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Back to SSG 18
ABS is able to assist owners in developing the fuel management plan for specific ships within a fleet as the Baltic Sea SECA entered into effect May, 2006, and the North Sea SECA applies from November, 2007.
Managing change from high sulphur
to low sulphur
By Andy Wright,
ABS London Engineering,
e-mail: awright @eagle.org
Ships entering SOx Emission Control Areas (SECA) that normally operate on high sulphur bunker fuels need to orchestrate the change to the specified low sulphur fuels in advance, so that the vessel is burning clean on entry into the area. Operators must also be able to demonstrate to the relevant authorities through appropriate documentation and records that they have complied with the low sulphur limits.
IMO designated SECAs limit the sulphur content of all fuel oils used in those defined areas to a maximum of 1.5 per cent or requires equivalent primary or secondary control measures to be applied.
The Baltic Sea SECA entered into effect in May, 2006, and the North Sea SECA applies from November, 2007. Regional controls apply in areas such as Californian waters where – from January 1, 2007 – auxiliary diesel engines and diesel-electric engines must use either marine gas oil or marine diesel oil at or below 0.5 per cent sulphur. Alternatively, the vessel may use control measures to reduce its emissions to the same level or, in certain situations, the vessel may pay a noncompliance fee.
The vessel must also maintain records showing when it entered and departed California waters and when it switched fuels. Records must also be kept regarding fuel purchases and sulphur content. The restriction will be further tightened on January 1, 2010, by restricting usage solely to marine gas oil at or below 0.1 per cent sulphur.
Several service tanks
Vessels constructed on or after July 1, 1998, are provided with at least two fuel oil service tanks having a capacity of at least eight hours at MCR of the propulsion plant and normal operating load at sea of the generator plant. (Chapter II-1/Reg.26.11 of Solas 74 as amended.)
In this case, one service tank is available for low sulphur fuel oil and could be designated as a service tank in which only low sulphur fuel oil is used. To achieve compliant changeover from the high to low sulphur fuels, the following procedure could be considered:
• The high sulphur fuel oil in a settling tank is discharged to the overflow tank through a valve at the tank’s bottom by gravity at a loading or unloading port outside the SECA.
• The high sulphur fuel oil in a service tank to be used for the low sulphur fuel oil is shifted to another service tank and/or the overflow tank.
• Upon completion of the fuel oil shifting/transference, a low sulphur fuel oil is transferred to the settling tank from a low sulphur fuel oil bunker tank and then is supplied to the service tank through fuel oil purifiers.
Where the MDO service tank also has a capacity of at least eight hours operation at MCR of the propulsion plant and normal operating load at sea of the generator plant, the change from high to low sulphur fuels should follow one of the following two procedures:
If using MDO during the change:
• The fuel oil in both a settling tank and a service tank is completely discharged to the overflow tank through a valve at the tank’s bottom by gravity after the fuel oil to the main engine and the auxiliary engines has been switched to MDO.
• Low sulphur fuel oil is transferred to the settling tank from a low sulphur fuel oil bunker tank.
• The low sulphur fuel oil is supplied to the service tank through fuel oil purifiers.
• After the service tank level has reached the minimum feasible level for the intended operation, the fuel oil is switched from MDO to the low sulphur fuel oil.
If not using MDO during the change, the following switching procedure should be carried out prior to entering the SECA, taking into account the time needed for the change to complete:
• The high sulphur fuel oil in the settling tank is completely discharged into an overflow tank under the condition that the service tank has been fully filled with a high sulphur fuel.
• The low sulphur fuel oil is transferred to the settling tank from a low sulphur fuel oil bunker tank.
• Once the temperature of the fuel oil in the settling tank has reached the temperature necessary for its purification, the high sulphur fuel oil in the service tank is discharged to an overflow tank up to the minimum feasible level for the intended operation.
• The low sulphur fuel oil in the settling tank is immediately supplied to the service tank through fuel oil purifiers.
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The Haahr Trumf, built in1964, delivers fuel to the Finnforest. Photo: Bent Mikkelsen |
Additional tanks
Containerships constructed before July 1, 1998, normally have additional settling and service tanks for low sulphur fuel oil, with each tank usually having a capacity of about 100 cbm. However bulk carriers, product carriers or oil carriers are not provided with such tanks.
For owners/operators who decide not to make the necessary structural modifications to install additional settling and/or service tanks on such existing vessels, it is still possible to effect an acceptable changeover from high to low sulphur fuels by considering the following:
Since there was no specific requirement for the capacity of HFO settling and service tanks in Solas, their capacity was usually less than is provided on post 1998 vessels. In this case, the fuel oil management procedure for switching from high to low sulphur fuels should be related to the safe operation of the ships.
Where an additional service tank and/or settling tank is not provided on vessels entering into a SECA, the switching procedure should be developed taking into account the ship’s crews’ knowledge and skill level.
Switching valves
If, as a consequence, it is not possible to follow the previously outlined procedures, the changeover can be achieved without discharging the high sulphur fuel oil in both the settling and the service tanks. Taking into account the risks to the safety of the vessel this procedure is performed by switching valves at the suction of the transfer pump.
The low sulphur fuel oil is transferred to the settling tank, mixing with the retained high sulphur fuel oil. The low sulphur fuel oil is then supplied to the service tank with the high sulphur fuel being separated by the purifiers.
Once again, this changeover should be carried out well prior to entering the SECA, taking into account the time required for the transition to low sulphur fuel.
If a shipowner does not intend to modify an existing vessel by adding the required additional settling and service tanks, a fuel oil management plan is to be prepared that takes into account the time required to complete the changeover from a high sulphur oil to a low sulphur oil prior to entering the SECA.
ABS is able to assist owners in developing the fuel management plan for specific ships within a fleet. The specific plans take into account the relative sulphur contents of the fuels, the capacity of each of the fuel oil settling and service tanks, the main and auxiliary engine outputs, the capacity of the fuel oil purifiers, the fuel service system and relevant safety issues.
Latest update 1-10-2007 11:25
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 CURRENT SSG |
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No 18/2008
Order a copy
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| CURRENT SST |
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No 17/2008
Köp numret
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2007