To be safe, employees must think about the job and plan controls for possible hazards. Refer to NFPA 70E for boundary distances at given voltage ranges. Some equipment will have a larger flash protection boundary, while others will have a lesser boundary. Note: These distances are not the same for all types of equipment. The prohibited approach is the distance that the employee must remain from exposed live parts in order to prevent flashover or arcing in the air. Prohibited approach (inner boundary)Ī distance from an exposed part that is considered the same as making contact with the live part. When the employee is at the restricted approach boundary, the employee or their tools could touch live parts if the employee is careless with their movements. The restricted approach is the closest to the exposed live parts that a qualified person can go without proper PPE (such as flame-resistant clothing) and insulated tools. Restricted approachĪn approach limit at a distance from an exposed live part in which there is an increased risk of shock. Working on equipment without proper qualification and training severely increases risk. A qualified person has received training on the potential hazards and the construction and operation of the equipment involved in a task.Īdditional requirements for qualified persons include the skills and techniques necessary to distinguish exposed live parts from other parts of electrical equipment and being able to determine the nominal voltage of exposed live parts. The limited approach is the closest an unqualified person can approach, only allowed further if a qualified person accompanies them. Limited approachĪn approach limit at a distance from an exposed live part where a shock hazard exists. The hazard in this boundary is the heat generated from a flash. This exposures may cause curable second-degree burns (1.2 calories/cm2). If an arc flash occurs, this boundary is where an employee would suffer heat exposure. The flash boundary is the farthest established boundary from the energy source. The risk from exposed live parts depends on your distance from those parts.Įxposed electrical components are hazardous, and if workers make contact with wires, terminals, or other parts, they’ll get shocked. These boundaries, listed from outermost to innermost, include flash protection, limited approach, restricted approach, and prohibited approach. Therefore, boundaries play a massive role in determining the amount of risk that employees face when conducting their work. It’s crucial to understand boundary locations before beginning work on equipment, as these define the employees’ potential exposure to an arc flash and the severity of hazards. The National Fire Protection Association ( NFPA) developed specific approach boundaries designed to protect employees working on or near energized equipment. It’s not uncommon for an injured employee to never regain their previous quality of life and they may also require extended medical care. Three factors determine the severity of an arc flash injury: proximity of the worker to the hazard, temperature, and the time it takes for the circuit to break.īecause of the violent nature of an arc flash exposure, employee injuries can be very serious. Accidental contact with particular parts.There are many things that can cause arc flashes, including:
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