Four-loop FIBC Bulk Bags are widely used for handling ore, mineral granules and other bulk materials. During a normal lift, all four loops are intended to participate in transferring the load.

This does not mean that each loop always carries exactly the same force. Differences in loop length, off-centre filling, forklift position, loop twisting and lifting angle can cause one loop to become tensioned before the others.

Preventing uneven loop loading requires control during filling, pre-lift inspection, equipment matching and forklift operation. Loop-strength data alone cannot address an unsuitable handling condition.

Why Do Four Loops Not Always Share the Load Equally?

Where the ore is evenly distributed, the four loops have consistent effective lengths and the lifting equipment is centred, the load is more likely to be distributed across all lifting points.

Actual operating conditions are not always symmetrical. If ore enters the bag from one side, it may form an off-centre pile and move the centre of gravity toward one panel.

A shorter loop can become tight before the remaining loops as the forklift tines rise. Until the other loops fully engage, the shorter loop and its attachment area may experience a greater force.

Unequal insertion depth can also change the loop angles. A loop concentrated at the tip of a tine or twisted around the equipment has a smaller effective contact area.

For this reason, a four-loop design should not be assessed by simply dividing the total weight by four. Actual loading depends on the geometry of the bag, material, loops and lifting equipment.

The Filling Process Determines the Centre of Gravity

The filling outlet should be positioned as close as practical to the centre of the FIBC. Continuous filling from one side can create an uneven distribution inside the bag.

Poorly flowing ore and large particles may not spread evenly through the body. Operators should observe the expansion of all four side panels during filling.

A weighing system should control the target load. Additional material should not be placed on one side merely because visible space remains in that part of the bag.

After filling, a bag that leans significantly, has one excessively expanded panel or does not rest evenly on its bottom should be checked before lifting.

The filling condition should be corrected while the bag remains fully supported on the ground.

Maintain Consistent Loop Length and Position

The reference Mineral FIBC Bulk Bag uses four soft side-seam lifting loops. The loops extend down the side panels and are sewn together with the body.

The production sheet lists a loop specification of 7 × 145 cm, a linear weight of 50 g/m and specified loop strength of ≥18000 N.

The meaning of the 145 cm value should be confirmed as a cutting or production dimension. The measurement that affects equipment engagement is the effective loop height after installation.

During incoming or finished-product inspection, the four effective loop lengths should be compared under the same measuring condition.

The loop-to-body positions should also be symmetrical. The downward extensions, sewing paths and attachment areas should be checked for skipped stitches, broken thread and significant variation.

The ≥18000 N figure is a loop-strength requirement. It does not prove that four loops will automatically carry equal forces during an actual lift and does not replace complete-bag testing.

How Can Forklift Operation Reduce Uneven Loading?

The forklift should approach the bag from a centred position. Both tines should enter to a similar depth, and the four loops should rest at suitable positions on the equipment.

Loops must not be twisted, knotted or concentrated at the tine tips. Twisted webbing has a different contact condition and may place a greater force on a limited group of fibres.

Before the bag leaves the ground, the tines should rise slowly so that all four loops become tensioned progressively.

The operator should check whether one loop becomes tight significantly earlier while another remains loose.

If the body begins to lean, it should be returned to the ground. The material distribution, loop lengths and tine positions should be checked before another lift is attempted.

During movement, the bag should remain at a low, stable handling height. Sudden acceleration, braking, rapid turning and excessive swinging should be avoided because they continuously change the load distribution.

Pre-Lift Inspection Points

Any adjustment should be made while the bag is fully supported on the ground. Personnel should never stand beneath a suspended bag or one that may move unexpectedly.

The Function of Side-Seam Lifting Loops

Side-seam loops create an attachment area that extends down the sides of the bag. Lifting forces can enter the body through the side panels and seams.

The reference configuration uses 180 g/m² uncoated fabric with minimum warp and weft strengths of 1600 N. The body panels use an outward-folded double-needle chain stitch.

These specifications provide defined requirements for the body and loop attachment structure. They cannot eliminate uneven loading caused by an off-centre material load or incorrect equipment use.

Where the target capacity, loop length or lifting method changes, the complete bag design and testing conditions should be reviewed again.

Matching the Loops to the Lifting Equipment

The buyer should provide forklift tine width, thickness, length and spacing. The intended use of hooks, a lifting beam or another system should also be specified.

The effective loop height must allow the equipment to enter without creating an excessive lifting angle. A webbing cutting length alone is not enough to confirm compatibility.

If the equipment can engage only two loops, a standard four-loop bag should not automatically be used at full load. Two-point lifting changes the intended load distribution and requires a suitable design and verification.

Mining applications requiring repeated lifting should define cyclic testing, pre-use inspection and discard criteria. The available component specifications do not independently establish a 6:1 or repeat-use classification.

FAQ

Does each loop carry 25% of the total load?

A fixed percentage cannot be assumed. The load may be relatively balanced under ideal conditions, but loop length, material position and lifting angle affect the actual distribution.

The total load should not simply be divided by four to determine the force on each loop.

Why can loading problems occur when loop strength is ≥18000 N?

The ≥18000 N figure is a specified loop-strength requirement. It does not ensure equal loading among the four loops.

Cuts, twisting, off-centre filling and incorrect tine placement can all change the actual operating condition.

Can lifting continue if one loop remains loose?

It should not continue without investigation. A loose loop may indicate that other loops are already carrying the load or that the centre of gravity has shifted.

Return the bag to the ground and check loop length, attachment position, material distribution and forklift placement.

Can a four-loop FIBC be handled using only two loops?

It should not be assumed suitable. Using only two loops changes the four-point load path and can increase forces on local loops and seams.

A purpose-designed and tested configuration is required where only two lifting points are available.

Does a twisted loop affect lifting?

Yes. Twisting changes the contact between the loop and the tine or hook and may concentrate forces on a smaller part of the webbing.

All loops should be flattened and checked for knots or severe folds before lifting.