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ABSTRACT
Screening and sifting are processes which are aimed at separating fragments according to their dimension. Although the term sifting theoretically refers to fine separations below the millimeter and the term screening to rough separations, the term screening usually comprises both types of separation. The particles which can be subjected to screening or sifting can be of mineral, plant, natural or artificial origin. The aim of screening can be extremely varied: separation of the largest fragments or elimination of the finest fragments, improvement of the efficiency of a process. This article describes the major equipment and current various screening techniques.
Read this article from a comprehensive knowledge base, updated and supplemented with articles reviewed by scientific committees.
Read the articleAUTHORS
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Pierre BLAZY: Honorary Professor - Former Director, École nationale supérieure de géologie (ENSG)
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Robert JOUSSEMET: Research engineer at the Environment and Mineralurgy Laboratory (LEM) - ENSG-INPL-CNRS-UMR 7569 - Manager of the Steval testing station (Station de valorisation des matières minérales et des substances résiduaires)
INTRODUCTION
Screening and sifting are unitary operations that separate a population of material fragments according to their size into two (or more) parts. This is achieved by using a surface equipped with openings that let through fragments of smaller dimensions than those of the openings, while retaining fragments of larger dimensions.
Although, theoretically, the term sieving is reserved for fine separations below the millimeter and the term screening for coarse separations, the term screening usually covers both fine and coarse separations.
Any set of particles can be subject to such a process. Particles can be of mineral (aggregates or fragmented rocks), vegetable (grains, flours), natural or artificial origin (various manufactured objects).
The purpose of screening can vary:
Separate larger fragments before reprocessing to improve fragmentation;
conversely, eliminate the finest fractions that may be a nuisance or that can be treated separately (e.g. agglomeration);
prepare particle size classes to meet commercial requirements (aggregates, coal) ;
improve the efficiency of a physical (e.g. gravimetric) or physico-chemical (e.g. flotation) treatment process by judicious selection of the particle size ranges to be treated.
Unless otherwise indicated, the percentages given in this text are by mass.
Descriptions of the main screening machines and techniques are the subject of this first dossier [J 3 101]; the criteria for selecting and designing screens, and their use in the specific field of mechanical ore preparation, are covered in the following dossier
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Screening
Screening surfaces
Also in our database
Bibliography
Software tools
Most of the available software packages are simulation models of complete mineral processing or aggregate production units. They always include a specific screening section. Examples include :
Usim-Pac: developed by BRGM and currently marketed by GASPEO http://www.gaspeo.net
Aggflow – The industry standard...
Events
SIM: Annual conference for mining and quarrying professionals http://www.lasim.org
INTERMAT (France) International exhibition of equipment and techniques for public works, construction and the materials industry (every 3 years). http://www.intermat.fr
...Standards and norms
- Test sieve – Metal fabrics, perforated metal sheets and electroformed foils – Nominal dimensions of openings. Classification number: X11-501 - NF ISO 565 - 11-90
- Specification for ware-cloth sieves for testing purposes - ASTME - 11-87
- Industrial screens – Metal fabrics, perforated sheets and electroformed foils – Designation and nominal dimensions of openings - ISO 2194 :1991 - 09-91
- Test sieve...
Directory
Manufacturers – Suppliers (non-exhaustive list)
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Screening equipment manufacturers
Allgaier (vibrating and circular screens) http://www.allgaier.de
Allis Mineral systems (USA) (BAVS banana screens) http://www.metsominerals.com
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Statistical and economic data
Investment costs are incurred when purchasing and installing an entire treatment unit.
It includes the following items:
material purchases 82.2% ;
equipment transport 4.1% ;
installation costs 10.3% ;
workforce 3.4%.
...
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