If you purchase resin in bulk, it has to be unloaded quickly and efficiently. A bulk unloading system is typically a powerful push-pull system located outside the plant. It provides powerful vacuum to pull the material from a railcar. Then the material is pushed up into the silo.
After the connection is made from source to destination and the pump is activated, loading continues until the level sensor shuts the pump down.
These systems are custom designed based on the specifics of the application. Multiple silos are common so there must be an easy way to switch material flow. Bulk unloading systems are usually protected from the weather by an enclosure.
Note: Transfer of materials from bulk delivery trucks to silos is typically accommodated by a blower system provided on the bulk truck itself. For this application, "truck fill" lines, from the top of the silo down to ground level are provided on each silo for connection to the truck's unloading system.