DUST CONTROL IN GRAIN ELEVATORS 
37 
UNITED STATES DEPARTMENT OF AGRICULTURE HOOD 
The use of a properly designed hood insures a permanent control 
of the air currents at the point of suction application, because the 
velocity maintained in the main lines is reduced until the velocity 
Fig. 28.— Grain trap 
at the hood intake is too low to pick up grain, chaff, or other material 
which might affect the weight. 
Experiments to determine the velocities at which various grains 
are lifted were conducted at the United States Department of Agri- 
culture experimental farm at Arlington Va. 
U. S. D. A. 
Velocity 
Control Valve 
U. 5. D. A. 
Inspection 
Trap 
Belt 
Fig. 29.— Controlled application of suction 
