MUTHYAMMALENGINEERING COLLEGE

UNDERWATER WELDINGPAPER PRESENTED BY

SUDERSON.B SHANKAR.P

Guided By , M.Maniyarasan&M.Soundarrajan,

AP/MECH

UNDERWATER WELDING

NEED FOR UNDERWATER WELDING

To repair the cracks in ships ,bridge and submarine.

For quick process in under water welding. To construction of pipe line in under sea. To weld any cracks in oil pipe line.

Requirement of underwater weldingPower supply requirements 400 Amp or

larger. DC generators, motor generators and rectifiers are acceptable power supplies.

Power converters. Welding Generator, Pre-Setup. Diesel Driven Welding Generator Amperage

and Voltage settings. Gas Manifolds.

Underwater Oxygen-Arc Welding Torches. 1.Collet or grip 2.Oxygen valve 3.Flash arrester Waterproofing Surface Electrodes. 1.Epoxy 152 2.Lee lac 30-l2093 3.Polyurethane

Difference between normal welding and underwater welding

Under water welding 1 . Underwater Welding & Burning: 6,500 – 10,000° F Under the Sea. 2. Under the water, metal sounds different. It’s high pitched but muffled like a siren entering a tunnel. It dissipates quickly out into the waves . Ground welding 1. In the electric arc, the temperature is very high of the order of 6,000-8,000 °C for the GTAW, GMAW, FCAW and SAW processes. 2. It up to 10,000 20,000 °C for the PAW process and well above the boiling point of the base and filler materials 

Sea driver equipmentFully insulated electrode holder.Oxygen cylinder.HOFR cable for power supply (double insulated cable).Dry suit, helmet and head light.Electrode core wire with heavy coating.

Classification of under water welding

Wet welding: In this process it is directly exposed to the environment. And special water proof electrode is used in this type of welding.

Dry welding: In this process it is seal by closed chamber filled with gas to elevated pressure. Gas tungsten arc welding is most commonly used.

Wet weldingIt is carried out directly at ambient water pressure with the

welder/driver in waterBy using water proof stick electrode and without any

physical barrier between water and weldingMostly used Gas metal arc welding.

Wet welding process

Advantage of wet weldingMinimal amount of equipment is needed.Operating speed is high.No seal chamber is required.

Disadvantage of wet weldingRepaid quenching of the weld metal by surrounding water.Decreases impact strength and losses.Hydrogen embattlement causes cracks.Poor visibility in water.Electric shock will occurred.

Application of wet weldingIt is key technology for repairing marine

structure .Welding is directly performed under water is

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.

Dry welding 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 0.5 bar of Oxygen) at the prevailing pressure.

Hyperbaric welding process

Advantages of Dry welding

More safety then wet welding.Good Quality weld.Surface monitoring.Non destructive testing possible.

Disadvantages of Dry welding

Higher cost of process, training, etc.Large quantity of costly and complex

equipment.More deep, more energy requirement.It should be weld only reachable place.

Application of underwater dry welding

To Maintain the oil pipe lines in under water.Construction of pipe line under sea.

Advance in under water weldingLASER BEAM WELDING

Risk involved in under water welding Electric shock explosion.Risk is to the life of the welder.High pressure is formed.Shark attack under deep sea welding.

Dangerous and difficulties Hydrogen 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.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 pressure

Future scope and developmentsPresent 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.