A bending limiter and a submarine cable protection device

Abstract

The present invention discloses a bending limiter and a submarine cable protection device. The male head of the bending limiter has arc surfaces with different curvatures, and the groove also has arc surfaces with different curvatures. The side surface of the outer locking part close to the male head has a first included angle relative to the central axis, and the side surface of the female head far from the male head has a second included angle relative to the central axis. The first included angle and the second included angle are substantially the same, increasing the contact area and improving the force distribution, so that the bending limiter has better anti-fatigue performance and reliability during long-term service. In addition, a reinforcing device and a barbed device for the submarine cable protection device are also proposed. The embedded reinforcing device structure is adopted to enhance the connection strength, which can significantly improve the connection strength and anti-pull-off ability of the submarine cable protection device. Moreover, the barbed device can be wedge-connected with the reinforcing device to ensure the stability of the system during long-term operation under the sea, effectively reducing the pull-off risk caused by scouring and fatigue loading during long-term service.

Description

Technical Field

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

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

[0003] Under the action of scour, the submarine cable at the mud entry end is exposed, resulting in an increase in the length of the spanning section, which in turn exacerbates the frequency and amplitude of the submarine cable sway. The bend limiter is prone to fatigue damage under long-term alternating loads, eventually leading to fracture or detachment. Currently, the structure of the bend limiter used in China still follows the traditional split-type design from abroad decades ago. This structure is prone to stress concentration when the male and female heads are in local contact, resulting in fracture failure. In addition, the cost of this type of bend limiter is relatively high, and existing domestic improvements mainly focus on material optimization to improve the tensile strength, but the core structural design problem has not been broken through. In addition, the innovative design of the supporting protection device for connecting the submarine cable to the wind turbine is insufficient, and the overall protection plan has not yet formed a systematic and optimized design.

[0004] Chinese patent document CN211508560U discloses a protection device for a wind power submarine cable, including a central positioning protection mechanism, a bending protection mechanism, and a bending limiting mechanism, which are connected in sequence. The central positioning protection system at the head end is embedded in the J-shaped pipe on the wind turbine, and the bending protection mechanism and the bending limiting mechanism are located at the spanning section of the submarine cable outside the J-shaped pipe to provide protection for the submarine cable to extend its service life. However, this solution still has the following problems: First, the structure of the bend limiter follows the traditional design and is prone to stress concentration during long-term service, increasing the risk of fracture and thus affecting the life of the submarine cable; second, the front end of the flexible anti-bending pipe uses a rigid flange as a connecting piece. However, in this connection form, the fastening between the flexible material and the flange is limited, and this connection part bears a large load, and there is a risk of pulling off under long-term action, reducing the reliability of the system.

[0005] In addition, the inventor previously proposed a bending limiter structure (CN119518579A), which includes a number of unit limiters connected end to end in sequence; each unit limiter is formed by splicing two limiting monomers with a cable through-hole inside and symmetrical about the central axis; each limiting monomer includes a female head, a male head, and a neck locking portion; the female head and the male head are located at both ends of the neck locking portion; the outer surface of the female head has a semi-circular convex surface structure; the inner surface of the male head is provided with a semi-circular concave surface structure, and the concave surface structure of the male head wraps the convex surface structure of the adjacent female head with a gap, enabling the female head to rotate inside the male head; an injury warning device is provided on the neck locking portion of each limiting monomer. However, although this bending limiter structure can effectively limit the bending degree of the submarine cable, according to further research on this structure, its ability to solve stress concentration is still limited. Therefore, how to optimize the structural settings of the bending limiter is the key to solving the problem of stress concentration and reducing the fracture risk. Summary of the Invention

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

[0007] Specifically, the present invention provides the following technical solutions: A bending limiter includes two bending limiter sub-units symmetrical about the central axis. The two bending limiter sub-units are detachably connected. The submarine cable passes through the cavity formed by the centers of the two bending limiter sub-units. Each bending limiter sub-unit includes a male head, a female head, a connecting neck, an outer locking portion, and a transition neck arranged in sequence. A groove is provided inside the female head. The male head has arc surfaces with different curvatures, and the groove also has arc surfaces with different curvatures. The side surface of the outer locking portion close to the male head has a first included angle relative to the central axis, and the side surface of the female head far from the male head has a second included angle relative to the central axis. The first included angle and the second included angle are substantially the same.

[0008] Furthermore, the connecting neck is composed 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 bending limiter sub-unit, and the two bending limiter sub-units are connected by bolts.

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

[0011] Furthermore, an embedded strengthening device is provided on the inner wall of the connection end head. The embedded strengthening device includes a strengthening rod, a U-shaped member, and a fixing ring. The embedded strengthening device is embedded in the connection end head through the strengthening rod. The U-shaped member is connected to the strengthening rod. The U-shaped members are arranged uniformly along the ring relative to the central axis. The fixing ring is provided close to the inner wall of the connection end head, and the fixing ring connects the annularly arranged U-shaped members into a whole.

[0012] Furthermore, each U-shaped member is connected to 3 of the strengthening rods, and / or, the embedded strengthening device is made of stainless steel.

[0013] Furthermore, the strengthener further includes a barbed device. The barbed device, the strengthener, and the bending limiter are connected in sequence. The barbed device includes a steel body, a protrusion located on the steel body, and a wedge-shaped block provided at the tail end. The protrusion is used to be stuck into the opening on the side wall of the fan, and the wedge-shaped block is used for wedge connection with the U-shaped member.

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

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

[0016] The fixing ring is integrally processed, and / or, the U-shaped member is integrally processed.

[0017] Furthermore, the material of the bending limiter is polyurethane, and / or, the material of the strengthener is polyurethane.

[0018] The beneficial effects of the present invention are as follows:

[0019] (1) Based on the stress distribution, the present invention optimizes the structure design of the bending limiter. By optimizing the force distribution of the bending limiter, the structural design optimizations of the male head, female head, connection neck, outer locking part, and transition neck components are specifically proposed to increase the contact area and improve the force distribution, enabling the bending limiter to have more excellent anti-fatigue performance and reliability during long-term service. The results of numerical simulation and model tests show that such structural optimization can significantly improve the service life of the bending limiter and the overall system.

[0020] (2) At the same time, based on the structural optimization of the bending limiter, the present invention proposes a structural setting of a strengthener. By adopting the structure of the embedded strengthening device, the connection strength is enhanced, and the connection strength and anti-pull-off ability of the submarine cable protection device can be significantly improved, ensuring the stability of the system during long-term operation under the sea.

[0021] (3) In addition, based on the submarine cable protection device, the present invention further proposes a barbed device. The barbed device can be wedge-connected with the strengthener and supplemented by bolt connection. When the submarine cable protection device serves on the seabed, the special wedge connection will gradually tighten after misalignment deformation, and at the same time supplemented by bolt locking, effectively reducing the risk of pulling off caused by scouring and fatigue loading during long-term service. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is an overall schematic diagram of the bender connection proposed by the present invention;

[0023] Figure 2 It is a structural diagram of the bender and the bender sub-unit proposed by the present invention;

[0024] Figure 3 It is a front view of the bender sub-unit proposed by the present invention;

[0025] Figure 4 It is a top view of the bender sub-unit proposed by the present invention;

[0026] Figure 5 It is Figure 3 the sectional view taken along line A-A in

[0027] Figure 6 It is a comparative diagram of the bender principle design between the traditional bender (left structure) and the bender of the present invention (right structure);

[0028] Figure 7 It is the numerical simulation calculation result of the force and deformation of the traditional bender;

[0029] Figure 8 It is the numerical simulation calculation result of the force and deformation of the bender of the present invention;

[0030] Figure 9 It is the simulation result diagram of the impact test of the bender of the present invention;

[0031] Figure 10 It is the simulation result diagram of the side pressure test of the bender of the present invention;

[0032] Figure 11 The structural principle schematic diagram of the submarine cable protection device proposed by the present invention is shown;

[0033] Figure 12 It is the structural sectional view of the strengthener proposed by the present invention;

[0034] Figure 13 It is the connection schematic diagram of the strengthener and the barbed structure proposed by the present invention;

[0035] Figure 14 It is the schematic diagram of the barbed structure proposed by the present invention.

[0036] Description of the reference numerals in the drawings: 1. Reinforcer; 11. Connecting end; 12. Connecting cylinder; 13. Connecting tail; 14. Embedded reinforcement device; 15. Reinforcing rod; 16. U-shaped part; 17. Fixed ring; 2. Bending limiter; 21. Bending limiter sub-unit; 22. Male head; 23. Female head; 24. Connecting neck; 25. Outer locking part; 26. Transition neck; 27. Groove; 28. Bolt hole; 3. Barbed device; 31. Protrusion; 32. Steel body; 33. Wedge block; 4. Threaded hole; 5. Bolt; 6. Cavity; 7. Submarine cable; 81. First contact point; 82. Second contact point; 83. Third contact point; 84. Fourth contact point; 85. Fifth contact point; 86. Sixth contact point; 87. Seventh contact point; 88. Eighth contact point; 89. Ninth contact point. Detailed implementation mode

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] Please refer to Figures 1-5 , the present invention provides a technical solution: a bending limiter 2, which includes two bending limiter sub-units 21 that are symmetric about the central axis. The two bending limiter sub-units 21 are detachably connected. The submarine cable 7 passes through the cavity 6 formed by the centers of the two bending limiter sub-units 21. Each bending limiter sub-unit 21 includes a male head 22, a female head 23, a connecting neck 24, an outer locking part 25, and a transition neck 26 arranged in sequence. A groove 27 is provided inside the female head 23. The male head 22 has arc surfaces with different curvatures, and the groove 27 also has arc surfaces with different curvatures. The side surface of the outer locking part 25 close to the male head 22 has a first included angle with respect to the central axis, and the side surface of the female head 23 away from the male head 22 has a second included angle with respect to the central axis. The first included angle and the second included angle are the same, so that the side surface of the outer locking part 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.

[0039] It should be noted that the same meaning here should be approximately the same meaning. This is because it is difficult to avoid certain production errors during production. Especially for different materials, their processing difficulty and precision have great uncertainties. Therefore, the approximately same meaning means that it is within the range that can make the two form a surface contact, and it cannot be required to be exactly the same. For example, depending on the material selection, the deviation can be ±0.1 degree, ±0.5 degree, ±1 degree, ±5 degrees or other angles. This is stipulated according to the production requirements when processing the angle, that is, the angle error between the two is not particularly large, resulting in the inability to achieve the fitting form of surface contact between the two, but there may be certain errors or deviations.

[0040] The inner side of the female head is provided with a groove. After the male head is inserted into the groove, local contact is formed when it is locked under force. On the one hand, the male head of the present invention adopts an arc surface with multiple different curvatures, which is connected by concave-convex transitions and matches the corresponding-shaped contact surface 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 groove of the female head, reducing stress concentration. On the other hand, before the bending limiter of the present invention is locked without 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 included angles of the two end faces are approximately the same, it can ensure that a surface-type fit is formed between the two, avoiding the point-contact force application method of the traditional bending limiter, greatly increasing the force-bearing area, and further dispersing local stress by increasing the thickness of the structure, thereby improving the overall fatigue resistance and reliability of the bending limiter.

[0041] Further, the connecting neck is composed of arcs with multiple different curvatures.

[0042] Through the design of connecting with arcs of multiple curvatures, after the bending limiter is locked, the connecting neck can be in full contact with the female head, improving the force uniformity and enhancing the structural stability.

[0043] Further, the transition neck has an arc surface with a large curvature.

[0044] For the traditional bending limiter, its transition neck generally adopts a straight-line structure, which will also cause local stress concentration. Therefore, by designing the transition neck as an arc surface with a large curvature, the concentrated stress at the outer locking part and the female head can be evenly distributed throughout the bending limiter, thereby reducing the local stress peak and improving the overall load-bearing capacity.

[0045] Further, a plurality of the bending limiters 2 can be connected end to end in sequence through the male head 22 and the female head 23.

[0046] According to the bending requirements of the submarine cable, a plurality of bending limiters can be connected end to end in sequence to meet the requirements of different working conditions.

[0047] Further, the material of the bending limiter 2 is polyurethane.

[0048] Further, it is preferred that the two bending limit sub-units are detachably connected by bolts. Bolt holes 28 are provided on the bending limit sub-units, and the number and positions of the bolt holes are arranged according to specific installation requirements.

[0049] As Figure 6 can be seen, in the design of the traditional bending limit, there are only 2 - 3 contact points (the first contact point 81, the second contact point 82, the third contact point 83) during locking. However, in the present invention, by optimizing the structures of the male head, female head, connecting neck, transition neck, and outer locking part, the contact points can be increased 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, the ninth contact point 89). Therefore, the overall contact area will increase significantly, effectively reducing the problem of local stress concentration.

[0050] According to the numerical simulation analysis of the mechanical response and deformation behavior of the bending limit structure of the present invention (see Figure 7 and Figure 8 ), it can be known that: under the same loading conditions, there is a significant stress concentration phenomenon in the traditional bending limit. The maximum stress and deformation are mainly concentrated in the connecting neck area where the male head and female head are in contact. The maximum equivalent (Mises) stress is 28 MPa, and the maximum logarithmic strain is 0.025, belonging to a typical small deformation mode.

[0051] In contrast, the bending limit structure of the present invention is more uniform in overall force. The maximum stress and deformation occur in the transition neck area of the structure. The maximum Mises stress is only 13 MPa, which is about 54% lower than that of the traditional structure; the maximum logarithmic strain is 0.008, also within the range of small deformation. This structure effectively weakens the local stress concentration phenomenon at the locking part, significantly improves the mechanical performance and fatigue life of the bending limit, and further enhances the protection ability of the submarine cable and its service life.

[0052] To further verify the durability of the bending limit of the present invention, simulation tests under impact load and side pressure load conditions were carried out:

[0053] Impact test simulation ( Figure 9 ): An 80 kg weight freely falls from a height of 80 cm to impact the surface of the bending limit. The simulation results show that the maximum contact pressure on the contact surface between the bending limit and the weight is 134 kN, and the maximum contact pressure on the contact surface between the bending limit and the bottom plate is 187 kN. The maximum equivalent stress appears in the fillet transition area in contact with the weight and the bottom plate, with a value of 47 MPa, which does not reach the material yield strength, indicating that the structure has not undergone obvious plastic deformation and meets the usage requirements under impact conditions.

[0054] Side pressure test simulation ( Figure 10): A vertical compressive load is gradually applied upward to the bending limiter through the loading plate. When the compressive load reaches a maximum of 78 kN, the maximum equivalent stress is 45 MPa, still lower than the material yield limit. At this time, the maximum deformation value of the bending limiter is 6 mm, which is negligible compared to its overall thickness, and the structural stability is good.

[0055] In summary, the bending limiter structure proposed by the present invention exhibits excellent performance in terms of stress distribution, impact resistance, and pressure resistance, and is suitable for long-term service requirements in complex marine environments.

[0056] In addition, the present invention also proposes a submarine cable protection device, which includes a bending limiter 2 and a strengthener 1 connected to the bending limiter 2. The strengthener 1 includes a connection end 11, a connection cylinder 12, and a connection tail 13. The shape and size of the connection tail 13 are the same as those of the male head 22 of the bending limiter 2.

[0057] Since the shape and size of the connection tail are the same as those of the male head of the bending limiter, the connection tail can be directly assembled and connected to the female head of the bending limiter, which can also ensure uniform force transmission and avoid local stress concentration.

[0058] Furthermore, the strengthener 1 is generally conical and made of polyurethane material.

[0059] Furthermore, an embedded strengthening device 14 is provided on the inner wall of the connection end 11. The embedded strengthening device 14 includes a strengthening rod 15, a U-shaped member 16, and a fixing ring 17. The embedded strengthening device 14 is embedded into the connection end 11 through the strengthening rod 15. The U-shaped member 16 is connected to the strengthening rod 15. The U-shaped members 16 are uniformly arranged in a ring relative to the central axis. The fixing ring 17 is provided close to the inner wall of the connection end 11, and the fixing ring 17 connects the annularly arranged U-shaped members 16 into a whole.

[0060] By setting the embedded strengthening device, higher structural strength and impact resistance can be further provided.

[0061] Furthermore, each U-shaped member 16 is connected to 3 strengthening rods 15, which can provide higher structural strength and impact resistance.

[0062] Furthermore, the embedded strengthening device 14 is made of 316L stainless steel, and the fixing ring 17 and the U-shaped member 16 can be integrally processed.

[0063] The stainless steel material can ensure corrosion resistance and long-term service performance. By means of integral processing, the structural integrity can be improved, and the separation and fracture caused by long-term scouring and fatigue load at the joint of rigid and flexible materials can be avoided.

[0064] Furthermore, the strengthener 1 further includes a barbed device 3. The barbed device 3, the strengthener 1 and the bending limiter 2 are connected in sequence. The barbed device includes a steel body 32, a protrusion 31 located on the steel body 32, and a wedge block 33 provided at the tail end. The protrusion 31 is used to be stuck into an opening on the side wall of the fan, and the wedge block 33 is used for wedge connection with the U-shaped member 16.

[0065] Furthermore, the barbed device 3 is made of 316L stainless steel to ensure corrosion resistance and long-term service performance.

[0066] Through the setting of the protrusion, the firm fixation of the barbed device and the fan can be realized, preventing the barbed device from slipping under the action of long-term scouring and dynamic loads. The design of the wedge block can make the cross-sectional area of its connection end the largest and gradually decrease along the length direction, enabling the barbed device to be reliably connected with the strengthener, and gradually tightening under the action of dynamic loads to improve the anti-pull-off ability.

[0067] 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 through a bolt 5.

[0068] At this time, the connection method between the barbed device and the strengthener adopts a combination of wedge connection and bolt connection to achieve double fixation and further improve the anti-pull-off ability.

[0069] Specifically, before installation, special lubricating oil needs to be applied to the inside of the U-shaped member and the surface of the wedge block to ensure assembly accuracy and reduce frictional damage. After installation, the left end of the wedge block is basically in contact with the U-shaped member, and the maximum gap at the right end does not exceed 5 mm to ensure a tight connection. When serving underwater, when the wedge block and the U-shaped member made of stainless steel are wedge-connected, the steel structures of the two will gradually tighten after misalignment and deformation, and at the same time, bolt locking is supplemented to effectively reduce the risk of pull-off caused by scouring and fatigue loading during long-term service.

Claims

1. A bending limiter, which comprises two bending limiter sub-units (21) that are symmetric about the central axis. The two bending limiter sub-units (21) are detachably connected. The submarine cable (7) passes through the cavity (6) formed by the centers of the two bending limiter sub-units (21). Each bending limiter sub-unit (21) includes 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) is provided inside the female head (23). It is characterized in that: The male head (22) has arc surfaces with different curvatures in multiple segments. 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 included angle relative to the central axis. The side surface of the female head (23) far from the male head (22) has a second included angle relative to the central axis. The first included angle and the second included angle are substantially the same. The connecting neck (24) is composed of arcs with different curvatures in multiple segments. The transition neck (26) has an arc surface with a large curvature.

2. The bend limiter according to claim 1, characterized in that: The bending limiter sub-unit (21) is provided with bolt holes (28). The two bending limiter sub-units (21) are connected by bolts.

3. A submarine cable protection device, which comprises a bending limiter as described in any one of claims 1-2, and a strengthener (1) connected to the bending limiter, the strengthener (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.

4. The submarine cable protection device according to claim 3, characterized in that: An embedded strengthening device (14) is arranged on the inner wall of the connecting end (11). The embedded strengthening device (14) includes a strengthening rod (15), a U-shaped part (16) and a fixing ring (17). The embedded strengthening device (14) is embedded into the connecting end (11) through the strengthening rod (15). The U-shaped part (16) is connected to the strengthening rod (15). The U-shaped parts (16) are arranged annularly and uniformly relative to the central axis. The fixing ring (17) is arranged close to the inner wall of the connecting end (11). The fixing ring (17) connects the annularly arranged U-shaped parts (16) into a whole.

5. The submarine cable protection device according to claim 4, wherein: Each U-shaped part (16) is connected to 3 strengthening rods (15), and / or, the embedded strengthening device is made of stainless steel, and / or, the fixing ring (17) and the U-shaped part (16) are both integrally processed.

6. The submarine cable protection device according to any one of claims 4-5, characterized in that: The strengthener (1) further includes a barbed device (3). The barbed device (3), the strengthener (1) and the bending limiter (2) are connected in sequence. The barbed device (3) 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 wedge block (33) is used for wedge connection with the U-shaped part (16).

7. The submarine cable protection device according to claim 6, characterized in that: A threaded hole (4) is arranged on the wedge block (33). The threaded hole (4) is connected to the bolt hole arranged on the U-shaped part (16) through a bolt (5).

8. The submarine cable protection device according to claim 6, wherein: The barbed device (3) is made of stainless steel.

9. The submarine cable protection device according to any one of claims 3-5, characterized in that: The material of the bending limiter is polyurethane, and / or, the material of the strengthener (1) is polyurethane.

Images