Definition
A big-bag (FIBC, Flexible Intermediate Bulk Container) is a flexible container for the transport and storage of bulk materials, made of woven polypropylene fabric, with a payload usually from 500 to 1500 kg, equipped with integrated loops for lifting by forklift or crane.
Over the last three decades of working with granulates in Chorula, several hundred thousand big-bags have passed through our hands. It is today the most common packaging unit in plastics logistics — and at the same time a unit whose seemingly simple construction conceals plenty of details that determine the safety and quality of the load. The word “intermediate” is no accident: a big-bag is a packaging intermediate between a 25 kg bag and bulk transport in a silo trailer. It holds as much as is hard to carry by hand, while remaining flexible enough that, once emptied, it takes up minimal space and is suitable for disposal or recycling.
The big-bag was invented in the 1970s, and its success stems from a very favourable ratio of payload to tare: a bag weighing 1.5–2.5 kg carries a tonne of material. For an industry in which every kilogram of axle payload and every minute of loading counts, this is a solution hard to beat.
Types of big-bag — A, B, C and D
The most important classification of big-bags concerns their electrostatic properties. Polymer granulates generate electrostatic charges during transfer, and in the presence of dust or flammable vapours an uncontrolled discharge can be a source of ignition. That is why the standard distinguishes four types:
- Type A — ordinary polypropylene fabric without antistatic properties. Used for non-flammable materials, in an environment free of flammable dusts and solvents. The cheapest and most common for inert granulates.
- Type B — fabric with a reduced breakdown voltage, limiting the energy of spark discharges. It prevents dangerous brush discharges but does not dissipate the charge. Used where no flammable vapours are present.
- Type C — conductive fabric with an interwoven grid of conductive threads, requiring earthing during filling and emptying. Safe for flammable materials and in explosion-hazard zones — provided the earthing is connected correctly. Omitting the earthing makes it more dangerous than Type A.
- Type D — antistatic (dissipative) fabric, dispersing the charge without earthing. The most convenient in operation in Ex zones, because it does not require connecting earthing — but sensitive to surface soiling, which can weaken its properties.
In terminal practice, the choice of type is not a matter of price but of risk assessment: which material, in which environment and with what equipment is being transloaded. The rule we apply is simple: if flammable dusts or solvent vapours may appear in the environment, Type A is ruled out. With polyolefin granulates (PE, PP) in a clean hall without flammable vapours, Type A can be sufficient, but when additives, powdered colourants or work near other installations are involved, we switch to Type C with a rigorous earthing procedure or Type D. The most common mistake on the market is treating Type C as “safer by default” — without connected and verified earthing its conductive grid accumulates charge and becomes a real hazard.
Technical characteristics
| Parameter | Typical value |
|---|---|
| Nominal payload | 500–1500 kg (most often 1000 kg) |
| Capacity | 0.5–2.5 m³ |
| Fabric material | polypropylene (PP), woven, 90–220 g/m² |
| Safety factor (SWL) | 5:1 (single-use), 6:1 (reusable) |
| Number of loops | 1, 2 or 4 (lifting loops) |
| Bottom | flat or with discharge (outlet valve) |
| Inlet | open, filling skirt or spout |
| Liner | optional: LDPE / LLDPE (food-grade) |
The construction of a big-bag is always a compromise between tare and strength. Four lifting loops distribute the load evenly and are the standard for loads of 1000 kg and more; one- and two-loop versions are found with lighter loads and automated filling.
It is worth understanding a few construction elements, because it is these that determine the bag’s suitability for a specific task:
- Bottom — flat (emptied by tipping over or cutting open) or with a discharge valve (outlet spout), which allows the material to be dosed and the bag to be emptied by gravity. For transloading onto a silo trailer, a discharge valve significantly simplifies and speeds up the work.
- Inlet — open (for filling by shovel or conveyor), with a filling skirt or with a spout. An inlet spout and a discharge spout together give a fully closed bag, protecting the material from the atmosphere.
- Liner — an internal LDPE/LLDPE film. We always use it where the material is hygroscopic or requires food grade. The liner is sometimes loose or glued to the fabric; the latter makes complete emptying easier, without residue in the corners.
- Fabric — a basis weight of 90–220 g/m², coated or uncoated. The coating increases tightness and resistance to moisture but hinders the bag’s breathing — which with some materials is an advantage and with others a disadvantage.
Applications
Big-bags today handle most of the bulk-material stream in industry. From our transloading practice the following dominate:
- polymer granulates (PE, PP, ABS, PS, PA, PVC, PET, recyclates and other plastics) — the largest group, a high-purity material requiring protection from contamination;
- mineral materials — lime, talc, bentonite, calcium carbonate, mineral meals;
- bulk chemicals and fertilisers — urea, salt, process additives;
- food products — sugar, starch, flour, groats (in a food-grade version with a liner).
It is precisely polymer granulates that are the cargo around which we built our terminal — and it is their quality requirements that set the standard of working with big-bags.
Big-bag versus other bulk material packaging
The big-bag is not the only intermediate packaging. In daily work we most often compare it with two alternatives:
- Octabin — a rigid octagonal cardboard container. It withstands stacking better and protects against deformation, is convenient with materials sensitive to pressure and for rack storage. It is, however, more expensive, heavier to dispose of and takes up a fixed volume. The choice between a big-bag and an octabin is usually a compromise between price and packaging rigidity.
- 25 kg bag (manually opened jumbo) — the smallest unit, used for small batches, retail distributor sales and high-unit-value materials. A 1000 kg big-bag replaces 40 bags of 25 kg, eliminating manual work and the risk of counting errors.
For large granulate streams the direction is unambiguous: big-bags at the import and storage stage, and then transfer to a silo trailer for bulk delivery. The 25 kg bag and the octabin are niche or supplementary solutions. We describe them in more detail in the bulk material packaging section.
Transport and logistics
The big-bag is an intermediate unit — it connects the world of production and sea containers with the world of bulk delivery to the customer’s plant. A typical chain looks like this: the producer fills big-bags on a packing line, packs them into sea containers (18–22 bags per 20-foot container), and after reaching Europe the load goes to a transloading terminal, where it is repacked or transferred into a silo trailer for the final stretch of delivery.
In the warehouse in Chorula we maintain a buffer of 2000 big-bags, which allows us to decouple the rhythm of sea deliveries from the rhythm of silo trailer orders and to make just-in-time deliveries to plants across Europe. Big-bags are stored on pallets or in stacks, always protected from UV (polypropylene degrades under radiation) and moisture.
Why is this buffer so important? Containers from Asia arrive in batches every few weeks, while processing plants take the material at the pace of production — often a few silo trailers a week, evenly. Without a buffer warehouse the importer would have to either maintain costly space near the factory or accept downtime. A transloading terminal with a stock of 2000 big-bags smooths out this imbalance: it receives the whole container at once and releases the material when it is needed. When stacking big-bags, a rule applies — bags with a discharge valve and a soft bottom do not tolerate high stacks without spacers, because deformation of the lower layers hinders later lifting and risks loss of tightness.
Big-bag to silo trailer transloading — step by step
This is an operation in which it is easiest to make a mistake costing the quality of an entire batch. Our process of big-bag to silo trailer transloading looks as follows:
- Receipt and identification — checking the batch number, the material certificate and the condition of the packaging. Each big-bag is linked to the delivery documentation.
- Lifting and positioning — a forklift or crane positions the big-bag over the feed hopper; a bag is never lifted by a single loop if four were provided.
- Quality control — visual assessment of the granulate, control of moisture and the absence of contaminants before discharge.
- Cleaning screen — the material passes through a screen that captures mechanical contaminants and any agglomerates.
- Gravity transfer into the silo trailer — without compressed air, without mechanical impacts, which protects the grain from abrasion and electrostatic charging. We describe this solution in more detail in the article on transloading without pneumatics.
- Quality documentation — issuing a transloading record with full batch traceability maintained.
For this reason, plastics producers — among our regular customers being, among others, LG Chem, Borealis, Synthos and Orlen — attach such great importance to the transloading method, not merely to the fact that the material was transferred.
Technical notes and safety
A few rules that in terminal practice determine safety:
- Never exceed the nominal payload. The SWL factor is a safety margin, not a reserve to be used.
- Check the loops and seams before every lift. The most common cause of failure is a damaged or UV-worn loop, not the fabric itself.
- Match the electrostatic type to the environment. Type C without connected earthing is more dangerous than Type A.
- Protect from UV and moisture. PP fabric loses strength after long exposure to sun — storage under a roof is not a convenience but a safety condition.
- Do not lift people or stay under a suspended load. A 1000 kg big-bag is a weight that, if it fails, does not forgive.
Standards and certificates
The basic construction standard for big-bags for non-dangerous materials is ISO 21898 (Packaging — Flexible intermediate bulk containers (FIBCs) for non-dangerous goods). Big-bags intended for dangerous goods are additionally subject to the requirements of ADR and UN certification for the relevant packing group, with permanent markings on the bag. Antistatic versions (types B/C/D) refer to the IEC 61340 series of standards on electrostatics.
For food materials the big-bag and its liner must meet the requirements for food contact in accordance with Regulation (EC) 1935/2004, with an appropriate declaration of material conformity.
Related topics
The big-bag is one of the links in the bulk-material chain. It is worth setting alongside other units and transloading technologies — you will find links in the section below and on the bulk material transport page in the PHS Magnum portal.
Sources
- ISO 21898 — Packaging — Flexible intermediate bulk containers (FIBCs) for non-dangerous goods.
- The European ADR Agreement — regulations on the transport of dangerous goods.
- IEC 61340-4-4 — electrostatic requirements for FIBCs.
- Regulation (EC) No 1935/2004 — materials intended for food contact.
- Operational practice of the SMIALA terminal, Chorula — Aleksy Pasternak.
