What is the cylinder on the top of the boiler face? What purpose does it serve? Did other railroads have this feature, or was it just CN?http://www.nps.gov/stea/planyourvisit/images/556_cn3254pullingoutofscranton.jpg I’ve been curious about this for years!
Thanks!
Acela026
It is a feedwater heater, and Elesco Feedwater Heater. Water was preheated before entering the boiler. There were many sizes locomotives and roads which used them. Some more saturated in steam can explain it more and name the various locomotives utilizing them. CNJ had a handful of Mikes as I remember, and the Canadians had several classes on their roads, too. Erie had a few…lets see what others will add…
In simple terms, it takes less energy to boil water at 212 degrees if it is already at 195 degrees (I think it was), as opposed to water at the ambient temperature it was in the tender. A feedwater heater used the already available exhausted steam to heat the incoming water.
As you would expect, this device found huge favour in Canada. CP and CN retrofitted almost every road engine and many switchers in the 1920’s, after the feedwater heater was invented.
Hopefully someone will come along to explain its’ operation and the actual output temperature, as well as the full extent of it’s deployment.
Bruce
The Pennsylvania Railroad at its Altoona testing plant compared two I1s Decapods, one with a feedwater heater and one without. The result showed a savings in coal consumption of 15- 16%. As explained above warmer water, less energy to get the job done.
There were two types of feedwater heaters, one mixed feedwater from the tender with steam expelled from the cylinder (Open System). A Worthington Feedwater Heater is of this type, side mounted and most popular. The other fed steam directly into the tender (Closed System). Both used the already heated steam leaving the cylinder thus not wasting this heat energy by simply letting it into the atmosphere.
Warmer water entering the boiler also reduced any shock to the metal inside the boiler. Early 1930’s, this device was quite common in usage by several railroads.
And note this one is an Elesco Feedwater heater manufactured by Elesco. There were other feedwater heaters on other locomotives placed elsewhere.
I always wondered how much the feedwater heaters raised the temperature of the water before it was injected into the boiler. Anybody know or have a link?
I can’t see why most railroads didn’t use them - using waste steam to heat incoming water makes the boiler more efficient. Were they maintenance intensive?
Since you can’t pump ice from a tank to a boiler, water was somewhat heated before entering the boiler. And of course, if you put 32.5degree water in 211 degree boiler you’d have an explosion! So, water was heated as best possible along the system into the boiler. But by running water past the steam lines of the boiler or past the exhaust, you could raise the temperature considerably. Presumably the ambient air temperature was a factor of how much warmer the water got before entering the boiler. As was noted above, it was considerable in many instances. And I’m sure it was considerable enough for railroads to invest in them weather the brow slung Elesco or any other.
The dilemma a railroad may have faced was the cost of fuel being cheaper than the maintenance required on the feedwater heater. Smaller railroads did not consider the consumption savings as much as large volume railroads and railroads with larger locomotives, for them the savings in consumption was a priority. The open style system also had a problem with lubrication oil used in the pump, sometimes it leaked into the warmed water and into the boiler.
It would follow then that roads in colder zones, like Candada and the US New England and Northern Tier would have utilized the feedwater heater more than roads where ambient tempertures never fell to the freezing mark or below.
Most of us are familiar with the principle of co-generation of electricity using what would otherwise be waste heat going up a stack, or spun off in heat exchangers that let warmed water run into a pond or a nearby stream. Inefficient as aitch. Or, as a francophone would say, haitch. [:D]
Why not use that steam in a heat exchanger, which is what the superheater and feedwater heaters were? You don’t need hot steam rising out of the stack for any reason…it just is hot. But, if you were to scavenge heat, you improve efficiency and can burn less fuel.
Also, cold water injected into a hot boiler cools the boiler. If you could put less-cool water into that nice toasty boiler interior, you keep pressure up and prevent shock processes. So, let’s use the waste heat going up the stack to warm the water.
Another benefit, although I don’t really know to what extent my claim pans out, a continuous feed of water to the boiler from a heater and feedwater pump reduces the chances of a catasrophic failure from the crown sheet being bared when too-busy or distracted crewmembers forget to check the water level in the boiler by glancing at the sight glass. God knows the books have many instances of crown sheet failures due to inattention, but I’ll bet very few were attributed to feedwater pump failures. (In know, I have drifted off topic a bit, but it’s all part of water supply issues to the toasty boiler.)
-Crandell
It is interesting to note that in Canada once the temperature dropped below zero most mainline and higher speed passenger trains had to be doubleheaded.
The normally assigned engine had to provide steam heat for the passenger cars, the feedwater heater, the dynamo, the air pumps, the steam heat line to the tender to keep the water above freezing, and a steam powered automatic coal stoker, if so equipped. There was not enough left for the drive pistons so that the trains could maintain a schedule. Then whatever freight engine capable of maintaining some sort of speed was hooked up ahead of the regular engine.
Beside matched pairs of Ten-Wheelers and Pacific’s, there are interesting pictures of Ten-Wheeler-Pacific combos as well as Pacific-Mikado’s and Royal Hudson-Mikado’s (passenger-freight combos). Apparently, when lifting the train from the station, the passenger loco would momentarily cut back on heat to the passenger cars to get up to speed, and then turn the duties over to the freight loco to maintain a running speed.
Steam engines never worked well in winter, and doubleheading passenger trains was an expensive way to run a railroad. Hard winters would be reflected in the yearly financial statements. Winter was a serious incentive to dieselize.
Bruce
IIRC, it was customary to replace one of the two steam injectors with a feedwater heater, so that even if the feedwater heater system failed, a standard injector would still be available.
I vaguely remember reading that feedwater heaters helped control the phenomenon of “creeping.” Apparently, a warm, idle locomotive had a tendency to drift if cold water was in the boiler. I’ll have to check my sources.
(I recently checked Alfred W. Bruce’s book, The Steam Locomotive in America, in which I first read about the problem of “night crawlers”. What typically happened was that at the end of a run, a locomotive was serviced and the warm boiler was filled with cold water. Because of the throttle design, expansion and contraction would lead to the throttle opening, and the engine beginning to move. Apparently, changes in the throttle arrangement and the adoption of the front-end throttle eliminated the problem with “night crawlers.” Just wanted to set the record straight.)
But at the end of the day, it was the quest for fuel conservation and thermal efficiency that drove the development of superheaters, feedwater heaters, the use of steam-driven appliances, and compounding.
Bruce, I found some information the 1922 Locomotive Up to Date, pp. 486-8. This is from the description of a Scottish-made heater.
“The manufactuers, G. & J. Weir, Ltd., of Cathcart, Glasgow, claim a fuel economy of not less than 10% with the use of this heater, when properly installed, as well as a decided increase in locomotive capacity, especially in heavy service.”
"In conclusion, it might be said that the latent heat from one pound of steam will heat ten pounds of water by nearly 100 degrees. So all the water the boiler uses can be heated as hot as this exhaust steam will heat it with but a small part of the exhaust (it runs from 12% to 16%, depending upon how cold the tank water may be). The remainder is amply sufficient to produce the required draft without any changes in the nozzle.
The water can be heated in this way to 220 degrees if the back pressure is five pounds, and then enters the boiler at that temperature instead of 60 degrees. This, of course, simply means that the heat that otherwise would be supplied by the coal to heat it from
Thanks Johnny, you’ve given us some great information.
Bruce
Since we’ve already heard how it works and what its benefits were, perhaps a couple of illustrations will help (even though they’re on a model) [swg]
As far as I know, all locos equipped with feedwater heaters were also fitted with an injector, for use if the pump should, for some reason, fail. In the example shown, it would be on the right (engineer’s) side of the loco and would feed cold water into the boiler through the same top feed check valve shown. Some locos had separate check valves, one on each side (usually) for the feedwater heater and the injector.
Wayne
I was under the impression, possibly mistaken, that steam locomotives usually had two separate systems available for injecting water into the boiler, whether or not one was through a feedwater heater. It was just too critical a function not to have some sort of back-up. Obviously, where one was a feedwater heater, or exhaust steam injector, that would be the preferred one to use due to the thermal efficiency. But I do not claim to be a steam expert.
John
I would agree, and feel that probably the fireman controlled the feedwater heater and pump, but both he and the hogger would have backup injectors.
-Crandell
Wayne! what great illustrations!
Thanks for the kind words, henry6. [:)]
Wayne
Despite the fact that it has nothing to do with the telegraph, I just happen to have in my collection of old railroad documentation the 1926 issue of the instruction book for the Operation and Maintenance of Elesco Locomotive Feed Water Heaters as published by The Superheater Company. The introduction to this manual states that the water would be raised to between 200 and 250 degrees. This increase in feed water temperature provides an effective increase in boiler capacity of from 12 to 15 percent. It also states that its use results in the savings of 12 to 15 percent of the waste heat in the exhaust system resulting in a fuel savings of 10 to 15 percent. Further, the waste steam used in the superheater is condensed and returned as purified water to the tank resulting in an effective increase in tank capacity of 12 to 15 percent and a further savings of about15 percent (their example assumes an 8000 gallon tank of which 1200 gallons of water from the steam condensed in the superheater would be returned to the tank and of that 1200 gallons another 200 gallons would be returned again.).
73, Chris
