An ultra-high pressure flexible metal seal structure and sealing method

Abstract

The application discloses a kind of ultra-high pressure flexible metal sealing structure and sealing method, structure includes upper flange, lower flange, bar, sealing steel ring, U-shaped main seal, main seal U-shaped inner support and lower support seat, sealing inner limit spring;Wherein, upper flange and lower flange are all set in bar outside, and the contact surface of two is circumferentially provided with sealing steel ring;Lower flange upper surface is concave downward and forms L-shaped annular groove, lower support seat is annular, and is arranged in L-shaped annular groove;Lower support seat end portion is convex upward and forms annular main seal U-shaped inner support, U-shaped main seal is annular, and is set in main seal U-shaped inner support outside, and the flexible of metal U-shaped main seal is realized self-adapting sealing under the wear of valve stem or sleeve large tolerance size, multiple sealing collaborative design gradient pressure bearing, realizes reliable slight adjustment sealing under ultra-high pressure working condition.

Description

Technical Field

[0001] This invention relates to the field of sealing structures. More specifically, this invention relates to an ultra-high pressure flexible metal sealing structure and sealing method. Background Technology

[0002] CN20221038080.1 - A Metal Sealing Structure for Unmachined Sleeve Surfaces. This invention discloses a metal sealing structure for unmachined sleeve surfaces. A sealing assembly is installed between the upper body and the sleeve. This sealing assembly includes a pressure ring, one or more sets of metal sealing rings, and a support ring arranged sequentially. The metal sealing ring sets include Y-shaped metal sealing rings and U-shaped metal sealing rings. The open end of the Y-shaped metal sealing ring faces upward, and the lower end of the Y-shaped metal sealing ring is placed inside the open end of the upper end of the U-shaped metal sealing ring. The upper end of the pressure ring rests against the inner wall end face of the upper body, and the lower end of the support ring abuts against the upper end face of the lower body. This invention features a large deformation capacity and is easily activated, achieving metal sealing on the surface of unmachined sleeves with good sealing effect and high strength. It overcomes the shortcomings of existing methods that make metal sealing on unmachined sleeve surfaces difficult.

[0003] CN 201820574542.3 - Metal Seal for Oil Wellhead Equipment. This utility model discloses a metal seal for an oil wellhead equipment, including a casing head, a tubing head, a hanger assembly, and a metal sealing device. The casing head is connected to the tubing head through the hanger assembly. The metal sealing device is disposed between the casing head and the hanger assembly. The metal sealing device includes an upper adjusting ring, a lower adjusting ring, an outer metal sealing ring, and an inner metal sealing ring. The inner metal sealing ring is fitted onto the hanger assembly. The outer circumference of the inner metal sealing ring is wedge-shaped, and the inner circumference of the outer metal sealing ring is wedge-shaped to cooperate with the inner metal sealing ring. The outer metal sealing ring is fitted onto the inner metal sealing ring. The upper adjusting ring is fitted onto the hanger assembly and abuts against the outer metal sealing ring. The lower adjusting ring is fitted onto the hanger assembly and abuts against the inner metal sealing ring. The metal seal of this utility model has strong corrosion resistance, a firm seal, and is easy to operate.

[0004] In existing technologies, wellhead devices mainly achieve sealing of machined or non-machined metal casings by using Y-shaped + U-shaped combined sealing rings and double-bevel combined sealing rings. Control valve stems mainly achieve stem sealing by using non-metallic plug combined seals. The main problems are that the seals are severely deformed after being stimulated by fluid pressure or squeezed by flanges, they are not resistant to ultra-high pressure, have short sealing life, and poor sealing reliability. Summary of the Invention

[0005] To achieve these objectives and other advantages according to the present invention, a preferred embodiment of the present invention provides an ultra-high pressure flexible metal sealing structure, including an upper flange, a lower flange, a rod, a sealing steel ring, a U-shaped main seal, a U-shaped inner support for the main seal, an inner limiting spring for the seal, and a lower support seat; The upper flange and the lower flange are both sleeved on the outside of the rod, and the upper flange and the lower flange are adapted to each other. A sealing steel ring is arranged circumferentially on the contact surface of the two flanges. The upper surface of the lower flange is recessed downward to form an L-shaped annular groove. The lower support seat is annular and is disposed in the L-shaped annular groove, close to the rod. The end of the lower support seat protrudes upward to form an annular main seal U-shaped inner support. The U-shaped main seal is annular and is sleeved on the outside of the main seal U-shaped inner support. The sealing inner limiting spring is disposed between the U-shaped groove of the U-shaped main seal and the U-shaped groove of the main seal U-shaped inner support. The rod is a valve stem or a sleeve.

[0006] Preferably, the U-shaped main seal is a U-shaped structure with its opening facing the direction of fluid pressure, and the U-shaped inner support of the main seal is a U-shaped structure with its opening facing away from the direction of fluid pressure. A combined sealing inner limiting spring is vertically installed inside the support, and when the U-shaped main seal is sleeved on the U-shaped inner support of the main seal, the sealing inner limiting spring is in a compressed state to provide the necessary support force for the sealing structure.

[0007] Preferably, the outer wall of the lower support is provided with at least one annular outer sealing groove, and an auxiliary outer seal is provided in the outer sealing groove. The auxiliary outer seal is a U-shaped non-metallic seal with a U-shaped spring inside its opening, and the U-shaped opening of the auxiliary outer seal faces the direction of fluid pressure.

[0008] Preferably, the inner wall of the lower support is provided with at least one annular inner sealing groove, and an auxiliary inner seal is provided in the inner sealing groove. The auxiliary inner seal is a non-metallic U-shaped structure, and a U-shaped spring is provided in its opening. The U-shaped opening of the auxiliary inner seal faces the direction of fluid pressure.

[0009] Preferably, the top of the U-shaped main seal is provided with an outer support for the main seal. The outer support for the main seal is annular and sleeved on the outside of the valve stem. The strength of the material of the outer support for the main seal is higher than that of the inner support for the U-shaped main seal, and the strength of the material of the inner support for the U-shaped main seal is higher than that of the U-shaped main seal. The inner top of the U-shaped main seal is provided with a guide surface, which is a conical surface. The outer side of the U-shaped groove supporting the main seal is a conical support surface, and the angle of the conical surface matches the angle of the guide surface of the U-shaped main seal. Preferably, the outer side of the U-shaped groove is a sealing surface, and a sealing boss is provided in the sealing surface area. The sealing boss is either a group of no less than two small-radius sealing bosses or a large-radius arc-shaped sealing boss, depending on the fluid pressure.

[0010] Preferably, the outer sealing surface of the U-shaped main seal is coated with soft metal.

[0011] Preferably, the combined sealing inner limit spring consists of a circumferential sealing inner limit spring and a circumferential sealing inner limit spring. The axis of the circumferential sealing inner limit spring is parallel to the valve stem axis, and there are no fewer than two springs evenly distributed around the circumference. Each spring can be set as a single spring or a set of springs depending on the pressure of the fluid. The spring can be a helical spring or other types of springs. The axis of the circumferential sealing inner limit spring rotates around the valve stem axis, and there are no fewer than two springs evenly distributed around the circumference. Alternatively, the number can be adjusted by stacking them along the valve stem axis according to the height of the main seal U-shaped inner support. The circumferential sealing inner limit spring can be a helical spring or other types of springs.

[0012] Preferably, the circumferential sealing inner limiting spring is always in a compressed state in the sealing structure, closely attached to the spring guide surface of the supporting main seal U-shaped inner support 8, the bottom of the circumferential sealing inner limiting spring is in contact with the bottom of the U-shaped groove of the main seal U-shaped inner support, and the top is in contact with the bottom of the U-shaped groove of the U-shaped main seal.

[0013] On the other hand, a sealing method for the aforementioned ultra-high pressure flexible metal sealing structure is also provided, comprising the following steps: Step 1: Tighten the connectors to fit the upper flange 1 and the lower flange 2 together. At this time, the sealing steel ring is squeezed and undergoes plastic deformation, filling the tiny gaps in the contact surface to achieve the initial seal between the upper and lower flanges. The U-shaped main seal guide surface slides and opens along the outer support surface of the inner support 8 of the main seal U-shape. The inner sealing boss of the U-shaped main seal 6 slightly contacts the valve stem or the outer surface of the sleeve to establish the initial main seal. The outer sealing boss of the U-shaped main seal 6 slightly contacts the inner cylindrical surface of the upper flange 1 to establish the initial main seal. Step 2: When high-pressure fluid flows in and the pressure does not exceed 140MPa, when the fluid pressure acts on the sealing structure, the U-shaped spring of the auxiliary inner seal expands outward to push the auxiliary inner seal and the outer side of the valve stem to achieve a seal. The U-shaped spring of the auxiliary inner seal expands outward to push the auxiliary outer seal and the inner side of the lower flange to achieve a seal. When the fluid pressure does not exceed 140MPa, the auxiliary inner seal and the auxiliary outer seal bear the main sealing pressure. When the fluid pressure exceeds 140 MPa, the effects of the auxiliary inner seal and auxiliary outer seal weaken. Some of the ultra-high pressure fluid passes through the sealing surfaces between the auxiliary inner seal and the valve stem, and between the auxiliary outer seal and the lower flange, entering the U-shaped groove of the U-shaped main seal and the U-shaped inner support of the main seal. The pressure of the ultra-high pressure fluid pushes the U-shaped main seal to expand outward, and its outer wall tightly fits against the inner wall of the flange groove, the valve stem, or the outer wall of the sleeve to achieve a seal. At the same time, the U-shaped inner support of the main seal expands outward synchronously to ensure that the guide surface of the U-shaped main seal always fits tightly against the support surface of the U-shaped inner support of the main seal during outward expansion. The deformation direction of the inner side of the main seal is limited to ensure uniform contact of the sealing surface and prevent the U-shaped main seal from deforming and failing under ultra-high pressure. Throughout the process of high-pressure fluid acting on the sealing structure, the circumferential seal inner limiting spring is always in a compressed state in the sealing structure, closely attached to the spring guide surface of the U-shaped inner support 8 supporting the main seal, providing axial support force for the sealing structure. The circumferential seal inner limiting spring is always in a compressed state in the sealing structure, with its bottom contacting the bottom of the U-shaped groove of the main seal U-shaped inner support and its top contacting the bottom of the U-shaped groove of the U-shaped main seal, providing circumferential support force for the sealing structure and ensuring that the sealing structure remains stable under ultra-high pressure. Step 3: When the valve stem surface experiences micro-wear due to repeated opening and closing rotation or corrosion, the soft metal coated on the outer sealing surface of the U-shaped main seal fills the micro-corrosion pits under the action of fluid pressure, achieving corrosion sealing without replacing the valve stem; Step 4: When the outer diameter tolerance of the sleeve surface is large due to processing or other reasons, or when it is skewed due to improper use, it is necessary to increase the number of circumferential seal inner limit springs or use a set of springs to increase the axial support force, increase the cross-sectional diameter of the circumferential seal inner limit spring to increase the circumferential support force, and achieve micro-adjustment of the seal without replacing the U-shaped main seal.

[0014] The present invention has at least the following beneficial effects: The ultra-high pressure flexible metal sealing structure of the present invention achieves reliable sealing under ultra-high pressure conditions through multi-seal collaborative design. The conical surface cooperation between the U-shaped main seal and the U-shaped inner support 8 of the main seal improves the sealing fit, and the soft metal coating enhances the micro-sealing performance. The auxiliary inner and outer seals form multiple lines of defense, and the spring compensation structure adapts to pressure fluctuations, effectively extending the sealing life.

[0015] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the ultra-high pressure flexible metal sealing structure in this invention.

[0017] Figure 2This is a schematic diagram of the installation of the U-shaped main seal and the U-shaped inner support of the main seal in this invention.

[0018] Figure 3 This is a schematic diagram of the sealed inner limiting spring in this invention.

[0019] Figure 4 This is a schematic diagram of the U-shaped inner support structure that supports the main seal in this invention.

[0020] Figure 5 This is a schematic diagram of one possible structure of the U-shaped main seal in this invention.

[0021] Figure 6 This is a schematic diagram of one possible structure of the U-shaped main seal in this invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0023] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious modifications will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0024] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0025] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0026] like Figure 1-6 As shown, a preferred embodiment of the present invention provides an ultra-high pressure flexible metal sealing structure, including an upper flange 1, a lower flange 2, a rod 3, a sealing steel ring 4, a U-shaped main seal 6, a U-shaped inner support for the main seal 8, and a lower support seat 9; the rod is a valve stem or a sleeve; The upper flange 1 and the lower flange are both sleeved on the outside of the rod 3, and the upper flange 1 and the lower flange are adapted to each other. Specifically, the lower flange 2 and the upper flange 1 are connected by bolts and nuts 5. A sealing steel ring 4 is provided circumferentially on the contact surface of the two. The upper surface of the lower flange is recessed downward to form an L-shaped annular groove. The lower support seat 9 is annular and is set in the L-shaped annular groove, close to the rod 3. The end of the lower support seat 9 protrudes upward to form an annular main seal U-shaped inner support. The U-shaped main seal 6 is annular and is sleeved on the outside of the main seal U-shaped inner support 8. The sealing inner limiting spring 7 is set between the U-shaped groove of the U-shaped main seal 6 and the U-shaped groove of the main seal U-shaped inner support. The rod 3 is a valve stem or a sleeve.

[0027] In the above technical solution, the sealing steel ring 4 is an annular metal seal set on the contact surface of the upper and lower flanges. At this time, the sealing steel ring 4 is compressed and undergoes plastic deformation, filling the tiny gaps in the contact surface to achieve the initial seal between the upper flange 1 and the lower flange 2. When fluid pressure acts on the sealing structure, the pressure pushes the U-shaped main seal 6 to expand outward, and its outer wall fits tightly against the inner wall of the flange groove. At the same time, the U-shaped inner support 8 of the main seal restricts the deformation direction of the inner side of the main seal, ensuring uniform contact of the sealing surface. During the tightening of the upper flange 1 and the lower flange 2, the guide surface of the U-shaped main seal 6 slides and opens along the outer support surface of the U-shaped inner support 8 of the main seal. The inner sealing boss of the U-shaped main seal 6 slightly contacts the valve stem (only slight contact is allowed when there is no fluid pressure to prevent excessive compression and damage to the sealing surface) or the outer surface of the sleeve to establish the initial main seal. The outer sealing boss of the U-shaped main seal 6 slightly contacts the inner cylindrical surface of the upper flange 1 to establish the initial main seal.

[0028] In another technical solution, the U-shaped main seal 6 is a U-shaped structure with its opening facing the direction of fluid pressure, and the U-shaped inner support 8 of the main seal is a U-shaped structure with its opening facing away from the direction of fluid pressure. A combined sealing inner limiting spring 7 is vertically installed inside it. When the U-shaped main seal 6 is sleeved on the U-shaped inner support of the main seal, the sealing inner limiting spring 7 is in a compressed state to provide the necessary support force for the sealing structure.

[0029] The combined sealing inner limit spring 7 consists of a circumferential sealing inner limit spring 7 and a circumferential sealing inner limit spring 7. The axis of the circumferential sealing inner limit spring 7 is parallel to the valve stem axis, and there are no fewer than two of them evenly distributed around the circumference. Each spring can be set as a single spring or a set of springs depending on the pressure of the fluid. The spring can be a helical spring or other types of springs. The axis of the circumferential sealing inner limit spring 7 rotates around the valve stem axis, and there are no fewer than two of them evenly distributed around the circumference. The number can also be adjusted by stacking them along the valve stem axis according to the height of the main sealing U-shaped inner support 8. The circumferential sealing inner limit spring 7 can be a helical spring or other types of springs.

[0030] The circumferential sealing inner limiting spring 7 is always in a compressed state in the sealing structure, closely attached to the spring guide surface 8-1 of the supporting U-shaped inner support 8 of the main seal, with the outer side being the support surface 8-2. The bottom of the circumferential sealing inner limiting spring 7 is in contact with the bottom of the U-shaped groove of the main seal U-shaped inner support, and the top is in contact with the bottom of the U-shaped groove of the U-shaped main seal 6.

[0031] In the above technical solution, the main seal U-shaped inner support 8 is a U-shaped structure with its opening facing away from the fluid pressure direction. A combined sealing inner limiting spring 7 is vertically installed inside. The sealing inner limiting spring 7 consists of a circumferential sealing inner limiting spring 7.1 and a circumferential sealing inner limiting spring 7.2. The axis of the circumferential sealing inner limiting spring 7.1 is parallel to the axis of the valve stem 3, and there are at least two springs evenly distributed around the circumference. Each spring can be a single spring or a set of springs depending on the fluid pressure. The springs can be helical springs or other types of springs. The axis of the circumferential sealing inner limiting spring 7.2 rotates around the axis of the valve stem 3, and there are at least two springs evenly distributed around the circumference. The number can be adjusted according to the fluid pressure, or the number can be increased by stacking them along the axis of the valve stem 3 to improve the supporting force, depending on the height of the main seal U-shaped inner support 8. When the U-shaped main seal 6 is fitted onto the main seal U-shaped inner support 8, both the circumferential sealing inner limiting springs 7.1 and 7.2 are in a compressed state.

[0032] The main seal U-shaped inner support 8 is a U-shaped annular support component, integrated with the lower support seat 9. Its opening, facing away from the fluid pressure direction, means the open side of the U-shaped structure faces away from the direction of high-pressure fluid flow. When the U-shaped main seal 6 expands outward under fluid pressure or when the valve stem experiences slight wear due to corrosion, the circumferential sealing inner limit spring 7.2 can release a certain thrust, pushing the support surface of the main seal U-shaped inner support 8 to always be tightly pressed against the guide surface of the U-shaped main seal 6, ensuring a seal between the U-shaped main seal 6 and the valve stem 3. This ensures adaptive sealing under ultra-high pressure conditions with slight wear on the valve stem or sleeve. The bottom of the circumferential sealing inner limit spring 7.1 contacts the bottom of the U-shaped groove of the main seal U-shaped inner support 8, and the top contacts the bottom of the U-shaped groove of the U-shaped main seal 6. It is used to transmit the axial pressure of the fluid and the axial tightening force of the upper flange 1 and the lower flange 2 between the main seal U-shaped inner support 8 and the U-shaped main seal 6, improving the stability and anti-extrusion capability of the main seal structure. The use of the sealing inner limit spring 7.2 enhances the support effect and assists in achieving rapid sealing. When the valve stem or sleeve tilts due to improper use or sudden severe operating conditions, the U-shaped main seal 6 is pushed inward by pressure to compress the U-shaped inner support 8. The U-shaped inner support structure tends to contract under stress. At this time, the circumferential sealing inner limiting spring 7.2 generates a radial elastic reaction force, and the circumferential sealing inner limiting spring 7.1 generates an axial elastic reaction force. These reaction forces limit excessive contraction and torsional deformation of the inner support, and are simultaneously transmitted to the U-shaped main seal 6 through the inner support, maintaining a stable deformation state of the main seal and preventing seal failure due to excessive deformation. Through the limiting effect of the U-shaped inner support 8, the U-shaped main seal 6 is ensured to always remain within a reasonable deformation range during pressure fluctuations, significantly improving the pressure adaptability and long-term stability of the sealing structure.

[0033] In addition, the top of the U-shaped main seal 6 is provided with a main seal outer support 10, which is annular and sleeved on the outside of the rod 3.

[0034] In the above technical solution, when the sealing structure is working, when fluid pressure acts on the U-shaped main seal 6, the main seal will deform outward and upward under pressure. Since the main seal outer support 10 is located at the top of the main seal, it can limit the excessive outward turning of the top of the main seal through its own rigidity, guide the deformation direction of the main seal to the radially outward, and ensure effective contact between the sealing surface and the flange groove wall.

[0035] In another technical solution, at least one annular outer sealing groove is provided on the outer side wall of the lower support 9, and an auxiliary outer seal 12 is provided in the outer sealing groove. The auxiliary outer seal 12 is a U-shaped non-metallic material, and a U-shaped spring is provided in its opening. The U-shaped opening of the auxiliary outer seal 12 faces the direction of fluid pressure.

[0036] In the above technical solution, the outer sealing groove refers to the circumferential groove machined on the outer wall of the lower support 9, used to install auxiliary sealing components. The auxiliary outer seal 12 is a U-shaped annular seal made of non-metallic material, with its U-shaped opening facing the direction of fluid pressure, i.e., the open side faces the high-pressure fluid. The U-shaped spring inside the opening is an annular spring that provides elastic support for the auxiliary seal. When fluid pressure acts on the sealing structure, the high-pressure fluid enters the inner side of the U-shaped opening of the auxiliary outer seal 12 through the gap, pushing the U-shaped seal to expand outward. The outer wall of the auxiliary outer seal 12 is pressed tightly against the inner wall of the L-shaped annular groove of the lower flange 2. At the same time, the U-shaped spring inside the opening of the auxiliary outer seal 12 is further compressed under pressure, generating an elastic reaction force, which enhances the contact pressure between the auxiliary seal and the groove wall. As the pressure increases, the fluid pressure and the spring force work together to increase the contact pressure of the sealing surface of the auxiliary outer seal 12 synchronously, forming dynamic sealing compensation. This auxiliary outer seal structure can form a second sealing defense line outside the main seal, effectively blocking the slight leakage through the main seal, and significantly improving the overall sealing reliability of the sealing structure.

[0037] In another technical solution, the inner wall of the lower support 9 is provided with at least one annular inner sealing groove, and an auxiliary inner seal 11 is provided in the inner sealing groove. The auxiliary inner seal 11 is a non-metallic U-shaped structure, and a U-shaped spring is provided in its opening. The U-shaped opening of the auxiliary inner seal 11 faces the direction of fluid pressure.

[0038] In the above technical solution, the inner sealing groove refers to the circumferential groove machined on the inner wall of the lower support 9, used to install the inner auxiliary seal; the auxiliary inner seal 11 is a U-shaped annular seal made of non-metallic material, and its structure is similar to that of the auxiliary outer seal. The U-shaped opening faces the direction of fluid pressure, that is, the open side faces the high-pressure fluid flow, and the U-shaped spring inside the opening provides elastic support. During operation, the high-pressure fluid enters the U-shaped opening of the auxiliary inner seal 11, pushing the seal to expand inward, so that its inner wall fits tightly against the outer wall of the rod 3. The spring inside the U-shaped opening is compressed under pressure, generating elastic force to enhance the sealing contact pressure. As the fluid pressure increases, the contact pressure increases synchronously, realizing dynamic sealing compensation. The auxiliary inner seal 11 can effectively prevent fluid leakage along the gap between the lower support 9 and the rod 3, forming a double auxiliary sealing system with the outer auxiliary outer seal 12. This structural design allows the sealing structure to maintain a stable sealing effect when the rod 3 moves or rotates axially, reducing the risk of leakage due to wear of the sealing surface caused by the movement of the rod, and improving the dynamic adaptability of the sealing structure.

[0039] When the fluid pressure is not extremely high, the auxiliary inner seal 11 and auxiliary outer seal 12 bear the role of sealing the fluid pressure. This ensures that the U-shaped main seal 6 and the sealing steel ring 4 only bear the sealing work of the ultra-high pressure fluid pressure and no longer bear the sealing task under low pressure. The auxiliary inner seal 11 and auxiliary outer seal 12 bear the main sealing task under slightly lower pressure. The sealing structure is used in sections according to the fluid pressure, thereby improving the overall life and reliability of the seal.

[0040] In another technical solution, the material strength of the outer support 10 of the main seal is higher than that of the inner U-shaped support 8 of the main seal, and the material strength of the inner U-shaped support 8 of the main seal is higher than that of the U-shaped main seal 6.

[0041] In the above technical solution, during the operation of the sealing structure, the outer support 10 of the main seal mainly bears the radial outward pressure transmitted by the U-shaped main seal 6 and the reaction force of the flange groove. Its high-strength material makes it resistant to deformation, ensuring stable support for the main seal. The inner U-shaped support 8 of the main seal needs to transmit fluid pressure and guide the deformation of the main seal. Its medium-to-high strength material allows it to withstand a certain amount of pressure while also possessing moderate elastic deformation capability, avoiding excessive rigidity that could damage the main seal. The U-shaped main seal 6 needs to achieve sealing through plastic deformation. Its lower strength but high plasticity material allows it to deform uniformly under pressure, tightly fitting the sealing surface. This material strength gradient design ensures a perfect match between the stress on each component and the material properties, guaranteeing both the structural stability of the supporting components and the deformation sealing effect of the sealing components, thus extending the overall service life of the sealing structure.

[0042] When the sealing surface of member 3 is in an unmachined state, the sealing inner limit spring 7 between the main seal U-shaped inner support 8 and the U-shaped main seal 6 is no longer installed, thereby increasing the flexibility of the U-shaped main seal 6 to adapt to the large tolerance dimensional range of the surface of member 3 and increasing the sealing capacity.

[0043] In another technical solution, a guide surface 6-2 is provided on the inner top of the U-shaped main seal 6. The guide surface is a conical surface, and the outer side of the U-shaped groove of the main seal U-shaped inner support 8 is a conical support surface. The angle of the conical surface matches the angle of the guide surface of the U-shaped main seal 6.

[0044] In the above technical solution, the inner top guide surface of the U-shaped main seal 6 refers to the conical inclined surface machined at the inner top of the main seal, which is used to guide the fit between the main seal and the inner support; the outer conical support surface of the U-shaped groove of the main seal U-shaped inner support 8 refers to the conical inclined surface machined on the outer side of the inner support, and the conical angle matching means that the inclination angles of the two conical surfaces are the same to ensure close contact.

[0045] When fluid pressure acts on the U-shaped main seal 6, the main seal tends to deform outwards and upwards under pressure. Because the guide surface of the U-shaped main seal 6 matches the conical support surface of the inner U-shaped support 8 at the same angle, the two conical surfaces maintain uniform contact during deformation. The inner support converts part of the radial force into axial support force through the conical support surface, guiding the main seal to deform in the preset direction. This conical surface fit structure avoids localized stress concentration between the main seal and the inner support, making the main seal more uniformly stressed and its deformation more stable. Simultaneously, the precise angle matching ensures uniform pressure distribution on the sealing surface, reducing localized wear or seal failure caused by uneven stress, and significantly improving the sealing reliability of the sealing surface.

[0046] In another technical solution, the outer side of the U-shaped groove of the U-shaped main seal 6 is the sealing surface, and a sealing boss 6-1 is provided in the sealing surface area. The sealing boss is either a group of no less than two small-radius sealing bosses or a large-radius arc-shaped sealing boss, depending on the fluid pressure.

[0047] In the above technical solution, the outer sealing surface of the U-shaped groove of the main seal U-shaped inner support 8 refers to the surface that contacts the U-shaped main seal 6, and the sealing boss refers to the protruding structure processed in the sealing surface area; the small radius sealing boss refers to the annular protrusion with a small radius, and there are no less than 2 in each group; the large radius arc-shaped sealing boss refers to the arc-shaped annular protrusion with a large radius, and its structure is selected according to the fluid pressure.

[0048] When the pressure exceeds 140MPa, use as follows: Figure 6 The sealing boss structure shown has only one large rounded corner. This large rounded corner, while meeting sealing requirements, minimizes stress concentration, thus addressing the issue of high stress and easy failure of the U-shaped main seal under ultra-high pressure. When the pressure is below 140MPa, a structure like this... Figure 5 The sealing structure shown has two small rounded corners, which allows for multiple points of contact and makes it easier to form a seal.

[0049] During operation, the U-shaped main seal 6, under pressure, comes into contact with the sealing surface of the U-shaped inner support 8 of the main seal, and the sealing boss contacts the inner wall of the main seal. For small-radius sealing bosses, multiple bosses form multiple sealing contact lines. Under fluid pressure, the bosses squeeze the main seal, generating high local pressure at the contact lines and preventing fluid from passing through. For large-radius arc-shaped sealing bosses, the arc structure makes the contact pressure more evenly distributed along the axial direction, and can form a wide range of sealing contact zones under high pressure, adapting to the sealing requirements under high pressure.

[0050] In another technical solution, the U-shaped main seal is made of stainless steel. The outer sealing surface of the U-shaped main seal 6 is coated with a soft metal, which is a nickel-based alloy.

[0051] In the above technical solution, the outer sealing surface of the U-shaped main seal 6 refers to the surface where the main seal contacts the inner wall of the L-shaped annular groove of the lower flange 2. Soft metal refers to a metal material with low hardness and good plasticity, such as copper, aluminum, or their alloys. Coating refers to forming a thin metal covering layer on the sealing surface through electroplating, spraying, or welding. When the sealing structure is working, the U-shaped main seal 6 expands outward under fluid pressure, and the soft metal coating on the outer sealing surface contacts the inner wall of the groove of the lower flange 2. Due to the low hardness and good plasticity of the soft metal, it undergoes plastic deformation under contact pressure, filling the tiny unevenness of the flange groove inner wall and the main seal sealing surface, enabling the two contact surfaces to fit tightly and eliminating microscopic gaps.

[0052] In another technical solution, the lower flange 2 and the upper flange 1 are connected by bolts and nuts 5.

[0053] In the above technical solution, the upper flange 1 and the lower flange 2 are connected by bolts and nuts 5. Pre-tightening the bolts and nuts 5 to press the sealing steel ring 4 can achieve a seal between the upper and lower flanges 2. Adjusting the pre-tightening force of the bolts and nuts 5 can adjust the sealing force between the U-shaped main seal 6 and the lower flange 2 and the rod 3. When the fluid is in an ultra-high pressure area, it is necessary to appropriately increase the pre-tightening force of the bolts and nuts 5 to ensure that the U-shaped main seal 6 and the lower flange 2 and the rod 3 form sufficient sealing force to undertake the main sealing task.

[0054] When slight wear occurs on the sealing surface of rod 3, the preload of bolts and nuts 5 is appropriately increased so that the soft metal coated on the outer sealing surface of the U-shaped groove of the U-shaped main seal 6 fills the micro gaps on the surface of rod 3 caused by wear, thereby enhancing the sealing effect and restoring the seal.

[0055] On the other hand, a preferred embodiment of the present invention also provides a sealing method for the ultra-high pressure flexible metal sealing structure, comprising the following steps: Step 1: Tighten the upper flange 11 and the lower flange 2 by means of connecting parts such as bolts and nuts 5 to make them fit together. At this time, the sealing steel ring 4 is squeezed and plastically deformed, filling the small gaps in the contact surface to achieve the initial seal between the upper flange 1 and the lower flange. The guide surface of the U-shaped main seal 6 slides and opens along the outer support surface of the inner support 8 of the main seal U-shape. The inner sealing boss of the U-shaped main seal 6 slightly contacts the valve stem or the outer surface of the sleeve to establish the initial main seal. The outer sealing boss of the U-shaped main seal 6 slightly contacts the inner cylindrical surface of the upper flange 11 to establish the initial main seal. Step 2: When high-pressure fluid flows in and the pressure does not exceed 140MPa, when the fluid pressure acts on the sealing structure, the U-shaped spring of the auxiliary inner seal expands outward to push the auxiliary inner seal and the outer side of the valve stem to achieve a seal. The U-shaped spring of the auxiliary inner seal expands outward to push the auxiliary outer seal and the inner side of the lower flange to achieve a seal. When the fluid pressure does not exceed 140MPa, the auxiliary inner seal 11 and the auxiliary outer seal 12 bear the main sealing pressure. When the fluid pressure exceeds 140MPa, the effects of the auxiliary inner seal 11 and the auxiliary outer seal 12 weaken. Some of the ultra-high pressure fluid passes through the sealing surface between the auxiliary inner seal 11 and the valve stem, and the sealing surface between the auxiliary outer seal 12 and the lower flange 2, entering the U-shaped groove of the U-shaped main seal 6 and the U-shaped inner support 8 of the main seal. The pressure of the ultra-high pressure fluid pushes the U-shaped main seal 6 to expand outward, and its outer wall tightly fits against the inner wall of the flange groove, the valve stem, or the outer wall of the sleeve to achieve a seal. At the same time, the U-shaped inner support 8 of the main seal expands outward synchronously to ensure that the guide surface of the U-shaped main seal 6 always fits tightly against the U-shaped inner support 8 of the main seal when it expands outward. The support surface can limit the deformation direction of the inner side of the main seal, ensuring uniform contact of the sealing surface and preventing the U-shaped main seal 6 from deforming and failing under ultra-high pressure; throughout the process of high-pressure fluid acting on the sealing structure, the circumferential sealing inner limit spring 7 is always in a compressed state in the sealing structure, closely attached to the spring guide surface of the supporting U-shaped inner support 8 of the main seal, providing axial support force for the sealing structure. The circumferential sealing inner limit spring 7 is always in a compressed state in the sealing structure, with its bottom contacting the bottom of the U-shaped groove of the main seal U-shaped inner support and its top contacting the bottom of the U-shaped groove of the U-shaped main seal 6, providing circumferential support force for the sealing structure and ensuring that the sealing structure remains stable under ultra-high pressure; Step 3: When the valve stem surface experiences micro-wear due to repeated opening and closing rotation or corrosion, the soft metal coated on the outer sealing surface of the U-shaped main seal 6 fills the micro-corrosion pits under the action of fluid pressure, achieving corrosion sealing without replacing the valve stem; When the outer diameter tolerance of the sleeve surface is large due to processing or other reasons, or when it is skewed due to improper use, it is necessary to increase the number of circumferential sealing inner limit springs 7 or use a set of springs to increase the axial support force, increase the cross-sectional diameter of the circumferential sealing inner limit springs 7 to increase the circumferential support force, and achieve micro-adjustment of the seal without replacing the U-shaped main seal 6.

[0056] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A flexible metal sealing structure under ultra-high pressure, characterized in that, Includes upper flange, lower flange, rod, sealing steel ring, U-shaped main seal, U-shaped inner support of the main seal, inner limit spring of the seal, and lower support seat; The upper flange and the lower flange are both sleeved on the outside of the rod, and the upper flange and the lower flange are adapted to each other. A sealing steel ring is arranged circumferentially on the contact surface of the two flanges. The upper surface of the lower flange is recessed downward to form an L-shaped annular groove. The lower support seat is annular and is disposed in the L-shaped annular groove, close to the rod. The end of the lower support seat protrudes upward to form an annular main seal U-shaped inner support. The U-shaped main seal is annular and is sleeved on the outside of the main seal U-shaped inner support. The sealing inner limiting spring is disposed between the U-shaped groove of the U-shaped main seal and the U-shaped groove of the main seal U-shaped inner support. The rod is a valve stem or a sleeve; The outer wall of the lower support is provided with at least one annular outer sealing groove, and an auxiliary outer seal is provided in the outer sealing groove. The auxiliary outer seal is a U-shaped non-metallic seal with a U-shaped spring in its opening. The U-shaped opening of the auxiliary outer seal faces the direction of fluid pressure. The inner wall of the lower support is provided with at least one annular inner sealing groove, and an auxiliary inner seal is provided in the inner sealing groove. The auxiliary inner seal is a non-metallic U-shaped structure, and a U-shaped spring is provided in its opening. The U-shaped opening of the auxiliary inner seal faces the direction of fluid pressure. The top of the U-shaped main seal is provided with an outer support for the main seal. The outer support for the main seal is annular and sleeved on the outside of the rod. The material strength of the outer support for the main seal is higher than that of the inner support for the U-shaped main seal, and the material strength of the inner support for the U-shaped main seal is higher than that of the U-shaped main seal. The inner top of the U-shaped main seal is provided with a guide surface, which is a conical surface. The outer side of the U-shaped groove supporting the main seal is a conical support surface, and the angle of the conical surface matches the angle of the guide surface of the U-shaped main seal. The combined sealing inner limit spring consists of a circumferential sealing inner limit spring and a circumferential sealing inner limit spring. The axis of the circumferential sealing inner limit spring is parallel to the axis of the rod, and there are no fewer than two of them evenly distributed around the circumference. The axis of the circumferential sealing inner limit spring rotates around the axis of the rod, and there are no fewer than two of them evenly distributed around the circumference. The circumferential sealing inner limiting spring is always in a compressed state in the sealing structure, closely attached to the spring guide surface of the supporting U-shaped inner support of the main seal. The bottom of the circumferential sealing inner limiting spring is in contact with the bottom of the U-shaped groove of the main seal U-shaped inner support, and the top is in contact with the bottom of the U-shaped groove of the U-shaped main seal. The circumferential sealing inner limiting spring is always in contact with both sides of the U-shaped groove of the main seal U-shaped inner support.

2. The ultra-high pressure flexible metal sealing structure according to claim 1, characterized in that, The U-shaped main seal is a U-shaped structure with its opening facing the direction of fluid pressure. The U-shaped inner support of the main seal is a U-shaped structure with its opening facing away from the direction of fluid pressure. A combined sealing inner limiting spring is vertically installed inside the support. When the U-shaped main seal is fitted onto the U-shaped inner support of the main seal, the sealing inner limiting spring is in a compressed state to provide the necessary support force for the sealing structure.

3. The ultra-high pressure flexible metal sealing structure according to claim 1, characterized in that, The outer side of the U-shaped groove is a sealing surface, and a sealing boss is provided in the sealing surface area. The sealing boss is either a group of no less than two small-radius sealing bosses or a large-radius arc-shaped sealing boss, depending on the fluid pressure.

4. The ultra-high pressure flexible metal sealing structure according to claim 1, characterized in that, The outer sealing surface of the U-shaped main seal is coated with soft metal.

5. A sealing method based on the ultra-high pressure flexible metal sealing structure according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Tighten the connectors to fit the upper and lower flanges together. At this time, the sealing steel ring is squeezed and undergoes plastic deformation, filling the tiny gaps in the contact surface to achieve the initial seal between the upper and lower flanges. The U-shaped main seal guide surface slides and opens along the inner and outer support surfaces of the main seal U-shape. The inner sealing boss of the U-shaped main seal slightly contacts the outer surface of the rod to establish the initial main seal. The outer sealing boss of the U-shaped main seal slightly contacts the inner cylindrical surface of the upper flange to establish the initial main seal. Step 2: When high-pressure fluid flows in and the pressure does not exceed 140MPa, when the fluid pressure acts on the sealing structure, the U-shaped spring of the auxiliary inner seal expands outward to push the auxiliary inner seal and the outer side of the rod to achieve a seal. The U-shaped spring of the auxiliary inner seal expands outward to push the auxiliary outer seal and the inner side of the lower flange to achieve a seal. When the fluid pressure does not exceed 140MPa, the auxiliary inner seal and the auxiliary outer seal bear the main sealing pressure. When the fluid pressure exceeds 140 MPa, the effects of the auxiliary inner seal and auxiliary outer seal weaken. Some of the ultra-high pressure fluid passes through the sealing surfaces between the auxiliary inner seal and the rod, and between the auxiliary outer seal and the lower flange, entering the U-shaped groove of the U-shaped main seal and the U-shaped inner support of the main seal. The pressure of the ultra-high pressure fluid pushes the U-shaped main seal to expand outward, and its outer wall tightly fits against the inner wall of the flange groove and the outer wall of the rod to achieve a seal. At the same time, the U-shaped inner support of the main seal expands outward synchronously to ensure that the guide surface of the U-shaped main seal always fits tightly against the support surface of the U-shaped inner support of the main seal during outward expansion. The deformation direction of the inner side of the main seal is controlled to ensure uniform contact of the sealing surface and prevent the U-shaped main seal from deforming and failing under ultra-high pressure. Throughout the process of high-pressure fluid acting on the sealing structure, the circumferential seal inner limiting spring is always in a compressed state in the sealing structure, closely attached to the spring guide surface of the U-shaped inner support of the main seal, providing axial support force for the sealing structure. The circumferential seal inner limiting spring is always in a compressed state in the sealing structure, with its bottom contacting the bottom of the U-shaped groove of the U-shaped inner support of the main seal and its top contacting the bottom of the U-shaped groove of the U-shaped main seal, providing circumferential support force for the sealing structure and ensuring that the sealing structure remains stable under ultra-high pressure. Step 3: When micro-wear appears on the valve stem surface, the soft metal coated on the outer sealing surface of the U-shaped main seal fills the micro-corrosion pits under the action of fluid pressure, achieving corrosion sealing without replacing the valve stem; When the outer diameter of the sleeve surface has a large tolerance or is skewed, increase the number of inner limit springs in the circumferential seal or use a set of springs to increase the axial support force, increase the cross-sectional diameter of the inner limit springs in the circumferential seal to increase the circumferential support force, and achieve micro-adjustment of the seal without replacing the U-shaped main seal.

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