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Electrical Standards

Electrical Standards. MODULE 10. Hazard Brainstorming. Where are electrical hazards on oil and gas well sites?. Statistics. Electrocution: Among most frequent causes of occupational injury death in US 295 fatalities/year; 4309 lost time 1992-2002: 9% decrease

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Electrical Standards

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  1. Electrical Standards MODULE 10

  2. Hazard Brainstorming • Where are electrical hazards on oil and gas well sites?

  3. Statistics • Electrocution: Among most frequent causes of occupational injury death in US • 295 fatalities/year; 4309 lost time • 1992-2002: 9% decrease • Most frequent cause: Overhead power lines

  4. Factors in Fatal Electrocutions • Safe work practices implemented and followed? • Adequate/required PPE provided and worn? • Lockout/tagout procedures implemented and followed? • OSHA, NEC, NESC compliance? • Worker and supervisor training adequate? • (from NIOSH)

  5. Types of Electrical Injuries • Electrocution (death due to electrical shock) • Electrical shock • Burns (ugly pictures here) • Falls

  6. Hazard Recognition • How can you sense electrical danger? • Cannot see, smell, taste, or hear danger • Can recognize unsafe conditions

  7. Electrical Terminology • Current – movement of electrical charge • Resistance – opposition to current flow • Voltage – measure of electrical force • Conductors – substances with little resistance to electricity (such as metals) • Insulators – substances with high resistance to electricity (such as wood, rubber, glass, & bakelite) • Grounding – a conductive connection to the earth (which acts as a protective measure)

  8. Electrical Shock • Received when current passes through body • Severity depends on: • Path of current through body • Amount of current flowing through body • Length of time body is in circuit • Also: voltage, moisture, heart cycle, health • Low voltage is NOT low hazard!

  9. Dangers of Electrical Shock • Currents >75 mA* can cause ventricular fibrillation (rapid, ineffective heartbeat) • mA = milliampere = 1/1,000 of an ampere • Death within minutes unless a defibrillator is used • 75 mA is not much current (a small power drill uses 30 times as much)

  10. Effects of Current on Body • 1 mA: Perception level, slight tingling. • 5 mA: Slight shock; not painful. • Can usually let go. • Involuntary reactions can cause injuries. • 6-30 mA: Painful shock • Muscular control lost • Freezing current or “let-go” range

  11. Effects of Current on Body • 50-150 mA: Extreme pain • Respiratory arrest; cannot let go • Death possible • 1000-4300 mA: Ventricular fibrillation • Muscular contraction; nerve damage • Death likely • 10000 mA: Cardiac arrest • Severe burns, probable death

  12. How Shock Happens • Connection between: • 2 wires of energized circuit • 1 wire of energized circuit and ground • Metallic part in contact with energized wire and ground

  13. Inadequate Wiring Hazards Wire Gauge WIRE • What happens when a wire is too small to carry the current safely? • Overheating • Risk of fire or short circuit • Fuse acts as sacrificial weak link • Fuse too strong? Other parts of the system break first

  14. 29 CFR 1910 and 29 CFR 1926 • 1910 Subpart S = Electrical • Revised 2/14/2007; effective in 180 days • 1910 Subpart I = PPE • 1910.137 Electrical Protective Devices • 1926 Subpart K = Electrical • Protect against recognized hazards

  15. Other Standards • NFPA 70E enacted to help meet CFR • Revised Subpart S based heavily on 2000 version • 2004 version now published • OSHA chose which provisions of 70E to adopt

  16. 29 CFR 1910 Subpart S • Electrical standards for general industry • § 302-308 and 399 updated: PM App. C • 5 main groups of standards: • Design safety standards § 302-330 • Safety-related work practices § 331-360 • Reserved: maintenance, special equipment • Definitions: § 399

  17. 1910.302 Electric utilization systems (PM Appendix C) • Applicability of regulations • By type of installation • By installation date

  18. General 1903.303

  19. 1910.303 (a) Approval • Conductors and equipment acceptable only if approved • Note: If installation is made in accordance with NEC or ANSI/NFPA it will be deemed in compliance. • See definitions

  20. 1910.303(b) Examination, installation, and use of equipment • Examination – shall be free of recognized hazards • Suitability (check listing/labeling) • Other factors listed in regulation • Installation and use – by instructions • Insulation integrity • Interrupting rating (fuses, breakers)

  21. 1910.303(b) Examination, installation, and use of equipment • Circuit impedance… • Deteriorating agents – water, gases, excessive temperature, corrosives… • Mechanical execution of work • Close unused openings for protection • Conductors racked for safe access • Internal parts not contaminated • No damaged parts

  22. 1910.303(b) Examination, installation, and use of equipment • Mounting and cooling • Firmly secured • Air circulation; clearance • Ventilation openings not obstructed

  23. 1910.303(c) Electrical connections • General – dissimilar metals • Terminals – connections • Splices – correctly performed, insulated

  24. 1910.303(d) Arcing parts • Some electrical equipment normally produces arcs, sparks, flames, molten metal • Keep isolated from combustible material

  25. 1910.303(e) Marking • Manufacturer and ratings must be marked • Voltage, current, wattage, etc. • Durable markings in environment

  26. 1910.303(f) Disconnecting means and circuits • Legibly marked to indicate purpose • Unless purpose is evident • Durable • Able to be locked open • Series combination rating = special marking

  27. Example of properly labeled electric service: motors, disconnects and breakers Subtitles & Transitions FOR EXAMPLE…

  28. 1910.303(g) 600 Volts, nominal, or less • Space about electric equipment • Space, not used for storage • Guarded when parts exposed • Entrances • Illumination • Headroom • Control boards in dedicated, protected space

  29. 1910.303(g) 600 Volts, nominal, or less • Guarding of live parts • Live parts  50 volts protected from people • Protection from damage • Warning signs for unqualified persons

  30. 1910.303(h) Over 600 volts, nominal • Enclosure / access control • Work space about equipment • Entrance and access to work space • Working space and guarding

  31. Wiring Design and Protection 1903.304

  32. 1910.304(a) Use and identification of grounding conductors • Grounded & equipment grounding conductors identifiable & distinguishable • Grounded = white or gray • Equipment grounding = green, or green with yellow strips, or bare • Polarity may not be reversed • Grounding devices not used for other purposes

  33. Polarity • Reversed polarity: Neutral (grounded) conductor connected to hot (ungrounded) terminal incorrectly • Most common on smaller branch circuits • 120 V receptacle outlets • Cord- and plug-connected equipment

  34. Example of properly labeled electric service: motors, disconnects and breakers Subtitles & Transitions FOR EXAMPLE…

  35. 1910.304(b) Branch circuits • Identification of multiwire branch circuits • For >1 voltage system in a building • ID phase and system • Permanently posted at each panelboard

  36. 1910.304(b) Branch circuits • Receptacles and cord connectors • Grounding type for 15A & 20A circuits • Receptacles only on circuits matching voltage and current rating • Grounding contacts grounded • Except portable / vehicle-mounted generators • Except replacement receptacles • Grounding contact connected to equipment grounding conductor

  37. 1910.304(b) Branch circuits • Receptacles and cord connectors • Replacement of receptacles • Grounding-type where grounding means exists • GFCI where required • Options for lack of grounding means • Plugs not interchangeable for different voltage, frequency, type of current

  38. 1910.304(b) Branch circuits • Ground-fault circuit interrupter (GFCI) • Bathroom or rooftops • Temporary wiring: • Including extension cords • If unavailable for less-usual type of receptacle: assured equipment grounding conductor program.

  39. 1910.304(b) Branch circuits • Outlet devices • Heavy-duty lampholders for >20A • Receptacle outlets: • Receptacle ampere rating  branch circuit • For 2 outlets on branch circuit: Table S-4

  40. 1910.304(b) Branch circuits • For 2 outlets on branch circuit: Table S-5 •  50 A: receptacle  branch-circuit rating • Cord connections: Outlet where flexible cords with plugs used

  41. 1910.304(c) Outside conductors, 600 volts, nominal, or less • Clearance • Power conductors on poles • Clearance of open conductors from ground: • 10 feet – above sidewalk, grade, platform • 12 feet – vehicular traffic • 15 feet – truck traffic • 18 feet – public streets, alleys, driveways

  42. 1910.304(c) Outside conductors, 600 volts, nominal, or less • Clearance from building openings • No outer jacket: 3 foot clearance, except above window • Not beneath or obstructing openings where materials may be moved • Above roofs: 8 ft above, 3 ft from edge • Pedestrians? Platform • Exceptions for slope, attachment

  43. 1910.304(d) Location of outdoor lamps • Location of outdoor lamps • Under energized equipment unless • Equipment can be locked out or • Clearance/other safeguards adequate

  44. 1910.304(e) Services • Disconnecting means • Main switch disconnects all, indicates on/off • Services over 600 volts, nominal • Accessible only to qualified; warning signs

  45. 1910.304(f) Overcurrent protection • 600 volts, nominal, or less • Protect conductors and equipment • Overcurrent devices readily accessible • To employees & building management • Not exposed to damage or ignitable material • Located/shielded to avoid injury/burns • On/off position clearly indicated • Vertical: up = on • Special rules for over 600 volts

  46. 1910.304(g) Grounding • Systems to be grounded • 3-wire DC: neutral conductor • 2-wire DC, >50V-300V, with exceptions • AC <50V in certain cases • AC 50V-1000V (unless exempt) under 4 conditions • Exemptions for AC 50V-1000V

  47. 1910.304(g) Grounding • Conductor to be grounded • Portable and vehicle-mounted generators: frame as grounding electrode • Grounding connections • Grounding path: permanent, continuous, effective

  48. Grounding • One conductor of the circuit intentionally grounded to earth • Protects circuit from lightning or other high voltage contact • Stabilizes the voltage in the system so “expected voltage levels” are not exceeded under normal conditions

  49. Grounding • Metal frames / enclosures of equipment grounded by permanent connection or bond • Equipment grounding conductor provides path for dangerous fault current to return to ground • If damage, corrosion, loosening, etc. impairs continuity, shock and burn hazards will develop

  50. Grounding Path • Shall have capacity to conduct safely any likely fault current. • Fault currents may be many times normal currents; can melt points of poor conductivity • High temperatures = hazard; can destroy ground-fault path

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