Five eccentric ultra-low temperature bidirectional compression butterfly valve

Abstract

The application discloses a five-eccentric ultra-low-temperature bidirectional pressure butterfly valve, which comprises a valve body, a valve shaft and a butterfly plate, a valve seat, a bellows and a limiting ring are arranged in the valve body, the two ends of the bellows are fixed on the valve seat and the limiting ring respectively, the valve seat is located in a movable groove formed by the limiting ring and the valve body, and the axial dimension of the valve seat is smaller than the dimension of the movable groove, a sealing ring is arranged on the butterfly plate, the inner diameter of the sealing ring is larger than the outer diameter of the installation position of the butterfly plate, the outer edge of the sealing ring is provided with a special spherical arc surface which is in abutment with the sealing surface of the valve seat to seal the valve, and the five-eccentric ultra-low-temperature bidirectional pressure butterfly valve is characterized in that the radially self-adapting floating sealing ring structure is arranged, the sealing between the sealing ring and the valve seat is uniform, the dynamic change formed by the bidirectional pressure is combined, the valve seat which is movable relative to the valve body is arranged, the self-sealing force of the valve seat is enhanced by the pressure of the bidirectional medium, the sealing effect is improved, and the sealing performance of the five-eccentric full-metal hard sealing butterfly valve under bidirectional equal pressure in the ultra-low-temperature working condition of LNG and the like is met.

Description

Technical Field

[0001] This invention relates to the field of butterfly valve technology, specifically to a five-eccentric cryogenic bidirectional pressure butterfly valve. Background Technology

[0002] A butterfly valve is a type of valve that uses a disc-shaped opening and closing element to rotate approximately 90 degrees to open, close, or regulate the flow of media. Butterfly valves are not only simple in structure, small in size, lightweight, economical in material consumption, small in installation dimensions, low in driving torque, and easy and quick to operate, but they also simultaneously possess excellent flow regulation and sealing characteristics, making them one of the fastest-growing valve types in the past decade. The use of butterfly valves is very widespread, and the variety and quantity used continue to expand, with trends towards high temperature, high pressure, large diameter, high sealing performance, long service life, excellent regulation characteristics, and multi-functionality. Their reliability and other performance indicators have reached a high level.

[0003] Butterfly valves can be divided into one-way butterfly valves and two-way butterfly valves. One-way butterfly valves require the disc to face the direction of media flow when closed; the media flows in only one direction. An arrow on the valve body indicates the direction of media flow, and this should be noted during installation. The installation and operating conditions of one-way butterfly valves are relatively limited, as they cannot withstand reverse media pressure. Therefore, they are prone to leakage or damage under back pressure. Two-way butterfly valves, on the other hand, can face or turn away from the direction of media flow, and the direction of media flow does not need to be considered during installation. There is no arrow on the valve body indicating the direction of media flow. Therefore, the sealing of two-way butterfly valves is particularly important. However, the sealing effect on both sides of existing two-way butterfly valves varies, and some two-way butterfly valves, due to unreasonable design, use a fixed sealing method, which easily leads to leakage over time. Summary of the Invention

[0004] In view of the prior art, the purpose of this invention is to provide a bidirectional pressure butterfly valve for butterfly valves, which achieves a stronger sealing effect by setting a dynamic sealing structure and can improve sealing performance by means of medium pressure.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a five-eccentric cryogenic bidirectional pressure butterfly valve, comprising a valve body, a valve shaft, and a butterfly plate. A sealing seat assembly is provided in the valve body. The sealing seat assembly includes a valve seat, a bellows, and a limiting ring. The two ends of the bellows are respectively fixed on the valve seat and the limiting ring. The limiting ring is fixedly disposed relative to the valve body. The valve seat is located in the movable groove formed by the limiting ring and the valve body, and the axial dimension of the valve seat is smaller than the dimension of the movable groove. A sealing ring is sleeved on the butterfly plate. The inner diameter of the sealing ring is larger than the outer diameter of the butterfly plate at the sealing ring installation location. The outer edge of the sealing ring is an irregular spherical arc surface that abuts against the sealing surface of the valve seat to seal the valve.

[0006] As a further provision of the above scheme, the valve body is also provided with a three-part retaining ring and a limiting bolt. The three-part retaining ring is locked in the retaining ring groove on the inner wall of the valve body, and the limiting bolt passes through the three-part retaining ring and presses against the end of the limiting ring, so that the other end of the limiting ring is tightly fixed to the stepped surface of the valve inner wall.

[0007] As a further feature of the above scheme, the two ends of the bellows are welded to the limiting ring and the valve seat end for sealing and fixing. The bellows is used to extend or contract when the valve seat moves relative to the limiting ring.

[0008] As a further provision of the above scheme, the butterfly plate is also provided with a pressure ring and screws for axially limiting and fixing the sealing ring relative to the butterfly plate. The valve body is also provided with a sealing gasket, a valve seat gasket and an anti-loosening washer. The sealing gasket is used for sealing and contacting the sealing ring with the butterfly plate, the valve seat gasket is used for sealing between the limiting ring and the valve body, and the anti-loosening washer is used for fixing the screws.

[0009] As a further feature of the above scheme, the valve shaft and the butterfly plate are connected by an axial key. A bushing and a positioning sleeve are also fitted on the valve shaft. The bushing is used to replace the direct wear between the valve body and the valve shaft. Two positioning sleeves are provided, respectively fitted on the upper and lower ends of the valve shaft relative to the butterfly plate. The positioning sleeves are axially movable relative to the valve shaft. The connection structure of the key and the setting of the positioning sleeves make the butterfly plate...

[0010] The five-eccentric cryogenic bidirectional pressure butterfly valve structure of the present invention has at least the following effects:

[0011] 1. The butterfly plate is fixed by a flat key and positioning sleeve to form an adaptive sealing floating. The cavity gap X formed by the setting that the inner diameter of the sealing ring is larger than the outer diameter of the positioning of the butterfly plate is further improved to enhance its adaptive movement effect. Thus, it can better adaptively adjust the sealing effect when applied to complex working conditions with alternating high and low temperatures.

[0012] 2. It is equipped with a sealing seat assembly structure and a floating valve seat. The movement of the valve seat is limited by a limiting ring connected to the valve seat, and a bellows is used to seal the movement gap. In the sealed state, the moving valve seat can obtain the self-sealing force of the valve seat by means of the pressure of the bidirectional medium to meet the dynamic changes formed by the bidirectional pressure, thereby improving the sealing effect and meeting the bidirectional equal pressure sealing performance of the five-eccentric all-metal hard seal butterfly valve in cryogenic conditions such as LNG. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of the five-eccentric ultra-low temperature bidirectional pressure butterfly valve of the present invention.

[0014] Figure 2This is a schematic diagram of the internal structure of the five-eccentric ultra-low temperature bidirectional pressure butterfly valve of the present invention.

[0015] Figure 3 For the present invention Figure 2 Enlarged view of point B in the middle.

[0016] Figure 4 This is a schematic diagram of the sealing seat assembly of the present invention.

[0017] Figure 5 This is a schematic diagram illustrating the pressure flow principle within the valve of the positive pressure sealing structure of this invention.

[0018] Figure 6 This is a schematic diagram illustrating the pressure flow principle within the valve of the reverse pressure sealing structure of the present invention.

[0019] Figure 7 This is a schematic diagram illustrating the eccentric principle of the five-eccentric cryogenic bidirectional pressure butterfly valve of the present invention.

[0020] Reference numerals in the attached diagram: 1. Valve body; 2. Valve seat; 3. Bellows; 4. Valve seat gasket; 5. Limiting ring; 6. Three-section retaining ring; 7. Limiting bolt; 8. Bushing; 9. Valve shaft; 10. Positioning sleeve; 11. Sealing gasket; 12. Sealing ring; 13. Pressure ring; 14. Anti-loosening washer; 15. Screw; 16. Butterfly plate; 17. Stepped surface of valve inner wall. Detailed Implementation

[0021] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, where there is no conflict, the embodiments and features described in these embodiments can be combined with each other.

[0022] like Figure 1-7 The present invention provides a five-eccentric cryogenic bidirectional pressure butterfly valve, such as... Figure 1-2 It includes a valve body 1, a valve shaft 9, and a butterfly plate 16, wherein, reference Figure 2-3 A sealing seat assembly is provided inside the valve body 1. The sealing seat assembly includes a valve seat 2, a bellows 3, and a limiting ring 5. The two ends of the bellows 3 are fixed to the valve seat 2 and the limiting ring 5, respectively. The limiting ring 5 is fixedly disposed relative to the valve body 1. The valve seat 2 is located in the movable groove formed by the limiting ring 5 and the valve body 1, and the axial dimension of the valve seat 2 is smaller than the dimension of the movable groove. A sealing ring 12 is sleeved on the butterfly plate 16. The inner diameter of the sealing ring 12 is larger than the outer diameter of the butterfly plate 16 where the sealing ring 12 is installed. The outer edge of the sealing ring 12 is a non-circular spherical arc surface that abuts against the sealing surface of the valve seat 2 to seal the valve.

[0023] As a further provision of the above scheme, the valve body 1 is also provided with a three-part retaining ring 6 and a limiting bolt 7. The three-part retaining ring 6 is locked in the retaining ring groove 18 on the inner wall of the valve body 1. The limiting bolt 7 passes through the three-part retaining ring 6 and presses against the end of the limiting ring 5, so that the other end of the limiting ring 5 is tightly fixed to the stepped surface 17 of the valve inner wall.

[0024] As a further feature of the above scheme, the two ends of the bellows 3 are welded to the limiting ring 5 and the end of the valve seat 2 for sealing and fixing. The bellows 3 is used to extend or contract when the valve seat 2 moves relative to the limiting ring 5.

[0025] As a further provision of the above scheme, the butterfly plate 16 is also provided with a pressure ring 13 and a screw 15 for axially limiting and fixing the sealing ring 12 relative to the butterfly plate 16. The valve body 1 is also provided with a sealing gasket 11, a valve seat gasket 4 and an anti-loosening washer 14. The sealing gasket 11 is used for sealing and contacting the sealing ring 12 and the butterfly plate 16. The valve seat gasket 4 is used for sealing the limiting ring 5 and the valve body 1. The anti-loosening washer 14 is used for fixing the screw 15.

[0026] As a further feature of the above scheme, the valve shaft 9 and the butterfly plate 16 are connected by an axial key. A bushing 8 and a positioning sleeve 10 are also fitted on the valve shaft 9. The bushing 8 is used to replace the direct wear between the valve body 1 and the valve shaft 9. Two positioning sleeves 10 are provided, respectively fitted on the upper and lower ends of the valve shaft 9 relative to the butterfly plate 16. The positioning sleeves 10 are axially movable relative to the valve shaft 9. The key connection structure and the positioning sleeves 10 allow the butterfly plate 16 to move relative to the valve shaft 9 within a certain axial range. Under the restriction of the positioning sleeves 10, the axial movement is not too large. Thus, under the reaction force of the valve seat 2, the sealing ring 12 adaptively adjusts its axial movement. This can form a uniform annular seal, improve the sealing effect, and avoid the problem of the butterfly plate 16 seizing relative to the valve seat 2.

[0027] All-metal moving seal structure:

[0028] The sealing ring 12 of the present invention is fixed to the butterfly plate 16 by means of screws 15 and pressure rings 13. However, the inner diameter of the sealing ring 12 is larger than the outer diameter of the butterfly plate 16 at the fixing point of the sealing ring 12, thus creating a cavity gap X between them. Figure 3As shown, the existence of this gap X allows the sealing ring 12 to float on the stepped plane of the butterfly plate 16, allowing for a small degree of adaptive radial movement. This structural feature enables the sealing ring 12 of this embodiment to adaptively abut against the sealing surface of the valve seat 2 under alternating high and low temperature conditions. Compared with the sealing ring 12 of the prior art, the sealing ring 12 of this embodiment is less prone to interference and seizing, thereby reducing the excessive contact pressure between the sealing ring 12 and the valve seat 2. This ensures that the valve closure reset of the butterfly plate 16 is in place and avoids rapid axial aging and damage caused by excessive compression of the sealing ring 12.

[0029] Further such as Figure 3 As shown, in this embodiment, the valve seat 2 is welded to one end of the bellows 3, and the other end of the bellows 3 is welded to the limiting ring 5. The connection between the two forms a welded ring 30, as shown. Figure 3 This arrangement allows the valve seat 2, bellows 3, and limiting ring 5 to form an integral sealing seat assembly. This sealing seat assembly is fixed within the valve body 1 cavity, and is secured to the valve inner wall stepped surface 17 by the flanged plane of the limiting ring 5. It also holds a valve seat gasket 4 to prevent media leakage between the valve inner wall stepped surface 17 and the limiting ring 5. Figure 3 The limiting ring 5 is fixed to the valve body 1 by the limiting bolt 7 and the three-piece retaining ring 6. The three-piece retaining ring 6 is locked in the retaining ring groove 18 to maintain axial fixation. The limiting bolt 7 is threaded and extends out of the three-piece retaining ring 6, abutting against the end face of the limiting ring 5, restricting the axial movement of the limiting ring 5. Under positive and negative pressure, the axial pressure generated in the medium will not affect the axial movement of the limiting ring 5. Instead, it will push the valve seat 2 to move circumferentially, and during the movement, the medium pressure will make it press more tightly against the valve body 1 or the limiting ring 5. The gap between the valve seat 2 and the limiting ring 5 is sealed by the expandable bellows 3. The limiting ring 5 will remain completely fixed, ensuring the medium seal between the sealing seat assembly and the inner wall of the valve body 1.

[0030] The sealing structure of the sealing ring 12 and the valve seat 2 is as follows: the sealing surface of the valve seat 2 is an elliptical cone cut into a circular shape, and the sealing surface of the sealing ring 12 is an irregular spherical arc surface. The sealing ring 12 and the valve seat 2 form a forced line sealing structure and a metal elastic line sealing structure, which can ensure that the sealing pair has a high specific pressure and can achieve high temperature and high pressure dual pressure line sealing performance.

[0031] The eccentric structure principle of the five-eccentric butterfly valve of this invention (elliptical cone oblique tangent circle sealing system (reference)) Figure 7 The structure, Figure 7 From Figure 2 (Schematic diagram taken from a cross-section along the AA direction)

[0032] Eccentricity 1: Axial eccentricity, the valve shaft is located behind the valve seat, so that the seal can completely and tightly surround and contact the entire valve seat.

[0033] Eccentricity 2: Radial eccentricity, the valve shaft center deviates from the valve body centerline, reducing the squeezing and scraping effect between the sealing ring and the valve seat when the valve is opened and closed.

[0034] Eccentricity 3: Angular eccentricity, where the central axis of the elliptical cone of the valve seat deviates from the center line of the valve body flow channel, eliminating the frictional interference of the sealing pair during opening and closing. The elliptical cone is obliquely cut at a specific angle to form a perfectly circular sealing surface. The included angle of the elliptical cone surface is not a constant value, i.e., α≠β.

[0035] Eccentricity 4: Positional eccentricity transforms the oblique section of the elliptical cone into a perfect circle, resulting in a circular geometric shape for the valve seat sealing section. This leads to a larger flow area and more uniform circumferential sealing pressure, but also makes it more prone to leaks. The above describes a four-eccentric structure.

[0036] Eccentric 5: Forced Line Seal. The five-eccentric butterfly valve is derived from the four-eccentric butterfly valve. The valve seat sealing surface of the five-eccentric butterfly valve is the same as that of the four-eccentric valve, but the sealing surface of the sealing ring changes from an eccentric circular conical curved plane to a non-circular spherical arc surface. The spherical arc sealing surface and the circular sealing surface of the valve body seat form a line seal pair. Forced line sealing is achieved through the medium pressure and the torque applied by the valve shaft. Due to the small contact area of ​​the line seal pair, a larger sealing specific pressure is obtained under the same torque and pressure, and the circular sealing specific pressure is uniform, ensuring zero-leakage performance. Under high temperature, ultra-low temperature, and temperature alternating conditions, the five-eccentric forced line seal pair deforms uniformly under thermal expansion and contraction, maintaining stable sealing performance.

[0037] The working principle of the bidirectional equal pressure sealing function of this invention is as follows:

[0038] In this embodiment of the invention, the butterfly plate 16 and the valve shaft 9 are connected by a flat key. Thus, the butterfly plate 16 is positioned in the valve body 1 by the positioning sleeve 10, and the sealing ring 12 is fixed to the butterfly plate 16 by the pressure ring 13 and the screw 15. The sealing ring 12, the butterfly plate 16, and the valve shaft 9 form a whole. The valve shaft 9 is driven to rotate by an external power mechanism to realize the opening and closing actions.

[0039] 1. The principle of positive pressure, such as Figure 5 As shown:

[0040] Since the valve seat 2, bellows 3 and limit ring 5 are welded together to form a movable sealing seat assembly, the sealing seat assembly is fixed to the inner wall stepped surface 17 of the valve by a three-opening retaining ring 6 and a limit bolt 7.

[0041] When the valve encounters such Figure 5 Under the positive pressure shown, the pressure area of ​​the medium acting on the sealing seat assembly is as follows: Figure 5 The annular surface of section A shown will generate a thrust F1 on this annular surface, which will push valve seat 2 towards... Figure 5As shown, the rightward movement is controlled by the three-part retaining ring 6 and the limiting bolt 7. The limiting ring 5 is fixed to the stepped surface 17 of the valve's inner wall, and thus the bellows 3 is compressed. Finally, the right side of the valve seat 2 abuts against the limiting ring 5 and stops moving. A seal is formed between the limiting ring 5 and the valve body 1 through the valve seat gasket 4, preventing leakage from the outer circumference of the valve seat 2. The medium can only flow from left to right through the medium flow channel in the middle of the valve body 1.

[0042] As described above, the valve shaft 9 of the present invention receives torque M, which drives the butterfly plate 16 to rotate clockwise. When the butterfly plate 16 reaches the closed position, the sealing ring 12 contacts the valve seat 2. At this time, the torque M causes the sealing ring 12 and the valve seat 2 to generate a cam effect, which makes the sealing ring 12 and the valve seat 2 form a torque sealing pressure.

[0043] Secondly, when under positive pressure, such as Figure 5 The medium pressure acts positively on the entire butterfly plate, forming pressure F2. Due to the gap between the valve body 1 shaft hole and the valve shaft 9, the deformation of the valve shaft 9, and the accumulated tolerance gap, the positive pressure F2 pushes the butterfly plate 16 towards the valve seat 2. This movement forms a tendency for the sealing ring 12 to move closer to the valve seat 2. Due to the radial eccentricity of the eccentricity 2, the valve shaft 9 is not at the center of the butterfly plate 16. Taking the center line of the valve shaft 9 as the boundary, the butterfly plate 16 forms two force areas of different sizes. An eccentric unbalanced torque M0 is formed on the butterfly plate 16. The eccentric unbalanced torque M0 pushes the butterfly plate 16 and the sealing ring 12 to rotate clockwise and close, causing the sealing ring 12 to tend to be close to the valve seat 2.

[0044] As shown above, under the combined force and torque of positive pressure F2, torque M, and eccentric unbalanced torque M0, the effect of enhancing zero-leakage sealing performance is achieved, and the greater the positive pressure, the better the sealing performance.

[0045] 2. Reverse pressure principle as follows Figure 6 As shown:

[0046] First, when the butterfly plate 16 is in the closed position, the torque M of the valve shaft 9 passes through the butterfly plate 16 and the sealing ring 12, forming a cam effect with the valve seat 2. The sealing ring 12 and the valve seat 2 form a torque sealing pressure ratio. When reverse pressure is applied, as... Figure 6 The medium pressure acts in the opposite direction on the entire butterfly plate 16. Due to the gap between the valve body 1 shaft hole and the valve shaft 9, the deformation of the valve shaft 9, and the accumulated tolerance gap, the reverse pressure F2' pushes the butterfly plate 16 toward the valve shaft 9. This movement creates a tendency for the sealing ring 12 to detach from the valve seat 2.

[0047] Third, due to the radial eccentricity of eccentricity 2, valve shaft 9 is not at the center of butterfly plate 16. Taking the center line of valve shaft 9 as the boundary, butterfly plate 16 forms two force areas of different sizes. When the butterfly plate 16 is pressed down in the opposite direction, an eccentric unbalanced torque M0' is formed. The eccentric unbalanced torque M0' pushes butterfly plate 16 and sealing ring 12 to rotate counterclockwise, causing sealing ring 12 to tend to detach from valve seat 2.

[0048] Based on the above principle, the existing conventional five-eccentric butterfly valve, under reverse pressure, tends to form a sealing ring 12 that separates from the valve seat 2, and its sealing performance becomes worse as the pressure increases.

[0049] This invention employs a valve seat 2 with a bellows telescopic function, effectively compensating for the tendency of the sealing ring 12 to detach from the valve seat 2 under reverse pressure. The principle is as follows: the valve seat 2, bellows 3, and limiting ring 5 are welded together to form a movable sealing seat assembly. The sealing seat assembly is fixed to the stepped surface of the valve inner wall by a three-part retaining ring 6 and a limiting bolt 7. Therefore, when reverse pressure occurs, the sealing ring 12 is positioned within the pressure area of ​​the sealing seat assembly based on the pressure of the pressure medium. Figure 6 The diagram shows the annular surface of section B. The reverse pressure medium generates a thrust F1' on this annular surface. This thrust F1' pushes the valve seat 2 towards the sealing ring 12. Simultaneously, based on the axial direction of the valve seat 2... Figure 6 The left side moves, the bellows 3 extends, and the extension of the bellows 3 also avoids the gap between the valve seat 2 and the limit ring 5. The axial movement of the valve seat 2 makes up for the gap of the sealing ring 12 retracting towards the valve shaft 9, so that the valve seat 2 and the sealing ring 12 maintain a good sealing pressure.

[0050] The bellows 3 and the movable and retractable valve seat 2 provided in this invention can fully meet the bidirectional equal pressure sealing performance requirements of the five-eccentric all-metal hard-seal butterfly valve under cryogenic conditions such as LNG.

[0051] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A five-eccentric cryogenic bidirectional butterfly valve, comprising a valve body (1), a valve shaft (9), and a butterfly plate (16), characterized in that: The valve body (1) is provided with a sealing seat assembly, which includes a valve seat (2), a bellows (3) and a limiting ring (5). The two ends of the bellows (3) are fixed on the valve seat (2) and the limiting ring (5) respectively. The limiting ring (5) is fixed relative to the valve body (1). The valve seat (2) is located in the movable groove formed by the limiting ring (5) and the valve body (1), and the axial dimension of the valve seat (2) is smaller than the size of the movable groove. A sealing ring (12) is fitted on the butterfly plate (16). The inner diameter of the sealing ring (12) is larger than the outer diameter of the butterfly plate (16) where the sealing ring (12) is installed. The outer edge of the sealing ring (12) is a non-circular spherical arc surface that abuts against the sealing surface of the valve seat (2) to seal the valve. The valve body (1) is also provided with a three-opening retaining ring (6) and a limiting bolt (7). The three-opening retaining ring (6) is inserted into the retaining ring groove (18) on the inner wall of the valve body (1). The limiting bolt (7) passes through the three-opening retaining ring (6) and presses against the end of the limiting ring (5), so that the other end of the limiting ring (5) is tightly fixed to the stepped surface (17) of the valve inner wall. The two ends of the bellows (3) are welded to the limiting ring (5) and the valve seat (2) for sealing and fixing. The bellows (3) is used to extend or contract when the valve seat (2) moves relative to the limiting ring (5).

2. The five-eccentric cryogenic bidirectional pressure butterfly valve according to claim 1, characterized in that: The butterfly plate (16) is also provided with a pressure ring (13) and screws (15) for axial positioning and fixing of the sealing ring (12) relative to the butterfly plate (16).

3. The five-eccentric cryogenic bidirectional pressure butterfly valve according to claim 2, characterized in that: The valve body (1) is also provided with a sealing gasket (11), a valve seat gasket (4) and an anti-loosening washer (14). The sealing gasket (11) is used for sealing contact between the sealing ring (12) and the butterfly plate (16). The valve seat gasket (4) is used for sealing between the limiting ring (5) and the valve body (1). The anti-loosening washer (14) is used for fixing the screw (15).

4. The five-eccentric cryogenic bidirectional pressure butterfly valve according to claim 1, characterized in that: The valve shaft (9) and the butterfly plate (16) are connected by an axial key. A bushing (8) and a positioning sleeve (10) are also fitted on the valve shaft (9). The bushing (8) is used to replace the direct wear between the valve body (1) and the valve shaft (9). There are two positioning sleeves (10), which are respectively fitted on the upper and lower ends of the valve shaft (9) relative to the butterfly plate (16). The positioning sleeves (10) are axially movable relative to the valve shaft (9).

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