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Butterfly valve, also known as flap valve, is a simple structure control valve, and can also be used for switching control of low pressure pipeline media. Butterfly valve refers to a valve whose closing member (valve flap or butterfly plate) is a disk that rotates around the valve shaft to achieve opening and closing. It mainly plays a cutting and throttling role in pipelines. The butterfly valve opening and closing member is a disc shaped butterfly plate that rotates around its own axis within the valve body to achieve the purpose of opening and closing or adjusting. Butterfly valves are applicable to pipelines conveying various corrosive and non corrosive fluid media in engineering systems such as generators, gas, natural gas, liquefied petroleum gas, urban gas, hot and cold air, chemical smelting, power generation, and environmental protection, and are used to regulate and cut off the flow of media. Butterfly valves are classified as: handle butterfly valves, turbine butterfly valves, pneumatic butterfly valves, electric butterfly valves, etc.
Basic Introduction
Butterfly valve: also known as electric butterfly valve
Definition: A valve whose opening and closing parts are disc shaped butterfly plates and can rotate around the axis of the valve body.
Structure: mainly composed of valve body, valve rod, butterfly plate and sealing ring. The valve body is cylindrical, with a short axial length and a built-in butterfly plate.
Working principle: The butterfly plate is driven by the valve rod. If it is rotated through 90 °, it can be opened and closed once. By changing the deflection angle of the butterfly plate, the flow rate of the medium can be controlled.
Operating conditions and media
Butterfly valves are applicable to pipelines conveying various corrosive and non corrosive fluid media in engineering systems such as generators, gas, natural gas, liquefied petroleum gas, urban gas, cold and hot air, chemical smelting, power generation, environmental protection, building water supply and drainage, etc., and are used to regulate and cut off the flow of media.
Functional purpose
"Butterfly valve" refers to a valve whose closure piece (valve flap or butterfly plate) is a disk that rotates around the valve shaft to achieve opening and closing. It mainly serves as a cutoff and throttling function on pipelines. The butterfly valve opening and closing member is a disc shaped butterfly plate that rotates around its own axis within the valve body to achieve the purpose of opening and closing or adjusting. The butterfly valve is usually less than 90 ° from full opening to full closing. The butterfly valve and the butterfly rod themselves have no self-locking ability. In order to position the butterfly plate, a worm gear reducer should be installed on the valve rod. The use of a worm gear reducer not only enables the butterfly plate to have self-locking ability, stop the butterfly plate at any position, but also improves the operational performance of the valve. Industrial butterfly valves are characterized by high temperature resistance, high applicable pressure range, and large nominal diameter. The valve body is made of carbon steel, and the sealing ring of the valve plate uses metal rings instead of rubber rings. Large high-temperature butterfly valves are manufactured by welding steel plates, and are mainly used for flue gas ducts and gas pipelines for high-temperature media.
Electric adjustment type
Electric regulating butterfly valve belongs to a variety of electric valves and electric regulating valves. The main connection methods are flange type and wafer type. It is an important execution unit in the field of industrial automation control.
Two main analysis points for the installation of electrically regulated butterfly valves:
1) The installation position, height, and inlet and outlet directions must meet the design requirements. Note that the direction of medium flow should be consistent with the arrow direction marked on the valve body, and the connection should be firm and tight.
2) Appearance inspection must be conducted before installation of electrically regulated butterfly valves. The nameplate of the valve should comply with the current national standard "General Purpose Valve Signs" GB12220. For valves with a working pressure greater than 1.0MPa and having a cutoff effect on the main pipe, strength and tightness tests should be conducted before installation. Only qualified products can be used. During the strength test, the test pressure shall be 1.5 times the nominal pressure, and the duration shall not be less than 5min. The valve shell and filler shall be free of leakage, which is considered qualified. Electric regulating butterfly valves can be divided into offset plate type, vertical plate type, inclined plate type, and lever type according to their structural forms. According to the sealing form, it can be divided into two types: soft sealing type and hard sealing type. The soft seal type generally adopts rubber ring seal, while the hard seal type usually adopts metal ring seal.
Selection rules
Stem diameter: for multi rotary rising stem valves. Cannot be assembled into an electric valve. Therefore, if the large valve stem diameter allowed by the electric butterfly valve device cannot pass through the valve stem of the equipped valve. The inner diameter of the hollow output shaft of the electric device must be greater than the outer diameter of the stem of the rising stem valve. For non rising stem valves in partial rotary valves and multi rotary valves, although the passage of the valve stem diameter is not considered, full consideration should also be given to the valve stem diameter and keyway dimensions when selecting and matching to ensure normal operation after assembly.
Operating torque: Operating torque is the main parameter for selecting the valve electric device. The movement process of electric butterfly valves can be controlled by the magnitude of stroke, torque, or axial thrust. As the working characteristics and utilization rate of valve electric devices depend on the type of valve, the operating specification of the device, and the position of the valve on the pipeline or equipment, valve electric butterfly valve devices are indispensable equipment for realizing valve program control, automatic control, and remote control. Therefore, the correct selection of valve electric devices is crucial to prevent overload (working torque higher than control torque). Generally, the basis for the correct selection of valve electric butterfly valve devices.
The output torque of the electric device shall be 1.21.5 times the large torque of the valve operation.
Electric butterfly valve operating thrust: There are two main structures of the valve electric device: one is without a thrust disc. The output torque is converted into output thrust through the valve stem nut in the thrust disc. Direct output torque; The other is to configure a thrust disk.
Number of output shaft revolutions: The number of output shaft revolutions of the valve electric device is related to the nominal diameter of the valve, the valve stem pitch, and the number of thread heads. "H is the valve opening height, which should be calculated based on M=HZS (M is the total number of turns that the electric device should meet. S is the valve rod transmission thread pitch, and Z is the number of valve rod thread heads.".
In the 1930s, the United States invented the butterfly valve, which was introduced to Japan in the 1950s. By the 1960s, pneumatic butterfly valves were widely adopted in Japan, while their promotion in China was after the 1970s. Small operating torque, small installation space, and light weight. Taking DN1000 as an example, the butterfly valve is about 2T, while the gate valve is about 3.5T. Moreover, the butterfly valve is easy to be combined with various driving devices, with good durability and reliability.
The disadvantage of rubber sealed butterfly valves is that when used for throttling purposes, improper use can cause cavitation, causing peeling off and damage to the rubber seats. 80 to 90 years for this metal. However, the correct selection depends on the operating conditions.
The relationship between the opening and flow of butterfly valves is basically linearly proportional. If used to control flow, its flow characteristics are also closely related to the flow resistance of the piping. For example, if the diameters and forms of the valves installed in two pipelines are identical, and the pipe loss coefficients are different, the flow rate of the valves will also vary greatly.
If the valve is in a large throttling range, cavitation is prone to occur on the back of the valve plate, which may damage the valve. Generally, it is used outside 15 °.
When the butterfly valve is in the middle opening degree, the opening shape formed at the front end of the valve body and the butterfly plate is centered on the valve shaft, and the two sides of the worm wheel butterfly valve are formed to complete different states. The front end of the butterfly plate on one side moves in the direction of water flow, while the other side moves against the direction of water flow. Therefore, one side of the valve body and the valve plate forms a nozzle shaped opening, while the other side is similar to a throttle hole shaped opening. The flow velocity on the nozzle side is much faster than that on the throttle side, and negative pressure will occur below the throttle side valve, Rubber seals often fall off.
The operating torque of butterfly valves varies due to different opening degrees and valve opening and closing directions. Horizontal butterfly valves, especially large diameter valves, cannot be ignored due to water depth and the torque caused by the difference between the upstream and downstream heads of the valve shaft. In addition, when an elbow is installed at the inlet side of the valve, a bias flow is formed, and the torque will increase. When the valve is at the intermediate opening, the operating mechanism needs to be self-locking due to the action of the water flow dynamic moment.
China has a large valve industry chain, but it is not a valve power. Overall, China has entered the ranks of the world's leading valve countries, but from the perspective of product quality, there is still a long gap between China and a powerful valve country. The low concentration of production in the industry, the low research and development capacity of valves matching high-end products, and the low level of manufacturing technology in the valve industry still exist, and the import and export trade deficit continues to expand.
There are absolutely not so many valve enterprises that can truly survive in the market. However, this high-speed fluctuation in the valve industry will bring enormous opportunities, and the result of the fluctuation will make the market operation more rational.
The road to localization of high-end valves is unusually bumpy. Basic components have become a bottleneck restricting the high-end development of China's manufacturing industry. During the 12th Five Year Plan period, the government will continue to strengthen the localization of high-end equipment components. Here, we select representative valves from several key development industries mentioned in the Implementation Plan for feasibility analysis of import substitution. From the analysis, we can see that the feasibility of valve import substitution varies greatly among various sub industries, and high-end valves require more policy guidance and scientific research support.
The valve industry plays a very important role in the development of the national economy as an important link in preparing for manufacturing. Due to the gap between China's domestic valve manufacturing industry and the international level, many key valves with high parameters, high temperature and pressure, and high weight have always relied on imports. In order to promote the localization of valves, after the "Opinions on Accelerating the Revitalization of the Equipment Manufacturing Industry" issued by the State Council, the relevant national departments have made a series of major deployments in accordance with the national requirements for the localization of major equipment, Led by the National Development and Reform Commission, the China Machinery Industry Federation and the China General Machinery Industry Association have jointly deployed and formulated valve localization plans for major equipment in relevant fields, and have coordinated with relevant departments for many times. Now, there is a consensus on valve localization in the domestic valve industry.
Actively adopt international standards for product design; Absorb foreign design structures (including patented technologies); Product testing and performance inspection shall be conducted in strict accordance with international standards; Absorb foreign production process experience and attach importance to the research, promotion and application of new materials; Understanding the technical parameters and operating conditions of imported high parameter valve products is a way to accelerate the localization process, promote the continuous updating of valve products, and comprehensively realize the localization of valves.
With the acceleration of the pace of restructuring in the valve industry, the future industry will be a competition between the quality and safety of valve products and product brands. Products will develop towards high technology, high parameters, strong corrosion resistance, and long service life. Only through continuous technological innovation, development of new products, and technical transformation can we gradually improve the technical level of products, meet domestic device requirements, and fully realize the localization of valves. Under the huge demand environment, the valve manufacturing industry in China will definitely present a better development prospect.
Main classification
By drive mode
(1) Electric butterfly valve
(2) Pneumatic butterfly valve
(3) Hydraulic butterfly valve
(4) Manual butterfly valve
Classified by structural form:
(1) Center seal butterfly valve
(2) Single eccentric sealing butterfly valve
(3) Double eccentric sealing butterfly valve
(4) Triple eccentric sealing butterfly valve
Material classification of sealing surface:
(1) Soft seal butterfly valve.
1) The sealing pair consists of a non-metallic soft material to a non-metallic soft material.
2) The sealing pair consists of a metal hard material versus a non-metallic soft material.
(2) Metal hard seal butterfly valve. The sealing pair consists of a metal hard material to a metal hard material.
Classified by sealing form:
(1) Forced sealing butterfly valve.
1) Elastic seal butterfly valve. The sealing specific pressure is generated by the elasticity of the valve seat or valve plate as the valve plate presses against the valve seat when the valve is closed.
2) External torque sealed butterfly valve. The seal specific pressure is generated by the torque applied to the valve shaft.
(2) Pressurized sealed butterfly valve. The sealing specific pressure is generated by pressurizing the elastic sealing element on the valve seat or valve plate
(3) Automatic sealing butterfly valve. The sealing specific pressure is automatically generated by the medium pressure.
By working pressure:
(1) Vacuum butterfly valve. Butterfly valves with a working pressure lower than the standard reactor atmospheric calendar.
(2) Low pressure butterfly valve. Butterfly valve with nominal pressure PN<1.6MPa.
(3) Medium pressure butterfly valve. Butterfly valves with a nominal pressure PN of 2.5 to 6.4 MPa.
(4) High pressure butterfly valve. The nominal pressure PN is 10. 0-80.0MPa butterfly valve.
(5) Ultra high pressure butterfly valve. Butterfly valves with nominal pressure PN>100MPa.
By operating temperature:
(1) High temperature. t> 450 ° C butterfly valve.
(2) Medium temperature butterfly valve. 120 C<t<450 ℃ butterfly valve.
(3) Normal temperature butterfly valve. - 40C<t<; Butterfly valve at 120 ° C.
(4) Low temperature butterfly valve. A butterfly valve of 100<t<- 40 ° C.
(5) Ultra low temperature butterfly valve. Butterfly valves with t<- 100 ° C.
By connection method:
1. The butterfly plate of the wafer butterfly valve is installed in the diameter direction of the pipeline. The valve is fully open. The wafer type butterfly valve has simple structure, small volume, and light weight. Butterfly valves have two sealing types: elastic seal and metal seal. Elastic sealing valve, the sealing ring can be embedded in the valve body or attached to the periphery of the butterfly plate.
2. Flange type butterfly valve The flange type butterfly valve is of a vertical plate structure, and the valve stem is an integral metal hard sealing valve. 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 surface of the butterfly plate is welded with stainless steel. The sealing ring of the soft sealing valve is made of nitrile rubber and installed on the butterfly plate.
(3) Lug type butterfly valve.
(4) Welded butterfly valve.
The welded butterfly valve is a non hermetic butterfly valve, widely used in pipelines with a medium temperature ≤ 300 ℃ and a nominal pressure of 0.1Mpa in the production process of building materials, metallurgy, mining, electric power, etc., to connect, open, close, or adjust the medium quality.
Structural characteristics
1. Butterfly valves are characterized by simple structure, small volume, light weight, low material consumption, small installation size, rapid switching, 90 ° reciprocating rotation, and small driving torque. They are used to cut off, connect, and regulate the medium in pipelines, and have good fluid control characteristics and closing sealing performance. butterfly valve
2. Butterfly valves can transport mud and store less liquid at the pipe orifice. Good sealing can be achieved under low pressure. Good adjustment performance.
3. The streamlined design of the butterfly plate reduces the loss of fluid resistance, making it an energy-saving product.
4. The valve rod is a through-stem structure, which has undergone tempering treatment, and has good comprehensive mechanical properties, corrosion resistance, and scratch resistance. When the butterfly valve is opened and closed, the valve stem only rotates without lifting. The packing of the valve stem is not easily damaged and the seal is reliable. It is fixed with the tapered pin of the butterfly plate, and the protruding end is designed to prevent the valve rod from collapsing when the connection between the valve rod and the butterfly plate accidentally breaks.
5. The connection methods include flange connection, wafer connection, butt welding connection, and lug wafer connection. The driving forms include manual, worm gear transmission, electric, pneumatic, hydraulic, electro-hydraulic linkage, and other executive mechanisms, which can achieve remote control and automatic operation.
advantage
1. Convenient and rapid opening and closing, labor-saving, low fluid resistance, and frequent operation.
2. Simple structure, small overall size, short structural length, small volume, light weight, suitable for large diameter valves.
3. It can transport mud and store less liquid at the pipe mouth.
4. Good sealing can be achieved under low pressure.
5. Good adjustment performance.
6. When fully open, the effective flow area of the valve seat channel is larger and the fluid resistance is smaller.
7. The opening and closing torque is relatively small. Due to the fact that the media acting on the butterfly plates on both sides of the rotating shaft are basically equal, the direction of the torque generated is opposite, so it is easier to open and close.
8. The sealing surface material is generally rubber or plastic, so the low pressure sealing performance is good.
9. Easy installation.
10. The operation is flexible and labor-saving, and manual, electric, pneumatic, and hydraulic modes can be selected.
shortcoming
1. The operating pressure and temperature range are small.
2. Poor sealing performance.
Butterfly valves can be divided into offset plate type, vertical plate type, inclined plate type, and lever type according to their structural forms. According to the sealing form, it can be divided into two types: soft sealing type and hard sealing type. The soft seal type generally adopts rubber ring seal, while the hard seal type usually adopts metal ring seal.
According to the connection type, it can be divided into flange connection and wafer connection; According to transmission mode, it can be divided into manual, gear transmission, pneumatic, hydraulic and electric.
Installation and maintenance
Wafer butterfly valve
1. During installation, the valve disc should be stopped in the closed position.
2. The opening position should be determined according to the rotation angle of the butterfly plate.
3. For butterfly valves with bypass valves, the bypass valve should be opened before opening.
4. The installation shall be carried out according to the installation instructions of the manufacturer. For heavy butterfly valves, a solid foundation shall be provided. Common faults
During continuous use, rubber elastomers in butterfly valves can tear, wear, age, wear through polymer composite materials to repair worn holes in butterfly valves, and even fall off. However, the traditional thermal vulcanization process is difficult to adapt to the needs of on-site repair, which requires the use of specialized equipment, consuming a large amount of thermal and electrical energy, time-consuming and laborious. Nowadays, the method of replacing traditional methods with polymer composite materials is gradually adopted, and the technology system of Fossil Blue is widely used. The superior adhesion and excellent wear and tear resistance of its products ensure that the service life of new components can be reached or even exceeded after repair, greatly reducing downtime.
Use options
The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline. Butterfly valves have simple structure, small size, and light weight. It consists of only a few parts. Moreover, it only needs to rotate 90 ° to quickly open and close, and the operation is simple. At the same time, the valve has good fluid control characteristics. When the butterfly valve is in the fully open position, the thickness of the butterfly plate is the resistance of the medium flowing through the valve body, so the pressure drop generated through the valve is very small, so it has good flow control characteristics.
If a butterfly valve is required for flow control, it is important to correctly select the size and type of valve. The structural principle of butterfly valves is particularly suitable for making large diameter valves. The commonly used butterfly valves include wafer type butterfly valves and flange type butterfly valves. Wafer type butterfly valves are used to connect the valve between two pipe flanges with double head bolts. Flange type butterfly valves have flanges on the valve, and bolts are used to connect the flanges on both ends of the valve to the pipe flange.
As a component used to achieve on-off and flow control in pipeline systems, butterfly valves have been widely used in many fields, such as petroleum, chemical industry, metallurgy, hydropower, and so on. In the well-known butterfly valve technology, the sealing form mostly adopts a sealing structure, and the sealing material is rubber, polytetrafluoroethylene, etc. Due to the limitations of structural characteristics, it is not suitable for industries such as high temperature and high pressure resistance, corrosion resistance, and wear resistance.
The existing comparative butterfly valve is a triple eccentric metal hard seal butterfly valve. The valve body and valve seat are connected components, and the sealing surface of the valve seat is welded with a temperature resistant and corrosion resistant alloy material. Multilayer soft laminated sealing rings are fixed on the valve plate. Compared to traditional butterfly valves, this type of butterfly valve has the advantages of high temperature resistance, easy operation, frictionless opening and closing, and compensates for sealing as the torque of the transmission mechanism increases during closing, improving the sealing performance of the butterfly valve and extending its service life.
However, the following problems still exist during the use of this butterfly valve:
1、 Due to the multi-layer soft and hard laminated sealing ring fixed to the valve plate, when the valve plate is normally open, the medium forms a positive erosion on its sealing surface, and the soft sealing belt in the metal sheet interlayer is directly affected by the erosion, which directly affects the sealing performance.
2、 Due to structural constraints, this structure is not suitable for valves with diameters below DN200, due to the overall structure of the valve plate being too thick and the large flow resistance.
3、 Due to the principle of a three eccentric structure, the sealing between the sealing surface of the valve plate and the valve seat relies on the torque of the transmission device to press the valve plate against the valve seat. In a positive flow state, the higher the medium pressure, the tighter the sealing pressure. When the medium in the flow path is countercurrent, the unit positive pressure between the valve plate and the valve seat is less than the medium pressure as the medium pressure increases, and the seal begins to leak.
A high-performance three-eccentric two-way hard sealing butterfly valve is characterized in that the valve seat sealing ring is composed of multiple layers of stainless steel sheets on both sides of a soft T-shaped sealing ring. The sealing surface between the valve plate and the valve seat is of an inclined conical structure, and a temperature resistant and corrosion resistant alloy material is deposited on the inclined conical surface of the valve plate; A structure in which the spring fixed between the adjusting ring pressing plate and the adjusting bolt on the pressing plate are assembled together.
This structure effectively compensates for the tolerance zone between the shaft sleeve and the valve body, as well as the elastic deformation of the valve stem under medium pressure, and solves the sealing problem that exists in the two-way exchange medium transportation process of the valve. The sealing ring is composed of multiple layers of stainless steel sheets on both sides of a soft T-shape, which has the dual advantages of metal hard sealing and soft sealing. It has zero leakage sealing performance regardless of low and high temperatures.
The test proves that when the pool is in a positive flow state (the flow direction of the medium is the same as the rotation direction of the butterfly plate), the pressure on the sealing surface is generated by the torque of the transmission device and the effect of the medium pressure on the valve plate. When the positive medium pressure increases, the tighter the compression between the inclined conical surface of the valve plate and the sealing surface of the valve seat, the better the sealing effect. When in a countercurrent state, the sealing between the valve plate and the valve seat relies on the torque of the driving device to press the valve plate against the valve seat. As the reverse medium pressure increases, when the unit positive pressure between the valve plate and valve seat is less than the medium pressure, the deformation stored by the spring of the adjusting ring after being loaded can compensate for the tight pressure on the sealing surface of the valve plate and valve seat, and play an automatic compensation role. Therefore, unlike the existing technology, the utility model does not install soft and hard multilayer sealing rings on the valve plate, but is directly installed on the valve body. Adding an adjusting ring between the pressure plate and the valve seat is a very ideal two-way hard sealing method. It will replace gate, globe, and globe valves.
Applicable occasions
Butterfly valves are suitable for flow regulation. Due to the relatively large pressure loss of butterfly valves in the pipeline, consideration should also be given to the robustness of the butterfly plate under the pressure of the pipeline medium when it is closed. In addition, it is necessary to consider the limitations of the operating temperature that resilient seat materials can withstand at high temperatures. The structural length and overall height of butterfly valves are small, with fast opening and closing speeds, and good fluid control characteristics. The structural principle of butterfly valves is suitable for manufacturing large diameter valves. When butterfly valves are required for flow control purposes, it is important to correctly select the size and type of butterfly valves to enable them to work properly and effectively.
Generally, in throttling, regulatory control, and mud media, short structure lengths and fast opening and closing speeds (1/4 revolution) are required. Butterfly valves are recommended for low pressure shutoff (low differential pressure).
Butterfly valves can be selected for two-position regulation, necked channels, low noise, cavitation and gasification, small leakage to the atmosphere, and abrasive media.
When using butterfly valves under special operating conditions such as throttling adjustment, strict sealing requirements, severe wear, low temperature (deep cold), etc., special triple or double eccentric butterfly valves with specially designed metal sealing belt adjustment devices are required.
The center line butterfly valve is suitable for fresh water, sewage, seawater, brine, steam, natural gas, food, medicine, oil, various acids and bases, and other pipelines that require complete sealing, zero leakage during gas testing, high service life requirements, and operating temperatures ranging from - 10 degrees to 150 degrees Celsius.
The soft seal eccentric butterfly valve is suitable for two-way opening, closing, and adjustment of ventilation and dust removal pipelines, and is widely used in gas pipelines and waterways in metallurgical, light industry, electric power, and petrochemical systems.
The metal to metal line sealed double eccentric butterfly valve is suitable for urban heating, gas supply, water supply, gas, oil, acid and alkali pipelines, as a regulating and throttling device.
In addition to being used as a program control valve for large pressure swing adsorption (PSA) gas separation devices, metal to metal face sealed triple eccentric butterfly valves can also be widely used in the fields of petroleum, petrochemical, chemical, metallurgical, electric power, and other fields as a good substitute for gate and globe valves.
working principle
Butterfly valve is a valve that uses a disc type opening and closing device to rotate back and forth about 90 ° to open, close, or regulate the flow of media. Butterfly valves not only have simple structure, small volume, light weight, low material consumption, small installation size, small driving torque, simple and rapid operation, but also can simultaneously have good flow regulation function and closing sealing characteristics. They are one of the fastest growing valve varieties in the past decade. Butterfly valves are widely used. The variety and quantity of its use are still expanding, and it is developing towards high temperature, high pressure, large diameter, high sealing performance, long life, excellent regulation characteristics, and one valve multi-function. Its reliability and other performance indicators have reached a high level.
With the application of chemical resistant synthetic rubber in butterfly valves, the performance of butterfly valves has been improved. Due to the characteristics of synthetic rubber such as corrosion resistance, erosion resistance, dimensional stability, good resilience, ease of forming, and low cost, it is possible to select synthetic rubber with different properties according to different usage requirements to meet the operating conditions of butterfly valves.
Due to the strong corrosion resistance, stable performance, non aging, low friction coefficient, easy forming, and dimensional stability of polytetrafluoroethylene (PTFE), and the ability to improve its comprehensive performance by filling and adding appropriate materials, a butterfly valve sealing material with better strength and lower friction coefficient can be obtained, which overcomes the limitations of synthetic rubber. Therefore, the polymer polymer materials represented by polytetrafluoroethylene and their filler modified materials can, It has been widely used in butterfly valves, further improving the performance of butterfly valves, and producing butterfly valves with a wider range of temperature and pressure, reliable sealing performance, and longer service life.
In order to meet the requirements of industrial applications such as high and low temperature, strong erosion, and long life, metal sealed butterfly valves have been greatly developed. 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 sealed butterfly valves have been widely used in industrial fields such as high and low temperatures, strong erosion, and long life. Large diameter (9-750mm), high pressure (42.0MPa), and wide temperature range (- 196-606 ℃) butterfly valves have emerged, bringing the technology of butterfly valves to a new level.
Butterfly valves have a small flow resistance when fully opened. "When opened at about 15 ° to 70 °, it also provides sensitive flow control, making butterfly valves very popular in the field of large-diameter regulation.".
Due to the wiping nature of the movement of the butterfly valve plate, most butterfly valves can be used for media with suspended solid particles. Depending on the strength of the seal, it can also be used in powder and granular media.
Butterfly valves are suitable for flow regulation. Due to the relatively large pressure loss of butterfly valves in the pipeline, which is about three times that of gate valves, when selecting butterfly valves, it is necessary to fully consider the impact of pressure loss on the pipeline system, and also consider the strength of the butterfly plate under the pressure of the pipeline medium when it is closed. In addition, it is necessary to consider the limitations of the operating temperature that resilient seat materials can withstand at high temperatures.
The butterfly valve has a small structural length and overall height, fast opening and closing speeds, and good fluid control characteristics. The structural principle of butterfly valves is suitable for manufacturing large diameter valves. When butterfly valves are required for flow control purposes, it is important to correctly select the specifications and types of butterfly valves to enable them to work properly and effectively.
Generally, in throttling, regulatory control, and mud media, short structure length, fast opening and closing speed, and low pressure cutoff (low pressure differential) are required. Butterfly valves are recommended. Butterfly valves can be selected for two-position regulation, reduced diameter channels, low noise, cavitation and vaporization, small leakage to the atmosphere, and abrasive media. Throttle adjustment is required under special operating conditions, or operating conditions such as strict sealing, severe wear, and low temperature (deep cooling).
Key points of construction and installation
1) The installation position, height, inlet and outlet directions must meet the design requirements, and the connection should be firm and tight. Working principle diagram of butterfly valve
2) The handle of various manual valves installed on insulated pipes shall not be downward.
3) Visual inspection must be conducted before valve installation. The nameplate of the valve should comply with the current national standard "General Purpose Valve Signs" GB 12220. For valves with a working pressure greater than 1.0 MPa and having a cutoff effect on the main pipe, strength and tightness tests should be conducted before installation, and they can only be used after passing the tests. During the strength test, the test pressure shall be 1.5 times the nominal pressure, and the duration shall not be less than 5min. The valve shell and filler shall be free of leakage, which is considered qualified. During the tightness test, the test pressure shall be 1.1 times the nominal pressure; The test pressure during the duration of the test shall meet the requirements of GB50243 standard, and it shall be deemed qualified if there is no leakage on the sealing surface of the valve flap.
1、 Key points of product selection
1. The main control parameters of butterfly valves are specifications and dimensions.
2. The butterfly valve is a single plate type air valve with simple structure, convenient processing, low cost, and easy operation, but its adjustment accuracy is poor, and it is only suitable for switching or rough adjustment in ventilation and air conditioning systems.
3. It can be operated manually, electrically, or zippered, and can be fixed at any angle within a 90 ° range.
4. Due to the limited bearing capacity of a single shaft and single valve plate, the valve has a short service life under conditions of large pressure difference and high flow rate. The valve can be divided into closed type and ordinary type, and thermal insulation and non thermal insulation.
5. The electric butterfly valve has only dual position control, and the electric actuator is the same as the multi leaf valve.
2、 Executive standards
"Air Volume Regulating Valves" JB/T7228-94
Manufacturing standard: GB/T 122387-89
Flange standard: JB79-59
Inspection standard: JB/T9092-99
3、 Relevant standard atlas
"Selection and Installation of Air Valves" 07K120
Installation considerations
The butterfly valve has a simple structure, small size, light weight, and relatively few components. Only a few key components can constitute the butterfly valve, which is also very convenient to open. You only need to select the switch to 90 degrees. The butterfly valve has excellent fluid control, allowing you to increase or decrease the flow at any time. The valve has certain resistance when transporting any fluid, and the resistance of the butterfly valve mainly comes from itself, For example, if you want to reduce the resistance to fluid, you only need to reduce the thickness of the butterfly valve body. Elastic seals have the defect of being limited by temperature.
Butterfly valves also have a wide range of applications, and if used to control flow, it is necessary to choose different types and valve body sizes, as butterfly valves are inherently suitable for valves with larger diameters when designed. Butterfly valves are not only widely used in general industries such as petroleum, gas, chemicals, and water treatment, but also in cooling water systems in thermal power plants.
