Electrical Safety and Health Lecture 16 PDF

2/7/23 Electrical EngI 425. Industrial Safety and Health Lecture # 16 Dr. Majed Moosa 1 Created by OTIEC Outreach Resources Workgroup PPT 10-hr. General Industry – Electrical v.03.01.17 1 Electrical Source of photos: OSHA PPT 10-hr. General Industry – Electrical v.03.01.17 2 Created by OTIEC...

2/7/23 Electrical EngI 425. Industrial Safety and Health Lecture # 16 Dr. Majed Moosa 1 Created by OTIEC Outreach Resources Workgroup PPT 10-hr. General Industry – Electrical v.03.01.17 1 Electrical Source of photos: OSHA PPT 10-hr. General Industry – Electrical v.03.01.17 2 Created by OTIEC Outreach Resources Workgroup 2 1 2/7/23 Introduction Lesson objectives: 1. Identify major electrical hazards 2. Describe types of electrical hazards 3. Describe electrical protection methods 4. Recognize employer requirements to protect workers from electrical hazards Source: OSHA 3 Created by OTIEC Outreach Resources Workgroup PPT 10-hr. General Industry – Electrical v.03.01.17 3 Introduction Definitions: • Electricity – movement of the free electrons between atoms; – Related terms: • Current – the movement of electrical charge • Resistance – opposition to current flow • Voltage – a measurement of electrical force PPT 10-hr. General Industry – Electrical v.03.01.17 Source: NIOSH 4 Created by OTIEC Outreach Resources Workgroup 4 2 2/7/23 Introduction • Conductors – substances, such as metals, that have little resistance to electricity • Insulators – substances, such as dry wood, rubber, glass and Bakelite, that have high resistance to electricity • Grounding – a conductive connection to the earth which acts as a protective measure PPT 10-hr. General Industry – Electrical v.03.01.17 5 Created by OTIEC Outreach Resources Workgroup 5 Electrical Hazards Serious injuries and death can be caused by electrical hazards such as arc flash, shocks, burns, falls, and fires. Source of graphics: OSHA PPT 10-hr. General Industry – Electrical v.03.01.17 6 Created by OTIEC Outreach Resources Workgroup 6 3 2/7/23 Electrical Hazards Examples of electrical hazards that could cause workers to be electrocuted. • https://www.osha.gov/video/shipyard_a ccidents/08_welder_electrocuted.html • https://www.osha.gov/video/shipyard_a ccidents/15_lockout_tagout_failure.html PPT 10-hr. General Industry – Electrical v.03.01.17 7 Created by OTIEC Outreach Resources Workgroup 7 Electrical Hazards BE SAFE: • Burns • • • • • Electrocution Shock Arc flash/arc blast Fire Explosions PPT 10-hr. General Industry – Electrical v.03.01.17 8 Created by OTIEC Outreach Resources Workgroup 8 4 2/7/23 Electrical Hazards Burns: • Most common shock-related injury • Three types of electrical burns: – Electrical – Arc flash – Thermal contact Source: OSHA PPT 10-hr. General Industry – Electrical v.03.01.17 9 Created by OTIEC Outreach Resources Workgroup 9 Electrical Hazards Electrocution: • Is fatal • Meaning: to kill with electrical shock • Results when a human is exposed to a lethal amount of electrical energy PPT 10-hr. General Industry – Electrical v.03.01.17 10 Created by OTIEC Outreach Resources Workgroup 10 5 2/7/23 Electrical Hazards Shock: • Body becomes part of electrical circuit • Reflex response to passage of electric current through the body PPT 10-hr. General Industry – Electrical v.03.01.17 Source: OSHA 11 Created by OTIEC Outreach Resources Workgroup 11 Electrical Hazards Arc Flash/Arc Blast • Arc flash – Sudden release of electrical energy through air when a high-voltage gap exists and there is a breakdown between conductors – Gives off thermal radiation (heat) and bright, intense light that can cause burns – Temperatures as high as 35,000°F PPT 10-hr. General Industry – Electrical v.03.01.17 12 Created by OTIEC Outreach Resources Workgroup 12 6 2/7/23 Electrical Hazards • Arc blast – high-voltage arcs can also produce considerable pressure waves by rapidly heating the air and creating a blast PPT 10-hr. General Industry – Electrical v.03.01.17 13 Created by OTIEC Outreach Resources Workgroup 13 Electrical Hazards Fire: • Most result from problems with "fixed wiring” • Problems with cords, plugs, receptacles, and switches also cause electrical fires PPT 10-hr. General Industry – Electrical v.03.01.17 14 Created by OTIEC Outreach Resources Workgroup 14 7 2/7/23 Electrical Hazards Explosions: • Occur when electricity ignites explosive mixture of material in the air • Note: – Electricity is source of these hazards – All hazards are of equal importance – Lesson focuses on eliminating electrical hazards PPT 10-hr. General Industry – Electrical v.03.01.17 15 Created by OTIEC Outreach Resources Workgroup 15 Electrical Hazards Examples of fatal accidents: • Case #1: Worker electrocuted when the ladder came in contact with overhead power lines • Case #2: Worker electrocuted when mast came in contact with high voltage overhead lines PPT 10-hr. General Industry – Electrical v.03.01.17 16 Created by OTIEC Outreach Resources Workgroup 16 8 2/7/23 Electrical Hazards • Case #3: Worker changing energized ballast on light fixture was electrocuted and fell to the concrete floor while working from an 8' fiberglass stepladder. 17 Created by OTIEC Outreach Resources Workgroup PPT 10-hr. General Industry – Electrical v.03.01.17 17 Electrical Hazards U.S. Bureau of Labor Statistics: • 156 electrocutions for 2014 • Up from 141 in 2013 Source of graphics: OSHA PPT 10-hr. General Industry – Electrical v.03.01.17 18 Created by OTIEC Outreach Resources Workgroup 18 9 2/7/23 Types of Electrical Hazards Contact with overhead power lines: • Overhead and buried power lines carry extremely high voltage • Risks – Electrocution (main risk) – Burns and falls Source: NIOSH PPT 10-hr. General Industry – Electrical v.03.01.17 19 Created by OTIEC Outreach Resources Workgroup 19 Types of Electrical Hazards • Cranes are not the only equipment that can reach overhead power lines. • Use of ladders or suspension in a man-basket under or near power lines are risks. PPT 10-hr. General Industry – Electrical v.03.01.17 Source: OSHA 20 Created by OTIEC Outreach Resources Workgroup 20 10 2/7/23 Types of Electrical Hazards • Important: the covering on an overhead power line is primarily for weather protection; therefore, workers need to know that if they touch a power line, covered or bare, death is probable. • https://www.osha.gov/dts/vtools/construct ion/ladder_powerline_fnl_eng_web.html PPT 10-hr. General Industry – Electrical v.03.01.17 21 Created by OTIEC Outreach Resources Workgroup 21 Types of Electrical Hazards Contact with energized sources: • Live parts – The major hazards • Electrical shock and burns • Electrical shock occurs when the body becomes part of the electric circuit Source: OSHA PPT 10-hr. General Industry – Electrical v.03.01.17 22 Created by OTIEC Outreach Resources Workgroup 22 11 2/7/23 Types of Electrical Hazards – Severity and effects of an electrical shock depend on a number of factors • • • • Pathway through the body Amount of current Length of time of the exposure Whether skin is wet or dry – Water • Great conductor • Allows current to flow more easily in wet conditions and through wet skin 23 Created by OTIEC Outreach Resources Workgroup PPT 10-hr. General Industry – Electrical v.03.01.17 23 (1,000 milliamperes = 1 amp; therefore, 15,000 milliamperes = 15 amp circuit) Current Chart Reaction Below 1 milliampere Generally not perceptible 1 milliampere Faint tingle 5 milliampere Slight shock felt; not painful but disturbing. Average individual can let go. Strong involuntary reactions can lead to other injuries 6-25 milliamperes (women) Painful shock, loss of muscular control 9-30 milliamperes (men) The freezing current or “let-go” range. Individual cannot let go, but can be thrown away from the circuit if extensor muscles are stimulated. 50-150 milliampres Extreme pain, respiratory arrest, severe muscular contractions. Death is possible. 1,000-4,300 milliamperes Rhythmic pumping action of the heart ceases. Muscular contraction and nerve damage occur; death likely 10,000 milliamperes Cardiac arrest, severe burns; death probable This table shows the body’s reaction when exposed to various levels of current. Source: OSHA PPT 10-hr. General Industry – Electrical v.03.01.17 24 Created by OTIEC Outreach Resources Workgroup 24 12 2/7/23 Types of Electrical Hazards • Damaged or bare wires – Fault current may travel through a body, causing electrical burns or death, if • Power supply is not grounded • Path has been broken • There are live parts or bare wires – Extreme conditions and rough treatment can change electrical equipment from safe to hazardous PPT 10-hr. General Industry – Electrical v.03.01.17 25 Created by OTIEC Outreach Resources Workgroup 25 Types of Electrical Hazards • Defective equipment or tools These photos show examples of defective equipment/tools. Source of photos: OSHA PPT 10-hr. General Industry – Electrical v.03.01.17 26 Created by OTIEC Outreach Resources Workgroup 26 13 2/7/23 Types of Electrical Hazards • Improper repairs – Examples of incidents • Ballast strap not replaced after repair = Electrocution of 11 year old boy • Cutting off bleed resistor on capacitor= causes 370-volt shock • Removing and leaving off terminal insulator on capacitor = causes 440-volt shock PPT 10-hr. General Industry – Electrical v.03.01.17 27 Created by OTIEC Outreach Resources Workgroup 27 Types of Electrical Hazards Improper use: • Extension and flexible cords – Care – Connection – Capacity Source: TEEX SH 46F1-HT06 PPT 10-hr. General Industry – Electrical v.03.01.17 28 Created by OTIEC Outreach Resources Workgroup 28 14 2/7/23 Types of Electrical Hazards – Capacity affected by • Size of wire – 14 gauge = 15 amps – 12 gauge = 20 amps • Length of the cord – UL tag capacity – In general any cord over 100 ft. requires one size larger cord (14 gauge to 12 gauge) PPT 10-hr. General Industry – Electrical v.03.01.17 Source: OSHA 29 Created by OTIEC Outreach Resources Workgroup 29 Types of Electrical Hazards • Power strips: – Can be over loaded because of multiple plug arrangement – Most have overload protection but often malfunction causing fire – Use fixed wiring when possible PPT 10-hr. General Industry – Electrical v.03.01.17 Source: UBATC 30 Created by OTIEC Outreach Resources Workgroup 30 15 2/7/23 Types of Electrical Hazards • Portable heaters and appliances: – Manufacturer recommendations not followed – Do not plug into a power strip! This causes overloads and fires. Source of photos: UBATC PPT 10-hr. General Industry – Electrical v.03.01.17 31 Created by OTIEC Outreach Resources Workgroup 31 Electrical Protection Methods Maintain safe distance from overhead power lines: • Staying away • Following table shows the safe power line clearance distance for various line voltages. • https://youtu.be/Y2MwX738e1Y Source of graphics: OSHA PPT 10-hr. General Industry – Electrical v.03.01.17 32 Created by OTIEC Outreach Resources Workgroup 32 16 2/7/23 Electrical Protection Methods Voltage Minimum Clearance Distance (nominal, kV, alternating current) (feet) Up to 50 10 Over 50 to 200 15 Over 200 to 350 20 Over 350 to 500 25 Over 500 to 750 35 Over 750 to 1000 45 Over 1000 (As established by the power line owner/operator or registered professional engineer who is a qualified person with respect to electrical transmission and distribution) This table shows the minimum clearance distances, in feet, for different power line voltages. Source: OSHA PPT 10-hr. General Industry – Electrical v.03.01.17 33 Created by OTIEC Outreach Resources Workgroup 33 Electrical Protection Methods Use ground-fault circuit interrupters (GFCI): • Designed to protect people from electrical shock • Detects ground faults and interrupts electric current • Limits duration of electrical shock PPT 10-hr. General Industry – Electrical v.03.01.17 Source: OSHA 34 Created by OTIEC Outreach Resources Workgroup 34 17 2/7/23 Electrical Protection Methods Three types of GFCI: • Receptacle GFCI • Temporary/portable GFCI • Circuit Breaker GFCI These photos show examples of the three types of GFCI. Source of photos: OSHA PPT 10-hr. General Industry – Electrical v.03.01.17 35 Created by OTIEC Outreach Resources Workgroup 35 Electrical Protection Methods Inspect portable tools and extension cords: • Workers need to inspect extension cords prior to their use for any cuts or abrasion. • Electric hand tools that are old, damaged, or misused may have damaged insulation inside. PPT 10-hr. General Industry – Electrical v.03.01.17 36 Created by OTIEC Outreach Resources Workgroup 36 18 2/7/23 Electrical Protection Methods Use power tools and equipment as designed: • Follow tool safety tips to avoid misusing equipment • Follow manufacturer’s instructions 37 Created by OTIEC Outreach Resources Workgroup PPT 10-hr. General Industry – Electrical v.03.01.17 37 Electrical Protection Methods • Common examples of misused equipment Source: TEEX SH 46F1-HT06 Source of photos: OSHA Source of photos: OSHA These photos show examples of equipment misuse. PPT 10-hr. General Industry – Electrical v.03.01.17 38 Created by OTIEC Outreach Resources Workgroup 38 19 2/7/23 Electrical Protection Methods Tool safety tips • Never carry a tool by the cord. • Never yank the cord to disconnect it. • Keep cords away from heat, oil, and sharp edges. • Disconnect when not in use and when changing accessories such as blades and bits. PPT 10-hr. General Industry – Electrical v.03.01.17 39 Created by OTIEC Outreach Resources Workgroup 39 Electrical Protection Methods • Avoid accidental starting. Do not hold fingers on the switch button while carrying a plugged-in tool. • Use gloves and appropriate footwear. • Store in dry a place when not using. PPT 10-hr. General Industry – Electrical v.03.01.17 40 Created by OTIEC Outreach Resources Workgroup 40 20 2/7/23 Electrical Protection Methods • Don’t use in wet/damp environments. • Keep working areas well lit. • Ensure that cords do not cause a tripping hazard. • Remove damaged tools from use. • Use double-insulated tools. PPT 10-hr. General Industry – Electrical v.03.01.17 41 Created by OTIEC Outreach Resources Workgroup 41 Electrical Protection Methods Follow lockout/tagout (LOTO) procedures: • Lockout/tagout – Essential safety procedure – Protects workers from injury while working on or near electrical circuits and equipment – Prevents contact with operating equipment parts such as, blades, gears, shafts, etc. PPT 10-hr. General Industry – Electrical v.03.01.17 Source: OSHA 42 Created by OTIEC Outreach Resources Workgroup 42 21 2/7/23 Electrical Protection Methods – LOTO prevents the unexpected release of hazardous gases, fluids, or solid matter in areas where workers are present. Source of photos: OSHA PPT 10-hr. General Industry – Electrical v.03.01.17 43 Created by OTIEC Outreach Resources Workgroup 43 Electrical Protection Methods Power source identification: • Mark all breakers accordingly for the circuits they protect • Mark all disconnect means accordingly for the equipment they service • Identify all voltages with proper labeling PPT 10-hr. General Industry – Electrical v.03.01.17 44 Created by OTIEC Outreach Resources Workgroup 44 22 2/7/23 Employer Requirements Employer requirements to protect workers: • Ensure overhead power line safety • Isolate electrical parts • Supply ground-fault circuit interrupters (GFCI) protection • Establish and implement an AEGCP • Ensure power tools are maintained in a safe condition PPT 10-hr. General Industry – Electrical v.03.01.17 45 Created by OTIEC Outreach Resources Workgroup 45 Employer Requirements Ensure proper guarding Provide training Enforce LOTO safety related work practices Ensure proper use of flexible cords and power strips • Ensure proper identification of power sources • • • • PPT 10-hr. General Industry – Electrical v.03.01.17 46 Created by OTIEC Outreach Resources Workgroup 46 23 2/7/23 What’s Wrong? Identify the hazards in these photos. Source of photos: TEEX SH 46F1-HT06 47 Created by OTIEC Outreach Resources Workgroup PPT 10-hr. General Industry – Electrical v.03.01.17 47 What’s Wrong? Identify the hazards in these photos. Source of photos: OSHA PPT 10-hr. General Industry – Electrical v.03.01.17 48 Created by OTIEC Outreach Resources Workgroup 48 24