CHEM 521 Safety Presentation

Hazard Symbols You Must Know

Take Electricity Seriously Over 30,000 non-fatal shocks occur each year. Over 30,000 non-fatal shocks occur each year. Over 600 deaths occur annually due to electrocution. Over 600 deaths occur annually due to electrocution. Source: Bureau of Labor Statistics

Electrical Accidents Leading Causes of Electrical Accidents: Leading Causes of Electrical Accidents: – Drilling and cutting through cables – Using defective tools, cables and equipment – Failure to maintain clearance distance of 10 feet – Failure to de-energize circuits and follow Lockout/Tagout procedures – Failure to guard live parts from accidental worker contact – Unqualified employees working with electricity – Improper installation/use of temporary electrical systems and equipment – By-passing electrical protective devices – Not using GFCI (ground fault circuit interrupters) devices – Missing ground prongs on extension cords

Hazards of Electricity Shock – Most common and can cause electrocution or muscle contraction leading to secondary injury which includes falls Shock – Most common and can cause electrocution or muscle contraction leading to secondary injury which includes falls Fires – Enough heat or sparks can ignite combustible materials Fires – Enough heat or sparks can ignite combustible materials Explosions – Electrical spark can ignite vapors in the air Explosions – Electrical spark can ignite vapors in the air Arc Flash can cause burns ranging from 14,000 degrees f. to 35,000 degrees f Arc Flash - can cause burns ranging from 14,000 degrees f. to 35,000 degrees f Arc Blast In a short circuit event copper can expand 67,000 times. The expansion causes a pressure wave. Air also expands adding to the pressure wave Arc Blast – In a short circuit event copper can expand 67,000 times. The expansion causes a pressure wave. Air also expands adding to the pressure wave

Fundamentals of Electricity Electrical current is the flow of electrons through a conductor. Electrical current is the flow of electrons through a conductor. A conductor is a material that allows electrons to flow through it. A conductor is a material that allows electrons to flow through it. An insulator resists the flow of electrons. An insulator resists the flow of electrons. Resistance opposes electron flow. Resistance opposes electron flow.

How Shocks Occur Current travels in closed circuits through conductors (water, metal, the human body). Current travels in closed circuits through conductors (water, metal, the human body). Shock occurs when the body becomes a part of the circuit. Shock occurs when the body becomes a part of the circuit. Current enters at one point & leaves at another. Current enters at one point & leaves at another.

Severity of the Shock Severity of the Shock depends on: Severity of the Shock depends on: – Amount of current Determined by voltage and resistance to flow Determined by voltage and resistance to flow – Path through the body – Duration of flow through the body – Other factors such as general health and individual differences.

Effects of Current Flow More than 3 milliamps (ma): painful shock More than 3 milliamps (ma): painful shock More than 10 ma: muscle contraction More than 10 ma: muscle contraction More than 20 ma: considered severe shock More than 20 ma: considered severe shock More than 30 ma: lung paralysis - usually temporary More than 30 ma: lung paralysis - usually temporary More than 50 ma: possible ventricular fibrillation (usually fatal) More than 50 ma: possible ventricular fibrillation (usually fatal) 100 ma to 4 amps: certain ventricular fibrillation (fatal) 100 ma to 4 amps: certain ventricular fibrillation (fatal) Over 4 amps: heart paralysis; severe burns Over 4 amps: heart paralysis; severe burns

Electrical Isolation We can be safe by keeping electricity away from us. We can: We can be safe by keeping electricity away from us. We can: – Insulate the conductors. Example: The insulation on extension cords. Example: The insulation on extension cords. – Elevate the conductors. Example: Overhead powerlines. Example: Overhead powerlines. – Guard the conductors by enclosing them. Example: Receptacle covers, boxes, & conduit. Example: Receptacle covers, boxes, & conduit.

Insulating the Conductors The first way to safeguard workers from electrically energized wires is through insulation. The first way to safeguard workers from electrically energized wires is through insulation. Rubber and plastic is put on wires to prevent shock, fires, short circuits and for strain relief. Rubber and plastic is put on wires to prevent shock, fires, short circuits and for strain relief. It is always necessary to check the insulation on equipment and cords before plugging them in. It is always necessary to check the insulation on equipment and cords before plugging them in. Remember, even the smallest defect will allow leakage! Remember, even the smallest defect will allow leakage!

Defective Extension Cords Photos depict hazardous condition

Defective Cord Incident Worker attempted to climb scaffold with electric drill.Worker attempted to climb scaffold with electric drill. Drill’s cord was damaged with bare wires showing.Drill’s cord was damaged with bare wires showing. The bare wire contacted the scaffolding.The bare wire contacted the scaffolding. The worker died!The worker died! Depicts hazardous condition

Guarding the Conductors The third way to safeguard workers from electrically energized wires is by guarding them. The third way to safeguard workers from electrically energized wires is by guarding them. Covers, boxes, and enclosures are often put around conductors to prevent worker contact. Covers, boxes, and enclosures are often put around conductors to prevent worker contact. It is always necessary to check that electrical boxes and panels are covered and free from missing “knock-outs”. It is always necessary to check that electrical boxes and panels are covered and free from missing “knock-outs”. Remember, electric equipment operating at 50 volts or more must be guarded! Remember, electric equipment operating at 50 volts or more must be guarded! Photo depicts hazardous condition

Guarding the Conductors Photos depict hazardous condition

Guarding the Conductors Photos depict hazardous condition

Equipment Grounding We can be safe by providing a separate, low resistance pathway for electricity when it does not follow normal flow (ground prong). We can be safe by providing a separate, low resistance pathway for electricity when it does not follow normal flow (ground prong). Grounding gives the stray current somewhere to go and keeps you from becoming part of the circuit. Grounding gives the stray current somewhere to go and keeps you from becoming part of the circuit.

Can You Rely on Grounding? Grounding will not work if the electricity can flow through you more easily than the ground. This can happen when: Grounding will not work if the electricity can flow through you more easily than the ground. This can happen when: – Your tool doesn’t have a ground pin. – You’re working in wet locations. – You’re touching a metal object.

What Must be Grounded? All circuits and extension cords. All circuits and extension cords. All noncurrent carrying metal parts. All noncurrent carrying metal parts. Portable & semi-portable tools and equipment unless double insulated. Portable & semi-portable tools and equipment unless double insulated.

Do Not Eliminate the Ground! You become the next-best path for current! Photos depict hazardous condition

Do Not Reverse Polarity The prongs are different sized so you can’t turn the plug around. If you do, the electrical fields within the motor are always energized. If there is moisture present, the case is likely to be “hot”. Even with double-insulated tools, you still could get a shock. Photo depicts hazardous condition

Circuit Interruption We can be safer by automatically shutting off the flow of electricity in the event of leakage, overload, or short circuit. We can be safer by automatically shutting off the flow of electricity in the event of leakage, overload, or short circuit. Ground Fault Circuit Interrupters (GFCI) are circuit protection (or “overcurrent”) devices that protect you, the worker. Ground Fault Circuit Interrupters (GFCI) are circuit protection (or “overcurrent”) devices that protect you, the worker. Circuit breakers & fuses protect equipment, not you, because they take too much current & too much time to trip. Circuit breakers & fuses protect equipment, not you, because they take too much current & too much time to trip.

Checking for Ground Continuity What else we should we notice here? Photo depicts hazardous condition

Temporary Wiring There must be separate circuits for electric tools and lighting, each labeled as such. There must be separate circuits for electric tools and lighting, each labeled as such. Light circuits do not require a GFCI. Light circuits do not require a GFCI. – Unless used in a wet location. Test branch circuits before use. Test branch circuits before use. Maintain vertical clearances. Maintain vertical clearances. Insulate wires from their supports. Insulate wires from their supports.

Extension Cords and Cables Must be in good shape without splices. Must be in good shape without splices. Cannot be secured with staples, nails or bare wire. Cannot be secured with staples, nails or bare wire. Must be protected from damage. Must be protected from damage. Must have a ground pin. Must have a ground pin. Should be inspected regularly and pulled from service if defective. Should be inspected regularly and pulled from service if defective. Cannot be repaired with electrical or duct tape. Must repair with heat-shrink sleeve or bonding/vulcanizing tape to retain original insulation properties. Cannot be repaired with electrical or duct tape. Must repair with heat-shrink sleeve or bonding/vulcanizing tape to retain original insulation properties. SUBPART Photos depict hazardous condition

Photo depicts hazardous condition

Safe Work Practices De-energized circuits and equipment must be locked/tagged out. De-energized circuits and equipment must be locked/tagged out.

Safe Work Practices No metal ladders for or near electrical work. No metal ladders for or near electrical work. No wet hands when plugging or unplugging cords/equipment. No wet hands when plugging or unplugging cords/equipment. No raising or lowering tools by the cord. No raising or lowering tools by the cord. Unless equipment is designed for it, cannot be used in damp and wet locations. Unless equipment is designed for it, cannot be used in damp and wet locations. 53 K SUBPART Photo depicts hazardous condition

Summary – Hazards & Protections Hazards Inadequate wiring Inadequate wiring Exposed electrical parts Exposed electrical parts Wires with bad insulation Wires with bad insulation Ungrounded electrical systems and tools Ungrounded electrical systems and tools Overloaded circuits Overloaded circuits Damaged power tools and equipment Damaged power tools and equipment Using the wrong PPE and tools Using the wrong PPE and tools Overhead power lines Overhead power lines All hazards are made worse in wet conditions All hazards are made worse in wet conditions Damaged extension cords Damaged extension cords Unqualified workers doing electrical work Unqualified workers doing electrical work 55 K SUBPART Protective Measures  Proper grounding  Use GFCI’s  Use fuses and circuit breakers  Guard live parts  Lockout/Tagout  Proper use of flexible cords  Close electrical panels by Competent Person  Employee training  Ensure Competent Person on site  Use proper approved electrical equipment  Qualified person install electrical devices