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Top 5 Tips for Fuel Switching Released

ExxonMobil has compiled a list of five top tips to help ship operators switch fuels and avoid maintenance issues when entering and exiting Emission Control Areas (ECAs).

ExxonMobil suggests that managing temperature change can help avoid thermal shock, which is vital in reducing the possibility of fuel pump seizures and engine shutdowns.  Switching fuels at the correct time is essential to meeting the 0.1% sulphur limit requirement in ECAs, and if not carried out correctly can leave the ship owner vulnerable to non-compliance and the risk of fines.

In light of these issues associated with fuel switching, ExxonMobil suggests the following:

  1. A clear switchover procedure. Ensuring the crew is familiar with the processes and testing the procedure prior to entering crowded and restricted waters, where there is a higher risk of grounding or collision, is crucial.
  1. Outline the best time to switchover. Each ship will have an optimal switchover time.  The ship operators should familiarise themselves with this and allow sufficient time for the fuel system to be flushed of all non-compliant fuels before entering an ECA.
  1. Avoid hazards by knowing the correct temperature and viscosity. The different viscosities between heavy fuel oil (HFO), low sulphur ECA fuel and marine gas oil (MGO) means that the appropriate temperature must be achieved to ensure the optimum viscosity at the injectors.  For instance, HFO is injected at 130°C and MGO needs to be cooled to 30°C in order to reach the correct viscosity for operation.  Major engine manufacturers typically recommend a maximum temperature change of 2°C per minute to help avoid thermal shock.
  1. Understand compatibility and potential risks. When fuels mix there is a risk of incompatibility which may result in clogged filters leading to engine starvation and even engine shutdown.  To understand whether fuels are compatible, an industry-standard spot test can be carried out on-board or a more thorough compatibility test can be requested from a reputable testing laboratory.
  1. The correct lubricant must be chosen. Cylinder oils should be of the correct alkalinity in order to neutralise the corrosive nature of the acid sulphur in the fuel.  When less sulphur is present, less sulphuric acid is produced. Too much alkalinity in the cylinder oil can lead to liner wear, while too little increases the risk of acid corrosion. When burning low-sulphur fuels in slow-speed engines, it is recommended that a lower base number lubricant be used.

In addition to these top-tips, ExxonMobil has developed two ECA category fuels, ExxonMobil Premium AFME 200 and ExxonMobil Premium HDME 50, to help operators comply with ECA requirements safely.

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