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

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

The interlocked three-way valve facilitates safe fuel switching between heavy fuel oil and diesel oil. It ensures that return lines are correctly routed to the appropriate day tank, preventing high-viscosity fuel contamination of low-viscosity service tanks or vice versa.