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Electrical Safety

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Electrical Safety Introduction Electricity is essential to modern life Some employees work with electricity directly Some indirectly Electricity is a serious ... – PowerPoint PPT presentation

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Title: Electrical Safety


1
Electrical Safety
2
Introduction
  • Electricity is essential to modern life
  • Some employees work with electricity directly
  • Some indirectly
  • Electricity is a serious workplace hazard
  • Electricity can be productive and safe

3
Agenda
  • Vocabulary
  • Misconceptions and myths about electricity
  • Electrical shock and other injuries
  • Electrical hazards
  • Electrical safety for maintenance and custodial
    employees
  • Electrical safety for offices and classrooms

4
Vocabulary
  • Voltage
  • Low voltage
  • High voltage
  • Current
  • Resistance
  • Conductor
  • Insulator
  • Ohms law

5
Voltage
  • Electromotive force
  • Electrical potential energy
  • Pressure
  • Measured in volts (V)

6
Low Voltage
  • Electrical installations and electrical equipment
    operating or intended to operate on systems of
    600 volts, nominal, or less.
  • All work performed directly on or in proximity
    to such electrical installations, equipment, or
    systems.

7
High Voltage
  • Electrical installations and electrical equipment
    operating or intended to operate on systems of
    more than 600 volts.
  • All work performed directly on or in proximity
    to such electrical installations, equipment, or
    systems.
  • Beyond the scope of this training.

8
Current
  • The continuous movement of electrons past a given
    point
  • Measured in amperes (amps) (A)
  • Sometimes the symbol I is used

9
Resistance
  • Opposition to the movement of electrons
  • Resistance is used for direct current
  • Measured in ohms (O)
  • Impedance is the proper term for alternating
    current
  • Resistance is commonly used

10
Conductor
  • A person who collects tickets on trains
  • A person who leads a orchestra, band, or choir

11
Conductor
  • A substance or thing that allows electricity (or
    heat) to flow by passing energy from particle to
    particle
  • Silver, copper, gold, aluminum

12
Insulator
  • A barrier that wraps conductive materials to
    protective against electric shock
  • A material with little or no conductive
    properties
  • High resistance
  • Glass, rubber, mica, and some plastics

13
Ohms Law
  • R V / A
  • One volt will cause a current of one ampere to
    flow through a conductor having the resistance of
    one ohm
  • V A R

14
Ohms Law
V (Volts)
A (Amps)
R (Ohms)
15
Electrical Misconceptions
  • Electricity tends to go to ground
  • After it reaches ground, it disappears
  • Ground serves as just one of the electrical
    loops that misdirected current can use to get
    back to the grounded power source

16
Misconception 2
  • If an electrical appliance or tool falls into a
    sink or tub of water, the item will short and
    trip the circuit breaker
  • This may not happen because the sink or tub may
    be non-conductive and therefore not part of the
    loop to ground

17
Misconception 3
  • AC reverse polarity is not hazardous
  • Many tools have switches in only one of the two
    conductors serving the item
  • The switch is supposed to be on the hot
    conductor supplying he power

18
Myths About Electricity
  • Electricity takes the path of least resistance
  • Current will take any conductive paths, high or
    low resistance, in order to return to the source
    that provides it power
  • Small amounts of current will flow through paths
    of high resistance

19
Myth 2
  • Double insulated power tools are doubly safe and
    will always provide safety
  • Double insulated power tools can be hazardous if
    dropped into water
  • Electrical current can flow out of the power tool
    into the water

20
Myth 3
  • It takes high voltage to kill120 volts AC is
    not dangerous
  • Current is the culprit that kills
  • Voltage is a factor in determining how much
    current will flow

21
Electrical Shock
  • A sudden and accidental stimulation of the bodys
    nervous system by an electrical current
  • Current will flow through the body when it
    becomes part of an electrical circuit

22
Electrical Shock Dynamics
23
Other Injuries
  • Burns
  • Falls
  • Injuries when machinery starts suddenly

24
Electrical Burns
  • Current passing through tissue generates extreme
    heat
  • Skin damage at entry and exit
  • Internal tissue damage
  • Result from arcs or flashes
  • Thermal burns from overheated wires or equipment
    or fires

25
Falls
  • Initiated by a shock
  • Muscles contract involuntarily
  • Worker can lose balance and fall

26
Machinery Injuries
  • Unexpected activation
  • Shock
  • Pinch
  • Crush
  • Shear

27
Electrical Hazards
  • Bare conductors
  • Insulation failure
  • Equipment failure
  • Static electricity
  • Heating and overheating
  • Electrical explosions

28
Bare Conductors
  • Live overhead wires most common
  • Working on rooftops
  • Repair of electrical systems
  • Capacitors

29
Insulation Failure
  • Heat and elevated temperatures
  • Moisture and humidity
  • Mechanical damage
  • Rodents, fungi
  • Chemical incompatibility

30
Equipment Failure
  • Older portable tools
  • Energized housing
  • Broken connections
  • Wrongly replaced internal wiring
  • Lack of grounding plug

31
Static Electricity
  • Occurs when two different materials contact and
    then separate
  • High voltage, low current
  • Flammable liquids
  • Lightning

32
Heating and Overheating
  • Use of electricity results in heat
  • Can cause accidental fires
  • Burns out equipment
  • Equipment failure and ignition
  • Hot surfaces

33
Electrical Explosions
  • Rapid overheating from overcurrents
  • Caused by short circuits, power surges, or
    lightning
  • Heated contaminants in oil-filledbreakers or
    transformers
  • Capacitors subject to wrong polarity

34
Safety for Maintenance and Custodial Employees
  • Qualified electrical workers
  • Engineered protection
  • Safety considerations
  • Safe practices
  • Lockout/tagout
  • Personal protective equipment (PPE)

35
Qualified Electrical Workers
  • A person, designated by the district,who by
    reason of experience orinstruction has
    demonstratedfamiliarity with the operationto be
    performed and thehazards involved

36
Engineered Protection
  • Insulation
  • Grounding
  • Circuit breakers
  • Fuses
  • Ground-fault circuit interrupters

37
Insulation
  • Parts of electrical equipment coated with a
    low-conductive material
  • Rubber mats to stand on
  • Rubber gloves
  • Insulated shoes

38
Grounding
  • Protects from shock
  • Safeguards against fire
  • Protects against damage to electrical equipment

39
System Grounding
  • One conductor of the circuit is intentionally
    connected to earth
  • Protects against high voltage contact
  • Stabilizes voltage in a system

40
Equipment Grounding
  • Equipment grounded by a permanent and continuous
    connection or bond
  • Provides a path for dangerous fault current to
    return to system ground
  • Enables protective devices to operate

41
Circuit Breakers
  • Guard against overloads of current
  • Ensure current flow does not produce heat that
    causes temperature to rise to dangerous levels
  • Break the current path
  • Thermal
  • Magnetic

42
Fuses
  • Guard against overloads of current
  • Ensure current flow does not produce heat that
    causes temperature to rise to dangerous levels
  • Break the current path
  • Melt when current exceeds a designated value

43
Ground-Fault Circuit Interrupters
  • Fast-acting electrical device sensitive to very
    low levels of current imbalance due to flow to
    ground
  • Reduces duration of a shock
  • Not an overcurrent device like a circuit breaker
    or fuse

44
Types of GFCI
  • Circuit-breaker type
  • Receptacle type
  • Permanently mounted type
  • Portable type
  • Cord connected type

45
Circuit-Breaker Type
  • A direct replacement for a standard circuit
    breaker
  • Installed in a panelboard
  • Includes the functions of a standard circuit
    breaker
  • Can protect an entire branch circuit with
    multiple outlets

46
Receptacle Type
  • A direct replacement for a standard receptacle
  • Protects one or more receptacle outlets
  • Protects additional non-GFCI type receptacles
    connected down stream
  • Very popular because of low cost

47
Permanently Mounted Type
  • Mounted in an enclosure
  • Designed to be permanently wired to the supply
  • Frequently used around large commercial swimming
    pools or similar wet areas

48
Portable Type
  • Designed to plug into existing non-GFCI protected
    outlets
  • Contain one or more receptacle outlets protected
    by the GFCI module
  • Easily transported from one location to another
  • Approved for outdoor use
  • Some are listed as rainproof

49
Cord Connected Type
  • Consists of an attachment plug which incorporates
    the GFCI module
  • Protects the cord and any equipment attached to
    the cord
  • Plug has non-standard appearance and is equipped
    with test and reset buttons

50
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51
Safety Considerations
  • Plan every job
  • Consider what could go wrong
  • Use proper tools
  • Procedures, drawings and related documents
  • Isolate equipment from energy sources
  • Identify hazards that may be present

52
Safety Considerations
  • Isolate hazards
  • Test every circuit, every conductor, every time
    before touching
  • Use PPE, when necessary
  • Do you have the skills, knowledge, tools, and
    experience to perform this work safely?

53
Safe Practices
  • Qualified and authorized electrical technician
  • Voltages and frequency should be identified so
    that proper precautions can be implemented
  • Ratings of overcurrent protection chould be
    checked to determine adequate protection

54
Safe Practices
  • Work on de-energized systems
  • Use buddy system for energized systems
  • Never touch a bare conductor until a system has
    been de-energized and verified
  • Enclose and lock all exposed conductors
  • All removed grounding cables should be replaced
    as soon as possible

55
Safe Practices
  • Cords should be inspected before using
  • Repair or replace if defective
  • All tools, equipment, and extension cords should
    be grounded
  • Use nonconductive tape measures near energized
    equipment

56
Safe Practices
  • Avoid working on electrical circuits or equipment
    while clothing and/or shoes are wet
  • Wet floor areas should be covered by dry wood or
    rubber matting
  • Remove rings, watches, keys, and other metal
    items before beginning work

57
Safe Practices
  • Plug power equipment into wall receptacles with
    power switches in the off position
  • Unplug equipment by grasping the plug
  • Check receptacles for missing or damaged parts

58
Personal Protective Equipment
  • Insulating gloves
  • Insulating blankets
  • Insulating sleeves
  • Floor covering
  • Safety helmets

59
Safety in Offices and Classrooms
  • Outlets
  • Cords
  • Machinery

60
Outlets
  • Do not overload outlets by using extension
    devices to increase the number of outlets at that
    socket

61
Cords
  • Keep cables, cords, and plugs clean and in good
    repair
  • Protect cords that cross aisles and walkways
  • Extension cords are for temporary use only
  • Extension cords must be 16 gauge or larger

62
Extension Cords
  • Extension cords should not
  • Be affixed to structures
  • Extend through walls, ceilings, and/or floors
  • Be placed under doors or floor coverings
  • Be subjected to physical or environmental damage

63
Multi-Outlet Strips
  • Multi-outlet strips and surge protectors are not
    considered extension cords
  • One multi-outlet strip should not be plugged into
    another

64
Machinery
  • Report damaged or defective equipment
  • Request repair or replacement
  • Unplug defective equipment
  • Carry equipment by the base
  • Never by the cord
  • Do not touch grounded metal parts

65
Summary
  • Work environments depend on electricity
  • Electrical hazards are in all environments
  • Electrical safety requires effort
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