ELECTRICAL SAFETY! It’s shocking! OSHA 29 CFR 1910.332

Introduction An average of one worker is electrocuted on the job every day. There are four main types of electrical injuries: Electrocution (death due to electrical shock) Electrical shock Burns Falls

Electrical Terminology Current – the movement of electrical charge Resistance – opposition to current flow Voltage – a measure of electrical force Conductors – substances, such as metals, that have little resistance to electricity Insulators – substances, such as wood, rubber, glass, and bakelite, that have high resistance to electricity Grounding – a conductive connection to the earth which acts as a protective measure

Leading causes of injury Unsafe work practices (cause of 75% of fatalities) Working with unsafe equipment Working in an unsafe environment

Qualified worker vs. Unqualified Worker OSHA Definitions Qualified worker vs. Unqualified Worker Qualified One who is familiar with the construction and operation of the equipment and hazards involved (licensed electrician). Or One who is undergoing “on-the-job” training and has demonstrated competency in performing the duties safely (apprentice).

OSHA Definitions Qualified workers Unqualified workers How to identify exposed energized parts How to safeguard or work on energized parts Unqualified workers How electricity works Risks of working with energized equipment Tasks to be performed only by qualified workers

Electrical Shock Received when current passes through the body Severity of the shock depends on: Path of current through the body Amount of current flowing through the body Length of time the body is in the circuit LOW VOLTAGE DOES NOT MEAN LOW HAZARD

Electrical Shock Dangers of Electrical Shock Defibrillator in use 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 Defibrillator in use * mA = milliampere = 1/1,000 of an ampere

Electrical Shock How is an electrical shock received? When two wires have different potential differences (voltages), current will flow if they are connected together. In most household wiring, the black wires are at 110 volts relative to ground. The white wires are at zero volts because they are connected to ground. If you come into contact with an energized (live) black wire, and you are also in contact with the white grounded wire, current will pass through your body and YOU WILL RECEIVE A SHOCK.

Electrical Shock If you are in contact with an energized wire or any energized electrical component, and also with any grounded object, YOU WILL RECEIVE A SHOCK!! You can even receive a shock when you are not in contact with a ground. If you contact both wires of a 240-volt cable, YOU WILL RECEIVE A SHOCK and possibly be electrocuted.

Electrical Hazards Shock Arc Blast

Rules of Electricity Electricity travels in a completed circuit Electricity always travels in the path of least resistance Electricity tries to travel to the ground

Effects on the Human Body 1 mA: Can be felt by the body 2-10 mA: Minor shock, might result in a fall 10-25 mA: Loss of muscle control, may not be able to let go of the current 25-75 mA: Painful, may lead to collapse or death 75-300 mA: Last 1/4 second, immediately fatal 110/120 Volts = 60 mA 220/240 Volts = 120 mA 440/480 Volts = 240 mA

Severity Of Shock Depends On: Amount of current flowing through body The path it takes through the body Elapsed time during shock

Body’s Resistance Skin offers most of the body’s electrical resistance Increased resistance Thick and callused skin (foot or hand) Dry skin Decreased resistance Thin skin (inner forearm) Wet or sweaty skin Broken or abraded skin (scratches)

Conductor vs. Insulator Stops electricity Does Not Conduct electricity Conductor Transfers electricity

General Electrical Hazards High-voltage overhead power lines Damaged insulation on wires Digging or trenching near buried lines Broken switches or plugs Overloaded circuits Overheated appliances or tools

Hazard Control Injuries typically occur when: Procedures are inappropriate Procedures are not followed Safety systems are circumvented

Portable Power Tools Inspect portable power tools before every use! Never use damaged equipment. Tag it out of service Have it repaired or replaced

Portable Electric Equipment UL approved equipment and cords Graded for hazardous locations Extension cords must have a ground wire polarity plug. Inspect for frays, breaks or other damage to the cord insulation Inspect for grease, oil or chemicals on cords Do not unplug or raise equipment by cord Do not use around combustible atmospheres (“Intrinsically Safe” only) Work in dry area - avoid water

Extension Cords Inspect and check for capacity For temporary work only Do not use as a rope to pull or lift objects Should not be fastened with staples or hung over hooks

Electrical Cord Inspection Deformed or mission pins Damaged outer jacket or insulation Evidence of internal damage If damaged, take out of service until repaired

Grounding Equipment Most electrical equipment is designed with a grounding system Do not use equipment with damaged grounding connectors Do not use adapters that interrupt the grounding connection

Static Electricity Created when materials rub together Can cause shocks or even minor skin burns Reduced or prevented by: Proper grounding Rubber matting Grounding wires, gloves, or shoes

Ground Fault Circuit Interrupters GFCIs reduce the likelihood of fatal shocks Detect small amount of earth current and automatically switch off the power Used with extension cords and portable tools Fuses and circuit breakers protect equipment, not people

Most effective piece of safety gear ever created…

contact with electricity! Never touch anyone in contact with electricity! What to do in emergencies: Shut off power Call for emergency help Administer First Aid/CPR If unable to shut off power, use a wooden chair, pole, or PVC to free the person.

Training Train employees working with electric equipment in safe work practices, including: Deenergizing electric equipment before inspecting or making repairs Using electric tools that are in good repair Using good judgment when working near energized lines Using appropriate protective equipment

Summary Protective Measures Hazards Proper grounding Inadequate wiring Using GFCI’s Using fuses and circuit breakers Guarding live parts Proper use of flexible cords Training Hazards 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 power lines All hazards are made worse in wet conditions