ISO 17829:2025

Overview

ISO 17829:2025 - Solid biofuels - Determination of length and diameter of pellets defines standardized methods to measure the diameter and length of solid biofuel pellets. The second edition expands the scope to include determination of pellet length fractions (for example pellets > 40 mm and particles < 10 mm) and procedures to calculate the average pellet length. The standard supports consistent quality control and compliance with pellet dimension requirements referenced in fuel specifications (ISO 17225 series).

Key topics and technical requirements

• Scope and principle: Measures pellet diameter class and pellet length along the pellet axis; enables quantification of shares of specified length classes and reporting of the longest pellet when > 40 mm are found.
• Measurement options:
  • Option A - Measuring block with built-in calliper and metal pin elements (example for 6 mm pellets uses 7 ± 0.1 mm pins); groove guides pellet along axis.
  • Option B - Manual measurement with a calliper (recommended digital) with minimum readability 0.1 mm.
• Apparatus: digital calliper, measuring block, balance (0.1 g readability), sieves with round holes of 3.15 mm and 5.6 mm (ISO 3310‑2).
• Sample preparation: Procedures for preparing test portions and handling coarse pellet fines (particles between 3.15 mm and 5.6 mm). Note: coarse pellet fines are removed before average length determination but are included when reporting specific size fractions.
• Procedures: Determination of diameter class (aligned with ISO 17225‑2), measuring individual pellet lengths, counting pellets above specified limits (e.g., > 40 mm), and computing average length and mass fractions.
• Validation: Automatic measurement equipment may be used if validated with appropriate reference pellets.
• Reporting and performance: Requirements for calculations, performance characteristics and test reports are defined (clauses 8–10).

Applications and users

ISO 17829:2025 is intended for:

• Pellet manufacturers and quality control labs verifying pellet dimensions for product specifications.
• Fuel suppliers and buyers ensuring compliance with ISO 17225 classes.
• Combustion system and boiler manufacturers, and logistics designers assessing fit for screw conveyors, silo outlets and burner feeding systems.
• Independent testing laboratories, regulators and certification bodies performing standardized pellet testing.

Practical benefits include avoiding handling and combustion issues caused by out‑of‑spec pellets, improving bulk density and combustion performance consistency, and enabling comparable quality data across suppliers.

Related standards

• ISO 17225‑1, ‑2, ‑6, ‑8 (fuel specifications and classes)
• ISO 5370 (fines content in pellets)
• ISO 14780 (sample preparation)
• ISO 18135 / ISO 21945 (sampling methods)
• ISO 16559 (vocabulary)

Keywords: ISO 17829:2025, solid biofuels, pellet length, pellet diameter, pellet measurement, pellet length fractions, measuring block, digital calliper, ISO 17225.