10 



BULLETIN 681, U. S. DEPARTMENT OF AGEICULTURE. 



Plate I shows the puffs of smoke, dust, and charred particles that 

 followed a flame issumg from the end (G) of the rehef pipe when an 

 explosion occurred in the attrition mill (Series 13). 



MATERIALS USED IN THE INVESTIGATION. 



DESIG- 

 NATION.' 



DESCRIPTION. 



A. 

 B. 



c. 



E'. 

 F. 



G. 

 II. 



I.. 

 J.. 



K. 



L. 



U. 



N. 

 O. 

 P. 

 Q. 

 R. 



S.. 



Fine oat hulls 



Elevator dust 



Oat hulls.... 



FIoui; direct from 

 store. 



Flour (oven dried) 



Graham flour 



Wheat scourings 



Corn 



Wheat shorts 



Coarse floor sweepings 

 Fine floor sweepings. . . 



Conveyor mixture 



No. 2 feed dust 



No. 1 feed dust 



Fine oat hull dust 



No. 3 elevator dust . . . 

 Barley malt sprouts. . . 



Malt sprouts 



Brewers' dried grain. . 



Dried grain 



Oat huUs, finely ground in an attrition mill, millstone, or other grinding 

 mill. 



Dust thathassettled on machines, beams, etc., inagrain elevator. Itis 

 a highly inflammable dust of a very light and line te.xture, and com- 

 posed 6i floating carbonaceous material of grain, outer skins, together 

 with foreign dust. 



The hulls stripped from oats, as in the preparation of oatmeal. 



The interior or endosperm of any grain reduced to a very fine powdery 

 state and free from the braimy co\ ering. It is composed mostly of 

 starch, and is highly inflammable when in suspension. 



Flour dried in an oven at about loO" F. 



This is wheat which is ground but not bolted. It contains all of the 

 flour, bran, and germy parts. 



A fluffy and inflammaljle dust taken from dust collectors which are con- 

 nected to the scouring or brush machines. It consists of foreign mate- 

 rials, such as dirt, smut, and portions of the light, thin, and loose outer 

 skins of the bran. 



Shelled corn. 



Composed of the finer portions of bran, germ, and some floury material, 

 separated from flour, in tiie process of milling. 



A coarser mill dust, settling on floor in immediate vicinity of mill. 



The lighter and finer mill dust which settles in the room and outside the 

 immediate vicinity of the attrition mill. 



A mixture of various materials as obtained from the end of the screw con- 

 veyor. 



Consists of very fine particles of bran, fuzz, smut dust, and dirt, taken 

 from the dust coUector which draws air from the flrst scourer. 



A material taken from the dust collector drawing the air through the 

 second scourer. It consists almost entirely of the outer layers of the 

 bran which have been removed by the scouring action of beaters. 



This material is very finely ground oat hulls, brought out by the con- 

 veyor in the form of dust. 



Floating dust gathered by hand from the beams and machinery in the 

 elevator. 



Consists of barley malt sprouts that have been used as mash material and 

 then dried. 



Consists of the radicles grown on the barley during the germinating proc- 

 ess, and later broken off and dried. 



This is the residue from a mash tub in a brewery or distillery, and con- 

 sists of malt, com, rice, hops, etc., which have been boiled and then 

 dried. 



This corresponds to "brewers' dried grain," except that the original 

 mash consists of corn, barley, malt, and the radicles grown on bariey 

 during the germinating process, which are later broken off and dried. 



EXPERIMENTAL WORK. 



The results of the investigation are reported, first, by describing 

 and summarizing briefly each one of the experiments performed, and, 

 second, by discussing each one of the factors mentioned in the scope 

 of the work (p. 12). 



PRELIMINARY TESTS. 



The experimental mill ])uilding at The Pennsylvania State CoUege 

 was completed in the spring of 1915, and the attrition mill, elevators, 

 and conveyor were installed during the early part of the summer. 

 During August several preliminary experiments were made for the 

 primary purpose of ascertaining if explosions would result from tlie 

 sparks emitted by foreign materials (nails, flint, matches, etc.) when 

 passing between the grinding disks along with the grain. 



