Welding processes have become increasingly important in almost all manufacturing industries and for structural application. Although a large number of techniques are available for welding in atmosphere, many of these techniques cannot be applied in offshore and marine application where presence of water is of major concern. In this regard, it is relevant to note that a great majority of offshore repairing and surfacing work is carried out at a relatively shallow depth, in the region intermittently covered by the water known as the splash zone. Though numerically, most ship repair and welding jobs are carried out at a shallow depth, the most technologically challenging task is repair at greater depths, especially in pipelines and repair of accidental failure. The advantages of underwater welding are largely of an economic nature, because underwater-welding for marine maintenance and repair jobs by passes the need to pull the structure out of the sea and saves valuable time and dry docking costs. It is also an important technique for emergency repairs which allow the damaged structure to be safely transported to dry facilities for permanent repair or scrapping. Underwater welding is applied in both inland and offshore environments, though seasonal weather inhibits offshore underwater welding during winter. In either location, surface supplied air is the most common diving method for underwater welders. Underwater welding is an important tool for underwater fabrication works. Underwater hyperbaric welding was invented by the Russian metallurgist Konstantin Khrenov in 1932. Hyperbaric welding is the process of welding at elevated pressures, normally underwater. Hyperbaric welding can either take place wet in the water itself or dry inside a specially constructed positive pressure enclosure and hence a dry environment. It is predominantly referred to as "hyperbaric welding" when used in a dry environment, and "underwater welding" when in a wet environment. The applications of hyperbaric welding are diverse—it is often used to repair ships, offshore oil platforms, and pipelines. Steel is the most common material welded.

1. Presented By: Rajat Jaiswal
Roll no.: 1712240127
Group: ME 84
A
Seminar Presentation on
UNDERWATER WELDING

2. INTRODUCTION
 Welding can be defined as the process of joining two similar or dissimilar
metallic components with the application of heat, with or without the
application of pressure and with or without the use of filler metal.
 Heat may be obtained by chemical reaction, electric arc, electrical resistance,
frictional heat, sound and light energy.
Figure.1 Arc welding process

3. HOW TO WELD HERE?

4. NOT A GOOD SOLUTION

5. Underwater welding is the process of welding at elevated pressures, normally
underwater.
Underwater welding can either take place wet in the water itself or dry inside a
specially constructed positive pressure enclosure and hence a dry environment.
It is predominantly referred to as "hyperbaric welding" when used in a dry
environment, and "underwater welding" when in a wetenvironment.
The applications of underwater welding are diverse—it is often used to repair
ships, offshore oil platforms, and pipelines. Steel is the most common material
welded.
Underwater welding is most commonly used for welding steel structures
including stainless steel. However it is being used for welding copper and
aluminium components also.
UNDERWATER WELDING

6. VERY HIGH PRESSURE
VERY LOW
TEMPERATURE
WET , GAS DISSOLVED IN
WATER
 Underwater welding method enables us to weld properly under these conditions.
 Underwater welding is an important tool for underwater fabrication works.
Figure.3 Variation in temperature and pressure with depth

7. BRIEF HISTORY
 1930s: Russian metallurgist Konstantin Khrenov made the first underwater weld in
lab test.
 In 1932 after successful experimentation in the labs, Khrenov traveled
with engineers to the Black Sea for further testing and after a successful
testing, underwater welding was born.
 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.
 1970s: Whitey Grubbs and Dale Anderson of Chicago Bridge & Iron(CB&I)
qualified an underwater wet welding procedure to American Welding Society
(AWS) standards.

8. CLASSIFICATION
WET WELDING DRY WELDING
In wet welding, the welding is
performed underwater, directly
exposed to the wet environment
In dry welding, a dry chamber is
created near the area to be
welded and the welder does the job
by staying inside the chamber
Figure.6 Dry welding
Figure.5 Wet welding

9. WET WELDING
 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 MMAW (manual
metal arc welding) is used.
 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/weldervia
cables and hoses.
Figure.7 Wet welding under water

10. PRINCIPLE OF OPERATION OF WET WELDING
 DC Power Supply is used with negative polarity.
 The welding circuit includes the knife switch which is operated on the surface by the
assistant upon the signal of welder/diver.
 The main reason for the use of the knife switch is that it cuts off the welding current.
For gripping the electrode, electrode holder with the twisted head isutilized.
Figure.8 Working process of a wet welding

11. ADVANTAGES OF WET WELDING
The versatility and low cost of wet welding makes this method highly desirable.
Other benefits include the speed with which the operation is carriedout.
It is less costly compared to dry welding.
The welder can reach portions of offshore structures that could not be welded using
other methods.
No enclosures are needed and no time is lost building. Readily available standard
welding machine and equipments are used. The equipment needed for mobilization
of a wet welded job is minimal.

12. DISADVANTAGES OF WETWELDING
There is rapid quenching of the weld metal by the surrounding water. Although quenching
increases the tensile strength of the weld, it decreases the ductility and impact strength of
the weldment and increases porosity and hardness.
Hydrogen Embrittlement – Large amount of hydrogen is present in the weld region,
resulting from the dissociation of the water vapour in the arcregion.
 The 𝐻2 dissolves in the Heat Affected Zone (HAZ) and the weld metal, which causes
Embrittlement, cracks and microscopic fissures. Cracks can grow and may result in
catastrophic failure of the structure.
Another disadvantage is poor visibility. The welder some times is not able to weld
properly.

13. DRYWELDING
hence a dry
 Inside a specially constructed positive pressure enclosure and
environment.
 Use for high quality welds as more control over conditions.
 Involves the weld being performed at the prevailing pressure in a chamber filled
with a gas mixture sealed around the structure being welded.
Figure.9 Dry welding in water

14. PRINCIPLE OF OPERATION OF DRY WELDING
 Underwater welding in a dry environment is made possible by encompassingthe
area to be welded with a physical barrier (weld chamber) that excludeswater.
 The weld chamber is designed and custom built to accommodate braces and other
structural members
 Water is displaced from within the chamber by air or a suitable gas mixture,
depending upon water depth and pressure at the work site.
Figure.10 Hyperbaric welding chamber

15. Better diver safety
Better quality welds
No build up of hydrogen and oxygen pockets
Allows for heat treatment before and after welding
Non destructive testing
 Surface monitoring possible
ADVANTAGES OF DRYWELDING

16. Requires large, complex equipment.
Chamber has to be fabricated differently for different applications
Cost is very high and increases with depth
At greater depths, the arc constricts and corresponding higher voltagesare
required.
DISADVANTAGES OF DRYWELDING

17. APPLICATION OF UNDERWATERWELDING
The important applications of underwater welding are:
 Offshore construction for tapping sea resources,
 Temporary repair work caused by ships 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.
 Repair and maintenance of underwater pipelines.

18. FUTURE DEVELOPMENTS
As we know that present trends are towards
automation. THOR – 1 (TIG Hyperbaric Orbital
Robot) is developed where diver performs pipefitting,
installs the track and orbital head on the pipe and the
rest process is automated.

19. CONCLUSIONS
 Underwater welding is an important tool for underwater fabricationworks.
 Nowadays, as a wide range of offshore structures as well as ships being constructed,
there is great interest to develop underwater weldingtechniques.
 Construction and repair of underwater pipelines can easily be done by underwater
welding.
 There is a great importance of underwater welding in ocean technology development
 Automation and mechanization of welding processes will be the major future trends
of underwater welding development.
 Automation can be achieved by implementing better sensors and welding process
control as well as by better understanding of the welding processes.

20. Thank you…