This document discusses various methods of underwater welding. It begins by classifying underwater welding into dry welding and wet welding. Dry welding involves welding inside a chamber that is sealed around the structure, while wet welding is performed directly under water. The document then describes the processes and equipment used for dry welding methods like hyperbaric and cavity welding. It also covers the principles, advantages, and disadvantages of wet welding. The document concludes by discussing applications of underwater welding, the effects of the wet environment on welds, and providing a graph showing the relationship between porosity and water pressure during welding.

1. 1
Study of Various Methods and
Parameters Involved in
Underwater Welding
Subject Code-ME1637
Under the guidance of:
Dr. A K Das
Presented By:
Abhishek Jain
1201076
Department of Mechanical Engineering
National Institute of Technology Patna

2. Contents
 Introduction
 Classification
 Wet Welding
 Dry Welding
 Advantages
 Disadvantages
 Schematic Diagram of Apparatus Required
 Risks
 Applications
 Effect of Wet environment on welds
 Porosity Curve
 References
2

3. INTRODUCTION TO
UNDERWATER WELDING
3

4. How can big ships or underwater Rigs be repaired ????
We can’t lift ships and then repair them.
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5. INTRODUCTION
 Underwater welding is an important tool for underwater
fabrication works.
 In 1946, special waterproof electrodes were developed
in Holland by ‘Vander Willingen'’.
 In recent years the number of offshore structures
including oil drilling rigs, pipelines, platforms are being
installed significantly.
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6. CLASSIFICATION
• Under water welding can be classified as :
i. Dry welding
ii. Wet welding
6

7. DRY WELDING
 A chamber is created near the area to be welded and
the welder does the job by staying inside the chamber.
 It produces high quality weld joints .
 The gas-tungsten arc welding process is used mostly for
pipe works
 Gas metal arc welding is the best process for this
welding.
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8. 8
CLASSIFICATION OF
DRY WELDING
There are two basic types of dry
welding :
i. Hyperbaric welding
ii. Cavity welding

9. Hyper baric welding:-
 It is carried out in
chamber sealed
around the structure to
be welded filled with a
gas to push water back.
 Gas generally used is a
breathable mixture of
helium and oxygen.
 The area under the floor
of the habitat is open to
water, so hyper baric
welding is termed as
“HABITAT-WELDING”
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An image for Habitat Welding

10. 10
Hyper = High, Baric = Pressure
Hyper Baric welding means high Pressure Welding

11. Cavity welding:-
 Cavity welding is another approach to weld in
water free environment.
 Conventional arrangements for feeding wire and
shielding gas
 Introducing cavity gas and the whole is surrounded
by a trumpet shaped nozzle through which high
velocity conical jet of water passes.
 It avoids the need for a habitat chamber and it
lends itself to automatic and remote control.
 The process is very suitable for flat structures.
11

12. Advantages:-
Welder/diver is safe.
Good
quality
welds are
formed.
Surface monitoring of
welders condition can
be done.
Non
destructive
testing of
weld is
easy.
12

13. Disadvantages:-
 The habitat welding requires large quantities of complex
equipment and much support equipment on the surface
 Cost is extremely high hence cannot be afforded by
normal or small firms.
13
Large habitat for
underwater
hyperbaric welding

14. WET WELDING
 Key technology for repairing marine structure
 Welding is performed under water directly exposed to
the wet environment
 Increased freedom movement makes more effective,
efficient and economical
 Supply is connected to the welder/driver via cables or
hoses
14

15.  Complete insulation of the
cables and hoses are
essential in case to prevent
the chance for electric
shock
 MMA (Manual Metal Arc)
welding is commonly used
process in the repair of
offshore platforms.
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16. PRINCIPLE OF OPERATION
 The work-piece is connected to the positive side of dc
source (Anode) and electrode to the negative side
(Cathode).
 The two parts of the circuit are brought together and
then slightly separated.
16

17.  An electric current
occurs in the gap and
causes a sustained
spark which melts the
bare metal forming a
weld pool.
 The flux covering the
electrode melts to
provide a shielding gas.
 Arc burns in the cavity
formed inside the flux
covering, which is
designed to burn
slower than the metal
barrel to the electrode.
17

18. Advantages
 The versatility and low
cost.
 Less costlier than dry
welding.
 Speed with which it is
carried out.
 No enclosures so no time is
lost for building.
18

19. Disadvantages
 Rapid quenching of the weld metal by the
surrounding water.
 Welders working under water are restricted in
manipulating arc.
 Hydrogen embrittlement causes cracks.
 Poor visibility due to water contaminance.
19

20. RISKS V/S PRECAUTIONS
 Risk of electric shock so precaution is taken
for checking the electrical insulation of
electrical welding equipments.
 Hydrogen and oxygen are produced by the
arc in wet welding which are potentially
explosive so precaution must be taken to
avoid the build up of pockets of gas
 The life or health of the welder will be in risk
from nitrogen introduction into the blood
stream, hence precautions include the
provision of an emergency air cylinder for the
welder.
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21. APPLICATIONS
 Offshore construction for tapping
sea resources.
 Temporary repair work caused by
ship’s collisions, or unexpected
accidents.
 Salvaging vessels sunk in the sea.
 Construction of large ships beyond
the capacity of existing docks.
 Maintenance of oil rigs.
21

22. 22Figure showing schematic diagram for
underwater welding or cutting

23. EFFECT OF WET ENVIRONMENT
Water dissociates into Oxygen and Hydrogen which dissolves in the
molten pool causing:
 Gas Inclusion Defects
 Porosity
 Water Inclusion as after some times hydrogen combines with
oxygen forming water vapor.
V-groove wet weld deposited at 100 m depth (a) and its radiographic
image (b)
(a)
(b)
23

24. Graph Between the Porosity and Water
Pressure during welding 24

25. 25
• Most Underwater Structures are formed using this method as the
method is economical, flexible, versatile, Speedy.
• Combined additions of titanium, boron, and manganese increased
the tensile strength of the steel wet welds due to microstructural
refinement and increased hardenability thus providing new dimensions
to underwater structures
CONCLUSION

26. REFERENCES
 www.Wikipedia.org
 Paper on Underwater Welding-Jyotsana Dutta
Majumdar (IIT KGP 2006)
 Manual for underwater welding, US Navy
 www.howstuffworks.com
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27. THANK YOU
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