DUST EXPLOSIONS IN GRAIN" SEPARATORS. 21 



fi'ees the tripping mechanism, causing a hammer within the tank to 

 strike a blow sufficient to break the bottle. The discharge of the 

 sulphuric acid into the water containing soda causes the formation 

 of carbon dioxide, which generates sufficient pressure to force the 

 water through the discharge pipe and the nozzles to all the crevices 

 of the separator. 



This extinguisher was designed in the Office of Public Roads and 

 Eural Engineering, after the completion of the work in the field, 

 I by Elmer Johnson, assistant mechanical engineer, and J. C. Wood- 

 son, assistant agricultural engineer. A full-sized working model was 

 constructed and has been tried out in the explosion galleries of the 

 Bureau of Mines at Pittsburgh, Pa., and since that time on four 

 different types of separators at the Arlington Experimental Farm. 

 A total of 27 tests with this extinguisher have been made, and in no 

 case did it fail to operate automatically and properly and to ex- 

 tinguish the fire before any damage was done. 



The locations of the fuses F shown in the sketch are those suitable 

 for the particular machine shown in the drawing. The locations, 

 however, will vary with each machine, and must be selected so that 

 the fuses are sure to be reached by the flame or the heat, but not so 

 placed that the wire connecting them is likely to be broken by the 

 straw or by the moving parts of the separator. 



The location of the nozzles depends upon the construction of the 

 machine, but the following points should be observed : 



Locate one nozzle directly above the cylinder, if possible; if not, 

 place it so that the beater will help diffuse the spray from that 

 nozzle. 



Run the pipe line along underneath the roof of the separator, with 

 the nozzles pointing downward. 



Install a sufficient number of nozzles along this line, and so locate 

 them that every chamber in the separator is thoroughly served by a 

 nozzle. 



Particular pains should be taken to serve dead air spaces, as it is 

 in these that dust is likely to accumulate. 



As the stacker end of the machine is less likely to contain any 

 closed chambers, it is probable that, in most types of machines, the 

 nozzles at this end may be 30 inches or more apart. 



The last nozzle along the pipe line and within the separator should 

 be just above the end of the shakers. 



One nozzle may be located in the wind stacker by means of a flexi- 

 ble connection from the pipe line. 



The tripping mechanism of this extinguisher is so arranged that 

 it may be released by hand, and also arranged so that it can be 

 locked while on the road. Two pounds pull is sufficient to release 

 it, but it has proved to be sufficiently rigid to withstand the jar and 



