Key Takeaways
Trade weighing: if you sell goods by measured weight, the weighing instrument needs an NMI-approved design and verification by a servicing licensee. Weighing used only internally does not need approval.
Packing obligations are separate: if you sell prepacked bags with a stated weight, packer obligations on quantity and labelling also apply. An approved filler does not by itself satisfy them.
Approval conditions affect operation: one NMI approval for a bulk bag weighing instrument requires the bag to be disconnected from the fill head during trade weighing. Read the approval certificate, not just the badge.
Bag ratings: under ISO 21898, single-trip bags carry a 5:1 safety factor and multi-trip bags 6:1. Never fill above the safe working load. Reuse also depends on inspection and the bag maker's instructions.
Static and dust: bag type selection depends on your product's ignition properties, the surrounding atmosphere and site controls. If your product can form an explosive dust cloud, area classification under AS/NZS 60079.10.2 should come first, with AS/NZS 4745 as the code of practice for handling combustible dusts.
Do you need trade-approved weighing?
You do if the price depends on the measured weight. Australian trade measurement law requires measuring instruments used for trade to have an NMI-approved design and to be verified by a servicing licensee. Equipment not used for trade does not need approval.
Instrument approval is only part of the picture. If you sell prepacked goods with a stated quantity, packers have their own duty to check that batches meet measurement requirements, and the trade measurement regulations include separate rules for packaging and marking.
If you are unsure how the rules apply to your bags, contact NMI before you buy. Retrofitting trade approval later can mean replacing the weighing system.
What trade approval means for a bulk bag filler
Approval number: ask for the instrument's NMI approval number and read the certificate's conditions.
Conditions of use: one NMI approval for a bulk bag class instrument requires the bag to be disconnected from the filling head during trade weighing. That condition affects how you run the filler.
Approval scope: some approvals cover a single instrument at a single site. The same Unimin approval is limited to one instrument at the company's own site.
Verification: the instrument must be verified by a servicing licensee before you use it for trade. NMI recommends regular checks by a licensed technician. Ask your servicing licensee what is required after repairs, adjustments or relocation.
Weighing accuracy: what to ask for
Scale accuracy and filling accuracy are different measures:
Scale accuracy: how closely the system measures the load.
Filling accuracy: how close each bag ends up to its target weight.
Manufacturer claims vary widely. National Bulk Equipment rates a hang-weigh bulk bag filler at ±0.5% of bag weight, and claims ±0.01% for its variable container filling system. Test conditions aren't published for either.
Ask suppliers:
for scale accuracy and filling accuracy at your fill rate on your product, with the test method
for the overfill they expect, which matters more commercially than headline scale accuracy
how the system handles fine feed, in-flight product and settling before the final weight
FIBC ratings: safe working load and safety factor
Every bulk bag should carry a label stating its safe working load (SWL) and safety factor.
5:1 single-trip: the bag should withstand five times its SWL before failing, and is designed for one fill.
6:1 multi-trip: designed for reuse. Whether a particular bag can be reused still depends on inspection, the manufacturer's instructions and operating conditions.
Some users reuse 5:1 bags, but bag manufacturers advise against it. UK lifting guidance says single-trip bags should be scrapped once emptied. Also check that hooks and loop handling suit the bag's loop design, and keep loops vertical and untwisted when lifting.
Static protection: FIBC Types A, B, C and D
Filling and emptying bulk bags can generate significant electrostatic charge. The amount depends on the product and the fill rate. IEC 61340-4-4 classifies bags into four types.
The table is a starting point only. The right bag depends on your product's ignition properties, whether flammable vapours or gases may be present, the bag's qualification, and the equipment and procedures around it.
Type | Static protection | Starting-point use limits |
|---|---|---|
A | None | Non-combustible products in non-flammable surroundings only |
B | Limits propagating brush discharges | The standard sets Type B requirements for combustible dust environments with minimum ignition energy above 3 mJ. Not for flammable vapour or gas atmospheres |
C | Conductive. Must be earthed before filling starts and stay earthed throughout | Requirements also cover flammable atmospheres and lower ignition energy dusts, provided the bag is earthed |
D | Static dissipative. The bag needs no earth connection | Requirements also cover flammable atmospheres and lower ignition energy dusts, within its qualification. Other conductive equipment and objects in the filling area may still need earthing |
IEC 61340-4-4 compliance does not by itself guarantee that the product will not generate hazardous discharges, such as cone discharges. For Type C bags, ask whether the filler includes earth monitoring that confirms the connection before filling starts.
Combustible dust and hazardous areas
Many powders handled in bulk bags are combustible, including flour, sugar, milk powder, starch, plastics and some chemicals.
Area classification: AS/NZS 60079.10.2 classifies areas where explosive dust clouds or combustible dust layers may be present. That classification informs which electrical and mechanical equipment is suitable. The standard's examples assume effective housekeeping, and poor housekeeping can widen the classified area.
Code of practice: AS/NZS 4745 is the overarching code of practice for handling combustible dusts in Australia and New Zealand.
This section is not a hazardous area selection guide. If your product is combustible:
have the area classified and the dust tested by competent specialists before you finalise the spec
give suppliers the zone classification and the dust's ignition properties
ask for equipment rated for that zone, and confirm the bag type with your hazardous area adviser
Machine safety and manual handling
Under WHS laws, the person conducting the business must manage risks from plant and hazardous manual tasks. For bulk bag fillers, ask suppliers about:
guarding and interlocks
emergency stops
pneumatic clamp and seal safety
reach heights for hanging loops
how filled bags are removed without people under suspended loads
Compliance checklist for your quote request
Trade use: yes or no. If yes, the NMI approval number and its conditions
Whether you sell prepacked bags with a stated weight, and who manages packer obligations
Required scale and filling accuracy, and verification arrangements
Bag SWL, safety factor and electrostatic type, as confirmed by your adviser
Whether the product is combustible, its tested ignition properties, and the area classification
Earthing or earth monitoring for conductive bags and equipment
Dust extraction and housekeeping requirements
Safety features: guarding, interlocks, e-stops and reach heights
FAQs
Do I need trade approval if I only weigh bags for my own records?
No. Equipment not used for trade does not need NMI approval. If the weight later appears on an invoice or determines price, it does, so decide before you buy.
Can I reuse bulk bags?
Only bags designed for multi-trip use, rated 6:1, should be considered for reuse, and only after inspection and in line with the manufacturer's instructions. Single-trip 5:1 bags are designed for one fill.
How do I know if my powder is combustible?
Dust testing by a specialist laboratory confirms combustibility and ignition properties. Use the results, with expert advice, for area classification and bag selection.
Ready to compare compliant systems? Get bulk bag filler quotes from Australian suppliers and include your trade-weighing, bag-type and dust requirements so each quote covers them.
