Warning

Hydrocarbons ignite almost spontaneously in the presence of oxygen. Never allow oxygen-carrying components to come in contact with oil or grease.

2-2.13 Post-dive Maintenance. After each use, rinse the torch in fresh water and dry it. Disassemble and inspect the flashback arrestor for corrosion damage due to electrolysis or clogging. (Frequent clogging or screen burn-out indicates either insufficient oxygen pressure or burning the electrode shorter than the 3-inch minimum.) Replace any damaged parts (see Figure 2-6a, b or c as applicable). All equipment should be thoroughly dry before storing. Secure hose ends with caps or tape to keep out debris. Store all equipment, including electrodes, in an oil-free environment. Electrodes which have been exposed to salt water will rust. They should be rinsed with fresh water, blown dry and stored separately to prevent damage to other rods.

Oxygen Arc Underwater Cutting

Figure 2-6a. Underwater Oxygen-Arc Cutting Torch Breakdown (Arcair).

SCREWS

RIGHT SIDE HANDLE

ROD HEAD

LEFTSIDE HANDLE

NEOPRONE WASHER HEAD NUT

SCREWS

RIGHT SIDE HANDLE

ROD HEAD

LEFTSIDE HANDLE

NEOPRONE WASHER HEAD NUT

Proper Use Arc Washer

NUTS

BLOW GUN NUT

CONNECTOR

NEOPRENE WASHER

Figure 2-6b. Underwater Oxygen-Arc Cutting Torch Breakdown (BROCO).

BLOW GUN NUT

CONNECTOR

NEOPRENE WASHER

NUTS

Figure 2-6b. Underwater Oxygen-Arc Cutting Torch Breakdown (BROCO).

■TORCH HEAD INSULATOR JACKET

TORCH HANDLE BASE NIPPLE

TRIGGER VALVE ASSEMBLY

■TORCH HEAD INSULATOR JACKET

TORCH HANDLE BASE NIPPLE

TRIGGER VALVE ASSEMBLY

Broco Torch Drawing

INLET NIPPLE EXTERNAL WASHER INTERNAL WASHER COLLET LOCKNUT

INLET NIPPLE EXTERNAL WASHER INTERNAL WASHER COLLET LOCKNUT

Figure 2-6c. Underwater Oxygen-ARC Cutting Torch Breakdown (Craftsweld).

2-3 EXOTHERMIC ELECTRODES

Broco Cutting Rods

The BROCO Ultrathermic electrode consists of seven small rods inside a thin steel tube (see Figure 2-2c). One of the seven rods is a special alloy that will burn independently after an arc is struck and oxygen is flowing through the tube. The remaining six rods are made of mild steel. The electrode is insulated with electrical tape. The 3/8-inch electrode is 18 or 36 inches long; the 1/4-inch comes only in 18-inch lengths. It will fit Arcair's Sea Torch, BROCO's BR-22 Underwater Cutting Torch and Craftsweld's Arc-Oxygen Cutting Torch by using the proper collet and washer combinations. The ultrathermic electrode will melt almost any material with its 10,000oF plus, tip heat.

The Arcair Sea-Jet cutting electrode consists of a thin mild steel tube enclosed in a spiral, mild steel spring-like wrapping, which is encased in a larger metal tube (see Figure 2-2d). The electrode is coated with waterproofing and insulating material. Like the Ultrathermic, the Sea-Jet will burn ferrous and non-ferrous materials such as concrete, rock, barnacles and other sea growth. The electrode is 3/8-inch in diameter and 18 inches long. It will also fit the Arcair, BROCO and the Craftsweld Torch.

When using the Ultrathermic or Sea-Jet cutting electrodes, an adapter kit will be necessary in order to achieve proper fit of the electrodes. The kits consist of a variety of collets and washers designed to adapt the torch for the standard 3/8- and 1/4-inch electrodes. Smaller adapters are available for other cutting or welding operations.

2-3.1 ELECTRODE AMPERAGE REQUIREMENTS. The exothermic electrodes will sustain ignition without electrical power as long as oxygen is flowing; therefore, the diver may call for SWITCH OFF once the electrode is burning. Although the exothermic electrodes will continue to burn when the current is off, it is recommended that electrical current be used to provide more heat and enhance the cutting process on all conductive material.

Table 2-4 lists recommended current settings for various cable lengths and sizes.

NOTE

The Sea-Jet electrode will operate on a wide range of amperage settings up to 400 amps. A 12-volt DC battery may be used for start up power and satisfactory cutting can be performed without power, however, the use of 200-300 amps will produce optimum cutting results. (Manufacturer's recommendations)

Correct power settings will result in quick, efficient cutting. The ultrathermic electrode requires only 150 amps at the torch working depth, as opposed to 200-300 for the Sea-Jet. Excessive current settings for the ultrathermic will result in rapid consumption of the electrode. With proper oxygen and power settings, the exothermic electrodes will burn for 45 to 55 seconds. A tong test ammeter is extremely useful in determining the exact amperage being used at the workpiece. Do not rely solely on the values as indicated by panel control knobs or meters, as these are not always accurate. Simply encircle the negative (-) welding lead with the tongs of the amperage tong meter and close them. A clear, accurate reading is instantly registered on the scale. The tongs open by a slight pressure of one finger on the trigger and are self-closing. (see Chapter 4, Figure 4-9).

Length (Feet) Amperage Setting for Cable Size Used

1/0

2/0

150

155

152

200

157

154

250

159

156

300

161

158

350

163

160

400

165

162

450

167

164

500

169

166

1. For greater cable lengths, add 2 amperes for each additional 50-foot length of power cable. (Based on manufacturer's data)

2-3.2 Oxygen Requirements. Exothermic cutting consumes a large volume of oxygen; therefore, a 3/8-inch inside diameter oxygen hose is required to maintain sufficient volume. The hose size is important because it is the oxygen volume together with heat that does the cutting while the pressure blows the slag away. A high volume, high flow regulator capable of delivering 70 CFM is necessary. A two-stage regulator is recommended. The cutting pressure must be 90 psi over bottom pressure (see Table 2-2).

2-3.3 Material Consumption. Table 2-5 is provided for planning purposes. It lists an approximate range of cut through various plate thicknesses. It is expected that actual lengths of cut will fall within the range of cut figures listed, as these figures were attained under actual field conditions. Allowances should be made for diver proficiency and underwater conditions such as visibility, metal cleanliness and current.

2-3.4 Advantages and Disadvantages of The Exothermic Electrode Cutting Process. Exothermic electrodes have the following advantages:

a. The cutting technique is very simple and readily mastered.

b. They will cut thin metal when the power is off.

c. Cutting is performed rapidly.

d. They will cut all ferrous and non-ferrous metals.

e. They are applicable to all metal thicknesses.

f. They will burn through concrete, rock, coral, marine growth and other non-conductive materials when the power is off.

g. The power required is within the capability of a 200-ampere welding power source.

h. A 12-volt battery can be used as an ignition source.

Electrode diameter

Plate Thickness

Range of cut per electrode1

1/4-in.

1/4-in.

20-25-ins.

1/2-in.

10-15-ins.

3/8-in.

1/2-in.

12-20-ins.

1-in.

9-14-ins.

1 1/2-ins.

8-12-ins.

1. Range of cut figures represent cuts made with and without power. The lower numbers were attained without power and the higher numbers with power. Obviously, a 20 percent increase in cutting rates can be realized by using power as apposed to allowing the electrode to burn independently.

1. Range of cut figures represent cuts made with and without power. The lower numbers were attained without power and the higher numbers with power. Obviously, a 20 percent increase in cutting rates can be realized by using power as apposed to allowing the electrode to burn independently.

2-3.4.1 Disadvantages of Exothermic Electrodes. The following are disadvantages of exothermic electrodes.

a. Larger volume of oxygen is required than with steel-tubular electrodes.

b. Burning time of the electrode is short; 45 to 55 seconds.

c. Contact with the work is not required to sustain ignition, thus electrode waste can occur.

2-3.5 Grounding the Work. Before conducting electric-arc cutting on conductive material, a ground cable must be attached to the work piece. The diver can either leave the surface with the cutting torch, ground cable and cutting electrodes or they can be lowered after arrival at the work site. The first task is to clean a spot for the ground clamp. The spot should be a position in front of the diver and should be scraped or wire brushed shiny clean. For diver safety, only C-type clamps are to be used as grounding clamps for underwater cutting or welding operations. The clamp must be firmly secured to the work piece and the cable should have sufficient slack to prevent the clamp from being pulled loose. The diver may elect to lightly tack weld the clamp in place where there is a possibility of it working loose. From time to time as the cut progresses, the diver may have to reposition the ground clamp to avoid becoming a part of the electrical circuit.

NOTE

Thick, gauntlet-type rubber gloves in good condition, worn over a pair of playtex-type gloves afford the best protection against electrical shock. They should be secured at the wrist to prevent slag from getting inside the glove. When working in cold water, wetsuit gloves in good condition, worn over surgical gloves are equally effective.

NOTE

A striker plate attached to the positive (+) clamp is a good idea for a starting point for rod ignition. The burning rod can then be used to clear off any marine growth, making a place for the ground clamp.

2-3.6 Exothermic Cutting Technique. The 1/4-inch electrode may be used to cut steel up to 1/2-inch in thickness. The 1/4-inch electrode leaves a narrow kerf and is preferable for fine cutting. When visibility is poor or when cutting heavier steel, the 3/8-inch electrode is more efficient. The following techniques are recommended:

a. Insert the electrode into the collet opening until it bottoms out on the washer. Tighten the collet nut. When ready to start the cut, hold the oxygen trigger down to get a steady flow of oxygen. Release the trigger slightly. Hold the electrode at an angle of 45o to 90o to the surface to be cut, depending on material thickness (see Figure 2-7). Call for SWITCH ON. Draw the tip of the electrode across the work and strike an arc. As soon as the arc is established, squeeze the trigger full open. Hold the tip of the electrode in the molten pool and drag the electrode along the line of cut. Apply a downward pressure until the electrode penetrates the full thickness of the material to be cut.

NOTE

Before beginning the cut, the diver should visually check the oxygen flow while holding the electrode in a horizontal position. Holding the oxygen trigger down for approximately 20 seconds allows time enough for cutting-gas pressure to build up along the full length of the hose. To ensure a clean cut, a 6-inch (minimum) oxygen emission should be maintained at the electrode tip.

How Cut Metal Using Electrode

Figure 2-7. Technique for Cutting Steel Using Exothermic Electrode.

b. To advance the cut, apply slight pressure to maintain electrode/work contact. Hold the electrode with the free hand as if holding a pool que, approximately 4 inches from the tip for a more stable cut. Move slowly at first, maintaining full penetration. Lack of penetration will be evident by back-spray, increased cutting noise and slag build-up. In such cases, stop advancement and go back and wash out all hangers to complete the cut. It is important to keep the electrode against the work while cutting and keep the tip of the electrode in the puddle. Do NOT try to hold an arc.

c. When the electrode has burned down to within 3 inches of the collet nut, break the contact, release the oxygen trigger and call for SWITCH OFF. When the phone talker has confirmed SWITCH OFF, tap the electrode twice to make sure the switch is off. Loosen the collet nut 1/2-turn and blow the cutting stub from the torch by squeezing the trigger. Insert a new electrode and repeat the starting procedure outlined in 2-3.6a. above.

d. For cutting material thicker than 1/2-inch, use a 3/8-inch electrode. A sawing motion often works well on thicker materials.

e. For materials several inches thick, a saw and wedge cutting technique similar to chopping a tree with an axe may be necessary to widen the cutting path.

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