ISO 7936:2022

Overview

ISO 7936:2022 - Coal: Determination and presentation of float and sink characteristics provides general directions for apparatus and procedures using relative density separation methods to determine float-and-sink (washability) characteristics of coal. It covers testing of samples from coal seams, and of feed, products and rejects from coal preparation plants. The 2022 second edition updates the standard with procedures for inorganic separation media (e.g., caesium and potassium formates) and aqueous suspensions such as zirconium dioxide.

Key topics and technical requirements

• Scope and purpose: Standardizes how float-and-sink (washability) data are produced and reported so results reliably inform plant design, performance assessment and resource evaluation.
• Sampling: Guidance on sample sources (seams, plants, cores), minimum sample mass, particle counts (aims to ensure statistical adequacy), and when larger bulk samples are necessary. References ISO 13909 series, ISO 18283 and related sampling documents.
• Separation media: Requirements and limitations for organic solutions, inorganic solutions (formates), and aqueous suspensions (zirconium dioxide). Includes safety considerations for organic media and accuracy limits for different media types.
• Apparatus: Descriptions for coarse and fine coal testing equipment and calibration needs (including hydrometer calibration guidance).
• Testing procedures: Stepwise directions for performing float-and-sink tests across size fractions, setting relative density intervals, drying/air-drying, and processing results.
• Reporting and data quality: Test report contents, validation of data (normative annex), and interpretation guidance.
• Annexes (informative/normative): Pre-treatment methods (drop shatter, wet tumbling), sample mass tables, data validation and interpretation, safe use of organic solutions, and hydrometer calibration.

Practical applications and users

ISO 7936:2022 is essential for professionals involved in:

• Coal preparation plant design and optimization
• Process engineers and plant operators monitoring washability and performance
• Geologists and resource evaluators predicting washed coal yield from seam samples
• Laboratory technicians performing float-and-sink testing and reporting results
• Consultants, regulators and procurement teams specifying test protocols and acceptance criteria

Benefits include consistent, reproducible coal washability data, reliable inputs for plant design and control, and standardized reporting for comparisons across projects and jurisdictions.

Related standards

• ISO 1213-1 / ISO 1213-2 (vocabulary)
• ISO 1953 (size analysis)
• ISO 13909-1 to -4 (mechanical sampling)
• ISO 18283 (manual sampling)
• ISO 14180, ISO 4077 (sampling guides)

Keywords: ISO 7936, float and sink, coal washability, relative density separation, coal preparation, sample mass, formate solutions, zirconium dioxide, hydrometer calibration.