36 BULLETIN 1373, U. S. DEPARTMENT OF AGRICULTURE 
SUCTION REGULATORS 
Equipment designed and tested by the Bureau of Chemistry (fig. 
29) places a dust-collecting installation under the absolute control of 
any agency that has supervision over the weighing of grain. The 
United States Department of Agriculture hood (p. 37) does not pick 
up grain or light material with a high air velocity in the branch pipe. 
f^f 
^Inspection Cover 
-G 
-3-4 
P— 
5y 
«* 
Fig. 27.— Grain trap 
The United States Department of Agriculture inspection trap (p. 44) 
shows the inspector the nature of the dust which is being drawn into 
the hood. The United States Department of Agriculture air-velocity 
control valve (p. 45) enables the inspector to control the air velocity 
in the branch line so that the dust-collecting installation will operate 
satisfactorily. 
