Glossary

Learn now about screening, sizing, and synonyms for screening machines! The glossary you need is provided here by KELLER Siebtechnik:

Here, you can find a list of important words whith descriptions or translations
A

Acceleration

This is the rate of change to speed, in most cases of the vibrations. This exerts a force on the moving mass, i.e. the screen and particles.

Adherent particle

This is a fine particle adhering to coarse material or the screening fabric.

Air jet analysis screen

This is a test screen for very fine material.

Adherent segregation

This clogs the screening surface, in most cases under the action of moisture, more rarely under adhesive forces or electrostatic buildup.

Angle of inclination β, screen angle

This is the angle the screen forms with the horizontal.

Agglomerate

A large number of clumped particles.

Amplitude

The distance a screen moves through from its highest to its centre point. The amplitude equals half of the distance between the movement’s highest and lowest point. See also Throw. The amplitude of a linear vibration is half of the total distance, that of an ellipsoidal vibration half of the ellipsis’s major axis.

Analysis screens

These exhibit defined mesh apertures serving to determine the distribution of particle sizes.

Aperture width

This is a measure of the aperture in a screen panel.

B

Backing fabric

Wide meshed screening fabric that protects the fine meshed layers.

Ball deck

This is the deck under the screening area that holds the cleaning balls (e.g. of rubber).

Bed depth

This is the vertical depth of the product on the screening deck and is usually 3–4 times the mesh aperture.

Bound moisture

This is the liquid bound hygroscopically in an input product sample, usually specified as a mass fraction of the sample in percent.

Bulk density

This is the weight per unit volume of loose material, applied normally to loose or powdery material with air inclusions and specified in kg/m³.

C

Consistency

This is the solid fraction of a suspension specified in percentage by weight or volume.

Control screen

This is the screen defining the largest particle size.

Counterflow

The input material runs down the screen inclination, and not in the direction of the upward conveying vibrations. This loosens up thoroughly the input material.

Conveyor speed

This is the speed at which the material is conveyed under vibration and/or the angle of inclination.

Circulation process

The input material keeps circulating e.g. in the comminution–screening circuit until it reaches the required fineness.

Critical speed (see also Resonance)

This is when the drive speed equals the natural frequency of a spring-mass system, in most cases an undesirable state.

Cumulative distribution

This is a method of depicting particle size distributions.

Crimping

A series of bends worked into a wire by preforming or weaving.

Clogging

This is material that adheres to and blocks the apertures in a screening fabric.

D

Debris

A general term for unwanted fine and coarse material

Deck

Deck or screening deck: That part of the screening machine bearing the screen linings.

Dwell time

This is the time a particle remains on the screen surface.

Deagglomeration

The separation of clumped particles.

Dedusting

Removal of very fine particles from the input material.

Discharge

This is the product quantity yielded by a treatment process, specifically the end product of a process cycle (e.g. screening yield or finished product).

Double crimp weave

Screening fabric with crimped warp and shute wires.

Dry screening

This is used to separate material that exhibits no surface moisture, hence no adhesive forces induced by surface tension.

E

Efficiency

This is the ratio of undersized to oversized product weight (mass) expressed as a percentage.

Effective screening area

This is that part of the screening deck available for separating the input material.

Electromagnetic screening machine

This is a screening machine moved by electromagnets.

Elliptical vibratory screen

This is a screening machine that executes elliptical screening movements.

Exciter

This is a resonating vibrator.

Eccentric

The eccentric and a linkage translates rotary movement into a linear stroke.

Eccentric shaft

This is an element of an unbalanced motor mounted on two eccentric bearings, hubs, or bushes.

Eccentricity

The maximum distance of a circular vibration from the centre (equalling the circle’s radius).

F

Feed capacity

This is the quantity a screening machine can process. It is the product of screen area in m² and the specific screening capacity in t/m²h.

Fines

These are particles smaller than a defined size. These are sometimes equated with the screenings (not recommended).

Flooding

Overloading in a screening machine.

Foreign body screen

This screening machine prevents coarse particles from entering the downstream screener, thus eliminating potential disruption to operations.

Frequency

The number of highest and lowest points that a screening machine passes in one second, measured in hertz (Hz).

G

g

This is the acceleration due to gravity, g = 9.81 m/s². The vibrational acceleration is often specified as a multiple of g, e.g. 1.5–6.6 g.

Gravity screening machine

This screening machine vibrates vertically at a speed of over 600 rpm and through a distance less than 2.5 cm.

H

Heavy goods

These are the heaviest goods during jigging.

I

Inertial force

This is the accelerating force generated by the screening machine, usually three to seven times the acceleration due to gravity (3–7 g).

Interstitial water

This is liquid, in most cases water, that is retained in the interstices between particles.

Inclined screening machine

Vibrating screen inclined at an angle of usually 10–45°.

K
L

Long stroke screen

This screen vibrates over a distance defined by the forces exerted by an unbalanced mass.

M

Mesh aperture

This is the size of the oblong or square openings in the screen lining through which the product passes.

Mesh count

This is the number of apertures per unit length in a wire screen fabric.

Mat thickness

This is the depth (thickness) of the input material running over the screening surface.

Multiple desk screen

This is a series of screening decks that are arranged in parallel under each other and that are intended to output multiple fractions in the one screening machine.

Mesh

This is the number of screen apertures per inch. This is the US measure for mesh aperture. It is inexact because it does not include the wire gauge.

Mean particle size

The weighted, averaged particle size in a sample, quantity, or batch of input material.

N

Near-mesh particle

This is the input particle size corresponding to about 90–110% of the mesh aperture. These particles can be screened with difficulty only. It is also a measure of the screening capacity.

O

Oblong mesh aperture

Elongated aperture in the screening fabric or perforated plate. This is usually the ratio 1:3 or 1:10.

Oblong mesh, broad mesh

This is a wire screen panel featuring apertures that are longer than wide or vice versa.

Outsize fraction

Oversize, undersize, or both in the product. This is specified as a percentage of the product quantity.

Open area

For wire screen panels: This is the ratio of the total mesh aperture area to the whole screen area expressed as a percentage. For perforated plates: This is the ratio of the total area of all holes to the total area of the perforated section of a plate expressed as a percentage.

Open screen area

This is the ratio of screen aperture area to screen panel area.

Output

This is the screened percentage of the input product, used to determine the screening efficiency.

Oversize

This is that part of the input material that did not or cannot pass through the apertures in the screen panel.

Overs

This is reject material following treatment.

P

Particle

This is a single constituent of matter of any size.

Particle size

This is the rated width of the smallest aperture in a screen panel through which a single particle can pass.

Particle size distribution

This is returned by a laboratory analysis on a product that has been passed through a large number of different mesh sizes and whose various weight fractions have been plotted as accumulative percentages on a graph.

Prescalping

This separates out a small part of the input material, generally undesirable oversizes.

Plain weave

In this weave, every warp wire passes alternately over and under every shute wire and vice versa.

Perforated plate

This is a plate perforated with holes of various shapes. The apertures can be oblong, slotted, round, or of another symmetrical shape.

Positive drive

This uses shaft eccentricity to define the throw.

Purity

This is the ratio of the number of OK particles in the product fraction to its total quantity. It is often used to specify the product quality.

Protective screening

This removes a small quantity of oversize (coarse contaminants) from the input material. A typical oversize fraction is less than 5%; at least 50% is smaller than half of the mesh width.

Q
R

Rated particle size

This is the particle size describing the discharged material.

Resonance

The exciting frequency that sets the spring-mass system vibrating at its natural frequency.

S

Sizing

This is the separation of particulate material into defined particle sizes.

Slide friction angle p

This is the angle at which a level surface must be inclined before the input material starts slipping under static conditions.

Scalping

This is the separation of the coarse oversize fraction from the input material. These are 50% larger in diameter or width than the largest particle in the screened material. Their quantity is normally 10–20% of the input material.

Size fraction

This is the range between two defined particle size limits in the input material.

Sample division

This is the representational division of the initial quantity until the quantity for analysis has been reached.

Screenings

This is the proportion of material that has passed through the screening medium, including contaminants and foreign particles.

Screened liquid

This is the liquid that has passed through the screen.

Selvage

This is the woven edge of the screening fabric.

Solid matter fraction

This is the content of solid matter in a suspension. This is specified in most cases as a percentage by weight or volume.

Sonic type screen

This is a screening machine that excites directly the screen lining at 50 or 60 Hz (in the audible range).

Surface moisture

This is the liquid adhering to the exposed surface of the particles in a sample. This is usually specified as the mass fraction of the sample in percent.

Segregation

This forms in a material bed when the effect of vibrations causes the finer material to migrate downwards and the coarser material upwards in the product bed.

Stratification

In this process, the shaking or vibrations cause the coarser particles to move to the surface of the product bed while the smaller particles slip through the gaps to the base of the bed.

Shute wire

These wires traverse at 90° to the screen’s longitudinal axis.

Screen analysis, particle size analysis

This returns the fractions of particle sizes in the total quantity.

Screenings

This is the quantity of input material that passes through the screen panel.

Screening fabric

This is the material that is fitted to the screening deck, synonymous with screening medium.

Screening capacity

The capacity of a screen for a particular task. Specifications without reference to the input material or separation accuracy are worthless.

Screening machine

This sizes a particulate mixture for industrial purposes. “screen” is also short for “screening surface” and “screen deck”.

Screen series

Standardised screen cascade.

Screen overs

These are that part of the input material that leaves the screen panel without first passing through the screen apertures.

Screen efficiency, screen quality

This is the ratio of screened fine material to the total fine material in the input quantity: n = mff/mf0.

Screen curvature

This is the increase to a convex screen panel.

Slotted screen

This screen panel consists of equally spaced wires of wedge shaped or trapezoidal cross section. The fine material then passes through apertures of increasing cross section.

Suspension, slurry

This is a mixture of liquid and solid matter.

Suspension density

This is the weight per unit volume of the suspension flow, a combination of its solid and liquid density, calculated as a function of the ratio of the solid to liquid weight fraction in the suspension.

Separation size

The particle size above and below which the over- and undersizes are equal. This is the target of separation.

Scalper

This is a heavy screening machine with fixed or moving gratings and round or specially designed discs or rollers. It is normally used for separating out relatively large chunks, e.g. larger than 100 mm.

T

Transverse tension

This is the tension in a screening fabric transverse to the direction of the conveyed material.

Test screen

This is a circular screen frame fitted with a taut screening fabric of standardised size.

Twill weave

In this weave type, every warp wire passes alternately over and under more than one shute wire and vice versa.

Throw

The distance between the two furthest positions of a screening cycle. The throw equals twice the amplitude.

Tumbler screen

This screen executes circular with superimposed tumbling movements.

Tailings

The flow of input material that runs over the screen surface.

U

Ultrasonic screen

This is excited at frequencies greater than 18 kHz.

Undersize

This is a particle that is smaller than the mesh aperture over at least one axis.

Unbalanced motor

This rotates to induce movements in a vibrating screen.

V

Vibrating screen

This is also called shaker screen or gyratory screen. It is a sizing machine.

W

Wet screening

This screening type uses a liquid that is generally supplied from shower heads.

Warp wire

The warp wires run along the length of the screening fabric.

Warp

All wires in the screen panel running parallel to the weave.

Weave

This describes the way the warp and shute wires cross each other.

Wire gauge

This is the diameter of a (screen) wire in the screen panel, measured prior to weaving.

Wire fabric, wire grating

This is a screen panel consisting of two layers of parallel wires woven or pressure welded together. The wires form equally sized square or oblong apertures that can be crimped prior to weaving.

Z

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