ExxonMobil’s “Top Tips” for Purchasing Marine Bunkers

Considering the huge commercial impact marine bunkers have on ship owners and operators, ExxonMobil has put together the following list of “top-tips” centered around five key fuel quality factors:

Water content

ISO 8217:2012 permitted water content compliance level is 0.5%.

If marine fuel is supplied at the 0.5% compliance level the water content alone could potentially cost you USD $6,000 per purchase of a 2000 metric tons of fuel, or $3 per metric ton.  Should you need to dispose of this water content while in Singapore, this could add another $3000 in costs, in addition to costs incurred from cleaning sludge from fuel oil purifiers.

Metal content

Aluminum and Silicon in marine fuels, known as catalytic fines, have the potential to cause significant engine damage.  This could lead to substantial repair costs and potential vessel delays. ISO 8217:2012 and ISO 8217:2005 allow for levels of catalytic fines up to 60mg/kg and 80mg/kg respectively. Major engine builders typically recommend the level of catalytic fines should be less than 15mg/kg at the engine inlet.

ExxonMobil notes their marine fuels normally have significantly lower levels of catalytic fines, with an average of 10mg/kg. These low levels help limit catalytic fine removal efforts, reduce abrasive wear on critical engine components and potentially avoid the cost of additional maintenance and possible breakdowns.

Marine fuel stability

To help meet the lower sulphur levels specified in changing marine industry regulations, there may be a tendency to blend marine fuel from a variety of different sources which may cause the resultant blend to become incompatible. Unstable fuels have the potential to cause sludge or heavy deposits to build up which may prove costly to resolve and may impede vessel performance.

Marine fuels which arrive at the terminal via an integrated supply chain, such as Exxonmobil’s, will successfully mitigate this issue.

Calculated Carbon Aromaticity Index (CCAI) level

CCAI level is the indicator of marine fuel combustion quality and it’s important that it is neither too high nor too low.  Poor quality marine fuel with an inappropriate CCAI level, caused by incompatible blend components, could cause poor combustion and has the potential to impact vessel performance.  ISO 8217:2012 states a max limit of 870 for most common residual marine fuel grades and ExxonMobil’s marine fuels sit within the working parameters of major engine manufacturers, helping to protect against poor performance.

Exxonmobil fuel laboratory chemistry test tube
Image (c) ExxonMobil

Laboratory analysis

Finally, ExxonMobil recommends that it is best practice to send fuel samples to an approved laboratory for analysis.  This allows operators to understand the quality of the marine fuel received and how to manage the marine fuel system on board their vessels.