GEAIN-DUST EXPLOSIOlSrS. 



9 



In figure 4, whicli is a diagramniatic view of the double damper 

 and principal parts of the mill equipment, it is seen that the conveyor 

 was lowered about 10 mches in order to make room for the double 

 damper. Otherwise, the arrangement is practically the same as that 

 hi figure 2. Tlie rehef valve at A was installed with the rehef pipe 



Fig. 4. — Elevation-attrition mill and conveyor. Double damper. 



as explamed in Series 13 (p. 18). The "spout to elevator," with its 

 shde under the screw conveyor, shows hov/ the ground material could 

 be "recirculated," as stated in several series of tests, by means of the 

 elevator and spouts shown in Plate II, figure 1. 



The two dampers were positively connected with each other by 

 means of a chain and sprocket wheels (fig. 3) and were so arranged 

 that they served as a double check for the flame propagated by explo- 

 sion in the attrition mill. Plate IV gives two views of this double 

 damper from opposite sides, figure 2 of the plate showing also the 

 screw conveyor, peepholes, and spout leading to the boot of the meal 

 or chop elevator. 



Plate III, figure 2, shows the removable hopper, with the sheet- 

 hon lining and swinging rehef valve as installed for Series 13. This 

 hopper was constructed so as to make a snug fit with the lower part ■ 

 of the hood of the attrition mill. When the hopper is in position 

 under the attrition mill, the relief pipe (R) (PL II, fig. 2) can be at- 

 tached to the stub spout containing the rehef valve. 

 50220°— 18— Bull. 681 2 



