Oxygen arc cutting Steel-Tubular Electrodes
The oxygen arc cutting steel-tubular electrode consists of a steel tube with a waterproofed flux coating which is applied during the manufacturing process. The electrode is 14 inches long with a 5/16-inch outer diameter and a bore diameter of slightly less than 1/8 inch. The waterproof flux coating is similar in composition to the coating on welding electrodes. The flux coating serves the following purposes: a. It promotes easy starting and maintenance of the arc. b. It liberates gases, thus forming a protective bubble around the arc. c. It serves as an electrical insulator, even in wet conditions, thereby assisting in safeguarding the diver in the event of accidental body contact while cutting. d. It prevents arcing from the side of the electrode when working in confined quarters.
Advantages of Steel-Tubular Electrodes.
Steel-tubular electrodes have the follow-ing advantages: a. The cutting technique is simple and readily mastered. b. Metals up to 2 inches in thickness can be cut. c. Cutting is performed rapidly. d. Neat, trim, narrow cuts are produced. e. The power required is within the capacity of a 400-ampere welding power supply. f. There is less electrode waste because the electrode must be in constant contact withthe metal being cut to sustain an arc.
Disadvantages of Steel-Tubular Electrodes
The disadvantages of the steel-tubular electrode are as follows:
- The burning time of the electrode is short (approximately one minute).
- It produces a narrow gap which may be difficult to locate in poor visibility conditions.
- A welding machine is required.
- The higher amperage requirement deteriorates electrode holder more rapidly than the exothermic process.
The steel-tubular electrode requires 300-400 amps at the torch working depth.
With proper power and oxygen pressure settings, satisfactory cutting results can be obtained. An amperage tong test ammeter is extremely useful in order to determine the exact amperage output of the welding generator. Do not rely solely on the values as indicated by panel control knobs or meters, as these arenot always accurate. Simply encircle the welding lead with the tongs of the test ammeter and close them. A clear, accurate reading will instantly register on the scale. The tongs open by a slight pressure of one finger on the trigger and are self-closing.
Steel-tubular electrode oxygen requirements.
To ensure sufficient oxygen flow to the torch, 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.
Steel-tubular electrode material consumption.
Satisfactory cutting may be accomplished using a wide range of oxygen pressure settings; however, supplying less than optimum volume to the torch will decrease cutting efficiency, slow down the operation and unnecessarily fatigue the diver. On the other hand, too much oxygen for a given plate thickness wastes oxygen and increases diver stress by creating excessive back pressure at the electrode tip.