Electrical StandardsMODULE 10
2 ©2006 TEEX
Hazard Brainstorming
Where are electrical hazards on oil and gas well sites?
3 ©2006 TEEX
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
4 ©2006 TEEX
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)
8 ©2006 TEEX
Electrical Shock
Received when current passes through body
Severity depends on: 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
Wire Gauge
WIRE
14 ©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:
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
General1903.303
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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
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
Subtitles & TransitionsFOR EXAMPLE…
Example of properly labeledelectric service: motors, disconnects and breakers
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1910.303(g) 600 Volts, nominal, or less
1. Space about electric equipment 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 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. Enclosure / access control
3. Work space about equipment
4. Entrance and access to work space
5. Working space and guarding
Wiring Design and Protection1903.304
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1910.304(a) Use and identification of grounding conductors
1. Grounded & equipment grounding conductors identifiable & distinguishable
Grounded = white or gray Equipment grounding = green, or green
with yellow strips, or bare
2. Polarity may not be reversed3. 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
Subtitles & TransitionsFOR EXAMPLE…
Example of properly labeledelectric service: motors, disconnects and breakers
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1910.304(b) Branch circuits
1. Identification of multiwire branch circuits
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 connectorsi. Grounding type for 15A & 20A circuits
Receptacles only on circuits matching voltage and current rating
ii. Grounding contacts grounded 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 connectorsiv. Replacement of receptacles
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: 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 devicesi. Heavy-duty lampholders for >20A
ii. Receptacle outlets: Receptacle ampere rating branch circuit For 2 outlets on branch circuit: Table S-4
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1910.304(b) Branch circuits
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:
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 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 Pedestrians? Platform Exceptions for slope, attachment
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1910.304(d) Location of outdoor lamps
d. Location of outdoor lamps Under energized equipment unless
Equipment can be locked out or Clearance/other safeguards adequate
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1910.304(e) Services
Disconnecting means Main switch disconnects all, indicates
on/off
Services over 600 volts, nominal Accessible only to qualified; warning
signs
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1910.304(f) Overcurrent protection
1. 600 volts, nominal, or lessi. Protect conductors and equipment iv. Overcurrent devices readily accessible
To employees & building management Not exposed to damage or ignitable material
v. Located/shielded to avoid injury/burnsvi. On/off position clearly indicatedvii. Vertical: up = on
2. Special rules for over 600 volts
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1910.304(g) Grounding
1. Systems to be groundedi. 3-wire DC: neutral conductor
ii. 2-wire DC, >50V-300V, with exceptions
iii. AC <50V in certain cases
iv. 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, equipmentvi. 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
Wiring Methods, Components, and Equipment for General Use
1903.305
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1910.305(a) Wiring methods
Not applicable to factory-assembled
1. General requirementsi. 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 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
Must be protected from abrasion Openings must be closed, with or without
wires running through
2. Covers and canopies 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. Appliances4. Motors5. Transformers6. Capacitors7. Storage batteries
Specific Purpose Equipment and Installations
1903.306
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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
Hazardous (Classified) Locations1903.307
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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: 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
Nonincendive equipment Nonincendive component
Oil immersion Hermetically sealed Other protection
techniques
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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: 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
Special Systems1910.308
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1910.308 Special systems
a. Systems over 600 volts, nominalb. Emergency power systemsc. Remote control, signaling, and power-
limited circuitsd. Fire alarm systemse. Communications systemsf. Solar photovoltaic systemsg. Integrated electrical systems
Definitions1910.399
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1904.399 Definitions
New version supersedes older version in CFR book
References for Further Information1910 SUBPART S APPENDIX A
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1910 Subpart S Appendix A
Nonmandatory references aid in understanding
Not a substitute for compliance with CFR Appendices B and C removed
Safety-Related Work Practices1910.331-1910.335
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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: Premises wiring Wiring for connection to supply Other wiring Vehicles excluded
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1910.332 Training
a. Scope: employees with electric shock risk not reduced to safe level by installation requirements
b. Training content: 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
Selection and Use of Work Practices
1910.333
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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. Deenergizing equipment
iii. Application of locks and tags
iv. Verification of deenergized condition
v. Reenergizing equipment after work
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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: 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: Requires safeguards No conductive cleaning materials,
including liquid solutions
10. Interlocks may only be defeated temporarily by qualified person
Use of Equipment1910.334
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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 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
Safeguards for Personnel Protection
1910.335
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1910.335(a) Use of protective equipment
Personal protective equipment 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
Subtitles & TransitionsFOR EXAMPLE…
Example of properly labeledelectric service: motors, disconnects and breakers
Subtitles & TransitionsFOR EXAMPLE…
Example of properly labeledelectric service: motors, disconnects and breakers
Subtitles & TransitionsFOR EXAMPLE…
Example of properly labeledelectric service: motors, disconnects and breakers
Subtitles & TransitionsFOR EXAMPLE…
Example of properly labeledelectric service: motors, disconnects and breakers
Subtitles & TransitionsFOR EXAMPLE…
Example of properly labeledelectric service: motors, disconnects and breakers
Subtitles & TransitionsFOR EXAMPLE…
Example of properly labeledelectric service: motors, disconnects and breakers
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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; nonmetallic-sheathed cable for temporary wiring
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