Are you working with electric supply conductors and equipment, and electric supply stations accessible only to qualified electrical workers, and are these conductors and equipment used by the utility in the exercise of its function as a utility? Maybe an easier way to ask the same question is: Are you required to follow the NESC or the NFPA?
But what does the NFPA cover and what does the NESC cover?
The 2009 NFPA 70E 90.2 “Scope” states:
“(A) Covered.
(4) Installations used by the electric utility, such as office buildings, warehouses, garages, machine shops, and recreational buildings, that are not an integral part of a generating plant, substation, or control center.
(B) Not Covered.
(5) Installations under the exclusive control of an electric utility where such installations: a. Consist of service drops or service laterals, and associated metering; or b. Are located in legally established easements or rights-of-way designated by or recognized by public service commissions, utility commissions, or other regulatory agencies having jurisdiction for such installations; or c. Are on property owned or leased by the electric utility for the purpose of communications, metering, generation, control, transformation, transmission, or distribution of electric energy.”
The 2007 NESC-C2 101 “Scope” states:
“This Code covers the electric supply conductors and equipment, along with the associated structural arrangements in electric supply stations, that are accessible only to qualified personnel. It also covers the conductors and equipment employed primarily for the utilization of electric power when such conductors and equipment are used by the utility in the exercise of its function as a utility.”
So if you are a qualified electrical worker working on energized lines, cables and equipment in a generating plant, a transmission line, a substation, a distribution line and up to the customer’s service point, you must follow the 2007 NESC 410.A.3, not NFPA 70E. This paragraph requires the employer to perform a hazard assessment to determine if the employee working on or near energized parts or equipment could be exposed to an electric arc.
OK! Is an employee reading meters potentially exposed to an electric arc? No. Is an employee operating a switch or breaker from a remote location potentially exposed to an electric arc? No. Is an engineer who enters an energized substation to conduct an engineering assessment, but will not operate any electrical equipment potentially exposed to an electric arc? No. Is a worker who enters an energized vault to conduct a visual inspection and will not do any work potentially exposed to an electric arc? No.
However, a worker who pulls an energized meter could be potentially exposed to an electric arc. A worker tying in an energized 13.2 kV overhead conductor with insulated gloves or hot sticks is potentially exposed to an electric arc. A worker who enters an energized vault to perform maintenance on the energized conductors or equipment is potentially exposed to an electric arc. In the cases above if the employer determines the potential arc flash exposure is greater than 2 cal/cm², the employer must ensure the exposed employee wears clothing that has an effective arc rating not less than the anticipated arc energy.
How does the employer do that? Very simple! For overhead systems energized at voltages above 1 kV, the employer must determine the maximum fault current and associated relay clearing time at the substation breaker for each voltage level, then refer to NESC Table 410-1 or 410-2 for the appropriate FR clothing rating required. Let’s say the employer operates a 13.2 kV distribution system, and the maximum fault current for the system is 14 kA, with a relay clearing time of 9.5 cycles. NESC Table 410-1 states the appropriate FR clothing rating for employees working on or near this 13.2 kV system is 4 calories. You’re done! The outer layer of the worker’s clothing must have a minimum arc rating of 4 calories.
But what does the current OSHA requirement specify in relation to FR clothing for qualified electrical workers? OSHA 1910.269(l)(6)(iii) states:
“The employer shall ensure that each employee who is exposed to the hazards of flames or electric arcs does not wear clothing that, when exposed to flames or electric arcs, could increase the extent of injury that would be sustained by the employee.”
OSHA 1910.269(l)(6)(iii) does not require the employer to ensure the exposed worker wears FR clothing. The employer has three options:
(1) De-energize the system (any potential for an arc is eliminated, but often hard to do).
(2) Move the worker further from the potential arc and work area (again probably fairly hard to do).
(3) Put the worker in FR clothing.
This paragraph requires the employer to ensure that the employee’s clothing does not ignite and make the employee’s injuries worse than if the clothing did ignite; pretty simple, and the 2007 NESC 410.3 provides a method for the employer to easily comply with the current OSHA regulation.
Fast-Forward
Fast-forward to the summer of 2011. We expect OSHA to publish the revisions to OSHA 1910.269 and OSHA 1926 Subpart V. OSHA is expected to require FR clothing if:
(i) The employee is subject to contact with energized circuit parts operating at more than 600 volts;
(ii) The employee’s clothing could be ignited by flammable material in the work area that could be ignited by an electric arc; or
(iii) The employee’s clothing could be ignited by molten metal or electric arcs from faulted conductors in the work area.
What will the FR clothing requirement be in the new regulations? During the public hearing on the revised rules, there were few if any comments on the technical determination of the FR clothing ratings, so we can probably assume what was published in the proposed rule will be carried forward into the final rule. The proposed OSHA 1926.960(g) states:
“(1) Hazard assessment. The employer shall assess the workplace to determine if each employee is exposed to hazards from flames or from electric arcs.
(2) Estimate of available heat energy. For each employee exposed to hazards from electric arcs, the employer shall make a reasonable estimate of the maximum available heat energy to which the employee would be exposed.
Note to paragraph (g)(2) of this section: This paragraph does not require the employer to estimate the heat energy exposure for every job task performed by each employee. The employer may make broad estimates that cover multiple system areas provided the employer uses reasonable assumptions about the energy exposure distribution throughout the system and provided the estimates represent the maximum exposure for those areas. For example, the employer could estimate the heat energy just outside a substation feeding a radial distribution system and use that estimate for all jobs performed on that radial system.”
Wow! Don’t the above paragraphs sound just like the procedure specified in the 2007 NESC 410.A.3? Yes, the NESC and OSHA are not trying to require the employer to hire a rocket scientist or spend a ton of money with consultants to develop an FR clothing program. You can do a complete fault current analysis on your system as it is configured today and get an arc rating. Then tomorrow the electrical system may be configured very differently with different generation, transmission lines in or out of services and other changes of the system that will change the fault current parameters you just calculated.
OK, this is all fine and great for overhead system with voltages above 1 kV, but what about voltages below 1 kV? The 2007 NESC 410.A.3 Exception 2 states:
“For secondary systems below 1000 V, applicable work rules required by this part and engineering controls shall be utilized to limit exposure. In lieu of performing an arc hazard analysis, clothing or a clothing system with a minimum effective arc rating of 4 cal/cm² shall be required to limit the likelihood of ignition.”
What? A minimum of 4 cal/cm² for voltages below 1 kV? First, understand the development of new sections of the NESC by the subcommittees occurs years before the final rule is published. NESC Subcommittee 8 developed this paragraph in early 2004, for the 2007 NESC, when little was known about low-voltage arcs in the electric utility industry. The best the subcommittee could do was recommend at least some type of FR clothing for low-voltage work. The subcommittee did strongly emphasize the use of applicable work rules and engineering controls to limit arc flash exposure at low voltages.
Fast-forward to the fall of 2011. The 2012 NESC will be published. In the 2012 NESC, Subcommittee 8 has developed a low-voltage arc hazard table for the electric utility industry.
At the September 2010 Subcommittee 8 meeting, the subcommittee made several revisions to the table including adding a separate row for pad-mounted transformers, network protectors and panel boards, and some minor changes to the calorie rating for several items.
So it looks like the low-voltage arc hazard analysis for qualified electrical workers, under the NESC, is pretty simple and straightforward now. Most T & D workers will need to be in 8-calorie clothing. The only exception is 480-volt self-contained meters, which require 20 calorie clothing.
Most FR clothing programs developed for T & D workers by utilities include an 8-calorie shirt, FR winter jacket, FR raingear, work gloves, hard hat and safety glasses. For workers who work in 480-volt transformer compartments, a face shield or balaclava should be seriously considered. The FR program may also include 8-calorie pants or one pair of FR coveralls to be worn when an arc could occur below the belt line. For T & D workers involved with energized 480-volt meters, a 20-calorie smock and face shield or balaclava is needed.
For 480-volt and high-voltage metal clad switchgear, engineering controls and remote switching and racking is the best option. If the equipment must be operated or racked out, energized arc flash suits may need to be considered.
I have assisted a number of utilities in developing an FR clothing program for generation, transmission, distribution and low voltage and the process is really pretty painless. For the average T & D worker, the task is very simple. For generation facilities and 480-volt systems, first make realistic assumptions about the arc flash, try to de-energize or implement engineering controls, then finally deal with reality.
FR Clothing Q&A
Am I required to label all my breakers and panels with arc rating and FR clothing requirements?
Installations under the exclusive control of an electric utility including generating plants, transmission lines, substations and distribution lines up to the customer’s service point fall under the 2007 NESC which DOES NOT require arc hazard labels. Installations used by the electric utility, such as office buildings, warehouses, garages, machine shops and recreational buildings that are not an integral part of a generating plant, substation, or control center fall under 2009 NFPA 70E, which requires arc hazard labels.
Can I layer FR clothing to increase the total arc rating of my clothing system? For instance, can I wear a 4-calorie FR undershirt under an 8-calorie FR shirt and get 12 calories of arc flash protection?
No, the outer layer must be rated for the anticipated arc flash exposure.
If I wear an outer layer of FR-rated clothing for the anticipated arc flash (an 8-calorie shirt for an 8-calorie exposure), can I wear a 50/50 undershirt under the 8-calorie FR outer shirt?
No, even though the outer layer may be fully rated, meaning it will not ignite or break open, the 8-calorie FR shirt will not stop all the heat energy from passing through the FR shirt. There could be enough heat energy passing through the FR shirt to ignite a 50/50 undershirt.
Do the 2007 NESC and OSHA 1910.269 require a face shield as part of my FR clothing?
No, the 2007 NESC Section 410.A.3 and OSHA 1910.269(l)(6)(iii) specify the type of clothing required if the employee will be exposed to an arc flash. There are no requirements for a face shield in NESC Section 410.A.3 or OSHA 1910.269(l)(6)(iii). However, OSHA 1910.133(a)(1) states:
“The employer shall ensure that each affected employee uses appropriate eye or face protection when exposed to eye or face hazards from flying particles, molten metal, liquid chemicals, acids or caustic liquids, chemical gases or vapors, or potentially injurious light radiation.”
Face shields are currently not common in overhead high-voltage (above 1 kV) live-line work practices. They are commonly used with FR clothing while working with energized 480-volt systems and high-voltage metal clad switchgear and devices. It should be noted that face shields are only rated up to 12 calories. In energized 480-volt systems and high-voltage metal clad switchgear and devices, a face shield may need to be replaced with an arc flash suit if a high arc hazard exists.
Is there another option to face shields?
Yes, a balaclava and safety glasses are an excellent option to replace face shields. Balaclavas typically have a much higher arc flash rating, are more comfortable and workable than a face shield, and provide better vision than a face shield.
How about hard hats, safety glasses and hand protection when exposed to a potential arc hazard?
Hard hats and safety glasses have proven to do an excellent job of protecting the wearer when exposed to arc hazards. Good quality leather gloves and rated insulated rubber gloves and protectors do an excellent job of protecting workers’ hands and should always be included in an FR clothing system. There is no NESC, OSHA or ASTM requirement that these PPE items be arc rated.
I have heard that FR clothing is scratchy and hot, and needs special laundering requirements. Is this true?
The clothing industry has recently begun offering lightweight, comfortable, wickable, multiple-colored FR materials with outstanding arc ratings. You would be hard-pressed to distinguish a non-FR shirt from an FR shirt made of these new materials. As for laundering requirements, each FR material has specific laundering recommendations. However, these new materials are becoming very forgiving.
Can I wear an FR short-sleeve shirt or a vest?
Not if you want protection of your arms. FR clothing provides protection if it totally covers the exposed body skin. If the shirt sleeves are rolled up and not buttoned all the way up, the wearer will not get adequate protection.
Do I need to wear an arc flash-rated flagging vest over my FR shirt or jacket?
Only if you are going to wear the flagging vest while you are working on or near energized conductors and an arc flash is possible.
What does the HCR 2 label mean on my clothing?
HRC 1, 2, 3 & 4 is an NFPA 70E labeling. It does affect FR clothing used in the electric utility industry and specified in the NESC. Under the NESC, we require the FR clothing to have a rating of the anticipated arc flash. The NFPA 70E developed the Hazard Risk Category (HRC) rating for workers required to follow the NFPA 70E. HRC1 = 4 cal/cm², HRC2 = 8 cal/cm², HRC3 = 25 cal/cm² and HRC4 = 40 cal/cm². The challenge with the NFPA 70E HRC rating is if an employer calculates a 9 cal/cm² exposure, HRC3 (25 cal/cm²) FR-rated clothing must be worn. Whereas with the NESC, if the employer calculates a 9 cal/cm² exposure, a 9 cal/cm² FR-rated clothing is acceptable.
About the Author: Brian Erga, president of ESCI Inc., has more than 36 years of electric utility expertise and holds a BSEE degree. An expert on safety practices and work methods related to the electric utility industry, he is a member of IEEE/ESMO, NSC, NFPA, ASTM F18 and a member of NESC Subcommittee 8, responsible for NESC Part 4 “Rules for the Operation of Electric Lines.”
