Plastic Regrind Bulk Density: kg/h, Litres and Hopper Volume

What bulk density describes

Plastic regrind bulk density is the net mass of a pile divided by the volume that pile occupies, including the spaces between pieces. It is different from the density or specific gravity of the solid resin itself. Irregular regrind can behave differently from virgin pellets in bulk density, flow and blending; the direction and size of the difference depend on the material and its condition.

Bulk density is affected by how material is handled and whether it is loose or compacted. For a meaningful comparison, describe the sample and use the same sampling and filling basis for each result. See the Ray-Ran bulk density apparatus information for the distinction between loose and compacted material, and Conair's hopper sizing note on variations associated with regrind shape and size.

Convert mass and volume

With bulk density expressed in kg/L, multiply usable volume in litres by density to estimate the mass it holds. For a continuous mass rate, divide kg/h by kg/L to estimate the corresponding material volume in L/h. One cubic metre equals 1000 litres, so 1 kg/L equals 1000 kg/m³.

The following is an arithmetic example, using assumed densities for two batches at the same 100 kg/h mass rate. The values are not standard densities for a particular resin or measured RHONG equipment results.

At the assumed densities, batch B needs approximately twice the material volume per hour and holds half as much mass in the same usable space. This is a volume comparison, not a prediction of whether either batch will flow consistently or bridge at an outlet.

Use the result in a purchase discussion

Check the equipment's usable storage volume, rather than assuming that every litre of its geometric or rated hopper volume is available. Fill and discharge controls, reserved space and outlet behaviour all affect the practical arrangement. If your starting point is a granulator's output rate, the separate guide to capacity in kg/h explains the mass-and-time side of the question.

For each sample, record its identity, particle shape and condition, batch, sampling and filling or compaction basis, measured container volume, net mass and calculated result. Record variation between samples as well. For an acceptance decision, agree on a method suited to the material with the other party. Include the required mass rate or usable hopper volume when requesting a comparison.

Density alone does not establish vacuum conveying capacity, flow behaviour, granulator throughput or drying time and quality. When selecting a vacuum loader, also define its operating requirements. When considering a general-purpose granulator, discuss the actual scrap and required output; this density comparison does not establish suitability for granulating or loading that material. Share the material and process details through contact when discussing equipment.