Added the photo below to steamlocomotive.info today. This is an operational Italian locomotive. In the photo, you'll note the locomotive doesn't have a conventional smokestack, but rather a strange chimney-thing coming out between the second and third drives. Does anyone know anything more about this strange critter?



Also added a video clip of the locomotive in operation at:

http://steamlocomotive.info/vidlocomotive.cfm?display=9682

From the Wikipedia article:

"The preheated feedwater is fed at full boiler pressure into the main boiler via clack valves."

Clack valves? Is that Euro-speak for check valves?

Walt L.

"Clack valves? Is that Euro-speak for check valves?"--CPR 4000

Yes, it is.

Somebody once said Great Britain and America were two countries divided by a common language. . .

If you want to see a Franco-Crosti boilered steam locomotive in action, watch the movie "Von Ryan's Express" starring Frank Sinatra. The movie is about a group of allied POWs who escape from an Italian POW camp near the end of the war and hijack a train to leave the country. Their train is powered by a conventional Italian 2-8-0. Near the end of the movie, the Nazis give pursuit using a Franco-Crosti equipped Italian 2-8-0.

Seems when you get a draft going you can switch to the side chimney, but does this engine still have the front stack, or what?

Most do for starting, although some Italian locomotive classes don't.

Why the need for two stacks? What's the harm of always routing through the FWH unless they're worried the low temperature will cause a lot of condensation and corrosion?

Note that the jointed boiler Mallet articulateds used the front segment as a FWH though I suppose it was not at boiler pressure.

Steve

I don't know about this loco, but somewhere I read about a steam engine that reused the steam and exhaust somehow. That might account for the oddly placed smoke stack.

Great movie for steam guys. I always remembered the line by the British guy when they lost the fireman on the engine "I can stoke the boiler sir, I know a bit about steam". Vito Scotti played a great part too as the cocky locomotive possessive Iti engine driver.

Thinking back, I thought the Franco Crositi boilers had the smoke stacks coming out the side of where the smoke box would be, and go back towards the cab, ending in the position where the stacks are on this engine?

The part going back towards the cab is the actual heat exchanger that is the main part of the Franco-Crosti boiler. Some locomotives had a single heat exchanger centered under the boiler, while other locomotives had two heat exchangers, one along each side of the boiler. Here's a photo of an Italian 2-8-0 with this arrangement:



You can see the cylindrical heat exchanger running back from the normal smokebox toward the locomotive cab, and the steam exhaust pipe running from the cylinder block back to the bottom of the small "smokebox" (where it apparently feeds two separate exhaust nozzles) at the end of the heat exchanger. Above that, you can see the unusual semi-rectangular exhaust stack in front of the cab. The locomotive has a matching assembly on the other side of the boiler. Note that there is no smokestackin the normal position. This is identical to the locomotive mentioned previously in the movie Von Ryan's Express.

As I understand it, the Franco-Crosti system worked pretty well and gave significant fuel savings. One problem that did occur was corrosion of the heat exchanger tubes on the "smoke" side. The exhaust gases were cool enough by the time they reached the end of the heat exchangers that condensation of water vapor in the exhaust products would occur. The condensed water mixes with sulfur in the exhaust gases and forms sulfuric acid which attacks the steel parts. Modern condensing heating boilers tackle this problem by using alloy tubes. I seem to recall reading that porcelin-coated tubes were used in the heat exchangers in some of these locomotives for the same reason.

Where in Italy is this?

In marine applications, it was common to have an economizer, which was a heat exchanger between the boiler and the uptakes to the stack. Feedwater was pumped through the economizer and into the boiler through check valves. The exhaust steam from the engine went into a condenser, and was used as feedwater again.

What I find interesting is that what would generally be wasted heat from both the combustion gasses AND the exhaust steam is used to heat the feedwater in the Franco-Crosti design. Every BTU seems to be used. Of course, that design make it impossible to use something like a Lempor exhaust. I wonder how freely the Franco-Crosti engines steamed, and can also imagine that the feedwater heaters were a bear to service.

Locomotives tended to be MUCH simpler than marine and especially stationary applications because of space limitations and the desire for reduced maintenance as opposed to maximum efficiency.

There's no reason two smaller Lempors couldn't be used with a Franco-Crosti boiler; as is, they appeared to use two double-nozzle exhaust systems which would likely be more efficient than a single one-nozzle system on conventional locomotives.