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810 Hand and Power Tool Safety
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Grounding

The term "ground" refers to a conductive body, usually the earth. "Grounding" a tool or electrical system means intentionally creating a low-resistance path to the earth. When properly done, current from a short or from lightning follows this path, thus preventing the buildup of voltages that would otherwise result in electrical shock, injury and even death.

Under certain conditions, even a small amount of electric current can result in fibrillation of the heart and death. An electric shock also can cause the user to fall off a ladder or other elevated work surface and be injured due to the fall.

Three-wire cords contain two current-carrying conductors and a grounding conductor. Any time an adapter is used to accommodate a two-hole receptacle, the adapter wire must be attached to a known ground.

Image of plug that is missing the ground prong
A very common hazard: missing ground prong.

To protect the worker from shock and burns at work, make sure electrical powered tools have a three-wire cord with a ground. To avoid hazards:

  • Ground all power supply systems, electrical circuits, and electrical equipment.
  • Frequently inspect electrical systems to insure that the path to ground is continuous.
  • Visually inspect all electrical equipment before use. Take any defective equipment out of service.
  • Do not remove ground prongs from three-prong equipment or extension cords. This is one of the most common electrical cord violations cited by OSHA.
  • Use double-insulated tools and equipment, distinctively marked.
  • Ground all exposed metal parts of equipment.
  • Ground metal parts of the following non-electrical equipment, as specified by the OSHA standard [29 CFR 1926.404(f)(7)(v)]:
    • Frames and tracks of electrically operated cranes.
    • Frames of non-electrically driven elevator cars to which electric conductors are attached.
    • Hand-operated metal shifting ropes or cables of electric elevators.
    • Metal partitions, grill work, and similar metal enclosures around equipment of over 1kV between conductors.

Knowledge Check Choose the best answer for the question.

3-7. What is one of the most common electrical cord violations cited by OSHA?