contamination concerns, or compatibility with the gas path.