Electrical Safety Electrical Arc Flash Protection

Transcription

1 Electrical Safety Electrical Arc Flash Protection

2 What is an Electric Arc? Electric Arc The passage of a substantial electric current through a gas, such as air or vaporized metal. An electric arc... Typically lasts less than one second Has an extremely high percentage of radiant energy Is explosive in nature Can ignite and/or melt most things in its path.

3 The Arc 1 2

4 Electrical Hazards ARC FLASH A dangerous condition associated with the release of energy caused by an electric arc due to either a phase to ground or phase to phase fault. Note that this explosive condition includes a broad spectrum of electromagnetic energy, vaporized metal (plasma), heat, pressure wave, fragments and a spray of molten metal projectiles. PLASMA - Superheated gas that is created by the arc flash and expands rapidly from the Arc location. C

5 Arc Flash This phase to ground or phase to phase fault can result from many factors, including dropped tools, accidental contact with electrical systems, build up of conductive dust, corrosion, and improper work procedures. Example of an arc flash C

6 Electrical Hazards Arc Blast Pressure wave caused by the expansion of gases and conducting materials with flying molten materials. (Arc temperature can reach 35,000 F - this is four times hotter than the surface of the sun. Fatal burns can occur at distances over 10 ft.).

7 Serious injuries and damage can result an arc flash/blast.

8 The Intensity of an Electric Arc Exposure The electric arc itself Its fault current Its duration Its configuration or enclosure Also known as Arc-in-a- Box C

9 The Intensity of an Electric Arc Exposure The number of phases involved. The system you re working on Its electrode gap Its available voltage Your location How close or far you are from the electric arc when it occurs

10 Possible Risks with Electric Arc Exposures Electrocution. Physical injury resulting from explosive forces. Burn injuries (without electrical contact) resulting from: Intense radiant energy Molten metal splatter Secondary fires (e.g., from transformer oils) The ignition or melting of clothing.

11 The most severe burns are caused by ignited clothing, not by the original flash fire or electric arc exposure. Burn Injuries

12 C

13 Are You in Compliance? Industry standards and regulations: OSHA 29 CFR 1910 Subpart S NEC NFPA 70E-2009 Edition Various ASTM Requirements

14 OSHA Regulations OSHA 29CFR 1910, Sub-part S- Electrical. Design safety standards for electrical systems. These regulations are contained in through Hazardous Locations

15 OSHA Regulations 29CFR (a)(1)(i) 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.

16 NFPA 70E NFPA 70E is: National consensus standard and a Standard for Electrical Safety in the Workplace. and is a part of the National Electrical Code and has been adopted by OSHA as an enforcement standard.

17 NFPA 70E 2009 Edition Standard Addresses hazards: Shock Arc Flash Requirements for shock and arc flash boundaries. Requirements for personal protective equipment. C

18 Content of NFPA 70E, Standard for Electrical Safety in the Workplace NFPA 70E 2009 Chapter 1 addresses safe installations, procedures for avoiding injury during electrical work, proper tools, and PPE. Chapter 2 addresses maintenance requirements. Chapter 3 addresses special equipment, i.e. battery rooms, electrolytic cells, lasers, and electronics. Chapter 4 addresses installation requirements similar to OSHA Subpart S.

19 Scope of Standard Covers electrical safety requirements for employee workplaces that are necessary for the protection of employees in their pursuit of gainful employment. Includes: Public & Private premises Mobile Homes, Recreational vehicles Floating Buildings Yards, Lots, Parking Lots Carnivals Industrial Substations Electrical Utility Installations

20 Job Tasks are Covered Under Installing conductors and other electrical equipment on industrial substations or buildings, residential or commercial. Connecting the installations to a supply of electricity. Installing other outside conductors. NFPA 70E *Examples Only

21 Job Tasks which are not covered under NFPA 70E Installations... In ships, watercraft, railway rolling stock, aircraft, or automotive vehicles other than mobile homes and RVs. In underground mines. Of railways for operation of rolling stock. Communication equip. under control of communication utilities. Under the control of electric utilities.

22 NFPA 70 E 2012 Goes into effect in September of 2012 Changes in wording Changes in procedures Ninth edition since publishing in 1979

23 Electrical Safety Program Principles Inspect/evaluate electrical equipment. Maintain equipment insulation and enclosures. Plan every job. Document first time procedures. De-energize, if possible.

24 Electrical Safety Program Principles Anticipate unexpected events. Identify and minimize the hazard. Protect from shock, burn, blast, and other hazards. Use the right tools for the job. Assess employee s ability. Audit these principles.

25 Electrical Safety Program Components Employee Training Procedures Working on or near live parts at 50V or greater Hazard Evaluation and Assessment Job Briefing Energized Electrical Work Permit System Inspection of Portable Cord & Plug Equipment and Flexible Cord Sets

26 Electrical Safety Program Controls Every conductor or circuit is considered live until proven otherwise. No bare-hand contact with exposed energized parts above 50V, unless using the bare handed method properly. LOTO- De-energizing electrical to make it safe is considered a potentially hazardous task.

27 Electrical Safety Program Controls Employer develops the programs and the employees apply them. Train employees to make them qualified. Identify & categorize tasks to be performed on or near exposed electrical. Identify & use precautions appropriate to the working environment.

28 Safeguards for Personal Protection Employers must provide personal protective equipment. Employees must wear it. Must be maintained in a safe condition and inspected. Non-conductive head protection must be worn. Appropriate tools should be used.

29 Who s Required To Do What? NFPA 70E (C) General: employees working in areas where there are electrical hazards shall be provided with, and shall use, protective equipment that is designed and constructed for the specific part of the body to be protected and for the work to be performed.

30 Personal Protective Equipment 70E 2009, Table 130.7(C)(9)(a)Hazard Risk Category Classifications,pages 29 thru 31. Based on task, voltage, type of equipment and notes (fault current and clearing time) the table shows: hazard / risk category if V-rated gloves are required if V-rated tools are required For any task, voltage, fault current or clearing times not listed in the table, do the calculation outlined in 70E, 130.3(A),page 25.

31 Protective Clothing For most low-energy work (240 volts or below), natural-fiber, non-melting clothing is adequate; some higher risk tasks require FR clothing. Most work on or near systems rated 480 volts and above requires at least one layer of flame-resistant (FR) clothing worn over natural-fiber clothing. High-energy tasks require FR flash suits and flash hoods worn over FR clothing.

32 Underlayers Meltable synthetic fibers shall be avoided in fabric underlayers (underwear) next to the skin. When the FR clothing system has been appropriately assessed to the hazard, then a cotton undergarment will provide additional protection.

33 Personal Protective Equipment (PPE) Requirements Required PPE includes: Flame-resistant clothing Flash suits (for high-energy arc exposure) Flash suit hoods Balaclava head covering Natural Fiber Clothing Fire Retardant Coveralls Insulating gloves Insulated tools This is in addition to normally used hard hat, safety shoes, safety glasses, and hearing protection.

34 NFPA 70E Provides Two Choices for Selecting the Appropriate PPE: Conduct an arc flash hazard analysis, and document the incident energy exposure. Duke Flux Software (Freeware) ArcPro II Software IEEE 1584 Standard As an alternate, use the Hazard Risk Category Classifications table to choose the PPE level required for the task.

35 Personal Protective Equipment Protective Clothing (non-melting) Hazard/Risk category Protective Clothing ATPV/ Cal/cm2 0 Untreated Cotton ATPV n/a 1 FR shirt and FR pants ATPV 4 cal/cm2 70E, page 34 ATPV=arc thermal performance value Cal/cm2 (Calories per Sq. Centimeter) 2 Cotton underwear plus FR shirt and FR pants 3 Cotton underwear plus FR shirt and FR pants plus FR coverall 4 Cotton underwear plus FR shirt and FR pants plus double layer switching coat and pants ATPV 8 cal/cm2 ATPV 25 cal/cm2 ATPV 40 cal/cm2.

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37 Products Available to Accomplish Safety Requirements Voltage rated gloves and protectors. Insulated/Insulating tools. Insulating blankets. Insulating protective shielding. Insulating sleeves. Dielectric footwear.

38 Hard Hats Z , Type 1, Class C,E,G - This is the ANSI stamp of approval that specifies the hard hat meets all safety requirements. Classifications under old and new standards: Z Z Application Test Voltage (Old Standard) (New Standard) A G General 2,200 B E Electrical 20,000 C C Conductive Not Tested

39 Additional Protective Equipment Face shields are available that are listed with ATPV ratings from many manufacturers... Do not use general duty face shields. Always wear safety glasses under face shields (no metal frames). Always wear a hard hat. Hearing protection is required. Protective hoods or parkas should be worn in conjunction with shields and hard hats.

40 Insulated Tools Insulated tools that meet ASTM F1505 and OSHA (c)(2). The tools are rated 1000V to be used on working with energized equipment.