A method for salvaging, repairing and replaying a large-section oil-filled submarine cable in deep waters

Abstract

The invention discloses a method for salvaging, repairing and replaying a large-section oil-filled submarine cable in a deep-water area, comprising: S1, cleaning the covering on the submarine cable around the fault point of the submarine cable, so that the submarine cable is fully exposed on the seabed; S2, cutting the fault point of the submarine cable on the seabed, and then salvaging the faulty section of the submarine cable; S3, salvaging one of the submarine cables remaining after cutting, partially cutting the cut end of the submarine cable again, testing, plugging and hanging buoys after cutting, and floating the submarine cable on the water; S4, salvaging the other submarine cable remaining after cutting, partially cutting and testing the cut end of the submarine cable again, and connecting a spare pipe cable adapted to the cut end of the submarine cable; S5, salvaging the submarine cable hung with a mark in step S3, and then connecting it with the spare pipe cable in step S4, and testing it; S6, slowly putting the repaired submarine cable into the water, and burying it for protection along the laying and replaying path. The method has significant economic and social benefits.

Description

Technical Field

[0001] The invention relates to the field of marine engineering, and in particular to a method for salvaging, repairing and replaying a large-section oil-filled submarine cable in a deep-water area. Background Art

[0002] Submarine cables are an important component of cross-sea power transmission projects. As one of the common types of submarine cables, oil-filled submarine cables have a high usage rate in existing cross-sea power transmission projects. Large-section oil-filled submarine cables are mainly composed of outer sheaths, armor layers, insulation layers, conductors and oil channels. They have many internal units and contain lead sheath vulnerable components. During the operation of large-section oil-filled submarine cables, they will be subject to complex wave flow loads and accidental loads such as hull anchor damage. Their structure and mechanical properties will be damaged, which will affect their power transmission capacity and cause huge economic losses. At the same time, the leakage of internal insulating oil will also cause marine pollution. Therefore, the submarine cable repair project must respond quickly. After a submarine cable failure occurs, it needs to go through diagnosis, fault location, maintenance, and reset operations, which takes a long time and has a great impact on the use of submarine cables. Safety and efficiency are the main requirements for the repair construction of large-section flexible pipe cables in deep sea oceans. As one of the most core steps in the submarine cable repair project, the salvage and playback construction of submarine cables should also be taken seriously. During the construction of submarine cable salvage and playback, the submarine cable experiences many working conditions and is subjected to complex loads. In the absence of standardized process guidance, secondary damage is prone to occur, further increasing maintenance costs and prolonging maintenance time.

[0003] Currently, there are few studies on the salvage and playback process of large-section oil-filled cables in deep waters. The salvage and maintenance conditions of submarine cables in deep waters are complex and the marine environment is harsh. Improper operation will cause secondary damage to the cables, greatly increasing the maintenance costs. In addition, the cable stress during the salvage and playback process is complex, and it is difficult to determine the specific construction process. The submarine cable salvage and recovery construction technology still lacks unified and standardized construction processes and technical guidance for key process links. Therefore, it is necessary to invent a construction process for the salvage and playback of large-section oil-filled submarine cables in deep waters, refine the key processes and important steps of salvage and playback, and use them to guide the construction process of salvage and playback. Summary of the invention

[0004] In order to overcome the deficiencies in the prior art, the present invention proposes a method for salvaging, repairing and replaying a large-section oil-filled submarine cable in deep waters. By analyzing the different environments and stages in the salvaging and replaying construction process of a large-section oil-filled cable in deep waters, the main parameter indicators and construction process flow are clarified, and the entire process and parameters of the salvaging and replaying construction of a large-section oil-filled cable in deep waters are indicated, which standardizes the construction, improves the construction safety, eliminates the inconsistency of construction methods, and has significant economic and social benefits.

[0005] In order to solve the above technical problems, the present invention is implemented by the following technical solutions:

[0006] A method for salvaging, repairing and replaying a large-section oil-filled submarine cable in deep waters, comprising the following steps:

[0007] S1. Clean the coverings on the submarine cable around the fault point of the submarine cable to fully expose the submarine cable on the seabed;

[0008] S2. Cut off the fault point of the submarine cable on the seabed, and then salvage the faulty section of the submarine cable;

[0009] S3, salvage one of the remaining submarine cables after cutting, partially cut off the cut end of the submarine cable again, test, plug and hang buoys after cutting, and float the submarine cable on the water;

[0010] S4, salvage the other submarine cable remaining after cutting, partially cut off and test the cut end of the submarine cable again, and connect a matching spare pipe cable to the cut end of the submarine cable;

[0011] S5, salvaging the submarine cable marked in step S3, then connecting it to the spare cable in step S4, and performing a sealing test;

[0012] S6. Slowly place the repaired submarine cable into the water and bury it along the laying and playback path for protection.

[0013] Preferably, the key steps and detailed processes in the salvage and playback process need to be parameterized and determined, and the specific steps are as follows:

[0014] The simulation software is used to simulate the process of submarine cable salvage and playback, and extract the key stress points, tension and curvature of the submarine cable;

[0015] According to the mechanical properties of submarine cables, judge the structural safety of submarine cables during construction;

[0016] Adjust parameters, seek a suitable salvage solution and set its parameters.

[0017] Further preferably, the steps of extracting the key stress points, tension and curvature of the submarine cable through simulation software are as follows:

[0018] Establish a parameter input model in the simulation software, and input basic setting parameters, environmental setting parameters, salvage ship setting parameters, submarine cable setting parameters, rope setting parameters and winch setting parameters into the parameter input model;

[0019] A parameter adjustment model is established in the simulation software, and the relationship between the parameters is adjusted using the parameter adjustment model to ensure the continuity of the connection points of the parameters;

[0020] A data generation model is established in the simulation software, and the force data at each position of the submarine cable is calculated using the data generation model based on the adjusted parameters.

[0021] More preferably, the basic setting parameters include analysis steps and analysis time.

[0022] More preferably, the environmental setting parameters include ocean current velocity, wave parameters, seabed topography and seabed soil parameters.

[0023] More preferably, the salvage ship setting parameters include the size of the salvage ship, the initial position of the salvage ship and the movement speed of the salvage ship.

[0024] More preferably, the submarine cable setting parameters include submarine cable length, unit length, submarine cable mechanical properties and fixing points.

[0025] More preferably, the cable setting parameters include cable salvaging speed and cable status.

[0026] More preferably, the capstan setting parameters include capstan shape and capstan position.

[0027] More preferably, the simulation software includes Orcaflex software.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] The present invention enriches the construction technology of deep-water submarine cable salvage and playback in the field of domestic emergency repair engineering. The actual working conditions are parameterized, the originally complex submarine cable salvage and playback process is abstracted into the linear problem of the submarine cable, the complex submarine cable stress is decoupled, and the safety of the submarine cable during the salvage and playback process is evaluated from different angles such as stretching and bending.

[0030] Numerical calculation software is used to determine the process parameters in the construction of deep-water submarine cable salvage and playback. Orcaflex numerical analysis software is used to simulate the process of submarine cable salvage and playback, and to determine the key process parameters and key stress positions of the submarine cable during the salvage and playback construction process. Further exploration of the influence of various parameters on key stress positions can be used to obtain a salvage and playback construction plan that fits the actual project and meets the project safety requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The deep-water salvage overall model constructed by the present invention Figure 1 ;

[0032] Figure 2 The deepwater salvage process model constructed by the present invention is Figure 2 .

[0033] Figure numerals: 1-salvage vessel, 2-cable, 3-submarine cable. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Some parts in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted. The positional relationships described in the drawings are only for illustrative purposes and cannot be understood as limitations on the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. All other embodiments obtained based on the embodiments in the present invention are within the scope of protection of the present invention.

[0035] In order to better explain the present invention, the following Figure 1-2 The specific embodiments are described in detail.

[0036] Orcaflex is a nonlinear time-domain finite element software program, mainly used for static and dynamic modeling of systems used in offshore construction environments, and is mainly used in marine engineering, marine engineering, oceanographic research, etc. Orcaflex is easy to use for dynamic calculation and analysis of slender structures in marine engineering and environmental loads. It has the characteristics of multi-tasking, batch processing, efficient analysis capabilities, and a convenient, intuitive, high-quality graphical user interface, which can easily and quickly build models. The Orcaflex system image display can choose wireframe or three-dimensional solid display, and can perform coupling analysis of floating bodies and wire rod structures. It can establish various seabed conditions, including flat seabed surfaces, two-dimensional seabed surfaces, and three-dimensional seabed surfaces. Orcaflex can be used to create finite element models, to create floating body models, to perform cable micro-element segment force analysis, cable suspension line analysis, cable water resistance micro-element analysis, and to perform numerical simulation of the submarine cable salvage process.

[0037] This embodiment provides a method for salvaging, repairing and replaying a large-section oil-filled submarine cable in deep waters, wherein the diameter of the large-section submarine cable is 138 mm, and comprises the following steps:

[0038] S1. Clear the covering on the submarine cable around the fault point of the submarine cable to fully expose the submarine cable 3 on the seabed.

[0039] S2. Cut off the fault point of the submarine cable on the seabed, and then salvage the faulty section of the submarine cable separately to the salvage vessel 1; specifically: use ROV on the seabed to perform a small-scale seabed lifting and cutting project. It should be noted that this seabed cutting needs to be performed twice at both ends of the submarine cable fault point to cut the submarine cable into three sections.

[0040] S3. Salvage one of the remaining submarine cables after cutting, and partially cut off the cut end of the submarine cable again. After cutting, test, seal and hang buoys to float the submarine cable on the water. Because after cutting off the fault point of the submarine cable, seawater will enter the original submarine cable structure, so this part needs to be cut off cleanly. Mainly test the electrical continuity, such as electrical continuity test. Generally, temporary joints or lead sheaths are used to seal to prevent seawater from flowing into the submarine cable again.

[0041] S4. Salvage the other submarine cable remaining after cutting, partially cut off and test the cut end of the submarine cable again, and connect the matching spare pipe cable to the cut end of the submarine cable; after the submarine cable is connected with the spare pipe cable, the tensioner and launching bridge can be used to control the stress of the remaining section, control the speed, stress and angle to move to the other end where the buoy has just been hung, and at the same time relax the spare pipe cable to play back and lay one end.

[0042] S5. Salvage the submarine cable marked in step S3, connect it to the spare cable in step S4, and perform a test; perform an electrical continuity test on the connected cable.

[0043] S6. The hull moves sideways, slowly placing the repaired submarine cable into the water, and burying it along the laying and playback path for protection.

[0044] The above method is mainly applicable to deep-water submarine cable repair projects, and the repaired section of the submarine cable moves greatly. It should be noted that the submarine cable is subjected to complex forces during the entire process. In order to ensure that the salvage process does not cause secondary damage to the submarine cable, thereby increasing the repair cost, it is necessary to parameterize the key steps and detailed processes in the salvage and playback process. The specific solutions are as follows:

[0045] Step 1: Use the orcaflex software to simulate the process of submarine cable salvage and playback, and extract the key stress points, tension, curvature and other results of the submarine cable. The specific operations are as follows:

[0046] Orcaflex software is used to simulate and analyze the forces on the submarine cable during salvage and playback. The simulation analysis methods include:

[0047] Step 1: Set the analysis step in General, considering the initial static placement of the submarine cable and the salvage water depth to set the analysis step time;

[0048] Step 2: According to the project requirements, set the ocean environment in Environment (including water depth, current velocity, wave parameters, seabed topography, seabed soil parameters, etc.);

[0049] Step 3: According to the project requirements, set the size of the salvage ship, the initial position of the salvage ship, the movement speed of the salvage ship, etc. in Vessels (floating body);

[0050] Step 4: According to the project requirements, set the submarine cable parameters in Lines, including the length of the submarine cable, the unit length, the mechanical properties of the submarine cable and the fixing points;

[0051] Step 5: According to the project requirements, set the state of cable 2 in Winches. The initial state of the cable is free, the initial tension is set to 0, and the cable speed must be set to ensure that the cable is salvaged to the salvage ship when the analysis is completed;

[0052] Step 6: According to the engineering requirements, imitate the shape of the real winch, set the shape of the winch to be cylindrical in Shapes, set it on one side of the salvage ship, and connect it to the cable;

[0053] Step 7: Fine-tune the relationship between parameters in All objects data (parameter relationship) to ensure the continuity of each connection point, and then submit the calculation.

[0054] Step 8: After the run is completed, select key data such as curvature and tension in Select Result, and output images and tables.

[0055] Step 2: According to the mechanical properties of the submarine cable, determine the structural safety of the submarine cable during the construction process. The specific requirements are as follows: During the entire construction process, the internal tension of the submarine cable should be less than or equal to the allowable installation tension of the submarine cable; During the entire construction process, the bending radius of each store in the overall linear shape of the submarine cable should be less than the minimum bending radius requirement of the submarine cable. (How to determine the structural safety, please give a detailed judgment process).

[0056] Step 3: Adjust parameters, find a suitable salvage plan and set its parameters.

[0057] The main parameters for salvaging, repairing and replaying large-section oil-filled submarine cables in deep waters are selected for the following reasons:

[0058] During the salvage construction process, the submarine cable is in a catenary shape and is in a dynamic change process. In order to ensure the safety of the submarine cable structure, the submarine cable cannot have a large tension and curvature during the salvage process, so it is necessary to control the relevant parameters in the salvage process. The main factors affecting the linearity of the submarine cable catenary are: cleaning length, lifting point height, hull movement speed, protection device (bending limiter) position and protection length. The cleaning length mainly affects the overall linearity of the submarine cable during the lifting process. Through data such as seawater depth, fault length, cutting length, and minimum bending radius, the length required for cleaning the covering during the salvage process can be roughly determined to avoid excessive cleaning that wastes time for subsequent burial maintenance, or the cleaning of the covering is too short, resulting in a small bending radius at the junction of the covered and uncovered cables. If the ratio of the salvage speed to the construction ship's speed is too large, the cable may be subjected to excessive tension, leading to cable tensile failure and failure of the original uncleaned soil layer, resulting in cable exposure and other safety risks; if the ratio of the two speeds is too small, the cable may be bent and damaged, so it is necessary to determine the speed range of the two. The length and position of the bend limiter mainly affect the bending stiffness of the cable and have a certain impact on the overall linearity.

[0059] During the playback process, the submarine cable is laid on the seabed in an "Ω" shape along the lateral displacement direction of the hull. Its overall linearity is related to the length of the rear cable, the moving speed of the hull, and the lowering speed. The length of the rear cable mainly affects the overall linearity of the submarine cable during the lowering process. When the rear cable is long, it is necessary to disperse the hanging points or install a bending limiter near the hanging points to avoid large bending damage. The moving speed of the hull and the lowering speed cooperate with each other to ensure that the submarine cable is laid on the seabed in a safe and linear manner.

[0060] This case takes the oil-filled submarine cable in a certain sea area as the research object. This type of submarine cable is mainly used for large-capacity power transmission across rivers and straits. The outer diameter of the submarine cable is 0.138m and the bending stiffness is 3.058kN﹒m 2 , the axial stiffness is 193.707E3kN, and the mass per unit length in air is 48kg / m.

[0061] In this model, the origin of the global coordinate is set at sea level, the Z axis is vertically upward, and the X and Y directions satisfy the right-hand rule. The cable is laid in the positive direction of the X axis.

[0062] Salvage model establishment: Establish a 700m long submarine cable, set the initial water depth to 100m, lay the submarine cable to the seabed, and lay it to the seabed in an "Ω" shape to ensure that there is enough spare length for the lifting process. The direct salvage process requires the addition of a bend limiter at the salvage point. The model adds a bend limiter at the salvage point with a length of 30m. To improve the accuracy of the calculation model, the submarine cable is divided into three parts. The bend limiter connection part is discretized into several units with a length of 0.5m, and the part within 40m close to the bend limiter is discretized into several units with a length of 0.5m. The rest of the cable is discretized into several units with a length of 2m. The salvage ship speed is 0.26m / s, and the lifting speed is 0.2m / s. The model schematic is as follows Figure 1 After the extraction results, the full cable tension and bending radius are both less than the specified value, and the salvage plan is feasible.

[0063] Build a 700m long submarine cable, fix both ends of the submarine cable at 170m on the left and right sides, set the initial water depth to 100m, and add a bend limiter in the middle with a length of 30m. Set the initial length of the cable and hang the submarine cable on the ship. Divide the submarine cable into three parts. The bend limiter connection part is discretized into several units with a length of 0.5m, the part within 40m close to the bend limiter is discretized into several units with a length of 0.5m, and the rest of the part is discretized into several units with a length of 2m. The playback ship speed is 0.26m / s, and the lowering speed is 0.23m / s. The model schematic is as follows Figure 2 After the extraction results, the full cable tension and bending radius are both less than the specified value, and the salvage plan is feasible.

[0064] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for salvaging, repairing and replaying a large-section oil-filled submarine cable in deep waters, characterized in that: The steps include: S1. Clear the covering on the submarine cable around the fault point of the submarine cable to fully expose the submarine cable on the seabed; S2. Cut off the fault point of the submarine cable on the seabed, and then salvage the faulty section of the submarine cable; S3, salvage one of the remaining submarine cables after cutting, partially cut off the cut end of the submarine cable again, test, plug and hang buoys after cutting, and float the submarine cable on the water; S4, salvage the other submarine cable remaining after cutting, partially cut off and test the cut end of the submarine cable again, and connect a suitable spare pipe cable to the cut end of the submarine cable; S5, salvaging the submarine cable marked in step S3, and then connecting it to the spare cable in step S4, and testing it; S6. Slowly place the repaired submarine cable into the water and bury it along the laying and playback path for protection; It is necessary to parameterize the key steps and detailed processes in the salvage and playback process. The specific steps are as follows: The simulation software is used to simulate the process of submarine cable salvage and playback, and extract the key stress points, tension and curvature of the submarine cable; According to the mechanical properties of submarine cables, the structural safety of submarine cables during construction can be judged; Adjust parameters, seek suitable salvage solutions and set parameters for them; The steps to extract the key stress points, tension and curvature of the submarine cable through simulation software are as follows: Establish a parameter input model in the simulation software, and input basic setting parameters, environmental setting parameters, salvage ship setting parameters, submarine cable setting parameters, rope setting parameters and winch setting parameters into the parameter input model; A parameter adjustment model is established in the simulation software, and the relationship between the parameters is adjusted using the parameter adjustment model to ensure the continuity of the connection points of the parameters; A data generation model is established in the simulation software, and the force data at each position of the submarine cable is calculated using the data generation model based on the adjusted parameters.

2. The method for salvaging, repairing and replaying a large-section oil-filled submarine cable in deep water according to claim 1 is characterized in that: The basic setting parameters include analysis steps and analysis time.

3. The method for salvaging, repairing and replaying a large-section oil-filled submarine cable in deep water according to claim 1 is characterized in that: The environmental setting parameters include ocean current velocity, wave parameters, seabed topography and seabed soil parameters.

4. The method for salvaging, repairing and replaying a large-section oil-filled submarine cable in deep water according to claim 1 is characterized in that: The salvage ship setting parameters include the size of the salvage ship, the initial position of the salvage ship and the movement speed of the salvage ship.

5. The method for salvaging, repairing and replaying a large-section oil-filled submarine cable in deep water according to claim 1 is characterized in that: The submarine cable setting parameters include submarine cable length, unit length, submarine cable mechanical properties and fixing points.

6. The method for salvaging, repairing and replaying a large-section oil-filled submarine cable in deep water according to claim 1 is characterized in that: The cable setting parameters include cable salvaging speed and cable status.

7. The method for salvaging, repairing and replaying a large-section oil-filled submarine cable in deep water according to claim 1 is characterized in that: The capstan setting parameters include capstan shape and capstan position.

8. The method for salvaging, repairing and replaying a large-section oil-filled submarine cable in deep water according to any one of claims 1 to 7, characterized in that: The simulation software includes Orcaflex software.

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