Product
U-Panel FIBC
A flat-bottom FIBC built from one U-shaped body panel and two flat side panels, giving a squarer filled footprint than a tubular bag. Chosen where the filled bag has to stack level on a pallet.
A U-panel bag is cut from three pieces of woven polypropylene: a single U-shaped panel that forms the base and two opposite walls, and two flat side panels sewn into the open edges. The bottom seam runs along the outside edge of the footprint instead of across it, so the filled bag rests on a flat fabric face.
That layout is what makes the construction useful. Once filled, the side panels pull flat and the bag holds a rectangular section, so a stack lines up on a pallet instead of settling into a round shape, and the stack height stays closer to the figure on the drawing.
Fabric and sewing sit between the two extremes: more metres and more seam than a circular-woven tubular bag, less than a four-panel body. Four corner loops are sewn into the vertical seams with reinforcement patches so lift load travels along the seam, and the top hem takes the filling spout, duffel or skirt.
Panel sizes, loop positions and print are fixed before weaving, and the same approved drawing is used for the production sheet and the in-house inspection, so what is measured on the bag can be traced back to one document.
Product Summary
A flat-bottom FIBC whose body is one U-shaped panel joined to two side panels, giving a squarer filled footprint than a tubular bag. It is the usual answer when a filled bag has to sit level in a stack at a workable sewing cost.
Core Construction
The body starts as three pieces of woven polypropylene: one U-shaped panel that wraps the base and two opposite walls, plus two flat side panels sewn into the open edges. Because the base is part of the U, the bottom seam runs outside the footprint rather than across it.
Corner seams are double-folded and chain-stitched with polypropylene thread. Four corner loops are sewn into the vertical seams with reinforcement patches, spreading lift load along the seam instead of into a single stitch line, and the top hem carries the filling spout, duffel or skirt.
Panel geometry is set by the draw programme before weaving, so the bag holds its rectangular section under load better than a circular-woven tube does once filled and stacked.
Key Benefits
| Benefit | Why It Matters |
|---|---|
| Squarer filled footprint | A U-panel bag holds a rectangular section under load, so pallet and stack dimensions stay predictable instead of bulging into a round shape. |
| Predictable stack height | Flat side walls bear against each other, so a two-high or three-high stack stays aligned on the pallet. |
| Fewer fabric metres than four-panel | Three body pieces instead of four cut fabric and sewing time, which is usually why this construction is quoted ahead of a four-panel bag. |
| Print area that stays flat | Side panels are flat before filling, so branding and handling instructions print with less distortion than on a circular body. |
| Familiar seam layout | Corner seam positions are well understood on filling lines, so existing bag-handling equipment usually needs no change. |
Configuration Options
| Option Group | Available Range | Notes |
|---|---|---|
| Size | 75 x 75 x 110 cm up to 100 x 100 x 150 cm (typical) | Quoted as filled length x width x height; allow 3-5 cm tolerance on woven panels. |
| SWL / Safety Factor | 500 kg to 1,200 kg at 5:1; 6:1 on request | Safe working load is confirmed per project against the loop and seam specification. |
| Top | Open top, filling spout, duffel top, or skirt with tie cord | Spout diameter follows the filling nozzle; a duffel needs a closure cord long enough to reach round the fill head. |
| Bottom | Flat bottom, discharge spout, or full-drop bottom | A full-drop bottom needs extra fabric in the U-panel and changes the folded packed height. |
| Lifting loops | Four corner loops, 25-30 cm clear height | Loop width and stitch pattern are matched to the SWL; single-trip and multi-trip loops are sewn differently. |
| Fabric & coating | 140-200 gsm woven PP, uncoated or laminated at 20-25 gsm | Coating closes the weave for fine powders; uncoated fabric passes air and suits granular loads. |
| Liner | None, loose PE liner, or sewn-in LDPE/HDPE liner | A liner adds a second closure to handle at the fill head; state whether it must be dust-tight or only moisture-resistant. |
| UV stabilisation | 50-300 hours of UV exposure protection depending on additive loading | The hours describe the additive target for the grade, not a guaranteed field life; state the storage and transit exposure expected. |
| Printing | Up to 4 colours per face, flexo on the side panels | Side panels are flat before filling, so registration holds better than on a circular body. |
| Packing | Bales of 20-100 pieces, or palletised on request | Packed volume runs roughly 25-30% above the same count of tubular bags. |
Performance & Range
Rated for free-flowing granular and powder loads of roughly 0.4-1.2 t per bag at a safety factor of 5:1, with the filled bag resting on its flat base and lifted by four corner loops on a single hook or a four-point spreader. The envelope assumes a uniformly distributed load, a vertical lift and no dragging. Bulk density above about 1.2 t/m3 reduces the usable fill volume at the same finished size, so the height is recalculated for dense minerals.
Validation & Testing
In-house: fabric weight and weave count checked on receipt, panel dimensions checked against the approved drawing, seam strength checked on production samples on the in-house tensile rig, and a trial fill with the customer's product where the fill line is available. Stitch count and loop position are inspected at the machine against the drawing. Third-party testing is arranged on request and quoted separately.
Limitations
Not the right answer for fine powders that have to be dust-tight without a liner, for sharp-edged scrap that cuts the flat side panel, or where a round section is needed to shed load in a narrow chute. Sewing cost is lower than a four-panel bag, but the corner seam is still the first place to look if a bag fails at the loop.
Selection Guidance
- Best For
- Granular minerals, resin pellets, sand and fertiliser where the filled bag has to keep a rectangular footprint for stacking or palletising.
- Consider Alternatives When
- Use a tubular bag when the load is round-shouldered, stacking shape does not matter and fabric cost is the driver; use a four-panel bag when print registration or dimensional control has to be tighter than a U-panel holds.
- Must Confirm Before Quoting
- Fill weight and bulk density, filled dimensions and pallet pattern, required safety factor, top and bottom closures, liner requirement, and the UV exposure expected between filling and use.
Test & Production Evidence
| Evidence Type | Evidence Note | Stage |
|---|---|---|
| Drawing / Artwork | Panel cut drawing and seam layout for the quoted size, issued as PDF before production. | Pre-production |
| Production Record | Machine sheet recording fabric batch, thread type, stitch count and operator for the run. | Production |
| Inspection Record | In-house dimension and seam inspection sheet from the run, showing measured values against the drawing. | Pre-shipment |
Evidence Note
The dimensional drawing and a general specification sheet can be shared publicly. Machine sheets and in-house inspection records for a specific order are shared on request with the order reference, once size and closure are confirmed.
Related Applications
Information Required for Quote
Fill weight per bag and bulk density of the product Required
The starting point for panel size and fabric weight.
Filled dimensions and pallet or stack pattern Required
Include how many bags high the stack will go and whether they sit on a pallet.
Safety factor, and whether the bag is single-trip or multi-trip Required
5:1 is the common single-trip target; multi-trip needs a heavier loop and seam.
Top and bottom closure type Required
Open top, spout, duffel or skirt; discharge spout or flat bottom.
Liner requirement, and whether it must be dust-tight or moisture-resistant
Sets liner gauge and how the liner is closed at the fill head.
Print artwork and number of colours
Vector artwork at final size; side panels are printed before bag making.