The structural feature of the concentric butterfly valve is that the valve stem axis, disc center, and body center are at the same position. The structure is simple and easy to manufacture. In order to overcome extrusion and scratching, the sealing seat is basically made of elastic materials such as rubber or PTFE, but it is also subject to temperature restrictions in use. This is why butterfly valves are traditionally considered not to be resistant to high temperatures.
Eccentric butterfly valves can also be subdivided into single eccentric butterfly valves, double offset butterfly valves and triple offset butterfly valves according to different structural forms.
The main structural feature of the single eccentric butterfly valve is that the center line of the stem deviates from the center line of the sealing surface, so that the upper and lower ends of the disc no longer become the axis of rotation, which disperses and reduces the excessive extrusion between the upper and lower ends of the disc and the seat. However, its The effect is not ideal.
Double offset butterfly valves have two offsets. They are that the stem deviates from the sealing surface area and the axis of the stem deviates from the channel center. The double eccentricity allows the butterfly plate to quickly separate from the valve seat after the valve is opened, greatly reducing excessive extrusion and scratching between the disc and the seat, reducing the opening torque, reducing wear, and significantly extending the life of the valve seat.
Triple offset butterfly valves have three offsets. Based on the double eccentric butterfly valve, the conical axis of the sealing surface deviates from the cylindrical axis of the body, and has a unique inclined cone sealing structure. Its biggest advantage is that it fundamentally changes the sealing structure. It is no longer a position seal, but a torque seal, that is, it completely relies on the contact surface pressure of the valve seat to achieve the sealing effect and achieve zero leakage, and the contact surface pressure is proportional to the medium pressure. The valve body and disc are made of high-strength metal materials, so they are resistant to high temperatures and high pressures.