Speaking of the dust explosion at Cleveland ast month which caused the destruction by fire the National (flour) Mills, the loss of two lives and the severe injury of four other persons, The American Miller says: “Just where and how the explosion occurred is difficut to determine. The first intimation those on the lower floor had of the catastrophe, was the noise of the explosion and the falling brick from the upper walls. The roof was blown to pieces, as were the upper portions of the walls. Like most dust explosions, this was a double one, a first explosion, local in character, followed by a greater one the philosophy of which is that the first explosion prepares the way for the second, by jarring the building full of dust. It is probable that the first explosion occurred on the third or fourth floor, and on the west side of the mill. The walls of the lower stories of the mill were left standing, but the floors all caved in.

At the time of the accident a man was working by the light of a lantern in the bran bin, which was connected with the dust room in the top part of the building, by a chute. It is thought that his lantern may have overturned and ignited the dust. Another opinion is that the fire originated in the smut room ; but those best qualified to judge, think that the fire originated in one of the bins from a lantern.”

Treating the case editorially, it remarks :

The awful catastrophe at the National Mills at Cleveland, on September 15, ranks as one of the most serious disasters of the kind that has occurred. It is quite true that flourdust explosions are comparatively rare, and, considering the vastness of the milling industry, it is also true the insurance companies attach altogether too much importance to the subject of flour dust explosions as an intrinsic part of the flour mill risk. In the vast majority of mills any explosion of dust is quite certain to be without destructive results. We know of scores of cases where such explosions have occurred with but trifling consequences. This is sure to be the case in small mills, where explosions have been common enough but have done little damage beyond burning the boiling cloth, or blowing out the windows, and possibly scorching some unwary miller. The same conditions can exist in the small mill as in the large mill, but the cubical contents of the charge are, of course, not so great.

In all destructive explosions of flourdust there seem to have been two distinct concussions. The primary explosion shakes the whole mill full of dust and at the same time fires it, which produces the second or destructive explosion. This will explain largely why dust explosions have proved so much more destructive in large than in small mills. For the Tradeston Mill at Glasgow, Walzmuehl at Budapest, Washburn A and the National Mills were all large mills.

Any substance that will burn can be made to explode as flour dust explodes. All that is needed is to divide it finely enough, diffuse it in the air in an inclosed space, and apply the match. The rapid combustion of the particles in an inclosed space then partakes of the nature of an explosion. Coal dust thrown into a stove is a familiar example. Dust in woodworking establishments is just as liable to explode as flour dust. Explosions have not been infrequent in such concerns. Of course flour milling is handicapped in a certain sense in the matter of preventing explosions, from the very fact that the aim and end of the business is to make dust. Still, much can be done to neutralize the conditions. Dust producing machines should be provided with dust collectors, and this applies to grain cleaning machinery as well as to purifiers, as their dust is quite as inflammable as flour dust. The dust room should not be a part of the mill proper, but a fragile structure without the mill. The mill should be kept clean so that dust may not find lodgment everywhere, to be shaken into the air by the primary explosion to furnish the charge for the destructive one that is to follow. Above all, there should be the greatest caution in the matter of lights, and one of the excellences of the incandescent electric light is its safety for mill use. When we. take into account the hundreds and thousands of mills in the country, many of them kept in the most uncleanly condition, it seems wonderful that the number of dust explosions has been so small.

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