english module3 electrical hazards

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Module 3Electrical Hazards

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Let’s start with a few case histories

“An employee was electrocuted while using a grinder with a frayed cord. The employee was

standing in water, wet-grinding stone countertops…”

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“A maintenance employee was electrocuted while attempting to change a light fixture…”

(no Lockout/Tagout)

“An employee was electrocuted when he made contact with a piece of equipment being hoisted from an excavation. The arm of the backhoe hoisting the equipment contacted an overhead power line…”

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Top Electrical Citations (FY 2005)Top Electrical Citations (FY 2005)

350

660

1157

1313

0 200 400 600 800 1000 1200 1400

1926.416

1926.403

1926.405

1926.404

Elec. Wiring Methods, Components and Equipment, General Use

Electrical, General Requirements

Electrical, Safety-Related Work Practices, General Requirements

Electrical, Wiring Design and Protection

Source: Citation statistics from Federal OSHA data for OSHA fiscal year 2005

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Causes of Causes of Electrocution FatalitiesElectrocution Fatalities

• Contact with Overhead Power lines• Contact with Live Circuits• Not following Lock/Tagout procedures• Poorly Maintained Extension Cords• Defective Power Tools

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Electrical InjuriesElectrical InjuriesThere are three direct and two indirect types of

electrical injuries:• Direct:

Electrocution or death due to electrical shockElectrical shockBurns

• Indirect:FallsFire

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Shock SeverityShock Severity• Severity of the shock

depends on:– Path of current through the

body– Amount of current flowing

through the body (amps)– Duration of the shocking

current through the body, • LOW VOLTAGE DOES NOT

MEAN LOW HAZARD

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Overhead Power Lines HazardOverhead Power Lines Hazard • Usually not insulated• Examples of equipment

that can contact power lines:– Crane – Ladder– Scaffold– Backhoe– Scissors lift– Raised dump truck bed– Aluminum paint roller

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It’s Your Job to Know!It’s Your Job to Know! Know the hazards of electricity Know the equipment Use Safe Work Practices Inspect your PPE before each use Don’t work on energized circuits without permission

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Safety-Related Safety-Related Work PracticesWork Practices

To protect workers from electrical shock:– Use barriers and guards to prevent passage

through areas of exposed energized equipment

– Pre-plan work, post hazard warningsand use protective measures

– Keep working spaces and walkways clear of cords

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“An employee working on a roof made contact with the service entrance riser into the home and was electrocuted…”

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• Special Training is required for work on electrical equipment. Such training is for Authorized Employees and it covers:– Safe Work Practices – Isolation of Electrical Sources – Test Equipment – Tools & PPE

• Only Authorized Employees may conduct electrical work

CautionCaution

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Control DevicesControl Devices

Control circuit devices such as…–push buttons –selector switches –interlocks

… may not be used as the sole means for de-energizing circuits or equipment.

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Control – Use GFCIControl – Use GFCI(ground-fault circuit interrupter)(ground-fault circuit interrupter)• Protects you from shock• Detects difference in current

between the black and white wires • If ground fault detected, GFCI

shuts off electricity in 1/40th of a second

• Use GFCI’s on all 120-volt, single-phase, 15- and 20-ampere receptacles, or have an assured equipment grounding conductor program.

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ELECTRICAL SAFETYELECTRICAL SAFETY Effects of Amount of AC Current

ma=1/1000th of an amp• 3 ma- painful shock which cause indirect

accidents• 10ma- muscle contraction...”no let go” danger• 30ma- lung paralysis- usually temporary• 50ma- possible ventricular fibrillation (heart

dysfunction, usually fatal)• 100 ma- certain ventricular fibrillation, fatal• 4 amps- heart paralysis, severe burns

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How it worksHow it works

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Are these safe practices?Are these safe practices?

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Lock & TagLock & Tag• Lock & Tag all Sources

– Place Lock & Tag on each disconnecting means used to de-energize circuits

– Attach lock to prevent operating the disconnecting means

– Place Tag with each lock

Note: Only the person who places the lock may remove it.

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Lockout Devices

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If a Lock cannot be applied…If a Lock cannot be applied…• A tag used without a lock must be supplemented

by at least one additional safety measure that provides a level of safety equal to that of a lock.

• Examples:– Removal of an isolating circuit element

such as a fuse– Blocking of a controlling switch – Opening of an extra disconnecting

device.

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TagoutThere many different kinds of tags and Lockout devices.

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Release Stored EnergyRelease Stored Energy• Stored electric energy must be released

before starting work.

– Discharge all Capacitors

– Short-Circuit & Ground all high capacitance elements

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Is it “Dead”?Is it “Dead”?• Verify System is De-

energized – Operate the equipment controls to check that equipment cannot berestarted.

Use test equipment to test the circuits & Use test equipment to test the circuits & electrical parts for voltage & currentelectrical parts for voltage & current

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Alerting others of hazardsAlerting others of hazardsUse barricades to prevent or limit access to

work areas with un-insulated energized conductors or circuit parts.

Use safety signs, safety symbols, or accident prevention tags to warn others about electrical hazards which may endanger them.

If signs and barricades do not provide sufficient warning and protection from electrical hazards, an attendant shall be stationed to warn and protect employees.

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Electrical ToolsElectrical Toolsand Cordsand Cords

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Portable Electric Tools Portable Electric Tools & Cords& Cords

• Portable equipment must be handled in a manner which will not cause damage.

• Flexible electric cords connected to equipment may not be used for raising or lowering the equipment.

• Flexible cords may not be fastened with staples or otherwise hung in such a fashion as could damage the outer jacket or insulation.

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Tools & EquipmentTools & Equipment– Use insulated tools or handling equipment

when working near exposed energized conductors or circuit parts.

– Use fuse handling equipment to remove or install fuses when the fuse terminals are energized.

– Ropes and handlines used near exposed energized parts must be nonconductive.

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Power Tool RequirementsPower Tool Requirements• Have a three-wire cord with

ground plugged into a grounded receptacle, or

• Be double insulated, or

• Be powered by a low-voltage isolation transformer

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Preventing Electrical Hazards - Preventing Electrical Hazards - ToolsTools

• Inspect tools before use

• Use the right tool correctly

• Protect your tools• Use double insulated

toolsDouble Insulated marking

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Any problems?Any problems?

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Clues that Electrical Hazards ExistClues 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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Beware of Old WiringBeware of Old Wiring• Removal of expansion tank (hot water).Removal of expansion tank (hot water).• Old style knob electrical wiring.Old style knob electrical wiring.• Victim contacted frayed wiring.Victim contacted frayed wiring.

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Wire PullingWire Pulling

• Avoid manual wire pulling and use a tugger or a handtool whenever possible• Communication between the puller and feeder to coordinate movements will make the job easier and safer.• Use lighter-weight tools.

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Reducing Body StrainsReducing Body Strains• CHANGE BODY POSITIONS. • Working overhead, at floor level, or in

cramped spaces forces the body into awkward postures.

• To relieve muscle tension and improve circulation, change body positions, alternate tasks, and stretch throughout the day.

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SummarySummary

Electrical equipment must be:– Listed and labeled– Free from hazards– Used in the proper manner

If you use electrical tools you must:– Be protected from electrical shock– Use them in a comfortable position– Be provided with necessary safety equipment

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Always remember…Always remember…It’s your It’s your lifelife!!

“A tree trimmer was electrocuted when he touched an overhead electrical line while descending a palm tree…”

“An employee was electrocuted while working on an A/C unit…”