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Y4 Question

Discussion in 'Licensing & Education' started by Stillfloatin, Aug 24, 2010.

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  1. Stillfloatin, Aug 24, 2010
    #1
    Stillfloatin

    Stillfloatin New Member

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    Hi all,

    I am currently reviewing my Y4 notes and have come across a question that i could use some help with.
    "Describe three types of wastage that may occur on the internal surfaces of a ship's side valve that is made of modular cast iron"
    I'm certain part of the answer is obviously corrosion............

    Any help would be greatly appreciated.
    Merman likes this.
  2. Jorge Lang, Aug 24, 2010
    #2
    Jorge Lang

    Jorge Lang Senior Member

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    First, welcome to Yacht Forums. While I am not an engineer, I would think biological growth would be a correct answer. I look forward to how the rest of us would respond.
  3. NYCAP123, Aug 24, 2010
    #3
    NYCAP123

    NYCAP123 Senior Member

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    Strictly a guess from a non-engineer: oxidation, electrolysis, wear. I await
    K1W1 or Marmots correct answers.
  4. K1W1, Aug 25, 2010
    #4
    K1W1

    K1W1 Senior Member

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    Hi,

    Are you sure it is a Modular Cast Iron Valve. Nodular is the normal term.

    Erosion from too high a flow rate/turbulence/lumps of sand,shell, rock etc blasting through the valve body.

    Wear and tear on the valve components especially around the seat and disc or gate components, packing area on the spindle.

    This could be what they are really looking for: Corrosion and in addition to rust there is this little one that appears sometimes.

    Graphitic corrosion - the porous graphite network, that makes up 4-5% of the total mass of the alloy, is impregnated with insoluble corrosion products. As a result, the cast iron retains its appearance and shape but is weaker structurally. Testing and identification of graphitic corrosion is accomplished by scraping through the surface with a knife to reveal the crumbling of the iron beneath. Where extensive graphitic corrosion occurs, usually the only solution is replacement of the damaged element.
    Merman likes this.
  5. FullaFlava, Aug 25, 2010
    #5
    FullaFlava

    FullaFlava New Member

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    In addition to the above, galvanic or electrolytic corrosion might be amongst the answers they are looking for as it is lower in the galvanic series than low alloy steel, stainless and brass.
    Merman likes this.
  6. Stillfloatin, Aug 25, 2010
    #6
    Stillfloatin

    Stillfloatin New Member

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    Thank you all for your great responses and the warm welcome. I thought my post may be met with " go back and do your home work". Its nice to see people helping each other out.
    K1W1 your absolutely right its nodular not modular it was typo on the past paper and I didn't notice until further researching the material and as the question does state the valve material in particular your probably right that they want you to specify corrosion related to the material.

    Once again all great responses now I have plenty of ammo for that question. If I get stuck again hopefully you guys don't mind if I put another question up.
    Merman likes this.