Preparing for low sulphur operations

Nov 28 2014

DNV GL has published ‘Sulphur Limits 2015 – Guidelines to ensure Compliance’.

This is a general overview of the regulatory background, describes potential difficulties associated with the fuel changeover procedure and discusses which technologies can best help vessels fulfil the new requirements.

In addition, DNV GL has developed a ship-specific fuel changeover calculator (FCO) to help shipowners and operators determine the ideal parameters for their vessel’s fuel changeover.

Come 1st January, 2015 low sulphur implementation date, switching to marine gas oil (MGO) is currently the most viable option for following the new threshold limit, the class society said.

This may appear to be a simple task, but the changeover procedure requires significant attention from the crew during operation, as well as extensive on board preparations before the entry into force date.

“Taking into account variables such as a vessel’s fuel system layout, any constraints on temperature and the variable sulphur content of fuels, the FCO calculator can significantly reduce the risk of human error during the preparation of the changeover process,” said Jörg Lampe, senior project engineer risk & safety, systems engineering at DNV GL.

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 changeover process, its costs and the maximum hourly consumption to meet constraints. “This kind of data ensures a cost-efficient, reliable fuel change-over and can also help demonstrate compliance for the respective authorities,” Lampe added.

Factors, such as the temperature and viscosity of the two fuels, as well potential incompatibilities are critical to performing the changeover procedure successfully.

As HFO’s and MGO’s operating temperature differs by about 100 deg C, the changeover may 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.

The fact that HFO and MGO are mixed in all ratios during the changeover procedure increases the risk of the fuels becoming incompatible. This may clog filters, causing the engine to shut down, DNV GL said.

Such complications can be avoided by preparing detailed guidelines for the fuel changeover, training crews to take a measured and careful approach to the procedure and by making informed decisions about the capabilities of a vessel. 

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