Plain Dutch weave

Figure 8.1 Different types of weaves, (a) Plain square weave, (b) Plain twilled weave, (c) Plain Dutch weave, (d) Twilled Dutch weave, (e) Reverse Dutch weave, (f) Duplex (twin warp) plain Dutch weave, (g) Betamesh Dutch weave, (h) Basket (braided or multibraid) weave...

The Twilled Square weave is the second most complex style the warp and shute wires are also the same diameter, but each shute wires passes over two warp wires before going under the next two warp wires. The pattern then repeats. The Plain Dutch weave has the same pattern as the Plain Square, but the warp wires are larger in diameter than the shute wires, which creates smaller pore sizes. The Reverse Dutch weave is the inverse of the Plain Dutch the shute wires are larger than the warp wires. Lastly, the most complex screen... 

Table 3.5 Effective Wicking Diameters for Several Dutch Twill and Plain Dutch Weaves...

For filtration purposes, the most widely used forms of woven wire are the Dutch or hollander weaves, wherein the warp and weft are of different diameter, generally with a corresponding difference in the relative numbers of warp and weft wires. If the warp wires are thicker, the result is the plain Dutch weave the alternative is for the weft wires to be the thicker, giving the reverse plain Dutch weave . 

Reverse plain Dutch weave is similar except that the thicker wire is in the weft (Figure 2.12). Reverse plain Dutch weave is substantially stronger, and is in fact the strongest filter weave in commercial production as a result, coupled with its good flow characteristics and high dirt-holding capacity, it is widely used industrially. 

PRD Plain Reverse Dutch weave. See weave patterns. 

DUTCH TWILL PLAIN OK SQUARE DUTCH WEAVE... 

Grootenhuis (Proc. Inst. Mech. Eng. [London], A168, 837—846 [1954]) presents data which indicate that for a series of screens, the total pressure drop equals the number of screens times the pressure drop for one screen, and is not affected by the spacing between screens or their orientation with respect to one another, and presents a correlation for frictional losses across plain square-mesh screens and sintered gauzes. Armour and Cannon (AIChE J., 14,415-420 [1968]) give a correlation based on a packed bed model for plain, twill, and dutch weaves. For losses through monofilament fabrics see Pedersen (Filtr. Sep., 11, 586-589 [1975]). For screens Inclined at an angle 0, use the normal velocity component V ... 

Septa may be made of metal, natural, or synthetic yams. Plain, twill, and dutch weaves are available in the metal cloths. In the natural and synthetic fiber cloths, plain, twill, chain, and satin weaves in monofilament, multifilament, and staple yams have been used. 

There are many types of weaving patterns for woven fabrics and the four basic types are plain weave, twill weave, satin weave, and plain reverse Dutch weave (Svarovsky 1990) as shown in Figure 22.66. The filtration performances of the four types of weaves are shown in Table 22.13. 

Note PRD, plain reverse Dutch weave. Source From Purchas (1967). 

A relatively new type of closed twill weave is available for colloidal separations. Whilst such fabrics have lower clean permeabilrties than plain or Dutch weaves, they are more easily cleaned and withstand heavy use. 

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. 

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 2.17 Three Dimensional Models of (a) Twilled Square, (b) Plain Dutch, and (c) Dutch Twill Weave Styles. Warp wires veer southeast (shown in red dark gray in print versions) and shute wires veer northeast (shown in gray light gray in print versions), bopp.com. 

Table 3.2 lists values for warp and shute wire diameters, along with calculated values for the screen thickness, surface area to volume ratio, eind void fraction, for edl available screens in the literature. Values of d and ds are obtained from the literature (Armour and Cannon, 1968 Paynter, 1970 Heckman, 1971 Burge and Blackmon, 1973b Cady, 1973) or from industry, where available. Tortuosity values are 1.0 for Plain Square and Twilled Square weaves and 1.3 for Reverse Twill, Plain Dutch, and Twilled Dutch weaves. 

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. 

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. 

Obvious uniformity is found in simple form with plain-weave metal cloth of light gauge wire. As the gauge of the wire becomes heavier and the weave is changed to a twilled or Dutch-type weave, we have a more elaborate medium that is generally used for filtration. The nature of the holes is more complex and more difficult to recognize with the unaided eye. Woven fabrics become more complicated due to the flexible nature of yams, and therefore it is more difficult to try to define the size of the hole in a woven fabric. The same is tme for media with random stmcture, such as felts, paper, fibrous and porous material. 

Filter fabrics are mainly woven in four common weaves plain, twill, plain reverse Dutch and satin. The first three are overlaps from wire cloth weaves but may have slightly different characteristics when put into the framework of woven non-metallic cloth. The weaves will not be detailed again here. The fourth weave is the satin weave where the shute (or warp) fibre passes over several warp (or shute) fibres, then under one in an alternating pattern. Figure 8.3 shows an over three-under one pattern for the satin weave (three shaft satin) see also Table 8.2. 

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