Edge filters involve the use of cartridge elements where the element is composed of a stack of discs or washers of paper, felt, plastic or metal, clamped together in compression. Liquid flow takes place from the outer edge inwards between the discs, which may be in intimate contact in the case of non-rigid disc materials, […]
The majority of the specific filter media discussed so far in this Section have been porous materials, usually continuous in original format, with an intrinsic porosity consequent upon their method of original manufacture. Somewhat like the assembled bar types of media described in Section 2D, there is a very useful group of filter elements that […]
A quite different use for metal in making filtration media comes in the structures that are built up from individual bars, rods or wires that may have been processed to change their shape. The filter elements made from these media are thus assembled rather than produced in sheets or rolls. As a result they are […]
Expanded metal is made from a metal sheet by a repetitive process that involves first cutting it to form a series of short slits, and then stretching the sheet to open up these slits into the characteristic diamond apertures (Figure 2.17). This may be followed by calendering (pressing between rolls) so as to flatten the […]
Perforated metal sheets are more rigid and can be made stronger than woven wire cloths and so they find particular applications in strainers, coarse filters and screens. Perforated metal strainers have a predictable and consistent performance because the size of the screen openings is controlled in the manufacturing process. In their simplest form they can […]
The crimping of the individual wires in a mesh goes a long way towards ensuring the stability of the mesh, and therefore the constancy of the apertures of the mesh, if the mesh is subject to movement or vibration in use. Where absolute stability is required, this can be achieved by sintering the mesh, so […]
The weave of any mesh is usually one of six basic types, but there are also some minor variations. Square mesh (Figure 2.9) has each weft wire passing alternately over and under each warp wire. The opening can be square or rectangular (much less commonly) and so this weave is more correctly referred to as […]
The weaving of wire is no different, in principle, from the weaving of any other yarn: warp wires are set up along the loom and weft wires across it. The product is a roll of woven mesh, which then is processed in a variety of ways, to produce the filter medium (or for many other […]
Media made from metals have already been mentioned, in Section 2C, in the form of sheets and tubes made from metal fibres and powders, usually sintered together to retain their structure. By far the greatest amount of filter media made from metal, however, is in the form either of woven wire or perforated sheets, which […]
As already mentioned, a major feature of the inorganic materials included here is their ability to operate at high temperatures. The importance of this particular set of applications is continually growing. Classed under this heading are media made from metal powder and fibres, ceramic powder and mineral wools, glass powder and carbon fibres (used for […]
