There are significant differences between eccentric butterfly valves and concentric butterfly valves in terms of structure, working principle, performance characteristics and application areas.
1. Structural differences
Concentric butterfly valve: Its structural characteristics are that the valve stem axis, butterfly plate center and body center are in the same position. This design allows the butterfly plate to rotate around the central axis when the valve is opened and closed, and the contact surface between the butterfly plate and the valve seat is relatively fixed.
Eccentric butterfly valve: Compared with the concentric butterfly valve, the valve stem of the eccentric butterfly valve deviates from the valve seat center. This design can be single eccentric (the valve stem axis deviates from the butterfly plate center), double eccentric (the valve stem axis deviates from both the butterfly plate center and the body center), or even triple eccentric (on the basis of double eccentricity, the conical axis of the butterfly plate sealing surface is also deviated from the body cylindrical axis). These eccentric designs are intended to improve the sealing performance of the valve and reduce wear.
2. Differences in working principles
Concentric butterfly valve: Due to structural limitations, there is always squeezing and scraping between the butterfly plate and the valve seat during the opening and closing process of the concentric butterfly valve, which will cause greater resistance and faster wear. In order to make up for this shortcoming, the valve seat of the concentric butterfly valve is usually made of elastic materials such as rubber or polytetrafluoroethylene, but the use of these materials is limited by temperature.
Eccentric butterfly valve: Through the eccentric design, the eccentric butterfly valve can reduce or eliminate the extrusion and scraping between the butterfly plate and the valve seat during opening and closing. Especially the double eccentric and triple eccentric butterfly valves, they can quickly separate the butterfly plate from the valve seat when opening, thereby significantly reducing the opening resistance and wear. This design not only improves the sealing performance of the valve, but also extends the service life of the valve.
3. Differences in performance characteristics
Concentric butterfly valve:
Advantages: simple structure, easy manufacturing, and low flow resistance.
Disadvantages: The butterfly plate and the valve seat are always in a state of extrusion and scraping, with large resistance and fast wear; the sealing material is limited by temperature and is not resistant to high temperature.
Eccentric butterfly valve:
Advantages: reliable sealing performance, strong corrosion resistance, and long service life; can reduce or eliminate the extrusion and scraping between the butterfly plate and the valve seat, reduce opening resistance and wear; suitable for high temperature and high pressure occasions.
Disadvantages: Compared with concentric butterfly valves, the structure is more complex and the manufacturing cost may be slightly higher.
4. Differences in application fields
Concentric butterfly valve: Due to its simple structure and low flow resistance, concentric butterfly valves are widely used in petrochemical, chemical, water treatment, food manufacturing, medicine and other industries, mainly used for interception and regulation of pipeline media.
Eccentric butterfly valve: Due to its advantages in sealing performance, corrosion resistance, service life and high temperature and high pressure adaptability, eccentric butterfly valves are widely used in medium and low pressure, large diameter pipelines and high temperature and high pressure occasions, such as water supply, drainage, electricity, metallurgy and other industries.
