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ASF Leak Detector Type D9 R325 / D9 R255 - Pressure Principle - Overview

Type D9 R325 - Article No.: 4141 0049 / Type D9 R255 - Article No.: 4141 0055


  • To monitor double-walled tanks.
  • Container types according to DIN EN 12285-1 (DIN 6608 Part 2), DIN EN 12285-2 (DIN 6616 Form A), DIN 6619, Part 2, DIN 6623, Part 2, DIN 6624, Part 2.
  • No permeation may pass through the inner tank wall into the interstitial space.Non-standard containers with a general building inspectorate approval.
  • For monitoring of water-polluting liquids, including flammable liquids with a flash point < 55°C.
  • The storage medium must not exceed the density allowed for the container.
  • The leak detector can be used for monitoring one or several underground tanks utilizing an appropriate manifold system.

The leak detector must be mounted outside the hazardous area (ex-zone)!


Product images

D9_R325Operating Conditions

  • The interstitial space of the container must be designed for the max. operating pressure of the leak detector.
  • For Type D9-255: Alarm switching value (255 mbar), allowed operating pressure in the interstitial space minimum 0,4 bar.
  • For Type D9-325: Alarm switching value (325 mbar), allowed operating pressure in the interstitial space minimum 0,5 bar.
  • Leak detection fluid may not be present in the interstitial space of the container.
  • The containers must be operated pressureless.
  • Appropriate manifolds together with a D9 leak detector may only be used for monitoring underground tanks.



  • Installation of a potential free relay
  • Installation in protective casing with exterior alarm and heating. (See product image)


  • Leak detector according to the principle of positive pressure with integrated pump and pressure relief.
  • The outside air is sucked through a vessel with dry beads (air dryer), which dries the air down to a relative humidity of <10%.
  • The saturation of the dry beads, depending on the humidity, is reached in about 12-15 months, identifiable by the color change, - initially orange - colorless at saturation.

Operating Pressure

in the interstitial space < 490 mbar

D9(1)Switching Values: relative pressure

Type D9 - 255

Alarm ON PAE = 255 mbar +30/0 mbar

Pump OFF PPA = ca. 360 mbar +/-15 mbar

Overpressure valve OPEN PSV < 400 mbar

Type D9 - 325

Alarm ON PAE = 325 mbar +30/0 mbar

Pump OFF PPA = ca. 450 mbar +/-15 mbar

Overpressure valve OPEN PSV < 500 mbar

For further data please see the Technical Description of the D9 leak detector.

Dryer / Drying Beads

Underground tanks = 180 cm3

Aboveground tanks:

Leak Detector Type D9 - Aboveground Tanks
Tank (m3) Air Dryer/cm3
180 530 850
< 13 180    
< 60   180+350  
< 100     350+500


Mounting Examples

Please click on the picture for a larger view!




ASF pdfTechnical Description D9 R325

ASF pdfData Sheet D9

ASF pdfD9 R325 Accessories & Assembly Kits

ASF_imageProduktbild D9 hochauflösend (1000x1000 px, 300 dpi)



ASF linkAdvantages of the new design of the ASF leak detection systems