🔍 Key Concepts
• Trace the fuel flow paths from each settling/day tank to each purifier and then to the mixing tank/main engine when different valves are open or closed.
• Recall the functional difference between an HFO purifier vs DO purifier and what must change in the piping if one machine is used to treat the other type of fuel.
• Think about how cross‑connection valves (like valve 6 between the two HFO purifiers) let you reroute suction or discharge from one purifier to another.
💭 Think About
• If valves 2 and 3 are closed, what normal HFO paths are being shut off, and which purifier (HFO or DO) loses its usual supply or discharge?
• When valve 6 is opened, which purifier is now able to receive or discharge which type of fuel, and from which settling tank? Sketch the new flow route step by step.
• For each answer choice, ask yourself: does this configuration require combining flows, separating clarifier/separator duties, or converting one purifier service (HFO/DO) into the other?
✅ Before You Answer
• Verify from the diagram which lines are HFO only, DO only, and which go to the mixing tank/main system.
• Confirm exactly where valves 2, 3, and 6 sit: are they on the inlet side, outlet side, or crossover between purifiers?
• For your chosen option, make sure the piping with 2 & 3 closed and 6 open still provides a complete flow path: from the correct fuel’s settling tank, through a suitable purifier, and back into the system without dead‑ending.