ISO 728:2021

Overview

ISO 728:2021 - "Coke - Size analysis by sieving" specifies standardized procedures for determining particle size distribution of coke by manual and/or low‑impact mechanical sieving. The standard covers test sieves with square or round holed apertures between 125 mm and 0.5 mm, rules for sample preparation (including moisture limits), sieving procedures for different size ranges, expression of results and calculation of mean coke size. Annex A gives guidance for sizing coke products greater than 125 mm.

Key topics and technical requirements

• Scope and aperture range: Sieving using test sieves with hole sizes from 125 mm down to 0.5 mm; guidance for >125 mm in Annex A.
• Sample moisture: Test samples must have less than 5.0% total moisture (see ISO 579 for moisture determination).
• Apparatus: Test sieves per ISO 3310‑1 / ISO 3310‑2, balance/scale (0.1% accuracy), trays, lids, hardwood block for tapping, brushes, receivers and optional low‑impact vibratory sieve shaker (shaker action must not degrade coke).
• Minimum sample masses: Table of minimum gross/sample masses by nominal top size (examples): Plus 125 mm - 2 000 kg; 125 mm - 1 000 kg; 22.4 mm - 30 kg; 4 mm - 1 kg.
• Sieving procedures:
  • Hand placing of particles is required for larger fractions (introduced for sizes from 125 mm down to 22.4 mm).
  • Division of minus‑22.4 mm material by mechanical divider or standard splitting methods to required test mass.
  • Manual sieving rules for 22.4–4.0 mm (controlled horizontal movement and number of movements) and for <4.0 mm (inclination, tapping, 5‑minute sieving intervals and brushing).
• Results and calculations: Express results as cumulative percentage by mass on sieves; method includes mean coke size calculation, precision statements (repeatability and reproducibility) and required test reporting.

Applications and users

ISO 728:2021 is used where consistent coke particle‑size data are required for quality control, process optimisation and contractual specifications:

• Coke producers and blending operations - verifying product grading and conformance.
• Steel and foundry plants - ensuring coke size distribution for furnace performance and burden permeability.
• Laboratories and QA/QC teams - routine testing, acceptance testing and inter‑laboratory comparisons.
• Equipment manufacturers - design and validation of low‑impact sieve shakers and sample division devices.
• Procurement and standards specialists - specifying contractual test methods for coke shipments.

Keywords: ISO 728:2021, coke size analysis, sieving, manual sieving, low impact mechanical sieving, test sieves, particle size distribution, coke sampling, mean coke size.

Related standards

• ISO 579 - Coke - Determination of total moisture
• ISO 3310‑1 / ISO 3310‑2 - Test sieves technical requirements
• ISO 13909‑5 / ISO 13909‑6 - Mechanical sampling and sample preparation for coke
• ISO 18283 - Manual sampling
• ISO 1213‑2 - Vocabulary for sampling, testing and analysis