Shock & awe
November 5, 2009
Every four minutes in the U.S. an arc flash occurs. Shock, electrocution, arc flash, and arc blast are responsible for one fatality every workday in the U.S., and some 8,000 workers are treated in emergency rooms for electrical contact injuries each year, according to the National Fire Protection Association (NFPA®).
These are among the most frightening, most lethal, safety incidents that can occur in the workplace. This explosive release of energy caused by an electrical fault contains thermal energy, acoustical energy, pressure wave and debris.
During an arc flash, arc temperatures can reach 35,000°F. Fatal burns can occur at distances greater than ten feet from the flash or blast â€” sometimes a sudden, thunderous detonation. Arc flash incidents account for four out of five electrically-related accidents and fatalities among employees qualified to be working on equipment such as motor control centers, circuit breakers, trans- formers, panel boards and junction boxes, according to OSHA.
If two essential ingredients of almost any safety program â€” maintenance and housekeeping â€” are lacking in areas with electrical equipment, the results can be disastrous. Typical causes of an arc flash or blast are mechanical breakdowns and failures; dirt, debris, dust and ionized air; current overload; and accidental contact.
What are the chances of an arc flash occurring?
Numerous risk factors come into play: 1) the condition of equipment; 2) tools being used; 3) adequacy of training; 4) the mental and physical agility of the employee; 5) the complexity of the task being performed; 6) available space to work in; 7) the need to use force; and 8) the number of times workers perform a job involving exposed live equipment, according to arc flash consultants, St. Claire, Inc., Farmington Hills, Michigan.
A long list of variables affects the size and intensity of an electrical arc flash or blast, according to St. Claire consultants: clearing time; available fault current; amperage; voltage; arc gap; distance from arc; three-phase versus single-phase; and the presence of a confined space working environment.
OSHA’s standards regulating work in confined spaces and energy lockout-tagout work practices can come into play to afford protection against an arc flash. The most specific OSHA mandates relating to electrical safety are found in 29 CFR 1910 Subpart S and 1910.1926 Subpart K for the construction industry. OSHA requires employers to assess their workplaces for electrical hazards and the need for personal protective equipment (PPE) in 29 CFR 1910.335(a)(1)(i), according to information provided by Lab Safety Supply on its website. But details on how to comply with this standard are left to the employer, according to Lab Safety Supply.
According to a November, 2006, letter of compliance interpretation written by OSHA in response to an inquiry from the consulting group ORC Worldwide, OSHA’s present requirements in Subpart S, Safety-Related Work Practices, are based on the NFPA Standard 70E®-1983. NFPA has updated the 70E® standard numerous times in the past quarter century, but OSHA has not conducted any rulemaking procedures to update Subpart S, according to the letter of interpretation.
Recent versions of NFPA 70E®, including the most recent edition, NFPA 70E®-2009, which went into effect September 5, 2008, contain very informative, instructional and detailed provisions regarding the types of PPE and flame-resistant (FR) clothing for employees working on electrical installations covered by OSHA’s Subpart S. But since OSHA has not updated Subpart S by adopting comparable NFPA provisions specifically related to the use of FR clothing to protect against arc flash hazards, OSHA’s existing Subpart S does not include a specific requirement for the use of FR clothing, according to the 2006 letter of interpretation, signed by then-OSHA chief Edwin G. Foulke, Jr.
ORC Worldwide asked: “How is OSHA enforcing 1910.132 and Subpart S with regard to the latest edition of NFPA 70E requirements (which at the time were contained in the 2004 edition)?
Foulke replied: “OSHA has not conducted a rulemaking to adopt the requirements of the latest edition of NFPA 70E® and, therefore, does not ‘enforce’ those requirements. However, industry consensus standards, such as 70E®, can be used by OSHA and employers as guides in making hazard analyses and selecting control measures.”
Foulke went on to state, “Such standards are sometimes used as evidence of hazard recognition and the availability of feasible means of abatement.”
In a more recent letter of interpretation (February, 2008), OSHA stated: “While the NFPA 70E® consensus standard has not been adopted as an OSHA standard, it is relevant as evidence that arc flash is a recognized hazard and the PPE is necessary to protect against that hazard.”
OSHA continued: “One way of ensuring that an employee is adequately protected (from an arc flash hazard) is to use the NFPA 70E® for assessing the factors in a specific situation and determining what protection to use.”
OSHA concluded: “One way for an employer to meet its obligations… would be to use the NFPA 70E® method of measuring the risk and determining the appropriate PPE.”
NFPA 70E®-2009 versus 70E®-2004 editions
“OSHA looks to the NFPA for safe work practices (regarding electrical jobs),” says David M. Hayes, a senior account manager with St. Claire, Inc. He calls 70E “the gold standard for electrical safety.”
To sum it up, says Hayes, NFPA 70E®-2009 “provides guidance on implementing appropriate work practices required to safeguard workers from injury while working on or near exposed electrical conductors or circuit parts that could become energized.”
NFPA 70E®-2009 contains three parts: Chapter one on safety-related work practices; chapter two on safety-related maintenance requirements; and chapter three on safety requirements for special equipment. NFPA 70E®-2004 contained a chapter four on installation safety requirements; this was dropped from the 2009 edition because it is part of NFPA Standard 70-2009, “The National Electrical Code (NEC),” according to the website e-Hazard.com.
The 2009 edition of NFPA 70E® includes important changes that require many companies to change the way they handle electrical safety. These changes affect labels on equipment, arc flash hazard analyses, required PPE, how the protection boundary is calculated, and training requirements.
“The 2009 edition supersedes the 2004 edition,” explains Jeffrey Sargent, NFPA senior electrical specialist. “Significant changes on determining arc-flash boundaries and selecting appropriate personal protective equipment for arc-flash and shock protection highlight the 2009 edition of the standard. Additionally, new information on the host and contract employer relationship and responsibilities has been added along with new provisions on employee training and what is needed to be considered a ‘qualified person’.”
Why should you have a sense of urgency about complying with NFPA 70E® 2009 if OSHA is not specifically referencing it?
Hugh Hoagland of e-Hazard.com offers these reasons: 1) 70E®-2009 is the only consensus standard for electrical safety; 2) it is used by OSHA compliance officers in citations for settlement; 3) attorneys have successfully used it on behalf of contractors several times; once for a $15-million case against IBM/Intel JV; and 4) “What will you use to comply with OSHA requirements?” he asks.
Adds NFPA’s Sargent: “The 2009 edition is the American National Standard on protecting personnel against electrical hazards. It provides a comprehensive set of requirements that can be used to meet the mandatory (via federal law) electrical safety requirements promulgated by OSHA for personnel in workplaces. There are a number of documents that address electrical worker safety and OSHA requirements but there is only one American National Standard developed through an ANSI-accredited consensus process and that is NFPA 70E®.
“Also, NFPA 70E® and OSHA are in lockstep when it comes to working on energized electrical equipment. Working on energized electrical conductors and circuit parts that expose personnel to shock and arc flash hazards is only permitted under very specific conditions specified in the OSHA requirements and in Section130.1(A) of NFPA 70E® 2009. Inconvenience is not a qualifying condition under which working on energized equipment is permitted.”
(If you are a member of NFPA, you can view the 98-page 70E®-2009 edition on the NFPA’s website, www.nfpa.org. It can be purchased in book or PDF format by members and non-members from the NFPA catalog. NFPA also offers a 70E® two-day workshop seminar, the standard and an accompanying handbook, and the requirements for electricians explained in video DVD-format.)
Here is how NFPA explains what you should know about the 2009 edition:
“PPE protects personnel and can significantly reduce the risk of injury in an arc flash. To help electrical engineers calculate incident energy â€” the vital first step in determining the correct type of PPE for a given task â€” revised Annex D consolidates all equations, adds new tables, and offers more options to detailed calculations.
“Improved work practices reduce risks,” states NFPA. Accordingly:
- To further reduce risks for second-degree thermal burns, cotton outerwear is no longer permitted for energy levels below 2 cal/cm2;
- An expanded Table in Article 130 covers added tasks such as thermographic imaging, and new equipment including arc-resistant switchgear;
- Added Article 350 provides first-time requirements for the protection of electrical employees in research and development labs;
- Expanded requirements for multi-employer relationships address potential areas of oversight;
- New recordkeeping requirements for training and safety program audits answer OSHA’s needs for records.
Determining level of protection
As you can see from the above information, NFPA 70E® covers a comprehensive range of electrical safety issues. One commonly asked question is: How do I determine what level of protection I need for my job task?
According to information on Lab Safety Supply’s website (www.labsafety.com), “first reference Table 130.7(C)(9)(a) of the NFPA 70E® 2009 edition. This will determine the hazard/risk category (HRC) of your job task (0-4). Second, consult Reference Table 130.7(C)(10) of the standard to determine what clothing and equipment is required based on the HRC that was determined. Third, Reference Table 130.7(C)(11) will determine what arc thermal protective value (ATPV) rating is necessary. Each FR garment is assigned an ATPV rating by the manufacturer. The ATPV value represents the amount of incident energy that would cause the onset of second-degree burns. It also signifies the amount of protection the clothing affords when an electrical arc comes in contact with the fabric.
Once you have determined the ATPV rating, find the ATPV rating on the garment (required on tag) that meets or exceeds your requirement.
Table 130.7(C)(11) lists these protective clothing characteristics: HRC 0 â€” Untreated Cotton, Wool, Rayon, Silk, or Blend. Fabric weight >4.5oz/Yd2 (1 layer), ATPV n/a; HRC 1 â€” FR Shirt and FR Pants or FR Coverall (1 layer), ATPV 4; HRC 2 â€” cotton underwear plus FR shirt and FR pants (1 or 2 layers), ATPV 8; HRC 3 â€” Cotton underwear plus FR shirt and FR pants plus FR coverall, cotton underwear plus two FR Coveralls (2 or 3 layers), ATPV 25; HRC 4 â€” Cotton underwear plus FR shirt and FR pants plus multilayer flash suit (3 or more layers), ATPV 40.
NFPA’s Sargent offers these final words of advice: “The technology behind the electrical safety requirements in NFPA 70E® is evolving and there is research being conducted in a number of different arenas that will impact future editions of the standard. The 2009 edition provides the best available and most current information on protecting workers against electrical hazards.”