FIELD OF INVENTION
The invention generally relates to removal of defective weld metal in the welding
of high thickness titanium tube to nipples in a header. More particularly, the
invention relates to a device for extension of power transmission and grinding
reach to remove defective metal in titanium tube to nipple welds. The invention
further relates to a process to remove defective metal in titanium tube to nipple
welds.
BACKGROUND OF THE INVENTION
In the manufacture of compact heat exchangers, the inlet and outlet headers are
connected together by means of tubes arranged in a particular configuration.
These connecting tubes form two concentric bundles, and involve a plurality of
titanium weld joints of smaller diameter tube-header nipple. These welded joints
formed in a sequential way, and spreaded in 3 pitch circle diameters over each
header, as shown in Figure 1.
Titanium is a reactive metal that interacts readily with oxygen, making it difficult
to weld. It requires meticulous preparation, skill, practice, extreme cleanliness
and shielding gas coverage, to carry out TIG welding. Added constraint being the
inadequate space-availability for handling/maneuverability of the welding torch
including placement of the purging gadget.
After carrying out the welding a non destructive examination (NDE) is carried out
for evaluation. This involves 100% visual inspection, radiography (RT), hydro
test and helium leak test. Any crack, lack of fusion (penetration), porosity on the
root or cap surface, is not permitted.

Making of 100% defect free weld joints in a first phase maintaining such
stringent acceptance standards, is almost impossible and rework of weld joint
becomes inevitable.
Rework essentially involves removal of weld metal in the first place. To remove
the weld metal, carbide burrs are only allowed. These carbide burrs require a
holding arrangement and a drive mechanism. Because of the bigger size of the
prior art drives and lack of maneuverability in a small space the available
grinding attachments can not be used.
Moreover this carbide burr with holding arrangement and drive mechanism need
to reach all well spots around the tube (360°) to remove the defective weld.
Carbide burr coupled with known pneumatic drives can not reach all the middle
row of tubes. Further, the inside part of the inner and outer rows of tubes can
not be accessed.
The known hand tools can not reach the spot due to limited space for entry. On
the other hand, removing titanium material using only manual force (with filing)
is not possible. Thus, a mechanised method needs to be employed for effective
weld metal removal. Apart from high speed of rotation of the tool, the weld
metal can be removed only by providing maneuverability and oscillating motion
to the drive. Hence a need exists to provide a power drive with an
extension/drive attachment to the carbide burr.

Further, there is a need to evolve a process for rework due to the problem of
constrained space, acceptance standard of weld joint and the nature of material.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a device for carrying out the
rework of Titanium tube to header nipple butt welding, which eliminates the
disadvantages of prior art.
A further object of the invention is to propose a process for carrying out rework
of Titanium tube to header nipple butt welding.
These and other objects and advantages of the invention will be apparent from
the ensuing description.
SUMMARY OF THE INVENTION
Accordingly, in a first aspect there is provided a device for extension of power
transmission and grinding reach to remove detective metal in titanium tube to
nipple welds, the device comprising a spindle having a length substantially equal
to cover a distance so as to accommodate at least one carbide burr at the distal
end, the proximal end of the spindle being attached to a pneumatic drive
enabled to provide a rotational movement to the spindle; at least two support
means each provided with a bearing supporting the spindle at two different

locations which ensures a smooth and vibration free rotation of the spindle; an
adapter having a first end and a second end, the second end being coupled to
the at least one collet means, the first end of the adapter comprising a threaded
end, and being connected to the distal end of the spindle the distal end having a
matching threaded portion; and the carbide burr comprising a shank being
releasably attached to the collet means.
In a second aspect, the invention provides a process to remove defective metal
in titanium tube to nipple welds, the method comprising the steps of providing a
pneumatic drive enabled to impart a rotational movement to an attachment;
selecting a spindle having a length substantially equal to a distance between the
pneumatic at least one carbide burr; rotatably connecting a proximal end of the
spindle to the pneumatic drive to allow the spindle to rotate corresponding to the
rotational movement of the drive; arranging at least two support means
bearingly supporting the spindle at two locations over the length of the spindle;
providing an adapter having two ends, the first end configured with a threaded
portion matching the threaded portion designed at a distal end of the spindle,
the adapter at a second end arranged with a coupling means; and connecting
the distal end of the spindle with the first end of the adapter, and coupling the
second end of the adapter with a shank of the at least one carbide burr.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure - 1 Shows location of the welded joints in a header.
Figure - 2 Schematically illustrates the device of the invention
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Figure -1 shows the locations of the welded joints between a tube (5) and a
nipple (6).
As shown in Figure 2, a grinding attachment is coupled to a pneumatic drive. At
the end of the pneumatic drive (1), a spindle (2) of required length is provided
for transmitting the drive (1). Any vibration to a carbide burr (4) results in
breakage of the burr (4) including damage to the weldment. It is therefore
essential that a smooth running of the spindle (2) is ensured during idle rotation
including operation. Accordingly, the spindle (2) bearingly supported at two
location to ensure vibration free smooth rotation.
From the spindle (2), the drive (1) is transmitted to the carbide burr (4). So the
end of the spindle (2) is threaded and coupled to an adopter (5). The adopter
(5) has got a collet means (3). This collet means (3) holds the shank of the
carbide burr (4) tightly.
With the grinding attachment, the drive (1) is transferred from the pneumatic
drive to the carbide burr without any vibration. Speed and stop/start is controlled
by means of a control means disposed on the pneumatic drive.

WE CLAIM
1. A device for extension of power transmission and grinding reach to
remove defective metal in titanium tube to nipple welds, the device
comprising:
- a spindle (2) having a length substantially equal to cover a distance so as
to accommodate at least one carbide burr (4) at the distal end, the
proximal end of the spindle (2) being attached to a pneumatic drive (1)
enabled to provide a rotational movement to the spindle (2);
- at least two support means each provided with a bearing which supports
the spindle (2) at two different locations to ensure a smooth and vibration
free rotation of the spindle (2);
- an adapter (5) having a first end and a second end, the second end being
coupled to the at least one collet means (3), the first end of the adapter
(5) comprising a threaded end, and being connected to the distal end of
the spindle (2), the distal end having a matching threaded portion; and
- the carbide burr (4) comprising a shank being releasably attached to the
collet means (3).
2. The device as claimed in claim 1, wherein the pneumatic drive (1)
comprises a control means to control the speed and on/off timings of the
drive.

3. A process to remove defective metal in titanium tube to nipple welds, the
method comprising the steps of:
- providing a pneumatic drive enabled to impart a rotational movement to
an attachment;
- selecting a spindle having a length substantially equal to a distance
between the pneumatic drive and an at least one carbide burr;
- rotatably connecting a proximal end of the spindle to the pneumatic drive
to allow the spindle to rotate corresponding to the rotational movement of
the drive;
- arranging at least two support means bearingly supporting the spindle at
two locations over the length of the spindle;
- providing an adapter having two ends, the first end configured with a first
threaded portion matching a second threaded portion designed at a distal
end of the spindle, the adapter at a second end arranged with a coupling
means; and
- connecting the distal end of the spindle with the first end of the adapter,
and coupling the second end of the adapter with a shank of the at least
one carbide burr.
4. A device for extension of power transmission and grinding reach to
remove defective metal in titanium tube to nipple welds, as substantially
herein described with reference to the accompanying drawings.
5. A process to remove defective metal in titanium tube to nipple welds, as
substantially herein described with reference to the accompanying
drawings.

The invention relates to a device for extension of power transmission and
grinding reach to remove defective metal in titanium tube to nipple welds, the
device comprising a spindle (2) having a length substantially equal to cover a
distance so as to accommodate at least one carbide burr (4) at the distal end,
the proximal end of the spindle (2) being attached to a pneumatic drive (1)
enabled to provide a rotational movement to the spindle (2); at least two support
means each provided with a bearing which supports the spindle (2) at two
different locations to ensure a smooth and vibration free rotation of the spindle
(2); an adapter (5) having a first end and a second end, the second end being
coupled to the at least one collet means (3), the first end of the adapter (5)
comprising a threaded end, and being connected to the distal end of the spindle
(2), the distal end having a matching threaded portion; and the carbide burr (4)
comprising a shank being releasably attached to the collet means (3).