The pressure wave from an arc flash incident is comprised of two parts, the rapid expansion of vaporized metal and the heating of surrounding air. Copper expands by a factor of approximately 67000 times in vaporizing. To put this in perspective water only expands 1670 times during vaporization. This rapid expansion creates a pressure wave that can place as much as 600lbs per square inch on a exposed individual working within 2 feet of the arc flash source.

When we determine the Hazard/Risk Category for arc flash, anything above a 4 is considered prohibited due to the sound, pressure and concussive forces present. Above this level these forces are more significant than the thermal values.

Ralf E. Lee’s “Pressures Developed by Arcs” Is required reading for anyone dealing with Arc Flash hazards.

Five men killed in Sunday’s blast at power plant in Middletown, Conn.

We all saw the headlines and if you were like me, the first question that came to mind was “Why is it taking so long to get information on the welfare of the crews at the facility?”

We sometimes forget that as contractors we need to have plans in place in the event of an emergency. We often look at our clients to tell us where to go and what to do during an emergency, but we rarely take the time to institute our own in-house emergency plan.

Emergency plans ensure continuity across company jobs for incident reporting, personnel management, resource management and damage assessment. Plans are developed to ensure communications at the company level during and immediately following an incident so that appropriate resources can be made available.

Response to any emergency needs to keep crew safety as the highest priority. Crews should not be allowed into hazard areas until deemed safe or a plan is put in place to minimize the hazard to acceptable levels.