Toxic materials in bulk bags are transferred via closed vacuum conveying
system for compound batching operation
Several years ago, the ITT Surprenant Division in Clinton, MA, now
the Surprenant Wire and Cable Division of FL Industries, faced a
major materials handling problem. Two of the fourteen ingredients
used to compound various insulations for Surprenant's specialty
conductors were toxic and had to be batched in substantial quantities.
The ingredients were received in powder form in 50-lb bags which
were opened on the production floor, hatched on platform scales
and manually dumped into a mixer or blender. Despite extensive use
of exhaust ducting and respiratory protection for the workers in
the area, Surprenant engineers were still concerned with the impact
of toxic contamination on the environment and the threat of not
meeting OSHA regulatory standards.
With plans already underway to update and automate their compounding
operations, Surprenant engineers decided to obtain the two toxic
ingredients in semibulk bags. The bags are lifted by a monorail-mounted
hoist and positioned in a bulk bag unloader. The weight of the bags
rests on the bed of the unloader, forming a dust-tight seal against
the ring on the discharge opening. The discharge spout or "neck"
of the bag can be pulled down into a vacuum-vented discharge chamber
and opened, after which the access hatch on the chamber is closed.
Agitator pads in the unloader bed gently massage the bottom of the
bag to promote the flow of the material into the discharge opening.
A screw at the bottom of the discharge chamber feeds material into
a vacuum conveying system for transfer to a closed storage bin.
Upon demand, an auger under the storage bin delivers material at a controlled
rate into a weigh hopper on the floor below. After weighing, the material is conveyed
by vacuum to a receiver positioned over a mixer or blender on the upper floor.
The entire material path from bag to mixer is enclosed and dust tight.
Because of the bulk packaging, the cost
per pound of materials is lower. In addition, handling costs in receiving, storing
and discharging the materials are sub