In this article:
- Hierarchy of risk control methods
- Human error
- Estimate of the likelihood of occurrence of an arc flash incident
- Energized electrical work permits
The 2018 Edition of the NFPA 70E Standard for Electrical Safety in the Workplace was released in late 2017 with little fanfare. However, there are several significant changes in this edition that have potentially wide-ranging implications for maintenance personnel collecting condition-based data on their electrical and electromechanical assets.
The NFPA 70 National Electrical Code (NEC) and the NFPA 70E are meant to work hand in hand. The NEC defines how to install listed electrical equipment properly, including ensuring that items such as cable ampacity, fuse and breaker ratings, conduit fill guidelines, and safe equipment clearances are correct. When electrical equipment has been designed, installed, and maintained properly and is operated under “normal” conditions with all hinged doors closed, covers on, and guards in place, workers are not exposed to any hazard. The NFPA 70E deals with how to reduce risk through safe work practices on equipment when it is under “abnormal” conditions, either intentionally or unintentionally, and the likelihood of occurrence of a shock exposure and arcing fault and arc flash are heightened.
Hierarchy of risk control methods
The first major change is that the Hierarchy of Risk Control Methods, previously a suggested nonmandatory requirement, has now been made mandatory to apply to any energized electrical work task to mitigate exposure or reduce risk. The hierarchy must be applied in sequence to reduce the inherent or initial risk to a residual risk level that is as low as reasonably practicable (ALARP).
The Hierarchy of Risk Control Methods consists of six controls, each which must be considered fully and eliminated as an option to reduce risk before moving to the next lower control of the hierarchy. (The effectiveness of the control reduces as we move down the hierarchy.)
1. Elimination – Eliminate the hazardous energy altogether. In the case of condition-based maintenance (CBM) inspections, most data collection must be performed with the electrical equipment energized and under “normal” load conditions, which usually means at least 60% of the normal operating load present. Infrared and ultrasound inspections must be performed energized and under normal load and, in the case of infrared, thermal stability must be achieved. Most motor current analysis (MCA) tests must be performed with the motor energized while oil sampling can be performed with equipment de-energized. The fact that taking an equipment shutdown would be inconvenient for the client is not necessarily sufficient cause to bypass elimination and move to the next control in the hierarchy.
2. Substitution – Involves replacing something that produces a hazard with something that does not produce a hazard. To be an effective control, the substitution of process or product must not produce another (new) hazard. If we agree that a given CBM work task must be performed with the electrical equipment energized, is there a way to substitute a way to see or listen inside the equipment or collect a sample without exposing energized conductors or circuit parts? The use of electrical maintenance safety devices (EMSD) such as properly sized and located infrared viewing panes or ultrasound ports or sensors may allow the qualified person to inspect the electrical equipment and collect data without any exposure to energized conductors or circuit parts. External oil sampling ports can be installed on transformers that allow the qualified person to gather a sample without opening the energized terminal chamber. Motor test access panels (MTAPs) can be installed to allow safe closed panel testing of motors.
3. Engineering controls – Involves a physical or design changes to the electrical equipment, rather than relying on worker’s behavior or requiring workers to wear protective clothing. There can be some confusion as to when a change is substitution versus engineering controls. My interpretation is that engineering controls are to protect the worker from himself (e.g., designing in more insulating, guarding, or finger-safe components) or implement design changes to reduce hazard levels (e.g., protective devices which reduce the maximum fault clearing time).
Engineering controls might include using high-resistant grounding instead of solidly grounded systems to limit the phase to ground fault current or selecting arc-resistant switchgear. In this manner, the work task will expose the qualified person to reduced electrical hazards and will reduce the resultant potential for injury. With this thinking, other examples of engineering controls would be tamper resistant hardware and door interlocks (limit switches) that prevent access into hazardous energized electrical equipment or automatically de-energize the electrical equipment if someone manages to open an access point. Touch-proof barriers inside of electrical equipment might also qualify as engineering controls – although they often need to be removed to perform Infrared inspections creating a secondary hazard for the thermographer.
4. Awareness – Ensures that the personnel involved in a work task have a documented job safety plan that was created by a qualified person. The job safety plan must include:
- A description of the job and individual work tasks.
- Identification of the electrical hazards associated with each work task.
- A documented shock risk assessment.
- A documented arc flash risk assessment.
- Use of work procedures involved as well as any special precautions and energy source controls.
5. Administrative controls – Includes using electrical safe work procedures and employee training. Specific training for qualified persons would include electrical safety training, lockout tagout training, emergency response training, First Aid / CPR (based on jurisdictional requirements), and PPE training. Training must be documented and retraining / certification must be performed at proper intervals. Even unqualified persons who will not be working on electrical equipment need to be trained on basic electrical safety practices. With the awareness and the administrative controls in place, only then can you move to the final control in the hierarchy.
6. Personal protective equipment – PPE includes equipment such as rubber insulating gloves with leather protectors, using insulated hand tools, arc-rated clothing, arc-rated face shields, and arc flash suits. PPE increases the physiological effort required to perform a work task, and is the least effective means of controlling hazards because of the high potential for PPE to be damaged, worn improperly, or selected incorrectly for the level of hazard that exists. Open-panel CBM data collection is inherently high-risk work without controls and should only be done as a last resort.
Beyond the formal adoption of the Hierarchy of Risk Control Methods, the NFPA 70E 2018 edition has also codified the need for human error to be considered as part of the risk assessment procedure (RAP) for any work task under consideration. The document recognizes that human error will drive up the likelihood of occurrence of an arcing fault and arc flash or shock exposure to the qualified person. For CBM inspections, the greatest risk of human error occurs when removing a bolt-on cover to be able to see into the electrical equipment to perform the CBM work task on the suspect conductors or circuit parts. Quite often, the exact internal nature of the electrical equipment is not known until it is opened as there is limited documentation on the electrical equipment construction available to the inspection personnel. They do not know just how close the energized conductors are, and are often working in restricted spaces.
Estimate of the likelihood of occurrence of an arc flash incident
Another change to NFPA 70E was the addition of Table 130.5(C). This table states that, on electrical equipment in any condition (normal or abnormal), performing infrared thermography and other non-contact inspections outside the Restricted Approach Boundary does not increase the likelihood of occurrence of an arcing fault and arc flash incident, so additional PPE is not required. However, the table further clarifies that this does not include opening equipment doors or covers that expose bare energized conductors or circuit parts which specifically does increase the likelihood of occurrence of an arcing fault and arc flash.
Although not specifically mentioned in Table 130.5(C), opening an EMSD cover like that on an infrared viewing pane does not expose bare conductors or circuit parts and so my interpretation, verified by others I have spoken to who were on the NFPA 70E technical committee, is that no PPE would be required. In this manner, the use of an EMSD and changing the work process to keep the equipment in a closed and guarded condition while performing the CBM task seems to follow substitution stage guidelines of the hierarchy of control.
Energized electrical work permits
Finally, the language around the energized electrical work permit (EEWP) requirements in the NFPA 70E should be mentioned. An EEWP is required whenever personnel will perform work within the restricted approach boundary or when personnel interact with equipment in such a way that an increased likelihood of injury from exposure to an arc flash hazard exists – even if conductors or circuit parts are not exposed during the work.
However, there is an exemption to the need for an EEWP for thermography, ultrasound, or visual inspections provided the restricted approach boundary is not crossed. At first blush, one might think that this gives a blanket EEWP exemption for open panel thermography. However, this only means that an EEWP may not be necessary but the Hierarchy of Risk Control Methods must still be followed when completing a risk assessment procedure.
In addition, an EEWP will still be needed if, in the process of removing the panel cover or opening a door, the restricted approach boundary will be crossed. In my experience, crossing the restricted approach boundary when removing a panel cover is a virtual certainty on most electrical equipment and so an EEWP should be executed. When opening a hinged door, this may not be the case but only prior user experience with the equipment will validate that assumption.
CBM data collection can provide valuable insight into electrical equipment health and drive more intelligent decision making as to when to perform physical intervention maintenance tasks. Most of this must be done with the electrical equipment energized and under normal load conditions to allow the technology to catch the anomalies. The NFPA 70E standard recognizes the risk inherent with CBM data collection and is pushing for safer data collection practices via the changes in the 2018 edition, including the formal adoption of the Hierarchy of Risk Control Methods as well as updates to other language and reference tables in the document.
End users and maintenance personnel should revisit their risk assessments of these work tasks and reconsider the implementation of EMSDs as a strategy to mitigate hazards and reduce risk and comply with the intent of NFPA 70E. Failure to do so not only puts people at increased risk of injury or death but could also result in an expensive legal lesson.