Nitrogen trifluoride cylinders

Nitrogen trifluoride is stored in glass flasks, in a gasometer over water, or under pressure in steel cylinders. It may be used as filling material for vapor pressure thermometers [W. Menzel a.nd F. Mohry, Z. anorg. allg. Chem. 210, 257 (1933)]. 

Nitrogen trifluoride gas is shipped as a compressed gas in steel cylinders and can also be provided by tube trailer. Metals suitable for use in NF3 systems at ambient temperatures are stainless steel, steel, brass, aluminium, copper, and nickel. Corrosion rates of less than 0.0025 mm/a at about 70°C have been measured for these materials [1,2]. However, the corrosion rate increases significantly in the presence of moisture or HF [2]. Fluorinated polymers such as Teflon, Kel-F, and Viton are not attacked by NF3 at ambient [1,2] and elevated temperatures [3]. These materials are recommended for flexible lines and fittings [1]. At elevated temperatures, where the reactivity is similar to that of fluorine, nickel and Monel are recommended as suitable materials for handling NF3 [1]. 

Nitrogen trifluoride cylinders must be securely supported while in use to prevent movement and straining of connections. Full cylinders must be stored in a well-ventilated area, protected from excessive heat (125°F or 51.7°C), located away fi om organic or flammable materials, and secured. Valve protection caps and valve outlet caps must be securely in place at all times when the cylinder is not in use. 

Nitrogen trifluoride cylinders must always be protected from mechanical shock or abuse and must never be heated with a torch or heat lamp. 

Nitrogen trifluoride is authorized for shipment as a nonflammable compressed gas in cylinders, including DOT/TC approved trailer tubes. Nitrogen trifluoride is normally compressed to 1450 psig (10 000 kPa) in cylinders. 

All cylinders authorized for nitrogen trifluoride must be requalified every 5 years in accordance with the requirements of 49 CFR 173.34 and CAN/CSA B339 [4, 7]. 

Leaks of nitrogen trifluoride in process lines or equipment may be detected by applying soap solution to the suspected area. Leaks will be indicated by bubble formation. Leaks on the cylinder or cylinder valve area can be detected in the same manner. If a leaking cylinder is found, move the cylinder to a well-ventilated area and contact the manufacturer. Proper safety precautions should be followed, especially for other than minor leaks, which will require the use of personal protective equipment, including self-contained breathing apparatus. 

The standard valve outlet connection for nitrogen trifluoride cylinders in the United States and Canada is Connection CGA 330. [7]... 

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