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Water In Fuel Oil - How Is It Handled On Ships?

written by: Raunekk • edited by: Lamar Stonecypher • updated: 9/2/2009

Auxiliary machineries on a ship use a different grades of fuel. Most of these fuel grades have water in them. It is difficult to remove this water completely from the fuels. So how do we go about it?

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    We have seen in the previous article how the presence of water in fuel oil can lead to microbial infestation which tend to degrade the quality of fuel oil. Since fuel oil is normally bunkered and stored on board ship in huge quantities, there must be ways to overcome this problem. Intuitively, your first response would be that why not remove this water from the oil - as simple as that. Yet, it is a technical fact that it is impossible to remove all the traces of water from the fuel oil flowing in the fuel oil system.

    So what is the alternative in such a case. Well if you cannot win over something, you better befriend the same. This simple principle comes in handy in this situation also. As it is not possible to remove all the water from the oil, why not mix it well with the fuel oil in order to increase the combustion efficiency, was what some people thought. Homogenizers and motor oil blenders were invented as a result of this deduction, and we will learn about these equipments now.

    A homogenizer is used in order to create a stable oil and water emulsion that can be burned in oil as well as the diesel engine. It is proved that such emulsion of water results in more combustion efficiency than the haphazardly suspended water molecules. Moreover, such emulsion is also believed to reduce solid emissions in the exhaust gas.

    Homogenizers are generally of two types

    • Rolling type
    • Impact type

    Both the types are used to break down the fuel particles into fine droplets in order to mix them efficiently with water. This emulsion process also breaks down agglomerates of asphaltenes and bituminous matters, which otherwise leads to solid particles in the exhaust and formation of sludge. It is also proved that homogenizers are able to reduce catalytic fines into extremely small particles, which are harmless to the system and thus increase fuel combustion efficiency.

    However, many manufacturers believe that homogenizers leads to formation of sludge which often remains partially un-burnt. And it is due to this reason that many owners do not prefer homogenizers on board and consider that it is better to remove water and other small particles from the system rather than churning them, which may cause a threat to the system later on.


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    Some of the auxiliary diesel engines require intermediate value of viscosity for fuel oils for smooth operation and increased efficiency. These intermediate viscosity fuels are extremely expensive and not so easily available. For this reason, some ships uses blenders to mix two grades of oils, usually a heavy oil and marine diesel oil to produce an balanced viscosity fuel suitable for use in auxiliary engines. This methods helps to increase fuel cost savings and thus eliminate the problems related to the need of an original intermediate viscosity fuel.

    Blenders consists of a blending unit, which mixes both fuels precisely and then pass it to the blender fuel supply tank. It is from the supply tank that the fuel is supplied to all the machinery of the ship. The samples from the blended fuel tanks are continuously taken for quality assessment, as incompatible fuels can produce a large quantity of sludge and sediments.


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