Overview
ISO 5370:2023 - Solid biofuels - Determination of fines content in pellets specifies a manual sieving method to quantify fines in wood and other solid biofuel pellets. The standard defines fines as the mass percentage of material passing through a sieve with 3,15 mm round holes (per ISO 3310-2). It is intended for use in laboratories, production sites and field locations where reliable measurement of pellet fines is required for quality control, regulatory compliance and safety.
Key topics and technical requirements
- Principle: Manual circular sieving of a test portion using a 3,15 mm perforated-plate sieve; fines are reported as mass % of the test portion.
- Apparatus: Circular sieve (recommended 400 mm diameter), collecting pan, sieve template to guide consistent circular motion, balance (readability 0,1 g), metronome/stopwatch and optional lubricants or roller tables for smooth motion.
- Sample preparation & size:
- Laboratory sampling per ISO 18135 or ISO 21945, with attention to fines stratification.
- Minimum test portion mass: 3 kg for pellets 6–8 mm diameter; 5 kg for pellets >8 up to 25 mm.
- Target sub‑portion for a single sieving run: approximately 500 g (adjusted by sieve diameter).
- Sieving procedure:
- Use template-guided circular rotations at a specified rotational speed (≈ 80 r/min for a 400 mm sieve; different speeds for other sieve sizes).
- Number of rotations depends on pellet type: ~10 rotations for residential/commercial pellets with low fines limits; ~20 rotations for commercial/industrial pellets.
- Weigh fines and retained fractions to calculate fines percentage.
- Additional determinations:
- Annex A: Coarse pellet fines (CPF) between 3,15 mm and 5,6 mm (uses a 5,6 mm sieve).
- Annex B: Determination of finer fractions (e.g.,
