RHEWUM Glossary: Technical vocabulary of screening technology

General term for unwanted products, both the coarse material as well as fines.

The changing of velocity, usually the vibrating motion, leads to acceleration. This results in a force acting on the particles thus moving them over the screen.

Several particles adhering together.

Testing sieve for very fine materials.

The distance from the highest point of the screen to its center. The amplitude is equal to half the length of the distance from the highest to the lowest point of the movement. See also stroke. In the case of linear motion the amplitude is half of the total movement; for elliptical motion it is half of the major axis of the ellipse.

The angle to the horizontal that a material will assume naturally when in a pile.

The angle to the horizontal at which material will slide on an inclined surface as determined by the nature of the material.

The inclination of a flat screen against the horizontal.

The opening size of the slots or squares on the screen panel through which the material passes.

Dimension defining an opening in a screening surface.

See Sieve Bend.

A special deck which retains balls (for example rubber balls) that strikes the underside of the screening surface.

Screening surfaces with different slopes arranged in series.

Stationary inclined screen

comprising longitudinal bars

spaced at regular intervals

on to which the material to be screened is fed at the upper end.

The vertical depth (mm) of material on a screen deck

which should typically be 3 - 4 x the screen aperture. At WA screens it can be up to 20 times the screen aperture.

Material that covers and closes the screen apertures.

Weight per unit volume of bulk material

expressed as the weight/unit volume

typically applied to loose and powdery material including air pockets

expressed in kg/m³.

In practice mostly moving the material in a stationary cylindric screen by rotating agitators. In theory also operating a vibrating screen at Fr > 1.

Screen determining the largest size of a product.

The material which remains in the grinding/screening or granulation/screening circuit until it matches the grain size distribution.

Separating particulate material according to the particle size or sizing it into groups.

Cementing of the screen surface by virtue of stickiness. Mostly resulting from moisture content

seldom from adhesion or electrostatic charging.

The dry solids content in a solid-liquid-suspension

expressed on weight or volume basis.

Speed with which the material is transported over the surface by vibration and/or slope.

Due to high slope

the material on a vibrating screen is flowing against the transport direction imposed by the vibrator. This results in a good deagglomeration of the material.

Successive bends in a wire which result from performing or weaving.

Condition at which the imposed frequency of vibration approximates the natural frequency of the mass-spring system. Usually applied in circumstances where the effects produced are undesirable.

The convexity of a screen deck.

The particle size at which equal proportions of material report to the oversize and undersize. The aim of the screening.

The part of the screen that supports the panels.

Removal of very fine particles from a feed by dry methods.

Thickness off the layer of material traversing the screen surface.

Removal of extremely fine particles < 500 µm from wet material by passing it over a screening surface.

Removal of process water with a dewatering screen.

Dismatching of particle heap.

Screen

mounted above another screen

with apertures normally at least twice the size of those in the lower deck

used to reduce the load and wear of the lower screening surface.

A woven wire screen cloth when the wires are corrugated in both directions.

Agitation by two out-of balance drives of different speed.

Separation of material containing no free liquid between the particles and therefore showing no adhesion due to surface tension of the liquid.

An assembly mounted on an off-center portion of a shaft

and used to convert rotary motion via levers to a reciprocating one.

Structural part of an out-of balance drive / comprising two eccentric bearings

hubs of bushes on one shaft.

Maximum displacement from the center line position in a circular oscillating motion

e.g. the radius of the circle.

Portion of screen deck available for material separation.

The percentage of product related to misplaced fines (undersize in oversize) calculated on a weight/weight (mass) basis: The percent of undersize in the feed that actually passes through the screening surface; n = % of feed which actually passes through

devided by % of undersize in the feed that should pass through (n = mff/mf0).

The liquid passing through a screening surface.

A machine which has motion created by an electromagnet.

A machine which moves elliptically.

Vibrator on a machine that operates on the resonant principle.

Particles smaller than a specified size. Sometimes used synonymously with undersize (this is not recommended).

Stationary inclined screen used to remove a proportion of the fines from a dry feed or a proportion of the liquid and the fines from a pulp or slurry

by force of gravity.

The lightest weight material from a density separation.

Feeding screen beyond its capacity.

Screening machine with transport of fines through a liquid (usually water) or a gas (usually air).

The number of times the screen peaks or troughs during 1 second. Measured in Hz.

See also Screen Number K.A dimensionless number

an important criterion characterizing the material on the screening surface. The relation of vibrational acceleration and gravity. Fr = K = ew²/g = 1.5 - approx. 5.5

Acceleration by gravity

g = 9.81 m/s² (= 32.2 ft/s²). Accelerations are usually expressed as multiples of one gravity

e.g. 1g

6.6g.

Acceleration force of the screen

which should typically be 3 – 7g.

Rugged screen comprising fixed or moving bars

discs

or shaped tumblers or rollers

normally used for screening comparatively large particles

e.g. > 100 mm.

Screen used pro prevent the entry of coarse particles into a machine which might interfere with its operation.

Vibrating screen with a motion which is substantially in a straight line in the vertical plane

normally installed horizontally

but may be inclined up to 8°.

Vibrating screen

installed at an angle between 10° and 45°.

Liquid

usually water

held within the particle

i.e. which is hygroscopic bound in a sample of a material

usually expressed as a weight percentage of the sample mass.

The weighted average particle size of a sample

batch or consignment of particulate material.

Number of openings per linear inch

counting from the center of a wire. American unit of measurement; imprecise

as the wire diameter is not mentioned.

Number of apertures per unit of linear measure in a woven wire cloth or wire screen.

Linear motion screening machine with different inclined

successively arranged screening surfaces (decks). Commonly referred to as banana screen. Used for coarse separations at high capacities.

That material very nearly to the size of the aperture

generally +/- 10 % of the aperture.

The particle size used to describe a product of a sizing operation.

For woven wire cloth and wire screens

the ratio of the total area of the apertures to the total area of the cloth or the screen. For perforated plate

the ratio of the total area of the holes to the total area of the perforated part of the plate.

Also Shaker

Sifter and Vibrating Screen. A machine with screening surface(s) used to classify material by particle size.

The oversize or undersize material (or both)

present in a product. Usually expressed in percent of the product.

That portion of the feed discharged from the screening surface without having passed through the apertures; the material that overflows a screen surface.

Screened product of a size greater than a specified size.

Discrete element of the material regardless of its size.

The results from a lab analysis when material is put through a number of sieves of different mesh size and the weight percentage of each size is plotted on a curve in Cumulative Percent Passing.

Smallest sieve aperture through which a particle will pass if presented in the most favourable attitude.

Concentration of a suspension. Commonly specified by weight but may be specified by volume.

Screening surface manufactured by punching apertures of various form in metal sheet

or screening surface consisting of a plate with uniform holes in a regular arrangement. The wholes may be square

slotted

circular or of another regular geometric shape.

Weave in which every warp wire crosses alternately above and below every weft wire and vice versa.

Stroke determined by eccentricity of the shaft.

Removal of a small amount of the feed

usually unwanted oversize lumps material.

In general

the material resulting from any preparation. In particular

the final material of a process; e.g. screened product

final product etc.

Strictly the removing of a small amount of oversize from a feed which is predominantly fines. Typically

the removal of oversize from a feed with approximately a maximum of 5 % oversize

and a minimum of 50 % half-size.

Screen or pair of screens to which a combined horizontal and vertical motion is imparted by a crankshaft and connecting rods

the screening surfaces being horizontal or inclined at a small angle.

Portion of the product in the product fraction. Important to determine the screening efficiency.

Elongated openings in woven wire screen and perforated plate also. Usually in a ratio of 1:3 or 1:10.

Humidification within troughs to assist flowability of product.

The frequency at which any mass-spring system will vibrate naturally.

The time a particle is actually on the screen surface.

Screen

in which the screening surface is formed into a cylinder or frustum of a cone

mounted on a horizontal or near horizontal rotating shaft or on revolving rollers. The material to be screened is fed into the interior of the revolving screen.

A screening surface made up of rods

replaceable individually.

Screen consisting of a number of horizontal rotating drums

fitted with elements arranged to provide screening apertures.

Representative splitting up of the initial quantity until the quantity of sample to be analyzed is reached.

The separation of part of the total feed as coarse oversize by retention on openings more than 50 % larger in diameter or width as the largest particle in undersize. Usually 10 - 20 % of the feed.

Device for carrying out the process of screening for industrial purposes. Note: The term "screen" is also a commonly used abbreviation for "screening surface" or "screen deck".

Simple

rectangular screen on which the material is transported and separated into two fractions.

A cylindrical drum of perforated plate or rigid wire screen revolving at Fr < 0.5.

Proportion to the onsize particles of the product fraction in relation to the quantity of the fraction. Often the required product quality.

Is formed in a bed of material when - by the vibration - the finer material deposits downward and the coarser material deposits to the top of the product bed by different specific gravities.

A finished edge of woven wire screen produced in the weaving process of finer meshes.

Screen with reciprocating motion.

Tensioning of a woven wire cloth across the direction of material flow.

Determination of size distribution by using analysing sieves with defined aperture.

Device for screening fine particles suspended in liquid by means of a stationary curved panel

whereby the finer particles are removed from the bulk of the liquid in the underflow. It is also used as a firststage dewatering device.

A standardized sieve scale.

Type of screen having a rotary motion substantially in the plane of the screening surface

normally used for the screening of comparatively small particles

e.g. < 1 mm.

The heaviest weight material fraction from adensity separation.

The interval between two quoted limiting sizes of the material with particle sizes between those limits.

Woven wire cloth in which one dimension of the apertures is greater than the other.

Mixture of liquids and solids.

Weight per Unit volume of slurry stream and is a combination of the respective density of the solids and liquid calculated in proportion of the weight percentage of the solids and liquid in the slurry.

Screen with directly agitated screening surface at 50 or 60 Hz (within hearable sound).

A series of screening surfaces

each located in progressively lower parallel planes along the vibrating screen in order to produce several fractions.

Fine particles sticking to the coarse grains or screen cloths.

A device attached to the sideplate from which stroke can be read directly (approx. 5 x).

Distance between the extreme positions of an oscillating motion. The stroke is equal to twice the amplitude.

Twice the amplitude

diameter of a circular motion.

Coarse-mesh screen cloth to protect fine-mesh separating screen cloths.

Liquid adhering to the exposed surfaces of the particles of a sample of material

normally expressed as a percentage of the sample mass.

Waste product in ore classification.

A cylindrical or traylike container with a screening surface bottom of standardized apertures.

Quantity

which can be processed by a screening machine. Product of the screening area in m² and specific screening capacity (t/m²h).

The material that passes through a screening surface

including contamination of foreign particles.

The sum of inherent and surface moisture.

A trough

transversally positioned between two screening surfaces.

Gyrating sifter with superimposed tumbling.

Weave in which every warp wire crosses alternately above and below every second weft wire and vice versa.

The way in which warp and weft wires cross each other.

Excitation of screen cloths by a frequency > 18 kHz.

Vibratory screen driven by an unbalance.

Type of screen on which the stroke is determined solely by the dynamic force of the counterweight.

That portion of the feed which has passed through the apertures of a screening surface.

Material having particle size smaller

at least in one dimension

than a specified aperture.

A screen with motion in a vertical plane which operates generally above 600 rpm at less than 2.5 cm stroke.

All wires running lengthwise of the cloth as woven.

Wires running parallel to the length of the cloth as woven.

Screening surface comprising wires of triangular or trapezoidal cross-section spaced from each other at a fixed dimension; the underflow thus passes through an aperture of increasing cross-section.

Wires running across to length of cloth

as woven.

Screening with the aid of a liquid

usually in the form of a spray.

Diameter of the wire for a woven wire cloth

as measured before weaving.

Screening surface

produced by a wire weaving process or by pressure-welding of two layers of parallel wires. The wires form square or rectangular apertures of uniform size. They may be precrimped before weaving.

The medium that is used for screening on the screen deck

synonymous with sieving or screening medium.