Leaks are a hidden nuisance in a compressed air system that can cause thousands of dollars in electricity per year. These leaks on average can account for up to 30% of the operation cost of a compressed air system. A leak will usually occur at connection joints, unions, valves, and fittings. This not only is a huge waste of energy but it can also cause a system to lose pressure along with lowering the life span of the compressor since it will have to run more often to make up for the loss of air from the leak.
There are two common ways to calculate how much compressed air a system is losing due to leaks. The first way is to turn off all of the point of use compressed air devices; once this has been complete turn on the air compressor and record the average time that it takes the compressor to cycle on and off. With the average cycle time you can calculate out the total percentage of leakage using the following formula.
The second method is to calculate out the percentage lost using a pressure gauge downstream from a receiver tank. This method requires one to know the total volume in the system to accurately estimate the leakage from the system. Once the compressor turns on wait until the system reaches the normal operating pressure for the process and record how long it takes to drop to a lower operating pressure of your choosing. Once this has been completed you can use the following formula to calculate out the total percentage of leakage.
The total percentage of the compressor that is lost should be under 10% if the system is properly maintained.
Once the total percentage of leakage has been calculated you can start to look at the cost of a single leak assuming that the leak is equivalent to a 1/16” diameter hole. This means that at 80 psig the leak is going to expel 3.8 SCFM. The average industrial air compressor can produce 4 SCFM using 1 horsepower of energy. Adding in the average energy cost of $0.25 per 1000 SCF generated one can calculate out the price per hour the leak is costing using the following calculation.
If you base the cost per year for a typical 8000 hr. of operating time per year you are looking at $480 per year for one 1/16” hole leak. As you can see the more leaks in the system the more costly it gets. If you know how much SCFM your system is consuming in leaks then that value can be plugged into the equitation instead of the assumed 3.8 SCFM.