Arc welding is one of the most effective processes for joining metals through melting. In simple terms, arc welding involves using a power supply to create an electric arc between an electrode and the metals to be fused together. The arc generates temperatures of 6500°F or more, melting the two metals together at the place where they are joined. The heat is so intense, and the metals can react with nitrogen and oxygen in the surrounding air, so slag or a shielding gas may be used to limit contact between the metals and the air.
Because of the heat and related properties, arc welding can pose hazards to welders, workers in the immediate area, and surrounding equipment and structures. That’s why it’s important to become familiar with all applicable safety practices and procedures when planning to use arc welding.
Electrical adequacy and safety
Because arc welding equipment uses a tremendous amount of electricity, one safety consideration is verifying the adequacy of the power supply. The system should provide enough electricity to run the arc welder without affecting the performance and safety of other equipment being used on the site. It’s also important to ensure that the welding equipment is safely connected to a proper ground, that the circuit being used has a correctly sized circuit breaker or fuse, and that some type of disconnecting switch or controller is located within a safe distance.
Given the extremely high temperatures produced during the arc welding process, steps should be taken to limit the potential of fire. Arc welding should only be performed above fire-resistant flooring surfaces such as concrete, with no gaps that could allow sparks or debris to enter. (However, welding should not take place immediately upon concrete, because moisture within the concrete could turn into steam and cause an explosion.)
Surrounding the welder’s area with metal sheets or fire-resistant curtains can prevent the spread of any fires that do occur and prevent sparks from reaching flammable materials nearby. Combustible materials should be removed from the immediate area, and dry-chemical fire extinguishers or extinguishing material such as buckets of sand and fire blankets should be close at hand. If the welding site involves a higher-than-normal risk of fire, such as flammable materials that cannot be moved, a designated fire watcher should be present while welding activity takes place.
In addition to generating heat, arc welding can produce potentially hazardous or toxic fumes. Welding rods and the metals or coatings used on them may contain hazardous chemicals such as lead, mercury, cadmium, zinc, and fluorine compounds. That’s why arc welding should take place only in properly ventilated areas or in workspaces with appropriate levels of artificial ventilation. Welders should also wear respirators when they may encounter hazardous fumes.
Having the right personal protective equipment (PPE) is also critically important when arc welding. That includes a flame-retardant welding jacket or leather apron, a welding helmet with the correct filter plate for the type of work being performed, safety glasses or goggles, flame-resistant gloves, hearing protection, and shoes or boots with toe protection and shoelace guards.
As with all aspects of workplace safety, training in the proper operation of arc welding equipment is vital. When possible, welding should be performed on a firebrick surface. Surfaces and the equipment itself must be kept free of grease and oil. If arc welding is being performed on a conductive surface such as steel flooring, an insulating mat should be used. The metal surfaces to be welded must be cleaned thoroughly to provide the best contact for the weld, and hot metal should be handled with pliers or tongs.
Welders should monitor the condition of the arc welding equipment to prevent it from overheating. When work stops for the day or an extended period, the equipment should be disconnected from the power source and the electrodes removed. If the welder is powered by a generator or similar combustion device, ventilation is critical. In addition, refueling or maintenance should not take place while the equipment is hot. Finally, it’s important to have appropriate first aid equipment close at hand.