Actions to be Taken When New Bunkers Differ Significantly from Existing Fuel

When the density of the new fuel differs from the existing fuel, the following steps are necessary:

• Adjustment of Purifier Settings: The gravity disc size (in manually controlled purifiers) must be selected according to the new fuel density. For automatic systems such as ALCAP purifiers, the operating parameters should be adjusted to maintain proper oil-water separation.
• Accurate Fuel Quantity Calculation: Since fuel inventory is often measured by volume, the new density must be used to recalculate the actual mass of fuel on board. This is important for both fuel management and stability calculations.
• Monitoring Centrifuge Performance: The oil-water interface inside the purifier should be closely monitored to prevent either oil loss through the water outlet or water carry-over into the clean oil side.

Variations in viscosity directly affect fuel atomization and combustion quality. The following actions should be taken:

• Adjustment of Viscosity Controller: The fuel oil heater and viscosity control system must be set so that the fuel reaches the required viscosity (typically 12–14 cSt) at the engine inlet for efficient atomization.
• Temperature Management: Proper heating of fuel lines must be ensured. Trace heating systems should be checked and maintained to prevent poor flow characteristics or “waxing,” especially if the new fuel has a higher pour point.

Cat fines are highly abrasive and can cause severe engine wear if not properly removed. The following precautions are essential:

• Maximizing Purification Efficiency: Operate purifiers at reduced throughput or in series (if arrangements permit) to increase residence time, thereby improving the removal of fine particles.
• Settling Tank Management: Maintain the settling tank temperature at approximately 85–90°C to promote the settling of cat fines at the bottom, which can then be drained periodically.
• Frequent Filter Inspection: Increase the frequency of inspection and cleaning of fuel oil filters, including automatic backwash filters, to prevent passage of abrasive particles to the engine.

Sulphur content has both operational and regulatory implications:

• Regulatory Compliance (MARPOL): Ensure that the sulphur content of the fuel complies with the limits applicable to the trading area (e.g., 0.50% globally or 0.10% in Emission Control Areas).
• Cylinder Lubrication Adjustment: Adjust the cylinder oil feed rate and select the appropriate Total Base Number (TBN). High sulphur fuels require higher TBN oils to neutralize acidic products, whereas low sulphur fuels require lower TBN oils to avoid deposit formation.
• Fuel Segregation: Avoid mixing the new fuel with existing fuel unless compatibility is confirmed, as incompatible fuels can form sludge and cause operational problems.

Excess water in fuel can lead to poor combustion and damage to engine components. The following measures should be taken:

• Settling and Draining: Allow the fuel to settle in the settling tank and regularly drain accumulated water from the bottom.
• Monitoring Purifier Operation: Ensure that the purifier is functioning effectively for water separation. Keep a close watch on water-in-oil alarms and discharge quality.
• Use of Homogenizer (if fitted): A homogenizer should only be used if purification is already optimized and water content remains within acceptable limits. It should not be relied upon as a primary method of water removal.