Under water welding ppt

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UNDERWATER WELDING TECHNOLOGY ,ART , COURAGE

Seminar On Underwater welding

Submitted to: submitted by:Department of Mechanical MOHAN BIHARI engineering 12EEJME0291

UNDERWATER WELDING

Mohan Bihari12eejme029m4ubihari@gmail.comSEMINAR ON2

First under water welding by British Admiralty DockyardIn 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.

3History

INTRODUCTION TO UNDERWATER WELDING

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We cant lift ship and then repair it. Hence comes the use of underwater welding5

Types of underwater weldingWet welding

Dry welding6

Hyperbaric welding is the process in which a chamber is sealed around the structure to be welded and is filled with a gas ( He and Oxygen) at the prevailing pressure.Dry Welding7

Dry welding can be of two typesLarge habitatMini habitat

Mini habitat for underwater welding.8

Large habitat for underwater welding

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Large habitat underwater welding

Advantages of dry weldingWelder /diver safetyGood weld qualitySurface monitoring10Higher cost of process, training, etcLarge quantity of costly and complex equipmentsMore deep, more energy requirement.Cant weld if weld spot is at unreachable placeDisadvantages

Wet weldingSimply means that job is performed directly in the waterIt involves using special rod and is similar to the process in ordinary air welding11

FIGURES SHOWING WET WELDING12

CheapestFastestTensile strength is highEase of access the weld spotNo waste of time in constructing habitatAdvantages of wet welding13

Rapid quenching decreases impact strength, Ductility.Hydrogen embrittlement.Poor visibility in water.Higher energy density of hydrogen, higher efficiency.Disadvantages14

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Figure showing schematic diagram for underwater welding or cutting

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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.Application of underwater welding

Dangers and difficultiesHydrogen and oxygen are dissociated from the water and will travel separately as bubblesOxygen cutting is about 60 percent efficientAbove river beds, especially in mud, because trapped methane gas in the proper concentrations can explode.

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There is a risk to the welder/diver of electric shock. There is a risk that defects may remain undetectedThe 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 pressure18

Safety measuresStart cutting at the highest point and work downwardBy withdrawing the electrode every few seconds to allow water to enter the cutGases may be vented to the surface with a vent tube (flexible hose) secured in place from the high point where gases would collect to a position above the waterline.

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Precautions include achieving adequate electrical insulation of the welding equipmentAreas and voids must be vented or made inert20

Future scope and developmentsDevelopment of alternative welding methods like friction welding, explosive welding, and stud welding. Present trend is 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. 21

22Thank you