AU2018201183B2

AU2018201183B2 - Tank and manufacturing method therefor

Info

Publication number: AU2018201183B2
Application number: AU2018201183A
Authority: AU
Inventors: Hideyuki Fujisawa; Shoji Okuda; Gaku Sato; Yuta Tsuji
Original assignee: Noritz Corp
Current assignee: Noritz Corp
Priority date: 2017-02-23
Filing date: 2018-02-19
Publication date: 2023-08-24
Anticipated expiration: 2038-02-19
Also published as: JP6858344B2; AU2018201183A1; JP2018136104A

Abstract

OF THE DISCLOSURE A tank includes a cylindrical shell plate having a peripheral wall portion on which a shell plate welded portion that extends in an axial direction is provided, and a bowl-shaped end plate having an opening peripheral edge portion that is brought into contact with an end portion of the shell plate in a fitted or abutted state, and being joined to the shell plate via an annular welded portion provided on a resulting contact part, wherein a start point/end point region of the annular welded portion is positioned within a half region on an opposite side to the shell plate welded portion in a circumferential direction of a tank main body. As a result, problems such as an increase in the likelihood of cracks forming in the annular welded portion due to variation in the internal pressure of the tank main body can be prevented. FIG. lB FIG. 1A TT'4 1 12 Ta AR2 30a3 Ta 2 (2a) 3 f(3 20 AR aWb / 1Sa 30a 12 Wa // 30 30 (20 --2 -: ------- I/L lb Wb Wa Sb 31'' 2 (2b) 3 33 3 31 AR 3(3B) 3 3 (3A) A I FIG. IC Enlarged View of Main Parts 1 12 30a AR1 Wa -SbM 30 31 3 (3A) AR1I 30a

Description

FIG. lB FIG. 1A TT'4 1 12 Ta AR2 30a3 Ta 2 (2a) 3 f(3

20 1SaaWb AR 30a

/ 12 Wa //

30 30

(20 -: - ------- I/L -2 lb Wb Wa Sb 31'' 2 (2b) 3 33 31 AR 3 3(3B) 3 3 (3A) A I

FIG. IC

Enlarged View of Main Parts 1 12 30a AR1 Wa -SbM 30 31

3 (3A) AR1I 30a

TITLE OF THE INVENTION TANK AND MANUFACTURING METHOD THEREFOR BACKGROUND OF THE INVENTION

Field of the Invention:

[0001] The present invention relates to a tank that is suitable for storing hot water for a hot water supply, which is generated by being heated using a heat source such as a heat pump, for example, or another fluid, and also to a tank manufacturing method.

[0002] A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that the document or matter was known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims.

[0003] A hot water storage tank used by a hot water supply device is known as an example as a tank. In this type of hot water storage tank, a tank main body is typically formed by joining a cylindrical shell plate to a bowl-shaped end plate (see Japanese Patent No. 5050744, for example). Here, the cylindrical shell plate is manufactured by rolling a metal plate and welding edge portions on respective sides of the metal plate to each other. As a result, the shell plate is provided with a welded portion (a shell plate welded portion) extending in an axial direction. The bowl-shaped end plate is manufactured by implementing deep drawing or the like on a metal plate. The end plate and the shell plate are joined by bringing an opening peripheral edge portion of the end plate into contact with an end portion of the shell plate in a fitted or abutted state, and then welding a resulting contact part in a circumferential direction. As a result, an annular welded portion is provided in the location of the joint between the shell plate and the end plate.

According to this configuration, hot water storage tanks of various capacities can be manufactured comparatively inexpensively using a thin plate-shaped metal plate as a raw material.

[0004] As described below, however, there is room for improvement in the prior art described above.

[0005] When hot water flows into and out of the tank main body, the internal pressure of the tank main body varies. Stress generated as a result acts on the shell plate, for example, of the tank main body so as to cause respective locations of the shell plate to deform by expanding and contracting in a radial direction. The shell plate welded portion is provided on the shell plate so as to extend in the axial direction, and therefore welding distortion often occurs along the shell plate welded portion in response to the deformation such that the circularity of the sectional shape of the shell plate is impaired in this part. This welding distortion is likely to be largest at the end portions of the shell plate. Therefore, when the internal pressure of the tank main body varies, the amount of deformation near the shell plate welded portion (including the shell plate welded portion; likewise hereafter) is larger than the amount of deformation in other regions of the shell plate. In this case, the largest amount of deformation is likely to occur specifically near the end portions of the shell plate.

[0006] Meanwhile, the annular welded portion joining the end plate to the shell plate has a start point/end point region in which a start point and an end point of the welding are disposed in substantially identical positions, and welding defects such as perforations (bum-through) are inherently more likely to occur in the start point/end point region than in other parts. The reasons for this are that the start point and the end point of the annular welded portion respectively serve as positions in which a welding torch is switched on and off, it is difficult to stabilize various conditions such as a voltage to be applied during welding and a shielding gas flow, and so on.

[0007] Conventionally, when an annular welded portion is provided to join an end plate to a shell plate, no attention whatsoever is paid to the position in which to provide the start point/end point region relative to the shell plate welded portion. Hence, the start point/end point region of the annular welded portion is provided in a position comparatively close to the shell plate welded portion.

[0008] According to this configuration, however, the start point/end point region of the annular welded portion is greatly affected by the large amount of deformation that occurs near the shell plate welded portion when the internal pressure of the tank main body varies, and as a result, the amount of deformation occurring therein increases. Accordingly, stress is concentrated in the start point/end point region of the annular welded portion, where welding defects are inherently more likely to occur, and therefore defects such as cracks are more likely to form in this part. This is undesirable in terms of improving the durability of the hot water storage tank.

[0009] Further, when the start point/end point region of the annular welded portion is disposed near the shell plate welded portion, where the welding distortion is large, it may be difficult to weld the shell plate to the end plate appropriately in a location corresponding to the start point/end point region of the annular welded portion. Accordingly, the welding quality in the start point/end point region of the annular welded portion decreases, and as a result, welding defects such as perforations become even more likely to occur in this part. These welding defects are also a major cause of a reduction in the durability of the hot water storage tank.

SUMMARY OF THE INVENTION

[0010] It is desirable to provide a tank and a manufacturing method therefor, with which the problems described above can be prevented or suppressed.

[0011] A tank for a hot water service/hot water device according to a first aspect of the present invention has a tank main body for accommodating a fluid in the interior thereof, the tank main body comprising a cylindrical shell plate having a peripheral wall portion on which a shell plate welded portion that extends in an axial direction is provided; and a bowl-shaped end plate having an opening peripheral edge portion that is brought into contact with an end portion of the shell plate in a fitted or abutted state, and being joined to the shell plate via an annular welded portion provided on a contact part between the opening peripheral edge portion and the end portion of the shell plate, wherein a start point/end point region of the annular welded portion is positioned within a half region on an opposite side to the shell plate welded portion in a circumferential direction of the tank main body, further comprising a reinforcement member joined to at least one of the shell plate and the end plate so as to straddle two regions on respective sides of the shell plate welded portion when seen from the axial direction of the tank main body, wherein the reinforcement member is a leg portion for supporting the tank main body.

[0012] Here, the "half region on an opposite side to the shell plate welded portion" corresponds to a region A shown in FIG. 4, for example. FIG. 4 is a sectional view (a planar sectional view) seen from the axial direction of a tank main body Ta. In the figure, the region A is a range extending from an angle 0 of 900to an angle 0 of 270° in a case

where the position of a shell plate welded portion Wa is set at an angle of 0° and the angle 0 is gradually increased in a fixed direction around a center 0 of the tank main body Ta.

[0013] Preferably, the start point/end point region of the annular welded portion is provided in a position that is substantially directly opposite to the shell plate welded portion across a center of the tank main body.

[0014] Preferably, the tank according to the present invention further includes a reinforcement member joined to at least one of the shell plate and the end plate so as to straddle two regions on respective sides of the shell plate welded portion when seen from the axial direction of the tank main body.

3a

[0015] Preferably, the reinforcement member is a leg portion for supporting the tank main body.

[0016] Preferably, the tank according to the present invention further includes an additional reinforcement member joined to at least one of the shell plate and the end plate so as to straddle two regions on respective sides of the start point/end point region when seen from the axial direction of the tank main body.

[0017] Preferably, the additional reinforcement member is a leg portion for supporting the tank main body.

[0018] A tank manufacturing method according to a second aspect of the present invention comprises a welding step of forming a tank main body by bringing an end portion of a cylindrical shell plate having a peripheral wall portion on which a shell plate welded portion that extends in an axial direction is provided, into contact with an opening peripheral edge portion of a bowl-shaped end plate in a fitted or abutted state, and joining the shell plate to the end plate by providing an annular welded portion in a resulting contact part, wherein a start point/end point region of the annular welded portion is positioned within a half region on an opposite side to the shell plate welded portion in a circumferential direction of the tank main body.

[0019] Other features and advantages of the present invention will become more apparent from the embodiments of the invention, which are described below with reference to the attached figures.

[0020] Where the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components, or group thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1A is a perspective view showing an example of a hot water storage tank to which the present invention is applied, FIG. 1B is an lb-lb sectional view of FIG. 1A, and FIG. IC is an enlarged view of the main parts of FIG. IB;

FIGS. 2A to 2D are schematic perspective views showing examples of processes for manufacturing the hot water storage tank shown in FIGS. 1A to IC;

FIG. 3 is a perspective view showing another example of the present invention; and

FIG. 4 is an illustrative view showing a positional relationship between a shell plate welded portion and a start point/end point region of an annular welded portion according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Preferred embodiments of the present invention will be described specifically below with reference to the figures.

[0023] FIGS. 1A to IC show a hot water storage tank T serving as an example of a tank to which the present invention is applied, while FIGS. 2A to 2D show a manufacturing method therefor. A configuration of the hot water storage tank T will be described below while referring to FIGS. 2A to 2D as appropriate.

[0024] The hot water storage tank T shown in FIGS. 1A to IC is used as a constituent element of a hot water storage type hot water supply device, for example, and is employed in an application for storing hot water heated using a heat pump or another predetermined heat source. As shown in FIG. 1A, the hot water storage tank T is configured to include a tank main body Ta formed from a metal such as stainless steel and formed by welding end plates 2 (2a, 2b) to the top and bottom of a shell plate 1, and a plurality of leg portions 3 for supporting the tank main body Ta in an upright attitude in a vertical height direction. Although not shown in the figures, pipes through which hot water for a hot water supply flows into and out of the tank main body Ta are connected respectively to an upper portion of the upper side end plate 2 (2a) and a lower portion of the lower side end plate 2 (2b).

[0025] As shown in FIG. 2A, the shell plate 1 is manufactured by rolling a flat plate-shaped metal plate la serving as a raw material into a cylindrical shape, and welding respective end edge portions 10 of the metal plate la to each other. The welding is performed by TIG welding, for example. Welding shown in FIG. 2C, to be described below, is also performed by TIG welding, and in these figures, a reference numeral 8 denotes a TIG welding torch. The shell plate 1 takes a cylindrical shape in which a shell plate welded portion Wa resulting from the aforesaid welding is provided on a peripheral wall portion 12 of the shell plate 1 so as to extend in an axial direction (the vertical height direction).

[0026] Each end plate 2 is formed by implementing deep drawing or the like on a metal late serving as a raw material such that substantially the entirety thereof takes the shape of a bowl that is open on one end side, and accordingly, each end plate 2 includes an opening peripheral edge portion 20 (also see FIG. 2B). As shown in FIG. 2C, the upper side and lower side end plates 2 are respectively joined to the shell plate 1 by bringing the opening peripheral edge portions 20 thereof into contact with an upper end portion and a lower end portion of the shell plate 1 in a fitted or abutted state, and then implementing welding around the entire circumference of the resulting contact parts. An annular welded portion Wb is formed in each of these welding positions, and therefore two annular welded portion Wb, i.e. upper side and lower side annular welded portions Wb, are provided. A start point/end point region P of each annular welded portion Wb is positioned substantially directly opposite to the shell plate welded portion Wa across a center 0 of the tank main body Ta, or in other words on or near a straight line L linking the shell plate welded portion Wa and the center 0 (also see FIG. IB). A start point (a welding start point) and an end point (a welding end point) of the annular welded portion Wb are disposed in substantially identical positions or very close to each other, and therefore, in the start point/end point region P, the start point and the end point are considered as a single region.

[0027] In FIG. 1A, each leg portion 3 is configured to include a bracket portion 30 joined to the tank main body Ta, and a leg main body portion 31 extending downward from the bracket portion 30. The bracket portion 30 is a metal plate having a substantially L-shaped or substantially V-shaped plane section, for example, and left and right side edge portions 30a of the bracket portion 30 are respectively welded to an outer surface of the tank main body Ta. An upper portion of the leg main body portion 31 is coupled to the bracket portion 30 using means such as bolts, and a lower end portion of the leg main body portion 31 can be fixed to a floor surface on which the hot water storage tank T is disposed using an anchor bolt or the like.

[0028] The plurality of leg portions 3 are attached to an outer peripheral surface of a region toward a lower portion of the shell plate 1 at substantially equal angular intervals. As shown more clearly in FIG. IC, however, a leg portion 3A is welded to both of two side regions ARI of the shell plate welded portion Wa so as to straddle the two side regions ARI (also see FIG. 2D). The leg portion 3A acts to reinforce a lower end vicinity Sb of the shell plate welded portion Wa, and corresponds to an example of a reinforcement member according to the present invention. In FIG. 1B, meanwhile, a leg portion 3B positioned on the opposite side across the center 0 of the tank main body Ta to the leg portion 3A is welded to both of two side regions AR2 of the start point/end point region P of the annular welded portion Wb so as to straddle the two side regions AR2. The leg portion 3B corresponds to an example of an additional reinforcement member according to the present invention.

[0029] Next, actions of the hot water storage tank T will be described.

[0030] First, a slight amount of welding distortion occurs in a region of the peripheral wall portion 12 of the shell plate 1 extending along the shell plate welded portion Wa. Upper and lower end vicinities Sa, Sb of the shell plate welded portion Wa are welded to the edge parts of the shell plate 1, and therefore a larger amount of welding distortion is likely to occur in the upper and lower end vicinities Sa, Sb. Hence, the upper and lower end vicinities Sa, Sb of the shell plate welded portion Wa constitute parts that are distorted so as to impair the circularity of the peripheral wall portion 12 of the shell plate 1. Therefore, when hot water flows into and out of the tank main body Ta such that the internal pressure of the tank main body Ta varies, the upper and lower end vicinities Sa, Sb of the shell plate welded portion Wa are more likely to deform by expanding and contracting greatly in a radial direction of the shell plate 1 than other parts of the shell plate 1.

[0031] Here, when the start point/end point region P of the annular welded portion Wb is positioned near the shell plate welded portion Wa, in contrast to this embodiment, the start point/end point region P is greatly affected by the large amount of deformation that occurs in the upper and lower end vicinities Sa, Sb of the shell plate welded portion Wa. As a result, the start point/end point region P may be distorted greatly when the internal pressure of the tank main body Ta varies.

[0032] In this embodiment, however, the start point/end point region P of the annular welded portion Wb is positioned substantially directly opposite to the shell plate welded portion Wa across the center 0 of the tank main body Ta, or in other words positioned as far away as possible from the shell plate welded portion Wa. Therefore, the action by which the shell plate welded portion Wa deforms greatly when the internal pressure of the tank main body Ta varies has almost no effect on the start point/end point region P of the annular welded portion Wb. Accordingly, the amount of distortion occurring in the start point/end point region P when the internal pressure of the tank main body Ta varies can be kept small. The start point/end point region P of the annular welded portion Wb is a part that is inherently likely to cause a reduction in welding quality, and it is therefore desirable to ensure that excessive stress does not concentrate in this part. According to this embodiment, this goal can be realized appropriately. Hence, cracks and so on are less likely to form in the start point/end point region P of the annular welded portion Wb, and as a result, the durability of the hot water storage tank T can be improved.

[0033] As described above, the bracket portion 30 of the leg portion 3 (3A) is joined to both of the side regions ARI of the shell plate welded portion Wa so as to straddle the two side regions ARI, and thereby reinforces the two side regions AR1. Therefore, when the internal pressure of the tank main body Ta varies, large deformation by the lower end vicinity Sb of the shell plate welded portion Wa in the radial direction of the shell plate 1 is suppressed. As a result, the danger of cracks and so on forming the lower end vicinity Sb of the shell plate welded portion Wa can be eliminated. In addition, distortion of the start point/end point region P of the annular welded portion Wb caused by deformation of the lower end vicinity Sb of the shell plate welded portion Wa can be further suppressed.

[0034] The bracket portion 30 of the leg portion 3 (3B) is joined to both of the side regions AR2 of the start point/end point region P of the annular welded portion Wb so as to straddle the two side regions AR2, and thereby reinforces the two side regions AR2. Hence, likewise with this configuration, an effect of preventing the start point/end point region P of the annular welded portion Wb from greatly deforming when the internal pressure of the tank main body Ta varies is obtained. As a result, the likelihood of cracks and so on forming in the start point/end point region P of the lower side annular welded portion Wb, among the two annular welded portions Wb on the upper side and the lower side, can be reduced even further. As for the start point/end point region P of the other annular welded portion Wb on the upper side, reinforcement is not implemented using the leg portions 3A, 3B, but as described above, the start point/end point region P of the upper side annular welded portion Wb is disposed far from the shell plate welded portion Wa, and on the basis of this configuration, an effect of reducing the likelihood of cracks and so on forming in the start point/end point region P is obtained. Hence, problems do not occur.

[0035] In this embodiment, as shown in FIG. 2C, when welding is implemented to provide the annular welded portion Wb, the start point/end point region P of the annular welded portion Wb forms a location where welding distortion caused by the shell plate welded portion Wa does not occur. In the start point/end point region P, therefore, the shell plate 1 and the end plate 2 can be brought into contact with each other appropriately. When, in contrast to this embodiment, the start point/end point region P of the annular welded portion Wb is positioned near the shell plate welded portion Wa, where a large amount of welding distortion occurs, the shell plate 1 and the end plate 2 cannot be brought into contact with each other appropriately in the location corresponding to the start point/end point region P, and as a result, a gap that causes a welding defect may be formed between the two plates, leading to a reduction in welding quality in the start point/end point region P. According to this embodiment, the danger of such a situation occurring can be eliminated appropriately.

[0036] FIG. 3 shows another embodiment of the present invention. In the figure, elements that are identical or similar to those of the above embodiment have been allocated identical reference symbols to the above embodiment, and duplicate description thereof has been omitted.

[0037] In the embodiment shown in FIG. 3, the bracket portion 30 of the leg portion 3A is joined to regions AR3 of the lower side end plate 2 (2b) instead of the shell plate 1. The regions AR3 are positioned on respective sides of the shell plate welded portion Wa when seen from above (an example of being seen from the axial direction according to the present invention).

[0038] According to this configuration, in contrast to the above embodiment, the bracket portion 30 is not joined to the two actual side regions ARI of the shell plate welded portion Wa, but since the end plate 2 and the shell plate 1 are joined integrally, the lower end vicinity Sb of the shell plate welded portion Wa can be reinforced so as not to deform easily likewise with the configuration shown in FIG. 3.

[0038] As is evident from this embodiment, according to the present invention, when the reinforcement member (the leg portion 3A) is used to implement reinforcement in order to suppress deformation in the vicinity of the shell plate welded portion caused by variation in the internal pressure of the tank main body, the reinforcement member does not necessarily have to be joined to the two actual side regions of the shell plate welded portion. In other words, it is sufficient to join the reinforcement member to parts that correspond to the two side regions of the shell plate welded portion when seen in the axial direction of the tank main body.

[0040] Although not shown in FIG. 3, a similar configuration to that described above can be applied likewise in a case where the leg portion 3B is used to reinforce the start point/end point region P of the lower side annular welded portion Wb. More specifically, a configuration in which the start point/end point region P of the lower side annular welded portion Wb is reinforced indirectly by joining the bracket portion 30 of the leg portion 3B to regions of the lower side end plate 2 (2b) that are on respective sides of the start point/end point region P of the lower side annular welded portion Wb when seen from above (i.e. regions below the two side regions AR2) may be employed.

[0041] FIG. 4 is the view that was referred to above in the section "SUMMARY OF THE INVENTION". In the present invention, the start point/end point region P of the annular welded portion Wb may be disposed in any position within a range A (a half region A on an opposite side to the shell plate welded portion Wa in a circumferential direction of the tank main body Ta) extending from an angle 0 of 90° to an angle 0 of 270°, as shown in the figure,

using the shell plate welded portion Wa as a reference (an angle of 0°). To dispose the start point/end point region P of the annular welded portion Wb far away from the shell plate welded portion Wa so that stress does not concentrate in the start point/end point region P, the start point/end point region P is preferably disposed at an angle 0 of substantially 180°, as in the above embodiments, but as long as the start point/end point region P is within the aforesaid range A, adverse effects on the start point/end point region P caused by welding distortion of the shell plate welded portion Wa can be effectively suppressed such that the intended effects of the present invention can be obtained.

[0042] The present inventors manufactured a tank main body having a similar configuration to the tank main body Ta of the hot water storage tank T shown in FIGS. 1A to 1C, and undertook an experiment to investigate the distribution of distortion (radial direction distortion) occurring in each part of the shell plate and the respective end plates both when pressure is applied to and when pressure is discharged from the interior of the tank main body. According to this experiment, it was found that the distortion occurring within the range A was smaller than the distortion occurring in other ranges. In the present invention, therefore, the fact that an effect of reducing the distortion occurring in the start point/end point region P of the annular welded portion is obtained by disposing the start point/end point region P within the range A is supported by the result of the aforesaid experiment.

[0043] The present invention is not limited to the content of the embodiments described above, and the specific configurations of the respective parts of the tank according to the present invention may be subjected to various design modifications freely within the intended scope of the present invention. The specific configurations of the respective processes of the tank manufacturing method according to the present invention may also be subjected to various modifications freely within the intended scope of the present invention.

[0044] In the above embodiments, the leg portion is used as the "reinforcement member" (including the additional reinforcement member) of the present invention, but the present invention is not limited thereto. For example, a pipe member such as a pipe joint or a pipe material or types of brackets for supporting various devices may also be used as the reinforcement member. Moreover, a metal plate having an appropriate shape such as a flat plate shape may be used as the reinforcement member, and this reinforcement member may be a specialized reinforcement member. In the above embodiments, the reinforcement members (the leg portions 3A, 3B) are provided only on the lower portion side of the tank main body so as to correspond to the lower side annular welded portion, but instead, or in addition, a reinforcement member may be provided on the upper portion side of the tank main body so as to correspond to the upper side annular welded portion.

[0045] The shell plate welded portion and the annular welded portion are not limited to TIG welding, and there are no limitations on the type of welding.

[0046] The tank according to the present invention is not limited to a hot water storage tank for a hot water supply device, and may be formed as a tank used in a different application. The fluid introduced into the tank main body is not limited to hot water, and another liquid or a fluid such as a gas may be used instead. Accordingly, the material of the tank is not limited to stainless steel.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A tank for a hot water service/hot water device having a tank main body for accommodating a fluid in the interior thereof, the tank main body comprising: a cylindrical shell plate having a peripheral wall portion on which a shell plate welded portion that extends in an axial direction is provided; and a bowl-shaped end plate having an opening peripheral edge portion that is brought into contact with an end portion of the shell plate in a fitted or abutted state, and being joined to the shell plate via an annular welded portion provided on a contact part between the opening peripheral edge portion and the end portion of the shell plate, wherein a start point/end point region of the annular welded portion is positioned within a half region on an opposite side to the shell plate welded portion in a circumferential direction of the tank main body, further comprising a reinforcement member joined to at least one of the shell plate and the end plate so as to straddle two regions on respective sides of the shell plate welded portion when seen from the axial direction of the tank main body, wherein the reinforcement member is a leg portion for supporting the tank main body.

2. A tank for a hot water service/hot water device having a tank main body for accommodating a fluid in the interior thereof, the tank main body comprising: a cylindrical shell plate having a peripheral wall portion on which a shell plate welded portion that extends in an axial direction is provided; and a bowl-shaped end plate having an opening peripheral edge portion that is brought into contact with an end portion of the shell plate in a fitted or abutted state, and being joined to the shell plate via an annular welded portion provided on a contact part between the opening peripheral edge portion and the end portion of the shell plate, wherein a start point/end point region of the annular welded portion is positioned within a half region on an opposite side to the shell plate welded portion in a circumferential direction of the tank main body, further comprising a reinforcement member joined to at least one of the shell plate and the end plate so as to straddle two regions on respective sides of the shell plate welded portion when seen from the axial direction of the tank main body, wherein the reinforcement member is a leg portion for supporting the tank main body, further comprising an additional reinforcement member joined to at least one of the shell plate and the end plate so as to straddle two regions on respective sides of the start point/end point region when seen from the axial direction of the tank main body, wherein the additional reinforcement member is a leg portion for supporting the tank main body.

3. The tank according to claim 1, wherein the start point/end point region of the annular welded portion is provided in a position that is substantially directly opposite to the shell plate welded portion across a center of the tank main body.