An arc flash is a short circuit through air that flashes over from one exposed live conductor to another conductor or to ground.
Simply put, an arc flash is a phenomenon where a flash over of electric current leaves its intended path and travels through the air from one conductor to another, or to ground. The results are often violent and when a human is in close proximity to the arc flash, serious injury and even death can occur.
Arc flash can be caused by many things including:- Dust
- Dropping tools
- Accidental touching
- Condensation
Material failure- Corrosion
- Faulty Installation
- Coming close to a high-amp source with a conductive object can cause the electricity to flash over.
- Dropping a tool or otherwise creating a spark can ignite an arc flash
- Equipment failure due to use of substandard parts, improper installation, or even normal wear and tear
- Breaks or gaps in insulation.
Three factors determine the severity of an arc flash injury:- Proximity of the worker to the hazard
- Temperature
- Time for circuit to break
Because of the violent nature of an arc flash exposure when an employee is injured, the injury is serious – even resulting in death. It’s not uncommon for an injured employee to never regain their past quality of life. Extended medical care is often required, sometimes costing huge expenses.
Arc Flash Terminology
- Arc Flash Boundary (ARC) - is the distance at which an electrical arc can flash outward, which may endanger employees working on electrical equipment.
- Flash Protection Boundary (FPB) - the calculated safe working distance from electrical equipment which would not expose the employee to the hazards associated with an electrical arc flash.
- Electrical Assessment - an analytical evaluation which would calculate the arc flash potential of an electrical component 1 hazard, used to establish the flash protection boundary and the correct level of required PPE, determined by an electrical engineer or the equivalent.
- Qualified Employees (per NFPA 70E, 2000 Edition, Standard for Electrical Safety Requirements for Employee Workplaces) - a qualified person shall be trained and knowledgeable of the construction and operation of equipment or a specific work method, and be trained to recognize and avoid the electrical hazards that might be present with respect to that equipment or work method.
Such persons shall also be familiar with the proper use of special precautionary techniques,personal protective equipment, insulating and shielding material!, and insulating tools and test equipment. A person can be considered qualified with respect to certain equipment and methods but still be unqualified for others. Such persons permitted to work within limited approach of exposed energized conductors and circuit parts shall at a minimum, be additionally trained in the following;- The skills and techniques necessary to distinguish exposed energized parts from other parts of the electric equipment.
- The skills and techniques necessary to determine the nominal voltage of exposed energized parts.
- The approach distance specified in the tables and the corresponding voltage to which the qualified person will be exposed.
- Employees will be capable of reading and understanding the attached PPE matrix, and listed approach boundaries and hazard risk category tables, which are necessary to perform the task safely.
Results from an Arc Flash:- Burns (Non FR clothing can burn onto skin)
- Fire (could spread rapidly through building)
- Flying objects (often molten metal)
- Blast pressure (upwards of 2,000 lbs. / sq.ft)
- Sound Blast (noise can reach 140 dB – loud as a gun)
- Heat (upwards of 35,000 degrees F)
Current Arc Flash Boundaries:
The arcflash boundaries are designed to keep employees safe while they are working near energized equipment.
- “Prohibited Approach Boundary” removed
- Conductive articles of jewelry and clothing must be removed
- Working space shall not be used for storage
- Barricades shall not be placed closer than the arc flash boundary when it is greater than the limited approach boundary
- Insulated tools must be used when working inside the restricted approach boundary
Reference: NFPA 70E 2015 Changes
The NFPA 70E gets updated every three years. The 2015 update includes some of the following changes:
- Revision to arc flash warning label content
- Elimination of PPE Hazard Category “0”
- Elimination of the Prohibited Approach Boundary
- Additional boundary requirements
- Revisions to selecting appropriate personal protective equipment (PPE)
- Updated training and retraining requirements
- Minor terminology changes (such as "work shoes" becomes "footwear”)
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). The issue here is the heat generated from a flash that results in burns.
Limited Approach:An approach limit at a distance from an exposed live part where a shock hazard exists.
Restricted Approach:An approach limit at a distance from an exposed live part which there is an increased risk of shock.
Prohibited Approach (inner boundary):A distance from an exposed part which is considered the same as making contact with the live part.This distance is not common between equipment. Some equipment will have a greater flash protection boundary while other equipment will have a lesser boundary.
Simply put, an arc flash is a phenomenon where a flash over of electric current leaves its intended path and travels through the air from one conductor to another, or to ground. The results are often violent and when a human is in close proximity to the arc flash, serious injury and even death can occur.
Arc flash can be caused by many things including:
- Dust
- Dropping tools
- Accidental touching
- Condensation
- Material failure
- Corrosion
- Faulty Installation
- Coming close to a high-amp source with a conductive object can cause the electricity to flash over.
- Dropping a tool or otherwise creating a spark can ignite an arc flash
- Equipment failure due to use of substandard parts, improper installation, or even normal wear and tear
- Breaks or gaps in insulation.
Three factors determine the severity of an arc flash injury:
- Proximity of the worker to the hazard
- Temperature
- Time for circuit to break
Because of the violent nature of an arc flash exposure when an employee is injured, the injury is serious – even resulting in death. It’s not uncommon for an injured employee to never regain their past quality of life. Extended medical care is often required, sometimes costing huge expenses.
Arc Flash Terminology
- Arc Flash Boundary (ARC) - is the distance at which an electrical arc can flash outward, which may endanger employees working on electrical equipment.
- Flash Protection Boundary (FPB) - the calculated safe working distance from electrical equipment which would not expose the employee to the hazards associated with an electrical arc flash.
- Electrical Assessment - an analytical evaluation which would calculate the arc flash potential of an electrical component 1 hazard, used to establish the flash protection boundary and the correct level of required PPE, determined by an electrical engineer or the equivalent.
- Qualified Employees (per NFPA 70E, 2000 Edition, Standard for Electrical Safety Requirements for Employee Workplaces) - a qualified person shall be trained and knowledgeable of the construction and operation of equipment or a specific work method, and be trained to recognize and avoid the electrical hazards that might be present with respect to that equipment or work method.
Such persons shall also be familiar with the proper use of special precautionary techniques,personal protective equipment, insulating and shielding material!, and insulating tools and test equipment. A person can be considered qualified with respect to certain equipment and methods but still be unqualified for others. Such persons permitted to work within limited approach of exposed energized conductors and circuit parts shall at a minimum, be additionally trained in the following;
- The skills and techniques necessary to distinguish exposed energized parts from other parts of the electric equipment.
- The skills and techniques necessary to determine the nominal voltage of exposed energized parts.
- The approach distance specified in the tables and the corresponding voltage to which the qualified person will be exposed.
- Employees will be capable of reading and understanding the attached PPE matrix, and listed approach boundaries and hazard risk category tables, which are necessary to perform the task safely.
Results from an Arc Flash:
- Burns (Non FR clothing can burn onto skin)
- Fire (could spread rapidly through building)
- Flying objects (often molten metal)
- Blast pressure (upwards of 2,000 lbs. / sq.ft)
- Sound Blast (noise can reach 140 dB – loud as a gun)
- Heat (upwards of 35,000 degrees F)
The arcflash boundaries are designed to keep employees safe while they are working near energized equipment.
- “Prohibited Approach Boundary” removed
- Conductive articles of jewelry and clothing must be removed
- Working space shall not be used for storage
- Barricades shall not be placed closer than the arc flash boundary when it is greater than the limited approach boundary
- Insulated tools must be used when working inside the restricted approach boundary
Reference: NFPA 70E 2015 Changes
The NFPA 70E gets updated every three years. The 2015 update includes some of the following changes:
- Revision to arc flash warning label content
- Elimination of PPE Hazard Category “0”
- Elimination of the Prohibited Approach Boundary
- Additional boundary requirements
- Revisions to selecting appropriate personal protective equipment (PPE)
- Updated training and retraining requirements
- Minor terminology changes (such as "work shoes" becomes "footwear”)
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). The issue here is the heat generated from a flash that results in burns.
Limited Approach:
An approach limit at a distance from an exposed live part where a shock hazard exists.
Restricted Approach:
An approach limit at a distance from an exposed live part which there is an increased risk of shock.
Prohibited Approach (inner boundary):
A distance from an exposed part which is considered the same as making contact with the live part.
This distance is not common between equipment. Some equipment will have a greater flash protection boundary while other equipment will have a lesser boundary.
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