TALKING PUBLIC SAFETY -- It was a hot day in July of 1973 in Kingman, Ariz. Tank Car #38214 sat in the rail yard holding 33,000 gallons of propane that was going to be transferred to storage tanks.
I remember early in my career going through Firefighter I/II and studying a BLEVE out of Kingman, Ariz., that killed 11 firefighters. This fire still today is used for training and operations when dealing with pressurized vessels.
So not to lose you too quickly, I should give some explanations and definitions. BLEVE -- Boiling Liquid Expanding Vapor Explosion. Water boils at 212 degree, a common known fact. Do you know what temperature propane boils at? Would you have guessed -44 degrees Fahrenheit? So propane turns from liquid to vapor at -44 degrees.
Pressurized vessel: A pressurized vessel is any container that has been designed to hold or contain gases or liquids at a pressure greatly different than ambient pressure.
It was a hot day in July of 1973 in Kingman, Ariz. Tank Car #38214 sat in the rail yard holding 33,000 gallons of propane that was going to be transferred to storage tanks. Prior to transferring the product a small leak was detected in one of the car's fittings.
In the first of several errors this fateful day, two rail yard workers attempted to stop the leak by hitting it with a large wrench. The spark ignited the gas shooting flames 70-80 feet in the air, engulfing the workers in flames.
The Kingman Volunteer Fire Department responded to find flames impinging on the vapor space of the tank. Ever wonder why when you fill your propane tanks they never completely fill them? Every container has about 20 percent vapor space that is needed during storage.
This is the most dangerous area for direct flame contact on a tank because there is nothing to absorb the heat, except for the metal. When steel reaches 400 degrees Fahrenheit it can no longer absorb heat and the integrity of the tank becomes a concern.
The firefighter’s plan of action was correct: apply water directly to the vapor space on the tank to protect this area. With adequate water flow (500 gallons per minute) and correct application, you can keep the tank at 212 degrees or lower, thus keeping the temperature well below the failure point.
This is where the second mistake was made that day. In an effort to obtain a water supply the initial lines deployed were 1-inch booster lines with the capability of flowing 30 gpm each, far below the 500 gpm needed.
Thirteen minutes after the original call for help, the tank BLEVE’d killing 12 firefighters and injuring a 13th. Temperatures from the fireball were believed to have reached 3,500 degrees as the tank car was spilt into two pieces with one half of the tanker traveling end over end some 1,200 feet down the track.
A crater measure 10 feet deep was all that was left of where the tank car was sitting. With the fire department completely lost, mutual aid came in from across the state. Fire departments, highway patrol, and the Air Force responded to the Kingman incident to extinguish fires this massive explosion caused.
Ask any firefighter who has gone through Firefighter I/II and Haz-Mat were sleeping in class if they can’t tell you about this incident.