Percentage open area

The tolerances with micromesh sieves are much better than those for woven-wire sieves the apertures being guaranteed to 2 pm of nominal size apertures except for the smaller aperture sieves. Each type of sieve has advantages and disadvantages [38] e.g. sieves having a large percentage open area are structurally weaker but measurement time is reduced. 

Whitby assumed a to be a function of several variables total load on sieve (W), Particle density (pj, mesh opening (5), percentage open area (Aq), sieve area (A), particle size (d) and bed depth on sieve (7). This function reduces to ... 

Wet print thickness=(Emulsion buildup + Screen thickness) X Percentage open area. 

Open Area The open area of a screen is the percentage of acdual openings versus total screen area and can be determined by the formulas given in Fig. 19-22. 

Square-mesh cloth is the conventional type of screen cloth, but there are many types of cloth with an oblong weave. This latter construction provides greater open area and capacity and in addition makes it possible to use stronger wire for the same size of screen opening and for the same percentage of open area. 

It is also common practice to classify filter media by their materials of construction. Examples are cotton, wool, linen, glass fiber, porosmooth surface caused by carrying the warp (or the weft) on the fabric surface over many weft (or warp) yarns. Intersections between warp and weft are kept to a minimum, just sufficient to hold the fabric firmly together and still provide a smooth fabric surface. The percentage of open area in a textile filter indicates the proportion of total fabric area that is open, and can be determined by the following relationship ... 

Fabric 500 0.0016 40 Percentage of open area not applicable to fabric media. 

Market grade (wire cloth) Screens that meet general industrial specifications and have a low percentage of open area. 

Open area—the average percentage of the cross-sectional area of the tower not blocked by the packing, and hence available for the flow of vapor and liquid. 

The open area is that percentage of the total surface that is open when viewed from inside the screen in general, the higher the mesh number the lower the open area. 

Screens can be woven of synthetic material snch as nylon and polyester. These alternatives offer performance advantages in certain screening applications. Another alternative is perforated steel plate. Weld profile and hnish shonld also be consistent with the materials being screened. These plates are also effective and are qnite dnrable. However, they have a low percentage of open area and therefore have lower capacity for a given screen area. 

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