JP2024044539A - Purge structure of flange connection and liquefied gas tank - Google Patents

Abstract

[Problem] To suppress outflow of fluid that may leak from a flange connection. [Solution] A liquefied gas tank 1 includes a tank body 10 for storing liquefied hydrogen LH, a pump barrel 2 having a barrel opening 2A with a top flange 2F and vertically penetrating the tank body 10, a pump 3 installed in the tank body 10 and discharging the liquefied hydrogen LH to the outside through the pump barrel 2, and a head plate 25 attached so as to be superimposed on the top flange 2F to form a flange connection part 4 and seal the barrel opening 2A. A purge space 6 isolated from the outside air is formed around the flange connection part 4. Furthermore, a supply pipe 61 for supplying purge gas to the purge space 6, and an exhaust pipe 62 for exhausting the purge gas together with the leaked gas from the purge space 6 are provided. [Selected Figure] Figure 2

Description

This disclosure relates to a purge structure for a flange connection and a liquefied gas tank to which the purge structure is applied.

Generally, a flange connection consists of an overlap between the flanges of two tubes. There are also flange connections consisting of an overlap between a flange of a tube and a sealing plate that closes the opening of the flange in the tube. When the tube body is for gas or liquid circulation, leakage of gas or liquid from the overlapped portion at the flange connection portion poses a problem.

The flange connection is also present in liquefied gas tanks that store low-temperature liquefied gas such as liquefied hydrogen and liquefied natural gas. The liquefied gas tank includes a pump barrel that penetrates the tank body vertically, and a pump installed in the tank body. The upper end of the pump barrel is provided with a barrel opening that allows the pump in the tank body to be removed during maintenance of the pump. The barrel opening is "closed" during tank operation by a head plate that constitutes the flange connection with the upper end flange of the pump barrel (see, for example, Patent Document 1). In liquefied gas tanks, leakage of the stored liquefied gas or its vaporized gas from the flange connection is a problem.

JP 2011-69466 A

Generally, an approach is taken to prevent leakage of gas or liquid from the flange connection portion by reinforcing the seal structure at the overlapping portion. However, for example, in the case of large-diameter flange connections, flange connections of gases with small molecular sizes, or flange connections of pipelines for the distribution of high-pressure fluids, it is assumed that even if the seal structure is strengthened, leakage cannot be sufficiently suppressed. It is necessary to do so.

An object of the present disclosure is to provide a purge structure for a flange connection part that can suppress the outflow of fluid leaking from the flange connection part, and a liquefied gas tank to which the purge structure is applied.

The purge structure of a flange connection part according to one aspect of the present disclosure includes a flange connection part consisting of an overlapping part between the flanges of two pipe bodies or an overlapping part between the flange of a pipe body and a sealing plate, a housing that defines a purge space isolated from the outside air around the overlapping part of the flange connection part, and a purge pipe that allows the supply of purge gas to the purge space and the exhaust of the purge gas.

A liquefied gas tank according to another aspect of the present disclosure is a liquefied gas tank having the above-mentioned flange connection portion purge structure, and includes a tank body for storing liquefied gas, a pump barrel having an upper end opening with a flange and vertically penetrating the tank body, a pump installed in the tank body and discharging the liquefied gas to the outside through the pump barrel, and a head plate attached so as to be overlapped with the flange and sealing the upper end opening, and the flange connection portion is composed of the overlapping portion of the flange of the upper end opening and the head plate.

The present disclosure provides a purge structure for a flange connection that can prevent fluid leaking from the flange connection from flowing out to the outside, and a liquefied gas tank to which the purge structure is applied.

FIG. 1 is a cross-sectional view schematically showing a liquefied gas tank to which a flange connection purge structure of the present disclosure is applied. FIG. 2 is a side view, partially in cross section, showing the vicinity of the upper end of the pump barrel of the liquefied gas tank. FIG. 3 is a top view, partially in cross section, showing the upper end of the pump barrel. FIG. 4 is a schematic diagram showing another example of the purging structure of the flange connection portion of the present disclosure.

Below, an embodiment of the purge structure for a flange connection according to the present disclosure will be described in detail with reference to the drawings. In this embodiment, an example is shown in which the purge structure is applied to a liquefied gas tank. The liquefied gas tank exemplified here is a flat-bottom tank that stores low-temperature liquefied gas. The stored liquefied gas is, for example, liquefied hydrogen, liquid helium, liquid nitrogen, liquefied natural gas, liquefied petroleum gas, or liquefied ammonia.

[Overall structure of liquefied gas tank]
1 is a cross-sectional view showing a schematic diagram of a liquefied gas tank 1 according to an embodiment of the present disclosure. The liquefied gas tank 1 is a flat-bottom tank having a multi-shell structure that is stationary on the ground and stores cryogenic liquefied hydrogen LH. The liquefied gas tank 1 includes a tank body 10 that stores the liquefied hydrogen LH, a pump barrel 2 (tube body) that is a structure for discharging the liquefied hydrogen LH from the tank body 10, and a submerged pump 3 that is installed in the tank body 10 while being immersed in the liquefied hydrogen LH.

The tank body 10 has a storage space that stores liquefied hydrogen LH. Although FIG. 1 shows a simple single-shell structure, the actual tank body 10 has a multi-shell structure such as a double-shell structure or a triple-shell structure. In the case of a double shell structure, the tank body 10 is composed of an outer tank installed on a foundation, an inner tank enclosed in the outer tank, and a cold insulation layer between the outer tank and the inner tank. Ru. Liquefied hydrogen LH is stored inside the inner tank. The cold insulation layer is filled with a powder heat insulating material such as granular perlite and a low boiling point gas. In the case of the triple shell structure, the tank body 10 has a structure further including an intermediate tank between the outer tank and the inner tank. In addition, the tank body 10 may be a tank having a shape other than a flat bottom, a tank buried underground, or the like.

The pump barrel 2 is a cylindrical body installed so as to vertically penetrate the tank body 10, and is an outlet pipe for discharging the liquefied hydrogen LH inside the tank body 10 to the outside. The pump barrel 2 has an internal barrel space 20 that is an internal space through which liquefied hydrogen LH flows. The pump barrel 2 includes an inner portion housed within the tank body 10 and a protruding portion extending upward from the tank body 10. The lower end 21 of the pump barrel 2 is arranged near the bottom plate of the tank body 10 and immersed in the liquefied hydrogen LH. The upper end 22 of the pump barrel 2 penetrates the tank roof 11 and is arranged at a predetermined height position. The barrel interior space 20 extends vertically between the lower end 21 and the upper end 22 and has an inner diameter that allows the pump 3 to pass therethrough.

The pump 3 is accommodated in the barrel space 20 near the lower end 21. A foot valve 23 is attached to the intake opening at the lower end 21 of the pump barrel 2. The pump 3 is placed on the foot valve 23. The foot valve 23 hangs down due to the weight of the pump 3, opening the intake opening at the lower end 21. As shown by the arrow in FIG. 1, the pump 3 takes in liquefied hydrogen LH from the tank body 10, increases the pressure, and sends the liquefied hydrogen LH to the barrel space 20. A discharge port 24 that discharges the liquefied hydrogen LH to the outside is protruded from the side near the upper end 22 of the pump barrel 2. When the pump 3 is operated, the liquefied hydrogen LH is discharged from the barrel space 20 through the discharge port 24.

At the upper end of the pump barrel 2, there is a barrel opening 2A (upper end opening) that communicates the barrel inner space 20 and the outer space, and a top flange 2F (tubular body flange) arranged on the outer peripheral edge of the barrel opening 2A. It is provided. The barrel opening 2A is sealed by a flange connection portion 4. The flange connection portion 4 consists of an overlapping portion of the top flange 2F and the head plate 25 (sealing plate). When the liquefied gas tank 1 is in operation, the barrel opening 2A is sealed by attaching the head plate 25 to the top flange 2F.

The head plate 25 is removed, for example, during maintenance of the pump 3. During maintenance, the pump 3 is taken in and out through the barrel opening 2A. This is performed by winding and unwinding a lifting wire connected to the pump 3 using a lifting device installed above the barrel opening 2A.

The portion of the pump barrel 2 that protrudes from the tank body 10 and the outer surface of the flange connection portion 4 are covered with a cold insulation material 5. The cold insulation material 5 may be a solid insulation material such as rigid urethane foam, a powder insulation material such as granular perlite, or an insulation block material made by packaging glass wool. The cold insulation material 5 may be bound around the periphery with a metal band such as a stainless steel band, and the outer periphery may be covered with moisture-proof tape or the like.

The flange connection portion 4 is provided with a purge structure capable of suppressing gas that may leak from the overlapping portion of the flange connection portion 4 from flowing out. The purge structure includes a purge space 6 arranged inside the cold insulating material 5 and around the flange connection part 4, and a supply pipe 61 and an exhaust pipe 62 communicating with the purge space 6. This purge structure will be explained in detail below.

[Purge structure]
Fig. 2 is a side view showing the vicinity of the upper end 22 of the pump barrel 2 of the liquefied gas tank 1, partially in cross section, and Fig. 3 is a top view thereof, showing the purge structure. Fig. 3 shows the auxiliary configuration of the purge structure in blocks. The purge structure is composed of a flange connection part 4, a cold insulation material 5, a purge space 6, and a supply pipe 61 and an exhaust pipe 62, which are purge pipes. The auxiliary configuration includes a gas supply device 71, a gas detection sensor 72, and a control unit 8.

A gasket 26 is incorporated into the flange connection portion 4 to ensure sealing. The gasket 26 is a ring-shaped sealing member that is interposed between the top flange 2F and the head plate 25 on the radial outside of the barrel opening 2A. It may be difficult to prepare a gasket 26 that is resistant to cryogenic liquefied hydrogen LH and provides perfect sealing against hydrogen, which has a small molecular size. In particular, when the barrel opening 2A has a large diameter or is subjected to high pressure, it becomes even more difficult to ensure sealing. Therefore, it may be necessary to assume a certain amount of hydrogen gas or liquefied hydrogen LH leaking from the flange connection portion 4.

In view of this, in this embodiment, a purge space 6 isolated from the outside air is provided around the overlapping portion of the top flange 2F and the head plate 25 at the flange connection portion 4. The purge space 6 is formed by a housing capable of partitioning a space isolated from the outside air. In this embodiment, an example is shown in which the housing that partitions the purge space 6 is a cold insulation material 5. The purge space 6 is a space formed in a ring shape along the outer periphery of the overlapping portion of the top flange 2F and the head plate 25. By disposing the purge space 6 in this manner, hydrogen gas or liquefied hydrogen LH leaking from the overlapping portion can be trapped in the purge space 6. The purge space 6 may be filled with a cold insulation material such as glass wool or granular perlite, or a seal gas.

The cold insulation material 5 includes a flange cold insulation material 51 and a barrel cold insulation material 52. The flange cold insulation material 51 envelops and covers the upper, lower and side surfaces of the flange connection portion 4. The barrel cold insulation material 52 covers the side surface of the portion extending from the upper end portion 22 of the pump barrel 2 to the tank roof 11 (Figure 1). An annular recess is provided in the flange cold insulation material 51 at a location corresponding to the side surface of the flange connection portion 4. Due to the formation of the recess, the side portion of the flange cold insulation material 51 and the side surface of the flange connection portion 4 are not in close contact with each other.

The recess in the flange cold insulation material 51 serves as a housing that divides the purge space 6. That is, in this embodiment, the flange cold insulation material 51 serves both to keep the flange connection portion 4 cool and to act as the housing. This eliminates the need for a dedicated housing member, simplifying the purge structure. Instead of the recess, a separately prepared duct-shaped housing may be attached to the side of the flange connection portion 4, with its outer periphery covered by the flange cold insulation material 51.

The supply pipe 61 and the exhaust pipe 62 are purge pipes that enable supply of purge gas to the purge space 6 and exhaust thereof. The supply piping 61 includes a supply side connecting pipe 63 and a supply terminal pipe 64. The supply side connecting pipe 63 is a pipe that guides the purge gas from the gas supply device 71 that is a supply source of the purge gas to the flange connection portion 4 . An inert gas can be used as the purge gas. Here, an example will be shown in which the gas supply device 71 is a supply source of nitrogen gas, and the nitrogen gas is guided to the vicinity of the flange connection part 4 through the supply side connecting pipe 63.

The supply terminal pipe 64 is a pipe for actually introducing purge gas into the purge space 6. An edge opening 64E at the tip of the supply terminal pipe 64 penetrates the flange cold insulator 51 and enters the purge space 6. The base end side of the supply terminal pipe 64 protrudes from the side circumferential surface of the flange cold insulating material 51 and is flange-connected to the terminal end of the supply side connecting pipe 63. The outer peripheral surface of the protruding portion of the supply terminal pipe 64 is covered with the auxiliary cold insulating material 53. Note that the supply side connecting pipe 63 and the supply terminal pipe 64 may be permanently installed pipes, but the supply side connecting pipe 63 may be a temporary pipe that is installed as needed. Further, the covering with the auxiliary cold insulating material 53 may be omitted. Furthermore, it is desirable to provide the supply side connecting pipe 63 with an on-off valve that can seal the purge space 6 when no gas leaks.

The exhaust pipe 62 includes an exhaust terminal pipe 65 and an exhaust side connecting pipe 66. The exhaust terminal pipe 65 is a pipe for leading out of the purge space 6 the purge gas supplied from the supply terminal pipe 64 to the purge space 6 . An edge opening 65E at the tip of the exhaust terminal pipe 65 penetrates the flange cold insulator 51 and enters the purge space 6. 2 and 3 show an example in which the exhaust terminal pipe 65 is arranged at a position opposite to the supply terminal pipe 64. This arrangement is just an example, and as long as both terminal pipes 64 and 65 are not too close to each other, they may be arranged at any position in the circumferential direction of these flange connection portions 4. However, if both terminal pipes 64 and 65 are arranged as opposite electrodes as shown in the figure, the efficiency of purging can be increased. The protruding portion of the exhaust terminal pipe 65 from the flange cold insulating material 51 is also covered with the auxiliary cold insulating material 53. The covering with this auxiliary cold insulating material 53 may also be omitted.

The exhaust side connecting pipe 66 is a pipe that discharges purge gas and gas leaking from the flange connection part 4 to the outside. In this embodiment, nitrogen gas and hydrogen gas are discharged by the exhaust side connecting pipe 66. The beginning end of the exhaust side connecting pipe 66 and the base end of the exhaust terminal pipe 65 are flange-connected. The end of the exhaust side connecting pipe 66 is connected to a tank that collects exhaust gas, or is led to equipment that dissipates the exhaust gas into the atmosphere or performs other appropriate processing. The exhaust side connecting pipe 66 may be a temporary pipe, and it is preferable to provide an opening and closing valve.

As described above, the gas supply device 71 is a supply source of purge gas such as nitrogen gas. The gas supply device 71 includes a tank for storing the purge gas and a pump device for supplying the purge gas from the tank through the supply pipe 61 to the purge space 6.

The gas detection sensor 72 is a sensor that detects gas leakage from the flange connection portion 4 . The gas detection sensor 72 includes a probe tube 73. The probe tube 73 is disposed so as to be drawn out from the outer circumferential surface 41 of the flange connection portion 4, through the purge space 6, through the flange cold insulating material 51, and to the outside. Gas components near the flange connection portion 4 are detected by the gas detection sensor 72 via the probe tube 73.

The tip 74 of the probe tube 73 is positioned on the outer periphery of the overlapping portion of the top flange 2F and the head plate 25, or near the outer periphery of the gasket 26. The tip 74 is an inlet for the gas to be detected, which in this embodiment is hydrogen gas. FIG. 3 shows an example in which the tip 74 is positioned opposite the edge opening 64E of the supply terminal pipe 64. Alternatively, the tip 74 may be positioned opposite the edge opening 65E of the exhaust terminal pipe 65, or shifted 90 degrees circumferentially from the edge openings 64E, 65E.

A detection nozzle 75 is attached to a portion of the probe tube 73 that extends from the flange cold insulating material 51 . The detection nozzle 75 is connected to the gas detection sensor 72 via piping or the like. As the gas detection sensor 72, for example, a hot wire semiconductor type sensor that utilizes a change in electrical conductivity caused by a metal oxide semiconductor adsorbing hydrogen gas can be used.

The control unit 8 controls the purge operation of the purge space 6 by controlling the operation of the gas supply device 71. When the control unit 8 issues an operation command, the gas supply device 71 sends nitrogen gas to the supply pipe 61 as a purge gas. The purge gas is supplied to the purge space 6 from the supply pipe 61. Pressured by the supply pressure of the purge gas, the gas present in the purge space 6 is discharged from the exhaust pipe 62 together with the purge gas. If hydrogen gas is leaking from the flange connection portion 4, nitrogen gas and hydrogen gas will be exhausted from the exhaust pipe 62.

The following two control modes can be exemplified as control modes of the gas supply device 71 by the control unit 8. In the first control example, the control section 8 operates the gas supply device 71 when the gas detection sensor 72 detects leakage of hydrogen gas from the flange connection section 4 . Since the gasket 26 is incorporated into the flange connection portion 4, a certain degree of sealing performance is ensured. Therefore, instead of performing the purge operation all the time, the gas supply device 71 is operated to perform the purge operation when the sealing performance is degraded for some reason and hydrogen gas leakage is detected by the gas detection sensor 72. . According to the first control example, the purge operation can be performed in a timely manner only when gas leakage from the flange connection portion 4 is detected.

In the second control example, the control unit 8 operates the gas supply device 71 at all times, regardless of whether hydrogen gas is leaking. That is, the gas supply device 71 always supplies purge gas to the purge space 6. In this embodiment, the flange cold insulation material 51 forms a housing that divides the purge space 6. If it is difficult to completely seal the interface between the flange cold insulation material 51 and the flange connection portion 4, the possibility of gas leakage from the interface cannot be completely eliminated. Therefore, at the stage when the gas detection sensor 72 detects gas leakage, gas leakage from the interface to the outside air may already occur. This problem can be solved by making the purge operation constantly performed. Therefore, according to the second control example in which the gas supply device 71 is constantly operated, the outflow of gas from the purge space 6 to the outside can be prevented in advance.

The above are examples of control by the control unit 8, but operation without the control unit 8 is also possible. For example, in the above first control example, if the gas detection sensor 72 detects a gas leak, an operator may manually start the gas supply device 71 to perform the above-mentioned purging operation. Also, in the above second control example, a control system such as the control unit 8 may be removed, and the gas supply device 71 may simply be operated at all times.

[Other embodiments]
4 is a schematic diagram showing another embodiment of the purging structure for a flange connection of the present disclosure. In the above embodiment, the purging structure is applied to a flange connection 4 consisting of an overlapping portion between a flange of a pipe body and a sealing plate. Here, a purging structure is applied to a flange connection 40 consisting of an overlapping portion between flanges of two pipe bodies.

The flange connection portion 40 is a connection portion between a first tube 201 (tube) having a first inner tube space 20A and a second tube 202 (tube) having a second inner tube space 20B. Here, a straight connection portion between the two is illustrated. A first flange F1 is provided at the end of the first tube 201, and a second flange F2 is provided at the end of the second tube 202. The first flange F1 and the second flange F2 are butt-connected with a gasket 260 interposed therebetween. The flange connection portion 40 allows the first pipe interior space 20A and the second pipe interior space 20B to communicate in a sealed state. The first tube body 201 and the second tube body 202 are pipes that transport extremely low temperature liquefied gas such as liquefied hydrogen or liquid helium.

The outer peripheral surface 410 of the flange connection portion 40 is covered by the housing 6H. The housing 6H is a housing that defines a purge space 6 that is isolated from the outside air around the overlapping portion of the first flange F1 and the second flange F2. A supply pipe 610 and an exhaust pipe 620 are attached to the housing 6H as purge pipes. The supply pipe 610 is a pipe that supplies purge gas to the purge space 6, and the exhaust pipe 620 is a pipe that draws out exhaust gas from the purge space 6.

When liquefied gas leaks from the flange connection portion 40, the vaporized gas is confined in the purge space 6 within the housing 6H without leaking to the outside. Then, due to the supply pressure of the purge gas supplied from the supply pipe 610, the leaked vaporized gas can be discharged from the exhaust pipe 620 together with the purge gas. Therefore, the vaporized gas can be collected in a recovery tank connected to the exhaust pipe 620 or processed in a predetermined processing facility without flowing out to the outside.

[Summary of this disclosure]
The specific embodiments described above include disclosures having the following configurations.

The purging structure of the flange connection part according to the first aspect of the present disclosure comprises a flange connection part consisting of an overlapping part between the flanges of two pipe bodies or an overlapping part between the flange of the pipe body and a sealing plate, a housing that defines a purged space isolated from the outside air around the overlapping part of the flange connection part, and a purge pipe that enables the supply of purged gas to the purged space and the exhaust of the purged gas.

According to the above-mentioned purge structure of the flange connection part, a purge space is arranged around the overlapping part of the flange connection part. Therefore, even if fluid inside the pipe leaks from the overlapping part, the fluid can be contained within the purge space without flowing out to the outside. Furthermore, since a purge pipe is connected to the purge space, the leaked fluid can be recovered or treated by a purge gas. Therefore, even if fluid leaks from the flange connection part, the outflow of the fluid to the outside can be suppressed.

The purge structure according to the second aspect may be the purge structure according to the first aspect, in which the purge space is an annular space formed along the outer periphery of the overlapping portion.

According to the second aspect, it is possible to form a purge space in a minimum amount of space while covering the outer periphery of the overlapping portion, which is a location where fluid leakage is possible.

The liquefied gas tank according to the third aspect of the present disclosure is a liquefied gas tank equipped with the above-mentioned flange connection part purge structure, and includes a tank body for storing liquefied gas, a pump barrel having an upper end opening with a flange and vertically penetrating the tank body, a pump installed in the tank body and discharging the liquefied gas to the outside through the pump barrel, and a head plate attached so as to be overlapped with the flange and sealing the upper end opening, and the flange connection part is composed of the overlapping part of the flange of the upper end opening and the head plate.

According to the liquefied gas tank of the third aspect, the purge space is arranged around the overlapping portion of the flange connection portion of the flange of the pump barrel and the head plate that seals the upper end opening of the pump barrel. The vaporized gas of the liquefied gas stored in the tank body may remain near the upper end of the pump barrel. Even if the gas in the pump barrel leaks from the overlapped portion, the above purge structure is provided, so the gas can be confined in the purge space and the leaked gas can be recovered or treated with the purge gas. Therefore, even if gas leaks from the flange connection portion, it is possible to suppress the leakage of the gas to the outside.

The liquefied gas tank according to a fourth aspect is the liquefied gas tank according to the third aspect, further comprising a cold insulating material that covers the outer surface of the flange connection part, and the housing that partitions the purge space may be the cold insulating material. .

According to the fourth aspect, the cold insulating material serves both as a cold insulator for the flange connection portion and as a housing that partitions the purge space. Therefore, a member dedicated to the housing is not required, and the structure can be simplified.

The liquefied gas tank according to the fifth aspect is the liquefied gas tank according to the third or fourth aspect, and may further include a gas detection sensor disposed at the overlapping part of the flange connection part.

According to the fifth aspect, by disposing a gas detection sensor, it is possible to determine whether or not gas is actually leaking from the overlapping portion.

A liquefied gas tank according to a sixth aspect includes a gas supply device that supplies the purge gas to the purge space through the purge pipe, and a control unit that controls the operation of the gas supply device in the liquefied gas tank according to the fifth aspect. , the control unit may operate the gas supply device when the gas detection sensor detects gas.

According to the sixth aspect, when gas leakage from the flange connection portion to the purge space is detected, the purge gas can be supplied to the purge space in a timely manner.

The liquefied gas tank according to the seventh aspect is the liquefied gas tank according to any one of the third to fifth aspects, further comprising a gas supply device that supplies the purge gas to the purge space through the purge piping, and a control unit that controls the operation of the gas supply device, and the control unit may operate the gas supply device at all times.

According to the seventh aspect, since purge gas is constantly supplied to the purge space, it is possible to prevent gas from flowing out from the housing to the outside.

1 Liquefied gas tank 10 Tank body 2 Pump barrel (tube body)
2A Barrel opening (top opening)
2F Top flange (pipe flange)
25 Head plate (sealing plate)
201 First tube (tube)
202 Second pipe (pipe)
3 Pump 4, 40 Flange connection part 5 Cold insulation material 51 Flange cold insulation material (cold insulation material)
6 Purge space 6H Housing 61, 610 Supply pipe (purge pipe)
62, 620 Exhaust piping (purge piping)
71 Gas supply device 72 Gas detection sensor 8 Control unit LH Liquefied hydrogen (liquefied gas)

Claims (7)

a flange connection portion formed by an overlapping portion between flanges of two pipe bodies or an overlapping portion between a flange of a pipe body and a sealing plate;
a housing that defines a purge space isolated from outside air around the overlapping portion of the flange connection portion;
a purge pipe that enables supply of a purge gas to the purge space and exhaust of the purge gas therefrom;
A purge structure for a flange connection comprising: In the flange connection purge structure according to claim 1,
In the purge structure of the flange connection part, the purge space is a space formed in an annular shape along the outer periphery of the overlapping part. A liquefied gas tank equipped with the purge structure for a flange connection according to claim 1 or 2,
A tank body for storing liquefied gas;
A pump barrel having an upper end opening with a flange and vertically penetrating the tank body;
a pump installed in the tank body and discharging the liquefied gas to the outside through the pump barrel;
a head plate attached to the flange so as to overlap the flange and sealing the upper end opening;
A liquefied gas tank, wherein the flange connection portion is an overlapping portion between the flange at the upper end opening and the head plate. The liquefied gas tank according to claim 3,
Further comprising a cold insulation material covering an outer surface of the flange connection portion,
A liquefied gas tank, wherein a housing that defines the purge space is the cooling material. The liquefied gas tank according to claim 3,
The liquefied gas tank further comprises a gas detection sensor disposed in the overlapping portion of the flange connection portion. The liquefied gas tank according to claim 5,
a gas supply device that supplies the purge gas to the purge space through the purge piping;
further comprising a control unit that controls the operation of the gas supply device,
The control unit is a liquefied gas tank that operates the gas supply device when the gas detection sensor detects gas. The liquefied gas tank according to claim 3,
a gas supply device that supplies the purge gas to the purge space through the purge piping;
further comprising a control unit that controls the operation of the gas supply device,
The control unit is a liquefied gas tank that constantly operates the gas supply device.

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