Overview - ISO 13317-4:2014 (Balance method)
ISO 13317-4:2014 specifies a balance method for determining particle size distribution (PSD) by gravitational liquid sedimentation. The technique measures the mass of particles that settle under gravity in a liquid and yields a mass-based distribution of equivalent spherical (Stokes) diameters. It is intended mainly for particles in the approximate range 1 μm to 100 μm, and requires sedimentation conditions where the particle Reynolds number is less than 0.25 so that Stokes’ law applies. The method is a direct mass measurement approach and does not rely on fitting parameters.
Key technical topics and requirements
- Principle: Sedimentation under gravity; particle diameter derived from settling time using Stokes’ law to obtain Stokes diameters. Results are cumulative by mass.
- Measurement apparatus: Sedimentation container, dispersion bath, detection tray, time-controlled valve, precision electronic balance, controller and PC. Typical setup components include stirrer, glove box and inlet/bypass plumbing.
- Balance precision: Electronic balance detection precision shall be at least 1% of the total particle mass collected in the detection tray.
- Sample and dispersion:
- Representative sampling and splitting per ISO 14488.
- Dispersion procedures per ISO 14887; use suitable dispersing agents if needed.
- Dispersion medium must avoid flocculation/agglomeration, be chemically stable, non-volatile and provide appropriate viscosity for measurement timing.
- Concentration limits: Volume concentration should be below 0.1% to avoid hindered settling; if higher, a hindrance function must be applied.
- Measurement steps: measure densities (particle and liquid), prepare and disperse suspension, record sedimentation curve G(t) (mass vs. time), stop when mass stabilizes, account for fines remaining in bath.
- Data analysis: Differential intercept method (tangent extrapolation to obtain cumulative mass fractions) and matrix/response-function reduction for more complete inversion of G(t) to q(x). Results are reported as mass-based PSD following ISO 9276-1 representation guidance.
Practical applications and users
This ISO balance method is used where mass-based particle size distribution is needed for materials in suspension. Typical users:
- Quality control and testing labs in pharmaceuticals, pigments, ceramics, mining, cement, and specialty chemicals
- Materials scientists and process engineers evaluating powder dispersion, settling behavior or sedimentation stability
- R&D teams requiring direct measurement of mass fractions by size when Stokes-diameter interpretation is appropriate
Related standards
- ISO 13317-1: General principles and guidelines
- ISO 13317-1/2/3: Other gravitational sedimentation parts (fixed pipette, X‑ray method)
- ISO 9276-1: Graphical representation of PSD results
- ISO 14488: Sampling and sample splitting
- ISO 14887: Dispersion procedures
Keywords: ISO 13317-4:2014, particle size distribution, gravitational liquid sedimentation, balance method, Stokes diameter, sedimentation, mass-based PSD, dispersion medium, hindered settling.
Open preview (PDF)Determination of particle size distribution by gravitational liquid sedimentation methods — Part 4: Balance method