Presentation on theme: "Outline Introduction Shock and Arc Flash"— Presentation transcript:
1 ELC 119R-S Electrical Safety Refresher for Subcontract Electrical Workers
2 Outline Introduction Shock and Arc Flash 2 Electrical Hazard Mitigation3 Technical work documentation (TWD)4 Safe switching procedures5 Wrap-Up
3 Introduction ~ 300 workplace electrocutions annually Estimated 20,000 shocks for every electrocution~ 4000 injuries annually requiring days away~3600 disabling electrical contact injuries annually10-15 workers hospitalized daily with electrical burns4-year average of 23 electrical events at SNL
4 Most Common Electrical Events at SNL Short circuit of energized parts to groundWorkers shocked from approaching nearer than a safe distance from exposed live partsWorkers shocked from faulty equipmentWorkers shocked from plugging/unplugging equipment
5 Module 1: Shock and Arc Flash The passage of electric current through thebody from contact with an electric circuit (conductors).Exposure to electrical energy may result in no injuryat all or may result in devastating damage or death.Electrocution is death by electrical energy resultingfrom the passing of a high magnitude electric currentthrough the body5
6 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 tissueEach of these interactions has seriousconsequences.6
7 Effects of Current on the Body Current ValueEffects< 1 maBarely Perceptible1-5 maPerceptible shock, reflex actions5 ma GFCI tripsAccepted as maximum harmless current6-10 maPainful shock, victim can “let-go”10-20 maPainful shock, victim can not let gomaVentricular Fibrillation possiblemaVentricular Fibrillation likely200 maSevere burns, severe muscular contractions, chest muscles clamp the heart and stop it for the duration of the shock.833 maCurrent used by 100 watt light bulb
8 Effect of Current Passing Through the Body Current can confuse or damage nerve control centers of lungs and heartHeat damage caused by dissipation of energy- body acts as a resistor.
10 Unfortunate mouse suffers a fatal phase to phase shock
11 Factors Affecting Shock Remember Ohm’s Law: E=IR Current: most important factor, though directly determined by voltage and body resistance.Path of current: greater chance for survivalif current passes through extremities onlyDuration of Shock: according to IEEE std. 80, the maximum safe duration can be determined by using: t (seconds) = .116/(V/R)
12 ExampleIf 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 = amps or ~28 ma
13 YES! Is He/She Stuck? Current Value Effects <1 ma Barely Perceptible1-5 maPerceptible shock, reflex actions5 ma GFCI tripsAccepted as maximum harmless current6-10 maPainful shock, victim can “let-go”10-20 maPainful shock, victim can not let gomaVentricular Fibrillation likelymaVentricular Fibrillation occurs200 maSevere burns, severe muscular contractions, chest muscles clamp the heart and stop it for the duration of the shock.833 maCurrent used by 100 watt light bulbYES!
14 Example continuedLet’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!
15 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.
17 Rescuing and Treatment Step 1 – Check to see that the area is safe to enterStep 2 - Call 911 immediatelyStep 3- Rescue the victim with an insulated device (hot stick, rope, dry wood, etc)Step 4 – Begin CPRStep 5 - Continue resuscitationStep 6 - Get medical attention for the victim
18 II Arc FlashA 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)
19 Nature of the Arc Arc results from passing of current through air Terminals vaporize and serve as conductive medium for ionized gassesFlash can extend further than 10’ from the sourcePressure wave caused by rapid expansion of gases with flying molten materials and shrapnelThe blast can destroy structures, and knock workers from ladders or across a room. The blast can rupture eardrums and collapse lungs.
21 Three Factors Affecting Arc Energy Available short circuit currentDuration of the arcDistance from the arc
22 Burns From the ArcFirst degree: surface only. Skin is usually red and tenderSecond degree: blistering of the skin. Most painfulThird degree: complete destruction of the skin with charring of tissue. Most dangerous –susceptible to infection. Skin can not heal itself.
25 Effects of the Arc- Burns Arcs have ignited clothing 10’ from the arc and can be fatal when within a few feet
26 Accelerator Flash Incident On October 11, 2004, at approximately 11:15 am,a subcontractor electrician working at an Accelerator Center receivedserious burn injuries requiring hospitalization dueto an electrical arc flash that occurred during theinstallation of a circuit breaker in an energized480-Volt (V) electrical panel.
31 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.
32 Module 2: Electrical Hazard Mitigation Plan your workAnalyze/identify the hazardsControl the hazardsPerform the workImprove the process for the next operation
33 1910 CFR 851 and NFPA 70EAll Department of Energy Facilities are contractually required by law follow 10 CFR 851- Worker Safety and Health Protection Plan851.23(a)(14) requires contractors to comply with NFPA 70E as a baseline.70E is the industry standard for addressing electrical hazards in the workplaceApplying 70E standards nothing more than using integrated safety management
34 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 A.1Most hazards can be controlled by insulating,guarding, or by simply working de-energized
35 Electrically Safe Work Condition First priority is to de-energizeReview safety planInspect 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 TestComplete workWhen the work is completed, test circuits, remove tools, and test gear, perform final check, and close enclosureNOTE: Equipment is not considered de-energized until locked out and verified
36 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
37 Shock Hazard AnalysisRequired ANYTIME a worker crosses the Limited Approach Boundary to exposed live partsMust 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
38 Shock Approach Boundaries Limited Approach Boundary (LAB)Level II authorization requiredOnly qualified workers may cross *Boundary must be physically establishedRestricted Approach Boundary (RAB)No unqualified workersShock PPE requiredShock PPE mainly consists of insulating gloves and toolsRefer to slide 44 for LAB and RAB approach distances and required PPE.
39 Flash Hazard AnalysisRequired ANYTIME a worker crosses the flash protection boundary (FPB)Must determine the Flash Protection Boundary and the PPE required for crossing this boundaryPPE and distances determined from table slide 44
40 Arc Flash ProtectionPPE and flash protection boundary (FPB) in CSSP will match that of arc flash hazard (AFH) label on equipmentIf 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.
41 Exposed Live Part Limited Approach Boundary (shock) Level II authorization requiredOnly qualified workers may cross – unqualified workers may cross if escorted by qualified worker and made aware of the hazardsBoundary must be physically establishedFlash Protection BoundaryDistance and PPE determined from table in slide 42PPE required of ANYONE inside this boundaryRestricted Approach Boundary (shock)No unqualified workersShock PPE requiredShock PPE mainly consists of insulating gloves and tools
42 Hazard Risk Categories (HRC) HRC 0: Single phase circuits operating at voltsHRC 1&2: Three-phase circuits operating between 120 and 600 voltsHRC 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.
43 Hazard Risk Categories (HRC) Hazard Risk Above Forty Calories: All equipment identified with a Level V (red) Arc Flash Hazard labelHazard 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.
44 Boundary and PPE Table Equipment Class HRC Flash Boundary LAB, RAB Required flash PPRequired shock PPEPPE Code208/ ø4’3’ – 6”, contactEWCClass 0 gloves with leather protectors and insulated toolsGreen120/240, 277/4803-ø non service entrance1, 26’4’, 1’EWC + accessoriesBlue3-ø service entrance3Contact FMOC project leadISCYellow4ESCOrangeEquipment labeled greater than 40 calories or 600 voltsNAContact SDR, CO, or PM for assistanceRedEWC: FR long sleeve shirt (min arc rating = 8) worn over untreated cotton t-shirt with FR pants (min arc rating = 11, safety glassesAccessories: hard hat w/FR rated face shield, hearing protection, and leather boots or shoesIWC: 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.
45 Example Arc Flash Labels Level I (HC-0) Label Level II (HC-1 and HC-2) Label
46 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
47 Worker Responsibilities Familiarize yourself with procedures and work plans- CSSPBe aware of your surroundingsObey all warnings signs and regulationsAlways use proper PPE (slide 44)Stop work if an unsafe and/or unexpected condition arisesConsider ALL electrical equipment energized unless locked out and verified de-energized
48 Worker Responsibilities Do NOT perform unjustified energized workDo not wear jewelry when performing energized workReport ALL accidents, regardless of severity to Safety Officer/SupervisorImmediately report to your supervisor, anyone known to be under the influence of drugs or alcoholBe aware of secondary hazards- beryllium, radiation, noise, etcBe responsible for your own safety!
49 Planning Your WorkPlanning 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!
50 Planning Your Work continued Consider ALL hazardsWhen 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?
51 Planning Your Work continued The meeting must cover the following questions:Do I thoroughly understand the job?Do I thoroughly understand my role in the job?Am I aware of all the hazards I may encounter?Am I knowledgeable of all the safety rules and required personal protective equipment that apply to the job?
52 Performing Your WorkAll circuits must be considered energized until LOTO’d and verified de-energizedSeveral events at SNL have been the result of failure to verify de-energizedPerformance of the 0 energy verification still requires PPE and boundary establishment (slide 44)Do you have to do this hot?Physically establish the limited approach boundary (slide 44)Boundary must keep unqualified workers out of areaBoundary must warn workers of the hazards inside the area
53 Performing Your Work Wear the appropriate PPE Shirt must be buttoned and sleeves rolled downFlash PPE is required when inside the flash protection boundary (slide 44)Crossing the restricted approach boundary requires gloves and insulated tools (slide 44)Maintain your glovesAre they out of testing date requirements?Use the right tools for the jobIs you meter rated for the task?Several events at SNL have occurred due to use of an inappropriate meterDo not deviate from job plan.If work outside of scope is required stop and re-evaluate with all involved co-workers.
54 Module 2 ConclusionSevere hazards associated with energized electrical workEnergized work is now the exception- not the norm- Turn –it-off!NFPA 70E provides sound guidance for electrical safety in the workplaceApplying the standard is basic ISMS- identify the hazard, control the hazardRemember there are two primary hazards (shock and flash) that must be analyzed and controlled independently
55 Module 3: TWD Requirements Q: What is considered energized work at SNL?A: Any activity inside the Limited Approach Boundary (LAB)Crossing the LAB for ANY reason must meet the 70E justification requirements of A.1 (slide 35)ALL energized work requires a technical work documentWhy? This should be your first question when asked to work energized.
56 Contract Specific Safety Plan (CSSP) The CSSP is the required technical work document for all energized work at SNL performed by a facilities subcontractorThe CSSP must incorporate the required energized work permit elements required in NFPA 70E 130.1B2
57 Content of the CSSPA description of the circuit/part to be worked on and its locationJustification of why the work must be performed energized. Remember that some troubleshooting could be accomplished with an Ohm meter.A description of safe work practices to be employed (second person, safety watch, Barriers, etc)Results of the shock hazard analysis (voltage the employee(s) will be exposed to) – slide 44Determination of shock approach boundaries (LAB, RAB, PAB) using table slide 44
58 Content of the CSSP continued 6. Results of the flash hazard analysis (determination of the Flash Protection Boundary and the caloric exposure based on table slide 447. The necessary personal protective equipment- shock and flashMeans used to restrict access of unqualified personnel to the area (chains, flagging, signage, etc)Evidence of completion of a pre-job briefing including topics covered- checklistEnergized work approvals (workers, Managers, Senior Managers)
59 Insulated ToolsInsulated tools, rated for the system voltage, are required when contacting any energized component. Insulated tools should be listed under # 3. Ground hooks shall also be listed here.If the insulated tool can prevent the user from crossing the restricted approach boundary and flash protection boundary, PPE will not be required (except safety glasses).
60 Module 4 Safe Switching Procedures Three hazards associated with switching breakers or disconnectsShockExplosionArc flash/blast
61 Shock Rare when switching because cover should be in place. Remember shock boundaries30,000 non-fatal shocks each year in the workplace…247 died from electrocution in 2006…down from 251 in 2005.
62 Breaker Explosion Counterfeit Products Improper Sizing Sub-standard componentsNo NRTL listingImproper SizingImproperly rated for available fault current
64 Operating Breakers and Disconnects Use one hand when possible.For side-handled switches, stand as far away to the side as possible to operate the switch.For panel-mounted breakers, do not stand in front of the panel when operating the breaker.Do not expose unprotected portions of the body/face to the potential blast.
65 Review – Switching Operations Disconnect RatingRequired PPE (Hazard Category)Up to and including 60 amps (< 600 volts)HC 0 *>60 up to and including 200 amps (< 600 volts)HC 2 *> 200 amps (< 600 volts) and all > 600 voltsMust be analyzed by a qualified person. Contact electrical safety for evaluation.Arc flash labels supersede this tablereference slide 44 for specifics
66 Module 4 Conclusion Switching can be hazardous Wear appropriate PPE Obtain AIC and clearing times prior to switchingNever switch breakers or disconnects under trip conditions - call facilitiesNever close a breaker or disconnect if uncomfortableUse Left hand rule to keep body away from disconnect when closing
67 Course Wrap-Up You seldom get a second chance with electricity Most electrical accidents are caused by unseen or unanticipated hazardsTake your time!Never deviate from proceduresIf circumstances or conditions change- STOP and re-evaluateWork on energized equipment is restricted at SNLMaintain tools, test equipment, and PPENever rely on others for your safety
68 Thanks for Viewing Questions: Greg Kirsch at 845-9497 Mark McNellis atMarc Williams at