Chapter 7 Fire and Explosions

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

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

Figure 7-1 Evolution of a Detonation

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

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

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.

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.

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.

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.

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.

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.

Figure 7-7 The Fire Triangle

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.

Correct steps in reporting a fire Give name and phone number Give fire location and extent of fire Give products involved in fire

The Hazards of Air Combustion Compression Absorption Concentrating oxygen Separation Mixing Oxidation

Fire Stages Incipient Stage Smoldering Stage Flame Stage Heat Stage

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.

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.

Types of Fire Extinguishers Carbon dioxide extinguishers Dry chemical fire extinguishers Foam fire extinguishers Halon fire extinguishers Water fire extinguishers

Figure 7-8 Carbon Dioxide Fire Extinguisher

Figure 7-9 Dry Chemical Fire Extinguishers

Figure 7-10 Foam Fire Extinguisher

Figure 7-11 Halon Fire Extinguisher

Figure 7-12 Water Fire Extinguisher

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.