LPG or LNG engine on a tug boat - will it work?

Discussion in 'Inboards' started by yodani, Nov 10, 2014.

  1. yodani
    Joined: Nov 2010
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    yodani Senior Member

    Hi all,

    I am still contemplating about my repowering I have to undertake for my fleet and just the other day I was looking at a Cummins LNG /LPG powered bus so It got me wondering - did anyone try to put an engine like that in a boat?

    - what would be the disadvantages besides the lack of refueling stations by the water?
    - is there any advantage to using gas?
    - will it be cheaper to run than a modern diesel?

    I have read a few papers about ferries being fitted with LNG engines but we are talking huge boats, I am asking here about the 50-300hp range of engines.

    Here in Romania one liter of Diesel is - 1.36 EURO and LPG is 0.66 EUR/liter. The stuff I read about the LPG running cars is that the consumption is about 30-40% more than a diesel. Would this be the same for a boat?

    My tugs behave more or less like a ferry and they do usually 21 to 34 hours before returning to harbor. I think it would be ok if the LPG gas on board would give me an autonomy of 50-60 hours. Today for a round trip we use aprox 500 liters of diesel at 21-24 l/h consumption. A modern diesel would bring that at about 16 liters/h so about 336 - 400 liters/trip.

    If I mount a few LPG tanks I would need about 50% more plus reserve - say - 1000 liters of gas on board. The existing diesel holding tanks are 2000 liters. Would this be possible?

    Are there any regulations that would forbid this kind of implementation? I know there are outboards and generators running on LNG or LPG.

    The refueling I can do by installing my own holding tank at the marina and buying in bulk so it will be cheaper still.

    The engines can be sourced from - Cummins for the tugs and from Kubota dual fuel for the smaller boats needing 50-60 hp engines.

    Any thoughts?

    Cheers,

    Daniel
     
  2. yodani
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    yodani Senior Member

  3. rasorinc
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    rasorinc Senior Member

    Lpg/lng

    LP is a byproduct of refining NG and does not need super high pressure to store so fuel tanks are lighter and smaller. NG requires great pressure's
    to store so thick steel, heavy, tanks are required. LP IS HEAVY AND FLOWS DOWNWARD. NG is light and flows upward.
     
  4. yodani
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    yodani Senior Member

  5. rasorinc
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    rasorinc Senior Member

    Check your tank requirements for the amount of fuel in gallons you need to store aboard your vessel. Tank requirements can weigh many thousands of
    of pounds which may require more thought. I ruled it out based on tank weight
    for my boat. Also, these tanks take up lots of space and must be well anchored.
    A loose tank can sink your boat.
     
  6. rasorinc
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    rasorinc Senior Member

    You might check the status of Adsorbed Natural Gas where they store it in a medium such as corn cobs or charcoal and it does not require the high pressure to store.They were testing this in some buses about 4 years ago.
     
  7. gonzo
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    gonzo Senior Member

    The electrical system may not be spark-proof, which can cause an explosion. Cars and trucks have open engine compartments, unlike boats.
     
  8. waikikin
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    waikikin Senior Member

    Thier was on Sydney Harbour maybe 15 years ago some water taxis that ran on lpg, they were a cat with engine over the tunnel so fume/gas could vent, drives were hydrolic, they didn't continue with the service for some reason.

    Jeff.
     
  9. yodani
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    yodani Senior Member

    I think the problem of space is not an issue as the boats are just tugs and are made of iron. The existing tanks are heavy too i would say 1000kg. The tanks used on buses are made of aluminium and are positioned on the roof giving them a range of up to 500km. They can't be too heavy because the bus would tip over.... The users are advising for composite material tanks as they last 20 years.

    The spark proof part is indeed a thing to consider but it can be solved with multiple gas detectors and alarms. If done well there should not be any leak and would not be any different from running gasoline engines inboard....wich we know are dangerous and blow up occasionaly :))

    I wonder why the Sidney water taxies stopped ? 15 years ago the fuel price was 50% lower so it might have been an economical reason.

    As I see only 6 month of work/year and taxes plus fuel prices increase by the hour it is hard for me to stay compettitive. Since I will repower with a EU grant i better do it rite and future proof. Winter is here so lots of time to think ...:))
     
  10. gonzo
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    gonzo Senior Member

    Gas engines require that starters, alternators, switches, breakers, etc. be spark-proof. A gas detector will not be effective if there is a lpg leak while you are running.
     
  11. Stumble
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    Stumble Senior Member

    To some extent there are already LNG tugs coming on the market, but all I could find was examples of new builds. I don't know if this is a necessary component, but from what I could find the tankage requirements seem difficult to meet with current designs.

    You might want to contact Sanmar in Istanbul since they have already built a few long tugs, and may be able to point you in the direction of suppliers or engineers with a better grasp on the problem. The only issue I see is that so far all the LNG tugs seem to be much larger than your installs, I don't know if an engine is available in your power range, since the only engine supplier I have seen was Rolls-Royce with twin 3000hp screws.
     
  12. yodani
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    yodani Senior Member

    Hi Greg,

    It seems we have been reading the same literature about LPG. The engines exist but the don't have the "marine" badge on them. If you use dry stack and keel cooling they should fit straight in. Scania, Iveco (FTP) and Cummins are the main suppliers for the engines with models ranging from 270 to 400hp.

    The main problem seems to be the storage of the gas and the supply. In our town we have NATURAL GAS at the pipe and there are suppliers of compressors that can fill the tanks straight on the boat so you avoid the temporary storage. Regulations are also a promblem as they don't exist at the moment...

    A truck running on LNG costs 25 to 30k € more than a Diesel. You would need a lot of work to get the money back :(
     
  13. gonzo
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    gonzo Senior Member

    I would say electrics, and the risk of explosion, are the main risk.
     
  14. Angélique
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    Angélique aka Angel (only by name)

    A search for "LNG Tug" gives lot of hits, but the words "first" and "concept" are very much seen. Which makes it look like it still requires a lot of effort and deep pockets + financial (and perhaps also physical) risks to take to get it out of the R&D stage.
     

  15. AndySGray
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    AndySGray Senior Member

    There are some easy and off the shelf solutions to the sparkproofing.

    Most of the larger diesels have an option for air start - much simpler than sparkproofing an electric starter.

    Some of the alternators have a brushless induction design - the CAT 3126 uses a Delco 30SI which has no brushes - they are ultra reliable and damn near indestructable.

    Is it possible to have a bulkhead(s) to physically separate the motor (and the gas) from other components (with forced ventilation) - with air start less of a battery req. - a shaft mounted alternator in a safe zone would be better.

    Also check out military surplus - ignition protected stuff is frequently specified...

    Assume you're going to get leaks and then design around it.
     
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