Dynamics of an Arc Flash

April 22, 2013

The Arc Flash – we have all read the articles and listen to the numbers but do we really understand what the dynamics of these events are like and what potential dangers our electrical workers can encounter when working in and around energized equipment.

35,000 degrees that is the temperature that is created in the arc gap, three and a half times the surface temperature of the sun. In a controlled industrial application it is exactly the same as a plasma cutter used for cutting through large blocks of solid steel and other metals.

When you super heat air from an ambient air temperature of 75 degrees to 35,000 degrees in the blink of an eye, you create the same dynamics as a bomb.  When a bomb explodes it is the rapid increase in heat that creates the expansive destructive forces that we are familiar with, So when we complete a HRC (Hazard Risk Analysis) and label our electrical equipment, all we are telling our electrician is how big a bomb he is standing in front of i.e. this is a CAT 1, 2, 3, or 4 bomb, that way he can dress appropriately with the proper PPE if the bomb were to go off.

In an Arc Flash like in a bomb, when it goes off -

You get thermal energy – that can easily ignite non – FR clothing

You get blinding white light – you can be temporarily blinded

You get noise – you are temporarily deaf

You get a pressure wave (concussive force) that can be 2200 lbs/sq/ft – it can collapse a lung, cause internal and soft tissue damage

You get molten metal, shrapnel traveling at 750 mph at 1900 degrees

All this is happening in a blink of an eye so without proper PPE your blinded temporarily, deaf temporarily, disoriented and being showered with molten metal and your clothing catches fire.


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