Bulk bags, also known as big bags and flexible intermediate bulk containers (FIBCs), are widely used across all industries in which bulk solid materials are transported, stored, processed or packaged. As a result, specialised designs of bulk bag handling equipment have been developed to fill them with maximum efficiency for virtually any low- to high-capacity application.
According to Albert Anglès, sales manager, Flexicon (Europe), the wide range of bulk bag filler configurations now available allows a user to fill as few as one bag per week or 20 bags per hour, dust-free. “Fillers range from basic stand-alone units to sophisticated systems with automatic pallet dispensers and roller conveyors,” he points out. “They can be fed by gravity or by a pneumatic, or mechanical conveyor, which connects to the fill head. The inlet of an empty bag is then attached to the fill head, which is height-adjustable to accommodate most popular bag sizes. Performance enhancements may include a vibratory deck to stabilise the bag, load cells for filling by weight, and options for combination drum and box filling.”
Bulk bag discharger/unloader designs are available for loading of bags using a forklift, or an electric hoist and trolley, which would eliminate the need for a forklift. He says: “Half-frame models rely on a forklift or hoist to suspend the bag, while split-frame models allow loading of bags in low headroom areas. Numerous performance enhancements are offered, including integral pneumatic and mechanical conveyors, pneumatic and hydraulic flow promotion devices, weigh batching controls, dust collection systems and receiving hoppers for manual dumping of minor ingredients from handheld sacks or containers.”
So, how might this work in action? By way of example. consider a new Flexicon Mobile Sanitary IBC Unloading and Conveying System transferring contamination-sensitive bulk solid materials from intermediate bulk containers (IBCs) to downstream processes, dust-free. The discharger frame is mounted on castors for in-plant mobility, while a hinged sub-frame supporting a surge hopper, flexible screw conveyor and support mast can pivot down for manoeuvring through doorways and low-headroom areas. The IBC frame is forklifted on to receiving cups, which position the IBC outlet onto the surge hopper inlet. Material flowing from the IBC into the charging adapter of a flexible screw conveyor is propelled at an incline, and discharged into elevated process equipment and storage vessels.
Taking a step back from the filling process itself, there is a sine qua non to be taken into account: the quality and suitability of the bags themselves, which must be beyond question. First, consider how, before a line of goods leaves a manufacturing plant, they will have been stored in containers that are safe, secure and sanitary; whether those contents consist of granular bulk or larger equipment, the container must have the strength to bear the weight and safeguard the contents from airborne contaminants and moisture. By the same measure, when products are stored and transported in quality bulk bags, the contents of each bag must arrive with the same clean and pure qualities as when they were packed.
“The efficiency, durability and ease-of-use that companies acquire from bulk bags come from the strong material used in the construction of such bags,” comments one leading bulk bag manufacturer, Western Bag & Supply. “The process of manufacturing bulk bags also entails high levels of scrutiny when made at qualified plants. Inspection helps ensure each bag can meet international safety standards for the transportation of products, chemicals, medicines and consumable goods.”
And what about safety factors relating to the filling of bulk bags? There are a range of ‘must dos’, according to BV Sarma, director of technical services at Pneumatic Conveying (Pneu-Con). “Lack of proper support will cause a filled bulk bag to lean dangerously to one side, creating a safety hazard to nearby personnel. The rule of thumb is the bag must be supported off the corners about 3” to 4” from the pallet during filling. This allows the fabric to stretch correctly and avoid leaning or slumping. The filler must also accommodate proper support, whether or not a pallet is used. A suitable filling frame will support the entire weight of a filled bag.”
Safety guidelines call for pre-inflating bag liners before use in most cases (formed/attached liners may not require pre-inflation). “The liner should extend past the fill spout or duffle, and it must be adequately secured during filling and discharge,” states Sarma. “Operators must tie off the liner within the fill spout or duffle in accordance with the manufacturer’s instructions. Choose a bulk bag filler with a pre-fill inflater for lined bags to make filling more efficient, safe, and a better end product. Consider pre-inflation methods such as a compressed air venturi or expander or a positive displacement blower.”
Before attaching the bag to the filling system, an inspection of bag loops, body, spout and bottom should be performed to ensure the package is suitable for filling, he states. “Also, a review of the equipment should include the spout seal, scale, height adjustment and any other attachment/support components. Just as important is that operators never exceed the safe working load (SWL) capacity of the bulk bag in use. FIBCs must never be filled to a level that affects the stability or that exceeds height-to-width limitations.”
Bags are typically rated at a 5:1 or 6:1 SWL ratio. For example, a bag rated to hold 2,000 pounds must pass a test at 10,000 pounds to meet the 5:1 standard. However, pushing those limits beyond the stated capacity may have dire consequences, such as a bag tipping over or bursting, the seams ripping open or the lift loops ripping off, he warns.