JP2014202386A - Method for assembling heat exchanger and flexure prevention tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger having a plurality of arranged heat transfer pipe and preventing flexure of the heat transfer pipe.SOLUTION: A plurality of communication gaps are formed in heat transfer pipe units having been stacked and arranged, by that gaps between heat transfer pipes in each of the heat transfer pipe units align in an inclined direction inclined to the vertical direction. A flexure prevention tool having a linear rod part is inserted from the outside of the heat transfer pipe units, and an additional heat transfer pipe unit is stacked and arranged.

Description

  The present invention relates to a heat exchanger assembling method and a deflection preventing jig.

  In a nuclear power plant equipped with a pressurized water reactor, a so-called steam generator is installed as a large heat exchanger that generates steam by transferring heat generated in the reactor to water (see Patent Document 1). In such a steam generator, a metal thin tube is used as a heat transfer tube. In the steam generator, a large number of such heat transfer tubes are supported by a tube support plate and regularly arranged, thereby realizing a large capacity heat exchange.

  When assembling such a steam generator, the operation is generally performed in a laid state. That is, a heat transfer tube unit is formed by arranging heat transfer tubes partially U-shaped at equal intervals in the horizontal direction, and a plurality of anti-vibration bars (so-called AVBs) are arranged on the heat transfer tube unit. A heat transfer tube unit is built on the vibration bar. By repeating this, the substantially cylindrical steam generator is assembled in the state of being laid down.

JP 2012-145284 A

  However, the heat transfer tube is supported from directly below the vibration isolation bar, so it will not bend, and at a position outside the vibration isolation bar, the heat transfer tube will be bent and it will be difficult to place the heat transfer tube with high accuracy. Become. In addition, since the heat transfer tubes are densely arranged, when the assembly proceeds, it becomes impossible to measure and repair the deflection of the heat transfer tubes. As a result, the arrangement accuracy of the heat transfer tubes in the finally assembled steam generator cannot be ensured, and the product characteristics such as the heat exchange rate may vary. In particular, the heat transfer tube used in the steam generator has a thin tube thickness, is easy to bend, and has a high density.

  The bending of the heat transfer tube during the assembly is not limited to the assembly of the steam generator used in the nuclear power plant, but a heat exchanger formed by arranging a large number of heat transfer tubes in the horizontal and vertical directions. This is a general problem that occurs during assembly.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to prevent the heat transfer tubes from being bent in a heat exchanger in which a plurality of heat transfer tubes are arranged.

  The present invention adopts the following configuration as means for solving the above-described problems.

  1st invention disposes the heat-transfer tube unit which consists of a plurality of heat-transfer tubes arranged at equal intervals in the horizontal direction by stacking the horizontal positions of the heat-transfer tubes by equal distances and with intervals in the vertical direction. A heat exchanger assembly method for assembling a heat exchanger, wherein a plurality of the heat transfer tube units stacked in advance are formed in a laminated body, and the gaps between the heat transfer tubes in each heat transfer tube unit are in the vertical direction. In contrast, a bending prevention jig having a straight bar portion is inserted from the outside of the heat transfer tube unit into the communication gap formed by connecting in an oblique direction that is inclined with respect to the heat transfer tube unit, and the heat transfer tube units are arranged in a stacked manner. Adopt the configuration.

  A second invention employs a configuration in which, in the first invention, at least a part of the heat transfer tube is curved, and the bending prevention jig is inserted in a region where the heat transfer tube is curved.

  According to a third aspect of the present invention, in the first or second aspect, the heat transfer tube units are stacked and arranged while installing a vibration isolation bar between the heat transfer tube units, and the stacking arrangement of the heat transfer tube units is completed. A configuration is adopted in which the anti-vibration bars are joined later, and the anti-bending jig is extracted after the anti-vibration bars are joined.

  A fourth invention is a deflection preventing jig, wherein a heat transfer tube unit comprising a plurality of heat transfer tubes arranged at equal intervals in the horizontal direction displaces the horizontal position of the heat transfer tubes by equal distances and through a spacer. The stack formed by stacking in the vertical direction includes a communication gap formed by connecting the gaps between the heat transfer tubes in each heat transfer tube unit in an oblique direction inclined with respect to the vertical direction. The structure which has the linear rod part inserted in this way is employ | adopted.

  5th invention employ | adopts the structure that the mark is provided with respect to the front-end | tip part of the insertion direction of the said rod part in the said 4th invention.

  6th invention employ | adopts the structure that the stopper larger than the clearance gap between the said heat exchanger tubes is provided in the rear-end part of the insertion direction of the said bar part in the said 4th or 5th invention.

  According to a seventh aspect, in the sixth aspect, the stopper is a ring member.

  According to the present invention, a heat transfer tube unit composed of a plurality of heat transfer tubes arranged at equal intervals in the horizontal direction is disposed by stacking the horizontal positions of the heat transfer tubes by equal distances and spaced apart in the vertical direction. When assembling the heat exchanger, the deflection preventing jig is inserted into a plurality of communication gaps formed by connecting the gaps between the heat transfer tubes in each heat transfer tube unit in an oblique direction inclined with respect to the vertical direction. As a result, when the heat transfer tube tries to bend by its own weight, the heat transfer tube hits the bending prevention jig inserted into the communication gap, and the deformation of the heat transfer tube is suppressed. Therefore, according to the present invention, it is possible to prevent the heat transfer tube from being bent in the heat exchanger in which a plurality of heat transfer tubes are arranged.

It is a schematic block diagram of the steam generator assembled with the assembly method of the steam generator in one Embodiment of this invention. It is sectional drawing which illustrated typically a part of steam generator assembled with the assembly method of the steam generator in one Embodiment of this invention. It is a perspective view of the bending prevention jig | tool used for the assembly method of the steam generator in one Embodiment of this invention. It is a schematic diagram for demonstrating the assembly method of the steam generator in one Embodiment of this invention. It is a schematic diagram for demonstrating the assembly method of the steam generator in one Embodiment of this invention. It is a schematic diagram for demonstrating the assembly method of the steam generator in one Embodiment of this invention. It is the perspective view which expanded some steam generators during an assembly. It is a schematic diagram for demonstrating the assembly method of the steam generator in one Embodiment of this invention.

  Hereinafter, an embodiment of a heat exchanger assembling method and a deflection preventing jig according to the present invention will be described with reference to the drawings. In the following description, a steam generator assembling method will be described as an example of a heat exchanger assembling method according to the present invention. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

  FIG. 1 is a schematic configuration diagram of a steam generator 1 assembled by the steam generator assembling method of the present embodiment. As shown in this figure, the steam generator 1 includes a heat exchanging unit 2, a body 3 surrounding the heat exchanging unit 2, and other well-known mechanical elements (not shown). In FIG. 1, the steam generator 1 is illustrated in a laid state. However, when installed in a nuclear power plant, the steam generator 1 is erected so that the direction indicated by the z-axis shown in FIG. 1 is vertically upward. The method for assembling the steam generator 1 according to the present embodiment is used when the steam generator 1 is assembled in the laid state (particularly when assembling the heat transfer tube group 52 and the vibration isolator 6 described below). It is. In the following description, the y direction shown in FIG. 1 is a vertical direction, and the x direction and the z direction are horizontal directions. Of the horizontal directions, the x direction is referred to as the left-right direction and the z direction is referred to as the front-rear direction.

  The heat exchanging unit 2 is configured by a tube support plate 4, a heat transfer tube group 5, and a vibration isolation fitting 6. The tube support plate 4 is a metal disk member that supports the heat transfer tube group 5, and a plurality of the front and back surfaces are oriented at equal intervals in the front-rear direction (z direction) with the front and back surfaces directed in the front-rear direction (z direction) In this embodiment, 5 sheets) are installed. In these tube support plates 4, through holes 4a to which the heat transfer tubes 5a constituting the heat transfer tube group 5 are connected are formed by the number of the heat transfer tubes 5a.

  The heat transfer tube assembly 5 is disposed between the tube support plates 4 and on the front side of the tube support plate 41 disposed on the most front side. As shown in FIG. 1, the heat transfer tube group 51 disposed between the tube support plates 4 includes a plurality of linear heat transfer tubes 5a1 arranged in the left-right direction (x direction) and the vertical direction (y direction). Is formed by. Further, the heat transfer tube group 52 arranged on the front side of the tube support plate 41 is constituted by a large number of U-shaped heat transfer tubes 5a2 as shown in FIG. In FIG. 1, only the lower half of the heat transfer tube group 5 is illustrated so that the tube support plate 4 can be easily seen.

  The heat transfer tube assembly 52 will be described in more detail. It can be understood that the heat transfer tube assembly 52 is formed by laminating and arranging the layers formed by the plurality of heat transfer tubes 5a2 with a gap in the vertical direction (y direction). These layers are hereinafter referred to as heat transfer tube units 10. Each heat transfer tube unit 10 has a configuration in which a plurality of heat transfer tubes 5a2 are arranged substantially concentrically along a horizontal plane (a surface parallel to the x-axis and the y-axis), centering on a heat transfer tube having a curved portion with the largest curvature. It is said that. The plurality of heat transfer tubes 5a2 constituting one heat transfer tube unit 10 gradually decrease in curvature of the curved portion toward the outer side in the radial direction, so that the clearance between the heat transfer tubes 5a2 becomes constant (that is, (Equally spaced). In addition, as shown in FIG. 1, the number of the heat exchanger tubes 5a which comprise each heat exchanger tube unit 10 changes with which position of the heat exchanger tube unit 10 is provided in the perpendicular direction (y direction). Here, the heat transfer tube unit 10 arranged at the center in the vertical direction (y direction) has the largest number of heat transfer tubes 5a and has a shape bulging outward in the radial direction. Alternatively, the number of the heat transfer tubes 5a included in the heat transfer tube unit 10 is gradually decreased toward the lower side, and the radial shape is gradually decreased. For this reason, the heat transfer tube assembly 52 has a substantially hemispherical shape as a whole.

  FIG. 2 is a cross-sectional view schematically showing a part of the heat transfer tube assembly 52. In this figure, the vibration isolator 6 is omitted. As shown in FIG. 2, the heat transfer tube unit 10 as described above is stacked so that the heat transfer tubes 5 a 2 are displaced by half a pitch with respect to the heat transfer tube units 10 adjacent in the vertical direction (y direction). . Furthermore, the heat transfer tube unit 10 is laminated and arranged with a certain gap with respect to the heat transfer tube units 10 adjacent in the vertical direction (y direction). That is, the heat transfer tube unit 10 composed of a plurality of heat transfer tubes 5a2 arranged at equal intervals in the horizontal direction is displaced by the same distance (half pitch in this embodiment) in the horizontal direction of the heat transfer tubes 5a2 and spaced in the vertical direction. The heat transfer tube assembly 52 is formed by stacking and arranging the layers. In addition, this clearance gap is ensured by the anti-vibration bar 6a mentioned later arrange | positioned between the heat exchanger tube units 10 mutually.

  In the heat transfer tube assembly 52 configured in this way, as shown in FIG. 2, the gap S between the heat transfer tubes 5a2 in each heat transfer tube unit 10 is connected in an oblique direction inclined with respect to the vertical direction (y direction). Arranged. As a result, a communication gap 20 extending in an oblique direction is formed. A large number of such communication gaps 20 are formed for each gap S between the heat transfer tubes 5a2. In addition, a maximum of two are provided so as to pass through a specific gap S. For example, when focusing on the gap Sa shown in FIG. 2, the communication gap 20 passing through the gap Sa includes a communication gap 21 that is inclined to the right with respect to the vertical direction (y direction) and a left side with respect to the vertical direction (y direction). An inclined communication gap 22 is formed. 2 is a cross-sectional view, the communication gap 21 is inclined to the right side and the communication gap 22 is inclined to the left side in FIG. However, the communication gap 21 and the communication gap 22 are curved along the U-shaped heat transfer tube 5a2 when viewed from above. For this reason, the actual shape of the communication gap 21 is a three-dimensional shape that spreads outward as it goes upward. Moreover, the actual shape of the communication gap 22 is a three-dimensional shape that is narrowed inward as it goes upward. In FIG. 2, in order to improve visibility, only one communication gap 21 and one communication gap 22 are shown with reference numerals.

  The vibration isolator 6 is formed by a plurality of V-shaped anti-vibration bars 6a connected to each other. In the heat transfer tube group 52, a plurality (6 in the present embodiment) of the vibration isolation bars 6a are disposed between the heat transfer tube units 10. The tip of each anti-vibration bar 6 a protrudes to the side of the heat transfer tube assembly 52. The anti-vibration bars 6a are connected by welding the ends of these anti-vibration bars 6a. Such a vibration isolator 6 fixes the position of the heat transfer tube 5a2 forming the heat transfer tube group 52 and prevents the heat transfer tube 5a2 from vibrating. The anti-vibration bar 6a functions as a spacer for securing a gap between the heat transfer tube units 10 when the heat transfer tube assembly 52 is assembled.

  Next, the deflection preventing jig 30 used for assembling the steam generator 1 configured as described above will be described with reference to FIG.

  FIG. 3 is a perspective view of the deflection preventing jig 30. As shown in this figure, the deflection preventing jig 30 is composed of a rod portion 31 and a ring member 32 (stopper). The rod portion 31 is a portion that is inserted into the communication gap 20 described above, and has a shape set in a straight line having a rectangular cross section. The bar 31 has a cross-sectional area that is set smaller than the opening area of the communication gap 20, and has a cross-sectional shape that can pass through the communication gap 20. In addition, a through hole 31 b is provided in the distal end portion 31 a of the rod portion 31. This through-hole 31b functions as a mark for easily confirming the chipped state of the tip portion 31a of the rod portion 31 visually. For example, when the through hole 31b cannot be confirmed when the deflection preventing jig 30 is extracted from the communication gap 20, it can be determined that the tip 31a of the bar 31 is broken and missing. Further, a mounting hole 31 d for mounting the ring member 32 is provided in the rear end portion 31 c of the rod portion 31.

  The outer shape of the ring member 32 is larger than the size (gap size) of the gap S between the heat transfer tubes 5a2, and the ring member 32 is provided at the rear end portion 31c of the rod portion 31 by being inserted into the mounting hole 31d. The ring member 32 functions as a stopper for preventing the bending prevention jig 30 inserted into the communication gap 20 from entering the heat transfer tube assembly 52. The ring member 32 is gripped by the operator when the bending prevention jig 30 inserted into the communication gap 20 is extracted. By this ring member 32, the bending prevention jig 30 can be easily extracted.

  Further, the bending prevention jig 30 is formed of, for example, resin or wood so as not to damage the metal heat transfer tube 5a2. Specifically, the deflection preventing jig 30 may be formed of a polyimide, nylon, or polyacetal resin. In particular, polyacetal-based resins are less likely to be crushed into powder, so that dust can be prevented from being generated by inserting / removing the bending prevention jig 30.

  When the rod portion 31 is inserted into the communication gap 20, the deflection preventing jig 30 as described above is brought into a close state or a contact state with respect to the intermediate portion of the heat transfer tube 5 a 2. In this state, the bending prevention jig 30 prevents the heat transfer tube 5 a 2 from being bent by the bar portion 31. As described above, the cross-sectional shape of the rod portion 31 of the deflection preventing jig 30 is a rectangular shape. For this reason, compared with the case where a cross section is circular, the contact area (support area) of the rod part 31 and the heat exchanger tube 5a2 can be enlarged, and it is possible to prevent the heat exchanger tube 5a2 from bending efficiently. It becomes. However, the rod portion 31 may be chamfered so as not to cause shaving due to sliding with the heat transfer tube 5a2.

  Next, with reference to FIGS. 4 to 8, the assembling method of the steam generator 1 according to the present embodiment will be described with a focus on the process of assembling the heat transfer tube assembly 52 and the vibration isolator 6 using the deflection preventing jig 30. explain. 4 to 6 and 8, (a) is a schematic cross-sectional view including a part of the heat transfer tube group 52 during assembly, and (b) is a view of FIG. 1 of the heat transfer tube group 52 during assembly. It is the front view seen from the left direction. 4 to 6 and 8, the anti-vibration bar 6a is omitted, and only a part of the deflection preventing jig 30 is illustrated. In the following description, it is assumed that the tube support plate 4 and the heat transfer tube 5a1 are already assembled in the body 3.

  In the method for assembling the steam generator 1 according to the present embodiment, the heat transfer tube units 10 are stacked and disposed in order from the bottom through the vibration isolation bars 6a. At this time, each heat transfer tube 5a2 is inserted into the tube support plate 41, whereby in the heat transfer tube unit 10 adjacent in the vertical direction (y direction), as shown in FIGS. 4 to 6 and FIG. Are arranged so as to be displaced by a half pitch in the horizontal direction.

  When the heat transfer tube units 10 are stacked and arranged in this manner, a communication gap 20 as shown in FIG. 2 is formed in the heat transfer tube assembly 52 (stacked body) being assembled. And such a communication gap 20 is extended by the amount by which the heat transfer tube unit 10 is laminated. In the method of assembling the steam generator 1 according to the present embodiment, as shown in FIGS. 4 to 6, the deflection preventing jig with respect to the communication gap 20 extending as the heat transfer tube units 10 are stacked as described above. Thirty rod portions 31 are inserted from the outside of the heat transfer tube assembly 52. That is, in the method of assembling the steam generator 1 of the present embodiment, the deflection preventing jig 30 is inserted into the communication gap 20 from the outside of the heat transfer tube unit 10, and the heat transfer tube unit 10 is further installed after the vibration isolation bar 6a is installed. By repeating the process of stacking and arranging, half of the heat transfer tube assembly 52 is assembled as shown in FIG.

  Note that the bending prevention jig 30 is not necessarily inserted into all the communication gaps 20. For example, since the heat transfer tube 5a2 that is a U-shaped tube is particularly easily bent at the outer edge portion of the heat transfer tube group 52, the heat transfer tube 5a2 may be inserted into the communication gap 20 positioned at the outer edge portion. As described above, the communication gap 21 of the communication gap 20 has a three-dimensional shape that spreads outward as it goes upward, and the communication gap 22 is a three-dimensional shape that squeezes inward as it goes upward. Shape. A plurality of the deflection preventing jigs 30 are inserted into the one communication gap 21 and the communication gap 22 at regular intervals as viewed from above, for example.

  Each deflection preventing jig 30 cannot be inserted deeper when the tip 31a abuts against the vibration isolating bar 6a, and is therefore inserted while avoiding the vibration isolating bar 6a. However, in order to fix the position of the anti-vibration bar 6a, a bending prevention jig 30 that abuts the tip 31a against the anti-vibration bar 6a may be inserted.

  Subsequently, as shown in FIG. 7, the heat transfer tubes 5 a 2 of the heat transfer tube units 10 adjacent in the vertical direction (y direction) are fixed by the binding band 40 in the region corresponding to the outer edge portion of the heat transfer tube assembly 52. As described above, when the heat transfer tubes 5 a 2 are fixed to each other by the binding band 40, a part of the heat transfer tubes 5 a 2 is supported by the bending prevention jig 30. For this reason, when attaching the binding band 40, it is possible to prevent a large load from acting on the heat transfer tube 5a2, and to prevent distortion or the like from occurring in the heat transfer tube 5a2.

  While inserting the heat transfer tube 5a2 into the tube support plate 41, the above-described half heat transfer tube assembly 52 is assembled, and the remaining heat transfer tube assembly 52 is similarly assembled on this half heat transfer tube assembly 52. Then, the vibration isolator 6 is formed by welding the tip of the vibration isolator bar 6a. Thus, since the heat transfer tube 5a2 is fixed, the flexure prevention jig 30 is extracted and the binding band 40 is removed after the formation of the vibration-proof fitting 6. The assembly of the steam generator 1 is completed through these steps.

  According to the method of assembling the steam generator 1 of the present embodiment as described above, the heat transfer tube unit 10 is displaced by a half pitch in the horizontal position of the heat transfer tube 5a2 and spaced in the vertical direction (y direction). When assembling the heat transfer tube assembly 52, the bending prevention jig 30 is inserted into the plurality of communication gaps 20. As a result, if the heat transfer tube 5a2 is bent by its own weight, the heat transfer tube 5a2 hits the bending prevention jig 30 inserted into the communication gap 20, and the deformation of the heat transfer tube 5a2 is suppressed. Therefore, according to the method for assembling the steam generator 1 of the present embodiment, it is possible to prevent the heat transfer tube 5a2 from being bent during the assembly.

  Further, in the method of assembling the steam generator 1 of the present embodiment, the bending of the heat transfer tube 5a2 having a curved portion is mainly prevented by the bending prevention jig 30. Since the bent portion of the heat transfer tube 5a2 is particularly likely to be bent, the effect of the bending preventing jig 30 becomes remarkable.

  Moreover, in the assembly method of the steam generator 1 of the said embodiment, the heat exchanger tube unit 10 is laminated and arrange | positioned, installing the anti-vibration bar 6a between each heat exchanger tube unit 10, and the heat exchanger tube unit 10 lamination | stacking arrangement | positioning. After completion, the anti-vibration bars 6a are joined together, and after the joining of the anti-vibration bars 6a is completed, the deflection preventing jig 30 is extracted. Since the position of the heat transfer tube 5a2 is fixed by the vibration isolation bar 6a (that is, the vibration isolation fitting 6) by completing the joining of the vibration isolation bars 6a, the heat transfer tube 5a2 bends even if the deflection preventing jig 30 is extracted. Absent. Therefore, according to the method of assembling the steam generator 1 of the above embodiment, it is possible to more reliably prevent the heat transfer tube 5a2 from being bent.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that 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 spirit of the present invention.

  For example, in the said embodiment, the example which applied this invention to the method of assembling the steam generator 1 was demonstrated. However, the present invention is not limited to this, and can be applied to other heat exchanger assembly methods.

  Moreover, in the said embodiment, the structure which uses the bending prevention jig | tool 30 only when assembling the heat exchanger tube group 52 formed of the U-shaped heat exchanger tube 5a2 was demonstrated. However, the present invention is not limited to this. For example, when assembling a heat transfer tube assembly composed of straight heat transfer tubes in another heat exchanger or the like, the heat transfer tube assembly is exposed. In this case, the bending prevention jig 30 can be used similarly.

  DESCRIPTION OF SYMBOLS 1 ... Steam generator, 2 ... Heat exchange part, 3 ... Body, 4 ... Pipe support plate, 4a ... Through-hole, 5 ... Heat transfer tube group, 5a ... Heat transfer tube, 5a1 ... Heat transfer tube 5a2 ... Heat transfer tube, 6 ... Vibration-proof fitting, 6a ... Vibration-proof bar, 10 ... Heat transfer tube unit, 20 ... Communication gap, 21 ... Communication gap, 22 ... Communication gap, 30 ... Deflection Prevention jig 31... Rod portion 31 a .. Tip portion 31 b .. Through hole 31 c .. Rear end portion 31 d .. Mounting hole 32 .. Ring member 40. Tube support plate, 51 ... Heat transfer tube assembly, 52 ... Heat transfer tube assembly, S ... Gap, Sa ... Gap

Claims (7)

A heat exchanger is formed by arranging a plurality of heat transfer tube units arranged in a horizontal direction at equal intervals in a horizontal direction by displacing the horizontal position of the heat transfer tubes by equal distances and at intervals in the vertical direction. A heat exchanger assembly method for assembling,
With respect to the communication gap formed by a plurality of laminated bodies composed of the heat transfer tube units previously laminated and formed by connecting the gaps between the heat transfer tubes in each heat transfer tube unit in an oblique direction inclined with respect to the vertical direction. An assembly method for a heat exchanger, wherein a deflection preventing jig having a straight bar portion is inserted from the outside of the heat transfer tube unit, and the heat transfer tube units are further stacked.   2. The heat exchanger assembling method according to claim 1, wherein at least a part of the heat transfer tube is curved, and the bending prevention jig is inserted in a region where the heat transfer tube is curved.   The heat transfer tube units are stacked and disposed while installing the vibration isolation bars between the heat transfer tube units, and the vibration isolation bars are bonded together after the stacked arrangement of the heat transfer tube units is completed. 3. The method of assembling a heat exchanger according to claim 1 or 2, wherein the deflection preventing jig is extracted after completion of the step. A heat transfer tube unit composed of a plurality of heat transfer tubes arranged at equal intervals in the horizontal direction displaces the position of the heat transfer tube in the horizontal direction by equal distances, and is laminated in a vertical direction via a spacer. A gap between the heat transfer tubes in the heat transfer tube unit is provided with a communication gap formed by connecting in an oblique direction inclined with respect to the vertical direction,
A deflection preventing jig having a linear bar portion inserted into the communication gap.   The bending prevention jig according to claim 4, wherein a mark is provided on a distal end portion of the rod portion in the insertion direction.   The deflection preventing jig according to claim 4 or 5, wherein a stopper larger than a gap dimension between the heat transfer tubes is provided at a rear end portion in the insertion direction of the rod portion.   The deflection preventing jig according to claim 6, wherein the stopper is a ring member.

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