?What is underwater welding
One of the most lucrative jobs in the world
UNDERWATER WELDING OVERVIEW
The installation of large patches, as well as the attachment of suitable pad-eyes presents a more
complicated problem to the diver than does underwater cutting. Considerable practice is necessary to achieve a consistently good standard of underwater welding for salvage work. As a result, the diver’s underwater welding techniques must conform to acceptable standards. Also, the ocean acts as a large heat sink and draws off the heat of the electrode. This may cause blow holes and possible loss of strength between the patch and hull. This is true because the gas cannot escape from the molten pool of metal due to sudden cooling by the surrounding water. Despite the above shortfalls, underwater welds of good strength that are acceptable for salvage work are possible. Unless otherwise specified, the term “underwater welding” as used in this manual refers to the wet welding technique where no mechanical barrier separates the welding arc from the surrounding water.
The two types of welding to be covered in this manual are:
- wet welding and
- dry welding at the “splash zone.”
Wet welding
Wet welding is accomplished with both the diver and the work completely submerged.
The wet welding process used for salvage operations is usually a simple underwater joining technique.
The materials required are commercially manufactured shielded metal arc equipment and
waterproofed electrodes. Minimal ancillary devices are needed. These include lighting, staging
and hand tools.
There are advantages to wet welding. The underwater welder can work freely on any portion of complex structures or on sections with restricted access, whereas other underwater techniques may encounter difficulties. Patching can be performed faster and at less cost because no time is lost in construction and installation of enclosures.
Because standard welding power sources and equipment are used, a wet welding job can be easily
mobilized at remote job sites. Wet welding also allows more freedom of patch design and size of patch sections.
Dry welding:
Dry welding at the “splash zone” is generally conducted in a dry box or cofferdam at atmospheric pressure.
Mini-Habitats
Mini-habitat welding makes use of a small, easily portable, gas-filled enclosure. Often mini-habitats are transparent plexiglas boxes, which are placed over the joint by a diver. Water is displaced by an inert gas or air supplied from the surface. In this instance welding is performed at elevated ambient pressures. Depending on the size of the enclosure, the diver is partially immersed in water (only the diver’s hands and the welding torch are inside the habitat). This method requires adequate visibility and is limited to areas with clear access. In general, dry welds are better than wet welds because cooling rates are slower. Both of the devices described above are methods of excluding water from the weld area, thereby creating a dry environment where dry welds and welds requiring more advanced