U.S. patent application number 14/238004 was filed with the patent office on 2014-06-19 for sidewall unit, fabricating method thereof, and fluid storage tank comprising the sidewall unit.
This patent application is currently assigned to TOKYO KIZAI KOGYOU CO., LTD.. The applicant listed for this patent is Tsuyoshi Iwashita. Invention is credited to Tsuyoshi Iwashita.
Application Number | 20140166648 14/238004 |
Document ID | / |
Family ID | 47668336 |
Filed Date | 2014-06-19 |
United States Patent
Application |
20140166648 |
Kind Code |
A1 |
Iwashita; Tsuyoshi |
June 19, 2014 |
SIDEWALL UNIT, FABRICATING METHOD THEREOF, AND FLUID STORAGE TANK
COMPRISING THE SIDEWALL UNIT
Abstract
A method of fabricating a sidewall unit includes a step of
providing members configuring the sidewall units, a step of forming
a first joint structure, a first step of eliminating distortion, a
step of forming a second joint structure, and a step of assembling
a sidewall unit. The step of eliminating distortion is a step to
eliminate distortion due to heat generated when welding members. In
the step, a force substantially vertical to a flange surface and a
force substantially horizontal to the flange surface are applied to
a joint structure before joining the joint structure and a sidewall
panel. A fluid storage tank using the sidewall units according to
the present invention can securely prevent leakage of fluid even
when a large quantity of fluid is stored therein.
Inventors: |
Iwashita; Tsuyoshi; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Iwashita; Tsuyoshi |
Tokyo |
|
JP |
|
|
Assignee: |
TOKYO KIZAI KOGYOU CO.,
LTD.
Tokyo
JP
|
Family ID: |
47668336 |
Appl. No.: |
14/238004 |
Filed: |
July 25, 2012 |
PCT Filed: |
July 25, 2012 |
PCT NO: |
PCT/JP2012/068819 |
371 Date: |
February 10, 2014 |
Current U.S.
Class: |
220/4.01 ;
29/428 |
Current CPC
Class: |
Y10T 29/49826 20150115;
B65D 90/024 20130101; E04H 7/06 20130101; B65D 7/04 20130101 |
Class at
Publication: |
220/4.01 ;
29/428 |
International
Class: |
B65D 8/00 20060101
B65D008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2011 |
JP |
2011-174750 |
Aug 23, 2011 |
JP |
2011-181379 |
Mar 29, 2012 |
JP |
2012-077874 |
Claims
1. A method for fabricating a sidewall unit for use in fabricating
a fluid storage tank having at least a bottom wall and a sidewall
configured with one cylindrical member or by stacking a plurality
of cylindrical members in height direction, at least one of the
cylindrical members being configured by joining a plurality of
sidewall units in circumferential direction, the method comprising:
(A) a step of providing members configuring the sidewall unit, the
members including: a rectangular sidewall plate; and a base member
having long sides and short sides, a circumferential joint flange
having long sides and short sides, and a plurality of reinforcing
members having two adjacent edges which intersect at a
predetermined angle included in a joint structure to be mounted to
each of two opposing circumferential edges of the sidewall plate;
(B) a step of forming a first joint structure by coupling the
circumferential joint flange with the base member in a positional
relationship where a long side of the circumferential joint flange
and a long side of the base member are parallel such that a
non-flange surface on the other side of a flange surface of the
circumferential joint flange intersects with one of surfaces of the
base member at a predetermined angle, and by coupling at least a
part of each of the two adjacent edges respectively with the
non-flange surface of the circumferential joint flange and the one
of surfaces of the base member such that the plurality of
reinforcing members stand with an interval with each other on a
side of an inner angle formed by the non-flange surface of the
circumferential joint flange and the one of surfaces of the base
member; (C) a first step of eliminating distortion for eliminating
distortion from the first joint structure by simultaneously
applying a force from the non-flange surface to the flange surface
and a force from the flange surface to the non-flange surface
respectively to a center part and to both ends in the longitudinal
direction of the first joint structure; (D) a step of forming a
second joint structure by the same steps as the steps (A) to (C);
and (E) a step of assembling the sidewall unit for coupling one of
the opposing circumferential edges of the curved sidewall plate
with the long side of the base member of the first joint structure
and coupling the other of the opposing circumferential edges of the
curved sidewall plate with the long side of the base member of the
second joint structure.
2. A method for fabricating a sidewall unit for use in fabricating
a fluid storage tank having at least a bottom wall and a sidewall
configured with one cylindrical member or by stacking a plurality
of cylindrical members in height direction, at least one of the
cylindrical members being configured by joining a plurality of
sidewall units in circumferential direction, the method comprising:
(A) a step of providing members configuring the sidewall units, the
members including: a rectangular sidewall plate; and a base member
having long sides and short sides, a circumferential joint flange
having long sides and short sides, and a plurality of reinforcing
members having two adjacent edges which intersect at a
predetermined angle included in a joint structure to be mounted to
each of two opposing circumferential edges of the sidewall plate;
(B) a first step of eliminating distortion and forming a first
joint structure to form the first joint structure while eliminating
distortion, the step including; forming a first intermediate
structure by temporarily coupling the circumferential joint flange
with the base member in a positional relationship where a long side
of the circumferential joint flange and a long side of the base
member are parallel such that a non-flange surface on the other
side of a flange surface of the circumferential joint flange
intersects with one of surfaces of the base member at a
predetermined angle, and by temporarily coupling at least a part of
each of the two adjacent edges respectively with the non-flange
surface of the circumferential joint flange and the one of surfaces
of the base member such that the plurality of reinforcing members
stand with an interval with each other on a side of an inner angle
formed by the non-flange surface of the circumferential joint
flange and the one of surfaces of the base member, forming a second
intermediate structure by the same step as the step of forming the
first intermediate structure, coupling of a circumferential joint
flange, each of the plurality of reinforcing members and the base
member of at least the first intermediate structure while temporary
binding the first intermediate structure and the second
intermediate structure, and releasing the temporary biding of the
first intermediate structure and the second intermediate structure
to obtain the first joint structure; (C) a step of forming a second
joint structure by the same steps as the steps (A) and (B); (D) a
step of assembling a sidewall unit for coupling one of the opposing
circumferential edges of the curved sidewall plate with the long
side of the base member of the first joint structure and coupling
the other of the opposing circumferential edges of the curved
sidewall plate with the long side of the base member of the second
joint structure.
3. A method according to claim 2, wherein the second joint
structure is formed from the second intermediate structure.
4. A method according to claim 2, further comprising a second step
of eliminating distortion to eliminate distortion from the first
joint structure, after the first step of eliminating distortion and
forming a first joint structure, by simultaneously applying a force
from the non-flange surface to the flange surface and a force from
the flange surface to the non-flange surface respectively to a
center part and to both ends in the longitudinal direction of the
first joint structure.
5. A method according to claim 1, further comprising a third step
of eliminating distortion to eliminate distortion from the first
joint structure by simultaneously applying a force from one of
surfaces of the base member to a surface opposite to the one of the
surfaces of the base member and a force from the surface opposite
to the one of the surfaces of the base member to the one of the
surfaces of the base member respectively to a center part and to
both ends in the longitudinal direction of the first joint
structure.
6. A method according to claim 1, wherein the coupling and/or the
temporary coupling of the circumferential joint flange, the base
member and the plurality of reinforcing members may be performed by
following a sequence of a step of coupling the circumferential
joint flange with each of the plurality of reinforcing members, a
step of coupling the circumferential joint flange with the base
member, and a step of coupling the plurality of reinforcing members
with the base member.
7. A method according to claim 1, wherein the coupling and/or the
temporary coupling of the circumferential joint flange, the base
member and the plurality of reinforcing members may be performed by
following a sequence of a step of coupling the circumferential
joint flange with the base member, and a step of coupling each of
the plurality of reinforcing members respectively with the
circumferential joint flange and the base member.
8. A method according to claim 1, wherein the coupling and/or the
temporary coupling of the circumferential joint flange, the base
member and the plurality of reinforcing members is sequentially
performed from coupling positions in vicinity of the center part to
coupling positions toward short side with respect to a long side of
the circumferential joint flange.
9. A method according to claim 1, wherein the plurality of
reinforcing members are coupled such that a space between the
plurality of reinforcing members is smaller in a center part than
that in end parts in the long side of the circumferential joint
flange.
10. A method according to claim 1, wherein each of the plurality of
reinforcing members is a panel and comprises: a first edge which is
longer than a short side of a base member and is coupled with the
base member and a sidewall plate; a second edge which intersects
with the first edge at a predetermined angle and is coupled to the
non-flange surface; a third edge which opposes to the first edge
and has a length corresponding to a short side of the base member;
and a fourth edge which opposes to the second edge and connects one
end of the first edge with one end of the third edge.
11. A method according to claim 10, further comprising one or both
of: a step of forming a notch part in a portion corresponding to a
crossing point of the first edge and the second edge; and a step of
forming a notch part in a portion corresponding to a coupling point
of the base member and the sidewall plate at the first edge.
12. A method according to claim 1, wherein the base member is
coupled with the circumferential joint flange so that it stands
from a portion other than end parts in short side of a non-flange
surface of the circumferential joint flange.
13. A method according to claim 1, further comprising a step of
forming a plurality of holes for passing mechanical fasteners over
a long side of the circumferential joint flange.
14. A method according to claim 13, wherein the plurality of holes
are formed such that a diameter thereof is larger in a center part
than that at an end of the long side of the circumferential joint
flange.
15. A method according to claim 1, further comprising a step of
forming a groove in the flange surface of the circumferential joint
flange for inserting a sealing layer.
16. A method according to claim 1, further comprising a step of
coupling a height-direction joint flange with a L-shaped cross
section at opposing two ends in height direction of the sidewall
unit.
17. A sidewall unit configuring a cylindrical member, the sidewall
unit used in a fluid storage tank having at least a bottom wall and
a sidewall configured with one cylindrical member or by stacking a
plurality of cylindrical members in height direction, the fluid
storage tank being configured by joining a plurality of sidewall
units in circumferential direction, the sidewall unit comprising: a
curved rectangular sidewall plate; and a pair of joint structures
mounted to each of two opposing circumferential edges of the
sidewall plate, each of the pair of joint structures including: a
base member having long sides and short sides; a circumferential
joint flange having long sides and short sides; and a plurality of
reinforcing members having two adjacent edges which intersect at a
predetermined angle, wherein: the circumferential joint flange and
the base member are coupled in a positional relationship where a
long side of the circumferential joint flange and a long side of
the base member are parallel such that a non-flange surface on the
other side of a flange surface of the circumferential joint flange
intersects with one of surfaces of the base member at a
predetermined angle, each of two adjacent edges of each of a
plurality of reinforcing members is coupled respectively with the
non-flange surface of the circumferential joint flange and the one
of surfaces of the base member such that the plurality of
reinforcing members stand with an interval with each other on a
side of an inner angle formed by the non-flange surface of the
circumferential joint flange and the one of surfaces of the base
member, and a long side of the base member in each of the pair of
joint structures is coupled to each of the opposing circumferential
edges of the sidewall plate.
18. A sidewall unit according to claim 17, wherein a space between
the plurality of reinforcing members is smaller in the center part
than that in end parts in the long side of the circumferential
joint flange.
19. A sidewall unit according to claim 17, wherein each of the
plurality of reinforcing members is a panel and comprises: a first
edge which is longer than a short side of a base member and is
coupled with the base member and a sidewall plate; a second edge
which intersects with the first edge at a predetermined angle and
is coupled to the non-flange surface; a third edge which opposes to
the first edge and has a length corresponding to a short side of
the base member; and a fourth edge which opposes to the second edge
and connects one end of the first edge with one end of the third
edge.
20. A sidewall unit according to claim 19, wherein a notch part is
formed in one or both of a portion corresponding to a crossing
point of the first edge and the second edge and a portion
corresponding to a coupling point of the base member and the
sidewall plate at the first edge.
21. A sidewall unit according to claim 17, wherein the base member
is coupled with the circumferential joint flange so that it stands
from a portion other than end parts in short side of a non-flange
surface of the circumferential joint flange.
22. A sidewall unit according to claim 17, wherein a plurality of
holes for passing mechanical fasteners are formed over a long side
of the circumferential joint flange.
23. A sidewall unit according to claim 22, wherein the plurality of
holes are formed such that a diameter thereof is larger in a center
part than that at an end of the long side of the circumferential
joint flange.
24. A sidewall unit according to claim 17, wherein a groove is
formed in the flange surface of the circumferential joint flange
for inserting a sealing layer.
25. A sidewall unit according to claim 17, wherein a
height-direction joint flange with a L-shaped cross section is
coupled at opposing two ends in height direction of the sidewall
unit.
26. A fluid storage tank comprising sidewall units fabricated with
a method according to claim 1.
27. A fluid storage tank comprising sidewall units according to
claim 17.
Description
TECHNICAL FIELD
[0001] The present invention relates to a knockdown-type fluid
storage tank, and in particular, the present invention relates to a
sidewall unit and a manufacturing method thereof for a
knockdown-type fluid storage tank configured with a plurality of
sidewall units, the sidewall unit being fabricated so as to prevent
leakage of the fluid from joints between the sidewall units even
when a large quantity of fluid is stored inside.
BACKGROUND ART
[0002] In general, a fluid storage tank having space inside for
storing fluid employs knockdown structure, except when seamless
structure may be employed. A knockdown-type fluid storage tank is
pre-fabricated in a factory as a plurality of units with predefined
size suitable for transportation. The plurality of fabricated units
is transported on vehicles to an installation site and is
assembled. At the installation site, the plurality of units is
joined in circumferential direction to make a cylindrical member,
and a plurality of cylindrical member is stacked in height
direction to assemble a fluid storage tank. Herein,
"circumferential direction" and/or "circumferential" refer to a
direction parallel to ground and "height direction" refers to a
direction perpendicular to the circumferential direction. Various
tanks, such as a cylindrical storage tank disclosed in Patent
Document 1, are proposed as a knockdown-type fluid storage
tank.
[0003] For a knockdown-type fluid storage tank, it is important how
to prevent leakage of fluid from joints between the units. The
following techniques are, for example, proposed to prevent leakage
of fluid in existing knockdown-type fluid storage tanks.
[0004] The technique disclosed in Patent Document 2 is to prevent
leakage with an improved joint structure between units. The
technique disclosed in claims, FIG. 5 and FIG. 6 of Patent Document
2 proposes an edge structure of each of the units such that a
trough is formed at a joint between two units and a paste sealant
is filled into the trough. As the technique of Patent Document 2,
various other techniques for preventing leakage of fluid with a
joint structure are proposed.
[0005] The technique disclosed in Patent Document 3 is to prevent
leakage with an improved application method of a sealant at a
joint. In the technique disclosed in Patent Document 3, a
moisture-curing sealant is applied from a side corresponding to an
internal side of a tank. When a surface of the sealant is
subsequently cured, water is filled in the tank. By filling water
in the tank, a pressure of water forces joints to open a little to
allow for uncured sealant entering inside the joints to improve
water sealing at the joints.
[0006] The technique disclosed in Patent Document 4 is to prevent
leakage with combining an improved joint-filling adhesive agent and
an improved joint structure. In the technique disclosed in Patent
Document 4, an adhesive agent for joint-filling in a tank having
one-component moisture-curing resin as a main component and
containing a silane coupling agent as an adhesion provider and
fiber filler is used to prevent leakage from joints between units.
Flanges filled with the joint-filling adhesive agent are covered
with metallic pressing members so that entire flange is
covered.
[0007] Patent Document 5 proposes a fluid storage tank configured
by mutually joining end edges of a plurality of plate body which
allows for improving workability during assembly and for reducing
related costs without deteriorating storage performance. For a
knockdown-type fluid storage tank, it is necessary to consider
workability during assembly of the fluid storage tank.
[0008] The prior art documents referred to in the above
descriptions are listed below. [0009] Patent Document 1: Japanese
Laid-Open Patent Publication 2009-012849A [0010] Patent Document 2:
Japanese Patent No. 63-006432B [0011] Patent Document 3: Japanese
Laid-Open Patent Publication 2010-013155A [0012] Patent Document 4:
Japanese Laid-Open Patent Publication 2005-105083A [0013] Patent
Document 5: Japanese Laid-Open Patent Publication 08-026381A
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0014] It is naturally a major premise that leakage of fluid from
joints is securely prevented in a knockdown-type fluid storage
tank, but at the same time, a structure of joints between units
configuring the fluid storage tank and a method for joining the
units on site are required to be simple as much as possible from a
viewpoint of ease of on-site assembly and de-assembly and of
fabricating cost. Thus, it is preferable that a bulk fluid storage
tank is configured to simplify an assembly process thereof at an
installation site such that the tank may be assembled by simply
opposing joint flanges of units and joining the joint flanges with
mechanical fasteners such as bolts and nuts for mutually joining
the units. Such simple-structured unit is also advantageous from a
viewpoint of fabricating cost.
[0015] Such joint structure and method for joining are also
advantageous to be employed for facilitating de-assembly of a fluid
storage tank. A bulk fluid storage tank is often not owned by a
company which needs the tank, but is leased from a leasing company
owning the tank. Then, it is advantageous from a viewpoint of
construction schedule and of cost if it is easy to de-assemble the
bulk fluid storage tank when returning to the leasing company after
use.
[0016] However, for example in a bulk fluid storage tank with a
capacity of 1,000 m.sup.3 or more, there has been a problem as
that, since internal pressure acting on units located in lower part
of the tank was extremely large, a slight distortion on a joint
flange surface of the units could have caused leakage of the fluid
from the joints between the units.
[0017] Even though various conventional techniques such as those
described in the above have been proposed to prevent leakage of
fluid, since the conventional techniques did not consider removal
of distortion due to welding heat at the joints when assembling a
tank, it was extremely difficult to solve the problem of leakage
especially in a bulk fluid storage tank storing fluid of a certain
level or more and the problem of ease of assembly and de-assembly
of the tank at the installation site and of fabricating cost, and
thus, it has been difficult to employ the conventional techniques
in the bulk fluid storage tank.
[0018] The present invention aims at providing a sidewall unit
configuring at least a part of a fluid storage tank which does not
cause leakage of fluid from joints between the units even when a
large quantity of fluid above a certain level is stored, and a
fluid storage tank using such sidewall units.
Means for Solving the Problem
[0019] The above problem may be solved by providing a step of
accurately eliminating distortion due to welding heat at joints for
joining with other sidewall units during a step of fabricating each
of sidewall units configuring at least a part of a fluid storage
tank, and by making a structure of the joints including joint
flanges as one which does not cause distortion at the joints under
a long term use while ensuring workability during joining.
[0020] According to a first aspect, the present invention provides
a method for fabricating a sidewall unit for use in fabricating a
fluid storage tank having at least a bottom wall and a sidewall.
The sidewall is configured with one cylindrical member or by
stacking a plurality of cylindrical members in height direction,
and at least one of the cylindrical members is configured by
joining a plurality of sidewall units in circumferential direction.
The method comprises a step of providing members configuring the
sidewall unit, a step of forming a first joint structure, a first
step of eliminating distortion, a step of forming a second joint
structure, and a step of assembling a sidewall unit. In the step of
providing members configuring the sidewall unit, a rectangular
sidewall plate and members included in a joint structure to be
mounted to each of two opposing circumferential edges of the
sidewall plate are prepared, wherein the members include a base
member having long sides and short sides, a circumferential joint
flange having long sides and short sides, and a plurality of
reinforcing members having two adjacent edges which intersect at a
predetermined angle.
[0021] In the step of forming a first joint structure, the first
joint structure is formed by coupling the circumferential joint
flange with the base member in a positional relationship where a
long side of the circumferential joint flange and a long side of
the base member are parallel such that a non-flange surface on the
other side of a flange surface of the circumferential joint flange
intersects with one of surfaces of the base member at a
predetermined angle, and by coupling at least a part of each of the
two adjacent edges respectively with the non-flange surface of the
circumferential joint flange and the one of surfaces of the base
member such that the plurality of reinforcing members stand with an
interval with each other on a side of an inner angle formed by the
non-flange surface of the circumferential joint flange and the one
of surfaces of the base member. Distortion in the first joint
structure is eliminated in a first step of eliminating distortion
by simultaneously applying a force from the non-flange surface to
the flange surface and a force from the flange surface to the
non-flange surface respectively to a center part and to both ends
in the longitudinal direction of the first joint structure.
[0022] The present method further comprises a step of forming a
second joint structure where the second joint structure is formed
in similar steps as providing members, forming the first joint
structure and eliminating distortion, and a step of assembling the
sidewall unit where one of the opposing circumferential edges of
the curved sidewall plate is coupled with the long side of the base
member of the first joint structure and the other of the opposing
circumferential edges of the curved sidewall plates is coupled with
the long side of the base member of the second joint structure.
[0023] According to a second aspect, the present invention also
provides a method for fabricating a sidewall unit used in
fabricating a fluid storage tank having at least a bottom wall and
a sidewall as in the first aspect. The sidewall is configured with
one cylindrical member or by stacking a plurality of cylindrical
members in height direction, and at least one of the cylindrical
members is configured by joining a plurality of sidewall units in
circumferential direction. The present method comprises a first
step of eliminating distortion and forming a first joint structure
to form the first joint structure while eliminating distortion, in
place of the step of forming the first joint structure and the
first step of eliminating distortion which are performed as
separate steps in the first aspect.
[0024] In the first step of eliminating distortion and forming a
first joint structure, a first intermediate structure is formed by
temporarily coupling the circumferential joint flange with the base
member in a positional relationship where a long side of the
circumferential joint flange and a long side of the base member are
parallel such that a non-flange surface on the other side of a
flange surface of the circumferential joint flange intersects with
one of surfaces of the base member at a predetermined angle, and by
temporarily coupling at least a part of each of the two adjacent
edges respectively with the non-flange surface of the
circumferential joint flange and the one of surfaces of the base
member such that the plurality of reinforcing members stand with an
interval with each other on a side of an inner angle formed by the
non-flange surface of the circumferential joint flange and the one
of surfaces of the base member. Then, a second intermediate
structure is formed by the same step as the step of forming the
first intermediate structure. Then, while temporary binding the
first intermediate structure and the second intermediate structure,
a circumferential joint flange, each of the plurality of
reinforcing members and the base member of at least the first
intermediate structure are coupled with each other and the
temporary biding of the first intermediate structure and the second
intermediate structure is released to obtain the first joint
structure. The second joint structure may be formed from the second
intermediate structure.
[0025] In one embodiment of the second aspect, the method may
further comprise a second step of eliminating distortion to
eliminate distortion from the first joint structure, after the
first step of eliminating distortion and forming a first joint
structure, by simultaneously applying a force from the non-flange
surface to the flange surface and a force from the flange surface
to the non-flange surface respectively to a center part and to both
ends in the longitudinal direction of the first joint
structure.
[0026] In one embodiment of the first and the second aspect, the
method may further comprise a third step of eliminating distortion
to eliminate distortion from the first joint structure by
simultaneously applying a force from one of surfaces of the base
member to a surface opposite to the one of the surfaces of the base
member and a force from the surface opposite to the one of the
surfaces of the base member to the one of the surfaces of the base
member respectively to a center part and to both ends in the
longitudinal direction of the first joint structure.
[0027] In one embodiment, coupling and/or temporary coupling of
members may be performed by following a sequence of a step of
coupling a circumferential joint flange with each of a plurality of
reinforcing members, a step of coupling the circumferential joint
flange with a base member, and a step of coupling the plurality of
reinforcing members with the base member. In another embodiment,
coupling and/or temporary coupling of members may also be performed
by following a sequence of a step of coupling a circumferential
joint flange with a base member, and a step of coupling each of a
plurality of reinforcing members respectively with the
circumferential joint flange and the base member. In addition, it
is preferable that coupling and/or temporary coupling of the
circumferential joint flange, the base member and the plurality of
reinforcing members is sequentially performed from coupling
positions in vicinity of the center part to coupling positions
toward short side with respect to a long side of the
circumferential joint flange.
[0028] Since the present invention allows for effective elimination
of distortion in the circumferential joint flange due to welding
heat when mutually coupling members configuring the sidewall unit
in fabricating the sidewall unit configuring at least a part of a
fluid storage tank, the sidewall units may be accurately mutually
joined. Generation of distortion in the circumferential joint
flange due to welding heat to weld the base member and the sidewall
plate may be reduced by having a base member, a rigid body with a
short side of predetermined length, intervene between the
circumferential joint flange and the sidewall plate, instead of
directly coupling the circumferential joint flange and the sidewall
plate. Further, when a high pressure is generated by fluid in a
tank, there may be a case where a conventional technique of
directly coupling the circumferential joint flange and the sidewall
plate is not enough to maintain an angle formed by the
circumferential joint flange and the sidewall plate, and a flange
surface of an adjacent circumferential joint flange may be pressed
to open from inside. The present invention, on the other hand, can
maintain an angle formed by a base member and the circumferential
joint flange by having the base member, a rigid body with a greater
thickness than that of the sidewall plate, intervene therebetween,
and thus, a flange surface of an adjacent circumferential joint
flange may not be pressed to open from inside, thereby a joint
between the circumferential joint flanges may be improved.
[0029] In another embodiment of the present invention, it is
preferable that a plurality of reinforcing members are coupled such
that a space between the plurality of reinforcing members is
smaller in a center part than that in end parts in the long side of
the circumferential joint flange. A reinforcing member may be a
panel and may comprise: a first edge which is longer than a short
side of a base member and is coupled with the base member and a
sidewall plate; a second edge which intersects with the first edge
at a predetermined angle and is coupled to a non-flange surface; a
third edge which opposes to the first edge and has a length
corresponding to a short side of the base member; and a fourth edge
which opposes to the second edge and connects one end of the first
edge with one end of the third edge. In a plurality of reinforcing
member, it is preferable that a notch part is formed in one or both
of a portion corresponding to a crossing point of the first edge
and the second edge and a portion corresponding to a coupling point
of the base member and the sidewall plate at the first edge.
[0030] Adopting such mounting position and shape of reinforcing
member allows for welding a circumferential joint flange and a base
member while maintaining an angle formed therebetween. Since a
plurality of reinforcing member allows for maintaining the angle
formed between the circumferential joint flange and the base member
even when a high pressure is generated by fluid in a tank, a flange
surface of adjacent circumferential joint flanges is not pressed to
open from inside and leakage of the fluid may be prevented.
[0031] In another embodiment of the present invention, it is
preferable that the method further comprises a step of forming a
plurality of holes for passing mechanical fasteners over a long
side of the circumferential joint flange, and that the plurality of
holes are formed such that a diameter thereof is larger in a center
part than that at an end of the long side of the circumferential
joint flange. It is also preferable that the method further
comprises a step of forming a groove in a flange surface of the
circumferential joint flange for inserting a sealing layer.
[0032] Joint strength between the circumferential joint flanges may
be further increased by varying strength of the mechanical
fasteners used for joining the circumferential joint flanges. In
addition, leakage of fluid in a tank may be securely prevented and
displacement of the sealing layer during assembling the fluid
storage tank may be avoided by providing a groove in a flange
surface of the circumferential joint flange for forming a sealing
layer.
[0033] According to a third embodiment, the present invention
provides a sidewall unit configuring a cylindrical member, the
sidewall unit used in a fluid storage tank having at least a bottom
wall and a sidewall configured with one cylindrical member or by
stacking a plurality of cylindrical members in height direction,
the fluid storage tank being configured by joining a plurality of
sidewall units in circumferential direction. The sidewall unit
comprises a curved rectangular sidewall plate and a pair of joint
structures mounted to each of two opposing circumferential edges of
the sidewall plate, and each of the pair of joint structures
includes a base member having long sides and short sides, a
circumferential joint flange having long sides and short sides, and
a plurality of reinforcing members having two adjacent edges which
intersect at a predetermined angle.
[0034] The circumferential joint flange and the base member are
coupled in a positional relationship where a long side of the
circumferential joint flange and a long side of the base member are
parallel such that a non-flange surface on the other side of a
flange surface of the circumferential joint flange intersects with
one of surfaces of the base member at a predetermined angle. Each
of two adjacent edges of each of a plurality of reinforcing members
is coupled respectively with the non-flange surface of the
circumferential joint flange and the one of surfaces of the base
member such that the plurality of reinforcing members stands with
an interval with each other on a side of an inner angle formed by
the non-flange surface of the circumferential joint flange and the
one of surfaces of the base member. Long side of the base member in
each of the pair of joint structures is coupled to each of the
opposing circumferential edges of the sidewall plates.
[0035] Use of the sidewall unit with such structure allows for
maintaining the angle formed between the circumferential joint
flange and the base member, and since the angle formed between the
circumferential joint flange and the base member may be maintained
even when a high pressure is generated by fluid in a tank, a flange
surface of adjacent circumferential joint flanges is not pressed to
open from inside and leakage of the fluid may be prevented.
[0036] According to a fourth aspect, the present invention provides
a fluid storage tank comprising sidewall units fabricated with a
method according to any one of claim 1 to claim 16.
[0037] According to a fifth aspect, the present invention provides
a fluid storage tank comprising sidewall units according to any one
of claim 17 to claim 25.
[0038] According to the present invention, a fluid storage tank, in
which leakage of fluid is securely prevented even when a large
quantity of fluid is stored, may be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is a perspective view of a bulk fluid storage tank
assembled using sidewalls according to one embodiment of the
present invention.
[0040] FIG. 2 is a perspective view of a bulk fluid storage tank
assembled using sidewalls according to another embodiment of the
present invention.
[0041] FIG. 3 is a perspective view of a sidewall according to one
embodiment of the present invention.
[0042] FIG. 4A is a perspective view of a part of a joint structure
and a sidewall plate included in a sidewall unit shown in FIG.
3.
[0043] FIG. 4B is a perspective view showing another embodiment of
a joint structure.
[0044] FIG. 4C is a perspective view showing further embodiment of
a joint structure.
[0045] FIG. 5(a) is a perspective view showing a shape of a
reinforcing member shown in FIG. 4.
[0046] FIG. 5(b) is a perspective view showing another shape of a
reinforcing member.
[0047] FIG. 6 is a view for describing a method to eliminate
distortion in a joint structure.
[0048] FIG. 7 is a view for describing a method to eliminate
distortion in a joint structure in a direction different from FIG.
6.
[0049] FIG. 8 is a view for describing a method to form a joint
structure while eliminating distortion therein.
[0050] FIG. 9 is a view for describing a method to form a joint
structure while eliminating distortion therein.
[0051] FIG. 10 is a perspective view showing a groove for arranging
a sealing layer provided on a joint flange surface.
[0052] FIG. 11 is a perspective view of a sidewall unit provided
with a joint flange in height direction.
BEST MODE FOR CARRYING OUT THE INVENTION
[0053] The present invention will now be described with reference
to specific embodiments illustrated in the accompanying
drawings.
1. Structure of Sidewall Unit
[0054] FIG. 1 shows an example of a bulk fluid storage tank
assembled using sidewalls according to one embodiment of the
present invention. A sidewall unit comprises joint structures on
both circumferential ends, and each of the joint structures
comprises a circumferential joint flange. The fluid storage tank is
assembled by joining a plurality of sidewall units in
circumferential direction by mutually joining joint structures via
a circumferential joint flange and stacking a plurality of
cylindrical members formed with a plurality of joined sidewall
units in height direction on a bottom wall separately fabricated.
Herein, "cylindrical member" is not limited to what is circular
cylindrical body but may include what is a polygonal cylindrical
body. A number of sidewall units and cylindrical members to be used
is not limited but may be appropriately selected depending on a
size and an application of a fluid storage tank. A sidewall unit
according to the present invention is more preferably used for a
bulk fluid storage tank with a capacity of at least 1,000 m.sup.3
or more, and can securely prevent leakage of fluid from joints
between the sidewall units even when used for a fluid storage tank
with an inner diameter of 12 m or more, a height of 10 m or more
and a capacity of 1,200 m.sup.3 or more.
[0055] A sidewall unit according to the present invention is
fabricated with a fabricating step including a step of eliminating
distortion in a joint structure generated due to welding heat, and
owing to the step of eliminating distortion, the sidewall unit
which does not cause leakage of fluid from joints between adjacent
sidewall units even when a high inner pressure acts on the fluid
storage tank may be obtained. A joint structure of the sidewall
unit according to the present invention has a special structure
which will be described in detail in the following, and owing to
the special structure, deformation of the joint structure may be
prevented because an angle formed by a circumferential joint flange
and a base member is maintained even when a high inner pressure is
applied thereto. Further, the special structure prevents
deformation of coupling between the joint structure and the
sidewall plate, and thus, effect of prevention of leakage of fluid
is extremely great even if a high inner pressure acts over a long
term, no need to mention over a short term. In a bulk fluid storage
tank, inner pressure acting on a sidewall especially at a lower
part of the tank is very large, but elimination of distortion due
to heat under fabrication of joints between sidewall units was not
conventionally considered, and thus, it was not possible to
securely prevent leakage of fluid from the joints in conventional
sidewall units which did not comprise the special structure as the
joint structure of the present invention.
[0056] The following are two main forms of a fluid storage tank
using sidewall units, and the sidewall unit according to the
present invention may be used in a fluid storage tank in any forms
including the following forms. One of the two forms is a fluid
storage tank 1 of cylindrical member stack type as shown in FIG. 1.
In the fluid storage tank 1 of cylindrical member stack-type, a
plurality of side wall units 10 mounted with a joint structure to
each of circumferential edges (i.e. short sides) of a horizontally
oriented sidewall plate are joined in circumferential direction to
form a cylindrical member 2, and a plurality of cylindrical members
2 are stacked in height direction on a bottom wall to be used as a
sidewall. Since inner pressure acting on upper portion of the fluid
storage tank 1 is smaller than that on lower portion, the sidewall
unit 10 according to the present invention may not necessarily be
used in the cylindrical members 2 configuring the sidewall in the
upper portion. That is, the sidewall unit according to the present
invention may be used for units positioned in lower portion of the
fluid storage tank 1, and conventional units may be used for units
positioned in upper portion of the fluid storage tank 1.
[0057] The other of the two forms is a fluid storage tank 1' of a
single cylindrical member type as shown in FIG. 2. In the fluid
storage tank 1' of a single cylindrical member type, a plurality of
side wall units 10' mounted with a joint structure to each of
circumferential edges (i.e. long sides) of a vertically oriented
sidewall plate are joined in circumferential direction to form a
cylindrical member 2' on a bottom wall, and a single cylindrical
member 2' is used as a sidewall of the fluid storage tank 1'. In
this case, all sidewall units should be the sidewall unit according
to the present invention.
[0058] Now, a structure of a sidewall unit 10 according to one
embodiment of the present invention is described with a fluid
storage tank 1 of stack type shown in FIG. 1 as an example. FIG. 3
shows a sidewall unit 10 according to one embodiment of the present
invention. The sidewall unit 10 comprises one sidewall plate 12 and
two joint structures 22, 24 mounted to each of opposing
circumferential edges 14, 16 of the sidewall plate 12. In the
following, the present invention will be described based on an
example where one cylindrical member 2 is configured with four
horizontally oriented sidewall units as shown in FIG. 1.
(Joint Structure)
[0059] FIG. 4A shows a joint structure 22 mounted to the
circumferential edge 14 of the sidewall plate 12. Since a joint
structure 24 normally has a same structure as the joint structure
22, only the joint structure 22 will be described in detail in the
following. The joint structure 22 has a base member 26, a
circumferential joint flange 28 and a plurality of reinforcing
member 30. In FIG. 4A, the sidewall plate 12 mounted to the joint
structure 22 is also shown.
[0060] The base member 26 and the circumferential joint flange 28
are coupled such that a non-flange surface 28A which is an opposite
surface of a flange surface 28B of the circumferential joint flange
28 intersects with one of surfaces 26A of the base member 26 at a
predetermined angle. The predetermined angle is an angle determined
depending on a diameter of the fluid storage tank 1, and is
preferably be 90 degrees or larger. This means that it is necessary
to arrange the flange surface 28B of the circumferential joint
flange 28 vertical with respect to the sidewall of the fluid
storage tank 1, while a main surface (i.e. the one of surfaces 26A)
of the base member is arranged along the sidewall of the
cylindrical fluid storage tank 1. Thus, an intersecting angle
between the non-flange surface 28A of the circumferential joint
flange 28 and the one of surfaces 26A of the base member 26 is 90
degrees or larger. The intersecting angle may be smaller as the
diameter of the fluid storage tank 1 to be assembled is larger, and
may be larger as the diameter of the fluid storage tank 1 to be
assembled is smaller. A positional relationship between a long side
28L of the circumferential joint flange 28 and a long side 26L of
the base member 26 may be substantially parallel. In FIG. 4A, the
base member 26 is shown as standing from an end in short side
direction of the non-flange surface 28A of the circumferential
joint flange 28, but it may be arranged such that the base member
26 stands from a position other than ends of the non-flange surface
28A of the circumferential joint flange 28, such as from center
part in the short side direction. In this case, the circumferential
joint flange 28 of the sidewall unit 10 intrudes inside the fluid
storage tank 1 as shown in FIG. 4B, and, by joining the adjacent
circumferential joint flanges 28 with mechanical fasteners for
example at the inside portions, the joint strength between the
adjacent circumferential joint flanges 28 may be increased to
achieve better prevention of leakage of fluid.
[0061] In FIG. 4A, the base member 26 is shown as standing from the
non-flange surface 28A, but it may be arranges such that the
circumferential joint flanges 28 stands from an end in the short
side direction of the one of surfaces 26A of the base member 26.
However, in such configuration, since a process to shave welding is
necessary at a joint between the circumferential joint flanges 28
and the base member 26 in a joint surface for joining the joint
structure 22 with other joint structures, not only a number of
processes is increased, but also there is a risk that the process
results in generating a gap between the flange surface 28B of the
circumferential joint flanges 28 and an end surface of the long
side 26L of the base member 26. In this case, it is necessary to
ensure sufficient accuracy of flatness to avoid leakage of fluid
from a joint surface between the joint structure 22 and an adjacent
structure.
[0062] At least a part of each of the two adjacent edges 30A and
30B of a plurality of reinforcing member 30 is coupled respectively
with the non-flange surface 28A of the circumferential joint flange
and the one of surfaces 26A of the base member 26 such that the
plurality of reinforcing members stands at a predetermined spacing
on a side of an inner angle formed by the non-flange surface 28A of
the circumferential joint flange 28 and the one of surfaces 26A of
the base member 26.
(Sidewall Plate)
[0063] The sidewall plate 12 may be a rectangular metal panel with
two opposing circumferential edges 14, 16 as short sides and two
opposing edges in height direction 18, 20 as long sides. The
sidewall plate 12 may be fabricated with any material such as steel
or stainless steel depending on fluid to be stored in the fluid
storage tank 1 or on life expectancy of the fluid storage tank 1
itself. A shape of the sidewall plate 112 may be any of
horizontally oriented rectangular, vertically oriented rectangular
or square depending on a shape of the fluid storage tank 1 and a
number of sidewall units 10 configuring one cylindrical member 2.
Thickness of the sidewall plate 12, length of the circumferential
edges 14, 16 and length of the edges in height direction 18, are
not limited but may be appropriately selected depending on a size
of the fluid storage tank 1. The sidewall plate 12 may be curved to
suit curvature of the sidewall of the fluid storage tank 1 at any
point of time before the joint structure is mounted to the
circumferential edges 14, 16.
(Base Member)
[0064] A base member 26 in the embodiment may be a metal panel
having two long sides 26L and two short sides 26S. The base member
26 may be fabricated with any material such as steel or stainless
steel depending on fluid to be stored in the fluid storage tank 1
or on life expectancy of the fluid storage tank 1 itself. One of
the two long sides 26L is an edge to be welded to couple with the
circumferential edge 14 of the sidewall plate 12, and thus, a
length thereof is preferably equal to a length of the
circumferential edge 14. A length of the two short sides 26S may
preferably be one which allows for securing a distance where
welding heat for welding the base member 26 and the sidewall plate
12 does not give any impact to a later-described circumferential
joint flange 28.
[0065] Thickness of the base member 26 is not limited but may be
appropriately selected depending on a size of the fluid storage
tank 1. The base member 26 is preferably fabricated thicker than
the sidewall plate 12. Use of the base member 26 thicker than the
sidewall plate 12 allows for rigidly maintaining the predetermined
angle between the base member 26 and the circumferential joint
flange 28. If the sidewall plate is directly coupled with the
circumferential joint flange as in the prior art, the angle between
the sidewall plate and the flange surface cannot be maintained
under a high pressure from fluid inside the tank, the opposing
flange surfaces between adjacent sidewall units may be forced to
open from a direction corresponding to inside of the tank to cause
leakage of the fluid.
(Circumferential Joint Flange)
[0066] A circumferential joint flange 28 in the embodiment may be a
metal plate having two long sides 28L and two short sides 28S. The
circumferential joint flange 28 may be fabricated with any material
such as steel or stainless steel depending on fluid to be stored in
the fluid storage tank 1 or on life expectancy of the fluid storage
tank 1 itself. Length of the long side 28L is preferably equal to
that of the long side 26L of the base member 26. Thickness and
length of the short side 28S of the circumferential joint flange 28
are not limited but preferably are ones sufficient for securing
joint strength with the circumferential joint flanges 28 of
adjacent sidewall units 10.
[0067] In the circumferential joint flange 28, holes 32 for passing
through fasteners such as bolts and nuts to mechanically join the
circumferential joint flange 28 with other circumferential joint
flanges 28 of adjacent sidewall units 10 may be provided. The hole
32 may not necessarily be provided at an even interval with respect
to the long side direction of the circumferential joint flange 28,
but may be provided at any interval depending on necessity. For
example, inner pressure which deforms a sidewall to outwardly bulge
acts to the sidewall 10 in a bulk fluid storage tank at a center
part in height direction which is away from a joint in height
direction. To address this, intervals between adjacent holes 32 may
be smaller (i.e. a number of the holes 32 is increased) toward the
center part from an edge in the long side direction (i.e. in the
height direction) of the circumferential joint flange 28 in order
to improve joint strength at corresponding portions of the
circumferential joint flange 28, as shown in FIG. 4C. Beside
varying intervals between the holes 32, or along with varying the
intervals thereof, a diameter of the hole 32 may be increased for
passing through a bolt with a larger diameter in order to improve
joint strength of the circumferential joint flanges 28. Positions
of the holes 32 are preferably closer to the base member as much as
possible.
(Reinforcing Member)
[0068] Each of a plurality of reinforcing member 30 may be a metal
plate and may be what has at least a first edge 30A at least a part
of which is welded to the one of surfaces 26A of the base member 26
and a second edge 30B which intersects with the first edge 30A at a
predetermined angle and is welded to at least a part of the
non-flange surface 28A of the circumferential joint flange 28.
Thus, the predetermined angle between the base member 26 and the
circumferential joint flange 28 may be maintained owing to the
first edge 30A and the second edge 30B. The predetermined angle is
an angle which may be determined depending on a diameter of the
fluid storage tank 1 as above described. Lengths of the first edge
30A and the second edge 30B are not limited. However, it is
preferable that the length of the first edge 30A is equal to that
at least of the short side 26S of the base member 26. In another
embodiment, it is preferable that the first edge 30A is longer than
the short side 26S of the base member 26 and is also welded to a
surface 12A of the sidewall plate 12. Deformation of coupling
between the base member 26 and the sidewall plate 12 against inner
pressure may be avoided and strength of the sidewall plate 12
against inner pressure may be increased by making the length of the
first edge 30A sufficient to cross from the one of surfaces 26A of
the base member 26 to the surface 12A of the sidewall plate.
[0069] The reinforcing member 30 may further be what has a third
edge 30C having a length corresponding to the short side 26S of the
base member 26 and a fourth edge 30D opposing to the second edge
30B and connecting one end of the first edge 30A with one end of
the third edge 30C, as shown in FIG. 5(a). A length of the third
edge 30C is preferably equal to that of the short side 26S of the
base member 26. In this case, the reinforcing member 30 is shaped
as a combination of a rectangle formed with the first edge 30A, the
second edge 30B and the third edge 30C and a triangle where a
portion of the first edge 30a to be coupled to the surface 12A of
the sidewall plate 12 and the fourth edge 30D are two adjacent
sides. By shaping the reinforcing member 30 as such, the rectangle
portion serves to retain the angle between the base member 26 and
the circumferential joint flange 28 and the triangle portion serves
to reinforce strength of the sidewall plate 12 against inner
pressure, and as a result, leakage of fluid from joints between
adjacent sidewall units 20 may be securely prevented even in a bulk
fluid storage tank where an inner pressure may be large.
[0070] In a plurality of reinforcing member 30, it is preferable
that a notch 31 is formed at a portion corresponding to a crossing
point of the first edge 30A and the second edge 30B, as shown in
FIG. 5(b). In a reinforcing member 30 without a notch 31, there is
a risk of stress concentrating to a crossing point of a first edge
30A and a second edge 30B when inner pressure acts on a joint
structure 22 and failure of the reinforcing member 30 is initiated
from the crossing point. Generation of such failure may be
prevented by providing the notch 31. Without the notch 31, welding
of the base member 26 with the circumferential joint flange 28 may
be discontinuous at the crossing point of the first edge 30A and
the second edge 30B. Providing the notch 31 is also advantageous in
that the base member 26 and the circumferential joint flange 28 may
be continuously welded.
[0071] In the embodiment, it is preferable that a step is provided
in halfway of the first edge 30A as shown in FIG. 5(a). This is
because that the reinforcing member 30 is formed to correspond to a
step between the one of surfaces 26A of the base member 26 and an
outer surface 12A of the sidewall plate 12 generated by coupling
the other surface 26B of the base member 26 with an inner surface
12B of the sidewall plate 12 to accommodate that the base member 26
being thicker than the sidewall plate 12, as shown in FIG. 4A.
Thus, when the reinforcing member 30 is used in an embodiment where
the one of surfaces 26A of the base member 26 is coupled to be
approximately flush with the outer surface 12A of the sidewall
plate, there is not need to provide any step in the first edge 30A.
In another embodiment, it is more preferable that a notch 34 is
formed at a portion corresponding to a coupling point of the
sidewall plate and the base member 26, i.e. at a portion
corresponding to the step in the first edge 30A, as shown in FIG.
5(b). Forming the notch 34 may provide effect of preventing
concentration of stress at a step and discontinuous welding between
the sidewall plate 12 and the base member 26, as the effect of the
notch 31.
[0072] Although an interval between each of a plurality of
reinforcing member 30 is even in the embodiment, it is not limited
as such and the plurality of reinforcing members 30 may be provided
at any interval depending on necessity. In another embodiment, a
plurality of reinforcing member 30 may be coupled at a smaller
interval in vicinity of a center part in a long side direction of
the circumferential joint flange 28 than at an end thereof, as
shown in FIG. 4C. It may be possible to effectively resist against
inner pressure acting at the center part in height direction of the
sidewall unit 10 by coupling the reinforcing members 30 at such
interval.
2. Fabricating Method of Sidewall Unit
[0073] Next, a fabricating method of sidewall unit according to the
present invention will be described using the sidewall unit 10
shown in FIG. 3 as an example with reference to FIG. 6 to FIG.
9.
(Preparation of Members)
[0074] In the method, members configuring the sidewall unit 10 are
firstly prepared. As above described, one sidewall unit 10
comprises at least one sidewall plate 12 and two joint structures
22, 24, and each of the joint structures 22 and 24 comprises at
least one base member 26, one circumferential joint flange 28, and
a plurality of reinforcing member 30. A number of the reinforcing
member 30 is not limited but may be appropriately selected
according to inner pressure acting on inner wall of the fluid
storage tank 1. A number of sidewall unit 10 used in the fluid
storage tank 1 may be appropriately selected according to size,
application and inner pressure of the fluid storage tank 1, thus,
numbers of members prepared for fabricating one fluid storage tank
1, i.e. sidewall plate 12, base member 26, circumferential joint
flange 28 and reinforcing member 30, may be varied depending on a
number of the sidewall units 10 to be used. For example, when the
fluid storage tank 1 is configured with four cylindrical members 2
and one cylindrical member 2 is configured with four sidewall units
10, then a number of sidewall units 10 to be used is 16.
(1) First Embodiment
Fabricating without Temporary Assembling
[0075] Fabricating method according to the first embodiment of the
present invention may comprise a step of forming a first joint
structure, a first step of eliminating distortion, a step of
forming a second joint structure, and a step of assembling a
sidewall unit. Depending on necessity, the method may comprise a
third step of eliminating distortion and/or an auxiliary step of
eliminating distortion. Unlike a fabricating method according to
the second embodiment described later, the fabricating method
according to the first embodiment is a method to form a joint
structure without temporary assembly of joint structures.
(Step of Forming a First Joint Structure)
[0076] A step of forming a first joint structure is a step for
forming a joint structure 22 or 24. Here, the joint structure 22 is
described as the first joint structure shown in FIG. 4A. In this
step, each of members is firstly arranged in a predetermined
position such that a non-flange surface 28A which is an opposite
surface of a flange surface 28B of a circumferential joint flange
28 matches with one of end surfaces of two long sides 26L of a base
member 26. At this point, one of surfaces 26A of the base member 26
and the non-flange surface 28A are positioned to intersect at a
predetermined angle. In addition, a plurality of reinforcing member
is arranged with an interval with each other on a side of an inner
angle formed by the non-flange surface 28A of the circumferential
joint flange 28 and the one of surfaces 26A of the base member 26.
A plurality of reinforcing member 30 is preferably arranged such
that a main surface of the reinforcing member 30 is perpendicular
to any of the one of surfaces 26A and the non-flange surface 28A. A
positional relationship of a long side 28L of the circumferential
joint flange 28 and a long side 26L of the base member 26 may be
substantially parallel.
[0077] Next, the long side 26L of the base member 26 and the
non-flange surface 28A of the circumferential joint flange 28, the
one of surfaces 26A of the base member 26 and at least a part of a
first edge 30A of the reinforcing member 30, and the non-flange
surface 28A of the circumferential joint flange 28 and at least a
part of a second edge 30B of the reinforcing member 30 are all
coupled by welding. Coupling here means welding the circumferential
joint flange 28 and a plurality of reinforcing member 30 with
strength sufficient to secure durability against inner pressure
when assembled as a fluid storage tank. Herein, it may be called as
a final coupling.
[0078] In general, heat shrink of material occurs when a welded
part cools down. Thus, when a side of the long side 26L facing to
the one of surfaces 26A of the base member 26 and the non-flange
surface 28A of the circumferential joint flange 28 are welded, a
force acts to the base member 26 and the circumferential joint
flange 28 as to reduce the inner angle formed by the one of
surfaces 26A and the non-flange surface 28A smaller than the
predetermined angle. However, in the present invention, an angle
formed by the one of surfaces 26A and the non-flange surface 28A
may be maintained against heat shrink caused by cooling of welding
heat by arranging the reinforcing members 30 which an angle formed
by the first edge 30A and the second edge 30B is the predetermined
angle in advance between the one of surfaces 26A and the non-flange
surface 28A.
[0079] Sequence of coupling the base member 26, the circumferential
joint flange 28 and a plurality of reinforcing member 30 is not
particularly limited. In one embodiment, coupling the base member
26, the circumferential joint flange 28 and a plurality of
reinforcing member 30 may be done in a sequence of firstly coupling
the circumferential joint flange 28 and each of a plurality of
reinforcing member 30, then coupling the circumferential joint
flange 28 and the base member 26, and finally coupling a plurality
of reinforcing member 30 and the base member 26. In another
embodiment, coupling the base member 26, the circumferential joint
flange 28 and a plurality of reinforcing member 30 may be done in a
sequence of firstly coupling the base member 26 and the
circumferential joint flange 28, then coupling each of a plurality
of reinforcing member 30 and the base member 26 and the
circumferential joint flange 28. In view of minimizing generation
of distortion due to welding heat, it is more preferable to couple
the circumferential joint flange 28 and a plurality of reinforcing
member 30 sequentially from a coupling point in vicinity of a
center part in a long side direction of the circumferential joint
flange 28 to a coupling point at an end thereof.
(First Step of Eliminating Distortion)
[0080] For a fabricating method of a sidewall unit according to the
present invention, it is most important to eliminate any distortion
in a joint structure so that the joint structure can withstand high
inner pressure acting in a fluid storage tank fabricated by joining
sidewall units. To achieve this, the present invention is
characterized in that it comprises a step of eliminating distortion
due to welding in a joint structure during a step of fabricating a
sidewall unit. FIG. 6 shows a first step of eliminating distortion
in a fabricated joint structure 22.
[0081] Degree of shrinking due to welding heat increases with
increase of welding length in welded members. Thus, the joint
structure 22 is distorted as that a center part of the
circumferential joint flange 28 in a long side (28L) direction
protrudes to a side of the non-flange surface 28A under influence
of welding heat for welding the base member 26 and the
circumferential joint flange 28 as well as the circumferential
joint flange 28 and a plurality of reinforcing member 30, as shown
FIG. 6(a) viewed from a side of the one of surfaces 26A of the base
member 26. It should be noted that degree of protrusion is
exaggerated for describing a step of the present invention in FIG.
6(a), as well as in FIG. 7(a) which will be described later.
[0082] In the first step of eliminating distortion, distortion in
the joint structure 22 may be eliminated by applying opposing
forces indicated by arrows in FIG. 6(a) to both ends and to a
center part in a long side direction of the joint structure 22.
Force applied to the center part in the long side direction may be
one in a direction toward a flange surface 28B from the non-flange
surface 28A, and force applied to both ends in the long side
direction may be one in a direction toward the non-flange surface
28A from the flange surface 28B. In particular, the first step of
eliminating distortion may be achieved by applying a force in a
direction toward the flange surface 28B with for an example a
hydraulic jack at the center part of the long side 26L of the base
member 26, while holding both ends in the long side direction of
the flange surface 28B of the joint structure 22 with a latching
tool. The joint structure 22 without distortion in the flange
surface 28B, i.e. with an accurately flat flange surface 28B as
shown in FIG. 6(b) may be thus obtained. This step of eliminating
distortion is done before coupling the joint structure 22 and the
sidewall plate 12 because it is substantially not possible to
eliminate distortion after coupling them.
[0083] Although it is shown as forces perpendicular to the
non-flange surface 28A and the flange surface 28B of the
circumferential joint flange 28 are applied in FIG. 6, direction of
applying force is not limited as such. There may be a case where a
force with an appropriate angle is applied from a direction
perpendicular to the non-flange surface 28A/flange surface 28B
depending on condition of distortion in the joint structure 22.
(Third Step of Eliminating Distortion)
[0084] FIG. 7 shows a third step of eliminating distortion for
eliminating distortion in another direction in a fabricated joint
structure 22. The joint structure 22 may be distorted as that a
center part of the base member 26 in a long side (26L) direction
protrudes to a side of the circumferential joint flange 28 under
influence of shrinking due to welding heat as described in the
above, as shown FIG. 7(a) viewed from a side of the non-flange
surface 28A of the circumferential joint flange 28.
[0085] To address this, in the third step of eliminating
distortion, distortion in the joint structure 22 may be eliminated
by applying opposing forces indicated by arrows in FIG. 7(a) to
both ends and to a center part in a long side direction of the
joint structure 22. Force applied to the center part in the long
side direction may be one in a direction toward another surface 26B
on the opposite side of one of surfaces 26A from the one of
surfaces 26A of the base member 26, and force applied to both ends
in the long side direction may be one in a direction toward the one
of surfaces 26A from the surface 26B of the base member 26. In
particular, the third step of eliminating distortion may be
achieved by applying a force in a direction toward the other
surface 26B with for an example a hydraulic jack at the center part
of the long side 28L of the circumferential joint flange 28, while
holding both ends in the long side direction of the other surface
26B of the joint structure 22 with a latching tool. The joint
structure 22 without distortion in the other surface 26B of the
base member 26, i.e. with an accurately flat surface 26B as shown
in FIG. 7(b) may be thus obtained.
[0086] Although it is shown as forces perpendicular to the one of
surfaces 26A and the other surface 26B of the base member 26 are
applied in FIG. 7, direction of applying force is not limited as
such. There may be a case where a force with an appropriate angle
is applied from a direction perpendicular to the one of surfaces
26A and the other surface 26B depending on condition of distortion
in the joint structure 22.
[0087] When considering only prevention of leakage of fluid in a
bulk fluid storage tank 1, the third step of eliminating distortion
is not necessarily be performed. It is because that leakage of
fluid in a bulk fluid storage tank 1 occurs when, in general, a
flange surface 28B of a circumferential joint flange 28 is not
accurately flat. Thus, as long as the flange surface 28B is flat,
distortion in a joint structure 22 does not immediately cause
leakage of fluid in the bulk fluid storage tank 1 even if the joint
structure 22 is distorted as to protrude to a direction
perpendicular to the one of surfaces 26A or the other surface 2613
of the base member 26. In this regard, the third step of
eliminating distortion may be abbreviated.
(Step of Forming a Second Joint Structure)
[0088] Then, a second joint structure may be formed with a step in
a series of the steps of forming a first joint structure, first
step of eliminating distortion, and third step of eliminating
distortion as necessary. Here, a joint structure 24 shown in FIG. 3
may be the second joint structure.
[0089] A sidewall plate 12 may be curved as to have a predetermined
curvature depending on a number of the sidewall unit 10 used to
fabricate the fluid storage tank 1. When the sidewall plate 12 is
used for the fluid storage tank 1 of cylindrical member stack-type
shown for example in FIG. 1, long sides thereof may be curved to be
arc, and when the sidewall plate 12 is used for the fluid storage
tank 1' of single cylindrical member type shown for example in FIG.
2, short sides thereof may be curved to be arc. A method well-known
to those in the art may be used for curving the sidewall plate
12.
(Step of Assembling Sidewall Units)
[0090] Next, in a step of assembling sidewall units, the sidewall
plate 12, the first joint structure 22 and the second joint
structure 24 may be coupled. The step of assembling sidewall units
includes a step of welding to couple an edge 14 which is one of
opposing circumferential edges 14, 16 of the curved sidewall plate
12 and the long side 26L of the base member 26 of the first joint
structure 22 and welding to couple an edge 16 which is the other of
the opposing circumferential edges 14, 16 of the curved sidewall
plate 12 and the long side 26L of the base member 26 of the second
joint structure 24. From a view point of durability against inner
pressure acting on the fluid storage tank 1, it is preferable that
the circumferential edges 14, 16 of the sidewall plate 12 and the
joint structures 22, 24 are coupled so that the other surface 26B
of the base member 26, i.e. the surface facing inside of the fluid
storage tank 1, is approximately flush with the surface 12B of the
sidewall plate 12 facing inside the fluid storage tank 1.
(Auxiliary Step of Eliminating Distortion)
[0091] In the sidewall unit according to the present invention, a
length of the short side 26S of the base member 26 in the joint
structure 22 shown for example in FIG. 4A is preferably one which
welding heat for welding the long side 26L of the base member 26 of
the joint structure 22 and the circumferential edge 14 of the
sidewall plate is transferred to the circumferential joint flange
28. It is because that if welding heat is transferred to the
circumferential joint flange 28, there is a risk of distortion
generated in the flange surface 28B of the circumferential joint
flange 28. However, there is a case where welding heat is
unavoidably transferred to the circumferential joint flange 28 and
distortion occurs and remains in the circumferential joint flange
28 in the sidewall unit 10 after coupling the sidewall plate 12 and
the joint structure. Even in a case where distortion due to
coupling the sidewall plate and the joint structure is not
generated, distortion from a step before coupling may not be
completely eliminated.
[0092] In one embodiment of the present invention, a fabricating
method of a sidewall unit may include an auxiliary step of
eliminating distortion for eliminating the above mentioned
distortion. This step may be one or both of the first step of
eliminating distortion and/or the third step of eliminating
distortion.
(2) Second Embodiment
Fabricating with Temporary Assembling
[0093] A fabricating method according to a second embodiment of the
present invention may comprise a combined step of a first step of
eliminating distortion and a step of forming a first joint
structure, a step of forming a second joint structure and a step of
assembling sidewall unit. In addition, the method may comprise a
second step of eliminating distortion, a third step of eliminating
distortion and/or an auxiliary step of eliminating distortion. In
the fabricating method according to the second embodiment, unlike
the fabricating method according to the first embodiment, an
intermediate structure which a base member 26, a circumferential
joint flange 28 and a plurality of reinforcing members 30 are
temporarily coupled with each other is made, and each of the
members is coupled (in contrast to the temporary coupling, it may
be called as final coupling) after two intermediate structures are
temporarily assembled and restrained. The members of the
intermediate structure are welded and welded parts are cooled while
two intermediate structures are restrained to restrict occurrence
of distortion during cooling. As a result, a joint structure which
distortion is eliminated therefrom may be fabricated.
(Combined Step of a First Step of Eliminating Distortion and a Step
of Forming a First Joint Structure)
[0094] A combined step of a first step of eliminating distortion
and a step of forming a first joint structure is a step of forming
a first joint structure while eliminating distortion. Here, the
joint structure 22 shown in FIG. 4A may be the first joint
structure and intermediate structures in the step may be a first
intermediate structure 22' and a second intermediate structure
22''. FIG. 8 shows the first intermediate structure 22' and FIG. 9
shows a state where the first intermediate structure 22' and the
second intermediate structure 22'' are temporarily assembled and
restrained.
[0095] In this combined step, like in the first embodiment, each of
members is arranged in a predetermined position such that a
non-flange surface 28A which is opposite to a flange surface 28B of
a circumferential joint flange 28 is matched with one of end
surfaces of two long sides 26L of a base member 26. One of surfaces
26A of the base member 26 and the non-flange surface 28A of the
circumferential joint flange 28 are arranged to intersect at a
predetermined angle. In addition, a plurality of reinforcing member
30 is arranged with a predetermined interval with each other on a
side of an inner angle formed by the non-flange surface 28A of the
circumferential joint flange 28 and the one of surfaces 26A of the
base member 26. It is preferable that the plurality of reinforcing
member 30 is arranged such that a main surface a reinforcing member
30 is perpendicular to both of the one of surfaces 26A and the
non-flange surface 28A. A positional relationship between a long
side 28L of the circumferential joint flange 28 and a long side 26L
of the base member 26 may be substantially parallel.
[0096] Then, as shown in FIG. 8, the long side 26L of the base
member 26 and the non-flange surface 28A of the circumferential
joint flange 28, the one of surfaces 26A and a first edge 30A of
the reinforcing member 30, and the non-flange surface 28A the
circumferential joint flange 28 and a second edge 30B of the
reinforcing member 30 are all temporarily coupled by welding. Here,
temporary coupling means the base member 26, the circumferential
joint flange 28 and the plurality of reinforcing member 30 are
arranged at a desired positional relationship with each other and
welded at a minimum strength sufficient to maintain the positional
relationship. Temporary coupling may be achieved by welding for
example 2 cm of a position to be coupled. The first intermediate
structure 22' shown in FIG. 8 is formed as such.
[0097] Order of temporary coupling the base member 26, the
circumferential joint flange 28 and the plurality of reinforcing
member 30 is not limited. In one embodiment, the temporary coupling
the base member 26, the circumferential joint flange 28 and the
plurality of reinforcing member 30 may be performed in an order as
that the circumferential joint flange 28 is temporarily coupled
with each of the plurality of reinforcing member 30, then the
circumferential joint flange 28 is temporarily coupled with the
base member 26, and lastly the plurality of reinforcing member 30
is coupled with the base member 26. In another embodiment, the
temporary coupling the base member 26, the circumferential joint
flange 28 and the plurality of reinforcing member 30 may be
performed in an order as that the base member 26 is temporarily
coupled with the circumferential joint flange 28, then each of the
plurality of reinforcing member 30 is coupled with the base member
26 and the circumferential joint flange 28. From a view point to
minimize generation of distortion due to welding heat, it is
preferable that the temporary coupling the base member 26, the
circumferential joint flange 28 and the plurality of reinforcing
member 30 may be sequentially performed from coupling points in
vicinity of center with respect to the long side 28L of the
circumferential joint flange 28 toward coupling points on the short
side 28S.
[0098] Next, a second intermediate structure 22'' is formed with a
similar step as forming the first intermediate structure 22'. In
this embodiment, the second intermediate structure 22'' is
explained as it is estimated to finally be a different joint
structure from the joint structure 24. In another embodiment, an
intermediate structure which is to be a joint structure 24 may be
an intermediate structure 22'', and in further embodiment, an
intermediate structure, which is to be a joint structure of a
counterpart coupled with the joint structure 22 via a
circumferential joint structure, may be an intermediate structure
22''.
[0099] As shown in FIG. 9, the formed first intermediate structure
22' and the formed intermediate structure 22'' are temporarily
assembled and restrained via the flange surface 28B of the
circumferential joint flange 28. The first intermediate structure
22' and the intermediate structure 22'' may be retained by joining
with a mechanical fastener.
[0100] Then, at least in the first intermediate structure 22', the
base member 26, the circumferential joint flange 28 and each of the
plurality of reinforcing member 30 are coupled with each other
(i.e. final coupling). Shrinkage of materials is generated at parts
coupled by welding, as previously described. In case where each of
members is not temporarily assembled or retained and is coupled in
a single state as a joint structure on one side, like in the first
embodiment, distortion as the center part in the long side
direction of the circumferential joint flange 28 protruding to a
side of the non-flange surface 28A is generated, as shown in FIG.
6(a). In the first embodiment, generated distortion may be
eliminated by applying force indicated by an arrow in FIG. 6(a) to
a first joint structure after forming thereof. In the second
embodiment, by coupling the first intermediate structure 22' and
the second intermediate structure 22'' under restraint, welding and
subsequent cooling of the members are performed with force
indicated by an arrow in FIG. 6(a) being constantly applied to both
of the first intermediate structure 22' and the second intermediate
structure 22''. Although distortion in the circumferential joint
flange 28 generally occurs when cooling, the first joint structure
may be formed while eliminating distortion (or, restricting
generation of distortion) as a result of that the two intermediate
structures are restrained even when cooling.
[0101] As in the first embodiment, when the surface 26A of the long
side 26 L of the base member 26 and the non-flange surface 28A of
the circumferential joint flange 28 are welded, a force to reduce
an inner angle formed by the surface 26A and the non-flange surface
28A to be smaller than a predetermined angle acts onto the base
member 26 and the circumferential joint flange 28. But, in the
present invention, since a plurality of reinforcing member 30 which
an angle formed by a first edge 30A and a second edge 30B thereof
is the predetermined angle is standing between the surface 26A and
the non-flange surface 28, the angle formed therebetween may be
maintained against shrinkage which occurs during cooling of welding
heat.
[0102] In addition, as in the first embodiment, order of coupling
(final coupling) the base member 26, the circumferential joint
flange 28 and the plurality of reinforcing member 30 is not
limited. In one embodiment, the coupling the base member 26, the
circumferential joint flange 28 and the plurality of reinforcing
member 30 may be performed in an order as that the circumferential
joint flange 28 is coupled with each of the plurality of
reinforcing member 30, then the circumferential joint flange 28 is
coupled with the base member 26, and lastly the plurality of
reinforcing member 30 is coupled with the base member 26. In
another embodiment, the coupling the base member 26, the
circumferential joint flange 28 and the plurality of reinforcing
member 30 may be performed in an order as that the base member 26
is coupled with the circumferential joint flange 28, then each of
the plurality of reinforcing member 30 is coupled with the base
member 26 and the circumferential joint flange 28. From a view
point to minimize generation of distortion due to welding heat, it
is preferable that the coupling the base member 26, the
circumferential joint flange 28 and the plurality of reinforcing
member 30 may be sequentially performed from coupling points in
vicinity of center with respect to the long side 28L of the
circumferential joint flange 28 toward coupling points on the short
side 28S.
[0103] Finally, in the temporarily assembled first intermediate
structure 22' and second intermediate structure 22'', the first
intermediate structure 22' becomes the first joint structure 22 by
releasing binding by the mechanical fastener.
(Second Step of Eliminating Distortion)
[0104] In the first step of eliminating distortion and the step of
forming a first joint structure, the first joint structure 22 may
be formed while eliminating distortion which the center part in the
long side direction of the circumferential joint flange 28
protruding to a side of the non-flange surface 28A when coupling
members. But, this step may not be enough to eliminate distortion
in the first joint structure. In such a case, a second step of
eliminating distortion may be performed which further eliminates
distortion in the first joint structure by simultaneously applying
force to the center part and to both ends in the long side
direction of the first joint structure 22, from the non-flange
surface 28A to the flange surface 28B and from the flange surface
28B to the non-flange surface 28A, respectively. The second step of
eliminating distortion may be performed with a similar procedure as
the first step of eliminating distortion in the first
embodiment.
[0105] In the formed first joint structure 22, there may be a case,
for example, where distortion as the center part in the long side
direction of the circumferential joint flange 28 is protruding to a
side of the flange surface 28B depending on welding condition at
temporary assembling. In such a case, the second step of
eliminating distortion may be a step to further eliminate
distortion in the first joint structure 22 by simultaneously
applying force to the center part and to both ends in the long side
direction of the first joint structure 22, from the flange surface
28B to the non-flange surface 28A and from the flange surface 28B
to the non-flange surface 28A, respectively.
(Third Step of Eliminating Distortion)
[0106] In the first joint structure 22 in the second embodiment,
distortion generated as the center part of the base member 26
protruding to a side of the circumferential joint flange 28 has not
yet been eliminated after the first step of eliminating distortion
and the step of forming the first joint structure, as shown in FIG.
7(a) viewed from a side of the non-flange surface 28A of the
circumferential joint flange 28. Thus, in case where such
distortion is generated, the third step of eliminating distortion
may further be performed. The third step of eliminating distortion
may be performed with a similar procedure as the third step of
eliminating distortion in the first embodiment.
(Step of Forming a Second Joint Structure)
[0107] Next, a second joint structure may be formed with a step in
a series of the first step of eliminating distortion and the step
of forming the first joint structure (a second step of eliminating
distortion and a third step of eliminating distortion may be
performed as necessary). Here, a joint structure 24 shown in FIG. 3
may be the second joint structure.
(Other Steps)
[0108] Then, as in the first embodiment, a sidewall unit 10 is
formed by bending the sidewall plate 12, coupling the sidewall
plate 12 and the first joint structure 22 and the second joint
structure 24, and performing auxiliary step of eliminating
distortion as necessary.
3. Fabricating a Fluid Storage Tank
[0109] A fluid storage tank 1 may be fabricated using a plurality
of sidewall unit 10 fabricated with a method for fabricating
thereof according to the present invention and/or a plurality of
sidewall unit 10 having a structure according to the present
invention. The fluid storage tank 1 shown in FIG. 1 may be
fabricated by stacking cylindrical members 2 formed by joining a
plurality of sidewall unit 10 in circumferential direction on a
separately prepared bottom wall 3 (not shown), joining the
cylindrical members 2, and further stacking and mutually joining a
required number of the similarly formed cylindrical members 2. A
fluid storage tank 1' shown in FIG. 2 may be fabricated by forming
a cylindrical member 2' on a separately prepared bottom wall 3'
(not shown) by joining a plurality of sidewall unit 10' in a
circumferential direction. A cat walk where a human can walk
thereon and a ladder for climbing to the cat walk may be provided
to the fluid storage tank 1 or 1', although not shown. The cat walk
may be used as temporary scaffolding for assembling the fluid
storage tank. The following describes fabricating a fluid storage
tank 1 shown in FIG. 1.
[0110] When fabricating a fluid storage tank 1 by stacking
cylindrical members 2 formed by joining a plurality of sidewall
unit 10 in circumferential direction, it is preferable that each of
a joint structure 22 and 24 of the sidewall unit 10 is positioned
to alternate in height direction in respective cylindrical member 2
as shown in FIG. 1. For example, when four sidewall units 10 are
used in one cylindrical member 2 as in the fluid storage tank 1
shown in FIG. 1, it is preferable that a cylindrical member 2 at a
second stage from a bottom is rotated for 45 degrees in a plane
angle with respect to a cylindrical member 2 at a first stage from
the bottom, and a cylindrical member 2 at a third stage from the
bottom is rotated for 45 degrees in a plane angle with respect to
the cylindrical member 2 at the second stage from the bottom. A
cylindrical member 2 at a fourth stage may be rotated similarly
with respect to the cylindrical member 2 at the third stage. As
such, a well-balanced fluid storage tank 1 may be obtained by
avoiding to position joining parts of the joint structures of the
cylindrical members 2 in a row in height direction.
(Bottom Wall)
[0111] Structure, thickness and material of a bottom wall 3 used in
a fluid storage tank are not particularly limited but may be those
which allow for appropriately storing fluid inside without leakage,
when used for a bulk fluid storage tank 1. In one embodiment, it is
preferable that the bottom wall 3 is pre-fabricated in a plant as a
plurality of unit with a predetermined size suitable for
transportation, and the plurality of unit fabricated is transported
to an installation site on vehicles and assembled using mechanical
fasteners such as bolts and nuts. Outermost periphery of the bottom
wall may be provided with a joint part for joining with a
cylindrical member 2.
(Mechanical Fastener)
[0112] One cylindrical member 2 is formed by placing flange
surfaces 28 of circumferential joint flanges 28 in joint structures
of adjacent sidewall units 10 in opposing position and joining them
using, for example, a mechanical fastener. It is preferable that
adjacent joint structures are joined as providing a hole 32 in a
circumferential joint flange 28 of each of the joint structures,
passing a bolt in the provided hole 32 and fastening the bolt with
a nut.
[0113] In general, the lower in a fluid storage tank 1, the larger
inner pressure applied to a wall surface therein. Thus, it is
preferable that strength for joining joint structures is larger for
cylindrical members 2 in a lower part than those in an upper part
of the tank. Either one or both of the following two methods may be
adopted to achieve what described in the above. One of the methods
is to use mechanical fastener with higher capacity for cylindrical
members 2 in lower part, and the other is to use more mechanical
fasteners for the cylindrical members 2 in lower part.
[0114] In case of the former, joint strength may be increased by
increasing a diameter of a bolt used as a mechanical fastener.
Therefore, it is preferable that a size of the hole 32 provided in
the circumferential joint flange 28 of the sidewall unit 10 is
larger for the flange 28 used in lower part of the fluid storage
tank 1. In addition, a fastener made from a material with higher
mechanical strength may be used for the cylindrical members 2 in
lower part of the fluid storage tank 1.
[0115] In case of the latter, it is preferable that a number of the
holes 32 provided in the circumferential joint flange 28 of the
sidewall unit 10 is more for the flange 28 used in lower part of
the fluid storage tank 1. In this case, it is preferable that a
number of the reinforcing member 30 is more for the sidewall units
in lower part of the fluid storage tank 1 fabricated by stacking
the cylindrical members 2 in height direction.
(Sealing Layer)
[0116] When joining the flange surfaces 28B of the circumferential
joint flange 28 in adjacent sidewall units 10 in opposing position,
it is preferable to arrange a sealing layer between the opposing
flange surfaces 28B for preventing leakage of fluid inside the
tank. The sealing layer may preferably be, although not limited, a
water-dilative elastic sealing layer, and may be arranged in areas
on one or both sides of the hole 32 on the flange surface 28B
corresponding to inner side or outer side of the tank. In addition,
another sealing layer such as a silicon sealing layer may further
be arranged in areas on one or both sides of the sealing layer
corresponding to inner side or outer side of the tank.
[0117] In order to further ensure prevention of fluid leakage, for
example, a groove 40 and/or 41 may be provided on the flange
surface 28B of the circumferential joint flange 28 for arranging a
sealing layer, as shown in FIG. 10. Arranging a sealing layer
inside such provided grooves 40, 41 allows for protecting the
sealing layer from being crushed even when the adjacent
circumferential joint flanges 28 are strongly joined. If a sealing
layer is arranged on the flange surface 28B without providing such
grooves 40, 41, the sealing layer is crushed when the adjacent
circumferential joint flanges 28 are strongly joined and effect of
preventing fluid leakage may be deteriorated. Other advantages of
providing the grooves 40, 41 are an effect to avoid drifting of the
sealing layer during assembly of a fluid storage tank and an ease
of aligning the adjacent circumferential joint flanges 28.
(Height-Direction Joint Flange)
[0118] In a fluid storage tank 1 fabricated by stacking a plurality
of cylindrical members 2 in height direction, the cylindrical
members obtained by joining a plurality of sidewall unit 10 in
circumferential direction, the cylindrical members may be stacked
by providing a height-direction joint flange at opposing ends in
height direction of each of the sidewall unit 10 and joining the
opposing flange surfaces of adjacent height-direction joint flanges
with for example mechanical fasteners. When the cylindrical members
2 are stacked in height direction, flange surfaces are tightly
closed with dead load of the cylindrical members 2. Since force
applied to the flange surfaces by the deal load of the cylindrical
members 2 is by far larger than pressure applied by fluid inside,
it is enough to use a conventional ordinary joint flange for the
height-direction joint flange. A height-direction joint flange for
this use may be formed by welding metal plate-like structures so as
to vertically stand from the sidewall unit 10 over the entire
length of the end in height direction of the sidewall unit 10.
[0119] In order to increase joint strength in height direction, a
steel member with a L-shaped cross section (also called an angle
steel) is preferably used as a height-direction joint flange as
shown in FIG. 11, mainly for the following reasons. Firstly, in a
height-direction joint flange 50 using an angle steel, one of plate
parts 51 is welded to a sidewall unit 10 for the entire length of
two opposing long sides of the plate part 51. This separates the
joining points between the height-direction joint flange 50 and the
sidewall unit 10 into two (i.e. joining points between two long
sides and the unit) to allow for diversifying stress and for
restricting welding heat for the height-direction joint flange 50
from being transferred to the flange itself. On the contrary, a
height-direction joint flange in a form of a plate welded to a
sidewall unit 10 is disadvantageous in that since joining point is
only one or multiple joining points are positioned close to each
other, stress is prone to be concentrated and welding heat is
easily transferred to a flange to cause distortion.
[0120] Secondly, a height-direction joint flange 50 using an angle
steel may maintain strength even if a thickness of the plate part
52 of the flange surface is reduced, when compared with a
height-direction joint flange in a form of a plate. A
height-direction joint flange 50 having a flange surface with
reduced thickness allows for improving air-tightness when opposing
flange surfaces are joined with mechanical fasteners. On the
contrary, a thickness of a flange surface of a height-direction
joint flange in a form of a plate is prone to be large to hinder
improving air-tightness when opposing flange surfaces are joined
with mechanical fasteners.
[0121] Although not shown in FIG. 11, it is preferable that a
sealing layer for preventing fluid leakage is provided in a flange
surface 52 of the height-direction joint flange 50. Details such as
type, arrangement and position of the sealing layer are similar to
those of the circumferential joint flange 28. In addition, grooves
for arranging the sealing layer may be provided as in the flange
surface 28B of the circumferential joint flange 28.
DESCRIPTION OF NUMERICAL SYMBOLS
[0122] 1, 1': A fluid storage tank [0123] 2, 2': Cylindrical member
[0124] 10, 10': Sidewall unit [0125] 12: Sidewall plate [0126] 14,
16: Circumferential edge [0127] 18, 20: Edge in height direction
[0128] 22, 24: Joint structure [0129] 22', 22'': Intermediate
structure [0130] 26: Base member [0131] 28: Circumferential joint
flange [0132] 30: Reinforcing member [0133] 32: Hole [0134] 40, 41:
Groove [0135] 50: Height-direction flange
* * * * *