At any juncture in which we discuss rail transportation response, we have to mention safety. We should always keep a safe distance from any railcars or locomotives and should always ensure that all rail traffic is stopped unless we are working on a separate siding. Access to railroad tracks almost invariably includes steep slopes of ballast that can lead to falls and the weight of the rail cars we work with in such situations — which are often derailed and possibly unstable — is tremendous. In addition, we should never walk on the rails, as the gauge — width between the tracks — of mainline U.S. railroads is four feet eight and one-half inches. If you are walking on a rail and slip, the rail gauge is the perfect distance for the average person to hit their head on the parallel rail if the fall is in that direction.
Let us now hypothetically imagine that we have a rail transportation Hazmat incident occurring in our response territory. How do we determine what is on board and begin to decipher the identity of rail cars that have possibly derailed and in doing so switched their order? Placards on each rail car carrying hazardous materials are one way in which we can gain insight into the matter, however what if the placards are not visible due to damage or car positioning? The conductor of the train should have in his or her possession a consist, which details each car in the train and the contents therein. Consists are — no pun intended —consistent, as a standard format for the documents exists. The consist should be kept in the cab of the lead locomotive, in easy reach of the conductor.
Let’s take a look at individual rail cars, namely tank cars as they carry the majority of hazardous materials by rail. When we look at a rail car of any type, we can easily determine “which end is which” by looking for the brake wheel — which is highly akin to a parking brake in a motor vehicle. The end that contains this circular wheel that is used by railroad personnel to lock the brakes down is termed the “B End” (for brake), and the opposite end is termed the — guess what? —“A End.” Rail cars are also bi-directional in that either end can lead down the tracks. Railcars can be further subdivided into quadrants for response purposes, all referenced by looking straight on at the B End (e.g. B End Right is on the right side of the car nearest the B End when looking at the B End, A End Left is on the A End left side when looking at the B End). The axles of a rail car are also referenced from the B End.
The markings scattered about a rail tank car can also provide valuable information to the emergency responder. The reporting marks on a rail tank car can be found on the left portion of each side of the rail car, on each end, and often on the B End top of the rail car. The reporting marks serve the same purpose as the license number on the license plate of a motor vehicle or the “N” number of an airplane--namely to serve as a unique identifier for that car. As private companies own all but a few rail tank cars in the U.S., the alphabetical code preceding the numerical portion of the reporting marks denotes the owner of the rail car. For instance, in the reporting marks UTLX 13911, the owner of the rail car is the Union Tank Car Company. In addition, DUPX would indicate DuPont, DODX would indicate the Department of Defense, and GATX would indicate the GATX Corporation to name but a few. Below the actual reporting marks can be viewed the load limit (maximum loaded weight) of the car in pounds and kilograms and the lightweight (unloaded car weight) also in pounds and kilograms.
On the right portion of each side of a rail tank car, additional information can be found. If a chemical name such as “Ethylene Oxide” is noted, the rail car is a dedicated tank car that can only carry the commodity indicated. The specification of the tank car can also be found in this area. The specification conveys detailed information about the car itself if responders know the manner in which to “decode” the information. For example, let us look at the following specification:
DOT111A 100 W5
In the above example, “DOT” is the authorizing agency (in this case the Department of Transportation, however “AAR” indicating the Association of American Railroads may also be seen). The numbers “111” indicates the class of tank car, and the “A” in most cases is simply a spacer. A “J” in the same space indicates that the car has a jacketed thermal protection system and tank head puncture-resistance system — also known as head shields. An “S” delineates that the car has head shields, and a “T” highlights the presence of a non-jacketed thermal protection system and head shields. The “100” indicates a tank test pressure of 100 psi, and the “W” indicates that the tank itself was fusion welded. An “AL” preceding the W denotes the tank is constructed of aluminum. Finally, the “5” is a code that indicates the fittings present, tank lining, and/or tank material. For further information on specification “decoding,” resources such as the “Field Guide to Tank Cars” published by the AAR can be consulted. Below the specification will be a qualification stencil on modern tank cars that will state the various test and inspection dates and the settings of any pressure relief valves.
In discussing rail tank cars we would be remiss if we did not broach the subject of the two main types of rail tank cars; general service (also known as non-pressure) and pressure. To visually discern the type of rail tank car we are dealing with, we simply need to look at the fittings or other protrusions emanating from the top and/or bottom of the car. If there are multiple protrusions from the top and/or bottom of the tank car, we are dealing with a general service rail car. If we only see one protrusion from the top of the rail car (a protective housing), we are dealing with a pressure rail tank car. While there are outliers to this methodology, they are the exception rather than the rule. General service rail tank cars may carry flammable or combustible liquids, other hazardous materials, or even non-hazardous materials such as corn syrup or milk. Pressure rail cars may carry LP gas, anhydrous ammonia, chlorine, carbon dioxide, or even flammable or combustible liquids.
In the case of a general service tank car, we may view protrusions from the top of the rail car such as a manway that allows for top filling and maintenance access, a “lunchbox” or “breadbox” protective cover over an air line fitting and siphon tube connection for offloading product, a pressure relief vent or valve, a vacuum breaker to prevent the formation of a vacuum inside the tank; a top operating, bottom opening valve that consists of a fitting on top of the rail car that is connected by a threaded rod to a bottom discharge valve, and/or bottom discharge valves. Within the protective housing of a pressure rail tank car we may find liquid valves, vapor valves and a pressure relief device. We may also find a sample valve for sampling product, a thermometer well for determining the temperature of product, and/or a gauging device for determining the level of the liquid phase of the product. Older slip tube gauging devices may no longer be used after April 2014, leaving only magnetic gauging devices in use.
We will next visit the topic of what pressure exactly demarcates a general service rail tank car from a pressure tank car. General service rail tank cars will have tank test pressures of 100 psi or below (normally either 60 psi or 100 psi) and pressure rail tank cars will have a tank test pressure of 100 psi up to 600 psi. When we speak about the pressure levels possibly inherent in rail tank cars, we must also address a means for relieving excess pressure. Rail tank cars may be fitted with a pressure relief vent, which is a rupture disc that is manufactured to rupture at a given pressure. Once the rupture disc has failed, the only way to restore the integrity of the system is to replace the rupture disc with a new one. Pressure relief vents are set to rupture at 33 percent of the tank burst pressure (tank burst pressure on a 60 psi test pressure general service tank is 240 psi and on a 100 psi general service tank is 500 psi). Alternatively, a pressure relief valve that will re-seat when the pressure level of the tank decreases below the activation pressure may be fitted. Pressure relief valves are set to activate at 75 percent of the tank test pressure. Rail tank cars carrying certain commodities may be fitted with a pressure relief valve that also incorporates a frangible rupture disc.
In summation, rail transportation is a transportation mode in which the conveyance of hazardous materials embodies unique equipment, terminology, and Hazmat response techniques. As hazardous materials responders, we should ensure that our knowledge of rail transportation is up to date if we have rail corridors traversing our jurisdiction. Even if we do not have rail lines in our territory we may be called upon to respond mutual aid to a rail incident in a neighboring jurisdiction and should train accordingly.
As always, be safe out there and be sure to visit the North Carolina Association of Hazardous Materials Responders website at www.nchazmat.com.