screening

screening [′skrēn·iŋ]

(atomic physics)

The reduction of the electric field about a nucleus by the space charge of the surrounding electrons.

(electromagnetism)

electric shielding

(engineering)

The separation of a mixture of grains of various sizes into two or more size-range portions by means of a porous or woven-mesh screening media.

The removal of solid particles from a liquid-solid mixture by means of a screen.

The material that has passed through a screen.

(industrial engineering)

The elimination of defective pieces from a lot by inspection for specified defects. Also known as detailing.

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Screening

A mechanical method of separating a mixture of solid particles into fractions by size. The mixture to be separated, called the feed, is passed over a screen surface containing openings of definite size. Particles smaller than the openings fall through the screen and are collected as undersize. Particles larger than the openings slide off the screen and are caught as oversize. A single screen separates the feed into only two fractions. Two or more screens may be operated in series to give additional fractions. Screening occasionally is done wet, but most commonly it is done dry.

Industrial screens may be constructed of metal bars, perforated or slotted metal plates, woven wire cloth, or bolting cloth. The openings are usually square but may be circular or rectangular. See Mechanical classification, Mechanical separation techniques, Sedimentation (industry)