ISO 9045:1990(en) Industrial screens and screening — Vocabulary

ISO 9045:1990(en) Industrial screens and screening — Vocabulary

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.

International Standard ISO 9045 was prepared by Technical Committee ISO/TC 24, Sieves, sieving and other sizing methods.

Introduction

ISO/TC 24 has prepared several International Standards covering test sieves, test sieving and industrial screens. Since these subjects are connected and the standards overlap, a vocabulary is needed to define terms which are used in the different contexts. Such a vocabulary could be unwieldy, however, since numerous terms are used in industrial screening practice, many of them for a particular material, type of screen or screening process. Accordingly, this International Standard has been compiled to cover the association of test sieves and test sieving with industrial screening, and to include only a selection of other terms which suffice to introduce industrial screening and screens.

Terms connected particularly with the test sieving process which is used in laboratory particle size analysis are defined in ISO 2395:1972, Test sieves and test sieving — Vocabulary.

1   Scope

This International Standard gives a vocabulary of selected terms which are frequently encountered in industrial screening.

It refers to screening processes in which screens with screening surfaces in accordance with IS04783-1, IS04783-2, IS04783-3 and ISO 9044 are used.

The terms defined are grouped into the following four sections:

a) material to be screened;

b) industrial screens;

c) the screening process;

d) products of screening.

2   Normative references

The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.

ISO 4783-1:1989, Industrial wire screens and woven wire cloth — Guide to the choice of aperture size and wire diameter combinations — Part 1 : Generalities.

ISO 4783-2:1989, Industrial wire screens and woven wire cloth — Guide to the choice of aperture size and wire diameter combinations — Part 2: Preferred combinations for woven wiredoth.

ISO 4783-3:1981, Industrial wire screens and woven wire doth — Guide to the choice of aperture size and wire diameter combinations — Part 3: Preferred combinations for pre-crimpedand pressure-welded wire screens.

ISO 9044:1990, Industrial woven wire doth — Technicalrequirements and testing.

3   Terms and definitions

3.1   Material to be screened

3.1.1

particle (deprecated: grain)

Discrete element of the material to be screened regardless of its size.

3.1.2

particle size

sieve size of a particle

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

3.1.3

agglomerate

Several particles adhering together.

3.1.4

fines

Particles smaller than a specified size.

3.1.5

inherent moisture

contained moisture

Liquid, usually water, held within a sample of a material, normally expressed as a percentage of the sample mass.

3.1.6

surface moisture

Liquid adhering to the exposed surfaces of the particles of a sample of material, normally expressed as a percentage of the sample mass.

3.1.7

bone dry

Material having no surface moisture.

3.1.8

bulk density

The mass in air per unit volume of bulk particulate material, including the voids within and between particles.

3.1.9

relative density (deprecated: specific gravity)

Ratio of the mass in air of a solid particle of a given volume to the mass of an equal volume of water.

3.1.10

per cent solids

Ratio of dry solids to the total solidliquid mixture of material, expressed as a percentage by mass.

3.1.11

angle of repose

Angle to the horizontal which a material will assume naturally when in a stationary pile.

3.1.12

feed

Material supplied to a screen for a screening process.

3.2   Industrial screens

3.2.1

screen

Device for carrying out the process of screening for industrial purposes.

Note 1 to entry: The term "screen" is also a commonly used abbreviation for "screening surface" or "screen deck" (see 3.2.2).

3.2.2

screening surface

screen deck

A sheet with regular openings of the same size in a regular arrangement for screening purposes (see 3.3.1).

3.2.3

woven wire cloth

wire screen

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.

Note 1 to entry: In English, flexible screening surfaces which can be rolled up are usually designated as "woven wire cloth". More rigid surfaces, predominantly made from precrimped wires and/or produced by pressure-welding, are designated as "wire screen".

3.2.4

perforated plate

Screening surface consisting of a plate with uniform holes in a regular arrangement. The holes may be square, slotted, circular or of another regular geometric shape.

3.2.5   percentage open area

(1) 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.

(2) For perforated plate, the ratio of the total area of the holes to the total area of the perforated part of the plate (excluding any non-perforated parts).

3.2.6

round hole equivalent

The dimensions of the square apertures in a perforated plate or in a woven wire cloth which will screen similarly to a perforated plate with specified round holes.

3.2.7

equivalent round hole

Diameter of the round holes in a perforated plate which will screen similarly to a perforated plate or a woven wire cloth with specified square apertures.

3.2.8

mesh count

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

3.2.9

wire diameter

Diameter of the wire for a woven wire cloth, as measured before weaving.

3.2.10

aperture size

Dimension defining an opening in a screening surface.

3.2.11

square mesh

Woven wire cloth with nominally square apertures.

3.2.12

slotted mesh

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

3.2.13

warp

All wires running lengthwise of the cloth as woven.

3.2.14

weft

shoot

All wires running crosswise of the cloth as woven.

3.2.15

type of weave

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

3.2.16

crimp

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

3.2.17

plain weave

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

3.2.18

twilled weave

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

3.2.19

punch side

Surface of a perforated plate which the punch entered.

3.2.20

plate thickness

Thickness of the plate before perforation.

3.2.21

pitch

Distance between corresponding points of two adjacent apertures in a woven wire cloth, a wire screen or a perforated plate.

3.2.22

bridge width

bar

Distance between the nearest edges of two adjacent holes in a perforated plate.

3.2.23

margin

Distance between the outside edges of the outside rows of holes and the edges of a perforated plate.

3.2.24

sifter

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. less than 1 mm.

3.2.25

grizzly

Rugged screen comprising fixed or moving bars, discs, or shaped tumblers or rollers, normally used for screening comparatively large particles, e.g. greater than 100 mm.

3.2.26

bar screen

Stationary inclined screen, comprising longitudinal bars, spaced at regular intervals, on to which the material to be screened is fed at the upper end.

3.2.27

rod screen

Screening surface consisting of parallel wire rods positioned at right angles to the flow of material on the screen.

3.2.28

wedge wire screen

profile wire deck

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

3.2.29

roll screen

Screen consisting of a number of horizontal rotating shafts, fitted with elements arranged to provide screening apertures.

3.2.30

revolving screen

trommel

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.

3.2.31

fixed screen

static screen

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.

3.2.32

guard screen

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

3.2.33

backing screen

Coarse screen placed under a finer screening surface for support.

3.2.34

undersize control screen

breakage screen

Screen used for the removal of undesirable undersize from a material.

3.2.35

relieving deck

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.

3.2.36

sieve bend

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 first-stage dewatering device.

3.2.37

reciprocating screen

jigging screen

Screen or pair of screens to which a combined horizontal and vertical motion is imparted by a crank-shaft and connecting rods, the screening surfaces being horizontal or inclined at a small angle.

3.2.38

vibrating screen

Screen oscillated either by mechanical or by electrical means.

3.2.39

resonance screen

Screen with a period of oscillation close to the natural period of oscillation of the resilient mounting.

3.2.40

inclined screen

Vibrating screen with a rectilinear or circular oscillating motion, normally installed at an angle between 10° and 36°.

3.2.41

horizontal screen

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°.

3.2.42

high speed screen

Inclined screen, with a rectilinear or circular oscillating motion, normally operated at a frequency greater than 20 Hz.

3.2.43

amplitude

Maximum displacement from the mean position in an oscillating motion. In the case of rectilinear motion it is half of the total movement; for elliptical motion it is half of the major axis of the ellipse.

3.2.44

stroke

throw

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

3.2.45

eccentricity

Maximum displacement from the mean position in a circular oscillating motion, e.g. the radius of the circle.

3.2.46

frequency

For vibrating screens, the number of oscillations made by the screen per unit of time, expressed in hertz (Hz).

3.2.47

edge preparation

The fabrication on the edges of a screen section for holding or tensioning purposes.

3.2.48

screen panel

Finished piece of screening medium complete with edge preparation.

3.2.49

hook

Metal edge used to stretch and/or to fasten the screen section.

3.2.50

end tensioning

Tensioning of the screen section parallel to the flow of the material on the screening surface.

3.2.51

side tensioning

Tensioning of the screen section at right angles to the flow of the material on the screening surface.

3.3   The screening process

3.3.1

screening

Industrial process of separation of solid particulate material according to particle size by causing part to remain on a screening surface provided with apertures through which the remainder passes.

3.3.2

sizing

Screening of particulate material into fractions, each defined by limits of size.

3.3.3

wet screening

Screening with the aid of a liquid, usually in the form of a spray.

3.3.4

dry screening

Screening without the aid of a liquid.

3.3.5

scalping

Removal of a small amount of the feed, usually unwanted oversize material.

3.3.6

dewatering

Removal of free water from solid material.

3.3.7

rinsing

Removal by spraying, usually with water, of fine or foreign material present among or adhering to larger particles.

3.3.8

de-sliming

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

3.3.9

de-dusting

polishing

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

3.3.10

overflow

That portion of the feed discharged from the screening surface without having passed through the apertures.

3.3.11

underflow

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

3.3.12

stratification

Process whereby the larger size particles rise to the top of a bed of material being shaken or vibrated, while the smaller size particles sift through the voids and find their way to the bottom of the bed.

3.3.13

pegging

The condition where particles wedge in the screen apertures.

3.3.14

blinding

clogging

The condition where very fine particles adhere to a screening surface and reduce the apertures or close them completely.

3.4   Products of screening

3.4.1

product

In general, the material resulting from any operation. In particular, the final material produced from a series of operations; e.g. screened product, finished product, etc.

3.4.2

size fraction

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

3.4.3

nominal size

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

3.4.4

mean size

The weighted average particle size of a sample, batch or consignment of particulate material.

3.4.5

near-sized material

near-mesh material

Particles approximating in size to the aperture size of the screening surface.

3.4.6

undersize

Screened product of a size smaller than a specified size.

3.4.7

oversize

Screened product of a size greater than a specified size.