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Author Topic: Query about real life engine use.  (Read 1687 times)

Badwebdiver

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Query about real life engine use.
« on: May 22, 2013, 09:39:45 »

I'd like to know from the real life sailors out there what's the standard practice for using the engine.   :captain:

Are ship engines made to go 100% most of the time?  Can they change quickly from full to half to stop to reverse?  On long voyages do they run continuously at full power most of the time?  I've know a few car drivers, especially with new vehicles, who tend to try to vary the speeds to run in the new engines.  Would this happen with a ship?


My own gut feeling on the sim has been to power at about 80-90% for cruising, saving 100% for emergency runs.  Altho I do slam from forward to reverse quite a lot, and also on the two engine setups use the classic one forward and one back for sharp cornering.

I'm curious to know what the real life practice is.
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clanky

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Re: Query about real life engine use.
« Reply #1 on: May 24, 2013, 17:36:24 »

A lot of different questions in there, I will try to answer them one by one.

Are ship engines made to go 100% most of the time?

Ship's engines have a rated called MCR (maximum continuous rating) and they are designed to be capable of running at this power indefinitely, but owners / operators often choose to run the engines at lower power either to suit schedules or to save on fuel.  On some engines if you want to run them at very low power ratings then it is necessary to fit different injector nozzles and sometimes even to blank off a turbocharger.

Can they change quickly from full to half to stop to reverse? 

Engines tend to have a manoeuvring range in which they can be easily stopped and started without causing too much thermal stress, depending on the size of the engine this is normally about 40-50% power output, when arriving into a port, the engine would usually be slowed gradually to manoeuvring speed and then it would be operated as required by the bridge, outside of these manoeuvring speeds the power output would be changed gradually (often by a load control program) unless an emergency situation requires a sudden change.

On long voyages do they run continuously at full power most of the time?

As above this depends on many factors, they can run on max power all the time, and in my experience run better at high loads), but for various reasons they are often run at low power settings.  When I have had to run the engine at low power outputs, I have always tried to get the captain to speed up for 1 hour every day to clear out any carbon build up.

  I've know a few car drivers, especially with new vehicles, who tend to try to vary the speeds to run in the new engines.  Would this happen with a ship?

Yes. When a ship is delivered the engine has been through testbed trials in a workshop and sea trials so it is already run in, but when any maintenance is carried out to the cylinder liners or piston rings then the load is increased steadily according to set manufacturers guidelines in order to run in the new piston rings / liners.

My own gut feeling on the sim has been to power at about 80-90% for cruising, saving 100% for emergency runs.  Altho I do slam from forward to reverse quite a lot, and also on the two engine setups use the classic one forward and one back for sharp cornering.

I'm curious to know what the real life practice is.

Real life practice varies from captain to captain, those who "slam from forward to reverse quite a lot" (the nautical terms are ahead and astern by the way) tend to feel my wrath rather quickly.

Really the engines should be used as gently as possible in order to maintain the ship in a safe position, but keeping the ship in a safe position has to be the over-riding factor.  As for one engine ahead / one astern then this would be common practice when manoeuvring at very low speeds, but not when on passage.  Putting the engine astern when the ship is moving ahead at any speed puts a huge load on the engine and risks damage.

Hope that helps clear things up.
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Trampship Man

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Re: Query about real life engine use.
« Reply #2 on: May 27, 2013, 18:15:34 »

Hey Clanky,
               This is `Trampship man`, I just decided to take a look on the forum after a very long absence. The very first name I came across was `Clanky`.  You may remember we had some pretty lengthy dialogues and also managed to get a bit of`stick` together from a moderator.
               Nice surprise to see that you`re still around mate, I was as `pleased as Punch`. Really !!!

Regards.
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Trampshipman

clanky

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Re: Query about real life engine use.
« Reply #3 on: May 28, 2013, 12:14:31 »

Hey TM, I do remember you, but as I am always a good boy, I can't imagine me ever getting stick from the mods :-) You must be mistaking me for someone else, sir!

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MokMok

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Re: Query about real life engine use.
« Reply #4 on: May 31, 2013, 09:01:25 »

Do ship's propulsion systems also have a gearbox and carburetors for controlling the fuel flow to the engines?
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clanky

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Re: Query about real life engine use.
« Reply #5 on: May 31, 2013, 12:59:59 »

Carburettors, no. Most ships engines use diesel fuel, so the fuel is injected directly into the cylinder, the ammount of fuel injected is control by the fuel pump which is controlled by the governor.

Some ships have gearboxes, but these are different to the gearboxes found in a car.  Depending on the size of the ship and the propeller the ideal propeller speed is usually between 90 - 250 RPM, some ships have slow speed engines which are directly coupled to the propeller and turn at the same speed whereas some ships use medium or even high speed engines so that they need to reduce the engine speed of maybe 500 RPM to a propeller speed of 125 RPM or similar.

For ships with direct drive engines when the propeller needs to turn in the astern direction the engine has to be stopped and started again so that the engine actually turns in the opposite direction, most ships which use medium speed engines and reduction gearboxes also use controllabe pitch propellers so that the engine only runs in one direction and astern thrust is achieved by tilting the propeller blades in the opposite direction.
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Badwebdiver

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Re: Query about real life engine use.
« Reply #6 on: June 10, 2013, 14:02:32 »

Clanky, thank you for your detailed reply, it was very informative.

I promise to try to run my ships in a manner you would prefer. :thumbs:

I knew about "ahead" and "astern" of course, just haven't gotten into practice to use them regularly.  Thanks for correcting my nautical grammar.  ;D
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