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Arc Flash in Mining

By Joel Bradbury

miner and electrical hazard symbols.

Very little can happen in mining without electricity. From drilling equipment and powered shovels to fixed and mobile conveyors, most equipment requires electrical power. Power stations, mobile substations, motor control centers (MCCs), and E-houses are numerous and can be spread over many miles.

It’s no surprise that electrical safety is extremely important in mining operations. In order to keep workers safe, MSHA covers electrical safety in the Code of Federal Regulations (CFR) Title 30, Part 56, Subpart K (Electricity). This regulation, however, does not cover arc flash safety or reference NFPA 70E (the go-to standard for electrical safety in most other industries). How, then, is arc flash in mining addressed?

A Step Forward in Mining Arc Flash Safety

MCC with an arc flash label.

The good news is NFPA 70E (2015) no longer excludes the mining industry. The exclusion was removed at the request of MSHA—signaling a positive change in mine safety. MSHA recommends the standard and encourages mine operators to use it.

NFPA 70E provides numerous best practices that can keep miners safe. These include performing risk assessments, as well as training workers about electrical safety and arc flashes. 

Avoid the Dangers of Arc Flash

So what is an arc flash? An arc flash is an explosive burst caused by a sudden, uncontrolled electrical arc. Temperatures of an arc flash can reach 35,000°F in 1/1000th of a second. The explosive burst of heat and light vaporizes metal and causes fatal burns. These accidents can kill or injure multiple employees in an instant.

The first step in reducing the dangers of arc flash incidents is to perform an arc flash risk assessment. Safety managers who perform the examination (as outlined in NFPA 70E) can improve safety by:

  • Collecting equipment data
  • Identifying modes of operation
  • Identifying bolted fault currents
  • Identifying arc fault currents
  • Identifying the devices' protective characteristics and duration of potential arc
  • Documenting voltages and equipment classes
  • Identifying working parameters
  • Determining incident energy for equipment
  • Identifying the required personal protective equipment (PPE)
  • Identifying the arc flash boundary

Performing these steps will help identify and reduce arc flash risks, keeping miners safe. Discover how to conduct an arc flash assessment and create an arc flash program with the comprehensive Practical Solution Guide to Arc Flash Hazards by EasyPower. The guide helps you avoid dangerous mishaps and improve your site’s electrical safety.

Train Miners in Arc Flash Safety

power switch tagged out as part of LOTO

Another important element in arc flash safety is training. Arc flash training ensures that workers know how to:

  • Identify hazards
  • Safely perform work on electrical equipment
  • Select the right PPE
  • Follow lockout/tagout (LO/TO) procedures

All workers who perform work that exposes them to an increased risk of arc flash should receive training to recognize and avoid arc flash hazards. Training should be site-specific to ensure that workers are aware of hazards present in their work area. Reviews should be conducted at least once each year to ensure miners are properly trained and know how to apply their training.

Worker training also includes LO/TO training, enabling workers to:

  • Understand how to follow LO/TO procedures for each unique piece of equipment
  • Know how to recognize when equipment is locked out and tagged out, preventing them from re-energizing equipment
  • Know how to safely re-energize equipment

Arc Flash Safety Solutions

If your mine does not yet have an arc flash program in place, following the standards in NFPA 70E will improve electrical safety and help change how workers view arc flash safety.

In a 2013 presentation, David B. Durocher (a senior member of IEEE) shared several case studies which demonstrated the importance of following NFPA 70E in mining operations. Durocher also identified several key elements to improve arc flash safety, including:

  • Understanding the work environment, maintenance requirements, and equipment condition
  • Using arc-reducing technology, like upstream switches, to reduce the severity of an arc flash hazard—in one example, reducing energy from 17.7 cal/cm2 to 2.9 cal/ cm2
  • Investing in arc reduction maintenance systems for MCCs
  • Using arc flash labels and signs to increase safety awareness and provide essential information where it’s needed most

(Source: “Arc Flash Compliance Implementation at Mining and Minerals Processing Facilities,” Presentation. November 21-22, 2013. Albuquerque, NM)

Arc Flash in Mining. An example arc flash label applied to a piece of equipment.

The dynamic nature of mining operations all but guarantees that systems will change more frequently than in other work environments. It’s extremely important to review your arc flash safety program each time a change is made. This will ensure you can document any increased or decreased arc flash risk, train workers on the new system, and update your arc flash warning labels to ensure information remains accurate.

Improve safety on your site with the helpful Best Practice Guide to Arc Flash Labeling by Graphic Products. This guide will walk you through how to create effective arc flash labels for your entire site.

Graphic Products also offers a versatile, mobile printing solution that can keep up with your site’s needs. DuraLabel Toro label and sign printer lets you print arc flash labels onsite and on-the-go with an optional lithium-ion battery. Keep up with system changes as they happen, and ensure that all your safety labeling remains current.

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