under water welding
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mahendra bm
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#1
05-02-2010, 06:29 AM


please send ppt also
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project report tiger
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#2
05-02-2010, 07:22 AM

please read topicideashow-to-Underwater-welding for getting more about under water welding
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amolchavan1989
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#3
09-10-2010, 10:33 AM

I want to about this topic in Brief, please help me by giving information. Thanks
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seminar surveyer
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#4
07-01-2011, 04:04 PM




.pdf   under water welding report.pdf (Size: 2.08 MB / Downloads: 920)

SUBMITTED BY:
Bhanu Pratap Singh

GUIDED BY:-
Mr. Brajesh Varshne

K A N P U R II N S T II T U T E O F T E C H N O L O G Y


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. 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, and platforms are being installed significantly. Some of these structures will experience failures of its elements during normal usage and during unpredicted occurrences like storms, collisions. Any repair method will require the use of underwater welding. Underwater welding provides a means to assemble or repair underwater. This is a highly useful technology available that allows repairs of ships damaged during hurricanes or wars. There are a couple of alternatives available, which include clamped and grouted repairs and bolted flanges. However, these alternatives do not always provide satisfactory results and also introduces high loading at offshore structures. Underwater welding is a highly specialized trade. Most are employed in the oil or shipping industry and the military.

CLASSIFICATION OF UNDERWATER WELDING
Underwater welding can be classified as 1) Wet Welding 2) 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.

WETWELDING
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. 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 and hoses. In wet welding MMA (manual metal arc welding) is used. It is carried out directly at ambient water pressure with the welder/diver in the water using water-proof stick electrode and without any physical barrier between water and welding arc [Oates, 1996]. Special precaution should be taken to produce underwater arc to protect it from surrounding water. Wet welding does not need any complicated experiment set up, it‘s economical and can be immediately applied in case of emergency and accident as it does not need water to be evacuated. However, difficulties in welding operation due to lack of visibility in water, presence of sea current, ground swells in shallow water and inferior weld qualities (increased porosities, reduced ductility, greater hardness in the heat affected zone, hydrogen pick up from the environment) are the notable disadvantages of wet welding technique.
Wet underwater welding commonly uses a variation of shielded metal arc welding, employing a waterproof electrode.[2] Other processes that are used include flux-cored arc welding and friction welding.[2] In each of these cases, the welding power supply is connected to the welding equipment through cables and hoses. The process is generally limited to low carbon equivalent steels, especially at greater depths, because of hydrogen-caused cracking.



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rahul1369
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#5
21-02-2011, 10:05 PM

thank you very very much
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nani351
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#6
24-02-2011, 10:53 PM

sir plz send me ppt :Confused
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seminar paper
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#7
18-02-2012, 02:02 PM

to get information about the topic underwater welding full report ppt and related topic refer the link bellow

topicideashow-to-underwater-welding--9768

topicideashow-to-underwater-welding?page=2

topicideashow-to-under-water-welding?page=2

topicideashow-to-underwater-welding?page=3

topicideashow-to-underwater-welding?pid=8343
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#8
24-02-2012, 09:01 AM

gd mrng...................i need ur help will u post me the under water welding total project and implimentation report..................because of i had decided to give the seminar and presentation on this advance topic.............
i had to submit this report tomorrow itself............
i am
b.tech finel year student
from
mechanical branch.



thank you.
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seminar paper
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#9
24-02-2012, 09:53 AM

to get information about the topic underwater welding full report ppt and related topic refer the link bellow

topicideashow-to-underwater-welding--9768

topicideashow-to-underwater-welding?page=2

topicideashow-to-under-water-welding?page=2

topicideashow-to-underwater-welding?page=3

topicideashow-to-underwater-welding?pid=8343
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project girl
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#10
27-12-2012, 06:01 PM

Underwater welding


.pptx   Underwater welding.pptx (Size: 318.56 KB / Downloads: 18)

What is welding?

Welding is a fabrication that joins materials, usually metals or thermoplastics, by causing coalescence.
This is often done by melting the work pieces and adding a filler material to form a pool of molten material (the weld pool) that cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld.

Introduction

Underwater welding was invented by the Russian metallurgist Konstantin Khrenov in 1932.
The first ever underwater welding was carried out by British Admiralty – Dockyard for sealing leaking ship rivets below the water line.
Underwater welding is an important tool for underwater fabrication works.

CLASSIFICATION

Underwater welding can be classified as-
1) Wet Welding
2) 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.

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. The increased freedom of movement makes wet welding the most effective, efficient and economical method.

Principle of operation of Wet Welding

The work to be welded is connected to one side of an electric circuit, and a metal electrode to the other side. These two parts of the circuit are brought together, and then separated slightly. The electric current jumps the gap and causes a sustained spark (arc), which melts the bare metal, forming a weld pool. At the same time, the tip of electrode melts, and metal droplets are project and implimentationed into the weld pool. During this operation, the flux covering the electrode melts to provide a shielding gas, which is used to stabilize the arc column and shield the transfer metal. The arc burns in a cavity formed inside the flux covering, which is designed to burn slower than the metal of the electrode.

Dry welding

Dry 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.
The gas tungsten arc welding process is employed for this process.

FUTURE OF UNDERWATER WELDING

The major efforts on research and development should be focused on the following topics:
1. Automation of the underwater welding. Present trend is towards automation to develop a technology, where welder performs pipefitting, installs the trace and the rest process is automated.
2. Developing automated Inspection technique of the welded structures.
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#11
29-05-2013, 12:18 PM

Underwater welding



.docx   Underwater welding.docx (Size: 404.99 KB / Downloads: 12)

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.
Underwater welding is an important tool for underwater fabrication works. In 1946, special waterproof electrodes were developed in Holland by ‘Van der Willingen’. In recent years the number of offshore structures including oil drilling rigs, pipelines, platforms are being installed significantly. Some of these structures will experience failures of its elements during normal usage and during unpredicted occurrences like storms, collisions. Any repair method will require the use of underwater welding.

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. 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 and hoses.

PRINCIPLE OF OPERATION OF WET WELDING

The process of underwater wet welding takes in the following manner:
The work to be welded is connected to one side of an electric circuit, and a metal electrode to the other side. These two parts of the circuit are brought together, and then separated slightly. The electric current jumps the gap and causes a sustained spark (arc), which melts the bare metal, forming a weld pool. At the same time, the tip of electrode melts, and metal droplets are project and implimentationed into the weld pool. During this operation, the flux covering the electrode melts to provide a shielding gas, which is used to stabilize the arc column and shield the transfer metal. The arc burns in a cavity formed inside the flux covering, which is designed to burn slower than the metal barrel of the electrode.

HYPERBARIC WELDING (DRY WELDING)

Hyperbaric welding is carried out in chamber sealed around the structure o 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 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.

RISKS INVOLVED

There is a risk to the welder/diver of electric shock. 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. Secondly, hydrogen and oxygen are produced by the arc in wet welding.
Precautions must be taken to avoid the build-up of pockets of gas, which are potentially explosive. The other main area of 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 narcosis following rapid surfacing after saturation diving.
For the structures being welded by wet underwater welding, inspection following welding may be more difficult than for welds deposited in air. Assuring the integrity of such underwater welds may be more difficult, and there is a risk that defects may remain undetected.

CONCLUSION

Precautions must be taken to avoid the build-up of pockets of gas, which are potentially explosive. The other main area of 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 narcosis following rapid surfacing after saturation diving.
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