Flexible Joint of Large-diameter and High-pressure Fiber Reinforced Flexible Composite Pipe

Abstract

The present invention relates to a flexible joint of a large-diameter and high-pressure fiber-reinforced flexible composite pipe, belonging to the field of fiber-reinforced thermoplastic pipes. The technical solution is as follows: The reinforcement layer is formed by helically winding fiber tapes, and the reinforcement layer has at least two layers of structure, and the helical winding directions of the fiber tapes in adjacent layers are opposite; the filling layer is arranged between adjacent layers of the reinforcement layer, and the filling layer is composed of an elastic material that can be extruded and deformed; the fiber tapes extend a certain distance beyond the end of the inner lining layer. The present invention provides thicker fiber tapes, reduces the number of times of fiber tape winding, is beneficial to the processing of fiber-reinforced flexible composite pipes, and facilitates the flexible connection of pipes; it can avoid the problem of stress concentration in the reinforcement layer caused by metal joints, and at the same time solves the problem of insufficient strength of welded joints. The technical solution of the present invention can meet the needs of oil and gas pipeline transportation and other application scenarios.

Description

Technical Field

[0001] The invention relates to a flexible joint of a large-caliber high-pressure fiber-reinforced flexible composite pipe, belonging to the field of pipeline transportation, in particular to the field of fiber-reinforced thermoplastic pipelines. Background Art

[0002] Reinforced Thermoplastic Pipes (RTP pipes for short) are high-pressure plastic composite pipes with good flexibility, corrosion resistance, high pressure resistance, impact resistance, wear resistance, light weight, easy connection, coiling, long-distance joint-free rapid laying, etc. They can well overcome the corrosion problem of steel pipes and the pressure resistance problem of plastic pipes. They can be used in oil and natural gas extraction, high-pressure long-distance natural gas transportation, and various pipeline fields that require high-pressure medium transportation. RTP products are usually composed of three layers, with the inner and outer layers being PE80, PE100 or above. The outer layer can be white (surface laying for UV protection) or black (underground laying) as needed; the middle layer is a reinforcement belt made of a composite of reinforcing materials, and the reinforcing materials can be high-strength fibers such as aramid fibers, polyester fibers or glass fibers.

[0003] The existing technical solutions use various types of fibers as reinforcement layers to improve the pressure bearing capacity of pipelines, and there are already many mature products. According to SYT 6662.2-2012 "Non-metallic composite pipes for petroleum and natural gas industry Part 2: Flexible composite high-pressure transmission pipes", the maximum inner diameter of the current general flexible composite pipe is 150mm, and the nominal pressure is 6.4MPa / 2.5MPa; the nominal pressure of flexible composite pipes with an inner diameter of less than 90mm is up to 12MPa. Some companies can process flexible composite pipes with a diameter of more than 1m, but the pressure bearing capacity is low, and they are mainly used for low-pressure water delivery.

[0004] Existing fiber-reinforced flexible composite pipe connections mainly use metal joints and fusion joints. Metal joints use a metal inner tube inserted into the pipeline, and the outer end of the pipeline is clamped by winding or cone sleeves. The metal joints are connected by threaded connection or flange connection. Fusion joints mainly refer to capacitor joints, in which thermoplastic materials are set in the cylindrical joint, and metal wires are pre-buried. The two ends of the pipe are butt-jointed and inserted into the joint, and then the protective layer of the pipe is energized and fused.

[0005] The existing connection technology has the following main problems: (1) Metal joints have local constraints on the pipe ends, and the pipe deformation is not coordinated after pressure, and the pressure bearing capacity is low; and the pipe reinforcement layer is squeezed through the metal joint to transmit the axial force. If the extrusion force is too large, it is easy to damage the fiber, and if it is too small, the constraint is insufficient, and it is difficult to achieve the ideal connection strength in practical applications. (2) Sleeves are set at the connection part and connected by welding. The protective layer of the pipes at both ends is directly fused to the joint, and the reinforcement layers cannot be effectively connected. The pipe is easily pulled out and fails under the action of the axial force.

[0006] Since the 21st century, the pipeline transportation industry has vigorously promoted the strategic development plan of "replacing steel with plastics". Flexible composite pipes have been listed as a key development direction due to their excellent performance and are developing towards high pressure and large diameter. In the field of oil and gas transportation, the pipeline pressure is high, and there is a clear demand for large diameter. At present, steel pipes are mainly used for long-distance pipelines, with the largest diameter reaching 1216 mm and the nominal pressure exceeding 10 MPa; the existing flexible composite pipe connection technologies are difficult to adapt to high-pressure and large-diameter pipelines.

[0007] Regarding the problem of connecting fiber-reinforced flexible composite pipes, Patent CN2021107151712 proposed a brand-new flexible connection method: welding the inner liner layer, then overlapping and winding the reinforcement layer according to the helix directions of each layer, and finally setting a protective layer outside the joint. This solution can avoid the problem of stress concentration in the reinforcement layer caused by metal joints and at the same time solve the problem of insufficient strength of welded joints. However, facing dozens of layers of reinforced fiber tapes, this solution has great construction difficulty and long construction time and is difficult to promote and apply.

[0008] For the processing of the reinforcement layer of existing fiber-reinforced flexible composite pipes, winding with tapes with a thickness of less than 1 mm is mainly used. For high-pressure pipelines, the reinforcement layer has a large thickness and requires multiple layers of winding, resulting in the need to arrange multiple groups of tape winding mechanisms on the pipeline production line, and it is difficult to control the coordination between equipment. At present, the fibers in the fiber tape are arranged straight and adhesives are added. When the fiber tape is wound and bent, the inner layer fibers are compressed and the outer layer fibers are stretched. If the fiber tape is too thick, the fibers will be unevenly stressed, affecting its strength; so the thickness of the fiber tape needs to be minimized during current construction. Adopting a reasonable tape winding structure and increasing the tape thickness can effectively reduce the number of times the fiber tape is wound and facilitate the processing of fiber-reinforced flexible composite pipes by the one-step forming method.

[0009] Based on the above background, developing thicker fiber tapes and reducing the number of times the fiber tape is wound is beneficial to the processing of fiber-reinforced flexible composite pipes and facilitates the flexible connection of pipes; developing flexible joints for large-diameter and high-pressure fiber-reinforced flexible composite pipes to meet the technical requirements of large-diameter and high-pressure flexible composite pipes can expand the application scope of composite pipes in the oil and gas output field. Summary of the Invention

[0010] The object of the present invention: To overcome the problems that the existing fiber-reinforced flexible composite pipe joints have low pressure-bearing capacity and are not suitable for large-diameter and high-pressure pipelines; to solve the problem of discontinuous force transmission in the reinforcement layer of flexible composite pipe joints; to provide a fiber tape with a larger thickness, reduce the number of times the fiber tape is wound, which is beneficial to the processing of fiber-reinforced flexible composite pipes and facilitates the flexible connection of pipes.

[0011] To achieve the above object, the technical solutions adopted by the present invention are as follows.

[0012] Flexible joint of large-diameter and high-pressure fiber-reinforced flexible composite pipe, including an inner lining layer, a reinforcing layer, and a filling layer, is characterized in that: a reinforcing layer is arranged outside the inner lining layer, the inner lining layer of the flexible joint is connected to the inner lining layer of the pipe, the reinforcing layer of the flexible joint is connected to the reinforcing layer of the pipe, and no protective layer is arranged outside the reinforcing layer of the flexible joint; the reinforcing layer is formed by spiral winding of fiber tapes, the reinforcing layer is a structure of at least two layers, and the spiral winding directions of the fiber tapes in adjacent layers are opposite; the filling layer is arranged between adjacent layers of the reinforcing layer, and the filling layer is composed of an elastic material that can be extruded and deformed; the fiber tape extends beyond the end of the inner lining layer by a certain distance, and the distance is more than 0.5 times the inner diameter of the inner lining layer; the fiber tape is formed by bonding at least two winding wires side by side with an adhesive, and the adhesive of the winding wire is close to the inner side of the pipe or located at the adjacent part between the winding wires.

[0013] The winding wire is formed by mutually spiral winding and knitting of at least three fiber bundles, and the twist of each fiber bundle of the winding wire is the same and greater than zero.

[0014] The spiral winding directions of the fiber bundles of the winding wires in adjacent layers are opposite.

[0015] An inner core is arranged at the middle position inside the winding wire, the cross-section of the inner core is circular or annular, and the inner core is an elastic material.

[0016] The filling layer is in a strip structure and is spiral wound into a cylindrical shape.

[0017] The filling layer is made of rubber material.

[0018] The inner fiber tapes of the flexible joint are long, the outer fiber tapes are short, and the lengths of the fiber tapes gradually decrease from the inner layer to the outer layer.

[0019] The single reinforcing layer of the flexible joint is formed by spiral winding of one fiber tape.

[0020] It also includes a wedge-shaped ring, which is characterized in that: the wedge-shaped ring is arranged at the end of the fiber tape, the wedge-shaped ring is an open ring, the wedge-shaped ring is composed of an elastic material that can be compressed and deformed, and the circumferential cross-section of the wedge-shaped ring is wedge-shaped.

[0021] The beneficial effects of the present invention are: (1) In the present invention, the reinforcing layers are overlapped in multiple layers, and the layers are transitioned through wedge-shaped rings, effectively enhancing the strength of the reinforcing layer at the joint part; (2) The flexible constraint of the reinforcing layer at the joint part can avoid the problem of stress concentration of the reinforcing layer caused by metal joints, and at the same time solve the problem of insufficient strength of welded joints; (3) Provide a thicker fiber tape, reduce the number of fiber tape winding times, which is beneficial to the processing of fiber-reinforced flexible composite pipes and is convenient for flexible connection of pipes; (4) The technical solution of the present invention can effectively and highly strengthen the connection of large-diameter and high-pressure fiber-reinforced flexible composite pipes, meeting the needs of oil and gas pipeline transportation and other application occasions. Description of the Drawings

[0022] Figure 1 This is a structural schematic diagram of the present invention.

[0023] Figure 2 This is a schematic diagram of the winding of the fiber tape according to the present invention.

[0024] Figure 3 is Figure 1 a partial enlarged view of.

[0025] Figure 4 This is a schematic cross-sectional view of the fiber tape according to the present invention.

[0026] Figure 5 This is a structural schematic diagram of the winding structure according to the present invention.

[0027] Figure 6 This is a schematic cross-sectional view of the winding according to the present invention.

[0028] In the figure: 1. Inner lining layer; 2. Reinforcing layer; 3. Protective layer; 4. Wedge ring; 21. Winding tape; 22. Filling layer; 211. Winding wire; 212. Adhesive; 2111. Fiber bundle; 2112. Inner core. Specific embodiments

[0029] The present invention is not limited by the following embodiments, and specific implementation manners can be determined according to the technical solution of the present invention and actual situations. The positional relationships such as up, down, left, right, front, back, inside, and outside are determined according to the layout direction of the Figure 1 accompanying drawings of the specification.

[0030] The flexible joint of the large-diameter high-pressure fiber-reinforced flexible composite pipe includes an inner lining layer 1, a reinforcing layer 2, and a filling layer 22.

[0031] The reinforcing layer 2 is arranged outside the inner lining layer 1. The inner lining layer 1 of the flexible joint is connected to the inner lining layer 1 of the pipeline, the reinforcing layer 2 of the flexible joint is connected to the reinforcing layer 2 of the pipeline, and the protective layer 3 is not arranged outside the reinforcing layer 2 of the flexible joint; the reinforcing layer 2 is formed by helically winding the fiber tape 21, and the reinforcing layer 2 has at least two layers of structure, and the helical winding directions of the adjacent layers of fiber tapes 21 are opposite.

[0032] The filling layer 22 is arranged between the adjacent layers of the reinforcing layer 2, and the filling layer 22 is composed of an extrudable elastic material. The filling layer 22 deforms and fills the gaps between the fiber tapes 21, and transfers the internal pressure of the pipeline layer by layer to the outer fiber tape 21.

[0033] The fiber tape 21 extends a certain distance beyond the end of the inner lining layer 1, and this distance is more than 0.5 times the inner diameter of the inner lining layer 1; the fiber tape 21 is formed by bonding at least 2 winding wires 211 side by side with an adhesive 212, and the adhesive 212 of the winding wire 211 is close to the inner side of the pipeline or located at the adjacent part between the winding wires 211. Such a setting can reduce the bending moment of inertia coefficient of the spiral winding of the fiber tape 21, make the winding of the fiber tape 21 softer, and facilitate fitting.

[0034] The winding wire 211 is formed by helically winding and braiding at least 3 fiber bundles 2111 with the same twist of each fiber bundle 2111 of the winding wire 211 and greater than zero. Using the fiber bundles 2111 to braid the winding wire 211 can make the winding wire 211 thicker, so that the fiber tape 21 is thicker, which is convenient for pipeline winding and pipeline butt joint construction. In addition, the twist of the fiber bundles 2111 is greater than zero, which can increase the anti-fatigue performance of the fibers.

[0035] The helical winding directions of the fiber bundles 2111 of the adjacent layer winding wires 211 are opposite. This can weaken the shear stress between the winding wires 211.

[0036] An inner core 2112 is arranged at the middle position inside the winding wire 211, the cross section of the inner core 2112 is circular or annular, and the inner core 2112 is made of an elastic material. When the inner core 2112 is compressed and deformed, it can enable the fiber bundles 2111 to stretch freely to a certain extent, which is convenient for the fiber tape 21 to fit tightly and for transmitting the internal pressure of the pipeline.

[0037] The filling layer 22 is in a strip structure and is helically wound into a cylindrical shape. Such a setting facilitates the winding and installation of the filling layer 22. During the pipeline butt joint process, the reinforcing layer 2 is wound layer by layer, and the filling layer 22 is helically wound and added at intervals to reinforce the adjacent fiber tapes 21 of the reinforcing layer 2.

[0038] The filling layer 22 is made of a rubber material. The filling layer 22 can deform freely to fill the gap between the reinforcing layers 2, which is convenient for the internal pressure to be transmitted to the outer layer of the reinforcing layer 2.

[0039] The inner layer fiber tape 21 of the flexible joint is long, the outer layer fiber tape 21 is short, and the length of the fiber tape 21 gradually decreases from the inner layer to the outer layer. During the pipeline butt joint process, after the inner lining layer 1 is welded, the reinforcing layer 2 is wound and connected layer by layer; the reinforcing layer 2 gradually transitions from the inner layer to the outer layer, which is beneficial to its force bearing.

[0040] The single reinforcing layer 2 of the flexible joint is formed by helically winding a fiber tape 21. This facilitates the butt joint installation of the flexible joint and makes it more convenient for the reinforcing layer 2 to be wound layer by layer.

[0041] It also includes a wedge-shaped ring 4, which is arranged at the end of the fiber belt 21. The wedge-shaped ring 4 is an open ring and is composed of an elastic material that can be compressed and deformed. The circumferential cross-section of the wedge-shaped ring 4 is wedge-shaped. Since the fiber belt 21 is relatively thick, the wedge-shaped ring 4 is arranged at the transition part between the fiber belts 21, which is beneficial to the force between layers and avoids stress concentration. The wedge-shaped ring 4 is set as an open ring, which is convenient for its installation during the docking process.

[0042] Embodiment 1

[0043] The inner diameter of the inner liner layer 1 is 800 mm. The inner liner layer 1 uses a polyethylene pipe with a wall thickness of 26 mm. The reinforcing layer 2 selects aramid fibers. The reinforcing layer 2 includes 8 fiber belts 21 with a total thickness of 30 mm. The winding direction of the fiber belt 21 in the reinforcing layer 2 forms an angle of 55° with the pipeline axis. Between adjacent layers of the reinforcing layer 2, the winding directions of the fiber belts 21 are opposite. The overlapping length of the innermost layer of fibers at the joint part is 1300 mm, the overlapping length of the outermost layer of fibers is 900 mm, and the overlapping lengths of the intermediate layers are evenly transitioned. After the reinforcing layer 2 is wound layer by layer, a filling layer 22 is generated by helically winding a rubber belt between layers. A polyethylene tape is wound around the outside of the joint as a protective layer 3, and the thickness of the protective layer 3 is about 4 mm.

[0044] For pipeline connection, first weld the inner liner layer 1, and then wind the reinforcing layer 2 layer by layer. The layers of the reinforcing layer 2 of the butt-jointed pipelines overlap each other and are pressed together. Through experiments and finite element analysis with the help of the Tsai-Wu criterion, the burst pressure of the pipeline described in Embodiment 1 is close to 37 MPa. The strength of the joint part is much higher than that of the pipeline itself, and the fiber strains of each layer at the joint part are uniform and slowly changing, and the stress state is good. (1) According to the existing metal joint structure form for simulation analysis, displacement constraints are applied to the inner liner layer 1 at the joint part, and a uniform pressure load of 1.8 MPa is applied to the outside of the protective layer 3; it is found through analysis that the burst pressure of the pipeline is about 25 MPa, and the failure part is concentrated at the metal buckling part; the technical solution of the present invention improves the pressure-bearing capacity of the pipeline joint by about 48% and avoids the contact between the medium in the pipe and the metal joint. (2) According to the existing welded joint for analysis, a cylindrical rigid sleeve is arranged outside the protective layer 3, and a lining layer identical to the protective layer 3 is arranged inside the rigid sleeve. The welded length at both ends of the joint is 200 mm; it is found through analysis that when the internal pressure of the pipeline reaches 9 MPa, the joint shows pull-off failure.

[0045] Summary: Through the solution of the present invention, the problem of stress concentration in the reinforcing layer 2 caused by metal joints is avoided, and the problem of insufficient strength of welded joints is solved. Through the technical solution of the present invention, large-diameter high-pressure fiber-reinforced flexible composite pipes can be effectively and highly strength-connected to meet the needs of oil and gas pipeline transportation and other application scenarios.

Claims

1. Flexible joint of large-diameter and high-pressure fiber-reinforced flexible composite pipe, including an inner lining layer, a reinforcing layer, and a filling layer, characterized in that: The reinforcing layer is arranged outside the inner lining layer. The inner lining layer of the flexible joint is connected to the inner lining layer of the pipe, and the reinforcing layer of the flexible joint is connected to the reinforcing layer of the pipe; the reinforcing layer is formed by helically winding fiber tapes, and the reinforcing layer has at least two layers of structure, and the helical winding directions of the fiber tapes in adjacent layers are opposite; The filling layer is arranged between adjacent layers of the reinforcing layer, and the filling layer is composed of an elastic material that can be extruded and deformed; The fiber tape extends beyond the end of the inner lining layer by a certain distance, and the distance is more than 0.5 times the inner diameter of the inner lining layer; the fiber tape is formed by bonding at least two winding wires side by side with an adhesive, and the adhesive of the winding wire is close to the inner side of the pipe or located at the adjacent part between the winding wires; A core is arranged at the middle position inside the winding wire, and the cross-section of the core is circular or annular, and the core is made of an elastic material; The winding wire includes a fiber bundle helically wound around the core; The winding wire is formed by helically winding and braiding at least three fiber bundles with each other, and the twist of each fiber bundle of the winding wire is the same and greater than zero; The helical winding directions of the fiber bundles of the winding wires in adjacent layers are opposite; The inner layer fiber tape is long, the outer layer fiber tape is short, and the length of the fiber tape gradually decreases from the inner layer to the outer layer.

2. The flexible joint of the large-diameter and high-pressure fiber-reinforced flexible composite pipe according to claim 1, characterized in that: The filling layer is in a strip structure and is helically wound into a cylindrical shape.

3. The flexible joint of the large-diameter high-pressure fiber-reinforced flexible composite pipe according to claim 1, characterized in that: The filling layer is made of rubber material.

4. The flexible joint of the large-diameter and high-pressure fiber-reinforced flexible composite pipe according to claim 1, characterized in that: The single reinforcing layer of the flexible joint is formed by helically winding a fiber tape.

5. The flexible joint of the large-diameter high-pressure fiber-reinforced flexible composite pipe according to claim 1 further comprises a wedge ring, and is characterized in that: A wedge-shaped ring is arranged at the end of the fiber tape. The wedge-shaped ring is an open ring, and the wedge-shaped ring is composed of an elastic material that can be compressed and deformed, and the circumferential cross-section of the wedge-shaped ring is wedge-shaped.

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