The selection of Filter Cloth is highly important in order to achieve good quality and high filtered cake dryness for Filter Press. Ladon has been supplying durable and high quality of Filter Cloth to Water Supplies Department, Drainage Services Department and private sector filter press end-users for decades. We can provide practical advice for suitable filter cloth material in handling different applications. Available material, but not limited to, including Polypropylene, Nylon, Rilsan etc.
Multifilament or continuous filament yarns are produced by the continuous extrusion of synthetic resins. The filaments are generally produced with a smooth surface. Multiples of these filaments are twisted together to form the yarn used in filter cloth. The filaments may be twisted in an S or Z twist (clockwise or counter clockwise) and the number of turns used per a given length determines other characteristics of the yarn i.e. the greater number of turns will reduce blinding (particle retention within the yarn structure) but decrease retention (collection efficiency). The resulting yarns may also be plied into groups either with the same type and weight (quite common) or in certain specialty applications with other yarn types. Multifilament yarns have high tensile strength and moderate collection efficiency. Filter cake release is moderately good.
Spun (staple) Yarn : Spun yarns are produced using a cotton or woolen manufacturing system which essentially combs short fibers into one direction and then twists them together. Continuously extruded synthetic filaments are chopped into short lengths so that they may be processed into yarn. These staple fibers are then twisted to create the strength to hold the yarn together for weaving. Today, filtration almost exclusively uses synthetic fiber (cotton and wool having very limited specialized applications). When using a “woolen system” a more lofted yarn is produced. The cotton system crates a tighter product. Spun yarns have low tensile strength, a greater surface area and have high collection efficiency. Filter cake release is poor without special finishes.
Monofilament yarns are single heavier extrusions not unlike fine fishing line. Usually filter cloth is manufactured with yarns of 6 mil. (0.15mm) or greater diameters. The extrusions are smooth have high tensile strength and in some cases are modified with fillers. This type of yarn has the best cake release properties and best resistance to blinding. Their general disadvantage was that fabrics produced with 100% monofilaments tended to serve the coarser filtration requirements. In recent years new weaving technology has allowed the manufacture of superfine fabrics, which has opened many application opportunities, including their use in fine process applications. Combination monofilament/multifilament fabrics are also very common today, offering the monofilament at the media surface and using the “back” multifilament filling yarns to enhance retention.
General – Filter cloth yarns have specific characteristics which are used when designing our medias. It should also be understood that designs combine yarns and a variety of weaves which will in turn change the overall result that may be achieved.
NEEDLED felts are constructed by punching a fibre batt into itself to hook and entangle fibers which then form a thin, relatively dense structure, either with or without using a light woven support scrim.
FILTRATION – Generally finished by singeing or calendered to remove the “fuzzy” surface. They offer good depth filtration and particle capture particularly in “polishing” applications. Felts are poorly resistant to blinding and they tend to lose their surface finish during operational life.
FILTER CLOTH WEAVING
Yarn is pulled from tension controlled creels and precisely wrapped onto warps in preparation for the loom. When positioned behind the loom the warp yarns (which run in the length of the cloth) are inserted through heddles. The heddles are raised and lowered to create a shed (opening) through which the fill yarn is inserted to create the weave pattern.
High speed, sophisticated, computer controlled looms raise and lower the heddles and “take up” the woven fabric, to create the geometric patterns of our filter cloth design. The precise positioning and tensioning of yarns creates the exact thread count (threads per inch or cm.) every time the pattern is manufactured. .
FILTER CLOTH WEAVE PATTERNS
The plain weave is one of the most simple weave patterns. In this type of weave, the warp and filling threads cross alternately. Plain-woven fabrics are generally the least pliable, but they are also the most stable. It has a high particle retention, low resistance to blinding and moderate cake release properties
The twill weave is a basic weave characterized by a diagonal rib, or twill line. Each end floats over at least two or more consecutive picks enabling a greater number of yarns per unit area than a plain weave, while not losing a great deal of fabric stability. It has moderate resistance to blinding and moderate cake release characteristics
The basket weave is a variation of the plain weave in which two or more warp yarns cross alternately with two or more filling yarns, resembling a plaited basket. This weave is more pliable and stronger than a plain weave, but is looser and not as stable. The basket weave is typically used for backing cloths and some basic filtration applications.
The leno weave is a locking type weave in which two or more warp threads cross over each other and interlace with one or more filling threads. It is used primarily to prevent shifting of fibers in open weave fabrics and only for backing cloths.
In a satin weave, the face of the fabric consists almost completely of warp or filling floats produced in the repeat of the weave, which causes one side of the fabric to look different than the other side. There is one filling thread, which floats over three or more warp threads, then under one. This is the most flexible of weave patterns and conforms very easily around most contoured surfaces. Most satin weaves are four, five, eight, or twelve harness satins and are typically used where good cake release is required.
Constructions – Innovations
- SK, HPR, Clip, single cloth, double cloth, fit issues. Reduce core related differential pressure plate failure.
- Velcro, grommet, “dog” reinforced holes, hem, rod
- Banding, latex, backing cloth
Innovations – HPR & SK feed neck
The unique high performance feed necks; (HPR molded rubber) and (SK plastic molded) are being used on a rapidly increasing number of applications throughout the world.
The unique construction is saving maintenance time and increasing the efficiency of filter press operation by; eliminating filtration at the feed core, improving core blow down efficiency and improving wear resistance.
A flat cloth is produced, without creases or twisting that is sometimes introduced when manufacturing stitched cloth necks. This flat construction guarantees the integrity of the filtration media at the feed area and consequently its resistance to folds, pinholes or poor cake release, which in turn improves the cloth life significantly. Encapsulation of the filter cloth is used to join the SK neck, and is used for lighter fabrics, polyesters and nylons where better joint designs are required.
No Product Loss – Insurance!
The welded feed necks cannot leak or bypass product through stitch holes, insuring there will be no sudden failures and yield losses when filtering expensive products. Improved Slurry Delivery
The uniform, open feed core delivery with an unrestricted and consistent slurry flow to the filter chamber reduces the potential for differential pressure, which can cause thick and thin cakes and even plate damage. This consistently formed filter cake is much more efficiently washed.
No Feed Core Clean Up Required
Any feed core plug is easily discharged with the filter cake, eliminating manual operator clean up time. This is the case both with and without core blowing capability as the softer core releases from the impervious feed necks with the cake.
Greater Abrasion Resistance
The feed necks are fully resistant to high velocity and abrasive slurries and all chemical conditions. This product is so effective that we will guarantee improved performance of your filter press. .