Underwater welding, first introduced by the British Admiralty, is a crucial method for repairing structures beneath water, utilizing electrical arcs for joining metals. The process includes wet welding, performed directly in water, and dry welding, which occurs in a controlled gas environment. Despite its efficiency and necessity for high-pressure applications, underwater welding poses risks such as electric shock and gas explosions, requiring strict safety precautions.

1. UNDERWATER WELDING
Presented by,
Lara fedrick.S, Vikas.P.S,
Indra Ganesan College Of Engineering,
Trichy-12.
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2. Introduction
 The fact that electric arc could operate was known for over
a 100 years
 The first ever underwater welding was carried out by
British Admiralty – Dockyard for sealing leaking ship
rivets below the water line.
 In 1946, special waterproof electrodes were developed in
Holland by ‘Van der Willingen’.
 Any repair method under the sea will require the use of
underwater welding.
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3. WELDING
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4. What is welding
 Welding is a process for joining two similar or dissimilar metals
by fusion.
 It joins different materials / alloys with or without the application
of pressure and with or without the use of filler metal.
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5. Necessity of underwater welding
 To provide a permanent joining between two metals inside
present under the water
 High pressure pipe lines cannot be joint using temporary fasteners
such as bolts and nuts. Hence welding is compulsory in high
pressure pipe linings.
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6. Principle
 The work to be welded is connected to one side of an electric circuit
by means of a cable. A flux-coated electrode is attached to a holder,
also connected via cable, both being attached to a power source.
 When the electrode makes contact with the work, an electrical
contact is made. The electric current jumps the gap and create a
spark (arc), which melts the base metal and the covering of the
electrode forming a common weld puddle.
 Complete insulation of the cable and hoses is essential in case to
prevent the chance for electric shock.
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7. Arrangement of
underwater welding
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8. Schematic diagram of
Underwater welding
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9. Requirements of
Underwater welding
 Power converters.
 Welding Generator, Pre-Setup
 Polarity.
 Gas Manifolds.
 Welding Generator Amperage and Voltage settings.
Underwater Oxygen-Arc Welding Torches
 Collet or grip
 Oxygen valve
 Flash arrester
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10. Classification
Wet welding Dry welding
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11. Wet welding
 Wet Welding indicates that welding is performed underwater,
directly exposed to the wet environment. It similar used as
ordinary air welding
 In this process we using special electrodes which is made of
copper coated , carbon/graphite electrodes.
 Welding power supply is located on the surface with connection
to the diver/welder via cables and hoses
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12. power Supply used : DC
Polarity : -ve polarity
 The power source should be a direct current machine rated at
300 or 400 Amps
 We must connect the polarity as a negative supply. If we connect dc supply
as a positive polarity electrolysis will occur and it causes rapid deterioration
on metallic components. 12

13. Figures of wet welding
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14. Advantages
 It is economical and fastest
method
 It has a high tensile strength
 Ease to access the weld spot
 Less time consumption for
welding
Disadvantages
 Poor visibility in water
during process
 It reduce the ductility and
impact strength of welded
material.
 It increase the hydrogen
embrittlement
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15. Dry welding
 In dry welding dry environment is made possible by
encompassing the area to be welded.
 The chamber is placed near the structure where to be weld.
 The chamber is filled with a gas (commonly helium containing
0.5 bar of oxygen) at the prevailing pressure
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16. There are two types of dry welding:
Large habitat
Mini habitat 16

17. Large habitat Mini habitat
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18. Advantages
 Welder/diver is safety
 Good quality weld
 Surface monitoring
 Non destructive testing
Disadvantages
 Highly cost equipment.
 Skilled labour required.
 We can’t weld unreachable
spot
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19. Developments of
underwater welding
 Wet welding has been used as an underwater welding technique
for a long time and is still being used.
 With recent acceleration in the construction of offshore structures
underwater welding has assumed increased importance.
 With recent acceleration in the construction of offshore structures
underwater welding has assumed increased importance.
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20. Risks & precaution
 Risk of electric shock so achieving electrical insulation of
electrical welding equipment's
 Hydrogen and oxygen are produced by the arc in wet welding are
potentially explosion so precaution must be taken to avoid the
build up of pockets of gas
 The life of the welder will be risk from nitrogen introduced into
the blood stream, precaution include the provision of an
emergency air gas supply 20

21. Application
 Offshore construction for tapping sea source
 Temporary repair work caused by ship collision, unexpected
accident
 Maintenance of ships
 Pipelines and Tunnels
 Oil refineries
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22. CONCLUSION
 Thus underwater welding facilities creating
permnant joint in a deep sea in effective way though
it may affect underwater welding habitats further
modification of developments in process can
improve effectiveness of underwater welding.
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23. References
 1) D. J Keats, Manual on Wet Welding.
 2) Annon, Recent advances in dry underwater pipeline welding,
Welding Engineer, 1974.
 3) Lythall, Gibson, Dry Hyperbaric underwater welding, Welding
Institute.
 4) W.Lucas, International conference on computer technology in
welding.
 5) Stepath M. D, Underwater welding and cutting yields slowly to
research, Welding Engineer, April 1973.
 6) Silva, Hazlett, Underwater welding with iron – powder
electrodes, Welding Journal, 1971
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24. Thank you
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