Issue link: https://www.e-digitaleditions.com/i/1242780
May 2020 / 29 FIBCs that have been correctly sized and properly filled are stable and safe to handle and stack, but stabil- ity must be maintained, not just after filling but during stacking, unstacking, transporting, and restacking. If FIBCs are to be stacked, unstacked, and restacked, the bottom FIBC, which has a more compressed base, must always be positioned on the bottom of the new stack. FIBCs that have become banana shaped, meaning they lean to one side, can't be corrected once they have been filled nor can they be stacked. These banana-shaped FIBCs are dangerous and expensive to handle. Choosing the right FIBC is critical, especially regarding its design and size, as the most expensive part of an FIBC filling system is the bulk bag itself. Over time, the FIBCs' cumulative costs usually far outweigh the one-time capital cost of the filling equip- ment. The wrong choice isn't only expensive in terms of wasted materials and high labor costs but could also lead to a loss of customers' confidence in FIBCs, lead- ing them to using drums, boxes, or 50-pound bags for material. Choosing a standard FIBC size at a reduced price that doesn't suit the application's exact needs and those of the end user can lead to disaster. Trials should always be conducted on the chosen filling equipment and discharger. And while filling an FIBC is relatively easy, discharging it may not be if incorrectly filled or the wrong type of bag is used. PBE For further reading Find more information on this topic in articles listed under "Bagging and packaging" and "Bags" in Powder and Bulk Engineering's comprehensive article index in the December 2019 issue or the article archive on PBE's website, www.powderbulk.com. Don Mackrill (dmackrill@spiroflow.com, 704-246-0992) is the chief operating officer for Spiroflow Systems. He's responsible for engineering, production, and field support. He has a BS in electrical and electronics engi- neering from the University of Saskatchewan and has spent 25 years in the bulk solids handling industry. Spiroflow Systems Monroe, NC 704-842-3437 www.spiroflow.com • The FIBC should be placed as close to a central position on the pallet as possible, especially after filling, as bags that aren't centered wouldn't likely be able to fit side by side in a trailer or container. • If the FIBCs are to be stacked with a pallet between the bags, close-slatted pallets (both top and bottom) should be used to prevent the FIBC's top and bottom from protruding through the slats, which could result in the bags pinching and tearing as they're handled and removed from the pallet. These types of pallets tend to be expensive and may only be financially justifiable for in-plant use if their return can be guaranteed. • For safe FIBC stacking, it's not advisable to stack bags 2 high if the bags are more than 5 feet tall or 3 high if they're more than 4 feet tall. Note that this applies regardless of whether they're on pallets or not. The general rule is that FIBCs shouldn't be stacked higher than twice their base width, as shown in Figure 4. As mentioned earlier, slip sheets are thick plastic or cardboard sheets that go under an FIBC to prevent con- tamination of the bag's bottom. Slip sheets can be used with or in lieu of a pallet when dealing with FIBCs. There are some restrictions to using slip sheets though. • Stability is reduced when stacking FIBCs that are placed on slip sheets. FIBCs with seam heights greater than 4 feet, 3 inches shouldn't be stacked at all when using slip sheets, not even at 2 high. And bags that have seam heights greater than 3 feet, 3 inches shouldn't be stacked more than 2 high when using skid sheets. • The same restrictions that apply to centering FIBCs on pallets also apply to slip sheets. • The general stacking rule applies for FIBCs on slip sheets as well. FIGURE 4 Filled and stacked FIBCs ready for shipment