It was 25 years ago, on July 5, 1973, that a propane tank car being off-loaded in Kingman, AZ, caught fire, resulting in a BLEVE - boiling liquid expanding vapor explosion - that killed 11 Kingman firefighters and one civilian. Captain Wayne Davis is the only firefighter in the area who was at...
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Kingman's equipment in service at the time of the explosion included four engines and a rescue vehicle. Station 2 was located just a half mile west of the Doxol Gas Distribution Plant, the site of the explosion. Fire protection features of the Doxol facility consisted of portable dry chemical extinguishers near the storage tanks and in the office. The nearest public-water-supply fire hydrant was 1,200 feet north of the site on Hoover Street.
July 5, 1973, was a typical summer day in Arizona. The temperature topped 100 degrees Fahrenheit and a light westerly wind was blowing in at 12 mph. Workers at the Doxol plant, located on the east side of Kingman two miles from the downtown area, were preparing to off-load a 33,500-gallon water-capacity rail car containing liquefied propane gas (LPG).
The Doxol Plant consisted of an office and two above-ground LPG storage tanks - one 30,000 gallons and the other 18,000 gallons. Located on the southwest side of Route 66, the office was approximately 70 feet from the highway. The two storage tanks were located at the rear of the office about 200 feet from the highway. (Stationary propane tanks are generally not insulated, and flame impingement on the vapor space can cause metal failure in much the same way as the rail car did in the Kingman incident.) Usually, four employees were present at the small facility - a clerk, the manager and two delivery personnel. At the time of the explosion, there were just three employees on duty at the plant. Just east of the Doxol plant were the Double G Tire Co., 600 feet away; the Country Kitchen restaurant; 800 feet away; and the Phillips Truck Stop, 900 feet away.
Racks to off-load rail cars were located on the south side of the rail siding with underground piping running to the storage tanks. Kingman was serviced by the Santa Fe Railroad, which had delivered the tank car to the Doxol plant exactly a month earlier. The delay in off-loading the rail car is believed to have occurred because the fuel demand during the summer is low and the bulk storage tanks were full.
The loading rack where the tank car was resting is 30 feet across the Santa Fe's main line southeast of the main Doxol facility, 450 feet from the highway. LPG tank cars at that time were not insulated and all of the valves were located within the dome cover at the top of the tank. This tank was constructed of 11/16-inch carbon steel with a hydrostatic test pressure of 340 psi and a rupture pressure of 500 psi. The pressure relief valve was set to expel excess pressure from the tank at 280 psi.
At 1:30 P.M., workers began to connect the hoses to the rail car to start the off-loading process. During such an off-loading procedure, liquid lines are attached to the two liquid valves in the dome cover housing at the top of the rail car. Vapors are collected and routed into the vapor space of the tank. After all connections are made, the valves are opened slowly at first so as not to trip the excess flow valves. Connections are routinely checked for leakage and the valves fully opened when no leaks are present.
Two men were involved in the off-loading operation that day. As the off-loading proceeded, one of the men detected a small leak in one of the connections. Connections were typically tightened by striking them with a non-sparking brass-alloy wrench. These workers, however, used an aluminum-alloy wrench.
Despite their efforts to tighten the connection, the leak continued. The liquid connection was once again struck with the wrench. That's when a fire erupted. It is thought that a spark was created as the wrench struck the steel fitting, because of magnesium being present in the alloy of the wrench.
Both men fell from the top of the tank car, their clothing on fire, resulting in severe burns from the fire and extreme heat. One of them later died of his burn injuries. The other man ran back to the office building where he was driven to a Arizona Depart-ment of Public Safety Office a quarter mile away to report the fire. It is believed that an ambulance was called for the injured man before a call was made to the fire department.
Kingman firefighters received the first call for help at 1:57 P.M. and arrived on scene three minutes later. Initially, a call went out to the Troxton Canyon and Hualapai fire districts for mutual aid assistance. The fire spread quickly and was impinging on the top of the rail car where the vapor space is located.