DUST CONTROL IN GRAIN ELEVATORS 19 
The individual dust collector has also been suggested. A small 
fan, mounted on the tripper and operated by the moving belt, pro- 
duces the suction necessary to collect the dust rising from the grain. 
The fan discharges into a small cyclone collector, mounted on the 
tripper, and the cyclone discharges the dust either into the grain 
entering the bin or into a receptacle, which can be emptied at a floor- 
sweep opening. The principal objection to this system is the disposi- 
tion of the exhaust from the small collector. This exhaust air car- 
ries with it much light, fine dust, which is difficult to separate from the 
air and the scattering of which constitutes an explosion hazard. A 
special collector for this work, which will collect all of the dust, may 
be leveloped, but the variation in the volume of dust which it will be 
necessary to handle at different times makes this difficult. To care 
for the exhaust of the cyclone it has been suggested that the exhaust 
pipe be extended into a cupola or monitor running over the path of 
travel of the tripper. Where closed bins are used it is possible to 
dispense with the cyclone collector and connect the fans so that they 
will exhaust into the bin into which the grain is running. In this 
case it will be necessary to have the bin vented sufficiently to prevent 
back pressure. 
AT BINS 
When grain is run into a bin from a spout, conveyor, or belt tripper 
the air in the bin is displaced and as the air is forced out of the bin 
it carries with it the dust separated from the grain entering the bin. 
The filling of a modern grain-storage bin displaces about 40,000 cubic 
feet of dust-laden air. Exhausting this dust-laden air inside the plant 
constitutes one of the greatest dust-explosion hazards and makes it 
almost impossible to keep the elevator properly cleaned. It is diffi- 
cult to understand why this practice is continued, when the method 
of controlling the dust is so simple and inexpensive. 
To care for the air displaced by the grain entering the bin, a gal- 
vanized-iron pipe, 12 inches in diameter, or of such dimensions that 
the velocity of the air in the pipe will not exceed 500 feet per minute, 
should lead by the most direct route from the bin to the outside 
of the building. Where fans installed on trippers exhaust into bins 
the vent should be larger. Some progressive elevator operators 
have vented to the outside air every bin in the house. This highly 
commendable practice is applicable to closed bins only. A hood 
to exclude rain, snow, etc., should be placed over the end of the 
vent (fig. 26). 
AT DISCHAEGES OF CONVEYOR BELTS 
When grain is discharged from a conveyor belt, the air traveling 
on its surf ace is disturbed and forms a large dust cloud unless some 
system of controlling it is provided. As conveyor belts may dis- 
charge into elevator legs, spouts, or bins, or upon other belts, different 
methods of dust control may be necessary for the different installa- 
tions. Equipment designed to collect the dust at points where 
conveyor belts discharge should collect only the light floating dust 
and keep the grain from entering the suction hood. When a belt 
discharges into an elevator boot, a hood at the edge of the receiving 
hopper of the leg (p. 6) can be used. When the belt discharges into a 
spout, a hood attached to the side of the spout opening can be used, 
