ISO 5074:2015

Overview

ISO 5074:2015 - "Hard coal - Determination of Hardgrove grindability index" is the ISO method for measuring the relative grindability of hard coal using the Hardgrove machine. The third edition (2015) defines the test principle, machine calibration, and preparation of standard reference coal samples. The standard clarifies that the term hard coal refers to coal rank (gross calorific value > 24 MJ/kg, moist, ash‑free) and not to physical hardness.

Key topics and requirements

• Test principle: Controlled milling of a prepared coal sample in a calibrated Hardgrove machine followed by sieve analysis of the ground product to derive the Hardgrove grindability index (HGI).
• Calibration: Procedures for calibrating the Hardgrove machine and generating the calibration chart using standard reference materials.
• Sample preparation & sampling: Mandates use of ISO 13909 and ISO 18283 for mechanical and manual sampling and details preparation steps needed to obtain a representative test sample.
• Reporting and equipment: Requires conformity with equipment, test procedure and reporting conventions, referencing ASTM D409 for related apparatus and procedural details.
• Definitions: Clear definition of “hard coal” based on calorific value and other relevant terms used in grindability testing.

Applications and users

• Pulverizer design and selection: Engineers use HGI values to estimate pulveriser throughput and power consumption for a specified product fineness.
• Power plants and utilities: Fuel characterization to optimize combustion performance and mill operation.
• Coal suppliers and traders: Quality assessment and specification of coal lots for sale or blending.
• Laboratories and QA/QC: Routine analytical testing of coal for process control and compliance.
• Research and standards bodies: Comparative studies of coal physical properties, grindability correlations, and method development.

Practical value

• Provides a reproducible, industry‑accepted grindability metric (HGI) to predict milling behaviour.
• Enables consistent communication of coal grindability across suppliers, plant operators, and equipment manufacturers.
• Supports plant energy-efficiency assessments and mill capacity planning through empirical relationships between HGI and pulverizer performance.

Related standards

• ISO 13909 - Hard coal and coke: Mechanical sampling
• ISO 18283 - Hard coal and coke: Manual sampling
• ASTM D409 - Standard Test Method for Grindability of Coal by the Hardgrove‑Machine Method (referenced for equipment and procedural alignment)

Keywords: ISO 5074, Hardgrove grindability index, Hardgrove machine, hard coal grindability, coal testing standard, grindability test, calibration, sample preparation, pulverizer power consumption.