Marine engineer - Ask me anything

Vovin

Mouseketeer
Joined
Sep 30, 2018
Have you every wondered how the lights stay on, where the sewage goes or how a ship moves and navigates?

If so I'd be happy to answer those questions and any others anybody may have (within reason). Just post a question below and I'll get back to you.

Me: A marine engineer who works on cruise ships who enjoys sharing knowledge.
 

Vovin

Mouseketeer
Joined
Sep 30, 2018
The weight and balance of an aircraft affect where the centre of gravity is. While it is important for stability reasons it doesnt really affect the performance, speed wise.

With aircraft, if the centre of gravity is forward then the aircraft is considered stable but less agile. The opposite is true for having the centre of gravity aft, it would make the aircraft unstable but more agile.

The location of the centre of gravity on a ship will have an impact on the steering capability. If it is forward then the rudders will cause more of a moment on the centre of gravity so itll turn quicker. Move it aft and the rudders lose their authority.

During rough weather the deck department will ballast the ship, lowering it in the water. This lowers the centre of gravity so that the ship is less effected by the rough weather. I'm sure theres a nautical term for this but it escapes me.

To move the centre of gravity forwards, starboard, port or aft the ship uses what's called heeling tanks. These tanks keep the ship level, the process is normally automatic.

Example: Mickey mouse gets into a fight with goofy because he insulted minnie. 2500 guests all rush to one side of the ship to watch, place bets etc. The weight of those people moving will cause the ship to list a small amount.
This is picked up by sensors onboard that automatically transfer ballast water to a heeling tank on the opposite side of the ship to where the fight is taking place. They may be a large security incident but at least the ship is nice and level
:-D

Edit: oh my goodness that's a long post, will try to be shorter next time.

Edit exit:
At 3:38 you will see the heeling system in operation, watch the Fantasy move
 
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  • icc2515

    DIS Veteran
    Joined
    Sep 11, 2010
    How many gallons of fresh water can a cruise ship make in a day. Does the gray water get dumped into the ocean? Are the gray and black water kept separate or run together? Is it safe to drink the water from the bathroom faucet?
     

    DisneYE

    DIS Veteran
    Joined
    Oct 7, 2013
    Thank you for being here and willing to share your knowledge

    What happens if there's a major engine failure in the middle of the ocean?
    Are there spare/back up engine(s) to fall on just in case?

    I'm in the mining industry and usually they have back up engines for most critical equipment in case of a major failure.
     

    KVH

    Mouseketeer
    Joined
    Jan 18, 2016
    I'll play. If they wanted to make the ships faster, what do they change? Hull design? Engines? Superstructure? Or does weather conditions and sea-state negate those changes which are possible?
     

    Welsh_Dragon

    DIS Veteran
    Joined
    Feb 23, 2019
    Do you have a Chief Engineer’s ticket and do you serve as Chief, or are you still working your way up the ranks? Have you only served on cruise ships or on other vessels as well? In your opinion which is the best flag to fly under and why?
     
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  • brentm77

    Mouseketeer
    Joined
    Jan 17, 2013
    At 3:38 you will see the heeling system in operation, watch the Fantasy move
    Great information and so cool to see the heeling system in action. Shouldn't have kept watching, because I teared up a bit when they did the "When you Wish" horn blast. So many happy memories!
     

    Vovin

    Mouseketeer
    Joined
    Sep 30, 2018
    How many gallons of fresh water can a cruise ship make in a day. Does the gray water get dumped into the ocean? Are the gray and black water kept separate or run together? Is it safe to drink the water from the bathroom faucet?
    I'll start with the question of the water being safe to drink. Yes, yes it is. I drink it all the time and I see all that happens.

    When the water is produced it is pure water, it has no impurities or even the minerals we naturally consume when we drink water.
    All the water produced onboard (methods will be discussed below) is put through a process. The water passes through a tank called a mineraliser, this tank contains calcite. As the water flows through it picks up the minerals and becomes mineralised. It also adjusts the pH of the water.
    Next the water passes through chlorination before heading to the potable water tank where itll sit ready to be used.
    The bridge dictates which tank is getting filled and which one is supplying the fresh water system as it affects stability. The water is then pumped around the ship in a loop so that theres no chance of stagnant water. The chlorine is monitored and kept within a set range to prevent any nasties in the water.


    Using my ship as an example which is a similar size to the Dream class; we have two methods of water production, reverse osmosis and evaporator.

    The reverse osmosis method uses really really fine filters that only water molecules can pass through.

    The evaporator method uses a vacuum to effectively boil seawater at lower temperatures. This saves energy. The evaporator plant generally runs off the waste heat from the main engines, bit this can be supplemented by the boilers if not enough heat is being produced.

    Each evaporator can produce 7-800 tonnes of water per day while the reverse osmosis plants can produce around 450 tonnes per day. Roughly 510,000 imp gallons a day.

    The majority of the time itll only be the 2 reverse osmosis plants running as cruise ships generally like to plod along so not enough heat is getting generated by the engines. They normally rely on filling up their fresh water at their home port.

    The grey water is generally stored in tanks in the engineering spaces and gradually introduced into the sewage treatment system. So when grey water tank fills up its then pumped. So yes, the grey and black water are mixed.

    The black water system is amazing yet gruesome at the same time. You have vacuum units situated in the engineering spaces which suck all the stuff humans produce into it. They even have a little window so you can see!
    Once these units reach a set level the black water is transferred and processed ready for the bio reactor.
    The bacteria that feast on your number 2's do not like fats very much. So we first filter it all through a screen press to remove the solids like toilet paper (once found someomes shirt clogging it up?!).
    The stuff thays filtered out has its moisture removed so it's just transferred to an incinerator.

    Once your waste has been through two stages of bacteria feasting it is then pumped into a bank of fine filters. These filters are close to the reverse osmosis filters mentioned above. This leaves what we call permeate, this water is then treated with chlorine and either pumped to a holding tank or disposed of overboard. It's worth noting that this water can technically be recycled so it's not harmful to the environment.

    Hope that's satisfied your curiosity a little bit.
     

    Vovin

    Mouseketeer
    Joined
    Sep 30, 2018
    Thank you for being here and willing to share your knowledge

    What happens if there's a major engine failure in the middle of the ocean?
    Are there spare/back up engine(s) to fall on just in case?

    I'm in the mining industry and usually they have back up engines for most critical equipment in case of a major failure.
    Hi there.

    Cruise ships generally have the diesel electric type of system. This allows them to have multiple engines that can be connected to the grid. It allows quicker response to telegraph input from the bridge. Basically you can be at full ahead and slam it in reverse with relative ease.
    Cargo ships cant do that as their propeller is connected directly to the crank shaft, so they have to physically stop their engine and start it in reverse.
    Back to your question. Let's say a cruise ship is cruising along at a leisurely pace and it's running 3 of its 6 engines. If a running engine develops a fault a standby engine is automatically stated and connected to the grid. In this case you will have a minuscule interruption to the speed.

    Ships post 2012 are designed to avoid a major failure by building in so much redundancy that a major fault would still allow the ship to get to port. Having said that though, things still happen.

    Bit of a struggle to think of a scenario but here it goes. You are sailing along and a boat hits the ship and punctures a hole in one of the engine rooms, you are unable to close the hole and the flooding is too much for the pumps to handle.
    The ship will still be able to operate but in a much reduced capacity, enough to get the ship to port.

    If all the generators fail and the ship has a blackout then the emergency generator will activate automatically and bring the essential loads back online, so in Disneys case itll be the aqueduct:-D
    The emergency generator will power the required pumps and systems needed to start one of the main engines.

    Believe it or not, if the emergency generator runs out of compressed air or battery power you have a hand crank diesel engine connected to a compressor. It's like a ride on mower engine...

    Hope that helps
     
  • Vovin

    Mouseketeer
    Joined
    Sep 30, 2018
    I'll play. If they wanted to make the ships faster, what do they change? Hull design? Engines? Superstructure? Or does weather conditions and sea-state negate those changes which are possible?
    You can do a few things to get more speed out of a ship.
    You can increase the engine power but that will only work up to a certian point as the propellers wouldn't be suitable. When propellers are designed they take into account the design of the ship, its displacement and it's intended power output/speed range. If the ship had a variable pitch propeller it would allow greater speed. But as I say, its only upto a point.

    The issue with hull design is you need to strike a balance with how hydro dynamic and how strong/stable it is. Having said that, ship builders employ special coatings to reduce resistance, they use a bulbous bow also. Super structure is sort of the same, not much can be done there.

    Wish I could be more helpful there, sorry.
     

    Vovin

    Mouseketeer
    Joined
    Sep 30, 2018
    Do you have a Chief Engineer’s ticket and do you serve as Chief, or are you still working your way up the ranks? Have you only served on cruise ships or on other vessels as well? In your opinion which is the best flag to fly under and why?
    I've got my seconds licence, I'm still working my way up. Chief one day!

    99% cruise ships, the other 1% is helping friends out with their boats.

    Ive only ever sailed under the bahamas flag, I'm quite lucky as an engineer as contract terms are good.
     

    Capt_BJ

    So Many Times
    Joined
    May 17, 2005
    I've been here for a long time

    willing to answer questions as I have for years

    I sat in the Captain's chair .......

    didn't sneak in ..... it was MY chair

    "During rough weather the deck department will ballast the ship, lowering it in the water. This lowers the centre of gravity so that the ship is less effected by the rough weather. I'm sure theres a nautical term for this but it escapes me. "

    and you have a license? :crazy2:

    I've got to talk to my friends in the examinations office . . .
     
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    Vovin

    Mouseketeer
    Joined
    Sep 30, 2018
    I've been here for a long time

    willing to answer questions as I have for years

    I sat in the Captain's chair .......

    didn't sneak in ..... it was MY chair

    "During rough weather the deck department will ballast the ship, lowering it in the water. This lowers the centre of gravity so that the ship is less effected by the rough weather. I'm sure theres a nautical term for this but it escapes me. "

    and you have a license? :crazy2:

    I've got to talk to my friends in the examinations office . . .
    I'm not a deck officer. I'm trying to answer people's questions from my point of view. I've got no issue if you want to add what I say or outright correct me.

    But to say that you need to talk to your friends at the examination office is just silly.
     
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    RogueX

    Mouseketeer
    Joined
    Aug 21, 2019
    Have you been instructed on how to deal with pirates (not the bottle of rum type) and other hostile encounters?
     

    Vovin

    Mouseketeer
    Joined
    Sep 30, 2018
    Have you been instructed on how to deal with pirates (not the bottle of rum type) and other hostile encounters?
    We dont tend to sail to hostile countries or through hostile waters when we can avoid it.
    We have regular drills such as bomb search, missing person, stowaway etc though.

    Cargo ships tend to prepare for pirate attack as they sail in places like the Gulf of Aiden, which is one hot spot for pirates. If you watch the film 'Captian Philip's' you'll get an idea of the things they do. Granted it's a film but itll give you an idea.
     

    DisneYE

    DIS Veteran
    Joined
    Oct 7, 2013
    Hi there.

    Cruise ships generally have the diesel electric type of system. This allows them to have multiple engines that can be connected to the grid. It allows quicker response to telegraph input from the bridge. Basically you can be at full ahead and slam it in reverse with relative ease.
    Cargo ships cant do that as their propeller is connected directly to the crank shaft, so they have to physically stop their engine and start it in reverse.
    Back to your question. Let's say a cruise ship is cruising along at a leisurely pace and it's running 3 of its 6 engines. If a running engine develops a fault a standby engine is automatically stated and connected to the grid. In this case you will have a minuscule interruption to the speed.

    Ships post 2012 are designed to avoid a major failure by building in so much redundancy that a major fault would still allow the ship to get to port. Having said that though, things still happen.

    Bit of a struggle to think of a scenario but here it goes. You are sailing along and a boat hits the ship and punctures a hole in one of the engine rooms, you are unable to close the hole and the flooding is too much for the pumps to handle.
    The ship will still be able to operate but in a much reduced capacity, enough to get the ship to port.

    If all the generators fail and the ship has a blackout then the emergency generator will activate automatically and bring the essential loads back online, so in Disneys case itll be the aqueduct:-D
    The emergency generator will power the required pumps and systems needed to start one of the main engines.

    Believe it or not, if the emergency generator runs out of compressed air or battery power you have a hand crank diesel engine connected to a compressor. It's like a ride on mower engine...

    Hope that helps
    Wow thank you so much for the reply.
    Very interesting info you provide here.
    What a treat to have a marine engineer on here.
     

    Welsh_Dragon

    DIS Veteran
    Joined
    Feb 23, 2019
    I've been here for a long time

    willing to answer questions as I have for years

    I sat in the Captain's chair .......

    didn't sneak in ..... it was MY chair

    "During rough weather the deck department will ballast the ship, lowering it in the water. This lowers the centre of gravity so that the ship is less effected by the rough weather. I'm sure theres a nautical term for this but it escapes me. "

    and you have a license? :crazy2:

    I've got to talk to my friends in the examinations office . . .
    The maritime industry has changed so much over the last 40/50 years. Now that ships have such a quick turn around in ports, do you think that young people still join the merchant navy to see the world? How long did it take to get your Master’s ticket? What type of vessel did you start your career on? What was your worst experience of your ship being arrested? You must have some stories to tell!
     
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