The eccentric butterfly valve is a type of butterfly valve that achieves performance improvement through the geometric center deviation design of the valve stem axis and the sealing surface. Its core features and classification are as follows:
Core structural features
Eccentric design principle
The valve stem axis deviates from the center of the butterfly plate, the center of the valve body or the center of the sealing surface, and the opening and closing friction is reduced by the offset.
Typical eccentric modes include single eccentric, double eccentric and triple eccentric, and the offset dimension increases step by step.
Classification and technological evolution
1. Single eccentric butterfly valve
Structure: Only the valve stem axis deviates from the center of the butterfly plate (eccentricity A).
Advantage: Disperse the stress of the sealing surface and reduce extrusion wear (20% lower torque than concentric butterfly valve).
Limitation: There is still scratching on the sealing surface, suitable for medium and low pressure conditions (PN≤1.6MPa).
2. Double eccentric butterfly valve
Structure: The valve stem deviates from the center of the butterfly plate and the center of the valve body at the same time (eccentricity A+B).
Advantages: The butterfly plate quickly leaves the valve seat during opening and closing, friction is reduced by 80%, and metal sealing is supported (temperature resistance ≤200℃).
Limitations: The seal depends on the position accuracy, and micro leakage is easy to occur under high pressure conditions.
3. Triple eccentric butterfly valve
Structure: Add the sealing surface cone angle offset (β angle) on the basis of double eccentricity.
Advantages:
Zero friction opening and closing: There is no contact wear between the butterfly plate and the valve seat throughout the whole process; High pressure sealing: Line contact elastic seal (pressure resistance PN16~PN40, temperature resistance 425~600℃);
Bidirectional zero leakage: The medium pressure in the main sealing direction enhances the seal, and the reverse direction is compensated by torque compression.
Breakthrough in sealing technology
Material adaptation
Soft seal: EPDM/PTFE valve seat is used for corrosive media (pH 0~14);
Metal hard seal: Overlaying carbide (Stellite 6), resistant to particle erosion and high temperature corrosion.
Structural Innovation
The inclined cone sealing surface evenly distributes stress, and the sealing pressure ratio is increased by 3 times;
The multi-layer elastic valve ring design compensates for thermal deformation (applicable to sudden temperature changes of ±200℃).