The issues of electrical hazards at site and steps to prevent.
1. The issues of electrical
hazards at site
and steps to prevent
Group Member: Ng Huoy Miin
Hoi Wei Han
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2. Contents
1. Basic Concepts.
2. Hazard Recognition.
3. Effects of Electricity on Human Body.
4. Electrical Hazard Protection.
5. Work Practices.
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3. Basic Concepts
Electrical hazard :
● A dangerous condition where a worker could make an electrical
contact with energized equipment or a conductor from which the
person may sustain an injury from shock.
The law requires safe work practices
● Under Occupational Health and Safety Act
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4. Why should we be concerned about electrical hazards?
● Electricity has long been recognized as a serious workplace
hazard.
● Exposing the employees to electric shock, electrocution,
burns, fires, and explosions.
● In 1999, for example, 278 workers died from electrocutions at
work ,almost 5 percent of all on-the-job fatalities that year (the
Bureau of Labor Statistics.)
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5. Electricity accidents result from :
1. Unsafe equipment or installation.
1. Unsafe environment.
1. Unsafe work practices.
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6. What affects the flow of electricity?
● Electricity flows more easily through some materials than others.
❖ Conductors:
➔ The substances such as metals.
➔ Generally offer very little resistance to the flow of electric current .
➔ A common but perhaps overlooked conductor is the surface or subsurface
of the earth.
➔ Even air, normally an insulator, can also become a conductor,
as occurs during an arc or lightning stroke.
❖ Insulators:
➔ Glass, plastic, porcelain, clay, pottery, dry wood, and similar substances
➔ Generally slow or stop the flow of electricity
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7. HOW DOES WATER AFFECT THE FLOW OF
ELECTRICITY?
● Pure water is a poor conductor.
● But small amounts of impurities in water like salt, acid, solvents, or other
materials can turn water itself and substances that generally act as
insulators into conductors or better conductors.
● The same is true of human skin.
● Dry skin has a fairly high resistance to electric current.
● But when skin is moist or wet, it acts as a conductor.
● Working with electricity in a damp or wet environment .
● Needs to exercise extra caution to prevent electrical hazards.
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8. The following is a list of a common electrical hazards
found on construction sites:
❏ Improper grounding.
❏ Exposed electrical parts.
❏ Inadequate wiring.
❏ Damaged Insulation.
❏ Overloaded Circuits.
❏ Damaged tools and equipments.
❏ Wet conditions.
❏ Overhead Power Lines.
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9. Improper grounding
➔ Improper grounding of circuitry and equipment.
➔ Grounding of the metal components
of the electrical wiring system
such as conduit, ceiling light fixtures,
switch plates and so on at 0 volts.
➔ Plugging of metal components
into circuits which is grounded improperly
will cause it becomes energized.
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10. Improper Grounding
➔Unwanted voltage will not be safely eliminated.
➔Leakage of current to the ground.
➔Removal of the ground pin.
➔Removing of the ground pin
removes a vital safety feature.
➔Electroshocked will occur!
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11. Exposed electrical parts
➔ Exposed wires or terminals are hazardous.
➔ Report these conditions to your supervisor.
➔ The missing circuit breakers of the electrical panels.
➔ Using of panel which the wires are exposed.
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12. ➔ All the openings must be enclosed.
➔ The outer insulation of
electrical cords must be
in perfect condition.
➔ The incontact of temporary
lighting system with potential
shocks and broken bulbs.
Exposed electrical parts
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15. Overhead power lines.
➔Lack of concern of overhead power lines on construction site.
➔Storing of equipments or materials under overhead power lines.
➔Not maintaining a distance of at least 10’ between equipment and
tools and overhead power lines.
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16. Overhead power lines.
➔Shocks and electrocutions occur where physical barriers are not
in place to prevent contact with the wires.
➔Examples of equipment that can contact power lines : Crane,
Ladder, Scaffold, Backhoe and so on.
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17. Overhead power lines
➔Not maintaining a safe distances between scaffolding and overhead
power lines.
➔Overhead power lines are very dangerous.
➔Never attempt to contact an overhead power line.
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18. Damaged insulation.
➔ Inadequate or defective insulation is a hazard.
➔No prevention to conductors by insulation from contacting with
each other or us.
➔Repairing the damaged cord with tape.
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19. Damaged insulation.
➔Using tools or extension cords with damaged insulation.
➔Hanging of extension cords from nails or sharp objects.
➔Running the extension cords through doors or windows.
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21. Overloaded circuits.
➔ Using power strips or surge protectors on construction sites.
➔ Should use a 3-way extension with a ground fault circuit
interrupter (GFCI) instead.
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22. Wet conditions.
➔ Wet conditions are hazardous.
➔ Damaged insulation will increase the hazard
in wet location.
➔Using tools in wet locations.
➔Water increases the risk of electric shock.
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23. Damaged tools and equipment.
➔Double insulated tools are labeled.
➔It will be marked “Double Insulated”.
➔It will have the following symbol:
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24. Effects of Electricity on Human Body
Three major types of electrical injuries
1. Electrocution
1. Electrical Shock
1. Burns
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25. WHAT causes shocks?
Electricity travels in closed circuits normally through a conductor.
A person’s body sometimes
may become an efficient
conductor of electricity, and
mistakenly becomes part of the
electric circuit,
which can cause electric
shock.
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26. ➔ electricity flows between
parts of the body
➔ through the body to a
ground or the earth
Shocks occur when a
person's body completes the
current path with:
➔ both wires of an electric circuit
➔ one wire of an energized circuit
and the ground;
➔ a metal part that accidentally
becomes energized due,
- to a break in its insulation; or
- another " conductor" that is
carrying a current.
When a person receives a
shock,
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27. What is the Danger of Static Electricity?
1. when friction causes a high level of static
electricity to build up at a specific spot on an
object.
2. handling plastic pipes and materials
3. during normal operation of rubberized drive
4. machine belts found in many worksites.
● build up on the surface of an object under the right
conditions
- can discharge to a person, causing a shock.
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28. ✓static electricity can potentially discharge
✓when sufficient amounts of flammable or
combustible substances are located nearby and
cause an explosion.
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29. What effects do shocks have on the body?
An electric shock can result in anything
1. from a slight tingling sensation
2. to immediate cardiac arrest.
The severity depends on the following:
1. the amount of current flowing through the body,
2. the current's path through the body,
3. the length of time the body remains in the circuit
4. the current's frequency.
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30. Burns
Burns are the most common shock-related injury.
An electrical accident can result in :
Arc burn Thermal BurnElectrical Burn
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31. Electrical burns
1. are among the most serious burns
2. require immediate medical attention.
3. They occur when electric current flows through tissues or bone,
4. generating heat that causes tissue damage.
Arc or flash burns
1. result from high temperatures
2. caused by an electric arc or explosion near the body.
3. These burns should be treated promptly.
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32. Thermal contact burns
1. are caused when the skin touches hot surfaces of overheated electric
conductors, conduits, or other energized equipment.
2. can be caused when clothing catches on fire,
3. as may occur when an electric arc is produced.
In addition to burns and shock,electricity poses other dangers
1. arcs that result from short circuits can cause injury or start a fire.
2. Extremely high-energy arcs can damage equipment,
3. causing fragmented metal to fly in all directions.
4. Even low-energy arcs can cause violent explosions in atmospheres that
contain flammable gases, vapors, or combust
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33. What should you do if someone “freezes” to a live electrical contact?
Act quickly, and remember to protect yourself
as well from electrocution or shock.
Shut off the current
immediately
If this is not possible,
Use any non-conducting materials and safely
push or pull the person away from the contact
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37. What Protection does Insulation Provide?
Insulators :
1. Glass, mica, rubber, or plastic
used to coat metals and other
conductors
- prevent shock, fires, and short
circuits.
1. must be suitable for the voltage
used and conditions such as
temperature and other
environmental factors (eg.
moisture, oil, gasoline, corrosive
fumes, or other substances ) that
could cause the insulator to fail.
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38. Types of Insulation
● Basic Insulation
- The insulation applied to live parts to provide
basic protection against electric shock.
● Supplementary Insulation
- An independent insulation, applied in addition to
basic insulation
- to ensure protection against electric shock in the
event of failure of the basic insulation.
● Double Insulation
- Insulation comprising of both basic and
supplementary insulation.
● Reinforced Insulation
- A single insulation system applied to live parts,
- provides a degree of protection against electric
shock equivalent to double insulation.
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39. How do you identify different
types of insulation?
1. Before connecting electrical equipment to a power
source, it's a good idea to check the insulation for any
exposed wires for possible defects.
2. Insulation covering flexible cords such as extension
cords is particularly vulnerable to damage.
3. It also specifies that the insulation used should be
suitable for the voltage and conditions.
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41. What is Guarding?
Recommended locations are a
room, vault, or similar enclosure;
a balcony, gallery, or elevated
platform; a site elevated 8 feet
(2.44 meters) or more above the
floor. Sturdy, permanent screens
also can serve as effective guards.
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It involves locating or
enclosing electric equipment
tomake sure people don't
accidentally come into
contact with its live parts.
Effective guarding requires equipment
with exposed parts operating at 50 volts
or more to be placed where it is
accessible only to authorized people
qualified to work with it.
42. What Protection does It Offer?
Signs may contain the word "
Danger," " Warning," or " Caution,"
to alerts people to the hazard and
gives an instruction, such as "
Danger/High Voltage/Keep Out."
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Conspicuous signs must be posted at
the entrances to electrical rooms and
similarly guarded locations to alert
people to the electrical hazard and to
forbid entry to unauthorized people.
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Grounding
a tool or electrical system means
intentionally creating a low-
resistance path that connects to the
earth.
This prevents the buildup of
voltages that could cause an
electrical accident.
A secondary protective
measure that provides protect
against electric shock. It does not guarantee that you
won't get a shock, be injured or
killed by an electrical current.
However, it does substantially
reduce the risks.
45. What Protection does It Offer?
● to protect machines, tools, and insulation
against damage.
● One wire, called the " neutral" or " grounded"
conductor, is grounded.
● In an ordinary low-voltage circuit, the white or
gray wire is grounded at the generator or
transformer and at the building's service
entrance.
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● An equipment ground helps protect
the equipment operator.
● furnishes a second path for the current
to pass through from the tool or
machine to the ground.
● This additional ground safeguards the
operator if a malfunction causes the
tool's metal frame to become
energized.
● activate the circuit protection devices.
47. circuit protection devices
● Protects worker from overcurrent
● Short circuits by automatically shutting off the electricity
Well-known examples of these devices are
Fuses and
Circuit breakers
Ground-fault circuit
interrupters
Arc-fault circuit
interrupters
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48. Fuses and circuit breakers
How do they work:
1. open or break the circuit automatically
- when too much current flows through them.
1. When that happens
- fuses melt and circuit breakers trip the circuit open.
➢ to protect conductors and equipment.
➢ prevent wires and other components from overheating
➢ open the circuit when there is a risk of a ground fault.
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50. Ground-fault circuit interrupters
➔ are used in
➔ These devices interrupt the flow of electricity within as little as 1/40 of a second
- prevent electrocution.
➔ compare the amount of
current going into
electric equipment
the amount of
current returning
from it
Circuit conductors
Wet location Construction Site High Risk Area
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51. Ground-fault circuit interrupters
➔OSHA requires the use of GFCIs on all construction sites.
➔is a fast-acting circuit breaker.
➔It senses small imbalances in the circuit caused by
current leakage to ground.
➔ If the difference exceeds 5 milliamperes，
- the device automatically shuts off the electric power.
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52. Arc-fault circuit interrupters
➔ Design to distinguish between normal and dangerous arcing conditions
➔ Trips during an arc fault-(power discharge between two conductors)
- Avoiding the high current that cause fires and sparking
➔ Provide protection from the effects of arc-faults
- By recognizing characteristics unique
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54. Personal Protective equipment
Foot protection
1. Footwear will be marked “Electric Hazards”
- If it’s approved for electrical work
1. Footwear must be kept dry
- even if it is marked “Electric Hazards”
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55. Head ProtectioN
1. Hard hat(insulated non-conductive)
2.Class B &E
3.Always wear your hat
4.Do not store anything in the top of your hat
while wearing it
Hand ProtectioN
1. Rubber insulating gloves
2. Classified by the level of voltage and protection
3. Should always be worn over rubber insulating
gloves
4. To provide the mechanical protection needed
against cuts, abrasions, and punctures. 55
56. Personal protective equipment
1. Use, store and maintain in a safe, reliable condition
1. Wear nonconductive head protection
- Due to not contact with exposed energized parts
1. Wear protective equipment for the face and eyes
- From electric arcs or flashes ,flying objects
- Resulting from electrical explosion
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57. Electrical Personal protective equipment with any of the
following defects may not be used:
● An embedded foreign object
● Any other defect that damages the
insulating properties
● Holes, tears, punctures, or
cuts are presents
● Texture changes
- Swelling, softening, hardening, or
becoming sticky or inelastic
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58. Role of tools
Help protect workers against electric hazards.
1. It's important to maintain tools regularly
- prevents them from becoming dangerous.
Check each tool before using it.
1. If you find a defect, immediately remove it from service
2. tag it so no one will use it until it has been repaired or replaced.
Handle energized conductors
1. check to make sure it is designed and constructed
- withstand the voltages and stresses to which it has been exposed.
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60. Basic procedures to follow
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1.Deenergize
The Equipment
2.Lockout &
Tag
Procedures
3.Maintain a
safe distance
from energized
parts.
Ensure that the equipment
remains deenergized use
insulating protective
equipment
61. Lock out/ Tag-out
1. Workers must ensure electricity is off and “locked-out”
- before work is performed.
1. The switch must be tagged.
1. The tag lets others know why the switch is off.
1. Locks and tags are warning signs.
1. Must be trained in lock-out/ tag-out procedure.
Protect you from the dangers of
● the accidental
● unexpected startup of electrical equipment .
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62. Only qualified electricians
- who have been trained in safe lockout procedures
- To maintain electrical equipment.
Each key should fit just one lock.
- one individual lock and key should be issued to each maintenance
worker
Only authorized worker
- Lockout and tag the equipment.
- Get permitted to remove it.
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Lock out/ Tag-out
63. Special training of employees need
● Familiar with the safety procedures for their particular jobs.
● Good judgment and common sense
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So what causes shock ? Basically electricity travels in closed circuits, usually through a conductor such as copper, aluminum, gold and silver. However sometimes a person’s body sometimes may become an efficient conductor of electricity, and becomes part of the electric circuit by mistake.
So when does shock occur? Shock occurs when a person’s body completes the current path with both wires of the electricity.
Eg. a person reaches for a door knob or other metal object on a cold, relatively dry day and receives a shock.
boards, poles, or sticks made of wood or
help stop or reduce the flow of electrical current.
