LNG ship trunk structure and construction method thereof

Abstract

The invention discloses an LNG ship trunk structure and a construction method thereof.The trunk structure is arranged between a dome deck and an inner deck and comprises two longitudinal plates and two transverse plates, longitudinal ribs of the dome deck and longitudinal ribs of the inner deck are cut off at the mounting positions of the transverse plates, the upper ends of the two longitudinal plates are connected with the dome deck in a welded mode, and the lower ends of the two longitudinal plates are connected with the inner deck in a welded mode; the lower ends of the two longitudinal plates are welded to the inner deck, the left sides and the right sides of the two longitudinal plates are welded to the cut-off positions of the longitudinal ribs, the two transverse plates are welded to the left side ends and the right side ends of the two longitudinal plates respectively, the upper ends of the two transverse plates are welded to the dome deck, and the lower ends of the two transverse plates are welded to the inner deck. According to the LNG ship trunk structure, the space in the trunk is maximized, the number of welding seams is reduced, the leakproofness of the structure is enhanced, the assembly difficulty is reduced, and the ship building time is saved.

Description

Technical Field

[0001] This invention relates to the field of shipbuilding technology, and in particular to an LNG ship cofferdam structure and its construction method. Background Technology

[0002] On membrane-type liquefied natural gas (LNG) carriers, the venting tank, as a key safety component of the MARK III or NO.96 cargo containment system, plays a crucial role in venting, pressure relief, and thermal insulation of the cargo tanks. During loading, unloading, and navigation, the venting tank continuously monitors and regulates the internal pressure to ensure the safety and stability of LNG throughout storage and transportation. Typically, the venting tank on an LNG carrier is located in a specific position between the dome deck and the inner deck, connected to a boil-off gas (BOG) treatment system to deliver the boil-off gas generated within the tank to reliquefaction units or gas turbines. To ensure the proper functioning of the venting tank and the airtightness of the cargo tanks, the hull structure in the installation area must be designed as a well-sealed enclosure, while also guaranteeing the strength, continuity, and ease of installation and maintenance of the venting tank. During the shipbuilding phase, strict helium leak testing is required for welds around the vent box cofferdam, such as the weld connecting the dome deck and the inner deck, to verify that the welding quality meets the airtightness requirements of the liquid cargo containment system.

[0003] Existing membrane-type LNG carrier cofferdam designs typically involve adding additional plates to the existing hull structure to create a closed cubic cofferdam around the vent box installation location. (See attached image) Figure 1 As shown, the existing LNG ship cofferdam structure includes a spacer plate 4 between the longitudinal ribs 3 on the lower surface of the dome deck 1 and the longitudinal ribs 3 on the upper surface of the inner deck 2, and a transverse plate 5 welded to the spacer plate. Notches are provided at the four corners of the transverse plate 5 to accommodate the longitudinal ribs 3. A patch plate 6, perfectly matching the shape of the longitudinal rib 3, is welded to the notches. The patch plate 6 is welded to the transverse plate 5. Welds exist between the upper and lower ends of the spacer plate 4 and the longitudinal ribs 3, between the longitudinal ribs 3 and the deck, and between the patch plate 6 and the transverse plate 5. Because the existing LNG ship cofferdam structure retains the original hull structure without modification, a large number of splicing welds are required around the cofferdam. This not only increases the welding workload but may also affect the overall strength and sealing reliability of the structure due to the density of welds, posing potential risks to subsequent helium testing and long-term operation. Therefore, it is necessary to optimize the existing cofferdam structure design to reduce the number of welds, improve the structural airtightness and strength, and simplify the construction process. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides an LNG ship cofferdam structure and its construction method, thereby solving the technical problems of existing LNG ship cofferdams used to house vent boxes, such as a large number of welds, a large amount of welding work, and low overall strength and sealing performance.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: An LNG carrier cofferdam structure is disclosed, which is used to house a venting box. The cofferdam structure is positioned between a dome deck and an inner deck. Longitudinal ribs are welded to the lower surface of the dome deck and the upper surface of the inner deck along the longitudinal direction. The longitudinal ribs of the dome deck and the inner deck are arranged opposite to each other. The cofferdam structure comprises two longitudinal plates and two transverse plates arranged in the transverse direction. Both longitudinal and transverse plates are continuous whole plates, perpendicular to the dome deck. The longitudinal ribs of the dome deck and the inner deck are cut off at the installation points of the transverse plates. The upper ends of the two longitudinal plates are welded to the dome deck, and the lower ends of the two longitudinal plates are welded to the inner deck. The left and right sides of the two longitudinal plates are welded to the cut-off points of the longitudinal ribs. The two transverse plates are welded to the left and right ends of the two longitudinal plates, respectively. The upper ends of the two transverse plates are welded to the dome deck, and the lower ends of the two transverse plates are welded to the inner deck.

[0006] In one implementation, the longitudinal plate is welded to the longitudinal bone at the cut-off point by deep penetration welding.

[0007] In one embodiment, an elbow plate is further provided between the longitudinal bone and the longitudinal plate, with one side of the elbow plate welded to the longitudinal bone and the other side of the elbow plate welded to the side of the longitudinal plate.

[0008] In one embodiment, the elbow plate is a triangular elbow plate, with its two straight edges welded to the sides of the longitudinal bone and the longitudinal plate, respectively.

[0009] This application also provides a method for constructing an LNG ship cofferdam structure, wherein the LNG ship cofferdam is the aforementioned LNG ship cofferdam structure, comprising the following steps: At the installation location of the LNG ship cofferdam structure, cut the longitudinal ribs on the lower surface of the dome deck and the upper surface of the inner deck. Place a longitudinal plate between the cut-off points of the longitudinal ribs. Weld the upper end of the longitudinal plate to the dome deck and the lower end of the longitudinal plate to the inner deck. Weld the cut-off ends of the longitudinal ribs to the sides of the longitudinal plate. Weld the sides of the transverse plates to the sides of the longitudinal plates. Weld the upper end of the transverse plates to the dome deck. Weld the lower ends of both transverse plates to the inner deck.

[0010] In one embodiment, an elbow plate is provided between the longitudinal bone and the longitudinal plate. The elbow plate is a triangular elbow plate, and its two straight edges are welded to the sides of the longitudinal bone and the longitudinal plate, respectively.

[0011] Compared with the prior art, this application has at least the following beneficial effects: In this application, the LNG ship cofferdam structure cuts off the longitudinal ribs on the lower surface of the longitudinal dome deck and the upper surface of the inner deck at the installation location. The two longitudinal plates, two transverse plates, and parts of the dome deck and inner deck are used to construct a closed cubic cofferdam structure. Only the end welds to the deck exist on the upper and lower sides of the longitudinal plates. The supplementary plates are eliminated on the transverse plates. Compared with the existing LNG ship cofferdam structures, this application designs some sealing components and strength-ensuring components outside the cofferdam plates, thereby maximizing the space inside the cofferdam. The four sides of the LNG ship cofferdam structure (two longitudinal plates and two transverse plates) have a total reduction of 12 welds, which enhances the airtightness of the structure, reduces the assembly difficulty, and saves shipbuilding time. Attached Figure Description

[0012] Figure 1 This is a structural diagram of an existing LNG ship cofferdam structure; Figure 2 This is a top view of the LNG ship cofferdam structure on the dome deck in the embodiments of this application; Figure 3 This is a top view of the LNG ship cofferdam structure on the inner deck in the embodiments of this application; Figure 4 This is a longitudinal view of the LNG ship cofferdam structure in an embodiment of this application; Figure 5 This is a lateral view of the LNG ship cofferdam structure in an embodiment of this application; Figure 6 This is a three-dimensional schematic diagram of the LNG ship cofferdam structure in the embodiments of this application; Reference numerals: 01, LNG ship cofferdam structure; 1, dome deck; 2, inner deck; 3, longitudinal skeleton; 4, spandrel plate; 5, transverse plate; 6, patch plate; 7, longitudinal plate; 8, transverse plate; 9, elbow plate. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0014] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0015] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms and should not be construed as indicating or implying relative importance. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0016] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical connection or internal connection between two components. They can be direct connection or indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0017] To better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings.

[0018] This embodiment provides an LNG ship cofferdam structure 01 for housing a venting box, such as... Figure 2-5 As shown, the LNG ship cofferdam structure 01 is located between the dome deck 1 and the inner deck 2. Longitudinal ribs 3 are welded longitudinally to the lower surface of the dome deck 1 and the upper surface of the inner deck 2. The longitudinal ribs 3 of the dome deck 1 and the inner deck 2 are arranged opposite to each other. The LNG ship cofferdam structure 01 includes two longitudinal plates 7 arranged longitudinally and two transverse plates 9 arranged transversely. Both the longitudinal plates 7 and the transverse plates 9 are continuous whole plates, perpendicular to the dome deck 1. The longitudinal ribs 3 of the dome deck 1 and the inner deck 2 are both cut off at the installation points of the transverse plates 9. The upper ends of the two longitudinal plates 7 are welded to the dome deck 1, and the lower ends of the two longitudinal plates 7 are welded to the inner deck 2. The left and right sides of the two longitudinal plates 7 are welded to the cut-off points of the longitudinal ribs 3. The two transverse plates 8 are welded to the left and right ends of the two longitudinal plates 7, respectively. The upper ends of the two transverse plates 8 are welded to the dome deck 1, and the lower ends of the two transverse plates 8 are welded to the inner deck 2.

[0019] like Figure 6As shown, in this embodiment, the two longitudinal plates 7, the two transverse plates 9, and part of the dome deck and inner deck form a closed cubic cofferdam structure. There are only welds between the ends and the deck on the upper and lower sides of the longitudinal plates 7. The supplementary plates on the transverse plates 5 are eliminated. Compared with the existing LNG ship cofferdam structure, the LNG ship cofferdam structure 01 in this embodiment has 12 fewer welds on its four sides (two longitudinal plates and two transverse plates), which enhances the airtightness of the structure.

[0020] To ensure the structural strength of the LNG ship cofferdam structure 01, in this embodiment, the longitudinal plate 7 and the longitudinal stiffener 3 are welded together at the cut-off point using deep penetration welding. An elbow plate 9 is also provided between the longitudinal stiffener 3 and the longitudinal plate 7. One side of the elbow plate 9 is welded to the longitudinal stiffener 3, and the other side of the elbow plate 9 is welded to the side edge of the longitudinal plate 7. In this embodiment, the elbow plate 9 is a triangular elbow plate, with its two straight edges welded to the sides of the longitudinal stiffener 3 and the longitudinal plate 7, respectively.

[0021] This application also provides a method for constructing the above-mentioned LNG ship cofferdam structure, including the following steps: At the installation location of the LNG ship cofferdam structure, cut off the longitudinal rib 3 on the lower surface of the longitudinal dome deck 1 and the longitudinal rib 3 on the upper surface of the inner deck 2. Place a longitudinal plate 7 between the cut-off points of the longitudinal rib 3. Weld the upper end of the longitudinal plate 7 to the dome deck 1 and the lower end of the longitudinal plate 7 to the inner deck 2. Weld the cut-off end of the longitudinal rib 3 to the side of the longitudinal plate 7. Weld the side of the transverse plate 8 to the side of the longitudinal plate. Weld the upper end of the transverse plate 8 to the dome deck 1. Weld the lower ends of both transverse plates 8 to the inner deck 2.

[0022] In this embodiment, the construction method of the well structure further includes: setting an elbow plate 9 between the longitudinal bone 3 and the longitudinal plate 7. The elbow plate 9 is a right-angle elbow plate, and the two straight edges of the elbow plate 9 are welded to the sides of the longitudinal bone 3 and the longitudinal plate 7, respectively.

[0023] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. An LNG carrier cofferdam structure, wherein the LNG carrier cofferdam structure is used to house a venting box, the LNG carrier cofferdam structure is disposed between a dome deck and an inner deck, and longitudinal ribs are welded along the longitudinal direction on the lower surface of the dome deck and the upper surface of the inner deck, the longitudinal ribs of the dome deck and the longitudinal ribs of the inner deck being arranged opposite to each other, characterized in that, The LNG ship cofferdam structure includes two longitudinal plates arranged in the longitudinal direction and two transverse plates arranged in the transverse direction. Both longitudinal and transverse plates are continuous whole plates and are perpendicular to the dome deck. The longitudinal ribs of the dome deck and the inner deck are cut off at the installation points of the transverse plates. The upper ends of the two longitudinal plates are welded to the dome deck, and the lower ends of the two longitudinal plates are welded to the inner deck. The left and right sides of the two longitudinal plates are welded to the cut-off points of the longitudinal ribs. The two transverse plates are welded to the left and right ends of the two longitudinal plates, respectively. The upper ends of the two transverse plates are welded to the dome deck, and the lower ends of the two transverse plates are welded to the inner deck.

2. The LNG ship cofferdam structure according to claim 1, characterized in that, The longitudinal plate and the longitudinal bone are welded together at the cut-off point by deep penetration welding.

3. The LNG ship cofferdam structure according to claim 1, characterized in that, An elbow plate is also provided between the longitudinal bone and the longitudinal plate. One side of the elbow plate is welded to the longitudinal bone, and the other side of the elbow plate is welded to the side of the longitudinal plate.

4. The LNG ship cofferdam structure according to claim 3, characterized in that, The elbow plate is a triangular elbow plate, with its two straight edges welded to the sides of the longitudinal bone and the longitudinal plate, respectively.

5. A method for constructing a cofferdam for an LNG carrier, characterized in that, The LNG ship cofferdam is the LNG ship cofferdam structure as described in any one of claims 1-4, and includes the following steps: At the installation location of the LNG ship cofferdam structure, cut the longitudinal ribs on the lower surface of the dome deck and the upper surface of the inner deck. Place a longitudinal plate between the cut-off points of the longitudinal ribs. Weld the upper end of the longitudinal plate to the dome deck and the lower end of the longitudinal plate to the inner deck. Weld the cut-off ends of the longitudinal ribs to the sides of the longitudinal plate. Weld the sides of the transverse plates to the sides of the longitudinal plates. Weld the upper end of the transverse plates to the dome deck. Weld the lower ends of both transverse plates to the inner deck.

6. The method for constructing a cofferdam for an LNG carrier according to claim 5, characterized in that, Also includes: An elbow plate is provided between the longitudinal bone and the longitudinal plate. The elbow plate is a triangular elbow plate, and its two straight edges are welded to the sides of the longitudinal bone and the longitudinal plate, respectively.

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