pH refers to the intensity of acid or alkaline materials in your water.
A pH value between 6.8 and 7.6 will be tolerated by most freshwater fish species. However, ideal pH ranges are species dependent.
Chlorine may be present in tap water. It is harmful to fish, damaging their gills and skin, and must not be introduced to the aquarium.
Carbonate refers to carbonate hardness (KH) in aquarium water. It is a measure of carbonates (CO3) and bicarbonates (HCO3) dissolved in the water. Ideal range is between 40-120 mg/L.
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The screen surface is the basic working part of the screening equipment . A hole of a certain size and shape is uniformly distributed on the sieve surface, and is generally referred to as a sieve hole. When sieving materials on the screen surface, the material passing through the screen holes is called the undersize product, and the material remaining on the screen surface is called the on-screen product. The effective area of ​​the screen surface (ie, the opening ratio) refers to the ratio of the area occupied by the screen hole to the area of ​​the entire screen surface. The larger the effective area, the greater the productivity of the screen area per unit area and the higher the screening efficiency. It can be seen that it is an important parameter to measure the quality of the screen surface. Generally, on the one hand, it is necessary to increase the effective area of ​​the screen surface as much as possible, and on the other hand, it is also considered that the screen surface strength is not reduced and the service life is significantly shortened.
At present, generally mild steel, high carbon steel, manganese steel, spring steel, stainless steel and other materials made of the screen surface, i.e. mainly metal screening surface; and made of rubber, nylon, polyurethane, other non-metallic materials sieve The surface is also growing and increasing, but it is still very small compared to the metal mesh surface, but the vibrating fine screen basically uses a nylon mesh surface.
According to the particle size of the material to be sieved and the process requirements of the screening operation, the sieve surface can generally be divided into the following types.
(1) Bar screen surface. The rod screen surface is composed of a set of steel rods arranged in parallel and having a certain section shape. The cross-sectional shapes of the commonly used different bars are shown in Fig. 1. The bars are arranged in parallel, and the spacing between the bars is the size of the mesh. Bar screens are generally used for fixed screens or heavy-duty vibrating screens and are suitable for screening coarse-grained materials with a particle size greater than 50nmm.
(2) Punching the screen surface. The punched screen surface is generally formed by punching a circular, square or rectangular mesh hole on a steel plate having a thickness of 5-12 mm. Compared with the screen surface of a circular or square sieve hole, the sieve surface of the rectangular sieve hole usually has a large effective area, light weight and high productivity, and is suitable for processing materials with high moisture content, but the separation precision of the sieved product is poor. .
The arrangement of the sieve holes on the punching sieve surface is shown in Fig. 2. The circular sieve holes are usually arranged in an equilateral triangle, and the square sieve holes can be arranged in parallel or diagonally arranged at right angles of the isosceles triangle, and the rectangular sieve holes are generally arranged with the sieve surface. The longitudinal axes are arranged at an angle and may be arranged in other ways.
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A certain distance should be maintained between the screen holes in order to wear and ensure the necessary screen strength. The hole pitch is generally determined empirically. If the mesh size is 10-100 mm, the pitch is 1 . 25 times. The punching screen is relatively strong and has a long service life, but the effective area is small, about 40%-60%. The mesh size is generally 12-50mm, which is suitable for screening of medium-grain materials.
(3) Weaving the screen surface. The woven screen surface is made of steel wire as warp and weft, and the mesh shape is square or rectangular (Fig. 3). In order to ensure that the mesh size distribution is uniform and the mesh is prevented from being displaced, grooves are alternately arranged at the intersection of the mesh wires. The woven screen has a large effective area (up to 75%), is light in weight, and is easy to manufacture, but has a short service life. At present, stainless steel or spring steel is used as the mesh to extend the service life, but the price is high. Woven screens are generally suitable for the screening of medium to fine grade materials.
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(4) Wavy screen surface. The screen strip is pressed into a wave shape in the transverse direction, and the two screen strips are combined to form a screen hole, which is a wave-shaped screen surface (Fig. 3). The screen strip can also be pressed into a wave shape in the longitudinal direction, and the screen surface composed of such a wave-shaped screen strip is also referred to as a string screen surface. The wavelength depends on the size of the mesh. Usually, the mesh holes are square, but the mesh holes of the string screen are rectangular. The sieve strip is made of elastic manganese steel, which can generate secondary vibration with small amplitude, thereby reducing the sticking and clogging of viscous materials or fine particles.
(5) Slotted screen surface. The slotted screen surface is made of stainless steel as a sieve strip, and has three structural types: strip, welded and braided (Fig. 4). The strip-slotted screen surface is an early type. Although the structure is reliable, it is complicated to manufacture, requires a lot of material, and has a small effective area. The welded slotted screen surface is 30% more material-saving than the strip-type strip, and the manufacturing is simple; and the braided strip screen has a large effective area, light weight, convenient assembly and disassembly, but a short service life. The cross-sectional shape of the screen of the slotted screen is circular or as shown in Fig. 4(d). The slit width can be 0.25 mm, 0.5 mm, 0.75 mm, lmm and 2 mm. The slotted screen surface is suitable for the dewatering, de-intermediation and de-sludge operations of medium and fine-grained materials.
(6) Non-metallic screen surface. The materials used in the manufacture of non-metallic screens in China are rubber, nylon and polyurethane. The common advantages of this type of screen surface are wear resistance, long service life, light weight and low noise, which can be widely used for screening of metal ore, coal and building materials. However, the use of China is not yet extensive.
Whether the screen surface can be evenly tightened and firm when installed on the screen box has a great influence on the screening efficiency and service life of the screen surface. The woven screen surface having a mesh diameter greater than 9.5 mm is usually fixed by a slatted surface of the sifted surface of the sifted surface of the sifter Punching screens with a thickness greater than 8 mm are fixed with beading and screws. Figure 5 is a relatively advanced screen tensioning device, and Figure 6 is a wooden screen tensioning plate for the slit screen.
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