The dual bag nozzle system was designed to reduce dust
from three major sources during bagging [USBM 1984a, b, 1986c; Cecala and
Muldoon 1985; Cecala and Thimons 1989]. The system is composed of an improved
bag clamp designed to reduce the amount of product blowback during bag filling
(Figure 4-12).
The clamp reduces blowback by making direct contact with
approximately 80% of the fill nozzle. The system incorporates a dual nozzle system,
which is a nozzle within a nozzle. The inner nozzle is the normal fill nozzle. The
outer nozzle incorporates an air exhaust system, which exhausts excess pressure from
the bag when it has finished filling. The exhaust system is powered by an eductor,
which uses the venturi effect to exhaust the bag at approximately 50 cfm.
Depressurizing the bag reduces the “rooster-tail” of product which spews from the
bag when it is ejected from the fill station. By reducing the blowback and rooster tail,
the amount of product and dust on the outside of the bag are minimized, which also
reduces the dust liberated during this process. During a field analysis on this dual bag
nozzle system, the bag operator’s dust exposure was reduced by 83% [USBM 1984a]