Intrinsic safety testing

Intrinsic safety 'Ex i' assessment and test is carried out to analyse whether each circuit in which spark or any thermal effect produced or electrical energy stored in normal operation and specified fault conditions, is capable of causing ignition of a given explosive atmosphere or not.

Products and designs sent for assessment and testing to 'intrinsic safety' type of explosion protection are examined to the requirements of IEC (AS/NZS) 60079.11, when read together with IEC (AS/NZS)60079.0

The circuit design is examined by reviewing the circuit schematics, interconnections diagrams, circuit board layouts. Most of this work is done on the desk using the knowledge of experts who have a design background and a complete knowledge of the intrinsic safety Standards.

The circuit (or an equivalent one made up in our laboratory) is then tested on the spark test apparatus.

Explosive gases are mixed and piped into this apparatus, and wires from the circuit under test are connected to an arrangement of tungsten wires being brought intermittently into contact with a cadmium disk. The purpose is to 'make and break' the circuit 1600 times inside an explosive atmosphere to check if the energy in the circuit may cause an ignition.

To measure the maximum temperature rise on the surface of the components, and to confirm that the temperature is less than that at which the explosive gas could ignite, power is applied to the components under test, and the temperature is measured.

The critical spacing distances on the electronic printed wiring board are measured on computer using gerber file and the relevant software driver.

To test that the internal circuits are adequately insulated from any metallic parts that may not be grounded, a high voltage test is applied between the metallic enclosure and the internal circuit.

There are several other tests that may be applicable. These include:

  • thermal endurance to heat and cold
  • Resistance to chemical agents for Group I
  • drop test
  • IP test
  • impact test on piezo-electric devices
  • battery short circuit test
  • small component ignition test
  • Optical isolators tests

A compliance test report is prepared, with a complete listing of all the safety components, and how compliance was determined.

Certification of the product is based on the test report and an audit of the manufacturing facility where the product is produced.

See our checklist for more information that should be reviewed before submitting for certification.

Book your test by filling out an application form.