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CE337 Construction safety management > TOPIC 4: Electrical Safety > Flashcards

TOPIC 4: Electrical Safety Flashcards

1
Q
  • The flow of electrical power or charge.
  • Causes 12% of young worker workplace deaths
  • About 5 workers are electrocuted every week.
A

Electricity

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2
Q

electrical movement (measured in amps)

A

Current

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3
Q

restriction to electrical flow

A

Resistance

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4
Q

a conductive connection to the earth which acts as a protective measure

A

Grounding

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5
Q

substances, like metals, with little resistance to electricity that alow electricity to flow

A

Conductors

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6
Q

substances with high resistance to electricity like glass, porcelain, plastic, and dry wood that **prevent electricity from getting to unwanted areas **

A

Insulators

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7
Q

measure of electrical force

A

Voltage

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8
Q

There are two classifications of electrical injuries:

A

direct
indirect

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9
Q

electrical injuries: direct

A
  • Electrocution due to electrical shock
  • Electrical shock
  • Burns
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10
Q

electrical injuries: indirect

A
  • Falls
  • Cardiac arrest
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11
Q

An () is received when electrical current passes through the body.

An () wil occur if a part of the body completes an electrical circuit by:
* Touching a live wire and an electrical ground *
* Static pressure build up within the body and touching something with a different pressure (example: Metal, wood, person)

A

electrical shock

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12
Q

SHOCK SEVERITY:
The severity of the shock depends on:

A
  • Path of current through the body
  • Amount of current flowing through the body (amps)
  • Duration of the shocking current through the body
  • Low voltage does not mean low hazard.
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13
Q

Effects of Electric Current in the Human Body

Below 1 miliampere

A

Generaly not perceptible

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14
Q

Effects of Electric Current in the Human Body

1 miliampere

A

Faint tingle

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15
Q

Effects of Electric Current in the Human Body

5 miliamperes

A

Slight shock felt; not painful but disturbing. Average individual
can let go. Strong involuntary reactions can lead to other
injuries.

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16
Q

Effects of Electric Current in the Human Body

6-25 miliamperes

A

Painful shock, loss of muscular control

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17
Q

Effects of Electric Current in the Human Body

9-30 miliamperes

A

The freezing current or “let-go” range. Individual cannot let go, but can be thrown away from the circuit if extensor muscles are stimulated.

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18
Q

Effects of Electric Current in the Human Body

50-150 miliamperes

A

Extreme pain, respiratory arrest, severe muscular contractions. Death is possible. 1,000–4,300 miliamperes

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19
Q

Effects of Electric Current in the Human Body

1000-4300
miliamperes

A

Rhythmic pumping action of the heart ceases. Muscular contraction and nerve damage occur; death likely. 10,000 miliamperes

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20
Q

Effects of Electric Current in the Human Body

10000 miliamperes

A

Cardiac arrest, severe burns; death probable

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21
Q
  • Among the most serious burns and require immediate medical attention.
  • Occur when electric current flows through tissues or bone, generating heat that causes tissue damage.
A

Electrical Burns

22
Q

Result from high temperatures
and pressure waves,
respectively, caused by an
** electric arc or explosion near
the body.** These burns should be
treated promptly.

A

ARC FLASH & ARC BLAST BURNS

23
Q

Caused when the skin touches
hot surfaces of overheated
electric conductors, conduits,
or other energized equipment.

A

THERMAL CONTACT BURNS

24
Q
  • When a person receives an electrical shock, sometimes the electrical stimulation causes the muscles to contract. This “freezing” effect makes the person unable to puLl free of the circuit.
  • It increases the length of exposure to electricity and because the current causes blisters, which reduce the body’s resistance and increases the current.
A

“Freezing” during shock

25
Q

In addition to muscle contractions that cause “freezing,” electrical shocks also can cause involuntary muscle reactions

These reactions can result in a wide range of other injuries from FALLS , including: (4)

A
  • bruises
  • wounds
  • bone fractures
  • death
26
Q

Protection Against Electrical Hazards

Electrical accidents are caused by a combination of unsafe
factors including: (3)

A
  • Unsafe equipment and/or instalation
  • Unsafe environment
  • Unsafe work practices
27
Q

Protection Against Electrical Hazards (4)

A
  1. Insulation
  2. Guarding
  3. Grounding
  4. Circuit Protection Devices
28
Q

Used to coat metals and other conductors help stop or reduce the flow of electrical current. This helps prevent shock, fires, and short circuits. (e.g. glass,
mica, rubber, or plastic)

A

Insulation

29
Q

Insulaion must be suitable for the voltage used and conditions (3)

A
  • temperature
  • moisture
  • gasoline, corrosive fumes, or other substances that could cause the insulator to fail
30
Q

Insulation
Color coding

A

green/ green with yellow stripes - Equipment grounding conductors

white/ grey - Insulation covering grounded conductors

black/ red - Ungrounded Conductors (Hot Wires)

31
Q

These are wires specificaly designed to connect the metal parts of electrical equipment to the ground. Their primary purpose is to prevent electric shock by ensuring that any fault current is safely
directed to the ground, thereby protecting users and equipment.

A

Equipment grounding conductors

32
Q

These are typicaly neutral wires that return current to the power source. They are connected to the ground at the main service panel, which helps to stabilize the electrical system and provide a path for fault currents.

A

Insulation covering grounded conductors

33
Q

Hot wires are the conductors that carry current from the power source to a device or appliance.
These wires are typicaly energized, meaning they carry live electricity, and can cause electric shock if touched.

A

Ungrounded Conductors (HotWires)

34
Q

() involves locating or enclosing electric equipment to make sure
people don’t accidentaly come into contact with its live parts.

Effective () 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.

A

Guarding

35
Q

Recommended Locations:
* room, vault, or similar enclosure
* a balcony, galery, or elevated platform; or a site elevated 8 feet (2.44 meters) or more above the floor
* Sturdy, permanent screens also can serve as effective guard

A

guarding

36
Q

guarding

Signages
Conspicuous signs must be posted at the entrances to electrical rooms and similarly guarded locations to alert people to the electrical hazard and to ()

e.g. “Danger”, “Warning”, “Caution”, “High Voltage Keep Out”

A

forbid entry to unauthorized people.

37
Q

() a tool or electrical system means
intentionaly creating a low-resistance path that connects to the earth. This prevents the buildup of
voltages that could cause an electrical accident.
() is normaly a secondary protective
measure to protect against electric shock. It does not guarantee that you won’t get a shock or be injured or kiled by an electrical current.

A

Grounding

38
Q

() limit or stop the flow of current automaticaly in the event of a ground fault, overload, or short circuit in the wiring system.

A

Circuit Protection Devices

39
Q

** Open or break the circuit automaticaly when too much current flows through them.** When that happens, fuses melt and circuit breakers trip the circuit open.

Philippines: 15-20 amps, 220 volts

A

Fuses and Circuit Breakers

40
Q

A fast acting circuit breaker designed to shut off electric power in the event of a ground fault within as little as 1/40 of a second. It works by comparing the amount of current going to and returning from equipment along the circuit conductors. When the amount going differs from the amount returning by approximately 5 miliamperes, the GFCI interrupts the current.

A

Ground-fault circuit interrupters (GCFI)

41
Q

An () is an unintentional electrical discharge or spark between two conductive surfaces, often caused
by damaged, corroded, or loose wiring, which can lead to high temperatures and potentialy start a fire.

() differ from standard current flows and are detected by Arc Fault Circuit Interrupters (AFCIs). These
devices monitor the circuit for irregular current patterns, characteristic of arc faults, such as sudden fluctuations or sparking sounds, and disconnect power if a fault is detected, preventing overheating and fires.

A

Arc-fault Devices

42
Q

Electrical accidents are largely preventable through safe work practices.
Examples of these practices include the folowing: (4)

A
  • deenergizing electric equipment before inspection or repair
  • keeping electric tools properly maintained
  • exercising caution when working near energized lines,
  • using appropriate protective equipment.
43
Q

An () is an electric power transmission line suspended by towers or poles.
Since most of the insulation is
provided by air, overhead power
lines are generaly the lowest
cost method of transmission for
large quantities of electric
power.

A

overhead power line

44
Q

Protection Against Overhead Power Lines

  • Ensure that you maintain a safe distance to the lines and, for very high voltage lines, ground any equipment such as cranes that can become energized.
  • Ensure that the lines have been deenergized and grounded by the owner or operator of the lines.
  • Employees unqualified to work with electricity, as well as mechanical equipment, should remain at least () away from overhead power lines. If the voltage is more than (), the clearance increases by 4 inches (10 centimeters) for each additional ()
A

10 feet (3.05 meters)
50,000 volts
10,000 volts

45
Q

Personal Protective Equipment

Employees who work directly with electricity should use the personal protective equipment required for the jobs they perform. (7)

A
  • rubber insulating gloves
  • hoods
  • sleeves
  • matting
  • blankets
  • line hose
  • industrial protective helmets
46
Q

Training for Employees

All employees should be trained to be thoroughly familiar with the safety procedures for their particular jobs. Moreover, good judgment and
common sense are integral to preventing electrical accidents.

Basic procedures: (4)

A
  • deenergize the equipment,
  • use lockout and tag procedures to ensure that the equipment remains deenergized
  • use insulating protective equipment
  • maintain a safe distance from energized parts
47
Q

Training for Employees

Electrical safe work practices training is required for anyone working near energized, or potentialy energized electrical circuits of fifty (50) or more volts to ground to become ()

Training should also be provided to employees who are not exposed to
energized parts, but operate electrical equipment

A

Qualified Electrical Worker

48
Q

Mandatory () (or refresher) training is required a minimum of every
three (3) years or when conditions change.

A

Retraining

49
Q

Sample checklist for basic electrical safety?

Inspect Cords and Plugs
* Check extension cords and plugs daily. Do not use, and discard cords and plugs if they are worn or damaged.
* Have any extension cord that feels more than comfortably warm checked by an electrician.

Eliminate Octopus Connections
* Do not plug several items into one outlet.
* Pul the plug, not the cord.
* Do not disconnect power supply by puling or jerking the cord from the outlet. Puling the cord causes wear and may cause a shock

A
  • Inspect Cords and Plugs
  • Eliminate Octopus Connections
50
Q

Sample checklist for basic electrical safety?

Never Break OFF the Third Prong on a Plug
* Replace broken 3-prong plugs and make sure the third prong is properly grounded.

Never Use Extension Cords as Permanent Wiring
* Use extension cords only to temporarily supply power to an area that doesnot have a power outlet.
* Keep extension cords away from heat, water and oil.
* Do not alow vehicles to pass over unprotected extension cords. Extension cords should be put in protective wireway, conduit, pipe or protected by placing planks alongside them.

A
  • Never Break OFF the Third Prong on a Plug
  • Never Use Extension Cords as Permanent Wiring

CE337 Construction safety management (8 decks)

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