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Butterfly valves are categorized based on various criteria, including structure, sealing materials, sealing method, working pressure, temperature range, and connection type. Here's a detailed overview:
1. **By Structure**
(1) **Center-Sealing Butterfly Valve**: The disc is centered relative to the valve body, providing a balanced seal.
(2) **Single-Eccentric Sealing Butterfly Valve**: The disc is offset slightly from the center, reducing friction during operation.
(3) **Double-Eccentric Sealing Butterfly Valve**: Features two offsets, improving sealing performance and reducing wear.
(4) **Triple-Eccentric Sealing Butterfly Valve**: Offers superior sealing and minimal leakage, ideal for high-pressure applications.
2. **By Sealing Material**
(1) **Soft-Seal Butterfly Valve**:
1) Sealing surfaces are made of non-metallic soft materials.
2) One side is metal, while the other is soft material.
(2) **Metal-Seal Butterfly Valve**: Both sealing surfaces are made of hard metallic materials, suitable for high-temperature or corrosive environments.
3. **By Sealing Method**
(1) **Forced Seal Butterfly Valve**:
1) **Elastomeric Seal**: Sealing is achieved by compressing the seat against the disc using flexibility.
2) **Torque Seal**: Sealing force is applied via the torque of the valve shaft.
(2) **Pressure Seal Butterfly Valve**: Sealing is generated by the elastic components of the seat or disc.
(3) **Automatic Seal Butterfly Valve**: Sealing pressure is automatically created by the media pressure inside the system.
4. **By Working Pressure**
(1) **Vacuum Butterfly Valve**: Designed for pressures below atmospheric.
(2) **Low-Pressure Butterfly Valve**: Nominal pressure PN < 1.6 MPa.
(3) **Medium-Pressure Butterfly Valve**: Nominal pressure PN between 2.5–6.4 MPa.
(4) **High-Pressure Butterfly Valve**: Nominal pressure PN between 10.0–80.0 MPa.
(5) **Ultra-High-Pressure Butterfly Valve**: Nominal pressure PN > 100 MPa.
5. **By Working Temperature**
(1) **High-Temperature Butterfly Valve**: Operating temperature t > 450°C.
(2) **Medium-Temperature Butterfly Valve**: Operating temperature between 120°C and 450°C.
(3) **Normal-Temperature Butterfly Valve**: Operating temperature between -40°C and 120°C.
(4) **Low-Temperature Butterfly Valve**: Operating temperature between -100°C and -40°C.
(5) **Ultra-Low-Temperature Butterfly Valve**: Operating temperature t < -100°C.
6. **By Connection Type**
(1) **Wafer-Type Butterfly Valve**: Installed between two flanges.
(2) **Flanged Butterfly Valve**: Connected via flanges for easy installation and maintenance.
(3) **Bellows-Sealed Butterfly Valve**: Uses a flexible bellows to prevent leakage.
(4) **Welded Butterfly Valve**: Directly welded into the pipeline for permanent sealing.
This classification helps in selecting the appropriate butterfly valve for specific applications, ensuring optimal performance, safety, and longevity.