Tank cars and Hazmat cargoes: Part 2

Tank cars and Hazmat cargoes:  Part 2


By Ernest H. Robl


In the previous installment, we looked at some of the basics of tank cars and their hazardous materials.  In this concluding second part, we’ll discuss what some of these factors mean for our model train layouts.


The implications

If you have a facility that either receives or originates shipments of both gasoline and diesel fuel, you need to have at least two stationary tanks that are larger than the smallest tank car handled.  The two stationary tanks may be obvious, but why the size specification?

Because tank cars can safely operate at track speed in only two conditions — completely full or completely empty.  Partially filled tank cars are only handled rarely and only at restricted speeds.

Why?  Because, in partly filled tank cars, the contents begin to slosh around during transit.  Under certain conditions — speed and track conditions — this can become severe enough to lead to a derailment, which can be particularly bad if there are hazardous materials involved.  Most tank cars for liquids to have some internal baffles to cut down on the movement of the contents, but these are still only partially effective if the car is less than full.  (And, to be fully effective, these baffles would have to be large enough to cause problems in cleaning or fully emptying the car.)

The problem with sloshing contents is also one of the reasons why there are so many different size tank cars for liquids.  The tank car size has to be appropriate to the size of the shipment.  Some industrial chemicals are also only used in relatively small quantities by some industries.



So, in addition to variations in size, we have tank cars that are pressurized (even for liquids, if the vapors are hazardous), thermally insulated, coated with special internal linings (where the contents would interact with the metal of the car) —and the list goes on.

Some tank cars have the tanks mounted at an angle to facilitate easier emptying.  In some cases, the middle of the tank is lower than the ends.  The latter type of tankcar is usually used for thicker liquids, which would not otherwise fully drain on their own.

Tank cars also have a variety of valves and hatches for filling and draining.  An important part of many tank cars is a relief valve that has to be opened before draining the contents.

If this valve is not opened and you begin to pump out the contents, the shell of the car may implode – yes, this can happen even with cars whose tank is made of steel.

Many newer tank cars have automatic relief valves that open when the contents are emptied.  This is indicated on the car white circular belly band.  (But these cannot be used for all commodities as the valve would allow escape of hazardous fumes.  In those cases, a special venting hose has to be hooked up, in addition to the discharge hose.


The good, the bad, and the confusing

Yes, model railroad manufacturers offer a wide variety of tank cars.  And, as these cars often operate in multiples between origin and destination, many manufacturers also offer sets of similar cars with different operating numbers.

The major problem for model railroaders who want to be authentic is that the manufacturers seldom tell you what the car is intended to carry.  A typical catalog listing may go something like this “VTG tank car registered with the DB.”  And that’s accompanied by a tiny illustration – too small to read the lettering on the car.

VTG is a large European railcar leasing company that manages thousands of cars, of which several thousand may be registered with the DB.  That doesn’t tell you very much, if you are modeling a fuel distribution center which receives gasoline and diesel fuel by railcar.  The particular VTG railcar may just be lettered for some other chemical – only you can’t see that in the catalog.



Another look at one of my models of a VTG tank cars-registered with the ÖBB—a view similar to but probably larger than you would find in a typical model catalog. 

Roco model 46074 depicts a car produced by Link-Hofmann-Busch (LHB) for VTG with a capacity of 88 cubic meters.  (That information was provided not in the catalog, but in a sheet enclosed with the model.)

But, neither the catalog nor the enclosed sheet actually tells you that this car is labeled and equipped for the transport of gasoline—which I had to determine from the UN number.


If you are lucky, you can go to a vendor or manufacturer Web site and pull up a large photo that does show you the lettering on the car, including the UN number.  If you are buying such a car on the used market and the listing photo does not clearly show the UN number, ask the seller.



By the way, it is much easier to model the destinations of tank cars than their origins.  Most tank cars originate – are filled – at huge tank farms at the end of a major pipeline or at large chemical processing complexes.

On the other hand, even a local agricultural coop may get an occasional tank car of diesel fuel or liquid fertilizer, which is then transferred to stationary tanks for sale to the coops member farmers.  And, local fuel distributors may have a siding just big enough to hold one or two tank cars with inbound fuel.  A few moderate-sized stationary tanks will hold this fuel for transfer to distribution trucks as needed.  Again, even the smallest fuel distributor would likely have at least three or four stationary tanks for the different products, which could include different grades of gasoline, diesel fuel, and perhaps heating oil.

So, it’s best to have these cars appear from “off-stage” in inbound trains, from which they are then switched either to a local freight or directly to the fuel distributor, if it is located near a major rail yard.

The same is true for industries.  A metal processing or manufacturing plant may use chemicals, such as acids or paint, in fairly small quantities, receiving only an occasional inbound tank car, along with other cars of raw materials used by that industry.  The industry would need storage tanks for each of the inbound liquids or gases.



A model of an older (smaller) diesel fuel car.  This car has the era IV style lettering —but already has the UN number for diesel fuel.  My model has some coupler issues that I need to fix and will probably be permanently coupled as the fuel car for my track construction work train, where such an older car would be perfectly appropriate.


A large industry, burning its own fuel to generate steam or for other purposes, may also receive inbound shipments of fuel oil.  Certainly most moderate-sized industries would be more likely to burn oil rather than coal, as handling of coal is a far more complex process than pumping out the contents of a tank car.


Finally, a car for transport of sulfuric acid, which is used to etch surfaces in metal fabrication, among other applications.  (The model does not have the details for the marker brackets installed yet.)  The destination for this car will be a metal fabrication plant on my layout.  Again, prior to purchase, I had to determine the content of the car by looking at the UN number.  Fortunately, I was able to find a high-enough resolution image of this car.


Take a look at the accompanying illustrations for ideas on how tank cars would fit into your layout.  Me?  I’m looking for some additional modest-size modern tank cars labeled for diesel fuel.  And, from manufacturers’ catalogs, they are not easy to identify.



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