Difference between triple eccentric butterfly valve and double eccentric butterfly valve
Time: October 31, 2020 13:28:42 Source: Yonglong Valve Reading: zero second
Difference between triple eccentric butterfly valve and double eccentric butterfly valve
The difference between the triple eccentric butterfly valve and double eccentric butterfly valve
butterfly valve
Foreign name: Trieccentric butterfly valve
The sealing performance of the traditional hard seal butterfly valve is not guaranteed, and the leakage is large. In order to change this situation, the hard seal butterfly valve has been reformed many times, and the three eccentric butterfly valve was born. Three eccentric butterfly valve is characterized by overlaying high-temperature and corrosion-resistant alloy materials on the sealing surface layer of the valve seat, and fixing multi-layer soft laminated seal rings on the butterfly plate. This process makes the three eccentric butterfly valve more resistant to high-temperature and high-pressure environment and corrosion than traditional butterfly valve products.
Specifically, the advantages of the three eccentric structure of the hard seal butterfly valve are:
The unique design of triple eccentric makes the metal hard seal more labor-saving. When the valve is opened and closed, there is no friction between the butterfly plate and the valve body during rotation. When the valve is closed, the torque of the transmission mechanism increases to provide a compensation seal, greatly improving the sealing performance of the triple eccentric butterfly valve, and extending the service life of the butterfly valve.
What are the three eccentricities of the three eccentric butterfly valve
The first eccentricity is that the valve shaft is located behind the valve plate shaft, so that the seal can completely and tightly surround the whole valve seat.
The second eccentricity is that the center line of the valve shaft deviates from the center line of the pipeline and the valve to avoid interference from the opening and closing of the valve.
The third eccentricity is that the cone shaft of the valve seat deviates from the center line of the valve shaft, which can eliminate friction during closing and opening, and achieve uniform compression sealing effect around the entire valve seat.
Difference between triple eccentric butterfly valve and double eccentric butterfly valve
1. 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 was created. Its structural feature is that the stem axis deviates from the center of the butterfly plate, so that the upper and lower ends of the butterfly plate no longer become the rotation axis, which disperses, and reduces the excessive extrusion between the upper and lower ends of the butterfly plate and the valve seat. However, due to the scratch phenomenon between the butterfly plate and the valve seat during the whole valve opening and closing process of the single eccentric structure, the application scope is similar to that of the concentric butterfly valve, so it is seldom used.
2. Double eccentric butterfly valve
Based on the single eccentric butterfly valve, the widely used double eccentric butterfly valve is further improved butterfly valve 。 The structure feature is that the shaft center of the valve stem deviates from both the center of the butterfly plate and the center of the body. The effect of double eccentricity enables the butterfly plate to quickly disengage from the valve seat after the valve is opened, greatly eliminating unnecessary excessive extrusion and scraping between the butterfly plate and the valve seat, reducing the opening resistance, reducing wear, and improving the service life of the valve seat. At the same time, the double eccentric butterfly valve can also use metal seat, which improves the application of butterfly valve in high-temperature field. However, because its sealing principle belongs to the position sealing structure, that is, the sealing surface of the butterfly plate and the valve seat is in line contact, and the elastic deformation caused by squeezing the valve seat through the butterfly plate produces a sealing effect, so the requirements for the closing position are very high (especially the metal valve seat), and the pressure bearing capacity is low, which is why people traditionally believe that butterfly valves are not resistant to high pressure and have large leakage.
High temperature resistance, hard sealing must be used, but the leakage is large; To achieve zero leakage, soft sealing must be used, but it is not resistant to high temperature. In order to overcome the contradiction of double eccentric butterfly valve, the butterfly valve was eccentric for the third time. The structural feature is that the conical axis of the sealing surface of the butterfly plate is inclined to the cylinder axis of the body while the position of the double eccentric valve stem axis is eccentric, that is, after the third eccentric, the sealing section of the butterfly plate is no longer true circle, but ellipse, and the shape of its sealing surface is also asymmetric, one side is inclined to the center line of the body, and the other side is parallel to the center line of the body. The biggest feature of this third eccentricity is that it has fundamentally changed the sealing structure. It is no longer a position seal, but a torque seal, 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. Therefore, it has solved the problem of zero leakage of metal valve seats at one stroke, and because the contact surface pressure is proportional to the medium pressure High pressure and high temperature resistance can be easily solved.
Triple eccentric butterfly valve is a kind of high-performance butterfly valve, which has been applied in many fields at present, and even has replaced gate valve, globe valve, ball valve and other products in some fields.
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