🔍 Key Concepts

• Location of the mixing tank in relation to the main engine supply and return lines • What happens to hot return fuel from the engine during changeover from HFO (heavy fuel oil) to DO (distillate oil) • How a vent line and moisture trap work compared to the main reason for having a mixing/buffer tank

💭 Think About

• Trace the flow of fuel from the service tanks, through the heaters and engine, and back to the mixing tank—what must be controlled during this loop? • During a rapid switch from hot heavy fuel to cold distillate, what could happen to pumps, injectors, and pipes if the temperature (and viscosity) changed suddenly? • Is venting and day-tank protection the primary design purpose of this tank, or side effects of how it is arranged in the system?

✅ Before You Answer

• Confirm which lines are connected to the mixing tank (engine return, booster pump suction, vents) in the illustration • Decide what single problem would be most serious for the fuel system if the mixing tank were removed entirely • Check whether preventing vapor venting or day tank overheating requires a dedicated tank, or if these could be solved more simply without a mixing tank