NFPA 70EElectrical Safety in the Workplace

Objectives

What NFPA 70E covers

Understand Arc Flash, Incident Energy, & Flash Protection Boundary

Standards, Enforcement, & Safe Practices

Arc Flash Hazard Analysis

Personal Protective Equipment

What the Standard Covers….

The installation of electric conductors, electric equipment, signaling and communications conductors and equipment, and raceways for the following: Public and private premises, including buildings, structures,

mobile homes, recreational vehicles, and floating buildings Yards, lots, parking lots, carnivals, and industrial substations Installations of conductors and equipment that connect to the

supply of electricity 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

NFPA 70E vs. Lockout/Tagout

NFPA 70E requires a justification for work on energized electrical equipment

NFPA 70E must only be followed as a last resort when electrical equipment cannot be shutdown

De-energization of equipment (Lockout/Tagout) should always be the first consideration

An Electrical Energized Work Permit must be obtained before any work on live equipment can proceed

Facts on Arc Flash Incidents

350 electrical-related fatalities each year 4,000 non-disabling occurrences from electrical contact 3,600 disabling occurrences from electrical contact 2,000 admitted to hospitals with serious burns from arc

flash Estimated 5-10 arc flash incidents/day in the US Arc Flash temperatures can exceed 35,000° F (the surface

of the sun is 9000° F) Arc Flash potential exists in any electrical equipment of 240

volts or more Arc Flash vaporizes the metal conductors blasting molten

metal outward with extreme force

Definitions

Arc Flash – is a dangerous condition related to the release of energy caused by an electrical arc. In particular, related to the unintentional or uncontrolled releases of such energy.

Incident energy – is energy impressed on a working surface from the arc source.

Flash Protection Boundary - a distance from exposed live parts within which a person could receive a 2nd degree burn

Regulatory Standards

OSHA 29 CFR 1910.333 - Live parts to which an employee may be exposed shall be de-energized before the employee works on or near them, unless the employer can demonstrate that de-energizing introduces additional or increased hazards or is infeasible.

OSHA 29 CFR 1910.335 - Employees working in areas where there are potential electrical hazards shall be provided with, and shall use, electrical protective equipment that is appropriate for the specific parts of the body to be protected and for the work to be performed.

Enforcement

OSHA WILL cite/fine employers using requirements from NFPA 70E

OSHA & NFPA most common areas related to arc flash: Switchboards Panel boards Industrial control panels Motor control centers Switch gear rooms

Results of an Arc Flash

Human Consequences Severe Burns Fatalities Trauma

Non-Human Consequences Downtime Loss of revenue Loss of product Equipment damage Regulatory impact OSHA citations & fines

Safe Practices

No worker has ever been injured or killed by an arc flash while working in an Electrically Safe Work Condition

Eliminate the Hazard Remove out-dated electrical equipment from service Schedule jobs around de-energizing of the electrical

equipment

Work Practice Controls Enforce safety rules and expectations Training & Education

Safe Practices

Adherence to Hierarchy of Controls Engineering, Administrative, PPE

Engineering Engineer barriers around hazardous areas Lock electrical vaults Erect high fences around transformers

Administrative Enforcement of Lockout/Tagout procedures

Personal Protective Equipment Insulated gloves/boots, face shield, fire resistant clothing,

etc.

Reducing Arc Flash Hazard by Design

Fault Current Fault current can be limited by using current limiting fuses.

Arcing Time Arcing time can be reduced by temporarily setting upstream

protective devices to lower set points during maintenances periods.

Distance Remote operators or robots can be used to perform activities

that are high risk for Arc Flash incidents like racking breakers on a live electrical bus.

Arc Flash Hazard Analysis

NFPA 70E, Part II, 2-1.3.3 – A flash hazard analysis shall be done before a person approaches any exposed electrical conductor or circuit part that has not been placed in an electrically safe working condition.

Arc Flash Hazard Analysis involves 3 calculations:

1. Calculate flash protection boundary distance

2. Calculate incident energy

3. Calculate hazard/risk category for PPE selection

Calculations

Flash Protection Boundary DB = [4.184 * Cf * En * (t / 0.2) * (610x/EB)]1/x (4) Consult IEEE 1584 (Institute of Electrical and Electronics

Engineers) for definitions of variables

Incident Energy Lg*En = K1 + K2 + 1.081 * Lg*Ia + 0.0011 * G Consult IEEE 1584 for definitions of variables

Calculations

PPE Follow chart below

Incident Energy cal/cm2

Arc Flash PPE Category

PPE Total Weight

(oz/yd2)

Break-open Threshold Energy (cal/cm2)

0-2 0 4.5-7 N/A

2-5 1 4.5-8 5

5-8 2 9-12 8

8-25 3 16-20 25

25-40 4 24-30 40

PPE Category Description

Arc Flash PPE Category 0 Cotton Shirts and Pants V-Rated Gloves Safety Glasses

Arc Flash PPE Category 1 Fire Resistant (FR) Long-

sleeved Shirt and Pants V-Rated Gloves Safety Glasses Hard Hat

Arc Flash PPE Category 2 Cotton Underwear FR Long-sleeved Shirt and

Pants V-Rated Gloves Safety glasses Hard Hat Double layer switching hood

PPE Category Description

Arc Flash PPE Category 3 Cotton Underwear FR Long-sleeved Shirt and

pats FR Coveralls V-Rated Gloves Safety Glasses FR hard hat liner Hard Hat Double layer switching hood Hearing protection

Arc Flash PPE Category 4 Cotton Underwear FR Long-sleeved Shirt and

Pants Double Layer Flash Suit V-Rated Gloves Safety glasses FR hard hat liner Hard Hat Double layer switching hood Hearing protection

What Does An Arc Flash Look Like?

Questions?