Bending limiter and submarine cable protection device

Abstract

The invention discloses a bending limiter and a submarine cable protection device, a male head of the bending limiter is provided with a plurality of sections of arc surfaces with different curvatures, a groove is also provided with arc surfaces with different curvatures, and the side surface of one side, close to the male head, of an outer locking part has a first included angle relative to a central axis; the side face of the side, away from the male head, of the female head has a second included angle relative to the central axis, the first included angle and the second included angle are roughly the same, the contact area is increased, stress distribution is improved, and the bending limiter has more excellent anti-fatigue performance and reliability in the long-term service process. In addition, the invention further provides a reinforcer and a barb device of the submarine cable protection device, an embedded reinforcement device structure is adopted, the connection strength is enhanced, the connection strength and the pull-off resistance of the submarine cable protection device can be remarkably improved, the barb device can be in wedge-shaped connection with the reinforcer, the stability of long-term operation of the system on the seabed is ensured, and the service life of the submarine cable protection device is prolonged. And the pulling-out risk caused by scouring and fatigue loading in the long-term service process is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of submarine cable protection for offshore wind power, and in particular to a bend limiter and a submarine cable protection device. Background Art

[0002] In recent years, the development and utilization of marine resources has continued to accelerate around the world, and offshore wind power and photovoltaic projects have developed rapidly, driving a substantial increase in demand for submarine cable protection. However, submarine cables have long been subject to dynamic loads such as waves and tides, and scouring has become a key bottleneck affecting their reliability. According to statistics, in insurance claims for offshore wind power and photovoltaic projects, the proportion of compensation for submarine cable failures is as high as 87.6%. Among them, the bend limiter, which is a submarine cable protection device, has an average annual failure rate of up to 50% in sea areas with poor sea conditions.

[0003] Under the action of scouring, the submarine cable at the mud end is exposed, resulting in an increase in the length of the suspended span, which in turn exacerbates the frequency and amplitude of the submarine cable shaking. The bend limiter is prone to fatigue damage under long-term alternating loads, which eventually leads to breakage or falling off. The bend limiter structure currently used in China still uses the traditional Hough design from decades ago. This structure is prone to stress concentration when the male and female heads are in partial contact, leading to breakage and failure. In addition, this type of bend limiter is relatively expensive, and the existing domestic improvements are mostly focused on material optimization to improve tensile strength, but have not yet broken through the core structural design problems. In addition, the supporting protective devices for the access of submarine cables to wind turbines are not innovative enough, and the overall protection plan has not yet formed a systematic and optimized design.

[0004] Chinese patent document CN211508560U discloses a wind power submarine cable protection device, including a center positioning protection mechanism, a bending protection mechanism, and a bending limiting mechanism, which are connected in sequence. The center positioning protection system at the head end is embedded in the J-shaped tube on the wind turbine, and the bending protection mechanism and the bending limiting mechanism are located outside the J-shaped tube at the suspended span section of the submarine cable, providing protection for the submarine cable to extend its service life. However, this solution still has the following problems: First, the bend limiter structure follows the traditional design, which is prone to stress concentration during long-term service, increasing the risk of breakage, and thus affecting the life of the submarine cable; second, the front end of the flexible anti-bending tube uses a rigid flange as a connector, but under this connection form, the tightness of the flexible material and the flange is limited, and the connection is subject to a large load. There is a risk of pulling off under long-term action, which reduces the reliability of the system.

[0005] In addition, the inventor has also proposed a bend limiter structure (CN119518579A), which includes several unit limiters connected end to end in sequence; each unit limiter is composed of two limiter monomers with cable through holes and symmetrical about the central axis; each limiter monomer includes a female head, a male head and a neck locking part; the female head and the male head are located at both ends of the neck locking part; the outer surface of the female head is a semicircular convex structure; the inner surface of the male head is provided with a semicircular concave structure, the concave structure of the male head wraps the convex structure of the adjacent female head and there is a gap, so that the female head can rotate inside the male head; the neck locking part of each limiter monomer is provided with a damage warning device. However, although this bend limiter structure can effectively limit the bending degree of the submarine cable, according to further research on the structure, its ability to solve stress concentration is still limited. Therefore, how to optimize the structural setting of the bend limiter is the key to solving the problem of stress concentration and reducing the risk of fracture. Summary of the invention

[0006] Aiming at the problems of local stress concentration, high failure rate in long-term service and poor reliability of existing bend limiters, as well as the deficiencies of the matching submarine cable protection device in anti-pull-off performance, the present invention proposes a bend limiter and a submarine cable protection device.

[0007] Specifically, the present invention provides the following technical solutions: a bend limiter, which includes two bend limiter sub-units symmetrical about a central axis, the two bend limiter sub-units are detachably connected, and the submarine cable passes through a cavity formed in the center of the two bend limiter sub-units, each bend limiter sub-unit includes a male head, a female head, a connecting neck, an external locking portion and a transition neck arranged in sequence, a groove is provided on the inner side of the female head, the male head has multiple arc surfaces with different curvatures, and the groove also has arc surfaces with different curvatures, the side surface of the external locking portion close to the male head has a first angle relative to the central axis, and the side surface of the female head away from the male head has a second angle relative to the central axis, and the first angle and the second angle are substantially the same.

[0008] Furthermore, the connecting neck is composed of a plurality of arcs with different curvatures, and / or the transition neck has an arc surface with a large curvature.

[0009] Furthermore, bolt holes are provided on the bend limiter subunits, and the two bend limiter subunits are connected by bolts.

[0010] In addition, the present invention also proposes a submarine cable protection device, which includes the above-mentioned bend limiter and a reinforcer connected to the bend limiter, the reinforcer includes a connecting end, a connecting cylinder and a connecting tail, and the shape and size of the connecting tail are the same as the male head of the bend limiter.

[0011] Furthermore, an embedded reinforcement device is provided on the inner wall of the connecting end, and the embedded reinforcement device includes a reinforcement rod, a U-shaped part and a fixing ring. The embedded reinforcement device is embedded in the connecting end through the reinforcement rod, and the U-shaped part is connected to the reinforcement rod. The U-shaped parts are evenly arranged in a ring shape relative to the central axis. The fixing ring is arranged close to the inner wall of the connecting end, and the fixing ring connects the U-shaped parts arranged in a ring shape into a whole.

[0012] Furthermore, each of the U-shaped members is connected to three of the reinforcing rods, and / or the embedded reinforcing device is made of stainless steel.

[0013] Furthermore, the reinforcer also includes a barb device, the barb device, the reinforcer and the bend limiter are connected in sequence, the barb device includes a steel body, a protrusion located on the steel body and a wedge block arranged at the tail end, the protrusion is used to snap into the opening of the side wall of the fan, and the wedge block is used to perform a wedge-shaped connection with the U-shaped part.

[0014] Furthermore, the wedge block is provided with a threaded hole, and the threaded hole is connected to the bolt hole provided on the U-shaped member through a bolt.

[0015] Furthermore, the embedded reinforcement device is made of stainless steel, and / or the barb device is made of stainless steel.

[0016] The fixing ring is processed in one piece, and / or the U-shaped part is processed in one piece.

[0017] Furthermore, the material of the bend limiter is polyurethane, and / or the material of the reinforcer is polyurethane.

[0018] The beneficial effects of the present invention are: (1) The present invention optimizes the structure of the bend limiter based on stress distribution. By optimizing the force distribution of the bend limiter, the present invention specifically proposes structural design optimization of the male head, female head, connecting neck, external locking part and transition neck, thereby increasing the contact area and improving the force distribution, so that the bend limiter has better fatigue resistance and reliability during long-term service. The numerical simulation and model test show that such structural optimization can significantly improve the service life of the bend limiter and the overall system.

[0019] (2) At the same time, based on the optimization of the bend limiter structure, the present invention proposes a structural setting of the reinforcer, which adopts an embedded reinforcement device structure to enhance the connection strength, and can significantly improve the connection strength and pull-off resistance of the submarine cable protection device, thereby ensuring the stability of the system in long-term operation on the seabed.

[0020] (3) In addition, based on the submarine cable protection device, the present invention further proposes a barb device, which can be connected to the reinforcing device in a wedge shape and combined with a bolt connection. When the submarine cable protection device is in service on the seabed, the special wedge connection will gradually tighten after being dislocated and deformed, and at the same time, it is assisted by bolt locking, which effectively reduces the risk of pulling off due to scouring and fatigue loading during long-term service. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is an overall schematic diagram of the bending limiter connection proposed by the present invention; Figure 2 A structural diagram of the bend limiter and the bend limiter subunit proposed by the present invention; Figure 3 A front view of the bending limiter subunit proposed by the present invention; Figure 4 A top view of the bending limiter subunit proposed in the present invention; Figure 5 for Figure 3 Middle AA section; Figure 6 It is a comparison diagram of the bending limiter design principles of the conventional bending limiter (the structure on the left) and the bending limiter of the present invention (the structure on the right); Figure 7 The numerical simulation results of the stress and deformation of the traditional bending limiter are shown; Figure 8 The numerical simulation calculation results of the stress and deformation of the bending limiter of the present invention are shown; Fig. 9 This is a diagram showing the simulation results of an impact test of the bending limiter of the present invention; Fig.10 This is a diagram showing the simulation results of the lateral pressure test of the bending limiter of the present invention; Fig.11 The figure is a schematic diagram of the structural principle of the submarine cable protection device proposed by the present invention; Fig.12 A structural cross-sectional view of the enhancer proposed by the present invention; Fig.13 A schematic diagram of the connection between the reinforcer and the barb structure proposed by the present invention; Fig.14 Schematic diagram of the barb structure proposed by the present invention.

[0022] Explanation of the reference numerals: 1. Reinforcer; 11. Connecting end; 12. Connecting cylinder; 13. Connecting tail; 14. Embedded reinforcement device; 15. Reinforcing rod; 16. U-shaped piece; 17. Fixing ring; 2. Bend limiter; 21. Bend limiter subunit; 22. Male head; 23. Female head; 24. Connecting neck; 25. External locking part; 26. Transition neck; 27. Groove; 28. Bolt hole; 3. Barb device; 31. Protrusion; 32. Steel body; 33. Wedge block; 4. Threaded hole; 5. Bolt; 6. Cavity; 7. Submarine cable; 81. 1st contact point; 82. 2nd contact point; 83. 3rd contact point; 84. 4th contact point; 85. 5th contact point; 86. 6th contact point; 87. 7th contact point; 88. 8th contact point; 89. 9th contact point. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] See also Figure 1-Figure 5 The present invention provides a technical solution: a bend limiter 2, which includes two bend limiter subunits 21 symmetrical about a central axis, the two bend limiter subunits 21 are detachably connected, a submarine cable 7 passes through a cavity 6 formed in the center of the two bend limiter subunits 21, each bend limiter subunit 21 includes a male head 22, a female head 23, a connecting neck 24, an external locking portion 25 and a transition neck 26 arranged in sequence, a groove 27 is provided on the inner side of the female head 23, the male head 22 has multiple arc surfaces with different curvatures, and the groove 27 also has arc surfaces with different curvatures, the side surface of the external locking portion 25 close to the male head 22 has a first angle with respect to the central axis, the side surface of the female head 23 away from the male head 22 has a second angle with respect to the central axis, the first angle and the second angle are the same, so that the side surface of the external locking portion 25 close to the male head 22 forms a surface contact with the side surface of the female head 23 away from the male head 22.

[0025] It should be noted that the meaning of "same" here should be "approximately the same". This is because certain production errors are inevitable during production, especially for different materials, the processing difficulty and precision are extremely uncertain. Therefore, "approximately the same" means that the two can form a range of surface contact, and cannot be required to be exactly the same. For example, depending on the material selection, the deviation can be ±0.1 degrees, ±0.5 degrees, ±1 degrees, ±5 degrees or other angles. This is required according to the production requirements when processing the angle. That is, the angular error between the two will not be particularly large, resulting in the inability to achieve the surface contact between the two, but there may be certain errors or deviations.

[0026] A groove is provided on the inner side of the female head. After the male head is inserted into the groove, local contact is formed when the force is locked. On the one hand, the male head of the present invention adopts a circular arc surface with multiple sections of different curvatures, which is connected by concave-convex transition and matches the contact surface of the corresponding shape on the inner side of the female head, which can ensure that the force on both is more uniform, and increase the number of contact points between the male head and the female head groove, reducing stress concentration. On the other hand, before the bending limiter of the present invention is locked under force, the outer locking part has no contact with the adjacent bending limiter; after locking, the outer locking part will contact the end of the female head of the previous bending limiter. Since the angles of the end faces of the two are roughly the same, it can be ensured that the two are formed in a surface fit, avoiding the point contact force mode of the traditional bending limiter, greatly increasing the force area, and further dispersing the local stress by increasing the thickness of the structure, thereby improving the overall fatigue resistance and reliability of the bending limiter.

[0027] Furthermore, the connecting neck is composed of a plurality of arcs with different curvatures.

[0028] Through the design of multi-section curvature arc connection, the connection neck of the bend limiter can fully contact with the female head after locking, thereby improving the uniformity of force and enhancing the structural stability.

[0029] Furthermore, the transition neck has an arc surface with a large curvature.

[0030] The transition neck of a traditional bend limiter generally adopts a straight line structure, which will also cause local stress concentration. Therefore, by designing the transition neck as a circular arc surface with a large curvature, the concentrated stress at the outer locking part and the female head can be evenly distributed to the entire bend limiter, thereby reducing the local stress peak and improving the overall load-bearing capacity.

[0031] Furthermore, a plurality of the bend limiters 2 can be connected end to end in sequence via the male connector 22 and the female connector 23 .

[0032] According to the bending limit requirements of the submarine cable, multiple bend limiters can be connected end to end in sequence to meet the requirements of different working conditions.

[0033] Furthermore, the material of the bend limiter 2 is polyurethane.

[0034] Furthermore, the two bend limiter sub-units are preferably detachably connected by bolts, and bolt holes 28 are provided on the bend limiter sub-units. The number and positions of the bolt holes are arranged according to specific installation requirements.

[0035] Depend on Figure 6 It can be seen that the design of the traditional bend limiter has only 2-3 contacts when locked (the first contact point 81, the second contact point 82, and the third contact point 83), while the present invention can increase the contact points to at least 6 (the fourth contact point 84, the fifth contact point 85, the sixth contact point 86, the seventh contact point 87, the eighth contact point 88, and the ninth contact point 89) by optimizing the structure of the male head, the female head, the connecting neck, the transition neck, and the outer locking part. Therefore, the overall contact area will be significantly increased, which can effectively reduce the problem of local stress concentration.

[0036] According to the numerical simulation analysis of the mechanical response and deformation behavior of the bending limiter structure of the present invention (see Figure 7 and Figure 8 ) It can be seen that: under the same loading conditions, the traditional bending limiter has a significant stress concentration phenomenon. The maximum stress and deformation are mainly concentrated in the connection neck area where the male head and the female head contact. The maximum equivalent (Mises) stress is 28MPa, and the maximum logarithmic strain is 0.025, which is a typical small deformation mode.

[0037] In contrast, the bend limiter structure of the present invention is more uniform in overall stress, with the maximum stress and deformation occurring in the transition neck area of ​​the structure. The maximum Mises stress is only 13MPa, which is about 54% lower than that of the traditional structure; the maximum logarithmic strain is 0.008, which is also within the small deformation range. This structure effectively reduces the local stress concentration phenomenon at the locking part, significantly improves the stress performance and fatigue life of the bend limiter, and thus enhances the protection capability of the submarine cable and its service life.

[0038] In order to further verify the durability of the bending limiter of the present invention, simulation tests under impact load and lateral pressure load conditions were carried out: Impact test simulation ( Fig. 9 ): A 80kg weight falls freely from a height of 80cm to impact the surface of the bend limiter. The simulation results show that the maximum contact pressure between the bend limiter and the weight is 134kN, and the maximum contact pressure between the bend limiter and the bottom plate is 187kN. The maximum equivalent stress appears in the fillet transition area in contact with the weight and the bottom plate, with a value of 47MPa, which does not reach the yield strength of the material, indicating that the structure has no obvious plastic deformation and meets the use requirements under impact conditions.

[0039] Lateral pressure test simulation ( Fig.10): A vertical compressive load is gradually applied to the upper part of the bend limiter through the loading plate. When the compressive load reaches a maximum of 78kN, the maximum equivalent stress is 45MPa, which is still lower than the yield limit of the material. At this time, the maximum deformation value of the bend limiter is 6mm, which is negligible relative to its overall thickness, and the structural stability is good.

[0040] In summary, the bending limiter structure proposed in the present invention shows superior performance in stress distribution, impact resistance and pressure resistance, and is suitable for long-term service requirements in complex marine environments.

[0041] In addition, the present invention also proposes a submarine cable protection device, which includes a bend limiter 2 and a reinforcer 1 connected to the bend limiter 2, the reinforcer 1 includes a connecting end 11, a connecting cylinder 12 and a connecting tail 13, and the shape and size of the connecting tail 13 are the same as the male head 22 of the bend limiter 2.

[0042] Since the shape and size of the connection tail are the same as the male head of the bend limiter, the connection tail can be directly assembled and connected with the female head of the bend limiter, which can also ensure uniform force transmission and avoid local stress concentration.

[0043] Furthermore, the reinforcer 1 is in a cone shape as a whole and is made of polyurethane material.

[0044] Furthermore, an embedded reinforcement device 14 is provided on the inner wall of the connecting end 11, and the embedded reinforcement device 14 includes a reinforcement rod 15, a U-shaped piece 16 and a fixing ring 17. The embedded reinforcement device 14 is embedded in the connecting end 11 through the reinforcement rod 15, and the U-shaped piece 16 is connected to the reinforcement rod 15. The U-shaped piece 16 is evenly arranged in a ring shape relative to the central axis. The fixing ring 17 is arranged close to the inner wall of the connecting end 11, and the fixing ring 17 connects the U-shaped pieces 16 arranged in a ring shape into a whole.

[0045] By providing an embedded reinforcement device, higher structural strength and impact resistance can be further provided.

[0046] Furthermore, each of the U-shaped members 16 is connected to the three reinforcing rods 15 , thereby providing higher structural strength and impact resistance.

[0047] Furthermore, the embedded reinforcement device 14 is made of 316L stainless steel, and the fixing ring 17 and the U-shaped member 16 can be integrally processed.

[0048] Stainless steel materials can ensure corrosion resistance and long-term service performance. Through integrated processing, the integrity of the structure can be improved, avoiding separation and fracture at the junction of rigid and flexible materials due to long-term erosion and fatigue loads.

[0049] Furthermore, the reinforcer 1 also includes a barb device 3, the barb device 3, the reinforcer 1 and the bend limiter 2 are connected in sequence, the barb device includes a steel body 32, a protrusion 31 located on the steel body 32 and a wedge block 33 arranged at the tail end, the protrusion 31 is used to snap into the opening of the side wall of the fan, and the wedge block 33 is used to perform a wedge connection with the U-shaped member 16.

[0050] Furthermore, the barb device 3 is made of 316L stainless steel to ensure corrosion resistance and long-term service performance.

[0051] The protrusions can be arranged to firmly fix the barb device to the fan, preventing the barb device from slipping off under long-term scouring and dynamic loads. The design of the wedge block can maximize the cross-sectional area of ​​the connection end and gradually reduce it along the length direction, so that the barb device can be reliably connected to the reinforcing device, and gradually tighten under dynamic loads to improve the pull-off resistance.

[0052] Furthermore, a threaded hole 4 is provided on the wedge block 33 , and the threaded hole 4 is connected to a bolt hole provided on the U-shaped member 16 via a bolt 5 .

[0053] At this time, the connection method between the barb device and the reinforcer adopts a combination of wedge connection and bolt connection to achieve double fixation and further improve the pull-off resistance.

[0054] Specifically, before installation, the inside of the U-shaped part and the surface of the wedge block must be coated with special lubricating oil to ensure assembly accuracy and reduce friction damage. After installation, the wedge block is basically in contact with the left end of the U-shaped part, and the maximum gap on the right end does not exceed 5mm, ensuring a tight connection. When serving on the seabed, when the wedge block and the U-shaped part made of stainless steel are connected in a wedge shape, the steel structures of the two will gradually tighten after misalignment and deformation, and are assisted by bolt locking, effectively reducing the risk of pull-off caused by scouring and fatigue loading during long-term service.

Claims

1. A bend limiter, comprising two bend limiter subunits (21) symmetrically arranged along a central axis, the two bend limiter subunits (21) being detachably connected to each other, a submarine cable (7) passing through a cavity (6) formed in the center of the two bend limiter subunits (21), each bend limiter subunit (21) comprising a male head (22), a female head (23), a connecting neck (24), an outer locking portion (25) and a transition neck (26) arranged in sequence, a groove (27) being provided on the inner side of the female head (23), characterized in that: The male head (22) has a plurality of arc surfaces with different curvatures, the groove (27) also has arc surfaces with different curvatures, the side surface of the outer locking portion (25) close to the male head (22) has a first angle relative to the central axis, and the side surface of the female head (23) away from the male head (22) has a second angle relative to the central axis, and the first angle and the second angle are substantially the same.

2. The bend limiter according to claim 1, characterized in that: The connecting neck (24) is composed of a plurality of arcs with different curvatures, and / or the transition neck (26) has an arc surface with a large curvature.

3. The bend limiter according to claim 1 or 2, characterized in that: The bend limiter subunit (21) is provided with a bolt hole (28), and the two bend limiter subunits (21) are connected via bolts.

4. A submarine cable protection device, comprising a bend limiter according to any one of claims 1 to 3, and a reinforcing device (1) connected to the bend limiter, the reinforcing device (1) comprising a connecting end (11), a connecting cylinder (12) and a connecting tail (13), characterized in that: The shape and size of the connecting tail (13) are the same as those of the male head (22) of the bending limiter.

5. The submarine cable protection device according to claim 4, characterized in that: The inner wall of the connecting end (11) is provided with an embedded reinforcement device (14), the embedded reinforcement device (14) comprising a reinforcement rod (15), a U-shaped member (16) and a fixing ring (17), the embedded reinforcement device (14) is embedded in the connecting end (11) via the reinforcement rod (15), the U-shaped member (16) is connected to the reinforcement rod (15), the U-shaped member (16) is evenly arranged along a ring relative to the central axis, the fixing ring (17) is arranged in close contact with the inner wall of the connecting end (11), and the fixing ring (17) connects the U-shaped members (16) arranged in a ring into a whole.

6. The submarine cable protection device according to claim 5, characterized in that: Each of the U-shaped parts (16) is connected to three of the reinforcing rods (15), and / or the embedded reinforcing device is made of stainless steel, and / or the fixing ring (17) and the U-shaped part (16) are integrally processed.

7. The submarine cable protection device according to any one of claims 5-6, characterized in that: The reinforcer (1) further comprises a barb device (3), wherein the barb device (3), the reinforcer (1) and the bend limiter (2) are connected in sequence, and the barb device (3) comprises a steel body (32), a protrusion (31) located on the steel body (32) and a wedge block (33) arranged at the rear end, and the wedge block (33) is used to form a wedge connection with the U-shaped member (16).

8. The submarine cable protection device according to claim 7, characterized in that: The wedge block (33) is provided with a threaded hole (4), and the threaded hole (4) is connected to a bolt hole provided on the U-shaped member (16) via a bolt (5).

9. The submarine cable protection device according to claim 7, characterized in that: The barb device (3) is made of stainless steel.

10. The submarine cable protection device according to any one of claims 4 to 6, characterized in that: The material of the bend limiter is polyurethane, and / or the material of the reinforcer (1) is polyurethane.

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