Abstract: Because of the defects of the thermal insulation
ball valve in the current technical field, the sealing material and sealing structure are improved, so that the sealing performance under high-temperature conditions can be ensured, and greatly improve its service life can be improved.
With the continuous development of domestic industry, the demand for thermal insulation
ball valves used on pipelines is also increasing. The requirements for thermal insulation ball valves are also getting higher and higher. When users select thermal insulation ball valves, they pay special attention to whether the valves have a good sealing performance to prevent medium leakage. Due to the good reliability of imported thermal insulation ball valves, users often use imported thermal insulation ball valves for important parts. However, imported thermal insulation ball valves are expensive, and there is a longer delivery period. They are inconvenient for after-sales service, which seriously affects the operation of the entire pipeline. In order to reduce the pipeline cost and realize the localization of the thermal insulation ball valve, domestic manufacturers also constantly strive to improve the quality and sealing reliability of domestic thermal insulation ball valves. They also strive to replace the imported thermal insulation ball valve. This article analyzes the high-temperature resistance of thermal insulation ball valves and puts forward improvement measures.
1. Put forward the questions
At present, the thermal insulation ball valve in the field of existing technology is also known as the jacket ball valve. It is based on the ball valve welding metal jacket between the jacket and the body, which constitutes a thermal insulation channel. The channel is injected with steam or other thermal insulation media, which can ensure that the valve medium can work normally. The thermal insulation ball valve has good thermal insulation. The diameter of the valve is consistent with the pipe diameter. It can effectively reduce the heat loss of the medium in the pipeline. It is mainly used in petroleum, chemical industry, metallurgy, pharmaceutical, food and other systems to transport media with high viscosity that will solidify at room temperature.
Due to the seal structure of valves and its corresponding sealing material constraints, the use of the temperature is less than 200℃. Under the condition of 200℃ for a long time, life is short. Although the seat can be selected for a short time of 300 ℃ high-strength graphite material, there are many parts in the valve that needs to be sealed. They still can not be sealed in high-temperature occasions, especially in radial sealing, the material of high-strength graphite is not suitable for radial sealing. Usually, the radial seal of the thermal insulation ball valve is use of O-ring sealing structure, therefore, the use of the whole valve temperature is directly restricted by the use of O-ring temperature. The current thermal insulation ball valves used on the O-ring are fluorine rubber, and the fluorine rubber service temperature is within 200℃. It can not be used in this limited temperature for a long time. It is far from meeting the requirements of many media in the market, such as the working condition of the medium for rosin. The use temperature of the insulation ball valve is required to be 300 ℃, which is conducive to the rosin medium to obtain more ideal liquidity. The traditional O-ring as a sealing part, can not meet its requirements.
2. Improvement measures
According to the problems existing in the ball valve, the sealing material and structure of the ball valve are improved.
(1) Firstly, the O-ring is usually used as the radial seal structure between the supporting ring and the valve body. The O-ring seal structure is abolished, and a step structure is directly machined on the supporting ring to form a sealing cavity between the supporting ring and the valve body. In a sealed cavity with high-temperature resistant material of flexible graphite seal ring, add a taper section of the gasket at the back of the sealing ring and install a washer fitted behind the special structure of the screw. Therefore, the sealing ring will produce a deformation. Both inside and outside the radial bearing ring and body, the thermal insulation ball valve in the radial can obtain a high temperature-resistant sealing structure. At the same time, the ball and the seat can produce the pre-tight sealing force, so that it is sealed through the screwed plug.
(2) There is also the corresponding improvement in the sealing structure of the seat. The inlaid structure is used. The groove is dug between the valve body and the support ring. The flexible graphite with good sealing performance and high-temperature resistance is installed at the bottom of the groove. It not only can play the role of sealing at the bottom of the seat, but also can play a role in the compensation of thermal expansion and contraction between the sealing pair. The flexible graphite is equipped with a high temperature-resistant metal seat. The use temperature can be raised to 425℃ for a long time so that it can solve the problem that the thermal insulation ball valve can not be used at 200℃ for a long time. The valve seat of different materials can be selected according to the requirements of actual working conditions.
3. Conclusion
Through the improvement of the sealing structure of the thermal insulation ball valve, the sealing performance is excellent. Especially the improved flexible graphite instead of O-ring is widely used at the temperature( no less than 425℃). With the development of the domestic industrial level and technological progress, its performance will continue to improve, and the scope of application will continue to expand. The thermal insulation ball valve is designed and manufactured according to the market demand. The valve has the characteristics of a compact structure. It is easy to operate, and it has reliable sealing and long service life. At present, the thermal insulation ball valve runs well in the user's working condition. The performance indicators have reached the design requirements. It has excellent properties for liquid media with easy solidification and high viscosity, especially for thick media like rosin.
