Any compressed air system must be controlled, regulated, and sized to ensure that an adequate volume of air, at a pressure and purity necessary to satisfy user requirements, is delivered to the most remote outlet during the period of heaviest anticipated use.
Some safety factor must be also incorporated into the system to accommodate additional pressure drop for some period of extremely high use if appropriate for the facility.
1. Locate and identify each process, workstation, or piece of equipment using compressed air.
2. Determine volume of air used at each location.
3. Determine pressure range required at each location.
4. Determine conditioning requirements for each item.
5. Establish how much time the individual tool or process will be in actual use for a specific period of time (duty cycle).
6. Establish the maximum number of locations that may be used simultaneously on each branch, main, and for the project as a whole (use factor).
7. Establish the extent of allowable leakage.
8. Establish any allowance for future expansion.
9. Make a preliminary piping layout and assign preliminary pressure drop.
10. Select the air compressor type, conditioning equipment, and air inlet locations making sure that consistent SCFM or ACFM is used for both the system and compressor capacity rating.
11. Produce a final piping layout and size the piping network.
Piping system design
Piping layout on the plans should be reasonably complete, with checking for space, clearances, interference, and equipment drops.
In order to use pressure drop tables, it is necessary to find the equivalent length of run from the compressor to the farthest point in the piping system.
The reason for this is that the various pipe-sizing tables are developed for a pressure drop using friction loss for a given length of pipe.
1. Measuring the actual length is the first step. In addition, the affects of the fittings must be considered.
2. Determine the actual pressure drop that will occur only in the piping system. Generally accepted practice is to allow 5% of the proposed system pressure for pipe friction loss. It is a good practice to oversize distribution mains to allow for future growth as well as the addition of conditioning equipment.
3. Size the piping using the appropriate charts, having calculated the SCFM and the allowable friction loss in each section of the piping being sized.
4. The temperature used to calculate the friction loss is 16ºC.