Incident Overview


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.

 

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Summary of Cylinder Construction Features


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.

 

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Incident Action Plan


Tactical Objectives

  1. Evaluate the potential for container failure.

  2. Start an evacuation.

Methods Of Extinguishment

This incident has almost everything working against emergency responders.

 

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Additional Factors


Additional Factors to Consider for this Operation Include:

  1. The rail car is being exposed to heavy fire impingement in the vapor space. Sources include both the pressure-fed liquid fire escaping from the propane car's relief valve and the flowing acetone fire. These fires will intensify rapidly over time and subject the propane car tank shell to even higher temperatures.

  2. The relief valve is venting liquid propane. Under normal circumstances, the relief valve would be positioned in the vapor space and would be venting propane vapor, not propane liquid. However, since the rail car is on its side, the relief valve is below the liquid propane level inside the tank. Consequently, as the internal pressure increases, the valve will function and vent liquid out onto the ground. It is very important to recognize that one cubic foot of propane will boil off into approximately 270 cubic feet of vapor (1 gallon of propane = 37 cubic feet of vapor). Therefore, the pressure-fed liquid propane fire will rapidly grow in intensity.

  3. It is also important to understand that venting of liquid will not lower the pressure in the container. Pressure will continue to rise as energy is applied to the liquid in the tank. It should be noted that similar conditions can exist when propane tank trucks are overturned since the relief valves are on top of the truck.

  4. The train derailment has occurred in a remote rural area with limited site access and limited water supplies to support firefighting operations. Unless adequate cooling water can quickly be placed on the burning propane and acetone rail cars, the propane rail car will very likely fail. This kind of failure is known as the BLEVE scenario. BLEVE stands for "Boiling Liquid Expanding Vapor Explosion" or more informally "Blast Leveling Everything Very Effectively".

  5. 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.


  6. Contact railroad authorities and ensure that the rail line has been closed upstream and downstream of the derailment and that railroad response specialists have been notified.

 

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 Incident Map


This is a top-perspective view of the incident area. Its purpose is only to get the general idea of the incident and surroundings.
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 Incident Video


In this section, we present an animated version of the incident.