Filter media nonwoven materials

Filter-medium selection embraces many types of construction fabrics of woven fibers, felts, and nonwoven fibers, porous or sintered solids, polymer membranes, or particulate solids in the form of a permeable bed. Media of all types are available in a wide choice of materials. 

Textiles, as a woven cloth or a nonwoven fabric, are probably the most common industrial filter medium, and are made from natural (cotton, silk, wool) and synthetic fibres. Wire cloths and meshes are also widely used in industrial filtrafions, produced by weaving monofilaments of ferrous or non-ferrous metals the simpler plain weave is used for sieving and sizing operations, and the more complex weaves such as Dutch twills are used on pressure and vacuum filters. At the small scale, particularly for laboratory use, filter papers are common, made from fibrous cellulosic materials, glass fibre or synthetic polymers these papers are made using developments from conventional paper manufacturing processes. 

The properties of a filter medium can be changed by layering a second medium onto the surface of the first to make a composite medium. Examples of these media include surface coated fabrics, laminated media (where two or more woven or nonwoven materials are fixed together, either firmly or loosely) and multilayer weaves. 

Abrasive particles contained in a hydraulic oil system, if unfiltered, enter the system, they would damage sensitive components like pumps, valves, and motors. The nonwoven hydraulic filter is designed to remove these parficles from the oU flow to prevent hydraulic system failure from any premature component wear. Nonwoven filters either contain novel materials, such as magnetic polymer fibres, or have special designed structures (eg, multilayer composite filter medium for serial filtration ) that are employed to filter the solid abrasive particulates, soft particles, corrosive chemical particles, and some microorganisms. 

The main filter, also a synthetic nonwoven material, bnt now usually with electrostatically charged fibres, is capable of particle ranoval down to 0.05 pm. The use of electrostatically charged fibres enables the fibres to be coarser than would otherwise be the case to catch these fine particles - the finer fibres would then need a higher pressure differential across the medium. The Health and Safety Execntive in the UK requires construction truck cabins, at risk from respirable crystalline silica (RCS), to have a main filter of class HI 1 for dust concentrations of less then 1 mg/m, or H12 or H13 for higher RCS concentrations. 

If odour control is also required, then this may be achieved by adding a separate activated carbon filter, or by adding a layer of this material (or of nonwoven fibres in which carbon particles are embedded) to the standard three-layer particulate filtration medium. 

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