Pressure drop & flow measuring
Two leak testing methods with air
ZELTWANGER Dichtheitsprüfung is the specialist in all testing methods using the medium of air. It is possible to use our devices and systems to conduct measurements using the flow and pressure change methods.
Flow measuring provides a measurement signal which corresponds to a possible leakage regardless of the size of the test volume and the measuring time. A conversion as with the pressure drop method is not necessary.
The mass flow method works according to the calorimetric principle (thermal method).
The result is available directly in cm³/min and, after being offset against the volume factor (ratio between reference and test volume), already corresponds to the leak rate. Both the test object and the reference volume are pressurized for the test. After a calming phase, the mass flow and the direction of flow between the reference and test volumes are determined.
The test pressure can be relative to the current ambient pressure, i.e., in excess pressure or negative pressure (vacuum test). It is also possible to execute the test in absolute pressure based on the absolute zero point.
The ideal application of the mass flow method is leak testing for large-volume test objects.
The mass flow in the supply line to the test object is measured using the flow method. Pressure changes in the test object are directly compensated for by a precision pressure regulator when the filling valve is open until a constant air flow is established at the sensor. Flow measuring provides a measurement signal which is output directly in the units of the leak rate regardless of the size of the test volume and the measurement time. A conversion as with the pressure drop method is not necessary.
The test pressure can be relative to the current ambient pressure, i.e., in excess pressure or negative pressure (vacuum test). In addition, it is possible to conduct measurements using the relative pressure method in this setup.
This combination is therefore very well suited for testing tasks in which the tightness of the component needs to be verified using the relative pressure method and a minimal flow needs to be demonstrated. Application examples may be valve tests or flow tests on pressure equalizing membranes or filter units.
The flow method is characterized by very fast test times. However, this method is not suitable for measuring small leaks.
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Leak testing with detection gases
For the localization of small leaks
Leak testing dictionary
We explain the most important terms