Increasingly, manufacturers are recognizing the advantages of transporting dry bulk ingredients in flexible intermediate bulk containers (FIBCs or bulk bags). The savings in ingredient costs, material handling, warehousing and transportation requirements can be substantial.
These benefits can only be realized when appropriate bulk bag filling equipment is applied. Properly designed FIBC bulk bag fillers deliver a dense, stable package that can be safely and easily stored, transported and discharged. The savings that properly filled FIBCs deliver can be augmented by automating the filling system to increase filled bag output.
Depending on the application, automated bulk bag filling systems can range from a single, microprocessor-controlled machine filling 10 bulk bags per hr, to multiple units each outputting 20 bags per hr, to a single, multistation filler production 70 one-ton bags per hr.
First, Fill Bulk Bags Properly
Any benefits from filling FIBCs in greater volume must be qualified by careful analysis of the quality of the resulting filled bag. For example, if you use one filling machine to fill 20bags per hr without proper densification, but then have to store them unstacked or in racks because the bags are leaning and unstable, you are paying a premium for storage space, transportation and labor.
It is most effective to specify a bulk bag filling machine that maximizes the ingredient in the bag and produces a straight and stable package. Then, once you can stack, convey and transport the filled bag efficiently, you can investigate automation techniques to best match your production rates and secure the highest efficiency for your operation. Look for a bulk bag filler designed to hang fill the bag to produce straight sides and to fill the corners of the bag first to maximize stability. A fill should also densify and compact the ingredient and weigh the bulk bag accurately and reliably.
Bulk Bag Filler Automation Opportunities
Filling a bulk bag comprises three main operational steps: rigging the bag, filling the bag and taking the filled bag away from the machine. Automation of an FIBC filling machine can be approached on four levels: 1) adding an automatic control system to a manual machine, 2) automating the removal of the filled bag and placing of the pallet (if necessary), 3) preweighing the ingredient to reduce overhead time associated with bag rigging and ingredient feeding, and 4) providing a multistation machine to simultaneously perform the three operational steps.
A typical filling operation requires the rigged bag or liner to be inflated, the weight of the machine or part of the machine to be tared out, the fill to be initiated, the densification and compaction to be cycled, and the fill rate to be slowed by some method in order to successfully achieve the target weight.
A microprocessor-based controller can automate almost all of these steps. Once the operator has rigged the bag and inflated it, taring the weighing system initiates the automated fill cycle, whereby the controller takes over the sequencing of starting and stopping ingredient flow into the bag, densification and weighting. A typical bulk bag filling system of this sort can achieve an output of up to 10 bags per hr depending on the maximum flowrate of ingredient into the bag. A manual system may be only capable of six to eight bags per hr.
Automatic Bulk Bag Removal
Typically the filled bulk bag is removed from the filling machine by a forklift truck. Providing a means of quickly freeing up the space inside the filling machine to rig a second bag, once the first is full, can increase the output rate and reduce the need for a dedicated forklift truck. Roller or chain conveyors can be positioned in the filler to remove the filled bag automatically. Conveyors, either motorized or gravity type, can be added to allow filled bag accumulation for later transport by forklift truck.
Pallet and slip sheet dispensers can be added to the system, along with additional motorized conveyors, to automatically position a pallet in the machine or to pick up the filled bag on a pallet. This eliminates the need for an operator to manually place the pallet in the machine.
Automatic bulk bag removal can increase the output of a stand-alone, microprocessor-controlled filler to 12 to 14 bags per hr. Filled bags with specially designed lifting loops can be handled easily with fork trucks. This may further increase system output as pallet need not be accommodated.
Preweighing Bulk Bags
The final step to increase the output of a single station filler is to reduce the time required to feed ingredient into the bag to meet a target weight. This can be done by preweighing the ingredient in a weigh hopper located directly above the filler. The “charge” of ingredient is fed into the hopper to the target weight while the system or operator removes the previously filled bag and rigs the next.
Once the new bag is rigged, the preweighed charge is dropped into the bag quickly. As soon as the charge has left the preweigh hopper the system begins to fill the next bag’s charge in the weigh hopper. In this configuration, the bulk bag filling machine itself does not perform weighing and, therefore, does not require a weighing system. However, the overall control system must be expanded to simultaneously perform weighing in the preweigh hopper while controlling the other functions associated with densification, automatic bag removal and pallet and slip sheet dispensing. Pre-weighing, in association with automated controls and automatic bag removal, can increase the output of a single filling station to 20 bags per hr.
Multiple Bulk Bag Fillers Increase Bulk Bagging Rate
For production rates greater than 20 bags per hr, multiple bulk bag fillers can be used. The capital cost versus production rate must be assessed to arrive at the most effective total system configuration. For example, if 30 bags per hr are required, two automatic bag removal systems would be most appropriate. If 40 bags per hr are required, two preweighed, automatic bag removal systems would be selected.
More bulk bag filling machines can be added and sequenced to further increase bag output. If more than 50 bags per hr are required a decision must be made based on available space, operator availability and associated labor costs and capital cost. A high-capacity system may be justified in this case.
If more than six bulk bags per hr are needed to be filled, it is worth considering automation possibilities. A single machine’s output can be enhanced by filling-specific controls, preweighing, and integrating conveyors and pallet and slip sheet dispensers. Further, increases in output can be achieved by applying multiple units as long as sequencing of the operator functions is carefully reviewed.
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