The top lift test loads an FIBC through its lifting loops to a multiple of its safe working load, typically five or six times depending on whether the bag is single trip or multi trip, and either cycles that load a set number of times or holds it for a defined period. The method is laid down in EN ISO 21898, and the bag passes if the loops, the seams and the body survive without a failure that would drop the contents. It is the single most important safety test for a jumbo bag, and a buyer should ask to see the result before the first order and periodically after that.
The test is normally done on a purpose-built rig at the plant or at an independent laboratory. The bag is filled with a test medium, lifted by its loops and the load is then increased using a hydraulic or mechanical system until the test load is reached.
Safety factor and test load
The safety factor is the ratio between the test load and the safe working load. A single trip bag is usually rated at 5:1, so a 1,000 kg bag is tested to around 5,000 kg. A multi trip bag is usually rated at 6:1, and a bag designed for repeated use in a demanding handling environment may be rated higher. The safety factor should be printed on the bag label and stated in your specification.
For a cyclic test the bag is lifted repeatedly between a low load and the full test load for a set number of cycles, which mimics the shock loading of a forklift. For a hold test the bag is held at the test load for a fixed time, and the operator watches the loops and seams for slippage or tearing.
Complementary tests
- Cyclic top lift, which repeats the lift to check the loop stitching under fatigue rather than under a single peak load.
- Drop test, in which a filled bag is dropped from a defined height onto a hard surface to check that the body and seams hold.
- Topple and righting tests for bags that may fall on their side during handling.
- Tear and tensile tests on fabric samples, which show whether the fabric meets the specified strength before it is sewn.
- UV exposure tests for bags that will be stored outdoors, since sunlight weakens polypropylene over time.
What to ask for and how to read it
Ask the plant for its most recent top lift test report for the same bag design, loop type and fabric weight that you are buying, not for a general certificate. The report should state the safe working load, the safety factor, the test load, the number of cycles or the hold time, and whether the test was done in house or at an external laboratory. A plant with an in-house rig can test your bag in front of you or on camera, and the better ones do this as a matter of routine.
Type approval certificates for the design are useful, but they say nothing about the batch in your container. For an ongoing supply, agree a frequency of batch testing in the order and ask for the reports with each shipment.
What Creston & Co does
We witness top lift tests at the plant during the audit and again on production batches where the order calls for it, and we send sealed samples to an NABL-accredited laboratory when an independent result matters. We keep the reports with the shipment file so you have them when your own safety team asks. If you want a second opinion on a plant's test documents, we can look at them in a free 20-minute sourcing review.