The offset of a butterfly valve is not a fixed value, but varies according to its structural type (such as single eccentric, double eccentric, triple eccentric) and design parameters (such as valve body size, sealing form)
1. Single eccentric butterfly valve
Offset definition: There is an eccentric distance between the valve stem axis and the valve plate sealing surface.
Function: Reduce the friction between the valve plate and the valve seat during opening and closing, and extend the service life.
Offset range: Usually small, the specific value depends on the design requirements, generally between a few millimeters and more than ten millimeters.
2. Double eccentric butterfly valve
Offset definition: On the basis of single eccentricity, an eccentric distance is added between the valve stem axis and the valve body channel axis.
Function: Further reduce the friction between the valve plate and the valve seat, improve the sealing performance, and is suitable for medium and high pressure conditions.
Offset range: Usually larger than the single eccentric butterfly valve, the specific value is determined by the design parameters, and may be between more than ten millimeters and tens of millimeters.
3. Triple eccentric butterfly valve
Offset definition: On the basis of double eccentricity, an angle eccentricity is added between the valve plate sealing surface and the valve body channel axis.
Function: To achieve zero friction between the valve plate and the valve seat when closed, suitable for high temperature, high pressure, and large diameter working conditions.
Offset range: The offset is the largest, and the specific value is determined by the design parameters, which may be between tens of millimeters and hundreds of millimeters.
4. Factors affecting the offset
Valve body size: The larger the valve body diameter, the larger the offset may be.
Sealing form: The offset of metal-sealed butterfly valves is usually larger than that of soft-sealed butterfly valves.
Working condition requirements: High pressure, high temperature, and large diameter working conditions require a larger offset.
5. Design principles of offset
Minimize friction: Through offset design, the friction between the valve plate and the valve seat during opening and closing is minimized.
Ensure sealing: The offset needs to match parameters such as the sealing surface angle and material elasticity to ensure sealing performance.
Structural strength: The offset design needs to consider the strength and rigidity of components such as the valve body and valve stem.
6. Measurement and verification of offset
Design phase: Verify the rationality of the offset through CAD modeling and finite element analysis (FEA).
Manufacturing phase: Use equipment such as coordinate measuring machines (CMM) to detect the machining accuracy of valve stems, valve plates and other components.
