Structure of secondary layer invar batten in ship liquid cargo tank and arrangement and installation method

Abstract

The invention relates to a ship liquid cargo tank sub-layer invar batten structure and an arrangement and installation method, the ship liquid cargo tank sub-layer invar batten structure comprises a first sub-layer invar batten, a plurality of second sub-layer invar battens and a third sub-layer invar batten, any two of the plurality of second sub-layer invar battens are connected through a second fixing part, and the third sub-layer invar batten is connected through a second fixing part. The first sub-layer invar batten is connected with the second sub-layer invar batten located at the first position through a first fixing part, the third sub-layer invar batten is connected with the second sub-layer invar batten located at the tail position through a third fixing part, and the connecting points serve as hinge points or stress release points. Small relative displacement or rotation can occur between connecting points, so that thermal stress is effectively absorbed and dispersed, excessive concentration of stress at a single position is avoided, the sectional type flexible connecting structure adapts to small deformation and unevenness of the base and can be finely adjusted along with changes of a ship body, additional internal stress is reduced, and the service life of the ship body is prolonged. And the overall sealing performance and integrity of the invar layer are improved.

Description

Technical Field

[0001] This invention relates to the field of marine Invar installation technology, and more specifically, to a structure and arrangement installation method for secondary Invars in a marine liquid cargo tank. Background Technology

[0002] The secondary Invar strips in cargo tanks are a crucial component of the secondary insulation layer. Large cargo ships with containment systems typically consist of multiple cargo tanks. Due to the hull shape of roll-on / roll-off (Ro-Ro) ships, the first cargo tank usually differs in shape from the others. The secondary Invar strips are vital components welded to the top and bottom of the first cargo tank. With the significant increase in shipbuilding speed and quality, the demand for the arrangement and installation of secondary Invar strips has also increased. Existing methods for arranging and installing secondary Invar strips are relatively outdated, and problems during installation can easily lead to the scrapping of Invar strips, causing substantial losses.

[0003] Based on the above situation, there is an urgent need to determine a method for arranging and installing the secondary Inductor strips that can avoid the risk of the entire secondary Inductor strips being scrapped and has extremely high reliability. Summary of the Invention

[0004] This application provides a secondary Invar structure for a ship's liquid cargo tank, which avoids the risk of the entire secondary Invar layer being scrapped and has extremely high reliability.

[0005] This application provides a method for arranging and installing secondary Invar strips in a ship's liquid cargo tank, including: a first sub-secondary Invar strip, a plurality of second sub-secondary Invar strips, and a third sub-secondary Invar strip. The plurality of second sub-secondary Invar strips are connected sequentially, and any two adjacent second sub-secondary Invar strips are connected by a second fixing component. The first sub-secondary Invar strip is connected to the first second sub-secondary Invar strip among the plurality of second sub-secondary Invar strips by a first fixing component, and the third sub-secondary Invar strip is connected to the last second sub-secondary Invar strip among the plurality of second sub-secondary Invar strips by a third fixing component.

[0006] In some optional embodiments, the first sub-layer Invar strip is provided with a plurality of first through holes, which are evenly distributed along the length of the first sub-layer Invar strip.

[0007] In some optional embodiments, each of the second sub-layer Invar strips is provided with a plurality of second through holes, which are uniformly arranged along the length of the second sub-layer Invar strip.

[0008] In some optional embodiments, each of the third sub-layer Invar strips is provided with a plurality of third through holes, and the plurality of third through holes are uniformly arranged in the length direction of the third sub-layer Invar strip.

[0009] In some optional embodiments, the first fixing component includes a first overlapping piece and a second overlapping piece, the first overlapping piece and the second overlapping piece clamping the mating area of ​​the first sub-sublayer Invar strip and the second sub-sublayer Invar strip, the first overlapping piece and the second overlapping piece being fixedly connected to the first sub-sublayer Invar strip and the second sub-sublayer Invar strip respectively.

[0010] In some optional embodiments, the first overlapping piece, the first sub-sub-layer Invar strip, and the second overlapping piece are connected by the first fixing element, and the first overlapping piece, the second sub-sub-layer Invar strip, and the second overlapping piece are connected by the second fixing element; or, the first overlapping piece, the first sub-sub-layer Invar strip, and the second overlapping piece are welded together.

[0011] In some optional embodiments, the first fixing component includes a third overlapping piece, which is connected to the first sub-sublayer Invar strip via a fourth fixing element, and the third overlapping piece is connected to the second sub-sublayer Invar strip via a fifth fixing element; or, the third overlapping piece is welded to the first sub-sublayer Invar strip, and the third overlapping piece is welded to the second sub-sublayer Invar strip.

[0012] On the other hand, this application also provides a method for arranging and installing secondary Invar strips in a ship's liquid cargo tank. The method involves the following steps to fabricate the structure of secondary Invar strips in any of the above-mentioned liquid cargo tanks. The method includes: measuring a first preset distance between the bow end of the ship's liquid cargo tank and one end of the secondary Invar strip in the tank; measuring a second preset distance between the stern end of the ship's liquid cargo tank and the other end of the secondary Invar strip; cutting the secondary Invar strip in the tank into a first sub-secondary Invar strip, multiple second sub-secondary Invar strips, and a third sub-secondary Invar strip according to the first and second preset distances; connecting any two adjacent second sub-secondary Invar strips using a second fixing component; connecting the first sub-secondary Invar strip to the first second sub-secondary Invar strip among the multiple second sub-secondary Invar strips using a first fixing component; and connecting the third sub-secondary Invar strip to the last second sub-secondary Invar strip among the multiple second sub-secondary Invar strips using a third fixing component.

[0013] In some optional embodiments, after the step of cutting the secondary Invar strips in the ship's cargo tank into a first sub-secondary Invar strip, a plurality of second sub-secondary Invar strips, and a third sub-secondary Invar strip according to the first preset distance and the second preset distance, the method further includes setting the number of first through holes according to the length of the first sub-secondary Invar strip; setting the number of second through holes according to the length of each of the second sub-secondary Invar strips; and setting the number of third through holes according to the length of each of the third sub-secondary Invar strips.

[0014] Compared with the prior art, the present invention has the following technical advantages: This application provides a structure for a secondary Invar layer in a ship's liquid cargo tank, including a first sub-secondary Invar layer, multiple second sub-secondary Invar layers, and a third sub-secondary Invar layer. Any two of the multiple second sub-secondary Invar layers are connected by a second fixing component. The first sub-secondary Invar layer is connected to the first second sub-secondary Invar layer by a first fixing component, and the third sub-secondary Invar layer is connected to the last second sub-secondary Invar layer by a third fixing component, forming a segmented flexible connection structure. These connection points act as hinge points or stress relief points. When the temperature changes drastically, the connection points can undergo slight relative displacement or rotation, thereby effectively absorbing and dispersing thermal stress and avoiding excessive stress concentration at a single location. This segmented flexible connection structure adapts to the slight deformation and unevenness of the substrate, and can be finely adjusted according to changes in the hull, reducing additional internal stress and improving the overall sealing and integrity of the Invar layer. Attached Figure Description

[0015] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the secondary Invar structure of a ship's liquid cargo tank according to an embodiment of the present invention; Figure 2 for Figure 1 A schematic diagram of the structure of the first sub-layer Invar strip in the provided embodiment; Figure 3 for Figure 1 A schematic diagram of the structure of the second sub-layer Invar strip in the provided embodiment; Figure 4 for Figure 1 A schematic diagram of the structure of the third sub-layer Invar strip in the provided embodiment.

[0016] in, Figures 1-4 The correspondence between the reference numerals and component names in the attached drawings is as follows: 1-First sub-layer Ingot strip; 11-First through hole; 2-Second sub-layer Ingot strip; 21-Second through hole; 3-Third sub-layer Ingot strip; 31-Third through hole; 4-First fixing component; 5-Second fixing component; 6-Third fixing component. Detailed Implementation

[0017] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0018] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0019] The secondary Invar strips in cargo tanks are a crucial component of the secondary insulation layer. Large Ro-Ro ships typically consist of multiple cargo tanks. Due to the ship's hull shape, the first cargo tank usually differs in shape from the others. The secondary Invar strips are vital components welded to the top and bottom of the first cargo tank. With the significant increase in shipbuilding speed and quality, the demand for the arrangement and installation of secondary Invar strips has also increased. Existing methods for arranging and installing secondary Invar strips are relatively outdated, and problems during installation can easily lead to the scrapping of Invar strips, causing substantial losses.

[0020] Based on the above situation, there is an urgent need to determine a method for arranging and installing the secondary Inductor strips that can avoid the risk of the entire secondary Inductor strips being scrapped and has extremely high reliability.

[0021] This application provides a secondary Invar structure for a ship's liquid cargo tank, which avoids the risk of complete scrapping of the secondary Invar layer and offers extremely high reliability. The following description refers to the accompanying drawings. Figures 1-4 The Invar structure of the secondary layer of the liquid cargo tank on the ship and its arrangement and installation method are described in detail.

[0022] The secondary Invar strip structure of a ship's cargo tank is mainly used for the inner walls of the cargo tanks on liquefied natural gas (LNG) carriers. Invar steel is a nickel-iron alloy, and due to its extremely low coefficient of thermal expansion, it is used as a key material to prevent the tank hull from shrinking and cracking due to ultra-low temperatures of less than or equal to -163°C. The secondary Invar strip is the core framework that supports and fixes the primary Invar plate.

[0023] This application provides a structure for a secondary Invar layer in a ship's liquid cargo tank, comprising: a first sub-secondary Invar layer 1, a plurality of second sub-secondary Invar layers 2, and a third sub-secondary Invar layer 3. The plurality of second sub-secondary Invar layers 2 are connected sequentially, and any two adjacent second sub-secondary Invar layers 2 are connected by a second fixing component 5. The first sub-secondary Invar layer 1 is connected to the first second sub-secondary Invar layer 2 among the plurality of second sub-secondary Invar layers 2 by a first fixing component 4, and the third sub-secondary Invar layer 3 is connected to the last second sub-secondary Invar layer 2 among the plurality of second sub-secondary Invar layers 2 by a third fixing component 6.

[0024] Specifically, although Invar steel has an extremely low coefficient of thermal expansion, the entire cargo tank system, including the Invars and the underlying hull structure, still experiences considerable shrinkage stress under large temperature variations, ranging from room temperature to -163°C. If the secondary Invar strips were a single rigid structure, these stresses could not be released, accumulating and leading to fatigue, deformation, or even cracking of the Invar material. Designing the secondary Invar strips into multiple segments—a first sub-secondary Invar strip 1, multiple second sub-secondary Invar strips 2, and a third sub-secondary Invar strip 3—connected by a first fixing component, a second fixing component 5, and a third fixing component 6, effectively acts as hinge points or stress release points. When temperatures change drastically, minute relative displacements or rotations can occur between the first sub-secondary Invar strip 1, the multiple second sub-secondary Invar strips 2, and the third sub-secondary Invar strip 3, effectively absorbing and dispersing thermal stress and preventing excessive stress concentration at a single location.

[0025] Furthermore, unavoidable installation errors exist during ship construction, and the hull structure itself is not an absolutely ideal geometric shape. During operation, the hull is subjected to slight bending and twisting due to wave action. Designing the secondary Invar layer into multiple segments—namely, the first sub-secondary Invar layer 1, multiple second sub-secondary Invar layers 2, and the third sub-secondary Invar layer 3—connected by the first fixing component 4, the second fixing component 5, and the third fixing component 6, respectively, allows for better adaptation to minor deformations and unevenness of the substrate compared to a rigid overall structure. It can be fine-tuned to follow changes in the hull, reducing additional internal stress caused by forced installation or substrate deformation, thus ensuring the overall sealing and integrity of the Invar layer.

[0026] Furthermore, Invar material is extremely expensive and requires extremely high processing precision. Manufacturing, transporting, and hoisting a very long, monolithic secondary Invar strip is extremely difficult, and it is prone to sagging, deformation, or damage due to its own weight. Designing the secondary Invar strip into multiple segments, namely the first sub-secondary Invar strip 1, multiple second sub-secondary Invar strips 2, and the third sub-secondary Invar strip 3, which are connected by the first fixing component 4, the second fixing component 5, and the third fixing component 6 respectively, greatly reduces the manufacturing difficulty, size, and weight of individual components. It is easier to perform high-precision machining and quality control in the factory. Shorter parts are easier to package and protect, and the transportation risk is lower. Workers can more easily handle, position, and adjust these shorter parts in a confined environment, which significantly improves installation efficiency and accuracy, and reduces labor costs and the risk of damage.

[0027] Furthermore, the liquid cargo tank requires regular inspection and maintenance. If a part is damaged, it is desirable to be able to replace only that part rather than affecting the entire sub-layer. The secondary Invar strips are designed in multiple segments: a first sub-secondary Invar strip 1, multiple second sub-secondary Invar strips 2, and a third sub-secondary Invar strip 3, connected by a first fixing component 4, a second fixing component 5, and a third fixing component 6, respectively. This clearly segmented design makes partial replacement possible. If a segment of a second sub-secondary Invar strip 2 is damaged, only that segment can be disassembled and replaced without disturbing the entire sub-layer structure, greatly simplifying the maintenance process and saving time and money.

[0028] In summary, the segmented secondary Invar strip structure, through the introduction of flexible connections, cleverly mitigates the enormous thermal and mechanical stresses generated by extreme temperature changes and hull deformation in the LNG cargo tank, thereby protecting the expensive Invar material from damage and ensuring the absolute airtightness and safety of the cargo tank. At the same time, this design also offers significant advantages in terms of ease of manufacturing, installation, and maintenance, representing a sophisticated engineering solution for achieving high reliability and safety under extreme operating conditions.

[0029] In some optional embodiments, the first sub-layer Invar strip 1 is provided with a plurality of first through holes 11, and the plurality of first through holes 11 are uniformly arranged in the length direction of the first sub-layer Invar strip 1.

[0030] Specifically, the first sub-layer Invar 1 typically needs to be fixed to the underlying substrate, such as a ship hull structure or insulation layer, by plug welding or spot welding. Without the first through-hole 11, welding can only be performed along the edges of the Invar. This can lead to: stress concentration during welding, as continuous edge welding generates significant thermal and shrinkage stresses, easily causing deformation or cracking of the Invar; and uneven connection strength, with a lack of effective connection points in the middle, potentially leading to warping or detachment under heavy loads. These uniformly distributed through-holes provide pre-defined, rationally distributed welding points. During welding, the welding torch can contact the substrate through these holes, forming uniformly distributed weld points. This is analogous to nailing it evenly to a base with many nails. Distributing the connection force evenly across the entire Invar prevents stress concentration, greatly improving the reliability of the connection and the stability of the overall structure.

[0031] Furthermore, welding is a process of rapid, localized heating and cooling, generating significant thermal stress. Invar materials are highly sensitive to stress, and improper welding techniques can easily lead to cracking. Decomposing a long weld into multiple discrete, spaced spot welds, each weld point creates an isolated, discontinuous heat-affected zone. The material regions between weld points remain free, effectively absorbing and buffering the thermal stress generated by adjacent weld points, preventing the accumulation of these stresses into a large overall stress field, thus greatly reducing the risk of Invar weld cracking. The structure of secondary Invar strips in ship cargo tanks requires precise positioning on a predetermined axis during installation. These evenly distributed through holes serve as positioning reference holes. Workers can temporarily fix the strip in the aligned position using locating pins through one or two key through holes before proceeding with subsequent welding operations. This ensures the straightness and positional accuracy of the entire strip installation and simplifies the installation process.

[0032] In summary, the first sub-layer Invar strip 1 is provided with uniformly distributed first through holes 11. By transforming continuous linear welding into discrete, uniformly distributed spot welding, the strength, stability and consistency of the connection with the substrate are optimized. It can effectively disperse and release welding thermal stress, prevent Invar material from cracking due to welding, and fundamentally ensure the ultra-high safety requirements of LNG cargo tanks.

[0033] In some optional embodiments, each second sub-layer Invar strip 2 is provided with a plurality of second through holes 21, and the plurality of second through holes 21 are uniformly arranged in the length direction of the second sub-layer Invar strip 2.

[0034] Specifically, the second sub-layer Invar 2 typically needs to be fixed to the underlying substrate, such as a ship hull structure or insulation layer, by plug welding or spot welding. Without the second through-hole 21, welding can only be performed along the edges of the Invar. This can lead to: stress concentration during welding, as continuous edge welding generates significant thermal and shrinkage stresses, easily causing deformation or cracking of the Invar; and uneven connection strength, with a lack of effective connection points in the middle, potentially leading to warping or detachment under heavy loads. These uniformly distributed through-holes provide pre-defined, rationally distributed welding points. During welding, the welding torch can contact the substrate through these holes, forming uniformly distributed weld points. This is analogous to nailing it evenly to a base with many nails. Distributing the connection force evenly across the entire Invar prevents stress concentration, greatly improving the reliability of the connection and the stability of the overall structure.

[0035] Furthermore, welding is a process of rapid, localized heating and cooling, generating significant thermal stress. Invar materials are highly sensitive to stress, and improper welding techniques can easily lead to cracking. Decomposing a long weld into multiple discrete, spaced spot welds, each weld point creates an isolated, discontinuous heat-affected zone. The material regions between weld points remain free, effectively absorbing and buffering the thermal stress generated by adjacent weld points, preventing the accumulation of these stresses into a large overall stress field, thus greatly reducing the risk of Invar weld cracking. The structure of secondary Invar strips in ship cargo tanks requires precise positioning on a predetermined axis during installation. These evenly distributed through holes serve as positioning reference holes. Workers can temporarily fix the strip in the aligned position using locating pins through one or two key through holes before proceeding with subsequent welding operations. This ensures the straightness and positional accuracy of the entire strip installation and simplifies the installation process.

[0036] In summary, the second sub-layer Invar strip 2 is provided with uniformly distributed second through holes 21. By transforming continuous linear welding into discrete, uniformly distributed spot welding, the strength, stability and consistency of the connection with the substrate are optimized. It can effectively disperse and release welding thermal stress, prevent Invar material from cracking due to welding, and fundamentally ensure the ultra-high safety requirements of LNG cargo tanks.

[0037] In some optional embodiments, each third sub-layer Invar strip 3 is provided with a plurality of third through holes 31, and the plurality of third through holes 31 are evenly arranged in the length direction of the third sub-layer Invar strip 3.

[0038] Specifically, the third sub-layer Invar 3 typically needs to be fixed to the underlying substrate, such as the hull structure or insulation layer, by plug welding or spot welding. Without the third through-hole 31, welding can only be performed along the edges of the Invar. This can lead to: stress concentration during welding, as continuous edge welding generates significant thermal and shrinkage stresses, easily causing deformation or cracking of the Invar; uneven connection strength, with a lack of effective connection points in the middle, potentially leading to warping or detachment under heavy loads. These uniformly distributed through-holes provide pre-defined, rationally distributed welding points. During welding, the welding torch can contact the substrate through these holes, forming uniformly distributed weld points. This is analogous to nailing it evenly to a base with many nails. Distributing the connection force evenly across the entire Invar prevents stress concentration, greatly improving the reliability of the connection and the stability of the overall structure.

[0039] Furthermore, welding is a process of rapid, localized heating and cooling, generating significant thermal stress. Invar materials are highly sensitive to stress, and improper welding techniques can easily lead to cracking. Decomposing a long weld into multiple discrete, spaced spot welds, each weld point creates an isolated, discontinuous heat-affected zone. The material regions between weld points remain free, effectively absorbing and buffering the thermal stress generated by adjacent weld points, preventing the accumulation of these stresses into a large overall stress field, thus greatly reducing the risk of Invar weld cracking. The structure of secondary Invar strips in ship cargo tanks requires precise positioning on a predetermined axis during installation. These evenly distributed through holes serve as positioning reference holes. Workers can temporarily fix the strip in the aligned position using locating pins through one or two key through holes before proceeding with subsequent welding operations. This ensures the straightness and positional accuracy of the entire strip installation and simplifies the installation process.

[0040] In summary, the third sub-layer Invar strip 3 is equipped with uniformly distributed third through holes 31. By transforming continuous linear welding into discrete, uniformly distributed spot welding, the strength, stability, and consistency of the connection with the substrate are optimized. This effectively disperses and releases welding thermal stress, prevents the Invar material from cracking due to welding, and fundamentally ensures the ultra-high safety requirements of the LNG cargo tank.

[0041] In some optional embodiments, the first fixing component 4 includes a first overlapping piece and a second overlapping piece, which clamp the mating area of ​​the first sub-sub-layer Invar strip 1 and the second sub-sub-layer Invar strip 2, and are fixedly connected to the first sub-sub-layer Invar strip 1 and the second sub-sub-layer Invar strip 2, respectively.

[0042] Specifically, the third fixing component 6 and the first fixing component 4 have the same structure. The key to the secondary Invar structure of a ship's cargo tank lies in achieving a secure connection while allowing for thermal expansion and contraction. Direct welding or rigid connections would fail due to unreleased stress. The first and second overlapping plates create a clever clamping hinge joint. These plates tightly clamp the mating areas of the first and second secondary Invar 1 and 2 from both sides, and are fixed by welding or bolts, providing mechanical strength and stability far exceeding that of a single-point connection. This effectively withstands various complex loads within the cargo tank. This connection joint itself possesses a certain degree of flexibility or slight freedom of movement; it does not rigidly fuse the first and second secondary Invar 1 and 2 into a single unit, but rather allows for extremely slight bending or rotation at the connection point while maintaining a secure fixation. This is like a very robust joint, ensuring force transmission while allowing for movement.

[0043] Furthermore, directly welding at the ends of the mating area between the first sub-layer Invar 1 and the second sub-layer Invar 2 is an extremely dangerous operation. The weld itself is a weak point in the material, and under repeated thermal stress cycles, fatigue cracks can easily form and propagate from the weld, leading to the failure of the entire structure. The first fixing component 4 shifts the welding position from the critical mating point between the first sub-layer Invar 1 and the second sub-layer Invar 2 to the lap surface between the lap piece and the Invar. This means that the weld heat-affected zone is located at a non-end position where the Invar is subjected to relatively less stress. Even if a minor defect occurs during welding, its impact is limited to the lap area and will not directly form a through crack path, greatly improving the safety margin of the system.

[0044] Furthermore, compared to a single connection point, two first and second overlapping plates of a certain length form a transition zone. Through their own elastic deformation, they can effectively disperse and absorb the peak stress concentrated at the connection point, preventing a sharp increase in stress at the Invar ends. The first and second overlapping plates tightly clamp the mating areas of the first sub-layer Invar 1 and the second sub-layer Invar 2 from both sides, forming a redundant system. Even if a minor defect occurs at the welding point of one overlapping plate with the Invar, the other overlapping plate can still provide sufficient connection strength, ensuring that the structure does not fail instantly and providing a time window for inspection and maintenance.

[0045] In some optional embodiments, the second fixing component 5 and the first fixing component 4 have the same structure, and the technical effects produced by the second fixing component 5 are similar to those produced by the first fixing component 4, and will not be described in detail here.

[0046] In some optional embodiments, the second fixing component 5 and the first fixing component 4 have the same structure, and the technical effects produced by the second fixing component 5 are similar to those produced by the first fixing component 4, and will not be described in detail here.

[0047] In some optional embodiments, the first overlapping piece, the first sub-sub-layer Invar 1, and the second overlapping piece are connected by a first fixing element, and the first overlapping piece, the second sub-sub-layer Invar 2, and the second overlapping piece are connected by a second fixing element; or, the first overlapping piece, the first sub-sub-layer Invar 1, and the second overlapping piece are welded together, and the first overlapping piece, the second sub-sub-layer Invar 2, and the second overlapping piece are welded together.

[0048] Specifically, the first and second overlapping pieces are tightly fixed to the first sub-layer Invar strip 1 and the second sub-layer Invar strip 2 to complete the force flow transmission and form a solid clamping structure, avoiding direct welding of the ends of the Invar strips and protecting the most vulnerable and stress-concentration-prone areas.

[0049] Optionally, the first overlapping piece, the first sub-layer Invar 1, and the second overlapping piece are connected by a first fixing element, and the first overlapping piece, the second sub-layer Invar 2, and the second overlapping piece are connected by a second fixing element, achieving true hinged connection and controllable flexibility. Mechanical connectors such as bolts are not absolutely rigid connections when tightened. Under load, they allow micron- or millimeter-level slippage and rotation between the connected parts. This controllable flexibility can absorb and release thermal stress extremely effectively, making it an ideal way to cope with repeated thermal cycling. The entire connection process is cold-working, completely avoiding the risks of thermal stress, deformation, and changes in material properties caused by welding. Both the first and second fixing elements are hinges, or both are fixing bolts.

[0050] Optionally, the first overlapping piece, the first sub-sub-layer Invar 1, and the second overlapping piece are welded together, and the first overlapping piece, the second sub-sub-layer Invar 2, and the second overlapping piece are welded together. The metallurgical bond strength formed by welding is usually higher than that of the sub-layer Invar itself. It can create an absolutely rigid, never-loosening connection node with excellent airtightness.

[0051] In some optional embodiments, the second fixing component 5 and the first fixing component 4 have the same structure, and the technical effects produced by the second fixing component 5 are similar to those produced by the first fixing component 4, and will not be described in detail here.

[0052] In some optional embodiments, the second fixing component 5 and the first fixing component 4 have the same structure, and the technical effects produced by the second fixing component 5 are similar to those produced by the first fixing component 4, and will not be described in detail here.

[0053] In some optional embodiments, the first fixing component 4 includes a third overlapping piece, which is connected to the first sub-sublayer Invar 1 via a fourth fixing element, and the third overlapping piece is connected to the second sub-sublayer Invar 2 via a fifth fixing element; alternatively, the third overlapping piece is welded to the first sub-sublayer Invar 1, and the third overlapping piece is welded to the second sub-sublayer Invar 2. Both the fourth and fifth fixing elements are hinges, or they are fixing bolts.

[0054] Specifically, the first fixing component 4 includes a third overlapping piece, which is connected to the first sub-layer Invar 1 via a fourth fixing element, and to the second sub-layer Invar 2 via a fifth fixing element. This allows for slight relative displacement and rotation between the overlapping piece and the Invar, partially absorbing and compensating for thermal stress. When the Invar is under tension or compression, a torsional moment is generated at the connection point, which can become a weak point in the structure and potentially accelerate fatigue damage.

[0055] The third overlapping piece is welded to the first sub-layer Invar strip 1, and the third overlapping piece is welded to the second sub-layer Invar strip 2. With only one overlapping piece and two weld seams, a very compact connection point is formed, minimizing the number of parts and assembly steps. If the welding process is mature, the manufacturing cost is low.

[0056] On the other hand, this application also provides a method for arranging and installing secondary Invar strips in a ship's liquid cargo tank. The method involves the following steps to create a structure for secondary Invar strips in a ship's liquid cargo tank as described in any of the above claims. The method includes: measuring a first preset distance between the bow end of the ship's liquid cargo tank and one end of the secondary Invar strip in the tank; measuring a second preset distance between the stern end of the ship's liquid cargo tank and the other end of the secondary Invar strip; cutting the secondary Invar strip in the tank into a first sub-secondary Invar strip 1, multiple second sub-secondary Invar strips 2, and a third sub-secondary Invar strip 3 according to the first and second preset distances; connecting any two adjacent second sub-secondary Invar strips 2 via a second fixing component 5; connecting the first sub-secondary Invar strip 1 to the first second sub-secondary Invar strip 2 among the multiple second sub-secondary Invar strips 2 via a first fixing component 4; and connecting the third sub-secondary Invar strip 3 to the last second sub-secondary Invar strip 2 among the multiple second sub-secondary Invar strips 2 via a third fixing component 6.

[0057] Specifically, by measuring the first and second preset distances on-site, and then calculating and cutting them on-site, the process ensures that the length of each Invar strip is tailored to the actual dimensions of the compartment at the current temperature. This allows the Invar strip to be in a natural relaxed state when installed, without being forced to stretch or compress, thus reserving space for its free contraction at low temperatures and eliminating the initial stress introduced by the installation to the greatest extent possible from the source.

[0058] Shipbuilding is a precision engineering process measured in millimeters, yet even so, there will inevitably be slight tolerances between the actual internal dimensions of a cargo tank and the theoretical design drawings. Simply prefabricating Invar strips according to the drawing lengths may result in installation difficulties on-site or forced installation leading to stress. The installation and arrangement method in this application abandons the rigid process of prefabrication according to drawings, adopting a flexible method of on-site measurement. This perfectly adapts to the unique internal contours of each cargo tank, ensuring that the total length of the secondary Invar strips perfectly matches the tank hull, avoiding forced assembly due to dimensional discrepancies, and guaranteeing smooth, aligned installation of all components, thereby achieving its intended flexible connection function.

[0059] All the preceding designs regarding the segmentation, overlap, and stress relief of the secondary Invar strips in ship cargo tanks share a common premise: the length of each Invar strip segment must be precise. If the length is incorrect, the flexible connection either cannot be installed or will be in a pre-tightened state immediately after installation, rendering it ineffective. This measurement and cutting process is the foundation and prerequisite for realizing all the previous ingenious structural designs. Precise, customized cutting is a crucial step in achieving multi-segment structures and flexible connections. It transforms the concepts of the first sub-secondary Invar strip 1, the second sub-secondary Invar strip 2, and the third sub-secondary Invar strip 3 from drawings into reality, and ensures that they can be effectively connected through the first fixing component 4, the second fixing component 5, and the third fixing component 6.

[0060] The secondary Invar strips form the supporting framework of the primary Invar sheets, and their straightness and continuity directly determine the quality of the primary layer's installation. If the secondary layer has installation stress or unevenness, it can cause wrinkles or stress concentration in the primary Invar sheets, compromising their seal. This precise installation method ensures that the entire secondary Invar strip forms a smooth, stable, and stress-free continuous support base after installation, guaranteeing the overall structural integrity of the entire Invar system and its absolute seal against liquefied natural gas.

[0061] In some optional embodiments, after the step of cutting the secondary Invar strips in the ship's liquid cargo tank into a first sub-secondary Invar strip 1, a plurality of second sub-secondary Invar strips 2 and a third sub-secondary Invar strip 3 according to a first preset distance and a second preset distance, the method further includes setting the number of first through holes 11 according to the length of the first sub-secondary Invar strip 1; setting the number of second through holes 21 according to the length of each second sub-secondary Invar strip 2; and setting the number of third through holes 31 according to the length of each third sub-secondary Invar strip 3.

[0062] Specifically, welding stress is directly related to weld length and the number of weld points. A long weld will generate a continuous and concentrated stress field. The connection between the Invar strip and the substrate requires a large number of weld points. If the weld points are distributed randomly, it will lead to uneven stress distribution, with stress concentration in some areas and insufficient connection in others. By setting the number of through holes according to the length, the welding requirements are quantified. Longer Invar strips bear greater potential thermal stress and require more weld points to provide sufficient connection strength and distribute stress, while shorter Invar strips bear less stress and require fewer weld points to meet the requirements. This avoids the arbitrariness caused by empirical estimation and ensures that the welding stress on each section of the Invar strip is evenly and reasonably distributed to a sufficient number of weld points, eliminating local stress peaks and greatly reducing the risk of Invar strip cracking due to welding.

[0063] The connection strength between Invar strips and the substrate is primarily determined by the number and strength of the weld points. If Invar strips of different lengths use the same number of weld points, the connection strength per unit length of a longer Invar strip will be lower than that of a shorter Invar strip, becoming a weak link. The method described above ensures that the connection strength is proportional to the length of the Invar strip, with longer Invar strips having more weld points and shorter Invar strips having fewer weld points. This ensures that the connection strength per unit length throughout the entire secondary system remains highly consistent, improving the overall integrity and reliability of the secondary support structure and preventing failure under load due to insufficient local connection strength. Welding itself involves time and cost. Too many weld points not only waste materials, time, and energy but also increase unnecessary thermal stress input. Too few weld points cannot guarantee safety. The minimum sufficient number of weld points is calculated for each section of Invar strip, achieving the optimal balance between cost, efficiency, and safety. This prevents the creation of unnecessary through holes in short Invar strips, saving welding time and materials, reducing unnecessary thermal damage, ensuring sufficient connections in long Invar strips, eliminating safety hazards, and maximizing construction efficiency and optimizing costs while ensuring absolute safety.

[0064] In this invention, the term "multiple" refers to at least two or more, unless otherwise explicitly defined. The terms "install," "connect," "link," and "fix" should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; "link" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0065] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A structure of a secondary layer of a waling in a liquid cargo hold of a ship, characterized in that, The structure of the ship liquid cargo tank middle layer tile strip comprises a first sub-middle layer tile strip (1), a plurality of second sub-middle layer tile strips (2) and a third sub-middle layer tile strip (3), the plurality of second sub-middle layer tile strips (2) are sequentially connected, any two adjacent second sub-middle layer tile strips (2) are connected through a second fixing component (5), the first sub-middle layer tile strip (1) and the first second sub-middle layer tile strip in the plurality of second sub-middle layer tile strips (2) are connected through a first fixing component (4), and the third sub-middle layer tile strip (3) and the last second sub-middle layer tile strip (2) in the plurality of second sub-middle layer tile strips (2) are connected through a third fixing component (6). The first sub-middle layer tile strip (1) is provided with a plurality of first through holes (11), and the plurality of first through holes (11) are uniformly arranged in the length direction of the first sub-middle layer tile strip (1).

2. The structure of the secondary layer of the cargo tank of the ship according to claim 1, characterized in that, Each second sub-middle layer tile strip (2) is provided with a plurality of second through holes (21), and the plurality of second through holes (21) are uniformly arranged in the length direction of the second sub-middle layer tile strip (2).

3. The structure of the secondary layer of the cargo tank of the ship according to claim 1, characterized in that, Each third sub-middle layer tile strip (3) is provided with a plurality of third through holes (31), and the plurality of third through holes (31) are uniformly arranged in the length direction of the third sub-middle layer tile strip (3).

4. The structure of the secondary layer of the cargo tank of the ship according to claim 1, characterized in that, The first fixing component (4) comprises a first lap piece and a second lap piece, the first lap piece and the second lap piece clamp the abutting regions of the first sub-middle layer tile strip (1) and the second sub-middle layer tile strip (2), and the first lap piece and the second lap piece are fixedly connected with the first sub-middle layer tile strip (1) and the second sub-middle layer tile strip (2) respectively.

5. The structure of the secondary layer of the cargo tank of the ship according to claim 1, characterized in that, The first lap piece, the first sub-middle layer tile strip and the second lap piece are connected through the first fixing element, the first lap piece, the second sub-middle layer tile strip and the second lap piece are connected through the second fixing element, or the first lap piece, the first sub-middle layer tile strip and the second lap piece are welded, and the first lap piece, the second sub-middle layer tile strip and the second lap piece are welded.

6. The structure of the secondary layer of the cargo tank of the ship according to claim 5, characterized in that, The first fixing component (4) comprises a third lap piece, the third lap piece is connected with the first sub-middle layer tile strip through a fourth fixing element, and the third lap piece is connected with the second sub-middle layer tile strip through a fifth fixing element; or the third lap piece is welded with the first sub-middle layer tile strip, and the third lap piece is welded with the second sub-middle layer tile strip.

7. The structure of a secondary layer of a cargo tank of a ship according to claim 1, wherein The structure of the ship liquid cargo tank middle layer tile strip can be manufactured through the following steps, and the arrangement installation method comprises the following steps:

8. A method of arranging and installing a secondary liner of a ship's liquid cargo tank, characterized in that, Measuring a first preset distance between a bow end inside a ship liquid cargo tank and one end of a ship liquid cargo tank middle layer tile strip; Measuring a second preset distance between a stern end inside the ship liquid cargo tank and the other end of the ship liquid cargo tank middle layer tile strip; Cutting the ship liquid cargo tank middle layer tile strip into a first sub-middle layer tile strip, a plurality of second sub-middle layer tile strips and a third sub-middle layer tile strip according to the first preset distance and the second preset distance; ​ connecting any two adjacent second sub-layer tiles through a second fixing component; connecting the first sub-layer tile and the first second sub-layer tile among the plurality of second sub-layer tiles through a first fixing component; connecting the third sub-layer tile and the last second sub-layer tile among the plurality of second sub-layer tiles through a third fixing component.

9. A method of installing a secondary shell gasket arrangement for a ship's liquid cargo tank according to claim 8, characterised in that, The method further comprises, setting the number of first through holes according to the length of the first sub-layer tile, setting the number of second through holes according to the length of each second sub-layer tile, and setting the number of third through holes according to the length of each third sub-layer tile.

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