Question 1

What does "Safety Factor" mean on a bulk bag?

Accepted Answer

Safety Factor (SF) is the ratio between a bag's tested breaking strength and its Safe Working Load (SWL), the maximum weight it's rated to carry in normal use. A 5:1 safety factor means the bag was built and tested to survive five times its rated load before failure. The number printed on a compliant bag is a manufacturing and testing standard, not a recommendation to load it beyond its rated weight.

Question 2

What's the difference between a 5:1 and a 6:1 safety factor?

Accepted Answer

A standard single-trip bag carries a 5:1 safety factor: tested to five times its SWL, built for one use. A UN-certified bag carries a 6:1 safety factor because it's rated to carry material classified as hazardous for transport. The 6:1 test protocol is also more demanding: 70 press-and-release lift cycles at four times the rated load, followed by a final proof cycle at six times the load.

Question 3

How is a bulk bag's safety factor tested?

Accepted Answer

Independent testing labs run a series of physical tests on a sample bag filled to its rated load, including a top lift test, a stacking test, a drop test, and others depending on the certification level. If a bag fails any required test, it cannot be certified or marked as meeting that safety factor.

Question 4

How often does UN certification need to be renewed?

Accepted Answer

UN-certified FIBC designs must be recertified annually as part of ongoing compliance, and any change to materials, construction, or the production process requires retesting before the design can keep its certification. This recertification applies to the manufacturer's design and production line, not to an individual bag after it has already carried a load.

Question 5

What happens if a bag fails a safety test?

Accepted Answer

A design that fails any required test cannot be certified and cannot legally carry UN markings or be sold as meeting that safety factor. Manufacturers typically have to adjust the fabric weight, construction, or stitching and resubmit the redesigned bag for a full new round of testing.

Question 6

Can a UN-certified bag be reused?

Accepted Answer

No, not in practice, even though it carries the same 6:1 rating as a general multi-trip bag. A UN bag earns its 6:1 rating because the cargo is hazardous, not because the bag itself is built for a second trip. Once it has carried a hazardous load, it should be treated as single-trip rather than reused for another shipment.

Category Archives: Safety & Compliance

Bulk Bag Safety Factors Explained: What 5:1 and 6:1 Actually Mean

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