Ultralow-temperature valve seat sealing kit

Abstract

The utility model provides an ultra-low temperature valve seat sealing kit which comprises a valve body, a valve core, a valve rod and a valve rod. The valve body is internally provided with a ball body in sealing fit; the valve seats are arranged on the two sides of the interior of the valve body, and the valve seats and the ball body are coaxially and rotationally installed; a groove is formed in the back of the valve seat, an O-shaped sealing ring is embedded in the groove, and the width of the groove is 10%-15% of the size of the sealing ring. According to the ultralow-temperature valve seat sealing kit, the groove is formed in the back of the valve seat to enable the O-shaped sealing ring to conduct auxiliary sealing, good sealing ring compression amount and good sealing ring stretching amount are formed through correct size matching of the O-shaped sealing ring and the groove, and therefore the sealing performance of the ultralow-temperature valve seat sealing kit is improved; the top-mounted ball valve solves the problem that a top-mounted ball valve in the prior art cannot achieve a good sealing effect in an ultralow-temperature environment.

Description

Technical Field

[0001] The present application relates to the field of valve seat technology, and in particular to an ultra-low temperature valve seat sealing kit. Background Art

[0002] Liquefied natural gas (LNG) is a clean energy source. Natural gas is a combustible gas that is naturally mined from gas fields and is mainly composed of methane. LNG is made by cooling gaseous natural gas to an ultra-low temperature of -162°C under normal pressure to condense it into liquid. After liquefaction, natural gas can greatly save storage and transportation space, and has the characteristics of high calorific value and high performance. Methane is a flammable and explosive dangerous good, so the performance requirements for cryogenic valves for liquefied natural gas are very high.

[0003] Since the temperature of liquefied natural gas (LNG) can reach -160℃, strict requirements are imposed on the deformation of metal materials and the low-temperature plasticity of sealing materials in ultra-low temperature environments. It is required that the deformation of the internal materials will not cause blocking, biting and abrasion, and the sealing materials will not produce low-temperature brittle damage and the materials are stable. The gas-liquid expansion ratio of LNG reaches 620:1. It is easy to gasify when heated or flashed, causing the medium pressure to increase sharply. LNG has the characteristics of small molecular weight, low viscosity and strong permeability, which can easily cause natural gas leakage. Therefore, LNG valves are flammable and explosive. Valve seat seal: The main material of the valve seat is metal. Metal will deform due to phase change in ultra-low temperature environment. Different materials have different sensitivities to temperature. There are differences in metal organization changes, expansion coefficients, deformation, etc., and the uncontrollable deformation has a serious impact on the valve sealing performance. Under normal temperature conditions, the elastic compression of the rubber O-ring can meet the valve sealing requirements. The low-temperature valve has exceeded the applicable temperature range of conventional O-rings. In order to meet the requirements of sealing at both normal and low temperatures, the seal adopts a lip seal ring structure. The base material of the lip seal ring is metal. On the one hand, it meets the performance under low temperature conditions. On the other hand, the lip seal ring structure can compensate for the deformation of the main body internals due to temperature changes, thereby ensuring the sealing performance of the product. Sealing of the valve stem packing: Conventional ball valves generally use O-ring seals or graphite packing seals at the valve stem. Due to the particularity of the LNG medium, these two structures are not applicable. The valve stem of a cryogenic ball valve is prone to frost, which not only reduces the performance of the valve stem seal, but also the up and down movement of the valve stem under frost conditions will scratch the valve stem seal. The top-mounted ball valve in the related technology cannot achieve a good sealing effect in an ultra-low temperature environment. Utility Model Content

[0004] The present application provides an ultra-low temperature valve seat sealing kit to solve the problem that the top-mounted ball valve in the prior art cannot achieve a good sealing effect in an ultra-low temperature environment.

[0005] The present application provides an ultra-low temperature valve seat sealing kit, comprising:

[0006] A valve body, wherein a ball body for sealing is arranged in the valve body;

[0007] A valve seat, the valve seat is arranged on both sides of the interior of the valve body, and the valve seat is coaxially rotatably installed with the ball;

[0008] A groove is provided on the back of the valve seat, an O-type sealing ring is embedded in the groove, and the groove width of the groove is 10% to 15% of the volume of the sealing ring.

[0009] In some possible implementations, the shape of the groove is one of a rectangle, a semicircle, a V-shape, a dovetail shape, or a triangle.

[0010] In some possible implementations, the compression amount of the sealing ring is 3% to 30%.

[0011] In some possible implementations, the depth of the groove is smaller than the cross-sectional diameter of the sealing ring.

[0012] In some possible implementations, the outer edge of the groove is provided with a rounded corner, and the radius of the rounded corner is 0.1-0.2 mm.

[0013] In some possible implementations, the surface roughness of the groove wall is 3.2-6.3 μm.

[0014] In some possible implementations, the surface roughness of the groove wall is less than or equal to 6.3 μm.

[0015] From the above content, it can be known that the present application provides an ultra-low temperature valve seat sealing kit, including: a valve body, in which a ball for sealing is provided; a valve seat, in which the valve seat is provided on both sides of the interior of the valve body, and the valve seat and the ball are coaxially rotatably installed; a groove is provided on the back of the valve seat, in which an O-type sealing ring is embedded, and the groove width of the groove is 10% to 15% of the volume of the sealing ring. The ultra-low temperature valve seat sealing kit provided by the present application adopts the groove on the back of the valve seat to make its O-type sealing ring perform auxiliary sealing, and the O-type sealing ring is correctly matched with the groove size, that is, a good sealing ring compression and stretching amount is formed, thereby improving the sealing performance of the ultra-low temperature valve seat sealing kit, and solving the problem that the top-mounted ball valve in the prior art cannot achieve a good sealing effect in an ultra-low temperature environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the embodiments are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0017] Figure 1A front view of a cryogenic valve seat seal kit in an embodiment provided in the present application;

[0018] Figure 2 A cross-sectional view of a cryogenic valve seat seal kit in an embodiment provided in the present application;

[0019] Figure 3 This is an exemplary diagram of the ultra-low temperature valve seat seal kit in the embodiment provided in the present application.

[0020] Illustration: 1-valve seat; 2-groove; 3-sealing ring. DETAILED DESCRIPTION

[0021] The following embodiments are described in detail, and examples thereof are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following embodiments do not represent all implementations consistent with the present application. They are only examples of systems and methods consistent with some aspects of the present application as detailed in the claims.

[0022] Liquefied natural gas (LNG) is a clean energy source. Natural gas is a combustible gas that is naturally mined from gas fields and is mainly composed of methane. LNG is made by cooling gaseous natural gas to an ultra-low temperature of -162°C under normal pressure to condense it into liquid. After liquefaction, natural gas can greatly save storage and transportation space, and has the characteristics of high calorific value and high performance. Methane is a flammable and explosive dangerous good, so the performance requirements for cryogenic valves for liquefied natural gas are very high.

[0023] Since the temperature of liquefied natural gas (LNG) can reach -160℃, strict requirements are imposed on the deformation of metal materials and the low-temperature plasticity of sealing materials in ultra-low temperature environments. It is required that the deformation of the internal materials will not cause blocking, biting and abrasion, and the sealing materials will not produce low-temperature brittle damage and the materials are stable. The gas-liquid expansion ratio of LNG reaches 620:1. It is easy to gasify when heated or flashed, causing the medium pressure to increase sharply. LNG has the characteristics of small molecular weight, low viscosity and strong permeability, which can easily cause natural gas leakage. Therefore, LNG valves are flammable and explosive. Valve seat seal: The main material of the valve seat is metal. Metal will deform due to phase change in ultra-low temperature environment. Different materials have different sensitivities to temperature. There are differences in metal organization changes, expansion coefficients, deformation, etc., and the uncontrollable deformation has a serious impact on the valve sealing performance. Under normal temperature conditions, the elastic compression of the rubber O-ring can meet the valve sealing requirements. The low-temperature valve has exceeded the applicable temperature range of conventional O-rings. In order to meet the requirements of sealing at both normal and low temperatures, the seal adopts a lip seal ring structure. The base material of the lip seal ring is metal. On the one hand, it meets the performance under low temperature conditions. On the other hand, the lip seal ring structure can compensate for the deformation of the main body internals due to temperature changes, thereby ensuring the sealing performance of the product. Sealing of the valve stem packing: Conventional ball valves generally use O-ring seals or graphite packing seals at the valve stem. Due to the particularity of the LNG medium, these two structures are not applicable. The valve stem of a cryogenic ball valve is prone to frost, which not only reduces the performance of the valve stem seal, but also the up and down movement of the valve stem under frost conditions will scratch the valve stem seal. The top-mounted ball valve in the related technology cannot achieve a good sealing effect in an ultra-low temperature environment.

[0024] Based on this, Figures 1 to 3 The present application provides an ultra-low temperature valve seat sealing kit, the ultra-low temperature valve seat sealing kit comprising:

[0025] A valve body, wherein a ball body for sealing is arranged in the valve body;

[0026] A valve seat 1, wherein the valve seat 1 is arranged on both sides of the interior of the valve body, and the valve seat 1 is coaxially rotatably mounted with the ball;

[0027] The back of the valve seat 1 is provided with a groove 2 , in which an O-type sealing ring 3 is embedded. The groove width of the groove 2 is 10% to 15% of the volume of the sealing ring 3 .

[0028] If the O-ring is to achieve a good sealing effect, it needs to be correctly matched with the groove size, that is, to form a good compression and stretching amount of the sealing ring. When the groove is designed and processed, if the compression amount is too low, it will cause leakage; otherwise, it will cause the stress relaxation of the O-ring and leak out. Not only that, if the stretching is excessive, it will accelerate the aging of the O-ring and cause leakage. When the size specifications of the O-ring are selected, its sealing performance and working state will be determined by the groove. Therefore, the design of the groove is crucial. The groove design includes the shape, size, accuracy and surface roughness of the groove. For dynamic sealing, the relative motion clearance must also be met. The groove design principle is: reasonable size, easy processing, easy to ensure accuracy, and convenient disassembly and assembly.

[0029] The groove size is determined by the size parameters of the O-ring. Its size can be calculated by volume, and is usually set at about 15% larger than the volume of the O-ring. The reasons are:

[0030] After the O-ring is installed, the compression amount is between 3% and 30%, so there should be space for the deformation of the O-ring.

[0031] b. For O-rings in oil, long-term immersion and increased operating temperature will cause the rubber material to expand, so there must be a margin in the groove.

[0032] c. When the valve seat moves, the O-ring will produce a slight rolling phenomenon. It is generally believed that there should be an appropriate gap between the assembled O-ring and the groove wall, but it should not be too large, otherwise it will become a harmful "clearance" under the action of alternating pressure, causing the O-ring to wear faster. The groove width should not be too narrow. If the margin is too small, the O-ring cannot roll, and the friction resistance will increase, causing serious wear. On the contrary, when the range of movement is large, it is also easy to wear, especially for static seals. If the working pressure is pulsating, the O-ring will not be stationary and will swim at the same pulsating frequency. Due to the unreasonable groove width, abnormal wear will occur and the life of the O-ring will be shortened. If you want to obtain a reasonable size, the cross-sectional area of ​​the O-ring should account for at least 85% of the cross-sectional area of ​​the rectangular groove, and the groove width must be greater than the maximum diameter of the O-ring after compression deformation. In most cases, the groove width is guaranteed to be 1.1~1.5 times the cross-sectional diameter of the O-ring. When the pressure is very high, a retaining ring needs to be added, and the groove width should also be increased. Different working modes, radial seal or axial seal, dynamic seal or static seal, hydraulic seal or pneumatic seal, have different seal groove sizes. The O-ring and seal groove size series are based on the national standard GB / T3452.3, and the groove size can also be calculated and designed based on the requirements for the compression and extension of the seal ring.

[0033] In some embodiments, the shape of the groove 2 is rectangular, semicircular, V-shaped, dovetail-shaped or triangular.

[0034] The most common groove shape is the rectangular groove. The advantage of the rectangular groove is that it is easy to process and it is easy to ensure that the O-ring has a reasonable amount of compression. In addition, the groove also has V-shaped, semicircular, dovetail and triangular shapes.

[0035] In some embodiments, the compression amount of the sealing ring is 3%~30%.

[0036] The necessary compression rate of the O-ring determines the depth of the groove. The depth of the groove plus the gap must be less than the cross-sectional diameter of the O-ring in the free state to ensure the required compression for sealing. The compression of the O-ring is composed of the compression δ' at the inner diameter of the O-ring and the compression δ'' at the outer diameter, that is, δ=δ'+δ''. When δ'=δ'', the cross-sectional center of the O-ring coincides with the cross-sectional center of the groove, and the circumferences of the two center circles are equal, indicating that the O-ring is not stretched during installation. If δ'>δ'', the circumference of the center circle of the O-ring cross section is less than the circumference of the center circle of the groove, indicating that the O-ring is installed in the groove in a stretched state; if δ'<δ'', the circumference of the center circle of the O-ring cross section is greater than the circumference of the center circle of the groove cross section. At this time, the O-ring is compressed axially, and the O-ring will bounce when disassembled. When designing the groove depth, you should first determine how the O-ring is used, and then select a reasonable compression deformation rate.

[0037] In some embodiments, the depth of the groove 2 is smaller than the cross-sectional diameter of the sealing ring.

[0038] In some embodiments, the outer edge of the groove 2 is provided with a rounded corner, and the radius of the rounded corner is 0.1-0.2 mm.

[0039] To prevent scratches on the O-ring during assembly, the outer edge of the groove must be rounded. The fillet radius is usually small, i.e. r=0.1~0.2mm, to avoid burrs when the valve seat is processed, and to ensure that the O-ring will not be squeezed out of the gap and the retaining ring is placed stably. The bottom fillet is mainly to prevent stress concentration. The fillet radius can be R=0.3~1mm for the dynamic seal groove and half of the diameter of the O-ring cross section for the static seal groove, i.e. R=d / 2.

[0040] There is usually a gap between the valve seat and the valve body, and its size is related to the working pressure of the medium and the hardness of the O-ring material. If the gap is too small, it will be difficult to manufacture and process; if the gap is too large, the O-ring will be squeezed into the gap and damaged. Generally, the greater the internal pressure, the smaller the gap; the greater the hardness of the O-ring material, the larger the gap can be. The given value of the gap is closely related to the manufacturing accuracy of the parts.

[0041] In some embodiments, the surface roughness of the groove wall of the groove 2 is 3.2-6.3 μm.

[0042] In some embodiments, the surface roughness of the groove wall of the groove 2 is less than or equal to 6.3 μm.

[0043] The surface roughness of the groove has a great influence on the sealing performance of the O-ring and the processability of the groove. The O-ring for static sealing does not move during operation, so the roughness of the groove wall is Ra=3.2~6.3μm. For the O-ring for reciprocating motion, since it often rolls in the groove, the roughness of the groove wall and the groove bottom should be lower, and the requirement is below Ra=6.3μm.

[0044] In short, the design of the groove should take into account multiple factors, including the size, shape, material of the O-ring and the working conditions of the system. Through reasonable design and optimization, it can ensure that the groove has good sealing performance and a long service life.

[0045] It can be seen from the above embodiments that the present application provides an ultra-low temperature valve seat sealing kit, comprising: a valve body, in which a ball for sealing is provided; a valve seat, in which the valve seat is provided on both sides of the interior of the valve body, and the valve seat and the ball are coaxially rotatably installed; a groove is provided on the back of the valve seat, in which an O-type sealing ring is embedded, and the groove width of the groove is 10% to 15% of the volume of the sealing ring. The ultra-low temperature valve seat sealing kit provided by the present application adopts the groove on the back of the valve seat to make its O-type sealing ring perform auxiliary sealing, and the O-type sealing ring is correctly matched with the groove size, that is, a good sealing ring compression and stretching amount is formed, thereby improving the sealing performance of the ultra-low temperature valve seat sealing kit, and solving the problem that the top-mounted ball valve in the prior art cannot achieve a good sealing effect in an ultra-low temperature environment.

[0046] Similar parts between the embodiments provided in this application can be referenced to each other. The specific implementation methods provided above are only a few examples under the general concept of this application and do not constitute a limitation on the protection scope of this application. For those skilled in the art, any other implementation methods expanded based on the scheme of this application without creative work belong to the protection scope of this application.

Claims

1. A cryogenic valve seat sealing kit, characterized in that: include: A valve body, wherein a ball body for sealing is arranged in the valve body; A valve seat (1), the valve seat (1) being arranged on both sides of the interior of the valve body, the valve seat (1) being coaxially rotatably mounted with the ball; The back of the valve seat (1) is provided with a groove (2), an O-type sealing ring (3) is embedded in the groove (2), and the groove width of the groove (2) is 10% to 15% of the volume of the sealing ring (3).

2. The ultra-low temperature valve seat sealing kit according to claim 1, characterized in that: The shape of the groove (2) is one of a rectangle, a semicircle, a V-shape, a dovetail shape or a triangle.

3. The ultra-low temperature valve seat sealing kit according to claim 1, characterized in that: The compression amount of the sealing ring (3) is 3% to 30%.

4. The ultra-low temperature valve seat sealing kit according to claim 1, characterized in that: The depth of the groove (2) is smaller than the cross-sectional diameter of the sealing ring (3).

5. The ultra-low temperature valve seat sealing kit according to claim 1, characterized in that: The outer edge of the groove (2) is provided with a rounded corner, and the radius of the rounded corner is 0.1-0.2 mm.

6. The ultra-low temperature valve seat sealing kit according to claim 1, characterized in that: The surface roughness of the groove wall of the groove (2) is 3.2-6.3 μm.

7. The ultra-low temperature valve seat sealing kit according to claim 1, characterized in that: The surface roughness of the groove wall of the groove (2) is less than or equal to 6.3 μm.

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