Transcript Electrical Safety for Construction

Electrical Safety
for Construction
Electrical regulations
 Subpart
K of 29 CFR 1926
1a
Electrical regulations
 Part
I - Safety requirements for
installing/using equipment
• approval of electrical components
• examination, installation, use of
electrical equipment
• guarding of electrical equipment
• overcurrent protection
• grounding of equipment
1b
Electrical regulations
 Part
II - Safety-related work
practices
• protection of employees
• passageways and open spaces
• lockout/tagging of circuits
1c
Electrical regulations
 Part
III - Safety-related
maintenance and environmental
considerations
• protection of wiring components
• environmental deterioration of
equipment
1d
Electrical regulations
 Part
IV - Safety requirements for
special equipment
• batteries and battery charging
• PPE
• emergency eyewash stations
1e
How electricity works
 Current
flows from a generating
source through conductors, to a
load
 Complete
circuits are
needed
2a
How electricity works
 Normal
route is through
conductors
 Shock
occurs
when the body
becomes a
part of the
electrical
circuit
2b
Ohm’s Law
E
I R
I = Current (amperes)
E = Voltage (volts)
R = Resistance (ohms)
Human Resistance
Body Area
Dry Skin
Wet Skin
Internal Organs
Ear to Ear
OHMS
600,000
1,000
400-600
100
Fatalities at 50 Volts
50 Volts
1,000 OHM = .05 amps (50 mA)
50 Volts
100 OHM
= .5 amps (500 mA)
Electric shock
 Occurs
when current enters the
body at one point and exits at
another
 Shock
occurs when you touch:
• both wires of an electric circuit;
• one wire of an energized circuit
and ground; or
• a metallic part that is “hot”
3a
Electric shock
 Severity
the:
of shock depends on
• amount of current
• path of the current
• amount of time
exposed
3b
Electric shock
 Effects
range from a tingle, to
cardiac arrest, severe
burns, and probable
death
 Typical
household
current of 15 amps
can cause death
3c
Electricity’s
Physiological Effect
00.001 amps
 00.015 amps
 00.020 amps
 00.100
 01.200
 15.000







Barely felt
“let go” threshold
Muscular paralysis
Ventricular
fibrillation
100 Watt light bulb
Common household
fuse
Effects of Current
1-8 mA = shock, not painful
8-15 mA = Pain
15-20 mA = Muscle contraction
20-100 mA = Severe pain & paralysis
of breathing muscles
100-1000 mA = Ventricular fibrillation
(Usually cause death)
> 1,000 mA = Heart stops
Grounding
 Protects
shock
you from electrical
 Safeguards
against fire
 Protects
electrical equipment
from damage
4a
Grounding
 Two
types of grounding include:
• Service or system
ground
• Equipment ground
4b
Circuit protective
devices
 At
construction sites, the most
common electrical hazard is the
ground fault electrical shock
 OSHA
requires either:
• Ground fault circuit interrupters
(GFCIs); or
• Assured Grounding Conductor
Program
5a
Circuit protective
devices
 Circuit
protective devices
include:
• fuses and circuit breakers protect conductors and equipment
• GFCIs - limit or shut off current
flow
5b
Ground fault circuit
interrupters
A
fast-acting circuit breaker
that senses small imbalances in
the circuit caused by current
leakage to ground
6a
1 AMP
COIL
1 AMP
PLUG
1 AMP
HOT
NEUTRAL
LOAD
1000 mA
COIL
995 mA
PLUG
5 mA
HOT
NEUTRAL
GROUND
LOAD
1000 mA
COIL
995 mA
1000 mA
PLUG
HOT
5 mA
NEUTRAL
1 AMP
GROUND
LOAD
Polarity
Assured Equipment
Grounding Conductor
program
 If
GFCIs are not used,
employers must have a
scheduled and recorded
Assured Equipment Grounding
Conductor program
7a
Assured Equipment
Grounding Conductor
program
 The
AEGC program is an
inspection program covering:
• all cord sets
• receptacles that are not part of a
permanent wiring structure
• equipment connected by cord and
plug
7b
Assured Equipment
Grounding Conductor
program
 Equipment
must be visually
inspected for damage/defects
before each day’s use
7c
Assured Equipment
Grounding Conductor
program
 Tests
must be performed:
• before the first use of new
equipment
• after suspected damage to
equipment
• at three month intervals
– continuity test
– grounding conductor test
7d
Lockout/Tagout
 Electrical
equipment
deactivated for repair must be
locked out and tagged at the
point where it can be energized
 Protects
maintenance workers
 Warns
others that work is being
performed
8a
Lockout/Tagout
 Only
the person who
locked/tagged the equipment
can turn it back on
 Before
equipment is energized,
a qualified person must conduct
tests and visual inspections
8b
Lockout/Tagout
 Each
lock/tag must be removed
by the person who applied it
8c
Lockout/Tagout
 If
the employee is absent, the
lock/tag can be removed by a
qualified person if:
• the employee who applied the lock
has left the premises
• it is visually determined that all
employees are clear of the
circuits/equipment
8d
Guarding requirements
 Any
live parts of electrical
equipment operating at 50 volts
or more must be guarded to
avoid accidental contact
9a
Guarding requirements
 Entrances
to areas with live
electrical parts must be marked
with warning signs
 Signs
should
forbid entrance
except by
qualified persons
9b
Insulation
 Check
equipment daily for
insulation breakdown
 Check
for:
• exposed wires
• broken wires
• scuffed insulation on extension
cords
10a
Insulation
 Use
non-conducting mats,
shields, or barriers when
necessary
 Use
nonconducting
coatings on
hand tools
10b
Personal protective
equipment
 Employers
must provide
electrical protective equipment
to employees
who work near
electrical
hazards
11a
Personal protective
equipment
 Use
appropriate equipment for
the hazards, including:
• helmets
• eye and face
protection
• gloves and
sleeves
• aprons
• protective footwear
11b