Overview of Orbital Welding Technology

Overview of Orbital Welding Technology
IJISET - International Journal of Innovative Science, Engineering & Technology, Vol. 2 Issue 12, December 2015.
www.ijiset.com
ISSN 2348 – 7968
Overview of Orbital Welding Technology
Omkar Joshi1, Dr. Arunkumar2
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Department of Mechanical Engineering, University of Mumbai, VIVA Institute of Technology, Virar , 401305, India
Principal, Department of Mechanical Engineering, University of Mumbai, VIVA Institute of Technology, Virar , 401305, India
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omkarj589@gmaail.com
arunprod@rediffmail.com
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Abstract
There are different welding technologies on welding
in the market. The orbital welding technology is the
main topic of this paper. In this paper the history of
the orbital welding, the basic concepts of the orbital
welding, the problems related to the orbital welding
are described. With that the solutions for the
problems where suggested in the paper. The orbital
welding technique is changing from last decade but
still there are requirement of improvement in this
technique related to the quality of weld, efficiency,
the productivity, simplicity. The overview of this
technology considering all above factors is
considered in this paper.
1.Introduction
Orbital welding is the technology to weld the pipes or
tubes. In case of pipelines this technology is used at a
large scale as the pipeline having number of pipes
joined together. These pipelines may have chances of
leakages at their joints. These leakages may be
harmful if the pipelines are used for gas supply or
any harmful liquid supply like acid etc. through it.
Also the leakage may cause loss in the productivity.
To overcome these problems the welding technology
is required to improve. As the use of pipeline is
increasing day by day hence the requirement of
orbital welding is also increases.
Like the pipe welding the tube welding is also
become primary requirement of the industries now
days. In some industries there is mass production of
these tubes or pipes hence the increase I productivity
is need of the industries. For that the improvement in
the orbital welding is required now.
From last ten years orbital welding has gaining
popularity steadily; this is mainly found due to
semiconductor industry’s requirements for better gas
distribution systems. These systems encompassed all
the requirements of a critical system. Orbital welding
did not get its start in the semiconductor industry but
found its growth there. The time has come to apply
orbital welding technology to a broad range of
industries.
For orbital welding in many precision or high purity
applications, the base material, tube diameter(s), weld
joint and part fit-up requirements, shielding-gas type
and purity, arc length, and tungsten electrode type, tip
geometry, and surface condition may already be
written into a specification covering the specific
application. In addition, orbital-welding equipment
suppliers can offer recommendations on equipment
setup and use. For those applications where no
specification exists, the engineer responsible for
welding must create the welding setup and develop
the welding procedures.
Orbital welding uses the gas-tungsten arc-welding
(GTAW) process as the source of the electric arc that
melts the base material and forms the weld. During
GTAW an electric arc forms between a tungsten
electrode and the work piece. To initiate the arc, an
RF or high-voltage signal will ionize the shielding
gas to generate a path for the weld current. A
capacitor dumps current into the arc to reduce arc
voltage to a point where the power supply can
regulate. The power supply responds to the demand
and provides current to maintain the arc.
2.History of Orbital Welding
Orbital welding first found use in the 1960’s when
the aerospace industry recognized the need for a
superior joining technique for aircraft hydraulic lines.
The solution: a mechanism to rotate a welding arc
from a tungsten electrode around a tube-weld joint.
Regulating weld current with a control system
automated the entire process. The result was a more
precise, reliable method than manual welding. Orbital
welding became practical for many industries in the
early 1980’s with the development of portable
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IJISET - International Journal of Innovative Science, Engineering & Technology, Vol. 2 Issue 12, December 2015.
www.ijiset.com
ISSN 2348 – 7968
combination power supply/control systems that
operated from 110-V AC. Currently, typical
industries using orbital welding include aerospace;
food, dairy, and beverage; nuclear; offshore;
pharmaceutical;
and
semiconductor.
Other
applications include boiler tubing and tube and pipe
fittings, valves, and regulators. Modern orbital
welding systems offer computer controls that store
welding schedules in memory. The skills of a
certified welder are thus built into the system,
enabling the production of enormous numbers of
identical welds and leaving little room for error or
defects
between these two extremes, with the individual
processes varying somewhat in heat input. To
calculate the heat input for arc welding procedures,
the following formula can be used: where Q = heat
3.General Problem in Manual Welding
By considering manual metal arc welding process,
electric arc welding is based on providing an electric
circuit comprising the Electric current source the feed
and return path, the electrode and the work piece.
The arc welding process involves the creation of a
suitable small gap between the electrode and the
work piece. When the circuit is made a large current
flows and an arc is formed between the electrode and
the work piece. The resulting high temperatures
causing the work piece and the electrode to melt, the
electrode is consumable. It includes metal for the
weld, a coating which burns off to form gases which
shield the weld from the air and flux which combines
with the nitrides and oxide generated at the weld.
When the weld solidifies a crust is formed from the
impurities created in the weld process (Slag). This is
easily chipped away.
The blue area results from oxidation at a
corresponding temperature of 600 °F (316 °C). This
is an accurate way to identify temperature, but does
not represent the HAZ width. The HAZ is the narrow
area that immediately surrounds the welded base
metal.
The effects of welding on the material surrounding
the weld can be detrimental—depending on the
materials used and the heat input of the welding
process used, the HAZ can be of varying size and
strength. The thermal diffusivity of the base material
plays a large role—if the diffusivity is high, the
material cooling rate is high and the HAZ is
relatively small. Conversely, a low diffusivity leads
to slower cooling and a larger HAZ. The amount of
heat injected by the welding process plays an
important role as well, as processes like oxyacetylene
welding have an concentrated heat input and increase
the size of the HAZ. Processes like laser beam
welding give a highly concentrated, limited amount
of heat, resulting in a small HAZ. Arc welding falls
Fig.1. Heat-affected zone in Manual welding
input (kJ/mm), V = voltage (V), I = current (A), and
S = welding speed (mm/min). The efficiency is
dependent on the welding process used, with shielded
metal arc welding having a value of 0.75, gas metal
arc welding and submerged arc welding, 0.9, and gas
tungsten arc welding, 0.8.
3.1.Distortion and cracking
Welding methods that involve the melting of metal at
the site of the joint necessarily are prone to shrinkage
as the heated metal cools. Shrinkage, in turn, can
introduce residual stresses and both longitudinal and
rotational distortion. Distortion can pose a major
problem, since the final product is not the desired
shape. To alleviate rotational distortion, the work
pieces can be offset, so that the welding results in a
correctly shaped piece. Other methods of limiting
distortion, such as clamping the work pieces in place,
cause the buildup of residual stress in the heataffected zone of the base material. These stresses can
reduce the strength of the base material, and can lead
to catastrophic failure through cold cracking, as in the
case of several of the Liberty ships. Cold cracking is
limited to steels, and is associated with the formation
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IJISET - International Journal of Innovative Science, Engineering & Technology, Vol. 2 Issue 12, December 2015.
www.ijiset.com
ISSN 2348 – 7968
of martensite as the weld cools. The cracking occurs
in the heat-affected zone of the base material. To
reduce the amount of distortion and residual stresses,
the amount of heat input should be limited, and the
welding sequence used should not be from one end
directly to the other, but rather in segments. The other
type of cracking, hot cracking or solidification
cracking, can occur with all metals, and happens in
the fusion zone of a weld. To diminish the probability
of this type of cracking, excess material restraint
should be avoided, and a proper filler material should
be utilized.
4.Orbital Welding Process
The orbital welding was initially used to done by
manually. In manual welding welder either used to
weld the tube or pipe by rotating weld head or by
rotating tube and keeping weld head as it is. In this
process the time required to weld was more and also
that weld was not continuous. This process was the
process at the start but then the orbital welding
techniques where introduced.
around the weld joint to make the required weld. An
orbital welding system consists of a power supply
and an orbital weld head.
The power supply/control system supplies and
controls the welding parameters according to the
specific weld program created or recalled from
memory. This supply provides the control
parameters, the arc welding current, the power to
drive the motor in the weld head, and switches the
shield gas on/off as necessary.
Orbital weld heads are normally of the enclosed type,
and provide an inert atmosphere chamber that
surrounds the weld joint. Standard enclosed orbital
weld heads are practical I welding tube sizes from
1/16inch to 6 inches with wall thicknesses of up to
154 inches. Larger diameters and wall thicknesses
can be accommodated with open style weld heads.
For the orbital welding the process was introduced
where the weld head was steady and the pipes where
rotating. The positioners were made which were used
to hold the tubes together and to weld them. In this
technique the positioner hold the job and rotate in
3600 rotation with the speed controlled by feed
control unit. These positioners were semi-automatic
positioners.
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Fig.3. Modern Orbital Welding
5. The Importance of Orbital Welding
Fig.2. Positioner for orbital welding
In modern techniques the computers were used for
orbital welding. In the orbital welding process the
tubes or pipes are clamped in place and an orbital
weld heads rotates an electrode and electric arc
There is very much impotence of orbital welding
technology in the welding field. There are many
reasons for using orbital welding equipment. The
ability to make high quality, consistent welds
repeatedly, at a speed close to the maximum weld
speed, offer many benefits to the user:
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IJISET - International Journal of Innovative Science, Engineering & Technology, Vol. 2 Issue 12, December 2015.
www.ijiset.com
ISSN 2348 – 7968
5.1. Productivity.
An orbital welding system will drastically outperform
manual welders, many times paying for the cost of
the orbital equipment in a single job.
5.2. Quality.
The quality of a weld created by an orbital welding
system (with the correct weld program) will be
superior to that of manual welding. In applications
such as semiconductor or pharmaceutical tube
welding, orbital welding is the only means to reach
the weld quality requirements.
5.3. Consistency.
Once a weld program has been established, an orbital
welding system can repeatedly perform the same
weld hundreds of times, eliminating the normal
variability, inconsistencies, errors, and defects of
manual welding.
5.4. Skill level.
Certified welders are increasingly hard to find. With
orbital welding equipment, you don't need a certified
welding operator. All it takes is a skilled mechanic
with some weld training.
5.5. Versatility.
Orbital welding may be used in applications where a
tube or pipe to be welded cannot be rotated or where
rotation of the part is not practical. In addition, orbital
welding may be used in applications where access
space restrictions limit the physical size of the
welding device. Weld heads may be used in rows of
boiler tubing, where it would be difficult for a
manual welder to use a welding torch or view the
weld joint.
Many other reasons exist for the use of orbital
equipment over manual welding. For example,
applications where inspection of the internal weld is
not practical for each weld created. By making a
sample weld coupon that passes certification, the
logic holds that if the sample weld is acceptable, that
successive welds created by an automatic machine
with the same input parameters should also be sound.
Orbital welding uses the gas tungsten arc welding
(GTAW) process as the source of the electric arc that
melts the base material and forms the weld. In the
GTAW process, an electric arc in established
between a tungsten electrode and the part to be
welded.
6.1 Material Weldability
The material selected varies according to the
application and environment the tubing must survive.
The mechanical, thermal, stability, and corrosion
resistance requirements of the application dictate the
material chosen. For complex applications, a
significant amount of testing is necessary to ensure
the long-term suitability of the chosen material from
a functionality and cost standpoint.
6.2. Weld Joint Fit-up
Weld joint fit-up depends on the weld specification
requirements for tube straightness, weld concavity,
reinforcement, and drop-through. If no specification
exists, the molten material must flow and compensate
for tube mismatch and any gap in the weld joint.
6.3. Shield Gases
An inert gas is required on the tube OD and ID
during welding to prevent the molten material from
combining with the oxygen in the ambient
atmosphere. The objective of the welder should be to
create a weld that has zero heat tint at the weld zone.
6.4. Tungsten Electrodes
The tungsten welding electrode the source of the
welding arc is one of the most important elements of
the welding system that is commonly ignored by
welding system users. While no one would refute the
importance of the ignition device on an automobile
air bag, the rip cord for a parachute, or quality tires
for automobiles, the importance of tungsten
electrodes for quality welding is often overlooked.
7. Application of Orbital Welding
Orbital welding is having number of applications in
different fields. Their applications are increases day
by day now. Some of their applications are listed
below.
6. Basic Requirements in Orbital Welding
7.1. Aerospace
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IJISET - International Journal of Innovative Science, Engineering & Technology, Vol. 2 Issue 12, December 2015.
www.ijiset.com
ISSN 2348 – 7968
The aerospace industry was the first to recognize the
advantages of automated orbital welding. The high
pressure systems of a single aircraft can contain more
than 1,500 welded joints, all automatically created
with orbital equipment.
7.2. Boiler tube
Boiler-tube installation and repair offer perfect
applications for orbital welding. Compact orbital
weld heads can be clamped in place between rows of
heat-exchanger tubing.
7.3. Food, dairy and beverage industries
These industries require consistent full penetration
welds on all weld jonts. For maximum piping-system
efficiency, the tubing and tube welds must be as
smooth as possible. Any pit, crevice, crack, or
incomplete weld joint can trap the fluid flowing
inside the tubing, becoming a harbor for bacteria.
7.8. Tube/pipe
regulators
fittings,
valves,
and
Hydraulic lines, liquid- and gas delivery systems, and
medical systems all require tubing with termination
fittings. Orbital systems provide a means to ensure
high productivity of welding and optimum weld
quality.
8. Conclusion
Now a day’s competition in the production industries
is increases. The customers are demanding the
products having good/high quality. There are no
chances for defects now in the product. To sustain in
this competitive life there is a need of the change in
the production.
The nuclear industry, with its severe operating
environment and associated specifications for high
quality welds, has long been an advocate of orbital
welding.
Optimizing the welding process improves weld
quality; increases weld speed, and reduce scrap and
rework costs. By achieving these goals the companies
can realize the lower cost per product with a good
quality and minimum delivery time. Using the orbital
welding technique with computer programming the
control on the use of electrode, input material, shield
can etc. can be achieved easily.
7.5. Offshore applications
Referances
Sub-sea hydraulic lines use materials whose
properties can be altered during the thermal changes
that accompany a typical weld cycle. Hydraulic joints
welded with orbital equipment offer superior
corrosion resistance and mechanical properties.
[1] S. A. David, S. S. Babu and J. M Vitek, Advances
in Welding Science and Technology, Oak Ridge
National Laboratory, FEB 0 5, 1996
7.4. Nuclear piping
7.6. Pharmaceutical industry
Pharmaceutical process lines and piping systems
deliver high-quality water to their processes. This
requires high quality welds to ensure a source of
water from the tubes uncontaminated by bacteria,
rust, or other contaminant. Orbital welding ensures
full-penetration welds with no overheating that could
undermine the corrosion resistance of the final weld
zone.
7.7. Semiconductor industry
The semiconductor industry requires piping systems
with extremely smooth internal surface finish to
prevent contaminant buildup on the tubing wall or
weld joints. Once large enough, a build-up of
particulate, moisture, or contaminant could release
and ruin the batch process.
[2] Bernard Mannion, Jack Heinzman, Understanding
the basic principles behind orbital tube welding,
article published in issue of Flow Control, December
1999.
[3] D. Yapp and S. A. Blackman, Recent
Developments in High Productivity Pipeline
Welding, Journal of the Brazilian Society of
Mechanical Science & Engineering, Volume 26,
January-March 2004, pg 90,15
[4] Shigeru Ohkita, Hatsuhiko Oikawa, Latest
Advances and Future Prospects of Welding
Technologies, Nippon Steel Technical Report No. 95
January 2007, pg 3,6.
[5] Barbara K. Henon, Considerations for Orbital
Welding of Corrosion Resistant Materials to the
ASME Bioprocessing Equipment (BPE) Standard,
Presented on the Stainless Steel America Conference
2008
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ISSN 2348 – 7968
[6] P. Kah and J. Martikainen, Current Trends in
Welding Processes AndMaterials: Improve in
Effectiveness,
Lappeenranta
University
of
Technology, 28th September 2011, pg 196,197
[7] Zhang Yuea , Han Lia , Sun Tailib , Li Qidongb ,
Zhang Xichuanb, Automatic Control System of
Copper Pipe and Aluminum Pipe Butt Resistance
Welding Machine, Procedia Engineering, 2011, pg.
1,5.
[8] M. A. Bodude, I. Momohjimoh, Studies on
Effects of Welding Parameters on the Mechanical
Properties of Welded Low-Carbon Steel, Journal of
Minerals and Materials Characterization and
Engineering, Volume 3, 2015, pg. 142,153
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