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ELC 119R-S Electrical Safety Refresher for Subcontract Electrical Workers. Outline. Introduction Shock and Arc Flash 2 Electrical Hazard Mitigation 3 Technical work documentation (TWD) 4 Safe switching procedures 5 Wrap-Up. Introduction. ~ 300 workplace electrocutions annually
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ELC 119R-SElectrical Safety Refresher for Subcontract Electrical Workers
Outline Introduction Shock and Arc Flash 2 Electrical Hazard Mitigation 3 Technical work documentation (TWD) 4 Safe switching procedures 5 Wrap-Up
Introduction ~ 300 workplace electrocutions annually Estimated 20,000 shocks for every electrocution ~ 4000 injuries annually requiring days away ~3600 disabling electrical contact injuries annually 10-15 workers hospitalized daily with electrical burns 4-year average of 23 electrical events at SNL
Most Common Electrical Events at SNL Short circuit of energized parts to ground Workers shocked from approaching nearer than a safe distance from exposed live parts Workers shocked from faulty equipment Workers shocked from plugging/unplugging equipment
Module 1: Shock and Arc Flash • The passage of electric current through the • body from contact with an electric circuit (conductors). • Exposure to electrical energy may result in no injury • at all or may result in devastating damage or death. • Electrocution is death by electrical energy resulting • from the passing of a high magnitude electric current • through the body 5
Why Are We Susceptible to Injury by Electric Shock? • Our highly developed nervous system makes us extremely sensitive to even very small electric currents. • The passage of current through the body results in heating of tissue Each of these interactions has serious consequences. 6
Effect of Current Passing Through the Body Current can confuse or damage nerve control centers of lungs and heart Heat damage caused by dissipation of energy- body acts as a resistor.
Factors Affecting ShockRemember Ohm’s Law: E=IR Current: most important factor, though directly determined by voltage and body resistance. Path of current: greater chance for survival if current passes through extremities only Duration of Shock: according to IEEE std. 80, the maximum safe duration can be determined by using: t (seconds) = .116/(V/R)
Example If an electrician gets a shock from a 277 volt light fixture, would he/she get “stuck” on the circuit? Let’s assume the worker was sweating and use a resistance value of 10,000 ohms. I =E/R I = 277/10,000 I = .0277 amps or ~28 ma
Is He/She Stuck? YES!
Example continued Let’s also assume that the path of the current is hand to hand. How long does this person have before the shock could be considered fatal? T = .116/(V/R) T = .116/(277/10,000) T = .116/.0277 T = 4.18 seconds!
Voltage Thresholds OSHA set threshold for hazardous energy at 50 volts Hazard from applications lower than 50 are usually thermal not shock: batteries, super capacitors, etc. At levels greater than 600 V, skin is usually penetrated driving resistance down.
Rescuing and Treatment Step 1 – Check to see that the area is safe to enter Step 2 - Call 911 immediately Step 3- Rescue the victim with an insulated device (hot stick, rope, dry wood, etc) Step 4 – Begin CPR Step 5 - Continue resuscitation Step 6 - Get medical attention for the victim
II Arc Flash A release of thermal energy from an electric arc by the vaporization and ionization of materials, reaching temperatures up to 35,000 °F. Exposure to these extreme temperatures both burns the skin directly and causes ignition of clothing. (2004 NFPA 70E)
Nature of the Arc Arc results from passing of current through air Terminals vaporize and serve as conductive medium for ionized gasses Flash can extend further than 10’ from the source Pressure wave caused by rapid expansion of gases with flying molten materials and shrapnel The blast can destroy structures, and knock workers from ladders or across a room. The blast can rupture eardrums and collapse lungs.
Three Factors Affecting Arc Energy Available short circuit current Duration of the arc Distance from the arc
Burns From the Arc First degree: surface only. Skin is usually red and tender Second degree: blistering of the skin. Most painful Third degree: complete destruction of the skin with charring of tissue. Most dangerous –susceptible to infection. Skin can not heal itself.
Effects of the Arc- Burns Arcs have ignited clothing 10’ from the arc and can be fatal when within a few feet
Accelerator Flash Incident On October 11, 2004, at approximately 11:15 am, a subcontractor electrician working at an Accelerator Center received serious burn injuries requiring hospitalization due to an electrical arc flash that occurred during the installation of a circuit breaker in an energized 480-Volt (V) electrical panel.
From the Type A Investigation… Description of Injuries: Electrician received third degree burns on the face, chest, and legs and second degree burns on the arms, involving approximately 50% of his body. Because of the seriousness of his condition, the Board was not able to interview him.
Module 2: Electrical Hazard Mitigation • Plan your work • Analyze/identify the hazards • Control the hazards • Perform the work • Improve the process for the next operation
1910 CFR 851 and NFPA 70E All Department of Energy Facilities are contractually required by law follow 10 CFR 851- Worker Safety and Health Protection Plan 851.23(a)(14) requires contractors to comply with NFPA 70E as a baseline. 70E is the industry standard for addressing electrical hazards in the workplace Applying 70E standards nothing more than using integrated safety management
TURN IT OFF! • Energized work no longer allowed at SNL unless: “de-energizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations” 70E 110.8.A.1 Most hazards can be controlled by insulating, guarding, or by simply working de-energized
Electrically Safe Work Condition First priority is to de-energize Review safety plan Inspect equipment, disconnect energy sources, and lock and tag energy sources. Post barricades and signs to establish the limited approach and flash protection boundaries. Open enclosure, identify shorting devices, and discharge energy-storage devices if applicable. Perform Zero Energy verification Test Complete work When the work is completed, test circuits, remove tools, and test gear, perform final check, and close enclosure NOTE: Equipment is not considered de-energized until locked out and verified
Energized Work - provided justification requirements (slide 34) are met • Strict requirements addressing worker qualifications: • Qualified Person: One who has the skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training on the hazards involved (Electrical Safety in the Workplace, 2004). • Energized work must be authorized by Senior Manager Facilities Engineering- see your contract Sandia delegated representative (SDR) • Shock and Flash Hazard Analyses required. This can be accomplished using the table on slide 44. Remember 2 different hazards- shock and flash
Shock Hazard Analysis Required ANYTIME a worker crosses the Limited Approach Boundary to exposed live parts Must determine approach boundaries (Limited and Restricted) and required shock PPE (usually gloves and insulated tools) Shock PPE required ANYTIME a worker crosses the Restricted Approach Boundary
Shock Approach Boundaries • Limited Approach Boundary (LAB) • Level II authorization required • Only qualified workers may cross * • Boundary must be physically established • Restricted Approach Boundary (RAB) • No unqualified workers • Shock PPE required • Shock PPE mainly consists of insulating gloves and tools • Refer to slide 44 for LAB and RAB approach distances and required PPE.
Flash Hazard Analysis Required ANYTIME a worker crosses the flash protection boundary (FPB) Must determine the Flash Protection Boundary and the PPE required for crossing this boundary PPE and distances determined from table slide 44
Arc Flash Protection • PPE and flash protection boundary (FPB) in CSSP will match that of arc flash hazard (AFH) label on equipment • If the electrical equipment is not provided with an AFH warning label, PPE and FPB in CSSP will be determined using the table in slide 44.
Exposed Live Part Limited Approach Boundary (shock) Level II authorization required Only qualified workers may cross – unqualified workers may cross if escorted by qualified worker and made aware of the hazards Boundary must be physically established Flash Protection Boundary Distance and PPE determined from table in slide 42 PPE required of ANYONE inside this boundary Restricted Approach Boundary (shock) No unqualified workers Shock PPE required Shock PPE mainly consists of insulating gloves and tools
Hazard Risk Categories (HRC) • HRC 0: Single phase circuits operating at 50-208 volts • HRC 1&2: Three-phase circuits operating between 120 and 600 volts • HRC 3&4: Three-phase service entrance equipment and switchgear operating between 120 and 600 volts, excluding those systems with a RED, Level V Arc Flash Hazard label.
Hazard Risk Categories (HRC) • Hazard Risk Above Forty Calories: All equipment identified with a Level V (red) Arc Flash Hazard label • Hazard Risk Greater Than 600 volts: Obtain flash hazard analysis. • Exception: HRC 2 PPE shall be worn In 15 kV manholes. Head, face and glove protection may be removed during cable terminations if no other work is being performed in the manhole.
Boundary and PPE Table EWC: FR long sleeve shirt (min arc rating = 8) worn over untreated cotton t-shirt with FR pants (min arc rating = 11, safety glasses Accessories: hard hat w/FR rated face shield, hearing protection, and leather boots or shoes IWC: EWC + accessories + FR coveralls (min arc rating = 25) and double –layer switching hood. ESC: 40-calorie switching suit w/rated hood and gloves, leather boots and shoes.
Example Arc Flash Labels Level I (HC-0) Label Level II (HC-1 and HC-2) Label
Electro-Magnetic Energy Whenever you have electric power, electric and magnetic fields will be generated. The electric field is often generated by the alternating voltage of the electrical system. The higher the voltage, the greater the electric field. Taken together, electric and magnetic fields are often referred to as electromagnetic radiation. The main effect of exposure to EME is heating of tissue and organs. There are rooftop antennas at Sandia that emit varying levels of EME so contact your ES&H coordinator before approaching them
Worker Responsibilities Familiarize yourself with procedures and work plans- CSSP Be aware of your surroundings Obey all warnings signs and regulations Always use proper PPE (slide 44) Stop work if an unsafe and/or unexpected condition arises Consider ALL electrical equipment energized unless locked out and verified de-energized
Worker Responsibilities • Do NOT perform unjustified energized work • Do not wear jewelry when performing energized work • Report ALL accidents, regardless of severity to Safety Officer/Supervisor • Immediately report to your supervisor, anyone known to be under the influence of drugs or alcohol • Be aware of secondary hazards- beryllium, radiation, noise, etc • Be responsible for your own safety!
Planning Your Work Planning is a key element in performing work safely and is the first step in the ISMS process. OSHA and 70E require a job briefing be held before any electrical work operation begins. All personnel involved in the job shall be briefed on the safety concerns, energy source controls and precautions regarding their assignments. Should work conditions change or unanticipated hazards appear, additional briefings should be held. Planning must be documented!
Planning Your Work continued Consider ALL hazards When changing a ballast, what hazards are involved besides electricity and working from heights? Is there an asbestos issue? Is the fixture in an area known to have dangerous levels of Beryllium? How about radiation?