Dust explosion risk in metal workings

Several episodes of metal dust explosions have been reported to have affected industries throughout the world, some of which have caused huge losses (Li et al., 2016). These dusts are typically wastes or by-products derived from machinery within metal manufacturing plants, which are collected in abatement systems (suction units, bag filters). A recent work by Marmo et al. (2017) has demonstrated the deflagration hazards of these dusts and how they are influenced by the particle size (mainly d10), chemical composition and metal oxide content. The dust samples studied in this work were collected from the following mechanical workings of metals. All these unit operations involve the generation of by-products or scraps that may be classified as dust, with different size distributions and chemical compositions, which of course depend on the nature of the processed goods. Among these, it is known that the aluminum industry is affected by a significant hazard, due to the high reactivity of aluminum dust. However, ferrous dust is also reactive and widespread. Light alloys, such as Magnesium alloys, are becoming frequent, especially in the automotive and aerospace industries. Therefore, new hazards are now coming to light. This work presents a study of 43 metal dust samples, collected at various process plants, and discusses how the unit operation that generated the dust samples may influence their ignition sensitivity and explosion violence. The paper includes size distribution and chemical characterization data, and SEM observations of the samples, as well as the results of KST and Pmax measurements. Of all the studied dusts, 59% were found to be explosible, according to the standard test (ISO 80079-20-2), while 100% of the samples collected at some of the dust abatement systems were explosible. Process dusts, such those collected at metal recovery plants from exhaust catalysts or foundry wastes, were found to be less hazardous. The findings of the work could contribute toward identifying the most hazardous operations and suggesting adequate explosion moderation measures for the metal manufacturing industry.