Tank cars

Can someone tell me the reason for tank cars of apparently similar capacity having one, two and three domes? Is it for the carriage of different grades
of material in the same car?
Thank you,
Don H.
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Just FYI, there are tank cars out there with up to 6 domes. The D&RGW used a 6-dome former wine tank in MOW service for several years.
It made sense in the first half of the 20th century to use several compartments in a tank car, but as volumes increased and shipping times decreased, the tank car fleet shifted to mostly single dome cars.

Yes. The liquids wouldn't be restricted to different grades of the same material though, one compartment could carry a completely different substance.
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On Sat, 14 Jun 2008 11:45:56 -0500, "Don Harstad"

Different commodities in multiple compartments. You may sometimes notice TWO or more different Hazmat Placards on a tank car like this, which indicates that two (or more) entirely different commodities are being shipped in the same car.
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On 6/17/2008 8:13 AM Mike Hudson spake thus:

So, how 'bout a tank car with milk in one side and sulfuric acid in the other? What if they get mixed up?
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David Nebenzahl wrote:

Never happen. They require different linings in the tank and the milk would require insulation.
A couple of proper examples Gas, diesel and kerosene different types of wine
Howard Garner
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wrote:

My understanding is that the multi-compartment tank cars were not operated like an LCL box car or baggage car, picking up partial loads at multiple stations. The multi-compartment tank cars would be loaded at one site and delivered to a different single site. Geezer
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On Tue, 17 Jun 2008 19:22:21 -0400, "Geezer"

This is exactly how it happens. I have delivered tank cars to Ashland Chemical in Doraville that have placards for two different chemicals, and thus two domes on the car on a number of occassions.
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On Tue, 17 Jun 2008 14:47:54 -0700, David Nebenzahl

Do you seriously think they would ship food commodities along with chemicals? Doesn't happen. And in fact, milk isn't shipped in tank cars these days. Also, it would generally be two different chemicals that would not have a detrimental reaction, because if the tank car derailed and spilled the contents a potential mix would be devastating.
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And the next question is, why do modern tank cars have no domes?
............................................................Bill
if you're

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On Thu, 19 Jun 2008 23:06:18 +1000, "Bill Whale"

They do have domes, they're just not as big as on the older cars. All the dome was was a cover for the valves. But a lot of cars now do have a small cover over the valves. Depends on the car
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snipped-for-privacy@earthlink.net wrote:

Not right! The dome was for the expansion of the product. It may also have covered various valves, etc. Today the control the loading to provide for the expansion, yesterday the filled the shell of the tank andthe dome took care of the expansion.
Howard Garner
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wrote: : > : >> And the next question is, why do modern tank cars have no domes? : >> : > : > They do have domes, they're just not as big as on the older cars. All : > the dome was was a cover for the valves. But a lot of cars now do : > have a small cover over the valves. Depends on the car : : Not right! : The dome was for the expansion of the product. It may also have covered : various valves, etc. : Today the control the loading to provide for the expansion, yesterday : the filled the shell of the tank andthe dome took care of the expansion. : : Howard Garner
I loaded tank cars at Pfizer Chemicals some years back. All I ever saw under the domes was pipes and pressure gauges. We had strict rules about how much material could be loaded into a car specifically to prevent expansion spills or tank/pipe ruptures.
I never got a good explanation why, but several materials were actually loaded through the 'discharge' valve on the bottom of the car. The air in the car vented out through a pipe on the top as it filled. It was your job if you overfilled and blew material out the top.
Len
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Len wrote: [...]

I suspect it was to reduce venting of gases. In you fill through the top valve, then gases from the fluid will mix with the air being displaced and vented outside the tank.
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I'm not sure how tank cars are filled, but it may be that filling from the bottom also minimized the disturbance of the material being loaded. If you use a hose to fill a water bucket, as the water shoots into the bucket from above, the water is stirred considerably and makes a lot of bubbles, etc. If you submerge the end of the hose. the water is still agititated but not nearly as much.
Like I said, just a thought as I really don't know how it is done...
dlm
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I'm not sure how tank cars are filled, but it may be that filling from the bottom also minimized the disturbance of the material being loaded. If you use a hose to fill a water bucket, as the water shoots into the bucket from above, the water is stirred considerably and makes a lot of bubbles, etc. If you submerge the end of the hose. the water is still agititated but not nearly as much.
Like I said, just a thought as I really don't know how it is done...
dlm
~~~~~~~ Also, filling from the bottom, with less agitation of the product, can reduce static electricity buildup and vaporization of the liquid. Note that large aircraft are fueled from the bottom. It's not just for the convenience of the workers. Val
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Len wrote:

<snip
My wife says that some of the heavy diesels would work, loaded that way, but she can't think of anything else. (Her stories with loading tankers, train and other, usually have to do with things like lox and hydrazine....)
mark
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wrote: : <snip : > I loaded tank cars at Pfizer Chemicals some years back. All I ever : > saw under the domes was pipes and pressure gauges. We had strict : > rules about how much material could be loaded into a car specifically : > to prevent expansion spills or tank/pipe ruptures. : > : > I never got a good explanation why, but several materials were : > actually loaded through the 'discharge' valve on the bottom of the : > car. The air in the car vented out through a pipe on the top as it : > filled. It was your job if you overfilled and blew material out the : > top. : : My wife says that some of the heavy diesels would work, loaded that way, but : she can't think of anything else. (Her stories with loading tankers, train : and other, usually have to do with things like lox and hydrazine....) : : mark
Er...were they trying to send a tank car to the moon?
We were dealing with things that were a bit less hazardous to life and limb. Things like citric acid slurry (check the ingredient list of your next Coke or Pepsi), ascorbic acid, and similar stuff.
Len
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Len wrote:

She was an engineer at KSC, and fueling rockets, for real. <g>

Ah, slurries. Yup.
mark "no slurry with the fringe on top?"
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So that people who own Tyco trains can pretend they are actually model railroaders ? ( rimshot )
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