ExxonMobil issues guidance for switching to low sulphur fuel

ExxonMobil Marine Ship at Port

The fuels landscape is set to dramatically change when the International Maritime Organization’s (IMO) 0.5% sulphur cap comes into force on 1 January 2020. Ahead of this, we have come up with some top tips to help the marine industry switch to low sulphur fuels while maintaining a vessel’s safe and reliable operation.

First, establish best practise: Prevention is always better than cure so it is advisable to:

  • Buy fuel that meets the latest ISO 8217:2017 specification
  • Only bunker from reputable fuel suppliers
  • Clean out bunker tank residues when necessary

Test for cat fines: Some new 0.5% sulphur fuels could contain elevated levels of cat fines, which if not properly treated, could trigger catastrophic engine damage. If laboratory testing shows a high concentration then:

  • Maintain storage tank temperatures at least 10°C above fuel pour point
  • Keep settling tanks at 85°C
  • Operate purifiers at optimum efficiency and minimum throughput
  • Drain water from fuel tanks to aid settling

Check for compatibility: There is a risk that two compliant fuels will not be compatible, which can trigger damaging sludge formation. It is therefore essential to:

  • Test the fuels for compatibility, ideally in a laboratory
  • Store fuels separately until testing has been carried out
  • If mixing is unavoidable, avoid comingling in excess of 80:20 mix ratio

Monitor for sludge: If sludge does start to form, it is essential to ensure against further fuel blending before any remedial action is taken as this may exacerbate the problem. Then:

  • Operate two or more separators in parallel at their lowest throughput
  • Increase the frequency of purifier discharge
  • Monitor and clean filters frequently

Depending on its features, it may also be possible to use a next generation cylinder condition monitoring service to test a fuel’s sulphur content in order to confirm it meets the revised IMO sulphur cap. Using fuels that do not comply with the emissions regulations could result in costly penalties.


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