25 July 2016

Consequences of Not Using Oxygen Free Nitrogen (OFN) whilst Brazing

PURGING is the elimination of a substance from a system. When purging with Nitrogen you not only force out the air and moisture present in the vessel or pipeline but also “inert” the atmosphere inside, i.e. decrease the oxygen content so that it cannot form explosive mixtures with hydrocarbons that might be present for example. The system can then be sealed to maintain that inert atmosphere, preventing the ingress of air and preventing corrosion.

Nitrogen purgeOxygen Free Nitrogen

A Nitrogen purge while brazing prevents the formation of scale on the inside of the pipeline by preventing oxidation. This scale can travel down the line causing blockages in capillary tubes, TEVs and filter driers. With the change from HCFCs like R22 that use mineral oil to the new HFC refrigerants that use POE oils, the brazing of HVAC piping has become an important issue. POE oils have a solvent effect and can cause descaling/scrubbing to the inside walls of the pipeline, loosening the scale so it can circulate through the system, resulting in inefficient operation (blockages) or even system damage.
Repairs resulting from scale build-up because of oxidation can be expensive and could be for the contractor’s account depending on the warranty conditions. So it is in the contractor’s best interest to always purge with Oxygen Free Nitrogen (OFN) while brazing when repairing or installing a system.
OFN can also be used for pressure testing and leak testing.
A-Gas has launched an easy-to-carry 2.2kg cylinder, available through all Metraclark branches on a rental basis. The connection is the standard Nitrogen connection so a normal nitrogen regulator can be used.
We would like to thank OTTC and Techniskills for their assistance in providing us with the pipeline photographs.

A-GAS SA has now introduced Nitrogen Multiple Cylinder Packs (MCPs) into the local market. These are primarily used for purging and pressure testing large units in the market. The advantage of MCPs is one unit containing a number of cylinders that can be moved safely and easily. It does away with the need for handling many loose high-pressure cylinders and thus decreases handling risks and the need to connect and disconnect multiple cylinders. MCPs boast robust construction and two outlet valves at opposite sides, allowing for easy valve access. Contact A-Gas for further information on how MCPs can make your life even easier!

Nitrogen MCP Cages