Open-Mouth, Valve or FIBC: Choosing the Right Bag Format Before You Buy the Machine
Here is the sequence most suppliers hope you skip: choosing the bag before choosing the machine. It is also the sequence that saves the most money, because bag format determines the filling head, the closing method, the pallet pattern and ultimately how your warehouse handles the product. Change your mind about the bag after installation and you are no longer buying a machine — you are rebuilding a line.
The three formats side by side
| Format | Typical fill weight | How it closes | Filling equipment |
|---|---|---|---|
| Open-mouth bag (PP woven / kraft / PE) | 10–50 kg | Sewn, taped or heat sealed after filling | Carousel or single-spout net-weight filler |
| Valve bag (pasted valve) | 10–50 kg | Valve self-closes; may be ultrasonically sealed | Impeller, turbine or air packer |
| FIBC / jumbo bag (with or without liner) | 500–2,000 kg | Spout tied or heat sealed; loops for lifting | Net-weight or metered bulk bag filler |
Open-mouth bags: the flexible default
If you pack several products, several weights, or sell into retail as well as industrial channels, open-mouth bags remain the most adaptable option. Modern lines place the bag automatically, open it, fill to a net-weight target, square the mouth and close it — all without an operator touching the bag. The equipment set-up for 25 kg flour uses the same principle whether it later handles feed or sugar.
The trade-off is that the closing step exists at all: either a sewing unit with thread, tape and crepe tape, or a heat sealer for laminated bags. Both need attention and consumables, and both are where most quality complaints on open-mouth lines originate. An automatic bag sewing station fed from a carousel bagging machine handles this reliably because the bag arrives squared rather than loose.
Valve bags: clean, compact and fast
A valve bag needs no separate closing machine — the valve closes under product pressure and, for moisture-sensitive products, can be ultrasonically sealed on the filler. For cement, minerals, gypsum and certain chemicals this removes an entire machine from the line, and the square brick shape of a filled valve bag stacks well on pallets.
The limitation is flexibility: valve bags are usually a single-product, single-weight proposition, and the bag itself is more expensive per unit than a plain open-mouth woven sack.
FIBC: for anything above half a tonne
Once unit weights move past roughly 500 kg, bags stop being handled by people and start being handled by forklifts or cranes. FIBCs provide the lowest cost per tonne packed and the lowest labour content of the three formats, with the important condition that the filling line must handle weighing, de-aeration and dust extraction properly — covered in detail in our article on filling and weighing jumbo bags accurately.
Five questions that will settle it
- Unit weight today and tomorrow. Anything trending above 500 kg points to FIBC.
- Product count and batch frequency. Many SKUs and frequent changeovers point to open-mouth.
- Dust behaviour and moisture sensitivity. Hygroscopic products favour heat-sealed open-mouth lined bags or sealed valve bags.
- Downstream handling. Does the customer receive pallets of small bags, or single bigbags lifted by crane?
- Labour availability. FIBCs remove operators; small bags need them at the pallet unless you add a palletizer.
Getting pallet handling right either way
Whatever the format, the load eventually lands on a pallet. Small bags stack in defined layer patterns handled well by a column palletizer; FIBCs are usually single-bag pallets or loaded straight onto trucks, with automatic truck loading systems used where truck turnaround time matters.
A note on choosing before specifying
The plant that decides its bag format first buys the right machine once. The plant that decides it later buys a conversion kit, then optimises around a compromise for the following ten years. The decision takes an afternoon; its consequences last a decade.
Recens supplies equipment for all three formats — open-mouth bagging carousels, valve-bag packing and FIBC filling lines — with the palletising and conveying matched to whichever route fits your product. Tell us what you pack and at what weights, and we will set out the options with their real operating costs.
WhatsApp: +86 150 3816 6007
Website: www.recenstec.com