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Types of underwater welding

Types of underwater welding

Underwater welding is to introduce direct arc in water, to join the things underwater. Mostly heavy structure cannot be transported to land to weld and underwater welding has made it easier to repair them inside the water. Underwater-welding has saves the valuable time that can be wasted in taking out the heavy structure. It is very important technique for emergency repairs. Special apparatus are used for such welding, including water proof electrodes and power supply system. There are two types of underwater welding:

  • Dry Welding:  In dry  welding the weld being performed in a chamber at raised pressure, chamber is filled with a gas mixture sealed around the structure being welded. It is also called as habitat welding. Dry welders have many more variables to work with than surface welders like different gas pressure, apparatus and restricted space. Dry welding includes several methods, depending on the repair, cost and other factors. The 4 kinds  of methods used by dry diver is
  1. Pressure welding: the work is done by the welder in a pressure vessel measuring 1 atmospheric unit of pressure.
  2. Habitat welding: Chamber in used in ambient pressure ,approximately the size of a small room to weld. Before entering, the chamber displaces its water into ocean or lake.
  3. Dry chamber welding: similar to habitat welding, but with a smaller chamber than habitat welding. The head and shoulders are inside the chamber (dressed in diving gear) and is open at the bottom for the diver to fit in.
  4. Dry spot welding: The habitat slims to the size of about the welder-diver’s head. It’s placed on the weld site and the welder places his electrode in the habitat, which seals around it.

With more depth , it is harder to build a good weld because of pressure of the gases near the weld site.

  • Wet Welding: Wet welding is done in wet environment in which the welder and the electrode directly open to the water. It is easy to learn but difficult to master. The 3 methods used in wet welding are :
  1. Pull or self consuming method: With the drag technique, the electrode is simply crawl across the work and the welder only has to apply a slight downward pressure, whilst the electrode is being eaten up. Even the welder must maintains the proper lead and slope angle, together with a right travel speed, the electrode will make a orderly bead of suitable profile, almost on its own.
  2. Oscillation technique: With the oscillation method the electrode is oscillated so that the point closest to the holder, and not the end closest to the work, is lifted and underneath in a perpendicular direction, i.e. the slope angle is constantly changed whilst welding. By this technique, metal deposition is least and it also prevents non-concentric burning of the electrode, mainly when welding in the root of a joint.
  3. Step back technique: This method is used to aid refinement to throat thickness and weld width, together with some refinement in the control of the cooling rate of the weld. Both of these methods however, demand a more ability and experience on behalf of the welder, together with an understanding of the solidification pattern of the weld and its effects upon the material. It’s a little more difficult due to the greater degree of control This technique is very well suited for fillet welds atleast.
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