Common Electrical Hazards in the Workplace Including Arc Flash. Presented by Ken Cohen, PhD, PE & CIH (Ret.)

Transcription

1 Common Electrical Hazards in the Workplace Including Arc Flash Presented by Ken Cohen, PhD, PE & CIH (Ret.) 1

2 What s New In February 1972, OSHA incorporated the 1971 edition of the National Fire Protection Association's (NFPA) National Electrical Code (NEC), NFPA On January 16, 1981, OSHA revised its Electrical standard with Part I of National Fire Protection Association's (NFPA) 70E On August 13, 2007, OSHA revised its Electrical standard to reference National Fire Protection Association's (NFPA) 70E

3 Common Hazards Common hazards when working with energized electrical equipment include: Electric Shock / Burns Blast Arc Flash Fast Fact: It doesn t take much for human skin to burn in fact an exposure of 203 F for just one-tenth of a second (6 cycles) is enough to cause a third degree burn! Electricity can KILL! 3

4 GFCI Protection Ground-Fault Circuit Interrupter Protection for Personnel - General Industry. All 125-volt, single-phase, 15- and 20-ampere receptacles installed in bathrooms or on rooftops shall have ground-fault circuit-interrupter protection for personnel. Receptacles installed in bathrooms or on rooftops shall have ground-fault circuit-interrupter protection for personnel. 4

5 GFCI Protection Ground-Fault Circuit Protection-Construction Site. (c) Ground-Fault Circuit Interrupters. All 120-volt, AC, single-phase, 15- and 20-ampere receptacle outlets on construction sites, which are not a part of the permanent wiring of the building or structure and which are in use by employees, shall have approved ground-fault circuit interrupters for personnel protection. Receptacle outlets (including cord sets) that are not part of the permanent wiring of the building shall have ground-fault circuitinterrupter protection for personnel. Note: A cord connector on an extension cord set is considered to be a receptacle outlet if the cord set is used for temporary electric power. Maintenance & Repair work IS construction 5

6 Flexible Cords Permitted Use Uses Permitted. Pendants; Wiring of fixtures; Connection of portable lamps or appliances; Portable and mobile signs; Elevator cables; Wiring of cranes and hoists; Appliances to permit removal for maintenance and repair Pendant, or Fixture Wiring Portable lamps, tools or appliances Stationary equipment to facilitate interchange 6

7 Prohibited Uses of Flexible Cords Uses Not Permitted. As a substitute for the fixed wiring of a structure; Where run through holes in walls, ceilings, or floors; Where run through doorways, windows, or similar openings; Where attached to building surfaces; Where concealed behind building walls, ceilings, or floors; or Where installed in raceways, except as otherwise permitted in this subpart. Substitute for fixed wiring Run through walls, ceilings, floors, doors, or windows Concealed behind or attached to building surfaces 7

8 Grounding Pin General. 1) A conductor used as a grounded conductor shall be identifiable and distinguishable from all other conductors. Ensure that grounding pin on extension cords is in place and operable All equipment grounding conductors shall be tested for continuity: Before first use Before return to service (repairs) Before use after an incident that may have caused damaged and Intervals not to exceed three (3) months 8

9 Splices Electrical Connections. (1) Conductors shall be spliced or joined with splicing devices identified for the use or by brazing, welding, or soldering with a fusible metal or alloy. Soldered splices shall first be spliced or joined to be mechanically and electrically secure without solder and then soldered. All splices and joints and the free ends of conductors shall be covered with an insulation equivalent to that of the conductors or with an insulating device identified for the purpose. Flexible cords may be used only in continuous lengths without splice or tap. Note: Black electrical tape does not provide suitable insulation and is not acceptable 9

10 Flexible Cords Pull at Joints and Terminals. a) Flexible cords and cables shall be connected to devices and fittings so that strain relief is provided which will prevent pull from being directly transmitted to joints or terminal screws. Strain relief must be provided Durably marked as to type, size, and number of conductors 10

11 Inadequate Wiring Hazards Using a portable tool with an extension cord that has a wire too small for the tool: The tool will draw more current than the cord can handle, causing overheating and a possible fire without tripping the circuit breaker The circuit breaker could be the right size for the circuit but not for the smaller-wire extension cord Wire Gauge WIRE Wire gauge measures wires ranging in size from number 36 to 0 American wire gauge (AWG) 11

12 Minimum Depth of Working Space Work Space About Electric Equipment. (3) Height. The work space shall be clear and extend from the grade, floor, or platform to the height required by subsection (f) of this section. However, other equipment associated with the electrical installation and located above or below the electric equipment may extend not more than 6 in. (153 mm) beyond the front of the electric equipment. Nominal voltage to ground Minimum clear distance for condition 2 3 Condition A Condition B Condition C m ft m ft m ft Condition A -- Exposed live parts on one side and no live or grounded parts on the other side Condition B -- Exposed live parts on one side and grounded parts on the other side Condition C -- Exposed live parts on both sides 12

13 Labeling of Breakers Identification of Equipment. (b) Services, Feeders, and Branch Circuits. Each service, feeder, and branch circuit, at its disconnecting means or overcurrent device, shall be legibly marked to indicate its purpose, unless located and arranged so the purpose is evident. Overcurrent devices or disconnecting devices: shall be legibly marked to indicate its purpose shall be of sufficient durability to withstand the environment involved. 13

14 Cabinets, Boxes and Fittings Energized Equipment or Systems. (b) After the required work on an energized system or equipment has been completed, an authorized person shall be responsible for: (1) Removing from the work area any temporary personnel protective equipment, and (2) Reinstalling all permanent barriers or covers. Conductors entering shall be protected Openings shall be effectively closed Cable is fastened within 12 from box or raceway 14

15 Cabinets, Boxes and Fittings Energized Equipment or Systems. (b) After the required work on an energized system or equipment has been completed, an authorized person shall be responsible for: (1) Removing from the work area any temporary personnel protective equipment, and (2) Reinstalling all permanent barriers or covers. Conductors entering shall be protected Openings shall be effectively closed Cable is fastened within 12 from box or raceway Exception note: when over 7 off grade level! 15

16 Cabinets, Boxes and Fittings Energized Equipment or Systems. (b) After the required work on an energized system or equipment has been completed, an authorized person shall be responsible for: (1) Removing from the work area any temporary personnel protective equipment, and (2) Reinstalling all permanent barriers or covers. Conductors entering shall be protected Openings shall be effectively closed 16

17 Cabinets, Boxes and Fittings Live Parts Fixtures, lampholders, lamps, rosettes, and receptacles shall have no live parts normally exposed to contact. In completed installations, each outlet box shall have a cover, faceplate, or fixture canopy. 17

18 Walk now through a hypothetical plant: and see what violations you can identify? 18

26 Arc Flash Event A dangerous release of energy created by an electrical fault Release will contain: Thermal energy Acoustical energy Pressure wave Debris 26

27 Arc Flash Event 27

28 Arc Flash Event Required PPE 28

29 Click Arc Flash on Video Event to Play... This video is for demonstration purposes only. Inclusion of this video does not constitute OSHA s endorsement of this product 29

30 Arc Flash Intensity Variables that effect the size and energy of an electric arc flash: Amperage Voltage Arc Gap Closure time Distance away from arc 3 phase v single phase Confined space 30

31 Arc Flash Events Can reach 35,000 F Fatal burns >10 feet Majority of hospital admissions are arc flash burns, not shock 30,000 arcs and 7000 burn injuries per year Over 2000 people admitted to burn centers yearly with severe arc flash burns 31

32 What Is a Burn? A chemical process which progressively injures skin; severity relates to depth 1 st : redness, pain not permanent 2 nd : blistering skin will regenerate 3 rd : total skin depth destroyed. Will not regenerate requires grafting 4 th : Underlying muscle damaged 32

33 Burn Injury Burn treatment requires approx. 1.5 days hospitalization per % burn Average hospitalization is 19 days, at costs exceeding $18,000/day Total hospitalization cost typically ranges from $200,000 to $750,000, with many over $1,000,000 USD 33

34 Arc Flash Protection Labeling Arc Flash Hazard labeling must be posted which identifies: Approach boundaries PPE required 34

35 Arc Protection: big and small! The making, or breaking, of an electrical circuit produces an arc. The intensity of the arc is dependant on the current load, the voltage, and the speed with which the gap is opened or closed. 35

36 Deenergized Equipment The most effective and fool-proof way to eliminate the risk of electrical shock or arc flash is to simply deenergize the equipment... 36

37 Lockout / Tagout A lock and a tag shall be placed on each disconnecting means used to deenergize circuits and equipment on which work is to be performed. Note: Electric equipment that have been deenergized but have not been locked out or tagged shall be treated as energized. 37

38 Working Live OSHA has also made allowances for not deenergizing electrical equipment when it would increase current hazards or create additional hazards, for example: interruption of life support equipment, deactivation of emergency alarm systems, shutdown of hazardous location ventilation equipment, removal of illumination for an area. Working live is also allowable due to infeasibility of deenergization (i.e. testing of electric circuits) 38

39 Hot Work Requirements Employer must develop and enforce safety-related work practices to prevent electric shock or other injuries resulting from either direct or indirect electrical contacts. These safety related work practices could include: Energized Electrical Work Permit Pre-work Job Briefing Personal Protective Equipment Insulated Tools Written Safety Program Qualified Person Training Flash Hazard Labeling 39

40 Qualified Persons Qualified person: One who has received training in and has demonstrated skills and knowledge in the construction and operation of electric equipment and installations and the hazards involved. The qualified person is determined and designated by the Employer! 40