Fire_prevention_and_control notes for engineering.ppt
- 1. FIRE PREVENTION AND CONTROL M. NGWENYA OSH PROMOTIONS OFFICER
- 2. INTRODUCTION Fire has provided men with so much advancement. It has broadened his food choice by enabling him to cook, and has also widened his living range by providing him with an external source of heat. Fire further enabled men to extract and work with metals However, fire is the most destructive, disruptive and costly cause of damage to buildings and other property. Historically, workplace fires have been one of the leading causes of worker injuries and deaths. Fire is often caused by momentary acts of carelessness or failure to take into account obvious hazards. It is therefore of paramount important to prevent fire out breaks in workplace. It is often cheaper and easier to prevent fires starting than to control or extinguish them once they are started
- 3. FIRE This is a chemical reaction (rapid oxidation process) which facilitates burning during which light, heat and smoke are created, and varies in intensity.
- 4. ELEMENTS OF FIRE Three essential elements must be present to cause and sustain a fire: Oxygen. Heat. Fuel (Combustible substance).
- 5. CONDITIONS ESSENTIAL TO CAUSE A FIRE: (REMOVAL OF ANY OF THE ABOVE ELEMENTS WILL STOP THE FIRE)
- 6. SOURCES OF FIRE: Friction. Mechanical Faults. Electrical faults. Chemical reactions. Spontaneous/self combustion. Hot surfaces. Lighting of matches or cigarette smoking. Lightning (impact releases electrical charges) Sparks. Open flames
- 7. IGNITION SOURCE Main sources of ignitions which often cause industrial fires include Electrical Poorly maintained electrical appliances (especially motors), overloaded circuits, abuse of appliances, using wrong appliances in hazardous areas and to a lesser extent static sparks cause a lot of fires.
- 8. IGNITION SOURCE CONT’D Friction Hot bearings, misaligned or broken machine parts, choking or jamming of materials and poor adjustment of power drives and conveyors. Open Flames Abuse and misuse of cutting and welding torches, gas burners and petrol/paraffin blow torches.
- 9. IGNITION SOURCE CONT’D Smoking and Matches Smoking in areas where combustible materials are present. Spontaneous Ignition Can be caused by oily waste and rubbish deposits in driers, ducts and flues, low grade material waste in storage and materials exposed to some form of heating.
- 10. IGNITION SOURCE CONT’D Hot Surfaces Materials exposed to the heat of boilers and furnaces, hot ducts, pipes and flues, electric irons and lamps and hot metal being processed. Combustion Sparks Caused by sparks released from rubbish burning, furnaces, fireboxes, process equipment and industrial trucks and tractors.
- 11. OXYGEN
- 12. OXYGEN Oxygen is an element from the atmospheric air that supports the combustion process. The main source of oxygen in a fire is air (21% oxygen). Other sources are oxidizing agents (e.g. hydrogen peroxide, sodium chlorate and nitric acid) and combustible substances containing oxygen (e.g. Ammonium nitrate).
- 13. FUEL
- 14. TYPE OF COMBUSTIBLES AND FLAMMABLE MATERIALS: Solids (carboneceous or simple organic materials): wood, grass, textile, paper, rags. Liquids (flammable): Petroleum products.ie petrol, diesel, paraffin, kerosene, lubricating oils. Gases: highly explosive due to their instability and reactiveness: acetylene, propane, hydrogen,butane,ammonia,methane. Metals: (when exposed to extreme temperatures) Aluminium, Magnesium, Calcium, Lithium, berilium, mercury, uranium, plutonium, sodium, titanium, sodium.
- 16. HEAT
- 17. HEAT: TEMPERATURES AT WHICH MATERIAL WILL BURN FALL INTO THREE CATEGORIES: FLASH POINT: The lowest temperature at which a flammable substance gives off vapours and just ‘flashes’ followed by extinguishment. It determines the conditions at which a flammable substance becomes flammable. FIRE POINT: Temperatures at which flame propagation is sustained after ignition. This temperature characterises the ability of a substance to burn independently. SPONTANEOUS IGNITION TEMPERATURE: Lowest temperature at which a substance produces sufficient flammable vapour and heat to start combustion ‘fire without the application of external flame’
- 18. TRANSMISSION OF HEAT: HEAT NORMALLY TRAVELS FROM HIGH TEMPERATURE REGIONS TO COOLER ONES USUALLY THROUGH: CONDUCTION: Transfer of heat within a solid material from hotter to cooler parts. Different materials conduct heat at different rates. Metals conduct heat well, asbestos so slowly that they are widely used as heat insulation. CONVECTION: The heat is only transmitted in liquids or gases where, when heated it expands becoming less dense, the lighter fluid will rise being displaced by colder denser fluid. The denser fluid becomes heated and rise again so circulation is set. RADIATION: Transfer of heat through a gas or vacuum in a similar way as light. The heat of the sun on earth reaches the earth in this manner.
- 19. FIRE CLASSES
- 20. FIRE CLASS LETTERING AND SYMBOL COLOUR OF CONTAINER CONTENT A – Organic materials i.e. paper, wood, textile, grass Green Triangle Red Water B – Flammable liquids i.e. petrol, paraffin, kerosene, thinners B Red Square French Blue Dry Powder C – Gases. Liquified petroleum gases, methane, butane C – Blue Circle Black Carbon Dioxide D – Metals. Cal, Na Yellow Brownish Star Dry powder with Asbestos/graphit e
- 21. METHODS OF EXTINGUISHMENT: QUENCHING (COOLING): water is used to lower the temperature of burning fuel to below its flash point. SMOTHERING: the fire is deprived of the oxygen needed to burn. Carbon dioxide or foam stop the air supply. STARVING: by shutting off the supply of fuel to the fire. The measures taken to control a fire sometimes combine two of the methods outlined above.
- 22. FIRE FIGHTING MEDIA/EQUIPMENT Sand. Fire extinguishers Fire Hydrants. Fire Hose Reel. Fire Blankets. Sprinkler System.
- 24. FIRE EXTINGUISHER: ADVANTAGES AND DISADVANTAGES. WATER – the most efficient, cheapest and most readily available medium of extinguishment. Has the best cooling properties than other extinguishing media as it prevent re-ignition and will readily penetrate to reach deep seated fires, but in some cases will seep through floors causing damage to ceiling and goods. This should not be used to fires involving electrically energised equipment and should not be mounted in close proximity to refrigerated areas as the water might freeze and the container corrode.
- 25. DRY POWDER The best and most versatile agent for flammable fires. The extinguisher can also be adapted for Class D fires by fitting special applicators and charging with special dry compounds. The powder is detrimental to delicate machinery and is sticky if multipurpose powders are used thus making cleaning operations difficult. Continuous vibrations cause the powder to compact within cylinders hence require frequent maintenance. The cooling ability is minimal and cannot extinguish deep seated fires hence the danger of re-ignition if heated surroundings exist.
- 26. CARBON DIOXIDE Is liquified at an approximate pressure of about 5 100 Kpa and reverts to a gas on discharge. It is clean to use, quick acting and is a non- conductor of electricity. Discharge is also controllable. The gas is rapidly dispersed in windy conditions, thereby limiting its effectiveness in outdoor operations.
- 27. FOR EFFECTIVE USE AND OPERATIONAL PROCEDURES FIRE EXTINGUISHERS MUST BE: The right type for each class of fire that may occur in the area. A reliable type. Available in sufficient quantities to match the extent of the fire hazard in the area. Mounted on escape routes, where they are accessible and in conspicuous position about 1,5 m above the ground. Maintained in perfect operating conditions, frequently inspected, checked against tempering and recharged as required. Operable by trained area personnel who can use them effectively and promptly.
- 28. OPERATING THE FIRE EXTINGUISHER. Pull the pin at the top of the fire extinguisher – the one that keeps the handle from being accidentally pressed. Aim the nozzle at the base of the fire. Squeeze the handle to discharge the extinguisher. If you release the handle, the discharge will stop. Remember to stand approximately 8 feet away Sweep the nozzle back and forth at the base of the fire. After the fire appears to be out, watch it carefully as it might re-ignite!
- 30. REQUIREMENTS/WAYS OF GUARDING AGAINST RISK OF FIRE: Have a ready fire fighting team: adequate staff should be incorporated to cover sickness, leave, absenteeism. The team should be well equipped, should operate equipment with conversant and confidence. Imperative for routes of escape to be kept free from obstruction, be conspicuously marked and accessible so that a way out to safety is unmistakable. Install automatic fire detecting systems – ensure functioning and audibility. Multistorey buildings should be made of fire resistance where connected to a fire station notify your intention for carrying out materials, a test of fire drill escape corridors.
- 31. CONT………………… Good Housekeeping: hot objects, sparks should be kept away from flammable substance. Reduce the degree of fire spread. Doors should be closed as one is escaping. Planned stacking and demarcation of areas is a must. Fire Drills: workers to be taught what to do in the event of an outbreak of fire in clear and concise instructions. Fire drills to be done regularly to keep the team up to standard/abreast
- 32. WHAT TO DO IN THE EVENT OF AN OUTBREAK OF A FIRE: Do not panic. Raise the alarm. Fight the fire. If becoming out of control, notify fire brigade and evacuate. Evacuate using the designated escape routes. Account for every person on the payroll and rescue anyone who might be trapped inside the plant, toilets, rest rooms. Assemble at a designed assembly point: Nobody should leave this point unless told to do so. Call the company fire team into action: only those trained should do the job. Call the Ambulance service or police if there are any causalities.