Question 42 MODE01 - Chief MODU Engineer

The Correct Answer is A. **Explanation for Option A (Correct):** A water content of 0.75% by volume means 0.75% of the fuel purchased is essentially non-combustible water. When this fuel is burned, the water reduces the **specific heating value (calorific value)** of the fuel oil because energy is required to heat and vaporize the water content during combustion. This loss of heating value directly leads to **increased fuel consumption** (the engine requires more volume of fuel to produce the same power) and negatively affects **engine efficiency**. Furthermore, paying for water as if it were usable fuel constitutes a significant **economic loss**. **Explanation of Incorrect Options:** **B) All water may be dealt with by proper use of centrifuges, thus not a significant onboard or economic/engineering problem.** * **Incorrect:** While centrifuges (purifiers) are used to reduce water content, they are not 100% effective, and they require energy, maintenance, and time. Most importantly, even if the water is fully removed onboard, the **economic loss** of having paid for 0.75% water remains. Additionally, this level of water content is a continuous problem requiring constant purification effort. **C) Economic loss of receiving less fuel, by volume, but still within ISO 8217:2010 fuel specifications.** * **Incorrect (Partial Truth/Misleading):** While there is an economic loss, the key issue is not just receiving "less fuel," but receiving fuel contaminated with water, which directly impacts combustion efficiency (addressed in A). Furthermore, ISO 8217:2010 specifications limit water content (Water and Sediment, W+S) to **0.50% by volume** for all common residual marine fuels (like RMG/RME grades). A water content of 0.75% **exceeds** the maximum allowable limit set by ISO 8217:2010, making the fuel off-specification (off-spec). **D) Vessel will have to use additional efforts to reduce the water content, the oily-water separators can deal with the discharge waste water.** * **Incorrect (Secondary/Incomplete):** This option correctly identifies the need for additional effort (purification), but incorrectly attributes the disposal solution. The water removed by the purifiers is typically contaminated fuel/sludge, which is routed to the sludge tank, not directly through the **Oily Water Separator (OWS)**. The OWS is designed to treat bilge water, not the concentrated fuel-oil/water mixture from the purifiers. More crucially, this option fails to address the **major consequence**: the impact on combustion and the heating value of the remaining fuel (the core issue addressed in A).