An overpressure is produced in the interstitial space of the pipe or armature using air or inert gas (nitrogen). The overpressure is set up at such a high level, that in case of a leak, air or inert gas will escape out of the interstitial space. Resulting drops of pressure are measured by the leak detector and used for the functions of the leak detector.

Leak detectors with integrated refill-function are able to compensate minor untightnesses in a defined range by refilling air or inert gas. Minor untightnesses related to the installation are normally very small and difficult to avoid.
Relevant untightnesses or leaks are not equalized and will cause a pressure drop to the alarm overpressure and the release of the alarm functions.

Calculation of the alarm pressure

The alarm pressure must be minimum 1 bar higher than the maximum pressure in the inner pipe. (in accordance to German TRbF 502 respective European standard  prEN 13160)  


Aspects to keep in mind:

With the use of overpressure leak detection systems no product enters the interstitial space even in case of a leak.

All equipment which can get into contact with the product shall be sufficient resistant against the product. (e.g. connection lines in the manhole chamber)

In case of permeation of hazardous vapors through the inner wall into the interstitial space, explosion protection is required. (e.g. inert-gas leak detection systems with plastic pipes for the transport of petrol)

3-D Animations

Monitoring of a pipe with overpressure (inert gas)
Monitoring of several pipes with overpressure