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When welding, two pieces of metal (similar in physical properties) are joined together, or fused to one another. Once welded, the two metals become stronger then when they were individual pieces. However, this process doesn't get completed without the health and physical hazards to our bodies. Some general hazards from welding include; heat, fumes, dust, smoke, penetration and impact.
Three Types of Welding
Arc Welding - In arc welding, the two metals are fused together by generating an electric arc between the base metals and a covered metal electrode. Heat is then produced by the arc, which melts the metal and mixes the molten deposits of the coated electrode.
The arc energy's source comes from a power supply that supplies direct or alternate currents. The electrodes carry the current to form the arc, producing a gas that shields the arc from the atmosphere, and adds metal to control the shape of the weld.
Gas Welding - During gas welding, the two metals are fused, or melted by their adjoining surfaces. This is accomplished by directing a gas flame over the metals until a molten puddle is created. Energy for gas welding is derived from the combustion of a fuel with oxygen or air. Some of the more popular fuels are, hydrogen, acetylene and Mapp gas. Gas welding is generally used in general maintenance work, brazing and soldering since it is slower and much easier to control than electric welding.
Oxygen and Arc Cutting - This is when the severing of removal of medal by a flame or arc is performed. The two common cutting processes are:
- Arc Cutting: Extreme heat of electric arc melts the metal.
- Oxygen Cutting: Metal heated by gas flame and oxygen jet cuts the metal.
Personal Safety Equipment
OSHA 29 CFR 1910.252 states "Helmets and hand shields shall protect the face, forehead, neck and ears to a vertical line in back of the ears, from the arc direct radiant energy, and weld splatter."
A helmet with a filter plate is intended to protect professionals from harmful arc rays and weld sparks and spatters that come in contact with the helmet. However, they are not intended to protect against grinding fragments, wire wheel bristles, slag chips and other hazards that can ricochet under the helmet onto the skin. To protect against these impact hazards, goggles or other appropriate eye protection must be worn.
OSHA requirements for arc cutting and arc welding with open arcs states that helmets or hand shields with filter lenses and cover plates will be used by not only the operator, but other personnel viewing the arc. A spectacle with a 'shade lense' is also recommended for general-purpose protection for viewers. Face shields, spectacles or goggles are required by users to wear when resistance welding or brazing in order to protect their face and eyes from welding hazards.
Protective Clothing - ANSI Z49.1.88-Welding and Cutting (4.3) states, appropriate protective clothing for any welding and cutting operation will vary with the size nature and location of the work to be performed. Clothing shall provide sufficient coverage and be made of suitable materials to minimize skin burns caused by sparks, spatter or radiation, covering all parts of the body is recommended to protect against ultraviolet and infrared ray flash burn.
Wear dark clothing under the face shield to reduce reflection, but heavier materials like heavy cotton or wool are preferred as the resist deterioration. Clothing items with rolled-up sleeves, pockets or pant cuffs are highly NOT recommended. ANSI requires all welders to wear a flame resistant glove, which will provide the heat resistance necessary for welding. Gloves with gauntlet style cuffs are recommended as they provide additional arm protection.
Other protective clothing that should be worn include, flame-resistant aprons made from leather, which protects the front of the body from sparks and radiant energy.
Proper ventilation is necessary to prevent welders and other workers from breathing in high levels of harmful airborne contaminants. Ventilation must be provided for all forms of welding, brazing and cutting. The right ventilation depends on:
- Volume of the space where welding occurs.
- The number of operations that generate contaminations.
- The natural airflow rate in the area welding is occurring
- Locations of welders breathing zones
Natural Ventilation - Natural ventilation is acceptable if the present work area meets the following requirements:
- The welding area is more that 10,000 square feet
- The ceiling is more than 16 feet tall
- Welding is not performed in a confined space
- Welding space does not contain structure barriers that obstruct ventilation.
Mechanical ventilation is required if your welding area did not fall in the previous guidelines.
Mechanical Ventilation - Broken up into two categories, low vacuum systems and high vacuum systems.
Low vacuum systems take large volumes of air at low velocities. Consisting of a hood located a certain distance from the workstation. Depending on how far from the welding location is the hood, will depend on how much ventilation is occurring. Hoods are recommended to be placed near the work area and provide an effective airflow of at least 100 linear feet (30m) per minute.
High vacuum systems are close-range extractors that target fumes as near to the work as possible. Fume extractors often have an immediate are of welding. Removing small volumes of air at such a high velocity will effectively remove potentially hazardous materials from reaching the breathing zone of the welder. Often equipped with a large fan, these systems pull the contaminates into a filtration system, with a HEPA (High Efficiency Particulate Absolute) filter or combination of HEPA filter and prefilter and then recirculate the clean air back into the work area. Some advantages are greater flexibility for job adaptation; more efficient means of fume removal and greater visibility to the welder due to a reduction of fumes and vapors.
To determine which type of ventilation if right for your work area, sampling to verify the concentration levels of toxic fumes are necessary, and respiratory protection is required. For more information, see OSHA 29 CFR 1910.252 on welding regulations.
Sources for More Information
ANSI Z49.1-88, American National Standards Institute-Safety in Welding and Cutting.
29 CFR 1910.251-257, Welding.
Safety in Welding and Cutting, American Welding Society, 1988.
Workplace Safety in Action: Safe Welding Operations, J.J. Keller & Associates, Inc., August, 1995