Underwater welding is described in detail in the U.S. Navy Underwater Cutting and Welding Manual. Before proceeding, the welder must be thoroughly familiar with applicable safety precautions and methods contained in the manual.

When welding is required for critical applications such as permanent welds or for welding on ship hulls, specifications are contained in ANSI/AWS D3.6-93, Specifications for Underwater Welding, published by the American Welding Society.

Although underwater welding does not have as many applications as underwater cutting, it is a useful process. The overall advantage is that underwater welding can significantly reduce the time spent on making repairs, both temporary and permanent, over those using other methods. In underwater construction and repair, it can be effectively used to attach patches to pipes, and for providing lifting or attaching points to steel H-piles and sheet pile.

A major disadvantage of welding is that it requires considerable practice to achieve a consistently good standard of welding. The problem is that the ocean acts as a large heat sink that draws heat off the electrode, which can cause holes in the welded material and possible loss of strength of the metal.

The two types of welding are discussed in the Navy Underwater Cutting and Welding Manual. They are:

• Wet welding where the diver is completely submerged.

• Dry welding at the "splash zone" where the welder is in a dry box or cofferdam at atmospheric pressure. It is essentially conventional welding. Details to exclude water from the weld area are provided in the Underwater Cutting and Welding Manual.

Shielded metal-arc welding is the most widely used process for wet welding. Specific welding procedures for underwater maintenance work on ships is addressed in the Underwater Ship Husbandry Manual (NAVSEA SO6OO-AA-PRO-OIO) and the Naval Ships' Technical Manual, Chapter 074 (NAVSEA S9086-CH-STM-010).

As with underwater cutting, serious injury or death can result when adequate precautions are not followed during underwater welding.

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