How to choose a butterfly valve?
Butterfly valve, also known as flip valve, is a simple structure of regulating valve, can be used for low-pressure pipeline medium switch control of the butterfly valve is the closing piece (disc or butterfly plate) for the disc, revolving around the valve shaft to open and close a valve.
Valves can be used to control the flow of air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media and other types of fluid. The cutting and throttling functions are mainly used in pipelines. The butterfly valve opening and closing piece 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 adjusting.
Development history of butterfly valve
In the 1930s, the United States invented the butterfly valve, introduced into Japan in the 1950s, until the 1960s it was widely used in Japan, and in China it was popularized after the 1970s. The main features of the butterfly valve are: small operating torque, small installation space and light weight. Taking DN1000 as an example, butterfly valve is about 2T, gate valve is about 3.5T, and butterfly valve is easy to combine with various driving devices, has good durability and reliability. The disadvantage of rubber sealing butterfly valve is that when it is used as throttle, cavitation will occur due to improper use, so that the rubber seat peeling, damage and other situations occur, so how to choose the right way is according to the requirements of working conditions. The relationship between butterfly valve opening and flow rate basically varies linearly. If it is used to control the flow rate, the flow characteristics are also closely related to the flow resistance of the piping, such as two pipes installed with the same valve diameter, form, and so on, and the pipe loss coefficient is different, the flow of the valve will be very different. If the valve is in a large throttling range, the back of the valve plate prone to cavitation, there is the possibility of damage to the valve, generally in 15 degrees outside the use. When the butterfly valve is in the middle opening, the opening shape formed between the valve body and the front end of the butterfly plate is centered on the valve shaft, and different states are formed on both sides. The front end of the butterfly plate on one side moves in the direction of flowing water, while the other side moves in the direction of counterflowing water. The nozzle side is much faster than the throttle side, and the throttle side valve will produce negative pressure below, often rubber seals will fall off. Operating torque of butterfly valve varies with opening and direction of valve opening and closing. Horizontal butterfly valve, especially large diameter valve, can not be ignored because of water depth, shaft and water head difference. In addition, when the valve inlet side is equipped with elbow, the bias current will increase and the torque will increase. When the valve is in the middle opening, the operating mechanism needs self locking because of the hydrodynamic moment.
China’s valve industry chain is numerous, but it is not a powerful valve country. Overall, China has entered the ranks of the world’s valve power, but from the product quality point of view, China is still a long way from the valve power. The problems of low concentration of production, low R&D capability of valves matched with high-end products, low manufacturing level of valves still exist, and the trade deficit between import and export is expanding. There are absolutely not many valve companies that can really survive in the market. But the valve industry’s high-speed shock will bring huge opportunities, the results of the shock will make the market operation more rational. The localization of high-end valves is “bumpy”. Basic parts have become a short board which restricts the development of high-end manufacturing industry in China. During the 12th Five-Year Plan period, the government will continue to increase the localization of high-end equipment parts. Here we select several key points mentioned in the Implementation Plan to develop representative valve industry for feasibility analysis of import substitution. It can be seen from the analysis that the feasibility of valve import substitution varies greatly among the sub-industries, and the high-end valves need more policy guidance and scientific research support.
Valve industry in the national economic development, as an important part of the equipment manufacturing industry, plays a very important role. Because the level of domestic valve manufacturing is still lagging behind the international advanced level, many key valves with high parameters, high temperature and pressure, high pound grade have been relying on imports, such as the European OMAL brand has been the main choice of domestic valve application industry. In order to promote the localization of valves, following the State Council’s “Several Opinions on Speeding up the Revitalization of Equipment Manufacturing Industry”, the relevant departments of the state have made a series of major deployments in accordance with the requirements of the state for the localization of major equipment, led by the State Development and Reform Commission, the China Machinery Industry Federation and the China General Machinery Industry Association. Together with the Association of Machinery Industry, the Association has formulated a plan for the localization of valves with major equipment in relevant fields, and has coordinated with relevant departments on many occasions. Nowadays, there is a consensus on the localization of valves in the domestic valve industry. Actively adopt international standards for product design; absorb foreign excellent design structure (including patent technology); product testing, performance testing strictly in accordance with international standards; absorb foreign production process experience to attach importance to the research and application of new materials; understand the technical parameters and operating conditions of imported high-parameter valve products, etc. It is a way to speed up the process of localization, promote the continuous update of valve products, and realize the nationalization of valves in an all-round way. With the accelerated pace of valve industry restructuring, the future industry will be the product quality safety and product brand competition, product to high technology, high parameters, strong corrosion resistance, high life direction, only through constant technological innovation, development of new products, technical transformation, can gradually improve product technical water Ping, to meet domestic equipment matching, fully realize the localization of valves. Under the huge demand environment, China’s valve manufacturing industry will surely show better prospects for development.
The working principle of butterfly valve
The butterfly valve is a kind of valve which opens, closes or adjusts the medium flow rate by the disc-type open and close parts reciprocating turning about 90 degrees. Butterfly valve is not only simple in structure, small in volume, light in weight, low in material consumption, small in installation size, small in driving torque, easy to operate and rapid, but also has good flow regulation function and close sealing characteristics. It is one of the fastest growing valve varieties in recent ten years. Butterfly valves are widely used. The variety and quantity of its use are still expanding, and developing towards high temperature, high pressure, large diameter, high sealing, long life, excellent regulation characteristics, and multi-function valve. Its reliability and other performance indicators have reached a high level.
With the application of synthetic rubber against chemical corrosion on butterfly valves, the performance of butterfly valves has been improved. Synthetic rubber has the characteristics of corrosion resistance, erosion resistance, size stability, good resilience, easy to form, low cost and so on, and can be selected according to different requirements of different properties of synthetic rubber to meet the operating conditions of butterfly valves.
Polytetrafluoroethylene (PTFE) has strong corrosion resistance, stable performance, not easy to aging, low friction coefficient, easy to form, size stability, and can be filled by adding appropriate materials to improve its comprehensive performance, get better strength, lower friction coefficient butterfly valve sealing material, overcome the limitations of synthetic rubber Therefore, the polymer materials represented by PTFE and the filling modification materials have been widely used in butterfly valves, so that the performance of butterfly valves has been further improved, and a butterfly valve with a wider range of temperature and pressure, reliable sealing performance and longer service life has been manufactured.
In order to meet the requirements of high and low temperature, strong erosion, long life and other industrial applications, metal seal butterfly valve has 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 high and low temperature, strong erosion, long life and other industrial fields. Large diameter (9-750 mm), high pressure (42.0 MPa), wide temperature range (-196-606) butterfly valves have emerged. So that the butterfly valve technology to a new level.
The butterfly valve has a smaller flow resistance when fully opened. The butterfly valve is widely used in large caliber adjustment fields because of its sensitive flow control when it is opened between 15 and 70 degrees.
Most butterfly valves can be used in media with suspended solids due to the wiping nature of the butterfly valve plate movement. According to the strength of seals, it can also be used in powder and granular media.
Butterfly valves are suitable for flow control. Because the pressure loss of butterfly valve in the pipe is relatively large, about three times that of gate valve, so when choosing butterfly valve, the influence of pressure loss on pipeline system should be fully considered, and the strength of butterfly plate under pipeline medium pressure should be considered when closing. In addition, the temperature limit of the elastomeric seat material at high temperatures must also be considered.
The butterfly valve has smaller structural length and overall height, faster opening and closing speed, and good fluid control characteristics. The structural principle of 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 correctly select the specifications and types of butterfly valve, so that it can work properly and effectively.
Usually, in throttling, regulating control and mud medium, short structure length, fast opening and closing speed, low pressure cut-off (pressure difference is small), butterfly valve is recommended. Butterfly valves are optional for dual-position regulation, shrinkage channels, low noise, cavitation and vaporization, small leakage into the atmosphere, and abrasive media. Under special working conditions, throttling adjustment, or strict sealing, severe wear and tear, low temperature (deep cold) and other working conditions.
Structure of butterfly valve
Butterfly valve has four main components, namely: the body, seat, operator or valve handle, and disk. High performance valves like this usually have a body that would usually fit in between two pipes. Most common body designs are the lug and the wafer. The lug type has these protruding lugs that provide bolt holes, while the wafer type does not have these protrusions and instead, is placed in between the pipes flanges and this in turn surrounds the bolt holes. Both types have their equal share of advantages and disadvantages. The wafer type costs less, but this design does not transfer the weight of the piping system directly through the body. And the lug type is more expensive, but allows removal of downstream piping.
Characteristics of butterfly valves
1. The butterfly valve has the characteristics of simple structure, small volume, light weight, low material consumption, small installation size, quick switch, 90 degree reciprocating rotation, small driving torque, etc. It is used to cut off, switch on and adjust the medium in the pipeline, and has good fluid control characteristics and sealing performance.
2, the butterfly valve can transport mud, and the least liquid is stored in the pipeline. Good seal can be achieved under low pressure. Good regulation performance.
3. The streamlined design of the butterfly plate makes the fluid resistance loss small. It can be said to be an energy saving product.
4. The valve stem is a through rod structure. After quenching and tempering, it has good comprehensive mechanical properties, corrosion resistance and scratch resistance. When the butterfly valve is opened and closed, the stem only rotates without lifting. The packing of the stem is not easy to be destroyed and the seal is reliable. Fixed with the butterfly plate cone pin, the extension end is punch-out-proof design, so as to avoid the valve stem collapse when the connection between the valve stem and the butterfly plate is accidentally broken.
5, the connection way is flange connection, clip pair connection, butt welding connection and lug clip connection.
Drive forms include manual, worm gear drive, electric, pneumatic, hydraulic, electro-hydraulic linkage and other actuators, which can realize long-distance control and automatic operation.
Advantages of butterfly valves
1, opening and closing is convenient, fast, labor-saving, low fluid resistance, and can be operated regularly.
2. It is simple in structure, small in size, short in length, small in volume and light in weight. It is suitable for large-diameter valves.
3. Mud can be transported and liquid stored at the pipe mouth minimum.
4, low pressure, can achieve a good seal.
5, good regulation performance.
6, full opening valve seat effective flow area is large, less fluid resistance.
7. Opening and closing torque is small, because the two sides of the rotating shaft butterfly plate by the medium action is basically equal, resulting in the opposite direction of torque, so opening and closing more labor-saving.
8, sealing surface materials generally use rubber, plastic, so low pressure sealing performance is good.
9, easy installation.
10, flexible and labor-saving operation, you can choose manual, electric, pneumatic, hydraulic methods.
Disadvantages of butterfly valves
1, the use of pressure and working temperature range is small.
2, poor sealing.
According to the structural form, butterfly valves can be divided into offset plate type, vertical plate type, inclined plate type and lever type.
According to the sealing form, it can be two types: soft sealing type and hard sealing type. Rubber seals are usually used for soft seals, and metal seals are usually used for hard seals.
According to the connection type can be divided into flange connection and clamp connection; according to the transmission mode can be divided into manual, gear transmission, pneumatic, hydraulic and electric several.
Main classification of butterfly valves
According to the driving mode of butterfly valve
(1) electric butterfly valve
(2) pneumatic butterfly valve
(3) hydraulic butterfly valve
(4) manual butterfly valve
According to the structural form of butterfly valve, it is divided into:
(1) Central sealed butterfly valve
(2) single eccentric seal butterfly valve
(3) double eccentric sealed butterfly valve
(4) three eccentric sealing butterfly valve
According to the sealing surface of butterfly valve, the material is divided into:
(1) soft sealed butterfly valve.
1) the sealing pair consists of non-metallic soft materials for non-metallic soft materials.
2) the sealing pair consists of metallic hard materials for non-metallic soft materials.
(2) metal hard seal butterfly valve. The sealing pair consists of metal hard materials for metal hard materials.
According to the sealing form of butterfly valve, it is divided into:
(1) forced seal butterfly valve.
1) Flexible Sealed Butterfly Valve: The sealing pressure is produced by the elasticity of the valve seat or disc when the valve is closed.
2) external torque sealed butterfly valve: the torque generated by the seal ratio is added to the valve shaft.
(2) pressurized sealing butterfly valve: Seal ratio pressure is generated by pressurization of the sealing element on the seat or valve plate.
(3) automatic sealing butterfly valve: Seal ratio pressure is automatically generated by medium pressure.
According to the working pressure of butterfly valve:
(1) vacuum butterfly valve. A butterfly valve whose working pressure is lower than the standard stack air pressure.
(2) low pressure butterfly valve. Nominal pressure PN<1.6MPa butterfly valve.
(3) medium pressure butterfly valve. The nominal pressure PN is 2.5–6.4MPa butterfly valve.
(4) high pressure butterfly valve. The nominal pressure PN is 10. 0–80.0MPa butterfly valve.
(5) ultra high pressure butterfly valve. Nominal pressure PN>100MPa butterfly valve.
According to the working temperature of the butterfly valve:
(1) high temperature. T>450 degree C butterfly valve.
(2) medium temperature butterfly valve. 120 butterfly valves at C<t<450 degrees.
(3) butterfly valve at room temperature. A butterfly valve of 40C<t<120 degree C.
(4) low temperature butterfly valve. One 100<t<, one 40 degree C butterfly valve.
(5) ultra low temperature butterfly valve. T< butterfly valve with a 100 degree C.
According to the connection mode of butterfly valve, it is divided into:
1. Clip butterfly valve.
The butterfly plate of the clip butterfly valve is installed in the diameter direction of the pipe. The valve is fully open.
The clamp butterfly valve has the advantages of simple structure, small volume and light weight. Butterfly valve has two types of seal: elastic seal and metal seal. The elastic sealing valve can be inlaid on the valve body or attached to the periphery of the butterfly plate.
2. Flanged butterfly valve
The flange type butterfly valve is a vertical plate type structure, and the valve stem is an integral metal seal valve sealing ring.
For the composite structure of flexible graphite plate and stainless steel plate, it is installed on the valve body, and the sealing surface of butterfly plate is overlaid with stainless steel. The sealing ring of the soft sealing valve is nitrile rubber and is mounted on the butterfly plate.
3. Lug butterfly valve
4. Welded butterfly valve
Welded butterfly valve is a kind of non-hermetic butterfly valve, widely used in building materials, metallurgy, mining, electric power production process medium temperature < 300 ~nominal pressure of 0.1 Mpa pipeline, to connect, open and close or adjust the amount of medium.
The electric control butterfly valve belongs to a variety of electric valve and electric control valve. The connection mode mainly includes flange type and clamp type. It is an important executive unit in the field of industrial automation control. Installation points of electric regulating butterfly valve two major analysis: installation position, height, inlet and outlet direction must meet the design requirements, pay attention to the direction of media flow should be consistent with the arrow direction marked by the valve body, the connection should be firmly and tightly. The appearance of electric butterfly valve must be inspected before installation. The nameplate of the valve should conform to the current national standard GB12220. Strength and tightness tests should be carried out before installation of valves with working pressure greater than 1.0 MPa and cut off on the main pipe. The qualified rear will be used. In the strength test, the test pressure is 1.5 times the nominal pressure, and the duration is not less than 5 minutes. The valve shell and packing should be qualified without leakage. Electrically operated butterfly valves can be divided into offset plate type, vertical plate type, inclined plate type and lever type according to the structural form; according to the sealing form can be divided into soft sealing type and hard sealing type; soft sealing type generally adopts rubber ring seal, hard sealing type usually uses metal ring seal.
Functional uses of butterfly valves
Butterfly valves are usually open to full closure less than 90 degrees, butterfly valves and the butterfly rod itself has no self-locking ability, in order to locate the butterfly plate, to add worm gear reducer on the stem. The use of worm gear reducer can not only make the butterfly plate have the ability of self-locking, so that the butterfly plate stops at any position, but also improve the operation performance of the valve. Industrial butterfly valve features: high temperature resistance, applicable pressure range is also higher, the valve nominal size is large, the valve body is made of carbon steel, the valve plate sealing ring using metal ring instead of rubber ring. Large and high temperature butterfly valves are manufactured by steel plate welding. They are mainly used for smoke channels and gas pipes in high temperature media.
How to choose a butterfly valve?
Butterfly disc is installed in the diameter direction of the pipe. 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 the fully open position, the thickness of the butterfly plate is the resistance when the medium flows through the valve body, so the pressure drop produced by the valve is very small, so it has a good flow control characteristics.
If butterfly valve is used as flow control, the main choice is to choose the size and type of valve correctly. The structural principle of butterfly valve is especially suitable for making large caliber valves. There are two kinds of butterfly valves commonly used for butterfly valves and butterfly valves. The butterfly valve is connected between two pipe flanges by double-head bolts. The flanged butterfly valve is the process of connecting the flanges on the valve with flanges and using bolts to connect the flanges on both ends of the valve to the pipe flange.
Butterfly valve is widely used in many fields, such as petroleum, chemical industry, metallurgy, hydropower and so on. In the well-known butterfly valve technology, the sealing structure is mostly used, sealing materials are rubber, polytetrafluoroethylene and so on. Due to structural limitations, it is not suitable for such industries as high temperature resistance, high pressure, corrosion resistance and wear resistance.
Existing one kind of more advanced butterfly valve is tri-eccentric metal hard-sealed butterfly valve, valve body and valve seat are connected components, valve seat sealing surface layer surfacing welding heat-resistant and corrosion-resistant alloy materials. Compared with the traditional butterfly valve, the butterfly valve has the advantages of high temperature resistance, easy operation, no friction when opening and closing, compensating sealing with the increase of the torque of the transmission mechanism, improving the sealing performance and prolonging the service life of the butterfly valve.
However, the butterfly valve still has the following problems during its use.
1. Because the multi-layer soft-hard laminated sealing ring is fixed on the valve plate, when the valve plate is normally open, the medium forms a positive scour on its sealing surface, and the soft sealing belt in the metal sheet sandwich is scoured, which directly affects the sealing performance.
2. Restricted by structural conditions, this structure is not suitable for valves with diameters below DN200, because 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 valve seat is to press the valve plate to the valve seat by the torque of the transmission device. When the flow is positive, the higher the medium pressure is, the tighter the seal is. The seal begins to leak when the unit positive pressure between the valve plate and the seat is less than the medium pressure when the flow channel medium is countercurrent.
The high-performance three-eccentric bidirectional hard-sealed butterfly valve is characterized in that the seat sealing ring is composed of multi-layer stainless steel sheets on both sides of the soft T-shaped sealing ring. The sealing surface of the valve plate and the valve seat is a diagonal cone structure, and the heat-resistant and corrosion-resistant alloy material is surfacing on the diagonal cone surface of the valve plate; the spring fixed between the regulating ring pressure plate and the regulating bolt on the regulating plate are assembled together.
This structure effectively compensates the tolerance belt between the sleeve 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 transportation. Using soft T-type multi-layer stainless steel sheets on both sides of the sealing ring, has the dual advantages of metal hard sealing and soft sealing, regardless of low temperature and high temperature, have zero leakage sealing performance.
It is proved that the pressure on the sealing surface is caused by the action of the torque of the transmission device and the pressure of the medium on the valve plate when the flow direction of the medium is the same as the rotation direction of the butterfly plate. The tighter the compression between the oblique conical surface of the valve plate and the sealing surface of the valve seat, the better the sealing effect. When the countercurrent is in condition, the seal between the valve plate and the valve seat causes the valve plate to press to the valve seat by the torque of the driving device. When the unit positive pressure between the valve plate and the seat is less than the medium pressure with the increase of the reverse medium pressure, the deformation energy stored in the spring of the regulating ring after loading compensates the tight pressure between the valve plate and the sealing surface of the valve seat automatically. Therefore, unlike the existing technology, the utility model installs soft and hard multi-layer sealing rings on the valve plate, but directly on the valve body, and adds a regulating ring between the pressure plate and the valve seat, which is an ideal two-way hard sealing mode. It will replace gate valves, globe valves and globe valves.
Suitable occasions for butterfly valves
Butterfly valves are suitable for flow control. Because the butterfly valve in the pipeline pressure loss is relatively large, should also consider the closure of the butterfly plate under the pressure of the pipeline medium. In addition, the temperature limit of the elastomeric seat material at high temperatures must also be considered. The butterfly valve has the advantages of small structure length and overall height, fast opening and closing speed, and good fluid control characteristics. The structure principle of butterfly valve is most suitable for making large diameter valve. When the butterfly valve is required to control the flow, the most important thing is to choose the correct size and type of butterfly valve, 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 (differential pressure), recommended butterfly valve.
Butterfly valves can be used in double-position regulation, shrinkage passage, low noise, cavitation and gasification phenomena, a small amount of air leakage, abrasive media.
When the butterfly valve is used under special conditions, such as throttling regulation, strict sealing, severe wear and tear, low temperature (deep cold) and so on, the special designed metal seal belt adjusting device is needed to use the special butterfly valve with triple eccentricity or double eccentricity.
The butterfly valve is suitable for fresh water, sewage, seawater, brine, steam, natural gas, food, medicine, oil, various acids and alkalis and other pipelines which require complete sealing, zero leakage in gas test, high life requirement and working temperature between – 10 and 150 degrees.
Soft-sealed eccentric butterfly valve is suitable for two-way opening and closing of ventilation and dust removal pipelines and is widely used in gas pipelines and waterways of metallurgy, light industry, electric power and petrochemical systems.
Metal-to-metal wire sealed double eccentric butterfly valve is suitable for urban heating, gas supply, water supply and other gas, oil, acid and alkali pipelines, as a regulating and throttling device.
Metal-to-metal tri-eccentric butterfly valves are not only used as program control valves for large pressure swing adsorption (PSA) gas separators, but also widely used in petroleum, petrochemical, chemical, metallurgical, electrical and other fields. They are good substitutes for time gate valves and globe valves.
At present, butterfly valves, as parts that control flow and pipe system, have been widely used in petroleum, chemical engineering, metallurgy, hydroelectricity, and other fields. Hermetic seal is the most-used known technique of butterfly valve seals, whose materials include rubber, PTFE, etc. But it is not suitable for processes that require corrosive, abrasive media, high temperature and pressure due to the restriction of its structure. Recently, there is a more advanced type of butterfly valves named triple offset metal-seated butterfly valve that uses high and cryogenic temperature resistant valve seat and body as the jointing components. Multilayer seal is fixed on the valve plate. Compared to traditional butterfly valves, this kind is better in high temperature resistance, operation, sealability, and life span, with no rubbing at startup and an increase of torque to compensate losing sealability at shutdown.
Yet, there are still problems existing during the process of using.
1. Sealability will be directly affected after the interlayer between pieces of sheet metal is frontally washed by the medium when the valve plate is open, since multilayer seal is fixed on the valve plate.
2. The flow coefficient of the thick valve plate is so big that it is not fit to valves under DN 200.
3.The principle of triple offset butterfly valve structure is that the seal between the surface of valve plate and valve seat hinges on the transmission gear. In co-current state, the sealability of the valve grows with the pressure brought by the medium. Whereas in counter-current state, as the medium’s pressure increases and becomes higher than that between the valve plate and seat, the seal starts leaking.
This utility model is aiming for a universal, high-performance bi-directional triple offset metal-seated butterfly valve with zero leakage, high sensitivity, long life span, high temperature resistance, anti-corrosion, superior abrasion resistance.
Its features are as follow:
The seal of the valve seat is composed of multilayer stainless sheetsteel on both sides of the flexible T-seal. This brings advantages of hard seal and soft seal. Also, high sealability will maintain no matter in cryogenic temperature or high temperature;
The sealing surface of valve plate and seat is oblique cone structure and welded with high temperature corrosion resistant alloy. And on co-current state, when the pressure from medium increases, the tighter between the oblique cone surface and the sealing surface of valve plate, the better the sealability is;
Springs fixed in the middle of the pressure plates assemble with adjustable bolts, which automatically and effectively make up for the tolerance zone between axle sleeve and valve body, as well as the elastic deformation caused by the pressure from mediums, thus it solves the problem of unstable sealability.
This utility model is capable of replacing gate valve, globe valve and ball valve because it is not like any other existed techniques that have to install both hard and soft multilayer seals, but rather, it cancels the step, while adding adjustable ring between the pressure plate and the valve seat, which is an ideal bidirectional hard sealing method.
Source: China Butterfly Valve Manufacturer – Yaang Pipe Industry Co., Limited (www.metallicsteel.com)
(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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