DUST EXPLOSION'S IIST GRAIlSr SEPARATORS. 15 



1. Prevalence and distribution of static electricity in and about 

 the separator. 



2. Inflammability of smut dust. 



3. Effect of introducing foreign material, accidentally or mali- 

 ciously, into the separator. 



MEASUREMENT OF DISCHARGES OF STATIC ELECTRICITY. 



Both steel and wooden separators were tested while threshing both 

 smutty and smut- free wheat and also oats. The common plan of pro- 

 cedure was to establish a good reliable " ground " by driving an iron 

 rod deep into the earth, pouring water around it, and connecting 

 one lead from a galvanometer to this rod. The other lead from the 

 galvanometer was loose and was touched in turn to cylinder shaft, 

 frame, blower, and all moving parts. 



On all machines tested strong discharges were obtained from 

 almost every part of the machine to the ground, but in many cases 

 the strongest appeared to be from the front wheels to the ground. 

 Strong discharges were also obtained between the cylinder shaft and 

 concaves, and slight ones between a moving and a stationary metallic 

 part, and between any two moving parts. The galvanometer used 

 in the tests was the ordinary two-coil instrument showing deflection 

 and direction but not magnitude of the current. 



FIELD EXPERIMENTS. 



At the close of the threshing season three day tests were run on 

 a donated separator in the field in northern Idaho, under as nearly 

 actual threshing conditions as could be secured at that time. As it 

 was impossible to obtain unthreshed smutty wheat, it was necessary 

 to make use of straw mixed with loose smut secured from a local mill. 

 At the time of the tests the temperature- was at least 50 degrees below 

 that prevailing during the threshing season, and the weather was 

 unusually damp. Because of the conditions existing, the results of 

 these tests can not be considered conclusive, but they tend to confirm 

 the deductions made from the investigations in the field during the 

 threshing season. 



STATIC ELECTRICITY AND ELECTRIFICATION OF SMUT DUST. 



The experimental work carried on during the investigations proved 

 conclusively that, under favorable atmospheric conditions, static 

 electricity is present on all types of machines. In the Pacific North- 

 Avest humidity conditions during the entire threshing season are 

 favorable for the production of static electricity. The air as a rule 

 is very hot and dry, with the humidity on certain days as low as T 

 per cent, the average being about 17 per cent for the middle of 

 the day. 



