- Flash protection boundary (outer boundary) The flash protection boundary is the farthest established boundary from the energy source. ...
- Limited approach boundary. ...
- Restricted approach boundary.
What determines the limited approach boundary?
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.
What is a limited approach boundary?
The Limited Approach Boundary (LAB) is the approach distance to exposed, energized electrical components within which a shock hazard exists . It is the approach limit for unqualified persons.
What is an arc flash limited approach boundary?
Limited Approach: An approach limit at a distance from an exposed live part where a shock hazard exists . ... This distance is not common between equipment. Some equipment will have a greater flash protection boundary while other equipment will have a lesser boundary.
What is the limited approach boundary for a 480 volt circuit?
Referencing the table for a 480-volt AC system yields a Limited Approach Boundary of 1 meter or 3 feet 6 inches and a Restricted Approach Boundary of 30 centimeters or 12 inches. Qualified workers must also be able to determine the Arc Flash Boundary for the job task they intend to perform.
What is the main purpose of the limited approach boundary for arc flash boundary?
There are two shock protection boundaries; the Limited Approach Boundary (LAB) and the Restricted Approach Boundary (RAB), and one Arc Flash Boundary (AFB) that must be established in order to provide a safe distance for personnel from exposed, energized electrical components.
What changes to NFPA 70E were recently adopted?
In the 2018 70E the table was modified to eliminate any clothing or PPE under 1.2 cal/cm2 , because it only deals with arc-rated clothing and other PPE. The table was renamed Table 130.5(G) and put into the body of the standard. Its use is “permitted”, meaning it’s an option—it can be used, but is not mandatory.
Who can cross the limited approach boundary?
NFPA 70 defines the 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.
How many approach boundaries are there?
Under NFPA 70E, there are three boundaries that are observed—limited approach, restricted approach, (the shock protection boundaries) and arc flash boundary.
What are the three shock protection boundaries?
There are three electrical shock hazard boundaries depending on the voltage of the appliance and termed the limited approach boundary, the restricted approach boundary, and the prohibited approach boundary .
Why is the arc flash boundary defined?
The Arc Flash Boundary has been developed by NFPA70e to minimize the risk of arc flash injury to electrical workers, working in proximity to energized electrical equipment. The Arc Flash Boundary determines the distance from the equipment at which the Incident Energy of an arc flash would be 1.2 cal/cm2 .
How do you find the arc flash boundary?
The arc flash boundary is calculated to 1.2 calories/cm2 of incident energy . That’s the distance where a worker without appropriate PPE would receive second-degree burns. Sometimes this boundary is the furthest one from the exposed equipment, other times the limited approach boundary is the furthest out.
How far can an arc flash travel?
The radiant energy released by an electric arc is capable of permanently injuring or killing a human being at distances of up to 20 feet (6.1 m) .
What is an exposed movable conductor?
* Exposed movable conductor describes a condition in which the distance between the conductor and a person is not under the control of the person . The term is normally applied to overhead line conductors supported by poles.
What is the limited approach boundary for an exposed fixed circuit part operating at 12470 volts?
NFPA 70E 130.4(D)(a) Shock Protection Approach Boundaries.
Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal: What is the limited approach boundary for an exposed fixed circuit part operating at 12,470 volts? A: 5 feet .
What are ATPV and EBT ratings?
Basically, EBT fabrics are typically more insulative than they are strong and ATPV materials are stronger than they are insulative. Usually, EBT indicates the garment is a knit and is more comfortable but essentially no less protective to the user.
