Development and Application of Metal Plane Sealing Butterfly Valve
**Abstract:** This paper introduces the structural features and working principle of the metal-sealed pneumatic butterfly valve. It details the development and application of this type of valve, analyzing its comprehensive performance and future development prospects.
**1. Introduction**
In recent years, with the advancement of modern industry, the use of butterfly valves has expanded significantly, now being applied to media with temperatures ranging from -184°C to over 538°C, and pressures varying from low to high. These valves are widely used in fields such as air separation, chemical processing, metallurgy, and wastewater treatment. As the demand for larger sizes, better performance, and longer service life increases, traditional rubber or plastic-sealed butterfly valves have become less suitable due to their susceptibility to wear, aging, and failure under continuous operation.
For example, in air separation plants that rely on cryogenic separation techniques, the process involves a molecular sieve pre-purification stage. The operating pressure typically ranges between 0.5 to 0.9 MPa, with temperatures between 10°C and 200°C. In such environments, frequent switching, large diameters, and temperature fluctuations cause rubber seals to degrade quickly, making replacement difficult and costly. To address these challenges, our company developed a series of metal-sealed pneumatic butterfly valves, which have been granted a national practical patent (Patent No.: ZL 97 2 24037.3).
**2. Features of the Metal-Sealed Pneumatic Butterfly Valve**
(1) The lever-type opening and closing mechanism minimizes seal sliding, reducing wear and extending service life.
(2) A connecting rod actuator is used, which provides maximum torque when the valve is closed and ensures self-locking for safe and reliable operation.
(3) The metal seal structure offers strong resistance to corrosion and wear, making it suitable for high-temperature environments and ensuring a long service life.
(4) Key components have been optimized to allow over 1 million valve operations.
(5) The control system uses non-contact electromagnetic reed switches, offering high sensitivity, accuracy, and compatibility with remote, pneumatic, and automatic control systems. This also allows for hands-free operation.
**3. Structure and Working Principle**
**3.1 Lever-Type Opening and Closing Mechanism**
As shown in Figure 1, the lever-type mechanism consists of a spindle, a lever, and a compression spring. When the valve is closed, the lever rotates counterclockwise around point O, driving the butterfly plate into contact with the sealing surface. This reduces relative sliding and minimizes wear. The axial pressure seal replaces the traditional external force squeeze method, enhancing reliability.
**3.2 Connecting Rod Actuator**
The connecting rod actuator, depicted in Figure 2, uses a piston and power arm to generate torque. The relationship between angles α and β determines the output torque. As β decreases and α increases, the torque value rises, reaching its peak when the valve is fully closed. This aligns with the required sealing torque during operation, ensuring efficient and stable performance.
**3.3 Flat Seal Design**
Unlike traditional spherical seals, the new flat seal design uses metal surfaces for contact. This eliminates the need for adjustable interference, improving sealing performance. The use of stainless steel and copper-based alloys enhances corrosion and wear resistance, allowing operation in a wide temperature range (-40°C to 300°C). The flat seal also enables self-compensation for wear, extending the valve’s lifespan.
Due to its rational design, the valve outperforms many domestic alternatives and has replaced similar foreign products in various applications.
**4. Test Results and Application**
In April 1997, our company successfully developed a PN1.0MPa DN300 pneumatic butterfly valve. Performance tests included:
- Air pressure: 0.4 MPa
- Pipeline pressure: 0.95 MPa
- Medium temperature: Room temperature
- Number of cycles: 1,500 times (required: 1,000 times/year)
- Opening/closing time: 10 seconds
A field simulation test was conducted under the following conditions:
- Air pressure: 0.4 MPa
- Pipeline pressure: 0.7 MPa
- Medium temperature: 150°C
- Number of cycles: 8,000 times (required: 1,000 times/year)
- Leakage test: Zero
After testing, all components were intact, and the valve performed reliably. Since then, we have developed larger models such as PN1.0MPa DN400, PN1.6MPa DN150, and DN200, which have been successfully applied in various industrial settings, including the Tianjin Iron Works’ 15,000 m³/day air separation plant.
These valves have proven effective in high-pressure, large-diameter applications, replacing previously imported models and filling a gap in the domestic market. They are now widely used in air separation, chemical, and gas industries, particularly for natural gas pipelines where fire safety, low maintenance, and cost-effectiveness are critical.
**About the Author:** Li Xiannian, male, 36 years old, is an engineer with a bachelor's degree. He has been involved in the research and development of air separation equipment, focusing on the design of metal-sealed pneumatic butterfly valves. His work earned him a national patent.
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