Overview
ISO 902:1976 specifies a conventional laboratory method for measuring the angle of repose (angle of rest) of aluminium oxide (alumina) used in aluminium production. The method determines the angle at the base of the conical bulk pile formed when alumina is poured through a standard funnel onto a perfectly horizontal plate. The standard replaces ISO Recommendation R 902-1968 and provides reproducible conditions and a calculation for reporting the angle of repose.
Key topics and requirements
- Principle: form a cone of bulk material by passing alumina through a funnel from a fixed height onto a horizontal, rigid plate and measure the cone dimensions.
- Apparatus essentials:
- Funnel: stainless steel with an inner nozzle diameter of 6 mm and a removable 1 mm mesh sieve.
- Base plate: polished, rigid, minimum 270 mm × 200 mm, engraved centre lines and three adjustable leveling feet.
- Height gauge (cylinder): polished metal cylinder with exact height 40.0 mm used to set nozzle height.
- Funnel support and clamp to fix nozzle position; avoid any vibration during filling.
- Sampling and sample condition: use the raw sample prepared and conserved as per ISO 802; sample temperature at test: 22 ± 4 °C. Sampling reference: ISO 2927.
- Test procedure highlights:
- Level plate; set nozzle so its tip contacts the height gauge, clamp and remove gauge.
- Feed material centrally through the funnel at a controlled rate 20–60 g/min; if sieve blocks, clear gently without vibrating apparatus.
- Stop feeding when cone apex touches the nozzle; mark base circumference and measure four diameters on engraved radii.
- Calculation:
- General formula: angle = arctan(2h / (d − di)), where h = cone height, d = mean of four diameters, di = nozzle inner diameter.
- For the described apparatus (h = 40 mm, di = 6 mm): angle = arctan(80 / (d − 6)).
- Test report must include method reference, numerical results (and form), any particular observations, and records of deviations or non‑standard operations.
Applications and users
- Useful for powder characterization and flowability assessment of aluminium oxide (alumina) in:
- Alumina producers and processors
- Aluminium smelters and supply-chain quality control
- Materials testing laboratories and R&D groups evaluating bulk handling, storage, dosing and silo/hopper design
- The angle of repose is a practical indicator of powder flow behavior, aiding decisions on handling equipment, hopper angles and process optimization.
Related standards
- ISO 802 - Sample preparation and preservation for testing
- ISO 2927 - Sampling of aluminium oxide
- See annex in ISO 902 for additional alumina test methods (ISO 803–ISO 3390 series) for complementary physical and chemical analyses.
Keywords: ISO 902:1976, angle of repose, aluminium oxide, alumina, measurement, powder flow, funnel method, bulk material testing.