28L Railway Wagon Compressed Air Reservoir Air Tank for Freight Car Brake System Product Overview This 28L compressed air reservoir is a core auxiliary pressure storage component specially designed for railway freight car braking systems. Also known as an air reservoir or air tank, it perfectly matches the 120-type air control valve system and is widely equipped on 70-ton railway wagons, including C70, P70 series gondola cars, covered goods wagons and part of hopper cars.