Leak detection device and tank with leak detection

Abstract

The objective is to provide a leak detection device that can reliably and easily detect leaks of cryogenic liquefied gas with a simple configuration. [Solution] This leak detection device is a leak detection device for detecting leaks from a tank that stores liquefied gas, and comprises a cutting unit and a disk unit, wherein the disk unit has a first disk with an opening formed thereon, a second disk with an opening formed thereon, and a film sandwiched between the first disk and the second disk, and the cutting unit has a laminated metal plate formed by laminating a first metal plate and a second metal plate having different coefficients of thermal expansion, and a cutter blade provided on the laminated metal plate, wherein the cutting unit is positioned so that the tip of the cutter blade is close to the film on the disk unit, and the laminated metal plate bends and deforms in response to temperature changes due to the leakage of liquefied gas, causing the cutter blade to cut the film.

Description

Technical Field

[0001] The present invention relates to a leakage detection device for detecting leakage of liquefied gas or the like, and a tank with leakage detection.

Background Art

[0002] In recent years, tanks for storing cryogenic liquefied gases such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), and liquefied ethylene gas (LEG) have been generally known. Further, for the purpose of reducing CO2 emissions, ships equipped with a tank for storing liquefied gas such as liquefied natural gas (LNG) and using the liquefied gas as fuel for the propulsion engine of the ship are also known.

[0003] In such a tank, it is important to detect damage that causes the cryogenic liquefied gas to leak to the outside. Therefore, a tank inspection device including a sensor unit in a heat insulation layer where a heat insulating material is disposed between an inner tank and an outer tank has been disclosed in a tank having an inner tank and an outer tank (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, it was difficult to install the tank inspection device of Patent Document 1 between the inner tank and the outer tank where the heat insulating material was disposed.

[0006] In addition, a leak detector that detects the leakage of low-temperature liquefied gas by sensing the temperature may be installed between the inner and outer tanks. In such cases, the leak detector is generally welded to a metal bottom plate located at the bottom between the inner and outer tanks via a metal plate. The cold temperature of the low-temperature liquefied gas in the inner tank is transferred to the bottom plate, causing the leak detector to detect a temperature close to that of the low-temperature liquefied gas.

[0007] When a leak detector detects a temperature close to that of low-temperature liquefied gas, it is difficult to determine whether there is an actual leak of liquefied gas from the inner tank or simply heat conduction, making it difficult to accurately and quickly detect leaks.

[0008] Therefore, the present invention aims to solve the above problems and provide a leak detection device that can reliably and easily detect liquefied gas leaks with a simple configuration, and can also quickly discharge the liquefied gas. [Means for solving the problem]

[0009] A leak detection device according to one aspect of the present invention is a leak detection device for detecting a leak from a tank storing liquefied gas, comprising a cutting unit and a disk unit, wherein the disk unit has a first disk with an opening formed thereon, a second disk with an opening formed thereon, and a film sandwiched between the first disk and the second disk, the cutting unit has a laminated metal plate formed by laminating a first metal plate and a second metal plate having different coefficients of thermal expansion, and a cutter blade provided on the laminated metal plate, the cutting unit is characterized in that the tip of the cutter blade is positioned close to the film on the disk unit, the laminated metal plate bends and deforms in response to temperature changes due to the leakage of liquefied gas, and the cutter blade cuts the film.

[0010] With this configuration, when liquefied gas leaks, the laminated metal plate rapidly bends and deforms due to the temperature change caused by the low-temperature liquefied gas, and the film can be reliably cut by the cutter blade provided on the laminated metal plate. This makes it possible to detect the leakage of liquefied gas. Furthermore, as described later, by configuring the system to discharge the liquefied gas when the film is cut, it is possible to prevent it from accumulating in the insulation layer and thus prevent serious accidents.

[0011] Furthermore, since the film is sandwiched between the first and second discs, it is possible to suppress the upward bending and bulging of the film that may occur due to pressure changes such as nitrogen gas filling the insulation layer, thereby avoiding malfunctions during film cutting.

[0012] Furthermore, because it operates mechanically, it does not require external power or a power source to operate, ensuring reliable operation even during power outages or emergencies, and reducing the risk of malfunction.

[0013] Furthermore, it has a simple structure consisting of a cutting unit made of laminated metal plates, a cutter blade provided on the laminated metal plates, a disc unit made of a first disc, a second disc, and a film sandwiched between the first and second discs. This results in a small number of parts, making assembly and maintenance easy and reducing costs.

[0014] Furthermore, the laminated metal plate, formed by bonding a first metal plate and a second metal plate having different coefficients of thermal expansion, reacts sensitively and deforms in the low-temperature environment of liquefied gas, thus possessing high responsiveness that allows it to operate simultaneously with the occurrence of leakage. Note that the laminated metal plate only needs to be able to bend and deform in response to temperature changes, and is not limited to double metal plates; triple or quadruple laminated metal plates may also be used.

[0015] Furthermore, this leak detection device is characterized in that the cutter blade of the cutting unit is positioned to cut the film exposed from the openings of the first and second discs, and the film is cut by deformation of the laminated metal plate.

[0016] This configuration ensures that the film exposed through the openings of the first and second discs is reliably ruptured.

[0017] Furthermore, this leak detection device is characterized in that the cutter blade of the cutting unit is provided near one end of the laminated metal plate and positioned to cut the film exposed from the openings of the first and second discs, and cuts the film near the end by deformation of the laminated metal plate.

[0018] This configuration improves the reliability of the film breaking operation. Furthermore, since the film is cut near the outer edges exposed through the openings of the first and second discs, it can be broken with less force than when the central portion is broken, ensuring reliable film breakage. In addition, even when the film expands upward, such as when the tank is vacuumed, the outer edges of the film are less likely to expand upward than the central portion, reducing the likelihood of malfunctions. Moreover, in configurations where liquefied gas can be discharged, breaking the film near the edges makes it less likely for film fragments to remain in the flow path after breaking, ensuring a reliable discharge passage.

[0019] Furthermore, this leak detection device is characterized in that the cutter blades of the cutting unit are provided in multiple locations near one end of the laminated metal plate, the laminated metal plate is elongated and rectangular in shape, and the cutter blades are provided at the front end and its left and right sides.

[0020] This configuration improves the reliability of the film tearing operation. Furthermore, since the laminated metal plate is elongated and rectangular in shape, and cutter blades are provided at the tip and both sides of the laminated metal plate, the reliability of the film tearing operation is further improved. In addition, the cutting area when the film is torn is increased, allowing for faster discharge.

[0021] Furthermore, in this leak detection device, it is desirable that the distance between the tip of the cutter blade and the surface of the film is 6 mm or less when the laminated metal plate is in its pre-deformation state.

[0022] According to this configuration, by setting the distance between the tip of the cutter blade and the surface of the film to 6 mm or less in the state before deformation of the laminated metal plate, even if the amount of deformation of the laminated metal plate is small, the cutter blade can surely reach the film and can surely cut it.

[0023] Further, it is desirable that the leakage detection device has a V-shaped blade tip for the cutter blade.

[0024] According to this configuration, since the blade tip of the cutter blade is V-shaped, the cutting performance of the film can be improved.

[0025] Further, in this leakage detection device, the cutting unit is characterized in that in the laminated metal plate, the first metal plate has a larger coefficient of thermal expansion than the second metal plate, and the first metal plate is installed so as to be located below the second metal plate.

[0026] According to this configuration, since the first metal plate having a larger coefficient of thermal expansion than the second metal plate is arranged to be below the laminated metal plate, when the liquefied gas leaks, the first metal plate is suddenly shrunk when exposed to extremely low temperature, and the laminated metal plate can be surely curved downward.

[0027] Further, it is desirable that the first metal plate is formed of a Ni-Cr-Fe-based alloy and the second metal plate is formed of invar in this leakage detection device.

[0028] According to this configuration, since the first metal plate is formed of a Ni-Cr-Fe-based alloy, a stable downward deformation operation can be obtained, and high toughness and excellent corrosion resistance can be maintained even in a low temperature range. Since the second metal plate is formed of invar, a low coefficient of thermal expansion can be maintained even in a low temperature range, and the difference in coefficient of thermal expansion from the first metal plate becomes larger, so that the laminated metal plate can be surely curved downward.

[0029] Furthermore, it is desirable that the disk unit in this leak detection device is sandwiched between the upper flange and the lower flange.

[0030] With this configuration, the disk unit is sandwiched between the upper and lower flanges, so the disk unit can be securely fixed between the flanges, preventing leakage of liquefied gas.

[0031] Furthermore, it is desirable that the disk unit of this leak detection device further includes a first gasket between the upper flange and the first disk, and a second gasket between the second disk and the lower flange.

[0032] With this configuration, the disk unit further includes a first gasket between the upper flange and the first disk, and a second gasket between the second disk and the lower flange, thereby improving the airtightness of the joint and reliably preventing leakage of liquefied gas. In addition, the pressure state inside the disk unit is stable, enabling reliable operation.

[0033] Furthermore, it is desirable that the disk unit of this leak detection device be detachably mounted between the upper flange and the lower flange.

[0034] With this configuration, the disc unit is detachably mounted between the upper and lower flanges. This allows the disc unit to be removed and replaced with a spare disc unit when the film breaks, enabling repeated use of the leak detection device and facilitating easy and quick maintenance.

[0035] Furthermore, it is desirable that the cutting unit of this leak detection device has one end where the cutter blade is located and the other end on the opposite side fixed to the upper flange in a cantilevered manner.

[0036] In this configuration, the cutting unit is cantilevered to the upper flange at one end where the cutter blade is located and at the other end. This allows the cutter blade to reliably and quickly contact the film without hindering the bending deformation of the laminated metal plate. As a result, rapid film cutting is possible in the event of leakage, improving leak detection performance.

[0037] Furthermore, this leak detection device is characterized by further comprising a proximity sensor for detecting deformation of the laminated metal plate of the cutting unit.

[0038] This configuration includes a proximity sensor that detects deformation of the laminated metal plate, enabling rapid and reliable detection of liquefied gas leaks and early detection of abnormalities. Furthermore, integration with a monitoring system facilitates remote monitoring and management.

[0039] Furthermore, this leak detection device is characterized in that the cutting unit has a detection target at one end of the laminated metal plate, the detection target is provided on the side opposite to the side where the cutter blade is located, and the proximity sensor detects the movement of the detection target due to the deformation of the laminated metal plate.

[0040] In this configuration, the object to be detected is provided at one end of the laminated metal plate, and the object to be detected is located on the side opposite to the side where the cutter blade is present. The proximity sensor detects the movement of the object to be detected due to the deformation of the laminated metal plate, thereby reliably detecting even minute deformations of the laminated metal plate, improving detection accuracy and preventing malfunctions.

[0041] Furthermore, this leak detection device is characterized in that the proximity sensor is provided close to the tip of the laminated metal plate, the object to be detected has an inclined surface that slopes backward from its lower end to its upper end, and the movement of the object to be detected is detected when the inclined surface of the object to be detected approaches the proximity sensor due to the bending deformation of the laminated metal plate.

[0042] In this configuration, the proximity sensor is positioned close to the tip of the laminated metal plate, and the object to be detected has an inclined surface that slopes backward from its lower end to its upper end. This configuration allows the inclined surface of the object to be detected to move closer to the proximity sensor in response to the bending deformation of the laminated metal plate, enabling highly accurate and stable detection of the object's movement. As a result, the accuracy of detecting deformation is improved.

[0043] Furthermore, a leak-detecting tank according to one aspect of the present invention comprises any of the above-mentioned leak detection devices, a tank for storing liquefied gas, and an outer casing on the outside of the tank, wherein a space is formed between the tank and the outer casing, and the leak detection device is positioned below the tank within the space.

[0044] This configuration includes a leak detection device, a tank for storing liquefied gas, and an outer casing on the outside of the tank. A space is formed between the tank and the outer casing, and the leak detection device is positioned below the tank within this space. This allows for efficient collection of liquefied gas leaking below the tank, enabling highly accurate leak detection.

[0045] Furthermore, this leak-detection tank is characterized by having a drain pipe connected to the lower part of the outer casing, the leak detection device being located in the drain pipe, and the liquefied gas being discharged when the film is cut by the cutter blade.

[0046] This configuration allows for the placement of a leak detection device in the drain pipe connected to the bottom of the outer casing, and the liquefied gas to be discharged when the film is cut by a cutter blade. This allows the leaked liquefied gas to be quickly guided to a safe drainage area, preventing gas from accumulating inside the outer casing. [Effects of the Invention]

[0047] According to the present invention, it is possible to provide a leak detection device and a tank with leak detection that can reliably and easily detect liquefied gas leaks with a simple configuration. [Brief explanation of the drawing]

[0048] [Figure 1] This figure shows a leak detection device according to a first embodiment of the present invention, where (a) is a plan view and (b) is a cross-sectional view taken along the line X-X' in (a). [Figure 2] This diagram shows the cutting unit, with (a) being a top view, (b) a front view, and (c) a side view. [Figure 3] This is a cross-sectional exploded view of the disk unit. [Figure 4] This diagram shows a gasket, with (a) being a plan view and (b) being a cross-sectional view. [Figure 5] This is a diagram showing the first disk, where (a) is a top view and (b) is a front view. [Figure 6] This is a diagram showing the second disk, where (a) is a top view and (b) is a front view. [Figure 7] This diagram shows the disk unit, with (a) being a plan view, (b) a cross-sectional view, and (c) an exploded cross-sectional view. [Figure 8] This diagram shows the installation status of the leak detection device; (a) is a plan view, and (b) is a cross-sectional view taken along the line X-X' in (a). [Figure 9] This figure shows an example of the installation location of a leak detection device. [Figure 10] This figure shows a leak detection device according to another embodiment, where (a) is a plan view, (b) is a front view before deformation of the double metal plate, and (c) is a front view after deformation of the double metal plate. [Modes for carrying out the invention]

[0049] <First Embodiment> (Structure of a leak detection device) A leak detection device according to one embodiment of the present invention will be described in detail below. However, the present invention is not limited by this embodiment. Furthermore, the components in the following embodiment include those that are easily substituted or substantially identical to those that are easily substituted by those skilled in the art. Moreover, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the spirit of the present invention.

[0050] In Figure 1, Figure 1(a) is a plan view showing the structure of the leak detection device 1 according to this embodiment, and Figure 1(b) is a cross-sectional view taken along the line X-X'. In Figure 2, Figure 2(a) is a plan view showing the structure of the cutting unit 3, Figure 2(b) is a front view, and (c) is a side view. Figure 3 is an exploded cross-sectional view showing the structure of the disk unit 5. In Figure 4, Figure 4(a) is a plan view of the first gasket 6 and the second gasket 10, and Figure 4(b) is a cross-sectional view.

[0051] In Figure 5, Figure 5(a) is a plan view showing the structure of the first disk 7, and Figure 5(b) is a front view. In Figure 6, Figure 6(a) is a plan view showing the structure of the second disk 9, and Figure 6(b) is a front view. In Figure 7, Figure 7(a) is a plan view showing the structure of the disk unit 5, Figure 7(b) is a cross-sectional view, and Figure 7(c) is an exploded cross-sectional view. In Figure 8, Figure 8(a) is a plan view showing the installation state of the leak detection device 1, and Figure 8(b) is a cross-sectional view taken along the line X-X'. Figure 9 shows an example of the installation location of the leak detection device.

[0052] The leak detection device 1 is installed in a tank 50 that stores liquefied gas such as LNG or methanol, and detects leaks of liquid liquefied gas from the tank 50. An outer casing 51 is provided on the outside of the tank 50. The outer casing 51 is an insulating casing, and an insulating layer 52 is formed between the tank 50 and the outer casing 51. A drain pipe 53 is connected downstream of the outer casing 51. In this embodiment, the leak detection device 1 is, as an example, installed on the drain pipe 53 (see Figure 9). This installation is desirable because it allows for early detection of liquefied gas leaks, but it is not limited to this, and the device can also be installed on the lower side of the outer casing, etc.

[0053] Furthermore, as shown in Figure 8, in this embodiment, the leak detection device 1 is connected to the drain pipe 53 by fastening the phase flange 14, upper flange 2, and lower flange 11, which are located at the downstream end of the drain pipe 53, with a second screw 15.

[0054] As shown in Figure 1, the leak detection device 1 comprises a cutting unit 3 and a disk unit 5. The disk unit 5 is sandwiched between an upper flange 2 and a lower flange 11. The upper flange 2 and the lower flange 11 are fastened together with a first screw 13.

[0055] The upper flange 2 is a component that connects to the mating flange 14 of the drain pipe 53, forms the outer frame of the leak detection device 1, and firmly fastens the upper side of the disk unit 5. A gasket 12 is provided on the upper part of the upper flange 2, which exhibits excellent sealing performance even in ultra-low temperature environments and can prevent leakage of liquefied gas. In addition, the cutting unit 3 is fixed to the inner surface of the upper flange 2 in a cantilevered manner, with one end containing the cutter blade 34 and the other end opposite it.

[0056] As shown in Figures 1 and 2, the cutting unit 3 has a double metal plate 31 which is a laminated metal plate formed by cold-press-welding a first metal plate 32 and a second metal plate 33 having different coefficients of thermal expansion, and a cutter blade 34 provided on the double metal plate 31.

[0057] The double metal plate 31 is a long, narrow rectangular, two-layer metal member fixed at one end in a cantilevered manner to the inner surface of the upper flange 2. It is formed by cold-press-welding a first metal plate 32 and a second metal plate 33, which have different coefficients of thermal expansion, so that the two types of metal plates appear as a single metal plate. The coefficient of thermal expansion of the first metal plate 32 is greater than that of the second metal plate 33, and since the first metal plate 32 is positioned below the double metal plate 31, if liquefied gas leaks, it will be exposed to extremely low temperatures (e.g., -162°C), causing the first metal plate 32 to contract rapidly and reliably bend the double metal plate 31 downwards.

[0058] The double metal plate 31 maintains a horizontal position at room temperature, but when liquefied gas leaked into the drain pipe flows in and reaches extremely low temperatures, the first metal plate 32 contracts, and due to the difference in thermal expansion coefficients between it and the second metal plate 33, it bends downward.

[0059] As an example of this embodiment, the first metal plate 32 is a Ni-Cr-Fe alloy, which has a large coefficient of thermal expansion and can provide stable downward deformation. In this embodiment, the first metal plate 32 is a Ni-Cr-Fe alloy, but it is not limited to Ni-Cr-Fe alloys as long as it has a large coefficient of thermal expansion, such as copper, nickel, Cu-Zn alloys, Ni-Cu alloys, Ni-Mn-Fe alloys, Mn-Ni-Cu alloys, and Ni-Mo-Fe alloys.

[0060] As an example of this embodiment, the second metal plate 33 is Invar, which has a low coefficient of thermal expansion and can provide stable downward deformation. In this embodiment, the second metal plate 33 is Invar, but it is not limited to Invar as long as it has a low coefficient of thermal expansion, such as silicon or ceramic.

[0061] Furthermore, the double metal plate 31 in this embodiment is an example of a multilayer metal plate, and a triple metal plate made of three types of metal plates laminated together, or a multilayer metal plate with even more layers, may be used as long as it is capable of bending and deformation.

[0062] As shown in Figure 2, a cutter blade 34 is attached to one end of the double metal plate 31, and moves downward in accordance with the deformation of the double metal plate 31 to cut the film 8. The cutter blade 34 consists of a cutter blade 4c at the tip of the double metal plate 31, and cutter blades 4a and 4b on its left and right sides, respectively. The arrangement of a total of three cutter blades 4a, 4b, and 4c ensures that the film 8 is reliably cut. In this embodiment, polyvinylidene chloride is used as the film 8 as an example, but aluminum foil or the like can also be used. In this embodiment, three cutter blades 34 are provided at one end of the double metal plate 31, but it is not limited to three; there may be two on the left and right, one, or four or more.

[0063] Furthermore, since the cutting edge of the cutter blade 34 in this embodiment is V-shaped, the cutting performance of the film 8 can be improved. In this embodiment, it is V-shaped, but it may also be U-shaped, a straight blade, a curved blade, or other shapes. The material of the cutter blade 34 may be stainless steel, special low-temperature resistant steel, superalloy, ceramic, etc.

[0064] The distance between the tip of the cutter blade 34 and the surface of the film 8 is preferably 6 mm or less, more preferably 1 to 3 mm, and in this embodiment, 2 mm, when the double metal plate 31 is not yet deformed. This ensures that even if the deformation of the double metal plate 31 is small, the cutter blade 34 can reliably reach the film 8 and reliably cut the film 8.

[0065] The cutter blade 34 is positioned to cut near the outer edge of the film 8 exposed through the openings of the first disc 7 and the second disc 9, and is a component for cutting near the edge of the film 8 by the deformation of the double metal plate 31. This allows the film 8 to be broken with less force than the central part, and ensures a reliable break.

[0066] Furthermore, even when the film 8 is vacuumed and bulges upward, the area near the outer edges of the film 8 does not bulge upward from the central area, making malfunctions less likely. Therefore, a configuration that cuts the film 8 near its edges is desirable. When the film 8 is ruptured, liquefied gas flows into the drain pipe 53, and the structure allows the liquefied gas to be discharged.

[0067] As shown in Figure 3, the disk unit 5 comprises a first gasket 6, a first disk 7 with an opening, a film 8, a second disk 9 with an opening, and a second gasket 10. The film 8 is sandwiched between the first disk 7 and the second disk 9.

[0068] As shown in Figure 1, the first gasket 6 is positioned between the upper flange 2 and the first disc 7 to improve the sealing performance of the joint. This ensures reliable prevention of liquefied gas leakage. The first gasket 6 is made of expanded graphite, ensuring high sealing performance even in cryogenic environments. As shown in Figure 4, the first gasket 6 is disc-shaped, but its shape is not limited to a disc.

[0069] As shown in Figure 3, the first disc 7 and the second disc 9, both with openings, are positioned vertically between the first gasket 6 and the second gasket 10, sandwiching and fixing the film 8 from both sides. This ensures that the film 8 is fixed and cut reliably when the cutter blade 34 cuts it. Preferably, the first disc 7 and the second disc 9 are made of a low-temperature resistant material such as stainless steel.

[0070] Film 8 is an ultra-thin tearing film sandwiched between the first disc 7 and the second disc 9. Normally, it maintains a sealed state, and when liquefied gas leaks, it is torn by the cutter blade 34 or physical impact, thereby detecting the liquefied gas leak and releasing the gas. Furthermore, this film 8 can be made of materials such as thin stainless steel sheets or resin films that are easily torn even at low temperatures.

[0071] As shown in Figure 1, the second gasket 10 is positioned between the second disc 9 and the lower flange 11 to improve the sealing performance of the joint. This ensures reliable prevention of liquefied gas leakage. The second gasket 10 is made of expanded graphite, ensuring high sealing performance even in cryogenic environments. As shown in Figure 4, the second gasket 10 is disc-shaped, but its shape is not limited to a disc.

[0072] The disk unit 5 is detachably attached between the upper flange 2 and the lower flange 11. Therefore, as shown in FIG. 7, by preparing the disk unit 5 including the first gasket 6, the first disk 7, the film 8, the second disk 9, and the second gasket 10 as a spare part, even after the liquefied gas leaks and the film 8 is broken due to the deformation of the double metal plate 31, by replacing it with the spare part disk unit 5, the leakage detection device 1 can be repeatedly used, and maintenance work can be performed easily and quickly.

[0073] Further, the lower flange 11 constitutes the outer frame of the leakage detection device 1 and firmly fastens the lower side of the disk unit 5.

[0074] (Leakage detection flow) Next, the flow of the leakage detection device 1 according to the present embodiment will be described.

[0075] First, connect the phase flange 14 of the drain pipe connected in the heat insulation layer 52 and the upper flange 2 of the leakage detection device 1, and install the leakage detection device 1.

[0076] Then, when the liquid liquefied gas leaks from the tank 50 for some reason and flows into the heat insulation layer 52 between the outer casing 51, the leaked liquefied gas is guided to the leakage detection device 1 arranged in the drain pipe 53 below the outer casing 51.

[0077] Then, when the double metal plate 31 of the leakage detection device 1 is exposed to extremely low temperature, the double metal plate 31 bends and deforms downward. Due to this bending deformation, the cutter blade 34 attached to the end of the double metal plate 31 descends and cuts the vicinity of the outer edge side of the film 8 exposed from the openings of the first disk 7 and the second disk 9.

[0078] As a result, the film 8 sandwiched between the first disk 7 and the second disk 9 is broken by the cutter blade 34, and the liquefied gas is quickly discharged and guided to a drip pan (not shown) installed below.

[0079] <Second Embodiment> Next, the second embodiment of the present invention will be described. The leakage detection device 1 of the first embodiment described above detects the leakage of liquefied gas by cutting the film 8 with the cutter blade 34 due to the deformation of the double metal plate 31, confirming the breakage of the film 8, and thereby confirming the discharge of the liquefied gas. However, the leakage detection device of the second embodiment further includes a sensor for detecting the deformation of the double metal plate, and detects the leakage by detecting the deformation of the double metal plate. Hereinafter, the same members as those in the first embodiment are denoted by the same reference numerals, and the description will mainly focus on the differences from the first embodiment.

[0080] As shown in FIG. 10, the leakage detection device 100 mainly includes a cutting unit 130, a proximity sensor 120 for detecting the deformation of the double metal plate 131, and a disk unit 5.

[0081] As shown in FIGS. 10(a) and 10(b), the cutting unit 130 includes a cutter blade 134 at the tip of the double metal plate 131 and a detected object 135 provided on the opposite side. The proximity sensor 120 is installed at a position close to the tip of the double metal plate 131.

[0082] The detected object 135 has an inclined surface that slopes from the front lower end to the rear upper end of the double metal plate 131. When the double metal plate 131 is curved and deformed downward, the inclined surface of the detected object 135 approaches the proximity sensor 120, and thus the movement of the detected object 135 is detected.

[0083] Specifically, as shown in FIG. 10(c), when liquefied gas leaks and the double metal plate 131 is curved and deformed downward due to a temperature change, the detected object 135 also moves downward along with the deformation. When the inclined surface of the detected object 135 approaches the proximity sensor 120, the proximity sensor 120 detects this and outputs an abnormal signal, thereby indicating that the liquefied gas is leaking.

[0084] Furthermore, the object to be detected 135 in this embodiment is made of an Fe-Cr alloy, for example, and retains its magnetism even at extremely low temperatures, thereby improving the detection accuracy of the proximity sensor 120. While the object to be detected 135 in this embodiment is made of an Fe-Cr alloy, it is not limited to this.

[0085] <Other Embodiments> As described above, preferred embodiments of the present invention have been explained with reference to the drawings, but it goes without saying that the present invention is not limited to the embodiments described above. Various modifications or changes within the scope of the claims also fall within the technical scope of the present invention.

[0086] For example, in the embodiment described above, the leak detection device 1 is connected to the flange 14 of the drain pipe, but the leak detection device may also be connected to the side of the tank or outer casing. Furthermore, the double metal plate described above is an example of a multilayer metal plate, and a triple metal plate made of three types of metal plates laminated together, or a multilayer metal plate with more layers, may be used as long as it is flexible and can be bent. Also, in the embodiment described above, the film 8 is sandwiched between the first disc 7 and the second disc 9, but the film may also be covered on either disc. [Explanation of Symbols]

[0087] 1. Leak detection device 2 Upper flange 3 Cutting Units 31 Double metal plate 32 1st metal plate 33 Second metal plate 34 cutter blades 35. Detected object 5 Disk Units 6. First gasket 7. Disc 1 8 film 9. Disc 2 10. Second gasket 11 Lower flange 12 Gaskets 13 First Screw 14-phase flange 15. Second screw 50 tanks 51 Exterior 52 Insulation layer 53 Drainage pipe 100 Leak detection device 120 proximity sensors 130 Cutting Unit 131 Double metal plate 134 Cutter blades 135 Detected object

Claims

1. A leak detection device for detecting leaks from a tank storing liquefied gas, comprising a cutting unit and a disk unit, The disk unit comprises a first disk having an opening, a second disk having an opening, and a film sandwiched between the first disk and the second disk. The cutting unit comprises a laminated metal plate formed by stacking a first metal plate and a second metal plate having different coefficients of thermal expansion, and a cutter blade provided on the laminated metal plate. The cutting unit is positioned such that the tip of the cutter blade is close to the film on the disc unit. Due to the temperature change caused by the leakage of liquefied gas, the laminated metal plate bends and deforms, and the cutter blade cuts the film. The cutting unit further includes a proximity sensor for detecting deformation of the laminated metal plate, The cutting unit includes a detection object at one end of the laminated metal plate, The object to be detected is provided on the side opposite to the side where the cutter blade is located. A leak detection device characterized in that the proximity sensor detects the movement of the object to be detected due to the deformation of the laminated metal plate.

2. The cutting unit is The cutter blade is positioned to cut the film exposed from the openings of the first and second discs. The film is cut by the deformation of the laminated metal plate. The leak detection device according to claim 1.

3. The cutting unit is The cutter blade is provided near one end of the laminated metal plate and positioned to cut the film exposed from the openings of the first and second discs. The film is characterized by being cut near the edge by deformation of the laminated metal plate. The leak detection device according to claim 2.

4. The cutting unit is Multiple cutter blades are provided near one end of the laminated metal plate, The laminated metal plate is in the shape of a long, narrow rectangle, The cutter blade is provided on the front end and left and right sides of the laminated metal plate, The leak detection device according to claim 1.

5. The cutting unit is The laminated metal plate is characterized in that the first metal plate has a greater coefficient of thermal expansion than the second metal plate, and the first metal plate is positioned below the laminated metal plate. The leak detection device according to claim 1.

6. The proximity sensor is provided in close proximity to the tip of the laminated metal plate, The object to be detected has an inclined surface that slopes backward from its lower end to its upper end. The movement of the object to be detected is detected when the inclined surface of the object to be detected approaches the proximity sensor due to the curvature deformation of the laminated metal plate. The leak detection device according to claim 1.

7. A leak detection device according to any one of claims 1 to 6, a tank for storing liquefied gas, and an outer casing on the outside of the tank, A space is formed between the tank and the exterior. A tank with leak detection, characterized in that the leak detection device is located below the tank in the space.

8. The exterior is equipped with a drain pipe connected to the lower part of the exterior, The leak detection device is located in the drain pipe, and the film is cut by the cutter blade, thereby releasing the liquefied gas. A tank with leak detection according to claim 7.

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