Arc Flash and Lockout/Tagout

Filed under Expert Tips
When dealing with electrical work there are two main types of hazards, arc flash and shock hazard."

Electrical Hazards During Servicing

Electrical work is very dangerous and it should only be performed by a qualified employee. It’s common to see employees work on electrical systems without adequate PPE (personal protective equipment) and without following the written lockout/tagout procedure. Electrical safety is crucial and there are three very important components: understanding the hazards, wearing the proper PPE, and doing a live-dead-live check before starting work. By understanding the relationship between arc flash and lockout/tagout and following these guidelines, qualified employees will remain safe on the job.

Arc Flash and Shock Hazard

When dealing with electrical work there are two main types of hazards, arc flash and shock hazard. Arc flash is an electrical explosion that happens during a fault, or short circuit condition. An electric arc can be seen when disconnecting two electrical components under load. Arc flashes are visually impressive and can also be seen in something simple like unplugging a small appliance from the wall outlet. In larger high voltage systems, arc flashes can be deadly because they can release large amounts of energy that can reach temperatures as high as 35,000 degrees Fahrenheit. On the job this can happen by operating an electrical disconnect and also bringing conductive materials near a live circuit. This can cause severe burns on human skin and ignite cloths on fire.

SONY DSCThe other type of hazard is a shock hazard. This occurs when the human body comes into contact with any live electrical components. A current, no matter how small it is, can cause death if it manages to make it to the heart. Shock hazards can also cause burns on the human skin.

Wearing the proper PPE will protect the qualified employee from these hazards; this information will be found on the arc flash labels which should be placed on every electrical panel. For a qualified worker to protect themselves from arc flashes and shocks it is important that he or she follow the PPE requirements. To select PPE the worker must locate the hazard risk category number listed on the arc flash label. This will be a number ranging from 0 to 4. Depending on the hazard risk category, that will determine what PPE must be selected. The categories are as follows,

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    • Category 0: Natural fiber long sleeve shirt and pants. Safety glasses. Ear plugs. Leather work boots. Leather gloves.
  • Category 1: Min 4 cal. AR long sleeve shirt and pants or AR coveralls. AR face shield. Hard hat. Safety glasses. Ear plugs. Leather work boots. Leather gloves.
  • Category 2: Min 8 cal. AR long sleeve shirt and pants or AR coveralls. AR flash suit hood or AR face shield and AR balaclava. Hard hat. Ear plugs. Leather work boots. Leather gloves.
  • Category 3: Min 25 cal. AR long sleeve shirt and pants, AR coveralls or AR flash suit. AR flash suit hood. AR gloves with leather protectors. Hard hat. Safety glasses. Ear plugs. Leather work boots.
  • Category 4: Min 40 cal. AR flash suit. AR flash suit hood. AR gloves with leather protectors. Hard hat. Safety glasses. Ear plugs. Leather work boots.

When dealing with electrical systems, the most important step is to do a live-dead-live check to ensure that there is no voltage present. This is done after the main power is cut off from the electrical system to be serviced. Before beginning any work, the qualified employee should, with the use of a voltmeter, do the following:

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  • Check the voltage on a known working circuit, for instance a power outlet. (Should read about 110-120V).
  • Check the voltage on the electrical system about to be serviced. (Should read 0V).
  • Go back to the known working circuit (power outlet in this example, should read 110-120V).

These steps are done to ensure that the voltmeter being used is functioning properly. Keep in mind that the PPE has to be worn during the live-dead-live process. Once it has been verified that the system is in fact de-energized it is safe to remove PPE.

Electricity is no joke and should never be taken lightly. It is recommended that all other personnel stay away from the electrical panel during serving but if it is necessary, that person should be a qualified employee. That qualified employee must understand these three main components of electrical safety and follow them every time.

ESC Services understands the difficulties that may arise when working with electrical systems. For more information on ESC’s arc flash and lockout/tagout procedures, please contact us.

About Gilbert Soto
Gilbert Soto is a Senior Lead Engineer for the ESC Services, a Rockwell Automation business. He manages lockout/tagout implementation projects for a variety of industries both domestically and internationally: including water treatment, adhesives, mining equipment manufacturing, hospitals, and food processing.