Particle size data for pneumatic conveying should describe the full distribution, particle shape and handling-related changes; a single average rarely captures the fractions that affect transport.
For a positive-pressure roots blower project, the useful dataset is a representative particle-size distribution tied to a stated measurement method, supported by practical shape information and connected to the condition in which the product will actually be conveyed.
Specify a Distribution, Not One Number
Two powders can have the same median size while behaving very differently. One may have a narrow distribution; the other may contain a small but important fine fraction and occasional oversize particles. Fines can increase dustiness, cohesion and filter loading. Oversize material can require greater transport margin, damage feeders or lodge in restrictions.
A procurement dataset should therefore report appropriate distribution percentiles or a full cumulative curve. It should also identify whether the percentages are based on mass, number or volume. These bases are not interchangeable and can emphasize different parts of the population.
Sampling location matters. Material collected before conveying may not represent the product at the receiver because attrition can create fines in the feeder, bends and terminal vessel. Where degradation is credible, inlet and outlet samples should be compared using the same preparation and measurement procedure.
Match the Test Method to the Material
Sieving is practical for many granular products and produces mass-based size fractions, but cohesive fines may blind the mesh or remain as agglomerates. Fragile particles can break during handling, while elongated particles may pass an opening in one orientation but not another.
Optical and laser-based techniques cover finer ranges and generate detailed distributions, but their result depends on dispersion energy, optical assumptions and the equivalent diameter reported by the instrument. A wet method can dissolve or swell some materials; a dry method can either leave agglomerates intact or break them apart if dispersion pressure is excessive.
Microscopy and image analysis become valuable when shape is commercially important. They can reveal flakes, needles, fibres, sharp crystals and rough surfaces that one equivalent diameter cannot describe. Images should be representative rather than selected only to show the most convenient particle.
Translate Shape into Process Risk
Rounded granules usually pack and flow differently from angular crystals. Fibrous or plate-like particles can interlock, bridge across feeder openings and show a larger aerodynamic response than a compact particle of similar mass. Sharp mineral grains may increase erosive wear, while soft agglomerates can generate a new fine fraction after only a few bends.
Shape information should therefore be connected to the feeder, pipe route and product-quality requirement. The designer may need to control air velocity, reduce severe impact locations or select a larger separation and filtration margin. These are system decisions; they cannot be made from particle size alone.
Acceptance limits should reflect the commercial risk. A food ingredient may be controlled by maximum fines and contamination, while an abrasive mineral may be controlled by oversize, wear and blockage potential. Stating these limits before testing helps the laboratory report the part of the distribution that actually changes the equipment decision.
Build a Material Data Record for the Blower Enquiry
The blower RFQ should identify material grade, size-distribution method, bulk and particle density, moisture range, temperature, expected fines, particle strength and any hazardous-dust classification. Route length, bore, bends, elevation, feeder leakage and receiver-filter resistance then determine the airflow and pressure duty.
Particle-size and shape data are most useful when they define a repeatable feed condition, sampling basis and transport-window assessment. Record the full size distribution, shape descriptors, moisture and changes after conveying; use route and solids-test evidence rather than an undefined average particle to establish operating assumptions.
Glossary
Cumulative distribution: Representation showing the proportion of particles below or above successive size limits.
Equivalent diameter: Diameter of an idealized particle that produces the same measured response as an irregular particle under a stated method.
Fine fraction: Small-size portion of a bulk material that can dominate cohesion, dustiness or filtration demand.
Image analysis: Measurement of particle dimensions and shape from calibrated static or dynamic images.
Oversize tail: Relatively small population of particles larger than the main distribution.
Particle morphology: Combined description of particle form, angularity, aspect ratio, roughness and related geometric features.
Representative sample: Material collected by a defined sampling procedure to reflect the relevant properties of a lot or process stream within stated limits.