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Electrical Safety

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Roofers 12-Hour OSHA ... Roofing Industry Partnership Electrical Safety Training Objectives After completing this unit, you will: Be familiar with the fundamental ... – PowerPoint PPT presentation

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Title: Electrical Safety


1
New England Roofing Industry Partnership
Electrical Safety
2
Training Objectives
SUBPART
Electrical Safety
K
1
  • 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
References
SUBPART
Electrical Safety
K
2
  • 29 CFR 1926.400 Subpart K
  • National Electric Code (NEC)

4
Take Electricity Seriously
SUBPART
Electrical Safety
K
3
  • 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
Electrical Accidents
SUBPART
Electrical Safety
K
4
  • 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
Harmful Effects of Electricity
SUBPART
Electrical Safety
K
5
  • 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
Fundamentals of Electricity
SUBPART
Electrical Safety
K
6
  • Voltage (E)
  • electrical pressure (water pressure)
  • Amperage (I)
  • electrical flow rate (gallons per minute)
  • Resistance (R)
  • restriction to electrical flow (pipe friction)

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

9
Current Flows in a Loop or Circuit
SUBPART
Electrical Safety
K
8
  • 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
How Shocks Occur
SUBPART
Electrical Safety
K
9
  • 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
Shocks Occur in Three Ways
SUBPART
Electrical Safety
K
10
  • Contact with both conductors
  • Contact with one conductor and ground
  • With a tool contact with hot metal part and
    ground (1), (2) (3)

12
Severity of the Shock
SUBPART
Electrical Safety
K
11
  • 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
He sweats - and he dies...
SUBPART
Electrical Safety
K
12
  • 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
Controlling Electrical Hazards
SUBPART
Electrical Safety
K
13
  • 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
Electrical Isolation
SUBPART
Electrical Safety
K
14
  • 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
Insulating the Conductors
SUBPART
Electrical Safety
K
15
  • 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
Defective Cord Incident
SUBPART
Electrical Safety
K
17
  • Attempting to climb scaffold with electric drill.
  • Drills cord was worn open.
  • The wire contacted the scaffolding.
  • The worker died!

19
Elevating the Conductors
SUBPART
Electrical Safety
K
18
  • The second way to safeguard workers from
    electrically energized wires is by elevating
    them.
  • 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 10
    feet of energized lines!

20
Working Near Overhead Lines
SUBPART
Electrical Safety
K
19
  • 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
Working Near Overhead Lines
SUBPART
Electrical Safety
K
20
  • 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 gt 50 kv.

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

23
Guarding the Conductors
SUBPART
Electrical Safety
K
22
  • The third way to safeguard workers from
    electrically energized wires is guarding them.
  • 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
Equipment Grounding
SUBPART
Electrical Safety
K
24
  • 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
Can You Rely on Grounding?
SUBPART
Electrical Safety
K
25
  • Grounding will not work if the electricity can
    flow through you more easily than the ground.
    This can happen when
  • Your tool doesnt have a ground pin.
  • Youre working in water.
  • Youre touching a metal object.

27
What Must be Grounded?
SUBPART
Electrical Safety
K
26
  • 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 cant
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
Circuit Interruption
SUBPART
Electrical Safety
K
29
  • 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
Circuit Protective Devices
SUBPART
Electrical Safety
K
30
  • Circuit Breakers and Fuses
  • Only protect the building, equipment, and tools
    from heat build-up!
  • Never depend on circuit breakers or fuses to
    prevent shocks!
  • Ground Fault Circuit Interrupter (GFCI)
  • Is the only device which will protect 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 cant let go of power
0.005 AMP GFCI Opens 0.003 AMP painful
shcok 0.001 AMP mild shock
33
GFCI Protection
SUBPART
Electrical Safety
K
32
  • 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
How a GFCI Works
SUBPART
Electrical Safety
K
33
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
Types of GFCI Protection
SUBPART
Electrical Safety
K
34
36
SUBPART
Electrical Safety
K
35
GFCI Testers
37
Assured Equipment Grounding Conductor Program
SUBPART
Electrical Safety
K
36
  • Requires the following
  • Written program and 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
Checking for Ground Continuity
SUBPART
Electrical Safety
K
37
What else we should we notice here?
39
Temporary Wiring
SUBPART
Electrical Safety
K
38
  • 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
Extension Cords and Cables
SUBPART
Electrical Safety
K
40
  • 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 only 3-wire extension cords designed
    for hard or extra hard usage (NEC 400).

42
Acceptable Cord Types
SUBPART
Electrical Safety
K
41
  • OSHA requires cords to meet the National Electric
    Codes (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-Whats the Difference?
45
SUBPART
Electrical Safety
K
44
Clever? Or Foolish?
46
Temporary Lighting
SUBPART
Electrical Safety
K
45
  • All bulbs must be guarded
  • No broken bulbs or empty sockets
  • Not suspended by conductors
  • Low voltage for wet locations

47
Portable Generators
SUBPART
Electrical Safety
K
46
  • 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 gt5kV

48
Safe Work Practices
SUBPART
Electrical Safety
K
47
  • 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
Safe Work Practices
SUBPART
Electrical Safety
K
48
  • 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
Safe Work Practices
SUBPART
Electrical Safety
K
49
  • 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.

51
Safe Work Practices
SUBPART
Electrical Safety
K
50
  • No metal ladders for or near electrical work.
  • No wet hands when plugging or unplugging.
  • No raising or lowering tools by the cords.
  • Unless equipment designed for, cannot be used in
    damp and wet locations, or in extremely hot or
    chemically destructive work environments.

52
Electrical Safety(1926.400 - .449)
SUBPART
Electrical Safety
K
51
  • Common OSHA Citations
  • .404(b)(1)(i) Branch circuits GFCI
    protection/Assured Equipment Grounding Conductor
    Program
  • .404(f)(6) Grounding path
  • .403(b)(2) Equipment installation and use
  • .404(b)(1)(ii) GFCI
  • .403(i)(2)(i) Guarding live parts

How can the hazards addressed by these Standards
best be corrected, controlled, or eliminated?
53
Review Questions
SUBPART
Electrical Safety
K
52
  • True or False?
  • Shocks and Electrocutions are the most common
    type of electrical accident and are the fourth
    leading cause of worker deaths.
  • The human body will not conduct electricity.
  • It takes at least 1 amp going through a worker to
    kill them.
  • Insulation on extension cords, elevated power
    lines, and receptacle box covers are examples of
    protection through isolation.

54
Review Questions
SUBPART
Electrical Safety
K
53
  • True or False?
  • All portable and semi-portable tools and
    equipment must be grounded unless double
    insulated.
  • You, your tools, and the materials you are
    working with, must never be closer than 3 feet of
    energized power lines!
  • Electric equipment operating at 50 volts more
    must be guarded!
  • All circuits and extension cords must be grounded.

55
Review Questions
SUBPART
Electrical Safety
K
54
  • True or False?
  • Circuit breakers and fuses are designed to
    protect the worker from electrocution.
  • GFCI protection or Assured Ground Continuity is
    required of all temporary circuits.
  • Extension cords are not required to have a
    ground prong when they are GFCI-protected.
  • It is OK to work on a circuit which has not
    been de-energized.
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