DUST EXPLOSIONS IN GRAIN SEPARATORS. LS 
suggested itself at the beginning of the study. The department, 
early in 1915, took this matter up with various representative manu- 
facturers with a view to observing the efficiency of such an installa- 
tion on threshing machines during operating conditions. ‘The in- 
vestigators collected information pertaining to the efficiency of such 
installations of this nature as were working in the field. 
In one case a machine equipped with a blower system of this kind 
threshed 27 days in 1914 and 20 days in 1915. During this time only 
one flash occurred in the dust pipe, but this did not cause a fire. 
The blower system consisted of two 15-inch fans mounted on the 
frame of the separator below the cylinder and a 20-inch suction fan 
mounted on the top of the separator. ‘These fans were so arranged 
that the draft passed up and around the cylinder in the direction of 
the travel of the grain and straw. The opening to the suction fan 
was 4 inches in width and extended across the separator. In addi-: 
tion to preventing the formation of an explosive mixture of dust and 
air, this arrangement had an additional value, according to the 
owner, in that it cleaned the grain during the threshing to such an 
extent that he was enabled to get a better price for it. The dust 
collected by this system was blown through a special 10-inch pipe to 
the straw stack. 
In another case a single suction fan was located beyond the ae 
der on the opposite side from the main drive belt. In two cases 
where fire occurred the fan drew the fire out of the machine before 
any damage was done. The discharge was so located that the fire 
did not reach the straw pile or the standing grain. 
One of the machines operating in a section of the territory where 
explosions were very frequent had two fans drawing dust from the 
ends and above the cylinder. In this machine, however, the arrange- 
ment was such that there was in the system a large square corner 
where smut, chaff, and dirt collected, thus defeating the true purpose 
of the fans. 
SPRINKLER SYSTEMS. 
In addition to developing an efficient grounding system to remove 
the static electricity generated during the operation of the machines, - 
and in addition to conducting experiments with blower systems, the 
investigators endeavored to determine the relative efficiency of types 
of sprinkler systems and fire extinguishers in use. It was found 
that there were many different types and patterns of sprinkler sys- 
tems in general use throughout the territory, but they were all 
included practically in three different classes: . 
1. The chemical fire extinguisher. 
2. Water with (a) air pressure, (0) steam pump compression. 
3. Hose from boiler to separator. 
