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Sometimes, workers cannot de-energize equipment that they will be working on or near. When that happens, it’s important to take precautions to protect them from accidental contact with live electricity.
Conditions for Working Live
For most purposes, OSHA requires that live parts be de-energized before employees begin working on or near them. OSHA permits work on or near exposed live parts only when:
- You can demonstrate that de-energizing introduces additional or increased hazards, or
- You can demonstrate that de-energizing is infeasible due to equipment design or operational limitations.
Safe Work Practices for Working Live
If you don’t de-energize the equipment, you’re required to comply with OSHA’s Safe Work Practices. These have to be included in your written procedures. The requirements for working on exposed live parts are found in 1910.333(c) and 1910.335. Its requirements cover:
Qualified persons. Only qualified persons may work on or near energized parts or equipment. To be considered “qualified,” workers have to be trained to work safely on energized circuits and to use special precautionary techniques, personal protective equipment (PPE), insulating and shielding materials, and insulated tools.
Work near overhead power lines. Unqualified persons who will be working near live overhead power lines must keep minimum clearance distances between themselves, any conductive equipment they are using, and the lines. For lines rated at 50 kilovolts (kVs) or less to ground, the minimum clearance distance is 10 feet; for higher voltages, workers should add 4 inches of clearance distance for every kV over 50. Qualified persons who are working inside minimum clearance distances to live overhead power lines must use insulated tools and PPE.
Vehicular and mechanical equipment. Vehicles or mechanical equipment with elevating parts that may come near overhead lines must observe the same clearance distances as personnel.
Illumination and a clear field of view. Whenever workers enter spaces containing exposed energized parts, there must be sufficient illumination for them to work safely. In addition, there must be no obstruction that prevents workers from clearly seeing the work they’re performing.
Confined or enclosed work spaces. When workers are in a confined or enclosed space (for example, a manhole or vault) that contains exposed energized parts, employees must be provided with protective shields, barriers, or insulating materials that will prevent accidental contact with these parts. If there are doors or hinged panels that could swing into the workers and push them into contact with exposed live parts, those must be secured.
Conductive materials and equipment. Sometimes, workers must handle long dimensional conductive objects (such as ducts and pipes) in areas with exposed live parts, energized conductors, or circuit parts. In such situations, you must put work practices in place (including insulation, guarding, and material-handling techniques) that will minimize the hazard.
Portable ladders. When portable ladders are used in areas where either the ladder or the worker could contact exposed, energized parts, they must have nonconductive side rails.
Clothing. Employees must not wear jewelry or clothing that could be conductive, such as watch bands, bracelets, rings, key chains, necklaces, metalized aprons, cloth with conductive thread, or metal headgear, if they might contact exposed, energized parts. It is acceptable to cover such items with insulating materials rather than removing them.
Housekeeping duties. Workers should not perform housekeeping duties in areas where they are at risk of contact with exposed live parts, unless safeguards such as insulation are put in place. In addition, they must not use electrically conductive cleaning materials (like steel wool, metalized cloth, silicon carbide, or conductive liquid solutions) close to energized parts.
Interlocks. Only a qualified person using appropriate safety equipment and safe work procedures may override an electrical safety interlock and then only temporarily while he or she is working on the equipment. When the work is finished the interlock system must be returned to its normal operation.
Tomorrow we’ll look at the additional lockout/tagout precautions that apply to electrical work.