Brazing is a metal joining process in which two or more metal items are joined together by melting and flowing filler material into the joint. Nitrogen is an inert gas making it ideal for use during brazing of copper tube. During brazing, temperatures of 620°C to 790°C are required, copper will react with the oxygen in air at these temperatures to form a scale of copper oxide on the inner walls of tubing and fittings. The resulting flakes of scale dislodged in operating refrigeration systems cause system blockages and damage to components. If the air in the copper tubing being brazed is replaced with a slow steady flow of nitrogen during brazing, the formation of copper oxides can be eliminated.
Nitrogen gas has long been used in the food packaging to help preserve the quality of the delivered product. During the packaging process, replacing oxygen in the packaging atmosphere with nitrogen as a non-chemical preservative to help prevent oxidation, preserves freshness, protects nutrients, prevents growth of aerobic microbes and extending the shelf life of the product.For safety and quality assurance, a leak test is a method for determining if vessels, pipes or other system components can safely withstand the internal pressures required during normal operations or any system surges. Pressure test are commonly used in many of industries, examples like refrigeration systems, checking seals in processing facilities, and ensuring the entire of newly-installed pipeline from supply to end use area. There are several ways to perform a pressure testing, the most common method as followings:
Hydrostatic testing performs pressure checks using water. This can work in some situations, but using water can have drawbacks. Moisture can be harmful to some types of systems, and the water content can accelerate corrosion, reducing a system’s lifespan.
Air can be another option for pneumatic testing, but the oxygen in the air can present problems when exposed to flammable substances. Also, air contains problematic moisture content.
Nitrogen is utilized within numerous industries for pressure testing, while best known is its use in the HVAC industry for pressure testing the copper coil, interconnect piping, containment vessels and equipment. There are several advantages to using nitrogen for pressure test or leak detection, nitrogen is inert and having very low moisture content, it’ prevents the formation of moisture during the leak testing process, thereby eliminating oxidation of the metal. So it is free from many of the problems associated with using air or water for pressure testing.