electrical
Post on 07-Jan-2016
29 Views
Preview:
DESCRIPTION
TRANSCRIPT
ElectricalElectrical
These handouts and documents with attachments are not final, complete, or definitive instruments. This information is for These handouts and documents with attachments are not final, complete, or definitive instruments. This information is for guidance purposes only. You should independently verify and satisfy yourself as to its accuracy. The AHBSIF does not guidance purposes only. You should independently verify and satisfy yourself as to its accuracy. The AHBSIF does not
assume any liability for damages arising from the use of this information or exhibits and attachments thereto and renders no assume any liability for damages arising from the use of this information or exhibits and attachments thereto and renders no opinion that any of the terms, conditions, and/or cited federal standards in this document and the exhibits and attachments opinion that any of the terms, conditions, and/or cited federal standards in this document and the exhibits and attachments
should be explicitly followed by the fund member. Seek specific guidance from the appropriate regulator (OSHA) or should be explicitly followed by the fund member. Seek specific guidance from the appropriate regulator (OSHA) or professional advisor.professional advisor.
Serious ExposureSerious Exposure
Electrocution is one of Electrocution is one of the top four causes of the top four causes of construction fatalitiesconstruction fatalities
Nearly half of those Nearly half of those fatalities were the result fatalities were the result of contact with overhead of contact with overhead power lines power lines
OSHA is making an OSHA is making an effort to focus more effort to focus more attention to these attention to these exposuresexposures
Applicable StandardsApplicable Standards
Electrical standards are among the Electrical standards are among the most frequently cited by OSHAmost frequently cited by OSHA No Lock Out/Tag OutNo Lock Out/Tag Out Improper Wiring MethodsImproper Wiring Methods Inadequate Components and EquipmentInadequate Components and Equipment
OSHA references the following for OSHA references the following for guidelinesguidelines Electric Safety Requirements for Electric Safety Requirements for
Employee Workplaces and codes (NFPA Employee Workplaces and codes (NFPA 70E)70E)
Basic TerminologyBasic Terminology
AmpsAmps – The amount of – The amount of electricity flowingelectricity flowing
VoltsVolts – The force at which the – The force at which the power flowspower flows
OhmsOhms – A unit of electrical – A unit of electrical resistanceresistance
WattsWatts – A unit of electrical – A unit of electrical powerpower
Physical EffectsPhysical Effects Amps are the true measure Amps are the true measure
of current absorbed, not voltsof current absorbed, not volts We are good conductors, the We are good conductors, the
human body is 70% waterhuman body is 70% water Involuntary muscle Involuntary muscle
contraction is the reason we contraction is the reason we are affectedare affected Can’t let go of energized objectCan’t let go of energized object Breathing is impairedBreathing is impaired Heart rhythm is disruptedHeart rhythm is disrupted
Physical EffectsPhysical Effects
1 1 mAmA
16 mA16 mA
20 mA20 mA
100 mA100 mA
2 amps2 amps
15 to 20 amps15 to 20 amps
Barely perceptibleBarely perceptible
Max current an average man can grasp Max current an average man can grasp and let goand let go
Paralysis of respiratory musclesParalysis of respiratory muscles
Ventricular fibrillation thresholdVentricular fibrillation threshold
Cardiac standstill and internal organ Cardiac standstill and internal organ damagedamage
Current required to trip common Current required to trip common household breakerhousehold breaker
Influencing Factors of a Influencing Factors of a ShockShock
Circumstances that affect the Circumstances that affect the outcome of an electric outcome of an electric shockshock;;
Circuit voltageCircuit voltage The bodies external (skin) The bodies external (skin)
and internal resistanceand internal resistance Total current flowing Total current flowing
through the bodythrough the body Current pathCurrent path The duration of the shockThe duration of the shock
Arc FlashArc Flash The result of a rapid release of The result of a rapid release of
energy due to an arcing fault, air is energy due to an arcing fault, air is the conductor.the conductor.
Arc faults are generally limited to Arc faults are generally limited to systems where the voltage is in systems where the voltage is in excess of 120 volts.excess of 120 volts.
Massive energy is discharged, Massive energy is discharged, vaporizing the copper and causing vaporizing the copper and causing an explosion.an explosion.
Arcs can produce temperatures up Arcs can produce temperatures up to 35,000° F.to 35,000° F.
Flash hazards can produce Flash hazards can produce pressure waves, concentrated pressure waves, concentrated sound blasts, and release deadly sound blasts, and release deadly shrapnel.shrapnel.
Arc FlashArc Flash
Arc flash and blast hazards were not Arc flash and blast hazards were not formally studied until the early 90’sformally studied until the early 90’s
Generally occur less frequently than Generally occur less frequently than electric shockelectric shock
NFPA 70E provides directives on NFPA 70E provides directives on reducing the occurrence and effects reducing the occurrence and effects of arc flashof arc flash
NFPA 70E – Flash Protection NFPA 70E – Flash Protection GuidelinesGuidelines
Compliance of NFPA 70E, Arc Flash Compliance of NFPA 70E, Arc Flash Protection requires the following:Protection requires the following: Justification for live workJustification for live work Work Permits when applicableWork Permits when applicable Approach BoundariesApproach Boundaries
Approach BoundariesApproach BoundariesLimited Approach BoundaryLimited Approach Boundary
Entered only by a Qualified Entered only by a Qualified Person or unqualified person Person or unqualified person escorted by QPescorted by QP
Restricted Approach BoundaryRestricted Approach Boundary Entered only by a Qualified Entered only by a Qualified
Person required to use shock Person required to use shock protection techniques and PPEprotection techniques and PPE
Prohibited Approach BoundaryProhibited Approach Boundary Entered only by a Qualified Entered only by a Qualified
Person requiring same Person requiring same protection as if in direct contact protection as if in direct contact with live partwith live part
Electric
Panel
Front
Flash Protection BoundaryFlash Protection Boundary
The Flash Protection The Flash Protection Boundary is the linear Boundary is the linear distance to prevent any distance to prevent any more than 2more than 2ndnd degree degree burns from a potential burns from a potential arc flasharc flash
Distance is usually four Distance is usually four feetfeet
Distances for all shock Distances for all shock protection boundaries protection boundaries can referenced in Table can referenced in Table 130.2(C) of NFPA 70E130.2(C) of NFPA 70E
Electric
Panel
Front
What kind of PPE is What kind of PPE is necessary?necessary?
The level of personal protective The level of personal protective equipment necessary for the equipment necessary for the exposure can be determined one of exposure can be determined one of two ways:two ways:
Shock Hazard AnalysisShock Hazard Analysis
- OR -- OR - Flash Hazard AnalysisFlash Hazard Analysis
Shock Hazard AnalysisShock Hazard Analysis
Must determine the following:Must determine the following: The operating voltage of the systemThe operating voltage of the system Shock protection boundariesShock protection boundaries Required personal protective equipment Required personal protective equipment
[ reference Tables 130.7(C)(9)(a) and 130.7(C)[ reference Tables 130.7(C)(9)(a) and 130.7(C)(10) NFPA 70E ](10) NFPA 70E ]
Flash Hazard AnalysisFlash Hazard Analysis
Must determine the following:Must determine the following: The flash protection boundaryThe flash protection boundary The incident energy exposure levelThe incident energy exposure level Protective clothing and PPEProtective clothing and PPE
Flash Hazard AnalysisFlash Hazard Analysis
The flash protection boundaryThe flash protection boundaryUse the flash protection boundary formula Use the flash protection boundary formula OROR default 130.3(A)default 130.3(A)
The incident energy exposure levelThe incident energy exposure leveldistance between workers face and chest from distance between workers face and chest from the arc source the arc source OROR 130.7(C)(9) and 130.7(C) 130.7(C)(9) and 130.7(C)(10)(10)
Protective clothing and PPEProtective clothing and PPEOnce incident energy is determined, safety Once incident energy is determined, safety equipment has to have a rating greater than or equipment has to have a rating greater than or equal to the incident energy availableequal to the incident energy available
Personal Protective Clothing, Personal Protective Clothing, NFPA 70ENFPA 70E
CategoryCategory Cal/cmCal/cm22 ClothingClothing
00 1.21.2 Untreated CottonUntreated Cotton
11 55 Flame retardant (FR) shirt and Flame retardant (FR) shirt and FR pantsFR pants
22 88 Cotton underwear FR shirt and Cotton underwear FR shirt and FR pants FR pants
33 2525 Cotton underwear FR shirt, FR Cotton underwear FR shirt, FR pants and FR coveralls pants and FR coveralls
44 4040 Cotton underwear FR shirt, FR Cotton underwear FR shirt, FR pants and double layer switching pants and double layer switching coat and pants coat and pants
Employer ResponsibilitiesEmployer Responsibilities
Equipment must be:Equipment must be: Free from recognized hazards Free from recognized hazards Suitable and identified through Suitable and identified through
listing, labeling, or certification of listing, labeling, or certification of purpose.purpose.
Designed with adequate Designed with adequate mechanical strength and durability mechanical strength and durability
Other items for considerationOther items for consideration Electrical insulationElectrical insulation Heating effects /conditions Heating effects /conditions
of useof use Arcing effectsArcing effects Use classificationsUse classifications
GuardingGuarding Live parts of electrical equipment operating at 50 Live parts of electrical equipment operating at 50
volts or more must be guarded against accidental volts or more must be guarded against accidental contact.contact.
Means of acceptable guarding include:Means of acceptable guarding include: Isolation in a cabinet, room, or vault accessible only Isolation in a cabinet, room, or vault accessible only
by qualified personsby qualified persons Use of partitions or screens to exclude unqualified Use of partitions or screens to exclude unqualified
personspersons Elevation of eight feet or more above the floorElevation of eight feet or more above the floor
Electric installations over 600 require special Electric installations over 600 require special protectionprotection metal-enclosedmetal-enclosed VaultVault controlled by lockcontrolled by lock
Lock Out / Tag OutLock Out / Tag Out
LOTO written LOTO written program program ComponentsComponents
Documented Documented energy control energy control proceduresprocedures
Employee Training Employee Training programprogram
Inspection programInspection program
Lock Out / Tag OutLock Out / Tag Out Purpose is to draw Purpose is to draw
attention to and disable attention to and disable a live energy source a live energy source during service and repair during service and repair work.work.
Lock Out physically Lock Out physically disables the energy disables the energy source, Tag Out provides source, Tag Out provides a warning onlya warning only
OnlyOnly the employee who the employee who placed the lock or tag placed the lock or tag may remove it!may remove it!
Safe Power ShutdownSafe Power Shutdown- 5 Steps -- 5 Steps -
Preparation and NotificationPreparation and Notification– – Understanding energy source and Understanding energy source and alerting all affected employeesalerting all affected employees
ShutdownShutdown – De-energizing procedure – De-energizing procedure IsolationIsolation – Properly locking all power – Properly locking all power
sourcessources Lock & Tag ApplicationLock & Tag Application
Color coding for different tradesColor coding for different trades Employee assigned locksEmployee assigned locks Photo tags, helps locate employee, Photo tags, helps locate employee,
makes associationmakes association ControlControl and Verificationand Verification– Control – Control
stored and residual energy with locks in stored and residual energy with locks in placeplace
Re-energizingRe-energizing- 3 Steps -- 3 Steps -
InspectionInspection – checking – checking the work area and the work area and surrounding surrounding machinery and for machinery and for employeesemployees
NotificationNotification – Make – Make notice to all affected notice to all affected employees as to what employees as to what will be re-energizedwill be re-energized
Removal of Tags Removal of Tags and Locksand Locks
Tags and LocksTags and Locks
Tags and Locks must be:Tags and Locks must be: DurableDurable – resist conditions of – resist conditions of
environmentenvironment StandardizedStandardized – color code and format – color code and format Substantial Substantial – strong enough to minimize – strong enough to minimize
false removalfalse removal IdentifiableIdentifiable – clear message, know who – clear message, know who
it is protectingit is protecting
Extension CordsExtension Cords Cords with missing ground prongs, insulation breeches, crimping Cords with missing ground prongs, insulation breeches, crimping
or crushing, must be removed from service.or crushing, must be removed from service. Splicing is prohibited, but new connectors are acceptableSplicing is prohibited, but new connectors are acceptable When unplugging, pull the plug, never tug on the cordWhen unplugging, pull the plug, never tug on the cord If a cord must cross a vehicle pathway it must be protectedIf a cord must cross a vehicle pathway it must be protected OSHA considers an extension cord temporary power, no matter OSHA considers an extension cord temporary power, no matter
the power source!the power source!
Service RatingsService RatingsHard ServiceHard Service (types S, ST, SO, STO)(types S, ST, SO, STO)
Junior Hard ServiceJunior Hard Service (types SJ, SJO, SJT, (types SJ, SJO, SJT, SJTO)SJTO)
Home use, small applianceHome use, small appliance (type SP)(type SP)
Ground Fault Circuit Ground Fault Circuit InterruptersInterrupters
Ground Fault Circuit Ground Fault Circuit Interrupters (GFCI’s) sense Interrupters (GFCI’s) sense changes in current (5 changes in current (5 milliamps) and stop energy milliamps) and stop energy flow.flow.
Devices stop current in 1/40 Devices stop current in 1/40 of a secondof a second
Never bypass any protective Never bypass any protective system or device designed system or device designed to keep you from contact to keep you from contact with electrical current.with electrical current.
All temporary power sources All temporary power sources must have GFCI protection must have GFCI protection either at main box, either at main box, extension cord, or tool.extension cord, or tool.
Portable GeneratorsPortable Generators Never use a generator Never use a generator
indoors or in an attached indoors or in an attached garage.garage.
Use extension cords with Use extension cords with adequate duty ratings. adequate duty ratings.
To prevent electrical To prevent electrical shock, make sure your shock, make sure your generator is properly generator is properly grounded.grounded.
Do not store fuel indoors or Do not store fuel indoors or try to refuel a generator try to refuel a generator while it's running. while it's running.
Turn off all equipment Turn off all equipment powered by the generator powered by the generator before shutting it downbefore shutting it down..
Other ConsiderationsOther Considerations
Environmental Deterioration of Environmental Deterioration of EquipmentEquipment - Unless specified for use in - Unless specified for use in such an environment, no conductors or such an environment, no conductors or equipment should be exposed to;equipment should be exposed to; Damp or wet locationsDamp or wet locations Gases, fumes, vapors, liquids, or Gases, fumes, vapors, liquids, or
other deteriorating agentsother deteriorating agents Excessive Temperatures Excessive Temperatures
Safe Work PracticesSafe Work Practices Always check the location of Always check the location of
overhead power lines (most overhead power lines (most common source of electrocution)common source of electrocution)
Stay away from energized power Stay away from energized power circuitscircuits
Locate all utilities prior to digging Locate all utilities prior to digging or jack hammeringor jack hammering
Protect electrical equipment in Protect electrical equipment in passageways from contactpassageways from contact
Keep walking and working Keep walking and working surfaces free of electrical cords surfaces free of electrical cords as much as possibleas much as possible
Always de-energize equipment Always de-energize equipment before repair or service workbefore repair or service work
Electrical ChecklistElectrical ChecklistExtension cords:Extension cords:
- No crimping or crushing- No crimping or crushing
- No missing insulation- No missing insulation
- No signs of stress at plug- No signs of stress at plug
All extension cords out of All extension cords out of high traffic areas:high traffic areas:
- Road ways (protective cover)- Road ways (protective cover)
- Driveways- Driveways
- Hallway, entrance, stairwell- Hallway, entrance, stairwell
Lock Out / Tag Out plan for all Lock Out / Tag Out plan for all maintenance operationsmaintenance operations
Equipment rated for duty Equipment rated for duty and environmentand environment
Proper PPE when necessaryProper PPE when necessary GFCI protection at box, cord, GFCI protection at box, cord, or toolor tool
Awareness of all overhead Awareness of all overhead power linespower lines
All tools double insulatedAll tools double insulated
Pre-job identification of all Pre-job identification of all underground utilitiesunderground utilities
Generators must have earth Generators must have earth groundground
top related