What Do You Wear?
Personal protective equipment and arc flash.
NFPA Journal®, July/August 2008
Do you need arc flash personal protective equipment (PPE) to operate equipment when there are no exposed live parts? This is a question I get asked several times a month when answering advisory service calls about NFPA 70E®, Electrical Safety in the Workplace®. First, I’ll look at how the 2004 edition of NFPA 70E addressed this question and then how the 2009 edition will address the issue.
The 2004 edition provided two contrasting answers. The first comprises three statements in the code. Section 130.7(C)(1) requires a person working within the flash protection boundary to wear protective clothing. Article 100 defines the flash protection boundary as "an approach distance from exposed live parts." And Section 110.1 defines the scope of Chapter 1 as being "for employees who work on or near exposed energized electrical conductors…." These three statements together mean that if there are no exposed live parts, there is no flash protection boundary, and you do not need arc flash PPE.
But as we know from experience, equipment can fail, and this may not be the best answer. During some failures, the resulting arc flash has caused equipment doors to bulge or become missiles and hot gasses escape to the area where the operators are standing. For that reason, the discussion is not yet closed.
Take a look at Table 130.7(C)(9)(a), which can be used in lieu of a flash hazard analysis per Section 130.7(C) (9)(a). This table provides the hazard/risk category (H/R) PPE required for various tasks on different equipment.
The first type of equipment listed is panel boards rated 240 volts and below. The first task listed for that equipment is "Circuit breaker (CB) or fused switch operation with covers on." The table requires H/R 0 PPE for that task. The second task for that type of equipment is "Circuit breaker (CB) or fused switch operation with covers off." The table also requires H/R 0 PPE for that task.
Look further in the table to "Metal Clad Switchgear, 1kV and Above." The first task listed is "Circuit breaker (CB) or fused switch operation with doors closed." That task requires H/R 2 PPE. Task "Circuit breaker (CB) or fused switch operation with doors open" also requires H/R 4 PPE. Thus, we can conclude that, even when operating equipment with no exposed live parts—that is, with the doors closed—the table requires PPE.
Another item to consider is whether the equipment has louvers for cooling. If so, wearing PPE is even more important, and the PPE should probably be at a higher level than the table specifies because the escaping hot gasses from an arc flash in the equipment will escape through the louvers.
As stated in the 2004 edition of the NFPA 70E Handbook, "the PPE for the respective tasks in Table 130.7(C) (9)(a) was not necessarily based on calculation but was considered to be reasonable based on the consensus judgment of the full 70E Technical Committee." Because the committee felt PPE for closed-door situations was important enough to address in Table 130.7(C)(9)(a), the prudent course is to use PPE even if not using Table 130.7(C)(9)(a).
For the 2009 edition of NFPA 70E, the committee is trying to clarify the issue in Fine Print Note (FPN) 1 after Section 130.7(C)(9), which says, in part, "The collective experience of the task group is that in most cases closed doors do not provide enough protection to eliminate the need for PPE for instances where the state of the equipment is known to readily change, i.e. doors open or closed, rack in or rack out."
Section 90.5 Part C defines explanatory material, which is denoted as an FPN, as "informational only and…not enforceable as requirements of this standard." The fact that the committee said in an FPN that, in its collective experience, closed doors do not provide enough protection, does not make wearing PPE a formal requirement, but it does provide some fairly clear guidance to organizations as they develop the PPE requirements for their hazard/risk assessments.
The addition of that FPN clarifies this issue and will make it easier for me to convince callers that they should wear PPE when operating equipment, even when the doors are closed. The subject of PPE for 240-volt and below panelboards is also easier to understand with the additions to the 2009 edition of NFPA 70E, and I will cover that in a future column.
Bill Buss is senior electrical engineer for NFPA and is staff liaison for NFPA 70E.