FIELD OF THE INVENTION
The invention relates to a semi-mechanized process of cleaning tubes in a
procedure of titanium tube to tube butt welding.
The invention further relates to a cleaning device for producing a defect-free butt
weld joint in titanium tube to tube welding procedure.
BACKGROUND OF THE INVENTION
During manufacturing of vertical shell and tube once through steam generators,
the tube portion is made up of helically wound coils of titanium. For making coils
of required length, in the stage prior to coiling stage, longer tubes. For example,
12 to 14m (approx) length are required. Accordingly, standard tubes are joined
by tube to tube butt welding. It may be necessary to have more than one butt
joint which are welded by automatic TIG welding machine.
Metal joining of Titanium material (tube to tube) is a very critical operation and
cleaning plays a very vital and critical role in this process to achieve Quality
welds. Cleaning process needs to cover the outer diameter, inner diameter
surfaces of the joining tubes, the welding apparatus, welding electrode and
welding consumable filler, the measuring devices and finally environmental
cleaning.

Thus, welding is carried out in a protected environment maintained with a
controlled humidity of 60 to 70% RH (relative humidity). High pure Argon gas of
99.998% purity is used as the shielding gas to provide three types of shielding -
viz shielding through tube inner diameter side called root shielding, torch
shielding on outer diameter side of the tube, and a trail shielding for the
completed weld portion. The weld joint details are shown in Figure 1. Welding is
done in down hand position (on outer diameter side of the tube fusing full tube
thickness) in the automatic TIG welding machine by rotating the butting tubes
together (360 degree rotation).
In the prior art process of titanium tube to tube welding, the tubes were cleaned
on their outer diameter side and on their inner diameter side manually by
blowing Argon gas through the tubes and by manual cleaning of tube ends closer
to the joints. For the tube inner side cleaning, cloth wound rods of shorter length
was passed through a short length of the tube (closer to the joint) to clean the
dust and dirt from the tube inner Diameter surfaces. Then, ethanol - spirit -
soaked cloth wound on the rod was manually passed to make further cleaning.
Final cleaning was done by cloth wound on the rod. This cloth cleaning and
spirit soaked cloth cleaning continued many times by changing over to fresh
cloth after every pass. When a spirit soaked cloth was no further picking-up soil,
and notified to be in stain-free condition, the cleaning stage was declared to be
satisfactory and final verification of cleaning was done using a fresh cloth, and
welding commenced. To improve the cleaning extent, consistency and
thoroughness, prior art then attempted a manual cleaning of the full titanium
tube length. It was found to be very tedious and also consistent results were not
obtained after cleaning. Titanium being a critical material, such inconsistencies

showed up as weld defects with visually - oxidized coloration on inner Diameter
surfaces when the tube joints were examined after cutting to smaller ring
shapes closer to joint (when the procedure was under finalization) or defects like
porosity in radiographic examination. An oxidized layer is disallowed due to
possibility of embrittlement and impairment of mechanical properties of the weld
joints. Further, during welding of a second layer over the first layer of oxidized
weld, there is a high possibility of developing cracks in the weldment.
According to the practice and standard, a bright silver colour represents a Quality
and clean weld which is free from oxidization. A golden colour of the weld
represents a slight oxidization and can be acceptably removed by emery paper
before proceeding for further welding. A grey colour and a white colour of the
weldment each indicates a heavily oxidized layer, which is not acceptable. The
colouration and defects result from ineffective cleaning, especially on the tube's
inner diameter side.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a semi-mechanized process
of cleaning tubes in titanium tube to tube butt welding procedure.
Another object of the invention is to propose a cleaning device for producing a
defect-free butt weld joint in titanium tube to tube welding procedure.

SUMMARY OF THE INVENTION
Accordingly, there is provided in one aspect of the invention a semi-mechanized
process of cleaning tubes in titanium tube to tube butt welding procedure, the
process comprising the steps of mechanically cleaning the inside and outside
surface of a titanium tube; providing a mechanized cleaning device having at
least a cleaning tool, a body, a plurality of guides, a pneumatic gun enabled to
transmit rotational and axial thrust on the cleaning tool to traverse over the
entire length of the tube; and a pair of clamping screw to hold the tube on the
device; disposing a spirit-soaked cloth in a slot configured on the cleaning tool;
clamping the tube with the device body by said screws; attaching a first end of
the cleaning tool to the pneumatic gun; activating a compressed air/gas source
to operate the pneumatic gun; moving the cleaning tool axially and rotatably
along the entire length the tube surface to clean; and repeating the mechanized
cleaning step till wipe test of the spirit soaked cloth indicates an acceptable
result.
In another aspect of the invention, there is provided a cleaning device for
producing a defect - free butt weld joint in titanium tube to tube welding
procedure comprising a body having holes configured at a distal end; a pair of
clamping screw to hold a tube to be cleaned at the distal end of the body
through said holes; a cleaning tool having at least one slot to hold soaked cloth;
a plurality of guides having slots corresponding to the slots of the cleaning tool
for guiding the tool during its axial and/or rotational movement; and a pneumatic
gun activable upon external supply of compressed air/gas for providing force to
the cleaning tool.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a generic view of weld joints details in a titanium tube to tube
welding procedure.
Figure 2 - shows photographic views of a titanium weldment without defect
(oxidation), and weldments with various degree of contamination and
oxidization.
Figure 3 - shows a mechanized cleaning device according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
Initially, both inside and outside surfaces are cleaned (overall general cleaning)
using lint free cloth manually. For inside cleaning, cloth balls are pushed using
Argon gas from one end to the other. Then, a long rod covered with cloth is
pushed al through the tube. To enhance the efficiency of the root to pick-up
grease and oil, the cloth used in this cleaning process is soaked with spirit
(Ethanol) and the solvent cleans the tube in a still better manner. Then, a
mechanized cleaning with the inventive device is carried-out.
As shown in figure 3, the mechanized cleaning device of the invention comprises
a body (2) with clamping screws (6) to hold a tube (1) to be cleaned in position,
the plurality of guides (3) with holes at the center keep a cleaning tool (4)

straight while cleaning; and a pneumatic gun (5). The supports are provided to
keep center of body the (2) and the center of holes in the guides (3) in line for
welding.
The compressed air or nitrogen (taken from cylinders) drives the pneumatic
gun (5) and the driven gun (5) comprises a cleaning tool (4) at its end as shown.
While operating the gun (5), the cleaning tool (4) rotates and moves forward
within the tube (1) (for full tube length) and the cloth connected to the
attachment (with spirit) cleans the inner diameter of the tube (1). The device
ensures cleaning of inner diameter of the tube (1) thorough a complete and
consistent cleaning of the inner diameter surfaces with the help of spirit soaked
lint free cloth (tied at the attachment) during its complete helical movement
inside the tube (1) (touching the full inner diameter surface).
After ensuring the first stage of cleaning of the tube surface (on Outer Diameter
side and Inner Diameter side), the tube ends are welded and pickled (as per
welding process requirement). Up to 50 mm from the edge preparation end of
the weld, the pickling is done. After pickling, the tubes (1) are moved to the
area where welding activity is planned. Temperature and humidity are controlled
in the welding area to maintain a dry atmosphere suitable for welding. Also,
thorough cleanliness of components, jobs, fixtures, and machines are maintained
in these areas based on periodic cleaning.
Once again, in the welding area, using spirit (Ethanol) the Inner Diameter
surface of the tubes and Outer Diameter surface of tubes are thoroughly
cleaned,

using the innovative device. After ensuring a complete and thorough cleanliness
of the tubes (1) on Outer Diameter and Inner Diameter sides based on two
consecutive spirit soaked lint free cloth wipe tests (for Outer Diameter) and
spirit soaked lint free cloth ball passage tests (for Inner Diameter), welding
clearance is given.
OPERATIONAL STEPS OF THE CLEANING DEVICE
1. Assemble the cleaning tool (4) through the holes in the guides (3).
2. Keep spirit soaked cloth in a slot of the cleaning tool (4) and wrap it.
Push the tool (4) into the Inner Diameter of the tube (1) tightly for
cleaning.
3. Clamp the body (2) of the cleaning device with the tube (1) by using
Clamping screw (6).
4. Attach other end of the cleaning tool (4) with pneumatic gun (5)
operated by compressed air/nitrogen.
5. Move the cleaning tool (4) forward and backward including rotating
through the gun (5) to clean the full length.
6. By this method, cleaning process is mechanized and contaminant free
inner surface of the tube is achieved consistently.

WE CLAIM:
1. A semi-mechanized process of cleaning tubes in a procedure of titanium
tube to tube butt welding , the process comprising the steps of:
- manually cleaning the inside and outside surface of a titanium tube;
- providing a mechanized cleaning device having at least a cleaning tool, a
body; a plurality of guides, a pneumatic gun enabled to transmit rotational
and axial thrust on the cleaning tool to traverse over the entire length of
the tube; and a pair of clamping screw to hold the tube on the device;
- disposing a spirit-soaked cloth in a slot configured on the cleaning tool;
- clamping the tube with the device body by said screws;
- attaching a first end of the cleaning tool to the pneumatic gun;
- activating a compressed air/gas source to operate the pneumatic gun;
- moving the cleaning tool axially and rotatably along the entire length of
the tube surface to clean; and
- repeating the mechanized cleaning step till wipe test of the spirit soaked
cloth indicates an acceptable result.
2. A cleaning device for producing a defect-free butt weld joint in titanium
tube to tube welding procedure comprising :
- a body having holes configured at a distal end;
- a pair of clamping screw to hold a tube to be cleaned at the distal end of
the body through said holes;
- a cleaning tool having at least one slot to hold soaked cloth;

- a plurality of guides having slots corresponding to the slots of the cleaning
tool for guiding the tool during its axial and/or rotational movement; and
- a pneumatic gun activable upon external supply of compressed air/gas for
providing force to the cleaning tool.

The invention relates to a semi-mechanized process of cleaning tubes in a
procedure of titanium tube to tube butt welding, the process comprising the
steps of manually cleaning the inside and outside surface of a titanium tube;
providing a mechanized cleaning device having at least a cleaning tool, a body; a
plurality of guides, a pneumatic gun enabled to transmit rotational and axial
thrust on the cleaning tool to traverse over the entire length of the tube; and a
pair of clamping screw to hold the tube on the device; disposing a spirit-soaked
cloth in a slot configured on the cleaning tool; clamping the tube with the device
body by said screws; attaching a first end of the cleaning tool to the pneumatic
gun; activating a compressed air/gas source to operate the pneumatic gun;
moving the cleaning tool axially and rotatably along the entire length of the tube
surface to clean; and repeating the mechanized cleaning step till wipe test of the
spirit soaked cloth indicates an acceptable result.