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With the rapid development of industrial technology, more stringent requirements have been placed on the valve industry, especially for butterfly valves used in low temperature media, in addition to meeting the performance of general valves, and more importantly, valve sealing at low temperatures. Reliability, flexibility of movement and some other special requirements for cryogenic valves. With the rapid development of industrial technology, more stringent requirements have been placed on the valve industry, especially for butterfly valves used in low temperature media, in addition to meeting the performance of general valves, and more importantly, valve sealing at low temperatures. Reliability, flexibility of movement and some other special requirements for cryogenic valves.
As is known, the butterfly valve has a compact structure, small volume, light weight and the same pressure, the same diameter of the gate valve can be reduced by 40% to 50%) fluid resistance is small, rapid opening and closing and other advantages. However, more than 80% of the valves used in the chemical industry such as Tianhuo liquefaction equipment, air separation equipment and pressure swing adsorption equipment in China are cut-off valves or gate valves, and the number of butterfly valves is small. The reason is mainly because the metal sealing butterfly valve has poor sealing performance under low temperature conditions, and other internal leakage and leakage due to unreasonable structure, which seriously affects the safety and normal operation of these low temperature equipment, and cannot meet the low temperature. Equipment requirements.
According to the continuous development of cryogenic devices in China, the requirements for cryogenic valves are increasing. In order to meet the needs of market economy development, the metal sealing butterfly valve is structurally improved, and a butterfly valve with high eccentric pure metal high sealing performance is developed. First, the national patent has been filed. Whether the medium is high temperature or low temperature can meet its needs. Now combined with its structural characteristics, only a brief introduction to low temperature performance.
First, the requirements for the sealing performance of low temperature disc valves:
There are two main reasons for the leakage of the cryogenic valve, one is internal leakage; the other is external leakage.
1) The main cause of internal leakage of the valve is the deformation of the sealing pair at low temperature. When the temperature of the medium drops to cause a phase change of the material, the volume change is caused, and the sealing surface with high grinding precision is warped and deformed, resulting in poor low temperature sealing. We have carried out low temperature test on DN250 valve. The medium is liquid nitrogen (-196 °C). The material of the butterfly plate is 1Cr18Ni9Ti (not subjected to low temperature treatment). The warpage deformation of the sealing surface is about 0.12mm, which is the main cause of internal leakage.
The newly developed butterfly valve has been changed from a flat seal to a tapered seal. The valve seat is a slanted conical elliptical sealing surface, which forms a sealing pair with a perfect circular elastic sealing ring embedded in the butterfly plate. The seal ring can float radially within the disc groove. When the valve is closed, the elastic sealing ring first contacts the short axis of the elliptical sealing surface, and the sealing ring is pushed inwardly as the valve stem rotates, forcing the elastic ring to contact the long axis of the oblique conical surface, eventually resulting in an elastic sealing ring. All contact with the elliptical sealing surface. Its seal is achieved by the deformation of the elastic ring. Therefore, when the valve body or the butterfly plate is deformed at a low temperature, it is absorbed and compensated by the elastic sealing ring, and no leakage or jamming occurs. When the valve is opened, this elastic deformation disappears immediately, and there is substantially no relative friction during the opening and closing process, so the service life is long.
As is known, the butterfly valve has a compact structure, small volume, light weight and the same pressure, the same diameter of the gate valve can be reduced by 40% to 50%) fluid resistance is small, rapid opening and closing and other advantages. However, more than 80% of the valves used in the chemical industry such as Tianhuo liquefaction equipment, air separation equipment and pressure swing adsorption equipment in China are cut-off valves or gate valves, and the number of butterfly valves is small. The reason is mainly because the metal sealing butterfly valve has poor sealing performance under low temperature conditions, and other internal leakage and leakage due to unreasonable structure, which seriously affects the safety and normal operation of these low temperature equipment, and cannot meet the low temperature. Equipment requirements.
According to the continuous development of cryogenic devices in China, the requirements for cryogenic valves are increasing. In order to meet the needs of market economy development, the metal sealing butterfly valve is structurally improved, and a butterfly valve with high eccentric pure metal high sealing performance is developed. First, the national patent has been filed. Whether the medium is high temperature or low temperature can meet its needs. Now combined with its structural characteristics, only a brief introduction to low temperature performance.
First, the requirements for the sealing performance of low temperature disc valves:
There are two main reasons for the leakage of the cryogenic valve, one is internal leakage; the other is external leakage.
1) The main cause of internal leakage of the valve is the deformation of the sealing pair at low temperature. When the temperature of the medium drops to cause a phase change of the material, the volume change is caused, and the sealing surface with high grinding precision is warped and deformed, resulting in poor low temperature sealing. We have carried out low temperature test on DN250 valve. The medium is liquid nitrogen (-196 °C). The material of the butterfly plate is 1Cr18Ni9Ti (not subjected to low temperature treatment). The warpage deformation of the sealing surface is about 0.12mm, which is the main cause of internal leakage.
The newly developed butterfly valve has been changed from a flat seal to a tapered seal. The valve seat is a slanted conical elliptical sealing surface, which forms a sealing pair with a perfect circular elastic sealing ring embedded in the butterfly plate. The seal ring can float radially within the disc groove. When the valve is closed, the elastic sealing ring first contacts the short axis of the elliptical sealing surface, and the sealing ring is pushed inwardly as the valve stem rotates, forcing the elastic ring to contact the long axis of the oblique conical surface, eventually resulting in an elastic sealing ring. All contact with the elliptical sealing surface. Its seal is achieved by the deformation of the elastic ring. Therefore, when the valve body or the butterfly plate is deformed at a low temperature, it is absorbed and compensated by the elastic sealing ring, and no leakage or jamming occurs. When the valve is opened, this elastic deformation disappears immediately, and there is substantially no relative friction during the opening and closing process, so the service life is long.
Tiancheng Mechanical And Electrical Co., Ltd. , http://www.hzlagenerators.com