Analysis of causation of a flour dust explosion in industrial plant

Common solids (e.g. flour, sugar, etc.) can be suspended and transported in air via pneumatic conveying systems. Finely divided solid substances dispersed into a dust cloud (e.g. into a silo) can form a potential explosive atmosphere, if in the right concentration with the oxidizing agent (e.g. air). In addition, it is known that the pneumatic handling of substance, which allows its transport at a certain velocity, can generate static charges; thus, a possible competent ignition source may be also created. In this paper, the causation of an actual dust explosion involving a flour silo being loaded from a tank truck through pneumatic conveying systems in an industrial plant is analyzed. All the mechanisms of static discharge applicable to the case in question are discussed, in light of both actual empirical data collected at the incident site, and theory. To fully explain the events that led to the explosion, plausible hypotheses, alternative to static discharge, were also evaluated.