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Abstract
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When applying partial inerting the gas (most often air) in which the explosible dust is dispersed is mixed with a fraction of inert gas (e.g. nitrogen) considerably smaller than that required for complete inerting. This reduces both the explosibility and the ignition sensitivity of the dust cloud. The effects on KSt (explosion violence) and MIE (minimum ignition energy) are particularly pronounced. This can facilitate the implementation of conventional protective methods that would otherwise have been difficult to use. The purpose of the present paper is to draw further attention to the additional degree of freedom that partial inerting offers in dust explosion protection. By using published data for coal dust and the new European CEN standard for vent sizing, it is shown that the minimum required areas for explosion venting are reduced considerably, due to reduced KSt and Pmax values, by even a moderate reduction in the content of oxygen in the atmosphere. It is also shown, using a qualitative probabilistic argument, how the marked increase of MIE obtained by partial inerting would justify a further reduction of minimum required vent areas.
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