Sealing gasket is a kind of raw material used to seal the interior of mechanical equipment, machinery equipment, pipelines, etc. What are the types? There are various types of sealing gaskets, which can be roughly divided into three categories according to their raw materials and structures. 1. Non-metallic gaskets: vulcanized rubber, asbestos rubber sheet, flexible high-purity graphite, polytetrafluoroethylene, etc., and the cross-sectional shape is a rectangular frame;
2. Metal composite gaskets: there are various metal clad gaskets and metal wound gaskets;
3. Metal gaskets: There are metal flat gaskets, wave gaskets, annular gaskets, toothed gaskets, lens gaskets, triangular gaskets, double cone rings, C-rings, hollow O-rings, etc. There are various types of sealing gaskets, and the raw materials are divided into three categories: non-metallic, semi-metallic and metal gaskets according to the theme of their structure. (1) Non-metallic gaskets: Non-metallic gaskets are soft, corrosion-resistant and low in price, but have poor high temperature and impact resistance; they are mostly used for flange sealing of medium and bottom pressure vessels or pipelines at room temperature and standing temperature. . Non-metallic gaskets include rubber sheets, asbestos pads, asbestos rubber sheets, flexible graphite pads and Teflon pads. ① Rubber pads, the key raw materials for making rubber pads and gaskets are natural rubber, nitrile rubber, neoprene, etc. In addition, special rubbers such as fluorine rubber have just begun to be used. Vulcanized rubber is widely used in the sealing of utensils and pipelines due to its high density, soft material, good resilience, easy to cut into various shapes, cost-effective, and easy to buy, but it is not resistant to high pressure. , It is very easy to melt and swell in mineral oil without corrosion, and it is very easy to embrittle and lose resilience at high temperatures.
②Asbestos, asbestos raw materials include wet asbestos and blue asbestos. Wet asbestos has high temperature resistance, good acid resistance, high compressive strength and weak alkali resistance, and most asbestos rubber sheets are produced by it; blue asbestos not only has good temperature resistance, but also has good alkali resistance, so it is often used. To produce acid-resistant asbestos rubber sheet. The normal application temperature of asbestos board cutting is below 550 degrees. Asbestos tape or rope can be used for bottom pressure vessels with large diameters. When applying asbestos rope, sodium silicate is generally pre-impregnated. Acids, alkalis, organic solvents and other substances can also be used for this type of gasket. ③Asbestos rubber sheet, asbestos rubber sheet is restrained by asbestos, vulcanized rubber and filler. Generally, asbestos chemical fibers account for 60%-85%. According to its different processing technology, characteristics and main uses, the main ones are high pressure asbestos rubber sheet, middle and bottom pressure asbestos rubber sheet and acid and alkali resistant asbestos rubber sheet. Asbestos rubber sheet has suitable compressive strength, ductility, flexibility and other characteristics. It is convenient and cost-effective to use it to make gaskets, so it has been quickly promoted and used in chemical plants.
④Flexible high-purity graphite, flexible high-purity graphite is a novel rubber seal with good resilience, flexibility and heat resistance, and has been rapidly promoted and used in chemical plants. ⑤ Polytetrafluoroethylene (commonly known as PTFE), polytetrafluoroethylene is known as "plastic" because of its acid resistance, temperature resistance, cold resistance, and wear resistance. Does not ignite, hygroscopicity is nearly zero. Its structure is high-density, and its molecular formula has no optical rotation. As a gasket, the surface can be guaranteed to be smooth and clean, and it does not stick to the metal flange. In addition to being corroded by molten alkali metals and their fluorine-containing element vapors, it is resistant to corrosion by a variety of acids, alkalis, salts, and vegetable oils and fats. (1) PTFE gaskets include pure PTFE, filled PTFE or swelled PTFE, etc. (2) Semi-metal gaskets (also known as metal composite gaskets). Although non-metallic raw materials have the advantages of very good flexibility, expansion and poor load capacity of anchor bolts. But its key point is that the compressive strength is not high, the resilience is poor, and it is not suitable for high pressure and high temperature places. Therefore, the fused metal raw material has high compressive strength and good resilience. Features that can withstand high temperatures. A gasket is produced that will construct the two together. That is, the semi-metal gasket. The semi-metallic gaskets mainly include metal clad gaskets, metal coil gaskets, metal corrugated gaskets, metal toothed gaskets, etc.
① Metal clad gasket (metal composite gasket). The gasket is made of metal as the material core, and the thickness of the outsourcing business is 0.25-0.5 mm metal metal sheet. According to the encapsulation, it can be divided into full encapsulation, half encapsulation, wave type encapsulation and two-layer encapsulation. Metal sheet metal sheets are selected according to the elastoplasticity, temperature resistance and corrosion resistance of the raw materials. The key is copper, galvanized steel plate, stainless steel plate, titanium, Monel alloy and so on. The most widely used are copper, galvanized steel and stainless steel. As a metal-clad core board, temperature resistance is a key assessment criterion. Generally, asbestos board or low-vulcanized rubber asbestos board, carbon fiber material with good heat resistance properties or porcelain chemical fiber and flexible high-purity graphite board are used. Another characteristic of metal-clad gaskets is that they can be made into various types of gaskets. A variety of heat exchanger tube boxes and non-annular high pressure vessel sealing requirements can be considered, while other composite gaskets cannot. ② Metal coiled gasket. The metal coiled gasket is made of thin metal corrugated belt and non-metallic such as asbestos or flexible high-purity graphite, which are alternately wound into a spiral shape, and the cause and effect nodes of the metal belt are welded by electric welding. Overseas, it is also called spiral gasket. ⑶ metal gasket. Under the stringent practical operating standards such as ultra-high pressure and its load circulation system, various metal materials are still the raw materials of choice for sealing gaskets. Common materials include copper, aluminum, high carbon steel, stainless steel, chromium-nickel Carbon steel, Titanium Monel, etc. In order to reduce the load of the anchor bolts and ensure a compact structure, in addition to the narrow overall width of the metal flat washer, a variety of ring gasket structures with line contact characteristics are selected. ①Flat metal gasket. There are two types of wide gaskets and narrow gaskets for flat applications. Due to the large pre-tightening force of the wide gasket, it is easy to cause the deformation of the flange of the anchor bolt. When the working pressure exceeds 1.96MPa, it is rarely used on the flange with a smooth surface. Narrow gaskets are very easy to torque and can be applied on pipelines with a working pressure of 6.27-9.8MPa. ② corrugated metal gasket. The thickness of the metal plate of the corrugated metal gasket is generally 0.25-0.8 mm. The thickness of the spacer is generally 40%-50% of the light wavelength. It is suitable for the application on the pipeline with smooth convex surface and working pressure of 3.34MPa. ③Toothed metal pad. Tooth-shaped metal gaskets are mostly used on pipelines of 6.77-9.8MPa. The meshing angle distance is about 1.5 mm, and the meshing angle and gear tooth angle are both 90 degrees. Its tightness is better than that of flat gaskets, and the clamping force is also smaller than that of flat gaskets.
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