Question 1100 Deck Safety

70% to pass

One major disadvantage of a low-speed diesel as compared to a steam main-propulsion system is _______________.

A the low efficiency of the system when a controllable pitch propeller is used
B a minimum speed for the engines that limits the minimum speed of the vessel
C the extra weight required for the diesel reduction gearing
D the higher fuel consumption per SHP
AI Explanation

The correct answer is B) a minimum speed for the engines that limits the minimum speed of the vessel. Low-speed diesel engines have a minimum operating speed, typically around 100-200 RPM, below which they cannot operate efficiently or reliably. This minimum speed requirement means that the vessel's propeller must also maintain a minimum rotational speed, limiting the vessel's ability to achieve very low speeds compared to a steam propulsion system, which can operate at much lower speeds. The other answer choices are incorrect because: A) the efficiency of a controllable pitch propeller is not a major disadvantage of low-speed diesels; C) the weight of the reduction gearing is not a significant disadvantage; and D) while low-speed diesels may have higher fuel consumption per shaft horsepower, this is not the major disadvantage being asked about in the question.

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