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Low sulfur operations

Hydrocarbon Engineering,

The stricter limitations on SOx that are due to come in to play are going to pose many challenges to ships operating in Emission Control Areas (ECAs). If not handled with due care and attention, switching from heavy fuel oil (HFO) to marine gas oil (MGO) can put equipment at risk and increase operational costs. In a new publication ‘Sulphur Limits 2015 – Guidelines to ensure Compliance,’ DNV GL experts offer a general overview on regulatory background, describe potential difficulties associated with the fuel change over procedure and discuss which technologies can best help vessels fulfil the new requirements. Also, DNV GL has developed a ship specific Fuel Change Over Calculator (FCO) to help ship owners and operators determine the ideal parameters for their vessel’s fuel change over.

New regulations

Ships that are operating in an ECA will have to use fuel that does not contain over 0.10% sulfur from January 1 2015 onwards. Switching to MGO is currently the most viable option for following the new threshold limit. This may appear to be a simple task, but the change over procedure actually requires significant attention from crews during operation as well as extensive onboard preparations before the entry into force data.

Jorg Lampe, Senior Project Engineer Risk & Safety, Systems Engineering, DNV GL said ‘taking into account variables such as a vessel’s fuel system layout, any constraints on temperature and the variable sulfur content of fuels, the FCO calculator can significantly reduce the risk of human error during the preparation of the change over process.’ The software uses a complex numerical simulation that is more accurate than previous linear models and delivers insight into the optimised lead time for the change over process, its costs and the maximum hourly consumption to meet constraints. Lampe added, ‘this kind of data ensures a cost efficient, reliable fuel change over and can also help demonstrate compliance for the respective authorities.’

Successful change over

Factors such as the temperature and viscosity of the two fuels along with potential incompatibilities are critical to performing the change over procedure successfully. As the operating temperatures of HFO and MGO differ by approximately 100 °C, the change over can cause a rapid fall in temperature and increase the danger of thermal shock to the equipment. Fuel systems also have to account for their difference in viscosity during operation, in order to avoid fuel pump failures and leakages. Also, the fact that HFO and MGO are mixed in all rations during the change over procedure increases the risk of the fuels becoming incompatible. This may clog filters, causing the engine to shut down.

The above complications can be avoided by preparing detailed guidelines for the fuel change over time, training crews to take a measured and careful approach to the procedure and by making informed decision about the capabilities of a vessel.

The DNV GL report is available to read here.

Edited by Claira Lloyd

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