ISO 13909-4:2025

Overview

ISO 13909-4:2025 - "Coal and coke - Mechanical sampling - Part 4: Preparation of test samples of coal" (Third edition) specifies how to prepare coal test samples from primary increments through to samples for specific laboratory tests. It addresses constitution, reduction, division, mixing and air-drying, and covers design aspects of preparation equipment and provisions for checking precision and bias. The standard is part of the ISO 13909 series on mechanical sampling of coal and coke.

Key technical topics and requirements

• Scope and purpose: Defines procedures from combining primary increments to producing test-ready samples for analyses such as moisture, size distribution and general chemical testing.
• Constitution of a sample: Combines increments by time-basis or mass-basis sampling and describes how to combine samples (Clause 5).
• Division and reduction: Details mechanical and manual division methods, including falling-stream dividers, riffle, flattened-heap, strip-mixing/splitting methods, and use of reduction mills (Clause 6–7).
• Mixing and air-drying: Requirements for homogenizing and air-drying samples prior to testing (Clauses 8–9).
• Preparation for specific tests: Instructions for preparing samples for total moisture determination, general analysis, size-analysis and other tests; includes handling of common samples and extraction of moisture samples (Clause 10).
• Reserve samples and equipment design: Guidance on maintaining reserve samples and design criteria for dividers, cutters and preparation systems (Clauses 11–12).
• Precision and bias control: Describes how preparation precision contributes to overall uncertainty, and references methods to assess precision and test for bias (Clause 4 and normative references).
• Normative references: Incorporates related standards such as ISO 589 (total moisture), ISO 3310-1 (test sieves), and other parts of ISO 13909 (Parts 1–3, 7, 8).

Practical applications and users

ISO 13909-4:2025 is intended for organizations involved in coal sampling and analysis:

• Coal producers and suppliers preparing representative test samples for contract verification and quality control.
• Power plants, utilities and coke producers verifying feedstock quality (moisture, size, calorific value).
• Testing laboratories performing standard chemical and physical analyses that require well-prepared samples.
• Sampling equipment designers and manufacturers ensuring dividers and reduction systems meet design criteria.
• Quality assurance, inspection bodies and auditors assessing conformity and estimating uncertainty of results.

Benefits include improved representativity of test samples, reduced sampling bias, clearer traceability between increments and test results, and standardized procedures that support reliable coal analysis and contractual compliance.

Related standards

• ISO 13909-1: General introduction to mechanical sampling
• ISO 13909-2: Sampling from moving streams (2025)
• ISO 13909-3: Sampling from stationary lots
• ISO 13909-7: Methods for determining precision of sampling, preparation and testing
• ISO 13909-8: Methods of testing for bias
• ISO 589: Hard coal - Determination of total moisture
• ISO 3310-1: Test sieves - Technical requirements

Keywords: ISO 13909-4:2025, coal sampling, sample preparation, mechanical sampling, test samples of coal, sample division, sample reduction, coal analysis, preparation systems, precision.