In short
In typical plants about 20–30% of the air produced is lost to leaks; the target for a well-kept system is below 10%. Leak flow grows with the square of the hole diameter: from 3 mm to 10 mm the loss rises about 11 times. Finding, tagging, repairing and re-measuring should be a repeating cycle.
What does a leak cost?
The values below are approximate free-air flows calculated at 7 bar for a typical hole: 1 mm ≈ 2.9 m³/h; 3 mm ≈ 26 m³/h; 5 mm ≈ 72 m³/h; 10 mm ≈ 290 m³/h.
Assuming about 0.1 kWh of electricity per m³ of air in a 7 bar system, a single 5 mm hole means roughly 8 kW continuously, or about 64,000 kWh over 8,000 hours a year. Multiply by your electricity price to find your own cost.
Where do leaks usually occur?
Most leaks come not from large pipes but from small connection points:
- Quick couplings, hose ends and clamps.
- Threaded fittings and their seals.
- Drains of filter-regulator-lubricator units.
- Valve and cylinder seals.
- Drains left open and unused open-ended lines.
How are leaks found?
Search when production is stopped, the environment is quiet and the line is pressurised.
- Ultrasonic detector: picks up the sound of a leak even in noisy surroundings; the fastest and most reliable method.
- Soap solution: a cheap and simple check for reachable connection points.
- Load/unload test: with production stopped, run the compressor and measure the load time (T) and unload time (t). The leak rate is roughly T / (T + t) × 100.
- Pressure-drop test: with system volume V (m³), pressure drop p1−p2 (bar) and time t (min), leak flow is roughly V × (p1−p2) / (t × 1.013) m³/min.
Tracking: find, tag, repair, re-measure
Finding leaks is not a one-off job; repaired leaks reappear over time. Set up a simple cycle:
- Tag every leak found and record its location, estimated flow and date.
- Set a repair-time target and re-measure after repair.
- Monitor consumption outside production hours continuously; it is the most practical indicator of the leak rate.
- Report monthly leak rate together with energy per unit of air (kWh/m³).
Frequently asked questions
What is an acceptable leak rate?
For new and well-maintained systems the target is usually below 10%. In many older plants it can reach 20–30%; a first goal may be to halve it.
Can I find leaks without an ultrasonic device?
Yes; soap solution, the load/unload test and the pressure-drop test let you confirm and estimate the rate. An ultrasonic detector is much faster for locating them.
Should I repair leaks first or lower the pressure?
Repair leaks first. Lowering pressure with leaks present hides the problem, while removing leaks leaves more room for lowering pressure as well.
Figures given are typical values; the real saving in your plant is determined by measurement.
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