What Are the Limitations of an Arc Flash Rated Suit?

A common misperception is that a person wearing an arc rated suit is “bulletproof” from the hazards associated with electricity.

There are three main potential hazards when working with electricity: Arc Flash, Arc Blast and Electric Shock. There are also several reasons PPE in general might be limited in its ability to protect workers.

Arc Flash

An arc flash suit can protect you from an arc flash provided that the incident energy level that the suit is exposed to is equal to or less than what the suit is rated for.

All arc tested suits will come labeled with an estimated arc thermal performance value (ATPV) level measured in calories/cm^2.

Oberon recommends having a risk assessment done before working on any electrical equipment to help identify the possible risks associated with the work task to be performed.

Once this analysis is done the appropriate ATPV level needed can be determined and the proper PPE selected.

This leaves two other potential electrical hazards that could harm you.

Arc Blast

The arc blast is a high pressure sound wave that is caused by a sudden arc fault. It can cause molten metal droplets to be propelled at high speeds as well as sudden expansion of air pressure that can blast out.

An arc flash suit offers some protection from these types of hazards, but only in a limited capacity.

For instance, if a blast pressure wave were to be strong enough to propel a worker across a room, an arc flash suit would not be able to protect the worker from the force of the wave.

Arc blast pressure is a valid concern and is attributed to fault current and containment size. However, its effects are mitigated when opening equipment doors or removing panels due to the factor of containment. Most work tasks are performed with equipment doors or panels removed, allowing the arc blast pressure to escape.

Incident energy and arc blast pressure do not correlate. Incident energy calculations are based on maximum available short circuit fault current, upstream protective device clearing time, and the working distance.

Electrical equipment could have a very high incident energy level with low fault current and a long clearing time. In this scenario, the arc blast pressure would be low due to the fault current, but the incident energy could be high enough to require a 100 cal/cm^2 arc flash suit.

Electric Shock

The last and most common type of electrical hazard that a worker can be exposed to is electrical shock.

Shocks are caused when contact is made by a worker with an electrical energy source. Arc flash suits are not tested or designed to protect workers from this type of hazard.

Typically, workers will wear rubber electrical gloves with protectors (usually leather) when there is a risk of electrical shock while performing their work task. They'll also ensure they're wearing dielectric footwear.

Other Limitations of PPE

There are several additional reasons why arc flash PPE may be limited in its protection:

• It’s “not enough” - If the ATPV of the PPE is less than the incident energy level of the hazard, a worker will not be adequately protected against serious injury or worse.
• It doesn’t fit - Garments that are too tight or too loose are not only uncomfortable and limit mobility (which can lead to Human Performance Errors), but they may compromise the effectiveness of the PPE should an incident occur. This is another reason why shared PPE is not recommended.
• It hasn’t been maintained properly - Not regularly testing the PPE where required, laundering when dirty with contaminants, and/or storing and handling the PPE carefully, can weaken or destroy the PPE and therefore its ability to protect the worker.
• It’s not worn properly - PPE that is not used and worn as intended may reduce or eliminate its protective value.
• It’s the last line of defense - Arc flash and shock PPE should always be used where appropriate, however as per the Hierarchy of Risk Controls, elimination, substitution, engineering controls and administrative controls should always be applied first against electrical hazards. A Risk Assessment should always be performed prior to any electrical work task.

Arc flash PPE can save lives but it's important to remember it's a last line of defense against these hazards and must be selected, used and maintained properly for maximum effectiveness and protection.

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