<![CDATA[The fuel oil purifier is a critical auxiliary equipment on board vessels, responsible for separating sediments, water, and sludge from fuel oil to ensure clean fuel supply for the main engine and auxiliary machinery. This study investigates the causes of fuel oil purifier malfunction on board MV. Lumoso Permai, a bulk carrier operated by PT. Lumoso Pratama Line, and proposes optimized maintenance strategies to prevent recurrence. During the author's sea practice period from September 2021 to September 2022, two primary operational problems were identified on the Mitsubishi SJ20T-60T type purifier. First, excessive fuel oil waste during the purification process was caused by the accumulation of sludge and contaminants on the bowl body and disc assembly, compounded by the selection of an incorrect gravity disc size. These conditions resulted in fuel overflow through the sludge port rather than discharge through the clean oil outlet. Second, the pilot valve malfunctioned due to worn O-rings and contaminant deposits obstructing the valve passages, preventing proper operating water flow for bowl opening and closing operations. The study employed a descriptive qualitative approach with data collected through direct observation, interviews with the Fourth Engineer, and documentation review. Analysis revealed that both problems were fundamentally attributable to inadequate adherence to the Planned Maintenance System (PMS) schedule and insufficient compliance with the manufacturer's instruction manual. The recommended corrective measures include implementing strict periodic bowl and disc cleaning schedules in accordance with the PMS, conducting routine pilot valve inspection and O-ring replacement, and ensuring proper gravity disc selection based on fuel specific gravity and operating temperature.]]>
