We examine how six steps of the Hierarchy of Risk Control pyramid can help employers and workers improve electrical safety by mitigating risk.
By Dean Katsiris, product manager and Dave Scheuerman, technical training manager, Littelfuse, Inc.
The 2018 version of NFPA 70E, Standard for Electrical Safety in the Workplace, has added a variety of new requirements for safe work practices to protect personnel by reducing exposure to major electrical hazards. Released in September 2017, the new edition is designed to help both employers and workers avoid injuries and fatalities as a result of shock, arc flash and arc blast.
Many of the changes in it were made to harmonize with the National Electrical Code® and CSA Z462, the Canadian Standards Association’s Workplace Electrical Safety Standard. This article provides a look at some of the most recent additions to the risk assessment procedure.
Looking at NFPA 70E, Article 110.1(H) states that every employer’s electrical safety program must include a risk assessment procedure. This procedure addresses employee exposure to electrical hazards and identifies the process that employees should use before work is started to identify hazards, assess risks and implement risk control according to the Hierarchy of Risk Control. The electrical safety program also must address the potential for human error.
The Human Factor
The human factor always will have a huge impact on workplace safety because human error is among the leading causes of incidents and injuries. The Informative Annex Q: Human Performance and Workplace Electrical Safety was added to the standard to help define human behaviors, whether conscious mistakes or inadvertent ones.
When it comes to improving safety from an electrical perspective, the potential for human error necessitates greater emphasis on the top part of the Hierarchy of Risk Control pyramid (see illustration), with a preference for automatic or automated safety mechanisms.
Workers always will be human, working under pressure and time constraints, prone to taking shortcuts, making mistakes and experiencing communication breakdowns. Rather than having electrical safety depend on fallible worker performance, the authors of the revised standard are making it clear that it’s better to design safety into the electrical system itself. A growing number of products can be designed to reduce the impact of human error. This can minimize the risk of injury to personnel and damage to equipment.
What Is the Hierarchy of Risk Control?
The Hierarchy of Risk Control is a reference for deciding how to make workplaces safer. Until recently, the industry’s focus has been on the three lowest and least effective levels of the hierarchy pyramid shown in the illustration:
- Safeguarding workers with the appropriate personal protective equipment (PPE)
- Changing the way employees work through administrative controls
- Increasing awareness by informing workers of possible hazards
The 2015 revision of NFPA 70E emphasized personal protective equipment (PPE) and hazard labeling, and in fact renamed Hazard Risk Categories to PPE Categories. The unstated implication was that PPE and labels are the primary ways to mitigate the risk of injury, but it also included an informational note on the Hierarchy of Risk Control.
In the newest edition of the standard, the Hierarchy now is in the main part of the standard in Article 110.1(H) (as well as illustrated on the standard’s cover), so any illusions that PPE and labels are the only components of a safety strategy now should be rectified.
Although we’ve described the three lowest levels as the least effective ways to achieve safety, they remain critical, foundational blocks in a safety strategy. They help employers avoid — but not prevent — unsafe situations and reduce the severity of injury, but they don’t necessarily reduce the number of unsafe practices.
However, it is even more important for workplace managers to focus their electrical safety efforts on the top of the pyramid:
- Elimination involves physically removing the hazard. Although this is difficult to achieve completely, it certainly is possible in some limited-scope scenarios.
- Substitution replaces existing equipment and controls with safer options.
- Engineering controls typically limit the fault current, duration or incident energy.
Let’s now review each of the segments within the Hierarchy of Control pyramid.
Article 105.4 of NFPA 70E states, “Hazard elimination shall be the first priority in the implementation of safety-related work practices.” Separating the worker from the hazard through thoughtful design is one simple way to mitigate the hazard. This may be done in the selection or retrofit of electrical equipment and components that incorporate modern communication protocols to keep the worker from entering the panel.
For example, it’s common for workers to open an electrical cabinet to update settings or trouble-shoot an issue by reading the fault codes on a relay. Retrofitting components, such as electromechanical relays, with more modern microprocessor-based relays doesn’t require maintenance personnel to enter the cabinet to maintain or calibrate them. These modern relays also can communicate with a PLC or factory software to provide remote diagnostic capabilities. Troubleshooting issues and controlling the relay remotely separates the worker from the hazard, minimizing potential shock and keeping them outside the arc-flash boundary.
A similar strategy is to mount a remote display and keypad in the door of the electrical panel. Workers can set up or reset the relay, view real-time data and troubleshoot fault codes while the panel door remains closed. This option doesn’t provide as much safety as remote access because the worker is still within the arc-flash boundary.
Substitution focuses on replacing existing equipment and controls with safer options, such as using current-limiting fuses to increase an industrial control panel’s short circuit current rating (SCCR). If the amount of available fault current of the system in which the panel is installed is greater than the panel’s SCCR and a short circuit occurs, the panel may undergo catastrophic damage and workers could be put at risk.
Current-limiting fuses operating in their current-limiting range will limit the maximum instantaneous peak current to a value substantially lower than the peak current that could flow if the fuse were not in the circuit.
For example, consider a system using UL Listed Class RK5, 200A fuses, in which the incident energy is calculated at 11.6 cal/cm2 or, if the table method had been used, PPE Category 3. The worker would need to wear a full set of PPE gear to work on an energized system.
However, by upgrading to UL Listed Class RK1, 200A fuses (which are the same physical size as the Class RK5 fuses), the incident energy can be reduced to just 3.5 cal./cm2, or PPE Category 1. This means that the worker now can wear considerable less PPE gear and still be protected while performing the task at hand. A simple substitution of current-limiting fuses can produce considerable risk reduction.
Engineering controls make it possible to “automate” safety, reducing the risk of electrical shock and limiting arc-flash incident energy. For example, arc-flash relays are designed to limit the time an arc persists in the event of a fault and thereby minimize the energy released in the system, regardless of whether the worker is wearing adequate PPE or has engaged a maintenance mode switch.
By using optical detection, it’s possible to detect and signal an arc flash in less than 1 ms. At this point, the determining factor in the incident energy is the circuit breaker’s instantaneous trip time. Even with that factored in, typical breaker trip times of 35-60 ms are a significant improvement over typical overcurrent trip times.
Some advanced arc-flash relays use light instead of current to detect the arc without worrying about coordination, inrush or other sources of temporary overcurrents. These relays detect and trip the connected breaker quickly. They may be designed into new equipment or retrofitted easily into existing equipment to reduce the potential incident energy levels. This helps make facilities safer while reducing potential damage from any arc faults that might occur.
While the items in the pyramid’s bottom portion are less effective at achieving safety, they should not be ignored. Increasing awareness of potential hazards is an important part of any employer’s responsibilities. NFPA 70E Article 130.5(H) lists the minimum requirements for information to be listed on equipment labels, including nominal system voltage, arc-flash boundary and either the available incident energy and the corresponding working distance or the arc-flash PPE category. Barriers such as warning tape offer another important way to boost hazard awareness. They can be used to alert people to stay away from energized equipment while electrical hazards are present.
The most commonly used administrative controls are designed to change the way people work. They include using job briefings, performing regular visual inspections, establishing safe work practices such as lockout/tagout (LOTO) and requiring periodic employee training.
Employers must verify that employees receive appropriate PPE. For details on the PPE categories, consult Informative Annex H: Guidance on Selection of Protective Clothing and Other Personal Protection Equipment in the back of the NFPA 70E Standard.
The six steps in the Hierarchy of Risk Control pyramid offer invaluable direction on how both employers and employees can enhance electrical safety by minimizing the risk of injury to personnel and damage to equipment.
To learn more about protecting against workplace arc-flash hazards, download a free white paper on the topic, “Key Considerations for Selecting an Arc-Flash Relay.”
Littelfuse, Inc., based in Chicago, is a participating Encompass™ Product Partner in the Rockwell Automation PartnerNetworkTM program. Littelfuse supplies fuses and protection relays used in industrial settings.
The Journal From Rockwell Automation and Our PartnerNetwork™ is published by Putman Media, Inc.