Planar arrangement of a membrane-type containment system and liquefied natural gas carrier

Abstract

This invention discloses a planar layout structure of a membrane-type enclosure system and a liquefied natural gas (LNG) carrier. From the outside in, it comprises a secondary insulation layer, a secondary shielding layer, a primary insulation layer, and a primary shielding layer. The secondary corrugated plate of the secondary shielding layer has first and second corrugations with a first wave spacing and perpendicular to each other. The primary corrugated plate of the primary shielding layer has third and fourth corrugations with a second wave spacing and perpendicular to each other. The first wave spacing is greater than the second wave spacing, and the peaks of the first and third corrugations, as well as the peaks of the second and fourth corrugations, do not coincide in the direction perpendicular to the corrugated plate surface. The offset is equal to half the greatest common factor of the two wave spacings. This invention, by offsetting the peak positions of the two corrugations, allows the stiffness weakness of one layer to be compensated by the other flat plate segment, achieving stiffness homogenization, avoiding simultaneous damage to both layers, and improving the fatigue life and redundancy reliability of the enclosure system.

Description

Technical Field

[0001] This invention relates to the field of cargo tank containment technology for liquefied natural gas (LNG) carriers, specifically to a planar layout structure of a membrane-type containment system and an LNG carrier. Background Technology

[0002] Existing membrane-type containment systems, from the cargo side to the hull side, consist of a primary shielding layer, a primary insulation layer, a secondary shielding layer, and a secondary insulation layer. Both the primary and secondary shielding layers employ a corrugated metal plate structure, with the corrugations designed to absorb thermal expansion and contraction caused by temperature changes.

[0003] In existing technologies, in the planar area of ​​an enclosure system, the main corrugations of the main shielding layer and the secondary corrugations of the secondary shielding layer typically either use the same wave pitch and are aligned in a direction perpendicular to the surface of the corrugated plate; or the main and secondary corrugations use different wave pitches, but the main corrugations start laying from the position aligned with the secondary corrugations, resulting in periodic alignment positions between the main and secondary corrugations. (Refer to...) Figure 1 As shown, in existing technologies, the crests of the main ripples and the crests of the secondary ripples always correspond on the same vertical line.

[0004] However, this alignment setup presents the following problems: the corrugation peaks are inherently weak points in the local structural stiffness. When the two corrugations are aligned, the peaks overlap at the same location, creating a "double flexible superposition," which leads to periodic stiffness abrupt changes along the corrugation extension direction. During the loading and unloading cycles of LNG carriers, the stress concentration at these stiffness abrupt changes is severe, easily triggering fatigue cracks and threatening the service life of the containment system.

[0005] Therefore, there is an urgent need for a membrane-type enclosure system that can improve stiffness distribution and disperse stress concentration. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the problems of abrupt stiffness changes, stress concentration, expansion joint overload, and easy crack penetration caused by the alignment of the corrugations of the primary and secondary shielding layers in existing membrane-type enclosure systems. The invention provides a planar arrangement structure for membrane-type enclosure systems that allows the peaks of the two corrugations to be staggered in the plane.

[0007] To address the aforementioned technical problems, this invention provides a planar layout structure for a membrane-type enclosure system, comprising, from the outside in: Secondary insulation layer, which is formed by splicing together secondary insulation boxes; The secondary shielding layer is formed by splicing together secondary corrugated plates. The secondary corrugated plates are provided with first and second corrugations that are perpendicular to each other. The first and second corrugations protrude toward the direction of the secondary insulation layer, and the first and second corrugations have the same first corrugation spacing. The main insulation layer is formed by splicing together main insulation boxes; The main shielding layer is formed by splicing together main corrugated plates. The main corrugated plates are provided with mutually perpendicular third and fourth corrugations. The third and fourth corrugations protrude toward the interior of the enclosure system, and the third and fourth corrugations have the same second wave spacing between them. The first wave spacing is greater than the second wave spacing, the first ripple is parallel to the third ripple, and the peaks of the first ripple and the third ripple do not coincide in the direction perpendicular to the plane of the main shielding layer, the second ripple is parallel to the fourth ripple, and the peaks of the second ripple and the fourth ripple do not coincide in the direction perpendicular to the plane of the main shielding layer.

[0008] Furthermore, the offset between the first and third corrugations and between the second and fourth corrugations in the direction perpendicular to the corrugation extension is equal to half the greatest common factor of the first and second corrugation spacing.

[0009] Furthermore, the ratio of the first wave spacing to the second wave spacing is 3:2.

[0010] Furthermore, the length and width of the secondary insulation box are equal to the length and width of the primary insulation box, and the height of the primary insulation box is less than or equal to the height of the secondary insulation box.

[0011] Furthermore, the length and width of the main insulation box are equal, and are the least common multiple of the first wave spacing and the second wave spacing.

[0012] Furthermore, a fixed anchor strip is installed at the center of the main insulation box and the secondary insulation box, and a sliding anchor strip is provided along the fixed anchor strip extending towards the edge of the main insulation box and the secondary insulation box. The apex of the main corrugated plate and the secondary corrugated plate is welded to the fixed anchor strip, and the side of the main corrugated plate and the secondary corrugated plate is welded to the sliding anchor strip or the fixed anchor strip.

[0013] Furthermore, the first wave spacing is 1.5 times the second wave spacing, the secondary insulation box and the main insulation box are square structures on the plane corresponding to the secondary insulation layer and the main insulation layer, the size of the secondary insulation box and the main insulation box is 3 times the second wave spacing, the third and fourth corrugations are set at the third quarter line of the main insulation box, the first and second corrugations are set at the quarter line near the edge of the secondary insulation box, and the vertex of the main insulation box is set at the center of the secondary insulation box.

[0014] Furthermore, an expansion joint is provided on the inner side of the main insulation box at the position corresponding to the third and fourth corrugations.

[0015] Furthermore, the orientation of the first corrugation and the second corrugation is reversed along the same corrugation extension direction at a position near the edge of the secondary corrugated plate to form a first small corrugation and a second small corrugation, and the main insulation layer is provided with receiving grooves corresponding to the first small corrugation and the second small corrugation.

[0016] Furthermore, the amplitude of the first ripple is smaller than the amplitude of the second ripple, and the amplitude of the third ripple is smaller than the amplitude of the fourth ripple.

[0017] The present invention also provides a liquefied natural gas carrier, including the planar arrangement structure of the above-described membrane-type enclosure system.

[0018] The beneficial effects of this invention are: 1. By setting different corrugation spacings for the primary and secondary shielding corrugated plates and staggering the two corrugations in a direction perpendicular to the corrugated plates, the corrugation peaks at the weakest point of one layer are precisely compensated by the flat plate segments at the strongest point of the other layer, thus avoiding the periodic stiffness abrupt changes in the prior art and effectively reducing stress concentration during the loading and unloading cycle of the enclosure system.

[0019] 2. The two layers of corrugated peaks are arranged alternately, and the stress concentration points are not on the same vertical line. When the main shielding layer develops a crack due to stress concentration at a certain corrugated peak, the secondary shielding layer is exactly the plane segment with strong stiffness at that position, which effectively improves the redundancy and reliability of the enclosure system.

[0020] 3. Because the crests of the secondary corrugations are staggered from those of the primary corrugations, the deformation of the secondary shielding layer at the corresponding position of the expansion joint is significantly reduced. The expansion joint only needs to bear the deformation of the primary shielding layer and is no longer overloaded, thus extending the fatigue life of the expansion joint.

[0021] 4. The side length of the main insulation box is taken as the least common multiple of the first wave spacing and the second wave spacing, so that the peak position relationship of the two layers of corrugations in each insulation box unit is kept in a staggered pattern, avoiding local alignment problems caused by mismatch between the box boundary and the corrugation period. Attached Figure Description

[0022] Figure 1 This is a prior art schematic diagram of the present invention; Figure 2 This is a schematic diagram of the overall structure of the present invention; Figure 3 This is an exploded view of the overall structure of the present invention; Figure 4 This is a schematic diagram of the misaligned structure of the present invention; Figure 5 This is a side view of the present invention.

[0023] Explanation of the labels in the diagram: 10. Secondary insulation layer; 11. Secondary insulation box; 12. Fixed anchor strip; 13. Sliding anchor strip; 20. Secondary shielding layer; 21. Secondary corrugated plate; 22. First corrugation; 23. Second corrugation; 24. First small corrugation; 25. Second small corrugation; 30. Main insulation layer; 31. Main insulation box; 32. Expansion joint; 40. Main shielding layer; 41. Main corrugated plate; 42. Third corrugation; 43. Fourth corrugation; P1, first wave spacing; P2, second wave spacing; d, offset amount. Detailed Implementation

[0024] 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.

[0025] like Figure 2 As shown, the membrane-type containment system of this embodiment includes, in sequence from the outside to the inside, a secondary insulation layer 10, a secondary shielding layer 20, a primary insulation layer 30, and a primary shielding layer 40, extending from the hull side to the cargo side. The containment system is entirely attached to the inner hull surface of the LNG carrier's cargo tank, used to isolate heat exchange between the LNG cargo and the hull structure, and to provide double-layer shielding to prevent cargo leakage.

[0026] Reference Figure 3 As shown, the secondary insulation layer 10 is formed by splicing multiple secondary insulation boxes 11, and is attached to the surface of the hull of the ship using resin putty and connectors to provide thermal insulation. In this embodiment, the thickness of the secondary insulation box 11 can be equal to or greater than the thickness of the main insulation box 31. The secondary insulation box 11 uses polyurethane foam as the base material, and plywood is set on both the inner and outer sides of the polyurethane foam to support the polyurethane, ensuring that the secondary insulation box 11 has sufficient strength. Furthermore, in this embodiment, the length and width of the secondary insulation box 11 are equal, and it has a square structure in plan. Anchoring strips for fixing the secondary shielding layer 20 are provided on the inner surface of the secondary insulation box 11 near the liquid cargo side.

[0027] The secondary shielding layer 20 is located on the surface of the secondary insulation layer 10 facing the liquid cargo side, and is formed by splicing multiple secondary corrugated plates 21. The secondary corrugated plates 21 are fixed to the surface of the secondary insulation box 11 facing the liquid cargo side by welding. (Refer to...) Figure 3 As shown, each secondary corrugated plate 21 has a first corrugation 22 and a second corrugation 23 that are perpendicular to each other, forming a two-dimensional cross-grid structure. The first corrugation 22 and the second corrugation 23 have the same first wave spacing P1, that is, the spacing between two adjacent corrugation peaks in the same direction is P1.

[0028] In this embodiment, the first corrugation 22 and the second corrugation 23 of the secondary corrugated plate 21 protrude towards the secondary insulation layer 10, that is, the protruding direction of the first corrugation 22 and the second corrugation 23 is away from the liquid cargo side and towards the secondary insulation layer 10. This orientation design makes the flat surface of the secondary corrugated plate 21 face the main insulation layer 30, and the protruding part of the corrugation is embedded in the surface of the secondary insulation layer 10, avoiding the need to open clearance grooves on the main insulation layer 30, which helps to maintain the integrity of the main insulation layer 30 and improve the strength and heat insulation effect of the main insulation layer 30. Furthermore, in order to facilitate welding between the secondary corrugated plates 21, the first corrugation 22 and the second corrugation 23 near the edge of the secondary corrugated plate 21 are flipped in opposite directions along the same corrugation extension direction to form the first small corrugation 24 and the second small corrugation 25, and receiving grooves corresponding to the first small corrugation 24 and the second small corrugation 25 are provided on the main insulation layer 30. Because the lengths of the first small corrugation 24 and the second small corrugation 25 are both relatively short, the size of the receiving groove on the main insulation layer 30 is small, and it will not affect the strength of the main insulation layer 30. At the same time, the presence of the first small corrugation 24 and the second small corrugation 25 blocks the passage formed between the first corrugation 22 and the second corrugation 23, thereby effectively blocking the convection of the protective gas filling the space between the main shielding layer 40 and the secondary shielding layer 20. The protective gas with a higher temperature at the top of the enclosure system will not continuously exchange heat with the protective gas with a lower temperature at the bottom of the enclosure system, thereby effectively reducing the evaporation of liquid cargo in the storage tank and thus reducing cargo loss.

[0029] Reference Figure 3 As shown, the main insulation layer 30 is located on the side of the secondary shielding layer 20 opposite to the secondary insulation layer 10, and is formed by splicing together multiple main insulation boxes 31. In this embodiment, the main insulation box 31 is also made of plywood sandwiching polyurethane foam. The height of the main insulation box 31 is less than or equal to the height of the secondary insulation box 11, and the main insulation box 31 has a square structure with equal length and width on the plane of the main shielding layer 40. Anchoring strips are also provided on the inner surface of the main insulation box 31 near the liquid cargo to fix the main shielding layer 40.

[0030] The main shielding layer 40 is located on the side of the main insulation layer 30 away from the secondary shielding layer 20. It is formed by splicing multiple main corrugated plates 41 and directly contacts the LNG cargo. The main shielding layer 40 is the first liquid-tight barrier of the containment system, and its sealing reliability is directly related to the safety of the LNG cargo.

[0031] like Figure 3As shown, each main corrugated plate 41 has mutually perpendicular third corrugations 42 and fourth corrugations 43, forming a two-dimensional intersecting grid structure. The third corrugations 42 and fourth corrugations 43 all have the same second wave spacing P2. The third corrugations 42 and fourth corrugations 43 of the main corrugated plate 41 bulge towards the interior of the enclosure system, i.e., the liquid cargo side, thereby avoiding the need for clearance grooves corresponding to the third corrugations 42 and fourth corrugations 43 on the main insulation layer 30. This improves the integrity of the main insulation layer 30 and ensures its strength and thermal insulation performance.

[0032] In this embodiment, since a primary insulation layer 30 provides insulation between the secondary corrugated plate 21 and the liquid cargo, the expansion and contraction of the secondary corrugated plate 21 is less than that of the primary corrugated plate 41. Therefore, the first corrugation spacing P1 is set to be greater than the second corrugation spacing P2. (Refer to...) Figure 4 As shown, during the installation of the enclosure system, the first corrugation 22 is parallel to the third corrugation 42, and the second corrugation 23 is parallel to the fourth corrugation 43. The crests of the first corrugation 22 and the third corrugation 42 do not coincide in the direction perpendicular to the plane of the main shielding layer 40, and the crests of the second corrugation 23 and the fourth corrugation 43 do not coincide in the direction perpendicular to the plane of the main shielding layer 40. That is, the two corrugations are staggered in the direction perpendicular to the surface of the corrugated plate.

[0033] Since the first wave spacing P1 and the second wave spacing P2 are both rational numbers, they must have a greatest common divisor G. Let P1 = p × G, P2 = q × G, where p and q are coprime, and G is the greatest common divisor. Let a peak of the first wave 22 be located at X1 = nP1, and a peak of the third wave 42 be located at X2 = mP2 + d (where d is the offset). When the peaks of the first wave 22 and the third wave 42 coincide, nP1 = mP2 + d, then the offset d = n × P1 - m × P2 (n and m are arbitrary integers). According to number theory, all possible values ​​of (n × P1 - m × P2) are exactly equal to all integer multiples of G (0, ±G, ±2G, ±3G…). Therefore, as long as there exists a misalignment d between the first ripple 22 and the third ripple 42 that is not an integer multiple of G, it can be guaranteed that the first ripple 22 and the third ripple 42 do not coincide in the direction perpendicular to the plane of the main shielding layer 40. Similarly, it can be guaranteed that the second ripple 23 and the fourth ripple 43 are misaligned.

[0034] Furthermore, in this embodiment, in order to facilitate the positioning of the secondary corrugated plate 21 and the main corrugated plate 41 during laying, and to avoid the misalignment effect being insignificant, the misalignment amount d between the first corrugation 22 and the third corrugation 42, and between the second corrugation 23 and the fourth corrugation 43 in the direction perpendicular to the corrugation extension is equal to 1 / 2 of the greatest common factor of the first corrugation spacing P1 and the second corrugation spacing P2.

[0035] Specifically, in this embodiment, the ratio of the first wave spacing P1 to the second wave spacing P2 is 3:2. This avoids both insufficient deformation margin between the primary and secondary shielding layers due to similar wave spacing and severe deformation inconsistency caused by excessively large gaps between the two layers, resulting in huge interlayer shear forces. This ratio creates a smooth gradient, preventing additional tensile and compressive stress on the interlayer insulation and bonding structure, and reducing the risk of debonding and insulation layer cracking. Furthermore, it avoids the 40° wave crest of the primary shielding layer being vertically aligned with the 20° wave crest of the secondary shielding layer, thus preventing the overlapping of the two corrugated protrusions during liquid cargo impacts and ship vibrations, which would lead to stress concentration and direct vertical transmission and amplification of impact loads. This disperses the load, preventing point-to-point stress superposition, weakening vibration transmission, and improving the film's fatigue life.

[0036] Reference Figure 3 As shown, the length and width of the secondary insulation box 11 are equal to those of the primary insulation box 31, meaning that the secondary insulation box 11 and the primary insulation box 31 have the same dimensions on the plane of the enclosure system. In the direction perpendicular to the plane of the enclosure system, the height of the primary insulation box 31 is less than or equal to the height of the secondary insulation box 11. Heat flow from the inner cryogenic liquid cargo sequentially through the primary shielding layer 40, the primary insulation layer 30, the secondary shielding layer 20, and the secondary insulation layer 10 to the hull shell. The thicker secondary insulation layer 10 serves as the final thermal insulation barrier for the hull steel structure, effectively raising the temperature of the inner shell plates and mitigating the risk of cryogenic brittle fracture. The relatively thin primary insulation layer 30 allows for a reasonable interlayer space between the primary and secondary shields, facilitating the flow of tracer gas and improving leak detection sensitivity. Simultaneously, it smooths the radial temperature gradient of the enclosure system, reduces the deformation difference between the primary and secondary shielding layers 20, and lowers the risk of insulation module debonding. In the event of a leak in the shielding layer, the thicker secondary insulation layer 10 can further buffer the transfer of cold energy and enhance the safety redundancy of the enclosure system.

[0037] Furthermore, the main insulation box 31 and the secondary insulation box 11 are square structures with equal length and width. The vertex of the main insulation box 31 corresponds to the center of the secondary insulation box 11, meaning the main insulation box 31 is offset by half a grid relative to the secondary insulation box 11 on the plane. This ensures that the seams of the two insulation layers are not in the same position, avoiding localized degradation of insulation performance and the accumulation of structural weak points caused by overlapping seams. Simultaneously, combined with the offset amount d of the corrugations, it ensures that the peaks of the two corrugations are naturally offset in both directions, eliminating the need for additional alignment adjustments during installation. Specifically, the side length of the square structure of the main insulation box 31 and the secondary insulation box 11 is the least common multiple of the first wave spacing P1 and the second wave spacing P2, meaning the length and width of the main insulation box 31 and the secondary insulation box 11 are the least common multiple of the first wave spacing P1 and the second wave spacing P2. This arrangement allows a single insulation box to accommodate an integer number of corrugations of the main shielding layer 40 and the secondary shielding layer 20. The corrugations can continuously penetrate the insulation box, preventing stress concentration caused by the transverse corrugations at the joints of the insulation box.

[0038] Reference Figure 5 As shown, in the specific arrangement of this embodiment: The first wave spacing P1 is 1.5 times the second wave spacing P2. Taking a first wave spacing P1 of 300mm and a second wave spacing P2 of 200mm as an example, the secondary insulation box 11 and the main insulation box 31 are square structures on the plane of the corresponding enclosure system. The length and width of the secondary insulation box 11 and the main insulation box 31 are 3 times the second wave spacing P2 and 2 times the first wave spacing P1, i.e., 600mm. The third corrugation 42 and the fourth corrugation 43 correspond to the main insulation box 31. The third corrugation 42 and the fourth corrugation 43 are set at the third-third line, that is, on the main insulation box 31 with a side length of 600mm, with the side of the main insulation box 31 as the starting point, the peaks of the third corrugation 42 and the fourth corrugation 43 are located at 200mm and 400mm respectively; the first corrugation 22 and the second corrugation 23 are set at the quarter line near the edge on the secondary insulation box 11, that is, on the secondary insulation box 11 with a side length of 600mm, the peaks of the first corrugation 22 and the second corrugation 23 are located at 150mm and 450mm respectively.

[0039] The positional difference between the peaks of the two corrugations is 200−150 = 50mm and 450−400 = 50mm, which is exactly equal to the offset d, verifying the correctness of the above arrangement.

[0040] like Figure 3As shown, fixed anchor bars 12 are installed at the center of the main insulation box 31 and the secondary insulation box 11, and sliding anchor bars 13 are provided along the direction of the fixed anchor bars 12 extending towards the edge of the insulation box. The sliding anchor bars 13 extend from the center of the insulation box to the four sides, forming an anchoring grid inside the insulation box together with the fixed anchor bars 12. The apexes of the main corrugated plate 41 and the secondary corrugated plate 21 are welded to the fixed anchor bars 12 to fix the corrugated plates in the center of the insulation box. The weld at the fixed anchor bars 12 is a rigid connection, and the corrugated plates cannot slide relative to each other at this position, ensuring the stability of the apex position of the corrugated plates. The sides of the main corrugated plate 41 and the secondary corrugated plate 21 are welded to the sliding anchor bars 13 or the fixed anchor bars 12. Specifically, when the main corrugated plate 41 and the secondary corrugated plate 21 are of similar size to the main insulation box 31 and the secondary insulation box 11, the sides of the main corrugated plate 41 and the secondary corrugated plate 21 are welded to the sliding anchor strip 13, allowing the corrugated plate to slide relative to each other along the direction of the sliding anchor strip 13 when the temperature deforms. This allows the corrugated plate to expand and elongate along the direction of the sliding anchor strip 13 when the temperature rises and to contract when the temperature falls, avoiding additional stress at the weld due to excessive constraint. When the main corrugated plate 41 and the secondary corrugated plate 21 are multiples of the size of the main insulation box 31 and the secondary insulation box 11, the center of the side of the main corrugated plate 41 and the secondary corrugated plate 21 is welded to the fixed anchor strip 12, and the other positions on the side are welded to the sliding anchor strip 13, which ensures the fixed position of the corrugated plate and avoids excessive constraint on the corrugated plate. The design principle of the anchoring system is "fixed at the center and sliding at the edge": the fixed anchor strip 12 is located at the center of the insulation box, which is the center of symmetry of the corrugated plate deformation. Fixing it at this point can ensure the symmetry of the deformation of the corrugated plate in all directions; the sliding anchor strip 13 is located in the direction from the center to the edge, allowing the corrugated plate to freely expand and contract in this direction, so that the temperature deformation is evenly distributed from the center to the edge, and the deformation is avoided from accumulating in a certain direction.

[0041] like Figure 3 As shown, an expansion joint 32 is provided on the inner side of the main insulation box 31, i.e., on the side facing the main shielding layer 40, corresponding to the crest positions of the third corrugation 42 and the fourth corrugation 43. The expansion joint 32 is a gap opened on the surface of the insulation box along the direction perpendicular to the corrugation extension, with a gap width of 2~5mm and a depth penetrating the surface layer of the insulation box on the side facing the main shielding layer 40. When the temperature change of the LNG liquid cargo causes the main corrugated plate 41 to expand and contract thermally, the third corrugation 42 and the fourth corrugation 43 undergo tensile or compressive deformation at the crest positions. If the main insulation layer 30 is a continuous seamless structure at this position, the deformation of the corrugations will be constrained by the insulation layer, generating shear stress at the contact surface between the main corrugated plate 41 and the main insulation layer 30. The expansion joint 32 provides a deformable gap at the peak of the corrugations in the main insulation layer 30. When the corrugations are stretched, the width of the expansion joint 32 increases, and when the corrugations are compressed, the width of the expansion joint 32 decreases, thereby absorbing the deformation of the corrugations, reducing the shear stress on the contact surface, and making the overall stress more uniform.

[0042] Because the corrugated peaks of the secondary shielding layer 20 are offset from those of the primary shielding layer 40, the corresponding position of the secondary shielding layer 20 at the expansion joint 32 is precisely the non-corrugated peak position of the secondary shielding layer 20. The deformation of the secondary shielding layer 20 at this position is mainly contributed by the uniform expansion and contraction of the entire panel, which is much smaller than the local deformation of the corrugated peak position. Therefore, the expansion joint 32 only needs to absorb the deformation of the corrugations of the primary shielding layer 40, and will not exceed the design deformation margin due to the superposition of the deformation of the two layers of corrugations, effectively extending the fatigue life of the expansion joint 32.

[0043] In this embodiment, the amplitude of the first corrugation 22 is smaller than that of the second corrugation 23, and the amplitude of the third corrugation 42 is smaller than that of the fourth corrugation 43. That is, in each layer of corrugated sheet, the two corrugations perpendicular to each other use different amplitudes. This is because the deformation of the containment system differs in different directions. LNG carrier cargo tanks are typically hull-shaped structures, with their length dimension greater than their width dimension. When the temperature changes at the same rate, the absolute thermal expansion and contraction deformation in the longitudinal direction is greater than that in the transverse direction. Therefore, the second corrugation 23 and the fourth corrugation 43, extending longitudinally, are given larger amplitudes to provide greater deformation absorption capacity; the first corrugation 22 and the third corrugation 42, extending transversely, are given smaller amplitudes to reduce the corrugation height while meeting the transverse deformation requirements, thus reducing the difficulty of corrugated sheet forming.

[0044] In this embodiment, the amplitude of the first ripple 22 and the third ripple 42 is 8 mm, and the amplitude of the second ripple 23 and the fourth ripple 43 is 12 mm.

[0045] During operation, LNG carriers experience temperature variations in their cargo tanks, ranging from approximately 20°C ambient temperature to approximately -163°C LNG temperature, a difference of about 183°C. During loading and unloading cycles, the cargo tanks also undergo multiple temperature fluctuations.

[0046] In existing technologies, the deformation of both corrugated layers is concentrated at the corrugation peaks, where the total deformation is approximately twice that of a single layer. Simultaneously, the expansion joint 32 is also located at this point, needing to absorb the deformation of both layers, easily exceeding the design allowance. In this invention, the corrugation peaks of the secondary shielding layer 20 are offset from those of the primary shielding layer 40. At the corrugation peak of the primary shielding layer 40, the secondary shielding layer 20 is precisely a flat plate segment, and its deformation is only the elastic deformation of the uniform expansion and contraction of the panel, far less than the local deformation at the corrugation peak. Therefore, the total deformation at this point is approximately equal to the deformation of a single layer, the deformation burden of the expansion joint 32 is halved, and the stress concentration is significantly reduced.

[0047] The manufacturing and assembly process of the membrane-type enclosure system in this embodiment is as follows: Step 1: Install the secondary insulation box 11 on the surface of the hull. The secondary insulation box 11 is fixed to the hull by resin putty and bolts, and the boxes are spliced ​​together to form a continuous secondary insulation layer 10. During installation, it is necessary to ensure the flatness of the box surface and the sealing of the splice seams.

[0048] Step 2: Lay the secondary corrugated plate 21 on the surface of the secondary insulation box 11, with the corrugated protrusions facing the secondary insulation layer 10. The apex of the secondary corrugated plate 21 is welded to the fixed anchor strip 12 on the secondary insulation box 11, and the side is welded to the sliding anchor strip 13 or the fixed anchor strip 12.

[0049] Step 3: Install the main insulation box 31 on the secondary shielding layer 20. The main insulation box 31 is staggered by half a grid relative to the secondary insulation box 11, that is, the vertex of the main insulation box 31 corresponds to the center of the secondary insulation box 11.

[0050] Step 4: Lay the main corrugated plate 41 on the surface of the main insulation box 31, with the corrugated protrusions facing the liquid cargo side. The apex of the main corrugated plate 41 is welded to the fixed anchor strip 12, and the side is welded to the sliding anchor strip 13 or the fixed anchor strip 12.

[0051] Step 5: Conduct a sealing test on all welds, including helium mass spectrometry leak detection and visual inspection, to ensure that the liquid tightness of the main shielding layer 40 and the secondary shielding layer 20 meets the design requirements.

[0052] The membrane-type containment system of the present invention can be applied to the liquid cargo tanks of liquefied natural gas (LNG) carriers. Furthermore, the containment system of the present invention can also be applied to other scenarios requiring the storage and transportation of cryogenic liquid cargoes, such as liquefied ethylene carriers and liquid hydrogen storage tanks.

[0053] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A planar layout structure for a membrane-type enclosure system, characterized in that, From the outside in, the following are included: Secondary insulation layer, which is formed by splicing together secondary insulation boxes; The secondary shielding layer is formed by splicing together secondary corrugated plates. The secondary corrugated plates are provided with first and second corrugations that are perpendicular to each other. The first and second corrugations protrude toward the direction of the secondary insulation layer, and the first and second corrugations have the same first corrugation spacing. The main insulation layer is formed by splicing together main insulation boxes; The main shielding layer is formed by splicing together main corrugated plates. The main corrugated plates are provided with mutually perpendicular third and fourth corrugations. The third and fourth corrugations protrude toward the interior of the enclosure system, and the third and fourth corrugations have the same second wave spacing between them. The first wave spacing is greater than the second wave spacing, the first ripple is parallel to the third ripple, and the peaks of the first ripple and the third ripple do not coincide in the direction perpendicular to the plane of the main shielding layer, the second ripple is parallel to the fourth ripple, and the peaks of the second ripple and the fourth ripple do not coincide in the direction perpendicular to the plane of the main shielding layer.

2. The planar layout structure of the membrane-type enclosure system according to claim 1, characterized in that: The offset between the first ripple and the third ripple, and between the second ripple and the fourth ripple, in the direction perpendicular to the ripple extension is equal to 1 / 2 of the greatest common factor of the first ripple spacing and the second ripple spacing.

3. The planar layout structure of the membrane-type enclosure system according to claim 1, characterized in that: The ratio of the first wave spacing to the second wave spacing is 3:

2.

4. The planar layout structure of the membrane-type enclosure system according to claim 1, characterized in that: The length and width of the secondary insulation box are equal to the length and width of the primary insulation box, and the height of the primary insulation box is less than or equal to the height of the secondary insulation box.

5. The planar layout structure of the membrane-type enclosure system according to claim 4, characterized in that: The length and width of the main insulation box are equal, and are the least common multiple of the first wave spacing and the second wave spacing.

6. The planar layout structure of the membrane-type enclosure system according to claim 1 or 5, characterized in that: A fixed anchor strip is installed at the center of the main insulation box and the secondary insulation box. A sliding anchor strip is provided along the fixed anchor strip extending towards the edge of the main insulation box and the secondary insulation box. The apex of the main corrugated plate and the secondary corrugated plate is welded to the fixed anchor strip. The side of the main corrugated plate and the secondary corrugated plate is welded to the sliding anchor strip or the fixed anchor strip.

7. The planar layout structure of the membrane-type enclosure system according to claim 1, characterized in that: The first wave spacing is 1.5 times the second wave spacing. The secondary insulation box and the main insulation box are square structures on the plane corresponding to the secondary insulation layer and the main insulation layer. The size of the secondary insulation box and the main insulation box is 3 times the second wave spacing. The third and fourth corrugations are set at the third quarter line of the main insulation box. The first and second corrugations are set at the quarter line near the edge of the secondary insulation box. The vertex of the main insulation box is set at the center of the secondary insulation box.

8. The planar layout structure of the membrane-type enclosure system according to claim 1, characterized in that: Expansion joints are provided on the inner side of the main insulation box at the positions corresponding to the third and fourth corrugations.

9. The planar layout structure of the membrane-type enclosure system according to claim 1, characterized in that: The first and second corrugations are reversed in opposite directions along the same corrugation extension direction near the edge of the secondary corrugated plate to form a first small corrugation and a second small corrugation. The main insulation layer is provided with receiving grooves corresponding to the first and second small corrugations.

10. The planar layout structure of the membrane-type enclosure system according to claim 1, characterized in that: The amplitude of the first ripple is smaller than the amplitude of the second ripple, and the amplitude of the third ripple is smaller than the amplitude of the fourth ripple.

11. A liquefied natural gas carrier, comprising a planar arrangement structure of a membrane-type enclosure system as described in any one of claims 1 to 10.

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