Mesh Count

The Mesh grade of the mesh/mesh refers to the number of wires per inch and this also influences mesh size (w) and wire strength (d)

Mesh = 25.4mm

w (mm) + d (mm)

Open Area

The open area of a screen (Ao) defines the mesh openings as a percentage of the entire screen surface and is based on the ratio between mesh size (w) and wire diameter (d).

Ao = ( w (mm) )2 x 100%
w (mm) + d (mm)

Mesh Count Open Area
Term Description
Absolute Filter Rating Filter rating at 99% efficiency
Nominal Filter Rating Filter rating at 70-90% efficiency
Aperture  Distance between wire threads, measured in microns or millimeters
 Pitch  Distance from centre to centre of wire threads
 SWG  Standard Wire Gauge (Imperial Measurement)
Imperial Mesh Number of apertures counted in a row, see mesh count above
Weft Wire threads running down the width of the roll
Warp Wire threads running down the length of the roll
Micron 1/1000 of a millimetre
Open Area Percentage of free area in mesh or metal, see illiustration above
Blinding Blockage or restriction of the apertures of a sieve or filter by particles
Differential pressure Pressure ratio upstream and downstream from the filter
Dry screening Screening powdered materials without liquid
Mesh analysis Separation of a bulk material sample and analysis of particle size
Mesh counter Optical device used to establish mesh count
Mesh fineness Number of wires per inch (Imperial measure)
Mesh thickness Calculated according to wire diameter and mesh type
Service life Operational life of a screen/mesh until it requires replacement
Square weave mesh Mesh woven with wires spaced at a distance, giving open apertures
Twilled weave Mesh type giving small filter pores