Transcript Electrical Standards MODULE 10

MODULE 10
Electrical Standards
Hazard Brainstorming
 Where are electrical hazards on oil and
gas well sites?
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Statistics
 Electrocution: Among most frequent
causes of occupational injury death in
US
 295 fatalities/year; 4309 lost time
 1992-2002: 9% decrease
 Most frequent cause: Overhead power
lines
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Factors in Fatal Electrocutions
 Safe work practices implemented and
followed?
 Adequate/required PPE provided and worn?
 Lockout/tagout procedures implemented and
followed?
 OSHA, NEC, NESC compliance?
 Worker and supervisor training adequate?
 (from NIOSH)
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Types of Electrical Injuries
 Electrocution (death due to electrical
shock)
 Electrical shock
 Burns (ugly pictures here)
 Falls
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Hazard Recognition
 How can you sense electrical danger?
 Cannot see, smell, taste, or hear danger
 Can recognize unsafe conditions
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Electrical Terminology
Current – movement of electrical charge
Resistance – opposition to current flow
Voltage – measure of electrical force
Conductors – substances with little
resistance to electricity (such as metals)
 Insulators – substances with high resistance
to electricity (such as wood, rubber, glass, &
bakelite)
 Grounding – a conductive connection to the
earth (which acts as a protective measure)
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Electrical Shock
 Received when current passes through
body
 Severity depends on:
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Path of current through body
Amount of current flowing through body
Length of time body is in circuit
Also: voltage, moisture, heart cycle, health
 Low voltage is NOT low hazard!
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Dangers of Electrical Shock
 Currents >75 mA* can cause ventricular
fibrillation (rapid, ineffective heartbeat)
 mA = milliampere = 1/1,000 of an ampere
 Death within minutes unless a defibrillator
is used
 75 mA is not much current
(a small power drill uses 30 times as much)
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Effects of Current on Body
 1 mA: Perception level, slight tingling.
 5 mA: Slight shock; not painful.
 Can usually let go.
 Involuntary reactions can cause injuries.
 6-30 mA: Painful shock
 Muscular control lost
 Freezing current or “let-go” range
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Effects of Current on Body
 50-150 mA: Extreme pain
 Respiratory arrest; cannot let go
 Death possible
 1000-4300 mA: Ventricular fibrillation
 Muscular contraction; nerve damage
 Death likely
 10000 mA: Cardiac arrest
 Severe burns, probable death
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How Shock Happens
 Connection between:
 2 wires of energized circuit
 1 wire of energized circuit and ground
 Metallic part in contact with energized wire
and ground
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Inadequate Wiring Hazards
 What happens when a wire is too small
to carry the current safely?
 Overheating
 Risk of fire or short circuit
 Fuse acts as sacrificial
weak link
 Fuse too strong?
Other parts of the system
break first
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Wire Gauge
WIRE
©2006 TEEX
29 CFR 1910 and 29 CFR 1926
 1910 Subpart S = Electrical
 Revised 2/14/2007; effective in 180 days
 1910 Subpart I = PPE
 1910.137 Electrical Protective Devices
 1926 Subpart K = Electrical
 Protect against recognized hazards
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Other Standards
 NFPA 70E enacted to help meet CFR
 Revised Subpart S based heavily on 2000
version
 2004 version now published
 OSHA chose which provisions of 70E to
adopt
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29 CFR 1910 Subpart S
 Electrical standards for general industry
 § 302-308 and 399 updated: PM App. C
 5 main groups of standards:
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Design safety standards § 302-330
Safety-related work practices § 331-360
Reserved: maintenance, special equipment
Definitions: § 399
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1910.302 Electric utilization
systems (PM Appendix C)
 Applicability of regulations
 By type of installation
 By installation date
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1903.303
General
1910.303 (a) Approval
 Conductors and equipment acceptable
only if approved
 Note: If installation is made in accordance
with NEC or ANSI/NFPA it will be deemed
in compliance.
 See definitions
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1910.303(b) Examination,
installation, and use of equipment
 Examination – shall be free of
recognized hazards
 Suitability (check listing/labeling)
 Other factors listed in regulation
 Installation and use – by instructions
 Insulation integrity
 Interrupting rating (fuses, breakers)
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1910.303(b) Examination,
installation, and use of equipment
 Circuit impedance…
 Deteriorating agents – water, gases,
excessive temperature, corrosives…
 Mechanical execution of work
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Close unused openings for protection
Conductors racked for safe access
Internal parts not contaminated
No damaged parts
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1910.303(b) Examination,
installation, and use of equipment
 Mounting and cooling
 Firmly secured
 Air circulation; clearance
 Ventilation openings not obstructed
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1910.303(c) Electrical
connections
 General – dissimilar metals
 Terminals – connections
 Splices – correctly performed, insulated
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1910.303(d) Arcing parts
 Some electrical equipment normally
produces arcs, sparks, flames, molten
metal
 Keep isolated from combustible material
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1910.303(e) Marking
 Manufacturer and ratings must be
marked
 Voltage, current, wattage, etc.
 Durable markings in environment
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1910.303(f) Disconnecting
means and circuits
 Legibly marked to indicate purpose
 Unless purpose is evident
 Durable
 Able to be locked open
 Series combination rating = special
marking
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Example of properly labeled
electric service: motors,
disconnects and breakers
FOR EXAMPLE…
Subtitles & Transitions
1910.303(g) 600 Volts, nominal,
or less
1. Space about electric equipment
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Space, not used for storage
Guarded when parts exposed
Entrances
Illumination
Headroom
Control boards in dedicated, protected
space
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1910.303(g) 600 Volts, nominal,
or less
2. Guarding of live parts
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Live parts  50 volts protected from
people
Protection from damage
Warning signs for unqualified persons
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1910.303(h) Over 600 volts,
nominal
2.
3.
4.
5.
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Enclosure / access control
Work space about equipment
Entrance and access to work space
Working space and guarding
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1903.304
Wiring Design and Protection
1910.304(a) Use and identification
of grounding conductors
1. Grounded & equipment grounding
conductors identifiable &
distinguishable
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Grounded = white or gray
Equipment grounding = green, or green
with yellow strips, or bare
2. Polarity may not be reversed
3. Grounding devices not used for other
purposes
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Polarity
 Reversed polarity: Neutral (grounded)
conductor connected to hot
(ungrounded) terminal
incorrectly
 Most common on smaller
branch circuits
 120 V receptacle outlets
 Cord- and plug-connected
equipment
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Example of properly labeled
electric service: motors,
disconnects and breakers
FOR EXAMPLE…
Subtitles & Transitions
1910.304(b) Branch circuits
1. Identification of multiwire branch
circuits
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For >1 voltage system in a building
ID phase and system
Permanently posted at each panelboard
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1910.304(b) Branch circuits
2. Receptacles and cord connectors
i.
Grounding type for 15A & 20A circuits
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Receptacles only on circuits matching voltage
and current rating
ii. Grounding contacts grounded
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Except portable / vehicle-mounted generators
Except replacement receptacles
iii. Grounding contact connected to
equipment grounding conductor
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1910.304(b) Branch circuits
2. Receptacles and cord connectors
iv. Replacement of receptacles
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Grounding-type where grounding means
exists
GFCI where required
Options for lack of grounding means
v. Plugs not interchangeable for different
voltage, frequency, type of current
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1910.304(b) Branch circuits
3. Ground-fault circuit interrupter (GFCI)
i. Bathroom or rooftops
ii. Temporary wiring:
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Including extension cords
If unavailable for less-usual type of
receptacle: assured equipment grounding
conductor program.
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1910.304(b) Branch circuits
4. Outlet devices
i. Heavy-duty lampholders for >20A
ii. Receptacle outlets:
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Receptacle ampere rating  branch circuit
For 2 outlets on branch circuit: Table S-4
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1910.304(b) Branch circuits
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For 2 outlets on branch circuit: Table S-5
 50 A: receptacle  branch-circuit rating
5. Cord connections: Outlet where
flexible cords with plugs used
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1910.304(c) Outside conductors,
600 volts, nominal, or less
 Clearance
1. Power conductors on poles
2. Clearance of open conductors from
ground:
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10 feet – above sidewalk, grade, platform
12 feet – vehicular traffic
15 feet – truck traffic
18 feet – public streets, alleys, driveways
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1910.304(c) Outside conductors,
600 volts, nominal, or less
3. Clearance from building openings
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No outer jacket: 3 foot clearance, except
above window
Not beneath or obstructing openings
where materials may be moved
4. Above roofs: 8 ft above, 3 ft from edge
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Pedestrians? Platform
Exceptions for slope, attachment
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1910.304(d) Location of outdoor
lamps
d. Location of outdoor lamps
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Under energized equipment unless
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Equipment can be locked out or
Clearance/other safeguards adequate
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1910.304(e) Services
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Disconnecting means
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Services over 600 volts, nominal
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Main switch disconnects all, indicates
on/off
Accessible only to qualified; warning
signs
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1910.304(f) Overcurrent
protection
1. 600 volts, nominal, or less
i. Protect conductors and equipment
iv. Overcurrent devices readily accessible
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To employees & building management
Not exposed to damage or ignitable material
v. Located/shielded to avoid injury/burns
vi. On/off position clearly indicated
vii. Vertical: up = on
2. Special rules for over 600 volts
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1910.304(g) Grounding
1. Systems to be grounded
i.
ii.
iii.
iv.
3-wire DC: neutral conductor
2-wire DC, >50V-300V, with exceptions
AC <50V in certain cases
AC 50V-1000V (unless exempt) under 4
conditions
v. Exemptions for AC 50V-1000V
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1910.304(g) Grounding
2. Conductor to be grounded
3. Portable and vehicle-mounted
generators: frame as grounding
electrode
4. Grounding connections
5. Grounding path: permanent,
continuous, effective
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Grounding
 One conductor of the circuit
intentionally grounded to earth
 Protects circuit from lightning
or other high voltage contact
 Stabilizes the voltage in the system so
“expected voltage levels” are not
exceeded under normal conditions
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Grounding
 Metal frames / enclosures of equipment
grounded by permanent connection or
bond
 Equipment grounding conductor
provides path for dangerous fault
current to return to ground
 If damage, corrosion, loosening, etc.
impairs continuity, shock and burn
hazards will develop
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Grounding Path
 Shall have capacity to conduct safely
any likely fault current.
 Fault currents may be many times
normal currents; can melt points of poor
conductivity
 High temperatures = hazard; can
destroy ground-fault path
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1910.304(g) Grounding
6. Supports, enclosures, equipment
vi. Exposed non-current-carrying metal
parts of cord- and plug-connected
equipment
7. Nonelectrical equipment
8. Methods of grounding fixed equipment
9. Grounding of systems and circuits
1000 volts and over (high voltage)
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Ground fault circuit interrupters
(GFCI’s)
 GFCI  overcurrent device like a fuse or
circuit breaker
 Designed to sense an imbalance in
current flow over the normal path
 Opens circuit if current in hot and
grounded wires differ by 5mA  1mA
 Must be installed correctly and tested
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1903.305
Wiring Methods, Components, and
Equipment for General Use
1910.305(a) Wiring methods
 Not applicable to factory-assembled
1. General requirements
i.
Metal parts as grounding conductors:
effectively bonded
ii. Internal insulated grounding conductor
for isolated enclosure
iii. No wiring systems in ventilation ducts
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1910.305(a) Wiring methods
2. Temporary wiring
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Restricted uses
Removed after project completion
Requirements for feeders and branch
circuits
Grounding receptacles
No bare conductors or earth returns
Disconnecting switches
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1910.305(a) Wiring methods
2.Temporary wiring, continued
 Lamps protected from contact or breakage
 Flexible cords protected from damage
 Cables supported
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1910.305(b) Cabinets, boxes,
and fittings
1. Conductors entering boxes, cabinets,
or fittings
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Must be protected from abrasion
Openings must be closed, with or without
wires running through
2. Covers and canopies
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Metal covers must be grounded
>600V: complete, secure, marked
enclosure
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1910.305(c) Switches
 Gravity must not close switches
 Warning if power may still be available
while switch is closed
 Faceplates where appropriate
 Grounding
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Switchboards, panelboards, and
enclosures for damp locations
 Switchboards and panelboards
 Switchboards with exposed live parts: in
dry places accessible only to qualified
persons
 Panelboards: in enclosures with no live
parts on front
 Switches dead when open
 Enclosures for wet locations
 Airspace, weatherproof
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1910.305(f) Conductors for
general wiring
 Insulated unless otherwise permitted
 Approved type for use
 Distinguishable by color or other means
 Grounded
 Ungrounded
 Equipment grounding
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1910.305(g) Flexible cords and
cables
 In general much more easily damaged
 Should not be used if recognized
options can be used instead
 Must be approved for conditions and
location
 Allowable purposes listed
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1910.305(g) Flexible cords and
cables
 May not be substituted for fixed wiring
 May not be run through walls, ceilings, floors,
doors, windows
 May not be attached to buildings
 May not be concealed in walls, ceilings, floors
 May not be spliced, except hard service #14
 Strain relief needed on connections
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Flexible cords: Acceptable?
 Short cord as part of a tool? Yes.
 Temporary use of extension cord for
tool/appliance? Yes.
 Obviously not temporary? No.
 Extended over distance to avoid
installing fixed outlet? No.
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1910.305(j) Equipment for
general use
1. Lighting fixtures, lampholders, lamps,
receptacles
2. Receptacles, cord connectors, and
attachment plugs (caps)
3. Appliances
4. Motors
5. Transformers
6. Capacitors
7. Storage batteries
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1903.306
Specific Purpose Equipment and
Installations
1910.306 Specific purpose
equipment and installations
a. Electric signs and outline lighting
b. Cranes and hoists
d. Electric welders—disconnecting
means
g. Induction and dielectric
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1903.307
Hazardous (Classified) Locations
1910.307 Hazardous (classified)
locations
 Classification based on flammable
vapors, liquids, gases, combustible
dusts or fibers
 Each area considered individually
 Classified by classes and divisions or
zones
 Documentation available for users,
designers, installers, maintainers of
electric equipment
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1910.307 Hazardous (classified)
locations
 Definitions of classes and divisions in
1910.399, Definitions
 Class I: flammable gases/vapors; explosive
or ignitable mixtures
 Class II: combustible dust
 Class III: easily ignitable fibers or flyings;
not likely to be in suspension
 Division 1 & 2 for each; Zones 0-2 for
Class I
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1910.307(c) Electrical
installations
 Equipment must be one of these:
 Intrinsically safe
 Approved for hazardous (classified)
location
 Approved and marked for class and properties
of material present
 Safe for hazardous (classified) location
 NFPA 70 referenced
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Conduits and equipment
d. Conduits: threaded, wrench-tight or
bonding jumper
e. Equipment in Division 2 locations:
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Division 1 approved equipment = OK
General-purpose equipment OK if
demonstrably not a source of ignition
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1910.307(f) Protection
techniques
 Explosionproof
apparatus
 Dust ignitionproof
 Dust-tight
 Purged and
pressurized
 Nonincendive circuit
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 Nonincendive
equipment
Nonincendive
component
 Oil immersion
 Hermetically sealed
 Other protection
techniques
©2006 TEEX
1910.307(g) Class I, Zone 0, 1,
and 2 locations
 Zone = alternative to divisions for Class
1
 Classified by chemical properties and
likelihood of combustible atmosphere
 Proper installation of conduit &
equipment to avoid sparks in
flammable/combustible atmosphere
 Protection techniques for certain zones
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1910.307(g) Class I, Zone 0, 1,
and 2 locations
 Special precaution: PE must classify
areas and specify equipment
 Listing and marking:
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Listed for Zone 0 = OK for Zone 1-2
Listed for Zone 1 = OK for Zone 2
(For same gas or vapor)
Marking requirements & exemption
 More information in NFPA 70
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1910.307(g) Class I, Zone 0
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1910.308
Special Systems
1910.308 Special systems
a. Systems over 600 volts, nominal
b. Emergency power systems
c. Remote control, signaling, and powerlimited circuits
d. Fire alarm systems
e. Communications systems
f. Solar photovoltaic systems
g. Integrated electrical systems
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1910.399
Definitions
1904.399 Definitions
 New version supersedes older version
in CFR book
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1910 SUBPART S APPENDIX A
References for Further Information
1910 Subpart S Appendix A
 Nonmandatory references aid in
understanding
 Not a substitute for compliance with CFR
 Appendices B and C removed
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1910.331-1910.335
Safety-Related Work Practices
1910.331 Scope
 Qualified persons (who have training in
avoiding the electrical hazards)
 Unqualified persons (with little or no
such training)
 Working on or near:
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Premises wiring
Wiring for connection to supply
Other wiring
Vehicles excluded
©2006 TEEX
1910.332 Training
a. Scope: employees with electric shock
risk not reduced to safe level by
installation requirements
b. Training content:
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Work practices for job assignments
1910.331-335 and others necessary
Qualified vs. unqualified
c. Classroom or on-the-job; risk based
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Employees to be Trained
 Electricians and welders
 Any others if:
 work they do or supervise
 comes close enough to exposed parts of
electric circuits 50V
 for hazard to exist
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1910.333
Selection and Use of Work
Practices
1910.333 (a)(1) Deenergized
parts
 Live parts deenergized before employee
works on or near them:
 Unless infeasible or causes greater hazard
 <50V not deenergized if no increased
exposure to burns or arcs
 Examples in CFR
 If not deenergized, other work practices
must protect employees
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1910.333(b) Working on or near
exposed deenergized parts
 If not locked out or tagged out, treated
as energized
 Lockout/tagout rules followed in order
 1910.147 provisions may also be OK
 Written copy of procedures available
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1910.333(b) Working on or near
exposed deenergized parts

Lockout/tagout steps in section (2):
ii.
iii.
iv.
v.
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Deenergizing equipment
Application of locks and tags
Verification of deenergized condition
Reenergizing equipment after work
©2006 TEEX
1910.333(c) Working on or near
exposed energized parts
 Only qualified persons may work on
energized electric circuit parts
 For work near overhead lines:
 Lines deenergized and grounded, or
 Other protective measures provided
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Working near overhead power
lines
 Unqualified person near energized lines
 Person and longest conductive object not
closer than 10 ft, + 4 in/10kV above 50kV
 For elevated or ground work
 Qualified person:
 Closer approach only with insulation
 Table S-5: distance varies by voltage
 Equipment: same distance as
unqualified
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Working near overhead power
lines
 Equipment: same distance as
unqualified, with exceptions:
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In transit, structure lowered: 4 ft +4 in/10kV
Insulating barriers, not part of vehicle
Aerial lift, insulated, with qualified person
Ground employees may not contact
equipment without protection or distance
 Employees may not stand at grounding
location when line contact possible
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1910.333(c) Working on or near
exposed energized parts
4. Illumination must allow safe work –
may not reach blindly in
5. Confined space work requires
protective insulation & secured doors
6. Conductive materials: prevent contact
with energized parts
7. Portable ladders: nonconductive
siderails
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1910.333(c) Working on or near
exposed energized parts
8. Conductive apparel not worn, or
insulated
9. Housekeeping near live parts:
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Requires safeguards
No conductive cleaning materials,
including liquid solutions
10. Interlocks may only be defeated
temporarily by qualified person
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1910.334
Use of Equipment
1910.334(a) Portable electric
equipment
 Handled in a manner to not cause
damage
 Cords not used to raise/lower
equipment
 Cords not stapled or hung in ways that
damage insulation
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1910.334(a) Portable electric
equipment
 Visual inspection required before use:
 Portable cord / plug connected equipment
 Extension cords
 For external defects and evidence of internal
damage
 If not exposed to damage, only when relocated
 Defect or damage: remove, do not use until
repaired and tested
 Plug and receptacle checked for compatibility
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1910.334(a) Portable electric
equipment
 Grounding type equipment: ground
must be maintained
 Conductive work locations (e.g. wet)
require approved equipment and cords
 Connecting plugs:
 Never plug or unplug live equipment with
wet hands
 Protect hands from conductive path (water)
 Locking connectors: properly secured
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1910.334(b) Electric power and
lighting circuits
 Never reenergize a blown fuse
 Never reenergize a circuit breaker until
it is safe (Overload or fault?)
 Never modify overcurrent protection
beyond § 304 requirements
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1910.334(c) and (d)
c. Test instruments and equipment
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

Only qualified persons may test electric
circuits or equipment
Test instruments must be visually
inspected
Must be rated for circuits & environment
d. Occasional use of flammable and
ignitable materials: Do not use
equipment that could ignite them
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1910.335
Safeguards for Personnel
Protection
1910.335(a) Use of protective
equipment
 Personal protective equipment
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
Must be provided with & use equipment
Maintained, inspected, and tested
Insulating material protected
Nonconductive head protection
Eye or face protection for arcs, flashes,
flying objects from explosions
 Insulated tools or handling equipment
 Shields, insulation for heating/arcing
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1910.335(b) Alerting techniques
 Techniques to warn and protect
employees:
 Safety signs and tags
 Barricades
 Attendants
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Relevant Standards Outside 29
CFR 1910
 29 CFR 1926 Subpart K: construction
 API RP 54
 Section 9.14 Generators, Motors, and
Lighting
 Section 10: Drilling and Well Servicing Rig
Electrical Systems
 API RP 14F for offshore wiring
 API RP 500 and 505: area classification
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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 around wire or
connection
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Example of properly labeled
electric service: motors,
disconnects and breakers
FOR EXAMPLE…
Subtitles & Transitions
Example of properly labeled
electric service: motors,
disconnects and breakers
FOR EXAMPLE…
Subtitles & Transitions
Example of properly labeled
electric service: motors,
disconnects and breakers
FOR EXAMPLE…
Subtitles & Transitions
Example of properly labeled
electric service: motors,
disconnects and breakers
FOR EXAMPLE…
Subtitles & Transitions
Example of properly labeled
electric service: motors,
disconnects and breakers
FOR EXAMPLE…
Subtitles & Transitions
Example of properly labeled
electric service: motors,
disconnects and breakers
FOR EXAMPLE…
Subtitles & Transitions
OSHA Resources
 Pub 3075 Controlling Electrical Hazards
 Small Business Handbook section
 Inspection Procedures
 Electrical Safety-Related Work Practices -Inspection Procedures and Interpretation
Guidelines
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Interpretations
 Training requirements for employees
who perform non-electrical work on
electrical equipment
 Qualifications for resetting circuits or
replacing fuses; electrical enclosures
must be approved
 Use of compressed air above 30 p.s.i.
for cleaning purposes; nonmetallicsheathed cable for temporary wiring
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