Can arc welding be performed in water?

The process of performing arc welding in water is known as underwater welding which is a highly specialized and useful technology available to assemble or repair under water. This method of welding is mostly used in oil or shipping industry, military applications and in maintaining underwater pipelines. It is also used to repair ships that are damaged during wars or hurricanes. 

Under water welding functions in the following manner:

One side of the electric circuit is connected to the work to be welded and the other end is connected to a metal electrode. These two parts are brought together and then separated to some extent in which the electric current jumps and causes an arc. This arc melts the bare metal thereby causing a weld pool. Simultaneously the tip of electrode also melts and the metal droplets are projected into the weld pool during which the flux covering the electrode melts to form a shielding gas. The gas stabilizes the arc column and protects the metal. 

The process of underwater welding can be classified into two types which are wet welding and dry welding. 

During wet welding, the welding is performed under water, directly exposed to the wet environment. It involves using a special electrode and the process is similar to open air welding. The increased freedom of movement in wet welding makes it the cheapest, fastest and effective method. The welding power supply is located on the surface and is connected to the welder via cables and hoses. The high speed of operation and less requirement of welding equipments makes this process of welding to be carried out immediately with minimal planning.  But lot of precautions should be taken during wet welding to make sure that the welder does not receive any electric shocks. Poor visibility of welder is yet another disadvantage of this method. 

During dry welding which is also known as hyperbaric welding, the welding is carried out in a chamber sealed around the structure to be welded. The chamber is filled with a gas, usually helium which contains 0.5 bar of oxygen and is fitted on to the pipeline. Then it is filled with a breathable mixture of gas which is described above and the pressure is maintained a little above the pressure at which the welding is to take place. Dry welding involves gas tungsten arc welding process. The welds of this method are of better quality compared to wet welding since water does not quench the welds. Also dry welding ensures the safety of arc welders as it is performed in a chamber which is immune to ocean currents and marine animals. But in contrast to wet welding, dry welding involves a huge cost and large welding equipments are required to support the chamber, the reusability of which is very limited.

by Oleg Gladshteyn

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