Docstoc

Electrical

Document Sample
Electrical Powered By Docstoc
					Electrical Safety / Lock-out
Tag-out
Introduction
l   Electrical safety / Lock-out / Tag-out procedures
    are part of the district safety program.
l   This presentation is designed to provide
    information for your use.
l   You will want to take specific notes on this
    presentation to remind yourselves of the process
    and what steps you need to take when you leave
    this class. You have been provided paper and
    pen for this purpose.
Agenda
l   Overview
l   Statistics
l   How Electricity Works
l   Resistors
l   Insulators / Conductors
l   How Shock Occurs
l   Shock & the Human Body
l   Burns & Other Injuries
l   Preventing Electrical Hazards
l   Insulation
l   Guarding
l   Grounding
l   Circuit Protection devices
l   Safe Work Practices
l   Overhead Lines
l   Tool Inspections
l   Lock-out / Tag-out
l   Care of Cords and Equipment
l   Summary
Overview
l We all use equipment and deal with
  electricity, and must be intimately
  involved in this process.
l All parts of the
  electrical puzzle      Text  Te Text
  must fit together            xt
  and work in order
  to help ensure the    Text Text Text
  safety of students
                         Text Te   Text
  and all staff.
                              xt
Statistics
l Over 6,000 work-related deaths occur each
  year in workplaces employing11 workers
  or more.
l Six percent of the fatalities, or around 347
  deaths, were the direct result of
  electrocutions at work

What makes these statistics more tragic is
 that, for the most part, these fatalities could
 have been easily avoided.
How Electricity Works
l   Operating an electric switch may be considered
    analogous to turning on a water faucet. Behind
    the faucet or switch there must be a source of water
    or electricity, with something to transport it, and
    with pressure to make it flow.
l   In the case of water, the source is a reservoir or
    pumping station; the transportation is through
    pipes; and the force to make it flow is pressure,
    provided by a pump.
l   For electricity, the source is the power generating
    station; current travels through electric conductors
    in the form of wires; and pressure, measured in
    volts, is provided by a generator.
Resistance
Resistance to the flow of electricity is
  measured in ohms and varies widely. It is
  determined by three factors:
l The nature of the substance itself
l The length and cross-sectional area (size)
  of the substance
l The temperature of the substance.
Insulators / Conductors
l   Some substances, such as metals, offer very little
    resistance to the flow of electric current and are
    called conductors.
l   Other substances, such as bakelite, porcelain,
    pottery, and dry wood, offer such a high
    resistance that they can be used to prevent the
    flow of electric current and are called insulators.
l   Dry wood has a high resistance, but when
    saturated with water its resistance drops to the
    point where it will readily conduct electricity.
    The same thing is true of human skin.
Insulators / Conductors
• When it is dry, skin has a fairly high resistance to
    electric current; but when it is moist, there is a
    radical drop in resistance.
•   Pure water is a poor conductor, but small
    amounts of impurities, such as salt and acid (both
    of which are contained in perspiration), make it a
    ready conductor.
•   When water is present either in the environment
    or on the skin, anyone working with electricity
    should exercise even more caution than they
    normally would.
How Shock Occurs
The severity of the shock received when a person
  becomes a part of an electric circuit is affected
  by three primary factors:
• The amount of current flowing through the body
  (measured in amperes)
• The path of the current through the body
• The length of time the body is in the circuit.
Other factors that may affect the severity of shock
  are the:
• Frequency of the current;
• Phase of the heart cycle when shock occurs
• General health of the person.
Shock & the Human Body
• The effects of electric shock depend upon the
  type of circuit, its voltage, resistance, current,
    pathway through the body, and duration of the
    contact.
•   Effects can range from a barely perceptible tingle
    to immediate cardiac arrest.
•   There are no absolute limits or even known
    values that show the exact injury from any given
    current.
Shock & the Human Body
• A difference of less than barely perceptible exists
  between a current that is
                            100 milliamperes
                                               and
    one that can kill.
•   Muscular contraction caused by stimulation may
    not allow the victim to free himself or herself
    from the circuit, and the increased duration of
    exposure increases the dangers to the shock
    victim.
•   For example, a current of 100 milliamperes for 3
    seconds is equivalent to a current of 900
    milliamperes applied for .03 seconds in causing
    ventricular fibrillation.
Shock & the Human Body

• The so-called low voltages can be
    extremely dangerous because, all other
    factors being equal, the degree of injury is
    proportional to the length of time the body
    is in the circuit.
•   LOW VOLTAGE DOES NOT IMPLY
    LOW HAZARD!
Shock & the Human Body
• A severe shock can cause considerably
  more damage to the body than is visible.
• For example, a person may suffer internal
    hemorrhages and destruction of tissues,
    nerves, and muscles.
•   In addition, shock is often only the
    beginning in a chain of events.
•   The final injury may well be from a fall,
    cuts, burns, or broken bones.
Shock & the Human Body
Current / Reaction:
•   1 Milliampere / Perception level. Just a faint tingle.
•   5 Milliamperes / Slight shock felt; not painful but disturbing.
•   Average individual can let go. However, strong involuntary reactions
    to shocks in this range can lead to injuries.
•   6-25 Milliamperes (women) / Painful shock, muscular control is lost.
•   9-30 Milliamperes (men) / This is called the freezing current or "let-
    go" range.
•   50-150 Milliamperes / Extreme pain, respiratory arrest, severe
    muscular contractions.*
    Individual cannot let go. Death is possible.
•   1,000-4,300 Milliamperes Ventricular fibrillation. (The rhythmic
    pumping action of the heart ceases.) Muscular contraction and nerve
    damage occur. Death is most likely.
•   10,000-Milliamperes Cardiac arrest, severe burns and probable
    death.
Burns & Other Injuries
The most common shock-related injury is a
  burn. Burns suffered in electrical accidents
  may be of three types:
l Electrical
l Arc
l Thermal contact
Burns & Other Injuries
l Electrical burns are the result of the
  electric current flowing through tissues or
  bone.
l Tissue damage is caused by the heat
  generated by the current flow through the
  body.
l Electrical burns are one of the most serious
  injuries you can receive and should be
  given immediate attention.
Burns & Other Injuries
l Arc or flash burns, on the other hand, are
  the result of high temperatures near the
  body and are produced by an electric arc or
  explosion.
l They should also be attended to promptly.
Burns & Other Injuries
l Finally, thermal contact burns are those
  normally experienced when the skin comes
  in contact with hot surfaces of overheated
  electric conductors, conduits, or other
  energized equipment.
l Additionally, clothing may be ignited in an
  electrical accident and a thermal burn will
  result.
l All three types of burns may be produced
  simultaneously.
Burns & Other Injuries
l Electric shock can also cause injuries of an
  indirect or secondary nature in which
  involuntary muscle reaction from the
  electric shock can cause bruises, bone
  fractures, and even death resulting from
  collisions or falls.
l In some cases, injuries caused by electric
  shock can be a contributory cause of
  delayed fatalities.
Burns & Other Injuries
l   In addition to shock and burn hazards, electricity
    poses other dangers.
l   For example, when a short circuit occurs, hazards
    are created from the resulting arcs.
l   If high current is involved, these arcs can cause
    injury or start a fire.
l   Extremely high-energy arcs can damage equipment,
    causing fragmented metal to fly in all directions.
l   Even low-energy arcs can cause violent explosions
    in atmospheres that contain flammable gases,
    vapors, or combustible dusts.
Preventing Electrical Hazards
l   Electrical accidents appear to be caused by a
    combination of three possible factors: unsafe
    equipment and/or installation; workplaces made
    unsafe by the environment; and unsafe work
    practices.
l   There are various ways of protecting people from
    the hazards caused by electricity.
l   These include: insulation; guarding; grounding;
    electrical protective devices; and safe work
    practices.
Preventing Electrical Hazards
These include:
l Insulation
l Guarding
l Grounding
l Electrical protective devices
l Safe work practices.
Insulation
l One way to safeguard individuals from
  electrically energized wires and parts is
  through insulation.
l An insulator is any material with high
  resistance to electric current.
Insulation
l   Insulators such as glass, mica, rubber, and
    plastic, are put on conductors to prevent shock,
    fires, and short circuits.
l   Before you prepare to work with electric
    equipment, it is imperative to check the
    insulation before making a connection to a power
    source to be sure there are no exposed wires.
l   The insulation of flexible cords, such as
    extension cords, is particularly vulnerable to
    damage.
Insulation
l   Conductors and cables are marked by the
    manufacturer to show the maximum voltage and
    American Wire Gage size, the type letter of the
    insulation, and the manufacturer's name or
    trademark.
l   Insulation is often color coded. In general,
    insulated wires used as equipment grounding
    conductors are either continuous green or green
    with yellow stripes.
Insulation
l The grounded conductors that complete a
  circuit are generally covered with
  continuous white or natural gray-colored
  insulation.
l The ungrounded conductors, or "hot
  wires," may be any color other than green,
  white, or gray.
l They are often colored black or red.
Guarding
Live parts of electric equipment operating at 50
  volts or more must be guarded against accidental
  contact. This is accomplished by:
l Location in a room, vault, or similar enclosure
  accessible only to qualified persons
l Use of permanent, substantial partitions or
  screens to exclude unqualified persons
l Location on a suitable balcony, gallery, or
  platform elevated and arranged to exclude
  unqualified persons
l Elevation of 8 feet (2.44 meters) or more above
  the floor.
Guarding
l   Entrances to rooms and other guarded locations
    containing exposed live parts must be marked
    with conspicuous warning signs forbidding
    unqualified persons to enter.
l   Indoor electric wiring of more than 600 volts,
    which is open to unqualified persons, must be
    made with metal-enclosed equipment or enclosed
    in a vault or area controlled by a lock. In
    addition, equipment must be marked with
    appropriate caution signs.
Grounding
l   Grounding is another method of protecting you
    from electric shock.
l   However, it is normally a secondary protective
    measure.
l   The "ground" refers to a conductive body, usually
    the earth, and means a conductive connection,
    whether intentional or accidental, by which an
    electric circuit or equipment is connected to earth or
    the ground plane.
l   By "grounding" a tool or electrical system, a low-
    resistance path to the earth is intentionally created.
Grounding
l   When properly done, this path offers sufficiently
    low resistance and has sufficient current carrying
    capacity to prevent the buildup of voltages that
    may result in a personnel hazard.
l   This does not guarantee that no one will receive a
    shock, be injured, or be killed.
l   It will, however, substantially reduce the
    possibility of such accidents, especially when
    used in combination with other safety measures
    discussed in this presentation.
Grounding
l   There are two kinds of required grounds.
l   One of these is called the "service or system
    ground."
l   In this instance, one wire-called "the neutral
    conductor" or "grounded conductor" is grounded. In
    an ordinary low-voltage circuit, the white (or gray)
    wire is grounded at the generator or transformer and
    again at the service
    entrance of the building.
l   This type of ground is primarily designed to protect
    machines, tools, and insulation against damage.
Grounding
l   To offer enhanced protection, an additional ground,
    called the "equipment ground," must be
    furnished by providing another path from the tool or
    machine through which the current can flow to the
    ground.
l   This additional ground safeguards the electric
    equipment operator in the event that a malfunction
    causes any metal on the tool to become accidentally
    energized.
l   The resulting heavy surge of current will then
    activate the circuit protection devices and open the
    circuit.
Circuit Protection Devices
EXTREMELY IMPORTANT
l Never remove a grounding device from
  any electrical source, tool, or equipment.
l Never remove the ground prong from an
  electrical cord or device of any kind.
l Never by-pass grounding or circuit breaker
  protection as any time.
l If you find any of the above have occurred,
  repair and / or report immediately.
Circuit Protection Devices
l Circuit protection devices are designed to
  automatically limit or shut off the flow of
  electricity in the event of a ground-fault,
  overload, or short circuit in the wiring
  system.
l Fuses, circuit breakers, and ground-fault
  circuit interrupters are three well-known
  examples of such devices
Circuit Protection Devices
l   Fuses and circuit-breakers are over-current
    devices that are placed in circuits to monitor the
    amount of current that the circuit will carry.
l   They automatically open or break the circuit
    when the amount of current flow becomes
    excessive and therefore unsafe.
l   Fuses are designed to melt when too much
    current flows through them.
l   Circuit breakers, on the other hand, are designed
    to trip open the circuit by electro-mechanical
    means.
Circuit Protection Devices
l Fuses and circuit breakers are intended
  primarily for the protection of conductors
  and equipment.
l They prevent over-heating of wires and
  components that might otherwise create
  hazards for operators.
l They also open the circuit under certain
  hazardous ground-fault conditions.
Circuit Protection Devices
l   The ground-fault circuit interrupter, or GFCI, is
    designed to shutoff electric power within as little as
    1/40 of a second.
l   It works by comparing the amount of current going
    to electric equipment against the amount of current
    returning from the equipment along the circuit
    conductors.
l   If the current difference exceeds 6 milliamperes, the
    GFCI interrupts the current quickly enough to
    prevent electrocution.
l   The GFCI is used in high-risk areas such as wet
    locations and construction sites.
Safe Work Practices
Employees and others working with electric
  equipment need to use safe work practices.
  These include:
l Deenergizing electric equipment before
  inspecting or making repairs
l Using electric tools that are in good repair;
  using good judgment when working
  near energized lines
l Using appropriate protective equipment
Overhead Lines
l When mechanical equipment is being
  operated near over-head lines, employees
  standing on the ground may not contact the
  equipment unless it is located so that the
  required clearance cannot be violated even
  at the maximum reach of the equipment.
l These employees and their mechanical
  equipment must stay at least 10 feet (3.05
  meters) away from overhead power lines
Overhead Lines
l Employees, whose occupations require
  them to work directly with electricity, must
  use the personal protective equipment
  required for the jobs they perform.
l This equipment may consist of rubber
  insulating gloves, hoods, sleeves, matting,
  blankets, line hose, and industrial
  protective helmets.
Overhead Lines
Perhaps the single most successful defense against
  electrical accidents is the continuous exercising of
  good judgment or common sense.
l All employees should be thoroughly familiar with
  the safety procedures for their particular jobs. When
  work is performed on electrical equipment, for
  example, some basic procedures are:
l Have the equipment deenergized.
l Ensure that the equipment remains deenergized by
  using some type of lockout and tag procedure.
l Use insulating protective equipment.
l Keep a safe distance from energized parts.
Tool Inspections
l   To maximize his or her own safety, an employee
    should always use tools that work properly.
l   Tools must be inspected before use and, those
    found questionable, removed from service and
    properly tagged.
l   Tools and other equipment should be regularly
    maintained.
l   Inadequate maintenance can cause equipment to
    deteriorate, resulting in an unsafe condition.
Lock-out / Tag-out
Electrical Policy:
l Electrical panels must be manned at all times
  while open and or being worked on.
l With the exception of when work is being
  performed on or in electrical panels, and the
  electrical panels are manned, all electrical panels
  must be closed at all times.
l Prior to any work being performed on an
  electrical panel, the power to the panel must be
  turned off, and checked to make sure the power
  is off.
Lock-out / Tag-out
l   When a problem with a breaker occurs in an
    electrical panel, make sure the breaker is in the
    off position, place electrical tape (not other tape
    is allowed), over the breaker in such a manner so
    -as-to- not allow the breaker to be turned on
    without removal of the tape.
l   Close the panel box, lock the panel cover if that
    feature is available, place a sign on the panel
    door noting the problem, the breaker number,
    and clearly indicate that the panel box is not to
    be opened by anyone but authorized and
    qualified repair personnel.
Lock-out / Tag-out
l   Be sure the sign is attached to the cover in such a
    manner that it cannot fall off and must be
    physically removed. Attach the electrical lock-
    out tag to the panel cover in addition to the sign.
l   Unless you are the qualified district electrician,
    this lock-out must not be removed or tampered
    with.
l   Lock any additional doors to the equipment, i.e.
    vault room, and place sign on the door indicating
    “No Admittance – Electrical Work in progress –
    Danger”
Lock-out / Tag-out
l   In any electrical panel or breaker problem, report
    the problem to the site administrator, the custodial
    staff on all shifts, and the maintenance department.
l   In the case of a non-emergency, a standard on-line
    work order can be used to notify the maintenance
    department.
l   In the case of an emergency or urgent problem, call
    the maintenance department director for assistance
    and notification.
l   In all cases, follow-up with an on-line work order
    and document the problem with dates, times, and
    names.
    Lock-out / Tag-out
l   For faulty electrical with powered equipment,
    disconnect the power to the unit completely by turning
    off the breaker, and disconnecting the power cord if
    possible.
l   Place a sign in the same manner as the panel box
    above.
l   Also state the problem with the unit if know and any
    hazards such as potential electrical shock. Install the
    lock-out tag on the power ‘on’ switch and tape the
    switch in the off position with electrical tape.
l   Inform essential personnel and staff that use the
    equipment.
Lock-out / Tag-out
l The lock-out tag must include certain
  information. This includes the name of the
  person installing the tag.
l This tag can only be removed by the
  person originally installing it or a qualified
  electrician.
  Lock-out / Tag-out
The removed tag must be returned to the custodial office
  and saved in a file that contains an explanation of:
l The electrical problem
l How the problem was handled
l Who found the problem
l Who installed the lock-out tag
l Who reported the problem
l Who repaired the problem
l Who removed the lock-out tag
l This is best served in an on-going report on the
  problem. Documentation is everything.
Lock-out / Tag-out
What Documentation Does:
l Gives you a great resource to follow-up with.
l Provides compliance with regulations.
l Instills a sense of completion to a problem.
l Provides exacting steps that need to be done as
  long as the file is open, which lends to a greater
  safety factor to all staff and students.
l Provides information for future reference.
Lock-out / Tag-out
l   What Timely Reporting Does
l   Puts the people who need to fix the problem on
    notice. (Always ask for a return call or message
    to be sure your message got to the person you
    need.)
l   Provides you with the right information when
    asked.
l   Follows the proper regulations and guidelines.
l   Offers the repair people the opportunity to get to
    the problem quicker.
l   Allows the problem to be taken care of faster.
Lock-out / Tag-out
l The same procedure for electrical panels
  must be followed for all mechanical
  equipment, and machinery.
l Lock-out / Tag-out procedures include air
  handlers, floor cleaning machines,
  vehicles, fork lifts, and all other equipment
  that is either motorized, pinches, grabs,
  lifts, or moves or operates by a power
  source or under it’s own power.
Care of Cords & Equipment




l   Power tools and extension cords must be
    inspected each time they are used.
l   They must be taken out of service immediately
    upon discovery of worn or broken insulation.
Care of Cords & Equipment




l   Electrical panel boxes must be secured and
    problems reported immediately.
l   Junction boxes, outlets, receptacles, and switches
    must be closed and problems reported.
Care of Cords & Equipment




l   Electrical within five (5) feet of any water source
    must have GFCI protection. Covers must be in
    place at all times.
l   No flammable chemicals or liquids can be stored
    near electrical or in electrical service rooms.
Care of Cords & Equipment




l   Electric panels must be kept clear of any
    obstructions at all times.
l   Storage is not allowed in electrical vault or
    service panel rooms. Find another place for
    storage of materials, products, etc.
Care of Cords & Equipment




l   If the power went out, and you needed to get to
    the electrical panel box breakers in this room,
    what could happen to you?
l   Think about it carefully!
Summary
l   Electricity can be helpful and also dangerous, if
    not respected.
l   Safety procedures must be followed in order to
    protect everyone when dealing with electrical.
l   Lock-out / Tag-out procedures for electrical must
    be followed to help ensure safety and regulatory
    compliance.
l   Lock-out / Tag-out includes other equipment
    besides electrical and must have the same
    reporting and documentation.
Electric / Lock-out Tag-out
questionnaire
l   Please click here to fill out the Electrical /
    Lock-out – Tag-out presentation
    questionnaire.

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:0
posted:8/2/2013
language:English
pages:60
yolanda tiffany yolanda tiffany
About