The prohibited approach boundary (PAB) is the distance away from a piece of energized electrical equipment. The distance of the boundary is determined by the amount of voltage running through the equipment.
Regarding this, what are the three limits of approach boundaries?
The NFPA 703® recognizes three arc flash boundary levels: the limited approach boundary, the restricted area, and the prohibited area boundary.
Likewise, what is restricted boundary? The Restricted Approach Boundary (RAB) is the approach limit for qualified persons to exposed, energized electrical components where there is an increased likelihood of electric shock due to electrical arc-over combined with inadvertent movement. Only qualified persons may cross this boundary.
Just so, what is required to cross the limited approach boundary?
NFPA 70 defines Limited Approach Boundary as “a shock protection boundary to be crossed by only qualified persons (at a distance from a live part) which is not to be crossed by unqualified persons unless escorted by a qualified person”.
What is flash protection boundary?
Flash Protection Boundary (outer boundary): The flash boundary is the farthest established boundary from the energy source. If an arc flash occurred, this boundary is where an employee would be exposed to a curable second degree burn (1.2 calories/cm2).
19 Related Question Answers Found
What is Arc Flash working distance?
Basically, the working distance is the distance between you and the point of origin of an arc flash. The point of origin for an arc flash will typically be inside a piece of electrical equipment, at an energized conductor or bus. A typical working distance for low voltage equipment might be 18 inches.
What is the limited approach boundary distance?
The limited approach boundary is the minimum distance from the energized item where unqualified personnel may safely stand. No untrained personnel may approach any closer to the energized item than this boundary.
How do you find the arc flash boundary?
The IEEE 1584 equation for the AFB is: DB = [(4.184 × Cf × Ein × (t/0.2) × (610x/EB)]1/x. EB = Incident energy in Joules per cm2 (J/cm2) at the AFB. This is normally 5 J/cm2, which is equal to 1.2 cal/cm2.
What is hrc1?
NFPA 70E is a safety standard that denotes Hazard Risk Categories (HRC) based upon an array of occupational duties. An HRC level is determined by the minimum amount of calories per square centimeter (ATPV or Cal/cm2).
How far away from an arc flash can a person be fatally burned?
Dangers of Arc Flashes Fatal burns can occur when the victim is several feet from the arc. Serious burns are common at a distance of 10 feet. Staged tests have shown temperatures greater than 437°F (225°C) on the neck and hands of a person standing close to an arc blast.
What is a flash hazard analysis?
Flash hazard analysis: A method to determine the risk of personal injury as a result of exposure to incident energy from an electrical arc flash. Flash protection boundary: An approach limit at a distance from live parts that is un-insulated with which a person could receive a second-degree burn.
What is an arc blast?
Blast: a destructive wave of highly compressed air spreading outward from an explosion. An arc blast is caused by the rapid expansion of air during an arc fault. This sudden expansion produces an intense pressure wave.
What is arc flash hazard?
An arc flash is an undesired electric discharge that travels through the air between conductors or from a conductor to a ground. The flash is immediate, but the result of these incidents can damage equipment and cause severe injury, including burns.
What is the limited approach boundary distance for an exposed fixed circuit?
Limited Approach Boundary – The Limited Approach Boundary (LAB) is identified as the “distance from an exposed energized electrical conductor or circuit part within which a shock hazard exists”. Best practice if for any unqualified person to stay 42” (3′ 6”) or more away from the hazard.
Which boundary is located farthest away from energized parts?
The arc flash boundary is the minimum “safe” distance from exposed energized conductors or circuit parts that has the potential for an arc flash.
Which approach boundary is the closest to the exposed energized parts?
The Restricted Approach Boundary is the shock protection boundary closest to the exposed energized parts and may only be crossed by qualified electrical workers following safe electrical work-practices which include wearing appropriate shock protection PPE and using insulated tools.
What is the limited approach boundary for a 480 volt circuit?
The limited approach boundary is a distance from the employee to an exposed energized circuit part within which a shock hazard exists. The typical nominal AC voltages that a maintenance person would be working on of 120, 208, 220, 240, 277, 380, and 480 all have a limited approach boundary of 42 inches.
What is incident energy analysis?
Incident energy is a measure of thermal energy at a working distance from an arc fault. The unit of incident energy is cal/cm2. Incident energy analysis is required for selecting arc rated Personal Protective Equipment (PPE) when work is performing at or near a potential source of an arc flash.
What is the minimum safe working distance from exposed electrical conductors?
Work at a safe distance The Occupational Safety and Health Administration (OSHA) requires that equipment be kept at least 10 feet away from power lines with voltages up to 50kV.
Which type of hazard control is most likely to eliminate hazards?
Elimination. Physically removed the hazard—is the most effective hazard control. For example, if employees must work high above the ground, the hazard can be eliminated by moving the piece they are working on to ground level to eliminate the need to work at heights.
At what voltage level is a shock protection boundary required?
All parts of the body inside the flash protection boundary have to be protected by suitable PPE. For example for voltage between 50 to 600 Volts, the flash protection boundary is 4 feet.
Is arc flash analysis required by OSHA?
OSHA requires employers to protect employees from electrical hazards, including arc flash. The most common OSHA standards cited for arc flash include: 29 CFR 1910.132(d)(1)—Requires employers to perform a PPE hazard assessment to determine necessary PPE.
Is compliance with NFPA 70e mandatory?
As a national consensus safety standard, NFPA 70E is not a law and it has not been incorporated into the Code of Federal Regulations. Therefore, compliance is not deemed mandatory. Even so, OSHA has cited NFPA 70E in cases where lack of compliance has resulted in a workplace accident.
Is NFPA 70e required by OSHA?
The short answer is no, because NFPA 70E® is not Incorporated by Reference in 29 CFR 1910.6. However, OSHA has several comparable standard requirements that are enforceable: 29 CFR 1910.132 (d)(1): Requires employers perform a personal protective equipment (PPE) hazard assessment to determine necessary PPE.