Learning about Steam (many questions)

I figured instead of making a whole plethora of topics for all my questions about steam locomotives I would just consolidate it all into this one topic. In another post I asked about turrets and dynamos and got exactly the answers I wanted. My next question is about efficiency. What was the most efficient fuel for steam locomotives? Coal, oil or wood? Another question is about restoration of locomotives. Is the first step of restoration a survey of feasibility? If so, how much do these cost and what do they include? What things do surveyors look for?
I'll start with these for now and ask more as each one is answered.

efficiency equals output over input. Boiler efficiency means how much of the heat released in the fuel get absorbed by the steam.
Among the losses in boilers, excess air is the big one. air absorbs alot of heat and takes it up the stack. ideally the stack temperature wont be much above steam temperature but in practice that means about 150 degress, so stack temp of 500 degrees is not uncommon. all the air that isnt oxygen that combines with the fuel, is uselessly heated up to 500 degrees and discarded.

Oil firing should require less excess air than coal firing, certainly in stationary boilers that is true, you can run O2 in the stack down to 2% burning oil, whereas with coal, even pulverized coal, 4% is about as low as you can go.
neglecting all else, oil should have a maximum practical efficiency of around 86%, where burning coal cant be expected to do better than about 75%
I dont know if oil burners in railroad locomotives ever advanced enough to realize that better efficiency than coal, but let us say they ought to have and certainly would have by the 70s.
Another big loss is moisture. Oil contains a few percent hydrogen, so there is some resultant water vapor in the flue gas, which will result in a loss of 1 or 2 % . coal contains very little hydrogen, so has the advantage there. Coal should be dry, but in practice generally isnt, often containing as much as 5% water as delivered. all that water has to be evaporated and pumped up the stack.

wood, even well seasoned hardwood, contains as much as 30% water , and green softwood contains up to 50% water! green wood burns fine when you put it on a hot fire, no fear, lots of nice volatile, they certainly burned green wood in the wood burning days, but that moisture content together with higher excess air requirements puts boiler efficiency burning wood no better than 65%.
Another important factor is fireside fouling. of the three fuels we mentioned, coal has the worst ash, requires frequent off line cleanings, with potentially the greatest losses of efficiency between cleanings. Wood has much less ash, but still requires frequent off line cleaning.
Oil fuel contains almost no ash, so depending on the method of firing, tube cleaning can be done online with steam soot blowers.
oil wins by a wide margin, and is very convenient to fire, but is very expensive. coal is highly variable. Wood though poor in heating value, is also very cheap. so the economics of the various fuels involves more factors than boiler efficiency alone.

So basically the more efficiency you want, the more money you pay. Makes sense. I never considered the fact that the water from the fuel has to be burned and results in a loss of efficiency.

#7470 wrote:So basically the more efficiency you want, the more money you pay. Makes sense. I never considered the fact that the water from the fuel has to be burned and results in a loss of efficiency.

Water is remarkable in its ability to absorb heat, both in heating up, 1 btu/lb per degree, and in phase change - at atmospheric pressure, each pound of water absorbs 970 BTU in making the change to vapor.
consider methane, CH4 , the main constituent of natural gas, 25% hydrogen by weight. The combustion of hydrogen in one pound of methane results in the formation of 1.25 lbs of water vapor 2H2 + 02 -> 2H2O . By Dulong's formula, we can estimate the heat released by the pound of methane combustion as (14544 * %C) + (62028 * %H) = 26415. the 1.25 lb of water will immediately absorb 1091 btu from the hot combustion gas, about 4% of that heat, and carry it up the stack. this is the difference between "high heating value" HHV, and "low heating value", LHV. its a substantial hit.

In principal that higher the hydrogenation, that is the lighter the hydrocarbon, the greater the loss, and the lower the efficiency. Anthracite coal is at one end of that spectrum, with less than 1% hydrogen, and methane is at the other, at 25%. #2 oil has about 12% hydrogen and #6 has about 9%.
pure hydrogen is a special case. the calculated loss due the moisture formed by combustion of 100% hydrogen would be 14.1% of HHV.

Wow that's great information, thanks for that!

When you ask about efficiency, do you mean 1st generation steam, as what we closed out the steam era with, 2nd generation steam which was basically the same, except taken to the pinnacle of thermal, mechanical and operational efficiency* or 3rd Generation steam, which basically would have been a microprocessor-controlled steam engine with condensed steam?

*2nd generation was designed many times after the close of steam, but I don't know of any actual production engines, though some of the french designs by Chapelon would have been there thermally.

As for restoration, the first question you need to ask is "why?". Why do you want to restore a steam engine? Because they are cool? Because you have an affinity for a particular engine? Because you think you have a crack business plan and an excellent opportunity to make some serious money cashing in on the steam-hungry railfans?

1) Because they are cool: well, odds are you aren't gonna get a large group and massive funding for that type of a goal. I'd suggest looking for a small, easy to rebuild engine. The best example of this would be either the 2ft gauge engines, or a small 0-4-0st engine.

2) Affinity for a particular engine: Congrats, now you have a laudable goal, though not necessarily a realistic one, but everyone has to start from somewhere. Obviously, with this scenario, you have either already selected the specific engine, or have a fairly small group to choose from. Assuming you have a particular engine, a study to determine not so much feasibility but requirements. (Feasibility suggests the possibility that the engine might not be the best candidate. In this case, you started investigating this engine because it was obvious that no other/no better choice existed/was available.). The MAIN things to look for here: what major parts are missing: the main side rods were torched? Well, that just about kills that right there because there is no where to get new rods forged. (Obviously it could be done somewhere, otherwise Tornado would never have turned its own wheels) Has a cylinder casting cracked? odds are thats an absolute project killer unless you can find a way to weld in a patch, and then can find a way to rebore the cylinder to the exact specifications needed. Good luck on finding that skill these days.

3) Great business plan: Now we are talking, here is where the fun begins. The first step here is to begin by defining your needs, once you know what the engine needs to be capable of to meet your plan goals, you can begin looking for engines that meet those needs and then select the engine based on the completed feasibility studies.

Awesome, awesome information J.D thanks! Restoration of steam has always interested me. Another question about restoration; where does one get experience needed to restore a steam locomotive? First hand practice and observation, asking questions from those who know? Does this mean that eventually steam won't be able to run as that generation slowly dwindles away? What is the best way for someone to learn THEN?

Obviously the best way is to get your hands dirty, join an ongoing restoration effort. Or sign on as a volunteer with a working railroad with a steam program... EBT, Strasburg, etc. I'm sure there has to be volunteer groups with the wester roads as well.

The other way, is harder, but to me, more fulfilling: book learning as much as you can, and then just doing the work, and redoing it when you screw it up. A video I once had about live steam (7.5inch gauge) builders had a guy who said he filled out a survey about his new lathe. When asked what his principal product was with the lathe, he answered honestly: scrap. He said he made every part on his engine at least four times. Obviously, when you get to a full size unit, the scrap is heavier and more expensive, but odds are, if you scrap a part and have to start over, you sure as $#!+ won't make the same mistake again.

Even if everyone who ever touched a running engine died tomorrow, we could learn the skills needed again, it would take time, but a lost skill just needs to be relearned. Between the books and videos we have now, there is enough of a tutorial to at least get started. The absolute hardest part about any engine is what each part does and its relationship to the other components.

Probably the single one most hardest task is resetting the valve timing. And that... I have no experience so I can't help you. Though I know there is an article somewhere about 614's restoration that included the resetting of her piston valves.

I live in MA. Unfortunately there are no steam operations close by. I have been trying to learn through books. I purchased the 1925 Locomotive Cyclopedia on ebay last summer and have been reading through it. What other books would you recommend?

That I'm afraid I can't help you with. I never lead a restoration effort, only participated in projects already underway on two railroads.

I'll have to defer to others on that question, sorry.

I have another question on babott bearings. Not sure on the spelling of babott. I know that the bearing is poured into the mold but how does one get an even coating of 1/4 inch?

Babbitt. a piece of shaft of the right diameter is set in the bearing to form the"inner half" of a mold. carefully fitted dams made of sheet metal are fitted to the ends to hold the dummy shaft at exactly the right height and keep the molten metal inside. the dummy shaft and dams are coated with carbon black to keep the babbitt metal from sticking.