This example illustrates a combustible dust cloud explosion pre-screening test. This test is performed based on procedures from VDI 2263, Part 1 (Section 2.1.1), “Dust fires and dust explosions; hazards, assessment, protective measures”, using a Modified Hartmann Apparatus with a 10 J AC electric arc. The material tested here is a fine metallic powder which was determined to have an Explosion Severity ratio of 0.4 – based on subsequent testing. The pre-screening test in the Modified Hartmann Apparatus is a precursor to the standard explosion screening test conducted per ASTM E1226 Section 13. Both tests, when used in conjunction, can be used as a tool to ascertain if a given sample of dust poses an explosion risk if suspended into a cloud in air in the presence of an ignition source.
Fauske & Associates (FAI) performs explosion tests every day using our Hartmann Dust Testing apparatus (we actually have several instruments running in parallel). The practicality of this device is its simplicity to test and determine if a process dust should be classified as combustible. Applications include, but are not limited, to combustible testing of floor and process samples per NFPA 654/OSHA CPL 03-00-008, R&D, process development, and commercial scale-up of starting materials, isolated intermediates and final products, including final packaged forms with excipients. The data can be used internally or shared using Material Safety Data Sheets. The device conforms to EU and UN test requirements, and it only uses a very small sample size (0.3 - 3.0 grams).
The modified Hartmann apparatus consists of a dispersion cup, a PTFE tube holder and a glass tube with a volume of 1.0 liter. By means of pressurized air a quantity of the powder sample is suspended in the presence of an ignition source. The ignition source used for the tests is a continuous spark generated by a high voltage transformer between two standardized electrodes placed near the bottom of the cylindrical tube. The energy content of the spark corresponds to an equivalent energy of about 10 Joule of a discharge spark.
Powder concentrations in air are between 30 mg - 3000 mg/liter (30 - 2500 g/m3). A powder is considered to be explosible if dust fires or explosions are observed during the tests. If no dust fires or explosions are observed in three-series of tests for any concentration, the powder is considered to be not explosible under the conditions of the test.
If you suspect you have a process that contains combustible dust, it would be prudent to contact us for dust screening advice. We would be happy to help you evaluate your dust hazards, so please contact us at dust@fauske.com.
