Pressure sensor arrangement for an LNG membrane tank and method of use

Abstract

This invention discloses a pressure sensor arrangement structure and usage method for LNG diaphragm tanks. The pressure sensor includes a main body and a cable. The main body includes a first end and a second end. The first end is fixed to a first corrugated plate, and the second end is fixed to an insulating box. A first through-hole is provided on the flat portion of the first corrugated plate. The first end has a sensing end face facing liquefied natural gas. A pressure sensing component and a second through-hole are provided on the first end. The sensing end face is flush with the inner surface of the flat portion, and the edge of the first end is sealed to the first through-hole. The pressure sensing component directly contacts the liquefied natural gas through the second through-hole to measure the liquid pressure at the corresponding liquid level. The pressure sensor arrangement structure and usage method for LNG diaphragm tanks provided in this application can obtain more accurate diaphragm tank pressure and intervene in a timely manner based on the pressure and damage status of the diaphragm tank.

Description

Technical Field

[0001] This invention relates to the field of membrane enclosure system technology, specifically to a pressure sensor arrangement structure and usage method for an LNG membrane tank. Background Technology

[0002] Liquefied natural gas (LNG) membrane tanks use corrugated stainless steel plates as the inner tank wall. The corrugated structure is designed to accommodate thermal expansion and contraction under cryogenic conditions. During transportation, the sloshing of the liquefied cargo can generate impact loads on the tank wall. The corrugated plates are at risk of fatigue damage in areas of stress concentration. Therefore, it is necessary to monitor the internal pressure distribution in real time to assess the structural safety status.

[0003] Currently, due to limitations in their materials and structure, some pressure sensors can only be placed under corrugated plates to indirectly measure the pressure of liquid cargo enclosed by the corrugated plates. However, this method suffers from inaccurate measurement.

[0004] To address the aforementioned issues, one feasible approach is to install a cryogenic pressure sensor on the diaphragm tank, which can directly contact the liquefied natural gas sensor to measure the pressure of the liquid cargo inside the tank.

[0005] Therefore, there is an urgent need for a pressure sensor arrangement structure in the aforementioned diaphragm tank, which would enable the diaphragm tank to measure the internal pressure more accurately while maintaining its sealing integrity. Summary of the Invention

[0006] The purpose of this invention is to provide a pressure sensor arrangement structure and usage method for LNG diaphragm tanks, which solves the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, this application provides a pressure sensor arrangement structure for an LNG diaphragm tank. The LNG diaphragm tank includes an insulating layer, the insulating layer includes a corrugated plate and an insulating box, the corrugated plate includes a first corrugated plate on which a pressure sensor is provided and a second corrugated plate on which no pressure sensor is provided, the first corrugated plate includes a corrugated portion and a flat portion, wherein the flat portion includes a flat area completely surrounded by the corrugated portion on the first corrugated plate, and the pressure sensor arrangement structure includes: the pressure sensor includes a body and a cable, the body includes a first end and a second end, the first end is fixed to the first corrugated plate, and the second end is fixed to the insulating box;

[0009] A first through hole is provided on the flat part of the first corrugated plate. The first end has a sensing end face facing the liquefied natural gas. A pressure sensing component and a second through hole are provided on the first end. The sensing end face is flush with the inner surface of the flat part. Furthermore, the edge of the first end is sealed to the first through hole. The pressure sensing component is in direct contact with the liquefied natural gas through the second through hole to measure the liquid pressure at the liquid level corresponding to the second through hole.

[0010] In the above implementation, a sleeve extending from the upper surface of the insulation box into the interior of the insulation box is provided in the thickness direction, and the second end of the pressure sensor is sealed in the sleeve.

[0011] In the above implementation, the second end of the pressure sensor is sealed in the gap between the two insulating boxes.

[0012] In the above implementation, the distance between the pressure sensor and the corrugated part is greater than or equal to one-eighth of the length of the longest side of the flat part.

[0013] In the above implementation, the distance between pressure sensors on the flat portion is greater than or equal to one-quarter of the length of the longest side of the flat portion.

[0014] In the above implementation, the first corrugated plate is arranged in the corner area of ​​the LNG membrane tank and at the horizontal center line position of each side of the LNG membrane tank.

[0015] In one of the above implementations, at at least one liquid level, multiple first corrugated plates are arranged horizontally around the LNG membrane tank at intervals or continuously to form a ring-shaped sensor arrangement belt, so as to determine the tilt direction of the liquid surface by comparing the pressure readings of pressure sensors at different orientations at the same liquid level.

[0016] In the above implementation, one end of the cable is connected to the pressure sensor, and the other end of the cable passes through the insulation layer and is connected to the signal receiving device located outside the LNG membrane tank.

[0017] Secondly, this application provides a method for using an LNG diaphragm tank, wherein the method employs the pressure sensor arrangement structure of the LNG diaphragm tank according to any one of the first aspects, and the pressure sensor is used to acquire the liquefied natural gas pressure reading at the corresponding position of the LNG diaphragm tank.

[0018] In the above implementation, the pressure readings of each pressure sensor at time i are obtained, where i is a positive integer greater than or equal to 1; the pressure index corresponding to the reading interval of the pressure reading at time i is determined, where the reading interval is determined based on historical pressure readings; based on each pressure index, the total pressure index of the LNG membrane tank at time i is determined, where the total pressure index is the sum, weighted sum, average, or weighted average of the pressure indices; the total pressure index at time i is compared with the preset warning pressure index, and a pressure warning is issued if the total pressure score at time i is greater than the preset warning pressure index.

[0019] In the above implementation, under navigation conditions, in response to the pressure warning at time i, the stress value of each region on the LNG membrane tank at time i is determined based on the pressure reading of the pressure sensor at time i; wind and wave data at time i is acquired; the region of the LNG membrane tank with the largest stress value at time i is determined; and the navigation direction and speed of the liquefied natural gas carrier are adjusted according to the wind and wave data to reduce the sway load on the region with the largest stress value at time i.

[0020] In the above implementation, the damage accumulation of each region of the LNG membrane tank at time i is determined based on the stress values ​​of each region from time 1 to time i; based on the damage accumulation, the remaining life of the corrugated plate at each region of the LNG membrane tank is predicted, and a maintenance warning is issued if the remaining life is less than the preset life.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. Improved accuracy and reliability of internal pressure monitoring in membrane tanks: According to the arrangement structure of the pressure sensor provided in this application, the sensing end face is flush with the inner surface of the flat part, avoiding disturbance of the liquid flow field by the sensor protrusion or depression; the pressure sensing component is in direct contact with the liquefied natural gas through the second through hole, which can truly reflect the liquid pressure at the corresponding liquid level, rather than an indirectly calculated value.

[0023] 2. Ensures the measurement stability of the sensor under the corrugated plate deformation environment: According to the arrangement structure of the pressure sensor provided in this application, by arranging the sensor in a flat area completely surrounded by the corrugated part and maintaining a sufficient distance between the sensor and the corrugated part, the influence of the corrugated structure deformation on the pressure measurement accuracy is effectively isolated; at the same time, the reasonable spacing avoids mutual interference of pressure fields between measuring points.

[0024] 3. Accurate monitoring of key areas of sloshing load is achieved: According to the pressure sensor arrangement structure provided in this application, the corrugated plate with sensors is set at the corner area and / or the horizontal center line of each surface. These areas are the key locations where liquid impact and stress concentration are most significant during liquid sloshing. It can effectively capture the main characteristics of sloshing load with fewer measuring points without significantly increasing the number of sensors.

[0025] 4. Enhanced the ship's proactive control capability against swaying: After the warning is triggered, the maximum stress area is identified based on the stress value distribution in each area, and the navigation direction and speed are proactively adjusted in combination with wind and wave data to reduce the sway load on that area from the source and avoid passively bearing the impact.

[0026] 5. Predictive maintenance of membrane enclosure systems has been achieved: Based on historical stress data, the damage accumulation in each area is tracked, the remaining life of the corrugated plate is predicted, and maintenance warnings are issued in advance to avoid sudden failures and extend the service life of membrane tanks. Attached Figure Description

[0027] Figure 1 A schematic diagram of liquefied natural gas provided in an embodiment of this application;

[0028] Figure 2 A schematic diagram of the membrane enclosure system provided in the embodiments of this application;

[0029] Figure 3 A schematic diagram of a pressure sensor provided in an embodiment of this application;

[0030] Figure 4 A schematic diagram of the first end provided in an embodiment of this application;

[0031] Figure 5 A schematic diagram illustrating the connection method of the pressure sensor provided in the embodiments of this application on the membrane maintenance system;

[0032] Figure 6 A schematic diagram illustrating the arrangement of the pressure sensor on a flat surface according to an embodiment of this application;

[0033] Figure 7 A schematic diagram illustrating the arrangement of the first corrugated plate provided in an embodiment of this application;

[0034] Figure 8 This is a schematic diagram of a cable routing method provided in an embodiment of this application;

[0035] Figure 9 A flowchart illustrating a pressure warning method for an LNG diaphragm tank provided in this application embodiment;

[0036] Figure 10A flowchart illustrating an LNG diaphragm tank sloshing adjustment method provided in this application embodiment;

[0037] Figure 11 A flowchart illustrating a predictive maintenance method for LNG membrane tanks provided in this application embodiment.

[0038] Explanation of reference numerals in the attached figures:

[0039] 1: LNG membrane tank;

[0040] 2: Membrane enclosure system; 22: Primary insulation layer; 23: Secondary insulation layer; 221: Primary shielding film; 222: Primary insulation box; 231: Secondary shielding film; 232: Secondary insulation box; 233: Corrugated section; 234: Flat section;

[0041] 3: Pressure sensor; 31: Main body; 32: Cable; 33: Signal receiving device; 311: First end; 312: Second end; 313: Sensing end face; 314: Second through hole; 315: Pressure sensing component;

[0042] 4: First corrugated plate; 41: First through hole; 42: Slot; 43: Sleeve. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0044] In the description of this invention, it should be understood that, unless otherwise stated, the terms "center," "perpendicular to the wall thickness direction," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0045] Furthermore, unless otherwise stated, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0046] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0047] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that they are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0048] The technical solution provided in this application will now be described in conjunction with the accompanying drawings.

[0049] Figure 1 The liquefied natural gas membrane tank provided in the embodiments of this application is shown, such as Figure 1 As shown, a liquefied natural gas membrane tank 1 is installed inside the bulkhead of the ship's hold. The liquefied natural gas membrane tank 1 can be an octahedron, a decahedron, or an irregular polyhedron formed by multiple planar parts and bent parts, and this application does not limit it.

[0050] It should be noted that in this article, "inner side" refers to the side closer to the liquefied natural gas, and "outer side" refers to the side closer to the bulkhead of the ship's hold; primary insulation layer 21 refers to the first layer of insulation structure directly facing the liquefied natural gas, and secondary insulation layer 22 refers to the second layer of insulation structure located outside the primary insulation layer. These two insulation layers together constitute the membrane enclosure system 2. The double-layer structure and anchoring arrangement of this membrane enclosure system will be described in detail below.

[0051] It is understood that the membrane enclosure system of the aforementioned membrane tank consists of an insulating layer, which may include a corrugated sheet and an insulating box.

[0052] Specifically, Figure 2 The membrane enclosure system provided in the embodiments of this application is illustrated, such as Figure 2 As shown, the membrane enclosure system 2 of the LNG membrane tank may include a double-layer structure consisting of a primary insulation layer 22 and a secondary insulation layer 23, wherein the primary insulation layer may be located inside the secondary insulation layer.

[0053] like Figure 2 As shown, the primary insulation layer 22 may include a primary shielding film 221 and a primary insulation box 222. The secondary insulation layer 23 may include a secondary shielding film 231 and a plurality of adjacently arranged secondary insulation boxes 232. Both the primary insulation box and the secondary insulation box may be composed of thermal insulation material sandwiched between two support plates.

[0054] It is understood that the primary shielding film 221 and the secondary shielding film 231 can be welded together from multiple corrugated plates. Taking the secondary shielding film 231 as an example, corrugated portions 233 perpendicular to each other can be provided on the corrugated plate. These corrugated portions can surround one or more flat portions 234 on the secondary shielding film. The flat portion 234 includes a flat area completely surrounded by the corrugated portions 233 on the corrugated plate.

[0055] In some embodiments, the corrugated plate may be made of stainless steel, and this application does not impose any restrictions on this.

[0056] Figure 3 A schematic diagram of a pressure sensor provided in an embodiment of this application is shown. (As shown) Figure 3 As shown, the pressure sensor 3 includes a body 31 and a cable 32. It can be understood that the body is used to sense and measure the pressure of liquefied natural gas, and the cable 32 is used to transmit the pressure signal to an external signal receiving device.

[0057] Specifically, the main body can be divided into a first end 311 and a second end 312 according to different fixing positions. The first end 311 is fixed to the corrugated plate, and the second end 312 is fixed to the insulation box.

[0058] Figure 4 A schematic diagram of the first end provided in an embodiment of this application is shown, as follows: Figure 4 As shown, the first end has a sensing end face 313 facing liquefied natural gas. A second through hole 314 can be provided on the sensing end face 313. The through hole has a flow space for liquefied natural gas, which can be connected to... Figure 3 The pressure sensing component 315 of the main body 31 is connected so that the pressure sensing component 315 can directly contact the liquefied natural gas through the second through hole 314 to measure the liquid pressure at the liquid level corresponding to the second through hole 314.

[0059] Figure 5 A schematic diagram showing the connection method of the pressure sensor provided in the embodiment of this application on the membrane enclosure system is shown.

[0060] In some embodiments, such as Figure 5 As shown, a first through hole 41 is provided on the flat part of the first corrugated plate 4.

[0061] A slot 42 can be pre-set in the thickness direction on the insulating box. The depth of the slot 42 is set so that the height of the sensing end face at the first end is flush with the flat part after the pressure sensor is placed in the slot. In this way, the sensing end face can be welded to the first through hole 41 to ensure airtightness.

[0062] In some other embodiments, a sleeve 43 may also be provided in the slot 42, and the second end 312 of the pressure sensor 3 may be sealed in the sleeve 43. By adjusting the depth of the second end 312 in the sleeve 43, the sensing end face is adjusted to be flush with the inner surface of the flat part, and then the edge of the first end 311 is sealed and connected to the first through hole 41.

[0063] For example, in some embodiments, the second end of the pressure sensor may be threaded. By screwing the thread into the sleeve 43, the height of the sensing end face of the first end can be adjusted so that the sensing end face is flush with the flat portion. Then, the sensing end face is welded to the first through hole 41 to ensure airtightness.

[0064] In some other embodiments, the pressure sensor 3 may not be housed in an insulating box. Figure 5 (Not shown), but instead the second end is sealed in the gap between the two insulating boxes, and is connected to the corrugated plate only through the first end.

[0065] It is understandable that a corrugated plate can be divided into a first corrugated plate 4 with a pressure sensor and a second corrugated plate without a pressure sensor, depending on whether a pressure sensor is provided on the flat part 234.

[0066] Specifically, for the first corrugated plate 4, in order not to affect the corrugated portion 233, the distance between the pressure sensor 3 and the corrugated portion 233 can be greater than or equal to one-eighth of the longest side length of the flat portion. For example, for a corrugated plate with a square diameter of 400 mm, the distance from the pressure sensor 3 to the corrugated portion should be greater than 50 mm.

[0067] Understandably, to better represent the pressure conditions of the flat section of a corrugated plate and improve the robustness of pressure testing, the flat section 234 can also be equipped with multiple pressure sensors 3. To avoid the pressure sensors being too tight, causing slots in the insulation box or instability due to excessively tight sleeves, the distance between the pressure sensors on the flat section 234 can be set to be greater than or equal to one-quarter of the longest side length of the flat section. For example, for a 400 mm square corrugated plate, the distance between the pressure sensors should be greater than 100 mm.

[0068] For example, the corrugated plate that meets the above distance requirements can be made of Figure 6 The pressure sensors shown are arranged as described in this application, which will not be elaborated further here.

[0069] Understandably, due to cost considerations, the membrane tank will not use a first corrugated plate 4 with a pressure sensor on every corrugated plate. Therefore, the first corrugated plate 4 needs to be placed at the location where the sloshing pressure is most important to the membrane tank.

[0070] It is understandable that the main factor affecting the pressure of the diaphragm tank is the sloshing of liquefied natural gas caused by wind and waves. Since the corner areas are weak points of the diaphragm tank, extra attention needs to be paid to their pressure. Furthermore, the diaphragm tank has a polyhedral structure, and the pressure at the horizontal center line of each face more accurately represents the pressure distribution on that face. Therefore, the first corrugated plate 4 can be placed at the horizontal center line of each face to achieve precise monitoring of the pressure on each face.

[0071] In other embodiments, the pressure sensor 3 can also be arranged in a ring at multiple preset liquid level heights, such as 5%, 30%, 50%, 70%, or 90% of the liquid level height. The above five liquid levels can respectively represent the extremely low liquid level, low liquid level, medium liquid level, medium-high liquid level, and high liquid level of the diaphragm tank. In this way, the above five typical liquid levels can better represent the overall pressure of the liquefied natural gas diaphragm tank 1.

[0072] In the above embodiments, multiple first corrugated plates are arranged at intervals or continuously around the LNG film tank in the horizontal direction to form a ring sensor arrangement belt, so as to determine the tilt direction of the liquid surface by comparing the pressure readings of pressure sensors at different positions at the same liquid level.

[0073] Figure 7 The arrangement of the first corrugated plate provided in the embodiment of this application is shown, such as... Figure 7 As shown, the first corrugated plate 4 can be arranged continuously. That is, along the horizontal center line or corner area of ​​each surface, the first corrugated plates are arranged continuously in sequence, and adjacent first corrugated plates are directly connected (e.g., lap welding), without setting a second corrugated plate.

[0074] In other embodiments, the first corrugated plate 4 and the second corrugated plate can be arranged at intervals. For example, one or two second corrugated plates can be connected between two first corrugated plates 4. The number of second corrugated plates between two first corrugated plates is not limited herein.

[0075] It is understood that in some embodiments, the pressure signal collected by the pressure sensor 3 at the aforementioned location can be transmitted outward via cable 32. Cable 32 can be connected to a signal receiving device 33 located outside the hull for further signal analysis. The signal receiving device 33 may include one or more of a signal acquisition unit, signal amplifier, digital-to-analog converter, central signal processor, or alarm device, which is not limited herein.

[0076] Figure 8 This application illustrates a cable routing method provided in an embodiment, such as... Figure 8 As shown, one end of cable 32 is connected to pressure sensor 3, and the other end of cable 32 passes through the insulation layer and connects to a signal receiving device located outside the LNG membrane tank. Specifically, cable 32 can pass downwards from the primary insulation box 222 along the thickness direction, then be sealed through the secondary insulation layer 23, and finally extend outside the hull through an opening in the hull to connect with the signal receiving device 33.

[0077] Through the aforementioned sensor arrangement and cable routing, the pressure signals collected by each pressure sensor 3 are stably transmitted to the external signal receiving device 33, thus providing a data foundation for subsequent pressure analysis and early warning judgment. Based on the above-mentioned pressure sensor arrangement, the specific methods for pressure early warning are explained below.

[0078] Embodiments of this application also provide a method for using an LNG diaphragm tank, wherein the method includes a pressure warning method for the LNG diaphragm tank or a predictive maintenance method for the LNG diaphragm tank.

[0079] Figure 9 This application illustrates a pressure warning method for an LNG diaphragm tank, as provided in an embodiment. Figure 9 As shown, the method includes:

[0080] S110: Obtain the pressure reading of each pressure sensor at time i, where i is a positive integer greater than or equal to 1.

[0081] It can be understood that the obtained pressure readings are the pressure readings of the horizontal center lines of each surface of the corner zone or the membrane tank. The i-th time refers to the discrete continuous monitoring time point, where i is a positive integer greater than 1, representing the i-th sampling time from the initial time. For example, i can be equal to 1, 2, 3, 5 or 10, which is not limited in this application.

[0082] According to S110, comprehensive and continuous monitoring of the internal pressure state of the membrane tank can be achieved through multi-point and multi-time pressure data acquisition, providing the original data basis for subsequent pressure analysis.

[0083] S120: Determine the pressure index corresponding to the reading interval of the pressure reading at time i, wherein the reading interval is determined based on historical pressure readings.

[0084] As can be understood, a reading interval refers to a pressure range defined based on statistical analysis of historical pressure readings. This range can be determined using parameters such as the maximum, minimum, mean, or standard deviation of historical data.

[0085] For example, for a 175,000 cubic meter membrane LNG carrier, the instantaneous peak impact is 5 to 30 kPa under normal and stable sea conditions, 30 to 400 kPa under moderate sea conditions, and 400 to 1000 kPa under severe sea conditions.

[0086] The pressure index is a quantitative score corresponding to each reading interval, used to convert continuous pressure readings into a discrete evaluation index. For example, the pressure index for the above reading intervals can be set to 30, 60, or 90.

[0087] The S120 can convert absolute pressure values ​​into relative pressure indices, eliminating dimensional differences caused by variations in installation location and liquid level between different sensors, and enabling standardized and comparable assessment of pressure conditions at various points.

[0088] S130: Determine the total pressure index of the LNG membrane tank at time i based on each pressure index, where the total pressure index is the sum, weighted sum, average, or weighted average of the pressure indices.

[0089] It is understood that in the embodiments of this application, the total pressure index is a single evaluation index that comprehensively reflects the overall pressure state of the membrane tank at time i.

[0090] It is understandable that the total pressure index can be determined through simple summation, or through weighted summation or weighted average. The weights can be set based on the importance of each pressure sensor's location (e.g., corner areas have higher weight than non-corner areas) or the liquid level. In this way, by comprehensively calculating the pressure indices from multiple points, dispersed local pressure information is integrated into a global pressure status index. This avoids the random errors of single-point monitoring and takes into account the differentiated impacts of different areas on the safe operation of the diaphragm tank, improving the comprehensiveness and accuracy of pressure assessment.

[0091] S140: Compare the total pressure index at time i with the preset warning pressure index, and issue a pressure warning if the total pressure score at time i is greater than the preset warning pressure index.

[0092] It is understandable that the preset warning pressure index refers to a total pressure index threshold pre-set based on factors such as the design pressure-bearing capacity of the diaphragm tank, the fatigue limit of the materials, and safety margins. If the total pressure index exceeds this threshold, the diaphragm tank is highly likely to experience excessive pressure due to swaying, leading to tank rupture. Therefore, a pressure warning needs to be issued to relevant personnel.

[0093] It is understood that the pressure warning mentioned above may include audible alarms or visual alarms, or it may be an alarm signal sent to the crew control room; this application does not limit this.

[0094] It is understandable that by setting quantitative thresholds to achieve automatic detection and timely warning of pressure anomalies, crew members can take intervention measures (such as adjusting speed, changing course, or activating the sloshing suppression system) before the pressure in the membrane tank exceeds the limit, thereby effectively reducing the risk of structural damage caused by liquid cargo sloshing in vulnerable areas such as corners and ensuring the operational safety of the membrane tank and the ship.

[0095] Based on the aforementioned pressure warning method, when the internal pressure of the membrane tank rises abnormally, issuing a warning alone is insufficient to eliminate the structural risks caused by swaying. It is also necessary to combine real-time stress analysis and wind and wave data to actively adjust the ship's navigation attitude to reduce sway load.

[0096] Therefore, after issuing a pressure warning in S140, it can also be based on, for example... Figure 10 The LNG diaphragm tank sloshing adjustment method shown adjusts the pressure of the LNG diaphragm tank. Specifically, the method includes:

[0097] S210: Under navigation conditions, in response to the pressure warning at time i, the stress value of each region of the LNG membrane tank at time i is determined based on the pressure reading of the pressure sensor at time i.

[0098] It is understandable that "navigation conditions" refers to the state in which a liquefied natural gas carrier is sailing at sea, as opposed to static conditions such as berthing or loading / unloading.

[0099] It is understood that, in response to the pressure warning at time i, the method for adjusting the swaying of the LNG membrane tank provided in this application is triggered after determining in S140 that the total pressure index exceeds the preset warning pressure index.

[0100] It is understood that stress values ​​can include structural stresses in various regions calculated by combining pressure readings with structural parameters of the membrane tank (such as wall thickness, corrugated plate geometry, material elastic modulus, etc.). In some embodiments, stress values ​​can be calculated using finite element analysis or empirical formulas, which is not limited herein.

[0101] S220: Obtain the wind and wave data at time i.

[0102] It is understood that wind and wave data refers to real-time marine environmental parameters obtained through ship weather stations, wave radar, or meteorological satellites. In some embodiments, wind and wave data may include wind speed, wind direction, wave height, wave period, and wave direction, which are not limited herein.

[0103] It is understandable that wind speed and wind direction refer to the average wind speed and the direction of incoming current at a specified height above the sea surface; wave surge height refers to the vertical distance from wave crest to wave trough; wave surge period refers to the time interval between adjacent wave crests passing through the same observation point; and wave surge direction refers to the direction from which the wave propagates.

[0104] It is understandable that the S220 can obtain information on external excitation sources that cause liquid cargo sloshing, providing a basis for decision-making on subsequent navigation attitude adjustments, so that sloshing suppression measures are matched with real-time sea conditions, and the pertinence and effectiveness of intervention measures are improved.

[0105] S230: Determine the region of the LNG membrane tank with the highest stress value at time i, and adjust the sailing direction and speed of the LNG carrier based on wind and wave data to reduce the sway load on the region with the highest stress value at time i.

[0106] It is understandable that the area with the highest stress value refers to the part of the membrane tank with the highest structural stress after S210 calculation, which is usually the corner area or the corrugated plate area at a specific location.

[0107] It is understandable that, in order to avoid the area with the highest stress being subjected to continuous impact, the sailing direction and speed can be adjusted to reduce the impact of wind and waves on the LNG membrane tank.

[0108] For example, the ship's course can be changed to deviate the angle between the bow and the swell direction from the most unfavorable angle (such as avoiding cross waves or head waves), and the ship's encounter frequency can be adjusted by accelerating or decelerating to avoid the inherent sloshing frequency of the liquid cargo, or the impact speed of the liquid cargo relative to the tank wall can be reduced.

[0109] By actively controlling the ship's navigation attitude, the S230 reduces the intensity of liquid cargo sloshing from the level of external excitation sources, directly reducing the sloshing load in the area of ​​maximum stress. This achieves a technological upgrade from "passive monitoring and early warning" to "active load control," effectively delaying the accumulation of fatigue damage in the weak areas of the membrane tank, extending the service life of the structure, and improving the overall navigation safety of liquefied natural gas carriers.

[0110] It is understandable that while the real-time sloshing adjustment method under the aforementioned navigation conditions can reduce the load impact of liquid cargo sloshing on the diaphragm tank in the short term, from a long-term operational perspective, fatigue damage will still accumulate in various areas of the diaphragm tank under repeated sloshing cycles, thus affecting the service life of the corrugated plates. To assess the long-term structural health of the diaphragm tank and plan maintenance strategies in advance, this application also provides a method for predicting remaining service life based on damage accumulation analysis.

[0111] Figure 11 This application illustrates a predictive maintenance method for LNG membrane tanks, as provided in an embodiment. Figure 11 As shown, the method includes:

[0112] S310: Based on the stress values ​​of each region of the LNG membrane tank at each time, determine the damage accumulation of each region of the LNG membrane tank at time i.

[0113] It can be understood that the stress value at each moment refers to the structural stress data of each region of the membrane tank at different times (from moment 1 to moment i) determined by the pressure reading in step S210.

[0114] It is understandable that damage accumulation refers to the state in which damage accumulates over time under stress on a membrane tank.

[0115] In some embodiments, the damage accumulation described above can be quantitatively characterized by the Miner linear cumulative damage method or the rainflow counting method, which is not limited herein.

[0116] For example, determining the damage accumulation of a membrane tank using the Miner linear cumulative damage method may include the following steps:

[0117] (1) Stress Cycle Extraction: Rainflow counting was used to process the irregular stress time history composed of stress values ​​at each time point before time i, extracting K constant-amplitude stress cycles, and recording the stress amplitude and mean stress of each stress cycle. Rainflow counting can identify closed cycles in the irregular stress history, discretizing the random swaying load into a set of fatigue cycles with clear stress amplitude and mean stress, thus making it suitable for subsequent Miner damage calculation.

[0118] (2) Fatigue life determination: Based on the stress-life curve of the corrugated plate material, determine the number of fatigue failure cycles corresponding to each stress amplitude. The stress-life curve can be obtained from fatigue test data of corrugated plate material (such as 36% Ni steel or stainless steel) in a low-temperature environment of liquefied natural gas (approximately -162℃), and mean stress correction (such as Goodman criterion or Gerber criterion) and low-temperature environment correction coefficient are introduced to reflect the influence of actual working conditions on the fatigue performance of the material.

[0119] (3) Damage accumulation calculation: Based on Miner's linear cumulative damage theory, the fatigue damage degree of each region at time i is calculated.

[0120] (4) Independent Calculation by Region: Considering the differences in geometry, constraints, and stress response in different regions of the membrane tank (such as corner areas, the horizontal center line of the first corrugated plate on each side, etc.), an independent stress time history database can be established for each region, and the above-mentioned rainflow counting and Miner cumulative calculation can be performed independently to obtain the differentiated fatigue damage degree of each region. According to S310, the stress data at each moment can be converted into fatigue damage history cumulative information, providing a quantitative basis for assessing the remaining life of the corrugated plate.

[0121] S320: Based on the damage accumulation, predict the remaining life of the corrugated plates in each area of ​​the LNG membrane tank, and issue a maintenance warning if the remaining life is less than the preset life.

[0122] It is understood that remaining service life refers to the number of voyages or the amount of time a corrugated sheet is expected to remain in safe service under its current fatigue accumulation state. In some embodiments, remaining service life can be determined by inverse calculation using the damage-life curve of the corrugated sheet material.

[0123] For example, in some embodiments, the aforementioned damage-life curve can be determined by fitting test data of the damage-life curve of corrugated plate material in the cryogenic environment of liquefied natural gas. Specifically, multiple sets of standard corrugated plate samples can be taken and fatigue tests can be conducted under stress ratios and temperature conditions simulating actual working conditions to obtain the number of fatigue failure cycles corresponding to different stress amplitudes. Then, the damage-life curve can be fitted, and the SN curve can be converted into a correspondence between damage degree and remaining life through Miner's linear cumulative damage theory.

[0124] It is understood that the preset lifespan can be a remaining lifespan threshold pre-set based on factors such as membrane tank design specifications, ship maintenance plans, or insurance requirements. For example, in some embodiments, the preset lifespan can be set to the remaining one annual maintenance cycle (e.g., 1 year) to facilitate alignment with the ship's classification survey plan.

[0125] It is understood that maintenance early warnings may include response actions such as prompting crew members to record areas to be inspected, sending maintenance suggestions to shore-based management systems, or arranging dry-docking maintenance plans, and this application does not limit these actions.

[0126] Understandably, according to S320, fatigue damage assessment results can be transformed into remaining life indicators that can guide operation and maintenance decisions, realizing the transformation from "post-failure maintenance" to "pre-emptive predictive maintenance". This enables managers to reasonably arrange maintenance windows before the corrugated plate fails, avoid liquid cargo leakage accidents caused by sudden structural failure, and ensure the long-term operational safety and economy of liquefied natural gas carriers.

[0127] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pressure sensor arrangement structure for an LNG diaphragm tank, wherein the LNG diaphragm tank (1) includes an insulating layer, the insulating layer includes a corrugated plate and an insulating box, the corrugated plate includes a first corrugated plate (4) on which the pressure sensor (3) is disposed and a second corrugated plate without which the pressure sensor is not disposed, the first corrugated plate (4) includes a corrugated portion (233) and a flat portion (234), wherein, The flat portion (234) includes a flat area completely surrounded by the corrugated portion (233) on the first corrugated plate (4), characterized in that the arrangement structure of the pressure sensor (3) includes: The pressure sensor (3) includes a body (31) and a cable (32). The body (31) includes a first end (311) and a second end (312). The first end (311) is fixed to the first corrugated plate (4), and the second end (312) is fixed to the insulation box. The first corrugated plate (4) has a first through hole (41) on its flat portion (234). The first end (311) has a sensing end face (313) facing the liquefied natural gas. The first end (311) is provided with a pressure sensing component (315) and a second through hole (314). The sensing end face (313) is flush with the inner surface of the flat portion (234). The edge of the first end (311) is sealed to the first through hole (41). The pressure sensing component (315) directly contacts the liquefied natural gas through the second through hole (314) to measure the liquid pressure at the liquid level corresponding to the second through hole (314).

2. The pressure sensor arrangement structure for the LNG diaphragm tank according to claim 1, characterized in that, A sleeve (43) extending from the upper surface of the insulation box to the inside of the insulation box is provided in the thickness direction on the insulation box, and the second end (312) of the pressure sensor (3) is sealed in the sleeve (43).

3. The pressure sensor arrangement structure for the LNG diaphragm tank according to claim 1, characterized in that, The second end (312) of the pressure sensor (3) is sealed in the gap between the two insulating boxes.

4. The pressure sensor arrangement structure for the LNG diaphragm tank according to claim 1, characterized in that, The distance between the pressure sensor (3) and the corrugated portion (233) is greater than or equal to one-eighth of the longest side length of the flat portion (234).

5. The pressure sensor arrangement structure for the LNG diaphragm tank according to claim 1, characterized in that, The distance between the pressure sensors (3) on the flat portion (234) is greater than or equal to one-quarter of the length of the longest side of the flat portion (234).

6. The pressure sensor arrangement structure for the LNG diaphragm tank according to claim 1, characterized in that, The first corrugated plate (4) is arranged in the corner area of ​​the LNG membrane tank (1) and at the horizontal center line position of each side of the LNG membrane tank.

7. The pressure sensor arrangement structure for an LNG diaphragm tank according to claim 1, characterized in that, At at least one liquid level, multiple first corrugated plates (4) are arranged horizontally around the LNG film tank (1) at intervals or continuously to form an annular sensor arrangement belt to determine the liquid surface tilt direction by comparing the pressure readings of pressure sensors (3) at different orientations at the same liquid level.

8. The pressure sensor arrangement structure for the LNG diaphragm tank according to claim 1, characterized in that, One end of the cable (32) is connected to the pressure sensor (3), and the other end of the cable (32) passes through the insulation layer and is connected to a signal receiving device located outside the LNG membrane tank (1).

9. A method of using an LNG membrane tank, characterized in that, The method employs the pressure sensor arrangement structure of the LNG diaphragm tank according to any one of claims 1 to 8, wherein the pressure sensor is used to obtain the liquefied natural gas pressure reading at the corresponding position of the LNG diaphragm tank.

10. The method according to claim 9, characterized in that, The method includes: Obtain the pressure reading of each pressure sensor at time i, where i is a positive integer greater than or equal to 1; Determine the pressure index corresponding to the reading interval of the pressure reading at time i, wherein the reading interval is determined based on historical pressure readings; Based on the pressure indices, the total pressure index of the LNG membrane tank at time i is determined, wherein the total pressure index is the sum, weighted sum, average, or weighted average of the pressure indices; The total pressure index at time i is compared with the preset warning pressure index, and a pressure warning is issued if the total pressure score at time i is greater than the preset warning pressure index.

11. The method according to claim 10, characterized in that, The LNG membrane tank is installed on the liquefied natural gas carrier. After comparing the total pressure index at time i with the preset warning pressure index, and issuing a pressure warning if the total pressure score at time i is greater than the preset warning pressure index, the process further includes: Under navigation conditions, in response to the pressure warning at time i, the stress value of each region on the LNG membrane tank at time i is determined based on the pressure reading of the pressure sensor at time i. Obtain the wind and wave data at time i; The region of the LNG membrane tank with the highest stress value at time i is determined, and the sailing direction and speed of the liquefied natural gas carrier are adjusted according to the wind and wave data to reduce the sway load on the region with the highest stress value at time i.

12. The method according to claim 9, characterized in that, The method includes: Based on the stress values ​​of each region of the LNG membrane tank from time 1 to time i, determine the damage accumulation of each region of the LNG membrane tank at time i. Based on the damage accumulation, the remaining lifespan of the corrugated plates in each area of ​​the LNG membrane tank is predicted, and a maintenance warning is issued if the remaining lifespan is less than the preset lifespan.

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