Atex: what does MIE mean?

For the most part, natural dusts are combustible products. Indeed coming across inert products is a rare occurrence. For example, products like aluminum and magnesium as any dusts from light metals, as well as materials which are likely to oxidize, are extremely dangerous.

In fact, under certain conditions fine dusts can induce a chemical process which is likely to turn into an explosion. There are remarkable differences in their exposure to inflammation or to the speed of the combustion. These Replica Watches factors determine the product dangerousness, therefore, the index describing these characteristics are of the utmost importance for the assessment of the ATEX risks.

MIE means Minimum Ignition Energy. It is known as the lowest electrical energy stored in a capacitor, which upon discharge is sufficient to ignite the most ignitable mixture of dust and air, under specified test conditions. In practical terms, it is the minimum energy required to start the ignition process of the combustible-comburent mixture. The test conditions expect that the material would be previously submitted to a complete drying process and that the fraction with granulometry exceeding 63 micron would be removed . This is considered the worst possible condition. In a real plant the MIE, as def2020-03-282020-03-28ined above, can hardly ignite the dust. Although it is obviously possible, the occurrence that all the three following conditions take place at the same time is difficult to imagine: a mixture air-dust with the highest inflammable proportions, a mixture with just the fraction below 63 micron and a mixture that is completely dry.

The MIE usually provides a prudential value to assess the power which is needed to ignite an explosion in a condition of potentially dangerous atmosphere. If the power available to ignite an explosion is not electrically but mechanically induced, it is required in a greater quantity because it is less concentrated. Again, in this case the MIE is a prudential value when it is considered as the minimum power required to ignite an explosion. In order to assess the risks, the MIE must be compared to the power generated by the considered equipment or plant. In a seeds storage plant an ordinary MIE value is rated around 50 mJ. The MIE for the largest part of cereals or oil seed ranges from 30 to 100 mJ.

A mechanical spark, for example the one generated by a hammer, is under 3 mJ, whereas the electrostatic spark of a body is over 300 mJ. If on the one hand a mechanical spark can never generate risk, on the other a person not wearing adequate clothing, especially static dissipative shoes, can ignite, as it happened in the past, a potentially explosive atmosphere.