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There are various types of washer, and the main materials of the structure are divided into three categories: non-metallic washer, semi-metallic washer and metal washer.
1. Non-metallic gaskets
Non-metallic gaskets are soft, corrosion-resistant and cheap, but have poor temperature and pressure resistance. Mainly used for flange sealing of medium and low pressure containers or pipelines at room temperature and medium temperature. Non-metallic gaskets include rubber pads, asbestos pads, asbestos rubber pads, flexible graphite pads and PTFE pads
(1) Rubber board. The main materials for manufacturing rubber pads are natural rubber, nitrile rubber, neoprene, etc. In addition, special rubbers such as fluoroelastomer are also used. Rubber is widely used in containers and pipes due to its dense structure, soft texture, good elasticity, easy to cut into various shapes, low price, and easy to buy. However, it is not resistant to high pressure, is easily soluble in mineral oil, and is not resistant to corrosion. It is easy to age at high temperatures and loses the ability to rebound.
(2) Asbestos. There are two types of asbestos materials: thermos asbestos and blue asbestos. Temperature asbestos has good heat resistance, alkali resistance, high tensile strength and poor acid resistance. Most asbestos rubber sheets are produced using it. Blue asbestos is not only good heat resistance, but also acid resistance, so it is mainly used to make acid-resistant asbestos rubber sheets. The normal operating temperature of asbestos board is less than 550 degrees. Large diameter low pressure containers can be made of asbestos straps or asbestos ropes. When using asbestos rope, it is usually impregnated with sodium silicate. This gasket can also be used in acid, alkali, solvent and other media.
3. Asbestos rubber sheet. Asbestos rubber sheets are compacted with asbestos, rubber and fillers. Generally, asbestos fiber accounts for 60% and 85%. There are mainly high-pressure asbestos rubber sheets, medium and low-pressure asbestos rubber sheets and oil-resistant asbestos rubber sheets. According to their proportion, process, performance and purpose, they mainly include high-pressure asbestos rubber sheets, medium and low-pressure asbestos rubber sheets and oil-resistant asbestos rubber sheets. Asbestos rubber sheets have suitable properties such as strength, elasticity, flexibility, heat resistance, etc. The gasket is easy to make and low-priced, and has been widely used in chemical companies, especially small and medium-sized chemical companies.
4. Flexible graphite. Flexible graphite is a new type of sealing material with good elasticity, flexibility and temperature resistance, and has been rapidly promoted and applied in chemical companies.
Polytetrafluoroethylene (PTFE). Polytetrafluoroethylene (PTFE) is known as the "king of plastics" for its superiority in chemical resistance, heat resistance, cold resistance and oil resistance. It is not easy to age, does not burn, and has almost no water absorption. Its structure is compact and has a polar molecular structure. As a gasket, the contact surface can be smooth and not stick to the metal flange. In addition to being corroded by molten alkali metals and fluorine-containing gases, it can also resist the corrosion of various acid, alkali, salt and fat solution media. The PTFE gaskets include pure PTFE, filled PTFE or expanded PTFE.
2. Semi-metal washer (also known as metal composite washer)
Non-metallic materials have the advantages of good flexibility, good compression, and low bolt load, but their main disadvantages are low strength and poor rebound, which are not suitable for high temperature and high pressure occasions, so the bonded metal materials have a higher strength. This gasket has good rebound performance and high temperature resistance. It is a gasket that combines two structures, namely a semi-metal gasket. The semi-metal gasket is formed by wrapping a non-metallic material in thin metal sheets of different materials. The metal material is in the outer layer and is resistant to high temperatures, while the non-metallic material is in the inner layer, which makes the gasket have good elasticity and rebound properties. The combined gasket can meet the requirements of high temperature and high pressure. Semi-metal gaskets mainly include metal-coated gaskets, metal winding gaskets, metal corrugated composite gaskets, metal tooth composite gaskets, etc. Yvonn Gu
Metal pad. The gasket is made of a non-metal core material, and the gasket thickness is 0.25~0.5mm. According to the state of the coating, it can be divided into full coating, semi-coated coating, corrugated coating, double cladding, etc. The board is selected according to the elastic-plasticity, heat resistance and corrosion resistance of the material. Mainly copper, galvanized iron, stainless steel, titanium, Monel alloy, etc. Commonly used are copper, galvanized iron and stainless steel. As a metal pad core material, heat resistance is the main evaluation index. Generally, asbestos boards or rubber asbestos boards, high-temperature resistant carbon fibers or ceramic fibers and flexible graphite boards are used. Another feature of metal pads is that it can be made into washers of various shapes. It can meet the needs of sealing a variety of heat exchanger tubes and non-circular pressure vessels, while other composite gaskets cannot.
(2) Metal wound gasket. The metal winding gasket is made by alternately winding the thin metal corrugated strip with non-metallic strips such as asbestos or flexible graphite into a spiral shape, and weld it at the beginning and ends of the metal strips. It is also called spiral gasket abroad. A sort of
3. Metal gaskets
Under harsh working conditions such as high temperature and high pressure and frequent load cycles, various metal materials are still the materials for sealing gaskets. Commonly used materials include copper, aluminum, low carbon steel, stainless steel, chromium-nickel alloy steel, titanium, Monel alloy, etc. etc. In order to reduce bolt load and ensure compact structure, in addition to the narrow width of the metal pad, various annular cushion structures with wire contact characteristics are also selected. The cross-sectional shapes of the metal gasket are flat, corrugated, toothed, octagonal, lens shape, etc.
1. Flat metal washer. Flat metal gaskets are used in different parts of wide and narrow gaskets. Due to the large preload force of wide spacers, they are prone to deformation of bolts and flanges. When the pressure exceeds 10 MPa, it is rarely used on smooth flanges. Narrow gaskets are easy to pre-tighten and can be used in 6.3~10 MPa pressure pipelines.
2. Corrugated metal gasket. The thickness of the metal plate of corrugated metal gasket is 0. The thickness of the 25-meter 8 mm gasket is generally 40% to 50% of the wavelength. Suitable for use on smooth and dense pipes.
3. Tooth-shaped metal pad. The top of the teeth is about 15mm, and the tip and root angle are 90°. The sealing performance is better than the flat gasket and the pressure is also less than the flat gasket.
1. Non-metallic gaskets
Non-metallic gaskets are soft, corrosion-resistant and cheap, but have poor temperature and pressure resistance. Mainly used for flange sealing of medium and low pressure containers or pipelines at room temperature and medium temperature. Non-metallic gaskets include rubber pads, asbestos pads, asbestos rubber pads, flexible graphite pads and PTFE pads
(1) Rubber board. The main materials for manufacturing rubber pads are natural rubber, nitrile rubber, neoprene, etc. In addition, special rubbers such as fluoroelastomer are also used. Rubber is widely used in containers and pipes due to its dense structure, soft texture, good elasticity, easy to cut into various shapes, low price, and easy to buy. However, it is not resistant to high pressure, is easily soluble in mineral oil, and is not resistant to corrosion. It is easy to age at high temperatures and loses the ability to rebound.
(2) Asbestos. There are two types of asbestos materials: thermos asbestos and blue asbestos. Temperature asbestos has good heat resistance, alkali resistance, high tensile strength and poor acid resistance. Most asbestos rubber sheets are produced using it. Blue asbestos is not only good heat resistance, but also acid resistance, so it is mainly used to make acid-resistant asbestos rubber sheets. The normal operating temperature of asbestos board is less than 550 degrees. Large diameter low pressure containers can be made of asbestos straps or asbestos ropes. When using asbestos rope, it is usually impregnated with sodium silicate. This gasket can also be used in acid, alkali, solvent and other media.
3. Asbestos rubber sheet. Asbestos rubber sheets are compacted with asbestos, rubber and fillers. Generally, asbestos fiber accounts for 60% and 85%. There are mainly high-pressure asbestos rubber sheets, medium and low-pressure asbestos rubber sheets and oil-resistant asbestos rubber sheets. According to their proportion, process, performance and purpose, they mainly include high-pressure asbestos rubber sheets, medium and low-pressure asbestos rubber sheets and oil-resistant asbestos rubber sheets. Asbestos rubber sheets have suitable properties such as strength, elasticity, flexibility, heat resistance, etc. The gasket is easy to make and low-priced, and has been widely used in chemical companies, especially small and medium-sized chemical companies.
4. Flexible graphite. Flexible graphite is a new type of sealing material with good elasticity, flexibility and temperature resistance, and has been rapidly promoted and applied in chemical companies.
Polytetrafluoroethylene (PTFE). Polytetrafluoroethylene (PTFE) is known as the "king of plastics" for its superiority in chemical resistance, heat resistance, cold resistance and oil resistance. It is not easy to age, does not burn, and has almost no water absorption. Its structure is compact and has a polar molecular structure. As a gasket, the contact surface can be smooth and not stick to the metal flange. In addition to being corroded by molten alkali metals and fluorine-containing gases, it can also resist the corrosion of various acid, alkali, salt and fat solution media. The PTFE gaskets include pure PTFE, filled PTFE or expanded PTFE.
2. Semi-metal washer (also known as metal composite washer)
Non-metallic materials have the advantages of good flexibility, good compression, and low bolt load, but their main disadvantages are low strength and poor rebound, which are not suitable for high temperature and high pressure occasions, so the bonded metal materials have a higher strength. This gasket has good rebound performance and high temperature resistance. It is a gasket that combines two structures, namely a semi-metal gasket. The semi-metal gasket is formed by wrapping a non-metallic material in thin metal sheets of different materials. The metal material is in the outer layer and is resistant to high temperatures, while the non-metallic material is in the inner layer, which makes the gasket have good elasticity and rebound properties. The combined gasket can meet the requirements of high temperature and high pressure. Semi-metal gaskets mainly include metal-coated gaskets, metal winding gaskets, metal corrugated composite gaskets, metal tooth composite gaskets, etc. Yvonn Gu
Metal pad. The gasket is made of a non-metal core material, and the gasket thickness is 0.25~0.5mm. According to the state of the coating, it can be divided into full coating, semi-coated coating, corrugated coating, double cladding, etc. The board is selected according to the elastic-plasticity, heat resistance and corrosion resistance of the material. Mainly copper, galvanized iron, stainless steel, titanium, Monel alloy, etc. Commonly used are copper, galvanized iron and stainless steel. As a metal pad core material, heat resistance is the main evaluation index. Generally, asbestos boards or rubber asbestos boards, high-temperature resistant carbon fibers or ceramic fibers and flexible graphite boards are used. Another feature of metal pads is that it can be made into washers of various shapes. It can meet the needs of sealing a variety of heat exchanger tubes and non-circular pressure vessels, while other composite gaskets cannot.
(2) Metal wound gasket. The metal winding gasket is made by alternately winding the thin metal corrugated strip with non-metallic strips such as asbestos or flexible graphite into a spiral shape, and weld it at the beginning and ends of the metal strips. It is also called spiral gasket abroad. A sort of
3. Metal gaskets
Under harsh working conditions such as high temperature and high pressure and frequent load cycles, various metal materials are still the materials for sealing gaskets. Commonly used materials include copper, aluminum, low carbon steel, stainless steel, chromium-nickel alloy steel, titanium, Monel alloy, etc. etc. In order to reduce bolt load and ensure compact structure, in addition to the narrow width of the metal pad, various annular cushion structures with wire contact characteristics are also selected. The cross-sectional shapes of the metal gasket are flat, corrugated, toothed, octagonal, lens shape, etc.
1. Flat metal washer. Flat metal gaskets are used in different parts of wide and narrow gaskets. Due to the large preload force of wide spacers, they are prone to deformation of bolts and flanges. When the pressure exceeds 10 MPa, it is rarely used on smooth flanges. Narrow gaskets are easy to pre-tighten and can be used in 6.3~10 MPa pressure pipelines.
2. Corrugated metal gasket. The thickness of the metal plate of corrugated metal gasket is 0. The thickness of the 25-meter 8 mm gasket is generally 40% to 50% of the wavelength. Suitable for use on smooth and dense pipes.
3. Tooth-shaped metal pad. The top of the teeth is about 15mm, and the tip and root angle are 90°. The sealing performance is better than the flat gasket and the pressure is also less than the flat gasket.