NFPA 70E Arc Flash
NFPA 70E, or the NFPA's Standard for Electrical Safety in the Workplace, outlines specific practices to be followed in protecting workers from electrical hazards such as arc flash.
The NFPA's Standards
The National Fire Protection Association (NFPA) is a non-profit organization that produces standards for safety. For example, the organization publishes the National Electrical Code (NEC), which describes proper installation of electrical systems. In many parts of the United States, this code has been incorporated into law.
For safe electrical work in an existing facility, the “go-to” standard is NFPA 70E. While it is not legally required in most areas, it is widely respected and followed, and is used as a reference for safe practices worldwide.
The Electrical Safety Program
To ensure that safety procedures are implemented and consistently applied, NFPA 70E requires companies to create a written electrical safety program. This program should include the training requirements for the types of work that will be done in the facility; assessments of any electrical hazards in the facility, such as arc flash; and the specific procedures for necessary maintenance on the facility's equipment. Up-to-date and accurate information on the facility's electrical systems are also needed, such as one-line diagrams and equipment specifications.
The goal of this kind of program is to protect the workers and facility from harm. An effective system should establish a culture of safety awareness that includes all employees. One key part of safety awareness is providing information about any hazards that exist, so NFPA 70E includes detailed requirements for hazard and equipment labeling. The current edition of the standard requires detailed labels, not just generic warnings.
Electrically Safe Work Conditions
Wherever possible, NFPA 70E requires the establishment of an “electrically safe work condition” before electrical work begins. This means that the equipment is fully de-energized and cannot be re-energized while work is still being performed. The following steps should be taken to create an electrically safe work condition:
- Determine all possible sources of electrical energy to the equipment.
- Shut down the equipment and disconnect each source of energy.
- Where possible, visually confirm that disconnections are complete.
- Apply appropriate lockout / tagout devices to prevent re-connection of those power sources.
- Verify that each part of the equipment is de-energized using appropriate test instruments, such as voltmeters. Until equipment is tested, assume that it is still energized.
- Use grounding devices where there is a possibility of induction or accidental contact with energized parts.
Once this process has been correctly followed, the equipment will no longer carry any significant current or charge. Creating an electrically safe work condition is the best defense against electrical hazards such as shock and arc flash (a sudden and dangerous burst of energy). As a result, this procedure should normally be used in all electrical work, with the following exceptions:
- De-energizing equipment would create a greater hazard. Examples include life-support equipment, ventilation equipment in a hazardous environment, or similar safety equipment that requires an energized state.
- De-energizing is not possible, due to equipment design. If the equipment is part of a larger, continuously-operating system, for example, it may not be possible to de-energize the necessary parts.
- The nature of the work to be performed requires that equipment be energized. A simple example would be checking voltage.
Dealing with Arc Flash
While electrically safe conditions are effective for protecting workers, the act of creating an electrically safe condition requires a worker to interact with equipment that is still powered.
Where live work must be performed, including the work of implementing an electrically safe condition, one of the major concerns is the risk of an arc flash. This hazard is especially dangerous because arc flashes occur most often during equipment maintenance, when a worker is interacting directly with the equipment. Small arcs can arise whenever equipment is installed or removed, and whenever disconnecting switches are opened or closed. If this arc is sustained, it can become incredibly destructive in the blink of an eye, becoming an arc flash. NFPA 70E focuses a significant part of its content on this one hazard.
The standard uses a sequence of protective elements to limit the likelihood of an arc flash occurring, and to limit the harm that results if there is an arc flash.
First, NFPA 70E requires protective boundaries around potentially-hazardous equipment as a beginning step for safety. These boundaries keep unprotected individuals at a safe distance. This arc flash boundary infographic shows the three major boundaries from NFPA 70E and explains how they can help keep your workers safe.
Next, informative and detailed labels are required for equipment that may pose an arc flash hazard. These labels ensure workers are aware of the equipment’s hazards before they are exposed to those hazards. DuraLabel printers from Graphic Products offer a reliable and versatile way to create long-lasting signs and labels for your electrical equipment.
Finally, the last line of defense against an arc flash is a worker's personal protective equipment (PPE), and NFPA 70E provides recommendations and requirements for that equipment. PPE comes in a variety of types and levels of protection, so the NFPA has allowed several ways for facilities to describe the kinds of PPE that will be needed for work. The simplest system is a series of categories, clearly shown in this arc flash reference chart.
