Underwater welding
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Underwater welding refers to a number of distinct welding processes that are performed underwater.
The two main categories of underwater welding techniques are wet underwater welding and dry underwater welding, or hyperbaric welding.
In wet underwater welding, a variation of shielded metal arc welding is commonly used, employing a waterproof electrode. Other processes that are used include flux-cored arc welding and friction welding. In each of these cases, the welding power supply is connected to the welding equipment through cables and hoses. The process is generally limited to low carbon equivalent steels, especially at greater depths, because of hydrogen-caused cracking.
In dry welding the weld is performed at the prevailing pressure in a chamber filled with a gas mixture sealed around the structure being welded. For this process, gas tungsten arc welding is often used, and the resulting welds are generally of high integrity.
The applications of underwater welding are diverse—it is often used to repair and construct ships, offshore oil platforms, and pipelines. Steel is the most common material welded. For deep water welds and other applications where high strength is necessary, dry water welding is most commonly used. Research into using dry water welding at depths of up to 1000 m are ongoing. In general, assuring the integrity of underwater welds can be difficult, especially wet underwater welds, because defects are difficult to detect.
For the structures being welded by wet underwater welding, inspection following welding may be more difficult than for welds deposited in air. Assuring the integrity of such underwater welds may be more difficult, and there is a risk that defects may remain undetected.
The risks of underwater welding include the risk of electric shock to the welder. To prevent this, the welding equipment ought to be properly insulated, and the amperage of the welding equipment should be controlled. Underwater welders must also consider the safety issues that normal divers face; most notably, the risk of decompression sickness due to the increased pressure of inhaled breathing gases. Another risk, generally limited to wet underwater welding, is buildup of hydrogen and oxygen pockets in the weld, because these are potentially explosive.
[edit] References
- Cary, Howard B. and Scott C. Helzer (2005). Modern Welding Technology. Upper Saddle River, New Jersey: Pearson Education. ISBN 0-13-113029-3. Pages 677-681.
[edit] External links
 Metalworking
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| Welding | |
| Arc welding: Shielded metal (MMA) | Gas metal (MIG) | Flux-cored | Submerged | Gas tungsten (TIG) | Plasma | |
| Other processes: Oxyfuel | Resistance | Spot | Forge | Ultrasonic | Electron beam | Laser beam | |
| Equipment: Power supply | Electrode | Filler metal | Shielding gas | Robot | Helmet | |
| Related: Heat-affected zone | Weldability | Residual stress | Arc eye | Underwater welding | |
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See also: Brazing | Soldering | Metalworking | Fabrication | Casting | Machining | Metallurgy | Jewelry |
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