Which of the following statements is correct about the nitrogen sweep process?

The nitrogen sweep process is employed during brazing to prevent oxidation of the metal surfaces being joined. When metals are heated during brazing, they can react with oxygen in the air, leading to the formation of oxides. This oxidation can weaken the joint and compromise the overall integrity of the HVAC system. By using a nitrogen sweep, a stream of nitrogen gas is introduced into the area being brazed, displacing oxygen and reducing the risk of oxidation. This is crucial for ensuring a strong, clean joint that will perform reliably.

The other statements do not accurately reflect the purpose or application of the nitrogen sweep process. For instance, the process does not specifically require a high-pressure system; it can be performed at various pressure levels depending on the requirements of the specific system. Furthermore, the nitrogen sweep is not limited to copper connections, as it can be beneficial for other types of metal joints as well. Finally, the nitrogen sweep should take place during brazing rather than after, as its primary function is to protect the joint while it is being formed, not afterwards.