Arc Flash

Expert advice given on NFPA 70E

Best practices for mitigating arc flash and combustible dust hazards.
By Scott Francis June 6, 2019
Courtesy: Westex by Milliken

On May 30, Plant Engineering aired a webinar on recent changes to NFPA 70E and personal protective equipment best practices for mitigating arc flash and combustible dust hazards.

Addressing human error in the risk assessment procedure sheds new light on PPE program “best practices” for both electric arc and combustible dust/flash fire hazards.

Error precursors, such as complacency – a safety killer, which can lead to a “normalization of deviance” company culture, must be countered with human performance tools. Human performance tools are covered in Annex Q of NFPA 70E.

Webinar attendees learnt how human performance tools and “best practice” PPE programs reduce the likelihood of incident occurrence and severity of burn injury from electric arc and combustible dust /flash fire hazards and improve the company’s safety culture.

The webinar in its entirety can be viewed on the Plant Engineering website. Attendee questions asked during the Westex by Milliken webinar include the following and were provided by Scott Francis, technical sales manager and webinar presenter.

1. In a repair shop setting, are non-electrical mechanics required to wear fire-resistant personal protective equipment (FR PPE) to simply turn a circuit breaker on or off? In the same repair shop situation, if a device can be used to keep the mechanic outside of the FR boundary while he opens or closes a breaker… does this violate any 70e laws?

Regarding FR PPE for turning a circuit breaker (CB) on or off, consult NFPA 70E, Table 130.5 (C), “Estimate of the Likelihood of Occurrence of an Arc Flash for ac and dc systems.” The table lists for the operation of a CB, switch, contactor or starter, on equipment in “normal” condition as a “no” for likelihood of occurrence of an arc flash. So, turning on/off CB is unlikely for an arc flash to occur on equipment in “normal” condition. If outside the arc flash boundary, arc flash PPE is not required via the consensus standard, NFPA 70E.

2. If a detailed risk assessment determines PPE is not required, and an employee is injured, will OSHA not cite the employer?

Not sure if OSHA will cite or not in this scenario. In the described scenario, it likely depends on how severe the injury was. OSHA will almost certainly want to closely review the “detailed risk assessment” to see why PPE was not required. Even for tasks in the 70E table 130.5 (C), that list “no” for the likelihood of occurrence, if the potential injury consequences are severe, it can make sense to don PPE even if the probability of incident occurrence is low.

3. I’ve heard a rumor that disconnecting the machine is no longer enough and that one must disconnect from the bus bar, is there any truth to that?

See NFPA 70E, article 120, Establishing an Electrically Safe Work Condition for guidance on lock out/tag out procedures. Not sure of your specific set up, however, In section 120.4 (A) (4) there is new material, as follows:

“Exception: Lockout/Tagout is not required for work on cord and plug connected equipment for which exposure to the hazards of unexpected energization of the equipment is controlled by the unplugging of the equipment from the energy source, provided that the plug is under the exclusive control of the employee performing the servicing and maintenance for the duration of the work.”

4. What are some of the most common errors associated with the human error risk assessment requirements of NFPA 70E?

Complacency, distractions and time pressure are all common error precursors that need to be countered with human performance tools.

5. To meet NFPA 70E, I just need to make sure my clothing has a label with the arc rating and an ASTM F1506 label stating it is flame resistant, correct?

You need quite a bit more than just PPE/clothing. You need to do a risk assessment by using the hierarchy of risk controls, take into account potential for human error, and if it’s determined that additional protective measures include PPE, make sure the body PPE is guaranteed fire resistant and has the appropriate arc rating for the arc flash hazard. Don’t forget other PPE for the head, hand and feet.

6. In general, what are the care and maintenance best practices for FR clothing?

Follow laundering instructions as listed on label in the FR/AR garment. If fabric is threadbare, with fraying and holes in it, that is usually a good time to retire the garment. If the fabric has been exposed to chlorine bleach, usually prohibited for most FR fabrics, the garment should be removed from service. Fabric softener is also prohibited from use. However, the fabric softener will wash out by washing FR clothing without fabric softener, so there is no need to pull fabric softener exposed FR garments from service. However, do NOT use fabric softener going forward.

For combustion to take place the dust (fuel) has to have proper particle dispersion, along with the other conditions for combustion, heat, oxygen. Courtesy: Westex by Milliken

For combustion to take place the dust (fuel) has to have proper particle dispersion, along with the other conditions for combustion, heat, oxygen. Courtesy: Westex by Milliken

7. I truly believe in the effectiveness of the “human performance” aspect of safety. Have you seen anyone put it into practice? Do you have a sample of a policy or meeting notes or a pre-job safety sheet that is actually used? Can you show an example?

I have not personally seen an example of a pre-job safety sheet used by a company. However, NFPA 70E lists the required specifics of a Job Safety Planning and Job Briefing in article 110 (I) and also in Annex Q.6.2 for a Pre-Job Briefing Tool.

8. How many washing before the FR clothing is mute?

You do not want to have to count the number of washings, so look for brands of FR/AR fabric that are guaranteed flame resistant for the life of the garment. Follow the fabric laundering instructions found on a garment label. If fabric is threadbare, with fraying and holes in it, that is usually a good time to retire the garment. If the fabric in the garment is intact, made by a trusted FR/AR fabric company that guarantees the FR fabric for lifetime, and the manufacturer’s laundry instructions have been followed, the FR of the fabric should be good. If FR is in question, a destructive fabric test for flame resistance can be used (ASTM D6413 – vertical flame test method) and can be checked to the char length criteria spelled out in ASTM F1506 or NFPA 2112.

9. In NFPA 70E 2018 is the Complex lock-out, tag-out (LOTO) added to ensure communication in the seven scenarios it gives for a complex LOTO?

Agreed, communication, along with coordinated communication with a key person who is responsible for the coordination. See 120.4 LOTO procedures in 2018 NFPA 70E.

10. Most dust testing requires the dust sent in must be dried out to a low moisture content. How do you get the testing lab to test at the moisture of the dust being conveyed?

Ask the specific testing lab. The lab likely needs to have the dust (fuel) in the form (dispersion), so that it will combust in the test cylinder. For combustion to take place the dust (fuel) has to have proper particle dispersion, along with the other conditions for combustion, heat, oxygen.

11. Our workers are in high heat environments routinely. Is there any information on the amount of heat transfer that occurs during an event through wet (sweat soaked) AR/FR fabric?

There has been some research done that showed a depression of the arc rating of various FR/AR fabrics when soaking wet.

12. How do you inspire crafts other than electricians to wear the FR gear?

People are visual. Showing other craft workers the consequences from clothing ignition from various short term thermal exposures like arc, flash fire via video can make a difference. Also, the FR/AR clothing has gotten more comfortable and just like regular work wear.

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Scott Francis
Author Bio: Scott Francis, technical sales manager, Westex by Milliken.