Plain filter media

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 liquid is passed under centrifugal force through a filter medium or perforated plate. Filtration occurs as the liquid passes through the interstices of the solid particles that have built up on the medium surface. Depending upon the degree of separation desired, fdter media can be a filter fabric of twilled weave, dutch weave or plain weave in either stainless steel or synthetic fibre. 

Ceramic powders can be sintered into a wide variety of porous shapes for use as filter elements. In the form of porous pottery, ceramics were one of the earliest materials used for filtration. Porous ceramic filters for use as cartridges are generally in the form of a plain cylinder with a thick wall, the thickness of which provides the depth of filter medium for retention of the solids in a filtration process. As far as tubular elements are concerned, these are either plain cylinders (i.e. open at both ends) or flanged candles (i.e. candles with a flange on the open end for fixing in the cartridge housing or to the tube plate of a candle filter). 

Fabrics of Woven Fibers For cake filtratiou these fabrics are the most common type of medium. A wide variety of materials are available some popular examples are listed in Table 18-10, with ratings for chemical and temperature resistance. In addition to the mate-ri of the fibers, a number of construction characteristics describe the filter cloth (1) weave, (2) style number, (3) weight, (4) count, (5) ply, and (6) yarn number. Of the many types of weaves available, only four are extensively used as filter media plain (square) weave, twill, chain weave, and satin. 

Flow through the clean medium will be determined by the geometric characteristics imposed on the medium by the weaver, in fitrming various patterns (plain, twill, sateen, etc.) fi om basic yams. In woven cloth, the latter are either sohd monofilaments, or are multifilamanets (which can be further subdivided into continuous or staple-fibre constmetions, depending on the type of filament used). In some cases, the sur ce of the medium may be modified to improve its ability to release the filter cake, etc. Nonwovens are paper-like, random arrays of fibres which can be obtained in many forms uniform fibres, mixed and conposhe pads, etc. These media, like wovens, can be supplied sur ce modified. 

---