It is the main pipe, when installed in the compressor room to connect the compressors, dryers and filters together in a logical arrangement using wet and dry headers. When installed in the downstream side of compressor room, a distribution header transmits the output of the compressed air room to general areas of the plant. Down-drop piping at the end-use connects the distribution header to the compressed air uses.
Header sizing should be large enough so the air velocity in the pipes does not exceed 20 fps (feet per second) in velocity at expected peak flows. Entry points into the header should be at a 45-degree angle to prevent back-pressure. Use of T-connections and two flows in opposite directions should be avoided.
Piping from the outlet of the compressor room to end-use down-drops should be sized so the air velocity does not exceed 30 fps or, in cases of very long runs, sized large enough so the total pressure differential does not exceed the 2 to 5 % percent pressure differential mentioned above.
Distribution-header pressure differential can be greatly reduced by installing a loop system rather than radial feeds. Use of smooth-bore pipe—such as aluminum or copper—can reduce losses. Take care not to downsize because of this effect or benefits could be lost.
Typically, they have multiple outlets fitted with ball valves for isolation. When compressed air, steam, etc. contain water vapor to be discharged, can be assembled vertically, and a drain valve can be installed at the bottom to regularly discharge condensed water from the headers to prevent water from entering the pneumatic instrument.