Paul,
Thank you for the references!
Just to help my own learning on the subject. I found an online articel that describes firing practices for different types of coal.
This is for stationary plants, far different than locomotives, but i'm guessing the general concepts pertain, but with even more complexity!
It seems the more volatile matter, the more air and volume is needed for efficient combustion. The more organic matter the thinner the fire needed. The article mentions Rock Springs coal specifically and states that 6-8" is ideal.
To Overmods point, with the throttle wide open and at high cutoff, I could see where it would be easy to tear holes in the fire. The articel also mentions the air needs to be very hot, ambient air will stop the combustion process. So holes in the fire would be very bad indeed.
That also I think answers a question I had about why the overfire air holes were eliminated started around 1948. Gordon McCulloh mentions it in his book A History of Union Pacific Steam but didn't mention why. All that cold air coming in the sides of the firebox was probably hurting combustion rather than helping. Sounds like focusing on good, hot primary are was more beneficial.
Again, many you you probably already understand these things, but the article was helpful for a novice like me.
The article link is here
https://www.gutenberg.org/files/22657/22657-h/chapters/coal.html
Thanks Overmod
Happy Fathers Day to all!
Beware of studying resources for firing pulverized coal in a Benson boiler. The load characteristics, turndown, heat balance and Rankine-cycle implementation are very different from most locomotive practice.
Start by reading this carefully, including memorization of as many of the backhead controls as you can:
https://www.railarchive.net/firing/
Then peruse this for the non-US-American view (I miss Claude Bersano so badly!)
http://users.fini.net/~bersano/english-anglais/HandbookForRailwaySteamLocomotiveEnginemen-BTC-1957-pg196.pdf
You might look into the reprinted 1947 Reading Railroad 'Firing the Steam Locomotive' (about $10 from Amazon but you may find a used copy from time to time from a place like Thriftbooks for less) which has some detail differences.
The overfire jets were never intended for thermodynamic performance: they are purely to avoid fines for visible smoke from the (many!) places that started imposing them. Note that there are two kinds of those guns/jets: those that use boiler steam to entrain atmosphere (doing some secondary-air preheat, but adding water to the flame and taking it away from the boiler, neither of which are good) vs. those that use main-reservoir brake air (terrible shrieking and the usual substantial chill as 140psi air exhausts to a partial vacuum, but a higher mass flow of burnable oxygen). I have always been a bit amused with the idea that the jets penetrate to the center of the gas plume, and that they don't disturb the gasdynamics of induced draft... neither of which really happen.
On the other hand, heating the primary air can be useful, just as it is for PC firing in high-pressure utility boilers (where there is room and power to arrange adequate 650F or better primary air without difficulties). An interesting device for Super-Power engines is the Snyder preheater, from the early Thirties but not gaining real traction til the late Forties, which is basically 3 staggered passes of 2" pipe with exhaust steam saturated at typical exhaust backpressure run through them arranged in the gap between mud ring and ashpan. Apparently C&O observed better than 10% saving (admittedly this is only about 0.7% overall gain based on the stoic heat content of the fuel, but it's a great dollar saving for what is basically a few tens of feet of pipe).
When you're a bit more comfortable with how flame 'works' in these boilers, look at some of the 'patent' circulation arrangements (like Nicholson syphons and American Arch 'security circulators' to see the conjoined advantages and drawbacks of circulating water through the radiant plume. You will not be surprised to see why there can be enhanced sooting when those things are too enthusiastically (or erroneously) provided.
(Incidental solution-left-to-the-reader exercise: the original implementations of arch tubes continued straight up to the inner wrapper near the top of the backhead, seemingly a nifty place to absorb a few radiant BTU at fourth-power Stefan-Boltzmann uptake. But many railroads, including ATSF, quietly abandoned that idea. Can you tell why?
Thanks for the references.
Looks like I have some "homework" to do!
Overmod (Incidental solution-left-to-the-reader exercise: the original implementations of arch tubes continued straight up to the inner wrapper near the top of the backhead, seemingly a nifty place to absorb a few radiant BTU at fourth-power Stefan-Boltzmann uptake. But many railroads, including ATSF, quietly abandoned that idea. Can you tell why?
Cinder cutting? Poor access to water side for descaling? Burn-through of the tubes?
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
Paul MilenkovicCinder cutting? Poor access to water side for descaling? Burn-through of the tubes?
There should be little cinder cutting as this is just about the hottest net part of the fire, where the plume coming up under the arch reverses direction to go forward under the crown. If anything you'd get glassing there if the ash is fusible.
The designs I've seen all have very careful provision of washout plugs on the backhead that line up with the tubes. That might actually have exacerbated the problem... but it made scaling an easy thing to rectify.
One of the most evil things in a staybolted firebox is the development of DNB, departure from nucleate boiling. Steam is a relatively good insulator, as anyone evennpassingly familiar with the Eisenhoffer/Leidenfrost effect knows. In DNB a larger and larger area flashes to steam, while the plate behind that area begins to overheat -- possibly very severely very fast.
The bright principle behind the arch tubes were to use them as longitudinal bars to hold the arch up and get a little extra free vertical circulation. But look at the situation a moment:
Water flow IN comes from a restricted volume at the throat;
The section of pipe above the arch is in a relatively high radiant heat flux, very subject to induced DNB;
The exit of the pipe butt-ends into the backhead space, virtually a flow stall for natural circulation in a pipe.
Note what happens when a relatively large mass of steam forms as a 'plug' in the hot upper bore -- it is above saturation pressure pretty quickly and this presses down against the natural-circulation rise of heated water as well as up toward the backhead. Expect to see thermal cycling -- lots and lots of thermal cycling!
A similar mechanism was in my opinion a likely cause of or contributor to the explosion of Allegheny 1642. One touted 'advantage' of Nicholsons was that in conditions of very low water their 'pumping action' would cause a welling-up that would tend to keep the crown covered... in fact, to amplify the tendency for the boiler to work more effectively than it already does with shallow water over the crown.
What actually happens is that the welling doesn't fully cover the crown; it spills this way and that, tending more and more to avoid overheated sections but quenching them fairly effectively when in contact. Steel generally doesn't like repeated overheating and quenching when under monotone load... it deforms and cracks and deforms...
La Locomotive a Vapeur: English Edition: Chapelon, Andre, Carpenter, George: 9780953652303: Amazon.com: Books
that are still pricey, I cannot tell if this is in the original French or is an English-language translation.
These would be the translation since George Carpenter was the translator.
His name would not appear on the listing of an original version.
Peter
$150 plus $3.99 shipping does not strike me as excessively pricy. I stumbled across a source selling brand new ones in shrink wrap for $99 about a decade ago, and all the 'serious correspondents' on the old steam_tech Yahoo group were overjoyed to get one at that price.
It's the 1938 French original that commands the astronomical price.
I've really been enjoying the machine side of the discussion, but I think you bring up a great point about the human side as well. There are plenty of pictures of "Jabelmann Power" shooting roiling columns of thick smoke skyward, but also many showing a "light" stack.
All the machine and fuel shortcomings aside, a good fireman definitely made a big impact. By the 1950's many of the more senior engine crews were transitioning to diesels, which were the more desried jobs. This left the younger, less experienced crews to the Challengers and Big Boys.
Overmod I stopped flying sailplanes when I realized, to my horror, that I could no longer recognize the changing terrain without frequent orientation using a map. Sailplanes require fairly frequent turns where you have to be sensitive to ridge and thermal lift and not concentrating on 'where you are going' -- and you might be pointing 'anywhere' once you have come to altitude. On the other hand when you commit to land there is usually no such thing as a go-round, and it becomes much more tedious to recover the aircraft the further away from the staging point you come to rest -- further both horizontally and vertically. Helicopters require more multiple control haptics than sailplanes...
I stopped flying sailplanes when I realized, to my horror, that I could no longer recognize the changing terrain without frequent orientation using a map.
Sailplanes require fairly frequent turns where you have to be sensitive to ridge and thermal lift and not concentrating on 'where you are going' -- and you might be pointing 'anywhere' once you have come to altitude. On the other hand when you commit to land there is usually no such thing as a go-round, and it becomes much more tedious to recover the aircraft the further away from the staging point you come to rest -- further both horizontally and vertically.
Helicopters require more multiple control haptics than sailplanes...
I did some sailplane flying out of Sugarbush, VT back in the mid 70s when I was 14-15 years old. I used the "iron compass" to navigate as the surrounding mountains and towns all seemed to blend together as one at about 2500 ft. With so many rail abandonments over the intervening decades I wonder if the old "iron compass" is even an option these days.. probably not..
railracer I've really been enjoying the machine side of the discussion, but I think you bring up a great point about the human side as well. There are plenty of pictures of "Jabelmann Power" shooting roiling columns of thick smoke skyward, but also many showing a "light" stack. All the machine and fuel shortcomings aside, a good fireman definitely made a big impact. By the 1950's many of the more senior engine crews were transitioning to diesels, which were the more desried jobs. This left the younger, less experienced crews to the Challengers and Big Boys.
Wasn't there something in one of the Steam Glory series or some other place where the Union Pacific had to substitute steam for first-gen diesels when they would have breakdowns? And the crews had to back-transition to steam -- like riding a bicycle, you never forget, but do you get rusty without current experience?
Thank you Overmod for the recommendation to look for Eugene Huddleston's book. I found a copy on ebay and have been thoughly enjoying it.
Overmod When you're a bit more comfortable with how flame 'works' in these boilers, look at some of the 'patent' circulation arrangements (like Nicholson syphons and American Arch 'security circulators' to see the conjoined advantages and drawbacks of circulating water through the radiant plume. You will not be surprised to see why there can be enhanced sooting when those things are too enthusiastically (or erroneously) provided. (Incidental solution-left-to-the-reader exercise: the original implementations of arch tubes continued straight up to the inner wrapper near the top of the backhead, seemingly a nifty place to absorb a few radiant BTU at fourth-power Stefan-Boltzmann uptake. But many railroads, including ATSF, quietly abandoned that idea. Can you tell why?
I took a look at some of the stats between the different Challenger series and noticed the series 5 Challengers had some differences from the series 3 and 4 Challengers.
One of which was reducing the surface area of the circulators from around 80 sq. ft to about 44 sq. ft. Kratville mentions this as an attempt to improve firing. I guess UP figured out the combustion quenching effect was costing more than the enhanced circualtion was gaining?
UP also went from a lot of 4" flues ( 177) and few 2-1/4"tubes (45) in series 3 and 4 to a lot of tubes (177) and fewer flues( around 60?) in series 5.
They also went back to the Type A superheater, so I'm not sure if that was just to accomodate the type A or if more tubes were better at making steam than a lot of flues?
railracerUP also went from a lot of 4" flues ( 177) and few 2-1/4"tubes (45) in series 3 and 4 to a lot of tubes (177) and fewer flues( around 60?) in series 5. They also went back to the Type A superheater, so I'm not sure if that was just to accomodate the type A or if more tubes were better at making steam than a lot of flues?
I personally suspect some of the 'adjustment' might have involved excessive superheat, or excessive warpage or 'cutting' of elements, with the engines being run at higher loads and speeds. The effective FGA between a given area of tubes and a "loaded" flue with elements changes with speed, which can result in the development of what Ross Rowland sometimes called 'crazy high' superheat when large locomotives like 614 were worked at high speed and a 'power' level of cutoff for suitable mass flow for a heavy consist. It would make sense to adjust the proportions once to suit any worst-case problems "forensically" observed.
I do not know for sure whether WPA restrictions made 'scarce wartime alloys' hard enough to get that the type E was too expensive or difficult to maintain, in addition to being 'too efficient for its own good' under some conditions. There are certainly people who would know this on RyPN.
There are many sources that talk about the maintenance issues with the type E on both the Challengers and Big Boys. Lots of plugging with water contaminants and burn out of the return bends. I seem to remember an article stating elements in the type A were a larger diameter therefore less susceptible to plugging and also were much simpler to maintain? An article written by Steve Lee mentions ( I can't remember the name of the article) the elements in the series 1 4000s Type Es were eventually shortened by 23" to reduce the issues with the return bends.
railracerLots of plugging with water contaminants and burn out of the return bends.
Yes, you are quite right.
Thanks for elaborating on those points!
I'm curious about BB 4014, now running and burning oil. I'd heard for years that a BB couldn't run properly on oil - but clearly does. I've no expertise here at all, just wondering how UP and the steam shop designed the oil burning equipment to produce enough steam for the 4014.
On a semi related note, I find it a tiny bit ironic that 4012 (as I recall) sits in Steamtown in Scranton PA - in the heart of anthracite country. Yes, I know anthracite burns very differently then soft coal, so boilers are designed differently.
There is an article somewhere on the UP steam site with detail pictures of the components of the Dickens-Barker burner. Austin described this as a 'modified Thomas burner' in West Chicago, but it is considerably more than that.
https://m.youtube.com/watch?v=Up1UaMVnv4M
An interesting characteristic is that the locomotive can hold nominal working pressure (necessary to work some of the auxiliaries properly) using only natural draft (no blower). That meant that the only time I saw the blower engaged was when the whistle had been enthusiastically blown (as enthusiastically as the West Chicago folks allowed, anyway, which was supposedly much less than Ed likes to do!) and even then it only needed cracking a small, virtually inaudible amount...
The arrangement and orientation of the tuyeres alone will tell you why this works so nicely.
(If I recall correctly (and this is largely second- or third-hand via Kratville) the late-'40s 'emergency' equipment involved two burners and a makeshift firepan, and was not reportedly successful although I don't remember learning any of the gruesome details.)
Anyway to compare with coal use on the Delaware & Hudson Challengers, burning anthracite?
D&H Challengers, like their 4-8-4s, were bituminous-burning locomotives.
railracerUP also went from a lot of 4" flues ( 177) and few 2-1/4"tubes (45) in series 3 and 4 to a lot of tubes (177) and fewer flues( around 60?) in series 5. They also went back to the Type A superheater, so...
SD70DudeUP burned the poor-quality coal because...
timz You're thinking of NP. UP coal wasn't great, but it was better than poor. When the UP 4-6+6-4s were new, one article mentioned they were designed to burn 11000 BTU-per-pound coal, or maybe it said 11500 BTU/lb -- don't recall. Powder River coal is 9000 BTU/lb or less, isn't it?
You're thinking of NP. UP coal wasn't great, but it was better than poor. When the UP 4-6+6-4s were new, one article mentioned they were designed to burn 11000 BTU-per-pound coal, or maybe it said 11500 BTU/lb -- don't recall. Powder River coal is 9000 BTU/lb or less, isn't it?
IIRC, PRB coal is less than 9,000 BTU/lb and has to be kept wet to prevent spontanaous combustion. There are several places in the Powder River basin where coals seams caught fire in geologic time and turned the soil above into some sort of brick. OTOH, sulfur is not an issue.
The last number I remember seeing for PRB coal-by-rail was 7550, and it was called 'subbituminous' in context.
Sounds reasonable. PRB coal is a higher quality coal than lignite, but a lower quality than the Rock Springs coal. The NP went to PRB coal from Colstrip in the mid 1920's as the Red Lodge coal seams were getting expensive to work. The strip mines at Colstrip were much cheaper to work with the advent of large electric shovels and draglines.
Coal from the Roundup mines is of higher quality, but those mines were adjacent to the Milwaukee and would have involved a direct interchange at Miles City or indirect interchange via the GN's Mossmain to Great Falls line.
The 1942 Railway Age article on UP's new 4-6+6-4s said they were designed for coal having 11800 BTUs per pound.
railracerBy the 1950's many of the more senior engine crews were transitioning to diesels, which were the more desried jobs. This left the younger, less experienced crews to the Challengers and Big Boys.
RTroy I'd heard for years that a BB couldn't run properly on oil - but clearly does.
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