Overview
ISO 3435:1977 - Continuous mechanical handling equipment - establishes a unified classification and symbolization of bulk materials to improve communication between manufacturers and users of handling equipment. The standard defines how to describe particle size, shape, cohesion/flowability, bulk (apparent) density, temperature and special material properties so that equipment selection, specification and procurement are accurate and repeatable.
Key Topics
- Scope: Classification and symbolization rules for bulk materials to be handled by continuous mechanical equipment.
- Granularity / Particle size: Materials are characterized by particle-size distribution and the maximum particle dimension (d), defined as the largest edge of the minimum rectangular parallelepiped enclosing a particle. Materials are split into classified (dmax/dmin ≤ 2.5) and unclassified (dmax/dmin > 2.5) types; users are encouraged to provide full granulometric analysis and samples when needed.
- Particle shape: Six shape classes (I–VI) describe angular, rounded, elongated, platelike and fibrous forms, with examples to aid consistent symbolization.
- Cohesion and flowability: A numerical scale (1–6) describes material flow behaviour from highly fluid (dust-like) to non-flowing, with associated natural repose-angle ranges used to infer handling behavior.
- Material properties: Lowercase letter symbols indicate functional properties relevant to transportability (examples: abrasive, corrosive, fragile, explosive, inflammable, dusty, wet - with percent moisture - sticky, hygroscopic, nauseating). Multiple property symbols may apply.
- Apparent bulk density: Expressed in tonnes per cubic metre (t/m3), defined as the mass per volume as delivered to the handling device.
- Temperature: Material temperature should be reported in °C; if variable, provide minimum and maximum.
Applications
ISO 3435:1977 is practical for:
- Specifying conveyors, bucket elevators, feeders, hoppers, chutes and screening equipment
- Sizing and selecting components for bulk solids handling (belts, screws, vibratory feeders, pneumatic systems)
- Preparing procurement questionnaires and vendor data sheets to avoid misunderstandings about material characteristics
- Risk assessment and process design where particle size, cohesion, density and special hazards affect performance and safety
Who uses this standard
- Equipment manufacturers and suppliers
- Plant/process engineers and designers
- Procurement teams and project managers
- Bulk materials handling consultants and safety engineers
Related standards
ISO 3435 was prepared by ISO/TC 101 (continuous mechanical handling). For complete equipment design and safety guidance, consult other ISO standards covering conveyors, hoppers, pneumatic conveying and bulk solids handling (refer to current ISO catalogs).
