under water welding-s.saravanakumar,ice,srptc

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2. INTRODUCTIONUnderwater welding is an important tool for under fabrication work.In 1946,special water proof electrodes were developed in HOLLAND by EVANDER WILLINGEN. 3. CLASSIFICATIONUnder water welding can be classified as : 4. This technology for repairing marine structure.welding is performed under water directly exposed to the wet environment. MMA (manual metal arc) welding is commonly used process in repair of offshore platform. 5. electrodeThe work is connected to the positive side of dc source and electrode to the negative. The two parts of the circuit are brought together and then slightly separated.An electric current occurs in gap and causes a sustainable spark which melts the bare metal to provide a shielding gas. Arc burns in the cavity formed inside the flux covering , which designed to burn slower than the metal barrel to the electrode. 6. Less costlier than dry welding. The versatility and low cost. DisadvantageHydrogen embritt lement causes cracks.poor visibility due to water contaminance. 7. A chamber is created near the area to be the welded.The welder does the job by staying inside the chamber. Gas metal arc welding is the best process for this welding. 8. HYPER BARIC WELDING IS WELL ESTABLISHED AND GENERALLY WELL RESEARCHED.Research being carried out for welding at a range of 500 to 1000m deep.THOR-1 is developed performs pipe fitting, installs the track and orbital head on pipe and rest process is automated. 9. Offshore construction for taping sea resources. Repair and maintenance of ship.Construction of large ship beyond the capacity of existing docks. 10. Alternative which include clamped and grouted repairs and the use of bolted flanges for the tie-ins not necessarily and are not always satisfactory.