Wood vs. Coal for Fueling Steam Engines

[Anonymous]

OS--

Hadn't ever heard that. Doesn't reflect that in large fixed boilers, although you burn gas when you can get it. The info I had generally regarded tube replacement, mechanical parts, etc. where oil was clearly superior (unless, of course it was loaded up with vanadium).

Interesting to hear about the NP equipment.

Yeah, eco and geo sure are fascinating.

The IGN lignite locos were good for a while, but can generally be regarded as a flop in the grand scheme of things. But the stuff is dirt cheap (another baaaaaaad pun) and the reclamation is generally outstanding since it starts out as pasture and ends back up that way. Needless to say, the IGN locomotives had to have large bunkers in their tenders and stopped often to refuel.

The area east and northeast of Austin is laced with old abandoned underground lignite mines. Not played out, just uneconomical. Somewhat OT but interesting: the only legal unlicensed lignite mine in the state is a brick operation where the lignite seam (fairly good stuff >6000) is overburden on the brick clay that they strip mine. They've tried all kinds of avenues of selling it for years but the quantities are not high enough.

Bottom line--you burn the fuel you can get the cheapest.

[Anonymous]

Now I seem to recall a Trains article back in the 70s about this -- might have been written by Charles Mizell. I never paid much attention to it back then, being a callow youth, but now I guess I'll have to find it and reread it.

This is what I saw in another forum in response to a question about overhaul intervals:

Jack Wheelihan said:
"At a really big back shop such as Altoona, West Burlington, Roanoke, Cheyenne, etc., it generally depended on the "class" of overhaul that an engine required. Such as a standard five year jacket & lagging ICC (now FRA) inspection, which also received new (or safe-ended) tubes, superheaters, running gear work, the time frame was only 1 to 2 weeks. A 15-year overhaul (10 years on an oil burning locomotive) would require a new fire box and possibly extensive boiler modifications/up-grades, and could take 3 to 4 weeks."

Rich Melvin elaborated:
"The thermal stresses in an oil burner's firebox are much greater than those in a coal burner. That big oil flame can be completely cut off instantly, which can allow the overall temperature in the firebox to change drastically in a very short period of time. By the same token, the flame can be brought back up to full intensity in a matter of seconds, raising the temperature quickly.

"On a coal burner, you have that bed of hot coals acting as a huge thermal sink and preventing any rapid changes in firebox temperature. Sure, you can stop the stoker and cut off the supply of coal to the fire, but that huge bed of burning coals acts to slow down any temperature drop and it happens very slowly. In an oil burner, the only thermal sink available is the firebrick around the firebox, and its mass and heat absorption value are nowhere near that of a hot bed of burning coal. Thus the thermal stresses set up in a coal burner's firebox are much less than those of an oil burner. This means fewer broken staybolts, cracked sheets, checks in knuckle sheets, etc."

dre, I would bet that in a central power station, the operators aren't so cavalier about turning the fuel flow on and off. Of course, on a railroad, the economic penalty for not doing this (extra fuel consumption) greatly outweighs the economic benefit (longer maintenance intervals).

OS

[Anonymous]

Makes perfectly good sense to me.

[lonewoof]

OK, second time lately I've seen reference to vanadium in locomotive fuel being a bad thing. Why is it bad?

[Anonymous]

Woof, I'm a hopeless amateur when it comes to boilers, but here's the extent of my knowledge:

Vanadium in conjunction with sodium is the primary source of slag in oil-fueled boilers. Most boilers are designed to run "dry" -- temperatures are not hot enough to melt the ash content of the fossil fuel they combust. Slag is bad in a dry boiler because it sticks to cool surfaces like tubes, clogging them. Vanadium pentoxide, the form vanadium will be in boilers, has a very low melting point, so it slags. Vanadium is a fairly widely distributed element in nature, so it is present in many crude oil stocks. Vanadium is present in many heavy residual oils. That's the kind of fuel you want to buy for a boiler, because it's cheap.

OS

[Anonymous]

Lets take a little different track (no pun intended) on consumables for steam locomotives. What about water? This can be a problem. In many places in the west an ample supply of water is limited and many times what is there was "bad water". The high mineral content of the bad water will foul the boiler and create problems. Several railroads had water conditioning plants to take some of the bad out of the bad water. I think some railroads in South America, in an attempt to cut down on water consumption, had condensers to condense the spent steam back into water and reuse it in the boiler.

[espeefoamer]

South African railways also experimented with condensing steam engines.They had enormous tenders.

[Anonymous]

The water issue has always kind of baffled me, too. We all have a sense how much "new" water a steam locomotive required. But what about ocean-going ships in the age of steam? They clearly couldn't use sea water in the boilers. But think about how much water the Titanic needed aboard to make a crossing. The answer seems to be condensers. It is just a guess on my part that size/weight ruled that out for most steam locomotives.

[CopCarSS]

QUOTE: ....Wonder where they found coal out on the plains {Promontory area}, to refuel the engine....Tenders were quite small then so they most likely had to haul some additional cars with coal with them...

It was the UP. They just brought a unit train with a couple 90MAC's down from the Power River Basin! [:D]

Seriously, though, I've heard Powder River coal is pretty awful stuff to burn in a steam locomotive. I heard a story about the Mid-Continent Railway museum getting a free load from the CNW or UP awhile back. I guess it was hard to burn well enough to do much with it. Not quite the nice stuff that comes from the Appalacian mountains.

[Anonymous]

lfish: The difference is that one had the ocean for a coolant, and the other the atmosphere. Think of the difference between sticking your hand into a 350 degree oven (safe if you don't touch metal) and into a pot of 212 degree boiling water (not safe!). The ability of air to absorb heat, compared to water, is immense, so the size of the condenser becomes huge in order to get enough surface area, and fluid flow (thinking of air as a fluid) to achieve the same amount of cooling that could be accomplished in a steamship with something between the size of a refrigerator and a small walk-in cooler. Steamships from a very early date were condensing, and if operating in saltwater also had evaporators to supply make-up water as well as potable water. As steamships age they develop leaks, losing pure water to the atmosphere, and then the ability of the evaporator to keep up with the demand for water becomes the key to keeping the boiler lit and having steam to turn the screw. Loosing the evaporator on a steamship with a heavy demand for makeup water can literally mean the death of the ship, if it happens to be in shoaling waters with an onshore wind at the moment the evaporator craps out. More than one large ship has been lost from want of makeup water.

Almost every railroad operating through desert regions had to treat boiler water to remove alkali, along with many other roads. UP, SP, Santa Fe, D&RGW, WP, and T&P all spent immense sums installing and operating water treatment plants, and washing and maintaining boilers to remove mineral deposits. They were all glad to be rid of that albatross when diesels arrived.

OS

[Anonymous]

Thanks, OS, and that was also a much better response than mine on the City of LA.
I'm going to stick my hand in an oven tonight to bear out your claim.

[Anonymous]

Just as long as you're not planning to stick your head in the oven. There are hot-lines for that problem (bad pun fully intended).

OS

[Anonymous]

Not to worry. This Fish is not for baking.

[Anonymous]

The south african condenser locomotives - Class 25C - were very succesful in technical terms. They could run up to 600 miles without the need of getting watered. The problem was that they were maintenence nightmares.

There was also an experiment with german class BR 52 with condensing tenders. Dunno however how many of them were built.

The another approach was Franc-Crosti system where exhaust steam was used to preheat feedwater - this also proved "right", but technically complex. Which didn't stop Italians from using many of such locos.

Overall however this "reuse" of exhaust steam often didn't justify the expense.