🔍 Key Concepts

• Flow path required to run two HFO purifiers in series (outlet of first feeding inlet of second) • How valves 2, 3, and 6 change the connections between the purifiers and the common supply/return headers • Difference between series flow (one after the other) and parallel flow (side‑by‑side from a common header)

💭 Think About

• Trace the fuel path on the drawing starting at the HFO settling tank: which purifier does it reach first, and how does it reach the day tank when the units are in series? • For each valve (2, 3, and 6), ask yourself: if this valve is OPEN, does fuel have a path that bypasses one of the purifiers, or is it forced to pass through both? • Compare what the path would look like if the purifiers were operating in parallel instead—how would you configure the same valves in that case, and what needs to change to convert that to series operation?

✅ Before You Answer

• Make sure the fuel cannot go directly from the supply header to the return header without passing through both purifiers. • Confirm that the outlet of the first purifier is connected only to the inlet of the second purifier (through valve 6) when in series. • Verify whether valve 3 being open would let fuel leave the purifier system after just one pass, and whether valve 2 being open would let fuel completely bypass the first purifier.