Question 170Motor Plants - QMED

The correct answer is D) Valves 2 and 3 CLOSED, and Valve 6 OPEN. This configuration allows the two heavy fuel oil purifiers to operate in series, with the fuel flowing through Valve 6 and being purified by both purifiers. Valves 2 and 3 are closed to isolate the individual purifiers and force the fuel to pass through both in sequence. This is the appropriate valve configuration for operating the two purifiers in series, as indicated by the schematic. The other answer choices are incorrect because they do not properly isolate the purifiers and allow the fuel to flow through both units in series.