Making the Switch to Receiving Ingredients in Bulk Bags

Receiving ingredients in bulk bags rather than small bags can improve your plant's bottom line. This article gives practical, step-by-step advice on how your plant can make the switch. Sections cover exploring bulk bag handling; planning to convert your plant to handling bulk bags; meeting to establish the bulk bag spec, filled bag quality, bag rejection procedure, and whether the bags can be reused; as well as organizing your plant to handle bulk bags.
If you're receiving dry bulk ingredients in "small" bags (typically 50 lb), you've probably considered receiving the ingredients in bulk bags to save money. The easy part is calculating how much money you'll save per ingredient-pound based on annual usage. The hard part is determining how to handle bulk bags in your plant.
Bulk bags require different equipment for emptying the bags, as well as different handling procedures to ensure worker safety, to control dust, and to reuse or discard the bags. But if you want to make the switch, you're probably prepared to explore these differences further.
Three planning steps are critical to a successful plant conversion.
Step 1. Once you've received literature and sample bags from the bulk bag manufacturers you've contacted, and you've also visited installations that discharge bulk bags, examine literature and any videotaped discharger demonstrations from the bulk bag discharger manufacturers.
Step 2. Some bulk bag discharger manufacturers also offer test center demonstrations. Plan to attend a manufacturer's demonstration, which typically lasts a full day. The manufacturer will charge for the demonstration, but the money will be well spent because you'll learn much about discharging bulk bags and receive hands-on training.
Before the visit, ship one or two bulk bags filled with your ingredient (or ingredients) to the manufacturer's test center, along with details of your discharging requirements (such as rate and dust containment). If your ingredient is a food, pharmaceutical, or hygroscopic material and requires a bulk bag with a polyethylene liner, ask the test center to demonstrate discharging with two or more discharges and bags that have different liners. Then you can see how each type of liner and discharger works as the liner is secured, punctured, and removed at discharge. (If your ingredient is toxic, ship a nontoxic simulant because a test center isn't equipped to handle toxic materials).
At the demonstration, the test center will discharge your ingredient from different bulk bags using various dischargers. You'll see first-hand how the equipment works, how dust is controlled, and how the bulk bags are handled and emptied. Ask the test center to refill your ingredient into bulk bags and ship them back to you after the demonstration.
Step 3. When you're comfortable with your bulk bag knowledge, determine how feasible it is to handle bulk bags in your plant. Consider these points: what bag size is right for your ingredient weight, whether your plant can handle stacked bulk bags, how the bulk bags will be lifted and moved, whether there's enough headroom at the discharge location, and what type of bulk bag outlet and discharge technique you need.
What bag size (height and base) is right for your ingredient weight? To contain about 1 ton of ingredient, typical bulk bag height (measured as side-seam height) ranges from 30 to 70 inches, and the base size (measured as base-seam dimensions) is commonly either 35 inches square or 35 by 41 inches. Ensure the bag height is tall enough to contain your ingredient weight but not so tall that it makes the bag unstable. Select a base size as large as possible for safely stacking the filled bags, and ensure the base size will permit press-fitting the filled bags on pallets into your truck or shipping container.
Can your plant handle stacked bulk bags? As long as the bulk bags are filled correctly – with straight sides, with the ingredient compacted to its highest bulk density, and with no more than 2 inches of fabric above the ingredient surface – the bags can be stacked two or three high on pallets. Three high is most efficient, but isn't always possible, depending on available headroom in your handling area and on the bag stability.
How will the bulk bags be lifted and moved in your plant? A bulk bag can be moved either by a forklift truck (with or without pallets) or by a hoist (without pallets). When placed on a pallet, the bag is lifted from its bottom. Without a pallet, the bag is lifted from its corner lifting loops.
Is there enough headroom at the discharge location? You'll need about 12 feet of headroom so a forklift truck or hoist can lift a bulk bag above the discharger's top (4 to 6 feet above the floor) without touching the ceiling. If you locate your discharger above downstream equipment, you'll need more headroom. If you lack sufficient headroom, you can locate the discharger to one side of the downstream equipment and use an inclined conveyor to move the discharged ingredient above the downstream equipment.
What type of bulk bag outlet and discharge technique will provide the production rate and dust containment you need? A bulk bag outlet is tied, and a bulk bag discharger has an access door that permits the operator to reach the bag bottom to untie the outlet. The outlet style varies, depending on whether the bag in lined. If you must contain dust, you'll need a lined bag and, at discharge, you must untie the outlet and seal the liner to the downstream process piping. This step takes extra time when readying the bulk bag for discharge.