Ensure electrical safety at your operation by understanding and implementing safety standards.

by Edward J. Muglach

It’s early in the morning. Your maintenance crew has been working all night repairing an electrical problem on a crusher motor. The repairs are complete and your electrician has gone to remove his lock and hold tag to re-energize the electrical system. You wait patiently for the crusher to start when, BAM! There is a bright flash of light and a loud noise from the switchgear building. All power in the plant is lost. “What happened?” you yell to the other employees as they are running toward the switchgear building.

You follow everyone to the switchgear building. There is a lot of smoke in the area, and you expect the worse. Just as you get to the building, your electrician walks out the door. An arc flash had been generated when he closed the disconnect switch, but he was wearing his Personnel Protection Equipment (PPE), that protected him from the arc flash. There is equipment damage, and you are going to have to be down a little longer, but there was no serious injury or loss of life.

What is an arc flash? An arc flash is the sudden release of electrical energy through the air when there is a breakdown between two or more current-carrying conductors or one conductor to ground. An arc flash gives off intense heat, light, and pressure.

The intense heat, up to 35,000 degrees Fahrenheit, can melt metal conductors allowing metal droplets to fly in all directions. The temperature increase can ignite clothing. The flash of light can blind employees, and the pressure from the rapidly heated air can place extreme forces on workers, damaging their hearing and causing other pressure related injuries. All of this can happen in a fraction of a second. Treatment of a worker that survives an arc flash incident can require years and may cost in excess of $1,000,000.

In an effort to prevent or significantly reduce electrical accidents, the Occupational Health and Safety Administration (OSHA) contracted the National Fire Prevention Association (NFPA) to develop a standard for working around electrical equipment. NFPA-70E, “Standard for Electrical Safety in the Workplace,” was developed to introduce standards and to develop guidelines for a workplace electrical safety program. NFPA-70E has been around since 1976, but was not well recognized until 2000 when tables were introduced to allow workers to choose PPE. In 2002, the equipment labeling requirement was introduced. OSHA revised its electrical standard, Subpart S of 29 CFR part 1910, to rely heavily on the information in NFPA-70E.