20 BULLETIN 37&, U. S. DEPARTMENT OF AGEICULTUEE. 



der as shown at B, and also from beneath the fan as shown at C, there 

 being another connection on the opposite side of the fan from C. 



The method of installing the fan necessarily^ will vary with the 

 type of separator. The object is to remove the dust from near the 

 cjdinder. The fan should be arranged to accomplish this. 



There is no way of demonstrating by experiment that either of 

 these methods actually prevents explosions, but the fact that no 

 such occurrences took place in the case of separators properly 

 equipped with either one of these devices, while explosions and fires 

 were constantly occurring in machines located near them and not 

 so equipped, warrants the belief that the devices proved eifective in 

 preventing explosions and consequent fires. 



AUTOMATIC FIRE EXTINGUISHER. 



Experiments conducted in the field during the threshing season, 

 and since that time on the Arlington Experimental Farm at Ar- 

 lington, Va., show that, under ordinary conditions, it is very diffi- 

 cult to secure a fire in a separator by the introduction of matches 

 or other foreign materials. This has been particularly the case 

 in experiments conducted on the Arlington Experimental Farm, in 

 which, owing to the lack of smut dust and proper atmospheric con- 

 ditions, it was impossible to secure an explosive mixture in the 

 separator. In order to set fire to the separator in these experiments, 

 it was necessary to introduce a flame and, to secure positive results, 

 use was made of waste and rags soaked in gasoline and ignited by a 

 flame from the outside. Bundles of matches fed in with the straw 

 did not cause a fire. 



However, since there is a possibility that fire will be caused under 

 certain conditions by the entrance into the separator of foreign ma- 

 terials, and since it was impossible to prove positively that either 

 grounding the separator or the use of the suction fan was a sure 

 preventive of fires, it was decided to design an automatic fire extin- 

 guisher that would afford protection irrespective of the cause of the 

 fire or explosion. Such a device is shown in Plates X and XI. It 

 consists of the following parts : Tank A mounted on top of the sepa- 

 rator ; within the tank a bottle, C, containing sulphuric acid ; a dis- 

 charge pipe, H ; a tripping mechanism composed of operating levers 

 G and main tripping fever L; a trigger, N; discharge nozzles, I; and 

 fuses, F, mounted in a wire line. In the discharge line between the 

 tank and the separator may be mounted a three-way valve, P, from 

 which there may be led, as at R, a hose connection for extinguishing 

 outside fires. The tank is filled with water containing soda. The 

 operation of the device is as follows : 



The presence of sufficient heat within the separator will melt one of 

 the fuses F. This breaks the wire line, releasing the trigger which 



