*New and improved version is the Uniweld NV1 Nitrogen Flow Indicator* Uniweld UNF3 Nitrogen Flow Indicator provides extremely low pressure precision gas flow control for nitrogen purging applications during the brazing of copper tubing in Air Conditioning and Refrigeration systems. The nitrogen must be flowing to displace the oxygen inside the tubing during the brazing process, preventing internal oxidation and the resulting scale. Scale build up inside the tubing can cause blockage in the TXV and within the Air Conditioning and Refrigeration system resulting in premature failure. The UNF3 Nitrogen Flow Indicator uses a float ball to visually confirm the nitrogen is flowing and allows the technician to first flush the copper lines at 25-35 CFH and then reduce the flow to 3-4 CFH during the brazing process thus conserving and saving nitrogen. If the ball does not rise in the tube there is no flow of nitrogen only static pressure and oxygen is not being displaced. The UNF3 maximum inlet pressure is 50 PSI and must be connected to a Nitrogen Regulator with 1/4 inch male flare outlet connection (Uniweld Part No. RHP400, RHP500, RHP800 – Sold Separately) to control the nitrogen gas pressure.