Overview
ISO 13909-4:2016, "Hard coal and coke - Mechanical sampling - Part 4: Coal - Preparation of test samples", specifies procedures for preparing coal test samples from primary increments through to samples ready for specific laboratory tests. This part of the ISO 13909 series focuses on the constitution, reduction, division, mixing and drying of coal samples and provides guidance on equipment design, precision checks and bias testing. It is the 2016, corrected edition and forms part of a comprehensive set of standards for mechanical sampling of coal and coke.
Key Topics and Requirements
- Scope of sample preparation: Procedures from combining primary increments to producing test-specific samples (e.g., moisture, size analysis, general analysis).
- Precision objectives: Guidance on estimating overall precision and target preparation/testing variance (V_PT), with recommended V_PT levels of 0.2 or less for ash and moisture testing.
- Constitution of samples: Rules for combining increments by time- or mass-basis and for weighted combination of prepared samples.
- Division methods: Detailed mechanical and manual division techniques, including:
- Mechanical dividers and falling-stream cutters (design, cutter velocity, mass of cut, cut interval)
- Manual methods such as riffle, flattened-heap, and strip-mixing and splitting.
- Reduction and mixing: Use of reduction mills, mixing procedures and recommendations for obtaining representative subsamples.
- Sample drying and storage: Air-drying guidance and considerations for moisture-sensitive samples, including when to remove samples off-line to avoid moisture loss.
- Preparation for specific tests: Procedures for extracting moisture samples, preparing size-analysis samples, and making common samples for multiple tests.
- Equipment design and quality checks: Guidance on divider design, preparation systems, and provisions for checking precision and testing for bias.
Practical Applications
- Ensures representative, reproducible coal and coke test samples for quality control, commercial trading, regulatory compliance and research.
- Supports laboratory analysts preparing samples for moisture determination, ash analysis, size distribution and other routine tests.
- Useful for plant sampling engineers, QA/QC managers, coal traders and inspectors who must demonstrate defensible sampling and sample-preparation practices.
Who Uses This Standard
- Coal and coke producers and processors
- Analytical laboratories and testing facilities
- Power plants and industrial end-users requiring guaranteed fuel specifications
- Regulatory agencies, certification bodies and auditors
- Equipment manufacturers (dividers, reduction mills) designing preparation systems
Related Standards (applicable)
Keywords: ISO 13909-4, coal sample preparation, mechanical sampling, sample reduction, riffle divider, flattened-heap, moisture sample, sample precision, coal testing standards.