Fuel oil tank protection

Old vessels, but unfortunately also many new ones, have bunkers in double hull and any shell damage can result in oil spill. This common practice has been stopped by new revised MARPOL Annex I, Regulation 13A. This regulation applies toall ships with an aggregate oil fuel capacity of 600m3 and above for which the building contract is placed on or after 1 August 2007, or the delivery of which is on or after 1 August 2010.

According to the new regulation, individual oil fuel tanks shall not have a capacity of over 2500m3. The provisions of this regulation will apply to all oil fuel tanks except small tanks with an individual capacity not greater than 30m3, provided that the aggregate capacity of such excluded tanks is not greater than 600m3.

For ships having an aggregate oil fuel capacity of 600m3 and above, oil fuel tanks shall be located above the moulded line of the bottom shell plating nowhere less than the distance h as specified: h = B/20m or h = 2.0m, whichever is the lesser. The minimum value of h = 0.76m.

For ships having an aggregate oil fuel capacity of 600m3 or more but less than 5000 m3, oil fuel tanks shall be located inboard of the moulded line of the side shell plating, nowhere less than the distance w which is measured at any cross-section at right angles to the side shell as specified: w = 0.4 + 2.4C/20,000m, “C” is the vessel’s total volume of oil fuel, in m3, at 98% tank filling.

The minimum value of w = 1.0m, however for individual tanks with an oil fuel capacity of less than 500m3 the minimum value is 0.76m.

For ships having an aggregate oil fuel capacity of 5000m3 and over, oil fuel tanks shall be located inboard of the moulded line of the side shell plating, nowhere less than the distance w which is measured at any cross-section at right angles to the side shell as specified below:

w = 0.5 + C/20,000m, or w = 2.0m, whichever is the lesser. The minimum value of w = 1.0m.

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