NFPA-99 Practice Exam

What substance should be used to purge joints during brazing to prevent the formation of copper oxide?

1. Copper

2. Oil free, dry nitrogen

3. Argon

4. Carbon dioxide

The correct answer is: Oil free, dry nitrogen

To prevent the formation of copper oxide during brazing, it’s essential to purge the joints with a suitable inert gas. The correct answer is oil free, dry nitrogen, which is commonly used for this purpose. Nitrogen acts as a shielding gas that can effectively displace oxygen in the joint area, thereby preventing the oxidation of the copper surfaces. Using oil free, dry nitrogen ensures that there is no moisture or oil contamination, which can further complicate the brazing process or introduce unwanted contaminants. The inert nature of nitrogen provides a protective atmosphere that is vital for creating a clean and effective joint, allowing for better bonding and reducing the likelihood of defects in the brazed joint. The other options do not serve this purpose effectively. While copper itself is used in the brazing process, it does not help in preventing oxidation. Argon and carbon dioxide are also not preferred for purging copper joints, as they may not provide the same level of protection against oxidation as dry nitrogen does. Therefore, using oil free, dry nitrogen is the most effective method for purging joints to prevent the formation of copper oxide during brazing.