Particle Size Analysis

Particle Size Analysis is used to determine how particles in a material are distributed by diameter. This property is critical because it directly influences material handling, dispersion behavior, chemical reactivity, and, for combustible dusts, dust combustibility and explosion severity. Depending on the material and the specific size range of interest, particle size is measured using different techniques in accordance with ASTM E2651, most commonly laser diffraction and sieve analysis.

Laser diffraction is the primary method for characterizing particles in the approximate size range of 0.5 to 1000 microns. The technique is based on the physical principle that particles scatter laser light at angles inversely proportional to their size, where smaller particles scatter light at larger angles. Testing is performed using a Cilas Particle Size Analyzer 990 operated in dry mode.

Laser diffraction results are reported as equivalent spherical diameters and are typically presented as a volume-based particle size distribution (Q3). Alternative distributions, such as number-based (Q0) or surface-area-based (Q2), can also be provided. Reports include particle size distribution data and graphs, along with key statistical values that summarize the results. These summaries include D10, the particle diameter below which 10% of the particles are smaller and which is useful for identifying the fine fraction; D50, the median particle diameter, where half of the particles are smaller and half are larger; and D90, the particle diameter below which 90% of the particles are smaller and which indicates the upper size range and the possible presence of larger particles or agglomerates.

Applicable Standard

For combustible dust characterization, particle size analysis serves as a critical supporting measurement in accordance with ASTM E1226, which addresses the explosibility of dust clouds. The particle size strongly affects dust dispersion and explosion severity.

Sieve analysis is a mechanical method used primarily for coarser materials that fall outside the effective range of laser diffraction. In this procedure, conducted using standard sieve specifications specified in ASTM E11, a sample is placed in a stack of sieves arranged with the largest opening at the top and progressively smaller openings toward the bottom, then shaken on a vibratory sieve shaker (Retsch AS 200) so that particles separate according to size. The mass retained on each sieve is measured to generate a weight-based particle size distribution, providing a complementary assessment for larger particle fractions.

Instruments

Cilas 990 Particle Size Analyzer laser diffraction instrument

Retsch AS200 Mechanical Sieve Shaker particle size analysis instrument

Sample Preparation

While testing may be conducted on as-received material, ASTM E1226 recommends preparing samples such that at least 95% of the material is smaller than 200 mesh, equivalent to 75 microns, to account for the accumulation of fines in processing systems. This analysis specifically reports the percentage of material smaller than 75 microns to confirm compliance with this guidance and to support conservative and representative explosibility testing. If you are unsure or have questions, call us at 1-844-ioKinetic to discuss.