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Working principle and characteristics of triple eccentric butterfly valve

August 9, 2021

Triple eccentric butterfly valve, also named triple offset butterfly valve.

Nowadays, butterfly valves have been used in many industries. In the beginning, the butterfly valve was only used for the interception and communication of water media. The triple eccentric design enhances the function of the butterfly valve and has become one of the valves with excellent performance in industrial industrial pipeline equipment. The triple eccentric butterfly valve, as the name implies, is that three independent offsets are designed as valves. In reality, many people do not know which one is a triple-eccentric butterfly valve because of insufficient cognition. In this article, let’s talk about the working principle and characteristics of the triple-eccentric butterfly valve.

triple offset butterfly valve-double flange- (5)

The working principle of the triple eccentric butterfly valve is that the valve body of the butterfly valve has a horizontal valve port connected to the pipeline in structure, and the valve port has a valve plate. The shaft is perpendicular to the valve port and penetrates the valve body and the valve plate. The edge of the valve plate is provided with an outer spherical surface, and the valve port is provided with a sealing surface that can be matched with the outer spherical surface. When the sealing surface and the outer spherical surface are matched and sealed, there is an eccentric distance a between the sealing line and the axis of the shaft, which is in the transverse center of the valve plate. The line is the eccentricity b between the center line of the valve port and the center line of the shaft, and there is an angle β between the connection line of the outer spherical surface and the center line of the valve port. This is the principle of the triple eccentric butterfly valve.
The triple eccentric butterfly valve cleverly puts the triple eccentricity on the valve plate, and adopts a partial outer spherical structure on the outer edge of the valve plate. This structure needs to be completed on a CNC machine with a self-designed simple fixture. The outer eccentric spherical surface is polished to reach a roughness of Ra0.4, the spherical surface is chrome-plated or made of Stellite alloy, and the hardness reaches HRC45-60.
Put the eccentric angle on the valve plate, and press the valve seat on the valve body with a pressing ring, which solves the difficulties encountered in the processing of ordinary triple eccentric butterfly valves. The valve body, valve plate and valve seat cannot be exchanged for pairing. Repair after damage A series of problems such as high cost, all parts are modularized, warehouse management is simple, processing is simple, maintenance is convenient, and the cost of spare parts is reduced.
The butterfly valve is suitable for making large-diameter valves. It can be widely used in the cutting of petroleum transportation pipelines, metallurgical steel plants, gas main pipeline adjustment and cutting, chemical smelting equipment medium adjustment and cutting, water treatment equipment inlet and outlet adjustment and shutdown, and cooling water in thermal power stations. System, natural gas, lye, sea water, acid and other industries.

The characteristics of the triple eccentric butterfly valve are as follows:
1. Simple structure, light weight, composed of only a few parts. easy to use.
2. After the valve plate is fully opened, the thickness of the butterfly plate is the only resistance for the medium to pass through the valve body. The pressure is small and the flow can be better controlled.
3. When the valve plate is closed, the specific pressure between the outer spherical surface of the valve plate and the sealing surface of the valve seat is generated by the driving torque applied to the shaft. Coupled with the elastic compensation of the M-type elastic valve seat, the sealing performance of the valve can be enhanced, and the service life is greatly improved.
Understand the working principle and characteristics of triple eccentric butterfly valve, then where can I buy high-quality triple eccentric butterfly valve products? of course, Tanghai 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

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

Application of low temperature butterfly valve

June 22, 2021

Article title: Application of low temperature triple eccentric butterfly valve
With the rapid development of industrial technology, more stringent requirements have been put forward for valves, especially for butterfly valves used in low temperature media. In addition to meeting the performance of general valves, it is more important that butterfly valves seal under low temperature conditions. Reliability, flexibility of action and some other special requirements for cryogenic valves. Now combined with its structural characteristics, a brief introduction to the performance of the cryogenic butterfly valve is given. Remarks: The cryogenic butterfly valve we are talking about here specifically refers to the low temperature triple eccentric butterfly valve.

triple offset valve parts-after-cryogenic process

Requirements for sealing performance of low temperature triple eccentric butterfly valve:
There are two main reasons for the leakage of the low temperature triple eccentric butterfly valve, one is internal leakage; the other is external leakage.
1. Internal leakage of butterfly valve:
The main reason for the internal leakage of the valve is the deformation of the sealing pair in the low temperature state. When the temperature of the medium drops to a phase change of the material, the volume changes, which causes the sealing surface with high grinding accuracy to warp and deform, resulting in poor low-temperature sealing. We conducted a low temperature test on the DN250 valve. The medium was liquid nitrogen (-196 ℃) and the butterfly plate material was 1Cr18Ni9Ti (without low temperature treatment). It was found that the sealing surface warped and deformed up to about

cryogenic triple offset butterfly valve 1

0.12mm, which is the main cause of internal leakage. And if the plane seal of the butterfly valve is changed to a cone seal. The valve seat is an oblique cone ellipse sealing surface, which forms a sealing pair with a round elastic sealing ring embedded on the butterfly plate. The sealing ring can float radially in the butterfly plate groove. When the valve is closed, the elastic sealing ring first contacts the short axis of the elliptical sealing surface. As the valve stem rotates, the sealing ring is gradually pushed inward, forcing the elastic ring to contact the long axis of the oblique cone surface, and finally the elastic sealing ring All contact with the oval sealing surface. Its sealing is achieved by the deformation of the elastic ring. Therefore, when the valve body or butterfly plate is deformed at low temperature, it will be absorbed and compensated by the elastic sealing ring, and leakage and jamming will not occur. When the valve is opened, this elastic deformation disappears immediately, and there is basically no relative friction during the opening and closing process, so the service life is long.
2. Leakage of butterfly valve:
One is that when the valve and the pipeline are connected by flanges, leakage occurs due to the unsynchronized contraction and relaxation of the connecting gasket, connecting bolts, and connecting materials at low temperatures. Therefore, we changed the connection between the valve body and the pipeline from a flange connection to a welded structure to avoid low temperature leakage. The second is leakage at the valve stem and packing. Generally, most valve packing adopts F4 because of its good self-sliding performance, low friction coefficient (friction coefficient for steel f=0.05 ~ 0.1), and unique chemical stability, so it is widely used. However, F4 also has shortcomings. First, the tendency of cold flow is large; second, the linear expansion coefficient is large, and the cold shrinkage at low temperature causes leakage, which causes a large amount of ice at the valve stem, so that the valve fails to open. The low-temperature triple-eccentric butterfly valve developed for this purpose adopts a self-shrinking sealing structure, that is, taking advantage of the large expansion coefficient of F4, and achieves the purpose of sealing at room temperature and low temperature through the reserved gap.
Design requirements for low temperature triple eccentric butterfly valve body and stem bushing:
1. The structure and shape of the cryogenic valve shell. The correct selection of materials is of great significance to the normal and reliable operation of the valve. Compared with the stop valve and gate valve, the structural characteristics of the butterfly valve not only avoid the irregular shape and uneven shell wall thickness, which can cause problems at low temperatures. Due to the small size of the butterfly valve, the shape of the valve body is basically symmetrical, so the heat capacity is small; the pre-cooling consumption is also small; the shape is regular and it is convenient to take measures to keep the valve cold. ,
2. Selection of stem bushing: Some low-temperature triple-eccentric butterfly valves are in operation, the rotating parts of the valve are sticky, and seizure occurs from time to time. The main reason is: unreasonable selection of matching materials, too small pre-cooling clearance, and processing Causes such as low accuracy. In the development of cryogenic valves, a series of measures have been taken to prevent the occurrence of the above phenomena. For the upper and lower bushings of the valve stem, SF-1 type composite bearings with low friction coefficient and self-lubricating properties are selected, which can be suitable for some special needs of cryogenic valves. The metal-sealed butterfly valve has the characteristics that some ordinary valves do not have, especially the small flow resistance, reliable sealing, rapid opening and closing, and long service life. The triple eccentric metal sealing butterfly valve is sealed by the deformation of the elastic ring, so it does not need to rely on the force of the medium, so it can be used for two-way sealing.
Related information: The difference of cryogenic valve and ordinary temperature valve; Cryogenic valve principle |standard |illustration |selection

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

Working principle and characteristics of triple eccentric butterfly valve

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

Application of low temperature butterfly valve

Classification and features of Eccentric butterfly valves

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