Gas leak detection device and gas leak detection method

Abstract

The present invention addresses the problem of providing a maintenance-free gas leak detection device and a gas leak detection method that simply detect the leakage of liquefied gas in a space to be detected and identify a leak site, the gas leak detection device being provided with: a plurality of thermal image cameras (1a, 1b) that detect the leakage of liquefied gas in a ship; the detection device is arranged towards detection objects (101, 102) containing liquefied gas. And a control device (2) that acquires thermal images from thermal image cameras (1a, 1b) that are arranged one by one on each of a plurality of straight lines in which the center angle (Ac) around the center (C) of a circumscribed ball (S) of the object to be detected (101, 102) is a predetermined angle.

Description

Technical Field

[0001] The present invention relates to a gas leak detection device and a gas leak detection method, and more particularly to a maintenance-free gas leak detection device and a gas leak detection method that can easily detect leakage of liquefied gas in a detection target space and identify the leakage location. Background Art

[0002] Liquefied gases such as liquefied ammonia and LPG (liquefied petroleum gas) are used as fuel in ships in addition to cargo, and demand is increasing.

[0003] If liquefied gas leaks inside a ship due to damage or deterioration of tanks storing liquefied gas or piping transporting liquefied gas, leak detection is necessary to ensure the safety of passengers.

[0004] Conventionally, as methods for detecting liquefied gas leakage, there are methods using semiconductor-type solid-state sensors and methods using constant-potential ionization-type electrochemical sensors.

[0005] Patent Document 1 describes a hydrogen gas leakage detection device that detects a temperature rise in a hydrogen storage portion made of a hydrogen storage alloy using a temperature sensor to determine the presence or absence of hydrogen gas leakage.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2008-020196 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] However, the aforementioned solid-state and electrochemical sensors must be selected based on the composition (type) of the liquefied gas being detected. Therefore, ships transporting or using multiple compositions (types) of liquefied gas must use multiple sensor types, increasing the number of sensors required.

[0011] Furthermore, these solid-state and electrochemical sensors require regular replacement and calibration, requiring significant effort and time. While scheduled vessels can handle this time-consuming and labor-intensive maintenance, tramp vessels cannot.

[0012] Furthermore, since the leaked liquefied gas vaporizes and diffuses into the space, if the leak site is far from the sensor installation site, it takes a long time for the vaporized gas to reach the sensor before being detected by the fixed gas detection sensor.

[0013] Furthermore, fixed gas detection sensors, such as the fixed temperature sensors described in Patent Document 1, have a limited detection area. Therefore, if the target space is large or if there are many devices, numerous sensors must be installed, resulting in significant installation effort, time, and expense. In such cases, a method using a ventilation fan to collect vaporized gas for detection is conceivable, but this requires extensive equipment and is associated with significant installation effort, time, and expense.

[0014] Using fixed gas detection sensors and temperature sensors to locate leaks requires a complex process, such as airtightness testing. Furthermore, for leaks from liquid delivery piping, installing a drip pan and a temperature sensor in that pan is an option. However, this method doesn't allow for accurate temperature readings until the leaked material collects in the pan, and liquefied gas leaks cannot be detected until the material has collected.

[0015] In addition, it is possible to consider using thermal image cameras to detect areas that have become cold due to leakage of liquefied gas. However, the shapes of tanks, pipes, etc. in ships are complex and are not only installed in the cabin but sometimes also in open spaces such as on the deck. Therefore, it is difficult to configure thermal image cameras on the surfaces of tanks, pipes, etc. in a way that does not create areas that cannot be photographed, i.e., blind spots.

[0016] Therefore, an object of the present invention is to provide a gas leak detection device and a gas leak detection method that can easily detect leakage of liquefied gas in a detection target space without leaving any undetectable locations, can identify the leakage location, and are maintenance-free.

[0017] Furthermore, other objects of the present invention will become apparent from the following description.

[0018] Means used to solve problems

[0019] The above-mentioned problems are solved by the following inventions. 1.

[0021] A gas leak detection device, characterized by comprising:

[0022] a plurality of thermal imaging cameras disposed in a ship so as to face a detection target space in which a detection target object containing liquefied gas is disposed and to be separated from each other; and

[0023] a control device that acquires the image captured by the thermal image camera as a thermal image,

[0024] The thermal image cameras are arranged one on each of two straight lines with a central angle of about 30° to about 180° around the center of the circumscribed sphere of the detection object, and two thermal image cameras are arranged in total. 2.

[0026] A gas leak detection device, characterized by comprising:

[0027] a plurality of thermal imaging cameras disposed in a ship so as to face a detection target space in which a detection target object containing liquefied gas is disposed and to be separated from each other; and

[0028] a control device that acquires the image captured by the thermal image camera as a thermal image,

[0029] The thermal image cameras are arranged one each on three straight lines with a central angle of approximately 120° around the center of the circumscribed sphere of the detection object, and a total of three thermal image cameras are arranged. 3.

[0031] A gas leak detection device, characterized by comprising:

[0032] a plurality of thermal imaging cameras disposed in a ship so as to face a detection target space in which a detection target object containing liquefied gas is disposed and to be separated from each other; and

[0033] a control device that acquires the image captured by the thermal image camera as a thermal image,

[0034] The thermal image cameras are arranged one each on four straight lines with a central angle of approximately 90° to approximately 110° around the center of the circumscribed sphere of the inspection object, and a total of four thermal image cameras are arranged. 4.

[0036] A gas leak detection device, characterized by comprising:

[0037] a plurality of thermal imaging cameras disposed in a ship so as to face a detection target space in which a detection target object containing liquefied gas is disposed and to be separated from each other; and

[0038] a control device that acquires the image captured by the thermal image camera as a thermal image,

[0039] The thermal image cameras are arranged one each at the front side, the rear side, the left side, the right side and the top side of the detection object space, and a total of five thermal image cameras are arranged. 5.

[0041] A gas leak detection device, characterized by comprising:

[0042] a plurality of thermal imaging cameras disposed in a ship so as to face a detection target space in which a detection target object containing liquefied gas is disposed and to be separated from each other; and

[0043] a control device that acquires the image captured by the thermal image camera as a thermal image,

[0044] The thermal imaging cameras are arranged two each on each axis of the xyz orthogonal coordinate system with the center of the circumscribed sphere of the detection object as the origin, for a total of six cameras.

[0045] The xyz orthogonal coordinates are rotated relative to the detection object space to prevent the thermal image camera from being configured on the ground of the detection object space. 6.

[0047] The gas leakage detection device described in any one of items 1 to 5 is characterized in that:

[0048] The control device determines that the liquefied gas is leaking when a ratio (α) of an area (At) of a temperature below a threshold temperature (Tr) in the thermal image to an area (A0) of the thermal image is greater than a threshold ratio (αr). 7.

[0050] The gas leakage detection device described in item 6 is characterized in that:

[0051] The threshold temperature (Tr) is set to any temperature between the saturation temperature of the liquefied gas at atmospheric pressure and the air temperature. 8.

[0053] The gas leakage detection device described in item 6 is characterized in that:

[0054] The area (A0) of the thermal image is the area of the thermal image based on one of the thermal image cameras. When the ratio (α) in the thermal image based on at least any one of the thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking. 9.

[0056] The gas leakage detection device described in item 6 is characterized in that:

[0057] The area (A0) of the thermal image is the sum of the areas of the multiple thermal images based on the multiple thermal image cameras. When the ratio (α) in the overall multiple thermal images based on the multiple thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking. 10.

[0059] A gas leak detection device, characterized by comprising:

[0060] a plurality of thermal imaging cameras disposed in a ship so as to face a detection target space in which a detection target object containing liquefied gas is disposed and to be separated from each other; and

[0061] a control device that acquires the image captured by the thermal image camera as a thermal image,

[0062] The control device determines that the liquefied gas is leaking when a ratio (α) of an area (At) of a temperature below a threshold temperature (Tr) in the thermal image to an area (A0) of the thermal image is greater than a threshold ratio (αr). 11.

[0064] The gas leakage detection device described in item 10 is characterized in that:

[0065] The threshold temperature (Tr) is set to any temperature between the saturation temperature of the liquefied gas at atmospheric pressure and the air temperature. 12.

[0067] The gas leakage detection device described in item 10 is characterized in that:

[0068] The area (A0) of the thermal image is the area of the thermal image based on one of the thermal image cameras. When the ratio (α) in the thermal image based on at least any one of the thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking. 13.

[0070] The gas leakage detection device described in item 10 is characterized in that:

[0071] The area (A0) of the thermal image is the sum of the areas of the multiple thermal images based on the multiple thermal image cameras. When the ratio (α) in the overall multiple thermal images based on the multiple thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking. 14.

[0073] A gas leak detection method, characterized in that:

[0074] In a ship, a plurality of thermal imaging cameras are arranged facing a detection target space in which a detection target object containing liquefied gas is located. Two thermal imaging cameras are arranged separately from each other, one on each of two straight lines having a central angle of approximately 30° to approximately 180° around the center of a sphere circumscribing the detection target object.

[0075] Using the thermal imaging camera to photograph the detection object space,

[0076] An image captured by the thermal image camera is acquired as a thermal image. 15.

[0078] A gas leak detection method, characterized in that:

[0079] In a ship, a plurality of thermal imaging cameras are arranged facing a detection target space in which a detection target object containing liquefied gas is located. Three thermal imaging cameras are arranged separately from each other, one on each of three straight lines with a central angle of approximately 120 degrees around the center of a circumscribed sphere surrounding the detection target object.

[0080] Using the thermal imaging camera to photograph the detection object space,

[0081] An image captured by the thermal image camera is acquired as a thermal image. 16.

[0083] A gas leak detection method, characterized in that:

[0084] In a ship, a plurality of thermal imaging cameras are arranged facing a detection target space in which a detection target containing liquefied gas is located. Four thermal imaging cameras are arranged, one each on four separate lines with a central angle of approximately 90° to approximately 110° around the center of a sphere circumscribing the detection target.

[0085] Using the thermal imaging camera to photograph the detection object space,

[0086] An image captured by the thermal image camera is acquired as a thermal image. 17.

[0088] A gas leak detection method, characterized in that:

[0089] In a ship, a plurality of thermal imaging cameras are arranged facing a detection target space where a detection object containing liquefied gas is arranged. The thermal imaging cameras are arranged separately from each other at the front, rear, left, right, and top sides of the detection target space, for a total of five cameras.

[0090] Using the thermal imaging camera to photograph the detection object space,

[0091] An image captured by the thermal image camera is acquired as a thermal image. 18.

[0093] A gas leak detection method, characterized in that:

[0094] In a ship, a plurality of thermal imaging cameras are arranged facing a detection target space in which a detection target object containing liquefied gas is arranged. Two thermal imaging cameras are arranged facing each other on each axis of the xyz orthogonal coordinate system with the center of the circumscribed sphere of the detection target as the origin, for a total of six thermal imaging cameras.

[0095] Using the thermal imaging camera to photograph the detection object space,

[0096] An image captured by the thermal image camera is acquired as a thermal image. 19.

[0098] The gas leakage detection method described in any one of items 14 to 18 is characterized in that:

[0099] When the ratio (α) of the area (At) of the region having a temperature below the threshold temperature (Tr) in the thermal image to the area (A0) of the thermal image is greater than or equal to a threshold ratio (αr), it is determined that the liquefied gas is leaking. 20.

[0101] The gas leakage detection method described in item 19 is characterized in that:

[0102] The threshold temperature (Tr) is set to any temperature between the saturation temperature of the liquefied gas at atmospheric pressure and the air temperature. twenty one.

[0104] The gas leakage detection method described in item 19 is characterized in that:

[0105] The area (A0) of the thermal image is the area of the thermal image based on one of the thermal image cameras. When the ratio (α) in the thermal image based on at least any one of the thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking. twenty two.

[0107] The gas leakage detection method described in item 19 is characterized in that:

[0108] The area (A0) of the thermal image is the sum of the areas of the multiple thermal images based on the multiple thermal image cameras. When the ratio (α) in the overall multiple thermal images based on the multiple thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking. twenty three.

[0110] A gas leak detection method, characterized in that:

[0111] In a ship, a plurality of thermal imaging cameras are arranged at intervals facing a detection target space where a detection target object containing liquefied gas is arranged.

[0112] Using the thermal imaging camera to photograph the detection object space,

[0113] acquiring an image captured by the thermal image camera as a thermal image,

[0114] When the ratio (α) of the area (At) of the region having a temperature below the threshold temperature (Tr) in the thermal image to the area (A0) of the thermal image is greater than or equal to a threshold ratio (αr), it is determined that the liquefied gas is leaking. twenty four.

[0116] The gas leakage detection method described in claim 23 is characterized in that:

[0117] The threshold temperature (Tr) is set to any temperature between the saturation temperature of the liquefied gas at atmospheric pressure and the air temperature. 25.

[0119] The gas leakage detection method described in claim 23 is characterized in that:

[0120] The area (A0) of the thermal image is the area of the thermal image based on one of the thermal image cameras. When the ratio (α) in the thermal image based on at least any one of the thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking. 26.

[0122] The gas leakage detection method described in claim 23 is characterized in that:

[0123] The area (A0) of the thermal image is the sum of the areas of the multiple thermal images based on the multiple thermal image cameras. When the ratio (α) in the overall multiple thermal images based on the multiple thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking.

[0124] Effects of the Invention

[0125] According to the present invention, a maintenance-free gas leak detection device and a gas leak detection method can be provided, which can easily detect leakage of liquefied gas in a detection target space without leaving any undetectable locations and can identify the leakage location. BRIEF DESCRIPTION OF THE DRAWINGS

[0126] Figure 1 This is a block diagram showing the configuration of the gas leak detection device according to the first embodiment.

[0127] Figure 2 The figures schematically show examples of thermal images taken by a thermal imaging camera, (a) is a normal image with no leakage, (b) is an image of a state in which leakage occurs from the weld portion of the tank, and (c) is an image of a state in which leakage occurs from the flange surface.

[0128] Figure 3 This is a flowchart showing the procedure of the gas leak detection method according to the embodiment.

[0129] Figure 4 It is a block diagram showing the configuration of a gas leak detection device according to a second embodiment.

[0130] Figure 5 It is a block diagram showing the configuration of a gas leak detection device according to a third embodiment.

[0131] Figure 6 This is a block diagram showing another example of the configuration of the gas leak detection device according to the third embodiment.

[0132] Figure 7 It is a block diagram showing the configuration of a gas leak detection device according to a fourth embodiment.

[0133] Figure 8 It is a block diagram showing the configuration of a gas leak detection device according to a fifth embodiment. DETAILED DESCRIPTION

[0134] [First embodiment]

[0135] Hereinafter, preferred embodiments of the present invention will be described.

[0136] Figure 1 This is a block diagram showing the configuration of the gas leak detection device according to the first embodiment.

[0137] like Figure 1 As shown, the gas leak detection device of this embodiment includes multiple thermal imaging cameras 1a and 1b. The multiple thermal imaging cameras 1a and 1b are arranged in a ship facing a detection target space 103 where detection targets 101 and 102 containing liquefied gas are located. The thermal imaging cameras 1a and 1b are arranged separately from each other.

[0138] The detection objects 101 and 102 containing liquefied gas are, for example, a tank 101 storing liquefied gas and / or a pipe 102 for transporting liquefied gas. However, the detection objects are not limited to the tank 101 and the pipe 102. Various articles containing liquefied gas may also be included in the detection objects.

[0139] The “tank for storing liquefied gas” includes various tanks such as a “fuel tank” and a “buffer tank”, and includes any of non-pressurized tanks, pressurized tanks, non-cryogenic tanks, and cryogenic tanks.

[0140] The liquefied gas contained in the detection targets 101 and 102 is not particularly limited, and examples thereof include liquefied ammonia gas and liquefied petroleum gas (LPG).

[0141] Furthermore, the tank 101 and the pipe 102 storing liquefied gas may contain both a gas phase and a liquid phase. Specifically, the liquefied gas stored as a liquid may vaporize and become a gas in a space above the liquid level within the tank 101 and the pipe 102. Furthermore, "gas leakage" includes the release of gas from the gas phase to the atmosphere, the release of liquefied gas from the liquid phase to the atmosphere, and the release of a gas-liquid mixture partially consisting of vaporized gas from both the gas and liquid phases to the atmosphere.

[0142] The detection object space 103 is, for example, a fuel conditioning room, but is not limited thereto, and may be in a cabin or on a deck. In addition, the detection object space 103 is not limited to a space enclosed by a ceiling, walls, and floor, but may be an open space identified as a certain area.

[0143] Thermal image cameras 1a and 1b are, for example, infrared thermal image cameras, and for example, "Chino Thermal Image Cameras CPA-T1000 / CPA-T800 / CPA-T500 manufactured by Chino Co., Ltd." can be used. The infrared thermal image camera can capture thermal images that are color-coded according to the surface temperature of the detection object (solid) such as the tank 101 and the piping 102.

[0144] This gas leak detection device includes a control device 2. The control device 2 receives image signals captured and output by the thermal imaging cameras 1a and 1b, and acquires the images captured by the thermal imaging cameras 1a and 1b as thermal images. The control device 2 displays the acquired thermal images on a display device (not shown).

[0145] When liquefied gas leaks into the atmosphere due to defects such as corrosion or loose joints on the inspection objects 101 and 102, the surfaces of the inspection objects 101 and 102 that come into contact with the low-temperature leaking liquefied gas absorb heat and cool to below ambient temperature. Furthermore, when the leaking liquefied gas vaporizes, the surfaces of the inspection objects 101 and 102 absorb the heat of vaporization and cool to below ambient temperature. The areas cooled by the liquefied gas leak can be easily and early identified in the thermal images captured by thermal imaging cameras 1a and 1b.

[0146] Figure 2 The figures schematically show examples of thermal images taken by a thermal imaging camera, (a) is a normal image with no leakage, (b) is an image of a state in which leakage occurs from the weld portion of the tank, and (c) is an image of a state in which leakage occurs from the flange surface.

[0147] like Figure 2 As shown in FIG, the cooled portion due to the leakage of liquefied gas is detected by thermal imaging cameras 1a and 1b. Figure 2 In FIG, a tank 101 and a pipe 102 are shown as detection objects. Figure 2 (a) shows a normal state of tank 101 and piping 102, with no leakage. Tank 101 is placed on a drip tray 107, and piping 102 is connected to a weld 104. Piping 102 is connected to other piping 102 via flange 105. Flange 105 is covered with thermal insulation material 106.

[0148] like Figure 2As shown in (b), when the liquefied gas in the tank 101 leaks from the welding part 104, the leaked liquefied gas 108 becomes low-temperature due to exposure to atmospheric pressure, and the leaked liquefied gas 109 dripping around the leakage part and on the drip tray 107 becomes low-temperature, which is detected in the thermal image taken by the thermal image cameras 1a and 1b.

[0149] In addition, if Figure 2 As shown in (c), when the liquefied gas in the tank 101 leaks from the mating surface of the flange 105, the leaked liquefied gas 109 drips from the gap of the insulating material 106 onto the drip tray 107, and its surrounding area becomes low temperature, which is detected in the thermal image taken by the thermal image cameras 1a and 1b.

[0150] In addition, if Figure 2 In either case of (b) or (c), by using a dedicated lens according to the type of liquefied gas in the tank 101, it is possible to detect the vaporized gas and further expand the detection area.

[0151] Furthermore, a zoom function that magnifies the leakage area improves the accuracy of leak area calculation. Furthermore, by recording the thermal image along with the capture time, the leak area and time can be determined even after the leak occurred.

[0152] Unless there are any malfunctions or other problems with the thermal imaging cameras 1a and 1b, no maintenance such as replacement or replenishment of sensors or reagents is required, and the thermal imaging cameras 1a and 1b are so-called maintenance-free.

[0153] When detecting a liquefied gas leak (cooling location) using thermal imaging cameras 1a and 1b, a threshold temperature (leak detection temperature) Tr can be set at any temperature between the saturation temperature of the target liquefied gas at atmospheric pressure and the air temperature. Furthermore, locations where the measured temperature Te is below the threshold temperature (leak detection temperature) Tr can be identified as cooling locations. Furthermore, cooling of the surfaces of detection objects 101 and 102 due to liquefied gas leakage may cause the temperature to drop below the saturation temperature of the target liquefied gas at atmospheric pressure.

[0154] Assuming the lowest winter temperature is -20°C, for example, if the target liquefied gas is liquefied ammonia, since its saturation temperature at atmospheric pressure is -33°C, the threshold temperature Tr can be between -33°C and -21°C. If the target liquefied gas is liquefied petroleum gas, since its saturation temperature at atmospheric pressure is -42°C, the threshold temperature Tr can be between -42°C and -21°C.

[0155] As described in this embodiment, when two thermal imaging cameras 1a and 1b are disposed separately from each other, one thermal imaging camera 1a and one thermal imaging camera 1b are disposed on each of two straight lines having a central angle Ac of approximately 30° to approximately 180° around the center C of the circumscribed sphere S surrounding the detection objects 101 and 102. If the central angle Ac is approximately 30° or greater, the thermal imaging cameras 1a and 1b can be considered to be separated from each other.

[0156] The relative positions of the thermal imaging cameras are preferably based on the circumscribed sphere of the detection object. This is because all detection objects are located within the circumscribed sphere, and no detection objects exist outside the circumscribed sphere. Therefore, the inside of the circumscribed sphere should be captured, and the outside of the circumscribed sphere does not need to be captured.

[0157] By using the circumscribed sphere defined by the inspection object as a reference, even in inspection spaces like fuel conditioning chambers where inspection objects such as tanks and piping are offset, or even if the inspection object exists in only one corner of the fuel conditioning chamber, the thermal imaging cameras can be positioned appropriately based on the shape and position of the inspection object to be imaged, regardless of the fuel conditioning chamber's shape or wall position. However, the thermal imaging cameras do not necessarily need to be positioned outside the circumscribed sphere; they can also be positioned on the surface of the circumscribed sphere or inside the sphere, as long as there are no blind spots where the surface of the inspection object cannot be imaged.

[0158] In addition, even if the detection target space where the detection object is set is not inside the cabin but in an open space such as on the deck, by using the circumscribed sphere determined by the detection object as a reference, each thermal image camera can be arranged at an appropriate position corresponding to the shape and position of the detection object to be photographed.

[0159] Furthermore, the plane including the center C of the circumscribed sphere S and the two straight lines on which the thermal imaging cameras 1a and 1b are arranged is not limited to a horizontal plane and may be an inclined plane or a vertical plane. Furthermore, the distance between the center C of the circumscribed sphere S and each thermal imaging camera need not be equal to each other and may be a different distance for each thermal imaging camera.

[0160] These situations also apply to other embodiments described later in which three or more thermal imaging cameras are used.

[0161] The thermal imaging cameras 1a and 1b are positioned so that no blind spots are created, preventing them from capturing images of the surfaces of the inspection targets 101 and 102. To avoid blind spots, it is preferable to position one thermal imaging camera 1a and one thermal imaging camera 1b on each of two straight lines whose center angles around the center of a circumscribed sphere S of the inspection targets are approximately 180°. If blind spots are created by using two thermal imaging cameras 1a and 1b depending on the shape and placement of the inspection targets 101 and 102, three or more thermal imaging cameras may be positioned, as in other embodiments described below.

[0162] Figure 3 This is a flowchart showing the procedure of the gas leak detection method according to the embodiment.

[0163] The control device 2 also has the function of analyzing the thermal images taken by the thermal image cameras 1a and 1b. Figure 3 As shown, the control device 2 executes the gas leak detection method of the embodiment. This gas leak detection method is also executed in the gas leak detection devices of other embodiments described later.

[0164] In step st1 , the control device 2 , which also functions as an image analysis device, sets the threshold temperature Tr (° C.), the threshold ratio αr, and the detection interval t (sec), and then proceeds to step st2 .

[0165] In step st2, the control device 2 measures the temperature Te (°C) in the thermal image (detection range) captured by the thermal image cameras 1a, 1b, calculates the area At of the region where the temperature Te (°C) is below the threshold temperature Tr (°C), and proceeds to step st3.

[0166] In step st3, the control device 2 determines whether the ratio α (=At / A0) of the area At to the area A0 of the thermal image is greater than or equal to a threshold ratio αr. If the ratio α is less than the threshold ratio αr, the control device 2 proceeds to step st4. If the ratio α is greater than or equal to the threshold ratio αr, the control device 2 proceeds to step st5. The threshold ratio αr is preferably set as low as possible, for example, preferably to approximately 1%.

[0167] Furthermore, the area A0 of the thermal image may be the area of a thermal image from a single thermal image camera or the sum of the areas of multiple thermal images from multiple thermal image cameras. If the area A0 of the thermal image is the area of a thermal image from a single thermal image camera, the process proceeds to step st5 if the ratio α is greater than or equal to the threshold ratio αr in the thermal image from at least one thermal image camera.

[0168] If the thermal image area A0 represents the entirety of multiple thermal images captured by multiple thermal imaging cameras, and if the ratio α is greater than or equal to the threshold ratio αr across the entirety of the thermal images, the process proceeds to step st5 . In this case, the threshold ratio is set to αr / n (∵n: the number of thermal imaging cameras) for determination. In this case, a region below the threshold temperature Tr (°C) is captured separately in multiple thermal images. Even if the area of this region in a single thermal image is small, the areas of these regions can be combined for accurate determination.

[0169] In step st4 , the control device 2 determines that there is no leakage of the liquefied gas, and returns to step st2 .

[0170] In step st5 , the control device 2 determines that there is a leakage of liquefied gas, transmits a leakage signal, records a thermal image, and proceeds to step st6 .

[0171] In step st6, the control device 2 notifies the ship of the presence of a liquefied gas leak based on the leak signal by sounding a warning sound with an alarm, playing a pre-recorded warning message, or emitting a warning light with a red lamp.

[0172] After the control device 2 takes measures to prevent the liquefied gas leakage, it restarts from step st1 . Alternatively, if the threshold temperature Tr (° C.), threshold ratio αr, and detection interval t (sec) do not need to be reset, it may restart from step st2 .

[0173] The gas leak detection method of the present invention uses the ratio α (=At / A0) of area At (the area where the temperature Te (°C) is below the threshold temperature Tr (°C)) to area A0 of the thermal image as a reference for determining the presence or absence of a gas leak, thereby achieving the following effects.

[0174] That is, by quantifying the region (area) below the threshold temperature Tr (° C.), rather than making a determination based on the temperature of a fixed point, a stable determination can be made.

[0175] Furthermore, if all image data were recorded, the storage data capacity would become enormous. However, in the gas leak detection device of the present invention, only the numerical value of the ratio α needs to be recorded, and thus the storage data capacity can be reduced.

[0176] Furthermore, if the threshold ratio αr is set in advance, the discrimination can be performed completely automatically.

[0177] Alternatively, a method that does not use the ratio α could be considered: comparing pixels between one acquired image and the next acquired image (detected after a detection interval t (seconds)). However, detecting temperatures that continuously and gradually change with gas leaks is difficult. In the gas leak detection method of the present invention, the area ratio α changes even when the temperature continuously and gradually changes, enabling reliable detection of gas leaks.

[0178] Furthermore, depending on the external environment, there may be air currents with a stronger force than the leaking gas. In this case, the flow of the leaking gas changes, making detection by comparing pixels difficult. In the gas leak detection method of the present invention, the area ratio α changes even when the flow of the leaking gas changes, thus enabling reliable detection of gas leaks.

[0179] [Second embodiment]

[0180] Figure 4 It is a block diagram showing the configuration of a gas leak detection device according to a second embodiment.

[0181] In this embodiment, if Figure 4 As shown, a plurality of thermal imaging cameras 1a, 1b, and 1c are arranged one on each of three straight lines having a center angle Ac of approximately 120° around the center C of a circumscribed sphere S surrounding the detection targets 101 and 102, for a total of three cameras.

[0182] By using three thermal imaging cameras 1 a , 1 b , and 1 c , it is possible to reduce blind spots on the surfaces of the detection targets 101 and 102 compared to the case of using two cameras.

[0183] The central angle Ac around the center C of the circumscribed sphere S can be appropriately set according to the shape and arrangement of the detection targets 101 and 102. The heights of the thermal imaging cameras 1a, 1b, and 1c can also be appropriately set according to the shape and arrangement of the detection targets 101 and 102.

[0184] In this embodiment, the plane including the center C of the circumscribed sphere S and the two straight lines on which any two thermal imaging cameras 1a, 1b (1a, 1c) (1b, 1c) are arranged is not limited to a horizontal plane and may be an inclined plane or a vertical plane. Furthermore, the thermal imaging cameras 1a, 1b, and 1c do not need to be arranged on a single plane including the center C of the circumscribed sphere S; two thermal imaging cameras 1a, 1b, and 1c may be arranged on three planes including the center C of the circumscribed sphere S.

[0185] In this embodiment as well, the gas leak detection method described in the first embodiment is executed by the control device 2 .

[0186] [Third embodiment]

[0187] Figure 5 It is a block diagram showing the configuration of a gas leak detection device according to a third embodiment.

[0188] In this embodiment, if Figure 5 As shown, multiple thermal image cameras 1a, 1b, 1c, and 1d are arranged one on each of four straight lines with a central angle Ac of approximately 90° to approximately 110° around the center C of the circumscribed sphere S surrounding the detection objects 101 and 102, for a total of four cameras.

[0189] By using four thermal imaging cameras 1 a , 1 b , 1 c , and 1 d , blind spots on the surfaces of the detection objects 101 and 102 are less likely to occur than in the case of using three thermal imaging cameras.

[0190] The central angle Ac around the center C of the circumscribed sphere S can be appropriately set according to the shape and arrangement of the detection targets 101 and 102. Furthermore, the heights of the thermal imaging cameras 1a, 1b, 1c, and 1d can also be appropriately set according to the shape and arrangement of the detection targets 101 and 102.

[0191] In this embodiment, the plane including the center C of the circumscribed sphere S and the two straight lines on which any two thermal imaging cameras are arranged is not limited to a horizontal plane and may also be an inclined plane or a vertical plane. Furthermore, the thermal imaging cameras 1a, 1b, 1c, and 1d do not need to be arranged on a single plane including the center C of the circumscribed sphere S. Two thermal imaging cameras may be arranged on each of four planes including the center C of the circumscribed sphere S.

[0192] Figure 6 This is a block diagram showing another example of the configuration of the gas leak detection device according to the third embodiment.

[0193] The central angle Ac between any two thermal image cameras is set to about 110°, and two cameras are arranged on each of the four planes including the center C of the circumscribed sphere S. Figure 6 As shown, four thermal imaging cameras 1a, 1b, 1c, and 1d are arranged at the vertices of a regular tetrahedron centered at the center C of the circumscribed sphere S. The central angle Ac in this case is 2tan ﹣1 √2≒109.47°.

[0194] In this embodiment as well, the gas leak detection method described in the first embodiment is executed by the control device 2 .

[0195] [Fourth embodiment]

[0196] Figure 7It is a block diagram showing the configuration of a gas leak detection device according to a fourth embodiment.

[0197] In this embodiment, if Figure 7 As shown, a plurality of thermal imaging cameras 1a, 1b, 1c, 1d, and 1e are arranged one each at the front, rear, left, right, and top sides of the detection target space 103, for a total of five cameras.

[0198] By using five thermal imaging cameras 1 a , 1 b , 1 c , 1 d , and 1 e , it is possible to reduce blind spots on the surfaces of the detection targets 101 and 102 compared to a case where four cameras are used.

[0199] In this embodiment, the thermal imaging camera 1e disposed on the upper side (ceiling) can capture the entire horizontal plane of the detection target space 103. In addition, by not disposing the thermal imaging camera on the lower side (ground), the placement and movement of the detection targets 101 and 102 within the detection target space 103 are not hindered.

[0200] In addition, the configuration position (direction and height) of the thermal image cameras 1a, 1b, 1c, 1d, and 1e can be appropriately set for each thermal image camera 1a, 1b, 1c, 1d, and 1e according to the shape and configuration of the detection object in the detection object space 103.

[0201] In this embodiment as well, the gas leak detection method described in the first embodiment is executed by the control device 2 .

[0202] [Fifth embodiment]

[0203] Figure 8 It is a block diagram showing the configuration of a gas leak detection device according to a fifth embodiment.

[0204] In this embodiment, if Figure 8 As shown, multiple thermal imaging cameras 1a, 1b, 1c, 1d, 1e, and 1f are arranged two each on opposite axes of the xyz orthogonal coordinate system with the center C of the inspection object as the origin within the inspection target space 103, for a total of six cameras. The xyz orthogonal coordinate system is rotated relative to the inspection target space 103 to prevent the thermal imaging cameras from being placed on the floor of the inspection target space 103.

[0205] By using six thermal imaging cameras 1 a , 1 b , 1 c , 1 d , 1 e , and 1 f , it is possible to avoid using five thermal imaging cameras and further prevent blind spots from being generated on the surfaces of the detection targets 101 and 102 .

[0206] In this embodiment, since the thermal imaging cameras 1a, 1b, 1c, 1d, 1e, and 1f can be arranged at point-symmetrical positions in all directions around the center C of the circumscribed sphere S of the detection object, it is possible to cope with various shapes and various arrangements of the detection objects in the detection object space 103. In addition, by not arranging the thermal imaging cameras on the lower side (ground), the arrangement and movement of the detection objects 101 and 102 in the detection object space 103 are not hindered.

[0207] In this embodiment, the central angle Ac between any two thermal image cameras is 90°, and the six thermal image cameras 1a, 1b, 1c, 1d, 1e, and 1f are arranged at the vertices of a regular octahedron with the center C of the circumscribed sphere S as the center.

[0208] In addition, the configuration position (direction and height) of the thermal image cameras 1a, 1b, 1c, 1d, 1e, and 1f can be appropriately set for each thermal image camera 1a, 1b, 1c, 1d, 1e, and 1f according to the shape and configuration of the detection object in the detection object space 103.

[0209] In this embodiment as well, the gas leak detection method described in the first embodiment is executed by the control device 2 .

[0210] Description of reference numerals:

[0211] 1a: Thermal imaging camera

[0212] 1b: Thermal imaging camera

[0213] 1c: Thermal imaging camera

[0214] 1d: Thermal imaging camera

[0215] 1e: Thermal imaging camera

[0216] 1f: Thermal imaging camera

[0217] 2: Control device

[0218] 101: Can (detection object)

[0219] 102: Piping (detection object)

[0220] 103: Detecting Object Space

[0221] 104: Welding area

[0222] 105: flange

[0223] 106: Insulation materials

[0224] 107: Drip tray

[0225] 108: Leakage of liquefied gas

[0226] 109: Leakage of liquefied gas

[0227] S: Sphere outside the detection object

[0228] C: Center of the outside ball

[0229] Ac: central angle

Claims

1. A gas leak detection device, characterized in that: have: A plurality of thermal imaging cameras are disposed in a vessel so as to face a detection target space in which a detection target object containing liquefied gas is disposed and to be separated from each other; as well as a control device that acquires the image captured by the thermal image camera as a thermal image, The thermal image cameras are arranged one on each of two straight lines with a central angle of about 30° to about 180° around the center of the circumscribed sphere of the detection object, and two thermal image cameras are arranged in total.

2. A gas leak detection device, characterized in that: have: A plurality of thermal imaging cameras are disposed in a vessel so as to face a detection target space in which a detection target object containing liquefied gas is disposed and to be separated from each other; as well as a control device that acquires the image captured by the thermal image camera as a thermal image, The thermal image cameras are arranged one each on three straight lines with a central angle of approximately 120° around the center of the circumscribed sphere of the detection object, and a total of three thermal image cameras are arranged.

3. A gas leak detection device, characterized in that: have: A plurality of thermal imaging cameras are disposed in a vessel so as to face a detection target space in which a detection target object containing liquefied gas is disposed and to be separated from each other; as well as a control device that acquires the image captured by the thermal image camera as a thermal image, The thermal image cameras are arranged one each on four straight lines with a central angle of approximately 90° to approximately 110° around the center of the circumscribed sphere of the inspection object, and a total of four thermal image cameras are arranged.

4. A gas leak detection device, characterized in that: have: A plurality of thermal imaging cameras are disposed in a vessel so as to face a detection target space in which a detection target object containing liquefied gas is disposed and to be separated from each other; as well as a control device that acquires the image captured by the thermal image camera as a thermal image, The thermal image cameras are arranged one each at the front side, the rear side, the left side, the right side and the top side of the detection object space, and a total of five thermal image cameras are arranged.

5. A gas leak detection device, characterized in that: have: A plurality of thermal imaging cameras are disposed in a vessel so as to face a detection target space in which a detection target object containing liquefied gas is disposed and to be separated from each other; as well as a control device that acquires the image captured by the thermal image camera as a thermal image, The thermal imaging cameras are arranged two each on opposite axes of the xyz orthogonal coordinate system with the center of the circumscribed sphere of the detection object as the origin, for a total of six cameras. The xyz orthogonal coordinates are rotated relative to the detection object space to prevent the thermal image camera from being configured on the ground of the detection object space.

6. The gas leakage detection device according to any one of claims 1 to 5, characterized in that: The control device determines that the liquefied gas is leaking when a ratio (α) of an area (At) of a temperature below a threshold temperature (Tr) in the thermal image to an area (A0) of the thermal image is greater than a threshold ratio (αr).

7. The gas leakage detection device according to claim 6, characterized in that: The threshold temperature (Tr) is set to any temperature between the saturation temperature of the liquefied gas at atmospheric pressure and the air temperature.

8. The gas leakage detection device according to claim 6, characterized in that: The area (A0) of the thermal image is the area of the thermal image based on one of the thermal image cameras. When the ratio (α) in the thermal image based on at least any one of the thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking.

9. The gas leakage detection device according to claim 6, characterized in that: The area (A0) of the thermal image is the sum of the areas of the multiple thermal images based on the multiple thermal image cameras. When the ratio (α) in the overall multiple thermal images based on the multiple thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking.

10. A gas leak detection device, characterized in that: have: a plurality of thermal imaging cameras disposed in a ship so as to face a detection target space in which a detection target object containing liquefied gas is disposed and to be separated from each other; and a control device that acquires the image captured by the thermal image camera as a thermal image, The control device determines that the liquefied gas is leaking when a ratio (α) of an area (At) of a temperature below a threshold temperature (Tr) in the thermal image to an area (A0) of the thermal image is greater than a threshold ratio (αr).

11. The gas leakage detection device according to claim 10, characterized in that: The threshold temperature (Tr) is set to any temperature between the saturation temperature of the liquefied gas at atmospheric pressure and the air temperature.

12. The gas leakage detection device according to claim 10, characterized in that: The area (A0) of the thermal image is the area of the thermal image based on one of the thermal image cameras. When the ratio (α) in the thermal image based on at least any one of the thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking.

13. The gas leakage detection device according to claim 10, characterized in that: The area (A0) of the thermal image is the sum of the areas of the multiple thermal images based on the multiple thermal image cameras. When the ratio (α) in the overall multiple thermal images based on the multiple thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking.

14. A gas leak detection method, characterized in that: In a ship, a plurality of thermal imaging cameras are arranged facing a detection target space in which a detection target object containing liquefied gas is located. Two thermal imaging cameras are arranged separately from each other, one on each of two straight lines having a central angle of approximately 30° to approximately 180° around the center of a sphere circumscribing the detection target object. Using the thermal imaging camera to photograph the detection object space, An image captured by the thermal image camera is acquired as a thermal image.

15. A gas leak detection method, characterized in that: In a ship, a plurality of thermal imaging cameras are arranged facing a detection target space in which a detection target object containing liquefied gas is located. Three thermal imaging cameras are arranged separately from each other, one on each of three straight lines with a central angle of approximately 120 degrees around the center of a circumscribed sphere surrounding the detection target object. Using the thermal imaging camera to photograph the detection object space, An image captured by the thermal image camera is acquired as a thermal image.

16. A gas leak detection method, characterized in that: In a ship, a plurality of thermal imaging cameras are arranged facing a detection target space in which a detection target containing liquefied gas is located. Four thermal imaging cameras are arranged, one each on four separate lines with a central angle of approximately 90° to approximately 110° around the center of a sphere circumscribing the detection target. Using the thermal imaging camera to photograph the detection object space, An image captured by the thermal image camera is acquired as a thermal image.

17. A gas leak detection method, characterized in that: In a ship, a plurality of thermal imaging cameras are arranged facing a detection target space where a detection object containing liquefied gas is arranged. The thermal imaging cameras are arranged separately from each other at the front, rear, left, right, and top sides of the detection target space, for a total of five cameras. Using the thermal imaging camera to photograph the detection object space, An image captured by the thermal image camera is acquired as a thermal image.

18. A gas leak detection method, characterized in that: In a ship, a plurality of thermal imaging cameras are arranged facing a detection target space in which a detection target object containing liquefied gas is arranged. Two thermal imaging cameras are arranged facing each other on each axis of the xyz orthogonal coordinate system with the center of the circumscribed sphere of the detection target as the origin, for a total of six thermal imaging cameras. Using the thermal imaging camera to photograph the detection object space, An image captured by the thermal image camera is acquired as a thermal image.

19. The gas leakage detection method according to any one of claims 14 to 18, characterized in that: When the ratio (α) of the area (At) of the region having a temperature below the threshold temperature (Tr) in the thermal image to the area (A0) of the thermal image is greater than or equal to a threshold ratio (αr), it is determined that the liquefied gas is leaking.

20. The gas leakage detection method according to claim 19, characterized in that: The threshold temperature (Tr) is set to any temperature between the saturation temperature of the liquefied gas at atmospheric pressure and the air temperature.

21. The gas leakage detection method according to claim 19, wherein: The area (A0) of the thermal image is the area of the thermal image based on one of the thermal image cameras. When the ratio (α) in the thermal image based on at least any one of the thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking.

22. The gas leakage detection method according to claim 19, characterized in that: The area (A0) of the thermal image is the sum of the areas of the multiple thermal images based on the multiple thermal image cameras. When the ratio (α) in the overall multiple thermal images based on the multiple thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking.

23. A gas leakage detection method, characterized in that: In a ship, a plurality of thermal imaging cameras are arranged at intervals from each other, facing a detection target space where a detection target object containing liquefied gas is arranged. Using the thermal imaging camera to photograph the detection object space, acquiring an image captured by the thermal image camera as a thermal image, When the ratio (α) of the area (At) of the region having a temperature below the threshold temperature (Tr) in the thermal image to the area (A0) of the thermal image is greater than or equal to a threshold ratio (αr), it is determined that the liquefied gas is leaking.

24. The gas leakage detection method according to claim 23, characterized in that: The threshold temperature (Tr) is set to any temperature between the saturation temperature of the liquefied gas at atmospheric pressure and the air temperature.

25. The gas leakage detection method according to claim 23, characterized in that: The area (A0) of the thermal image is the area of the thermal image based on one of the thermal image cameras. When the ratio (α) in the thermal image based on at least any one of the thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking.

26. The gas leakage detection method according to claim 23, characterized in that: The area (A0) of the thermal image is the sum of the areas of the multiple thermal images based on the multiple thermal image cameras. When the ratio (α) in the overall multiple thermal images based on the multiple thermal image cameras is greater than the threshold ratio (αr), it is determined that the liquefied gas is leaking.

Images