I believe that Diesel fuel has a higher freezing point then gas. #2 turns to jelly if left in superlow temperatures, so there's actually a heater in the fuel tank or some such and by running the engine it doesn't get a chance to gel up.
I may be full of it on that though.
The engine is left idleing because (1) they do not have anti-freeze, (2) the cost of fuel is cheap compaired to haveing a locomotive down for freeze up i.e. the engine block could crack and the whole engine has to be replace.
Rodney
YoHo1975 wrote: I believe that Diesel fuel has a higher freezing point then gas. #2 turns to jelly if left in superlow temperatures, so there's actually a heater in the fuel tank or some such and by running the engine it doesn't get a chance to gel up. I may be full of it on that though.
No, you're very close. There are 3 main worries. One is the coolant freezing. Antifreeze isn't generally practical in EMD and GE engines because of how likely water leaks are versus the damage caused when antifreeze gets in the lube oil.
The two other reasons are the fuel. Diesel fuel has two critical temps to worry about - the cloud point and the pour point. The cloud point is the temp where parafin (wax) in the fuel crystalizes. You can spec the cloud point to be lower in the winter, but it'll cost you more for the fuel. The fuel will still flow, but the parafin crystals will clog the fuel filter.
The pour point is the temp the fuel turns to a gel and won't flow at all. You can spec the pour point, too, but the lower you spec it, the more it costs you. The most common method refiners use to reduce the pour point is blending with #1 fuel oil (kerosene and/or jet fuel).
Even with the engines left idling, keeping the fuel system happy requires some technology. The engines all have fuel pumps that supply a steady flow to the engine with significant return to the tank, even when in notch 8. This flow is warmed by passing thru the injectors (high pressure pump on GEs) before going back to the tank. In very cold climates, this is not enough to keep the fuel in the tank above the cloud point, so most road use fuel preheater which are heat exchangers between the fuel suppy line (upstream of the filters) and the engine cooling system. UP also uses a "hot well" partition in the fuel tank to keep the fuel near the suction line warm. The fuel return line is directed to the hot well.
There actually is a fourth worry. A stone cold engine is difficult to start. Not because of cold lube oil or fuel so much as lousy combustion. You can either specify high cetane rating or use ether to assist. One is expesive and the other can be dangerous and risky.
The autostart and APU systems are the current state of the art with regard to cold weather shutdown.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
I really do hate having to get out of my nice warm switcher to go around and start all the engines around our shop when it starts to get cold, but in turn i also hate having to put them back in the shop because trhey got too cold and dumped their water.
oltmannd wrote: YoHo1975 wrote: I believe that Diesel fuel has a higher freezing point then gas. #2 turns to jelly if left in superlow temperatures, so there's actually a heater in the fuel tank or some such and by running the engine it doesn't get a chance to gel up. I may be full of it on that though. No, you're very close. There are 3 main worries. One is the coolant freezing. Antifreeze isn't generally practical in EMD and GE engines because of how likely water leaks are versus the damage caused when antifreeze gets in the lube oil.The two other reasons are the fuel. Diesel fuel has two critical temps to worry about - the cloud point and the pour point. The cloud point is the temp where parafin (wax) in the fuel crystalizes. You can spec the cloud point to be lower in the winter, but it'll cost you more for the fuel. The fuel will still flow, but the parafin crystals will clog the fuel filter.The pour point is the temp the fuel turns to a gel and won't flow at all. You can spec the pour point, too, but the lower you spec it, the more it costs you. The most common method refiners use to reduce the pour point is blending with #1 fuel oil (kerosene and/or jet fuel).Even with the engines left idling, keeping the fuel system happy requires some technology. The engines all have fuel pumps that supply a steady flow to the engine with significant return to the tank, even when in notch 8. This flow is warmed by passing thru the injectors (high pressure pump on GEs) before going back to the tank. In very cold climates, this is not enough to keep the fuel in the tank above the cloud point, so most road use fuel preheater which are heat exchangers between the fuel suppy line (upstream of the filters) and the engine cooling system. UP also uses a "hot well" partition in the fuel tank to keep the fuel near the suction line warm. The fuel return line is directed to the hot well.There actually is a fourth worry. A stone cold engine is difficult to start. Not because of cold lube oil or fuel so much as lousy combustion. You can either specify high cetane rating or use ether to assist. One is expesive and the other can be dangerous and risky.The autostart and APU systems are the current state of the art with regard to cold weather shutdown.
Mr. Dictionary:
How's does Alaska Railroad keep it's fuel tanks from freezing at -20F {Outside}?
chefjavier wrote: oltmannd wrote: YoHo1975 wrote: I believe that Diesel fuel has a higher freezing point then gas. #2 turns to jelly if left in superlow temperatures, so there's actually a heater in the fuel tank or some such and by running the engine it doesn't get a chance to gel up. I may be full of it on that though. No, you're very close. There are 3 main worries. One is the coolant freezing. Antifreeze isn't generally practical in EMD and GE engines because of how likely water leaks are versus the damage caused when antifreeze gets in the lube oil.The two other reasons are the fuel. Diesel fuel has two critical temps to worry about - the cloud point and the pour point. The cloud point is the temp where parafin (wax) in the fuel crystalizes. You can spec the cloud point to be lower in the winter, but it'll cost you more for the fuel. The fuel will still flow, but the parafin crystals will clog the fuel filter.The pour point is the temp the fuel turns to a gel and won't flow at all. You can spec the pour point, too, but the lower you spec it, the more it costs you. The most common method refiners use to reduce the pour point is blending with #1 fuel oil (kerosene and/or jet fuel).Even with the engines left idling, keeping the fuel system happy requires some technology. The engines all have fuel pumps that supply a steady flow to the engine with significant return to the tank, even when in notch 8. This flow is warmed by passing thru the injectors (high pressure pump on GEs) before going back to the tank. In very cold climates, this is not enough to keep the fuel in the tank above the cloud point, so most road use fuel preheater which are heat exchangers between the fuel suppy line (upstream of the filters) and the engine cooling system. UP also uses a "hot well" partition in the fuel tank to keep the fuel near the suction line warm. The fuel return line is directed to the hot well.There actually is a fourth worry. A stone cold engine is difficult to start. Not because of cold lube oil or fuel so much as lousy combustion. You can either specify high cetane rating or use ether to assist. One is expesive and the other can be dangerous and risky.The autostart and APU systems are the current state of the art with regard to cold weather shutdown.Mr. Dictionary:How's does Alaska Railroad keep it's fuel tanks from freezing at -20F {Outside}?
My, how arrogant. But never matter. The system as described works the same. And by the way, operating temperature in Alaska is -60F.
RWM
Let us not forget the most important reason, to keep the cabs warm, so the toliets don't freeze.
Nick
Take a Ride on the Reading with the: Reading Company Technical & Historical Society http://www.readingrailroad.org/
nbrodar wrote: Let us not forget the most important reason, to keep the cabs warm, so the toliets don't freeze. Nick
Conrail used to put antifreeze in the toilets!
Frozen toilets aren't too messy. It's when they start to thaw....
oltmannd wrote: nbrodar wrote: Let us not forget the most important reason, to keep the cabs warm, so the toliets don't freeze. NickConrail used to put antifreeze in the toilets!Frozen toilets aren't too messy. It's when they start to thaw....
Can you say EEEEEWWWWW!
I remember anti-freezing the toilets. My current employer doesn't. Randy can probably answer this better, But I'm pretty sure antifreeze doesn't work with the Microphoe units.
nbrodar wrote: oltmannd wrote: nbrodar wrote: Let us not forget the most important reason, to keep the cabs warm, so the toliets don't freeze. NickConrail used to put antifreeze in the toilets!Frozen toilets aren't too messy. It's when they start to thaw....Can you say EEEEEWWWWW! I remember anti-freezing the toilets. My current employer doesn't. Randy can probably answer this better, But I'm pretty sure antifreeze doesn't work with the Microphoe units.Nick
My current employer had other toilet issues.....
Those Micorphot toilets are like little sewage treatment plants on wheels. I think you're right about antifreeze - it'd kill the little digester beasties.
oltmannd wrote: nbrodar wrote: oltmannd wrote: nbrodar wrote: Let us not forget the most important reason, to keep the cabs warm, so the toliets don't freeze. NickConrail used to put antifreeze in the toilets!Frozen toilets aren't too messy. It's when they start to thaw....Can you say EEEEEWWWWW! I remember anti-freezing the toilets. My current employer doesn't. Randy can probably answer this better, But I'm pretty sure antifreeze doesn't work with the Microphoe units.NickMy current employer had other toilet issues.....Those Micorphot toilets are like little sewage treatment plants on wheels. I think you're right about antifreeze - it'd kill the little digester beasties.
The microphors had immersion heaters to keep the water from freezing in the freshwater tank . The reliability of the heaters was dubious , when they froze they naturally expanded.... expanded into the electrical cabinet , cab, cab heater pipes etc. They were most difficult to remove from older GE's as they were jammed between the rear cab wall and the main electrical cabinet wall.... oh and they are made of stainless steel .. forget about cutting them out !
There is still anti freeze in the crappers , just not glycol , still hurts when it splashes on your parts.
At one time is was said that the worst thing you could to do a diesel engine was to start it. So, the wisdom was, once you get it started, never turn it off...with one or two exceptions, such as critical maintenance. The reasoning was that rebuilding/replacing a damaged diesel was much more costly in the long run than letting it idle for hours. The internal parts would take a beating much like a gas engine does on start-up before tolerances are improved by the right temps and before lube can coat all the appropriate surfaces.
Has the technology changed sufficiently that this is no longer an issue?
nbrodar wrote:Let us not forget the most important reason, to keep the cabs warm, so the toliets don't freeze. Nick
There is also the matter of the air brake system in the cab. If the air freezes up the brakes will do goofy things, or not work at all. There are a number of check valves beneath the floor that can get jammed with even small pieces of ice on the lines. If the moisture traps (spitter valves) on the main res don't work so good, or the crew shuts them off, the ice in the lines gets worse.
Mike WSOR engineer | HO scale since 1988 | Visit our club www.WCGandyDancers.com
oh and they are made of stainless steel .. forget about cutting them out !
I know this is a family forum, but a (cough, cough) ceramic privy (cough, cough) is considered the height of engineering overdesign, and some males of the human species with overactive imaginations use that metaphor to describe some females of the human species such as a certain Mr. Lionel Ritchie who had a hit song about a fired-clay structure.
But stainless steel. Forget about brick! Something that dulls cutting tools and only softens when exposed to a torch. Is the GE locomotive stainless-steel commode going to provide a new metaphor?
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
selector wrote:At one time is was said that the worst thing you could to do a diesel engine was to start it. So, the wisdom was, once you get it started, never turn it off...with one or two exceptions, such as critical maintenance. The reasoning was that rebuilding/replacing a damaged diesel was much more costly in the long run than letting it idle for hours. The internal parts would take a beating much like a gas engine does on start-up before tolerances are improved by the right temps and before lube can coat all the appropriate surfaces.Has the technology changed sufficiently that this is no longer an issue?
My understanding is that modern diesel engines have an electric lube oil pump. The pump is supposed to be run a few seconds before cranking the engine making sure that the bearings are properly lubricated. In addition to reducing wear, this also reduces the torque needed to start the engine.
my understanding is that the eletrical oil pump is for the turbo only, and does not feed the main gallerys . the mains are fed once the engine is started
Correct -- on an EMD the prelube pump is just for the turbo.
The more important concern about startup and shutdown than lubrication of the prime mover (except for the turbo) is expansion and contraction of the crankcase, which can lead to coolant leaks around the seals. In the good old days when fuel was cheap it was more economical to leave the engine running to avoid the problems of leaks, the time it took to start the engine and wait for it to come up to operating temperature before putting it under load, and worry about the batteries not having enough oomph to get it started -- along with the freezeup, fuel gelling, and oil gelling difficulties. Today the engine designs are much more tolerant of frequent startup and shutdown, and assuming the ambient temperature is not sub-freezing it's more economical to go through shutdown and startup if the locomotive isn't going to be needed for 4 or more hours.
Railway Man wrote: Correct -- on an EMD the prelube pump is just for the turbo.
The turbo "soakback" pump is primarily for cooling the turbo bearing after the engine is shut down. There is little load on the turbo bearing on startup, so no real need to pre-lube. Even the main and conrod bearings in the engine, which do have a pretty high load on start up, have enough residual lube so that you don't need to prelube until you are shut down for roughly a day.
You're absolutely correct. I could claim faulty memory but I should have just pulled the manual off the shelf and refreshed my memory.
Slightly off topic, but....
Does anyone know why diesel cars and trucks don't have similar gelling problems? Or how they overcome it?
/Bob
On an ES44 Prelube --- is for Main Bearings, Turbo and Power Assemblies.
Another comment: Rail roads are installing Automatic Start Engine Systems which disable auto Stop if Out Side Temperature is below <45 F
anotheroldbiker wrote: Slightly off topic, but....Does anyone know why diesel cars and trucks don't have similar gelling problems? Or how they overcome it? /Bob
Oh they do! But winter blend fuels are used to overcome it, to a point.
The key measurement is cloud point, the temperature at which waxes start to form in the fuel and clog fuel filters. Clouding will generally not occur until ambient temperature is 5-10F belowe the cloud point. #2 diesel has a cloud point between 20F and 40F depending on how it is refined. #1 diesel has a cloud point typically around -40F, which is sufficient for almost the very coldest climates. Even so, many diesel vehicle designs for vehicles that might end up in cold climates have a fuel heater/bypass system so when the vehicle is running, some fuel is heated and recirculated to the fuel tank.
#1 diesel has a lower energy content (95% of #2), is more expensive to refine, and has diminished lubricating qualities compared to #2. Highway diesel during winter months is a blend of #2 and #1 depending upon time of year and climate of the locale; sometimes in northern latitudes straight #1 is marketed side-by-side with winterized blend for those who want it/ Generally a 50-50 blend is good enough for all but the very coldest locales. The danger is filling up a large tank at a low latitude and driving due north.
Here's more than most want to know:
http://www.exxon.com/USA-English/GFM/Products_Services/Fuels/Diesel_Fuels_FAQ.asp
By idling in notch 3.
Dan
Interesting. Thanks for your response.
Our community is FREE to join. To participate you must either login or register for an account.