Diese Präsentation wurde erfolgreich gemeldet.
Die SlideShare-Präsentation wird heruntergeladen. ×

Electrical Safety in Construction.ppt


Hier ansehen

1 von 34 Anzeige

Weitere Verwandte Inhalte

Ähnlich wie Electrical Safety in Construction.ppt (20)

Aktuellste (20)


Electrical Safety in Construction.ppt

  1. 1. Electrical Safety for Construction
  2. 2. V = Voltage (volts) I = Current (amperes) R = Resistance (ohms) V I R Ohm’s Law
  3. 3. Water Analogy for voltage and current
  4. 4. Electric shock  Occurs when current enters the body at one point and exits at another  Shock occurs when you touch: • both wires of an electric circuit; • one wire of an energized circuit and ground; or • a metallic part that is “hot” or become “live” 3a
  5. 5. Electric shock  Severity of shock depends on the: • amount of current • path of the current • amount of time exposed 3b
  6. 6. Body Area OHMS Dry Skin 600,000 Wet Skin 1,000 Internal Organs 400-600 Ear to Ear 100 Human Resistance
  7. 7. Electric shock  Effects range from a tingle, to cardiac arrest, severe burns, and probable death 3c
  8. 8.  1-8 mA = shock, not painful  8-15 mA = Painful, Curent Threshold  ------------------------------------------------------------  15-20 mA = Muscle contraction  20-100 mA = Severe pain & paralysis of breathing muscles  100-1000 mA = Ventricular fibrillation  (Usually cause death)  > 1,000 mA = Heart stops Effects of Current
  9. 9. 230 Volts 1,000 OHM = 0.230 amps (230 mA) Fatalities at 230 Volts
  10. 10. Grounding/Earthing  Protects you from electrical shock  Safeguards against fire  Protects electrical equipment from damage 4a
  11. 11. Grounding  Two types of grounding include: • Service or system ground • Equipment ground 4b
  12. 12. Circuit protective devices  At construction sites, the most common electrical hazard is the ground fault electrical shock  As per Norms we must provide : • Ground fault circuit interrupters (GFCIs) 5a
  13. 13. Ground fault circuit interrupters  A fast-acting circuit breaker that senses small imbalances in the circuit caused by current leakage to ground 6a
  15. 15. 1000 mA PLUG COIL LOAD HOT NEUTRAL 1000 mA 1 AMP 5 mA GROUND 995 mA
  16. 16. RCCB’s
  17. 17. Rubber mats  Protects person from Electric shock during accidental contact with live conductors or live equipment body.  Available in different ratings as below  3.3 KV : Class A : 2mm thick  11 KV : Class B : 2.5 mm thick  33 KV : Class C : 3 mm thick  66 KV : Class D : 3.5 mm thick
  18. 18. Rubber mats
  19. 19. Rubber mat :  Few important points: 1. Appropriate rated rubber mat should be used as per voltage level 2. Mat should be kept clean always 3. There should not be any cracks or holes in the rubber mat
  20. 20. Lockout/Tagout  Electrical equipment deactivated for repair must be locked out and tagged at the point where it can be energized  Protects maintenance workers  Warns others that work is being performed 8a
  21. 21. Lock out-Tag outs
  22. 22. Lockout/Tagout  Only the person who locked/tagged the equipment can turn it back on  Before equipment is energized, a qualified person must conduct tests and visual inspections 8b
  23. 23. Lockout/Tagout  Each lock/tag must be removed by the person who applied it 8c
  24. 24. Lockout/Tagout  If the employee is absent, the lock/tag can be removed by a qualified person if: • the employee who applied the lock has left the premises • it is visually determined that all employees are clear of the circuits/equipment 8d
  25. 25. Guarding requirements  Entrances to areas with live electrical parts must be marked with warning signs  Signs should forbid entrance except by qualified persons 9b
  26. 26. Insulation  Check equipment daily for insulation breakdown  Check for: • exposed wires • broken wires • scuffed insulation on extension cords 10a
  27. 27. Insulation  Use non-conducting mats, shields, or barriers when necessary  Use non- conducting coatings on hand tools 10b
  28. 28. Personal protective equipment 11b
  29. 29. Cable routing safe practices
  30. 30. What is IP rating ??  An IP Rating (also known as an Ingress Protection Rating or International Protection Rating) is a way of showing the effectiveness of electrical enclosures in blocking foreign bodies such as dust, moisture, liquids, and accidental contact.
  31. 31. IP chart for solids Lev el size Effective against Description X — X means there is no data available to specify a protection rating with regard to this criterion. 0 — No protection against contact and ingress of objects 1 > 50 mm 2.0 in Any large surface of the body, such as the back of a hand, but no protection against deliberate contact with a body part 2 > 12.5 mm 0.49 in Fingers or similar objects 3 > 2.5 mm 0.098 in Tools, thick wires, etc. 4 > 1 mm 0.039 in Most wires, slender screws, large ants etc. 5 Dust protected Ingress of dust is not entirely prevented, but it must not enter in sufficient quantity to interfere with the satisfactory operation of the equipment. 6 Dust-tight No ingress of dust; complete protection against contact (dust- tight). A vacuum must be applied. Test duration of up to 8 hours based on airflow.
  32. 32. IP chart for liquids Level Protection against Effective against X — Not specified 0 None No protection against water 1 Dripping water Dripping water (vertically falling drops) 2 Dripping water when tilted at 15° Vertically dripping water shall have no harmful effect when the enclosure is tilted at an angle of 15° 3 Spraying water Water falling as a spray at any angle up to 60° from the vertical shall have no harmful effect, 4 Splashing of water Water splashing against the enclosure from any direction shall have no harmful effect 5 Water jets Water projected by a nozzle (6.3 mm (0.25 in) against enclosure from any direction shall have no harmful effects. 6 Powerful water jets Water projected in powerful jets (12.5 mm (0.49 in)) against the enclosure from any direction shall have no harmful effects. 7 Immersion, up to 1 meter (3 ft 3 in) depth Ingress of water in harmful quantity shall not be possible when the enclosure is immersed in water under defined conditions of pressure and time (up to 1 meter (3 ft 3 in) of submersion). 8 Immersion, 1 meter (3 ft 3 in) or more depth The equipment is suitable for continuous immersion in water under conditions that shall be specified by the manufacturer. However, with certain types of equipment, it can mean that water can enter but only in such a manner that it produces no harmful effects.
  33. 33. Bottom line  Safety is everyone’s responsibility and not just safety officer’s.  We all must strive to achieve zero accidents at our site
  34. 34. Thank you