Step by step
- Find the tag. Locate the sewn tag at a seam or the card inside the document pouch; if neither is legible, quarantine the bag.
- Confirm the rating. Read the SWL and the ratio, and check your planned fill weight is at or below the SWL.
- Match the static letter. Compare the type letter to what your hazardous-area assessment allows in that room.
- Note date and lot. Record both on the receiving paperwork for rotation and traceability.
- Read the handling rules. Brief the crew on the fill, lift and discharge instructions and pictograms before first use.
Where the label lives
Most bulk bags carry a sewn fabric tag stitched into a side seam near the top, or a printed card slipped inside a clear document pouch on one panel. Some makers do both. Either way it rides with the bag for its whole service life, from the bale it arrived in to the recycler who takes it at the end.
If the tag is torn off, faded past reading or covered in product, treat the bag as unidentified. Nobody on the floor can then say what it may lift, so it should not be lifted. Set it aside and tell whoever buys your bags; we would rather swap a bale than guess at a rating.
Every field, and what it tells a buyer
Layouts differ between factories, but a complete tag answers the same questions. Here is each field and the decision it supports.
| Field on the tag | What it tells you |
|---|---|
| Maker or brand mark | Who built it and who answers questions about its design, test records and handling instructions. |
| SWL (safe working load) | The heaviest fill the bag is rated to carry, usually given in kilograms and pounds. Your fill weight must sit at or below it. |
| Safety factor, 5:1 or 6:1 | The ratio between the test load and the SWL. 5:1 marks a single-trip bag; 6:1 marks a multi-trip design. |
| Static type, A, B, C or D | How the fabric handles electrostatic charge, which decides where the bag may be filled and emptied. |
| Standard | The specification it was designed and type-tested against, for example ISO 21898. |
| Date of manufacture | When it was sewn. Useful for rotation and for spotting old stock that sat outdoors. |
| Lot or batch number | Ties the bag to a production run, so a problem can be traced and the rest of that run pulled. |
| Fill and discharge instructions | How the maker intends the bag to be loaded, lifted and emptied. |
| Pictograms | Picture warnings that cross language barriers on a busy dock. |
Reading SWL and safety factor as a pair
These two numbers only make sense together. Multiply the SWL by the ratio and you get the load the design had to survive in testing. A 2,000 lb bag at 5:1 was tested to 2,000 x 5 = 10,000 lb. The same SWL at 6:1 means 2,000 x 6 = 12,000 lb.
The manufacturer handling guidelines published in 2023 say multi-trip standard-duty FIBCs must reach 6 x SWL in the final destruction test, which is 6,000 kg for a 1,000 kg bag, and pass a 4,000 kg compression test held for six hours. Single-trip designs are tested to 5 x SWL, and that guide recommends they are not re-used.
Never round either figure in your head. A tag reading 1,000 kg is about 2,205 lb (1,000 x 2.20462), not a loose 2,200 or a hopeful 2,500. Plan fills against the printed rating only. Our page on the FIBC safety factor walks through the test loads for every common rating.
The static mark
Static type is printed as a letter, often inside a symbol. Type A is plain polypropylene with no static protection, meant for non-flammable product where no flammable dust or vapour is present. Type B uses fabric with low breakdown voltage that prevents high-energy propagating brush discharges; it is not groundable and suits dry flammable powders only where no flammable vapours or gases are around.
Type C has conductive threads woven through it and must be connected to ground during filling and discharge; unconnected, it is useless and unsafe. Look for its grounding tab and the earthing instruction beside it. Type D is static-dissipative fabric that bleeds charge away safely without a ground connection.
The tag tells you what the bag is. It does not tell you what your room needs. Follow your site's hazardous-area assessment, then check NFPA 77, IEC 61340-4-4 and the maker's documents for the conditions each type was qualified under.
Standard, date and lot
ISO 21898:2024, published on 16 August 2024, replaced the 2004 edition. It sets materials, construction, design, type-test and marking requirements for FIBCs carrying non-dangerous solid materials. A tag citing the older edition is not automatically wrong, but ask the maker what changed for that design. Bags for dangerous goods fall under separate transport rules, and their markings look different.
The date matters more than people think. Sunlight weakens woven polypropylene, so a bag sewn long ago and stored under open sky deserves a harder look. The lot number is your recall handle: write it on the receiving paperwork so one bad bale can be matched to its siblings.
Instructions and pictograms
Below the ratings, most tags carry short handling rules in words and pictures. Typical symbols include:
- Lift with every loop on the hook or forks, never one corner.
- Do not stand or walk beneath a raised bag.
- Keep away from rain and direct sun while stored.
- Do not drag the bag across the floor or tilt it on forks.
- Ground the tab before filling (Type C only).
- Single trip only, where the ratio is 5:1.
Checking a tag against your order
When a load lands, pull one bag from each bale and compare its tag to the purchase order: SWL, ratio, static letter, top and bottom style, dimensions and liner. Photograph the tag. That photo becomes the reorder spec, and it ends most arguments about what was promised before they start.
Sending us a clear tag photo with a request is the fastest way to price a repeat job. If the photo shows a 5:1 bag that you hoped to run twice, we will say so, and quote a 6:1 design instead.
Questions
Is the SWL printed in pounds or kilograms?
Often both. Many factories rate in kilograms first, so a 1,000 kg bag shows about 2,205 lb. Plan against the exact printed figure, not a rounded one.
What if a bag has no tag at all?
Do not fill it. Without a tag nobody can confirm the rating, ratio or static type. Report the shortage to your supplier and keep the bag out of the line.
Can I add my own label to a bag?
You can add a product or lot label for your own tracking, ideally in the document pouch. Never cover or replace the maker's tag, since the ratings belong to the maker.
Does a 6:1 mark mean any used bag can go round again?
No. A 6:1 design can be reused only under a proper reuse programme, after inspection, and never for food or pharma. A once-used 5:1 bag goes to a recycler.
Sources
Standards named here (ISO 21898, IEC 61340-4-4, NFPA 77) are summarised, not quoted: read the standard and the bag maker's documents before you rely on a rating.