Underwater welding is an important tool for underwater fabrication works. In 1946, special waterproof electrodes were developed in Holland by ËœVander Willingen’â„¢.  In recent years the number of offshore structures including oil drilling rigs, pipelines, platforms are being installed significantly. Underwater welding is a type of welding which takes place underwater.

In underwater welding, the environment around the welder is wet. and uses welding equipment which has been customized for wet environment,commonly use under water techniques are hyperbaric enclosure welding, wet Underwater-welding, high pressure water jet welding,

other welding processes: friction welding, resistance welding, arc welding, tig welding, mig welding, oxyacetylene welding, electron beam welding, laser beam welding,and main risks for the welder performing Underwater-welding are the potential for electric shock,and the possibility of producing in the arc mixtures of hydrogen and oxygen in pockets, which might set up an explosion,and There are three main ways to perform Underwater-welding. One is to build an enclosure, a pit, around the place of repair and to pump away all the water: that amounts to prepare the conditions for normal welding in air, although the place may be deep under sea level. Another method of Underwater-welding consists in preparing an enclosure to be filled with gas (helium) under high pressure (hyperbaric) to push water back, and have the welder, fitted with breathing mask and other protective equipment, weld quite normally out of water but under pressure. The third is the wet Underwater-welding method, where no attempts are made to dry up the location of welding. Instead the power of the arc generates a bubble of a mixture of gases which lets metal melting and joining occur more orless normally, using specially covered electrodes to avoid that too much hydrogen be absorbed in the weld. The skilled welder must also be a diver, equipped for Underwater-welding, with all the extra equipment and protection a welder must use. There is also a less used method of Underwater-welding which features a special torch which sprays a cone of high pressure water, within which protective gas under pressure insulates the weld location from the water during welding.

Advantages

CONCLUSION
Alternatives which include clamped and grouted repairs (which may introduce unacceptably high loading on offshore structures) and the use of bolted flanges for the tie-ins are not necessarily and are not always satisfactory.