Leaks are a constant source of worry for compressed air system users. A significant source of energy waste, leaks often account for up to a thirty percent loss in the compressor’s output. To help reduce compressed air leaks, United States Department of Energy (DOE) provides Tip Sheets containing information on leak sources, along with suggestions for preventing and repairing leaks.
In addition to causing compressor output losses, compressed air leaks can also contribute to issues within system operations. For example, leaks are known to cause fluctuations in system pressure, which in turn causes air tools and other air-operated equipment to perform less efficiently. This problem can potentially affect production across the entire compressed air system. Additionally, leaks can lead to excess compressor capacity, resulting in higher costs. Unnecessary system cycling and increased run time will decrease product service life and add to the supply equipment.
The DOE suggests that the best way to detect leaks is to utilize an ultrasonic acoustic detector, which can recognize high frequency hissing sounds commonly associated with air leaks. These portable units are easy to use, but because costs and sensitivities may very, the department suggests testing a detector before purchasing it.
In the event that a compressed air leak occurs, the DOE maintains that simply fixing it once is not an effective solution. Rather, the department advises incorporating a leak detection program into manufacturing facility operations. Successful programs ought to include identification and tagging, tracking, repair, verification, and employee involvement. Facilities should set a reasonable target for cost-effective leak reduction: between five and ten percent of total system flow is typical for industrial facilities.
To illustrate the necessity of leak protection programs, consider the following DOE example:
A chemical plant has undertaken a leak prevention program following a compressed air leak at its facility. The leaks, which were approximately equivalent to different orifice sizes, were 100 leaks of 1/32 inch at 90 psig, 50 leaks of 1/16 inch at 90 psig, and 10 leaks of 1/4 inch at 100 psig. If the chemical plant were to calculate its annual cost savings after the leaks were eliminated (number of leaks x leakage rate [cfm] x kW/cfm x number of hours x $/kWh) (assuming sharp-edged orifices), the savings would appear:
- 1/32 inch leaks = 100 x 1.5 x 0.61 x 0.18 x 7000 x 0.05 = $5,765
- 1/16 inch leaks = 50 x 5.9 x 0.61 x 0.18 x 7000 x 0.05 = $11,337
- 1/4 inch leaks = 10 x 104 x 0.61 x 0.18 x 7000 x 0.05 = $39, 967
The total cost savings for the chemical plant would amount to $57,069. It is important to note that savings from the elimination of just 10 leaks, at 1/4 inch each, account for almost seventy percent of overall savings. The DOE advises that as leaks are identified, facilities should prioritize them and fix the largest leaks first.