Electrical Safety Adapted from Region IV - OSHA INSY 3020 2006.

Electrical Safety

Adapted from Region IV - OSHA

INSY 3020

2006

What is Electricity?What is Electricity?• Electricity is the movement of electrons.

• Fundamental quantities include:– Electrical Potential (Volts), V– Current (Amperes, or Amps), I– Resistance (Ohms, miliohms, microohms), R

• Main Relationship – OHM’s LAW

V = I R

What kinds of hazards are associated with Electricity?

•Hazards include: •Shocks, •Electrocution, •Arc Blast, •Burns, •Explosions.

Electricity and the Human BodyElectricity and the Human Body• ~1ma: Sensation on hands.• >3ma: Painful shock which can cause

indirect accidents.• >10ma: Muscle contraction, “no-let-go”

danger.• >30ma: Lung paralysis• >50ma: Possible ventricular fibrillation.• 100ma - 4A: Certain ventricular fibrillation

Protective TriangleProtective Triangle

Keep AwayKeep Away GroundingGrounding

GFCIGFCI

Electrocution TriangleElectrocution Triangle

ElectricityElectricity PathPath

TimeTime

FatalityFatality•An employee received a fatal electric shock while operating a high pressure water sprayer which was connected to a portable light with a receptacle built into the handle. •The portable light was being used as an extension cord, and was not approved for wet or damp locations. •The electrical cord had been spliced and the cord had been laying in water at the time of the accident.

FatalityFatality

Contact with bare conductorsLive overhead lines

7,200 Volts

Contact with bare conductorsLive overhead lines

Equipment Failure

OSHA Electrical Standard29CFR 1910 Subpart S

• Based in part on NFPA 70 E

Standard Includes… “Premises Wiring”

• Installations of electric conductors and equipment within or on buildings or other structures, and on other premises – yards, – parking, and other lots, – industrial substations;

…Equipment• A general term including

– material, – fittings, – devices, – appliances, – fixtures, – apparatus, and the like,

• used as a part of, or in connection with, an electrical installation.

1910.332Training

• Who needs to be trained in Electrical Safety?

• Employees who face a risk of electric shock that is not reduced to a safe level – electrical installation requirements of

1910.303 through 1910.308.

1910.333Working with Electricity

Live parts (50 Volts or more) shall be de-energized before working on them.Unless the employer can

demonstrate infeasibility or greater hazard.


Written procedure. De-energize equipment & release

stored energy. LOTO (will discuss in later lecture) Verify de-energization & test. Re-energize.


No conductive materials or equipment.

Nonconductive ladders. No conductive apparel. Housekeeping – no steel wool or

conductive liquids.

Tools

Non-Rated tool with cushioned grip.

Rated insulated tool . Tool should be marked with rating.

Insulated Tools

1910.334 Use of Portable Equipment

Includes cordsets (extension cords).

Cord & Plug connected equipment.


Don’t abuse, damage, or use for a rope.

Visually inspect before use. If damaged …

Shall be removed from service & not used until repaired.


Extension cords shall be grounded unless used with double insulated tools.

Don’t mess with the grounding pin. One of the most common violations

No 3-wire grounding adapters, unless the ground continuity is maintained.


Damp/Wet locations require approved equipment

Don’t plug in or unplug stuff with wet hands.

1910.334Test Equipment

Test instruments used only by qualified employees.

Visually inspected before use, including leads and probes.

Rating of equipment (voltage):Test leads rated for full voltage.Designed for environment.

1910.335Protective Equipment

Employees working in areas where there are potential electrical hazards shall use electrical PPE.

PPE – Separate Section (Subpart I)Personal Protective Equipment = PPEWill discuss in later lectureElectrical PPE– ASTM F Standards.

Will use signage AND barriers where necessary to prevent contact with current

1910.335Protective Equipment

Maintain & periodically test according to 1910.137.

Protect the insulating capability against damage.

Nonconductive head protection. Face & Eye Protection for arc blast.

Electric Arc Hazards Electric Arcs can reach temperatures of

34,000oF The arcs can vaporize metal, burn skin,

and ignite clothing. Vaporized copper expands 67,000 times

in volume. High pressures can develop in enclosures,

causing covers and molten metal to fly.

Arc Hazards When clothing ignites, it can greatly

increase the amount of skin area burned, and the chance of a fatality.

Heat levels of 1.2 cal/cm2 per second for one second can cause second degree burns to exposed skin.

Most arc exposure times are less than 1 second.

Arc Hazards Regular cotton work

clothing will typically not ignite at heat levels up to 1-2 cal/cm2.

Heavy denim might work for about 5-10 cal/cm2.

Arc Heat Example 480 Volt arc in a box. 6 cycles, at a

12 inch distance.16,000A 8 - 11 cal/cm2

24,000A 9 – 14 cal/cm2

38,000A 17 – 24 cal/cm2

50,000A 32 – 38 cal/cm2

Commonly Cited Violations

• 1910.305(b)(1): Unused openings

• 1910.303(g)(2): Exposed live parts

• 1910.305(b)(2): Missing covers

• 1910.304(f): Defective Ground

• 1910.305(g)(1)(iii): Prohibited uses of flexible cords.

Commonly Cited Violations

• 1910.303(f): Unlabeled disconnects

• 1910.305(g)(2)(iii): Strain relief

• 1910.303(b)(2): Listed & labeled

• 1910.303(b)(1): General Duty Clause

• 1910.303(g)(1): Access & working space.

Blocked Electrical Panels

Strain on Conductors

Inadequate Strain Relief on Cord

Exposed Live Parts

Employee’s cap is hung on power strip energized to 120VAC

Exposed Live Parts

Exposed live parts

Missing breakers inside of circuit breaker panel

Ungrounded Cords

Ground pin missing on extension cord

Damaged Faceplate

Utility BoxesUtility boxes are not approved for usage as extension cords.

Receptacles in Wet LocationsReceptacles in Wet Locations

Receptacles in wet or damp locations need covers.

Damaged FaceplateDamaged Faceplate

Portable Electric ToolsPortable Electric Tools• Inspect before usage.• Remove from service tools

with damaged cords.• Use grounded or double

insulated tools.• Check continuity of tool.

Rubber GlovesRubber Gloves• Must be air tested daily

before usage.• Must be electrically tested

every 6 months or replaced.• Before issuance gloves may

be stored for up to 1 year without being tested.

Hazard Assessment

• Employers are required to assess the workplace to determine the hazards present – Must also determine whether hazards exist that

require the use of personal protective equipment

• Must look for hazards that are present or are likely to be present.

46 workerskil l ed

by

electrocution

19 workerskilled

Working on

Power transmission lines

11 w or ker s k il l ed inst al l ing equipment

4w or ker s k i l l ed inst al l ingduct w or k

2 workerskilledwhen ladders

contactedpower lines

2 w o r k er s k i l l ed b y d ef ec t i v e el ec t r i c a l

eq u i p men t

2 w or ker s k i l l eddur ing maint enance/

r emoval of equipment

2w or ker s k i l l ed w or k ing

on el ect r ic signs

1w or ker k i l l ed by under gr ound pow er

1worker killed standing in water

adjacent to disconnect

Would You Risk Your Life for a job like

this?

Questions & Comments????

Electrical Safety Adapted from Region IV - OSHA INSY 3020 2006.

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Transcript of Electrical Safety Adapted from Region IV - OSHA INSY 3020 2006.