Purifier

A purifier is a high-speed centrifugal separator that removes water and solid contaminants from fuel oil or lubricating oil before it reaches the engine. In the fuel oil system, purifiers are essential for removing the catalytic aluminium-silica fines present in residual fuels, which can cause severe wear in fuel pumps and injection valves if their concentration exceeds approximately 15 mg/kg at the engine inlet. Purifiers operate on the principle that centrifugal force separates liquids and solids of differing densities, with sludge and water collecting at the periphery for periodic discharge. Engineers set and verify the purifier's gravity disc size, temperature, feed rate, and discharge interval according to the oil's density and the maker's instructions. MARPOL Annex I requires sludge generated during purification to be retained on board in a dedicated sludge tank and recorded in the Oil Record Book Part I; it may only be discharged to port reception facilities or incinerated on board in an approved incinerator. Classification societies such as Lloyd's Register and DNV publish IACS Unified Requirements relating to fuel treatment systems that govern minimum purifier capacity and arrangement.