wedge wire and wedge wire screen manufacturer

Wedge wire screen is ZHEHAN's most advantageous product, as early as 2013, we became the largest wedge wire screen manufacturer in China.

In 2015, we developed advanced metal cleaning technology, which increased the corrosion resistance of stainless steel filter element products by 40%.

This blog mainly introduces the related knowledge of wedge wire.

Johnson screens related products page please check: Wedge Wire Screen

                                                                                        Johnson Screen

What is wedge wire?

Wedge wire is the raw material for producing a wedge wire screen(Johnson screen) and wedge wire filter element.

I just drew a picture of wedge wire, which I believe is a more intuitive explanation of what wedge wire is.

Brief Introduction of Characteristics and Properties of Various Filter Material Used for Manufacturing Filter Core

Metal filter wire mesh 

The filter mesh is also a braided filter medium. Its material is mainly metal. All metals and alloys that can be drawn, such as stainless steel, brass, Monel nickel-copper alloy, nickel, silver and so on, can be used as the material of metal wire mesh.

Recently, there are also filters made of plastic precursor silk. Because the material is metal material, the surface of the filter is smooth, wear-resistant, corrosion-resistant and high temperature-resistant, basically does not produce shrinkage and extension phenomenon, is not easy to be blocked by particles, easy to clean and regenerate, and its service life is much longer than that of the fiber filter cloth. An only one-time investment is more expensive, but operation cost is lower than the filter cloth.

Today's protagonist is wedge wire, So let's talk about the advantages of wedge wire.

1. Firm structure

2. Corrosion resistance

3. Not easy to block

4. Easy to clean

5. High opening rate

Compared with other kinds of the stainless steel filter element, wedge wire filter(Johnson screen) has obvious advantages. Wedge wire filter is your best choice when you use it in harsh environments.
 
There are also plain weave and twill weave. 

The filter can be installed directly on the leaf filter or drum filter for filtering purposes (generally only for rough filtering), and can also be used as a support for cloth and filter paper. At this time, the filter must be rolled to make it's surface smooth, and then installed with filter media such as filter cloth, in order to avoid damaging the supporting filter media. At present, our country's industrial wire woven screen is made of copper, tin, bronze, stainless steel, carbon steel and other materials. 

Filter cloth 

This is the most widely used filter medium in the industry.

The filter cloth can be divided into textile filter cloth and non-textile filter cloth.

The compositions are natural fibers (cotton, wool, silk, hemp) or synthetic fibers. The filtration performance of filter cloth depends on the material, fabric weaving, and post-processing.

(1) Textile filter cloth

Textile filter cloth is woven from three different types of yarns: single yarn (single strand yarn), multi-filament long yarn (fixed length yarn) and staple yarn (multi-strand yarn). Single filaments are usually drawn from synthetic fibers into single filaments with a diameter of 0.16-0.32 (in some cases even 1). The filter cloth woven from it has the advantages of smooth surface, simple void, small specific resistance, minimum blockage, easy cleaning, and optimum slag discharge performance, but it is not suitable for precise filtration because of its trapping particle diameter trap. When the suspension with wide particle size distribution is separated, the separation effect is affected.

Multi-filament filament yarn is twisted by more than two strands of the precursor. It is woven into filter cloth with good tensile strength, better particle retention performance than single filament, and slightly worse slag discharge performance.

Staple fibers are made of natural cotton, wool fibers or synthetic staple fibers twisted in strands. Because of their fluffy fibers, staple fibers have good particle retention performance and good sealing performance. However, the shortcomings of staple fibers are that the pore is easily blocked by particles, and the cleaning and slag unloading performance is poor. 

There are also three weaving methods of filter cloth: plain weave, twill weave, and satin weave. Generally speaking, plain cloth has compact structure and small pore, so it has good particle retention, high clarity of filtrate, long service life and low price.

The disadvantages are high specific resistance, easy blockage, and poor slag discharge performance. Satin fabric has the largest pore, small specific resistance, not easy to plug, and good slag discharge performance. However, the ability of particle interception is low, the filtration is serious and the filtration effect is poor.

Twist filter cloth has the middle performance, strong anti-friction ability, high filtration speed, and longest service life, so it is widely used. 

Following is a brief introduction to the use of conditions of filter cloth woven from different materials for reference. 

Cotton cloth:
The filter cloth woven from the ordinary cotton yarn can only be used for separating neutral, acidic and alkaline filters below 100 C.

In alkaline medium, cotton filter cloth will swell. Shrinkage occurs in water and aluminum sulfate solutions.

Therefore, the solution should be soaked before use to pre-shrink it. The resistance of cotton filter cloth to mildew is weak, and the resistance can be improved only when it is pretreated with copper ammonia solution when it is easy to produce mildew. 

Nitrocotton fabric has a hard surface, easy to discharge residue, and is stable to concentrated sulfuric acid, nitric acid, and its mixed acid, hydrochloric acid solution and zinc chloride solution, but not alkali-resistant. It is easy to be corroded in reducing substances and organic solvents. Nitrocotton filter cloth has very dangerous flammability, which limits its use to a certain extent. 

Wool weaving: 
Generally made of sheep wool, the corrosion resistance of acid filter pulp is slightly better than that of cotton cloth. The service life of cotton cloth in treating 5% - 6% concentrated inorganic acid material is close to that of cotton cloth in neutral material.

It is not resistant to high temperature and alkali, nor to sodium and calcium hypochlorite damage. The cloth made of camel hair is stable to inorganic acids. Wool fabrics are slightly inferior to cotton fabrics in strength and particle retention, and their prices are much higher than cotton fabrics. 

Polyvinyl chloride cloth: 
For acid, salt, mineral oil and microorganism, it has stabilization energy, but the strong alkali action will be destroyed by the oxidant. It has a smooth surface, which is good for slag unloading but can only be used below 60 C. 

Polypropylene cloth:
Strong acid (organic and inorganic), alkali corrosion resistance and elasticity. The highest temperature can reach 110 C, the price is low, but the strength of the cloth is weak. It can be used for fiber filter pulp and coarse crystal filter. Polypropylene cloth has a smooth surface, soft texture, good slag discharge performance, low intrigue density, and can resist acid, alkali and strong oxidant corrosion and microbial action. But it can dissolve in xylene, tetrachloroethane solvent, low moisture absorption, below 0.3%, safe use temperature below 100 C, commonly used in pigments, dyes, solvents and other filtration. 

Polyamide (nylon 66) cloth:
In wet and dry conditions, they have high strength, long life, excellent wear resistance, and thermal stability. Generally, they can be used at 120 - 150 C. The chemical stability of alkaline filter pulp is good and can be used to 100 C, but in acidic medium, it is only at room temperature that it is stable for dilute acidic materials. 

Polyester fabric:
It has high strength, flexibility, good linen resistance, long life, and excellent particle retention performance. Chemical stability can resist acid corrosion. The alkali resistance is slightly worse, but better than that of acrylonitrile fibers. Polyester cloth also has high resistance to microbial action. There are many kinds of polyester filter cloth and they are widely used. At present, polyester 734. 

Ollen cloth:
It is made of 85% acrylonitrile, acrylate and vinylpyridine copolymers. It has high thermal stability and wears resistance. It has good corrosion resistance to inorganic acids. It dissolves in concentrated sulfuric acid with a concentration of more than 80%. It also has certain corrosion resistance to weak alkali and strong alkali at room temperature. It will not be corroded by common solvents, greases, neutral salts, and most acid salts.

Interwoven fabric:
The filter cloth interwoven with polyacrylonitrile and polyester fibers has a smooth surface and high mechanical strength. It is not blocked by pollutants and is easy to discharge slag. It has the chemical properties of two kinds of fibers. It is especially suitable for the filtration of acid gypsum slurry in sewage treatment and phosphoric acid plant. According to foreign reports, its service life is also long, and it is a promising new filter cloth.
 
(2) Non-textile filter cloth 
The paper filter cloth of 0.2-2 thickness was made by heating various fibers together with certain resin adhesives and solvents. The fiber structure of the filter cloth is not regular but disordered and closely arranged, so its strength is worse than that of textile filter cloth, it is stronger than filter paper, and its porosity is thicker than filter paper, so its specific resistance is smaller than filter paper. Nonwoven filter cloth has been used in press and horizontal disc filter, mainly for clarification and filtration, purification of solid particles in low concentration suspension. For example, the filtration of beverages, latex, varnishes, lubricants and plant gums. The filtration mechanism of non-textile filter cloth is roughly classified filtration, i.e. large particles (more than 100) are intercepted from the surface layer of the filter cloth, and small particles with high dispersibility are intercepted from the inner layer of the filter cloth. 

(3) Post-processing of filter fabric weaving 
In order to improve the filtering properties, physical and mechanical properties of the filter cloth, the woven filter cloth can be finished after weaving. The processing methods are as follows:

Calendering: The filter cloth is rolled under the hot roller to make the surface of the blank cloth smooth and reduce the porosity between the yarns, so as to improve the filter cloth's ability to collect particles and removing slag. The strength of filter cloth decreases slightly after polishing.  

Picking up: In other words, on the side of the filter cloth blank, the fibers of the yarn bundle on the surface of the filter cloth are made to produce soft fluff, which can improve the ability of the filter cloth to intercept small and fine particles, improve the separation effect and improve the clarity of the filtrate.  

Hot rolling: This is limited to synthetic fiber filter cloth. The purpose is to improve the thermal stability or mechanical strength of the filter cloth and make it more suitable for operation at higher temperatures. The filter cloth woven from single filament must be hot-rolled. 

Filter Mat

Synthetic fibers (such as polyacrylonitrile, nylon, polypropylene, etc.) or wool fibers are arranged in an irregular and dense manner. Resin adhesives (such as thermal bonding) can be added or not, and felt of different thickness can be made by compaction and resistance. It is mounted on a press or drum vacuum filter. When the pleated metal mesh is used to shape the filter element, it can be used as a component of the filter element. The filter mechanism of felt belongs to deep filtration. Synthetic fiber filter mat has the advantages of anti-corrosion, anti-mildew, good particle retention, etc. It is more widely used than felt.

Filter liner

Filtration liner is a plastic filter medium made of asbestos and cellulose. Its thickness is 2-5mm, the diameter of fibers is 200-250 A, and the diameter of cellulose fibers is 20-30 A. In addition, asbestos fibers form a void in the liner, which can be used in the filter press. If diatomite particles are filled in the liner, the porosity of the liner can be increased. Because the voidage of the filter liner is very fine, it is mainly used for precise filtration to treat suspension with low solid content and fine particles. 

Filtration Membrane (Porous Precision Microporous Membrane)

With cellulose ester, polyvinyl chloride, polyethylene or polytetrafluoroethylene, and other macromolecule materials, the film with a thickness of 0.2-150 um and pore size of 0.1-60 um are processed by a specific process and installed on special equipment. The filtration accuracy of this porous membrane can reach 0.1um. Mainly used in the pharmaceutical industry and biochemical wastewater treatment with bacteria, such as supergroup and precision filtering occasions.

Employees as stainless steel filter elements, I predict that in the next ten years, wedge wire filter will become the mainstream of the filtration system.