Performance, structural characteristics and applic

Performance, structural characteristics and application of double eccentric hemispherical valve

with the continuous development of industry, the demand for ball valves, especially under high temperature and high pressure severe conditions, is increasing, requiring ball valves to have higher performance of wear resistance, erosion resistance, high temperature resistance, corrosion resistance and so on. Although the ball center and valve seat of the traditional full bore ball valve are surface hardened by surfacing, spraying and other technologies, its service life, cost and performance still cannot meet the requirements, such as industrial silicon, coal chemical industry, blast furnace gas, gas and other harsh working conditions. Double eccentric hemispherical valve is a new product developed by absorbing the advantages of ball valves, V-shaped valves and track ball valves with different structures. The ball valve adopts double eccentric sealing structure, with small wear, small torque, good sealing performance and long service life. The valve seat and hemisphere are treated by special hardening process, which is especially suitable for the requirements of wear resistance, erosion resistance, corrosion resistance and high temperature resistance under harsh working conditions

2. Structural features

2.1. Hemisphere

the hemisphere of double eccentric hemisphere valve adopts double eccentric design, which has reliable sealing effect, instant disconnection, small torque and long service life. It can be used in the harsh working conditions of conveying granular media. Its structural principle is that the hemispherical center line is offset from the center line of the valve stem by dimension a, and offset from the center line of the valve seat by dimension B. when fully opened, the sphere and the valve seat are completely separated, and there is a certain gap. The radius of gyration is divided into long radius and short radius. The tangent of the long radius rotation track will form a gap with the sealing surface of the valve seat θ Transition angle: when the valve is opened and closed, the hemisphere has a gradual separation from the valve seat surface (as shown in the figure, when the opening is 10 °, the core has been completely separated) and gradual extrusion, so as to reduce the mechanical wear and abrasion between the valve seat and the hemisphere during opening and closing, and improve the service life

1. Bottom cover 2 Retainer 3 Valve seat 4 Hemisphere 5 Valve body 6 Filler 7 Support 8 Shaft 1 Valve seat 2 Hemispherical

2.2. Valve seat

(1) the valve seat adopts floating design to reduce the processing difficulty and ensure that the center line of the valve seat coincides with the center point of the hemispherical sphere, so as to improve the sealing performance. There is a gap d between the valve seat and the valve body. During assembly, the center line can be automatically aligned by using hemispherical positioning, so as to ensure the full contact between the sealing surface of the valve seat and the hemispherical sphere, solve the leakage caused by machining accuracy errors, and improve the service performance and service life of the ball valve

1. Retainer 2 Valve seat 3 Hemisphere 4 Valve body

(2) the seal between the valve seat and the valve body adopts a hard sealing structure, which is suitable for the isothermal and high-pressure working conditions of omnia 7 and Swarovski Galaxy S5. The size c value of the sealing contact surface between the valve seat and the valve body is small, and the accuracy requirements of their respective sealing surfaces are high. During assembly, the retainer is installed with an electric impact wrench, which is not only the retainer is engaged with the valve body to prevent loosening, but also the friction rotation of the valve seat, which conforms to the principle of mechanical vibration engagement, so that the valve seat and the valve body film, paper, food packaging, textile fiber, high molecular materials, springs, composite materials and products can be reliably sealed

(3) the valve seat and valve body and the valve seat and hemispherical body adopt two-point hard sealing, so the valve can be used in high temperature and high pressure conditions

2.3. Other parts

the valve adopts modular design as a whole, with simple structure, good reliability and high versatility. The valve rod adopts anti ejection structure. The driving mode is diversified, and the connection size of valve rod, support and actuator meets the ISO5211 standard, which can be directly assembled with various standard actuators. The commonly used driving methods include manual, pneumatic, hydraulic, pneumatic hydraulic and electric, which improves the application performance of the double eccentric hemispherical valve

3. Scope of use

double eccentric hemispherical valve is suitable for valves required by various general industries, such as water, sewage, wastewater, steam, gas, pulp and other media. If the sealing pair adopts Cr Mn Si cemented carbide and has fire-resistant, explosion-proof and anti-static functions, it is suitable for medium and high temperature media requirements, such as gas, coke oven gas, water gas and natural gas. If the sealing pair (hemispherical body, valve seat) and the flow passage of the valve body are treated by the special process of tungsten carbide, it has the advantages of high efficiency and energy saving, good wear resistance, reliable sealing performance, light operation, rapid opening and closing, long service life and so on. It is an ideal choice for valves used in pipelines in the industrial silicon industry. Due to the characteristics of instantaneous separation and instantaneous compression between the hemispherical body and the valve seat, it is suitable for the harsh working conditions with particles in the medium. The following points are for reference: it can be widely used in various pipeline controls in blast furnace pulverized coal injection, pulverizing system and dust removal system in metallurgy, beneficiation, electric power and other production processes. In the process of instantaneous separation and instantaneous compression, the hemispherical body and the valve seat have a squeezing and cutting effect, which can remove the scaling and adhesion on the sealing surface and ensure the tightness and reliability of the seal. It is an ideal choice for valves used to transport two-phase mixed fluid media in process flows such as solution pulp, slurry ash, etc. that are easy to precipitate, scale, and crystallize

4. Conclusion

at present, a variety of specifications of double eccentric hemispherical valves have been applied to various projects in different industries, with good results, and are gradually expanding the scope of use