While workers performing electric arc welding are subject to hazards related to the inhalation of toxic fumes, eye hazards, burns, or fires, the most potentially perilous hazard they face is electrical shock, which can result in electrocution and other horrific physiological problems. Preventing electrical shock should therefore be a top priority within a company safety program that also addresses the other hazards associated with electric arc welding.
Why is preventing electrical shock so important? Most electric arc welding machines used in mechanical construction push up to 600 V and generate a current between 10-600 A. However, it only takes 70-100 milliamps (mA) to kill a human being, and a mA is only one one-thousandth of a simple amp.
The key to preventing electrical shock is to ensure welders protect themselves from becoming the path of least resistance for electricity traveling to ground, and from becoming part of the actual welding circuit. While most welders thoroughly understand the former concept and keep it foremost in their minds, the latter concept is often overlooked.
For example, a welder in the Midwest recently became part of a welding circuit and remained there for close to 10 seconds until the electrode burned down enough to break the circuit. Fortunately, he survived, but the incident left him bleeding from the nose and mouth and shook him up so much that he seriously contemplated finding another way to make a living.
In this case, the incident was a perfect storm of four events. First, the worker was kneeling on two pipes covered in sheet metal that were electrically connected to the pipe he was welding. Second, it was an extremely hot day, and he was sweating so profusely that his welding gloves and pants were soaking wet. Third, his work cable was clamped to a structural steel beam and not directly to the work itself. Fourth, the work cable was clamped 60 feet away from the welding machine.
The combination of the first two events decreased resistance to a path that the current was not supposed to travel. The combination of the second two events increased resistance in the path that the current was supposed to travel. As a result, the current travelled from the electrode through the work, the welder’s wet welding glove, his body, the sheet metal covered pipe, the steel beam, the work cable, and finally back to the welding machine. Remove any one of the four events that led to the incident, and it probably would not have occurred.
BETTER SAFE THAN SORRY
The lessons from the incident are straightforward and, while the missing protective measures are somewhat obvious, they’re certainly well worth revisiting.
• Make sure welders know how and why to insulate themselves from the anticipated electrode circuit, any unintended and perhaps inconspicuous electrode circuit paths, the work itself, and from ground;
• Ensure welders do not weld in wet environments, and emphasize proper insulation when the work environment and/or their clothing, including their gloves, are even slightly damp; and
• Require welders to clamp their work cables directly to the work itself and as close to the weld as practical. This safe-work practice is recommended by welding machine manufacturers in their operators’ manuals. When there is no place on the work to clamp a standard spring-style work cable clamp, use a magnetic clamp. There are several manufacturers that make effective, high-quality magnetic clamps that are capable of functioning effectively up to 600 A.
Protecting welders from other common electric arc welding hazards can be easily accomplished by:
• Preventing overexposure to welding fumes with adequate ventilation, such as effective local exhaust, industrial-grade fans, and, when necessary, point-of-operation ventilation systems such as smoke eaters;
• Having standard safe work practices in place, such as requiring welders to position their bodies away from welding fumes and to position their welding helmets so that the fumes can’t rise up underneath them and into the breathing zone;
• Requiring adequate eye protection at all times. In addition to wearing standard safety glasses underneath their welding helmets while they are welding, welders should use, at a minimum, a No. 10, and sometimes a No. 12 or No. 14, helmet filter plate, depending on the size of the electrode and the amount of current that will be generated;
• Protecting against burns with proper clothing, including leather boots that cover the ankles, flame-resistant pants, and a flame-resistant long-sleeve shirt or flame-resistant coveralls. High- quality welding gloves that are in good condition are also necessary. A welding cap is a good idea, too, unless the welder is using
a combination hardhat/welding helmet rig; and
• Guarding against workplace fires through a combination of good housekeeping and a fire watch at the end of each day. Anything that’s flammable or combustible should be removed from the hot work area or somehow isolated before welding begins. And, a designated fire watch should observe the work area for at least 30 minutes after the welding or any other hot work has stopped for the day. The fire watch should look for smoke, smoldering materials, flames, etc.
The good news is that electric arc welding is extremely safe when performed properly. To learn more about electric arc welding safety, welders should read the safety instructions in a welding machine manufacturer’s operator’s manual before welding with that particular machine.
Publication date: 6/22/2015