How to size a ballistic separator.
Start with more than tonnes per hour.

Start with the stream that actually reaches the separator

A plant’s total intake is not automatically the load on every machine in the line.

If a trommel, manual sorting station or another upstream process removes material first, the ballistic separator receives only the remaining selected stream. Its composition may also be different from the original intake.

Mark the proposed separator inlet on the process diagram. Record the quantity and condition of material at that point. For an existing line, use measurements from that stream where available. For a new plant, identify which figures are measured and which are design estimates.

For example, suppose a plant receives 20 t/h and an assumed 45% of that mass reaches the proposed separator. The estimated separator feed is:

20 t/h × 0.45 = 9 t/h

This is a hypothetical mass-balance example, not a recommended design split. If the upstream removal rate changes, the separator load changes with it. The volume share also cannot be assumed to equal the mass share.

Convert tonnes per hour into cubic metres per hour

Mass flow describes how much material enters by weight. Volumetric flow describes how much space that material occupies. Bulk density connects the two:

Volumetric flow (m³/h) = mass flow (t/h) ÷ bulk density (t/m³)

Bulk density includes the voids between items. It is different from the density of the plastic, paper or metal itself.

Consider two hypothetical feed conditions at the same mass flow:

Halving the assumed density doubles the calculated volume. These values illustrate the conversion only; they are not typical density ranges or a capacity rating for a MIND machine.

When comparing a capacity expressed in m³/h with a project target in t/h, first establish a bulk density representative of the feed entering the machine. Keep the original units visible in the comparison so the conversion can be checked.

The conversion is only a first check. It does not establish separation quality, acceptable object size or mechanical loading. A calculated volume within a published rating is not, by itself, proof that a machine suits the application.

Use density from the relevant feed condition

For an initial estimate, a weighed quantity and its known occupied volume can provide a bulk-density value. Record the sampling point and filling method, and repeat the measurement across representative conditions. Agree a more detailed sampling method with the equipment supplier when developing the design.

A density measured in a compacted transport load should not be used without checking whether it represents the loosened material entering the separator. Likewise, a single convenient sample should not stand in for all shifts or seasons.

Describe peaks as well as averages

An hourly average can hide a very uneven feed pattern. A loader emptying a batch into a hopper may create a different inlet load from a continuously metered conveyor, even when both deliver the same total mass over an hour.

Record the normal operating rate, the observed peak rate, the duration of peaks and the measurement interval. “Peak load” is incomplete unless the time basis is clear: a short surge and a sustained high load are different design conditions.

Daily tonnage also needs a realistic operating-time assumption. In a hypothetical project, 72 tonnes processed during eight effective feeding hours requires an average of 9 t/h. If only six hours are available for feeding, the required average becomes 12 t/h. Scheduled shift length and effective feeding time should therefore be stated separately.

Discuss the intended feed-control method alongside machine size. A larger separator does not automatically resolve an uncontrolled discharge from the equipment ahead of it. Any capacity allowance should follow the project’s measured variation and operating plan, rather than an unexplained percentage added to the average.

Define the material beyond its weight

Two streams with the same calculated volume may still require different configurations. Include a short material description with the flow figures:

Photographs and video help explain these descriptions. For an initial enquiry, show the actual proposed feed and its delivery pattern, rather than only the waste before upstream treatment.

Machine configuration is part of the assessment. Discuss the working width and length, paddle surfaces and perforations, deck inclination and infeed arrangement. These details must follow the material and the required separation result. Confirm which options are available for the proposed model.

Link capacity to a defined separation result

The useful question is how much representative material a separator can process while achieving the agreed output requirements.

Ballistic separation commonly produces flat or flexible 2D material and rolling or rigid 3D material. Perforated paddles can provide a screened fine fraction. These are physical separation groups, not guarantees of individual material purity.

Define what the next process needs from each output. A film-recovery route may require a different assessment from a line preparing mixed combustible material. “Good separation” is too vague to use as a trial acceptance criterion.

For a chosen target material, distinguish two measurements:

• Recovery: the mass of that target material in the desired output divided by its mass in the feed.
• Purity: the mass of that target material in the desired output divided by the total mass of that output.

For example, if a trial feed contains 100 kg of target material and 80 kg reaches the desired output, recovery is 80%. If that output weighs 160 kg in total, purity is 50%. These are hypothetical calculations showing why the two measures should be reported separately.

A useful trial record links the measured inlet rate to output sampling over a corresponding stable operating period, allowing for material travel time. Record machine settings, test duration, feed condition and any interruptions. Check the other outputs for lost target material and investigate unexplained differences between measured input and output mass.

Check the feed and discharge equipment

A separator selection also creates requirements for the equipment around it. Review how material enters, how it is distributed, and how each output is removed.

Check the feeding conveyor or other metering equipment, the spread of material across the inlet, and the transfer into each discharge conveyor. The receiving equipment must handle the expected volume and behaviour of its own stream, including changes during normal operation.

For your project, establish the receiving capacity of each downstream route. Dividing the incoming tonnage equally between three conveyors is not a valid substitute for an expected output balance. The streams may differ substantially in both mass and occupied volume.

Check installation height, support requirements, available space and maintenance access alongside the process data. A suitable separation duty still needs a workable installation.

What to send with a sizing enquiry

A practical first enquiry should contain:

1. A process diagram showing the proposed separator inlet and output routes.
2. The material source, composition, size range and preparation method.
3. Effective feeding hours and required daily tonnage.
4. Moisture conditions and expected material variation.
5. The target materials and required output quality.
6. Feed video, site dimensions and relevant installation constraints.

Label unknown values clearly. A brief with a few explicit uncertainties is more useful than a detailed table of unsupported assumptions.