Weaving of wires

There are several available weaves of woven wire. Some of these weaves lead the product to be called woven fabric. The basic types of weaves of wire cloth, which are woven for filtration purposes, are plain, twilled, plain Dutch, twilled Dutch, plain reverse Dutch, duplex (twin warp) plain Dutch, Betamesh and braided (basket of multibraid)—see Figure 8.1. 

FIGURE 9.9 (See color insert following page 212.) Weaving of wires (Courtesy of Barbara Berk Design). 

Wire - The diameter of wire used in weaving cloth measured by gauge or decimal inch. 

In weaving of textiles, a comb-like arrangement of flattened steel wires fixed in a frame. The reed keeps the warp threads in position, acts as a guide for the shuttle and beats up the weft to the cloth it also determines the number of warp threads per inch of width of the cloth. 

Perforated sheets and screens are used for coarse separation, as supports for filter cloths or as filter aids. Metallic cloths are characterized by the method of wire weaves as well as by the size and form of holes and by the wire thickness. Metallic cloths may be manufactured with more than 50,(XX) holes/cm and with hole sizes less than 20... 

Numerous variants of these basic weaves exist, with many being specific to particular suppliers of wire cloths - Purchas and Sutherland (2002) summarise... 

Dutch weave section than diameter of wires laid in the other direction ... 

There are a number of different filter materials. Wire screens are the most common. Several t5 es of wire screens are available, such as the square mesh with plain weave and the square mesh with Dutch twill. There are also depth filtration media, such as sintered metal powder and random metal fibers. Advantages and disadvantages of different filter materials are shown in Table 1. 

The woven wire-type, sintered media can be made either with a single layer or several layers of woven wire sintered with the powder. By controlling the particle size of the powder or the wire gauge and weave of the woven metal, the porosity of the sintered product can be made with precision from 400 to under 1 pm. 

This new correlation works very well at explaining bubble point performance of other LAD meshes as well. For example, similar results are seen by comparing the performance of the 200 X 1400 and the 250 x 1370. These two weaves have nearly the same number of wires per inch in both directions, yet the 250 x 1370 outperforms the 200 x 1400 with a lower Dp. The big difference between the two meshes is in comparing /"d values. The 250 x 1370 has a higher ratio of 0.68 while the 200 x 1400 has a lower ratio of 0.57 Therefore, the 250 x 1370 has a larger value of X. This matches with the trend that larger values of X correspond to lower values of Dp. 

Filter packages are usually a stack of screens, going from coarse to fine in the streamline direction, on top of a support plate with holes for further distribution of the flow. Screens are plain-weave, or sometimes twill-weave, steel wire fabrics. Their fineness is indicated in mesh (threads per inch), openings per cm, or pore size in microns. For example, 325 mesh = 16 800 opening s cm 40 pm. 500 mesh (25 pm) filtration is common in melt spinning. For even finer filtration, steel nonwoven materials are used, with a filter fineness going down to 5 pm. 

Highly conductive flexible textiles can be prepared by weaving thin wires of various metals such as brass and aluminum. These textiles have been developed for higher degrees of conductivity. 

Mineral textiles contribute higher performance properties to textiles from which they are composed. Basalt and asbestos fibers, for example, have resiliencies suited for textile-type sheetings, flame-resistant blankets, and stage curtains. Silica-based (glass) fibers offer strong reinforcement properties, making them suitable for flame-retardant and protective textiles, such as in spacesuit fabric constructions. Furthermore, metal fiber reinforcements are useful as a weave of steel wire for concrete reinforcement in construction. 

If the fibres or filaments are first spun into a continuous yam, then the resultant yam can be woven or knitted into a fabric, and such interlaced materials are the woven fabrics covered here. If the material used in the weaving process is a single filament of wire or plastic, then the resultant material may be counted as a fabric, but is more often called a mesh, and is also covered separately later. 

The key dimensions of wire mesh are illustrated in Figure 2.8, for plain weave and square mesh (the usual form for plain woven wire meshes). Aperture width, w, is the distance across the aperture, between the bounding wires, measured in the projected plane at the mid positions. The wire diameter, d, is the diameter of the wire forming the mesh. The pitch, p, is the distance between the middle points of two adjacent wires and therefore is the sum of the aperture width and the wire diameter ... 

A summary of the main types of weave for wire cloth is given in Table 2.9, while Table 2.10 compares the performance characteristics of wire mesh media with other forms of metalhc filter media. 

Impingement demister systems are designed to intercept liquid particles before the gas outlet. They are usually constructed from wire mesh or metal plates and liquid droplets impinge on the internal surfaces of the mist mats or plate labyrinth as the gas weaves through the system. The intercepted droplets coalesce and move downward under gravity into the liquid phase. The plate type devices or vane packs are used where the inlet stream is dirty as they are much less vulnerable to clogging than the mist mat. 

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