A-A-59503D, COMMERCIAL ITEM DESCRIPTION: NITROGEN, TECHNICAL (24-OCT-2019) [SUPERSEDING BB-N-411C]

A-A-59503D, COMMERCIAL ITEM DESCRIPTION: NITROGEN, TECHNICAL (24-OCT-2019) [SUPERSEDING BB-N-411C]., This commercial item description (CID) covers two types of nitrogen: gaseous and liquid. Each type of nitrogen can be obtained in three different technical grades based primarily on nitrogen and oxygen content. Liquid nitrogen is used as a cooling agent for low temperature and cryogenic processes to shield temperature-sensitive materials and equipment from the effects of heat. Gaseous nitrogen is used to purge or pressurize systems or provide inert atmospheres. The list of intended uses includes, but is not limited to: pressurizing fuel tanks, hydraulic system accumulators, aircraft struts, rocket engine propellant systems, and carbon dioxide cylinders; purging aircraft oxygen converters; and purging and calibrating instruments. Since some systems are sensitive to oil contamination, gaseous nitrogen is divided into two classes: oil free and oil tolerant. Class 1, oil free nitrogen, is used for applications that cannot tolerate hydrocarbons, such as the purging of oxygen equipment. Class 2, oil tolerant nitrogen, is used for pressurizing oil-containing systems such as aircraft struts.