this is the best presentation to get the clear idea and knowledge about Under Water Welding. this the best way to get to know about this topic. and this presentation is from Army institute of Technology pune.

1. Under Water
Welding
By-
Guide-
Amandeep Saini Prof. Dr. R. B. Patil
T.E. Mech
T120220805

2. Introduction
 The fact that electric arc could operate under water 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.
 Underwater wet welding technique was misunderstood for a long time, and it was a
synonym for low quality weld full of porosity and cracks with poor mechanical properties
like low ductility and due to micro structural issues prone to cracking.
 Through time, that status has been changed, and today underwater welding projects, both
dry and wet, are used in most complex and difficult objects with a high level of quality
assurance.

3. Classification of Under Water Welding
 Underwater welding can be divided in two main types with sub classification as follows:
 Wet underwater welding is considered as welding at the ambient pressure where there is no
mechanical barrier between welder-diver and surrounding water.
 Dry underwater welding is considered as welding in dry ambient atmosphere, under
atmospheric or hyperbaric pressure where welder-diver is divided from surrounding water
by means of mechanical barriers.

4. Under Water Wet Welding
 Wet Welding indicates that welding is performed underwater,
directly exposed to the wet environment.
 A special electrode is used and welding is carried out manually just
as one does in open air welding.
 Welding power supply is located on the surface with connection to
the diver/welder via cables and hoses.
 In wet welding MMAW (manual metal arc welding), with a DC
power supply is used. The electrode is kept in negative polarity.

5. Equipment Needed
 Diving equipment
 Welding power sources
 Safety switch
 Communication system
 Welding cables and holders
 Mechanical tools system
 Human resources

6. Advantages of Wet Under Water Welding
 The versatility and low cost of wet welding makes this method
highly desirable.
 The increased freedom of movement makes wet welding the most
effective, efficient and economical method.
 The speed of the operation is extremely high.
 As the equipment’s are very minimum, the welding can be
performed in a shorter time with minimal planning.

7. Disadvantages of Wet Under Water Welding
 Electric arc instability.
 The rapid cooling leads to great hardness in the heat-affected zone, low toughness in the
welded joint and the appearance of porosity due to the capture of gas bubbles.
 This process is susceptible to Hydrogen Embrittlement.
 This increases the susceptibility to the appearance of cold cracks, brings about porosity and
degrades the mechanical properties of the joint.
 The high oxygen content in the electric arc column, molten metal in the transfer and weld
pool, which leads to oxidation, reduction of the proportion of alloy elements and the
degradation of mechanical properties.

8. Under Water Dry Welding
 Depending on water depth, shape and type of underwater structure as
well as ease of arranging other necessary facilities underwater dry
welding could be performed in several ways:
• Dry welding at one atmosphere.
• Dry welding in a habitat.
• Dry chamber welding.
• Hyperbaric welding

9. Dry Welding at One Atmosphere
 Dry underwater welding in Cofferdam is characterized by
the fact that the welder and the welding site are in dry
atmosphere, without the presence of water. All the activities are
performed at the atmospheric pressure.
 Special problem in working in such a narrow confined
space is the occurrence of vapors and gases which may have
an explosive character.
 The main advantage of such welding is better quality of weld related to wet underwater welding,
flexibility in the selection of the procedure and the welding technology and higher working safety.

10. Dry Welding in a Habitat
 Welding at ambient pressure in a large chamber from
which water was displaced and where such
atmosphere is achieved that welder has no need to
use diving equipment.
 Weld properties are equivalent to one welded in
normal conditions.
 However, much more fit-up time is necessary to fix the habitat and prepare it for welding.

11. Dry Chamber Welding
 Welding at ambient pressure in a simple open
bottomed dry chamber, that at least
accommodates the head and shoulders of a
diver-welder in full diving equipment.
 Welder-diver is partly immersed in water but
welding is performed in a dry atmosphere.
 Habitat is smaller and less complex than in case of dry habitat welding.
 Due to smaller size of habitat other operating facilities are also less expensive.

12. Hyperbaric Welding
 Hyperbaric welding is carried out in chamber sealed around the structure to be welded.
 The chamber is filled with a gas (commonly helium containing 0.5 bar of oxygen) at the
prevailing pressure.
 The habitat is sealed onto the pipeline and filled with a breathable mixture of helium and
oxygen, at or slightly above the ambient pressure at which the welding is to take place.
 This method produces high-quality weld joints that meet X-ray and code requirements.
 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.

13. Advantages of Dry Welding
 Welder/diver safety
 Good quality welds
 Surface monitoring
 Non-destructive testing (NDT)

14. Disadvantages of Dry Under Water Welding
 The habitat welding requires large quantities of complex equipment and much support
equipment on the surface.
 The chamber is extremely complex.
 Cost of habitat welding is extremely high and increases with depth.
 Work depth has an effect on habitat welding.
 At greater depths, the arc constricts and corresponding higher voltages are required.
 One cannot use the same chamber for another job, if it is a different one.

15. Advancements
 Friction Welding:
• Friction welding is a solid state welding process which produces coalescence of materials by
the heat obtained from mechanically-induced sliding motion between rubbing surfaces.
• When a suitable high temperature has been reached, rotational motion ceases and additional
pressure is applied and coalescence occurs.
• It has the ability to produce high quality welds in a short cycle time. No filler metal is
required and flux is not used.
• The process is capable of welding most of the similar or dissimilar metals. It also produces a
fine-grained forged weld without any weld dilution, or weld inclusions.

16. Laser Welding
 Because of its coherent nature, Laser has
found its application here too.
 The focused laser beam is made to
irradiate the work piece or joint at the
given level and speed.
 A shroud gas protects the weld pool from undue oxidation and provides with the required
oxygen flow.
 Laser heating fuses the work piece or plate edges and joins once the beam is withdrawn.

17. Conclusion
 All the possible ways to weld under water were studied and
it was concluded that if the points like weld quality, safety
and the provision for further heat treatments are
considered. Then, Dry Welding is the best way to weld.
There is a lot of scope in the latest technologies like THOR-
I(TIG Hyperbaric Orbital Rotator), Friction Welding & Laser
Welding.

18. References
 Verma, Ketan and Garg, Harish K., “Underwater Welding-Recent Trends and Future Scope”,
International Journal on Emerging Technologies, Chandigarh Group of Colleges (Gharuan Campus)
Mohali,(PB)
 Doc.dr.sc. Ivica Garašić, Prof.dr.sc. Zoran Kožuh, “Underwater Welding and Cutting”, Advanced
production technologies
 Davies, A.C., “Welding”, 10th Edition, Cambridge University Press, 1996, pp 343-482
 Colligan, K., “Material Flow Behavior during Friction Welding of Aluminum”, Supplement To The
Welding Journal, July 1999, Sponsored by the American Welding Society and the Welding Research
Council, Welding Research
 https://en.wikipedia.org/wiki/Hyperbaric_welding

19. Thank You!