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Bunker supplier ExxonMobil has issued a set of guidelines that are designed to prevent the cross-contamination of marine fuels during storage and handling.

ExxonMobil's latest bunker-related guidelines explain how the requirement to use low-sulphur fuels in Emission Control Areas (ECA) presents challenges for bunker buyers and suppliers. Under Marpol Annex VI, ships are required to be able to switch to a low-sulphur fuel prior to entering an ECA. Many modern ships will have separate fuel storage for high- and low- sulphur fuels, which is designed to simplify the switching process and reduce the risk of cross-contamination.

Three key issues are highlighted by ExxonMobil; they are:

1. The need for carrying both HFO and ECA category fuel
2. Maintaining strict fuel segregation
3. Always follow ISO 8217 guidelines

"Supplying ECA-compliant fuel raises a number of challenges, but essentially it's about segregation, it's about tank storage, so that there's separate tank storage ashore, on board floating supply ships, the barges and indeed the vessel itself," Peter Hall, CEO of the International Bunker Industry Association (IBIA) explains, referring to how segregation is required throughout the supply chain to avoid cross-contamination.

"The key thing to do is avoid cross-contamination, be aware of the fuel you are using and its implications. It's about knowledge, it's about education, it's about communication," added Hall.

Ashley Jenkins, Director at Whitaker Tankers Ltd, says that the segregation of its tanks is "a big issue" for the firm. Referring to one of the company's vessels, he says: "On a tanker of this size, we have five sets of tanks, two of which will be an ECA-compliant grade, two with regular sulphur and one with marine gas oil, all of which we take care to keep segregated, and not just by compartment - dedicated compartment - but also by segregated and dedicated pumps and hoses. Literally everything - through to the load point, to the actual manifold of the customer - is segregated and dedicated."

ExxonMobil lists the following guidelines:

Storage

- Drain tanks at least daily for accumulated water

- Ensure the fuel is maintained at the appropriate temperature

- Clean fuel tank bottoms at regular scheduled intervals

- Maintain fuel tank vents with the correct size mesh screening

Treatment of fuel

- Check self-cleaning filters regularly

- Keep strainers clean

- Ensure wire mesh is in good condition

- Maintain fuel at the appropriate temperature

When operating centrifugal purifiers

- Ensure fuel is within appropriate density parameters for the efficient operation of the purifier

- Check that the purifier inlet temperature is correct for the viscosity of the fuel in use

- Make sure that the purifier is operating at the minimum practical setting throughout to suit the vessel operation

Handle fuel

- At the correct temperature, pressure and viscosity

- Clean fuel filters regularly

- Calibrate the pressure, temperature and viscosity control systems