Download Electrical Hazards

ELECTRICAL HAZARDS
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ELECTRICAL HAZARDS
• SHOCK. Electric shock occurs when the
human body becomes part of the path
through which current flows.
• The direct result can be electrocution.
• The indirect result can be injury
resulting from a fall or movement into
machinery because of a shock
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ELECTRICAL HAZARDS
• BURNS. Burns can result when a person
touches electrical wiring or equipment that is
energized.
• ARC-BLAST. Arc-blasts occur from highamperage currents arcing through the air.
This can be caused by accidental contact with
energized components or equipment failure.
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ELECTRICAL HAZARDS
• ARC-BLAST. The three primary
hazards associated with an arc-blast are:
• Thermal radiation.
• Pressure Wave.
• Projectiles.
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ELECTRICAL HAZARDS
• EXPLOSIONS. Explosions occur when
electricity provides a source of ignition
for an explosive mixture in the
atmosphere.
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ELECTRICAL HAZARDS
• FIRES. Electricity is one of the most
common causes of fires both in the home
and in the workplace. Defective or
misused electrical equipment is a major
cause.
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EFFECTS ON THE
HUMAN BODY
Depends on:
Current and Voltage
Resistance
Path through body
Duration of shock
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Effects of AC Electricity
• More than 3 mA- Painful shock- cause
indirect accident
• More than 10 mA- Muscle contraction –
“No Let Go” danger
• More than 30 mA- Lung paralysis, usually
temporary
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Effects of AC Electricity
• More than 50 mA- Ventricular fibrillation,
usually fatal
• 100 mA to 4 A- Certain ventricular
fibrillation, fatal
• Over 4 A- Heart paralysis, severe burns
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1910.303(b)
Examination of equipment
• Electrical equipment must be free of
recognized hazards that are likely to cause
death or serious physical harm to
employees.
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1910.303(b)
Examination of equipment
Safety of equipment must be determined using
the following considerations:
Suitability for installation and use
Mechanical strength and durability
Electrical insulation
Heating effects under conditions of use
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1910.303(b)
Examination of equipment
Safety of equipment must be determined using
the following considerations:
• Arcing effects
• Classification by type, size, voltage, current
capacity and specific use
• Other factors
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1910.303(c)
Splices
Conductors must be spliced with:
Splicing devices suitable for the use
Brazing, welding or soldering (with a
mechanically and electrically secure joint
before soldering & then soldered)
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1910.303(c)
Splices
All splices and joints and the free ends of
conductors must be covered with an
insulation equivalent to that of the
conductors or with an insulating device
suitable for the purpose.
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1910.303(e)
Marking
Electrical equipment may not be used
unless the manufacturer’s name, trademark
or other identification is on the equipment.
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1910.303(e)
Marking
• Other markings must be provided giving
voltage, current, wattage, or other ratings as
necessary.
• Markings must be durable enough to
withstand the environment.
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1910.303(f)
Identification
Each disconnecting means must be legibly
marked to indicate its purpose, unless
located and arranged so that its purpose is
evident.
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1910.303(f)
Identification
These markings must be durable enough to
withstand their environment.
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1910.303(g)(1)
600 volts, nominal, or less
Working space about electrical equipment.
This section refers to a person qualified to
work on electrical equipment, usually an
electrician.
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1910.303(g)(1)(i)
Working clearances
• Except as required or permitted, the
dimension of the working space in front of
live parts (operating at 600 volts or less)
and likely to require examination,
adjustment, servicing, or maintenance must
be at least three feet.(See table S-1).
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1910.303(g)(1)(i)
Working clearances
• The workspace in front of electrical
equipment must not be less than 30 inches
wide.
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1910.303(g)(1)(ii)
Working clearances
• Working spaces required for this standard
may not be used for storage.
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1910.303(g)(2)
600 Volts or less
Guarding of live parts operating at 50 Volts or
more.
The purpose of this requirement is to
protect any person who is in the vicinity of
electrical equipment against accidental
contact, not just electricians.
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1910.303(g)(2)
600 Volts or less
Guarding of live parts.
(i) Guard against accidental contact by:
(A) Location accessible only to qualified
persons
(B) Permanent, substantial partitions or
screens
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1910.303(g)(2)
600 Volts or less
Guarding of live parts.
(i) Guard against accidental contact by:
(C) Location on a suitable elevated balcony or
platform
(D) Elevation of 8 feet or more above the
floor or other working surface
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1910.303(g)(2)
600 Volts or less
Guardian of live parts.
In locations where electrical equipment
would be exposed to physical damage,
enclosures or guardians must be so arranged
and of such strength as to prevent such
damage.
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1910.303(h)(3)
Over 600 Volts
Workspace around equipment.
Sufficient space must be provided and
maintained around electrical equipment to
permit ready and safe operation and
maintenance.
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1910.303(h)(3)(ii)
Illumination (Over 600 Volts)
• Adequate illumination must be provided for
all working spaces around electrical
equipment.
• The lights and switches must be arranged so
that persons making repairs or turning on
lights wont contact live ports.
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1910.303(h)(3)(
Elevation of unguarded live pa
• Unguarded live parts above working space
must be maintained at elevations not less
than specified in Table S-3.
• The minimum is 8 feet.
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1910.30
Grounded and grounding condu
(1) Identification of conductors.
The grounded conductor is an energized
circuit conductor that is connected to earth
through the system ground. It is
commonly referred to as the neutral.
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1910.304(a
Grounded and grounding conductors
(1) Identification of conductors.
The equipment grounding conductor is not an
energized conductor under normal
conditions. It is energized only if there is a
leak or fault in the normal current path and
directs current back to the source.
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1910.304
Grounded and grounding conduc
(1) Identification of conductors.
The National Electric Code requires that:
The grounded conductor (neutral) be
continuous white or natural gray.
The equipment grounding conductor be
green, green with yellow stripes or bare.
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1910.304(a)(2)
Polarity of connections
No grounded conductor may be attached to
any terminal or lead so as to reverse
designated polarity.
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1910.304(a)(2)
Polarity of connections
Reversed polarity is a condition when neutral
conductor is incorrectly connected to the
“hot” terminal of a plug, receptacle or other
connector.
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1910.304(e)
Overcurrent protection
(1) 600 volts or less.
(i) Conductors and equipment must be
protected from overcurrent.
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1910.304(e)
Overcurrent protection
(1) 600 volts or less.
Fuses and circuit breakers are designed to
disconnect a circuit from its supply source
when a maximum allowable heat is
reached.
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1910.304(e)
Overcurrent protection
(1) 600 volts or less
(iv) Location. Overcurrent devices must be
readily accessible but not located where
they will be exposed to physical damage
or in the vicinity of easily ignitable
material.
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1910.304(f)
Grounding
(4) Grounding path.
The path to ground from circuits, equipment,
and enclosures must be permanent and
continuous
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1910.304(f)
Grounding
(5)(v) Tools likely to be used in wet and
conductive locations need not be grounded
if supplied through an isolating transformer
with an ungrounded secondary of not over
50 volts.
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1910.304(f)
Grounding
(5)(v) Listed or labeled portable tools and
appliances protected by an approved system
of double insulation, or its equivalent, need
not be grounded. However, they must be
distinctively marked.
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Electrical Tools
Double Insulated
•
•
•
•
They work with GFCIs
Casing must be labeled
Tool must be inspected
Extension cord must be three-prong
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1910.305
(a)Wiring methods.
(1) General requirements.
(ii) No wiring system of any type shall be in
ducts used to transport dust, loose stock or
flammable vapors, or used for vapor
removal or ventilation of commercial-type
cooking equipment.
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1910.305
(a)Wiring methods.
(2) Temporary wiring.
Temporary electrical power and lighting
wiring may be of a class less than would be
required for a permanent installation.
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1910.305
(a)Wiring methods.
(2) Temporary wiring.
(i) Uses permitted, 600 volts or less.
(A) During and for remodeling, maintenance
repair, or demolition or similar activities.
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1910.305
(a)Wiring methods.
(i)Uses permitted, 600 volts or less.
(B) For experimental or developmental work
(C) For a period not to exceed 90 days for
Christmas decorative lighting, carnivals,
and similar purposes.
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1910.305
(a)Wiring methods.
(2) Temporary wiring.
(i) Uses permitted, over 600 volts.
Only during tests, experiments and
emergencies.
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1910.305
(a)Wiring methods.
(F) Lamps for general illumination must be
protected from accidental contact or
breakage.
Protection can be provided by an elevation of
7 feet or by a suitable fixture with a guard.
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1910.305
(a)Wiring methods.
(G) Flexible cords and cables must be
protected from accidental damage.Sharp
corners or projections must be avoided.
Protection must be provided when passing
through doorways or other pinch points.
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1910.305(b)(
Conductors entering boxe
cabinets, or fitting
• Conductors entering boxes, cabinets, or
fittings must be protected from abrasion.
• Unused openings in cabinets, boxes, and
fittings must be effectively closed.
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1910.305(b)(2)
Electrical box covers
• All pull boxes, junction boxes, and fittings
must be provided with approved covers.
• Metal covers must be grounded.
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1910.305(b)(2)
Electrical box covers
• Outlet boxes must have a cover or a
faceplate.
• Outlet box covers with holes for flexible
cords must bushings or smooth, wellrounded surfaces.
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1910.30
(d)Switchboards and panelboards
• Panelboards must be mounted in approved
cabinets or boxes and must be dead front.
• Others are accessible only to qualified
persons.
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1910.305(g)(1)(i)
Flexible cords and cables.
Allowed uses:
Pendants
Wiring fixtures
Portable lamps or appliances
Elevator cables
Wiring cranes or hoists
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1910.305(g)(1)(i)
Flexible cords and cables.
Allowed uses:
Connect stationary equipment to facilitate
frequent interchange
Prevent transmission of noise or vibration
For removal for maintenance/repair
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1910.305(g)(1)(iii)
Flexible cords and cables.
May not be used:
As a substitute for the fixed wiring of a
structure.
Where run through holes in walls, ceilings
or floors.
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1910.305(g)(1)(iii)
Flexible cords and cables.
May not be used:
Where run through doorways, windows, or
similar openings
Where attached to building surfaces
Where concealed behind building walls,
ceilings, or floors.
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1910.305(g)(2)
Flexible cords and cables.
(ii) Flexible cords must be used only in
continuous lengths without splice or tap.
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1910.305(g)(2)
Flexible cords and cables.
(ii) Hard service flex cords, No. 12 or larger,
may be repaired if spliced so that the splice
retains the insulation, outer sheath
properties, and usage characteristics of the
original cord.
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1910.305(g)(2)
Flexible cords and cables.
(iii) Flexible cords must be connected to
devices and fittings so that strain relief is
provided which will prevent pull off from
being directly transmitted to joints or
terminal screws.
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1910.305(j)
Equipment for general use.
(2)(ii) A receptacle installed in a wet or damp
location must be suitable for the location.
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1910.307
Hazardous (classified) locations.
(b) Electrical installations.
Equipment, wiring, and installations of
equipment in hazardous (classified)
locations must be intrinsically safe,
approved for the location, or safe for the
location.
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Hazardous Locations
Class I locations
• Locations in which flammable gasses or
vapors are or may be present in the air in
quantities sufficient to produce explosive or
ignitable mixtures.
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Hazardous Locations
Class I, Division 1
Location in which hazardous concentrations
of flammable gases or vapors may exist:
(a) Under normal operating conditions
(b) Because of repair or maintenance
operations or leakage
(c) Because of breakdown or faulty operation
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Hazardous Locations
Class I, Division 2
Location in which flammable gases or vapors are:
(a) Normally confined within closed containers or
systems
(b) Normally kept below hazardous concentrations
by ventilation
(c) Normally kept below hazardous concentrations
by positive-pressure ventilation (adjacent to
Division 1)
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Hazardous Locations
Class II Locations
Locations which are hazardous because of the
presence of combustible dust.
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Hazardous Locations
Class II, Division 1
Location where combustible dust may be
present due to:
(a) Normal operations
(b) Mechanical failure or abnormal operation
of machinery or equipment
(c) combustible dust of an electrically
conductive nature may be present.
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Hazardous Locations
Class II, Division 2
Location where:
(a) Combustible dust will not normally be in
suspension in ignitable quantities
(b) Dusts may be in suspension as a result of
an infrequent malfunction of handling or
processing equipment.
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Hazardous Locations
Class III Locations
Locations that are hazardous because of the
presence of easily ignitable fibers or flyings
but in which such fibers or flyings are not
likely to be in suspension in the air in
quantities sufficient to produce ignitable
mixtures.
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Hazardous Locations
Class III, Division 1
Locations in which easily ignitable fibers or
materials producing combustible flyings are
handled, manufactured or used.
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Hazardous Locations
Class III, Division 2
Location in which easily ignitable fibers are
stored or handled, except in the process of
manufacture.
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1910.331 - .335
Electrical Safe Work Practices
Covers work practices rather than electrical
equipment and installations.
This should be a part of your Lockout/Tagout
program
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Electrical Protective Equipment
29 CFR1910.137 (59 FR 4435)
(a) Design Requirements
(b) In-service Care and Use
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Electrical Protective Equipment
29 CFR1910.137 (59 FR 4435)
(a)Design Requirements
Insulating blankets,matting, covers, line hose,
gloves, and sleeves made of rubber shall
meet specified requirements for
manufacture, marking, electrical properties,
workmanship and finish.
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(b) In-service Care and Use
• Electrical protective equipment shall be
maintained in a safe, reliable condition.
• Specific requirements for in-service care
and use are given for insulating blankets,
covers, line hose, gloves, and sleeves made
of rubber.
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Qualified Employee
(Qualified Person)
One knowledgeable in the construction and
operation of the electric power generation,
transmission, and distribution equipment
involved, along with the associated hazards.
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Qualified Employee
(Qualified Person)
• Must have the training required by
paragraph(a)(2)(ii).
• Has undergone on-the-job training and has
demonstrated an ability to perform duties
safely under the direct supervision of a
qualified person.
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One employee was
climbing a metal
ladder to hand an
electric drill to the
journey installer on a
scaffold about five
feet above him. When
the victim reached
the third rung from
the bottom of the
ladder he received an
electric shock that
killed him.
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The employee was attempting to correct an electrical problem
involving two non-operational lamps. He proceeded to the area
where he thought the problem was. He had not shut off the power at
the circuit breaker panel nor had he tested the wires to see if they
were live. He was electrocuted when he grabbed the two live wires
with his left hand and then fell from the ladder.
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Review
• What are Electrical Hazards?
• Why is it important to examine equipment?
• How do we identity Electrical Hazards?
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The material presented in this slide show
presentation is for reference purposes only.
In no way is the material in substitution for
any federal or state regulation.
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