Submarine pipeline installation method

Abstract

The invention relates to a submarine pipeline installation method. The submarine pipeline installation method comprises the steps that S1, a process pipe section is formed in a coast assembly area through machining, the process pipe section is sealed, a plurality of balance weight bases are installed on the process pipe section, and an air bag is installed on the process pipe section; and S2, the process pipe section is hoisted to the sea surface, tugboats are connected to the front end and the rear end of the process pipe section in the axial direction, and the tugboats are used for hauling the process pipe section to the installation sea area. And S3, the tugboat is unfastened, the process pipe section is fixed to a lifting rope of the sea-based crane, and the position of the process pipe section is adjusted, so that the sea surface position of the process pipe section is matched with the seabed position. And S4, water is injected into the process pipe section so that the process pipe section can sink, and the sinking speed of the process pipe section is controlled through the sea-based crane. And S5, undersea butt joint is conducted on the process pipe sections through diving operation. And S6, all the process pipe sections are transported to the seabed one by one for butt joint, and the submarine pipeline is formed. The mounting method is convenient to transport, and the underwater construction difficulty can be reduced.

Description

Technical Field

[0001] This invention relates to the field of submarine pipeline construction technology, and in particular to a method for installing submarine pipelines. Background Technology

[0002] High-density polyethylene (HDPE) pipes are widely used in large-scale projects such as seawater supply and drainage and marine dredging due to their excellent corrosion resistance, flexibility, light weight, and long service life. In related technologies, the laying of subsea pipelines mainly involves using tugboats to tow cement or steel pipes along the coast to the installation area, then pre-excavating a foundation or constructing a base on the seabed, injecting water into the pipeline to lower it, and finally installing the pipeline on the foundation using diving operations. However, for HDPE pipe installation, when the pipe diameter is large, such as DN1200 or larger, its buoyancy is significant, requiring numerous counterweights to be installed on the seabed for fixation. Laying numerous counterweights leads to longer underwater operation times, increased construction difficulty, and longer labor costs. Furthermore, during surface transportation, HDPE pipes, due to their high buoyancy, are prone to severe rollover under the influence of waves, causing significant difficulties for transportation and submerged pipe operations. Summary of the Invention

[0003] The purpose of this invention is to propose a method for installing submarine pipelines that is convenient for transportation and easy to install.

[0004] To achieve this objective, the present invention adopts the following technical solution:

[0005] A method for installing a submarine pipeline is provided, comprising the following steps:

[0006] Step S1: Several process pipe sections are processed in the coastal assembly area, each process pipe section is sealed, and multiple counterweight bases are installed on the process pipe section at intervals along its axial direction. Airbags are installed on the process pipe section. The counterweight base includes an upper counterweight base and a lower counterweight base that are interlocked with each other in the vertical direction. The weight of the upper counterweight base is less than the weight of the lower counterweight base.

[0007] Step S2: Hoist the process pipe section to the sea surface and make the process pipe section float on the sea surface. The airbag is located above the waterline. Connect tugboats to the front and rear ends of the process pipe section in the axial direction. Use the tugboats to tow the process pipe section to the installation sea area. During towing, the tugboat at the front is used to drive the process pipe section forward, and the tugboat at the rear is used to drive the process pipe section backward.

[0008] Step S3: Untie the tugboat and fix the process pipe section to the hoisting rope of the sea-based crane. Adjust the position of the process pipe section so that the sea surface position of the process pipe section matches the seabed position. Inflate the airbag so that the airbag is in an inflated state.

[0009] Step S4: Inject water into the process pipe section to make the process pipe section sink, and use the sea-based crane to control the sinking speed of the process pipe section;

[0010] Step S5: Underwater docking of the process pipe section is carried out through diving operations;

[0011] Step S6: Repeat steps S2 to S5 above to transport all the process pipe sections one by one to the seabed for docking to form a subsea pipeline.

[0012] As a preferred embodiment of the subsea pipeline installation method, the end of the process pipe section is provided with a flange for docking, and multiple process lugs are provided around the flange. Each process lug is provided with a process hole. During underwater docking, a jack is inserted into the corresponding process holes of two adjacent flanges, and the jack is used to drive the two adjacent process pipe sections to dock.

[0013] As a preferred embodiment of the subsea pipeline installation method, the process lugs are configured in three parts, with one process lug located at the top of the process pipe section and the other two process lugs located on both sides of the process pipe section along the horizontal direction.

[0014] As a preferred method for installing submarine pipelines, during underwater docking, divers first measure the relative positions of two adjacent process pipe sections, and then adjust the relative positions of the two adjacent process pipe sections using the sea-based crane so that the flange spacing between the two adjacent process pipe sections is 0.4 to 0.6 m. Then, the jacks are inserted into the process holes.

[0015] As a preferred method for installing submarine pipelines, in step S5, the two flanges after docking are first pre-fixed, and then the axial position of the process pipe section is checked and adjusted. After the flange at the other end is in the correct position, the two flanges after docking are locked.

[0016] As a preferred method for installing submarine pipelines, in step S4, when the entire process pipe section is below the sea surface, the sealing plate used for sealing the end of the process pipe section is removed.

[0017] As a preferred method for installing submarine pipelines, in step S4, the process pipe section is lowered in multiple time periods. After each time period is completed, the process pipe section is brought to a standstill, and its position is adjusted.

[0018] As a preferred method for installing submarine pipelines, in step S2, the connection point on the process pipe section is located higher than the connection point on the tugboat.

[0019] As a preferred method for installing submarine pipelines, in step S3, the connection points between the sea-based crane and the process pipe section are symmetrically distributed on both sides of the process pipe section in the horizontal direction.

[0020] As a preferred embodiment of the subsea pipeline installation method, the method further includes step S7: after the subsea pipeline is installed, backfill the bottom of the subsea pipeline with crushed stone.

[0021] The advantages of this invention compared to the prior art are:

[0022] The subsea pipeline installation method of the present invention assembles the process pipe section and the counterweight base in a coastal assembly area. On the one hand, the counterweight base increases the gravity of the process pipe section and prevents it from rolling during transport, reducing transportation difficulties. On the other hand, it avoids underwater installation of the process pipe section and the counterweight base, reducing underwater laying operations of the counterweight base, lowering construction difficulty, and shortening the overall installation time. Attached Figure Description

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0024] Figure 1 This is a schematic diagram (axial direction) of a process pipe section according to an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram (radial) of a process pipe section according to an embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram showing the connection between the process pipe section and the tugboat in an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram of the process pipe section and the sea-based crane in an embodiment of the present invention.

[0028] Figure 5 This is a schematic diagram of the process pipe section being installed by sinking in an embodiment of the present invention.

[0029] Figure 6 This is a schematic diagram of a flange according to an embodiment of the present invention.

[0030] In the picture:

[0031] 1. Process pipe section; 2. Flange; 21. Process lug; 22. Process hole; 3. Sealing plate; 4. Counterweight base; 41. Upper counterweight base; 42. Lower counterweight base; 5. Airbag; 6. Tugboat; 7. Offshore crane; 71. Lifting rope; 8. Seabed. Detailed Implementation

[0032] The advantages and features of the present invention, as well as methods of implementing them, will become apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms. These embodiments are provided merely to complete the disclosure of the invention and to enable those skilled in the art to fully understand the scope of the invention, which is defined only by the scope of the claims. The same reference numerals denote the same constituent elements throughout the specification.

[0033] The present invention will now be described in detail with reference to the accompanying drawings.

[0034] like Figures 1 to 6 As shown, this invention provides a method for installing a subsea pipeline. The subsea pipeline is used in the drainage system of an enclosed harbor basin. The subsea pipeline is segmented into multiple process pipe sections 1 to facilitate processing and transportation. The process pipe sections 1 are connected to the outlet of the enclosed harbor basin, as well as between adjacent process pipe sections 1, via flanges 2. The installation method of the subsea pipeline specifically includes the following steps:

[0035] Step S1: Several process pipe sections 1 are processed and formed in the coastal assembly area. Each process pipe section 1 is sealed, and multiple counterweight bases 4 are installed at intervals along its axial direction on the process pipe section 1. Airbags 5 are installed on the process pipe sections 1. The counterweight bases 4 are designed to be detachable and include an upper counterweight base 41 and a lower counterweight base 42. The bottom of the upper counterweight base 41 has a groove that mates with the surface of the process pipe section 1, and the top of the lower counterweight base 42 has a groove that mates with the surface of the process pipe section 1. During installation, the upper counterweight base 41 and the lower counterweight base 42 are fastened together vertically and fixed to each other with bolts. The weight of the upper counterweight base 41 is less than the weight of the lower counterweight base 42.

[0036] Specifically, process pipe section 1 is fabricated in the coastal assembly area. Process pipe section 1 is composed of multiple HDPE pipes spliced ​​together, with adjacent pipes joined via a heat-fusion process along the axial direction of process pipe section 1. Flanges 2 are installed at both ends of process pipe section 1 along its axial direction. Sealing plates 3 are installed on the flanges 2 at both ends of process pipe section 1 to seal the pipe section. Sealing plates 3 are circular plates and are bolted to the flanges 2. To improve the sealing performance of sealing plates 3, a sealing gasket is sandwiched between the sealing plate 3 and the flange 2. Counterweight bases 4 are evenly spaced along the axial direction of process pipe section 1. When installing the counterweight bases 4, multiple lower counterweight bases 42 are first arranged in the assembly area according to the design drawings, and then process pipe section 1 is hoisted into the grooves of the lower counterweight bases 42. Finally, upper counterweight bases 41 are hoisted one by one and fastened to their corresponding lower counterweight bases 42, and then secured with bolts. The cross-sectional area of ​​the upper counterweight 41 is smaller than that of the lower counterweight 42, so that the weight of the upper counterweight 41 is less than that of the lower counterweight 42. The purpose of this structure is to ensure that the center of gravity of each counterweight base 4 is located below the process pipe section 1. When the entire process pipe section 1 floats on the sea surface, its center of gravity is lower, preventing it from rolling over. After the counterweight base 4 is installed, airbags 5 are installed on the process pipe section 1. The number of airbags 5 is set to an even number, and they are evenly installed on both sides of the process pipe section 1 in the horizontal direction. The airbags 5 are fixed to the counterweight base 4 by strapping, or fixed to the process pipe section 1, or simultaneously fixed to both the counterweight base 4 and the process pipe section 1. Since the airbags 5 need to be removed after the process pipe section 1 is installed, the installation position of the airbags 5 needs to facilitate subsequent removal operations. The airbags 5 are used to provide buoyancy during the sinking of the process pipe section 1 to reduce the sinking speed. Therefore, the airbag 5 should be installed above the waterline of the process pipe section 1 during sea transport to avoid buoyancy during transport.

[0037] Step S2: Hoist process pipe section 1 to the sea surface and make it float. Airbag 5 is positioned above the waterline. Connect tugboats 6 to both ends of process pipe section 1 along its axial direction, and use the tugboats 6 to tow process pipe section 1 to the installation area. During towing, the tugboat 6 at the front propels process pipe section 1 forward, and the tugboat 6 at the rear propels process pipe section 1 backward. Specifically, a shore-based crane is used to hoist process pipe section 1 to the sea surface, where it floats due to its own buoyancy. The tugboats 6 are used to tow process pipe section 1 to the installation area. Since process pipe section 1 needs to turn when entering the harbor basin area, tugboats 6 are connected to both ends of process pipe section 1 to avoid turning on the sea surface. The tugboat 6 at the front propels process pipe section 1 forward, and the tugboat 6 at the rear propels process pipe section 1 backward. Based on the actual movement path of process pipe section 1, the turning and towing of process pipe section 1 can be completed by reasonably selecting either the tugboat 6 at the front or the tugboat 6 at the rear. At the same time, by connecting tugboats 6 at both ends of process pipe section 1, after process pipe section 1 is transported to the installation sea area, the two tugboats 6 can work simultaneously to correct the position of process pipe section 1 so that the sea surface position of process pipe section 1 matches the seabed position.

[0038] To facilitate the towing of process pipe section 1, the connection point on process pipe section 1 is higher than the connection point on tugboat 6. Process pipe section 1 and tugboat 6 are directly connected by a cable, with the connection point between the cable and process pipe section 1 higher than the connection point between the cable and tugboat 6, to avoid tugboat 6 bearing part of the weight of process pipe section 1. Specifically, the connection point of process pipe section 1 is approximately 2.2m above the water surface, the connection point of tugboat 6 is approximately 1m above the water surface, and the angle between the cable and the sea surface is controlled at approximately 15°.

[0039] Step S3: Untie the tugboat 6 and secure the process pipe section 1 to the hoisting rope 71 of the sea-based crane 7. Adjust the position of the process pipe section 1 so that its sea surface position matches its seabed position. Specifically, after the process pipe section 1 reaches the installation area, it needs to be lowered to the seabed. During this process, the sea-based crane 7 is used to hoist the process pipe section 1. Multiple sets of hoisting ropes 71 are distributed axially along the process pipe section 1 to ensure uniform stress distribution. The hoisting ropes 71 are fixed in an "A" shape, meaning each rope 71 has two connection points on the process pipe section 1, located horizontally on both sides of the section. These connection points are symmetrically distributed on both sides of the process pipe section 1. This hoisting method prevents uneven horizontal stress on the process pipe section 1 during descent and avoids rollover.

[0040] Step S4: Water is injected into process pipe section 1 to cause it to sink. The sinking speed of process pipe section 1 is controlled by the sea-based crane 7. Specifically, one sealing plate 3 is equipped with a water injection pipe, and the other sealing plate 3 is equipped with an exhaust pipe. During water injection, water is injected into process pipe section 1 through the water injection pipe, and the air inside process pipe section 1 is discharged through the exhaust pipe. Through water injection, process pipe section 1 sinks to its installation position on the seabed 8 under its own weight. When process pipe section 1 is completely below the sea surface, the sealing plate 3 loses its function, so the sealing plate 3 at the end of process pipe section 1 is removed to prevent the sealing plate 3 from being hoisted to the seabed, thereby reducing the difficulty of subsequent disassembly and transportation. During the sinking process of process pipe section 1, the airbag 5 provides buoyancy to process pipe section 1 and counterweight base 4 to reduce the sinking speed. The volume of the airbag 5 can be adaptively calculated based on the overall weight of the process pipe section 1 and the counterweight base 4, so that the airbag 5 can provide buoyancy during the sinking of the process pipe section 1 to reduce the sinking speed.

[0041] To prevent significant positional shifts in process pipe segment 1 after sinking, the sinking process pipe segment 1 is divided into multiple stages. A hoisting rope 71 is deployed using a sea-based crane 7 to slowly lower process pipe segment 1. The entire sinking process is divided into multiple stages; after each stage, the sea-based crane 7 stops deploying the hoisting rope 71, allowing process pipe segment 1 to come to a stop. Once stopped, process pipe segment 1 will automatically adjust its position to directly above its installation location on the seabed under the influence of gravity, preventing positional shifts due to ocean currents or uneven buoyancy during sinking. Alternatively, a towing cable can be attached to process pipe segment 1 for positional adjustments. Through multi-stage sinking, process pipe segment 1 finally reaches its installation location on the seabed 8.

[0042] Step S5: Underwater docking of process pipe section 1 is carried out via diving operations. Specifically, divers descend to the seabed to dock process pipe section 1 with the outlet of the harbor basin, and to dock two adjacent process pipe sections 1. After the underwater docking is completed, the sea-based crane 7 is dismantled, and the airbag 5 is disassembled and recovered.

[0043] Step S6: Repeat steps S2 to S5 to transport all process pipe sections 1 one by one to the seabed for docking to form a subsea pipeline.

[0044] Specifically, the flange 2 has multiple process lugs 21 around its periphery, each with a process hole 22. The process lugs 21 are used for positioning during underwater docking. Optionally, three process lugs 21 are used, with one located at the top of the process pipe section 1 and the other two horizontally distributed on either side of the process pipe section 1. During underwater docking, divers first visually observe the relative positions of adjacent process pipe sections 1. It should be noted that when installing the first process pipe section 1, the relative position between the process pipe section 1 and the harbor outlet flange is observed. Then, the sea-based crane 7 is directed to move the process pipe section 1 so that the distance between the flanges 2 corresponding to adjacent process pipe sections 1 is 0.4–0.6 m, or the distance between the process pipe section 1 and the harbor outlet flange is 0.4–0.6 m. Then, jacks are inserted into the process holes 22. Because adjusting the position of process pipe section 1 using the naval crane 7 is difficult, when the distance between two adjacent flanges 2 is small, jacks are used directly for alignment adjustment. During alignment adjustment, the process holes 22 on the two flanges 2 are used for guidance to ensure proper alignment. Also, the port basin outlet flange is relatively fixed, or the flanges 2 on the already installed process pipe section 1 are also relatively fixed. The flanges 2 on the process pipe section 1 to be installed are relatively movable. When using jacks, appropriate tooling can be configured according to the actual situation, fixing both ends of the jacks to the relatively fixed flange 2 and the relatively movable flange 2 respectively. The jacks are used to drive the two adjacent process pipe sections 1, or to align process pipe section 1 with the port basin outlet flange. After alignment, bolts are installed on the two flanges 2 to secure them.

[0045] Specifically, after the two flanges 2 are joined, they are pre-fixed. This can be done by inserting pins into the flange holes, or by installing bolts in some of the flange holes. After the flanges 2 are pre-fixed, the position of the process pipe section 1 is checked to prevent it from shifting away from the end where the flanges 2 are joined. If a shift in the position of the process pipe section 1 is detected, it is adjusted promptly. That is, when the diver detects a shift in the axial position of the process pipe section 1, the underwater crane 7 is directed to move the process pipe section 1 to match its design position. Once the position of the process pipe section 1 is correct, the two joined flanges 2 are tightened with bolts.

[0046] Specifically, this also includes step S7: after the subsea pipeline is installed, backfilling the bottom of the subsea pipeline with gravel. Before installing the subsea pipeline, the seabed 8 needs to be cleared to expose a solid installation foundation, and leveling work needs to be carried out on the installation foundation. After the subsea pipeline is installed, the installation area is backfilled with gravel to fix and protect the counterweight base 4 and the pipe. Finally, the airbag 5 and other auxiliary equipment are removed and transported back to the coastal assembly area for reuse.

[0047] The beneficial effects of this embodiment are as follows: By assembling the process pipe section 1 and the counterweight base 4 in the coastal assembly area, on the one hand, the counterweight base 4 can be used to increase the gravity of the process pipe section 1 and prevent it from rolling over during transport, thus reducing transportation difficulties. On the other hand, it can avoid installing the process pipe section 1 and the counterweight base 4 underwater, reducing underwater laying operations of the counterweight base 4, lowering construction difficulty, and shortening the overall installation time.

[0048] Although embodiments of the invention have been described above with reference to the accompanying drawings, the invention is not limited to the above embodiments, but can be made in various forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical spirit or essential characteristics of the invention. Therefore, it should be understood that the above embodiments are exemplary in all respects and not restrictive.

Claims

1. A method of installing a subsea pipeline, characterised in that, The method comprises the following steps: S1. Forming a plurality of process pipe sections in a coastal assembly area, sealing each process pipe section, and installing a plurality of weight bases on the process pipe sections at intervals along the axial direction of the process pipe sections, wherein the process pipe sections are provided with air bags, the weight bases comprise an upper weight base and a lower weight base which are mutually engaged in the vertical direction, and the weight of the upper weight base is less than that of the lower weight base; S2. Hoisting the process pipe sections to the sea surface and floating the process pipe sections on the sea surface, wherein the air bags are located above the waterline, towboats are connected to the front and rear ends of the process pipe sections in the axial direction, and the process pipe sections are towed to an installation sea area by using the towboats, wherein during the towing, the towboat located at the front end is used to drive the process pipe sections to advance, and the towboat located at the rear end is used to drive the process pipe sections to retreat; S3. Releasing the towboats, fixing the process pipe sections to the hoisting ropes of a sea-based crane, and adjusting the position of the process pipe sections so that the position of the process pipe sections on the sea surface matches the position of the process pipe sections on the seabed; S4. Injecting water into the process pipe sections to make the process pipe sections sink, and controlling the sinking speed of the process pipe sections by using the sea-based crane; S5. Subsea butt joining the process pipe sections by using diving operations; S6. Repeating the above steps S2 to S5 to transport all the process pipe sections to the seabed one by one to form a submarine pipeline.

2. A method of subsea pipeline installation according to claim 1, characterised in that, The end of the process pipe section is provided with a flange for butt joining, a plurality of process ear plates are arranged on the periphery of the flange, each process ear plate is provided with a process hole, and during the subsea butt joining, a jack is arranged in the process hole corresponding to the flanges of two adjacent process pipe sections, and the jack is used to drive the two adjacent process pipe sections to be butt joined.

3. A method of subsea pipeline installation according to claim 2, characterised in that, The process ear plates are arranged in three, one of which is located on the top of the process pipe section, and the other two are located on the two sides of the process pipe section in the horizontal direction.

4. A method of subsea pipeline installation according to claim 2, characterised in that, During the subsea butt joining, the relative positions of two adjacent process pipe sections are first measured by divers, the relative positions of the two adjacent process pipe sections are adjusted by the sea-based crane so that the distance between the flanges corresponding to the two adjacent process pipe sections is 0.4-0.6 m, and then the jack is arranged in the process hole.

5. A method of subsea pipeline installation according to claim 2, characterised in that, In step S5, the two flanges after butt joining are first pre-fixed, then the axial position of the process pipe section is checked and adjusted, the position of the flange at the other end is correct, and then the two flanges after butt joining are locked.

6. The method of subsea pipeline installation of claim 1, wherein, In step S4, when all the process pipe sections are located below the sea surface, the sealing plates for sealing the ends of the process pipe sections are removed.

7. The method of subsea pipeline installation of claim 1, wherein, In step S4, the process pipe sections are sunk in multiple time periods, the process pipe sections are made to be stationary after sinking in each time period, and the position of the process pipe sections is adjusted.

8. The method of subsea pipeline installation of claim 1, wherein, In step S2, the connection point position on the process pipe section is higher than the connection point position on the towboat.

9. The method of subsea pipeline installation of claim 1, wherein, In step S3, the connection points between the sea-based crane and the process pipe sections are symmetrically distributed on the two sides of the process pipe section in the horizontal direction.

10. A method of installing a subsea pipeline according to any one of claims 1 to 9, characterised in that, Also included is a step S7 of backfilling the seabed with rubble at the bottom of the seabed pipeline after the seabed pipeline has been installed.

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