Regular steam engines and Condensing steam engines

[cherokee woman]

Just got through watching "Trains & Locomotives on RFD-TV.
Have a couple of questions:

1. What is the difference between a regular steam engine
and a condensing steam engine?

2. Were condensing steam engines ever used here in
North America?

2a. If they were, how did they do here?

[Hugh Jampton]

Copied from; http://www.twaintimes.net/boat/sbpage3.htm
"A "condensing" steam engine does not exhaust its spent steam. Instead the spent steam is piped into a devise which, like a car radiator, cools the steam turning it back in to liquid water (cooling and condensing the steam). That still very hot water is pumped back into the boilers where it is reheated and reused. Since the returning water is still very hot it requires less heat to bring it back up to boiling temperature. A big savings in fuel and boiler maintenance"

They were mainly used as boat engines. The problem with locos is the need to find the space to fit the condenser and still remain within the loading gauge.

[Sterling1]

Another problem with condensing engines was as detailed in the "Great Book of Trains" was that since the steam wasn't expelled in the normal way a non condensing engine would, a blower fan of some type was need in place of the exhasust pipe.

South African Railways (SAR) built some condensing units in this way. Initially the fan would blow the smoke out but one of the main problems was that the grit from the smoke would destroy the blower fan blades. The blower fan was used to draw the fire in place of the exhaust pipe from the cylinders.

Yes these locomotives could go a long way without watering, the steamer would still eventually have to stop to water as some of the steam would leak out as in the case of South African Railways' class 25 4-8-4s.

Yes the condensing equipment was bulky and complex which is one of the reasons why eventually diesels went to SAR.

BTW the SAR class 25 were pretty well reliable once the troubles were figured out and dealt with. And to top that, the gauge on which these locmotives ran on was 3' 6" not standard 4' 8 1/2"

[tmcc man]

I know that a regular steamer is powered like this: The water in the pipes is heated by the coal, wood, etc., and this causes the water to boil, and when the psi is high enough the pressure is used to power the pistons, and that fires the drive rods, and it then powers the engine. I am going to guess that condensing means its definition, the water being recycled

[ben10ben]

In a condensing engine, or so I'm told, you also get the benefit of 14.7 PSI of atmospheric pressure acting on the piston in addition to whatever the boiler pressure acting on it is.

As stated above, they were much more common on marine engines, as you had a very large heatsink in which to condense the steam. Some notable examples are the steamboat NATCHEZ(both the modern one operating and the famous one that raced the ROB'T. E. LEE), as well as the GORDON C. GREENE, WAKEROBIN(which sank about a month ago), and the world-famous DELTA QUEEN.

[jchnhtfd]

More or less the usual problem with railroad steam engines -- cost vs. benefit. Condensing engines (rail, marine, stationary power; piston or turbine -- it doesn't matter a bit) require very high quality water to work for any length of time at all. Also, there is the space and weight of the condensor, and the extra maintenance. If adequate quality water is available in an adequate supply, it's a lot simpler and cheaper. SAR used condensing steam simply because they had long stretches with no reliable water supply at all, never mind adequate water. Condensing engines are used in marine applications mostly because salt water is really bad news in a boiler, and in stationary applications because the weight/space problems don't matter and it is reasonable to trade the extra maintenance required for the extra efficiency obtained -- and often there isn't enough water, anyway, at least for really big plants.

[CSSHEGEWISCH]

ATSF, who was a firm believer in keeping it simple, hauled tankcars of locomotive water to Hackberry AZ rather than deal with the complexities of operating condensing locomotives across the Arizona desert. In the end, FT's solved the water problem, anyway.