Trains.com

What was the purpose of steam lines on tank cars?

3093 views
17 replies
1 rating 2 rating 3 rating 4 rating 5 rating
  • Member since
    February 2003
  • From: Guelph, Ontario
  • 4,819 posts
What was the purpose of steam lines on tank cars?
Posted by Ulrich on Friday, February 12, 2021 7:17 AM

In the January issue of RMC (page 21 top) there's an ad for a GATC  tank car... states that car complete with steam line inlet/outlet. Judging from the lettering on the car it is 1970s era. What would be the purpose of steam lines on such a car, and what would be the source of the steam?

  • Member since
    December 2001
  • From: Northern New York
  • 25,018 posts
Posted by tree68 on Friday, February 12, 2021 7:19 AM

Thick cargoes like asphalt.  

A facility that handles such commodities would have an appropriate source of steam.

The Susquehanna currently handles asphalt to a location between Binghampton and Syracuse.

LarryWhistling
Resident Microferroequinologist (at least at my house) 
Everyone goes home; Safety begins with you
My Opinion. Standard Disclaimers Apply. No Expiration Date
Come ride the rails with me!
There's one thing about humility - the moment you think you've got it, you've lost it...

  • Member since
    May 2019
  • 1,768 posts
Posted by MMLDelete on Friday, February 12, 2021 7:48 AM

But what about when the car is underway?

  • Member since
    May 2003
  • From: US
  • 25,292 posts
Posted by BaltACD on Friday, February 12, 2021 8:36 AM

Lithonia Operator
But what about when the car is underway?

The car is not being unloaded while it is underway.  While underway the contents of the car will be cooling consistent with the temperature loss characteristics of the cargo.

I don't know how long a car must be on steam for the contents to be flowable once it is at the consignees facility.

Never too old to have a happy childhood!

              

  • Member since
    April 2007
  • 4,557 posts
Posted by Convicted One on Friday, February 12, 2021 10:46 AM

Ulrich
What would be the purpose of steam lines on such a car, and what would be the source of the steam?

 

Molten Sulphur too. you might find this informative. (I didn't realize the Sulphur had such a low melting point.)  I've seen numerous molten sulphur transfer trains, but always just took it for granted that the originating source must have been "crucible like" furnaces.  Now seeing the lower temperature melt point, things make more sense

 

https://railroads.dot.gov/sites/fra.dot.gov/files/fra_net/4083/Molten%20Sulphur%20Rail%20Tank%20Car%20Loading%20and%20Unloading%20Operations_Final%20with%20Appendices.pdf

  • Member since
    April 2007
  • 4,557 posts
Posted by Convicted One on Friday, February 12, 2021 10:52 AM

BaltACD
I don't know how long a car must be on steam for the contents to be flowable once it is at the consignees facility.

 

I was surprised to see "24-48 hours" mentioned for the molten sulphur.

  • Member since
    June 2019
  • 313 posts
Posted by Juniata Man on Friday, February 12, 2021 11:02 AM

Lots of products from chemicals to animal tallow must be heated in the car before they may be unloaded. Each product requires varying amounts of time on heat and this info is communicated to the consignee. I'll add that some products must be heated with hot water rather than steam because of the temperature difference between the two. Steam heat can damage some products as well as the interior lining of the car.

  • Member since
    September 2003
  • 21,669 posts
Posted by Overmod on Friday, February 12, 2021 11:02 AM

Lithonia Operator
But what about when the car is underway?

For a variety of reasons it's preferable to let some of these loads cool to the point they don't slosh or move in transport.  Part of the decision of how much insulation to apply to a car, and what type various parts of the insulation are, is overall economics.

Steam is generally used in preference to,say, Calrod-like electrical elements not only because of first cost but its high heat transfer at relatively low peak temperature.  Anyone who has suffered with any design of 'freeze plug' block heater understands heat-transfer concerns when excessive spot temperature degrades or cokes the material adjacent to the heating surface.  A sizable length of steam heating coil is easy to arrange, drain, and maintain, and providing process steam at the unloading point is not that difficult to support.

  • Member since
    December 2001
  • From: Northern New York
  • 25,018 posts
Posted by tree68 on Friday, February 12, 2021 11:16 AM

Convicted One
I was surprised to see "24-48 hours" mentioned for the molten sulphur.

Likely governed by how long it's been off heat.  I wouldn't be surprised to find the same type of number for asphalt.

LarryWhistling
Resident Microferroequinologist (at least at my house) 
Everyone goes home; Safety begins with you
My Opinion. Standard Disclaimers Apply. No Expiration Date
Come ride the rails with me!
There's one thing about humility - the moment you think you've got it, you've lost it...

  • Member since
    September 2003
  • 21,669 posts
Posted by Overmod on Friday, February 12, 2021 11:52 AM

tree68
 
Convicted One
I was surprised to see "24-48 hours" mentioned for the molten sulphur.

Perhaps also by the cost-effective length of piping and steam temperature provided.  If the operation can wait that time, they could economize on the likely reheating costs...
  • Member since
    December 2017
  • From: I've been everywhere, man
  • 4,269 posts
Posted by SD70Dude on Friday, February 12, 2021 1:30 PM

Some tank cars (think sulphur and tar/asphalt) have permanent placards painted on them that say "HOT".  And if you switch them not long after they are loaded they can indeed be quite warm.

Greetings from Alberta

-an Articulate Malcontent

  • Member since
    May 2003
  • From: US
  • 25,292 posts
Posted by BaltACD on Friday, February 12, 2021 1:30 PM

Tank cars are Private Owner cars, as such they ARE NOT subject to the Demurrage Rules that railroad owned cars are.  They nominally operate under 'trip leases' where the owner of the car is not the shipper and/or consignee of the car.  The trip lease specifies who pays what in the handling of the car at either/both the shipper/consignee facility and how long the car may remain at a facility for 'free'.

Never too old to have a happy childhood!

              

  • Member since
    April 2007
  • 4,557 posts
Posted by Convicted One on Friday, February 12, 2021 5:53 PM

SD70Dude
.  And if you switch them not long after they are loaded they can indeed be quite warm.

 

Being more familiar with the properties of sulphur now, after reading the above PDF...the melting point and the autoignition temperature are both lower than I would have guessed.

In fact, it woukd be possible to  blunder and use superheated  steam to heat sulpur above it's autoignition temperature.  Of course in the absence of oxygen, it wouldn't ignite. But once you open that vent to drain the tank, whoaaa!

 

I wonder if any bonehead has ever done that?

  • Member since
    May 2003
  • From: US
  • 25,292 posts
Posted by BaltACD on Friday, February 12, 2021 6:07 PM

Or if you heat the car and don't let it vent as it cools

Never too old to have a happy childhood!

              

  • Member since
    April 2016
  • 1,447 posts
Posted by Shadow the Cats owner on Friday, February 12, 2021 6:40 PM

Here at my work we have some tank cars that are heated also.  Why we haul some chemicals that require in transit heating to maintain certain tempatures to be usable at the final customer.  How it is done is via a diesel fired heater that is frame mounted on the tractor and we use quick connect fittings that pump hot coolant thru loops in the outer jacket of the trailer.  

  • Member since
    September 2003
  • 21,669 posts
Posted by Overmod on Friday, February 12, 2021 6:41 PM

Convicted One
In fact, it would be possible to  blunder and use superheated  steam to heat sulfur above its autoignition temperature.  Of course in the absence of oxygen, it wouldn't ignite. But once you open that vent to drain the tank, whoaaa!

Probably not as much of an issue as you think.  The superheated steam is not sparged as in a fireless cooker; it is in closed pipes with a relatively low surface area, and any excess heat would begin to radiate increasingly well from the upper part of the car long before you got to the 832F at any tank vent areas needed to put sulfur in vapor phase.  Remember that there is very little added enthalpy per degree added in superheat; it is a pressure enhancer far more than a heat-content enhancer, and you can calculate the saturation pressure of the steam in long pipes needed to get the bulk of the sulfur up to that autoignition temperature -- about 491F if anyone's not familiar.  That's way outside a pressure that would even accidentally be piped to car heating stations... assuming a process-heat system at a plant utilizing elemental sulfur would produce steam at that pressure (let alone then superheat it further and circulate the steam fast enough to keep the superheat in the piping volume).

I would also at least suspect that some kind of gas blanketing is used when the tank is drained, which would minimize any oxidation well short of fire.  You do raise the interesting question of how hot you'd have to get sulfur to produce a critical-mixture explosion mixing with ambient air... I don't have the reference sources to assess that.  Erik?  Have your CRC rubber bible handy?

  • Member since
    April 2007
  • 4,557 posts
Posted by Convicted One on Friday, February 12, 2021 10:58 PM

Overmod
d to get the bulk of the sulfur up to that autoignition temperature -- about 491F if anyone's not familiar.  That's way outside a pressure that would even accidentally be piped to car heating stations... assuming a process-heat system at a plant utilizing elemental sulfur would produce steam at that pressure

 I was just wondering in an "suppose all the holes in the swiss cheese happened to line up" sort of way. I'll acknowlege that it would be highly improbable.  You'd have to have a number of mistakes made, not the least of which being having someone totally incompetent do the plumbing.

 But, I have seen some fairly impressive results when automatic controls fail.

 Had a large, several hundred gallon, domestic water tank on the roof of one of our highrises, that had a dedicated air compressor connected to provide an air cushion above the water in the tank.

The pressure switch failed one weekend and the compressor ran continuously, until one of the most obnoxious lawyers you could imagine came in early in the morning to prep for a 9 AM trial,  And when he flushed the urinal, got what was likely the biggest "improbable" surprise of his life.   Crying

 

 

  • Member since
    September 2003
  • 21,669 posts
Posted by Overmod on Friday, February 12, 2021 11:45 PM

You would need steam above 615psi, soaking for long enough to get all the liquid to temperature; I don't know how quickly convection would accelerate the heating above the 240 to 250-degree range, but I suspect it would be measurable.

A number that I don't think has been mentioned yet is the flash point, which is listed as 320 degrees F, at which point the vapor pressure is relatively slight.  Where the concern would be there is spills, as in disconnected hoses, around a flame source; a crew might not realize that flash ignition (producing prompt noxious gas) might occur at a temperature radically lower than that for sustained combustion of the liquid -- and that is saturation temp for only 75psi steam.

Join our Community!

Our community is FREE to join. To participate you must either login or register for an account.

Search the Community

Newsletter Sign-Up

By signing up you may also receive occasional reader surveys and special offers from Trains magazine.Please view our privacy policy