SWL and SF

Safety work load and Safety Factor

SWL - Safety work load - Maximum carrying weight of a big bag

FIBC (Flexible intermediate bulk containers) are designed for a specific Safety Work load (SWL). Common SWLs are 500kg, 1000kg, 1200kg, 1250kg, 1500kg or 2000kg. The SWL is determined by the customer. Often the Safety work load is chosen to achieve a maximal load weight on a truck of 24 or 25mt. Depending on the size of the big bag they often have a SWL of 1000 or 1250kg. A higher SWL results in stronger FIBC fabric used.

SF - Safety factor - One way versus multi trip big bags

One way big bags

Big Bags are usually used only one time. They are filled and sold to a customer where they are emptied. Usually it is not economical to collect the FIBC afterwards or to ask the customer to return the empty bag. Often FIBC are used in food industry where it would not be hygienic to reuse them. Sometimes the FIBCs are never emptied and serve as a permanent waste bag. The Safety factor (SF) for one way FIBC is 5:1, meaning that the bulk bag did burst only after reaching five times its safety work load (SWL) in the test rig. A 1000kg bulk bag did therefore burst on more than 5t load. A 2000kg big bag bursts after 10t load in the test rig.

One way big bags cannot be “repaired”. Is is not allowed to reuse these big bags.

Multi trip big bags

Sometimes a multi trip big bag is more economical than a single trip one. This is usually the case when all big bags are emptied at the same place and can be easily collected. Furthermore, it should not be a food big bag. In this case the big bags can be returned to the filling place and reused for a limited number of times. These multi trip bulk bags are constructed stronger and achieve a safety factor (SF) of 6:1 which means that the bulk bag did burst after more than six times its safety work load (SWL) during testing. On multi trip bulk bags an additional multi trip label can be added to count the number of circles. Of course multi trip FIBC cannot be used infinite times. However there is no rule how often they should be used.

Multi trip big bags cannot be repaired. Damaged multi trip big bags must not be used. It is not allowed to fill in different materials into the FIBC on its different trips.

Certification of SWL and SF

All our FIBCs are tested either inhouse or certified by respected testing institutes. The certificates name the safety work load and the safety factor. On request we will deliver the test reports for your FIBC.

Labeling Bulk Bags

Every bulk bag has a label which states clearly the SWL and SF of the bag. Multi trip bulk bags sometimes have an additional trip label to count the number of trips.

UN bags

Un bags for dangerous goods have a SWL and a maximum stacking load but no SF. They are always for one way trip usage.