FIELD OF THE INVENTION
The present invention relates to a device and process for pre bending a wear bar
panel and welding of wear bars to the panel in one side to control distortion.
BACKGROUND OF THE INVENTION
Distortion is the perennial problem in any welded structures. The distortion
would results in many undesirable situations. It is known that the distortion
cannot be avoided but only minimized. That too, when the welds are placed on
one side, the problem becomes more complex. Once distortion has occurred, it is
common practice that one has to go for correction of distortion either
mechanically or thermally. Alternative method is to apply weld sequence to
control distortion so that the correction is minimum or avoided. In certain cases,
weld sequence alone cannot give desirable results. Hence weld sequence
coupled with other techniques are to be employed to control distortion.
US Patent Document US 7028882 describes a method for depositing an overlay
weld on a boiler tube panel comprising a plurality of tubes with adjacent tubes
joined together and then straightening the bow that occurs due to overlaying.
However, there is no device and process available to control distortion during the
weld sequence, so that no correction of distortion becomes necessary after
completion of the welding.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to provide a device for positioning the
wear bar panel in pre bent condition and welding of wear bars to the panel in
one side to control distortion.
Another object of the invention is to provide a device for positioning the wear
bar panel in pre bent condition and welding of wear bars to the panel in one side
to control distortion, which reduces the welder fatigue.
A still another object of the invention is to provide a process in a device for
positioning the wear bar panel in prebent condition and welding the wear bars to
the panel in one side to control distortion.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a device consisting of
support means that are made to a desired and pre calculated sizes. On the said
device a wear bar panel is positioned in pre bent condition so that the wear bars
on topside of each tube can be welded to achieve good control on distortion.
After placing the panel on the pre-bending device, suitable dead weights are
alternatingly added on either ends of the panel so that the panel is held in pre-
bent position.

According to a second aspect of the invention, there is provided a process for
pre-bending a wearing bar panel and welding of wear bars to the panel in one
side to control distortion. The process comprising a step of prebending a wear
bar panel and welding the wearing bars to the panel in one side to control
distortion, the method comprising the steps of providing a device of the
invention; placing the wear bar panel in a direction opposite to that of bending
direction likely to be caused by welding; alternatingly adding appropriate dead
weights on either side of the panel such that the panel is maintained on the
device in pre-bent position; carrying - out the welding according to pre-selected
weld-sequence; and removing the dead - weights after completion of welding.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The proposed invention will be better understood by the following description
with reference to the accompanying drawings:
Figure 1 Shows the front view of a conventional method of placing a wear
bar panel on the ground for welding.
Figure 2 Shows the side view of the conventional method of placing the
wear bar panel on the Ground for welding.
Figure 3 Shows a device according to the invention for positioning the
wear bar panel in pre bent condition.

Figure 4 Shows the wear bar panel positioned in the device of Fig. -3 in the
pre bent condition with dead weights, for welding the wear bars to
the panel.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
A wear bar panel (6) is a structure having several tubes connected together and
on each tube a rod (9) (called as wear bar) is welded on topside only, as shown
in Figure 1. The panel (6) is a one of the components used in boilers and the
wear bars (9) protect the panel (6) from damages likely to be caused by the
solid coal hitting from surroundings. In Figure 2, the side view of the wear bar
panel (6) is shown. But welding is a process, which produces distortion in the
structure. By the said conventional method of positioning the panel during
welding (as shown in Figures 1&2), the distortion is high, and thus calls for
rework to a larger extent.
The distortion is defined as change in shape and dimensions of the structure.
The distortion is caused by uneven expansion and contraction of the structure
during welding and results in unwanted consequences like affecting the load
carrying capacity, mismatching problem, correction involving cost, and loss of
aesthetics. These problems may result in rejection / un-necessary rework of the
panel.

While weld sequence is considered to be one of the methods of controlling
distortion, there are instances, where weld sequence alone cannot give desirable
results. In such circumstances, weld sequencing coupled with other techniques
for example, per setting / bending, welding from center to end, back step
welding etc. may be applied to get desired results.
This invention provides a device (5) for positioning a wear bar panel (6) in pre
bent condition and comprising: a plurality of supporting means (7) fabricated in
different shape and size, on which the wear bar panel (6) can be positioned in
bent condition prior to welding. The process involves positioning the panel (6)
on the supporting means (7) and alternatingly adding dead weights (8) on either
side of the panel (6), so that the panel (6) is held in pre-bent position on the
device (5). Then welding is carried out as per the designed sequence. After the
welding is completed the dead weights (8) on the panel (6) are removed.
The said device (5) has been designed and fabricated such a way that the wear
bar panel (6) can be placed in the direction opposite to that of bending likely to
be caused by welding. With this device (5), the welding of the wear bars (9) to
the panel (6) can be carried out with ease so that the welder fatigue is
minimized largely and the rework cost and rework time is reduced by way of
reduction in correction of distortion.
Figure 3 shows the prebending device (5) for keeping the wear bar panel (6)
prior to welding. There are at least (7) support means (7). Each support means
(7) is unique except in length and is fabricated with two horizontal channels (1,
2) and one vertical channel (3) to form an I-section. On top of the

I-section, a rod (4) is placed, so that the wear bar panel (6) after assembly of
wear bars (9), is placed smoothly in curved shape prior to welding.
The developed device makes it possible to position the wear bar panel (6) in pre
bent condition without any difficulty. After welding of the wear bars (9), the
dead weights (8) can be removed and the panel (6) can be set free.
The proposed invention as narrated herein above should not be read and
construed in a restrictive manner, as some modifications, adaptations and
alterations are possible within the scope and limit of the invention as defined in
the encompassed appended claims.

WE CLAIM
1. A device (5) for prebending a wear bar panel (6) and welding of wearing
bars (9) to the panel (6) in one side to control distortion, comprising a
plurality of support means (7) each having different heights, each support
means (7) configured by fabricating two horizontal channel (1,2) with at
least one vertical channel (3) to form an I-section, a rod (4) being fixedly
placed on top of the I-section such that the panel (6) after assembly with
a plurality of wear bars (9) can be smoothly placed in the curved shaped
device.
2. A process for pre-bending a wear bar panel (6) and welding of wearing
bars (9) to the panel (6) in one side to control distortion, the method
comprising the steps of:

- providing a device (5) as claimed in claim 1;
- placing the wear bar panel (6) in a direction opposite to that of bending
direction likely to be caused by welding;
- alternatingly adding dead weights (8) on either side of the panel such that
the panel (6) is maintained on the device in pre-bent position;
- carrying - out the welding according to pre-selected weld-sequence; and

- removing the dead - weights after completion of welding.
3. A device for prebending a wear bar panel and welding of wearing bars to
the panel in one side to control distortion as substantially described herein
and illustrated with reference to the accompanying drawing.
Dated this 31st Day of JULY 2008.

This invention relates to a device for positioning the wear bar panel in pre bent
condition and the device thereof comprising: the features of a pre-calculated, designed and fabricated supporting means on which the wear bar panel can be positioned. The process comprising of placement of panel in tack welded
condition, adding dead weight alternatively on either side to keep the panel pre-bent condition, application of weld sequence to minimize distortion. After positioning the welding of wear bars to the panel can be carried out with ease so that the welder fatigue is minimized largely and the rework cost and time is
reduced by way of reduction in correction of distortion.