ISO 5370:2023

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., <1 mm, <0,5 mm).
  • Annexes C/D: Performance and research data; Annexes support quality control and method validation.

Practical applications and users

ISO 5370:2023 is used for:

• Quality control in pellet manufacturing and production lines.
• Third‑party and in‑house testing laboratories validating batch quality.
• Compliance testing for suppliers and purchasers (shipping, storage, standards conformity).
• Risk management for transport, storage and combustion systems to reduce dust inhalation risks and explosion hazards. Typical users: pellet manufacturers, QA/QC personnel, testing labs, fuel traders, appliance manufacturers, and regulatory bodies.

Related standards (normative references)

• ISO 3310-2 - Test sieves of perforated metal plate
• ISO 3310-1 - Test sieves of metal wire cloth (for fines < 3,15 mm)
• ISO 16559 - Solid biofuels - Vocabulary
• ISO 18135 / ISO 21945 - Sampling methods for solid biofuels

Keywords: ISO 5370:2023, solid biofuels, fines content, pellet fines, 3.15 mm sieve, coarse pellet fines (CPF), sieving method, pellet quality control.