ELECTRICAL SAFETY Part 2: Working Safely
ELECTRICITY - THE DANGERS SHOCK BURNS ARC FLASH FALLS
ELECTRICAL SHOCK An electrical shock is a current flow through the body. The shock occurs when any part of your body completes a circuit by being: • In contact with two wires • In contact with a wire and ground • In contact with a metal part that is in contact with a wire in a circuit and ground.
ELECTRICAL SHOCK The response could range from a faint tingling sensation to death. You can perceive a currentas low as 1 milliamp. At 5 mA you will feel a slight shock. Most people can let go.
ELECTRICAL SHOCK “Can’t Let Go” Current 10 mA to 30 mA Painful shock and sustainedmuscle contraction.
ELECTRICAL SHOCK 50 mA to 150 mAExtreme pain, respiratory arrest, severemuscle contractions, possible death1,000 mA to 4,300 mA Ventricular fibrillation, muscle contractions, nerve damage, deathlikely.
ELECTRICAL SHOCK The duration and the amount of current affect the severity of an electrical shockinjury. Death can occur in 2 seconds with a current of 0.1 amps (100 milliamps). 100 mA for 3 seconds is as dangerous as 900 mA for 0.03 seconds.
ELECTRICAL SHOCK • Other factors that may affect the severity of the shock are: • The voltage of the current. • • The presence of moisture. • The phase of the heart cycle when the shock occurs. • The general health of the person prior to the shock.
ELECTRICAL SHOCK High voltages increase shock injuriesbecause a higher voltage produces agreater current. I = E/R Resistance - the lower the resistance, thegreater the current will be. R = E/I
ELECTRICAL SHOCK Resistance between major extremities of an average human body is 1,500 ohms hand to hand or hand to foot. If you grabbed a wire carrying 120 volts alternating current how much current would flow through your body? I = E/R
ELECTRICAL SHOCK PATHWAYS 2. Right foot left foot path 1. Right hand left hand 4. Left hand left foot path 3. Right hand right foot path
ELECTRICAL BURNS Electrical burns are the result of heat generated by the flow of electric current through the body. The dark spot is where thecurrent entered the body.
ELECTRICAL BURNS Electricity arced through the air as a result of a power box explosion. The arc was drawn to this man’s arm pits because of perspiration.
ELECTRICAL BURNS Current exited this man at his knees, catching his clothing on fire and burning his upper leg.
ELECTRICAL BURNS The current exited the foot of this man. Because of severe internal injuries, the foot had to be amputated a few days later.
ELECTRICAL BURNS This worker was shocked by a tool he was holding. A few days later.
ARC FLASH An arc flash is a shortcircuit through the air. It can occur if a conductiveobject gets too close to ahigh-amp current sourceor by equipment failure such as opening orclosing disconnects.
FALLS Workers who get shocked while on a ladder or other elevated location can fall, resulting in serious injury or death.
ELECTRICAL HAZARDS Electrical shocks, fires or falls can result from: • Improper grounding • Improper PPE• Improper tools• Overloaded circuits • Exposed electrical parts• Overhead power lines• Inadequate wiring• Defective insulation • Wet conditions
ELECTRICAL HAZARDS Exposed Electrical Parts
ELECTRICAL HAZARDS Overhead Power Lines NIOSH Case Study Untrained worker raising a 21 foot fence rail under a 7,200 volt power line. Worker was electrocuted.
ELECTRICAL HAZARDS Inadequate Wiring Wire Gauge- wire size or diameter Ampacity - the maximum amount of current a wire can carry safely without overheating Incorrect wiring practices can cause fires! If you touch live electrical parts, you will be shocked. Overloaded wires get hot!
ELECTRICAL HAZARDS CopperWire Ampacity TableWire Gauge Maximum Ampacity14 15 12 20 10 30 8 45 6 65 4 85 2 115 0 150 2/0 175 4/0 250
ELECTRICAL HAZARDS Defective Insulation
ELECTRICAL HAZARDS Defective Insulation Screw penetrated insulation creating a small arc flash.
ELECTRICAL HAZARDS Wet Conditions Wet clothing, high humidity, and perspiration also increase your chances of being electrocuted.
ELECTRICAL HAZARDS Improper grounding
ELECTRICAL HAZARDS Improper grounding
ELECTRICAL HAZARDS Overloaded Circuits Too much current in a circuit can lead to a fire or electrical shock.
THE REGULATIONS CalOSHA Low voltage (600V) Electrical Safety Orders Article 3, § 2320.1 Only qualified persons shall work on electrical equipment or systems. A qualified person is defined as a person designated by the employer, who by reason of experience or instruction has demonstrated familiarity with the operation to be performed and the hazards involved.
THE REGULATIONS § 2320.2 Work SHALL NOT be perform on energized parts of equipment or systems until the following conditions are met: Responsible supervision has determined that the work is to be performed while the equipment or system are energized. Involved personnel have received instructionson the work techniques and hazards involvedin working on energized equipment.
THE REGULATIONS § 2320.2 (cont’d) Suitable personal protective equipment and safeguards (approved insulated gloves or insulated tools) are provided and used. Approved insulated glovesshall be worn for voltages in excess of 250 volts to ground.
THE REGULATIONS § 2320.2 (cont’d) Suitable barriers or approved insulating material shall be provided and used to prevent accidental contact with energized parts. 6. Suitable eye protection has been provided and used.
THE REGULATIONS § 2320.2 (cont’d) Where required for personnel protection, suitable barricades, tags, or signs are in place.
THE REGULATIONS • § 2320.2 (cont’d) • Each employee who is exposed to the hazardsof flames or electric arcs wears apparel that, when exposed to flames or electric arcs, does not increase the extent of injury that would be sustained by the employee.
THE REGULATIONS § 2320.3All electrical equipment and systems shall be treated as energized until tested or otherwise proven to be de-energized.
THE REGULATIONS General Safety Orders § 3314(g) A hazardous energy control procedure shall be developed and utilized by the employer when employees are engaged in the cleaning, repairing, servicing, setting-up or adjusting of prime movers, machinery and equipment. LOCKOUT/TAGOUT
LOCKOUT/TAGOUT Overview of Procedures Must use own lock and keep key on his/her person until job is done. Procedures apply to all Sources of energy - electrical, thermal, hydraulic, pneumatic, mechanical, etc.
LOCKOUT/TAGOUT Notify all affected employees. Identify all applicable isolating devices - breakers, switches, valves, etc.
LOCKOUT/TAGOUT Obtain a padlock and tag from lockoutstation. Isolate source of power at the circuit breaker on MCC paneland at other sourcesof hazardous energy.
LOCKOUT/TAGOUT On the tag, write name, date, time and why equipment is locked out. BLOCK DRAIN BLEEDTEST Test to be sure there is no release of hazardous energy.
LOCKOUT/TAGOUT • Always take precautions to guard against the possibility of faulty switches or short circuits when locking out equipment. Test the equipment with a meter when doing electrical work.
THE REGULATIONS Do not use conductive measuring tapes or ropes when working near energized parts of equipment. Legibly mark each motor controller to indicate the motor it controls and provide a corresponding marking on each motor. When a circuit is discontinued, remove the conductors from the raceway or treat the circuit as if it is in use.
THE REGULATIONS Do not use conductive fish tape in raceways entering enclosures with exposed energized parts unless the parts are isolated by barriers. At least 3 feet of cleared space (no storage) shall be available in the direction of access to control panels, circuit breakers, switchboards, fused switches, and similar equipment.
THE REGULATIONS All electrical equipment shall have markings giving voltage, current, wattage, or other ratings. Circuit breakers shall clearly indicate whether they are in the open “off” or closed “on” position.
THE REGULATIONS Flexible cords or cables SHALL NOT be used • as a substitute for fixed wiring of a structure, • where run through holes in walls, ceilings or floors, • where run through doorways, windows or similar openings, • where attached to building surfaces, or • where concealed behind building walls, ceilings or floors
THE REGULATIONS Flexible cords shall be used only in continuous lengths without splice or tap. Hard service flexible cords No. 12 or larger can be spliced as long as the splice retains the insulation, outer sheath properties, and usage characteristics of the cord.
GROUND FAULT CIRCUITINTERRUPTER Use a GFCI when working on circuits or using electrical equipment in damp or wet areas.
DOUBLE INSULATED TOOLS Use double insulated toolsif GFCI is not available. Always check cord and plug on all power tools before use