There are 2 key aspects to sizing your piping correctly: max system CFM requirements and minimum required operating pressure.
- A study needs to be completed to determine what the max demand in the system (in CFM) is going to be. This needs to be a worst case scenario, with even momentary uses being considered
- Momentary uses of compressed air are considered any usage of your air for a period of time that is less than a minute. Examples of these momentary uses are; dust collector blow down valves, large air cylinder/ ram actuation, sometimes diaphragm pumps, and etc.These can be compensated with point of use storage rather than increased piping sizes (and increased initial cost) throughout your whole facility.
- There are many charts that can be found online that show the CFM ratings of compressed air through traditional pipe based on PSI and distance. Usually aluminum pipe fittings manufacturers provide flow charts specifically for their products. Be careful on this as some size their piping based on OD (outside diameter) whereas others on ID (inside diameter). Teseo Flow Chart
Minimum required operating pressure
- Knowing the minimum allowed operation pressure in your system is highly critical to knowing what size pipe you need. This should be based off of manufacturer’s minimum requirements, not necessarily what you have been used to or were previously operating at.
- The ideal compressed air distribution system has less than 3 PSI of pressure drop from the outlet of the cleanup equipment to any given point of use in the plant.
- Example: if the highest pressure requirement of any piece of equipment in your plant is 95 PSI and you have a properly designed system that has less than 3 PSI of pressure drop to your point of use, then your minimum system operating pressure would be 98 PSI. Running your system at any pressure higher than 98 PSI is simply a waste of energy.
Fast fact: For every a 2 PSI operating above minimum requirements is costing you 1% in energy.
- Too small of pipe causes lost efficiency and pressure drop. Undersized piping restricts air flow and the only way to overcome that restriction is to increase the air pressure. So, if you need to operate your system at 125 PSI just to get 100 PSI at your point of use that means 25 PSI of overpressurization; resulting in 12.5 % of wasted energy costs. Remember this is for the life of the system, not a one-off expense like installing a properly sized and designed compressed air distribution system.
- Oversized piping causes no harm, it is simply a poor use of capital investment. If you are looking to install large piping just for additional storage, it is not nearly as cost effective as installing strategically placed and properly sized receiver tanks. For instance, 500 feet of one inch pipe is about the equivalent of 18 gallons of storage and 500 feet of 2 in pipe is the equivalent of 77 gallons of storage. The difference is only 59 gallons which would have minimal amount of benefit to any system and would cost much more to install than simply installing a 60 gallon tank. The only time installing oversized piping may be worth it, is if you are planning future expansion in which you would need larger piping to meet the increased air demand.