How To Fill Bulk Bags

How to fill bulk bags?  I understand why many people ask that question. You business is growing, you are thinking about increasing the size of your bagged bulk material for shipment to your customers. No more just offering skids full of 50 or 100lb bags. You need to ship a skid with a 2000lb FIBC on it. Maybe even multiple bulk bag sizes.

Each application for bulk bag filling can be very different. Custom designs and manufacturing is required and a supplier needs to be able to provide the highest quality automation control systems for bulk bag filling.  We at Sterling Systems & Controls can handle that for you.  Sterling Systems works with numerous customers to address this question of how to fill bulk bags.

As an example, Systems & Controls has designed and manufactured an automation and process control system for bulk bag filling in an application where the automation and process control system includes a Motor Starter Process Control Panel. Included in this control panel (at right) is a PLC with discrete and analog outputs, an HMI 10” color touchscreen, custom automation software by Sterling Systems including all MOA (Manual-Off-Automatic) switches with running indicating lights, four (4) motor starters, and all necessary fusing, wiring etc. to meet the application requirements. The Motor Starter Process Control Panel is also interfaced to a pallet dispenser PLC using Ethernet IP messaging.  Sterling Systems & Controls is a UL Listed control panel manufacturer.

The operator interface touchscreen displays the automated bag filling process (screenshot below).  This touchscreen is mounted in the door of the control panel and has a system overview screen graphically depicting all of the equipment being automated and that explains how to fill bulk bags. Operators can adjust operating parameters for the control system at the touchscreen. These parameters include, but are not limited to, equipment timers, weight set points and others. Multiple levels of security is also provided as part of the automation system so that adjustments can be made by selected individuals.

Sequence of Operation (How to Fill Bulk Bags, Example of Automating Bulk Bag Filling)
  • An empty pallet is on the in-feed pallet conveyor .  With the system in the AUTO mode, if there is a pallet on the conveyor confirmed by a photo-eye and no pallet on the conveyor mounted on the deck, the in-feed conveyor will start to index the empty pallet forward.  If there were a pallet in the bulk bag filling station confirmed by a photo-eye, the in-feed conveyor will hold the pallet in place.
  • A surge hopper is at the inlet and it maintains a continuous flow of material while empty bulk bags are being installed on the filling machine.  Mounted to the discharge of the surge hopper is a pneumatically operated slide gate valve with a variable positioning actuator.  When filling in a fast mode, the valve is fully open.  At the first weight preset the valve partially closes for a moderate rate of feed.  At the next preset, the valve fully closes and the vibrating deck is actuated for a preset, adjustable time cycle to increase density in the bag.  When the “densification cycle” is completed and the scale is stabilized, the valve will partially open to “dribble” the last amount of material as required into the bag, then close when the target weight is achieved.
  • The swing-down bulk bag filler head lowers to a position that allows the operator to load a new bulk bag, then raises to the filling position.  The lowering and swinging to a loading position is initiated through pushbuttons.  When the operator is ready, the load pushbutton is depressed.  This signals the motor to reverse, lowering the fill head and releasing the pneumatically actuated latches that release the fill head to swing into the loading position.  When the operator attaches the bag loops to the fill head, the latches are closed manually.  The bulk bag filling nozzle is placed over an inflatable cuff which seals the bulk bag to the fill head.  The operator depresses a pushbutton on the fill head to activate the inflatable cuff.  The operator also presses a pushbutton that actuates the motor to reverse, moving the fill head to the up position.  As the fill head moves up, a limit switch closes to actuate a solenoid valve that swings the head into the filling position.
  • The fill head includes a fan that blows open the bag to get the bag in the proper shape for filling.  A spring loaded pushbutton must be held depressed to allow the fan to operate.  When the pushbutton is released the fan stops.  When the operator believes the bag has been properly inflated, the pushbutton is released.  This can be going on as the fill head moves to the filling position.
  • When the fill head is in at the correct height for filling, a limit switch is activated to stop the motor.  This switch will activate a timed cycle that will first Tare the scale, open the slide valve allowing the bulk bag to begin filling.
  • During the filling operation it may be necessary to vibrate the bulk bag to pack the material, thus making more room for material.  This is normally accomplished at various weight set points.  When this is activated, a set of four (4) bellows are pneumatically inflated to lift the deck away from the load cells before the vibrator starts.  Some material requires more packing others.
  • When the target weight is achieved and the fill valve closes a second time, an adjustable cycle begins that allows the in-flight material to clear the fill chute, the fill cuff deflates releasing the fill nozzle, the latches supporting the bag loops release and the loops fall to release the bag.  The fill head then indexes up to a release height, closing the highest limit switch.  This is the signal for the powered roller deck to activate, moving the pallet with the filled bag onto the staging conveyor and an empty pallet to move forward.
  • The pallet with the filled bag will move forward, indexing to the last photo-eye.  If there is already a pallet with a filled bag at this position, the pallet will index to the second position.  If the second position has a pallet with a filled bag, the pallet will index to the first position.  If filled bag pallets occupy all of the zones of the staging conveyor, a filled bag pallet will not index onto the staging conveyor until a pallet is removed from the staging conveyor.  When a pallet is removed, the staging conveyor will automatically start to index a waiting pallet into that empty position.

Each bulk bag filling system can be unique to fit your exact application.  Give Sterling Systems & Controls, a call at 1-815-281-5378, email at, and at visit the rest of our website at