18 BULLETIN 681, U. S. DEPARTMENT OF AGEICULTTJRE. 



was discovered that the wooden platform and floor near the remov- 

 able hopper of the attrition mOl had been set on fire, evidently by 

 some smoldering grain that had not been removed after the experi- 

 ments of the preceding day. This result strongly suggests a greater 

 use of sheet iron, or other noncombustible material, in miUing 

 plants. 



SERIES 13. 



Ohject. — The object of this experiment was to note the effect 

 of a pressure-relief pipe. 



Conditions. — It had been suggested that a means for automatically 

 reheving the pressure, due to an explosion, might aid materially 

 in preventmg the propagation of the flame to a dangerous part of 

 the mill. Accordingly, a device (PL II, fig. 2, and PI. I, fig, 1) 

 consisting of a pipe 5 inches in diameter and 8^ feet long, with a 

 rectangular end containing a light sheet-iron rehef valve, which 

 remained closed by its method of overhead suspension (fig. 3), was 

 installed. This end of the relief pipe was inserted in the hopper 

 (PI. Ill, fig. 2), which had been lined with galvanized iron on account 

 of the many fires that had occurred in the wooden hopper. 



Results. — 



1. In nearly all of the 14 explosions with the damper in service 

 a flame and puff of smoke were observed at the end of the relief 

 pipe (G), indicating that the relief valve opened properly. 



2. In four out of eight instances, however, flames were observed 

 getting past the double damper, although never as far as the con- 

 veyor end. 



SERIES 14 AND 15. 



Ohject. — The primary object of these last experiments was to 

 determine whether certain grain products, such as oat hulls, con- 

 taming considerable dust, barley malt sprouts, malt sprouts, brewers' 

 dried grain, and "dried grain," aU of which had been recently re- 

 ceived from various manufacturers, would give an explosion under 

 severe conditions in an attrition mill. Incidentally, obs,ervations 

 were made of the effects due to the relief pipe and double damper. 



Results. — 



1. By means of the electric arc, explosions were ob tamed with 

 dusty oat huUs, malt sprouts, barley malt sprouts, brewers' dried 

 grains, and various mixtures (Table 16). 



2. Out of 45 explosions with the damper in service, four flames 

 passed the damper, one of them extending as far as the end of the screw 

 conveyor. 



3. In all cases of explosions, puffs of smoke were observed at the 

 end (G) of the relief pipe (PL I, fig. 1). 



