Electrical Safety

1. New England Roofing Industry Partnership Electrical Safety

2. SUBPART Electrical Safety K 1 Training Objectives • After completing this unit, you will: • Be familiar with the fundamental concepts of electricity. • Understand the potential effects of electricity on the human body. • Be able to recognize common electrical hazards. • Be familiar with electrical protective devices. • Be knowledgeable about safe work practices.

3. SUBPART Electrical Safety K 2 References • 29 CFR 1926.400; Subpart K • National Electric Code (NEC)

4. SUBPART Electrical Safety K 3 Take Electricity Seriously • Electricity is the second leading cause of death in construction. • Electrocutions make up 12% of construction fatalities annually. • Over 30,000 non-fatal shocks occur each year. • Over 600 deaths occur annually due to electrocution.

5. SUBPART Electrical Safety K 4 Electrical Accidents • Leading Causes of Electrical Accidents: • Drilling and cutting through cables • Using defective tools, cables and equipment • Failure to maintain clearance distances • Failure to de-energize circuits and follow Lockout/Tagout procedures • Failure to guard live parts from accidental worker contact • Unqualified personnel working with electricity • Improper installation/use of temporary electrical systems and equipment • By-passing electrical protective devices

6. SUBPART Electrical Safety K 5 Harmful Effects of Electricity • Shock – Most common and possibly causing electrocution or muscle contraction leading to secondary injury • Burns – Resistance causes heat • Fires – Enough heat or spark can ignite combustible materials • Explosions – Electrical spark can ignite vapors in air

7. SUBPART Electrical Safety K 6 Fundamentals of Electricity • Voltage (E) • electrical pressure (water pressure) • Amperage (I) • electrical flow rate (gallons per minute) • Resistance (R) • restriction to electrical flow (pipe friction)

8. SUBPART Electrical Safety K 7 Fundamentals of Electricity • Electrical current is the flow of electrons through a conductor. • A conductor is a material that allows electrons to flow through it. • An insulatorresists the flow of electrons. • Resistance opposes electron flow.

9. SUBPART Electrical Safety K 8 Current Flows in a Loop or Circuit • Circuits are AC (alternating current) or DC (direct current). • Current is usually AC. • AC current has five parts: (1) Electrical source (2) HOT wire to the tool. (3) The tool itself (4) NEUTRAL wire returns electricity from the tool (5) GROUND

10. SUBPART Electrical Safety K 9 How Shocks Occur • Current travels in closed circuits through conductors (water, metal, the human body). • Shock occurs when the body becomes a part of circuit. • Current enters one point & leaves at another.

11. SUBPART Electrical Safety K 10 Shocks Occur in Three Ways • Contact with both conductors • Contact with one conductor and ground • With a tool: contact with “hot” metal part and ground (1), (2) & (3)

12. SUBPART Electrical Safety K 11 Severity of the Shock • Severity of the Shock depends on: • Amount of current • Determined by voltage and resistance to flow • Path through the body • Duration of flow through the body • Other factors such as general health and individual differences.

13. SUBPART Electrical Safety K 12 He sweats - and he dies... Luling, La. - A man was electrocuted when his sweat dripped into the electric drill he was using to build a swing set in his backyard, the coroner said. Richard Miller was pronounced dead Sunday at St. Charles Hospital, said David Vial, St. Charles Parish coroner. Miller, 54, had been using an electric drill in 90 degree heat, Vial said Monday. “Apparently the man was sweating profusely,” Vial said. “He probably was pushing against the drill with his chest and his perspiration went into the drill itself and made a contact.” The Associated Press.

14. SUBPART Electrical Safety K 13 Controlling Electrical Hazards • Employers must follow the OSHA Electrical Standards (Subpart K) • Subpart K includes four proactive methods: • Electrical Isolation • Equipment Grounding • Circuit Interruption • Safe Work Practices

15. SUBPART Electrical Safety K 14 Electrical Isolation • We can be safe by keeping electricity away from us. We can: • Insulate the conductors. • Example: The insulation on extension cords. • Elevate the conductors. • Example: Overhead powerlines. • Guard the conductors by enclosing them. • Example: Receptacle covers, boxes, & conduit.

16. SUBPART Electrical Safety K 15 Insulating the Conductors • The first way to safeguard workers from electrically energized wires is through insulation. • Rubber and plastic is put on wires to prevent shock, fires, and short circuits. • It is always necessary to check the insulation on equipment and cords before plugging them in. • Remember, even the smallest defect will allow leakage!

17. SUBPART Electrical Safety K 20 16 Defective Extension Cords This cord was hard-usage, but has been worn out.

18. SUBPART Electrical Safety K 17 Defective Cord Incident • Attempting to climb scaffold with electric drill. • Drill’s cord was worn open. • The wire contacted the scaffolding. • The worker died!

19. SUBPART Electrical Safety K 18 Elevating the Conductors • The second way to safeguard workers from electrically energized wires is by elevatingthem. • Wires are often elevated by the power company. • It is always necessary to check the location of overhead lines before you begin work and throughout the day. • Remember, never allow yourself, your tools, or the materials you are working with be within 10feet of energized lines!

20. SUBPART Electrical Safety K 19 Working Near Overhead Lines • Clearance of worker and any equipment, tool, material, or scaffold near uninsulated lines • Less than 50 kv = 10 feet. • More than 50 kv = 10 feet + 0.4 inches for each 1 kv • Clearance near insulated lines • Less than 300 volts = 3 feet. • 300 - 50 kv = 10 feet.

21. SUBPART Electrical Safety K 20 Working Near Overhead Lines • Cranes, Derricks, Hoists • 50 kv or less = minimum distance is 10 feet. • Over 50 kv = 10 feet + 0.4 for each kv over. • In transit; no load = 4 foot minimum up to 50 kv. • In transit; no load = 10 foot minimum if > 50 kv.

22. SUBPART Electrical Safety K 21 Overhead Line Incident • Two workers were attempting to remove a metal pole. • Pole made contact with 7200 volts. • One worker died.

23. SUBPART Electrical Safety K 22 Guarding the Conductors • The third way to safeguard workers from electrically energized wires is guardingthem. • Covers, boxes, and enclosures are often put around conductors to prevent worker contact. • It is always necessary to check that electrical boxes and panels are covered and free from missing “knock-outs”. • Remember, electric equipment operating at 50 volts more must be guarded!

24. SUBPART Electrical Safety K 23

25. SUBPART Electrical Safety K 24 Equipment Grounding • We can be safe by providing a separate, low resistance pathway for electricity when it does not follow normal flow. • Grounding gives the stray current somewhere to go and keeps you from becoming part of the circuit.

26. SUBPART Electrical Safety K 25 Can You Rely on Grounding? • Grounding will not work if the electricity can flow through you more easily than the ground. This can happen when: • Your tool doesn’t have a ground pin. • You’re working in water. • You’re touching a metal object.

27. SUBPART Electrical Safety K 26 What Must be Grounded? • All circuits and extension cords. • All noncurrent carrying metal parts. • Portable & semi-portable tools and equipment unless double insulated. • Exemption for portable generators if less than 5 kV. • No grounding by-pass devices!

28. SUBPART Electrical Safety K 27 Do Not Eliminate the Ground! You become the next-best path for current!

29. SUBPART Electrical Safety K 28 Do Not Reverse Polarity The prongs are different sized so you can’t turn the plug around. If you do, the electrical fields within the motor are always energized. If there is moisture present, the case is likely to be “hot”. Even with double-insulated tool, you still could get a shock.

30. SUBPART Electrical Safety K 29 Circuit Interruption • We can be safer by automatically shutting off the flow electricity in the event of leakage, overload, or short circuit. • Fuses, circuit breakers, & Ground Fault Circuit Interrupters (GFCI) are circuit protection (or “overcurrent”) devices. • Remember, circuit breakers & fuses protect equipment, not you, because they take too much current & too much time to trip.

31. SUBPART Electrical Safety K 30 Circuit Protective Devices • Circuit Breakers and Fuses • Onlyprotect the building, equipment, and toolsfrom heat build-up! • Never depend on circuit breakers or fuses to prevent shocks! • Ground Fault Circuit Interrupter (GFCI) • Is the only device which willprotect the worker from shock and electrocution!

32. SUBPART Electrical Safety K 31 GFCI vs. Circuit Breaker Shock Protection 15 AMP Circuit Breaker Blows 4.000 AMP – burns, heart paralysis 0.100 AMP – certain heart failure, fatal 0.050 AMP – possible heart failure 0.030 AMP – temporary lung paralysis 0.015 AMP – can’t let go of power 0.005 AMP GFCI Opens 0.003 AMP – painful shcok 0.001 AMP – mild shock

33. SUBPART Electrical Safety K 32 GFCI Protection • All temporary circuits are required to have GFCI protection or: • Equipment & cords must be included in an Assured Equipment Grounding Conductor Program • An extension cord is a temporary circuit (attach GFCI to front, not end of cord). • Types: receptacle, circuit breaker and portable • Must be wired correctly and tested.

34. SUBPART Electrical Safety K 33 How a GFCI Works The GFCI detects ‘leakage’ of 4-6 milliamps & opens the circuit in 1/40th of a second. It will work without the ground plug but not fastest enough if you are The ground .

35. SUBPART Electrical Safety K 34 Types of GFCI Protection

36. SUBPART Electrical Safety K 35 GFCI Testers

37. SUBPART Electrical Safety K 36 Assured Equipment Grounding Conductor Program • Requires the following: • Written programand specific procedures • Program implemented by a Competent Person • Equipment grounding conductors must be tested(tools, extension cords, and circuits): • At least every three months for cords & tools • At least every six months for receptacles • Results recorded - equipment coded (colored tape)

38. SUBPART Electrical Safety K 37 Checking for Ground Continuity What else we should we notice here?

39. SUBPART Electrical Safety K 38 Temporary Wiring • There must be separate circuits for electric tools and lighting, each labeled as such. • Light circuits do not require a GFCI. • Unless used in a wet location. • Test branch circuits before use. • Maintain vertical clearances. • Insulate wires from their supports.

40. SUBPART Electrical Safety K 39 Permanent Equipment in Temporary Use What is wrong with using this as a ‘splitter’?

41. SUBPART Electrical Safety K 40 Extension Cords and Cables • Must be in good shape without splices. • Cannot be secured with staples, nails or bare wire. • Must be protected from damage. • Must have a ground pin. • Should be inspected regularly and pulled from service if defective. • OSHA permits only3-wire extension cords designed for hard or extra hard usage (NEC 400).

42. SUBPART Electrical Safety K 41 Acceptable Cord Types • OSHA requires cords to meet the National Electric Code’s (NEC) Table 400-4 hard usage or extra hard usage ratings. • Look for markings stamped on cords. • Acceptable Cord Types • Extra Hard Use Markings: S, ST, SO, STO • Hard Usage Markings: SJ, SJO, SJT, SJTO

43. SUBPART Electrical Safety K 42

44. SUBPART Electrical Safety K 43 Extension Cords-What’s the Difference?

45. SUBPART Electrical Safety K 44 Clever? Or Foolish?

46. SUBPART Electrical Safety K 45 Temporary Lighting • All bulbs must be guarded • No broken bulbs or empty sockets • Not suspended by conductors • Low voltage for wet locations

47. SUBPART Electrical Safety K 46 Portable Generators • The frame of the portable generator need not be grounded if: • the generator supplies only cord and plug connected equipment. • The non-current carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame. • GFCI is required if >5kV

48. SUBPART Electrical Safety K 47 Safe Work Practices • Before work begins, employer must must determine where exposed and concealed energized circuits are located. • Once found, warning signs must be posted. • Workers need to know the location, hazards, and protective measures.

49. SUBPART Electrical Safety K 48 Safe Work Practices • Person in charge determines if performance of work could bring contact with energy. • Distance of the worker to the energy source should be considered first. • Tools, materials, and processes should also be considered to see if they could potentially shorten the safe separation distance. • Examples: Metal Flashing, Re-bar, Bull-floats, etc.

50. SUBPART Electrical Safety K 49 Safe Work Practices • Must not permit work near electric circuit unless the worker is protected by: • De-energizing the circuit and grounding it. • Guarding it effectively by insulation. • Other means (maintaining safe separation) • De-energized circuits and equipment must be locked/tagged out.