FIELD OF INVENTION
The present invention relates to an apparatus for fabrication of welded walls /
panels made of tubes of various sizes and specifications for high temperature
and high pressure applications.
The invention also relates to an apparatus for doing the hot correction of
panels in trial assembly base without disturbing the setting of panels in an
innovative way.
More particularly, the invention relates to an apparatus which can enable the
hot correction of panel at trial assembly base itself. This is considered as
more accurate, safe and efficient with reduced manpower and cycle time for
trial assembly of water wall panels.
Further, the invention relates to a method of making hot correction (bow
correction) in the panels.
PRIOR ART / PATENT SEARCH
A patent search was carried out and the following are the results.
The search on apparatus/fixture for bow correction of panels in spiral water
wall assembly yielded no results. Similarly search on bow correction
arrangement in trial assembly/in supercritical boilers yielded no results.

It has been found that similar to the present invention no such patents are
available to do panel bow correction in trial assembly.
BACKGROUND OF INVENTION
In power plants, the spiral and vertical panels / walls form the walls
surrounding the furnace, where the fuel is burnt and the heat is transferred
to the medium flowing inside the tubes. The furnace walls consist of setting
of required number of panels as per drawing. The Length of the panels varies
from 2 to 20 meters and the number of tubes per panel / wall varies from 22
tubes to 400 tubes with outside Diameter ranging from 38.1 mm to 76.1 mm.
These panels have to be set accurately in trial assembly and do the
corrections if needed to enable correct attachment tacking and joining the
other panels or loose tubes at site.
Trial assembly base is made up of several I beams arranged in parallel
connected with C channel on top of I beams. These C channels will act as a
base for spreading the panels over it followed by setting of panels,
attachment markings and full welding. Individual panels after fabrication will
be kept on trial assembly base by (Electric Overhead Transport) EOT crane.
After keeping all panels setting of panels is done in defined layout. After
setting if any panel need hot correction due to longitudinal bow or transverse
bow, it will be moved outside from trial assembly base by (Electric Overhead
Transport) EOT crane to the stands, and subsequently putting back to the
Trial assembly base after correction by EOT crane. Since the basic activities
of EOT crane is for Loading, Unloading, and Movement using it for panel /
wall setting affects other regular works. Thus, the present art of performing

the hot correction of panels by taking out from trial assembly by EOT crane
requires more time and more man power, which is not desirable.
Hence there is a need to find out a safe and simple method for doing the hot
correction of panels at Trial assembly base itself by placing the panel over
some support, doing the correction and keeping the panel again without
much disturbance.
OBJECTS OF THE INVENTION
The objects of the invention are to reduce the time for hot correcting in
panels at trial assembly at the same location without any unnecessary
movement and additional manpower. Moreover, it is a safe and efficient
method to carry out the work without disturbing the panel setting.
SUMMARY OF THE INVENTION
Accordingly, there is provided an apparatus consist of one C channel frame.
The C channel frame is fitted with two nuts and bolts for locking C channel
frame on trial assembly C channel base. The one end of the Pipe is welded on
the center of the square plate as well as the other end of the pipe is welded
on the center of the C channel frame. Square plate will act as a support for
keeping the panel over the apparatus for carrying out hot correction. The two
angle stiffeners are welded on both pipe and square plate for adding
strength. The C channel frame is having two threaded holes at each side.
After keeping the C channel frame over Trial Assembly C channel base, the
apparatus can be locked by the use of nut and bolts at both sides. Panels

required for hot correction will be lifted by EOT crane at such height so that
apparatus can be inserted under the panel and locked over the trial assembly
C channel base. Normally two apparatus are required for one panel hot
correction. After keeping the panel over square plate of the apparatus, hot
correction will be carried out and after completion apparatus will be taken out
by EOT crane and panel will be kept back on trial assembly base to resume
its original position. The apparatus consists of one C channel frame with two
nut and bolts, pipe and square plate connected by angle stiffener kept on
trial assembly C channel base as shown in the figure 1.
Normally panels will be having transverse Bow, curved shape at longitudinal
side shown in figure-4. This bow is measured by putting thread on center of
tube at both ends. In the middle of the panel the thread will not be matching
with center line of tube. That displacement from center will calculate the
bow. For correcting this type bow triangle type heating is suggested to
straighten the curved portion in the longitudinal side of panel.
After placing the panel on the apparatus triangle is marked roughly with chalk
piece at middle of panel on top and bottom both sides. Triangle size is
approximately decided as per bow. If the bow is in between 0 to 15 mm one
triangle covering 8-9 tubes is heated. If the bow is in between 16 to 20 mm
normally two triangles will be marked with 1.5 to 2 m distance between
them. For more than 20mm normally three triangles will be marked with
1.5m to 2m distance between them.
Heating is done on tubes and fin of the panel covered inside the triangle at a
red hot temp i.e 400°C to 500°C. Heating should always done from the
vertex of the triangle to the base of the triangle with the help of heating

torch. First tube-1 is heated at top followed by same tube heated at bottom,
then tube-2 is heated at top followed by heating tube-2 from bottom. This
process will be carried out till we heat the tube-9 at top and bottom by using
two numbers of heating torch simultaneously.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1 - Shows the block diagram of the Apparatus used for doing hot
correction of panels kept on trial assembly C channel base.
Fig.2 - Shows the block diagram of the Apparatus (A) with work piece
(panel) kept on trial assembly C channel base.
Fig.3 - Shows the actual diagram of the Apparatus (A) with work piece
(panel) kept on trial assembly C channel base.
Fig.4- Shows the diagram of panel with bow and triangle marking for
heating.
Fig.5- Shows the actual diagram of panel with triangle marked.
Fig.6- Shows the actual diagram of panel with triangle marked and
heating being done with the help of heating torch.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION

The apparatus (A) comprises of a C Channel Frame (1) having two nuts and
bolts (2) fixed at side of the C Channels Frame (1). One end of pipe (2) is
welded on the center of the C channel frame (1) whereas the other end of
the pipe is welded on the center of the square plate (5). Two Stiffeners (4)
are welded on both pipe (3) and square plate (5). The whole Apparatus is
represented as (A). The Panels (7) required for hot correction will be lifted by
EOT crane at such height so that apparatus can be inserted under the panel
and locked over the trial assembly C channel base (6) with the help of nut
and bolts (2). Normally two apparatus are required for one panel hot
correction.
After keeping the panel (7) over square plate (5) of the apparatus, hot
correction will be carried out and after completion apparatus will be taken out
by EOT crane and panel will be kept back on trial assembly base to resume
its original position. The apparatus consists of one C channel frame (1) with
two nut and bolts (2), pipe (3) and square plate (5) connected by angle
stiffener (4) kept on the trial assembly base.
Once the panel hot correction is completed, the apparatus (A) is removed
and completed panel will be put back to its original position on trial assembly
to proceed for further works.
Normally panels (7) will be having transverse Bow (10), curved shape (9) at
longitudinal side shown in figure-4. This bow is measured by putting thread
on center of tube at both ends. In the middle of the panel the thread will not
be matching with center line of tube. That displacement from center will

calculate the bow (10). For correcting this type bow triangle type heating is
suggested to straighten the curved portion in the longitudinal side of panel.
After placing the panel (7) on the apparatus (A) triangle (8) is marked
roughly with chalk piece at middle of panel (7) on top and bottom both sides.
Triangle (8) size is approximately decided as per bow (10). If the bow (10) is
less than 15 mm one triangle (8) covering 8-9 tubes is heated. If the bow
(10) is more than 15mm and less than 20mm two triangles (8) will be
marked. If the bow (10) is more than 20 mm normally two three triangles (8)
will be marked with 1.5 to 2 m distance between them.
Heating is done on tubes and fin of the panel (7) covered inside the triangle
(8) at a red hot temp i.e 400°C to 500°C. Heating should always done from
the vertex of the triangle to the base of the triangle with the help of heating
torch (12). First tube-1 is heated at top followed by same tube heated at
bottom, then tube-2 is heated at top followed by heating tube-2 from
bottom. This process will be carried out till we heat the tube-9 at top and
bottom by using two nos of heating torch (12) simultaneously. Refer fig-5
and fig-6.
After completing the heating process panel (7) will be allowed to cool at
normal temperature. While cooling, the bow will be relieved and panel length
side will be straightened.

We Claim: -
1) An apparatus (A) for carrying out bow correction in panels (7) at trial
assembly of spiral water wall panels comprising:
a pipe (3) positioned vertically on a C channel frame (1) at first end of the
pipe (3) and the second end of the pipe (3) is fixed to a square plate (5) at
its center;
two angle stiffeners (4) are welded between pipe (3) and square plate (5) on
both sides of the pipe (3) for imparting strength to the assembly;
the C channel frame (1) placed over a trial assembly C channel base (6) and
locked by nuts and bolts (2);
the said assembly providing a stable square plate (5) surface which will act
as a support for keeping the panel (7) that are lifted by EOT crane and
placed over it, any adjustment for stability if required at this stage, is done by
to and fro movement of C channel frame (1) over C channel base (6) and
relocked again by nut-bolt (2) for further carrying out the main activity of
bow correction of panels (7).
2) The apparatus as claimed in claim 1 wherein one end of pipe (3) is welded
to the center of square plate (5).
3) The apparatus as claimed in claim 1 wherein the other end of pipe (3) is
welded at the center of C channel frame (1) so that the pipe (3) is held at
upright position.
4) A method of performing hot correction of bow in panels (7) by placing it
over a pair of apparatus (A) as claimed in claim 1 comprising:

lifting a panel (7) by an EOT crane and placing it over a pair of apparatus
(A);
sliding the pair of apparatuses with C channel frame (1) over C channel base
(6) so that the underside of panel (7) sits over the top surface of square
plate (5) in a stable manner;
locking the C channel frame (1) on C channel base (6);
measuring the bow (10) of panel (7) at center with the help of a thread;
marking a single triangle over the tube by a chalk covering 8-9 tubes if the
amount of bow is less than 15 m.m;
marking a double triangle over the tube by a chalk covering 8-9 tubes if the
bow is more than 15mm and less than 20mm;
marking a triple triangle over the tube if the amount of bow is more than 20
m.m and marked with 1.5 to 2.0-meter distance;
performing hot correction by heating each tube at 400°C to 500°C in a
sequence by taking first tube top and then bottom, then the second tube top
and bottom, then the third tube top and bottom and proceeding till the ninth
tube top and bottom heating is completed and then following up cooling the
tubes at normal temperature, thus by cooling, the transverse bow (10) will be
relieved and the panel length side will be straightened.
5) The method as claimed in claim (4) where the transverse bow (10) is
corrected and the curved shape (9) is straightened in longitudinal direction.