🔍 Key Concepts

• Viscosity vs. temperature for heavy fuel oil (how heating changes viscosity) • Locations of steam/heating coils and final heaters in the MO-0058 fuel system • Function and typical temperature of the settling tank, service tank, and main engine supply/header

💭 Think About

• Trace the flow of heavy fuel oil from the settling tank all the way to the main engine on the diagram. At which points is the oil deliberately heated the most? • At each answer choice location, ask yourself: is the fuel mainly for storage/transfer, purification, or for injection to the engine? Which of those uses requires the fuel to be thinnest (lowest viscosity)? • Compare whether the three‑way valve, transfer pump discharge, settling tank, or engine header would normally handle the hottest fuel in operation.

✅ Before You Answer

• Verify which components on the diagram have heating coils or pre‑heaters drawn and where they are located relative to each answer choice. • Check where the viscosimeter is installed; that is usually close to where the desired (lowest) viscosity must be tightly controlled. • Confirm which of the four listed locations is closest (in flow path) to the final heaters and the main engine fuel injectors, where fuel must be at injection temperature.