First in a series of articles Questions People Ask Us?
There is no doubt that wearing gloves is clumsy and makes the electrical worker’s job more difficult. It is not surprising, then, that D.L. Steiner, Inc. is often asked whether or not workers are required to wear their gloves when working on a de-energized panelboard, control panel, or PLC cabinet. The answer to this question has three parts.
Part One: an Observation to Clarify the Situation
What is being considered here is a cabinet in which the local switch has been turned to the off position in order to isolate the internal components from the feed voltage supply. This is not the same as a cabinet or panel that has been completely isolated from its power source. When a cabinet has been removed from all voltage and appropriately locked out and tested for the absense of voltage, no shock or arc-flash hazard remains. In the case of a cabinet where a local switch has merely been turned off, however, a line-side voltage is still present, even though the internal components are de-energized, having been isolated from the voltage by an integrated isolating switch. So in such a case if the internal components are free from dangerous voltage, are gloves still needed?
Part Two: Questions to Guide Action
This question is answered with a question – two questions actually. The first involves shock protection: What is theRestricted Approach Boundary? Simply put, this is the distance (which varies with voltage) where qualified workers must restrict their approach to energized electrical conductors over 50 Volts, unless using proper personal protective equipment (PPE) and voltage-rated tools (see NFPA 70E, section 130.2[C] for an explanation). Answering this question goes a long way in determining “Are gloves still needed?”
Consider the Restricted Approach Boundary to be a protective bubble that extends around energized components. The line voltage determines the size of this protective bubble. If workers are working on components sufficiently removed from the exposed energized conductors so that hands will not be placed within the Restricted Approach Boundary, there is no requirement to wear insulating gloves. Conversely, if electrical workers’ hands will “penetrate” or are likely to penetrate the protective bubble, they definitely face a shock hazard and should be wearing insulating gloves of an appropriate voltage rating.
The simplest situation for determining to glove or not to glove is when 120/240 Volts feeds the equipment. In this case, the Restricted Approach Boundary is “avoid contact” (see NFPA 70E, Table 130.2[C] for a complete listing of boundary dimensions with their corresponding voltages). If electrical workers are careful to avoid contact with energized components, they can work on adjacent de-energized components without wearing insulating gloves.
If the feed voltage is 480 Volts, the Restricted Approach Boundary grows to one foot. Workers can work on de-energized components that are more than one foot from the energized conductor without wearing protective gloves. But if their hands will or are likely to encroach the boundary, insulating gloves of the appropriate rating must be worn.
Is that all there is to it? Not quite. So far this discussion has only considered gloves as a protection from the hazard of electrical shock. But they are also intended to protect from a second electrical hazard, namely, arc-flash. Since we know there is a Restricted Approach Boundary for electrical shock; there is also an Arc Flash Protection Boundary. This naturally leads to the next key question: What is the Arc-Flash Protection Boundary? Whenever workers enter this boundary, they have placed themselves within an area that, should an arc-flash incident occur, could result in severe and damaging burns. These burns most frequently afflict the hands, because these body parts are typically closest to the potential arc source and therefore must vulnerable to arc burns.
By definition, the Arc Flash Protection Boundary is “the distance from a prospective arc source within which a person could receive a second degree burn if and arc flash were to occur.” (NFPA 70E Art. 100). Consequently, any worker who crosses this boundary is at risk of third degree burns and death. The NFPA 70E requires that workers wear appropriate PPE (including gloves) as a thermal barrier. Thermal hand protection may be in the form of leather gloves, arc-rated gloves, or rubber insulated gloves with leather protectors depending on the particular circumstances involved (see NFPA 70E, Table 130.7[C] for PPE requirements in the vicinity of arch flash hazards).
This question is not easy to answer, as it is not directly related to voltage levels or any single factor, but instead involves a combination of electrical conditions. The clearest indication of this boundary occurs when an arc-flash hazard analysis has been performed on the electrical equipment in question. In such a situation, each electrical device will have an electrical hazard label identifying the Arc-Flash Protection Boundary for that device. On some pieces of equipment with very low levels of arc-flash potential energy, workers may find the Arc-Flash Protection Boundary to be small enough to permit them to work on portions of the de-energized cabinet without wearing gloves. Typically, however, the Arc-Flash Protection Boundary will be large enough that gloves are required while working on de-energized components within the cabinet.
When an arc-flash hazard analysis has not been performed, NFPA 70E stipulates a default boundary of four feet in some situations when the voltage to a device is between 50 and 600 Volts (see NFPA 70E 130.3[A] for the conditions that create these situations). Obviously working in a cabinet or bucket in the presence of a live feed a four-foot boundary will require workers to wear gloves to protect their hands, even when working on de-energized electrical components within that equipment.
Knowing both the Restricted Approach Boundary and the Arc-Flash Protection Boundary helps workers properly protect their hands from the dangers of shock and arc-flash. In most cases, workers will discover that this protection involves wearing either leather gloves or rubber insulating gloves with leather protectors.
Part Three: An Option to Consider
Anyone who has ever worn voltage-rated gloves, with their bulky leather protectors, realizes just how clumsy such attire can be. When a delicate touch is needed, workers are tempted to forego protective gloves and risk injury from shock or arc-flash by doing the work barehanded. This leads us to yet anotherquestion: Is there no other solution? Yes, there is!
It’s a fundamental fact: when workers’ hands, or other body parts, will be placed within a Restricted Approach Boundary or an Arc-Flash Protection Boundary, they need protection. The most typical protection is to wear gloves; however, an acceptable alternative is to place guards on the conductors so that workers cannot make accidental contact with energized components. With such guards in positions, the equipment is now touch-safe, and the need to wear protective gloves is removed. Much of the newer electrical equipment, in fact, is being manufactured with touch-safe guards already in place, making them easier to maintain and repair when these services are required.
Workers should not gamble their safety by failing to use front-line protection from the hazards of electrical shock and arc-flash. Following the guidelines presented above will help electrical workers accurately determine when glove use is essential to protect against serious hand injury.