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Transcript
1
Electrical Safety
2
Electricity - The Dangers
• About 5 workers are
electrocuted every week
• Causes 12% of young
worker workplace deaths
• Takes very little
electricity to cause harm
3
Electrical Terms
• Current -- electrical movement (measured in amps)
• Circuit -- complete path of the current.
Includes electricity source, a conductor, and the output
device or load (such as a lamp, tool, or heater)
• Resistance -- restriction to electrical flow
• Conductors – substances, like metals, with little
resistance to electricity that allow electricity to flow
• Grounding – a conductive connection to the earth
which acts as a protective measure
• Insulators -- substances with high resistance to
electricity like glass, porcelain, plastic, and dry wood
that prevent electricity from getting to unwanted areas
4
Electrical Injuries
There are four main types of electrical injuries:
• Direct:
Electrocution or death due to electrical shock
Electrical shock
Burns
• Indirect - Falls
5
Electrical Shock
Received when current passes
through the body
Severity of the shock depends on:
1. Path
2. Amount of current
3. Length of time
•
LOW VOLTAGE DOES NOT
MEAN LOW HAZARD
6
Effects of Electric Current on the
Human Body
• 1 mA (milliamp) Barely perceptible
• 16 mA Max “let go” current
• 20 mA Paralysis of respiratory muscles
• 100 mA Ventricular fibrillation
• 2 Amps Cardiac standstill and internal organ damage
• 15/20 Amps Fuse/breaker opens circuit
* mA = milliampere = 1/1,000 of an ampere
7
Dangers of Electrical Shock
Currents more than 75 mA
can cause a rapid,
ineffective heartbeat --
death will occur in a few
minutes unless a
defibrillator is used
Defibrillator in use
75 mA is not much current – a small power drill uses 30 times
as much
8
9
Ground-Fault Circuit Interrupter
• This device protects you from
dangerous shock
• The GFCI detects a difference in
current between the positive and
neutral wires
(This could happen when electrical
equipment is not working correctly,
causing current “leakage” – known as
a ground fault.)
• If a ground fault is detected, the GFCI
can shut off electricity flow in as little
as 1/40 of a second, protecting you
from a dangerous shock
10
Burns
• Most common shock-related
injury
• Typically occurs on hands
• Very serious injury that
needs immediate attention
11
Falls
• Electric shock can also
cause indirect injuries
• Workers in elevated
locations who experience a
shock may fall, resulting in
serious injury or death
12
Electrical Hazards and How to
Control Them
Why?
13
Electrical accidents are caused
by a combination of three factors:
1. Unsafe equipment and/or
installation,
2. Workplaces made unsafe by
the environment, and
3. Unsafe work practices
14
15
16
Grounding
Grounding creates a lowresistance path from a tool
to the earth to disperse
unwanted current.
17
Tools -Preventing Electrical Hazards
• Inspect tools before use
• Use the right tool
correctly
• Use double insulated
tools
• Others?
Double Insulated marking
18
Exposed Electrical Parts
19
Control – Isolate Electrical Parts
• Use guards or barriers
• Replace covers
What about 50 volts or more?
20
Control – Close Openings
• Junction boxes, pull
boxes and fittings must
have approved covers
• Unused openings in
cabinets, boxes and
fittings must be closed
(no missing knockouts)
Photo shows violations
of these two requirements
21
Overhead Power Lines
Equipment that can
contact power lines?
What is the minimum
distance?
22
23
Cords & Wires
Cords can be damaged by:
Aging
Door or window edges
Staples or fastenings
Activity in the area
Remove cords by pulling on the plugs, not the cords
24
Clues that Electrical Hazards Exist
• Tripped circuit breakers or
blown fuses
• Warm tools, wires, cords,
connections, or junction
boxes
• GFCI that shuts off a circuit
• Worn or frayed insulation
25
Safety-Related Work Practices
Avoid Wet
Conditions!
26
No Bare Ground on Temp Circuits
Romex
No Ground
No
Strain Relief
Temp Cord
27
GFCI Needed
Exposed Elec. Conductor
Splices
1910.303(c)
28
No Ground
1910.304(f)(4)
29
30
You Find the Standard
31
1910.305(g)(2)(iii)
32
Flex Cords Protected From Damage
1910.305(a)(2)(iii)(g)
33
Too Many Conductors
Per Conduit
1910.305(b)(2)
34
Improper Use of Junction Box
1910.305(g)(1)
Flex Cord Protection
1910.305(a)(2)(iii)(G)
35
Flex Cords-Continuous
Length
1910.305(g)(2)(ii)
36
Exposed Elec. Conductor
1910.303(g)(2)(i)
Strain Relief
1910.305(g)(2)(iii)
37
50v or more shall be guarded
1910.303(g)(2)(i)
38
Equip. Free From Recognized Hazards
1910.303(b)(1)
Metal Shavings
39
40
Machine Guarding???
Exposed Elec. Parts
1910.303(g)(2)(i)
41
(g)(2)(No Strain Relief
1910.305(g)(2)(iii)
42
Exposed Thermostat
1910.303(g)(2)(i)
43
Summary
Electrical equipment must be:
 Listed and labeled
 Free from hazards
 Used in the proper manner
If you use electrical tools you must be:
 Protected from electrical shock
 Provided necessary safety
equipment
44
The movement of electricity
measured in amps is called
A.Voltage
B.Current
C.Resistance
45
A conductive connection to the
earth which acts as a protective
measure is called.
A. Resistance
B. Current
C.Grounding
D.Insulator’’
46
The most common electrical
related injury is
A. Falls
B. Electrical burns
C. Electrocution
47
How many amps can cause
your heart to go into
ventricular fibrillation.
A. 75 mA
B. 15 Amps
C. 20 Amps
48
At what voltage is an
electrical conductor
required to be protected
against contact?
A. 50 volts
B. 120 volts
C. 30 volts
49
Credits
• Some photos from safteng.net used with permission.
• Disclaimer: Some of the photos or videos used in this
presentation are from numerous sources, most of
which are not identifiable. We do not claim any
ownership of these videos. Not do we have any
association with the owners. And only use them to
illustrate the concepts of our safety programs. If
copyright owners wish to have their pictures or videos
removed from this presentation at any time please,
just let us know.
50