Sieven

Sieven is a technique used to separate and classify particles in a granular or powdered material by passing the material through a sieve with openings of specified size. The material that is larger than the openings is retained, while finer particles pass through to the next sieving stage. The process is used in both dry and wet contexts and can be performed manually or with mechanical equipment.

Equipment and procedure: Sieve stacks or nest sets consist of sequential screens with progressively smaller openings. Commonly a sieve shaker or vibrator is used to promote separation; manual shaking or tapping can suffice for small samples. Wet sieving may be employed for sticky or clayey materials, with the liquid helping to separate particles.

Sizes and standards: Openings are described in millimeters, micrometers, or sieve numbers. Nesting allows multi-stage classification from coarsest to finest. Standards such as ISO 3310-1 or ASTM E11 define test sieves, aperture tolerances, and testing procedures to ensure repeatability.

Applications: Sieven is used in food production (separating flour, sugar, spices), agriculture and seed cleaning, soil texture analysis, mining and mineral processing, pharmaceutical granulation, and construction aggregate quality control.

Limitations and notes: Sieving is less effective for extremely fine powders or highly cohesive materials and may cause particle breakage or encrusting; accuracy depends on operator technique, sample dryness, and proper calibration. Alternatives include filtration, sedimentation, and centrifugation.