Overview
ISO 7119:1981 defines a practical, standardized method for calculating the drive power of screw conveyors used in continuous handling of loose bulk materials. It applies to screw conveyors operating in a horizontal or inclined position (up to ~20°) with a regular, controlled and continuous feed. The standard excludes special-purpose screws such as extracting, calibrating, mixing, moistening, steeply inclined (>20°) and vertical screws. ISO 7119 is intended for designers, OEMs and engineers who need reliable power calculation and conveyor sizing guidance for bulk-material handling systems.
Key topics and requirements
- Scope and applicability: horizontal and moderately inclined screw conveyors for continuous flow of bulk materials; exclusions listed above.
- Power component model: total shaft power is the sum of three terms:
- PH – power required to progress (convey) the material,
- PN – power to run the screw at no-load,
- Pst – power due to inclination (lifting or lowering material).
- Total power: P = PH + PN + Pst
- Capacity and flow: the standard gives a method to calculate volumetric and mass flow based on screw geometry (diameter, pitch), rotational speed and a trough-filling coefficient (p) that reflects the degree of filling.
- Empirical parameters: introduces the progress resistance coefficient (A) and provides guidance on typical ranges (A generally in the order of 2–4) and how material properties affect A and filling coefficient p.
- Typical filling-coefficient guidance: examples for common operating cases (e.g., p ≈ 0.45 for free-flowing, non-abrasive materials; p ≈ 0.3 for typical bulk materials; p ≈ 0.15 for heavy, very abrasive materials).
- Practical formulae and variables: symbols and units are defined (screw diameter, pitch, length, speed, bulk density, mass flow, lifting height, gravity, etc.).
- Informative annex: example values for bulk density and progress resistance coefficients for a range of materials to support selections.
Applications and users
- Bulk-material handling design in industries such as mining, aggregates, cement, food processing, agriculture, coal and chemicals.
- Mechanical engineers, conveyor designers, plant layout engineers, procurement/specification teams, and maintenance planners who need to:
- size drives and gearboxes,
- select motor ratings,
- verify conveyor performance under expected loading and inclination,
- estimate energy consumption for material transport.
Related standards
- ISO 2148 (nomenclature for continuous mechanical handling equipment) is referenced for terminology.
- ISO 7119 was developed by ISO/TC 101 and is based on FEM (European Mechanical Handling Confederation) Section II work.
Keywords: ISO 7119, screw conveyors, drive power calculation, continuous mechanical handling equipment, bulk materials, conveyor design, progress resistance coefficient, trough filling coefficient.
Open preview (PDF)Continuous mechanical handling equipment for loose bulk materials — Screw conveyors — Design rules for drive power
