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Thread: Not so safe system

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    Marian Gray's Avatar
    Marian Gray Guest

    Default Re: Not so safe system


  2. Likes j.sabourn, happy daze john in oz liked this post
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    Default Re: Not so safe system

    Going back to the original post regarding the saga cruise liner, it's propulsion system was with azimuth thrusters, these are powered by electric motors, with electricity for them supplied by conventional diesel generators that also supply all the other electrical load to operate the vessel, hotel, navigation etc.
    I have no experience of azimuth propulsion but do have some experience of diesel electric propulsion.
    The gear required to convert the 220v output from the d.g's to the required voltage to power the electric motor used as the main propulsion system is quite complicated and requires a hefty computer control system, if your really interested just Google diesel electric propulsion for ships.
    The vessel I was on with that system was a 6000 dwt chemical tanker , 100 MTRS long, with 14 stainless steel cargo tanks each fitted with hydraulic driven deepwell cargo pumps. We were trading u.K and north European ports, stanlow,rotterdam, tees,antwerp,le havre,hamburg, Rouen etc. in port roughly every 3 days either loading or discharging with tank cleaning at sea.
    So I spent a lot of time under pilotage and berthing/unberthing, which I invariably did myself.
    Now despite what the diesel electric propulsion systems manufacturing blurb will tell you you have to be very careful with engine movement when berthing as if, for example, you required a quick burst of full ahead and full stbd rudder to kick the stern in, you had to actually do it quite slowly as asking the computer control systems to suddenly increase. Output power to the propulsion motor whilst still maintaining electrical load for all other on-board systems would result in the whole electrical system to go into safe mode, where propulsion power is restricted to 50% whilst keeping the rest of the electrical load intact. This would require the duty engineer to scroll through his computer screen and reset the systems, resulting in frantic annoyed telephone calls from the chief engineer and a number of minutes of buttock clenching from self and quizzical looks from the pilot
    .......,
    Regarding forest products and ships loading in B.C for Europe, the dedicated forest products ships I sailed on all had timber load lines assigned which took into account deck cargo water absorption en route and all deck timber cargo lashing were fitted with quick release senhouse slips so that in the event of a major list developing you could just pop out onto the deck cargo, knock open the senhouse slip and let the cargo go overboard.......yeah, as if!!!!!.
    I have also done the same run on conventional geared bulk carriers without assigned timber load lines but when doing stabilty calculations you had, if I recall correctly, you had to allow for 15 % by weight of the deck cargo for water absorption, which is a bit daft when you consider the amount of time those tree logs spent floating in water either being brought down from the logging site or waiting in the sawmills pools before being taken into the mill itself for cutting into sawn timber.
    Rgds
    J.A

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    Default Re: Not so safe system

    A number of cruise companies are now having ships built that will use gas, LPG, mainly rather than diesel.
    Cleaner but can be a hazard if not correctly maintained.
    Happy daze John in Oz.

    Life is too short to blend in.

    John Strange R737787
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    Default Re: Not so safe system

    No offence John but any fuel system used on ships can be hazard if not properly maintained. The number of times engine room fires break out and the cause is often linked to a fuel leak or more often than not a fractured fuel line spraying diesel or fuel oil onto a hot surface.
    I would have thought cruise ships going down the gas route would be more likely use LNG than LPG. Although LPG has a higher calorific value than LNG. LNG is cheaper and more readily available than bulk LPG. But I may well be wrong.

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    Default Re: Not so safe system

    John Post #2
    As If ? That is what I told the Chief mate when he shouted "Jenkins get a hammer and let go those stenhouse slips" the deck cargo of logs on No four hatch where hanging over the side, they stayed there, until we got to Garstton.
    Des
    R510868
    Lest We Forget

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    Default Re: Not so safe system

    James, having been on a ship on fire while in port from just that I am fully aware of the dangers.
    I was pointing out that the passengers would not have a bloody clue, and it is still a fairly new concept so could pose a few problems.

    When the first LPG run vehicles were introduced here in Oz there were many that caught fire, but over time the problems were resolved and LPG became very popular and there are still a good number of cars still using it.
    Happy daze John in Oz.

    Life is too short to blend in.

    John Strange R737787
    World Traveller

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