Flexible intermediate bulk containers (fIBCs) are large, collapsible woven containers designed for transporting and storing of dry, flowable materials, such as powders, grains and granules, in industrial settings. This one-page reference summarizes the available options for flexible IBCs.
Normally made of woven polypropylene cloth, with capacities of 1,000 kg, fIBCs are cost-effective devices that can be reused and recycled (Figure 1). Liners may be added to the fIBCs to make them hygienic, reduce maintenance requirements and improve cleaning costs.
FIGURE 1. Flexible IBCs are cost-effective devices for transporting and storing dry, flowable solid materials
fIBC configurations
Five common configurations of fIBCs include the following:
U-panel. This type of fIBC is a three-piece bag with one “U”-shaped piece making up the bottom and two sides with two separate pieces making the other side panels. These are the most popular and maintain a square shape when filled.
Circular. This two-piece bag has one body tube and a base. The body tube is seamless. They are not truly circular and resemble a square bag when filled.
Four-panel. This a five-piece bag made of four side panels and a base. This configuration has more stitching than the first two, resulting in more opportunities for failure.
Baffled. This type refers to any of the previous three bags with baffles added. Baffles are fabric panels or strings sewn inside the corners of a bulk bag. Baffles improve stability, stackability, and capacity.
Single loop and double loop. Made of a single tubular body, the fabric is extended into lifting loops, giving it greater strength and making it easier to lift.
fIBC top openings
fIBCs have four main types of top openings that may be selected according to user needs. The four types are listed below:
Open. Open top openings are ideal for quick filling.
Tie down. A flap secures the contents. Flaps are favored for quick-filling applications.
Duffle. The sides of the bag extend up, resembling a duffel bag. Extended sides are gathered and tied to secure the load.
Spout. A cylindrical tube is sewn into the top of the bag and interfaces with filling equipment, providing a controlled filling method. The spout is a necked-down version of the duffle. A spout can be tied off or cinched to secure the load. The spout top is the most common opening on fIBCs.
fIBC bottom openings
Bottom opening options for fIBCs are more numerous than top openings. Several types are reported:
Plain. In this case, no bag opening is included. Plain-bottom bags are cut open to discharge and are therefore single-use.
Spout. This is the most popular opening and consists of a tube sewn into the bottom panel. Tube dimensions vary, with 14 in. in diameter by 18 in. in length common.
Conical spout. Conical spouts are designed to alleviate the collection of materials in the bottom corners of the bag.
Duffle. The entire bottom of the bag opens for rapid discharge. Some duffle bottoms include a flap.
Diaper. A flap the size of the bottom of the bag is sewn onto one side of the bag and the other side is tied off (also known as a full drop).
Spout with flap. The spout (described previously) includes a flap to protect the bag’s contents.
fIBC lifting loops
Lifting loops are the “handles” located near the upper portion of a bulk bag used to hoist the bag from above. Several configurations are available.
Standard. A single strap, forming a loop, with each free end attached to the same top corner of the bag, repeated at each corner.
Single stevedore strap. A single strap is threaded through the four lifting loops and the loose ends of the strap are connected.
Double stevedore straps. A strap is threaded through two adjacent lifting loops and the loose ends of the strap are connected. A second strap is similarly threaded through the remaining two lifting loops.
Ancillary loops. A loop is added around each of the four corner loops to extend them.
Hood lift. A panel is attached to opposite sides of the top of the bag, making a tunnel for lifting.
Side-seam loops. The standard loops are formed from four straps. Each strap starts and ends at a different bottom corner of the bag. The straps are fastened along the length (side seam) of the vertical corner of the bag.
Sleeve lift. Two loops of material are formed on opposite sides of the top perimeter of the bag. Each loop runs along the entire length of one side.
Cross-corner loops. In this case, four lifting loops are each attached to adjacent sides of the bag, near the same corner of the top perimeter of the bag. Loops are not attached to a side seam.
Editor’s note: The content in this column was adapted from the following article and references therein: Bowser, T., Industrial Use of IBCs, Chem. Eng., April 2025, pp. 20–28.