Compressor Leak Detection
Air leaks waste 20 to 30% of compressed air in most plants. Learn how to find, tag, and repair leaks using ultrasonic detection, and how to build a leak management program.
The Cost of Leaks
Compressed air leaks are the largest source of waste in compressed air systems. Most plants lose 20 to 30% of their compressed air to leaks. In a plant spending $100,000 per year on compressed air electricity, that is $20,000 to $30,000 wasted.
A single 3mm leak at 7 bar wastes about 11 L/s of free air, costing approximately $1,500 to $2,500 per year. Most plants have dozens of leaks of this size or larger.
| Leak Size (mm) | Air Wasted (L/s) | Annual Cost ($) |
|---|---|---|
| 1 | 1.2 | ~200 to 300 |
| 3 | 11 | ~1,500 to 2,500 |
| 5 | 31 | ~4,000 to 6,500 |
| 10 | 124 | ~16,000 to 26,000 |
How to Find Leaks
- Ultrasonic detector: The most reliable method. Leaks produce high-frequency ultrasonic sound (above human hearing). An ultrasonic detector converts this to an audible signal. Can pinpoint leaks in noisy environments.
- Soap solution: Spray soapy water on suspected leak points. Bubbles form at leaks. Simple and effective for accessible fittings.
- Listening (audible): Large leaks can be heard. In a quiet plant (all equipment off), walk around and listen. Not effective in noisy plants.
- Ultrasonic leak tag: Use an ultrasonic detector to locate and tag each leak. Record location, size, and estimated cost. Prioritise repair by cost.
Common Leak Locations
- Hose and tube fittings: The most common leak point. Loose or worn fittings, damaged threads.
- Quick-connect couplings: Worn O-rings and internal seals. Often neglected because they look fine externally.
- Valves: Packing leaks on manual valves. Internal seat leaks on shut-off valves (air continues to flow when 'closed').
- Flanges and threaded connections: Loose bolts, degraded gaskets, thread sealant failure.
- Filter and regulator housings: Drain valve leaks, bowl seal degradation, cracked bowls.
- Pneumatic cylinders and actuators: Worn piston seals, rod seal failure. Often difficult to detect.
- Condensate drains: Automatic drains that stick open. Very common and very wasteful.
Building a Leak Management Program
- Survey the entire plant with an ultrasonic detector. Tag every leak with a numbered tag.
- Record each leak: location, size (estimated), and calculated annual cost.
- Rank by cost. Repair the most expensive leaks first.
- Repair leaks. Replace worn fittings, couplings, and seals. Tighten loose connections.
- Re-survey after repairs to verify all leaks are fixed.
- Schedule quarterly leak surveys. New leaks develop constantly.
- Educate operators to report leaks they hear or see.
Leak repair is the highest-ROI maintenance
A leak survey costs about $1,000 to $3,000 (or can be done in-house with a $1,000 ultrasonic detector). Repairing leaks typically saves $5,000 to $30,000 per year. The payback is usually less than 6 months. No other maintenance activity has a higher or faster ROI.
Tip: Lower the system pressure before a leak survey. At lower pressure, leaks are easier to distinguish from background noise because the ultrasonic signal from leaks is more distinct. Also, turning off equipment that generates ultrasonic noise (like other compressors) makes leak detection easier.