8 Classifications of Butterfly Valves

There are many types of butterfly valves, and their advantages are obvious. They are often used to control various types of fluids such as water, gas, steam, various corrosive media, mud, oil, liquid metal and radioactive media. They are mainly used for cutting off pipes and throttling.

This article mainly introduces the 8 classifications of butterfly valves so that everyone can judge whether they are suitable for their own use based on the characteristics of each category.

 01 According to the connection 
1. Wafer butterfly valve
The butterfly plate of the wafer butterfly valve is installed in the diameter direction of the pipe, and the valve is in a fully open state. Wafer butterfly valve has simple structure, small size and light weight. Butterfly valves have two sealing forms: elastic sealing and metal sealing. For elastic sealing valves, the sealing ring can be embedded in the valve body or attached to the periphery of the butterfly plate.

2. Flange butterfly valve
The flange butterfly valve has a vertical plate structure, and the valve stem is an integral metal hard seal. The sealing ring of the valve is a composite structure of flexible graphite plate and stainless steel plate, which is installed on the valve body. The sealing of the butterfly plate is overlay welded with stainless steel. The sealing ring of the soft seal valve is made of nitrile rubber and is installed on the butterfly plate.

3. Welded butterfly valve
Welded butterfly valve is a non-sealed butterfly valve, which is widely used in pipelines with medium temperature ≤300℃ and nominal pressure of 0.1 MPa in the production processes of building materials, metallurgy, mining, electric power, etc., to connect, open and close or adjust the medium quality. 

4. Threaded butterfly valve
Threaded butterfly valves refer to valves with internal or external threads on the valve body that are connected to the pipe threads.

5. Clamp butterfly valve
A reducer should be installed on the valve stem of the clamp butterfly valve to stop the butterfly plate at any position to improve the operating performance of the valve. The nominal diameter of the clamp butterfly valve is large and the valve body is made of carbon steel. Its cost is high and the valve plate The sealing ring uses a metal ring instead of a rubber ring.

 02 According to driving mode 
1. Electric butterfly valve
It uses electricity as the driving force and is composed of an electric actuator and a butterfly valve. Therefore, it is relatively less affected by temperature, pressure, and climate, but it is not suitable for working in humid conditions. It can be realized by driving the butterfly valve plate with an electric actuator. The opening and closing action has a larger action torque than ordinary butterfly valves. It is generally used in large-diameter pipelines and can also be used for the control and regulation of water, air, mud, oil, and corrosive media.

2. Manual butterfly valve
Manual butterfly valves include handle butterfly valves and turbine butterfly valves. The manual butterfly valve has a simple structure, small size and light weight, and consists of only a few parts. Moreover, it only needs to be rotated 90° to quickly open and close, which is simple to operate. At the same time, the valve has good fluid control characteristics.

3. Pneumatic butterfly valve
Using compressed air as the driving force, it is composed of a pneumatic actuator and a butterfly valve. It is relatively small in size and light in weight. When installing the pneumatic butterfly valve, you can choose accessories, such as pressure reducing valves, solenoid valves, limit switches, etc., which are better than electric butterfly valves. Butterfly valves act and respond faster.

Pneumatic butterfly valves are generally used in small-diameter pipelines and can also be used to control gas, air, water, oil, mud, and corrosive media.
 

4. Hydraulic butterfly valve
The 0.5-second hydraulically controlled quick-closing valve, also known as the 0.5-second electro-hydraulic quick-closing valve, is mainly used in high-safety systems such as steam turbine extraction pipelines and blast furnace gas residual pressure power generation devices (TRT), as well as in seawater, sewage, smoke and other media. It is used as an emergency shut-off valve on industrial pipeline networks such as gas, air, and oil products.

 03 According to sealing material 
1. Soft seal butterfly valve
The sealing pair is composed of a non-metal soft material and a non-metal soft material or a metal hard material and a non-metal soft material. Commonly used materials include ordinary nitrile rubber, fluorine rubber, wear-resistant EPDM rubber, anti-corrosion polytetrafluoroethylene, UPVC, etc. The sealing performance of soft-sealed butterfly valves is better than that of hard-sealed butterfly valves.

2. Hard seal butterfly valve
The sealing pair is composed of metal hard materials on metal hard materials. It is mainly used in high-temperature and high-pressure working conditions. The commonly used material is STL alloy surfacing.

 04 According to sealing form 
1. Forced sealing butterfly valve
Including elastic sealing butterfly valves (the sealing specific pressure is generated by the valve plate extruding the valve seat when the valve is closed, and the elasticity of the valve seat or valve plate) and applied torque sealing butterfly valves (the sealing specific pressure is generated by the torque applied to the valve shaft).

2. Pressurized sealed butterfly valve
The sealing specific pressure is generated by the charging of elastic sealing elements on the valve seat or valve plate.

3. Automatic sealing butterfly valve
The sealing specific pressure is automatically generated by the medium pressure.

 05 According to structural form 
1. Concentric butterfly valve (center line butterfly valve)
Concentric butterfly valves (centerline butterfly valves) generally use soft seals. The structural characteristics of concentric butterfly valves are that the valve stem axis, butterfly plate center, and body center are at the same position. The structure is simple and easy to manufacture.

The disadvantage is that the butterfly plate and valve seat are always in a state of extrusion and scratching, with large resistance and rapid wear. In order to overcome extrusion and scratching and ensure sealing performance, the valve seat is basically made of elastic materials such as rubber or polytetrafluoroethylene. But it is also subject to temperature restrictions when in use.

2. Single eccentric butterfly valve
The single eccentric butterfly valve uses a hard seal. 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 center of the butterfly plate, so that the upper and lower ends of the butterfly plate are It no longer becomes the axis of rotation, dispersing and reducing excessive extrusion between the upper and lower ends of the butterfly plate and the valve seat.

However, due to the single eccentric structure, the scratching phenomenon between the butterfly plate and the valve seat does not disappear during the entire switching process of the valve. Its application scope is similar to that of the concentric butterfly valve, so it is not widely used.

3. Double eccentric butterfly valve
The double eccentric butterfly valve is further improved on the basis of the single eccentric butterfly valve and is currently the most widely used.

Its structural feature is that the axis of the valve stem is deviated from the center of the butterfly plate and the center of the body. The double eccentric effect enables the butterfly plate to quickly separate from the valve seat after the valve is opened, greatly eliminating unnecessary excessive extrusion and scratching between the butterfly plate and the valve seat, reducing the opening resistance, reducing wear, and improving improves valve seat life. The scratching is greatly reduced, and the double eccentric butterfly valve can also use a metal valve seat, which improves the application of butterfly valves in high temperature fields.

The sealing principle of the double eccentric butterfly valve is a positional 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 the butterfly plate squeezing the valve seat produces a sealing effect, so the closing position is very demanding, especially Metal valve seat, low pressure bearing capacity.

4. Triple eccentric butterfly valve
In order to overcome the contradiction of the double eccentric butterfly valve, the butterfly valve was eccentric for the third time. Its structural feature is that while the axial position of the double-eccentric valve stem is eccentric, the conical axis of the butterfly plate sealing surface is deflected from the body cylinder axis. That is to say, after the third eccentricity, the sealing section of the butterfly plate does not change. It is not a true circle, but an ellipse, and the shape of its sealing surface is therefore asymmetrical. 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 the triple eccentric butterfly valve is that it fundamentally changes the sealing structure. It is no longer a position seal, but a torsion 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.

The triple eccentric butterfly valve is currently the best-performing valve. It has the excellent sealing performance of a soft-sealed butterfly valve and the high-temperature, high-pressure, and corrosion-resistant characteristics of a hard-sealed butterfly valve.

 06 According to work pressure 
1. Vacuum butterfly valve
Butterfly valve with nominal pressure lower than standard atmospheric pressure.

2. Low pressure butterfly valve
Butterfly valve with nominal pressure PN<1.6MPa.

3. Medium pressure butterfly valve
Butterfly valve with nominal pressure PN of 2.5--6.4MPa.

4. High-pressure butterfly valve
Butterfly valve with nominal pressure PN of 10.0--80.0MPa.

5. Ultra-high pressure butterfly valve
Butterfly valve with nominal pressure PN>100MPa.

 07 According to operating temperature 
1. High temperature butterfly valve
Butterfly valve with working temperature: t>450 ℃.

2. Medium temperature butterfly valve
Butterfly valve with working temperature: 120℃<t<450℃.

3. Normal temperature butterfly valve
Butterfly valve with operating temperature: -40℃<t<120℃.

4. Low temperature butterfly valve
Butterfly valve with operating temperature: -100℃<t<-40℃.

5. Ultra-low temperature butterfly valve
Butterfly valve with working temperature: t<-100℃.

 08 According to valve body material 
1. Ordinary materials: Ductile iron, cast steel (carbon steel)

2. Stainless steel material: SUS304, SUS316, SUS316L

3. Anti-corrosion and other special materials: UPVC, CPVC, PTFE

The above is a comprehensive introduction to butterfly valves. Fleyenda Flow hopes it will provide some guidance for you when purchasing products.