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I was watching Mighty Ships on the Smithsonian channel. This show was about Umiak I, largest ice breaking bulk carrier. https://en.m.wikipedia.org/wiki/Umiak_I The ship was 3 days into it's 5 day or so trip when it encountered solid ice off of Labrador. The captain requested full power, 91 rpm, from the running speed of 71 rpm, to handle the ice, 3m to 6m! The narrator said that the rpm change had to be done in stages so that the engine could be warmed up. Would not the engine already be warm? Stroke on this 30,000 hp engine was stated to be 15' ! Jim | ||
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Tinker Sailor Soldier Pie |
Yes, the engine would be warmed up. But going from around 70% load to 100% load is always done in stages, not only for efficiency sake but also for the health of the engine. The ramp up time at those higher load ranges are programmed in to be anywhere from 10 minutes to 20 minutes to possibly longer. On the Wartsila engines I operate now, the ramp up time from 70% to 100% is ten minutes. Going from 0% load to 70% load can be done relatively quickly, like a minute. So yes, technically the engine is warmed up already, but the engine still likes to ease into full power. The power to fuel ratio curve at those higher load ranges is very steep. The engine burns a crazy amount of fuel at 100% compared to 70% and believe it or not, allowing for that ramp up time helps the engine run more efficiently. ~Alan Acta Non Verba NRA Life Member (Patron) God, Family, Guns, Country Men will fight and die to protect women... because women protect everything else. ~Andrew Klavan "Once there was only dark. If you ask me, light is winning." ~Rust Cohle | |||
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The engine itself is already warmed up, when it comes to coolant temp etc. But then when going to full power, the cylinder heads and exhaust gas temperatures will climb quite a bit and the metal will still expand with the additional combustion heat. These motors are huge, and so are the parts, so a little dimensional instability in a cylinder head could be catastrophic if it heats up too quickly. | |||
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Thanks for the information!  Jim | |||
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אַרְיֵה |
I know that I give you a bunch of shit when you spout off on a topic where you are really not qualified, but on this one you sound as if you really do know what you're talking about. Giving credit where credit is due. Thanks for that information. הרחפת שלי מלאה בצלופחים | |||
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A little off topic but what type of centrifuge do you use on your fuel system? I'm alright it's the rest of the world that's all screwed up! | |||
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| Partial dichotomy |
To add a bit to what's been said, the engine in question is a 2 stroke engine and as Jimmy said, the engine parts, particularly in this case have expansion to do. 2 stroke propulsion diesels have a huge stroke due to the design of that engine. On a 2 stroke, you don't have "perfect" scavenging like you do a 4 stroke engine. SIGforum: For all your needs! Imagine our influence if every gun owner in America was an NRA member! Click the box>>>  | |||
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| Tinker Sailor Soldier Pie |
Alfa Laval SA 821's. ~Alan Acta Non Verba NRA Life Member (Patron) God, Family, Guns, Country Men will fight and die to protect women... because women protect everything else. ~Andrew Klavan "Once there was only dark. If you ask me, light is winning." ~Rust Cohle | |||
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I was just curious.I service centrifuges in non marine applications.I have dealt with the Alfa 204 and 206. Have some experience with Westphalia but primarily deal with Seital I'm alright it's the rest of the world that's all screwed up! | |||
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| We gonna get some oojima in this house!  |
Wow! what kind of flywheel system is needed for such a long stroke. About how much would it weigh? ----------------------------------------------------------- TCB all the time... | |||
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| Tinker Sailor Soldier Pie |
My experience is primarily with Alfa Laval. The 821's are babies compared to those associated with slow speed diesels. One needs chain falls to take those bad boys apart. Just miserable.
Big...and heavy. But relative to smaller engines, probably not as big as you would expect. ~Alan Acta Non Verba NRA Life Member (Patron) God, Family, Guns, Country Men will fight and die to protect women... because women protect everything else. ~Andrew Klavan "Once there was only dark. If you ask me, light is winning." ~Rust Cohle | |||
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| Partial dichotomy |
Here's a pic of the flywheel on the Sulzer EMD I worked on. This was an 11,400HP five cylinder engine.  The propeller shaft is approximately 2 foot diameter for comparison. Like Alan said, maybe not as big as you'd expect, but still pretty hefty. Another couple of pics taken inside the crankcase for perspective purposes.   SIGforum: For all your needs! Imagine our influence if every gun owner in America was an NRA member! Click the box>>> | |||
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| Member |
Based strictly upon the show about Umiak I, they showed the ship stopping at night, to avoid going into the loading dock at night. They were stopped in the ice! They stopped the engine! The chief engineer had several 3rd mates go down into the engine with rags to wipe up accumulated oil, up to 1-1/2" thick! The chief engineer then inspected the engine internals for wear and any damage, reminded me of the scenes on the San Pablo, e.g. Sand Pebbles, if you magnified X 100! The oil capacity was 30,000 gals., maybe liters? They said they never changed the oil for the life of the engine! The discussion of the oil centrifuges mentioned previously helps me understand this! When the Umiak I was going through the ice during the day, the Captain explained how they followed the previous channel made, last month, but now completely frozen over to stay within the rules established to protect the environment because the native Canadians?, still hunted on the ice. You could see the track in the ice and snow! The round trip is made every month, carrying supplies to the mine, and returning with nickel ore. Interesting show for a landlubber! You people helped fill in my limited knowledge of what was on the show! A funny statement by the Captain was how rank did not count during the poker game being played while the ship was stopped for the night! Jim | |||
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| Partial dichotomy |
Probably not 3rd mates, but maybe should have been.  Seriously, a mate is a ship's officer in the deck department and wouldn't do that work unless it was offered as overtime. I'm not sure where they were talking about, but if there was that kind of oil accumulated anywhere but in the crankcase, they've got problems. The air box of the engine does get like that and maybe that's what he was referring to. 2 stroke engines use a separate cylinder oil supply that's a consumable and what isn't burned, ends up in the scavenge air box. Messy job to clean during a pistol pull.SIGforum: For all your needs! Imagine our influence if every gun owner in America was an NRA member! Click the box>>> | |||
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I deal with units that range from 3gpm to 40gpm.We have 60GPM in our group that require chain falls.Been told they are no fun. I'm alright it's the rest of the world that's all screwed up! | |||
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Yes, this is true. The reason we change oil in cars (and other things) is because it gets contaminated with unburnt fuel, hydrocarbons etc. With a centrifuge, you can get the exact specific gravity set for the oil, and the centrifuge will spin out all of the contaminates in the oil into the waste tank. They also have fine micron filters for the particles (metal shavings etc.). These motors are also very low RPM usually 100 rpm +/- and have a very large capacity sump, so they don't overheat the oil like the smaller motors. The 1993 Corvette (and newer) switched to synthetic oil because the oil temps were so high. Even with synthetic, those cars would run 250-270F oil temps. | |||
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