DUST CONTKOL IN GEAIN ELEVATORS 
47 
were not operating than when they were running. In tests Nos. 1 
and 4, when the fans were operating, the total shrinkage loss was 140 
pounds for a total weight of 232,600 pounds; in tests Nos. 2 and 3, 
when the fans were not operating, the loss was 180 pounds in a total 
weight of 232,700 pounds. The largest shrinkage loss occurred in 
test No. 2 when the fans were not running. The losses in all cases 
were low. The results indicate that the effect on grain weights when 
suction is applied is practically the same as in the normal handling 
of grain without dust-collecting equipment. 
Preliminary investigations were conducted by the Bureau of Chem- 
istry in 1918 in a number of terminal elevators to determine the 
quantity of dust collected while elevating carlots of grain. The 
results of tests on 39 cars showed an average of 73^ pounds of dust 
collected per car. Several cars in this lot contained very dusty oats 
and several others contained screenings. An average of 19 pounds of 
dust per car was removed from four cars of No. 3 white oats. In 
spite of the fact that these tests were made with 1918 equipment, 
which was not so designed that at all fan speeds it would be impossible 
to lift heavy particles from the moving grain stream, the quantity of 
dust gathered by the dust-collecting system probably would not 
exceed the natural loss incurred without dust-collecting equipment. 
Table 7. — Shrinkage when grain is handled with and without suction 
Test No. 
First 
weight 
Second 
weight 
Differ- 
ence in 
weight 
Differ- 
ence per 
1,000 
bushels 
Shrink- 
age 
Remarks 
1- > 
Pounds 
116, 440 
116,420 
116, 280 
116, 160 
Pounds 
116,380 
116, 280 
116, 240 
116, 080 
Pounds 
60 
140 
40 
80 
Pounds 
30.9 
72.3 
21.3 
41.6 
Per cent 
0.052 
.120 
.034 
.069 
2 _ 
3 
Fans off. 
Do. 
4 
Recent tests conducted by the supervisor of the Minnesota Rail- 
road and Warehouse Commission in an elevator equipped with a 
dust-collecting system, designed and installed so that only the light 
floating dust is removed, showed the following results : 5 
During the unloading of a car containing 50,000 pounds of flax 
screenings, 13 J^ pounds of dirt, refuse, and fibrous material was 
collected. In the unloading of another car containing 50,000 pounds 
of No. 2 northern wheat, only 253^ ounces of dust was collected. 
These two tests were conducted on the extreme grades of material 
generally handled in a terminal grain elevator. 
The quantity of dust removed by a dust-collecting system depends 
upon the design and upon the control of the air currents. If proper 
care is taken in installing the equipment, no more dust will be ex- 
hausted from the plant by a. dust-control system than naturally 
settles when no dust-control measures are applied. In the one case 
the explosion hazard is greatly reduced with the removal of the dust 
to the outside of the plant; in the other case the explosion hazard is 
increased, with the gradual accumulation of dust within the plant. 
6 "The Removal of Floating Dust in Grain Elevators," a report prepared by the Underwriters Labo- 
ratories and published by The National Safety Council, 1924, p. 31-32. 
