Installation of an apparatus for determination of the minimum ignition energy of dusts

Status:

completed 03/1989

Aims:

In consideration of the particular practical relevance of the minimum ignition energy to the assessment of dust explosion hazards and to the selection of suitable measures for explosion prevention and protection, the objective of the project was to create suitable conditions for routine determination of the minimum ignition energy of dusts.

Activities/Methods:

The project foresaw the installation of test apparatus by means of which reliable results suitable for practical application can be obtained with a minimum of effort. Comparative tests were employed in order to assure that within the limits of the measurement tolerances, consistent results are obtained irrespective of the test apparatus previously employed by the BG Institute for Occupational Safety (BIA) (modified Hartmann apparatus, 20 l laboratory apparatus) and in comparison with those obtained by other test bodies (e.g. the institution for statutory accident insurance and prevention in the foodstuffs industry and the catering trade, the BVS mining test facility, or CIBA-GEIGY).

Results:

Installation of the apparatus extended the BIA's facilities for determination of explosion characteristics of dusts. The "minimum ignition energy" (MIE) can be determined with a minimum of effort by this variable-energy capacitor discharge apparatus, by means of which the minimum ignition energy determination can be measured routinely over five energy decades (< 10 mJ to 100 J). The apparatus, which includes a triple arc path (triggered by pilot arc) and additional inductance, can be adapted to both explosion vessels employed for minimum ignition energy measurement (modified Hartmann apparatus and 20 l sphere). Concrete results for the minimum ignition energy of dusts permit a comprehensive response to BG enquiries regarding measures for explosion prevention involving the elimination of effective ignition sources. A condition is that the results obtained in the pilot tests are confirmed by the comparative tests to be performed in the follow-on project 3028, "Testing of the apparatus for determination of the minimum ignition energy of dusts" (both internally and in conjunction with other test bodies), and that the validity of the data obtained by BIA is thus assured.

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