KR101058163B1 - Welding defect detection system and detection method of liquefied natural gas storage tank - Google Patents

Abstract

The welding failure detection method of the liquefied natural gas storage tank according to the present invention, for detecting the welding failure in the welding portion of the barrier coupled to the heat insulating layer for insulating the storage space to hermetically store the storage space where the liquefied natural gas is stored, a) injecting a detection gas between the insulation layer and the barrier; and b) detecting a gas leak in the air around the welding area by approaching the welding area with a gas detection device capable of detecting the detection gas and generating a detection signal. Monitoring the air around the welding site for the presence of gas. According to the present invention, welding defects can be easily and efficiently detected for a wide welding portion of the primary barrier by using a gas for detection and a gas detection apparatus capable of detecting the same.

Description

Welding defect detection system and detection method for liquefied natural gas storage tank {SYSTEM AND METHOD FOR DETECTING DEFECTIVE OF WELDING PART OF LNG TANK}

The present invention relates to a liquefied natural gas storage tank, and more particularly, a welding defect detection system of a liquefied natural gas storage tank for detecting a welding failure of the primary barrier for hermetically sealing the storage space in which the liquefied natural gas is stored. It is about a method.

Liquefied natural gas storage tank is for storing or transporting ultra low temperature Liquefied Natural Gas (Liquefied Natural Gas, LNG) at about -165 ° C, and has a spherical type and a membrane type. Membrane type liquefied natural gas storage tank is widely used because of its larger loading capacity and simpler manufacturing than the spherical type liquefied natural gas storage tank.

In general, membrane type liquefied natural gas storage tank is provided with two barriers to seal the liquefied natural gas, and is divided into Mark-III type and NO-96 type according to the insulation sealing structure. The Mark-III type has a primary barrier made of stainless steel and a secondary barrier made of metal or fiberglass composite material. In contrast, the NO-96 type is made of Inva steel with a very low coefficient of thermal expansion (CTE) for both primary and secondary barriers. In addition, the Mark-III type forms an insulation layer by using an insulation pad in which a polyurethane plate insulation board having low thermal conductivity is combined with a protection plate having a high compressive strength such as plywood. On the other hand, the NO-96 type forms a heat insulating layer made of pearlite insulating material.

 In Mark-III type, a plurality of barrier sheets made of stainless steel are welded together to form a primary barrier. In the NO-96 type, a plurality of barrier sheets made of Invar steel are welded to form a primary barrier. Since the primary barriers of each of these types of liquefied natural gas storage tanks are directly in contact with the liquefied natural gas, high airtightness is required to prevent the liquefied natural gas from leaking. Defects or minute gaps in the welds of the primary barrier can lead to leakage of liquefied natural gas, which can significantly reduce safety. Therefore, if there is a welding defect in the welding part of the primary barrier, it must be detected in advance and the defect must be removed.

As a method for detecting a weld failure of a welding portion of a primary barrier, a method of applying a reaction material to a welding portion and injecting a reaction gas into a space between the primary barrier and the heat insulating layer is known. This detection method uses the principle that the reaction material applied to the welding site is discolored by reacting with the reaction gas. If there is a leak in the weld area due to a poor welding, the reaction gas filled in the space between the primary barrier and the insulation layer leaks through the leaking area, and the reaction material is discolored by the leaking reaction gas, thereby detecting the welding failure. It is.

However, the welding defect detection method as described above has a disadvantage in that the post-treatment is cumbersome and the detection work time is long because the reaction material applied to the welding portion is removed after detecting the welding defect. In addition, since a gas harmful to the human body is used as a reaction gas for discoloring the reaction material, safety problems may occur when the welding defect is detected.

The present invention is to solve the above problems, by using a gas detection device that can detect the gas and the detection gas harmless to the human body, the detection operation is safe and the working time can be shortened liquefied natural It is an object of the present invention to provide a welding failure detection system and detection method for a gas storage tank.

Welding failure detection method of the liquefied natural gas storage tank according to one aspect of the present invention for achieving the above object, the welding of the barrier coupled to the heat insulating layer for insulating the storage space to hermetically store the storage space where the liquefied natural gas is stored In order to detect a welding defect in the site, a) injecting a detection gas between the insulating layer and the barrier, b) welding the gas detection device capable of generating a detection signal by detecting the detection gas Accessing the site and monitoring the air around the welding site for the presence of the detection gas leaking into the air around the welding site.

In the step b) it is possible to guide the air around the welding site to the gas detection device using a blowing fan.

In step b), the gas sensing device may be moved at a constant speed along the welding portion, and the movement of the gas sensing device may include a rail installed at a predetermined distance from the surface of the barrier and the gas sensing device mounted thereon. This can be done via a mover that can move along the rail. Here, when the detection signal is generated, the mobile device may be stopped.

Welding failure detection method of a liquefied natural gas storage tank according to another aspect of the present invention for achieving the above object, the welding of the barrier coupled to the insulating layer for insulating the storage space to hermetically store the storage space where the liquefied natural gas is stored A method for detecting welding defects at a site, the method comprising: a) disposing a plurality of gas detection devices on a surface of the barrier; and b) a gas for detection by the gas detection device between the insulation layer and the barrier. And c) when the injection of the detection gas is completed, using the plurality of gas detection apparatuses, whether the detection gas leaked in the air around the welding site is present or not. Monitoring; and d) if there is a gas detecting device detecting the detecting gas among the plurality of gas detecting devices. Locating the leaked site where the gas leaked.

Step c) detects the air around the welding portion while taking time from the time when the injection of the detection gas is completed, and step d) detects the detection gas first of the plurality of gas detection devices The first detection time of the first gas detection device is checked, the second detection time of the second gas detection device which detects the detection gas for the second time among the plurality of gas detection devices, and the detection gas Diffusion rate, the distance between the first gas detector and the second gas detector, the distance between the leak site and the first gas detector, the distance between the leak site and the second gas detector, The first detection time and the second detection time can be used to locate the leak.

And the location of the leak can be represented by the following equation.

Where d ₁ is the distance between the leak and the first gas detector, L is the distance between the first gas detector and the second gas detector, t ₁ is the first gas detection time, and t ₂ is the second gas The detection time.

In addition, in step c), the air around the welding site is blown at a constant speed toward the plurality of gas detection apparatus, the location of the leaking site can be represented by the following equation.

Where d ₃ is the distance between the leak and the first gas detector, d ₄ is the distance between the first gas detector and the second gas detector, t ₃ is the first gas detection time, and t ₄ is the second Gas detection time.

In addition, in the step a), the plurality of gas sensing devices may be arranged at regular intervals.

In addition, the detection gas may include any one selected from the group consisting of alcohol gas and carbon dioxide.

Welding failure detection system of the liquefied natural gas storage tank according to an aspect of the present invention for achieving the above object, the welding of the barrier coupled to the insulating layer for insulating the storage space to hermetically store the storage space where the liquefied natural gas is stored A detection signal is generated by detecting a welding defect at a site, and a gas injection device for injecting a detection gas between the heat insulation layer and the barrier, and detecting the detection gas leaked from the air around the welding site. It includes a gas sensing device.

Welding failure detection system of the liquefied natural gas storage tank according to the present invention may further include a blowing fan for inducing air around the welding site to the gas detection device.

In addition, the welding failure detection system of the liquefied natural gas storage tank according to the present invention further includes a rail installed a predetermined distance away from the welding portion, and a moving device mounted on the gas detection device and moving along a constant speed along the rail. In addition, the movement device may be controlled by the movement signal.

In addition, the gas detection apparatus has an output means for outputting the detection signal to inform the user, the output of the output means may be varied according to the size of the detection signal.

Welding failure detection system of the liquefied natural gas storage tank according to another aspect of the present invention for achieving the above object, the welding of the barrier coupled to the insulating layer for insulating the storage space to hermetically store the storage space where the liquefied natural gas is stored In order to detect a welding defect in the site, a gas injection device for injecting a detection gas between the heat insulating layer and the barrier, and detects the detection gas leaked from the air around the welding site and generates a detection signal And a central processing unit for receiving the detection signals from the plurality of gas detection devices, and finding a leaked site where the detection gas leaks through the plurality of detection signals.

The welding failure detection system of the liquefied natural gas storage tank according to the present invention may further include a blower for blowing air around the welding portion at a constant speed toward the plurality of gas detection devices.

According to the present invention, welding defects can be easily and efficiently detected for a wide welding portion of the primary barrier by using a gas for detection and a gas detection apparatus capable of detecting the same.

In addition, according to the present invention, there is an effect that the detection operation time is shortened as compared with the conventional welding failure detection method that is to apply the reaction material to the welding site and remove the reaction material after the welding failure detection.

In addition, according to the present invention, by using a detection gas that is not harmful to the human body, such as alcohol gas or carbon dioxide, the risk of safety problems during the welding failure detection operation is greatly reduced.

Hereinafter, a welding failure detection system and a detection method of a liquefied natural gas storage tank according to the present invention will be described with reference to the accompanying drawings through various embodiments.

1 and 2 illustrate a method for detecting a welding failure of the primary barrier of the liquefied natural gas storage tank using a welding failure detection system of the liquefied natural gas storage tank according to an embodiment of the present invention.

As shown in Figure 1 and 2, the welding failure detection system of the liquefied natural gas storage tank according to an embodiment of the present invention by detecting the welding failure in the construction step of the liquefied natural gas storage tank of the liquefied natural gas storage tank It can improve stability and reliability.

The liquefied natural gas storage tank includes an outer heat insulating layer 12 and an inner heat insulating layer 13, and a storage space for insulating the outermost tank wall 11 and the storage space of the liquefied natural gas formed inside the tank wall 11. It includes a primary barrier 14, a secondary barrier 15 disposed between the outer heat insulating layer 12 and the inner heat insulating layer 13 to directly surround and prevent the leakage of liquefied natural gas. The primary barrier 14 is formed by welding a plurality of barrier sheets 16 made of metal, such as stainless steel or Invar steel, to the surface of the inner heat insulating layer 13. The primary barrier 14 is a part directly contacting the cryogenic liquefied natural gas, high airtightness is required, and if there is a coupling in the primary barrier 14, the liquefied natural gas may leak and lead to a large accident. Therefore, if there is a bond in the primary barrier 14, it should be detected and removed at the construction stage. The welding failure detection system according to an embodiment of the present invention can detect defects on the welded portions 17 and 18 of the primary barrier 14 that are relatively prone to defects.

Welding failure detection system of the liquefied natural gas storage tank according to an embodiment of the present invention is welded with the gas injection device 21 for injecting the inspection gas into the space between the primary barrier 14 and the inner heat insulating layer 13 And a gas sensing device 22 capable of sensing a test gas in the air around the areas 17 and 18. As the inspection gas, a single gas or a mixed gas of a kind that is not harmful to the human body, such as alcohol gas or carbon dioxide, may be used.

As shown in FIGS. 2 and 3, the gas detecting device 22 detects a test gas and generates a detection signal 23, a signal amplifier 24 for amplifying a detection signal, and a detection signal. And output means such as a lamp 25 and a buzzer 26 for outputting the light in a visual and audio manner. Since the operating principle of the device for detecting a gas for detection, such as alcohol gas or carbon dioxide is well known, a detailed description thereof will be omitted. The detection signal generated when the detection unit 23 detects the inspection gas may increase in proportion to the concentration of the inspection gas, and the output of the lamp 25 and the buzzer 26 may increase in proportion to the magnitude of the detection signal. Can be. As an output means for outputting a sensing signal generated by the sensing unit 23, various devices using a display for displaying letters or symbols or other sensory methods may be used.

In addition, a blower fan 27 is installed at one side of the gas detector 22 to guide the air around the welded portions 17 and 18 to the gas detector 22. The use of the blower fan 27 allows the gas detector 22 to contact the air around the welds 17 and 18 more quickly.

Hereinafter, a process of detecting a welding failure of the liquefied natural gas storage tank using the welding joint detection system according to the present embodiment will be described.

After the primary barrier 14 of the liquefied natural gas storage tank is constructed, as shown in FIG. 1, the gas injection device 21 detects the space between the primary barrier 14 and the internal insulation layer 13. Gas is injected. The gas for detection is filled in the space between the primary barrier 14 and the internal heat insulation layer 13 to reach a constant pressure higher than atmospheric pressure. This is because the pressure of the charged detection gas must be higher than the atmospheric pressure so that the detection gas can quickly move to the outside of the primary barrier 14 through the leak portion P ₁ . Injection of the gas for detection may be made through a temporary inlet formed temporarily on one side of the primary barrier 14, and used to fill nitrogen for pressure check between the primary barrier 14 and the internal thermal insulation layer 13. It may be made through the injection port.

After filling the gas for detection, the gas sensing device 22 is moved by the user to monitor the air around the welded areas 17 and 18. At this time, the gas sensing device 22 is preferably moved along the welding portion (17, 18). As shown in FIG. 2, if there is a gap in the welded areas 17 and 18 due to a poor welding, a gas for detection leaks through the leaked area P ₁ , and the gas detection device 22 includes a welded area ( 17) (18) detects the leaked detection gas in the air around and outputs a detection signal through the lamp 25 and the buzzer (26). The user can confirm the presence of the leaking portion P ₁ through the light of the lamp 25 and the sound of the buzzer 26.

If the brightness of the lamp 25 or the sound of the buzzer 26 changes according to the concentration of the gas for detection, the user may detect the brightness of the lamp 25 and the change in the sound of the buzzer 26 while the gas sensing device 22 is detected. By moving the position of the leak site (P ₁ ) can be found. If a leaking part (P ₁ ) is found, the user can repair it to eliminate the welding defect. When the welding failure detection and repair work is completed for the entire welded area (17) (18), the detection gas is exhausted in the space between the primary barrier 14 and the inner heat insulating layer (13). By using this welding failure detection method, it is possible to easily and efficiently perform welding failure detection on the welded portions 17 and 18 of the primary barrier 14.

Figure 4 shows a method for detecting the welding failure of the primary barrier using the welding failure detection system of the liquefied natural gas storage tank according to another embodiment of the present invention. In the description of the welding failure detection system according to the present embodiment, the same parts as the welding failure detection systems shown in FIGS. 1 and 2 will be described with the same reference numerals.

The welding failure detection system according to another embodiment of the present invention fills the gas for detection in the space between the primary barrier 14 and the inner insulation layer 13, as in the welding failure detection system shown in FIGS. 1 and 2. The detection device 22 is the same in that it detects the welding gas leaking through the leaking portion (P ₁ ) due to the welding failure to detect the welding failure. However, in the welding failure detection system according to another embodiment of the present invention, the gas detection device 31 is moved by the moving device 34 as compared with the welding failure detection system in which the gas detection device 31 is manually moved by a user. The difference is that it is automatically moved along the welds 17 and 18.

Welding failure detection system according to another embodiment of the present invention, in addition to the gas injection device 21 (see Fig. 1) and the gas detection device 31, the gas detection device 31 along the welding portion (17) (18) It further comprises a moving device 34 and a rail 39 for moving automatically. The rails 39 are spaced apart from the surface of the primary barrier 14 by a predetermined distance in parallel to the welded portions 17 and 18. The mover 34 rests on the rail 39 to move along the rail 39. The gas sensing device 22 is mounted on the moving device 34 to monitor the air around the welded areas 17 and 18 while automatically moving along the welded areas 17 and 18.

As shown in FIGS. 4 and 5, the moving device 34 includes a body 35 on which the gas sensing device 31 is mounted, and a plurality of wheels 36 coupled to the body 35 to be in contact with the rail 39. ), A driving device 37 for driving the plurality of wheels 36, and a driving control device 38 for controlling the driving device 37. The drive control device 38 moves or stops the body 35 by controlling the operation of the drive device 37 and adjusts the moving speed of the body 35. The drive controller 38 can be controlled by a user.

The welding failure detection method using the welding failure detection system of the liquefied natural gas storage tank according to another embodiment of the present invention having such a configuration is as follows.

When the gas for detection is filled in the space between the primary barrier 14 and the inner insulation layer 13 to a pressure higher than atmospheric pressure, the moving device 34 is operated to move the gas detector 31 along the rail 39. Move at speed. At this time, when the moving device 34 operates at the time of leaking part P ₂ due to a poor welding, the filled detection gas leaks through the leaking part P ₂ to weld the parts 17 and 18. ) May be set to a time point that is sufficiently spread around. In addition, the moving speed of the moving device 34 is set to a speed at which the gas detecting device 31 can sufficiently contact the detection gas leaked out of the air around the welded areas 17 and 18. After the detection gas is filled, the timing at which the mobile device 34 moves and the moving speed of the mobile device 34 may be appropriately adjusted according to the diffusion speed of the detection gas or the surrounding environment.

As shown in FIG. 4, if there is a leaking part P ₂ due to a poor welding in the welding parts 17 and 18 (see FIG. 1), the filled detection gas diffuses around the welding parts 17 and 18. Then, the gas detecting device 31 detects the leaked detection gas when moving around the leak portion (P ₂ ). At this time, the gas detection device 31 generates a detection signal, and when the detection signal is generated, the lamp 32 and the buzzer 33 operate, and the driving control device 38 stops the driving device 37. Therefore, the gas detector 31 stops around the leaked portion P2, and the user can find the leaked portion P ₂ through the stop position of the gas detector 31. The time point at which the drive control device 38 stops the drive device 37 may be set to a time point at which the detection signal of the gas detection device 31 increases and starts to decrease. At this time, the gas detection device 31 may stop at a position closer to the leak portion (P ₂ ). In this embodiment, the drive control device 38 may operate irrespective of the detection signal generated by the gas detection device 31.

In the present embodiment, since the rails 39 are difficult to be disposed in the entire welded portions 17 and 18 of the primary barrier 14, the welding failure detection work for the entire welded portions 17 and 18 is constant. It can be executed by dividing by size. In the welding failure detection method according to this embodiment, since the gas detecting device 31 is automatically moved along the welding portions 17 and 18 by the moving device 34, the trouble of the user during the welding failure detection operation is greatly increased. Can be less.

6 and 7 illustrate a welding failure detection system of a liquefied natural gas storage tank according to another embodiment of the present invention and two methods of detecting welding failure of a primary barrier using the welding failure detection system.

Welding failure detection system according to another embodiment of the present invention is an essential component gas injection device 21 for injecting the detection gas into the space between the primary barrier 14 and the inner heat insulating layer 13 (see Fig. 1) ), A leaking part that detects a gas for detection and receives a detection signal from a plurality of gas detection devices 41 and 42 and a plurality of gas detection devices 41 and 42 that generate a detection signal. (P ₃ ) includes a central processing unit (43) for calculating (P ₄ ), an optional component with a timer (44) for measuring the detection time of the detection gas, the pressure for detecting the filling pressure of the detection gas Sensor 45, a blower 46 for forming a constant velocity airflow around the welded areas 17 and 18, a lamp 47 for outputting a detection result, a buzzer 48, and a display 49; .

FIG. 6 illustrates a method of detecting a welding failure and finding a leaking portion P ₃ using the welding failure detection system according to the present embodiment when the air around the welding portions 17 and 18 is in a stable state without flow. It is shown. In the welding failure detection operation, first, a plurality of gas detection devices 41 and 42 are disposed along the welding portions 17 and 18. As shown in FIG. 1, the entire welded portion 17, 18 of the primary barrier 14 has a checkerboard shape in which the straight welded portion 17 in the front-rear direction and the straight welded portion 18 in the left-right direction cross each other. Since the plurality of gas detection devices (41) (42) is preferably arranged at regular intervals in the front, rear, left and right directions in a predetermined region of the primary barrier (14). 6 shows only two gas detection devices 41 and 42 typically arranged in the left and right directions.

When a plurality of gas detectors 41 and 42 are disposed, a gas for detection is injected into the space between the primary barrier 14 and the internal heat insulation layer 13. When the pressure of the gas for detection filled in the space between the primary barrier 14 and the internal insulation layer 13 reaches a constant pressure higher than atmospheric pressure, the plurality of gas detection devices 41 and 42 operate to operate the welding site 17. The air around the (18) starts to be monitored, and the timer 44 is activated to time from the point at which the gas detectors 41 and 42 operate. If a leaking part P ₃ is present in the welded parts 17 and 18 due to poor welding, the gas for detection leaks and diffuses at a constant speed around the leaked part P ₃ .

The gas to be detected spreads first reaches the gas detector 41 closest to the leaked portion P ₃ , and the gas detector 41 which first detects the gas to be detected in the air transmits a detection signal to a central processing unit ( 43). At this time, the central processing unit 43 checks the position and the first detection time of the first gas detection device 41 that first detected the gas for detection. When the gas for detection is further diffused and reaches the gas detector 42 closest to the leak site P ₃ , the gas detector 42 detects this and transmits the detection signal to the central processing unit 43. do. The central processing unit 43 checks the position and second detection time of the second gas detection device 42 which secondly detected the gas for detection, and then calculates the location of the leaked portion P ₃ . The location of the leaked portion (P ₃ ) is the diffusion rate of the gas for detection, the distance from the leaked portion (P ₃ ) to the first gas detector (41), and the second gas detector (42) at the leaked portion (P ₃ ). Equation 1 to Equation 3 below, with the distance to the first gas detector 41 and the second gas detector 42, the first gas detection time, and the second gas detection time as variables. Calculated by

Where V ₁ is the diffusion velocity of the gas for detection, d ₁ is the distance between the leak site (P ₃ ) and the first gas detector (41), d ₂ is the leak site (P ₃ ) and the second gas detector The distance between 42, L represents the distance between the first gas detector 41 and the second gas detector 42, t ₁ is the first gas detection time, t ₂ is the second gas detection time. In Equation 3, since the variables L, t ₁ , and t ₂ are all known values, the leaked area P ₃ may be found by obtaining a distance from the leaked area P ₃ to the first gas detector 41. .

Of course, the position of the leak portion (P ₃₎ may represent the distance from the leak (P ₃₎ up to the second gas sensing device 42, as shown in the following equation (4) such.

The central processing unit 43 calculates the leaked portion P ₃ , and then outputs the result through the display 49, and informs the user in a visual and audio manner through the lamp 47 and the buzzer 48. Can be. If a leak signal P ₃ does not exist and a plurality of gas detectors 41 and 42 start detecting the air around the welded portions 17 and 18, the detection signal does not occur even after a certain time. The central processing unit 43 may determine that there is no leakage part P ₃ and notify the user through the lamp 47, the buzzer 48, or the display 49.

In this embodiment, the central processing unit 43 for calculation of the central processing unit 43 has been described as calculating the leak (P ₃₎ after receiving the two detecting signals, a more accurate leak (P ₃₎ After receiving the three or more detection signals may calculate the leak portion (P ₃ ). In addition, the welding failure detection operation for the entire primary barrier 14 may be divided into a size of a predetermined area that can be covered by the plurality of gas detection devices 41 and 42 at once.

In detecting a welding failure by the welding failure detection method, using a gas for detection and a plurality of gas detection devices (41, 42) capable of detecting the same, the position of the leaking portion (P ₃ ) in the same way as described above Except for calculating the sub-steps, the additional steps can be changed and adjusted according to the situation.

The welding failure detection method shown in FIG. 7 uses a blower 46 to create a flow of air in a predetermined direction and speed around the welded areas 17 and 18, and provides a plurality of gas detection devices 41 and 42. Use it to find the leak (P ₄ ). By controlling the air flow around the welded areas 17 and 18 by using the blower 46, when the irregular air flows around the welded areas 17 and 18, the position of the leaked area P ₄ is adjusted. You can find out more accurately.

In this welding failure detection method, a plurality of gas detection devices (41) (42) are arranged in a line along the welding areas (17) (18), and starts monitoring the air around the welding areas (17) (18). The lower side blower 46 flows the air around the welding part 17 and 18 at a constant speed toward the some gas-sensing device 41 and 42. FIG. Therefore, when the leaked portion P ₄ is present, the detection gas leaked through the leaked portion P ₄ is diffused toward the gas detectors 41 and 42 at the same speed as that of the flowing air.

As shown in Figure 7, leaks (P ₄₎ is when exists for a leak detection gas is diffused at a constant speed toward a plurality of gas sensors 41 and 42, detecting the gas for which diffusion is leaks, In turn (P ₄ ) to the gas detector 42 located far from the gas detector 41 close to. When the gas for detection reaches the gas detector 41 closest to the leaked portion P ₄ , the corresponding gas detector 41 detects this and transmits a detection signal to the central processing unit 43. At this time, the central processing unit 43 first checks the position and the first detection time of the first gas detection device 41 for detecting the detection gas. Subsequently, when the gas for detection is further diffused to reach another gas detecting device 42, the corresponding gas detecting device 42 detects this and transmits the detection signal to the central processing unit. The central processing unit checks the position of the gas detection unit 42 which secondly detected the gas for detection and the second detection time, and then calculates the position of the leaked portion P ₄ . Here, the calculation for the leaked portion (P ₄ ) may be made through the following equations (5) to (7).

Here, V ₂ is the diffusion speed of the detection gas blown by the blower 46, d ₃ is the distance between the leak site (P ₄ ) and the first gas detector 41, d ₄ is the first gas Distance between the detector 41 and the second gas detector 42, d ₅ is the distance between the leak site P ₄ and the second gas detector 42, t ₃ is the first gas detection time, t ₄ represents the second gas detection time. In Equation 3, since the variables d ₄ , t ₃ , and t ₄ are all known values, the leaked area P ₄ can be found by finding the distance from the leaked area P ₄ to the first gas detector 41. have.

In the detection of welding failure using the welding failure detection method according to the present embodiment, welding failure detection for the entire primary barrier 14 can be covered by a plurality of gas detection devices 41 and 42 at once. It may be executed by dividing the size into a predetermined area. In addition, additional steps such as the number of arrangements of the gas detectors 41 and 42, the interval between arrangements, and the speed of air flow through the blower 46 may be variously changed according to circumstances.

As described above, the welding failure detection system and detection method for the LNG storage tank according to the present invention utilize a gas for detecting a gas that is not harmful to the body and a gas detection device capable of detecting the same, thereby welding the wide primary barrier 14. Weld defects on the portions 17 and 18 can be detected easily and efficiently. Welding failure detection system and detection method of the liquefied natural gas storage tank according to the present invention can be usefully used to detect the welding failure of the liquefied natural gas storage tank of various types in which a welding site exists.

The present invention described above is not limited to the configuration and operation as shown and described. That is, the present invention can be variously changed and modified within the spirit and scope of the claims described.

1 and 2 are a perspective view and a side cross-sectional view showing a method for detecting a welding failure of the primary barrier using a welding failure detection system of the liquefied natural gas storage tank according to an embodiment of the present invention.

3 is a block diagram showing the configuration of a gas detection apparatus of the welding failure detection system of the liquefied natural gas storage tank shown in FIG.

Figure 4 is a side cross-sectional view showing a method for detecting the welding failure of the primary barrier using the welding failure detection system of the liquefied natural gas storage tank according to another embodiment of the present invention.

5 is a block diagram showing a part of the configuration of the welding failure detection system shown in FIG.

6 and 7 are side cross-sectional views illustrating two methods of detecting a welding failure of a primary barrier using a welding failure detection system of a liquefied natural gas storage tank according to another embodiment of the present invention.

FIG. 8 is a block diagram showing a part of a welding failure detection system of a liquefied natural gas storage tank according to another embodiment of the present invention used in the welding failure detection method shown in FIGS. 6 and 7.

♣ Explanation of symbols for the main parts of the drawing ♣

11: tank wall 12: outer insulation layer

13: inner insulation layer 14: primary barrier layer

15: secondary barrier layer 16: barrier sheet

17, 18: welding part 21: gas injection device

22, 31, 41, 42: gas detector 23: detector

24: signal amplifier 27: blowing fan

34: moving device 37: driving device

38 drive control device 39 rail

43: central processing unit 44: timer

Claims (19)

delete In the welding failure detection method of the liquefied natural gas storage tank for detecting a welding failure in the welding portion of the barrier coupled to the insulating layer for insulating the storage space to hermetically store the storage space for the liquefied natural gas, a) injecting gas for detection between the thermal insulation layer and the barrier; b) monitoring the air around the welding site to detect the presence of the detection gas leaked in the air around the welding site by approaching the welding site by detecting a gas for detecting the gas for detection; Including monitoring; The welding failure detection method of the liquefied natural gas storage tank, characterized in that in the step b) using the blowing fan to guide the air around the welding site to the gas detection device. In the welding failure detection method of the liquefied natural gas storage tank for detecting a welding failure in the welding portion of the barrier coupled to the insulating layer for insulating the storage space to hermetically store the storage space for the liquefied natural gas, a) injecting gas for detection between the thermal insulation layer and the barrier; b) monitoring the air around the welding site to detect the presence of the detection gas leaked in the air around the welding site by approaching the welding site by detecting a gas for detecting the gas for detection; Including monitoring; The welding failure detection method of the liquefied natural gas storage tank, characterized in that for moving the gas detection device at a constant speed along the welding portion in step b). Claim 4 was abandoned when the registration fee was paid. Welding failure of the liquefied natural gas storage tank, characterized in that for moving the gas detection device using a rail installed a predetermined distance away from the surface of the barrier, and the mobile device equipped with the gas detection device and movable along the rail. Detection method. Claim 5 was abandoned upon payment of a set-up fee. The method of claim 4, wherein The welding failure detection method of a liquefied natural gas storage tank, characterized in that for stopping the moving device when the detection signal occurs. delete In the welding failure detection method of the liquefied natural gas storage tank for detecting a welding failure in the welding portion of the barrier coupled to the insulating layer for insulating the storage space to hermetically store the storage space for the liquefied natural gas, a) placing a plurality of gas sensing devices on a surface of said barrier; b) injecting a gas for detection that the gas sensing device can detect between the thermal insulation layer and the barrier; c) when the injection of the detection gas is complete, using the plurality of gas detection apparatus to monitor the air around the welding site whether the detection gas leaked in the air around the welding site; d) if there is a gas detecting device for detecting the detection gas among the plurality of gas detecting device to find the location of the leaking site leaking the detection gas; Step c) detects the air around the welding area while taking a time from the time when the injection of the detection gas is completed, In step d), the first detection time of the first gas detection device that first detects the detection gas among the plurality of gas detection devices is checked, and the detection gas is second in the plurality of gas detection devices. Check the second detection time of the second gas detection device that detects, the diffusion rate of the detection gas, the distance between the first gas detection device and the second gas detection device, the leaked site and the first gas Liquefied natural gas storage tank, characterized in that for finding the location of the leak site using the distance between the detection device, the distance between the leak site and the second gas detection device, the first detection time and the second detection time. Welding defect detection method The method of claim 7, wherein The location of the leaking site is a welding failure detection method of a liquefied natural gas storage tank, characterized in that the following equation.

Where d ₁ is the distance between the leak and the first gas detector, L is the distance between the first gas detector and the second gas detector, t ₁ is the first gas detection time, and t ₂ is the second Gas detection time) The method of claim 7, wherein In step c), the air around the welding site is blown at a constant speed toward the plurality of gas detection device, the location of the leaked site of the liquefied natural gas storage tank, characterized in that Welding defect detection method.

(Where d ₃ is the distance between the leak and the first gas detector, d ₄ is the distance between the first gas detector and the second gas detector, t ₃ is the first gas detection time, and t ₄ is two Second gas detection time) Claim 10 was abandoned upon payment of a setup registration fee. The method of claim 7, wherein The welding failure detection method of the liquefied natural gas storage tank, characterized in that the plurality of gas detection device in the step a) is arranged at a predetermined interval. Claim 11 was abandoned upon payment of a setup registration fee. The method according to claim 2 or 7, The detection gas is a welding failure detection method of a liquefied natural gas storage tank, characterized in that it comprises any one selected from the group consisting of alcohol gas and carbon dioxide. delete In the welding failure detection system of the liquefied natural gas storage tank for detecting the welding failure in the welding portion of the barrier coupled to the heat insulating layer for insulating the storage space for hermetically storing the storage space for the liquefied natural gas, A gas injection device for injecting gas for detection between the heat insulation layer and the barrier; A gas detector for detecting a gas leaked from the air around the welding part and generating a detection signal; Blowing fan for guiding the air around the welding portion to the gas detection device ; welding failure detection system of a liquefied natural gas storage tank comprising a. In the welding failure detection system of the liquefied natural gas storage tank for detecting the welding failure in the welding portion of the barrier coupled to the heat insulating layer for insulating the storage space for hermetically storing the storage space for the liquefied natural gas, A gas injection device for injecting gas for detection between the heat insulation layer and the barrier; A gas detector for detecting a gas leaked from the air around the welding part and generating a detection signal; A rail installed at a predetermined distance from the welding portion; And a mobile device mounted to the gas detecting device and capable of moving at a constant speed along the rail. Claim 15 was abandoned upon payment of a registration fee. The method of claim 14, The moving device is a welding failure detection system of the liquefied natural gas storage tank, characterized in that the movement operation is controlled by the detection signal. Claim 16 was abandoned upon payment of a setup registration fee. The method according to claim 13 or 14, The gas detection device has a welding failure detection system of the liquefied natural gas storage tank, characterized in that it has an output means for outputting the detection signal to inform the user. Claim 17 has been abandoned due to the setting registration fee. The method of claim 16, The output of the output means welding failure detection system of the liquefied natural gas storage tank, characterized in that the variable according to the magnitude of the detection signal. In the welding failure detection system of the liquefied natural gas storage tank for detecting the welding failure in the welding portion of the barrier coupled to the heat insulating layer for insulating the storage space for hermetically storing the storage space for the liquefied natural gas, A gas injection device for injecting gas for detection between the heat insulation layer and the barrier; A plurality of gas detection devices for detecting the detection gas leaked from the air around the welding part and generating a detection signal; A central processing unit which receives the detection signals from the plurality of gas detection devices and finds a leaked site where the detection gas leaks through the received plurality of detection signals; And a blower for blowing air around the welding portion at a constant speed toward the plurality of gas detectors. The welding failure detection system of a liquefied natural gas storage tank comprising: a. delete

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