DUST CONTROL IN GRAIN ELEVATORS 3 
The layout of the dust-collecting system was carefully studied in 
each plant. All the points where suction was applied, floor sweeps 
installed, or natural ventilation provided were carefully noted. The 
dust conditions at various points in the grain-handling system were 
noted, and the causes for those conditions were determined as nearly 
as possible. A drawing of the dust-collecting systems and detail 
drawings of all dust-control applications were made. The efficiency 
of the dust-control equipment and the effect of suction at various 
points were observed. Other data to assist in determining the 
proper methods of controlling dust at various points were obtained. 
At all suction hoods observations were made to determine whether 
the air velocity was great enough to lift and carry grain while collect- 
ing dust. When a hood apparently was not functioning satisfactorily 
notation was made of its construction and installation, its distance 
from the fan, and the number of elbows and suction connections at- 
tached to the main duct and branch through which the suction was 
provided. Tests were made to determine the air velocity at the point 
of application of suction by means of an anemometer inserted beneath 
the hood. 
Pitot tubes were employed, according to the methods commonly 
used, for testing the performance of the fans of the dust-collecting 
system. The fan speed was recorded by a speed counter. 
The apparatus developed in the dust-explosion prevention labo- 
ratory of the Bureau of Chemistry to determine the quantity of dust 
present in the air 2 was used to determine the density of dust clouds 
at various points. 
In all these surveys an effort was made to improve the equipment 
found. A public-service patent was granted to the Department of 
Agriculture for an improved design for a piece of equipment to re- 
place one which was unsatisfactory. Many of the recommendations 
submitted to the officials of the elevators visited have been adopted. 
Laboratory work.— The air velocity which will collect the dust but 
will not lift the grain was determined in the laboratory. Hoods 
providing a permanent and assured control of the air velocity at the 
point of application of suction and an efficient grain trap were de- 
signed and tested. All equipment recommended in this bulletin has 
been tested, so far as possible in the laboratory, under conditions 
similar to those existing in grain elevators. 
METHODS OF DUST CONTROL 
The dust conditions in a grain elevator are effectively controlled 
only when (1) dust clouds are eliminated at their point of origin by 
the application of suction, (2) dust accumulations are promptly re- 
moved from the building, either by a vacuum cleaning system or by 
a floor-sweep system, and (3) the elevator and equipment are well 
ventilated, 
In this bulletin the mechanical methods of controlling dust con- 
ditions have been divided into dust collection and dust removal. 
Dust collection deals with the methods of removing dust clouds at 
their source by means of induced air currents, supplied through 
specially designed hoods connected to a fan system. Dust removal 
2 L. J. Trostel and H. W. Frevert, "Collection and Examination of Explosive Dusts in Air," published 
in Industrial and Engineering Chemistry (1923), vol. 15, no. 3, p. 232. 
