Screens, blinding vibrating

Vibration Amplitude and Frequency Speed and amplitude of vibration should be designed to convey the material properly and to prevent blinding of the cloth. They are somewhat dependent upon the size and weight of the material being handled and are related to the angle of installation and the type of screen surface. The object, of course, is to see that the feed is properly stratified for the most efficient separation. 

High-frequency vibrating motion similar to that produced by the Hummer electric, or the Leahy No-Blind screen. 

Screening (Fig. 1C) is a type of surface filtration to separate solids and liquid by screens with openings smaller than particle size. It is usually employed among the first few steps of a SLS process. Vibrations and other mechanism are often applied to avoid blinding of the screens. 

Vibrating screens are particularly prone to blinding when moisture is present. With stone below 10 mm, one solution is to use wet screening, in which water is sprayed on to the mat so that the fine fraction is washed through as a slurry. 

If damp or sticky, predry or use heater above the screen to reduce moisture to <3%. Avoid resonance frequencies. Usual angle of operation is 12 to 18° for wet, inclined vibrating screen to 7 to 11°. Capacity decreases if the angle of inclination is too high. Blinding is mainly caused by material that is 1 to 1.5 times the hole size. Feed thickness should not exceed 4 X aperture size for 1.6 Mg/m and not exceed 2 to 3 X aperture size for 0.8 Mg/m. ... 

Because there are no cross-wires, and because the taut wires can vibrate, there is less tendency for blinding , but some elongated particles inevitably pass the screen. 

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