Thermal stress compensation device for double-walled pipes and application

Abstract

The application provides a temperature difference stress compensation device for double-wall pipes and an application. The temperature difference stress compensation device for double-wall pipes comprises an inner pipe assembly and an outer pipe assembly. The inner pipe assembly comprises an inner end pipe and an inner bellows connected with each other. The outer pipe assembly is coaxially sleeved outside the inner pipe assembly and comprises an outer end pipe and an outer bellows connected with each other. The outer circumferential surface of the inner end pipe is provided with a ring-shaped guide sliding plate. The outer wall surface of the guide sliding plate is embedded with a sliding sheet. The sliding sheet abuts against the outer end pipe. The application can guarantee the coaxiality of the inner end pipe and the outer end pipe during thermal expansion and cold contraction, and simultaneously enable the two pipes to freely slide relative to each other in the axial direction to decouple the axial displacement constraint of the inner pipe and the outer pipe, effectively solving the problem that the double-wall pipe needs to be flexibly compensated for the axial thermal expansion displacement and the radial thermal expansion displacement.

Description

Technical Field

[0001] This invention relates to the field of expansion joint technology, and more specifically, to a thermal stress compensation device for double-walled pipes and its application. Background Technology

[0002] With the implementation of the IMO Tier III emission regulations, liquefied natural gas (LNG) has become the most mature transitional fuel in the shipping industry due to its advantages such as cleanliness, low carbon emissions, and economy. Therefore, newly built container ships and LNG carriers generally adopt LNG dual-fuel power systems. As the key to connecting the gas supply valve group and the dual-fuel engine, the double-walled pipeline is usually composed of an inner and outer pipe coaxially mounted, and its safe operation is of paramount importance.

[0003] Because the inner pipe is used to transport high-pressure, low-temperature media (such as LNG with a pressure of up to 30 MPa and a temperature of -163°C), and the annular gap between the inner and outer pipes is usually connected to the atmosphere or filled with inert gases such as nitrogen to achieve ventilation, explosion protection and cold insulation functions; because the space in the ship's engine room is limited and it always operates under low-frequency vibration and temperature fluctuation conditions, the double-walled pipeline will generate huge axial and radial stresses; if they are not effectively released, they can easily lead to pipeline deformation, weld cracking or fatigue failure, which in turn can cause gas leakage.

[0004] To address this, Chinese Patent CN108266289A provides a high-pressure gas double-walled pipe, including an inner pipe and an outer pipe. An outer pipe elbow is provided at intervals on the outer pipe as a compensating element. An elastic support is provided in the annular space between the outer pipe and the inner pipe, which can absorb stress, vibration, and release thermal expansion displacement, and has a long service life. However, since the addition of elbows will increase the friction resistance of the internal medium, it will inevitably cause pipeline impact vibration, which is not conducive to the long-term safe operation of the pipeline.

[0005] Chinese patent CN218625962U discloses a double-walled expansion joint for combustible gas pipelines, including an inner protective pipe and an outer protective pipe sleeved outside the inner protective pipe; the inner protective pipe is provided with an inner corrugated pipe, and the outer protective pipe is provided with an outer corrugated pipe; a double-walled pipe flange is provided at each end of the inner and outer protective pipes, and an airtight annular space is formed between the inner and outer protective pipes; ventilation holes are provided on the double-walled pipe flanges to discharge leaked gas in the airtight annular space. This solution can absorb vibration and some thermal expansion displacement, but it does not consider the effect of thermal expansion stress of the outer pipe; because the inner pipe is in deep cryogenic contraction under actual working conditions, while the outer pipe is at ambient temperature or elongated due to heating, the deformation of the inner and outer corrugated pipes is uneven, which can easily cause stress concentration or even excessive deformation of one side of the corrugated pipe, leading to failure.

[0006] Chinese patent CN106813036A discloses a gas fuel pipeline compensator with a double-wall structure, including flanges, a protective cover, an outer bellows, and an inner bellows. The inner bellows and two flanges form the inner cavity of the compensator for gas fuel, while the inner and outer bellows and the two flanges form the outer cavity of the compensator for air. Each flange has evenly distributed circumferential holes that communicate with the outer cavity of the compensator. One end of the protective cover is fixed to one flange, and the other end is a free end resting on the other flange. This design not only has extremely stringent requirements for installation coaxiality, but also results in excessively high stress in part of the pipeline due to the consistent deformation trend and amount of the two bellows, affecting operational safety. Summary of the Invention

[0007] The problem solved by this invention is to provide a device that can effectively absorb the thermal expansion and contraction stress of double-walled pipes while reducing changes in pipe routing, so as to achieve long-term and safe operation of double-walled pipes.

[0008] To address the aforementioned problems, this invention provides a temperature difference stress compensation device for double-walled pipes, comprising an inner pipe assembly and an outer pipe assembly. The inner pipe assembly includes a connected inner end pipe and an inner corrugated pipe. The outer pipe assembly is coaxially sleeved outside the inner pipe assembly and includes a connected outer end pipe and an outer corrugated pipe. The outer circumferential surface of the inner end pipe is provided with an annular guide slide plate, and the outer wall surface of the guide slide plate is embedded with a sliding plate, which abuts against the outer end pipe.

[0009] Preferably, the guide slide includes a support plate welded to the inner end tube, and the outer wall surface of the support plate is provided with a groove for limiting the assembly of the sliding piece; there are multiple grooves and they are arranged at equal intervals along the outer periphery of the support plate.

[0010] Preferably, the sliding piece extends along the length of the inner end tube and has a length and width of L1 and L2, respectively, wherein L1 = (1.05-1.10) × L2, and the thickness of the support plate is D, wherein L1 = (0.7-0.9) × D.

[0011] Preferably, the distance between the outer wall of the guide plate and the inner wall of the outer end tube is 1-2 mm.

[0012] Preferably, the minimum distance between the guide slide and the inner bellows is 80-120mm.

[0013] Preferably, there are two inner end tubes located at both ends of the inner corrugated tube, and two outer end tubes located at both ends of the outer corrugated tube.

[0014] Preferably, the inner tube assembly includes an inner intermediate tube, and there are two inner corrugated tubes located on both sides of the inner intermediate tube; the outer tube assembly includes an outer intermediate tube, and there are two outer corrugated tubes located on both sides of the outer intermediate tube; the inner intermediate tube is provided with a guide plate, the guide plate is annular and has a groove on its outer circumference, a sliding piece is provided in the groove, and the sliding piece abuts against the outer intermediate tube.

[0015] Preferably, the temperature difference stress compensation device for the double-walled pipe further includes a flow guide tube, which is disposed between the inner end pipe and the inner middle pipe to protect the inner corrugated pipe from the impact of the medium.

[0016] The present invention also discloses the application of the above-mentioned double-walled tube thermal stress compensation device in a ship dual-fuel gas supply system.

[0017] Compared with the prior art, the thermal stress compensation device and application for double-walled pipes described in this invention have the following beneficial effects: 1) It ensures the coaxiality of the inner and outer end pipes during thermal expansion and contraction, and allows them to slide freely relative to each other in the axial direction to decouple the axial displacement constraints of the inner and outer pipes, effectively solving the problem that double-walled pipes need to flexibly compensate for both axial and radial thermal expansion displacements; 2) At the same time, guide slide plates are set on the inner end pipe and the inner middle pipe, which can forcibly constrain the relative posture of the inner pipe assembly and the outer pipe assembly, ensuring that they always maintain a very high coaxiality under any thermal deformation state, avoiding jamming caused by eccentric friction; 3) By limiting the material and size of the sliding plate, it has good mobility in both the axial and radial (circumferential) directions, and is not prone to jamming due to uneven stress caused by installation deviation or thermal deformation. Attached Figure Description

[0018] Figure 1 This is a cross-sectional schematic diagram of the thermal stress compensation device for double-walled pipes according to an embodiment of the present invention;

[0019] Figure 2 This is another cross-sectional schematic diagram of the thermal stress compensation device for double-walled pipes described in an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the assembly of the intermediate guide slide plate according to an embodiment of the present invention;

[0021] Figure 4 This is a schematic diagram of the structure of the intermediate guide slide plate according to an embodiment of the present invention.

[0022] Explanation of reference numerals in the attached figures:

[0023] 1-Inner end tube; 2-Guide slide plate; 3-Outer end tube; 4-Inner corrugated tube; 5-Outer corrugated tube; 6-Inner intermediate tube; 7-Outer intermediate tube; 8-Flow guide tube; 9-Support plate; 91-Groove; 10-Sliding plate. Detailed Implementation

[0024] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Without conflict, the technical features of the embodiments of the present invention can be combined with each other.

[0025] With the widespread use of clean fuels such as liquefied natural gas in dual-fuel propulsion systems of ships, double-walled pipe designs are commonly adopted in gas supply pipelines to ensure transportation safety. The inner pipe transports cryogenic media, while the outer pipe forms a protective annular cavity. However, under prolonged low-frequency vibration conditions, the inner pipe contracts due to the cryogenic medium, while the outer pipe may expand due to ambient temperature or heat tracing, leading to reverse thermal displacement. If the stress generated by thermal expansion and contraction is not effectively released, it severely affects the pipeline's sealing performance and long-term operational safety. Therefore, the applicant proposes the following technical solution:

[0026] like Figure 1-4 As shown, a temperature difference stress compensation device for a double-walled pipe includes an inner pipe assembly and an outer pipe assembly. The inner pipe assembly includes an inner end pipe 1 and an inner corrugated pipe 4 connected together. The outer pipe assembly is coaxially sleeved outside the inner pipe assembly and includes an outer end pipe 3 and an outer corrugated pipe 5 connected together. The outer circumferential surface of the inner end pipe 1 is provided with an annular guide plate 2. The outer wall surface of the guide plate 2 is embedded with a sliding piece 10, which abuts against the outer end pipe 3.

[0027] This design ensures the coaxiality of the inner end pipe 1 and the outer end pipe 3 during thermal expansion and contraction, while allowing them to slide freely relative to each other in the axial direction to decouple the axial displacement constraints of the inner and outer pipes. This effectively solves the problem of flexible compensation for both axial and radial thermal expansion displacements in double-walled pipes.

[0028] Preferably, the guide slide plate 2 includes a support plate 9 welded to the inner end tube 1. The outer wall surface of the support plate 9 is provided with a groove 91 for limiting the assembly of the sliding piece 10. There are multiple grooves 91 and they are arranged at equal intervals along the outer periphery of the support plate 9.

[0029] This design utilizes grooves 91 to circumferentially and radially limit the sliding plates 10, ensuring they remain embedded within the predetermined track when the double-walled tube undergoes axial displacement due to thermal expansion and contraction, preventing circumferential movement or detachment due to vibration or friction. The evenly spaced sliding plates 10 ensure uniform distribution of support points for the inner end tube 1 and outer end tube 3, effectively absorbing and buffering vibration energy to prevent increased gaps or impact noise caused by vibration. The number of grooves 91 can be adjusted according to the pressure of the internal medium and the diameter of the double-walled tube, preferably 8-12.

[0030] As an example, the sliding plate 10 extends along the length direction of the inner end tube 1 and has a length and width of L1 and L2 respectively, wherein L1 = (1.05-1.10) × L2, and the thickness of the support plate 9 is D, wherein L1 = (0.7-0.9) × D.

[0031] Since the support plate 9 is usually an annular plate, its thickness D represents the material's stiffness reserve. Limiting L1 to 0.7 to 0.9 times D effectively ensures the overall structural strength of the support plate and prevents it from breaking due to excessively wide slots. It also maximizes the contact area of ​​the sliding piece 10, ensuring the stability of the sliding contact between them. Since the length L1 is only 5% to 10% larger than the width L2, the circumferential dimension of the sliding piece 10 is strictly limited so that its long side is arranged along the pipe axis when embedded in the groove 91. This effectively prevents the sliding piece 10 from rotating or tilting under circumferential stress. Since double-walled pipes often have a slight angular deflection at the same time as axial displacement during thermal expansion and contraction, this setting allows the sliding piece to have good mobility in both the axial and radial (circumferential) directions, making it less prone to jamming due to uneven stress caused by installation deviations or thermal deformation.

[0032] Preferably, the single-sided distance between the outer diameter of the support plate 9 and the inner diameter of the outer end pipe 3 is 1-2 mm. This arrangement allows the outer and inner pipes of the double-walled pipeline to undergo tensile or compressive compensation based on the actual temperature difference with the environment, rather than only compressing or stretching in one direction. This minimizes the temperature difference stress between the inner and outer pipes, ensuring the long-term safe operation of the double-walled pipeline system. By adding a sliding structure, the relative radial displacement of the inner bellows 4 and the outer bellows 5 can be controlled. Without affecting the tensile or compressive deformation of the inner bellows 4 and the outer bellows 5, the concentricity of the double-walled pipes can be maximized, thereby indirectly reducing the bending or shear stress of the circumferential weld caused by their misalignment, ensuring the long-term safe operation of the double-walled pipeline system.

[0033] Preferably, the minimum distance between the guide slide plate 2 and the inner bellows 4 is 80-120mm. This setting ensures that the inner bellows 4 can freely expand within its elastic limit, while the guide slide plate 2 can smoothly take over and guide subsequent linear motion, providing sufficient buffer margin for the axial compression, tension, and radial / angular deflection of the inner bellows 4; and providing sufficient radial and axial operating clearance for subsequent welding operations, reducing assembly difficulty.

[0034] Preferably, the sliding plate 10 is a PTFE sliding plate. Because PTFE material has an extremely wide temperature tolerance range and does not become brittle at low temperatures, it ensures that the sliding plate maintains good low-friction characteristics in extreme cryogenic environments, allowing the inner and outer tubes to slide freely and smoothly relative to each other to release thermal stress; it can effectively resist media leakage or external environmental corrosion, and at the same time absorb the energy brought by high-frequency vibration to buffer and dampen shocks, extending the service life of the product.

[0035] As an example, there are two inner end tubes 1, located at both ends of the inner bellows 4, and two outer end tubes 3, located at both ends of the outer bellows 5. This arrangement ensures that the inner bellows 4 and outer bellows 5 only undergo axial deformation to effectively avoid bending fatigue, while also attenuating vibrations from equipment such as engines, resulting in a long service life.

[0036] Preferably, the inner tube assembly includes an inner intermediate tube 6, and there are two inner corrugated tubes 4 located on both sides of the inner intermediate tube 6; the outer tube assembly includes an outer intermediate tube 7, and there are two outer corrugated tubes 5 located on both sides of the outer intermediate tube 7; the inner intermediate tube 6 is provided with a guide plate 2, the guide plate 2 is annular and has a groove on its outer circumference, and a sliding piece 10 is provided in the groove, the sliding piece 10 abutting against the outer intermediate tube 7.

[0037] This setting can forcibly constrain the relative posture of the inner tube assembly and the outer tube assembly, ensuring that they always maintain a very high coaxiality under any thermal deformation state, avoiding jamming caused by eccentric friction; at the same time, it can effectively absorb and offset lateral loads, ensuring that the inner bellows 4 and the outer bellows 5 only bear pure axial stress, thus significantly extending their service life.

[0038] As an example, the double-walled pipe temperature difference stress compensation device also includes a flow guide tube 8, which is disposed between the inner end pipe 1 and the inner middle pipe 6 to protect the inner corrugated pipe 4 from the impact of the medium.

[0039] This design utilizes the guide tube 8 as a protective barrier between the medium and the inner bellows 4 to guide the medium to pass smoothly, avoiding direct impact of high-speed medium on the inner bellows 4, and significantly extending the service life of the entire compensation structure; at the same time, it restricts the disorderly flow of the medium at the inner bellows 4 to reduce pressure loss during transportation and improve the overall transportation efficiency of the pipeline system.

[0040] As an example of the present invention, there are two guide tubes 8, which are respectively located on both sides of the inner intermediate tube 6; wherein one end of the guide tube 8 located at the upstream end is welded to the inner end tube 1, and the other end abuts against the inner intermediate tube 6; one end of the guide tube 8 located at the downstream end abuts against the inner end tube 1, and the other end is welded to the inner intermediate tube 6.

[0041] This design provides ample axial sliding space for the guide tube 8. Regardless of thermal expansion and contraction of the pipeline, the guide tube 8 can adapt to length changes through relative sliding at the contact end, thereby relieving the axial force on the guide tube 8 itself. This ensures that the medium is always confined to the surface of the guide tube 8 and flows smoothly, effectively preventing the inner bellows 4 from being impacted by fluid eddies and mechanically worn. It also ensures that the guide tube 8 and the inner intermediate pipe 6 always maintain extremely high coaxiality, thus enhancing the bending rigidity and operational stability of the entire compensation structure.

[0042] The present invention also discloses an assembly method for the temperature difference stress compensation device for double-walled pipes, comprising:

[0043] Step S1: Weld the guide slide plate 2 to the outer circumference of the inner end tube 1 and the inner middle tube 6, and embed the sliding piece 10 into the groove 91 to form the guide slide plate 2; Step S2: Weld the inner end tube 1 to the inner bellows 4, connect the inner middle tube 6 between the two inner bellows 4, and install the guide tube 8 between the inner end tube 1 and the inner middle tube 6.

[0044] Step S3: Coaxially sleeve the outer end tube 3 around the outside of the inner tube assembly, connect the outer middle tube 7 between the two outer corrugated tubes 5 and sleeve it around the outside of the inner middle tube 6, and weld the outer corrugated tube 5 to the outer end tube 3.

[0045] The inner end pipe 1 of the double-walled pipe thermal stress compensation device is welded to the double-arm pipeline system, and the outer end pipe 3 is welded to the external protective pipeline or equipment shell.

[0046] This invention also discloses the application of the aforementioned double-walled pipe thermal stress compensation device in a ship dual-fuel gas supply system. This invention can be applied to double-walled pipe systems in dual-fuel powered ships and in the transportation of cryogenic media such as liquid hydrogen, liquid oxygen, and LNG; it can solve the problems of thermal expansion stress release and vibration absorption in double-walled pipes with limited space and dimensions, and eliminates the problem of uneven deformation of the inner and outer corrugated pipes caused by uneven thermal expansion deformation of the inner and outer pipes in double-walled pipes. It can significantly reduce the risk of excessive deformation of one of the inner or outer corrugated pipes and extend its service life.

[0047] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A temperature difference stress compensation device for a double-walled pipe, comprising an inner pipe assembly and an outer pipe assembly, wherein the inner pipe assembly includes a connected inner end pipe (1) and an inner corrugated pipe (4), and the outer pipe assembly is coaxially sleeved outside the inner pipe assembly and includes a connected outer end pipe (3) and an outer corrugated pipe (5), characterized in that, The outer circumferential surface of the inner end tube (1) is provided with an annular guide plate (2), and the outer wall surface of the guide plate (2) is embedded with a sliding piece (10), which abuts against the outer end tube (3).

2. The thermal stress compensation device for double-walled pipes according to claim 1, characterized in that, The guide slide plate (2) includes a support plate (9) welded to the inner end tube (1). The outer wall surface of the support plate (9) is provided with grooves (91). There are multiple grooves (91) and they are arranged at equal intervals along the outer periphery of the support plate (9) for limiting the assembly of the sliding piece (10).

3. The thermal stress compensation device for double-walled pipes according to claim 2, characterized in that, The sliding plate (10) extends along the length direction of the inner end tube (1) and has a length and width of L1 and L2 respectively, wherein L1 = (1.05-1.10) × L2, and the thickness of the support plate (9) is D, wherein L1 = (0.7-0.9) × D.

4. The thermal stress compensation device for double-walled pipes according to claim 1, characterized in that, The distance between the outer wall of the guide slide plate (2) and the inner wall of the outer end tube (3) is 1-2 mm.

5. The thermal stress compensation device for double-walled pipes according to claim 4, characterized in that, The minimum distance between the guide slide plate (2) and the inner bellows (4) is 80-120mm.

6. The thermal stress compensation device for double-walled pipes according to claim 4 or 5, characterized in that, There are two inner end tubes (1) located at both ends of the inner corrugated tube (4), and there are two outer end tubes (3) located at both ends of the outer corrugated tube (5).

7. The thermal stress compensation device for double-walled pipes according to claim 1, characterized in that, The inner tube assembly includes an inner intermediate tube (6), and there are two inner corrugated tubes (4) located on both sides of the inner intermediate tube (6); the outer tube assembly includes an outer intermediate tube (7), and there are two outer corrugated tubes (5) located on both sides of the outer intermediate tube (7). The inner intermediate tube (6) is provided with a guide plate (2), which is annular and has a groove on its outer circumference. A sliding piece (10) is provided in the groove, and the sliding piece (10) abuts against the outer intermediate tube (7).

8. The thermal stress compensation device for double-walled pipes according to claim 7, characterized in that, The double-walled pipe temperature difference stress compensation device also includes a flow guide tube (8), which is set between the inner end pipe (1) and the inner middle pipe (6) to protect the inner corrugated pipe (4) from the impact of the medium.

9. The application of the double-walled tube thermal stress compensation device according to any one of claims 1-8 in a ship dual-fuel gas supply system.

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