Sinking system and sinking method for HDPE pipeline

Abstract

The present invention relates to the technical field of HDPE pipeline sinking, and in particular to a sinking system and sinking method for an HDPE pipeline. The sinking system for an HDPE pipeline comprises a plurality of airbags, slings, sacrificial ropes, first extension slings and / or second extension slings, wherein the airbags are connected to the slings via the sacrificial ropes, and the slings wrap around an HDPE pipeline to be sunk; and the first extension slings and / or the second extension slings are mounted between the airbags and the slings and are configured to increase the distance between the airbags and the slings. In the sinking system, by arranging the first extension slings and / or the second extension slings between the airbags and the slings, the pipeline is sunk for the first time after being filled with water, without being sunk in place in one go, thereby effectively reducing the bending stress on the pipeline at the initial stage of sinking; and then based on the depth of first sinking, the first extension slings and / or the second extension slings are selected to increase the distance between the airbags and the slings, such that the pipeline is sunk more stably and accurately.

Description

A immersion system and immersion method for HDPE pipes

[0001] This case claims priority to Chinese invention patent application filed on January 22, 2025 (application number 202510103523.7), which is incorporated herein by reference in its entirety. Technical Field

[0002] This invention relates to the field of HDPE pipe immersion technology, and particularly to an immersion system and immersion method for HDPE pipes. Background Technology

[0003] HDPE (High Density Polyethylene) pipes are well-suited for use as seawater intake pipes in seawater cooling systems due to their superior properties, such as reliable connections, strong impact resistance, outstanding crack resistance, aging resistance, and corrosion resistance.

[0004] The commonly used method for pipe laying is to first fabricate pipe sections on land, seal both ends of the sections with temporary sealing walls, and then slide them into the water to make them float. They are then towed to the designed location. After positioning, loads are applied to the pipe sections to sink them into a pre-dug underwater trench. Finally, the sealing walls are removed, connecting the pipe sections into a single unit. However, when HDPE pipes are used as seaside intake pipes for seawater cooling systems, these pipes are characterized by large diameters (inner diameter exceeding 3m), heavy weights (pipe section lengths exceeding 5.5m, weight per meter exceeding 0.9t / m), and long pipe sections (single pipe section lengths approximately 100-500 meters). Using traditional laying methods can easily lead to incomplete laying of HDPE pipes, increasing unnecessary adjustments and unduly extending the construction period. Furthermore, the traditional pipe laying method involves a single, repetitive laying process, which can easily cause excessive bending and damage to the HDPE pipes, increasing construction costs. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing pipe laying technology, which is not suitable for laying large-diameter, heavy-duty, and long HDPE pipes, easily leading to damage to HDPE pipes and low laying accuracy. This invention provides a laying system and method for HDPE pipes.

[0006] In a first aspect, the present invention provides a dredging system for HDPE pipes, comprising a plurality of airbags, slings, sacrificial ropes, a first extension sling, and / or a second extension sling; the airbags are connected to the slings via the sacrificial ropes, and the slings wrap around the HDPE pipe to be dredged; the first extension sling and / or the second extension sling are installed between the airbags and the slings, and the first extension sling and / or the second extension sling are used to extend the distance between the airbags and the slings.

[0007] Traditional methods of laying pipelines in one go can easily cause excessive bending damage to large-diameter, heavy, and long HDPE pipelines, and the laying accuracy is low, making it difficult to withstand the influence of ocean currents. The laying system for HDPE pipelines provided by this invention, however, uses a first and / or second extension sling between the airbag and the sling. After the pipeline is filled with water, the initial laying of the HDPE pipeline is achieved, eliminating the need for a single, complete laying. This effectively reduces the bending stress on the pipeline during the initial laying period, protecting its structural integrity. Then, depending on the initial laying depth, the first and / or second extension slings are used to extend the distance between the airbag and the sling, allowing for smoother secondary or tertiary laying in subsequent operations. This step-by-step laying method avoids the positioning deviation problems of traditional one-time laying. Finally, by fine-tuning the air pressure within the airbag, precise laying of the HDPE pipeline is achieved, significantly improving construction accuracy. Through precise step-by-step laying and air pressure fine-tuning, the extensive subsequent adjustment work caused by incomplete laying in traditional methods is significantly reduced. The more precise placement of the pipeline effectively shortened the construction period and improved overall construction efficiency. Furthermore, during multiple placements, the pipeline gradually adapted to the dynamic forces of ocean currents, avoiding the risks of impact or displacement caused by ocean currents in single-stage placements. This phased operation enhanced the pipeline's resistance to ocean currents during placement, ensuring its stability and safety.

[0008] Preferably, when only the first growth strap is provided, the upper end of the sacrificial rope and the upper end of the first growth strap are both connected to the airbag, the lower end of the sacrificial rope and the lower end of the first growth strap are both connected to the strap, and the length of the first growth strap is greater than or equal to the length of the sacrificial rope.

[0009] The length of the first extension sling is greater than the length of the sacrificial rope, providing a wider operational range for pipe laying. In the initial stage of pipe laying, the sacrificial rope connects the airbag and the pipe, limiting excessive pipe depth and preventing bending damage to large-diameter, heavy pipes caused by rapid or excessively deep initial laying. Once the initial laying is complete, the sacrificial rope can be cut to release the length of the first extension sling, precisely controlling the depth of the second laying and gradually achieving accurate pipe positioning and laying to the designed depth. The sacrificial rope and the first extension sling have a clear division of labor and work together throughout the laying process, significantly reducing the number of adjustments and complexity during the laying operation, thereby improving construction efficiency and shortening the construction period.

[0010] Preferably, when both the first and second lengthening slings are provided, the upper ends of the sacrificial rope and the first lengthening sling are both connected to the airbag, the lower end of the sacrificial rope is connected to the sling, the lower end of the first lengthening sling is connected between the two ends of the sacrificial rope, the upper end of the second lengthening sling is connected to the lower end of the first lengthening sling, and the lower end of the second lengthening sling is connected to the sling, and the lengths of both the first and second lengthening slings are greater than or equal to the length of the sacrificial rope.

[0011] By using sacrificial ropes, first extension slings, and second extension slings in a tiered manner, multi-stage immersion operations can be achieved, improving the adaptability and flexibility of the immersion system to meet the needs of different water depths, ocean current intensities, and pipeline lengths. The immersion depth at each stage can be controlled by using sacrificial ropes and extension slings of varying lengths, preventing the pipeline from being subjected to excessive bending moment loads during the immersion phase. This is particularly effective in protecting large-diameter, heavy-duty, and long HDPE pipelines.

[0012] In a second aspect, the present invention provides a method for immersing HDPE pipes, using the aforementioned immersion system for HDPE pipes, comprising the following steps:

[0013] S1: Inflate the airbags pre-installed with the installed HDPE pipe, and control the inflation level so that the joint end of the installed HDPE pipe floats to a distance of 0.8m-1.2m from the bottom of the trench; select the length of the first extension sling L1 and / or the length of the second extension sling L2, connect several airbags to the slings through sacrificial ropes, wrap the slings around the HDPE pipe to be submerged, and select the first extension sling and / or the second extension sling to be arranged between the airbags and the slings according to the number of times the sacrificial rope is cut N; moor and position the HDPE pipe to be submerged on the water surface.

[0014] S2: Release the airbag fixing rope of the HDPE pipe to be laid, first open the water valve at the non-connecting end of the HDPE pipe to be laid to fill it with water, and then open the air valve at the connecting end of the HDPE pipe to be laid to allow the HDPE pipe to be laid to vent and sink, thus completing the first laying of the HDPE pipe to be laid.

[0015] S3: After the HDPE pipe to be submerged is first submerged and stabilized, the axial deviation of the HDPE pipe to be submerged is measured. If the axial deviation of the HDPE pipe to be submerged exceeds 1m, the horizontal position and elevation of the HDPE pipe to be submerged are adjusted a second time until the axial deviation of the HDPE pipe to be submerged is ≤1m.

[0016] S4: Cut the sacrificial rope between the two ends of the first growth sling, release the first growth sling, and complete the second sinking of the HDPE pipe to be laid. If the height H2 of the HDPE pipe to be laid after the second sinking is less than or equal to L2+1, continue to deflate the airbag to adjust the height of the HDPE pipe to be laid, so that the docking end of the HDPE pipe to be laid is aligned with the docking end of the already installed HDPE pipe, and complete the sinking of the HDPE pipe to be laid.

[0017] If the height H2 of the HDPE pipe to be laid after the second laying is greater than L2+1 from the bottom of the trench, then cut the sacrificial rope located between the two ends of the second extension sling, release the second extension sling, and complete the third laying of the HDPE pipe to be laid. After that, continue to deflate the airbag to adjust the height of the HDPE pipe to be laid, so that the docking end of the HDPE pipe to be laid is aligned with the docking end of the already installed HDPE pipe, and complete the laying of the HDPE pipe to be laid.

[0018] The HDPE pipe immersion method provided by this invention employs airbag buoyancy assistance and a gradual release of extension slings, avoiding the need for a single, all-in-one immersion operation. By employing staged immersion (initial, secondary (or even tertiary), and final airbag deflation for fine-tuning of the immersion depth), the bending stress experienced by the pipe during immersion is significantly reduced, thus protecting the structural integrity of the HDPE pipe. The immersion depth and suspension state of the pipe are controlled by cutting the sacrificial rope and adjusting the airbag deflation volume, ensuring that each stage of immersion achieves the precise position required by the design. After the initial immersion, the pipe axis deviation is measured and adjusted to ensure a deviation ≤1m, greatly reducing subsequent position adjustments caused by incomplete immersion in traditional methods. Through the rational arrangement and flexible length selection of the first and second extension slings, the immersion steps and depth can be adjusted according to specific construction environments (such as different water depths and trench conditions), demonstrating strong adaptability.

[0019] The multi-stage immersion method for HDPE pipes provided by this invention significantly improves the protection, accuracy, and efficiency of pipe immersion by combining airbag-assisted buoyancy, multiple releases of elongating slings, and gradual, precise adjustments, overcoming the shortcomings of traditional one-time immersion methods. This method has significant advantages in protecting the HDPE pipe structure, reducing construction risks, improving project quality, and enhancing economic benefits, providing an innovative solution for the marine immersion of large-diameter, heavy-duty, and ultra-long HDPE pipes.

[0020] Preferably, in S1, the number of times the sacrificial rope is cut, N, is determined. If the height H1 from the bottom of the trench after the HDPE pipe to be laid is less than or equal to L1+L2+1, then N=1. If the sacrificial rope is cut only once, then the second extension sling is not used.

[0021] If the height H1 from the bottom of the trench after the first immersion of the HDPE pipe is greater than L1+L2+1, then N=2. If the sacrificial rope is cut only twice, then both the first and second extension slings will be used.

[0022] When N=1, without using a second extension sling, the construction workers only need to cut the sacrificial rope once to complete the operation, simplifying the sinking process. When N=2, by pre-arranging and rationally using both types of extension slings, there is no need to repeatedly adjust the sling settings, significantly improving the efficiency of the sinking operation. By precisely controlling the number of times the sacrificial rope is cut and the use of the slings through the cleaning logic, trial operations are reduced, ensuring rapid completion of the sinking operation.

[0023] Preferably, the air bladder reserved in S1 for the installed HDPE pipe is located within 0-40m of the joint end of the installed HDPE pipe.

[0024] The reserved airbag is located within a 0-40m range of the docking end. By inflating it, local buoyancy is achieved, causing the docking end of the installed HDPE pipe to float slightly. This provides sufficient support and ensures the stability of the docking end.

[0025] Preferably, in S2, starting from the docking end of the HDPE pipe to be laid, the fixing ropes of the airbag to the HDPE pipe to be laid are sequentially released towards the non-docking end of the HDPE pipe to be laid.

[0026] Using this method of releasing the fixing ropes, starting from the docking end of the HDPE pipe to be submerged, the fixing ropes of the airbags are released sequentially towards the non-docking ends, prioritizing the release of the airbags at the docking ends to facilitate subsequent water filling operations of the HDPE pipe to be submerged.

[0027] Preferably, the length L1 of the first extension sling is 4m and the length L2 of the second extension sling is 1m.

[0028] The first extension sling (4m) and the second extension sling (1m) provide the system with flexible adjustment space for immersion. By selecting the appropriate sling combination and the number of times the sacrificial rope is cut, the immersion depth of the HDPE pipe can be precisely controlled, ensuring that the pipe position meets the predetermined requirements. When the initial immersion depth of the pipe meets the conditions, the longer first extension sling is used, allowing the system to gradually place the pipe and make fine adjustments. If greater depth adjustments are required, the second extension sling can be used for further fine adjustments.

[0029] Preferably, in S2, the HDPE pipe to be laid is initially laid to a depth of 4.5m, and the single laying depth of the HDPE pipe is no more than 5m.

[0030] Limiting the maximum descent depth to 5m per descent effectively prevents uneven stress or pipeline damage caused by excessive descent. Controlling the depth of each descent avoids sudden excessive loads during the descent process, reducing impact on the pipeline. An initial descent depth of 4.5m is appropriate, ensuring a stable descent of the pipeline and maintaining a certain level of buoyancy, preventing premature contact with the bottom of the trench and affecting subsequent descent operations.

[0031] Preferably, in step S2, when filling the HDPE pipe to be submerged with water, a crane vessel is used to lift the docking end of the HDPE pipe to be submerged, so that the air valve is above the water; when the HDPE pipe to be submerged sinks to 9-10 pipe sections, the lifting points of the crane vessel are released.

[0032] Lifting the air valve to the water surface facilitates the smooth release of gas, preventing gas buildup or blockage. By controlling the timely release of gas during the pipeline's descent, buoyancy caused by gas accumulation is prevented, which could lead to instability or pipeline floating, affecting the overall efficiency of the descent operation. Releasing the lifting points when the pipeline reaches 9-10 sections signifies that the initial descent is essentially complete, allowing for further fine-tuning based on the pipeline's descent status. This method of gradually releasing the lifting points ensures precise control at each stage of the pipeline's descent, preventing sudden acceleration or uneven settlement.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. The HDPE pipe immersion system provided by this invention, by setting a first and / or second extension sling between the airbag and the sling, allows for the initial immersion of the HDPE pipe after water filling, eliminating the need for a single, complete immersion. This effectively reduces bending stress on the pipe during the initial immersion phase and protects its structural integrity. Then, depending on the initial immersion depth, the first and / or second extension slings are used to extend the distance between the airbag and the sling, allowing for smoother secondary or tertiary immersion in subsequent operations. This step-by-step immersion method avoids the positioning deviation problems of traditional one-time immersion. Finally, by fine-tuning the air pressure within the airbag, precise immersion of the HDPE pipe is achieved, significantly improving construction accuracy. Through precise step-by-step immersion and air pressure fine-tuning, the extensive subsequent adjustments required due to incomplete immersion in traditional methods are significantly reduced. More accurate pipe immersion effectively shortens the construction period and improves overall construction efficiency. Furthermore, during multiple immersion processes, the pipeline can gradually adapt to the dynamic forces brought by ocean currents, avoiding the risks of impact or displacement under the influence of ocean currents that occur with single-stage immersion methods. The phased operation enhances the pipeline's resistance to ocean currents during immersion, ensuring the stability and safety of the immersion process.

[0035] 2. The HDPE pipe immersion method provided by this invention employs airbag buoyancy assistance and a gradual release of extension slings, avoiding the need for a single, one-time immersion of the pipe. By immersing in stages (initial, secondary (or even tertiary), and final airbag deflation for fine-tuning the immersion depth), the bending stress on the pipe during immersion is significantly reduced, thus protecting the structural integrity of the HDPE pipe. The immersion depth and suspension state of the pipe are controlled by cutting the sacrificial rope and adjusting the airbag deflation volume, ensuring that each stage of immersion achieves the precise position required by the design. After the initial immersion, the pipe axis deviation is measured and adjusted to ensure a deviation ≤1m, significantly reducing subsequent position adjustments caused by incomplete immersion in traditional methods. Through the reasonable arrangement and flexible length selection of the first and second extension slings, the immersion steps and depth can be adjusted according to the specific construction environment (such as different water depths and trench conditions), demonstrating strong adaptability.

[0036] 3. The HDPE pipe immersion method provided by this invention significantly improves the protection, accuracy, and efficiency of pipe immersion by combining airbag-assisted buoyancy, multiple releases of lengthening slings, and gradual precise adjustments, overcoming the shortcomings of traditional one-time immersion methods. This method has significant advantages in protecting the HDPE pipe structure, reducing construction risks, improving project quality, and enhancing economic benefits, providing an innovative solution for the marine immersion of large-diameter, heavy-duty, and ultra-long HDPE pipes. Attached image description:

[0037] Figure 1 is a schematic diagram of the immersion system for HDPE pipes in Example 2;

[0038] Figure 2 is a schematic diagram of the immersion system for HDPE pipes in Example 3;

[0039] Figure 3 is a schematic diagram of the three sinking processes;

[0040] Figure 4 is a schematic diagram of the four sinking processes;

[0041] Figure 5 is a schematic diagram of the floating of an installed HDPE pipe;

[0042] Figure 6 is a schematic diagram of the water filling process for the HDPE pipeline to be laid.

[0043] Figure 7 is a schematic diagram of the HDPE pipe to be submerged after water filling;

[0044] Figure 8 is a schematic diagram of the HDPE pipe to be laid down by cutting the rope once.

[0045] In the diagram, the markings are: 1-airbag, 21-first growth sling, 22-second growth sling, 23-sling, 24-sacrificial rope, 3-crane vessel, 100-HDPE pipe to be laid, and 200-HDPE pipe already installed. Detailed Implementation

[0046] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0047] Unless otherwise specified, the use of terms such as "upper," "lower," "left," "right," "center," "inner," and "outer" to indicate orientation or positional relationships in the description of specific embodiments of the present invention is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is typically placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0048] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," and "parallel" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, or parallel, but rather that it can be slightly tilted or have a deviation. For example, "horizontal" merely means that its direction is more horizontal relative to "vertical," not that the structure must be completely horizontal, but that it can be slightly tilted. Alternatively, it can be simplified to mean that the corresponding device / component / element, when set in a "horizontal," "vertical," "suspended," or "parallel" direction, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the present invention.

[0049] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing between identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0050] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as two, three, four, five, six, seven, eight, or nine, and can even exceed nine.

[0051] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to common connection methods in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0052] Example 1

[0053] Traditional pipe-laying methods, which involve placing the pipe into position in one go, are prone to excessive bending damage to large-diameter, heavy, and long HDPE pipes. Furthermore, the laying accuracy is low, and the pipes are susceptible to the influence of ocean currents. Therefore, this embodiment provides a laying system for HDPE pipes, including several airbags 1, slings 23, sacrificial ropes 24, a first extension sling 21, and / or a second extension sling 22. The airbags 1 are connected to the slings 23 via the sacrificial ropes 24, and the slings 23 wrap around the HDPE pipe 100 to be laid. The first extension sling 21 and / or the second extension sling 22 are installed between the airbags 1 and the slings 23, extending the distance between them.

[0054] The HDPE pipe immersion system provided in this embodiment utilizes a first extension sling 21 and / or a second extension sling 22 between the airbag 1 and the sling 23. After the pipe is filled with water, the HDPE pipe 100 is initially immersed, eliminating the need for a single, complete immersion. This effectively reduces bending stress on the pipe during the initial immersion phase, protecting its structural integrity. Then, depending on the initial immersion depth, the first extension sling 21 and / or the second extension sling 22 are used to extend the distance between the airbag 1 and the sling 23, allowing for smoother secondary or tertiary immersion in subsequent operations. This gradual immersion method avoids the positioning deviation problems of traditional one-time immersion. Finally, by fine-tuning the air pressure within the airbag 1, precise immersion of the HDPE pipe is achieved, significantly improving construction accuracy. Through precise step-by-step immersion and air pressure fine-tuning, the extensive subsequent adjustments required due to incomplete immersion in traditional methods are significantly reduced. More accurate pipe immersion effectively shortens the construction period and improves overall construction efficiency. Furthermore, during multiple immersion processes, the pipeline can gradually adapt to the dynamic forces brought by ocean currents, avoiding the risks of impact or displacement under the influence of ocean currents that occur with single-stage immersion methods. The phased operation enhances the pipeline's resistance to ocean currents during immersion, ensuring the stability and safety of the immersion process.

[0055] Example 2

[0056] Based on Embodiment 1, as shown in Figure 1, this embodiment only sets up a first extension sling 21. The upper end of the sacrificial rope 24 and the upper end of the first extension sling 21 are both connected to the airbag 1. The lower end of the sacrificial rope 24 and the lower end of the first extension sling 21 are both connected to the sling 23. The length of the first extension sling 21 is greater than or equal to the length of the sacrificial rope 24.

[0057] The length of the first extension sling 21 is greater than the length of the sacrificial rope 24, providing a wider operating range for pipe laying. In the initial stage of pipe laying, the sacrificial rope 24 connects the airbag 1 and the HDPE pipe 100 to be laid, limiting excessive pipe depth and preventing bending damage to large-diameter, heavy pipes caused by excessively rapid or deep laying. Once the initial laying is complete, the sacrificial rope 24 can be cut to release the length of the first extension sling 21, precisely controlling the depth of the secondary laying and gradually achieving accurate pipe positioning and laying to the designed depth. The sacrificial rope 24 and the first extension sling 21 have a clear division of labor and work together throughout the laying process, significantly reducing the number of adjustments and complexity during laying operations, thereby improving construction efficiency and shortening the construction period.

[0058] Example 3

[0059] Unlike Embodiment 2, as shown in Figure 2, in this embodiment, when both a first lengthening sling 21 and a second lengthening sling 22 are provided, the upper end of the sacrificial rope 24 and the upper end of the first lengthening sling 21 are both connected to the airbag 1, the lower end of the sacrificial rope 24 is connected to the sling 23, and the lower end of the first lengthening sling 21 is connected between the two ends of the sacrificial rope 24, preferably at half the length of the sacrificial rope 24; the upper end of the second lengthening sling 22 is connected to the lower end of the first lengthening sling 21, and the lower end of the second lengthening sling 22 is connected to the sling 23. The lengths of both the first lengthening sling 21 and the second lengthening sling 22 are greater than or equal to the length of the sacrificial rope 24.

[0060] This embodiment, through the step-by-step arrangement of sacrificial rope 24, first extension sling 21, and second extension sling 22, enables multi-stage immersion operations, improving the adaptability and flexibility of the immersion system to meet the needs of different water depths, ocean current intensities, and pipeline lengths. The immersion depth at each stage can be controlled by using sacrificial rope 24 and extension sling 23 of varying lengths, preventing the pipeline from experiencing excessive bending moment loads during the immersion phase. This is particularly effective in protecting large-diameter, heavy-duty, and long HDPE pipelines.

[0061] Example 4

[0062] As shown in Figures 3-8, this embodiment provides a method for immersing HDPE pipes, using the immersion system for HDPE pipes provided in Embodiment 1, including the following steps:

[0063] S1: As shown in Figure 5, the diver inflates the airbag 1 reserved for the installed HDPE pipe 200. In this embodiment, the airbag 1 reserved for the installed HDPE pipe 200 is located within a range of 0-40m from the joint end of the installed HDPE pipe 200 towards the non-joint end. The diver controls the inflation degree of the airbag 1 reserved for the installed HDPE pipe 200 so that the joint end of the installed HDPE pipe 200 floats to a distance of 0.8m-1.2m from the bottom of the trench. By inflating, local buoyancy is achieved for the installed HDPE pipe 200, causing the joint end of the installed HDPE pipe 200 to float slightly, ensuring the stability of the joint end.

[0064] Select the length L1 of the first extension sling 21 and / or the length L2 of the second extension sling 22. Specifically, the length L1 of the first extension sling 21 can be 4m-5m, preferably L1=4m; the length L2 of the second extension sling 22 can be 1m-2m, preferably L2=1m. Connect several airbags 1 to the slings 23 via sacrificial ropes 24. The slings 23 wrap around the HDPE pipe 100 to be lowered. Based on the number of times N the sacrificial rope 24 is cut, select the first extension sling 21 and / or the second extension sling 22 to be arranged between the airbags 1 and the slings 23.

[0065] If the height H1 from the bottom of the trench after the first placement of the HDPE pipe 100 is less than or equal to L1+L2+1, then N=1. If the sacrificial rope 24 is cut only once, then the second growth sling 22 is not used.

[0066] If the height H1 from the bottom of the trench after the first immersion of the HDPE pipe 100 is greater than L1+L2+1, then N=2. If the sacrificial rope 24 is cut only twice, then both the first extension sling 21 and the second extension sling 22 will be used.

[0067] The HDPE pipe 100 to be submerged is moored and positioned on the water surface.

[0068] S2: After verifying the mooring and positioning measurements at both ends of the HDPE pipe 100 to be submerged, starting from the docking end of the HDPE pipe 100 to be submerged, sequentially release the fixing ropes of the airbag 1 to the non-docking end of the HDPE pipe 100 to facilitate the subsequent water filling operation of the HDPE pipe 100 to be submerged. Once all the fixing ropes of the airbags of the HDPE pipe 100 to be submerged are released, the conditions for water release are met.

[0069] After the divers checked the positioning anchors and the tightness of the airbag binding slings 23 of the HDPE pipe 100 to be submerged and found no abnormalities, they first opened the water valve at the non-connecting end of the HDPE pipe 100 to fill it with water. Then, they opened the air valve at the connecting end of the HDPE pipe 100 to allow the HDPE pipe 100 to be submerged to vent air and sink. The preset airbags 1 then activated in sequence to perform the buoyancy operation, as shown in Figure 6, thus completing the first submersion of the HDPE pipe 100.

[0070] In this embodiment, the HDPE pipe 100 to be laid is initially laid 4.5m deep, and the single laying depth of the HDPE pipe 100 to be laid is no more than 5m.

[0071] In this embodiment, when filling the HDPE pipe 100 to be submerged with water, as shown in Figure 7, a crane vessel 3 can be used to lift the docking end of the HDPE pipe 100 to be submerged, so that the air valve is above the water to prevent water from entering the air valve prematurely. When the HDPE pipe 100 to be submerged has sunk to about 9-10 pipe sections remaining, the lifting points of the crane vessel 3 are released. During the water filling process of the HDPE pipe 100 to be submerged, the positioning anchor of the HDPE pipe 100 to be submerged is not released, and the axis and mileage position of the HDPE pipe 100 to be submerged are monitored to ensure a safe distance of more than 5 meters between the HDPE pipe 100 to be submerged and the already installed HDPE pipe 200.

[0072] S3: After the HDPE pipe 100 to be laid down is first laid down and stabilized, the axial deviation of the HDPE pipe 100 to be laid down is measured. If the axial deviation of the HDPE pipe 100 to be laid down exceeds 1m, the horizontal position and elevation of the HDPE pipe 100 to be laid down are adjusted a second time by the winches on the crane boats and barges at both ends of the HDPE pipe 100 to be laid down until the axial deviation of the HDPE pipe 100 to be laid down is ≤1m.

[0073] S4: As shown in Figures 3 and 8, cut the sacrificial rope 24 located between the two ends of the first growth sling 21, release the first growth sling 21, and complete the secondary sinking of the HDPE pipe 100 to be sinked.

[0074] If the height H2 of the HDPE pipe 100 to be laid after the second laying is less than or equal to L2+1, then continue to deflate the airbag 1 to adjust the height of the HDPE pipe 100 to be laid (for example, the third laying as shown in Figure 3), so that the docking end of the HDPE pipe 100 to be laid is aligned with the docking end of the installed HDPE pipe 200, and the laying of the HDPE pipe 100 to be laid is completed.

[0075] As shown in Figure 4, if the height H2 of the HDPE pipe 100 to be laid after the second laying is greater than L2+1 from the bottom of the trench, then the sacrificial rope 24 located between the two ends of the second extension sling 22 is cut, the second extension sling 22 is released, and the third laying of the HDPE pipe 100 to be laid is completed. Then, the airbag 1 is deflated to adjust the height of the HDPE pipe 100 to be laid (for example, the fourth laying as shown in Figure 4), so that the docking end of the HDPE pipe 100 to be laid is aligned with the docking end of the installed HDPE pipe 200, and the laying of the HDPE pipe 100 to be laid is completed.

[0076] The HDPE pipe immersion method provided in this embodiment employs buoyancy assistance from airbag 1 and a gradual release of the extension slings, avoiding the need for a single, all-in-one immersion operation. By immersing in stages (initial, secondary (or even tertiary), and final airbag 1 deflation for fine-tuning of the immersion depth), the bending stress experienced by the pipe during immersion is significantly reduced, thus protecting the structural integrity of the HDPE pipe. The immersion depth and suspension state of the pipe are controlled by cutting the sacrificial rope 24 and adjusting the deflation amount of airbag 1, ensuring that each stage of immersion achieves the precise position required by the design. After the initial immersion, the pipe axis deviation is measured and adjusted to ensure a deviation ≤1m, significantly reducing subsequent position adjustments caused by incomplete immersion in traditional methods. Through the reasonable arrangement and flexible length selection of the first and second extension slings 21, the immersion steps and depth can be adjusted according to the specific construction environment (such as different water depths and trench conditions), demonstrating strong adaptability.

[0077] The multi-stage immersion method for HDPE pipelines provided in this embodiment significantly improves the protection, accuracy, and efficiency of pipeline immersion by combining the buoyancy assistance of airbag 1, multiple releases of the elongating slings, and gradual precise adjustments, overcoming the shortcomings of traditional one-time immersion methods. This method has significant advantages in protecting the HDPE pipeline structure, reducing construction risks, improving project quality, and enhancing economic benefits, providing an innovative solution for the marine immersion of large-diameter, heavy-duty, and ultra-long HDPE pipelines.

[0078] In embodiment 4, the fixing rope is used to temporarily tie and fix the HDPE pipe 100 to be submerged to the airbag 1. It can be tied at any position on the HDPE pipe 100 to be submerged and the airbag 1. The purpose of the fixing rope is to reduce the displacement of the HDPE pipe 100 to be submerged relative to the airbag 1, that is, to form the connection relationship between the HDPE pipe 100 to be submerged and the airbag 1 on the upper left side of Figure 5. Since the fixing rope occupies a relatively small proportion in the figure, and it is known to those skilled in the art how to tie two objects together, the fixing rope is not shown in the figure.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A submersion system for HDPE pipes, characterized in that, Includes several airbags (1), slings (23), sacrificial ropes (24), a first extension sling (21) and / or a second extension sling (22); The airbag (1) is connected to the sling (23) via the sacrificial rope (24), and the sling (23) wraps around the HDPE pipe (100) to be lowered; the first extension sling (21) and / or the second extension sling (22) are installed between the airbag (1) and the sling (23), and the first extension sling (21) and / or the second extension sling (22) are used to extend the distance between the airbag (1) and the sling (23).

2. The immersion system for HDPE pipes according to claim 1, characterized in that, When only the first growth strap (21) is set, the upper end of the sacrificial rope (24) and the upper end of the first growth strap (21) are both connected to the airbag (1), and the lower end of the sacrificial rope (24) and the lower end of the first growth strap (21) are both connected to the strap (23). The length of the first growth strap (21) is ≥ the length of the sacrificial rope (24).

3. The immersion system for HDPE pipes according to claim 1, characterized in that, When both the first growth strap (21) and the second growth strap (22) are provided, the upper end of the sacrificial rope (24) and the upper end of the first growth strap (21) are connected to the airbag (1), the lower end of the sacrificial rope (24) is connected to the strap (23), the lower end of the first growth strap (21) is connected between the two ends of the sacrificial rope (24), the upper end of the second growth strap (22) is connected to the lower end of the first growth strap (21), the lower end of the second growth strap (22) is connected to the strap (23), and the length of the first growth strap (21) and the length of the second growth strap (22) are both greater than or equal to the length of the sacrificial rope (24).

4. A method for immersing HDPE pipes, characterized in that, The immersion system for HDPE pipes according to any one of claims 1-3 includes the following steps: S1: Inflate the airbag (1) reserved for the installed HDPE pipe (200) and control the inflation degree so that the joint end of the installed HDPE pipe (200) floats to a distance of 0.8m-1.2m from the bottom of the trench; Select the length L1 of the first growth sling (21) and / or the length L2 of the second growth sling (22), connect several airbags (1) to the sling (23) through the sacrificial rope (24), and wrap the HDPE pipe (100) to be laid. According to the number of times N of cutting the sacrificial rope (24), select to arrange the first growth sling (21) and / or the second growth sling (22) between the airbags (1) and the sling (23); The HDPE pipe (100) to be submerged is moored and positioned on the water surface; S2: Release the fixing rope of the airbag (1) of the HDPE pipe (100) to be laid, first open the water valve of the non-connecting end of the HDPE pipe (100) to be laid to fill with water, and then open the air valve of the connecting end of the HDPE pipe (100) to be laid to allow the HDPE pipe (100) to be laid to vent and sink, thus completing the first laying of the HDPE pipe (100). S3: After the HDPE pipe (100) to be laid down is first laid down and stabilized, the axial deviation of the HDPE pipe (100) to be laid down is measured. If the axial deviation of the HDPE pipe (100) to be laid down exceeds 1m, the horizontal position and elevation of the HDPE pipe (100) to be laid down are adjusted a second time until the axial deviation of the HDPE pipe (100) to be laid down is ≤1m. S4: Cut the sacrificial rope (24) located between the two ends of the first growth sling (21), release the first growth sling (21), and complete the secondary sinking of the HDPE pipe (100) to be sinked. If the height H2 of the HDPE pipe (100) to be sinked after the secondary sinking is less than or equal to L2+1, then continue to deflate the airbag (1) to adjust the height of the HDPE pipe (100) to be sinked, so that the docking end of the HDPE pipe (100) to be sinked is aligned with the docking end of the installed HDPE pipe (200), and complete the sinking of the HDPE pipe (100). If the height H2 of the HDPE pipe (100) to be laid after the second laying is greater than L2+1 from the bottom of the trench, then cut the sacrificial rope (24) between the two ends of the second growth sling (22), release the second growth sling (22), and complete the third laying of the HDPE pipe (100). Then continue to deflate the airbag (1) to adjust the height of the HDPE pipe (100) to be laid, so that the docking end of the HDPE pipe (100) to be laid is aligned with the docking end of the installed HDPE pipe (200), and complete the laying of the HDPE pipe (100).

5. The HDPE pipe immersion method according to claim 4, characterized in that, In S1, the number of times N is cut for the sacrificial rope (24) is determined. If the height H1 from the bottom of the trench after the HDPE pipe (100) is first laid is less than or equal to L1+L2+1, then N = 1. If the sacrificial rope (24) is cut only once, then the second growth sling (22) is not used. If the height H1 of the HDPE pipe (100) to be laid after the first laying is greater than L1+L2+1, then N=2. If the sacrificial rope (24) is cut only twice, then both the first growth sling (21) and the second growth sling (22) will be used.

6. The HDPE pipe immersion method according to claim 4, characterized in that, The airbag (1) reserved in S1 for the installed HDPE pipe (200) is located within 0-40m of the joint end of the installed HDPE pipe (200).

7. The HDPE pipe immersion method according to claim 4, characterized in that, In S2, starting from the docking end of the HDPE pipe (100) to be laid, the fixing ropes of the airbag (1) of the HDPE pipe (100) to be laid are sequentially released to the non-docking end of the HDPE pipe (100).

8. The HDPE pipe immersion method according to claim 4, characterized in that, The length L1 of the first growth sling (21) is 4m, and the length L2 of the second growth sling (22) is 1m.

9. A method for immersing HDPE pipes according to claim 4, characterized in that, The HDPE pipe (100) to be laid in S2 is initially laid to a depth of 4.5m, and the single laying depth of the HDPE pipe (100) to be laid is no more than 5m.

10. A method for immersing HDPE pipes according to claim 4, characterized in that, In S2, when filling the HDPE pipe (100) to be submerged with water, use a crane (3) to lift the docking end of the HDPE pipe (100) to be submerged, so that the air valve is above the water; when the HDPE pipe (100) to be submerged sinks to the 9th-10th pipe section, release the lifting point of the crane (3).

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