A low-wear and dynamic sealing male and female ball support structure for a deepwater riser flexible joint

Abstract

The present invention relates to a low-wear, dynamic-seal male and female ball support structure for a deepwater riser flexible joint. A guide rod is disposed between the lower male ball and the upper male ball, and a preload spring is sleeved on the guide rod. A dual-pass sealing structure I is disposed between the upper female ball and the upper male ball, and a dual-pass sealing structure II is disposed between the lower female ball and the lower male ball. Dual-pass sealing structures I and II have identical components, with the first sealing structure utilizing a "J+O" combination sealing ring, and the second sealing structure utilizing an O-ring. Preload springs are employed between the upper and lower female and male balls, ensuring that the upper and lower sets of female and male balls are always in a preloaded state. This ensures a seal between the male and female balls while also enabling controllable preload and friction between the balls, thereby extending the service life of the flexible joint.

Description

Technical Field

[0001] The present invention relates to a flexible joint male and female ball support structure, and in particular to a novel low-wear and dynamic-sealed male and female ball support structure for a deepwater riser flexible joint, which is suitable for the use of flexible joints for deepwater risers or watertight pipes under long-term and high internal pressure loads. Background Art

[0002] In marine underwater energy exploration and production systems, the riser system serves as the connection between the surface platform and underwater equipment. It is the "throat" for media transmission between the platform and subsea equipment and is a key component of deepwater riser production systems. Deepwater riser flexible joints are key components connecting the riser system to the floating platform. They reduce shear and bending forces on the riser, alleviating stress between the riser system and the floating platform caused by ocean currents. They can also withstand significant tensile and compressive loads, significantly improving the performance of offshore oil industry equipment.

[0003] Oil States Industries (OSI) and Lord, both in the United States, are leading manufacturers and suppliers of deepwater riser flexible joints. OSI's flexible joints offer a free swing angle of ±20° and withstand internal pressures exceeding 10,000 psi (69 MPa). Lord's riser flexible joints have an operating pressure of 69 MPa, a maximum swing angle of ±10°, and a 20-year service life.

[0004] As my country's offshore oil and gas exploration and production gradually move into deepwater depths of 2 to 3 km, external loads such as waves and winds are subjecting deepwater riser flexible joints to harsh operating conditions with greater swing angles and longer durations. Chinese customers are placing higher technical demands on the development of deepwater riser flexible joints: a maximum pressure of 69 MPa, a maximum swing angle of ±25°, and a service life of 30 years. Consequently, these demands place even higher demands on the dynamic sealing and wear resistance of the male and female ball and socket supports of the flexible joints.

[0005] In the existing structure, the flexible joint ball socket supports the female ball and the male ball in a generally hard contact (e.g. Figure 1 ), the contact force between the male and female balls cannot be controlled, and excessive friction causes severe wear on the male and female balls, resulting in a service life of the flexible joint of less than 20 years. To further meet the requirement for a long service life of the flexible joint (30 years), a new design of a low-wear and dynamic sealing male and female ball support structure for the marine riser flexible joint is needed. Summary of the Invention

[0006] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology and propose a new low-wear and dynamic sealing male and female ball support structure for a deep-water riser flexible joint, which not only ensures the seal between the male and female balls, but also makes the preload and friction between the male and female balls controllable, so that the flexible joint has a longer service life.

[0007] The solution of the present invention is:

[0008] A low-wear and dynamic-sealing male and female ball support structure for a deepwater riser flexible joint includes an upper connecting pipe, a lower connecting pipe, an upper elastic element, a lower elastic element, an upper female ball, a lower female ball, an upper male ball, a lower male ball, a preload spring, a positioning plate, and a guide rod.

[0009] One end of the upper connecting pipe is connected to the upper oil pipe, and the other end is connected to the upper elastic element with a bolt. The upper elastic element is bonded to the outside of the upper female sphere. The upper connecting pipe, the upper female sphere, and the upper elastic element form an upper swing assembly; one end of the lower connecting pipe is connected to the lower oil pipe, and the other end is connected to the lower elastic element with a bolt. The lower elastic element is bonded to the outside of the lower female sphere. The lower connecting pipe, the lower female sphere, and the lower elastic element form a lower swing assembly; the upper swing assembly is fixedly connected to the upper connecting shell, and the lower swing assembly is fixedly connected to the lower connecting shell; the neck of the lower male sphere is inserted into the upper male sphere, and the overall structure composed of the two is installed between the upper female sphere and the lower female sphere; a positioning plate is installed between the upper connecting shell and the lower connecting shell, and the upper connecting shell, the lower connecting shell, and the positioning plate are fixed by bolts;

[0010] The lower part of the lower male sphere is designed with a step, and a guide rod is set between the step of the lower male sphere and the upper male sphere, and a pre-compression spring is sleeved on the guide rod;

[0011] A double-track sealing structure I is set between the upper yin sphere and the upper yang sphere, and a double-track sealing structure II is set between the lower yin sphere and the lower yang sphere. The double-track sealing structure I and the double-track sealing structure II have the same composition, both including a first sealing structure and a second sealing structure. The first sealing structure is realized by a "J+O" type combined sealing ring, which includes a J-type sealing ring and a first O-type sealing ring. The first O-type sealing ring is embedded in the groove of the J-type sealing ring; the second sealing structure is realized by the second O-type sealing ring.

[0012] Preferably, the "J"-shaped sealing ring is made of reinforced polytetrafluoroethylene sealing material.

[0013] Preferably, the first O-ring and the second O-ring are both made of rubber material with a Shore hardness of 60-80.

[0014] Preferably, the free length L0 of the preload spring and the spring stiffness coefficient K are selected according to the following formula:

[0015] ΔL=L0-L

[0016] 2F≥K×ΔL≥F

[0017] Where: ΔL is the compression of the preload spring; L is the length of the spring after compression; F is the minimum preload of the double-pass sealing structure I and the double-pass sealing structure II.

[0018] Preferably, F is obtained through finite element analysis.

[0019] Preferably, the inner diameter of the hole in the positioning plate matches the outer diameter of the axial hole in the neck of the lower male sphere.

[0020] Preferably, a threaded hole is provided on the lower step of the lower male sphere, a light hole is provided on the upper male sphere, the lower end of the guide rod is processed with an external thread, the lower end of the guide rod is fixed in the threaded hole of the lower step of the lower male sphere through the external thread, and the upper end is inserted into the light hole of the upper male sphere.

[0021] The beneficial effects of the present invention compared with the prior art are:

[0022] (1) The present invention uses a pre-stressed spring between the female and male spheres to provide an approximately constant elastic support force, so that the female and male spheres are always in a pre-stressed state, which not only ensures that the contact force between the female and male spheres is controllable, but also keeps the sealing ring between the female and male spheres in a compressed state, so that the flexible joint has a longer service life.

[0023] (2) The present invention uses "J+O" and "O" type combined sealing rings for double-pass sealing between the female and male spheres, ensuring reliable sealing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the hard contact between the female and male spheres in the existing flexible joint structure;

[0025] Figure 2 Schematic diagram of the low-wear and dynamic sealing male and female ball support structure of the present invention;

[0026] Figure 3 Schematic diagram of the dynamic seal structure of the male and female balls and the required preload of the present invention, wherein (a) is a schematic diagram of the dynamic seal structure, (b) is a schematic diagram of the finite element analysis, (c) is the first seal structure and dimensions, and (d) is the second seal structure and dimensions;

[0027] Figure 4 This is a schematic diagram of the preload spring and spring force calculation of the present invention;

[0028] Figure 5 This is an outline diagram of the low-wear and dynamic sealing male and female ball support structure of the flexible joint of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to the accompanying drawings.

[0030] like Figure 2 As shown, the low-wear and dynamic sealing male and female ball support structure of the present invention includes an upper connecting tube 10, a lower connecting tube 11, an upper elastic element 12, a lower elastic element 13, an upper female sphere 1, a lower female sphere 6, an upper male sphere 2, a lower male sphere 5, a preload spring 4 (preload spring 7 after compression), a positioning plate 8, and a guide rod 9.

[0031] One end of the upper connecting pipe 10 is connected to the upper oil pipe, and the other end is connected to the upper elastic element 12 with bolts. The upper elastic element 12 is bonded to the outside of the upper female sphere 1, and the upper connecting pipe 10, the upper female sphere 1, and the upper elastic element 12 form an upper swinging assembly; one end of the lower connecting pipe 11 is connected to the lower oil pipe, and the other end is connected to the lower elastic element 13 with bolts. The lower elastic element 13 is bonded to the outside of the lower female sphere 6, and the lower connecting pipe 11, the lower female sphere 6, and the lower elastic element 13 form a lower swinging assembly; the upper swinging assembly is fixedly connected to the upper connecting shell 3, and the lower swinging assembly is fixedly connected to the lower connecting shell 14; the neck of the lower male sphere 5 is inserted into the upper male sphere 2, and the integral structure composed of the two is installed between the upper female sphere 1 and the lower female sphere 6; a positioning plate 8 is installed between the upper connecting shell 3 and the lower connecting shell 14, and the upper connecting shell 3, the lower connecting shell 14, and the positioning plate 8 are fixed by bolts.

[0032] The upper connecting pipe 10 and the lower connecting pipe 11 are connected to the upper and lower oil pipelines, respectively. The upper connecting pipe 10 and the lower connecting pipe 11 are connected to the upper elastic element 12 and the lower elastic element 13, as well as the upper and lower female spheres 1 and 6, respectively, to form two swinging assemblies. The outer sides of the two swinging assemblies are connected to the upper connecting shell 3 and the lower connecting shell 14. The upper male sphere 2 and the lower male sphere 5 are installed between the upper and lower female spheres 1 and 6 of the two swinging assemblies for support and protection. A preload spring 7 and a guide rod 9 are installed between the upper and lower male spheres 2 and 5. A positioning plate 8 is installed between the upper and lower connecting shells 3 and 14. The upper and lower connecting shells 3 and 14 are fixed to the positioning plate 8 by bolts. The inner diameter of the hole in the positioning plate 8 matches the outer diameter of the neck of the lower male sphere 5, providing a positioning and guiding function to prevent the upper and lower male spheres 2 and 5 from deflecting. A step is designed at the lower part of the lower male sphere 5 , and a guide rod 9 is provided between the step of the lower male sphere 5 and the upper male sphere 2 , and a preload spring 7 is sleeved on the guide rod 9 .

[0033] Specifically, a threaded hole is provided on the lower step of the lower male sphere 5, a light hole is provided on the upper male sphere 2, and the lower end of the guide rod 9 is processed with an external thread. The lower end of the guide rod 9 is fixed in the threaded hole of the lower step of the lower male sphere 5 through the external thread, and the upper end is inserted into the light hole of the upper male sphere 2.

[0034] like Figure 3As shown, a dual-stage sealing structure using a "J+O" and "O" combination of sealing rings is employed between the upper female sphere 1 and the upper male sphere 2 (as well as the lower female sphere 6 and the lower male sphere 5), ensuring a reliable seal. Specifically, dual-stage sealing structure I is provided between the upper female sphere 1 and the upper male sphere 2, and dual-stage sealing structure II is provided between the lower female sphere 6 and the lower male sphere 5. Dual-stage sealing structures I and II are identical in composition, each comprising a first sealing structure and a second sealing structure. The first sealing structure is implemented using a "J+O" combination of sealing rings, comprising a J-ring 15 and a first O-ring 16, which is embedded in a groove within the J-ring. The second sealing structure is implemented using a second O-ring 17.

[0035] The J-type sealing ring 15 is made of reinforced polytetrafluoroethylene material, and the first O-type sealing ring 16 and the second O-type sealing ring 17 are made of fluororubber material with a Shore hardness of 60 to 80. Figure 3 In order to obtain the minimum preload F of the "J+O" and "O" type combined seal rings, a finite element simulation calculation was performed on the combined seal structure, as shown in (a). Figure 3 As shown in (b).

[0036] A pre-compression spring is used between the upper male sphere 2 and the lower male sphere 5, so that the upper and lower pairs of female and male spheres are always in a pre-compression state, which is beneficial to the sealing between the male and female balls and can control the pre-compression force and friction between the male and female balls, so that the flexible joint has a longer service life.

[0037] In order to ensure the seal between the female and male balls under high pressure and relative motion, a double seal is set between the female and male balls. The first seal structure is realized by a "J+O" type combined seal ring, the seal groove is rectangular, and the size is 16.04×8.34mm. The second seal structure is realized by an O-type seal ring, the seal groove is rectangular, and the size is 10.4×7.13mm. The structure of the first seal ring is as follows Figure 3 As shown in (c), the second sealing ring structure dimensions are as follows Figure 3 As shown in (d).

[0038] The long side of the J-shaped sealing ring fits against the inner surface of the female ball. Its maximum outer diameter is 256.46mm. The long side is 13.5mm long and the short side is 8.32mm long. The exposed thickness of the long side, excluding the groove, is 3.21mm. The first O-ring has a diameter of 9mm and an inner diameter of 226.37mm.

[0039] The second O-ring has a diameter of 9 mm and an inner diameter of 259.72 mm.

[0040] like Figure 4As shown, a preload spring 4 (preload spring 7 in compressed state) is installed between the upper male sphere 2 and the lower male sphere 5. To prevent the preload spring 7 from becoming unstable under pressure, a guide rod 9 is passed through the preload spring 7. To reduce the preload between the female and male spheres while ensuring a reliable seal, the free length L0 of the preload spring 4 and the spring stiffness coefficient K are usually selected according to the following formula:

[0041] ΔL=L0-L (1)

[0042] 2F≥K×ΔL≥F (2)

[0043] Where: ΔL is the spring compression

[0044] L0 is the free length of the spring;

[0045] L is the length of the spring after compression;

[0046] K is the spring stiffness coefficient;

[0047] F is the minimum pre-pressure of the sealing ring.

[0048] The appearance diagram of the new deepwater riser flexible joint with low wear and dynamic sealing male and female ball support structure is as follows Figure 5 shown.

[0049] The present invention discloses a novel low-wear and dynamically sealed male and female ball support structure for a deepwater riser flexible joint. A preload spring is used between the male and female balls to keep the male and female balls in a preloaded state at all times, thereby ensuring the seal between the male and female balls and making the preload and friction between the male and female balls controllable, thereby extending the service life of the flexible joint.

[0050] The technologies not disclosed in the present invention are common knowledge to those skilled in the art.

Claims

1. A low-wear and dynamic-sealing male and female ball support structure for a deepwater riser flexible joint, characterized by: It comprises an upper connecting tube (10), a lower connecting tube (11), an upper elastic element (12), a lower elastic element (13), an upper female sphere (1), a lower female sphere (6), an upper male sphere (2), a lower male sphere (5), a preload spring (4), a positioning plate (8), and a guide rod (9); One end of the upper connecting pipe (10) is connected to the upper oil delivery pipe, and the other end is connected to the upper elastic element (12) by bolts. The upper elastic element (12) is bonded to the outer side of the upper female sphere (1). The upper connecting pipe (10), the upper female sphere (1), and the upper elastic element (12) form an upper swing assembly. One end of the lower connecting pipe (11) is connected to the lower oil delivery pipe, and the other end is connected to the lower elastic element (13) by bolts. The lower elastic element (13) is bonded to the outer side of the lower female sphere (6). The lower connecting pipe (11), the lower female sphere ( 6), the lower elastic element (13) forms a lower swing assembly; the upper swing assembly is fixedly connected to the upper connecting shell (3), and the lower swing assembly is fixedly connected to the lower connecting shell (14); the neck of the lower male sphere (5) is inserted into the upper male sphere (2), and the overall structure composed of the two is installed between the upper female sphere (1) and the lower female sphere (6); a positioning plate (8) is installed between the upper connecting shell (3) and the lower connecting shell (14), and the upper connecting shell (3), the lower connecting shell (14), and the positioning plate (8) are fixed by bolts; The lower part of the lower male sphere (5) is designed with a step, and a guide rod (9) is provided between the step of the lower male sphere (5) and the upper male sphere (2), and a pre-compression spring is sleeved on the guide rod (9); A double-pass sealing structure I is provided between the upper female sphere (1) and the upper male sphere (2), and a double-pass sealing structure II is provided between the lower female sphere (6) and the lower male sphere (5). The double-pass sealing structure I and the double-pass sealing structure II have the same composition and both include a first sealing structure and a second sealing structure. The first sealing structure is implemented by a "J+O" type combined sealing ring, which includes a J-type sealing ring (15) and a first O-type sealing ring (16). The first O-type sealing ring (16) is embedded in the groove of the J-type sealing ring (15); and the second sealing structure is implemented by a second O-type sealing ring (17).

2. The low-wear and dynamic-sealing male and female ball support structure for a deepwater riser flexible joint according to claim 1, characterized in that: The J-shaped sealing ring (15) adopts enhanced polytetrafluoroethylene sealing material.

3. The low-wear and dynamic-sealing male and female ball support structure for a deepwater riser flexible joint according to claim 1, characterized in that: The first O-type sealing ring and the second O-type sealing ring are both made of rubber material with a Shore hardness of 60 to 80.

4. The low-wear and dynamic-sealing male and female ball support structure for a deepwater riser flexible joint according to claim 1, characterized in that: The free length L0 of the preload spring and the spring stiffness coefficient K are selected according to the following formula: ΔL=L0-L 2F≥K×ΔL≥F Where: ΔL is the compression of the preload spring; L is the length of the spring after compression; F is the minimum preload of the double-pass sealing structure I and the double-pass sealing structure II.

5. The low-wear and dynamic-sealing male and female ball support structure for a deepwater riser flexible joint according to claim 4, characterized in that: The F is obtained through finite element analysis.

6. The low-wear and dynamic-sealing male and female ball support structure for a deepwater riser flexible joint according to claim 1, characterized in that: The inner diameter of the hole in the positioning plate (8) matches the outer diameter of the axial hole in the neck of the lower male sphere (5).

7. The low-wear and dynamic-seal male and female ball support structure for a deepwater riser flexible joint according to claim 1, characterized in that: A threaded hole is provided on the lower step of the lower male sphere (5), a light hole is provided on the upper male sphere (2), and an external thread is processed on the lower end of the guide rod (9). The lower end of the guide rod (9) is fixed in the threaded hole of the lower step of the lower male sphere (5) through the external thread, and the upper end is inserted into the light hole of the upper male sphere (2).

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