Although standards have developed and evolved to help keep workers safe around electrical equipment, the fact is that tens of thousands of electrical accidents still occur each year in industrial environments. According to the National Fire Protection Assn. (NFPA), hundreds of deaths and thousands of disabling injuries occur each year that are caused by shock, electrocution, arc flash and arc blast.
Arc flashes are the most common electrical incidences. Responsible for about 80% of the electrical-related injuries, arc flashes can cause severe personal injury and equipment damage when an arc fault superheats the air around it, expanding and creating a pressure wave within an electrical enclosure. Explosions can be as hot as 35,000 °F, and can send shrapnel and molten metal flying out from equipment (Figure 1).
The NFPA 70E standard dictates the precautions that manufacturers should take with their electrical equipment. Originally developed at the request of the U.S. Occupational Safety and Health Administration (OSHA), it provides guidelines on hazard/risk classifications, personal protective equipment (PPE), arc flash boundaries, and more.
Push Back on OEMs
Because it is the factories that are mandated to keep their own workers safe, the bulk of the responsibility falls to them to make sure equipment is properly labeled, the appropriate level of PPE is provided, and workers are properly trained to demonstrate safe procedures. Despite the standards, levels of awareness vary throughout industry.
Though responsibility for arc flash safety has not traditionally fallen to the OEMs, as standards tighten, users are beginning to put some of the burden back on the machine builder. "Some customers are requiring us to isolate the high-voltage areas from the low voltage that we would use for PLCs and sensors on the machine," says Chris Lovendahl, sales manager for Concep Machine, which makes custom machines and factory automation systems in Northbrook, Ill. "We are physically separating them so that technicians can de-bug or troubleshoot the controls system without the requirements for the protective gear."
Filamatic, a liquid filling and packaging machine maker in Baltimore, also has been separating high-voltage and low-voltage components. "We put logic on one side, power on the other side of the panel," says Jack Chopper, chief electrical engineer. "That way if you need to troubleshoot the logic, you can open up the panel, no problem. You don't want to create a situation where somebody's trying to work on the logic right above a high-voltage area."
Filamatic takes other steps as well, including data taps and/or Lexan windows in panel doors so they don't have to be opened as often, installing interlocks and other hardware that make it harder for users to open panels without thinking, and coordinating fuse protection. A trend toward finger-safe devices also plays a part in improving safety, Chopper says. "It used to be lugs were wide open," he says, describing how easy it would be to create a fault by dropping a wrench across open copper bus bars. "Now the risk is lowered because of finger-safe devices."
It's a growing debate as to just how much responsibility machine builders should take with regard to arc flash safety, according to Wayne Tompkins, global marketing manager for Rockwell Automation. "What we're starting to see is that the end user is pushing back on them saying you need to design me a safe machine," he says. One thing that machine builders are beginning to do, he adds, is to install different levels of breakers. An end user could place a breaker in maintenance mode, for example, so that it would trip faster in the event of an arc flash, reducing the energy incident. "We see customers telling OEMs they have to use these types of equipment."
Lacking Proper Training
These sorts of solutions are increasingly necessary in part because of demands from users who are becoming more aware of arc flash hazards, Chopper says, but also because of just the opposite: more people servicing these units with less training than their predecessors.
Government agencies such as OSHA and NFPA have been trying to raise awareness of the electrical hazards, refining standards to improve safety. In 2007, OSHA changed how it defines a "qualified person" from one familiar with the construction and operation of the equipment and the hazards involved to one who has actually received the proper training and has demonstrated skills and knowledge in the construction and operation of the equipment, and the installations and the hazards involved.