Describe what the powder does, not only what it is called.
Names such as flour, protein powder, detergent or seasoning are too broad to predict filling performance. Two grades can differ in particle size, shape, moisture response, fat or oil content, static, aeration and the proportion of fines. Those differences affect whether the product floods through an outlet, holds a bridge, ratholes down the centre of a hopper, clings to surfaces or separates during transfer.
Observe the product when it is poured, stored, transferred and refilled. Note whether it forms a steady stream, breaks into lumps, releases a persistent dust cloud, compacts after vibration or separates into visibly different fractions. Include the timing of the behaviour: a product that runs well in a small sample can become less stable after several minutes in a production hopper.
| Observed behaviour | Possible filling effect | Evidence to collect |
|---|---|---|
| Bridging or ratholing | Interrupted feed can leave the dosing chamber or screw starved and create low or inconsistent fills. | Photographs or video of the hopper, time to interruption, refill level and the product condition when the issue occurs. |
| Flooding or uncontrolled dribble | Product can continue to move after the commanded dose and contaminate the pack rim or seal area. | Discharge behaviour after cut-off, nozzle condition, hopper head and any change after refill. |
| Aeration | The same mass occupies more volume, can settle after filling and may change the output of a volumetric route. | Loose-density method, time since transfer or mixing, settling time and finished-pack headspace. |
| Compaction | Density and screw loading may increase during storage or vibration, moving the fill result from the original setting. | Density before and after handling, hopper residence time and fill results through a sustained run. |
| Segregation | Mixed particles can separate, changing composition, density and dosing behaviour during the batch. | Samples from the beginning, middle and end of transfer or filling, together with the transfer method. |
| Static or adhesion | Product can cling to tooling, chutes, sensors and pack surfaces, affecting cut-off and clean presentation. | Material surfaces involved, humidity or process condition where relevant, and locations where build-up appears. |
Use a repeatable bulk-density method and record the product state.
Bulk density is mass divided by the volume occupied by the bulk powder. The number is useful only when the measurement method is recorded. A gently filled vessel can represent loose or aerated material, while a tapped or settled test represents a more compact condition. Neither should be substituted for the actual production state without explanation.
For pack sizing, the lowest expected density is often the demanding condition because the target weight occupies the greatest volume. For volumetric dosing, a density change can alter the mass delivered by the same screw revolutions or chamber volume. For weight-based filling, density still affects feed rate, cut-off behaviour, hopper capacity and the time available for settling before the pack is closed.
Keep the density record with the trial result.
State the vessel volume, filling method, whether the sample was tapped or settled, the number of repeats, the product batch and how long the material had been stored or handled. Do not compare figures measured by different methods as though they describe the same condition.
Test start-up, stable running and refill as different hopper states.
Hopper head, agitation and refill method can change the load on an auger, the feed to a weigh hopper and the amount of entrained air in the powder. The trial should therefore include the beginning of a batch, a stable middle period, a representative refill and a controlled stop and restart. If the production route uses a vacuum conveyor, screw feeder or manual tipping, use that intended method during the test where practicable.
Agitation is not a universal cure. It may prevent one powder from bridging but can compact another, increase dust or damage a fragile blend. Hopper geometry, outlet size, surface finish and the position of any agitator should be reviewed with the representative material rather than selected from a generic product label.
Use behaviour evidence to decide which filling principle to compare.
| Starting condition | Route worth evaluating | Trial question |
|---|---|---|
| Cohesive or fine powder requiring controlled displacement | Auger filling | Can the hopper, screw, tube and nozzle maintain repeatable feed and clean cut-off across the whole batch? |
| Free-flowing particulate product where mass control is central | Weigh filling | Can the feeder approach the target cleanly without excessive dribble, breakage or cycle variation? |
| Powder packed into bags formed from roll film | VFFS with a matched dosing system | Can the product settle and remain clear of the seal area within the bagging cycle? |
| Frequent small batches and product changes | Semi-automatic filling | Can the operator present the pack consistently and can the contact path be cleaned at the required frequency? |
Prepare a sample that represents production, including the difficult condition.
- Use the production grade and a representative batch, not a substitute powder chosen only for convenience.
- Include enough material for stable running, a normal refill and the full pack range.
- Record storage, transport and mixing history where these can change aeration, moisture or segregation.
- Supply the smallest pack opening, largest dose-volume condition and intended closure or film.
- Bring the current safety data and any dust, allergen, containment or cleaning requirements.
Where the powder may create a health or fire and explosion hazard, product-specific assessment is required. The UK Health and Safety Executive publishes guidance on DSEAR and the safe handling of combustible dusts. Machinery selection must follow the competent site assessment and representative material data.