Insulated containment structure for LNG membrane tanks

Abstract

The application belongs to the technical field of low-temperature liquefied gas storage and transportation, and relates to an adiabatic shielding structure of an LNG film tank, which comprises an adiabatic module and a shielding film, the shielding film is provided with a corrugated part protruding towards the adiabatic module, the adiabatic module is provided with an avoiding groove on the side facing the shielding film, and the adiabatic module further comprises a reinforcing block assembled in the avoiding groove, and the supporting strength of the reinforcing block is greater than that of the adiabatic module; the reinforcing block has a proximal end close to the shielding film and a distal end away from the shielding film, the proximal end is provided with an adaptive groove, and the corrugated part is accommodated in the adaptive groove; the proximal end is fixed with the adiabatic module, and the distal end has a gap with the groove bottom of the avoiding groove; the side wall of the reinforcing block is arranged in close contact with the side groove wall of the avoiding groove, and a freedom degree allowing the reinforcing block to slide relative to the adiabatic module is arranged between the side wall and the side groove wall. The application disperses and transmits loads through the reinforcing block, compensates for the difference in thermal expansion in the vertical direction by means of the gap, so as to protect the adiabatic module and the shielding film and maintain the sealing function of the tank body.

Description

Technical Field

[0001] This invention relates to the field of cryogenic liquefied gas storage and transportation technology, and in particular to an insulation shielding structure for an LNG membrane tank. Background Technology

[0002] LNG membrane tanks store and transport liquefied natural gas at ultra-low temperatures of approximately -162°C. The tank body employs a multi-layered composite structure, consisting of a secondary insulation module, a secondary shielding layer, a primary insulation module, and a primary shielding layer, from the outside in. To accommodate thermal expansion and contraction under cryogenic conditions and hull deformation, the primary and secondary shielding layers utilize corrugated metal membrane plate structures. The corrugations absorb contraction deformation caused by temperature changes and bending deformation of the hull beams in waves, thereby preventing the shielding layers from being damaged by excessive stretching or compression.

[0003] In existing designs of LNG membrane tanks, the main insulation module is typically made of polyurethane foam board or plywood. Because the secondary shielding layer has corrugations protruding towards the main insulation module, corresponding clearance grooves need to be created on the main insulation module to accommodate these corrugations. These clearance grooves are empty, meaning the overall load is not effectively supported at these points. When the LNG tank is subjected to loads from liquid weight, hull deformation, and temperature fluctuations, the load concentrates on the inner sidewall of the clearance groove, especially at the junction of the sidewall and top wall. This junction experiences stress concentration due to geometric abrupt changes, becoming a weak point in the structure. After long-term operation, the groove wall is prone to fatigue failure, leading to damage to the secondary shielding layer in that area. Since the secondary shielding layer is a metal membrane sheet, its damage directly affects the tank's sealing function and, in severe cases, even jeopardizes the safety of the entire tank structure. Summary of the Invention

[0004] Therefore, the present invention provides a thermal insulation shielding structure for an LNG membrane tank. By reinforcing blocks to disperse and transfer loads, gaps are used to compensate for differences in thermal expansion in the vertical direction, and the thermal stress in the horizontal direction is released through sliding degrees of freedom, thereby protecting the thermal insulation module and the shielding membrane and maintaining the sealing function of the tank.

[0005] To solve the above technical problems, the present invention provides a heat insulation shielding structure for an LNG membrane tank, comprising a heat insulation module and a shielding membrane stacked together, wherein the shielding membrane has corrugated portions protruding toward the heat insulation module, the heat insulation module has a relief groove on the side facing the shielding membrane, and further comprises a reinforcing block, wherein the reinforcing block is assembled in the relief groove.

[0006] The supporting strength of the reinforcing block is greater than that of the thermal insulation module;

[0007] The reinforcing block has a proximal end and a distal end, with the proximal end close to the shielding film; the proximal end is provided with an adapter groove, and the corrugated portion is received within the adapter groove;

[0008] When the reinforcing block is assembled into the clearance groove, the proximal end is fixed to the heat insulation module, and there is a gap between the distal end and the bottom of the clearance groove.

[0009] When the reinforcing block is assembled into the clearance groove, the side wall of the reinforcing block is fitted to the side wall of the clearance groove, and there is a degree of freedom between the side wall and the side wall that allows the reinforcing block to slide relative to the insulation module.

[0010] Preferably, the width of the gap is related to the coefficient of thermal expansion of both the reinforcing block and the insulation module, and the width of the gap is not less than the difference between the shrinkage of the reinforcing block and the insulation module under extreme low temperature conditions.

[0011] Preferably, the gap width is determined in the following manner:

[0012] ;

[0013] ;

[0014] ;

[0015] , and These are the gap width, minimum width, and maximum width, respectively. and The coefficients of thermal expansion of the insulation module and the reinforcing block are respectively. ; Δ represents the absolute value of the temperature difference from room temperature to extreme low temperature conditions; H represents the depth of the clearance groove; and Δ represents the sum of assembly tolerance and manufacturing tolerance.

[0016] Preferably, the insulation module is made of polyurethane; the reinforcing block is made of plywood or high-density polyurethane.

[0017] Preferably, the heat insulation module has a reinforcing layer on the side facing the shielding film, the reinforcing layer is fixed to the heat insulation module, and the proximal end of the reinforcing block is fixed to the reinforcing layer.

[0018] Preferably, the supporting strength of the reinforcing layer is greater than the supporting strength of the insulation module.

[0019] Preferably, the proximal end of the reinforcing block is fixed to the reinforcing layer by means of adhesive bonding, screwing, or snap-fit ​​connection.

[0020] Preferably, the reinforcing block is constructed as an arch bridge-shaped structure that utilizes the principle of an arch bridge to distribute the load.

[0021] Preferably, the sidewall of the adapter groove is an inclined surface that slopes inward from the proximal end to the distal end into the groove.

[0022] Preferably, the cross-section of the adapter groove is trapezoidal, circular, or elliptical.

[0023] The thermal insulation shielding structure for the LNG membrane tank described in this invention, by setting reinforcing blocks to protect the thermal insulation module and the shielding membrane, has the following advantages compared to the prior art:

[0024] Firstly, reinforcing blocks are installed within the original empty channel structure of the clearance channel. Since the supporting strength of the reinforcing blocks is greater than that of the insulation modules, when the overall load is applied to the clearance channel area, the load is no longer borne solely by the empty channel wall, but is supported and transferred through the reinforcing blocks. As the main load-bearing component, the reinforcing blocks transfer the load to the insulation modules through their near-end fixed connections. Simultaneously, the lateral load is dispersed and transferred to the surrounding structure of the clearance channel through the fit between the sidewalls and the side channel walls. This avoids concentrated load application on the inner sidewalls of the clearance channel, especially avoiding stress concentration at the connection between the sidewalls and the top wall. This change in the mechanical path fundamentally eliminates the risk of preferential failure of the clearance channel walls, thereby protecting the shielding membrane located in this area and maintaining the sealing function of the tank.

[0025] Secondly, by leaving a gap between the far end of the reinforcing block and the bottom of the relief groove, the gap between the bottom of the relief groove and the far end of the reinforcing block gradually decreases but does not disappear during the cooling process, thereby avoiding interference and compressive stress damage caused by the difference in thermal expansion coefficients.

[0026] Third, the reinforcing block sidewall and the relief groove sidewall are fitted together with a degree of freedom that allows for relative sliding. This fitted arrangement ensures that lateral loads can be effectively transferred through the contact surface, allowing the reinforcing block to distribute the load to the relief groove sidewall when subjected to lateral forces, thus maintaining the overall stability of the structure. The allowance for relative sliding allows the reinforcing block and the insulation module to freely expand and contract in the horizontal direction, avoiding shear stress at the interface due to inconsistent horizontal contraction. If a rigid connection is used between the sidewall and the side groove wall, the difference in contraction during cooling will generate shear force at the connection interface, leading to interface tearing or material failure. By retaining the degree of sliding freedom, thermal stress at the interface is released, significantly improving the reliability of the structure under extreme temperature alternation conditions. Attached Figure Description

[0027] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0028] Figure 1 This is a three-dimensional schematic diagram of the thermal insulation shielding structure of the LNG membrane tank in an embodiment of the present invention;

[0029] Figure 2 yes Figure 1 The front view of the thermal shielding structure of the LNG membrane tank shown.

[0030] Figure 3 yes Figure 1 A schematic diagram of the reinforcing block in the thermal shielding structure of the LNG membrane tank shown.

[0031] Figure 4 yes Figure 3 The front view of the reinforced block shown;

[0032] Figure 5 yes Figure 2 The diagram shows the structure of the LNG membrane tank with the reinforcing blocks hidden in the thermal insulation shielding structure.

[0033] 2. Insulation module; 21. Clearance groove; 211. Groove bottom; 212. Side groove wall;

[0034] 4. Shielding film; 41. Corrugated section;

[0035] 6. Reinforcing block; 61. Proximal end; 62. Distal end; 63. Side wall; 64. Adaptor groove;

[0036] 8. Gap;

[0037] 10. Reinforcing layer. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0039] Reference Figures 1-2 As shown, this embodiment of the invention proposes a heat insulation shielding structure for an LNG membrane tank, including a heat insulation module 2 and a shielding membrane 4 stacked together; the shielding membrane 4 has a corrugated portion 41 protruding toward the heat insulation module 2, and the heat insulation module 2 has a relief groove 21 on the side facing the shielding membrane 4; the heat insulation shielding structure also includes a reinforcing block 6, which is assembled in the relief groove 21, and the supporting strength of the reinforcing block 6 is greater than the supporting strength of the heat insulation module 2.

[0040] Specifically, in this embodiment, the insulation module is the main insulation layer of the LNG membrane tank, which is made of polyurethane foam board. Polyurethane foam board has good insulation performance and a certain structural strength, which can provide support and insulation protection for the shielding membrane. The shielding membrane is the secondary shielding layer of the LNG membrane tank, which adopts a corrugated metal membrane plate structure, such as stainless steel, aluminum alloy or Invar alloy; the corrugated part 41 protrudes towards the insulation module 2 to absorb the shrinkage deformation caused by temperature changes and the bending deformation of the hull beam in waves.

[0041] like Figure 5 As shown, since the shielding film 4 has a corrugated portion 41 protruding towards the heat insulation module 2, the heat insulation module 2 needs to have a corresponding clearance groove 21 to accommodate the protruding corrugations of the shielding film 4. In this embodiment, the clearance groove 21 is a blind groove along the thickness direction of the heat insulation module 2, that is, the clearance groove 21 extends from the surface of the heat insulation module 2 facing the shielding film 4 into the interior of the heat insulation module 2.

[0042] The reinforcing block 6 is assembled within the clearance groove 21, and the supporting strength of the reinforcing block 6 is greater than that of the insulation module 2. Exemplarily, the reinforcing block 6 is made of plywood, which has high strength and rigidity, and its supporting strength is significantly greater than that of polyurethane foam board. In another embodiment, the reinforcing block can also be made of high-density polyurethane, which has a higher density and strength than ordinary polyurethane foam board, and can also provide superior supporting strength compared to the insulation module 2. The fact that the supporting strength of the reinforcing block 6 is greater than that of the insulation module 2 means that when the overall load is applied to the clearance groove 21 area, the load is mainly borne by the reinforcing block 6.

[0043] like Figure 3 and Figure 4 The reinforcing block 6 has a proximal end 61 and a distal end 62. The proximal end 61 is close to the shielding film 4, and the distal end 62 is away from the shielding film 4. The proximal end 61 is provided with an adapter groove 64, and the corrugated portion 41 is received within the adapter groove 64. In this embodiment, the adapter groove 64 is a blind groove, which is recessed from the surface of the proximal end 61 of the reinforcing block 6 into the interior of the reinforcing block 6. The depth H of the adapter groove 64 is greater than the height of the corrugated portion 41, so that the corrugated portion 41 can be completely received within the adapter groove 64. The width of the adapter groove 64 is also greater than the width of the corrugated portion 41, so that there is a deformation gap between the corrugated portion 41 and the inner wall of the adapter groove 64, supporting the deformation of the corrugated portion 41 under extreme low temperature conditions.

[0044] like Figure 3 , Figure 4 and Figure 5As shown, when the reinforcing block 6 is assembled into the clearance groove 21, the proximal end 61 is fixed to the thermal insulation module 2, and there is a gap between the distal end 62 and the bottom 211 of the clearance groove 21. In this embodiment, the proximal end 61 is fixed to the thermal insulation module 2 by adhesive bonding. Specifically, the surface of the proximal end 61 of the reinforcing block 6 is bonded to the surface of the thermal insulation module 2 facing the shielding film 4 by low-temperature adhesive. In another embodiment, the proximal end 61 can also be fixed to the thermal insulation module 2 by screwing or snap-fit ​​connection. There is a gap 8 between the distal end 62 and the bottom 211 of the clearance groove 21, which is used to absorb the deformation caused by the difference in the coefficient of thermal expansion between the reinforcing block 6 and the thermal insulation module 2.

[0045] Specifically, insulation module 2 is made of polyurethane foam, which has a relatively large coefficient of thermal expansion, typically around 60~90×10⁻⁶ at room temperature. -6 / Kelvin; Reinforcing block 6 is made of plywood, which has a low coefficient of thermal expansion, typically around 5~10×10 at room temperature. -6 / Kelvin. Due to the significant difference in their coefficients of thermal expansion, during the extreme low-temperature operation from room temperature to approximately -162°C, the shrinkage of the insulation module 2 along the depth direction of the relief groove 21 is greater than that of the reinforcing block 6. The bottom 211 of the relief groove 21 will move downwards further. If there is not a sufficient gap 8 between the distal end 62 and the bottom 211 at room temperature, the bottom 211 of the relief groove 21 will catch up with and press against the distal end 62 of the reinforcing block 6 after cooling, generating compressive stress and potentially leading to structural damage. By leaving a gap 8 between the distal end 62 and the bottom 211, the gap between the bottom 211 of the relief groove 21 and the distal end 62 of the reinforcing block 6 gradually decreases but does not disappear during the cooling process, thereby avoiding interference and compressive stress damage caused by the difference in thermal expansion coefficients.

[0046] like Figure 3 , Figure 4 and Figure 5 As shown, when the reinforcing block 6 is assembled into the clearance groove 21, the side wall 63 of the reinforcing block 6 is fitted against the side groove wall 212 of the clearance groove 21, and there is a degree of freedom between the side wall 63 and the side groove wall 212 that allows the reinforcing block 6 to slide relative to the insulation module 2. In this embodiment, the side wall 63 of the reinforcing block 6 and the side groove wall 212 of the clearance groove 21 are only fitted together. Fitting should be understood as: the two surfaces are in contact with each other and maintain normal contact pressure, but there is no adhesive, no mechanical locking, and no interference fit between the contact surfaces. This contact state is normal contact and tangential freedom.

[0047] It is understandable that the side wall 63 of the reinforcing block 6 contacts the side groove wall 212 of the clearance groove 21, and they are pressed against each other in the normal direction (perpendicular to the side wall 63 direction), so the lateral load can be transmitted through the contact surface; however, in the tangential direction (parallel to the side wall 63 direction), there is no constraint between the two, and when there is a difference in thermal expansion in the horizontal direction, the reinforcing block 6 can slide freely along the side wall surface.

[0048] The close fit between sidewall 63 and side groove wall 212 ensures that lateral loads can be effectively transferred through the contact surface, allowing the reinforcing block 6 to distribute the load to the side groove wall 212 of the relief groove 21 when subjected to lateral forces, thus maintaining the overall stability of the structure. Furthermore, the tangential freedom between the two allows the reinforcing block 6 and the insulation module 2 to freely expand and contract in the horizontal direction, avoiding shear stress at the interface due to inconsistent horizontal contraction. If a rigid connection were used between sidewall 63 and side groove wall 212, the difference in contraction during cooling would generate shear force at the connection interface, leading to interface tearing or material failure. By preserving sliding freedom, thermal stress at the interface is released, significantly improving the reliability of the structure under extreme temperature alternation conditions.

[0049] In this embodiment, as Figure 2 and Figure 5 As shown, the width of the gap 8 is related to the thermal expansion coefficients of both the reinforcing block 6 and the insulation module 2, and the gap width is not less than the difference in shrinkage between the reinforcing block 6 and the insulation module 2 under extreme low temperature conditions.

[0050] Specifically, the gap width is determined as follows:

[0051] ;

[0052] ;

[0053] ;

[0054] , and These are the gap width, minimum width, and maximum width, respectively. and The coefficients of thermal expansion of the insulation module and the reinforcing block are respectively. ; Δ represents the absolute value of the temperature difference from room temperature to extreme low temperature conditions; H represents the depth of the clearance groove; and Δ represents the sum of assembly tolerance and manufacturing tolerance.

[0055] The meanings of the above calculation methods are as follows: In the exemplary scheme, the insulation module 2 is made of polyurethane, which has a large coefficient of thermal expansion; the reinforcing block 6 is made of plywood or high-density polyurethane, which has a small coefficient of thermal expansion. During the extreme low-temperature operation from room temperature to -162℃, the shrinkage of the insulation module 2 along the depth direction of the relief groove 21 is greater than the shrinkage of the reinforcing block 6 along its height direction. The difference between the two shrinkage amounts is... The difference in shrinkage represents the reduction in the gap between the bottom of the clearance groove 21 and the distal end 62 of the reinforcing block 6 during the cooling process. If the gap reserved at room temperature is less than this reduction, the bottom of the clearance groove 21 will press against the distal end 62 of the reinforcing block 6 after cooling, generating compressive stress and potentially leading to structural damage. Therefore, The minimum gap width required to ensure that the gap does not disappear under extreme low temperature conditions. On the other hand, the gap width should not be too large, otherwise it will affect the positioning accuracy of the reinforcing block 6 in the relief groove 21 and the lateral support stability.

[0056] For example, Take 70×10 -6 Kelvin, Take 8×10 -6 Kelvin, If the value is 182 Kelvin and H is 50 mm, then... mm; taking the sum of assembly tolerance and manufacturing tolerance as 0.5 mm, then mm. Therefore, the gap width It should be set to 0.56mm~1.06mm. In actual assembly, the gap width is set to 0.8mm to ensure that the bottom of the relief groove 21 will not press against the far end of the reinforcing block 6 under extreme low temperature conditions, and to ensure that the reinforcing block 6 has sufficient positioning accuracy and support stability in the relief groove 21 at room temperature.

[0057] In another embodiment, such as Figure 1 As shown, a reinforcing layer 10 is provided on the side of the insulation module 2 facing the shielding film 4. The reinforcing layer 10 is fixed to the insulation module 2, and the proximal end 61 of the reinforcing block 6 is fixed to the reinforcing layer 10. In this embodiment, the reinforcing layer 10 is made of plywood, and its support strength is greater than that of the insulation module 2. The reinforcing layer 10 is fixed to the surface of the insulation module 2 facing the shielding film 4 by adhesive bonding. The reinforcing layer 10 is configured to provide local reinforcement to the side of the main insulation module facing the shielding film 4, so that the proximal end 61 of the reinforcing block 6 can be fixed to the stronger reinforcing layer 10, improving the reliability of the fixed connection. The proximal end 61 of the reinforcing block 6 is fixed to the reinforcing layer 10 by adhesive bonding, screwing, or snap-fit ​​connection.

[0058] In this embodiment, the reinforcing block 6 is constructed as an arch-shaped structure that utilizes the arch bridge principle to distribute loads. Specifically, the outer contour of the adapter groove 64 is arched, making the reinforcing block 6 form an arch-like structure. When a load is applied to the reinforcing block 6, the arched structure can convert the vertically downward pressure into a diagonal thrust along the arched sidewalls, thereby distributing the load to both sides and the bottom of the reinforcing block 6, preventing the load from concentrating in a localized area. The arch-shaped structure utilizes the arch bridge principle, that is, when an arched structure bears a vertical load, it can convert the load into compressive stress along the arch direction, thereby fully utilizing the compressive strength of the material and improving its load-bearing capacity.

[0059] Furthermore, the sidewalls of the adapter groove 64 are inclined surfaces that slope inward from the proximal end 61 to the distal end 62. In this embodiment, the cross-section of the adapter groove 64 is trapezoidal. The width of the groove opening of the adapter groove 64 is greater than the width of the groove bottom, that is, the adapter groove 64 gradually narrows from the groove opening to the groove bottom. Through the above-mentioned inclined setting, the outer contour of the adapter groove 64 is generally arched, so that the reinforcing block 6 is constructed as an arch bridge structure that distributes the load using the principle of an arch bridge. In addition, the cross-section of the adapter groove 64 is preferably trapezoidal, which helps to reduce the processing difficulty. In another embodiment, the cross-section of the adapter groove 64 can also be circular or elliptical, as long as it can make the outer contour of the adapter groove arched.

[0060] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A thermal insulation shielding structure for an LNG membrane tank, comprising a stacked thermal insulation module and a shielding membrane, wherein the shielding membrane has corrugated portions protruding toward the thermal insulation module, and the thermal insulation module has a clearance groove on the side facing the shielding membrane, characterized in that, It also includes a reinforcing block, which is assembled in the clearance groove; The supporting strength of the reinforcing block is greater than that of the thermal insulation module; The reinforcing block has a proximal end and a distal end, with the proximal end close to the shielding film; the proximal end is provided with an adapter groove, and the corrugated portion is received within the adapter groove; When the reinforcing block is assembled into the clearance groove, the proximal end is fixed to the heat insulation module, and there is a gap between the distal end and the bottom of the clearance groove. When the reinforcing block is assembled into the clearance groove, the side wall of the reinforcing block is fitted to the side wall of the clearance groove, and there is a degree of freedom between the side wall and the side wall that allows the reinforcing block to slide relative to the insulation module.

2. The thermal insulation shielding structure of the LNG membrane tank according to claim 1, characterized in that... The width of the gap is related to the coefficient of thermal expansion of both the reinforcing block and the insulation module, and the width of the gap is not less than the difference in shrinkage between the reinforcing block and the insulation module under extreme low temperature conditions.

3. The thermal insulation shielding structure of the LNG membrane tank according to claim 2, characterized in that... The gap width is determined as follows: ； ； ； , and These are the gap width, minimum width, and maximum width, respectively. and The coefficients of thermal expansion of the insulation module and the reinforcing block are respectively. ; Δ represents the absolute value of the temperature difference from room temperature to extreme low temperature conditions; H represents the depth of the clearance groove; and Δ represents the sum of assembly tolerance and manufacturing tolerance.

4. The thermal insulation shielding structure of the LNG membrane tank according to claim 2 or 3, characterized in that... The insulation module is made of polyurethane; the reinforcing block is made of plywood or high-density polyurethane.

5. The thermal insulation shielding structure of the LNG membrane tank according to claim 1, characterized in that... The insulation module has a reinforcing layer on the side facing the shielding film. The reinforcing layer is fixed to the insulation module, and the near end of the reinforcing block is fixed to the reinforcing layer.

6. The thermal insulation shielding structure of the LNG membrane tank according to claim 5, characterized in that... The supporting strength of the reinforcing layer is greater than that of the insulation module.

7. The thermal insulation shielding structure of the LNG membrane tank according to claim 5 or 6, characterized in that... The near end of the reinforcing block is fixed to the reinforcing layer by means of adhesive bonding, screwing, or snap-fit ​​connection.

8. The thermal insulation shielding structure of the LNG membrane tank according to claim 1, characterized in that: The reinforcing block is constructed as an arch bridge-shaped structure that utilizes the principle of arch bridges to distribute the load.

9. The thermal insulation shielding structure of the LNG membrane tank according to claim 8, characterized in that... The sidewall of the adapter groove is an inclined surface that slopes inward from the proximal end to the distal end.

10. The thermal insulation shielding structure of the LNG membrane tank according to claim 9, characterized in that... The cross-section of the adapter groove is trapezoidal, circular, or elliptical.

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