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osha ppt .pptx

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osha ppt .pptx

  1. 1. 3. DRY CHEMICALS TYPE FIRE EXTINGUISHER ● This type is suitable for tracking gas fire, fires is electrical equipment. The chemical powder employed is usually sodium based and when applied to a fire undergoes chemical reaction. ● Chemical dry powders containing mixtures of sodium, potassium and barium compounds have been found useful in extinguishing fires in metals such as sodium and magnesium. ● The chemical powder is contained in the main shell and CO2 gas is held under high pressure in a sealed cartridge. When the extinguisher is operated, the cartridge is broken allowing CO2 gas to escape to the main shell and push out the powder in the form of fog.
  2. 2. OPERATION Carry the extinguisher to the place of fire and keep it upright. Remove the safety clip and strike the knob located in the cap to activate the piercing mechanism which in turn breaks the sealing disc of the cartridge. Direct the stream of escaping powder at the base of the flame. For effective result stand about 5 to 8 feet away and direct the stream near the seat of the fire, progress forward, moving the nozzle rapidly with a side to side sweeping motion. When using on outdoor fires always operate extinguisher from the upwind side for the fire.
  3. 3. 4. CARBON-DI-OXIDE TYPE FIRE EXTINGUISHER. ● CO2 is effective as an extinguishing agent primarily because it reduces the oxygen content of air to a point where combustion cannot continue. ● CO2 is non-combustible and does not react with most substances. Being a gas it can penetrate and spread to all areas affected by fires. ● These fire extinguishers are used for putting out fires in petroleum products, gaseous substances under pressure and also in sophisticated electrical and electronic apparatus. Carbon-di-oxide extinguishers are not to be used in ● Fires involving chemicals that contain their own oxygen supply. ● Fires involving reactive metals such as sodium, potassium and magnesium.
  4. 4. OPERATION Carry the extinguisher to the place of fire. Remove the safety pin and operate the discharge device or unscrew the valve depending on the design. Direct the jet at the base of fire, starting at one edge and sweeping across the surface of the burning material. When used in open air, the operator should stand on the up-wind side of the fire and should apply the gas in a downwind direction as close as possible to the fire. On fires in electrical equipment first switch off the current then direct the jet or horn straight at the fire.
  5. 5. 5. HALON TYPE FIRE EXTINGUISHER ● Halon is the most effective extinguishing agent than any other extinguishing agent. It is ideal for intense and rapid flammable fires. ● Halon is non-conductive and leaves no traces, when applied. So it is also suitable for electrical fires, computer rooms etc. ● Halon extinguishing the fire by interrupting the chain reactions which takes place at the flame zone for continuance of fire. ● Halon is twice as effective as carbon-di-oxide on a weight basis and five times as effective as carbon-di-oxide on volume basis.
  6. 6. OPERATION Carry the extinguisher to the place of fire, remove the safety pin and operate the discharge device. When operated it is discharged as a semiliquid jet at a high velocity and evaporate rapidly to cover a fire in a blanket of mist. The halogenated extinguishing agents are known as Halons. Halogenated extinguishing agents are hydrogen in which one or more hydrogen atoms have been replaced by atoms from the halogen series i.e., fluorine, chlorine, bromine and iodine. There are many halogenated but only two are most effective and less toxic. They are Halons 1301nand Halon 1211.

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