How to Specify an FIBC

01 — What is the material, and how does it behave?

Not just the commercial trade name — the mechanical behaviour. Is it a fine powder, a free-flowing granule, a flake, an irregular pellet, or a heavy dense solid? Does it aerate and fluidise, or does it consolidate and bridge?

Is it abrasive to woven polymers? Hygroscopic in damp air? Corrosive to standard additives? Does it generate combustible dust clouds? Powder behaviour dictates seam sift-proofing; bridging tendencies dictate bottom discharge sizing; flammability drives electrostatic safety type.

02 — What is the bulk density?

Expressed in kg/m³ (or lbs/cu.ft). This is the single number most inquiries omit, and without it no engineer can size the bag accurately — only guess.

Because 1,000 kg of mineral sand requires a fraction of the volume of 1,000 kg of agricultural chaff, bulk density is the vital link between weight and geometric dimensions.

03 — What is the fill weight / SWL?

The Safe Working Load (SWL), in kilograms. Coastal FIBC engineers bags from 500 kg to 2,000 kg SWL.

Specify the actual maximum weight your filling system will dispense into the bag, not just nominal target averages.

04 — How many trips will the bag make?

One single trip (filled, shipped, discharged, disposed or recycled): 5:1 safety factor.

Multi-trip usage (returned, cleaned, inspected, and refilled), or severe critical consequences of failure: 6:1 safety factor. This single decision alters fabric GSM, seam tensile requirements, and loop reinforcement.

05 — What dimensions do you require?

If you already have a qualified bag drawing, provide exact dimensions. If not, dimensions are derived using the basic formula: Volume required (m³) = Fill weight (kg) ÷ Bulk density (kg/m³).

For example: 1,000 kg of material at a bulk density of 700 kg/m³ requires 1.43 m³. On a standard 95 × 95 cm base (0.9025 m²), that corresponds to a fill height of 1.58 m. Specify a body height of 160–165 cm to leave headspace for spout tying.

Always verify dimensions against pallet borders, container door heights, and warehouse racking clearances.

06 — Which construction type?

Baffle, Four Panel, Circular, or U-Panel. The choice depends on powder fineness, container freight optimization, and load density.

Baffle bags hold cubic geometry for ocean freight savings. Circular bags remove vertical seams for zero powder sifting. U-Panel provides continuous unbroken bottom strength for heavy loads.

07 — Coated or uncoated fabric, and what fabric GSM?

Coated polypropylene prevents moisture penetration and stops fine powders from sifting through fabric weave pores.

Uncoated fabric allows air exchange for materials that need to breathe (such as grains or potatoes). Fabric GSM is calculated against load rating and abrasion severity.

08 — Do you require an internal liner?

A liner provides chemical or hermetic barriers that fabric alone cannot supply. Options include loosely inserted gusseted liners, tabbed liners, glued liners, or form-fit bottle liners in LDPE, EVOH, or conductive film.

09 — How is the bag lifted?

Cross-corner loops stand open naturally, allowing forklift tines to enter smoothly without a second operator.

Corner-seam loops attach to vertical joints. Stevedore straps facilitate ship crane lifting. Continuous sleeves provide even weight distribution.

10 — How is the bag filled?

Filling spouts clamp onto automated filling heads to keep dust sealed. Skirt tops provide wide openings for mechanical hoppers. Open tops suit simple low-cost aggregate loading.

11 — How is the bag discharged?

Flat bottom bags are single-use and cut open. Discharge spouts offer controlled gravity drop. Iris closures permit operators to choke or shut off product flow mid-stream. Full open bottoms prevent cohesive materials from bridging.

12 — Storage, transit, and markings

State outdoor exposure expectations so we can engineer sufficient UV stabilization. Specify required external print: up to 4 colours for branding, batch traceability codes, or hazard warnings.