Liquid cargo containment system and maintenance method

Abstract

The present invention discloses a liquid cargo containment system and maintenance method, belonging to the field of natural gas storage technology. The system comprises a primary shielding layer, a secondary shielding layer, an insulating layer, and a detection pipeline. One end of the detection pipeline is connected to a gas input pipeline, and the other end is provided with a first branch pipe and a second branch pipe. The first branch pipe extends between the primary shielding layer and the secondary shielding layer, and the second branch pipe extends into the insulating layer. A first temperature monitoring unit is provided in the first branch pipe, a second temperature monitoring unit is provided in the second branch pipe, and a first pressure differential detection unit is further provided between the first and second branches. The present invention ensures accurate monitoring of liquid cargo leakage by dually monitoring the peripheral temperature and pressure of the membrane tank, avoiding the problem of false alarms of liquid cargo leakage caused by pressure fluctuations due to other factors in conventional monitoring methods.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural gas storage, and in particular relates to a liquid cargo containment system and a maintenance method. Background Art

[0002] As a clean and efficient energy source, liquefied natural gas (LNG) is primarily transported in cryogenic, atmospheric, or pressurized tanks. Due to its low temperature and high compression, LNG requires high sealing and stability requirements during transportation. Regulations for LNG transportation typically require that natural gas tanks have a complete or partially complete secondary shielding system for cargo containment. This secondary shielding layer is filled with dry protective gas to ensure that any leaks are contained within the shielding atmosphere, preventing explosions caused by mixing of the cargo with air.

[0003] Existing liquid natural gas storage tanks primarily incorporate pressure monitors and gas monitors within the cargo containment system. These monitors analyze the gas pressure and composition within the cargo containment system to determine whether there has been a leak of liquid cargo. However, while pressure monitors can quickly identify leaks based on pressure fluctuations caused by liquid cargo leaks, the increase in flash steam within the membrane tank causes the membrane tank to expand, which in turn changes the space between the membrane tank and the containment system, causing pressure fluctuations in the protective gas area and leading to misjudgments of liquid cargo leaks. Gas monitors, on the other hand, require specific analysis of gas components, resulting in high accuracy but low detection efficiency. By the time the gas monitor detects natural gas in the protective gas, the leaked natural gas from the membrane tank has already spread throughout the containment system. Summary of the Invention

[0004] In response to one or more of the above-mentioned defects or improvement needs in the prior art, the present invention provides a liquid cargo containment system to solve the problems of liquid cargo leakage detection error and low detection efficiency in the existing containment system.

[0005] To achieve the above objectives, the present invention provides a liquid cargo containment system, comprising:

[0006] a main shielding layer, wherein the main shielding layer encloses and forms a liquid cargo accommodating space;

[0007] A secondary shielding layer, the secondary shielding layer is arranged outside the primary shielding layer;

[0008] an insulating layer, the insulating layer being arranged on the periphery of the secondary shielding layer;

[0009] a detection pipeline, one end of which is connected to the gas input pipeline, and the other end of which is provided with a first branch pipe and a second branch pipe, the first branch pipe extending between the primary shielding layer and the secondary shielding layer, and the second branch pipe extending into the insulating layer;

[0010] The space between the primary shielding layer and the secondary shielding layer is connected to the first branch pipe, and a first temperature monitoring unit is provided in the first branch pipe;

[0011] The space within the insulating layer is connected to the second branch pipe, and a second temperature monitoring unit is provided in the second branch pipe;

[0012] A first pressure difference detection unit is further provided between the first branch pipe and the second branch pipe.

[0013] As a further improvement of the present invention, the main shielding layer and the secondary shielding layer are both welded by corrugated plates, and the corrugated plates include a straight portion and a node portion connecting the straight portions, and the node portion is arranged in a concave and convex corrugation; one end of the first branch pipe connecting the space between the main shielding layer and the secondary shielding layer is located between two adjacent node portions.

[0014] As a further improvement of the present invention, the portion of the first branch pipe extending into the space between the main shielding layer and the secondary shielding layer includes a first curved pipe section arranged in an arc shape, the first curved pipe section can be bent and deformed, and a through hole connected to the outside is opened on the first curved pipe section.

[0015] As a further improvement of the present invention, the first temperature monitoring unit is a fiber grating sensor, which includes a transmission optical fiber arranged in the first branch pipe, a grating arranged in series on the transmission optical fiber, and a fiber grating order demodulator connected to one end of the transmission optical fiber facing the gas input pipeline.

[0016] As a further improvement of the present invention, the portion of the first branch pipe extending into the space within the insulating layer includes a second curved pipe section arranged in an arc shape, and the second curved pipe section can be bent and deformed.

[0017] As a further improvement of the present invention, there are multiple detection pipelines, and the multiple detection pipelines are connected to the gas output pipeline and the gas input pipeline through branch pipes.

[0018] As a further improvement of the present invention, a second pressure difference detection unit is provided between two adjacent detection pipelines.

[0019] As a further improvement of the present invention, the gas input pipeline is a nitrogen supply pipeline, and the nitrogen supply pipeline is embedded in the insulating layer; the detection pipeline also includes a gas output pipeline, the first branch pipe is connected to the gas output pipeline, and the gas output pipeline is embedded inside the nitrogen supply pipeline.

[0020] The present application also includes a maintenance method for a liquid cargo containment system, wherein maintenance is performed through the liquid cargo containment system, and the plurality of detection pipelines are connected to a gas output pipeline and a gas input pipeline through a branch pipe, and the method comprises the following steps:

[0021] obtaining a pressure difference between the first branch pipe and the second branch pipe through a first pressure difference detection unit, comparing the pressure difference obtained by the first pressure difference detection unit with a standard pressure difference, and determining whether a natural gas leak occurs based on the difference between the first pressure difference detection unit and the standard pressure difference;

[0022] Acquire temperatures monitored by the first temperature monitoring unit and the second temperature monitoring unit; acquire a first standard temperature of the space between the primary shielding layer and the secondary shielding layer, and acquire a second standard temperature of the space within the insulating layer; compare the real-time temperature acquired by the first temperature monitoring unit with the first standard temperature to obtain a first difference, and compare the real-time temperature acquired by the second temperature monitoring unit with the second standard temperature to obtain a second difference; and determine whether a natural gas leak occurs based on the first difference and the second difference;

[0023] If natural gas leaks, the gas output pipeline will extract the natural gas from the leak location through the detection pipeline; if no leakage occurs, the first pressure difference detection unit, the first temperature monitoring unit and the second temperature monitoring unit will continuously monitor the pressure difference and temperature of the liquid cargo containment system.

[0024] As a further improvement of the present invention, the gas output pipeline extracts natural gas from the leakage location through the detection pipeline, specifically comprising:

[0025] The gas output pipeline draws gas from the space between the primary shielding layer and the secondary shielding layer through the first branch of the detection pipeline at the leak location; the gas input pipeline injects protective gas into the space between the primary shielding layer and the secondary shielding layer through the first branch of the detection pipeline on both sides of the leak location.

[0026] The above-mentioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0027] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0028] (1) The liquid cargo containment system of the present invention monitors the relative pressure of the space between the primary shielding layer and the secondary shielding layer, and the space between the secondary shielding layer and the insulating layer, through a first pressure differential detection unit. When the pressure differential between the two fluctuates, it indicates that leakage may occur in the primary shielding layer and the secondary shielding layer. On the other hand, the present invention monitors the temperature changes of the space between the primary shielding layer and the secondary shielding layer, and the space within the insulating layer, through a first temperature monitoring unit and a second temperature monitoring unit, respectively, to determine whether natural gas has leaked from the membrane tank. The present invention ensures accurate monitoring of liquid cargo leakage through dual monitoring of the peripheral temperature and pressure of the membrane tank, avoiding the problem of false alarms of liquid cargo leakage caused by pressure fluctuations due to other factors in conventional monitoring methods.

[0029] (2) The liquid cargo containment system of the present invention is characterized in that one end of the first branch pipe connecting the space between the primary shielding layer and the secondary shielding layer is located between two adjacent node portions, and the two adjacent node portions and the straight portion form a concave accommodating space. When the film tank contracts or expands slightly, it does not cause squeezing on the end of the first branch pipe, thereby ensuring the stable detection of the pressure difference by the first pressure difference detection unit and the accuracy of the temperature monitoring by the first temperature monitoring unit.

[0030] (3) The liquid cargo containment system of the present invention can, by arranging the gas output pipeline inside the gas input pipeline, mitigate the influence of the temperature and pressure of the insulating layer space on the gas output pipeline on the one hand, and can also reduce the installation space required for arranging the gas output pipeline inside the insulating layer on the other hand, thereby saving the installation of fixing accessories for the gas output pipeline inside the insulating layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 2 is a schematic diagram of the overall structure of the liquid cargo containment system according to an embodiment of the present invention;

[0032] Figure 2 1 is a schematic diagram of an airflow for replacing gas between a primary shielding layer and a secondary shielding layer in a maintenance method for a liquid cargo containment system according to an embodiment of the present invention;

[0033] Figure 3 2 is a schematic diagram of an airflow of a protective gas injected between a primary shielding layer and a secondary shielding layer in a maintenance method of a liquid cargo containment system according to an embodiment of the present invention;

[0034] Figure 4 Schematic diagram of the airflow for discharging leaked natural gas from the primary shielding layer in the maintenance method of the liquid cargo containment system according to an embodiment of the present invention.

[0035] In all the drawings, the same reference numerals represent the same technical features, specifically:

[0036] 101. Main shielding layer; 102. Secondary shielding layer; 103. Insulation layer; 104. First branch pipe; 105. Second branch pipe; 106. First temperature monitoring unit; 107. Gas input pipeline; 108. First differential pressure detection unit; 109. Straight portion; 110. Flower node portion; 111. First bend section; 112. Second bend section; 113. Second differential pressure detection unit; 114. Gas output pipeline. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0038] In the description of the present invention, it should be understood that, unless otherwise specified, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0039] Furthermore, unless otherwise specified, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means at least two, for example, two, three, etc., unless otherwise specified.

[0040] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0041] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0042] Example:

[0043] See also Figures 1 to 4 The liquid cargo containment system in a preferred embodiment of the present invention includes a primary shielding layer 101, a secondary shielding layer 102, and an insulating layer 103. The primary shielding layer 101 is used to enclose a liquid cargo storage space, the secondary shielding layer 102 is arranged on the periphery of the primary shielding layer 101 to form a first layer of protection, and the insulating layer 103 is arranged on the periphery of the secondary shielding layer 102 to form a second layer of protection; and a detection pipeline, one end of which is connected to a gas input pipeline 107, and the other end of which is provided with a first branch pipe 104 and a second branch pipe 105. The first branch pipe The tube 104 extends between the main shielding layer 101 and the secondary shielding layer 102, the second branch tube 105 extends into the insulating layer 103, and the space between the main shielding layer 101 and the secondary shielding layer 102 is connected to the first branch tube 104, and a first temperature monitoring unit 106 is provided in the first branch tube 104, the space in the insulating layer 103 is connected to the second branch tube 105, and a second temperature monitoring unit is provided in the second branch tube 105, and a first pressure difference detection unit 108 is also provided between the first branch tube 104 and the second branch tube 105.

[0044] Specifically, the present application utilizes a first branch pipe 104 and a second branch pipe 105 of the detection pipeline to extend into the spaces between the primary shielding layer 101, the secondary shielding layer 102, and the insulating layer 103, respectively. When a membrane tank leaks, the natural gas within the primary shielding layer 101 first leaks into the space between the primary and secondary shielding layers 101, 102, causing pressure fluctuations within the primary and secondary shielding layers 101, 102. Secondly, the liquefied natural gas within the primary shielding layer 101 leaks into the secondary shielding layer 102, causing the temperature within the secondary shielding layer 102 to drop, further affecting the temperature of the protective gas within the insulating layer 103 and causing pressure fluctuations within the insulating layer 103. At this point, the first differential pressure detection unit 108 located between the first branch pipe 104 and the second branch pipe 105 can detect the pressure differential fluctuations between the two, thereby enabling membrane tank leak monitoring. On the other hand, the main shielding layer 101, the secondary shielding layer 102 and the insulating layer 103 are independent of each other, and the space between each layer is relatively isolated. When the natural gas in the main shielding layer 101 leaks, it will cause the natural gas to leak into the space between the main shielding layer 101 and the secondary shielding layer 102, thereby causing the temperature of the protective gas between the main shielding layer 101 and the secondary shielding layer 102 to drop, while there is no leakage between the secondary shielding layer 102 and the insulating layer 103, resulting in relatively little change in the temperature of the protective gas in the insulating layer 103. At this time, the first temperature monitoring unit 106 and the second temperature monitoring unit can monitor the temperature in the main shielding layer 101, the secondary shielding layer 102 and the insulating layer 103 respectively. By monitoring the gas temperature between the two layers, the leakage of the membrane tank can be secondary judged, thereby realizing accurate monitoring of the liquid cargo leakage. The present invention ensures accurate monitoring of the liquid cargo leakage through dual monitoring of the peripheral temperature and pressure of the membrane tank, avoiding the problem of false alarm of the liquid cargo leakage caused by pressure fluctuations due to other factors in conventional monitoring methods.

[0045] Furthermore, as an optional embodiment of the present invention, the primary shielding layer 101 and the secondary shielding layer 102 are both welded from corrugated sheet metal. The corrugated sheet metal includes multiple straight portions 109 and node portions 110 connecting the straight portions 109. The node portions 110 are arranged in a concave-convex corrugated pattern. One end of the first branch pipe 104, which connects the space between the primary shielding layer 101 and the secondary shielding layer 102, is located between two adjacent node portions 110. To accommodate the contraction of the subcooled liquefied natural gas injected into the membrane tank and the expansion of the membrane tank caused by the vaporization of flash steam, the primary shielding layer 101 is typically made of corrugated sheet metal. The node portions 110, which have concave-convex corrugations, adapt to the expansion and contraction of the membrane tank to prevent damage to the membrane tank. At the same time, one end of the first branch pipe 104 connecting to the space between the main shielding layer 101 and the secondary shielding layer 102 is located between the two adjacent flower nodes 110. The two adjacent flower nodes 110 and the straight portion 109 form a concave accommodating space. When the film tank shrinks or expands slightly, it will not cause squeezing on the end of the first branch pipe 104, ensuring the stable detection of the pressure difference by the first pressure difference detection unit 108 and the accuracy of the temperature monitoring by the first temperature monitoring unit 106.

[0046] Furthermore, as an optional embodiment of the present invention, the portion of the first branch pipe 104 extending into the space between the primary shielding layer 101 and the secondary shielding layer 102 includes a curved first bend section 111. This first bend section 111 is bendable and has a through hole that connects to the outside. When natural gas leaks or flash steam accumulates within the primary shielding layer 101, the membrane tank will deform accordingly, and the sidewalls of the primary and secondary shielding layers 101, 102, will compress the end of the first branch pipe 104, thereby affecting pressure differential and temperature monitoring. To address this issue, the end of the first branch pipe 104 extending into the space between the primary and secondary shielding layers 101, 102, is configured as a curved first bend section 111. When pressure is applied, the first bend section 111 deforms to absorb the pressure between the primary and secondary shielding layers 101, 102, and prevent damage to the first temperature monitoring unit 106 within the first branch pipe 104.

[0047] Furthermore, as an optional embodiment of the present invention, the portion of the first branch pipe 104 extending into the space between the primary shielding layer 101 and the secondary shielding layer 102 includes a first detection section and a second detection section. The first curved section 111 is disposed on the first detection section, the second detection section is disposed between the first detection section and the straight portion 109, and the first temperature monitoring unit 106 is disposed on the second detection section. The first detection section is primarily used to cooperate with the first branch pipe 104 to monitor the pressure between the primary shielding layer 101 and the secondary shielding layer 102, while the second detection section is primarily used to monitor the temperature of the space between the primary shielding layer 101 and the secondary shielding layer 102. The first detection section provides protection outside the second detection section, thereby reducing the possibility of pressure damage to the first temperature monitoring unit 106 therein or affecting the monitoring results.

[0048] Furthermore, as an optional embodiment of the present invention, the first temperature monitoring unit 106 in this application is a fiber Bragg grating (FBG) sensor. The first temperature monitoring unit 106 includes a transmission optical fiber disposed within the first branch tube 104, with a grating arranged in series on the transmission optical fiber. The end of the transmission optical fiber facing the gas input pipeline 107 is connected to a fiber Bragg grating (FBG) interrogator. Fiber Bragg grating sensors primarily monitor temperature changes by analyzing optical signals using a fiber Bragg grating (FBG) interrogator based on changes in the geometric length and refractive index of the optical fiber caused by temperature changes. By configuring the portion of the first branch tube 104 extending into the space between the primary shielding layer 101 and the secondary shielding layer 102 as a first detection section and a second detection section, and by providing protection outside the second detection section through the first detection section, the impact of pressure changes on the detection accuracy of the fiber Bragg grating sensor can be reduced.

[0049] Furthermore, as an optional embodiment of the present invention, the gas input pipeline 107 in this application is a nitrogen supply pipeline, which is embedded in the insulating layer 103. The detection pipeline also includes a gas output pipeline 114, which is connected to the first branch pipe 104 and embedded in the nitrogen supply pipeline. As a transmission pipeline for protective gas in the liquid cargo containment system, the nitrogen supply pipeline has high strength and can be isolated from the interior space of the insulating layer 103 to a certain extent. By arranging the gas output pipeline 114 inside the nitrogen supply pipeline, it can, on the one hand, reduce the impact of the temperature and pressure in the insulating layer 103 on the gas output pipeline 114, and on the other hand, reduce the installation space required for the gas output pipeline 114 in the insulating layer 103, saving the installation of fixing accessories for the gas output pipeline 114 in the insulating layer 103.

[0050] Furthermore, as an optional embodiment of the present invention, the portion of the first branch pipe 104 extending into the space within the insulating layer 103 includes a second curved pipe section 112 arranged in an arc shape. This second curved pipe section 112 is bendable and deformable. The space between the primary shielding layer 101 and the secondary shielding layer 102 serves as the first impact zone for liquid cargo leakage. Its internal pressure fluctuates relatively significantly, making the first branch pipe 104 more likely to deform. The space within the insulating layer 103 can also contract or expand to a certain extent due to temperature fluctuations in the space between the primary and secondary shielding layers 101, 102. Therefore, the second curved pipe section 112 is provided in the space where the first branch pipe 104 extends into the insulating layer 103. This reduces the probability of pressure damage to the first branch pipe 104 and improves the overall operational stability of the liquid cargo containment system.

[0051] Furthermore, as an optional embodiment of the present invention, multiple detection pipelines are provided, and each of these detection pipelines is connected to the gas output pipeline 114 and the gas input pipeline 107 via a branch pipe. Due to the large overall size of the membrane tank, the multiple detection pipelines are arranged around the periphery of the membrane tank, enabling monitoring of different areas of the membrane tank and precise monitoring of the leakage area of ​​the membrane tank. Furthermore, the detection pipelines are all connected to the gas input pipeline 107 and the gas output pipeline 114. When a leak occurs in the area where one of the detection pipelines is located, the leaked natural gas can be prevented from escaping to other areas by increasing the output of protective gas to the leak location and extracting the mixed gas to the side of the leak location, thereby reducing natural gas contamination of the space between the primary shielding layer 101 and the secondary shielding layer 102.

[0052] Furthermore, as an optional embodiment of the present invention, a second differential pressure detection unit 113 is provided between two adjacent detection pipelines. When a natural gas leak is detected in one of the detection pipelines, the second differential pressure detection unit 113 can compare the pressures between the two detection pipelines to further ensure the accuracy of the differential pressure detection and avoid misjudgments.

[0053] Furthermore, as an optional embodiment of the present invention, the present invention also includes a method for maintaining a liquid cargo containment system, which includes the following steps:

[0054] The first differential pressure detection unit 108 obtains the differential pressure between the first branch pipe 104 and the second branch pipe 105, compares the differential pressure obtained by the first differential pressure detection unit 108 with the standard differential pressure, and determines whether a natural gas leak occurs based on the difference between the differential pressure obtained by the first differential pressure detection unit 108 and the standard differential pressure;

[0055] Obtaining temperatures monitored by the first temperature monitoring unit 106 and the second temperature monitoring unit; obtaining a first standard temperature of the space between the primary shielding layer 101 and the secondary shielding layer 102, and obtaining a second standard temperature of the space within the insulating layer 103; comparing the real-time temperature obtained by the first temperature monitoring unit 106 with the first standard temperature to obtain a first difference, and comparing the real-time temperature obtained by the second temperature monitoring unit with the second standard temperature to obtain a second difference; and determining whether a natural gas leak occurs based on the first difference and the second difference;

[0056] If natural gas leaks, the gas output pipeline 114 extracts natural gas from the leak location through the detection pipeline; if no leakage occurs, the first pressure difference detection unit 108, the first temperature monitoring unit 106 and the second temperature monitoring unit continuously monitor the pressure difference and temperature of the liquid cargo containment system.

[0057] Furthermore, as an optional embodiment of the present invention, the gas output pipeline 114 extracts the natural gas from the leakage location through the detection pipeline, specifically including: the gas output pipeline 114 extracts the gas from the space between the primary shielding layer 101 and the secondary shielding layer 102 through the first branch pipe 104 of the detection pipeline at the leakage location; the gas input pipeline 107 injects protective gas into the space between the primary shielding layer 101 and the secondary shielding layer 102 through the first branch pipes 104 of the detection pipelines on both sides of the leakage location, such as Figure 4 As shown, the red line in the figure represents the flow direction of the leaked gas being extracted to the gas output pipeline 114, and the blue line in the figure represents the flow direction of the protective gas being injected between the primary shielding layer 101 and the secondary shielding layer 102 through the gas input pipeline 107.

[0058] Furthermore, as an optional embodiment of the present invention, before monitoring the liquid cargo containment system, the air between the primary shielding layer 101 and the secondary shielding layer 102 is replaced with a protective gas, such as Figure 2 As shown, the red line in the figure represents the flow direction of the air between the primary shielding layer 101 and the secondary shielding layer 102 being extracted to the gas output pipeline 114, and the blue line in the figure represents the flow direction of the protective gas injected into the space between the primary shielding layer 101 and the secondary shielding layer 102 by the gas input pipeline 107, which includes the following steps:

[0059] S1. Mark the first branches 104 of the detection pipelines in sequence, inject protective gas into the first branch 104 of one of the detection pipelines through the gas input pipeline 107, and extract gas from the first branch 104 next to the first branch 104 through the gas output pipeline 114;

[0060] S2, the gas input pipeline 107 injects protective gas through the first branch pipe 104 from which gas was previously extracted, and the gas output pipeline 114 extracts gas from the first branch pipe 104 adjacent to the first branch pipe 104;

[0061] S3. Repeat step S2 until the protective gas is injected into each first branch pipe 104.

[0062] Furthermore, as an optional embodiment of the present invention, before monitoring the liquid cargo containment system, the gas pressure between the primary shielding layer 101 and the secondary shielding layer 102 is adjusted to a set value, such as Figure 3 As shown in the figure, the blue line represents the flow direction of the protective gas injected between the main shielding layer 101 and the secondary shielding layer 102 by the gas input pipeline 107, which includes the following steps: the gas input pipeline 107 continuously injects protective gas into each first branch pipe 104 until the pressure in the space between the main shielding layer 101 and the secondary shielding layer 102 reaches a set pressure value; the gas input pipeline 107 extracts gas from at least one of the first branches 104, so that the amount of gas output by the gas output pipeline 114 is the same as the amount of protective gas input by the gas input pipeline 107.

[0063] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A liquid cargo containment system, characterized in that: include: a main shielding layer, wherein the main shielding layer encloses and forms a liquid cargo accommodating space; A secondary shielding layer, the secondary shielding layer is arranged outside the primary shielding layer; an insulating layer, the insulating layer being arranged on the periphery of the secondary shielding layer; a detection pipeline, one end of which is connected to the gas input pipeline, and the other end of which is provided with a first branch pipe and a second branch pipe, the first branch pipe extending between the primary shielding layer and the secondary shielding layer, and the second branch pipe extending into the insulating layer; The space between the primary shielding layer and the secondary shielding layer is connected to the first branch pipe, and a first temperature monitoring unit is provided in the first branch pipe; the primary shielding layer and the secondary shielding layer are both welded by corrugated plates, and the corrugated plates include a plurality of straight portions and flower nodes connecting the straight portions, and the flower nodes are arranged in a concave and convex corrugation; one end of the first branch pipe communicating with the space between the primary shielding layer and the secondary shielding layer is located between two adjacent flower nodes; the portion of the first branch pipe extending into the space between the primary shielding layer and the secondary shielding layer includes a first curved pipe section arranged in an arc shape, the first curved pipe section can be bent and deformed, and a through hole connected to the outside is opened on the first curved pipe section; the portion of the first branch pipe extending into the space inside the insulating layer includes a second curved pipe section arranged in an arc shape, and the second curved pipe section can be bent and deformed; The space within the insulating layer is connected to the second branch pipe, and a second temperature monitoring unit is provided in the second branch pipe; A first pressure difference detection unit is further provided between the first branch pipe and the second branch pipe.

2. The liquid cargo containment system according to claim 1, characterized in that: The first temperature monitoring unit is a fiber Bragg grating sensor, which includes a transmission fiber arranged in the first branch pipe, a grating arranged in series on the transmission fiber, and a fiber Bragg grating demodulator connected to one end of the transmission fiber facing the gas input pipeline.

3. The liquid cargo containment system according to claim 1, characterized in that: There are multiple detection pipelines, and the multiple detection pipelines are connected to the gas output pipeline and the gas input pipeline through branch pipes.

4. The liquid cargo containment system according to claim 3, characterized in that: A second pressure difference detection unit is further provided between two adjacent detection pipelines.

5. The liquid cargo containment system according to claim 1, characterized in that: The gas input pipeline is a nitrogen supply pipeline, which is embedded in the insulating layer; the detection pipeline also includes a gas output pipeline, the first branch pipe is connected to the gas output pipeline, and the gas output pipeline is embedded in the nitrogen supply pipeline.

6. A method for maintaining a liquid cargo containment system, wherein the maintenance is performed using the liquid cargo containment system according to any one of claims 1 to 5, wherein there are multiple detection pipelines, and the multiple detection pipelines are connected to the gas output pipeline and the gas input pipeline through branch pipes; characterized in that: The steps include: obtaining a pressure difference between the first branch pipe and the second branch pipe through a first pressure difference detection unit, comparing the pressure difference obtained by the first pressure difference detection unit with a standard pressure difference, and determining whether a natural gas leak occurs based on the difference between the first pressure difference detection unit and the standard pressure difference; Obtain the temperatures monitored by the first temperature monitoring unit and the second temperature monitoring unit; obtain the first standard temperature of the space between the primary shielding layer and the secondary shielding layer, and obtain the second standard temperature of the space within the insulating layer; Comparing the real-time temperature obtained by the first temperature monitoring unit with the first standard temperature to obtain a first difference, and comparing the real-time temperature obtained by the second temperature monitoring unit with the second standard temperature to obtain a second difference; determining whether a natural gas leak occurs based on the first difference and the second difference; If natural gas leaks, the gas output pipeline will extract the natural gas from the leak location through the detection pipeline; if no leakage occurs, the first pressure difference detection unit, the first temperature monitoring unit and the second temperature monitoring unit will continuously monitor the pressure difference and temperature of the liquid cargo containment system.

7. The maintenance method of the liquid cargo containment system according to claim 6, characterized in that: The gas output pipeline extracts the natural gas from the leaking location through the detection pipeline, specifically including: The gas output pipeline draws gas from the space between the primary shielding layer and the secondary shielding layer through the first branch of the detection pipeline at the leak location; the gas input pipeline injects protective gas into the space between the primary shielding layer and the secondary shielding layer through the first branch of the detection pipeline on both sides of the leak location.

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