745 Welding, Cutting, and Brazing Safety

Welding Processes and Hazards

Controlling welding hazards includes avoiding eye injury, respiratory protection, ventilation of the work area, protective clothing, and having safe equipment to use.

Gas Welding

Oxy-acetylene Welding/Cutting

Oxy-acetylene welding or cutting is also called torch or gas welding or cutting. Two metals are joined by melting or fusing their adjoining surfaces in the process. This is done by directing a flame from burning gas (usually acetylene) to melt metal at a joint to be welded, and is a common method for welding iron, steel, cast iron, and copper.

Since gas welding is slower and easier to control than electric arc welding, it is commonly used in general maintenance work, brazing, and soldering.

• Equipment: Oxyacetylene equipment consists of a cylinder of acetylene, a cylinder of oxygen, two regulators, two lengths of hose with fittings, a welding torch with tips, and either a cutting attachment or a separate cutting torch. Accessories include a friction igniter to light the torch, an apparatus wrench to fit the various connections on the regulators, the cylinders, and the torches; goggles with filter lenses for eye protection; and gloves for protection of the hands. Flame-resistant clothing is worn when necessary.
• Acetylene: Acetylene (chemical formula C2H2) is a fuel gas made up of carbon and hydrogen. When burned with oxygen, acetylene produces a very hot flame, having a temperature between 5700°F and 6300°F. Acetylene gas is colorless, but has a distinct, easily recognized odor.
• MAPP Gas: MAPP (methylacetylene-propadiene) gas is an all-purpose industrial fuel that has the high flame temperature of acetylene and the handling characteristics of propane.
• MAPP is not sensitive to shock and nonflammable in the absence of oxygen. There is no chance of an explosion if a cylinder is bumped, jarred, or dropped. The cylinders may be stored or transported in any position with no danger of an explosive air pocket being formed.
• MAPP toxicity is rated "very slight," but high concentrations (5,000 ppm) may have an anesthetic effect. Local eye or skin contact with MAPP gas vapor causes no adverse effect. However, the liquid fuel will cause dangerous frostlike burns due to the temperature at which MAPP gas should be stored.
• Oxygen: Oxygen is a colorless, tasteless, odorless gas that is slightly heavier than air. Oxygen will not bum by itself, but it will support combustion when combined with other gases.
• Take extreme care to ensure compressed oxygen does not become contaminated with hydrogen or hydrocarbon gases or liquids.
• A highly explosive mixture will be formed if uncontrolled compressed oxygen becomes contaminated. Oxygen should NEVER come in contact with oil or grease.
• Oxygen cylinders are supplied in several sizes. The size most commonly used 9 1/8 inches in diameter, weighs about 145 pounds, and has a capacity of 200 cubic feet. At 70°F, the gas is under a pressure of 1800 psi.

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