Martin, this is the railway system I was mentioning in my posts above. The Ferrocaril Central Del Peru was state owned, while the Cerro Mining Corporation based out of New York owned a good portion of it, and all of it beyond La Oroya. The highest pass we drove over was called Ticlio (TEEK-leoh), but I am unsure the railway got that high (15,000). It probably used a nearby valley.
La Oroya, if my memory is correct, sits a roughly 12,000 feet, but Cerro de Pasco, where I witnessed the arrival of the first diesel, was at 14,300 feet. The Golf Clubhouse that served as our vantage point was at 14,400'.
I don't see how altitude could effect the pressure inside a closed and pressure regulated boiler. It should boil at the exact same temperature internally. What would be affected would be the pressure on the boiler from a metallurgical stress standpoint as the outside pressure is less at altitude than at sea level. However the difference in pressure is only a few psi and from the standpoint of a couple hundred psi working pressure it's basically nothing and would know no difference. If steam engine boilers were open containers at atmospheric pressure, the boiling temperature would change. It would go down. We wouldn't be able to harness it though! I see no way from a boiling point perspective that altitude could change anything. The same would still be true in the vacuum of space.
What I could see happening is that the fire takes more effort to get hot as it directly relates to the amount of oxygen present in the air but since I've never fired a steam engine, I couldn't tell you how this translates into real world operation.
blue streak 1 wrote:Yes altitude does make a difference. If the grate area is big enough to burn the fuel at say 90% efficiency less heat is needed to boil water and the steam pressure is the same. That is why feed water heaters were so important. Got the water closer to boiling so heat from boiler did not have to raise temp. So there may be better steaming at altitude.
The engines I fire at 5500 ft do not have feedwater heaters. We do have lifting injectors which also preheat but we also use crosshead pumps which don't preheat. I repeat - altitude does not make a difference because the water in the boiler is not boiling at atmospheric pressure and the difference between 200 psig at sealevel and at 10,000 ft is negligable.
dd
selector wrote:I was present as a nearly 11-year-old when the first diesel ever to make it up to the altitude made its maiden voyage. I can recall what surely were 120 or more "gringo" staff and families at the Cerro Golf Course overlooking a very shallow horseshoe curve that crosse part of what used to be in Ripley's Believe it or not as the highest golf course on the planet. We knew the engine's arrival was imminent and hurried from our various home to watch it come around a bluff and wind across the golf course, a distance of perhaps 400 meters only. I may well have been an FM, come to think of it. In any event, the train was typically short for the road and the altitude, perhaps 15-20 cars or so, but the point is while the diesel led the consist, it was assisted by one of the trusty Consolidations at the rear. The diesel was incapable on its own. That changed not much later with an addition or some form of improvement/augmentation that the engineers performed on it.-Crandell
I was present as a nearly 11-year-old when the first diesel ever to make it up to the altitude made its maiden voyage. I can recall what surely were 120 or more "gringo" staff and families at the Cerro Golf Course overlooking a very shallow horseshoe curve that crosse part of what used to be in Ripley's Believe it or not as the highest golf course on the planet. We knew the engine's arrival was imminent and hurried from our various home to watch it come around a bluff and wind across the golf course, a distance of perhaps 400 meters only.
I may well have been an FM, come to think of it. In any event, the train was typically short for the road and the altitude, perhaps 15-20 cars or so, but the point is while the diesel led the consist, it was assisted by one of the trusty Consolidations at the rear. The diesel was incapable on its own. That changed not much later with an addition or some form of improvement/augmentation that the engineers performed on it.
-Crandell
The engines I saw many times when I lived at 14,400' AMSL in the Peruvian Andes in the late 50's did not have feedwater heaters.
This is how I see it. I hope an engineer or physicist can help us out with this. While less heat is needed to get the water to boil, that only works where the boiler starts cold and equalized to the outer atmosphere. If it has more than five or six PSI above that, then more heat is needed. That same water will boil none the less, but it will take longer since the firebox of a given size will not produce the BTU's that it can being fired well at sea level. So the equation works as long as the boiler is producing the psi that gets to the piston surface area. The expansion coefficient of the steam, even when relatively cool, is still going to do the work necessary, although not quite as efficiently as at sea level because the steam won't have the latent energy in it in the way of heat.
Similarly, the safeties have a nearly negligible sensitivity to the pressure at sea level because they are purely mechanical. They only respond effectively to the absolute pressure working on their springs. If less heat makes the water turn to steam, the pressure in the boiler will rise only until it is sufficient to lift the safeties. That may be a predetermined 180 psi, 200, 250, 500... That is the beauty of the steam engine and any pressure vessel...it works everywhere, even in outer space if you build it right. If you can get the pressure to the cylinders, even with ice-cubes, you will get the work that 200 psi will do for you.
Altitude doesn't make a difference. Yes water boils at lower temperatures at the lower pressure of high altitude, but the water in the boiler is still at operating pressure. The steam pressure gauge actual measures the difference between external pressure and internal boiler pressure - but the needle reading is corrected for atmospheric pressure at sea-level. So if the guage reads 200 psi at 10,000 feet - you still have about 200 psi working pressure.
One would have to be above about 14,000 or 15,000 feet elevation for the lower oxygen content to start impacting the flame temperature. Even then, increasing the blower setting a bit should compensate.
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