Screening is important operations. They rely on separation of particles according to their size. Screening in performed using screens equipped with one or two screen surfaces called also decks. A single screen provides two products.
- The product from the top is called the oversize or plus product (QG)
- The one which passes through the screen is the undersize or minus product (QD)
Material passing one screen surface but remaining on the next one in a double deck screen is an intermediate product.
During ideal screening, the plus product contains only particles greater than the size of openings of the screen surface while minus product consists of particles smaller than the opening. In real operations the oversized particles are present in the minus product and some undersized particles are in the plus product. It results from adhesion of small particles to large ones and that some particles never get into contact with the screen surface. The presence of large particles in the undersize product may be caused by greater than nominal openings or rupture of the screen surface.
To Find the Efficiency of Screening:
Example: The Feed material to the screen contains 35% (- 5mm). After screening the oversized fraction contains 10% (-5mm) and undersized contains 82% of (-5mm). Efficiency of screening is to be calculated.
Let us find the Values of A, B and C for calculating
The overall Efficiency percentage of screening is calculated by multiplying all the efficiencies.
