What are butterfly valves?
Butterfly valve, also known as flip valve, is a simple structure control valve, which can be used for switch control of low-pressure pipeline media. Butterfly valve refers to a valve whose closing parts (disc or butterfly plate) are discs and rotate around the valve axis to open and close.
Butterfly valves can be used to control the flow of air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. It mainly plays the role of cutting off and throttling in the pipeline. The opening and closing part of butterfly valve is a disc-shaped butterfly plate, which rotates around its own axis in the valve body to achieve the purpose of opening and closing or regulating.
Development History of Butterfly Valve
In the 1930s, the butterfly valve was invented in the United States. It was introduced into Japan in the 1950s. It was not widely used in Japan until the 1960s, but it was popularized in China after the 1970s. The main features of butterfly valve are small operating moment, small installation space and light weight. Take DN1000 as an example, butterfly valve is about 2T, while gate valve is about 3.5T, and butterfly valve is easy to be combined with various driving devices, so it has good durability and reliability. The disadvantage of rubber sealed butterfly valve is that when it is used as throttle, the improper use will cause cavitation, which will lead to rubber seat peeling and damage, so how to choose it correctly depends on the working conditions. The relationship between the opening of butterfly valve and the flow rate basically shows a linear proportional change. If it is used to control flow, its flow characteristics are closely related to the flow resistance of piping. For example, the caliber and form of valves installed in two pipes are identical, and the flow rate of valves varies greatly with different loss coefficients of pipes. If the valve is in a larger throttling range, the back of the valve plate is prone to cavitation, which may damage the valve, generally used outside 15 degrees. When the butterfly valve is in the middle opening, the shape of the opening formed by the valve body and the front end of the butterfly plate is centered on the valve shaft, and the two sides form different states. The front end of the butterfly plate on one side moves in the direction of downstream water and the other side moves in the direction of countercurrent water. Therefore, one side of the valve body and the valve plate forms a nozzle-like opening, the other side is similar to the orifice-shaped opening, and the flow speed of the nozzle side is much faster than that of the throttle side. Negative pressure will occur under the valve, and rubber seals will often fall off. The operating moment of butterfly valve varies with the opening and opening direction of the valve. Horizontal butterfly valve, especially large-caliber valve, can not be ignored because of the depth of water and the difference between the shaft and the head of the valve. In addition, when the elbow of the valve inlet side device forms a bias flow, the torque will increase. When the valve is in the middle opening, the operating mechanism needs self-locking because of the action of the hydrodynamic moment.
China’s valve industry chain is numerous, but it is not a powerful country in valve industry. Generally speaking, China has entered the ranks of the world’s valve powers, but there is still a long gap between China and the world’s valve powers in terms of product quality. The phenomena of low production concentration, low R&D capability of high-end products, low manufacturing technology level of the valve industry still exist, and the trade deficit between import and export continues to expand. There are absolutely not so many valve companies that can really survive in the market. But the high-speed shocks in the valve industry will bring huge opportunities, and the results of the shocks will make the market operation more rational. The road to localization of high-end valves is unusually bumpy. Infrastructure has become a short-board restricting the development of high-end manufacturing industry in China. During the 12th Five-Year Plan period, the government will continue to intensify the localization of high-end equipment components. Here we select several key points mentioned in the Implementation Plan to develop representative valve industry for feasibility analysis of import substitution. From the analysis, it can be seen that the feasibility of valve import substitution varies greatly among various sub-industries, and high-end valves need more policy guidance and scientific research support urgently.
Valve industry, as an important part of equipment manufacturing industry, plays a very important role in the development of national economy. Because of the gap between domestic valve manufacturing level and international advanced level, many key valves with high parameters, high temperature, high pressure and high pound class originally depended on imports. For example, YAANG brand has always been the main choice for domestic valve application industry. In order to promote the localization of valves, after the State Council issued “Several Opinions on Accelerating the Revitalization of Equipment Manufacturing Industry”, the relevant departments of the State made a series of major deployments in accordance with the requirements of the nationalization of major equipment made by the State, and led by the National Development and Reform Commission, together with the China Machinery Industry Federation and the China General Machinery Industry Association, deployed and formulated related fields. Valve localization schemes for major equipment have been coordinated with relevant departments for many times. Nowadays, there is a consensus on valve localization in domestic valve industry. Actively adopt international standards for product design; absorb foreign excellent design structure (including patented technology); conduct product testing and performance testing strictly in accordance with international standards; absorb foreign production process experience and attach importance to the research and application of new materials; clarify the technical parameters and working conditions of imported high-parameter valve products is to speed up the process of localization and promote valve products. Discontinuous renewal is the way to realize the localization of valves in an all-round way. With the acceleration of the reorganization of the valve industry, the future industry will be the competition between product quality and safety and product brands. The products will develop in the direction of high technology, high parameters, strong corrosion resistance and long service life. Only through continuous technological innovation, development of new products and technological transformation, can the technology level of products be gradually improved to meet the domestic equipment matching and realize the valve in an all-round way. Nationalization. Under the huge demand environment, the valve manufacturing industry in China will show a better development prospects.
Main Classification of Butterfly Valves
According to the driving mode
- Electric butterfly valve: electric butterfly valve belongs to a variety of electric valves and electric control valves. The main connection modes of electric butterfly valve are flange type and clamp type, and the main sealing modes of electric butterfly valve are rubber seal and metal seal. Electric butterfly valve controls the switch of butterfly valve by power signal. This product can be used as cut-off valve, control valve and check valve in pipeline system. With manual control device, once power failure occurs, it can be temporarily operated manually without affecting the use.
- Pneumatic butterfly valve: pneumatic butterfly valve is composed of pneumatic actuator and butterfly valve. Pneumatic butterfly valve is a kind of pneumatic valve with circular butterfly plate rotating with the stem for opening and closing. It is mainly used as a cut-off valve. It can also be designed to have the function of regulating or section valve as well. At present, butterfly valve is used more and more in low-pressure large and medium-caliber pipelines. Pneumatic butterfly valve classification: stainless steel pneumatic butterfly valve, hard seal pneumatic butterfly valve, soft seal pneumatic butterfly valve, carbon steel pneumatic butterfly valve. The main advantages of pneumatic butterfly valve are simple structure, small size, light weight, low cost. The pneumatic butterfly valve is especially prominent. It is installed in high-altitude dark channel. It is easy to operate through two-position five-way solenoid valve control, and it can also adjust the flow medium.
- Hydraulic butterfly valve: hydraulic butterfly valve is widely used in blast furnace gas network system in metallurgical industry to prevent gas tempering in the pipe. In order to prevent sudden drop of pressure in the steam turbine when the steam turbine load is thrown off, the exhaust pipe and steam in each heater are poured into the steam turbine, resulting in the vicious accident of breaking the turbine blade and damaging the turbine generator, it is used as an emergency shut-off valve in the power industry. When dangerous conditions occur in the system, emergency shut-off can be implemented in 0.5 seconds to achieve reliable cut-off of pipelines. Effectively prevent steam and condensate backfilling at the tail of steam turbine, and protect the safety of steam turbine unit.
- Manual butterfly valve: manual butterfly valve is installed in the diameter direction of the pipeline. In the cylindrical channel of the butterfly valve body, the disc butterfly plate rotates around the axis, and the rotation angle is between 0 – 90. When the rotation angle is between 0 and 90 the valve is fully open. The butterfly valve is simple in structure, small in volume and light in weight, and consists of only a few parts. The valve can be switched on and off quickly only by rotating 90 degrees. The operation is simple and the valve has good fluid control characteristics.
According to the structural form:
- Central Sealed Butterfly Valve
- Single eccentric sealed butterfly valve
- Double eccentric sealed butterfly valve
- Tri-eccentric sealed butterfly valve
Sealing surface material quality:
- Soft-sealed butterfly valve.
- The sealing pair is composed of non-metallic soft material and non-metallic soft material.
- The sealing pair is composed of metal hard material and non-metal soft material.
- Metal hard seal butterfly valve. The sealing pair is composed of metal hard material to metal hard material.
According to the sealed form:
- Forced sealing butterfly valve.
- Flexible Sealed Butterfly Valve: The specific pressure of sealing is generated by the elasticity of the valve seat or valve plate when the valve closes.
- External Torque Sealed Butterfly Valve: The specific pressure of the seal is generated by the torque applied on the valve shaft.
- Pressure-filled sealed butterfly valve: The specific pressure of the seal is generated by the pressure of the elastic sealing element on the seat or valve plate.
- Automatic Sealing Butterfly Valve: Sealing specific pressure is automatically generated by medium pressure.
According to work pressure:
- Vacuum butterfly valve. Butterfly valve with working pressure lower than standard reactor atmospheric pressure.
- Low pressure butterfly valve. Butterfly valve with nominal pressure PN < 1.6 MPa.
- Medium pressure butterfly valve. Butterfly valves with nominal pressure PN of 2.5-6.4 MPa.
- High pressure butterfly valve. The nominal pressure PN is 10. Butterfly valves of 0-80.0 MPa.
- Super high pressure butterfly valve. Butterfly valve with nominal pressure PN > 100MPa.
The difference between vacuum butterfly valve and ordinary butterfly valve?
Common butterfly valve series products are applicable to pressure greater than or equal to atmospheric pressure, suitable medium for water, flue gas, cement, slag, etc. It is widely used in food, medicine, petrochemical industry, industrial environment, high-rise buildings and pipelines as the best device for regulating flow and cutting off fluid.
Vacuum gate valve, vacuum ball valve, vacuum butterfly valve and a series of vacuum valve products are evolved from the improvement of ordinary valves. The difference is that their pressure is less than atmospheric pressure, which is better than ordinary valves in air tightness. They are suitable for vacuum pipelines with medium of water, steam and water. They are most widely used in condensation and vacuum negative pressure systems of steam turbines in thermal power plants, and their main functions are opening and closing devices. It acts as a vacuum isolation seal.
Advantages of Vacuum Valves
- Opening speed is fast, labor-saving and fluid resistance is small.
- The shape of the valve is not much different from that of the ordinary valve. It is simple and has good manufacturing technology.
- The flow direction of media is not restricted.
- Small erosion on sealing surface
- Wide range of applications
The vacuum butterfly valve has the following characteristics:
Pressure is below atmospheric pressure and pressure drop on disc should not exceed 1 kg/cm 2. The working temperature of the medium depends on the process of using the device. Temperature generally does not exceed the range of – 70 ~150 ~C. The most basic requirement for such valves is to ensure the high sealing of the connection and the compactness of the structure and gasket material.
According to the medium pressure vacuum valve can be divided into four groups:
- 1) Low vacuum valve: medium pressure P = 760-1 mm Hg column;
- 2) Medium Vacuum Valve: P = 1 x 10-3 mm Hg column.
- 3) High vacuum valve: P = 1 *10-4~1 *10-7 mm mercury column;
- 4) Ultra-high vacuum valve: P < 1 *10-8 mm mercury column.
Vacuum bellows globe valve with straight line motion is widely used in vacuum valves. Gate valves are limited, but for large diameter, ball valves, plunger valves and butterfly valves are also available. The plug valves used as vacuum valves have not been popularized because they need oil lubrication to make oil vapor possible into the vacuum system, which is not allowed. Vacuum valve closures are sealed with rubber or metal seals. The bellows of bellows stop valves are made of stainless steel, high zinc brass JI80, plastics and other materials. The diaphragm seal can be used for the shutoff parts of small diameter (less than 10 mm in diameter). Spherical cock valves can be used in low and medium vacuum.
According to working temperature:
- High temperature. Butterfly valve with T > 450 degree C.
- Medium temperature butterfly valve. 120 C < T < 450 C butterfly valve.
- Butterfly valves at room temperature. A butterfly valve with 40C < T < 120 degree C.
- Low temperature butterfly valve. A butterfly valve of 100 < T < 140 degree C.
- Ultra-low temperature butterfly valve. T < 100 degree C butterfly valve.
According to the connection mode:
- Butterfly valve: the butterfly plate of the clamp butterfly valve is installed in the diameter direction of the pipeline. The valve is fully open. The clamp butterfly valve has the advantages of simple structure, small volume and light weight. Butterfly valve has elastic seal and metal seal. Elastic sealing valve, sealing ring can be inlaid on the body or attached to the butterfly plate.
- Flanged butterfly valve, is vertical plate structure, and the stem is the sealing ring of integral metal hard sealing valve.
- For the composite structure of flexible graphite plate and stainless steel plate, it is installed on the valve body, butterfly plate sealing surface is surfacing stainless steel. The sealing ring of the soft sealing valve is made of NBR and is installed on the butterfly plate.
- Lug butterfly valve
- Welded butterfly valve, is a kind of non-hermetic butterfly valve. It is widely used in pipes with medium temperature less than 300 C and nominal pressure of 0.1Mpa in the production process of building materials, metallurgy, mining and electric power. It is used to connect, open and close or regulate medium volume.
1. Concentric Butterfly Valves:
The butterfly valve is characterized in that the valve stem axis, the butterfly plate and the body are at the same position. The structure is simple and convenient to manufacture. A common rubber valve belongs to this category. The disadvantage is that the butterfly plate and the valve seat are always in a state of being squeezed and scraped, resulting in a large resistance distance and a rapid wear. In order to overcome the extrusion, scratching and ensure sealing performance, the valve seat is basically made of elastic materials such as rubber or PTFE, but it is also limited in temperature by use, which is the reason why people traditionally considered that the butterfly valve is not resistant to high temperatures.
2. Single Eccentric Butterfly Valve:
In order to solve the extrusion problem of the butterfly plate and seat of concentric butterfly valve, a single eccentric butterfly valve is produced. Its structure characteristic is that the axial center of the valve stem deviates from the center of the butterfly plate, so that the upper and lower ends of the butterfly plate no longer become the rotary shaft center, which reduces the over extrusion between the upper and lower ends of the butterfly plate and the seat. However, the scraping phenomenon between butterfly plate and valve seat has not disappeared in the whole process of valve switch with single eccentricity, which is similar to concentric butterfly valve in application scope, so it is not used much.
The triple offset butterfly valve is eccentric at the axial position of the double eccentric stem, and the center line of the conical sealing surface is deflected by an angle with respect to the center line of the valve to form a third eccentricity. The third eccentricity allows the valve seat and the disc to be completely disengaged throughout the entire stroke of the valve. The contact between the disc and the valve seat is only a moment in sealing, thus greatly reducing the friction of switching process between the valve seat and the disc. Since the sealing is achieved by the compression between the valve seat and the sealing ring on the butterfly plate, the sealing specific pressure can be applied by the torque of the valve stem. If the valve structure is designed properly, an extremely high sealing effect can be achieved. The design of triple offset butterfly valve can solve the problem of high temperature resistance and leakage prevention. As a high performance valve, the triple offset butterfly valve has become the first choice in the regulating valve market with its unique structural characteristics and performance advantages.
Butterfly valves are usually less than 90 degrees open to close. Butterfly valves and butterfly rods have no self-locking ability. In order to locate the butterfly plate, worm gear reducer should be installed on the valve stem. The use of worm gear reducer can not only make the butterfly plate have self-locking ability, make the butterfly plate stop at any position, but also improve the operation performance of the valve. Industrial butterfly valves are characterized by high temperature resistance, high pressure range, large nominal diameter, carbon steel body and metal ring instead of rubber ring. Large high temperature butterfly valve is welded by steel plate, mainly used for flue gas duct and gas pipeline of high temperature medium.
The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline. The butterfly valve is simple in structure, small in volume and light in weight. It is composed of only a few parts. It can be opened and closed quickly only by rotating 90 degrees. It is easy to operate. At the same time, the valve has good fluid control characteristics. When the butterfly valve is in full open position, the butterfly plate thickness is the resistance of the medium flowing through the valve body, so the pressure drop generated by the valve is very small, so it has better flow control characteristics.
If butterfly valve is required to be used as flow control, the main thing is to select the correct size and type of valve. The structure principle of butterfly valve is especially suitable for making large caliber valves. Commonly used butterfly valves are butterfly valves and flange butterfly valves. The clamp butterfly valve is connected between two pipeline flanges by double-head bolts. The flange butterfly valve is connected with flanges on the valve. The flanges on both ends of the valve are connected with bolts in the process of using the pipeline flanges.
Butterfly valve, as a component used to realize on-off and flow control of pipeline system, has been widely used in many fields such as petroleum, chemical industry, metallurgy, hydropower and so on. In the well-known butterfly valve technology, its sealing form mostly uses the sealing structure, the sealing material is rubber, PTFE and so on. Due to the limitation of structural characteristics, it is not suitable for high temperature, high pressure, corrosion and wear resistance industries.
A more advanced butterfly valve is a three-eccentric metal hard-sealed butterfly valve. The valve body and seat are connected components. The sealing surface layer of the valve seat is surfaced with heat-resistant and corrosion-resistant alloy materials. The multi-layer soft overlapping seal ring is fixed on the valve plate. Compared with the traditional butterfly valve, the butterfly valve has the advantages of high temperature resistance, light operation, no friction in opening and closing. When closing, the seal is compensated with the increase of the torque of the transmission mechanism, which improves the sealing performance and prolongs the service life of the butterfly valve.
However, the butterfly valve still has the following problems in use:
1. Because the multi-layer soft and hard overlapping seal ring is fixed on 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 interlayer is eroded, which directly affects the sealing performance.
2. Restricted by structural conditions, this structure is not suitable for making valves with diameters below DN200. The reason is that the overall structure of the valve plate is too thick and the flow resistance is large.
3. Because of the principle of tri-eccentric structure, the seal between the sealing surface of the valve plate and the seat is to press the valve plate to the seat by the moment of the transmission device. In the positive flow state, the higher the medium pressure, the tighter the sealing extrusion. When the flow channel medium countercurrent, with the increase of the medium pressure, the unit positive pressure between the valve plate and the seat is less than the medium pressure, the seal begins to leak.
The high performance three eccentric two-way hard seal butterfly valve is characterized in that the seat seal ring is composed of multi-layer stainless steel sheets on both sides of the soft T-shaped seal ring. The sealing surface of the valve plate and seat is oblique conical structure. The temperature-resistant and corrosion-resistant alloy material is surfaced on the oblique conical surface of the valve plate. The spring fixed between the adjusting ring pressure plate and the adjusting bolt on the pressure plate are assembled together.
This structure effectively compensates the tolerance zone between the Bush and the valve body and the elastic deformation of the valve stem under the medium pressure, and solves the sealing problem of the valve in the process of two-way interchangeable medium transmission. The sealing ring is composed of soft T-shaped multi-layer stainless steel sheets on both sides. It has double advantages of hard metal seal and soft seal. It has zero leakage sealing performance at low temperature and high temperature.
The test proves that the pressure on the sealing surface is caused by the action of the moment of the transmission device and the pressure of the medium on the valve plate in the positive flow state of the tank (the direction of the medium flow is the same as that of the butterfly plate rotation). The tighter the extrusion between the oblique conical surface of the valve plate and the sealing surface of the valve seat, the better the sealing effect. When in countercurrent condition, the seal between the valve plate and the seat presses the valve plate to the seat by the moment of the driving device. With the increase of reverse medium pressure, when the unit positive pressure between the valve plate and the seat is less than the medium pressure, the spring of the regulating ring can compensate the tight pressure between the valve plate and the sealing surface of the valve seat automatically. Therefore, unlike the existing technology, the utility model does not install soft and hard multi-layer sealing rings on the valve plate, but directly installs them on the valve body. Adding adjusting rings between the pressure plate and the valve seat is an ideal bidirectional hard sealing method. It will replace gate valve, globe valve and spherical valve.
Butterfly valves are suitable for flow regulation. Because the pressure loss of the butterfly valve in the pipeline is relatively large, the rigidity of the butterfly plate under the pressure of the pipeline medium should also be considered when closing. In addition, the working temperature limitation of elastic seat material at high temperature must also be considered. The structure length and overall height of the butterfly valve are small, the opening and closing speed is fast, and it has good fluid control characteristics. The structure principle of the butterfly valve is most suitable for making large caliber valves. When the butterfly valve is required to control the flow, the most important thing is to select the size and type of butterfly valve correctly so that it can work properly and effectively.
Usually, in the medium of throttling, regulating control and mud, the structure length is short and the opening and closing speed is fast (1/4 turn). Low pressure cut-off (low pressure difference), butterfly valve is recommended.
Butterfly valves can be used when there are two-position adjustments, shrinkage channels, low noise, cavitation and gasification, a small amount of leakage to the atmosphere, and abrasive media.
When using butterfly valves under special working conditions such as throttling regulation, strict sealing, severe wear and low temperature (deep cold), special designed metal seal belt regulating device with special triple or double eccentric special butterfly valves should be used.
Butterfly valves are suitable for freshwater, sewage, seawater, brine, steam, natural gas, food, medicine, oil products, various acids and alkalis and other pipelines which require complete sealing, zero gas test leakage, high service life and working temperature ranging from – 10 degrees to 150 degrees.
Soft-sealed eccentric butterfly valve is suitable for two-way opening and closing and regulation of ventilation and dust removal pipelines. It is widely used in gas pipelines and waterways of metallurgical, light industry, electric power and petrochemical systems.
The metal-to-metal double eccentric butterfly valve is suitable for gas, oil, acid and alkali pipelines such as urban heating, gas supply, water supply, etc., as a regulating and throttling device.
Metal-to-metal tri-eccentric butterfly valve can be widely used in petroleum, petrochemical, chemical, metallurgical, power and other fields, besides being used as a program control valve of large pressure swing adsorption (PSA) gas separation device. It is also a good substitute for gate valve and globe valve.
The rubber elastomer in butterfly valve will tear, wear, aging, perforation and even fall off during continuous use. The traditional thermal vulcanization process is difficult to meet the needs of site repair. Special equipment is used to repair, which consumes a lot of heat and energy, and takes time and effort. Nowadays, polymer composites are gradually used to replace traditional methods, of which the most widely used is the Fushilan technology system. The excellent adhesion, abrasion resistance and tear resistance of the products ensure that the service life of the new components can be reached or even exceeded after repair, and greatly shorten the downtime.
- When installing, the disc should stop at the closed position.
- The opening position should be determined by the rotation angle of the butterfly plate.
- Butterfly valves with bypass valves should be opened before opening.
- The butterfly valves with heavy weight should be installed according to the installation instructions of the manufacturer.
Key Points of Construction and Installation of Butterfly Valve
- Installation location, height, import and export direction must meet the design requirements, and the connection should be firm and tight. All kinds of manual valves installed on the insulation pipeline shall not have downward handles.
- The appearance inspection must be carried out before the valve is installed. The nameplate of the valve should comply with the current national standard “General Valve Mark” GB 12220. For valves with working pressure greater than 1.0 MPa and cutting off effect on main pipe, strength and tightness test should be carried out before installation, and the valves can be used only after they are qualified. In the strength test, the test pressure is 1.5 times of the nominal pressure, and the duration is not less than 5 minutes. The valve shell and packing should be qualified without leakage. The test pressure is 1.1 times of the nominal pressure in the tightness test, and the test pressure should meet the requirements of GB 50243 standard for the duration of the test, with no leakage on the valve sealing surface as the qualification.
- The main control parameters of butterfly valves are specifications and sizes.
- The butterfly valve is a single-plate air valve, which has simple structure, convenient processing, low cost and easy operation, but its adjustment accuracy is poor. It is only suitable for the occasion of switch or rough adjustment in the ventilation and air conditioning system.
- It can be operated manually, electrically or zipper, and fixed at any angle in the range of 90 degrees.
- Because of the limited bearing capacity of the single-axis single valve plate, the service life of the valve is short under the conditions of high pressure difference and high flow rate. The valve can be divided into closed type and ordinary type, heat preservation and non-heat preservation.
- The electric butterfly valve has only two-position control, and the electric actuator is the same as the multi-leaf valve.
The butterfly valve has simple structure, small volume, light weight and few components. It can be made up of several key components. It is very convenient to open the butterfly valve. It only needs to select the switch to 90 degrees. The butterfly valve has a very good control of the fluid, and can increase or decrease the flow at any time. The valve has certain resistance when it transports any fluid. The resistance of butterfly valve mainly comes from itself, such as the thickness of butterfly valve body. If you want to reduce the resistance to fluid, you only need to reduce the thickness of butterfly valve body.
Elastic seals have temperature limitations.
Butterfly valves have a wide range of applications. If they are used to control flow, different types and sizes of valves need to be chosen, because butterfly valves are more suitable for some large caliber valves when they are designed. Butterfly valves are not only widely used in petroleum, gas, chemical industry, water treatment and other general industries, but also used in the cooling water system of thermal power plants.
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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