Arc Welding

Arc Welding

What is Arc Welding? Generalized term used to describe

welding that uses an electric arc between an electrode and the base material to melt and join the metals.

Common Names and Variations: • Shielded Metal Arc Welding (SMAW)

“Stick Welding”• Gas metal arc welding (GMAW) = Metal

inert gas (MIG), Flux-cored arc welding (FCAW), Submerged arc welding (SAW)

• Gas tungsten arc welding (GTAW) or Tungsten inert gas (TIG) welding

Stick Welding Cut-Away

Photo Courtesy of Lincoln Electric (http://www.lincolnelectric.com/knowledge/articles/content/arcweldfund.asp)

Hazards• Welding is an inherently dangerous

occupation.• Even without malfunction the process

exposes those around it to heat, radiation, foreign objects (slag), gases, and high electrical current.

• Malfunctions in equipment often leads to very dangerous situations.

Hazard: Heat• The arc produced during welding can

exceed 3000 degrees Celsius.• Molten metal particles “splash” off the

weld and can cause burns and fires.

Protection: Heat Personal Protective Equipment

(PPE) is used to protect the worker from heat, light and slag.

Welding blankets are used to protect surrounding areas from slag.

Wearing PPE in hot climates poses the risk of overheating. Hydration and ventilation are a must.

Hazard: Radiation Welding exposes the welder and anyone around the

work area to Ultraviolet (UV) Radiation. This exposure poses two risks:

1. Flash Burn - A burning of the surface of the eyeballs and/or skin caused by the UV rays. Same effects as sun burn.

2. Retinal Burn - Burning of the retinal nerve caused by the projecting of the extremely bright arc on the back of the eyeball.

Protection: Radiation Flash burn and retinal burn can be prevented through the proper use of PPE. A high quality shade can prevent

eye damage and is required (OSHA 1926.353(e)). The shade number used should correspond to the work being performed. Clothes that completely cover the body prevent flash burn to the skin.

Those working near the welder should be protected from flash burn by a welding barrier that is set-up around the area.

Hazard: Gases A welder is faced with different hazards related

to the gases they are exposed to.1. The welding process produces toxic fumes. The

zinc oxide and magnesium oxide fumes can cause Metal Fume Fever. The symptoms of which can include: headache, fever, chills, muscle aches, thirst, nausea, vomiting, chest soreness, fatigue, gastrointestinal pain, weakness, and tiredness. (American Welding Society)

Hazard: Gases2. The shielding gases used in welding, while

inert, can cause asphyxiation in enclosed spaces. The gases are used in the welding process to displace oxygen from the area of the weld. If the gases are contained in a small area the worker’s oxygen levels will be depleted.

3. The gas cylinders used in the welding carry the same risks of rupture and explosion as any compressed gas cylinder.

Protection: Gases In order to protect the worker from toxic gases

and from the displacement of available oxygen proper ventilation is required (OSHA 1926.353(a)).

OSHA regulation (1926.353(b)) requires lifelines and full-time spotters to be used for welding in confined spaces.

Care should be taken in the transport and use of all gas cylinders.

Hazard: Electrical Current Arc welding draws a large amount

of current and passes it through the piece of material in front of the worker. Anytime electricity is involved there is a risk of injury/death.

Protection: Electrical Current

In order to avoid electrical shock welding should be done in a dry environment. Avoid moist conditions and standing water.

In hot climates there is the possibility of sweat soaked clothing becoming an electrocution hazard.

Electrical equipment should be inspected frequently. Splices must be rated at least as high as the conductors they are joining and no splices can be present in the 10 feet of conductor closest to the welding torch (OSHA 1926.351(b)).

The Numbers The risk from fatal injuries from welding is more

than four deaths per 1,000 workers over a working lifetime.

For the construction industry, welders flash (burn to the eyes) accounts for 5.6% of all construction eye injuries.

1/4 of all welding injuries are eye injuries. Explosions and electrocutions are rare but tend to

be very serious.

Specific Cases A construction worker was killed on June 30,

2004 in when a welding torch apparently ignited his clothes while he was working inside a steel drainage pipe at a construction site at Highway 29 in Napa. The man was trapped inside the pipe and burned to death.

On August 21, 1989 in British Columbia a welder was discovered unconscious inside a titanium tank he had been finish welding valves. The argon gas used to shield the weld displaced the oxygen in the bottom of the tank and worker died of asphyxiation.