Welding is a process that allows metals to be joined together. The fabrication process for this is done by melting metal pieces together with a filler material forming a small puddle of molten metal known as a welding bead or a weld puddle. When this weld puddle or welding bead cools it forms a very strong joint between the work pieces.
Constructing or repairing structures or ships while welding underwater presents many obstacles that need to be overcome when joining metal work pieces together. Underwater welding is a very useful technology that allows many opportunities over alternatives available. Some alternatives include bolted flanges, grouted and clamped repairs, but these alternative repair methods don’t always provide acceptable results. Most underwater welding is done in the shipping or oil industry and is considered a very specialized trade.
There are two main categories in the underwater welding process which are; Wet Welding and Dry Welding. Wet Welding is performed underwater where the welding is being done while being exposed to water. This is possible using a special electrode to weld with which is then used as if in an open aired environment. Wet Welding is most effective as it provides the freedom of movement for the welder, because of this wet welding is efficient, economical and the most utilized choice for repair work underwater.
Dry Welding is carried out within a sealed chamber placed around metal pieces that need to be joined or on a section of a structure that needs to be welded; this fabrication process is known as Hyperbaric welding. The chamber fitted around the work area is then filled with a gas made up of 0.5 bar oxygen and helium. This welding process is called, Gas Tungsten arc welding, in which the pressure in the chamber is slightly higher than the pressure of the weld taking place.
The advantage of using wet welding over dry welding is that wet welding is very cost effective and the speed in which repair tasks can be accomplished is very fast. Also, the equipment required for wet welding are not many allowing repairs to be carried out immediately. The disadvantages with wet welding are that while working directly in the water the welds are quenched rapidly which decreases the impact strength of the weld and makes it very porous. Also, precautions regarding voltage need to be taken or else the diver can be exposed to electric shocks.
The advantages of dry welding are that the welds are of a much better quality as compared to wet welding where the welds become porous because of being quenched rapidly by working directly within water. The disadvantageous are that large support surface equipment is required, and the cost involved increase with the depth of the work that needs to be done.
Considering the benefits of both wet and dry welding the main concern is always the diver’s safety, which constantly challenges this specialized trade now and without doubt into the depths of the future.
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