Welding Processes and Hazards
Protecting yourself when performing welding operations depends on your understanding of the hazards involved and the proper way to control them. Controlling welding hazards includes
avoiding eye injury, respiratory protection, ventilation of the work area, protective clothing, and having safe equipment to use.
Welding Safety – Texas A&M FabLab
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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 burn 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.
Arc Welding and Cutting
Arc welding is the process in which fusion is produced by heating with an electric arc that is generated between an electrode and the surface of the base metal.
Arc cutting is the process in which the cutting or removal of metals is done by melting with the heat of an arc between an electrode and base metal.
Arc welding and cutting types include:
- Flux Core Arc Welding (FCAW) is an arc welding process where coalescence is produced by heating with an arc between a continuous filler metal electrode and the work.
- Submerged Arc Welding (SAW) also known as Sub Arc and automatic welding. This is an arc welding process which produces coalescence by heating with an arc or arcs between a bare metal
electrode or electrodes and the work.
- Shielded Metal Arc (SMAW) is an arc welding process which produces coalescence by heating with an electric arc between a covered metal electrode and the surface of the base metal.
- Gas Metal Arc (GMAW or MIG): This is also called stick welding. This is an arc welding process where coalescence is produced by heating with an arc between a continuous
filler metal electrode (typically a steel alloy wire) and the work.
- Gas Tungsten Arc/Tungsten Inert Gas Welding (GTAW or TIG), also called Heli-arc welding, is an arc welding process where coalescence is produced by heating with an arc
between a single tungsten electrode and the work.
- Plasma Arc Welding, also called plasma welding, is an arc welding process similar to gas tungsten arc welding (GTAW). The electric arc is formed between an electrode
(which is usually but not always made of sintered tungsten) and the workpiece.
- Plasmas Arc Cutting: This is also called plasma cutting. The metal is cut by melting a localized area with a constricted arc and removing the molten material with a
high-velocity jet of hot, ionized gas in this process.
- Carbon Arc Cutting: This is also called Arc Gouging and Air-arcing.
For more information on arc welding, read Safe Arc Welding by Lincoln Electric.
Railroad Thermite Welding – Sweden
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Laser Welding Steel Sheets
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Robotic Welding Competition
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Other Welding Processes
Thermite welding: Thermite welding uses a chemical reaction to produce intense heat instead of using gas fuel or electric current.
Pressure welding: Pressure welding uses heat along with impact-type pressure to join the pieces.
Laser Welding: Laser welding uses a focused beam of light to achieve very precise welds. The major hazard of this powerful beam is to the eyes, which can be partially blinded
when hit with the beam. Special eye protection must be used, and care must be taken with any reflective surfaces since both the original and reflected beams are extremely dangerous.
Electron Beam Welding: This method uses a focused beam of electrons to produce high precision and deep penetration welds. Since x-rays are produced as a by-product, the process
should be enclosed and shielded with lead or other materials suitable for preventing x-ray exposure. All doors, ports, and other openings must have proper seals and should be checked periodically
to prevent x-ray leakage.
Operators should wear film badges to detect accidental radiation exposure. The high voltages required also present an electrical hazard.
Robot Welding: Many industries are beginning to use robot welders in place of human workers on the assembly line. This removes workers from the hazard but focuses on job
elimination rather than workplace improvements.
In 2013, an employee was prepping steel using a grinder. He was working by himself on the first level of an oil rig platform sub-base. Another Fitter/Welder was working
on the second level of the platform, while the crew supervisor was working on the second level of the platform. The worker was using a grinder and was standing inside a recessed box, where
the oxygen acetylene torch hoses were also present. A leak from the acetylene hose provided the fuel source and a spark from the grinder provided the ignition source for a flash fire to occur.
This fire resulted in serious burns to his legs and feet. He was admitted to the hospital for ten days for burn injuries. The investigation concluded the fire occurred due to a defective splice
on the acetylene hose that allowed the acetylene to leak, causing a fire and the serious injury.
Welding Hazards and Precautions
The 5 Most Common Welding Hazards
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Safe procedures and practices must always be used when working around or with arc welding equipment to avoid being injured.
Avoid the following hazards in arc welding:
- radiation from the arc, in the form of ultraviolet and infrared rays
- flying sparks and globules of molten metal
- electric shock
- metal fumes
Radiation: Radiation from the arc is hazardous to the eyes. Eyes should be protected from radiation from the arc by use of an arc welding helmet or face shield with approved lenses.
- Cover the face, hands, arms, and other skin surfaces to prevent exposure to the radiation.
- Gloves should be worn and other parts of the body covered by clothing of sufficient weight to shut out the rays of the arc.
- Without proper clothing, burns comparable to sunburn will result.
Arc Flash: When possible, shield arc-welding operations so no one may accidentally look directly at the arc or have it shine or reflect into his or her eyes.
- An arc “flash” may cause a person to be temporarily blinded.
- The severity of an arc flash and the time it will take to recover varies with the length of time a person was exposed to the arc.
- Long exposure has been known to cause permanent damage to the retina of the eye.
- If someone is severely “flashed,” medical personnel should provide special treatment at once.
Welding Hazards and Precautions (Continued)
Avoid the possibility of dangerous electric shock by using insulated electrode holders and wearing dry leathers and gloves.
- When possible, avoid using arc-welding equipment in wet or damp areas.
- Never perform arc-welding in an area that is not well ventilated.
Electric Shock Protection – Expert Village - eHow
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Flying sparks and molten metal: Flying sparks usually accompany arc welding. These present a hazard if they strike unprotected skin, lodge on flammable clothing, or hit any other flammable material.
- When arc welding, wear suitable weight clothing and cuff less trousers.
- Cover pockets so they will not collect sparks, and remove any flammable materials, such as matches, plastic combs, or gas lighters.
- Wear the proper foot protection. Wear high top boots with steel toes.
Hot metal and burns: Hot metal will cause severe burns. Never handle it with bare hands until it has cooled naturally or has been quenched in the quenching tank. Therefore, use leather gloves with
tight fitting cuffs that fit over the sleeves of the jacket. Many welders wear a full set of leathers that consists of the following:
Welding PPE Case Study
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- jacket or set of sleeves
- gauntlet gloves
- welders hat liner
In gas welding, the high temperatures of the welding flame and the sparks will burn skin. Gas welding can also cause radiation burns due to infrared rays emitted by the red-hot material.
Wear flame-resistant or flame-retardant clothing and hair protection at all times.
In 2011, an employee was tasked to pin weld the inside insulation of the metal duct and wipe the surface with a propanol solution for shipment. The employee noticed
that one pin weld of the duct failed. He decided to replace the defective pin. When he drove a new weld, the sparks from the weld ignited the residue of the propanol on his glove.
His right hand caught fire and caused second-degree burns.
Gases and fumes: Fluxes used in certain welding and brazing processes produce vapors that are irritating to the eyes, nose, throat, and lungs. Welding fumes and gases
generally come from the following sources:
- base material being welded or the filler material used
- coatings and paints on the metal or electrode coatings;
- shielding gases supplied from cylinders;
- chemical reactions due to ultraviolet light of the arc and heat; and
- contaminants in the air from cleaners and degreasers.
Perform welding in a well-ventilated area and always wear approved safety goggles. Here are a few options:
- The darkest shade of the goggles that still show a clear outline of the work without producing eyestrain is recommended.
- Sunglasses are not adequate.
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