6 Main Factors That Affect the Screen Performance of Mining Screens

What is Screen Performance?

While there is no universally accepted definition of screen performance, the most common criteria used is efficiency – which is a measure of how complete size separation is achieved; it allows you to know if you are over screening or under screening a material.

The mining screen is installed on the crusher for aggregate processing.

Mining Screen for Aggregate Processing

Aggregates are distributed evenly on the mining screen deck.

Aggregates Distributed on Screen Deck

Main Factors

Particle Size
The smaller the particle size to the aperture, the higher the probability of passing the screen, while the nearer the particle size, the lower the probability of passing the screen. Near-sized particles also tend to plug the apertures thereby reducing the available open area.
Particle Shape
Spherical particles pass with equal probability in any orientation, while elongated, flat and irregularly shaped particles pass with less probability in some orientations. In addition, they may hinder other particles from passing and reduce screening efficiency even further.

Particle Shapes and Sizes

Particle Screening Diagram
Moisture
The moisture content in the material has a significant effect on screening efficiency, so do clays and other sticky materials as they tend to agglomerate and "blind" the screen apertures.
Feed Rate
Generally, particles must travel to the bottom of the screen bed before they have an opportunity to pass through the screen, while feed rate affects the bed depth. Typically, the bed depth at the discharge end shall be reduced to less than 4 times the aperture size or at least equal to aperture size.
Screen Angle
Screen angle change the shape of the aperture relative to what the particle sees. The higher angles produce higher particle speeds, which makes particles have fewer opportunities to pass through the apertures.

Mining Screen Angle

Effect of Mining Screen Angle on Aperture
Vibration
Vibrations must be enough to prevent pegging and blinding but not to cause the particles to bounce from the screening surface. Higher vibration rates can be applied with higher feed rates because the increased bed depth acts as a cushion that inhibits particle bounce. Generally lower speeds and higher amplitudes are used for coarse material and the inverse for finer material.

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