Why is purging necessary before brazing copper pipes?

Purging is a crucial step before brazing copper pipes because it serves to remove any oxidants and contaminants present inside the pipes. When the surfaces of the copper pipes are exposed to air, they can develop oxidation, which can interfere with the brazing process. Oxidants can hinder the flow of the brazing filler metal, preventing a proper bond and potentially leading to weak joints. By purging the pipes with an inert gas, such as nitrogen, any unwanted materials are flushed out, ensuring a clean environment for brazing. This process is essential for achieving a strong, durable connection that is free from defects caused by contaminants.