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Westex Arc Flash Video, cal/cm2 translation

Westex Arc Flash Video, cal/cm2 translation

Westex Arc Flash Video, cal/cm2 translation

(OP)
Working project where we calculated incident energy level 2-3 times max 40cal/cm2 limit.  Plant operators and a process control location are located very close to switchgear.  Personnel exist here 99% of time outside of shutdown.  I apologise, cant be more specific.

These operators do not touch switchgear.  Still, recommending either major modifications to switchgear or complete relocation of control location for long run.  

Westex.com has great arc flash videos.  Focused on this one
http://www.westex.com/video-library.html?MediabaseID=108&tab=3

Impressive.  But, website said that arc radius used was 12", front of maniquin's visor one foot from arc.  But, arc flash energy level normally calculated 18" or 24"? Our is 24".  Since Westex is trying to demonstrate FR fabric, think they simply lowered radius to 12" so get higher cal/cm2 number?

If "translated" the blast they are showing to a 24" radius, drop Westex 35cal/cm2 number by factor of 4 to 9cal/cm2, correct?

Anyone have idea for whether Westex cal/cm2 number is accurate?  In different discussion thread re terrible Barranca Refineria blast in Columbia some poster thought would be about 50cal/cm2 blast?

Would like to say our incident energy is 9-14 times Westex example and help get changed.
 

RE: Westex Arc Flash Video, cal/cm2 translation

I think your assumptions of the Westex videos is accurate, you can always call them for details, I know the guy who did all of those tests but not sure if it is appropriate to post his name here.

Sounds like you need to look at mitigation strageties but hard to recommend anything without knowing anything about your equipment. But here is a good place to start
http://www.cbsnuclear.com/downloads/EPRI-presentation-on-remote-racking-and-switching-for-arc-flash-mitigation.pdf

RE: Westex Arc Flash Video, cal/cm2 translation

The equations in IEEE 1584 cover calculation of the arc-flash energy.  But you have to assume a working distance.  This is supposed to be the distance from the likely source of an arc to the worker's torso or head.  Increasing the assumed working distance does reduce the incident energy roughly as the inverse square of the distance.  

I have no reason to question the Westex data.  The energy is a function of the voltage, which you haven't told us, the fault current, and the arc duration.  If you want to know the arc-flash energy for your specific situation, it is not that difficult to determine and there are on-line arc-flash calculators that can give you an approximation.  To really know what the actual hazard is, I'd recommend an arc-flash hazard analysis.  Then you'll have actual data to base decisions on.   

David Castor
www.cvoes.com

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