Underwater-Welding manufacture procesess .pp.pptx

UNDERWATER WELDING
Presented by
RAVINDHER GAJA
CBIT
• Saturday, March 22, 2025
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Outline
• Importance Of Underwater Welding
• Principle Of Operation
• Classification
• Wet/Dry Underwater Welding
• Advantages& Disadvantages
• Risk Involved & Safety
• Applications
• Future Scope
• References
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Saturday, March 22,
2025
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what is an Under water welding???
Many of us won't have heard of under water welding but it's
actually a very important thing in many industries. Underwater
welding includes a lot of different processes that join steel on
offshore oil platforms, pipelines & ships etc. under water. At
present, underwater welding becomes more sophisticated and
can be done deeper. GTAW has been used to weld pipes at depths
of 200 ft (61 m)

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Principle of Operation
_
Power Supply
- +
work
Knife switch
electrode
Waterproof Electrode
Holder
• The welding circuit must include a positive type of switch,
usually a knife switch operated on the surface and commanded
by the welder and is used for safety reasons.
• When DC is used with +ve polarity, electrolysis will take place
and cause rapid deterioration of any metallic components in the
electrode holder.
• For wet welding AC is not used on account of electrical safety
and difficulty in maintaining an arc underwater

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Underwater welding is classified into two
categories
1.Welding in-the-wet environment
2.Welding in-the-dry environment
Dry welding Wet welding

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 As the name implies, underwater wet welding is done
in an environment where the base metal and the arc
are surrounded entirely by water. In wet welding MMA
(manual metal arc welding) is used.
Welding in the wet environment
A special electrode is used and
welding is carried out manually
just as one does in open air
welding.
The increased freedom of
movement makes wet welding the
most effective, efficient and
economical method.
 Welding power supply is located
on the surface with connection to
the diver/welder via cables

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Advantages
• cheapest and fastest method
• tensile strength is high
• easy of access the weld spot
• no habitat, no construction,
• no waste of time
Disadvantages
• Rapid quenching decreases impact
strength, ductility
• Hydrogen embrittlement,cracks
• Poor visibility in water

Hyperbaric(dry) welding
 Hyperbaric welding is a welding in which a chamber is
sealed around the structure to be welded and is filled with
breathable gas(commonly helium containing 0.5 bar of
oxygen) at the prevailing pressure. at which the welding
is to take place. This method produces high-quality weld
joints
 The gas tungsten arc welding process is employed for
this process. The area under the floor of the Habitat is
open to water. Thus the welding is done in the dry but at
the hydrostatic pressure of the sea water surrounding the
Habitat
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Dry welding
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Advantages of Dry welding
• Welder/diver safety
• Good quality welds
• Surface monitoring
• Non destructive testing
Disadvantages
• Higher cost of process,training,etc.,.
• Large quantity of costly and complex
equipments.
• More deep,more energy is required
• Can’t be weld,if weld spot is at
unreachable places

Risk Involved & safety
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 Electric shock Explosion.
 Precautions include achieving adequate electrical insulation of the welding
equipment, shutting off the electricity supply immediately the arc is
extinguished, and limiting the open-circuit voltage of MMA (SMA) welding sets
 Hydrogen and Oxygen are produced during welding.
 Precautions must be taken to avoid the build-up of pockets of gas, which are
potentially explosive
 risk is to the life or health of the welder/diver from nitrogen
introduced into the blood steam during exposure to air at increased
pressure.
 Precautions include the provision of an emergency air or gas supply, stand-by
divers, and decompression chambers to avoid nitrogen
 Inspection of welds.

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• Application of Underwater
Welding
• Offshore construction for tapping sea
resources,
• Temporary repair work caused by
ship’s collisions or unexpected
accidents.
• Salvaging vessels sunk in the sea
• Repair and maintenance of ships
• Construction of large ships beyond
the capacity of existing docks.

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• Scope for further developments
• Wet MMA is still being used for underwater
repairs, but the quality of wet welds is poor
and are prone to hydrogen cracking. Dry
Hyperbaric welds are better in quality than wet
welds. Present trend is towards automation.
THOR – 1 (TIG Hyperbaric Orbital Robot) is
developed where diver performs pipefitting,.
• Developments of driverless Hyperbaric
welding system is an even greater challenge
in developments like pipe preparation and
aligning, automatic electrode.
• This is in testing stage in deep waters.
Explosive and friction welding are also to be
tested in deep waters.
Friction welding (FRW)

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REFERENCE
 Underwater Welding –Present Status And Future
Scope.Jyotsna Dutta Majumdar.Department Of
Metallurgical And Materials Engineering, Indian Institute
Of Technology, Kharagpur, West Bengal, India
 Underwater Welding Amit Mukund Joshi (Mechanical
Engineer) ,Junior Research Fellow Mechanical
Engineering Department ,Indian Institute Of
Technology ,I.I.T – Bombay
 Annon, Recent Advances In Dry Underwater Pipeline
Welding, Welding Engineer, 1974.
 Lythall, Gibson, Dry Hyperbaric Underwater Welding,
Welding Institute.

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THANK YOU

Underwater-Welding manufacture procesess .pp.pptx

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