Problems not solved by antistatic fabrics [flexible intermediate bulk containers]

The volume of a flexible intermediate bulk container (FIBC) is 1.5-2.5 m/sup 3/ and during filling the ullage can contain a dust cloud particularly if the FIBC is inflated prior to filling. Some 70% of industrial powders can form flammable dust clouds and a dust explosion can result from ignition. Full assessment of the dust explosion hazard requires consideration not only of electrostatic discharges-spark, propagating brush, brush and cone-but also of burning powder from upstream units. Spark discharges emanating from insulated metal components can be eliminated by earthing. Propagating brush discharges associated with the accumulation of high charge densities on nonconducting layers can be controlled by the anti-static fabrics but a decision has to be made as to whether or not a nonanti-static fabric will be safe. The breakdown voltage of the fabric can be used to assess its capacity to be the source of propagating brush discharges. Antistatic fabrics do not necessarily eliminate the possibility of brush and/or cone discharges from the bulk powder within the FIBC.