Arc flash safety is important for anyone who works with or near electrical equipment. An arc flash is a sudden and violent release of electrical energy that can cause severe injuries, fires, and even death.
In this article, you will learn what an arc flash is, what causes it, and how to prevent it. You will also discover the best practices for risk assessment, hazard identification, personal protective equipment (PPE), and safe work practices in electrical environments.
By mastering arc flash safety, you can protect yourself, your co-workers, and your workplace from this serious electrical hazard. Let’s dive in.
What is Arc Flash?
An arc flash, or a flashover, is a flashover of electric current that leaves its intended path and travels through the air from one conductor to another or the ground. The results are often violent, and when a human is near the arc flash, serious injury and even death can occur.
An arc flash can reach temperatures up to 35,000°F (19,400°C), four times hotter than the sun’s surface. It can also produce intense light, sound, pressure, and molten metal.
An arc flash is different from an arc blast, which is the explosive force that results from the rapid expansion of air and metal due to the heat of the arc flash. An arc blast can create pressures of up to 2,000 pounds per square foot (9,300 kg/m2), which can knock down walls, doors, and windows.
Effects of arc flash
- Severe burns, both external and internal
- Eye damage and blindness from the ultraviolet light
- Hearing loss and ear damage from the sound blast
- Lung damage and intoxication from the inhalation of hot gases and vaporized metal
- Fire that can spread rapidly through the building
- Flying objects and shrapnel from the explosion
- Electrocution and shock from the current
Causes of Arc flash
- Dust, dirt, moisture, or corrosion that can reduce the insulation of the conductors
- Dropping tools, accidental touching, or improper use of equipment that can create a short circuit
- Faulty wiring, loose connections, or failure in the electrical system
- Human error, such as mislabeling, incorrect testing, or lack of training
Arc Flash Safety: How to safeguard your workplace
1. Perform a Risk Assessment and Hazard Identification
Conduct a risk assessment and identify the potential hazards in the electrical system. Evaluate the likelihood and severity of an arc flash occurrence and the possible consequences for the workers and the workplace.
A risk assessment is done by a qualified person who follows the standards and guidelines of the National Fire Protection Association (NFPA) 70E, the code of practice for electrical safety in the workplace.
The methods and formulas for calculating the arc flash risk and hazard levels are based on factors such as:
- Voltage, current, and resistance of the electrical system
- Distance and exposure time of the worker to the arc flash
- Configuration and condition of the electrical equipment
- Presence and effectiveness of protective devices, such as fuses and circuit breakers
Based on the risk assessment, assign an arc flash hazard category to each electrical equipment, ranging from 1 to 4, with 4 being the most dangerous and the minimum PPE required for working on or near the equipment.
Types of safe approach boundaries:
a) Flash protection boundary:
This is the outermost boundary, where a worker can be exposed to a second-degree burn in case of an arc flash. It is usually 4 feet (1.2 m) from the equipment but varies by voltage and current.
b) Limited approach boundary:
Only qualified persons can cross the limited approach boundary and must use appropriate PPE and tools. The limited approach boundary is 3.5 feet (1.1 m) from the equipment.
c) Restricted approach boundary:
In this area, a worker can be exposed to an increased risk of arc flash from the live parts. Only qualified persons can cross the restricted approach boundary and must have a written work permit and a qualified observer. The restricted approach boundary is 1 foot (0.3 m) from the equipment.
d) Prohibited approach boundary:
The boundary where a worker can be exposed to the same risk as touching the live parts. No one can cross the prohibited approach boundary unless the equipment is de-energized and verified.
2. Wearing Personal Protective Equipment (PPE)
Protective equipment (PPE) is workers’ last defense against arc flash hazards and are clothing and gear that workers wear to protect themselves from the effects of an arc flash. These
PPE is selected based on the arc flash hazard category of the equipment, the level of exposure, and the type of work.
The table of PPE requirements for each arc flash hazard category:
PPE Category | PPE Requirements | |
Arc-rated Clothing | Shirts, pants, coveralls, jackets, and hoods with an ATPV value (in calories/cm2) covering the entire body except hands and feet. | |
Arc-rated Gloves | Gloves covering the entire hand and wrist, worn over rubber-insulating gloves for shock protection. | |
Arc-rated Face Shield | Transparent shield covering the entire face and neck, featuring a chin cup, wraparound design, anti-fog/anti-scratch coating, and VLT of at least 70%. | |
Safety Goggles | Eye protection with polycarbonate lenses, side shields, or wraparound design, worn under the arc-rated face shield for added protection. | |
Hearing Protection | Ear plugs with an NRR (noise reduction rating) of at least 25 dB for protection against noise and pressure during an arc flash. | |
Hard Hat | Non-conductive hard hat made of plastic or fiberglass, featuring a suspension system, chin strap, and brim for impact and heat protection, worn under the arc-rated hood for extra safeguarding. | |
Leather Footwear | Leather footwear with steel toe, rubber sole, high-top design, and lace-up closure for protection against heat and flame, worn over arc-rated clothing for additional safety. |
Note: Always adhere to NFPA 70E guidelines and consult with safety professionals for proper PPE selection based on specific work conditions and hazards.
How to Choose the Right Arc Flash Gear
Choosing the right arc flash clothing and gear is essential for ensuring the safety and comfort of the workers. Arc flash clothing and gear should be selected based on the following criteria:
- Risk assessment
The risk assessment and hazard identification determine the equipment’s arc flash hazard category. The arc flash hazard category indicates the minimum level of protection required for the workers and the safe approach boundaries for the equipment.
- Level of exposure
The work’s distance and duration determine the exposure level to the arc flash. It indicates the heat energy the workers can be exposed to in case of an arc flash.
- Nature of the job
The type of work indicates the degree of risk and complexity involved in the task and the likelihood and frequency of an arc flash occurrence. The type of work can be classified into three categories: de-energized, energized, and live work.
De-energized
- De-energized work is performed on electrical equipment disconnected from the power source and verified to be voltage-free.
- It is the safest and preferred method of working on electrical equipment, as it eliminates the risk of arc flash and shock.
- It requires lockout/tagout (LOTO) procedures, which are the steps to isolate and secure the electrical equipment from accidental or unauthorized re-energization.
- Requires voltage testers to verify the electrical equipment is de-energized and safe to work on and requires the minimum level of PPE, such as safety glasses, gloves, and footwear.
Energized work
- Energized work is performed on electrical equipment connected to the power source and has voltage present.
- It is the most hazardous and least recommended method of working on electrical equipment, as it poses the highest risk of arc flash and shock.
- It should only be done when de-energizing the equipment creates a greater hazard, such as emergency repairs, testing, or troubleshooting.
- Energized work requires a written work permit, precautions, and procedures to be followed.
- Energized work usually requires the highest level of PPE, such as arc-rated clothing.
Live work
- Live work is performed on electrical equipment connected to the power source with current flowing through it.
- It is the most dangerous and prohibited method of working on electrical equipment, exposing the worker to the full potential of arc flash and shock.
- Live work should never be done unless necessary for the continuity of service, such as life support systems, critical infrastructure, or national security.
- It requires a special authorization that approves and regulates the need for live work and the worker’s qualifications and responsibilities.
- It requires using a live-line tool such as a hot stick, a shotgun stick, or a clamp stick; hence requires the maximum level of PPE.
How to maintain and inspect PPE
PPE for arc flash should be maintained and inspected according to the manufacturer’s instructions and the NFPA 70E guidelines.
- Cleaning
Clean using mild detergent and water and dried using low heat or air drying. Do not use bleach, chlorine, starch, or fabric softener, as these can cause damage.
- Storage and handling
Store in a clean, dry, and cool place, away from any ignition or abrasion sources, to prevent any exposure to moisture, heat, or chemicals that can affect the integrity and performance.
- Inspection and testing
Inspect and test for any signs of wear and tear that can compromise the safety and effectiveness of the PPE before and after each use, and at least once a year by a qualified person.
- Repair and replacement
Repair following the manufacturer’s instructions and the NFPA 70E standards if any issues are found during the inspection and testing of the PPE.
3. Practices safe work in Electrical Environments
Workers follow these actions to prevent the risk of arc flash and shock in electrical environments.
Some of the Safe work practices include:
- Planning and preparation
Plan and prepare for the work on or near the electrical equipment by identifying the hazards, assessing the risks, and selecting the appropriate PPE and tools. Plan for the emergency response by knowing the location and operation of the fire extinguishers, first aid kits, and have the contact information of the emergency services.
- De-energization and verification:
De-energize and verify the electrical equipment before using them. Ensure the electrical equipment is de-energized and safe to work on by testing each phase conductor and each circuit part.
- Energized work permit and observer:
Obtain a written work permit and have a qualified observer before working on energized electrical equipment. Communicate and coordinate with the observer to monitor and assist the worker.
- Live-line tool and authorization
When using a live-line tool, have special authorization and use and maintain it properly. Follow the instructions and directions of the special authorization, which should specify the qualifications and responsibilities of the workers involved.
- Safe approach boundaries and distances
Respect and maintain the safe approach boundaries and distances for the electrical equipment. Keep a safe distance from the arc flash source and avoid direct or indirect contact with the live parts or the ground.
4. Arc Flash Prevention Measures
These are the actions and strategies that workers and employers can implement to reduce the occurrence and severity of arc flash incidents in electrical environments.
The prevention measures
- Design and engineering:
The design and engineering of the electrical system and equipment should follow the NFPA 70 standards and specifications. The design must consider the arc flash potential and hazard and incorporate the appropriate protective systems to detect the arc flash before it becomes dangerous.
- Maintenance and testing:
The maintenance the electrical system and equipment through regular inspection, cleaning, lubrication, and calibration of the electrical components and devices. Identify and correct damages in the electrical system and equipment that can contribute to an arc flash.
- Training and education:
The workers’ training and education must incorporate the awareness and understanding of the arc flash hazards, safety and prevention measures. The training provides the workers with information and resources on the arc flash standards, regulations, and responsibilities.
5. Arc Flash Incident Investigation and Reporting
Workers follow these processes to analyze and document the causes and consequences of an arc flash incident in electrical environments.
Flash incident investigation and reporting
- Notification and response:
The notification and response include the immediate notification and activation of the emergency services and the supervisors and the prompt and proper response and rescue of the victims and the scene.
- Investigation and analysis:
The investigation and analysis of the arc flash incident must follow the NFPA 921 standards and techniques for the systematic and scientific collection, examination, and evaluation of the data and the evidence. The investigation and analysis determine and verify the cause and effect of the arc flash incident and assess the contributing and mitigating factors.
- Reporting and documentation:
Follow the NFPA 921 formats to report and document the arc flash incidents and communicate the findings and conclusions of the investigation and analysis and the recommendations and suggestions for improving and preventing the arc flash incident.
FAQs
1. What are the safety measures for arc flash?
The safety measures for arc flash are the actions and strategies that workers and employers can implement to prevent or minimize the risk of arc flash and shock in electrical environments. The safety measures for arc flash include risk assessment and hazard identification, personal protective equipment (PPE), safe work practices, arc flash prevention measures, and arc flash incident investigation and reporting.
2. What are the three hazards of arc flash?
The three hazards of arc flash are the heat, the light, and the pressure, which can cause severe injuries, fires, and even death. The heat of an arc flash can reach temperatures of up to 35,000°F (19,400°C), which can cause severe burns, both external and internal. The light of an arc flash can produce intense ultraviolet rays, which can cause eye damage and blindness. The pressure of an arc flash can create a powerful sound blast and a shock wave, which can cause hearing loss, ear damage, and lung damage.
3. What is the safety distance for arc flash?
The safety distance for arc flash is from the exposed live parts where a worker can be exposed to a certain level of arc flash risk. The safety distance for arc flash is determined by the arc flash hazard category of the equipment, which indicates the minimum level of PPE required for working on or near the equipment and the safe approach boundaries for the workers. The safe approach boundaries are the flash protection boundary, the limited approach boundary, the restricted approach boundary, and the prohibited approach boundary, defined by the NFPA 70E.
4. What PPE is needed for arc flash?
The PPE needed for arc flash is the clothing and gear workers wear to protect themselves from the effects of an arc flash, such as burns, eye damage, hearing loss, and electrocution. The PPE needed for arc flash is selected based on the arc flash hazard category of the equipment, the level of exposure, and the type of work. The PPE for arc flash includes arc-rated clothing, arc-rated gloves, arc-rated face shields, safety glasses or goggles, hearing protection, hard hat, and leather footwear.
Conclusion
Arc flash safety is vital for anyone who works with or near electrical equipment. By mastering arc flash safety, you can protect yourself, your co-workers, and your workplace from this serious electrical hazard.
To master arc flash safety, you must learn and follow the best practices for risk assessment, hazard identification, personal protective equipment (PPE), safe work practices, arc flash prevention measures, and arc flash incident investigation and reporting.
Doing so can reduce or eliminate the occurrence and severity of arc flash incidents and ensure a safe and productive electrical environment.