Presented by idoldear.com Hyperbaric Welding Presented by idoldear.com

Abstract Hyperbaric welding is the important tool for underwater fabrication works, special water proof electrodes are used to weld under the water, In recent years number of offshore structures including oil drilling rigs, pipelines, platforms are being installed significantly. In these applications there might be a failures occuring due to crashes lot of usage. So any repair method will use the under water welding for rectifying the failures.

Introduction: 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.

Invention: Underwater hyperbaric welding was invented by the Russian metallurgist Konstantin Khrenov in 1932. Research into using dry hyperbaric welding at depths of up to 1,000 metres (3,300 ft) is ongoing now a days.

Classification: Under water welding can be classified as Wet Welding Dry 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.

Wet welding under water

Dry 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.

Power supply: 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. Power Supply used : DC Polarity : -ve polarity When DC is used with +ve polarity, electrolysis will take place and cause rapid deterioration of any metallic components in the electrode holder. For wet welding AC is not used on account of electrical safety and difficulty in maintaining an arc underwater

Risks Involved: There is a risk to the welder of electric shock. The life or health of the welder from nitrogen introduced into the blood steam during exposure to air at increased pressure. For the structures being welded by wet underwater welding, inspection following welding may be more difficult

Advantages: Wet welding is less costly compared to dry welding. The welder can reach portions of offshore structures that could not be welded using other methods. Joint preparation, pipe alignment, NDT inspection, etc. are monitored visually Good Quality Welds

Limitations: welding requires large quantities of complex equipment and much support equipment on the surface. The chamber is extremely complex. One cannot use the same chamber for another job, if it is a different one. There is rapid quenching of the weld metal by the surrounding water. The main disadvantage is poor visibility. The welder some times is not able to weld properly.

Applications: Oil drilling rigs Underwater pipelines Offshore Oil platforms Marine Ships