Development and Application of Metal Plane Sealing Butterfly Valve
**Abstract:** This paper presents the structural characteristics and operational mechanism of a metal-air-sealed pneumatic butterfly valve. It provides a detailed description of the development and application of this type of valve, along with an analysis of its overall performance and future potential.
**1 Introduction**
In recent years, with the rapid advancement of modern industry, the application of butterfly valves has expanded significantly. They are now used in media with temperatures ranging from -184°C to over 538°C, and pressures varying from low to high. These valves are widely utilized in industries such as air separation, chemical processing, metallurgy, and wastewater treatment. As the demand for larger sizes, higher performance, and longer service life increases, traditional rubber or plastic-sealed butterfly valves have shown limitations. For example, in air separation plants that rely on cryogenic separation, the switching valves are exposed to frequent operations, large temperature fluctuations, and high pressure, leading to seal wear and failure. To address these challenges, our company has developed a series of metal-enhanced pneumatic sealing butterfly valves, which have been granted a national practical patent (Patent No.: ZL 97 2 24037.3).
**2 Features of Metal-Seal Pneumatic Butterfly Valves**
(1) The lever-type opening and closing mechanism minimizes seal sliding, reducing wear and tear.
(2) A connecting rod actuator is employed, which allows the valve to generate maximum torque when closed and features self-locking capabilities for enhanced safety.
(3) The use of a metal-seal structure offers excellent resistance to corrosion and wear, making it suitable for high-temperature environments and ensuring a long service life.
(4) Key components have been optimized, enabling the valve to withstand over 1 million opening and closing cycles.
(5) The control system uses non-contact electromagnetic reed switches, providing high signal sensitivity, accuracy, and compatibility with remote and automatic control systems, allowing operation without manual intervention.
**3 Structure and Working Principle**
**3.1 Lever-Type Opening and Closing Mechanism**
As shown in Figure 1, the lever-type structure ensures minimal relative movement between the sealing surfaces during operation. When the valve is closed, the spindle and lever are secured with a conical pin, and the lever rotates around point O, driving the butterfly plate into contact with the sealing surface. This design reduces wear and enables axial pressure sealing, replacing traditional external force-based sealing methods.
**3.2 Linkage Actuator**
Figure 2 illustrates the linkage actuator, where the piston moves under gas pressure, causing the connecting rod to rotate the rocker arm and produce torque. The relationship between angles α and β determines the output torque, which is maximized when the valve is fully closed. This feature aligns with the torque requirements of the valve during both open and closed states.
**3.3 Flat Seal Design**
Unlike conventional spherical seals, the new metal-seal design uses flat contact between the disc and seat, offering better sealing performance. The metal components—such as stainless steel surfacing and copper-based alloys—provide high resistance to wear and corrosion, operating effectively in a wide temperature range (-40°C to 300°C). The lever mechanism also allows for self-sealing and automatic compensation for wear, significantly extending the valve’s lifespan.
**4 Test Results and Application**
In April 1997, our company successfully developed a PN1.0MPa DN300 pneumatic butterfly valve. Performance tests showed it could operate 1,500 times at room temperature, while field simulation tests confirmed zero leakage after 8,000 cycles at 150°C. The valve demonstrated excellent durability and reliability. Subsequent models, including DN400, DN500, and DN600, were applied in major projects like the Changzhi Steel 6,000 air separation plant and Tianjin Iron Works’ 15,000 air separation plant, where they performed exceptionally well. These valves have replaced imported products and filled a domestic market gap.
**5 Conclusion**
The metal-seal pneumatic butterfly valve has proven to be a reliable and efficient solution for various industrial applications. Its superior performance, long service life, and cost-effectiveness make it a strong competitor to both domestic and international alternatives. With ongoing improvements and expanding applications, this technology is set to play a key role in the future of valve systems across multiple sectors.
**About the Author:** Li Xiannian is a 36-year-old engineer with a bachelor's degree. He has been involved in the research and development of air separation equipment, focusing on metal-seal pneumatic butterfly valves. His work on this technology earned a national patent.
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