Arc flash
Arc flash is a dangerous event that releases a tremendous amount of energy, creating intense heat and pressure waves. To prevent arc flash hazards, it's crucial to implement comprehensive safety procedures and preventative measures. These include risk assessments, safe work practices, and the use of appropriate personal protective equipment (PPE). [5] [2]
An arc flash may be caused by factors such as unintentional tool contact with live parts, equipment failure, corrosion, loose contacts, worn insulation, dust, incorrect installation, and incorrect work procedures. The possibility of an arc flash increases when there are exposed energized electrical conductors or circuit parts, or when safe work procedures are not followed. [2] [2]
Key preventative measures include:
- De-energizing equipment and following lockout/tagout procedures whenever possible.
- Ensuring conductors and circuit parts are in safe working condition.
- Using lower energy equipment or current limiting devices.
- Guarding energized electrical conductors and circuit parts.
- Using arc flash approach boundaries and barricades.
- Increasing working distance.
- Using non-contact instruments or procedures where possible.
- Using non-sparking tools.
- Implementing work permits, safe work procedures and job planning.
- Posting signs alerting of the hazards.
- Regular inspection for wear and tear of insulation, corrosion, poor connections, and excessive moisture.
- Routine inspections of circuit breakers and relays.
- Keeping electrical drawings current.
[4] [4] [4] Approach boundaries are crucial for safety. These include: [4]
- Arc flash boundary: The distance at which a person without PPE may receive a second-degree burn (5 J/cm2).
- Limited approach boundary: The distance a person may approach with appropriate PPE, supervised by a qualified person, when a shock hazard exists.
- Restricted approach boundary: The distance only a qualified person may approach, with increased likelihood of electric shock.
- Qualified persons must be trained and knowledgeable about equipment, work methods, PPE, and safety procedures.
[1] [1] [1] [3] Selecting the right PPE is essential. Workers must know how to select, use, and care for their PPE, understanding its limitations. Methods for selecting PPE include: [3]
- Incident energy analysis: Based on the distance between the worker and the arc flash source, determining the energy of the flash to define the required PPE protection level.
- Arc flash PPE category method: Using risk assessment to determine if arc flash-rated PPE is needed, selecting one of four PPE categories based on working distance, fault current, and clearing time.
[3] [3] [3] Required PPE includes appropriate clothing and footwear, a hard hat (Class G or E), a face shield, a balaclava or hood, safety glasses or goggles, heavy-duty leather/arc-rated/rubber insulating gloves, hearing protection, and appropriate footwear. All PPE must be suitable for the expected energy levels of an arc flash. [3]
Relevant standards and regulations include:
- CSA Z463 "Maintenance of Electrical systems"
- CSA Z462 "Workplace Electrical Safety"
- NFPA 70B "Recommended Practice for Electrical Equipment Maintenance"
- NFPA 70E "Standard for Electrical Safety in the Workplace"
- ANSI/NETA MTS "Standard for Maintenance Testing Specifications for Electrical Power Equipment and Systems"
- OSHA 29 CFR 1910
- OSHA 29 CFR 1926
Important Safety Note:
Always verify safety information with your organization's specific guidelines and local regulations.
References
Page links are approximateOccupational Safety and Health Standards (OSHA 29 CFR 1910) - 1910 Subpart I App B - Nonmandatory Compliance Guidelines for Hazard Assessment and Personal Protective Equipment Selection
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Safety and Health Regulations for Construction (OSHA 29 CFR 1926) - 1926.954 - Personal protective equipment
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