1) Butterfly valve is a kind of valve that opens, closes and adjusts the fluid passage by reciprocating about 90 degrees with a disc type opening and closing member . The butterfly valve is not only simple in structure, small in size, light in weight, low in material consumption, small in installation size, small in driving torque, easy to operate and fast, and also has good flow control function and closed sealing characteristics. One of the years to develop zui fast valve varieties. Especially in the developed countries of the United States, Japan, Germany, France, Italy, etc., the use of butterfly valves is very extensive. The variety and quantity of the products are still expanding, and the development of high temperature, high pressure, large diameter, high sealing, long life, excellent regulation characteristics and multi-valve function, the reliability and other performance indicators are higher. Level and partial replacement of shut-off valves , gate valves and ball valves . With the advancement of butterfly valve technology. In the short-term foreseeable, especially in the field of large and medium-sized caliber, medium and low pressure, butterfly valves will become the dominant valve form.
The original butterfly valve is a simple, unclosed flapper valve. It is commonly used as a flow regulating valve and a damping valve in a water piping system .
With the application of chemically resistant synthetic rubber on butterfly valves, the performance of butterfly valves is improved. Synthetic rubber has the characteristics of corrosion resistance, erosion resistance, dimensional stability, good resilience, easy forming, low cost, etc., and can select different properties of synthetic rubber according to different use requirements to meet the working conditions of the butterfly valve. It is widely used in the manufacture of linings and elastomeric seats for butterfly valves.
Because polytetrafluoroethylene (PTFE) has strong corrosion resistance, stable performance, is not easy to age, has low friction coefficient, is easy to form, and is dimensionally stable, and can improve its comprehensive performance by filling and adding appropriate materials to obtain better strength. The butterfly valve sealing material with lower friction coefficient overcomes some limitations of synthetic rubber. Therefore, the polymer polymeric material represented by polytetrafluoroethylene and its filling modified material have been widely used in butterfly valves, thus making butterfly valves The performance has been further improved, and a butterfly valve with a wider temperature, a wider pressure range, a sealing performance and a longer service life has appeared.
In order to meet the requirements of industrial applications such as high and low temperature, strong erosion and long life, metal sealing butterfly valves have been greatly developed in the past decade. With the application of high temperature resistance, low temperature resistance, strong corrosion resistance, strong erosion resistance and high strength alloy materials in butterfly valves, metal sealing butterfly valves have been widely used in industrial fields such as high and low temperature, strong erosion and long life. Butterfly valves with large diameter (9750mm), high pressure (2.2kN/cm 2 ) and wide temperature range (-102～606°C) have emerged, which has brought the butterfly valve technology to a new level.
Due to the application of computer-aided design (CAD) and computer-aided manufacturing (CAM) and flexible manufacturing systems (FMS) in the valve industry, the design and manufacture of butterfly valves has reached a new level. Not only has the valve design and calculation method been completely innovated, but also the heavy and repetitive routine design work of professional technicians has been alleviated, so that the technicians have more energy to improve the technical performance of the product and the research and development of new products, shortening the cycle and improving the cycle. Labor productivity. Especially in the field of metal sealing butterfly valves, due to the application of CAD/CAM, a three-dimensional sealing pair designed by CAD and manufactured by cAM numerical control has appeared, so that the sealing surface of the valve does not have any extrusion, abrasion and wear during the opening and closing process. Thus, the sealing and service life of the butterfly valve are increased by orders of magnitude.
When the butterfly valve is fully open, it has a small flow resistance. When it is opened between about 15° and 70°, it can perform sensitive flow control. Therefore, in the field of large-diameter adjustment, the application of the butterfly valve is very common, and Gradually become the dominant valve type.
Due to the wiping nature of the butterfly valve plate, most butterfly valves can be used for media with suspended solid particles and can be used for powdered and granular media depending on the strength of the seal.
3.2.2 Classification of butterfly valves
There are many types of butterfly valves and there are many classification methods.
1. Classified by structure
(1) Center seal butterfly valve (2) Single eccentric sealing butterfly valve (3) Double eccentric sealing butterfly valve (4) Triple eccentric sealing butterfly valve
2. Classified by sealing surface material
(1) Soft sealing butterfly valve
1) The sealing pair is made of a non-metallic soft material to a non-metallic soft material.
2) The sealing pair is made of a metal hard material to a non-metallic soft material.
(2) Metal hard seal butterfly valve. The sealing pair is composed of a metal hard material and a metal hard material.
3. Classified by seal
(1) Forced sealing of the butterfly valve.
1) Elastic sealing butterfly valve. The sealing specific pressure is generated by the valve plate pressing the valve seat, the valve seat or the valve plate when the valve is closed.
2) External torque sealing butterfly valve. The seal specific pressure is generated by the torque applied to the valve shaft.
(2) Pressure sealing butterfly valve. The seal specific pressure is generated by the pressure of the elastomeric sealing element on the valve seat or valve plate.
(3) Automatic sealing butterfly valve. The seal specific pressure is automatically generated by the medium pressure.
4. Classified by work pressure
(1) Vacuum butterfly valve. Butterfly valves with a working pressure lower than the standard atmospheric pressure.
(2) Low pressure butterfly valve. Butterfly valve with nominal pressure PN ≤ 1.6MPa.
(3) Medium pressure butterfly valve. The nominal pressure PN is a butterfly valve of 2.5 ∽ 6.4 MPa.
(4) High pressure butterfly valve. The nominal pressure PN is 10.0 ∽ 80. OMPa butterfly valve.
(5) Ultra high pressure butterfly valve. Butterfly valve with nominal pressure PN>100MPa.
5. Classified by operating temperature
(1) High temperature butterfly valve. t>450 °C butterfly valve.
(2) Medium temperature butterfly valve. 120 ° C
6. Classified by connection
(1) wafer type butterfly valve (2) flange type butterfly valve
(3) Ear type butterfly valve (4) Welded butterfly valve
(2) Butterfly valve sealing principle - midline butterfly valve
Butterfly valve sealing principle
1. Sealing principle of the midline butterfly valve Figure 3-83 shows the typical sealing structure of the midline butterfly valve.
The sealing principle is that the sealing surface of the valve plate ensures that the sealing surface has a suitable surface roughness value, and the synthetic rubber valve seat forms a suitable surface roughness value of the sealing surface during the molding. When the valve is closed, the outer sealing surface of the valve plate is pressed against the synthetic rubber valve seat by the rotation of the valve plate, so that the synthetic rubber valve seat is elastically deformed to form an elastic force as a sealing specific pressure to ensure the sealing of the valve.
The seal of the door.
The sealing structure shown in Figure 3-84 uses a composite valve seat made of polytetrafluoroethylene and synthetic rubber. The characteristic is that the elasticity of the valve seat is still provided by synthetic rubber and utilizes the characteristics of low friction coefficient, non-wearing and aging, and the use of polytetrafluoroethylene as the sealing material of the valve seat, thereby improving the life of the butterfly valve. .
The sealing structure shown in Figure 3-85 uses a composite valve seat made of Teflon, synthetic rubber and phenolic resin to make the valve seat more elastic and stronger.
The sealing structure shown in Figure 3-86 is based on the sealing structure of Figure 3-84. The valve plate is completely covered with Teflon to make the butterfly valve corrosion-resistant.
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