Sieving & Classification

Tumbler screening machine operating principle

The tumbler screening machine separates particles mechanically according to their size.

The product is fed onto a vibrating screen. The vibratory motion aids the distribution of the product across the mesh, whilst facilitating the passage of particles through the apertures.

Particles smaller than the mesh apertures pass through and form the undersize fraction, while larger particles are retained and discharged separately.

Depending on the equipment configuration, multiple screens can be used to obtain different size fractions.

Advantages of the tumbler screening machine

• Precise and reproducible particle size separation;
• Adjustable vibration frequency and amplitude to control the residence time of the product on the screen;
• Separation into several particle size fractions;
• Suitable for a wide range of product particle sizes;
• Control of particle size distribution.

Centrifugal sifter operating principle

The centrifugal sifter uses a rotor to set the product in motion inside a cylindrical screen.

The rotation of the rotor drives the particles towards the screen. Particles that are fine enough pass through the apertures and form the undersize fraction, while larger particles are retained and then discharged.

Advantages of the centrifugal sifter

• Suitable for low-density powders;
• Suitable for cohesive powders;
• Removal of agglomerates and unwanted particles;
• Consistent feed rate to the screen.

Turbo-sifter operating principle

The turbo-sifter carries out particle size separation of dry powders using air-assisted sieving.

The product is fed into the centre of the sieving chamber. A fan generates a high-volume air flow that continuously conveys the particles towards the screening surface.

Particles smaller than the mesh apertures pass through the screen and are carried by the air flow to a cyclone or filter, where they are collected. Larger particles, which cannot pass through the apertures, are retained by the screen and discharged separately.

To minimise clogging of the mesh, in particular by particles close in size to the mesh apertures, a compressed air system ensures continuous clearing of the screening surface.

Advantages of the turbo-sifter

• Suitable for powders that are difficult to sieve;
• Capable of achieving low cut sizes;
• Effective dispersion of the particles within the sieving chamber;
• Minimisation of mesh blockages;
• Reduction of particle agglomeration.

Air classifier operating principle

The air classifier separates fine powders by particle size, exploiting the differences in particle behaviour within an air stream.

The product to be classified is fed into the system and dispersed into the air flow.

The particles are then directed towards a rotating classifying wheel, the speed of which can be adjusted to tailor the separation fineness to the characteristics of the product and the required specifications.

Under the combined action of the air flow and centrifugal force, the particles are separated according to size. Particles that are sufficiently fine pass through the classification system and form the fine fraction, while coarser particles are rejected and discharged separately.

Advantages of the air classifier

• Suitable for the classification of fine and ultra-fine powders;
• Screenless classification, eliminating the clogging issues associated with sieving;
• Adjustable cut point to match the target fineness;
• Very high classification fineness;
• Reproducible classification results;
• Complementary to grinding and micronisation operations.