The item under review is a Modular Assembly, Reservoir Pressurization (Part Number 732-11610), which is designed to be used with Boeing aircraft B747, B767, and B777. The modular assembly is a pneumatic manifold, which provides a means of supplying the engine bleed air flow required to pressurize the aircraft hydraulic reservoir. Its components consist of a body/manifold, two check valves, two filters and a depressurization bleed valve. It is mounted on the aircraft by means of four mounting lugs. Its function is to pressurize the hydraulic reservoir, at the return port of the hydraulic system, and thereby prevent hydraulic pump cavitation. The unit also includes a bleed valve to facilitate safe maintenance of the system and is equipped with filters. The unit does not provide regulation, relief, or venting functions.
[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/N321811