RMSC Safety Sentinel – September 2017

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September 2017

Understanding Arc Flash

Two maintenance workers respond to a co-workers request for help. They begin to troubleshoot a component of the factory’s electric system. They need the power on in order to identify where the problem begins. Suddenly an improperly stored item falls into the electric cabinet and causes an arc flash. The worker standing close by was blinded by flying materials, and severely burned on his face, neck, arms and chest; the second worker only receives minimal burns from flying material.

An arc flash occurs when a flashover of electric current leaves its intended path and travels through the air from one conductor to another, or to the ground. When a worker is in proximity of the arc flash the results can be catastrophic – serious injury is likely; even death can occur.

What Causes an Arc Flash?

Arc flash can occur spontaneously if electric equipment fails but they are most often caused by the following six factors:

Dust/Debris Accumulation                                 Dropping Tools

Accidentally Contacting Live Parts                   Condensation/Moisture

Corrosion                                                              Faulty Installation

There are three factors that influence the severity of an injury sustained from an arc flash. First the proximity of the worker to where the flash occurs. If the worker is using good switching techniques like working right-handed, with his lungs full of air, standing to the side of the disconnect then the resultant injury will be minimized. The second factor is temperature – the higher the voltage the higher the temperature. The third and final factor is the time needed for the circuit to break – and cut off the flow of electric energy.

The typical results of arc flash include the following: severe burns where non-FR garments melt into the victim’s skin; fires that have the potential to spread rapidly depending on specific circumstances; flying objects and molten metal; blast pressure in excess of 2000 lbs/ft2; intense heat around approximately 35000 oF; and a sound pressure of around 140 decibels.

How to Prevent an Arc Flash

The most effective and fool-proof way to ensure that you don’t become an arc flash victim is to always de-energize the circuit before attempting work. Other effective arc flash controls include the use of good electric safe work techniques; insulation on tools and in the work environment; proper use of guarding and barricades; Ground Fault Circuit Interrupters (GFCI); and proper system grounding.

If you must work on live electric circuits use of good work techniques is absolutely essential. A safety-related written plan should be developed and enforced on prevention of electric shock from either direct or indirect electric exposure. These safety-related work plans should include at a minimum: the details of a permitting system for energized electric work; personal protective equipment requirements; insulated tools/mats; job briefings prior to engaging in work.

For more information on loss control services contact David Witte, email: dwitte@rmsc.com, P: 502-708-3132   www.RMSC.com

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