Can ultrasound be used to determine the volumetric flow rate, financial loss, and size of a compressed air leak?

The LeakExpert app can be used to estimate the loss caused by a compressed air leak as a volumetric flow rate in L/min. Based on the estimated flow rate and the specified operating and cost data, the associated financial loss can also be calculated.

How is the leakage loss determined?

A compressed air leak generates turbulent flow, which produces ultrasonic signals. The intensity of these signals is related to the amount of gas escaping.

LeakExpert records the ultrasonic signal across a broad frequency range and uses a calculation method based on practical measurements to estimate the leakage flow rate.

The result is influenced by factors including:

• the system pressure,
• the pressure difference between the system and its surroundings,
• the type of gas,
• the shape and condition of the leak,
• the measurement distance,
• the orientation of the sensor,
• reflected ultrasonic signals,
• ultrasonic background noise.

The displayed volumetric flow rate is therefore a technically based estimate rather than a direct flow measurement.

How is the financial loss calculated?

To calculate the financial loss, the estimated volumetric flow rate is combined with the relevant operating conditions. These may include:

• the annual operating time,
• the cost of generating compressed air,
• the selected currency.

The result indicates the approximate annual cost caused by the detected leak. This supports the assessment and prioritization of necessary repairs.

Example values for compressed air leaks

The following table shows example leakage losses for idealized circular openings at an operating pressure of 6 bar. The values are provided for guidance only. Actual leaks may differ significantly depending on their shape and condition.

* rounded values
** Calculation basis: 70 kW compressor, net electricity price of €0.14/kWh, total compressed-air costs of 1.57 euro cents/m³, and 8,760 operating hours per year.

The table provides theoretical reference values. The actual geometric size of a real leak cannot be determined unambiguously from the measured ultrasonic signal.

Can the diameter of the leak be determined?

The diameter or geometric size of an actual leak cannot be determined reliably from the ultrasonic signal.

In practice, leaks are rarely ideal circular openings. They may occur as gaps, cracks, porous areas, damaged seals, or loose connections. Different leak geometries can have very different dimensions even when the volumetric flow rate is the same.

A circular opening calculated from the estimated flow rate can therefore only be used as a theoretical reference value. It does not necessarily represent the actual size or shape of the leak.