In a pneumatic system, various pneumatic components like air cylinder, direction control valves, solenoid valves, air operated valves or mechanical valves are connected through flexible tube or hose for flow of compressed air. Sometimes rigid piping is also used in application area like welding, but use of flexible tube is present in most of the cases in the industry. For normal industrial application, PU (polyurethane) tube or Nylon tube is used. The standard size of the PU tubes are 2.5 mm OD, 4 mm OD, 6 mm OD, 8mm OD, 10 mm OD, 12 mm OD, 14 mm OD and 16 mm OD.
There are other types of tubing which are used for specific application like antistatic PU tube, Fluoropolymer tubing, 2/3 layer tubing etc. PU tubes comes in different colors like green tube, red tube, yellow tube, blue tube, black tube, transparent tube etc. Tubes must be cut properly before connecting it to the fittings for optimal efficiency. PU Tube should be cut properly by using tube cutter. Tubes also come in coiled form and generally referred as coiled tube.