1. Concentric Butterfly Valve:
Structural Definition: The axis of rotation of the valve disc coincides perfectly with both the center of the valve body and the center of the valve disc itself.
Sealing and Friction Characteristics: During the opening and closing process, the edge of the valve disc remains in constant friction with the sealing surface throughout the entire stroke. This makes the sealing surface prone to wear, resulting in a shorter service life; furthermore, the high frictional resistance necessitates a higher operating torque for opening and closing.
Applications:
Suitable for low-pressure, normal-temperature media where sealing requirements are not particularly stringent-such as general tap water pipelines, HVAC water systems, etc.
2. Double-Eccentric Butterfly Valve:
Definition: Building upon the single-eccentric design, a second eccentricity is introduced-the valve stem is offset from the center of the valve body's sealing surface.
Sealing and Friction Characteristics: The two eccentricities work in tandem to ensure that the valve disc completely disengages from the sealing surface throughout the entire opening and closing process, thereby achieving "zero friction." The double-eccentric structure features a "tighter-as-it-closes" sealing function.
Applications:
Conditions requiring specific sealing performance, such as urban low-pressure gas distribution networks, wastewater treatment plants, and the handling of normal-temperature clean fluids in the food and pharmaceutical industries.
3. Triple-Eccentric Butterfly Valve:
Definition: Building upon the double-eccentric design, a third eccentricity is introduced-the metal sealing surface of the valve disc is angled relative to the geometric plane of the disc itself.
Sealing and Friction Characteristics:
It retains the advantage of the double-eccentric design-"zero friction throughout the entire opening and closing process." When fully closed, the angled sealing surface forms a "wedge-fit" with the valve body's sealing surface, thereby achieving a "metal-to-metal hard seal."
Applications:
Severe operating conditions, such as high-temperature steam pipelines in power plants, chemical pipelines for acid and alkali transport, long-distance oil and gas transmission pipelines, and hot oil pipelines in refineries.
