SAURAV SHARMA 2013UGMM001 ITESH KUMAR TAMSOY 2013UGMM002 NISHANT KUMAR 2013UGMM017

Screening Screening is the practise of taking granulated ore material and separating it into multiple grades by particle size. This process occurs in variety of industries such as mining and mineral processing,agriculture, pharmaceutical, food,plastics and recycling. General categories Screening fall under two general categories: Dry screening and wet screening. From these categories, screening separates a flow of material into grades, these grades are then either further processed to an intermediary product or a finished product.Additionally the machines can be categorised into moving screen and static screen machines, as well as by whether the screens are horizontal or inclined. Application The mining and mineral processing industry uses screening for a variety of processing applications. For example, after mining the minerals is transported to a primary crusher. Before crushing large boulder are scalped on a shaker with 0.25 in (6.4mm) thick shielding screening. Further downstream after crushing the material can pass through screens with opening or slots that continue to become smaller. Finally, screening is used to make a final separation to produce saleable products based on grade or a size range.

Process A screening machine consist of a drive that induces vibration, a screen media that causes particle separation, and a deck which holds the screen media and that causes particle separation,and a deck which holds the screen media and the drive and the drive and is the mode for the vibration. There are physical factors that make screening practical. For example, vibration, g force bed density, and material shape all facilitate the rate or cut. Electrostatic forces can also hinder screening efficiency in way of water attraction causing sticking or plugging, or very dry material generate a charge that cause it to attract to the screen itself. As with any industrial process there is a group of terms that identify and define what screening is. Terms like blinding, contamination, frequency, amplitude, and others describe the basic characteristics of screening, and those characteristics in turn shape the overall method of dry or wet screening.

MODEL OF SCREENING PROCESS

Types of mechanical screening There are a number of types of mechanical screening equipment that cause segregation. These types are based on the motion of the machine through its motor drive. Circle-throw vibrating equipment -This type of equipment has an eccentric shaft that causes the frame of the frame of the shaker to lurch at a given angle. This lurching action literally throws the material forward and up. As the machine returns to its base state the materials falls by gravity to physically lower level. This type of screening is used also in mining operations for large material with sizes that range from six inches to+20 mesh. High frequency vibrating equipment - High frequency vibration equipment is a shaker whose frame is fixed and the drive vibrates only the screen cloth. High frequency vibration equipment is for particles that are in this particle size range of an 1/8 in (3mm) down to a +150 mesh.These shakers are usually set at a steep angle relative to the horizontal level plane.Angles range from 25 to 45 degrees relative to the horizontal level plane.

* Gyratory equipment -This types of equipment has an eccentric drive or weight that causes the shaker to travel in orbital path. The material rolls over the screen and falls with the induction of gravity and directional shifts. Rubber balls trays provide an additional mechanical means to cause the material to fall through. The ball also provide a throwing action for the material to find an open slot to fall through. The shaker is a shallow angle relative to the horizontal level plane. Usually, no more than 2 to 5 degrees relative to the horizontal level plane. * Trommel Screens - Trommel screens have a rotating drum with screen panels around the diameter of the drum and is on a shall angle. The feed material always sits at the bottom of the drum and as it rotates. Always comes into contact with clean screen. The oversize travels to the end of the drum as it does not pass through the screen, while the undersize passes through the screen into a launder below.

GYRATOR SCREENER

CHEMICAL TUMBLER SCREENER

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