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Presentation on theme: "ELECTRICAL SAFTY & HARDZE"— Presentation transcript:


2 Certificate This is to certify that
DHRUVI BARIA (ID_009)(ENROLLMENT_006) JUI GAJJAR (ID_008)(ENROLLMENT_022) AAKASH PARMAR (ID_017)(ENROLLMENT_061) VATSAL VAIDYA (ID_004)(ENROLLMENT_122) Of class Electrical Eng.-1 has completed their active learning assignment for the term ending in December 2013. DATE:21/11/2013 Sign of teacher Head of the department

3 OBJECTIVES Electrical Injuries Classification of Exposure
Electrical Hazards Electrical Hazard Control

High Voltage >600 volts: typically associated with “outdoor” electrical transmission. Accounts for 60% of electrocutions. Note: some people classify >480 volts as high voltage. Low Voltage: <600 volts: typically associated with “indoor” electrical service. Accounts for 32% of electrocutions (OSHA). Low voltage does not imply safe voltage.

5 ELECTRICAL HAZARDS Shock :Conductors vs. Resistors :Grounding
:The Ground Fault Accident :GFCIs Burns Falls Fire

6 ELECTRICAL SHOCK An electrical shock can occur upon contact of a human’s body with any source of voltage high enough to cause sufficient current through the muscles or hair. The minimum current a human can feel is thought to be about 1 milli ampere(1mA).

7 Electricity wants to find the path of least resistance to the ground.
Human tissues and body fluids are relatively good conductors because of high water content. So if a person touches an energized bare wire or faulty equipment while grounded, electricity will instantly pass through the body to the ground, causing a harmful, potentially fatal, shock.

Electrical Current Voltage at 10000ohms Voltage at 1000ohms Maximum power(watt) Physiological effect 0.001A 10V 1V 0.01W Threshold of feeling an electric shock,pain. 0.005A 50V 5V 0.25W Maximum current which would be harmless V 10-20V 1-4W Sustained muscular contraction “can not let go”current 0.05A 500V 25W Ventricular interference respiratory difficulty. A V V W Ventricular fibrillation can be fatal 6A 60000V 6000V 400000W Sustained ventricular contraction followed by normal heart rhythm. These are the operation parameters for a defibrillator. Temporary respiratory paralysis and possibly burns.

Grounding is a method of protecting employees from electric shock. By grounding an electrical system, a low-resistance path to earth through a ground connection is intentionally created. This path offers low resistance and has sufficient current-carrying capacity to prevent the build-up of hazardous voltages. A three pronged cord offers a grounding connection.

10 White wire (neutral or common wire), returns the power.
Black wire (hot wire), is connected to the switch and fuse and carries the power. Green (or ground wire). Three wires for each cord and terminal. A two prong plug has a hot prong and a return prong, no ground prong.  In any case, never remove the third (grounding) prong from any three-prong piece of equipment.

A ground fault accident occurs when a person touches or grasps an electrically energized object while the feet or other body parts are in contact with the ground or a grounded surface. In some cases a ground fault accident occurs when the opposite hand touches the ground or a grounded object.

12 Ground Fault Accident Example
A lady working in kitchen use toaster if a part of coil or other live wire contact with metal body of toaster whole body become a conductor. Whenever she touch it The current went through her body as a result, causing cardiac arrest and death.

13 Ground-Fault Circuit-Interrupters
(GFCI’s) GFCI’s are to be used when using electrical equipment in a wet environment. GFCI’s are designed to detect any leakage of current in an electrical circuit. GFCI’s turn off or “trip” the circuit whenever the leakage is greater than 5/1000 of an ampere. For comparison two 60 Watt light bulbs draw a total of 1 ampere of current.

14 Three types of GFCI’s A GFCI receptacle used in place of standard receptacle. A portable GFCI plugs into a standard receptacle. A GFCI circuit breaker combines leakage current detection with the function of a circuit breaker. Whenever working in a wet area, or outdoors, employees should use one of these types of GFCI’s.

15 Electrical Burns Most common nonfatal electrical injury. Types:
Internal: “deep tissue”. Skin: “entry” and “exit” points. Arc: “flash” burns from heat and radiant energy. Common sites of visible skin burns are the hands and feet.

16 Circuits may produce electrical burns with relatively massive amounts of tissue destruction by heating the tissues. This is due to the physical property of friction from the passage of electrons and by destruction of cell membranes by producing holes in the membranes.

17 Falls Involuntary muscle contractions can “throw” workers and cause falls. If working at elevation, the fall may cause serious injury or death.

18 Example of falls A worker fell from the top of a 12-story building and landed on the concrete below. A short-circuited electric drill was found dangling from the building's top floor. Detectives discovered that the grounding prong was missing from the drill's plug. A nail was lodged in the rubber tread of the work boot, allowing electricity to flow through the victim's body to the ground. The electrical current caused muscle contractions strong enough to throw the man from the building, resulting in death.

19 Fire In the United States 25% of fires are caused by electricity.
A build-up of dust, trash and spider webs increases the potential for fire to start in the electrical system. Unprotected light bulbs in work areas are another potential hazard. They can be hit, broken and cause a fire. Electrical wiring can be hit when drilling holes or driving nails in walls causing a fire.

20 Many fires result from defects in, or misuse of the power delivery system.
Wiring often fails due to faulty installation, overloading, physical damage, aging and deterioration by chemical action, heat, moisture and weather. Such wiring should be replaced and new circuits installed. Typical home and office electrical systems run like this: The electrical service enters the house and connects to a main electrical panel. From the main electrical panel, wires run in different directions throughout the house/building to power lights, outlets, ceiling fans, air conditioners, and various other direct-wired electrical appliances.

21 Typical home and office electrical systems run like this:
The electrical service enters the house and connects to a main electrical panel. From the main electrical panel, wires run in different directions throughout the house/building to power lights, outlets, ceiling fans, air conditioners, and various other direct-wired electrical appliances.

22 To keep the wire from getting too hot and starting a fire, circuit wiring attempts to contain the amount of electrical load on the branch circuit by limiting the number of potential electrical appliances that can be running at the same time on that circuit. For example, only so many outlets are put on one branch circuit or larger pieces of electrical equipment are put on circuits dedicated to that equipment only. The homeowner or worker can plug in and run too many appliances on the same circuit at one time and overload the circuit.

23 Each circuit must be protected by a fuse or circuit breaker that will blow or “trip” when its safe carrying capacity is surpassed. If a fuse blows or circuit breaker trips repeatedly while in normal use (not overloaded), check for shorts and other faults in the line or devices. Do not resume use until the trouble is fixed.

24 It is hazardous to overload electrical circuits by using extension cords and multi-plug outlets.
Use extension cords only when necessary and make sure they are heavy enough for the job. Avoid creating an “octopus” by inserting several plugs into a multi-plug outlet connected to a single wall outlet. (CDC)

25 Dimmed lights, reduced output from heaters and poor television pictures are all symptoms of an overloaded circuit. Keep the total load at any one time safely below maximum capacity. When using a high wattage device such as a heater, iron or power tool, turn off all unnecessary lights and devices. Try to connect into a circuit with little electrical power demand.

26 Electrical Hazard Control
Extension cords should only be used on a temporary basis in situations where fixed wiring is not feasible. DO NOT use extension cords as permanent wiring. They may not be able to carry the load. However, if it is necessary to use an extension cord, never run it across walkways or aisles. It causes a potential tripping hazard. It wears down the insulation.

27 Wall receptacles should be designed and installed so that no current-carrying parts will be exposed, and outlet plates should be kept tight to eliminate the possibility of shock. Replace or repair electrical appliances that over heated, sparked, shorted out, smoked or have damaged cords or cracked equipment.

28 If wires are exposed, they may cause a shock to a worker comes into contact with them.
Cords should not be hung on nails, run over or wrapped around objects, knotted or twisted. This may break the wire or insulation. Short circuits are usually caused by bare wires touching due to breakdown of insulation. Electrical tape or any other kind of tape is not adequate! Cords in areas of water or other conductive liquid must be approved for those locations.

29 When the outer jacket of a cord is damaged, the cord may no longer be water-resistant.
The insulation can absorb moisture, which may then result in a short circuit or excessive current leakage to the ground. These cords should be replaced immediately. Electric cords should be examined on a routine basis for fraying and exposed wiring.

30 Electrical cords should be examined visually before use on any shift for external defects such as:
fraying and exposed wiring loose parts deformed or missing parts damage to outer jacket or insulation evidence of internal damage such as pinched or crushed outer jacket If any defects are found the electric cords should be removed from service immediately.

31 Pull the plug not the cord
Pull the plug not the cord. Pulling the cord could break a wire, causing a short circuit.

32 Plug your microwave or any other large appliances into an outlet that is not shared with other appliances. Do not tamper with fuses as this is a potential fire hazard. Do not overload circuits as this may cause the wires to heat and ignite insulation or other combustibles.

33 Keep office equipment properly cleaned and maintained.
Ensure lamps are free from contact with flammable material. Always use lights bulbs with the recommended wattage for your lamp and ceiling fixtures. Be aware of the odor of burning plastic or wire. Always follow the manufacturer recommendations when using or installing new office equipment. Wiring installations should always be made by a licensed electrician or other qualified person. All electrical appliances should have the label of a testing laboratory.

34 Overloading!

35 Missing grounding prong!

36 Missing outlet cover!

37 Electrical tape is not a fix!

38 Pinched cord!



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