FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
1. Title of the invention: METHOD OF REPLACING FURNACE WALL TUBE
2. Applicant(s)
NAME NATIONALITY ADDRESS
MITSUBISHI POWER, LTD. Japanese 3-1, Minatomirai 3-Chome, Nishiku,
Yokohama-shi, Kanagawa
2208401, Japan
3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it
is to be performed.
1
TECHNICAL FIELD
[0001] This invention relates to a method of replacing a furnace wall tube of a furnace
5 wall of a boiler.
BACKGROUND
[0002] In the case where a furnace wall tube of a furnace wall of a boiler deteriorates or
has damage such as a crack, the corresponding portion of the furnace wall tube needs to be
10 replaced. In the general work of replacing a furnace wall tube, as shown in FIG. 12, a
scaffold 101 is installed in a furnace inside 100 of a furnace after stoppage of operation of the
boiler, and a worker 103 and a worker 104 perform the work of replacing a furnace wall tube
105 from the furnace inside 100 and an outside furnace 102 of the furnace, respectively.
This method needs time for the installation of the scaffold 101, and thus the work period is
15 prolonged. As a result, the boiler stop period is also prolonged, whereby the loss due to the
boiler stop increases. In order to shorten the work period, the workers shall perform the
work just from the furnace outside 102 of the furnace, thereby eliminating the need of
installing the scaffold 101 in the furnace inside 100 of the furnace.
[0003] In this regard, Patent Document 1 discloses the method of, in the case where a
20 damaged furnace wall tube (damaged tube) of a boiler is to be repaired and welded during the
operation of the boiler, welding an existing tube and a new tube from the outside surface of
the furnace wall, after cutting out and removing the damaged portion of the damaged tube,
and inserting the new tube. In this method, an opening is drilled in the outside surface of the
furnace wall of the circumferential grooves interposing a circumferential joint part of the
25 existing tube and the new tube, just enough to allow a part of a small-sized torch head for
automatic TIG welding to be inserted, and automatic TIG welding is performed first to the
inner surfaces of the tubes of the circumferential grooves excluding the opening by the
inserted welding torch, and after an insertion tube which fits the opening is temporarily
2
attached to the opening, TIG welding is manually performed on the outer circumference of the
temporarily attached portion of the insertion tube.
Citation List
5 Patent Literature
[0004]
Patent Document 1: JP Patent No. 3615826
SUMMARY
10 Technical Problem
[0005] However, the method disclosed in Patent Document 1 needs that the opening is
drilled, enough to allow the torch head for automatic TIG welding to be inserted into the tube,
and welding is performed, and thereafter the insertion tube which fits the opening is
temporarily attached to the opening, and TIG welding is manually performed on the outer
15 circumference of the temporarily attached portion of the insertion tube.
[0006] By taking the circumstances described above into consideration, it is an object of
at least one embodiment of the present disclosure to provide a method of replacing a furnace
wall tube in a shorter work period.
20 Solution to Problem
[0007] (1) The method of replacing a furnace wall tube according to at least one
embodiment of the present invention is a method of replacing a furnace wall tube of a furnace
wall of a boiler. The furnace wall includes a plurality of the furnace wall tubes disposed so
as to be spaced away from one another, and a plate-like fin part connecting adjacent furnace
25 wall tubes. The method includes a specification step of specifying a furnace wall
replacement portion including a furnace wall tube replacement portion corresponding to a part
in a length direction of at least one of the plurality of furnace wall tubes, a cutting step of
cutting out the furnace wall replacement portion from an outside of a furnace of the boiler, a
3
removing step of removing the cut-out furnace wall replacement portion from the furnace wall
to the outside of the furnace of the boiler, a first welding step of performing circumferential
welding to a furnace wall tube renewal portion corresponding to the furnace wall tube
replacement portion removed from the furnace wall, and the furnace wall tube after removal
of the furnace wall replacement portion, from the outside 5 of the furnace of the boiler, and a
second welding step of, after the first welding step, inserting and welding a fin part renewal
portion corresponding to a part of the fin part included in the furnace wall replacement portion
removed from the furnace wall, to the furnace wall from the outside of the furnace of the
boiler.
10 [0008] The method according to above (1) enables to perform the work of replacing the
furnace wall tube simply from the outside of the furnace of the boiler, and this eliminates the
need of installing a scaffold inside the furnace of the boiler. Accordingly, it is possible to
shorten the work period for the replacement of the furnace wall tube.
[0009] (2) In the method according to above (1) in some embodiments, the part of the fin
15 part included in the furnace wall replacement portion extends so as to protrude over both end
portions of the furnace wall tube replacement portion in a length direction of the furnace wall
tube replacement portion.
[0010] When the circumferential welding is performed to the furnace wall tube renewal
portion and the furnace wall tube from the outside of the furnace of the boiler, a welding
20 machine including a welding head to be inserted between adjacent furnace wall tubes is used.
At the time of the circumferential welding, the welding machine needs to be partially inserted
between the adjacent furnace wall tubes on the opposite side to the furnace wall tube renewal
portion with respect to a weld portion in the length direction of the furnace wall tube. In the
method according to above (2), the part of the fin part extending so as to protrude over the
25 both end portions of the furnace wall tube replacement portion in the length direction of the
furnace wall tube replacement portion is removed, and thus a gap allowing a part of the
welding machine to be inserted is formed between the adjacent furnace wall tubes on the
opposite side to the furnace wall tube renewal portion with respect to the weld portion in the
4
length direction of the furnace wall tube. This enables to install the welding machine so as
to be able to perform then circumferential welding.
[0011] (3) In the method according to above (1) or (2) in some embodiments, in each of
the first welding step and the second welding step, welding is performed under the state where
the furnace wall tube renewal portion and the 5 fin part renewal portion are covered with a
covering member from at least one of an inside of the furnace of the boiler and the outside of
the furnace of the boiler.
[0012] In some cases, during the work of replacing the furnace wall tube, wind blows
from the inside of the furnace to the outside of the furnace of the boiler or from the outside of
10 the furnace to the inside of the furnace. Such blowing wind disturbs shield gas, resulting in
that proper welding is hardly performed. In the method according to above (3), welding is
performed under the state where the furnace wall tube renewal portion and the fin part
renewal portion are covered with the covering member from at least one of the inside of the
furnace of the boiler and the outside of the furnace of the boiler, whereby the covering
15 member enables to suppress the disturbance of shield gas even with such wind blowing from
the inside of the furnace to the outside of the furnace of the boiler, or from the outside of the
furnace to the inside of the furnace, resulting in enabling to perform proper welding.
[0013] (4) In the method according to any one of above (1) to (3) in some embodiments,
in the first welding step, the circumferential welding is performed under the state where
20 bubble foam is injected into the furnace wall tube from a cut end portion of the furnace wall
tube after removal of the furnace wall tube replacement portion.
[0014] In some cases, during the work of replacing the furnace wall tube, the air having
flowed inside the furnace wall tube blows as wind from the cut end portion. Such blowing
wind disturbs the shield gas, resulting in that proper welding is hardly performed. In the
25 method according to above (4), the injection of bubble foam into the furnace wall tube from
the cut end portion suppresses the wind from blowing from the cut end portion, thereby
suppressing the shield gas from being disturbed, resulting in enabling to perform proper
welding.
5
[0015] (5) The method according to any one of above (1) to (4) in some embodiments
further includes a grooving step to be performed before the first welding step. The grooving
step includes the steps of grooving the cut end portions of the furnace wall tube after cuttingout
of the furnace wall tube replacement portion, and grooving both end portions of the
5 furnace wall tube renewal portion.
[0016] In the method according to above (5) in some cases, the grooving performed to
each of the cut end portions of the furnace wall tube and the end portions of the furnace wall
tube renewal portion enables to facilitate the welding of the furnace wall tube renewal portion
and the furnace wall tube, and further to increase the strength in welding.
10 [0017] (6) In the method according to above (5) in some embodiments, single V grooving
is performed to one of the cut end portion and the end portion of the furnace wall tube
renewal portion to be welded to the cut end portion, and single U grooving is performed to the
other.
[0018] The method according to above (6) enables to form a proper penetration bead
15 while ensuring higher tolerance in a groove gap, as compared with the case where the single
V grooving or the single U grooving is performed to the both of the cut end portion and the
end portion of the furnace wall tube renewal portion.
[0019] (7) The method according to above (5) or (6) in some embodiments further include
a tack welding step after the grooving step, of performing tack welding under the state where
20 a groove formed on the cut end portion and a groove formed on the end portion of the furnace
wall tube renewal portion are disposed to be opposed to each other.
[0020] In the method according to above (7), the tack welding is performed under the
state where the groove formed on the cut end portion and the groove formed on the end
portion of the furnace wall tube renewal portion are disposed to be opposed to each other,
25 thereby enabling to reduce misalignment in the circumferential direction of the furnace wall
tube and a groove gap, prior to the circumferential welding of the furnace wall tube renewal
portion and the furnace wall tube.
Advantageous Effects
6
[0021] According to at least one embodiment of the present invention, the work of
replacing the furnace wall tube is able to be performed simply from the outside of the furnace
of the boiler, and this eliminates the need of installing a scaffold inside the furnace of the
boiler. Accordingly, it is possible to shorten the work period for replacing the furnace wall
5 tube.
BRIEF DESCRIPTION OF DRAWINGS
[0022] FIG. 1 is a front view of a part of a furnace wall of a boiler including a furnace
wall tube to be replaced by a method of replacing a furnace wall tube according to a first
10 embodiment of the present disclosure, viewed from an outside of a furnace of the boiler.
FIG. 2 is a flowchart for describing the method of replacing the furnace wall tube
according to the first embodiment of the present disclosure.
FIG. 3 is a front view of the part viewed from the outside of the furnace of the boiler,
under the state where a furnace wall tube replacement portion and a fin part replacement
15 portion are removed from the furnace wall of the boiler including the furnace wall tube to be
replaced by the method of replacing the furnace wall tube according to the first embodiment
of the present disclosure.
FIG. 4 is a front view of the part viewed from the outside of the furnace of the boiler,
under the state where a furnace wall tube renewal portion is welded to the furnace wall of the
20 boiler including the furnace wall tube to be replaced by the method of replacing the furnace
wall tube according to the first embodiment of the present disclosure.
FIG. 5 is a diagram illustrating the state where circumferential welding is performed to
the furnace wall tube replacement portion on the furnace wall of the boiler from the outside of
the furnace of the boiler, by the method of replacing the furnace wall tube according to the
25 first embodiment of the present disclosure.
FIG. 6 is a diagram for describing operation of a torch part of a circumferential welding
machine to be used in the method of replacing the furnace wall tube according to the first
embodiment of the present disclosure.
7
FIG. 7 is a front view of the part viewed from the outside of the furnace of the boiler,
under the state where the furnace wall tube renewal portion and the fin part renewal portion
are welded to the furnace wall of the boiler including the furnace wall tube to be replaced by
the method of replacing the furnace wall tube according to the first embodiment of the present
5 disclosure.
FIG. 8 is a flowchart for describing a method of replacing a furnace wall tube according
to a second embodiment of the present disclosure.
FIG. 9A is a diagram illustrating an example of a groove shape which is able to be
formed on a cut end portion of a furnace wall tube and an end portion of a furnace wall tube
10 renewal portion, in the method of replacing the furnace wall tube according to the second
embodiment of the present disclosure.
FIG. 9B is a diagram illustrating an example of the groove shape which is able to be
formed on the cut end portion of the furnace wall tube and the end portion of the furnace wall
tube renewal portion, in the method of replacing the furnace wall tube according to the second
15 embodiment of the present disclosure.
FIG. 9C is a diagram illustrating an example of the groove shape which is able to be
formed on the cut end portion of the furnace wall tube and the end portion of the furnace wall
tube renewal portion, in the method of replacing the furnace wall tube according to the second
embodiment of the present disclosure.
20 FIG. 10 is a diagram for describing operation in tack welding, in the method of
replacing the furnace wall tube according to the second embodiment of the present disclosure.
FIG. 11 is a cross sectional view illustrating one example of operation in circumferential
welding, in the method of replacing the furnace wall tube according to the second
embodiment of the present disclosure.
25 FIG. 12 is a diagram for describing a conventional method of replacing the furnace wall
tube.
DETAILED DESCRIPTION
8
[0023] Several embodiments of the present invention will be described below with
reference to the drawings. However, the scope of the present invention is not limited to the
embodiments below. The dimensions, materials, shapes, relative positions and the like of
components described in the embodiments below shall be interpreted as illustrative only and
5 not limitative of the scope of the present invention.
[0024] (Embodiment 1)
FIG. 1 is a front view of a part of a furnace wall 1 of a boiler including a furnace wall
tube 2 to be replaced by a method of replacing a furnace wall tube according to the first
embodiment of the present disclosure, viewed from the outside of the furnace of the boiler.
10 The furnace wall 1 includes a plurality of the furnace wall tubes 2 which extend in the vertical
direction and are disposed so as to be spaced away from one another, and plate-like fin parts 3
which connect adjacent furnace wall tubes 2.
[0025] The method of replacing the furnace wall tube according to the first embodiment
will be described next on the basis of the flowchart shown in FIG. 2.
15 First, a furnace wall replacement portion 8 (refer to FIG. 1) which is a portion to be
replaced is specified, and the furnace wall replacement portion 8 is marked (step S1
(specification step)). In FIG. 1, a mark 6 indicating the area of the furnace wall replacement
portion 8 is drawn by a broken line as an example, or may not be drawn by a broken line.
Any marking form is available, as long as the marking form indicates the area of the furnace
20 wall replacement portion 8.
[0026] The furnace wall replacement portion 8 in the furnace wall 1 includes a furnace
wall tube replacement portion 4 which is a part of the furnace wall tube 2 in the length
direction, and a fin part replacement portion 5 which is a part of the fin part 3 connected to the
furnace wall tube replacement portion 4. It is noted that although two of the furnace wall
25 tubes 2 include the furnace wall tube replacement portion 4 in FIG. 1, just one tube, or three
or more of the tubes, not limited to two tubes, may include the portion. The fin part
replacement portion 5 extends so as to protrude over both end portions 4a, 4a of the furnace
wall tube replacement portion 4 in the length direction of the furnace wall tube replacement
9
portion 4, between the furnace wall tube 2 including the furnace wall tube replacement
portion 4 and a furnace wall tube 2’ which is disposed adjacent to the furnace wall tube 2 and
includes none of the furnace wall tube replacement portion 4. In the case where two or more
of the furnace wall tubes 2 include the furnace wall tube replacement portion 4, the fin part
replacement portion 5 extends so as 5 to protrude over the both end portions 4a, 4a of the
furnace wall tube replacement portion 4 in the length direction of the furnace wall tube
replacement portion 4, also between the adjacent furnace wall tubes 2, 2.
[0027] As shown in FIG. 2, after the mark 6 is put in step S1, the furnace wall
replacement portion 8 is cut out along the mark 6 by use of an arbitrary cutting device from
10 the outside of the furnace of the boiler (step S2 (cutting step)). After the cutting along the
mark 6, the cut-out furnace wall replacement portion 8 is removed to the outside of the
furnace of the boiler (step S3 (removing step)).
[0028] As shown in FIG. 3, by the work in step S2 and step S3, an opening hole 7
communicating between the outside of the furnace and the inside of the furnace of the boiler
15 is formed in the furnace wall 1. By the removal of the furnace wall tube replacement portion
4 (refer to FIG. 1), cut end portions 12 are formed so that the insides of the furnace wall tubes
2 are opened, at the end portions of the furnace wall tubes 2 after the removal of the furnace
wall tube replacement portion 4 (refer to FIG. 1). By the removal of the fin part replacement
portion 5 (refer to FIG. 1), a gap 10 is formed so as to extend upward and downward in the
20 vertical direction over each of the cut end portions 12, between the furnace wall tube 2
including the furnace wall tube replacement portion 4 and the furnace wall tube 2’ which is
disposed adjacent to the furnace wall tube 2 and includes none of the furnace wall tube
replacement portion 4. In the case where two or more of the furnace wall tubes 2 include the
furnace wall tube replacement portion 4, the gap 10 is formed so as to extend upward and
25 downward in the vertical direction over each of the cut end portions 12, also between the
adjacent furnace wall tubes 2, 2. It is noted that the respective gaps 10 are included as a part
of the opening hole 7.
[0029] As shown in FIG. 2, after step S3, a furnace wall tube renewal portion 14 (refer to
10
FIG. 4) corresponding to the furnace wall tube replacement portion 4 and the furnace wall
tube 2 after the removal of the furnace wall tube replacement portion 4 are welded from the
outside of the furnace of the boiler (step S4 (first welding step)). As shown in FIG. 4, the
furnace wall tube renewal portion 14 and the furnace wall tube 2 are subjected to
circumferential welding under the state where 5 the end portions of the furnace wall tube
renewal portion 14 and the cut end portions 12 (refer to FIG. 3) of the furnace wall tube 2 are
opposed respectively, whereby weld portions 15 are formed along the outer peripheral
surfaces of the furnace wall tube renewal portion 14 and the furnace wall tube 2.
[0030] FIG. 5 shows a circumferential welding machine 20 configured to perform
10 circumferential welding to the furnace wall tube renewal portion 14 and the furnace wall tube
2. The circumferential welding machine 20 includes a power supply 21 and an operation
panel 22 disposed outside the furnace of the boiler, and a welding head part 24 which is
electrically connected to the power supply 21 via a wiring 23 and is allowed to be installed to
the furnace wall tube renewal portion 14 and the furnace wall tube 2 from the outside of the
15 furnace of the boiler. As the circumferential welding machine 20, for example, the machine
disclosed in JP Patent No. 4442763 is available.
[0031] Since the welding head part 24 is installed so as to surround the outer peripheral
surfaces of the furnace wall tube renewal portion 14 and the furnace wall tube 2, a part of the
welding head part 24 is positioned in the gaps 10. As described above, by the removal of the
20 fin part replacement portion 5 (refer to FIG. 1) from the furnace wall 1, the gaps 10 are
formed so as to extend upward and downward in the vertical direction over the respective cut
end portions 12, between the adjacent furnace wall tubes 2, 2 and between the adjacent
furnace wall tubes 2, 2’. This enables to install the welding head part 24 so as to be able to
perform circumferential welding.
25 [0032] As shown in FIG. 6, the welding head part 24 includes a torch part 30 which is
rotatable along the outer peripheral surfaces of the furnace wall tube renewal portion 14 and
the furnace wall tube 2 (refer to FIG. 5). The torch part 30 includes a torch main body 31, a
ceramic plate 32 disposed on the torch main body 31, and an electrode 33 disposed so as to
11
protrude from the ceramic plate 32. The circumferential welding is performed in the manner
that the torch part 30 performs welding while moving along the outer peripheral surfaces of
the furnace wall tube renewal portion 14 and the furnace wall tube 2 to the inside of the
furnace of the boiler through the gap 10 and to the outside of the furnace of the boiler through
5 the next gap 10.
[0033] As shown in FIG. 2, after step S4, a fin part renewal portion 16 (refer to FIG. 7)
corresponding to the fin part replacement portion 5 is inserted and welded to the portion after
the removal of the fin part replacement portion 5, from the outside of the furnace of the boiler
(step S5 (second welding step)). As shown in FIG. 7, the fin part renewal portion 16 is
10 welded to the furnace wall tube renewal portion 14, the furnace wall tube 2 to which the
furnace wall tube renewal portion 14 is welded, the fin part 3, and the furnace wall tube 2',
whereby a weld portion 17 is formed along the outer edge of the fin part renewal portion 16.
The function of the fin part 3 is to prevent gas from leaking from the inside of the furnace of
the boiler, and thus it is sufficient that the fin part renewal portion 16 is welded simply from
15 the outside of the furnace of the furnace wall 1.
[0034] In some cases, during the welding work in steps S3 and S4, wind blows from the
inside of the furnace to the outside of the furnace of the boiler or from the outside of the
furnace to the inside of the furnace. Such blowing wind disturbs shield gas, resulting in that
proper welding is hardly performed. Therefore, in order to suppress the disturbance of the
20 shield gas due to such wind, the welding may be performed under the state where the furnace
wall tube renewal portion 14 and the fin part renewal portion 16 are covered with a covering
member. The covering member may be installed to the inside of the furnace of the boiler,
the outside of the furnace of the boiler, or the both of the inside of the furnace and the outside
of the furnace of the boiler.
25 [0035] In the case where the covering member is installed to the inside of the furnace of
the boiler, the covering member needs to be recovered through the narrow gap 10 to the
outside of the furnace of the boiler after the welding of the furnace wall tube renewal portion
14. Therefore, a foldable sheet-like covering member (for example, the curtain disclosed in
12
JP UH7-15162) shall be used, in order to be passed through the gap 10. In this case, unless
such a sheet-like covering member is positioned away by a certain distance from the furnace
wall tube renewal portion 14 and the fin part renewal portion 16, the circumferential welding
is not able to be performed. Thus, in order to ensure such a distance, an arbitrary spacer
shall be disposed between the sheet-like covering member, 5 and the furnace wall tube renewal
portion 14 and the fin part renewal portion 16.
[0036] In the case where the covering member is disposed to the outside of the furnace of
the boiler, the sheet-like covering member for the installation to the inside of the furnace of
the boiler and the spacer may be used, or alternatively a box-like covering member (for
10 example, the shield box disclosed in JP AH11-277238) is available because the constraints of
the installation space of the case of the installation to the outside of the furnace of the boiler
are less, as compared with the case of the installation to the inside of the furnace.
[0037] As described above, the welding is performed under the state where the furnace
wall tube renewal portion 14 and the fin part renewal portion 16 are covered with the covering
15 member from at least one of the inside of the furnace of the boiler or the outside of the
furnace of the boiler, whereby the covering member enables to suppress the disturbance of
shield gas even with wind blowing from the inside of the furnace to the outside of the furnace
of the boiler, or from the outside of the furnace to the inside of the furnace, resulting in
enabling to perform proper welding.
20 [0038] In some cases, during the welding work in steps S3 and S4, the air having flowed
inside the furnace wall tube 2 blows as wind from the cut end portion 12. Also in the case
where such wind blows, the shield gas is disturbed, and thus proper welding is hardly
performed. Therefore, the circumferential welding shall be performed under the state where
bubble foam (for example, SUNFORM P-30, foaming agent for gas shield produced by
25 Sugimura Chemical Industry Co., Ltd.) is injected in the furnace wall tube 2 from the cut end
portion 12 of the furnace wall tube 2. The injection of bubble foam in the furnace wall tube
2 from the cut end portion 12 suppresses the wind from blowing from the cut end portion 12,
thereby suppressing the shield gas from being disturbed, resulting in enabling to perform
13
proper welding.
[0039] As described above, the work of replacing the furnace wall tube 2 is able to be
performed simply from the outside of the furnace of the boiler, and this eliminates the need of
installing a scaffold inside the furnace of the boiler. Accordingly, it is possible to shorten the
5 work period for replacing the furnace wall tube 2.
[0040] (Embodiment 2)
Next, the method of replacing a furnace wall tube according to the second embodiment
will be described. The method of replacing the furnace wall tube according to the second
embodiment further includes the step of performing grooving to the furnace wall tube 2 and
10 the furnace wall tube renewal portion 14 before circumferential welding, in addition to the
steps in the first embodiment. It is noted that, in the second embodiment, common reference
codes are assigned to the same configuration requirements as those in the first embodiment,
and the detailed descriptions thereof will be omitted.
[0041] As shown in the flowchart of FIG. 8, steps S1 to S3 in the method of replacing the
15 furnace wall tube according to the second embodiment are the same as those according to the
first embodiment. In the second embodiment, after the completion of step S3, grooving is
performed to the cut end portions 12 (refer to FIG. 3) of the furnace wall tube 2 and the end
portions of the furnace wall tube renewal portion 14 (step S11 (grooving step)).
[0042] As shown in FIG. 9 A, single V grooving may be performed to the cut end portion
20 12 of the furnace wall tube 2 and the end portion of the furnace wall tube renewal portion 14.
Alternatively, as shown in FIG. 9B, single U grooving may be performed to the cut end
portion 12 of the furnace wall tube 2 and the end portion of the furnace wall tube renewal
portion 14. In general, in the single V groove, tolerance with respect to the groove gap is
large, and a penetration bead is formed rarely. In the single U groove, a proper penetration
25 bead is formed, and tolerance with respect to the groove gap tends to be narrow. Therefore,
in order to obtain the advantages of both of the single V groove and the single U groove, as
shown in FIG. 9C, the single V grooving shall be performed to either one of the cut end
portion 12 of the furnace wall tube 2 and the end portion of the furnace wall tube renewal
14
portion 14, and the single U grooving shall be performed to the other. This enables to form a
proper penetration bead while ensuring higher tolerance with respect to the groove gap, as
compared with the case where the single V grooving or the single U grooving is performed to
the both of the cut end portion 12 and the end portion of the furnace wall tube renewal portion
5 14.
[0043] As shown in FIG. 8, after the completion of step S11, tack welding is performed
under the state where the groove formed on the cut end portion 12 and the groove formed on
the end portion of the furnace wall tube renewal portion 14 are disposed to be opposed to each
other (step S12 (tack welding step)). As shown in FIG. 10, a groove 12a formed on the cut
10 end portion 12 and a groove 14a formed on the end portion of the furnace wall tube renewal
portion 14 are aligned so as to be opposed to each other by use of a groove aligning device 40.
[0044] The groove aligning device 40 has a plate-like main body 41 including a recessed
groove part 42 in which the furnace wall tube 2 and the furnace wall tube renewal portion 14
are fitted, and two position adjusting members 43, 44. The main body 41 includes a
15 rectangular opening hole 45, and allows the grooves 12a, 14a to be viewed through the
opening hole 45 from the outside of the furnace of the boiler under the state where the furnace
wall tube 2 and the furnace wall tube renewal portion 14 are fitted in the recessed groove part
42. It is noted that the opening hole 45 may have any shape, not limited to a rectangle, as
long as it does not hinder the tack welding work to be described later.
20 [0045] The position adjusting members 43, 44 have U-type bolts 43a, 44a, and nuts 43b,
43c and nuts 44b, 44c to be screwed to the U-type bolts 43a, 44a, respectively. The furnace
wall tube 2 and the furnace wall tube renewal portion 14 are hooked by the curve portions of
the U-type bolts 43a, 44a, respectively, from the inside of the furnace of the boiler, and two
liner portions of the each extend so as to pass through the gaps 10 and penetrate the main
25 body 41 from the inside of the furnace to the outside of the furnace of the boiler, and the nuts
43b, 43c and the nuts 44b, 44c are screwed to the two linear portions, respectively, from the
outside of the furnace of the boiler, so that the respective nuts are contacted to a surface 41a
of the main body 41 positioned outside the furnace of the boiler. One of the linear portions
15
of each of the U-type bolts 43a, 44a has a slip-off stopping part 43d or 44d, correspondingly,
at the end portion thereof. This prevents the U-type bolts 43a, 44a from slipping down into
the inside of the furnace of the boiler because the slip-off stopping parts 43d, 44d are brought
into contact with the main body 41 even when the U-type bolts 43a, 44a move toward the
5 inside of the furnace of the boiler.
[0046] When the tightening of the respective nuts is adjusted, relative positions between
the furnace wall tube 2 and the furnace wall tube renewal portion 14 are adjusted. This
enables to fix the groove 12a and the groove 14a under opposed positions. Under the state,
the tack welding is performed to the groove 12a and the groove 14a by TIG welding through
10 the opening hole 45. The tack welding enables to reduce misalignment in the
circumferential direction and the groove gap, and allows the misalignment and the groove gap
to fall within the tolerance for the subsequent first welding step (refer to FIG. 8). After the
tack welding, the nuts 43b, 43c and the nuts 44b, 44c are loosened, and the groove aligning
device 40 is removed from the furnace wall tube 2 and the furnace wall tube renewal portion
15 14.
[0047] As shown in FIG. 8, after step S12, step S4 and step S5 are performed in the same
manner as the first embodiment, whereby the work of replacing the furnace wall tube 2 is
completed. It is noted that, in step S5, as shown in FIG. 11, the circumferential welding may
be performed by use of an annular insert ring 50 between the groove 12a and the groove 14a.
20 The circumferential welding performed by use of the insert ring 50 enables to form a smooth
and uniform penetration bead on the inner surface of the furnace wall tube 2.
[0048] The second embodiment produces the same effects as those in the first
embodiment, and in addition the grooving to each of the cut end portions 12 of the furnace
wall tube 2 and the both end portions of the furnace wall tube renewal portion 14 enables to
25 facilitate welding to the furnace wall tube renewal portion 14 and the furnace wall tube 2, and
further to increase the strength in welding.
Reference Signs List
16
[0049]
1 Furnace wall
2 Furnace wall tube
3 Fin part
5 4 Furnace wall tube replacement portion
4a End portion (of furnace wall tube replacement portion)
5 Fin part replacement portion
6 Mark
7 Opening hole
10 8 Furnace wall replacement portion
10 Gap
12 Cut end portion
12a Groove
14 Furnace wall tube renewal portion
15 14a Groove
15 Weld portion
16 Fin part renewal portion
17 Weld portion
20 Circumferential welding machine
20 21 Power supply
22 Operation panel
23 Wiring
24 Welding head part
30 Torch part
25 31 Torch main body
32 Ceramic plate
33 Electrode
40 Groove aligning device
17
41 Main body
42 Recessed groove part
43 Position adjusting member
43a U-type bolt
5 43b Nut
43c Nut
43d Slip-off stopping part
44 Position adjusting member
44a U-type bolt
10 44b Nut
44c Nut
44d Slip-off stopping part
45 Opening hole
50 Insert ring
15
18
I/We Claim:
1. A method of replacing a furnace wall tube of a furnace wall of a boiler,
the furnace wall including:
a plurality of the furnace wall tubes disposed 5 so as to be spaced away from one
another; and
a plate-like fin part connecting adjacent furnace wall tubes,
the method of replacing the furnace wall tube comprising:
a specification step of specifying a furnace wall replacement portion including a
10 furnace wall tube replacement portion corresponding to a part in a length direction of at least
one of the plurality of furnace wall tubes;
a cutting step of cutting out the furnace wall replacement portion from an outside
of a furnace of the boiler;
a removing step of removing the cut-out furnace wall replacement portion from
15 the furnace wall to the outside of the furnace of the boiler;
a first welding step of performing circumferential welding to a furnace wall tube
renewal portion corresponding to the furnace wall tube replacement portion removed from the
furnace wall, and the furnace wall tube after removal of the furnace wall replacement portion,
from the outside of the furnace of the boiler; and
20 a second welding step of, after the first welding step, inserting and welding a fin
part renewal portion corresponding to a part of the fin part included in the furnace wall
replacement portion removed from the furnace wall, to the furnace wall from the outside of
the furnace of the boiler.
25 2. The method of replacing the furnace wall tube according to claim 1, wherein
the part of the fin part included in the furnace wall replacement portion extends so as to
protrude over both end portions of the furnace wall tube replacement portion in a length
direction of the furnace wall tube replacement portion.
19
3. The method of replacing the furnace wall tube according to claim 1 or 2, wherein
in each of the first welding step and the second welding step, the welding is performed
under a state of the furnace wall tube renewal portion and the fin part renewal portion covered
with a covering member from at least one of an 5 inside of the furnace of the boiler and the
outside of the furnace of the boiler.
4. The method of replacing the furnace wall tube according to any one of claims 1 to 3,
wherein
10 in the first welding step, the circumferential welding is performed under a state of
bubble foam injected into the furnace wall tube from a cut end portion of the furnace wall
tube after removal of the furnace wall tube replacement portion.
5. The method of replacing the furnace wall tube according to any one of claims 1 to 4, the
15 method further comprising:
a grooving step to be performed before the first welding step,
the grooving step including the steps of:
grooving the cut end portions of the furnace wall tube after cutting-out of the
furnace wall tube replacement portion; and
20 grooving both end portions of the furnace wall tube renewal portion.
6. The method of replacing the furnace wall tube according to claim 5, wherein
single V grooving is performed to one of the cut end portion and the end portion of the
furnace wall tube renewal portion to be welded to the cut end portion, and single U grooving
25 is performed to the other.
7. The method of replacing the furnace wall tube according to claim 5 or 6, the method
further comprising:
20
a tack welding step of, after the grooving step, performing tack welding under a state of
a groove formed on the cut end portion and a groove formed on the end portion of the furnace
wall tube renewal portion disposed to be opposed to each other.