22 
BULLETIN 1373, U. S. DEPARTMENT OF AGRICULTURE 
by a difference in construction. The marine tower in elevators 
where boats are unloaded is usually Yery dusty, and the control of 
the dust at this point is given little attention. One elevator superin- 
tendent has partially met this situation by installing a vent leading 
from the garner bin through the roof of the tower (fig. 18). This 
vent, a 30-inch pipe, capped with a ventilating hood, relieves the 
pressure created in the bin by the grain discharged from the leg and 
prevents to some extent the dissemination of dust within the tower. 
The principle of this installation is the same as that for the installa- 
tion recommended for the control 
ventilator thmph f <j U st in garners, scale hoppers, 
Roof of Mar/no -, -. • ° ' * r J 
To^er. an d DmS. 
Another point where dust 
clouds generally prevail is around 
turn heads or circle spouts on the 
distributing floor or in the base- 
ment, especially where two or 
more of the spouts are connected 
or where they enter elevator 
boots, hoppers, or bins having 
other spouts leading into them. 
In such cases the pressure pro- 
duced by the grain flowing into 
the boot, hopper, or bin forces 
dust-laden air out of any open 
spouts leading from a turn head 
or circle spout to the same boot, 
hopper, or bin. A simple way to 
remedy this condition is to place 
in each spout a flap valve con- 
sisting of a piece of belting, which 
is so suspended that the spout 
will always be closed except when 
grain flows through it. In addi- 
tion, the boot, hopper, or bin into which the grain is discharged should 
have dust-control equipment (p. 34). 
Fig. 18.— Ventilating system in a marine tower 
DUST REMOVAL 
Dust accumulations and deposits are removed from the floors, 
walls, ledges, and equipment of an elevator and conveyed to a central 
point of deposit outside the plant by a number of methods. 
BRUSH-AND-BROOM METHOD 
The dust, brushed down from overhead structures by hand 
brushes, is swept into piles by floor brushes and removed from 
the building in sacks or baskets or through a chute or spout leading to a 
