Steam & Excursion > Question on Steam Engines

Hello-

Let me preface this post by stating that I am a software guy and know very little about the intricacies of steam locomotives. Other than the basics (heat creates steam (pressure), pressure moves pistons, pistons move rods, rods turn wheels), I don't know a whole lot. So if this question seems elementary, my apologies.

Is any of the steam in a steam engine reused? My impression is that it is not...that it all escapes or is vented during operation. If I am correct (and please, tell me if I am not), then is it not feasible to close the system and keep the steam, condense it back to water and reuse it? (I do realize that a certain amount is going to escape no matter what). It seems that, if that were possible, it would reduce the need to take on water as frequently. In addition, it would also mean not having to stop as much. It also seems that this would also reduce the amount of minerals and whatever else is in the water that ends up damaging the boiler and the tubing (since said particulates are not being added in nearly as often).

Okay...take it easy on me! :)

Kevin Morgan
Arvada, CO
ColoradoRailfan.com

> Okay...take it easy on me! :)

No need to apologize, Kevin. How else are you going to learn.

In North America, "condensing" closed loop steam locomotives were non-existant. I don't even think there were even any experiments built with it.

However, after about 1925 most new locomotives were built with, and many older ones retrofitted, some form of feedwater heater which used about 25% of the spent steam from the cylinders to preheat the fresh water being pumped into the boiler, thus recycling that portion of the heat and water.

There were condensing engines in use in other parts of the world, however.

Hope this answers your question.

-John

Nothing is free, and all that extra equipment would just add weight & maintenance. I think some African roads used it though. For the most part, steam's last dying act was to shoot up through the stack as exhaust. That explosive action and venture effect sucked air through the grates to make the fire burn hotter, and was then pulled through the tubes & flues to help heat the water on it's way to the stack. After that, it became a cloud again, condensed, and rained down someplace else at a later date.

Here's a partial answer;

http://en.wikipedia.org/wiki/Compound_locomotive

Condensing was more common in shipboard engines, since there was a great pool of cold salt water... under the ship.

The South African railways tried it with condensing units, but this proved overly complex with extended tenders with onboard radiators:

http://en.wikipedia.org/wiki/South_African_Class_25_4-8-4

Edit: class 25, not 26
http://en.wikipedia.org/wiki/South_African_Class_26_4-8-4

And by the time the technology was available in North America, the existing tank infrastructure was already available to new engines.



Edited 1 time(s). Last edit at 12/18/14 13:09 by nicknack.

Don't forget feedwater systems, guys. Virtually all the big "modern" U.S. locomotives had some form of feedwater heating system, where some of the exhausted/spent steam is used to preheat feed water, prior to that feed water entering the boiler.

Check out the South African steam - did just that (had condenser coils on the tender) The whole steam cycle used more than once was why there were compounds and Mallets - the steam was used twice (through high and low pressure cylinders). But, realistically, this had the biggest benefit (in a standard steam locomotive) when there was a paucity of (good) water (which is one reason why South African steam became some of the most developed). This concept is one of the key reasons there was a drive (heh) towards turbine locomotives. To make the steam engine more efficient in a locomotive.


This gives a basic explanation of the SA steam
http://en.wikipedia.org/wiki/South_African_Class_25_4-8-4
http://en.wikipedia.org/wiki/Condensing_steam_locomotive

I believe the French and Germans had projects, and there were a few NA locomotives with condensers. But, you're basically right - steam in most NA locomotives was used once and expelled, released or leaked. Attempting to make a steam locomotive more efficient than an internal combustion engine is "the holy grail".

Well, compound steam locomotives, like Mallets use steam twice, correct?

Is it true that pure steam is invisible to the eye?



Edited 2 time(s). Last edit at 12/18/14 13:16 by wabash2800.

Specific question on feedwater heaters: Where were they on UP's Challengers and 4000s? I know the 800s were/are there on the smokebox (not delivered with, but added later on I assume as all delivery pics I've seen don't have them there).

up3985 Wrote:
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> Specific question on feedwater heaters: Where were
> they on UP's Challengers and 4000s?

The 4000 and 3900 class locomotives had Elesco Exhaust Steam Injectors, which was mounted longitudinally under the front portion of the Fireman's side walkway.

I know the
> 800s were/are there on the smokebox (not delivered
> with, but added later on I assume as all delivery
> pics I've seen don't have them there).

The 800 class locomotives were delivered with the Sellers Exhaust Steam Injector system (that was the big "sewer pipe" running forward on the Fireman's side), and toward the end of steam, early 1950s, a number of FEF-2 and FEF-3 locomotives were up-graded to the Worthington S Type Feedwater systems.

ColoradoRailfan Wrote:
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> Is any of the steam in a steam engine reused?

You've gotten some good answers - my take:

On locomotives with feedwater heater systems, some of the steam gets reused to pre-heat the water going into the boiler.

Condensing and reusing water is possible in theory, but in practice railroads determined that the cost of maintaining condensing systems weren't offset by cost reductions elsewhere (fewer water towers, fewer water service employees, etc.).

If it doesn't save money, there's no incentive to do it.

True steam is, in fact, invisible if I remember anything from my high school science classes.

Marty Harrison
Knob Noster, MO

livesteamer Wrote:
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> True steam is, in fact, invisible if I remember
> anything from my high school science classes.

Correct you are.... in fact with high pressure it
becomes downright dangerous because you can't see
a steam leak. On ships and in high pressure stationary
situations, many times a leak is found in a high pressure
line by rolling a newspaper and seeing when it gets shredded.
It is an old way, pre-infrared tech., but works. I have
witnessed this done.

Yes Steam is invisible to the eye, what you see is the steam condensing back into water. I have seen wooden broom handles used to find leaks on high pressure steam leaks

CB

Efficiency means getting the steam exhaust smooth and fast out of the cylinders and through the stack. That flow also pulls the needed heat through the boiler from the fire. Any other system drops efficiency. great question.

Great question - especially for those of us born in the diesel era. To add a question, wouldn't condensing the steam back to water be too inefficient anyway since the ratio of water becoming steam is so much greater than steam condensing into water?

"Other than the basics (heat creates steam (pressure), pressure moves pistons, pistons move rods, rods turn wheels), "

Kevin...

Thanks for the GREAT question.....

One subtle concept is important to grasp: The concept of 'superheated' steam.
The perfection of the Schmidt Superheater, of German origin, (utilizing steam-only tubes inside the flues of the loco boiler), about 1910, made the BIGGEST difference between the locos of the 19th century/era and the modern, 20th-century designs.

It was the Schmidt Superheater that moved high HP locos from 'pressure' only machines to true-er "heat engines".
The use of superheated steam arises after many minutes of steady-load and draft conditions in the firebox.

SO yes, in 'starting' the pressure is what gets us going. However, that low-efficiency use of steam is tremendously costly in terms of fuel and water.
Once underway, the whole heat-generating system comes 'on-line' and the amount of steam flowing OUT of the units, exceeds the amount of steam ENTERING the units!
[The superheated steam molecules are vibrating at a much higher temperature and are further separated, physically, thus the 'more steam' concept --however, the steam pressure remains virtually the same].

The superheated state of the steam is actually much 'hotter' than the so-called 'saturated steam'. The gaseous state of water, Steam, is said to be 'saturated' when it is at the same temperature as the water in the boiler --it is 'heat-saturated' -- not related to moisture content.

When saturated steam is removed from the contact with the hot water, on its journey to the cylinders, some of the steam condenses into visible water vapor.
It condenses because its flowing to a lower-pressure vessel --hence, partial condensation.

In this scenario, we're running an 1890s/early 20th century, saturated machine. That means its almost all a 'pressure-machine', as in your postulation. The saturated steam is used once and up the stack. Late in the 1800s, many manufacturers tried many schemes of 'compounding' ---- meaning re-using what pressure remained in the steam in larger cylinders.
The larger diameter pistons were used to produce the same piston-THRUST as the smaller high pressure pistons. Superheating changed ALL that!

The advent of modern Super Power locos, obviated the need for 'recycling' the exhausted, saturated steam.
"Marine' [ships'] engines took advantage of the greater spaces that were available for compound engines, steam-evacuated condensing schemes and many other heat economizing solutions.

Locos also were capable of running at very small 'admission periods' of the power strokes. The superheated steam NEVER condensed in the piping or the cylinders; but, at speed, very little full-pressure boiler-steam was consumed --compared to the old 'saturated-pig' engines! [CALM Down, you 'saturated' fans!].

So, soon you will begin to grasp the true meaning of 'heat' engines.
Over time, Steamer reciprocating engines led to the internal-combustion engines; the Parson's steam turbines, also superheated, led to the jet-propulsion engines and that led to the turbo-prop engines and today's turbo-fan engines. ALL of these related uses of fuel relied on the concept of the massive amounts of HEAT doing the 'work' and NOT on the minimal amounts of 'pressure' involved. Think: "Heat engines", not 'pressure engines'.

So, when you watch a jet-plane take-off, thank the German engineers that perfected the concept of successful superheating -- and what evolved from that germinal idea....

Look to the application of the superheater to loco boilers, for the 'heat recovery' aspects of loco efficiencies.

Recirculating, saturated engines never would be able to do the great amount of heavy-hauling required of American freight railroads.
The Brits, and other users of lighter, smaller locos, experimented with many schemes of water-conserving. But, these all were virtually small 'teakettles' -pulling light, 4-wheel frt. cars, 'goods trains'....

You can BEST observe superheated locos when they're let free to roam at high speeds and short cut-offs ---- where the water, and fuel, savings become immense.
Heavy grades, though, soon drag the locos back to the heavy-blast exhausts and a near-saturated running state. Diesel power, a common addition to today's excursions can limit the steamer's
ability to gradually heat-up and actually get to a "Superheated State"! Today's crews, often prematurely, grab for the diesel [helper] tractive effort before the boiler gets a chance to heat-up! Heating that whole System up to the superheat-state takes TIME and patience. Today's RRers have a very short 'tolerance-period' ... so, the poor steamers can waste a LOT of water and fuel by being captive to the slog-state concept !!!

In 2015, save your pennies & catch up with the ex-SP 4449, when she comes out of her reconditioning and latest upgrades.
Hopefully, Doyle will be able to haul a decent train that heats-her-up -- into superheat!
Then, hold onto your hats, Boys!

Wes C.

wcamp1472 Wrote:
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> In 2015, save your pennies & catch up with the
> ex-SP 4449, when she comes out of her
> reconditioning and latest upgrades.
> Hopefully, Doyle will be able to haul a decent
> train that heats-her-up -- into superheat!
> Then, hold onto your hats, Boys!
>
> Wes C.

Can't tell you how many times I have experienced that, i.e you can simply hear the change in her exhaust SOUND.

Jack,

I especially love it when when Doyle 'squeezes the throttle down' --longer 'dwell-time' for the steam in the units: BLUE HOT! --- (since the multiple-poppet front-end throttle is AFTER
[down-stream of] the units!)...


Happy Christmas to ALL, and to ALL a Good 2015!
May Santa be able to bring you your fondest wishes and favorite 'toys'.. { "The only difference between the Men and the Boys, is the price of their 'Toys',,,").

Also, commit to 'giving back' --- to someone who'll be 'blown-away' by your thoughtfulness!
Your kindness can change our future.
Share the wealth!

I'm deeply thankful to Todd --for birthing this concept of TO; and, for his dedication to making it continuously better!

Wes C.

True, but also impurities in the water and if you included the stack, what you burn for fuel too, correct?

CountryBoy Wrote:
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> Yes Steam is invisible to the eye, what you see is
> the steam condensing back into water. I have seen
> wooden broom handles used to find leaks on high
> pressure steam leaks
>
> CB