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CHAPTER NINE

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Electrical InjuriesThere are four main types of electrical

injuries: Direct:

– Electrocution or death due to electrical shock– Electrical shock– Burns

Indirect:– Falls

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Electrical ShockAn electrical shock is received when electrical current passes through the body.

You will get an electrical shock if a part of your body completes an electrical circuit by… Touching a live wire and an electrical ground, or Touching a live wire and another wire at a different voltage.

Shock 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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Burns Most common shock-related injury Occurs when you touch electrical wiring or

equipment that is improperly used or maintained

Typically occurs on hands Very serious injury that needs immediate

attention

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Falls

Electric shock can also cause indirect injuries

Workers in elevated locations who experience a shock may fall, resulting in serious injury or death

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Electrical Hazards and How to Control Them

Electrical accidents are caused by a combination of three factors:– Unsafe equipment

and/or installation, – Workplaces made

unsafe by the environment, and

– Unsafe work practices.

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Hazard – Exposed Electrical Parts

Cover removed from wiring or breaker box

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Control – Isolate Electrical Parts Use guards or

barriers

Replace covers

Guard live parts of electric equipment operating at 50 volts or more against accidental contact

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Control – Isolate Electrical Parts - Cabinets, Boxes & Fittings

Conductors going into them must be protected, and unused

openings must be closed

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Control – Close Openings Junction boxes, pull

boxes and fittings must have approved covers

Unused openings in cabinets, boxes and fittings must be closed (no missing knockouts)

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Hazard - Inadequate Wiring Hazard - wire too small for the

current Example - portable tool with an

extension cord that has a wire too small for the tool– The tool will draw more current

than the cord can handle, causing overheating and a possible fire without tripping the circuit breaker

– The circuit breaker could be the right size for the circuit but not for the smaller-wire extension cord

Wire Gauge

WIRE

Wire gauge measures wires ranging in size from number 36 to 0 American wire gauge (AWG)

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Control – Use the Correct Wire Wire used depends

on operation, building materials, electrical load, and environmental factors

Use fixed cords rather than flexible cords

Use the correct extension cord

Must be 3-wire type and designed for hard or extra-hard use

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Hazard – Defective Cords & Wires Plastic or rubber

covering is missing

Damaged extension cords & tools

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Hazard – Damaged Cords Cords can be damaged by:

– Aging

– Door or window edges

– Staples or fastenings

– Abrasion from adjacent materials

– Activity in the area Improper use can cause

shocks, burns or fire

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Control – Cords & Wires Insulate live wires Check before use Use only cords that are 3-wire

type Use only cords marked for hard or

extra-hard usage Use only cords, connection

devices, and fittings equipped with strain relief

Remove cords by pulling on the plugs, not the cords

Cords not marked for hard or extra-hard use, or which have been modified, must be taken out of service immediately

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Hazard – Improper Grounding Tools plugged into

improperly grounded circuits may become energized

Broken wire or plug on extension cord

Some of the most frequently violated OSHA standards

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Control – Ground Tools & Equipment

Ground power supply systems, electrical circuits, and electrical equipment

Frequently inspect electrical systems to insure path to ground is continuous

Inspect electrical equipment before use

Don’t remove ground prongs from tools or extension cords

Ground exposed metal parts of equipment

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Control – Use GFCI (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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Control - Assured Equipment Grounding Conductor ProgramProgram must cover:

– All cord sets– Receptacles not part of a building or structure – Equipment connected by plug and cord

Program requirements include:– Specific procedures adopted by the employer– Competent person to implement the program– Visual inspection for damage of equipment

connected by cord and plug

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Hazard – Overloaded CircuitsHazards may result from: Too many devices plugged into a

circuit, causing heated wires and possibly a fire

Damaged tools overheating Lack of overcurrent protection Wire insulation melting, which

may cause arcing and a fire in the area where the overload exists, even inside a wall

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Control - Electrical Protective Devices Automatically opens circuit if

excess current from overload or ground-fault is detected – shutting off electricity

Includes GFCI’s, fuses, and circuit breakers

Fuses and circuit breakers are overcurrent devices. When too much current:

Fuses melt Circuit breakers trip open

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Safety-Related Work 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 warnings and use protective measures

– Keep working spaces and walkways clear of cords

Use special insulated tools when working on fuses with energized terminals

Don’t use worn or frayed cords and cables

Don’t fasten extension cords with staples, hang from nails, or suspend by wire.

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Preventing Electrical Hazards - Planning Plan your work with others Plan to avoid falls Plan to lock-out and tag-out

equipment Remove jewellery Avoid wet conditions and

overhead power lines

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Preventing Electrical Hazards - PPE• Proper foot protection (not

tennis shoes)

• Rubber insulating gloves, hoods, sleeves, matting, and blankets

• Hard hat (insulated - nonconductive)

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Preventing Electrical Hazards – Proper Wiring and Connectors

• Use and test GFCI’s

• Check switches and insulation

• Use three prong plugs

• Use extension cords only when necessary & assure in proper condition and right type for job

• Use correct connectors

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TrainingTrain employees working with electrical

equipment in safe work practices, including : Deenergize electric equipment before

inspecting or repairing Using cords, cables, and electric tools that are

in good condition Lockout / Tagout recognition and procedures Use appropriate protective equipment

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Summary – Hazards & ProtectionsHazards Inadequate wiring Exposed electrical parts Wires with bad insulation Ungrounded electrical

systems and tools Overloaded circuits Damaged power tools and

equipment Using the wrong PPE and

tools Overhead powerlines All hazards are made

worse in wet conditions

Protective Measures•Proper grounding•Use GFCI’s•Use fuses and circuit breakers•Guard live parts•Lockout/Tagout•Proper use of flexible cords•Close electric panels•Training

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1926.450 Scope, application and definitions

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What Is A Scaffold?An elevated, temporary work

platform

Three basic types: Supported scaffolds -- platforms

supported by rigid, load bearing members, such as poles, legs, frames, & outriggers

Suspended scaffolds -- platforms suspended by ropes or other non-rigid, overhead support

Aerial Lifts -- such as “cherry pickers” or “boom trucks”

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Hazards Falls from elevation –

caused by slipping, unsafe access, and the lack of fall protection

Struck by falling tools / debris

Electrocution – from overhead power lines

Scaffold collapse - caused by instability or overloading

Bad planking giving way

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Definitions

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1926.451 General requirements Capacity Platform construction Supported scaffolds Suspension scaffolds Scaffold access Scaffold use Fall protection Falling object protection

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Scaffold capacity and platform constructionPlatforms must:

• be fully planked or decked with no more than 1 inch gaps

• be able to support its weight & 4 times maximum load

• be at least 18 inches wide This is not a properly

constructed scaffold

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• No large gaps in front edge of platforms

• Each abutted end of plank must rest on a separate support surface

• Overlap platforms at least 12 inches over supports, unless restrained to prevent movement

Planks not properly overlapped

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• No paint on wood platforms

• Use scaffold grade wood

• Fully planked between front upright and guardrail support

• Component pieces used must match and be of the same type

• Erect on stable and level ground

• Lock wheels and braces

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Supported ScaffoldsPlatforms supported by legs, outrigger beams, brackets, poles, uprights, posts, & frames

Restrain from tipping by guys, ties, or braces

Scaffold poles, legs, posts, frames, and uprights must be on base plates and mud sills or other firm foundation

This support is not adequate!

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Scaffold Support Examples

Base plate

Mud sills

Good support Inadequate support – in danger of collapse?

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Suspension ScaffoldsPlatforms suspended by ropes or wires.

Rope must be capable of supporting 6 times the load

Train employees to recognize hazards

Secure/tie to prevent swaying

Mandatory requirements : Support atleast four times the

operating load of the scaffold. Support 1.5 times the scaffold load

when operating at the stall load of the hoist.

The greater of these two requirements is the one that applies.

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Scaffold AccessProvide access when scaffold platforms are

more than 2 feet above or below a point of access

No access by crossbraces

Permitted types of access: Ladders, such as portable, hook-on,

attachable, stairway type, and built-ins Stair towers Ramps and walkways

May use building stairs and come out window.

Can access from another scaffold, structure or hoist

Do not access by crossbraces

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Requirements for safe scaffold useDon’t work on snow

or ice covered platforms or during storms or high windsUse tag lines on

swinging loadsProtect suspension

ropes from heat & acid.Don’t use shore or

lean - to scaffolds.A covered scaffold has special

wind load considerations

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Moving scaffolds

Employees can’t be on a moving scaffold unless:• Surface is level• Height to base ratio is 2

to 1• Outriggers are installed

on both sides of scaffoldsCompetent person must be

on site to supervise

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Scaffold inspection

Competent person inspects scaffolds for visible defects before each shift and after any alterations

Defective parts must be immediately repaired

Deformed bearer

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Scaffold ErectionScaffolds can only be

erected, moved, dismantled or altered under the supervision of a competent person

Competent person selects & directs these workers and determines the feasibility of fall protection

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Fall protectionIf a worker on a scaffold

can fall more than 10 feet, protect them by:

Guardrails, and/or

Personal Fall Arrest Systems (PFAS)

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•A guardrail or personal fall arrest system is required on all sides except the side where the work is being done.•You must be trained how to properly use PFAS

PFAS include anchorage, lifeline and body harness.

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Falling Object Protection• Wear hardhats

• Barricade area below scaffold to forbid entry into that area

• Use panels or screens if material is stacked higher than the toeboard

• Build a canopy or erect a net below the scaffold that will contain or deflect falling objects

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1926.452 Requirements for specific types of Scaffolds

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1926.453 Aerial liftsAerial lifts are vehicle mounted mechanisms used

to elevate workers to locations above the ground that would otherwise be inaccessible to them.

Types : Extensible boom platforms Aerial ladders Articulating boom platforms Vertical towers

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1926.454 Training requirementsTrain employees on scaffold hazards and procedures to control the hazards

The training must include:• Nature of electrical, fall, and falling object hazards • How to deal with electrical hazards and fall protection systems• Proper use of the scaffold• Scaffold load capacities

Retrain as necessary

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1926.500 Scope application and defintions

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1926.501 Duty to have fall protectionOSHA requires employees to provide fall protections systems

that must meet certain criteria:• Walking and working surfaces must have sufficient strength

and structural integrity to support employees safely. • Employers must provide protection to employees working in

areas with unprotected sides or edges 6 feet or more above a lower level.

• Specific types of protection are required in work areas with leading edges, in hoist areas, in work areas with holes, ramps, runways, and other walkways, in areas where excavations are being conducted, where dangerous equipment is being used, during overhand bricklaying, in roofing, in precast concrete erection, in residential construction, and in work areas with wall openings.

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Hard hats are required when workers may be exposed to falling objects.

Other requirements include either

1)use of toeboards, screens or guardrail systems; or

2)use of a canopy structure; or

3)barricading area to which objects could fall and prohibiting employees from entrance.

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Guard ramps, runways, and other walkways

Walkways and Ramps

Guard ramps, runways, and other walkways

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In residential construction, you must be protected if you can fall more than 6 feet

Fall Protection -Residential Construction

In residential construction, you must be protected if you can fall more than 6 feet

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Unprotected edge

Unprotected Sides & Edges

Unprotected sides and edges must have guardrails or equivalent

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Sides & Edges - Improper Guarding

This 1/4" nylon rope alone is not a proper way to guard this open floor

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• Holes more than 6 feet high must be protected• This opening could be made safe by using a guardrail, or strong cover

Sky Lights and Other Openings

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• Cover completely and securely• If no cover, can guard with a guardrail

Floor Holes

ImproperlyCovered

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• Use PFAS when working on formwork or rebar• Cover or cap protruding rebar

Concrete Forms and Rebar

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Guard excavations more than 6 feet deep when they are not readily seen because of plant growth or other visual barriers

Excavations

In addition to needing guarding, this excavation is not properly shored

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If you work on roofs and can fall more than 6 feet, you must be protected

Roofs

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If you work near wall openings 6 feet or more above lower levels you must be protected from falling

Wall opening

Wall Openings

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1926.502 Fall protection systems and criteria

Personal Fall Arrest System

(PFAS)

Other fall protection systems include positioning device, warning line, controlled access and safety monitoring system

Safety NetGuardrails

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Guardrails

• Top edge of the guardrail must be 39-45 inches above the walking/working level.• Intermediate structural members must be installed between the top edge of the guardrail and the walking surface when the wall is atleast 21 inches high.

Top Rail

Mid- Rail

Toeboard

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Safety line anchorages

Must be independent of any platform anchorage and capable of supporting at least 5,000 lbs. per worker

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Personal fall arrest systems

• You must be trained how to properly use PFAS.

• PFAS = anchorage, lifeline and body harness.

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Fall protection plan

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Lanyards and PFAS in use

Fall protection systems and work practices must be in place before you start work.

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1926.503 Training requirementsEmployers must provide fall protection training.

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The training must include: The nature of fall hazards in the work area; The correct procedures for erecting, maintaining, disassembling, and

inspecting the fall protection systems to be used; The use and operation of guardrail systems, personal fall arrest systems,

safety net systems, warning line systems, safety monitoring systems, controlled access zones, and other protection;

The role of each employee in the safety monitoring system when this system is used;

The limitations on the use of mechanical equipment during the performance of roofing work on low-sloped roofs;

The correct procedures for the handling and storage of equipment and materials and the erection of overhead protection; and

The role of employees in fall protection plans. The standards of subpart MThe employer must verify compliance with the training requirements by

preparing a written certification record. The employer must retrain any employee when the employer has reason to

believe that the trained employee does not have the understanding and skill required.

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1926.550 Cranes and Derricks

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General requirements Equipment knowledge : Companies are required

to comply with manufacturer’s specifications and

limitations. Equipment modifications : The manufacturers

must give written approval for any and all modifications before they are made.

Crane certification : Cranes used in construction are exempt from certification. However they must be properly inspected by a competent person.

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Competent person The competent person

must inspect all machinery and equipment prior to each use, and during use, to make sure it is in safe operating condition.

If it needs fixing, take it out of service and don’t use it until it is fixed

BrokenTrack

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Inspections

Crane wasn’t inspectedand tipped over

•Frequent inspections•Periodic inspections

Inspection of the hoisting machinery must be made by a competent person

The employer must maintain a record of these inspections

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Types of cranes Hammerhead tower cranes Overhead and gantry cranes Derricks Floating cranes and derricks

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Crane hazards Improper load rating Excessive speeds No hand signals Inadequate inspection and maintenance Unguarded parts Unguarded swing radius Working too close to power lines Improper exhaust system Shattered windows No steps/guardrails walkways No boom angle indicator Not using outriggers

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Improper loads or speeds can result in the tipping of the crane

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Improper Load

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Improper Load

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Power lines

Stay clear from power lines at least 10 feet

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General requirementsAll motor vehicles must have A system of operating, emergency and parking

brakes. Two headlights, two tail lights, break lights Audible warning device (horn) Audible alarm system for backing up. Cabs must be equipped with safety glass, windshield

wipers and a system for defogging the windows Seats and safety belts for every passenger

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Requirements for industrial trucks

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Forked truck training requirements

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Multimedia – Crane Safety

http://www.osha.gov/SLTC/video/cranesafety/video.html