Lecture 9 -_fire_hazard


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Lecture 9 -_fire_hazard

  1. 1. Topic 8 : Fire Hazard Topic Learning Outcome: 1) Describe the definition of Fire hazard 2) Explain the possible source of fire hazard. 3) Describe the identifying and assessing technique of fire hazard. 4) Describe the fire hazard control and prevention strategies.
  2. 2. Fire On Petroleum Bulk Storage Tank A huge fire and explosion involving two units of bulk storage tanks took place on 17th August 2008 at a terminal located at the south of Malaysia. The bulk storage tanks are used for the storage of petroleum products for export. Tank 1 which contains unleaded gasoline (ULG) was reported to be on fire at about 6.40 pm on Sunday, 17th August 2008. DOSH's headquarter office received report of the accident from DOSH's Johor office on 18th August 2008 and immediately fetched the Forensic Engineering Division and Major Hazard Division officers to the location of the accident. At about 7.15 pm, 18th August 2008, the fire spread to Tank 2 (Naphta) which was located beside Tank 1 due to heavy wind and ensuing flame.
  3. 3. What is Fire Hazard?  Fire hazards are conditions that favor fire development or growth.  Three elements are required to start and sustain fire: (1) oxygen, (2) fuel, and (3) heat.  Because oxygen is naturally present in most earth environments, fire hazards usually involve the mishandling of fuel or heat  Fire or combustion is a chemical reaction between oxygen and a combustible fuel.  To start a fire, source of ignition such as a spark, flame and high temperature are needed.  The ignition temperature or combustion point is the temperature at which a given fuel can burst into flame.
  4. 4. Fire Triangle @ Combustion Triangle  Diagram for understanding the necessary ingredients for most fires.  The triangle illustrates the three elements a fire needs to ignite: heat , fuel, and an oxygen.  A fire naturally occurs when the elements are present and combined in the right mixture.  The fire extinguishes by removing any one of the elements in the fire triangle Fire Triangle or Combustion Triangle
  5. 5. Fire Triangle @ Combustion Triangle Without sufficient heat, a fire cannot begin, and it cannot continue. Heat can be removed by the application of a substance which reduces the amount of heat available to the fire reaction. This is often water, which requires heat for phase change from water to steam. Introducing sufficient quantities and types of powder or gas in the flame reduces the amount of heat available for the fire reaction in the same manner. Turning off the electricity in an electrical fire removes the ignition source.
  6. 6. Fire Triangle @ Combustion Triangle Without fuel, a fire will stop. Fuel can be removed naturally, as where the fire has consumed all the burnable fuel, or manually, by mechanically or chemically removing the fuel from the fire. Fuel separation is an important factor in fire suppression, and is the basis for most major tactics, such as controlled burn. The fire stops because a lower concentration of fuel vapour in the flame leads to a decrease in energy release and a lower temperature. Removing the fuel thereby decreases the heat.
  7. 7. Fire Triangle @ Combustion Triangle Without sufficient oxygen, a fire cannot begin, and it cannot continue. With a decreased oxygen concentration, the combustion process slows. In most cases, there is plenty of air left when the fire goes out so this is commonly not a major factor.
  8. 8. Source of Fire Hazard? Types of Fire Sources/materials Class A fires Solid materials: wood, plastics, textiles, paper, clothing. Class B fires Flammable liquids and gasses. Class C fires Electrical (live electricity situations, exclude fires in other materials started by electricity). Class D fires Combustible, easily oxidized metals such as aluminum, magnesium, titanium and zirconium. Special categories Extremely active oxidizers or mixtures, flammables containing oxygen, nitric acid, hydrogen peroxide, and solid missile propellant.
  9. 9. Source of Fire Hazard? FUELS Materials Solids Wood, plastics, textiles, paper, clothing, fabric curtain, etc. Liquids Petrol, diesel, kerosene, etc. Gases Ammonia, Carbon monoxide • Fuels can be SOLIDS, LIQUIDS, VAPORS or GASES.
  10. 10. Source of Fire Hazard? • Flammable liquid are categorized as below: Flash point The lowest temperature for a given fuel at which vapors are produced in sufficient concentrations to flash in the presence of a source of ignition. Fire point The minimum temperature at which the vapors continue to burn, given a source of ignition. Auto-ignition The lowest point at which the vapors of a liquid or solid self-ignite without a source of ignition. Acetone, Diesel, Ethanol, methanol etc.
  11. 11. Source of Fire Hazard? Others source of fire hazard are : • Failure of electrical systems and equipments • Lightning strikes • Presence of a flammable gas or liquid mixture • Hot surfaces; e.g: furnaces, chimneys • Hot engines • Heated surfaces
  12. 12. Identifying and assessing Fire hazard in industries: 1. Identify hazard • Ignition sources • Fuel sources 2. Identify those at significant risk • Visitors • Workers • Disabled staff/ guests 3. Evaluate, Remove or reduce hazards • Replace strong ignition source with a weaker OR, • Use a less flammable fuel source 4. Evaluate protection & precautions measures • Fire escapes, alarms, doors, extinguishers, signs, lighting • Staff training, evacuation plans, fire drills 5. Record • Plan, Inform, Instruct and training 6. Review • All material changes
  13. 13. Identifying and assessing Fire hazard in industries: 3. Evaluate, Remove or reduce hazards • Replace strong ignition source with a weaker OR, • Use a less flammable fuel source Evaluate : 1.Risk of fire Occurring : Accidentally, by act, omission or deliberately. 2. Risk to People by fire spread : Convection, Conduction, Radiation Remove or Reduce : 1. Ignition sources, fuel sources, oxygen sources 2. Risk to people : adequate fire precaution
  14. 14. Identifying and assessing Fire hazard in industries: 5. Record • Plan, Inform, Instruct and training Step 5.1 : Record the significant findings and action taken • No one the correct format – a few sheets of paper or a line drawing may sufficient. Step 5.2 : Emergency plan • People know what to do based on the step 5.1 taken. Step 5.3 Inform, Instruct, cooperate and coordinate • Staff to receive information & instruction on induction • Cooperation's and coordination between different responsible persons is not an option. Step 5.4 Fire Safety training • To explain the emergency procedures
  15. 15. Fire hazard control and prevention strategies: 1. Work- site analysis. • Fire hazard should be surveyed at each part of workplace. Combustible materials should be identified and stored properly. • Fire extinguisher must be easily located and readily available. 2. Maintenance and housekeeping • Regular maintenance schedule should be follow. • Example : worn bearings on a motor shaft can overheat and ignite nearby flammable materials. • Good housekeeping helps prevent fires. 3. Training • Everyone must be a partners in the prevention and control of fires. -End-