A DOT-112 railroad tank car transporting propane has been involved in a high-speed derailment in a remote rural area approximately 500 feet from a two-lane road. The rail car is overturned on its right side and the car's topside relief valve is below the liquid level in the tank.
An adjacent rail car of acetone has been breached and is on fire. A running pool fire of burning acetone is exposing the propane rail car to intense heat. The propane rail car's relief valve is functioning due to the increased internal pressure in the car.
Since the relief valve is below the liquid level, liquid propane is being forced out of the relief valve and is exposing the upper half (right side) of the car to heavy fire.
Railroad tank cars are a principal means of moving bulk propane from refineries and gas plants to bulk plants. The rail car is simply a large cargo tank on a rail car chassis.
Small rail cars have water capacities between 11,000 and 12,000 gallons, while modern "jumbo" tank cars can have capacities as high as 34,500 gallons.
Like propane cargo tank trucks, rail cars are equipped with a topside pressure relief valve. To measure product temperature, pressure, and liquid, gauges are installed on the top of the tank. The liquid and vapor connections on the tank are protected and enclosed inside a dome cover.
The derailment is located near a rural two-lane road. Spectators and emergency response vehicles will quickly back up on the road. Given the size of the fire, limited water supply, and limited access to the derailment site, the Incident Commander should use the available emergency response resources to isolate the area and begin evacuation of people on the highway. The minimum initial evacuation zone should be 3,000 feet based on the North American Emergency Response Guidebook.
Note: This recommendation is consistent with findings based on actual projectile distances from 52 actual LPG rail car BLEVEs. Projectiles traveled up to 2,700 feet.
(See Campbell, J. A., Estimating the Magnitude of Macro-Hazards, Society of Fire Protection Engineers, Report 81-2, Boston, Massachusetts, 1981.)
This initial evacuation area may need to be expanded based on actual hazards and risks encountered.
This is a top-perspective view of the incident area. Its purpose is only to get the general idea of the incident and surroundings.
In this section, we present an animated version of the incident.