Electrical and Arc Flash Safety

Q:    (Do you know) of any studies / documented history conducted on the effects of arc flash events and the medical impact from the pressure associated with the blast?  For example, we have a client who has a 100 cal suit available for use. While it would “protect” from the 100 cal arc flash, the impact to the body from a close proximity blast could be severe.   

   
A:    I do not want to imply that arc blast is a myth but there is a  myth traveling around that you might as well not wear arc flash gear past 40 cal because the blast will kill you.  I have heard this hundreds of times and it simply is NOT true.

There are really no full studies of arc blast pressure.  IEEE 1584 now has additional data and this should be published in 2012 or 2013 but for now the data is VERY limited.  Only one paper below has data and that data has been shown to be based on a microphone which washed out at about 1 PSI.  I know of NO deaths from pressure wave.  Many knockdowns.  All the deaths I know of are from thermal burns from clothing ignition or lung burns from breathing in the hot gasses (usually from the clothing fire or subsequent fires from burning oil [oil filled cables and transformers]).  The pressures could be big but anecdotally it isn’t very convincing that there will be lots of deaths from blast alone.  I do believe pressure waves can be an issue but it isn’t half as bad as we are currently led to believe by some salespeople. I have done about 100,000 arcs and we can knock a mannequin down but we don’t usually destroy them (I did break an arm off once by putting it across a disconnect).  We are not against equipment that eliminates the arc blast, but last month I learned of a group of workers who refused to wear 100 cal suits for a potential 100 cal event because the equipment company trained them and pushed this idea that the blast will kill you and the suit will “leave a nice corpse”.  This has NO evidence to support it and leads people to doubt the real science.  I challenge the equipment manufacturers to donate – as some have – to IEEE 1584 so real science can be done on this and help to answer a very complicated question without fear and trembling, but with knowledge and integrity.  Again, always ask what they are selling. “) “Ignorance isn’t what you don’t know,it’s what you know’; wrong, Yogi Berra.

Here are the papers I have read. There are probably more but this is a good start.

[1] R. H. Lee, “Pressures developed by arcs,”  IEEE Transactions on Industry Applications, vol.  IA-23, no. 4, pp. 760-764, July/Aug. 1987.

[2] D. Sweeting and A. D. Stokes, “Energy transfers within arcing faults in electrical systems,” Proceedings of the 8th International Conference on Electric Fuses and their Applications (ICEFA), Clermont-Ferrand, pp. 169-178, Sept. 10-12, 2007.

[3] B. Koch, principal investigator for IREQ, CEA No. 046 D 549  Characterization of Secondary Arcing Faults Part 3: General Summary and Guidelines for Protection against Arcing Fault Effects. Quebec: Canadian Electrical Association, 1991.

[4] J. E. Bowen, M. W. Wactor, G. H. Miller, and M. Capelli-Schellpfeffer, “Catch the wave,” IEEE Industry Applications Magazine, vol. 10, no. 4, pp. 59-67, July/Aug. 2004.

[5] R. L. Doughty, T. E. Neal, T. A. Dear, and A. H. Bingham, “Testing update on protective clothing & equipment for electric arc exposure,” IEEE Industry Applications Society Magazine, vol. 5, no. 1, pp. 37-49, Jan./Feb. 1999.

[6] Neal, T. E. and R. F. Parry, “Shrapnel, pressure, and noise,” IEEE Industry Applications Society Magazine, vol. 11, no. 3, pp. 49-53, May/June 2005.

[7] R. A. Jones, etal., “Staged tests increase awareness of arc-flash hazards in electrical equipment,” IEEE Transactions on Industry Applications, vol. 36, no. 2, pp. 659-667, Mar./Apr. 2000.

 Email e-Hazard or ArcWear with a question!