TAILIEUCHUNG - UNDERWATER WELDING

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. | UNDERWATER WELDING Amit Mukund Joshi Mechanical Engineer Junior Research Fellow Mechanical Engineering Department Indian Institute of Technology - Bombay 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. 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. 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. The power source should be a direct .

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