This Place Exploded A Long Time Ago

9 Aug


Given a large enough suspension of combustible flour or grain dust in the air, a significant explosion can occur. A historical example of the destructive power of grain explosions is the 1878 explosion of the Washburn “A” Mill in Minneapolis, Minnesota, which killed eighteen, leveled two nearby mills, damaged many others and caused a destructive fire that gutted much of the nearby milling district. (The Washburn “A” mill was later rebuilt and continued to be used until 1965.) Another example occurred in 1998, when the DeBruce grain elevator in Wichita, Kansas, exploded and killed seven people.[34] The most recent example is an explosion on October 29, 2011, at the Bartlett Grain Company in Atchison, Kansas. The death toll was six people. Two more men received severe burns, but the remaining four were not hurt.[35]

Almost any finely-divided organic substance becomes an explosive material when dispersed as an air suspension; hence, a very fine flour is dangerously explosive in air suspension. This poses a significant risk when milling grain to produce flour, so mills go to great lengths to remove sources of sparks. These measures include carefully sifting the grain before it is milled or ground to remove stones which could strike sparks from the millstones, and the use of magnets to remove metallic debris able to strike sparks.

The earliest recorded flour explosion took place in an Italian mill in 1785, but there have been many since. The following two references give numbers of recorded flour and dust explosions in the United States in 1994[36] and 1997[37] In the ten-year period up to and including 1997, there were 129 explosions.

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