E2 Underwater Cutting Equipment

E-2.1 Arcwater Cutting. Water arc cutting is essentially a melting process. Water is used to blow the molten metal out of the kerf. Since the cutting is dependent solely on the melting action of the arc, all the power available, up to 500 amps may be used. The process is limited to one manufacturer and may prove valuable when gouging out welds or cutting thin metal.

E-2.2 Principles of Operation. The process consists of striking an arc underwater between a carbon-graphite, copper-coated and waterproofed electrode and the workpiece. The metal is instantly transformed into a molten state and is blown away by a high-pressure jet of water which exits the torch through an orifice located directly below the electrode opening in the torch.

E-2.3 Applications. This process can be used for the following applications:

a. It can be used on almost all metals found in ships and underwater structures.

b. To remove defective fillet welds for rewelding.

c. To cut metal in a manner similar to the underwater oxygen-arc process.

NOTE

Cutting material in excess of one inch with this process is not practical.

d. Cracked butt or seam welds can be grooved for weld repair.

E-2.4 Necessary Equipment. The following equipment is required when using the arcwater underwater cutting process.

E-2.4.1 Power. A DC welding generator capable of providing a constant open-circuit voltage of 60 volts and 350-500 amperes. This process calls for reverse polarity. That is: electrode positive (+).

E-2.4.2 Water. The process requires a constant supply of sea water or fresh water supplied at a flow-rate of 3.5 gallons per minute at 90 psi over bottom pressure. A ship's firemain will normally provide sufficient pressure for this process.

E-2.4.3 Arcwater torch. The arcwater torch (Figure E-1) is electrically insulated and completely waterproofed except in the area where the electrode is inserted. It is small and well balanced, designed to minimize diver fatigue.

E-2.4.4 Electrodes. The arcwater torch is designed to use especially formulated, copper-coated waterproofed electrodes. The electrodes dimensions are 5/16" x 9" and are completely waterproofed except the end which is inserted into the torch. The arc end has a special waterproofing which is removed by lightly tapping the electrode against the work.

Figure E-1. Arcwater Torch Assembly.

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