GEAIN-DUST EXPLOSIONS. 3 



Early in the investigation it became obvious that experimental work 

 was necessary to determine the circumstances under which the ex- 

 plosions and fires might originate and to establish definitely the possible 

 causes. Because of the equipment available in connection with its 

 milling course and its convenient location to Eastern mills, The 

 Pennsylvania State College was selected as the best place for an 

 experimental mill. This phase of the dust-explosion work was 

 accordingly assigned to the experimental department of that insti- 

 tution, the experiments being conducted under a cooperative agree- 

 ment between the Department of Agriculture and The Pennsylvania 

 State College. The materials were furnished by various milling 

 companies at the request of the department. This bulletin gives a 

 description of the equipment of the mill, the manner in which the 

 experiments were carried on, and the results obtained, together with 

 an outhne of conditions conducive to explosions in grinding machines 

 and the effect of various preventive devices. 



Aside from the relation of explosions and fires to grinding processes 

 in the milling industry, the phase of the grain-dust explosion problem 

 discussed in this bulletin, the department engineers have established 

 a number of additional possible causes, among which may be men- 

 tioned: The use of open flames, lanterns, gas jets, etc., defective elec- 

 trical equipment, frictional electricity produced by friction of pulleys 

 and belts, choke-ups and friction in elevator legs, inefficient methods 

 of dust removal and collection, and the continuance of dust rooms. 



Recent investigations by the bureau have revealed the surprising 

 fact that many of the owners and operators of large grain mills and 

 elevators are unfamUiar with the circumstances surrounding grain- 

 dust explosions, as a result of which dangerous conditions are per- 

 mitted to exist. Recently a fire, originating in a dust explosion at 

 the top of the elevator leg in one of the large grain elevators in the 

 East, destroyed almost 1,000,000 bushels of grain. The present cri- 

 sis makes it imperative that all known precautionary methods be 

 adopted. The Department of Agriculture is therefore redoubling 

 its' efforts, and has arranged to conduct a special emergency cam- 

 paign throughout the United States, to the end that grain dealers 

 and millers may become familiar with the work already done. The 

 field engineers will assist the millers and operators of grain elevators 

 in the installation of preventive devices already developed by the 

 Bureau of Chemistry. 



THRASHING-MACHINE EXPLOSIONS. 



The second division of the department's investigations into the 

 matter of grain-dust explosions comprises an extensive study of 

 thrashing-machine explosions, which has been confined largely to 



