The majority of filter manufacturers offer woven wire filter elements in nominal ratings. This simply means that a very small number of screen openings may be larger than the specified retention rating. Further, no surface media such as the screens referred to here can be rated "absolute" for irregular-shaped solids. Surface media rated absolute would be only for spherically-shaped solids since elongated solids could pass an opening lengthwise because its girth can be smaller than the absolute retention rating of the media.
Surface media can be rated absolute only for spherical solids, A.,
small amounts of irregular-shaped solids, B., could pass through openings lengthwise.
Woven Wire...
Woven wire media are generally available in a variety of weaves. Each has slightly varying
retention characteristics even at the same rating. For example, the opening in a square
weave is as the name implies. However, the opening in twilled weave can be more triangular
in shape. This will have some effect on retention but the effect will be, for the most
part, unmeasurable. When selecting woven wire media manufacturers experience will assist
in determining the weave that displays the best strength, solids release and flow
characteristics for each retention rating.
Woven wire generally has the best all around
performance for most applications. Wire mesh screens have a high percentage of open area
for high flows and extended runtimes. The strength of wire mesh and its resistance to
abrasion make it economical over the life of the screen. For most forms of solids to be
removed, the wire mesh screens have good release characteristics to make cleaning easy.
Coarse wire mesh screens are dimensionally stable but some fine screens which are woven
with very small diameter wire are prone to stretch and flex. Normal operation with low
pressure drop will not usually be detrimental to these fine mesh screens. Underlayment,
overlayment and wire winding are often used to protect these screens.
Finer retentions than 700 mesh is not a "standard" because they tend to be extremely fragile. However, for applications in this retention range that require metallic screens because of temperature or chemical compatibility,, special laminated screens or other types of cleanable media are available.
RPA Process Technologies
9151 Shaver Road
Portage, MI 49024
Toll Free (US only):
1-800-656-3344
Voice: +1 269 323-1313
Fax: +1 269 323-0065
www.RPAprocess.com
info@RPAprocess.com
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