Electrical Safety Adapted from Region IV - OSHA INSY

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 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 Triangle Keep Away Grounding GFCI

Electrocution Triangle Electricity Path Time

Fatality 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.

Fatality

Contact with bare conductors Live overhead lines 7,200 Volts

Contact with bare conductors Live overhead lines

Equipment Failure

OSHA Electrical Standard 29CFR 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.

Training 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 through

Working 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.

Working with Electricity  Written procedure.  De-energize equipment & release stored energy.  LOTO (will discuss in later lecture)  Verify de-energization & test.  Re-energize.

Working with Electricity  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

Use of Portable Equipment  Includes cordsets (extension cords).  Cord & Plug connected equipment.

Use of Portable 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.

Use of Portable Equipment  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.

Use of Portable Equipment  Damp/Wet locations require approved equipment  Don’t plug in or unplug stuff with wet hands.

Test 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.

Protective Equipment  Employees working in areas where there are potential electrical hazards shall use electrical PPE.  PPE – Separate Section (Subpart I)  Personal Protective Equipment = PPE  Will discuss in later lecture  Electrical PPE– ASTM F Standards.  Will use signage AND barriers where necessary to prevent contact with current

Protective Equipment  Maintain & periodically test according to  Protect the insulating capability against damage.  Nonconductive head protection.  Face & Eye Protection for arc blast.

Electric Arc Hazards Electric Arcs can reach temperatures of 34,000 o F 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/cm 2 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/cm 2.  Heavy denim might work for about 5-10 cal/cm 2.

Arc Heat Example  480 Volt arc in a box. 6 cycles, at a 12 inch distance. 16,000A8 - 11cal/cm 2 24,000A9 – 14cal/cm 2 38,000A17 – 24cal/cm 2 50,000A32 – 38cal/cm 2

Commonly Cited Violations (b)(1):Unused openings (g)(2):Exposed live parts (b)(2):Missing covers (f):Defective Ground (g)(1)(iii):Prohibited uses of flexible cords.

Commonly Cited Violations (f): Unlabeled disconnects (g)(2)(iii):Strain relief (b)(2):Listed & labeled (b)(1):General Duty Clause (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 Boxes Utility boxes are not approved for usage as extension cords.

Receptacles in Wet Locations Receptacles in wet or damp locations need covers.

Receptacles in Wet Locations Receptacles in wet or damp locations need covers.

Damaged Faceplate

Portable Electric Tools Inspect before usage. Remove from service tools with damaged cords. Use grounded or double insulated tools. Check continuity of tool.

Rubber 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.

ELECTRICAL RELATED FATALITIES FY-02 OSHA – REGION IV Alabama | Florida | Georgia Kentucky | Mississippi | North Carolina South Carolina | Tennessee

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