Why is purging lines with dry nitrogen during brazing important?

Why is purging lines with dry nitrogen during brazing important?

• A. To purge moisture and prevent oxide and moisture from contaminating system; helps keep lines dry prior to vacuum.
• B. To introduce moisture.
• C. To increase temperature of the system.
• D. To color the refrigerant.

Answer: (B)

Purging with dry nitrogen during brazing keeps the lines in a dry, inert state by displacing air and moisture from the interior. This protects the metal surfaces from oxidation and prevents moisture from being carried into the system as you braze, which helps ensure clean, dry joints. When you later evacuate the system, having moisture or oxides present makes it harder to reach a proper deep vacuum and can lead to corrosion or refrigerant contamination. Introducing moisture would defeat the purpose, so the best practice is to purge to remove moisture and oxygen and keep the lines dry.

Purging with dry nitrogen during brazing keeps the lines in a dry, inert state by displacing air and moisture from the interior. This protects the metal surfaces from oxidation and prevents moisture from being carried into the system as you braze, which helps ensure clean, dry joints. When you later evacuate the system, having moisture or oxides present makes it harder to reach a proper deep vacuum and can lead to corrosion or refrigerant contamination. Introducing moisture would defeat the purpose, so the best practice is to purge to remove moisture and oxygen and keep the lines dry.