FROM THE ARCHIVES: Managing the risk of arc flash
Understanding the data and the standards for a deadly plant danger.
As an extension of Plant Engineering’s successful Arc Flash University series, the Manufacturing/Automation Summit brought in industry experts Joe Weigel and Lanny Floyd to discuss ways to manage and prevent arc flash incidents. Weigel is product manager for Square D Services at Schneider Electric; and Floyd is principal consultant for electrical safety and technology at DuPont Engineering, editor-in-chief of IEEE Industry Applications magazine, and an IEEE Fellow.
Understanding arc flash risks requires knowing the data. “Arc flash occurs five to 10 times a day in the U.S.,” Weigel said. “Major injuries can be as serious as third- or fourth-degree burns. The average cost just for medical treatment is about $1.5 million. The total cost including litigation can easily be $8 million to $10 million, and in some cases even higher. There’s an average of about one fatality from arc flash per day.”
Some of the nonhuman consequences of arc flash include downtime, lost revenue, loss of product, equipment damage—the equipment is almost always destroyed, and regulatory impact—OSHA will always investigate, according to Weigel.
“No one knew how to do arc flash calculations until 1999 because the research and work had not been done,” explained Weigel. “Arc flash calculations are very complex and should be done only by a licensed electrical engineer acquainted with power systems design as well as the techniques to do this kind of analysis.”
Managing risk requires Code compliance. Weigel offered examples of what facilities must do to comply. “They have to have a safety program with defined responsibilities in a written document that’s available to the workers,” he said. “The goal of an electrical safety program should be work conditions that are free from burns, shock, electrocution, arc flash, and arc blast. Those are the electrical hazards. The written document explains requirements such as who does the energized work permit and who is responsible for lockout/tagout. They have to provide an arc flash hazard analysis and training for workers. They have to provide personal protective equipment tools for safe work such as insulated screwdrivers, wrenches, and voltage-rated instruments. Electrical equipment must have labels that warn qualified people that there are arc flash and shock hazards.”
The employer has most of the responsibilities to provide safe work practices and training. The employees must understand the company’s policy and follow the safe work practices. “Training is probably the cheapest and fastest way to lower your risk,” said Weigel.
Turning off the power
De-energizing electrical equipment is a fundamental requirement of all safety programs. “Anytime you allow work to be done energized, you’re taking a risk and so are the people doing the work,” Weigel said. “Live parts shall be de-energized before the employee works on or near it unless the employer can demonstrate that de-energizing introduces additional or increased hazards or is infeasible due to operational limitations. There’s way too much work that goes on energized than there should be.”
However, there are some justifications to working on energized systems, according to Weigel. “Infeasibility would be tasks such as voltage testing, troubleshooting, diagnostics, and infrared thermography,” he said. “Those are all justifications. However, it still has to be done safely.”
Proper electrical equipment maintenance can significantly reduce risk. “Maintenance is not well done in this country on electrical systems,” Weigel said. “Circuit breakers usually fail in a closed position with no indication of failure. They will supply power reliably until there’s an event. Then it doesn’t know what to do. It can’t operate because it hasn’t been lubricated in 20 years.”
Floyd said the goal is zero. “We have to eliminate this very serious injury from the workplace,” he said. “It’s a sudden and immediate disruption to operations, whether you are a financial institution, a hospital, or a petrochemical plant or any other industrial or commercial facility.”
Floyd discussed the standards that are relevant to the issue of arc flash mitigation. “This is fundamental: The grounding and bonding of an industrial power system must be designed and installed correctly for the circuit breakers and fuses to operate properly,” he said. “The standard that covers grounding and bonding is IEEE 142.”
According to Floyd, IEEE 141 provides the guidance on how to design an electric power system for reliability and safety. “IEEE 242 relates to protective coordination studies,” he said.
“The IEEE 1584 standard guides the arc flash instant energy analysis,” said Floyd. “It’s not just for how to select PPE. It’s about doing the analysis on the facility design so that you can reduce the possibility or the severity of injury. The IEEE 902 standard is the guide for maintenance, operation, and safety. NFPA-70B details recommended practices for electrical equipment maintenance.”
Floyd offered smart motor control centers (MCCs) as an example of how engineering controls can lower arc flash and electrical shock risks. “This is where automation and control really shine in electrical safety,” he said. “The major manufacturers of MCCs and substation equipment are bringing out innovative products that enable people to do maintenance and troubleshooting and analysis tasks in a way that’s inherently safer than the traditional way of doing maintenance.”
Smart MCCs allow electrical workers to remotely access information regarding status and operation of the MCC and the equipment connected to it without opening the door. “Having the MCC door open and having hands and tools in the compartment that has high-energy circuits creates a potential for exposure to an arc event—an accident waiting to happen,” Floyd said.
Other engineering controls include infrared windows that allow thermographers to inspect electrical equipment without opening the doors; high-resistance grounding, which reduces the frequency and magnitude of arcing faults; remote racking; and remote switching.
Administrative controls include hazard assessments, maintenance and reliability programs, personnel training, energized work permits, planning, and audits, according to Floyd.
“Joe already emphasized this, and I will emphasize it further,” said Floyd. “Circuit breakers must function as designed and as specified in the design of the facility. If maintenance is not done religiously and if you have an arc flash and if the circuit breaker doesn’t function as it’s supposed to, then all the tables, and all the arc flash analysis, and all the PPE won’t protect the worker.”
Risk management necessarily requires responsibility and accountability. “All facets of quality and excellence within the organization start at the top,” Floyd said. “How solid is management committed to establishing goals, setting the priorities, allocating the resources, and establishing the ability to reward success in arc flash mitigation efforts? Is this commitment visible to the people most at risk? Is it visible to the resources needed to make a difference in the program?
“A commitment from the top is very fundamental to any objective in the business world,” Floyd concluded. “At the working level, there’s a lot of work that needs to be done on arc flash training.”
Five to 10 arc flash explosions occur in electrical equipment every day in the United States, according to statistics compiled by Cap-Schell, Inc., a Chicago-based research and consulting firm that specializes in preventing workplace injuries and deaths.
Injuries from arc flash events range from minor injuries to third-degree burns and potential death due to the energy released.
Other injuries include blindness, hearing loss, nerve damage, and cardiac arrest.
The costs of arc flash are both human and financial. Those costs include:
- The average cost of medical treatment for survivors of serious arc flash injuries is $1.5 million.
- Total costs, including litigation can be as much as $10 million.
Nonhuman costs include:
- Lost revenue
- Loss of product
- Equipment damage
- Regulatory impact
- OSHA citation and fines.
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