Leak Testing of Infrared Housings

Description of Technical Challenge

AIM Infrarot-Module GmbH is a German company located in Heilbronn that specializes in advanced IR-solutions such as infrared detectors and thermal sights. After evaluating alternative leak testing methods, the company has now changed from leak testing in a water bath to using gas leak detection with hydrogen tracer gas.

Infrared camera

Camera housings of this kind are typically tested at E-4 mbarl/s leak rates

Infrared cameras are used in a wide range of applications such as research, industrial processes, safety and security as well as for environmental protection. Designed for use outdoors, they are typically tested at E-4 mbarl/s leak rates. Leak testing of assembled camera housings is usually done by putting the component in a water bath for several minutes and waiting for bubbles. An alternative method, consisting of comparing the camera weight before and after immersion in water, can help to determine if each camera is watertight or not. In both cases, since any remaining water inside the camera would probably cause fogging on the lenses, cameras are normally dried at 60C°after leak check, which is extremely time-consuming. The negative effects of the water bath method are:

  • Water can damage electronics
  • Water bath test requires drying the camera housings
  • Difficult to impossible to determine the position of each leak
  • Smallest leaks are missed
  • Operator dependent leak test
  • Impossible to quantify the leaks

The INFICON Solution

Before leak testing, the housing is evacuated from air and filled with hydrogen tracer gas (5% H2/95% N2) to a very small overpressure. Filling the housing should be done in a way that ensures a maximum concentration of tracer gas on the inside. The TGF11 Tracer Gas Filler by INFICON evacuates the air before filling and ensures that the tracer gas reaches all parts inside the product.

Once filling with tracer gas is completed, the leak testing can begin. All points of interest are scanned by moving the sniffing hand probe of the Sensistor Sentrac Hydrogen Leak Detector across those areas. If any leak is present, the tracer gas will escape from the leak and be detected by the leak detector. The exact leak location can be determined by moving the probe tip back and forth and is found where the highest leak rate is shown. After locating a leak, it is easy to measure it and determine if it is big enough to leak water.  When the test is complete the TGF11 Tracer Gas Filler removes the tracer gas in a controlled way avoiding contamination of the test area. This ensures the following test will be as quick and precise as the previous one.

Benefits of Hydrogen/Helium Leak Testing

  • Fast pinpointing of the exact leak position
  • No time wasted in cleaning up or drying after testing
  • No operator interpretation of the leak size - precise measurement obtained
  • Reliable detection of even the smallest leaks
  • Homogeneous tracer gas distribution inside the test object

For best leak limits and more detailed information about leak detection on camera housings, contact the INFICON sales office nearest to you.