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Flammability, Combustion, and Fire Protection. Objectives. Know and understand: Principles of combustible and flammable liquids, including limits, and classification Basics of fire chemistry Fire classes How extinguishing agents work Be familiar with Types of fire extinguishers

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objectives
Objectives
  • Know and understand:
    • Principles of combustible and flammable liquids, including limits, and classification
    • Basics of fire chemistry
    • Fire classes
    • How extinguishing agents work
  • Be familiar with
    • Types of fire extinguishers
    • How to control flammable liquid hazards
    • Basic fire prevention and protection
fire hazards
Fire Hazards
  • Annual $2.2 billion loss
  • Over 300 workplace deaths
  • Over 3% of workplace fatalities
  • Fire losses can be catastrophic
    • Unlike other hazards, the event may not be self- limiting
  • Fire hazards MUST be controlled to a low level of probability, as losses are so high
flammability limits
Flammability limits
  • Lower explosive limit, LEL (also LFL)
    • The minimum concentration of vapor in air below which a spread of flame does not occur when the vapor is in contact with a source of ignition
    • Acetone LEL = 2.5%
  • Upper explosive limit, UEL (also UFL)
    • The maximum concentration of vapor in air above which a spread of flame does not occur when the vapor is in contact with a source of ignition.
    • Acetone UEL = 12.8%
  • Explosive range (also flammable range)
    • The spread between the LEL and UEL
    • Acetone explosive range = 2.5 - 12.8%
slide5

Explosive energy

Concentration

UEL

LEL

relationship between toxicity and flammability
Relationship between toxicity and flammability

Toluene Example:

O2 deficient

TLV PEL IDLH LEL UEL

1 - 100 ppm 1000-5000 ppm 1-20 percent

  • TLV=50 ppm,
  • PEL = 200 ppm,
  • IDLH = 500 ppm,
  • LEL = 1.1%,
  • UEL 7.1%
definitions
Definitions
  • Ignition temperature
    • The temperature at which ignition (production of flame) and burning will be continued after the source of ignition or the source of heat is removed
  • Flash point
    • The lowest temperature at which enough vapor is given off near the surface of a liquid to produce a flammable mixture with air.
  • Flammable liquid
    • Liquids with a flash point below 100 F
  • Combustible liquid
    • Liquids with a flash point 100 F or greater
fire types
Fire Types
  • Flame fire
    • Gases or vapors
    • High burning rate
  • Surface fire
    • Burning rate may be slow
  • Explosion
    • An event leading to a rapid increase of pressure
explosions
Explosions
  • Deflagration
    • Combustion wave propagates at subsonic velocity
  • Detonation
    • Combustion wave propagates at supersonic velocity
  • Gas or vapor explosion
    • Combustion of pre-mixed gas or vapor
  • Dust explosion
    • Finely divided solids, suspended in air
explosions11
Explosions
  • BLEVE
    • Boiling Liquid Expanding Vapor Explosion
    • Flash evaporation after vessel rupture
    • May not involve combustion
chemistry of fire
Chemistry of Fire
  • Combustion
    • Rapid oxidation
  • Combustion components
    • Oxygen
      • Atmosphere (21%)
      • Chemical oxidizers
    • Fuel
      • Solids
        • Surface-to-mass ratio
      • Gaseous
      • Liquids (vapors)
      • BGases
chemistry of fire13
Chemistry of Fire
  • Combustion components (cont.)
    • Heat
      • Heat of combustion
      • Other sources of heat: (ignition)
        • Chemical reactions
          • Decay
          • Slow oxidation
        • Electricity
          • Arcing
          • Resistance
        • Mechanical friction
    • Chemical Chain Reaction
      • Propagated by free radicals
products of combustion
Heat

Soot, smoke

Carbon dioxide

Carbon monoxide

Incomplete combustion

Hydrogen cyanide

Hydrogen sulfide

Phosgene

Acid Gases

Hydrogen Chloride

Sulfur dioxide

Nitrogen oxides

Ammonia

Acrolein

Metal Fumes

Products of combustion
the fire triangle
The Fire Triangle
  • Four components:
    • Oxygen
    • Heat
    • Fuel
    • Reaction
  • Removing any component stops the fire
extinguishing a fire
Extinguishing a fire
  • Cooling
    • Applying water
  • Removing Fuel
    • Shut off supply to gas or liquid fires
    • Pump liquid from burning tanks
  • Limiting oxygen
    • Mechanical smothering
    • Foam
    • Displace oxygen with inert gas
  • Interrupt chain reaction
    • Capture free radicals using an extinguishing agent
fire classification
Fire Classification
  • Class A
    • Ordinary combustibles
    • Wood, paper, rubbish
    • Extinguish with water
  • Class B
    • Flammable liquids
    • Water may aggravate a burning liquid fire
    • Extinguish with foam, chemical agents
fire classification18
Fire Classification
  • Class C
    • Fires in electrical equipment
    • Use non-conductive extinguishing agent
  • Class D
    • Combustible metal fires
    • Extinguish by smothering with dry powder
    • Water will cause burning metals to explode
  • Special categories
extinguishing agents
Extinguishing agents
  • Water
    • Removes heat from a fire
    • Streams, spray or fog
    • Best for Class A fires
    • Not for electrical or combustible metal fires
      • Water mist may be used on electrical fires. These are special fire extinguishers, filled with distilled water, that produce a fine mist (no solid stream of water)
  • Foam
    • Excludes oxygen from burning liquid fires
    • Aqueous Film Forming Foam (AFFF)
    • Fire can re-ignite if foam breaks down
extinguishing agents20
Extinguishing agents
  • Inert Gases
    • Displaces oxygen
    • Carbon dioxide, nitrogen
  • Halogenated Hydrocarbons
    • Inhibit chain reactions
    • HALON (bromo-fluoro-chloro-hyrdrocarbons)
    • Carbon tetrachloride (historically)
    • Ozone depleting
    • New, more ozone-friendly agents are available
extinguishing agents21
Extinguishing agents
  • Dry Chemical
    • Inhibit chain reactions
    • Sodium or potassium bicarbonate
    • For Class B or C fires
  • Multipurpose Dry Chemical
    • Monoammonium phosphate
    • For Class A, B, or C fires
    • Excludes oxygen by coating surfaces
  • Dry Powder
    • Excludes oxygen from burning metal
    • Sodium chloride, graphite
fire extinguishers
Fire Extinguishers
  • Water
    • For Class A fires
    • Minimum 2 1/2 gallons or 2A
    • "A" unit rating = 5 quart water or equivalent
    • Usually stored pressure type
    • Inverting soda-acid extinguisher are obsolete and dangerous
  • Foam
    • For Class A or B
    • Stored pressure
fire extinguishers23
Fire Extinguishers
  • Dry Chemical
    • Class ABC or BC
    • "B" unit rating = 1 square foot flammable liquid fire
    • No rating for "C“
    • Stored pressure or cartridge- operated
fire extinguishers24
Fire Extinguishers
  • Liquified Gas
    • CO2, Class BC
    • HALON, Class ABC
  • Dry powder
    • Class D (no rating)
    • Cartridge operated
osha requirements for fire extinguishers
OSHA Requirements for Fire Extinguishers
  • Placement
    • Maximum 75 foot travel distance for "A" or "D“
    • Maximum 50 foot travel distance for "B“
  • Inspection
    • Monthly visual
    • Annual maintenance
    • 5-year hydrotest
      • 12 yr. hydrotest for dry chemical or HALON (6 yr. recharge)
  • Training and Education
    • For all workplaces with fire extinguishers
using a fire extinguisher
Using a Fire Extinguisher
  • P.A.S.S.
    • Pull Pin
    • Aim at base of fire
    • Squeeze handle
    • Sweep back and forth
controlling fire hazards
Controlling Fire Hazards
  • Flammable liquid safety
    • Limit quantities
    • Store liquids in flammable liquid cabinets or rooms
    • Use "Safety" cans
    • Ventilation
    • Pressure relief valves
controlling fire hazards28
Controlling Fire Hazards
  • Flammable liquid safety
    • Controlling ignition sources
      • Grounding and bonding
      • Non-sparking tools
      • Approved dispensing hoses
      • Classified "explosion proof" wiring
      • "Hot Work Permit“
        • For welding, etc.
        • Test for LEL
        • Observer stands by with extinguisher or fire hose
controlling fire hazards29
Controlling Fire Hazards
  • Fire Suppression Systems
    • Automatic sprinklers
      • Wet pipe (buildings)
      • Dry pipe (industrial)
    • Deluge
    • Dry chemical
    • CO2, HALON