I've been trying to find the limits on arc flash...what tasks or equipment have been documented to cause an arc flash, what are the upper and lower limits in terms of voltage, number of victims, types of injuries, etc.
"OSHA Arc-Flash Injury Data Analysis", Carig M. Wellman, paper ESW2012-28, looks at arc flash injuries. Figue 3 shows a chart showing the type of injury (burns, smoke inhalation, shocks, fatalities). The text points out that based on the data analyzed from April, 1984 through June, 2007, 11% of injuries at 480 V resulted in fatalities, while there were zero fatalities below 480 V.
If Wellman had just a few months more data, he would have come across case #201282837 which occurred on August 18, 2007:
Quote:
At approximately 4:00 p.m. on August 18, 2007, Employee #1 and a coworker were removing the 120/240-volt electrical panel at a building in Doraville, GA. The two men had arrived at work at 3:00 p.m. dressed in tank tops and jean shorts and were waiting for Georgia Power to deenergize the circuit, which was scheduled for 5:00 p.m. Before Georgia Power arrived, however, they began to remove the panel by disconnecting circuit breakers and removing the panel's supports. At approximately 4:00 p.m., the coworker was on a ladder above the panel, and Employee #1 was standing on the ground in front of it when there was an arc flash and fire. The workers were transported to Grady Memorial Hospital for treatment. Employee #1 suffered severe burns over 60 percent of his body and died on October 15, 2007. The coworker's legs were badly burned and he was sent home to recover.
This seems to confirm that it is certainly not only possible to create a good sized arc flash below 480 V but that it can even lead all the way to a fatality.
I was however not able to find a case from 2007 to 2011 at least in which more than one fatality occurred. From a pure numbers case, the highest number of injuries that I uncovered was case #200375723 on 10/28/2011:
Quote:
On October 28, 2011, Employees #1 through #4, with Loris Healthcare System, and Employee #5, an electrician with Cayce Company, Inc. (an electric contractor), were adding a circuit to the outside of Sea Coast Medical Center to power mobile medical equipment. They were preparing to pull electrical wire through a recently-installed conduit. Employee #1, the Plant Services Supervisor, removed the factory-installed protective tape from the energized bus bar of a 480 volt, 3000 Amp main breaker panel in the main electrical room. He was standing directly in front of the open panel with his hands inside it. When Employee #1 used a screw driver to scrape away tape adhesive, an arc flash occurred. He was engulfed in flame and received third-degree burns over approximately 48 percent of his body, primarily from the waist upward. Employee #1 died approximately three weeks later. Employee #2, an electrician/data communications technician who was standing beside Employee #1, approximately 1 ft from the front of the panel, was hospitalized for third-degree burns on his face and arms. Employee #3, who was standing approximately 6 ft from Employee #1, was treated at Sea Coast Medical Center for smoke inhalation. Employee #4, who was approximately 12 to 16 ft from the panel and walking away from it, was struck by flying debris but uninjured. Employee #5, who was working approximately 8 ft from the panel, received a first-degree burn on his upper arm from a piece of flying slag from the bus bar. This task was nonroutine for the employees of Loris Healthcare System; standard practice was reported to be that all energized electrical work was to be performed by contractors. Factors in the incident included failure to wear arc flash PPE, lack of a cover on the main panel, and failure to prohibit employees from working in proximity of energized electrical parts.
That makes 1 fatality, 2 serious injuries, and 2 minor injuries, for a total of 5 victims.
For the data from 2007-2011, I did not find any cases with more than 1 fatality. Fatalities themselves are very few in total numbers. The vast majority of cases are serious burn injuries requiring hospitalization. However keep in mind the same thing that Wellman notes...the database is based on accidents that OSHA investigated. It is thus a sampling and definitely not a random or statistical sampling so we can certain draw some conclusions about the "scope" of arc flashes but we cannot do any data mining looking for things like the ratio of serious injuries to fatalities.
