What is the maximum time allowed for brazing cleaned copper joints?

The maximum time allowed for brazing cleaned copper joints is indeed eight hours. This timeframe is critical in ensuring that the copper surfaces remain suitable for brazing without contamination that could compromise the quality and integrity of the joint. When copper is cleaned, it's exposed to the environment, which can lead to oxidation or the accumulation of contaminants.

If the cleaned surfaces are not brazed within this specified period, they need to be cleaned again to create a proper bond during the brazing process. This time limit is established to maintain a high standard of quality in medical gas systems, where reliability and safety are paramount. Adhering to this time constraint helps to ensure that the brazing process is effective and that the joints formed will meet the stringent requirements outlined in NFPA 99 standards.