electrical safety13

Electrical SafetyBy

Autry Technology Center

You shall be able to identify:

The injuries and fatalities while working near electricity.

Basic electrical principles.

Workers at risk.

Basic electrical hazards. Safe work practices associated with electricity.

Crane contacts electrical lines; causes fire; tires begin to burn

Each year contact with overhead power lines result in fatalities, serious injury and property damage.

Unintentional contact with overhead power lines resulted in the following: Based on accident statistics in one state

19 serious accidents from July 1999 through September 2005.

16 fatalities. Based on national statistics (NSC–2004)

309 fatalities occurred from 1999 to 2001.

These statistics only represent facts that have been reported to these agencies; the actual number of fatalities and suffering are far greater.

Electricity - The Dangers

About 5 workers are electrocuted every week

Causes 12% of young worker workplace deaths

Takes very little electricity to cause harm

Significant risk of causing fires

Fact: an electrical arc generates temperatures in excess of 35,000 degrees F.

This is hot enough to vaporize steel.

Electrical Shock Injury; Note entry and exit point

These accidents can be prevented with improved supervisor and worker safety training and better coordination of work with all utilities involved.

Same injury a few days later

Exit point on bottom of foot

At-Risk Workers

Equipment operators of mobile equipment, dump trucks, drill rigs, cranes, etc. and employees who work around this equipment

Emergency service personnel who respond to car crashes involving power poles and overhead lines, downed power lines, respond to fires involving electrical lines near structures

Employees working from ladders Employees working with electrical equipment

At-Risk Workers Employees working from roofs where

power lines enter building Employees who work from scaffolds Employees who work from Man lifts or

bucket trucks around power lines And Any employee who is near overhead

power lines for any reason such as tree trimmers, highway workers, forklift operators, etc.

Electrical Shock

An 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.

Electrical Harm

Estimated Effects of AC Currents (U.S. Standard 60 Hz)

1 milliamp (mA)

Barely perceptible

16 mA Maximum current an average man can grasp and “let go”

20 – 30 mA Paralysis of respiratory muscles

100 mA Ventricular fibrillation threshold

2 Amps Cardiac standstill and internal organ damage

15/20/30 Amps

Common U.S. household breakers

PATH: Harm is related to the path by which current passes through the body.

Dangers of Electrical Shock

Currents greater than 75 mA* can cause ventricular fibrillation (rapid, ineffective heartbeat). Will cause death in a few minutes

unless a defibrillator is used. 75 mA is not much current – a

small power drill uses 30 times as much current.

Defibrillator in use

Fundamentals of Electrical Hazards

To flow electricity must have a complete path. Electricity flows through conductors

water, metal, the human body

Insulators are non-conductors. The human body is a conductor.

Electrical Injuries

There are four main types of electrical injuries: Direct:

Electrocution or death due to electrical shockElectrical shockBurns

Indirect - Falls

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

Hit live wire changing a light ballast; lost right index finger

High Voltage Electricity Follows the Path of Least Resistance to Ground

Fact: High Voltage Electricity Follows all Paths to

Ground

Worker subjected to arc flash

Fire resistant shirt

Electrical Damage to the Body If you touch a power

line, electricity will attempt to travel through your body

When electricity travels through the body, it heats up and burns body tissue internally

Electricity leaves the body violently, causing burns or even blowing an exit hole

The Sad

Reality- this victim

contacted an overhead power line while working from an aerial bucket

Myths

Fact: Possibly Dead Wrong! Electricity Travels at the

speed of light, 186,000 miles per second. If you touch another person that is in contact with a high voltage wire you will instantly become part of the electrical circuit.

You Can Safely Shove a Person Away From Contact With an Energized Power

Car and Truck Tires Are Made of Rubber and Are Non-Conductive

Fact: Tires contain Carbon Black. Carbon Black is a

conductive material used to make the tires conductive for a better radio signal and to make them last longer.

If an overhead electrical line falls upon your vehicle stay on or inside the vehicle if at all possible. If you must leave your vehicle do not touch the vehicle and

ground at the same time. Jump clear and Keep both feet together and hop away.

Myths

I Can Safely Use a Tree Limb To Move an Overhead Powerline

Fact: Tree limbs are conductive. Fresh tree limbs are

very electrically conductive due to the moisture content.

High voltage electricity will conduct through most items that have contamination or moisture.

Myths

Overhead Powerlines Laying on the Ground Are Safe To Be Near.

Fact: Just because a power line is laying on the ground

does not mean it is not energized. Always consider downed power lines live! High voltage electricity can enter the ground from

the power line. This can create different electrical potentials near the

wire that could cause electrocution by contact through your footwear.

Myths

I Can Look-Up and Estimate the Distance to The Powerline.

Fact: Few people have the ability to judge vertical

distance accurately. Don’t take a chance with your safety and the

safety of those working around you. Call the owner of the powerlines at least 72

hours prior to working within 50 feet of energized overhead power lines.

Myths

I’ve Been Shocked by Electricity Before, So I Know What Electricity Will Do.

Fact: Unless you have seen the destructive

power of High Voltage Electricity first hand you have no idea what it can do to material, objects and to people compared to household voltages.

Myths

A Powerline Falls Across Your Vehicle, You Should Not Try to Drive Away.

Fact: You should try to drive away if at all possible.

If your vehicle will not start stay inside and warn others to stay away until an electrical line worker tell you it is safe to leave the vehicle.

Myths

Scaffold Too Close to Power Lines• The possibility of

electrocution is a serious consideration when working near power lines.

• Check the clearance distances listed in the OSHA standards.

Ladder Too Close to Energized Electrical Equipment

If using ladders where the employee or the ladder could contact exposed energized electrical equipment, they must have nonconductive siderails such as wood or fiberglass.

This is an unsafe condition

It’s up to you to prevent contacts with electricity.

Don’t Put Your Life on the Line!