Characteristics and principle of metal plane sealing butterfly valve

In recent years, with the development of modern industry, the use of butterfly valve has expanded from low-pressure water supply to medium with temperature higher than 538 ℃ and - 184 ℃ and pressure from low to high It is widely used in air separation, chemical industry, metallurgy, sewage treatment and other fields Moreover, the caliber is larger and larger, the performance requirements are higher, and the service life requirements are longer At present, most of the butterfly valves produced at home and abroad are rubber and plastic seals, which are easy to wear and aging, and can not reach the continuous operation cycle of the equipment Taking air separation as an example, today's air separation equipment mainly based on the principle of cryogenic separation adopts molecular sieve pre purification process, with working pressure of 0.5-0.9mpa, medium temperature range of 10-200 ℃ Its switching valve uses large temperature difference, large diameter, frequent switching, rubber seal ring of valve is easy to wear and aging, and replacement is also difficult In view of these situations, our company has developed a series of metal plane seal pneumatic butterfly valves with connecting rod reinforcement This new type of butterfly valve has obtained the national practical type (No.: zl97224037.3) 2 The features of the metal plane seal pneumatic butterfly valve (1) adopt the lever type opening and closing structure, so that the relative sliding between the sealing pairs is very small and the relative wear is reduced (2) the actuator adopts the connecting rod force increasing mechanism When the butterfly valve is in the closed state, the drive device can output Zui large torque, and has self-locking performance, safe and reliable operation (3) adopt metal plane sealing structure, with strong corrosion resistance and wear resistance, suitable for high temperature environment and long service life (4) the key components are optimized to make the total number of valve opening and closing more than 1 × 106 (5) the control system of the valve adopts non-contact electromagnetic reed switch, which is not limited by environmental conditions, and has sensitive signal and high accuracy It can realize remote control, pneumatic control and automatic control, and can also realize unmanned operation when matching with equipment 3 Structure and working principle 3.1 lever type opening and closing structure When the butterfly valve is closed, the main shaft and the lever are fastened with taper pin, rotate counterclockwise around o point, the lever drives the butterfly plate AB with the pin with hole, and the compression spring drives the butterfly plate to be fixed o n the fulcrum n of the lever, and rotates with the rotation of the main shaft lever When the upper end B of the butterfly plate contacts with the sealing surface of the valve body, the sealing is achieved The opening process is the opposite In the process of opening and closing, the relative sliding between the sealing pairs is very small, reducing the relative wear In the closed state, it is axial pressure seal, which changes the traditional external force extrusion seal 3.2 connecting rod force increasing actuator: connecting rod force increasing actuator, the piston moves to the right under the action of air source pressure, the piston rod with power arm slides in the box, the connecting rod drives the rocker to rotate clockwise, and the output torque The length (H) of the connecting rod is the same as that of the rocker, which is equal to the distance from the tank center to the output center According to the analysis of the force, P = q / cos α = SIN-1 (1-sin β) m torque = phcos (90 - α - β) = qhsin (α + β) / cos (α + β) From the above formula, the β angle decreases, the α angle increases, and the M torque increases When β = 0 ° and α = 90 ° (the butterfly valve is in the closed state), the drive device outputs Zui large torque, while the torque in the opening and closing process is small This characteristic contains exactly the curve of butterfly valve operating torque on the curve to meet the sealing torque required by the butterfly valve in the closed or open state 3.3 plane sealing structure: in the past, the sealing pair of pneumatic butterfly valve generally used spherical sealing The sealing pressure is the radial extrusion force, and the sealing interference can not be adjusted arbitrarily The sealing performance depends on the interference of the sealing material Therefore, it is very important to select the sealing material and the interference in the design In the work, especially in the pre purification process of molecular sieve, the switching valve works in the range of 10-200 ℃, when the rubber sealing ring is used, the linear expansion coefficient of rubber is very large, which is greatly affected by the temperature change, so it is difficult to determine the interference accurately If the interference is large, not only the friction is increased, but also the phenomenon of "edge gnawing" and "tongue turning" often occurs, which makes the seal fail If the interference is small, the leakage will occur Even if the interference is reasonable, and the valve switches frequently, it will fail due to wear after a period of operation If non rubber sealing materials are used, their elastic deformation is very small, radial sealing interference is difficult to control, manufacturing is quite complex and cost is very high At the same time, for the rubber sealing material, the constant change of temperature causes premature aging of rubber sealing ring due to temperature fatigue damage For the large-diameter pneumatic butterfly valve equipped with large air separation equipment, it is very difficult to replace the sealing ring The new sealed pneumatic butterfly valve adopts the metal plane sealing structure, the valve disc as a non vulnerable part adopts the stainless steel hardfacing carbide, the seat sealing ring adopts the copper base alloy or stainless steel hardfacing cobalt alloy, they have strong corrosion resistance and wear resistance, the service temperature range is large, and they can be used for a long time between - 40 and 300 ℃, so the service life is much longer than the rubber seal Many As the moving mechanism of the valve plate adopts the form of lever, when the valve plate is closed, the valve plate and the valve seat become a plane contact seal, and then the lever is equivalent to the cam mechanism If the main shaft continues to rotate, then the valve plate continues to move forward to achieve the balance of force When there is working medium pressure, it can also achieve self sealing, ensuring the reliability of sealing When the whole sealing surface is worn, it also has the feature of automatically compensating the amount of seal wear, thus prolonging the service life Due to the reasonable structure of the valve, its service performance is better than other domestic valves, and it has been able to replace similar products abroad.