Underwater welding is an essential process for under water fabrication. Any repair of offshore structures like pipelines, oil drilling rigs and platforms require underwater welding.
CLASSIFICATION It can be classified as either: wet welding or dry welding.
(I)Wet welding Wet welding is carried out under water and directly exposed to wet environment. Special electrodes are used and it is the most effective due its freedom of movement.
ADVANTAGES OF WET WELDING
-it is versatile and inexpensive -it is fast -no time is wasted building enclosures
DISADVANTAGES OF WET WELDING
-Rapid quenching of the weld metal increases hardness and porosity. -There is hydrogen embrittlement of the weldment -poor visibility
(II)DRY WELDING(HYPERBARIC WELDING) . This process is carried out in a chamber that is sealed around the structure to be welded. A gas(in most cases Helium with oxygen at 0.5 bar) is used to fill the chamber at prevailing pressures.
ADVANTAGES OF DRY WELDING
-it is safer than wet welding -produces high quality welds since there is no rapid quenching. -it allows for surface monitoring of the weldment mostly through non-destructive testing
DISADVANTAGES OF DRY WELDING
-requires complex equipment -cost of welding increases with depth
RISKS INVOLVED
-explosions due to gas build-up -welder electric shocks -nitrogen can enter the blood stream causing health issues.
