I hate to admit my ignorance but how were classic 8,000 or 10,000 gallon tank cars carrying, say, gasoline or oil, unloaded: by pumping through an outlet up in the dome or by gravity through a valve under the belly? I’m not thinking of modern propane tank cars or those now carrying cornstarch or whatnot, just the good old standard cars of the thirties, forties, and even later, usually carrying petroleum products. I presume such classic cars were always fllled through the dome which must have contained a filler pipe as well as the pressure vents. Thanks for enlightening this dummy. Jim here.
You are correct, tank cars are normally loaded via the dome and unloaded through an outlet under the tank. Some tank cars were/are equiped with steam connections to handle high viscosity products such as tar and bunker C oil.
Hope this helps.
Rob
Thank you, Rob. If you have time for another reply, where did those steam connections connect? Jim here.
Jimsabol
I’m not sure if the steam lines were connected at the dome, but they loop around the inside of the tank. Both ends connect to a steam boiler. I found a couple of tank car pieces you might be interested in.
RMC May 2004, Essential freight cars: 12 UTLX class X-3 tank cars, Ted Culotta.
RMC June 2008, Essential freight cars: 42. Modeling Spencer Kellogg 231: a standard tank car tanker, Ted Culotta.
Hope this helps Rob
Having unloaded a few tank cars myself I can add to the replies you received. Yes there was usually a bottom outlet but not everyone used them. We used one of the top outlets to remove the liquid. On top the car there are usually 4 valves. The two valves that are on the long axis of the car have standpipes that reach nearly to the bottom. We called them liquid valves The other two valves which sit on the cross axis of the car are vapor space valves and have no pipe that extends beyond the shell of the tank. We called those vapor valves.
Depending on the product being unloaded we would use one of two different methods to unload the car using only the top valves.
-
If the product was reasonably safe in contact with air we would open one of the vapor valves and connect a self priming pump to one of the liquid valves. The self priming pump would remove any gas in the line and then remove nearly all the liquid in the tank.
-
If the product was dangerous, or evaporated at a low temperature we would use a compressor to empty the tank car. The inlet of the compressor would be piped up to the vapor space of the tank to receive the load and the outlet of the compressor would be piped to one of the vapor valves of the tank car. One of the liquid valves of the tank car would be connected to the liquid fill pipe of the storage tank. The compressor would remove vapor from the storage tank, creating a slight vacuum, and push the vapor into the tank car, creating an elevated pressure in the tank car. This difference in pressure would push the liquid up the standpipe and into the storage tank. Once the liquid level in the tank car fell to the bottom of the stand pipe the pressure in the tank car would quickly drop and we would stop the compressor and disconnect our lines.
Unloading entirely from the top minimized the chances of causing a spill, however it came at the price of never being able to entirely emp
A book you might enjoy is “General American Tank Car Journeys,” published in 1930 by General American Tank Car (now GATX). It details, with copious illustrations, every product from petroleum to pickles shipped in a tank car, including where their origins, destinations, sizes, loading and unloading, rarity, and you name it. Try abebooks.com – it’s hard to find.
RWM
The “classic” steam coil equipped tank cars I remember (there may have been other arrangements) had the steam connections under the center of the car. They were just a straight piece of pipe maybe 2 1/2 in. O.D. hanging down a foot or so. Don’t recall what kind of coupling they had, if any - some of them may have just had threaded ends. The coils were on the outside of the lower half of the tank, but the whole tank was jacketed so you couldn’t see them.
They could probably be modeled with a couple short pieces of wire sticking straight down near the middle of the car. Whatever you do, make sure you disconnect the lines before moving the car [:-^].
Thanks to Rob, JonathanS, Railway Man, and DSO17. You’ve given me a real education! Jim Sabol here.
Hi!
You all beat me to providing answers to the original posting! May I add…
I worked at 3 edible oil refineries in the 1960s (and 3 petroleum refineries after that) and had a very close relationship with those “regular” and “jumbo” tank cars that contained soybean, cottonseed, corn, peanut, and other edible oils. They all had steam coils and were as the previous posters indicated.
Frankly, working with those tank cars was a dirty, dangerous, and uncomfortable job. If a car was in dedicated service (i.e. always holding soybean oil), it was not necessary to clean them out (usually). But otherwise, someone had to get inside and sqeegee out the remnants, and otherwise do what it took to clean them out. Definitely NOT a fun job!
As a side note, I recall a “pumper” that emptied a 10k tank of soybean oil into a large storage tank of corn oil. The problem was that all the corn oil - valued at about 15 cents/lb, had to be devalued to soybean oil - valued at 9 cents/lb. Other than a tongue lashing, the pumper came out OK.
ENJOY!
Mobilman44