JP2018127860A - Construction method of tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a construction method of a tank which achieves simultaneous construction of bottom linear laying work and portal trestle installation work, and can achieve further shortening of a construction period.SOLUTION: A construction method of a tank includes: a first laying step of laying an outer annular plate 61 having such a size that a portal trestle 10 can be installed on an outermost peripheral part 1a along the inside of an outer tank 2; a second laying step of laying a bottom liner plate 62 in a central part 1b surrounded by the laid outer annular plate 61 after the first laying step; and a third laying step of laying an inner annular plate 63 on an intermediate gap part 1c between the laid outer annular plate 61 and the bottom liner plate 62 after the second laying step, and installs the portal trestle 10 on the laid outer annular plate 61.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a tank construction method.

  A double-shell tank having an inner tank and an outer tank is used for storing low-temperature liquids such as LNG (liquefied natural gas) and LPG (liquefied petroleum gas). Patent Document 1 below discloses a method for constructing a cylindrical tank having a metal inner tank and a concrete outer tank. In this cylindrical tank construction method, in order to shorten the construction period of the cylindrical tank, a metal inner tank and a concrete outer tank are simultaneously constructed.

  Specifically, while assembling the side wall of the outer tank on the foundation plate ahead of the side wall of the inner tank, a jackup device is installed on the side wall of the outer tank in the middle of assembly, and the jackup device constitutes the inner tank. The body (including at least one of the roof part, knuckle part, and inner tank side plate) is raised, and the inner tank side plate is attached to the lower side of the lifting body one after another, so that the metal inner tank and concrete made Realizes simultaneous construction with outer tank.

International Publication No. 2012/137671

  By the way, in the said conventional method, in order to support the next inner tank side board attached to the lower side of the lifting body raised with the jackup apparatus, the gate type mount frame is installed. The portal frame is installed on the bottom liner laid on the base plate. Therefore, in the above-described conventional method, the laying operation of the bottom liner is a critical path for the installation work of the portal frame.

  The present invention has been made in view of the above circumstances, and provides a tank construction method capable of realizing a simultaneous construction of a bottom liner laying operation and a gate-type gantry installation operation to further shorten the work period. With the goal.

  In order to solve the above-described problems, the present invention provides a basic plate building process for building a basic plate, an outer tank building step for building an outer tank on the basic plate, and a jack-up device inside the outer tank. An inner tank construction step of constructing an inner tank by alternately repeating the lifting of the lifting body and the welding of the inner tank side plate to the lower side of the raised lifting body, Furthermore, a bottom liner laying step for laying a bottom liner on the foundation plate, and a gate-type gantry for supporting the lifting body or the inner tank side plate before welding on the bottom liner laid on the foundation plate A plurality of gate-type frame installation steps along the inner side of the outer tub, and the bottom liner laying step includes the gate-type frame at the outermost peripheral portion along the inner side of the outer tub. Lay out an outer annular plate of a size that can be installed After the first laying step, after the first laying step, the second laying step of laying the bottom liner plate in the center part surrounded by the laid outer annular plate, and after the second laying step, A third laying step of laying an inner annular plate in an intermediate gap between the outer annular plate and the bottom liner plate, and in the gate-type gantry mounting step, on the laid outer annular plate, A method of installing the gate-type mount is adopted.

  Further, in the present invention, in the portal gantry installation step, the portal gantry is installed on the laid outer annular plate after the first laying step and at least before the third laying step. The method of, is adopted.

  Further, in the present invention, in the gate-type gantry installation step, a first gate-type gantry is installed in a region facing the construction port for taking in the inner tank side plate formed in the outer tub, and is opposed to the construction port. A second gate-type gantry having a smaller length in the tank radial direction than the first gate-type gantry is installed in a region where the outer annular plate is in the tank radial direction. Use a technique that is larger than the frame.

  In the present invention, a method is adopted in which the outer annular plate has a fan shape in plan view.

According to the present invention, when the bottom liner is laid on the base plate, the outer annular plate disposed on the outermost peripheral portion along the inner side of the outer tub is laid before the bottom liner plate and the inner annular plate. Since the outer annular plate has a size that allows the portal frame to be installed, the portal frame can be installed without waiting for the bottom liner plate and the inner annular plate to be laid. Once the portal frame is installed, the construction work can be shortened because the construction of the inner tank can be carried out by the jack-up device.
Therefore, in the present invention, it is possible to realize the simultaneous construction of the bottom liner laying work and the gate-type gantry mounting work, and the construction period can be further shortened.

It is explanatory drawing which shows the 1st process (a basic version construction process and an outer tank construction process) of the construction method in the embodiment of the present invention. It is explanatory drawing which shows the 2nd process (1st laying process of a bottom part liner laying process) of the construction method in embodiment of this invention. It is a top view which shows the outer annular plate laid on the basic | foundation board in embodiment of this invention. It is explanatory drawing which shows the 3rd process (The 2nd laying process of a bottom part liner laying process, and a portal mount installation process) of the construction method in embodiment of this invention. It is a plane enlarged view which shows the magnitude relationship of the outer annular plate and the gate type mount frame in embodiment of this invention. It is explanatory drawing which shows the 4th process (inner tank construction process) of the construction method in embodiment of this invention. It is explanatory drawing which shows the 5th process (inner tank construction process) of the construction method in embodiment of this invention. It is explanatory drawing which shows the 6th process (inner tank construction process) of the construction method in embodiment of this invention. It is explanatory drawing which shows the 7th process (inner tank construction process) of the construction method in embodiment of this invention. It is explanatory drawing which shows the 8th process (cooling material arrangement | positioning process) of the construction method in embodiment of this invention.

  Hereinafter, a tank construction method of the present invention will be described with reference to the drawings. In the following description, a construction method of a ground type PC (prestressed concrete) double shell storage tank for storing LNG will be exemplified. In the following drawings, for convenience of explanation, some parts are enlarged or omitted, and the dimensional ratios and the like of each component shown in the drawings are not always the same.

Drawing 1 is an explanatory view showing the 1st process (basic version construction process and outer tank construction process) of the construction method in the embodiment of the present invention. 1A is an overall view, and FIG. 1B is an enlarged view of a region A shown in FIG.
First, in this method, as shown to Fig.1 (a), the substantially disk-shaped base plate 1 is built (base plate construction process). The base plate 1 is made of concrete, and an inner tank anchor strap 4 and a corner angle 100 are embedded in the outer peripheral edge portion thereof.

  Next, in this method, the outer tank 2 is constructed on the basic version 1 (outer tank construction process). As shown in FIG. 1A, the outer tub 2 is constructed at the peripheral edge of the substantially disc-shaped base plate 1. The outer tub 2 is a PC (prestressed concrete) constructed by placing the outer tub side plate 3 (side plate) on the upper end of the corner angle 100 by welding and placing concrete 5 using the outer tub side plate 3 as an inner mold. ) A wall. A plurality of outer tank side plates 3 are arranged on the inner wall surface 2 a of the outer tank 2.

  As shown in FIG. 1B, the corner angle 100 is formed in an L shape in cross section. Note that the corner angle 100 does not necessarily have to be formed in an L shape when viewed in cross section, and may be a shape having at least one of a horizontal portion and a vertical portion, for example. A headed stud 101 that applies a pulling load to the base plate 1 is joined to the lower portion of the corner angle 100 so that the outer tank side plate 3 welded to the upper end of the corner angle 100 does not tilt. Further, a separator cone 102 for installing the outer mold frame 200 may be joined to the back surface of the corner angle 100.

  The outer tank side plate 3 is formed in a rectangular plate shape. A stiffener 110 is joined to the rear surface 3b opposite to the front surface 3a facing the tank inside of the outer tank side plate 3. The stiffener 110 is embedded in the concrete 5. In addition, a separator cone 120 for installing the outer mold frame 200 is joined to the back surface 3 b of the outer tank side plate 3. The separator cone 120 is also embedded in the concrete 5.

  The outer tank side plate 3 includes a lateral stiffener 110A and a vertical stiffener 110B as the stiffener 110. The lateral stiffener 110A is embedded in the concrete 5 so as to extend in the horizontal direction, and increases the shear resistance of the outer tank side plate 3 due to prestress. The vertical stiffener 100 </ b> B is embedded in the concrete 5 so as to extend in the vertical direction, and suppresses expansion of the outer tank side plate 3 into the tank due to the placement pressure of the concrete 5.

  In the outer tank construction process, the first-stage outer tank side plate 3 is assembled by welding to the upper end of the corner angle 100 as shown in FIG. Next, the concrete 5 is placed using the assembled outer tank side plate 3 and the corner angle 100 as an inner mold. The outer mold frame 200 is connected to the inner mold frame via a separator 201 connected to the separator cones 102 and 120.

  The assembling of the outer tank side plate 3 and the placing of the concrete 5 are parallel operations with a certain interval. Thereby, the protrusion part P of the outer tank side board 3 of the height which has not laid concrete 5 can be restrained to a certain fixed range. Since the protruding portion P is a portion that receives the wind load by the outer tub side plate 3 alone, buckling of the outer tub side plate 3 due to the wind load can be prevented by suppressing the protruding portion P within a certain range.

FIG. 2 is an explanatory diagram showing a second step (first laying step of the bottom liner laying step) of the construction method according to the embodiment of the present invention.
In this method, after the base plate construction step, the bottom liner 6 is laid on the base plate 1 in parallel with the outer tank construction step described above (bottom liner construction step) as shown in FIG. In the bottom liner laying step, first, the outer annular plate 61 is laid on the outermost peripheral portion 1a along the inner side of the outer tub 2 (first laying step).

FIG. 3 is a plan view showing the outer annular plate 61 laid on the foundation plate 1 in the embodiment of the present invention.
The outer annular plate 61 is formed in a fan shape in plan view. On the outer diameter side of the outer annular plate 61, a plurality of holes 61a are formed at intervals along the arc shape on the outer diameter side. The inner tank anchor strap 4 shown in FIG. 2 is inserted into the hole 61a, and an anchor box (not shown) that houses the lower end of the inner tank anchor strap 4 is engaged therewith.

In the bottom liner laying step, first, a fan-shaped outer annular plate 61 is laid in an annular shape on the outermost peripheral portion 1a of the base plate 1 (first laying step). The outer annular plate 61 may be laid in one route from the tank 0 degree (reference) to 360 degrees in order, or two routes from the tank 0 degree to 180 degrees and the tank 180 degrees to 360 degrees. You may go on.
Next, the bottom liner plate 62 is laid on the central portion 1b of the base plate 1 surrounded by the outer annular plate 61 laid in an annular shape (second laying step). The bottom liner plate 62 is made of a plurality of liner materials and is laid in a polygonal shape in plan view.

  Finally, the inner annular plate 63 is laid in the intermediate gap 1c between the outer annular plate 61 laid in an annular shape and the bottom liner plate 62 laid in a polygonal shape (third laying step). The inner annular plate 63 is an adjustment plate that covers the intermediate gap portion 1 c, and is laid across the outer annular plate 61 and the bottom liner plate 62. As described above, the bottom liner 6 can be laid on the entire surface of the base plate 1 inside the outer tub 2.

FIG. 4 is an explanatory diagram showing a third step (a second laying step of the bottom liner laying step and a portal mount installation step) of the construction method according to the embodiment of the present invention.
In this method, after the first laying step of the bottom liner laying step described above, the gate-type pedestal 10 is installed on the outer annular plate 61 laid in an annular shape (gate-type pedestal setting step). The gate-type gantry 10 supports the inner tank side plate 9 before welding to the lifting body 60 or the lifting body 60 for constructing the inner tank in the inner tank construction process described later (see FIG. 6 to be described later). .

  In addition, under the gate-type gantry 10, a cold insulation structure 12 such as a pearlite concrete block or a lightweight structural concrete block is temporarily placed, and the cold insulation work of the annular portion 13 (see FIG. 6 described later) is performed by the cold insulation structure 12. . A plurality of the gate-type mounts 10 are installed along the inner side of the base end portion of the outer tub 2, and a cylindrical inner tub formed by combining a plurality of inner tub side plates 9 should be finally lowered onto the base plate 1. It is installed so as to straddle the annular region X which is a region.

FIG. 5 is an enlarged plan view showing the size relationship between the outer annular plate 61 and the gate-type gantry 10 in the embodiment of the present invention.
The outer annular plate 61 has a size that allows the portal frame 10 to be installed. In the gate-type gantry installation process, the first gate-type gantry 10A is installed in a region facing the construction port 8 for taking in the inner tank side plate 9 formed in the outer tub 2, and the tank diameter is set in a region not facing the construction port 8. A second portal frame 10B having a length in the direction smaller than that of the first portal frame 10A is installed.

  The first portal frame 10A is longer in the tank radial direction than the second portal frame 10B in order to take the inner tank side plate 9 from the construction port 8. Further, the length of the outer annular plate 61 in the tank radial direction is larger than that of the first portal frame 10A. The length of the first portal frame 10A in the tank radial direction is L1, the length of the second portal frame 10B in the tank radial direction is L2, and the length of the outer annular plate 61 in the tank radial direction is L3. Then, there is a relationship of L2 <L1 <L3.

  Further, the first gate-type gantry 10A and the second gate-type gantry 10B are both installed so as to straddle the hole 61a (inner tank anchor strap 4) formed in the outer annular plate 61 (see FIG. 4). ). At least a length L4 is ensured from the inner diameter side end of the first gate-type gantry 10A whose length in the tank radial direction is larger than that of the second portal gantry 10B to the inner diameter-side end of the outer annular plate 61. ing. The length L4 secures a work area for welding the inner annular plate 63, and is secured, for example, about 1 to 2 m.

  As described above, in this method, when the bottom liner 6 is laid on the base plate 1, the outer annular plate 61 disposed on the outermost peripheral portion 1a along the inner side of the outer tub 2 is replaced with the bottom liner plate 62 and the inner liner plate 62. Lay down prior to the annular plate 63. Since the outer annular plate 61 has a size that allows the portal frame 10 to be installed, the portal frame 10 can be installed without waiting for the bottom liner plate 62 and the inner annular plate 63 to be installed. . When the gate-type gantry 10 is installed, the construction period can be shortened because it is possible to proceed to an inner tank construction process described later.

  Further, in this method, as shown in FIG. 4, after the outer annular plate 61 is laid (first laying step), at least before the inner annular plate 63 is laid (third laying step), the portal frame 10 is installed. . In this method, since the outer annular plate 61 having a size that allows the portal frame 10 to be installed is laid, there is no need to install the portal frame so as to straddle the outer annular plate and the inner annular plate unlike the conventional method. The simultaneous installation of the laying operation of the bottom liner 6 and the installation operation of the portal frame 10 can be realized. Note that the portal frame 10 may be installed after the outer annular plate 61 is laid (first laying step) and before the bottom liner plate 62 is laid (second laying step).

  Further, in this method, in the portal mount installation process, as shown in FIG. 5, the first portal mount 10 </ b> A is provided in a region facing the construction port 8 for taking in the inner tank side plate 9 formed in the outer tank 2. A second gate-type gantry 10B having a smaller length in the tank radial direction than the first gate-type gantry 10A is installed in a region not installed and opposed to the construction port 8, and the length of the outer annular plate 61 in the tank diametrical direction is set. The height is larger than that of the first gate-type gantry 10A. Thus, by laying the outer annular plate 61 according to the long first gate-type gantry 10A, it is not necessary to use the outer annular plate 61 having a different length, and the workability is improved.

  In this method, the outer annular plate 61 has a fan shape in plan view, so that the outer annular plate 61 is secured in the outermost peripheral portion 1a of the base plate 1 in the tank radial direction without leaving a gap. Can be laid in an annular shape.

Drawing 6 is an explanatory view showing the 4th process (inner tank construction process) of the construction method in the embodiment of the present invention. Drawing 7 is an explanatory view showing the 5th process (inner tank construction process) of the construction method in the embodiment of the present invention.
Next, in this method, the inner tank is constructed by alternately repeating the raising of the lifting body 60 by the jack-up device 19 and the welding of the inner tank side plate 9 to the lower side of the raised lifting body 60 (the inner tank). Construction process). In the inner tank construction process, first, as shown in FIG. 6, a plurality of jackup devices 19 are installed in the outer tank 2.

  A suspension side mount 70 is installed in the middle part of the outer tub 2. The suspension side mount 70 is detachably fastened and fixed to an anchor plate (not shown) embedded in the outer tub 2. Further, the suspended side base 80 is installed on the knuckle plate 11 assembled on the gate base 10. A jack body 19 a of the jack-up device 19 is connected to the suspended side base 80. Further, the suspension rod base 70 is connected to a jack rod 19b that strokes by the operation of the jack body 19a.

  When the jack-up device 19 is thus installed, the knuckle plate 11 is lifted, and the inner tank side plate 9 is carried into the lower space formed by the jack-up. The inner tank side plate 9 is transported to a predetermined welding position, and the adjacent inner tank side plates 9 are welded to each other so as to be joined together in the circumferential direction so as to be cylindrical as a whole. Next, the upper end portion of the inner tank side plate 9 is assembled to the lower end portion of the knuckle plate 11. Further, the upper end portion of the knuckle plate 11 is assembled to the outer peripheral edge portion of the inner tank roof 14 assembled on the roof mount 7.

  Next, as shown in FIG. 7, the roof mount 7 is removed, and the lifting body 60 including the inner tank roof 14, the knuckle plate 11, and the inner tank side plate 9 is lifted by the jack-up device 19. When the lifting body 60 is raised by an amount corresponding to the vertical width of the inner tank side plate 9 by the jack-up device 19, the next inner tank side plate 9 is carried into the space formed below the inner tank side plate 9 by the jack-up. When the carried inner tank side plate 9 is joined in the circumferential direction of the tank, the upper end thereof and the lower end of the lifting body 60 (inner tank side plate 9) are welded. Thus, in this method, the raising of the inner tank side plate 9 by the jack-up device 19 and the welding of the next inner tank side plate 9 to the lower side of the raised inner tank side plate 9 are alternately repeated.

  Moreover, the outer tank roof 22 is assembled on the inner tank roof 14 in this process. The outer tank roof 22 is connected to the inner tank roof 14 by a connecting material (not shown), and is assembled integrally with the inner tank roof 14. Moreover, if the outer tank 2 is assembled, the jack point of the suspension side will be changed to the top part. In this manner, while changing the jack point on the suspension side, the raising of the inner tank side plate 9 by the jack-up device 19 and the welding of the next inner tank side plate 9 to the lower side of the raised inner tank side plate 9 are alternately performed. The first structure 9a excluding the lowermost stage of the inner tank side plate 9 is assembled.

  In addition, if the cold insulation work of the annular part 13 is completed under the gate-shaped mount 10, the leg part 10a arrange | positioned inside the tank rather than the annular part 13 will be replaced on the annular part 13 (refer FIG. 7). By such replacement, there is no interference on the inside of the tank with respect to the annular portion 13, so that the inside of the tank can be kept cold. In the cold insulation work inside the tank, the bottom cooling resistance reducing material 39 and the foam glass 40 are placed on the bottom liner 6. Then, a pearlite concrete block (not shown) and an inner tank bottom plate (not shown) are laid on top of each other in this order.

FIG. 8 is an explanatory diagram showing a sixth step (inner tank construction step) of the construction method according to the embodiment of the present invention.
In this method, the lowermost stage of the inner tank side plate 9 is assembled on the annular portion 13 separately from the first structure 9a. After disassembling the portal frame 10, when the lowermost stage of the inner tank side plate 9 is placed on the annular portion 13, the adjacent inner tank side plates 9 are welded together and joined together in the circumferential direction so as to be cylindrical as a whole. The second structure 9b is assembled. After assembling the second structure 9b, the inner tank anchor strap 4 installed on the base plate 1 is attached. Further, an elevating staircase 23 is provided outside the outer tub 2. Further, the pump barrel 25 is carried inside the outer tub 2.

FIG. 9 is an explanatory diagram showing a seventh step (inner tank construction step) of the construction method according to the embodiment of the present invention.
Next, in this method, as shown in FIG. 9, the first structure 9a is jacked down, the lower end portion of the first structure 9a is lowered to the upper end portion of the second structure 9b, and the first structure 9a is lowered. The structure 9a and the second structure 9b are welded, and the inner tank 30 is assembled. In this method, the lowermost assembly of the inner tub 30 is separated from the assembly of the inner tub 30 by the jack-up device 19, and the second structure 9 b that is the lowermost tier of the inner tub 30 is fixed on the annular portion 13. Is going ahead of schedule. Therefore, in this method, for example, fixing the inner tank 30 on the annular portion 13 which takes about one month does not become a critical path, and the construction period can be shortened compared to the conventional method.

When the inner tub 30 is completed, the outer tub roof 22 is disconnected from the inner tub roof 14 by a connecting material (not shown) and installed on the upper end of the outer tub 2 assembled to the top. A roof staircase 24 is provided on the outer tank roof 22. A pump barrel 25 is also installed.
Thereafter, the suspended side base 80 is removed and the jack-up device 19 is removed. Then, tension work of the outer tub 2 is performed. Then, after the construction port 8 is closed, it is filled with water and a pressure and airtight test is performed.

FIG. 10 is an explanatory diagram showing an eighth step (cold material arranging step) of the construction method according to the embodiment of the present invention.
Finally, as shown in FIG. 10, a cold insulating material 44 is disposed between the inner and outer tanks 15 between the inner tank 30 and the outer tank 2, and the cold insulating material is also provided between the inner tank roof 14 and the outer tank roof 22. The LNG tank 50 is constructed through the painting work and the pipe cold insulation work.

  As described above, according to the above-described embodiment, the basic version construction process for constructing the basic version 1, the outer tank construction process for constructing the outer tank 2 on the basic version 1, and the jack inside the outer tank 2 The LNG tank which has the inner tank construction | assembly process which builds the inner tank 30 by repeating the raising of the lifting body 60 by the up apparatus 19, and the welding of the inner tank side plate 9 to the lower side of the raised lifting body 60 alternately. 50, a bottom liner laying step of laying the bottom liner 6 on the base plate 1, and a lifting body 60 or an inner tank before welding on the bottom liner 6 laid on the base plate 1 A plurality of gate-type mounts 10 that support the side plates 9 are installed along the inside of the outer tub 2, and the bottom liner laying step is the outermost periphery along the inner side of the outer tub 2. The outer annular pre-sized so that the portal frame 10 can be installed in the part 1a. A first laying step of laying the belt 61, a second laying step of laying the bottom liner plate 62 in the central portion 1b surrounded by the outer annular plate 61 laid after the first laying step, and a second laying step And a third laying step of laying the inner annular plate 63 in the intermediate gap portion 1c between the laid outer annular plate 61 and the bottom liner plate 62. In the gate-type gantry installing step, By adopting the method of installing the gate-type gantry 10 on the outer annular plate 61, the construction work of the bottom liner 6 and the installation work of the gate-type gantry 10 can be realized simultaneously, further shortening the construction period. Can be planned.

  As mentioned above, although preferred embodiment of this invention was described referring drawings, this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  For example, in the above embodiment, the case where the present invention is applied to an LNG tank is illustrated, but the present invention can also be applied to a tank that stores other low-temperature liquids (for example, LPG).

DESCRIPTION OF SYMBOLS 1 Base plate 1a Outermost peripheral part 1b Center part 1c Middle clearance part 2 Outer tank 6 Bottom liner 8 Construction port 9 Inner tank side plate 10 Gate-type frame 10A First gate-type frame 10B Second gate-type frame 19 Jack-up device 30 Inner tank 50 LNG tank (tank)
60 Lifting body 61 Outer annular plate 61a Hole 62 Bottom liner plate 63 Inner annular plate

Claims (4)

A basic version construction process for constructing a basic version, an outer tank construction process for constructing an outer tank on the basic version, a lift of the lifting body by a jack-up device inside the outer tank, and the raised body An inner tank construction step of alternately repeating the welding of the inner tank side plate to the lower side and constructing the inner tank, and a tank construction method comprising:
further,
A bottom liner laying step of laying a bottom liner on the foundation plate;
On the bottom liner laid on the foundation plate, a gate-type frame installation step of installing a plurality of gate-type frames that support the lifting body or the inner tank side plate before welding along the inside of the outer tank; , And
The bottom liner laying step includes
A first laying step of laying an outer annular plate of a size capable of installing the portal frame on the outermost peripheral portion along the inner side of the outer tub;
After the first laying step, a second laying step of laying a bottom liner plate at the center surrounded by the laid outer annular plate;
After the second laying step, a third laying step of laying an inner annular plate in an intermediate gap portion between the laid outer annular plate and the bottom liner plate,
In the gate-type gantry installation step, the tank-type gantry is installed on the laid outer annular plate.   The gate-type gantry is installed on the outer annular plate laid after the first laying step and before at least the third laying step in the gate-type gantry installation step. Item 2. A tank construction method according to Item 1. In the gate-type gantry installation step, the first gate-type gantry is installed in a region facing the construction port for taking in the inner tank side plate formed in the outer tub, and in a region not facing the construction port, the tank radial direction Installing a second gate-type frame having a length smaller than that of the first gate-type frame;
3. The tank construction method according to claim 1, wherein a length of the outer annular plate in a tank radial direction is larger than that of the first portal frame.   The tank construction method according to any one of claims 1 to 3, wherein the outer annular plate has a fan shape in plan view.

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