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ExxonMobil Insights: Switching between high and low sulfur fuels

Mar 15, 2017 03:34 PM

In the latest edition of ExxonMobil Insights, technical liaison manager John LaRese discusses best practices for changing between high and low sulfur fuels as vessels move in and out of Emission Control Areas (ECAs).

In order to help vessel operators navigate changes in the marine industry, ExxonMobil has launched its Insight video series, which offers best practice advice on various issues — from understanding ECA regulations to fuel storage and handling measures.

The fifth and final video in the series tackles the issue of changing between high and low sulfur fuels as vessels move in and out of ECAs.

Fuel switching when entering ECAs

ECA zones bring two key challenges. First, how to ensure that vessels have compliant fuel on board. And second, how to ensure fuel is managed and switched correctly so that when ships cross into an ECA they're consuming the right sulfur level fuel and not cross-contaminating.

To help avoid these issues ExxonMobil has compiled five key fuel-switching tips:

• Have a clear switchover procedure — It is important to ensure that the crew is familiar with the process. Ensure this is tested prior to entering crowded and restricted channels where there is a higher risk of grounding or collision.

• Outline the best time to switch over — Differing for each vessel, operators must allow sufficient time for the fuel system to be flushed of all non-compliant fuel before arriving at an ECA limit.

• Know the correct temperature and viscosity — The viscosities of heavy fuel oil (HFO), ECA fuels and marine gas oil (MGO) are very different. Major engine manufacturers typically recommend a maximum temperature change of 2 degrees centigrade per minute to help avoid thermal shock.

• Understand compatibility — In order to understand if 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.

• Choose the correct lubricant — Cylinder oils need to be sufficiently alkaline to neutralize any corrosive acidic sulfur in the fuel. However, when less sulfur is present, less sulfuric 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-sulfur fuels in slow-speed engines, it is recommended that a lower base number lubricant is used.

To watch all videos in the ExxonMobil Insight video series, or to learn more about ExxonMobil’s specialist low sulfur offerings,visit

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