protecting your workers fromthe hazards of arc fl ash

This image, taken from high-speed, specially fi ltered digital video shot during testing in Ferraz Shawmut’s high-power lab, illustrates the type of blast that can occur.

The explosive power of an arc fl ash

The many intense hazards created by arcing faults in today’s industrial power systems arise from two factors — the tremendous amounts of power that can be delivered to such arcs and the workers’ close proximity to them.

When an arcing fault is established, current passes through ionized air. Large volumes of ionized gases, along with molten metal from the vaporized conductors, are rapidly expelled. As the arc runs its course — generally in less than 0.2 seconds — electrical energy continues to be converted into extremely hazardous forms of energy, including:

■ Intense heat capable of causing severe, often fatal, burns, even beyond typical working distances.

■ A thermoacoustic shock wave that can result in ruptured eardrums, collapsed lungs or fatal injuries.

■ Molten metal, at temperatures typically exceeding 1000°C, reaching distances of several feet.

■ Shrapnel that can impact a nearby worker at high velocity, resulting in physical trauma.

■ Blinding light, which can cause immediate vision damage and increase the potential for future deterioration.

■ Toxic smoke, including combustion byproducts and copper oxides.

■ Contact with energized components — the explosive nature of an arc fault increases the possibility that an energized conductor or component will make contact with workers in the area.

Stay current on standards and regulations

Being responsible for your workers’ safety means being up to date on the various regulatory and consensus standards applicable to arc fl ash hazards. The four major industry stan-dards that have the most impact are OSHA regulations, NFPA 70E, IEEE Standard 1584, and NFPA 70, National Electrical Code.®

OSHA regulations

OSHA regulations mandate that employers provide a safe workplace. Specifi cally, OSHA Standard 29 CFR Part 1910, Subpart S, addresses safety-related practices for electrical work. It makes clear that, with very few exceptions, equip-ment must be deenergized before work is performed, and lockout/tagout procedures must be followed.

However, if equipment cannot be deenergized prior to work, the standard requires that:

■ Employees are properly protected by personal protectiveequipment (PPE) appropriate for the work being performed.

■ Employers perform an electrical hazard assessment to determine if hazards are present or likely to be present, select the necessary PPE, and communicate those selection decisions to each affected employee.

See the box (far right) for specifi c text from Subpart S. In addition, OSHA 29 CFR Part 1910 contains many other sections that pertain to electrical safety and arc fl ash hazards. They address safety requirements, personal protective equipment, and general environmental controls, such as lockout/tagout.

The NFPA 70E standard

For details on how to conduct an electrical hazard assessment or how to select PPE, you must look to national consensus standards.

NFPA 70E, Standard for Electrical Safety in the Workplace, is one of the foremost consensus standards for electrical safety. Developed by the National Fire Protection Association, it addresses employee protection from the electrical hazards of shock and arc fl ash.

Referenced in OSHA 29CFR Part 1910, Subpart S, Appendix A, NFPA 70E is considered by OSHA to be the rec-ognized industry practice for electrical safety. In its standard interpretation of the relevance of NFPA 70E, OSHA states:

Industry consensus standards, such as NFPA 70E, can be used by employers as guides to making the assessments and equipment selections required by the standard. Similarly, in OSHA enforcement actions, they can be used as evidence of whether the employer acted reasonably.

Chapter 1 of NFPA 70E provides guidance on establishing electrically safe work conditions and developing such safety-related work practices as a safety program and worker training.

And while it emphasizes that working on live parts is “the last alternative work practice,” NFPA 70E contains extensive requirements for working on or near electrical conductors or circuit parts that have not been put into an “electrically safe condition.” One of the requirements is electrical hazard analysis, which includes arc fl ash hazard analysis.

IEEE Standard 1584 TM-2002

As implied by its title, Guide for Performing Arc Flash Hazard Calculations, IEEE Standard 1584 provides techniques for performing a comprehensive arc fl ash hazard analysis.

Its systematic, nine-step approach enables designers and facility operators to determine the arc fl ash-protection boundary, defi ned as “an approach limit at a distance from exposed live parts within which a person could receive a second-degree burn if an electrical arc fl ash were to occur.”

Of course, there are other benefi ts to performing an electrical hazard analysis. By providing an in-depth look at your plant’s electrical system, it supplies data that can be used to improve overall system performance, reduce downtime and manage costs.

NFPA 70, the National Electrical Code®

While the NEC has traditionally addressed installation tech-niques intended to prevent fi re, electrocution and shock hazard, it now contains requirements related to arc fl ash hazards.

Section 110-16, Flash Protection, requires that markings be placed on switchboards, panelboards, industrial control panels and motor control centers to warn qualifi ed persons of potential arc fl ash hazards.

Ferraz Shawmut current-limiting fuses and fi nger-safe devices can help reduce the risk of arc fl ash.

We can help you mitigate arc fl ash hazards

Personal protective equipment is a worker’s last line of defense against arc fl ash hazards. In addition, here are ways to reduce the hazard level:

■ Upgrade branch circuit fuses to Ferraz Shawmut’s Amp-Trap 2000® current-limiting fuses. Extensive testing to IEEE 1584 test protocols has shown that these fuses — our A6D Class RK1, A4BQ Class L, and AJT Class J — limit arc fl ash incident energies to very low values for arc fault currents within their current-limiting range. Applied properly, they can reduce the category of PPE required to protect workers.

■ Make sure you have the right fuses on hand. Obsolete and out-of-stock fuses increase the potential for dangerous misapplications. Ferraz Shawmut’s inventory analysis and upgrade services help ensure that your inventory is complete and up to date.

■ Provide safety training for your staff. In addition to in-depth seminars on arc fl ash hazards designed for engineers and safety managers, we provide circuit protection safety training for electrical workers, purchasing professionals and storeroom personnel.

■ Use IP20-rated devices wherever possible. Ferraz Shawmut offers a complete line of fi nger-safe products, including Socomec disconnect switches, UltraSafe™ fuse holders, and our FSPDB, the industry’s fi rst fi nger-safe power distribution block.

Visit ferrazshawmut.com/arcfl ash for the latest developments in arc fl ash safety and our online arc fl ash calculator.

Visit the Arc Flash Info Center

Arc fl ash safety is an expansive topic — and one that continues to evolve. Ferraz Shawmut’s Arc Flash Info Center is a valuable, 24-hour source of current information.

Visit ferrazshawmut.com/arcfl ash, and you’ll fi nd more about current limitation, other suggestions for reducing arc fl ash energies, and an online calculator you can use to determine incident energies and PPE categories for Ferraz Shawmut fuses. You can also register for our “keep me informed” alerts, and be the fi rst to know about new arc fl ash solutions.

OSHA outlines these employer responsibilities in Standard 29 CFR Part 1910, Subpart S:

• Equipment must be deenergized before work is performed

In addressing work on electrical equipment, 1910.333(a)(1) states:Live parts to which an employee may be exposed shall be deenergized before the employee works on or near them, unless the employer can demonstrate that deen-ergizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations.

• Lockout/tagout procedures must be used

In Note 2 of 1910.333(b)(2), it states: Lockout and tagging procedures that comply with paragraphs (c) through (f) of 1910.147 will also be deemed to comply with paragraph (b)(2) of this section, provided that:

[1] The procedures address the electrical safety hazards covered by this Subpart; and

[2] The procedures also incorporate the requirements of paragraphs (b)(2)(iii)(D) and (b)(2)(iv)(B) of this section

• If equipment cannot be deenergized prior to work:

• Employees must be properly protectedWhen employees are required to work where there is a potential electrical hazard, 29 CFR Part 1910.335 mandates that employees:…shall be provided with, and shall use electrical protective equipment that is appropriate for the specifi c parts of the body to be protected and for the work to be performed.

In addition, the appendix to Part 1910 Sub-part S includes NFPA 70E as a reference that provides “information which can be helpful in understanding and complying with the require-ments contained in Subpart S”.

• Employers are responsible for performing a hazard assessment

29 CFR Part 1910.132(d), hazard assessment and equipment selection, states: The employer shall assess the workplace to determine if hazards are present, or are likely to be present, which necessitate the use of personal protective equipment (PPE). If such hazards are present, or likely to be present, the employer shall:

1910.132(d)(1)(i)Select, and have each affected employee use, the types of PPE that will protect the affected employee from the hazards identifi ed in the hazard assessment;

1910.132(d)(1)(ii)Communicate selection decisions to each affected employee; and,

1910.132(d)(1)(iii)Select PPE that properly fi ts each affected employee.

This is the section referenced in the OSHA standard interpretation that discusses the relevance of NFPA 70E. The remainder of 1910.132 outlines the requirements for the design, application, proper selection, training and documentation required for the use of personal protective equipment.

Should you have specifi c questions about arc fl ash hazards, arc fl ash hazard mitigation, or circuit protection in general, contact your Ferraz Shawmut sales representative or fi eld engineer, or call our Technical Services applications engineers at 978-465-4853.

Protecting your workers from the hazards of arc fl ash is a big responsibility, but it doesn’t have to be a diffi cult task. With our assistance, you’ll see how Ferraz Shawmut products and services can help mitigate arc fl ash hazards.

OSHA Standards

If previous statistics hold true, the explosive energy released during arcing

faults will send more than 2,000 workers to burn centers this year.

This type of event — an arc fl ash — can occur in any type of plant,

and can result from something as simple as a tool accidentally dropped on

an energized part. The cost to human life can be incalculable. The cost to

a business, in medical expenses, equipment replacement and downtime,

can easily exceed $1 million.

Today, that cost can also include signifi cant fi nes. OSHA has become

much more vigilant, and is using the requirements of NFPA 70E, Standard

for Electrical Safety in the Workplace, to judge whether an employer “acted

reasonably” in protecting its workers from arc fl ash hazards.

As an employer, you have a moral responsibility to protect your

employees from harm. And now, the fi nancial and legal obligations inherent

in electrical accidents are even greater.

Why arc fl ash is a vital — and timely — topic

© 2005 Ferraz Shawmut

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