Submerged Arc Welding: Underwater Welding

Article From welding-advisors.com

Brief Summary:

The limitations of Underwater-welding concern the inevitable bulky and expensive setup to provide the welder with all the support needed, for respiration, for protection from cold, for special welding equipment, for remote surveillance camera, for special non destructive testing.
The main risks for the welder performing Underwater-welding are the potential for electric shock, the possibility of producing in the arc mixtures of hydrogen and oxygen in pockets, which might set up an explosion, and the common danger sustained by divers, of having nitrogen diffuse in the blood in dangerous proportions. Curiously the risk of drowning is not listed with the hazards of Underwater-welding.
First there were no demands for quality. Underwater-welding was just applied to weld a patch until a more thorough repair could be performed. But as soon as more experience was gained, ambitious individuals and companies joined forces to improve results and to establish achievable specifications.
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 or less 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.
Underwater-welding has nothing to do and should not be confused with Submerged Arc Welding which is a specialized process is performed outside water.

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