Change the qualitative thinking regarding the application scenarios of check valves
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This post was last edited by Refinery Operator on 2011-7-15 18:42. In the past, butterfly valves, as components used to control the opening and closing of pipelines as well as flow rates, have been widely utilized in many fields such as petroleum, chemicals, metallurgy, and hydropower. In the well-known butterfly valve technology, sealing is typically achieved through a sealing structure, with sealing materials such as rubber and polytetrafluoroethylene being used. Due to limitations in its structural properties, it is not suitable for applications requiring high temperature and pressure resistance, as well as corrosion and wear resistance. With the continuous improvement of technical and equipment standards, the excellent performance of three-eccentric metal hard-sealed ball valves, along with their compact size, ease of operation and maintenance, will ensure their widespread use. Everyone can discuss the usage status of this type of control valve currently in use at their own units. To serve as a starting point for further discussion, I would like to provide a brief introduction to the three-eccentric metal hard-sealed butterfly valve: A relatively advanced type of butterfly valve is the three-eccentric metal hard-sealed butterfly valve, in which the valve body and the valve seat are integrated components, with the sealing surface of the valve seat being clad with heat-resistant and corrosion-resistant alloy materials. Multi-layer soft folded sealing rings are fixed on the valve plate; compared to traditional butterfly valves, this type of butterfly valve offers advantages such as high temperature resistance, easy operation, friction-free opening and closing. When closed, the sealing is enhanced as the torque applied by the actuation mechanism increases, which improves the sealing performance of the butterfly valve and extends its service life. However, this type of butterfly valve still has the following problems during use: First, since the multi-layered soft and hard gasket assembly is fixed on the valve disc, when the valve disc is in the open position, the medium exerts direct erosion on its sealing surface; as a result, the soft sealing strip located in the metal layer is damaged by this erosion, which directly affects the sealing performance. II. Due to structural constraints, this design is not suitable for valves with a diameter of DN200 or less, as the overall structure of the valve disc is too thick, resulting in high flow resistance. III. Due to the principle of the three-eccentric structure, the sealing between the sealing surface of the valve disc and the valve seat is achieved by the torque of the actuation mechanism, which presses the valve disc against the valve seat. In the forward flow state, the higher the medium pressure, the tighter the sealing compression. When the flow medium flows in reverse, as the pressure of the medium increases and the unit normal pressure between the valve plate and the valve seat becomes less than the pressure of the medium, leakage in the seal begins. A high-performance triple-eccentric two-way hard-sealed butterfly valve, characterized in that: the valve seat sealing ring is composed of multiple layers of stainless steel sheets on both sides of a flexible T-shaped sealing ring. The sealing surfaces of the valve plate and the valve seat are of a inclined cone shape, with heat-resistant and corrosion-resistant alloy materials welded onto the inclined cone surface of the valve plate ； A structure in which a spring fixed between the adjustment ring pressure plates is assembled with the adjustment bolts on the pressure plates. This structure effectively compensates for the tolerance gaps between the shaft sleeve and the valve body, as well as the elastic deformation of the valve stem under medium pressure, thereby resolving the sealing issues that arise during two-way media transfer. A sealing ring is formed using multiple layers of stainless steel sheets on both sides of a flexible T-shaped structure, combining the advantages of both metal hard sealing and soft sealing; it provides zero-leakage sealing performance in both low-temperature and high-temperature conditions. Tests have shown that in the forward flow condition of the tank (where the direction of fluid flow is the same as the direction of rotation of the butterfly valve disc), the pressure on the sealing surface is generated by the torque exerted by the actuation mechanism and the pressure of the fluid acting on the valve disc. As the positive medium pressure increases, the inclined conical surface of the valve plate presses more tightly against the sealing surface of the valve seat, resulting in an improved sealing effect. In the reverse flow condition, the seal between the valve disc and the valve seat is maintained by the torque of the driving mechanism, which presses the valve disc against the valve seat. As the reverse medium pressure increases, when the unit normal pressure between the valve plate and the valve seat is less than the medium pressure, the deformation energy stored in the spring of the adjustment ring under load compensates for the sealing force between the valve plate and the valve seat, thereby providing automatic compensation. Therefore, unlike existing technologies that use multiple layers of soft and hard sealing rings on the valve plate, this utility model installs them directly on the valve body; adding an adjustment ring between the pressure plate and the valve seat represents an ideal method for achieving bidirectional hard sealing. It can replace gate valves, globe valves, and ball valves. This post was last edited by fushan on 2007-1-17 20:43]
Introduction to the structure of metal double-seal butterfly valves: Ordinary metal-sealed butterfly valves feature a double-eccentric or triple-eccentric design. The sealing geometry of the butterfly disc is conical or spherical. The elasticity of the seal ring is achieved through radial compression of the butterfly disc and the thrust from the flowing medium, creating a \"keying effect\" that enables flexible contact between the seal ring elements, thus ensuring sealing in the forward direction; however, the sealing performance in the reverse direction is poor. Therefore, it can only be used in systems such as heating, water supply, oil and gas, metallurgy, and energy, in pipelines where only unidirectional sealing is required. The metal double-direction sealing butterfly valve builds on the advantages of the aforementioned single-direction sealing butterfly valves; its butterfly plate features a parabolic sealing geometry. Whether the flow enters from the front or the back, a \"keying effect\" can be generated on the butterfly plate, allowing the sealing ring to make flexible contact and thus achieving double-direction sealing. Operating principle of the three-eccentric metal dual-seal butterfly valve: To address the shortcomings of single-seal butterfly valves in terms of sealing performance, to expand the range of applications for these valves, and to meet higher requirements in various operating conditions, the newly developed three-eccentric metal dual-seal butterfly valve uses an eccentric parabolic-shaped sealing surface instead of a spherical sealing surface. Three-eccentric metal double-seal butterfly valve, where H1 and H2 represent axial and radial eccentricity respectively, and a represents angular eccentricity. The curvature of the eccentric parabolic sealing surface varies, and the direction of this variation is opposite to that of the opening and closing movement of the butterfly valve, which makes it easier for the butterfly valve to disengage from or get stuck in the valve seat during operation. When the butterfly plate is open, the valve seat is in a relaxed state and can float within the grooves of the valve body. When the butterfly plate is closed, the valve seat moves along with the insertion of the butterfly plate to reach the optimal sealing position; under the pressure exerted by the butterfly plate, the sealing force between the valve seat, the butterfly plate, and the valve increases gradually until it reaches its maximum value. The valve seat becomes oval-shaped due to this pressure, with the long axis being b and the short axis being R. There is the following relationship between the circumferences of their inner holes: π(b+R) > 2πR. The compression amount can be determined from the sealing specific pressure, and the major axis b can be derived to obtain the angular eccentricity value a. When the valve is closed, each cross-section of the valve seat is compressed by the butterfly plate and the stem, resulting in elastic deformation in two directions. The valve seat is subjected to an outward tensile force in the long-axis direction, and an inward compressive stress in the short-axis direction. The long and short axes undergo elastic deformation in different directions. Stress effects can be generated regardless of whether the medium enters from the forward or reverse direction, thereby achieving sealing. Structural features of the three-eccentric double-sealing butterfly valve: The floating structure of this valve, along with the curved shape of its eccentric parabolic sealing surface, effectively reduces the frictional torque on the valve seat as well as the value of radial eccentricity H2 (in other words, it reduces the eccentric torque). Under the same operating conditions, the H2 eccentricity value of the three-eccentric metal double-sealing butterfly valve is 40% to 60% that of a single-eccentric butterfly valve. The torque exerted on the valve shaft is reduced; using the same materials and driving force, the three-eccentric metal double-sealing butterfly valve can meet higher requirements of the process compared to a single-eccentric metal sealing butterfly valve. During the use of valves, corrosion and damage to their seat are inevitable; ordinary butterfly valves can only be shut down for maintenance in order to replace the seat. The perimeter of the sealing circle of the seat of a three-eccentric metal double-seal butterfly valve increases as the angular eccentricity a increases. When the seat is corroded or damaged, it is sufficient to adjust the direction of operation, which in turn increases both the angular eccentricity a and the amount of elastic compression of the seat. By grinding the area between the butterfly plate and the valve seat, damage to the valve seat can be eliminated. The floating of the valve seat ensures an optimal sealing position between the butterfly plate and the valve seat once the valve is closed, thereby preventing leaks. Advantages and specifications of the three-eccentric metal double-seal butterfly valve: · The elastic metal seal ring and valve seat ensure zero leakage. · The parabolic seal guarantees continuous double-direction zero leakage performance of the valve. · The three-eccentric parabolic geometry of the butterfly disc matches the valve’s opening and closing trajectory, making operation easier at full rotation. · The all-metal structure combined with zero leakage performance endows the valve with \"inherent fire safety\" characteristics. · The butterfly valve’s sealing surfaces are coated with a super-hard layer, enhancing their durability. According to Clause 6.4 of China’s standard JB/T8527-97 \"Metal Sealed Butterfly Valves\", an arrow indicating the sealing direction of the butterfly valve shall be marked on its body. For butterfly valves with one-way sealing, the word \"Sealing Direction\" is indicated on the arrow; for those with two-way sealing, the word \"Primary Sealing Direction\" is indicated on the arrow. Article 7.2 stipulates that during testing, for one-way sealed butterfly valves, pressure should be applied in the direction indicated on the valve body; for two-way sealed butterfly valves, pressure should be applied at both ends. In the case of two-way sealing, the leakage rate in the reverse direction should not exceed twice that in the forward direction. This post was last edited by fushan on 2007-1-17 20:48]
Development and Applications of Three-Eccentric Butterfly Valves In many countries in the Asia-Pacific region, due to limitations in the local capabilities for valve design and manufacturing, as well as the influence of traditional textbooks, there remains a significant prejudice against butterfly valves. Meanwhile, the advanced industrial countries in Europe and the United States are actively promoting and using butterfly valves. The reason is simple: butterfly valves are not what they used to be. The excellent performance of butterfly valves is closely related to their continuous eccentricity, evolution, and development. To meet the requirements of various operating conditions, butterfly valves have evolved from concentric design to single-eccentric, double-eccentric, and triple-eccentric designs. The evolution of butterfly valves, as well as a brief introduction to the development and applications of 3-eccentric butterfly valves, are as follows:
I. Classification of Butterfly Valves
1. Concentric Butterfly Valve
The structural feature of this type of butterfly valve is that the axis of the valve stem, the center of the butterfly disc, and the center of the valve body are all in the same position. It has a simple structure and is easy to manufacture. Common rubber-lined butterfly valves fall into this category. The disadvantage is that the butterfly plate and the valve seat are constantly under compression and scraping, resulting in a large flow resistance and rapid wear. To overcome compression and scraping and ensure sealing performance, the valve seat is generally made of elastic materials such as rubber or polytetrafluoroethylene; however, this also imposes temperature limitations on its use, which is why butterfly valves are traditionally considered unsuitable for high temperatures. 2. Single-eccentric butterfly valve: To address the problem of compression between the butterfly disc and the valve seat in concentric butterfly valves, the single-eccentric butterfly valve was developed. Its structural feature is that the axis of the valve stem is offset from the center of the butterfly disc, which means that the upper and lower ends of the butterfly disc are no longer the rotation axis; this reduces and alleviates the excessive compression between those ends and the valve seat. However, due to the fact that the scraping between the butterfly disc and the valve seat does not cease throughout the entire opening and closing process of the valve in a single-eccentric design, and its application range is similar to that of concentric butterfly valves, it is not widely used. 3. Double-eccentric butterfly valve: The double-eccentric butterfly valve, which is a further improved version of the single-eccentric butterfly valve, is currently the most widely used type. Its structural feature is that the axis of the valve stem is offset from both the center of the butterfly plate and the center of the body. The effect of double eccentricity enables the butterfly disc to quickly disengage from the valve seat once the valve is opened, significantly reducing unnecessary excessive compression and scraping between the butterfly disc and the valve seat, decreasing the opening force, minimizing wear, and extending the lifespan of the valve seat. Scratching is significantly reduced, and this also allows double-eccentric butterfly valves to use metal seats, thereby enhancing the applicability of butterfly valves in high-temperature environments. However, because its sealing principle relies on a position-based sealing mechanism – that is, the sealing surfaces of the butterfly plate and the valve seat are in line contact, and sealing is achieved through the elastic deformation of the valve seat caused by the pressure exerted by the butterfly plate – high requirements are placed on its closed position (especially for metal valve seats), and its pressure resistance is low. This is why it is traditionally believed that butterfly valves cannot handle high pressures and suffer from high leakage rates. 4. Three-eccentric butterfly valve: Must be able to withstand high temperatures; a hard seal is required, but it results in high leakage rates ； To achieve zero leakage, soft seals must be used, but they cannot withstand high temperatures. To overcome the contradiction of the double-eccentric butterfly valve, a third eccentricity was applied to the butterfly valve. Its structural feature is that, in addition to the double eccentricity of the valve stem axis, the conical axis of the butterfly valve’s sealing surface is also tilted relative to the cylinder axis of the valve body; in other words, after the third level of eccentricity, the sealing cross-section of the butterfly valve is no longer circular but elliptical, and as a result its sealing surface becomes asymmetric – one side being inclined relative to the center line of the valve body while the other side remains parallel to it. The most significant feature of this third type of eccentric design is that it fundamentally changes the sealing mechanism: it is no longer a position-based seal but rather a torque-based seal. In other words, sealing is achieved not through the elastic deformation of the valve seat, but entirely based on the pressure at the contact surface between the valve components. This approach solves the problem of zero leakage in metal valve seats. Moreover, since the contact surface pressure is proportional to the medium pressure, high pressure and high temperature conditions can also be handled easily. II. Development of three-eccentric disc valves Since their introduction, three-eccentric disc valves have undergone continuous improvement and development in order to meet increasingly stringent operating conditions. Even the most basic requirement of zero leakage can be achieved with a theoretically three-eccentric disc valve, but in practice it still relies on careful design and precise manufacturing. Based on the analysis and summary of the strengths and weaknesses of three-eccentric disc valves from other brands, Baty Valve Co., Ltd. has developed its own unique three-eccentric disc valve, Tritec, with the following features: 1. API specification. As is well known, API609 has effectively become the international standard for valves used in important industrial pipelines. Tritec, on the other hand, is designed and manufactured in full compliance with the latest 1997 version of the API609 specifications. What’s more valuable is that Tritec’s basic design is not limited to just one set of specifications; it can comply with various standards such as API, BS5155, ANSI B 16.34, and ASME SEC VIII. This ensures that Tritec can be utilized in all industrial fields. 2. Dual safety design: In strict compliance with the specifications of API609, Tritec installs two separate thrust rings on the upper and lower sides of the butterfly valve to prevent deformation of the butterfly plate, misalignment of the valve stem, and seizure of the sealing surfaces caused by fluid pressure and temperature. This ensures the proper operation of the valve under all operating conditions ； At the same time, to prevent sudden accidents caused by valve stem damage or expulsion due to unknown reasons, separate mechanisms for preventing the valve stem from escaping have been designed on both the inside and outside of the lower part of the valve; this also helps ensure that Tritec’s pressure rating can reach up to 2500 pounds. 3. Dead zone-free design: During the design process, Tritec took special account of applications in control systems, making full use of the sealing principle of triple-eccentric butterfly valves. This ensures that the butterfly disc does not scrape against the valve seat when the valve is opened or closed; the torque from the valve stem is transmitted directly to the sealing surface via the butterfly disc, meaning there is almost no friction between the butterfly disc and the valve seat. As a result, the jumping phenomenon that occurs when opening ordinary valves is eliminated, and instability issues caused by friction and other factors at low valve opening angles are removed – in other words, the dead zone (zone without effective control) is eliminated. This means that Tritec can enter the controllable range starting from an opening angle of 0 degrees, all the way up to 90 degrees. Its control ratio is more than twice that of ordinary butterfly valves, with a maximum control ratio of over 100:1. This creates favorable conditions for Tritec to be used as a control valve, especially in large-diameter applications where the cost of globe valves is extremely high. Moreover, globe valves cannot achieve zero leakage; in situations requiring emergency shutdown, a separate shut-off valve must be installed alongside the globe valve. Tritec combines control and shut-off functions in one unit, resulting in significant economic benefits. 4. Valve seat structure of the body There are two types of valve seat installation structures for three-eccentric butterfly valves; in most cases, they are installed on the butterfly disc for convenience, but Tritec adopts a body-valve seat structure, with the valve seat mounted on the body. Its advantage is that, compared to butterfly valve seats, **it reduces the likelihood of the seat coming into direct contact with the medium, thereby minimizing erosion of the seat and extending its service life. 5. Thin-plate valve seat structure: Tritec’s valve seats are composed of layers of stainless steel sheets and graphite sheets; this structure effectively prevents the impact of tiny solid particles in the medium, as well as seal surface damage that can result from thermal expansion. Even in the event of minor damage, no leakage occurs, which is something impossible with double-eccentric butterfly valves or other types of three-eccentric butterfly valves. 6. Replaceable sealing pairs The sealing pairs offered by Tritec are truly unique: not only can the valve seat itself be replaced, but since the butterfly valve’s sealing surface is separate from the butterfly plate itself, this sealing surface can also be replaced. In other words, when the butterfly valve’s sealing surface is damaged, there is no need to send the valve back to the manufacturer or disassemble it thoroughly; simply replacing the sealing surface is sufficient. This not only **reduces maintenance costs** but also **lowers the amount of time required for repairs, as well as the intensity and complexity of such repairs**. 7. Balanced fixed structure: Based on the shape characteristics of the sealing surfaces in three-eccentric butterfly valves, Tritec employs a bolt arrangement with an elliptical distribution for fixing the sealing pairs. This not only ensures precise positioning but also allows each bolt to bear equal forces, thereby preventing loosening of the sealing pairs and leakage caused by uneven stress distribution. 8. Essential fire-resistant construction Many valves claim to have a fire-resistant structure, but the vast majority of them use a dual-seat design (soft and hard seats) in order to reduce leakage, which is actually very dangerous. Because incomplete combustion of the soft-sealed valve seat during a fire can cause stress and temperature-induced deformation in the metal support for the valve seat, thereby leading to a failure in its fire-resistant capabilities. Therefore, Europe and the United States are gradually phasing out such fire-resistant valves that do not live up to their name. Tritrc has zero leakage, thus it does not require the assistance of soft seals; it features a truly fire-resistant design, and it holds certification for fire resistance testing in accordance with API607, API6FA, and BS6755 Part 2. This ensures that Tritec can be used in various hazardous areas such as the oil and petrochemical industries. A prime example of this is in conservative Britain, where Tritec controls almost all the valves used in the various key areas of its North Sea oil fields. 9. High-seal packing structure Regarding valve leakage issues, traditional approaches have tended to focus on leakage at the valve seat, that is, internal leakage, while ignoring leakage at the packing area, that is, external leakage. In fact, in today’s society where environmental issues are receiving increasing attention, it is an undeniable fact that the hazards caused by external leaks are far greater than those caused by internal leaks. The Tritec triple-eccentric butterfly valve is a rotary-type valve; its valve stem moves only by 90°. Compared to valves such as gate valves and globe valves, whose valve stems undergo multiple rotational reciprocating movements, the wear on the sealing elements of this valve is very low, resulting in a relatively long service life. Furthermore, since Tritec adopts the highest standard designs for sealing mechanisms to prevent external leaks, it ensures that the leakage level remains below 100 ppm when subjected to external leak tests in accordance with EPA21 standards. In fact, according to the existing Tritec test results, under Lloyd’s monitoring, the external leakage level is as low as 7 ppm. All these indicators indicate that Tritec can be highly effective in pipelines carrying toxic and hazardous fluids in various fields such as the chemical industry. III. Applications of Three-Eccentric Butterfly Valves In summary, as the culmination of the latest advancements in valve technology, the three-eccentric butterfly valve combines the advantages of various types of valves while overcoming their shortcomings; it is bound to receive increasing attention from users and designers alike. Tritec from Badia Valve Co., Ltd. can reach a maximum pressure rating of 2500 pounds; its standard diameter is 48 inches. It is available in butt, lug, flange, ring joint, butt weld, jacketed, and various other configurations in terms of length. Moreover, thanks to the wide range of material options available for Tritec, it can handle high and low temperatures as well as various corrosive substances such as acids and bases. Especially in the field of large-diameter valves, it is steadily replacing bulky gate and ball valves due to its leak-free advantage; similarly, it is also gradually replacing heavy-duty stop valves in control valves, thanks to its excellent control capabilities. As a fact, to date, Tritec has been used in various important pipelines for process control across a wide range of industrial sectors, including oil and gas extraction in China, offshore platforms, oil refining, petrochemicals, inorganic chemicals, and energy generation.
I. Classification of Butterfly Valves
1. Concentric Butterfly Valve
The structural feature of this type of butterfly valve is that the axis of the valve stem, the center of the butterfly disc, and the center of the valve body are all in the same position. It has a simple structure and is easy to manufacture. Common rubber-lined butterfly valves fall into this category. The disadvantage is that the butterfly plate and the valve seat are constantly under compression and scraping, resulting in a large flow resistance and rapid wear. To overcome compression and scraping and ensure sealing performance, the valve seat is generally made of elastic materials such as rubber or polytetrafluoroethylene; however, this also imposes temperature limitations on its use, which is why butterfly valves are traditionally considered unsuitable for high temperatures. 2. Single-eccentric butterfly valve: To address the problem of compression between the butterfly disc and the valve seat in concentric butterfly valves, the single-eccentric butterfly valve was developed. Its structural feature is that the axis of the valve stem is offset from the center of the butterfly disc, which means that the upper and lower ends of the butterfly disc are no longer the rotation axis; this reduces and alleviates the excessive compression between those ends and the valve seat. However, due to the fact that the scraping between the butterfly disc and the valve seat does not cease throughout the entire opening and closing process of the valve in a single-eccentric design, and its application range is similar to that of concentric butterfly valves, it is not widely used. 3. Double-eccentric butterfly valve: The double-eccentric butterfly valve, which is a further improved version of the single-eccentric butterfly valve, is currently the most widely used type. Its structural feature is that the axis of the valve stem is offset from both the center of the butterfly plate and the center of the body. The effect of double eccentricity enables the butterfly disc to quickly disengage from the valve seat once the valve is opened, significantly reducing unnecessary excessive compression and scraping between the butterfly disc and the valve seat, decreasing the opening force, minimizing wear, and extending the lifespan of the valve seat. Scratching is significantly reduced, and this also allows double-eccentric butterfly valves to use metal seats, thereby enhancing the applicability of butterfly valves in high-temperature environments. However, because its sealing principle relies on a position-based sealing mechanism – that is, the sealing surfaces of the butterfly plate and the valve seat are in line contact, and sealing is achieved through the elastic deformation of the valve seat caused by the pressure exerted by the butterfly plate – high requirements are placed on its closed position (especially for metal valve seats), and its pressure resistance is low. This is why it is traditionally believed that butterfly valves cannot handle high pressures and suffer from high leakage rates. 4. Three-eccentric butterfly valve: Must be able to withstand high temperatures; a hard seal is required, but it results in high leakage rates ； To achieve zero leakage, soft seals must be used, but they cannot withstand high temperatures. To overcome the contradiction of the double-eccentric butterfly valve, a third eccentricity was applied to the butterfly valve. Its structural feature is that, in addition to the double eccentricity of the valve stem axis, the conical axis of the butterfly valve’s sealing surface is also tilted relative to the cylinder axis of the valve body; in other words, after the third level of eccentricity, the sealing cross-section of the butterfly valve is no longer circular but elliptical, and as a result its sealing surface becomes asymmetric – one side being inclined relative to the center line of the valve body while the other side remains parallel to it. The most significant feature of this third type of eccentric design is that it fundamentally changes the sealing mechanism: it is no longer a position-based seal but rather a torque-based seal. In other words, sealing is achieved not through the elastic deformation of the valve seat, but entirely based on the pressure at the contact surface between the valve components. This approach solves the problem of zero leakage in metal valve seats. Moreover, since the contact surface pressure is proportional to the medium pressure, high pressure and high temperature conditions can also be handled easily. II. Development of three-eccentric disc valves Since their introduction, three-eccentric disc valves have undergone continuous improvement and development in order to meet increasingly stringent operating conditions. Even the most basic requirement of zero leakage can be achieved with a theoretically three-eccentric disc valve, but in practice it still relies on careful design and precise manufacturing. Based on the analysis and summary of the strengths and weaknesses of three-eccentric disc valves from other brands, Baty Valve Co., Ltd. has developed its own unique three-eccentric disc valve, Tritec, with the following features: 1. API specification. As is well known, API609 has effectively become the international standard for valves used in important industrial pipelines. Tritec, on the other hand, is designed and manufactured in full compliance with the latest 1997 version of the API609 specifications. What’s more valuable is that Tritec’s basic design is not limited to just one set of specifications; it can comply with various standards such as API, BS5155, ANSI B 16.34, and ASME SEC VIII. This ensures that Tritec can be utilized in all industrial fields. 2. Dual safety design: In strict compliance with the specifications of API609, Tritec installs two separate thrust rings on the upper and lower sides of the butterfly valve to prevent deformation of the butterfly plate, misalignment of the valve stem, and seizure of the sealing surfaces caused by fluid pressure and temperature. This ensures the proper operation of the valve under all operating conditions ； At the same time, to prevent sudden accidents caused by valve stem damage or expulsion due to unknown reasons, separate mechanisms for preventing the valve stem from escaping have been designed on both the inside and outside of the lower part of the valve; this also helps ensure that Tritec’s pressure rating can reach up to 2500 pounds. 3. Dead zone-free design: During the design process, Tritec took special account of applications in control systems, making full use of the sealing principle of triple-eccentric butterfly valves. This ensures that the butterfly disc does not scrape against the valve seat when the valve is opened or closed; the torque from the valve stem is transmitted directly to the sealing surface via the butterfly disc, meaning there is almost no friction between the butterfly disc and the valve seat. As a result, the jumping phenomenon that occurs when opening ordinary valves is eliminated, and instability issues caused by friction and other factors at low valve opening angles are removed – in other words, the dead zone (zone without effective control) is eliminated. This means that Tritec can enter the controllable range starting from an opening angle of 0 degrees, all the way up to 90 degrees. Its control ratio is more than twice that of ordinary butterfly valves, with a maximum control ratio of over 100:1. This creates favorable conditions for Tritec to be used as a control valve, especially in large-diameter applications where the cost of globe valves is extremely high. Moreover, globe valves cannot achieve zero leakage; in situations requiring emergency shutdown, a separate shut-off valve must be installed alongside the globe valve. Tritec combines control and shut-off functions in one unit, resulting in significant economic benefits. 4. Valve seat structure of the body There are two types of valve seat installation structures for three-eccentric butterfly valves; in most cases, they are installed on the butterfly disc for convenience, but Tritec adopts a body-valve seat structure, with the valve seat mounted on the body. Its advantage is that, compared to butterfly valve seats, **it reduces the likelihood of the seat coming into direct contact with the medium, thereby minimizing erosion of the seat and extending its service life. 5. Thin-plate valve seat structure: Tritec’s valve seats are composed of layers of stainless steel sheets and graphite sheets; this structure effectively prevents the impact of tiny solid particles in the medium, as well as seal surface damage that can result from thermal expansion. Even in the event of minor damage, no leakage occurs, which is something impossible with double-eccentric butterfly valves or other types of three-eccentric butterfly valves. 6. Replaceable sealing pairs The sealing pairs offered by Tritec are truly unique: not only can the valve seat itself be replaced, but since the butterfly valve’s sealing surface is separate from the butterfly plate itself, this sealing surface can also be replaced. In other words, when the butterfly valve’s sealing surface is damaged, there is no need to send the valve back to the manufacturer or disassemble it thoroughly; simply replacing the sealing surface is sufficient. This not only **reduces maintenance costs** but also **lowers the amount of time required for repairs, as well as the intensity and complexity of such repairs**. 7. Balanced fixed structure: Based on the shape characteristics of the sealing surfaces in three-eccentric butterfly valves, Tritec employs a bolt arrangement with an elliptical distribution for fixing the sealing pairs. This not only ensures precise positioning but also allows each bolt to bear equal forces, thereby preventing loosening of the sealing pairs and leakage caused by uneven stress distribution. 8. Essential fire-resistant construction Many valves claim to have a fire-resistant structure, but the vast majority of them use a dual-seat design (soft and hard seats) in order to reduce leakage, which is actually very dangerous. Because incomplete combustion of the soft-sealed valve seat during a fire can cause stress and temperature-induced deformation in the metal support for the valve seat, thereby leading to a failure in its fire-resistant capabilities. Therefore, Europe and the United States are gradually phasing out such fire-resistant valves that do not live up to their name. Tritrc has zero leakage, thus it does not require the assistance of soft seals; it features a truly fire-resistant design, and it holds certification for fire resistance testing in accordance with API607, API6FA, and BS6755 Part 2. This ensures that Tritec can be used in various hazardous areas such as the oil and petrochemical industries. A prime example of this is in conservative Britain, where Tritec controls almost all the valves used in the various key areas of its North Sea oil fields. 9. High-seal packing structure Regarding valve leakage issues, traditional approaches have tended to focus on leakage at the valve seat, that is, internal leakage, while ignoring leakage at the packing area, that is, external leakage. In fact, in today’s society where environmental issues are receiving increasing attention, it is an undeniable fact that the hazards caused by external leaks are far greater than those caused by internal leaks. The Tritec triple-eccentric butterfly valve is a rotary-type valve; its valve stem moves only by 90°. Compared to valves such as gate valves and globe valves, whose valve stems undergo multiple rotational reciprocating movements, the wear on the sealing elements of this valve is very low, resulting in a relatively long service life. Furthermore, since Tritec adopts the highest standard designs for sealing mechanisms to prevent external leaks, it ensures that the leakage level remains below 100 ppm when subjected to external leak tests in accordance with EPA21 standards. In fact, according to the existing Tritec test results, under Lloyd’s monitoring, the external leakage level is as low as 7 ppm. All these indicators indicate that Tritec can be highly effective in pipelines carrying toxic and hazardous fluids in various fields such as the chemical industry. III. Applications of Three-Eccentric Butterfly Valves In summary, as the culmination of the latest advancements in valve technology, the three-eccentric butterfly valve combines the advantages of various types of valves while overcoming their shortcomings; it is bound to receive increasing attention from users and designers alike. Tritec from Badia Valve Co., Ltd. can reach a maximum pressure rating of 2500 pounds; its standard diameter is 48 inches. It is available in butt, lug, flange, ring joint, butt weld, jacketed, and various other configurations in terms of length. Moreover, thanks to the wide range of material options available for Tritec, it can handle high and low temperatures as well as various corrosive substances such as acids and bases. Especially in the field of large-diameter valves, it is steadily replacing bulky gate and ball valves due to its leak-free advantage; similarly, it is also gradually replacing heavy-duty stop valves in control valves, thanks to its excellent control capabilities. As a fact, to date, Tritec has been used in various important pipelines for process control across a wide range of industrial sectors, including oil and gas extraction in China, offshore platforms, oil refining, petrochemicals, inorganic chemicals, and energy generation.
Thank you for the introduction, OP. I hadn’t paid much attention to this before. Foreign standards generally specify that butterfly valves should be used for valves with a diameter of DN250 or more; therefore, this design standard is also followed in China