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Structure diagram of double eccentric butterfly valve

January 11, 2022

Double eccentric butterfly valves are often referred to as high performance butterfly valves. On the basis of the single eccentric butterfly valve, the most widely used double eccentric butterfly valve is further improved and formed.
Structural features of double eccentric butterfly valve: The center of rotation of the valve plate (ie the center of the valve shaft) forms a dimension α offset with the valve plate sealing section, and a dimension b offset with the centerline of the valve body.

double eccentric butterfly valve structure diagram

Sealing principle of double eccentric butterfly valve: On the basis of the single eccentric sealing butterfly valve, the center of rotation of the valve plate (ie the center of the valve shaft) is offset by a dimension b with the center line of the valve body. When the double eccentric sealing butterfly valve is in a fully open state, The valve plate sealing surface will be completely separated from the valve seat sealing surface, and a gap y larger than the X gap in the single eccentric sealing butterfly valve is formed between the valve plate sealing surface and the valve seat sealing surface, thereby reducing the opening and closing of the valve plate. Mechanical wear and abrasion between the two sealing surfaces of the butterfly valve seal pair.

high performance-double eccentric-butterlfy valve-wafer-lug-flanged (6)

In the usual design, when the valve plate is rotated from 0° to 8° to 12°, the sealing surface of the valve plate can be completely separated from the sealing surface of the valve seat, so that during the opening and closing process of the butterfly valve, the sealing surface between the valve plate and the valve seat is separated. Compared with mechanical wear, the extrusion angle stroke is shorter, so that the mechanical wear and extrusion deformation are further reduced, and the sealing performance of the butterfly valve is further improved.

The main reasons for the failure of the sealing performance of the double eccentric butterfly valve sealing pair
① During the opening and closing process of the butterfly valve, when the valve plate rotates and squeezes the elastic soft valve seat, the valve plate and the valve seat are mechanically worn and scratched;
②After the valve plate squeezes the elastic valve seat, the elastic valve seat or the elastic layer of the valve plate will produce permanent plastic deformation, cold flow, elastic failure, etc.;
③The material of the elastic valve seat or the elastic layer of the valve plate is aging and failing, etc.;
④ Medium cavitation and erosion of the sealing surface.

Features of double eccentric butterfly valve
①The structure is more complicated than the single eccentric sealing butterfly valve, and the cost is slightly higher;
②The sealing performance is better than that of the single eccentric sealing butterfly valve;
③The service life is longer than that of the single eccentric sealing butterfly valve, and the operating pressure is also higher.
Difference: Double eccentric butterfly valve can use metal seat, which improves the application of butterfly valve in high temperature field. However, because its sealing principle is a positional sealing structure, that is, the sealing surface of the disc and the valve seat is in line contact, and the elastic deformation caused by the disc extrusion of the valve seat produces a sealing effect, so it has high requirements for the closing position (especially metal Valve seat), low pressure bearing capacity, which is why traditionally people think that butterfly valves are not resistant to high pressure and have large leakage.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Video of double eccentric butterfly valve:

Application of double eccentric butterfly valve and triple eccentric butterfly valve

December 29, 2021

Butterfly valves can be divided into centerline butterfly valves, single eccentric butterfly valves, double eccentric butterfly valves and triple eccentric butterfly valves. These butterfly valves are widely used in our production and life. Because of some defects of the centerline butterfly valve itself, it is not suitable for the environment where the temperature and pressure are too high or too low, so the butterfly valve is continuously improved, and this is the new design of single eccentric, double eccentric, and triple eccentric. Improvement is a breakthrough. Nowadays, the

Double eccentric-lug butterfly valve-D72F-150lbP-stainless steel (4)

application range of double eccentric butterfly valve and triple eccentric butterfly valve is wider and wider. This article will introduce the application of double eccentric butterfly valve and triple eccentric butterfly valve.

Application of double eccentric butterfly valve
The double eccentric butterfly valve is designed with eccentric structure and is widely used in the fluid pipeline system of water supply and drainage, sewage, construction, petroleum, chemical, textile, paper, hydropower, metallurgy, energy and other projects for regulation and interception.
Under normal circumstances, the seat material of the double eccentric butterfly valve is made of tetrafluoroethylene, which can effectively prevent corrosion. In addition, metal sealing seat can also be used to adapt to the high temperature environment. However, the double eccentric butterfly valve adopts metal sealing seat. The sealing surface of the butterfly plate and the seat is in line contact. The seal is a positional sealing structure. This sealing structure cannot withstand high pressure. If used in high pressure conditions, it will cause a lot of leakage. Therefore, do not use double eccentric butterfly valves with metal seal seats in high-pressure working environments or systems that require tight shut-off.

Application of triple eccentric butterfly valve

triple eccentric butterfly valve-lug

The triple eccentric butterfly valve is currently the most technologically advanced butterfly valve. It not only absorbs the advantages of other butterfly valve products, but also avoids the shortcomings of other butterfly valves, and has been valued by more and more users and technicians. The triple eccentric butterfly valve has a lot of leeway in the selection of sealing materials, and can deal with corrosive media such as high and low temperatures and various acids and alkalis. In addition, the triple eccentric butterfly valve can achieve zero leakage and is particularly suitable for making large-diameter valves. When used as a cut-off valve, it can replace gate valves and ball valves; when used as a flow adjustment, it can replace bulky shut-off valves.
At present, triple eccentric butterfly valves are used in important pipelines in large industrial fields such as petroleum exploration, petroleum refining, petrochemical, and energy power generation. As people continue to study, it is believed that triple eccentric butterfly valves will be applied to more and more fields.
If you want to know more about double eccentric butterfly valve and triple eccentric butterfly valve, please visit the official website of “Tanghai Valve”. If you have valve requirements in this area, you are also welcome to inquire and order.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D.
Video of center-lined butterfly valve: https://youtu.be/NuSZH_AJcwY
Video of double eccentric butterfly valve: https://youtu.be/yOw2xp3bIaE
Video of triple eccentric butterfly valve: https://youtu.be/AkRwg2X1Wh0

Introduction to the applicable occasions of butterfly valve

September 24, 2021

Butterfly valve is one of the most commonly used valves in piping systems. It has a wide range of applications. It can not only be used to cut off the flowing medium in the pipeline, but also can be used for flow adjustment. When the

Fluorine lined butterfly valve-PTFE-WAFER (10)

fluid in the pipeline passes through the butterfly valve, the pressure loss is about 3 times that of the gate valve, and the pressure loss is relatively large. Therefore, two factors should be considered when choosing a butterfly valve. One is the pressure loss experienced by the piping system, and the other is the pressure of the pipeline medium and the working temperature that the elastic valve seat material can withstand when the butterfly valve is closed.
The structural length of the butterfly valve is short, the overall height is also small, the operating torque is short, it can be opened and closed quickly, and fluid control can be performed well. The structural principle of the butterfly valve makes it most suitable for making large-diameter valves. When the butterfly valve is required to be used for flow control, in order to make it work more effectively, it is necessary to select the correct size and type of the butterfly valve.

What occasions are butterfly valves suitable for?

Double eccentric-wafer butterfly valve-D372F-150lbP-stainless steel (1)

1. It is required to be used for throttling and regulating control in the pipeline, and the valve structure is required to be short in length and fast in opening and closing. It is recommended to use a butterfly valve.
2. On pipelines that require two-position adjustment and necking, low noise is required, cavitation is generated, a small amount of leakage into the atmosphere, and the circulating medium is corrosive, a butterfly valve can be selected.
3. Under special working conditions where there are strict requirements for sealing, low temperature containing impurities, and easy to cause wear, it is recommended to use butterfly valves, and to use metal-sealed triple-eccentric or double-eccentric butterfly valves.
4. In petroleum, petrochemical, chemical, metallurgical, electric power and other fields, it is recommended to use metal hard-seal triple-eccentric butterfly valves. In many cases, they can replace gate valves and globe valves.
5. The center line butterfly valve is suitable for the environment with strict requirements on sealing performance and zero leakage. The center line butterfly valve is most suitable for fresh water, sewage, sea water, salt water, steam, natural gas, oil and oil at a working temperature of -10-150℃. Used in pipelines of various acid and alkali media.

triple offset butterfly valve-double flange- (5)

6. The double eccentric butterfly valve is very suitable for use in urban heating, gas, water and gas pipelines, as a device for intercepting or adjusting flow.
7. Eccentric soft sealing butterfly valves are widely used in gas pipelines and waterways in metallurgy, light industry, electric power and petrochemical systems. Used as a two-way opening, closing and adjustment of the ventilation and dust removal pipeline.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Single eccentric|double eccentric|triple eccentric butterfly valve structure principle (diagram)

July 30, 2021

The evolution of butterfly valve sealing structure: single eccentric butterfly valve, double eccentric butterfly valve and triple eccentric butterfly valve

Butterfly valves have been widely used due to their low cost, small size, light weight and long life. With the development of my country’s industry, various industries have more and more stringent requirements for the performance of equipment, especially in some gas pipelines or other hazardous material pipelines, the butterfly valve must achieve zero leakage, so the sealing structure design of the butterfly valve has always been important Research topics.

With the rapid development of modern industrial technology, butterfly valves are widely used in pipeline control systems, especially large-diameter pipeline control systems where other control valves are difficult to apply. Generally, the valve seat of the butterfly valve is a fixed type, and its materials are polymer and metal. The polymer valve seat is mainly suitable for working conditions with lower temperature. Although the metal seat butterfly valve can meet the higher temperature and pressure However, the elasticity of the metal valve seat is lower than that of the polymer valve seat, and the sealing performance is poor. The improvement of various performances of butterfly valves is closely related to its continuous improvement. For example, the development of butterfly valve sealing structure technology has successively experienced the evolution process of ordinary butterfly valve, single eccentric butterfly valve, double eccentric butterfly valve and triple eccentric butterfly valve.

Since the rotation center of the butterfly plate (that is, the center of the valve shaft) and the sealing section of the butterfly plate are set eccentrically according to a, the butterfly plate sealing surface gradually separates from the valve seat sealing surface during the opening process of the butterfly valve, and the butterfly plate rotates to 20°～25° , The sealing surface of the butterfly plate is completely separated from the sealing surface of the valve seat. When the valve is fully opened, a gap x is formed between the two sealing surfaces, so that the relative mechanical wear and extrusion between the two sealing surfaces of the butterfly valve is greatly reduced during the opening and closing process. Ensure the sealing of the butterfly valve.

Since the rotation center of the butterfly plate (that is, the center of the valve shaft) and the center line of the valve body are offset by size b on the basis of the single eccentric butterfly valve, the sealing surface of the butterfly plate will be faster than the single eccentric sealing butterfly valve during the opening process of the butterfly valve. When the butterfly plate rotates to 8°～12°, the butterfly plate sealing surface is completely separated from the valve seat sealing. When it is fully opened, a larger gap y is formed between the two sealing surfaces. This type of butterfly valve is designed , Which greatly reduces the mechanical wear and extrusion deformation between the two sealing surfaces, and improves the sealing performance of the butterfly valve.

There are different types of eccentric sealing butterfly valves, and the fields of application and their respective characteristics are naturally different. But fundamentally speaking, the basic principles of eccentric sealing butterfly valves are similar.

Structural characteristics of single eccentric butterfly valve:

single eccentric butterfly valve structure diagram

1. The center of rotation of the disc plate (that is, the center of the valve shaft) is located on the center line of the valve body, and an A-size offset is formed on the sealing section of the valve plate. The single eccentric butterfly valve is that the rotation center of the disc plate is on the center line of the valve body, and the valve plate deviates a distance from the sealing surface, which is suitable for soft sealing.
2. When the valve is closed, the valve seat and the sealing surface of the valve plate are in a relatively interference contact state. To achieve the seal, it is mainly by pressing the sealing ring to expand in the peripheral direction to produce the sealing specific pressure and the pipeline pressure against the valve plate. It can only be sealed in one direction because of the strong force.
3. When the valve is opened, the contact side of the valve plate and the valve seat is separated from the valve seat, and the other side is always two-point contact along the axial direction of the half circumference. Repeated opening and closing of the sealing ring is easy to be damaged, which affects the sealing performance. It is impossible to achieve a metal seal.
4. From a geometric point of view, it is obvious that X does not exist in the above figure, and in turn there is a certain amount of interference.
Structural features of double eccentric butterfly valve:

double eccentric butterfly valve structure diagram

The center of rotation of the valve plate (that is, the center of the valve shaft) forms an offset of dimension A on the sealing section of the valve plate, and forms an offset of dimension B with the center of the valve body.
Since the center line of the valve seat and the center line of the valve body form a β angle offset on the basis of the double eccentric butterfly valve, the sealing surface of the butterfly plate immediately leaves the sealing surface of the valve seat at the moment of opening during the valve opening process of the butterfly valve. Only at the moment of closing does it contact and compress the seat sealing surface. When fully opened, a gap y is formed between the two sealing surfaces, which is the same as that of the double eccentric sealing butterfly valve. The design of this type of butterfly valve completely eliminates the mechanical wear and abrasion between the two sealing surfaces, making the butterfly valve more effective in its sealing performance and use. The life span has been greatly improved.

Structural features of triple eccentric butterfly valve:

triple eccentric butterfly valve structure diagram

The center of rotation of the valve plate (that is, the center of the valve shaft) forms an offset A on the sealing section of the valve plate, and an offset b from the center of the valve body; the centerline of the valve body sealing surface and the centerline of the valve seat (ie the centerline of the valve body) An angular offset of β is formed.
The uniqueness of the triple eccentric butterfly valve is that the stem shaft on which the butterfly plate is installed is a three-segment shaft structure. This three-segment shaft type valve stem has two shaft sections concentric, and the center line of the central shaft is deviated from the two ends of the axis by a center distance. , The butterfly plate is installed on the intermediate shaft section. Such an eccentric structure makes the butterfly plate a double eccentric shape when in the fully open position, and a single eccentric shape when the butterfly plate rotates to the closed position. Due to the effect of the eccentric shaft, when it is close to closing, the butterfly plate moves a distance into the sealing cone surface of the valve seat, and the butterfly plate matches the sealing surface of the valve seat to achieve reliable sealing performance.
Related Knowledge: Common Sense of Eccentric Butterfly Valve

Related Products: Electric Triple Eccentric Butterfly Valve Pneumatic Triple Eccentric Butterfly Valve

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Installation instructions of double eccentric butterfly valve

July 24, 2020

Installation instructions of double eccentric butterfly valve:
1. Before installation, you must carefully check whether the valve’s mark and certificate of conformity meet the requirements for use, and clean it after verification.

Double eccentric-wafer butterfly valve-D72F-150lbP-stainless steel (3)

Uninstalled valves should be stored in a dry room. Valves stored for a long time should be cleaned regularly, dried and coated with anti-rust oil. Blind plates shall be used to protect the flange sealing surface at both ends of the valve.
2. Install according to the flow direction of the medium; horizontal installation is preferred.
3. The connecting bolts of the butterfly valve and the pipeline should be tightened several times in the diagonal direction during installation, and no single piece should be tightened at a time to prevent the flange connection from leaking due to uneven force.
4. When installing the butterfly valve, the butterfly plate should be in the closed position to prevent debris from entering the valve cavity and scratching the sealing surface. When the user wants to test the pressure, be sure to install the flange pair on both ends and test the pressure.
5. When connecting the valve to the pipeline, it is required to use butt-welded steel flanges or special butterfly valve flanges on the pipeline. If flat-welded steel flanges are used, the inner hole of the flange must be the same size as the inner hole of the gasket to ensure the effective sealing surface of the gasket.
6. When the electric butterfly valve leaves the factory, the opening and closing stroke of the control mechanism has been adjusted. In order to prevent the direction from being wrong when the power is turned on, the user must manually move to 1/3 of the closed position before turning on the power for the first time. And check whether the direction of the indicator plate is consistent with the opening direction of the valve.
7. When the valve is in use, if any malfunction is found, stop using it immediately

Tanghai Valve is the best manufacturer of double eccentric butterfly valve in China. We produce the best quality products with competitive low prices. Main products: butterfly valve, lug type butterfly valve, wafer type butterfly valve, U-type butterfly valve, double flange butterfly valve, gate valves, check valves, globe valves, valve parts (Valve body, Valve disc, Valve shaft, Valve seat…)

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Classification and features of Eccentric butterfly valves

July 24, 2020

Eccentric butterfly valves are divided into single eccentric butterfly valves, double eccentric butterfly valves, triple eccentric butterfly valves, and variable eccentric butterfly valves. Contrast with concentric butterfly valve. A butterfly valve whose stem axis deviates from the center of the disc and the center of the body at the same time, and the sealing pair is an oblique vertebra is called an eccentric butterfly valve.

high performance-double eccentric-butterlfy valve-wafer-lug-flanged (5)

Structure classification of eccentric butterfly valve:
Single eccentric butterfly valve
In order to solve the problem of the extrusion of the butterfly plate and the valve seat of the concentric butterfly valve, a single eccentric butterfly valve was produced. Its structural feature is that the shaft center of the valve stem deviates from the center of the butterfly plate, so that the lower end of the butterfly plate no longer becomes the rotation axis. Disperse and reduce the excessive squeezing between the lower end of the butterfly plate and the valve seat.
Double eccentric butterfly valve
On the basis of the single eccentric butterfly valve, the double eccentric butterfly valve is the most widely used double eccentric butterfly valve. Its structural feature is that the axis of the valve stem deviates from the center of the butterfly plate and the center of the body. The double eccentric effect enables the butterfly plate to be released from the valve seat immediately after the valve is opened, which greatly eliminates unnecessary excessive extrusion and scratching of the butterfly plate and the valve seat, reduces the opening resistance, reduces wear and improves The life of the valve seat is improved.
Triple eccentric butterfly valve
To withstand high temperatures, hard seals must be used, but the amount of leakage is large; for zero leakage, soft seals must be used, but they are not resistant to high temperatures. In order to overcome the contradiction of the double eccentric butterfly valve, the butterfly valve was eccentric for the third time. The so-called third eccentricity means that the shape of the sealing pair is not a positive cone, but an oblique cone.
Variable eccentric butterfly valve
The uniqueness of the variable eccentric butterfly valve is that the valve stem shaft where the butterfly plate is installed is a three-segment shaft structure. The three-segment shaft type valve stem has two shaft sections concentric, and the center line of the central shaft is offset from the two ends of the axis by a center distance , The butterfly plate is installed on the intermediate shaft section. Such an eccentric structure makes the butterfly plate a double eccentric shape when in the fully open position, and a single eccentric shape when the butterfly plate rotates to the closed position. Due to the effect of the eccentric shaft, when close to closing, the butterfly plate moves a

triple eccentric butterfly valve-lug

distance into the sealing cone surface of the valve seat, and the butterfly plate matches the sealing surface of the valve seat to achieve reliable sealing performance.

Features of eccentric butterfly valve:

The butterfly valve and the upper and lower valve shafts are connected by special-shaped holes and special-shaped shafts. During the opening and closing process of the butterfly plate, the function of the butterfly plate floating up and down, left and right, without a pin link, reduces the interference area between the butterfly plate and the valve seat. Thereby greatly reducing the torque. The floating structure of the butterfly plate realizes the single eccentric manufacturing process and the use function of variable eccentricity.
There is an over-position stopper for the butterfly plate in the inner cavity of the valve body to ensure that the butterfly plate is not in place when it is closed.
Bushings are used between the upper and lower valve shaft holes of the valve body cavity and the upper and lower valve shaft holes of the butterfly plate to prevent large particles in the medium from entering the valve shaft holes.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Posts

Structure diagram of double eccentric butterfly valve

Application of double eccentric butterfly valve and triple eccentric butterfly valve

Introduction to the applicable occasions of butterfly valve

Single eccentric|double eccentric|triple eccentric butterfly valve structure principle (diagram)

Installation instructions of double eccentric butterfly valve

Classification and features of Eccentric butterfly valves

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