The item under consideration is a fractional distillation cold box, model numbers GN, TN, and OA, which is installed within an Air Separation Unit (“ASU”) after importation. The purpose of the ASU is to produce gaseous or liquid nitrogen, oxygen, or argon products through the cryogenic distillation and refrigeration of air. Feed air is first processed in separate air filtration, compression, and purification systems of the ASU before it is sent to the cold box. The cold box is a prefabricated, painted carbon steel enclosure comprised of various components including a reboiler and condenser system, a heat exchanger, distillation columns, pressure vessels, pipework, valves, and instruments. The function of the cold box is to separate air into its component gases using their differing boiling points by distillation.
[1] Please importantly note that only the relevant portion of the related is displayed above. You may refer to the said customs ruling for the entire ruling explanation.
[1]. https://rulings.cbp.gov/ruling/N320452