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Double offset butterfly valve design

Author:Site Editor     Publish Time: 2018-12-17      Origin:Site

The two eccentricities of the double offset butterfly valve refer to the eccentricity of the rotating center line of the disc and the eccentricity of the sealing line and the eccentricity of the center line of rotation of the disc and the center line of the channel.

 

Here is the content list:

  • How to optimize structure of butterfly valve?

  • What is principle of double offset butterfly valve?

  • What leads to butterfly valve seal leakage?

  • What is structure design of butterfly valve?

 

 

How to optimize structure of valve?

Triple offset butterfly valve plate can be detached from the valve seat instantaneously, eliminating the scraping phenomenon caused by the pressing of the butterfly plate and the valve seat, and simultaneously reducing the opening and closing torque and improving the sealing performance. The butterfly valve sealing is a line contact seal, and the elastic deformation caused by the butterfly plate pressing the metal seat sealing ring produces a sealing effect. When the medium pressure acts, if the deformation of the seat seal is not uniform or small, the butterfly plate and the valve seat may be separated or the seal pressure between the butterfly plate and the seat seal may be insufficient, resulting in seal failure, so the valve deformation control of the seat seal is very high when closed. The butterfly valve caused by the deformation of the sealing ring cannot realize the problem of two-way sealing, and the structure of the valve seat sealing ring is optimized.

 

What is principle of double offset butterfly valve?

The sealing principle of the double offset butterfly valve is that the butterfly valve can be sealed when the actual sealing specific pressure generated between the butterfly plate and the valve seat is greater than the required sealing specific pressure. The seal specific pressure is determined by the amount of elastic deformation generated by the valve seat. The cross-sectional shape of the butterfly seal's metal seal seat and disc seal is circular. Because the area of the medium acting on the valve seat is only the arc segment of the valve seat, the force arm is short and the amount of elastic deformation is small. The valve seat and the butterfly plate can only form a reliable seal when the medium pressure difference is low. For the pressure test of the butterfly valve of DN250, when the medium flow direction is positive and the medium pressure difference is greater than 0.3MPa, the valve will produce obvious visible leakage. When the flow direction of the medium is reversed and the pressure difference of the medium is greater than 0.8 MPa, the butterfly valve cannot be sealed again after one switch, and the valve seat has plastic deformation.

 

What leads to butterfly valve seal leakage?

The problem of seal leakage under the high-pressure difference of the butterfly valve is analyzed. Since the butterfly plate is mounted on the valve stem (the valve stem is equivalent to the simple support beam), when the medium pressure is positively applied to the butterfly plate, the force received by the butterfly plate is transmitted to the valve stem, and the valve stem will be Produces elastic deformation. At the same time, the butterfly plate also elastically deforms due to the action of the medium pressure, and the elastic deformation of the valve seat is smaller than the elastic deformation generated by the butterfly plate and the valve stem, resulting in a decrease in the sealing specific pressure formed between the butterfly plate and the valve seat. . When the actual seal specific pressure is less than the required seal specific pressure, the butterfly valve cannot achieve sealing. When the medium pressure acts on the butterfly plate in reverse, the amount of elastic deformation generated by the disc and the valve stem is greater than the limit of the elastic deformation of the valve seat. At this point, the actual seal specific pressure is greater than the allowable seal specific pressure, resulting in plastic deformation of the valve seat.

 

What is structure design of butterfly valve?

In the case that the butterfly valve cannot be used for medium pressure difference, the valve seat is designed to have a high resilience structure, which improves the sealing performance of the disc and the valve seat, and can achieve good even if the pressure of the flowing medium is increased. Compared with the triple offset butterfly valve, the valve has low processing cost, good economic efficiency and two-way sealing function. When the medium is flowing forward, under the pressure of the medium, the long arc segment of the valve seat generates a rotation torque around the root of the valve seat. Due to the long arm of the new valve seat, a large elastic deformation can be generated, and the deformation is increased. The fit area and the fit between the disc and the disc increase the sealing performance between the seat and the disc. The greater the medium pressure, the greater the seal pressure between the seat and the disc, and the better the sealing performance. When the medium flows in the opposite direction, the medium causes the disc to elastically deform. At this time, the disc presses the long arc segment of the valve seat, and the long arc segment of the valve seat is pressed around the root of the valve seat under the pressure of the disc and the medium.

 

When it comes to the front rotation moving, the front end of the long arc segment of the valve seat will resist the end cover groove, and at the same time, a certain elastic deformation will be generated, which increases the elastic deformation range of the valve seat and improves the sealing performance between the valve seat and the butterfly plate. Our valves use domestic leading technology, welcome customers from everywhere to buy.


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