NFPA 70E Electrical Safety in the Workplace

Transcription

1 NFPA 70E Electrical Safety in the Workplace

2 Objectives What NFPA 70E covers Understand Arc Flash, Incident Energy, & Flash Protection Boundary Standards, Enforcement, & Safe Practices Arc Flash Hazard Analysis Personal Protective Equipment

3 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

4 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

5 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

6 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 2 nd degree burn

7 Regulatory Standards OSHA 29 CFR 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 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.

8 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

9 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

10 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

11 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.

12 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.

13 Arc Flash Hazard Analysis NFPA 70E, Part II, 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

14 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 + K * Lg*Ia * G Consult IEEE 1584 for definitions of variables

15 Calculations PPE Follow chart below Incident Energy cal/cm2 Arc Flash PPE Category PPE Total Weight (oz/yd2) Break-open Threshold Energy (cal/cm2) N/A

16 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) Longsleeved 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

17 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

18 What Does An Arc Flash Look Like?

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20 Questions?