Download - 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!