JP3803359B1 - Basic structure of structure using heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably keep a base portion of a structure warm, to suppress the replacement cost of an insulated wire in a conductive tube to be replaced in the event of a failure without spending a great deal of labor in embedding work, and to be versatile Provides the foundation structure of extremely high structure.
SOLUTION: A first end connection box that is exposed from a base portion and connects adjacent end portions of one end portion of a conductive tube, and an adjacent end portion that is exposed from the base portion and is the other end portion of the conductive tube It consists of a second end connection box that connects each other, from the inside of the conductive tube, the first end connection box, the second end connection box, and the cable or insulated wire connected in series to the power source And an induced current that is opposite to the primary circuit current is generated through the conductive tube, the first end connection box, and the second end connection box, thereby generating heat in the conductive tube. A heating device comprising a secondary circuit to be operated.
[Selection] Figure 1

Description

The present invention relates to a basic structure of a structure, and more particularly to a basic structure of a cryogenic liquid storage tank.
About.

Conventionally, low temperature liquids such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG), and contents that require heat insulation such as heavy oil are stored in a tank.
Such low-temperature liquids and fluids such as high-viscosity heavy oil have different purposes for heat insulation.

In particular, the low-temperature liquid heats the foundation and the like in contact with the ground in order to thermally insulate the tank and the ground and prevent freezing, and does not heat the contents.
On the other hand, a storage tank for high-viscosity heavy oil or the like heats and keeps the contents at a certain temperature so as not to solidify or become highly viscous due to a temperature drop of the contents.

In addition, there are two types of storage tanks: the ground system and the underground system. In the case of the ground system, a heating device is installed in the foundation concrete part at the bottom of the tank that comes into contact with the ground as a measure to prevent freezing.
Furthermore, in the case of the underground system, the bottom foundation and the side concrete wall or the surrounding ground may be heated and kept warm to prevent cold.

As a heating device for the base part of the cryogenic liquid storage tank, a method of heating by flowing a heat medium such as hot water through a trace pipe embedded in the base part has been conventionally used.
However, this method requires ancillary equipment for producing hot water or the like, and there is a problem that maintenance management is necessary and maintenance cost is high.

  For this reason, the development of a heating device that requires almost no maintenance and the use of clean energy electricity has been studied, and there is a heating method that uses a skin current as one of such electric heating methods.

Such a heating method is disclosed in Patent Document 1 (Japanese Patent Publication No. 46-588).
In other words, as shown in FIG. 8, the skin current heating tube device 100 electrically connects both ends of a plurality of high magnetic tubes 102 and 104 arranged in parallel to each other via connection lines 101 and 108. In addition, the insulated wires 110 are arranged in series inside the high magnetic tubes 102 and 104, and both ends of the insulated wires 110 are connected to the AC power source 112.

  Thus, when electricity is supplied from the AC power source 112, current flows in the direction of the arrow 114 in FIG. Due to the current flowing through the insulated wire 110, an induced current in the opposite direction to the current flowing through the insulated wire 110 is generated on the inner surface portions of the high magnetic tubes 102 and 104, and flows in the direction of the arrow 116 in FIG. The high magnetic tubes 102 and 104 generate heat.

In the case of a ground tank, this skin current heating tube device 100 is generally installed at the bottom of a structure.
In the case of an underground tank, such a skin current heating tube device heats the ground around the tank. For example, the skin current heating tube device disclosed in Patent Document 1 is surrounded around a storage tank that is a structure. In this arrangement, the soil around the tank is heated to prevent cold heat from affecting the adjacent structures, and this method is disclosed in Patent Document 2 (Japanese Patent Publication No. 56-678). .

  That is, as shown in the longitudinal sectional view of FIG. 9A and the plan view of FIG. 9B, such a basic structure 200 has a plurality of U-shaped ferromagnetic tubes 202 spaced apart by a fixed distance. And it is embed | buried in the earth 206 of the outer peripheral side of the surface 201 of a tank. The upper ends of these ferromagnetic tubes 202 are coupled to a connection box 210 provided below the ground surface 208 of the ground 206.

These connection boxes 210 are connected via a connection pipe 214 to a lead-in box 213 of a protection pipe 212 arranged on the ground.
The insulated wire 216 is inserted into the protective tube 212 and connected in series to the AC power supply 218 from the lead-in box 213 through the connection tube 214, the connection box 210, and the inside of the U-shaped ferromagnetic tube 202. Has been.

Thus, when a current is passed from the AC power source 218 to the insulated wire 216, a current flows in the direction of the arrow 215 in FIG. 9A, and this constitutes a primary circuit.
Then, by the action of the current flowing through the primary circuit, a reverse induced current is generated in the ferromagnetic tube 202 and the connection box 210 in a loop shape in the direction of the arrow 220 in FIG. Is formed so that the ground 206 on the outer peripheral side of the surface 201 of the tank can be heated.

  The insulated wire 216 in the ferromagnetic tube 202 can be inserted and exchanged via the lead-in box 213, so that the ferromagnetic tube 202 remains intact in the event of a failure. Thus, the insulated wire 216 inserted through the ferromagnetic tube 202 can be easily replaced.

  Further, as shown in FIG. 9A, since the insulated wire 216 is reciprocated in the protective tube 212 positioned above the ground surface 208 of the ground 206, a current is supplied from the AC power source 218. , Currents in opposite directions flow in the protective tube 212, so that no induced current is generated in the protective tube 212. For this reason, the protective tube 212 does not generate heat.

  Further, Patent Document 3 (Japanese Patent Publication No. 56-48387) discloses a skin current heating tube disclosed in Patent Document 1 described above as a basic structure of a tank for holding contents such as heavy oil that needs to be maintained. A method of applying the apparatus is disclosed.

  In this tank basic structure 300, as shown in the plan view of FIG. 10A and the longitudinal sectional view of FIG. The bottom part and the foundation part in the ground below the tank 306 are installed in a curved shape, and the contents in the tank 306 and the tank 306 are heated.

  That is, in such a tank basic structure 300, as shown in the plan view of FIG. 10 (a), the outer peripheral portion of the tank is centered so that the circular tank 306 is heated uniformly. The electric heating tubes 302 are curved and arranged so that the arrangement density of the electric heating tubes 302 is larger than that.

And the insulated wire is inserted in these electric heating tubes 302, and the circuit connected with a power supply is formed.
As a result, when a current is passed from the power source to the insulated wire, an induced current is generated in the heating tube 302 covering the insulated wire, the heating tube 302 generates heat, and the ground 308 below the tank 306 can be heated. It is configured.

  In such a tank basic structure 300, the electric heating tubes 302 are curved and arranged so that the arrangement density of the electric heating tubes 302 is larger in the outer peripheral portion of the tank than in the central portion of the circular tank 306. Therefore, the inside of the tank 306 and the ground 308 below the tank 306 can be heated uniformly, and the contents in the tank 306 can be managed at a desired temperature.

Further, as shown in FIG. 10 (a), an end box (pull box) 304 is disposed at the end of the plurality of electric heating tubes 302. When a failure occurs, the end box 304 is removed and the insulated wire can be replaced.
Japanese Patent Publication No.46-588 Japanese Patent Publication No. 56-678 Japanese Patent Publication No. 56-48387 Japanese Patent Application No. 2005-190385

  However, in the structure 200 of the basic portion of the tank disclosed in Patent Document 2 (Japanese Patent Publication No. 56-678), a plurality of U-shaped ferromagnetic tubes 202 are arranged so as to surround the surface 201 of the tank. Therefore, a great deal of labor is required for laying work.

  In addition, since the ferromagnetic tube 202 is U-shaped, the insulated wire 104 in the ferromagnetic tube 202 that is replaced when a failure occurs becomes a U-shaped reciprocal distance, and wasteful replacement costs increase. In the operation of inserting the insulated wire 204 into the letter-shaped ferromagnetic tube 202, the insulated wire 104 is caught in the U-shaped portion, so that the replacement work is difficult and takes time and effort.

  Furthermore, in the tank basic structure 300 disclosed in Patent Document 3 (Japanese Patent Publication No. 56-48387), the electric heating tube 302 installed at the bottom of the tank 306 and the basic portion in the ground below the tank 306 includes: It has a curved shape.

  For this reason, the electric heating tube 302 is bent into a curved shape, and the bending rate is calculated for each construction unit, that is, according to the size of the tank 306, and a bending process or the like is performed to obtain a plurality of electric heating tubes of different shapes. It is necessary to prepare 302, and versatility is very poor, and the cost increases. When applied to a cryogenic liquid storage tank, the heating tube cannot be installed at the bottom of the tank for the purpose of heating.

For this reason, the inventors of the present invention can reliably heat and keep the basic portion of the structure in Patent Document 4 (Japanese Patent Application No. 2005-190385), and the laying operation of the heating device is simple, and the heating device is The basic structure of the structure using the heating apparatus which has extremely high versatility has been already proposed while the replacement cost of the insulated wire in the conductive tube to be replaced in the event of a failure can be suppressed.
As shown in FIG. 11, the basic structure 400 of this structure includes a so-called induction heating device 402, and a plurality of conductive tubes 404 are installed in parallel on the basic structure 401 portion of the structure. A pull box 408 with an opening / closing lid 406 is connected to both ends of the conductive tube 404.

Further, the pull boxes 408 provided at the ends of the conductive tube 404 are connected to each other via a connection pipe 410. Then, through this connection pipe 410, the bottom side 412 and the bottom side 412 on the base side of the pull box 408 are electrically connected by connecting them via a jumper wire 413 and a terminal 415 provided on the bottom side 412. ing.

Inside the conductive tube 404, the pull box 408, and the connection pipe 410, an insulated wire 416 connected in series to the AC power source 414 is disposed.
As shown in FIG. 12, the heating device 402 is disposed in the foundation 401 of the tank 418 that is a structure, and the pull box 408 and the connecting pipe 410 are arranged from the foundation wall surface 420 of the foundation 401. It is installed to be outside.

  In the heating apparatus 402 configured as described above, the AC power source 414 of the AC power source 42 is turned on, and the power source 42 passes through the conductive tube 404, the pull box 408, and the connection pipe 410, and is connected in series so as to return to the power source 42 again. A current flows in the insulated wire 416 like the primary circuit A shown in FIG.

  Further, when a current flows through the insulated wire 416 as in the primary circuit A, the induced current is looped in the inner surface portion of the conductive tube 404 as in the secondary circuit B, which is a flow opposite to this direction. The conductive tube 404 is heated by the Joule heat generated by the induced current, and the tank base 401 to be heated is heated.

Patent Document 4 (Japanese Patent Application No. 2005-190385) proposes a basic structure 400 of a structure including a so-called series heating device 402.
In the heating device 402 of the basic structure 400 of this structure, as shown in FIG. 13, one end of the insulated wire 416 is connected to the AC power source 414, and the other end 416 a of the insulated wire 416 is connected to the terminal side. The pull box 408 is connected to the bottom surface 412.

Then, the other end of the jumper wire 413 connected to the bottom surface 412 of the pull box 408 on the start end side is connected to the AC power source 414.
In this state, when a current is passed from the AC power source 414, the current passes through the conductive tube 404, the pull box 408, the insulated wire 416 in the connection pipe 410, and reaches the bottom surface 412 of the pull box 408 on the terminal side. It flows as C.

  Then, from the bottom surface 412 of the pull box 408 on the terminal end side, again through the conductive tube 404, the pull box 408, the connection pipe 40, and finally via the jumper wire 413 connected to the bottom surface 412 of the pull box 408 on the start end side. The current is returned to the AC power source 414, and the current flows as the external circuit D in the conductive tube 404 in the direction opposite to the internal circuit C.

As a result, the conductive tube 404 generates heat, and the tank base 401 to be heated is heated.
In any of the above cases, the jumper wire 413 is disposed together with the insulated wire 416 in the connection pipe 410, and the current passing through the connection pipe 410 and the current passing through the jumper wire 413 are in opposite directions. Therefore, no induced current is generated in the connection pipe 410. Therefore, the connection pipe 410 does not generate heat, and is configured to prevent damage to the insulated wire 416 and the jumper wire 413 due to overheating in the connection pipe 410.

  With this configuration, in the unlikely event that the insulated wire 416 is defective, the open / close lid 406 of the pull box 408 provided at both ends of the conductive tube 404 is removed, and the defective insulated wire 416 is pulled out. Since the insulated wire 416 is inserted again into the conductive tube 404 connected to the pull box 408 and electrically connected, the work efficiency is extremely high.

  However, in the basic structure 400 of the structure including the heating device 402 of Patent Document 4 (Japanese Patent Application No. 2005-190385), the pull box 408, the connection pipe 410 connecting the pull boxes 408 to each other, and the bottom surface 412 of the pull box 408 are provided. The provided terminals 415, jumper wires 413, and the like must be provided, resulting in a complicated configuration, a large number of parts, labor and time for construction, and high cost.

  In addition, when the number of parts is large and the number of electrical connection points is large as described above, an electrical contact failure often occurs, and there is a possibility that it cannot function reliably as a heating device.

  In view of such a current situation, the present invention can reliably keep the basic portion of the structure, has a complicated structure, has a small number of parts, and is easy to lay the heating device. An object of the present invention is to provide a basic structure of a structure using a heating device with extremely high versatility, while the replacement cost of an insulated wire in a conductive tube to be replaced can be suppressed.

The present invention was invented in order to achieve the above-described problems and objects in the prior art, and the basic structure of the present invention is as follows.
Two conductive tubes embedded in the base portion of the structure and arranged side by side at a predetermined interval;
A first end connection box that is exposed from the base portion and connects adjacent ends of one end of the conductive tube;
A second end connection box that is exposed from the base portion and connects adjacent ends of the other end of the conductive tube;
With a heating unit connected in a loop,
A primary circuit consisting of a cable or an insulated wire passing through the inside of the conductive tube, a first end connection box, a second end connection box and connected in series to a power source;
When a current is passed from the power source through the primary circuit, an induced current opposite to the primary circuit current is passed through the conductive tube, the first end connection box, and the second end connection box. In the vicinity of their inner surface,
A secondary circuit comprising a conductive tube, a first end connection box, and a second end connection box, which heats the conductive tube thereby;
The heating apparatus comprised from these is provided.

  By configuring in this way, the two conductive tubes are connected to each other by one end connection box, so that the basic structure provided with the heating device disclosed in the conventional Patent Document 4 Compared to 400, the number of end connection boxes (pull boxes) can be reduced, and connection piping 410 for connecting the pull boxes 408 to each other, terminals 415 provided on the bottom surface 412 of the pull box 408, jumper wires 413, and the like are provided. There is no need, the configuration is not complicated, the number of parts is small, the construction is simple, and the cost can be reduced.

In addition, since the number of parts is small as described above, the number of electrical connection portions is reduced, and electrical contact failure does not occur, and the device can function reliably.
Therefore, the basic part of the structure can be reliably heated and kept warm, the structure is not complicated, the number of parts is small, the heating device is easy to lay, and the inside of the conductive tube that is replaced when the heating device fails The cost of replacing the insulated wire can be reduced, and a basic structure of a structure using a highly versatile heating device can be provided.

  Further, the basic structure of the present invention includes a plurality of sets of the heat generating units, and these heat generating units are connected to each other through connection pipes that connect between adjacent end connection boxes and are exposed from the base portion. It is characterized by being.

Further, in the basic structure of the present invention, the plurality of sets of heat generating units are connected via the first connection pipe that connects between the adjacent first end connection boxes and is exposed from the basic part. It is characterized by that.

  Further, in the basic structure of the present invention, the plurality of sets of heat generating units are connected via the second connection pipe that connects between the adjacent second end connection boxes and is exposed from the basic part. It is characterized by that.

  By configuring in this way, a plurality of sets of heat generating units can be arranged on the base portion of the structure, so that the base portion of the structure can be heated uniformly, and the number of connecting pipes is also It can be reduced as compared with the foundation structure 400 provided with the conventional heating device of Patent Document 4.

The basic structure of the present invention is characterized in that the induced current is configured to flow through a wall surface on a basic side of the first end connection box and the second end connection box.
Thus, since the induced current flows through the wall surface on the foundation side of the first end connection box and the second end connection box, it is safe without leaking to the outside of these end connection boxes. .

The foundation structure of the present invention is characterized in that the end connection box is attached to the outside of the foundation portion.
With this configuration, the pull box is exposed outside the base portion of the tank. In the event of a failure, the insulated wire in the conductive tube can be replaced via the exposed pull box. In addition, the workability is very good, and the maintenance of the heating device is very easy.

The foundation structure of the present invention is characterized in that the end connection box is attached to the foundation portion in a partially embedded state.
By configuring in this way, the pull box can be held firmly, and by adjusting the amount of pull-out of the pull-out that protrudes from the end of the foundation structure, the pull box does not get in the way and what construction It can be installed on site.

Further, the basic structure of the present invention is characterized in that the heating device is embedded in the basic portion so as to be stacked in a plurality of stages.
By comprising in this way, while being able to heat the basic | foundation part of a structure more efficiently than when a heating apparatus is one step | paragraph, it can respond easily also when partially required heat quantity differs.

Further, the basic structure of the present invention is characterized in that the heating device is embedded in a plurality of stages in the base portion so that the position of the heat generating unit is shifted.
Since the heat generating unit is displaced so that the position of the heat generating unit is shifted in this way, it is embedded in multiple layers in the upper and lower layers, so that the basic portion of the structure can be heated more efficiently and partially. Even if the amount of heat is different, it can be easily handled.

Moreover, the foundation structure of this invention is characterized by the said heating apparatus being installed in parallel with respect to the foundation bottom face of the said structure.
Moreover, the foundation part of the whole structure can be efficiently heated by installing in parallel with the foundation bottom face of the structure.

The basic structure of the present invention is characterized in that three heating devices are connected in parallel to a three-phase power source.
By configuring in this way, the number of power supplies to be installed can be reduced to one for the three circuits, so that the cost for power supply installation can be suppressed. Moreover, since the number of power supplies can be reduced, power management is easy.

The basic structure of the present invention is characterized in that a plurality of the heating devices are arranged on the basic portion.
With this configuration, even if the heating device fails, only a part of the basic structure of the structure needs to be repaired, so that the influence of the failure can be minimized.

The basic structure of the present invention is characterized in that the structure is a cryogenic liquid storage tank.
By configuring in this way, it is possible to reliably prevent the frost heaving phenomenon that the ground around the storage tank of the frozen liquid freezes and rises, and the tank is not damaged or damaged, and the contents of the tank are not leaked. .

Further, the basic structure of the present invention is embedded in the base portion of the structure, a plurality of conductive tubes arranged in parallel at a predetermined interval,
A starting-end connection box connected to a power-source-side starting end of the conductive tube;
A termination connection box connected to the final end of the conductive tube;
A first end connection box that is exposed from the base portion and connects adjacent ends of one end of the conductive tube;
A second end connection box that is exposed from the base portion and connects adjacent ends of the other end of the conductive tube;
The first end connection box and the second end connection box are connected to each other via the conductive tube;
An internal circuit consisting of a cable or an insulated wire passing through the inside of the starting connection box, the inside of the conductive tube, the first end connection box, the second end connection box, and the termination connection box;
From the end of the internal circuit, a termination connection box, a conductive tube, a first end connection box,
An external circuit connected in series with the power supply so that a current flows in a direction opposite to the internal circuit via the second end connection box and the start end connection box;
A current application circuit comprising:
A heating device configured to generate heat when the current is supplied from the power source through the internal circuit and the external circuit of the current application circuit is provided.

  By configuring in this way, the two conductive tubes are connected to each other by one end connection box, so that the basic structure provided with the heating device disclosed in the conventional Patent Document 4 Compared to 400, the number of end connection boxes (pull boxes) can be reduced, and connection piping 410 for connecting the pull boxes 408 to each other, terminals 415 provided on the bottom surface 412 of the pull box 408, jumper wires 413, and the like are provided. There is no need, the configuration is not complicated, the number of parts is small, the construction is simple, and the cost can be reduced.

In addition, since the number of parts is small as described above, the number of electrical connection portions is reduced, and electrical contact failure does not occur, and the device can function reliably.
Therefore, the basic part of the structure can be reliably heated and kept warm, the structure is not complicated, the number of parts is small, the heating device is easy to lay, and the inside of the conductive tube that is replaced when the heating device fails The cost of replacing the insulated wire can be reduced, and a basic structure of a structure using a highly versatile heating device can be provided.

  In addition, compared to the above basic structure that generates induced current, the amount of connecting piping can be reduced, so there is no complicated configuration, the number of parts is small, construction is simple, and costs are reduced. can do.

  According to the present invention, since the two conductive tubes are connected to each other by one end connection box, the configuration is not complicated, the number of parts is small, and the construction is simple. Cost can also be reduced.

In addition, since the number of parts is small, the number of electrical connection portions is reduced, and electrical contact failure does not occur, and the device can function reliably.
Therefore, the basic part of the structure can be reliably heated and kept warm, the structure is not complicated, the number of parts is small, the heating device is easy to lay, and the inside of the conductive tube that is replaced when the heating device fails The cost of replacing the insulated wire can be reduced, and a basic structure of a structure using a highly versatile heating device can be provided.

Hereinafter, embodiments (examples) of the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a configuration diagram of a basic structure of a structure provided with a heating device according to a first embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of a main part taken along line XX in FIG. 1, and FIG. The principal part expanded sectional view of the YY line of FIG. 1, FIG. 4 is a block diagram at the time of using a three-phase power supply for the basic structure of the structure provided with the heating apparatus which is the 1st Example of this invention. is there.

In FIG. 1, the code | symbol 10 has shown the basic structure of the structure provided with the heating apparatus 12 of this invention.
The foundation structure 10 is applied to a foundation portion 14 of a structure such as a cryogenic liquid storage tank, for example, and the heating device 12 of the present invention is embedded in the foundation portion 14.

As shown in FIG. 1, the heating device 12 includes a plurality of heat generating units 16 arranged at a predetermined interval.
The heat generating unit 16 includes a linear first conductive tube 18 embedded in the base portion 14 of the structure, and a second conductive tube embedded substantially parallel to the first conductive tube 18 at a predetermined interval. A tube 20.

Further, as shown in FIG. 1, the second conductive tube 20 includes a central substantially straight line portion 22 and bent portions 24 and 26 formed at both ends thereof.
One end 18 a of the first conductive tube 18 and one end 20 a of the second conductive tube 20 are connected to a first end connection box (pull box) 28.

That is, the first end connection box 28 is provided with a nozzle 30 for connecting to one end 18 a of the first conductive tube 18, and one end of the nozzle 30 and the first conductive tube 18. 18a is connected by welding.

On the other hand, in the first end connection box 28, the bent portion 2 of the one end portion 20a of the second conductive tube 20 is provided.
The nozzle 32 for connecting with the 4 end part 24a is provided, and this nozzle 32 and the edge part 24a of the bending part 24 of the one end part 20a of the 2nd conductive tube 20 are connected by welding.

Further, the other end 18 b of the first conductive tube 18 and the other end 20 b of the second conductive tube 20 are connected to the second end connection box 34.
That is, the second end connection box 34 is provided with a nozzle 36 for connection to the other end 18 b of the first conductive tube 18. The end 18b is connected by welding.

  On the other hand, the second end connection box 34 is provided with a nozzle 38 for connecting to the end portion 26a of the bent portion 26 of the other end portion 18b of the second conductive tube 20. The end portion 26a of the bent portion 26 of the other end portion 20b of the second conductive tube 20 is connected by welding.

The first end connection box 28 and the second end connection box 34 are respectively provided with openable and closable lids 29 and 31 attached to a pull box.
Therefore, the heat generating unit 16 includes the first conductive tube 18, the second conductive tube 20, the first end connection box 28, and the second end connection box 34 connected in a loop. Yes.

As shown in FIG. 1, in the heating device 12 of this embodiment, a plurality of heat generating units 16 configured as described above are provided, and in this embodiment, three sets (16a to 16c) are provided. The heat generating units 16 are connected to each other through the connection pipe 40 that connects the adjacent first end connection boxes 28 and is exposed from the base portion 14.

In this case, the connection pipe 40 is, for example, a conduit tube or a combination of a conduit tube and a flexible conduit tube.
In this case, as shown in FIG. 1, only one connection pipe 40 is connected to the first end connection box 28 of the end-side heat generation unit 16c. In the first end connection box 28, the heat generating unit 16 having connection pipes 40 located on both sides is provided.
Two connection pipes 40 are connected to connect a and 16c.

Furthermore, in the heat generating unit 16a on the start end side, one side of the connection pipe 40 is a power supply pipe to the AC power source 42.
The first conductive tube 18, the second conductive tube 20, the first end connection box 28, and the second end connection box 34 of the heat generating unit 16 configured as described above are provided with an alternating current. Power supply 42
Insulated electric wires 44 connected in series are arranged.

  In this embodiment, an insulated wire having a structure in which the outside of the conductor is insulated by an insulating layer is used as the insulated wire 44, but the present invention is not limited to this. It is also possible to use a cable having a structure in which a sheath layer for protecting wounds is provided on the outside of the insulating layer, and it may be appropriately selected according to the installation environment.

In addition, as for such an insulated wire and a cable, it is desirable to apply what has heat resistance in all.
That is, as shown in FIG. 1, the insulated wire 44 connected to the AC power supply 42 is first introduced into the first end connection box 28 of the heat generating unit 16 a on the start end side, and the first conductive tube 18.
And is introduced into the second end connection box 34.

Then, the insulated wire 44 is introduced from the second end connection box 34 through the second conductive tube 20 and again into the first end connection box 28.
Thus, the insulated wire 44 returned to the first end connection box 28 of the heat generating unit 16a on the start end side passes through the connection pipe 40 to the first end connection box 28 of the adjacent intermediate heat generating unit 16b. be introduced.

In the intermediate heat generation unit 16b, the insulated wire 44 is formed in a loop shape in the same manner as the heat generation unit 16a on the start end side, in the first conductive tube 18, the second end connection box 34, the second conductive tube. 20, is again introduced into the first end connection box 28, passes through the connection pipe 40, and is introduced into the first end connection box 28 of the adjacent heat generating unit 16 c on the terminal side.

  Further, in the heat generating unit 16c on the end side, the insulated wire 44 is formed in a loop shape in the same manner as the heat generating unit 16a on the start end side, in the first conductive tube 18, the second end connection box 34, and the second conductive wire. It passes through the tube 20 and is again introduced into the first end connection box 28.

The insulated wire 44 introduced into the first end connection box 28 again by the terminal-side heat generation unit 16c is connected to the first end connection box of the intermediate heat generation unit 16b via the connection pipe 40. 28, passing through the heat generating unit 16a on the start end side and connected in series to the AC power source 42.

  As shown in FIG. 2, which is a cross-sectional view taken along the line XX of FIG. 1, the insulated electric wire 44 disposed inside the first conductive tube 18 and the second conductive tube 20 having a substantially cylindrical cross-sectional shape. Are inserted into the conductive tubes 18 and 20 in a free state.

  At this time, the interval between the adjacent first conductive tube 18 and the second conductive tube 20 is not particularly limited. For example, the width in the longitudinal direction of the basic structure 10 of the structure may be 100 m. For example, the distance between the adjacent conductive tube 18 and the conductive tube 20 is preferably 1 m.

The conductive tubes 18 and 20 are magnetic tubes, and for example, general-purpose carbon steel tubes that are JIS standard products having an outer diameter of 20 mm to 61 mm may be used.
Furthermore, it can be set as the electrically conductive pipes 18 and 20 of desired length by connecting the general purpose carbon steel pipe which has standard length beforehand by multiple welding in the elongate direction.

  Thus, by using standard carbon steel pipes as the conductive pipes 18 and 20, the heating device 12 can be provided relatively easily at any construction site, such as development cost and construction cost. Can be suppressed.

Furthermore, the first end connection box 28 and the second end connection box 34 generally have a cylindrical shape, a box shape, or the like, and are preferably made of carbon steel, stainless steel, or a combination thereof.

If the insulated wire 44 is defective, the open / close lids 29 and 31 of the first end connection box 28 and the second end connection box 34 provided at both ends of the conductive tube 18 and the conductive tube 20 are provided. Can be handled by simply pulling out the defective insulated wire 44 and inserting the good insulated wire 44 into the conductive tubes 18 and 20 connected to the pull boxes 28 and 34 and electrically connecting them. Very high efficiency.

Further, as shown in FIG. 3, the heating device 12 configured by disposing these components up to the entire width of the base portion 14 is disposed in the base 48 of the tank 46 that is a structure. The first end connection box 28, the second end connection box 34, and the connection pipe 40 are installed so as to be outside the foundation wall surface 50 of the foundation 48.

The foundation 48 portion is preferably made of concrete.
In the present embodiment, the first end connection box 28 and the second end connection box 34 are attached to the foundation wall surface 50 of the foundation 48, but the present invention is not limited to this. The end connection boxes 28 and 34 may be attached in a state where they are partially embedded (not shown).

  Further, a heat insulating layer 52 is provided between the foundation 48 and the tank 46. For example, if the contents in the tank 46 are a low-temperature liquid, the temperature of the tank 46 is not easily transmitted to the foundation 48 directly. Yes.

The heating device 12 configured as described above is configured such that when the AC power source 42 is turned on, the current flows in the insulated wire 44 connected to the AC power source 42 as shown by the arrow A in FIG. The first end connection box 28, the first conductive tube 18, the second end connection box 34, and the second conductive tube 20 of the heat generating unit 16a pass through the first end connection box 28 again. Flows in a loop.

Then, the current from the first end connection box 28 of the heat generating unit 16a on the start end side passes through the connection pipe 40 in the insulated wire 44, and the first end connection box 28 of the adjacent intermediate heat generating unit 16b. Flowing into.

In the intermediate heat generating unit 16b, as in the heat generating unit 16a on the start end side, the current flows through the insulated wire 44 as shown by the arrow A in FIG. It flows through the tube 18, the second end connection box 34, and the second conductive tube 20, and again flows in a loop shape to the first end connection box 28.

Then, the current from the first end connection box 28 of the intermediate heat generation unit 16b passes through the connection pipe 40 in the insulated wire 44, and the first end connection box 28 of the adjacent heat generation unit 16c on the terminal side. Flowing into.

In the end-side heat generating unit 16c, as in the heat-generating unit 16a on the starting end side, the current flows through the insulated wire 44 as shown by the arrow A in FIG. It flows through the conductive tube 18, the second end connection box 34, and the second conductive tube 20, and again flows in a loop shape to the first end connection box 28.

Then, the current reaching the heat generating unit 16c on the end side is the first current of the intermediate heat generating unit 16b through the connection pipe 40 as shown by the arrow A in FIG.
Flows through the end connection box 28 and the heat generating unit 16a on the start end side to the AC power source 42.

In this way, the current from the AC power supply 42 passes through the first end connection box 28, the first conductive tube 18, the second end connection box 34, and the second conductive tube 20. A current flows in the insulated wires 44 connected in series as in the primary circuit A shown in FIG.

Further, when a current flows in the insulated wire 44 as in the primary circuit A, an induced current flows in the insulated wire 44 as in the secondary circuit B, which is a flow opposite to this direction, as shown in FIG. become.
That is, in the heat generating unit 16, the bottom of the first end connection box 28, the base-side wall surface 28 a passes through the second conductive tube 20, and the bottom of the second end connection box 34, the base-side wall surface 34 a. In this way, a loop-shaped induced current reaching the first conductive tube 18 is generated in these inner surface portions.

As a result, the first conductive tube 18 and the second conductive tube 20 are heated by the Joule heat generated by the induced current, and are electrically heated to the base 48 of the tank to be heated.
The secondary circuits B are respectively generated in the heat generating units 16, and in the first embodiment shown in FIG. 1, three secondary circuits B are formed by the heat generating units 16a to 16c. It will be.

In this case, since the induced current flows through the wall surfaces 28a and 34a on the foundation side of the first end connection box 28 and the second end connection box 34 in this way, these end connection boxes 28 , 34 is safe without leaking outside.

  The heating device 12 for heating the conductive tubes 18 and 20 by the induced current generated in the first conductive tube 18 and the second conductive tube 20 is already disclosed in Patent Document 1 (Japanese Patent Publication No. 46-588). This is a known technique.

  The current flowing in the conductive tubes 18 and 20 flows in a concentrated manner near the inner surface of the depth S of the conductive tubes 18 and 20 represented by the following relational expression. Little voltage appears.

  This is because the thickness of the conductive tube is more than several times the skin depth of the conductive tube determined by the power supply frequency, the electrical resistivity and the relative permeability of the conductive tube, and the length of the conductive tube is sufficiently larger than its diameter. When the current is large, the current flowing in the conductive tube flows only to the inner surface of the conductive tube, and almost no voltage appears on the outer surface of the conductive tube. Does not flow.

The relational expression is described below.
S = 5030 SQRT (ρ / μf)
Where t = 2S, L> d
S (cm) ··· skin depth ρ (Ωcm) · · · Conductivity tube resistivity µ · · · Conductive tube relative permeability f (Hz) · · · Power frequency SQRT (ρ / µf) · ·・ ・ (Ρ / μf) square root t (cm) ・ ・ ・ thickness of conductive tube d (cm) ・ ・ ・ inner diameter of conductive tube L (cm) ・ ・ ・ length of conductive tube Therefore, even if the outer surfaces of the conductive tubes 18 and 20 are short-circuited with a low-impedance electric wire, almost no current flows, and it is safe to make contact with the foundation 48 that is an object to be heated, and can be used as the heating device 12. it can.

  In the connection pipe 40, as shown in FIG. 1, the insulated wires 44 are reciprocated and the currents flowing through these are opposite to each other. It will not occur.

This is because it is not necessary to heat the portions other than the foundation 48 and, if heated reversely, there is a risk of overheating, so that the connection pipe 40 can be prevented from being heated.
According to the foundation structure 10 including the heating device 12 of the present invention using such a principle, the conductive tube 18, the induced tube 18, 20, the conductive tube 18, Only 20 can be heated, and only the base 48 portion of the tank 46 can be heated.

Further, as shown in FIG. 4, such a heating device 12 may be a basic structure 10 that uses three series circuits connected in parallel to one three-phase power source 54.
If the three-phase power supply 54 is used as described above, the number of power supplies can be reduced and the cost can be reduced as compared with the case where one circuit is provided with one power supply, and power management becomes extremely easy.

Furthermore, in this embodiment, the number of heat generating units 16 is three in this embodiment,
Depending on the size of the tank 46, this number can be changed as appropriate.
A plurality of heating devices 12 may be arranged on the base 48 portion of the tank 46.

Furthermore, the heating device 12 may be embedded in the base 48 portion of the tank 46 so as to be stacked in a plurality of stages.
By comprising in this way, the base part of a structure can be heated more efficiently than the time of the heating apparatus 12 having one stage.

  In this case, as shown in FIG. 5, the heating device 12 is stacked vertically on the base portion in a plurality of stages so that the position of the heat generating unit 16 is shifted (as indicated by the dashed line in FIG. 5). You may make it embed.

  In this case, the method of shifting the position of the heat generating unit 16 is not particularly limited. As shown in FIG. 5, the heating device 12 is positioned in the longitudinal direction in addition to the substantially point-symmetric arrangement. It is possible to change as appropriate, for example, by shifting the positions.

In this way, the base portion is embedded in a plurality of stages so as to be displaced so that the position of the heat generating unit is vertically stacked, so that the base portion of the structure can be uniformly heated more efficiently.
Moreover, it is desirable to install the heating device 12 in parallel with the bottom of the structure.

  By constructing in this way, it is possible to suppress the depth of the foundation portion of the structure from being deepened. For example, the amount of concrete used for the foundation portion is installed vertically around the tank. It can be reduced compared to the case.

Moreover, the foundation part of the whole structure can be efficiently heated by installing in parallel with respect to the bottom part of a structure.
Further, in this embodiment, the adjacent first end connection boxes 28 are connected to each other by a connection pipe 40.
Although not shown in the drawing, the second end connection boxes 34 can be connected to each other via the connection pipe 40.

  By configuring in this way, the two conductive tubes 18 and 20 are connected to each other by one end connection box 28 and 34, so that the heating disclosed in the conventional patent document 4 is performed. Compared to the basic structure 400 shown in FIG. 11 provided with the apparatus, the number of end connection boxes (pull boxes) can be reduced, and the connection pipe 410 connecting the pull boxes 408 to each other, and the bottom surface 412 of the pull box 408 There is no need to provide the provided terminals 415, jumper wires 413, and the like, the configuration is not complicated, the number of parts is small, the construction is simple, and the cost can be reduced.

In addition, since the number of parts is small as described above, the number of electrical connection portions is reduced, and electrical contact failure does not occur, and the device can function reliably.
Therefore, the base portion of the structure can be surely kept warm, the structure is not complicated, the number of parts is small, the heating device is easily laid, and the heating device can be replaced in the event of a failure. The replacement cost of the insulated wire can be suppressed, and a basic structure of a structure using a highly versatile heating device can be provided.

FIG. 6 shows a second embodiment of the basic structure of the structure provided with the heating device of the present invention.
The basic structure of the structure provided with the heating device of FIG. 6 is basically the same configuration as the basic structure of the structure provided with the heating device of the embodiment shown in FIG. The same reference numerals are assigned and detailed description thereof is omitted.

  That is, in the heating device 12 of this embodiment, the start end connection box 21 connected to the power supply side start end of the first conductive tube 18 and the termination connection box 23 connected to the final end of the first conductive tube 18 are provided. I have.

And as shown in FIG. 6, the 1st end part connection box 2 in the position which opposes and opposes
8 and the second end connection box 34 are connected to each other via the first conductive tube 18. Then, the first end connection box 28 and the second end connection box 34 which are opposed to each other and are displaced from each other are connected to each other via the second conductive tube 20 disposed obliquely.

The circuit of the second embodiment shown in FIG. 6 is different from the circuit of the first embodiment, and is not divided into a primary circuit and a secondary circuit.
Such a substructure 10 includes a start end connection box 21, a first conductive tube 18, a second conductive tube 20, a first end connection box 28, a second end connection box 34, and a termination connection box 2.
3, an insulated wire 44 is inserted, and thereby an internal circuit C is formed.

  That is, one end portion of the insulated wire 44 is connected to the terminal 25 provided on the wall surface 21 a on the foundation side of the start end connection box 21, and the other end portion of the insulated wire 44 is connected to the wall surface on the foundation side of the termination connection box 23. It is connected to a terminal 27 provided in 23a.

  Therefore, in the heating apparatus 12 configured as described above, when the AC power source 42 is turned on, the current flows in the insulated wire 44 connected to the AC power source 42 as shown by the arrow C in FIG. The first end connection box 21, the first conductive tube 18, the second end connection box 34, and the second conductive tube 20 arranged obliquely pass through the second end connection box 34 and are displaced in position. The first end connection box 28 flows.

Then, from the first end connection box 28, current flows in the insulated wire 44 through the first conductive tube 1.
8 flows to the second end connection box 34 which is opposed to the first end connection box 28 and shifted in position.

Similarly, a current is passed through the insulated wire 44 between the first end connection box 28 and the second end connection box 34 via the first conductive tube 18 and the second conductive tube 20. Thus, it flows into the termination connection box 23.

In this way, the internal circuit C is formed as shown in FIG.
In addition, such a basic structure 10 includes a terminal connection box 23, a first conductive tube 18, a second conductive tube 20, a first end connection box 28, a second end connection box 34, and a start end connection box. An external circuit D is formed in the opposite direction to the internal circuit C so that a current flows through the inner surface of 21.

  That is, as described above, the current flowing through the insulated wire 44 up to the termination connection box 23 is supplied from the terminal 27 provided on the foundation-side wall surface 23 a of the termination connection box 23 to the foundation-side wall surface of the termination connection box 23. The first end connection box 28 located at a position facing the terminal connection box 23 is reached from 23 a through the first conductive tube 18.

Then, the second end connection box whose position is shifted from the first end connection box 28 so as to face the first end connection box 28 through the second conductive tube 20 disposed obliquely. 34. Subsequently, the first end connection box 28 arranged so as to face the second end connection box 34 is reached via the first conductive tube 18.

Similarly, between the first end connection box 28 and the second end connection box 34,
The first conductive tube 18 and the second conductive tube 20 are reached to the starting end connection box 21.
Then, the current reaches the AC power source 42 through the insulated wire 44 from the terminal 25 provided on the wall surface 21 a on the foundation side of the starting end connection box 21.

In this way, the external circuit D is formed as shown in FIG.
A current application circuit is formed by such an internal circuit C and an external circuit D, and when the current flows through the current application circuit as described above, the conductive tubes 18 and 20 generate heat and are heated. The tank foundation is heated.

With such a circuit, the connection pipe 40 for connecting the first end connection boxes 28 to each other can be omitted. Therefore, the amount of the connection pipe 40 and the insulated wire 44 wired in the connection pipe 40 is the same as that of the embodiment of FIG. Since it can be reduced in comparison, the cost can be greatly reduced.

Further, as shown in FIG. 7, also in the circuit of the second embodiment, the basic structure 10 in which three series circuits are connected in parallel to one three-phase power source 54 can be used.
If the three-phase power supply 54 is used as described above, the number of power supplies can be reduced and the cost can be reduced as compared with the case where one circuit is provided with one power supply, and power management becomes extremely easy.

  In the embodiment described above, the conductive tube 20 facing the conductive tube 18 is bent near both ends of the heat conducting tube 18 and the conductive tube 20 so as to be arranged in parallel at a predetermined interval as much as possible. Is preferred.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to this. For example, the present invention may be applied not only to the basic structure of a tank but also to an underground tank. In this case, a conductive tube is embedded and installed in the bottom foundation structure and the side wall structure, and the end connection box 28 is attached to the upper part of the tank side wall.

Further, it is natural that these basic structures may be provided with a spare conductive tube between the conductive tubes arranged in parallel in the foundation.
Furthermore, the circuit connected to the three-phase power source can be variously modified without departing from the object of the present invention, for example, the circuits of the first embodiment and the second embodiment may be mixed.

FIG. 1 is a configuration diagram of a basic structure of a structure provided with a heating device according to a first embodiment of the present invention. 2 is an enlarged cross-sectional view of a main part taken along line XX of FIG. 3 is an enlarged cross-sectional view of a main part taken along line YY in FIG. FIG. 4 is a configuration diagram in the case where a three-phase power source is used for the basic structure of the structure including the heating device according to the first embodiment of the present invention. FIG. 5: is a block diagram of another Example of the basic structure of the structure provided with the heating apparatus which is the 1st Example of this invention. FIG. 6 is a block diagram of a basic structure of a structure provided with a heating device according to a second embodiment of the present invention. FIG. 7: is a block diagram at the time of using a three-phase power supply for the basic structure of the structure provided with the heating apparatus which is the 2nd Example of this invention. FIG. 8 is a diagram illustrating the principle of a conventional skin current heating tube apparatus. FIG. 9 is a schematic diagram illustrating the basic structure of a conventional tank. FIG. 10 is a schematic diagram illustrating the basic structure of a conventional tank. FIG. 11 is a schematic diagram illustrating the basic structure of a conventional tank. FIG. 12 is a schematic diagram illustrating the basic structure of a conventional tank. FIG. 13 is a schematic view illustrating the basic structure of a conventional tank.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Base structure 12 Heating device 14 Base part 16 Heat generating unit 16a-16c Heat generating unit 18 Conductive tube 20 Conductive tube 21 Starting end connection box 23 End connecting box 24 Bending part 25 Terminal 26 Bending part 27 Terminal 28 End connecting box 28a Wall surface 29, 31 Opening / closing lid 30 Nozzle 32 Nozzle 34 End connection box 34a Wall surface 36 Nozzle 38 Nozzle 40 Connection pipe 42 AC power supply 44 Insulated wire 46 Tank 48 Foundation 50 Foundation wall surface 52 Heat insulation layer 54 Three-phase power supply 100 Skin current heating tube device 101 Connection line 102 High magnetic tube 104 Insulated wire 110 Insulated wire 112 AC power source 200 Structure of tank basic portion 201 Surface 202 Ferromagnetic tube 204 Insulated wire 206 Ground 208 Ground surface 210 Connection box 212 Protective tube 213 Retraction box 214 Connection tube 216 Insulated wire 218 AC source 00 Foundation structure 302 Electric heating tube 304 End box 306 Tank 308 Ground 400 Foundation structure 401 Foundation 402 Heating device 404 Conductive tube 406 Opening / closing lid 408 Pull box 410 Connection pipe 412 Bottom surface 413 Jumper wire 414 AC power source 415 Terminal 416 Insulated wire 418 Tank 420 Base wall surface A Primary circuit B Secondary circuit C Internal circuit D External circuit

Claims (23)

Two conductive tubes embedded in the base portion of the structure and arranged side by side at a predetermined interval;
A first end connection box that is exposed from the base portion and connects adjacent ends of one end of the conductive tube;
A second end connection box that is exposed from the base portion and connects adjacent ends of the other end of the conductive tube;
With a heating unit connected in a loop,
A primary circuit consisting of a cable or an insulated wire passing through the inside of the conductive tube, a first end connection box, a second end connection box and connected in series to a power source;
When a current is passed from the power source through the primary circuit, an induced current opposite to the primary circuit current is passed through the conductive tube, the first end connection box, and the second end connection box. In the vicinity of their inner surface,
A secondary circuit comprising a conductive tube, a first end connection box, and a second end connection box, which heats the conductive tube thereby;
A basic structure characterized by comprising a heating device comprising:   2. A plurality of sets of the heat generating units are provided, and the heat generating units are connected to each other through connection pipes that connect adjacent end connection boxes and are exposed from a base portion. The basic structure described in 1. The plurality of sets of heat generating units are connected via a first connection pipe that connects between adjacent first end connection boxes and is exposed from a base portion. The basic structure described. Wherein the plurality of sets of heating unit to each other, connected between the adjacent second end connection box, that are connected via a second connection pipe which is exposed from the base portion to claim 2, wherein The basic structure described . The said induced current is comprised so that it may flow through the wall surface by the side of the foundation of a 1st end part connection box and a 2nd end part connection box, The any one of Claim 1 to 4 characterized by the above-mentioned. Foundation structure.   The foundation structure according to any one of claims 1 to 5, wherein the end connection box is attached to the outside of the foundation portion.   The foundation structure according to any one of claims 1 to 6, wherein the end connection box is partially embedded in the foundation portion.   The foundation structure according to any one of claims 1 to 7, wherein the heating device is embedded in the foundation portion so as to be vertically stacked in a plurality of stages.   The foundation structure according to claim 8, wherein the heating device is embedded in the foundation portion so as to be vertically stacked in a plurality of stages so that the position of the heat generating unit is shifted.   The foundation structure according to any one of claims 1 to 9, wherein the heating device is installed in parallel to the foundation bottom surface of the structure.   The three said heating apparatuses are connected to the three-phase power supply in parallel, The foundation structure in any one of Claim 1 to 10 characterized by the above-mentioned.   The foundation structure according to any one of claims 1 to 11, wherein a plurality of the heating devices are arranged on the foundation portion.   The foundation structure according to any one of claims 1 to 12, wherein the structure is a cryogenic liquid storage tank. A plurality of conductive tubes embedded in the base portion of the structure and arranged side by side at a predetermined interval;
A starting-end connection box connected to a power-source-side starting end of the conductive tube;
A termination connection box connected to the final end of the conductive tube;
A first end connection box that is exposed from the base portion and connects adjacent ends of one end of the conductive tube;
A second end connection box that is exposed from the base portion and connects adjacent ends of the other end of the conductive tube;
The first end connection box and the second end connection box are connected to each other via the conductive tube;
An internal circuit consisting of a cable or an insulated wire passing through the inside of the starting connection box, the inside of the conductive tube, the first end connection box, the second end connection box, and the termination connection box;
From the end of the internal circuit, a termination connection box, a conductive tube, a first end connection box,
An external circuit connected in series with the power supply so that a current flows in a direction opposite to the internal circuit via the second end connection box and the start end connection box;
A current application circuit comprising:
A basic structure comprising a heating device configured to heat a conductive tube when a current is supplied from the power source through an internal circuit and an external circuit of a current application circuit. The foundation according to claim 14, wherein the current flowing through the external circuit is configured to flow through a wall surface on a foundation side of the first end connection box and the second end connection box. Construction.   The foundation structure according to claim 14, wherein the end connection box is attached to an outside of the foundation portion.   The foundation structure according to any one of claims 14 to 16, wherein the end connection box is attached to the foundation portion in a partially embedded state.   The foundation structure according to any one of claims 14 to 17, wherein the heating device is embedded in the foundation portion so as to be vertically stacked in a plurality of stages.   The foundation structure according to claim 18, wherein the heating device is embedded in the foundation portion so as to be vertically stacked in a plurality of stages so that the position of the heat generating unit is shifted.   The foundation structure according to any one of claims 14 to 19, wherein the heating device is installed in parallel to the foundation bottom face of the structure.   The foundation structure according to any one of claims 14 to 20, wherein the three heating devices are connected in parallel to a three-phase power source.   The foundation structure according to any one of claims 14 to 21, wherein a plurality of the heating devices are arranged on the foundation portion.   The foundation structure according to any one of claims 14 to 22, wherein the structure is a cryogenic liquid storage tank.

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