Glossary of  Filtration and Textile Terminology

A short glossary of the most common filtration and textile terminology.

Air Permeability – Measurement of the volume of air which would pass through a unit area of filter media at a given pressure differential.
The DIN standard is given as L/dm2.min @ 20Pa measures volume of air (litres) which would pass through square decimetre of material each minute with pressure differential of 20 Pa

Blinding – Blocking of filter media by particles becoming entrapped within the weave. The resulting drop in porosity would be seen as a reduction in the gas flow rate to a level where the capacity of the filtration equipment is unacceptable. Blinding would be reflected in the drop in air permeability

Cake Side – Opposite sides of a cloth, particularly calendered materials often have different appearances, the side to be presented to the cake would normally be the smoother of the two sides

Calendering – Process in which fabric is passed between heated rollers at high pressure to close the weave and smooth the surface

Extension – Percentage by which fabric strip has been extended when it breaks in strength testing (see tensile strength). Extension at break is not necessarily a good indication of low load extensions.

Filter Cake – The solids discharged from filter equipment

Filtrate – Name given to the filtered liquid discharged from filter equipment

Heat Setting – The process of shrinking and heat stabilisation of a fabric to eliminate shrinkage in operation

Mesh Opening – Physical measurement of the size of the pore in open mesh fabric

Monofilament – Single, continuous extruded yarn

Multifilament – A number of fine fibres in continuous lengths twisted together to create a single yarn

Open mesh – A fabric with defined mesh opening, usually woven in a plain weave using monofilament yarn

Open area – The percentage of open mesh fabric which is free space. Mesh woven using finer monofilament yarn would have higher open area than those woven with thicker diameter yarns. Higher open area results in a higher capacity but with a lower strength

Tensile Strength – Measurement of force required to break a strip of material, normally quoted as either Newtons or Kilograms per 5 cm strip.

Thread Count – Number of warp and weft yarns per centimetre

Warp – Term given to the threads running along the length direction of fabric

Weft – Term given to the threads running along the width direction of fabric