Butterfly valve types and their own characteristics
Butterfly valves come in various types, each designed for specific applications and environments. They can be classified based on structure, sealing material, sealing method, working pressure, operating temperature, and connection type.
First, by structure: (1) Center-sealed butterfly valves feature a sealing surface located at the center of the disc, offering good sealing performance but limited to lower pressure applications. (2) Single-eccentric butterfly valves have an offset between the disc and the seat, reducing friction and wear. (3) Double-eccentric butterfly valves further improve sealing and reduce wear by having two offsets. (4) Triple-eccentric butterfly valves are designed for high-performance sealing, especially in critical applications where tight closure is essential.
Second, by sealing material: (1) Soft-seated butterfly valves use non-metallic materials such as rubber or PTFE for the sealing surfaces, providing excellent sealing and low leakage. These can be either non-metal to non-metal or metal to non-metal. (2) Metal-seated butterfly valves use hard metals for both the disc and seat, suitable for high-temperature and high-pressure environments.
Third, by sealing method: (1) Forced-seal butterfly valves rely on mechanical force to create a seal. This includes elastomeric-seal valves, where the disc compresses the seat, and torque-seal valves, which use the valve shaft's torque for sealing. (2) Pressure-seal butterfly valves use elastic components to generate sealing pressure. (3) Automatic-seal butterfly valves depend on the media pressure itself to create a seal, making them ideal for high-pressure systems.
Fourth, by working pressure: (1) Vacuum butterfly valves operate under sub-atmospheric pressure. (2) Low-pressure valves have a nominal pressure (PN) less than 1.6 MPa. (3) Medium-pressure valves range from 2.5 to 6.4 MPa. (4) High-pressure valves operate at PN 10.0 to 80.0 MPa. (5) Ultra-high-pressure valves are used when PN exceeds 100 MPa.
Fifth, by operating temperature: (1) High-temperature valves function above 450°C. (2) Medium-temperature valves work between 120°C and 450°C. (3) Normal-temperature valves operate between 40°C and 120°C. (4) Low-temperature valves are used between -40°C and 100°C. (5) Ultra-low-temperature valves are designed for temperatures below -100°C.
Lastly, by connection type: (1) Wafer-type butterfly valves are compact and fit between two flanges. (2) Flanged butterfly valves use flanges for connection, making them suitable for larger pipelines. (3) Bellows-sealed butterfly valves provide a leak-proof seal using a flexible bellows. (4) Welded butterfly valves are permanently connected through welding, ideal for high-purity or hazardous applications.
Each classification helps in selecting the most appropriate butterfly valve for a given system, ensuring optimal performance, safety, and longevity.
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