© 2012 delmar, cengage learning chapter 7 fire and explosions
TRANSCRIPT
© 2012 Delmar, Cengage Learning
Chapter 7 Fire and Explosions
© 2012 Delmar, Cengage Learning
Fires, Explosions, and Detonations
• The lowest temperature at which an air-hydrocarbon mixture will explode or burn is called the ignition temperature
• A detonation wave for air-hydrocarbon mixtures expands at 4,000 to 8,000 fps
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Chemical Explosions
• A rapidly building, self-contained fire that generates gases and vapors capable of exceeding the pressure ratings of the equipment it is in.
• Thermal explosions, combustion explosions, condensed phase explosions, physical explosions, and nuclear explosions.
• Thermal explosions are the most common explosions in the chemical industry
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Figure 7-1 Evolution of a Detonation
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Texas City Fire and Explosion• April 16, 1947• One of the worst industrial accidents to occur
in the U.S.• The S.S. Grandcamp was carrying
ammonium nitrate• It killed 581 bystanders, the ships crew, and
volunteer firefighters• It knocked two airplanes out of the air• Approximately 880 tons of ammonium nitrate
had exploded
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Phillips and Arco Explosions• In 1980 the CPI began the process of
integrating new technology.
• The new technology allowed for a smaller workforce
• With less skilled workers and new technology to learn safety began to lag
• Contract labor began to perform work in plants• Chemical hazards were not regulated• Prevention of catastrophic release was not
regulated
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• On Oct. 22 1989 employees at Phillips were asked to remove a polyethylene blockage. They refused and the jobs was given to contract workers.
• 85,000 lbs. of high-pressure gases were dumped from the reactor system.
• The explosion killed 23 workers and the entire plant was destroyed.
• The explosion registered a 3.5 on the Richter scale.
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• On July 5, 1990 ARCO was having trouble with a safety system on a wastewater tank.
• When the tank exploded it killed 17 men.
• The Phillips and ARCO incidents led directly to the development of the PSM standard.
• An industrial partnership was formed between education, government, and industry.
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Polymers and Fires• Polymers are natural or synthetic
compounds linked together in long chains.
• When polymers burn:• Temperatures in an enclosed room will reach
over 1,500°F.• Toxic fumes fill the room. Oxygen levels can
drop below 10%.• The best protection is a self-contained
breathing apparatus.
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Flammable and Explosive Materials
• Fire is a chemical process that requires fuel, heat, and oxygen in the correct proportions to chemically react together.
• Chemicals with flashpoints below 100°F are flammable substances.
• Burnable material with flashpoints above 100°F are referred to as combustibles.
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Radiation Hazards
• Radiation sickness occurs when a person is exposed to harmful radiation, and the individual cells in the body begin to break down.
• The tern distance refers to the drop-off of radiation, because radiation drops off with square of the distance of one foot of the source.
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Fundamentals of Fire Prevention, Protection, and Control
• Analyze the physical layout of the plant and surrounding structures.
• Ensure that firefighting equipment is available and strategically placed.
• Develop structured safety training programs.
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Figure 7-7 The Fire Triangle
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The Chemistry of Fire
• It is important to be constantly aware of the following:
• Ingredients of a fire• Fire prevention and control measures• Properties of flammable and combustible materials
• The effects of absorbed heat include an increase in volume, temperature, change of state, chemical change, and electrical transfer.
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• Correct steps in reporting a fire1. Give name and phone number
2. Give fire location and extent of fire
3. Give products involved in fire
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The Hazards of Air
• Combustion
• Compression
• Absorption
• Concentrating oxygen
• Separation
• Mixing
• Oxidation
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Fire Stages
• Incipient Stage
• Smoldering Stage
• Flame Stage
• Heat Stage
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Ignition Temperature
• The ignition temperature is described as the lowest temperature at which a substance will automatically ignite. This process does not require a flame to occur. If the mixture is within its flammability limits and has reached its ignition temperature it will ignite.
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Fire Classification System• Class A fires involve combustible
material such as wood, paper or plastic.• Class B fires involve combustible and
flammable gases and liquids and grease.• Class C fires are categorized as
electrical fires.• Class D fires cover combustible metals.
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Types of Fire Extinguishers
• Carbon dioxide extinguishers
• Dry chemical fire extinguishers
• Foam fire extinguishers
• Halon fire extinguishers
• Water fire extinguishers
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Figure 7-8 Carbon Dioxide Fire Extinguisher
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Figure 7-9 Dry Chemical Fire Extinguishers
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Figure 7-10 Foam Fire Extinguisher
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Figure 7-11 Halon Fire Extinguisher
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Figure 7-12 Water Fire Extinguisher
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Fire Extinguisher Use• Identify the type of material involved.
• Select the appropriate fire extinguisher.
• Test the extinguisher.
• Approach upwind of the fire.
• Aim at the base of the flames, using a sweeping motion.
• Back away from the fire before the extinguisher is emptied.
• NEVER turn your back on a fire.