Overview
ISO 15968:2016 specifies a standardized immersion test to determine the apparent density and water absorption of direct reduced iron in the form of hot briquetted iron (HBI). The method is intended for use in production quality control, contractual verification and research, and its apparent density result can help demonstrate compliance with the IMO Code of Safe Practice for Solid Bulk Cargoes.
Key topics and technical requirements
- Scope: Applies specifically to HBI; method is based on immersion in water.
- Sampling & preparation:
- Follow ISO 10835 for sampling and sample preparation.
- Obtain a test sample sufficient for at least 100 briquettes.
- Sieve sample on a 40 mm test sieve to discard −40 mm material.
- Prepare at least 4 test portions, each with ≥6 briquettes.
- Oven-dry test portions to constant mass at 105 °C ± 5 °C and cool to room temperature.
- Apparatus:
- Oven, two water vessels, suspension device, wire basket or suspension wire, test sieve (ISO 3310 compliant), thermometer and balances.
- Balance accuracy: 0.1 g for immersed weighing; 1 g for dry mass measurements.
- Water: free of impurities (use distilled/deionized or freshly boiled/filtered if in doubt).
- Procedure:
- Weigh dried briquettes in air (m1), soak in water at 22 °C ± 5 °C until bubbling ceases (up to 60 min), surface-dry and weigh in air (m2).
- Determine submerged mass either by the wire basket (entire test portion) or wire suspension (individual briquettes).
- Calculations:
- Apparent density (ρa) is calculated from the measured masses in air and submerged readings and the water density at test temperature.
- Water absorption (a) is calculated as the percentage increase in mass: (m2 − m1)/m1 × 100%, reported to 0.1%.
- Record density results to two decimal places; repeatability r = 0.2 g/cm3 for acceptance.
- Reporting & verification:
- Test report must include reference to ISO 15968, sample ID, lab details, dates, test conditions (drying time, immersion period, water type/temperature), and results.
- Regular apparatus verification (sieves, balances, suspension device, thermometer) is recommended.
Applications - who uses ISO 15968:2016
- Steel producers and direct reduction plants performing HBI quality control
- Laboratory testing services and QA/QC teams
- Buyers and sellers using contractual specifications for HBI shipments
- Regulatory bodies and maritime safety auditors referencing IMO density requirements
- Research organizations studying direct reduced iron properties
Related standards
- ISO 10835 - Direct reduced iron and hot briquetted iron: sampling and sample preparation
- ISO 3310-1 / ISO 3310-2 - Test sieves (metal wire cloth / perforated plate)
- ISO 11323 - Iron ore and direct reduced iron vocabulary
Keywords: ISO 15968:2016, hot briquetted iron, HBI, apparent density, water absorption, immersion test, direct reduced iron, quality control, IMO.