Step by step
- Check the bag. Read the tag for SWL, ratio and static type, and inspect loops, seams and fabric.
- Hang it from all loops. Hook every loop onto the fill frame and let the bag drop to its full height.
- Seal the spout. Clamp the fill spout, or the liner spout then the fabric spout, onto the fill head; ground Type C tabs.
- Fill and settle. Meter product in on a load cell, vibrating to densify, and stop at or below the SWL.
- Tie and lower. Tie the spout, lower the bag to its pallet, release the loops and move it with all loops on the forks.
- Discharge under control. Lift by every loop onto the station, open the spout inside the access chamber, meter the flow and stay clear beneath.
Before anything flows
Start with the tag. Confirm the SWL covers the planned fill weight, that the static type is right for the room, and that the top and bottom match your equipment. A spout top suits a sealed fill head. A duffle or open top suits a chute or bucket loader. A flat bottom means a cut-open discharge; a spout bottom means a controlled one.
Inspect the bag visually for damage, as the manufacturer handling guidelines ask before each use. Check loops, seams, panels and the spout ties. A bag with cut fabric, pulled stitching or a chalky surface from sun does not go on the frame.
Then check the machine side. Is the scale zeroed and calibrated? Are the hooks, latches and inflatable seal intact? Is the conveyor or auger feeding at its normal rate, and is the extraction fan running? Five minutes of walking round the filler beats an hour of scooping spilt powder off the mezzanine.
Fill heads, frames and densifying
Most fillers hang the bag by its loops from hooks or a loop-release arm, so the bag takes shape while the spout is clamped to a fill head. An inflatable collar or band clamp seals the spout so dust does not escape. Some heads include a vent or dust extraction port to let displaced air out.
Simpler set-ups fill an open-top bag under a chute, sitting on a pallet inside a frame that holds the loops up. That works for coarse aggregate but sheds more dust.
Powders arrive full of air and settle over time. Filling on a vibrating table, or pulsing the deck during the fill, packs product tighter so the bag stands straighter and you fit the planned weight in the planned volume. It also cuts the slump that makes a bag lean on the trailer.
Vibration does not change the SWL. Weigh as you go on a load cell under the frame, and stop at or below the rated load, never above it because the bag still looks empty at the top.
Static during fill and discharge
Moving powder builds charge. For a Type C bag, clip the ground cable to the grounding tab before product moves, and leave it on until the fill is closed. Do the same at discharge. A Type C bag that is not connected to ground is useless and unsafe.
Type B and Type D bags do not take a ground connection. Which type belongs at your station is set by your site's hazardous-area assessment, NFPA 77, IEC 61340-4-4 and the bag maker's documents, so check them before switching types.
Ties, closures and the lift away
Spout tops usually carry a tie cord, and many bottom spouts have an inner tie plus an outer petal or star closure. Fold the spout neatly, tie it tight, and tuck the tails away from the loops. With a liner, tie the film spout on its own before tying the fabric.
Lower the full bag gently to its pallet or the floor before releasing the loops. Then pick it up with a forklift that has rounded tines or a lifting bar, with every loop engaged and the mast tilted back slightly. Lifting by one or two loops of a four-loop bag puts the full load where the design never meant it to go.
Sharp or narrow tines can slice a loop. Check fork tips for burrs and file them smooth, or fit a loop-lifting bar or a purpose-made hook frame that spreads the load evenly.
How the product behaves
Free-flowing granules such as pellets or seed pour quickly and level themselves. Cohesive powders bridge across a spout or form a rat-hole, a narrow channel that empties while the walls hang on. Hot product straight off a dryer can soften film and fabric, so ask the bag maker what temperature a design tolerates before filling warm material.
Watch the filled shape. A bag that leans, bulges at one panel or settles unevenly will ride badly on a trailer and may topple in storage. Usually the cause is an off-centre fill spout, a twisted loop, uneven densifying, or a pallet that is smaller than the footprint. Stop, lower the bag, straighten the loops and recentre the head before resuming.
Dust, people and training
Dust escapes at three points: the fill seal, the spout tie and the discharge chamber. Extraction at the head and a sealed access door cut most of it. Operators still need eye protection, gloves and whatever respiratory protection the product's safety data sheet calls for. Train new staff on the frame, the forklift and the station before they run a shift alone, and lock out moving equipment before anyone clears a jam.
Discharge stations
A discharge frame or station holds the bag above a hopper. The spout drops into an access chamber with a glove port or door, where an operator unties it behind a dust seal. An iris valve or spout clamp then meters the flow. Massaging paddles or vibration help powders that bridge.
For cut-open flat bottoms, the bag is lowered onto a knife or cross-cutter over a grate. That is fast but final: the bag cannot be closed again and is single use by construction.
- Hoist by every loop, using a bar, hooks or a frame rated for the load.
- Raise the bag only as high as the station needs.
- Never reach under a raised bag to free a stuck spout; lower it first.
- Keep the area clear of anyone not running the discharge.
Questions
Why is standing under a raised bag so dangerous?
A loop, seam or hook can fail without warning, and a filled bag can weigh a ton or more. The handling rules and the tag pictograms forbid it.
Can I fill a bag past its SWL if it still has room?
No. Volume and weight are separate. Fill to the weight on the tag; a dense product can hit the SWL long before the bag looks full.
Can a bag be partly emptied and closed again?
A spout bottom with ties can be retied after partial discharge, then lowered and stored. A cut-open flat bottom cannot be closed.
Do one- and two-loop bags lift the same way?
They are designed for a single hook through their loops, often in sets. Follow the maker's instructions for that design.
Can a 6:1 bag go back on the filler after discharge?
Only within a reuse programme, after cleaning and inspection, for a compatible product. A 5:1 bag is a single-trip bag.
Sources
Standards named here (ISO 21898, IEC 61340-4-4, NFPA 77) are summarised, not quoted: read the standard and the bag maker's documents before you rely on a rating.