Title of Invention

APPARATUS AND PROCESS OF WELDING OF FLAT FINS OF TUBES OF PANELS OF BOILER PLANT TO PRODUCE A BOILER TUBE ASSEMBLY

Abstract This invention relates to a process of welding of flat fins to tube of panels of boiler plant to produce a boiler tube assembly comprising the steps of longitudinal tack welding by stationary tubes (1) by conventional gas metal are welding (GMAW) to continuously fed flat steel fins (2) arranged between the tubes at the top side in down hand position of the tube and simultaneously welding the fin at the bottom side of the tube by pulsed GMAW procedure in the overhead position.
Full Text FILED OF INVENTION
The invention relates to an apparatus and process for the longitudinal welding of
tubes of flat sheets or fins, which serve the purpose of gas tight tube walls for
industrial and power station boiler plant. More particularly, the invention relates
to the process for the simultaneous longitudinal (GMA) gas metal arc welding of
tube to sheet (fin) panels using pulsed and conventional procedure.
BACKGROUND OF THE INVENTION
To produce industrial and power-station boiler plants, thousands of meters of
welded joints have to be made between the boiler wall tubes and flat steel fins
arranged in between. These so called tube walls form a large part of industrial
or power-station boilers. It is known that the conventional GMA (Gas Metal Arc)


Welding process in particular is used to weld such tube walls. The process is
distinguished by high deposition efficiency and a low frequency of defects.
However, so far the welding is being carried out normally in the so called gravity
position, i.e. in the horizontal plane. This means that hitherto welding always
had to be carried out in two passes during the welding of the boiler tube walls,
for the quality requirements call for substantial through welding between tube
and flat fin. In this arrangement, the welding head is fixed and the parts to be
joined are moved. The joints are thus welded first of all on both sides from
above in a first pass. Then the parts to be welded to one another are turned
and finish-welded at the remaining two sides in a second pass. But this
procedure necessitates a relatively high proportion of handling and welding time
in the entire fabrication process. Since the possibilities of increasing the welding
speed have in the meantime been exhausted, only the use of another welding
process is suitable for accelerating the entire process.
U.S. Patent No. 5,532,445 discloses an invention which claims by combined
oscillation GMAW being carried out on the underside at the same time as SAW is
carried out in a known manner on the top side and there by boiler tube walls can
be welded in a single operation, i.e. from above as well as simultaneously from
below (overhead position).


US Patent No. 6852945 relates to welding of boiler tube panel by making use of
laser combined with twin arc welding and discloses an apparatus and proves of
manufacturing of boiler tube to fin welding.
European Patent No. GB 1182927 relates to flanged steel pipe for use as boiler
tubes which is formed in two operations, the latter of which is by cold drawing,
through the cross-sectional reduction of the flange portions.
U.S. Patent No. 3999029 relates to slightly deforming the metal tubing to be
welded so that it assumes a slightly out of round or ovular configuration by
passing the tubing through ovalling rolls ahead of the welding station. Also,
ahead of the welding station but after the ovalling rolls, the fin or metal plate to
be welded to the tube is continuously fed into a position laterally adjacent to the
flattened side of the ova led tube. The ovaled tube and the metal fin or plate
are advanced in this configuration at the same rate of speed towards the welding
station. Sliding high frequency electrical power contacts are brought into contact
with both the advancing ovaled tube and the metal fin or plate slightly in
advance of the welding point. Rounding rolls or drawing dies are provided


adjacent to the welding point to bring the ovaled tube back into round. Also at
the welding point, means are provided to hold the metal fin or the plate so that
the rerounding of the tubes brings the tubes and the fin or plate into close
physical contact at the weld point, thereby providing the necessary welding
force. By means of such a method and apparatus the V-shaped gap necessary
for high frequency electrical welding is formed and the weld is made without
having to significantly deform the stiff metal strip, fin or plate.
European Patent GB 1182927 relates to the flanged steel tube for use as boiler
tubes is formed in two operations, the latter of which is by cold drawing, wherein
the cross-sectional reduction of the flange portions is greater than that of the
tube portion. A tube is passed three times between a plug and co-operating
roller dies, to form a flanged tube, which is given a further two passes between a
plug and co-operating roller dies, stepped to limit the metal flow. During the
final pass a plug is used having a diameter 1-5 mm. greater than that of the
plug used in the preceding pass.

-
Japanese Patent JP 4158921 relates to the tube being heated partially with the
high frequency heating of a heating device, it is formed with the prestage
forming roll, a fin part is formed by projecting the part to be worked to the
outside of the tube, and a rough steel tube with fin is made. Next, the fin part is
heated again with a re-heating device, it is subjected finish-forming for the
constant diameter with a sizing roll on a finishing device and the steel tube with
fin is formed.
European Patent GB 1204035 relates to welding by fusion for making heat
exchangers by SAW process using twin oscillating wires or strip as filler material.
European Patent KR 840001978B relates to a high-frequency current welder, in
which, the separated metal strips move continuously forward along their length
to the welding point at comparatively high speed.
US Patent 6,364,374 relates to methods and devices for joining two or more
panels together. The methods allow joining of panels of material such as glass
fiberboard, and are particularly useful for forming ducts or tubes. Fasteners
provided have two planar members, joined together, and the planar members
have protrusions that are integral to the planar members and intended to at least
partially protrude the panels joined by the devices.


US Patent 6,872,911 relates to a method for welding a first component part to a
second component part, the energy to melt melting regions being supplied by a
laser beam. In this context, the laser beam is directed through the first
component part, which is made of a non-absorbing material, to the second
component part. The second component part is made of a material which
strongly absorbs laser beam. At least one stop is provided outside melting
regions.
US Patent 7,028,882 relates to a process and apparatus for boiler tube panel
welding and straightening. An apparatus and process for depositing an Overlay
weld on a boiler tube panel comprising a plurality of tubes with adjacent tubes
joined together with membranes there between, and then straightening the
panel in response to bowing that occurs as a result of depositing the overlay
weld. The apparatus generally comprises an overlay welding apparatus that
deposits an overlay weld on a surface of a boiler tube panel, and a straightening
apparatus for straightening the panel following deposition of the overlay weld.
The straightening process entails placing the boiler tube panel between two
members, and pressing a portion of the panel there between.


All the above prior arts suffer from the difficulties that the processes and devices
are to go through involvement of costly implements and time consuming and
cumbersome process steps.
The present invention is aimed to remove the above difficulties of prior arts by
developing a simple process of welding of fins to boiler tubes and apparatus to
carry out the same.
DESCRIPTION OF THE INVENTION
It is an object of the invention to propose a simple cost effective and time saving
apparatus and process for simultaneous welding of boiler tube to fin from both
sides.
Another object of the invention is to provide an apparatus and process for
welding of boiler tube to fin, which is many fold productive.



A further object of the invention is to propose an apparatus and process for welding of
boiler tube to fin, which can be processed throughout the thickness of the tubes (i.e.
both the sides) without the problem of distortion and other quality problems.
These are other objects and advantages of the invention will be apparent from the
ensuing description.
SUMMARY OF THE INVENTION
The present invention is provided with a process of welding of flat fins to tube of panels
of boiler plant to produce a boiler tube assembly comprising the steps of longitudinal
tack welding of stationery tubes by conventional gas metal arc welding (GMAW) to
continuously fed flat steel fins arranged between the tubes at the topside in down hand
position of the tube and simultaneously welding the fin at the bottom side of the tube
by pulsed GMAW procedure in the overhead position.

DETAILED PECSRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
This invention relates to an apparatus for welding of flat fins to tubes of panels of boiler
plant to produce a boiler tube assembly comprising a support structure to keep the
boiler tubes longitudinally and in stationery positions, a GMW welding machine for
welding the fins at top side of the tube in down hand position and a pulsed GMA
welding machine to weld the fins simultaneously at the bottom side of the tube in
overhead position with the help of forehand welding torches.
In the proposed invention an apparatus and process for welding of boiler tube panel
has been developed which enables the tube and fin to be fed continuously and joining
of tube to fin is achieved by conventional GMAW (Gas Metal Arc Welding) in the down
hand position and pulsed GMAW in the overhead position from the bottom. The
advantages of the invention can be seen, inter alia, in the background that the boiler
tube walls can be welded in a single operation by employing PULSECON GMAW
procedure, i.e. instead of fusion welding in top and bottom side in two step operation or
by slower single pass welding. Consequently, an enormous time saving occurs as the
fabrication process is shortened by about less than 80%. Further, the capital
attachment required for


the apparatus of this welding process is minimum compared to other processes
and equipments involved with those. In this case, the job will be stationary and
the torches move with little offset to ensure proper penetration. This process is
economical as the weld can be carried out at a speed of 700 mm / min.
The proposed invention will be better understood from the following description
with reference to the accompanying drawing in which Figure 1 shows a typical
arrangement of the torches on the fins for welding and with arrangement of
tubes.
For the fabrication of gas-tight boiler-tube walls, the tubes (1) have to be welded
to flat steel fins (2) arranged in between. As shown in Figure 1, the fin is tack
welded to both sides of the tubes and kept stationary. The straightness of the
weld joint is ensured.

Welding is carried out with conventional GMAW (3) procedure at the top side i.e.
in down hand position. Simultaneously, the welding at the bottom side was
carried out using pulsed GMAW process (4) in the overhead position, at a rate of
700 mm / min, using the forehand technique. The same welding can be carried
out with multiple torches for welding on a series of tubes and fins assembly.
In the laboratory test a tube of dia. 51 x 3.6 mm thick and fins made of 6 mm
thick plates were tack welded. The tack-welded tubes were held on a shop
made fixture. Welding was carried out successfully at a speed of 700 mm / min.
A typical parameter is indicated below. Semi automated process was used, in
which, the torches moved and the job kept stationary.

The invention as narrated herein with an exemplary embodiment should not be
read in a restrictive manner as various adaptations, alterations and modifications
are possible within the teaching of the invention as defined in the appended
claims.

A further object of the invention is to propose an apparatus and process for welding of
boiler tube to fin, which can be processed throughout the thickness of the tubes (i.e. both
the sides) without the problem of distortion and other quality problems.
These are other objects and advantages of the invention will be apparent from the ensuing
description.
SUMMARY OF THE INVENTION
The present invention is provided with A process of welding of flat fins to tube of panels
of boiler plant to produce a boiler tube assembly comprising the step of placing the
tube longitudinally in stationery position by means of a support structure; and tack
welding both sides of fin to stationery tubes; and ensuring the proper straightness
alignment; characterised in that a combined effect of welding by conventional gas
metal arc welding to continuously fed flat steel fins at top side in down hand position
of the tube and simultaneously welding the fin at the bottom side of the tube by
pulsed GMAW process in the overhead position wherein the welding steps are carried
out at a speed of 700 mm/min and for both the GMAW and pulsed GMAW steps
shielding gas is maintained at 80% Ar + 20% CO2 wherein the other parameters of
welding in down hand position are maintained as gas flow rate LPM - 18-20,
Voltage V - 23-24, Current A - 185-190, Stick out - 15-20 to achieve required
penetration of welding as per specification.

WE CLAIM
1. A process of welding of flat fins to tube of panels of boiler plant to
produce a boiler tube assembly comprising the step of:
placing the tube longitudinally in stationery position by means of a
support structure;
tack welding both sides of fin to stationery tubes;
ensuring the proper straightness alignment;
characterized in that a combined effect of welding by conventional gas metal
arc welding to continuously fed flat steel fins at top side in down hand
position of the tube and simultaneously welding the fin at the bottom side of
the tube by pulsed GMAW process in the overhead position wherein the
welding steps are carried out at a speed of 700 mm/min and for both the
GMAW and pulsed GMAW steps shielding gas is maintained at 80% Ar +
20% CO2 wherein the other parameters of welding in down hand position are
maintained as gas flow rate LPM - 18-20, Voltage V - 23-24, Current A -
185-190, Stick out - 15-20 to achieve required penetration of welding as per
specification.
2. A process as claimed in the preceding claim wherein at the overhead
position other parameters of welding step are maintained as
gas flow rate LPM - 18-20
Voltage V - 21-22
Current A - 170-175
Stick out - 15-20,
to achieve required penetration of welding as per specification.
3. A process as claimed in the preceding claims wherein the welding
steps are carried out by parallel welding using multiple torches to produce a boiler
tube assembly.

4. A process as claimed in claim 1 wherein a tube of diameter 51 x 3.6
mm thick and fins of 6 mm thick plates are welded.
5. An apparatus for welding of flat fins to tubes of panels of boiler plant
to produce a boiler tube assembly as claimed in claim 1 comprising a
support structure to keep the boiler tubes longitudinally and in
stationery positions, a GWW welding machine for welding the fins at
top side of the tube in down hand position and a pulsed GMA
welding machine to weld the fins simultaneously at the bottom side
of the tube in overhead position with the help of forehand welding
torches.
6. A process of welding of flat fins to tubes of panels of boiler plant to
produce a boiler tube assembly as herein described.


This invention relates to a process of welding of flat fins to tube of panels of
boiler plant to produce a boiler tube assembly comprising the steps of
longitudinal tack welding by stationary tubes (1) by conventional gas metal are
welding (GMAW) to continuously fed flat steel fins (2) arranged between the
tubes at the top side in down hand position of the tube and simultaneously
welding the fin at the bottom side of the tube by pulsed GMAW procedure in the
overhead position.

Documents:

00283-kol-2007 correspondence-1.1.pdf

00283-kol-2007 form-18.pdf

0283-kol-2007 abstract.pdf

0283-kol-2007 assignment.pdf

0283-kol-2007 claims.pdf

0283-kol-2007 correspondence others.pdf

0283-kol-2007 description(complete).pdf

0283-kol-2007 drawings.pdf

0283-kol-2007 form-1.pdf

0283-kol-2007 form-2.pdf

0283-kol-2007 form-3.pdf

283-KOL-2007-ABSTRACT.pdf

283-kol-2007-amanded claims 1.1.pdf

283-KOL-2007-AMANDED CLAIMS.pdf

283-KOL-2007-CANCELLED PAGES.pdf

283-kol-2007-correspondence 1.1.pdf

283-KOL-2007-CORRESPONDENCE.1.3.pdf

283-kol-2007-correspondence.pdf

283-KOL-2007-DESCRIPTION (COMPLETE).pdf

283-KOL-2007-EXAMINATION REPORT.1.3.pdf

283-kol-2007-examination report.pdf

283-KOL-2007-FORM 1.pdf

283-KOL-2007-FORM 18.1.3.pdf

283-kol-2007-form 18.pdf

283-KOL-2007-FORM 2.pdf

283-KOL-2007-FORM 3.1.3.pdf

283-kol-2007-form 3.pdf

283-KOL-2007-FORM-27.pdf

283-KOL-2007-GPA.1.3.pdf

283-kol-2007-gpa.pdf

283-kol-2007-granted-abstract.pdf

283-kol-2007-granted-claims.pdf

283-kol-2007-granted-description (complete).pdf

283-kol-2007-granted-drawings.pdf

283-kol-2007-granted-form 1.pdf

283-kol-2007-granted-form 2.pdf

283-KOL-2007-GRANTED-LETTER PATENT.pdf

283-kol-2007-granted-specification.pdf

283-kol-2007-others.pdf

283-KOL-2007-REPLY TO EXAMINATION REPORT.1.3.pdf

283-KOL-2007-REPLY TO EXAMINATION REPORT.pdf

283-kol-2007-reply to examination report1.1.pdf

Abstract.jpg


Patent Number 248132
Indian Patent Application Number 283/KOL/2007
PG Journal Number 25/2011
Publication Date 24-Jun-2011
Grant Date 20-Jun-2011
Date of Filing 26-Feb-2007
Name of Patentee BHARAT HEAVY ELECTRICALS LIMITED
Applicant Address REGIONAL OPERATIONS DIVISION (ROD), PLOT NO: 9/1, DJBLOCK 3RD FLOOR, KARUNAMOYEE, SALT LAKE CITY, KOLKATA-700091, HAVING ITS REGISTERED OFFICE AT BHEL HOUSE, SIRI FORT, NEW DELHI-110049, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 RAJASEKARAN, NAINIAPPAN BHARAT HEAVY ELECTRICALS LIMITED, CORPORATE RESEARCH AND DEVELOPMENT, VIKASNAGAR, HYDERABAD-500 093
2 ROHIRA, KANHAIYALAL BHARAT HEAVY ELECTRICALS LIMITED, CORPORATE RESEARCH AND DEVELOPMENT, VIKASNAGAR, HYDERABAD-500 093
3 UMA SHANKER, GANAPATHI BHARAT HEAVY ELECTRICALS LIMITED, CORPORATE RESEARCH AND DEVELOPMENT, VIKASNAGAR, HYDERABAD-500 093
4 ASOKKUMAR, KALIDASS BHARAT HEAVY ELECTRICALS LIMITED, CORPORATE RESEARCH AND DEVELOPMENT, VIKASNAGAR, HYDERABAD-500 093
PCT International Classification Number B23K 9/173
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA