The purpose of the interlocked three-way valve shown in the illustration is to __________. Illustration MO-0058

Correct Answer: Option D — change fuel from heavy to light oil or vice-versa while insuring that oil is returned to the proper day tank

Interlocked three-way valves in heavy fuel supply systems safely manage the thermal transition between distillate and residual fuels, ensuring return lines route to the appropriate day tanks to prevent cross-contamination of marine gas oil and heavy fuel.