Diameter for factory wide air distribution plumbing is sized with increased future demands in anticipation. Additionally, the pipes accumulate scales and dusts on the internal walls from long term usage and the flow efficiency will be reduced. For these reasons, one size larger diameter than currently needed is generally selected.

When one size larger diameter is selected, the air flow increases by 3 times but the material cost increases only by 50%. Therefore, it is generally more beneficial to select tubes of larger diameter. The key to diameter sizing is to divide the system in two, "distribution" and "equipment connection" sections, and design to the following parameters.

	1.	Air volume to be handled
	2.	Max. air pressure used by air equipment
	3.	Plumbing length
	4.	Types and quantity of connection fittings in the system

"Distribution" and "Equipment Connection" designs are explained.

(a) Pipe Diameter Sizing for Distribution Section

	1.	Suppress terminal pressure drop to less than 0.5Kg/cm2
	2.	Size the pipe diameter based on the sum of air volume needed for all the equipment to be used.
	3.	Set the initial air pressure higher in the amount of pressure drop than the max. pressure needed for the highest rated air equipment.
	4.	Select connection fittings with consideration for air flow resistances (see [Table])
	5.	If pressure drop is a concern for long line lengths, provide an air tank in a intermediate location to prevent the pressure loss.

(b) Pipe Diameter Sizing for Equipment Connections

1.

Size pipe diameter based on max. air volume requirement of individual device connected.

(c) Cautionary Points on Equipment Connection Pipes (nylon & urethane tubes) and LCA

	1.	Make certain that used tubes do not have any external damages.
	2.	Cut off sections where damaged by repeated/prolonged usage.
	3.	Do not bend/fold tubes near connection fittings. (Min. bend radius for 6mm DIA. tube: 30mm, 8mm DIA. : 50mm)
	4.	When connecting to quick fitting threads, clean sealant off the internal threads of mating equipment.

Previous #072 and this #073 have been discussions on air system plumbing designs and usages.