Use Flexible Bulk Containers Safely.

Sources of static charge buildup and discharge are significant hazards

Flexible intermediate-bulk containers, also referred to as bulk bags or FIBCs, are packages designed to hold 500-1,000 kg of solids. The bags are woven from synthetic fiber, typically polypropylene, which is extrusion-coated with thin film to keep the product from leaking out of the weave.

FIBCs have been increasingly used for bulk shipments over the past 10-15 years. This has occurred at the expense of smaller containers, such as bags and drums, because of the significant savings that can result when switching to FIBCs. Higher operating efficiencies are also possible because fewer containers are handled for a given quantity of material. This leads to lower handling and shipping costs, faster transfer of product into and out of the container and a reduction in the amount of waste to be dealt with after the container is emptied. Furthermore, since one container is used and therefore must be opened and closed only twice -- once for filling and once for emptying -- less product is lost to the surrounding environment. This improves general plant housekeeping and reduces the probability for exposing personnel to the product.

When confronted with a choice between FIBCs and traditional containers, the engineer should take into account five main considerations: economics, product quality, regulatory requirements, processability and safety. The first four topics are mentioned only briefly in this paper, with safety issues making up the bulk of the remaining discussion.

General considerations

When one is faced with the decision to switch to FIBCs or to design the product-handling system of a new process, a life-cycle cost analysis is a powerful method to compare FIBCs with other shipping alternatives, such as drums, small bags, or rigid intermediate bulk containers.

Life-cycle cost analysis: The life-cycle cost analysis must include economic factors, such as the amount of capital invested in container inventory and in loading and unloading equipment, and the variable costs associated with handling and shipping. The latter includes the use of special materials-handling devices such as fork lifts, hoists, special close-slat pallets, and protective outer cardboard boxes where necessary. Container recycling can help to reduce the life-cycle cost, since the cost of refurbishing a bulk bag is only about 60% of the cost of a new bag. Finally, the life-cycle analysis must include the used-bag disposal cost. This may involve landfilling, incineration, or fees for recycling FIBCs to virgin polymer.

Product quality: The second general consideration is product quality. Product contamination is usually the primary quality issue. Reactions with atmospheric oxygen or moisture in the air may degrade the final-product performance, or may lead to physical changes within the material that result in a hard-to-process or non-processable mass. Special liners that act as barriers to the contaminant should be considered where this is an issue.

Another source of contamination may originate from the bag material itself. Anti-static agents that are employed in the packaging materials may end up in the product, either from chemical absorption or as a result of mechanical abrasion.

Contamination may also occur where bags are cleaned and reused. This can be avoided by adopting a closed-cycle philosophy when recycling. The bag should be used only for one specific product, and care must be taken to ensure that the bag is properly cleaned before reuse.

Finally, robustness of the package can also be considered a quality issue. The FIBC must be sufficiently strong for the intended product, handling method and mode of transportation. Any hazards that could adversely effect the …