I. central butterfly valve
The structure of the butterfly valve is characterized in that the stem axis, the butterfly plate centre and the body centre are in the same position. Simple structure and convenient manufacture. The common rubber lined butterfly valve belongs to this type. The disadvantage is that the butterfly plate and valve seat are always in the state of extrusion, scraping, large resistance distance and fast wear. In order to overcome extrusion, scraping, ensure sealing performance, the valve seat is basically made of rubber or polytetrafluoroethylene and other elastic materials, but it is also limited by temperature in use, which is why people traditionally think that butterfly valves are not resistant to high temperature.
II. Single eccentric butterfly valve
In order to solve the extrusion problem between the butterfly plate and the valve seat of the concentric butterfly valve, a single eccentric butterfly valve is produced. Its structural feature is that the valve stem axis deviates from the butterfly plate centre, so that the upper and lower ends of the butterfly plate no longer become the rotation axis, and the butterfly plate is scattered, and the excessive extrusion between the upper and lower ends of the butterfly plate and the valve seat is reduced.
III. double eccentric butterfly valve
The structure of the double eccentric butterfly valve is characterized in that the axis of the valve rod deviates from both the centre of the butterfly plate and the centre of the body. Its effect enables the butterfly plate to break away from the valve seat immediately after the valve is opened, greatly eliminating the unnecessary over extrusion and scraping between the butterfly plate and the valve seat, reducing the opening distance, reducing the wear and improving the valve seat life. At the same time, the double eccentric butterfly valve can also use the metal seat, which improves the application of butterfly valve in the field of high temperature.
IV. three eccentric butterfly valves
To withstand high temperature, the hard seal must be used, but the leakage is large; to zero leakage, the soft seal must be used, but not high temperature. In order to overcome the contradiction of double eccentric butterfly valve, the third eccentric of butterfly valve was carried out. The structure is characterized in that the conical axis of the sealing surface of the butterfly plate deviates from the cylinder axis of the body when the shaft axis of the double eccentric valve rod is eccentric, that is to say, after the third eccentric, the sealing section of the butterfly plate is no longer true circle, but ellipse and the sealing surface shape is also asymmetric because of this, one side is inclined to the centre line of the body, the other side is parallel to the centerline of the body.
The third eccentricity is characterized by fundamentally changing the sealing structure, no longer position sealing, but torque sealing, that is, it does not rely on the elastic deformation of the valve seat, but completely relies on the contact surface pressure of the valve seat to achieve the sealing effect, so it solves the problem of zero leakage of the metal valve seat at one stroke, and because the contact surface pressure is proportional to the medium pressure, high pressure and high-temperature resistance is also facing the edge And solution.
As a manufacturer of the fluid control valve, Zhengfeng valve has not only won the trust of customers but also continuously reflected the enterprise value. China control valve is a hot industrial product, which is widely used in various industries, such as power plants, chemical plants, food and pharmaceutical plants and steel plants.