Question 416General Subjects - 1st Asst/Chief

The correct answer is C) 98°C. The recommended upper limit for preheating residual fuel oil prior to centrifugation on motor ships is typically 98°C. This temperature range helps reduce the fuel viscosity to the optimal level for efficient removal of solids and moisture during the centrifugation process. Preheating the fuel to a lower temperature, such as 85°C (option A), may not reduce the viscosity enough for optimal centrifugation. Conversely, preheating to higher temperatures like 112°C (option D) could potentially damage the fuel or the centrifugation equipment. The other options, 90°C (option B) and 112°C (option D), are not the recommended upper limit for typical motor vessel applications.