KEVOS® MAKEOS · Pneumatics
Compressed Air Leak Cost
How much air does this leak waste, and what does it cost each year?
Air lost through a leak hole by choked-flow theory (or a measured leak flow), the compressor power it uses and its yearly energy cost.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Equivalent hole diameter | mm | Diameter of a round hole with the same leakage (estimate from an ultrasonic survey). |
| Line pressure (gauge) | bar | Pressure in the line at the leak. |
| Discharge coefficient | Discharge coefficient of the leak path (about 0.6–0.8). | |
| Line air temperature | °C | Temperature of the air in the line. |
| Measured leak flow (0 = use hole) | L/s free air | Leak flow measured by a flow meter or leak-down test, in litres per second of free air; 0 to estimate from the hole. |
| Compressor specific power | kW per m³/min | Compressor package power per m³/min of free air delivery, from the compressor data sheet or an air audit (about 6–7 for many screw compressors at 7 bar). |
| Pressurised hours per year | h | Hours per year the system is under pressure. |
| Electricity price | AUD/kWh | Electricity price per kWh. |
Method and formulas
- Choked mass flow ṁ = Cd A p₀ √(k ÷ (R T₀)) × (2 ÷ (k + 1))^((k + 1)/(2(k − 1))), with p₀ absolute, k = 1.4, R = 287 J/kg·K.
- Flow of free air = ṁ ÷ ρ_free (1.204 kg/m³ at 1.013 bar, 20 °C).
- Power = free air (m³/min) × specific power; cost = power × hours × price.
- Example: a 3 mm leak at 7 bar wastes 7.1573 L/s, about 2.7914 kW, costing $4,187 a year.
Limitations
- Choked flow applies when line pressure exceeds about 0.9 bar gauge; real leak paths vary widely.
- Compressor part-load behaviour may mean savings are lower than the average specific power suggests.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Prioritise leaks found in a leak survey
- Justify a leak repair programme
- Estimate savings from lowering line pressure
Who it is for
- Maintenance engineers
- Energy and utilities managers
- Design engineers
What you get
- Leak flow in free air
- Compressor power wasted
- Energy and cost per year
Interpreting the result
- Fix the largest leaks first; a leak survey usually pays back within months.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3032–3041. Topic reference; no source tables or recommended settings are reproduced.
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