Basic Electrical Safety Faculty of Science & Health

1. BasicElectrical SafetyFaculty of Science & Health Safe-Lab Module Alan Hughes January 2017 Ver.1.0

2. Why this Module! Encouraging Electrical Safety In an Educational & Active Research Environment Specifically • Avoid Injury, Death – You & Others • Avoid Equipment Damage & Loss of Research • Awareness of your moral & legal responsibility to yourself, colleagues & to all others By increasing your • awareness of potential dangers & how to avoid creating them • awareness of your skills & Limitations • providing sources of advice & information January 2016 Ver. 1.1

3. Overview of Module! Encouraging Electrical Safety in an Educational and Research Environment • Information sources • Overview of Electrical Basics • Electrical Equipment • Specific laboratory examples January 2016 Ver.1.1

4. Where to get more information • Your Supervisor, Manager, Head of Department • Department Safety Statements • Department Safety Committees & Safety Officer • DCU safety - WEB • Edinburgh University H&S - WEB • University London H&S – WEB • These PP slides on Faculty Safety web site • Safety in Schools Department of education document January 2016 Ver.1.1

5. TODAY January 2016 Ver.1.1

6. Content • [ I ] Basic Electrical Theory[ Ladybird version, no maths  ] • Voltage & Current • Electricity in the body & effects on the body • Electricity & associated hazards • [ II ] Electrical Equipment • Electrocution • General Electrical Guidelines & Precautions • Safety features: fuses, ELCBs, cables, connections, equipment design [ III ] Specific Hazards & Personal Safety • A few Do’s , Don’ts & Watch-out-for’s January 2016 Ver.1.1

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8. [ I ]ElectricityBasic Electrical Theory January 2016 Ver.1.1

9. Basic Electrical Theory Electricityis the flow of electrons around a circuit • Voltage[a driving force] causes Current[e - ] to flow • AC / DC - - Negligible difference wrt Safety • Single Phase / Three Phase. - if 3 phase get a professional • SI units Volts , Amps / milli-Amps and for power Watts, energykWHrs • Circuitnecessary for current to flow • astartpoint - a route - anendpoint Cannot keep pouring water into a sealed bottle October 2016 Ver. 1.4

10. Voltage, Current and Resistance Water analogy Water flow : electrical current flow Water pressure : voltage Conductor : pipe Pump : battery High resistance : Narrow, long pipe Low resistance : Wide short pipe Switch : Slam shut, on/off valve • Voltage increases => Current increases • Resistance decreases => Current increases Voltage = Current / Resistance - Ohms Law October 2016 Ver. 1.4

11. VoltagesAC = = DC • Low Voltage0 => 50V • Batteries: AA, AAA, PP3, MP3 player, Android/i-Phone • Car, trucks, busses 12 / 24 / 48 • Phone or laptop charger, Christmas tree LEDs, Garden lights • High Voltage [high tension, HT ] 100 => 300V • EU Mains, Electrophoresis, DART power lines, Capacitors SM-PSUs • Very High Voltage [EHT ]1KV + • ESB pylons, TV tubes, photocopiers, X-Ray machines, Mass Spectrometers January 2016 Ver.1.1

12. The complete circuit A complete Circuit or loop is necessary for current to flow January 2016 Ver.1.1

13. A complete circuit . -Complete Circuitor loop is necessary for current to flow - Current takes the path of least resistance January 2016 Ver.1.1

14. Summary - basic Electrical Theory • Voltagecauses aCurrentto flow • Big voltage => Big current • Water analogy • AComplete Circuit is necessary for currentto flow • Bird on H.T. wires  • Power Voltage X Current October 2016 Ver. 1.4

15. Electricity &Human Body January 2016 Ver.1.1

16. ‘Normal’Electricityin the body • Muscles • Muscles control all body movements, activated using small electrical currents Including & very importantly, those that keep us alive: our Breathing and our Heart beat • The brain controls voluntary muscles using small current pulses along nerves • Some local autonomous circuits for involuntary muscles e.g. Heart January 2016 Ver.1.1

17. ‘External’Electricity in the body • External Current through the body overrides all biological control and causes: • Loss of muscle control, respiratory, paralysis including ‘Inability to let go’ • Spasms & Involuntary movement • Fibrillation of the Heart [no heart pumping] • Burns - external & internal January 2016 Ver.1.1

18. Just a little current can kill It is the Currentdriven through the body by Voltage that creates danger • Keep voltages low • Do not make your • body part of a circuit October 2016 Ver. 1.4

19. Just a Little Current Can Kill • • 1 mA, slight tingle is felt. • • 5 mA, slight shock is felt, not painful but disturbing. The average individual can let go, involuntary reactions can lead to injuries. • • 6-25 mA, painful shock, muscular control is lost • • 9 – 30 mA, called the freezing current or “let-go” range. many humans cannot get their muscles to work, and they can’t open their hand to let go of a live conductor. • • 50-150 mA, there will be extreme pain, respiratory arrest, and severe muscular contractions. Individual cannot let go, death is possible. • • 1000-4300 mA, there is ventricular fibrillation. Muscular contraction and nerve damage occur. Death is most likely. • • 10,000+ mA, Cardiac arrest, severe burns and probable death. January 2016 Ver. 1.1

20. Electricity&Associated Hazards January 2016 Ver.1.1

21. Electricity - associated hazards • Life support muscles • Diaphragm and breathing • Heart Fibrillation Random, uncoordinated heart contractions De-fibrillation: High voltages (3000 V at 20 A) fraction of a second • Burns - death of tissue • Internal [organs] • External [skin] Usually at Exit & Entry areas • Indirect Injury • Falls from ladder • Thrown back. Fall to ground, onto sharp edge • Drop objects, injure an innocent bystander • Thermal burns – Very hot equipment surface, explosion • Wires & cables Indirectly probably the most common “electrical” injury October 2016 Ver. 1.4

22. Electricity - associated Hazards Wires & cables Trailing leads Trips, falls & injury Equipment damage Re-route, tidy up, cover over October 2016 Ver. 1.4

23. Exit & entry Burns January 2016 Ver.1.1

24. END[ I ] Electrical Theory Section January 2016 Ver.1.1

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26. Electrical Appliances Safety guiding principles • keep currents and voltages to a minimum • insideapparatus and awayfrom our bodies • when a fault is detected Trip out January 2016 Ver.1.1

27. Electrical Appliances Minimise voltages [ and thus minimise current ] • Inherently safe - Low voltage / low current Keep Voltages away from our bodies • Enclosures • Insulation • Connections safe & secure Trip out when fault detected • Safety features – Fuses, ELCBs, Switches January 2016 Ver.1.1

28. Electrical cables & plugs Mains cable • BrownLive - power • Blue Neutral • Green/yellow Earth October 2016 Ver. 1.4

29. Electrical plugs, cables & fuses Mains cable • BrownLive power • Blue Neutral • Green/yellow Earth L N October 2016 Ver. 1.4

30. Electrical fuses & ELCBs October 2016 Ver. 1.4

31. L N L N E Live, Neutral, Earth & Fuses January 2016 Ver.1.1

32. Live, Neutral, Earth & Fuses L N January 2016 Ver.1.1

33. ELCB Electric Leakage Circuit Breaker RCD Residual Current Device RCCB Residual Current Circuit Breaker MCB Magnetic Circuit Breakers RCBO Residual Current Breaker with Over-current protection • current difference of > 30 mA • for a duration of ~ 30 ms L L N N E October 2016 Ver. 1.4

34. Fuse Vs ELCB • A Fuse breaks the circuit • When too much current attempts to flow through an appliance • Usually the excess current is in Amps [Very dangerous] and it happens in less than a second • Must be replaced • AnELCBbreaks the circuit • When there is a difference between the current flowing in the Live and in the Neutral wires • Usually operates when the difference is ~ 30mA [borderline safe] • Operates very fast, in a small fraction of a second • Is resettable October 2016 Ver. 1.4

35. Electrical extension boards Emergency Stop Switch • Avoid where possible • Do not daisy-chain • Check total current • Know where they are • Check occasionally October 2016 Ver. 1.4

36. Electrical summary • The Live and Neutral wires carry current to equipment • The Earth wire is there to protect you. • The Earth wire can act like a back-upNeutral wire, • Many appliances have metal cases e.g. kettles, toasters, dishwashers, washing machines etc. • The Fuse is very thin piece of wire. • The wire has a quite low melting point. As current flows through the wire it heats up. • If too large a current flows it melts, thus breaking the circuit • Use appropriate fuse size/rating • ELCBs, RCDs Important Safety Devices • Leakage-to-earth sensors with trip out October 2016 Ver. 1.4

37. Electricity Safety Summary • High Voltage causes High current • Keep voltages low • Electricity require a circuit • Ensure your body does nor complete the circuit • Electric current takes the easiest path • Ensure that all equipment has an earth connection • When a fault occurs • All equipment should have fuses and ELCBs • Wires & cables Probably the single most common electrical hazard October 2016 Ver. 1.4

38. Equipment & Laboratory Guidelines • Use low & safe voltages: Mains voltages are dangerous 230 VAC • Select equipment appropriate for environment & use • Avoid electricity where its use could be dangerous. • Use equipment as per manufacturer’s instruction & design • Ensure adequate maintenance, damaged case, frayed leads • Insulate and enclose live parts • Ground casings to earth • Prevent conducting parts from becoming live. Earth, double insulation, separate supply from earth, limit electric power • Rubbing, Induction & Capacitance effects can build up static electricity • Avoid use of daisy-chained power extension boards • Toxic - Beryllium heat sinks, Incomplete burning can produce carbon monoxide & other toxicfumes October 2016 Ver. 1.4

39. Electrical Hazards & Safety • Safety in Schools Department of education document • 1.3 Electrical Services & equipment Pages 10 & 11 • 3.1 General Electrical safety precautions Pages 20 & 21 • Good Housekeeping • Well organised & laid out laboratories • Adequate Class control • Water • Water & electricity do not go well together • Water makes you a better conductor allowing MORE current to flow • Mains • Avoid direct working with mains. Use low voltages • Check all leads for: Fraying, Proper clamping, Proper earthing. • Repairing • Do not repair, competency required • Trust nobody, remove fuse, use phase tester • One hand behind back, tip cautiously with back of hand Note: Switch Mode PSU, laptop chargers, CF lamps [high voltages persists on capacitors long after switch off] October 2016 Ver. 1.4

40. Environmental issues • Don’t waste power -Turn off • 15c per kWh • Use Low power versions of equipment • Flat screen Vs old CRT tube TV • Lighting: LED, fluorescent, CFL, Filament • Reduce and recycle, waste considerations! • Avoid hazardous materials • Mercury fluorescent tubes & CFLs • Cadmium & lead from re-chargeable batteries October 2016 Ver. 1.4

41. Electrical Hazards & Personal Safety • Used where! • Office & home 95% • Laboratory 5% • Trailing wires, faulty wires • Mains • Avoid direct working with mains. Use low voltages • Check all leads for: Fraying, Proper clamping, Proper earthing. • Repairing • Do not repair, competency required • Trust nobody, remove fuse, use phase tester • One hand behind back, tip cautiously with back of hand Note: Switch Mode PSU, laptop chargers, CF lamps [high voltages persists on capacitors long after switch off] January 2016 Ver.1.1

42. Some examples of electrical hazards • Electronics experiments • Use acceptable low voltage Mains operated LT power supplies • Wrong connection – IC / electrical component over heats, shatters • Van De Graaff generator High voltage Low current ! • Teltron tubes High voltage Vacuum implosion • Magnetic experiments High currents Heart pace makers • Hot plates Burns • Electrophoresis High voltages • Trailing Power and Signal wires - Protect & Tidy them up October 2016 Ver. 1.4

43. Sometimes forgotten hazards • Medical / Sports equipment • Very strict regulations on equipment operation, design, repair • Never modify or tamper with such equipment • ECG measurements. even a few micro amps direct to the heart can have massive consequences [basis of a heart pacemaker ] • Pace makers • Susceptible to strong magnetic fields [NMR! ], • Possibly RF & Micro waves interference • Chemical Solvents • Flammable environments require specialised electrical equipment E.g. Spark-free fridge for storage of samples dissolved in solvents • Cold rooms / water cooling • Equipment moved from cold room can get condensation on its internal electrical circuits. Avoid this movement, Use L.T. and give lots of time to acclimatise October 2016 Ver. 1.4

44. Yet more examples • RF & µW • Capacitive coupling, no need to touch, • Both can burn severely internally and externally depending on how focused. Think of them like an open air μ-wave oven • EHT • Static, OK [Very low current, moderate power] nearby Solvents! • Will jump considerable distances, • Beware of capacitors • Power • Heating effect in body => internal burns / damage • Contact burns, deep burns & necrosis • Trailing Power and Signal wires - Protect & Tidy them up January 2016 Ver.1.1

45. Specific Hazards & Personal Safety • Other Laboratory Situations ? • Other Office Situations ? • Other Home Situations ? January 2016 Ver.1.1

46. Electrocution • Prevention & Training : Where are red mushroom switches ? • Response: Immediately cut power, red buttons / switch / plug • If in any doubt - Do not touch victim. • One hand behind back, stand on insulation, tip with back of hand • Use insulating rod / stick to move wires from victim. • Call for assistance • Talk & reassure victim • If unconscious then use first aid, CPR January 2016 Ver.1.1

47. END[ II ]Theory Section Electrical Appliances January 2016 Ver.1.1

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50. SUMMARY January 2016 Ver.1.1