Presentation Title ( Arial, Font size 28 ) Electrical Safety at Office

Transcription

1 Presentation Title ( Arial, Font size 28 ) Electrical Safety at Office Date, Venue, etc..( Arial, Font size 18 ) Bombay Chamber of Commerce & Industry (West End Hotel Mumbai April-12)

2 Electrical Safety - Overview

3 Electricity - Statistics Electricity has long been recognized as a serious workplace hazard. Exposes employees to electric shock, electrocution, burns, fires, and explosions. 5 percent of on-the-job fatalities are due to electricity, out of which 12% constitute young work force. Most of these fatalities could have been easily avoided. Message Box (Arial, Font size 18 Bold)

4 Electrical Terms Current- Flow of electricity (Measured in Amperes) Voltage- Potential difference (Measured in Volts) Resistance- Restriction to flow of electricity Depends upon the metal used, it s length, diameter & temperature (Measured in Ohms) Conductor- A substance which offers little resistance to flow of electricity (Ex: Silver, copper, aluminum etc.)

5 Electrical Terms (contd ) Insulator- Substance with high resistance to flow of electricity (Ex: Porcelain, plastic, glass, dry wood) Earthing / Grounding- A protective circuit with a high conductive connection to the earth.

6 Injuries due to Electrical Hazards Three main types of Electrical Hazards: Direct: Electric shock. Burns. Death due to electric shock / electrocution. Indirect: Fall due to electric shock & subsequent injuries / death. Fire.

7 Electric Shock Electricity travels in closed circuits, and its normal route is through a conductor. Electric shock occurs when the body becomes a part of the circuit. The metal parts of electric tools and machines may become energized if there is a break in the insulation of the tool or machine wiring. A worker using these tools and machines is made less vulnerable to electric shock when there is a low-resistance path from the metallic case of the tool or machine to the ground.

8 Severity of Electric Shock Severity of the shock depends on: Path of current through the body. Amount of current flowing through the body. Length of time the body is in the circuit. Other factors that may affect the severity of the shock are: - The voltage of the current. - The presence of moisture - The general health of the person prior to the shock.

9 Dangers of Electric Shock Currents above 10 ma can paralyze or freeze muscles. When this freezing happens, a person is no longer able to release a tool, wire, or other object. In fact, the electrified object may be held even more tightly, resulting in longer exposure to the shocking current. For this reason, hand-held tools that give a shock can be very dangerous.

10 Dangers of Electric Shock (contd ) If the person can t let go of the tool, current continues through the body for a longer time, which can lead to respiratory paralysis (the muscles that control breathing cannot move) & the person stops breathing for a period of time. Usually, it takes about 30 ma of current to cause respiratory paralysis. Currents greater than 75 ma can cause ventricular fibrillation (rapid, ineffective heartbeat); will cause death in a few minutes unless a defibrillator is used.

11 Burn Injuries The most common shock-related injury is a burn. Burns suffered in electrical incidents may be one or more of the following three types. Electrical burns cause tissue damage, and are the result of heat generated by the flow of electrical current through the body. Arc or Flash burns are caused by high temperatures near the body produced by an electrical arc or explosion. Thermal contact burns occur when skin comes in contact with overheated electric equipment, or when clothing is ignited by an electrical incident.

12 Indirect effects of Electric Shock Electric shock can also cause indirect or secondary injuries. Workers in elevated locations who experience a shock can fall, resulting in serious injury or death

13 Electrical Fire When current flows through the circuit, heat is produced in overcoming the conductor resistance. Heat produced is directly proportional to the resistance, to the time and to the square of the current (W = I2Rt ). The short-circuit current depends upon impedance of the circuit feeding the fault. The impedance is made up of two separate components: impedance of the Tr/r which is feeding the fault plus that of the secondary conductors which run to the point of the fault.

14 Electrical Fire For the sake of clarity, let's assume there are negligible line impedances between the transformer secondary and the fault. Ex: Full-load secondary current (I sec) = 10,000 VA / 240 V = 42 A. Tr/r impedance = 5%. The short-circuit current (I sec S.C) at the transformer's secondary terminals: I sec S.C = (100% / %Z ) x I sec = (100 / 5) * 42= 840A. Heat Produced is proportional to square of this current.

15 Electrical Fires

16 Causes of Electrical Hazards Electrical shocks, fires, or falls result from these hazards: Exposed electrical parts. Inadequate wiring. Defective insulation. Improper grounding. Overloaded circuits. Wet conditions. Damaged tools and equipment. Improper PPE.

17 Factors influencing Electrical Hazards Electrical Hazards are caused by combination of three factors: Unsafe equipment / installation. Work place made unsafe by environment. Unsafe work practices.

18 Earthing Earthing is basic protection against electrical shock. Connecting an electrical equipment with metal casing to the Earth with a wire of negligible resistance is known as Earthing or Grounding. There are 2 types of Earthing systems a) Pipe Earthing & b) Plate Earthing. Motors, Generators, Transformers etc. are inductive loads and heaters, lights etc are resistive loads.

19 Earthing G.I. Pipe can be used for domestic earting where load is below 100 A and non-inductive. If the load is above 100 A & inductive in nature then, Plate Earthing is recommended. Plate should be made of Copper with G.I. coating. General grounding wire should be of 8 SWG. The pit resistance should not be more than 4 5 Ohms.

20 Ground Fault Circuit Interrupter (GFCI) Interrupts the electric power within as little as 1/40 of a second when the amount of current going differs from the amount returning, by about 5 ma. Must be tested to ensure it is working correctly. There is one disadvantage to grounding: a break in the grounding system may occur without the user's knowledge. Using a ground-fault circuit interrupter (GFCI) is one way of overcoming grounding deficiencies

21 Office Equipment Electrical accidents usually occur as a result of faulty or defective equipment, unsafe installation, or misuse of equipment on the part of office workers. Generally, equipment like computers, copiers, printers, coffee makers, space heaters are used in office area. Always follow standards while purchasing equipment like coffee makers, space heaters etc. Purchase equipment with grounded three-prong plugs. Never remove the third (grounding) prong from any three-prong piece of equipment.

22 Overload Hazards If too many devices are plugged into a circuit, the current will heat the wires to a very high temperature, which may cause a fire. If the wire insulation melts, arcing may occur and cause a fire in the area where the overload exists, even inside a wall. If the circuit breakers or fuses are too big (high current rating) for the wires they are supposed to protect, an overload in the circuit will not be detected and the current will not be shut off. A circuit with improper over current protection devices or one with no over current protection devices at all is a hazard. If Switches/Outlets Feel Warm Contact Facilities Management ASAP.

23 Surge Protectors / Power Strips Surge suppressors can manage the small surges and spikes sometimes generated by the turning on and off of appliances. They may even protect against a large surge generated from outside sources like lightning or problems along the power lines to the office or house. In the event of a large surge or spike, the surge suppressor is a one-time-use protector and will likely have to be replaced. Higher the energy absorption capacity of the Surge Protector, better it gives protection for the load. Power Strips are Not Surge Protectors.

24 Surge Protectors / Power Strips Look for Surge Protectors listed as a Transient Voltage Surge Suppressor. Never Overload the Capacity of the Power Strip or the Surge Protector Only Plug One Surge Protector or Power Strip into a Single Electrical Outlet. Never Plug a Surge Protector or Power Strip into Another Surge Protector or Power Strip.

25 How to Determine the Capacity of a Power Cord, Power Strip, or a Surge Protector Total Watts Should Not Exceed 80% (0.80) of the Rated Capacity of the Power Strip. Example Surge Protector Rated at 15 Amps 15 Amps X 250 Volts = 3750 VA Watts X 0.80 = 3000 Watts Capacity of the Surge Protector

26 Example of Multiple Items Plugged into a Surge Protector Multiple Items Plugged into a 15 Amp Surge Protector: (Assume line voltage to be 250V) Computer 2 amps = 400 Watts. Monitor 1.2 amps = 240 Watts. Coffee Maker 3.2 A = 650 Watts Laser Printer Idle 2 amps = 400 Watts Printing 9.5 amps = 1900 watts.

27 Example of Multiple Items Plugged into a Surge Protector Total Wattage While Printer is Idle: 400 (Computer) (Monitor) (Coffee Maker) (Printer in Idle) = 1690 Watts. Total Wattage While Printer is Printing: 400 (Computer) (Monitor) (Coffee Maker) (Printer Printing) = 3190 Watts. While printing, the load exceeds the capacity of the surge protector of 3000 Watts. Plug the Printer into a Separate Surge Protector.

28 Electrical Fires in Office 1. Heat-producing equipment - copiers, work processors, coffee makers and hot plates - are often overlooked as a potential fire hazard. Keep them away from anything that might burn. 2. Electrical appliances can be fire hazardous. Be sure to turn off all appliances at the end of the day. Use only grounded appliances plugged into grounded outlets (three prong plug). 3. Keep extension cords clear of doorways and other areas where they can be stepped on or chafed and never plug one extension cord into another.

29 Electrical Fires in Office 5. Do not allow combustible material (boxes, paper, etc.) to build up in inappropriate storage locations (near sources of ignition). 6. Avoid the use of space heaters of any type in your office. Often, these heaters are placed under desks or in closed quarters. The heat from these units can catch paper on fire or melt the insulation around electrical appliances. 8. Good housekeeping is essential to fire safety.

30 Electrical Fires in Office Electrical Fires Majority Caused by Aging Wiring and Misuse of Surge Protectors. Extension Cords - Leading Cause of Home Electrical Fires. The best time to think about fire safety is before a fire starts.

31 Electrical Fires in Office Learn the location of fire escape routes and how to activate the fire alarm. Participate in practice fire drills on a regular basis. Become familiar with stairway exits - elevators may not function during a fire, or may expose passengers to heat, gas and smoke. If electrical equipment malfunctions or gives off a strange odor, disconnect it and call the appropriate maintenance personnel. Promptly disconnect and replace cracked, frayed, or broken electrical cords.

32 Office Safety - First Aid Make sure all employees know the proper way to handle an electrical situation. Most important is all employees should know CPR in case the person has stopped breathing. they should perform this until medical attention arrives or the person can breath on their own again. If the person is still touching the electrical device it would be dangerous to just grab them you may get shocked also. Try to turn off the power flow or grab them with electric safety gloves or a stationary object in the area. Once they are clear of danger and breathing on their own give them room to breath and have them lay still until medical attention arrives.

33 Summary Periodically Inspect Outlets, Appliances, Plugs and Cords Do Not Exceed the Capacity of the Electrical Outlet, Power Strip, or Surge Protector. Appliances, Extension Cords, Power Strips, Surge Protectors must be of standard quality. Use Ground-Fault Circuit Interrupter (GFCI) Plugs & Test the GFCI Plug Every Month.

34 Summary The main switches should be provided at a place easily accessible to put off supply in case of an emergency. Do not insert wires directly into the plug socket without a matching plug pin to use any electrical appliance even for temporary basis. Do not connect a fuse / switch in the neutral circuit. Do not replace fuse, unless the fault is detected and rectified.

35 Clues that Electrical Hazards Exist Tripped circuit breakers or blown fuses. Warm tools, wires, cords, connections, or junction boxes. Tripped GFCI / ELCB that shuts off a circuit. Worn or frayed insulation around wire or connection

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